Novel white matter tract integrity metrics sensitive to Alzheimer disease progression.

PubMed

Fieremans, E; Benitez, A; Jensen, J H; Falangola, M F; Tabesh, A; Deardorff, R L; Spampinato, M V S; Babb, J S; Novikov, D S; Ferris, S H; Helpern, J A

2013-01-01

Along with cortical abnormalities, white matter microstructural changes such as axonal loss and myelin breakdown are implicated in the pathogenesis of Alzheimer disease. Recently, a white matter model was introduced that relates non-Gaussian diffusional kurtosis imaging metrics to characteristics of white matter tract integrity, including the axonal water fraction, the intra-axonal diffusivity, and the extra-axonal axial and radial diffusivities. This study reports these white matter tract integrity metrics in subjects with amnestic mild cognitive impairment (n = 12), Alzheimer disease (n = 14), and age-matched healthy controls (n = 15) in an effort to investigate their sensitivity, diagnostic accuracy, and associations with white matter changes through the course of Alzheimer disease. With tract-based spatial statistics and region-of-interest analyses, increased diffusivity in the extra-axonal space (extra-axonal axial and radial diffusivities) in several white matter tracts sensitively and accurately discriminated healthy controls from those with amnestic mild cognitive impairment (area under the receiver operating characteristic curve = 0.82-0.95), while widespread decreased axonal water fraction discriminated amnestic mild cognitive impairment from Alzheimer disease (area under the receiver operating characteristic curve = 0.84). Additionally, these white matter tract integrity metrics in the body of the corpus callosum were strongly correlated with processing speed in amnestic mild cognitive impairment (r = |0.80-0.82|, P < .001). These findings have implications for the course and spatial progression of white matter degeneration in Alzheimer disease, suggest the mechanisms by which these changes occur, and demonstrate the viability of these white matter tract integrity metrics as potential neuroimaging biomarkers of the earliest stages of Alzheimer disease and disease progression.

Impaired adenosine monophosphate-activated protein kinase signalling in dorsal root ganglia neurons is linked to mitochondrial dysfunction and peripheral neuropathy in diabetes

PubMed Central

Smith, Darrell R.; Saleh, Ali; Schapansky, Jason; Marquez, Alexandra; Gomes, Suzanne; Akude, Eli; Morrow, Dwane; Calcutt, Nigel A.; Fernyhough, Paul

2012-01-01

Mitochondrial dysfunction occurs in sensory neurons and may contribute to distal axonopathy in animal models of diabetic neuropathy. The adenosine monophosphate-activated protein kinase and peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α) signalling axis senses the metabolic demands of cells and regulates mitochondrial function. Studies in muscle, liver and cardiac tissues have shown that the activity of adenosine monophosphate-activated protein kinase and PGC-1α is decreased under hyperglycaemia. In this study, we tested the hypothesis that deficits in adenosine monophosphate-activated protein kinase/PGC-1α signalling in sensory neurons underlie impaired axonal plasticity, suboptimal mitochondrial function and development of neuropathy in rodent models of type 1 and type 2 diabetes. Phosphorylation and expression of adenosine monophosphate-activated protein kinase/PGC-1α and mitochondrial respiratory chain complex proteins were downregulated in dorsal root ganglia of both streptozotocin-diabetic rats and db/db mice. Adenoviral-mediated manipulation of endogenous adenosine monophosphate-activated protein kinase activity using mutant proteins modulated neurotrophin-directed neurite outgrowth in cultures of sensory neurons derived from adult rats. Addition of resveratrol to cultures of sensory neurons derived from rats after 3–5 months of streptozotocin-induced diabetes, significantly elevated adenosine monophosphate-activated protein kinase levels, enhanced neurite outgrowth and normalized mitochondrial inner membrane polarization in axons. The bioenergetics profile (maximal oxygen consumption rate, coupling efficiency, respiratory control ratio and spare respiratory capacity) was aberrant in cultured sensory neurons from streptozotocin-diabetic rats and was corrected by resveratrol treatment. Finally, resveratrol treatment for the last 2 months of a 5-month period of diabetes reversed thermal hypoalgesia and attenuated foot skin intraepidermal nerve fibre loss and reduced myelinated fibre mean axonal calibre in streptozotocin-diabetic rats. These data suggest that the development of distal axonopathy in diabetic neuropathy is linked to nutrient excess and mitochondrial dysfunction via defective signalling of the adenosine monophosphate-activated protein kinase/PGC-1α pathway. PMID:22561641

LGI1 tunes intrinsic excitability by regulating the density of axonal Kv1 channels.

PubMed

Seagar, Michael; Russier, Michael; Caillard, Olivier; Maulet, Yves; Fronzaroli-Molinieres, Laure; De San Feliciano, Marina; Boumedine-Guignon, Norah; Rodriguez, Léa; Zbili, Mickael; Usseglio, Fabrice; Formisano-Tréziny, Christine; Youssouf, Fahamoe; Sangiardi, Marion; Boillot, Morgane; Baulac, Stéphanie; Benitez, María José; Garrido, Juan-José; Debanne, Dominique; El Far, Oussama

2017-07-18

Autosomal dominant epilepsy with auditory features results from mutations in leucine-rich glioma-inactivated 1 (LGI1), a soluble glycoprotein secreted by neurons. Animal models of LGI1 depletion display spontaneous seizures, however, the function of LGI1 and the mechanisms by which deficiency leads to epilepsy are unknown. We investigated the effects of pure recombinant LGI1 and genetic depletion on intrinsic excitability, in the absence of synaptic input, in hippocampal CA3 neurons, a classical focus for epileptogenesis. Our data indicate that LGI1 is expressed at the axonal initial segment and regulates action potential firing by setting the density of the axonal Kv1.1 channels that underlie dendrotoxin-sensitive D-type potassium current. LGI1 deficiency incurs a >50% down-regulation of the expression of Kv1.1 and Kv1.2 via a posttranscriptional mechanism, resulting in a reduction in the capacity of axonal D-type current to limit glutamate release, thus contributing to epileptogenesis.

The intriguing nature of dorsal root ganglion neurons: linking structure with polarity and function.

PubMed

Nascimento, Ana Isabel; Mar, Fernando Milhazes; Sousa, Mónica Mendes

2018-05-02

Dorsal root ganglion (DRG) neurons are the first neurons of the sensory pathway. They are activated by a variety of sensory stimuli that are then transmitted to the central nervous system. An important feature of DRG neurons is their unique morphology where a single process -the stem axon- bifurcates into a peripheral and a central axonal branch, with different functions and cellular properties. Distinctive structural aspects of the two DRG neuron branches may have important implications for their function in health and disease. However, the link between DRG axonal branch structure, polarity and function has been largely neglected in the field, and relevant information is rather scattered across the literature. In particular, ultrastructural differences between the two axonal branches are likely to account for the higher transport and regenerative ability of the peripheral DRG neuron axon when compared to the central one. Nevertheless, the cell intrinsic factors contributing to this central-peripheral asymmetry are still unknown. Here we critically review the factors that may underlie the functional asymmetry between the peripheral and central DRG axonal branches. Also, we discuss the hypothesis that DRG neurons may assemble a structure resembling the axon initial segment that may be responsible, at least in part, for their polarity and electrophysiological features. Ultimately, we suggest that the clarification of the axonal ultrastructure of DRG neurons using state-of-the-art techniques will be crucial to understand the physiology of this peculiar cell type. Copyright © 2018. Published by Elsevier Ltd.

Kinesin Mutations Cause Motor Neuron Disease Phenotypes by Disrupting Fast Axonal Transport in Drosophila

PubMed Central

Hurd, D. D.; Saxton, W. M.

1996-01-01

Previous work has shown that mutation of the gene that encodes the microtubule motor subunit kinesin heavy chain (Khc) in Drosophila inhibits neuronal sodium channel activity, action potentials and neurotransmitter secretion. These physiological defects cause progressive distal paralysis in larvae. To identify the cellular defects that cause these phenotypes, larval nerves were studied by light and electron microscopy. The axons of Khc mutants develop dramatic focal swellings along their lengths. The swellings are packed with fast axonal transport cargoes including vesicles, synaptic membrane proteins, mitochondria and prelysosomal organelles, but not with slow axonal transport cargoes such as cytoskeletal elements. Khc mutations also impair the development of larval motor axon terminals, causing dystrophic morphology and marked reductions in synaptic bouton numbers. These observations suggest that as the concentration of maternally provided wild-type KHC decreases, axonal organelles transported by kinesin periodically stall. This causes organelle jams that disrupt retrograde as well as anterograde fast axonal transport, leading to defective action potentials, dystrophic terminals, reduced transmitter secretion and progressive distal paralysis. These phenotypes parallel the pathologies of some vertebrate motor neuron diseases, including some forms of amyotrophic lateral sclerosis (ALS), and suggest that impaired fast axonal transport is a key element in those diseases. PMID:8913751

Trafficking Mechanisms Underlying Neuronal Voltage-gated Ion Channel Localization at the Axon Initial Segment

PubMed Central

Vacher, Helene; Trimmer, James S.

2012-01-01

Summary Voltage-gated ion channels are diverse and fundamental determinants of neuronal intrinsic excitability. Voltage-gated K+ (Kv) and Na+ (Nav) channels play complex yet fundamentally important roles in determining intrinsic excitability. The Kv and Nav channels located at the axon initial segment (AIS) play a unique and especially important role in generating neuronal output in the form of anterograde axonal and backpropagating action potentials, Aberrant intrinsic excitability in individual neurons within networks contributes to synchronous neuronal activity leading to seizures. Mutations in ion channel genes gives rise to a variety of seizure-related “Channelopathies”, and many of the ion channel subunits associated with epilepsy mutations are localized at the AIS, making this a hotspot for epileptogenesis. Here we review the cellular mechanisms that underlie the trafficking of Kv and Nav channels found at the AIS, and how Kv and Nav channel mutations associated with epilepsy can alter these processes. PMID:23216576

Reversible acute axonal polyneuropathy associated with Wernicke-Korsakoff syndrome: impaired physiological nerve conduction due to thiamine deficiency?

PubMed

Ishibashi, S; Yokota, T; Shiojiri, T; Matunaga, T; Tanaka, H; Nishina, K; Hirota, H; Inaba, A; Yamada, M; Kanda, T; Mizusawa, H

2003-05-01

Acute axonal polyneuropathy and Wernicke-Korsakoff encephalopathy developed simultaneously in three patients. Nerve conduction studies (NCS) detected markedly decreased compound muscle action potentials (CMAPs) and sensory nerve action potentials (SNAPs) with minimal conduction slowing; sympathetic skin responses (SSRs) were also notably decreased. Sural nerve biopsies showed only mild axonal degeneration with scattered myelin ovoid formation. The symptoms of neuropathy lessened within two weeks after an intravenous thiamine infusion. CMAPs, SNAPs, and SSRs also increased considerably. We suggest that this is a new type of peripheral nerve impairment: physiological conduction failure with minimal conduction delay due to thiamine deficiency.

Gradual Loss of Myelin and Formation of an Astrocytic Scar during Wallerian Degeneration in the Human Spinal Cord

ERIC Educational Resources Information Center

A. Buss, G. A. Brook; B. Kakulas; D. Martin; R. Franzen; J. Schoenen; J. Noth; A. B. Schmitt

2004-01-01

Axons undergo Wallerian degeneration distal to a point of injury. Experimental investigations have documented many of the cellular and molecular events that underlie this behaviour. Since relatively little is known about such events in human CNS pathologies and current experimental intervention strategies indicate the possibility of significant…

Mild fluid percussion injury in mice produces evolving selective axonal pathology and cognitive deficits relevant to human brain injury.

PubMed

Spain, Aisling; Daumas, Stephanie; Lifshitz, Jonathan; Rhodes, Jonathan; Andrews, Peter J D; Horsburgh, Karen; Fowler, Jill H

2010-08-01

Mild traumatic brain injury (TBI) accounts for up to 80% of clinical TBI and can result in cognitive impairment and white matter damage that may develop and persist over several years. Clinically relevant models of mild TBI for investigation of neurobiological changes and the development of therapeutic strategies are poorly developed. In this study we investigated the temporal profile of axonal and somal injury that may contribute to cognitive impairments in a mouse model of mild TBI. Neuronal perikaryal damage (hematoxylin and eosin and Fluoro-Jade C), myelin integrity (myelin basic protein and myelin-associated glycoprotein), and axonal damage (amyloid precursor protein), were evaluated by immunohistochemistry at 4 h, 24 h, 72 h, 4 weeks, and 6 weeks after mild lateral fluid percussion brain injury (0.9 atm; righting time 167 +/- 15 sec). At 3 weeks post-injury spatial reference learning and memory were tested in the Morris water maze (MWM). Levels of damage to neuronal cell bodies were comparable in the brain-injured and sham groups. Myelin integrity was minimally altered following injury. Clear alterations in axonal damage were observed at various time points after injury. Axonal damage was localized to the cingulum at 4 h post-injury. At 4 and 6 weeks post-injury, axonal damage was evident in the external capsule, and was seen at 6 weeks in the dorsal thalamic nuclei. At 3 weeks post-injury, injured mice showed an impaired ability to learn the water maze task, suggesting injury-induced alterations in search strategy learning. The evolving localization of axonal damage points to ongoing degeneration after injury that is concomitant with a deficit in learning.

Identification of a Peripheral Nerve Neurite Growth-Promoting Activity by Development and Use of an in vitro Bioassay

NASA Astrophysics Data System (ADS)

Sandrock, Alfred W.; Matthew, William D.

1987-10-01

The effective regeneration of severed neuronal axons in the peripheral nerves of adult mammals may be explained by the presence of molecules in situ that promote the effective elongation of neurites. The absence of such molecules in the central nervous system of these animals may underlie the relative inability of axons to regenerate in this tissue after injury. In an effort to identify neurite growth-promoting molecules in tissues that support effective axonal regeneration, we have developed an in vitro bioassay that is sensitive to substrate-bound factors of peripheral nerve that influence the growth of neurites. In this assay, neonatal rat superior cervical ganglion explants are placed on longitudinal cryostat sections of fresh-frozen sciatic nerve, and the regrowing axons are visualized by catecholamine histofluorescence. Axons are found to regenerate effectively over sciatic nerve tissue sections. When ganglia are similarly explanted onto cryostat sections of adult rat central nervous system tissue, however, axonal regeneration is virtually absent. We have begun to identify the molecules in peripheral nerve that promote effective axonal regeneration by examining the effect of antibodies that interfere with the activity of previously described neurite growth-promoting factors. Axonal elongation over sciatic nerve tissue was found to be sensitive to the inhibitory effects of INO (for inhibitor of neurite outgrowth), a monoclonal antibody that recognizes and inhibits a neurite growth-promoting activity from PC-12 cell-conditioned medium. The INO antigen appears to be a molecular complex of laminin and heparan sulfate proteoglycan. In contrast, a rabbit antiserum that recognizes laminin purified from mouse Engelbreth-Holm-Swarm (EHS) sarcoma, stains the Schwann cell basal lamina of peripheral nerve, and inhibits neurite growth over purified laminin substrata has no detectable effect on the rate of axonal regeneration in our assay.

Central nervous system correlates of behavioral deficits following simian immunodeficiency virus infection.

PubMed

Weed, Michael R; Hienz, Robert D; Brady, Joseph V; Adams, Robert J; Mankowski, Joseph L; Clements, Janice E; Zink, M Christine

2003-08-01

Despite the high incidence of cognitive and motor impairment in acquired immunodeficiency syndrome (AIDS) patients, the mechanisms of AIDS-related central nervous system (CNS) pathology are not completely understood. Infection with simian immunodeficiency virus (SIV) in macaques provides an excellent model of AIDS, including human immunodeficiency virus (HIV)-induced CNS pathology and cognitive/behavioral impairment. Co-inoculation with two SIV strains, SIV/17E-Fr and SIV/DeltaB670, accelerates SIV CNS disease, producing SIV encephalitis in over 90% of pig-tailed macaques within 3 months. In the present study, this SIV model was employed to identify cellular and viral correlates of behavioral impairment following SIV infection. Measures of psychomotor speed (simple reaction time), fine motor control (bimanual motor task), and general motor activity (home cage movement) were all adversely affected by SIV disease. Prior to euthanasia, performance was significantly impaired in both a simple reaction time task in 6 of 12 monkeys and a bimanual motor task in 5 of 6 monkeys. All monkeys evaluated (11 of 11) showed significant reductions in spontaneous motor activity. Significant correlations were found between impaired performance on the bimanual motor test and axonal damage (accumulation of beta-amyloid precursor protein in the corpus callosum) as well as increased microglial activation and macrophage infiltration (levels of CD68 and Ham56 immunostaining). These results suggest that axonal damage is related to the behavioral impairment induced by infection with SIV. The axonal damage may result from neuroimmune responses, including microglial and macrophage activation. Therefore, axonal damage may be a morphologic manifestation of neuronal dysfunction that underlies development of behavioral impairment in HIV/SIV CNS infection.

The energy cost of action potential propagation in dopamine neurons: clues to susceptibility in Parkinson's disease.

PubMed

Pissadaki, Eleftheria K; Bolam, J Paul

2013-01-01

Dopamine neurons of the substantia nigra pars compacta (SNc) are uniquely sensitive to degeneration in Parkinson's disease (PD) and its models. Although a variety of molecular characteristics have been proposed to underlie this sensitivity, one possible contributory factor is their massive, unmyelinated axonal arbor that is orders of magnitude larger than other neuronal types. We suggest that this puts them under such a high energy demand that any stressor that perturbs energy production leads to energy demand exceeding supply and subsequent cell death. One prediction of this hypothesis is that those dopamine neurons that are selectively vulnerable in PD will have a higher energy cost than those that are less vulnerable. We show here, through the use of a biology-based computational model of the axons of individual dopamine neurons, that the energy cost of axon potential propagation and recovery of the membrane potential increases with the size and complexity of the axonal arbor according to a power law. Thus SNc dopamine neurons, particularly in humans, whose axons we estimate to give rise to more than 1 million synapses and have a total length exceeding 4 m, are at a distinct disadvantage with respect to energy balance which may be a factor in their selective vulnerability in PD.

The energy cost of action potential propagation in dopamine neurons: clues to susceptibility in Parkinson's disease

PubMed Central

Pissadaki, Eleftheria K.; Bolam, J. Paul

2013-01-01

Dopamine neurons of the substantia nigra pars compacta (SNc) are uniquely sensitive to degeneration in Parkinson's disease (PD) and its models. Although a variety of molecular characteristics have been proposed to underlie this sensitivity, one possible contributory factor is their massive, unmyelinated axonal arbor that is orders of magnitude larger than other neuronal types. We suggest that this puts them under such a high energy demand that any stressor that perturbs energy production leads to energy demand exceeding supply and subsequent cell death. One prediction of this hypothesis is that those dopamine neurons that are selectively vulnerable in PD will have a higher energy cost than those that are less vulnerable. We show here, through the use of a biology-based computational model of the axons of individual dopamine neurons, that the energy cost of axon potential propagation and recovery of the membrane potential increases with the size and complexity of the axonal arbor according to a power law. Thus SNc dopamine neurons, particularly in humans, whose axons we estimate to give rise to more than 1 million synapses and have a total length exceeding 4 m, are at a distinct disadvantage with respect to energy balance which may be a factor in their selective vulnerability in PD. PMID:23515615

The Absence of Sensory Axon Bifurcation Affects Nociception and Termination Fields of Afferents in the Spinal Cord

PubMed Central

Tröster, Philip; Haseleu, Julia; Petersen, Jonas; Drees, Oliver; Schmidtko, Achim; Schwaller, Frederick; Lewin, Gary R.; Ter-Avetisyan, Gohar; Winter, York; Peters, Stefanie; Feil, Susanne; Feil, Robert; Rathjen, Fritz G.; Schmidt, Hannes

2018-01-01

A cGMP signaling cascade composed of C-type natriuretic peptide, the guanylyl cyclase receptor Npr2 and cGMP-dependent protein kinase I (cGKI) controls the bifurcation of sensory axons upon entering the spinal cord during embryonic development. However, the impact of axon bifurcation on sensory processing in adulthood remains poorly understood. To investigate the functional consequences of impaired axon bifurcation during adult stages we generated conditional mouse mutants of Npr2 and cGKI (Npr2fl/fl;Wnt1Cre and cGKIKO/fl;Wnt1Cre) that lack sensory axon bifurcation in the absence of additional phenotypes observed in the global knockout mice. Cholera toxin labeling in digits of the hind paw demonstrated an altered shape of sensory neuron termination fields in the spinal cord of conditional Npr2 mouse mutants. Behavioral testing of both sexes indicated that noxious heat sensation and nociception induced by chemical irritants are impaired in the mutants, whereas responses to cold sensation, mechanical stimulation, and motor coordination are not affected. Recordings from C-fiber nociceptors in the hind limb skin showed that Npr2 function was not required to maintain normal heat sensitivity of peripheral nociceptors. Thus, the altered behavioral responses to noxious heat found in Npr2fl/fl;Wnt1Cre mice is not due to an impaired C-fiber function. Overall, these data point to a critical role of axonal bifurcation for the processing of pain induced by heat or chemical stimuli. PMID:29472841

The Impact of Motor Axon Misdirection and Attrition on Behavioral Deficit Following Experimental Nerve Injuries

PubMed Central

Alant, Jacob Daniel de Villiers; Senjaya, Ferry; Ivanovic, Aleksandra; Forden, Joanne; Shakhbazau, Antos; Midha, Rajiv

2013-01-01

Peripheral nerve transection and neuroma-in-continuity injuries are associated with permanent functional deficits, often despite successful end-organ reinnervation. Axonal misdirection with non-specific reinnervation, frustrated regeneration and axonal attrition are believed to be among the anatomical substrates that underlie the poor functional recovery associated with these devastating injuries. Yet, functional deficits associated with axonal misdirection in experimental neuroma-in-continuity injuries have not yet been studied. We hypothesized that experimental neuroma-in-continuity injuries would result in motor axon misdirection and attrition with proportional persistent functional deficits. The femoral nerve misdirection model was exploited to assess major motor pathway misdirection and axonal attrition over a spectrum of experimental nerve injuries, with neuroma-in-continuity injuries simulated by the combination of compression and traction forces in 42 male rats. Sciatic nerve injuries were employed in an additional 42 rats, to evaluate the contribution of axonal misdirection to locomotor deficits by a ladder rung task up to 12 weeks. Retrograde motor neuron labeling techniques were utilized to determine the degree of axonal misdirection and attrition. Characteristic histological neuroma-in-continuity features were demonstrated in the neuroma-in-continuity groups and poor functional recovery was seen despite successful nerve regeneration and muscle reinnervation. Good positive and negative correlations were observed respectively between axonal misdirection (p<.0001, r2=.67), motor neuron counts (attrition) (p<.0001, r2=.69) and final functional deficits. We demonstrate prominent motor axon misdirection and attrition in neuroma-in-continuity and transection injuries of mixed motor nerves that contribute to the long-term functional deficits. Although widely accepted in theory, to our knowledge, this is the first experimental evidence to convincingly demonstrate these correlations with data inclusive of the neuroma-in-continuity spectrum. This work emphasizes the need to focus on strategies that promote both robust and accurate nerve regeneration to optimize functional recovery. It also demonstrates that clinically relevant neuroma-in-continuity injuries can now also be subjected to experimental investigation. PMID:24282624

Molecular, Cellular and Functional Events in Axonal Sprouting after Stroke

PubMed Central

Kathirvelu, Balachander; Schweppe, Catherine A; Nie, Esther H

2016-01-01

Stroke is the leading cause of adult disability. Yet there is a limited degree of recovery in this disease. One of the mechanisms of recovery is the formation of new connections in the brain and spinal cord after stroke: post-stroke axonal sprouting. Studies indicate that post-stroke axonal sprouting occurs in mice, rats, primates and humans. Inducing post-stroke axonal sprouting in specific connections enhances recovery; blocking axonal sprouting impairs recovery. Behavioral activity patterns after stroke modify the axonal sprouting response. A unique regenerative molecular program mediates this aspect of tissue repair in the CNS. The types of connections that are formed after stroke indicate three patterns of axonal sprouting after stroke: Reactive, Reparative and Unbounded Axonal Sprouting. These differ in mechanism, location, relationship to behavioral recovery and, importantly, in their prospect for therapeutic manipulation to enhance tissue repair. PMID:26874223

The effects of voluntary running exercise coincidence with social isolation after early weaning on monoaminergic axonal development.

PubMed

Ishikawa, J; Ishikawa, A

2013-01-29

The axonal development of serotonin (5-HT)-, noradrenaline (NA)-, or tyrosine hydroxylase (TH)-containing monoaminergic neurons is affected by rearing conditions during the juvenile period. Impaired monoaminergic axonal development is implicated in the pathophysiology of emotional and cognitive dysfunction. On the other hand, exercise may have beneficial effects on emotional and learning performance in adults. We have examined whether voluntary running exercise during social isolation after early weaning (early weaning/social isolation; EI) from postnatal day (PD) 14-28 could prevent the impaired monoaminergic axonal development associated with EI. Compared with control animals reared with their dam and siblings until PD28, the EI animals showed lower density of 5-HT and NA axons in the dorsal-medial prefrontal cortex (mPFC) and basolateral nucleus of the amygdala and of NA- and TH-containing axons in the ventral-mPFC. These adverse effects of EI were not observed in rats taking part in voluntary running (EI+R) when these animals were compared to controls. The 5-HT axon density in the ventral-mPFC was significantly higher in the EI+R rats than that in the EI rats, although both these values were significantly lower than those in the control rats. The density of monoaminergic axons in the dentate gyrus and CA3 of the hippocampus was not affected by either EI or EI+R. These results suggest that the beneficial effects of voluntary running may be because of the modulation of monoaminergic axonal morphology. Our findings will hopefully provide the basis for future research into the beneficial effects of voluntary exercise during the juvenile period on brain development and emotional and cognitive performance. Copyright © 2012 IBRO. Published by Elsevier Ltd. All rights reserved.

Infrasonic noise induces axonal degeneration of cultured neurons via a Ca²⁺ influx pathway.

PubMed

Cheng, Haoran; Wang, Bing; Tang, Chi; Feng, Guodong; Zhang, Chen; Li, Ling; Lin, Tian; Du, Fang; Duan, Hong; Shi, Ming; Zhao, Gang

2012-07-20

Infrasound is a kind of environmental noise. It can evoke biological resonance in organismic tissues including the central nervous system (CNS), causing displacement and distortion of cellular architectures. Several studies have revealed that certain intensity infrasound can impair normal functions of the brain, but the underlying mechanisms still remain largely unknown. Growing evidence has demonstrated that axonal degeneration is responsible for a variety of CNS dysfunctions. To explore whether neuronal axons are affected under infrasonic insults, we exposed cultured hippocampal neurons to infrasound with a frequency of 16 Hz and a pressure level of 130 dB for 1h, and examined the morphological and molecular changes of neuronal axons by immunocytochemistry and Western blotting, respectively. Our results showed that infrasound exposure significantly resulted in axonal degeneration of cultured hippocampal neurons, which was relatively independent of neuronal cell death. This infrasound-induced axonal degeneration can be significantly blocked by Ca²⁺ chelator EGTA and Rho kinase inhibitor Fasudil, but not by proteasome inhibitor MG132. Moreover, calcium imaging and RhoA activation assays revealed a great enhancement of Ca²⁺ influx within axons and RhoA activation after infrasound exposure, respectively. Depletion of Ca²⁺ by EGTA markedly inhibited this Ca²⁺ influx and attenuated RhoA activation as well. Thus, our findings revealed that axonal degeneration may be one of the important mechanisms underlying infrasound-induced CNS impairment, and Ca²⁺ influx pathway is likely implicated in the process. Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.

Current Opportunities for Clinical Monitoring of Axonal Pathology in Traumatic Brain Injury

PubMed Central

Tsitsopoulos, Parmenion P.; Abu Hamdeh, Sami; Marklund, Niklas

2017-01-01

Traumatic brain injury (TBI) is a multidimensional and highly complex disease commonly resulting in widespread injury to axons, due to rapid inertial acceleration/deceleration forces transmitted to the brain during impact. Axonal injury leads to brain network dysfunction, significantly contributing to cognitive and functional impairments frequently observed in TBI survivors. Diffuse axonal injury (DAI) is a clinical entity suggested by impaired level of consciousness and coma on clinical examination and characterized by widespread injury to the hemispheric white matter tracts, the corpus callosum and the brain stem. The clinical course of DAI is commonly unpredictable and it remains a challenging entity with limited therapeutic options, to date. Although axonal integrity may be disrupted at impact, the majority of axonal pathology evolves over time, resulting from delayed activation of complex intracellular biochemical cascades. Activation of these secondary biochemical pathways may lead to axonal transection, named secondary axotomy, and be responsible for the clinical decline of DAI patients. Advances in the neurocritical care of TBI patients have been achieved by refinements in multimodality monitoring for prevention and early detection of secondary injury factors, which can be applied also to DAI. There is an emerging role for biomarkers in blood, cerebrospinal fluid, and interstitial fluid using microdialysis in the evaluation of axonal injury in TBI. These biomarker studies have assessed various axonal and neuroglial markers as well as inflammatory mediators, such as cytokines and chemokines. Moreover, modern neuroimaging can detect subtle or overt DAI/white matter changes in diffuse TBI patients across all injury severities using magnetic resonance spectroscopy, diffusion tensor imaging, and positron emission tomography. Importantly, serial neuroimaging studies provide evidence for evolving axonal injury. Since axonal injury may be a key risk factor for neurodegeneration and dementias at long-term following TBI, the secondary injury processes may require prolonged monitoring. The aim of the present review is to summarize the clinical short- and long-term monitoring possibilities of axonal injury in TBI. Increased knowledge of the underlying pathophysiology achieved by advanced clinical monitoring raises hope for the development of novel treatment strategies for axonal injury in TBI. PMID:29209266

Human TUBB3 mutations perturb microtubule dynamics, kinesin interactions, and axon guidance

PubMed Central

Tischfield, Max A.; Baris, Hagit N.; Wu, Chen; Rudolph, Guenther; Van Maldergem, Lionel; He, Wei; Chan, Wai-Man; Andrews, Caroline; Demer, Joseph L.; Robertson, Richard L.; Mackey, David A.; Ruddle, Jonathan B.; Bird, Thomas D.; Gottlob, Irene; Pieh, Christina; Traboulsi, Elias I.; Pomeroy, Scott L.; Hunter, David G.; Soul, Janet S.; Newlin, Anna; Sabol, Louise J.; Doherty, Edward J.; de Uzcátegui, Clara E.; de Uzcátegui, Nicolas; Collins, Mary Louise Z.; Sener, Emin C.; Wabbels, Bettina; Hellebrand, Heide; Meitinger, Thomas; de Berardinis, Teresa; Magli, Adriano; Schiavi, Costantino; Pastore-Trossello, Marco; Koc, Feray; Wong, Agnes M.; Levin, Alex V.; Geraghty, Michael T.; Descartes, Maria; Flaherty, Maree; Jamieson, Robyn V.; Møller, H. U.; Meuthen, Ingo; Callen, David F.; Kerwin, Janet; Lindsay, Susan; Meindl, Alfons; Gupta, Mohan L.; Pellman, David; Engle, Elizabeth C.

2011-01-01

We report that eight heterozygous missense mutations in TUBB3, encoding the neuron-specific β-tubulin isotype III, result in a spectrum of human nervous system disorders we now call the TUBB3 syndromes. Each mutation causes the ocular motility disorder CFEOM3, whereas some also result in intellectual and behavioral impairments, facial paralysis, and/or later-onset axonal sensorimotor polyneuropathy. Neuroimaging reveals a spectrum of abnormalities including hypoplasia of oculomotor nerves, and dysgenesis of the corpus callosum, anterior commissure, and corticospinal tracts. A knock-in disease mouse model reveals axon guidance defects without evidence of cortical cell migration abnormalities. We show the disease-associated mutations can impair tubulin heterodimer formation in vitro, although folded mutant heterodimers can still polymerize into microtubules. Modeling each mutation in yeast tubulin demonstrates that all alter dynamic instability whereas a subset disrupts the interaction of microtubules with kinesin motors. These findings demonstrate normal TUBB3 is required for axon guidance and maintenance in mammals. PMID:20074521

Crystal Structure of a Fibroblast Growth Factor Homologous Factor (FHF) Defines a Conserved Surface on FHFs for Binding and Modulation of Voltage-gated Sodium Channels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Goetz, R.; Dover, K; Laezza, F

2009-01-01

Voltage-gated sodium channels (Nav) produce sodium currents that underlie the initiation and propagation of action potentials in nerve and muscle cells. Fibroblast growth factor homologous factors (FHFs) bind to the intracellular C-terminal region of the Nav alpha subunit to modulate fast inactivation of the channel. In this study we solved the crystal structure of a 149-residue-long fragment of human FHF2A which unveils the structural features of the homology core domain of all 10 human FHF isoforms. Through analysis of crystal packing contacts and site-directed mutagenesis experiments we identified a conserved surface on the FHF core domain that mediates channel bindingmore » in vitro and in vivo. Mutations at this channel binding surface impaired the ability of FHFs to co-localize with Navs at the axon initial segment of hippocampal neurons. The mutations also disabled FHF modulation of voltage-dependent fast inactivation of sodium channels in neuronal cells. Based on our data, we propose that FHFs constitute auxiliary subunits for Navs.« less

Possible Effects of Synaptic Imbalances on Oligodendrocyte–Axonic Interactions in Schizophrenia: A Hypothetical Model

PubMed Central

Mitterauer, Bernhard J.; Kofler-Westergren, Birgitta

2011-01-01

A model of glial–neuronal interactions is proposed that could be explanatory for the demyelination identified in brains with schizophrenia. It is based on two hypotheses: (1) that glia–neuron systems are functionally viable and important for normal brain function, and (2) that disruption of this postulated function disturbs the glial categorization function, as shown by formal analysis. According to this model, in schizophrenia receptors on astrocytes in glial–neuronal synaptic units are not functional, loosing their modulatory influence on synaptic neurotransmission. Hence, an unconstrained neurotransmission flux occurs that hyperactivates the axon and floods the cognate receptors of neurotransmitters on oligodendrocytes. The excess of neurotransmitters may have a toxic effect on oligodendrocytes and myelin, causing demyelination. In parallel, an increasing impairment of axons may disconnect neuronal networks. It is formally shown how oligodendrocytes normally categorize axonic information processing via their processes. Demyelination decomposes the oligodendrocyte–axonic system making it incapable to generate categories of information. This incoherence may be responsible for symptoms of disorganization in schizophrenia, such as thought disorder, inappropriate affect and incommunicable motor behavior. In parallel, the loss of oligodendrocytes affects gap junctions in the panglial syncytium, presumably responsible for memory impairment in schizophrenia. PMID:21647404

α-Synuclein induced toxicity in brain stem serotonin neurons mediated by an AAV vector driven by the tryptophan hydroxylase promoter.

PubMed

Wan, Oi Wan; Shin, Eunju; Mattsson, Bengt; Caudal, Dorian; Svenningsson, Per; Björklund, Anders

2016-05-23

We studied the impact of α-synuclein overexpression in brainstem serotonin neurons using a novel vector construct where the expression of human wildtype α-synuclein is driven by the tryptophan hydroxylase promoter, allowing expression of α-synuclein at elevated levels, and with high selectivity, in serotonergic neurons. α-Synuclein induced degenerative changes in axons and dendrites, displaying a distorted appearance, suggesting accumulation and aggregation of α-synuclein as a result of impaired axonal transport, accompanied by a 40% loss of terminals, as assessed in the hippocampus. Tissue levels of serotonin and its major metabolite 5-HIAA remained largely unaltered, and the performance of the α-synuclein overexpressing rats in tests of spatial learning (water maze), anxiety related behavior (elevated plus maze) and depressive-like behavior (forced swim test) was not different from control, suggesting that the impact of the developing axonal pathology on serotonin neurotransmission was relatively mild. Overexpression of α-synuclein in the raphe nuclei, combined with overexpression in basal forebrain cholinergic neurons, resulted in more pronounced axonal pathology and significant impairment in the elevated plus maze. We conclude that α-synuclein pathology in serotonergic or cholinergic neurons alone is not sufficient to impair non-motor behaviors, but that it is their simultaneous involvement that determines severity of such symptoms.

Impaired JIP3-dependent axonal lysosome transport promotes amyloid plaque pathology

PubMed Central

Gowrishankar, Swetha; Wu, Yumei

2017-01-01

Lysosomes robustly accumulate within axonal swellings at Alzheimer’s disease (AD) amyloid plaques. However, the underlying mechanisms and disease relevance of such lysosome accumulations are not well understood. Motivated by these problems, we identified JNK-interacting protein 3 (JIP3) as an important regulator of axonal lysosome transport and maturation. JIP3 knockout mouse neuron primary cultures accumulate lysosomes within focal axonal swellings that resemble the dystrophic axons at amyloid plaques. These swellings contain high levels of amyloid precursor protein processing enzymes (BACE1 and presenilin 2) and are accompanied by elevated Aβ peptide levels. The in vivo importance of the JIP3-dependent regulation of axonal lysosomes was revealed by the worsening of the amyloid plaque pathology arising from JIP3 haploinsufficiency in a mouse model of AD. These results establish the critical role of JIP3-dependent axonal lysosome transport in regulating amyloidogenic amyloid precursor protein processing and support a model wherein Aβ production is amplified by plaque-induced axonal lysosome transport defects. PMID:28784610

Axonal Transport: How High Microtubule Density Can Compensate for Boundary Effects in Small-Caliber Axons

PubMed Central

Wortman, Juliana C.; Shrestha, Uttam M.; Barry, Devin M.; Garcia, Michael L.; Gross, Steven P.; Yu, Clare C.

2014-01-01

Long-distance intracellular axonal transport is predominantly microtubule-based, and its impairment is linked to neurodegeneration. In this study, we present theoretical arguments that suggest that near the axon boundaries (walls), the effective viscosity can become large enough to impede cargo transport in small (but not large) caliber axons. Our theoretical analysis suggests that this opposition to motion increases rapidly as the cargo approaches the wall. We find that having parallel microtubules close enough together to enable a cargo to simultaneously engage motors on more than one microtubule dramatically enhances motor activity, and thus minimizes the effects of any opposition to transport. Even if microtubules are randomly placed in axons, we find that the higher density of microtubules found in small-caliber axons increases the probability of having parallel microtubules close enough that they can be used simultaneously by motors on a cargo. The boundary effect is not a factor in transport in large-caliber axons where the microtubule density is lower. PMID:24559984

Concussive Brain Trauma in the Mouse Results in Acute Cognitive Deficits and Sustained Impairment of Axonal Function

PubMed Central

Creed, Jennifer A.; DiLeonardi, Ann Mae; Fox, Douglas P.; Tessler, Alan R.

2011-01-01

Abstract Concussive brain injury (CBI) accounts for approximately 75% of all brain-injured people in the United States each year and is particularly prevalent in contact sports. Concussion is the mildest form of diffuse traumatic brain injury (TBI) and results in transient cognitive dysfunction, the neuropathologic basis for which is traumatic axonal injury (TAI). To evaluate the structural and functional changes associated with concussion-induced cognitive deficits, adult mice were subjected to an impact on the intact skull over the midline suture that resulted in a brief apneic period and loss of the righting reflex. Closed head injury also resulted in an increase in the wet weight:dry weight ratio in the cortex suggestive of edema in the first 24 h, and the appearance of Fluoro-Jade-B-labeled degenerating neurons in the cortex and dentate gyrus of the hippocampus within the first 3 days post-injury. Compared to sham-injured mice, brain-injured mice exhibited significant deficits in spatial acquisition and working memory as measured using the Morris water maze over the first 3 days (p<0.001), but not after the fourth day post-injury. At 1 and 3 days post-injury, intra-axonal accumulation of amyloid precursor protein in the corpus callosum and cingulum was accompanied by neurofilament dephosphorylation, impaired transport of Fluoro-Gold and synaptophysin, and deficits in axonal conductance. Importantly, deficits in retrograde transport and in action potential of myelinated axons continued to be observed until 14 days post-injury, at which time axonal degeneration was apparent. These data suggest that despite recovery from acute cognitive deficits, concussive brain trauma leads to axonal degeneration and a sustained perturbation of axonal function. PMID:21299360

Akt1-Inhibitor of DNA binding2 is essential for growth cone formation and axon growth and promotes central nervous system axon regeneration

PubMed Central

Ko, Hyo Rim; Kwon, Il-Sun; Hwang, Inwoo; Jin, Eun-Ju; Shin, Joo-Ho; Brennan-Minnella, Angela M; Swanson, Raymond; Cho, Sung-Woo; Lee, Kyung-Hoon; Ahn, Jee-Yin

2016-01-01

Mechanistic studies of axon growth during development are beneficial to the search for neuron-intrinsic regulators of axon regeneration. Here, we discovered that, in the developing neuron from rat, Akt signaling regulates axon growth and growth cone formation through phosphorylation of serine 14 (S14) on Inhibitor of DNA binding 2 (Id2). This enhances Id2 protein stability by means of escape from proteasomal degradation, and steers its localization to the growth cone, where Id2 interacts with radixin that is critical for growth cone formation. Knockdown of Id2, or abrogation of Id2 phosphorylation at S14, greatly impairs axon growth and the architecture of growth cone. Intriguingly, reinstatement of Akt/Id2 signaling after injury in mouse hippocampal slices redeemed growth promoting ability, leading to obvious axon regeneration. Our results suggest that Akt/Id2 signaling is a key module for growth cone formation and axon growth, and its augmentation plays a potential role in CNS axonal regeneration. DOI: http://dx.doi.org/10.7554/eLife.20799.001 PMID:27938661

Axonal Degeneration Is Mediated by the Mitochondrial Permeability Transition Pore

PubMed Central

Barrientos, Sebastian A.; Martinez, Nicolas W.; Yoo, Soonmoon; Jara, Juan S.; Zamorano, Sebastian; Hetz, Claudio; Twiss, Jeffery L.; Alvarez, Jaime; Court, Felipe A.

2011-01-01

Axonal degeneration is an active process that has been associated with neurodegenerative conditions triggered by mechanical, metabolic, infectious, toxic, hereditary and inflammatory stimuli. This degenerative process can cause permanent loss of function, so it represents a focus for neuroprotective strategies. Several signaling pathways are implicated in axonal degeneration, but identification of an integrative mechanism for this self-destructive process has remained elusive. Here, we show that rapid axonal degeneration triggered by distinct mechanical and toxic insults is dependent on the activation of the mitochondrial permeability transition pore (mPTP). Both pharmacological and genetic targeting of cyclophilin D, a functional component of the mPTP, protects severed axons and vincristine-treated neurons from axonal degeneration in ex vivo and in vitro mouse and rat model systems. These effects were observed in axons from both the peripheral and central nervous system. Our results suggest that the mPTP is a key effector of axonal degeneration, upon which several independent signaling pathways converge. Since axonal and synapse degeneration are increasingly considered early pathological events in neurodegeneration, our work identifies a potential target for therapeutic intervention in a wide variety of conditions that lead to loss of axons and subsequent functional impairment. PMID:21248121

Restraint of presynaptic protein levels by Wnd/DLK signaling mediates synaptic defects associated with the kinesin-3 motor Unc-104

PubMed Central

Asghari Adib, Elham; Stanchev, Doychin T; Xiong, Xin; Klinedinst, Susan; Soppina, Pushpanjali; Jahn, Thomas Robert; Hume, Richard I

2017-01-01

The kinesin-3 family member Unc-104/KIF1A is required for axonal transport of many presynaptic components to synapses, and mutation of this gene results in synaptic dysfunction in mice, flies and worms. Our studies at the Drosophila neuromuscular junction indicate that many synaptic defects in unc-104-null mutants are mediated independently of Unc-104’s transport function, via the Wallenda (Wnd)/DLK MAP kinase axonal damage signaling pathway. Wnd signaling becomes activated when Unc-104’s function is disrupted, and leads to impairment of synaptic structure and function by restraining the expression level of active zone (AZ) and synaptic vesicle (SV) components. This action concomitantly suppresses the buildup of synaptic proteins in neuronal cell bodies, hence may play an adaptive role to stresses that impair axonal transport. Wnd signaling also becomes activated when pre-synaptic proteins are over-expressed, suggesting the existence of a feedback circuit to match synaptic protein levels to the transport capacity of the axon. PMID:28925357

Sharing is Caring: The Role of Actin/Myosin-V in Synaptic Vesicle Transport between Synapses in vivo

NASA Astrophysics Data System (ADS)

Gramlich, Michael

Inter-synaptic vesicle sharing is an important but not well understood process of pre-synaptic function. Further, the molecular mechanisms that underlie this inter-synaptic exchange are not well known, and whether this inter-synaptic vesicle sharing is regulated by neural activity remains largely unexplored. I address these questions by studying CA1/CA3 Hippocampal neurons at the single synaptic vesicle level. Using high-resolution tracking of individual vesicles that have recently undergone endocytosis, I observe long-distance axonal transport of synaptic vesicles is partly mediated by the actin network. Further, the actin-dependent transport is predominantly carried out by Myosin-V. I develop a correlated-motion analysis to characterize the mechanics of how actin and Myosin-V affect vesicle transport. Lastly, I also observe that vesicle exit rates from the synapse to the axon and long-distance vesicle transport are both regulated by activity, but Myosin-V does not appear to mediate the activity dependence. These observations highlight the roles of the axonal actin network, and Myosin-V in particular, in regulating inter-synaptic vesicle exchange.

White Matter Damage and Cognitive Impairment after Traumatic Brain Injury

ERIC Educational Resources Information Center

Kinnunen, Kirsi Maria; Greenwood, Richard; Powell, Jane Hilary; Leech, Robert; Hawkins, Peter Charlie; Bonnelle, Valerie; Patel, Maneesh Chandrakant; Counsell, Serena Jane; Sharp, David James

2011-01-01

White matter disruption is an important determinant of cognitive impairment after brain injury, but conventional neuroimaging underestimates its extent. In contrast, diffusion tensor imaging provides a validated and sensitive way of identifying the impact of axonal injury. The relationship between cognitive impairment after traumatic brain injury…

Mutant Huntingtin Impairs Axonal Trafficking in Mammalian Neurons In Vivo and In Vitro

PubMed Central

Trushina, Eugenia; Dyer, Roy B.; Badger, John D.; Ure, Daren; Eide, Lars; Tran, David D.; Vrieze, Brent T.; Legendre-Guillemin, Valerie; McPherson, Peter S.; Mandavilli, Bhaskar S.; Van Houten, Bennett; Zeitlin, Scott; McNiven, Mark; Aebersold, Ruedi; Hayden, Michael; Parisi, Joseph E.; Seeberg, Erling; Dragatsis, Ioannis; Doyle, Kelly; Bender, Anna; Chacko, Celin; McMurray, Cynthia T.

2004-01-01

Recent data in invertebrates demonstrated that huntingtin (htt) is essential for fast axonal trafficking. Here, we provide direct and functional evidence that htt is involved in fast axonal trafficking in mammals. Moreover, expression of full-length mutant htt (mhtt) impairs vesicular and mitochondrial trafficking in mammalian neurons in vitro and in whole animals in vivo. Particularly, mitochondria become progressively immobilized and stop more frequently in neurons from transgenic animals. These defects occurred early in development prior to the onset of measurable neurological or mitochondrial abnormalities. Consistent with a progressive loss of function, wild-type htt, trafficking motors, and mitochondrial components were selectively sequestered by mhtt in human Huntington's disease-affected brain. Data provide a model for how loss of htt function causes toxicity; mhtt-mediated aggregation sequesters htt and components of trafficking machinery leading to loss of mitochondrial motility and eventual mitochondrial dysfunction. PMID:15340079

Genetic variants in autism-related CNTNAP2 impair axonal growth of cortical neurons.

PubMed

Canali, Giorgia; Garcia, Marta; Hivert, Bruno; Pinatel, Delphine; Goullancourt, Aline; Oguievetskaia, Ksenia; Saint-Martin, Margaux; Girault, Jean-Antoine; Faivre-Sarrailh, Catherine; Goutebroze, Laurence

2018-06-01

The CNTNAP2 gene, coding for the cell adhesion glycoprotein Caspr2, is thought to be one of the major susceptibility genes for autism spectrum disorder (ASD). A large number of rare heterozygous missense CNTNAP2 variants have been identified in ASD patients. However, most of them are inherited from an unaffected parent, questioning their clinical significance. In the present study, we evaluate their impact on neurodevelopmental functions of Caspr2 in a heterozygous genetic background. Performing cortical neuron cultures from mouse embryos, we demonstrate that Caspr2 plays a dose-dependent role in axon growth in vitro. Loss of one Cntnap2 allele is sufficient to elicit axonal growth alteration, revealing a situation that may be relevant for CNTNAP2 heterozygosity in ASD patients. Then, we show that the two ASD variants I869T and G731S, which present impaired binding to Contactin2/TAG-1, do not rescue axonal growth deficits. We find that the variant R1119H leading to protein trafficking defects and retention in the endoplasmic reticulum has a dominant-negative effect on heterozygous Cntnap2 cortical neuron axon growth, through oligomerization with wild-type Caspr2. Finally, we identify an additional variant (N407S) with a dominant-negative effect on axon growth although it is well-localized at the membrane and properly binds to Contactin2. Thus, our data identify a new neurodevelopmental function for Caspr2, the dysregulation of which may contribute to clinical manifestations of ASD, and provide evidence that CNTNAP2 heterozygous missense variants may contribute to pathogenicity in ASD, through selective mechanisms.

Spectroscopic Axonal Damage of the Right Locus Coeruleus Relates to Selective Attention Impairment in Early Stage Relapsing-Remitting Multiple Sclerosis

ERIC Educational Resources Information Center

Gadea, Marien; Martinez-Bisbal, M. Carmen; Marti-Bonmati, Luis; Espert, Raul; Casanova, Bonaventura; Coret, Francisco; Celda, Bernardo

2004-01-01

Lower levels of N-acetylaspartate (NAA), a marker of axonal damage, have been found in the normal-appearing white matter (NAWM) of relapsing-remitting multiple sclerosis (RRMS) patients with low physical disability. However, its relation to the clinical status of these patients remains unclear. We explored the association between NAA levels…

Aberrant Axonal Arborization of PDF Neurons Induced by Aβ42-Mediated JNK Activation Underlies Sleep Disturbance in an Alzheimer's Model.

PubMed

Song, Qian; Feng, Ge; Huang, Zehua; Chen, Xiaoman; Chen, Zhaohuan; Ping, Yong

2017-10-01

Impaired sleep patterns are common symptoms of Alzheimer's disease (AD). Cellular mechanisms underlying sleep disturbance in AD remain largely unknown. Here, using a Drosophila Aβ42 AD model, we show that Aβ42 markedly decreases sleep in a large population, which is accompanied with postdevelopmental axonal arborization of wake-promoting pigment-dispersing factor (PDF) neurons. The arborization is mediated in part via JNK activation and can be reversed by decreasing JNK signaling activity. Axonal arborization and impaired sleep are correlated in Aβ42 and JNK kinase hemipterous mutant flies. Image reconstruction revealed that these aberrant fibers preferentially project to pars intercerebralis (PI), a fly brain region analogous to the mammalian hypothalamus. Moreover, PDF signaling in PI neurons was found to modulate sleep/wake activities, suggesting that excessive release of PDF by these aberrant fibers may lead to the impaired sleep in Aβ42 flies. Finally, inhibition of JNK activation in Aβ42 flies restores nighttime sleep loss, decreases Aβ42 accumulation, and attenuates neurodegeneration. These data provide a new mechanism by which sleep disturbance could be induced by Aβ42 burden, a key initiator of a complex pathogenic cascade in AD.

A novel ALS-associated variant in UBQLN4 regulates motor axon morphogenesis.

PubMed

Edens, Brittany M; Yan, Jianhua; Miller, Nimrod; Deng, Han-Xiang; Siddique, Teepu; Ma, Yongchao C

2017-05-02

The etiological underpinnings of amyotrophic lateral sclerosis (ALS) are complex and incompletely understood, although contributions to pathogenesis by regulators of proteolytic pathways have become increasingly apparent. Here, we present a novel variant in UBQLN4 that is associated with ALS and show that its expression compromises motor axon morphogenesis in mouse motor neurons and in zebrafish. We further demonstrate that the ALS-associated UBQLN4 variant impairs proteasomal function, and identify the Wnt signaling pathway effector beta-catenin as a UBQLN4 substrate. Inhibition of beta-catenin function rescues the UBQLN4 variant-induced motor axon phenotypes. These findings provide a strong link between the regulation of axonal morphogenesis and a new ALS-associated gene variant mediated by protein degradation pathways.

Microtubule-Targeting Agents Eribulin and Paclitaxel Differentially Affect Neuronal Cell Bodies in Chemotherapy-Induced Peripheral Neuropathy.

PubMed

Benbow, Sarah J; Wozniak, Krystyna M; Kulesh, Bridget; Savage, April; Slusher, Barbara S; Littlefield, Bruce A; Jordan, Mary Ann; Wilson, Leslie; Feinstein, Stuart C

2017-07-01

Chemotherapy-induced peripheral neuropathy (CIPN) is a common side effect of anticancer treatment with microtubule-targeted agents (MTAs). The frequency of severe CIPN, which can be dose limiting and even life threatening, varies widely among different MTAs. For example, paclitaxel induces a higher frequency of severe CIPN than does eribulin. Different MTAs also possess distinct mechanisms of microtubule-targeted action. Recently, we demonstrated that paclitaxel and eribulin differentially affect sciatic nerve axons, with paclitaxel inducing more pronounced neurodegenerative effects and eribulin inducing greater microtubule stabilizing biochemical effects. Here, we complement and extend these axonal studies by assessing the effects of paclitaxel and eribulin in the cell bodies of sciatic nerve axons, housed in the dorsal root ganglia (DRG). Importantly, the microtubule network in cell bodies is known to be significantly more dynamic than in axons. Paclitaxel induced activating transcription factor 3 expression, a marker of neuronal stress/injury. Paclitaxel also increased expression levels of acetylated tubulin and end binding protein 1, markers of microtubule stability and growth, respectively. These effects are hypothesized to be detrimental to the dynamic microtubule network within the cell bodies. In contrast, eribulin had no significant effect on any of these parameters in the cell bodies. Taken together, DRG cell bodies and their axons, two distinct neuronal cell compartments, contain functionally distinct microtubule networks that exhibit unique biochemical responses to different MTA treatments. We hypothesize that these distinct mechanistic actions may underlie the variability seen in the initiation, progression, persistence, and recovery from CIPN.

Optimization of interneuron function by direct coupling of cell migration and axonal targeting.

PubMed

Lim, Lynette; Pakan, Janelle M P; Selten, Martijn M; Marques-Smith, André; Llorca, Alfredo; Bae, Sung Eun; Rochefort, Nathalie L; Marín, Oscar

2018-06-18

Neural circuit assembly relies on the precise synchronization of developmental processes, such as cell migration and axon targeting, but the cell-autonomous mechanisms coordinating these events remain largely unknown. Here we found that different classes of interneurons use distinct routes of migration to reach the embryonic cerebral cortex. Somatostatin-expressing interneurons that migrate through the marginal zone develop into Martinotti cells, one of the most distinctive classes of cortical interneurons. For these cells, migration through the marginal zone is linked to the development of their characteristic layer 1 axonal arborization. Altering the normal migratory route of Martinotti cells by conditional deletion of Mafb-a gene that is preferentially expressed by these cells-cell-autonomously disrupts axonal development and impairs the function of these cells in vivo. Our results suggest that migration and axon targeting programs are coupled to optimize the assembly of inhibitory circuits in the cerebral cortex.

Declarative and Procedural Memory in Danish Speaking Children with Specific Language Impairment

ERIC Educational Resources Information Center

Lum, Jarrad A. G.; Bleses, Dorthe

2012-01-01

It has been proposed that the language problems in specific language impairment (SLI) arise from basal ganglia abnormalities that lead to impairments with procedural and working memory but not declarative memory. In SLI, this profile of memory functioning has been hypothesized to underlie grammatical impairment but leave lexical knowledge…

Studies on the transport of secretory granules in the magnocellular hypothalamic neurons of the rat. II. Action of vincristine on axonal flow and neurotubules in the paraventricular and supraoptic nuclei.

PubMed

Flament-Durand, J; Couck, A M; Dustin, P

1975-11-26

Intrathecal administration of 20 mug of vincristine sulphate in the rat induced in vivo the formation of paracrystalline inclusions mainly in axonal processes. This is associated with an impairment in the migration of neurosecretory granules as shown by their accumulation in the perikarya of the magnocellular neurons. The granules are intermixed with numerous dense bodies of various shape, sometimes with a fibrillar content, and probably of lysosomal origin. In addition to the impairment of the flow of neurosecretory granules, there is also a striking accumulation of mitochondria and synaptic vesicles, and an apparent proliferation of the smooth endoplasmic reticulum. In the posterior lobe, the axonal endings contain a large number of neurosecretory granules, intermingled with bodies of varying shapes and electron density. Occasionally, a dense membrane surrounding a group of elementary granules is observed, reacting positively for acid phosphatase. This suggests an attempted crinophagia.

Genotype/phenotype correlations in AARS-related neuropathy in a cohort of patients from the United Kingdom and Ireland.

PubMed

Bansagi, Boglarka; Antoniadi, Thalia; Burton-Jones, Sarah; Murphy, Sinead M; McHugh, John; Alexander, Michael; Wells, Richard; Davies, Joanna; Hilton-Jones, David; Lochmüller, Hanns; Chinnery, Patrick; Horvath, Rita

2015-08-01

Charcot-Marie-Tooth disease (CMT) is the most common inherited neuropathy with heterogeneous clinical presentation and genetic background. The axonal form (CMT2) is characterised by decreased action potentials indicating primary axonal damage. The underlying pathology involves axonal degeneration which is supposed to be related to axonal protein dysfunction caused by various gene mutations. The overlapping clinical manifestation of CMT2 with distal hereditary motor neuropathy (dHMN) and intermediate CMT causes further diagnostic difficulties. Aminoacyl-tRNA synthetases have been implicated in the pathomechanism of CMT2. They have an essential role in protein translation by attaching amino acids to their cognate tRNAs. To date six families have been reported worldwide with dominant missense alanyl-tRNA synthetase (AARS) mutations leading to clinically heterogeneous axonal neuropathies. The pathomechanism of some variants could be explained by impaired amino acylation activity while other variants implicating an editing defect need to be further investigated. Here, we report a cohort of six additional families originating from the United Kingdom and Ireland with dominant AARS-related neuropathies. The phenotypic manifestation was distal lower limb predominant sensorimotor neuropathy but upper limb impairment with split hand deformity occasionally associated. Nerve conduction studies revealed significant demyelination accompanying the axonal lesion in motor and sensory nerves. Five families have the c.986G>A, p.(Arg329His) variant, further supporting that this is a recurrent loss of function variant. The sixth family, of Irish origin, had a novel missense variant, c.2063A>G, p.(Glu688Gly). We discuss our findings and the associated phenotypic heterogeneity in these families, which expands the clinical spectrum of AARS-related neuropathies.

Excitability properties of motor axons in adults with cerebral palsy

PubMed Central

Klein, Cliff S.; Zhou, Ping; Marciniak, Christina

2015-01-01

Cerebral palsy (CP) is a permanent disorder caused by a lesion to the developing brain that significantly impairs motor function. The neurophysiological mechanisms underlying motor impairment are not well understood. Specifically, few have addressed whether motoneuron or peripheral axon properties are altered in CP, even though disruption of descending inputs to the spinal cord may cause them to change. In the present study, we have compared nerve excitability properties in seven adults with CP and fourteen healthy controls using threshold tracking techniques by stimulating the median nerve at the wrist and recording the compound muscle action potential over the abductor pollicis brevis. The excitability properties in the CP subjects were found to be abnormal. Early and late depolarizing and hyperpolarizing threshold electrotonus was significantly larger (i.e., fanning out), and resting current–threshold (I/V) slope was smaller, in CP compared to control. In addition resting threshold and rheobase tended to be larger in CP. According to a modeling analysis of the data, an increase in leakage current under or through the myelin sheath, i.e., the Barrett–Barrett conductance, combined with a slight hyperpolarization of the resting membrane potential, best explained the group differences in excitability properties. There was a trend for those with greater impairment in gross motor function to have more abnormal axon properties. The findings indicate plasticity of motor axon properties far removed from the site of the lesion. We suspect that this plasticity is caused by disruption of descending inputs to the motoneurons at an early age around the time of their injury. PMID:26089791

Disruption of the Axonal Trafficking of Tyrosine Hydroxylase mRNA Impairs Catecholamine Biosynthesis in the Axons of Sympathetic Neurons

PubMed Central

Gioio, Anthony E.

2017-01-01

Abstract Tyrosine hydroxylase (TH) is the enzyme that catalyzes the rate-limiting step in the biosynthesis of the catecholamine neurotransmitters. In a previous communication, evidence was provided that TH mRNA is trafficked to the axon, where it is locally translated. In addition, a 50-bp sequence element in the 3′untranslated region (3’UTR) of TH mRNA was identified that directs TH mRNA to distal axons (i.e., zip-code). In the present study, the hypothesis was tested that local translation of TH plays an important role in the biosynthesis of the catecholamine neurotransmitters in the axon and/or presynaptic nerve terminal. Toward this end, a targeted deletion of the axonal transport sequence element was developed, using the lentiviral delivery of the CRISPR/Cas9 system, and two guide RNA (gRNA) sequences flanking the 50-bp cis-acting regulatory element in rat superior cervical ganglion (SCG) neurons. Deletion of the axonal transport element reduced TH mRNA levels in the distal axons and reduced the axonal protein levels of TH and TH activity as measured by phosphorylation of SER40 in SCG neurons. Moreover, deletion of the zip-code diminished the axonal levels of dopamine (DA) and norepinephrine (NE). Conversely, the local translation of exogenous TH mRNA in the distal axon enhanced TH levels and activity, and elevated axonal NE levels. Taken together, these results provide direct evidence to support the hypothesis that TH mRNA trafficking and local synthesis of TH play an important role in the synthesis of catecholamines in the axon and presynaptic terminal. PMID:28630892

Disruption of the Axonal Trafficking of Tyrosine Hydroxylase mRNA Impairs Catecholamine Biosynthesis in the Axons of Sympathetic Neurons.

PubMed

Aschrafi, Armaz; Gioio, Anthony E; Dong, Lijin; Kaplan, Barry B

2017-01-01

Tyrosine hydroxylase (TH) is the enzyme that catalyzes the rate-limiting step in the biosynthesis of the catecholamine neurotransmitters. In a previous communication, evidence was provided that TH mRNA is trafficked to the axon, where it is locally translated. In addition, a 50-bp sequence element in the 3'untranslated region (3'UTR) of TH mRNA was identified that directs TH mRNA to distal axons (i.e., zip-code). In the present study, the hypothesis was tested that local translation of TH plays an important role in the biosynthesis of the catecholamine neurotransmitters in the axon and/or presynaptic nerve terminal. Toward this end, a targeted deletion of the axonal transport sequence element was developed, using the lentiviral delivery of the CRISPR/Cas9 system, and two guide RNA (gRNA) sequences flanking the 50-bp cis- acting regulatory element in rat superior cervical ganglion (SCG) neurons. Deletion of the axonal transport element reduced TH mRNA levels in the distal axons and reduced the axonal protein levels of TH and TH activity as measured by phosphorylation of SER40 in SCG neurons. Moreover, deletion of the zip-code diminished the axonal levels of dopamine (DA) and norepinephrine (NE). Conversely, the local translation of exogenous TH mRNA in the distal axon enhanced TH levels and activity, and elevated axonal NE levels. Taken together, these results provide direct evidence to support the hypothesis that TH mRNA trafficking and local synthesis of TH play an important role in the synthesis of catecholamines in the axon and presynaptic terminal.

Live-cell imaging of retrograde transport initiation in primary neurons.

PubMed

Nirschl, Jeffrey J; Holzbaur, Erika L F

2016-01-01

Axonal transport is an essential function in neurons, as mutations in either motor proteins or their adaptors cause neurodegeneration. While some mutations cause a complete block in axonal transport, other mutations affect transport more subtly. This is especially true of mutations identified in human patients, many of which impair but do not block motor function in the cell. Dissecting the pathogenic mechanisms of these more subtle mutations requires assays that can tease apart the distinct phases of axonal transport, including transport initiation, sustained/regulated motility, and cargo-specific sorting or delivery. Here, we describe a live-cell photobleaching assay to assess retrograde flux from the distal axon tip, a measure for distal transport initiation. We have previously used this method to show that the CAP-Gly domain of DCTN1 is required for efficient retrograde transport initiation in the distal axon, but it is not required to maintain retrograde flux along the mid-axon (Moughamian & Holzbaur, 2012). This approach has allowed us to examine the effects of disease-causing mutations in the axonal transport machinery, and in combination with other assays, will be useful in determining the mechanisms and regulation of axonal transport in normal and diseased conditions. Copyright © 2016 Elsevier Inc. All rights reserved.

Calpain-mediated cleavage of collapsin response mediator protein-2 drives acute axonal degeneration

PubMed Central

Zhang, Jian-Nan; Michel, Uwe; Lenz, Christof; Friedel, Caroline C.; Köster, Sarah; d’Hedouville, Zara; Tönges, Lars; Urlaub, Henning; Bähr, Mathias; Lingor, Paul; Koch, Jan C.

2016-01-01

Axonal degeneration is a key initiating event in many neurological diseases. Focal lesions to axons result in a rapid disintegration of the perilesional axon by acute axonal degeneration (AAD) within several hours. However, the underlying molecular mechanisms of AAD are only incompletely understood. Here, we studied AAD in vivo through live-imaging of the rat optic nerve and in vitro in primary rat cortical neurons in microfluidic chambers. We found that calpain is activated early during AAD of the optic nerve and that calpain inhibition completely inhibits axonal fragmentation on the proximal side of the crush while it attenuates AAD on the distal side. A screening of calpain targets revealed that collapsin response mediator protein-2 (CRMP2) is a main downstream target of calpain activation in AAD. CRMP2-overexpression delayed bulb formation and rescued impairment of axonal mitochondrial transport after axotomy in vitro. In vivo, CRMP2-overexpression effectively protected the proximal axon from fragmentation within 6 hours after crush. Finally, a proteomic analysis of the optic nerve was performed at 6 hours after crush, which identified further proteins regulated during AAD, including several interactors of CRMP2. These findings reveal CRMP2 as an important mediator of AAD and define it as a putative therapeutic target. PMID:27845394

Central Processing Energetic Factors Mediate Impaired Motor Control in ADHD Combined Subtype but Not in ADHD Inattentive Subtype

ERIC Educational Resources Information Center

Egeland, Jens; Ueland, Torill; Johansen, Susanne

2012-01-01

Participants with attention-deficit/hyperactivity disorder (ADHD) are often impaired in visuomotor tasks. However, little is known about the contribution of modal impairment in motor function relative to central processing deficits or whether different processes underlie the impairment in ADHD combined (ADHD-C) versus ADHD inattentive (ADHD-I)…

CD8+ T Cells Cause Disability and Axon Loss in a Mouse Model of Multiple Sclerosis

PubMed Central

Schmalstieg, William F.; Sauer, Brian M.; Wang, Huan; German, Christopher L.; Windebank, Anthony J.; Rodriguez, Moses; Howe, Charles L.

2010-01-01

Background The objective of this study was to test the hypothesis that CD8+ T cells directly mediate motor disability and axon injury in the demyelinated central nervous system. We have previously observed that genetic deletion of the CD8+ T cell effector molecule perforin leads to preservation of motor function and preservation of spinal axons in chronically demyelinated mice. Methodology/Principal Findings To determine if CD8+ T cells are necessary and sufficient to directly injure demyelinated axons, we adoptively transferred purified perforin-competent CD8+ spinal cord-infiltrating T cells into profoundly demyelinated but functionally preserved perforin-deficient host mice. Transfer of CD8+ spinal cord-infiltrating T cells rapidly and irreversibly impaired motor function, disrupted spinal cord motor conduction, and reduced the number of medium- and large-caliber spinal axons. Likewise, immunodepletion of CD8+ T cells from chronically demyelinated wildtype mice preserved motor function and limited axon loss without altering other disease parameters. Conclusions/Significance In multiple sclerosis patients, CD8+ T cells outnumber CD4+ T cells in active lesions and the number of CD8+ T cells correlates with the extent of ongoing axon injury and functional disability. Our findings suggest that CD8+ T cells may directly injure demyelinated axons and are therefore a viable therapeutic target to protect axons and motor function in patients with multiple sclerosis. PMID:20814579

The Dyslexia-susceptibility Protein KIAA0319 Inhibits Axon Growth Through Smad2 Signaling

PubMed Central

Franquinho, Filipa; Nogueira-Rodrigues, Joana; Duarte, Joana M.; Esteves, Sofia S.; Carter-Su, Christin; Monaco, Anthony P.; Molnár, Zoltán; Velayos-Baeza, Antonio; Brites, Pedro; Sousa, Mónica M.

2017-01-01

Abstract KIAA0319 is a transmembrane protein associated with dyslexia with a presumed role in neuronal migration. Here we show that KIAA0319 expression is not restricted to the brain but also occurs in sensory and spinal cord neurons, increasing from early postnatal stages to adulthood and being downregulated by injury. This suggested that KIAA0319 participates in functions unrelated to neuronal migration. Supporting this hypothesis, overexpression of KIAA0319 repressed axon growth in hippocampal and dorsal root ganglia neurons; the intracellular domain of KIAA0319 was sufficient to elicit this effect. A similar inhibitory effect was observed in vivo as axon regeneration was impaired after transduction of sensory neurons with KIAA0319. Conversely, the deletion of Kiaa0319 in neurons increased neurite outgrowth in vitro and improved axon regeneration in vivo. At the mechanistic level, KIAA0319 engaged the JAK2-SH2B1 pathway to activate Smad2, which played a central role in KIAA0319-mediated repression of axon growth. In summary, we establish KIAA0319 as a novel player in axon growth and regeneration with the ability to repress the intrinsic growth potential of axons. This study describes a novel regulatory mechanism operating during peripheral nervous system and central nervous system axon growth, and offers novel targets for the development of effective therapies to promote axon regeneration. PMID:28334068

MicroRNA-26a supports mammalian axon regeneration in vivo by suppressing GSK3β expression.

PubMed

Jiang, J-J; Liu, C-M; Zhang, B-Y; Wang, X-W; Zhang, M; Saijilafu; Zhang, S-R; Hall, P; Hu, Y-W; Zhou, F-Q

2015-08-27

MicroRNAs are emerging to be important epigenetic factors that control axon regeneration. Here, we report that microRNA-26a (miR-26a) is a physiological regulator of mammalian axon regeneration in vivo. We demonstrated that endogenous miR-26a acted to target specifically glycogen synthase kinase 3β (GSK3β) in adult mouse sensory neurons in vitro and in vivo. Inhibition of endogenous miR-26a in sensory neurons impaired axon regeneration in vitro and in vivo. Moreover, the regulatory effect of miR-26a was mediated by increased expression of GSK3β because downregulation or pharmacological inhibition of GSK3β fully rescued axon regeneration. Our results also suggested that the miR-26a-GSK3β pathway regulated axon regeneration at the neuronal soma by controlling gene expression. We provided biochemical and functional evidences that the regeneration-associated transcription factor Smad1 acted downstream of miR-26a and GSK3β to control sensory axon regeneration. Our study reveals a novel miR-26a-GSK3β-Smad1 signaling pathway in the regulation of mammalian axon regeneration. Moreover, we provide the first evidence that, in addition to inhibition of GSK3β kinase activity, maintaining a lower protein level of GSK3β in neurons by the microRNA is necessary for efficient axon regeneration.

ESCRT-II controls retinal axon growth by regulating DCC receptor levels and local protein synthesis

PubMed Central

Konopacki, Filip A.; Dwivedy, Asha; Bellon, Anaïs; Blower, Michael D.

2016-01-01

Endocytosis and local protein synthesis (LPS) act coordinately to mediate the chemotropic responses of axons, but the link between these two processes is poorly understood. The endosomal sorting complex required for transport (ESCRT) is a key regulator of cargo sorting in the endocytic pathway, and here we have investigated the role of ESCRT-II, a critical ESCRT component, in Xenopus retinal ganglion cell (RGC) axons. We show that ESCRT-II is present in RGC axonal growth cones (GCs) where it co-localizes with endocytic vesicle GTPases and, unexpectedly, with the Netrin-1 receptor, deleted in colorectal cancer (DCC). ESCRT-II knockdown (KD) decreases endocytosis and, strikingly, reduces DCC in GCs and leads to axon growth and guidance defects. ESCRT-II-depleted axons fail to turn in response to a Netrin-1 gradient in vitro and many axons fail to exit the eye in vivo. These defects, similar to Netrin-1/DCC loss-of-function phenotypes, can be rescued in whole (in vitro) or in part (in vivo) by expressing DCC. In addition, ESCRT-II KD impairs LPS in GCs and live imaging reveals that ESCRT-II transports mRNAs in axons. Collectively, our results show that the ESCRT-II-mediated endocytic pathway regulates both DCC and LPS in the axonal compartment and suggest that ESCRT-II aids gradient sensing in GCs by coupling endocytosis to LPS. PMID:27248654

Inner membrane fusion mediates spatial distribution of axonal mitochondria

PubMed Central

Yu, Yiyi; Lee, Hao-Chih; Chen, Kuan-Chieh; Suhan, Joseph; Qiu, Minhua; Ba, Qinle; Yang, Ge

2016-01-01

In eukaryotic cells, mitochondria form a dynamic interconnected network to respond to changing needs at different subcellular locations. A fundamental yet unanswered question regarding this network is whether, and if so how, local fusion and fission of individual mitochondria affect their global distribution. To address this question, we developed high-resolution computational image analysis techniques to examine the relations between mitochondrial fusion/fission and spatial distribution within the axon of Drosophila larval neurons. We found that stationary and moving mitochondria underwent fusion and fission regularly but followed different spatial distribution patterns and exhibited different morphology. Disruption of inner membrane fusion by knockdown of dOpa1, Drosophila Optic Atrophy 1, not only increased the spatial density of stationary and moving mitochondria but also changed their spatial distributions and morphology differentially. Knockdown of dOpa1 also impaired axonal transport of mitochondria. But the changed spatial distributions of mitochondria resulted primarily from disruption of inner membrane fusion because knockdown of Milton, a mitochondrial kinesin-1 adapter, caused similar transport velocity impairment but different spatial distributions. Together, our data reveals that stationary mitochondria within the axon interconnect with moving mitochondria through fusion and fission and that local inner membrane fusion between individual mitochondria mediates their global distribution. PMID:26742817

A novel ALS-associated variant in UBQLN4 regulates motor axon morphogenesis

PubMed Central

Edens, Brittany M; Yan, Jianhua; Miller, Nimrod; Deng, Han-Xiang; Siddique, Teepu; Ma, Yongchao C

2017-01-01

The etiological underpinnings of amyotrophic lateral sclerosis (ALS) are complex and incompletely understood, although contributions to pathogenesis by regulators of proteolytic pathways have become increasingly apparent. Here, we present a novel variant in UBQLN4 that is associated with ALS and show that its expression compromises motor axon morphogenesis in mouse motor neurons and in zebrafish. We further demonstrate that the ALS-associated UBQLN4 variant impairs proteasomal function, and identify the Wnt signaling pathway effector beta-catenin as a UBQLN4 substrate. Inhibition of beta-catenin function rescues the UBQLN4 variant-induced motor axon phenotypes. These findings provide a strong link between the regulation of axonal morphogenesis and a new ALS-associated gene variant mediated by protein degradation pathways. DOI: http://dx.doi.org/10.7554/eLife.25453.001 PMID:28463112

Maternal chewing during prenatal stress ameliorates stress-induced hypomyelination, synaptic alterations, and learning impairment in mouse offspring.

PubMed

Suzuki, Ayumi; Iinuma, Mitsuo; Hayashi, Sakurako; Sato, Yuichi; Azuma, Kagaku; Kubo, Kin-Ya

2016-11-15

Maternal chewing during prenatal stress attenuates both the development of stress-induced learning deficits and decreased cell proliferation in mouse hippocampal dentate gyrus. Hippocampal myelination affects spatial memory and the synaptic structure is a key mediator of neuronal communication. We investigated whether maternal chewing during prenatal stress ameliorates stress-induced alterations of hippocampal myelin and synapses, and impaired development of spatial memory in adult offspring. Pregnant mice were divided into control, stress, and stress/chewing groups. Stress was induced by placing mice in a ventilated restraint tube, and was initiated on day 12 of pregnancy and continued until delivery. Mice in the stress/chewing group were given a wooden stick to chew during restraint. In 1-month-old pups, spatial memory was assessed in the Morris water maze, and hippocampal oligodendrocytes and synapses in CA1 were assayed by immunohistochemistry and electron microscopy. Prenatal stress led to impaired learning ability, and decreased immunoreactivity of myelin basic protein (MBP) and 2',3'-cyclic nucleotide 3'-phosphodiesterase (CNPase) in the hippocampal CA1 in adult offspring. Numerous myelin sheath abnormalities were observed. The G-ratio [axonal diameter to axonal fiber diameter (axon plus myelin sheath)] was increased and postsynaptic density length was decreased in the hippocampal CA1 region. Maternal chewing during stress attenuated the prenatal stress-induced impairment of spatial memory, and the decreased MBP and CNPase immunoreactivity, increased G-ratios, and decreased postsynaptic-density length in the hippocampal CA1 region. These findings suggest that chewing during prenatal stress in dams could be an effective coping strategy to prevent hippocampal behavioral and morphologic impairments in their offspring. Copyright © 2016 Elsevier B.V. All rights reserved.

Chronic alcoholism-mediated impairment in the medulla oblongata: a mechanism of alcohol-related mortality in traumatic brain injury?

PubMed

Lai, Xiao-ping; Yu, Xiao-jun; Qian, Hong; Wei, Lai; Lv, Jun-yao; Xu, Xiao-hu

2013-01-01

Alcohol-related traumatic brain injury (TBI) is a common condition in medical and forensic practice, and results in high prehospital mortality. We investigated the mechanism of chronic alcoholism-related mortality by examining the effects of alcohol on the synapses of the medulla oblongata in a rat model of TBI. Seventy adult male Sprague-Dawley rats were randomly assigned to either ethanol (EtOH) group, EtOH-TBI group, or control groups (water group, water-TBI group). To establish chronic alcoholism model, rats in the EtOH group were given EtOH twice daily (4 g/kg for 2 weeks and 6 g/kg for another 2 weeks). The rats also received a minor strike on the occipital tuberosity with an iron pendulum. Histopathologic and ultrastructure changes and the numerical density of the synapses in the medulla oblongata were examined. Expression of postsynaptic density-95 (PSD-95) in the medulla oblongata was measured by ELISA. Compared with rats in the control group, rats in the chronic alcoholism group showed: (1) minor axonal degeneration; (2) a significant decrease in the numerical density of synapses (p < 0.01); and (3) compensatory increase in PSD-95 expression (p < 0.01). Rats in the EtOH-TBI group showed: (1) high mortality (50%, p < 0.01); (2) inhibited respiration before death; (3) severe axonal injury; and (4) decrease in PSD-95 expression (p < 0.05). Chronic alcoholism induces significant synapse loss and axonal impairment in the medulla oblongata and renders the brain more susceptible to TBI. The combined effects of chronic alcoholism and TBI induce significant synapse and axon impairment and result in high mortality.

Decreased Axon Caliber Underlies Loss of Fiber Tract Integrity, Disproportional Reductions in White Matter Volume, and Microcephaly in Angelman Syndrome Model Mice

PubMed Central

Judson, Matthew C.; Burette, Alain C.; Shen, Mark D.; Rumple, Ashley M.; Del Cid, Wilmer A.; Paniagua, Beatriz

2017-01-01

Angelman syndrome (AS) is a debilitating neurodevelopmental disorder caused by loss of function of the maternally inherited UBE3A allele. It is currently unclear how the consequences of this genetic insult unfold to impair neurodevelopment. We reasoned that by elucidating the basis of microcephaly in AS, a highly penetrant syndromic feature with early postnatal onset, we would gain new insights into the mechanisms by which maternal UBE3A loss derails neurotypical brain growth and function. Detailed anatomical analysis of both male and female maternal Ube3a-null mice reveals that microcephaly in the AS mouse model is primarily driven by deficits in the growth of white matter tracts, which by adulthood are characterized by densely packed axons of disproportionately small caliber. Our results implicate impaired axon growth in the pathogenesis of AS and identify noninvasive structural neuroimaging as a potentially valuable tool for gauging therapeutic efficacy in the disorder. SIGNIFICANCE STATEMENT People who maternally inherit a deletion or nonfunctional copy of the UBE3A gene develop Angelman syndrome (AS), a severe neurodevelopmental disorder. To better understand how loss of maternal UBE3A function derails brain development, we analyzed brain structure in a maternal Ube3a knock-out mouse model of AS. We report that the volume of white matter (WM) is disproportionately reduced in AS mice, indicating that deficits in WM development are a major factor underlying impaired brain growth and microcephaly in the disorder. Notably, we find that axons within the WM pathways of AS model mice are abnormally small in caliber. This defect is associated with slowed nerve conduction, which could contribute to behavioral deficits in AS, including motor dysfunction. PMID:28663201

Sodium Channel β2 Subunits Prevent Action Potential Propagation Failures at Axonal Branch Points.

PubMed

Cho, In Ha; Panzera, Lauren C; Chin, Morven; Hoppa, Michael B

2017-09-27

Neurotransmitter release depends on voltage-gated Na + channels (Na v s) to propagate an action potential (AP) successfully from the axon hillock to a synaptic terminal. Unmyelinated sections of axon are very diverse structures encompassing branch points and numerous presynaptic terminals with undefined molecular partners of Na + channels. Using optical recordings of Ca 2+ and membrane voltage, we demonstrate here that Na + channel β2 subunits (Na v β2s) are required to prevent AP propagation failures across the axonal arborization of cultured rat hippocampal neurons (mixed male and female). When Na v β2 expression was reduced, we identified two specific phenotypes: (1) membrane excitability and AP-evoked Ca 2+ entry were impaired at synapses and (2) AP propagation was severely compromised with >40% of axonal branches no longer responding to AP-stimulation. We went on to show that a great deal of electrical signaling heterogeneity exists in AP waveforms across the axonal arborization independent of axon morphology. Therefore, Na v β2 is a critical regulator of axonal excitability and synaptic function in unmyelinated axons. SIGNIFICANCE STATEMENT Voltage-gated Ca 2+ channels are fulcrums of neurotransmission that convert electrical inputs into chemical outputs in the form of vesicle fusion at synaptic terminals. However, the role of the electrical signal, the presynaptic action potential (AP), in modulating synaptic transmission is less clear. What is the fidelity of a propagating AP waveform in the axon and what molecules shape it throughout the axonal arborization? Our work identifies several new features of AP propagation in unmyelinated axons: (1) branches of a single axonal arborization have variable AP waveforms independent of morphology, (2) Na + channel β2 subunits modulate AP-evoked Ca 2+ -influx, and (3) β2 subunits maintain successful AP propagation across the axonal arbor. These findings are relevant to understanding the flow of excitation in the brain. Copyright © 2017 the authors 0270-6474/17/379519-15$15.00/0.

Trafficking of cholesterol from cell bodies to distal axons in Niemann Pick C1-deficient neurons.

PubMed

Karten, Barbara; Vance, Dennis E; Campenot, Robert B; Vance, Jean E

2003-02-07

Niemann Pick type C (NPC) disease is a progressive neurodegenerative disorder. In cells lacking functional NPC1 protein, endocytosed cholesterol accumulates in late endosomes/lysosomes. We utilized primary neuronal cultures in which cell bodies and distal axons reside in separate compartments to investigate the requirement of NPC1 protein for transport of cholesterol from cell bodies to distal axons. We have recently observed that in NPC1-deficient neurons compared with wild-type neurons, cholesterol accumulates in cell bodies but is reduced in distal axons (Karten, B., Vance, D. E., Campenot, R. B., and Vance, J. E. (2002) J. Neurochem. 83, 1154-1163). We now show that NPC1 protein is expressed in both cell bodies and distal axons. In NPC1-deficient neurons, cholesterol delivered to cell bodies from low density lipoproteins (LDLs), high density lipoproteins, or cyclodextrin complexes was transported into axons in normal amounts, whereas transport of endogenously synthesized cholesterol was impaired. Inhibition of cholesterol synthesis with pravastatin in wild-type and NPC1-deficient neurons reduced axonal growth. However, LDLs restored a normal rate of growth to wild-type but not NPC1-deficient neurons treated with pravastatin. Thus, although LDL cholesterol is transported into axons of NPC1-deficient neurons, this source of cholesterol does not sustain normal axonal growth. Over the lifespan of NPC1-deficient neurons, these defects in cholesterol transport might be responsible for the observed altered distribution of cholesterol between cell bodies and axons and, consequently, might contribute to the neurological dysfunction in NPC disease.

Dendrobium nobile Lindl alkaloid, a novel autophagy inducer, protects against axonal degeneration induced by Aβ25-35 in hippocampus neurons in vitro.

PubMed

Li, Li-Sheng; Lu, Yan-Liu; Nie, Jing; Xu, Yun-Yan; Zhang, Wei; Yang, Wen-Jin; Gong, Qi-Hai; Lu, Yuan-Fu; Lu, Yang; Shi, Jing-Shan

2017-04-01

Axonal degeneration is a pathological symbol in the early stage of Alzheimer's disease (AD), which can be triggered by amyloid-β (Aβ) peptide deposition. Growing evidence indicates that deficit of autophagy eventually leads to the axonal degeneration. Our previous studies have shown that Dendrobium nobile Lindl alkaloid (DNLA) had protective effect on neuron impairment in vivo and in vitro; however, the underlying mechanisms is still unclear. We exposed cultured hippocampus neurons to Aβ 25-35 to investigate the effect of DNLA in vitro. Axonal degeneration was evaluated by immunofluorescence staining and MTT assay. Neurons overexpressing GFP-LC3B were used to measure the formation of autophagosome. Autophagosome-lysosome fusion, the lysosomal pH, and cathepsin activity were assessed to reflect autophagy process. Proteins of interest were analyzed by Western blot. DNLA pretreatment significantly inhibited axonal degeneration induced by Aβ 25-35 peptide in vitro. Further studies revealed DNLA treatment increased autophagic flux through promoting formation and degradation of autophagosome in hippocampus neurons. Moreover, enhancement of autophagic flux was responsible for the protective effects of DNLA on axonal degeneration. DNLA prevents Aβ 25-35 -induced axonal degeneration via activation of autophagy process and could be a novel therapeutic target. © 2017 John Wiley & Sons Ltd.

The Parkinsonian mimetic, 6-OHDA, impairs axonal transport in dopaminergic axons

PubMed Central

2014-01-01

6-hydroxydopamine (6-OHDA) is one of the most commonly used toxins for modeling degeneration of dopaminergic (DA) neurons in Parkinson's disease. 6-OHDA also causes axonal degeneration, a process that appears to precede the death of DA neurons. To understand the processes involved in 6-OHDA-mediated axonal degeneration, a microdevice designed to isolate axons fluidically from cell bodies was used in conjunction with green fluorescent protein (GFP)-labeled DA neurons. Results showed that 6-OHDA quickly induced mitochondrial transport dysfunction in both DA and non-DA axons. This appeared to be a general effect on transport function since 6-OHDA also disrupted transport of synaptophysin-tagged vesicles. The effects of 6-OHDA on mitochondrial transport were blocked by the addition of the SOD1-mimetic, Mn(III)tetrakis(4-benzoic acid)porphyrin chloride (MnTBAP), as well as the anti-oxidant N-acetyl-cysteine (NAC) suggesting that free radical species played a role in this process. Temporally, microtubule disruption and autophagy occurred after transport dysfunction yet before DA cell death following 6-OHDA treatment. The results from the study suggest that ROS-mediated transport dysfunction occurs early and plays a significant role in inducing axonal degeneration in response to 6-OHDA treatment. PMID:24885281

Modeling Axonal Defects in Hereditary Spastic Paraplegia with Human Pluripotent Stem Cells

PubMed Central

Denton, Kyle R.; Xu, Chongchong; Shah, Harsh; Li, Xue-Jun

2016-01-01

BACKGROUND Cortical motor neurons, also known as upper motor neurons, are large projection neurons whose axons convey signals to lower motor neurons to control the muscle movements. Degeneration of cortical motor neuron axons is implicated in several debilitating disorders, including hereditary spastic paraplegia (HSP) and amyotrophic lateral sclerosis (ALS). Since the discovery of the first HSP gene, SPAST that encodes spastin, over 70 distinct genetic loci associated with HSP have been identified. How the mutations of these functionally diverse genes result in axonal degeneration and why certain axons are affected in HSP remains largely unknown. The development of induced pluripotent stem cell (iPSC) technology has provided researchers an excellent resource to generate patient-specific human neurons to model human neuropathologic processes including axonal defects. METHODS In this article, we will frst review the pathology and pathways affected in the common forms of HSP subtypes by searching the PubMed database. We will then summurize the findings and insights gained from studies using iPSC-based models, and discuss the challenges and future directions. RESULTS HSPs, a heterogeneous group of genetic neurodegenerative disorders, are characterized by lower extremity weakness and spasticity that result from retrograde axonal degeneration of cortical motor neurons. Recently, iPSCs have been generated from several common forms of HSP including SPG4, SPG3A, and SPG11 patients. Neurons derived from HSP iPSCs exhibit disease-relevant axonal defects, such as impaired neurite outgrowth, increased axonal swellings, and reduced axonal transport. CONCLUSION These patient-derived neurons offer unique tools to study the pathogenic mechanisms and explore the treatments for rescuing axonal defects in HSP, as well as other diseases involving axonopathy. PMID:27956894

Decreased Axon Flare Reaction to Electrical Stimulation in Patients With Chronic Demyelinating Inflammatory Polyneuropathy.

PubMed

Kokotis, Panagiotis; Schmelz, Martin; Papagianni, Aikaterini E; Zambelis, Thomas; Karandreas, Nikos

2017-03-01

In chronic inflammatory demyelinating polyradiculopathy (CIDP), the impairment of unmyelinated nerve fibers appears unexpected. The measurement of the electrically induced axon flare reflex is a clinical test to assess the peripheral C-nociceptor function. In this study, we compared the flare area in patients suffering from CIDP with healthy subjects. We examined 18 patients fulfilling the criteria for CIDP (11 men, mean age 51.8 years, SD 15.1) and 18 age-matched adult healthy volunteers (control group) (11 men, mean age 51.9 years, SD 15.8). The flare responses were elicited by transcutaneous electrical stimulation and recorded by laser Doppler imaging. There was a significant reduction of electrically induced maximum flare area in the foot dorsum of patients with CIDP (t-value 2.08, P = 0.04) which proved to be length-dependent measured by a numerical index comparing the results with the forearm and thigh. The repeatedmeasures ANOVA revealed statistically significant smaller flare areas in all body regions for the CIDP group (P < 0.001). The axon flare reaction to electrical stimulation was decreased in patients with chronic demyelinating inflammatory polyneuropathy. The evaluation of the axon flare response can be proposed as a noninvasive objective functional test to detect an impaired C-fiber function in CIDP patients with the advantages of simplicity of the procedure, time economy, and objectivity.

Nebula/DSCR1 upregulation delays neurodegeneration and protects against APP-induced axonal transport defects by restoring calcineurin and GSK-3β signaling.

PubMed

Shaw, Jillian L; Chang, Karen T

2013-01-01

Post-mortem brains from Down syndrome (DS) and Alzheimer's disease (AD) patients show an upregulation of the Down syndrome critical region 1 protein (DSCR1), but its contribution to AD is not known. To gain insights into the role of DSCR1 in AD, we explored the functional interaction between DSCR1 and the amyloid precursor protein (APP), which is known to cause AD when duplicated or upregulated in DS. We find that the Drosophila homolog of DSCR1, Nebula, delays neurodegeneration and ameliorates axonal transport defects caused by APP overexpression. Live-imaging reveals that Nebula facilitates the transport of synaptic proteins and mitochondria affected by APP upregulation. Furthermore, we show that Nebula upregulation protects against axonal transport defects by restoring calcineurin and GSK-3β signaling altered by APP overexpression, thereby preserving cargo-motor interactions. As impaired transport of essential organelles caused by APP perturbation is thought to be an underlying cause of synaptic failure and neurodegeneration in AD, our findings imply that correcting calcineurin and GSK-3β signaling can prevent APP-induced pathologies. Our data further suggest that upregulation of Nebula/DSCR1 is neuroprotective in the presence of APP upregulation and provides evidence for calcineurin inhibition as a novel target for therapeutic intervention in preventing axonal transport impairments associated with AD.

Nebula/DSCR1 Upregulation Delays Neurodegeneration and Protects against APP-Induced Axonal Transport Defects by Restoring Calcineurin and GSK-3β Signaling

PubMed Central

Shaw, Jillian L.; Chang, Karen T.

2013-01-01

Post-mortem brains from Down syndrome (DS) and Alzheimer's disease (AD) patients show an upregulation of the Down syndrome critical region 1 protein (DSCR1), but its contribution to AD is not known. To gain insights into the role of DSCR1 in AD, we explored the functional interaction between DSCR1 and the amyloid precursor protein (APP), which is known to cause AD when duplicated or upregulated in DS. We find that the Drosophila homolog of DSCR1, Nebula, delays neurodegeneration and ameliorates axonal transport defects caused by APP overexpression. Live-imaging reveals that Nebula facilitates the transport of synaptic proteins and mitochondria affected by APP upregulation. Furthermore, we show that Nebula upregulation protects against axonal transport defects by restoring calcineurin and GSK-3β signaling altered by APP overexpression, thereby preserving cargo-motor interactions. As impaired transport of essential organelles caused by APP perturbation is thought to be an underlying cause of synaptic failure and neurodegeneration in AD, our findings imply that correcting calcineurin and GSK-3β signaling can prevent APP-induced pathologies. Our data further suggest that upregulation of Nebula/DSCR1 is neuroprotective in the presence of APP upregulation and provides evidence for calcineurin inhibition as a novel target for therapeutic intervention in preventing axonal transport impairments associated with AD. PMID:24086147

WldS but not Nmnat1 protects dopaminergic neurites from MPP+ neurotoxicity.

PubMed

Antenor-Dorsey, Jo Ann V; O'Malley, Karen L

2012-02-08

The WldS mouse mutant ("Wallerian degeneration-slow") delays axonal degeneration in a variety of disorders including in vivo models of Parkinson's disease. The mechanisms underlying WldS -mediated axonal protection are unclear, although many studies have attributed WldS neuroprotection to the NAD+-synthesizing Nmnat1 portion of the fusion protein. Here, we used dissociated dopaminergic cultures to test the hypothesis that catalytically active Nmnat1 protects dopaminergic neurons from toxin-mediated axonal injury. Using mutant mice and lentiviral transduction of dopaminergic neurons, the present findings demonstrate that WldS but not Nmnat1, Nmnat3, or cytoplasmically-targeted Nmnat1 protects dopamine axons from the parkinsonian mimetic N-methyl-4-phenylpyridinium (MPP+). Moreover, NAD+ synthesis is not required since enzymatically-inactive WldS still protects. In addition, NAD+ by itself is axonally protective and together with WldS is additive in the MPP+ model. Our data suggest that NAD+ and WldS act through separate and possibly parallel mechanisms to protect dopamine axons. As MPP+ is thought to impair mitochondrial function, these results suggest that WldS might be involved in preserving mitochondrial health or maintaining cellular metabolism.

White matter microstructure changes induced by motor skill learning utilizing a body machine interface.

PubMed

Wang, Xue; Casadio, Maura; Weber, Kenneth A; Mussa-Ivaldi, Ferdinando A; Parrish, Todd B

2014-03-01

The purpose of this study is to identify white matter microstructure changes following bilateral upper extremity motor skill training to increase our understanding of learning-induced structural plasticity and enhance clinical strategies in physical rehabilitation. Eleven healthy subjects performed two visuo-spatial motor training tasks over 9 sessions (2-3 sessions per week). Subjects controlled a cursor with bilateral simultaneous movements of the shoulders and upper arms using a body machine interface. Before the start and within 2days of the completion of training, whole brain diffusion tensor MR imaging data were acquired. Motor training increased fractional anisotropy (FA) values in the posterior and anterior limbs of the internal capsule, the corona radiata, and the body of the corpus callosum by 4.19% on average indicating white matter microstructure changes induced by activity-dependent modulation of axon number, axon diameter, or myelin thickness. These changes may underlie the functional reorganization associated with motor skill learning. Copyright © 2013 Elsevier Inc. All rights reserved.

The structure and organization of lanceolate mechanosensory complexes at mouse hair follicles

PubMed Central

Li, Lishi; Ginty, David D

2014-01-01

In mouse hairy skin, lanceolate complexes associated with three types of hair follicles, guard, awl/auchene and zigzag, serve as mechanosensory end organs. These structures are formed by unique combinations of low-threshold mechanoreceptors (LTMRs), Aβ RA-LTMRs, Aδ-LTMRs, and C-LTMRs, and their associated terminal Schwann cells (TSCs). In this study, we investigated the organization, ultrastructure, and maintenance of longitudinal lanceolate complexes at each hair follicle subtype. We found that TSC processes at hair follicles are tiled and that individual TSCs host axonal endings of more than one LTMR subtype. Electron microscopic analyses revealed unique ultrastructural features of lanceolate complexes that are proposed to underlie mechanotransduction. Moreover, Schwann cell ablation leads to loss of LTMR terminals at hair follicles while, in contrast, TSCs remain associated with hair follicles following skin denervation in adult mice and, remarkably, become re-associated with newly formed axons, indicating a TSC-dependence of lanceolate complex maintenance and regeneration in adults. DOI: http://dx.doi.org/10.7554/eLife.01901.001 PMID:24569481

The structure and organization of lanceolate mechanosensory complexes at mouse hair follicles.

PubMed

Li, Lishi; Ginty, David D

2014-02-25

In mouse hairy skin, lanceolate complexes associated with three types of hair follicles, guard, awl/auchene and zigzag, serve as mechanosensory end organs. These structures are formed by unique combinations of low-threshold mechanoreceptors (LTMRs), Aβ RA-LTMRs, Aδ-LTMRs, and C-LTMRs, and their associated terminal Schwann cells (TSCs). In this study, we investigated the organization, ultrastructure, and maintenance of longitudinal lanceolate complexes at each hair follicle subtype. We found that TSC processes at hair follicles are tiled and that individual TSCs host axonal endings of more than one LTMR subtype. Electron microscopic analyses revealed unique ultrastructural features of lanceolate complexes that are proposed to underlie mechanotransduction. Moreover, Schwann cell ablation leads to loss of LTMR terminals at hair follicles while, in contrast, TSCs remain associated with hair follicles following skin denervation in adult mice and, remarkably, become re-associated with newly formed axons, indicating a TSC-dependence of lanceolate complex maintenance and regeneration in adults. DOI: http://dx.doi.org/10.7554/eLife.01901.001.

Clinical and electrophysiologic attributes as predictors of results of autonomic function tests

NASA Technical Reports Server (NTRS)

Wu, C. L.; Denq, J. C.; Harper, C. M.; O'Brien, P. C.; Low, P. A.

1998-01-01

Autonomic dysfunction is a feature of some neuropathies and not others. It has been suggested that some clinical and electrophysiologic attributes are predictable of autonomic impairment detected using laboratory testing; however, dear guidelines are unavailable. We evaluated 138 relatively unselected patients with peripheral neuropathy who underwent neurologic evaluation, electromyography (EMG), nerve conduction studies, and autonomic function tests to determine which variables were predictive of laboratory findings of autonomic failure. The variables evaluated were 1) clinical somatic neuropathic findings, 2) clinical autonomic symptoms, and 3) electrophysiologic findings. Autonomic symptoms were strongly predictive (Rs = 0.40, p < 0.001) of autonomic failure. Among the non-autonomic indices, absent ankle reflexes were mildly predictive (Rs = 0.19, p = 0.022) of autonomic impairment, but all others were not (duration, clinical pattern, severity, weakness, sensory loss). Electrophysiologic changes of an axonal neuropathy predicted autonomic impairment while demyelinating neuropathy did not. We conclude that autonomic studies will most likely be abnormal in patients who have symptoms of autonomic involvement and those who have an axonal neuropathy.

Molecular Analysis of Sensory Axon Branching Unraveled a cGMP-Dependent Signaling Cascade.

PubMed

Dumoulin, Alexandre; Ter-Avetisyan, Gohar; Schmidt, Hannes; Rathjen, Fritz G

2018-04-24

Axonal branching is a key process in the establishment of circuit connectivity within the nervous system. Molecular-genetic studies have shown that a specific form of axonal branching—the bifurcation of sensory neurons at the transition zone between the peripheral and the central nervous system—is regulated by a cyclic guanosine monophosphate (cGMP)-dependent signaling cascade which is composed of C-type natriuretic peptide (CNP), the receptor guanylyl cyclase Npr2, and cGMP-dependent protein kinase Iα (cGKIα). In the absence of any one of these components, neurons in dorsal root ganglia (DRG) and cranial sensory ganglia no longer bifurcate, and instead turn in either an ascending or a descending direction. In contrast, collateral axonal branch formation which represents a second type of axonal branch formation is not affected by inactivation of CNP, Npr2, or cGKI. Whereas axon bifurcation was lost in mouse mutants deficient for components of CNP-induced cGMP formation; the absence of the cGMP-degrading enzyme phosphodiesterase 2A had no effect on axon bifurcation. Adult mice that lack sensory axon bifurcation due to the conditional inactivation of Npr2-mediated cGMP signaling in DRG neurons demonstrated an altered shape of sensory axon terminal fields in the spinal cord, indicating that elaborate compensatory mechanisms reorganize neuronal circuits in the absence of bifurcation. On a functional level, these mice showed impaired heat sensation and nociception induced by chemical irritants, whereas responses to cold sensation, mechanical stimulation, and motor coordination are normal. These data point to a critical role of axon bifurcation for the processing of acute pain perception.

Impaired Statistical Learning in Developmental Dyslexia

ERIC Educational Resources Information Center

Gabay, Yafit; Thiessen, Erik D.; Holt, Lori L.

2015-01-01

Purpose: Developmental dyslexia (DD) is commonly thought to arise from phonological impairments. However, an emerging perspective is that a more general procedural learning deficit, not specific to phonological processing, may underlie DD. The current study examined if individuals with DD are capable of extracting statistical regularities across…

Stress and Fear Extinction

PubMed Central

Maren, Stephen; Holmes, Andrew

2016-01-01

Stress has a critical role in the development and expression of many psychiatric disorders, and is a defining feature of posttraumatic stress disorder (PTSD). Stress also limits the efficacy of behavioral therapies aimed at limiting pathological fear, such as exposure therapy. Here we examine emerging evidence that stress impairs recovery from trauma by impairing fear extinction, a form of learning thought to underlie the suppression of trauma-related fear memories. We describe the major structural and functional abnormalities in brain regions that are particularly vulnerable to stress, including the amygdala, prefrontal cortex, and hippocampus, which may underlie stress-induced impairments in extinction. We also discuss some of the stress-induced neurochemical and molecular alterations in these brain regions that are associated with extinction deficits, and the potential for targeting these changes to prevent or reverse impaired extinction. A better understanding of the neurobiological basis of stress effects on extinction promises to yield novel approaches to improving therapeutic outcomes for PTSD and other anxiety and trauma-related disorders. PMID:26105142

Kamikihi-to (KKT) rescues axonal and synaptic degeneration associated with memory impairment in a mouse model of Alzheimer's disease, 5XFAD.

PubMed

Tohda, Chihiro; Nakada, Rie; Urano, Takuya; Okonogi, Akira; Kuboyama, Tomoharu

2011-12-01

Alzheimer's disease (AD) is a chronic progressive neurodegenerative disorder. Current agents for AD are employed for symptomatic therapy and insufficient to cure. We consider that this is quite necessary for AD treatment and have investigated axon/synapse formation-promoting activity. The aim of this study is to investigate the effects of Kamikihi-to [KKT; traditional Japanese (Kampo) medicine] on memory deficits in an AD model, 5XFAD. KKT (200 mg/kg, p.o.) was administered for 15 days to 5XFAD mice. Object recognition memory was tested in vehicle-treated wild-type and 5XFAD mice and KKT-treated 5XFAD mice. KKT-treated 5XFAD mice showed significant improvement of object recognition memory. KKT treatment significantly reduced the number of amyloid plaques in the frontal cortex and hippocampus. Only inside of amyloid plaques were abnormal structures such as bulb-like axons and swollen presynaptic boutons observed. These degenerated axons and presynaptic terminals were significantly reduced by KKT treatment in the frontal cortex. In primary cortical neurons, KKT treatment significantly increased axon length when applied after Aβ(25-35)-induced axonal atrophy had progressed. In conclusion, KKT improved object recognition memory deficit in an AD model 5XFAD mice. Restoration of degenerated axons and synapses may be associated with the memory recovery by KKT.

Single prolonged stress impairs social and object novelty recognition in rats.

PubMed

Eagle, Andrew L; Fitzpatrick, Chris J; Perrine, Shane A

2013-11-01

Posttraumatic stress disorder (PTSD) results from exposure to a traumatic event and manifests as re-experiencing, arousal, avoidance, and negative cognition/mood symptoms. Avoidant symptoms, as well as the newly defined negative cognitions/mood, are a serious complication leading to diminished interest in once important or positive activities, such as social interaction; however, the basis of these symptoms remains poorly understood. PTSD patients also exhibit impaired object and social recognition, which may underlie the avoidance and symptoms of negative cognition, such as social estrangement or diminished interest in activities. Previous studies have demonstrated that single prolonged stress (SPS), models PTSD phenotypes, including impairments in learning and memory. Therefore, it was hypothesized that SPS would impair social and object recognition memory. Male Sprague Dawley rats were exposed to SPS then tested in the social choice test (SCT) or novel object recognition test (NOR). These tests measure recognition of novelty over familiarity, a natural preference of rodents. Results show that SPS impaired preference for both social and object novelty. In addition, SPS impairment in social recognition may be caused by impaired behavioral flexibility, or an inability to shift behavior during the SCT. These results demonstrate that traumatic stress can impair social and object recognition memory, which may underlie certain avoidant symptoms or negative cognition in PTSD and be related to impaired behavioral flexibility. Copyright © 2013 Elsevier B.V. All rights reserved.

Synuclein impairs trafficking and signaling of BDNF in a mouse model of Parkinson's disease.

PubMed

Fang, Fang; Yang, Wanlin; Florio, Jazmin B; Rockenstein, Edward; Spencer, Brian; Orain, Xavier M; Dong, Stephanie X; Li, Huayan; Chen, Xuqiao; Sung, Kijung; Rissman, Robert A; Masliah, Eliezer; Ding, Jianqing; Wu, Chengbiao

2017-06-20

Recent studies have demonstrated that hyperphosphorylation of tau protein plays a role in neuronal toxicities of α-synuclein (ASYN) in neurodegenerative disease such as familial Alzheimer's disease (AD), dementia with Lewy bodies (DLB) and Parkinson's disease. Using a transgenic mouse model of Parkinson's disease (PD) that expresses GFP-ASYN driven by the PDGF-β promoter, we investigated how accumulation of ASYN impacted axonal function. We found that retrograde axonal trafficking of brain-derived neurotrophic factor (BDNF) in DIV7 cultures of E18 cortical neurons was markedly impaired at the embryonic stage, even though hyperphosphorylation of tau was not detectable in these neurons at this stage. Interestingly, we found that overexpressed ASYN interacted with dynein and induced a significant increase in the activated levels of small Rab GTPases such as Rab5 and Rab7, both key regulators of endocytic processes. Furthermore, expression of ASYN resulted in neuronal atrophy in DIV7 cortical cultures of either from E18 transgenic mouse model or from rat E18 embryos that were transiently transfected with ASYN-GFP for 72 hrs. Our studies suggest that excessive ASYN likely alters endocytic pathways leading to axonal dysfunction in embryonic cortical neurons in PD mouse models.

Motor and sensory neuropathy due to myelin infolding and paranodal damage in a transgenic mouse model of Charcot–Marie–Tooth disease type 1C

PubMed Central

Lee, Samuel M.; Sha, Di; Mohammed, Anum A.; Asress, Seneshaw; Glass, Jonathan D.; Chin, Lih-Shen; Li, Lian

2013-01-01

Charcot–Marie–Tooth disease type 1C (CMT1C) is a dominantly inherited motor and sensory neuropathy. Despite human genetic evidence linking missense mutations in SIMPLE to CMT1C, the in vivo role of CMT1C-linked SIMPLE mutations remains undetermined. To investigate the molecular mechanism underlying CMT1C pathogenesis, we generated transgenic mice expressing either wild-type or CMT1C-linked W116G human SIMPLE. Mice expressing mutant, but not wild type, SIMPLE develop a late-onset motor and sensory neuropathy that recapitulates key clinical features of CMT1C disease. SIMPLE mutant mice exhibit motor and sensory behavioral impairments accompanied by decreased motor and sensory nerve conduction velocity and reduced compound muscle action potential amplitude. This neuropathy phenotype is associated with focally infolded myelin loops that protrude into the axons at paranodal regions and near Schmidt–Lanterman incisures of peripheral nerves. We find that myelin infolding is often linked to constricted axons with signs of impaired axonal transport and to paranodal defects and abnormal organization of the node of Ranvier. Our findings support that SIMPLE mutation disrupts myelin homeostasis and causes peripheral neuropathy via a combination of toxic gain-of-function and dominant-negative mechanisms. The results from this study suggest that myelin infolding and paranodal damage may represent pathogenic precursors preceding demyelination and axonal degeneration in CMT1C patients. PMID:23359569

Diffusion fMRI detects white-matter dysfunction in mice with acute optic neuritis

PubMed Central

Lin, Tsen-Hsuan; Spees, William M.; Chiang, Chia-Wen; Trinkaus, Kathryn; Cross, Anne H.; Song, Sheng-Kwei

2014-01-01

Optic neuritis is a frequent and early symptom of multiple sclerosis (MS). Conventional magnetic resonance (MR) techniques provide means to assess multiple MS-related pathologies, including axonal injury, demyelination, and inflammation. A method to directly and non-invasively probe white-matter function could further elucidate the interplay of underlying pathologies and functional impairments. Previously, we demonstrated a significant 27% activation-associated decrease in the apparent diffusion coefficient of water perpendicular to the axonal fibers (ADC⊥) in normal C57BL/6 mouse optic nerve with visual stimulation using diffusion fMRI. Here we apply this approach to explore the relationship between visual acuity, optic nerve pathology, and diffusion fMRI in the experimental autoimmune encephalomyelitis (EAE) mouse model of optic neuritis. Visual stimulation produced a significant 25% (vs. baseline) ADC⊥ decrease in sham EAE optic nerves, while only a 7% (vs. baseline) ADC⊥ decrease was seen in EAE mice with acute optic neuritis. The reduced activation-associated ADC⊥ response correlated with post-MRI immunohistochemistry determined pathologies (including inflammation, demyelination, and axonal injury). The negative correlation between activation-associated ADC⊥ response and visual acuity was also found when pooling EAE-affected and sham groups under our experimental criteria. Results suggest that reduction in diffusion fMRI directly reflects impaired axonal-activation in EAE mice with optic neuritis. Diffusion fMRI holds promise for directly gauging in vivo white-matter dysfunction or therapeutic responses in MS patients. PMID:24632420

Brain injury tolerance limit based on computation of axonal strain.

PubMed

Sahoo, Debasis; Deck, Caroline; Willinger, Rémy

2016-07-01

Traumatic brain injury (TBI) is the leading cause of death and permanent impairment over the last decades. In both the severe and mild TBIs, diffuse axonal injury (DAI) is the most common pathology and leads to axonal degeneration. Computation of axonal strain by using finite element head model in numerical simulation can enlighten the DAI mechanism and help to establish advanced head injury criteria. The main objective of this study is to develop a brain injury criterion based on computation of axonal strain. To achieve the objective a state-of-the-art finite element head model with enhanced brain and skull material laws, was used for numerical computation of real world head trauma. The implementation of new medical imaging data such as, fractional anisotropy and axonal fiber orientation from Diffusion Tensor Imaging (DTI) of 12 healthy patients into the finite element brain model was performed to improve the brain constitutive material law with more efficient heterogeneous anisotropic visco hyper-elastic material law. The brain behavior has been validated in terms of brain deformation against Hardy et al. (2001), Hardy et al. (2007), and in terms of brain pressure against Nahum et al. (1977) and Trosseille et al. (1992) experiments. Verification of model stability has been conducted as well. Further, 109 well-documented TBI cases were simulated and axonal strain computed to derive brain injury tolerance curve. Based on an in-depth statistical analysis of different intra-cerebral parameters (brain axonal strain rate, axonal strain, first principal strain, Von Mises strain, first principal stress, Von Mises stress, CSDM (0.10), CSDM (0.15) and CSDM (0.25)), it was shown that axonal strain was the most appropriate candidate parameter to predict DAI. The proposed brain injury tolerance limit for a 50% risk of DAI has been established at 14.65% of axonal strain. This study provides a key step for a realistic novel injury metric for DAI. Copyright © 2016 Elsevier Ltd. All rights reserved.

Impaired Expression of Neuronal Nitric Oxide Synthase in the Gracile Nucleus Is Involved in Neuropathic Changes in Zucker Diabetic Fatty Rats with and without 2,5-Hexanedione Intoxication

PubMed Central

Ma, Sheng-Xing; Peterson, Richard G.; Magee, Edward M.; Lee, Paul; Lee, Wai-Nang Paul; Li, Xi-Yan

2015-01-01

These studies examined the influence of 2,5-hexanedione (2,5-HD) intoxication on expression of neuronal nitric oxide synthase (nNOS) in the brainstem nuclei in Zucker Diabetic Fatty (ZDF) vs. lean control (LC) rats. Functional neuropathic changes were also investigated following axonal damage and impaired axonal transport induced by the treatment. Animals were intoxicated by i.p. injection of 2,5-HD plus unilateral administration of 2,5-HD over the sciatic nerve. The mechanical thresholds and withdrawal latencies to heat and cold stimuli on the foot were measured at baseline and after intoxication. The medulla sections were examined by nNOS immunohistochemistry and NADPH-diaphorase histochemistry at the end of the treatments. The mechanical thresholds and withdrawal latencies were significantly decreased while nNOS immunostained neurons and NADPH-diaphorase positive cells were selectively reduced in the gracile nucleus at baseline in ZDF vs. LC rats. NADPH-diaphorase reactivity and nNOS positive neurons were increased in the ipsilateral gracile nucleus in LC rats following 2,5-HD intoxication, but its up-regulation was attenuated in ZDF rats. These results suggest that diabetic and chemical intoxication-induced nNOS expression is selectively reduced in the gracile nucleus in ZDF rats. Impaired axonal damage-induced nNOS expression in the gracile nucleus is involved in neuropathic pathophysiology in type II diabetic rats. PMID:26519861

The power of projectomes: genetic mosaic labeling in the larval zebrafish brain reveals organizing principles of sensory circuits.

PubMed

Robles, Estuardo

2017-09-01

In no vertebrate species do we possess an accurate, comprehensive tally of neuron types in the brain. This is in no small part due to the vast diversity of neuronal types that comprise complex vertebrate nervous systems. A fundamental goal of neuroscience is to construct comprehensive catalogs of cell types defined by structure, connectivity, and physiological response properties. This type of information will be invaluable for generating models of how assemblies of neurons encode and distribute sensory information and correspondingly alter behavior. This review summarizes recent efforts in the larval zebrafish to construct sensory projectomes, comprehensive analyses of axonal morphologies in sensory axon tracts. Focusing on the olfactory and optic tract, these studies revealed principles of sensory information processing in the olfactory and visual systems that could not have been directly quantified by other methods. In essence, these studies reconstructed the optic and olfactory tract in a virtual manner, providing insights into patterns of neuronal growth that underlie the formation of sensory axon tracts. Quantitative analysis of neuronal diversity revealed organizing principles that determine information flow through sensory systems in the zebrafish that are likely to be conserved across vertebrate species. The generation of comprehensive cell type classifications based on structural, physiological, and molecular features will lead to testable hypotheses on the functional role of individual sensory neuron subtypes in controlling specific sensory-evoked behaviors.

Axonal autophagosomes recruit dynein for retrograde transport through fusion with late endosomes

PubMed Central

Cheng, Xiu-Tang; Zhou, Bing; Lin, Mei-Yao; Cai, Qian

2015-01-01

Efficient degradation of autophagic vacuoles (AVs) via lysosomes is an important cellular homeostatic process. This is particularly challenging for neurons because mature acidic lysosomes are relatively enriched in the soma. Although dynein-driven retrograde transport of AVs was suggested, a fundamental question remains how autophagosomes generated at distal axons acquire dynein motors for retrograde transport toward the soma. In this paper, we demonstrate that late endosome (LE)–loaded dynein–snapin complexes drive AV retrograde transport in axons upon fusion of autophagosomes with LEs into amphisomes. Blocking the fusion with syntaxin17 knockdown reduced recruitment of dynein motors to AVs, thus immobilizing them in axons. Deficiency in dynein–snapin coupling impaired AV transport, resulting in AV accumulation in neurites and synaptic terminals. Altogether, our study provides the first evidence that autophagosomes recruit dynein through fusion with LEs and reveals a new motor–adaptor sharing mechanism by which neurons may remove distal AVs engulfing aggregated proteins and dysfunctional organelles for efficient degradation in the soma. PMID:25940348

A Novel Variant in the HINT1 Gene in a Girl with Autosomal Recessive Axonal Neuropathy with Neuromyotonia: Thorough Neurological Examination Gives the Clue.

PubMed

Rauchenzauner, Markus; Frühwirth, Martin; Hecht, Martin; Kofler, Markus; Witsch-Baumgartner, Martina; Fauth, Christine

2016-04-01

We report a girl with autosomal recessive axonal neuropathy with neuromyotonia (ARAN-NM) who presented with asymmetric gait impairment, foot drop, and action myotonia on fast handgrip. Electrophysiological studies showed symmetrical axonal motor greater than sensory neuropathy, and neuromyotonic discharges on needle electromyography. ARAN-NM was confirmed by molecular genetic testing, which revealed a novel homozygous missense variant c.100G > A [p.(Glu34Lys)] in HINT1. This case shows that the diagnosis of ARAN-NM, as a new entity, has to be considered in the differential diagnosis of polyneuropathy in combination with neuromyotonia/action myotonia in children, even with asymmetric clinical presentation. Georg Thieme Verlag KG Stuttgart · New York.

Activity-dependent modulation of the axonal conduction of action potentials along rat hippocampal mossy fibers.

PubMed

Chida, Kuniaki; Kaneko, Kenya; Fujii, Satoshi; Yamazaki, Yoshihiko

2015-01-01

The axonal conduction of action potentials in the nervous system is generally considered to be a stable signal for the relaying of information, and its dysfunction is involved in impairment of cognitive function. Recent evidence suggests that the conduction properties and excitability of axons are more variable than traditionally thought. To investigate possible changes in the conduction of action potentials along axons in the central nervous system, we recorded action potentials from granule cells that were evoked and conducted antidromically along unmyelinated mossy fibers in the rat hippocampus. To evaluate changes in axons by eliminating any involvement of changes in the somata, two latency values were obtained by stimulating at two different positions and the latency difference between the action potentials was measured. A conditioning electrical stimulus of 20 pulses at 1 Hz increased the latency difference and this effect, which lasted for approximately 30 s, was inhibited by the application of an α-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA)/kainate receptor antagonist or a GluK1-containing kainate receptor antagonist, but not by an AMPA receptor-selective antagonist or an N-methyl-d-aspartate receptor antagonist. These results indicated that axonal conduction in mossy fibers is modulated in an activity-dependent manner through the activation of GluK1-containing kainate receptors. These dynamic changes in axonal conduction may contribute to the physiology and pathophysiology of the brain. © 2014 Federation of European Neuroscience Societies and John Wiley & Sons Ltd.

Parabrachial origin of calcitonin gene-related peptide-immunoreactive axons innervating Meynert's basal nucleus.

PubMed

Knyihár-Csillik, E; Boncz, I; Sáry, G; Nemcsók, J; Csillik, B

1999-06-01

Meynert's basal nucleus is innervated by calcitonin gene-related peptide (CGRP)-immunoreactive axons synapsing with cholinergic principal cells. Origin of CGRP-immunopositive axons was studied in the albino rat. Since beaded axons containing the nicotinic acetylcholine receptor (nAChR) are also present in the basal nucleus, the microstructural arrangement raises the question whether or not an interaction between CGRP and nAChR exists like in the neuromuscular junction. We found that electrolytic lesion of the parabrachial nucleus results in degeneration of CGRP-immunoreactive axons in the ipsilateral nucleus basalis and induces shrinkage of principal cholinergic neurons while the contralateral nucleus basalis remains intact. Electrolytic lesions in the thalamus, caudate-putamen, and hippocampus did not induce alterations in Meynert's basal nucleus. Disappearance of CGRP after lesions of the parabrachial nucleus does not impair presynaptic nAChR in the basal nucleus, suggesting that, unlike in the neuromuscular junction, CGRP is not involved in the maintenance of nAChR in the basal forebrain. It is concluded that the parabrachial nucleus is involved in the activation of the nucleus basalis-prefrontal cortex system, essential in gnostic and mnemonic functions. Copyright 1999 Academic Press.

Reliable, responsive pacemaking and pattern generation with minimal cell numbers: the crustacean cardiac ganglion.

PubMed

Cooke, Ian M

2002-04-01

Investigations of the electrophysiology of crustacean cardiac ganglia over the last half-century are reviewed for their contributions to elucidating the cellular mechanisms and interactions by which a small (as few as nine cells) neuronal network accomplishes extremely reliable, rhythmical, patterned activation of muscular activity-in this case, beating of the neurogenic heart. This ganglion is thus a model for pacemaking and central pattern generation. Favorable anatomy has permitted voltage- and space-clamp analyses of voltage-dependent ionic currents that endow each neuron with the intrinsic ability to respond with rhythmical, patterned impulse activity to nonpatterned stimulation. The crustacean soma and initial axon segment do not support impulse generation but integrate input from stretch-sensitive dendrites and electrotonic and chemically mediated synapses on axonal processes in neuropils. The soma and initial axon produce a depolarization-activated, calcium-mediated, sustained potential, the "driver potential," so-called because it drives a train of impulses at the "trigger zone" of the axon. Extreme reliability results from redundancy and the electrotonic coupling and synaptic interaction among all the neurons. Complex modulation by central nervous system inputs and by neurohormones to adjust heart pumping to physiological demands has long been demonstrated, but much remains to be learned about the cellular and molecular mechanisms of action. The continuing relevance of the crustacean cardiac ganglion as a relatively simple model for pacemaking and central pattern generation is confirmed by the rapidly widening documentation of intrinsic potentials such as plateau potentials in neurons of all major animal groups. The suite of ionic currents (a slowly inactivating calcium current and various potassium currents, with variations) observed for the crustacean cardiac ganglion have been implicated in or proven to underlie a majority of the intrinsic potentials of neurons involved in pattern generation.

Role of the Axon Initial Segment in the Control of Spontaneous Frequency of Nigral Dopaminergic Neurons In Vivo.

PubMed

Meza, Rodrigo C; López-Jury, Luciana; Canavier, Carmen C; Henny, Pablo

2018-01-17

The spontaneous tonic discharge activity of nigral dopamine neurons plays a fundamental role in dopaminergic signaling. To investigate the role of neuronal morphology and architecture with respect to spontaneous activity in this population, we visualized the 3D structure of the axon initial segment (AIS) along with the entire somatodendritic domain of adult male mouse dopaminergic neurons, previously recorded in vivo We observed a positive correlation of the firing rate with both proximity and size of the AIS. Computational modeling showed that the size of the AIS, but not its position within the somatodendritic domain, is the major causal determinant of the tonic firing rate in the intact model, by virtue of the higher intrinsic frequency of the isolated AIS. Further mechanistic analysis of the relationship between neuronal morphology and firing rate showed that dopaminergic neurons function as a coupled oscillator whose frequency of discharge results from a compromise between AIS and somatodendritic oscillators. Thus, morphology plays a critical role in setting the basal tonic firing rate, which in turn could control striatal dopaminergic signaling that mediates motivation and movement. SIGNIFICANCE STATEMENT The frequency at which nigral dopamine neurons discharge action potentials sets baseline dopamine levels in the brain, which enables activity in motor, cognitive, and motivational systems. Here, we demonstrate that the size of the axon initial segment, a subcellular compartment responsible for initiating action potentials, is a key determinant of the firing rate in these neurons. The axon initial segment and all the molecular components that underlie its critical function may provide a novel target for the regulation of dopamine levels in the brain. Copyright © 2018 the authors 0270-6474/18/380733-12$15.00/0.

The ciliogenic transcription factor Rfx3 is required for the formation of the thalamocortical tract by regulating the patterning of prethalamus and ventral telencephalon.

PubMed

Magnani, Dario; Morlé, Laurette; Hasenpusch-Theil, Kerstin; Paschaki, Marie; Jacoby, Monique; Schurmans, Stéphane; Durand, Bénédicte; Theil, Thomas

2015-05-01

Primary cilia are complex subcellular structures that play key roles during embryogenesis by controlling the cellular response to several signaling pathways. Defects in the function and/or structure of primary cilia underlie a large number of human syndromes collectively referred to as ciliopathies. Often, ciliopathies are associated with mental retardation (MR) and malformation of the corpus callosum. However, the possibility of defects in other forebrain axon tracts, which could contribute to the cognitive disorders of these patients, has not been explored. Here, we investigate the formation of the corticothalamic/thalamocortical tracts in mice mutant for Rfx3, which regulates the expression of many genes involved in ciliogenesis and cilia function. Using DiI axon tracing and immunohistochemistry experiments, we show that some Rfx3(-/-) corticothalamic axons abnormally migrate toward the pial surface of the ventral telencephalon (VT). Some thalamocortical axons (TCAs) also fail to leave the diencephalon or abnormally project toward the amygdala. Moreover, the Rfx3(-/-) VT displays heterotopias containing attractive guidance cues and expressing the guidance molecules Slit1 and Netrin1. Finally, the abnormal projection of TCAs toward the amygdala is also present in mice carrying a mutation in the Inpp5e gene, which is mutated in Joubert Syndrome and which controls cilia signaling and stability. The presence of identical thalamocortical malformations in two independent ciliary mutants indicates a novel role for primary cilia in the formation of the corticothalamic/thalamocortical tracts by establishing the correct cellular environment necessary for its development. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Substance P immunoreactivity exhibits frequent colocalization with kisspeptin and neurokinin B in the human infundibular region.

PubMed

Hrabovszky, Erik; Borsay, Beáta Á; Rácz, Kálmán; Herczeg, László; Ciofi, Philippe; Bloom, Stephen R; Ghatei, Mohammad A; Dhillo, Waljit S; Liposits, Zsolt

2013-01-01

Neurons synthesizing neurokinin B (NKB) and kisspeptin (KP) in the hypothalamic arcuate nucleus represent important upstream regulators of pulsatile gonadotropin-releasing hormone (GnRH) neurosecretion. In search of neuropeptides co-expressed in analogous neurons of the human infundibular nucleus (Inf), we have carried out immunohistochemical studies of the tachykinin peptide Substance P (SP) in autopsy samples from men (21-78 years) and postmenopausal (53-83 years) women. Significantly higher numbers of SP-immunoreactive (IR) neurons and darker labeling were observed in the Inf of postmenopausal women than in age-matched men. Triple-immunofluorescent studies localized SP immunoreactivity to considerable subsets of KP-IR and NKB-IR axons and perikarya in the infundibular region. In postmenopausal women, 25.1% of NKB-IR and 30.6% of KP-IR perikarya contained SP and 16.5% of all immunolabeled cell bodies were triple-labeled. Triple-, double- and single-labeled SP-IR axons innervated densely the portal capillaries of the infundibular stalk. In quadruple-labeled sections, these axons formed occasional contacts with GnRH-IR axons. Presence of SP in NKB and KP neurons increases the functional complexity of the putative pulse generator network. First, it is possible that SP modulates the effects of KP and NKB in axo-somatic and axo-dendritic afferents to GnRH neurons. Intrinsic SP may also affect the activity and/or neuropeptide release of NKB and KP neurons via autocrine/paracrine actions. In the infundibular stalk, SP may influence the KP and NKB secretory output via additional autocrine/paracrine mechanisms or regulate GnRH neurosecretion directly. Finally, possible co-release of SP with KP and NKB into the portal circulation could underlie further actions on adenohypophysial gonadotrophs.

Short- and long-term effects of LRRK2 on axon and dendrite growth.

PubMed

Sepulveda, Bryan; Mesias, Roxana; Li, Xianting; Yue, Zhenyu; Benson, Deanna L

2013-01-01

Mutations in leucine-rich repeat kinase 2 (LRRK2) underlie an autosomal-dominant form of Parkinson's disease (PD) that is clinically indistinguishable from idiopathic PD. The function of LRRK2 is not well understood, but it has become widely accepted that LRRK2 levels or its kinase activity, which is increased by the most commonly observed mutation (G2019S), regulate neurite growth. However, growth has not been measured; it is not known whether mean differences in length correspond to altered rates of growth or retraction, whether axons or dendrites are impacted differentially or whether effects observed are transient or sustained. To address these questions, we compared several developmental milestones in neurons cultured from mice expressing bacterial artificial chromosome transgenes encoding mouse wildtype-LRRK2 or mutant LRRK2-G2019S, Lrrk2 knockout mice and non-transgenic mice. Over the course of three weeks of development on laminin, the data show a sustained, negative effect of LRRK2-G2019S on dendritic growth and arborization, but counter to expectation, dendrites from Lrrk2 knockout mice do not elaborate more rapidly. In contrast, young neurons cultured on a slower growth substrate, poly-L-lysine, show significantly reduced axonal and dendritic motility in Lrrk2 transgenic neurons and significantly increased motility in Lrrk2 knockout neurons with no significant changes in length. Our findings support that LRRK2 can regulate patterns of axonal and dendritic growth, but they also show that effects vary depending on growth substrate and stage of development. Such predictable changes in motility can be exploited in LRRK2 bioassays and guide exploration of LRRK2 function in vivo.

Hypomyelination, memory impairment, and blood-brain barrier permeability in a model of sleep apnea.

PubMed

Kim, Lenise Jihe; Martinez, Denis; Fiori, Cintia Zappe; Baronio, Diego; Kretzmann, Nélson Alexandre; Barros, Helena Maria Tannhauser

2015-02-09

We investigated the effect of intermittent hypoxia, mimicking sleep apnea, on axonal integrity, blood-brain barrier permeability, and cognitive function of mice. Forty-seven C57BL mice were exposed to intermittent or sham hypoxia, alternating 30s of progressive hypoxia and 30s of reoxigenation, during 8h/day. The axonal integrity in cerebellum was evaluated by transmission electron microscopy. Short- and long-term memories were assessed by novel object recognition test. The levels of endothelin-1 were measured by ELISA. Blood-brain barrier permeability was quantified by Evans Blue dye. After 14 days, animals exposed to intermittent hypoxia showed hypomyelination in cerebellum white matter and higher serum levels of endothelin-1. The short and long-term memories in novel object recognition test was impaired in the group exposed to intermittent hypoxia as compared to controls. Blood-brain barrier permeability was similar between the groups. These results indicated that hypomyelination and impairment of short- and long-term working memories occurred in C57BL mice after 14 days of intermittent hypoxia mimicking sleep apnea. Copyright © 2014 Elsevier B.V. All rights reserved.

Clues to the Foundations of Numerical Cognitive Impairments: Evidence From Genetic Disorders

PubMed Central

Simon, Tony J.

2011-01-01

Several neurodevelopmental disorders of known genetic etiology generate phenotypes that share the characteristic of numerical and mathematical cognitive impairments. This article reviews some of the main findings that suggest a possible key role that spatial and temporal information processing impairments may play in the atypical development of numerical cognitive competence. The question of what neural substrate might underlie these impairments is also addressed, as are the challenges for interpreting neural structure/cognitive function mapping in atypically developing populations. PMID:21761998

Reduced Synapse and Axon Numbers in the Prefrontal Cortex of Rats Subjected to a Chronic Stress Model for Depression

PubMed Central

Csabai, Dávid; Wiborg, Ove; Czéh, Boldizsár

2018-01-01

Stressful experiences can induce structural changes in neurons of the limbic system. These cellular changes contribute to the development of stress-induced psychopathologies like depressive disorders. In the prefrontal cortex of chronically stressed animals, reduced dendritic length and spine loss have been reported. This loss of dendritic material should consequently result in synapse loss as well, because of the reduced dendritic surface. But so far, no one studied synapse numbers in the prefrontal cortex of chronically stressed animals. Here, we examined synaptic contacts in rats subjected to an animal model for depression, where animals are exposed to a chronic stress protocol. Our hypothesis was that long term stress should reduce the number of axo-spinous synapses in the medial prefrontal cortex. Adult male rats were exposed to daily stress for 9 weeks and afterward we did a post mortem quantitative electron microscopic analysis to quantify the number and morphology of synapses in the infralimbic cortex. We analyzed asymmetric (Type I) and symmetric (Type II) synapses in all cortical layers in control and stressed rats. We also quantified axon numbers and measured the volume of the infralimbic cortex. In our systematic unbiased analysis, we examined 21,000 axon terminals in total. We found the following numbers in the infralimbic cortex of control rats: 1.15 × 109 asymmetric synapses, 1.06 × 108 symmetric synapses and 1.00 × 108 myelinated axons. The density of asymmetric synapses was 5.5/μm3 and the density of symmetric synapses was 0.5/μm3. Average synapse membrane length was 207 nm and the average axon terminal membrane length was 489 nm. Stress reduced the number of synapses and myelinated axons in the deeper cortical layers, while synapse membrane lengths were increased. These stress-induced ultrastructural changes indicate that neurons of the infralimbic cortex have reduced cortical network connectivity. Such reduced network connectivity is likely to form the anatomical basis for the impaired functioning of this brain area. Indeed, impaired functioning of the prefrontal cortex, such as cognitive deficits are common in stressed individuals as well as in depressed patients. PMID:29440995

LKB1 Regulates Mitochondria-Dependent Presynaptic Calcium Clearance and Neurotransmitter Release Properties at Excitatory Synapses along Cortical Axons.

PubMed

Kwon, Seok-Kyu; Sando, Richard; Lewis, Tommy L; Hirabayashi, Yusuke; Maximov, Anton; Polleux, Franck

2016-07-01

Individual synapses vary significantly in their neurotransmitter release properties, which underlie complex information processing in neural circuits. Presynaptic Ca2+ homeostasis plays a critical role in specifying neurotransmitter release properties, but the mechanisms regulating synapse-specific Ca2+ homeostasis in the mammalian brain are still poorly understood. Using electrophysiology and genetically encoded Ca2+ sensors targeted to the mitochondrial matrix or to presynaptic boutons of cortical pyramidal neurons, we demonstrate that the presence or absence of mitochondria at presynaptic boutons dictates neurotransmitter release properties through Mitochondrial Calcium Uniporter (MCU)-dependent Ca2+ clearance. We demonstrate that the serine/threonine kinase LKB1 regulates MCU expression, mitochondria-dependent Ca2+ clearance, and thereby, presynaptic release properties. Re-establishment of MCU-dependent mitochondrial Ca2+ uptake at glutamatergic synapses rescues the altered neurotransmitter release properties characterizing LKB1-null cortical axons. Our results provide novel insights into the cellular and molecular mechanisms whereby mitochondria control neurotransmitter release properties in a bouton-specific way through presynaptic Ca2+ clearance.

Circuit Architecture of VTA Dopamine Neurons Revealed by Systematic Input-Output Mapping.

PubMed

Beier, Kevin T; Steinberg, Elizabeth E; DeLoach, Katherine E; Xie, Stanley; Miyamichi, Kazunari; Schwarz, Lindsay; Gao, Xiaojing J; Kremer, Eric J; Malenka, Robert C; Luo, Liqun

2015-07-30

Dopamine (DA) neurons in the midbrain ventral tegmental area (VTA) integrate complex inputs to encode multiple signals that influence motivated behaviors via diverse projections. Here, we combine axon-initiated viral transduction with rabies-mediated trans-synaptic tracing and Cre-based cell-type-specific targeting to systematically map input-output relationships of VTA-DA neurons. We found that VTA-DA (and VTA-GABA) neurons receive excitatory, inhibitory, and modulatory input from diverse sources. VTA-DA neurons projecting to different forebrain regions exhibit specific biases in their input selection. VTA-DA neurons projecting to lateral and medial nucleus accumbens innervate largely non-overlapping striatal targets, with the latter also sending extensive extra-striatal axon collaterals. Using electrophysiology and behavior, we validated new circuits identified in our tracing studies, including a previously unappreciated top-down reinforcing circuit from anterior cortex to lateral nucleus accumbens via VTA-DA neurons. This study highlights the utility of our viral-genetic tracing strategies to elucidate the complex neural substrates that underlie motivated behaviors. Copyright © 2015 Elsevier Inc. All rights reserved.

Beyond Columnar Organization: Cell Type- and Target Layer-Specific Principles of Horizontal Axon Projection Patterns in Rat Vibrissal Cortex

PubMed Central

Narayanan, Rajeevan T.; Egger, Robert; Johnson, Andrew S.; Mansvelder, Huibert D.; Sakmann, Bert; de Kock, Christiaan P.J.; Oberlaender, Marcel

2015-01-01

Vertical thalamocortical afferents give rise to the elementary functional units of sensory cortex, cortical columns. Principles that underlie communication between columns remain however unknown. Here we unravel these by reconstructing in vivo-labeled neurons from all excitatory cell types in the vibrissal part of rat primary somatosensory cortex (vS1). Integrating the morphologies into an exact 3D model of vS1 revealed that the majority of intracortical (IC) axons project far beyond the borders of the principal column. We defined the corresponding innervation volume as the IC-unit. Deconstructing this structural cortical unit into its cell type-specific components, we found asymmetric projections that innervate columns of either the same whisker row or arc, and which subdivide vS1 into 2 orthogonal [supra-]granular and infragranular strata. We show that such organization could be most effective for encoding multi whisker inputs. Communication between columns is thus organized by multiple highly specific horizontal projection patterns, rendering IC-units as the primary structural entities for processing complex sensory stimuli. PMID:25838038

The role of muscle spindles in the development of the monosynaptic stretch reflex

PubMed Central

Wang, Zhi; Li, LingYing

2012-01-01

Muscle sensory axons induce the development of specialized intrafusal muscle fibers in muscle spindles during development, but the role that the intrafusal fibers may play in the development of the central projections of these Ia sensory axons is unclear. In the present study, we assessed the influence of intrafusal fibers in muscle spindles on the formation of monosynaptic connections between Ia (muscle spindle) sensory axons and motoneurons (MNs) using two transgenic strains of mice. Deletion of the ErbB2 receptor from developing myotubes disrupts the formation of intrafusal muscle fibers and causes a nearly complete absence of functional synaptic connections between Ia axons and MNs. Monosynaptic connectivity can be fully restored by postnatal administration of neurotrophin-3 (NT-3), and the synaptic connections in NT-3-treated mice are as specific as in wild-type mice. Deletion of the Egr3 transcription factor also impairs the development of intrafusal muscle fibers and disrupts synaptic connectivity between Ia axons and MNs. Postnatal injections of NT-3 restore the normal strengths and specificity of Ia–motoneuronal connections in these mice as well. Severe deficits in intrafusal fiber development, therefore, do not disrupt the establishment of normal, selective patterns of connections between Ia axons and MNs, although these connections require the presence of NT-3, normally supplied by intrafusal fibers, to be functional. PMID:22490553

Class I PI3-kinase or Akt inhibition do not impair axonal polarization, but slow down axonal elongation.

PubMed

Diez, Héctor; Benitez, Ma José; Fernandez, Silvia; Torres-Aleman, Ignacio; Garrido, Juan José; Wandosell, Francisco

2016-11-01

PI3K proteins family have multiple and essential functions in most cellular events. This family is composed of class I, class II and class III PI3Ks, which upstream and downstream elements are not completely elucidated. Previous studies using the broad PI3K inhibitor, LY294002 allowed to propose that PI3 kinase>Akt pathway is a key element in the determination of axonal polarity in hippocampal neurons. Recently, new inhibitors with a higher selectivity for class I PI3K have been characterized. In the present study we have examined this widely accepted theory using a new class I PI3K inhibitor (GDC-0941), as well as Akt inhibitors, and PTEN phosphatase constructs to reduce PIP3 levels. Our present data show that both, class I PI3K inhibitor and Akt inhibitor did not alter axon specification in hippocampal neurons, but greatly reduced axon length. However, in the same experiments LY294002 effectively impeded axonal polarization, as previously reported. Our biochemical data show that both, class I PI3K and Akt inhibitors, effectively block downstream elements from Akt to S6K1 activity. Both inhibitors are stable in culture medium along the time period analysed, maintaining the inhibition better than LY294002. Besides, we found evidence that LY294002 directly inhibits mTORC1. However, further analysis using an mTORC1 inhibitor showed no change in neuron polarity. Same result was obtained using a general class III PI3K inhibitor. Interestingly, we found that either, wild-type PTEN, or a phosphatase-dead form of PTEN, disrupted axonal polarization, strongly suggesting that the role of PTEN in axonal polarity can be independent of PIP3. Copyright © 2016 Elsevier B.V. All rights reserved.

Differential expression of glucose-metabolizing enzymes in multiple sclerosis lesions.

PubMed

Nijland, Philip G; Molenaar, Remco J; van der Pol, Susanne M A; van der Valk, Paul; van Noorden, Cornelis J F; de Vries, Helga E; van Horssen, Jack

2015-12-04

Demyelinated axons in multiple sclerosis (MS) lesions have an increased energy demand in order to maintain conduction. However, oxidative stress-induced mitochondrial dysfunction likely alters glucose metabolism and consequently impairs neuronal function in MS. Imaging and pathological studies indicate that glucose metabolism is altered in MS, although the underlying mechanisms and its role in neurodegeneration remain elusive. We investigated expression patterns of key enzymes involved in glycolysis, tricarboxylic acid (TCA) cycle and lactate metabolism in well-characterized MS tissue to establish which regulators of glucose metabolism are involved in MS and to identify underlying mechanisms. Expression levels of glycolytic enzymes were increased in active and inactive MS lesions, whereas expression levels of enzymes involved in the TCA cycle were upregulated in active MS lesions, but not in inactive MS lesions. We observed reduced expression and production capacity of mitochondrial α-ketoglutarate dehydrogenase (αKGDH) in demyelinated axons, which correlated with signs of axonal dysfunction. In inactive lesions, increased expression of lactate-producing enzymes was observed in astrocytes, whereas lactate-catabolising enzymes were mainly detected in axons. Our results demonstrate that the expression of various enzymes involved in glucose metabolism is increased in both astrocytes and axons in active MS lesions. In inactive MS lesions, we provide evidence that astrocytes undergo a glycolytic shift resulting in enhanced astrocyte-axon lactate shuttling, which may be pivotal for the survival of demyelinated axons. In conclusion, we show that key enzymes involved in energy metabolism are differentially expressed in active and inactive MS lesions. Our findings imply that, in addition to reduced oxidative phosphorylation activity, other bioenergetic pathways are affected as well, which may contribute to ongoing axonal degeneration in MS.

Pyramidal tract stimulation restores normal corticospinal tract connections and visuomotor skill after early postnatal motor cortex activity blockade

PubMed Central

Salimi, I; Friel, KM; Martin, JH

2008-01-01

Motor development depends on forming specific connections between the corticospinal tract (CST) and the spinal cord. Blocking CST activity in kittens during the critical period for establishing connections with spinal motor circuits results in permanent impairments in connectivity and function. The changes in connections are consistent with the hypothesis that the inactive tract is less competitive in developing spinal connections than the active tract. In this study we tested the competition hypothesis by determining if activating CST axons, after prior silencing during the critical period, abrogated development of aberrant corticospinal connections and motor impairments. In kittens, we inactivated motor cortex by muscimol infusion between postnatal weeks 5-7. We next electrically stimulated CST axons in the medullary pyramid 2.5 hours daily, between weeks 7-10. In controls (n=3), CST terminations were densest within the contralateral deeper, premotor, spinal layers. After prior inactivation (n=3), CST terminations were densest within the dorsal, somatic sensory, layers. There were more ipsilateral terminations from the active tract. During visually guided locomotion, there was a movement endpoint impairment. Stimulation after inactivation (n=6) resulted in significantly fewer terminations in the sensory layers and more in the premotor layers, and fewer ipsilateral connections from active cortex. Chronic stimulation reduced the current threshold for evoking contralateral movements by pyramidal stimulation, suggesting strengthening of connections. Importantly, stimulation significantly improved stepping accuracy. These findings show the importance of activity-dependent processes in specifying CST connections. They also provide a strategy for harnessing activity to rescue CST axons at risk of developing aberrant connections after CNS injury. PMID:18632946

Outer Electrospun Polycaprolactone Shell Induces Massive Foreign Body Reaction and Impairs Axonal Regeneration through 3D Multichannel Chitosan Nerve Guides

PubMed Central

Behrens, Peter; Wienecke, Soenke; Chakradeo, Tanmay; Glasmacher, Birgit

2014-01-01

We report on the performance of composite nerve grafts with an inner 3D multichannel porous chitosan core and an outer electrospun polycaprolactone shell. The inner chitosan core provided multiple guidance channels for regrowing axons. To analyze the in vivo properties of the bare chitosan cores, we separately implanted them into an epineural sheath. The effects of both graft types on structural and functional regeneration across a 10 mm rat sciatic nerve gap were compared to autologous nerve transplantation (ANT). The mechanical biomaterial properties and the immunological impact of the grafts were assessed with histological techniques before and after transplantation in vivo. Furthermore during a 13-week examination period functional tests and electrophysiological recordings were performed and supplemented by nerve morphometry. The sheathing of the chitosan core with a polycaprolactone shell induced massive foreign body reaction and impairment of nerve regeneration. Although the isolated novel chitosan core did allow regeneration of axons in a similar size distribution as the ANT, the ANT was superior in terms of functional regeneration. We conclude that an outer polycaprolactone shell should not be used for the purpose of bioartificial nerve grafting, while 3D multichannel porous chitosan cores could be candidate scaffolds for structured nerve grafts. PMID:24818158

Outer electrospun polycaprolactone shell induces massive foreign body reaction and impairs axonal regeneration through 3D multichannel chitosan nerve guides.

PubMed

Duda, Sven; Dreyer, Lutz; Behrens, Peter; Wienecke, Soenke; Chakradeo, Tanmay; Glasmacher, Birgit; Haastert-Talini, Kirsten

2014-01-01

We report on the performance of composite nerve grafts with an inner 3D multichannel porous chitosan core and an outer electrospun polycaprolactone shell. The inner chitosan core provided multiple guidance channels for regrowing axons. To analyze the in vivo properties of the bare chitosan cores, we separately implanted them into an epineural sheath. The effects of both graft types on structural and functional regeneration across a 10 mm rat sciatic nerve gap were compared to autologous nerve transplantation (ANT). The mechanical biomaterial properties and the immunological impact of the grafts were assessed with histological techniques before and after transplantation in vivo. Furthermore during a 13-week examination period functional tests and electrophysiological recordings were performed and supplemented by nerve morphometry. The sheathing of the chitosan core with a polycaprolactone shell induced massive foreign body reaction and impairment of nerve regeneration. Although the isolated novel chitosan core did allow regeneration of axons in a similar size distribution as the ANT, the ANT was superior in terms of functional regeneration. We conclude that an outer polycaprolactone shell should not be used for the purpose of bioartificial nerve grafting, while 3D multichannel porous chitosan cores could be candidate scaffolds for structured nerve grafts.

Prevention of posttraumatic axon sprouting by blocking CRMP2-mediated neurite outgrowth and tubulin polymerization

PubMed Central

Wilson, Sarah M.; Xiong, Wenhui; Wang, Yuying; Ping, Xingjie; Head, Jessica D.; Brittain, Joel M.; Gagare, Pravin D.; Ramachandran, P. Veeraraghavan; Jin, Xiaoming; Khanna, Rajesh

2012-01-01

Epileptogenesis following traumatic brain injury (TBI) is likely due to a combination of increased excitability, disinhibition, and increased excitatory connectivity via aberrant axon sprouting. Targeting these pathways could be beneficial in the prevention and treatment of posttraumatic epilepsy. Here, we tested this possibility using the novel anticonvulsant (R)-N-benzyl 2-acetamido-3-methoxypropionamide ((R)-lacosamide (LCM) which acts on both voltage-gated sodium channels and collapsin response mediator protein 2 (CRMP2), an axonal growth/guidance protein. LCM inhibited CRMP2-mediated neurite outgrowth, an effect phenocopied by CRMP2 knockdown. Mutation of LCM binding sites in CRMP2 reduced the neurite inhibitory effect of LCM by ~8-fold. LCM also reduced CRMP2-mediated tubulin polymerization. Thus, LCM selectively impairs CRMP2-mediated microtubule polymerization which underlies its neurite outgrowth and branching. To determine whether LCM inhibits axon sprouting in vivo, LCM was injected into rats subjected to partial cortical isolation, an animal model of posttraumatic epileptogenesis that exhibits axon sprouting in cortical pyramidal neurons. Two weeks following injury, excitatory synaptic connectivity of cortical layer V pyramidal neurons was mapped using patch clamp recordings and laser scanning photostimulation of caged glutamate. In comparison to injured control animals, there was a significant decrease in the map size of excitatory synaptic connectivity in LCM-treated rats, suggesting that LCM treatment prevented enhanced excitatory synaptic connectivity due to posttraumatic axon sprouting. These findings suggest, for the first time, that LCM’s mode of action involves interactions with CRMP2 to inhibit posttraumatic axon sprouting. PMID:22433297

Doublecortin associates with microtubules preferentially in regions of the axon displaying actin-rich protrusive structures

PubMed Central

Tint, Irina; Jean, Daphney; Baas, Peter W.; Black, Mark M.

2009-01-01

Here we studied doublecortin (DCX) in cultured hippocampal and sympathetic neurons during axonal development. In both types of neurons, DCX is abundant in the growth cone, where it primarily localizes with microtubules. Its abundance is lowest on microtubules in the neck region of the growth cone and highest on microtubules extending into the actin-rich lamellar regions. Interestingly, the microtubule polymer richest in DCX is also deficient in tau. In hippocampal neurons but not sympathetic neurons, discrete focal patches of microtubules rich in DCX and deficient in tau are present along the axonal shaft. Invariably, these patches have actin-rich protrusions resembling those of growth cones. Many of the DCX/actin filament patches exhibit vigorous protrusive activity and also undergo a proximal-to-distal redistribution within the axon at average rates ≈ 2 μm/min, and thus closely resemble the growth-cone-like waves described by previous authors. Depletion of DCX using siRNA had little effect on the appearance of the growth cone or on axonal growth in either type of neuron. However, DCX depletion significantly delayed collateral branching in hippocampal neurons and also significantly lowered the frequency of actin-rich patches along hippocampal axons. Branching by sympathetic neurons, which occurs by growth cone splitting, was not impaired by DCX depletion. These findings reveal a functional relationship between the DCX/actin filament patches and collateral branching. Based on the striking resemblance of these patches to growth cones, we discuss the possibility that they reflect a mechanism for locally boosting morphogenetic activity to facilitate axonal growth and collateral branching. PMID:19726658

A Select Subset of Electron Transport Chain Genes Associated with Optic Atrophy Link Mitochondria to Axon Regeneration in Caenorhabditis elegans.

PubMed

Knowlton, Wendy M; Hubert, Thomas; Wu, Zilu; Chisholm, Andrew D; Jin, Yishi

2017-01-01

The role of mitochondria within injured neurons is an area of active interest since these organelles are vital for the production of cellular energy in the form of ATP. Using mechanosensory neurons of the nematode Caenorhabditis elegans to test regeneration after neuronal injury in vivo , we surveyed genes related to mitochondrial function for effects on axon regrowth after laser axotomy. Genes involved in mitochondrial transport, calcium uptake, mitophagy, or fission and fusion were largely dispensable for axon regrowth, with the exception of eat-3/Opa1 . Surprisingly, many genes encoding components of the electron transport chain were dispensable for regrowth, except for the iron-sulfur proteins gas-1, nduf-2.2, nduf-7 , and isp-1 , and the putative oxidoreductase rad-8 . In these mutants, axonal development was essentially normal and axons responded normally to injury by forming regenerative growth cones, but were impaired in subsequent axon extension. Overexpression of nduf-2.2 or isp-1 was sufficient to enhance regrowth, suggesting that mitochondrial function is rate-limiting in axon regeneration. Moreover, loss of function in isp-1 reduced the enhanced regeneration caused by either a gain-of-function mutation in the calcium channel EGL-19 or overexpression of the MAP kinase DLK-1. While the cellular function of RAD-8 remains unclear, our genetic analyses place rad-8 in the same pathway as other electron transport genes in axon regeneration. Unexpectedly, rad-8 regrowth defects were suppressed by altered function in the ubiquinone biosynthesis gene clk-1 . Furthermore, we found that inhibition of the mitochondrial unfolded protein response via deletion of atfs-1 suppressed the defective regrowth in nduf-2.2 mutants. Together, our data indicate that while axon regeneration is not significantly affected by general dysfunction of cellular respiration, it is sensitive to the proper functioning of a select subset of electron transport chain genes, or to the cellular adaptations used by neurons under conditions of injury.

A Select Subset of Electron Transport Chain Genes Associated with Optic Atrophy Link Mitochondria to Axon Regeneration in Caenorhabditis elegans

PubMed Central

Knowlton, Wendy M.; Hubert, Thomas; Wu, Zilu; Chisholm, Andrew D.; Jin, Yishi

2017-01-01

The role of mitochondria within injured neurons is an area of active interest since these organelles are vital for the production of cellular energy in the form of ATP. Using mechanosensory neurons of the nematode Caenorhabditis elegans to test regeneration after neuronal injury in vivo, we surveyed genes related to mitochondrial function for effects on axon regrowth after laser axotomy. Genes involved in mitochondrial transport, calcium uptake, mitophagy, or fission and fusion were largely dispensable for axon regrowth, with the exception of eat-3/Opa1. Surprisingly, many genes encoding components of the electron transport chain were dispensable for regrowth, except for the iron-sulfur proteins gas-1, nduf-2.2, nduf-7, and isp-1, and the putative oxidoreductase rad-8. In these mutants, axonal development was essentially normal and axons responded normally to injury by forming regenerative growth cones, but were impaired in subsequent axon extension. Overexpression of nduf-2.2 or isp-1 was sufficient to enhance regrowth, suggesting that mitochondrial function is rate-limiting in axon regeneration. Moreover, loss of function in isp-1 reduced the enhanced regeneration caused by either a gain-of-function mutation in the calcium channel EGL-19 or overexpression of the MAP kinase DLK-1. While the cellular function of RAD-8 remains unclear, our genetic analyses place rad-8 in the same pathway as other electron transport genes in axon regeneration. Unexpectedly, rad-8 regrowth defects were suppressed by altered function in the ubiquinone biosynthesis gene clk-1. Furthermore, we found that inhibition of the mitochondrial unfolded protein response via deletion of atfs-1 suppressed the defective regrowth in nduf-2.2 mutants. Together, our data indicate that while axon regeneration is not significantly affected by general dysfunction of cellular respiration, it is sensitive to the proper functioning of a select subset of electron transport chain genes, or to the cellular adaptations used by neurons under conditions of injury. PMID:28539870

Early and Selective Impairments in Axonal Transport Kinetics of Synaptic Cargoes Induced by Soluble Amyloid β-Protein Oligomers

PubMed Central

Tang, Yong; Scott, David A.; Das, Utpal; Edland, Steven D.; Radomski, Kryslaine; Koo, Edward H.; Roy, Subhojit

2013-01-01

The downstream targets of amyloid β (Aβ)-oligomers remain elusive. One hypothesis is that Aβ-oligomers interrupt axonal transport. Although previous studies have demonstrated Aβ-induced transport blockade, early effects of low-n soluble Aβ-oligomers on axonal transport remain unclear. Furthermore, the cargo selectivity for such deficits (if any) or the specific effects of Aβ on the motility kinetics of transported cargoes are also unknown. Toward this, we visualized axonal transport of vesicles in cultured hippocampal neurons treated with picomolar (pm) levels of cell-derived soluble Aβ-oligomers. We examined select cargoes thought to move as distinct organelles and established imaging parameters that allow organelle tracking with consistency and high fidelity – analyzing all data in a blinded fashion. Aβ-oligomers induced early and selective diminutions in velocities of synaptic cargoes but had no effect on mitochondrial motility, contrary to previous reports. These changes were N-methyl d-aspartate receptor/glycogen synthase kinase-3β dependent and reversible upon washout of the oligomers. Cluster-mode analyses reveal selective attenuations in faster-moving synaptic vesicles, suggesting possible decreases in cargo/motor associations, and biochemical experiments implicate tau phosphorylation in the process. Collectively, the data provide a biological basis for Aβ-induced axonal transport deficits. PMID:22309053

Decreased number and increased volume with mitochondrial enlargement of cerebellar synaptic terminals in a mouse model of chronic demyelination.

PubMed

Nguyen, Huy Bang; Sui, Yang; Thai, Truc Quynh; Ikenaka, Kazuhiro; Oda, Toshiyuki; Ohno, Nobuhiko

2018-05-23

Impaired nerve conduction, axonal degeneration, and synaptic alterations contribute to neurological disabilities in inflammatory demyelinating diseases. Cerebellar dysfunction is associated with demyelinating disorders, but the alterations of axon terminals in cerebellar gray matter during chronic demyelination are still unclear. We analyzed the morphological and ultrastructural changes of climbing fiber terminals in a mouse model of hereditary chronic demyelination. Three-dimensional ultrastructural analyses using serial block-face scanning electron microscopy and immunostaining for synaptic markers were performed in a demyelination mouse model caused by extra copies of myelin gene (PLP4e). At 1 month old, many myelinated axons were observed in PLP4e and wild-type mice, but demyelinated axons and axons with abnormally thin myelin were prominent in PLP4e mice at 5 months old. The density of climbing fiber terminals was significantly reduced in PLP4e mice at 5 months old. Reconstruction of climbing fiber terminals revealed that PLP4e climbing fibers had increased varicosity volume and enlarged mitochondria in the varicosities at 5-month-old mice. These results suggest that chronic demyelination is associated with alterations and loss of climbing fiber terminals in the cerebellar cortex, and that synaptic changes may contribute to cerebellar phenotypes observed in hereditary demyelinating disorders.

Modifications of Gustatory Nerve Synapses onto Nucleus of the Solitary Tract Neurons Induced by Dietary Sodium-Restriction During Development

PubMed Central

MAY, OLIVIA L.; ERISIR, ALEV; HILL, DAVID L.

2008-01-01

The terminal fields of nerves carrying gustatory information to the rat brainstem show a remarkable amount of expansion in the nucleus of the solitary tract (NTS) as a result of early dietary sodium restriction. However, the extent to which these axonal changes represent corresponding changes in synapses is not known. To identify the synaptic characteristics that accompany the terminal field expansion, the greater superficial petrosal (GSP), chorda tympani (CT), and glossopharyngeal (IX) nerves were labeled in rats fed a sodium-restricted diet during pre- and postnatal development. The morphology of these nerve terminals within the NTS region where the terminal fields of all three nerves overlap was evaluated by transmission electron microscopy. Compared to data from control rats, CT axons were the most profoundly affected. The density of CT arbors and synapses quadrupled as a result of the near life-long dietary manipulation. In contrast, axon and synapse densities of GSP and IX nerves were not modified in sodium-restricted rats. Furthermore, compared to controls, CT terminals displayed more instances of contacts with postsynaptic dendritic protrusions and IX terminals synapsed more frequently with dendritic shafts. Thus, dietary sodium restriction throughout pre- and postnatal development had differential effects on the synaptic organization of the three nerves in the NTS. These anatomical changes may underlie the impact of sensory restriction during development on the functional processing of taste information and taste-related behaviors. PMID:18366062

Modifications of gustatory nerve synapses onto nucleus of the solitary tract neurons induced by dietary sodium-restriction during development.

PubMed

May, Olivia L; Erisir, Alev; Hill, David L

2008-06-01

The terminal fields of nerves carrying gustatory information to the rat brainstem show a remarkable amount of expansion in the nucleus of the solitary tract (NTS) as a result of early dietary sodium restriction. However, the extent to which these axonal changes represent corresponding changes in synapses is not known. To identify the synaptic characteristics that accompany the terminal field expansion, the greater superficial petrosal (GSP), chorda tympani (CT), and glossopharyngeal (IX) nerves were labeled in rats fed a sodium-restricted diet during pre- and postnatal development. The morphology of these nerve terminals within the NTS region where the terminal fields of all three nerves overlap was evaluated by transmission electron microscopy. Compared to data from control rats, CT axons were the most profoundly affected. The density of CT arbors and synapses quadrupled as a result of the near life-long dietary manipulation. In contrast, axon and synapse densities of GSP and IX nerves were not modified in sodium-restricted rats. Furthermore, compared to controls, CT terminals displayed more instances of contacts with postsynaptic dendritic protrusions and IX terminals synapsed more frequently with dendritic shafts. Thus, dietary sodium restriction throughout pre- and postnatal development had differential effects on the synaptic organization of the three nerves in the NTS. These anatomical changes may underlie the impact of sensory restriction during development on the functional processing of taste information and taste-related behaviors.

Structural Correlates of Reading the Mind in the Eyes in Autism Spectrum Disorder.

PubMed

Sato, Wataru; Uono, Shota; Kochiyama, Takanori; Yoshimura, Sayaka; Sawada, Reiko; Kubota, Yasutaka; Sakihama, Morimitsu; Toichi, Motomi

2017-01-01

Behavioral studies have shown that individuals with autism spectrum disorder (ASD) have impaired ability to read the mind in the eyes. Although this impairment is central to their social malfunctioning, its structural neural correlates remain unclear. To investigate this issue, we assessed Reading the Mind in the Eyes Test, revised version (Eyes Test) and acquired structural magnetic resonance images in adults with high-functioning ASD ( n = 19) and age-, sex- and intelligence quotient-matched typically developing (TD) controls ( n = 19). On the behavioral level, the Eyes Test scores were lower in the ASD group than in the control group. On the neural level, an interaction between group and Eyes Test score was found in the left temporoparietal junction (TPJ). A positive association between the Eyes Test score and gray matter volume of this region was evident in the control group, but not in the ASD group. This finding suggests that the failure to develop appropriate structural neural representations in the TPJ may underlie the impaired ability of individuals with ASD to read the mind in the eyes. These behavioral and neural findings provide support for the theories that impairments in processing eyes and the ability to infer others' mental states are the core symptoms of ASD, and that atypical features in the social brain network underlie such impairments.

Aurora kinase B regulates axonal outgrowth and regeneration in the spinal motor neurons of developing zebrafish.

PubMed

Gwee, Serene S L; Radford, Rowan A W; Chow, Sharron; Syal, Monisha D; Morsch, Marco; Formella, Isabel; Lee, Albert; Don, Emily K; Badrock, Andrew P; Cole, Nicholas J; West, Adrian K; Cheung, Steve N S; Chung, Roger S

2018-02-21

Aurora kinase B (AurkB) is a serine/threonine protein kinase with a well-characterised role in orchestrating cell division and cytokinesis, and is prominently expressed in healthy proliferating and cancerous cells. However, the role of AurkB in differentiated and non-dividing cells has not been extensively explored. Previously, we have described a significant upregulation of AurkB expression in cultured cortical neurons following an experimental axonal transection. This is somewhat surprising, as AurkB expression is generally associated only with dividing cells Frangini et al. (Mol Cell 51:647-661, 2013); Hegarat et al. (J Cell Biol 195:1103-1113, 2011); Lu et al. (J Biol Chem 283:31785-31790, 2008); Trakala et al. (Cell Cycle 12:1030-1041, 2014). Herein, we present the first description of a role for AurkB in terminally differentiated neurons. AurkB was prominently expressed within post-mitotic neurons of the zebrafish brain and spinal cord. The expression of AurkB varied during the development of the zebrafish spinal motor neurons. Utilising pharmacological and genetic manipulation to impair AurkB activity resulted in truncation and aberrant motor axon morphology, while overexpression of AurkB resulted in extended axonal outgrowth. Further pharmacological inhibition of AurkB activity in regenerating axons delayed their recovery following UV laser-mediated injury. Collectively, these results suggest a hitherto unreported role of AurkB in regulating neuronal development and axonal outgrowth.

A Novel Internal Fixator Device for Peripheral Nerve Regeneration

PubMed Central

Chuang, Ting-Hsien; Wilson, Robin E.; Love, James M.; Fisher, John P.

2013-01-01

Recovery from peripheral nerve damage, especially for a transected nerve, is rarely complete, resulting in impaired motor function, sensory loss, and chronic pain with inappropriate autonomic responses that seriously impair quality of life. In consequence, strategies for enhancing peripheral nerve repair are of high clinical importance. Tension is a key determinant of neuronal growth and function. In vitro and in vivo experiments have shown that moderate levels of imposed tension (strain) can encourage axonal outgrowth; however, few strategies of peripheral nerve repair emphasize the mechanical environment of the injured nerve. Toward the development of more effective nerve regeneration strategies, we demonstrate the design, fabrication, and implementation of a novel, modular nerve-lengthening device, which allows the imposition of moderate tensile loads in parallel with existing scaffold-based tissue engineering strategies for nerve repair. This concept would enable nerve regeneration in two superposed regimes of nerve extension—traditional extension through axonal outgrowth into a scaffold and extension in intact regions of the proximal nerve, such as that occurring during growth or limb-lengthening. Self-sizing silicone nerve cuffs were fabricated to grip nerve stumps without slippage, and nerves were deformed by actuating a telescoping internal fixator. Poly(lactic co-glycolic) acid (PLGA) constructs mounted on the telescoping rods were apposed to the nerve stumps to guide axonal outgrowth. Neuronal cells were exposed to PLGA using direct contact and extract methods, and they exhibited no signs of cytotoxic effects in terms of cell morphology and viability. We confirmed the feasibility of implanting and actuating our device within a sciatic nerve gap and observed axonal outgrowth following device implantation. The successful fabrication and implementation of our device provides a novel method for examining mechanical influences on nerve regeneration. PMID:23102114

Disconnection of network hubs and cognitive impairment after traumatic brain injury.

PubMed

Fagerholm, Erik D; Hellyer, Peter J; Scott, Gregory; Leech, Robert; Sharp, David J

2015-06-01

Traumatic brain injury affects brain connectivity by producing traumatic axonal injury. This disrupts the function of large-scale networks that support cognition. The best way to describe this relationship is unclear, but one elegant approach is to view networks as graphs. Brain regions become nodes in the graph, and white matter tracts the connections. The overall effect of an injury can then be estimated by calculating graph metrics of network structure and function. Here we test which graph metrics best predict the presence of traumatic axonal injury, as well as which are most highly associated with cognitive impairment. A comprehensive range of graph metrics was calculated from structural connectivity measures for 52 patients with traumatic brain injury, 21 of whom had microbleed evidence of traumatic axonal injury, and 25 age-matched controls. White matter connections between 165 grey matter brain regions were defined using tractography, and structural connectivity matrices calculated from skeletonized diffusion tensor imaging data. This technique estimates injury at the centre of tract, but is insensitive to damage at tract edges. Graph metrics were calculated from the resulting connectivity matrices and machine-learning techniques used to select the metrics that best predicted the presence of traumatic brain injury. In addition, we used regularization and variable selection via the elastic net to predict patient behaviour on tests of information processing speed, executive function and associative memory. Support vector machines trained with graph metrics of white matter connectivity matrices from the microbleed group were able to identify patients with a history of traumatic brain injury with 93.4% accuracy, a result robust to different ways of sampling the data. Graph metrics were significantly associated with cognitive performance: information processing speed (R(2) = 0.64), executive function (R(2) = 0.56) and associative memory (R(2) = 0.25). These results were then replicated in a separate group of patients without microbleeds. The most influential graph metrics were betweenness centrality and eigenvector centrality, which provide measures of the extent to which a given brain region connects other regions in the network. Reductions in betweenness centrality and eigenvector centrality were particularly evident within hub regions including the cingulate cortex and caudate. Our results demonstrate that betweenness centrality and eigenvector centrality are reduced within network hubs, due to the impact of traumatic axonal injury on network connections. The dominance of betweenness centrality and eigenvector centrality suggests that cognitive impairment after traumatic brain injury results from the disconnection of network hubs by traumatic axonal injury. © The Author (2015). Published by Oxford University Press on behalf of the Guarantors of Brain.

Spatacsin and spastizin act in the same pathway required for proper spinal motor neuron axon outgrowth in zebrafish.

PubMed

Martin, Elodie; Yanicostas, Constantin; Rastetter, Agnès; Alavi Naini, Seyedeh Maryam; Maouedj, Alissia; Kabashi, Edor; Rivaud-Péchoux, Sophie; Brice, Alexis; Stevanin, Giovanni; Soussi-Yanicostas, Nadia

2012-12-01

Hereditary spastic paraplegias (HSPs) are rare neurological conditions caused by degeneration of the long axons of the cerebrospinal tracts, leading to locomotor impairment and additional neurological symptoms. There are more than 40 different causative genes, 24 of which have been identified, including SPG11 and SPG15 mutated in complex clinical forms. Since the vast majority of the causative mutations lead to loss of function of the corresponding proteins, we made use of morpholino-oligonucleotide (MO)-mediated gene knock-down to generate zebrafish models of both SPG11 and SPG15 and determine how invalidation of the causative genes (zspg11 and zspg15) during development might contribute to the disease. Micro-injection of MOs targeting each gene caused locomotor impairment and abnormal branching of spinal cord motor neurons at the neuromuscular junction. More severe phenotypes with abnormal tail developments were also seen. Moreover, partial depletion of both proteins at sub-phenotypic levels resulted in the same phenotypes, suggesting for the first time, in vivo, a genetic interaction between these genes. In conclusion, the zebrafish orthologues of the SPG11 and SPG15 genes are important for proper development of the axons of spinal motor neurons and likely act in a common pathway to promote their proper path finding towards the neuromuscular junction. Copyright © 2012 Elsevier Inc. All rights reserved.

Chronic restraint stress during early Theiler’s virus infection exacerbates the subsequent demyelinating disease in SJL mice: II. CNS disease severity

PubMed Central

Young, Erin E.; Sieve, Amy N.; Vichaya, Elisabeth G.; Carcoba, Luis M.; Young, Colin R.; Ambrus, Andrew; Storts, Ralph; Welsh, C. Jane R.; Meagher, Mary W.

2010-01-01

Theiler’s murine encephalomyelitis virus (TMEV) infection is a well-characterized model of multiple sclerosis (MS). Previous research has shown that chronic restraint stress (RS) during early TMEV infection exacerbates behavioral signs of disease. The present data suggest RS-induced increases in CNS inflammation, demyelination, and axonal degeneration may underlie this exacerbation. In addition, we report that males exhibit greater CNS inflammation and higher numbers of demyelinating lesions while females show greater susceptibility to RS-induced exacerbation. These findings indicate RS during early TMEV infection increases CNS lesion formation during the late phase and suggest the effects of RS are sex-dependent. PMID:20167380

Inner tegument proteins of Herpes Simplex Virus are sufficient for intracellular capsid motility in neurons but not for axonal targeting

PubMed Central

Müller, Oliver; Ivanova, Lyudmila; Bialy, Dagmara; Pohlmann, Anja; Binz, Anne; Hegemann, Maike; Viejo-Borbolla, Abel; Rosenhahn, Bodo; Bauerfeind, Rudolf; Sodeik, Beate

2017-01-01

Upon reactivation from latency and during lytic infections in neurons, alphaherpesviruses assemble cytosolic capsids, capsids associated with enveloping membranes, and transport vesicles harboring fully enveloped capsids. It is debated whether capsid envelopment of herpes simplex virus (HSV) is completed in the soma prior to axonal targeting or later, and whether the mechanisms are the same in neurons derived from embryos or from adult hosts. We used HSV mutants impaired in capsid envelopment to test whether the inner tegument proteins pUL36 or pUL37 necessary for microtubule-mediated capsid transport were sufficient for axonal capsid targeting in neurons derived from the dorsal root ganglia of adult mice. Such neurons were infected with HSV1-ΔUL20 whose capsids recruited pUL36 and pUL37, with HSV1-ΔUL37 whose capsids associate only with pUL36, or with HSV1-ΔUL36 that assembles capsids lacking both proteins. While capsids of HSV1-ΔUL20 were actively transported along microtubules in epithelial cells and in the somata of neurons, those of HSV1-ΔUL36 and -ΔUL37 could only diffuse in the cytoplasm. Employing a novel image analysis algorithm to quantify capsid targeting to axons, we show that only a few capsids of HSV1-ΔUL20 entered axons, while vesicles transporting gD utilized axonal transport efficiently and independently of pUL36, pUL37, or pUL20. Our data indicate that capsid motility in the somata of neurons mediated by pUL36 and pUL37 does not suffice for targeting capsids to axons, and suggest that capsid envelopment needs to be completed in the soma prior to targeting of herpes simplex virus to the axons, and to spreading from neurons to neighboring cells. PMID:29284065

Oligodendrocytes and Progenitors Become Progressively Depleted within Chronically Demyelinated Lesions

PubMed Central

Mason, Jeffrey L.; Toews, Arrel; Hostettler, Janell D.; Morell, Pierre; Suzuki, Kinuko; Goldman, James E.; Matsushima, Glenn K.

2004-01-01

To understand mechanisms that may underlie the progression of a demyelinated lesion to a chronic state, we have used the cuprizone model of chronic demyelination. In this study, we investigated the fate of oligodendrocytes during the progression of a demyelinating lesion to a chronic state and determined whether transplanted adult oligodendrocyte progenitors could remyelinate the chronically demyelinated axons. Although there is rapid regeneration of the oligodendrocyte population following an acute lesion, most of these newly regenerated cells undergo apoptosis if mice remain on a cuprizone diet. Furthermore, the oligodendrocyte progenitors also become progressively depleted within the lesion, which appears to contribute to the chronic demyelination. Interestingly, even if the mice are returned to a normal diet following 12 weeks of exposure to cuprizone, remyelination and oligodendrocyte regeneration does not occur. However, if adult O4+ progenitors are transplanted into the chronically demyelinated lesion of mice treated with cuprizone for 12 weeks, mature oligodendrocyte regeneration and remyelination occurs after the mice are returned to a normal diet. Thus, the formation of chronically demyelinated lesions induced by cuprizone appears to be the result of oligodendrocyte depletion within the lesion and not due to the inability of the chronically demyelinated axons to be remyelinated. PMID:15111314

Premise and Prediction – How Optic Nerve Head Biomechanics Underlies the Susceptibility and Clinical Behavior of the Aged Optic Nerve Head

PubMed Central

Burgoyne, Claude F.; Downs, J. Crawford

2009-01-01

We propose that age-related alterations in optic nerve head (ONH) biomechanics underlie the clinical behavior and increased susceptibility of the aged ONH to glaucomatous damage. The literature which suggests that the aged ONH is more susceptible to glaucomatous damage at all levels of intraocular pressure is reviewed. The relevant biomechanics of the aged ONH are discussed and a biomechanical explanation for why, on average, the stiffened peripapillary scleral and lamina cribrosa connective tissues of the aged eye should lead to a shallow (senile sclerotic) form of cupping is proposed. A logic for why age-related axon loss and the optic neuropathy of glaucoma in the aged eye may overlap is discussed. Finally, we argue for a need to characterize all forms of clinical cupping into prelaminar and laminar components so as to add precision to the discussion of clinical cupping which does not currently exist. Such characterization may lead to the early detection of ONH axonal and connective tissue pathology in ocular hypertension and eventually aid in the assessment of etiology in all forms of optic neuropathy including those that may be purely age-related. PMID:18552618

KIF1A mediates axonal transport of BACE1 and identification of independently moving cargoes in living SCG neurons.

PubMed

Hung, Christy O Y; Coleman, Michael P

2016-11-01

Neurons rely heavily on axonal transport to deliver materials from the sites of synthesis to the axon terminals over distances that can be many centimetres long. KIF1A is the neuron-specific kinesin with the fastest reported anterograde motor activity. Previous studies have shown that KIF1A transports a subset of synaptic proteins, neurofilaments and dense-core vesicles. Using two-colour live imaging, we showed that beta-secretase 1 (BACE1)-mCherry moves together with KIF1A-GFP in both the anterograde and retrograde directions in superior cervical ganglions (SCG) neurons. We confirmed that KIF1A is functionally required for BACE1 transport by using KIF1A siRNA and a KIF1A mutant construct (KIF1A-T312M) to impair its motor activity. We further identified several cargoes that have little or no co-migration with KIF1A-GFP and also move independently from BACE1-mCherry. Together, these findings support a primary role for KIF1A in the anterograde transport of BACE1 and suggest that axonally transported cargoes are sorted into different classes of carrier vesicles in the cell body and are transported by cargo-specific motor proteins through the axon. © 2016 The Authors. Traffic published by John Wiley & Sons Ltd.

Massive accumulation of luminal protease-deficient axonal lysosomes at Alzheimer's disease amyloid plaques.

PubMed

Gowrishankar, Swetha; Yuan, Peng; Wu, Yumei; Schrag, Matthew; Paradise, Summer; Grutzendler, Jaime; De Camilli, Pietro; Ferguson, Shawn M

2015-07-14

Through a comprehensive analysis of organellar markers in mouse models of Alzheimer's disease, we document a massive accumulation of lysosome-like organelles at amyloid plaques and establish that the majority of these organelles reside within swollen axons that contact the amyloid deposits. This close spatial relationship between axonal lysosome accumulation and extracellular amyloid aggregates was observed from the earliest stages of β-amyloid deposition. Notably, we discovered that lysosomes that accumulate in such axons are lacking in multiple soluble luminal proteases and thus are predicted to be unable to efficiently degrade proteinaceous cargos. Of relevance to Alzheimer's disease, β-secretase (BACE1), the protein that initiates amyloidogenic processing of the amyloid precursor protein and which is a substrate for these proteases, builds up at these sites. Furthermore, through a comparison between the axonal lysosome accumulations at amyloid plaques and neuronal lysosomes of the wild-type brain, we identified a similar, naturally occurring population of lysosome-like organelles in neuronal processes that is also defined by its low luminal protease content. In conjunction with emerging evidence that the lysosomal maturation of endosomes and autophagosomes is coupled to their retrograde transport, our results suggest that extracellular β-amyloid deposits cause a local impairment in the retrograde axonal transport of lysosome precursors, leading to their accumulation and a blockade in their further maturation. This study both advances understanding of Alzheimer's disease brain pathology and provides new insights into the subcellular organization of neuronal lysosomes that may have broader relevance to other neurodegenerative diseases with a lysosomal component to their pathology.

Massive accumulation of luminal protease-deficient axonal lysosomes at Alzheimer’s disease amyloid plaques

PubMed Central

Gowrishankar, Swetha; Yuan, Peng; Wu, Yumei; Schrag, Matthew; Paradise, Summer; Grutzendler, Jaime; De Camilli, Pietro; Ferguson, Shawn M.

2015-01-01

Through a comprehensive analysis of organellar markers in mouse models of Alzheimer’s disease, we document a massive accumulation of lysosome-like organelles at amyloid plaques and establish that the majority of these organelles reside within swollen axons that contact the amyloid deposits. This close spatial relationship between axonal lysosome accumulation and extracellular amyloid aggregates was observed from the earliest stages of β-amyloid deposition. Notably, we discovered that lysosomes that accumulate in such axons are lacking in multiple soluble luminal proteases and thus are predicted to be unable to efficiently degrade proteinaceous cargos. Of relevance to Alzheimer’s disease, β-secretase (BACE1), the protein that initiates amyloidogenic processing of the amyloid precursor protein and which is a substrate for these proteases, builds up at these sites. Furthermore, through a comparison between the axonal lysosome accumulations at amyloid plaques and neuronal lysosomes of the wild-type brain, we identified a similar, naturally occurring population of lysosome-like organelles in neuronal processes that is also defined by its low luminal protease content. In conjunction with emerging evidence that the lysosomal maturation of endosomes and autophagosomes is coupled to their retrograde transport, our results suggest that extracellular β-amyloid deposits cause a local impairment in the retrograde axonal transport of lysosome precursors, leading to their accumulation and a blockade in their further maturation. This study both advances understanding of Alzheimer’s disease brain pathology and provides new insights into the subcellular organization of neuronal lysosomes that may have broader relevance to other neurodegenerative diseases with a lysosomal component to their pathology. PMID:26124111

Effect of prenatal exposure to ethanol on the ultrastructure of layer V of mature rat somatosensory cortex.

PubMed

al-Rabiai, S; Miller, M W

1989-12-01

Recent data have shown that the structure and function of layer V pyramidal neurons, e.g. corticospinal neurons, is altered by prenatal exposure to ethanol. We examined the effect of ethanol on the ultrastructure of layer V in somatosensory cortex. Timed pregnant rats were fed a diet containing 6.7% (v/v) ethanol (E) or pair-fed a nutritionally matched control diet (C). Thirty-day-old offspring of these mothers were prepared by standard electron microscopic techniques. The somata of pyramidal and local circuit neurons and the neuropil were analysed. Prenatal exposure to ethanol induced alterations in the somata of both populations of neurons. The parallel stacking of cisternae characteristic of C-treated rats was disorganized in E-treated rats. Moreover, the Golgi complex and lysosomes occupied a larger fraction of the somata of E-treated rats. The number and frequency of symmetric axosomatic synapses, but not asymmetric axosomatic synapses, formed by both types of neurons were significantly greater in E-treated rats. Gestational exposure to ethanol produced a variety of changes in the neuropil. Dendrites, particularly dendritic shafts, occupied less space in E-treated rats. In contrast, axons accounted for significantly more of the neuropil in E-treated rats than in controls. This increase in axonal space was due to a significantly greater coverage by non-myelinated axons and a significantly smaller coverage by myelinated axons in E-treated rats than in C-treated rats. Although the overall frequency of synapses was similar in both treatment groups, there were significantly more asymmetric synapses in E-treated rats, and most of these were axospinous synapses. These differences may contribute to documented physiological changes such as the lower rate of glucose utilization in layer V of somatosensory cortex of E-treated rats and they may underlie the mental retardation which is characteristic of children with foetal alcohol syndrome.

Impairment of immunity to Candida and Mycobacterium in humans with bi-allelic RORC mutations*

PubMed Central

Halwani, Rabih; Ma, Cindy S.; Wong, Natalie; Soudais, Claire; Henderson, Lauren A.; Marzouqa, Hiyam; Shamma, Jamal; Gonzalez, Marcela; Martinez-Barricarte, Rubén; Okada, Chizuru; Avery, Danielle T.; Latorre, Daniela; Deswarte, Caroline; Jabot-Hanin, Fabienne; Torrado, Egidio; Fountain, Jeffrey; Belkadi, Aziz; Itan, Yuval; Boisson, Bertrand; Migaud, Mélanie; Arlehamn, Cecilia S. Lindestam; Sette, Alessandro; Breton, Sylvain; McCluskey, James; Rossjohn, Jamie; de Villartay, Jean-Pierre; Moshous, Despina; Hambleton, Sophie; Latour, Sylvain; Arkwright, Peter D.; Picard, Capucine; Lantz, Olivier; Engelhard, Dan; Kobayashi, Masao; Abel, Laurent; Casanova, Jean-Laurent

2015-01-01

Human inborn errors of immunity mediated by the cytokines interleukin (IL)-17A/F underlie mucocutaneous candidiasis, whereas inborn errors of interferon (IFN)-γ immunity underlie mycobacterial disease. We report the discovery of bi-allelic RORC loss-of-function mutations in seven individuals from three kindreds of different ethnic origins with both candidiasis and mycobacteriosis. The lack of functional RORγ and RORγT isoforms resulted in the absence of IL-17A/F-producing T cells in these individuals, probably accounting for their chronic candidiasis. Unexpectedly, leukocytes from RORγ- and RORγT-deficient individuals also displayed an impaired IFN-γ response to Mycobacterium. This principally reflected profoundly defective IFN-γ production by circulating γδ T cells and CD4+CCR6+ CXCR3+ αβ T cells. In humans, both mucocutaneous immunity to Candida and systemic immunity to Mycobacterium require RORγ, or RORγT, or both. PMID:26160376

GABAergic Synapses at the Axon Initial Segment of Basolateral Amygdala Projection Neurons Modulate Fear Extinction.

PubMed

Saha, Rinki; Knapp, Stephanie; Chakraborty, Darpan; Horovitz, Omer; Albrecht, Anne; Kriebel, Martin; Kaphzan, Hanoch; Ehrlich, Ingrid; Volkmer, Hansjürgen; Richter-Levin, Gal

2017-01-01

Inhibitory synaptic transmission in the amygdala has a pivotal role in fear learning and its extinction. However, the local circuits formed by GABAergic inhibitory interneurons within the amygdala and their detailed function in shaping these behaviors are not well understood. Here we used lentiviral-mediated knockdown of the cell adhesion molecule neurofascin in the basolateral amygdala (BLA) to specifically remove inhibitory synapses at the axon initial segment (AIS) of BLA projection neurons. Quantitative analysis of GABAergic synapse markers and measurement of miniature inhibitory postsynaptic currents in BLA projection neurons after neurofascin knockdown ex vivo confirmed the loss of GABAergic input. We then studied the impact of this manipulation on anxiety-like behavior and auditory cued fear conditioning and its extinction as BLA related behavioral paradigms, as well as on long-term potentiation (LTP) in the ventral subiculum-BLA pathway in vivo. BLA knockdown of neurofascin impaired ventral subiculum-BLA-LTP. While this manipulation did not affect anxiety-like behavior and fear memory acquisition and consolidation, it specifically impaired extinction. Our findings indicate that modification of inhibitory synapses at the AIS of BLA projection neurons is sufficient to selectively impair extinction behavior. A better understanding of the role of distinct GABAergic synapses may provide novel and more specific targets for therapeutic interventions in extinction-based therapies.

Multimotor Transport in a System of Active and Inactive Kinesin-1 Motors

PubMed Central

Scharrel, Lara; Ma, Rui; Schneider, René; Jülicher, Frank; Diez, Stefan

2014-01-01

Long-range directional transport in cells is facilitated by microtubule-based motor proteins. One example is transport in a nerve cell, where small groups of motor proteins, such as kinesins and cytoplasmic dynein, work together to ensure the supply and clearance of cellular material along the axon. Defects in axonal transport have been linked to Alzheimer’s and other neurodegenerative diseases. However, it is not known in detail how multimotor-based cargo transport is impaired if a fraction of the motors are defective. To mimic impaired multimotor transport in vitro, we performed gliding motility assays with varying fractions of active kinesin-1 motors and inactive kinesin-1 motor mutants. We found that impaired transport manifests in multiple motility regimes: 1), a fast-motility regime characterized by gliding at velocities close to the single-molecule velocity of the active motors; 2), a slow-motility regime characterized by gliding at close-to zero velocity or full stopping; and 3), a regime in which fast and slow motilities coexist. Notably, the transition from the fast to the slow regime occurred sharply at a threshold fraction of active motors. Based on single-motor parameters, we developed a stochastic model and a mean-field theoretical description that explain our experimental findings. Our results demonstrate that impaired multimotor transport mostly occurs in an either/or fashion: depending on the ratio of active to inactive motors, transport is either performed at close to full speed or is out of action. PMID:25028878

Transcallosal Projections Require Glycoprotein M6-Dependent Neurite Growth and Guidance.

PubMed

Mita, Sakura; de Monasterio-Schrader, Patricia; Fünfschilling, Ursula; Kawasaki, Takahiko; Mizuno, Hidenobu; Iwasato, Takuji; Nave, Klaus-Armin; Werner, Hauke B; Hirata, Tatsumi

2015-11-01

The function of mature neurons critically relies on the developmental outgrowth and projection of their cellular processes. It has long been postulated that the neuronal glycoproteins M6a and M6b are involved in axon growth because these four-transmembrane domain-proteins of the proteolipid protein family are highly enriched on growth cones, but in vivo evidence has been lacking. Here, we report that the function of M6 proteins is required for normal axonal extension and guidance in vivo. In mice lacking both M6a and M6b, a severe hypoplasia of axon tracts was manifested. Most strikingly, the corpus callosum was reduced in thickness despite normal densities of cortical projection neurons. In single neuron tracing, many axons appeared shorter and disorganized in the double-mutant cortex, and some of them were even misdirected laterally toward the subcortex. Probst bundles were not observed. Upon culturing, double-mutant cortical and cerebellar neurons displayed impaired neurite outgrowth, indicating a cell-intrinsic function of M6 proteins. A rescue experiment showed that the intracellular loop of M6a is essential for the support of neurite extension. We propose that M6 proteins are required for proper extension and guidance of callosal axons that follow one of the most complex trajectories in the mammalian nervous system. © The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

White matter pathology and disconnection in the frontal lobe in cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL).

PubMed

Craggs, Lucinda J L; Yamamoto, Yumi; Ihara, Masafumi; Fenwick, Richard; Burke, Matthew; Oakley, Arthur E; Roeber, Sigrun; Duering, Marco; Kretzschmar, Hans; Kalaria, Raj N

2014-08-01

Magnetic resonance imaging indicates diffuse white matter (WM) changes are associated with cognitive impairment in cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL). We examined whether the distribution of axonal abnormalities is related to microvascular pathology in the underlying WM. We used post-mortem brains from CADASIL subjects and similar age cognitively normal controls to examine WM axonal changes, microvascular pathology, and glial reaction in up to 16 different regions extending rostro-caudally through the cerebrum. Using unbiased stereological methods, we estimated length densities of affected axons immunostained with neurofilament antibody SMI32. Standard immunohistochemistry was used to assess amyloid precursor protein immunoreactivity per WM area. To relate WM changes to microvascular pathology, we also determined the sclerotic index (SI) in WM arterioles. The degree of WM pathology consistently scored higher across all brain regions in CADASIL subjects (P<0.01) with the WM underlying the primary motor cortex exhibiting the most severe change. SMI32 immunoreactive axons in CADASIL were invariably increased compared with controls (P<0.01), with most prominent axonal abnormalities observed in the frontal WM (P<0.05). The SIs of arterioles in CADASIL were increased by 25-45% throughout the regions assessed, with the highest change in the mid-frontal region (P=0.000). Our results suggest disruption of either cortico-cortical or subcortical-cortical networks in the WM of the frontal lobe that may explain motor deficits and executive dysfunction in CADASIL. Widespread WM axonal changes arise from differential stenosis and sclerosis of arterioles in the WM of CADASIL subjects, possibly affecting some axons of projection neurones connecting to targets in the subcortical structures. © 2013 The Authors. Neuropathology and Applied Neurobiology published by John Wiley & Sons Ltd on behalf of British Neuropathological Society.

Integrated microfluidic platforms for investigating neuronal networks

NASA Astrophysics Data System (ADS)

Kim, Hyung Joon

This dissertation describes the development and application of integrated microfluidics-based assay platforms to study neuronal activities in the nervous system in-vitro. The assay platforms were fabricated using soft lithography and micro/nano fabrication including microfluidics, surface patterning, and nanomaterial synthesis. The use of integrated microfluidics-based assay platform allows culturing and manipulating many types of neuronal tissues in precisely controlled microenvironment. Furthermore, they provide organized multi-cellular in-vitro model, long-term monitoring with live cell imaging, and compatibility with molecular biology techniques and electrophysiology experiment. In this dissertation, the integrated microfluidics-based assay platforms are developed for investigation of neuronal activities such as local protein synthesis, impairment of axonal transport by chemical/physical variants, growth cone path finding under chemical/physical cues, and synaptic transmission in neuronal circuit. Chapter 1 describes the motivation, objectives, and scope for developing in-vitro platform to study various neuronal activities. Chapter 2 introduces microfluidic culture platform for biochemical assay with large-scale neuronal tissues that are utilized as model system in neuroscience research. Chapter 3 focuses on the investigation of impaired axonal transport by beta-Amyloid and oxidative stress. The platform allows to control neuronal processes and to quantify mitochondrial movement in various regions of axons away from applied drugs. Chapter 4 demonstrates the development of microfluidics-based growth cone turning assay to elucidate the mechanism underlying axon guidance under soluble factors and shear flow. Using this platform, the behaviors of growth cone of mammalian neurons are verified under the gradient of inhibitory molecules and also shear flow in well-controlled manner. In Chapter 5, I combine in-vitro multicellular model with microfabricated MEA (multielectrode array) or nanowire electrode array to study electrophysiology in neuronal network. Also, "diode-like" microgrooves to control the number of neuronal processes is embedded in this platform. Chapter 6 concludes with a possible future direction of this work. Interfacing micro/nanotechnology with primary neuron culture would open many doors in fundamental neuroscience research and also biomedical innovation.

PTEN inhibition prevents rat cortical neuron injury after hypoxia-ischemia.

PubMed

Zhao, J; Qu, Y; Wu, J; Cao, M; Ferriero, D M; Zhang, L; Mu, D

2013-05-15

Alterations in axon-dendrite polarity impair functional recovery in the developing CNS after hypoxia-ischemia (HI) injury. PTEN (phosphatase and tensin homolog deleted on chromosome 10) signaling pathway mediates the formation of neuronal polarity. However, its role in cerebral HI injury is not fully understood. In this study, we investigated the role of PTEN pathway in regulation of axon-dendrite polarity using an oxygen-glucose deprivation (OGD) model with rat cortical neurons. We found that the activity of PTEN and glycogen synthase kinase 3β (GSK-3β) was increased after OGD, along with the decrease of the activity in protein kinase B (Akt) and collapsin response mediator protein-2 (CRMP-2). Pretreatment with bpv, a potent inhibitor of PTEN, caused a decrease of the activity in PTEN and GSK-3β, and a significant increase of the activity in Akt and CRMP-2. Simultaneously, the morphological polarity of neurons was maintained and neuronal apoptosis was reduced. Moreover, inhibition of PTEN rescued vesicle recycling in axons. These findings suggested that the PTEN/Akt/GSK-3β/CRMP-2 pathway is involved in the regulation of axon-dendrite polarity, providing a novel route for protecting neurons following neonatal HI. Copyright © 2013 IBRO. Published by Elsevier Ltd. All rights reserved.

Proteasome stress leads to APP axonal transport defects by promoting its amyloidogenic processing in lysosomes.

PubMed

Otero, María Gabriela; Fernandez Bessone, Ivan; Hallberg, Alan Earle; Cromberg, Lucas Eneas; De Rossi, María Cecilia; Saez, Trinidad M; Levi, Valeria; Almenar-Queralt, Angels; Falzone, Tomás Luis

2018-06-11

Alzheimer disease (AD) pathology includes the accumulation of poly-ubiquitylated (also known as poly-ubiquitinated) proteins and failures in proteasome-dependent degradation. Whereas the distribution of proteasomes and its role in synaptic function have been studied, whether proteasome activity regulates the axonal transport and metabolism of the amyloid precursor protein (APP), remains elusive. By using live imaging in primary hippocampal neurons, we showed that proteasome inhibition rapidly and severely impairs the axonal transport of APP. Fluorescence cross-correlation analyses and membrane internalization blockage experiments showed that plasma membrane APP does not contribute to transport defects. Moreover, by western blotting and double-color APP imaging, we demonstrated that proteasome inhibition precludes APP axonal transport by enhancing its endo-lysosomal delivery, where β-cleavage is induced. Taken together, we found that proteasomes control the distal transport of APP and can re-distribute Golgi-derived vesicles to the endo-lysosomal pathway. This crosstalk between proteasomes and lysosomes regulates the intracellular APP dynamics, and defects in proteasome activity can be considered a contributing factor that leads to abnormal APP metabolism in AD.This article has an associated First Person interview with the first author of the paper. © 2018. Published by The Company of Biologists Ltd.

Proteolipid Protein Is Required for Transport of Sirtuin 2 into CNS Myelin

PubMed Central

Werner, Hauke B.; Kuhlmann, Katja; Shen, Siming; Uecker, Marina; Schardt, Anke; Dimova, Kalina; Orfaniotou, Foteini; Dhaunchak, Ajit; Brinkmann, Bastian G.; Möbius, Wiebke; Guarente, Lenny; Casaccia-Bonnefil, Patrizia; Jahn, Olaf; Nave, Klaus-Armin

2009-01-01

Mice lacking the expression of proteolipid protein (PLP)/DM20 in oligodendrocytes provide a genuine model for spastic paraplegia (SPG-2). Their axons are well myelinated but exhibit impaired axonal transport and progressive degeneration, which is difficult to attribute to the absence of a single myelin protein. We hypothesized that secondary molecular changes in PLPnull myelin contribute to the loss of PLP/DM20-dependent neuroprotection and provide more insight into glia-axonal interactions in this disease model. By gel-based proteome analysis, we identified >160 proteins in purified myelin membranes, which allowed us to systematically monitor the CNS myelin proteome of adult PLPnull mice, before the onset of disease. We identified three proteins of the septin family to be reduced in abundance, but the nicotinamide adenine dinucleotide (NAD+)-dependent deacetylase sirtuin 2 (SIRT2) was virtually absent. SIRT2 is expressed throughout the oligodendrocyte lineage, and immunoelectron microscopy revealed its association with myelin. Loss of SIRT2 in PLPnull was posttranscriptional, suggesting that PLP/DM20 is required for its transport into the myelin compartment. Because normal SIRT2 activity is controlled by the NAD+/NADH ratio, its function may be coupled to the axo-glial metabolism and the long-term support of axons by oligodendrocytes. PMID:17634366

Deficiency of the Survival of Motor Neuron Protein Impairs mRNA Localization and Local Translation in the Growth Cone of Motor Neurons.

PubMed

Fallini, Claudia; Donlin-Asp, Paul G; Rouanet, Jeremy P; Bassell, Gary J; Rossoll, Wilfried

2016-03-30

Spinal muscular atrophy (SMA) is a neurodegenerative disease primarily affecting spinal motor neurons. It is caused by reduced levels of the survival of motor neuron (SMN) protein, which plays an essential role in the biogenesis of spliceosomal small nuclear ribonucleoproteins in all tissues. The etiology of the specific defects in the motor circuitry in SMA is still unclear, but SMN has also been implicated in mediating the axonal localization of mRNA-protein complexes, which may contribute to the axonal degeneration observed in SMA. Here, we report that SMN deficiency severely disrupts local protein synthesis within neuronal growth cones. We also identify the cytoskeleton-associated growth-associated protein 43 (GAP43) mRNA as a new target of SMN and show that motor neurons from SMA mouse models have reduced levels ofGAP43mRNA and protein in axons and growth cones. Importantly, overexpression of two mRNA-binding proteins, HuD and IMP1, restoresGAP43mRNA and protein levels in growth cones and rescues axon outgrowth defects in SMA neurons. These findings demonstrate that SMN plays an important role in the localization and local translation of mRNAs with important axonal functions and suggest that disruption of this function may contribute to the axonal defects observed in SMA. The motor neuron disease spinal muscular atrophy (SMA) is caused by reduced levels of the survival of motor neuron (SMN) protein, which plays a key role in assembling RNA/protein complexes that are essential for mRNA splicing. It remains unclear whether defects in this well characterized housekeeping function cause the specific degeneration of spinal motor neurons observed in SMA. Here, we describe an additional role of SMN in regulating the axonal localization and local translation of the mRNA encoding growth-associated protein 43 (GAP43). This study supports a model whereby SMN deficiency impedes transport and local translation of mRNAs important for neurite outgrowth and stabilization, thus contributing to axon degeneration, muscle denervation, and motor neuron cell death in SMA. Copyright © 2016 the authors 0270-6474/16/363811-10$15.00/0.

[Clinical Neuropsychology of Dementia with Lewy Bodies].

PubMed

Nagahama, Yasuhiro

2016-02-01

Dementia with Lewy bodies (DLB) shows lesser memory impairment and more severe visuospatial disability than Alzheimer disease (AD). Although deficits in both consolidation and retrieval underlie the memory impairment, retrieval deficit is predominant in DLB. Visuospatial dysfunctions in DLB are related to the impairments in both ventral and dorsal streams of higher visual information processing, and lower visual processing in V1/V2 may also be impaired. Attention and executive functions are more widely disturbed in DLB than in AD. Imitation of finger gestures is impaired more frequently in DLB than in other mild dementia, and provides additional information for diagnosis of mild dementia, especially for DLB. Pareidolia, which lies between hallucination and visual misperception, is found frequently in DLB, but its mechanism is still under investigation.

Causal Link between the Cortico-Rubral Pathway and Functional Recovery through Forced Impaired Limb Use in Rats with Stroke

PubMed Central

Ishida, Akimasa; Isa, Kaoru; Umeda, Tatsuya; Kobayashi, Kazuto; Kobayashi, Kenta; Hida, Hideki

2016-01-01

Intensive rehabilitation is believed to induce use-dependent plasticity in the injured nervous system; however, its causal relationship to functional recovery is unclear. Here, we performed systematic analysis of the effects of forced use of an impaired forelimb on the recovery of rats after lesioning the internal capsule with intracerebral hemorrhage (ICH). Forced limb use (FLU) group rats exhibited better recovery of skilled forelimb functions and their cortical motor area with forelimb representation was restored and enlarged on the ipsilesional side. In addition, abundant axonal sprouting from the reemerged forelimb area was found in the ipsilateral red nucleus after FLU. To test the causal relationship between the plasticity in the cortico-rubral pathway and recovery, loss-of-function experiments were conducted using a double-viral vector technique, which induces selective blockade of the target pathway. Blockade of the cortico-rubral tract resulted in deficits of the recovered forelimb function in FLU group rats. These findings suggest that the cortico-rubral pathway is a substrate for recovery induced by intensive rehabilitation after ICH. SIGNIFICANCE STATEMENT The research aimed at determining the causal linkage between reorganization of the motor pathway induced by intensive rehabilitative training and recovery after stroke. We clarified the expansion of the forelimb representation area of the ipsilesional motor cortex by forced impaired forelimb use (FLU) after lesioning the internal capsule with intracerebral hemorrhaging (ICH) in rats. Anterograde tracing showed robust axonal sprouting from the forelimb area to the red nucleus in response to FLU. Selective blockade of the cortico-rubral pathway by the novel double-viral vector technique clearly revealed that the increased cortico-rubral axonal projections had causal linkage to the recovery of reaching movements induced by FLU. Our data demonstrate that the cortico-rubral pathway is responsible for the effect of intensive limb use. PMID:26758837

Zebrafish embryos exposed to alcohol undergo abnormal development of motor neurons and muscle fibers.

PubMed

Sylvain, Nicole J; Brewster, Daniel L; Ali, Declan W

2010-01-01

Children exposed to alcohol in utero have significantly delayed gross and fine motor skills, as well as deficiencies in reflex development. The reasons that underlie the motor deficits caused by ethanol (EtOH) exposure remain to be fully elucidated. The present study was undertaken to investigate the effects of embryonic alcohol exposure (1.5%, 2% and 2.5% EtOH) on motor neuron and muscle fiber morphology in 3 days post fertilization (dpf) larval zebrafish. EtOH treated fish exhibited morphological deformities and fewer bouts of swimming in response to touch, compared with untreated fish. Immunolabelling with anti-acetylated tubulin indicated that fish exposed to 2.5% EtOH had significantly higher rates of motor neuron axon defects. Immunolabelling of primary and secondary motor neurons, using znp-1 and zn-8, revealed that fish exposed to 2% and 2.5% EtOH exhibited significantly higher rates of primary and secondary motor neuron axon defects compared to controls. Examination of red and white muscle fibers revealed that fish exposed to EtOH had significantly smaller fibers compared with controls. These findings indicate that motor neuron and muscle fiber morphology is affected by early alcohol exposure in zebrafish embryos, and that this may be related to deficits in locomotion. Copyright 2010 Elsevier Inc. All rights reserved.

The excimer lamp induces cutaneous nerve degeneration and reduces scratching in a dry-skin mouse model.

PubMed

Kamo, Atsuko; Tominaga, Mitsutoshi; Kamata, Yayoi; Kaneda, Kazuyuki; Ko, Kyi C; Matsuda, Hironori; Kimura, Utako; Ogawa, Hideoki; Takamori, Kenji

2014-12-01

Epidermal hyperinnervation, which is thought to underlie intractable pruritus, has been observed in patients with atopic dermatitis (AD). The epidermal expression of axonal guidance molecules has been reported to regulate epidermal hyperinnervation. Previously, we showed that the excimer lamp has antihyperinnervative effects in nonpruritic dry-skin model mice, although epidermal expression of axonal guidance molecules was unchanged. Therefore, we investigated the antipruritic effects of excimer lamp irradiation and its mechanism of action. A single irradiation of AD model mice significantly inhibited itch-related behavior 1 day later, following improvement in the dermatitis score. In addition, irradiation of nerve fibers formed by cultured dorsal root ganglion neurons increased bleb formation and decreased nerve fiber expression of nicotinamide mononucleotide adenylyl transferase 2, suggesting degenerative changes in these fibers. We also analyzed whether attaching a cutoff excimer filter (COF) to the lamp, thus decreasing cytotoxic wavelengths, altered hyperinnervation and the production of cyclobutane pyrimidine dimer (CPD), a DNA damage marker, in dry-skin model mice. Irradiation with COF decreased CPD production in keratinocytes, as well as having an antihyperinnervative effect, indicating that the antipruritic effects of excimer lamp irradiation with COF are due to induction of epidermal nerve degeneration and reduced DNA damage.

Genetic Contributions to Changes of Fiber Tracts of Ventral Visual Stream in 22q11.2 Deletion Syndrome

PubMed Central

Kikinis, Zora; Makris, Nikos; Finn, Christine T.; Bouix, Sylvain; Lucia, Diandra; Coleman, Michael J.; Tworog-Dube, Erica; Kikinis, Ron; Kucherlapati, Raju; Shenton, Martha E.; Kubicki, Marek

2013-01-01

Patients with 22q11.2 deletion syndrome (22q11.2DS) represent a population at high risk for developing schizophrenia, as well as learning disabilities. Deficits in visuo-spatial memory are thought to underlie some of the cognitive disabilities. Neuronal substrates of visuo-spatial memory include the inferior fronto-occipital fasciculus (IFOF) and the inferior longitudinal fasciculus (ILF), two tracts that comprise the ventral visual stream. Diffusion Tensor Magnetic Resonance Imaging (DT-MRI) is an established method to evaluate white matter (WM) connections in vivo. DT-MRI scans of nine 22q11.2DS young adults and nine matched healthy subjects were acquired. Tractography of the IFOF and the ILF was performed. DT-MRI indices, including Fractional anisotropy (FA) (measure of WM changes), axial diffusivity (AD, measure of axonal changes) and radial diffusivity (RD, measure of myelin changes) of each of the tracts and each group were measured and compared. The 22q11.2DS group showed statistically significant reductions of FA in IFOF in the left hemisphere. Additionally, reductions of AD were found in the IFOF and the ILF in both hemispheres. These findings might be the consequence of axonal changes, which is possibly due to fewer, thinner, or less organized fibers. No changes in RD were detected in any of the tracts delineated, which is in contrast to findings in schizophrenia patients where increases in RD are believed to be indicative of demyelination. We conclude that reduced axonal changes may be key to understanding the underlying pathology of WM leading to the visuo-spatial phenotype in 22q11.2DS. PMID:23612843

Genome-wide analysis of genetic susceptibility to language impairment in an isolated Chilean population

PubMed Central

Villanueva, Pia; Newbury, Dianne F; Jara, Lilian; De Barbieri, Zulema; Mirza, Ghazala; Palomino, Hernán M; Fernández, María Angélica; Cazier, Jean-Baptiste; Monaco, Anthony P; Palomino, Hernán

2011-01-01

Specific language impairment (SLI) is an unexpected deficit in the acquisition of language skills and affects between 5 and 8% of pre-school children. Despite its prevalence and high heritability, our understanding of the aetiology of this disorder is only emerging. In this paper, we apply genome-wide techniques to investigate an isolated Chilean population who exhibit an increased frequency of SLI. Loss of heterozygosity (LOH) mapping and parametric and non-parametric linkage analyses indicate that complex genetic factors are likely to underlie susceptibility to SLI in this population. Across all analyses performed, the most consistently implicated locus was on chromosome 7q. This locus achieved highly significant linkage under all three non-parametric models (max NPL=6.73, P=4.0 × 10−11). In addition, it yielded a HLOD of 1.24 in the recessive parametric linkage analyses and contained a segment that was homozygous in two affected individuals. Further, investigation of this region identified a two-SNP haplotype that occurs at an increased frequency in language-impaired individuals (P=0.008). We hypothesise that the linkage regions identified here, in particular that on chromosome 7, may contain variants that underlie the high prevalence of SLI observed in this isolated population and may be of relevance to other populations affected by language impairments. PMID:21248734

IMMUNODEFICIENCIES. Impairment of immunity to Candida and Mycobacterium in humans with bi-allelic RORC mutations.

PubMed

Okada, Satoshi; Markle, Janet G; Deenick, Elissa K; Mele, Federico; Averbuch, Dina; Lagos, Macarena; Alzahrani, Mohammed; Al-Muhsen, Saleh; Halwani, Rabih; Ma, Cindy S; Wong, Natalie; Soudais, Claire; Henderson, Lauren A; Marzouqa, Hiyam; Shamma, Jamal; Gonzalez, Marcela; Martinez-Barricarte, Rubén; Okada, Chizuru; Avery, Danielle T; Latorre, Daniela; Deswarte, Caroline; Jabot-Hanin, Fabienne; Torrado, Egidio; Fountain, Jeffrey; Belkadi, Aziz; Itan, Yuval; Boisson, Bertrand; Migaud, Mélanie; Arlehamn, Cecilia S Lindestam; Sette, Alessandro; Breton, Sylvain; McCluskey, James; Rossjohn, Jamie; de Villartay, Jean-Pierre; Moshous, Despina; Hambleton, Sophie; Latour, Sylvain; Arkwright, Peter D; Picard, Capucine; Lantz, Olivier; Engelhard, Dan; Kobayashi, Masao; Abel, Laurent; Cooper, Andrea M; Notarangelo, Luigi D; Boisson-Dupuis, Stéphanie; Puel, Anne; Sallusto, Federica; Bustamante, Jacinta; Tangye, Stuart G; Casanova, Jean-Laurent

2015-08-07

Human inborn errors of immunity mediated by the cytokines interleukin-17A and interleukin-17F (IL-17A/F) underlie mucocutaneous candidiasis, whereas inborn errors of interferon-γ (IFN-γ) immunity underlie mycobacterial disease. We report the discovery of bi-allelic RORC loss-of-function mutations in seven individuals from three kindreds of different ethnic origins with both candidiasis and mycobacteriosis. The lack of functional RORγ and RORγT isoforms resulted in the absence of IL-17A/F-producing T cells in these individuals, probably accounting for their chronic candidiasis. Unexpectedly, leukocytes from RORγ- and RORγT-deficient individuals also displayed an impaired IFN-γ response to Mycobacterium. This principally reflected profoundly defective IFN-γ production by circulating γδ T cells and CD4(+)CCR6(+)CXCR3(+) αβ T cells. In humans, both mucocutaneous immunity to Candida and systemic immunity to Mycobacterium require RORγ, RORγT, or both. Copyright © 2015, American Association for the Advancement of Science.

Human spinal cord injury: motor unit properties and behaviour.

PubMed

Thomas, C K; Bakels, R; Klein, C S; Zijdewind, I

2014-01-01

Spinal cord injury (SCI) results in widespread variation in muscle function. Review of motor unit data shows that changes in the amount and balance of excitatory and inhibitory inputs after SCI alter management of motoneurons. Not only are units recruited up to higher than usual relative forces when SCI leaves few units under voluntary control, the force contribution from recruitment increases due to elevation of twitch/tetanic force ratios. Force gradation and precision are also coarser with reduced unit numbers. Maximal unit firing rates are low in hand muscles, limiting voluntary strength, but are low, normal or high in limb muscles. Unit firing rates during spasms can exceed voluntary rates, emphasizing that deficits in descending drive limit force production. SCI also changes muscle properties. Motor unit weakness and fatigability seem universal across muscles and species, increasing the muscle weakness that arises from paralysis of units, motoneuron death and sensory impairment. Motor axon conduction velocity decreases after human SCI. Muscle contractile speed is also reduced, which lowers the stimulation frequencies needed to grade force when paralysed muscles are activated with patterned electrical stimulation. This slowing does not necessarily occur in hind limb muscles after cord transection in cats and rats. The nature, duration and level of SCI underlie some of these species differences, as do variations in muscle function, daily usage, tract control and fibre-type composition. Exploring this diversity is important to promote recovery of the hand, bowel, bladder and locomotor function most wanted by people with SCI. © 2013 Scandinavian Physiological Society. Published by John Wiley & Sons Ltd.

Is hemiplegic cerebral palsy equivalent to amblyopia of the corticospinal system?

PubMed

Eyre, Janet A; Smith, Martin; Dabydeen, Lyvia; Clowry, Gavin J; Petacchi, Eliza; Battini, Roberta; Guzzetta, Andrea; Cioni, Giovanni

2007-11-01

Subjects with severe hemiplegic cerebral palsy have increased ipsilateral corticospinal projections from their noninfarcted cortex. We investigated whether their severe impairment might, in part, be caused by activity-dependent, competitive displacement of surviving contralateral corticospinal projections from the affected cortex by more active ipsilateral corticospinal projections from the nonaffected cortex, thereby compounding the impairment. Transcranial magnetic stimulation (TMS) characterized corticospinal tract development from each hemisphere over the first 2 years in 32 healthy children, 14 children with unilateral stroke, and 25 with bilateral lesions. Magnetic resonance imaging and anatomic studies compared corticospinal tract growth in 13 patients with perinatal stroke with 46 healthy subjects. Infants with unilateral lesions initially had responses after TMS of the affected cortex, which became progressively more abnormal, and seven were eventually lost. There was associated hypertrophy of the ipsilateral corticospinal axons projecting from the noninfarcted cortex. Magnetic resonance imaging and anatomic studies demonstrated hypertrophy of the corticospinal tract from the noninfarcted hemisphere. TMS findings soon after the stroke did not predict impairment; subsequent loss of responses and hypertrophy of ipsilateral corticospinal axons from the noninfarcted cortex predicted severe impairment at 2 years. Infants with bilateral lesions maintained responses to TMS from both hemispheres with a normal pattern of development. Rather than representing "reparative plasticity," increased ipsilateral projections from the noninfarcted cortex compound disability by competitively displacing surviving contralateral corticospinal projections from the infarcted cortex. This may provide a pathophysiological explanation for why signs of hemiplegic cerebral palsy appear late and progress over the first 2 years of life.

Dynamic Motor Compensations with Permanent, Focal Loss of Forelimb Force after Cervical Spinal Cord Injury

PubMed Central

López-Dolado, Elisa; Lucas-Osma, Ana M.

2013-01-01

Abstract Incomplete cervical lesion is the most common type of human spinal cord injury (SCI) and causes permanent paresis of arm muscles, a phenomenon still incompletely understood in physiopathological and neuroanatomical terms. We performed spinal cord hemisection in adult rats at the caudal part of the segment C6, just rostral to the bulk of triceps brachii motoneurons, and analyzed the forces and kinematics of locomotion up to 4 months postlesion to determine the nature of motor function loss and recovery. A dramatic (50%), immediate and permanent loss of extensor force occurred in the forelimb but not in the hind limb of the injured side, accompanied by elbow and wrist kinematic impairments and early adaptations of whole-body movements that initially compensated the balance but changed continuously over the follow-up period to allow effective locomotion. Overuse of both contralateral legs and ipsilateral hind leg was evidenced since 5 days postlesion. Ipsilateral foreleg deficits resulted mainly from interruption of axons that innervate the spinal cord segments caudal to the lesion, because chronic loss (about 35%) of synapses was detected at C7 while only 14% of triceps braquii motoneurons died, as assessed by synaptophysin immunohistochemistry and retrograde neural tracing, respectively. We also found a large pool of propriospinal neurons projecting from C2–C5 to C7 in normal rats, with topographical features similar to the propriospinal premotoneuronal system of cats and primates. Thus, concurrent axotomy at C6 of brain descending axons and cervical propriospinal axons likely hampered spontaneous recovery of the focal neurological impairments. PMID:23249275

Critical role of the axonal guidance cue EphrinB2 in lung growth, angiogenesis, and repair.

PubMed

Vadivel, Arul; van Haaften, Tim; Alphonse, Rajesh S; Rey-Parra, Gloria-Juliana; Ionescu, Lavinia; Haromy, Al; Eaton, Farah; Michelakis, Evangelos; Thébaud, Bernard

2012-03-01

Lung diseases characterized by alveolar damage currently lack efficient treatments. The mechanisms contributing to normal and impaired alveolar growth and repair are incompletely understood. Axonal guidance cues (AGC) are molecules that guide the outgrowth of axons to their targets. Among these AGCs, members of the Ephrin family also promote angiogenesis, cell migration, and organogenesis outside the nervous system. The role of Ephrins during alveolar growth and repair is unknown. We hypothesized that EphrinB2 promotes alveolar development and repair. We used in vitro and in vivo manipulation of EphrinB2 signaling to assess the role of this AGC during normal and impaired lung development. In vivo EphrinB2 knockdown using intranasal siRNA during the postnatal stage of alveolar development in rats arrested alveolar and vascular growth. In a model of O(2)-induced arrested alveolar growth in newborn rats, air space enlargement, loss of lung capillaries, and pulmonary hypertension were associated with decreased lung EphrinB2 and receptor EphB4 expression. In vitro, EphrinB2 preserved alveolar epithelial cell viability in O(2), decreased O(2)-induced alveolar epithelial cell apoptosis, and accelerated alveolar epithelial cell wound healing, maintained lung microvascular endothelial cell viability, and proliferation and vascular network formation. In vivo, treatment with intranasal EphrinB2 decreased alveolar epithelial and endothelial cell apoptosis, preserved alveolar and vascular growth in hyperoxic rats, and attenuated pulmonary hypertension. The AGC EphrinB2 may be a new therapeutic target for lung repair and pulmonary hypertension.

Human Periodontal Ligament-Derived Stem Cells Promote Retinal Ganglion Cell Survival and Axon Regeneration After Optic Nerve Injury.

PubMed

Cen, Ling-Ping; Ng, Tsz Kin; Liang, Jia-Jian; Zhuang, Xi; Yao, Xiaowu; Yam, Gary Hin-Fai; Chen, Haoyu; Cheung, Herman S; Zhang, Mingzhi; Pang, Chi Pui

2018-06-01

Optic neuropathies are the leading cause of irreversible blindness and visual impairment in the developed countries, affecting more than 80 million people worldwide. While most optic neuropathies have no effective treatment, there is intensive research on retinal ganglion cell (RGC) protection and axon regeneration. We previously demonstrated potential of human periodontal ligament-derived stem cells (PDLSCs) for retinal cell replacement. Here, we report the neuroprotective effect of human PDLSCs to ameliorate RGC degeneration and promote axonal regeneration after optic nerve crush (ONC) injury. Human PDLSCs were intravitreally injected into the vitreous chamber of adult Fischer rats after ONC in vivo as well as cocultured with retinal explants in vitro. Human PDLSCs survived in the vitreous chamber and were maintained on the RGC layer even at 3 weeks after ONC. Immunofluorescence analysis of βIII-tubulin and Gap43 showed that the numbers of surviving RGCs and regenerating axons were significantly increased in the rats with human PDLSC transplantation. In vitro coculture experiments confirmed that PDLSCs enhanced RGC survival and neurite regeneration in retinal explants without inducing inflammatory responses. Direct cell-cell interaction and elevated brain-derived neurotrophic factor secretion, but not promoting endogenous progenitor cell regeneration, were the RGC protective mechanisms of human PDLSCs. In summary, our results revealed the neuroprotective role of human PDLSCs by strongly promoting RGC survival and axonal regeneration both in vivo and in vitro, indicating a therapeutic potential for RGC protection against optic neuropathies. Stem Cells 2018;36:844-855. © AlphaMed Press 2018.

Putting theory of mind in its place: psychological explanations of the socio-emotional-communicative impairments in autistic spectrum disorder.

PubMed

Boucher, Jill

2012-05-01

In this review, the history of the theory of mind (ToM) theory of autistic spectrum disorder (ASD) is outlined (in which ToM is indexed by success on false belief tasks), and the explanatory power and psychological causes of impaired ToM in ASD are critically discussed. It is concluded that impaired ToM by itself has only limited explanatory power, but that explorations of the psychological precursors of impaired ToM have been fruitful in increasing understanding of mindreading impairments in ASD (where 'mindreading' refers those abilities that underlie triadic interaction as well as ToM). It is argued that early explanations of impaired mindreading are untenable for various reasons, but that impairments of dyadic interaction in ASD that could lead to impaired ability to represent others' mental states may be the critical psychological cause, or causes, of impaired ToM. The complexity of causal routes to impaired ToM is emphasized.

The immunoglobulin-like domains 1 and 2 of the protein tyrosine phosphatase LAR adopt an unusual horseshoe-like conformation

PubMed Central

Biersmith, Bridget H.; Hammel, Michal; Geisbrecht, Erika R.; Bouyain, Samuel

2011-01-01

Neurogenesis depends on exquisitely regulated interactions between macromolecules on the cell surface and in the extracellular matrix. In particular, interactions between proteoglycans and members of the type IIa subgroup of receptor protein tyrosine phosphatases underlie critical developmental processes such as the formation of synapses at the neuromuscular junction and the migration of axons to their appropriate targets. We report here the crystal structures of the first and second immunoglobulin-like domains of the Drosophila type IIa receptor Dlar and its mouse homologue LAR. These two domains adopt an unusual antiparallel arrangement that has not been previously observed in tandem repeats of immunoglobulin-like domains and that is presumably conserved in all type IIa receptor protein tyrosine phosphatases. PMID:21402080

Persistence of the cell-cycle checkpoint kinase Wee1 in SadA- and SadB-deficient neurons disrupts neuronal polarity.

PubMed

Müller, Myriam; Lutter, Daniela; Püschel, Andreas W

2010-01-15

Wee1 is well characterized as a cell-cycle checkpoint kinase that regulates the entry into mitosis in dividing cells. Here we identify a novel function of Wee1 in postmitotic neurons during the establishment of distinct axonal and dendritic compartments, which is an essential step during neuronal development. Wee1 is expressed in unpolarized neurons but is downregulated after neurons have extended an axon. Suppression of Wee1 impairs the formation of minor neurites but does not interfere with axon formation. However, neuronal polarity is disrupted when neurons fail to downregulate Wee1. The kinases SadA and SadB (Sad kinases) phosphorylate Wee1 and are required to initiate its downregulation in polarized neurons. Wee1 expression persists in neurons that are deficient in SadA and SadB and disrupts neuronal polarity. Knockdown of Wee1 rescues the Sada(-/-);Sadb(-/-) mutant phenotype and restores normal polarity in these neurons. Our results demonstrate that the regulation of Wee1 by SadA and SadB kinases is essential for the differentiation of polarized neurons.

Signals to promote myelin formation and repair

PubMed Central

Taveggia, Carla; Feltri, Maria Laura; Wrabetz, Lawrence

2011-01-01

The myelin sheath wraps large axons in both the CNS and the PNS, and is a key determinant of efficient axonal function and health. Myelin is targeted in a series of diseases, notably multiple sclerosis (MS). In MS, demyelination is associated with progressive axonal damage, which determines the level of patient disability. Few treatments are available for combating myelin damage in MS and related disorders. These treatments, which largely comprise anti-inflammatory drugs, only show limited efficacy in subsets of patients. More-effective treatment of myelin disorders will probably result from early intervention with combinatorial therapies that target inflammation and other processes—for example, signaling pathways that promote remyelination. Indeed, evidence suggests that such pathways might be impaired in pathology and, hence, contribute to the failure of remyelination in such diseases. In this article, we review the molecular basis of signaling pathways that regulate myelination in the CNS and PNS with a focus on differentiation of myelinating glia. We also discuss factors such as extracellular molecules that act as modulators of these pathways. Finally, we consider the few preclinical and clinical trials of agents that augment this signaling. PMID:20404842

ENA/VASP downregulation triggers cell death by impairing axonal maintenance in hippocampal neurons.

PubMed

Franco, D Lorena; Rezával, Carolina; Cáceres, Alfredo; Schinder, Alejandro F; Ceriani, M Fernanda

2010-06-01

Neurodegenerative diseases encompass a broad variety of motor and cognitive disorders that are accompanied by death of specific neuronal populations or brain regions. Cellular and molecular mechanisms underlying these complex disorders remain largely unknown. In a previous work we searched for novel Drosophila genes relevant for neurodegeneration and singled out enabled (ena), which encodes a protein involved in cytoskeleton remodeling. To extend our understanding on the mechanisms of ENA-triggered degeneration we now investigated the effect of silencing ena ortholog genes in mouse hippocampal neurons. We found that ENA/VASP downregulation led to neurite retraction and concomitant neuronal cell death through an apoptotic pathway. Remarkably, this retraction initially affected the axonal structure, showing no effect on dendrites. Reduction in ENA/VASP levels blocked the neuritogenic effect of a specific RhoA kinase (ROCK) inhibitor, thus suggesting that these proteins could participate in the Rho-signaling pathway. Altogether these observations demonstrate that ENA/VASP proteins are implicated in the establishment and maintenance of the axonal structure and that a change on their expression levels triggers neuronal degeneration. 2010 Elsevier Inc. All rights reserved.

Mirror Me: Imitative Responses in Adults with Autism

ERIC Educational Resources Information Center

Schunke, Odette; Schöttle, Daniel; Vettorazzi, Eik; Brandt, Valerie; Kahl, Ursula; Bäumer, Tobias; Ganos, Christos; David, Nicole; Peiker, Ina; Engel, Andreas K; Brass, Marcel; Münchau, Alexander

2016-01-01

Dysfunctions of the human mirror neuron system have been postulated to underlie some deficits in autism spectrum disorders including poor imitative performance and impaired social skills. Using three reaction time experiments addressing mirror neuron system functions under simple and complex conditions, we examined 20 adult autism spectrum…

Working Memory and Language Learning: A Review

ERIC Educational Resources Information Center

Archibald, Lisa M. D.

2017-01-01

Children with speech, language, and communication needs (SLCN) form a highly heterogeneous group, including those with an unexplained delay in language development known as specific language impairment (SLI). There is growing recognition that multiple mechanisms underlie the range of profiles observed in these children. Broadly speaking, both the…

Neural correlates of impaired cognitive control over working memory in schizophrenia.

PubMed

Eich, Teal S; Nee, Derek Evan; Insel, Catherine; Malapani, Chara; Smith, Edward E

2014-07-15

One of the most common deficits in patients with schizophrenia (SZ) is in working memory (WM), which has wide-reaching impacts across cognition. However, previous approaches to studying WM in SZ have used tasks that require multiple cognitive-control processes, making it difficult to determine which specific cognitive and neural processes underlie the WM impairment. We used functional magnetic resonance imaging to investigate component processes of WM in SZ. Eighteen healthy controls (HCs) and 18 patients with SZ performed an item-recognition task that permitted separate neural assessments of 1) WM maintenance, 2) inhibition, and 3) interference control in response to recognition probes. Before inhibitory demands, posterior ventrolateral prefrontal cortex (VLPFC), an area involved in WM maintenance, was activated to a similar degree in both HCs and patients, indicating preserved maintenance operations in SZ. When cued to inhibit items from WM, HCs showed reduced activation in posterior VLPFC, commensurate with appropriately inhibiting items from WM. However, these inhibition-related reductions were absent in patients. When later probed with items that should have been inhibited, patients showed reduced behavioral performance and increased activation in mid-VLPFC, an area implicated in interference control. A mediation analysis indicated that impaired inhibition led to increased reliance on interference control and reduced behavioral performance. In SZ, impaired control over memory, manifested through proactive inhibitory deficits, leads to increased reliance on reactive interference-control processes. The strain on interference-control processes results in reduced behavioral performance. Thus, inhibitory deficits in SZ may underlie widespread impairments in WM and cognition. © 2013 Society of Biological Psychiatry Published by Society of Biological Psychiatry All rights reserved.

Protein O-Mannosyltransferases Affect Sensory Axon Wiring and Dynamic Chirality of Body Posture in the Drosophila Embryo.

PubMed

Baker, Ryan; Nakamura, Naosuke; Chandel, Ishita; Howell, Brooke; Lyalin, Dmitry; Panin, Vladislav M

2018-02-14

Genetic defects in protein O-mannosyltransferase 1 (POMT1) and POMT2 underlie severe muscular dystrophies. POMT genes are evolutionarily conserved in metazoan organisms. In Drosophila , both male and female POMT mutants show a clockwise rotation of adult abdominal segments, suggesting a chirality of underlying pathogenic mechanisms. Here we described and analyzed a similar phenotype in POMT mutant embryos that shows left-handed body torsion. Our experiments demonstrated that coordinated muscle contraction waves are associated with asymmetric embryo rolling, unveiling a new chirality marker in Drosophila development. Using genetic and live-imaging approaches, we revealed that the torsion phenotype results from differential rolling and aberrant patterning of peristaltic waves of muscle contractions. Our results demonstrated that peripheral sensory neurons are required for normal contractions that prevent the accumulation of torsion. We found that POMT mutants show abnormal axonal connections of sensory neurons. POMT transgenic expression limited to sensory neurons significantly rescued the torsion phenotype, axonal connectivity defects, and abnormal contractions in POMT mutant embryos. Together, our data suggested that protein O-mannosylation is required for normal sensory feedback to control coordinated muscle contractions and body posture. This mechanism may shed light on analogous functions of POMT genes in mammals and help to elucidate the etiology of neurological defects in muscular dystrophies. SIGNIFICANCE STATEMENT Protein O-mannosyltransferases (POMTs) are evolutionarily conserved in metazoans. Mutations in POMTs cause severe muscular dystrophies associated with pronounced neurological defects. However, neurological functions of POMTs remain poorly understood. We demonstrated that POMT mutations in Drosophila result in abnormal muscle contractions and cause embryo torsion. Our experiments uncovered a chirality of embryo movements and a unique POMT -dependent mechanism that maintains symmetry of a developing system affected by chiral forces. Furthermore, POMTs were found to be required for proper axon connectivity of sensory neurons, suggesting that O-mannosylation regulates the sensory feedback controlling muscle contractions. This novel POMT function in the peripheral nervous system may shed light on analogous functions in mammals and help to elucidate pathomechanisms of neurological abnormalities in muscular dystrophies. Copyright © 2018 the authors 0270-6474/18/381850-16$15.00/0.

dnc-1/dynactin 1 Knockdown Disrupts Transport of Autophagosomes and Induces Motor Neuron Degeneration

PubMed Central

Ikenaka, Kensuke; Kawai, Kaori; Katsuno, Masahisa; Huang, Zhe; Jiang, Yue-Mei; Iguchi, Yohei; Kobayashi, Kyogo; Kimata, Tsubasa; Waza, Masahiro; Tanaka, Fumiaki; Mori, Ikue; Sobue, Gen

2013-01-01

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by the progressive loss of motor neurons. We previously showed that the expression of dynactin 1, an axon motor protein regulating retrograde transport, is markedly reduced in spinal motor neurons of sporadic ALS patients, although the mechanisms by which decreased dynactin 1 levels cause neurodegeneration have yet to be elucidated. The accumulation of autophagosomes in degenerated motor neurons is another key pathological feature of sporadic ALS. Since autophagosomes are cargo of dynein/dynactin complexes and play a crucial role in the turnover of several organelles and proteins, we hypothesized that the quantitative loss of dynactin 1 disrupts the transport of autophagosomes and induces the degeneration of motor neuron. In the present study, we generated a Caenorhabditis elegans model in which the expression of DNC-1, the homolog of dynactin 1, is specifically knocked down in motor neurons. This model exhibited severe motor defects together with axonal and neuronal degeneration. We also observed impaired movement and increased number of autophagosomes in the degenerated neurons. Furthermore, the combination of rapamycin, an activator of autophagy, and trichostatin which facilitates axonal transport dramatically ameliorated the motor phenotype and axonal degeneration of this model. Thus, our results suggest that decreased expression of dynactin 1 induces motor neuron degeneration and that the transport of autophagosomes is a novel and substantial therapeutic target for motor neuron degeneration. PMID:23408943

Regional Myelin and Axon Damage and Neuroinflammation in the Adult Mouse Brain After Long-Term Postnatal Vanadium Exposure.

PubMed

Azeez, Idris A; Olopade, Funmilayo; Laperchia, Claudia; Andrioli, Anna; Scambi, Ilaria; Onwuka, Silas K; Bentivoglio, Marina; Olopade, James O

2016-09-01

Environmental exposure to vanadium occurs in areas of persistent burning of fossil fuels; this metal is known to induce oxidative stress and oligodendrocyte damage. Here, we determined whether vanadium exposure (3 mg/kg) in mice during the first 3 postnatal months leads to a sustained neuroinflammatory response. Body weight monitoring, and muscle strength and open field tests showed reduction of body weight gain and locomotor impairment in vanadium-exposed mice. Myelin histochemistry and immunohistochemistry for astrocytes, microglia, and nonphosphorylated neurofilaments revealed striking regional heterogeneity. Myelin damage involved the midline corpus callosum and fibers in cortical gray matter, hippocampus, and diencephalon that were associated with axonal damage. Astrocyte and microglial activation was identified in the same regions and in the internal capsule; however, no overt myelin and axon damage was observed in the latter. Double immunofluorescence revealed induction of high tumor necrosis factor (TNF) immunoreactivity in reactive astrocytes. Western blotting analysis showed significant induction of TNF and interleukin-1β expression. Together these findings show that chronic postnatal vanadium exposure leads to functional deficit and region-dependent myelin damage that does not spare axons. This injury is associated with glial cell activation and proinflammatory cytokine induction, which may reflect both neurotoxic and neuroprotective responses. © 2016 American Association of Neuropathologists, Inc. All rights reserved.

Microtubule and Cell Contact Dependency of ER-bound PTP1B Localization in Growth Cones

PubMed Central

Fuentes, Federico

2009-01-01

PTP1B is an ER-bound protein tyrosine phosphatase implied in the regulation of cell adhesion. Here we investigated mechanisms involved in the positioning and dynamics of PTP1B in axonal growth cones and evaluated the role of this enzyme in axons. In growth cones, PTP1B consistently localizes in the central domain, and occasionally at the peripheral region and filopodia. Live imaging of GFP-PTP1B reveals dynamic excursions of fingerlike processes within the peripheral region and filopodia. PTP1B and GFP-PTP1B colocalize with ER markers and coalign with microtubules at the peripheral region and redistribute to the base of the growth cone after treatment with nocodazole, a condition that is reversible. Growth cone contact with cellular targets is accompanied by invasion of PTP1B and stable microtubules in the peripheral region aligned with the contact axis. Functional impairment of PTP1B causes retardation of axon elongation, as well as reduction of growth cone filopodia lifetime and Src activity. Our results highlight the role of microtubules and cell contacts in the positioning of ER-bound PTP1B to the peripheral region of growth cones, which may be required for the positive role of PTP1B in axon elongation, filopodia stabilization, and Src activity. PMID:19158394

Masked Priming Effects in Aphasia: Evidence of Altered Automatic Spreading Activation

ERIC Educational Resources Information Center

Silkes, JoAnn P.; Rogers, Margaret A.

2012-01-01

Purpose: Previous research has suggested that impairments of automatic spreading activation may underlie some aphasic language deficits. The current study further investigated the status of automatic spreading activation in individuals with aphasia as compared with typical adults. Method: Participants were 21 individuals with aphasia (12 fluent, 9…

Soluble CD14 in cerebrospinal fluid is associated with markers of inflammation and axonal damage in untreated HIV-infected patients: a retrospective cross-sectional study.

PubMed

Jespersen, Sofie; Pedersen, Karin Kæreby; Anesten, Birgitta; Zetterberg, Henrik; Fuchs, Dietmar; Gisslén, Magnus; Hagberg, Lars; Trøseid, Marius; Nielsen, Susanne Dam

2016-04-21

HIV-associated cognitive impairment has declined since the introduction of combination antiretroviral treatment (cART). However, milder forms of cognitive impairment persist. Inflammation in the cerebrospinal fluid (CSF) has been associated with cognitive impairment, and CSF neurofilament light chain protein (NFL) and CSF neopterin concentrations are increased in those patients. Microbial translocation in HIV infection has been suggested to contribute to chronic inflammation, and lipopolysaccharide (LPS) and soluble CD14 (sCD14) are markers of microbial translocation and the resulting monocyte activation, respectively. We hypothesised that microbial translocation contributes to inflammation and axonal damage in the central nervous system (CNS) in untreated HIV infection. We analyzed paired samples of plasma and CSF from 62 HIV-infected, untreated patients without cognitive symptoms from Sahlgrenska University Hospital, Gothenburg, Sweden. Measurements of neopterin and NFL in CSF were available from previous studies. Plasma and CSF sCD14 was measured using ELISA (R&D, Minneapolis, MN), and plasma and CSF LPS was measured using LAL colorimetric assay (Lonza, Walkersville, MD, USA). Univariate and multivariate regression analyses were performed. LPS in plasma was associated with plasma sCD14 (r = 0.31, P = 0.015), and plasma sCD14 was associated with CSF sCD14 (r = 0.32, P = 0.012). Furthermore, CSF sCD14 was associated with NFL (r = 0.32, P = 0.031) and neopterin (r = 0.32, P = 0.012) in CSF. LPS was not detectable in CSF. In a multivariate regression model CSF sCD14 remained associated with NFL and neopterin after adjusting for age, CD4+ cell count, and HIV RNA in CSF. In a group of untreated, HIV-infected patients LPS was associated with sCD14 in plasma, and plasma sCD14 was associated CSF sCD14. CSF sCD14 were associated with markers of CNS inflammation and axonal damage. This suggest that microbial translocation might be a driver of systemic and CNS inflammation. However, LPS was not detectable in the CSF, and since sCD14 is a marker of monocyte activation sCD14 may be increased due to other causes than microbial translocation. Further studies regarding cognitive impairment and biomarkers are warranted to fully understand causality.

Axon-glial disruption: the link between vascular disease and Alzheimer's disease?

PubMed

Horsburgh, Karen; Reimer, Michell M; Holland, Philip; Chen, Guiquan; Scullion, Gillian; Fowler, Jill H

2011-08-01

Vascular risk factors play a critical role in the development of cognitive decline and AD (Alzheimer's disease), during aging, and often result in chronic cerebral hypoperfusion. The neurobiological link between hypoperfusion and cognitive decline is not yet defined, but is proposed to involve damage to the brain's white matter. In a newly developed mouse model, hypoperfusion, in isolation, produces a slowly developing and diffuse damage to myelinated axons, which is widespread in the brain, and is associated with a selective impairment in working memory. Cerebral hypoperfusion, an early event in AD, has also been shown to be associated with white matter damage and notably an accumulation of amyloid. The present review highlights some of the published data linking white matter disruption to aging and AD as a result of vascular dysfunction. A model is proposed by which chronic cerebral hypoperfusion, as a result of vascular factors, results in both the generation and accumulation of amyloid and injury to white matter integrity, resulting in cognitive impairment. The generation of amyloid and accumulation in the vasculature may act to perpetuate further vascular dysfunction and accelerate white matter pathology, and as a consequence grey matter pathology and cognitive decline.

Review on the APP/PS1KI mouse model: intraneuronal Abeta accumulation triggers axonopathy, neuron loss and working memory impairment.

PubMed

Bayer, T A; Wirths, O

2008-02-01

Accumulating evidence points to an important role of intraneuronal Abeta as a trigger of the pathological cascade of events leading to neurodegeneration and eventually to Alzheimer's disease (AD) with its typical clinical symptoms, like memory impairment and change in personality. As a new concept, intraneuronal accumulation of Abeta instead of extracellular Abeta deposition has been introduced to be the disease-triggering event in AD. The present review compiles current knowledge on the amyloid precursor protein (APP)/PS1KI mouse model with early and massive intraneuronal Abeta42 accumulation: (1) The APP/PS1KI mouse model exhibits early robust brain and spinal cord axonal degeneration and hippocampal CA1 neuron loss. (2) At the same time-point, a dramatic, age-dependent reduced ability to perform working memory and motor tasks is observed. (3) The APP/PS1KI mice are smaller and show development of a thoracolumbar kyphosis, together with an incremental loss of body weight. (4) Onset of the observed behavioral alterations correlates well with robust axonal degeneration in brain and spinal cord and with abundant hippocampal CA1 neuron loss.

PI(3,5)P2 biosynthesis regulates oligodendrocyte differentiation by intrinsic and extrinsic mechanisms

PubMed Central

Mironova, Yevgeniya A; Lenk, Guy M; Lin, Jing-Ping; Lee, Seung Joon; Twiss, Jeffery L; Vaccari, Ilaria; Bolino, Alessandra; Havton, Leif A; Min, Sang H; Abrams, Charles S; Shrager, Peter; Meisler, Miriam H; Giger, Roman J

2016-01-01

Proper development of the CNS axon-glia unit requires bi-directional communication between axons and oligodendrocytes (OLs). We show that the signaling lipid phosphatidylinositol-3,5-bisphosphate [PI(3,5)P2] is required in neurons and in OLs for normal CNS myelination. In mice, mutations of Fig4, Pikfyve or Vac14, encoding key components of the PI(3,5)P2 biosynthetic complex, each lead to impaired OL maturation, severe CNS hypomyelination and delayed propagation of compound action potentials. Primary OLs deficient in Fig4 accumulate large LAMP1+ and Rab7+ vesicular structures and exhibit reduced membrane sheet expansion. PI(3,5)P2 deficiency leads to accumulation of myelin-associated glycoprotein (MAG) in LAMP1+perinuclear vesicles that fail to migrate to the nascent myelin sheet. Live-cell imaging of OLs after genetic or pharmacological inhibition of PI(3,5)P2 synthesis revealed impaired trafficking of plasma membrane-derived MAG through the endolysosomal system in primary cells and brain tissue. Collectively, our studies identify PI(3,5)P2 as a key regulator of myelin membrane trafficking and myelinogenesis. DOI: http://dx.doi.org/10.7554/eLife.13023.001 PMID:27008179

Facial emotion recognition in patients with focal and diffuse axonal injury.

PubMed

Yassin, Walid; Callahan, Brandy L; Ubukata, Shiho; Sugihara, Genichi; Murai, Toshiya; Ueda, Keita

2017-01-01

Facial emotion recognition impairment has been well documented in patients with traumatic brain injury. Studies exploring the neural substrates involved in such deficits have implicated specific grey matter structures (e.g. orbitofrontal regions), as well as diffuse white matter damage. Our study aims to clarify whether different types of injuries (i.e. focal vs. diffuse) will lead to different types of impairments on facial emotion recognition tasks, as no study has directly compared these patients. The present study examined performance and response patterns on a facial emotion recognition task in 14 participants with diffuse axonal injury (DAI), 14 with focal injury (FI) and 22 healthy controls. We found that, overall, participants with FI and DAI performed more poorly than controls on the facial emotion recognition task. Further, we observed comparable emotion recognition performance in participants with FI and DAI, despite differences in the nature and distribution of their lesions. However, the rating response pattern between the patient groups was different. This is the first study to show that pure DAI, without gross focal lesions, can independently lead to facial emotion recognition deficits and that rating patterns differ depending on the type and location of trauma.

Defective lysosomal proteolysis and axonal transport are early pathogenic events that worsen with age leading to increased APP metabolism and synaptic Abeta in transgenic APP/PS1 hippocampus.

PubMed

Torres, Manuel; Jimenez, Sebastian; Sanchez-Varo, Raquel; Navarro, Victoria; Trujillo-Estrada, Laura; Sanchez-Mejias, Elisabeth; Carmona, Irene; Davila, Jose Carlos; Vizuete, Marisa; Gutierrez, Antonia; Vitorica, Javier

2012-11-22

Axonal pathology might constitute one of the earliest manifestations of Alzheimer disease. Axonal dystrophies were observed in Alzheimer's patients and transgenic models at early ages. These axonal dystrophies could reflect the disruption of axonal transport and the accumulation of multiple vesicles at local points. It has been also proposed that dystrophies might interfere with normal intracellular proteolysis. In this work, we have investigated the progression of the hippocampal pathology and the possible implication in Abeta production in young (6 months) and aged (18 months) PS1(M146L)/APP(751sl) transgenic mice. Our data demonstrated the existence of a progressive, age-dependent, formation of axonal dystrophies, mainly located in contact with congophilic Abeta deposition, which exhibited tau and neurofilament hyperphosphorylation. This progressive pathology was paralleled with decreased expression of the motor proteins kinesin and dynein. Furthermore, we also observed an early decrease in the activity of cathepsins B and D, progressing to a deep inhibition of these lysosomal proteases at late ages. This lysosomal impairment could be responsible for the accumulation of LC3-II and ubiquitinated proteins within axonal dystrophies. We have also investigated the repercussion of these deficiencies on the APP metabolism. Our data demonstrated the existence of an increase in the amyloidogenic pathway, which was reflected by the accumulation of hAPPfl, C99 fragment, intracellular Abeta in parallel with an increase in BACE and gamma-secretase activities. In vitro experiments, using APPswe transfected N2a cells, demonstrated that any imbalance on the proteolytic systems reproduced the in vivo alterations in APP metabolism. Finally, our data also demonstrated that Abeta peptides were preferentially accumulated in isolated synaptosomes. A progressive age-dependent cytoskeletal pathology along with a reduction of lysosomal and, in minor extent, proteasomal activity could be directly implicated in the progressive accumulation of APP derived fragments (and Abeta peptides) in parallel with the increase of BACE-1 and gamma-secretase activities. This retard in the APP metabolism seemed to be directly implicated in the synaptic Abeta accumulation and, in consequence, in the pathology progression between synaptically connected regions.

[Cognitive impairments accompanying the burnout syndrome - a review].

PubMed

Riedrich, Karin; Weiss, Elisabeth M; Dalkner, Nina; Reininghaus, Eva; Papousek, Ilona; Schwerdtfeger, Andreas; Lackner, Helmut K; Reininghaus, Bernd

2017-03-01

The rising prevalence of the burnout syndrome has increasingly moved it into the focus of scientific interest. In addition to emotional exhaustion and depersonalization, particularly reduced personal accomplishment has strong societal and economic effects. In recent years reduced personal accomplishment has increasingly been linked to cognitive impairment. However, up to now only a few studies have objectively assessed cognitive deficits in burnout patients. This article gives an overview of 16 studies which examined cognitive abilities in burnout patients. The findings are partly contradictory, probably due to methodical differences. Consensus has emerged concerning impairments of executive functions, i.a. vigilance, and memory updating and monitoring. Multifactorial causation may underlie the cognitive impairments. Targeted longitudinal studies are necessary in order to identify the affected cognitive functions and be able to make causal inferences on links between the burnout syndrome and specific cognitive impairments.

Endosome-mediated retrograde axonal transport of P2X3 receptor signals in primary sensory neurons

PubMed Central

Chen, Xu-Qiao; Wang, Bin; Wu, Chengbiao; Pan, Jin; Yuan, Bo; Su, Yuan-Yuan; Jiang, Xing-Yu; Zhang, Xu; Bao, Lan

2012-01-01

Neurotrophins and their receptors adopt signaling endosomes to transmit retrograde signals. However, the mechanisms of retrograde signaling for other ligand/receptor systems are poorly understood. Here, we report that the signals of the purinergic (P)2X3 receptor, an ATP-gated ion channel, are retrogradely transported in dorsal root ganglion (DRG) neuron axons. We found that Rab5, a small GTPase, controls the early sorting of P2X3 receptors into endosomes, while Rab7 mediates the fast retrograde transport of P2X3 receptors. Intraplantar injection and axonal application into the microfluidic chamber of α, β-methylene-ATP (α, β-MeATP), a P2X selective agonist, enhanced the endocytosis and retrograde transport of P2X3 receptors. The α, β-MeATP-induced Ca2+ influx activated a pathway comprised of protein kinase C, rat sarcoma viral oncogene and extracellular signal-regulated protein kinase (ERK), which associated with endocytic P2X3 receptors to form signaling endosomes. Disruption of the lipid rafts abolished the α, β-MeATP-induced ERK phosphorylation, endocytosis and retrograde transport of P2X3 receptors. Furthermore, treatment of peripheral axons with α, β-MeATP increased the activation level of ERK and cAMP response element-binding protein in the cell bodies of DRG neurons and enhanced neuronal excitability. Impairment of either microtubule-based axonal transport in vivo or dynein function in vitro blocked α, β-MeATP-induced retrograde signals. These results indicate that P2X3 receptor-activated signals are transmitted via retrogradely transported endosomes in primary sensory neurons and provide a novel signaling mechanism for ligand-gated channels. PMID:22157653

Decreased spinal synaptic inputs to phrenic motor neurons elicit localized inactivity-induced phrenic motor facilitation

PubMed Central

Streeter, K.A.; Baker-Herman, T.L.

2014-01-01

Phrenic motor neurons receive rhythmic synaptic inputs throughout life. Since even brief disruption in phrenic neural activity is detrimental to life, on-going neural activity may play a key role in shaping phrenic motor output. To test the hypothesis that spinal mechanisms sense and respond to reduced phrenic activity, anesthetized, ventilated rats received micro-injections of procaine in the C2 ventrolateral funiculus (VLF) to transiently (~30 min) block axon conduction in bulbospinal axons from medullary respiratory neurons that innervate one phrenic motor pool; during procaine injections, contralateral phrenic neural activity was maintained. Once axon conduction resumed, a prolonged increase in phrenic burst amplitude was observed in the ipsilateral phrenic nerve, demonstrating inactivity-induced phrenic motor facilitation (iPMF). Inhibition of tumor necrosis factor alpha (TNFα) and atypical PKC (aPKC) activity in spinal segments containing the phrenic motor nucleus impaired ipsilateral iPMF, suggesting a key role for spinal TNFα and aPKC in iPMF following unilateral axon conduction block. A small phrenic burst amplitude facilitation was also observed contralateral to axon conduction block, indicating crossed spinal phrenic motor facilitation (csPMF). csPMF was independent of spinal TNFα and aPKC. Ipsilateral iPMF and csPMF following unilateral withdrawal of phrenic synaptic inputs were associated with proportional increases in phrenic responses to chemoreceptor stimulation (hypercapnia), suggesting iPMF and csPMF increase phrenic dynamic range. These data suggest that local, spinal mechanisms sense and respond to reduced synaptic inputs to phrenic motor neurons. We hypothesize that iPMF and csPMF may represent compensatory mechanisms that assure adequate motor output is maintained in a physiological system in which prolonged inactivity ends life. PMID:24681155

Morphological and functional changes in TRPM8-expressing corneal cold thermoreceptor neurons during aging and their impact on tearing in mice.

PubMed

Alcalde, Ignacio; Íñigo-Portugués, Almudena; González-González, Omar; Almaraz, Laura; Artime, Enol; Morenilla-Palao, Cruz; Gallar, Juana; Viana, Félix; Merayo-Lloves, Jesús; Belmonte, Carlos

2018-08-01

Morphological and functional alterations of peripheral somatosensory neurons during the aging process lead to a decline of somatosensory perception. Here, we analyze the changes occurring with aging in trigeminal ganglion (TG), TRPM8-expressing cold thermoreceptor neurons innervating the mouse cornea, which participate in the regulation of basal tearing and blinking and have been implicated in the pathogenesis of dry eye disease (DED). TG cell bodies and axonal branches were examined in a mouse line (TRPM8 BAC -EYFP) expressing a fluorescent reporter. In 3 months old animals, about 50% of TG cold thermoreceptor neurons were intensely fluorescent, likely providing strongly fluorescent axons and complex corneal nerve terminals with ongoing activity at 34°C and low-threshold, robust responses to cooling. The remaining TRPM8 + corneal axons were weakly fluorescent with nonbeaded axons, sparsely ramified nerve terminals, and exhibited a low-firing rate at 34°C, responding moderately to cooling pulses as do weakly fluorescent TG neurons. In aged (24 months) mice, the number of weakly fluorescent TG neurons was strikingly high while the morphology of TRPM8 + corneal axons changed drastically; 89% were weakly fluorescent, unbranched, and often ending in the basal epithelium. Functionally, 72.5% of aged cold terminals responded as those of young animals, but 27.5% exhibited very low-background activity and abnormal responsiveness to cooling pulses. These morpho-functional changes develop in parallel with an enhancement of tear's basal flow and osmolarity, suggesting that the aberrant sensory inflow to the brain from impaired peripheral cold thermoreceptors contributes to age-induced abnormal tearing and to the high incidence of DED in elderly people. © 2018 Wiley Periodicals, Inc.

Progressive Motor Deficit is Mediated by the Denervation of Neuromuscular Junctions and Axonal Degeneration in Transgenic Mice Expressing Mutant (P301S) Tau Protein.

PubMed

Yin, Zhuoran; Valkenburg, Femke; Hornix, Betty E; Mantingh-Otter, Ietje; Zhou, Xingdong; Mari, Muriel; Reggiori, Fulvio; Van Dam, Debby; Eggen, Bart J L; De Deyn, Peter P; Boddeke, Erik

2017-01-01

Tauopathies include a variety of neurodegenerative diseases associated with the pathological aggregation of hyperphosphorylated tau, resulting in progressive cognitive decline and motor impairment. The underlying mechanism for motor deficits related to tauopathy is not yet fully understood. Here, we use a novel transgenic tau mouse line, Tau 58/4, with enhanced neuron-specific expression of P301S mutant tau to investigate the motor abnormalities in association with the peripheral nervous system. Using stationary beam, gait, and rotarod tests, motor deficits were found in Tau 58/4 mice already 3 months after birth, which deteriorated during aging. Hyperphosphorylated tau was detected in the cell bodies and axons of motor neurons. At the age of 9 and 12 months, significant denervation of the neuromuscular junction in the extensor digitorum longus muscle was observed in Tau 58/4 mice, compared to wild-type mice. Muscle hypotrophy was observed in Tau 58/4 mice at 9 and 12 months. Using electron microscopy, we observed ultrastructural changes in the sciatic nerve of 12-month-old Tau 58/4 mice indicative of the loss of large axonal fibers and hypomyelination (assessed by g-ratio). We conclude that the accumulated hyperphosphorylated tau in the axon terminals may induce dying-back axonal degeneration, myelin abnormalities, neuromuscular junction denervation, and muscular atrophy, which may be the mechanisms responsible for the deterioration of the motor function in Tau 58/4 mice. Tau 58/4 mice represent an interesting neuromuscular degeneration model, and the pathological mechanisms might be responsible for motor signs observed in some human tauopathies.

Axodendritic sorting and pathological missorting of Tau are isoform-specific and determined by axon initial segment architecture.

PubMed

Zempel, Hans; Dennissen, Frank J A; Kumar, Yatender; Luedtke, Julia; Biernat, Jacek; Mandelkow, Eva-Maria; Mandelkow, Eckhard

2017-07-21

Subcellular mislocalization of the microtubule-associated protein Tau is a hallmark of Alzheimer disease (AD) and other tauopathies. Six Tau isoforms, differentiated by the presence or absence of a second repeat or of N-terminal inserts, exist in the human CNS, but their physiological and pathological differences have long remained elusive. Here, we investigated the properties and distributions of human and rodent Tau isoforms in primary forebrain rodent neurons. We found that the Tau diffusion barrier (TDB), located within the axon initial segment (AIS), controls retrograde (axon-to-soma) and anterograde (soma-to-axon) traffic of Tau. Tau isoforms without the N-terminal inserts were sorted efficiently into the axon. However, the longest isoform (2N4R-Tau) was partially retained in cell bodies and dendrites, where it accelerated spine and dendrite growth. The TDB (located within the AIS) was impaired when AIS components (ankyrin G, EB1) were knocked down or when glycogen synthase kinase-3β (GSK3β; an AD-associated kinase tethered to the AIS) was overexpressed. Using superresolution nanoscopy and live-cell imaging, we observed that microtubules within the AIS appeared highly dynamic, a feature essential for the TDB. Pathomechanistically, amyloid-β insult caused cofilin activation and F-actin remodeling and decreased microtubule dynamics in the AIS. Concomitantly with these amyloid-β-induced disruptions, the AIS/TDB sorting function failed, causing AD-like Tau missorting. In summary, we provide evidence that the human and rodent Tau isoforms differ in axodendritic sorting and amyloid-β-induced missorting and that the axodendritic distribution of Tau depends on AIS integrity. © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.

Endosome-mediated retrograde axonal transport of P2X3 receptor signals in primary sensory neurons.

PubMed

Chen, Xu-Qiao; Wang, Bin; Wu, Chengbiao; Pan, Jin; Yuan, Bo; Su, Yuan-Yuan; Jiang, Xing-Yu; Zhang, Xu; Bao, Lan

2012-04-01

Neurotrophins and their receptors adopt signaling endosomes to transmit retrograde signals. However, the mechanisms of retrograde signaling for other ligand/receptor systems are poorly understood. Here, we report that the signals of the purinergic (P)2X(3) receptor, an ATP-gated ion channel, are retrogradely transported in dorsal root ganglion (DRG) neuron axons. We found that Rab5, a small GTPase, controls the early sorting of P2X(3) receptors into endosomes, while Rab7 mediates the fast retrograde transport of P2X(3) receptors. Intraplantar injection and axonal application into the microfluidic chamber of α, β-methylene-ATP (α, β-MeATP), a P2X selective agonist, enhanced the endocytosis and retrograde transport of P2X(3) receptors. The α, β-MeATP-induced Ca(2+) influx activated a pathway comprised of protein kinase C, rat sarcoma viral oncogene and extracellular signal-regulated protein kinase (ERK), which associated with endocytic P2X(3) receptors to form signaling endosomes. Disruption of the lipid rafts abolished the α, β-MeATP-induced ERK phosphorylation, endocytosis and retrograde transport of P2X(3) receptors. Furthermore, treatment of peripheral axons with α, β-MeATP increased the activation level of ERK and cAMP response element-binding protein in the cell bodies of DRG neurons and enhanced neuronal excitability. Impairment of either microtubule-based axonal transport in vivo or dynein function in vitro blocked α, β-MeATP-induced retrograde signals. These results indicate that P2X(3) receptor-activated signals are transmitted via retrogradely transported endosomes in primary sensory neurons and provide a novel signaling mechanism for ligand-gated channels.

Utilization of MRI for Cerebral White Matter Injury in a Hypobaric Swine Model-Validation of Technique.

PubMed

McGuire, Jennifer A; Sherman, Paul M; Dean, Erica; Bernot, Jeremy M; Rowland, Laura M; McGuire, Stephen A; Kochunov, Peter V

2017-05-01

Repetitive hypobaric exposure in humans induces subcortical white matter change, observable on magnetic resonance imaging (MRI) and associated with cognitive impairment. Similar findings occur in traumatic brain injury (TBI). We are developing a swine MRI-driven model to understand the pathophysiology and to develop treatment interventions. Five miniature pigs (Sus scrofa domestica) were repetitively exposed to nonhypoxic hypobaria (30,000 feet/FIO 2 100%/transcutaneous PO 2 >90%) while under general anesthesia. Three pigs served as controls. Pre-exposure and postexposure MRIs were obtained that included structural sequences, dynamic contrast perfusion, and diffusion tensor quantification. Statistical comparison of individual subject and group change was performed utilizing a two-tailed t test. No structural imaging change was noted on T2-weighted or three-dimensional fluid-attenuated inversion recovery imaging between MRI 1 and MRI 2. No absolute difference in dynamic contrast perfusion was observed. A trend (p = 0.084) toward increase in interstitial extra-axonal fluid was noted. When individual subjects were examined, this trend toward increased extra-axonal fluid paralleled a decrease in contrast perfusion rate. This study demonstrates high reproducibility of quantitative noninvasive MRI, suggesting MRI is an appropriate assessment tool for TBI and hypobaric-induced injury research in swine. The lack of fluid-attenuated inversion recovery change may be multifactorial and requires further investigation. A trend toward increased extra-axonal water content that negatively correlates with dynamic contrast perfusion implies generalized axonal injury was induced. This study suggests this is a potential model for hypobaric-induced injury as well as potentially other axonal injuries such as TBI in which similar subcortical white matter change occurs. Further development of this model is necessary. Reprint & Copyright © 2017 Association of Military Surgeons of the U.S.

Synapto-protective drugs evaluation in reconstructed neuronal network.

PubMed

Deleglise, Bérangère; Lassus, Benjamin; Soubeyre, Vaneyssa; Alleaume-Butaux, Aurélie; Hjorth, Johannes J; Vignes, Maéva; Schneider, Benoit; Brugg, Bernard; Viovy, Jean-Louis; Peyrin, Jean-Michel

2013-01-01

Chronic neurodegenerative syndromes such as Alzheimer's and Parkinson's diseases, or acute syndromes such as ischemic stroke or traumatic brain injuries are characterized by early synaptic collapse which precedes axonal and neuronal cell body degeneration and promotes early cognitive impairment in patients. Until now, neuroprotective strategies have failed to impede the progression of neurodegenerative syndromes. Drugs preventing the loss of cell body do not prevent the cognitive decline, probably because they lack synapto-protective effects. The absence of physiologically realistic neuronal network models which can be easily handled has hindered the development of synapto-protective drugs suitable for therapies. Here we describe a new microfluidic platform which makes it possible to study the consequences of axonal trauma of reconstructed oriented mouse neuronal networks. Each neuronal population and sub-compartment can be chemically addressed individually. The somatic, mid axon, presynaptic and postsynaptic effects of local pathological stresses or putative protective molecules can thus be evaluated with the help of this versatile "brain on chip" platform. We show that presynaptic loss is the earliest event observed following axotomy of cortical fibers, before any sign of axonal fragmentation or post-synaptic spine alteration. This platform can be used to screen and evaluate the synapto-protective potential of several drugs. For instance, NAD⁺ and the Rho-kinase inhibitor Y27632 can efficiently prevent synaptic disconnection, whereas the broad-spectrum caspase inhibitor zVAD-fmk and the stilbenoid resveratrol do not prevent presynaptic degeneration. Hence, this platform is a promising tool for fundamental research in the field of developmental and neurodegenerative neurosciences, and also offers the opportunity to set up pharmacological screening of axon-protective and synapto-protective drugs.

The axonal guidance cue semaphorin 3C contributes to alveolar growth and repair.

PubMed

Vadivel, Arul; Alphonse, Rajesh S; Collins, Jennifer J P; van Haaften, Tim; O'Reilly, Megan; Eaton, Farah; Thébaud, Bernard

2013-01-01

Lung diseases characterized by alveolar damage such as bronchopulmonary dysplasia (BPD) in premature infants and emphysema lack efficient treatments. Understanding the mechanisms contributing to normal and impaired alveolar growth and repair may identify new therapeutic targets for these lung diseases. Axonal guidance cues are molecules that guide the outgrowth of axons. Amongst these axonal guidance cues, members of the Semaphorin family, in particular Semaphorin 3C (Sema3C), contribute to early lung branching morphogenesis. The role of Sema3C during alveolar growth and repair is unknown. We hypothesized that Sema3C promotes alveolar development and repair. In vivo Sema3C knock down using intranasal siRNA during the postnatal stage of alveolar development in rats caused significant air space enlargement reminiscent of BPD. Sema3C knock down was associated with increased TLR3 expression and lung inflammatory cells influx. In a model of O2-induced arrested alveolar growth in newborn rats mimicking BPD, air space enlargement was associated with decreased lung Sema3C mRNA expression. In vitro, Sema3C treatment preserved alveolar epithelial cell viability in hyperoxia and accelerated alveolar epithelial cell wound healing. Sema3C preserved lung microvascular endothelial cell vascular network formation in vitro under hyperoxic conditions. In vivo, Sema3C treatment of hyperoxic rats decreased lung neutrophil influx and preserved alveolar and lung vascular growth. Sema3C also preserved lung plexinA2 and Sema3C expression, alveolar epithelial cell proliferation and decreased lung apoptosis. In conclusion, the axonal guidance cue Sema3C promotes normal alveolar growth and may be worthwhile further investigating as a potential therapeutic target for lung repair.

Mitochondrial dynamics and bioenergetic dysfunction is associated with synaptic alterations in mutant SOD1 motor neurons

PubMed Central

Magrané, Jordi; Sahawneh, Mary Anne; Przedborski, Serge; Estévez, Álvaro G.; Manfredi, Giovanni

2012-01-01

Mutations in Cu,Zn superoxide dismutase (SOD1) cause familial amyotrophic lateral sclerosis (FALS), a rapidly fatal motor neuron disease. Mutant SOD1 has pleiotropic toxic effects on motor neurons, among which mitochondrial dysfunction has been proposed as one of the contributing factors in motor neuron demise. Mitochondria are highly dynamic in neurons; they are constantly reshaped by fusion and move along neurites to localize at sites of high-energy utilization, such as synapses. The finding of abnormal mitochondria accumulation in neuromuscular junctions, where the SOD1-FALS degenerative process is though to initiate, suggests that impaired mitochondrial dynamics in motor neurons may be involved in pathogenesis. We addressed this hypothesis by live imaging microscopy of photo-switchable fluorescent mitoDendra in transgenic rat motor neurons expressing mutant or wild type human SOD1. We demonstrate that mutant SOD1 motor neurons have impaired mitochondrial fusion in axons and cell bodies. Mitochondria also display selective impairment of retrograde axonal transport, with reduced frequency and velocity of movements. Fusion and transport defects are associated with smaller mitochondrial size, decreased mitochondrial density, and defective mitochondrial membrane potential. Furthermore, mislocalization of mitochondria at synapses among motor neurons, in vitro, correlates with abnormal synaptic number, structure, and function. Dynamics abnormalities are specific to mutant SOD1 motor neuron mitochondria, since they are absent in wild type SOD1 motor neurons, they do not involve other organelles, and they are not found in cortical neurons. Taken together, these results suggest that impaired mitochondrial dynamics may contribute to the selective degeneration of motor neurons in SOD1-FALS. PMID:22219285

Thermoregulation in multiple sclerosis.

PubMed

Davis, Scott L; Wilson, Thad E; White, Andrea T; Frohman, Elliot M

2010-11-01

Multiple sclerosis (MS) is a progressive neurological disorder that disrupts axonal myelin in the central nervous system. Demyelination produces alterations in saltatory conduction, slowed conduction velocity, and a predisposition to conduction block. An estimated 60-80% of MS patients experience temporary worsening of clinical signs and neurological symptoms with heat exposure. Additionally, MS may produce impaired neural control of autonomic and endocrine functions. This review focuses on five main themes regarding the current understanding of thermoregulatory dysfunction in MS: 1) heat sensitivity; 2) central regulation of body temperature; 3) thermoregulatory effector responses; 4) heat-induced fatigue; and 5) countermeasures to improve or maintain function during thermal stress. Heat sensitivity in MS is related to the detrimental effects of increased temperature on action potential propagation in demyelinated axons, resulting in conduction slowing and/or block, which can be quantitatively characterized using precise measurements of ocular movements. MS lesions can also occur in areas of the brain responsible for the control and regulation of body temperature and thermoregulatory effector responses, resulting in impaired neural control of sudomotor pathways or neural-induced changes in eccrine sweat glands, as evidenced by observations of reduced sweating responses in MS patients. Fatigue during thermal stress is common in MS and results in decreased motor function and increased symptomatology likely due to impairments in central conduction. Although not comprehensive, some evidence exists concerning treatments (cooling, precooling, and pharmacological) for the MS patient to preserve function and decrease symptom worsening during heat stress.

COMPUTATIONAL ANALYSIS OF SWALLOWING MECHANICS UNDERLYING IMPAIRED EPIGLOTTIC INVERSION

PubMed Central

Pearson, William G.; Taylor, Brandon K; Blair, Julie; Martin-Harris, Bonnie

2015-01-01

Objective Determine swallowing mechanics associated with the first and second epiglottic movements, that is, movement to horizontal and full inversion respectively, in order to provide a clinical interpretation of impaired epiglottic function. Study Design Retrospective cohort study. Methods A heterogeneous cohort of patients with swallowing difficulties was identified (n=92). Two speech-language pathologists reviewed 5ml thin and 5ml pudding videofluoroscopic swallow studies per subject, and assigned epiglottic component scores of 0=complete inversion, 1=partial inversion, and 2=no inversion forming three groups of videos for comparison. Coordinates mapping minimum and maximum excursion of the hyoid, pharynx, larynx, and tongue base during pharyngeal swallowing were recorded using ImageJ software. A canonical variate analysis with post-hoc discriminant function analysis of coordinates was performed using MorphoJ software to evaluate mechanical differences between groups. Eigenvectors characterizing swallowing mechanics underlying impaired epiglottic movements were visualized. Results Nineteen of 184 video-swallows were rejected for poor quality (n=165). A Goodman-Kruskal index of predictive association showed no correlation between epiglottic component scores and etiologies of dysphagia (λ=.04). A two-way analysis of variance by epiglottic component scores showed no significant interaction effects between sex and age (f=1.4, p=.25). Discriminant function analysis demonstrated statistically significant mechanical differences between epiglottic component scores: 1&2, representing the first epiglottic movement (Mahalanobis distance=1.13, p=.0007); and, 0&1, representing the second epiglottic movement (Mahalanobis distance=0.83, p=.003). Eigenvectors indicate that laryngeal elevation and tongue base retraction underlie both epiglottic movements. Conclusion Results suggest that reduced tongue base retraction and laryngeal elevation underlie impaired first and second epiglottic movements. The styloglossus, hyoglossus and long pharyngeal muscles are implicated as targets for rehabilitation in dysphagic patients with impaired epiglottic inversion. PMID:27426940

Inhibiting the Mitochondrial Calcium Uniporter during Development Impairs Memory in Adult Drosophila.

PubMed

Drago, Ilaria; Davis, Ronald L

2016-09-06

The uptake of cytoplasmic calcium into mitochondria is critical for a variety of physiological processes, including calcium buffering, metabolism, and cell survival. Here, we demonstrate that inhibiting the mitochondrial calcium uniporter in the Drosophila mushroom body neurons (MBn)-a brain region critical for olfactory memory formation-causes memory impairment without altering the capacity to learn. Inhibiting uniporter activity only during pupation impaired adult memory, whereas the same inhibition during adulthood was without effect. The behavioral impairment was associated with structural defects in MBn, including a decrease in synaptic vesicles and an increased length in the axons of the αβ MBn. Our results reveal an in vivo developmental role for the mitochondrial uniporter complex in establishing the necessary structural and functional neuronal substrates for normal memory formation in the adult organism. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.

Neural Underpinnings of Impaired Predictive Motor Timing in Children with Developmental Coordination Disorder

ERIC Educational Resources Information Center

Debrabant, Julie; Gheysen, Freja; Caeyenberghs, Karen; Van Waelvelde, Hilde; Vingerhoets, Guy

2013-01-01

A dysfunction in predictive motor timing is put forward to underlie DCD-related motor problems. Predictive timing allows for the pre-selection of motor programmes (except "program" in computers) in order to decrease processing load and facilitate reactions. Using functional magnetic resonance imaging (fMRI), this study investigated the neural…

Cognitive Mechanisms Underlying Action Prediction in Children and Adults with Autism Spectrum Condition

ERIC Educational Resources Information Center

Schuwerk, Tobias; Sodian, Beate; Paulus, Markus

2016-01-01

Recent research suggests that impaired action prediction is at the core of social interaction deficits in autism spectrum condition (ASC). Here, we targeted two cognitive mechanisms that are thought to underlie the prediction of others' actions: statistical learning and efficiency considerations. We measured proactive eye movements of 10-year-old…

Prevention of Blast-Related Injuries

DTIC Science & Technology

2015-07-14

pathology of traumatic axonal injury involves distinct injury processes, neurofilament compaction (NFC) and impaired axoplasmic transport (IAT)1. In rat...assessments and may render diagnosis of blast related pathology even more difficult. These neuronal injury changes in the grey matter that appeared...were from blast studies using rodents16,17 and impulse noise18. A putative pathological implication for microglia comes from studies by Kane et al

Tau-mediated synaptic and neuronal dysfunction in neurodegenerative disease.

PubMed

Tracy, Tara E; Gan, Li

2018-05-09

The accumulation of pathological tau in the brain is associated with neuronal deterioration and cognitive impairments in tauopathies including Alzheimer's disease. Tau, while primarily localized in the axons of healthy neurons, accumulates in the soma and dendrites of neurons under pathogenic conditions. Tau is found in both presynaptic and postsynaptic compartments of neurons in Alzheimer's disease. New research supports that soluble forms of tau trigger pathophysiology in the brain by altering properties of synaptic and neuronal function at the early stages of disease progression, before neurons die. Here we review the current understanding of how tau-mediated synaptic and neuronal dysfunction contributes to cognitive decline. Delineating the mechanisms by which pathogenic tau alters synapses, dendrites and axons will help lay the foundation for new strategies that can restore neuronal function in tauopathy. Copyright © 2018 Elsevier Ltd. All rights reserved.

Clinical and neurophysiological investigation of a large family with dominant Charcot-Marie-Tooth type 2 disease with pyramidal signs.

PubMed

Neves, Eduardo Luis de Aquino; Kok, Fernando

2011-06-01

Charcot-Marie-Tooth (CMT) disease is a hereditary neuropathy of motor and sensory impairment with distal predominance. Atrophy and weakness of lower limbs are the first signs of the disease. It can be classified, with the aid of electromyography and nerve conduction studies, as demyelinating (CMT1) or axonal (CMT2). Clinical and neurophysiological investigation of a large multigenerational family with CMT2 with autosomal dominant mode of transmission. Fifty individuals were evaluated and neurophysiological studies performed in 22 patients. Thirty individuals had clinical signs of motor-sensory neuropathy. Babinski sign was present in 14 individuals. Neurophysiological study showed motor-sensory axonal polyneuropathy. The clinical and neurophysiological characteristics of this family does not differ from those observed with other forms of CMT, except for the high prevalence of Babinski sign.

Titanium oxide as substrate for neural cell growth.

PubMed

Carballo-Vila, Mónica; Moreno-Burriel, Berta; Chinarro, Eva; Jurado, José R; Casañ-Pastor, Nieves; Collazos-Castro, Jorge E

2009-07-01

Titanium oxide has antiinflammatory activity and tunable electrochemical behavior that make it an attractive material for the fabrication of implantable devices. The most stable composition is TiO2 and occurs mainly in three polymorphs, namely, anatase, rutile, and brookite, which differ in its crystallochemical properties. Here, we report the preparation of rutile surfaces that permit good adherence and axonal growth of cultured rat cerebral cortex neurons. Rutile disks were obtained by sinterization of TiO2 powders of commercial origin or precipitated from hydrolysis of Ti(IV)-isopropoxide. Commercial powders sintered at 1300-1600 degrees C produced rutile surfaces with abnormal grain growth, probably because of impurities of the powders. Neurons cultured on those surfaces survived in variable numbers and showed fewer neurites than on control materials. On the other hand, rutile sintered from precipitated powders had less contaminants and more homogenous grain growth. By adjusting the thermal treatment it was possible to obtain surfaces performing well as substrate for neuron survival for at least 10 days. Some surfaces permitted normal axonal elongation, whereas dendrite growth was generally impaired. These findings support the potential use of titanium oxide in neuroprostheses and other devices demanding materials with enhanced properties in terms of biocompatibility and axon growth promotion.

MiR-34a Regulates Axonal Growth of Dorsal Root Ganglia Neurons by Targeting FOXP2 and VAT1 in Postnatal and Adult Mouse.

PubMed

Jia, Longfei; Chopp, Michael; Wang, Lei; Lu, Xuerong; Zhang, Yi; Szalad, Alexandra; Zhang, Zheng Gang

2018-04-10

Hyperglycemia impairs nerve fibers of dorsal root ganglia (DRG) neurons, leading to diabetic peripheral neuropathy (DPN). However, the molecular mechanisms underlying DPN are not fully understood. Using a mouse model of type II diabetes (db/db mouse), we found that microRNA-34a (miR-34a) was over-expressed in DRG, sciatic nerve, and foot pad tissues of db/db mice. In vitro, high glucose significantly upregulated miR-34a in postnatal and adult DRG neurons, which was associated with inhibition of axonal growth. Overexpression and attenuation of miR-34a in postnatal and adult DRG neurons suppressed and promoted, respectively, axonal growth. Bioinformatic analysis suggested that miR-34a putatively targets forkhead box protein P2 (FOXP2) and vesicle amine transport 1 (VAT1), which were decreased in diabetic tissues and in cultured DRG neurons under high glucose conditions. Dual-luciferase assay showed that miR-34a downregulated FOXP2 and VAT1 expression by targeting their 3' UTR. Gain-of- and loss-of-function analysis showed an inverse relation between augmentation of miR-34a and reduction of FOXP2 and VAT1 proteins in postnatal and adult DRG neurons. Knockdown of FOXP2 and VAT1 reduced axonal growth. Together, these findings suggest that miR-34a and its target genes of FOXP2 and VAT1 are involved in DRG neuron damage under hyperglycemia.

Opposing Effects of Maternal Hypo- and Hyperthyroidism on the Stability of Thalamocortical Synapses in the Visual Cortex of Adult Offspring.

PubMed

Strobl, Marie-Therese J; Freeman, Daniel; Patel, Jenica; Poulsen, Ryan; Wendler, Christopher C; Rivkees, Scott A; Coleman, Jason E

2017-05-01

Insufficient or excessive thyroid hormone (TH) levels during fetal development can cause long-term neurological and cognitive problems. Studies in animal models of perinatal hypo- and hyperthyroidism suggest that these problems may be a consequence of the formation of maladaptive circuitry in the cerebral cortex, which can persist into adulthood. Here we used mouse models of maternal hypo- and hyperthyroidism to investigate the long-term effects of altering thyroxine (T4) levels during pregnancy (corresponding to embryonic days 6.5-18.5) on thalamocortical (TC) axon dynamics in adult offspring. Because perinatal hypothyroidism has been linked to visual processing deficits in humans, we performed chronic two-photon imaging of TC axons and boutons in primary visual cortex (V1). We found that a decrease or increase in maternal serum T4 levels was associated with atypical steady-state dynamics of TC axons and boutons in V1 of adult offspring. Hypothyroid offspring exhibited axonal branch and bouton dynamics indicative of an abnormal increase in TC connectivity, whereas changes in hyperthyroid offspring were indicative of an abnormal decrease in TC connectivity. Collectively, our data suggest that alterations to prenatal T4 levels can cause long-term synaptic instability in TC circuits, which could impair early stages of visual processing. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

Nitric oxide reversibly impairs axonal conduction in Guinea pig spinal cord.

PubMed

Ashki, Negin; Hayes, Keith C; Shi, Riyi

2006-12-01

Increased expression of the inducible and neuronal isoforms of nitric oxide synthase (NOS), and elevated concentrations of nitric oxide (NO) metabolites, are present within the central nervous system (CNS) following neurotrauma and are implicated in the pathogenesis of the accompanying neurologic deficits. We tested the hypothesis that elevated extracellular concentrations of NO introduced by the donor Spermine NONOate, induce reversible axonal conduction deficits in neurons of the guinea pig spinal cord. The compound action potential (CAP) and compound membrane potential (CMP) of excised ventral cord white matter were recorded before, during, and after bathing the tissue (30 min) in varying concentrations (0.25-3.0 mM) of Spermine NONOate. The principal results were a rapid onset, dose-dependent, reduction in amplitude of the CAP (p < 0.05) accompanied by depolarization of the CMP during NO exposure. These effects were largely reversible on washout, at low concentration of the donor (0.5 mM), but were only partially reversed at higher concentrations. Changes in the electrophysiological properties were not evident when the donor had been a priori depleted of NO. The results extend previous reports that NO induces reversible axonal conduction deficits. They provide new evidence of dissociation of the effects of NO on CAP and CMP during washout, and after prolonged exposure to the donor. They add support to the emerging concept that immune-mediated axonal conduction failure contributes to reversible neurologic deficits following neurotrauma and aid in understanding clinical phenomena such as spinal shock and neurologic recovery.

Alterations of Hippocampal Myelin Sheath and Axon Sprouting by Status Convulsion and Regulating Lingo-1 Expression with RNA Interference in Immature and Adult Rats.

PubMed

Song, Xiao-Jie; Han, Wei; He, Rong; Li, Tian-Yi; Xie, Ling-Ling; Cheng, Li; Chen, Heng-Sheng; Jiang, Li

2018-03-01

Seizure-induced brain damage is age-dependent, as evidenced by the different alterations of neural physiopathology in developing and mature brains. However, little is known about the age-dependent characteristics of myelinated fiber injury induced by seizures. Considering the critical functions of oligodendrocyte progenitor cells (OPCs) in myelination and Lingo-1 signaling in regulating OPCs' differentiation, the present study aimed to explore the effects of Lingo-1 on myelin and axon in immature and adult rats after status convulsion (SC) induced by lithium-pilocarpine, and the differences between immature and adult brains. Dynamic variations in electrophysiological activity and spontaneous recurrent seizures were recorded by electroencephalogram monitoring after SC. The impaired microstructures of myelin sheaths and decrease in myelin basic protein caused by SC were observed through transmission electron microscopy and western blot analysis respectively, which became more severe in adult rats, but improved gradually in immature rats. Aberrant axon sprouting occurred in adult rats, which was more prominent than in immature rats, as shown by a Timm stain. This damage was improved or negatively affected after down or upregulating Lingo-1 expression. These results demonstrated that in both immature and adult brains, Lingo-1 signaling plays important roles in seizure-induced damage to myelin sheaths and axon growth. The plasticity of the developing brain may provide a potential window of opportunity to prevent the brain from damage.

Exosomes derived from high-glucose-stimulated Schwann cells promote development of diabetic peripheral neuropathy.

PubMed

Jia, Longfei; Chopp, Michael; Wang, Lei; Lu, Xuerong; Szalad, Alexandra; Zhang, Zheng Gang

2018-06-22

Schwann cells actively interact with axons of dorsal root ganglia (DRG) neurons. Exosomes mediate intercellular communication by transferring their biomaterials, including microRNAs (miRs) into recipient cells. We hypothesized that exosomes derived from Schwann cells stimulated by high glucose (HG) exosomes accelerate development of diabetic peripheral neuropathy and that exosomal cargo miRs contribute to this process. We found that HG exosomes contained high levels of miR-28, -31a, and -130a compared to exosomes derived from non-HG-stimulated Schwann cells. In vitro, treatment of distal axons with HG exosomes resulted in reduction of axonal growth, which was associated with elevation of miR-28, -31a, and -130a and reduction of their target proteins of DNA methyltransferase-3α, NUMB (an endocytic adaptor protein), synaptosome associated protein 25, and growth-associated protein-43 in axons. In vivo, administration of HG exosomes to sciatic nerves of diabetic db/db mice at 7 wk of age promoted occurrence of peripheral neuropathy characterized by impairment of nerve conduction velocity and induction of mechanic and thermal hypoesthesia, which was associated with substantial decreases in intraepidermal nerve fibers. Our findings demonstrate a functional role of exosomes derived from HG-stimulated Schwann cells in mediating development of diabetic peripheral neuropathy.-Jia, L., Chopp, M., Wang, L., Lu, X., Szalad, A., Zhang, Z. G. Exosomes derived from high-glucose-stimulated Schwann cells promote development of diabetic peripheral neuropathy.

Ascorbic acid ameliorates behavioural deficits and neuropathological alterations in rat model of Alzheimer's disease.

PubMed

Olajide, Olayemi Joseph; Yawson, Emmanuel Olusola; Gbadamosi, Ismail Temitayo; Arogundade, Tolulope Timothy; Lambe, Ezra; Obasi, Kosisochukwu; Lawal, Ismail Tayo; Ibrahim, Abdulmumin; Ogunrinola, Kehinde Yomi

2017-03-01

Exploring the links between neural pathobiology and behavioural deficits in Alzheimer's disease (AD), and investigating substances with known therapeutic advantages over subcellular mechanisms underlying these dysfunctions could advance the development of potent therapeutic molecules for AD treatment. Here we investigated the efficacy of ascorbic acid (AA) in reversing aluminium chloride (AlCl 3 )-induced behavioural deficits and neurotoxic cascades within prefrontal cortex (PFC) and hippocampus of rats. A group of rats administered oral AlCl 3 (100mg/kg) daily for 15days showed degenerative changes characterised by significant weight loss, reduced exploratory/working memory, frontal-dependent motor deficits, cognitive decline, memory dysfunction and anxiety during behavioural assessments compared to control. Subsequent analysis showed that oxidative impairment-indicated by depleted superoxide dismutase and lipid peroxidation (related to glutathione-S-transferase activity), cholinergic deficits seen by increased neural acetylcholinesterase (AChE) expression and elevated lactate dehydrogenase underlie behavioural alterations. Furthermore, evidences of proteolysis were seen by reduced Nissl profiles in neuronal axons and dendrites which correspond to apoptotic changes observed in H&E staining of PFC and hippocampal sections. Interestingly, AA (100mg/kg daily for 15days) significantly attenuated behavioural deficits in rats through inhibition of molecular and cellular stressor proteins activated by AlCl 3. Our results showed that the primary mechanisms underlying AA therapeutic advantages relates closely with its abilities to scavenge free radicals, prevent membrane lipid peroxidation, modulate neuronal bioenergetics, act as AChE inhibitor and through its anti-proteolytic properties. These findings suggest that supplementing endogenous AA capacity through its pharmacological intake may inhibit progression of AD-related neurodegenerative processes and behavioural alterations. Copyright © 2017 Elsevier B.V. All rights reserved.

Oxycodone Self-Administration Induces Alterations in Expression of Integrin, Semaphorin and Ephrin Genes in the Mouse Striatum.

PubMed

Yuferov, Vadim; Zhang, Yong; Liang, Yupu; Zhao, Connie; Randesi, Matthew; Kreek, Mary J

2018-01-01

Oxycodone is one a commonly used medication for pain, and is also a widely abused prescription opioid, like other short-acting MOPr agonists. Neurochemical and structural adaptations in brain following chronic MOPr-agonist administration are thought to underlie pathogenesis and persistence of opiate addiction. Many axon guidance molecules, such as integrins, semaphorins, and ephrins may contribute to oxycodone-induced neuroadaptations through alterations in axon-target connections and synaptogenesis, that may be implicated in the behaviors associated with opiate addiction. However, little is known about this important area. The aim of this study is to investigate alterations in expression of selected integrin, semaphorin, ephrins, netrin, and slit genes in the nucleus accumbens (NAc) and caudate putamen (CPu) of mice following extended 14-day oxycodone self-administration (SA), using RNAseq. Methods: Total RNA from the NAc and CPu were isolated from adult male C57BL/6J mice within 1 h after the last session of oxycodone in a 14-day self-administration paradigm (4h/day, 0.25 mg/kg/infusion, FR1) or from yoked saline controls. Gene expressions were examined using RNA sequencing (RNA-Seq) technology. RNA-Seq libraries were prepared using Illumina's TruSeq® Stranded Total RNA LT kit. The reads were aligned to the mouse reference genome (version mm10) using STAR. DESeq2 was applied to the counts of protein coding genes to estimate the fold change between the treatment groups. False Discovery Rate (FDR) q < 0.1 were used to select genes that have a significant expression change. For selection of a subset of genes related to axon guidance pathway, REACTOME was used. Results: Among 38 known genes of the integrin, semaphorin, and ephrin gene families, RNA-seq data revealed up-regulation of six genes in the NAc: heterodimer receptor, integrins Itgal, Itgb2 , and Itgam , and its ligand semaphorin Sema7a , two semaphorin receptors, plexins Plxnd1 and Plxdc1 . There was down-regulation of eight genes in this region: two integrin genes Itga3 and Itgb8 , semaphorins Sema3c, Sema4g, Sema6a, Sema6d , semaphorin receptor neuropilin Nrp2 , and ephrin receptor Epha3 . In the CPu, there were five differentially expressed axon guidance genes: up-regulation of three integrin genes, Itgal, Itgb2, Itga1 , and down-regulation of Itga9 and ephrin Efna3 were thus observed. No significant alterations in expression of Netrin-1 or Slit were observed. Conclusion: We provide evidence for alterations in the expression of selective axon guidance genes in adult mouse brain following chronic self-administration of oxycodone. Further examination of oxycodone-induced changes in the expression of these specific axon guidance molecules and integrin genes in relation to behavior may provide new insights into development of addiction to oxycodone.

Associations between Drug Use and Deviant Behavior in Teenagers. Health Sciences Program Reprint Series, 96-23D.

ERIC Educational Resources Information Center

Hays, Ron D.; Ellickson, Phyllis L.

1996-01-01

Drug use and delinquency share many common antecedents: early antisocial behavior, difficulties in school, impaired family relationships, delinquent or drug-using peers, and rebelliousness. But these common factors could underlie a cluster of problem behaviors or lead to distinctly different behavioral manifestations. Using data from 1,363 West…

Poor Phonemic Discrimination Does Not Underlie Poor Verbal Short-Term Memory in Down Syndrome

ERIC Educational Resources Information Center

Purser, Harry R. M.; Jarrold, Christopher

2013-01-01

Individuals with Down syndrome tend to have a marked impairment of verbal short-term memory. The chief aim of this study was to investigate whether phonemic discrimination contributes to this deficit. The secondary aim was to investigate whether phonological representations are degraded in verbal short-term memory in people with Down syndrome…

Effects of Age and Hearing Loss on Gap Detection and the Precedence Effect: Broadband Stimuli

ERIC Educational Resources Information Center

Roberts, Richard A.; Lister, Jennifer J.

2004-01-01

Older listeners with normal-hearing sensitivity and impaired-hearing sensitivity often demonstrate poorer-than-normal performance on tasks of speech understanding in noise and reverberation. Deficits in temporal resolution and in the precedence effect may underlie this difficulty. Temporal resolution is often studied by means of a gap-detection…

Axonal disruption in white matter underlying cortical sulcus tau pathology in chronic traumatic encephalopathy.

PubMed

Holleran, Laurena; Kim, Joong Hee; Gangolli, Mihika; Stein, Thor; Alvarez, Victor; McKee, Ann; Brody, David L

2017-03-01

Chronic traumatic encephalopathy (CTE) is a progressive degenerative disorder associated with repetitive traumatic brain injury. One of the primary defining neuropathological lesions in CTE, based on the first consensus conference, is the accumulation of hyperphosphorylated tau in gray matter sulcal depths. Post-mortem CTE studies have also reported myelin loss, axonal injury and white matter degeneration. Currently, the diagnosis of CTE is restricted to post-mortem neuropathological analysis. We hypothesized that high spatial resolution advanced diffusion MRI might be useful for detecting white matter microstructural changes directly adjacent to gray matter tau pathology. To test this hypothesis, formalin-fixed post-mortem tissue blocks from the superior frontal cortex of ten individuals with an established diagnosis of CTE were obtained from the Veterans Affairs-Boston University-Concussion Legacy Foundation brain bank. Advanced diffusion MRI data was acquired using an 11.74 T MRI scanner at Washington University with 250 × 250 × 500 µm 3 spatial resolution. Diffusion tensor imaging, diffusion kurtosis imaging and generalized q-sampling imaging analyses were performed in a blinded fashion. Following MRI acquisition, tissue sections were tested for phosphorylated tau immunoreactivity in gray matter sulcal depths. Axonal disruption in underlying white matter was assessed using two-dimensional Fourier transform analysis of myelin black gold staining. A robust image co-registration method was applied to accurately quantify the relationship between diffusion MRI parameters and histopathology. We found that white matter underlying sulci with high levels of tau pathology had substantially impaired myelin black gold Fourier transform power coherence, indicating axonal microstructural disruption (r = -0.55, p = 0.0015). Using diffusion tensor MRI, we found that fractional anisotropy (FA) was modestly (r = 0.53) but significantly (p = 0.0012) correlated with axonal disruption, where lower FA was associated with greater axonal disruption in white matter directly adjacent to hyperphosphorylated tau positive sulci. In summary, our findings indicate that axonal disruption and tau pathology are closely associated, and high spatial resolution ex vivo diffusion MRI has the potential to detect microstructural alterations observed in CTE tissue. Future studies will be required to determine whether this approach can be applied to living people.

Defective lysosomal proteolysis and axonal transport are early pathogenic events that worsen with age leading to increased APP metabolism and synaptic Abeta in transgenic APP/PS1 hippocampus

PubMed Central

2012-01-01

Background Axonal pathology might constitute one of the earliest manifestations of Alzheimer disease. Axonal dystrophies were observed in Alzheimer’s patients and transgenic models at early ages. These axonal dystrophies could reflect the disruption of axonal transport and the accumulation of multiple vesicles at local points. It has been also proposed that dystrophies might interfere with normal intracellular proteolysis. In this work, we have investigated the progression of the hippocampal pathology and the possible implication in Abeta production in young (6 months) and aged (18 months) PS1(M146L)/APP(751sl) transgenic mice. Results Our data demonstrated the existence of a progressive, age-dependent, formation of axonal dystrophies, mainly located in contact with congophilic Abeta deposition, which exhibited tau and neurofilament hyperphosphorylation. This progressive pathology was paralleled with decreased expression of the motor proteins kinesin and dynein. Furthermore, we also observed an early decrease in the activity of cathepsins B and D, progressing to a deep inhibition of these lysosomal proteases at late ages. This lysosomal impairment could be responsible for the accumulation of LC3-II and ubiquitinated proteins within axonal dystrophies. We have also investigated the repercussion of these deficiencies on the APP metabolism. Our data demonstrated the existence of an increase in the amyloidogenic pathway, which was reflected by the accumulation of hAPPfl, C99 fragment, intracellular Abeta in parallel with an increase in BACE and gamma-secretase activities. In vitro experiments, using APPswe transfected N2a cells, demonstrated that any imbalance on the proteolytic systems reproduced the in vivo alterations in APP metabolism. Finally, our data also demonstrated that Abeta peptides were preferentially accumulated in isolated synaptosomes. Conclusion A progressive age-dependent cytoskeletal pathology along with a reduction of lysosomal and, in minor extent, proteasomal activity could be directly implicated in the progressive accumulation of APP derived fragments (and Abeta peptides) in parallel with the increase of BACE-1 and gamma-secretase activities. This retard in the APP metabolism seemed to be directly implicated in the synaptic Abeta accumulation and, in consequence, in the pathology progression between synaptically connected regions. PMID:23173743

Axonal guidance signaling pathway interacting with smoking in modifying the risk of pancreatic cancer: a gene- and pathway-based interaction analysis of GWAS data.

PubMed

Tang, Hongwei; Wei, Peng; Duell, Eric J; Risch, Harvey A; Olson, Sara H; Bueno-de-Mesquita, H Bas; Gallinger, Steven; Holly, Elizabeth A; Petersen, Gloria; Bracci, Paige M; McWilliams, Robert R; Jenab, Mazda; Riboli, Elio; Tjønneland, Anne; Boutron-Ruault, Marie Christine; Kaaks, Rudolph; Trichopoulos, Dimitrios; Panico, Salvatore; Sund, Malin; Peeters, Petra H M; Khaw, Kay-Tee; Amos, Christopher I; Li, Donghui

2014-05-01

Cigarette smoking is the best established modifiable risk factor for pancreatic cancer. Genetic factors that underlie smoking-related pancreatic cancer have previously not been examined at the genome-wide level. Taking advantage of the existing Genome-wide association study (GWAS) genotype and risk factor data from the Pancreatic Cancer Case Control Consortium, we conducted a discovery study in 2028 cases and 2109 controls to examine gene-smoking interactions at pathway/gene/single nucleotide polymorphism (SNP) level. Using the likelihood ratio test nested in logistic regression models and ingenuity pathway analysis (IPA), we examined 172 KEGG (Kyoto Encyclopedia of Genes and Genomes) pathways, 3 manually curated gene sets, 3 nicotine dependency gene ontology pathways, 17 912 genes and 468 114 SNPs. None of the individual pathway/gene/SNP showed significant interaction with smoking after adjusting for multiple comparisons. Six KEGG pathways showed nominal interactions (P < 0.05) with smoking, and the top two are the pancreatic secretion and salivary secretion pathways (major contributing genes: RAB8A, PLCB and CTRB1). Nine genes, i.e. ZBED2, EXO1, PSG2, SLC36A1, CLSTN1, MTHFSD, FAT2, IL10RB and ATXN2 had P interaction < 0.0005. Five intergenic region SNPs and two SNPs of the EVC and KCNIP4 genes had P interaction < 0.00003. In IPA analysis of genes with nominal interactions with smoking, axonal guidance signaling $$\\left(P=2.12\\times 1{0}^{-7}\\right)$$ and α-adrenergic signaling $$\\left(P=2.52\\times 1{0}^{-5}\\right)$$ genes were significantly overrepresented canonical pathways. Genes contributing to the axon guidance signaling pathway included the SLIT/ROBO signaling genes that were frequently altered in pancreatic cancer. These observations need to be confirmed in additional data set. Once confirmed, it will open a new avenue to unveiling the etiology of smoking-associated pancreatic cancer.

The association of visuospatial working memory with dysthymic disorder in pre-pubertal children.

PubMed

Franklin, T; Lee, A; Hall, N; Hetrick, S; Ong, J; Haslam, N; Karsz, F; Vance, A

2010-02-01

Visuospatial working memory (VSWM) deficits have not been investigated specifically in children with dysthymic disorder (DD), although they are associated with impairments in attention that commonly occur in DD. This study investigates VSWM impairment in children with DD. A cross-sectional study of VSWM in 6- to 12-year-old children with medication-naive DD (n=26) compared to an age-, gender- and 'performance IQ' (PIQ)-matched healthy control group (n=28) was completed. The DD group demonstrated impairment in VSWM, including impairment in the spatial span and strategy components of VSWM. Furthermore, the VSWM impairment remained after controlling for spatial span. Inattentive symptoms were significantly associated with the VSWM impairment. This study of children with DD found deficits in performance on VSWM tasks, suggesting that fronto-striatal-parietal neural networks that underlie processes of attention and the executive component of VSWM are dysfunctional in children with DD. These findings further our understanding of DD and suggest more specific interventions that might improve functioning.

Exposure to As, Cd and Pb-mixture impairs myelin and axon development in rat brain, optic nerve and retina

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rai, Nagendra Kumar; Ashok, Anushruti; Developmental Toxicology, Council of Scientific and Industrial Research-Indian Institute of Toxicology Research

Arsenic (As), lead (Pb) and cadmium (Cd) are the major metal contaminants of ground water in India. We have reported the toxic effect of their mixture (metal mixture, MM), at human relevant doses, on developing rat astrocytes. Astrocyte damage has been shown to be associated with myelin disintegration in CNS. We, therefore, hypothesized that the MM would perturb myelinating white matter in cerebral cortex, optic nerve (O.N.) and retina. We observed modulation in the levels of myelin and axon proteins, such as myelin basic protein (MBP), proteolipid protein, 2′-, 3′-cyclic-nucleotide-3′-phosphodiesterase, myelin-associated glycoprotein and neurofilament (NF) in the brain of developingmore » rats. Dose and time-dependent synergistic toxic effect was noted. The MBP- and NF-immunolabeling, as well as luxol-fast blue (LFB) staining demonstrated a reduction in the area of intact myelin-fiber, and an increase in vacuolated axons, especially in the corpus-callosum. Transmission electron microscopy (TEM) of O.N. revealed a reduction in myelin thickness and axon-density. The immunolabeling with MBP, NF, and LFB staining in O.N. supported the TEM data. The hematoxylin and eosin staining of retina displayed a decrease in the thickness of nerve-fiber, plexiform-layer, and retinal ganglion cell (RGC) count. Investigating the mechanism revealed a loss in glutamine synthetase activity in the cerebral cortex and O.N., and a fall in the brain derived neurotrophic factor in retina. An enhanced apoptosis in MBP, NF and Brn3b-containing cells justified the diminution in myelinating axons in CNS. Our findings for the first time indicate white matter damage by MM, which may have significance in neurodevelopmental-pediatrics, neurotoxicology and retinal-cell biology. - Highlights: • As, Cd and Pb-mixture, at human relevant dose, demyelinate developing rat CNS. • The attenuation in myelin and axon is synergistic. • The optic nerve and brain demonstrate reduced glutamine synthetase. • The retina exhibits diminished neurotrophin levels and cellular differentiation. • The toxic effect is apoptotic.« less

Tau elevations in the brain extracellular space correlate with reduced amyloid-β levels and predict adverse clinical outcomes after severe traumatic brain injury.

PubMed

Magnoni, Sandra; Esparza, Thomas J; Conte, Valeria; Carbonara, Marco; Carrabba, Giorgio; Holtzman, David M; Zipfel, Greg J; Stocchetti, Nino; Brody, David L

2012-04-01

Axonal injury is believed to be a major determinant of adverse outcomes following traumatic brain injury. However, it has been difficult to assess acutely the severity of axonal injury in human traumatic brain injury patients. We hypothesized that microdialysis-based measurements of the brain extracellular fluid levels of tau and neurofilament light chain, two low molecular weight axonal proteins, could be helpful in this regard. To test this hypothesis, 100 kDa cut-off microdialysis catheters were placed in 16 patients with severe traumatic brain injury at two neurological/neurosurgical intensive care units. Tau levels in the microdialysis samples were highest early and fell over time in all patients. Initial tau levels were >3-fold higher in patients with microdialysis catheters placed in pericontusional regions than in patients in whom catheters were placed in normal-appearing right frontal lobe tissue (P = 0.005). Tau levels and neurofilament light-chain levels were positively correlated (r = 0.6, P = 0.013). Neurofilament light-chain levels were also higher in patients with pericontusional catheters (P = 0.04). Interestingly, initial tau levels were inversely correlated with initial amyloid-β levels measured in the same samples (r = -0.87, P = 0.000023). This could be due to reduced synaptic activity in areas with substantial axonal injury, as amyloid-β release is closely coupled with synaptic activity. Importantly, high initial tau levels correlated with worse clinical outcomes, as assessed using the Glasgow Outcome Scale 6 months after injury (r = -0.6, P = 0.018). Taken together, our data add support for the hypothesis that axonal injury may be related to long-term impairments following traumatic brain injury. Microdialysis-based measurement of tau levels in the brain extracellular space may be a useful way to assess the severity of axonal injury acutely in the intensive care unit. Further studies with larger numbers of patients will be required to assess the reproducibility of these findings and to determine whether this approach provides added value when combined with clinical and radiological information.

Oxidative stress, insulin resistance, dyslipidemia and type 2 diabetes mellitus

PubMed Central

Tangvarasittichai, Surapon

2015-01-01

Oxidative stress is increased in metabolic syndrome and type 2 diabetes mellitus (T2DM) and this appears to underlie the development of cardiovascular disease, T2DM and diabetic complications. Increased oxidative stress appears to be a deleterious factor leading to insulin resistance, dyslipidemia, β-cell dysfunction, impaired glucose tolerance and ultimately leading to T2DM. Chronic oxidative stress, hyperglycemia and dyslipidemia are particularly dangerous for β-cells from lowest levels of antioxidant, have high oxidative energy requirements, decrease the gene expression of key β-cell genes and induce cell death. If β-cell functioning is impaired, it results in an under production of insulin, impairs glucose stimulated insulin secretion, fasting hyperglycemia and eventually the development of T2DM. PMID:25897356

Intermediate filament aggregates cause mitochondrial dysmotility and increase energy demands in giant axonal neuropathy

PubMed Central

Israeli, Eitan; Dryanovski, Dilyan I.; Schumacker, Paul T.; Chandel, Navdeep S.; Singer, Jeffrey D.; Julien, Jean P.; Goldman, Robert D.; Opal, Puneet

2016-01-01

Intermediate filaments (IFs) are cytoskeletal polymers that extend from the nucleus to the cell membrane, giving cells their shape and form. Abnormal accumulation of IFs is involved in the pathogenesis of number neurodegenerative diseases, but none as clearly as giant axonal neuropathy (GAN), a ravaging disease caused by mutations in GAN, encoding gigaxonin. Patients display early and severe degeneration of the peripheral nervous system along with IF accumulation, but it has been difficult to link GAN mutations to any particular dysfunction, in part because GAN null mice have a very mild phenotype. We therefore established a robust dorsal root ganglion neuronal model that mirrors key cellular events underlying GAN. We demonstrate that gigaxonin is crucial for ubiquitin–proteasomal degradation of neuronal IF. Moreover, IF accumulation impairs mitochondrial motility and is associated with metabolic and oxidative stress. These results have implications for other neurological disorders whose pathology includes IF accumulation. PMID:27000625

Top-down cortical input during NREM sleep consolidates perceptual memory.

PubMed

Miyamoto, D; Hirai, D; Fung, C C A; Inutsuka, A; Odagawa, M; Suzuki, T; Boehringer, R; Adaikkan, C; Matsubara, C; Matsuki, N; Fukai, T; McHugh, T J; Yamanaka, A; Murayama, M

2016-06-10

During tactile perception, long-range intracortical top-down axonal projections are essential for processing sensory information. Whether these projections regulate sleep-dependent long-term memory consolidation is unknown. We altered top-down inputs from higher-order cortex to sensory cortex during sleep and examined the consolidation of memories acquired earlier during awake texture perception. Mice learned novel textures and consolidated them during sleep. Within the first hour of non-rapid eye movement (NREM) sleep, optogenetic inhibition of top-down projecting axons from secondary motor cortex (M2) to primary somatosensory cortex (S1) impaired sleep-dependent reactivation of S1 neurons and memory consolidation. In NREM sleep and sleep-deprivation states, closed-loop asynchronous or synchronous M2-S1 coactivation, respectively, reduced or prolonged memory retention. Top-down cortical information flow in NREM sleep is thus required for perceptual memory consolidation. Copyright © 2016, American Association for the Advancement of Science.

AlphaB-crystallin regulates remyelination after peripheral nerve injury

PubMed Central

Lim, Erin-Mai F.; Nakanishi, Stan T.; Hoghooghi, Vahid; Eaton, Shane E. A.; Palmer, Alexandra L.; Frederick, Ariana; Stratton, Jo A.; Stykel, Morgan G.; Zochodne, Douglas W.; Biernaskie, Jeffrey; Ousman, Shalina S.

2017-01-01

AlphaB-crystallin (αBC) is a small heat shock protein that is constitutively expressed by peripheral nervous system (PNS) axons and Schwann cells. To determine what role this crystallin plays after peripheral nerve damage, we found that loss of αBC impaired remyelination, which correlated with a reduced presence of myelinating Schwann cells and increased numbers of nonmyelinating Schwann cells. The heat shock protein also seems to regulate the cross-talk between Schwann cells and axons, because expected changes in neuregulin levels and ErbB2 receptor expression after PNS injury were disrupted in the absence of αBC. Such dysregulations led to defects in conduction velocity and motor and sensory functions that could be rescued with therapeutic application of the heat shock protein in vivo. Altogether, these findings show that αBC plays an important role in regulating Wallerian degeneration and remyelination after PNS injury. PMID:28137843

Conditional genetic deletion of PTEN after a spinal cord injury enhances regenerative growth of CST axons and motor function recovery in mice

PubMed Central

Danilov, Camelia A.; Steward, Oswald

2015-01-01

Previous studies indicate that conditional genetic deletion of phosphatase and tensin homolog (PTEN) in neonatal mice enhances the ability of axons to regenerate following spinal cord injury (SCI) in adults. Here, we assessed whether deleting PTEN in adult neurons post-SCI is also effective, and whether enhanced regenerative growth is accompanied by enhanced recovery of voluntary motor function. PTENloxP/loxP mice received moderate contusion injuries at cervical level 5 (C5). One group received unilateral injections of adeno-associated virus expressing CRE (AAV-CRE) into the sensorimotor cortex; controls received a vector expressing green fluorescent protein (AAV-GFP) or injuries only (no vector injections). Forelimb function was tested for 14 weeks post-SCI using a grip strength meter (GSM) and a hanging task. The corticospinal tract (CST) was traced by injecting mini-ruby BDA into the sensorimotor cortex. Forelimb gripping ability was severely impaired immediately post-SCI but recovered slowly over time. The extent of recovery was significantly greater in PTEN-deleted mice in comparison to either the AAV-GFP group or the injury only group. BDA tract tracing revealed significantly higher numbers of BDA-labeled axons in caudal segments in the PTEN-deleted group compared to control groups. In addition, in the PTEN-deleted group, there were exuberant collaterals extending from the main tract rostral to the lesion, into and around the scar tissue at the injury site. These results indicate that PTEN deletion in adult mice shortly post-SCI can enhance regenerative growth of CST axons and forelimb motor function recovery. PMID:25704959

Bilateral Cervical Contusion Spinal Cord Injury in Rats

PubMed Central

Anderson, Kim D.; Sharp, Kelli G.; Steward, Oswald

2009-01-01

There is increasing motivation to develop clinically relevant experimental models for cervical SCI in rodents and techniques to assess deficits in forelimb function. Here we describe a bilateral cervical contusion model in rats. Female Sprague-Dawley rats received mild or moderate cervical contusion injuries (using the Infinite Horizons device) at C5, C6, or C7/8. Forelimb motor function was assessed using a Grip Strength Meter (GSM); sensory function was assessed by the von Frey hair test; the integrity of the corticospinal tract (CST) was assessed by biotinylated dextran amine (BDA) tract tracing. Mild contusions caused primarily dorsal column (DC) and gray matter (GM) damage while moderate contusions produced additional damage to lateral and ventral tissue. Forelimb and hindlimb function was severely impaired immediately post-injury, but all rats regained the ability to use their hindlimbs for locomotion. Gripping ability was abolished immediately after injury but recovered partially, depending upon the spinal level and severity of the injury. Rats exhibited a loss of sensation in both fore- and hindlimbs that partially recovered, and did not exhibit allodynia. Tract tracing revealed that the main contingent of CST axons in the DC was completely interrupted in all but one animal whereas the dorsolateral CST (dlCST) was partially spared, and dlCST axons gave rise to axons that arborized in the GM caudal to the injury. Our data demonstrate that rats can survive significant bilateral cervical contusion injuries at or below C5 and that forepaw gripping function recovers after mild injuries even when the main component of CST axons in the dorsal column is completely interrupted. PMID:19559699

The relationship between white matter brain metabolites and cognition in normal aging: the GENIE study.

PubMed

Charlton, R A; McIntyre, D J O; Howe, F A; Morris, R G; Markus, H S

2007-08-20

Magnetic resonance spectroscopy (MRS) has demonstrated age-related changes in brain metabolites that may underlie micro-structural brain changes, but few studies have examined their relationship with cognitive decline. We performed a cross-sectional study of brain metabolism and cognitive function in 82 healthy adults (aged 50-90) participating in the GENIE (St GEorge's Neuropsychology and Imaging in the Elderly) study. Absolute metabolite concentrations were measured by proton chemical shift imaging within voxels placed in the centrum semiovale white matter. Cognitive abilities assessed were executive function, working memory, information processing speed, long-term memory and fluid intelligence. Correlations showed that all cognitive domains declined with age. Total creatine (tCr) concentration increased with age (r=0.495, p<0.001). Regression analyses were performed for each cognitive variable, including estimated intelligence and the metabolites, with age then added as a final step. A significant relationship was observed between tCr and executive function, long-term memory, and fluid intelligence, although these relationships did not remain significant after age was added as a final step in the regression. The regression analysis also demonstrated a significant relationship between N-acetylaspartate (NAA) and executive function. As there was no age-related decline in NAA, this argues against axonal loss with age; however the relationship between NAA and executive function independent of age and estimated intelligence is consistent with white matter axonal integrity having an important role in executive function in normal individuals.

Diminished superoxide generation is associated with respiratory chain dysfunction and changes in the mitochondrial proteome of sensory neurons from diabetic rats.

PubMed

Akude, Eli; Zherebitskaya, Elena; Chowdhury, Subir K Roy; Smith, Darrell R; Dobrowsky, Rick T; Fernyhough, Paul

2011-01-01

Impairments in mitochondrial function have been proposed to play a role in the etiology of diabetic sensory neuropathy. We tested the hypothesis that mitochondrial dysfunction in axons of sensory neurons in type 1 diabetes is due to abnormal activity of the respiratory chain and an altered mitochondrial proteome. Proteomic analysis using stable isotope labeling with amino acids in cell culture (SILAC) determined expression of proteins in mitochondria from dorsal root ganglia (DRG) of control, 22-week-old streptozotocin (STZ)-diabetic rats, and diabetic rats treated with insulin. Rates of oxygen consumption and complex activities in mitochondria from DRG were measured. Fluorescence imaging of axons of cultured sensory neurons determined the effect of diabetes on mitochondrial polarization status, oxidative stress, and mitochondrial matrix-specific reactive oxygen species (ROS). Proteins associated with mitochondrial dysfunction, oxidative phosphorylation, ubiquinone biosynthesis, and the citric acid cycle were downregulated in diabetic samples. For example, cytochrome c oxidase subunit IV (COX IV; a complex IV protein) and NADH dehydrogenase Fe-S protein 3 (NDUFS3; a complex I protein) were reduced by 29 and 36% (P < 0.05), respectively, in diabetes and confirmed previous Western blot studies. Respiration and mitochondrial complex activity was significantly decreased by 15 to 32% compared with control. The axons of diabetic neurons exhibited oxidative stress and depolarized mitochondria, an aberrant adaption to oligomycin-induced mitochondrial membrane hyperpolarization, but reduced levels of intramitochondrial superoxide compared with control. Abnormal mitochondrial function correlated with a downregulation of mitochondrial proteins, with components of the respiratory chain targeted in lumbar DRG in diabetes. The reduced activity of the respiratory chain was associated with diminished superoxide generation within the mitochondrial matrix and did not contribute to oxidative stress in axons of diabetic neurons. Alternative pathways involving polyol pathway activity appear to contribute to raised ROS in axons of diabetic neurons under high glucose concentration.

Miro's N-Terminal GTPase Domain Is Required for Transport of Mitochondria into Axons and Dendrites

PubMed Central

Babic, Milos; Russo, Gary J.; Wellington, Andrea J.; Sangston, Ryan M.; Gonzalez, Migdalia

2015-01-01

Mitochondria are dynamically transported in and out of neuronal processes to maintain neuronal excitability and synaptic function. In higher eukaryotes, the mitochondrial GTPase Miro binds Milton/TRAK adaptor proteins linking microtubule motors to mitochondria. Here we show that Drosophila Miro (dMiro), which has previously been shown to be required for kinesin-driven axonal transport, is also critically required for the dynein-driven distribution of mitochondria into dendrites. In addition, we used the loss-of-function mutations dMiroT25N and dMiroT460N to determine the significance of dMiro's N-terminal and C-terminal GTPase domains, respectively. Expression of dMiroT25N in the absence of endogenous dMiro caused premature lethality and arrested development at a pupal stage. dMiroT25N accumulated mitochondria in the soma of larval motor and sensory neurons, and prevented their kinesin-dependent and dynein-dependent distribution into axons and dendrites, respectively. dMiroT25N mutant mitochondria also were severely fragmented and exhibited reduced kinesin and dynein motility in axons. In contrast, dMiroT460N did not impair viability, mitochondrial size, or the distribution of mitochondria. However, dMiroT460N reduced dynein motility during retrograde mitochondrial transport in axons. Finally, we show that substitutions analogous to the constitutively active Ras-G12V mutation in dMiro's N-terminal and C-terminal GTPase domains cause neomorphic phenotypic effects that are likely unrelated to the normal function of each GTPase domain. Overall, our analysis indicates that dMiro's N-terminal GTPase domain is critically required for viability, mitochondrial size, and the distribution of mitochondria out of the neuronal soma regardless of the employed motor, likely by promoting the transition from a stationary to a motile state. PMID:25855186

Inter-hemispheric wave propagation failures in traumatic brain injury are indicative of callosal damage.

PubMed

Spiegel, Daniel P; Laguë-Beauvais, Maude; Sharma, Gaurav; Farivar, Reza

2015-04-01

Approximately 3.2-5.3 million Americans live with the consequences of a traumatic brain injury (TBI), making TBI one of the most common causes of disability in the world. Visual deficits often accompany TBI but physiological and anatomical evidence for injury in mild TBI is lacking. Axons traversing the corpus callosum are particularly vulnerable to TBI. Hemifield representations of early visual areas are linked by bundles of fibers that together cross the corpus callosum while maintaining their topographic relations. Given the increased vulnerability of the long visual axons traversing the corpus callosum, we hypothesized that inter-hemispheric transmission for vision will be impaired following mild TBI. Using the travelling wave paradigm (Wilson, Blake, & Lee 2001), we measured inter-hemispheric transmission in terms of both speed and propagation failures in 14 mild TBI patients and 14 age-matched controls. We found that relative to intra-hemispheric waves, inter-hemispheric waves were faster and that the inter-hemispheric propagation failures were more common in TBI patients. Furthermore, the transmission failures were topographically distributed, with a bias towards greater failures for transmission across the upper visual field. We discuss the results in terms of increased local inhibition and topographically-selective axonal injury in mild TBI. Copyright © 2015 Elsevier Ltd. All rights reserved.

Cerebral white matter blood flow and energy metabolism in multiple sclerosis.

PubMed

Steen, Christel; D'haeseleer, Miguel; Hoogduin, Johannes M; Fierens, Yves; Cambron, Melissa; Mostert, Jop P; Heersema, Dorothea J; Koch, Marcus W; De Keyser, Jacques

2013-09-01

Cerebral blood flow (CBF) is reduced in normal-appearing white matter (NAWM) of subjects with multiple sclerosis (MS), but the underlying mechanism is unknown. The objective of this article is to assess the relationship between reduced NAWM CBF and both axonal mitochondrial metabolism and astrocytic phosphocreatine (PCr) metabolism. Ten healthy controls and 25 MS subjects were studied with 3 Tesla magnetic resonance imaging. CBF was measured using pseudo-continuous arterial spin labeling. N-acetylaspartate/creatine (NAA/Cr) ratios (axonal mitochondrial metabolism) were obtained using (1)H-MR spectroscopy and PCr/β-ATP ratios using (31)P-MR spectroscopy. In centrum semiovale NAWM, we assessed correlations between CBF and both NAA/Cr and PCr/β-ATP ratios. Subjects with MS had a widespread reduction in CBF of NAWM (centrum semiovale, periventricular, frontal and occipital), and gray matter (frontoparietal cortex and thalamus). Compared to controls, NAA/Cr in NAWM of the centrum semiovale of MS subjects was decreased, whereas PCr/β-ATP was increased. We found no correlations between CBF and PCr/β-ATP. CBF and NAA/Cr correlated in controls (p = 0.02), but not in MS subjects (p = 0.68). Our results suggest that in MS patients there is no relationship between reduced CBF in NAWM and impaired axonal mitochondrial metabolism or astrocytic PCr metabolism.

Increased CNV-Region deletions in mild cognitive impairment (MCI) and Alzheimer's disease (AD) subjects in the ADNI sample

PubMed Central

Guffanti, Guia; Torri, Federica; Rasmussen, Jerod; Clark, Andrew P.; Lakatos, Anita; Turner, Jessica A.; Fallon, James H.; Saykin, Andrew J.; Weiner, Michael; Vawter, Marquis P.; Knowles, James A.; Potkin, Steven G.; Macciardi, Fabio

2014-01-01

We investigated the genome-wide distribution of CNVs in the Alzheimer's disease (AD) Neuroimaging Initiative (ADNI) sample (146 with AD, 313 with Mild Cognitive Impairment (MCI), and 181 controls). Comparison of single CNVs between cases (MCI and AD) and controls shows overrepresentation of large heterozygous deletions in cases (p-value < 0.0001). The analysis of CNV-Regions identifies 44 copy number variable loci of heterozygous deletions, with more CNV-Regions among affected than controls (p = 0.005). Seven of the 44 CNV-Regions are nominally significant for association with cognitive impairment. We validated and confirmed our main findings with genome re-sequencing of selected patients and controls. The functional pathway analysis of the genes putatively affected by deletions of CNV-Regions reveals enrichment of genes implicated in axonal guidance, cell–cell adhesion, neuronal morphogenesis and differentiation. Our findings support the role of CNVs in AD, and suggest an association between large deletions and the development of cognitive impairment PMID:23583670

Neuroimaging Impaired Response Inhibition and Salience Attribution in Human Drug Addiction: A Systematic Review.

PubMed

Zilverstand, Anna; Huang, Anna S; Alia-Klein, Nelly; Goldstein, Rita Z

2018-06-06

The impaired response inhibition and salience attribution (iRISA) model proposes that impaired response inhibition and salience attribution underlie drug seeking and taking. To update this model, we systematically reviewed 105 task-related neuroimaging studies (n > 15/group) published since 2010. Results demonstrate specific impairments within six large-scale brain networks (reward, habit, salience, executive, memory, and self-directed networks) during drug cue exposure, decision making, inhibitory control, and social-emotional processing. Addicted individuals demonstrated increased recruitment of these networks during drug-related processing but a blunted response during non-drug-related processing, with the same networks also being implicated during resting state. Associations with real-life drug use, relapse, therapeutic interventions, and the relevance to initiation of drug use during adolescence support the clinical relevance of the results. Whereas the salience and executive networks showed impairments throughout the addiction cycle, the reward network was dysregulated at later stages of abuse. Effects were similar in alcohol, cannabis, and stimulant addiction. Copyright © 2018 Elsevier Inc. All rights reserved.

Conditional depletion of intellectual disability and Parkinsonism candidate gene ATP6AP2 in fly and mouse induces cognitive impairment and neurodegeneration

PubMed Central

Dubos, Aline; Castells-Nobau, Anna; Meziane, Hamid; Oortveld, Merel A.W.; Houbaert, Xander; Iacono, Giovanni; Martin, Christelle; Mittelhaeuser, Christophe; Lalanne, Valérie; Kramer, Jamie M.; Bhukel, Anuradha; Quentin, Christine; Slabbert, Jan; Verstreken, Patrik; Sigrist, Stefan J.; Messaddeq, Nadia; Birling, Marie-Christine; Selloum, Mohammed; Stunnenberg, Henk G.; Humeau, Yann; Schenck, Annette; Herault, Yann

2015-01-01

ATP6AP2, an essential accessory component of the vacuolar H+ ATPase (V-ATPase), has been associated with intellectual disability (ID) and Parkinsonism. ATP6AP2 has been implicated in several signalling pathways; however, little is known regarding its role in the nervous system. To decipher its function in behaviour and cognition, we generated and characterized conditional knockdowns of ATP6AP2 in the nervous system of Drosophila and mouse models. In Drosophila, ATP6AP2 knockdown induced defective phototaxis and vacuolated photoreceptor neurons and pigment cells when depleted in eyes and altered short- and long-term memory when depleted in the mushroom body. In mouse, conditional Atp6ap2 deletion in glutamatergic neurons (Atp6ap2Camk2aCre/0 mice) caused increased spontaneous locomotor activity and altered fear memory. Both Drosophila ATP6AP2 knockdown and Atp6ap2Camk2aCre/0 mice presented with presynaptic transmission defects, and with an abnormal number and morphology of synapses. In addition, Atp6ap2Camk2aCre/0 mice showed autophagy defects that led to axonal and neuronal degeneration in the cortex and hippocampus. Surprisingly, axon myelination was affected in our mutant mice, and axonal transport alterations were observed in Drosophila. In accordance with the identified phenotypes across species, genome-wide transcriptome profiling of Atp6ap2Camk2aCre/0 mouse hippocampi revealed dysregulation of genes involved in myelination, action potential, membrane-bound vesicles and motor behaviour. In summary, ATP6AP2 disruption in mouse and fly leads to cognitive impairment and neurodegeneration, mimicking aspects of the neuropathology associated with ATP6AP2 mutations in humans. Our results identify ATP6AP2 as an essential gene for the nervous system. PMID:26376863

Conditional depletion of intellectual disability and Parkinsonism candidate gene ATP6AP2 in fly and mouse induces cognitive impairment and neurodegeneration.

PubMed

Dubos, Aline; Castells-Nobau, Anna; Meziane, Hamid; Oortveld, Merel A W; Houbaert, Xander; Iacono, Giovanni; Martin, Christelle; Mittelhaeuser, Christophe; Lalanne, Valérie; Kramer, Jamie M; Bhukel, Anuradha; Quentin, Christine; Slabbert, Jan; Verstreken, Patrik; Sigrist, Stefan J; Messaddeq, Nadia; Birling, Marie-Christine; Selloum, Mohammed; Stunnenberg, Henk G; Humeau, Yann; Schenck, Annette; Herault, Yann

2015-12-01

ATP6AP2, an essential accessory component of the vacuolar H+ ATPase (V-ATPase), has been associated with intellectual disability (ID) and Parkinsonism. ATP6AP2 has been implicated in several signalling pathways; however, little is known regarding its role in the nervous system. To decipher its function in behaviour and cognition, we generated and characterized conditional knockdowns of ATP6AP2 in the nervous system of Drosophila and mouse models. In Drosophila, ATP6AP2 knockdown induced defective phototaxis and vacuolated photoreceptor neurons and pigment cells when depleted in eyes and altered short- and long-term memory when depleted in the mushroom body. In mouse, conditional Atp6ap2 deletion in glutamatergic neurons (Atp6ap2(Camk2aCre/0) mice) caused increased spontaneous locomotor activity and altered fear memory. Both Drosophila ATP6AP2 knockdown and Atp6ap2(Camk2aCre/0) mice presented with presynaptic transmission defects, and with an abnormal number and morphology of synapses. In addition, Atp6ap2(Camk2aCre/0) mice showed autophagy defects that led to axonal and neuronal degeneration in the cortex and hippocampus. Surprisingly, axon myelination was affected in our mutant mice, and axonal transport alterations were observed in Drosophila. In accordance with the identified phenotypes across species, genome-wide transcriptome profiling of Atp6ap2(Camk2aCre/0) mouse hippocampi revealed dysregulation of genes involved in myelination, action potential, membrane-bound vesicles and motor behaviour. In summary, ATP6AP2 disruption in mouse and fly leads to cognitive impairment and neurodegeneration, mimicking aspects of the neuropathology associated with ATP6AP2 mutations in humans. Our results identify ATP6AP2 as an essential gene for the nervous system. © The Author 2015. Published by Oxford University Press.

Altered hippocampal replay is associated with memory impairment in mice heterozygous for the Scn2a gene.

PubMed

Middleton, Steven J; Kneller, Emily M; Chen, Shuo; Ogiwara, Ikuo; Montal, Mauricio; Yamakawa, Kazuhiro; McHugh, Thomas J

2018-06-04

An accumulating body of experimental evidence has implicated hippocampal replay occurring within sharp wave ripples (SPW-Rs) as crucial for learning and memory in healthy subjects. This raises speculation that neurological disorders impairing memory disrupt either SPW-Rs or their underlying neuronal activity. We report that mice heterozygous for the gene Scn2a, a site of frequent de novo mutations in humans with intellectual disability, displayed impaired spatial memory. While we observed no changes during encoding, to either single place cells or cell assemblies, we identified abnormalities restricted to SPW-R episodes that manifest as decreased cell assembly reactivation strengths and truncated hippocampal replay sequences. Our results suggest that alterations to hippocampal replay content may underlie disease-associated memory deficits.

Caffeine and central noradrenaline: effects on mood, cognitive performance, eye movements and cardiovascular function.

PubMed

Smith, Andrew; Brice, Carolyn; Nash, Jon; Rich, Neil; Nutt, David J

2003-09-01

There have been numerous studies on the effects of caffeine on behaviour and cardiovascular function. It is now important to clarify the mechanisms that underlie such effects, and the main objective of the present study was to investigate whether changes in central noradrenaline underlie some of the behavioural and cardiovascular effects of caffeine. This was examined using a clonidine challenge paradigm. Twenty-four healthy volunteers were assigned to one of four conditions: (i) clonidine/caffeine; (ii) clonidine/placebo; (iii) placebo/caffeine: (iv) placebo/placebo. Baseline measurements of mood, cognitive performance, saccadic eye movements and cardiovascular function were recorded. Subsequently, volunteers were given either clonidine (200 microg) or placebo and consumed coffee containing caffeine (1.5 mg/kg) or placebo. The test battery was then repeated 30 min, 150 min and 270 min later. A second cup of coffee (with the same amount of caffeine as the first) was consumed 120 min after the first cup. The results showed that clonidine reduced alertness, impaired many aspects of performance and slowed saccadic eye movements; caffeine removed many of these impairments. Both clonidine and caffeine influenced blood pressure (clonidine reduced it, caffeine raised it) but the effects appeared to be independent, suggesting that separate mechanisms were involved. In addition, there were some behavioural effects of caffeine that were independent of the clonidine effect (e.g. effects on speed of encoding of new information) and these may reflect other neurotransmitter systems (e.g cholinergic effects). Overall, the results suggest that caffeine counteracts reductions in the turnover of central noradrenaline. This mechanism may underlie the beneficial effects of caffeine seen in low alertness states.

Addiction and disability: moral and policy issues.

PubMed

Wasserman, David

2004-02-01

This article discusses the conceptual, ethical, and policy issues raised by the legal classification of drug addiction as an impairment, and of some nonusing drug addicts as people with disabilities. It focuses on the questions of (1) what moral judgments, if any, underlie the classification of addiction as an impairment; (2) whether it makes sense to apportion the burdens of drug addiction between chemical, biological, social, political, and other causes; (3) how considerations of distributive justice may compel or constrain measures to ease the burdens of drug addiction; and (4) whether it is justifiable to deny the current users of illegal substances legal protections available to the current users of legal substances.

Effort-Based Decision-Making in Schizophrenia.

PubMed

Culbreth, Adam J; Moran, Erin K; Barch, Deanna M

2018-08-01

Motivational impairment has long been associated with schizophrenia but the underlying mechanisms are not clearly understood. Recently, a small but growing literature has suggested that aberrant effort-based decision-making may be a potential contributory mechanism for motivational impairments in psychosis. Specifically, multiple reports have consistently demonstrated that individuals with schizophrenia are less willing than healthy controls to expend effort to obtain rewards. Further, this effort-based decision-making deficit has been shown to correlate with severity of negative symptoms and level of functioning, in many but not all studies. In the current review, we summarize this literature and discuss several factors that may underlie aberrant effort-based decision-making in schizophrenia.

Functional Near-Infrared Spectroscopy Brain Imaging Investigation of Phonological Awareness and Passage Comprehension Abilities in Adult Recipients of Cochlear Implants

ERIC Educational Resources Information Center

Bisconti, Silvia; Shulkin, Masha; Hu, Xiaosu; Basura, Gregory J.; Kileny, Paul R.; Kovelman, Ioulia

2016-01-01

Purpose: The aim of this study was to examine how the brains of individuals with cochlear implants (CIs) respond to spoken language tasks that underlie successful language acquisition and processing. Method: During functional near-infrared spectroscopy imaging, CI recipients with hearing impairment (n = 10, mean age: 52.7 ± 17.3 years) and…

Conditional genetic deletion of PTEN after a spinal cord injury enhances regenerative growth of CST axons and motor function recovery in mice.

PubMed

Danilov, Camelia A; Steward, Oswald

2015-04-01

Previous studies indicate that conditional genetic deletion of phosphatase and tensin homolog (PTEN) in neonatal mice enhances the ability of axons to regenerate following spinal cord injury (SCI) in adults. Here, we assessed whether deleting PTEN in adult neurons post-SCI is also effective, and whether enhanced regenerative growth is accompanied by enhanced recovery of voluntary motor function. PTEN(loxP/loxP) mice received moderate contusion injuries at cervical level 5 (C5). One group received unilateral injections of adeno-associated virus expressing CRE (AAV-CRE) into the sensorimotor cortex; controls received a vector expressing green fluorescent protein (AAV-GFP) or injuries only (no vector injections). Forelimb function was tested for 14weeks post-SCI using a grip strength meter (GSM) and a hanging task. The corticospinal tract (CST) was traced by injecting mini-ruby BDA into the sensorimotor cortex. Forelimb gripping ability was severely impaired immediately post-SCI but recovered slowly over time. The extent of recovery was significantly greater in PTEN-deleted mice in comparison to either the AAV-GFP group or the injury only group. BDA tract tracing revealed significantly higher numbers of BDA-labeled axons in caudal segments in the PTEN-deleted group compared to control groups. In addition, in the PTEN-deleted group, there were exuberant collaterals extending from the main tract rostral to the lesion and into and around the scar tissue at the injury site. These results indicate that PTEN deletion in adult mice shortly post-SCI can enhance regenerative growth of CST axons and forelimb motor function recovery. Copyright © 2015 Elsevier Inc. All rights reserved.

Alteration of synaptic connectivity of oligodendrocyte precursor cells following demyelination

PubMed Central

Sahel, Aurélia; Ortiz, Fernando C.; Kerninon, Christophe; Maldonado, Paloma P.; Angulo, María Cecilia; Nait-Oumesmar, Brahim

2015-01-01

Oligodendrocyte precursor cells (OPCs) are a major source of remyelinating oligodendrocytes in demyelinating diseases such as Multiple Sclerosis (MS). While OPCs are innervated by unmyelinated axons in the normal brain, the fate of such synaptic contacts after demyelination is still unclear. By combining electrophysiology and immunostainings in different transgenic mice expressing fluorescent reporters, we studied the synaptic innervation of OPCs in the model of lysolecithin (LPC)-induced demyelination of corpus callosum. Synaptic innervation of reactivated OPCs in the lesion was revealed by the presence of AMPA receptor-mediated synaptic currents, VGluT1+ axon-OPC contacts in 3D confocal reconstructions and synaptic junctions observed by electron microscopy. Moreover, 3D confocal reconstructions of VGluT1 and NG2 immunolabeling showed the existence of glutamatergic axon-OPC contacts in post-mortem MS lesions. Interestingly, patch-clamp recordings in LPC-induced lesions demonstrated a drastic decrease in spontaneous synaptic activity of OPCs early after demyelination that was not caused by an impaired conduction of compound action potentials. A reduction in synaptic connectivity was confirmed by the lack of VGluT1+ axon-OPC contacts in virtually all rapidly proliferating OPCs stained with EdU (50-ethynyl-20-deoxyuridine). At the end of the massive proliferation phase in lesions, the proportion of innervated OPCs rapidly recovers, although the frequency of spontaneous synaptic currents did not reach control levels. In conclusion, our results demonstrate that newly-generated OPCs do not receive synaptic inputs during their active proliferation after demyelination, but gain synapses during the remyelination process. Hence, glutamatergic synaptic inputs may contribute to inhibit OPC proliferation and might have a physiopathological relevance in demyelinating disorders. PMID:25852473

N-myc Downstream-Regulated Gene 1 Is Mutated in Hereditary Motor and Sensory Neuropathy–Lom

PubMed Central

Kalaydjieva, Luba; Gresham, David; Gooding, Rebecca; Heather, Lisa; Baas, Frank; de Jonge, Rosalein; Blechschmidt, Karin; Angelicheva, Dora; Chandler, David; Worsley, Penelope; Rosenthal, Andre; King, Rosalind H. M.; Thomas, P. K.

2000-01-01

Hereditary motor and sensory neuropathies, to which Charcot-Marie-Tooth (CMT) disease belongs, are a common cause of disability in adulthood. Growing awareness that axonal loss, rather than demyelination per se, is responsible for the neurological deficit in demyelinating CMT disease has focused research on the mechanisms of early development, cell differentiation, and cell-cell interactions in the peripheral nervous system. Autosomal recessive peripheral neuropathies are relatively rare but are clinically more severe than autosomal dominant forms of CMT, and understanding their molecular basis may provide a new perspective on these mechanisms. Here we report the identification of the gene responsible for hereditary motor and sensory neuropathy–Lom (HMSNL). HMSNL shows features of Schwann-cell dysfunction and a concomitant early axonal involvement, suggesting that impaired axon-glia interactions play a major role in its pathogenesis. The gene was previously mapped to 8q24.3, where conserved disease haplotypes suggested genetic homogeneity and a single founder mutation. We have reduced the HMSNL interval to 200 kb and have characterized it by means of large-scale genomic sequencing. Sequence analysis of two genes located in the critical region identified the founder HMSNL mutation: a premature-termination codon at position 148 of the N-myc downstream-regulated gene 1 (NDRG1). NDRG1 is ubiquitously expressed and has been proposed to play a role in growth arrest and cell differentiation, possibly as a signaling protein shuttling between the cytoplasm and the nucleus. We have studied expression in peripheral nerve and have detected particularly high levels in the Schwann cell. Taken together, these findings point to NDRG1 having a role in the peripheral nervous system, possibly in the Schwann-cell signaling necessary for axonal survival. PMID:10831399

Biomarker evidence of axonal injury in neuroasymptomatic HIV-1 patients.

PubMed

Jessen Krut, Jan; Mellberg, Tomas; Price, Richard W; Hagberg, Lars; Fuchs, Dietmar; Rosengren, Lars; Nilsson, Staffan; Zetterberg, Henrik; Gisslén, Magnus

2014-01-01

Prevalence of neurocognitive impairment in HIV-1 infected patients is reported to be high. Whether this is a result of active HIV-related neurodegeneration is unclear. We examined axonal injury in HIV-1 patients by measuring the light subunit of neurofilament protein (NFL) in CSF with a novel, sensitive method. With a cross-sectional design, CSF concentrations of neurofilament protein light (NFL) (marker of neuronal injury), neopterin (intrathecal immunoactivation) and CSF/Plasma albumin ratio (blood-brain barrier integrity) were analyzed on CSF from 252 HIV-infected patients, subdivided into untreated neuroasymptomatics (n = 200), HIV-associated dementia (HAD) (n = 14) and on combinations antiretroviral treatment (cART) (n = 85), and healthy controls (n = 204). 46 HIV-infected patients were included in both treated and untreated groups, but sampled at different timepoints. Furthermore, 78 neuroasymptomatic patients were analyzed before and after treatment initiation. While HAD patients had the highest NFL concentrations, elevated CSF NFL was also found in 33% of untreated neuroasymptomatic patients, mainly in those with blood CD4+ cell counts below 250 cells/μL. CSF NFL concentrations in the untreated neuroasymptomatics and treated groups were equivalent to controls 18.5 and 3.9 years older, respectively. Neopterin correlated with NFL levels in untreated groups while the albumin ratio correlated with NFL in both untreated and treated groups. Increased CSF NFL indicates ongoing axonal injury in many neuroasymptomatic patients. Treatment decreases NFL, but treated patients retain higher levels than controls, indicating either continued virus-related injury or an aging-like effect of HIV infection. NFL correlates with neopterin and albumin ratio, suggesting an association between axonal injury, neuroinflammation and blood-brain barrier permeability. NFL appears to be a sensitive biomarker of subclinical and clinical brain injury in HIV and warrants further assessment for broader clinical use.

Development of a central nervous system axonal myelination assay for high throughput screening.

PubMed

Lariosa-Willingham, Karen D; Rosler, Elen S; Tung, Jay S; Dugas, Jason C; Collins, Tassie L; Leonoudakis, Dmitri

2016-04-22

Regeneration of new myelin is impaired in persistent multiple sclerosis (MS) lesions, leaving neurons unable to function properly and subject to further degeneration. Current MS therapies attempt to ameliorate autoimmune-mediated demyelination, but none directly promote the regeneration of lost and damaged myelin of the central nervous system (CNS). Development of new drugs that stimulate remyelination has been hampered by the inability to evaluate axonal myelination in a rapid CNS culture system. We established a high throughput cell-based assay to identify compounds that promote myelination. Culture methods were developed for initiating myelination in vitro using primary embryonic rat cortical cells. We developed an immunofluorescent phenotypic image analysis method to quantify the morphological alignment of myelin characteristic of the initiation of myelination. Using γ-secretase inhibitors as promoters of myelination, the optimal growth, time course and compound treatment conditions were established in a 96 well plate format. We have characterized the cortical myelination assay by evaluating the cellular composition of the cultures and expression of markers of differentiation over the time course of the assay. We have validated the assay scalability and consistency by screening the NIH clinical collection library of 727 compounds and identified ten compounds that promote myelination. Half maximal effective concentration (EC50) values for these compounds were determined to rank them according to potency. We have designed the first high capacity in vitro assay that assesses myelination of live axons. This assay will be ideal for screening large compound libraries to identify new drugs that stimulate myelination. Identification of agents capable of promoting the myelination of axons will likely lead to the development of new therapeutics for MS patients.

Pathfinding in a large vertebrate axon tract: isotypic interactions guide retinotectal axons at multiple choice points

PubMed Central

Pittman, Andrew J.; Law, Mei-Yee; Chien, Chi-Bin

2008-01-01

Summary Navigating axons respond to environmental guidance signals, but can also follow axons that have gone before—pioneer axons. Pioneers have been studied extensively in simple systems, but the role of axon-axon interactions remains largely unexplored in large vertebrate axon tracts, where cohorts of identical axons could potentially use isotypic interactions to guide each other through multiple choice points. Furthermore, the relative importance of axon-axon interactions compared to axon-autonomous receptor function has not been assessed. Here we test the role of axon-axon interactions in retinotectal development, by devising a technique to selectively remove or replace early-born retinal ganglion cells (RGCs). We find that early RGCs are both necessary and sufficient for later axons to exit the eye. Furthermore, introducing misrouted axons by transplantation reveals that guidance from eye to tectum relies heavily on interactions between axons, including both pioneer-follower and community effects. We conclude that axon-axon interactions and ligand-receptor signaling have coequal roles, cooperating to ensure the fidelity of axon guidance in developing vertebrate tracts. PMID:18653554

Giant axonal neuropathy–associated gigaxonin mutations impair intermediate filament protein degradation

PubMed Central

Mahammad, Saleemulla; Murthy, S.N. Prasanna; Didonna, Alessandro; Grin, Boris; Israeli, Eitan; Perrot, Rodolphe; Bomont, Pascale; Julien, Jean-Pierre; Kuczmarski, Edward; Opal, Puneet; Goldman, Robert D.

2013-01-01

Giant axonal neuropathy (GAN) is an early-onset neurological disorder caused by mutations in the GAN gene (encoding for gigaxonin), which is predicted to be an E3 ligase adaptor. In GAN, aggregates of intermediate filaments (IFs) represent the main pathological feature detected in neurons and other cell types, including patients’ dermal fibroblasts. The molecular mechanism by which these mutations cause IFs to aggregate is unknown. Using fibroblasts from patients and normal individuals, as well as Gan–/– mice, we demonstrated that gigaxonin was responsible for the degradation of vimentin IFs. Gigaxonin was similarly involved in the degradation of peripherin and neurofilament IF proteins in neurons. Furthermore, proteasome inhibition by MG-132 reversed the clearance of IF proteins in cells overexpressing gigaxonin, demonstrating the involvement of the proteasomal degradation pathway. Together, these findings identify gigaxonin as a major factor in the degradation of cytoskeletal IFs and provide an explanation for IF aggregate accumulation, the subcellular hallmark of this devastating human disease. PMID:23585478

Loss of autophagy in pro-opiomelanocortin neurons perturbs axon growth and causes metabolic dysregulation.

PubMed

Coupé, Bérengère; Ishii, Yuko; Dietrich, Marcelo O; Komatsu, Masaaki; Horvath, Tamas L; Bouret, Sebastien G

2012-02-08

The hypothalamic melanocortin system, which includes neurons that produce pro-opiomelanocortin (POMC)-derived peptides, is a major negative regulator of energy balance. POMC neurons begin to acquire their unique properties during neonatal life. The formation of functional neural systems requires massive cytoplasmic remodeling that may involve autophagy, an important intracellular mechanism for the degradation of damaged proteins and organelles. Here we investigated the functional and structural effects of the deletion of an essential autophagy gene, Atg7, in POMC neurons. Lack of Atg7 in POMC neurons caused higher postweaning body weight, increased adiposity, and glucose intolerance. These metabolic impairments were associated with an age-dependent accumulation of ubiquitin/p62-positive aggregates in the hypothalamus and a disruption in the maturation of POMC-containing axonal projections. Together, these data provide direct genetic evidence that Atg7 in POMC neurons is required for normal metabolic regulation and neural development, and they implicate hypothalamic autophagy deficiency in the pathogenesis of obesity. Copyright © 2012 Elsevier Inc. All rights reserved.

Loss of Autophagy in Proopiomelanocortin Neurons Perturbs Axon Growth and Causes Metabolic Dysregulation

PubMed Central

Coupé, Bérengère; Ishii, Yuko; Dietrich, Marcelo O; Komatsu, Masaaki; Horvath, Tamas L.; Bouret, Sebastien G.

2012-01-01

Summary The hypothalamic melanocortin system, which includes neurons that produce proopiomelanocortin (POMC)-derived peptides, is a major negative regulator of energy balance. POMC neurons begin to acquire their unique properties during neonatal life. The formation of functional neural systems requires massive cytoplasmic remodeling that may involve autophagy, an important intracellular mechanism for the degradation of damaged proteins and organelles. Here we investigated the functional and structural effects of the deletion of an essential autophagy gene, Atg7, in POMC neurons. Lack of Atg7 in POMC neurons caused higher post-weaning body weight, increased adiposity, and glucose intolerance. These metabolic impairments were associated with an age-dependant accumulation of ubiquitin/p62-positive aggregates in the hypothalamus and a disruption in the maturation of POMC-containing axonal projections. Together, these data provide direct genetic evidence that Atg7 in POMC neurons is required for normal metabolic regulation and neural development, and they implicate hypothalamic autophagy deficiency in the pathogenesis of obesity. PMID:22285542

Nrp2 is sufficient to instruct circuit formation of mitral-cells to mediate odour-induced attractive social responses.

PubMed

Inokuchi, Kasumi; Imamura, Fumiaki; Takeuchi, Haruki; Kim, Ryang; Okuno, Hiroyuki; Nishizumi, Hirofumi; Bito, Haruhiko; Kikusui, Takefumi; Sakano, Hitoshi

2017-07-21

Odour information induces various innate responses that are critical to the survival of the individual and for the species. An axon guidance molecule, Neuropilin 2 (Nrp2), is known to mediate targeting of olfactory sensory neurons (primary neurons), to the posteroventral main olfactory bulb (PV MOB) in mice. Here we report that Nrp2-positive (Nrp2 + ) mitral cells (MCs, second-order neurons) play crucial roles in transmitting attractive social signals from the PV MOB to the anterior part of medial amygdala (MeA). Semaphorin 3F, a repulsive ligand to Nrp2, regulates both migration of Nrp2 + MCs to the PV MOB and their axonal projection to the anterior MeA. In the MC-specific Nrp2 knockout mice, circuit formation of Nrp2 + MCs and odour-induced attractive social responses are impaired. In utero, electroporation demonstrates that activation of the Nrp2 gene in MCs is sufficient to instruct their circuit formation from the PV MOB to the anterior MeA.

Ongoing Oxidative Stress Causes Subclinical Neuronal Dysfunction in the Recovery Phase of EAE

PubMed Central

Radbruch, Helena; Bremer, Daniel; Guenther, Robert; Cseresnyes, Zoltan; Lindquist, Randall; Hauser, Anja E.; Niesner, Raluca

2016-01-01

Most multiple sclerosis (MS) patients develop over time a secondary progressive disease course, characterized histologically by axonal loss and atrophy. In early phases of the disease, focal inflammatory demyelination leads to functional impairment, but the mechanism of chronic progression in MS is still under debate. Reactive oxygen species generated by invading and resident central nervous system (CNS) macrophages have been implicated in mediating demyelination and axonal damage, but demyelination and neurodegeneration proceed even in the absence of obvious immune cell infiltration, during clinical recovery in chronic MS. Here, we employ intravital NAD(P)H fluorescence lifetime imaging to detect functional NADPH oxidases (NOX1–4, DUOX1, 2) and, thus, to identify the cellular source of oxidative stress in the CNS of mice affected by experimental autoimmune encephalomyelitis (EAE) in the remission phase of the disease. This directly affects neuronal function in vivo, as monitored by cellular calcium levels using intravital FRET–FLIM, providing a possible mechanism of disease progression in MS. PMID:27014271

Looking you in the mouth: abnormal gaze in autism resulting from impaired top-down modulation of visual attention.

PubMed

Neumann, Dirk; Spezio, Michael L; Piven, Joseph; Adolphs, Ralph

2006-12-01

People with autism are impaired in their social behavior, including their eye contact with others, but the processes that underlie this impairment remain elusive. We combined high-resolution eye tracking with computational modeling in a group of 10 high-functioning individuals with autism to address this issue. The group fixated the location of the mouth in facial expressions more than did matched controls, even when the mouth was not shown, even in faces that were inverted and most noticeably at latencies of 200-400 ms. Comparisons with a computational model of visual saliency argue that the abnormal bias for fixating the mouth in autism is not driven by an exaggerated sensitivity to the bottom-up saliency of the features, but rather by an abnormal top-down strategy for allocating visual attention.

Size-Sensitive Perceptual Representations Underlie Visual and Haptic Object Recognition

PubMed Central

Craddock, Matt; Lawson, Rebecca

2009-01-01

A variety of similarities between visual and haptic object recognition suggests that the two modalities may share common representations. However, it is unclear whether such common representations preserve low-level perceptual features or whether transfer between vision and haptics is mediated by high-level, abstract representations. Two experiments used a sequential shape-matching task to examine the effects of size changes on unimodal and crossmodal visual and haptic object recognition. Participants felt or saw 3D plastic models of familiar objects. The two objects presented on a trial were either the same size or different sizes and were the same shape or different but similar shapes. Participants were told to ignore size changes and to match on shape alone. In Experiment 1, size changes on same-shape trials impaired performance similarly for both visual-to-visual and haptic-to-haptic shape matching. In Experiment 2, size changes impaired performance on both visual-to-haptic and haptic-to-visual shape matching and there was no interaction between the cost of size changes and direction of transfer. Together the unimodal and crossmodal matching results suggest that the same, size-specific perceptual representations underlie both visual and haptic object recognition, and indicate that crossmodal memory for objects must be at least partly based on common perceptual representations. PMID:19956685

Atf3 mutant mice show reduced axon regeneration and impaired regeneration-associated gene induction after peripheral nerve injury

PubMed Central

Gey, Manuel; Wanner, Renate; Schilling, Corinna; Pedro, Maria T.; Sinske, Daniela

2016-01-01

Axon injury in the peripheral nervous system (PNS) induces a regeneration-associated gene (RAG) response. Atf3 (activating transcription factor 3) is such a RAG and ATF3's transcriptional activity might induce ‘effector’ RAGs (e.g. small proline rich protein 1a (Sprr1a), Galanin (Gal), growth-associated protein 43 (Gap43)) facilitating peripheral axon regeneration. We provide a first analysis of Atf3 mouse mutants in peripheral nerve regeneration. In Atf3 mutant mice, facial nerve regeneration and neurite outgrowth of adult ATF3-deficient primary dorsal root ganglia neurons was decreased. Using genome-wide transcriptomics, we identified a neuropeptide-encoding RAG cluster (vasoactive intestinal peptide (Vip), Ngf, Grp, Gal, Pacap) regulated by ATF3. Exogenous administration of neuropeptides enhanced neurite growth of Atf3 mutant mice suggesting that these molecules might be effector RAGs of ATF3's pro-regenerative function. In addition to the induction of growth-promoting molecules, we present data that ATF3 suppresses growth-inhibiting molecules such as chemokine (C-C motif) ligand 2. In summary, we show a pro-regenerative ATF3 function during PNS nerve regeneration involving transcriptional activation of a neuropeptide-encoding RAG cluster. ATF3 is a general injury-inducible factor, therefore ATF3-mediated mechanisms identified herein might apply to other cell and injury types. PMID:27581653

MAPK3 at the Autism-Linked Human 16p11.2 Locus Influences Precise Synaptic Target Selection at Drosophila Larval Neuromuscular Junctions.

PubMed

Park, Sang Mee; Park, Hae Ryoun; Lee, Ji Hye

2017-02-01

Proper synaptic function in neural circuits requires precise pairings between correct pre- and post-synaptic partners. Errors in this process may underlie development of neuropsychiatric disorders, such as autism spectrum disorder (ASD). Development of ASD can be influenced by genetic factors, including copy number variations (CNVs). In this study, we focused on a CNV occurring at the 16p11.2 locus in the human genome and investigated potential defects in synaptic connectivity caused by reduced activities of genes located in this region at Drosophila larval neuromuscular junctions, a well-established model synapse with stereotypic synaptic structures. A mutation of rolled , a Drosophila homolog of human mitogen-activated protein kinase 3 ( MAPK3 ) at the 16p11.2 locus, caused ectopic innervation of axonal branches and their abnormal defasciculation. The specificity of these phenotypes was confirmed by expression of wild-type rolled in the mutant background. Albeit to a lesser extent, we also observed ectopic innervation patterns in mutants defective in Cdk2, Gα q , and Gp93, all of which were expected to interact with Rolled MAPK3. A further genetic analysis in double heterozygous combinations revealed a synergistic interaction between rolled and Gp93 . In addition, results from RT-qPCR analyses indicated consistently reduced rolled mRNA levels in Cdk2 , Gα q , and Gp93 mutants. Taken together, these data suggest a central role of MAPK3 in regulating the precise targeting of presynaptic axons to proper postsynaptic targets, a critical step that may be altered significantly in ASD.

Developmental Profiling of Spiral Ganglion Neurons Reveals Insights into Auditory Circuit Assembly

PubMed Central

Lu, Cindy C.; Appler, Jessica M.; Houseman, E. Andres; Goodrich, Lisa V.

2011-01-01

The sense of hearing depends on the faithful transmission of sound information from the ear to the brain by spiral ganglion (SG) neurons. However, how SG neurons develop the connections and properties that underlie auditory processing is largely unknown. We catalogued gene expression in mouse SG neurons from embryonic day 12 (E12), when SG neurons first extend projections, up until postnatal day 15 (P15), after the onset of hearing. For comparison, we also analyzed the closely-related vestibular ganglion (VG). Gene ontology analysis confirmed enriched expression of genes associated with gene regulation and neurite outgrowth at early stages, with the SG and VG often expressing different members of the same gene family. At later stages, the neurons transcribe more genes related to mature function, and exhibit a dramatic increase in immune gene expression. Comparisons of the two populations revealed enhanced expression of TGFβ pathway components in SG neurons and established new markers that consistently distinguish auditory and vestibular neurons. Unexpectedly, we found that Gata3, a transcription factor commonly associated with auditory development, is also expressed in VG neurons at early stages. We therefore defined new cohorts of transcription factors and axon guidance molecules that are uniquely expressed in SG neurons and may drive auditory-specific aspects of their differentiation and wiring. We show that one of these molecules, the receptor guanylyl cyclase Npr2, is required for bifurcation of the SG central axon. Hence, our data set provides a useful resource for uncovering the molecular basis of specific auditory circuit assembly events. PMID:21795542

Disconnection and hyper-connectivity underlie reorganization after TBI: A rodent functional connectomic analysis

PubMed Central

Harris, N.G.; Verley, D.R.; Gutman, B.A.; Thompson, P.M.; Yeh, H.J.; Brown, J.A.

2016-01-01

While past neuroimaging methods have contributed greatly to our understanding of brain function after traumatic brain injury (TBI), resting state functional MRI (rsfMRI) connectivity methods have more recently provided a far more unbiased approach with which to monitor brain circuitry compared to task-based approaches. However, current knowledge on the physiologic underpinnings of the correlated blood oxygen level dependent signal, and how changes in functional connectivity relate to reorganizational processes that occur following injury is limited. The degree and extent of this relationship remain to be determined in order that rsfMRI methods can be fully adapted for determining the optimal timing and type of rehabilitative interventions that can be used post-TBI to achieve the best outcome. Very few rsfMRI studies exist after experimental TBI and therefore we chose to acquire rsfMRI data before and at 7, 14 and 28 days after experimental TBI using a well-known, clinically-relevant, unilateral controlled cortical impact injury (CCI) adult rat model of TBI. This model was chosen since it has widespread axonal injury, a well-defined time-course of reorganization including spine, dendrite, axonal and cortical map changes, as well as spontaneous recovery of sensorimotor function by 28 d post-injury from which to interpret alterations in functional connectivity. Data were co-registered to a parcellated rat template to generate adjacency matrices for network analysis by graph theory. Making no assumptions about direction of change, we used two-tailed statistical analysis over multiple brain regions in a data-driven approach to access global and regional changes in network topology in order to assess brain connectivity in an unbiased way. Our main hypothesis was that deficits in functional connectivity would become apparent in regions known to be structurally altered or deficient in axonal connectivity in this model. The data show the loss of functional connectivity predicted by the structural deficits, not only within the primary sensorimotor injury site and pericontused regions, but the normally connected homotopic cortex, as well as subcortical regions, all of which persisted chronically. Especially novel in this study is the unanticipated finding of widespread increases in connection strength that dwarf both the degree and extent of the functional disconnections, and which persist chronically in some sensorimotor and subcortically connected regions. Exploratory global network analysis showed changes in network parameters indicative of possible acutely increased random connectivity and temporary reductions in modularity that were matched by local increases in connectedness and increased efficiency among more weakly connected regions. The global network parameters: shortest path-length, clustering coefficient and modularity that were most affected by trauma also scaled with the severity of injury, so that the corresponding regional measures were correlated to the injury severity most notably at 7 and 14 days and especially within, but not limited to, the contralateral cortex. These changes in functional network parameters are discussed in relation to the known time-course of physiologic and anatomic data that underlie structural and functional reorganization in this experiment model of TBI. PMID:26730520

Disconnection and hyper-connectivity underlie reorganization after TBI: A rodent functional connectomic analysis.

PubMed

Harris, N G; Verley, D R; Gutman, B A; Thompson, P M; Yeh, H J; Brown, J A

2016-03-01

While past neuroimaging methods have contributed greatly to our understanding of brain function after traumatic brain injury (TBI), resting state functional MRI (rsfMRI) connectivity methods have more recently provided a far more unbiased approach with which to monitor brain circuitry compared to task-based approaches. However, current knowledge on the physiologic underpinnings of the correlated blood oxygen level dependent signal, and how changes in functional connectivity relate to reorganizational processes that occur following injury is limited. The degree and extent of this relationship remain to be determined in order that rsfMRI methods can be fully adapted for determining the optimal timing and type of rehabilitative interventions that can be used post-TBI to achieve the best outcome. Very few rsfMRI studies exist after experimental TBI and therefore we chose to acquire rsfMRI data before and at 7, 14 and 28 days after experimental TBI using a well-known, clinically-relevant, unilateral controlled cortical impact injury (CCI) adult rat model of TBI. This model was chosen since it has widespread axonal injury, a well-defined time-course of reorganization including spine, dendrite, axonal and cortical map changes, as well as spontaneous recovery of sensorimotor function by 28 d post-injury from which to interpret alterations in functional connectivity. Data were co-registered to a parcellated rat template to generate adjacency matrices for network analysis by graph theory. Making no assumptions about direction of change, we used two-tailed statistical analysis over multiple brain regions in a data-driven approach to access global and regional changes in network topology in order to assess brain connectivity in an unbiased way. Our main hypothesis was that deficits in functional connectivity would become apparent in regions known to be structurally altered or deficient in axonal connectivity in this model. The data show the loss of functional connectivity predicted by the structural deficits, not only within the primary sensorimotor injury site and pericontused regions, but the normally connected homotopic cortex, as well as subcortical regions, all of which persisted chronically. Especially novel in this study is the unanticipated finding of widespread increases in connection strength that dwarf both the degree and extent of the functional disconnections, and which persist chronically in some sensorimotor and subcortically connected regions. Exploratory global network analysis showed changes in network parameters indicative of possible acutely increased random connectivity and temporary reductions in modularity that were matched by local increases in connectedness and increased efficiency among more weakly connected regions. The global network parameters: shortest path-length, clustering coefficient and modularity that were most affected by trauma also scaled with the severity of injury, so that the corresponding regional measures were correlated to the injury severity most notably at 7 and 14 days and especially within, but not limited to, the contralateral cortex. These changes in functional network parameters are discussed in relation to the known time-course of physiologic and anatomic data that underlie structural and functional reorganization in this experiment model of TBI. Copyright © 2015 Elsevier Inc. All rights reserved.

TCTEX1D2 mutations underlie Jeune asphyxiating thoracic dystrophy with impaired retrograde intraflagellar transport.

PubMed

Schmidts, Miriam; Hou, Yuqing; Cortés, Claudio R; Mans, Dorus A; Huber, Celine; Boldt, Karsten; Patel, Mitali; van Reeuwijk, Jeroen; Plaza, Jean-Marc; van Beersum, Sylvia E C; Yap, Zhi Min; Letteboer, Stef J F; Taylor, S Paige; Herridge, Warren; Johnson, Colin A; Scambler, Peter J; Ueffing, Marius; Kayserili, Hulya; Krakow, Deborah; King, Stephen M; Beales, Philip L; Al-Gazali, Lihadh; Wicking, Carol; Cormier-Daire, Valerie; Roepman, Ronald; Mitchison, Hannah M; Witman, George B

2015-06-05

The analysis of individuals with ciliary chondrodysplasias can shed light on sensitive mechanisms controlling ciliogenesis and cell signalling that are essential to embryonic development and survival. Here we identify TCTEX1D2 mutations causing Jeune asphyxiating thoracic dystrophy with partially penetrant inheritance. Loss of TCTEX1D2 impairs retrograde intraflagellar transport (IFT) in humans and the protist Chlamydomonas, accompanied by destabilization of the retrograde IFT dynein motor. We thus define TCTEX1D2 as an integral component of the evolutionarily conserved retrograde IFT machinery. In complex with several IFT dynein light chains, it is required for correct vertebrate skeletal formation but may be functionally redundant under certain conditions.

Hereditary spastic paraplegia: clinico-pathologic features and emerging molecular mechanisms

PubMed Central

Fink, John K.

2014-01-01

Hereditary spastic paraplegia (HSP) is a syndrome designation describing inherited disorders in which lower extremity weakness and spasticity are the predominant symptoms. There are more than 50 genetic types of HSP. HSP affects individuals diverse ethnic groups with prevalence estimates ranging from 1.2 to 9.6 per 100,000 [39, 70, 77, 154, 185]. Symptoms may begin at any age. Gait impairment that begins after childhood usually worsens very slowly over many years. Gait impairment that begins in infancy and early childhood may not worsen significantly. Post mortem studies consistently identify degeneration of corticospinal tract axons (maximal in the thoracic spinal cord) and degeneration of fasciculus gracilis fibers (maximal in the cervico-medullary region). HSP syndromes thus appear to involve motor-sensory axon degeneration affecting predominantly (but not exclusively) the distal ends of long central nervous system (CNS) axons. In general, proteins encoded by HSP genes have diverse functions including axon transport (e.g. SPG30/KIF1A, SPG10/KIF5A and possibly SPG4/Spastin); endoplasmic reticulum morphology (e.g. SPG3A/Atlastin, SPG4/Spastin, SPG12/reticulon 2, and SPG31/REEP1, all of which interact); mitochondrial function (e.g. SPG13/chaperonin 60/heat shock protein 60, SPG7/paraplegin; and mitochondrial ATP6; 4) myelin formation (e.g. SPG2/Proteolipid protein and SPG42/Connexin 47); 5) protein folding and ER-stress response (SPG6/NIPA1, SPG8/K1AA0196 (Strumpellin), SGP17/BSCL2 (Seipin) [113-115], “mutilating sensory neuropathy with spastic paraplegia” due to CcT5 mutation and presumably SPG18/ERLIN2); 6) corticospinal tract and other neurodevelopment (e.g. SPG1/L1 cell adhesion molecule and SPG22/thyroid transporter MCT8); 7) fatty acid and phospholipid metabolism (e.g. SPG28/DDHD1, SPG35/FA2H, SPG39/NTE, SPG54/DDHD2, and SPG56/CYP2U1); and 8) endosome membrane trafficking and vesicle formation (e.g. SPG47/AP4B1, SPG48/KIAA0415, SPG50/AP4M1, SPG51/AP4E, SPG52/AP4S1, and VSPG53/VPS37A). The availability of animal models (including bovine, murine, zebrafish, Drosophila, and C. elegans) for many types of HSP permits exploration of disease mechanisms and potential treatments. This review highlights emerging concepts of this large group of clinically similar disorders. For recent review of HSP including historical descriptions, differential diagnosis, and additional references see [78]. PMID:23897027

Hereditary spastic paraplegia: clinico-pathologic features and emerging molecular mechanisms.

PubMed

Fink, John K

2013-09-01

Hereditary spastic paraplegia (HSP) is a syndrome designation describing inherited disorders in which lower extremity weakness and spasticity are the predominant symptoms. There are more than 50 genetic types of HSP. HSP affects individuals of diverse ethnic groups with prevalence estimates ranging from 1.2 to 9.6 per 100,000. Symptoms may begin at any age. Gait impairment that begins after childhood usually worsens very slowly over many years. Gait impairment that begins in infancy and early childhood may not worsen significantly. Postmortem studies consistently identify degeneration of corticospinal tract axons (maximal in the thoracic spinal cord) and degeneration of fasciculus gracilis fibers (maximal in the cervico-medullary region). HSP syndromes thus appear to involve motor-sensory axon degeneration affecting predominantly (but not exclusively) the distal ends of long central nervous system (CNS) axons. In general, proteins encoded by HSP genes have diverse functions including (1) axon transport (e.g. SPG30/KIF1A, SPG10/KIF5A and possibly SPG4/Spastin); (2) endoplasmic reticulum morphology (e.g. SPG3A/Atlastin, SPG4/Spastin, SPG12/reticulon 2, and SPG31/REEP1, all of which interact); (3) mitochondrial function (e.g. SPG13/chaperonin 60/heat-shock protein 60, SPG7/paraplegin; and mitochondrial ATP6); (4) myelin formation (e.g. SPG2/Proteolipid protein and SPG42/Connexin 47); (5) protein folding and ER-stress response (SPG6/NIPA1, SPG8/K1AA0196 (Strumpellin), SGP17/BSCL2 (Seipin), "mutilating sensory neuropathy with spastic paraplegia" owing to CcT5 mutation and presumably SPG18/ERLIN2); (6) corticospinal tract and other neurodevelopment (e.g. SPG1/L1 cell adhesion molecule and SPG22/thyroid transporter MCT8); (7) fatty acid and phospholipid metabolism (e.g. SPG28/DDHD1, SPG35/FA2H, SPG39/NTE, SPG54/DDHD2, and SPG56/CYP2U1); and (8) endosome membrane trafficking and vesicle formation (e.g. SPG47/AP4B1, SPG48/KIAA0415, SPG50/AP4M1, SPG51/AP4E, SPG52/AP4S1, and VSPG53/VPS37A). The availability of animal models (including bovine, murine, zebrafish, Drosophila, and C. elegans) for many types of HSP permits exploration of disease mechanisms and potential treatments. This review highlights emerging concepts of this large group of clinically similar disorders.

Dysfunctional overnight memory consolidation in ecstasy users.

PubMed

Smithies, Vanessa; Broadbear, Jillian; Verdejo-Garcia, Antonio; Conduit, Russell

2014-08-01

Sleep plays an important role in the consolidation and integration of memory in a process called overnight memory consolidation. Previous studies indicate that ecstasy users have marked and persistent neurocognitive and sleep-related impairments. We extend past research by examining overnight memory consolidation among regular ecstasy users (n=12) and drug naïve healthy controls (n=26). Memory recall of word pairs was evaluated before and after a period of sleep, with and without interference prior to testing. In addition, we assessed neurocognitive performances across tasks of learning, memory and executive functioning. Ecstasy users demonstrated impaired overnight memory consolidation, a finding that was more pronounced following associative interference. Additionally, ecstasy users demonstrated impairments on tasks recruiting frontostriatal and hippocampal neural circuitry, in the domains of proactive interference memory, long-term memory, encoding, working memory and complex planning. We suggest that ecstasy-associated dysfunction in fronto-temporal circuitry may underlie overnight consolidation memory impairments in regular ecstasy users. © The Author(s) 2014.

Transient Hypothyroidism During Lactation Arrests Myelination in the Anterior Commissure of Rats. A Magnetic Resonance Image and Electron Microscope Study.

PubMed

Lucia, Federico S; Pacheco-Torres, Jesús; González-Granero, Susana; Canals, Santiago; Obregón, María-Jesús; García-Verdugo, José M; Berbel, Pere

2018-01-01

Thyroid hormone deficiency at early postnatal ages affects the cytoarchitecture and function of neocortical and telencephalic limbic areas, leading to impaired associative memory and in a wide spectrum of neurological and mental diseases. Neocortical areas project interhemispheric axons mostly through the corpus callosum and to a lesser extent through the anterior commissure (AC), while limbic areas mostly project through the AC and hippocampal commissures. Functional magnetic resonance data from children with late diagnosed congenital hypothyroidism and abnormal verbal memory processing, suggest altered ipsilateral and contralateral telencephalic connections. Gestational hypothyroidism affects AC development but the possible effect of transient and chronic postnatal hypothyroidism, as occurs in late diagnosed neonates with congenital hypothyroidism and in children growing up in iodine deficient areas, still remains unknown. We studied AC development using in vivo magnetic resonance imaging and electron microscopy in hypothyroid and control male rats. Four groups of methimazole (MMI) treated rats were studied. One group was MMI-treated from postnatal day (P) 0 to P21; some of these rats were also treated with L-thyroxine (T4) from P15 to P21, as a model for early transient hypothyroidism. Other rats were MMI-treated from P0 to P150 and from embryonic day (E) 10 to P170, as a chronic hypothyroidism group. The results were compared with age paired control rats. The normalized T2 signal using magnetic resonance image was higher in MMI-treated rats and correlated with the number and percentage of myelinated axons. Using electron microscopy, we observed decreased myelinated axon number and density in transient and chronic hypothyroid rats at P150, unmyelinated axon number increased slightly in chronic hypothyroid rats. In MMI-treated rats, the myelinated axon g-ratio and conduction velocity was similar to control rats, but with a decrease in conduction delays. These data show that early postnatal transient and chronic hypothyroidism alters AC maturation that may affect the transfer of information through the AC. The alterations cannot be recovered after delayed T4-treatment. Our data support the neurocognitive delay found in late T4-treated children with congenital hypothyroidism.

Cannabinoid Receptors Modulate Neuronal Morphology and AnkyrinG Density at the Axon Initial Segment

PubMed Central

Tapia, Mónica; Dominguez, Ana; Zhang, Wei; del Puerto, Ana; Ciorraga, María; Benitez, María José; Guaza, Carmen; Garrido, Juan José

2017-01-01

Neuronal polarization underlies the ability of neurons to integrate and transmit information. This process begins early in development with axon outgrowth, followed by dendritic growth and subsequent maturation. In between these two steps, the axon initial segment (AIS), a subcellular domain crucial for generating action potentials (APs) and maintaining the morphological and functional polarization, starts to develop. However, the cellular/molecular mechanisms and receptors involved in AIS initial development and maturation are mostly unknown. In this study, we have focused on the role of the type-1 cannabinoid receptor (CB1R), a highly abundant G-protein coupled receptor (GPCR) in the nervous system largely involved in different phases of neuronal development and differentiation. Although CB1R activity modulation has been related to changes in axons or dendrites, its possible role as a modulator of AIS development has not been yet explored. Here we analyzed the potential role of CB1R on neuronal morphology and AIS development using pharmacological and RNA interference approaches in cultured hippocampal neurons. CB1R inhibition, at a very early developmental stage, has no effect on axonal growth, yet CB1R activation can promote it. By contrast, subsequent dendritic growth is impaired by CB1R inhibition, which also reduces ankyrinG density at the AIS. Moreover, our data show a significant correlation between early dendritic growth and ankyrinG density. However, CB1R inhibition in later developmental stages after dendrites are formed only reduces ankyrinG accumulation at the AIS. In conclusion, our data suggest that neuronal CB1R basal activity plays a role in initial development of dendrites and indirectly in AIS proteins accumulation. Based on the lack of CB1R expression at the AIS, we hypothesize that CB1R mediated modulation of dendritic arbor size during early development indirectly determines the accumulation of ankyrinG and AIS development. Further studies will be necessary to determine which CB1R-dependent mechanisms can coordinate these two domains, and what may be the impact of these early developmental changes once neurons mature and are embedded in a functional brain network. PMID:28179879

Effects of sub-lethal neurite outgrowth inhibitory concentrations of chlorpyrifos oxon on cytoskeletal proteins and acetylcholinesterase in differentiating N2a cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Flaskos, J., E-mail: flaskos@vet.auth.gr; Nikolaidis, E.; Harris, W.

2011-11-15

Previous work in our laboratory has shown that sub-lethal concentrations (1-10 {mu}M) of chlorpyrifos (CPF), diazinon (DZ) and diazinon oxon (DZO) inhibit the outgrowth of axon-like neurites in differentiating mouse N2a neuroblastoma cells concomitant with altered levels and/or phosphorylation state of axonal cytoskeleton and growth-associated proteins. The aim of the present work was to determine whether chlorpyrifos oxon (CPO) was capable of inhibiting N2a cell differentiation in a similar manner. Using experimental conditions similar to our previous work, sub-lethal concentrations (1-10 {mu}M) of CPO were found to inhibit N2a cell differentiation. However, unlike previous studies with DZ and DZO, theremore » was a high level of sustained inhibition of acetylcholinesterase (AChE) in CPO treated cells. Impairment of neurite outgrowth was also associated with reduced levels of growth associated protein-43 and neurofilament heavy chain (NFH), and the distribution of NFH in cells stained by indirect immunofluorescence was disrupted. However, in contrast to previous findings for DZO, the absolute level of phosphorylated NFH was unaffected by CPO exposure. Taken together, the findings suggest that sub-lethal concentrations of CPO inhibit axon outgrowth in differentiating N2a cells and that this effect involves reduced levels of two proteins that play key roles in axon outgrowth and maintenance. Although the inhibition of neurite outgrowth is unlikely to involve AChE inhibition directly, further work will help to determine whether the persistent inhibition of AChE by CPO can account for the different effects induced by CPO and DZO on the levels of total and phosphorylated NFH. -- Highlights: Black-Right-Pointing-Pointer Sub-lethal levels of chlorpyrifos oxon inhibit neurite outgrowth in N2a cells Black-Right-Pointing-Pointer Acetylcholinesterase exhibits sustained inhibition throughout exposure Black-Right-Pointing-Pointer The levels of neurofilament heavy chain and GAP-43 protein are reduced Black-Right-Pointing-Pointer Neurofilament heavy chain forms aggregates in cell bodies Black-Right-Pointing-Pointer Thus at least two axon-associated cytoskeletal proteins are disrupted by this agent.« less

The special status of verbal knowledge in semantic memory: evidence from performance of semantically impaired subjects on verbalizable and non-verbalizable versions of the object decision task.

PubMed

Zannino, Gian Daniele; Perri, Roberta; Monaco, Marco; Caltagirone, Carlo; Luzzi, Simona; Carlesimo, Giovanni A

2014-01-01

According to the semantic hub hypothesis, a supramodal semantic hub is equally needed to deal with verbal and extraverbal "surface" representations. Damage to the supramodal hub is thought to underlie the crossmodal impairment observed in selective semantic deficits. In the present paper, we provide evidence supporting an alternative view: we hold that semantic impairment is not equal across domains but affects verbal behavior disproportionately. We investigated our hypothesis by manipulating the verbal load in an object decision task. Two pathological groups showing different levels of semantic impairment were enrolled together with their normal controls. The severe group included 10 subjects with semantic dementia and the mild group 10 subjects with Alzheimer's disease. In keeping with our hypothesis, when shifting from the low verbal load to the high verbal load condition, brain-damaged individuals, as compared to controls, showed a disproportionate impairment as a function of the severity of their semantic deficit. Copyright © 2013 Elsevier Inc. All rights reserved.

Disruption of centrifugal inhibition to olfactory bulb granule cells impairs olfactory discrimination.

PubMed

Nunez-Parra, Alexia; Maurer, Robert K; Krahe, Krista; Smith, Richard S; Araneda, Ricardo C

2013-09-03

Granule cells (GCs) are the most abundant inhibitory neuronal type in the olfactory bulb and play a critical role in olfactory processing. GCs regulate the activity of principal neurons, the mitral cells, through dendrodendritic synapses, shaping the olfactory bulb output to other brain regions. GC excitability is regulated precisely by intrinsic and extrinsic inputs, and this regulation is fundamental for odor discrimination. Here, we used channelrhodopsin to stimulate GABAergic axons from the basal forebrain selectively and show that this stimulation generates reliable inhibitory responses in GCs. Furthermore, selective in vivo inhibition of GABAergic neurons in the basal forebrain by targeted expression of designer receptors exclusively activated by designer drugs produced a reversible impairment in the discrimination of structurally similar odors, indicating an important role of these inhibitory afferents in olfactory processing.

Multidisciplinary Interventions in Motor Neuron Disease

PubMed Central

Williams, U. E.; Philip-Ephraim, E. E.; Oparah, S. K.

2014-01-01

Motor neuron disease is a neurodegenerative disease characterized by loss of upper motor neuron in the motor cortex and lower motor neurons in the brain stem and spinal cord. Death occurs 2–4 years after the onset of the disease. A complex interplay of cellular processes such as mitochondrial dysfunction, oxidative stress, excitotoxicity, and impaired axonal transport are proposed pathogenetic processes underlying neuronal cell loss. Currently evidence exists for the use of riluzole as a disease modifying drug; multidisciplinary team care approach to patient management; noninvasive ventilation for respiratory management; botulinum toxin B for sialorrhoea treatment; palliative care throughout the course of the disease; and Modafinil use for fatigue treatment. Further research is needed in management of dysphagia, bronchial secretion, pseudobulbar affect, spasticity, cramps, insomnia, cognitive impairment, and communication in motor neuron disease. PMID:26317009

Botulinum neurotoxin type C protease induces apoptosis in differentiated human neuroblastoma cells.

PubMed

Rust, Aleksander; Leese, Charlotte; Binz, Thomas; Davletov, Bazbek

2016-05-31

Neuroblastomas constitute a major cause of cancer-related deaths in young children. In recent years, a number of translation-inhibiting enzymes have been evaluated for killing neuroblastoma cells. Here we investigated the potential vulnerability of human neuroblastoma cells to protease activity derived from botulinum neurotoxin type C. We show that following retinoic acid treatment, human neuroblastoma cells, SiMa and SH-SY5Y, acquire a neuronal phenotype evidenced by axonal growth and expression of neuronal markers. Botulinum neurotoxin type C which cleaves neuron-specific SNAP25 and syntaxin1 caused apoptotic death only in differentiated neuroblastoma cells. Direct comparison of translation-inhibiting enzymes and the type C botulinum protease revealed one order higher cytotoxic potency of the latter suggesting a novel neuroblastoma-targeting pathway. Our mechanistic insights revealed that loss of ubiquitous SNAP23 due to differentiation coupled to SNAP25 cleavage due to botulinum activity may underlie the apoptotic death of human neuroblastoma cells.

Tuberous Sclerosis: A New Frontier in Targeted Treatment of Autism.

PubMed

Davis, Peter E; Peters, Jurriaan M; Krueger, Darcy A; Sahin, Mustafa

2015-07-01

Tuberous sclerosis complex (TSC) is a genetic disorder with a high prevalence of autism spectrum disorder (ASD). Tremendous progress in understanding the pathogenesis of TSC has been made in recent years, along with initial trials of medical treatment aimed specifically at the underlying mechanism of the disorder. At the cellular level, loss of TSC1 or TSC2 results in upregulation of the mechanistic target of rapamycin (mTOR) pathway. At the circuitry level, TSC and mTOR play crucial roles in axonal, dendritic, and synaptic development and function. In this review, we discuss the molecular mechanism underlying TSC, and how this disease results in aberrant neural connectivity at multiple levels in the central nervous system, leading to ASD symptoms. We then review recent advances in mechanism-based treatments of TSC, and the promise that these treatments provide for future mechanism-based treatment of ASD. Because of these recent advances, TSC represents an ideal model for how to make progress in understanding and treating the mechanisms that underlie ASD in general.

Dopamine neurons in culture express VGLUT2 explaining their capacity to release glutamate at synapses in addition to dopamine.

PubMed

Dal Bo, Gregory; St-Gelais, Fannie; Danik, Marc; Williams, Sylvain; Cotton, Mathieu; Trudeau, Louis-Eric

2004-03-01

Dopamine neurons have been suggested to use glutamate as a cotransmitter. To identify the basis of such a phenotype, we have examined the expression of the three recently identified vesicular glutamate transporters (VGLUT1-3) in postnatal rat dopamine neurons in culture. We found that the majority of isolated dopamine neurons express VGLUT2, but not VGLUT1 or 3. In comparison, serotonin neurons express only VGLUT3. Single-cell RT-PCR experiments confirmed the presence of VGLUT2 mRNA in dopamine neurons. Arguing for phenotypic heterogeneity among axon terminals, we find that only a proportion of terminals established by dopamine neurons are VGLUT2-positive. Taken together, our results provide a basis for the ability of dopamine neurons to release glutamate as a cotransmitter. A detailed analysis of the conditions under which DA neurons gain or loose a glutamatergic phenotype may provide novel insight into pathophysiological processes that underlie diseases such as schizophrenia, Parkinson's disease and drug dependence.

Affective brain areas and sleep disordered breathing

PubMed Central

Harper, Ronald M.; Kumar, Rajesh; Macey, Paul M.; Woo, Mary A.; Ogren, Jennifer A.

2014-01-01

The neural damage accompanying the hypoxia, reduced perfusion, and other consequences of sleep-disordered breathing found in obstructive sleep apnea, heart failure (HF), and congenital central hypoventilation syndrome (CCHS), appears in areas that serve multiple functions, including emotional drives to breathe, and involve systems that serve affective, cardiovascular, and breathing roles. The damage, assessed with structural magnetic resonance imaging (MRI) procedures, shows tissue loss or water content and diffusion changes indicative of injury, and impaired axonal integrity between structures; damage is preferentially unilateral. Functional MRI responses in affected areas also are time- or amplitude- distorted to ventilatory or autonomic challenges. Among the structures injured are the insular, cingulate, and ventral medial prefrontal cortices, as well as cerebellar deep nuclei and cortex, anterior hypothalamus, raphé, ventrolateral medulla, basal ganglia and, in CCHS, the locus coeruleus. Raphé and locus coeruleus injury may modify serotonergic and adrenergic modulation of upper airway and arousal characteristics. Since both axons and gray matter show injury, the consequences to function, especially to autonomic, cognitive, and mood regulation, are major. Several affected rostral sites, including the insular and cingulate cortices and hippocampus, mediate aspects of dyspnea, especially in CCHS, while others, including the anterior cingulate and thalamus, participate in initiation of inspiration after central breathing pauses, and the medullary injury can impair baroreflex and breathing control. The ancillary injury associated with sleep-disordered breathing to central structures can elicit multiple other distortions in cardiovascular, cognitive, and emotional functions in addition to effects on breathing regulation. PMID:24746053

Electro-mechanical response of a 3D nerve bundle model to mechanical loads leading to axonal injury.

PubMed

Cinelli, I; Destrade, M; Duffy, M; McHugh, P

2018-03-01

Traumatic brain injuries and damage are major causes of death and disability. We propose a 3D fully coupled electro-mechanical model of a nerve bundle to investigate the electrophysiological impairments due to trauma at the cellular level. The coupling is based on a thermal analogy of the neural electrical activity by using the finite element software Abaqus CAE 6.13-3. The model includes a real-time coupling, modulated threshold for spiking activation, and independent alteration of the electrical properties for each 3-layer fibre within a nerve bundle as a function of strain. Results of the coupled electro-mechanical model are validated with previously published experimental results of damaged axons. Here, the cases of compression and tension are simulated to induce (mild, moderate, and severe) damage at the nerve membrane of a nerve bundle, made of 4 fibres. Changes in strain, stress distribution, and neural activity are investigated for myelinated and unmyelinated nerve fibres, by considering the cases of an intact and of a traumatised nerve membrane. A fully coupled electro-mechanical modelling approach is established to provide insights into crucial aspects of neural activity at the cellular level due to traumatic brain injury. One of the key findings is the 3D distribution of residual stresses and strains at the membrane of each fibre due to mechanically induced electrophysiological impairments, and its impact on signal transmission. Copyright © 2017 John Wiley & Sons, Ltd.

Differential effects of myostatin deficiency on motor and sensory axons.

PubMed

Jones, Maria R; Villalón, Eric; Northcutt, Adam J; Calcutt, Nigel A; Garcia, Michael L

2017-12-01

Deletion of myostatin in mice (MSTN -/- ) alters structural properties of peripheral axons. However, properties like axon diameter and myelin thickness were analyzed in mixed nerves, so it is unclear whether loss of myostatin affects motor, sensory, or both types of axons. Using the MSTN -/- mouse model, we analyzed the effects of increasing the number of muscle fibers on axon diameter, myelin thickness, and internode length in motor and sensory axons. Axon diameter and myelin thickness were increased in motor axons of MSTN -/- mice without affecting internode length or axon number. The number of sensory axons was increased without affecting their structural properties. These results suggest that motor and sensory axons establish structural properties by independent mechanisms. Moreover, in motor axons, instructive cues from the neuromuscular junction may play a role in co-regulating axon diameter and myelin thickness, whereas internode length is established independently. Muscle Nerve 56: E100-E107, 2017. © 2017 Wiley Periodicals, Inc.

Metacognitive capacity as a predictor of insight in first-episode psychosis.

PubMed

Vohs, Jenifer L; Lysaker, Paul H; Liffick, Emily; Francis, Michael M; Leonhardt, Bethany L; James, Alison; Buck, Kelly D; Hamm, Jay A; Minor, Kyle S; Mehdiyoun, Nikki; Breier, Alan

2015-05-01

Impaired insight is common in the first episode of psychosis (FEP). Although considerable research has examined the factors that are associated with impaired insight in chronic psychosis, less is known about the factors that underlie and sustain poor insight in FEP. Impaired metacognition, or the ability to form integrated representations of self and others, is a promising potential contributor to poor insight in FEP. To explore this possibility, the authors assessed insight and metacognition in 40 individuals with FEP and then examined the relationship between these areas and social cognition domains, neurocognitive domains, and psychotic symptoms. Correlation analyses revealed that improved insight was associated with higher metacognition, better vocabulary and Theory of Mind scores, and fewer symptoms. The domain of metacognitive mastery also predicted clinical insight. Results support the need to develop an integrative therapeutic approach focused on improving metacognition, hence addressing poor insight in FEP.

The Role of Eye Movement Driven Attention in Functional Strabismic Amblyopia

PubMed Central

2015-01-01

Strabismic amblyopia “blunt vision” is a developmental anomaly that affects binocular vision and results in lowered visual acuity. Strabismus is a term for a misalignment of the visual axes and is usually characterized by impaired ability of the strabismic eye to take up fixation. Such impaired fixation is usually a function of the temporally and spatially impaired binocular eye movements that normally underlie binocular shifts in visual attention. In this review, we discuss how abnormal eye movement function in children with misaligned eyes influences the development of normal binocular visual attention and results in deficits in visual function such as depth perception. We also discuss how eye movement function deficits in adult amblyopia patients can also lead to other abnormalities in visual perception. Finally, we examine how the nonamblyopic eye of an amblyope is also affected in strabismic amblyopia. PMID:25838941

Dysfunction of Rapid Neural Adaptation in Dyslexia.

PubMed

Perrachione, Tyler K; Del Tufo, Stephanie N; Winter, Rebecca; Murtagh, Jack; Cyr, Abigail; Chang, Patricia; Halverson, Kelly; Ghosh, Satrajit S; Christodoulou, Joanna A; Gabrieli, John D E

2016-12-21

Identification of specific neurophysiological dysfunctions resulting in selective reading difficulty (dyslexia) has remained elusive. In addition to impaired reading development, individuals with dyslexia frequently exhibit behavioral deficits in perceptual adaptation. Here, we assessed neurophysiological adaptation to stimulus repetition in adults and children with dyslexia for a wide variety of stimuli, spoken words, written words, visual objects, and faces. For every stimulus type, individuals with dyslexia exhibited significantly diminished neural adaptation compared to controls in stimulus-specific cortical areas. Better reading skills in adults and children with dyslexia were associated with greater repetition-induced neural adaptation. These results highlight a dysfunction of rapid neural adaptation as a core neurophysiological difference in dyslexia that may underlie impaired reading development. Reduced neurophysiological adaptation may relate to prior reports of reduced behavioral adaptation in dyslexia and may reveal a difference in brain functions that ultimately results in a specific reading impairment. Copyright © 2016 Elsevier Inc. All rights reserved.

Overview of Social Cognitive Dysfunctions in Rare Developmental Syndromes With Psychiatric Phenotype

PubMed Central

Morel, Aurore; Peyroux, Elodie; Leleu, Arnaud; Favre, Emilie; Franck, Nicolas; Demily, Caroline

2018-01-01

Rare neurodevelopmental syndromes often present social cognitive deficits that may underlie difficulties in social interactions and increase the risk of psychosis or autism spectrum disorders. However, little is known regarding the specificities of social cognitive impairment across syndromes while it remains a major challenge for the care. Our review provides an overview of social cognitive dysfunctions in rare diseases associated with psychiatric symptoms (with a prevalence estimated between 1 in 1,200 and 1 in 25,000 live births: 22q11.2 deletion syndrome, Angelman syndrome, Fragile X syndrome, Klinefelter syndrome, Prader–Willi syndrome, Rett syndrome, Smith–Magenis syndrome, Turner syndrome, and Williams syndrome) and shed some light on the specific mechanisms that may underlie these skills in each clinical presentation. We first detail the different processes included in the generic expression “social cognition” before summarizing the genotype, psychiatric phenotype, and non-social cognitive profile in each syndrome. Then, we offer a systematic review of the social cognitive abilities and the disturbed mechanisms they are likely associated with. We followed the PRISMA process, including the definition of the relevant search terms, the selection of studies based on clear inclusion, and exclusion criteria and the quality appraisal of papers. We finally provide insights that may have considerable influence on the development of adapted therapeutic interventions such as social cognitive training (SCT) therapies specifically designed to target the psychiatric phenotype. The results of this review suggest that social cognition impairments share some similarities across syndromes. We propose that social cognitive impairments are strongly involved in behavioral symptoms regardless of the overall cognitive level measured by intelligence quotient. Better understanding the mechanisms underlying impaired social cognition may lead to adapt therapeutic interventions. The studies targeting social cognition processes offer new thoughts about the development of specific cognitive training programs, as they highlight the importance of connecting neurocognitive and SCT techniques. PMID:29774207

Impaired diffusion tensor imaging findings in the corpus callosum and cingulum may underlie impaired learning and memory abilities in systemic lupus erythematosus.

PubMed

Shapira-Lichter, I; Weinstein, M; Lustgarten, N; Ash, E; Litinsky, I; Aloush, V; Anouk, M; Caspi, D; Hendler, T; Paran, D

2016-10-01

Memory impairment is prevalent in systemic lupus erythematosus (SLE); however, its pathogenesis is unknown. In a previous functional magnetic resonance imaging (fMRI) study we demonstrated altered brain activity dynamics and less brain deactivation in patients with SLE as compared with healthy controls, when performing a learning and memory task. Our findings localized this impairment to the default mode network (DMN), and particularly to its anterior medial prefrontal cortex node. In addition, altered networking of the hippocampal subsystem of the DMN was seen in patients with SLE when performing this task, as well as atrophy of the left hippocampus. The present study aimed to search for a structural substrate for the altered recruitment pattern observed in fMRI studies using diffusion tensor imaging (DTI). Using DTI, we characterized brain diffusivity in 10 patients with SLE and nine healthy controls. Two tracts associated with the DMN were reconstructed: the corpus callosum (CC) and the cingulum bundle. The CC was segmented according to the Witelson segmentation scheme and the cingulum was segmented into superior and descending bundles. A significant increase in mean diffusivity (MD) was seen in patients with SLE without neuropsychiatric SLE (NPSLE) as compared with healthy controls in all five segments of the CC (segment 1: p = 0.043; segment 2: p = 0.005; segment 3: p = 0.003; segment 4: p = 0.012; segment 5: p = 0.023) as well as in the descending portion of the left cingulum bundle (p = 0.026). Increased MD values in the CC and the left cingulum may indicate impaired organization/reduced integrity of these tracts, which may underlie the abnormal pattern of brain activity recruitment of the DMN observed during a verbal learning and memory task. Taking into account the central role of the left hippocampus in verbal memory, the abnormal integrity of the left cingulum may contribute to the reduced performance of patients with SLE on verbal memory tasks. © The Author(s) 2016.

Breakdown of local information processing may underlie isoflurane anesthesia effects.

PubMed

Wollstadt, Patricia; Sellers, Kristin K; Rudelt, Lucas; Priesemann, Viola; Hutt, Axel; Fröhlich, Flavio; Wibral, Michael

2017-06-01

The disruption of coupling between brain areas has been suggested as the mechanism underlying loss of consciousness in anesthesia. This hypothesis has been tested previously by measuring the information transfer between brain areas, and by taking reduced information transfer as a proxy for decoupling. Yet, information transfer is a function of the amount of information available in the information source-such that transfer decreases even for unchanged coupling when less source information is available. Therefore, we reconsidered past interpretations of reduced information transfer as a sign of decoupling, and asked whether impaired local information processing leads to a loss of information transfer. An important prediction of this alternative hypothesis is that changes in locally available information (signal entropy) should be at least as pronounced as changes in information transfer. We tested this prediction by recording local field potentials in two ferrets after administration of isoflurane in concentrations of 0.0%, 0.5%, and 1.0%. We found strong decreases in the source entropy under isoflurane in area V1 and the prefrontal cortex (PFC)-as predicted by our alternative hypothesis. The decrease in source entropy was stronger in PFC compared to V1. Information transfer between V1 and PFC was reduced bidirectionally, but with a stronger decrease from PFC to V1. This links the stronger decrease in information transfer to the stronger decrease in source entropy-suggesting reduced source entropy reduces information transfer. This conclusion fits the observation that the synaptic targets of isoflurane are located in local cortical circuits rather than on the synapses formed by interareal axonal projections. Thus, changes in information transfer under isoflurane seem to be a consequence of changes in local processing more than of decoupling between brain areas. We suggest that source entropy changes must be considered whenever interpreting changes in information transfer as decoupling.

Breakdown of local information processing may underlie isoflurane anesthesia effects

PubMed Central

Sellers, Kristin K.; Priesemann, Viola; Hutt, Axel

2017-01-01

The disruption of coupling between brain areas has been suggested as the mechanism underlying loss of consciousness in anesthesia. This hypothesis has been tested previously by measuring the information transfer between brain areas, and by taking reduced information transfer as a proxy for decoupling. Yet, information transfer is a function of the amount of information available in the information source—such that transfer decreases even for unchanged coupling when less source information is available. Therefore, we reconsidered past interpretations of reduced information transfer as a sign of decoupling, and asked whether impaired local information processing leads to a loss of information transfer. An important prediction of this alternative hypothesis is that changes in locally available information (signal entropy) should be at least as pronounced as changes in information transfer. We tested this prediction by recording local field potentials in two ferrets after administration of isoflurane in concentrations of 0.0%, 0.5%, and 1.0%. We found strong decreases in the source entropy under isoflurane in area V1 and the prefrontal cortex (PFC)—as predicted by our alternative hypothesis. The decrease in source entropy was stronger in PFC compared to V1. Information transfer between V1 and PFC was reduced bidirectionally, but with a stronger decrease from PFC to V1. This links the stronger decrease in information transfer to the stronger decrease in source entropy—suggesting reduced source entropy reduces information transfer. This conclusion fits the observation that the synaptic targets of isoflurane are located in local cortical circuits rather than on the synapses formed by interareal axonal projections. Thus, changes in information transfer under isoflurane seem to be a consequence of changes in local processing more than of decoupling between brain areas. We suggest that source entropy changes must be considered whenever interpreting changes in information transfer as decoupling. PMID:28570661

Network Disruption and Cerebrospinal Fluid Amyloid-Beta and Phospho-Tau Levels in Mild Cognitive Impairment.

PubMed

Canuet, Leonides; Pusil, Sandra; López, María Eugenia; Bajo, Ricardo; Pineda-Pardo, José Ángel; Cuesta, Pablo; Gálvez, Gerardo; Gaztelu, José María; Lourido, Daniel; García-Ribas, Guillermo; Maestú, Fernando

2015-07-15

Synaptic dysfunction is a core deficit in Alzheimer's disease, preceding hallmark pathological abnormalities. Resting-state magnetoencephalography (MEG) was used to assess whether functional connectivity patterns, as an index of synaptic dysfunction, are associated with CSF biomarkers [i.e., phospho-tau (p-tau) and amyloid beta (Aβ42) levels]. We studied 12 human subjects diagnosed with mild cognitive impairment due to Alzheimer's disease, comparing those with normal and abnormal CSF levels of the biomarkers. We also evaluated the association between aberrant functional connections and structural connectivity abnormalities, measured with diffusion tensor imaging, as well as the convergent impact of cognitive deficits and CSF variables on network disorganization. One-third of the patients converted to Alzheimer's disease during a follow-up period of 2.5 years. Patients with abnomal CSF p-tau and Aβ42 levels exhibited both reduced and increased functional connectivity affecting limbic structures such as the anterior/posterior cingulate cortex, orbitofrontal cortex, and medial temporal areas in different frequency bands. A reduction in posterior cingulate functional connectivity mediated by p-tau was associated with impaired axonal integrity of the hippocampal cingulum. We noted that several connectivity abnormalities were predicted by CSF biomarkers and cognitive scores. These preliminary results indicate that CSF markers of amyloid deposition and neuronal injury in early Alzheimer's disease associate with a dual pattern of cortical network disruption, affecting key regions of the default mode network and the temporal cortex. MEG is useful to detect early synaptic dysfunction associated with Alzheimer's disease brain pathology in terms of functional network organization. In this preliminary study, we used magnetoencephalography and an integrative approach to explore the impact of CSF biomarkers, neuropsychological scores, and white matter structural abnormalities on neural function in mild cognitive impairment. Disruption in functional connectivity between several pairs of cortical regions associated with abnormal levels of biomarkers, cognitive deficits, or with impaired axonal integrity of hippocampal tracts. Amyloid deposition and tau protein-related neuronal injury in early Alzheimer's disease are associated with synaptic dysfunction and a dual pattern of cortical network disorganization (i.e., desynchronization and hypersynchronization) that affects key regions of the default mode network and temporal areas. Copyright © 2015 the authors 0270-6474/15/3510326-06$15.00/0.

IL-1β impairs retrograde flow of BDNF signaling by attenuating endosome trafficking.

PubMed

Carlos, Anthony J; Tong, Liqi; Prieto, G Aleph; Cotman, Carl W

2017-02-02

Pro-inflammatory cytokines accumulate in the brain with age and Alzheimer's disease and can impair neuron health and cognitive function. Brain-derived neurotrophic factor (BDNF) is a key neurotrophin that supports neuron health, function, and synaptic plasticity. The pro-inflammatory cytokine interleukin-1β (IL-1β) impairs BDNF signaling but whether it affects BDNF signaling endosome trafficking has not been studied. This study uses an in vitro approach in primary hippocampal neurons to evaluate the effect of IL-1β on BDNF signaling endosome trafficking. Neurons were cultured in microfluidic chambers that separate the environments of the cell body and its axon terminal, enabling us to specifically treat in axon compartments and trace vesicle trafficking in real-time. We found that IL-1β attenuates BDNF signaling endosomes throughout networks in cultures. In IL-1β-treated cells, overall BDNF endosomal density was decreased, and the colocalization of BDNF endosomes with presynaptic terminals was found to be more than two times higher than in control cultures. Selective IL-1β treatment to the presynaptic compartment in microfluidic chamber attenuated BDNF endosome flux, as measured by reduced BDNF-GFP endosome counts in the somal compartment. Further, IL-1β decreased the BDNF-induced phosphorylation of Erk5, a known BDNF retrograde trafficking target. Mechanistically, the deficiency in trafficking was not due to impaired endocytosis of the BDNF-TrkB complex, or impaired transport rate, since BDNF endosomes traveled at the same rate in both control and IL-1β treatment groups. Among the regulators of presynaptic endosome sorting is the post-translational modification, ubiquitination. In support of this possibility, the IL-1β-mediated suppression of BDNF-induced Erk5 phosphorylation can be rescued by exogenous ubiquitin C-terminal hydrolase L1 (UCH-L1), a deubiquitinating enzyme that regulates ubiquitin and endosomal trafficking. We observed a state of neurotrophic resistance whereby, in the prolonged presence of IL-1β, BDNF is not effective in delivering long-distance signaling via the retrograde transport of signaling endosomes. Since IL-1β accumulation is an invariant feature across many neurodegenerative diseases, our study suggest that compromised BDNF retrograde transport-dependent signaling may have important implications in neurodegenerative diseases.

Mitochondria localize to injured axons to support regeneration

PubMed Central

Han, Sung Min; Baig, Huma S.; Hammarlund, Marc

2016-01-01

SUMMARY Axon regeneration is essential to restore the nervous system after axon injury. However, the neuronal cell biology that underlies axon regeneration is incompletely understood. Here we use in vivo single-neuron analysis to investigate the relationship between nerve injury, mitochondrial localization, and axon regeneration. Mitochondria translocate into injured axons, so that average mitochondria density increases after injury. Moreover, single-neuron analysis reveals that axons that fail to increase mitochondria have poor regeneration. Experimental alterations to axonal mitochondrial distribution or mitochondrial respiratory chain function result in corresponding changes to regeneration outcomes. Axonal mitochondria are specifically required for growth cone migration, identifying a key energy challenge for injured neurons. Finally, mitochondrial localization to the axon after injury is regulated in part by dual-leucine zipper kinase-1 (DLK-1), a conserved regulator of axon regeneration. These data identify regulation of axonal mitochondria as a new cell biological mechanism that helps determine the regenerative response of injured neurons. PMID:28009276

Increased mitochondrial content in remyelinated axons: implications for multiple sclerosis

PubMed Central

Zambonin, Jessica L.; Zhao, Chao; Ohno, Nobuhiko; Campbell, Graham R.; Engeham, Sarah; Ziabreva, Iryna; Schwarz, Nadine; Lee, Sok Ee; Frischer, Josa M.; Turnbull, Doug M.; Trapp, Bruce D.; Lassmann, Hans; Franklin, Robin J. M.

2011-01-01

Mitochondrial content within axons increases following demyelination in the central nervous system, presumably as a response to the changes in energy needs of axons imposed by redistribution of sodium channels. Myelin sheaths can be restored in demyelinated axons and remyelination in some multiple sclerosis lesions is extensive, while in others it is incomplete or absent. The effects of remyelination on axonal mitochondrial content in multiple sclerosis, particularly whether remyelination completely reverses the mitochondrial changes that follow demyelination, are currently unknown. In this study, we analysed axonal mitochondria within demyelinated, remyelinated and myelinated axons in post-mortem tissue from patients with multiple sclerosis and controls, as well as in experimental models of demyelination and remyelination, in vivo and in vitro. Immunofluorescent labelling of mitochondria (porin, a voltage-dependent anion channel expressed on all mitochondria) and axons (neurofilament), and ultrastructural imaging showed that in both multiple sclerosis and experimental demyelination, mitochondrial content within remyelinated axons was significantly less than in acutely and chronically demyelinated axons but more numerous than in myelinated axons. The greater mitochondrial content within remyelinated, compared with myelinated, axons was due to an increase in density of porin elements whereas increase in size accounted for the change observed in demyelinated axons. The increase in mitochondrial content in remyelinated axons was associated with an increase in mitochondrial respiratory chain complex IV activity. In vitro studies showed a significant increase in the number of stationary mitochondria in remyelinated compared with myelinated and demyelinated axons. The number of mobile mitochondria in remyelinated axons did not significantly differ from myelinated axons, although significantly greater than in demyelinated axons. Our neuropathological data and findings in experimental demyelination and remyelination in vivo and in vitro are consistent with a partial amelioration of the supposed increase in energy demand of demyelinated axons by remyelination. PMID:21705418

Increased mitochondrial content in remyelinated axons: implications for multiple sclerosis.

PubMed

Zambonin, Jessica L; Zhao, Chao; Ohno, Nobuhiko; Campbell, Graham R; Engeham, Sarah; Ziabreva, Iryna; Schwarz, Nadine; Lee, Sok Ee; Frischer, Josa M; Turnbull, Doug M; Trapp, Bruce D; Lassmann, Hans; Franklin, Robin J M; Mahad, Don J

2011-07-01

Mitochondrial content within axons increases following demyelination in the central nervous system, presumably as a response to the changes in energy needs of axons imposed by redistribution of sodium channels. Myelin sheaths can be restored in demyelinated axons and remyelination in some multiple sclerosis lesions is extensive, while in others it is incomplete or absent. The effects of remyelination on axonal mitochondrial content in multiple sclerosis, particularly whether remyelination completely reverses the mitochondrial changes that follow demyelination, are currently unknown. In this study, we analysed axonal mitochondria within demyelinated, remyelinated and myelinated axons in post-mortem tissue from patients with multiple sclerosis and controls, as well as in experimental models of demyelination and remyelination, in vivo and in vitro. Immunofluorescent labelling of mitochondria (porin, a voltage-dependent anion channel expressed on all mitochondria) and axons (neurofilament), and ultrastructural imaging showed that in both multiple sclerosis and experimental demyelination, mitochondrial content within remyelinated axons was significantly less than in acutely and chronically demyelinated axons but more numerous than in myelinated axons. The greater mitochondrial content within remyelinated, compared with myelinated, axons was due to an increase in density of porin elements whereas increase in size accounted for the change observed in demyelinated axons. The increase in mitochondrial content in remyelinated axons was associated with an increase in mitochondrial respiratory chain complex IV activity. In vitro studies showed a significant increase in the number of stationary mitochondria in remyelinated compared with myelinated and demyelinated axons. The number of mobile mitochondria in remyelinated axons did not significantly differ from myelinated axons, although significantly greater than in demyelinated axons. Our neuropathological data and findings in experimental demyelination and remyelination in vivo and in vitro are consistent with a partial amelioration of the supposed increase in energy demand of demyelinated axons by remyelination.

Recreational stimulants, herbal, and spice cannabis: The core psychobiological processes that underlie their damaging effects.

PubMed

Parrott, Andrew C; Hayley, Amie C; Downey, Luke A

2017-05-01

Recreational drugs are taken for their positive mood effects, yet their regular usage damages well-being. The psychobiological mechanisms underlying these damaging effects will be debated. The empirical literature on recreational cannabinoids and stimulant drugs is reviewed. A theoretical explanation for how they cause similar types of damage is outlined. All psychoactive drugs cause moods and psychological states to fluctuate. The acute mood gains underlie their recreational usage, while the mood deficits on withdrawal explain their addictiveness. Cyclical mood changes are found with every central nervous system stimulant and also occur with cannabis. These mood state changes provide a surface index for more profound psychobiological fluctuations. Homeostatic balance is altered, with repetitive disturbances of the hypothalamic-pituitary-adrenal axis, and disrupted cortisol-neurohormonal secretions. Hence, these drugs cause increased stress, disturbed sleep, neurocognitive impairments, altered brain activity, and psychiatric vulnerability. Equivalent deficits occur with novel psychoactive stimulants such as mephedrone and artificial "spice" cannabinoids. These psychobiological fluctuations underlie drug dependency and make cessation difficult. Psychobiological stability and homeostatic balance are optimally restored by quitting psychoactive drugs. Recreational stimulants such as cocaine or MDMA (3.4-methylenedioxymethamphetamine) and sedative drugs such as cannabis damage human homeostasis and well-being through similar core psychobiological mechanisms. Copyright © 2017 John Wiley & Sons, Ltd.

Creatine pretreatment protects cortical axons from energy depletion in vitro

PubMed Central

Shen, Hua; Goldberg, Mark P.

2012-01-01

Creatine is a natural nitrogenous guanidino compound involved in bioenergy metabolism. Although creatine has been shown to protect neurons of the central nervous system (CNS) from experimental hypoxia/ischemia, it remains unclear if creatine may also protect CNS axons, and if the potential axonal protection depends on glial cells. To evaluate the direct impact of creatine on CNS axons, cortical axons were cultured in a separate compartment from their somas and proximal neurites using a modified two-compartment culture device. Axons in the axon compartment were subjected to acute energy depletion, an in vitro model of white matter ischemia, by exposure to 6 mM sodium azide for 30 min in the absence of glucose and pyruvate. Energy depletion reduced axonal ATP by 65%, depolarized axonal resting potential, and damaged 75% of axons. Application of creatine (10 mM) to both compartments of the culture at 24 h prior to energy depletion significantly reduced axonal damage by 50%. In line with the role of creatine in the bioenergy metabolism, this application also alleviated the axonal ATP loss and depolarization. Inhibition of axonal depolarization by blocking sodium influx with tetrodotoxin also effectively reduced the axonal damage caused by energy depletion. Further study revealed that the creatine effect was independent of glial cells, as axonal protection was sustained even when creatine was applied only to the axon compartment (free from somas and glial cells) for as little as 2 h. In contrast, application of creatine after energy depletion did not protect axons. The data provide the first evidence that creatine pretreatment may directly protect CNS axons from energy deficiency. PMID:22521466

Cocaine impairs serial-feature negative learning and blood-brain barrier integrity.

PubMed

Davidson, Terry L; Hargrave, Sara L; Kearns, David N; Clasen, Matthew M; Jones, Sabrina; Wakeford, Alison G P; Sample, Camille H; Riley, Anthony L

2018-07-01

Previous research has shown that diets high in fat and sugar [a.k.a., Western diets (WD)] can impair performance of rats on hippocampal-dependent learning and memory problems, an effect that is accompanied by selective increases in hippocampal blood brain barrier (BBB) permeability. Based on these types of findings, it has been proposed that overeating of a WD (and its resulting obesity) may be, in part, a consequence of impairments in these anatomical substrates and cognitive processes. Given that drug use (and addiction) represents another behavioral excess, the present experiments assessed if similar outcomes might occur with drug exposure by evaluating the effects of cocaine administration on hippocampal-dependent memory and on the integrity of the BBB. Experiment 1 of the present series of studies found that systemic cocaine administration in rats also appears to have disruptive effects on the same hippocampal-dependent learning and memory mechanism that has been proposed to underlie the inhibition of food intake. Experiment 2 demonstrated that the same regimen of cocaine exposure that produced disruptions in learning and memory in Experiment 1 also produced increased BBB permeability in the hippocampus, but not in the striatum. Although the predominant focus of previous research investigating the etiologies of substance use and abuse has been on the brain circuits that underlie the motivational properties of drugs, the current investigation implicates the possible involvement of hippocampal memory systems in such behaviors. It is important to note that these positions are not mutually exclusive and that neuroadaptations in these two circuits might occur in parallel that generate dysregulated drug use in a manner similar to that of excessive eating. Copyright © 2018 Elsevier Inc. All rights reserved.

Regulation of Synaptic Amyloid-β Generation through BACE1 Retrograde Transport in a Mouse Model of Alzheimer's Disease

PubMed Central

Ye, Xuan; Chang, Qing; Jeong, Yu Young; Cai, Huaibin; Kusnecov, Alexander

2017-01-01

Amyloid-β (Aβ) peptides play a key role in synaptic damage and memory deficits in the early pathogenesis of Alzheimer's disease (AD). Abnormal accumulation of Aβ at nerve terminals leads to synaptic pathology and ultimately to neurodegeneration. β-site amyloid precursor protein (APP) cleaving enzyme 1 (BACE1) is the major neuronal β-secretase for Aβ generation. However, the mechanisms regulating BACE1 distribution in axons and β cleavage of APP at synapses remain largely unknown. Here, we reveal that dynein–Snapin-mediated retrograde transport regulates BACE1 trafficking in axons and APP processing at presynaptic terminals. BACE1 is predominantly accumulated within late endosomes at the synapses of AD-related mutant human APP (hAPP) transgenic (Tg) mice and patient brains. Defective retrograde transport by genetic ablation of snapin in mice recapitulates late endocytic retention of BACE1 and increased APP processing at presynaptic sites. Conversely, overexpressing Snapin facilitates BACE1 trafficking and reduces synaptic BACE1 accumulation by enhancing the removal of BACE1 from distal AD axons and presynaptic terminals. Moreover, elevated Snapin expression via stereotactic hippocampal injections of adeno-associated virus particles in mutant hAPP Tg mouse brains decreases synaptic Aβ levels and ameliorates synapse loss, thus rescuing cognitive impairments associated with hAPP mice. Altogether, our study provides new mechanistic insights into the complex regulation of BACE1 trafficking and presynaptic localization through Snapin-mediated dynein-driven retrograde axonal transport, thereby suggesting a potential approach of modulating Aβ levels and attenuating synaptic deficits in AD. SIGNIFICANCE STATEMENT β-Site amyloid precursor protein (APP) cleaving enzyme 1 (BACE1) trafficking and synaptic localization significantly influence its β secretase activity and amyloid-β (Aβ) production. In AD brains, BACE1 is accumulated within dystrophic neurites, which is thought to augment Aβ-induced synaptotoxicity by Aβ overproduction. However, it remains largely unknown whether axonal transport regulates synaptic APP processing. Here, we demonstrate that Snapin-mediated retrograde transport plays a critical role in removing BACE1 from presynaptic terminals toward the soma, thus reducing synaptic Aβ production. Adeno-associated virus–mediated Snapin overexpression in the hippocampus of mutant hAPP mice significantly decreases synaptic Aβ levels, attenuates synapse loss, and thus rescues cognitive deficits. Our study uncovers a new pathway that controls synaptic APP processing by enhancing axonal BACE1 trafficking, thereby advancing our fundamental knowledge critical for ameliorating Aβ-linked synaptic pathology. PMID:28159908

Peripheral neuropathy associated with erythrophagocytic lymphohistiocytosis.

PubMed Central

Boutin, B; Routon, M C; Rocchiccioli, F; Mayer, M; Leverger, G; Robain, O; Ponsot, G; Arthuis, M

1988-01-01

A 12 year old patient who developed clinical, biochemical and histological features of erythrophagocytic lymphohistiocytosis is described. In contrast to previously reported cases, the prominent neurological feature was a subacute sensorimotor polyneuropathy. Sural nerve biopsy showed a marked reduction of myelinated fibres and severe axonal lesions, absence of histiocyte infiltration and deposits of IgM along the epineurium. In addition to the hypertriglyceridaemia previously described in this condition, an elevation of plasma very long-chain fatty acids and phytanic acid was found which suggests a transient impairment of peroxisomal functions. Images PMID:3346698

[Pay attention to the secondary optic neuropathy and the safe appropriate applications of optic neuroprotection].

PubMed

Zhong, Y

2016-12-11

Secondary optic neuropathy of optic nerve abnormalities is the leading cause of persistent visual impairment. Previous ocular neuroprotection studies have proved that the nerve growth factor and other agents are of significant in the preservation of optic nerve axon and retinal ganglion cells. However, finding novel safe and effective approach as well as the appropriate applications of optic neuroprotection should be highly emphasized and would be very helpful in the treatment of optic neuropathy. (Chin J Ophthalmol, 2016, 52: 881 - 884) .

Recurrent laryngeal nerve alterations in developing spontaneously hypertensive rats.

PubMed

da Silva, Greice Anne Rodrigues; Mendes, Vania Alice de Aguiar; Genari, Adriana Borges; Castania, Jaci Ayrton; Salgado, Hélio Cesar; Fazan, Valéria Paula Sassoli

2016-01-01

It is well known that the recurrent laryngeal nerve not only innervates the larynx but also contains baroreceptor fibers, as demonstrated by physiological studies. Because hypertension has a negative impact on both peripheral nerve morphology and the baroreflex, we investigated the recurrent laryngeal nerve morphological alterations related to the development of hypertension. We compared morphological and morphometric aspects of different segments of the recurrent laryngeal nerve in male and female spontaneously hypertensive rats in different ages: 5, 8, and 20 weeks (n = 6 per group). Blood pressure and heart rate were recorded in anesthetized animals, followed by removal of the right and left recurrent laryngeal nerves for epoxy resin embedding and light microscopy analysis. Computer software was used for morphometric analysis. The blood pressure was significantly higher in 20-week-old animals compared to those at 5 weeks. Body weight increased significantly with age, as did the nerve fascicles. For the myelinated fibers and respective axons, there was a reduction of fiber size, more evident on the axon, associated with a reduction of the small myelinated fibers percentage in animals with high blood pressure. Also, 20-week-old animals showed a significant reduction of the blood vessel percentage of occupancy compared to younger ages. No differences were observed between genders. Hypertension development impaired axon growth, affecting mainly the small myelinated fibers. Males and females were affected equally. The alterations of the endoneural blood vessels probably played an important role on the small fibers alterations. © 2015 The American Laryngological, Rhinological and Otological Society, Inc.

Synaptic potentials recorded by the sucrosegap method from the rabbit superior cervical ganglion

PubMed Central

Kosterlitz, H. W.; Lees, G. M.; Wallis, D. I.

1970-01-01

1. Compound ganglionic potentials evoked by stimulation of the preganglionic nerves to the superior cervical ganglion of the rabbit were recorded by the sucrose-gap method. 2. When the distal part of the ganglion was bathed in flowing isotonic sucrose solution or sodium-deficient solutions, ganglionic action potentials were no longer evoked, only large synaptic potentials. 3. The compound synaptic potential, which remained unaltered for more than 1 h, originated in a population of cells at the interface between the Krebs and sucrose solutions. Hexamethonium reduced the size but did not alter the time course of the synaptic potential. 4. It is suggested that a higher concentration of sodium ions is required for the generation of ganglionic action potentials than for either conduction in the postganglionic axons or production of synaptic potentials. 5. When lithium replaced sodium in the solution bathing the distal part of the ganglion, the synaptic potential was greatly reduced in amplitude. Impulse propagation in the postganglionic axons was only slightly impaired when lithium replaced sodium in the solution bathing the axons. 6. A quantitative assessment of the potency of the ganglion-blocking drugs nicotine, pentolinium, hexamethonium and pempidine was made by measuring the depression of the synaptic potentials produced by bathing the distal part of the ganglion in flowing isotonic sucrose solution. The concentrations which produced a 50% depression were 8·1 μM nicotine, 26·5 μM pentolinium, 111 μM hexamethonium and 22·2 μM pempidine. PMID:5492898

Sqstm1 knock-down causes a locomotor phenotype ameliorated by rapamycin in a zebrafish model of ALS/FTLD.

PubMed

Lattante, Serena; de Calbiac, Hortense; Le Ber, Isabelle; Brice, Alexis; Ciura, Sorana; Kabashi, Edor

2015-03-15

Mutations in SQSTM1, encoding for the protein SQSTM1/p62, have been recently reported in 1-3.5% of patients with amyotrophic lateral sclerosis and frontotemporal lobar degeneration (ALS/FTLD). Inclusions positive for SQSTM1/p62 have been detected in patients with neurodegenerative disorders, including ALS/FTLD. In order to investigate the pathogenic mechanisms induced by SQSTM1 mutations in ALS/FTLD, we developed a zebrafish model. Knock-down of the sqstm1 zebrafish ortholog, as well as impairment of its splicing, led to a specific phenotype, consisting of behavioral and axonal anomalies. Here, we report swimming deficits associated with shorter motor neuronal axons that could be rescued by the overexpression of wild-type human SQSTM1. Interestingly, no rescue of the loss-of-function phenotype was observed when overexpressing human SQSTM1 constructs carrying ALS/FTLD-related mutations. Consistent with its role in autophagy regulation, we found increased mTOR levels upon knock-down of sqstm1. Furthermore, treatment of zebrafish embryos with rapamycin, a known inhibitor of the mTOR pathway, yielded an amelioration of the locomotor phenotype in the sqstm1 knock-down model. Our results suggest that loss-of-function of SQSTM1 causes phenotypic features characterized by locomotor deficits and motor neuron axonal defects that are associated with a misregulation of autophagic processes. © The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Extracellular caspase-6 drives murine inflammatory pain via microglial TNF-α secretion

PubMed Central

Berta, Temugin; Park, Chul-Kyu; Xu, Zhen-Zhong; Xie, Ruo-Gang; Liu, Tong; Lü, Ning; Liu, Yen-Chin; Ji, Ru-Rong

2014-01-01

Increasing evidence indicates that the pathogenesis of neuropathic pain is mediated through spinal cord microglia activation. The intracellular protease caspase-6 (CASP6) is known to regulate neuronal apoptosis and axonal degeneration; however, the contribution of microglia and CASP6 in modulating synaptic transmission and pain is unclear. Here, we found that CASP6 is expressed specifically in C-fiber axonal terminals in the superficial spinal cord dorsal horn. Animals exposed to intraplantar formalin or bradykinin injection exhibited CASP6 activation in the dorsal horn. Casp6-null mice had normal baseline pain, but impaired inflammatory pain responses. Furthermore, formalin-induced second-phase pain was suppressed by spinal injection of CASP6 inhibitor or CASP6-neutralizing antibody, as well as perisciatic nerve injection of CASP6 siRNA. Recombinant CASP6 (rCASP6) induced marked TNF-α release in microglial cultures, and most microglia within the spinal cord expressed Tnfa. Spinal injection of rCASP6 elicited TNF-α production and microglia-dependent pain hypersensitivity. Evaluation of excitatory postsynaptic currents (EPSCs) revealed that rCASP6 rapidly increased synaptic transmission in spinal cord slices via TNF-α release. Interestingly, the microglial inhibitor minocycline suppressed rCASP6 but not TNF-α–induced synaptic potentiation. Finally, rCASP6-activated microglial culture medium increased EPSCs in spinal cord slices via TNF-α. Together, these data suggest that CASP6 released from axonal terminals regulates microglial TNF-α secretion, synaptic plasticity, and inflammatory pain. PMID:24531553

Intracellular calcium release through IP3R or RyR contributes to secondary axonal degeneration.

PubMed

Orem, Ben C; Pelisch, Nicolas; Williams, Joshua; Nally, Jacqueline M; Stirling, David P

2017-10-01

Severed CNS axons often retract or dieback away from the injury site and fail to regenerate. The precise mechanisms underlying acute axonal dieback and secondary axonal degeneration remain poorly understood. Here we investigate the role of Ca 2+ store mediated intra-axonal Ca 2+ release in acute axonal dieback and secondary axonal degeneration. To differentiate between primary (directly transected) and "bystander" axonal injury (axons spared by the initial injury but then succumb to secondary degeneration) in real-time we use our previously published highly focal laser-induced spinal cord injury (LiSCI) ex vivo model. Ascending spinal cord dorsal column axons that express YFP were severed using an 800 nm laser pulse while being imaged continuously using two-photon excitation microscopy. We inhibited two major intra-axonal Ca 2+ store channels, ryanodine receptors (RyR) and IP 3 R, with ryanodine or 2-APB, respectively, to individually determine their role in axonal dieback and secondary axonal degeneration. Each antagonist was dissolved in artificial CSF and applied 1h post-injury alone or in combination, and continuously perfused for the remainder of the imaging session. Initially following LiSCI, transected axons retracted equal distances both distal and proximal to the lesion. However, by 4h after injury, the distal axonal segments that are destined for Wallerian degeneration had significantly retracted further than their proximal counterparts. We also found that targeting either RyR or IP 3 R using pharmacological and genetic approaches significantly reduced proximal axonal dieback and "bystander" secondary degeneration of axons compared to vehicle controls at 6h post-injury. Combined treatment effects on secondary axonal degeneration were similar to either drug in isolation. Together, these results suggest that intra-axonal Ca 2+ store mediated Ca 2+ release through RyR or IP 3 R contributes to secondary axonal degeneration following SCI. Copyright © 2017 Elsevier Inc. All rights reserved.

Neurocognitive Aging and the Hippocampus Across Species

PubMed Central

Leal, Stephanie L; Yassa, Michael A.

2016-01-01

There is extensive evidence that aging is associated with impairments in episodic memory. Many of these changes have been ascribed to neurobiological alterations to the hippocampal network and its input pathways. A cross-species consensus is beginning to emerge suggesting that subtle synaptic and functional changes within this network may underlie the majority of age-related memory impairments. In this review, we survey convergent data from animal and human studies that have contributed significantly to our understanding of the brain-behavior relationships in this network, particularly in the aging brain. We utilize a cognitive as well as a neurobiological perspective, and synthesize data across approaches and species to reach a more detailed understanding of age-related alterations in hippocampal memory function. PMID:26607684

Neural signatures of cognitive and emotional biases in depression

PubMed Central

Fossati, Philippe

2008-01-01

Functional brain imaging studies suggest that depression is a system-level disorder affecting discrete but functionally linked cortical and limbic structures, with abnormalities in the anterior cingulate, lateral, ami medial prefrontal cortex, amygdala, ami hippocampus. Within this circuitry, abnormal corticolimbic interactions underlie cognitive deficits ami emotional impairment in depression. Depression involves biases toward processing negative emotional information and abnormal self-focus in response to emotional stimuli. These biases in depression could reflect excessive analytical self-focus in depression, as well as impaired cognitive control of emotional response to negative stimuli. By combining structural and functional investigations, brain imaging studies mav help to generate novel antidepressant treatments that regulate structural and factional plasticity within the neural network regulating mood and affective behavior.

Myosin Heads Are Displaced from Actin Filaments in the In Situ Beating Rat Heart in Early Diabetes

PubMed Central

Jenkins, Mathew J.; Pearson, James T.; Schwenke, Daryl O.; Edgley, Amanda J.; Sonobe, Takashi; Fujii, Yutaka; Ishibashi-Ueda, Hatsue; Kelly, Darren J.; Yagi, Naoto; Shirai, Mikiyasu

2013-01-01

Diabetes is independently associated with a specific cardiomyopathy, characterized by impaired cardiac muscle relaxation and force development. Using synchrotron radiation small-angle x-ray scattering, this study investigated in the in situ heart and in real-time whether changes in cross-bridge disposition and myosin interfilament spacing underlie the early development of diabetic cardiomyopathy. Experiments were conducted using anesthetized Sprague-Dawley rats 3 weeks after treatment with either vehicle (control) or streptozotocin (diabetic). Diffraction patterns were recorded during baseline and dobutamine infusions simultaneous with ventricular pressure-volumetry. From these diffraction patterns myosin mass transfer to actin filaments was assessed as the change in intensity ratio (I1,0/I1,1). In diabetic hearts cross-bridge disposition was most notably abnormal in the diastolic phase (p < 0.05) and to a lesser extent the systolic phase (p < 0.05). In diabetic rats only, there was a transmural gradient of contractile depression. Elevated diabetic end-diastolic intensity ratios were correlated with the suppression of diastolic function (p < 0.05). Furthermore, the expected increase in myosin head transfer by dobutamine was significantly blunted in diabetic animals (p < 0.05). Interfilament spacing did not differ between groups. We reveal that impaired cross-bridge disposition and radial transfer may thus underlie the early decline in ventricular function observed in diabetic cardiomyopathy. PMID:23473489

Axon-Axon Interactions Regulate Topographic Optic Tract Sorting via CYFIP2-Dependent WAVE Complex Function.

PubMed

Cioni, Jean-Michel; Wong, Hovy Ho-Wai; Bressan, Dario; Kodama, Lay; Harris, William A; Holt, Christine E

2018-03-07

The axons of retinal ganglion cells (RGCs) are topographically sorted before they arrive at the optic tectum. This pre-target sorting, typical of axon tracts throughout the brain, is poorly understood. Here, we show that cytoplasmic FMR1-interacting proteins (CYFIPs) fulfill non-redundant functions in RGCs, with CYFIP1 mediating axon growth and CYFIP2 specifically involved in axon sorting. We find that CYFIP2 mediates homotypic and heterotypic contact-triggered fasciculation and repulsion responses between dorsal and ventral axons. CYFIP2 associates with transporting ribonucleoprotein particles in axons and regulates translation. Axon-axon contact stimulates CYFIP2 to move into growth cones where it joins the actin nucleating WAVE regulatory complex (WRC) in the periphery and regulates actin remodeling and filopodial dynamics. CYFIP2's function in axon sorting is mediated by its binding to the WRC but not its translational regulation. Together, these findings uncover CYFIP2 as a key regulatory link between axon-axon interactions, filopodial dynamics, and optic tract sorting. Copyright © 2018 The Authors. Published by Elsevier Inc. All rights reserved.

Nucleus basalis of Meynert degeneration precedes and predicts cognitive impairment in Parkinson's disease.

PubMed

Schulz, Jonathan; Pagano, Gennaro; Fernández Bonfante, Juan Alberto; Wilson, Heather; Politis, Marios

2018-05-01

Currently, no reliable predictors of cognitive impairment in Parkinson's disease exist. We hypothesized that microstructural changes at grey matter T1-weighted MRI and diffusion tensor imaging in the cholinergic system nuclei and associated limbic pathways underlie cognitive impairment in Parkinson's disease. We performed a cross-sectional comparison between patients with Parkinson's disease with and without cognitive impairment. We also performed a longitudinal 36-month follow-up study of cognitively intact Parkinson's disease patients, comparing patients who remained cognitively intact to those who developed cognitive impairment. Patients with Parkinson's disease with cognitive impairment showed lower grey matter volume and increased mean diffusivity in the nucleus basalis of Meynert, compared to patients with Parkinson's disease without cognitive impairment. These results were confirmed both with region of interest and voxel-based analyses, and after partial volume correction. Lower grey matter volume and increased mean diffusivity in the nucleus basalis of Meynert was predictive for developing cognitive impairment in cognitively intact patients with Parkinson's disease, independent of other clinical and non-clinical markers of the disease. Structural and microstructural alterations in entorhinal cortex, amygdala, hippocampus, insula, and thalamus were not predictive for developing cognitive impairment in Parkinson's disease. Our findings provide evidence that degeneration of the nucleus basalis of Meynert precedes and predicts the onset of cognitive impairment, and might be used in a clinical setting as a reliable biomarker to stratify patients at higher risk of cognitive decline.

Transgenic mice overexpressing the extracellular domain of NCAM are impaired in working memory and cortical plasticity

PubMed Central

Brennaman, Leann H.; Kochlamazashvili, Gaga; Stoenica, Luminita; Nonneman, Randall J.; Moy, Sheryl S.; Schachner, Melitta; Dityatev, Alexander; Maness, Patricia F.

2011-01-01

The neural cell adhesion molecule, NCAM, is a pivotal regulator of neural development, with key roles in axonal and dendritic growth and synaptic plasticity. Alterations in NCAM expression or proteolytic cleavage have been linked to human neuropsychiatric disorders such as schizophrenia, bipolar disorder and Alzheimer’s disease, and may contribute to cognitive dysfunction. We have generated mice overexpressing the NCAM extracellular (EC) proteolytic cleavage fragment which has been reported to be increased in schizophrenic versus normal brains. These mice show impaired GABAergic innervation and reduced number of apical dendritic spines on pyramidal neurons in the prefrontal cortex (PFC). Here, these NCAM-EC transgenic mice were subjected to behavioral tasks and electrophysiological measurements to determine the impact of structural abnormalities in the PFC on synaptic and cognitive functions. NCAM-EC mice exhibited impaired working memory in a delayed non-match-to-sample task, which requires PFC function, but showed no differences in anxiety, olfactory abilities, or sociability. Transgenic mice displayed impaired long- and short-term potentiation in the PFC but normal synaptic plasticity in the hippocampus, suggesting that the abnormal synaptic innervation in NCAM-EC mice impairs PFC plasticity and alters working memory. These findings may have implications for cognitive dysfunctions observed in neuropsychiatric disorders. PMID:21515372

Modeling of axonal endoplasmic reticulum network by spastic paraplegia proteins.

PubMed

Yalçın, Belgin; Zhao, Lu; Stofanko, Martin; O'Sullivan, Niamh C; Kang, Zi Han; Roost, Annika; Thomas, Matthew R; Zaessinger, Sophie; Blard, Olivier; Patto, Alex L; Sohail, Anood; Baena, Valentina; Terasaki, Mark; O'Kane, Cahir J

2017-07-25

Axons contain a smooth tubular endoplasmic reticulum (ER) network that is thought to be continuous with ER throughout the neuron; the mechanisms that form this axonal network are unknown. Mutations affecting reticulon or REEP proteins, with intramembrane hairpin domains that model ER membranes, cause an axon degenerative disease, hereditary spastic paraplegia (HSP). We show that Drosophila axons have a dynamic axonal ER network, which these proteins help to model. Loss of HSP hairpin proteins causes ER sheet expansion, partial loss of ER from distal motor axons, and occasional discontinuities in axonal ER. Ultrastructural analysis reveals an extensive ER network in axons, which shows larger and fewer tubules in larvae that lack reticulon and REEP proteins, consistent with loss of membrane curvature. Therefore HSP hairpin-containing proteins are required for shaping and continuity of axonal ER, thus suggesting roles for ER modeling in axon maintenance and function.

Coexpression of high-voltage-activated ion channels Kv3.4 and Cav1.2 in pioneer axons during pathfinding in the developing rat forebrain.

PubMed

Huang, Chia-Yi; Chu, Dachen; Hwang, Wei-Chao; Tsaur, Meei-Ling

2012-11-01

Precise axon pathfinding is crucial for establishment of the initial neuronal network during development. Pioneer axons navigate without the help of preexisting axons and pave the way for follower axons that project later. Voltage-gated ion channels make up the intrinsic electrical activity of pioneer axons and regulate axon pathfinding. To elucidate which channel molecules are present in pioneer axons, immunohistochemical analysis was performed to examine 14 voltage-gated ion channels (Kv1.1-Kv1.3, Kv3.1-Kv3.4, Kv4.3, Cav1.2, Cav1.3, Cav2.2, Nav1.2, Nav1.6, and Nav1.9) in nine axonal tracts in the developing rat forebrain, including the optic nerve, corpus callosum, corticofugal fibers, thalamocortical axons, lateral olfactory tract, hippocamposeptal projection, anterior commissure, hippocampal commissure, and medial longitudinal fasciculus. We found A-type K⁺ channel Kv3.4 in both pioneer axons and early follower axons and L-type Ca²⁺ channel Cav1.2 in pioneer axons and early and late follower axons. Spatially, Kv3.4 and Cav1.2 were colocalized with markers of pioneer neurons and pioneer axons, such as deleted in colorectal cancer (DCC), in most fiber tracts examined. Temporally, Kv3.4 and Cav1.2 were expressed abundantly in most fiber tracts during axon pathfinding but were downregulated beginning in synaptogenesis. By contrast, delayed rectifier Kv channels (e.g., Kv1.1) and Nav channels (e.g., Nav1.2) were absent from these fiber tracts (except for the corpus callosum) during pathfinding of pioneer axons. These data suggest that Kv3.4 and Cav1.2, two high-voltage-activated ion channels, may act together to control Ca²⁺ -dependent electrical activity of pioneer axons and play important roles during axon pathfinding. Copyright © 2012 Wiley Periodicals, Inc.

αII Spectrin Forms a Periodic Cytoskeleton at the Axon Initial Segment and Is Required for Nervous System Function.

PubMed

Huang, Claire Yu-Mei; Zhang, Chuansheng; Ho, Tammy Szu-Yu; Oses-Prieto, Juan; Burlingame, Alma L; Lalonde, Joshua; Noebels, Jeffrey L; Leterrier, Christophe; Rasband, Matthew N

2017-11-22

Spectrins form a submembranous cytoskeleton proposed to confer strength and flexibility to neurons and to participate in ion channel clustering at axon initial segments (AIS) and nodes of Ranvier. Neuronal spectrin cytoskeletons consist of diverse β subunits and αII spectrin. Although αII spectrin is found in neurons in both axonal and somatodendritic domains, using proteomics, biochemistry, and superresolution microscopy, we show that αII and βIV spectrin interact and form a periodic AIS cytoskeleton. To determine the role of spectrins in the nervous system, we generated Sptan1 f/f mice for deletion of CNS αII spectrin. We analyzed αII spectrin-deficient mice of both sexes and found that loss of αII spectrin causes profound reductions in all β spectrins. αII spectrin-deficient mice die before 1 month of age and have disrupted AIS and many other neurological impairments including seizures, disrupted cortical lamination, and widespread neurodegeneration. These results demonstrate the importance of the spectrin cytoskeleton both at the AIS and throughout the nervous system. SIGNIFICANCE STATEMENT Spectrin cytoskeletons play diverse roles in neurons, including assembly of excitable domains such as the axon initial segment (AIS) and nodes of Ranvier. However, the molecular composition and structure of these cytoskeletons remain poorly understood. Here, we show that αII spectrin partners with βIV spectrin to form a periodic cytoskeleton at the AIS. Using a new αII spectrin conditional knock-out mouse, we show that αII spectrin is required for AIS assembly, neuronal excitability, cortical lamination, and to protect against neurodegeneration. These results demonstrate the broad importance of spectrin cytoskeletons for nervous system function and development and have important implications for nervous system injuries and diseases because disruption of the spectrin cytoskeleton is a common molecular pathology. Copyright © 2017 the authors 0270-6474/17/3711311-12$15.00/0.

Biomarker Evidence of Axonal Injury in Neuroasymptomatic HIV-1 Patients

PubMed Central

Price, Richard W.; Hagberg, Lars; Fuchs, Dietmar; Rosengren, Lars; Nilsson, Staffan; Zetterberg, Henrik; Gisslén, Magnus

2014-01-01

Background Prevalence of neurocognitive impairment in HIV-1 infected patients is reported to be high. Whether this is a result of active HIV-related neurodegeneration is unclear. We examined axonal injury in HIV-1 patients by measuring the light subunit of neurofilament protein (NFL) in CSF with a novel, sensitive method. Methods With a cross-sectional design, CSF concentrations of neurofilament protein light (NFL) (marker of neuronal injury), neopterin (intrathecal immunoactivation) and CSF/Plasma albumin ratio (blood-brain barrier integrity) were analyzed on CSF from 252 HIV-infected patients, subdivided into untreated neuroasymptomatics (n = 200), HIV-associated dementia (HAD) (n = 14) and on combinations antiretroviral treatment (cART) (n = 85), and healthy controls (n = 204). 46 HIV-infected patients were included in both treated and untreated groups, but sampled at different timepoints. Furthermore, 78 neuroasymptomatic patients were analyzed before and after treatment initiation. Results While HAD patients had the highest NFL concentrations, elevated CSF NFL was also found in 33% of untreated neuroasymptomatic patients, mainly in those with blood CD4+ cell counts below 250 cells/μL. CSF NFL concentrations in the untreated neuroasymptomatics and treated groups were equivalent to controls 18.5 and 3.9 years older, respectively. Neopterin correlated with NFL levels in untreated groups while the albumin ratio correlated with NFL in both untreated and treated groups. Conclusions Increased CSF NFL indicates ongoing axonal injury in many neuroasymptomatic patients. Treatment decreases NFL, but treated patients retain higher levels than controls, indicating either continued virus-related injury or an aging-like effect of HIV infection. NFL correlates with neopterin and albumin ratio, suggesting an association between axonal injury, neuroinflammation and blood-brain barrier permeability. NFL appears to be a sensitive biomarker of subclinical and clinical brain injury in HIV and warrants further assessment for broader clinical use. PMID:24523921

Cortical Deficits of Glutamic Acid Decarboxylase 67 Expression in Schizophrenia: Clinical, Protein, and Cell Type-Specific Features

PubMed Central

Curley, Allison A.; Arion, Dominique; Volk, David W.; Asafu-Adjei, Josephine K.; Sampson, Allan R.; Fish, Kenneth N.; Lewis, David A.

2012-01-01

Objective Cognitive deficits in schizophrenia are associated with altered activity of the dorsolateral prefrontal cortex, which has been attributed to lower expression of the 67 kDa isoform of glutamic acid decarboxylase (GAD67), the major γ-aminobutyric acid (GABA)-synthesizing enzyme. However, little is know n about the relationship of prefrontal GAD67 m RNA levels and illness severity, translation of the transcript into protein, and protein levels in axon terminals, the key site of GABA production and function. Method Quantitative polymerase chain reaction was used to measure GAD67 m RNA levels in postmortem specimens of dorsolateral prefrontal cortex from subjects with schizophrenia and matched comparison subjects with no know n history of psychiatric or neurological disorders (N=42 pairs). In a subset of this cohort in which potential confounds of protein measures were controlled (N=19 pairs), Western blotting was used to quantify tissue levels of GAD67 protein in tissue. In five of these pairs, multilabel confocalimm unofluorescence was used to quantify GAD67 protein levels in the axon terminals of parvalbumin-containing GABA neurons, which are know n to have low levels of GAD67 m RNA in schizophrenia. Results GAD67 m RNA levels were significantly lower in schizophrenia subjects (by 15%), but transcript levels were not associated with predictors or measures of illness severity or chronicity. In schizophrenia subjects, GAD67 protein levels were significantly lower in total gray matter (by 10%) and in parvalbumin axon terminals (by 49%). Conclusions The findings that lower GAD67 m RNA expression is com m on in schizophrenia, that it is not a consequence of having the illness, and that it leads to less translation of the protein, especially in the axon terminals of parvalbumin-containing neurons, support the hypothesis that lower GABA synthesis in parvalbumin neurons contributes to dorsolateral prefrontal cortex dysfunction and impaired cognition in schizophrenia. PMID:21632647

Cortical deficits of glutamic acid decarboxylase 67 expression in schizophrenia: clinical, protein, and cell type-specific features.

PubMed

Curley, Allison A; Arion, Dominique; Volk, David W; Asafu-Adjei, Josephine K; Sampson, Allan R; Fish, Kenneth N; Lewis, David A

2011-09-01

Cognitive deficits in schizophrenia are associated with altered activity of the dorsolateral prefrontal cortex, which has been attributed to lower expression of the 67 kDa isoform of glutamic acid decarboxylase (GAD67), the major γ-aminobutyric acid (GABA)-synthesizing enzyme. However, little is known about the relationship of prefrontal GAD67 mRNA levels and illness severity, translation of the transcript into protein, and protein levels in axon terminals, the key site of GABA production and function. Quantitative polymerase chain reaction was used to measure GAD67 mRNA levels in postmortem specimens of dorsolateral prefrontal cortex from subjects with schizophrenia and matched comparison subjects with no known history of psychiatric or neurological disorders (N=42 pairs). In a subset of this cohort in which potential confounds of protein measures were controlled (N=19 pairs), Western blotting was used to quantify tissue levels of GAD67 protein in tissue. In five of these pairs, multilabel confocal immunofluorescence was used to quantify GAD67 protein levels in the axon terminals of parvalbumin-containing GABA neurons, which are known to have low levels of GAD67 mRNA in schizophrenia. GAD67 mRNA levels were significantly lower in schizophrenia subjects (by 15%), but transcript levels were not associated with predictors or measures of illness severity or chronicity. In schizophrenia subjects, GAD67 protein levels were significantly lower in total gray matter (by 10%) and in parvalbumin axon terminals (by 49%). The findings that lower GAD67 mRNA expression is common in schizophrenia, that it is not a consequence of having the illness, and that it leads to less translation of the protein, especially in the axon terminals of parvalbumin-containing neurons, support the hypothesis that lower GABA synthesis in parvalbumin neurons contributes to dorsolateral prefrontal cortex dysfunction and impaired cognition in schizophrenia.

ATPase-deficient mitochondrial inner membrane protein ATAD3A disturbs mitochondrial dynamics in dominant hereditary spastic paraplegia

PubMed Central

Cooper, Helen M.; Yang, Yang; Ylikallio, Emil; Khairullin, Rafil; Woldegebriel, Rosa; Lin, Kai-Lan; Euro, Liliya; Palin, Eino; Wolf, Alexander; Trokovic, Ras; Isohanni, Pirjo; Kaakkola, Seppo; Auranen, Mari; Lönnqvist, Tuula; Wanrooij, Sjoerd

2017-01-01

Abstract De novo mutations in ATAD3A (ATPase family AAA-domain containing protein 3A) were recently found to cause a neurological syndrome with developmental delay, hypotonia, spasticity, optic atrophy, axonal neuropathy, and hypertrophic cardiomyopathy. Using whole-exome sequencing, we identified a dominantly inherited heterozygous variant c.1064G > A (p.G355D) in ATAD3A in a mother presenting with hereditary spastic paraplegia (HSP) and axonal neuropathy and her son with dyskinetic cerebral palsy, both with disease onset in childhood. HSP is a clinically and genetically heterogeneous disorder of the upper motor neurons. Symptoms beginning in early childhood may resemble spastic cerebral palsy. The function of ATAD3A, a mitochondrial inner membrane AAA ATPase, is yet undefined. AAA ATPases form hexameric rings, which are catalytically dependent on the co-operation of the subunits. The dominant-negative patient mutation affects the Walker A motif, which is responsible for ATP binding in the AAA module of ATAD3A, and we show that the recombinant mutant ATAD3A protein has a markedly reduced ATPase activity. We further show that overexpression of the mutant ATAD3A fragments the mitochondrial network and induces lysosome mass. Similarly, we observed altered dynamics of the mitochondrial network and increased lysosomes in patient fibroblasts and neurons derived through differentiation of patient-specific induced pluripotent stem cells. These alterations were verified in patient fibroblasts to associate with upregulated basal autophagy through mTOR inactivation, resembling starvation. Mutations in ATAD3A can thus be dominantly inherited and underlie variable neurological phenotypes, including HSP, with intrafamiliar variability. This finding extends the group of mitochondrial inner membrane AAA proteins associated with spasticity. PMID:28158749

HDAC1/2-Dependent P0 Expression Maintains Paranodal and Nodal Integrity Independently of Myelin Stability through Interactions with Neurofascins.

PubMed

Brügger, Valérie; Engler, Stefanie; Pereira, Jorge A; Ruff, Sophie; Horn, Michael; Welzl, Hans; Münger, Emmanuelle; Vaquié, Adrien; Sidiropoulos, Páris N M; Egger, Boris; Yotovski, Peter; Filgueira, Luis; Somandin, Christian; Lühmann, Tessa C; D'Antonio, Maurizio; Yamaguchi, Teppei; Matthias, Patrick; Suter, Ueli; Jacob, Claire

2015-01-01

The pathogenesis of peripheral neuropathies in adults is linked to maintenance mechanisms that are not well understood. Here, we elucidate a novel critical maintenance mechanism for Schwann cell (SC)-axon interaction. Using mouse genetics, ablation of the transcriptional regulators histone deacetylases 1 and 2 (HDAC1/2) in adult SCs severely affected paranodal and nodal integrity and led to demyelination/remyelination. Expression levels of the HDAC1/2 target gene myelin protein zero (P0) were reduced by half, accompanied by altered localization and stability of neurofascin (NFasc)155, NFasc186, and loss of Caspr and septate-like junctions. We identify P0 as a novel binding partner of NFasc155 and NFasc186, both in vivo and by in vitro adhesion assay. Furthermore, we demonstrate that HDAC1/2-dependent P0 expression is crucial for the maintenance of paranodal/nodal integrity and axonal function through interaction of P0 with neurofascins. In addition, we show that the latter mechanism is impaired by some P0 mutations that lead to late onset Charcot-Marie-Tooth disease.

Conservation, expression, and knockdown of zebrafish plxnb2a and plxnb2b.

PubMed

Perälä, Nina; Peitsaro, Nina; Sundvik, Maria; Koivula, Henri; Sainio, Kirsi; Sariola, Hannu; Panula, Pertti; Immonen, Tiina

2010-10-01

In mice lacking Plexin B2, a receptor of the axon guidance molecules Semaphorin 4C and Semaphorin 4D, the closure of the neural tube and structural organization of the cerebellum are severely impaired. We cloned two Plexin B2 orthologs, plxnb2a and plxnb2b, in zebrafish, which is a widely used model for the development of the vertebrate central nervous system (CNS). The predicted proteins, Plexin B2a and Plexin B2b, contain all the conserved and functional domains of the plexin B-subfamily. During embryonic development, plxnb2a is expressed, e.g., in pharyngeal arches while plxnb2b expression is more confined to neuronal structures like the cerebellum. However, both plxnb2a and plxnb2b are expressed at the midbrain-hindbrain boundary, in the otic vesicles, facial ganglia, and pectoral fins. Knockdown of both plxnb2a and plxnb2b simultaneously (>95% and 45%, respectively) resulted in normal CNS structure, axon guidance and swimming performance of the morphants.

Aging of Cerebral White Matter

PubMed Central

Liu, Huan; Yang, Yuanyuan; Xia, Yuguo; Zhu, Wen; Leak, Rehana K.; Wei, Zhishuo; Wang, Jianyi; Hu, Xiaoming

2016-01-01

White matter (WM) occupies a large volume of the human cerebrum and is mainly composed of myelinated axons and myelin-producing glial cells. The myelinated axons within WM are the structural foundation for efficient neurotransmission between cortical and subcortical areas. Similar to neuron-enriched gray matter areas, WM undergoes a series of changes during the process of aging. WM malfunction can induce serious neurobehavioral and cognitive impairments. Thus, age-related changes in WM may contribute to the functional decline observed in the elderly. In addition, aged WM becomes more susceptible to neurological disorders, such as stroke, traumatic brain injury (TBI), and neurodegeneration. In this review, we summarize the structural and functional alterations of WM in natural aging and speculate on the underlying mechanisms. We also discuss how age-related WM changes influence the progression of various brain disorders, including ischemic and hemorrhagic stroke, TBI, Alzheimer’s disease, and Parkinson’s disease. Although the physiology of WM is still poorly understood relative to gray matter, WM is a rational therapeutic target for a number of neurological and psychiatric conditions. PMID:27865980

Aging of cerebral white matter.

PubMed

Liu, Huan; Yang, Yuanyuan; Xia, Yuguo; Zhu, Wen; Leak, Rehana K; Wei, Zhishuo; Wang, Jianyi; Hu, Xiaoming

2017-03-01

White matter (WM) occupies a large volume of the human cerebrum and is mainly composed of myelinated axons and myelin-producing glial cells. The myelinated axons within WM are the structural foundation for efficient neurotransmission between cortical and subcortical areas. Similar to neuron-enriched gray matter areas, WM undergoes a series of changes during the process of aging. WM malfunction can induce serious neurobehavioral and cognitive impairments. Thus, age-related changes in WM may contribute to the functional decline observed in the elderly. In addition, aged WM becomes more susceptible to neurological disorders, such as stroke, traumatic brain injury (TBI), and neurodegeneration. In this review, we summarize the structural and functional alterations of WM in natural aging and speculate on the underlying mechanisms. We also discuss how age-related WM changes influence the progression of various brain disorders, including ischemic and hemorrhagic stroke, TBI, Alzheimer's disease, and Parkinson's disease. Although the physiology of WM is still poorly understood relative to gray matter, WM is a rational therapeutic target for a number of neurological and psychiatric conditions. Copyright © 2016 Elsevier B.V. All rights reserved.

Intracellular Protein Shuttling: A Mechanism Relevant for Myelin Repair in Multiple Sclerosis?

PubMed Central

Göttle, Peter; Küry, Patrick

2015-01-01

A prominent feature of demyelinating diseases such as multiple sclerosis (MS) is the degeneration and loss of previously established functional myelin sheaths, which results in impaired signal propagation and axonal damage. However, at least in early disease stages, partial replacement of lost oligodendrocytes and thus remyelination occur as a result of resident oligodendroglial precursor cell (OPC) activation. These cells represent a widespread cell population within the adult central nervous system (CNS) that can differentiate into functional myelinating glial cells to restore axonal functions. Nevertheless, the spontaneous remyelination capacity in the adult CNS is inefficient because OPCs often fail to generate new oligodendrocytes due to the lack of stimulatory cues and the presence of inhibitory factors. Recent studies have provided evidence that regulated intracellular protein shuttling is functionally involved in oligodendroglial differentiation and remyelination activities. In this review we shed light on the role of the subcellular localization of differentiation-associated factors within oligodendroglial cells and show that regulation of intracellular localization of regulatory factors represents a crucial process to modulate oligodendroglial maturation and myelin repair in the CNS. PMID:26151843

Abnormal Mitochondrial Dynamics and Synaptic Degeneration as Early Events in Alzheimer’s Disease: Implications to Mitochondria-Targeted Antioxidant Therapeutics

PubMed Central

Reddy, P. Hemachandra; Tripathy, Raghav; Troung, Quang; Thirumala, Karuna; Reddy, Tejaswini P.; Anekonda, Vishwanath; Shirendeb, Ulziibat P.; Calkins, Marcus J.; Reddy, Arubala P.; Mao, Peizhong; Manczak, Maria

2011-01-01

Synaptic pathology and mitochondrial oxidative damage are early events in Alzheimer’s disease (AD) progression. Loss of synapses and synaptic damage are the best correlate of cognitive deficits found in AD patients. Recent research on amyloid bet (Aβ) and mitochondria in AD revealed that Aβ accumulates in synapses and synaptic mitochondria, leading to abnormal mitochondrial dynamics and synaptic degeneration in AD neurons. Further, recent studies using live-cell imaging and primary neurons from amyloid beta precursor protein (AβPP) transgenic mice revealed that reduced mitochondrial mass, defective axonal transport of mitochondria and synaptic degeneration, indicating that Aβ is responsible for mitochondrial and synaptic deficiencies. Tremendous progress has been made in studying antioxidant approaches in mouse models of AD and clinical trials of AD patients. This article highlights the recent developments made in Aβ-induced abnormal mitochondrial dynamics, defective mitochondrial biogenesis, impaired axonal transport and synaptic deficiencies in AD. This article also focuses on mitochondrial approaches in treating AD, and also discusses latest research on mitochondria-targeted antioxidants in AD. PMID:22037588

Towards the concept of disease-modifier in post-stroke or vascular cognitive impairment: a consensus report.

PubMed

Bordet, Régis; Ihl, Ralf; Korczyn, Amos D; Lanza, Giuseppe; Jansa, Jelka; Hoerr, Robert; Guekht, Alla

2017-05-24

Vascular cognitive impairment (VCI) is a complex spectrum encompassing post-stroke cognitive impairment (PSCI) and small vessel disease-related cognitive impairment. Despite the growing health, social, and economic burden of VCI, to date, no specific treatment is available, prompting the introduction of the concept of a disease modifier. Within this clinical spectrum, VCI and PSCI remain advancing conditions as neurodegenerative diseases with progression of both vascular and degenerative lesions accounting for cognitive decline. Disease-modifying strategies should integrate both pharmacological and non-pharmacological multimodal approaches, with pleiotropic effects targeting (1) endothelial and brain-blood barrier dysfunction; (2) neuronal death and axonal loss; (3) cerebral plasticity and compensatory mechanisms; and (4) degenerative-related protein misfolding. Moreover, pharmacological and non-pharmacological treatment in PSCI or VCI requires valid study designs clearly stating the definition of basic methodological issues, such as the instruments that should be used to measure eventual changes, the biomarker-based stratification of participants to be investigated, and statistical tests, as well as the inclusion and exclusion criteria that should be applied. A consensus emerged to propose the development of a disease-modifying strategy in VCI and PSCI based on pleiotropic pharmacological and non-pharmacological approaches.

The Genetics of Axon Guidance and Axon Regeneration in Caenorhabditis elegans

PubMed Central

Chisholm, Andrew D.; Hutter, Harald; Jin, Yishi; Wadsworth, William G.

2016-01-01

The correct wiring of neuronal circuits depends on outgrowth and guidance of neuronal processes during development. In the past two decades, great progress has been made in understanding the molecular basis of axon outgrowth and guidance. Genetic analysis in Caenorhabditis elegans has played a key role in elucidating conserved pathways regulating axon guidance, including Netrin signaling, the slit Slit/Robo pathway, Wnt signaling, and others. Axon guidance factors were first identified by screens for mutations affecting animal behavior, and by direct visual screens for axon guidance defects. Genetic analysis of these pathways has revealed the complex and combinatorial nature of guidance cues, and has delineated how cues guide growth cones via receptor activity and cytoskeletal rearrangement. Several axon guidance pathways also affect directed migrations of non-neuronal cells in C. elegans, with implications for normal and pathological cell migrations in situations such as tumor metastasis. The small number of neurons and highly stereotyped axonal architecture of the C. elegans nervous system allow analysis of axon guidance at the level of single identified axons, and permit in vivo tests of prevailing models of axon guidance. C. elegans axons also have a robust capacity to undergo regenerative regrowth after precise laser injury (axotomy). Although such axon regrowth shares some similarities with developmental axon outgrowth, screens for regrowth mutants have revealed regeneration-specific pathways and factors that were not identified in developmental screens. Several areas remain poorly understood, including how major axon tracts are formed in the embryo, and the function of axon regeneration in the natural environment. PMID:28114100

Exclusion of Integrins from CNS Axons Is Regulated by Arf6 Activation and the AIS

PubMed Central

Franssen, Elske H. P.; Zhao, Rong-Rong; Koseki, Hiroaki; Kanamarlapudi, Venkateswarlu; Hoogenraad, Casper C.

2015-01-01

Integrins are adhesion and survival molecules involved in axon growth during CNS development, as well as axon regeneration after injury in the peripheral nervous system (PNS). Adult CNS axons do not regenerate after injury, partly due to a low intrinsic growth capacity. We have previously studied the role of integrins in axon growth in PNS axons; in the present study, we investigate whether integrin mechanisms involved in PNS regeneration may be altered or lacking from mature CNS axons by studying maturing CNS neurons in vitro. In rat cortical neurons, we find that integrins are present in axons during initial growth but later become restricted to the somato-dendritic domain. We investigated how this occurs and whether it can be altered to enhance axonal growth potential. We find a developmental change in integrin trafficking; transport becomes predominantly retrograde throughout axons, but not dendrites, as neurons mature. The directionality of transport is controlled through the activation state of ARF6, with developmental upregulation of the ARF6 GEF ARNO enhancing retrograde transport. Lowering ARF6 activity in mature neurons restores anterograde integrin flow, allows transport into axons, and increases axon growth. In addition, we found that the axon initial segment is partly responsible for exclusion of integrins and removal of this structure allows integrins into axons. Changing posttranslational modifications of tubulin with taxol also allows integrins into the proximal axon. The experiments suggest that the developmental loss of regenerative ability in CNS axons is due to exclusion of growth-related molecules due to changes in trafficking. PMID:26019348

L1CAM/Neuroglian controls the axon-axon interactions establishing layered and lobular mushroom body architecture.

PubMed

Siegenthaler, Dominique; Enneking, Eva-Maria; Moreno, Eliza; Pielage, Jan

2015-03-30

The establishment of neuronal circuits depends on the guidance of axons both along and in between axonal populations of different identity; however, the molecular principles controlling axon-axon interactions in vivo remain largely elusive. We demonstrate that the Drosophila melanogaster L1CAM homologue Neuroglian mediates adhesion between functionally distinct mushroom body axon populations to enforce and control appropriate projections into distinct axonal layers and lobes essential for olfactory learning and memory. We addressed the regulatory mechanisms controlling homophilic Neuroglian-mediated cell adhesion by analyzing targeted mutations of extra- and intracellular Neuroglian domains in combination with cell type-specific rescue assays in vivo. We demonstrate independent and cooperative domain requirements: intercalating growth depends on homophilic adhesion mediated by extracellular Ig domains. For functional cluster formation, intracellular Ankyrin2 association is sufficient on one side of the trans-axonal complex whereas Moesin association is likely required simultaneously in both interacting axonal populations. Together, our results provide novel mechanistic insights into cell adhesion molecule-mediated axon-axon interactions that enable precise assembly of complex neuronal circuits. © 2015 Siegenthaler et al.

An ex vivo laser-induced spinal cord injury model to assess mechanisms of axonal degeneration in real-time.

PubMed

Okada, Starlyn L M; Stivers, Nicole S; Stys, Peter K; Stirling, David P

2014-11-25

Injured CNS axons fail to regenerate and often retract away from the injury site. Axons spared from the initial injury may later undergo secondary axonal degeneration. Lack of growth cone formation, regeneration, and loss of additional myelinated axonal projections within the spinal cord greatly limits neurological recovery following injury. To assess how central myelinated axons of the spinal cord respond to injury, we developed an ex vivo living spinal cord model utilizing transgenic mice that express yellow fluorescent protein in axons and a focal and highly reproducible laser-induced spinal cord injury to document the fate of axons and myelin (lipophilic fluorescent dye Nile Red) over time using two-photon excitation time-lapse microscopy. Dynamic processes such as acute axonal injury, axonal retraction, and myelin degeneration are best studied in real-time. However, the non-focal nature of contusion-based injuries and movement artifacts encountered during in vivo spinal cord imaging make differentiating primary and secondary axonal injury responses using high resolution microscopy challenging. The ex vivo spinal cord model described here mimics several aspects of clinically relevant contusion/compression-induced axonal pathologies including axonal swelling, spheroid formation, axonal transection, and peri-axonal swelling providing a useful model to study these dynamic processes in real-time. Major advantages of this model are excellent spatiotemporal resolution that allows differentiation between the primary insult that directly injures axons and secondary injury mechanisms; controlled infusion of reagents directly to the perfusate bathing the cord; precise alterations of the environmental milieu (e.g., calcium, sodium ions, known contributors to axonal injury, but near impossible to manipulate in vivo); and murine models also offer an advantage as they provide an opportunity to visualize and manipulate genetically identified cell populations and subcellular structures. Here, we describe how to isolate and image the living spinal cord from mice to capture dynamics of acute axonal injury.

Mild traumatic brain injury results in depressed cerebral glucose uptake: An (18)FDG PET study.

PubMed

Selwyn, Reed; Hockenbury, Nicole; Jaiswal, Shalini; Mathur, Sanjeev; Armstrong, Regina C; Byrnes, Kimberly R

2013-12-01

Moderate to severe traumatic brain injury (TBI) in humans and rats induces measurable metabolic changes, including a sustained depression in cerebral glucose uptake. However, the effect of a mild TBI on brain glucose uptake is unclear, particularly in rodent models. This study aimed to determine the glucose uptake pattern in the brain after a mild lateral fluid percussion (LFP) TBI. Briefly, adult male rats were subjected to a mild LFP and positron emission tomography (PET) imaging with (18)F-fluorodeoxyglucose ((18)FDG), which was performed prior to injury and at 3 and 24 h and 5, 9, and 16 days post-injury. Locomotor function was assessed prior to injury and at 1, 3, 7, 14, and 21 days after injury using modified beam walk tasks to confirm injury severity. Histology was performed at either 10 or 21 days post-injury. Analysis of function revealed a transient impairment in locomotor ability, which corresponds to a mild TBI. Using reference region normalization, PET imaging revealed that mild LFP-induced TBI depresses glucose uptake in both the ipsilateral and contralateral hemispheres in comparison with sham-injured and naïve controls from 3 h to 5 days post-injury. Further, areas of depressed glucose uptake were associated with regions of glial activation and axonal damage, but no measurable change in neuronal loss or gross tissue damage was observed. In conclusion, we show that mild TBI, which is characterized by transient impairments in function, axonal damage, and glial activation, results in an observable depression in overall brain glucose uptake using (18)FDG-PET.

Diffusion tensor imaging of normal-appearing white matter in mild cognitive impairment and early Alzheimer disease: preliminary evidence of axonal degeneration in the temporal lobe.

PubMed

Huang, J; Friedland, R P; Auchus, A P

2007-01-01

Diffusion tensor imaging (DTI) is a sensitive technique for studying cerebral white matter. We used DTI to characterize microstructural white matter changes and their associations with cognitive dysfunction in Alzheimer disease (AD) and mild cognitive impairment (MCI). We studied elderly subjects with mild AD (n = 6), MCI (n = 11), or normal cognition (n = 8). A standardized clinical and neuropsychological evaluation was conducted on each subject. DTI images were acquired, and fractional anisotropy (FA), axial diffusivity (DA), and radial diffusivity (DR) of normal-appearing white matter (NAWM) in frontal, temporal, parietal, and occipital lobes were determined. These diffusion measurements were compared across the 3 groups, and significant differences were further examined for correlations with tests of cognitive function. Compared with normal controls, AD subjects demonstrated decreased FA and increased DR in the temporal, parietal, and frontal NAWM and decreased DA in temporal NAWM. MCI subjects also showed decreased FA and decreased DA in temporal NAWM, with decreased FA and increased DR in parietal NAWM. Diffusion measurements showed no differences in occipital NAWM. Across all subjects, temporal lobe FA and DR correlated with episodic memory, frontal FA and DR correlated with executive function, and parietal DR significantly correlated with visuospatial ability. We found evidence for functionally relevant microstructural changes in the NAWM of patients with AD and MCI. These changes were present in brain regions serving higher cortical functions, but not in regions serving primary functions, and are consistent with a hypothesized loss of axonal processes in the temporal lobe.

Corruption of the dentate gyrus by "dominant" granule cells: Implications for dentate gyrus function in health and disease.

PubMed

Scharfman, Helen E; Myers, Catherine E

2016-03-01

The dentate gyrus (DG) and area CA3 of the hippocampus are highly organized lamellar structures which have been implicated in specific cognitive functions such as pattern separation and pattern completion. Here we describe how the anatomical organization and physiology of the DG and CA3 are consistent with structures that perform pattern separation and completion. We then raise a new idea related to the complex circuitry of the DG and CA3 where CA3 pyramidal cell 'backprojections' play a potentially important role in the sparse firing of granule cells (GCs), considered important in pattern separation. We also propose that GC axons, the mossy fibers, already known for their highly specialized structure, have a dynamic function that imparts variance--'mossy fiber variance'--which is important to pattern separation and completion. Computational modeling is used to show that when a subset of GCs become 'dominant,' one consequence is loss of variance in the activity of mossy fiber axons and a reduction in pattern separation and completion in the model. Empirical data are then provided using an example of 'dominant' GCs--subsets of GCs that develop abnormally and have increased excitability. Notably, these abnormal GCs have been identified in animal models of disease where DG-dependent behaviors are impaired. Together these data provide insight into pattern separation and completion, and suggest that behavioral impairment could arise from dominance of a subset of GCs in the DG-CA3 network. Copyright © 2015 Elsevier Inc. All rights reserved.

Emotional see-saw affects rationality of decision-making: Evidence for metacognitive impairments.

PubMed

Folwarczny, Michał; Kaczmarek, Magdalena C; Doliński, Dariusz; Szczepanowski, Remigiusz

2018-05-01

This research investigated the cognitive mechanisms that underlie impairments in human reasoning triggered by the emotional see-saw technique. It has previously been stated that such manipulation is effective as it presumably induces a mindless state and cognitive deficits in compliant individuals. Based on the dual-system architecture of reasoning (system 2) and affective decision-making (system 1), we challenged the previous theoretical account by indicating that the main source of compliance is impairment of the meta-reasoning system when rapid affective changes occur. To examine this hypothesis, we manipulated affective feelings (system 1 processing) by violating participants' expectations regarding reward and performance in a go/no-go task in which individuals were to inhibit their responses to earn money. Aside from the go/no-go performance, we measured rationality (meta-reasoning system 2) in decision-making by asking participants to comply with a nonsensical request. We found that participants who were exposed to meta-reasoning impairments due to the emotional see-saw phenomenon exhibited mindless behavior. Copyright © 2018 Elsevier B.V. All rights reserved.

Modeling of axonal endoplasmic reticulum network by spastic paraplegia proteins

PubMed Central

Yalçın, Belgin; Zhao, Lu; Stofanko, Martin; O'Sullivan, Niamh C; Kang, Zi Han; Roost, Annika; Thomas, Matthew R; Zaessinger, Sophie; Blard, Olivier; Patto, Alex L; Sohail, Anood; Baena, Valentina; Terasaki, Mark; O'Kane, Cahir J

2017-01-01

Axons contain a smooth tubular endoplasmic reticulum (ER) network that is thought to be continuous with ER throughout the neuron; the mechanisms that form this axonal network are unknown. Mutations affecting reticulon or REEP proteins, with intramembrane hairpin domains that model ER membranes, cause an axon degenerative disease, hereditary spastic paraplegia (HSP). We show that Drosophila axons have a dynamic axonal ER network, which these proteins help to model. Loss of HSP hairpin proteins causes ER sheet expansion, partial loss of ER from distal motor axons, and occasional discontinuities in axonal ER. Ultrastructural analysis reveals an extensive ER network in axons, which shows larger and fewer tubules in larvae that lack reticulon and REEP proteins, consistent with loss of membrane curvature. Therefore HSP hairpin-containing proteins are required for shaping and continuity of axonal ER, thus suggesting roles for ER modeling in axon maintenance and function. DOI: http://dx.doi.org/10.7554/eLife.23882.001 PMID:28742022

Evidence That Descending Cortical Axons Are Essential for Thalamocortical Axons to Cross the Pallial-Subpallial Boundary in the Embryonic Forebrain

PubMed Central

Chen, Yijing; Magnani, Dario; Theil, Thomas; Pratt, Thomas; Price, David J.

2012-01-01

Developing thalamocortical axons traverse the subpallium to reach the cortex located in the pallium. We tested the hypothesis that descending corticofugal axons are important for guiding thalamocortical axons across the pallial-subpallial boundary, using conditional mutagenesis to assess the effects of blocking corticofugal axonal development without disrupting thalamus, subpallium or the pallial-subpallial boundary. We found that thalamic axons still traversed the subpallium in topographic order but did not cross the pallial-subpallial boundary. Co-culture experiments indicated that the inability of thalamic axons to cross the boundary was not explained by mutant cortex developing a long-range chemorepulsive action on thalamic axons. On the contrary, cortex from conditional mutants retained its thalamic axonal growth-promoting activity and continued to express Nrg-1, which is responsible for this stimulatory effect. When mutant cortex was replaced with control cortex, corticofugal efferents were restored and thalamic axons from conditional mutants associated with them and crossed the pallial-subpallial boundary. Our study provides the most compelling evidence to date that cortical efferents are required to guide thalamocortical axons across the pallial-subpallial boundary, which is otherwise hostile to thalamic axons. These results support the hypothesis that thalamic axons grow from subpallium to cortex guided by cortical efferents, with stimulation from diffusible cortical growth-promoting factors. PMID:22412988

Retrograde and Wallerian Axonal Degeneration Occur Synchronously after Retinal Ganglion Cell Axotomy

PubMed Central

Kanamori, Akiyasu; Catrinescu, Maria-Magdalena; Belisle, Jonathan M.; Costantino, Santiago; Levin, Leonard A.

2013-01-01

Axonal injury and degeneration are pivotal pathological events in diseases of the nervous system. In the past decade, it has been recognized that the process of axonal degeneration is distinct from somal degeneration and that axoprotective strategies may be distinct from those that protect the soma. Preserving the cell body via neuroprotection cannot improve function if the axon is damaged, because the soma is still disconnected from its target. Therefore, understanding the mechanisms of axonal degeneration is critical for developing new therapeutic interventions for axonal disease treatment. We combined in vivo imaging with a multilaser confocal scanning laser ophthalmoscope and in vivo axotomy with a diode-pumped solid-state laser to assess the time course of Wallerian and retrograde degeneration of unmyelinated retinal ganglion cell axons in living rats for 4 weeks after intraretinal axotomy. Laser injury resulted in reproducible axon loss both distal and proximal to the site of injury. Longitudinal polarization-sensitive imaging of axons demonstrated that Wallerian and retrograde degeneration occurred synchronously. Neurofilament immunostaining of retinal whole-mounts confirmed axonal loss and demonstrated sparing of adjacent axons to the axotomy site. In vivo fluorescent imaging of axonal transport and photobleaching of labeled axons demonstrated that the laser axotomy model did not affect adjacent axon function. These results are consistent with a shared mechanism for Wallerian and retrograde degeneration. PMID:22642911

Overexpression of Pax6 results in microphthalmia, retinal dysplasia and defective retinal ganglion cell axon guidance

PubMed Central

Manuel, Martine; Pratt, Thomas; Liu, Min; Jeffery, Glen; Price, David J

2008-01-01

Background The transcription factor Pax6 is expressed by many cell types in the developing eye. Eyes do not form in homozygous loss-of-function mouse mutants (Pax6Sey/Sey) and are abnormally small in Pax6Sey/+ mutants. Eyes are also abnormally small in PAX77 mice expressing multiple copies of human PAX6 in addition to endogenous Pax6; protein sequences are identical in the two species. The developmental events that lead to microphthalmia in PAX77 mice are not well-characterised, so it is not clear whether over- and under-expression of Pax6/PAX6 cause microphthalmia through similar mechanisms. Here, we examined the consequences of over-expression for the eye and its axonal connections. Results Eyes form in PAX77+/+ embryos but subsequently degenerate. At E12.5, we found no abnormalities in ocular morphology, retinal cell cycle parameters and the incidence of retinal cell death. From E14.5 on, we observed malformations of the optic disc. From E16.5 into postnatal life there is progressively more severe retinal dysplasia and microphthalmia. Analyses of patterns of gene expression indicated that PAX77+/+ retinae produce a normal range of cell types, including retinal ganglion cells (RGCs). At E14.5 and E16.5, quantitative RT-PCR with probes for a range of molecules associated with retinal development showed only one significant change: a slight reduction in levels of mRNA encoding the secreted morphogen Shh at E16.5. At E16.5, tract-tracing with carbocyanine dyes in PAX77+/+ embryos revealed errors in intraretinal navigation by RGC axons, a decrease in the number of RGC axons reaching the thalamus and an increase in the proportion of ipsilateral projections among those RGC axons that do reach the thalamus. A survey of embryos with different Pax6/PAX6 gene dosage (Pax6Sey/+, Pax6+/+, PAX77+ and PAX77+/+) showed that (1) the total number of RGC axons projected by the retina and (2) the proportions that are sorted into the ipsilateral and contralateral optic tracts at the optic chiasm vary differently with gene dosage. Increasing dosage increases the proportion projecting ipsilaterally regardless of the size of the total projection. Conclusion Pax6 overexpression does not obviously impair the initial formation of the eye and its major cell-types but prevents normal development of the retina from about E14.5, leading eventually to severe retinal degeneration in postnatal life. This sequence is different to that underlying microphthalmia in Pax6+/- heterozygotes, which is due primarily to defects in the initial stages of lens formation. Before the onset of severe retinal dysplasia, Pax6 overexpression causes defects of retinal axons, preventing their normal growth and navigation through the optic chiasm. PMID:18507827

Altered impulse activity modifies synaptic physiology and mitochondria in crayfish phasic motor neurons.

PubMed

Nguyen, P V; Atwood, H L

1994-12-01

1. Crayfish phasic motor synapses produce large initial excitatory postsynaptic potentials (EPSPs) that fatigue rapidly during high-frequency stimulation. Periodic in vivo stimulation of an identified phasic abdominal extensor motor neuron (axon 3) induced long-term adaptation (LTA) of neuromuscular transmission: initial EPSP amplitude became smaller and synaptic depression was significantly reduced. We tested the hypothesis that activity-induced synaptic fatigue-resistance seen during LTA was dependent upon, or correlated with, mitochondrial oxidative competence. 2. Periodic unilateral conditioning stimulation of axon 3 entering each of two adjacent homologous abdominal segments (segments 2 and 3) increased the synaptic stamina in both "conditioned" axons; mean final EPSP amplitudes, recorded after 20 min of 5-Hz test stimulation, were significantly larger than those measured with the same protocol from contralateral unstimulated axons. 3. During 5-Hz test stimulation of the conditioned axon 3 of segment 3, acute superfusion with 0.8 mM dinitrophenol or 20 mM sodium azide [inhibitors of oxidative adenosinetriphosphate (ATP) synthesis] produced increased synaptic depression. Drug-free saline superfusion of the conditioned axon 3 of segment 2 in these same animals did not affect the increased synaptic fatigue resistance seen in this segment. Thus both successful induction (in axon 3 of saline-perfused segment 2) and attenuation (in axon 3 of drug-perfused segment 3) of the increased synaptic stamina can be demonstrated with this twin-segment conditioning protocol. 4. Confocal microscopic imaging of mitochondrial rhodamine-123 (Rh123) fluorescence was used to assess relative oxidative competence of conditioned and unconditioned phasic axons. Conditioned phasic axons showed significantly higher mean mitochondrial Rh123 fluorescence than contralateral unstimulated axons. In the same preparations that showed increased postconditioning Rh123 fluorescence, the synaptic fatigue resistance measured from conditioned axon 3 was also significantly greater than that recorded from contralateral unstimulated axon 3. 5. Axotomy of the phasic extensor nerve root (containing axon 3), before in vivo conditioning stimulation of its decentralized segment, prevented induction of both the increased synaptic stamina in axon 3 and the enhanced mitochondrial fluorescence in decentralized motor axons of the nerve root. Hence, induction of both changes requires axonal transport of materials between the soma and the motor synapses of axon 3. 5. Axotomy of the phasic extensor nerve root (containing axon 3), before in vivo conditioning stimulation of its decentralized segment, Prevented induction of both the increased synaptic stamina in axon 3 and the enhanced mitochondrial fluorescence in decentralized motor axons of the nerve root Hence, induction of both changes requires axonal transport of materials between the soma and the motor synapses of axon 3 6. Because mitochondrial Rh123 fluorescence is primarily dependent upon the oxidative activity of these organelles, our findings suggest that conditioning stimulation of phasic extensor axon 3 increases its mitochondrial oxidative competence and that the enhanced synaptic stamina seen during LTA in axon 3 is correlated with, and dependent upon, oxidative activity.(ABSTRACT TRUNCATED AT 400 WORDS)

Identified motor terminals in Drosophila larvae show distinct differences in morphology and physiology

NASA Technical Reports Server (NTRS)

Lnenicka, G. A.; Keshishian, H.

2000-01-01

In Drosophila, the type I motor terminals innervating the larval ventral longitudinal muscle fibers 6 and 7 have been the most popular preparation for combining synaptic studies with genetics. We have further characterized the normal morphological and physiological properties of these motor terminals and the influence of muscle size on terminal morphology. Using dye-injection and physiological techniques, we show that the two axons supplying these terminals have different innervation patterns: axon 1 innervates only muscle fibers 6 and 7, whereas axon 2 innervates all of the ventral longitudinal muscle fibers. This difference in innervation pattern allows the two axons to be reliably identified. The terminals formed by axons 1 and 2 on muscle fibers 6 and 7 have the same number of branches; however, axon 2 terminals are approximately 30% longer than axon 1 terminals, resulting in a corresponding greater number of boutons for axon 2. The axon 1 boutons are approximately 30% wider than the axon 2 boutons. The excitatory postsynaptic potential (EPSP) produced by axon 1 is generally smaller than that produced by axon 2, although the size distributions show considerable overlap. Consistent with vertebrate studies, there is a correlation between muscle fiber size and terminal size. For a single axon, terminal area and length, the number of terminal branches, and the number of boutons are all correlated with muscle fiber size, but bouton size is not. During prolonged repetitive stimulation, axon 2 motor terminals show synaptic depression, whereas axon 1 EPSPs facilitate. The response to repetitive stimulation appears to be similar at all motor terminals of an axon. Copyright 2000 John Wiley & Sons, Inc.

Physical Biology of Axonal Damage.

PubMed

de Rooij, Rijk; Kuhl, Ellen

2018-01-01

Excessive physical impacts to the head have direct implications on the structural integrity at the axonal level. Increasing evidence suggests that tau, an intrinsically disordered protein that stabilizes axonal microtubules, plays a critical role in the physical biology of axonal injury. However, the precise mechanisms of axonal damage remain incompletely understood. Here we propose a biophysical model of the axon to correlate the dynamic behavior of individual tau proteins under external physical forces to the evolution of axonal damage. To propagate damage across the scales, we adopt a consistent three-step strategy: First, we characterize the axonal response to external stretches and stretch rates for varying tau crosslink bond strengths using a discrete axonal damage model. Then, for each combination of stretch rates and bond strengths, we average the axonal force-stretch response of n = 10 discrete simulations, from which we derive and calibrate a homogenized constitutive model. Finally, we embed this homogenized model into a continuum axonal damage model of [1-d]-type in which d is a scalar damage parameter that is driven by the axonal stretch and stretch rate. We demonstrate that axonal damage emerges naturally from the interplay of physical forces and biological crosslinking. Our study reveals an emergent feature of the crosslink dynamics: With increasing loading rate, the axonal failure stretch increases, but axonal damage evolves earlier in time. For a wide range of physical stretch rates, from 0.1 to 10 /s, and biological bond strengths, from 1 to 100 pN, our model predicts a relatively narrow window of critical damage stretch thresholds, from 1.01 to 1.30, which agrees well with experimental observations. Our biophysical damage model can help explain the development and progression of axonal damage across the scales and will provide useful guidelines to identify critical damage level thresholds in response to excessive physical forces.

Myelinated sensory and alpha motor axon regeneration in peripheral nerve neuromas

NASA Technical Reports Server (NTRS)

Macias, M. Y.; Lehman, C. T.; Sanger, J. R.; Riley, D. A.

1998-01-01

Histochemical staining for carbonic anhydrase and cholinesterase (CE) activities was used to analyze sensory and motor axon regeneration, respectively, during neuroma formation in transected and tube-encapsulated peripheral nerves. Median-ulnar and sciatic nerves in the rodent model permitted testing whether a 4 cm greater distance of the motor neuron soma from axotomy site or intrinsic differences between motor and sensory neurons influenced regeneration and neuroma formation 10, 30, and 90 days later. Ventral root radiculotomy confirmed that CE-stained axons were 97% alpha motor axons. Distance significantly delayed axon regeneration. When distance was negligible, sensory axons grew out sooner than motor axons, but motor axons regenerated to a greater quantity. These results indicate regeneration differences between axon subtypes and suggest more extensive branching of motor axons within the neuroma. Thus, both distance from injury site to soma and inherent motor and sensory differences should be considered in peripheral nerve repair strategies.

Squid Giant Axon Contains Neurofilament Protein mRNA but does not Synthesize Neurofilament Proteins.

PubMed

Gainer, Harold; House, Shirley; Kim, Dong Sun; Chin, Hemin; Pant, Harish C

2017-04-01

When isolated squid giant axons are incubated in radioactive amino acids, abundant newly synthesized proteins are found in the axoplasm. These proteins are translated in the adaxonal Schwann cells and subsequently transferred into the giant axon. The question as to whether any de novo protein synthesis occurs in the giant axon itself is difficult to resolve because the small contribution of the proteins possibly synthesized intra-axonally is not easily distinguished from the large amounts of the proteins being supplied from the Schwann cells. In this paper, we reexamine this issue by studying the synthesis of endogenous neurofilament (NF) proteins in the axon. Our laboratory previously showed that NF mRNA and protein are present in the squid giant axon, but not in the surrounding adaxonal glia. Therefore, if the isolated squid axon could be shown to contain newly synthesized NF protein de novo, it could not arise from the adaxonal glia. The results of experiments in this paper show that abundant 3H-labeled NF protein is synthesized in the squid giant fiber lobe containing the giant axon's neuronal cell bodies, but despite the presence of NF mRNA in the giant axon no labeled NF protein is detected in the giant axon. This lends support to the glia-axon protein transfer hypothesis which posits that the squid giant axon obtains newly synthesized protein by Schwann cell transfer and not through intra-axonal protein synthesis, and further suggests that the NF mRNA in the axon is in a translationally repressed state.

Axon Regeneration in C. elegans

PubMed Central

Hammarlund, Marc; Jin, Yishi

2014-01-01

Single axon transection by laser surgery has made C. elegans a new model for axon regeneration. Multiple conserved molecular signaling modules have been discovered through powerful genetic screening. in vivo imaging with single cell and axon resolution has revealed unprecedented cellular dynamics in regenerating axons. Information from C. elegans has greatly expanded our knowledge of the molecular and cellular mechanisms of axon regeneration. PMID:24794753

White matter integrity deficits in prefrontal-amygdala pathways in Williams syndrome.

PubMed

Avery, Suzanne N; Thornton-Wells, Tricia A; Anderson, Adam W; Blackford, Jennifer Urbano

2012-01-16

Williams syndrome is a neurodevelopmental disorder associated with significant non-social fears. Consistent with this elevated non-social fear, individuals with Williams syndrome have an abnormally elevated amygdala response when viewing threatening non-social stimuli. In typically-developing individuals, amygdala activity is inhibited through dense, reciprocal white matter connections with the prefrontal cortex. Neuroimaging studies suggest a functional uncoupling of normal prefrontal-amygdala inhibition in individuals with Williams syndrome, which might underlie both the extreme amygdala activity and non-social fears. This functional uncoupling might be caused by structural deficits in underlying white matter pathways; however, prefrontal-amygdala white matter deficits have yet to be explored in Williams syndrome. We used diffusion tensor imaging to investigate prefrontal-amygdala white matter integrity differences in individuals with Williams syndrome and typically-developing controls with high levels of non-social fear. White matter pathways between the amygdala and several prefrontal regions were isolated using probabilistic tractography. Within each pathway, we tested for between-group differences in three measures of white matter integrity: fractional anisotropy (FA), radial diffusivity (RD), and parallel diffusivity (λ(1)). Individuals with Williams syndrome had lower FA, compared to controls, in several of the prefrontal-amygdala pathways investigated, indicating a reduction in white matter integrity. Lower FA in Williams syndrome was explained by significantly higher RD, with no differences in λ(1), suggestive of lower fiber density or axon myelination in prefrontal-amygdala pathways. These results suggest that deficits in the structural integrity of prefrontal-amygdala white matter pathways might underlie the increased amygdala activity and extreme non-social fears observed in Williams syndrome. Copyright © 2011 Elsevier Inc. All rights reserved.

Action Potential Dynamics in Fine Axons Probed with an Axonally Targeted Optical Voltage Sensor.

PubMed

Ma, Yihe; Bayguinov, Peter O; Jackson, Meyer B

2017-01-01

The complex and malleable conduction properties of axons determine how action potentials propagate through extensive axonal arbors to reach synaptic terminals. The excitability of axonal membranes plays a major role in neural circuit function, but because most axons are too thin for conventional electrical recording, their properties remain largely unexplored. To overcome this obstacle, we used a genetically encoded hybrid voltage sensor (hVOS) harboring an axonal targeting motif. Expressing this probe in transgenic mice enabled us to monitor voltage changes optically in two populations of axons in hippocampal slices, the large axons of dentate granule cells (mossy fibers) in the stratum lucidum of the CA3 region and the much finer axons of hilar mossy cells in the inner molecular layer of the dentate gyrus. Action potentials propagated with distinct velocities in each type of axon. Repetitive firing broadened action potentials in both populations, but at an intermediate frequency the degree of broadening differed. Repetitive firing also attenuated action potential amplitudes in both mossy cell and granule cell axons. These results indicate that the features of use-dependent action potential broadening, and possible failure, observed previously in large nerve terminals also appear in much finer unmyelinated axons. Subtle differences in the frequency dependences could influence the propagation of activity through different pathways to excite different populations of neurons. The axonally targeted hVOS probe used here opens up the diverse repertoire of neuronal processes to detailed biophysical study.

An αII Spectrin-Based Cytoskeleton Protects Large-Diameter Myelinated Axons from Degeneration.

PubMed

Huang, Claire Yu-Mei; Zhang, Chuansheng; Zollinger, Daniel R; Leterrier, Christophe; Rasband, Matthew N

2017-11-22

Axons must withstand mechanical forces, including tension, torsion, and compression. Spectrins and actin form a periodic cytoskeleton proposed to protect axons against these forces. However, because spectrins also participate in assembly of axon initial segments (AISs) and nodes of Ranvier, it is difficult to uncouple their roles in maintaining axon integrity from their functions at AIS and nodes. To overcome this problem and to determine the importance of spectrin cytoskeletons for axon integrity, we generated mice with αII spectrin-deficient peripheral sensory neurons. The axons of these neurons are very long and exposed to the mechanical forces associated with limb movement; most lack an AIS, and some are unmyelinated and have no nodes. We analyzed αII spectrin-deficient mice of both sexes and found that, in myelinated axons, αII spectrin forms a periodic cytoskeleton with βIV and βII spectrin at nodes of Ranvier and paranodes, respectively, but that loss of αII spectrin disrupts this organization. Avil-cre;Sptan1 f/f mice have reduced numbers of nodes, disrupted paranodal junctions, and mislocalized Kv1 K + channels. We show that the density of nodal βIV spectrin is constant among axons, but the density of nodal αII spectrin increases with axon diameter. Remarkably, Avil-cre;Sptan1 f/f mice have intact nociception and small-diameter axons, but severe ataxia due to preferential degeneration of large-diameter myelinated axons. Our results suggest that nodal αII spectrin helps resist the mechanical forces experienced by large-diameter axons, and that αII spectrin-dependent cytoskeletons are also required for assembly of nodes of Ranvier. SIGNIFICANCE STATEMENT A periodic axonal cytoskeleton consisting of actin and spectrin has been proposed to help axons resist the mechanical forces to which they are exposed (e.g., compression, torsion, and stretch). However, until now, no vertebrate animal model has tested the requirement of the spectrin cytoskeleton in maintenance of axon integrity. We demonstrate the role of the periodic spectrin-dependent cytoskeleton in axons and show that loss of αII spectrin from PNS axons causes preferential degeneration of large-diameter myelinated axons. We show that nodal αII spectrin is found at greater densities in large-diameter myelinated axons, suggesting that nodes are particularly vulnerable domains requiring a specialized cytoskeleton to protect against axon degeneration. Copyright © 2017 the authors 0270-6474/17/3711323-12$15.00/0.

Axon tension regulates fasciculation/defasciculation through the control of axon shaft zippering

PubMed Central

Šmít, Daniel; Fouquet, Coralie; Pincet, Frédéric; Zapotocky, Martin; Trembleau, Alain

2017-01-01

While axon fasciculation plays a key role in the development of neural networks, very little is known about its dynamics and the underlying biophysical mechanisms. In a model system composed of neurons grown ex vivo from explants of embryonic mouse olfactory epithelia, we observed that axons dynamically interact with each other through their shafts, leading to zippering and unzippering behavior that regulates their fasciculation. Taking advantage of this new preparation suitable for studying such interactions, we carried out a detailed biophysical analysis of zippering, occurring either spontaneously or induced by micromanipulations and pharmacological treatments. We show that zippering arises from the competition of axon-axon adhesion and mechanical tension in the axons, and provide the first quantification of the force of axon-axon adhesion. Furthermore, we introduce a biophysical model of the zippering dynamics, and we quantitatively relate the individual zipper properties to global characteristics of the developing axon network. Our study uncovers a new role of mechanical tension in neural development: the regulation of axon fasciculation. DOI: http://dx.doi.org/10.7554/eLife.19907.001 PMID:28422009

GSK3β regulates AKT-induced central nervous system axon regeneration via an eIF2Bε-dependent, mTORC1-independent pathway.

PubMed

Guo, Xinzheng; Snider, William D; Chen, Bo

2016-03-14

Axons fail to regenerate after central nervous system (CNS) injury. Modulation of the PTEN/mTORC1 pathway in retinal ganglion cells (RGCs) promotes axon regeneration after optic nerve injury. Here, we report that AKT activation, downstream of Pten deletion, promotes axon regeneration and RGC survival. We further demonstrate that GSK3β plays an indispensable role in mediating AKT-induced axon regeneration. Deletion or inactivation of GSK3β promotes axon regeneration independently of the mTORC1 pathway, whereas constitutive activation of GSK3β reduces AKT-induced axon regeneration. Importantly, we have identified eIF2Bε as a novel downstream effector of GSK3β in regulating axon regeneration. Inactivation of eIF2Bε reduces both GSK3β and AKT-mediated effects on axon regeneration. Constitutive activation of eIF2Bε is sufficient to promote axon regeneration. Our results reveal a key role of the AKT-GSK3β-eIF2Bε signaling module in regulating axon regeneration in the adult mammalian CNS.

Motoneuron axon pathfinding errors in zebrafish: Differential effects related to concentration and timing of nicotine exposure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Menelaou, Evdokia; Paul, Latoya T.; Perera, Surangi N.

Nicotine exposure during embryonic stages of development can affect many neurodevelopmental processes. In the developing zebrafish, exposure to nicotine was reported to cause axonal pathfinding errors in the later born secondary motoneurons (SMNs). These alterations in SMN axon morphology coincided with muscle degeneration at high nicotine concentrations (15–30 μM). Previous work showed that the paralytic mutant zebrafish known as sofa potato exhibited nicotine-induced effects onto SMN axons at these high concentrations but in the absence of any muscle deficits, indicating that pathfinding errors could occur independent of muscle effects. In this study, we used varying concentrations of nicotine at differentmore » developmental windows of exposure to specifically isolate its effects onto subpopulations of motoneuron axons. We found that nicotine exposure can affect SMN axon morphology in a dose-dependent manner. At low concentrations of nicotine, SMN axons exhibited pathfinding errors, in the absence of any nicotine-induced muscle abnormalities. Moreover, the nicotine exposure paradigms used affected the 3 subpopulations of SMN axons differently, but the dorsal projecting SMN axons were primarily affected. We then identified morphologically distinct pathfinding errors that best described the nicotine-induced effects on dorsal projecting SMN axons. To test whether SMN pathfinding was potentially influenced by alterations in the early born primary motoneuron (PMN), we performed dual labeling studies, where both PMN and SMN axons were simultaneously labeled with antibodies. We show that only a subset of the SMN axon pathfinding errors coincided with abnormal PMN axonal targeting in nicotine-exposed zebrafish. We conclude that nicotine exposure can exert differential effects depending on the levels of nicotine and developmental exposure window. - Highlights: • Embryonic nicotine exposure can specifically affect secondary motoneuron axons in a dose-dependent manner. • The nicotine-induced secondary motoneuron axonal pathfinding errors can occur independent of any muscle fiber alterations. • Nicotine exposure primarily affects dorsal projecting secondary motoneurons axons. • Nicotine-induced primary motoneuron axon pathfinding errors can influence secondary motoneuron axon morphology.« less

Dendritic Spine Pathology in Schizophrenia

PubMed Central

Glausier, Jill R.; Lewis, David A.

2012-01-01

Schizophrenia is a neurodevelopmental disorder whose clinical features include impairments in perception, cognition and motivation. These impairments reflect alterations in neuronal circuitry within and across multiple brain regions that are due, at least in part, to deficits in dendritic spines, the site of most excitatory synaptic connections. Dendritic spine alterations have been identified in multiple brain regions in schizophrenia, but are best characterized in layer 3 of the neocortex, where pyramidal cell spine density is lower. These spine deficits appear to arise during development, and thus are likely the result of disturbances in the molecular mechanisms that underlie spine formation, pruning, and/or maintenance. Each of these mechanisms may provide insight into novel therapeutic targets for preventing or repairing the alterations in neural circuitry that mediate the debilitating symptoms of schizophrenia. PMID:22546337

Glia to axon RNA transfer.

PubMed

Sotelo, José Roberto; Canclini, Lucía; Kun, Alejandra; Sotelo-Silveira, José Roberto; Calliari, Aldo; Cal, Karina; Bresque, Mariana; Dipaolo, Andrés; Farias, Joaquina; Mercer, John A

2014-03-01

The existence of RNA in axons has been a matter of dispute for decades. Evidence for RNA and ribosomes has now accumulated to a point at which it is difficult to question, much of the disputes turned to the origin of these axonal RNAs. In this review, we focus on studies addressing the origin of axonal RNAs and ribosomes. The neuronal soma as the source of most axonal RNAs has been demonstrated and is indisputable. However, the surrounding glial cells may be a supplemental source of axonal RNAs, a matter scarcely investigated in the literature. Here, we review the few papers that have demonstrated that glial-to-axon RNA transfer is not only feasible, but likely. We describe this process in both invertebrate axons and vertebrate axons. Schwann cell to axon ribosomes transfer was conclusively demonstrated (Court et al. [2008]: J. Neurosci 28:11024-11029; Court et al. [2011]: Glia 59:1529-1539). However, mRNA transfer still remains to be demonstrated in a conclusive way. The intercellular transport of mRNA has interesting implications, particularly with respect to the integration of glial and axonal function. This evolving field is likely to impact our understanding of the cell biology of the axon in both normal and pathological conditions. Most importantly, if the synthesis of proteins in the axon can be controlled by interacting glia, the possibilities for clinical interventions in injury and neurodegeneration are greatly increased. Copyright © 2013 Wiley Periodicals, Inc.

Axonal transport: cargo-specific mechanisms of motility and regulation.

PubMed

Maday, Sandra; Twelvetrees, Alison E; Moughamian, Armen J; Holzbaur, Erika L F

2014-10-22

Axonal transport is essential for neuronal function, and many neurodevelopmental and neurodegenerative diseases result from mutations in the axonal transport machinery. Anterograde transport supplies distal axons with newly synthesized proteins and lipids, including synaptic components required to maintain presynaptic activity. Retrograde transport is required to maintain homeostasis by removing aging proteins and organelles from the distal axon for degradation and recycling of components. Retrograde axonal transport also plays a major role in neurotrophic and injury response signaling. This review provides an overview of axonal transport pathways and discusses their role in neuronal function.

Axon diameter and intra-axonal volume fraction of the corticospinal tract in idiopathic normal pressure hydrocephalus measured by q-space imaging.

PubMed

Kamiya, Kouhei; Hori, Masaaki; Miyajima, Masakazu; Nakajima, Madoka; Suzuki, Yuriko; Kamagata, Koji; Suzuki, Michimasa; Arai, Hajime; Ohtomo, Kuni; Aoki, Shigeki

2014-01-01

Previous studies suggest that compression and stretching of the corticospinal tract (CST) potentially cause treatable gait disturbance in patients with idiopathic normal pressure hydrocephalus (iNPH). Measurement of axon diameter with diffusion MRI has recently been used to investigate microstructural alterations in neurological diseases. In this study, we investigated alterations in the axon diameter and intra-axonal fraction of the CST in iNPH by q-space imaging (QSI) analysis. Nineteen patients with iNPH and 10 age-matched controls were recruited. QSI data were obtained with a 3-T system by using a single-shot echo planar imaging sequence with the diffusion gradient applied parallel to the antero-posterior axis. By using a two-component low-q fit model, the root mean square displacements of intra-axonal space ( =  axon diameter) and intra-axonal volume fraction of the CST were calculated at the levels of the internal capsule and body of the lateral ventricle, respectively. Wilcoxon's rank-sum test revealed a significant increase in CST intra-axonal volume fraction at the paraventricular level in patients (p<0.001), whereas no significant difference was observed in the axon diameter. At the level of the internal capsule, neither axon diameter nor intra-axonal volume fraction differed significantly between the two groups. Our results suggest that in patients with iNPH, the CST does not undergo irreversible axonal damage but is rather compressed and/or stretched owing to pressure from the enlarged ventricle. These analyses of axon diameter and intra-axonal fraction yield insights into microstructural alterations of the CST in iNPH.

ARF6 directs axon transport and traffic of integrins and regulates axon growth in adult DRG neurons.

PubMed

Eva, Richard; Crisp, Sarah; Marland, Jamie R K; Norman, Jim C; Kanamarlapudi, Venkateswarlu; ffrench-Constant, Charles; Fawcett, James W

2012-07-25

Integrins are involved in axon growth and regeneration. Manipulation of integrins is a route to promoting axon regeneration and understanding regeneration failure in the CNS. Expression of α9 integrin promotes axon regeneration, so we have investigated α9β1 trafficking and transport in axons and at the growth cone. We have previously found that α9 and β1 integrins traffic via Rab11-positive recycling endosomes in peripheral axons and growth cones. However, transport via Rab11 is slow, while rapid transport occurs in vesicles lacking Rab11. We have further studied α9 and β1 integrin transport and traffic in adult rat dorsal root ganglion axons and PC12 cells. Integrins are in ARF6 vesicles during rapid axonal transport and during trafficking in the growth cone. We report that rapid axonal transport of these integrins and their trafficking at the cell surface is regulated by ARF6. ARF6 inactivation by expression of ACAP1 leads to increased recycling of β1 integrins to the neuronal surface and to increased anterograde axonal transport. ARF6 activation by expression of the neuronal guanine nucleotide exchange factors, ARNO or EFA6, increases retrograde integrin transport in axons and increases integrin internalization. ARF6 inactivation increases integrin-mediated outgrowth, while activation decreases it. The coordinated changes in integrin transport and recycling resulting from ARF6 activation or inactivation are the probable mechanism behind this regulation of axon growth. Our data suggest a novel mechanism of integrin traffic and transport in peripheral axons, regulated by the activation state of ARF6, and suggest that ARF6 might be targeted to enhance integrin-dependent axon regeneration after injury.

An Integrated MRI and MRS Approach to Evaluation of Multiple Sclerosis with Cognitive Impairment

NASA Astrophysics Data System (ADS)

Liang, Zhengrong; Li, Lihong; Lu, Hongbing; Huang, Wei; Tudorica, Alina; Krupp, Lauren

Magnetic resonance imaging and spectroscopy (MRI/MRS) plays a unique role in multiple sclerosis (MS) evaluation, because of its ability to provide both high image contrast and significant chemical change among brain tissues. The image contrast renders the possibility of quantifying the tissue volumetric and texture variations, e.g., cerebral atrophy and progressing speed, reflecting the ongoing destructive pathologic processes. Any chemical change reflects an early sign of pathological alteration, e.g., decreased N-acetyl aspartate (NAA) in lesions and normal appearing white matter, related to axonal damage or dysfunction. Both MRI and MRS encounter partial volume (PV) effect, which compromises the quantitative capability, especially for MRS. This work aims to develop a statistical framework to segment the tissue mixtures inside each image element, eliminating theoretically the PV effect, and apply the framework to the evaluation of MS with cognitive impairment. The quantitative measures from MRI/MRS neuroimaging are strongly correlated with the qualitative neuropsychological scores of Brief Repeatable Battery (BRB) test on cognitive impairment, demonstrating the usefulness of the PV image segmentation framework in this clinically significant problem.

Fascicular nerve stimulation and recording using a novel double-aisle regenerative electrode

NASA Astrophysics Data System (ADS)

Delgado-Martínez, I.; Righi, M.; Santos, D.; Cutrone, A.; Bossi, S.; D'Amico, S.; Del Valle, J.; Micera, S.; Navarro, X.

2017-08-01

Objective. As artificial prostheses become more refined, they are most often used as a therapeutic option for hand amputation. By contrast to extra- or intraneural interfaces, regenerative nerve electrodes are designed to enable electrical interfaces with regrowing axonal bundles of injured nerves, aiming to achieve high selectivity for recording and stimulation. However, most of the developed designs pose an obstacle to the regrowth mechanisms due to low transparency and cause impairment to the nerve regeneration. Approach. Here we present the double-aisle electrode, a new type of highly transparent, non-obstructive regenerative electrode. Using a double-side thin-film polyimide planar multi-contact electrode, two nerve fascicles can regenerate without physical impairment through two electrically isolated aisles. Main results. We show that this electrode can be used to selectively record and stimulate fascicles, acutely as well as chronically, and allow regeneration in nerve gaps of several millimeters without impairment. Significance. This multi-aisle regenerative electrode may be suitable for neuroprosthetic applications, such as prostheses, for the restoration of hand function after amputation or severe nerve injuries.

Systemic Prenatal Insults Disrupt Telencephalon Development

PubMed Central

Robinson, Shenandoah

2006-01-01

Infants born prematurely are prone to chronic neurologic deficits including cerebral palsy (CP), epilepsy, cognitive delay, behavioral problems, and neurosensory impairments. In affected children, imaging and neuropathological findings demonstrate significant damage to white matter. The extent of cortical damage has been less obvious. Advances in the understanding of telencephalon development provide insights into how systemic intrauterine insults affect the developing white matter, subplate and cortex, and lead to multiple neurologic impairments. In addition to white matter oligodendrocytes and axons, other elements at risk for perinatal brain injury include subplate neurons, GABAergic neurons migrating through white matter and subplate, and afferents of maturing neurotransmitter systems. Common insults including hypoxia-ischemia and infection often affect the developing brain differently than the mature brain, and insults precipitate a cascade of damage to multiple neural lineages. Insights from development can identify potential targets for therapies to repair the damaged neonatal brain before it has matured. PMID:16061421

Alcohol Binge Drinking during Adolescence or Dependence during Adulthood Reduces Prefrontal Myelin in Male Rats

PubMed Central

Vargas, Wanette M.; Bengston, Lynn; Gilpin, Nicholas W.; Whitcomb, Brian W.

2014-01-01

Teen binge drinking is associated with low frontal white matter integrity and increased risk of alcoholism in adulthood. This neuropathology may result from alcohol exposure or reflect a pre-existing condition in people prone to addiction. Here we used rodent models with documented clinical relevance to adolescent binge drinking and alcoholism in humans to test whether alcohol damages myelinated axons of the prefrontal cortex. In Experiment 1, outbred male Wistar rats self-administered sweetened alcohol or sweetened water intermittently for 2 weeks during early adolescence. In adulthood, drinking behavior was tested under nondependent conditions or after dependence induced by 1 month of alcohol vapor intoxication/withdrawal cycles, and prefrontal myelin was examined 1 month into abstinence. Adolescent binge drinking or adult dependence induction reduced the size of the anterior branches of the corpus callosum, i.e., forceps minor (CCFM), and this neuropathology correlated with higher relapse-like drinking in adulthood. Degraded myelin basic protein in the gray matter medial to the CCFM of binge rats indicated myelin was damaged on axons in the mPFC. In follow-up studies we found that binge drinking reduced myelin density in the mPFC in adolescent rats (Experiment 2) and heavier drinking predicted worse performance on the T-maze working memory task in adulthood (Experiment 3). These findings establish a causal role of voluntary alcohol on myelin and give insight into specific prefrontal axons that are both sensitive to alcohol and could contribute to the behavioral and cognitive impairments associated with early onset drinking and alcoholism. PMID:25355229

Cell therapy for spinal cord injury with olfactory ensheathing glia cells (OECs).

PubMed

Gómez, Rosa M; Sánchez, Magdy Y; Portela-Lomba, Maria; Ghotme, Kemel; Barreto, George E; Sierra, Javier; Moreno-Flores, M Teresa

2018-07-01

The prospects of achieving regeneration in the central nervous system (CNS) have changed, as most recent findings indicate that several species, including humans, can produce neurons in adulthood. Studies targeting this property may be considered as potential therapeutic strategies to respond to injury or the effects of demyelinating diseases in the CNS. While CNS trauma may interrupt the axonal tracts that connect neurons with their targets, some neurons remain alive, as seen in optic nerve and spinal cord (SC) injuries (SCIs). The devastating consequences of SCIs are due to the immediate and significant disruption of the ascending and descending spinal pathways, which result in varying degrees of motor and sensory impairment. Recent therapeutic studies for SCI have focused on cell transplantation in animal models, using cells capable of inducing axon regeneration like Schwann cells (SchCs), astrocytes, genetically modified fibroblasts and olfactory ensheathing glia cells (OECs). Nevertheless, and despite the improvements in such cell-based therapeutic strategies, there is still little information regarding the mechanisms underlying the success of transplantation and regarding any secondary effects. Therefore, further studies are needed to clarify these issues. In this review, we highlight the properties of OECs that make them suitable to achieve neuroplasticity/neuroregeneration in SCI. OECs can interact with the glial scar, stimulate angiogenesis, axon outgrowth and remyelination, improving functional outcomes following lesion. Furthermore, we present evidence of the utility of cell therapy with OECs to treat SCI, both from animal models and clinical studies performed on SCI patients, providing promising results for future treatments. © 2018 Wiley Periodicals, Inc.

Loss of Magel2 impairs the development of hypothalamic Anorexigenic circuits

PubMed Central

Maillard, Julien; Park, Soyoung; Croizier, Sophie; Vanacker, Charlotte; Cook, Joshua H.; Prevot, Vincent; Tauber, Maithe; Bouret, Sebastien G.

2016-01-01

Prader–Willi syndrome (PWS) is a genetic disorder characterized by a variety of physiological and behavioral dysregulations, including hyperphagia, a condition that can lead to life-threatening obesity. Feeding behavior is a highly complex process with multiple feedback loops that involve both peripheral and central systems. The arcuate nucleus of the hypothalamus (ARH) is critical for the regulation of homeostatic processes including feeding, and this nucleus develops during neonatal life under of the influence of both environmental and genetic factors. Although much attention has focused on the metabolic and behavioral outcomes of PWS, an understanding of its effects on the development of hypothalamic circuits remains elusive. Here, we show that mice lacking Magel2, one of the genes responsible for the etiology of PWS, display an abnormal development of ARH axonal projections. Notably, the density of anorexigenic α-melanocyte-stimulating hormone axons was reduced in adult Magel2-null mice, while the density of orexigenic agouti-related peptide fibers in the mutant mice appeared identical to that in control mice. On the basis of previous findings showing a pivotal role for metabolic hormones in hypothalamic development, we also measured leptin and ghrelin levels in Magel2-null and control neonates and found that mutant mice have normal leptin and ghrelin levels. In vitro experiments show that Magel2 directly promotes axon growth. Together, these findings suggest that a loss of Magel2 leads to the disruption of hypothalamic feeding circuits, an effect that appears to be independent of the neurodevelopmental effects of leptin and ghrelin and likely involves a direct neurotrophic effect of Magel2. PMID:27288456

Downregulation of Glutamine Synthetase via GLAST Suppression Induces Retinal Axonal Swelling in a Rat Ex Vivo Hydrostatic Pressure Model

PubMed Central

Yoshitomi, Takeshi; Zorumski, Charles F.; Izumi, Yukitoshi

2011-01-01

Purpose. High levels of glutamate can be toxic to retinal GCs. Thus, effective buffering of extracellular glutamate is important in preserving retinal structure and function. GLAST, a major glutamate transporter in the retina, and glutamine synthetase (GS) regulate extracellular glutamate accumulation and prevent excitotoxicity. This study was an examination of changes in function and expression of GLAST and GS in ex vivo rat retinas exposed to acute increases in ambient pressure. Methods. Ex vivo rat retinas were exposed to elevated hydrostatic pressure for 24 hours. The expression of GLAST and GS were examined using immunochemistry and real-time PCR analysis. Also examined were the effects of (2S,3S)-3-[3-[4-(trifluoromethyl) benzoylamino] benzyloxy] aspartate (TFB-TBOA), an inhibitor of glutamate transporters, and l-methionine-S-sulfoximine (MSO), an inhibitor of GS. Results. In this acute model, Western blot and real-time RT-PCR analyses revealed that substantially (75 mm Hg), but not moderately (35 mm Hg), elevated pressure depressed GLAST expression, diminished GS activity, and induced axonal swelling between the GC layer and the inner limiting membrane. However, at the moderately elevated pressure (35 mm Hg), administration of either TFB-TBOA or MSO also induced axonal swelling and excitotoxic neuronal damage. MSO did not depress GLAST expression but TFB-TBOA significantly suppressed GS, suggesting that downregulation of GS during pressure loading may result from impaired GLAST expression. Conclusions. The retina is at risk during acute intraocular pressure elevation due to downregulation of GS activity resulting from depressed GLAST expression. PMID:21775659

Downregulation of glutamine synthetase via GLAST suppression induces retinal axonal swelling in a rat ex vivo hydrostatic pressure model.

PubMed

Ishikawa, Makoto; Yoshitomi, Takeshi; Zorumski, Charles F; Izumi, Yukitoshi

2011-08-22

PURPOSE. High levels of glutamate can be toxic to retinal GCs. Thus, effective buffering of extracellular glutamate is important in preserving retinal structure and function. GLAST, a major glutamate transporter in the retina, and glutamine synthetase (GS) regulate extracellular glutamate accumulation and prevent excitotoxicity. This study was an examination of changes in function and expression of GLAST and GS in ex vivo rat retinas exposed to acute increases in ambient pressure. METHODS. Ex vivo rat retinas were exposed to elevated hydrostatic pressure for 24 hours. The expression of GLAST and GS were examined using immunochemistry and real-time PCR analysis. Also examined were the effects of (2S,3S)-3-[3-[4-(trifluoromethyl) benzoylamino] benzyloxy] aspartate (TFB-TBOA), an inhibitor of glutamate transporters, and l-methionine-S-sulfoximine (MSO), an inhibitor of GS. RESULTS. In this acute model, Western blot and real-time RT-PCR analyses revealed that substantially (75 mm Hg), but not moderately (35 mm Hg), elevated pressure depressed GLAST expression, diminished GS activity, and induced axonal swelling between the GC layer and the inner limiting membrane. However, at the moderately elevated pressure (35 mm Hg), administration of either TFB-TBOA or MSO also induced axonal swelling and excitotoxic neuronal damage. MSO did not depress GLAST expression but TFB-TBOA significantly suppressed GS, suggesting that downregulation of GS during pressure loading may result from impaired GLAST expression. CONCLUSIONS. The retina is at risk during acute intraocular pressure elevation due to downregulation of GS activity resulting from depressed GLAST expression.

Sympathetic axonopathies and hyperinnervation in the small intestine smooth muscle of aged Fischer 344 rats

PubMed Central

Phillips, Robert J.; Hudson, Cherie N.; Powley, Terry L.

2013-01-01

It is well documented that the intrinsic enteric nervous system of the gastrointestinal (GI) tract sustains neuronal losses and reorganizes as it ages. In contrast, age-related remodeling of the extrinsic sympathetic projections to the wall of the gut is poorly characterized. The present experiment, therefore, surveyed the sympathetic projections to the aged small intestine for axonopathies. Furthermore, the experiment evaluated the specific prediction that catecholaminergic inputs undergo hyperplastic changes. Jejunal tissue was collected from 3-, 8-, 16-, and 24-month-old male Fischer 344 rats, prepared as whole mounts consisting of the muscularis, and processed immunohistochemically for tyrosine hydroxylase, the enzymatic marker for norepinephrine, and either the protein CD163 or the protein MHCII, both phenotypical markers for macrophages. Four distinctive sympathetic axonopathy profiles occurred in the small intestine of the aged rat: (1) swollen and dystrophic terminals, (2) tangled axons, (3) discrete hyperinnervated loci in the smooth muscle wall, including at the bases of Peyer's patches, and (4) ectopic hyperplastic or hyperinnervating axons in the serosa/subserosal layers. In many cases, the axonopathies occurred at localized and limited foci, involving only a few axon terminals, in a pattern consistent with incidences of focal ischemic, vascular, or traumatic insult. The present observations underscore the complexity of the processes of aging on the neural circuitry of the gut, with age-related GI functional impairments likely reflecting a constellation of adjustments that range from selective neuronal losses, through accumulation of cellular debris, to hyperplasias and hyperinnervation of sympathetic inputs. PMID:24104187

Chlorpyrifos, chlorpyrifos-oxon, and diisopropylfluorophosphate inhibit kinesin-dependent microtubule motility

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gearhart, Debra A.; Sickles, Dale W.; Buccafusco, Jerry J.

2007-01-01

Diisopropylfluorophosphate, originally developed as a chemical warfare agent, is structurally similar to nerve agents, and chlorpyrifos has extensive worldwide use as an agricultural pesticide. While inhibition of cholinesterases underlies the acute toxicity of these organophosphates, we previously reported impaired axonal transport in the sciatic nerves from rats treated chronically with subthreshold doses of chlorpyrifos. Those data indicate that chlorpyrifos (and/or its active metabolite, chlorpyrifos-oxon) might directly affect the function of kinesin and/or microtubules-the principal proteins that mediate anterograde axonal transport. The current report describes in vitro assays to assess the concentration-dependent effects of chlorpyrifos (0-10 {mu}M), chlorpyrifos-oxon (0-10 {mu}M), andmore » diisopropylfluorophosphate (0-0.59 nM) on kinesin-dependent microtubule motility. Preincubating bovine brain microtubules with the organophosphates did not alter kinesin-mediated microtubule motility. In contrast, preincubation of bovine brain kinesin with diisopropylfluorophosphate, chlorpyrifos, or chlorpyrifos-oxon produced a concentration-dependent increase in the number of locomoting microtubules that detached from the kinesin-coated glass cover slip. Our data suggest that the organophosphates-chlorpyrifos-oxon, chlorpyrifos, and diisopropylfluorophosphate-directly affect kinesin, thereby disrupting kinesin-dependent transport on microtubules. Kinesin-dependent movement of vesicles, organelles, and other cellular components along microtubules is fundamental to the organization of all eukaryotic cells, especially in neurons where organelles and proteins synthesized in the cell body must move down long axons to pre-synaptic sites in nerve terminals. We postulate that disruption of kinesin-dependent intracellular transport could account for some of the long-term effects of organophosphates on the peripheral and central nervous system.« less

Low Piconewton Towing of CNS Axons against Diffusing and Surface-Bound Repellents Requires the Inhibition of Motor Protein-Associated Pathways

NASA Astrophysics Data System (ADS)

Kilinc, Devrim; Blasiak, Agata; O'Mahony, James J.; Lee, Gil U.

2014-11-01

Growth cones, dynamic structures at axon tips, integrate chemical and physical stimuli and translate them into coordinated axon behaviour, e.g., elongation or turning. External force application to growth cones directs and enhances axon elongation in vitro; however, direct mechanical stimulation is rarely combined with chemotactic stimulation. We describe a microfluidic device that exposes isolated cortical axons to gradients of diffusing and substrate-bound molecules, and permits the simultaneous application of piconewton (pN) forces to multiple individual growth cones via magnetic tweezers. Axons treated with Y-27632, a RhoA kinase inhibitor, were successfully towed against Semaphorin 3A gradients, which repel untreated axons, with less than 12 pN acting on a small number of neural cell adhesion molecules. Treatment with Y-27632 or monastrol, a kinesin-5 inhibitor, promoted axon towing on substrates coated with chondroitin sulfate proteoglycans, potent axon repellents. Thus, modulating key molecular pathways that regulate contractile stress generation in axons counteracts the effects of repellent molecules and promotes tension-induced growth. The demonstration of parallel towing of axons towards inhibitory environments with minute forces suggests that mechanochemical stimulation may be a promising therapeutic approach for the repair of the damaged central nervous system, where regenerating axons face repellent factors over-expressed in the glial scar.

Targeting the neurophysiology of cognitive systems with transcranial alternating current stimulation (tACS)

PubMed Central

Fröhlich, Flavio; Sellers, Kristin K.; Cordle, Asa L.

2015-01-01

Cognitive impairment represents one of the most debilitating and most difficult symptom to treat of many psychiatric illnesses. Human neurophysiology studies have suggested specific pathologies of cortical network activity correlate with cognitive impairment. However, we lack (1) demonstration of causal relationships between specific network activity patterns and cognitive capabilities and (2) treatment modalities that directly target impaired network dynamics of cognition. Transcranial alternating current stimulation (tACS), a novel non-invasive brain stimulation approach, may provide a crucial tool to tackle these challenges. We here propose that tACS can be used to elucidate the causal role of cortical synchronization in cognition and, eventually, to enhance pathologically weakened synchrony that may underlie cognitive deficits. To accelerate such development of tACS as a treatment for cognitive deficits, we discuss studies on tACS and cognition (all performed in healthy participants) according to the Research Domain Criteria (RDoC) of the National Institute of Mental Health. PMID:25547149

Cognitive correlates of pragmatic language comprehension in adult traumatic brain injury: A systematic review and meta-analyses.

PubMed

Rowley, Dane A; Rogish, Miles; Alexander, Timothy; Riggs, Kevin J

2017-01-01

Effective pragmatic comprehension of language is critical for successful communication and interaction, but this ability is routinely impaired following Traumatic Brain Injury (TBI) (1,2). Individual studies have investigated the cognitive domains associated with impaired pragmatic comprehension, but there remains little understanding of the relative importance of these domains in contributing to pragmatic comprehension impairment following TBI. This paper presents a systematic meta-analytic review of the observed correlations between pragmatic comprehension and cognitive processes following TBI. Five meta-analyses were computed, which quantified the relationship between pragmatic comprehension and five key cognitive constructs (declarative memory; working memory; attention; executive functions; social cognition). Significant moderate-to-strong correlations were found between all cognitive measures and pragmatic comprehension, where declarative memory was the strongest correlate. Thus, our findings indicate that pragmatic comprehension in TBI is associated with an array of domain general cognitive processes, and as such deficits in these cognitive domains may underlie pragmatic comprehension difficulties following TBI. The clinical implications of these findings are discussed.

Time course of ongoing activity during neuritis and following axonal transport disruption.

PubMed

Satkeviciute, Ieva; Goodwin, George; Bove, Geoffrey M; Dilley, Andrew

2018-05-01

Local nerve inflammation (neuritis) leads to ongoing activity and axonal mechanical sensitivity (AMS) along intact nociceptor axons and disrupts axonal transport. This phenomenon forms the most feasible cause of radiating pain, such as sciatica. We have previously shown that axonal transport disruption without inflammation or degeneration also leads to AMS but does not cause ongoing activity at the time point when AMS occurs, despite causing cutaneous hypersensitivity. However, there have been no systematic studies of ongoing activity during neuritis or noninflammatory axonal transport disruption. In this study, we present the time course of ongoing activity from primary sensory neurons following neuritis and vinblastine-induced axonal transport disruption. Whereas 24% of C/slow Aδ-fiber neurons had ongoing activity during neuritis, few (<10%) A- and C-fiber neurons showed ongoing activity 1-15 days following vinblastine treatment. In contrast, AMS increased transiently at the vinblastine treatment site, peaking on days 4-5 (28% of C/slow Aδ-fiber neurons) and resolved by day 15. Conduction velocities were slowed in all groups. In summary, the disruption of axonal transport without inflammation does not lead to ongoing activity in sensory neurons, including nociceptors, but does cause a rapid and transient development of AMS. Because it is proposed that AMS underlies mechanically induced radiating pain, and a transient disruption of axonal transport (as previously reported) leads to transient AMS, it follows that processes that disrupt axonal transport, such as neuritis, must persist to maintain AMS and the associated symptoms. NEW & NOTEWORTHY Many patients with radiating pain lack signs of nerve injury on clinical examination but may have neuritis, which disrupts axonal transport. We have shown that axonal transport disruption does not induce ongoing activity in primary sensory neurons but does cause transient axonal mechanical sensitivity. The present data complete a profile of key axonal sensitivities following axonal transport disruption. Collectively, this profile supports that an active peripheral process is necessary for maintained axonal sensitivities.

Neurocircuitry of Mood Disorders

PubMed Central

Price, Joseph L; Drevets, Wayne C

2010-01-01

This review begins with a brief historical overview of attempts in the first half of the 20th century to discern brain systems that underlie emotion and emotional behavior. These early studies identified the amygdala, hippocampus, and other parts of what was termed the ‘limbic' system as central parts of the emotional brain. Detailed connectional data on this system began to be obtained in the 1970s and 1980s, as more effective neuroanatomical techniques based on axonal transport became available. In the last 15 years these methods have been applied extensively to the limbic system and prefrontal cortex of monkeys, and much more specific circuits have been defined. In particular, a system has been described that links the medial prefrontal cortex and a few related cortical areas to the amygdala, the ventral striatum and pallidum, the medial thalamus, the hypothalamus, and the periaqueductal gray and other parts of the brainstem. A large body of human data from functional and structural imaging, as well as analysis of lesions and histological material indicates that this system is centrally involved in mood disorders. PMID:19693001

Localization of mRNA in vertebrate axonal compartments by in situ hybridization.

PubMed

Sotelo-Silveira, José Roberto; Calliari, Aldo; Kun, Alejandra; Elizondo, Victoria; Canclini, Lucía; Sotelo, José Roberto

2011-01-01

The conclusive demonstration of RNA in vertebrate axons by in situ hybridization (ISH) has been elusive. We review the most important reasons for difficulties, including low concentration of axonal RNAs, localization in specific cortical domains, and the need to isolate axons. We demonstrate the importance of axon micro-dissection to obtain a whole mount perspective of mRNA distribution in the axonal territory. We describe a protocol to perform fluorescent ISH in isolated axons and guidelines for the preservation of structural and molecular integrity of cortical RNA-containing domains (e.g., Periaxoplasmic Ribosomal Plaques, or PARPs) in isolated axoplasm.

Selective rab11 transport and the intrinsic regenerative ability of CNS axons

PubMed Central

Koseki, Hiroaki; Donegá, Matteo; Lam, Brian YH; Petrova, Veselina; van Erp, Susan; Yeo, Giles SH; Kwok, Jessica CF; ffrench-Constant, Charles

2017-01-01

Neurons lose intrinsic axon regenerative ability with maturation, but the mechanism remains unclear. Using an in-vitro laser axotomy model, we show a progressive decline in the ability of cut CNS axons to form a new growth cone and then elongate. Failure of regeneration was associated with increased retraction after axotomy. Transportation into axons becomes selective with maturation; we hypothesized that selective exclusion of molecules needed for growth may contribute to regeneration decline. With neuronal maturity rab11 vesicles (which carry many molecules involved in axon growth) became selectively targeted to the somatodendritic compartment and excluded from axons by predominant retrograde transport However, on overexpression rab11 was mistrafficked into proximal axons, and these axons showed less retraction and enhanced regeneration after axotomy. These results suggest that the decline of intrinsic axon regenerative ability is associated with selective exclusion of key molecules, and that manipulation of transport can enhance regeneration. PMID:28829741

Inhibiting poly(ADP-ribosylation) improves axon regeneration.

PubMed

Byrne, Alexandra B; McWhirter, Rebecca D; Sekine, Yuichi; Strittmatter, Stephen M; Miller, David M; Hammarlund, Marc

2016-10-04

The ability of a neuron to regenerate its axon after injury depends in part on its intrinsic regenerative potential. Here, we identify novel intrinsic regulators of axon regeneration: poly(ADP-ribose) glycohodrolases (PARGs) and poly(ADP-ribose) polymerases (PARPs). PARGs, which remove poly(ADP-ribose) from proteins, act in injured C. elegans GABA motor neurons to enhance axon regeneration. PARG expression is regulated by DLK signaling, and PARGs mediate DLK function in enhancing axon regeneration. Conversely, PARPs, which add poly(ADP-ribose) to proteins, inhibit axon regeneration of both C. elegans GABA neurons and mammalian cortical neurons. Furthermore, chemical PARP inhibitors improve axon regeneration when administered after injury. Our results indicate that regulation of poly(ADP-ribose) levels is a critical function of the DLK regeneration pathway, that poly-(ADP ribosylation) inhibits axon regeneration across species, and that chemical inhibition of PARPs can elicit axon regeneration.

Inhibiting poly(ADP-ribosylation) improves axon regeneration

PubMed Central

Byrne, Alexandra B; McWhirter, Rebecca D; Sekine, Yuichi; Strittmatter, Stephen M; Miller, David M; Hammarlund, Marc

2016-01-01

The ability of a neuron to regenerate its axon after injury depends in part on its intrinsic regenerative potential. Here, we identify novel intrinsic regulators of axon regeneration: poly(ADP-ribose) glycohodrolases (PARGs) and poly(ADP-ribose) polymerases (PARPs). PARGs, which remove poly(ADP-ribose) from proteins, act in injured C. elegans GABA motor neurons to enhance axon regeneration. PARG expression is regulated by DLK signaling, and PARGs mediate DLK function in enhancing axon regeneration. Conversely, PARPs, which add poly(ADP-ribose) to proteins, inhibit axon regeneration of both C. elegans GABA neurons and mammalian cortical neurons. Furthermore, chemical PARP inhibitors improve axon regeneration when administered after injury. Our results indicate that regulation of poly(ADP-ribose) levels is a critical function of the DLK regeneration pathway, that poly-(ADP ribosylation) inhibits axon regeneration across species, and that chemical inhibition of PARPs can elicit axon regeneration. DOI: http://dx.doi.org/10.7554/eLife.12734.001 PMID:27697151

In Vitro Analysis of the Role of Schwann Cells on Axonal Degeneration and Regeneration Using Sensory Neurons from Dorsal Root Ganglia.

PubMed

López-Leal, Rodrigo; Diaz, Paula; Court, Felipe A

2018-01-01

Sensory neurons from dorsal root ganglion efficiently regenerate after peripheral nerve injuries. These neurons are widely used as a model system to study degenerative mechanisms of the soma and axons, as well as regenerative axonal growth in the peripheral nervous system. This chapter describes techniques associated to the study of axonal degeneration and regeneration using explant cultures of dorsal root ganglion sensory neurons in vitro in the presence or absence of Schwann cells. Schwann cells are extremely important due to their involvement in tissue clearance during axonal degeneration as well as their known pro-regenerative effect during regeneration in the peripheral nervous system. We describe methods to induce and study axonal degeneration triggered by axotomy (mechanical separation of the axon from its soma) and treatment with vinblastine (which blocks axonal transport), which constitute clinically relevant mechanical and toxic models of axonal degeneration. In addition, we describe three different methods to evaluate axonal regeneration using quantitative methods. These protocols constitute a valuable tool to analyze in vitro mechanisms associated to axonal degeneration and regeneration of sensory neurons and the role of Schwann cells in these processes.

Axonal abnormalities in vanishing white matter.

PubMed

Klok, Melanie D; Bugiani, Marianna; de Vries, Sharon I; Gerritsen, Wouter; Breur, Marjolein; van der Sluis, Sophie; Heine, Vivi M; Kole, Maarten H P; Baron, Wia; van der Knaap, Marjo S

2018-04-01

We aimed to study the occurrence and development of axonal pathology and the influence of astrocytes in vanishing white matter. Axons and myelin were analyzed using electron microscopy and immunohistochemistry on Eif2b4 and Eif2b5 single- and double-mutant mice and patient brain tissue. In addition, astrocyte-forebrain co-culture studies were performed. In the corpus callosum of Eif2b5- mutant mice, myelin sheath thickness, axonal diameter, and G-ratio developed normally up to 4 months. At 7 months, however, axons had become thinner, while in control mice axonal diameters had increased further. Myelin sheath thickness remained close to normal, resulting in an abnormally low G-ratio in Eif2b5- mutant mice. In more severely affected Eif2b4-Eif2b5 double-mutants, similar abnormalities were already present at 4 months, while in milder affected Eif2b4 mutants, few abnormalities were observed at 7 months. Additionally, from 2 months onward an increased percentage of thin, unmyelinated axons and increased axonal density were present in Eif2b5 -mutant mice. Co-cultures showed that Eif2b5 mutant astrocytes induced increased axonal density, also in control forebrain tissue, and that control astrocytes induced normal axonal density, also in mutant forebrain tissue. In vanishing white matter patient brains, axons and myelin sheaths were thinner than normal in moderately and severely affected white matter. In mutant mice and patients, signs of axonal transport defects and cytoskeletal abnormalities were minimal. In vanishing white matter, axons are initially normal and atrophy later. Astrocytes are central in this process. If therapy becomes available, axonal pathology may be prevented with early intervention.

Piezoelectric ceramic (PZT) modulates axonal guidance growth of rat cortical neurons via RhoA, Rac1, and Cdc42 pathways.

PubMed

Wen, Jianqiang; Liu, Meili

2014-03-01

Electrical stimulation is critical for axonal connection, which can stimulate axonal migration and deformation to promote axonal growth in the nervous system. Netrin-1, an axonal guidance cue, can also promote axonal guidance growth, but the molecular mechanism of axonal guidance growth under indirect electric stimulation is still unknown. We investigated the molecular mechanism of axonal guidance growth under piezoelectric ceramic lead zirconate titanate (PZT) stimulation in the primary cultured cortical neurons. PZT induced marked axonal elongation. Moreover, PZT activated the excitatory postsynaptic currents (EPSCs) by increasing the frequency and amplitude of EPSCs of the cortical neurons in patch clamp assay. PZT downregulated the expression of Netrin-1 and its receptor Deleted in Colorectal Cancer (DCC). Rho GTPase signaling is involved in interactions of Netrin-1 and DCC. PZT activated RhoA. Dramatic decrease of Cdc42 and Rac1 was also observed after PZT treatment. RhoA inhibitor Clostridium botulinum C3 exoenzyme (C3-Exo) prevented the PZT-induced downregulation of Netrin-1 and DCC. We suggest that PZT can promote axonal guidance growth by downregulation of Netrin-1 and DCC to mediate axonal repulsive responses via the Rho GTPase signaling pathway. Obviously, piezoelectric materials may provide a new approach for axonal recovery and be beneficial for clinical therapy in the future.

Changes in microtubule stability and density in myelin-deficient shiverer mouse CNS axons

NASA Technical Reports Server (NTRS)

Kirkpatrick, L. L.; Witt, A. S.; Payne, H. R.; Shine, H. D.; Brady, S. T.

2001-01-01

Altered axon-Schwann cell interactions in PNS myelin-deficient Trembler mice result in changed axonal transport rates, neurofilament and microtubule-associated protein phosphorylation, neurofilament density, and microtubule stability. To determine whether PNS and CNS myelination have equivalent effects on axons, neurofilaments, and microtubules in CNS, myelin-deficient shiverer axons were examined. The genetic defect in shiverer is a deletion in the myelin basic protein (MBP) gene, an essential component of CNS myelin. As a result, shiverer mice have little or no compact CNS myelin. Slow axonal transport rates in shiverer CNS axons were significantly increased, in contrast to the slowing in demyelinated PNS nerves. Even more striking were substantial changes in the composition and properties of microtubules in shiverer CNS axons. The density of axonal microtubules is increased, reflecting increased expression of tubulin in shiverer, and the stability of microtubules is drastically reduced in shiverer axons. Shiverer transgenic mice with two copies of a wild-type myelin basic protein transgene have an intermediate level of compact myelin, making it possible to determine whether the actual level of compact myelin is an important regulator of axonal microtubules. Both increased microtubule density and reduced microtubule stability were still observed in transgenic mouse nerves, indicating that signals beyond synaptogenesis and the mere presence of compact myelin are required for normal regulation of the axonal microtubule cytoskeleton.

A morphological study of diffuse axonal injury in a rat model by lateral head rotation trauma.

PubMed

Xiaoshengi, He; Guitao, Yang; Xiang, Zhang; Zhou, Fei

2010-03-01

Morphology in diffuse axonal injury (DAI) by lateral head rotation was investigated. SD rats were divided into injury (n=9) and sham (n=3) groups. A device was used to produce lateral rotational acceleration of the rats' heads. At different survival times three rats were killed for light and electron microscopic examination of the brain tissue. Sagittal sections were made from medulla oblongata and immunolabelled for NF68. At post-traumatic 30 min, NF68 immunolabelling showed a small number ofswollen and irregular axons. Ultrastructurally slightly-separated myelin lamellae and disorderly arranged neurofilaments occurred. At 2 and 24 h axonal damage became more severe. Increases in immunolabelled axonal swellings, disconnected axons and axonal retraction bulbs appeared. EM provided evidence of myelin separation, peri-axonal spaces, blank areas in axoplasm, loss of microtubules, peripheral accumulation of mitochondria and clumped neurofilaments for DAI. A tendency was noted for greater labelling with NF68 as axonal damage increased. The disorderly arrangement of NFs occurred at early stage of post-traumatic axonal changes.

S6 Kinase Inhibits Intrinsic Axon Regeneration Capacity via AMP Kinase in Caenorhabditis elegans

PubMed Central

Hubert, Thomas; Wu, Zilu; Chisholm, Andrew D.

2014-01-01

The ability of axons to regrow after injury is determined by the complex interplay of intrinsic growth programs and external cues. In Caenorhabditis elegans mechanosensory neuron, axons exhibit robust regenerative regrowth following laser axotomy. By surveying conserved metabolic signaling pathways, we have identified the ribosomal S6 kinase RSKS-1 as a new cell-autonomous inhibitor of axon regeneration. RSKS-1 is not required for axonal development but inhibits axon regrowth after injury in multiple neuron types. Loss of function in rsks-1 results in more rapid growth cone formation after injury and accelerates subsequent axon extension. The enhanced regrowth of rsks-1 mutants is partly dependent on the DLK-1 MAPK cascade. An essential output of RSKS-1 in axon regrowth is the metabolic sensor AMP kinase, AAK-2. We further show that the antidiabetic drug phenformin, which activates AMP kinase, can promote axon regrowth. Our data reveal a new function for an S6 kinase acting through an AMP kinase in regenerative growth of injured axons. PMID:24431434

GSK3 controls axon growth via CLASP-mediated regulation of growth cone microtubules

PubMed Central

Hur, Eun-Mi; Saijilafu; Lee, Byoung Dae; Kim, Seong-Jin; Xu, Wen-Lin; Zhou, Feng-Quan

2011-01-01

Suppression of glycogen synthase kinase 3 (GSK3) activity in neurons yields pleiotropic outcomes, causing both axon growth promotion and inhibition. Previous studies have suggested that specific GSK3 substrates, such as adenomatous polyposis coli (APC) and collapsin response mediator protein 2 (CRMP2), support axon growth by regulating the stability of axonal microtubules (MTs), but the substrate(s) and mechanisms conveying axon growth inhibition remain elusive. Here we show that CLIP (cytoplasmic linker protein)-associated protein (CLASP), originally identified as a MT plus end-binding protein, displays both plus end-binding and lattice-binding activities in nerve growth cones, and reveal that the two MT-binding activities regulate axon growth in an opposing manner: The lattice-binding activity mediates axon growth inhibition induced by suppression of GSK3 activity via preventing MT protrusion into the growth cone periphery, whereas the plus end-binding property supports axon extension via stabilizing the growing ends of axonal MTs. We propose a model in which CLASP transduces GSK3 activity levels to differentially control axon growth by coordinating the stability and configuration of growth cone MTs. PMID:21937714

The "waiting period" of sensory and motor axons in early chick hindlimb: its role in axon pathfinding and neuronal maturation.

PubMed

Wang, G; Scott, S A

2000-07-15

During embryonic development motor axons in the chick hindlimb grow out slightly before sensory axons and wait in the plexus region at the base of the limb for approximately 24 hr before invading the limb itself (Tosney and Landmesser, 1985a). We have investigated the role of this waiting period by asking, Is the arrest of growth cones in the plexus region a general property of both sensory and motor axons? Why do axons wait? Does eliminating the waiting period affect the further development of motor and sensory neurons? Here we show that sensory axons, like motor axons, pause in the plexus region and that neither sensory nor motor axons require cues from the other population to wait in or exit from the plexus region. By transplanting older or younger donor limbs to host embryos, we show that host axons innervate donor limbs on a schedule consistent with the age of the grafted limbs. Thus, axons wait in the plexus region for maturational changes to occur in the limb rather than in the neurons themselves. Both sensory and motor axons innervate their appropriate peripheral targets when the waiting period is eliminated by grafting older donor limbs. Therefore, axons do not require a prolonged period in the plexus region to sort out and project appropriately. Eliminating the waiting period does, however, accelerate the onset of naturally occurring cell death, but it does not enhance the development of central projections or the biochemical maturation of sensory neurons.

Acutely damaged axons are remyelinated in multiple sclerosis and experimental models of demyelination.

PubMed

Schultz, Verena; van der Meer, Franziska; Wrzos, Claudia; Scheidt, Uta; Bahn, Erik; Stadelmann, Christine; Brück, Wolfgang; Junker, Andreas

2017-08-01

Remyelination is in the center of new therapies for the treatment of multiple sclerosis to resolve and improve disease symptoms and protect axons from further damage. Although remyelination is considered beneficial in the long term, it is not known, whether this is also the case early in lesion formation. Additionally, the precise timing of acute axonal damage and remyelination has not been assessed so far. To shed light onto the interrelation between axons and the myelin sheath during de- and remyelination, we employed cuprizone- and focal lysolecithin-induced demyelination and performed time course experiments assessing the evolution of early and late stage remyelination and axonal damage. We observed damaged axons with signs of remyelination after cuprizone diet cessation and lysolecithin injection. Similar observations were made in early multiple sclerosis lesions. To assess the correlation of remyelination and axonal damage in multiple sclerosis lesions, we took advantage of a cohort of patients with early and late stage remyelinated lesions and assessed the number of APP- and SMI32- positive damaged axons and the density of SMI31-positive and silver impregnated preserved axons. Early de- and remyelinating lesions did not differ with respect to axonal density and axonal damage, but we observed a lower axonal density in late stage demyelinated multiple sclerosis lesions than in remyelinated multiple sclerosis lesions. Our findings suggest that remyelination may not only be protective over a long period of time, but may play an important role in the immediate axonal recuperation after a demyelinating insult. © 2017 The Authors GLIA Published by Wiley Periodicals, Inc.

Cerebellar afferents originating from the medullary reticular formation that are different from mossy, climbing or monoaminergic fibers in the rat.

PubMed

Luo, Yuanjun; Sugihara, Izumi

2014-05-30

Integration of cortical Purkinje cell inputs and brain stem inputs is essential in generating cerebellar outputs to the cerebellar nuclei (CN). Currently, collaterals of climbing and mossy fiber axons, noradrenergic, serotoninergic and cholinergic axons, and collaterals of rubrospinal axons are known to innervate the CN from the brain stem. We investigated whether other afferents to the CN from the medulla exist in the rat. Retrograde labeling revealed the presence of neurons that project to the CN but not to the cerebellar cortex in the median reticular formation in the rostrodorsal medulla (tentatively named 'caudal raphe interpositus area', CRI). Anterograde tracer injection into the CRI labeled abundant axonal terminals in the CN, mainly in the ventral parvocellular part of the posterior interposed and lateral nucleus. Axonal reconstruction showed that a single CRI axon projected to the CN with 170-1086 varicosities, more broadly and densely than collaterals of a mossy or climbing fiber axon. CRI axons had no or a few collaterals that projected to the granular and Purkinje cell layers of the cerebellar cortex with some small terminals, indicating that these axons are different from mossy fiber axons. CRI axons also had collaterals that projected to the medial vestibular nucleus and an ascending branch that was not reconstructed. The location of the CRI, electron microscopic observations, and immunostaining results all indicated that CRI axons are not monoaminergic. We conclude that CRI axons form a type of afferent projection to the CN that is different from mossy, climbing or monoaminergic fibers. Copyright © 2014 Elsevier B.V. All rights reserved.

Premyelinated central axons express neurotoxic NMDA receptors: relevance to early developing white-matter injury

PubMed Central

Huria, Tahani; Beeraka, Narasimha Murthy; Al-Ghamdi, Badrah; Fern, Robert

2015-01-01

Ischemic-type injury to developing white matter is associated with the significant clinical condition cerebral palsy and with the cognitive deficits associated with premature birth. Premyelinated axons are the major cellular component of fetal white matter and loss of axon function underlies the disability, but the cellular mechanisms producing ischemic injury to premyelinated axons have not previously been described. Injury was found to require longer periods of modelled ischemia than at latter developmental points. Ischemia produced initial hyperexcitability in axons followed by loss of function after Na+ and Ca2+ influx. N-methyl-D-aspartate- (NMDA) type glutamate receptor (GluR) agonists potentiated axon injury while antagonists were protective. The NMDA GluR obligatory Nr1 subunit colocalized with markers of small premyelinated axons and expression was found at focal regions of axon injury. Ischemic injury of glial cells present in early developing white matter was NMDA GluR independent. Axons in human postconception week 18 to 23 white matter had a uniform prediameter expansion phenotype and postembedded immuno-gold labelling showed Nr1 subunit expression on the membrane of these axons, demonstrating a shared key neuropathologic feature with the rodent model. Premyelinated central axons therefore express high levels of functional NMDA GluRs that confer sensitivity to ischemic injury. PMID:25515212

Demonstration of ion channel synthesis by isolated squid giant axon provides functional evidence for localized axonal membrane protein translation.

PubMed

Mathur, Chhavi; Johnson, Kory R; Tong, Brian A; Miranda, Pablo; Srikumar, Deepa; Basilio, Daniel; Latorre, Ramon; Bezanilla, Francisco; Holmgren, Miguel

2018-02-02

Local translation of membrane proteins in neuronal subcellular domains like soma, dendrites and axon termini is well-documented. In this study, we isolated the electrical signaling unit of an axon by dissecting giant axons from mature squids (Dosidicus gigas). Axoplasm extracted from these axons was found to contain ribosomal RNAs, ~8000 messenger RNA species, many encoding the translation machinery, membrane proteins, translocon and signal recognition particle (SRP) subunits, endomembrane-associated proteins, and unprecedented proportions of SRP RNA (~68% identical to human homolog). While these components support endoplasmic reticulum-dependent protein synthesis, functional assessment of a newly synthesized membrane protein in axolemma of an isolated axon is technically challenging. Ion channels are ideal proteins for this purpose because their functional dynamics can be directly evaluated by applying voltage clamp across the axon membrane. We delivered in vitro transcribed RNA encoding native or Drosophila voltage-activated Shaker K V channel into excised squid giant axons. We found that total K + currents increased in both cases; with added inactivation kinetics on those axons injected with RNA encoding the Shaker channel. These results provide unambiguous evidence that isolated axons can exhibit de novo synthesis, assembly and membrane incorporation of fully functional oligomeric membrane proteins.

Axonal interferon responses and alphaherpesvirus neuroinvasion

NASA Astrophysics Data System (ADS)

Song, Ren

Infection by alphaherpesviruses, including herpes simplex virus (HSV) and pseudorabies virus (PRV), typically begins at a peripheral epithelial surface and continues into the peripheral nervous system (PNS) that innervates this tissue. Inflammatory responses are induced at the infected peripheral site prior to viral invasion of the PNS. PNS neurons are highly polarized cells with long axonal processes that connect to distant targets. When the peripheral tissue is first infected, only the innervating axons are exposed to this inflammatory milieu, which include type I interferon (e.g. IFNbeta) and type II interferon (i.e. IFNgamma). IFNbeta can be produced by all types of cells, while IFNgamma is secreted by some specific types of immune cells. And both types of IFN induce antiviral responses in surrounding cells that express the IFN receptors. The fundamental question is how do PNS neurons respond to the inflammatory milieu experienced only by their axons. Axons must act as potential front-line barriers to prevent PNS infection and damage. Using compartmented cultures that physically separate neuron axons from cell bodies, I found that pretreating isolated axons with IFNbeta or IFNgamma significantly diminished the number of HSV-1 and PRV particles moving from axons to the cell bodies in an IFN receptor-dependent manner. Furthermore, I found the responses in axons are activated differentially by the two types of IFNs. The response to IFNbeta is a rapid, axon-only response, while the response to IFNgamma involves long distance signaling to the PNS cell body. For example, exposing axons to IFNbeta induced STAT1 phosphorylation (p-STAT1) only in axons, while exposure of axons to IFNgamma induced p-STAT1 accumulation in distant cell body nuclei. Blocking transcription in cell bodies eliminated IFNgamma-, but not IFNbeta-mediated antiviral effects. Proteomic analysis of IFNbeta- or IFNgamma-treated axons identified several differentially regulated proteins. Therefore, unlike treatment with IFNgamma, IFNbeta induces a non-canonical, local antiviral response in axons. The activation of a local IFNbeta response in axons represents a new paradigm for early cytokine control of neuroinvasion. And the two response modes induced by the two distinct types of IFN erect an efficient and appropriate barrier against PNS infection.

A HuD-ZBP1 ribonucleoprotein complex localizes GAP-43 mRNA into axons through its 3' untranslated region AU-rich regulatory element.

PubMed

Yoo, Soonmoon; Kim, Hak H; Kim, Paul; Donnelly, Christopher J; Kalinski, Ashley L; Vuppalanchi, Deepika; Park, Michael; Lee, Seung J; Merianda, Tanuja T; Perrone-Bizzozero, Nora I; Twiss, Jeffery L

2013-09-01

Localized translation of axonal mRNAs contributes to developmental and regenerative axon growth. Although untranslated regions (UTRs) of many different axonal mRNAs appear to drive their localization, there has been no consensus RNA structure responsible for this localization. We recently showed that limited expression of ZBP1 protein restricts axonal localization of both β-actin and GAP-43 mRNAs. β-actin 3'UTR has a defined element for interaction with ZBP1, but GAP-43 mRNA shows no homology to this RNA sequence. Here, we show that an AU-rich regulatory element (ARE) in GAP-43's 3'UTR is necessary and sufficient for its axonal localization. Axonal GAP-43 mRNA levels increase after in vivo injury, and GAP-43 mRNA shows an increased half-life in regenerating axons. GAP-43 mRNA interacts with both HuD and ZBP1, and HuD and ZBP1 co-immunoprecipitate in an RNA-dependent fashion. Reporter mRNA with the GAP-43 ARE competes with endogenous β-actin mRNA for axonal localization and decreases axon length and branching similar to the β-actin 3'UTR competing with endogenous GAP-43 mRNA. Conversely, over-expressing GAP-43 coding sequence with its 3'UTR ARE increases axonal elongation and this effect is lost when just the ARE is deleted from GAP-43's 3'UTR. We have recently found that over-expression of GAP-43 using an axonally targeted construct with the 3'UTRs of GAP-43 promoted elongating growth of axons, while restricting the mRNA to the cell body with the 3'UTR of γ-actin had minimal effect on axon length. In this study, we show that the ARE in GAP-43's 3'UTR is responsible for localization of GAP-43 mRNA into axons and is sufficient for GAP-43 protein's role in elongating axonal growth. © 2013 International Society for Neurochemistry.

Relationship of acute axonal damage, Wallerian degeneration, and clinical disability in multiple sclerosis.

PubMed

Singh, Shailender; Dallenga, Tobias; Winkler, Anne; Roemer, Shanu; Maruschak, Brigitte; Siebert, Heike; Brück, Wolfgang; Stadelmann, Christine

2017-03-17

Axonal damage and loss substantially contribute to the incremental accumulation of clinical disability in progressive multiple sclerosis. Here, we assessed the amount of Wallerian degeneration in brain tissue of multiple sclerosis patients in relation to demyelinating lesion activity and asked whether a transient blockade of Wallerian degeneration decreases axonal loss and clinical disability in a mouse model of inflammatory demyelination. Wallerian degeneration and acute axonal damage were determined immunohistochemically in the periplaque white matter of multiple sclerosis patients with early actively demyelinating lesions, chronic active lesions, and inactive lesions. Furthermore, we studied the effects of Wallerian degeneration blockage on clinical severity, inflammatory pathology, acute axonal damage, and long-term axonal loss in experimental autoimmune encephalomyelitis using Wallerian degeneration slow (Wld S ) mutant mice. The highest numbers of axons undergoing Wallerian degeneration were found in the perilesional white matter of multiple sclerosis patients early in the disease course and with actively demyelinating lesions. Furthermore, Wallerian degeneration was more abundant in patients harboring chronic active as compared to chronic inactive lesions. No co-localization of neuropeptide Y-Y1 receptor, a bona fide immunohistochemical marker of Wallerian degeneration, with amyloid precursor protein, frequently used as an indicator of acute axonal transport disturbance, was observed in human and mouse tissue, indicating distinct axon-degenerative processes. Experimentally, a delay of Wallerian degeneration, as observed in Wld S mice, did not result in a reduction of clinical disability or acute axonal damage in experimental autoimmune encephalomyelitis, further supporting that acute axonal damage as reflected by axonal transport disturbances does not share common molecular mechanisms with Wallerian degeneration. Furthermore, delaying Wallerian degeneration did not result in a net rescue of axons in late lesion stages of experimental autoimmune encephalomyelitis. Our data indicate that in multiple sclerosis, ongoing demyelination in focal lesions is associated with axonal degeneration in the perilesional white matter, supporting a role for focal pathology in diffuse white matter damage. Also, our results suggest that interfering with Wallerian degeneration in inflammatory demyelination does not suffice to prevent acute axonal damage and finally axonal loss.

Association of Cerebrospinal Fluid Neurofilament Light Concentration With Alzheimer Disease Progression.

PubMed

Zetterberg, Henrik; Skillbäck, Tobias; Mattsson, Niklas; Trojanowski, John Q; Portelius, Erik; Shaw, Leslie M; Weiner, Michael W; Blennow, Kaj

2016-01-01

The extent to which large-caliber axonal degeneration contributes to Alzheimer disease (AD) progression is unknown. Cerebrospinal fluid (CSF) neurofilament light (NFL) concentration is a general marker of damage to large-caliber myelinated axons. To test whether CSF NFL concentration is associated with cognitive decline and imaging evidence of neurodegeneration and white matter change in AD. A commercially available immunoassay was used to analyze CSF NFL concentration in a cohort of patients with AD (n = 95) or mild cognitive impairment (MCI) (n = 192) and in cognitively normal individuals (n = 110) from the Alzheimer's Disease Neuroimaging Initiative. The study dates were January 2005 to December 2007. The NFL analysis was performed in November 2014. Correlation was investigated among baseline CSF NFL concentration and longitudinal cognitive impairment, white matter change, and regional brain atrophy within each diagnostic group. Cerebrospinal fluid NFL concentration (median [interquartile range]) was higher in the AD dementia group (1479 [1134-1842] pg/mL), stable MCI group (no progression to AD during follow-up; 1182 [923-1687] pg/mL), and progressive MCI group (MCI with progression to AD dementia during follow-up; 1336 [1061-1693] pg/mL) compared with control participants (1047 [809-1265] pg/mL) (P < .001 for all) and in the AD dementia group compared with the stable MCI group (P = .01). In the MCI group, a higher CSF NFL concentration was associated with faster brain atrophy over time as measured by changes in whole-brain volume (β = -4177, P = .003), ventricular volume (β = 1835, P < .001), and hippocampus volume (β = -54.22, P < .001); faster disease progression as reflected by decreased Mini-Mental State Examination scores (β = -1.077, P < .001) and increased Alzheimer Disease Assessment Scale cognitive subscale scores (β = 2.30, P < .001); and faster white matter intensity change (β = 598.7, P < .001). Cerebrospinal fluid NFL concentration is increased by the early clinical stage of AD and is associated with cognitive deterioration and structural brain changes over time. This finding corroborates the contention that degeneration of large-caliber axons is an important feature of AD neurodegeneration.

How Language Is Embodied in Bilinguals and Children with Specific Language Impairment

PubMed Central

Adams, Ashley M.

2016-01-01

This manuscript explores the role of embodied views of language comprehension and production in bilingualism and specific language impairment. Reconceptualizing popular models of bilingual language processing, the embodied theory is first extended to this area. Issues such as semantic grounding in a second language and potential differences between early and late acquisition of a second language are discussed. Predictions are made about how this theory informs novel ways of thinking about teaching a second language. Secondly, the comorbidity of speech, language, and motor impairments and how embodiment theory informs the discussion of the etiology of these impairments is examined. A hypothesis is presented suggesting that what is often referred to as specific language impairment may not be so specific due to widespread subclinical motor deficits in this population. Predictions are made about how weaknesses and instabilities in speech motor control, even at a subclinical level, may disrupt the neural network that connects acoustic input, articulatory motor plans, and semantics. Finally, I make predictions about how this information informs clinical practice for professionals such as speech language pathologists and occupational and physical therapists. These new hypotheses are placed within the larger framework of the body of work pertaining to semantic grounding, action-based language acquisition, and action-perception links that underlie language learning and conceptual grounding. PMID:27582716

Hippocampal Insulin Resistance Impairs Spatial Learning and Synaptic Plasticity

PubMed Central

Piroli, Gerardo G.; Lawrence, Robert C.; Wrighten, Shayna A.; Green, Adrienne J.; Wilson, Steven P.; Sakai, Randall R.; Kelly, Sandra J.; Wilson, Marlene A.; Mott, David D.; Reagan, Lawrence P.

2015-01-01

Insulin receptors (IRs) are expressed in discrete neuronal populations in the central nervous system, including the hippocampus. To elucidate the functional role of hippocampal IRs independent of metabolic function, we generated a model of hippocampal-specific insulin resistance using a lentiviral vector expressing an IR antisense sequence (LV-IRAS). LV-IRAS effectively downregulates IR expression in the rat hippocampus without affecting body weight, adiposity, or peripheral glucose homeostasis. Nevertheless, hippocampal neuroplasticity was impaired in LV-IRAS–treated rats. High-frequency stimulation, which evoked robust long-term potentiation (LTP) in brain slices from LV control rats, failed to evoke LTP in LV-IRAS–treated rats. GluN2B subunit levels, as well as the basal level of phosphorylation of GluA1, were reduced in the hippocampus of LV-IRAS rats. Moreover, these deficits in synaptic transmission were associated with impairments in spatial learning. We suggest that alterations in the expression and phosphorylation of glutamate receptor subunits underlie the alterations in LTP and that these changes are responsible for the impairment in hippocampal-dependent learning. Importantly, these learning deficits are strikingly similar to the impairments in complex task performance observed in patients with diabetes, which strengthens the hypothesis that hippocampal insulin resistance is a key mediator of cognitive deficits independent of glycemic control. PMID:26216852

Perception of emotion-related conflict in human communications: what are the effects of schizophrenia?

PubMed

Mitchell, Rachel L C; Rossell, Susan L

2014-12-15

Our ability to make sense of emotional cues is of paramount importance for understanding state of mind and communicative intent. However, emotional cues often conflict with each other; this presents a significant challenge for people with schizophrenia. We conducted a theoretical review to determine the extent and types of impaired processing of emotion-related conflict in schizophrenia; we evaluated the relationship with medication and symptoms, and considered possible mediatory mechanisms. The literature established that people with schizophrenia demonstrated impaired function: (i) when passively exposed to emotion cues whilst performing an unrelated task, (ii) when selectively attending to one source of emotion cues whilst trying to ignore interference from another source, and (iii) when trying to resolve conflicting emotion cues and judge meta-communicative intent. These deficits showed associations with both negative and positive symptoms. There was limited evidence for antipsychotic medications attenuating impaired emotion perception when there are conflicting cues, with further direct research needed. Impaired attentional control and context processing may underlie some of the observed impairments. Neuroanatomical correlates are likely to involve interhemispheric transfer via the corpus callosum, limbic regions such as the amygdala, and possibly dorsolateral prefrontal and anterior cingulate cortex through their role in conflict processing. Crown Copyright © 2014. Published by Elsevier Ireland Ltd. All rights reserved.

Postnatal Erythropoietin Mitigates Impaired Cerebral Cortical Development Following Subplate Loss from Prenatal Hypoxia–Ischemia

PubMed Central

Jantzie, Lauren L.; Corbett, Christopher J.; Firl, Daniel J.; Robinson, Shenandoah

2015-01-01

Preterm birth impacts brain development and leads to chronic deficits including cognitive delay, behavioral problems, and epilepsy. Premature loss of the subplate, a transient subcortical layer that guides development of the cerebral cortex and axonal refinement, has been implicated in these neurological disorders. Subplate neurons influence postnatal upregulation of the potassium chloride co-transporter KCC2 and maturation of γ-amino-butyric acid A receptor (GABAAR) subunits. We hypothesized that prenatal transient systemic hypoxia–ischemia (TSHI) in Sprague–Dawley rats that mimic brain injury from extreme prematurity in humans would cause premature subplate loss and affect cortical layer IV development. Further, we predicted that the neuroprotective agent erythropoietin (EPO) could attenuate the injury. Prenatal TSHI induced subplate neuronal loss via apoptosis. TSHI impaired cortical layer IV postnatal upregulation of KCC2 and GABAAR subunits, and postnatal EPO treatment mitigated the loss (n ≥ 8). To specifically address how subplate loss affects cortical development, we used in vitro mechanical subplate ablation in slice cultures (n ≥ 3) and found EPO treatment attenuates KCC2 loss. Together, these results show that subplate loss contributes to impaired cerebral development, and EPO treatment diminishes the damage. Limitation of premature subplate loss and the resultant impaired cortical development may minimize cerebral deficits suffered by extremely preterm infants. PMID:24722771

Automated Axon Counting in Rodent Optic Nerve Sections with AxonJ.

PubMed

Zarei, Kasra; Scheetz, Todd E; Christopher, Mark; Miller, Kathy; Hedberg-Buenz, Adam; Tandon, Anamika; Anderson, Michael G; Fingert, John H; Abràmoff, Michael David

2016-05-26

We have developed a publicly available tool, AxonJ, which quantifies the axons in optic nerve sections of rodents stained with paraphenylenediamine (PPD). In this study, we compare AxonJ's performance to human experts on 100x and 40x images of optic nerve sections obtained from multiple strains of mice, including mice with defects relevant to glaucoma. AxonJ produced reliable axon counts with high sensitivity of 0.959 and high precision of 0.907, high repeatability of 0.95 when compared to a gold-standard of manual assessments and high correlation of 0.882 to the glaucoma damage staging of a previously published dataset. AxonJ allows analyses that are quantitative, consistent, fully-automated, parameter-free, and rapid on whole optic nerve sections at 40x. As a freely available ImageJ plugin that requires no highly specialized equipment to utilize, AxonJ represents a powerful new community resource augmenting studies of the optic nerve using mice.

Membrane potential dynamics of axons in cultured hippocampal neurons probed by second-harmonic-generation imaging

NASA Astrophysics Data System (ADS)

Nuriya, Mutsuo; Yasui, Masato

2010-03-01

The electrical properties of axons critically influence the nature of communication between neurons. However, due to their small size, direct measurement of membrane potential dynamics in intact and complex mammalian axons has been a challenge. Furthermore, quantitative optical measurements of axonal membrane potential dynamics have not been available. To characterize the basic principles of somatic voltage signal propagation in intact axonal arbors, second-harmonic-generation (SHG) imaging is applied to cultured mouse hippocampal neurons. When FM4-64 is applied extracellularly to dissociated neurons, whole axonal arbors are visualized by SHG imaging. Upon action potential generation by somatic current injection, nonattenuating action potentials are recorded in intact axonal arbors. Interestingly, however, both current- and voltage-clamp recordings suggest that nonregenerative subthreshold somatic voltage changes at the soma are poorly conveyed to these axonal sites. These results reveal the nature of membrane potential dynamics of cultured hippocampal neurons, and further show the possibility of SHG imaging in physiological investigations of axons.

Automated Axon Counting in Rodent Optic Nerve Sections with AxonJ

NASA Astrophysics Data System (ADS)

Zarei, Kasra; Scheetz, Todd E.; Christopher, Mark; Miller, Kathy; Hedberg-Buenz, Adam; Tandon, Anamika; Anderson, Michael G.; Fingert, John H.; Abràmoff, Michael David

2016-05-01

We have developed a publicly available tool, AxonJ, which quantifies the axons in optic nerve sections of rodents stained with paraphenylenediamine (PPD). In this study, we compare AxonJ’s performance to human experts on 100x and 40x images of optic nerve sections obtained from multiple strains of mice, including mice with defects relevant to glaucoma. AxonJ produced reliable axon counts with high sensitivity of 0.959 and high precision of 0.907, high repeatability of 0.95 when compared to a gold-standard of manual assessments and high correlation of 0.882 to the glaucoma damage staging of a previously published dataset. AxonJ allows analyses that are quantitative, consistent, fully-automated, parameter-free, and rapid on whole optic nerve sections at 40x. As a freely available ImageJ plugin that requires no highly specialized equipment to utilize, AxonJ represents a powerful new community resource augmenting studies of the optic nerve using mice.

Unpredictable chronic mild stress differentially impairs social and contextual discrimination learning in two inbred mouse strains.

PubMed

van Boxelaere, Michiel; Clements, Jason; Callaerts, Patrick; D'Hooge, Rudi; Callaerts-Vegh, Zsuzsanna

2017-01-01

Alterations in the social and cognitive domain are considered important indicators for increased disability in many stress-related disorders. Similar impairments have been observed in rodents chronically exposed to stress, mimicking potential endophenotypes of stress-related psychopathologies such as major depression disorder (MDD), anxiety, conduct disorder, and posttraumatic stress disorder (PTSD). Data from numerous studies suggest that deficient plasticity mechanisms in hippocampus (HC) and prefrontal cortex (PFC) might underlie these social and cognitive deficits. Specifically, stress-induced deficiencies in neural plasticity have been associated with a hypodopaminergic state and reduced neural plasticity persistence. Here we assessed the effects of unpredictable chronic mild stress (UCMS) on exploratory, social and cognitive behavior of females of two inbred mouse strains (C57BL/6J and DBA/2J) that differ in their dopaminergic profile. Exposure to chronic stress resulted in impaired circadian rhythmicity, sociability and social cognition in both inbred strains, but differentially affected activity patterns and contextual discrimination performance. These stress-induced behavioral impairments were accompanied by reduced expression levels of brain derived neurotrophic factor (BDNF) in the prefrontal cortex. The strain-specific cognitive impairment was coexistent with enhanced plasma corticosterone levels and reduced expression of genes related to dopamine signaling in hippocampus. These results underline the importance of assessing different strains with multiple test batteries to elucidate the neural and genetic basis of social and cognitive impairments related to chronic stress.

Regulated viral BDNF delivery in combination with Schwann cells promotes axonal regeneration through capillary alginate hydrogels after spinal cord injury.

PubMed

Liu, Shengwen; Sandner, Beatrice; Schackel, Thomas; Nicholson, LaShae; Chtarto, Abdelwahed; Tenenbaum, Liliane; Puttagunta, Radhika; Müller, Rainer; Weidner, Norbert; Blesch, Armin

2017-09-15

Grafting of cell-seeded alginate capillary hydrogels into a spinal cord lesion site provides an axonal bridge while physically directing regenerating axonal growth in a linear pattern. However, without an additional growth stimulus, bridging axons fail to extend into the distal host spinal cord. Here we examined whether a combinatory strategy would support regeneration of descending axons across a cervical (C5) lateral hemisection lesion in the rat spinal cord. Following spinal cord transections, Schwann cell (SC)-seeded alginate hydrogels were grafted to the lesion site and AAV5 expressing brain-derived neurotrophic factor (BDNF) under control of a tetracycline-regulated promoter was injected caudally. In addition, we examined whether SC injection into the caudal spinal parenchyma would further enhance regeneration of descending axons to re-enter the host spinal cord. Our data show that both serotonergic and descending axons traced by biotinylated dextran amine (BDA) extend throughout the scaffolds. The number of regenerating axons is significantly increased when caudal BDNF expression is activated and transient BDNF delivery is able to sustain axons after gene expression is switched off. Descending axons are confined to the caudal graft/host interface even with continuous BDNF expression for 8weeks. Only with a caudal injection of SCs, a pathway facilitating axonal regeneration through the host/graft interface is generated allowing axons to successfully re-enter the caudal spinal cord. Recovery from spinal cord injury is poor due to the limited regeneration observed in the adult mammalian central nervous system. Biomaterials, cell transplantation and growth factors that can guide axons across a lesion site, provide a cellular substrate, stimulate axon growth and have shown some promise in increasing the growth distance of regenerating axons. In the present study, we combined an alginate biomaterial with linear channels with transplantation of Schwann cells within and beyond the lesion site and injection of a regulatable vector for the transient expression of brain-derived neurotrophic factor (BDNF). Our data show that only with the full combination axons extend across the lesion site and that expression of BDNF beyond 4weeks does not further increase the number of regenerating axons. Copyright © 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

A single mild fluid percussion injury induces short-term behavioral and neuropathological changes in the Long-Evans rat: support for an animal model of concussion.

PubMed

Shultz, Sandy R; MacFabe, Derrick F; Foley, Kelly A; Taylor, Roy; Cain, Donald P

2011-10-31

Brain concussion is a serious public health concern and is associated with short-term cognitive impairments and behavioral disturbances that typically occur in the absence of significant brain damage. The current study addresses the need to better understand the effects of a mild lateral fluid percussion injury on rat behavior and neuropathology in an animal model of concussion. Male Long-Evans rats received either a single mild fluid percussion injury or a sham-injury, and either a short (24h) or long (4 weeks) post-injury recovery period. After recovery, rats underwent a detailed behavioral analysis consisting of tests for rodent anxiety, cognition, social behavior, sensorimotor function, and depression-like behavior. After testing all rats were sacrificed and brains were examined immunohistochemically with markers for microglia/macrophage activation, reactive astrocytosis, and axonal injury. Injured rats (mean injury force: 1.20 ±.03 atm) displayed significant short-term cognitive impairments in the water maze and significantly more anxiolytic-like behavior in the elevated-plus maze compared to sham controls. Neuropathological analysis of the brains of injured rats showed an acute increase in reactive astrogliosis and activated microglia in cortex and evidence of axonal injury in the corpus callosum. There were no significant long-term effects on any behavioral or neuropathological measure 4 weeks after injury. These short-term behavioral and neuropathological changes are consistent with findings in human patients suffering a brain concussion, and provide further evidence for the use of a single mild lateral fluid percussion injury to study concussion in the rat. Copyright © 2011 Elsevier B.V. All rights reserved.

A Novel Closed-Head Model of Mild Traumatic Brain Injury Using Focal Primary Overpressure Blast to the Cranium in Mice

PubMed Central

Guley, Natalie H.; Rogers, Joshua T.; Del Mar, Nobel A.; Deng, Yunping; Islam, Rafiqul M.; D'Surney, Lauren; Ferrell, Jessica; Deng, Bowei; Hines-Beard, Jessica; Bu, Wei; Ren, Huiling; Elberger, Andrea J.; Marchetta, Jeffrey G.; Rex, Tonia S.; Honig, Marcia G.

2016-01-01

Abstract Mild traumatic brain injury (TBI) from focal head impact is the most common form of TBI in humans. Animal models, however, typically use direct impact to the exposed dura or skull, or blast to the entire head. We present a detailed characterization of a novel overpressure blast system to create focal closed-head mild TBI in mice. A high-pressure air pulse limited to a 7.5 mm diameter area on the left side of the head overlying the forebrain is delivered to anesthetized mice. The mouse eyes and ears are shielded, and its head and body are cushioned to minimize movement. This approach creates mild TBI by a pressure wave that acts on the brain, with minimal accompanying head acceleration-deceleration. A single 20-psi blast yields no functional deficits or brain injury, while a single 25–40 psi blast yields only slight motor deficits and brain damage. By contrast, a single 50–60 psi blast produces significant visual, motor, and neuropsychiatric impairments and axonal damage and microglial activation in major fiber tracts, but no contusive brain injury. This model thus reproduces the widespread axonal injury and functional impairments characteristic of closed-head mild TBI, without the complications of systemic or ocular blast effects or head acceleration that typically occur in other blast or impact models of closed-skull mild TBI. Accordingly, our model provides a simple way to examine the biomechanics, pathophysiology, and functional deficits that result from TBI and can serve as a reliable platform for testing therapies that reduce brain pathology and deficits. PMID:26414413

Double-Edge Sword of Sustained ROCK Activation in Prion Diseases through Neuritogenesis Defects and Prion Accumulation

PubMed Central

Alleaume-Butaux, Aurélie; Nicot, Simon; Pietri, Mathéa; Baudry, Anne; Dakowski, Caroline; Tixador, Philippe; Ardila-Osorio, Hector; Haeberlé, Anne-Marie; Bailly, Yannick; Peyrin, Jean-Michel; Launay, Jean-Marie; Kellermann, Odile; Schneider, Benoit

2015-01-01

In prion diseases, synapse dysfunction, axon retraction and loss of neuronal polarity precede neuronal death. The mechanisms driving such polarization defects, however, remain unclear. Here, we examined the contribution of RhoA-associated coiled-coil containing kinases (ROCK), key players in neuritogenesis, to prion diseases. We found that overactivation of ROCK signaling occurred in neuronal stem cells infected by pathogenic prions (PrPSc) and impaired the sprouting of neurites. In reconstructed networks of mature neurons, PrPSc-induced ROCK overactivation provoked synapse disconnection and dendrite/axon degeneration. This overactivation of ROCK also disturbed overall neurotransmitter-associated functions. Importantly, we demonstrated that beyond its impact on neuronal polarity ROCK overactivity favored the production of PrPSc through a ROCK-dependent control of 3-phosphoinositide-dependent kinase 1 (PDK1) activity. In non-infectious conditions, ROCK and PDK1 associated within a complex and ROCK phosphorylated PDK1, conferring basal activity to PDK1. In prion-infected neurons, exacerbated ROCK activity increased the pool of PDK1 molecules physically interacting with and phosphorylated by ROCK. ROCK-induced PDK1 overstimulation then canceled the neuroprotective α-cleavage of normal cellular prion protein PrPC by TACE α-secretase, which physiologically precludes PrPSc production. In prion-infected cells, inhibition of ROCK rescued neurite sprouting, preserved neuronal architecture, restored neuronal functions and reduced the amount of PrPSc. In mice challenged with prions, inhibition of ROCK also lowered brain PrPSc accumulation, reduced motor impairment and extended survival. We conclude that ROCK overactivation exerts a double detrimental effect in prion diseases by altering neuronal polarity and triggering PrPSc accumulation. Eventually ROCK emerges as therapeutic target to combat prion diseases. PMID:26241960

Novel C12orf65 mutations in patients with axonal neuropathy and optic atrophy.

PubMed

Tucci, Arianna; Liu, Yo-Tsen; Preza, Elisabeth; Pitceathly, Robert D S; Chalasani, Annapurna; Plagnol, Vincent; Land, John M; Trabzuni, Daniah; Ryten, Mina; Jaunmuktane, Zane; Reilly, Mary M; Brandner, Sebastian; Hargreaves, Iain; Hardy, John; Singleton, Andrew B; Abramov, Andrey Y; Houlden, Henry

2014-05-01

Charcot-Marie Tooth disease (CMT) forms a clinically and genetically heterogeneous group of disorders. Although a number of disease genes have been identified for CMT, the gene discovery for some complex form of CMT has lagged behind. The association of neuropathy and optic atrophy (also known as CMT type 6) has been described with autosomaldominant, recessive and X-linked modes of inheritance. Mutations in Mitofusin 2 have been found to cause dominant forms of CMT6. Phosphoribosylpyrophosphate synthetase-I mutations cause X-linked CMT6, but until now, mutations in the recessive forms of disease have never been identified. We here describe a family with three affected individuals who inherited in an autosomal recessive fashion a childhood onset neuropathy and optic atrophy. Using homozygosity mapping in the family and exome sequencing in two affected individuals we identified a novel protein-truncating mutation in the C12orf65 gene, which encodes for a protein involved in mitochondrial translation. Using a variety of methods we investigated the possibility of mitochondrial impairment in the patients cell lines. We described a large consanguineous family with neuropathy and optic atrophy carrying a loss of function mutation in the C12orf65 gene. We report mitochondrial impairment in the patients cell lines, followed by multiple lines of evidence which include decrease of complex V activity and stability (blue native gel assay), decrease in mitochondrial respiration rate and reduction of mitochondrial membrane potential. This work describes a mutation in the C12orf65 gene that causes recessive form of CMT6 and confirms the role of mitochondrial dysfunction in this complex axonal neuropathy.

Association of a History of Child Abuse With Impaired Myelination in the Anterior Cingulate Cortex: Convergent Epigenetic, Transcriptional, and Morphological Evidence.

PubMed

Lutz, Pierre-Eric; Tanti, Arnaud; Gasecka, Alicja; Barnett-Burns, Sarah; Kim, John J; Zhou, Yi; Chen, Gang G; Wakid, Marina; Shaw, Meghan; Almeida, Daniel; Chay, Marc-Aurele; Yang, Jennie; Larivière, Vanessa; M'Boutchou, Marie-Noël; van Kempen, Léon C; Yerko, Volodymyr; Prud'homme, Josée; Davoli, Maria Antonietta; Vaillancourt, Kathryn; Théroux, Jean-François; Bramoullé, Alexandre; Zhang, Tie-Yuan; Meaney, Michael J; Ernst, Carl; Côté, Daniel; Mechawar, Naguib; Turecki, Gustavo

2017-12-01

Child abuse has devastating and long-lasting consequences, considerably increasing the lifetime risk of negative mental health outcomes such as depression and suicide. Yet the neurobiological processes underlying this heightened vulnerability remain poorly understood. The authors investigated the hypothesis that epigenetic, transcriptomic, and cellular adaptations may occur in the anterior cingulate cortex as a function of child abuse. Postmortem brain samples from human subjects (N=78) and from a rodent model of the impact of early-life environment (N=24) were analyzed. The human samples were from depressed individuals who died by suicide, with (N=27) or without (N=25) a history of severe child abuse, as well as from psychiatrically healthy control subjects (N=26). Genome-wide DNA methylation and gene expression were investigated using reduced representation bisulfite sequencing and RNA sequencing, respectively. Cell type-specific validation of differentially methylated loci was performed after fluorescence-activated cell sorting of oligodendrocyte and neuronal nuclei. Differential gene expression was validated using NanoString technology. Finally, oligodendrocytes and myelinated axons were analyzed using stereology and coherent anti-Stokes Raman scattering microscopy. A history of child abuse was associated with cell type-specific changes in DNA methylation of oligodendrocyte genes and a global impairment of the myelin-related transcriptional program. These effects were absent in the depressed suicide completers with no history of child abuse, and they were strongly correlated with myelin gene expression changes observed in the animal model. Furthermore, a selective and significant reduction in the thickness of myelin sheaths around small-diameter axons was observed in individuals with history of child abuse. The results suggest that child abuse, in part through epigenetic reprogramming of oligodendrocytes, may lastingly disrupt cortical myelination, a fundamental feature of cerebral connectivity.

Regulation of neuronal axon specification by glia-neuron gap junctions in C. elegans.

PubMed

Meng, Lingfeng; Zhang, Albert; Jin, Yishi; Yan, Dong

2016-10-21

Axon specification is a critical step in neuronal development, and the function of glial cells in this process is not fully understood. Here, we show that C. elegans GLR glial cells regulate axon specification of their nearby GABAergic RME neurons through GLR-RME gap junctions. Disruption of GLR-RME gap junctions causes misaccumulation of axonal markers in non-axonal neurites of RME neurons and converts microtubules in those neurites to form an axon-like assembly. We further uncover that GLR-RME gap junctions regulate RME axon specification through activation of the CDK-5 pathway in a calcium-dependent manner, involving a calpain clp-4 . Therefore, our study reveals the function of glia-neuron gap junctions in neuronal axon specification and shows that calcium originated from glial cells can regulate neuronal intracellular pathways through gap junctions.

Neuron-to-neuron transmission of α-synuclein fibrils through axonal transport

PubMed Central

Freundt, Eric C.; Maynard, Nate; Clancy, Eileen K.; Roy, Shyamali; Bousset, Luc; Sourigues, Yannick; Covert, Markus; Melki, Ronald; Kirkegaard, Karla; Brahic, Michel

2012-01-01

Objective The lesions of Parkinson's disease spread through the brain in a characteristic pattern that corresponds to axonal projections. Previous observations suggest that misfolded α-synuclein could behave as a prion, moving from neuron to neuron and causing endogenous α-synuclein to misfold. Here, we characterized and quantified the axonal transport of α-synuclein fibrils and showed that fibrils could be transferred from axons to second-order neurons following anterograde transport. Methods We grew primary cortical mouse neurons in microfluidic devices to separate soma from axonal projections in fluidically isolated microenvironments. We used live-cell imaging and immunofluorescence to characterize the transport of fluorescent α-synuclein fibrils and their transfer to second-order neurons. Results Fibrillar α-synuclein was internalized by primary neurons and transported in axons with kinetics consistent with slow component-b of axonal transport (fast axonal transport with saltatory movement). Fibrillar α-synuclein was readily observed in the cell bodies of second-order neurons following anterograde axonal transport. Axon-to-soma transfer appeared not to require synaptic contacts. Interpretation These results support the hypothesis that the progression of Parkinson's disease can be caused by neuron-to-neuron spread of α-synuclein aggregates and that the anatomical pattern of progression of lesions between axonally connected areas results from the axonal transport of such aggregates. That the transfer did not appear to be transsynaptic gives hope that α-synuclein fibrils could be intercepted by drugs during the extra-cellular phase of their journey. PMID:23109146

Comparative analysis of the electroencephalogram in patients with Alzheimer's disease, diffuse axonal injury patients and healthy controls using LORETA analysis.

PubMed

Ianof, Jéssica Natuline; Fraga, Francisco José; Ferreira, Leonardo Alves; Ramos, Renato Teodoro; Demario, José Luiz Carlos; Baratho, Regina; Basile, Luís Fernando Hindi; Nitrini, Ricardo; Anghinah, Renato

2017-01-01

Alzheimer's disease (AD) is a dementia that affects a large contingent of the elderly population characterized by the presence of neurofibrillary tangles and senile plaques. Traumatic brain injury (TBI) is a non-degenerative injury caused by an external mechanical force. One of the main causes of TBI is diffuse axonal injury (DAI), promoted by acceleration-deceleration mechanisms. To understand the electroencephalographic differences in functional mechanisms between AD and DAI groups. The study included 20 subjects with AD, 19 with DAI and 17 healthy adults submitted to high resolution EEG with 128 channels. Cortical sources of EEG rhythms were estimated by exact low-resolution electromagnetic tomography (eLORETA) analysis. The eLORETA analysis showed that, in comparison to the control (CTL) group, the AD group had increased theta activity in the parietal and frontal lobes and decreased alpha 2 activity in the parietal, frontal, limbic and occipital lobes. In comparison to the CTL group, the DAI group had increased theta activity in the limbic, occipital sublobar and temporal areas. The results suggest that individuals with AD and DAI have impairment of electrical activity in areas important for memory and learning.

HDAC1/2-Dependent P0 Expression Maintains Paranodal and Nodal Integrity Independently of Myelin Stability through Interactions with Neurofascins

PubMed Central

Brügger, Valérie; Engler, Stefanie; Pereira, Jorge A.; Ruff, Sophie; Horn, Michael; Welzl, Hans; Münger, Emmanuelle; Vaquié, Adrien; Sidiropoulos, Páris N. M.; Egger, Boris; Yotovski, Peter; Filgueira, Luis; Somandin, Christian; Lühmann, Tessa C.; D’Antonio, Maurizio; Yamaguchi, Teppei; Matthias, Patrick; Suter, Ueli; Jacob, Claire

2015-01-01

The pathogenesis of peripheral neuropathies in adults is linked to maintenance mechanisms that are not well understood. Here, we elucidate a novel critical maintenance mechanism for Schwann cell (SC)–axon interaction. Using mouse genetics, ablation of the transcriptional regulators histone deacetylases 1 and 2 (HDAC1/2) in adult SCs severely affected paranodal and nodal integrity and led to demyelination/remyelination. Expression levels of the HDAC1/2 target gene myelin protein zero (P0) were reduced by half, accompanied by altered localization and stability of neurofascin (NFasc)155, NFasc186, and loss of Caspr and septate-like junctions. We identify P0 as a novel binding partner of NFasc155 and NFasc186, both in vivo and by in vitro adhesion assay. Furthermore, we demonstrate that HDAC1/2-dependent P0 expression is crucial for the maintenance of paranodal/nodal integrity and axonal function through interaction of P0 with neurofascins. In addition, we show that the latter mechanism is impaired by some P0 mutations that lead to late onset Charcot-Marie-Tooth disease. PMID:26406915

Detection of reduced interhemispheric cortical communication during task execution in multiple sclerosis patients using functional near-infrared spectroscopy

NASA Astrophysics Data System (ADS)

Jimenez, Jon J.; Yang, Runze; Nathoo, Nabeela; Varshney, Vishal P.; Golestani, Ali-Mohammad; Goodyear, Bradley G.; Metz, Luanne M.; Dunn, Jeff F.

2014-07-01

Multiple sclerosis (MS) impairs brain activity through demyelination and loss of axons. Increased brain activity is accompanied by increases in microvascular hemoglobin oxygen saturation (oxygenation) and total hemoglobin, which can be measured using functional near-infrared spectroscopy (fNIRS). Due to the potentially reduced size and integrity of the white matter tracts within the corpus callosum, it may be expected that MS patients have reduced functional communication between the left and right sides of the brain; this could potentially be an indicator of disease progression. To assess interhemispheric communication in MS, we used fNIRS during a unilateral motor task and the resting state. The magnitude of the change in hemoglobin parameters in the motor cortex was significantly reduced in MS patients during the motor task relative to healthy control subjects. There was also a significant decrease in interhemispheric communication between the motor cortices (expressed as coherence) in MS patients compared to controls during the motor task, but not during the resting state. fNIRS assessment of interhemispheric coherence during task execution may be a useful marker in disorders with white matter damage or axonal loss, including MS.

Effects of Acutely Elevated Hydrostatic Pressure in a Rat Ex Vivo Retinal Preparation

PubMed Central

Yoshitomi, Takeshi; Zorumski, Charles F.; Izumi, Yukitoshi

2010-01-01

Purpose. A new experimental glaucoma model was developed by using an ex vivo rat retinal preparation to examine the effects of elevated hydrostatic pressure on retinal morphology and glutamine synthetase (GS) activity. Methods. Ex vivo rat retinas were exposed to elevated hydrostatic pressure for 24 hours in the presence of glutamate or glutamate receptor antagonists and examined histologically. GS activity was assessed by colorimetric assay. Results. Pressure elevation induced axonal swelling in the nerve fiber layer. Axonal swelling was prevented by a combination of non-N-methyl-d-aspartate (non-NMDA) receptor antagonist and an NMDA receptor antagonist, indicating that the damage results from activation of both types of glutamate receptor. When glial function was preserved, the typical changes induced by glutamate consisted of reversible Müller cell swelling resulting from excessive glial glutamate uptake. The irreversible Müller cell swelling in hyperbaric conditions may indicate that pressure disrupts glutamate metabolism. Indeed, elevated pressure inhibited GS activity. In addition, glutamate exposure after termination of pressure exposure exhibited apparent Müller cell swelling. Conclusions. These results suggest that the neural degeneration observed during pressure elevation is caused by impaired glial glutamate metabolism after uptake. PMID:20688725

Differential effects of Rho GTPases on axonal and dendritic development in hippocampal neurones.

PubMed

Ahnert-Hilger, G; Höltje, M; Grosse, G; Pickert, G; Mucke, C; Nixdorf-Bergweiler, B; Boquet, P; Hofmann, F; Just, I

2004-07-01

Formation of neurites and their differentiation into axons and dendrites requires precisely controlled changes in the cytoskeleton. While small GTPases of the Rho family appear to be involved in this regulation, it is still unclear how Rho function affects axonal and dendritic growth during development. Using hippocampal neurones at defined states of differentiation, we have dissected the function of RhoA in axonal and dendritic growth. Expression of a dominant negative RhoA variant inhibited axonal growth, whereas dendritic growth was promoted. The opposite phenotype was observed when a constitutively active RhoA variant was expressed. Inactivation of Rho by C3-catalysed ADP-ribosylation using C3 isoforms (Clostridium limosum, C3(lim) or Staphylococcus aureus, C3(stau2)), diminished axonal branching. By contrast, extracellularly applied nanomolar concentrations of C3 from C. botulinum (C3(bot)) or enzymatically dead C3(bot) significantly increased axon growth and axon branching. Taken together, axonal development requires activation of RhoA, whereas dendritic development benefits from its inactivation. However, extracellular application of enzymatically active or dead C3(bot) exclusively promotes axonal growth and branching suggesting a novel neurotrophic function of C3 that is independent from its enzymatic activity.

Neuronal growth cones respond to laser-induced axonal damage

PubMed Central

Wu, Tao; Mohanty, Samarendra; Gomez-Godinez, Veronica; Shi, Linda Z.; Liaw, Lih-Huei; Miotke, Jill; Meyer, Ronald L.; Berns, Michael W.

2012-01-01

Although it is well known that damage to neurons results in release of substances that inhibit axonal growth, release of chemical signals from damaged axons that attract axon growth cones has not been observed. In this study, a 532 nm 12 ns laser was focused to a diffraction-limited spot to produce site-specific damage to single goldfish axons in vitro. The axons underwent a localized decrease in thickness (‘thinning’) within seconds. Analysis by fluorescence and transmission electron microscopy indicated that there was no gross rupture of the cell membrane. Mitochondrial transport along the axonal cytoskeleton immediately stopped at the damage site, but recovered over several minutes. Within seconds of damage nearby growth cones extended filopodia towards the injury and were often observed to contact the damaged site. Turning of the growth cone towards the injured axon also was observed. Repair of the laser-induced damage was evidenced by recovery of the axon thickness as well as restoration of mitochondrial movement. We describe a new process of growth cone response to damaged axons. This has been possible through the interface of optics (laser subcellular surgery), fluorescence and electron microscopy, and a goldfish retinal ganglion cell culture model. PMID:21831892

Mitofusin2 mutations disrupt axonal mitochondrial positioning and promote axon degeneration

PubMed Central

Misko, Albert; Sasaki, Yo; Tuck, Elizabeth; Milbrandt, Jeffrey; Baloh, Robert H.

2012-01-01

Summary Alterations in mitochondrial dynamics (fission, fusion and movement) are implicated in many neurodegenerative diseases, from rare genetic disorders such as Charcot-Marie-Tooth disease, to common conditions including Alzheimer’s disease. However, the relationship between altered mitochondrial dynamics and neurodegeneration is incompletely understood. Here we show that disease associated MFN2 proteins suppressed both mitochondrial fusion and transport, and produced classic features of segmental axonal degeneration without cell body death, including neurofilament filled swellings, loss of calcium homeostasis, and accumulation of reactive oxygen species. By contrast, depletion of Opa1 suppressed mitochondrial fusion while sparing transport, and did not induce axonal degeneration. Axon degeneration induced by mutant MFN2 proteins correlated with the disruption of the proper mitochondrial positioning within axons, rather than loss of overall mitochondrial movement, or global mitochondrial dysfunction. We also found that augmenting expression of MFN1 rescued the axonal degeneration caused by MFN2 mutants, suggesting a possible therapeutic strategy for Charcot-Marie-Tooth disease. These experiments provide evidence that the ability of mitochondria to sense energy requirements and localize properly within axons is key to maintaining axonal integrity, and may be a common pathway by which disruptions in axonal transport contribute to neurodegeneration. PMID:22442078

Motoneuron axon pathfinding errors in zebrafish: Differential effects related to concentration and timing of nicotine exposure

PubMed Central

Menelaou, Evdokia; Paul, Latoya T.; Perera, Surangi N.; Svoboda, Kurt R.

2015-01-01

Nicotine exposure during embryonic stages of development can affect many neurodevelopmental processes. In the developing zebrafish, exposure to nicotine was reported to cause axonal pathfinding errors in the later born secondary motoneurons (SMN). These alterations in SMN axon morphology coincided with muscle degeneration at high nicotine concentrations (15–30µM). Previous work showed that the paralytic mutant zebrafish known as sofa potato, exhibited nicotine-induced effects onto SMN axons at these high concentrations but in the absence of any muscle deficits, indicating that pathfinding errors could occur independent of muscle effects. In this study, we used varying concentrations of nicotine at different developmental windows of exposure to specifically isolate its effects onto subpopulations of motoneuron axons. We found that nicotine exposure can affect SMN axon morphology in a dose-dependent manner. At low concentrations of nicotine, SMN axons exhibited pathfinding errors, in the absence of any nicotine-induced muscle abnormalities. Moreover, the nicotine exposure paradigms used affected the 3 subpopulations of SMN axons differently, but the dorsal projecting SMN axons were primarily affected. We then identified morphologically distinct pathfinding errors that best described the nicotine-induced effects on dorsal projecting SMN axons. To test whether SMN pathfinding was potentially influenced by alterations in the early born primary motoneuron (PMN), we performed dual labeling studies, where both PMN and SMN axons were simultaneously labeled with antibodies. We show that only a subset of the SMN axon pathfinding errors coincided with abnormal PMN axonal targeting in nicotine-exposed zebrafish. We conclude that nicotine exposure can exert differential effects depending on the levels of nicotine and developmental exposure window. PMID:25668718

Variable laterality of corticospinal tract axons that regenerate after spinal cord injury as a result of PTEN deletion or knock-down

PubMed Central

Willenberg, Rafer; Zukor, Katherine; Liu, Kai; He, Zhigang; Steward, Oswald

2016-01-01

Corticospinal tract (CST) axons from one hemisphere normally extend and terminate predominantly in the contralateral spinal cord. We previously showed that deleting PTEN in the sensorimotor cortex enables CST axons to regenerate after spinal cord injury and that some regenerating axons extend along the “wrong” side. Here, we characterize the degree of specificity of regrowth in terms of laterality. PTEN was selectively deleted via cortical AAV-Cre injections in neonatal PTEN-floxed mice. As adults, mice received dorsal hemisection injuries at T12 or complete crush injuries at T9. CST axons from one hemisphere were traced by unilateral BDA injections in PTEN-deleted mice with spinal cord injury and in non-injured PTEN-floxed mice that had not received AAV-Cre. In non-injured mice, 97.9 ± 0.7% of BDA-labeled axons in white matter and 88.5 ± 1.0% of BDA-labeled axons in grey matter were contralateral to the cortex of origin. In contrast, laterality of CST axons that extended past a lesion due to PTEN deletion varied across animals. In some cases, regenerated axons extended predominantly on the ipsilateral side, in other cases, axons extended predominantly contralaterally, and in others, axons were similar in numbers on both sides. Similar results were seen in analyses of cases from previous studies using shRNA-mediated PTEN knock-down. These results indicate that CST axons that extend past a lesion due to PTEN deletion or knock-down do not maintain the contralateral rule of the non-injured CST, highlighting one aspect for how resultant circuitry from regenerating axons may differ from that of the uninjured CST. PMID:26878190

Characterizing Brain Structures and Remodeling after TBI Based on Information Content, Diffusion Entropy

PubMed Central

Fozouni, Niloufar; Chopp, Michael; Nejad-Davarani, Siamak P.; Zhang, Zheng Gang; Lehman, Norman L.; Gu, Steven; Ueno, Yuji; Lu, Mei; Ding, Guangliang; Li, Lian; Hu, Jiani; Bagher-Ebadian, Hassan; Hearshen, David; Jiang, Quan

2013-01-01

Background To overcome the limitations of conventional diffusion tensor magnetic resonance imaging resulting from the assumption of a Gaussian diffusion model for characterizing voxels containing multiple axonal orientations, Shannon's entropy was employed to evaluate white matter structure in human brain and in brain remodeling after traumatic brain injury (TBI) in a rat. Methods Thirteen healthy subjects were investigated using a Q-ball based DTI data sampling scheme. FA and entropy values were measured in white matter bundles, white matter fiber crossing areas, different gray matter (GM) regions and cerebrospinal fluid (CSF). Axonal densities' from the same regions of interest (ROIs) were evaluated in Bielschowsky and Luxol fast blue stained autopsy (n = 30) brain sections by light microscopy. As a case demonstration, a Wistar rat subjected to TBI and treated with bone marrow stromal cells (MSC) 1 week after TBI was employed to illustrate the superior ability of entropy over FA in detecting reorganized crossing axonal bundles as confirmed by histological analysis with Bielschowsky and Luxol fast blue staining. Results Unlike FA, entropy was less affected by axonal orientation and more affected by axonal density. A significant agreement (r = 0.91) was detected between entropy values from in vivo human brain and histologically measured axonal density from post mortum from the same brain structures. The MSC treated TBI rat demonstrated that the entropy approach is superior to FA in detecting axonal remodeling after injury. Compared with FA, entropy detected new axonal remodeling regions with crossing axons, confirmed with immunohistological staining. Conclusions Entropy measurement is more effective in distinguishing axonal remodeling after injury, when compared with FA. Entropy is also more sensitive to axonal density than axonal orientation, and thus may provide a more accurate reflection of axonal changes that occur in neurological injury and disease. PMID:24143186

Characterizing brain structures and remodeling after TBI based on information content, diffusion entropy.

PubMed

Fozouni, Niloufar; Chopp, Michael; Nejad-Davarani, Siamak P; Zhang, Zheng Gang; Lehman, Norman L; Gu, Steven; Ueno, Yuji; Lu, Mei; Ding, Guangliang; Li, Lian; Hu, Jiani; Bagher-Ebadian, Hassan; Hearshen, David; Jiang, Quan

2013-01-01

To overcome the limitations of conventional diffusion tensor magnetic resonance imaging resulting from the assumption of a Gaussian diffusion model for characterizing voxels containing multiple axonal orientations, Shannon's entropy was employed to evaluate white matter structure in human brain and in brain remodeling after traumatic brain injury (TBI) in a rat. Thirteen healthy subjects were investigated using a Q-ball based DTI data sampling scheme. FA and entropy values were measured in white matter bundles, white matter fiber crossing areas, different gray matter (GM) regions and cerebrospinal fluid (CSF). Axonal densities' from the same regions of interest (ROIs) were evaluated in Bielschowsky and Luxol fast blue stained autopsy (n = 30) brain sections by light microscopy. As a case demonstration, a Wistar rat subjected to TBI and treated with bone marrow stromal cells (MSC) 1 week after TBI was employed to illustrate the superior ability of entropy over FA in detecting reorganized crossing axonal bundles as confirmed by histological analysis with Bielschowsky and Luxol fast blue staining. Unlike FA, entropy was less affected by axonal orientation and more affected by axonal density. A significant agreement (r = 0.91) was detected between entropy values from in vivo human brain and histologically measured axonal density from post mortum from the same brain structures. The MSC treated TBI rat demonstrated that the entropy approach is superior to FA in detecting axonal remodeling after injury. Compared with FA, entropy detected new axonal remodeling regions with crossing axons, confirmed with immunohistological staining. Entropy measurement is more effective in distinguishing axonal remodeling after injury, when compared with FA. Entropy is also more sensitive to axonal density than axonal orientation, and thus may provide a more accurate reflection of axonal changes that occur in neurological injury and disease.

A Comparative Morphometric Analysis of Three Cranial Nerves in Two Phocids: The Hooded Seal (Cystophora cristata) and the Harbor Seal (Phoca vitulina).

PubMed

Wohlert, Dennis; Kröger, Jürgen; Witt, Martin; Schmitt, Oliver; Wree, Andreas; Czech-Damal, Nicole; Siebert, Ursula; Folkow, Lars; Hanke, Frederike D

2016-03-01

While our knowledge about the senses of pinnipeds has increased over the last decades almost nothing is known about the organization of the neuroanatomical pathways. In a first approach to this field of research, we assessed the total number of myelinated axons of three cranial nerves (CNs) in the harbor (Phoca vitulina, Pv) and hooded seal (Cystophora cristata, Cc). Axons were counted in semithin sections of the nerves embedded in Epon and stained with toluidine blue. In both species, the highest axon number was found within the optic nerve (Pv 187,000 ± 8,000 axons, Cc 481,600 ± 1,300 axons). Generally, considering absolute axon numbers, far more axons were counted within the optic and trigmenial nerve (Pv 136,700 ± 2,500 axons, Cc 179,300 ± 6,900 axons) in hooded in comparison to harbor seals. The axon counts of the vestibulocochlear nerve are nearly identical for both species (Pv 87,100 ± 8,100 axons, Cc 86,600 ± 2,700 axons). However, when comparing cell density, the cell density is almost equal for all nerves for both species except for the optic nerve in which cell density was particularly higher than in the other nerves and higher in hooded in comparison to harbor seals. We here present the first comparative analysis of three CNs in two phocid seals. While the CNs of these closely related species share some general characteristics, pronounced differences in axon numbers/densities are apparent. These differences seem to reflect differences in e.g. size, habitat, and/or functional significance of the innervated sensory systems. © 2015 Wiley Periodicals, Inc.

The local expression and trafficking of tyrosine hydroxylase mRNA in the axons of sympathetic neurons.

PubMed

Gervasi, Noreen M; Scott, Shane S; Aschrafi, Armaz; Gale, Jenna; Vohra, Sanah N; MacGibeny, Margaret A; Kar, Amar N; Gioio, Anthony E; Kaplan, Barry B

2016-06-01

Synthesis and regulation of catecholamine neurotransmitters in the central nervous system are implicated in the pathogenesis of a number of neuropsychiatric disorders. To identify factors that regulate the presynaptic synthesis of catecholamines, we tested the hypothesis that the rate-limiting enzyme of the catecholamine biosynthetic pathway, tyrosine hydroxylase (TH), is locally synthesized in axons and presynaptic nerve terminals of noradrenergic neurons. To isolate pure axonal mRNA and protein, rat superior cervical ganglion sympathetic neurons were cultured in compartmentalized Campenot chambers. qRT-PCR and RNA in situ hybridization analyses showed that TH mRNA is present in distal axons. Colocalization experiments with nerve terminal marker proteins suggested that both TH mRNA and protein localize in regions of the axon that resemble nerve terminals (i.e., synaptic boutons). Analysis of polysome-bound RNA showed that TH mRNA is present in polysomes isolated from distal axons. Metabolic labeling of axonally synthesized proteins labeled with the methionine analog, L-azidohomoalanine, showed that TH is locally synthesized in axons. Moreover, the local transfection and translation of exogenous TH mRNA into distal axons facilitated axonal dopamine synthesis. Finally, using chimeric td-Tomato-tagged constructs, we identified a sequence element within the TH 3'UTR that is required for the axonal localization of the reporter mRNA. Taken together, our results provide the first direct evidence that TH mRNA is trafficked to the axon and that the mRNA is locally translated. These findings raise the interesting possibility that the biosynthesis of the catecholamine neurotransmitters is locally regulated in the axon and/or presynaptic nerve terminal. Published by Cold Spring Harbor Laboratory Press for the RNA Society.

R7 Photoreceptor Axon Growth Is Temporally Controlled by the Transcription Factor Ttk69, Which Inhibits Growth in Part by Promoting Transforming Growth Factor-β/Activin Signaling

PubMed Central

Kniss, Jonathan S.; Holbrook, Scott

2013-01-01

Work on axon growth has classically focused on understanding how extrinsic cues control growth cone dynamics independent of the cell body. However, more recently, neuron-intrinsic transcription factors have been shown to influence both normal and regenerative axon growth, suggesting that understanding their mechanism of action is of clinical importance. We are studying axon targeting in the Drosophila visual system and here show that the BTB/POZ zinc-finger transcription factor Tramtrack69 (Ttk69) plays an instructive role in inhibiting the growth of R7 photoreceptor axon terminals. Although ttk69 mutant R7 axons project to the correct medullar target layer, M6, their terminals fail to remain retinotopically restricted and instead grow laterally within M6. This overgrowth is not caused by an inability to be repelled by neighboring R7 axons or by an inability to recognize and initiate synapse formation with postsynaptic targets. The overgrowth is progressive and occurs even if contact between ttk69 mutant R7 axons and their normal target layer is disrupted. Ttk69 is first expressed in wild-type R7s after their axons have reached the medulla; ttk69 mutant R7 axon terminal overgrowth begins shortly after this time point. We find that expressing Ttk69 prematurely in R7s collapses their growth cones and disrupts axon extension, indicating that Ttk69 plays an instructive role in this process. A TGF-β/Activin pathway was shown previously to inhibit R7 axon terminal growth. We find that Ttk69 is required for normal activation of this pathway but that Ttk69 likely also inhibits R7 axon growth by a TGF-β/Activin-independent mechanism. PMID:23345225

Chronic stress impairs spatial memory and motivation for reward without disrupting motor ability and motivation to explore.

PubMed

Kleen, Jonathan K; Sitomer, Matthew T; Killeen, Peter R; Conrad, Cheryl D

2006-08-01

This study uses an operant, behavioral model to assess the daily changes in the decay rate of short-term memory, motivation, and motor ability in rats exposed to chronic restraint. Restraint decreased reward-related motivation by 50% without altering memory decay rate or motor ability. Moreover, chronic restraint impaired hippocampal-dependent spatial memory on the Y maze (4-hr delay) and produced CA3 dendritic retraction without altering hippocampal-independent maze navigation (1-min delay) or locomotion. Thus, mechanisms underlying motivation for food reward differ from those underlying Y maze exploration, and neurobiological substrates of spatial memory, such as the hippocampus, differ from those that underlie short-term memory. Chronic restraint produces functional, neuromorphological, and physiological alterations that parallel symptoms of depression in humans. Copyright 2006 APA, all rights reserved.

Lexical Processing in School-Age Children with Autism Spectrum Disorder and Children with Specific Language Impairment: The Role of Semantics.

PubMed

Haebig, Eileen; Kaushanskaya, Margarita; Ellis Weismer, Susan

2015-12-01

Children with autism spectrum disorder (ASD) and specific language impairment (SLI) often have immature lexical-semantic knowledge; however, the organization of lexical-semantic knowledge is poorly understood. This study examined lexical processing in school-age children with ASD, SLI, and typical development, who were matched on receptive vocabulary. Children completed a lexical decision task, involving words with high and low semantic network sizes and nonwords. Children also completed nonverbal updating and shifting tasks. Children responded more accurately to words from high than from low semantic networks; however, follow-up analyses identified weaker semantic network effects in the SLI group. Additionally, updating and shifting abilities predicted lexical processing, demonstrating similarity in the mechanisms which underlie semantic processing in children with ASD, SLI, and typical development.

Lexical Processing in School-Age Children with Autism Spectrum Disorder and Children with Specific Language Impairment: The Role of Semantics

PubMed Central

Haebig, Eileen; Kaushanskaya, Margarita; Weismer, Susan Ellis

2016-01-01

Children with autism spectrum disorder (ASD) and specific language impairment (SLI) often have immature lexical-semantic knowledge; however, the organization of lexical-semantic knowledge is poorly understood. This study examined lexical processing in school-age children with ASD, SLI, and typical development, who were matched on receptive vocabulary. Children completed a lexical decision task, involving words with high and low semantic network sizes and nonwords. Children also completed nonverbal updating and shifting tasks. Children responded more accurately to words from high than from low semantic networks; however, follow-up analyses identified weaker semantic network effects in the SLI group. Additionally, updating and shifting abilities predicted lexical processing, demonstrating similarity in the mechanisms which underlie semantic processing in children with ASD, SLI, and typical development. PMID:26210517

Alcohol and behavioral control: cognitive and neural mechanisms.

PubMed

Vogel-Sprott, M; Easdon, C; Fillmore, M; Finn, P; Justus, A

2001-01-01

This article represents the proceedings of a symposium at the 2000 RSA Meeting in Denver, Colorado. The organizer/chair was Muriel Vogel-Sprott. The presentations were (1) Alcohol-induced impairment of inhibitory control: Some commonalities with attention deficit hyperactivity disorder, by Mark Fillmore; (2) Neural interactions that underlie response inhibition under alcohol: A functional magnetic resonance imaging investigation, by Craig Easdon; (3) Intentional control of behavior under alcohol, by Muriel Vogel-Sprott; and (4) Working memory and the disinhibiting effects of alcohol on passive avoidance learning, by Alicia Justius and Peter Finn.

Neuropsychology of reward learning and negative symptoms in schizophrenia.

PubMed

Nestor, Paul G; Choate, Victoria; Niznikiewicz, Margaret; Levitt, James J; Shenton, Martha E; McCarley, Robert W

2014-11-01

We used the Iowa Gambling Test (IGT) to examine the relationship of reward learning to both neuropsychological functioning and symptom formation in 65 individuals with schizophrenia. Results indicated that compared to controls, participants with schizophrenia showed significantly reduced reward learning, which in turn correlated with reduced intelligence, memory and executive function, and negative symptoms. The current findings suggested that a disease-related disturbance in reward learning may underlie both cognitive and motivation deficits, as expressed by neuropsychological impairment and negative symptoms in schizophrenia. Copyright © 2014 Elsevier B.V. All rights reserved.

A further assessment of decision-making in anorexia nervosa.

PubMed

Adoue, C; Jaussent, I; Olié, E; Beziat, S; Van den Eynde, F; Courtet, P; Guillaume, S

2015-01-01

Anorexia nervosa (AN) may be associated with impaired decision-making. Cognitive processes underlying this impairment remain unclear, mainly because previous assessments of this complex cognitive function were completed with a single test. Furthermore, clinical features such as mood status may impact this association. We aim to further explore the hypothesis of altered decision-making in AN. Sixty-three adult women with AN and 49 female controls completed a clinical assessment and were assessed by three tasks related to decision-making [Iowa Gambling Task (IGT), Balloon Analogue Risk Task (BART), Probabilistic Reversal Learning Task (PRLT)]. People with AN had poorer performance on the IGT and made less risky choices on the BART, whereas performances were not different on PRLT. Notably, AN patients with a current major depressive disorder showed similar performance to those with no current major depressive disorder. These results tend to confirm an impaired decision making-process in people with AN and suggest that various cognitive processes such as inhibition to risk-taking or intolerance of uncertainty may underlie this condition Furthermore, these impairments seem unrelated to the potential co-occurent major depressive disorders. Copyright © 2014 Elsevier Masson SAS. All rights reserved.

Personality impairment in male pedophiles.

PubMed

Cohen, Lisa J; McGeoch, Pamela G; Watras-Gans, Sniezyna; Acker, Sara; Poznansky, Olga; Cullen, Ken; Itskovich, Yelena; Galynker, Igor

2002-10-01

Despite the large body of literature on the psychological sequelae of childhood sexual abuse, the literature on the psychopathology of pedophiles is surprisingly underdeveloped. The present article explores the hypothesis that pedophiles evidence deficits in interpersonal functioning (lack of assertiveness and empathy, passive-aggressiveness) and in self-concept, which might contribute to the motivation for pedophilic acts, as well as elevated sociopathy, impulsivity, and propensity for cognitive distortions, which might underlie the inhibitory failure. Twenty male heterosexual pedophiles (DSM-IV criteria) recruited from an outpatient clinic for sex offenders were compared with 24 demographically similar, healthy male controls using 3 personality instruments: the Millon Clinical Multiaxial Inventory-II, the Dimensional Assessment of Personality Impairment-Questionnaire, and the Temperament and Character Inventory. The data suggested that pedophiles have impaired interpersonal functioning, specifically, reduced assertiveness and elevated passive-aggressiveness, as well as impaired self-concept. Regarding disinhibitory traits, pedophiles demonstrated elevated sociopathy and propensity for cognitive distortions. Our data are consistent with previous reports of pathologic personality traits in pedophiles and lend support to a hypothesis that such pathology is related to both motivation for and failure to inhibit pedophilic behavior. Such information could potentially have important treatment implications.

Dominance of objects over context in a mediotemporal lobe model of schizophrenia.

PubMed

Talamini, Lucia M; Meeter, Martijn

2009-08-04

A large body of evidence suggests impaired context processing in schizophrenia. Here we propose that this impairment arises from defective integration of mediotemporal 'what' and 'where' routes, carrying object and spatial information to the hippocampus. We have previously shown, in a mediotemporal lobe (MTL) model, that the abnormal connectivity between MTL regions observed in schizophrenia can explain the episodic memory deficits associated with the disorder. Here we show that the same neuropathology leads to several context processing deficits observed in patients with schizophrenia: 1) failure to choose subordinate stimuli over dominant ones when the former fit the context, 2) decreased contextual constraints in memory retrieval, as reflected in increased false alarm rates and 3) impaired retrieval of contextual information in source monitoring. Model analyses show that these deficits occur because the 'schizophrenic MTL' forms fragmented episodic representations, in which objects are overrepresented at the expense of spatial contextual information. These findings highlight the importance of MTL neuropathology in schizophrenia, demonstrating that it may underlie a broad spectrum of deficits, including context processing and memory impairments. It is argued that these processing deficits may contribute to central schizophrenia symptoms such as contextually inappropriate behavior, associative abnormalities, conversational drift, concreteness and delusions.

TVA-based assessment of visual attentional functions in developmental dyslexia

PubMed Central

Bogon, Johanna; Finke, Kathrin; Stenneken, Prisca

2014-01-01

There is an ongoing debate whether an impairment of visual attentional functions constitutes an additional or even an isolated deficit of developmental dyslexia (DD). Especially performance in tasks that require the processing of multiple visual elements in parallel has been reported to be impaired in DD. We review studies that used parameter-based assessment for identifying and quantifying impaired aspect(s) of visual attention that underlie this multi-element processing deficit in DD. These studies used the mathematical framework provided by the “theory of visual attention” (Bundesen, 1990) to derive quantitative measures of general attentional resources and attentional weighting aspects on the basis of behavioral performance in whole- and partial-report tasks. Based on parameter estimates in children and adults with DD, the reviewed studies support a slowed perceptual processing speed as an underlying primary deficit in DD. Moreover, a reduction in visual short term memory storage capacity seems to present a modulating component, contributing to difficulties in written language processing. Furthermore, comparing the spatial distributions of attentional weights in children and adults suggests that having limited reading and writing skills might impair the development of a slight leftward bias, that is typical for unimpaired adult readers. PMID:25360129

A Novel Approach for Studying the Physiology and Pathophysiology of Myelinated and Non-Myelinated Axons in the CNS White Matter.

PubMed

Li, Lijun; Velumian, Alexander A; Samoilova, Marina; Fehlings, Michael G

2016-01-01

Advances in brain connectomics set the need for detailed knowledge of functional properties of myelinated and non-myelinated (if present) axons in specific white matter pathways. The corpus callosum (CC), a major white matter structure interconnecting brain hemispheres, is extensively used for studying CNS axonal function. Unlike another widely used CNS white matter preparation, the optic nerve where all axons are myelinated, the CC contains also a large population of non-myelinated axons, making it particularly useful for studying both types of axons. Electrophysiological studies of optic nerve use suction electrodes on nerve ends to stimulate and record compound action potentials (CAPs) that adequately represent its axonal population, whereas CC studies use microelectrodes (MEs), recording from a limited area within the CC. Here we introduce a novel robust isolated "whole" CC preparation comparable to optic nerve. Unlike ME recordings where the CC CAP peaks representing myelinated and non-myelinated axons vary broadly in size, "whole" CC CAPs show stable reproducible ratios of these two main peaks, and also reveal a third peak, suggesting a distinct group of smaller caliber non-myelinated axons. We provide detailed characterization of "whole" CC CAPs and conduction velocities of myelinated and non-myelinated axons along the rostro-caudal axis of CC body and show advantages of this preparation for comparing axonal function in wild type and dysmyelinated shiverer mice, studying the effects of temperature dependence, bath-applied drugs and ischemia modeled by oxygen-glucose deprivation. Due to the isolation from gray matter, our approach allows for studying CC axonal function without possible "contamination" by reverberating signals from gray matter. Our analysis of "whole" CC CAPs revealed higher complexity of myelinated and non-myelinated axonal populations, not noticed earlier. This preparation may have a broad range of applications as a robust model for studying myelinated and non-myelinated axons of the CNS in various experimental models.

A Novel Approach for Studying the Physiology and Pathophysiology of Myelinated and Non-Myelinated Axons in the CNS White Matter

PubMed Central

Samoilova, Marina

2016-01-01

Advances in brain connectomics set the need for detailed knowledge of functional properties of myelinated and non-myelinated (if present) axons in specific white matter pathways. The corpus callosum (CC), a major white matter structure interconnecting brain hemispheres, is extensively used for studying CNS axonal function. Unlike another widely used CNS white matter preparation, the optic nerve where all axons are myelinated, the CC contains also a large population of non-myelinated axons, making it particularly useful for studying both types of axons. Electrophysiological studies of optic nerve use suction electrodes on nerve ends to stimulate and record compound action potentials (CAPs) that adequately represent its axonal population, whereas CC studies use microelectrodes (MEs), recording from a limited area within the CC. Here we introduce a novel robust isolated "whole" CC preparation comparable to optic nerve. Unlike ME recordings where the CC CAP peaks representing myelinated and non-myelinated axons vary broadly in size, "whole" CC CAPs show stable reproducible ratios of these two main peaks, and also reveal a third peak, suggesting a distinct group of smaller caliber non-myelinated axons. We provide detailed characterization of "whole" CC CAPs and conduction velocities of myelinated and non-myelinated axons along the rostro-caudal axis of CC body and show advantages of this preparation for comparing axonal function in wild type and dysmyelinated shiverer mice, studying the effects of temperature dependence, bath-applied drugs and ischemia modeled by oxygen-glucose deprivation. Due to the isolation from gray matter, our approach allows for studying CC axonal function without possible "contamination" by reverberating signals from gray matter. Our analysis of "whole" CC CAPs revealed higher complexity of myelinated and non-myelinated axonal populations, not noticed earlier. This preparation may have a broad range of applications as a robust model for studying myelinated and non-myelinated axons of the CNS in various experimental models. PMID:27829055

In vivo quantification of demyelination and recovery using compartment-specific diffusion MRI metrics validated by electron microscopy.

PubMed

Jelescu, Ileana O; Zurek, Magdalena; Winters, Kerryanne V; Veraart, Jelle; Rajaratnam, Anjali; Kim, Nathanael S; Babb, James S; Shepherd, Timothy M; Novikov, Dmitry S; Kim, Sungheon G; Fieremans, Els

2016-05-15

There is a need for accurate quantitative non-invasive biomarkers to monitor myelin pathology in vivo and distinguish myelin changes from other pathological features including inflammation and axonal loss. Conventional MRI metrics such as T2, magnetization transfer ratio and radial diffusivity have proven sensitivity but not specificity. In highly coherent white matter bundles, compartment-specific white matter tract integrity (WMTI) metrics can be directly derived from the diffusion and kurtosis tensors: axonal water fraction, intra-axonal diffusivity, and extra-axonal radial and axial diffusivities. We evaluate the potential of WMTI to quantify demyelination by monitoring the effects of both acute (6weeks) and chronic (12weeks) cuprizone intoxication and subsequent recovery in the mouse corpus callosum, and compare its performance with that of conventional metrics (T2, magnetization transfer, and DTI parameters). The changes observed in vivo correlated with those obtained from quantitative electron microscopy image analysis. A 6-week intoxication produced a significant decrease in axonal water fraction (p<0.001), with only mild changes in extra-axonal radial diffusivity, consistent with patchy demyelination, while a 12-week intoxication caused a more marked decrease in extra-axonal radial diffusivity (p=0.0135), consistent with more severe demyelination and clearance of the extra-axonal space. Results thus revealed increased specificity of the axonal water fraction and extra-axonal radial diffusivity parameters to different degrees and patterns of demyelination. The specificities of these parameters were corroborated by their respective correlations with microstructural features: the axonal water fraction correlated significantly with the electron microscopy derived total axonal water fraction (ρ=0.66; p=0.0014) but not with the g-ratio, while the extra-axonal radial diffusivity correlated with the g-ratio (ρ=0.48; p=0.0342) but not with the electron microscopy derived axonal water fraction. These parameters represent promising candidates as clinically feasible biomarkers of demyelination and remyelination in the white matter. Copyright © 2016 Elsevier Inc. All rights reserved.

Two different immunostaining patterns of beta-amyloid precursor protein (APP) may distinguish traumatic from nontraumatic axonal injury.

PubMed

Hayashi, Takahito; Ago, Kazutoshi; Nakamae, Takuma; Higo, Eri; Ogata, Mamoru

2015-09-01

Immunostaining for beta-amyloid precursor protein (APP) is recognized as an effective tool for detecting traumatic axonal injury, but it also detects axonal injury due to ischemic or other metabolic causes. Previously, we reported two different patterns of APP staining: labeled axons oriented along with white matter bundles (pattern 1) and labeled axons scattered irregularly (pattern 2) (Hayashi et al. (Leg Med (Tokyo) 11:S171-173, 2009). In this study, we investigated whether these two patterns are consistent with patterns of trauma and hypoxic brain damage, respectively. Sections of the corpus callosum from 44 cases of blunt head injury and equivalent control tissue were immunostained for APP. APP was detected in injured axons such as axonal bulbs and varicose axons in 24 of the 44 cases of head injuries that also survived for three or more hours after injury. In 21 of the 24 APP-positive cases, pattern 1 alone was observed in 14 cases, pattern 2 alone was not observed in any cases, and both patterns 1 and 2 were detected in 7 cases. APP-labeled injured axons were detected in 3 of the 44 control cases, all of which were pattern 2. These results suggest that pattern 1 indicates traumatic axonal injury, while pattern 2 results from hypoxic insult. These patterns may be useful to differentiate between traumatic and nontraumatic axonal injuries.

Mechanosensing is critical for axon growth in the developing brain

PubMed Central

Pillai, Eva K.; Sheridan, Graham K.; Svoboda, Hanno; Viana, Matheus; da F. Costa, Luciano; Guck, Jochen; Holt, Christine E.; Franze, Kristian

2016-01-01

During nervous system development, neurons extend axons along well-defined pathways. The current understanding of axon pathfinding is based mainly on chemical signalling. However, growing neurons interact not only chemically but also mechanically with their environment. Here we identify mechanical signals as important regulators of axon pathfinding. In vitro, substrate stiffness determined growth patterns of Xenopus retinal ganglion cell (RGC) axons. In vivo atomic force microscopy revealed striking stiffness gradient patterns in the embryonic brain. RGC axons grew towards the tissue’s softer side, which was reproduced in vitro in the absence of chemical gradients. To test the importance of mechanical signals for axon growth in vivo, we altered brain stiffness, blocked mechanotransduction pharmacologically, and knocked down the mechanosensitive ion channel Piezo1. All treatments resulted in aberrant axonal growth and pathfinding errors, suggesting that local tissue stiffness–read out by mechanosensitive ion channels–is critically involved in instructing neuronal growth in vivo. PMID:27643431

Pharmacogenetic stimulation of neuronal activity increases myelination in an axon-specific manner.

PubMed

Mitew, Stanislaw; Gobius, Ilan; Fenlon, Laura R; McDougall, Stuart J; Hawkes, David; Xing, Yao Lulu; Bujalka, Helena; Gundlach, Andrew L; Richards, Linda J; Kilpatrick, Trevor J; Merson, Tobias D; Emery, Ben

2018-01-22

Mounting evidence suggests that neuronal activity influences myelination, potentially allowing for experience-driven modulation of neural circuitry. The degree to which neuronal activity is capable of regulating myelination at the individual axon level is unclear. Here we demonstrate that stimulation of somatosensory axons in the mouse brain increases proliferation and differentiation of oligodendrocyte progenitor cells (OPCs) within the underlying white matter. Stimulated axons display an increased probability of being myelinated compared to neighboring non-stimulated axons, in addition to being ensheathed with thicker myelin. Conversely, attenuating neuronal firing reduces axonal myelination in a selective activity-dependent manner. Our findings reveal that the process of selecting axons for myelination is strongly influenced by the relative activity of individual axons within a population. These observed cellular changes are consistent with the emerging concept that adaptive myelination is a key mechanism for the fine-tuning of neuronal circuitry in the mammalian CNS.

Maximizing functional axon repair in the injured central nervous system: Lessons from neuronal development.

PubMed

Kaplan, Andrew; Bueno, Mardja; Hua, Luyang; Fournier, Alyson E

2018-01-01

The failure of damaged axons to regrow underlies disability in central nervous system injury and disease. Therapies that stimulate axon repair will be critical to restore function. Extensive axon regeneration can be induced by manipulation of oncogenes and tumor suppressors; however, it has been difficult to translate this into functional recovery in models of spinal cord injury. The current challenge is to maximize the functional integration of regenerating axons to recover motor and sensory behaviors. Insights into axonal growth and wiring during nervous system development are helping guide new approaches to boost regeneration and functional connectivity after injury in the mature nervous system. Here we discuss our current understanding of axonal behavior after injury and prospects for the development of drugs to optimize axon regeneration and functional recovery after CNS injury. Developmental Dynamics 247:18-23, 2018. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

Visualization of Motor Axon Navigation and Quantification of Axon Arborization In Mouse Embryos Using Light Sheet Fluorescence Microscopy.

PubMed

Liau, Ee Shan; Yen, Ya-Ping; Chen, Jun-An

2018-05-11

Spinal motor neurons (MNs) extend their axons to communicate with their innervating targets, thereby controlling movement and complex tasks in vertebrates. Thus, it is critical to uncover the molecular mechanisms of how motor axons navigate to, arborize, and innervate their peripheral muscle targets during development and degeneration. Although transgenic Hb9::GFP mouse lines have long served to visualize motor axon trajectories during embryonic development, detailed descriptions of the full spectrum of axon terminal arborization remain incomplete due to the pattern complexity and limitations of current optical microscopy. Here, we describe an improved protocol that combines light sheet fluorescence microscopy (LSFM) and robust image analysis to qualitatively and quantitatively visualize developing motor axons. This system can be easily adopted to cross genetic mutants or MN disease models with Hb9::GFP lines, revealing novel molecular mechanisms that lead to defects in motor axon navigation and arborization.

Identifying motor and sensory myelinated axons in rabbit peripheral nerves by histochemical staining for carbonic anhydrase and cholinesterase activities

NASA Technical Reports Server (NTRS)

Riley, Danny A.; Sanger, James R.; Matloub, Hani S.; Yousif, N. John; Bain, James L. W.

1988-01-01

Carbonic anhydrase (CA) and cholinesterase (CE) histochemical staining of rabbit spinal nerve roots and dorsal root ganglia demonstrated that among the reactive myeliated axons, with minor exceptions, sensory axons were CA positive and CE negative whereas motor axons were CA negative and CE positive. The high specificity was achieved by adjusting reaction conditions to stain subpopulations of myelinated axons selectively while leaving 50 percent or so unstained. Fixation with glutaraldehyde appeared necessary for achieving selectivity. Following sciatic nerve transection, the reciprocal staining pattern persisted in damaged axons and their regenerating processes which formed neuromas within the proximal nerve stump. Within the neuromas, CA-stained sensory processes were elaborated earlier and in greater numbers than CE-stained regenerating motor processes. The present results indicate that histochemical axon typing can be exploited to reveal heterogeneous responses of motor and sensory axons to injury.

Contribution of cytoskeletal elements to the axonal mechanical properties

PubMed Central

2013-01-01

Background Microtubules, microfilaments, and neurofilaments are cytoskeletal elements that affect cell morphology, cellular processes, and mechanical structures in neural cells. The objective of the current study was to investigate the contribution of each type of cytoskeletal element to the mechanical properties of axons of dorsal root and sympathetic ganglia cells in chick embryos. Results Microtubules, microfilaments, and neurofilaments in axons were disrupted by nocodazole, cytochalasin D, and acrylamide, respectively, or a combination of the three. An atomic force microscope (AFM) was then used to compress the treated axons, and the resulting corresponding force-deformation information was analyzed to estimate the mechanical properties of axons that were partially or fully disrupted. Conclusion We have found that the mechanical stiffness was most reduced in microtubules-disrupted-axons, followed by neurofilaments-disrupted- and microfilaments-disrupted-axons. This suggests that microtubules contribute the most of the mechanical stiffness to axons. PMID:24007256

Optic nerve regeneration in the mouse is a complex trait modulated by genetic background

PubMed Central

Wang, Jiaxing; Li, Ying; King, Rebecca; Struebing, Felix L.

2018-01-01

Purpose The present study is designed to identify the influences of genetic background on optic nerve regeneration using the two parental strains (C57BL/6J and DBA/2J) and seven BXD recombinant inbred mouse strains. Methods To study regeneration in the optic nerve, Pten was knocked down in the retinal ganglion cells using adenoassociated virus (AAV) delivery of shRNA, and a mild inflammatory response was induced with an intravitreal injection of zymosan with CPT-cAMP. The axons of the retinal ganglion cells were damaged by optic nerve crush (ONC). Following a 12-day survival period, regenerating axons were labeled by cholera toxin B, and 2 days later, the regenerating axons within the optic nerve were examined. The number of axons at 0.5 mm and 1 mm from the crush site were counted. In addition, we measured the distance that five axons had grown down the nerve and the longest distance a single axon reached. Results The analysis revealed a considerable amount of differential axonal regeneration across the seven BXD strains and the parental strains. There was a statistically significant difference (p=0.014 Mann–Whitney U test) in the regenerative capacity in the number of axons reaching 0.5 mm from a low of 236.1±24.4 axons in the BXD102 mice to a high of 759.8±79.2 axons in the BXD29 mice. There were also statistically significant differences (p=0.014 Mann–Whitney U test) in the distance axons traveled. Looking at a minimum of five axons, the shortest distance was 787.2±46.5 µm in the BXD102 mice, and the maximum distance was 2025.5±223.3 µm in the BXD29 mice. Conclusions Differences in genetic background can have a profound effect on axonal regeneration causing a threefold increase in the number of regenerating axons at 0.5 mm from the crush site and a 2.5-fold increase in the distance traveled by at least five axons in the damaged optic nerve. PMID:29463955

The L1-type cell adhesion molecule Neuroglian is necessary for maintenance of sensory axon advance in the Drosophila embryo.

PubMed

Martin, Veronica; Mrkusich, Eli; Steinel, Martin C; Rice, Jason; Merritt, David J; Whitington, Paul M

2008-04-08

Cell adhesion molecules have long been implicated in the regulation of axon growth, but the precise cellular roles played by individual cell adhesion molecules and the molecular basis for their action are still not well understood. We have used the sensory system of the Drosophila embryo to shed light on the mechanism by which the L1-type cell adhesion molecule Neuroglian regulates axon growth. We have found a highly penetrant sensory axon stalling phenotype in neuroglian mutant embryos. Axons stalled at a variety of positions along their normal trajectory, but most commonly in the periphery some distance along the peripheral nerve. All lateral and dorsal cluster sensory neurons examined, except for the dorsal cluster neuron dbd, showed stalling. Sensory axons were never seen to project along inappropriate pathways in neuroglian mutants and stalled axons showed normal patterns of fasciculation within nerves. The growth cones of stalled axons possessed a simple morphology, similar to their appearance in wild-type embryos when advancing along nerves. Driving expression of the wild-type form of Neuroglian in sensory neurons alone rescued the neuroglian mutant phenotype of both pioneering and follower neurons. A partial rescue was achieved by expressing the Neuroglian extracellular domain. Over/mis-expression of Neuroglian in all neurons, oenocytes or trachea had no apparent effect on sensory axon growth. We conclude that Neuroglian is necessary to maintain axon advance along axonal substrates, but is not required for initiation of axon outgrowth, axon fasciculation or recognition of correct growth substrates. Expression of Neuroglian in sensory neurons alone is sufficient to promote axon advance and the intracellular region of the molecule is largely dispensable for this function. It is unlikely, therefore, that Nrg acts as a molecular 'clutch' to couple adhesion of F-actin within the growth cone to the extracellular substrate. Rather, we suggest that Neuroglian mediates sensory axon advance by promoting adhesion of the surface of the growth cone to its substrate. Our finding that stalling of a pioneer sensory neuron is rescued by driving Neuroglian in sensory neurons alone may suggest that Neuroglian can act in a heterophilic fashion.

Heterogeneity of the Axon Initial Segment in Interneurons and Pyramidal Cells of Rodent Visual Cortex

PubMed Central

Höfflin, Felix; Jack, Alexander; Riedel, Christian; Mack-Bucher, Julia; Roos, Johannes; Corcelli, Corinna; Schultz, Christian; Wahle, Petra; Engelhardt, Maren

2017-01-01

The microdomain that orchestrates action potential initiation in neurons is the axon initial segment (AIS). It has long been considered to be a rather homogeneous domain at the very proximal axon hillock with relatively stable length, particularly in cortical pyramidal cells. However, studies in other brain regions paint a different picture. In hippocampal CA1, up to 50% of axons emerge from basal dendrites. Further, in about 30% of thick-tufted layer V pyramidal neurons in rat somatosensory cortex, axons have a dendritic origin. Consequently, the AIS is separated from the soma. Recent in vitro and in vivo studies have shown that cellular excitability is a function of AIS length/position and somatodendritic morphology, undermining a potentially significant impact of AIS heterogeneity for neuronal function. We therefore investigated neocortical axon morphology and AIS composition, hypothesizing that the initial observation of seemingly homogeneous AIS is inadequate and needs to take into account neuronal cell types. Here, we biolistically transfected cortical neurons in organotypic cultures to visualize the entire neuron and classify cell types in combination with immunolabeling against AIS markers. Using confocal microscopy and morphometric analysis, we investigated axon origin, AIS position, length, diameter as well as distance to the soma. We find a substantial AIS heterogeneity in visual cortical neurons, classified into three groups: (I) axons with somatic origin with proximal AIS at the axon hillock; (II) axons with somatic origin with distal AIS, with a discernible gap between the AIS and the soma; and (III) axons with dendritic origin (axon-carrying dendrite cell, AcD cell) and an AIS either starting directly at the axon origin or more distal to that point. Pyramidal cells have significantly longer AIS than interneurons. Interneurons with vertical columnar axonal projections have significantly more distal AIS locations than all other cells with their prevailing phenotype as an AcD cell. In contrast, neurons with perisomatic terminations display most often an axon originating from the soma. Our data contribute to the emerging understanding that AIS morphology is highly variable, and potentially a function of the cell type. PMID:29170630

The L1-type cell adhesion molecule Neuroglian is necessary for maintenance of sensory axon advance in the Drosophila embryo

PubMed Central

Martin, Veronica; Mrkusich, Eli; Steinel, Martin C; Rice, Jason; Merritt, David J; Whitington, Paul M

2008-01-01

Background Cell adhesion molecules have long been implicated in the regulation of axon growth, but the precise cellular roles played by individual cell adhesion molecules and the molecular basis for their action are still not well understood. We have used the sensory system of the Drosophila embryo to shed light on the mechanism by which the L1-type cell adhesion molecule Neuroglian regulates axon growth. Results We have found a highly penetrant sensory axon stalling phenotype in neuroglian mutant embryos. Axons stalled at a variety of positions along their normal trajectory, but most commonly in the periphery some distance along the peripheral nerve. All lateral and dorsal cluster sensory neurons examined, except for the dorsal cluster neuron dbd, showed stalling. Sensory axons were never seen to project along inappropriate pathways in neuroglian mutants and stalled axons showed normal patterns of fasciculation within nerves. The growth cones of stalled axons possessed a simple morphology, similar to their appearance in wild-type embryos when advancing along nerves. Driving expression of the wild-type form of Neuroglian in sensory neurons alone rescued the neuroglian mutant phenotype of both pioneering and follower neurons. A partial rescue was achieved by expressing the Neuroglian extracellular domain. Over/mis-expression of Neuroglian in all neurons, oenocytes or trachea had no apparent effect on sensory axon growth. Conclusion We conclude that Neuroglian is necessary to maintain axon advance along axonal substrates, but is not required for initiation of axon outgrowth, axon fasciculation or recognition of correct growth substrates. Expression of Neuroglian in sensory neurons alone is sufficient to promote axon advance and the intracellular region of the molecule is largely dispensable for this function. It is unlikely, therefore, that Nrg acts as a molecular 'clutch' to couple adhesion of F-actin within the growth cone to the extracellular substrate. Rather, we suggest that Neuroglian mediates sensory axon advance by promoting adhesion of the surface of the growth cone to its substrate. Our finding that stalling of a pioneer sensory neuron is rescued by driving Neuroglian in sensory neurons alone may suggest that Neuroglian can act in a heterophilic fashion. PMID:18397531

C. elegans dystroglycan coordinates responsiveness of follower axons to dorsal/ventral and anterior/posterior guidance cues

PubMed Central

Johnson, Robert P.; Kramer, James M.

2012-01-01

Neural development in metazoans is characterized by the establishment of initial process tracts by pioneer axons and the subsequent extension of follower axons along these pioneer processes. Mechanisms governing the fidelity of follower extension along pioneered routes are largely unknown. In C. elegans, formation of the right angle-shaped lumbar commissure connecting the lumbar and preanal ganglia is an example of pioneer/follower dynamics. We find that the dystroglycan ortholog DGN-1 mediates the fidelity of follower lumbar commissure axon extension along the pioneer axon route. In dgn-1 mutants, the axon of the pioneer PVQ neuron faithfully establishes the lumbar commissure, but axons of follower lumbar neurons, such as PVC, frequently bypass the lumbar commissure and extend along an oblique trajectory directly toward the preanal ganglion. In contrast, disruption of the UNC-6/netrin guidance pathway principally perturbs PVQ ventral guidance to pioneer the lumbar commissure. Loss of DGN-1 in unc-6 mutants has a quantitatively similar effect on follower axon guidance regardless of PVQ axon route, indicating that DGN-1 does not mediate follower/pioneer adhesion. Instead, DGN-1 appears to block premature responsiveness of follower axons to a preanal ganglion-directed guidance cue which mediates ventral-to-anterior reorientation of lumbar commissure axons. Deletion analysis shows that only the most N-terminal DGN-1 domain is required for these activities. These studies suggest that dystroglycan modulation of growth cone responsiveness to conflicting guidance cues is important for restricting follower axon extension to the tracts laid down by pioneers. PMID:22275151

The corpus callosum in primates: processing speed of axons and the evolution of hemispheric asymmetry

PubMed Central

Phillips, Kimberley A.; Stimpson, Cheryl D.; Smaers, Jeroen B.; Raghanti, Mary Ann; Jacobs, Bob; Popratiloff, Anastas; Hof, Patrick R.; Sherwood, Chet C.

2015-01-01

Interhemispheric communication may be constrained as brain size increases because of transmission delays in action potentials over the length of axons. Although one might expect larger brains to have progressively thicker axons to compensate, spatial packing is a limiting factor. Axon size distributions within the primate corpus callosum (CC) may provide insights into how these demands affect conduction velocity. We used electron microscopy to explore phylogenetic variation in myelinated axon density and diameter of the CC from 14 different anthropoid primate species, including humans. The majority of axons were less than 1 µm in diameter across all species, indicating that conduction velocity for most interhemispheric communication is relatively constant regardless of brain size. The largest axons within the upper 95th percentile scaled with a progressively higher exponent than the median axons towards the posterior region of the CC. While brain mass among the primates in our analysis varied by 97-fold, estimates of the fastest cross-brain conduction times, as conveyed by axons at the 95th percentile, varied within a relatively narrow range between 3 and 9 ms across species, whereas cross-brain conduction times for the median axon diameters differed more substantially between 11 and 38 ms. Nonetheless, for both size classes of axons, an increase in diameter does not entirely compensate for the delay in interhemispheric transmission time that accompanies larger brain size. Such biophysical constraints on the processing speed of axons conveyed by the CC may play an important role in the evolution of hemispheric asymmetry. PMID:26511047

Death Receptor 6 Promotes Wallerian Degeneration in Peripheral Axons.

PubMed

Gamage, Kanchana K; Cheng, Irene; Park, Rachel E; Karim, Mardeen S; Edamura, Kazusa; Hughes, Christopher; Spano, Anthony J; Erisir, Alev; Deppmann, Christopher D

2017-03-20

Axon degeneration during development is required to sculpt a functional nervous system and is also a hallmark of pathological insult, such as injury [1, 2]. Despite similar morphological characteristics, very little overlap in molecular mechanisms has been reported between pathological and developmental degeneration [3-5]. In the peripheral nervous system (PNS), developmental axon pruning relies on receptor-mediated extrinsic degeneration mechanisms to determine which axons are maintained or degenerated [5-7]. Receptors have not been implicated in Wallerian axon degeneration; instead, axon autonomous, intrinsic mechanisms are thought to be the primary driver for this type of axon disintegration [8-10]. Here we survey the role of neuronally expressed, paralogous tumor necrosis factor receptor super family (TNFRSF) members in Wallerian degeneration. We find that an orphan receptor, death receptor 6 (DR6), is required to drive axon degeneration after axotomy in sympathetic and sensory neurons cultured in microfluidic devices. We sought to validate these in vitro findings in vivo using a transected sciatic nerve model. Consistent with the in vitro findings, DR6 -/- animals displayed preserved axons up to 4 weeks after injury. In contrast to phenotypes observed in Wld s and Sarm1 -/- mice, preserved axons in DR6 -/- animals display profound myelin remodeling. This indicates that deterioration of axons and myelin after axotomy are mechanistically distinct processes. Finally, we find that JNK signaling after injury requires DR6, suggesting a link between this novel extrinsic pathway and the axon autonomous, intrinsic pathways that have become established for Wallerian degeneration. Copyright © 2017 Elsevier Ltd. All rights reserved.

Can injured adult CNS axons regenerate by recapitulating development?

PubMed

Hilton, Brett J; Bradke, Frank

2017-10-01

In the adult mammalian central nervous system (CNS), neurons typically fail to regenerate their axons after injury. During development, by contrast, neurons extend axons effectively. A variety of intracellular mechanisms mediate this difference, including changes in gene expression, the ability to form a growth cone, differences in mitochondrial function/axonal transport and the efficacy of synaptic transmission. In turn, these intracellular processes are linked to extracellular differences between the developing and adult CNS. During development, the extracellular environment directs axon growth and circuit formation. In adulthood, by contrast, extracellular factors, such as myelin and the extracellular matrix, restrict axon growth. Here, we discuss whether the reactivation of developmental processes can elicit axon regeneration in the injured CNS. © 2017. Published by The Company of Biologists Ltd.

Neuronal Growth and Behavioral Alterations in Mice Deficient for the Psychiatric Disease-Associated Negr1 Gene

PubMed Central

Singh, Katyayani; Loreth, Desirée; Pöttker, Bruno; Hefti, Kyra; Innos, Jürgen; Schwald, Kathrin; Hengstler, Heidi; Menzel, Lutz; Sommer, Clemens J.; Radyushkin, Konstantin; Kretz, Oliver; Philips, Mari-Anne; Haas, Carola A.; Frauenknecht, Katrin; Lilleväli, Kersti; Heimrich, Bernd; Vasar, Eero; Schäfer, Michael K. E.

2018-01-01

Neuronal growth regulator 1 (NEGR1), a member of the immunoglobulin superfamily cell adhesion molecule subgroup IgLON, has been implicated in neuronal growth and connectivity. In addition, genetic variants in or near the NEGR1 locus have been associated with obesity and more recently with learning difficulties, intellectual disability and psychiatric disorders. However, experimental evidence is lacking to support a possible link between NEGR1, neuronal growth and behavioral abnormalities. Initial expression analysis of NEGR1 mRNA in C57Bl/6 wildtype (WT) mice by in situ hybridization demonstrated marked expression in the entorhinal cortex (EC) and dentate granule cells. In co-cultures of cortical neurons and NSC-34 cells overexpressing NEGR1, neurite growth of cortical neurons was enhanced and distal axons occupied an increased area of cells overexpressing NEGR1. Conversely, in organotypic slice co-cultures, Negr1-knockout (KO) hippocampus was less permissive for axons grown from EC of β-actin-enhanced green fluorescent protein (EGFP) mice compared to WT hippocampus. Neuroanatomical analysis revealed abnormalities of EC axons in the hippocampal dentate gyrus (DG) of Negr1-KO mice including increased numbers of axonal projections to the hilus. Neurotransmitter receptor ligand binding densities, a proxy of functional neurotransmitter receptor abundance, did not show differences in the DG of Negr1-KO mice but altered ligand binding densities to NMDA receptor and muscarinic acetylcholine receptors M1 and M2 were found in CA1 and CA3. Activity behavior, anxiety-like behavior and sensorimotor gating were not different between genotypes. However, Negr1-KO mice exhibited impaired social behavior compared to WT littermates. Moreover, Negr1-KO mice showed reversal learning deficits in the Morris water maze and increased susceptibility to pentylenetetrazol (PTZ)-induced seizures. Thus, our results from neuronal growth assays, neuroanatomical analyses and behavioral assessments provide first evidence that deficiency of the psychiatric disease-associated Negr1 gene may affect neuronal growth and behavior. These findings might be relevant to further evaluate the role of NEGR1 in cognitive and psychiatric disorders. PMID:29479305

Role of Class III phosphoinositide 3-kinase in the brain development: possible involvement in specific learning disorders.

PubMed

Inaguma, Yutaka; Matsumoto, Ayumi; Noda, Mariko; Tabata, Hidenori; Maeda, Akihiko; Goto, Masahide; Usui, Daisuke; Jimbo, Eriko F; Kikkawa, Kiyoshi; Ohtsuki, Mamitaro; Momoi, Mariko Y; Osaka, Hitoshi; Yamagata, Takanori; Nagata, Koh-Ichi

2016-10-01

Class III phosphoinositide 3-kinase (PIK3C3 or mammalian vacuolar protein sorting 34 homolog, Vps34) regulates vesicular trafficking, autophagy, and nutrient sensing. Recently, we reported that PIK3C3 is expressed in mouse cerebral cortex throughout the developmental process, especially at early embryonic stage. We thus examined the role of PIK3C3 in the development of the mouse cerebral cortex. Acute silencing of PIK3C3 with in utero electroporation method caused positional defects of excitatory neurons during corticogenesis. Time-lapse imaging revealed that the abnormal positioning was at least partially because of the reduced migration velocity. When PIK3C3 was silenced in cortical neurons in one hemisphere, axon extension to the contralateral hemisphere was also delayed. These aberrant phenotypes were rescued by RNAi-resistant PIK3C3. Notably, knockdown of PIK3C3 did not affect the cell cycle of neuronal progenitors and stem cells at the ventricular zone. Taken together, PIK3C3 was thought to play a crucial role in corticogenesis through the regulation of excitatory neuron migration and axon extension. Meanwhile, when we performed comparative genomic hybridization on a patient with specific learning disorders, a 107 Kb-deletion was identified on 18q12.3 (nt. 39554147-39661206) that encompasses exons 5-23 of PIK3C3. Notably, the above aberrant migration and axon growth phenotypes were not rescued by the disease-related truncation mutant (172 amino acids) lacking the C-terminal kinase domain. Thus, functional defects of PIK3C3 might impair corticogenesis and relate to the pathophysiology of specific learning disorders and other neurodevelopmental disorders. Acute knockdown of Class III phosphoinositide 3-kinase (PIK3C3) evokes migration defects of excitatory neurons during corticogenesis. PIK3C3-knockdown also disrupts axon outgrowth, but not progenitor proliferation in vivo. Involvement of PIK3C3 in neurodevelopmental disorders might be an interesting future subject since a deletion mutation in PIK3C3 was detected in a patient with specific learning disorders (SLD). © 2016 International Society for Neurochemistry.

Human umbilical cord blood mononuclear cells and chorionic plate-derived mesenchymal stem cells promote axon survival in a rat model of optic nerve crush injury

PubMed Central

CHUNG, SOKJOONG; RHO, SEUNGSOO; KIM, GIJIN; KIM, SO-RA; BAEK, KWANG-HYUN; KANG, MYUNGSEO; LEW, HELEN

2016-01-01

The use of mesenchymal stem cells (MSCs) in cell therapy in regenerative medicine has great potential, particularly in the treatment of nerve injury. Umbilical cord blood (UCB) reportedly contains stem cells, which have been widely used as a hematopoietic source and may have therapeutic potential for neurological impairment. Although ongoing research is dedicated to the management of traumatic optic nerve injury using various measures, novel therapeutic strategies based on the complex underlying mechanisms responsible for optic nerve injury, such as inflammation and/or ischemia, are required. In the present study, a rat model of optic nerve crush (ONC) injury was established in order to examine the effects of transplanting human chorionic plate-derived MSCs (CP-MSCs) isolated from the placenta, as well as human UCB mononuclear cells (CB-MNCs) on compressed rat optic nerves. Expression markers for inflammation, apoptosis, and optic nerve regeneration were analyzed, as well as the axon survival rate by direct counting. Increased axon survival rates were observed following the injection of CB-MNCs at at 1 week post-transplantation compared with the controls. The levels of growth-associated protein-43 (GAP-43) were increased after the injection of CB-MNCs or CP-MSCs compared with the controls, and the expression levels of hypoxia-inducible factor-1α (HIF-1α) were also significantly increased following the injection of CB-MNCs or CP-MSCs. ERM-like protein (ERMN) and SLIT-ROBO Rho GTPase activating protein 2 (SRGAP2) were found to be expressed in the optic nerves of the CP-MSC-injected rats with ONC injury. The findings of our study suggest that the administration of CB-MNCs or CP-MSCs may promote axon survival through systemic concomitant mechanisms involving GAP-43 and HIF-1α. Taken together, these findings provide further understanding of the mechanisms repsonsible for optic nerve injury and may aid in the development of novel cell-based therapeutic strategies with future applications in regenerative medicine, particularly in the management of optic nerve disorders. PMID:26986762

Mutations in COA7 cause spinocerebellar ataxia with axonal neuropathy.

PubMed

Higuchi, Yujiro; Okunushi, Ryuta; Hara, Taichi; Hashiguchi, Akihiro; Yuan, Junhui; Yoshimura, Akiko; Murayama, Kei; Ohtake, Akira; Ando, Masahiro; Hiramatsu, Yu; Ishihara, Satoshi; Tanabe, Hajime; Okamoto, Yuji; Matsuura, Eiji; Ueda, Takehiro; Toda, Tatsushi; Yamashita, Sumimasa; Yamada, Kenichiro; Koide, Takashi; Yaguchi, Hiroaki; Mitsui, Jun; Ishiura, Hiroyuki; Yoshimura, Jun; Doi, Koichiro; Morishita, Shinichi; Sato, Ken; Nakagawa, Masanori; Yamaguchi, Masamitsu; Tsuji, Shoji; Takashima, Hiroshi

2018-06-01

Several genes related to mitochondrial functions have been identified as causative genes of neuropathy or ataxia. Cytochrome c oxidase assembly factor 7 (COA7) may have a role in assembling mitochondrial respiratory chain complexes that function in oxidative phosphorylation. Here we identified four unrelated patients with recessive mutations in COA7 among a Japanese case series of 1396 patients with Charcot-Marie-Tooth disease (CMT) or other inherited peripheral neuropathies, including complex forms of CMT. We also found that all four patients had characteristic neurological features of peripheral neuropathy and ataxia with cerebellar atrophy, and some patients showed leukoencephalopathy or spinal cord atrophy on MRI scans. Validated mutations were located at highly conserved residues among different species and segregated with the disease in each family. Nerve conduction studies showed axonal sensorimotor neuropathy. Sural nerve biopsies showed chronic axonal degeneration with a marked loss of large and medium myelinated fibres. An immunohistochemical assay with an anti-COA7 antibody in the sural nerve from the control patient showed the positive expression of COA7 in the cytoplasm of Schwann cells. We also observed mildly elevated serum creatine kinase levels in all patients and the presence of a few ragged-red fibres and some cytochrome c oxidase-negative fibres in a muscle biopsy obtained from one patient, which was suggestive of subclinical mitochondrial myopathy. Mitochondrial respiratory chain enzyme assay in skin fibroblasts from the three patients showed a definitive decrease in complex I or complex IV. Immunocytochemical analysis of subcellular localization in HeLa cells indicated that mutant COA7 proteins as well as wild-type COA7 were localized in mitochondria, which suggests that mutant COA7 does not affect the mitochondrial recruitment and may affect the stability or localization of COA7 interaction partners in the mitochondria. In addition, Drosophila COA7 (dCOA7) knockdown models showed rough eye phenotype, reduced lifespan, impaired locomotive ability and shortened synaptic branches of motor neurons. Our results suggest that loss-of-function COA7 mutation is responsible for the phenotype of the presented patients, and this new entity of disease would be referred to as spinocerebellar ataxia with axonal neuropathy type 3.

Deletion of the Fractalkine Receptor, CX3CR1, Improves Endogenous Repair, Axon Sprouting, and Synaptogenesis after Spinal Cord Injury in Mice

PubMed Central

Wei, Ping; Guan, Zhen

2017-01-01

Impaired signaling via CX3CR1, the fractalkine receptor, promotes recovery after traumatic spinal contusion injury in mice, a benefit achieved in part by reducing macrophage-mediated injury at the lesion epicenter. Here, we tested the hypothesis that CX3CR1-dependent changes in microglia and macrophage functions also will enhance neuroplasticity, at and several segments below the injury epicenter. New data show that in the presence of inflammatory stimuli, CX3CR1-deficient (CX3CR1−/−) microglia and macrophages adopt a reparative phenotype and increase expression of genes that encode neurotrophic and gliogenic proteins. At the lesion epicenter (mid-thoracic spinal cord), the microenvironment created by CX3CR1−/− microglia/macrophages enhances NG2 cell responses, axon sparing, and sprouting of serotonergic axons. In lumbar spinal cord, inflammatory signaling is reduced in CX3CR1−/− microglia. This is associated with reduced dendritic pathology and improved axonal and synaptic plasticity on ventral horn motor neurons. Together, these data indicate that CX3CR1, a microglia-specific chemokine receptor, is a novel therapeutic target for enhancing neuroplasticity and recovery after SCI. Interventions that specifically target CX3CR1 could reduce the adverse effects of inflammation and augment activity-dependent plasticity and restoration of function. Indeed, limiting CX3CR1-dependent signaling could improve rehabilitation and spinal learning. SIGNIFICANCE STATEMENT Published data show that genetic deletion of CX3CR1, a microglia-specific chemokine receptor, promotes recovery after traumatic spinal cord injury in mice, a benefit achieved in part by reducing macrophage-mediated injury at the lesion epicenter. Data in the current manuscript indicate that CX3CR1 deletion changes microglia and macrophage function, creating a tissue microenvironment that enhances endogenous repair and indices of neuroplasticity, at and several segments below the injury epicenter. Interventions that specifically target CX3CR1 might be used in the future to reduce the adverse effects of intraspinal inflammation and augment activity-dependent plasticity (e.g., rehabilitation) and restoration of function. PMID:28264978

L1CAM/Neuroglian controls the axon–axon interactions establishing layered and lobular mushroom body architecture

PubMed Central

Siegenthaler, Dominique; Enneking, Eva-Maria; Moreno, Eliza

2015-01-01

The establishment of neuronal circuits depends on the guidance of axons both along and in between axonal populations of different identity; however, the molecular principles controlling axon–axon interactions in vivo remain largely elusive. We demonstrate that the Drosophila melanogaster L1CAM homologue Neuroglian mediates adhesion between functionally distinct mushroom body axon populations to enforce and control appropriate projections into distinct axonal layers and lobes essential for olfactory learning and memory. We addressed the regulatory mechanisms controlling homophilic Neuroglian-mediated cell adhesion by analyzing targeted mutations of extra- and intracellular Neuroglian domains in combination with cell type–specific rescue assays in vivo. We demonstrate independent and cooperative domain requirements: intercalating growth depends on homophilic adhesion mediated by extracellular Ig domains. For functional cluster formation, intracellular Ankyrin2 association is sufficient on one side of the trans-axonal complex whereas Moesin association is likely required simultaneously in both interacting axonal populations. Together, our results provide novel mechanistic insights into cell adhesion molecule–mediated axon–axon interactions that enable precise assembly of complex neuronal circuits. PMID:25825519

Functional ionotropic glutamate receptors on peripheral axons and myelin.

PubMed

Christensen, Pia Crone; Welch, Nicole Cheryl; Brideau, Craig; Stys, Peter K

2016-09-01

Neurotransmitter-dependent signaling is traditionally restricted to axon terminals. However, receptors are present on myelinating glia, suggesting that chemical transmission may also occur along axons. Confocal microscopy and Ca(2+) -imaging using an axonally expressed FRET-based reporter was used to measure Ca(2+) changes and morphological alterations in myelin in response to stimulation of glutamate receptors. Activation of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) or N-methyl-D-aspartate (NMDA) receptors induced a Ca(2+) increase in axon cylinders. However, only the latter caused structural alterations in axons, despite similar Ca(2+) increases. Myelin morphology was significantly altered by NMDA receptor activation, but not by AMPA receptors. Cu(2+) ions influenced the NMDA receptor-dependent response, suggesting that this metal modulates axonal receptors. Glutamate increased ribosomal signal in Schwann cell cytoplasm. Axon cylinders and myelin of peripheral nervous system axons respond to glutamate, with a consequence being an increase in Schwann cell ribosomes. This may have implications for nerve pathology and regeneration. Muscle Nerve 54: 451-459, 2016. © 2016 Wiley Periodicals, Inc.

Axon growth regulation by a bistable molecular switch.

PubMed

Padmanabhan, Pranesh; Goodhill, Geoffrey J

2018-04-25

For the brain to function properly, its neurons must make the right connections during neural development. A key aspect of this process is the tight regulation of axon growth as axons navigate towards their targets. Neuronal growth cones at the tips of developing axons switch between growth and paused states during axonal pathfinding, and this switching behaviour determines the heterogeneous axon growth rates observed during brain development. The mechanisms controlling this switching behaviour, however, remain largely unknown. Here, using mathematical modelling, we predict that the molecular interaction network involved in axon growth can exhibit bistability, with one state representing a fast-growing growth cone state and the other a paused growth cone state. Owing to stochastic effects, even in an unchanging environment, model growth cones reversibly switch between growth and paused states. Our model further predicts that environmental signals could regulate axon growth rate by controlling the rates of switching between the two states. Our study presents a new conceptual understanding of growth cone switching behaviour, and suggests that axon guidance may be controlled by both cell-extrinsic factors and cell-intrinsic growth regulatory mechanisms. © 2018 The Author(s).

Validity of hearing impairment calculation methods for prediction of self-reported hearing handicap.

PubMed

John, Andrew B; Kreisman, Brian M; Pallett, Stephen

2012-01-01

Worker's compensation for hearing loss caused by occupational noise exposure is calculated by varying methods, from state to state within the United States (US), with many employing arithmetic formulas based on the pure-tone audiogram, to quantify hearing loss. Several assumptions unsupported or weakly supported by empirical data underlie these formulas. The present study evaluated the ability of various arithmetic hearing impairment calculations to predict a self-reported hearing handicap in a sample of presenting with sensorineural hearing loss. 204 adults (127 male, 77 female) ranging in age from 18 to 94 served as participants. The sample was selected to exclude patients who had been referred for hearing testing for a medicolegal examination or a hearing conservation appointment. A hearing handicap was measured by the Hearing Handicap Inventory for Adults/for the Elderly (HHIA/E). The covariance analysis of linear structural equations was used to assess the relative strength of correlation with the HHIA/E score among the six formulas and various forms of pure-tone average. The results revealed that all the hearing impairment calculations examined were significantly, but weakly, correlated with the self-reported hearing impairment scores. No significant differences among the predictive abilities of the impairment calculations were evident; however, the average binaural impairment assigned differed significantly among the six calculations examined. Individuals who demonstrated 0% impairment had significantly lower (i.e., better) HHIA/E scores compared to those with non-zero impairment for each formula. These results supported the idea that audiometric data provided an insufficient explanation for real-world hearing difficulties.

Drosophila melanogaster Hedgehog cooperates with Frazzled to guide axons through a non-canonical signalling pathway.

PubMed

Ricolo, Delia; Butí, Elisenda; Araújo, Sofia J

2015-08-01

We report that the morphogen Hedgehog (Hh) is an axonal chemoattractant in the midline of Drosophila melanogaster embryos. Hh is present in the ventral nerve cord during axonal guidance and overexpression of hh in the midline causes ectopic midline crossing of FasII-positive axonal tracts. In addition, we show that Hh influences axonal guidance via a non-canonical signalling pathway dependent on Ptc. Our results reveal that the Hh pathway cooperates with the Netrin/Frazzled pathway to guide axons through the midline in invertebrates. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

Calcium overloading in traumatic axonal injury by lateral head rotation: a morphological evidence in rat model.

PubMed

He, Xiao-Sheng; Xiang, Zhang; Zhou, Fei; Fu, Luo-An; Shuang, Wang

2004-05-01

The study investigated morphologically axonal calcium overloading and its relationship with axonal structural changes. Twelve SD rats were divided into an injury and a sham group. The rat model of traumatic axonal injury (TAI) by lateral head rotation was produced. The oxalate-pyroantimonate technique for calcium localization was used to process the rat's medulla oblongata tissues with thin sections observed electron-microscopically for axonal structure and calcium precipitates on it. The axonal damage in medulla oblongata appeared at 2 h post-injury, gradually became diffuse and severe, and continued to exist at 24 hours. At 2 hours, calcium precipitates were deposited on separated lamellae and axolemma, but were rarely distributed in the axoplasm. At 6 hours, calcium precipitates occurred on separated lamellae and axolemma in much higher density, but on axoplasm in extremely small amounts. Some axons, though lacking structural changes of the myelin sheath, sequestered plenty of calcium deposits on their swollen mitochondria. At 24 hours, damaged axons presented with much more severe lamellae separation and calcium deposits. Axonal calcium overloading developed in rat TAI model using lateral head rotation. This was significantly related to structural damage in the axons. These findings suggest the feasibility of using calcium antagonists in cope the management of human DAI in its very early stage.

Activation of epidermal growth factor receptor mediates receptor axon sorting and extension in the developing olfactory system of the moth Manduca sexta.

PubMed

Gibson, Nicholas J; Tolbert, Leslie P

2006-04-10

During development of the adult olfactory system of the moth Manduca sexta, olfactory receptor neurons extend axons from the olfactory epithelium in the antenna into the brain. As they arrive at the brain, interactions with centrally derived glial cells cause axons to sort and fasciculate with other axons destined to innervate the same glomeruli. Here we report studies indicating that activation of the epidermal growth factor receptor (EGFR) is involved in axon ingrowth and targeting. Blocking the EGFR kinase domain pharmacologically leads to stalling of many axons in the sorting zone and nerve layer as well as abnormal axonal fasciculation in the sorting zone. We also find that neuroglian, an IgCAM known to activate the EGFR through homophilic interactions in other systems, is transiently present on olfactory receptor neuron axons and on glia during the critical stages of the sorting process. The neuroglian is resistant to extraction with Triton X-100 in the sorting zone and nerve layer, possibly indicating its stabilization by homophilic binding in these regions. Our results suggest a mechanism whereby neuroglian molecules on axons and possibly sorting zone glia bind homophilically, leading to activation of EGFRs, with subsequent effects on axon sorting, pathfinding, and extension, and glomerulus development. Copyright 2006 Wiley-Liss, Inc.

Activation of EGF Receptor Mediates Receptor Axon Sorting and Extension in the Developing Olfactory System of the Moth Manduca sexta

PubMed Central

Gibson, Nicholas J.; Tolbert, Leslie P.

2008-01-01

During development of the adult olfactory system of the moth Manduca sexta, olfactory receptor neurons extend axons from the olfactory epithelium in the antenna into the brain. As they arrive at the brain, interactions with centrally-derived glial cells cause axons to sort and fasciculate with other axons destined to innervate the same glomeruli. Here we report studies that indicate that activation of the epidermal growth factor receptor (EGFR) is involved in axon ingrowth and targeting. Blocking the EGFR kinase domain pharmacologically leads to stalling of many axons in the sorting zone and nerve layer, as well as abnormal axonal fasciculation in the sorting zone. We also find that neuroglian, an IgCAM known to activate the EGFR through homophilic interactions in other systems, is transiently present on olfactory receptor neuron axons and on glia during the critical stages of the sorting process. The neuroglian is resistant to extraction with Triton X-100 in the sorting zone and nerve layer, possibly indicating its stabilization by homophilic binding in these regions. Our results suggest a mechanism whereby neuroglian molecules on axons and possibly sorting zone glia bind homophilically, leading to activation of EGFRs with subsequent effects on axon sorting, pathfinding, and extension, and glomerulus development. PMID:16498681

Antidromic propagation of action potentials in branched axons: implications for the mechanisms of action of deep brain stimulation.

PubMed

Grill, Warren M; Cantrell, Meredith B; Robertson, Matthew S

2008-02-01

Electrical stimulation of the central nervous system creates both orthodromically propagating action potentials, by stimulation of local cells and passing axons, and antidromically propagating action potentials, by stimulation of presynaptic axons and terminals. Our aim was to understand how antidromic action potentials navigate through complex arborizations, such as those of thalamic and basal ganglia afferents-sites of electrical activation during deep brain stimulation. We developed computational models to study the propagation of antidromic action potentials past the bifurcation in branched axons. In both unmyelinated and myelinated branched axons, when the diameters of each axon branch remained under a specific threshold (set by the antidromic geometric ratio), antidromic propagation occurred robustly; action potentials traveled both antidromically into the primary segment as well as "re-orthodromically" into the terminal secondary segment. Propagation occurred across a broad range of stimulation frequencies, axon segment geometries, and concentrations of extracellular potassium, but was strongly dependent on the geometry of the node of Ranvier at the axonal bifurcation. Thus, antidromic activation of axon terminals can, through axon collaterals, lead to widespread activation or inhibition of targets remote from the site of stimulation. These effects should be included when interpreting the results of functional imaging or evoked potential studies on the mechanisms of action of DBS.

Diffuse traumatic axonal injury in mice induces complex behavioural alterations that are normalized by neutralization of interleukin-1β.

PubMed

Ekmark-Lewén, Sara; Flygt, Johanna; Fridgeirsdottir, Gudrun A; Kiwanuka, Olivia; Hånell, Anders; Meyerson, Bengt J; Mir, Anis K; Gram, Hermann; Lewén, Anders; Clausen, Fredrik; Hillered, Lars; Marklund, Niklas

2016-04-01

Widespread traumatic axonal injury (TAI) results in brain network dysfunction, which commonly leads to persisting cognitive and behavioural impairments following traumatic brain injury (TBI). TBI induces a complex neuroinflammatory response, frequently located at sites of axonal pathology. The role of the pro-inflammatory cytokine interleukin (IL)-1β has not been established in TAI. An IL-1β-neutralizing or a control antibody was administered intraperitoneally at 30 min following central fluid percussion injury (cFPI), a mouse model of widespread TAI. Mice subjected to moderate cFPI (n = 41) were compared with sham-injured controls (n = 20) and untreated, naive mice (n = 9). The anti-IL-1β antibody reached the target brain regions in adequate therapeutic concentrations (up to ~30 μg/brain tissue) at 24 h post-injury in both cFPI (n = 5) and sham-injured (n = 3) mice, with lower concentrations at 72 h post-injury (up to ~18 μg/g brain tissue in three cFPI mice). Functional outcome was analysed with the multivariate concentric square field (MCSF) test at 2 and 9 days post-injury, and the Morris water maze (MWM) at 14-21 days post-injury. Following TAI, the IL-1β-neutralizing antibody resulted in an improved behavioural outcome, including normalized behavioural profiles in the MCSF test. The performance in the MWM probe (memory) trial was improved, although not in the learning trials. The IL-1β-neutralizing treatment did not influence cerebral ventricle size or the number of microglia/macrophages. These findings support the hypothesis that IL-1β is an important contributor to the processes causing complex cognitive and behavioural disturbances following TAI. © 2016 Federation of European Neuroscience Societies and John Wiley & Sons Ltd.

Motor cortex electrical stimulation augments sprouting of the corticospinal tract and promotes recovery of motor function

PubMed Central

Carmel, Jason B.; Martin, John H.

2014-01-01

The corticospinal system—with its direct spinal pathway, the corticospinal tract (CST) – is the primary system for controlling voluntary movement. Our approach to CST repair after injury in mature animals was informed by our finding that activity drives establishment of connections with spinal cord circuits during postnatal development. After incomplete injury in maturity, spared CST circuits sprout, and partially restore lost function. Our approach harnesses activity to augment this injury-dependent CST sprouting and to promote function. Lesion of the medullary pyramid unilaterally eliminates all CST axons from one hemisphere and allows examination of CST sprouting from the unaffected hemisphere. We discovered that 10 days of electrical stimulation of either the spared CST or motor cortex induces CST axon sprouting that partially reconstructs the lost CST. Stimulation also leads to sprouting of the cortical projection to the magnocellular red nucleus, where the rubrospinal tract originates. Coordinated outgrowth of the CST and cortical projections to the red nucleus could support partial re-establishment of motor systems connections to the denervated spinal motor circuits. Stimulation restores skilled motor function in our animal model. Lesioned animals have a persistent forelimb deficit contralateral to pyramidotomy in the horizontal ladder task. Rats that received motor cortex stimulation either after acute or chronic injury showed a significant functional improvement that brought error rate to pre-lesion control levels. Reversible inactivation of the stimulated motor cortex reinstated the impairment demonstrating the importance of the stimulated system to recovery. Motor cortex electrical stimulation is an effective approach to promote spouting of spared CST axons. By optimizing activity-dependent sprouting in animals, we could have an approach that can be translated to the human for evaluation with minimal delay. PMID:24994971

Alpha-Synuclein Pathology in Sensory Nerve Terminals of the Upper Aerodigestive Tract of Parkinson’s Disease Patients

PubMed Central

Mu, Liancai; Chen, Jingming; Sobotka, Stanislaw; Nyirenda, Themba; Benson, Brian; Gupta, Fiona; Sanders, Ira; Adler, Charles H.; Caviness, John N.; Shill, Holly A.; Sabbagh, Marwan; Samanta, Johan E.; Sue, Lucia I.; Beach, Thomas G.

2015-01-01

Dysphagia is common in Parkinson’s disease (PD) and causes significant morbidity and mortality. PD dysphagia has usually been explained as dysfunction of central motor control, much like other motor symptoms that are characteristic of the disease. However, PD dysphagia does not correlate with severity of motor symptoms nor does it respond to motor therapies. It is known that PD patients have sensory deficits in the pharynx, and that impaired sensation may contribute to dysphagia. However, the underlying cause of the pharyngeal sensory deficits in PD is not known. We hypothesized that PD dysphagia with sensory deficits may be due to degeneration of the sensory nerve terminals in the upper aerodigestive tract (UAT). We have previously shown that Lewy-type synucleinopathy (LTS) is present in the main pharyngeal sensory nerves of PD patients, but not in controls. In this study, the sensory terminals in UAT mucosa were studied to discern the presence and distribution of LTS. Whole-mount specimens (tongue-pharynx-larynx-upper esophagus) were obtained from 10 deceased human subjects with clinically diagnosed and neuropathologically confirmed PD (five with dysphagia and five without) and four age-matched healthy controls. Samples were taken from six sites and immunostained for phosphorylated α-synuclein (PAS). The results showed the presence of PAS-immunoreactive (PAS-ir) axons in all the PD subjects and in none of the controls. Notably, PD patients with dysphagia had more PAS-ir axons in the regions that are critical for initiating the swallowing reflex. These findings suggest that Lewy pathology affects mucosal sensory axons in specific regions of the UAT and may be related to PD dysphagia. PMID:26041249

Altered distribution of ATG9A and accumulation of axonal aggregates in neurons from a mouse model of AP-4 deficiency syndrome

PubMed Central

De Pace, Raffaella; Damme, Markus; Mattera, Rafael; Jarnik, Michal; Hoffmann, Victoria; Morris, H. Douglas; Han, Tae-Un; Mancini, Grazia M. S.; Buonanno, Andrés

2018-01-01

The hereditary spastic paraplegias (HSP) are a clinically and genetically heterogeneous group of disorders characterized by progressive lower limb spasticity. Mutations in subunits of the heterotetrameric (ε-β4-μ4-σ4) adaptor protein 4 (AP-4) complex cause an autosomal recessive form of complicated HSP referred to as “AP-4 deficiency syndrome”. In addition to lower limb spasticity, this syndrome features intellectual disability, microcephaly, seizures, thin corpus callosum and upper limb spasticity. The pathogenetic mechanism, however, remains poorly understood. Here we report the characterization of a knockout (KO) mouse for the AP4E1 gene encoding the ε subunit of AP-4. We find that AP-4 ε KO mice exhibit a range of neurological phenotypes, including hindlimb clasping, decreased motor coordination and weak grip strength. In addition, AP-4 ε KO mice display a thin corpus callosum and axonal swellings in various areas of the brain and spinal cord. Immunohistochemical analyses show that the transmembrane autophagy-related protein 9A (ATG9A) is more concentrated in the trans-Golgi network (TGN) and depleted from the peripheral cytoplasm both in skin fibroblasts from patients with mutations in the μ4 subunit of AP-4 and in various neuronal types in AP-4 ε KO mice. ATG9A mislocalization is associated with increased tendency to accumulate mutant huntingtin (HTT) aggregates in the axons of AP-4 ε KO neurons. These findings indicate that the AP-4 ε KO mouse is a suitable animal model for AP-4 deficiency syndrome, and that defective mobilization of ATG9A from the TGN and impaired autophagic degradation of protein aggregates might contribute to neuroaxonal dystrophy in this disorder. PMID:29698489

Loss of Magel2 impairs the development of hypothalamic Anorexigenic circuits.

PubMed

Maillard, Julien; Park, Soyoung; Croizier, Sophie; Vanacker, Charlotte; Cook, Joshua H; Prevot, Vincent; Tauber, Maithe; Bouret, Sebastien G

2016-08-01

Prader-Willi syndrome (PWS) is a genetic disorder characterized by a variety of physiological and behavioral dysregulations, including hyperphagia, a condition that can lead to life-threatening obesity. Feeding behavior is a highly complex process with multiple feedback loops that involve both peripheral and central systems. The arcuate nucleus of the hypothalamus (ARH) is critical for the regulation of homeostatic processes including feeding, and this nucleus develops during neonatal life under of the influence of both environmental and genetic factors. Although much attention has focused on the metabolic and behavioral outcomes of PWS, an understanding of its effects on the development of hypothalamic circuits remains elusive. Here, we show that mice lacking Magel2, one of the genes responsible for the etiology of PWS, display an abnormal development of ARH axonal projections. Notably, the density of anorexigenic α-melanocyte-stimulating hormone axons was reduced in adult Magel2-null mice, while the density of orexigenic agouti-related peptide fibers in the mutant mice appeared identical to that in control mice. On the basis of previous findings showing a pivotal role for metabolic hormones in hypothalamic development, we also measured leptin and ghrelin levels in Magel2-null and control neonates and found that mutant mice have normal leptin and ghrelin levels. In vitro experiments show that Magel2 directly promotes axon growth. Together, these findings suggest that a loss of Magel2 leads to the disruption of hypothalamic feeding circuits, an effect that appears to be independent of the neurodevelopmental effects of leptin and ghrelin and likely involves a direct neurotrophic effect of Magel2. © The Author 2016. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Alpha-Synuclein Pathology in Sensory Nerve Terminals of the Upper Aerodigestive Tract of Parkinson's Disease Patients.

PubMed

Mu, Liancai; Chen, Jingming; Sobotka, Stanislaw; Nyirenda, Themba; Benson, Brian; Gupta, Fiona; Sanders, Ira; Adler, Charles H; Caviness, John N; Shill, Holly A; Sabbagh, Marwan; Samanta, Johan E; Sue, Lucia I; Beach, Thomas G

2015-08-01

Dysphagia is common in Parkinson's disease (PD) and causes significant morbidity and mortality. PD dysphagia has usually been explained as dysfunction of central motor control, much like other motor symptoms that are characteristic of the disease. However, PD dysphagia does not correlate with severity of motor symptoms nor does it respond to motor therapies. It is known that PD patients have sensory deficits in the pharynx, and that impaired sensation may contribute to dysphagia. However, the underlying cause of the pharyngeal sensory deficits in PD is not known. We hypothesized that PD dysphagia with sensory deficits may be due to degeneration of the sensory nerve terminals in the upper aerodigestive tract (UAT). We have previously shown that Lewy-type synucleinopathy (LTS) is present in the main pharyngeal sensory nerves of PD patients, but not in controls. In this study, the sensory terminals in UAT mucosa were studied to discern the presence and distribution of LTS. Whole-mount specimens (tongue-pharynx-larynx-upper esophagus) were obtained from 10 deceased human subjects with clinically diagnosed and neuropathologically confirmed PD (five with dysphagia and five without) and four age-matched healthy controls. Samples were taken from six sites and immunostained for phosphorylated α-synuclein (PAS). The results showed the presence of PAS-immunoreactive (PAS-ir) axons in all the PD subjects and in none of the controls. Notably, PD patients with dysphagia had more PAS-ir axons in the regions that are critical for initiating the swallowing reflex. These findings suggest that Lewy pathology affects mucosal sensory axons in specific regions of the UAT and may be related to PD dysphagia.

A Critical Period for Postnatal Adaptive Plasticity in a Model of Motor Axon Miswiring

PubMed Central

Castiblanco-Urbina, Maria A.; Winzeck, Stefan; Sundermeier, Julia; Theis, Fabian J.; Fouad, Karim; Huber, Andrea B.

2015-01-01

The correct wiring of neuronal circuits is of crucial importance for precise neuromuscular functionality. Therefore, guidance cues provide tight spatiotemporal control of axon growth and guidance. Mice lacking the guidance cue Semaphorin 3F (Sema3F) display very specific axon wiring deficits of motor neurons in the medial aspect of the lateral motor column (LMCm). While these deficits have been investigated extensively during embryonic development, it remained unclear how Sema3F mutant mice cope with these errors postnatally. We therefore investigated whether these animals provide a suitable model for the exploration of adaptive plasticity in a system of miswired neuronal circuitry. We show that the embryonically developed wiring deficits in Sema3F mutants persist until adulthood. As a consequence, these mutants display impairments in motor coordination that improve during normal postnatal development, but never reach wildtype levels. These improvements in motor coordination were boosted to wildtype levels by housing the animals in an enriched environment starting at birth. In contrast, a delayed start of enriched environment housing, at 4 weeks after birth, did not similarly affect motor performance of Sema3F mutants. These results, which are corroborated by neuroanatomical analyses, suggest a critical period for adaptive plasticity in neuromuscular circuitry. Interestingly, the formation of perineuronal nets, which are known to close the critical period for plastic changes in other systems, was not altered between the different housing groups. However, we found significant changes in the number of excitatory synapses on limb innervating motor neurons. Thus, we propose that during the early postnatal phase, when perineuronal nets have not yet been formed around spinal motor neurons, housing in enriched environment conditions induces adaptive plasticity in the motor system by the formation of additional synaptic contacts, in order to compensate for coordination deficits. PMID:25874621

The role of melatonin in the neurodevelopmental etiology of schizophrenia: A study in human olfactory neuronal precursors.

PubMed

Galván-Arrieta, Tania; Trueta, Citlali; Cercós, Montserrat G; Valdés-Tovar, Marcela; Alarcón, Salvador; Oikawa, Julian; Zamudio-Meza, Horacio; Benítez-King, Gloria

2017-10-01

Dim light exposure of the mother during pregnancy has been proposed as one of the environmental factors that affect the fetal brain development in schizophrenia. Melatonin circulating levels are regulated by the environmental light/dark cycle. This hormone stimulates neuronal differentiation in the adult brain. However, little is known about its role in the fetal human brain development. Olfactory neuronal precursors (ONPs) are useful for studying the physiopathology of neuropsychiatric diseases because they mimic all the stages of neurodevelopment in culture. Here, we first characterized whether melatonin stimulates neuronal differentiation in cloned ONPs obtained from a healthy control subject (HCS). Then, melatonin effects were evaluated in primary cultures of ONPs derived from a patient diagnosed with schizophrenia (SZ) and an age- and gender-matched HCS. Axonal formation was evidenced morphologically by tau immunostaining and by GSK3β phosphorylated state. Potassium-evoked secretion was assessed as a functional feature of differentiated neurons. As well, we report the expression of MT1/2 receptors in human ONPs for the first time. Melatonin stimulated axonal formation and ramification in cloned ONPs through a receptor-mediated mechanism and enhanced the amount and velocity of axonal and somatic secretion. SZ ONPs displayed reduced axogenesis associated with lower levels of pGSK3β and less expression of melatonergic receptors regarding the HCS ONPs. Melatonin counteracted this reduction in SZ cells. Altogether, our results show that melatonin signaling is crucial for functional differentiation of human ONPs, strongly suggesting that a deficit of this indoleamine may lead to an impaired neurodevelopment which has been associated with the etiology of schizophrenia. © 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Sexual divergence in microtubule function: the novel intranasal microtubule targeting SKIP normalizes axonal transport and enhances memory.

PubMed

Amram, N; Hacohen-Kleiman, G; Sragovich, S; Malishkevich, A; Katz, J; Touloumi, O; Lagoudaki, R; Grigoriadis, N C; Giladi, E; Yeheskel, A; Pasmanik-Chor, M; Jouroukhin, Y; Gozes, I

2016-10-01

Activity-dependent neuroprotective protein (ADNP), essential for brain formation, is a frequent autism spectrum disorder (ASD)-mutated gene. ADNP associates with microtubule end-binding proteins (EBs) through its SxIP motif, to regulate dendritic spine formation and brain plasticity. Here, we reveal SKIP, a novel four-amino-acid peptide representing an EB-binding site, as a replacement therapy in an outbred Adnp-deficient mouse model. We discovered, for the first time, axonal transport deficits in Adnp(+/-) mice (measured by manganese-enhanced magnetic resonance imaging), with significant male-female differences. RNA sequencing evaluations showed major age, sex and genotype differences. Function enrichment and focus on major gene expression changes further implicated channel/transporter function and the cytoskeleton. In particular, a significant maturation change (1 month-five months) was observed in beta1 tubulin (Tubb1) mRNA, only in Adnp(+/+) males, and sex-dependent increase in calcium channel mRNA (Cacna1e) in Adnp(+/+) males compared with females. At the protein level, the Adnp(+/-) mice exhibited impaired hippocampal expression of the calcium channel (voltage-dependent calcium channel, Cacnb1) as well as other key ASD-linked genes including the serotonin transporter (Slc6a4), and the autophagy regulator, BECN1 (Beclin1), in a sex-dependent manner. Intranasal SKIP treatment normalized social memory in 8- to 9-month-old Adnp(+/-)-treated mice to placebo-control levels, while protecting axonal transport and ameliorating changes in ASD-like gene expression. The control, all d-amino analog D-SKIP, did not mimic SKIP activity. SKIP presents a novel prototype for potential ASD drug development, a prevalent unmet medical need.

IgM-monoclonal gammopathy neuropathy and tremor: A first epidemiologic case control study

PubMed Central

Ahlskog, Matthew C.; Kumar, Neeraj; Mauermann, Michelle L.; Klein, Christopher J.

2012-01-01

Introduction Small case series suggest tremor occurs frequently in IgM-monoclonal gammopathy of undetermined significance (IgM-MGUS) neuropathy. Epidemiologic study to confirm this association is lacking. Whether the neuropathy or another remote IgM-effect is causal remains unsettled. Materials and methods An IgM-MGUS neuropathy case cohort (n=207) was compared to age, gender, and neuropathy impairment score (NIS) matched, other-cause neuropathy controls (n=414). Tremor details were extracted from structured neurologic evaluation. All patients underwent nerve conductions. Results Tremor occurrence was significantly higher in IgM-MGUS case cohort (29%) than in control cohort (9.2%) (p=0.001). In IgM-MGUS cases, tremor was associated with worse NIS (p=0.025) and demyelinating nerve conductions (p=0.020), but 11 of 60 (18%) IgM-MGUS cases with tremor had axonal neuropathy. In other-cause neuropathy controls, tremor was associated with axonal nerve conductions (p=0.03) but not with NIS severity (p=0.57). Tremor occurrence associated with older age in controls, (p=0.004) but not in IgM-MGUS cases (p=0.272). Most IgM-MGUS tremor cases (49/60) had a postural-kinetic tremor, 8 had rest tremor, 3 had mixed rest-action. Alternative causes of tremor was identified in 42% of IgM-MGUS cases, the most common type is inherited essential tremor 6/60 (p=0.04). Conclusions This first epidemiologic case-control study validates association between IgM-MGUS neuropathy and tremor. Among IgM-MGUS neuropathy cases, severity as well as type of neuropathy (demyelinating over axonal) correlated with tremor occurrence. IgM-MGUS paraproteinemia may increase tremor expression in persons recognized with common other risk factors for tremor. PMID:22475624

DISC1 Causes Associative Memory and Neurodevelopmental Defects in Fruit Flies

PubMed Central

Furukubo-Tokunaga, Katsuo; Kurita, Kazuki; Honjo, Ken; Pandey, Himani; Ando, Tetsuya; Takayama, Kojiro; Arai, Yuko; Mochizuki, Hiroaki; Ando, Mai; Kamiya, Atsushi; Sawa, Akira

2016-01-01

Originally found in a Scottish family with diverse mental disorders, the DISC1 protein has been characterized as an intracellular scaffold protein that associates with diverse binding partners in neural development. To explore its functions in a genetically tractable system, we expressed the human DISC1 in fruit flies (Drosophila melanogaster). As in mammalian neurons, DISC1 is localized to diverse subcellular domains of developing fly neurons including the nuclei, axons and dendrites. Overexpression of DISC1 impairs associative memory. Experiments with deletion/mutation constructs have revealed the importance of amino terminal domain (46–290) for memory suppression whereas carboxyl domain (598–854) and the amino terminal residues (1–45) including the nuclear localization signal (NLS1) are dispensable. DISC1 overexpression also causes suppression of axonal and dendritic branching of mushroom body neurons, which mediate a variety of cognitive functions in the fly brain. Analyses with deletion constructs reveal that protein domains 598–854 and 349–402 are both required for the suppression of axonal branching while amino-terminal domains including NLS1 are dispensable. In contrast, NLS1 was required for the suppression of dendritic branching, suggesting a mechanism involving gene expression. Moreover, domain 403–596 is also required for the suppression of dendritic branching. We also show that overexpression of DISC1 suppresses glutamatergic synaptogenesis in developing neuromuscular junctions. Deletion/mutation experiments have revealed the importance of protein domains 403–596 and 349–402 for synaptic suppression, while amino terminal domains including NLS1 are dispensable. Finally, we show that DISC1 functionally interacts with the fly homolog of Dysbindin (DTNBP1) via direct protein-protein interaction in developing synapses. PMID:26976042

Peak alpha frequency is a neural marker of cognitive function across the autism spectrum.

PubMed

Dickinson, Abigail; DiStefano, Charlotte; Senturk, Damla; Jeste, Shafali Spurling

2018-03-01

Cognitive function varies substantially and serves as a key predictor of outcome and response to intervention in autism spectrum disorder (ASD), yet we know little about the neurobiological mechanisms that underlie cognitive function in children with ASD. The dynamics of neuronal oscillations in the alpha range (6-12 Hz) are associated with cognition in typical development. Peak alpha frequency is also highly sensitive to developmental changes in neural networks, which underlie cognitive function, and therefore, it holds promise as a developmentally sensitive neural marker of cognitive function in ASD. Here, we measured peak alpha band frequency under a task-free condition in a heterogeneous sample of children with ASD (N = 59) and age-matched typically developing (TD) children (N = 38). At a group level, peak alpha frequency was decreased in ASD compared to TD children. Moreover, within the ASD group, peak alpha frequency correlated strongly with non-verbal cognition. As peak alpha frequency reflects the integrity of neural networks, our results suggest that deviations in network development may underlie cognitive function in individuals with ASD. By shedding light on the neurobiological correlates of cognitive function in ASD, our findings lay the groundwork for considering peak alpha frequency as a useful biomarker of cognitive function within this population which, in turn, will facilitate investigations of early markers of cognitive impairment and predictors of outcome in high risk infants. © 2017 Federation of European Neuroscience Societies and John Wiley & Sons Ltd.

Learning to swim, again: Axon regeneration in fish.

PubMed

Rasmussen, Jeffrey P; Sagasti, Alvaro

2017-01-01

Damage to the central nervous system (CNS) of fish can often be repaired to restore function, but in mammals recovery from CNS injuries usually fails due to a lack of axon regeneration. The relatively growth-permissive environment of the fish CNS may reflect both the absence of axon inhibitors found in the mammalian CNS and the presence of pro-regenerative environmental factors. Despite their different capacities for axon regeneration, many of the physiological processes, intrinsic molecular pathways, and cellular behaviors that control an axon's ability to regrow are conserved between fish and mammals. Fish models have thus been useful both for identifying factors differing between mammals and fish that may account for differences in CNS regeneration and for characterizing conserved intrinsic pathways that regulate axon regeneration in all vertebrates. The majority of adult axon regeneration studies have focused on the optic nerve or spinal axons of the teleosts goldfish and zebrafish, which have been productive models for identifying genes associated with axon regeneration, cellular mechanisms of circuit reestablishment, and the basis of functional recovery. Lampreys, which are jawless fish lacking myelin, have provided an opportunity to study regeneration of well defined spinal cord circuits. Newer larval zebrafish models offer numerous genetic tools and the ability to monitor the dynamic behaviors of extrinsic cell types regulating axon regeneration in live animals. Recent advances in imaging and gene editing methods are making fish models yet more powerful for investigating the cellular and molecular underpinnings of axon regeneration. Copyright © 2016 Elsevier Inc. All rights reserved.

Antisense Morpholino Oligonucleotides Reduce Neurofilament Synthesis and Inhibit Axon Regeneration in Lamprey Reticulospinal Neurons.

PubMed

Zhang, Guixin; Jin, Li-qing; Hu, Jianli; Rodemer, William; Selzer, Michael E

2015-01-01

The sea lamprey has been used as a model for the study of axonal regeneration after spinal cord injury. Previous studies have suggested that, unlike developing axons in mammal, the tips of regenerating axons in lamprey spinal cord are simple in shape, packed with neurofilaments (NFs), and contain very little F-actin. Thus it has been proposed that regeneration of axons in the central nervous system of mature vertebrates is not based on the canonical actin-dependent pulling mechanism of growth cones, but involves an internal protrusive force, perhaps generated by the transport or assembly of NFs in the distal axon. In order to assess this hypothesis, expression of NFs was manipulated by antisense morpholino oligonucleotides (MO). A standard, company-supplied MO was used as control. Axon retraction and regeneration were assessed at 2, 4 and 9 weeks after MOs were applied to a spinal cord transection (TX) site. Antisense MO inhibited NF180 expression compared to control MO. The effect of inhibiting NF expression on axon retraction and regeneration was studied by measuring the distance of axon tips from the TX site at 2 and 4 weeks post-TX, and counting the number of reticulospinal neurons (RNs) retrogradely labeled by fluorescently-tagged dextran injected caudal to the injury at 9 weeks post-TX. There was no statistically significant effect of MO on axon retraction at 2 weeks post-TX. However, at both 4 and 9 weeks post-TX, inhibition of NF expression inhibited axon regeneration.

Axonal ensheathment and septate junction formation in the peripheral nervous system of Drosophila.

PubMed

Banerjee, Swati; Pillai, Anilkumar M; Paik, Raehum; Li, Jingjun; Bhat, Manzoor A

2006-03-22

Axonal insulation is critical for efficient action potential propagation and normal functioning of the nervous system. In Drosophila, the underlying basis of nerve ensheathment is the axonal insulation by glial cells and the establishment of septate junctions (SJs) between glial cell membranes. However, the details of the cellular and molecular mechanisms underlying axonal insulation and SJ formation are still obscure. Here, we report the characterization of axonal insulation in the Drosophila peripheral nervous system (PNS). Targeted expression of tau-green fluorescent protein in the glial cells and ultrastructural analysis of the peripheral nerves allowed us to visualize the glial ensheathment of axons. We show that individual or a group of axons are ensheathed by inner glial processes, which in turn are ensheathed by the outer perineurial glial cells. SJs are formed between the inner and outer glial membranes. We also show that Neurexin IV, Contactin, and Neuroglian are coexpressed in the peripheral glial membranes and that these proteins exist as a complex in the Drosophila nervous system. Mutations in neurexin IV, contactin, and neuroglian result in the disruption of blood-nerve barrier function in the PNS, and ultrastructural analyses of the mutant embryonic peripheral nerves show loss of glial SJs. Interestingly, the murine homologs of Neurexin IV, Contactin, and Neuroglian are expressed at the paranodal SJs and play a key role in axon-glial interactions of myelinated axons. Together, our data suggest that the molecular machinery underlying axonal insulation and axon-glial interactions may be conserved across species.

Axon Response to Guidance Cues Is Stimulated by Acetylcholine in Caenorhabditis elegans

PubMed Central

Xu, Yan; Ren, Xing-Cong; Quinn, Christopher C.; Wadsworth, William G.

2011-01-01

Gradients of acetylcholine can stimulate growth cone turning when applied to neurons grown in culture, and it has been suggested that acetylcholine could act as a guidance cue. However, the role acetylcholine plays in directing axon migrations in vivo is not clear. Here, we show that acetylcholine positively regulates signaling pathways that mediate axon responses to guidance cues in Caenorhabditis elegans. Mutations that disrupt acetylcholine synthesis, transportation, and secretion affect circumferential axon guidance of the AVM neuron and in these mutants exogenously supplied acetylcholine improves AVM circumferential axon guidance. These effects are not observed for the circumferential guidance of the DD and VD motor neuron axons, which are neighbors of the AVM axon. Circumferential guidance is directed by the UNC-6 (netrin) and SLT-1 (slit) extracellular cues, and exogenously supplied acetylcholine can improve AVM axon guidance in mutants when either UNC-6– or SLT-1–induced signaling is disrupted, but not when both signaling pathways are perturbed. Not in any of the mutants does exogenously supplied acetylcholine improve DD and VD axon guidance. The ability of acetylcholine to enhance AVM axon guidance only in the presence of either UNC-6 or SLT-1 indicates that acetylcholine potentiates UNC-6 and SLT-1 guidance activity, rather than acting itself as a guidance cue. Together, our results show that for specific neurons acetylcholine plays an important role in vivo as a modulator of axon responses to guidance cues. PMID:21868605

A HuD-ZBP1 ribonucleoprotein complex localizes GAP-43 mRNA into axons through its 3′ untranslated region AU-rich regulatory element

PubMed Central

Yoo, Soonmoon; Kim, Hak Hee; Kim, Paul; Donnelly, Christopher J.; Kalinski, Ashley L.; Vuppalanchi, Deepika; Park, Michael; Lee, Seung Joon; Merianda, Tanuja T.; Perrone-Bizzozero, Nora I.; Twiss, Jeffery L.

2013-01-01

Localized translation of axonal mRNAs contributes to developmental and regenerative axon growth. Although untranslated regions (UTRs) of many different axonal mRNAs appear to drive their localization, there has been no consensus RNA structure responsible for this localization. We recently showed that limited expression of ZBP1 protein restricts axonal localization of both β-actin and GAP-43 mRNAs. β-actin 3′UTR has a defined element for interaction with ZBP1, but GAP-43 mRNA shows no homology to this RNA sequence. Here, we show that an AU-rich element (ARE) in GAP-43’s 3′UTR is necessary and sufficient for its axonal localization. Axonal GAP-43 mRNA levels increase after in vivo injury, and GAP-43 mRNA shows an increased half-life in regenerating axons. GAP-43 mRNA interacts with both HuD and ZBP1, and HuD and ZBP1 coimmunoprecipitate in an RNA-dependent fashion. Reporter mRNA with the GAP-43 ARE competes with endogenous β-actin mRNA for axonal localization and decreases axon length and branching similar to the β-actin 3′UTR competing with endogenous GAP-43 mRNA. Conversely, overexpressing GAP-43 coding sequence with it’s 3′UTR ARE increases axonal elongation and this effect is lost when just the ARE is deleted from GAP-43’s 3′UTR. PMID:23586486

Pharmacologically inhibiting kinesin-5 activity with monastrol promotes axonal regeneration following spinal cord injury

PubMed Central

Xu, Chen; Klaw, Michelle C.; Lemay, Michel A.; Baas, Peter W.; Tom, Veronica J.

2014-01-01

While it is well established that the axons of adult neurons have a lower capacity for regrowth, some regeneration of certain CNS populations after spinal cord injury (SCI) is possible if their axons are provided with a permissive substrate, such as an injured peripheral nerve. While some axons readily regenerate into a peripheral nerve graft (PNG), these axons almost always stall at the distal interface and fail to re-innervate spinal cord tissue. Treatment of the glial scar at the distal graft interface with chondroitinase ABC (ChABC) can improve regeneration, but most regenerated axons need further stimulation to extend beyond the interface. Previous studies demonstrate that pharmacologically inhibiting kinesin-5, a motor protein best known for its essential role in mitosis but also expressed in neurons, with the pharmacological agent monastrol increases axon growth on inhibitory substrates in vitro. We sought to determine if monastrol treatment after a SCI improves functional axon regeneration. Animals received complete thoracic level 7 (T7) transections and PNGs and were treated intrathecally with ChABC and either monastrol or DMSO vehicle. We found that combining ChABC with monastrol significantly enhanced axon regeneration. However, there were no further improvements in function or enhanced c-Fos induction upon stimulation of spinal cord rostral to the transection. This indicates that monastrol improves ChABC-mediated axon regeneration but that further treatments are needed to enhance the integration of these regrown axons. PMID:25447935

Cell intrinsic control of axon regeneration

PubMed Central

Mar, Fernando M; Bonni, Azad; Sousa, Mónica M

2014-01-01

Although neurons execute a cell intrinsic program of axonal growth during development, following the establishment of connections, the developmental growth capacity declines. Besides environmental challenges, this switch largely accounts for the failure of adult central nervous system (CNS) axons to regenerate. Here, we discuss the cell intrinsic control of axon regeneration, including not only the regulation of transcriptional and epigenetic mechanisms, but also the modulation of local protein translation, retrograde and anterograde axonal transport, and microtubule dynamics. We further explore the causes underlying the failure of CNS neurons to mount a vigorous regenerative response, and the paradigms demonstrating the activation of cell intrinsic axon growth programs. Finally, we present potential mechanisms to support axon regeneration, as these may represent future therapeutic approaches to promote recovery following CNS injury and disease. PMID:24531721

Combination of Engineered Schwann Cell Grafts to Secrete Neurotrophin and Chondroitinase Promotes Axonal Regeneration and Locomotion after Spinal Cord Injury

PubMed Central

Pressman, Yelena; Moody, Alison; Berg, Randall; Muir, Elizabeth M.; Rogers, John H.; Ozawa, Hiroshi; Itoi, Eiji; Pearse, Damien D.; Bunge, Mary Bartlett

2014-01-01

Transplantation of Schwann cells (SCs) is a promising therapeutic strategy for spinal cord repair. SCs introduced into lesions support axon regeneration, but because these axons do not exit the transplant, additional approaches with SCs are needed. Here, we transplanted SCs genetically modified to secrete a bifunctional neurotrophin (D15A) and chondroitinase ABC (ChABC) into a subacute contusion injury in rats. We examined the effects of these modifications on graft volume, SC number, degradation of chondroitin sulfate proteoglycans (CSPGs), astrogliosis, SC myelination of axons, propriospinal and supraspinal axon numbers, locomotor outcome (BBB scoring, CatWalk gait analysis), and mechanical and thermal sensitivity on the hind paws. D15A secreted from transplanted SCs increased graft volume and SC number and myelinated axon number. SCs secreting ChABC significantly decreased CSPGs, led to some egress of SCs from the graft, and increased propriospinal and 5-HT-positive axons in the graft. SCs secreting both D15A and ChABC yielded the best responses: (1) the largest number of SC myelinated axons, (2) more propriospinal axons in the graft and host tissue around and caudal to it, (3) more corticospinal axons closer to the graft and around and caudal to it, (4) more brainstem neurons projecting caudal to the transplant, (5) increased 5-HT-positive axons in the graft and caudal to it, (6) significant improvement in aspects of locomotion, and (7) improvement in mechanical and thermal allodynia. This is the first evidence that the combination of SC transplants engineered to secrete neurotrophin and chondroitinase further improves axonal regeneration and locomotor and sensory function. PMID:24478364

Nogo-66 Receptor Antagonist Peptide (NEP1-40) Administration Promotes Functional Recovery and Axonal Growth After Lateral Funiculus Injury in the Adult Rat

PubMed Central

Cao, Y.; Shumsky, J. S.; Sabol, M. A.; Kushner, R. A.; Strittmatter, S.; Hamers, F. P. T.; Lee, D. H. S.; Rabacchi, S. A.; Murray, M.

2010-01-01

Objective The myelin protein Nogo inhibits axon regeneration by binding to its receptor (NgR) on axons. Intrathecal delivery of an NgR antagonist (NEP1-40) promotes growth of injured corticospinal axons and recovery of motor function following a dorsal hemisection. The authors used a similar design to examine recovery and repair after a lesion that interrupts the rubrospinal tract (RST). Methods Rats received a lateral funiculotomy at C4 and NEP1-40 or vehicle was delivered to the cervical spinal cord for 4 weeks. Outcome measures included motor and sensory tests and immunohistochemistry. Results Gait analysis showed recovery in the NEP1-40-treated group compared to operated controls, and a test of forelimb usage also showed a beneficial effect. The density of labeled RST axons increased ipsilaterally in the NEP1-40 group in the lateral funiculus rostral to the lesion and contralaterally in both gray and white matter. Thus, rubrospinal axons exhibited diminished dieback and/or growth up to the lesion site. This was accompanied by greater density of 5 HT and calcitonin gene-related peptide axons adjacent to and into the lesion/matrix site in the NEP1-40 group. Conclusions NgR blockade after RST injury is associated with axonal growth and/or diminished dieback of severed RST axons up to but not into or beyond the lesion/matrix site, and growth of serotonergic and dorsal root axons adjacent to and into the lesion/matrix site. NgR blockade also supported partial recovery of function. The authors’ results indicate that severed rubrospinal axons respond to NEP1-40 treatment but less robustly than corticospinal, raphe-spinal, or dorsal root axons. PMID:18056009

Herpes Simplex Virus Membrane Proteins gE/gI and US9 Act Cooperatively To Promote Transport of Capsids and Glycoproteins from Neuron Cell Bodies into Initial Axon Segments

PubMed Central

Howard, Paul W.; Howard, Tiffani L.

2013-01-01

Herpes simplex virus (HSV) and other alphaherpesviruses must move from sites of latency in ganglia to peripheral epithelial cells. How HSV navigates in neuronal axons is not well understood. Two HSV membrane proteins, gE/gI and US9, are key to understanding the processes by which viral glycoproteins, unenveloped capsids, and enveloped virions are transported toward axon tips. Whether gE/gI and US9 function to promote the loading of viral proteins onto microtubule motors in neuron cell bodies or to tether viral proteins onto microtubule motors within axons is not clear. One impediment to understanding how HSV gE/gI and US9 function in axonal transport relates to observations that gE−, gI−, or US9− mutants are not absolutely blocked in axonal transport. Mutants are significantly reduced in numbers of capsids and glycoproteins in distal axons, but there are less extensive effects in proximal axons. We constructed HSV recombinants lacking both gE and US9 that transported no detectable capsids and glycoproteins to distal axons and failed to spread from axon tips to adjacent cells. Live-cell imaging of a gE−/US9− double mutant that expressed fluorescent capsids and gB demonstrated >90% diminished capsids and gB in medial axons and no evidence for decreased rates of transport, stalling, or increased retrograde transport. Instead, capsids, gB, and enveloped virions failed to enter proximal axons. We concluded that gE/gI and US9 function in neuron cell bodies, in a cooperative fashion, to promote the loading of HSV capsids and vesicles containing glycoproteins and enveloped virions onto microtubule motors or their transport into proximal axons. PMID:23077321

Roof Plate-Derived Radial Glial-like Cells Support Developmental Growth of Rapidly Adapting Mechanoreceptor Ascending Axons.

PubMed

Kridsada, Kim; Niu, Jingwen; Haldipur, Parthiv; Wang, Zhiping; Ding, Long; Li, Jian J; Lindgren, Anne G; Herrera, Eloisa; Thomas, Gareth M; Chizhikov, Victor V; Millen, Kathleen J; Luo, Wenqin

2018-06-05

Spinal cord longitudinal axons comprise some of the longest axons in our body. However, mechanisms that drive this extra long-distance axonal growth are largely unclear. We found that ascending axons of rapidly adapting (RA) mechanoreceptors closely abut a previously undescribed population of roof plate-derived radial glial-like cells (RGLCs) in the spinal cord dorsal column, which form a network of processes enriched with growth-promoting factors. In dreher mutant mice that lack RGLCs, the lengths of ascending RA mechanoreceptor axon branches are specifically reduced, whereas their descending and collateral branches, and other dorsal column and sensory pathways, are largely unaffected. Because the number and intrinsic growth ability of RA mechanoreceptors are normal in dreher mice, our data suggest that RGLCs provide critical non-cell autonomous growth support for the ascending axons of RA mechanoreceptors. Together, our work identifies a developmental mechanism specifically required for long-range spinal cord longitudinal axons. Copyright © 2018 The Authors. Published by Elsevier Inc. All rights reserved.

Target-Derived Neurotrophins Coordinate Transcription and Transport of Bclw to Prevent Axonal Degeneration

PubMed Central

Cosker, Katharina E.; Pazyra-Murphy, Maria F.; Fenstermacher, Sara J.

2013-01-01

Establishment of neuronal circuitry depends on both formation and refinement of neural connections. During this process, target-derived neurotrophins regulate both transcription and translation to enable selective axon survival or elimination. However, it is not known whether retrograde signaling pathways that control transcription are coordinated with neurotrophin-regulated actions that transpire in the axon. Here we report that target-derived neurotrophins coordinate transcription of the antiapoptotic gene bclw with transport of bclw mRNA to the axon, and thereby prevent axonal degeneration in rat and mouse sensory neurons. We show that neurotrophin stimulation of nerve terminals elicits new bclw transcripts that are immediately transported to the axons and translated into protein. Bclw interacts with Bax and suppresses the caspase6 apoptotic cascade that fosters axonal degeneration. The scope of bclw regulation at the levels of transcription, transport, and translation provides a mechanism whereby sustained neurotrophin stimulation can be integrated over time, so that axonal survival is restricted to neurons connected within a stable circuit. PMID:23516285

GDF10 Is a Signal for Axonal Sprouting and Functional Recovery after Stroke

PubMed Central

Li, S; Nie, EH; Yin, Y; Benowitz, LI; Tung, S; Vinters, HV; Bahjat, FR; Stenzel-Poore, MP; Kawaguchi, R; Coppola, G; Carmichael, ST

2016-01-01

Stroke produces a limited process of neural repair. Axonal sprouting in cortex adjacent to the infarct is part of this recovery process, but the signal that initiates axonal sprouting is not known. Growth and Differentiation Factor 10 (GDF10) is induced in peri-infarct neurons in mouse, non-human primate and human. GDF10 promotes axonal outgrowth in vitro in mouse, rat and human neurons through TGFβRI/II signaling. Using pharmacogenetic gain and loss of function studies, GDF10 produces axonal sprouting and enhanced functional recovery after stroke; knocking down GDF10 blocks axonal sprouting and reduces recovery. RNA-seq from peri-infarct cortical neurons indicates that GDF10 downregulates PTEN and upregulates PI3 kinase signaling and induces specific axonal guidance molecules. Unsupervised genome-wide association analysis of the GDF10 transcriptome shows that it is not related to neurodevelopment but may partially overlap with other CNS injury patterns. GDF10 is a stroke-induced signal for axonal sprouting and functional recovery. PMID:26502261

Axonal Transport and Morphology: How Myelination gets Nerves into Shape

NASA Astrophysics Data System (ADS)

Jung, Peter; Zhao, Peng; Monsma, Paula; Brown, Tony

2011-03-01

The local caliber of mature axons is largely determined by neurofilament (NF) content. The axoskeleton, mainly consisting of NFs, however, is dynamic. NFs are assembled in the cell body and are transported by molecular motors on microtubule tracks along the axon at a slow rate of fractions of mm per day. We combine live cell fluorescent imaging techniques to access NF transport in myelinated and non-myelinated segments of axons with computational modeling of the active NF flow to show that a), myelination locally slows NF transport rates by regulating duty ratios and b), that the predicted increase in axon caliber agrees well with experiments. This study, for the first time, links NF kinetics directly to axonal morphology, providing a novel conceptual framework for the physical understanding of processes leading to the formation of axonal structures such as the ``Nodes of Ranvier'' as well as abnormal axonal swellings associated with neurodegenerative diseases like Amyotrophic lateral sclerosis (ALS). NSF grants # IOS-0818412(PJ) and IOS-0818653 (AB).

Reversing the Outcome of Synapse Elimination at Developing Neuromuscular Junctions In Vivo: Evidence for Synaptic Competition and Its Mechanism

PubMed Central

Turney, Stephen G.; Lichtman, Jeff W.

2012-01-01

During mammalian development, neuromuscular junctions and some other postsynaptic cells transition from multiple- to single-innervation as synaptic sites are exchanged between different axons. It is unclear whether one axon invades synaptic sites to drive off other inputs or alternatively axons expand their territory in response to sites vacated by other axons. Here we show that soon-to-be-eliminated axons rapidly reverse fate and grow to occupy vacant sites at a neuromuscular junction after laser removal of a stronger input. This reversal supports the idea that axons take over sites that were previously vacated. Indeed, during normal development we observed withdrawal followed by takeover. The stimulus for axon growth is not postsynaptic cell inactivity because axons grow into unoccupied sites even when target cells are functionally innervated. These results demonstrate competition at the synaptic level and enable us to provide a conceptual framework for understanding this form of synaptic plasticity. PMID:22745601

Axonal GABAA receptors.

PubMed

Trigo, Federico F; Marty, Alain; Stell, Brandon M

2008-09-01

Type A GABA receptors (GABA(A)Rs) are well established as the main inhibitory receptors in the mature mammalian forebrain. In recent years, evidence has accumulated showing that GABA(A)Rs are prevalent not only in the somatodendritic compartment of CNS neurons, but also in their axonal compartment. Evidence for axonal GABA(A)Rs includes new immunohistochemical and immunogold data: direct recording from single axonal terminals; and effects of local applications of GABA(A)R modulators on action potential generation, on axonal calcium signalling, and on neurotransmitter release. Strikingly, whereas presynaptic GABA(A)Rs have long been considered inhibitory, the new studies in the mammalian brain mostly indicate an excitatory action. Depending on the neuron that is under study, axonal GABA(A)Rs can be activated by ambient GABA, by GABA spillover, or by an autocrine action, to increase either action potential firing and/or transmitter release. In certain neurons, the excitatory effects of axonal GABA(A)Rs persist into adulthood. Altogether, axonal GABA(A)Rs appear as potent neuronal modulators of the mammalian CNS.

Age may contribute to the increased frequency of axonal Guillain-Barré syndrome.

PubMed

Hawkes, Maximiliano A; Wilken, Miguel; Vázquez, Gabriel; Farez, Mauricio F

2017-12-01

The frequency of axonal Guillain-Barré syndrome (GBS) varies among countries. Previous studies supporting the high frequency of axonal GBS in South America have been carried out with pediatric populations. We seek to determine the frequency of axonal GBS in both children and adults in South America. This is a retrospective cohort analysis of patients who were diagnosed with GBS between January 2006 and December 2013 in a neurological center in Buenos Aires, Argentina. Adults and children with a diagnosis of GBS were included and classified by applying Ho and colleagues' criteria 1 for axonal GBS. The study included 105 patients with GBS. Among 58 adults, only 5 individuals were classified as axonal GBS compared with 16 of 47 children. The frequency of axonal GBS was significantly higher in children than in adults (34% vs. 8.6%, P = 0.0001). As shown in a cohort of South American patients, age may impact the frequency of axonal GBS. Muscle Nerve 56: 1311-1313, 2017. © 2017 Wiley Periodicals, Inc.

Genetic analysis of an overlapping functional requirement for L1- and NCAM-type proteins during sensory axon guidance in Drosophila.

PubMed

Kristiansen, Lars V; Velasquez, Emma; Romani, Susana; Baars, Sigrid; Berezin, Vladimir; Bock, Elisabeth; Hortsch, Michael; Garcia-Alonso, Luis

2005-01-01

L1- and NCAM-type cell adhesion molecules represent distinct protein families that function as specific receptors for different axon guidance cues. However, both L1 and NCAM proteins promote axonal growth by inducing neuronal tyrosine kinase activity and are coexpressed in subsets of axon tracts in arthropods and vertebrates. We have studied the functional requirements for the Drosophila L1- and NCAM-type proteins, Neuroglian (Nrg) and Fasciclin II (FasII), during postembryonic sensory axon guidance. The rescue of the Neuroglian loss-of-function (LOF) phenotype by transgenically expressed L1- and NCAM-type proteins demonstrates a functional interchangeability between these proteins in Drosophila photoreceptor pioneer axons, where both proteins are normally coexpressed. In contrast, the ectopic expression of Fasciclin II in mechanosensory neurons causes a strong enhancement of the axonal misguidance phenotype. Moreover, our findings demonstrate that this functionally redundant specificity to mediate axon guidance has been conserved in their vertebrate homologs, L1-CAM and NCAM.

Cannabis and adolescent brain development.

PubMed

Lubman, Dan I; Cheetham, Ali; Yücel, Murat

2015-04-01

Heavy cannabis use has been frequently associated with increased rates of mental illness and cognitive impairment, particularly amongst adolescent users. However, the neurobiological processes that underlie these associations are still not well understood. In this review, we discuss the findings of studies examining the acute and chronic effects of cannabis use on the brain, with a particular focus on the impact of commencing use during adolescence. Accumulating evidence from both animal and human studies suggests that regular heavy use during this period is associated with more severe and persistent negative outcomes than use during adulthood, suggesting that the adolescent brain may be particularly vulnerable to the effects of cannabis exposure. As the endocannabinoid system plays an important role in brain development, it is plausible that prolonged use during adolescence results in a disruption in the normative neuromaturational processes that occur during this period. We identify synaptic pruning and white matter development as two processes that may be adversely impacted by cannabis exposure during adolescence. Potentially, alterations in these processes may underlie the cognitive and emotional deficits that have been associated with regular use commencing during adolescence. Copyright © 2014 Elsevier Inc. All rights reserved.

Exercise counteracts declining hippocampal function in aging and Alzheimer's disease.

PubMed

Intlekofer, Karlie A; Cotman, Carl W

2013-09-01

Alzheimer's disease (AD) afflicts more than 5.4 million Americans and ranks as the most common type of dementia (Thies and Bleiler, 2011), yet effective pharmacological treatments have not been identified. Substantial evidence indicates that physical activity enhances learning and memory for people of all ages, including individuals that suffer from cognitive impairment. The mechanisms that underlie these benefits have been explored using animal models, including transgenic models of AD. Accumulating research shows that physical activity reinstates hippocampal function by enhancing the expression of brain-derived neurotrophic factor (BDNF) and other growth factors that promote neurogenesis, angiogenesis, and synaptic plasticity. In addition, several studies have found that physical activity counteracts age- and AD-associated declines in mitochondrial and immune system function. A growing body of evidence also suggests that exercise interventions hold the potential to reduce the pathological features associated with AD. Taken together, animal and human studies indicate that exercise provides a powerful stimulus that can countervail the molecular changes that underlie the progressive loss of hippocampal function in advanced age and AD. 2012 Published by Elsevier Inc

Prevalence of Cognitive Impairment and Dementia in Malays - Epidemiology of Dementia in Singapore Study.

PubMed

Hilal, Saima; Tan, Chuen S; Xin, Xu; Amin, Shaik M; Wong, Tien Y; Chen, Christopher; Venketasubramanian, Narayanaswamy; Ikram, Mohammad K

2017-01-01

To study the prevalence of cognitive impairment and dementia in communitydwelling Malays from Singapore; and to examine differences in prevalence among Chinese and Malays. Subjects (≥ 60 years) - drawn from the Malay component of the on-going multiethnic Epidemiology of Dementia in Singapore study - were screened using locally validated Abbreviated Mental Test and Progressive Forgetfulness Questionnaire. Subsequently, screen-positive participants underwent detailed neuropsychological assessments and neuroimaging. Cognitive impairment no dementia (CIND) and dementia were diagnosed based on accepted criteria. A total of 966 Malay subjects were included, of whom 102 had CIND-mild, 135 CINDmoderate, and 27 dementia. The overall age-standardized prevalence of any cognitive impairment was 25.5%, including 2% of dementia. The prevalence of any cognitive impairment increased with age from 14·9% in those aged 60-64 years to 40.2% in age ≥80 years. Women had a higher prevalence of CIND and dementia than men. Compared to previously published data from EDIS on Chinese, Malay were nearly twice more likely to have any cognitive impairment (Odds ratios adjusted for age, demographic and cardiovascular risk factors, and ApoEε4 carrier: 2.03, 95% confidence interval: 1.48-2.77). Among elderly Malays, the overall prevalence of any cognitive impairment was 25.5%. Even with a similar protocol of recruitment and assessment and adjusting for known risk factors, the prevalence of cognitive impairment was higher in Malays compared to Chinese. Further research is needed to unravel other factors that may underlie these ethnic differences in the occurrence of cognitive impairment. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

Live Imaging of Calcium Dynamics during Axon Degeneration Reveals Two Functionally Distinct Phases of Calcium Influx

PubMed Central

Yamagishi, Yuya; Tessier-Lavigne, Marc

2015-01-01

Calcium is a key regulator of axon degeneration caused by trauma and disease, but its specific spatial and temporal dynamics in injured axons remain unclear. To clarify the function of calcium in axon degeneration, we observed calcium dynamics in single injured neurons in live zebrafish larvae and tested the temporal requirement for calcium in zebrafish neurons and cultured mouse DRG neurons. Using laser axotomy to induce Wallerian degeneration (WD) in zebrafish peripheral sensory axons, we monitored calcium dynamics from injury to fragmentation, revealing two stereotyped phases of axonal calcium influx. First, axotomy triggered a transient local calcium wave originating at the injury site. This initial calcium wave only disrupted mitochondria near the injury site and was not altered by expression of the protective WD slow (WldS) protein. Inducing multiple waves with additional axotomies did not change the kinetics of degeneration. In contrast, a second phase of calcium influx occurring minutes before fragmentation spread as a wave throughout the axon, entered mitochondria, and was abolished by WldS expression. In live zebrafish, chelating calcium after the first wave, but before the second wave, delayed the progress of fragmentation. In cultured DRG neurons, chelating calcium early in the process of WD did not alter degeneration, but chelating calcium late in WD delayed fragmentation. We propose that a terminal calcium wave is a key instructive component of the axon degeneration program. SIGNIFICANCE STATEMENT Axon degeneration resulting from trauma or neurodegenerative disease can cause devastating deficits in neural function. Understanding the molecular and cellular events that execute axon degeneration is essential for developing treatments to address these conditions. Calcium is known to contribute to axon degeneration, but its temporal requirements in this process have been unclear. Live calcium imaging in severed zebrafish neurons and temporally controlled pharmacological treatments in both zebrafish and cultured mouse sensory neurons revealed that axonal calcium influx late in the degeneration process regulates axon fragmentation. These findings suggest that temporal considerations will be crucial for developing treatments for diseases associated with axon degeneration. PMID:26558774

Blocked, delayed, or obstructed: What causes poor white matter development in intrauterine growth restricted infants?

PubMed

Tolcos, Mary; Petratos, Steven; Hirst, Jonathan J; Wong, Flora; Spencer, Sarah J; Azhan, Aminath; Emery, Ben; Walker, David W

2017-07-01

Poor white matter development in intrauterine growth restricted (IUGR) babies remains a major, untreated problem in neonatology. New therapies, guided by an understanding of the mechanisms that underlie normal and abnormal oligodendrocyte development and myelin formation, are required. Much of our knowledge of the mechanisms that underlie impaired myelination come from studies in adult demyelinating disease, preterm brain injury, or experimental models of hypoxia-ischemia. However, relatively less is known for IUGR which is surprising because IUGR is a leading cause of perinatal mortality and morbidity, second only to premature birth. IUGR is also a significant risk factor for the later development of cerebral palsy, and is a greater risk compared to some of the more traditionally researched antecedents - asphyxia and inflammation. Recent evidence suggests that the white matter injury and reduced myelination in the brains of some preterm babies is due to impaired maturation of oligodendrocytes thereby resulting in the reduced capacity to synthesize myelin. Therefore, it is not surprising that the hypomyelination observable in the central nervous system of IUGR infants has similarly lead to investigations identifying a delay or blockade in the progress of maturation of oligodendrocytes in these infants. This review will discuss current ideas thought to account for the poor myelination often present in the neonate's brain following IUGR, and discuss novel interventions that are promising as treatments that promote oligodendrocyte maturation, and thereby repair the myelination deficits that otherwise persist into infancy and childhood and lead to neurodevelopmental abnormalities. Copyright © 2017 Elsevier Ltd. All rights reserved.

Disrupted white matter structural connectivity in heroin abusers.

PubMed

Sun, Yan; Wang, Gui-Bin; Lin, Qi-Xiang; Lu, Lin; Shu, Ni; Meng, Shi-Qiu; Wang, Jun; Han, Hong-Bin; He, Yong; Shi, Jie

2017-01-01

Neurocognitive impairment is one of the factors that put heroin abusers at greater risk for relapse, and deficits in related functional brain connections have been found. However, the alterations in structural brain connections that may underlie these functional and neurocognitive impairments remain largely unknown. In the present study, we investigated topological organization alterations in the structural network of white matter in heroin abusers and examined the relationships between the network changes and clinical measures. We acquired diffusion tensor imaging datasets from 76 heroin abusers and 78 healthy controls. Network-based statistic was applied to identify alterations in interregional white matter connectivity, and graph theory methods were used to analyze the properties of global networks. The participants also completed a battery of neurocognitive measures. One increased subnetwork characterizing widespread abnormalities in structural connectivity was present in heroin users, which mainly composed of default-mode, attentional and visual systems. The connection strength was positively correlated with increases in fractional anisotropy in heroin abusers. Intriguingly, the changes in within-frontal and within-temporal connections in heroin abusers were significantly correlated with daily heroin dosage and impulsivity scores, respectively. These findings suggest that heroin abusers have extensive abnormal white matter connectivity, which may mediate the relationship between heroin dependence and clinical measures. The increase in white matter connectivity may be attributable to the inefficient microstructure integrity of white matter. The present findings extend our understanding of cerebral structural disruptions that underlie neurocognitive and functional deficits in heroin addiction and provide circuit-level markers for this chronic disorder. © 2015 Society for the Study of Addiction.

Methamphetamine exposure during brain development alters the brain acetylcholine system in adolescent mice

PubMed Central

Siegel, Jessica A.; Park, Byung S.; Raber, Jacob

2013-01-01

Children exposed to methamphetamine during brain development as a result of maternal drug use have long-term hippocampus-dependent cognitive impairments, but the mechanisms underlying these impairments are not understood. The acetylcholine system plays an important role in cognitive function and potential methamphetamine-induced acetylcholine alterations may be related to methamphetamine-induced cognitive impairments. In this study, we investigated the potential long-term effects of methamphetamine exposure during hippocampal development on the acetylcholine system in adolescence mice on postnatal day 30 and in adult mice on postnatal day 90. Methamphetamine exposure increased the density of acetylcholine neurons in regions of the basal forebrain and the area occupied by acetylcholine axons in the hippocampus in adolescent female mice. In contrast, methamphetamine exposure did not affect the density of GABA cells or total neurons in the basal forebrain. Methamphetamine exposure also increased the number of muscarinic acetylcholine receptors in the hippocampus of adolescent male and female mice. Our results demonstrate for the first time that methamphetamine exposure during hippocampal development affects the acetylcholine system in adolescent mice and that these changes are more profound in females than males. PMID:21824143

Electron microscopic examination of the myelinated axons of corpus callosum in perfused young and old rats.

PubMed

Sargon, Mustafa F; Denk, C Cem; Celik, H Hamdi; Surucu, H Selcuk; Aldur, M Mustafa

2007-07-01

In this study, the myelinated axons of parts of the corpus callosums of young and old rats were examined under the electron microscope and a grading system was performed for quantitating the ultrastructural pathological changes of these axons. Except the old splenium group, the only ultrastructural pathological change, observed in the myelinated axons was the separation in myelin configuration. In addition to this finding, in the old splenium group, in some of the myelinated axons, an interruption was observed in the myelin configuration. Additionally, these ultrastructural pathological findings were present in the larger sized myelinated axons of the corpus callosum.

A supercritical density of fast Na+ channels ensures rapid propagation of action potentials in GABAergic interneuron axons

PubMed Central

Hu, Hua; Jonas, Peter

2014-01-01

Fast-spiking, parvalbumin-expressing GABAergic interneurons/basket cells (BCs) play a key role in feedforward and feedback inhibition, gamma oscillations, and complex information processing. For these functions, fast propagation of action potentials (APs) from the soma to the presynaptic terminals is important. However, the functional properties of interneuron axons remain elusive. Here, we examined interneuron axons by confocally targeted subcellular patch-clamp recording in rat hippocampal slices. APs were initiated in the proximal axon ~20 μm from the soma, and propagated to the distal axon with high reliability and speed. Subcellular mapping revealed a stepwise increase of Na+ conductance density from the soma to the proximal axon, followed by a further gradual increase in the distal axon. Active cable modeling and experiments with partial channel block indicated that low axonal Na+ conductance density was sufficient for reliability, but high Na+ density was necessary for both speed of propagation and fast-spiking AP phenotype. Our results suggest that a supercritical density of Na+ channels compensates for the morphological properties of interneuron axons (small segmental diameter, extensive branching, and high bouton density), ensuring fast AP propagation and high-frequency repetitive firing. PMID:24657965

SRF phosphorylation by glycogen synthase kinase-3 promotes axon growth in hippocampal neurons.

PubMed

Li, Cong L; Sathyamurthy, Aruna; Oldenborg, Anna; Tank, Dharmesh; Ramanan, Narendrakumar

2014-03-12

The growth of axons is an intricately regulated process involving intracellular signaling cascades and gene transcription. We had previously shown that the stimulus-dependent transcription factor, serum response factor (SRF), plays a critical role in regulating axon growth in the mammalian brain. However, the molecular mechanisms underlying SRF-dependent axon growth remains unknown. Here we report that SRF is phosphorylated and activated by GSK-3 to promote axon outgrowth in mouse hippocampal neurons. GSK-3 binds to and directly phosphorylates SRF on a highly conserved serine residue. This serine phosphorylation is necessary for SRF activity and for its interaction with MKL-family cofactors, MKL1 and MKL2, but not with TCF-family cofactor, ELK-1. Axonal growth deficits caused by GSK-3 inhibition could be rescued by expression of a constitutively active SRF. The SRF target gene and actin-binding protein, vinculin, is sufficient to overcome the axonal growth deficits of SRF-deficient and GSK-3-inhibited neurons. Furthermore, short hairpin RNA-mediated knockdown of vinculin also attenuated axonal growth. Thus, our findings reveal a novel phosphorylation and activation of SRF by GSK-3 that is critical for SRF-dependent axon growth in mammalian central neurons.

In vivo imaging and quantitative analysis of changes in axon length using transgenic zebrafish embryos.

PubMed

Kanungo, Jyotshnabala; Lantz, Susan; Paule, Merle G

2011-01-01

We describe an imaging procedure to measure axon length in zebrafish embryos in vivo. Automated fluorescent image acquisition was performed with the ImageXpress Micro high content screening reader and further analysis of axon lengths was performed on archived images using AcuityXpress software. We utilized the Neurite Outgrowth Application module with a customized protocol (journal) to measure the axons. Since higher doses of ethanol (2-2.5%, v/v) have been shown to deform motor neurons and axons during development, here we used ethanol to treat transgenic [hb9:GFP (green fluorescent protein)] zebrafish embryos at 28 hpf (hours post-fertilization). These embryos express GFP in the motor neurons and their axons. Embryos after ethanol treatment were arrayed in 384-well plates for automated fluorescent image acquisition in vivo. Average axon lengths of high dose ethanol-treated embryos were significantly lower than the control. Another experiment showed that there was no significant difference in the axon lengths between the embryos grown for 24h at 22°C and 28.5°C. These test experiments demonstrate that using axon development as an end-point, compound screening can be performed in a time-efficient manner. Published by Elsevier Inc.

The Extract of Roots of Sophora flavescens Enhances the Recovery of Motor Function by Axonal Growth in Mice with a Spinal Cord Injury.

PubMed

Tanabe, Norio; Kuboyama, Tomoharu; Kazuma, Kohei; Konno, Katsuhiro; Tohda, Chihiro

2015-01-01

Although axonal extension to reconstruct spinal tracts should be effective for restoring function after spinal cord injury (SCI), chondroitin sulfate proteoglycan (CSPG) levels increase at spinal cord lesion sites, and inhibit axonal regrowth. In this study, we found that the water extract of roots of Sophora flavescens extended the axons of mouse cortical neurons, even on a CSPG-coated surface. Consecutive oral administrations of S. flavescens extract to SCI mice for 31 days increased the density of 5-HT-positive axons at the lesion site and improved the motor function. Further, the active constituents in the S. flavescens extract were identified. The water and alkaloid fractions of the S. flavescens extract each exhibited axonal extension activity in vitro. LC/MS analysis revealed that these fractions mainly contain matrine and/or oxymatrine, which are well-known major compounds in S. flavescens. Matrine and oxymatrine promoted axonal extension on the CSPG-coated surface. This study is the first to demonstrate that S. flavescens extract, matrine, and oxymatrine enhance axonal growth in vitro, even on a CSPG-coated surface, and that S. flavescens extract improves motor function and increases axonal density in SCI mice.

3D axon growth by exogenous electrical stimulus and soluble factors.

PubMed

Tang-Schomer, Min D

2018-01-01

Axon growth and alignment are fundamental processes during nervous system development and neural regeneration after injury. The present study investigates the effects of exogenous stimulus of electrical signals and soluble factors on axon 3D growth, using a silk protein material-based 3D brain tissue model. Electrical stimulus was delivered via embedded gold wires positioned at the interface of the scaffold region and the center matrix gel-filled region, spanning the axon growth area. This setup delivered applied electrical field directly to growing axons, and the effects were compared to micro-needle assisted local delivery of soluble factors of extracellular (ECM) components and neurotrophins. Dissociated rat cortical neurons were exposed to an alternating field of 80 mV/mm at 0.5 Hz to 2 kHz or soluble factors for up to 4 days, and evaluated by of β III-tubulin immunostaining, confocal imaging and 3D neurite tracing. 0.5-20 Hz were found to promote axon growth, with 2 Hz producing the biggest effect of ∼30% axon length increase compared to control cultures. Delivery of ECM components of laminin and fibronectin resulted significantly greater axon initial length increases compared to neurotrophic factors, such as BDNF, GDNF, NGF and NT3 (all at 1 μM). Though axon lengths under 2 Hz stimulation and LN or FN exposure were statistically similar, significant AC-induced axon alignment was found under all frequencies tested. The effects included perpendicular orientation of axons trespassing an electrode, large populations of aligned axon tracts in parallel to the field direction with a few perpendicularly aligned along the middle point of the EF. These findings are consistent with the hypothesis that an electrode in AC field could act as an alternating cathode that attracts the growing tip of the axon. These results demonstrate the use of alternating electric field stimulation to direct axon 3D length growth and orientation. Our study provides basis for further optimizing stimulation parameters, in conjunction of delivery of growth promoting soluble factors to direct axon growth in a brain mimetic 3D environment. This system provides a platform for studying the effects of exogenous signals on nervous system development and for testing neuromodulation approaches for neurological diseases. Copyright © 2017 Elsevier B.V. All rights reserved.

The Molecular and Cellular Mechanisms of Axon Guidance in Mossy Fiber Sprouting

PubMed Central

Koyama, Ryuta; Ikegaya, Yuji

2018-01-01

The question of whether mossy fiber sprouting is epileptogenic has not been resolved; both sprouting-induced recurrent excitatory and inhibitory circuit hypotheses have been experimentally (but not fully) supported. Therefore, whether mossy fiber sprouting is a potential therapeutic target for epilepsy remains under debate. Moreover, the axon guidance mechanisms of mossy fiber sprouting have attracted the interest of neuroscientists. Sprouting of mossy fibers exhibits several uncommon axonal growth features in the basically non-plastic adult brain. For example, robust branching of axonal collaterals arises from pre-existing primary mossy fiber axons. Understanding the branching mechanisms in adulthood may contribute to axonal regeneration therapies in neuroregenerative medicine in which robust axonal re-growth is essential. Additionally, because granule cells are produced throughout life in the neurogenic dentate gyrus, it is interesting to examine whether the mossy fibers of newly generated granule cells follow the pre-existing trajectories of sprouted mossy fibers in the epileptic brain. Understanding these axon guidance mechanisms may contribute to neuron transplantation therapies, for which the incorporation of transplanted neurons into pre-existing neural circuits is essential. Thus, clarifying the axon guidance mechanisms of mossy fiber sprouting could lead to an understanding of central nervous system (CNS) network reorganization and plasticity. Here, we review the molecular and cellular mechanisms of axon guidance in mossy fiber sprouting by discussing mainly in vitro studies. PMID:29896153

Axonal regeneration in zebrafish spinal cord

PubMed Central

Hui, Subhra Prakash

2018-01-01

Abstract In the present review we discuss two interrelated events—axonal damage and repair—known to occur after spinal cord injury (SCI) in the zebrafish. Adult zebrafish are capable of regenerating axonal tracts and can restore full functionality after SCI. Unlike fish, axon regeneration in the adult mammalian central nervous system is extremely limited. As a consequence of an injury there is very little repair of disengaged axons and therefore functional deficit persists after SCI in adult mammals. In contrast, peripheral nervous system axons readily regenerate following injury and hence allow functional recovery both in mammals and fish. A better mechanistic understanding of these three scenarios could provide a more comprehensive insight into the success or failure of axonal regeneration after SCI. This review summarizes the present understanding of the cellular and molecular basis of axonal regeneration, in both the peripheral nervous system and the central nervous system, and large scale gene expression analysis is used to focus on different events during regeneration. The discovery and identification of genes involved in zebrafish spinal cord regeneration and subsequent functional experimentation will provide more insight into the endogenous mechanism of myelination and remyelination. Furthermore, precise knowledge of the mechanism underlying the extraordinary axonal regeneration process in zebrafish will also allow us to unravel the potential therapeutic strategies to be implemented for enhancing regrowth and remyelination of axons in mammals. PMID:29721326

Axonal regeneration in zebrafish spinal cord.

PubMed

Ghosh, Sukla; Hui, Subhra Prakash

2018-03-01

In the present review we discuss two interrelated events-axonal damage and repair-known to occur after spinal cord injury (SCI) in the zebrafish. Adult zebrafish are capable of regenerating axonal tracts and can restore full functionality after SCI. Unlike fish, axon regeneration in the adult mammalian central nervous system is extremely limited. As a consequence of an injury there is very little repair of disengaged axons and therefore functional deficit persists after SCI in adult mammals. In contrast, peripheral nervous system axons readily regenerate following injury and hence allow functional recovery both in mammals and fish. A better mechanistic understanding of these three scenarios could provide a more comprehensive insight into the success or failure of axonal regeneration after SCI. This review summarizes the present understanding of the cellular and molecular basis of axonal regeneration, in both the peripheral nervous system and the central nervous system, and large scale gene expression analysis is used to focus on different events during regeneration. The discovery and identification of genes involved in zebrafish spinal cord regeneration and subsequent functional experimentation will provide more insight into the endogenous mechanism of myelination and remyelination. Furthermore, precise knowledge of the mechanism underlying the extraordinary axonal regeneration process in zebrafish will also allow us to unravel the potential therapeutic strategies to be implemented for enhancing regrowth and remyelination of axons in mammals.

Axonal properties determine somatic firing in a model of in vitro CA1 hippocampal sharp wave/ripples and persistent gamma oscillations

PubMed Central

Traub, Roger D.; Schmitz, Dietmar; Maier, Nikolaus; Whittington, Miles A.; Draguhn, Andreas

2012-01-01

Evidence has been presented that CA1 pyramidal cells, during spontaneous in vitro sharp wave/ripple (SPW-R) complexes, generate somatic action potentials that originate in axons. ‘Participating’ (somatically firing) pyramidal cells fire (almost always) at most once during a particular SPW-R whereas non-participating cells virtually never fire during an SPW-R. Somatic spikelets were small or absent, while ripple-frequency EPSCs and IPSCs occurred during the SPW-R in pyramidal neurons. These experimental findings could be replicated with a network model in which electrical coupling was present between small pyramidal cell axonal branches. Here, we explore this model in more depth. Factors that influence somatic participation include: (i) the diameter of axonal branches that contain coupling sites to other axons, because firing in larger branches injects more current into the main axon, increasing antidromic firing probability; (ii) axonal K+ currents; and (iii) somatic hyperpolarization and shunting. We predict that portions of axons fire at high frequency during SPW-R, while somata fire much less. In the model, somatic firing can occur by occasional generation of full action potentials in proximal axonal branches, which are excited by high-frequency spikelets. When the network contains phasic synaptic inhibition, at the axonal gap junction site, gamma oscillations result, again with more frequent axonal firing than somatic firing. Combining the models, so as to generate gamma followed by sharp waves, leads to strong overlap between the population of cells firing during gamma the population of cells firing during a subsequent sharp wave, as observed in vivo. PMID:22697272

Axonal localization and mitochondrial association of precursor microRNA 338

PubMed Central

Vargas, Jose Norberto S.; Kar, Amar N.; Kowalak, Jeffrey A.; Gale, Jenna R.; Aschrafi, Armaz; Chen, Cai-Yun; Gioio, Anthony E.; Kaplan, Barry B.

2016-01-01

microRNAs (miRNAs) selectively localize to subcompartments of the neuron, such as dendrites, axons and presynaptic terminals, where they regulate the local protein synthesis of their putative target genes. In addition to mature miRNAs, precursor miRNAs (pre-miRNAs) have also been shown to localize to somatodendritic and axonal compartments. miRNA-338 (miR-338) regulates the local expression of several nuclear-encoded mitochondrial mRNAs within axons of sympathetic neurons. Previous work has shown that precursor miR-338 (pre-miR-338) introduced into the axon can be locally processed into mature miR-338, where it can regulate local ATP synthesis. However, the mechanisms underlying the localization of pre-miRNAs to the axonal compartment remain unknown. In this study, we investigated the axonal localization of pre-miR-338. Using proteomic and biochemical approaches, we provide evidence for the localization of pre-miR-338 to distal neuronal compartments and identify several constituents of the pre-miR-338 ribonucleoprotein complex. Furthermore, we found that pre-miR-338 is associated with the mitochondria in axons of superior cervical ganglion (SCG) neurons. The maintenance of mitochondrial function within axons requires the precise spatio-temporal synthesis of nuclear-encoded mRNAs, some of which are regulated by miR-338. Therefore, the association of pre-miR-338 with axonal mitochondria could serve as a reservoir of mature, biologically active miRNAs, which could coordinate the intra-axonal expression of multiple nuclear-encoded mitochondrial mRNAs. PMID:27229124

Meninges-derived cues control axon guidance.

PubMed

Suter, Tracey A C S; DeLoughery, Zachary J; Jaworski, Alexander

2017-10-01

The axons of developing neurons travel long distances along stereotyped pathways under the direction of extracellular cues sensed by the axonal growth cone. Guidance cues are either secreted proteins that diffuse freely or bind the extracellular matrix, or membrane-anchored proteins. Different populations of axons express distinct sets of receptors for guidance cues, which results in differential responses to specific ligands. The full repertoire of axon guidance cues and receptors and the identity of the tissues producing these cues remain to be elucidated. The meninges are connective tissue layers enveloping the vertebrate brain and spinal cord that serve to protect the central nervous system (CNS). The meninges also instruct nervous system development by regulating the generation and migration of neural progenitors, but it has not been determined whether they help guide axons to their targets. Here, we investigate a possible role for the meninges in neuronal wiring. Using mouse neural tissue explants, we show that developing spinal cord meninges produce secreted attractive and repulsive cues that can guide multiple types of axons in vitro. We find that motor and sensory neurons, which project axons across the CNS-peripheral nervous system (PNS) boundary, are attracted by meninges. Conversely, axons of both ipsi- and contralaterally projecting dorsal spinal cord interneurons are repelled by meninges. The responses of these axonal populations to the meninges are consistent with their trajectories relative to meninges in vivo, suggesting that meningeal guidance factors contribute to nervous system wiring and control which axons are able to traverse the CNS-PNS boundary. Copyright © 2017 Elsevier Inc. All rights reserved.