Speed and segmentation control mechanisms characterized in rhythmically-active circuits created from spinal neurons produced from genetically-tagged embryonic stem cells

PubMed Central

Sternfeld, Matthew J; Hinckley, Christopher A; Moore, Niall J; Pankratz, Matthew T; Hilde, Kathryn L; Driscoll, Shawn P; Hayashi, Marito; Amin, Neal D; Bonanomi, Dario; Gifford, Wesley D; Sharma, Kamal; Goulding, Martyn; Pfaff, Samuel L

2017-01-01

Flexible neural networks, such as the interconnected spinal neurons that control distinct motor actions, can switch their activity to produce different behaviors. Both excitatory (E) and inhibitory (I) spinal neurons are necessary for motor behavior, but the influence of recruiting different ratios of E-to-I cells remains unclear. We constructed synthetic microphysical neural networks, called circuitoids, using precise combinations of spinal neuron subtypes derived from mouse stem cells. Circuitoids of purified excitatory interneurons were sufficient to generate oscillatory bursts with properties similar to in vivo central pattern generators. Inhibitory V1 neurons provided dual layers of regulation within excitatory rhythmogenic networks - they increased the rhythmic burst frequency of excitatory V3 neurons, and segmented excitatory motor neuron activity into sub-networks. Accordingly, the speed and pattern of spinal circuits that underlie complex motor behaviors may be regulated by quantitatively gating the intra-network cellular activity ratio of E-to-I neurons. DOI: http://dx.doi.org/10.7554/eLife.21540.001 PMID:28195039

Monosynaptic rabies virus reveals premotor network organization and synaptic specificity of cholinergic partition cells.

PubMed

Stepien, Anna E; Tripodi, Marco; Arber, Silvia

2010-11-04

Movement is the behavioral output of neuronal activity in the spinal cord. Motor neurons are grouped into motor neuron pools, the functional units innervating individual muscles. Here we establish an anatomical rabies virus-based connectivity assay in early postnatal mice. We employ it to study the connectivity scheme of premotor neurons, the neuronal cohorts monosynaptically connected to motor neurons, unveiling three aspects of organization. First, motor neuron pools are connected to segmentally widely distributed yet stereotypic interneuron populations, differing for pools innervating functionally distinct muscles. Second, depending on subpopulation identity, interneurons take on local or segmentally distributed positions. Third, cholinergic partition cells involved in the regulation of motor neuron excitability segregate into ipsilaterally and bilaterally projecting populations, the latter exhibiting preferential connections to functionally equivalent motor neuron pools bilaterally. Our study visualizes the widespread yet precise nature of the connectivity matrix for premotor interneurons and reveals exquisite synaptic specificity for bilaterally projecting cholinergic partition cells. Copyright © 2010 Elsevier Inc. All rights reserved.

Morphological Characteristics of Motor Neurons Do Not Determine Their Relative Susceptibility to Degeneration in a Mouse Model of Severe Spinal Muscular Atrophy

PubMed Central

Mutsaers, Chantal A.; Thomson, Derek; Hamilton, Gillian; Parson, Simon H.; Gillingwater, Thomas H.

2012-01-01

Spinal muscular atrophy (SMA) is a leading genetic cause of infant mortality, resulting primarily from the degeneration and loss of lower motor neurons. Studies using mouse models of SMA have revealed widespread heterogeneity in the susceptibility of individual motor neurons to neurodegeneration, but the underlying reasons remain unclear. Data from related motor neuron diseases, such as amyotrophic lateral sclerosis (ALS), suggest that morphological properties of motor neurons may regulate susceptibility: in ALS larger motor units innervating fast-twitch muscles degenerate first. We therefore set out to determine whether intrinsic morphological characteristics of motor neurons influenced their relative vulnerability to SMA. Motor neuron vulnerability was mapped across 10 muscle groups in SMA mice. Neither the position of the muscle in the body, nor the fibre type of the muscle innervated, influenced susceptibility. Morphological properties of vulnerable and disease-resistant motor neurons were then determined from single motor units reconstructed in Thy.1-YFP-H mice. None of the parameters we investigated in healthy young adult mice – including motor unit size, motor unit arbor length, branching patterns, motor endplate size, developmental pruning and numbers of terminal Schwann cells at neuromuscular junctions - correlated with vulnerability. We conclude that morphological characteristics of motor neurons are not a major determinant of disease-susceptibility in SMA, in stark contrast to related forms of motor neuron disease such as ALS. This suggests that subtle molecular differences between motor neurons, or extrinsic factors arising from other cell types, are more likely to determine relative susceptibility in SMA. PMID:23285108

A SMN-Dependent U12 Splicing Event Essential for Motor Circuit Function

PubMed Central

Lotti, Francesco; Imlach, Wendy L.; Saieva, Luciano; Beck, Erin S.; Hao, Le T.; Li, Darrick K.; Jiao, Wei; Mentis, George Z.; Beattie, Christine E.; McCabe, Brian D.; Pellizzoni, Livio

2012-01-01

SUMMARY Spinal muscular atrophy (SMA) is a motor neuron disease caused by deficiency of the ubiquitous survival motor neuron (SMN) protein. To define the mechanisms of selective neuronal dysfunction in SMA, we investigated the role of SMN-dependent U12 splicing events in the regulation of motor circuit activity. We show that SMN deficiency perturbs splicing and decreases the expression of a subset of U12 intron-containing genes in mammalian cells and Drosophila larvae. Analysis of these SMN target genes identifies Stasimon as a novel protein required for motor circuit function. Restoration of Stasimon expression in the motor circuit corrects defects in neuromuscular junction transmission and muscle growth in Drosophila SMN mutants and aberrant motor neuron development in SMN-deficient zebrafish. These findings directly link defective splicing of critical neuronal genes induced by SMN deficiency to motor circuit dysfunction, establishing a molecular framework for the selective pathology of SMA. PMID:23063131

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

The ALS gene FUS regulates synaptic transmission at the Drosophila neuromuscular junction

PubMed Central

Machamer, James B.; Collins, Sarah E.; Lloyd, Thomas E.

2014-01-01

Mutations in the RNA binding protein Fused in sarcoma (FUS) are estimated to account for 5–10% of all inherited cases of amyotrophic lateral sclerosis (ALS), but the function of FUS in motor neurons is poorly understood. Here, we investigate the early functional consequences of overexpressing wild-type or ALS-associated mutant FUS proteins in Drosophila motor neurons, and compare them to phenotypes arising from loss of the Drosophila homolog of FUS, Cabeza (Caz). We find that lethality and locomotor phenotypes correlate with levels of FUS transgene expression, indicating that toxicity in developing motor neurons is largely independent of ALS-linked mutations. At the neuromuscular junction (NMJ), overexpression of either wild-type or mutant FUS results in decreased number of presynaptic active zones and altered postsynaptic glutamate receptor subunit composition, coinciding with a reduction in synaptic transmission as a result of both reduced quantal size and quantal content. Interestingly, expression of human FUS downregulates endogenous Caz levels, demonstrating that FUS autoregulation occurs in motor neurons in vivo. However, loss of Caz from motor neurons increases synaptic transmission as a result of increased quantal size, suggesting that the loss of Caz in animals expressing FUS does not contribute to motor deficits. These data demonstrate that FUS/Caz regulates NMJ development and plays an evolutionarily conserved role in modulating the strength of synaptic transmission in motor neurons. PMID:24569165

Aberrant regulation of DNA methylation in amyotrophic lateral sclerosis: a new target of disease mechanisms.

PubMed

Martin, Lee J; Wong, Margaret

2013-10-01

Amyotrophic lateral sclerosis (ALS) is the third most common adult-onset neurodegenerative disease. A diagnosis is fatal owing to degeneration of motor neurons in brain and spinal cord that control swallowing, breathing, and movement. ALS can be inherited, but most cases are not associated with a family history of the disease. The mechanisms causing motor neuron death in ALS are still unknown. Given the suspected complex interplay between multiple genes, the environment, metabolism, and lifestyle in the pathogenesis of ALS, we have hypothesized that the mechanisms of disease in ALS involve epigenetic contributions that can drive motor neuron degeneration. DNA methylation is an epigenetic mechanism for gene regulation engaged by DNA methyltransferase (Dnmt)-catalyzed methyl group transfer to carbon-5 in cytosine residues in gene regulatory promoter and nonpromoter regions. Recent genome-wide analyses have found differential gene methylation in human ALS. Neuropathologic assessments have revealed that motor neurons in human ALS show significant abnormalities in Dnmt1, Dnmt3a, and 5-methylcytosine. Similar changes are seen in mice with motor neuron degeneration, and Dnmt3a was found abundantly at synapses and in mitochondria. During apoptosis of cultured motor neuron-like cells, Dnmt1 and Dnmt3a protein levels increase, and 5-methylcytosine accumulates. Enforced expression of Dnmt3a, but not Dnmt1, induces degeneration of cultured neurons. Truncation mutation of the Dnmt3a catalytic domain and Dnmt3a RNAi blocks apoptosis of cultured neurons. Inhibition of Dnmt catalytic activity with small molecules RG108 and procainamide protects motor neurons from excessive DNA methylation and apoptosis in cell culture and in a mouse model of ALS. Thus, motor neurons can engage epigenetic mechanisms to cause their degeneration, involving Dnmts and increased DNA methylation. Aberrant DNA methylation in vulnerable cells is a new direction for discovering mechanisms of ALS pathogenesis that could be relevant to new disease target identification and therapies for ALS.

Comparison of independent screens on differentially vulnerable motor neurons reveals alpha-synuclein as a common modifier in motor neuron diseases

PubMed Central

Kaifer, Kevin A.; Osman, Erkan Y.; Carella, Francesco; Tiberi, Ariana; Ross, Jolill; Pennetta, Giuseppa; Lorson, Christian L.

2017-01-01

The term “motor neuron disease” encompasses a spectrum of disorders in which motor neurons are the primary pathological target. However, in both patients and animal models of these diseases, not all motor neurons are equally vulnerable, in that while some motor neurons are lost very early in disease, others remain comparatively intact, even at late stages. This creates a valuable system to investigate the factors that regulate motor neuron vulnerability. In this study, we aim to use this experimental paradigm to identify potential transcriptional modifiers. We have compared the transcriptome of motor neurons from healthy wild-type mice, which are differentially vulnerable in the childhood motor neuron disease Spinal Muscular Atrophy (SMA), and have identified 910 transcriptional changes. We have compared this data set with published microarray data sets on other differentially vulnerable motor neurons. These neurons were differentially vulnerable in the adult onset motor neuron disease Amyotrophic Lateral Sclerosis (ALS), but the screen was performed on the equivalent population of neurons from neurologically normal human, rat and mouse. This cross species comparison has generated a refined list of differentially expressed genes, including CELF5, Col5a2, PGEMN1, SNCA, Stmn1 and HOXa5, alongside a further enrichment for synaptic and axonal transcripts. As an in vivo validation, we demonstrate that the manipulation of a significant number of these transcripts can modify the neurodegenerative phenotype observed in a Drosophila line carrying an ALS causing mutation. Finally, we demonstrate that vector-mediated expression of alpha-synuclein (SNCA), a transcript decreased in selectively vulnerable motor neurons in all four screens, can extend life span, increase weight and decrease neuromuscular junction pathology in a mouse model of SMA. In summary, we have combined multiple data sets to identify transcripts, which are strong candidates for being phenotypic modifiers, and demonstrated SNCA is a modifier of pathology in motor neuron disease. PMID:28362802

Comparison of independent screens on differentially vulnerable motor neurons reveals alpha-synuclein as a common modifier in motor neuron diseases.

PubMed

Kline, Rachel A; Kaifer, Kevin A; Osman, Erkan Y; Carella, Francesco; Tiberi, Ariana; Ross, Jolill; Pennetta, Giuseppa; Lorson, Christian L; Murray, Lyndsay M

2017-03-01

The term "motor neuron disease" encompasses a spectrum of disorders in which motor neurons are the primary pathological target. However, in both patients and animal models of these diseases, not all motor neurons are equally vulnerable, in that while some motor neurons are lost very early in disease, others remain comparatively intact, even at late stages. This creates a valuable system to investigate the factors that regulate motor neuron vulnerability. In this study, we aim to use this experimental paradigm to identify potential transcriptional modifiers. We have compared the transcriptome of motor neurons from healthy wild-type mice, which are differentially vulnerable in the childhood motor neuron disease Spinal Muscular Atrophy (SMA), and have identified 910 transcriptional changes. We have compared this data set with published microarray data sets on other differentially vulnerable motor neurons. These neurons were differentially vulnerable in the adult onset motor neuron disease Amyotrophic Lateral Sclerosis (ALS), but the screen was performed on the equivalent population of neurons from neurologically normal human, rat and mouse. This cross species comparison has generated a refined list of differentially expressed genes, including CELF5, Col5a2, PGEMN1, SNCA, Stmn1 and HOXa5, alongside a further enrichment for synaptic and axonal transcripts. As an in vivo validation, we demonstrate that the manipulation of a significant number of these transcripts can modify the neurodegenerative phenotype observed in a Drosophila line carrying an ALS causing mutation. Finally, we demonstrate that vector-mediated expression of alpha-synuclein (SNCA), a transcript decreased in selectively vulnerable motor neurons in all four screens, can extend life span, increase weight and decrease neuromuscular junction pathology in a mouse model of SMA. In summary, we have combined multiple data sets to identify transcripts, which are strong candidates for being phenotypic modifiers, and demonstrated SNCA is a modifier of pathology in motor neuron disease.

CDK-5 regulates the polarized trafficking of neuropeptide-containing dense-core vesicles in C. elegans motor neurons

PubMed Central

Goodwin, Patricia R.; Sasaki, Jennifer M.; Juo, Peter

2012-01-01

The polarized trafficking of axonal and dendritic proteins is essential for the structure and function of neurons. Cyclin-dependent kinase-5 (CDK-5) and its activator CDKA-1/p35 regulate diverse aspects of nervous system development and function. Here, we show that CDK-5 and CDKA-1/p35 are required for the polarized distribution of neuropeptide-containing dense-core vesicles (DCVs) in C. elegans cholinergic motor neurons. In cdk-5 or cdka-1/p35 mutants, the predominantly axonal localization of DCVs containing INS-22 neuropeptides was disrupted and DCVs accumulated in dendrites. Time-lapse microscopy in DB class motor neurons revealed decreased trafficking of DCVs in axons and increased trafficking and accumulation of DCVs in cdk-5 mutant dendrites. The polarized distribution of several axonal and dendritic markers, including synaptic vesicles, was unaltered in cdk-5 mutant DB neurons. We found that microtubule polarity is plus-end out in axons and predominantly minus-end out in dendrites of DB neurons. Surprisingly, cdk-5 mutants had increased amounts of plus-end-out microtubules in dendrites, suggesting that CDK-5 regulates microtubule orientation. However, these changes in microtubule polarity are not responsible for the increased trafficking of DCVs into dendrites. Genetic analysis of cdk-5 and the plus-end-directed axonal DCV motor unc-104/KIF1A suggest that increased trafficking of UNC-104 into dendrites cannot explain the dendritic DCV accumulation. Instead, we found that mutations in the minus-end-directed motor cytoplasmic dynein, completely block the increased DCVs observed in cdk-5 mutant dendrites without affecting microtubule polarity. We propose a model where CDK-5 regulates DCV polarity by both promoting DCV trafficking in axons and preventing dynein-dependent DCV trafficking into dendrites. PMID:22699897

The dusp1 Immediate Early Gene is Regulated by Natural Stimuli Predominantly in Sensory Input Neurons

PubMed Central

Horita, Haruhito; Wada, Kazuhiro; Rivas, Miriam V.; Hara, Erina; Jarvis, Erich D.

2010-01-01

Many immediate early genes (IEGs) have activity-dependent induction in a subset of brain subdivisions or neuron types. However, none have been reported yet with regulation specific to thalamic-recipient sensory neurons of the telencephalon or in the thalamic sensory input neurons themselves. Here, we report the first such gene, dual specificity phosphatase 1 (dusp1). Dusp1 is an inactivator of mitogen-activated protein kinase (MAPK), and MAPK activates expression of egr1, one of the most commonly studied IEGs, as determined in cultured cells. We found that in the brain of naturally behaving songbirds and other avian species, hearing song, seeing visual stimuli, or performing motor behavior caused high dusp1 upregulation, respectively, in auditory, visual, and somatosensory input cell populations of the thalamus and thalamic-recipient sensory neurons of the telencephalic pallium, whereas high egr1 upregulation occurred only in subsequently connected secondary and tertiary sensory neuronal populations of these same pathways. Motor behavior did not induce high levels of dusp1 expression in the motor-associated areas adjacent to song nuclei, where egr1 is upregulated in response to movement. Our analysis of dusp1 expression in mouse brain suggests similar regulation in the sensory input neurons of the thalamus and thalamic-recipient layer IV and VI neurons of the cortex. These findings suggest that dusp1 has specialized regulation to sensory input neurons of the thalamus and telencephalon; they further suggest that this regulation may serve to attenuate stimulus-induced expression of egr1 and other IEGs, leading to unique molecular properties of forebrain sensory input neurons. PMID:20506480

The UBR-1 ubiquitin ligase regulates glutamate metabolism to generate coordinated motor pattern in Caenorhabditis elegans

PubMed Central

Chitturi, Jyothsna; Hung, Wesley; Rahman, Anas M. Abdel; Wu, Min; Lim, Maria A.; Calarco, John; Dennis, James W.

2018-01-01

UBR1 is an E3 ubiquitin ligase best known for its ability to target protein degradation by the N-end rule. The physiological functions of UBR family proteins, however, remain not fully understood. We found that the functional loss of C. elegans UBR-1 leads to a specific motor deficit: when adult animals generate reversal movements, A-class motor neurons exhibit synchronized activation, preventing body bending. This motor deficit is rescued by removing GOT-1, a transaminase that converts aspartate to glutamate. Both UBR-1 and GOT-1 are expressed and critically required in premotor interneurons of the reversal motor circuit to regulate the motor pattern. ubr-1 and got-1 mutants exhibit elevated and decreased glutamate level, respectively. These results raise an intriguing possibility that UBR proteins regulate glutamate metabolism, which is critical for neuronal development and signaling. PMID:29649217

Gap Junction-Mediated Signaling from Motor Neurons Regulates Motor Generation in the Central Circuits of Larval Drosophila.

PubMed

Matsunaga, Teruyuki; Kohsaka, Hiroshi; Nose, Akinao

2017-02-22

In this study, we used the peristaltic crawling of Drosophila larvae as a model to study how motor patterns are regulated by central circuits. We built an experimental system that allows simultaneous application of optogenetics and calcium imaging to the isolated ventral nerve cord (VNC). We then investigated the effects of manipulating local activity of motor neurons (MNs) on fictive locomotion observed as waves of MN activity propagating along neuromeres. Optical inhibition of MNs with halorhodopsin3 in a middle segment (A4, A5, or A6), but not other segments, dramatically decreased the frequency of the motor waves. Conversely, local activation of MNs with channelrhodopsin2 in a posterior segment (A6 or A7) increased the frequency of the motor waves. Since peripheral nerves mediating sensory feedback were severed in the VNC preparation, these results indicate that MNs send signals to the central circuits to regulate motor pattern generation. Our results also indicate segmental specificity in the roles of MNs in motor control. The effects of the local MN activity manipulation were lost in shaking-B 2 ( shakB 2 ) or ogre 2 , gap-junction mutations in Drosophila , or upon acute application of the gap junction blocker carbenoxolone, implicating electrical synapses in the signaling from MNs. Cell-type-specific RNAi suggested shakB and ogre function in MNs and interneurons, respectively, during the signaling. Our results not only reveal an unexpected role for MNs in motor pattern regulation, but also introduce a powerful experimental system that enables examination of the input-output relationship among the component neurons in this system. SIGNIFICANCE STATEMENT Motor neurons are generally considered passive players in motor pattern generation, simply relaying information from upstream interneuronal circuits to the target muscles. This study shows instead that MNs play active roles in the control of motor generation by conveying information via gap junctions to the central pattern-generating circuits in larval Drosophila , providing novel insights into motor circuit control. The experimental system introduced in this study also presents a new approach for studying intersegmentally coordinated locomotion. Unlike traditional electrophysiology methods, this system enables the simultaneous recording and manipulation of populations of neurons that are genetically specified and span multiple segments. Copyright © 2017 the authors 0270-6474/17/372045-16$15.00/0.

Crosstalk between p38, Hsp25 and Akt in spinal motor neurons after sciatic nerve injury

NASA Technical Reports Server (NTRS)

Murashov, A. K.; Ul Haq, I.; Hill, C.; Park, E.; Smith, M.; Wang, X.; Wang, X.; Goldberg, D. J.; Wolgemuth, D. J.

2001-01-01

The p38 stress-activated protein kinase pathway is involved in regulation of phosphorylation of Hsp25, which in turn regulates actin filament dynamic in non-neuronal cells. We report that p38, Hsp25 and Akt signaling pathways were specifically activated in spinal motor neurons after sciatic nerve axotomy. The activation of the p38 kinase was required for induction of Hsp25 expression. Furthermore, Hsp25 formed a complex with Akt, a member of PI-3 kinase pathway that prevents neuronal cell death. Together, our observations implicate Hsp25 as a central player in a complex system of signaling that may both promote regeneration of nerve fibers and prevent neuronal cell death in the injured spinal cord.

The anatomical, cellular and synaptic basis of motor atonia during rapid eye movement sleep

PubMed Central

Chen, Michael C.

2016-01-01

Abstract Rapid eye movement (REM) sleep is a recurring part of the sleep–wake cycle characterized by fast, desynchronized rhythms in the electroencephalogram (EEG), hippocampal theta activity, rapid eye movements, autonomic activation and loss of postural muscle tone (atonia). The brain circuitry governing REM sleep is located in the pontine and medullary brainstem and includes ascending and descending projections that regulate the EEG and motor components of REM sleep. The descending signal for postural muscle atonia during REM sleep is thought to originate from glutamatergic neurons of the sublaterodorsal nucleus (SLD), which in turn activate glycinergic pre‐motor neurons in the spinal cord and/or ventromedial medulla to inhibit motor neurons. Despite work over the past two decades on many neurotransmitter systems that regulate the SLD, gaps remain in our knowledge of the synaptic basis by which SLD REM neurons are regulated and in turn produce REM sleep atonia. Elucidating the anatomical, cellular and synaptic basis of REM sleep atonia control is a critical step for treating many sleep‐related disorders including obstructive sleep apnoea (apnea), REM sleep behaviour disorder (RBD) and narcolepsy with cataplexy. PMID:27060683

Neural correlates of motor learning in the vestibulo-ocular reflex: dynamic regulation of multimodal integration in the macaque vestibular system

PubMed Central

Sadeghi, Soroush G.; Minor, Lloyd B.; Cullen, Kathleen E.

2010-01-01

Motor learning is required for the reacquisition of skills that have been compromised as a result of brain lesion or disease, as well as for the acquisition of new skills. Behaviors with well-characterized anatomy and physiology are required to yield significant insight into changes that occur in the brain during motor learning. The vestibulo-ocular-reflex (VOR) is well suited to establish connections between neurons, neural circuits, and motor performance during learning. Here we examined the linkage between neuronal and behavioural VOR responses in alert behaving monkeys (macaca mulatta) during the impressive recovery that occurs after unilateral vestibular loss. We show, for the first time, that motor learning is characterized by the dynamic reweighting of inputs from different modalities (i.e., vestibular versus extra-vestibular) at the level of the single neurons which constitute the first central stage of vestibular processing. Specifically, two types of information, which did not influence neuronal responses prior to the lesion, had an important role during compensation. First, unmasked neck proprioceptive inputs played a critical role in the early stages of this process demonstrated by faster and more substantial recovery of vestibular responses in proprioceptive sensitive neurons. Second, neuronal and VOR responses were significantly enhanced during active relative to passive head motion later in the compensation process (>3 weeks). Taken together, our findings provide evidence linking the dynamic regulation of multimodal integration at the level of single neurons and behavioural recovery, suggesting a role for homeostatic mechanisms in VOR motor learning. PMID:20668199

Cell death cascade and molecular therapy in ADAR2-deficient motor neurons of ALS.

PubMed

Yamashita, Takenari; Kwak, Shin

2018-06-23

TAR DNA-binding protein (TDP-43) pathology in the motor neurons is the most reliable pathological hallmark of amyotrophic lateral sclerosis (ALS), and motor neurons bearing TDP-43 pathology invariably exhibit failure in RNA editing at the GluA2 glutamine/arginine (Q/R) site due to down-regulation of adenosine deaminase acting on RNA 2 (ADAR2). Conditional ADAR2 knockout (AR2) mice display ALS-like phenotype, including progressive motor dysfunction due to loss of motor neurons. Motor neurons devoid of ADAR2 express Q/R site-unedited GluA2, and AMPA receptors with unedited GluA2 in their subunit assembly are abnormally permeable to Ca 2+ , which results in progressive neuronal death. Moreover, analysis of AR2 mice has demonstrated that exaggerated Ca 2+ influx through the abnormal AMPA receptors overactivates calpain, a Ca 2+ -dependent protease, that cleaves TDP-43 into aggregation-prone fragments, which serve as seeds for TDP-43 pathology. Activated calpain also disrupts nucleo-cytoplasmic transport and gene expression by cleaving molecules involved in nucleocytoplasmic transport, including nucleoporins. These lines of evidence prompted us to develop molecular targeting therapy for ALS by normalization of disrupted intracellular environment due to ADAR2 down-regulation. In this review, we have summarized the work from our group on the cell death cascade in sporadic ALS and discussed a potential therapeutic strategy for ALS. Copyright © 2018 Elsevier Ireland Ltd and the Japan Neuroscience Society. All rights reserved.

LGR5/GPR49 is implicated in motor neuron specification in nervous system.

PubMed

Song, Shao-jun; Mao, Xing-gang; Wang, Chao; Han, An-guo; Yan, Ming; Xue, Xiao-yan

2015-01-01

The biological roles of stem cell marker LGR5, the receptor for the Wnt-agonistic R-spondins, for nervous system are poorly known. Bioinformatics analysis in normal human brain tissues revealed that LGR5 is closely related with neuron development and functions. Interestingly, LGR5 and its ligands R-spondins (RSPO2 and RSPO3) are specifically highly expressed in projection motor neurons in the spinal cord, brain stem and cerebral. Inhibition of Notch activity in neural stem cells (NSCs) increased the percentage of neuronal cells and promoted LGR5 expression, while activation of Notch signal decreased neuronal cells and inhibited the LGR5 expression. Furthermore, knockdown of LGR5 inhibited the expression of neuronal markers MAP2, NeuN, GAP43, SYP and CHRM3, and also reduced the expression of genes that program the identity of motor neurons, including Isl1, Lhx3, PHOX2A, TBX20 and NEUROG2. Our data demonstrated that LGR5 is highly expressed in motor neurons in nervous system and is involved in their development by regulating transcription factors that program motor neuron identity. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

Differential screening of mutated SOD1 transgenic mice reveals early up-regulation of a fast axonal transport component in spinal cord motor neurons.

PubMed

Dupuis, L; de Tapia, M; René, F; Lutz-Bucher, B; Gordon, J W; Mercken, L; Pradier, L; Loeffler, J P

2000-08-01

In the present study we analyze the molecular mechanisms underlying motor neuron degeneration in familial amyotrophic lateral sclerosis (FALS). For this, we used a transgenic mouse model expressing the Cu/Zn superoxide dismutase (SOD1) gene with a Gly(86) to Arg (G86R) mutation equivalent to that found in a subset of human FALS. Using an optimized suppression subtractive hybridization method, a cDNA specifically up-regulated during the asymptomatic phase in the lumbar spinal cord of G86R mice was identified by sequence analysis as the KIF3-associated protein (KAP3), a regulator of fast axonal transport. RT-PCR analysis revealed that KAP3 induction was an early event arising long before axonal degeneration. Immunohistochemical studies further revealed that KAP3 protein predominantly accumulates in large motor neurons of the ventral spinal cord. We further demonstrated that KAP3 up-regulation occurs independent of any change in the other components of the kinesin II complex. However, since the ubiquitous KIF1A motor is up-regulated, our results show an early and complex rearrangement of the fast axonal transport machinery in the course of FALS pathology. Copyright 2000 Academic Press.

Molecular Mechanisms of Neurodegeneration in Spinal Muscular Atrophy.

PubMed

Ahmad, Saif; Bhatia, Kanchan; Kannan, Annapoorna; Gangwani, Laxman

2016-01-01

Spinal muscular atrophy (SMA) is an autosomal recessive motor neuron disease with a high incidence and is the most common genetic cause of infant mortality. SMA is primarily characterized by degeneration of the spinal motor neurons that leads to skeletal muscle atrophy followed by symmetric limb paralysis, respiratory failure, and death. In humans, mutation of the Survival Motor Neuron 1 (SMN1) gene shifts the load of expression of SMN protein to the SMN2 gene that produces low levels of full-length SMN protein because of alternative splicing, which are sufficient for embryonic development and survival but result in SMA. The molecular mechanisms of the (a) regulation of SMN gene expression and (b) degeneration of motor neurons caused by low levels of SMN are unclear. However, some progress has been made in recent years that have provided new insights into understanding of the cellular and molecular basis of SMA pathogenesis. In this review, we have briefly summarized recent advances toward understanding of the molecular mechanisms of regulation of SMN levels and signaling mechanisms that mediate neurodegeneration in SMA.

Optogenetic and pharmacological evidence that somatostatin‐GABA neurons are important regulators of parasympathetic outflow to the stomach

PubMed Central

Lewin, Amanda E.; Vicini, Stefano; Richardson, Janell; Dretchen, Kenneth L.; Gillis, Richard A.

2016-01-01

Key points The dorsal motor nucleus of the vagus (DMV) in the brainstem consists primarily of vagal preganglionic neurons that innervate postganglionic neurons of the upper gastrointestinal tract.The activity of the vagal preganglionic neurons is predominantly regulated by GABAergic transmission in the DMV.The present findings indicate that the overwhelming GABAergic drive present at the DMV is primarily from somatostatin positive GABA (Sst‐GABA) DMV neurons.Activation of both melanocortin and μ‐opioid receptors at the DMV inhibits Sst‐GABA DMV neurons.Sst‐GABA DMV neurons may serve as integrative targets for modulating vagal output activity to the stomach. Abstract We have previously shown that local GABA signalling in the brainstem is an important determinant of vagally‐mediated gastric activity. However, the neural identity of this GABA source is currently unknown. To determine this, we focused on the somatostatin positive GABA (Sst‐GABA) interneuron in the dorsal motor nucleus of the vagus (DMV), a nucleus that is intimately involved in regulating gastric activity. Also of particular interest was the effect of melanocortin and μ‐opioid agonists on neural activity of Sst‐GABA DMV neurons because their in vivo administration in the DMV mimics GABA blockade in the nucleus. Experiments were conducted in brain slice preparation of transgenic adult Sst‐IRES‐Cre mice expressing tdTomato fluorescence, channelrhodopsin‐2, archaerhodopsin or GCaMP3. Electrophysiological recordings were obtained from Sst‐GABA DMV neurons or DiI labelled gastric‐antrum projecting DMV neurons. Our results show that optogenetic stimulation of Sst‐GABA neurons results in a robust inhibition of action potentials of labelled premotor DMV neurons to the gastric‐antrum through an increase in inhibitory post‐synaptic currents. The activity of the Sst‐GABA neurons in the DMV is inhibited by both melanocortin and μ‐opioid agonists. These agonists counteract the pronounced inhibitory effect of Sst‐GABA neurons on vagal pre‐motor neurons in the DMV that control gastric motility. These observations demonstrate that Sst‐GABA neurons in the brainstem are crucial for regulating the activity of gastric output neurons in the DMV. Additionally, they suggest that these neurons serve as targets for converging CNS signals to regulate parasympathetic gastric function. PMID:26959279

Optogenetic and pharmacological evidence that somatostatin-GABA neurons are important regulators of parasympathetic outflow to the stomach.

PubMed

Lewin, Amanda E; Vicini, Stefano; Richardson, Janell; Dretchen, Kenneth L; Gillis, Richard A; Sahibzada, Niaz

2016-05-15

The dorsal motor nucleus of the vagus (DMV) in the brainstem consists primarily of vagal preganglionic neurons that innervate postganglionic neurons of the upper gastrointestinal tract. The activity of the vagal preganglionic neurons is predominantly regulated by GABAergic transmission in the DMV. The present findings indicate that the overwhelming GABAergic drive present at the DMV is primarily from somatostatin positive GABA (Sst-GABA) DMV neurons. Activation of both melanocortin and μ-opioid receptors at the DMV inhibits Sst-GABA DMV neurons. Sst-GABA DMV neurons may serve as integrative targets for modulating vagal output activity to the stomach. We have previously shown that local GABA signalling in the brainstem is an important determinant of vagally-mediated gastric activity. However, the neural identity of this GABA source is currently unknown. To determine this, we focused on the somatostatin positive GABA (Sst-GABA) interneuron in the dorsal motor nucleus of the vagus (DMV), a nucleus that is intimately involved in regulating gastric activity. Also of particular interest was the effect of melanocortin and μ-opioid agonists on neural activity of Sst-GABA DMV neurons because their in vivo administration in the DMV mimics GABA blockade in the nucleus. Experiments were conducted in brain slice preparation of transgenic adult Sst-IRES-Cre mice expressing tdTomato fluorescence, channelrhodopsin-2, archaerhodopsin or GCaMP3. Electrophysiological recordings were obtained from Sst-GABA DMV neurons or DiI labelled gastric-antrum projecting DMV neurons. Our results show that optogenetic stimulation of Sst-GABA neurons results in a robust inhibition of action potentials of labelled premotor DMV neurons to the gastric-antrum through an increase in inhibitory post-synaptic currents. The activity of the Sst-GABA neurons in the DMV is inhibited by both melanocortin and μ-opioid agonists. These agonists counteract the pronounced inhibitory effect of Sst-GABA neurons on vagal pre-motor neurons in the DMV that control gastric motility. These observations demonstrate that Sst-GABA neurons in the brainstem are crucial for regulating the activity of gastric output neurons in the DMV. Additionally, they suggest that these neurons serve as targets for converging CNS signals to regulate parasympathetic gastric function. © 2016 The Authors. The Journal of Physiology © 2016 The Physiological Society.

SMN regulates axonal local translation via miR-183/mTOR pathway

PubMed Central

Kye, Min Jeong; Niederst, Emily D.; Wertz, Mary H.; Gonçalves, Inês do Carmo G.; Akten, Bikem; Dover, Katarzyna Z.; Peters, Miriam; Riessland, Markus; Neveu, Pierre; Wirth, Brunhilde; Kosik, Kenneth S.; Sardi, S. Pablo; Monani, Umrao R.; Passini, Marco A.; Sahin, Mustafa

2014-01-01

Reduced expression of SMN protein causes spinal muscular atrophy (SMA), a neurodegenerative disorder leading to motor neuron dysfunction and loss. However, the molecular mechanisms by which SMN regulates neuronal dysfunction are not fully understood. Here, we report that reduced SMN protein level alters miRNA expression and distribution in neurons. In particular, miR-183 levels are increased in neurites of SMN-deficient neurons. We demonstrate that miR-183 regulates translation of mTor via direct binding to its 3′ UTR. Interestingly, local axonal translation of mTor is reduced in SMN-deficient neurons, and this can be recovered by miR-183 inhibition. Finally, inhibition of miR-183 expression in the spinal cord of an SMA mouse model prolongs survival and improves motor function of Smn-mutant mice. Together, these observations suggest that axonal miRNAs and the mTOR pathway are previously unidentified molecular mechanisms contributing to SMA pathology. PMID:25055867

Repetitive acute intermittent hypoxia increases expression of proteins associated with plasticity in the phrenic motor nucleus

PubMed Central

Satriotomo, Irawan; Dale, Erica A.; Dahlberg, Jenny M.; Mitchell, Gordon S.

2015-01-01

Acute intermittent hypoxia (AIH) initiates plasticity in respiratory motor control, including phrenic long term facilitation (pLTF). Since pLTF is enhanced by preconditioning with repetitive exposure to AIH (rAIH), we hypothesized that a rAIH protocol consisting of 3 AIH exposures per week for 10 weeks (3×wAIH; AIH: 10, 5-min episodes of 10.5% O2; 5-min normoxic intervals) would enhance expression of molecules that play key roles in pLTF within the phrenic motor nucleus. Immunohistochemical analyses revealed that 3×wAIH for 10 weeks increased serotonin terminal density in the C4 phrenic motor nucleus and serotonin 2A (5-HT2A) receptor expression in presumptive phrenic motor neurons. Immunoreactive brain derived neurotrophic factor (BDNF) and its high affinity receptor (TrkB) also increased following 3×wAIH. 3×wAIH also increased expression of another hypoxia-sensitive growth factor known to elicit phrenic motor facilitation, vascular endothelial growth factor (VEGF), and its receptor (VEGFR-2). Kinases “downstream” from TrkB and VEGFR-2 were up-regulated in or near presumptive phrenic motor neurons, including phosphorylated extracellular-signal regulated kinase (p-ERK) and protein kinase B (p-AKT). Thus, 3×wAIH up-regulates neurochemicals known to be associated with phrenic motor plasticity. Since 3×wAIH upregulates pro-plasticity molecules without evidence for CNS pathology, it may be a useful therapeutic tool in treating disorders that cause respiratory insufficiency, such as spinal injury or motor neuron disease. PMID:22704858

GIRK Channels Modulate Opioid-Induced Motor Activity in a Cell Type- and Subunit-Dependent Manner

PubMed Central

Kotecki, Lydia; Hearing, Matthew; McCall, Nora M.; Marron Fernandez de Velasco, Ezequiel; Pravetoni, Marco; Arora, Devinder; Victoria, Nicole C.; Munoz, Michaelanne B.; Xia, Zhilian; Slesinger, Paul A.; Weaver, C. David

2015-01-01

G-protein-gated inwardly rectifying K+ (GIRK/Kir3) channel activation underlies key physiological effects of opioids, including analgesia and dependence. GIRK channel activation has also been implicated in the opioid-induced inhibition of midbrain GABA neurons and consequent disinhibition of dopamine (DA) neurons in the ventral tegmental area (VTA). Drug-induced disinhibition of VTA DA neurons has been linked to reward-related behaviors and underlies opioid-induced motor activation. Here, we demonstrate that mouse VTA GABA neurons express a GIRK channel formed by GIRK1 and GIRK2 subunits. Nevertheless, neither constitutive genetic ablation of Girk1 or Girk2, nor the selective ablation of GIRK channels in GABA neurons, diminished morphine-induced motor activity in mice. Moreover, direct activation of GIRK channels in midbrain GABA neurons did not enhance motor activity. In contrast, genetic manipulations that selectively enhanced or suppressed GIRK channel function in midbrain DA neurons correlated with decreased and increased sensitivity, respectively, to the motor-stimulatory effect of systemic morphine. Collectively, these data support the contention that the unique GIRK channel subtype in VTA DA neurons, the GIRK2/GIRK3 heteromer, regulates the sensitivity of the mouse mesolimbic DA system to drugs with addictive potential. PMID:25948263

Glutamatergic drive facilitates synaptic inhibition of dorsal vagal motor neurons after experimentally induced diabetes in mice

PubMed Central

Boychuk, Carie R.

2016-01-01

The role of central regulatory circuits in modulating diabetes-associated glucose dysregulation has only recently been under rigorous investigation. One brain region of interest is the dorsal motor nucleus of the vagus (DMV), which contains preganglionic parasympathetic motor neurons that regulate subdiaphragmatic visceral function. Previous research has demonstrated that glutamatergic and GABAergic neurotransmission are independently remodeled after chronic hyperglycemia/hypoinsulinemia. However, glutamatergic circuitry within the dorsal brain stem impinges on GABAergic regulation of the DMV. The present study investigated the role of glutamatergic neurotransmission in synaptic GABAergic control of DMV neurons after streptozotocin (STZ)-induced hyperglycemia/hypoinsulinemia by using electrophysiological recordings in vitro. The frequency of spontaneous inhibitory postsynaptic currents (sIPSCs) was elevated in DMV neurons from STZ-treated mice. The effect was abolished in the presence of the ionotropic glutamate receptor blocker kynurenic acid or the sodium channel blocker tetrodotoxin, suggesting that after STZ-induced hyperglycemia/hypoinsulinemia, increased glutamatergic receptor activity occurs at a soma-dendritic location on local GABA neurons projecting to the DMV. Although sIPSCs in DMV neurons normally demonstrated considerable amplitude variability, this variability was significantly increased after STZ-induced hyperglycemia/hypoinsulinemia. The elevated amplitude variability was not related to changes in quantal release, but rather correlated with significantly elevated frequency of sIPSCs in these mice. Taken together, these findings suggest that GABAergic regulation of central vagal circuitry responsible for the regulation of energy homeostasis undergoes complex functional reorganization after several days of hyperglycemia/hypoinsulinemia, including both glutamate-dependent and -independent forms of plasticity. PMID:27385796

Expression of Sex Steroid Hormone Receptors in Vagal Motor Neurons Innervating the Trachea and Esophagus in Mouse

PubMed Central

Mukudai, Shigeyuki; Ichi Matsuda, Ken; Bando, Hideki; Takanami, Keiko; Nishio, Takeshi; Sugiyama, Yoichiro; Hisa, Yasuo; Kawata, Mitsuhiro

2016-01-01

The medullary vagal motor nuclei, the nucleus ambiguus (NA) and dorsal motor nucleus of the vagus (DMV), innervate the respiratory and gastrointestinal tracts. We conducted immunohistochemical analysis of expression of the androgen receptor (AR) and estrogen receptor α (ERα), in relation to innervation of the trachea and esophagus via vagal motor nuclei in mice. AR and ERα were expressed in the rostral NA and in part of the DMV. Tracing experiments using cholera toxin B subunit demonstrated that neurons of vagal motor nuclei that innervate the trachea and esophagus express AR and ERα. There was no difference in expression of sex steroid hormone receptors between trachea- and esophagus-innervating neurons. These results suggest that sex steroid hormones may act on vagal motor nuclei via their receptors, thereby regulating functions of the trachea and esophagus. PMID:27006520

The water extract of Liuwei dihuang possesses multi-protective properties on neurons and muscle tissue against deficiency of survival motor neuron protein.

PubMed

Tseng, Yu-Ting; Jong, Yuh-Jyh; Liang, Wei-Fang; Chang, Fang-Rong; Lo, Yi-Ching

2017-10-15

Deficiency of survival motor neuron (SMN) protein, which is encoded by the SMN1 and SMN2 genes, induces widespread splicing defects mainly in spinal motor neurons, and leads to spinal muscular atrophy (SMA). Currently, there is no effective treatment for SMA. Liuwei dihuang (LWDH), a traditional Chinese herbal formula, possesses multiple therapeutic benefits against various diseases via modulation of the nervous, immune and endocrine systems. Previously, we demonstrated water extract of LWDH (LWDH-WE) protects dopaminergic neurons and improves motor activity in models of Parkinson's disease. This study aimed to investigate the potential protection of LWDH-WE on SMN deficiency-induced neurodegeneration and muscle weakness. The effects of LWDH-WE on SMN deficiency-induced neurotoxicity and muscle atrophy were examined by using SMN-deficient NSC34 motor neuron-like cells and SMA-like mice, respectively. Inducible SMN-knockdown NSC34 motor neuron-like cells were used to mimic SMN-deficient condition. Doxycycline (1 µg/ml) was used to induce SMN deficiency in stable NSC34 cell line carrying SMN-specific shRNA. SMAΔ7 mice were used as a severe type of SMA mouse model. Cell viability was measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) and lactate dehydrogenase (LDH) assays. Apoptotic cells and neurite length were observed by inverted microscope. Protein expressions were examined by western blots. Muscle strength of animals was evaluated by hind-limb suspension test. LWDH-WE significantly increased SMN protein level, mitochondrial membrane potential and cell viability of SMN-deficient NSC34 cells. LWDH-WE attenuated SMN deficiency-induced down-regulation of B-cell lymphoma-2 (Bcl-2) and up-regulation of cytosolic cytochrome c and cleaved caspase-3. Moreover, LWDH-WE prevented SMN deficiency-induced inhibition of neurite outgrowth and activation of Ras homolog gene family, member A (RhoA)/ Rho-associated protein kinase (ROCK2)/ phospho-LIM kinase (p-LIMK)/ phospho-cofilin (p-cofilin) pathway. Furthermore, in SMA-like mice, LWDH-WE improved muscle strength and body weight accompanied with up-regulation of SMN protein in spinal cord, brain, and gastrocnemius muscle tissues. The present study demonstrated that LWDH-WE protects motor neurons against SMN deficiency-induced neurodegeneration, and it also improves the muscle strength of SMA-like mice, suggesting the potential benefits of LWDH-WE as a complementary prescription for SMN deficiency-related diseases. Copyright © 2017 Elsevier GmbH. All rights reserved.

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.

MTHFSD and DDX58 are novel RNA-binding proteins abnormally regulated in amyotrophic lateral sclerosis.

PubMed

MacNair, Laura; Xiao, Shangxi; Miletic, Denise; Ghani, Mahdi; Julien, Jean-Pierre; Keith, Julia; Zinman, Lorne; Rogaeva, Ekaterina; Robertson, Janice

2016-01-01

Tar DNA-binding protein 43 (TDP-43) is an RNA-binding protein normally localized to the nucleus of cells, where it elicits functions related to RNA metabolism such as transcriptional regulation and alternative splicing. In amyotrophic lateral sclerosis, TDP-43 is mislocalized from the nucleus to the cytoplasm of diseased motor neurons, forming ubiquitinated inclusions. Although mutations in the gene encoding TDP-43, TARDBP, are found in amyotrophic lateral sclerosis, these are rare. However, TDP-43 pathology is common to over 95% of amyotrophic lateral sclerosis cases, suggesting that abnormalities of TDP-43 play an active role in disease pathogenesis. It is our hypothesis that a loss of TDP-43 from the nucleus of affected motor neurons in amyotrophic lateral sclerosis will lead to changes in RNA processing and expression. Identifying these changes could uncover molecular pathways that underpin motor neuron degeneration. Here we have used translating ribosome affinity purification coupled with microarray analysis to identify the mRNAs being actively translated in motor neurons of mutant TDP-43(A315T) mice compared to age-matched non-transgenic littermates. No significant changes were found at 5 months (presymptomatic) of age, but at 10 months (symptomatic) the translational profile revealed significant changes in genes involved in RNA metabolic process, immune response and cell cycle regulation. Of 28 differentially expressed genes, seven had a ≥ 2-fold change; four were validated by immunofluorescence labelling of motor neurons in TDP-43(A315T) mice, and two of these were confirmed by immunohistochemistry in amyotrophic lateral sclerosis cases. Both of these identified genes, DDX58 and MTHFSD, are RNA-binding proteins, and we show that TDP-43 binds to their respective mRNAs and we identify MTHFSD as a novel component of stress granules. This discovery-based approach has for the first time revealed translational changes in motor neurons of a TDP-43 mouse model, identifying DDX58 and MTHFSD as two TDP-43 targets that are misregulated in amyotrophic lateral sclerosis. © The Author (2015). Published by Oxford University Press on behalf of the Guarantors of Brain. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

FOXO3a is broadly neuroprotective in vitro and in vivo against insults implicated in motor neuron diseases

PubMed Central

Mojsilovic-Petrovic, Jelena; Nedelsky, Natalia; Boccitto, Marco; Mano, Itzhak; Georgiades, Savvas N.; Zhou, Weiguo; Liu, Yuhong; Neve, Rachael L.; Taylor, J. Paul; Driscoll, Monica; Clardy, Jon; Merry, Diane; Kalb, Robert G.

2009-01-01

Aging is a risk factor for the development of adult-onset neuro-degenerative diseases. While some of the molecular pathways regulating longevity and stress resistance in lower organisms are defined (i.e., those activating the transcriptional regulators DAF-16 and HSF-1 in C. elegans), their relevance to mammals and disease susceptibility are unknown. We studied the signaling controlled by the mammalian homolog of DAF-16, FOXO3a, in model systems of motor neuron disease. Neuron death elicited in vitro by excitotoxic insult or the expression of mutant SOD1, mutant p150glued or polyQ expanded androgen receptor was abrogated by expression of nuclear-targeted FOXO3a. We identify a compound (Psammaplysene A, PA) that increases nuclear localization of FOXO3a in vitro and in vivo and show that PA also protects against these insults in vitro. Administration of PA to invertebrate model systems of neurodegeneration similarly blocked neuron death in a DAF-16/FOXO3a-dependent manner. These results indicate that activation of the DAF-16/FOXO3a pathway, genetically or pharmacologically, confers protection against the known causes of motor neuron diseases. PMID:19553463

Prolyl Isomerase Pin1 Regulates Neuronal Differentiation via β-Catenin

PubMed Central

Nakamura, Kazuhiro; Kosugi, Isao; Lee, Daniel Y.; Hafner, Angela; Sinclair, David A.

2012-01-01

The Wnt/β-catenin pathway promotes proliferation of neural progenitor cells (NPCs) at early stages and induces neuronal differentiation from NPCs at late stages, but the molecular mechanisms that control this stage-specific response are unclear. Pin1 is a prolyl isomerase that regulates cell signaling uniquely by controlling protein conformation after phosphorylation, but its role in neuronal differentiation is not known. Here we found that whereas Pin1 depletion suppresses neuronal differentiation, Pin1 overexpression enhances it, without any effects on gliogenesis from NPCs in vitro. Consequently, Pin1-null mice have significantly fewer upper layer neurons in the motor cortex and severely impaired motor activity during the neonatal stage. A proteomic approach identified β-catenin as a major substrate for Pin1 in NPCs, in which Pin1 stabilizes β-catenin. As a result, Pin1 knockout leads to reduced β-catenin during differentiation but not proliferation of NPCs in developing brains. Importantly, defective neuronal differentiation in Pin1 knockout NPCs is fully rescued in vitro by overexpression of β-catenin but not a β-catenin mutant that fails to act as a Pin1 substrate. These results show that Pin1 is a novel regulator of NPC differentiation by acting on β-catenin and provides a new postphosphorylation signaling mechanism to regulate developmental stage-specific functioning of β-catenin signaling in neuronal differentiation. PMID:22645310

Cholestenoic acids regulate motor neuron survival via liver X receptors

PubMed Central

Theofilopoulos, Spyridon; Griffiths, William J.; Crick, Peter J.; Yang, Shanzheng; Meljon, Anna; Ogundare, Michael; Kitambi, Satish Srinivas; Lockhart, Andrew; Tuschl, Karin; Clayton, Peter T.; Morris, Andrew A.; Martinez, Adelaida; Reddy, M. Ashwin; Martinuzzi, Andrea; Bassi, Maria T.; Honda, Akira; Mizuochi, Tatsuki; Kimura, Akihiko; Nittono, Hiroshi; De Michele, Giuseppe; Carbone, Rosa; Criscuolo, Chiara; Yau, Joyce L.; Seckl, Jonathan R.; Schüle, Rebecca; Schöls, Ludger; Sailer, Andreas W.; Kuhle, Jens; Fraidakis, Matthew J.; Gustafsson, Jan-Åke; Steffensen, Knut R.; Björkhem, Ingemar; Ernfors, Patrik; Sjövall, Jan; Arenas, Ernest; Wang, Yuqin

2014-01-01

Cholestenoic acids are formed as intermediates in metabolism of cholesterol to bile acids, and the biosynthetic enzymes that generate cholestenoic acids are expressed in the mammalian CNS. Here, we evaluated the cholestenoic acid profile of mammalian cerebrospinal fluid (CSF) and determined that specific cholestenoic acids activate the liver X receptors (LXRs), enhance islet-1 expression in zebrafish, and increase the number of oculomotor neurons in the developing mouse in vitro and in vivo. While 3β,7α-dihydroxycholest-5-en-26-oic acid (3β,7α-diHCA) promoted motor neuron survival in an LXR-dependent manner, 3β-hydroxy-7-oxocholest-5-en-26-oic acid (3βH,7O-CA) promoted maturation of precursors into islet-1+ cells. Unlike 3β,7α-diHCA and 3βH,7O-CA, 3β-hydroxycholest-5-en-26-oic acid (3β-HCA) caused motor neuron cell loss in mice. Mutations in CYP7B1 or CYP27A1, which encode enzymes involved in cholestenoic acid metabolism, result in different neurological diseases, hereditary spastic paresis type 5 (SPG5) and cerebrotendinous xanthomatosis (CTX), respectively. SPG5 is characterized by spastic paresis, and similar symptoms may occur in CTX. Analysis of CSF and plasma from patients with SPG5 revealed an excess of the toxic LXR ligand, 3β-HCA, while patients with CTX and SPG5 exhibited low levels of the survival-promoting LXR ligand 3β,7α-diHCA. Moreover, 3β,7α-diHCA prevented the loss of motor neurons induced by 3β-HCA in the developing mouse midbrain in vivo.Our results indicate that specific cholestenoic acids selectively work on motor neurons, via LXR, to regulate the balance between survival and death. PMID:25271621

Energy Homeostasis and Abnormal RNA Metabolism in Amyotrophic Lateral Sclerosis

PubMed Central

Liu, Yu-Ju; Tsai, Po-Yi; Chern, Yijuang

2017-01-01

Amyotrophic lateral sclerosis (ALS) is a fatal motor neuron disease that is clinically characterized by progressive muscle weakness and impaired voluntary movement due to the loss of motor neurons in the brain, brain stem and spinal cord. To date, no effective treatment is available. Ample evidence suggests that impaired RNA homeostasis and abnormal energy status are two major pathogenesis pathways in ALS. In the present review article, we focus on recent studies that report molecular insights of both pathways, and discuss the possibility that energy dysfunction might negatively regulate RNA homeostasis via the impairment of cytoplasmic-nuclear shuttling in motor neurons and subsequently contribute to the development of ALS. PMID:28522961

Tau Deficiency Down-Regulated Transcription Factor Orthodenticle Homeobox 2 Expression in the Dopaminergic Neurons in Ventral Tegmental Area and Caused No Obvious Motor Deficits in Mice

PubMed Central

Tang, Xiaolu; Jiao, Luyan; Zheng, Meige; Yan, Yan; Nie, Qi; Wu, Ting; Wan, Xiaomei; Zhang, Guofeng; Li, Yonglin; Wu, Song; Jiang, Bin; Cai, Huaibin; Xu, Pingyi; Duan, Jinhai; Lin, Xian

2018-01-01

Tau protein participates in microtubule stabilization, axonal transport, and protein trafficking. Loss of normal tau function will exert a negative effect. However, current knowledge on the impact of tau deficiency on the motor behavior and related neurobiological changes is controversial. In this study, we examined motor functions and analyzed several proteins implicated in the maintenance of midbrain dopaminergic (DA) neurons (mDANs) function of adult and aged tau+/+, tau+/−, tau−/− mice. We found tau deficiency could not induce significant motor disorders. However, we discovered lower expression levels of transcription factors Orthodenticle homeobox 2 (OTX2) of mDANs in older aged mice. Compared with age-matched tau+/+ mice, there were 54.1% lower (p = 0.0192) OTX2 protein (OTX2-fluorescence intensity) in VTA DA neurons of tau+/−mice and 43.6% lower (p = 0.0249) OTX2 protein in VTA DA neurons of tau−/−mice at 18 months old. Combined with the relevant reports, our results suggested that tau deficiency alone might not be enough to mimic the pathology of Parkinson’s disease. However, OTX2 down-regulation indicates that mDANs of tau-deficient mice will be more sensitive to toxic damage from MPTP. PMID:29337233

Muscles innervated by a single motor neuron exhibit divergent synaptic properties on multiple time scales.

PubMed

Blitz, Dawn M; Pritchard, Amy E; Latimer, John K; Wakefield, Andrew T

2017-04-01

Adaptive changes in the output of neural circuits underlying rhythmic behaviors are relayed to muscles via motor neuron activity. Presynaptic and postsynaptic properties of neuromuscular junctions can impact the transformation from motor neuron activity to muscle response. Further, synaptic plasticity occurring on the time scale of inter-spike intervals can differ between multiple muscles innervated by the same motor neuron. In rhythmic behaviors, motor neuron bursts can elicit additional synaptic plasticity. However, it is unknown whether plasticity regulated by the longer time scale of inter-burst intervals also differs between synapses from the same neuron, and whether any such distinctions occur across a physiological activity range. To address these issues, we measured electrical responses in muscles innervated by a chewing circuit neuron, the lateral gastric (LG) motor neuron, in a well-characterized small motor system, the stomatogastric nervous system (STNS) of the Jonah crab, Cancer borealis In vitro and in vivo , sensory, hormonal and modulatory inputs elicit LG bursting consisting of inter-spike intervals of 50-250 ms and inter-burst intervals of 2-24 s. Muscles expressed similar facilitation measured with paired stimuli except at the shortest inter-spike interval. However, distinct decay time constants resulted in differences in temporal summation. In response to bursting activity, augmentation occurred to different extents and saturated at different inter-burst intervals. Further, augmentation interacted with facilitation, resulting in distinct intra-burst facilitation between muscles. Thus, responses of multiple target muscles diverge across a physiological activity range as a result of distinct synaptic properties sensitive to multiple time scales. © 2017. Published by The Company of Biologists Ltd.

Astrocytes influence the severity of spinal muscular atrophy

PubMed Central

Rindt, Hansjörg; Feng, Zhihua; Mazzasette, Chiara; Glascock, Jacqueline J.; Valdivia, David; Pyles, Noah; Crawford, Thomas O.; Swoboda, Kathryn J.; Patitucci, Teresa N.; Ebert, Allison D.; Sumner, Charlotte J.; Ko, Chien-Ping; Lorson, Christian L.

2015-01-01

Systemically low levels of survival motor neuron-1 (SMN1) protein cause spinal muscular atrophy (SMA). α-Motor neurons of the spinal cord are considered particularly vulnerable in this genetic disorder and their dysfunction and loss cause progressive muscle weakness, paralysis and eventually premature death of afflicted individuals. Historically, SMA was therefore considered a motor neuron-autonomous disease. However, depletion of SMN in motor neurons of normal mice elicited only a very mild phenotype. Conversely, restoration of SMN to motor neurons in an SMA mouse model had only modest effects on the SMA phenotype and survival. Collectively, these results suggested that additional cell types contribute to the pathogenesis of SMA, and understanding the non-autonomous requirements is crucial for developing effective therapies. Astrocytes are critical for regulating synapse formation and function as well as metabolic support for neurons. We hypothesized that astrocyte functions are disrupted in SMA, exacerbating disease progression. Using viral-based restoration of SMN specifically to astrocytes, survival in severe and intermediate SMA mice was observed. In addition, neuromuscular circuitry was improved. Astrogliosis was prominent in end-stage SMA mice and in post-mortem patient spinal cords. Increased expression of proinflammatory cytokines was partially normalized in treated mice, suggesting that astrocytes contribute to the pathogenesis of SMA. PMID:25911676

The AMPA receptor subunit GluR1 regulates dendritic architecture of motor neurons

NASA Technical Reports Server (NTRS)

Inglis, Fiona M.; Crockett, Richard; Korada, Sailaja; Abraham, Wickliffe C.; Hollmann, Michael; Kalb, Robert G.

2002-01-01

The morphology of the mature motor neuron dendritic arbor is determined by activity-dependent processes occurring during a critical period in early postnatal life. The abundance of the AMPA receptor subunit GluR1 in motor neurons is very high during this period and subsequently falls to a negligible level. To test the role of GluR1 in dendrite morphogenesis, we reintroduced GluR1 into rat motor neurons at the end of the critical period and quantitatively studied the effects on dendrite architecture. Two versions of GluR1 were studied that differed by the amino acid in the "Q/R" editing site. The amino acid occupying this site determines single-channel conductance, ionic permeability, and other essential electrophysiologic properties of the resulting receptor channels. We found large-scale remodeling of dendritic architectures in a manner depending on the amino acid occupying the Q/R editing site. Alterations in the distribution of dendritic arbor were not prevented by blocking NMDA receptors. These observations suggest that the expression of GluR1 in motor neurons modulates a component of the molecular substrate of activity-dependent dendrite morphogenesis. The control of these events relies on subunit-specific properties of AMPA receptors.

Mutant PFN1 causes ALS phenotypes and progressive motor neuron degeneration in mice by a gain of toxicity

PubMed Central

Yang, Chunxing; Danielson, Eric W.; Qiao, Tao; Metterville, Jake; Brown, Robert H.; Landers, John E.; Xu, Zuoshang

2016-01-01

Mutations in the profilin 1 (PFN1) gene cause amyotrophic lateral sclerosis (ALS), a neurodegenerative disease caused by the loss of motor neurons leading to paralysis and eventually death. PFN1 is a small actin-binding protein that promotes formin-based actin polymerization and regulates numerous cellular functions, but how the mutations in PFN1 cause ALS is unclear. To investigate this problem, we have generated transgenic mice expressing either the ALS-associated mutant (C71G) or wild-type protein. Here, we report that mice expressing the mutant, but not the wild-type, protein had relentless progression of motor neuron loss with concomitant progressive muscle weakness ending in paralysis and death. Furthermore, mutant, but not wild-type, PFN1 forms insoluble aggregates, disrupts cytoskeletal structure, and elevates ubiquitin and p62/SQSTM levels in motor neurons. Unexpectedly, the acceleration of motor neuron degeneration precedes the accumulation of mutant PFN1 aggregates. These results suggest that although mutant PFN1 aggregation may contribute to neurodegeneration, it does not trigger its onset. Importantly, these experiments establish a progressive disease model that can contribute toward identifying the mechanisms of ALS pathogenesis and the development of therapeutic treatments. PMID:27681617

Developing grasshopper neurons show variable levels of guanylyl cyclase activity on arrival at their targets.

PubMed

Ball, E E; Truman, J W

1998-04-27

The ability of certain grasshopper neurons to respond to exogenously applied donors of nitric oxide (NO) by producing cyclic GMP (cGMP) depends on their developmental state. ODQ, a selective blocker of NO-sensitive guanylyl cyclase, blocks cGMP production at 10(-5) M, thus confirming the nature of the response. Experiments in which the distal axon is separated from its proximal stump before application of an NO donor show that guanylyl cyclase is distributed uniformly throughout the neuron. In the locust abdomen, where segments are formed sequentially, the pattern of guanylyl cyclase up-regulation is predictable and sequential from anterior to posterior. There are two patterns of innervation by cGMP-expressing motor neurons. In the first, typified by muscle 187, an innervating neuron begins to be NO responsive on arrival at its muscle and continues to be so over most of the remainder of embryonic development, including the formation of motor end plates. In the second, typified by a neuron innervating muscle 191, the neuron extends well along the muscle, apparently laying down a number of sites of contact with it, before it becomes NO responsive. In both patterns, however, NO responsiveness marks the neuron's transition from growth cone elongation to the production of lateral branches. Individual muscles receive innervation from multiple motor neurons, some of which express transient NO sensitivity during development and others which do not. With the exception of the leg motor neuron SETi, the first motor neuron to reach any muscle is usually not NO responsive. We suggest that cGMP plays a role in, or reflects, the early stages of communication between a target and specific innervating neurons.

Network feedback regulates motor output across a range of modulatory neuron activity

PubMed Central

Spencer, Robert M.

2016-01-01

Modulatory projection neurons alter network neuron synaptic and intrinsic properties to elicit multiple different outputs. Sensory and other inputs elicit a range of modulatory neuron activity that is further shaped by network feedback, yet little is known regarding how the impact of network feedback on modulatory neurons regulates network output across a physiological range of modulatory neuron activity. Identified network neurons, a fully described connectome, and a well-characterized, identified modulatory projection neuron enabled us to address this issue in the crab (Cancer borealis) stomatogastric nervous system. The modulatory neuron modulatory commissural neuron 1 (MCN1) activates and modulates two networks that generate rhythms via different cellular mechanisms and at distinct frequencies. MCN1 is activated at rates of 5–35 Hz in vivo and in vitro. Additionally, network feedback elicits MCN1 activity time-locked to motor activity. We asked how network activation, rhythm speed, and neuron activity levels are regulated by the presence or absence of network feedback across a physiological range of MCN1 activity rates. There were both similarities and differences in responses of the two networks to MCN1 activity. Many parameters in both networks were sensitive to network feedback effects on MCN1 activity. However, for most parameters, MCN1 activity rate did not determine the extent to which network output was altered by the addition of network feedback. These data demonstrate that the influence of network feedback on modulatory neuron activity is an important determinant of network output and feedback can be effective in shaping network output regardless of the extent of network modulation. PMID:27030739

Progranulin contributes to endogenous mechanisms of pain defense after nerve injury in mice.

PubMed

Lim, Hee-Young; Albuquerque, Boris; Häussler, Annett; Myrczek, Thekla; Ding, Aihao; Tegeder, Irmgard

2012-04-01

Progranulin haploinsufficiency is associated with frontotemporal dementia in humans. Deficiency of progranulin led to exaggerated inflammation and premature aging in mice. The role of progranulin in adaptations to nerve injury and neuropathic pain are still unknown. Here we found that progranulin is up-regulated after injury of the sciatic nerve in the mouse ipsilateral dorsal root ganglia and spinal cord, most prominently in the microglia surrounding injured motor neurons. Progranulin knockdown by continuous intrathecal spinal delivery of small interfering RNA after sciatic nerve injury intensified neuropathic pain-like behaviour and delayed the recovery of motor functions. Compared to wild-type mice, progranulin-deficient mice developed more intense nociceptive hypersensitivity after nerve injury. The differences escalated with aging. Knockdown of progranulin reduced the survival of dissociated primary neurons and neurite outgrowth, whereas addition of recombinant progranulin rescued primary dorsal root ganglia neurons from cell death induced by nerve growth factor withdrawal. Thus, up-regulation of progranulin after neuronal injury may reduce neuropathic pain and help motor function recovery, at least in part, by promoting survival of injured neurons and supporting regrowth. A deficiency in this mechanism may increase the risk for injury-associated chronic pain. © 2011 The Authors Journal of Cellular and Molecular Medicine © 2011 Foundation for Cellular and Molecular Medicine/Blackwell Publishing Ltd.

Regulation of Survival Motor Neuron Protein by the Nuclear Factor-Kappa B Pathway in Mouse Spinal Cord Motoneurons.

PubMed

Arumugam, Saravanan; Mincheva-Tasheva, Stefka; Periyakaruppiah, Ambika; de la Fuente, Sandra; Soler, Rosa M; Garcera, Ana

2018-06-01

Survival motor neuron (SMN) protein deficiency causes the genetic neuromuscular disorder spinal muscular atrophy (SMA), characterized by spinal cord motoneuron degeneration. Since SMN protein level is critical to disease onset and severity, analysis of the mechanisms involved in SMN stability is one of the central goals of SMA research. Here, we describe the role of several members of the NF-κB pathway in regulating SMN in motoneurons. NF-κB is one of the main regulators of motoneuron survival and pharmacological inhibition of NF-κB pathway activity also induces mouse survival motor neuron (Smn) protein decrease. Using a lentiviral-based shRNA approach to reduce the expression of several members of NF-κB pathway, we observed that IKK and RelA knockdown caused Smn reduction in mouse-cultured motoneurons whereas IKK or RelB knockdown did not. Moreover, isolated motoneurons obtained from the severe SMA mouse model showed reduced protein levels of several NF-κB members and RelA phosphorylation. We describe the alteration of NF-κB pathway in SMA cells. In the context of recent studies suggesting regulation of altered intracellular pathways as a future pharmacological treatment of SMA, we propose the NF-κB pathway as a candidate in this new therapeutic approach.

Quantitation of Contacts Among Sensory, Motor, and Serotonergic Neurons in the Pedal Ganglion of Aplysia

PubMed Central

Zhang, Han; Wainwright, Marcy; Byrne, John H.; Cleary, Leonard J.

2003-01-01

Present models of long-term sensitization in Aplysia californica indicate that the enhanced behavioral response is due, at least in part, to outgrowth of sensory neurons mediating defensive withdrawal reflexes. Presumably, this outgrowth strengthens pre-existing connections by formation of newsynapses with follower neurons. However, the relationship between the number of sensorimotor contacts and the physiological strength of the connection has never been examined in intact ganglia. As a first step in addressing this issue, we used confocal microscopy to examine sites of contact between sensory and motor neurons in naive animals. Our results revealed relatively fewcontacts between physiologically connected cells. In addition, the number of contact sites was proportional to the amplitude of the EPSP elicited in the follower motor neuron by direct stimulation of the sensory neuron. This is the first time such a correlation has been observed in the central nervous system. Serotonin is the neurotransmitter most closely examined for its role in modulating synaptic strength at the sensorimotor synapse. However, the structural relationship of serotonergic processes and sensorimotor synapses has never been examined. Surprisingly, serotonergic processes usually made contact with sensory and motor neurons at sites located relatively distant from the sensorimotor synapse. This result implies that heterosynaptic regulation is due to nondirected release of serotonin into the neuropil. PMID:14557611

Spinal neurons require Islet1 for subtype-specific differentiation of electrical excitability

PubMed Central

2014-01-01

Background In the spinal cord, stereotypic patterns of transcription factor expression uniquely identify neuronal subtypes. These transcription factors function combinatorially to regulate gene expression. Consequently, a single transcription factor may regulate divergent development programs by participation in different combinatorial codes. One such factor, the LIM-homeodomain transcription factor Islet1, is expressed in the vertebrate spinal cord. In mouse, chick and zebrafish, motor and sensory neurons require Islet1 for specification of biochemical and morphological signatures. Little is known, however, about the role that Islet1 might play for development of electrical membrane properties in vertebrates. Here we test for a role of Islet1 in differentiation of excitable membrane properties of zebrafish spinal neurons. Results We focus our studies on the role of Islet1 in two populations of early born zebrafish spinal neurons: ventral caudal primary motor neurons (CaPs) and dorsal sensory Rohon-Beard cells (RBs). We take advantage of transgenic lines that express green fluorescent protein (GFP) to identify CaPs, RBs and several classes of interneurons for electrophysiological study. Upon knock-down of Islet1, cells occupying CaP-like and RB-like positions continue to express GFP. With respect to voltage-dependent currents, CaP-like and RB-like neurons have novel repertoires that distinguish them from control CaPs and RBs, and, in some respects, resemble those of neighboring interneurons. The action potentials fired by CaP-like and RB-like neurons also have significantly different properties compared to those elicited from control CaPs and RBs. Conclusions Overall, our findings suggest that, for both ventral motor and dorsal sensory neurons, Islet1 directs differentiation programs that ultimately specify electrical membrane as well as morphological properties that act together to sculpt neuron identity. PMID:25149090

Specialized Motor-Driven dusp1 Expression in the Song Systems of Multiple Lineages of Vocal Learning Birds

PubMed Central

Horita, Haruhito; Kobayashi, Masahiko; Liu, Wan-chun; Oka, Kotaro; Jarvis, Erich D.; Wada, Kazuhiro

2012-01-01

Mechanisms for the evolution of convergent behavioral traits are largely unknown. Vocal learning is one such trait that evolved multiple times and is necessary in humans for the acquisition of spoken language. Among birds, vocal learning is evolved in songbirds, parrots, and hummingbirds. Each time similar forebrain song nuclei specialized for vocal learning and production have evolved. This finding led to the hypothesis that the behavioral and neuroanatomical convergences for vocal learning could be associated with molecular convergence. We previously found that the neural activity-induced gene dual specificity phosphatase 1 (dusp1) was up-regulated in non-vocal circuits, specifically in sensory-input neurons of the thalamus and telencephalon; however, dusp1 was not up-regulated in higher order sensory neurons or motor circuits. Here we show that song motor nuclei are an exception to this pattern. The song nuclei of species from all known vocal learning avian lineages showed motor-driven up-regulation of dusp1 expression induced by singing. There was no detectable motor-driven dusp1 expression throughout the rest of the forebrain after non-vocal motor performance. This pattern contrasts with expression of the commonly studied activity-induced gene egr1, which shows motor-driven expression in song nuclei induced by singing, but also motor-driven expression in adjacent brain regions after non-vocal motor behaviors. In the vocal non-learning avian species, we found no detectable vocalizing-driven dusp1 expression in the forebrain. These findings suggest that independent evolutions of neural systems for vocal learning were accompanied by selection for specialized motor-driven expression of the dusp1 gene in those circuits. This specialized expression of dusp1 could potentially lead to differential regulation of dusp1-modulated molecular cascades in vocal learning circuits. PMID:22876306

The Small GTP-Binding Protein Rhes Influences Nigrostriatal-Dependent Motor Behavior During Aging.

PubMed

Pinna, Annalisa; Napolitano, Francesco; Pelosi, Barbara; Di Maio, Anna; Wardas, Jadwiga; Casu, Maria Antonietta; Costa, Giulia; Migliarini, Sara; Calabresi, Paolo; Pasqualetti, Massimo; Morelli, Micaela; Usiello, Alessandro

2016-04-01

Here we aimed to evaluate: (1) Rhes mRNA expression in mouse midbrain, (2) the effect of Rhes deletion on the number of dopamine neurons, (3) nigrostriatal-sensitive behavior during aging in knockout mice. Radioactive in situ hybridization was assessed in adult mice. The beam-walking test was executed in 3-, 6- and 12-month-old mice. Immunohistochemistry of midbrain tyrosine hydroxylase (TH)-positive neurons was performed in 6- and 12-month-old mice. Rhes mRNA is expressed in TH-positive neurons of SNpc and the ventral tegmental area. Moreover, lack of Rhes leads to roughly a 20% loss of nigral TH-positive neurons in both 6- and 12-month-old mutants, when compared with their age-matched controls. Finally, lack of Rhes triggers subtle alterations in motor performance and coordination during aging. Our findings indicate a fine-tuning role of Rhes in regulating the number of TH-positive neurons of the substantia nigra and nigrostriatal-sensitive motor behavior during aging. © 2016 International Parkinson and Movement Disorder Society.

TNF-α contributes to up-regulation of Nav1.3 and Nav1.8 in DRG neurons following motor fiber injury.

PubMed

He, Xin-Hua; Zang, Ying; Chen, Xi; Pang, Rui-Ping; Xu, Ji-Tian; Zhou, Xiang; Wei, Xu-Hong; Li, Yong-Yong; Xin, Wen-Jun; Qin, Zhi-Hai; Liu, Xian-Guo

2010-11-01

A large body of evidence has demonstrated that the ectopic discharges of action potentials in primary afferents, resulted from the abnormal expression of voltage gated sodium channels (VGSCs) in dorsal root ganglion (DRG) neurons following peripheral nerve injury are important for the development of neuropathic pain. However, how nerve injury affects the expression of VGSCs is largely unknown. Here, we reported that selective injury of motor fibers by L5 ventral root transection (L5-VRT) up-regulated Nav1.3 and Nav1.8 at both mRNA and protein level and increased current densities of TTX-S and TTX-R channels in DRG neurons, suggesting that nerve injury may up-regulate functional VGSCs in sensory neurons indirectly. As the up-regulated Nav1.3 and Nav1.8 were highly co-localized with TNF-α, we tested the hypothesis that the increased TNF-α may lead to over-expression of the sodium channels. Indeed, we found that peri-sciatic administration of recombinant rat TNF-α (rrTNF) without any nerve injury, which produced lasting mechanical allodynia, also up-regulated Nav1.3 and Nav1.8 in DRG neurons in vivo and that rrTNF enhanced the expression of Nav1.3 and Nav1.8 in cultured adult rat DRG neurons in a dose-dependent manner. Furthermore, inhibition of TNF-α synthesis, which prevented neuropathic pain, strongly inhibited the up-regulation of Nav1.3 and Nav1.8. The up-regulation of the both channels following L5-VRT was significantly lower in TNF receptor 1 knockout mice than that in wild type mice. These data suggest that increased TNF-α may be responsible for up-regulation of Nav1.3 and Nav1.8 in uninjured DRG neurons following nerve injury. Copyright © 2010 International Association for the Study of Pain. Published by Elsevier B.V. All rights reserved.

Network feedback regulates motor output across a range of modulatory neuron activity.

PubMed

Spencer, Robert M; Blitz, Dawn M

2016-06-01

Modulatory projection neurons alter network neuron synaptic and intrinsic properties to elicit multiple different outputs. Sensory and other inputs elicit a range of modulatory neuron activity that is further shaped by network feedback, yet little is known regarding how the impact of network feedback on modulatory neurons regulates network output across a physiological range of modulatory neuron activity. Identified network neurons, a fully described connectome, and a well-characterized, identified modulatory projection neuron enabled us to address this issue in the crab (Cancer borealis) stomatogastric nervous system. The modulatory neuron modulatory commissural neuron 1 (MCN1) activates and modulates two networks that generate rhythms via different cellular mechanisms and at distinct frequencies. MCN1 is activated at rates of 5-35 Hz in vivo and in vitro. Additionally, network feedback elicits MCN1 activity time-locked to motor activity. We asked how network activation, rhythm speed, and neuron activity levels are regulated by the presence or absence of network feedback across a physiological range of MCN1 activity rates. There were both similarities and differences in responses of the two networks to MCN1 activity. Many parameters in both networks were sensitive to network feedback effects on MCN1 activity. However, for most parameters, MCN1 activity rate did not determine the extent to which network output was altered by the addition of network feedback. These data demonstrate that the influence of network feedback on modulatory neuron activity is an important determinant of network output and feedback can be effective in shaping network output regardless of the extent of network modulation. Copyright © 2016 the American Physiological Society.

Adrenoceptor-Mediated Post- and Pre-Synaptic Regulations of the Reticulospinal Neurons in Rat Caudal Pontine Reticular Nucleus.

PubMed

Yang, Nian; Qiao, Qi-Cheng; Liu, Yu-Hui; Zhang, Ji-Qiang; Hu, Zhi-An; Zhang, Jun

2016-12-01

The central noradrenergic system participates in diverse nervous functions. Nevertheless, our knowledge of the action of adrenoceptors in motor regulation is still lacking. Intriguingly, reticulospinal neurons in the caudal pontine reticular nucleus (PnC) receive fairly dense noradrenergic innervation and play an important role in motor control. Here, after demonstrating the expression of α1- and α2-adrenoceptors in the PnC, we found that noradrenaline elicited a post-synaptic effect (inward or outward whole-cell current at -70 mV holding) on PnC reticulospinal neurons. The α1- and α2-adrenoceptors were co-expressed in individual PnC reticulospinal neurons to mediate an inward and an outward current component at -70 mV holding, respectively, which, when superposed, produced the overall post-synaptic effects of noradrenaline (NA). More importantly, the activation of post-synaptic α1- or α2-adrenoceptors indeed exerted opposing modulations (excitation vs. inhibition) on the firing activities of individual PnC reticulospinal neurons. Furthermore, the activation and inhibition of the Na + -permeable non-selective cationic conductance (NSCC) were demonstrated to be coupled to α1- and α2-adrenoceptors, respectively. Additionally, the activation of α2-adrenoceptors activated K + conductance. Pre-synaptically, the α2-adrenoceptors were expressed to attenuate the miniature excitatory postsynaptic current (mEPSC) in PnC reticulospinal neurons, but not to affect the miniature inhibitory postsynaptic current (mIPSC). Consistently, the evoked EPSC in PnC reticulospinal neurons was suppressed after the activation of pre-synaptic α2-adrenoceptors. Thus, the excitatory input and post-synaptic dynamics of PnC reticulospinal neurons are indeed intricately modulated by the activation of α1- and α2-adrenoceptors, through which motor control may be regulated in an adaptive manner by the central noradrenergic system.

Sleep-Active Neurons: Conserved Motors of Sleep

PubMed Central

Bringmann, Henrik

2018-01-01

Sleep is crucial for survival and well-being. This behavioral and physiological state has been studied in all major genetically accessible model animals, including rodents, fish, flies, and worms. Genetic and optogenetic studies have identified several neurons that control sleep, making it now possible to compare circuit mechanisms across species. The “motor” of sleep across animal species is formed by neurons that depolarize at the onset of sleep to actively induce this state by directly inhibiting wakefulness. These sleep-inducing neurons are themselves controlled by inhibitory or activating upstream pathways, which act as the “drivers” of the sleep motor: arousal inhibits “sleep-active” neurons whereas various sleep-promoting “tiredness” pathways converge onto sleep-active neurons to depolarize them. This review provides the first overview of sleep-active neurons across the major model animals. The occurrence of sleep-active neurons and their regulation by upstream pathways in both vertebrate and invertebrate species suggests that these neurons are general and ancient components that evolved early in the history of nervous systems. PMID:29618588

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.

SMN control of RNP assembly: from post-transcriptional gene regulation to motor neuron disease

PubMed Central

Li, Darrick K.; Tisdale, Sarah; Lotti, Francesco; Pellizzoni, Livio

2014-01-01

At the post-transcriptional level, expression of protein-coding genes is controlled by a series of RNA regulatory events including nuclear processing of primary transcripts, transport of mature mRNAs to specific cellular compartments, translation and ultimately, turnover. These processes are orchestrated through the dynamic association of mRNAs with RNA binding proteins and ribonucleoprotein (RNP) complexes. Accurate formation of RNPs in vivo is fundamentally important to cellular development and function, and its impairment often leads to human disease. The survival motor neuron (SMN) protein is key to this biological paradigm: SMN is essential for the biogenesis of various RNPs that function in mRNA processing, and genetic mutations leading to SMN deficiency cause the neurodegenerative disease spinal muscular atrophy. Here we review the expanding role of SMN in the regulation of gene expression through its multiple functions in RNP assembly. We discuss advances in our understanding of SMN activity as a chaperone of RNPs and how disruption of SMN-dependent RNA pathways can cause motor neuron disease. PMID:24769255

Direct interaction of microtubule- and actin-based transport motors

NASA Technical Reports Server (NTRS)

Huang, J. D.; Brady, S. T.; Richards, B. W.; Stenolen, D.; Resau, J. H.; Copeland, N. G.; Jenkins, N. A.

1999-01-01

The microtubule network is thought to be used for long-range transport of cellular components in animal cells whereas the actin network is proposed to be used for short-range transport, although the mechanism(s) by which this transport is coordinated is poorly understood. For example, in sea urchins long-range Ca2+-regulated transport of exocytotic vesicles requires a microtubule-based motor, whereas an actin-based motor is used for short-range transport. In neurons, microtubule-based kinesin motor proteins are used for long-range vesicular transport but microtubules do not extend into the neuronal termini, where actin filaments form the cytoskeletal framework, and kinesins are rapidly degraded upon their arrival in neuronal termini, indicating that vesicles may have to be transferred from microtubules to actin tracks to reach their final destination. Here we show that an actin-based vesicle-transport motor, MyoVA, can interact directly with a microtubule-based transport motor, KhcU. As would be expected if these complexes were functional, they also contain kinesin light chains and the localization of MyoVA and KhcU overlaps in the cell. These results indicate that cellular transport is, in part, coordinated through the direct interaction of different motor molecules.

Heat shock protein 70.1 (Hsp70.1) affects neuronal cell fate by regulating lysosomal acid sphingomyelinase.

PubMed

Zhu, Hong; Yoshimoto, Tanihiro; Yamashima, Tetsumori

2014-10-03

The inducible expression of heat shock protein 70.1 (Hsp70.1) plays cytoprotective roles in its molecular chaperone function. Binding of Hsp70 to an endolysosomal phospholipid, bis(monoacylglycero)phosphate (BMP), has been recently shown to stabilize lysosomal membranes by enhancing acid sphingomyelinase (ASM) activity in cancer cells. Using the monkey experimental paradigm, we have reported that calpain-mediated cleavage of oxidized Hsp70.1 causes neurodegeneration in the hippocampal cornu ammonis 1 (CA1), whereas expression of Hsp70.1 in the motor cortex without calpain activation contributes to neuroprotection. However, the molecular mechanisms of the lysosomal destabilization/stabilization determining neuronal cell fate have not been elucidated. To elucidate whether regulation of lysosomal ASM could affect the neuronal fate, we analyzed Hsp70.1-BMP binding and ASM activity by comparing the motor cortex and the CA1. We show that Hsp70.1 being localized at the lysosomal membrane, lysosomal lipid BMP levels, and the lipid binding domain of Hsp70.1 are crucial for Hsp70.1-BMP binding. In the postischemic motor cortex, Hsp70.1 being localized at the lysosomal membrane could bind to BMP without calpain activation and decreased BMP levels, resulting in increasing ASM activity and lysosomal stability. However, in the postischemic CA1, calpain activation and a concomitant decrease in the lysosomal membrane localization of Hsp70.1 and BMP levels may diminish Hsp70.1-BMP binding, resulting in decreased ASM activity and lysosomal rupture with leakage of cathepsin B into the cytosol. A TUNEL assay revealed the differential neuronal vulnerability between the CA1 and the motor cortex. These results suggest that regulation of ASM activation in vivo by Hsp70.1-BMP affects lysosomal stability and neuronal survival or death after ischemia/reperfusion. © 2014 by The American Society for Biochemistry and Molecular Biology, Inc.

Oligodendrocyte- and Neuron-Specific Nogo-A Restrict Dendritic Branching and Spine Density in the Adult Mouse Motor Cortex.

PubMed

Zemmar, Ajmal; Chen, Chia-Chien; Weinmann, Oliver; Kast, Brigitt; Vajda, Flora; Bozeman, James; Isaad, Noel; Zuo, Yi; Schwab, Martin E

2018-06-01

Nogo-A has been well described as a myelin-associated inhibitor of neurite outgrowth and functional neuroregeneration after central nervous system (CNS) injury. Recently, a new role of Nogo-A has been identified as a negative regulator of synaptic plasticity in the uninjured adult CNS. Nogo-A is present in neurons and oligodendrocytes. However, it is yet unclear which of these two pools regulate synaptic plasticity. To address this question we used newly generated mouse lines in which Nogo-A is specifically knocked out in (1) oligodendrocytes (oligoNogo-A KO) or (2) neurons (neuroNogo-A KO). We show that both oligodendrocyte- and neuron-specific Nogo-A KO mice have enhanced dendritic branching and spine densities in layer 2/3 cortical pyramidal neurons. These effects are compartmentalized: neuronal Nogo-A affects proximal dendrites whereas oligodendrocytic Nogo-A affects distal regions. Finally, we used two-photon laser scanning microscopy to measure the spine turnover rate of adult mouse motor cortex layer 5 cells and find that both Nogo-A KO mouse lines show enhanced spine remodeling after 4 days. Our results suggest relevant control functions of glial as well as neuronal Nogo-A for synaptic plasticity and open new possibilities for more selective and targeted plasticity enhancing strategies.

Insulin/IGF1 Signaling Inhibits Age-Dependent Axon Regeneration

PubMed Central

Byrne, Alexandra B.; Walradt, Trent; Gardner, Kathryn E.; Hubbert, Austin; Reinke, Valerie; Hammarlund, Marc

2014-01-01

Summary The ability of injured axons to regenerate declines with age yet the mechanisms that regulate axon regeneration in response to age are not known. Here we show that axon regeneration in aging C. elegans motor neurons is inhibited by the conserved insulin/IGF1 receptor DAF-2. DAF-2’s function in regeneration is mediated by intrinsic neuronal activity of the forkhead transcription factor DAF-16/FOXO. DAF-16 regulates regeneration independently of lifespan, indicating that neuronal aging is an intrinsic, neuron specific, and genetically regulated process. In addition, we found that daf-18/PTEN inhibits regeneration independently of age and FOXO signaling, via the TOR pathway. Finally, DLK-1, a conserved regulator of regeneration, is downregulated by insulin/IGF1 signaling, bound by DAF-16 in neurons, and is required for both DAF-16- and DAF-18-mediated regeneration. Together, our data establish that insulin signaling specifically inhibits regeneration in aging adult neurons, and that this mechanism is independent of PTEN and TOR. PMID:24440228

Spatial Elucidation of Spinal Cord Lipid- and Metabolite- Regulations in Amyotrophic Lateral Sclerosis

NASA Astrophysics Data System (ADS)

Hanrieder, Jörg; Ewing, Andrew G.

2014-06-01

Amyotrophic lateral sclerosis (ALS) is a devastating, rapidly progressing disease of the central nervous system that is characterized by motor neuron degeneration in the brain stem and the spinal cord. We employed time of flight secondary ion mass spectrometry (ToF-SIMS) to profile spatial lipid- and metabolite- regulations in post mortem human spinal cord tissue from ALS patients to investigate chemical markers of ALS pathogenesis. ToF-SIMS scans and multivariate analysis of image and spectral data were performed on thoracic human spinal cord sections. Multivariate statistics of the image data allowed delineation of anatomical regions of interest based on their chemical identity. Spectral data extracted from these regions were compared using two different approaches for multivariate statistics, for investigating ALS related lipid and metabolite changes. The results show a significant decrease for cholesterol, triglycerides, and vitamin E in the ventral horn of ALS samples, which is presumably a consequence of motor neuron degeneration. Conversely, the biogenic mediator lipid lysophosphatidylcholine and its fragments were increased in ALS ventral spinal cord, pointing towards neuroinflammatory mechanisms associated with neuronal cell death. ToF-SIMS imaging is a promising approach for chemical histology and pathology for investigating the subcellular mechanisms underlying motor neuron degeneration in amyotrophic lateral sclerosis.

Lack of GPR88 enhances medium spiny neuron activity and alters motor- and cue-dependent behaviors.

PubMed

Quintana, Albert; Sanz, Elisenda; Wang, Wengang; Storey, Granville P; Güler, Ali D; Wanat, Matthew J; Roller, Bryan A; La Torre, Anna; Amieux, Paul S; McKnight, G Stanley; Bamford, Nigel S; Palmiter, Richard D

2012-11-01

The striatum regulates motor control, reward and learning. Abnormal function of striatal GABAergic medium spiny neurons (MSNs) is believed to contribute to the deficits in these processes that are observed in many neuropsychiatric diseases. The orphan G protein-coupled receptor GPR88 is robustly expressed in MSNs and is regulated by neuropharmacological drugs, but its contribution to MSN physiology and behavior is unclear. We found that, in the absence of GPR88, MSNs showed increased glutamatergic excitation and reduced GABAergic inhibition, which promoted enhanced firing rates in vivo, resulting in hyperactivity, poor motor coordination and impaired cue-based learning in mice. Targeted viral expression of GPR88 in MSNs rescued the molecular and electrophysiological properties and normalized behavior, suggesting that aberrant MSN activation in the absence of GPR88 underlies behavioral deficits and its dysfunction may contribute to behaviors observed in neuropsychiatric disease.

Purmorphamine as a Shh Signaling Activator Small Molecule Promotes Motor Neuron Differentiation of Mesenchymal Stem Cells Cultured on Nanofibrous PCL Scaffold.

PubMed

Bahrami, Naghmeh; Bayat, Mohammad; Mohamadnia, Abdolreza; Khakbiz, Mehrdad; Yazdankhah, Meysam; Ai, Jafar; Ebrahimi-Barough, Somayeh

2017-09-01

There is variety of stem cell sources but problems in ethical issues, contamination, and normal karyotype cause many limitations in obtaining and using these cells. The cells in Wharton's jelly region of umbilical cord are abundant and available stem cells with low immunological incompatibility, which could be considered for cell replacement therapy. Small molecules have been presented as less expensive biologically active compounds that can regulate different developmental process. Purmorphamine (PMA) is a small molecule that, according to some studies, possesses certain differentiation effects. In this study, we investigated the effect of the PMA on Wharton's jelly mesenchymal stem cell (WJ-MSC) differentiation into motor neuronal lineages instead of sonic hedgehog (Shh) on PCL scaffold. After exposing to induction media for 15 days, the cells were characterized for expression of motor neuron markers including PAX6, NF-H, Islet1, HB9, and choline acetyl transferase (ChAT) by quantitative reverse transcription (PCR) and immunocytochemistry. Our results demonstrated that induced WJ-MSCs with PMA could significantly express motor neuron markers in RNA and protein levels 15 days post induction. These results suggested that WJ-MSCs can differentiate to motor neuron-like cells with PMA on PCL scaffold and might provide a potential source in cell therapy for nervous system.

Nerve growth factor reduces apoptotic cell death in rat facial motor neurons after facial nerve injury.

PubMed

Hui, Lian; Yuan, Jing; Ren, Zhong; Jiang, Xuejun

2015-01-01

To assess the effects of nerve growth factor (NGF) on motor neurons after induction of a facial nerve lesion, and to compare the effects of different routes of NGF injection on motor neuron survival. This study was carried out in the Department of Otolaryngology Head & Neck Surgery, China Medical University, Liaoning, China from October 2012 to March 2013. Male Wistar rats (n = 65) were randomly assigned into 4 groups: A) healthy controls; B) facial nerve lesion model + normal saline injection; C) facial nerve lesion model + NGF injection through the stylomastoid foramen; D) facial nerve lesion model + intraperitoneal injection of NGF. Apoptotic cell death was detected using the terminal deoxynucleotidyl transferase dUTP nick end-labeling assay. Expression of caspase-3 and p53 up-regulated modulator of apoptosis (PUMA) was determined by immunohistochemistry. Injection of NGF significantly reduced cell apoptosis, and also greatly decreased caspase-3 and PUMA expression in injured motor neurons. Group C exhibited better efficacy for preventing cellular apoptosis and decreasing caspase-3 and PUMA expression compared with group D (p<0.05). Our findings suggest that injections of NGF may prevent apoptosis of motor neurons by decreasing caspase-3 and PUMA expression after facial nerve injury in rats. The NGF injected through the stylomastoid foramen demonstrated better protective efficacy than when injected intraperitoneally.

Mutant SOD1 in cell types other than motor neurons and oligodendrocytes accelerates onset of disease in ALS mice

PubMed Central

Yamanaka, Koji; Boillee, Severine; Roberts, Elizabeth A.; Garcia, Michael L.; McAlonis-Downes, Melissa; Mikse, Oliver R.; Cleveland, Don W.; Goldstein, Lawrence S. B.

2008-01-01

Dominant mutations in ubiquitously expressed superoxide dismutase (SOD1) cause familial ALS by provoking premature death of adult motor neurons. To test whether mutant damage to cell types beyond motor neurons is required for the onset of motor neuron disease, we generated chimeric mice in which all motor neurons and oligodendrocytes expressed mutant SOD1 at a level sufficient to cause fatal, early-onset motor neuron disease when expressed ubiquitously, but did so in a cellular environment containing variable numbers of non-mutant, non-motor neurons. Despite high-level mutant expression within 100% of motor neurons and oligodendrocytes, in most of these chimeras, the presence of WT non-motor neurons substantially delayed onset of motor neuron degeneration, increasing disease-free life by 50%. Disease onset is therefore non-cell autonomous, and mutant SOD1 damage within cell types other than motor neurons and oligodendrocytes is a central contributor to initiation of motor neuron degeneration. PMID:18492803

Neurons other than motor neurons in motor neuron disease.

PubMed

Ruffoli, Riccardo; Biagioni, Francesca; Busceti, Carla L; Gaglione, Anderson; Ryskalin, Larisa; Gambardella, Stefano; Frati, Alessandro; Fornai, Francesco

2017-11-01

Amyotrophic lateral sclerosis (ALS) is typically defined by a loss of motor neurons in the central nervous system. Accordingly, morphological analysis for decades considered motor neurons (in the cortex, brainstem and spinal cord) as the neuronal population selectively involved in ALS. Similarly, this was considered the pathological marker to score disease severity ex vivo both in patients and experimental models. However, the concept of non-autonomous motor neuron death was used recently to indicate the need for additional cell types to produce motor neuron death in ALS. This means that motor neuron loss occurs only when they are connected with other cell types. This concept originally emphasized the need for resident glia as well as non-resident inflammatory cells. Nowadays, the additional role of neurons other than motor neurons emerged in the scenario to induce non-autonomous motor neuron death. In fact, in ALS neurons diverse from motor neurons are involved. These cells play multiple roles in ALS: (i) they participate in the chain of events to produce motor neuron loss; (ii) they may even degenerate more than and before motor neurons. In the present manuscript evidence about multi-neuronal involvement in ALS patients and experimental models is discussed. Specific sub-classes of neurons in the whole spinal cord are reported either to degenerate or to trigger neuronal degeneration, thus portraying ALS as a whole spinal cord disorder rather than a disease affecting motor neurons solely. This is associated with a novel concept in motor neuron disease which recruits abnormal mechanisms of cell to cell communication.

RNA-Sequencing Analysis Reveals a Regulatory Role for Transcription Factor Fezf2 in the Mature Motor Cortex

PubMed Central

Clare, Alison J.; Wicky, Hollie E.; Empson, Ruth M.; Hughes, Stephanie M.

2017-01-01

Forebrain embryonic zinc finger (Fezf2) encodes a transcription factor essential for the specification of layer 5 projection neurons (PNs) in the developing cerebral cortex. As with many developmental transcription factors, Fezf2 continues to be expressed into adulthood, suggesting it remains crucial to the maintenance of neuronal phenotypes. Despite the continued expression, a function has yet to be explored for Fezf2 in the PNs of the developed cortex. Here, we investigated the role of Fezf2 in mature neurons, using lentiviral-mediated delivery of a shRNA to conditionally knockdown the expression of Fezf2 in the mouse primary motor cortex (M1). RNA-sequencing analysis of Fezf2-reduced M1 revealed significant changes to the transcriptome, identifying a regulatory role for Fezf2 in the mature M1. Kyoto Encyclopedia Genes and Genomes (KEGG) pathway analyses of Fezf2-regulated genes indicated a role in neuronal signaling and plasticity, with significant enrichment of neuroactive ligand-receptor interaction, cell adhesion molecules and calcium signaling pathways. Gene Ontology analysis supported a functional role for Fezf2-regulated genes in neuronal transmission and additionally indicated an importance in the regulation of behavior. Using the mammalian phenotype ontology database, we identified a significant overrepresentation of Fezf2-regulated genes associated with specific behavior phenotypes, including associative learning, social interaction, locomotor activation and hyperactivity. These roles were distinct from that of Fezf2-regulated genes identified in development, indicating a dynamic transition in Fezf2 function. Together our findings demonstrate a regulatory role for Fezf2 in the mature brain, with Fezf2-regulated genes having functional roles in sustaining normal neuronal and behavioral phenotypes. These results support the hypothesis that developmental transcription factors are important for maintaining neuron transcriptomes and that disruption of their expression could contribute to the progression of disease phenotypes. PMID:28936162

Connectivity of Pacemaker Neurons in the Neonatal Rat Superficial Dorsal Horn

PubMed Central

Ford, Neil C.; Arbabi, Shahriar; Baccei, Mark L.

2014-01-01

Pacemaker neurons with an intrinsic ability to generate rhythmic burst-firing have been characterized in lamina I of the neonatal spinal cord, where they are innervated by high-threshold sensory afferents. However, little is known about the output of these pacemakers, as the neuronal populations which are targeted by pacemaker axons have yet to be identified. The present study combines patch clamp recordings in the intact neonatal rat spinal cord with tract-tracing to demonstrate that lamina I pacemaker neurons contact multiple spinal motor pathways during early life. Retrograde labeling of premotor interneurons with the trans-synaptic virus PRV-152 revealed the presence of burst-firing in PRV-infected lamina I neurons, thereby confirming that pacemakers are synaptically coupled to motor networks in the spinal ventral horn. Notably, two classes of pacemakers could be distinguished in lamina I based on cell size and the pattern of their axonal projections. While small pacemaker neurons possessed ramified axons which contacted ipsilateral motor circuits, large pacemaker neurons had unbranched axons which crossed the midline and ascended rostrally in the contralateral white matter. Recordings from identified spino-parabrachial and spino-PAG neurons indicated the presence of pacemaker activity within neonatal lamina I projection neurons. Overall, these results show that lamina I pacemakers are positioned to regulate both the level of activity in developing motor circuits as well as the ascending flow of nociceptive information to the brain, thus highlighting a potential role for pacemaker activity in the maturation of pain and sensorimotor networks in the CNS. PMID:25380417

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.

Contralateral migration of oculomotor neurons is regulated by Slit/Robo signaling.

PubMed

Bjorke, Brielle; Shoja-Taheri, Farnaz; Kim, Minkyung; Robinson, G Eric; Fontelonga, Tatiana; Kim, Kyung-Tai; Song, Mi-Ryoung; Mastick, Grant S

2016-10-22

Oculomotor neurons develop initially like typical motor neurons, projecting axons out of the ventral midbrain to their ipsilateral targets, the extraocular muscles. However, in all vertebrates, after the oculomotor nerve (nIII) has reached the extraocular muscle primordia, the cell bodies that innervate the superior rectus migrate to join the contralateral nucleus. This motor neuron migration represents a unique strategy to form a contralateral motor projection. Whether migration is guided by diffusible cues remains unknown. We examined the role of Slit chemorepellent signals in contralateral oculomotor migration by analyzing mutant mouse embryos. We found that the ventral midbrain expresses high levels of both Slit1 and 2, and that oculomotor neurons express the repellent Slit receptors Robo1 and Robo2. Therefore, Slit signals are in a position to influence the migration of oculomotor neurons. In Slit 1/2 or Robo1/2 double mutant embryos, motor neuron cell bodies migrated into the ventral midbrain on E10.5, three days prior to normal migration. These early migrating neurons had leading projections into and across the floor plate. In contrast to the double mutants, embryos which were mutant for single Slit or Robo genes did not have premature migration or outgrowth on E10.5, demonstrating a cooperative requirement of Slit1 and 2, as well as Robo1 and 2. To test how Slit/Robo midline repulsion is modulated, we found that the normal migration did not require the receptors Robo3 and CXCR4, or the chemoattractant, Netrin 1. The signal to initiate contralateral migration is likely autonomous to the midbrain because oculomotor neurons migrate in embryos that lack either nerve outgrowth or extraocular muscles, or in cultured midbrains that lacked peripheral tissue. Overall, our results demonstrate that a migratory subset of motor neurons respond to floor plate-derived Slit repulsion to properly control the timing of contralateral migration.

A neurotransmitter transporter encoded by the Drosophila inebriated gene

PubMed Central

Soehnge, Holly; Huang, Xi; Becker, Marie; Whitley, Penn; Conover, Diana; Stern, Michael

1996-01-01

Behavioral and electrophysiological studies on mutants defective in the Drosophila inebriated (ine) gene demonstrated increased excitability of the motor neuron. In this paper, we describe the cloning and sequence analysis of ine. Mutations in ine were localized on cloned DNA by restriction mapping and restriction fragment length polymorphism (RFLP) mapping of ine mutants. DNA from the ine region was then used to isolate an ine cDNA. In situ hybridization of ine transcripts to developing embryos revealed expression of this gene in several cell types, including the posterior hindgut, Malpighian tubules, anal plate, garland cells, and a subset of cells in the central nervous system. The ine cDNA contains an open reading frame of 658 amino acids with a high degree of sequence similarity to members of the Na+/Cl−-dependent neurotransmitter transporter family. Members of this family catalyze the rapid reuptake of neurotransmitters released into the synapse and thereby play key roles in controlling neuronal function. We conclude that ine mutations cause increased excitability of the Drosophila motor neuron by causing the defective reuptake of the substrate neurotransmitter of the ine transporter and thus overstimulation of the motor neuron by this neurotransmitter. From this observation comes a unique opportunity to perform a genetic dissection of the regulation of excitability of the Drosophila motor neuron. PMID:8917579

The Peroxisome Proliferator-activated Receptor γ (PPARγ) Controls Natural Protective Mechanisms against Lipid Peroxidation in Amyotrophic Lateral Sclerosis*

PubMed Central

Benedusi, Valeria; Martorana, Francesca; Brambilla, Liliana; Maggi, Adriana; Rossi, Daniela

2012-01-01

Recent evidence highlights the peroxisome proliferator-activated receptors (PPARs) as critical neuroprotective factors in several neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS). To gain new mechanistic insights into the role of these receptors in the context of ALS, here we investigated how PPAR transcriptional activity varies in hSOD1G93A ALS transgenic mice. We demonstrate that PPARγ-driven transcription selectively increases in the spinal cord of symptomatic hSOD1G93A mice. This phenomenon correlates with the up-regulation of target genes, such as lipoprotein lipase and glutathione S-transferase α-2, which are implicated in scavenging lipid peroxidation by-products. Such events are associated with enhanced PPARγ immunoreactivity within motor neuronal nuclei. This observation, and the fact that PPARγ displays increased responsiveness in cultured hSOD1G93A motor neurons, points to a role for this receptor in neutralizing deleterious lipoperoxidation derivatives within the motor cells. Consistently, in both motor neuron-like cultures and animal models, we report that PPARγ is activated by lipid peroxidation end products, such as 4-hydroxynonenal, whose levels are elevated in the cerebrospinal fluid and spinal cord from ALS patients. We propose that the accumulation of critical concentrations of lipid peroxidation adducts during ALS progression leads to the activation of PPARγ in motor neurons. This in turn triggers self-protective mechanisms that involve the up-regulation of lipid detoxification enzymes, such as lipoprotein lipase and glutathione S-transferase α-2. Our findings indicate that anticipating natural protective reactions by pharmacologically modulating PPARγ transcriptional activity may attenuate neurodegeneration by limiting the damage induced by lipid peroxidation derivatives. PMID:22910911

Abundance of gap junctions at glutamatergic mixed synapses in adult Mosquitofish spinal cord neurons

PubMed Central

Serrano-Velez, Jose L.; Rodriguez-Alvarado, Melanie; Torres-Vazquez, Irma I.; Fraser, Scott E.; Yasumura, Thomas; Vanderpool, Kimberly G.; Rash, John E.; Rosa-Molinar, Eduardo

2014-01-01

“Dye-coupling”, whole-mount immunohistochemistry for gap junction channel protein connexin 35 (Cx35), and freeze-fracture replica immunogold labeling (FRIL) reveal an abundance of electrical synapses/gap junctions at glutamatergic mixed synapses in the 14th spinal segment that innervates the adult male gonopodium of Western Mosquitofish, Gambusia affinis (Mosquitofish). To study gap junctions’ role in fast motor behavior, we used a minimally-invasive neural-tract-tracing technique to introduce gap junction-permeant or -impermeant dyes into deep muscles controlling the gonopodium of the adult male Mosquitofish, a teleost fish that rapidly transfers (complete in <20 mS) spermatozeugmata into the female reproductive tract. Dye-coupling in the 14th spinal segment controlling the gonopodium reveals coupling between motor neurons and a commissural primary ascending interneuron (CoPA IN) and shows that the 14th segment has an extensive and elaborate dendritic arbor and more gap junctions than do other segments. Whole-mount immunohistochemistry for Cx35 results confirm dye-coupling and show it occurs via gap junctions. Finally, FRIL shows that gap junctions are at mixed synapses and reveals that >50 of the 62 gap junctions at mixed synapses are in the 14th spinal segment. Our results support and extend studies showing gap junctions at mixed synapses in spinal cord segments involved in control of genital reflexes in rodents, and they suggest a link between mixed synapses and fast motor behavior. The findings provide a basis for studies of specific roles of spinal neurons in the generation/regulation of sex-specific behavior and for studies of gap junctions’ role in regulating fast motor behavior. Finally, the CoPA IN provides a novel candidate neuron for future studies of gap junctions and neural control of fast motor behaviors. PMID:25018700

Plasticity of vagal brainstem circuits in the control of gastrointestinal function

PubMed Central

Browning, Kirsteen N; Travagli, R. Alberto

2010-01-01

The afferent vagus transmits sensory information from the gastrointestinal (GI) tract and other viscera to the brainstem via a glutamatergic synapse at the level of the nucleus of the solitary tract (NTS). Second order NTS neurons integrate this sensory information with inputs from other CNS regions that regulate autonomic functions and homeostasis. Glutamatergic and GABAergic neurons are responsible for conveying the integrated response to other nuclei, including the adjacent dorsal motor nucleus of the vagus (DMV). The preganglionic neurons in the DMV are the source of the parasympathetic motor response back to the GI tract. The glutamatergic synapse between the NTS and DMV is unlikely to be tonically active in regulating gastric motility and tone although almost all neurotransmitters tested so far modulate transmission at this synapse. In contrast, the tonic inhibitory GABAergic input from the NTS to the DMV appears to be critical in setting the tone of gastric motility and, under basal conditions, is unaffected by many neurotransmitters or neurohormones. This review is based, in part, on a presentation by Dr Browning at the 2009 ISAN meeting in Sydney, Australia and discusses how neurohormones and macronutrients modulate glutamatergic transmission to NTS neurons and GABAergic transmission to DMV neurons in relation to sensory information that is received from the GI tract. These neurohormones and macronutrients appear to exert efficient “on-demand” control of the motor output from the DMV in response to ever-changing demands required to maintain homeostasis. PMID:21147043

Localization of the kinesin adaptor proteins trafficking kinesin proteins 1 and 2 in primary cultures of hippocampal pyramidal and cortical neurons.

PubMed

Loss, Omar; Stephenson, F Anne

2015-07-01

Neuronal function requires regulated anterograde and retrograde trafficking of mitochondria along microtubules by using the molecular motors kinesin and dynein. Previous work has established that trafficking kinesin proteins (TRAKs),TRAK1 and TRAK2, are kinesin adaptor proteins that link mitochondria to kinesin motor proteins via an acceptor protein in the mitochondrial outer membrane, etc. the Rho GTPase Miro. Recent studies have shown that TRAK1 preferentially controls mitochondrial transport in axons of hippocampal neurons by virtue of its binding to both kinesin and dynein motor proteins, whereas TRAK2 controls mitochondrial transport in dendrites resulting from its binding to dynein. This study further investigates the subcellular localization of TRAK1 and TRAK2 in primary cultures of hippocampal and cortical neurons by using both commercial antibodies and anti-TRAK1 and anti-TRAK2 antibodies raised in our own laboratory (in-house). Whereas TRAK1 was prevalently localized in axons of hippocampal and cortical neurons, TRAK2 was more prevalent in dendrites of hippocampal neurons. In cortical neurons, TRAK2 was equally distributed between axons and dendrites. Some qualitative differences were observed between commercial and in-house-generated antibody immunostaining. © 2015 Wiley Periodicals, Inc.

Early functional impairment of sensory-motor connectivity in a mouse model of spinal muscular atrophy

PubMed Central

Mentis, George Z.; Blivis, Dvir; Liu, Wenfang; Drobac, Estelle; Crowder, Melissa E.; Kong, Lingling; Alvarez, Francisco J.; Sumner, Charlotte J.; O'Donovan, Michael J.

2011-01-01

SUMMARY To define alterations of neuronal connectivity that occur during motor neuron degeneration, we characterized the function and structure of spinal circuitry in spinal muscular atrophy (SMA) model mice. SMA motor neurons show reduced proprioceptive reflexes that correlate with decreased number and function of synapses on motor neuron somata and proximal dendrites. These abnormalities occur at an early stage of disease in motor neurons innervating proximal hindlimb muscles and medial motor neurons innervating axial muscles, but only at end-stage disease in motor neurons innervating distal hindlimb muscles. Motor neuron loss follows afferent synapse loss with the same temporal and topographical pattern. Trichostatin A, which improves motor behavior and survival of SMA mice, partially restores spinal reflexes illustrating the reversibility of these synaptic defects. De-afferentation of motor neurons is an early event in SMA and may be a primary cause of motor dysfunction that is amenable to therapeutic intervention. PMID:21315257

Compartmentalized Regulation of Parkin-Mediated Mitochondrial Quality Control in the Drosophila Nervous System In Vivo.

PubMed

Sung, Hyun; Tandarich, Lauren C; Nguyen, Kenny; Hollenbeck, Peter J

2016-07-13

In neurons, the normal distribution and selective removal of mitochondria are considered essential for maintaining the functions of the large asymmetric cell and its diverse compartments. Parkin, a E3 ubiquitin ligase associated with familial Parkinson's disease, has been implicated in mitochondrial dynamics and removal in cells including neurons. However, it is not clear how Parkin functions in mitochondrial turnover in vivo, or whether Parkin-dependent events of the mitochondrial life cycle occur in all neuronal compartments. Here, using the live Drosophila nervous system, we investigated the involvement of Parkin in mitochondrial dynamics, distribution, morphology, and removal. Contrary to our expectations, we found that Parkin-deficient animals do not accumulate senescent mitochondria in their motor axons or neuromuscular junctions; instead, they contain far fewer axonal mitochondria, and these displayed normal motility behavior, morphology, and metabolic state. However, the loss of Parkin did produce abnormal tubular and reticular mitochondria restricted to the motor cell bodies. In addition, in contrast to drug-treated, immortalized cells in vitro, mature motor neurons rarely displayed Parkin-dependent mitophagy. These data indicate that the cell body is the focus of Parkin-dependent mitochondrial quality control in neurons, and argue that a selection process allows only healthy mitochondria to pass from cell bodies to axons, perhaps to limit the impact of mitochondrial dysfunction. Parkin has been proposed to police mitochondrial fidelity by binding to dysfunctional mitochondria via PTEN (phosphatase and tensin homolog)-induced putative kinase 1 (PINK1) and targeting them for autophagic degradation. However, it is unknown whether and how the PINK1/Parkin pathway regulates the mitochondrial life cycle in neurons in vivo Using Drosophila motor neurons, we show that parkin disruption generates an abnormal mitochondrial network in cell bodies in vivo and reduces the number of axonal mitochondria without producing any defects in their axonal transport, morphology, or metabolic state. Furthermore, while cultured neurons display Parkin-dependent axonal mitophagy, we find this is vanishingly rare in vivo under normal physiological conditions. Thus, both the spatial distribution and mechanism of mitochondrial quality control in vivo differ substantially from those observed in vitro. Copyright © 2016 the authors 0270-6474/16/367375-17$15.00/0.

Compartmentalized Regulation of Parkin-Mediated Mitochondrial Quality Control in the Drosophila Nervous System In Vivo

PubMed Central

Sung, Hyun; Tandarich, Lauren C.; Nguyen, Kenny

2016-01-01

In neurons, the normal distribution and selective removal of mitochondria are considered essential for maintaining the functions of the large asymmetric cell and its diverse compartments. Parkin, a E3 ubiquitin ligase associated with familial Parkinson's disease, has been implicated in mitochondrial dynamics and removal in cells including neurons. However, it is not clear how Parkin functions in mitochondrial turnover in vivo, or whether Parkin-dependent events of the mitochondrial life cycle occur in all neuronal compartments. Here, using the live Drosophila nervous system, we investigated the involvement of Parkin in mitochondrial dynamics, distribution, morphology, and removal. Contrary to our expectations, we found that Parkin-deficient animals do not accumulate senescent mitochondria in their motor axons or neuromuscular junctions; instead, they contain far fewer axonal mitochondria, and these displayed normal motility behavior, morphology, and metabolic state. However, the loss of Parkin did produce abnormal tubular and reticular mitochondria restricted to the motor cell bodies. In addition, in contrast to drug-treated, immortalized cells in vitro, mature motor neurons rarely displayed Parkin-dependent mitophagy. These data indicate that the cell body is the focus of Parkin-dependent mitochondrial quality control in neurons, and argue that a selection process allows only healthy mitochondria to pass from cell bodies to axons, perhaps to limit the impact of mitochondrial dysfunction. SIGNIFICANCE STATEMENT Parkin has been proposed to police mitochondrial fidelity by binding to dysfunctional mitochondria via PTEN (phosphatase and tensin homolog)-induced putative kinase 1 (PINK1) and targeting them for autophagic degradation. However, it is unknown whether and how the PINK1/Parkin pathway regulates the mitochondrial life cycle in neurons in vivo. Using Drosophila motor neurons, we show that parkin disruption generates an abnormal mitochondrial network in cell bodies in vivo and reduces the number of axonal mitochondria without producing any defects in their axonal transport, morphology, or metabolic state. Furthermore, while cultured neurons display Parkin-dependent axonal mitophagy, we find this is vanishingly rare in vivo under normal physiological conditions. Thus, both the spatial distribution and mechanism of mitochondrial quality control in vivo differ substantially from those observed in vitro. PMID:27413149

Low-Frequency Oscillations and Control of the Motor Output

PubMed Central

Lodha, Neha; Christou, Evangelos A.

2017-01-01

A less precise force output impairs our ability to perform movements, learn new motor tasks, and use tools. Here we show that low-frequency oscillations in force are detrimental to force precision. We summarize the recent evidence that low-frequency oscillations in force output represent oscillations of the spinal motor neuron pool from the voluntary drive, and can be modulated by shifting power to higher frequencies. Further, force oscillations below 0.5 Hz impair force precision with increased voluntary drive, aging, and neurological disease. We argue that the low-frequency oscillations are (1) embedded in the descending drive as shown by the activation of multiple spinal motor neurons, (2) are altered with force intensity and brain pathology, and (3) can be modulated by visual feedback and motor training to enhance force precision. Thus, low-frequency oscillations in force provide insight into how the human brain regulates force precision. PMID:28261107

Sensory neurons do not induce motor neuron loss in a human stem cell model of spinal muscular atrophy.

PubMed

Schwab, Andrew J; Ebert, Allison D

2014-01-01

Spinal muscular atrophy (SMA) is an autosomal recessive disorder leading to paralysis and early death due to reduced SMN protein. It is unclear why there is such a profound motor neuron loss, but recent evidence from fly and mouse studies indicate that cells comprising the whole sensory-motor circuit may contribute to motor neuron dysfunction and loss. Here, we used induced pluripotent stem cells derived from SMA patients to test whether sensory neurons directly contribute to motor neuron loss. We generated sensory neurons from SMA induced pluripotent stem cells and found no difference in neuron generation or survival, although there was a reduced calcium response to depolarizing stimuli. Using co-culture of SMA induced pluripotent stem cell derived sensory neurons with control induced pluripotent stem cell derived motor neurons, we found no significant reduction in motor neuron number or glutamate transporter boutons on motor neuron cell bodies or neurites. We conclude that SMA sensory neurons do not overtly contribute to motor neuron loss in this human stem cell system.

Central circuitries for body temperature regulation and fever.

PubMed

Nakamura, Kazuhiro

2011-11-01

Body temperature regulation is a fundamental homeostatic function that is governed by the central nervous system in homeothermic animals, including humans. The central thermoregulatory system also functions for host defense from invading pathogens by elevating body core temperature, a response known as fever. Thermoregulation and fever involve a variety of involuntary effector responses, and this review summarizes the current understandings of the central circuitry mechanisms that underlie nonshivering thermogenesis in brown adipose tissue, shivering thermogenesis in skeletal muscles, thermoregulatory cardiac regulation, heat-loss regulation through cutaneous vasomotion, and ACTH release. To defend thermal homeostasis from environmental thermal challenges, feedforward thermosensory information on environmental temperature sensed by skin thermoreceptors ascends through the spinal cord and lateral parabrachial nucleus to the preoptic area (POA). The POA also receives feedback signals from local thermosensitive neurons, as well as pyrogenic signals of prostaglandin E(2) produced in response to infection. These afferent signals are integrated and affect the activity of GABAergic inhibitory projection neurons descending from the POA to the dorsomedial hypothalamus (DMH) or to the rostral medullary raphe region (rMR). Attenuation of the descending inhibition by cooling or pyrogenic signals leads to disinhibition of thermogenic neurons in the DMH and sympathetic and somatic premotor neurons in the rMR, which then drive spinal motor output mechanisms to elicit thermogenesis, tachycardia, and cutaneous vasoconstriction. Warming signals enhance the descending inhibition from the POA to inhibit the motor outputs, resulting in cutaneous vasodilation and inhibited thermogenesis. This central thermoregulatory mechanism also functions for metabolic regulation and stress-induced hyperthermia.

Distinct projection targets define subpopulations of mouse brainstem vagal neurons that express the autism-associated MET receptor tyrosine kinase.

PubMed

Kamitakahara, Anna; Wu, Hsiao-Huei; Levitt, Pat

2017-12-15

Detailed anatomical tracing and mapping of the viscerotopic organization of the vagal motor nuclei has provided insight into autonomic function in health and disease. To further define specific cellular identities, we paired information based on visceral connectivity with a cell-type specific marker of a subpopulation of neurons in the dorsal motor nucleus of the vagus (DMV) and nucleus ambiguus (nAmb) that express the autism-associated MET receptor tyrosine kinase. As gastrointestinal disturbances are common in children with autism spectrum disorder (ASD), we sought to define the relationship between MET-expressing (MET+) neurons in the DMV and nAmb, and the gastrointestinal tract. Using wholemount tissue staining and clearing, or retrograde tracing in a MET EGFP transgenic mouse, we identify three novel subpopulations of EGFP+ vagal brainstem neurons: (a) EGFP+ neurons in the nAmb projecting to the esophagus or laryngeal muscles, (b) EGFP+ neurons in the medial DMV projecting to the stomach, and (b) EGFP+ neurons in the lateral DMV projecting to the cecum and/or proximal colon. Expression of the MET ligand, hepatocyte growth factor (HGF), by tissues innervated by vagal motor neurons during fetal development reveal potential sites of HGF-MET interaction. Furthermore, similar cellular expression patterns of MET in the brainstem of both the mouse and nonhuman primate suggests that MET expression at these sites is evolutionarily conserved. Together, the data suggest that MET+ neurons in the brainstem vagal motor nuclei are anatomically positioned to regulate distinct portions of the gastrointestinal tract, with implications for the pathophysiology of gastrointestinal comorbidities of ASD. © 2017 Wiley Periodicals, Inc.

A stem-cell based bioassay to critically assess the pathology of dysfunctional neuromuscular junctions.

PubMed

Chipman, Peter H; Zhang, Ying; Rafuse, Victor F

2014-01-01

Pluripotent stem cells can be directed to differentiate into motor neurons and assessed for functionality in vitro. An emerging application of this technique is to model genetically inherited diseases in differentiated motor neurons and to screen for new therapeutic targets. The neuromuscular junction (NMJ) is essential to the functionality of motor neurons and its dysfunction is a primary hallmark of motor neuron disease. However, mature NMJs that possess the functional and morphological characteristics of those formed in vivo have so far not been obtained in vitro. Here we describe the generation and analysis of mature NMJs formed between embryonic stem cell-derived motor neurons (ESCMNs) and primary myotubes. We compared the formation and maturation of NMJs generated by wild-type (NCAM+/+) ESCMNs to those generated by neural cell adhesion molecule null (NCAM-/-) ESCMNs in order to definitively test the sensitivity of this assay to identify synaptic pathology. We find that co-cultures using NCAM-/- ESCMNs replicate key in vivo NCAM-/- phenotypes and reveal that NCAM influences neuromuscular synaptogenesis by controlling the mode of synaptic vesicle endocytosis. Further, we could improve synapse formation and function in NCAM-/- co-cultures by chronic treatment with nifedipine, which blocks an immature synaptic vesicle recycling pathway. Together, our results demonstrate that this ESCMN/myofiber co-culture system is a highly sensitive bioassay for examining molecules postulated to regulate synaptic function and for screening therapeutics that will improve the function of compromised NMJs.

ATF3 expression improves motor function in the ALS mouse model by promoting motor neuron survival and retaining muscle innervation.

PubMed

Seijffers, Rhona; Zhang, Jiangwen; Matthews, Jonathan C; Chen, Adam; Tamrazian, Eric; Babaniyi, Olusegun; Selig, Martin; Hynynen, Meri; Woolf, Clifford J; Brown, Robert H

2014-01-28

ALS is a fatal neurodegenerative disease characterized by a progressive loss of motor neurons and atrophy of distal axon terminals in muscle, resulting in loss of motor function. Motor end plates denervated by axonal retraction of dying motor neurons are partially reinnervated by remaining viable motor neurons; however, this axonal sprouting is insufficient to compensate for motor neuron loss. Activating transcription factor 3 (ATF3) promotes neuronal survival and axonal growth. Here, we reveal that forced expression of ATF3 in motor neurons of transgenic SOD1(G93A) ALS mice delays neuromuscular junction denervation by inducing axonal sprouting and enhancing motor neuron viability. Maintenance of neuromuscular junction innervation during the course of the disease in ATF3/SOD1(G93A) mice is associated with a substantial delay in muscle atrophy and improved motor performance. Although disease onset and mortality are delayed, disease duration is not affected. This study shows that adaptive axonal growth-promoting mechanisms can substantially improve motor function in ALS and importantly, that augmenting viability of the motor neuron soma and maintaining functional neuromuscular junction connections are both essential elements in therapy for motor neuron disease in the SOD1(G93A) mice. Accordingly, effective protection of optimal motor neuron function requires restitution of multiple dysregulated cellular pathways.

Emotion regulation through execution, observation, and imagery of emotional movements

PubMed Central

Shafir, Tal; Taylor, Stephan F.; Atkinson, Anthony P.; Langenecker, Scott A.; Zubieta, Jon-Kar

2014-01-01

According to Damasio’s somatic marker hypothesis, emotions are generated by conveying the current state of the body to the brain through interoceptive and proprioceptive afferent input. The resulting brain activation patterns represent unconscious emotions and correlate with subjective feelings. This proposition implies a corollary that the deliberate control of motor behavior could regulate feelings. We tested this possibility, hypothesizing that engaging in movements associated with a certain emotion would enhance that emotion and/or the corresponding valence. Furthermore, because motor imagery and observation are thought to activate the same mirror-neuron network engaged during motor execution, they might also activate the same emotional processing circuits, leading to similar emotional effects. Therefore, we measured the effects of motor execution, motor imagery and observation of whole-body dynamic expressions of emotions (happiness, sadness, fear) on affective state. All three tasks enhanced the corresponding affective state, indicating their potential to regulate emotions. PMID:23561915

Focal expression of mutant huntingtin in the songbird basal ganglia disrupts cortico-basal ganglia networks and vocal sequences

PubMed Central

Tanaka, Masashi; Singh Alvarado, Jonnathan; Murugan, Malavika; Mooney, Richard

2016-01-01

The basal ganglia (BG) promote complex sequential movements by helping to select elementary motor gestures appropriate to a given behavioral context. Indeed, Huntington’s disease (HD), which causes striatal atrophy in the BG, is characterized by hyperkinesia and chorea. How striatal cell loss alters activity in the BG and downstream motor cortical regions to cause these disorganized movements remains unknown. Here, we show that expressing the genetic mutation that causes HD in a song-related region of the songbird BG destabilizes syllable sequences and increases overall vocal activity, but leave the structure of individual syllables intact. These behavioral changes are paralleled by the selective loss of striatal neurons and reduction of inhibitory synapses on pallidal neurons that serve as the BG output. Chronic recordings in singing birds revealed disrupted temporal patterns of activity in pallidal neurons and downstream cortical neurons. Moreover, reversible inactivation of the cortical neurons rescued the disorganized vocal sequences in transfected birds. These findings shed light on a key role of temporal patterns of cortico-BG activity in the regulation of complex motor sequences and show how a genetic mutation alters cortico-BG networks to cause disorganized movements. PMID:26951661

C-terminals in the mouse branchiomotor nuclei originate from the magnocellular reticular formation

PubMed Central

Matsui, Toshiyasu; Hongo, Yu; Haizuka, Yoshinori; Kaida, Kenichi; Matsumura, George; Martin, Donna M.; Kobayashi, Yasushi

2013-01-01

Large cholinergic synaptic boutons called "C-terminals" contact motoneurons and regulate their excitability. C-terminals in the spinal somatic motor nuclei originate from cholinergic interneurons in laminae VII and X that express a transcription factor Pitx2. Cranial motor nuclei contain another type of motoneuron: branchiomotor neurons. Although branchiomotor neurons receive abundant C-terminal projections, the neural source of these C-terminals remains unknown. In the present study, we first examined whether cholinergic neurons express Pitx2 in the reticular formation of the adult mouse brainstem, as in the spinal cord. Although Pitx2-positive cholinergic neurons were observed in the magnocellular reticular formation and region around the central canal in the caudal medulla, none was present more rostrally in the brainstem tegmentum. We next explored the origin of C-terminals in the branchiomotor nuclei by using biotinylated dextran amine (BDA). BDA injections into the magnocellular reticular formation of the medulla and pons resulted in the labeling of numerous C-terminals in the branchiomotor nuclei: the ambiguous, facial, and trigeminal motor nuclei. Our results revealed that the origins of C-terminals in the branchiomotor nuclei are cholinergic neurons in the magnocellular reticular formation not only in the caudal medulla, but also at more rostral levels of the brainstem, which lacks Pitx2-positive neurons. PMID:23756176

Peroxisome proliferator activator receptor gamma coactivator-1alpha (PGC-1α) improves motor performance and survival in a mouse model of amyotrophic lateral sclerosis

PubMed Central

2011-01-01

Background Amyotrophic lateral sclerosis (ALS) is a devastating neurodegenerative disease that affects spinal cord and cortical motor neurons. An increasing amount of evidence suggests that mitochondrial dysfunction contributes to motor neuron death in ALS. Peroxisome proliferator-activated receptor gamma co-activator-1α (PGC-1α) is a principal regulator of mitochondrial biogenesis and oxidative metabolism. Results In this study, we examined whether PGC-1α plays a protective role in ALS by using a double transgenic mouse model where PGC-1α is over-expressed in an SOD1 transgenic mouse (TgSOD1-G93A/PGC-1α). Our results indicate that PGC-1α significantly improves motor function and survival of SOD1-G93A mice. The behavioral improvements were accompanied by reduced blood glucose level and by protection of motor neuron loss, restoration of mitochondrial electron transport chain activities and inhibition of stress signaling in the spinal cord. Conclusion Our results demonstrate that PGC-1α plays a beneficial role in a mouse model of ALS, suggesting that PGC-1α may be a potential therapeutic target for ALS therapy. PMID:21771318

Physical Exercise Modulates L-DOPA-Regulated Molecular Pathways in the MPTP Mouse Model of Parkinson's Disease.

PubMed

Klemann, Cornelius J H M; Xicoy, Helena; Poelmans, Geert; Bloem, Bas R; Martens, Gerard J M; Visser, Jasper E

2018-07-01

Parkinson's disease (PD) is characterized by the degeneration of dopaminergic (DA) neurons in the substantia nigra pars compacta (SNpc), resulting in motor and non-motor dysfunction. Physical exercise improves these symptoms in PD patients. To explore the molecular mechanisms underlying the beneficial effects of physical exercise, we exposed 1-methyl-4-phenyl-1,2,3,6-tetrahydropyrimidine (MPTP)-treated mice to a four-week physical exercise regimen, and subsequently explored their motor performance and the transcriptome of multiple PD-linked brain areas. MPTP reduced the number of DA neurons in the SNpc, whereas physical exercise improved beam walking, rotarod performance, and motor behavior in the open field. Further, enrichment analyses of the RNA-sequencing data revealed that in the MPTP-treated mice physical exercise predominantly modulated signaling cascades that are regulated by the top upstream regulators L-DOPA, RICTOR, CREB1, or bicuculline/dalfampridine, associated with movement disorders, mitochondrial dysfunction, and epilepsy-related processes. To elucidate the molecular pathways underlying these cascades, we integrated the proteins encoded by the exercise-induced differentially expressed mRNAs for each of the upstream regulators into a molecular landscape, for multiple key brain areas. Most notable was the opposite effect of physical exercise compared to previously reported effects of L-DOPA on the expression of mRNAs in the SN and the ventromedial striatum that are involved in-among other processes-circadian rhythm and signaling involving DA, neuropeptides, and endocannabinoids. Altogether, our findings suggest that physical exercise can improve motor function in PD and may, at the same time, counteract L-DOPA-mediated molecular mechanisms. Further, we hypothesize that physical exercise has the potential to improve non-motor symptoms of PD, some of which may be the result of (chronic) L-DOPA use.

Progranulin promotes peripheral nerve regeneration and reinnervation: role of notch signaling.

PubMed

Altmann, Christine; Vasic, Verica; Hardt, Stefanie; Heidler, Juliana; Häussler, Annett; Wittig, Ilka; Schmidt, Mirko H H; Tegeder, Irmgard

2016-10-22

Peripheral nerve injury is a frequent cause of lasting motor deficits and chronic pain. Although peripheral nerves are capable of regrowth they often fail to re-innervate target tissues. Using newly generated transgenic mice with inducible neuronal progranulin overexpression we show that progranulin accelerates axonal regrowth, restoration of neuromuscular synapses and recovery of sensory and motor functions after injury of the sciatic nerve. Oppositely, progranulin deficient mice have long-lasting deficits in motor function tests after nerve injury due to enhanced losses of motor neurons and stronger microglia activation in the ventral horn of the spinal cord. Deep proteome and gene ontology (GO) enrichment analysis revealed that the proteins upregulated in progranulin overexpressing mice were involved in 'regulation of transcription' and 'response to insulin' (GO terms). Transcription factor prediction pointed to activation of Notch signaling and indeed, co-immunoprecipitation studies revealed that progranulin bound to the extracellular domain of Notch receptors, and this was functionally associated with higher expression of Notch target genes in the dorsal root ganglia of transgenic mice with neuronal progranulin overexpression. Functionally, these transgenic mice recovered normal gait and running, which was not achieved by controls and was stronger impaired in progranulin deficient mice. We infer that progranulin activates Notch signaling pathways, enhancing thereby the regenerative capacity of partially injured neurons, which leads to improved motor function recovery.

Cervical spinal erythropoietin induces phrenic motor facilitation via ERK and Akt signaling

PubMed Central

Dale, Erica A.; Satriotomo, Irawan; Mitchell, Gordon S.

2012-01-01

Erythropoietin (EPO) is typically known for its role in erythropoiesis, but is also a potent neurotrophic/neuroprotective factor for spinal motor neurons. Another trophic factor regulated by Hypoxia-Inducible Factor-1, vascular endothelial growth factor (VEGF), signals via ERK and Akt activation to elicit long-lasting phrenic motor facilitation (pMF). Since EPO also signals via ERK and Akt activation, we tested the hypothesis that EPO elicits similar pMF. Using retrograde labeling and immunohistochemical techniques, we demonstrate in adult, male, Sprague-Dawley rats that EPO and its receptor, EPO-R, are expressed in identified phrenic motor neurons. Intrathecal EPO at C4 elicits long-lasting pMF; integrated phrenic nerve burst amplitude increased >90 min post-injection (63±12% baseline 90 min post-injection; p<0.001). EPO increased phosphorylation (and presumed activation) of ERK (1.6 fold vs controls; p<0.05) in phrenic motor neurons; EPO also increased pAkt (1.6 fold vs controls; p<0.05). EPO-induced pMF was abolished by the MEK/ERK inhibitor U0126 and the PI3 kinase/Akt inhibitor LY294002, demonstrating that ERK MAP kinases and Akt are both required for EPO-induced pMF. Pre-treatment with U0126 and LY294002 decreased both pERK and pAkt in phrenic motor neurons (p<0.05), indicating a complex interaction between these kinases. We conclude that EPO elicits spinal plasticity in respiratory motor control. Since EPO expression is hypoxia-sensitive, it may play a role in respiratory plasticity in conditions of prolonged or recurrent low oxygen. PMID:22539857

The novel gene tank, a tumor suppressor homolog, regulates ethanol sensitivity in Drosophila.

PubMed

Devineni, Anita V; Eddison, Mark; Heberlein, Ulrike

2013-05-08

In both mammalian and insect models of ethanol intoxication, high doses of ethanol induce motor impairment and eventually sedation. Sensitivity to the sedative effects of ethanol is inversely correlated with risk for alcoholism. However, the genes regulating ethanol sensitivity are largely unknown. Based on a previous genetic screen in Drosophila for ethanol sedation mutants, we identified a novel gene, tank (CG15626), the homolog of the mammalian tumor suppressor EI24/PIG8, which has a strong role in regulating ethanol sedation sensitivity. Genetic and behavioral analyses revealed that tank acts in the adult nervous system to promote ethanol sensitivity. We localized the function of tank in regulating ethanol sensitivity to neurons within the pars intercerebralis that have not been implicated previously in ethanol responses. We show that acutely manipulating the activity of all tank-expressing neurons, or of pars intercerebralis neurons in particular, alters ethanol sensitivity in a sexually dimorphic manner, since neuronal activation enhanced ethanol sedation in males, but not females. Finally, we provide anatomical evidence that tank-expressing neurons form likely synaptic connections with neurons expressing the neural sex determination factor fruitless (fru), which have been implicated recently in the regulation of ethanol sensitivity. We suggest that a functional interaction with fru neurons, many of which are sexually dimorphic, may account for the sex-specific effect induced by activating tank neurons. Overall, we have characterized a novel gene and corresponding set of neurons that regulate ethanol sensitivity in Drosophila.

The Novel Gene tank, a Tumor Suppressor Homolog, Regulates Ethanol Sensitivity in Drosophila

PubMed Central

Eddison, Mark; Heberlein, Ulrike

2013-01-01

In both mammalian and insect models of ethanol intoxication, high doses of ethanol induce motor impairment and eventually sedation. Sensitivity to the sedative effects of ethanol is inversely correlated with risk for alcoholism. However, the genes regulating ethanol sensitivity are largely unknown. Based on a previous genetic screen in Drosophila for ethanol sedation mutants, we identified a novel gene, tank (CG15626), the homolog of the mammalian tumor suppressor EI24/PIG8, which has a strong role in regulating ethanol sedation sensitivity. Genetic and behavioral analyses revealed that tank acts in the adult nervous system to promote ethanol sensitivity. We localized the function of tank in regulating ethanol sensitivity to neurons within the pars intercerebralis that have not been implicated previously in ethanol responses. We show that acutely manipulating the activity of all tank-expressing neurons, or of pars intercerebralis neurons in particular, alters ethanol sensitivity in a sexually dimorphic manner, since neuronal activation enhanced ethanol sedation in males, but not females. Finally, we provide anatomical evidence that tank-expressing neurons form likely synaptic connections with neurons expressing the neural sex determination factor fruitless (fru), which have been implicated recently in the regulation of ethanol sensitivity. We suggest that a functional interaction with fru neurons, many of which are sexually dimorphic, may account for the sex-specific effect induced by activating tank neurons. Overall, we have characterized a novel gene and corresponding set of neurons that regulate ethanol sensitivity in Drosophila. PMID:23658154

Survival motor neuron protein in motor neurons determines synaptic integrity in spinal muscular atrophy.

PubMed

Martinez, Tara L; Kong, Lingling; Wang, Xueyong; Osborne, Melissa A; Crowder, Melissa E; Van Meerbeke, James P; Xu, Xixi; Davis, Crystal; Wooley, Joe; Goldhamer, David J; Lutz, Cathleen M; Rich, Mark M; Sumner, Charlotte J

2012-06-20

The inherited motor neuron disease spinal muscular atrophy (SMA) is caused by deficient expression of survival motor neuron (SMN) protein and results in severe muscle weakness. In SMA mice, synaptic dysfunction of both neuromuscular junctions (NMJs) and central sensorimotor synapses precedes motor neuron cell death. To address whether this synaptic dysfunction is due to SMN deficiency in motor neurons, muscle, or both, we generated three lines of conditional SMA mice with tissue-specific increases in SMN expression. All three lines of mice showed increased survival, weights, and improved motor behavior. While increased SMN expression in motor neurons prevented synaptic dysfunction at the NMJ and restored motor neuron somal synapses, increased SMN expression in muscle did not affect synaptic function although it did improve myofiber size. Together these data indicate that both peripheral and central synaptic integrity are dependent on motor neurons in SMA, but SMN may have variable roles in the maintenance of these different synapses. At the NMJ, it functions at the presynaptic terminal in a cell-autonomous fashion, but may be necessary for retrograde trophic signaling to presynaptic inputs onto motor neurons. Importantly, SMN also appears to function in muscle growth and/or maintenance independent of motor neurons. Our data suggest that SMN plays distinct roles in muscle, NMJs, and motor neuron somal synapses and that restored function of SMN at all three sites will be necessary for full recovery of muscle power.

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

SMN is required for sensory-motor circuit function in Drosophila

PubMed Central

Imlach, Wendy L.; Beck, Erin S.; Choi, Ben Jiwon; Lotti, Francesco; Pellizzoni, Livio; McCabe, Brian D.

2012-01-01

Summary Spinal muscular atrophy (SMA) is a lethal human disease characterized by motor neuron dysfunction and muscle deterioration due to depletion of the ubiquitous Survival Motor Neuron (SMN) protein. Drosophila SMN mutants have reduced muscle size and defective locomotion, motor rhythm and motor neuron neurotransmission. Unexpectedly, restoration of SMN in either muscles or motor neurons did not alter these phenotypes. Instead, SMN must be expressed in proprioceptive neurons and interneurons in the motor circuit to non-autonomously correct defects in motor neurons and muscles. SMN depletion disrupts the motor system subsequent to circuit development and can be mimicked by the inhibition of motor network function. Furthermore, increasing motor circuit excitability by genetic or pharmacological inhibition of K+ channels can correct SMN-dependent phenotypes. These results establish sensory-motor circuit dysfunction as the origin of motor system deficits in this SMA model and suggest that enhancement of motor neural network activity could ameliorate the disease. PMID:23063130

Gastrointestinal-projecting neurones in the dorsal motor nucleus of the vagus exhibit direct and viscerotopically organized sensitivity to orexin.

PubMed

Grabauskas, Gintautas; Moises, Hylan C

2003-05-15

Orexin (hypocretin)-containing projections from lateral hypothalamus (LH) are thought to play an important role in the regulation of feeding behaviour and energy balance. In rodent studies, central administration of orexin peptides increases food intake, and orexin neurones in the LH are activated by hypoglycaemia during fasting. In addition, administration of orexins into the fourth ventricle or the dorsal motor nucleus of the vagus (DMV) has been shown to stimulate gastric acid secretion and motility, respectively, via vagal efferent pathways. In this study, whole-cell recordings were obtained from DMV neurones in rat brainstem slices to investigate the cellular mechanism(s) by which orexins produce their gastrostimulatory effects. To determine whether responsiveness to orexins might be differentially expressed among distinct populations of preganglionic vagal motor neurones, recordings were made from neurones whose projections to the gastrointestinal tract had been identified by retrograde labelling following apposition of the fluorescent tracer DiI to the gastric fundus, corpus or antrum/pylorus, the duodenum or caecum. Additionally, the responses of neurones to orexins were compared with those produced by oxytocin, which acts within the DMV to stimulate gastric acid secretion, but inhibits gastric motor function. Bath application of orexin-A or orexin-B (30-300 nM) produced a slow depolarization, accompanied by increased firing in 47 of 102 DMV neurones tested, including 70 % (30/43) of those that projected to the gastric fundus or corpus. In contrast, few DMV neurones that supplied the antrum/pylorus (3/13), duodenum (4/18) or caecum (1/13) were responsive to these peptides. The depolarizing responses were concentration dependent and persisted during synaptic isolation of neurones with TTX or Cd2+, indicating they resulted from activation of postsynaptic orexin receptors. They were also associated with a small increase in membrane resistance, and in voltage-clamp recordings orexin-A induced an inward current that reversed near the estimated equilibrium potential for K+, indicating the depolarization was due in large part to a reduction in K+ conductance. Orexins did not affect synaptically evoked excitation, but did reduce membrane excitability in a subset of gastric-projecting DMV neurones by enhancing GABA-mediated synaptic input. Lastly, although many DMV neurones responded to orexins and oxytocin with excitation, for the most part these peptides modulated excitability of distinct populations of gastric-projecting vagal motor neurones. These results indicate that orexins act preferentially within the DMV to directly excite vagal motor neurones that project to gastric fundus and corpus. In this way, release of endogenous orexins from descending hypothalamic projections into the DMV may mediate the increase in gastric acid secretion and motor activity associated with the cephalic phase of feeding.

Gastrointestinal-projecting neurones in the dorsal motor nucleus of the vagus exhibit direct and viscerotopically organized sensitivity to orexin

PubMed Central

Grabauskas, Gintautas; Moises, Hylan C

2003-01-01

Orexin (hypocretin)-containing projections from lateral hypothalamus (LH) are thought to play an important role in the regulation of feeding behaviour and energy balance. In rodent studies, central administration of orexin peptides increases food intake, and orexin neurones in the LH are activated by hypoglycaemia during fasting. In addition, administration of orexins into the fourth ventricle or the dorsal motor nucleus of the vagus (DMV) has been shown to stimulate gastric acid secretion and motility, respectively, via vagal efferent pathways. In this study, whole-cell recordings were obtained from DMV neurones in rat brainstem slices to investigate the cellular mechanism(s) by which orexins produce their gastrostimulatory effects. To determine whether responsiveness to orexins might be differentially expressed among distinct populations of preganglionic vagal motor neurones, recordings were made from neurones whose projections to the gastrointestinal tract had been identified by retrograde labelling following apposition of the fluorescent tracer DiI to the gastric fundus, corpus or antrum/pylorus, the duodenum or caecum. Additionally, the responses of neurones to orexins were compared with those produced by oxytocin, which acts within the DMV to stimulate gastric acid secretion, but inhibits gastric motor function. Bath application of orexin-A or orexin-B (30–300 nm) produced a slow depolarization, accompanied by increased firing in 47 of 102 DMV neurones tested, including 70 % (30/43) of those that projected to the gastric fundus or corpus. In contrast, few DMV neurones that supplied the antrum/pylorus (3/13), duodenum (4/18) or caecum (1/13) were responsive to these peptides. The depolarizing responses were concentration dependent and persisted during synaptic isolation of neurones with TTX or Cd2+, indicating they resulted from activation of postsynaptic orexin receptors. They were also associated with a small increase in membrane resistance, and in voltage-clamp recordings orexin-A induced an inward current that reversed near the estimated equilibrium potential for K+, indicating the depolarization was due in large part to a reduction in K+ conductance. Orexins did not affect synaptically evoked excitation, but did reduce membrane excitability in a subset of gastric-projecting DMV neurones by enhancing GABA-mediated synaptic input. Lastly, although many DMV neurones responded to orexins and oxytocin with excitation, for the most part these peptides modulated excitability of distinct populations of gastric-projecting vagal motor neurones. These results indicate that orexins act preferentially within the DMV to directly excite vagal motor neurones that project to gastric fundus and corpus. In this way, release of endogenous orexins from descending hypothalamic projections into the DMV may mediate the increase in gastric acid secretion and motor activity associated with the cephalic phase of feeding. PMID:12679367

In search for a gold-standard procedure to count motor neurons in the spinal cord.

PubMed

Ferrucci, Michela; Lazzeri, Gloria; Flaibani, Marina; Biagioni, Francesca; Cantini, Federica; Madonna, Michele; Bucci, Domenico; Limanaqi, Fiona; Soldani, Paola; Fornai, Francesco

2018-03-14

Counting motor neurons within the spinal cord and brainstem represents a seminal step to comprehend the anatomy and physiology of the final common pathway sourcing from the CNS. Motor neuron loss allows to assess the severity of motor neuron disorders while providing a tool to assess disease modifying effects. Counting motor neurons at first implies gold standard identification methods. In fact, motor neurons may occur within mixed nuclei housing a considerable amount of neurons other than motor neurons. In the present review, we analyse various approaches to count motor neurons emphasizing both the benefits and bias of each protocol. A special emphasis is placed on discussing automated stereology. When automated stereology does not take into account site-specificity and does not distinguish between heterogeneous neuronal populations, it may confound data making such a procedure a sort of "guide for the perplex". Thus, if on the one hand automated stereology improves our ability to quantify neuronal populations, it may also hide false positives/negatives in neuronal counts. For instance, classic staining for antigens such as SMI-32, SMN and ChAT, which are routinely considered to be specific for motor neurons, may also occur in other neuronal types of the spinal cord. Even site specificity within Lamina IX may be misleading due to neuronal populations having a size and shape typical of motor neurons. This is the case of spinal border cells, which often surpass the border of Lamina VII and intermingle with motor neurons of Lamina IX. The present article discusses the need to join automated stereology with a dedicated knowledge of each specific neuroanatomical setting.

How to make spinal motor neurons.

PubMed

Davis-Dusenbery, Brandi N; Williams, Luis A; Klim, Joseph R; Eggan, Kevin

2014-02-01

All muscle movements, including breathing, walking, and fine motor skills rely on the function of the spinal motor neuron to transmit signals from the brain to individual muscle groups. Loss of spinal motor neuron function underlies several neurological disorders for which treatment has been hampered by the inability to obtain sufficient quantities of primary motor neurons to perform mechanistic studies or drug screens. Progress towards overcoming this challenge has been achieved through the synthesis of developmental biology paradigms and advances in stem cell and reprogramming technology, which allow the production of motor neurons in vitro. In this Primer, we discuss how the logic of spinal motor neuron development has been applied to allow generation of motor neurons either from pluripotent stem cells by directed differentiation and transcriptional programming, or from somatic cells by direct lineage conversion. Finally, we discuss methods to evaluate the molecular and functional properties of motor neurons generated through each of these techniques.

Cognitive-motor interactions of the basal ganglia in development

PubMed Central

Leisman, Gerry; Braun-Benjamin, Orit; Melillo, Robert

2014-01-01

Neural circuits linking activity in anatomically segregated populations of neurons in subcortical structures and the neocortex throughout the human brain regulate complex behaviors such as walking, talking, language comprehension, and other cognitive functions associated with frontal lobes. The basal ganglia, which regulate motor control, are also crucial elements in the circuits that confer human reasoning and adaptive function. The basal ganglia are key elements in the control of reward-based learning, sequencing, discrete elements that constitute a complete motor act, and cognitive function. Imaging studies of intact human subjects and electrophysiologic and tracer studies of the brains and behavior of other species confirm these findings. We know that the relation between the basal ganglia and the cerebral cortical region allows for connections organized into discrete circuits. Rather than serving as a means for widespread cortical areas to gain access to the motor system, these loops reciprocally interconnect a large and diverse set of cerebral cortical areas with the basal ganglia. Neuronal activity within the basal ganglia associated with motor areas of the cerebral cortex is highly correlated with parameters of movement. Neuronal activity within the basal ganglia and cerebellar loops associated with the prefrontal cortex is related to the aspects of cognitive function. Thus, individual loops appear to be involved in distinct behavioral functions. Damage to the basal ganglia of circuits with motor areas of the cortex leads to motor symptoms, whereas damage to the subcortical components of circuits with non-motor areas of the cortex causes higher-order deficits. In this report, we review some of the anatomic, physiologic, and behavioral findings that have contributed to a reappraisal of function concerning the basal ganglia and cerebellar loops with the cerebral cortex and apply it in clinical applications to attention deficit/hyperactivity disorder (ADHD) with biomechanics and a discussion of retention of primitive reflexes being highly associated with the condition. PMID:24592214

Motor neurons and oligodendrocytes arise from distinct cell lineages by progenitor recruitment

PubMed Central

Ravanelli, Andrew M.; Appel, Bruce

2015-01-01

During spinal cord development, ventral neural progenitor cells that express the transcription factors Olig1 and Olig2, called pMN progenitors, produce motor neurons and then oligodendrocytes. Whether motor neurons and oligodendrocytes arise from common or distinct progenitors in vivo is not known. Using zebrafish, we found that motor neurons and oligodendrocytes are produced sequentially by distinct progenitors that have distinct origins. When olig2+ cells were tracked during the peak period of motor neuron formation, most differentiated as motor neurons without further cell division. Using time-lapse imaging, we found that, as motor neurons differentiated, more dorsally positioned neuroepithelial progenitors descended to the pMN domain and initiated olig2 expression. Inhibition of Hedgehog signaling during motor neuron differentiation blocked the ventral movement of progenitors, the progressive initiation of olig2 expression, and oligodendrocyte formation. We therefore propose that the motor neuron-to-oligodendrocyte switch results from Hedgehog-mediated recruitment of glial-fated progenitors to the pMN domain subsequent to neurogenesis. PMID:26584621

Respiratory function after selective respiratory motor neuron death from intrapleural CTB–saporin injections

PubMed Central

Nichols, Nicole L.; Vinit, Stéphane; Bauernschmidt, Lorene; Mitchell, Gordon S.

2015-01-01

Amyotrophic lateral sclerosis (ALS) causes progressive motor neuron degeneration, paralysis and death by ventilatory failure. In rodent ALS models: 1) breathing capacity is preserved until late in disease progression despite major respiratory motor neuron death, suggesting unknown forms of compensatory respiratory plasticity; and 2) spinal microglia become activated in association with motor neuron cell death. Here, we report a novel experimental model to study the impact of respiratory motor neuron death on compensatory responses without many complications attendant to spontaneous motor neuron disease. In specific, we used intrapleural injections of cholera toxin B fragment conjugated to saporin (CTB–SAP) to selectively kill motor neurons with access to the pleural space. Motor neuron survival, CD11b labeling (microglia), ventilatory capacity and phrenic motor output were assessed in rats 3–28 days after intrapleural injections of: 1) CTB–SAP (25 and 50 μg), or 2) unconjugated CTB and SAP (i.e. control; (CTB + SAP). CTB–SAP elicited dose-dependent phrenic and intercostal motor neuron death; 7 days post-25 μg CTB–SAP, motor neuron survival approximated that in end-stage ALS rats (phrenic: 36 ± 7%; intercostal: 56 ± 10% of controls; n = 9; p < 0.05). CTB–SAP caused minimal cell death in other brainstem or spinal cord regions. CTB–SAP: 1) increased CD11b fractional area in the phrenic motor nucleus, indicating microglial activation; 2) decreased breathing during maximal chemoreceptor stimulation; and 3) diminished phrenic motor output in anesthetized rats (7 days post-25 μg, CTB–SAP: 0.3 ± 0.07 V; CTB + SAP: 1.5 ± 0.3; n = 9; p < 0.05). Intrapleural CTB–SAP represents a novel, inducible model of respiratory motor neuron death and provides an opportunity to study compensation for respiratory motor neuron loss. PMID:25476493

Mutant TDP-43 in motor neurons promotes the onset and progression of ALS in rats

PubMed Central

Huang, Cao; Tong, Jianbin; Bi, Fangfang; Zhou, Hongxia; Xia, Xu-Gang

2011-01-01

Amyotrophic lateral sclerosis (ALS) is characterized by progressive motor neuron degeneration, which ultimately leads to paralysis and death. Mutation of TAR DNA binding protein 43 (TDP-43) has been linked to the development of an inherited form of ALS. Existing TDP-43 transgenic animals develop a limited loss of motor neurons and therefore do not faithfully reproduce the core phenotype of ALS. Here, we report the creation of multiple lines of transgenic rats in which expression of ALS-associated mutant human TDP-43 is restricted to either motor neurons or other types of neurons and skeletal muscle and can be switched on and off. All of these rats developed progressive paralysis reminiscent of ALS when the transgene was switched on. Rats expressing mutant TDP-43 in motor neurons alone lost more spinal motor neurons than rats expressing the disease gene in varying neurons and muscle cells, although these rats all developed remarkable denervation atrophy of skeletal muscles. Intriguingly, progression of the disease was halted after transgene expression was switched off; in rats with limited loss of motor neurons, we observed a dramatic recovery of motor function, but in rats with profound loss of motor neurons, we only observed a moderate recovery of motor function. Our finding suggests that mutant TDP-43 in motor neurons is sufficient to promote the onset and progression of ALS and that motor neuron degeneration is partially reversible, at least in mutant TDP-43 transgenic rats. PMID:22156203

Non-chemosensitive parafacial neurons simultaneously regulate active expiration and airway patency under hypercapnia in rats.

PubMed

de Britto, Alan A; Moraes, Davi J A

2017-03-15

Hypercapnia or parafacial respiratory group (pFRG) disinhibition at normocapnia evokes active expiration in rats by recruitment of pFRG late-expiratory (late-E) neurons. We show that hypercapnia simultaneously evoked active expiration and exaggerated glottal dilatation by late-E synaptic excitation of abdominal, hypoglossal and laryngeal motoneurons. Simultaneous rhythmic expiratory activity in previously silent pFRG late-E neurons, which did not express the marker of ventral medullary CO 2 -sensitive neurons (transcription factor Phox2b), was also evoked by hypercapnia. Hypercapnia-evoked active expiration, neural and neuronal late-E activities were eliminated by pFRG inhibition, but not after blockade of synaptic excitation. Hypercapnia produces disinhibition of non-chemosensitive pFRG late-E neurons to evoke active expiration and concomitant cranial motor respiratory responses controlling the oropharyngeal and upper airway patency. Hypercapnia produces active expiration in rats and the recruitment of late-expiratory (late-E) neurons located in the parafacial respiratory group (pFRG) of the ventral medullary brainstem. We tested the hypothesis that hypercapnia produces active expiration and concomitant cranial respiratory motor responses controlling the oropharyngeal and upper airway patency by disinhibition of pFRG late-E neurons, but not via synaptic excitation. Phrenic nerve, abdominal nerve (AbN), cranial respiratory motor nerves, subglottal pressure, and medullary and spinal neurons/motoneurons were recorded in in situ preparations of juvenile rats. Hypercapnia evoked AbN active expiration, exaggerated late-E discharges in cranial respiratory motor outflows, and glottal dilatation via late-E synaptic excitation of abdominal, hypoglossal and laryngeal motoneurons. Simultaneous rhythmic late-E activity in previously silent pFRG neurons, which did not express the marker of ventral medullary CO 2 -sensitive neurons (transcription factor Phox2b), was also evoked by hypercapnia. In addition, hypercapnia-evoked AbN active expiration, neural and neuronal late-E activities were eliminated by pFRG inhibition, but not after blockade of synaptic excitation. On the other hand, pFRG inhibition did not affect either hypercapnia-induced inspiratory increases in respiratory motor outflows or CO 2 sensitivity of the more medial Phox2b-positive neurons in the retrotrapezoid nucleus (RTN). Our data suggest that neither RTN Phox2b-positive nor other CO 2 -sensitive brainstem neurons activate Phox2b-negative pFRG late-E neurons under hypercapnia to produce AbN active expiration and concomitant cranial motor respiratory responses controlling the oropharyngeal and upper airway patency. Hypercapnia produces disinhibition of non-chemosensitive pFRG late-E neurons in in situ preparations of juvenile rats to activate abdominal, hypoglossal and laryngeal motoneurons. © 2016 The Authors. The Journal of Physiology © 2016 The Physiological Society.

Sensorimotor function is modulated by the serotonin receptor 1d, a novel marker for gamma motor neurons

PubMed Central

Enjin, Anders; Leão, Katarina E.; Mikulovic, Sanja; Le Merre, Pierre; Tourtellotte, Warren G.; Kullander, Klas

2012-01-01

Gamma motor neurons (MNs), the efferent component of the fusimotor system, regulate muscle spindle sensitivity. Muscle spindle sensory feedback is required for proprioception that includes sensing the relative position of neighboring body parts and appropriately adjust the employed strength in a movement. The lack of a single and specific genetic marker has long hampered functional and developmental studies of gamma MNs. Here we show that the serotonin receptor 1d (5-ht1d) is specifically expressed by gamma MNs and proprioceptive sensory neurons. Using mice expressing GFP driven by the 5-ht1d promotor, we performed whole-cell patch-clamp recordings of 5-ht1d∷GFP+ and 5-ht1d∷GFP− motor neurons from young mice. Hierarchal clustering analysis revealed that gamma MNs have distinct electrophysiological properties intermediate to fast-like and slow-like alpha MNs. Moreover, mice lacking 5-ht1d displayed lower monosynaptic reflex amplitudes suggesting a reduced response to sensory stimulation in motor neurons. Interestingly, adult 5-ht1d knockout mice also displayed improved coordination skills on a beam-walking task, implying that reduced activation of MNs by Ia afferents during provoked movement tasks could reduce undesired exaggerated muscle output. In summary, we show that 5-ht1d is a novel marker for gamma MNs and that the 5-ht1d receptor is important for the ability of proprioceptive circuits to receive and relay accurate sensory information in developing and mature spinal cord motor circuits. PMID:22273508

The autism susceptibility gene met regulates zebrafish cerebellar development and facial motor neuron migration

PubMed Central

Elsen, Gina E.; Choi, Louis Y.; Prince, Victoria E.; Ho, Robert K.

2009-01-01

During development, Met signaling regulates a range of cellular processes including growth, differentiation, survival and migration. The Met gene encodes a tyrosine kinase receptor, which is activated by Hgf (hepatocyte growth factor) ligand. Altered regulation of human MET expression has been implicated in autism. In mouse, Met signaling has been shown to regulate cerebellum development. Since abnormalities in cerebellar structure have been reported in some autistic patients, we have used the zebrafish to address the role of Met signaling during cerebellar development and thus further our understanding of the molecular basis of autism. We find that zebrafish met is expressed in the cerebellar primordium, later localizing to the ventricular zone (VZ), with the hgf1 and hgf2 ligand genes expressed in surrounding tissues. Morpholino knockdown of either Met or its Hgf ligands leads to a significant reduction in the size of the cerebellum, primarily as a consequence of reduced proliferation. Met signaling knockdown disrupts specification of VZ-derived cell types, and also reduces granule cell numbers, due to an early effect on cerebellar proliferation and/or as an indirect consequence of loss of signals from VZ-derived cells later in development. These patterning defects preclude analysis of cerebellar neuronal migration, but we have found that Met signaling is necessary for migration of hindbrain facial motor neurons. In summary, we have described roles for Met signaling in coordinating growth and cell type specification within the developing cerebellum, and in migration of hindbrain neurons. These functions may underlie the correlation between altered MET regulation and Autism Spectrum Disorders. PMID:19732764

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

Isl1 Is required for multiple aspects of motor neuron development

PubMed Central

Liang, Xingqun; Song, Mi-Ryoung; Xu, ZengGuang; Lanuza, Guillermo M.; Liu, Yali; Zhuang, Tao; Chen, Yihan; Pfaff, Samuel L.; Evans, Sylvia M.; Sun, Yunfu

2011-01-01

The LIM homeodomain transcription factor Islet1 (Isl1) is expressed in multiple organs and plays essential roles during embryogenesis. Isl1 is required for the survival and specification of spinal cord motor neurons. Due to early embryonic lethality and loss of motor neurons, the role of Isl1 in other aspects of motor neuron development remains unclear. In this study, we generated Isl1 mutant mouse lines expressing graded doses of Isl1. Our study has revealed essential roles of Isl1 in multiple aspects of motor neuron development, including motor neuron cell body localization, motor column formation and axon growth. In addition, Isl1 is required for survival of cranial ganglia neurons. PMID:21569850

A PI3-kinase-mediated negative feedback regulates neuronal excitability.

PubMed

Howlett, Eric; Lin, Curtis Chun-Jen; Lavery, William; Stern, Michael

2008-11-01

Use-dependent downregulation of neuronal activity (negative feedback) can act as a homeostatic mechanism to maintain neuronal activity at a particular specified value. Disruption of this negative feedback might lead to neurological pathologies, such as epilepsy, but the precise mechanisms by which this feedback can occur remain incompletely understood. At one glutamatergic synapse, the Drosophila neuromuscular junction, a mutation in the group II metabotropic glutamate receptor gene (DmGluRA) increased motor neuron excitability by disrupting an autocrine, glutamate-mediated negative feedback. We show that DmGluRA mutations increase neuronal excitability by preventing PI3 kinase (PI3K) activation and consequently hyperactivating the transcription factor Foxo. Furthermore, glutamate application increases levels of phospho-Akt, a product of PI3K signaling, within motor nerve terminals in a DmGluRA-dependent manner. Finally, we show that PI3K increases both axon diameter and synapse number via the Tor/S6 kinase pathway, but not Foxo. In humans, PI3K and group II mGluRs are implicated in epilepsy, neurofibromatosis, autism, schizophrenia, and other neurological disorders; however, neither the link between group II mGluRs and PI3K, nor the role of PI3K-dependent regulation of Foxo in the control of neuronal excitability, had been previously reported. Our work suggests that some of the deficits in these neurological disorders might result from disruption of glutamate-mediated homeostasis of neuronal excitability.

Spinal motor neurons are regenerated after mechanical lesion and genetic ablation in larval zebrafish.

PubMed

Ohnmacht, Jochen; Yang, Yujie; Maurer, Gianna W; Barreiro-Iglesias, Antón; Tsarouchas, Themistoklis M; Wehner, Daniel; Sieger, Dirk; Becker, Catherina G; Becker, Thomas

2016-05-01

In adult zebrafish, relatively quiescent progenitor cells show lesion-induced generation of motor neurons. Developmental motor neuron generation from the spinal motor neuron progenitor domain (pMN) sharply declines at 48 hours post-fertilisation (hpf). After that, mostly oligodendrocytes are generated from the same domain. We demonstrate here that within 48 h of a spinal lesion or specific genetic ablation of motor neurons at 72 hpf, the pMN domain reverts to motor neuron generation at the expense of oligodendrogenesis. By contrast, generation of dorsal Pax2-positive interneurons was not altered. Larval motor neuron regeneration can be boosted by dopaminergic drugs, similar to adult regeneration. We use larval lesions to show that pharmacological suppression of the cellular response of the innate immune system inhibits motor neuron regeneration. Hence, we have established a rapid larval regeneration paradigm. Either mechanical lesions or motor neuron ablation is sufficient to reveal a high degree of developmental flexibility of pMN progenitor cells. In addition, we show an important influence of the immune system on motor neuron regeneration from these progenitor cells. © 2016. Published by The Company of Biologists Ltd.

Kinesin Khc-73/KIF13B modulates retrograde BMP signaling by influencing endosomal dynamics at the Drosophila neuromuscular junction

PubMed Central

Gray, Lindsay; Tsurudome, Kazuya; El-Mounzer, Wassim; Elazzouzi, Fatima; Baim, Christopher; Calderon, Mario R.; Kauwe, Grant

2018-01-01

Retrograde signaling is essential for neuronal growth, function and survival; however, we know little about how signaling endosomes might be directed from synaptic terminals onto retrograde axonal pathways. We have identified Khc-73, a plus-end directed microtubule motor protein, as a regulator of sorting of endosomes in Drosophila larval motor neurons. The number of synaptic boutons and the amount of neurotransmitter release at the Khc-73 mutant larval neuromuscular junction (NMJ) are normal, but we find a significant decrease in the number of presynaptic release sites. This defect in Khc-73 mutant larvae can be genetically enhanced by a partial genetic loss of Bone Morphogenic Protein (BMP) signaling or suppressed by activation of BMP signaling in motoneurons. Consistently, activation of BMP signaling that normally enhances the accumulation of phosphorylated form of BMP transcription factor Mad in the nuclei, can be suppressed by genetic removal of Khc-73. Using a number of assays including live imaging in larval motor neurons, we show that loss of Khc-73 curbs the ability of retrograde-bound endosomes to leave the synaptic area and join the retrograde axonal pathway. Our findings identify Khc-73 as a regulator of endosomal traffic at the synapse and modulator of retrograde BMP signaling in motoneurons. PMID:29373576

Motor cortex stimulation and neuropathic pain: how does motor cortex stimulation affect pain-signaling pathways?

PubMed

Kim, Jinhyung; Ryu, Sang Baek; Lee, Sung Eun; Shin, Jaewoo; Jung, Hyun Ho; Kim, Sung June; Kim, Kyung Hwan; Chang, Jin Woo

2016-03-01

Neuropathic pain is often severe. Motor cortex stimulation (MCS) is used for alleviating neuropathic pain, but the mechanism of action is still unclear. This study aimed to understand the mechanism of action of MCS by investigating pain-signaling pathways, with the expectation that MCS would regulate both descending and ascending pathways. Neuropathic pain was induced in Sprague-Dawley rats. Surface electrodes for MCS were implanted in the rats. Tactile allodynia was measured by behavioral testing to determine the effect of MCS. For the pathway study, immunohistochemistry was performed to investigate changes in c-fos and serotonin expression; micro-positron emission tomography (mPET) scanning was performed to investigate changes of glucose uptake; and extracellular electrophysiological recordings were performed to demonstrate brain activity. MCS was found to modulate c-fos and serotonin expression. In the mPET study, altered brain activity was observed in the striatum, thalamic area, and cerebellum. In the electrophysiological study, neuronal activity was increased by mechanical stimulation and suppressed by MCS. After elimination of artifacts, neuronal activity was demonstrated in the ventral posterolateral nucleus (VPL) during electrical stimulation. This neuronal activity was effectively suppressed by MCS. This study demonstrated that MCS effectively attenuated neuropathic pain. MCS modulated ascending and descending pain pathways. It regulated neuropathic pain by affecting the striatum, periaqueductal gray, cerebellum, and thalamic area, which are thought to regulate the descending pathway. MCS also appeared to suppress activation of the VPL, which is part of the ascending pathway.

Heavy metals in locus ceruleus and motor neurons in motor neuron disease.

PubMed

Pamphlett, Roger; Kum Jew, Stephen

2013-12-12

The causes of sporadic amyotrophic lateral sclerosis (SALS) and other types of motor neuron disease (MND) remain largely unknown. Heavy metals have long been implicated in MND, and it has recently been shown that inorganic mercury selectively enters human locus ceruleus (LC) and motor neurons. We therefore used silver nitrate autometallography (AMG) to look for AMG-stainable heavy metals (inorganic mercury and bismuth) in LC and motor neurons of 24 patients with MND (18 with SALS and 6 with familial MND) and in the LC of 24 controls. Heavy metals in neurons were found in significantly more MND patients than in controls when comparing: (1) the presence of any versus no heavy metal-containing LC neurons (MND 88%, controls 42%), (2) the median percentage of heavy metal-containing LC neurons (MND 9.5%, control 0.0%), and (3) numbers of individuals with heavy metal-containing LC neurons in the upper half of the percentage range (MND 75%, controls 25%). In MND patients, 67% of remaining spinal motor neurons contained heavy metals; smaller percentages were found in hypoglossal, nucleus ambiguus and oculomotor neurons, but none in cortical motor neurons. The majority of MND patients had heavy metals in both LC and spinal motor neurons. No glia or other neurons, including neuromelanin-containing neurons of the substantia nigra, contained stainable heavy metals. Uptake of heavy metals by LC and lower motor neurons appears to be fairly common in humans, though heavy metal staining in the LC, most likely due to inorganic mercury, was seen significantly more often in MND patients than in controls. The LC innervates many cell types that are affected in MND, and it is possible that MND is triggered by toxicant-induced interactions between LC and motor neurons.

Heavy metals in locus ceruleus and motor neurons in motor neuron disease

PubMed Central

2013-01-01

Background The causes of sporadic amyotrophic lateral sclerosis (SALS) and other types of motor neuron disease (MND) remain largely unknown. Heavy metals have long been implicated in MND, and it has recently been shown that inorganic mercury selectively enters human locus ceruleus (LC) and motor neurons. We therefore used silver nitrate autometallography (AMG) to look for AMG-stainable heavy metals (inorganic mercury and bismuth) in LC and motor neurons of 24 patients with MND (18 with SALS and 6 with familial MND) and in the LC of 24 controls. Results Heavy metals in neurons were found in significantly more MND patients than in controls when comparing: (1) the presence of any versus no heavy metal-containing LC neurons (MND 88%, controls 42%), (2) the median percentage of heavy metal-containing LC neurons (MND 9.5%, control 0.0%), and (3) numbers of individuals with heavy metal-containing LC neurons in the upper half of the percentage range (MND 75%, controls 25%). In MND patients, 67% of remaining spinal motor neurons contained heavy metals; smaller percentages were found in hypoglossal, nucleus ambiguus and oculomotor neurons, but none in cortical motor neurons. The majority of MND patients had heavy metals in both LC and spinal motor neurons. No glia or other neurons, including neuromelanin-containing neurons of the substantia nigra, contained stainable heavy metals. Conclusions Uptake of heavy metals by LC and lower motor neurons appears to be fairly common in humans, though heavy metal staining in the LC, most likely due to inorganic mercury, was seen significantly more often in MND patients than in controls. The LC innervates many cell types that are affected in MND, and it is possible that MND is triggered by toxicant-induced interactions between LC and motor neurons. PMID:24330485

The structure and function of serially homologous leg motor neurons in the locust. I. Anatomy.

PubMed

Wilson, J A

1979-01-01

Twenty-one prothoracic and 17 mesothoracic motor neurons innervating leg muscles have been identified physiologically and subsequently injected with dye from a microelectrode. A tract containing the primary neurites of motor neurons innervating the retractor unquis, levator and depressor tarsus, flexor tibiae, and reductor femora is described. All motor neurons studied have regions in which their dendritic branches overlap with those of other leg motor neurons. Identified, serially homologous motor neurons in the three thoracic ganglia were found to have: (1) cell bodies at similar locations and morphologically similar primary neurites (e.g., flexor tibiae motor neurons), (2) cell bodies at different locations in each ganglion and morphologically different primary neurites in each ganglion (e.g., fast retractor unguis motor neurons), or (3) cell bodies at similar locations and morphologically similar primary neurites but with a functional switch in one ganglion relative to the function of the neurons in the other two ganglia. As an example of the latter, the morphology of the metathoracic slow extensor tibiae (SETi) motor neurons was similar to that of pro- and mesothoracic fast extensor tibiae (FETi) motor neurons. Similarly the metathoracic FETi bears a striking resemblance to the pro- and the mesothoracic SETi. It is proposed that in the metathoracic ganglion the two extensor tibiae motor neurons have switched functions while retaining similar morphologies relative to the structure and function of their pro- and mesothoracic serial homologues.

Gaskell revisited: new insights into spinal autonomics necessitate a revised motor neuron nomenclature.

PubMed

Fritzsch, Bernd; Elliott, Karen L; Glover, Joel C

2017-11-01

Several concepts developed in the nineteenth century have formed the basis of much of our neuroanatomical teaching today. Not all of these were based on solid evidence nor have withstood the test of time. Recent evidence on the evolution and development of the autonomic nervous system, combined with molecular insights into the development and diversification of motor neurons, challenges some of the ideas held for over 100 years about the organization of autonomic motor outflow. This review provides an overview of the original ideas and quality of supporting data and contrasts this with a more accurate and in depth insight provided by studies using modern techniques. Several lines of data demonstrate that branchial motor neurons are a distinct motor neuron population within the vertebrate brainstem, from which parasympathetic visceral motor neurons of the brainstem evolved. The lack of an autonomic nervous system in jawless vertebrates implies that spinal visceral motor neurons evolved out of spinal somatic motor neurons. Consistent with the evolutionary origin of brainstem parasympathetic motor neurons out of branchial motor neurons and spinal sympathetic motor neurons out of spinal motor neurons is the recent revision of the organization of the autonomic nervous system into a cranial parasympathetic and a spinal sympathetic division (e.g., there is no sacral parasympathetic division). We propose a new nomenclature that takes all of these new insights into account and avoids the conceptual misunderstandings and incorrect interpretation of limited and technically inferior data inherent in the old nomenclature.

A Hox regulatory network establishes motor neuron pool identity and target-muscle connectivity.

PubMed

Dasen, Jeremy S; Tice, Bonnie C; Brenner-Morton, Susan; Jessell, Thomas M

2005-11-04

Spinal motor neurons acquire specialized "pool" identities that determine their ability to form selective connections with target muscles in the limb, but the molecular basis of this striking example of neuronal specificity has remained unclear. We show here that a Hox transcriptional regulatory network specifies motor neuron pool identity and connectivity. Two interdependent sets of Hox regulatory interactions operate within motor neurons, one assigning rostrocaudal motor pool position and a second directing motor pool diversity at a single segmental level. This Hox regulatory network directs the downstream transcriptional identity of motor neuron pools and defines the pattern of target-muscle connectivity.

Isl1 is required for multiple aspects of motor neuron development.

PubMed

Liang, Xingqun; Song, Mi-Ryoung; Xu, ZengGuang; Lanuza, Guillermo M; Liu, Yali; Zhuang, Tao; Chen, Yihan; Pfaff, Samuel L; Evans, Sylvia M; Sun, Yunfu

2011-07-01

The LIM homeodomain transcription factor Islet1 (Isl1) is expressed in multiple organs and plays essential roles during embryogenesis. Isl1 is required for the survival and specification of spinal cord motor neurons. Due to early embryonic lethality and loss of motor neurons, the role of Isl1 in other aspects of motor neuron development remains unclear. In this study, we generated Isl1 mutant mouse lines expressing graded doses of Isl1. Our study has revealed essential roles of Isl1 in multiple aspects of motor neuron development, including motor neuron cell body localization, motor column formation and axon growth. In addition, Isl1 is required for survival of cranial ganglia neurons. Copyright © 2011 Elsevier Inc. All rights reserved.

Mutant TDP-43 within motor neurons drives disease onset but not progression in amyotrophic lateral sclerosis.

PubMed

Ditsworth, Dara; Maldonado, Marcus; McAlonis-Downes, Melissa; Sun, Shuying; Seelman, Amanda; Drenner, Kevin; Arnold, Eveline; Ling, Shuo-Chien; Pizzo, Donald; Ravits, John; Cleveland, Don W; Da Cruz, Sandrine

2017-06-01

Mutations in TDP-43 cause amyotrophic lateral sclerosis (ALS), a fatal paralytic disease characterized by degeneration and premature death of motor neurons. The contribution of mutant TDP-43-mediated damage within motor neurons was evaluated using mice expressing a conditional allele of an ALS-causing TDP-43 mutant (Q331K) whose broad expression throughout the central nervous system mimics endogenous TDP-43. TDP-43 Q331K mice develop age- and mutant-dependent motor deficits from degeneration and death of motor neurons. Cre-recombinase-mediated excision of the TDP-43 Q331K gene from motor neurons is shown to delay onset of motor symptoms and appearance of TDP-43-mediated aberrant nuclear morphology, and abrogate subsequent death of motor neurons. However, reduction of mutant TDP-43 selectively in motor neurons did not prevent age-dependent degeneration of axons and neuromuscular junction loss, nor did it attenuate astrogliosis or microgliosis. Thus, disease mechanism is non-cell autonomous with mutant TDP-43 expressed in motor neurons determining disease onset but progression defined by mutant acting within other cell types.

A Role for SMN Exon 7 Splicing in the Selective Vulnerability of Motor Neurons in Spinal Muscular Atrophy

PubMed Central

Ruggiu, Matteo; McGovern, Vicki L.; Lotti, Francesco; Saieva, Luciano; Li, Darrick K.; Kariya, Shingo; Monani, Umrao R.; Burghes, Arthur H. M.

2012-01-01

Spinal muscular atrophy (SMA) is an inherited motor neuron disease caused by homozygous loss of the Survival Motor Neuron 1 (SMN1) gene. In the absence of SMN1, inefficient inclusion of exon 7 in transcripts from the nearly identical SMN2 gene results in ubiquitous SMN decrease but selective motor neuron degeneration. Here we investigated whether cell type-specific differences in the efficiency of exon 7 splicing contribute to the vulnerability of SMA motor neurons. We show that normal motor neurons express markedly lower levels of full-length SMN mRNA from SMN2 than do other cells in the spinal cord. This is due to inefficient exon 7 splicing that is intrinsic to motor neurons under normal conditions. We also find that SMN depletion in mammalian cells decreases exon 7 inclusion through a negative feedback loop affecting the splicing of its own mRNA. This mechanism is active in vivo and further decreases the efficiency of exon 7 inclusion specifically in motor neurons of severe-SMA mice. Consistent with expression of lower levels of full-length SMN, we find that SMN-dependent downstream molecular defects are exacerbated in SMA motor neurons. These findings suggest a mechanism to explain the selective vulnerability of motor neurons to loss of SMN1. PMID:22037760

Patterns of Spinal Sensory-Motor Connectivity Prescribed by a Dorsoventral Positional Template

PubMed Central

Sürmeli, Gülşen; Akay, Turgay; Ippolito, Gregory; Tucker, Philip W; Jessell, Thomas M

2011-01-01

Summary Sensory-motor circuits in the spinal cord are constructed with a fine specificity that coordinates motor behavior, but the mechanisms that direct sensory connections with their motor neuron partners remain unclear. The dorsoventral settling position of motor pools in the spinal cord is known to match the distal-to-proximal position of their muscle targets in the limb, but the significance of invariant motor neuron positioning is unknown. An analysis of sensory-motor connectivity patterns in FoxP1 mutant mice, where motor neuron position has been scrambled, shows that the final pattern of sensory-motor connections is initiated by the projection of sensory axons to discrete dorsoventral domains of the spinal cord without regard for motor neuron subtype, or indeed, the presence of motor neurons. By implication, the clustering and dorsoventral settling position of motor neuron pools serves as a determinant of the pattern of sensory input specificity, and thus motor coordination. PMID:22036571

C-terminals in the mouse branchiomotor nuclei originate from the magnocellular reticular formation.

PubMed

Matsui, Toshiyasu; Hongo, Yu; Haizuka, Yoshinori; Kaida, Kenichi; Matsumura, George; Martin, Donna M; Kobayashi, Yasushi

2013-08-26

Large cholinergic synaptic boutons called "C-terminals" contact motoneurons and regulate their excitability. C-terminals in the spinal somatic motor nuclei originate from cholinergic interneurons in laminae VII and X that express a transcription factor Pitx2. Cranial motor nuclei contain another type of motoneuron: branchiomotor neurons. Although branchiomotor neurons receive abundant C-terminal projections, the neural source of these C-terminals remains unknown. In the present study, we first examined whether cholinergic neurons express Pitx2 in the reticular formation of the adult mouse brainstem, as in the spinal cord. Although Pitx2-positive cholinergic neurons were observed in the magnocellular reticular formation and region around the central canal in the caudal medulla, none was present more rostrally in the brainstem tegmentum. We next explored the origin of C-terminals in the branchiomotor nuclei by using biotinylated dextran amine (BDA). BDA injections into the magnocellular reticular formation of the medulla and pons resulted in the labeling of numerous C-terminals in the branchiomotor nuclei: the ambiguous, facial, and trigeminal motor nuclei. Our results revealed that the origins of C-terminals in the branchiomotor nuclei are cholinergic neurons in the magnocellular reticular formation not only in the caudal medulla, but also at more rostral levels of the brainstem, which lacks Pitx2-positive neurons. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

Redox Regulation in Amyotrophic Lateral Sclerosis

PubMed Central

Parakh, Sonam; Spencer, Damian M.; Halloran, Mark A.; Soo, Kai Y.; Atkin, Julie D.

2013-01-01

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease that results from the death of upper and lower motor neurons. Due to a lack of effective treatment, it is imperative to understand the underlying mechanisms and processes involved in disease progression. Regulations in cellular reduction/oxidation (redox) processes are being increasingly implicated in disease. Here we discuss the possible involvement of redox dysregulation in the pathophysiology of ALS, either as a cause of cellular abnormalities or a consequence. We focus on its possible role in oxidative stress, protein misfolding, glutamate excitotoxicity, lipid peroxidation and cholesterol esterification, mitochondrial dysfunction, impaired axonal transport and neurofilament aggregation, autophagic stress, and endoplasmic reticulum (ER) stress. We also speculate that an ER chaperone protein disulphide isomerase (PDI) could play a key role in this dysregulation. PDI is essential for normal protein folding by oxidation and reduction of disulphide bonds, and hence any disruption to this process may have consequences for motor neurons. Addressing the mechanism underlying redox regulation and dysregulation may therefore help to unravel the molecular mechanism involved in ALS. PMID:23533690

Respiratory function after selective respiratory motor neuron death from intrapleural CTB-saporin injections.

PubMed

Nichols, Nicole L; Vinit, Stéphane; Bauernschmidt, Lorene; Mitchell, Gordon S

2015-05-01

Amyotrophic lateral sclerosis (ALS) causes progressive motor neuron degeneration, paralysis and death by ventilatory failure. In rodent ALS models: 1) breathing capacity is preserved until late in disease progression despite major respiratory motor neuron death, suggesting unknown forms of compensatory respiratory plasticity; and 2) spinal microglia become activated in association with motor neuron cell death. Here, we report a novel experimental model to study the impact of respiratory motor neuron death on compensatory responses without many complications attendant to spontaneous motor neuron disease. In specific, we used intrapleural injections of cholera toxin B fragment conjugated to saporin (CTB-SAP) to selectively kill motor neurons with access to the pleural space. Motor neuron survival, CD11b labeling (microglia), ventilatory capacity and phrenic motor output were assessed in rats 3-28days after intrapleural injections of: 1) CTB-SAP (25 and 50μg), or 2) unconjugated CTB and SAP (i.e. control; (CTB+SAP). CTB-SAP elicited dose-dependent phrenic and intercostal motor neuron death; 7days post-25μg CTB-SAP, motor neuron survival approximated that in end-stage ALS rats (phrenic: 36±7%; intercostal: 56±10% of controls; n=9; p<0.05). CTB-SAP caused minimal cell death in other brainstem or spinal cord regions. 1) increased CD11b fractional area in the phrenic motor nucleus, indicating microglial activation; 2) decreased breathing during maximal chemoreceptor stimulation; and 3) diminished phrenic motor output in anesthetized rats (7days post-25μg, 0.3±0.07V; CTB+SAP: 1.5±0.3; n=9; p<0.05). Intrapleural CTB-SAP represents a novel, inducible model of respiratory motor neuron death and provides an opportunity to study compensation for respiratory motor neuron loss. Copyright © 2014 Elsevier Inc. All rights reserved.

Neurotrophic requirements of human motor neurons defined using amplified and purified stem cell-derived cultures.

PubMed

Lamas, Nuno Jorge; Johnson-Kerner, Bethany; Roybon, Laurent; Kim, Yoon A; Garcia-Diaz, Alejandro; Wichterle, Hynek; Henderson, Christopher E

2014-01-01

Human motor neurons derived from embryonic and induced pluripotent stem cells (hESCs and hiPSCs) are a potentially important tool for studying motor neuron survival and pathological cell death. However, their basic survival requirements remain poorly characterized. Here, we sought to optimize a robust survival assay and characterize their response to different neurotrophic factors. First, to increase motor neuron yield, we screened a small-molecule collection and found that the Rho-associated kinase (ROCK) inhibitor Y-27632 enhances motor neuron progenitor proliferation up to 4-fold in hESC and hiPSC cultures. Next, we FACS-purified motor neurons expressing the Hb9::GFP reporter from Y-27632-amplified embryoid bodies and cultured them in the presence of mitotic inhibitors to eliminate dividing progenitors. Survival of these purified motor neurons in the absence of any other cell type was strongly dependent on neurotrophic support. GDNF, BDNF and CNTF all showed potent survival effects (EC(50) 1-2 pM). The number of surviving motor neurons was further enhanced in the presence of forskolin and IBMX, agents that increase endogenous cAMP levels. As a demonstration of the ability of the assay to detect novel neurotrophic agents, Y-27632 itself was found to support human motor neuron survival. Thus, purified human stem cell-derived motor neurons show survival requirements similar to those of primary rodent motor neurons and can be used for rigorous cell-based screening.

Neurotrophic Requirements of Human Motor Neurons Defined Using Amplified and Purified Stem Cell-Derived Cultures

PubMed Central

Lamas, Nuno Jorge; Johnson-Kerner, Bethany; Roybon, Laurent; Kim, Yoon A.; Garcia-Diaz, Alejandro; Wichterle, Hynek; Henderson, Christopher E.

2014-01-01

Human motor neurons derived from embryonic and induced pluripotent stem cells (hESCs and hiPSCs) are a potentially important tool for studying motor neuron survival and pathological cell death. However, their basic survival requirements remain poorly characterized. Here, we sought to optimize a robust survival assay and characterize their response to different neurotrophic factors. First, to increase motor neuron yield, we screened a small-molecule collection and found that the Rho-associated kinase (ROCK) inhibitor Y-27632 enhances motor neuron progenitor proliferation up to 4-fold in hESC and hiPSC cultures. Next, we FACS-purified motor neurons expressing the Hb9::GFP reporter from Y-27632-amplified embryoid bodies and cultured them in the presence of mitotic inhibitors to eliminate dividing progenitors. Survival of these purified motor neurons in the absence of any other cell type was strongly dependent on neurotrophic support. GDNF, BDNF and CNTF all showed potent survival effects (EC50 1–2 pM). The number of surviving motor neurons was further enhanced in the presence of forskolin and IBMX, agents that increase endogenous cAMP levels. As a demonstration of the ability of the assay to detect novel neurotrophic agents, Y-27632 itself was found to support human motor neuron survival. Thus, purified human stem cell-derived motor neurons show survival requirements similar to those of primary rodent motor neurons and can be used for rigorous cell-based screening. PMID:25337699

Motor Neurons Tune Premotor Activity in a Vertebrate Central Pattern Generator

PubMed Central

2017-01-01

Central patterns generators (CPGs) are neural circuits that drive rhythmic motor output without sensory feedback. Vertebrate CPGs are generally believed to operate in a top-down manner in which premotor interneurons activate motor neurons that in turn drive muscles. In contrast, the frog (Xenopus laevis) vocal CPG contains a functionally unexplored neuronal projection from the motor nucleus to the premotor nucleus, indicating a recurrent pathway that may contribute to rhythm generation. In this study, we characterized the function of this bottom-up connection. The X. laevis vocal CPG produces a 50–60 Hz “fast trill” song used by males during courtship. We recorded “fictive vocalizations” in the in vitro CPG from the laryngeal nerve while simultaneously recording premotor activity at the population and single-cell level. We show that transecting the motor-to-premotor projection eliminated the characteristic firing rate of premotor neurons. Silencing motor neurons with the intracellular sodium channel blocker QX-314 also disrupted premotor rhythms, as did blockade of nicotinic synapses in the motor nucleus (the putative location of motor neuron-to-interneuron connections). Electrically stimulating the laryngeal nerve elicited primarily IPSPs in premotor neurons that could be blocked by a nicotinic receptor antagonist. Our results indicate that an inhibitory signal, activated by motor neurons, is required for proper CPG function. To our knowledge, these findings represent the first example of a CPG in which precise premotor rhythms are tuned by motor neuron activity. SIGNIFICANCE STATEMENT Central pattern generators (CPGs) are neural circuits that produce rhythmic behaviors. In vertebrates, motor neurons are not commonly known to contribute to CPG function, with the exception of a few spinal circuits where the functional significance of motor neuron feedback is still poorly understood. The frog hindbrain vocal circuit contains a previously unexplored connection from the motor to premotor region. Our results indicate that motor neurons activate this bottom-up connection, and blocking this signal eliminates normal premotor activity. These findings may promote increased awareness of potential involvement of motor neurons in a wider range of CPGs, perhaps clarifying our understanding of network principles underlying motor behaviors in numerous organisms, including humans. PMID:28219984

Recapitulation of spinal motor neuron-specific disease phenotypes in a human cell model of spinal muscular atrophy

PubMed Central

Wang, Zhi-Bo; Zhang, Xiaoqing; Li, Xue-Jun

2013-01-01

Establishing human cell models of spinal muscular atrophy (SMA) to mimic motor neuron-specific phenotypes holds the key to understanding the pathogenesis of this devastating disease. Here, we developed a closely representative cell model of SMA by knocking down the disease-determining gene, survival motor neuron (SMN), in human embryonic stem cells (hESCs). Our study with this cell model demonstrated that knocking down of SMN does not interfere with neural induction or the initial specification of spinal motor neurons. Notably, the axonal outgrowth of spinal motor neurons was significantly impaired and these disease-mimicking neurons subsequently degenerated. Furthermore, these disease phenotypes were caused by SMN-full length (SMN-FL) but not SMN-Δ7 (lacking exon 7) knockdown, and were specific to spinal motor neurons. Restoring the expression of SMN-FL completely ameliorated all of the disease phenotypes, including specific axonal defects and motor neuron loss. Finally, knockdown of SMN-FL led to excessive mitochondrial oxidative stress in human motor neuron progenitors. The involvement of oxidative stress in the degeneration of spinal motor neurons in the SMA cell model was further confirmed by the administration of N-acetylcysteine, a potent antioxidant, which prevented disease-related apoptosis and subsequent motor neuron death. Thus, we report here the successful establishment of an hESC-based SMA model, which exhibits disease gene isoform specificity, cell type specificity, and phenotype reversibility. Our model provides a unique paradigm for studying how motor neurons specifically degenerate and highlights the potential importance of antioxidants for the treatment of SMA. PMID:23208423

Neuron-specific antioxidant OXR1 extends survival of a mouse model of amyotrophic lateral sclerosis.

PubMed

Liu, Kevin X; Edwards, Benjamin; Lee, Sheena; Finelli, Mattéa J; Davies, Ben; Davies, Kay E; Oliver, Peter L

2015-05-01

Amyotrophic lateral sclerosis is a devastating neurodegenerative disorder characterized by the progressive loss of spinal motor neurons. While the aetiological mechanisms underlying the disease remain poorly understood, oxidative stress is a central component of amyotrophic lateral sclerosis and contributes to motor neuron injury. Recently, oxidation resistance 1 (OXR1) has emerged as a critical regulator of neuronal survival in response to oxidative stress, and is upregulated in the spinal cord of patients with amyotrophic lateral sclerosis. Here, we tested the hypothesis that OXR1 is a key neuroprotective factor during amyotrophic lateral sclerosis pathogenesis by crossing a new transgenic mouse line that overexpresses OXR1 in neurons with the SOD1(G93A) mouse model of amyotrophic lateral sclerosis. Interestingly, we report that overexpression of OXR1 significantly extends survival, improves motor deficits, and delays pathology in the spinal cord and in muscles of SOD1(G93A) mice. Furthermore, we find that overexpression of OXR1 in neurons significantly delays non-cell-autonomous neuroinflammatory response, classic complement system activation, and STAT3 activation through transcriptomic analysis of spinal cords of SOD1(G93A) mice. Taken together, these data identify OXR1 as the first neuron-specific antioxidant modulator of pathogenesis and disease progression in SOD1-mediated amyotrophic lateral sclerosis, and suggest that OXR1 may serve as a novel target for future therapeutic strategies. © The Author (2015). Published by Oxford University Press on behalf of the Guarantors of Brain.

Differential regulation of striatal motor behavior and related cellular responses by dopamine D2L and D2S isoforms.

PubMed

Radl, Daniela; Chiacchiaretta, Martina; Lewis, Robert G; Brami-Cherrier, Karen; Arcuri, Ludovico; Borrelli, Emiliana

2018-01-02

The dopamine D2 receptor (D2R) is a major component of the dopamine system. D2R-mediated signaling in dopamine neurons is involved in the presynaptic regulation of dopamine levels. Postsynaptically, i.e., in striatal neurons, D2R signaling controls complex functions such as motor activity through regulation of cell firing and heterologous neurotransmitter release. The presence of two isoforms, D2L and D2S, which are generated by a mechanism of alternative splicing of the Drd2 gene, raises the question of whether both isoforms may equally control presynaptic and postsynaptic events. Here, we addressed this question by comparing behavioral and cellular responses of mice with the selective ablation of either D2L or D2S isoform. We establish that the presence of either D2L or D2S can support postsynaptic functions related to the control of motor activity in basal conditions. On the contrary, absence of D2S but not D2L prevents the inhibition of tyrosine hydroxylase phosphorylation and, thereby, of dopamine synthesis, supporting a major presynaptic role for D2S. Interestingly, boosting dopamine signaling in the striatum by acute cocaine administration reveals that absence of D2L, but not of D2S, strongly impairs the motor and cellular response to the drug, in a manner similar to the ablation of both isoforms. These results suggest that when the dopamine system is challenged, D2L signaling is required for the control of striatal circuits regulating motor activity. Thus, our findings show that D2L and D2S share similar functions in basal conditions but not in response to stimulation of the dopamine system.

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

Kv7.2 regulates the function of peripheral sensory neurons.

PubMed

King, Chih H; Lancaster, Eric; Salomon, Daniela; Peles, Elior; Scherer, Steven S

2014-10-01

The Kv7 (KCNQ) family of voltage-gated K(+) channels regulates cellular excitability. The functional role of Kv7.2 has been hampered by the lack of a viable Kcnq2-null animal model. In this study, we generated homozygous Kcnq2-null sensory neurons using the Cre-Lox system; in these mice, Kv7.2 expression is absent in the peripheral sensory neurons, whereas the expression of other molecular components of nodes (including Kv7.3), paranodes, and juxtaparanodes is not altered. The conditional Kcnq2-null animals exhibit normal motor performance but have increased thermal hyperalgesia and mechanical allodynia. Whole-cell patch recording technique demonstrates that Kcnq2-null sensory neurons have increased excitability and reduced spike frequency adaptation. Taken together, our results suggest that the loss of Kv7.2 activity increases the excitability of primary sensory neurons. © 2014 Wiley Periodicals, Inc.

TRPV2 enhances axon outgrowth through its activation by membrane stretch in developing sensory and motor neurons.

PubMed

Shibasaki, Koji; Murayama, Namie; Ono, Katsuhiko; Ishizaki, Yasuki; Tominaga, Makoto

2010-03-31

Thermosensitive TRP (thermo TRP) channels are well recognized for their contributions to sensory transduction, responding to a wide variety of stimuli including temperature, nociceptive stimuli, touch, and osmolarity. However, the precise roles for the thermo TRP channels during development have not been determined. To explore the functional importance of thermo TRP channels during neural development, the temporal expression was determined in embryonic mice. Interestingly, TRPV2 expression was detected in spinal motor neurons in addition to the dorsal root ganglia from embryonic day 10.5 and was localized in axon shafts and growth cones, suggesting that the channel is important for axon outgrowth regulation. We revealed that endogenous TRPV2 was activated in a membrane stretch-dependent manner in developing neurons by knocking down the TRPV2 function with dominant-negative TRPV2 and TRPV2-specific shRNA and significantly promoted axon outgrowth. Thus, for the first time we revealed that TRPV2 is an important regulator for axon outgrowth through its activation by membrane stretch during development.

Reduced sensory synaptic excitation impairs motor neuron function via Kv2.1 in spinal muscular atrophy.

PubMed

Fletcher, Emily V; Simon, Christian M; Pagiazitis, John G; Chalif, Joshua I; Vukojicic, Aleksandra; Drobac, Estelle; Wang, Xiaojian; Mentis, George Z

2017-07-01

Behavioral deficits in neurodegenerative diseases are often attributed to the selective dysfunction of vulnerable neurons via cell-autonomous mechanisms. Although vulnerable neurons are embedded in neuronal circuits, the contributions of their synaptic partners to disease process are largely unknown. Here we show that, in a mouse model of spinal muscular atrophy (SMA), a reduction in proprioceptive synaptic drive leads to motor neuron dysfunction and motor behavior impairments. In SMA mice or after the blockade of proprioceptive synaptic transmission, we observed a decrease in the motor neuron firing that could be explained by the reduction in the expression of the potassium channel Kv2.1 at the surface of motor neurons. Chronically increasing neuronal activity pharmacologically in vivo led to a normalization of Kv2.1 expression and an improvement in motor function. Our results demonstrate a key role of excitatory synaptic drive in shaping the function of motor neurons during development and the contribution of its disruption to a neurodegenerative disease.

Reduced sensory synaptic excitation impairs motor neuron function via Kv2.1 in spinal muscular atrophy

PubMed Central

Fletcher, Emily V.; Simon, Christian M.; Pagiazitis, John G.; Chalif, Joshua I.; Vukojicic, Aleksandra; Drobac, Estelle; Wang, Xiaojian; Mentis, George Z.

2017-01-01

Behavioral deficits in neurodegenerative diseases are often attributed to the selective dysfunction of vulnerable neurons via cell-autonomous mechanisms. Although vulnerable neurons are embedded in neuronal circuits, the contribution of their synaptic partners to the disease process is largely unknown. Here, we show that in a mouse model of spinal muscular atrophy (SMA), a reduction in proprioceptive synaptic drive leads to motor neuron dysfunction and motor behavior impairments. In SMA mice or after the blockade of proprioceptive synaptic transmission we observed a decrease in the motor neuron firing which could be explained by the reduction in the expression of the potassium channel Kv2.1 at the surface of motor neurons. Increasing neuronal activity pharmacologically by chronic exposure in vivo led to a normalization of Kv2.1 expression and an improvement in motor function. Our results demonstrate a key role of excitatory synaptic drive in shaping the function of motor neurons during development and the contribution of its disruption to a neurodegenerative disease. PMID:28504671

Motor Force Homeostasis in Skeletal Muscle Contraction

PubMed Central

Chen, Bin; Gao, Huajian

2011-01-01

In active biological contractile processes such as skeletal muscle contraction, cellular mitosis, and neuronal growth, an interesting common observation is that multiple motors can perform coordinated and synchronous actions, whereas individual myosin motors appear to randomly attach to and detach from actin filaments. Recent experiment has demonstrated that, during skeletal muscle shortening at a wide range of velocities, individual myosin motors maintain a force of ∼6 pN during a working stroke. To understand how such force-homeostasis can be so precisely regulated in an apparently chaotic system, here we develop a molecular model within a coupled stochastic-elastic theoretical framework. The model reveals that the unique force-stretch relation of myosin motor and the stochastic behavior of actin-myosin binding cause the average number of working motors to increase in linear proportion to the filament load, so that the force on each working motor is regulated at ∼6 pN, in excellent agreement with experiment. This study suggests that it might be a general principle to use catch bonds together with a force-stretch relation similar to that of myosin motors to regulate force homeostasis in many biological processes. PMID:21767492

Hox repertoires for motor neuron diversity and connectivity gated by a single accessory factor, FoxP1.

PubMed

Dasen, Jeremy S; De Camilli, Alessandro; Wang, Bin; Tucker, Philip W; Jessell, Thomas M

2008-07-25

The precision with which motor neurons innervate target muscles depends on a regulatory network of Hox transcription factors that translates neuronal identity into patterns of connectivity. We show that a single transcription factor, FoxP1, coordinates motor neuron subtype identity and connectivity through its activity as a Hox accessory factor. FoxP1 is expressed in Hox-sensitive motor columns and acts as a dose-dependent determinant of columnar fate. Inactivation of Foxp1 abolishes the output of the motor neuron Hox network, reverting the spinal motor system to an ancestral state. The loss of FoxP1 also changes the pattern of motor neuron connectivity, and in the limb motor axons appear to select their trajectories and muscle targets at random. Our findings show that FoxP1 is a crucial determinant of motor neuron diversification and connectivity, and clarify how this Hox regulatory network controls the formation of a topographic neural map.

Drosophila motor neuron retraction during metamorphosis is mediated by inputs from TGF-β/BMP signaling and orphan nuclear receptors.

PubMed

Boulanger, Ana; Farge, Morgane; Ramanoudjame, Christophe; Wharton, Kristi; Dura, Jean-Maurice

2012-01-01

Larval motor neurons remodel during Drosophila neuro-muscular junction dismantling at metamorphosis. In this study, we describe the motor neuron retraction as opposed to degeneration based on the early disappearance of β-Spectrin and the continuing presence of Tubulin. By blocking cell dynamics with a dominant-negative form of Dynamin, we show that phagocytes have a key role in this process. Importantly, we show the presence of peripheral glial cells close to the neuro-muscular junction that retracts before the motor neuron. We show also that in muscle, expression of EcR-B1 encoding the steroid hormone receptor required for postsynaptic dismantling, is under the control of the ftz-f1/Hr39 orphan nuclear receptor pathway but not the TGF-β signaling pathway. In the motor neuron, activation of EcR-B1 expression by the two parallel pathways (TGF-β signaling and nuclear receptor) triggers axon retraction. We propose that a signal from a TGF-β family ligand is produced by the dismantling muscle (postsynapse compartment) and received by the motor neuron (presynaptic compartment) resulting in motor neuron retraction. The requirement of the two pathways in the motor neuron provides a molecular explanation for the instructive role of the postsynapse degradation on motor neuron retraction. This mechanism insures the temporality of the two processes and prevents motor neuron pruning before postsynaptic degradation.

Slit and semaphorin signaling governed by Islet transcription factors positions motor neuron somata within the neural tube

PubMed Central

Lee, Hojae; Kim, Minkyung; Kim, Namhee; Macfarlan, Todd; Pfaff, Samuel L.; Mastick, Grant S.; Song, Mi-Ryoung

2015-01-01

Motor neurons send out axons to peripheral muscles while their cell bodies remain in the ventral spinal cord. The unique configuration of motor neurons spanning the border between the CNS and PNS has been explained by structural barriers such as boundary cap (BC) cells, basal lamina and radial glia. However, mechanisms in motor neurons that retain their position have not been addressed yet. Here we demonstrate that the Islet1 (Isl1) and Islet2 (Isl2) transcription factors, which are essential for acquisition of motor neuron identity, also contribute to restrict motor neurons within the neural tube. In mice that lack both Isl1 and Isl2, large numbers of motor neurons exited the neural tube, even prior to the appearance of BC cells at the ventral exit points. Transcriptional profiling of motor neurons derived from Isl1 null embryonic stem cells revealed that transcripts of major genes involved in repulsive mechanisms were misregulated. Particularly, expression of Neuropilin1 (Npr1) and Slit2 mRNA was diminished in Islet mutant mice, and these could be target genes of the Islet proteins. Consistent with this mechanism, Robo and Slit mutations in mice and knockdown of Npr1 and Slit2 in chick embryos caused motor neurons to migrate to the periphery. Together, our study suggests that Islet genes engage Robo-Slit and Neuropilin-Semaphorin signaling in motor neurons to retain motor somata within the CNS. PMID:25843547

Functional Diversification of Motor Neuron-specific Isl1 Enhancers during Evolution

PubMed Central

Kim, Namhee; Park, Chungoo; Jeong, Yongsu; Song, Mi-Ryoung

2015-01-01

Functional diversification of motor neurons has occurred in order to selectively control the movements of different body parts including head, trunk and limbs. Here we report that transcription of Isl1, a major gene necessary for motor neuron identity, is controlled by two enhancers, CREST1 (E1) and CREST2 (E2) that allow selective gene expression of Isl1 in motor neurons. Introduction of GFP reporters into the chick neural tube revealed that E1 is active in hindbrain motor neurons and spinal cord motor neurons, whereas E2 is active in the lateral motor column (LMC) of the spinal cord, which controls the limb muscles. Genome-wide ChIP-Seq analysis combined with reporter assays showed that Phox2 and the Isl1-Lhx3 complex bind to E1 and drive hindbrain and spinal cord-specific expression of Isl1, respectively. Interestingly, Lhx3 alone was sufficient to activate E1, and this may contribute to the initiation of Isl1 expression when progenitors have just developed into motor neurons. E2 was induced by onecut 1 (OC-1) factor that permits Isl1 expression in LMCm neurons. Interestingly, the core region of E1 has been conserved in evolution, even in the lamprey, a jawless vertebrate with primitive motor neurons. All E1 sequences from lamprey to mouse responded equally well to Phox2a and the Isl1-Lhx3 complex. Conversely, E2, the enhancer for limb-innervating motor neurons, was only found in tetrapod animals. This suggests that evolutionarily-conserved enhancers permit the diversification of motor neurons. PMID:26447474

Functional Diversification of Motor Neuron-specific Isl1 Enhancers during Evolution.

PubMed

Kim, Namhee; Park, Chungoo; Jeong, Yongsu; Song, Mi-Ryoung

2015-10-01

Functional diversification of motor neurons has occurred in order to selectively control the movements of different body parts including head, trunk and limbs. Here we report that transcription of Isl1, a major gene necessary for motor neuron identity, is controlled by two enhancers, CREST1 (E1) and CREST2 (E2) that allow selective gene expression of Isl1 in motor neurons. Introduction of GFP reporters into the chick neural tube revealed that E1 is active in hindbrain motor neurons and spinal cord motor neurons, whereas E2 is active in the lateral motor column (LMC) of the spinal cord, which controls the limb muscles. Genome-wide ChIP-Seq analysis combined with reporter assays showed that Phox2 and the Isl1-Lhx3 complex bind to E1 and drive hindbrain and spinal cord-specific expression of Isl1, respectively. Interestingly, Lhx3 alone was sufficient to activate E1, and this may contribute to the initiation of Isl1 expression when progenitors have just developed into motor neurons. E2 was induced by onecut 1 (OC-1) factor that permits Isl1 expression in LMCm neurons. Interestingly, the core region of E1 has been conserved in evolution, even in the lamprey, a jawless vertebrate with primitive motor neurons. All E1 sequences from lamprey to mouse responded equally well to Phox2a and the Isl1-Lhx3 complex. Conversely, E2, the enhancer for limb-innervating motor neurons, was only found in tetrapod animals. This suggests that evolutionarily-conserved enhancers permit the diversification of motor neurons.

Reduced motor neuron excitability is an important contributor to weakness in a rat model of sepsis.

PubMed

Nardelli, Paul; Vincent, Jacob A; Powers, Randall; Cope, Tim C; Rich, Mark M

2016-08-01

The mechanisms by which sepsis triggers intensive care unit acquired weakness (ICUAW) remain unclear. We previously identified difficulty with motor unit recruitment in patients as a novel contributor to ICUAW. To study the mechanism underlying poor recruitment of motor units we used the rat cecal ligation and puncture model of sepsis. We identified striking dysfunction of alpha motor neurons during repetitive firing. Firing was more erratic, and often intermittent. Our data raised the possibility that reduced excitability of motor neurons was a significant contributor to weakness induced by sepsis. In this study we quantified the contribution of reduced motor neuron excitability and compared its magnitude to the contributions of myopathy, neuropathy and failure of neuromuscular transmission. We injected constant depolarizing current pulses (5s) into the soma of alpha motor neurons in the lumbosacral spinal cord of anesthetized rats to trigger repetitive firing. In response to constant depolarization, motor neurons in untreated control rats fired at steady and continuous firing rates and generated smooth and sustained tetanic motor unit force as expected. In contrast, following induction of sepsis, motor neurons were often unable to sustain firing throughout the 5s current injection such that force production was reduced. Even when firing, motor neurons from septic rats fired erratically and discontinuously, leading to irregular production of motor unit force. Both fast and slow type motor neurons had similar disruption of excitability. We followed rats after recovery from sepsis to determine the time course of resolution of the defect in motor neuron excitability. By one week, rats appeared to have recovered from sepsis as they had no piloerection and appeared to be in no distress. The defects in motor neuron repetitive firing were still striking at 2weeks and, although improved, were present at one month. We infer that rats suffered from weakness due to reduced motor neuron excitability for weeks after resolution of sepsis. To assess whether additional contributions from myopathy, neuropathy and defects in neuromuscular transmission contributed to the reduction in force generation, we measured whole-muscle force production in response to electrical stimulation of the muscle nerve. We found no abnormality in force generation that would suggest the presence of myopathy, neuropathy or defective neuromuscular transmission. These data suggest disruption of repetitive firing of motor neurons is an important contributor to weakness induced by sepsis in rats and raise the possibility that reduced motor neuron excitability contributes to disability that persists after resolution of sepsis. Copyright © 2016 Elsevier Inc. All rights reserved.

Nitrergic ventro-medial medullary neurons activated during cholinergically induced active (REM) sleep in the cat

PubMed Central

Pose, Inés; Sampogna, Sharon; Chase, Michael H.; Morales, Francisco R.

2010-01-01

The rostral ventro-medial medullary reticular formation is a complex structure that is involved with a variety of motor functions. It contains glycinergic neurons that are activated during active (REM) sleep (AS); these neurons appear to be responsible for the postsynaptic inhibition of motoneurons that occurs during this state. We have reported that neurons in this same region contain nitric oxide (NO) synthase and that they innervate brainstem motor pools. In the present study we examined the c-fos expression of these neurons after carbachol-induced active sleep (C-AS). Three control and four experimental cats were employed to identify c-fos expressing nitrergic neurons using immunocytochemical techniques to detect the Fos protein together with neuronal nitric oxide synthase (nNOS) or NADPH-diaphorase activity. The classical neurotransmitter content of the nitrergic cells in this region was examined through the combination of immunocytochemical techniques for the detection of glutamate, glycine, choline acetyltransferase (ChAT), tyrosine hydroxilase (TH) or GABA together with nNOS. During C-AS, there was a 1074% increase in the number of nitrergic neurons that expressed c-fos. These neurons did not contain glycine, ChAT, TH or GABA, but a subpopulation (15%) of them displayed glutamate-like immunoreactivity. Therefore, some of these neurons contain both an excitatory neurotransmitter (glutamate) and an excitatory neuromodulator (NO); the neurotransmitter content of the rest of them remains to be determined. Because some of the nitrergic neurons innervate brainstem motoneurons it is possible that they participate in the generation of tonic and excitatory phasic motor events that occur during AS. We also suggest that these nitrergic neurons may be involved in autonomic regulation during this state. In addition, because NO has trophic effects on target neurons, the present findings represent the first, albeit indirect, evidence for a possible trophic function of this nature during AS. PMID:21044662

Rilmenidine promotes MTOR-independent autophagy in the mutant SOD1 mouse model of amyotrophic lateral sclerosis without slowing disease progression

PubMed Central

Perera, Nirma D.; Sheean, Rebecca K.; Lau, Chew L.; Shin, Yea Seul; Beart, Philip M.; Horne, Malcolm K.; Turner, Bradley J.

2018-01-01

ABSTRACT Macroautophagy/autophagy is the main intracellular catabolic pathway in neurons that eliminates misfolded proteins, aggregates and damaged organelles associated with ageing and neurodegeneration. Autophagy is regulated by both MTOR-dependent and -independent pathways. There is increasing evidence that autophagy is compromised in neurodegenerative disorders, which may contribute to cytoplasmic sequestration of aggregation-prone and toxic proteins in neurons. Genetic or pharmacological modulation of autophagy to promote clearance of misfolded proteins may be a promising therapeutic avenue for these disorders. Here, we demonstrate robust autophagy induction in motor neuronal cells expressing SOD1 or TARDBP/TDP-43 mutants linked to amyotrophic lateral sclerosis (ALS). Treatment of these cells with rilmenidine, an anti-hypertensive agent and imidazoline-1 receptor agonist that induces autophagy, promoted autophagic clearance of mutant SOD1 and efficient mitophagy. Rilmenidine administration to mutant SOD1G93A mice upregulated autophagy and mitophagy in spinal cord, leading to reduced soluble mutant SOD1 levels. Importantly, rilmenidine increased autophagosome abundance in motor neurons of SOD1G93A mice, suggesting a direct action on target cells. Despite robust induction of autophagy in vivo, rilmenidine worsened motor neuron degeneration and symptom progression in SOD1G93A mice. These effects were associated with increased accumulation and aggregation of insoluble and misfolded SOD1 species outside the autophagy pathway, and severe mitochondrial depletion in motor neurons of rilmenidine-treated mice. These findings suggest that rilmenidine treatment may drive disease progression and neurodegeneration in this mouse model due to excessive mitophagy, implying that alternative strategies to beneficially stimulate autophagy are warranted in ALS. PMID:28980850

Behavioral impact of neurotransmitter-activated GPCRs: Muscarinic and GABAB receptors regulate C. elegans locomotion

PubMed Central

Dittman, Jeremy S; Kaplan, Joshua M

2008-01-01

Neurotransmitter released from presynaptic terminals activates both ligand-gated ion channels (ionotropic receptors) and a variety of G protein-coupled receptors (GPCRs). These neurotransmitter receptors are expressed on both pre- and postsynaptic cells. Thus, each neurotransmitter acts on multiple receptor classes, generating a large repertoire of physiological responses. The impact of many ionotropic receptors on neuronal activity and behavior has been clearly elucidated; however, much less is known about how neurotransmitter-gated GPCRs regulate neurons and circuits. In C. elegans, both Acetylcholine (ACh) and GABA are released in the nerve cord and mediate fast neuromuscular excitation and inhibition during locomotion. Here we identify a muscarinic receptor (GAR-2) and the GABAB receptor dimer (GBB-1/2) that detect synaptically released ACh and GABA, respectively. Both GAR-2 and GBB-1/2 inhibited cholinergic motor neurons when ACh and GABA levels were enhanced. Loss of either GPCR resulted in movement defects, suggesting that these receptors are activated during locomotion. When the negative feedback provided by GAR-2 was replaced with positive feedback, animals became highly sensitive to ACh levels and locomotion was severely impaired. Thus, conserved GPCRs act in the nematode motor circuit to provide negative feedback and to regulate locomotory behaviors that underlie navigation. PMID:18614679

A neural circuit mechanism for regulating vocal variability during song learning in zebra finches.

PubMed

Garst-Orozco, Jonathan; Babadi, Baktash; Ölveczky, Bence P

2014-12-15

Motor skill learning is characterized by improved performance and reduced motor variability. The neural mechanisms that couple skill level and variability, however, are not known. The zebra finch, a songbird, presents a unique opportunity to address this question because production of learned song and induction of vocal variability are instantiated in distinct circuits that converge on a motor cortex analogue controlling vocal output. To probe the interplay between learning and variability, we made intracellular recordings from neurons in this area, characterizing how their inputs from the functionally distinct pathways change throughout song development. We found that inputs that drive stereotyped song-patterns are strengthened and pruned, while inputs that induce variability remain unchanged. A simple network model showed that strengthening and pruning of action-specific connections reduces the sensitivity of motor control circuits to variable input and neural 'noise'. This identifies a simple and general mechanism for learning-related regulation of motor variability.

Phrenic Long-Term Facilitation Requires PKCθ Activity within Phrenic Motor Neurons

PubMed Central

Devinney, Michael J.; Fields, Daryl P.; Huxtable, Adrianne G.; Peterson, Timothy J.; Dale, Erica A.

2015-01-01

Acute intermittent hypoxia (AIH) induces a form of spinal motor plasticity known as phrenic long-term facilitation (pLTF); pLTF is a prolonged increase in phrenic motor output after AIH has ended. In anesthetized rats, we demonstrate that pLTF requires activity of the novel PKC isoform, PKCθ, and that the relevant PKCθ is within phrenic motor neurons. Whereas spinal PKCθ inhibitors block pLTF, inhibitors targeting other PKC isoforms do not. PKCθ is highly expressed in phrenic motor neurons, and PKCθ knockdown with intrapleural siRNAs abolishes pLTF. Intrapleural siRNAs targeting PKCζ, an atypical PKC isoform expressed in phrenic motor neurons that underlies a distinct form of phrenic motor plasticity, does not affect pLTF. Thus, PKCθ plays a critical role in spinal AIH-induced respiratory motor plasticity, and the relevant PKCθ is localized within phrenic motor neurons. Intrapleural siRNA delivery has considerable potential as a therapeutic tool to selectively manipulate plasticity in vital respiratory motor neurons. PMID:26019328

Beadex Function in the Motor Neurons Is Essential for Female Reproduction in Drosophila melanogaster

PubMed Central

Kairamkonda, Subhash; Nongthomba, Upendra

2014-01-01

Drosophila melanogaster has served as an excellent model system for understanding the neuronal circuits and molecular mechanisms regulating complex behaviors. The Drosophila female reproductive circuits, in particular, are well studied and can be used as a tool to understand the role of novel genes in neuronal function in general and female reproduction in particular. In the present study, the role of Beadex, a transcription co-activator, in Drosophila female reproduction was assessed by generation of mutant and knock down studies. Null allele of Beadex was generated by transposase induced excision of P-element present within an intron of Beadex gene. The mutant showed highly compromised reproductive abilities as evaluated by reduced fecundity and fertility, abnormal oviposition and more importantly, the failure of sperm release from storage organs. However, no defect was found in the overall ovariole development. Tissue specific, targeted knock down of Beadex indicated that its function in neurons is important for efficient female reproduction, since its neuronal knock down led to compromised female reproductive abilities, similar to Beadex null females. Further, different neuronal class specific knock down studies revealed that Beadex function is required in motor neurons for normal fecundity and fertility of females. Thus, the present study attributes a novel and essential role for Beadex in female reproduction through neurons. PMID:25396431

Accelerated high-yield generation of limb-innervating motor neurons from human stem cells

PubMed Central

Amoroso, Mackenzie W.; Croft, Gist F.; Williams, Damian J.; O’Keeffe, Sean; Carrasco, Monica A.; Davis, Anne R.; Roybon, Laurent; Oakley, Derek H.; Maniatis, Tom; Henderson, Christopher E.; Wichterle, Hynek

2013-01-01

Human pluripotent stem cells are a promising source of differentiated cells for developmental studies, cell transplantation, disease modeling, and drug testing. However, their widespread use even for intensely studied cell types like spinal motor neurons is hindered by the long duration and low yields of existing protocols for in vitro differentiation and by the molecular heterogeneity of the populations generated. We report a combination of small molecules that within 3 weeks induce motor neurons at up to 50% abundance and with defined subtype identities of relevance to neurodegenerative disease. Despite their accelerated differentiation, motor neurons expressed combinations of HB9, ISL1 and column-specific markers that mirror those observed in vivo in human fetal spinal cord. They also exhibited spontaneous and induced activity, and projected axons towards muscles when grafted into developing chick spinal cord. Strikingly, this novel protocol preferentially generates motor neurons expressing markers of limb-innervating lateral motor column motor neurons (FOXP1+/LHX3−). Access to high-yield cultures of human limb-innervating motor neuron subtypes will facilitate in-depth study of motor neuron subtype-specific properties, disease modeling, and development of large-scale cell-based screening assays. PMID:23303937

Kisspeptin: past, present, and prologue.

PubMed

Steiner, Robert A

2013-01-01

Research in the nineteenth and early twentieth century established that the brain awakens reproduction, governs reproductive activity in the adult of virtually all vertebrates. By 1950, nearly 100 years later, scientists realized that the hypothalamus and its neurosecretory products play a key role in regulating gonadal function in both males and females. Another 20 years would be required to reveal the chemical identity of GnRH and establish that neurons producing GnRH represent the final common pathway through which the brain regulates gonadotropin secretion. It had also become clear that GnRH neurons behave more like motor neurons-better perhaps at going than stopping-and are themselves regulated by a complex network of afferent inputs, which guide the tempo of sexual maturation, regulate estrous and menstrual cycles, control seasonal breeding, and stop reproduction under adversity. In 2003, the revelation that kisspeptin and its receptor are critical for reproduction opened a floodgate of research documenting the role of kisspeptin neurons as central processors of reproduction. Today, there is wide consensus that kisspeptin signaling in the brain is essential, providing the impetus to GnRH neurons to awaken at puberty and reigning the activity of these neurons when discretion is advised. We celebrate this watershed moment-with full knowledge that time and discovery will provide context and perspective to even these heady days.

Dysfunction in endoplasmic reticulum-mitochondria crosstalk underlies SIGMAR1 loss of function mediated motor neuron degeneration.

PubMed

Bernard-Marissal, Nathalie; Médard, Jean-Jacques; Azzedine, Hamid; Chrast, Roman

2015-04-01

Mutations in Sigma 1 receptor (SIGMAR1) have been previously identified in patients with amyotrophic lateral sclerosis and disruption of Sigmar1 in mouse leads to locomotor deficits. However, cellular mechanisms underlying motor phenotypes in human and mouse with disturbed SIGMAR1 function have not been described so far. Here we used a combination of in vivo and in vitro approaches to investigate the role of SIGMAR1 in motor neuron biology. Characterization of Sigmar1(-/-) mice revealed that affected animals display locomotor deficits associated with muscle weakness, axonal degeneration and motor neuron loss. Using primary motor neuron cultures, we observed that pharmacological or genetic inactivation of SIGMAR1 led to motor neuron axonal degeneration followed by cell death. Disruption of SIGMAR1 function in motor neurons disturbed endoplasmic reticulum-mitochondria contacts, affected intracellular calcium signalling and was accompanied by activation of endoplasmic reticulum stress and defects in mitochondrial dynamics and transport. These defects were not observed in cultured sensory neurons, highlighting the exacerbated sensitivity of motor neurons to SIGMAR1 function. Interestingly, the inhibition of mitochondrial fission was sufficient to induce mitochondria axonal transport defects as well as axonal degeneration similar to the changes observed after SIGMAR1 inactivation or loss. Intracellular calcium scavenging and endoplasmic reticulum stress inhibition were able to restore mitochondrial function and consequently prevent motor neuron degeneration. These results uncover the cellular mechanisms underlying motor neuron degeneration mediated by loss of SIGMAR1 function and provide therapeutically relevant insight into motor neuronal diseases. © The Author (2015). Published by Oxford University Press on behalf of the Guarantors of Brain. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Differential neuronal vulnerability identifies IGF-2 as a protective factor in ALS

PubMed Central

Allodi, Ilary; Comley, Laura; Nichterwitz, Susanne; Nizzardo, Monica; Simone, Chiara; Benitez, Julio Aguila; Cao, Ming; Corti, Stefania; Hedlund, Eva

2016-01-01

The fatal disease amyotrophic lateral sclerosis (ALS) is characterized by the loss of somatic motor neurons leading to muscle wasting and paralysis. However, motor neurons in the oculomotor nucleus, controlling eye movement, are for unknown reasons spared. We found that insulin-like growth factor 2 (IGF-2) was maintained in oculomotor neurons in ALS and thus could play a role in oculomotor resistance in this disease. We also showed that IGF-1 receptor (IGF-1R), which mediates survival pathways upon IGF binding, was highly expressed in oculomotor neurons and on extraocular muscle endplate. The addition of IGF-2 induced Akt phosphorylation, glycogen synthase kinase-3β phosphorylation and β-catenin levels while protecting ALS patient motor neurons. IGF-2 also rescued motor neurons derived from spinal muscular atrophy (SMA) patients from degeneration. Finally, AAV9::IGF-2 delivery to muscles of SOD1G93A ALS mice extended life-span by 10%, while preserving motor neurons and inducing motor axon regeneration. Thus, our studies demonstrate that oculomotor-specific expression can be utilized to identify candidates that protect vulnerable motor neurons from degeneration. PMID:27180807

Spinal cord-specific deletion of the glutamate transporter GLT1 causes motor neuron death in mice.

PubMed

Sugiyama, Kaori; Tanaka, Kohichi

2018-03-04

Amyotrophic lateral sclerosis (ALS) is a chronic neurodegenerative disorder characterized by the selective loss of motor neurons. The precise mechanisms that cause the selective death of motor neurons remain unclear, but a growing body of evidence suggests that glutamate-mediated excitotoxicity has been considered to play an important role in the mechanisms of motor neuron degeneration in ALS. Reductions in glutamate transporter GLT1 have been reported in animal models of ALS and the motor cortex and spinal cord of ALS patients. However, it remains unknown whether the reduction in GLT1 has a primary role in the induction of motor neuron degeneration in ALS. Here, we generated conditional knockout mice that lacked GLT1 specifically in the spinal cord by crossing floxed-GLT1 mice and Hoxb8-Cre mice. Hoxb8-Cre/GLT1 flox/flox mice showed motor deficits and motor neuron loss. Thus, loss of the glial glutamate transporter GLT1 is sufficient to cause motor neuron death in mice. Copyright © 2018 Elsevier Inc. All rights reserved.

Localization and expression of ciliary neurotrophic factor (CNTF) in postmortem sciatic nerve from patients with motor neuron disease and diabetic neuropathy

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

Lee, D.A.; Gross, L.; Wittrock, D.A.

1996-08-01

Ciliary neurotrophic factor (CNTF) is thought to play an important role in the maintenance of the mature motor system. The factor is found most abundantly in myelinating Schwann cells in the adult sciatic nerve. Lack of neuronal growth factors has been proposed as one possible etiology of amyotrophic lateral sclerosis (ALS) and spinal muscular atrophy (SMA). Growth factor replacement therapies are currently being evaluated as a treatment for motor neuron disease. In this report we determined whether the expression of CNTF in sciatic nerve differed in patients with motor neuron disease compared to controls or patients with another form ofmore » axonopathy. We identified 8 patients (7 with ALS and 1 with SMA) with motor neuron disease and 6 patients with diabetic motor neuropathy who had autopsy material available. Immunoperoxidase staining showed reduced CNTF expression in nerves of patients with motor neuron disease but not in patients with diabetic motor neuropathy. Decreased CNTF appears be associated with primary motor neuron disease rather than a generalized process of axon loss. This result supports suggestions that CNTF deficiency may be an important factor in the development of motor neuron disease. 20 refs., 4 figs., 1 tab.« less

Bioenergetic status modulates motor neuron vulnerability and pathogenesis in a zebrafish model of spinal muscular atrophy

PubMed Central

Boyd, Penelope J.; Shorrock, Hannah K.; Carter, Roderick N.; Powis, Rachael A.; Thomson, Sophie R.; Thomson, Derek; Graham, Laura C.; Motyl, Anna A. L.; Highley, J. Robin; Becker, Thomas; Becker, Catherina G.; Heath, Paul R.

2017-01-01

Degeneration and loss of lower motor neurons is the major pathological hallmark of spinal muscular atrophy (SMA), resulting from low levels of ubiquitously-expressed survival motor neuron (SMN) protein. One remarkable, yet unresolved, feature of SMA is that not all motor neurons are equally affected, with some populations displaying a robust resistance to the disease. Here, we demonstrate that selective vulnerability of distinct motor neuron pools arises from fundamental modifications to their basal molecular profiles. Comparative gene expression profiling of motor neurons innervating the extensor digitorum longus (disease-resistant), gastrocnemius (intermediate vulnerability), and tibialis anterior (vulnerable) muscles in mice revealed that disease susceptibility correlates strongly with a modified bioenergetic profile. Targeting of identified bioenergetic pathways by enhancing mitochondrial biogenesis rescued motor axon defects in SMA zebrafish. Moreover, targeting of a single bioenergetic protein, phosphoglycerate kinase 1 (Pgk1), was found to modulate motor neuron vulnerability in vivo. Knockdown of pgk1 alone was sufficient to partially mimic the SMA phenotype in wild-type zebrafish. Conversely, Pgk1 overexpression, or treatment with terazosin (an FDA-approved small molecule that binds and activates Pgk1), rescued motor axon phenotypes in SMA zebrafish. We conclude that global bioenergetics pathways can be therapeutically manipulated to ameliorate SMA motor neuron phenotypes in vivo. PMID:28426667

Control of arousal by the orexin neurons

PubMed Central

Alexandre, Chloe; Andermann, Mark L; Scammell, Thomas E

2013-01-01

The orexin-producing neurons in the lateral hypothalamus play an essential role in promoting arousal and maintaining wakefulness. These neurons receive a broad variety of signals related to environmental, physiological and emotional stimuli; they project to almost every brain region involved in the regulation of wakefulness; and they fire most strongly during active wakefulness, high motor activation, and sustained attention. This review focuses on the specific neuronal pathways through which the orexin neurons promote wakefulness and maintain high level of arousal, and how recent studies using optogenetic and pharmacogenetic methods have demonstrated that the locus coeruleus, the tuberomammillary nucleus, and the basal forebrain are some of the key sites mediating the arousing actions of orexins. PMID:23683477

Electrophilic nitro-fatty acids prevent astrocyte-mediated toxicity to motor neurons in a cell model of familial amyotrophic lateral sclerosis via nuclear factor erythroid 2-related factor activation.

PubMed

Diaz-Amarilla, Pablo; Miquel, Ernesto; Trostchansky, Andrés; Trias, Emiliano; Ferreira, Ana M; Freeman, Bruce A; Cassina, Patricia; Barbeito, Luis; Vargas, Marcelo R; Rubbo, Homero

2016-06-01

Nitro-fatty acids (NO2-FA) are electrophilic signaling mediators formed in tissues during inflammation, which are able to induce pleiotropic cytoprotective and antioxidant pathways including up regulation of Nuclear factor erythroid 2-related factor 2 (Nrf2) responsive genes. Amyotrophic Lateral Sclerosis (ALS) is a fatal neurodegenerative disease characterized by the loss of motor neurons associated to an inflammatory process that usually aggravates the disease progression. In ALS animal models, the activation of the transcription factor Nrf2 in astrocytes confers protection to neighboring neurons. It is currently unknown whether NO2-FA can exert protective activity in ALS through Nrf2 activation. Herein we demonstrate that nitro-arachidonic acid (NO2-AA) or nitro-oleic acid (NO2-OA) administrated to astrocytes expressing the ALS-linked hSOD1(G93A) induce antioxidant phase II enzyme expression through Nrf2 activation concomitant with increasing intracellular glutathione levels. Furthermore, treatment of hSOD1(G93A)-expressing astrocytes with NO2-FA prevented their toxicity to motor neurons. Transfection of siRNA targeted to Nrf2 mRNA supported the involvement of Nrf2 activation in NO2-FA-mediated protective effects. Our results show for the first time that NO2-FA induce a potent Nrf2-dependent antioxidant response in astrocytes capable of preventing motor neurons death in a culture model of ALS. Copyright © 2016 Elsevier Inc. All rights reserved.

Motor neuronal activity varies least among individuals when it matters most for behavior

PubMed Central

Cullins, Miranda J.; Shaw, Kendrick M.; Gill, Jeffrey P.

2014-01-01

How does motor neuronal variability affect behavior? To explore this question, we quantified activity of multiple individual identified motor neurons mediating biting and swallowing in intact, behaving Aplysia californica by recording from the protractor muscle and the three nerves containing the majority of motor neurons controlling the feeding musculature. We measured multiple motor components: duration of the activity of identified motor neurons as well as their relative timing. At the same time, we measured behavioral efficacy: amplitude of grasping movement during biting and amplitude of net inward food movement during swallowing. We observed that the total duration of the behaviors varied: Within animals, biting duration shortened from the first to the second and third bites; between animals, biting and swallowing durations varied. To study other sources of variation, motor components were divided by behavior duration (i.e., normalized). Even after normalization, distributions of motor component durations could distinguish animals as unique individuals. However, the degree to which a motor component varied among individuals depended on the role of that motor component in a behavior. Motor neuronal activity that was essential for the expression of biting or swallowing was similar among animals, whereas motor neuronal activity that was not essential for that behavior varied more from individual to individual. These results suggest that motor neuronal activity that matters most for the expression of a particular behavior may vary least from individual to individual. Shaping individual variability to ensure behavioral efficacy may be a general principle for the operation of motor systems. PMID:25411463

Arc mRNA induction in striatal efferent neurons associated with response learning.

PubMed

Daberkow, D P; Riedy, M D; Kesner, R P; Keefe, K A

2007-07-01

The dorsal striatum is involved in motor-response learning, but the extent to which distinct populations of striatal efferent neurons are differentially involved in such learning is unknown. Activity-regulated, cytoskeleton-associated (Arc) protein is an effector immediate-early gene implicated in synaptic plasticity. We examined arc mRNA expression in striatopallidal vs. striatonigral efferent neurons in dorsomedial and dorsolateral striatum of rats engaged in reversal learning on a T-maze motor-response task. Male Sprague-Dawley rats learned to turn right or left for 3 days. Half of the rats then underwent reversal training. The remaining rats were yoked to rats undergoing reversal training, such that they ran the same number of trials but ran them as continued-acquisition trials. Brains were removed and processed using double-label fluorescent in situ hybridization for arc and preproenkephalin (PPE) mRNA. In the reversal, but not the continued-acquisition, group there was a significant relation between the overall arc mRNA signal in dorsomedial striatum and the number of trials run, with rats reaching criterion in fewer trials having higher levels of arc mRNA expression. A similar relation was seen between the numbers of PPE(+) and PPE(-) neurons in dorsomedial striatum with cytoplasmic arc mRNA expression. Interestingly, in behaviourally activated animals significantly more PPE(-) neurons had cytoplasmic arc mRNA expression. These data suggest that Arc in both striatonigral and striatopallidal efferent neurons is involved in striatal synaptic plasticity mediating motor-response learning in the T-maze and that there is differential processing of arc mRNA in distinct subpopulations of striatal efferent neurons.

Uptake of inorganic mercury by human locus ceruleus and corticomotor neurons: implications for amyotrophic lateral sclerosis

PubMed Central

2013-01-01

Background Environmental toxins are suspected to play a role in the pathogenesis of amyotrophic lateral sclerosis (ALS). In an attempt to determine which pathways these toxins can use to enter motor neurons we compared the distribution of mercury in the CNS of a human and of mice that had been exposed to inorganic mercury. Results In the human who had been exposed to metallic mercury, mercury was seen predominantly in the locus ceruleus and corticomotor neurons, as well as in scattered glial cells. In mice that had been exposed to mercury vapor or mercuric chloride, mercury was present in lower motor neurons in the spinal cord and brain stem. Conclusions In humans, inorganic mercury can be taken up predominantly by corticomotor neurons, possibly when the locus ceruleus is upregulated by stress. This toxin uptake into corticomotor neurons is in accord with the hypothesis that ALS originates in these upper motor neurons. In mice, inorganic mercury is taken up predominantly by lower motor neurons. The routes toxins use to enter motor neurons depends on the nature of the toxin, the duration of exposure, and possibly the amount of stress (for upper motor neuron uptake) and exercise (for lower motor neuron uptake) at the time of toxin exposure. PMID:24252585

Spinal Accessory Motor Neurons in the Mouse: A Special Type of Branchial Motor Neuron?

PubMed

Watson, Charles; Tvrdik, Petr

2018-04-16

The spinal accessory nerve arises from motor neurons in the upper cervical spinal cord. The axons of these motor neurons exit dorsal to the ligamentum denticulatum and form the spinal accessory nerve. The nerve ascends in the spinal subarachnoid space to enter the posterior cranial fossa through the foramen magnum. The spinal accessory nerve then turns caudally to exit through the jugular foramen alongside the vagus and glossopharyngeal nerves, and then travels to supply the sternomastoid and trapezius muscles in the neck. The unusual course of the spinal accessory nerve has long prompted speculation that it is not a typical spinal motor nerve and that it might represent a caudal remnant of the branchial motor system. Our cell lineage tracing data, combined with images from public databases, show that the spinal accessory motor neurons in the mouse transiently express Phox2b, a transcription factor that is required for development of brain stem branchial motor nuclei. While this is strong prima facie evidence that the spinal accessory motor neurons should be classified as branchial motor, the evolutionary history of these motor neurons in anamniote vertebrates suggests that they may be considered to be an atypical branchial group that possesses both branchial and somatic characteristics. Anat Rec, 2018. © 2018 Wiley Periodicals, Inc. © 2018 Wiley Periodicals, Inc.

Embryonic stem cells and prospects for their use in regenerative medicine approaches to motor neurone disease.

PubMed

Christou, Y A; Moore, H D; Shaw, P J; Monk, P N

2007-10-01

Human embryonic stem cells are pluripotent cells with the potential to differentiate into any cell type in the presence of appropriate stimulatory factors and environmental cues. Their broad developmental potential has led to valuable insights into the principles of developmental and cell biology and to the proposed use of human embryonic stem cells or their differentiated progeny in regenerative medicine. This review focuses on the prospects for the use of embryonic stem cells in cell-based therapy for motor neurone disease or amyotrophic lateral sclerosis, a progressive neurodegenerative disease that specifically affects upper and lower motor neurones and leads ultimately to death from respiratory failure. Stem cell-derived motor neurones could conceivably be used to replace the degenerated cells, to provide authentic substrates for drug development and screening and for furthering our understanding of disease mechanisms. However, to reliably and accurately culture motor neurones, the complex pathways by which differentiation occurs in vivo must be understood and reiterated in vitro by embryonic stem cells. Here we discuss the need for new therapeutic strategies in the treatment of motor neurone disease, the developmental processes that result in motor neurone formation in vivo, a number of experimental approaches to motor neurone production in vitro and recent progress in the application of stem cells to the treatment and understanding of motor neurone disease.

Induction of parkinsonism-related proteins in the spinal motor neurons of transgenic mouse carrying a mutant SOD1 gene.

PubMed

Morimoto, Nobutoshi; Nagai, Makiko; Miyazaki, Kazunori; Ohta, Yasuyuki; Kurata, Tomoko; Takehisa, Yasushi; Ikeda, Yoshio; Matsuura, Tohru; Asanuma, Masato; Abe, Koji

2010-06-01

Amyotrophic lateral sclerosis is a progressive and fatal disease caused by selective death of motor neurons, and a number of these patients carry mutations in the superoxide dismutase 1 (SOD1) gene involved in ameliorating oxidative stress. Recent studies indicate that oxidative stress and disruption of mitochondrial homeostasis is a common mechanism for motor neuron degeneration in amyotrophic lateral sclerosis and the loss of midbrain dopamine neurons in Parkinson's disease. Therefore, the present study investigated the presence and alterations of familial Parkinson's disease-related proteins, PINK1 and DJ-1, in spinal motor neurons of G93ASOD1 transgenic mouse model of amyotrophic lateral sclerosis. Following onset of disease, PINK1 and DJ-1 protein expression increased in the spinal motor neurons. The activated form of p53 also increased and translocated to the nuclei of spinal motor neurons, followed by increased expression of p53-activated gene 608 (PAG608). This is the first report demonstrating that increased expression of PAG608 correlates with activation of phosphorylated p53 in spinal motor neurons of an amyotrophic lateral sclerosis model. These results provide further evidence of the profound correlations between spinal motor neurons of amyotrophic lateral sclerosis and parkinsonism-related proteins.

Prenatal exposure to cannabinoids evokes long-lasting functional alterations by targeting CB1 receptors on developing cortical neurons.

PubMed

de Salas-Quiroga, Adán; Díaz-Alonso, Javier; García-Rincón, Daniel; Remmers, Floortje; Vega, David; Gómez-Cañas, María; Lutz, Beat; Guzmán, Manuel; Galve-Roperh, Ismael

2015-11-03

The CB1 cannabinoid receptor, the main target of Δ(9)-tetrahydrocannabinol (THC), the most prominent psychoactive compound of marijuana, plays a crucial regulatory role in brain development as evidenced by the neurodevelopmental consequences of its manipulation in animal models. Likewise, recreational cannabis use during pregnancy affects brain structure and function of the progeny. However, the precise neurobiological substrates underlying the consequences of prenatal THC exposure remain unknown. As CB1 signaling is known to modulate long-range corticofugal connectivity, we analyzed the impact of THC exposure on cortical projection neuron development. THC administration to pregnant mice in a restricted time window interfered with subcerebral projection neuron generation, thereby altering corticospinal connectivity, and produced long-lasting alterations in the fine motor performance of the adult offspring. Consequences of THC exposure were reminiscent of those elicited by CB1 receptor genetic ablation, and CB1-null mice were resistant to THC-induced alterations. The identity of embryonic THC neuronal targets was determined by a Cre-mediated, lineage-specific, CB1 expression-rescue strategy in a CB1-null background. Early and selective CB1 reexpression in dorsal telencephalic glutamatergic neurons but not forebrain GABAergic neurons rescued the deficits in corticospinal motor neuron development of CB1-null mice and restored susceptibility to THC-induced motor alterations. In addition, THC administration induced an increase in seizure susceptibility that was mediated by its interference with CB1-dependent regulation of both glutamatergic and GABAergic neuron development. These findings demonstrate that prenatal exposure to THC has long-lasting deleterious consequences in the adult offspring solely mediated by its ability to disrupt the neurodevelopmental role of CB1 signaling.

Induction of mice adult bone marrow mesenchymal stem cells into functional motor neuron-like cells.

PubMed

Abdullah, Rafal H; Yaseen, Nahi Y; Salih, Shahlaa M; Al-Juboory, Ahmad Adnan; Hassan, Ayman; Al-Shammari, Ahmed Majeed

2016-11-01

The differentiation of mesenchymal stem cells (MSC) into acetylcholine secreted motor neuron-like cells, followed by elongation of the cell axon, is a promising treatment for spinal cord injury and motor neuron cell dysfunction in mammals. Differentiation is induced through a pre-induction step using Beta- mercaptoethanol (BME) followed by four days of induction with retinoic acid and sonic hedgehog. This process results in a very efficient differentiation of BM-MSCs into motor neuron-like cells. Immunocytochemistry showed that these treated cells had specific motor neural markers: microtubule associated protein-2 and acetylcholine transferase. The ability of these cells to function as motor neuron cells was assessed by measuring acetylcholine levels in a culture media during differentiation. High-performance liquid chromatography (HPLC) showed that the differentiated cells were functional. Motor neuron axon elongation was then induced by adding different concentrations of a nerve growth factor (NGF) to the differentiation media. Using a collagen matrix to mimic the natural condition of neural cells in a three-dimensional model showed that the MSCs were successfully differentiated into motor neuron-like cells. This process can efficiently differentiate MSCs into functional motor neurons that can be used for autologous nervous system therapy and especially for treating spinal cord injuries. Copyright © 2016 Elsevier B.V. All rights reserved.

Protective effects of long-term lithium administration in a slowly progressive SMA mouse model.

PubMed

Biagioni, Francesca; Ferrucci, Michela; Ryskalin, Larisa; Fulceri, Federica; Lazzeri, Gloria; Calierno, Maria Teresa; Busceti, Carla L; Ruffoli, Riccardo; Fornai, Francesco

2017-12-01

In the present study we evaluated the long-term effects of lithium administration to a knock-out double transgenic mouse model (Smn-/-; SMN1A2G+/-; SMN2+/+) of Spinal Muscle Atrophy type III (SMA-III). This model is characterized by very low levels of the survival motor neuron protein, slow disease progression and motor neuron loss, which enables to detect disease-modifying effects at delayed time intervals. Lithium administration attenuates the decrease in motor activity and provides full protection from motor neuron loss occurring in SMA-III mice, throughout the disease course. In addition, lithium prevents motor neuron enlargement and motor neuron heterotopy and suppresses the occurrence of radial-like glial fibrillary acidic protein immunostaining in the ventral white matter of SMA-III mice. In SMA-III mice long-term lithium administration determines a dramatic increase of survival motor neuron protein levels in the spinal cord. These data demonstrate that long-term lithium administration during a long-lasting motor neuron disorder attenuates behavioural deficit and neuropathology. Since low level of survival motor neuron protein is bound to disease severity in SMA, the robust increase in protein level produced by lithium provides solid evidence which calls for further investigations considering lithium in the long-term treatment of spinal muscle atrophy.

Sodium Pumps Mediate Activity-Dependent Changes in Mammalian Motor Networks

PubMed Central

Picton, Laurence D.; Nascimento, Filipe; Broadhead, Matthew J.; Sillar, Keith T.

2017-01-01

Ubiquitously expressed sodium pumps are best known for maintaining the ionic gradients and resting membrane potential required for generating action potentials. However, activity- and state-dependent changes in pump activity can also influence neuronal firing and regulate rhythmic network output. Here we demonstrate that changes in sodium pump activity regulate locomotor networks in the spinal cord of neonatal mice. The sodium pump inhibitor, ouabain, increased the frequency and decreased the amplitude of drug-induced locomotor bursting, effects that were dependent on the presence of the neuromodulator dopamine. Conversely, activating the pump with the sodium ionophore monensin decreased burst frequency. When more “natural” locomotor output was evoked using dorsal-root stimulation, ouabain increased burst frequency and extended locomotor episode duration, whereas monensin slowed and shortened episodes. Decreasing the time between dorsal-root stimulation, and therefore interepisode interval, also shortened and slowed activity, suggesting that pump activity encodes information about past network output and contributes to feedforward control of subsequent locomotor bouts. Using whole-cell patch-clamp recordings from spinal motoneurons and interneurons, we describe a long-duration (∼60 s), activity-dependent, TTX- and ouabain-sensitive, hyperpolarization (∼5 mV), which is mediated by spike-dependent increases in pump activity. The duration of this dynamic pump potential is enhanced by dopamine. Our results therefore reveal sodium pumps as dynamic regulators of mammalian spinal motor networks that can also be affected by neuromodulatory systems. Given the involvement of sodium pumps in movement disorders, such as amyotrophic lateral sclerosis and rapid-onset dystonia parkinsonism, knowledge of their contribution to motor network regulation also has considerable clinical importance. SIGNIFICANCE STATEMENT The sodium pump is ubiquitously expressed and responsible for at least half of total brain energy consumption. The pumps maintain ionic gradients and the resting membrane potential of neurons, but increasing evidence suggests that activity- and state-dependent changes in pump activity also influence neuronal firing. Here we demonstrate that changes in sodium pump activity regulate locomotor output in the spinal cord of neonatal mice. We describe a sodium pump-mediated afterhyperpolarization in spinal neurons, mediated by spike-dependent increases in pump activity, which is affected by dopamine. Understanding how sodium pumps contribute to network regulation and are targeted by neuromodulators, including dopamine, has clinical relevance due to the role of the sodium pump in diseases, including amyotrophic lateral sclerosis, parkinsonism, epilepsy, and hemiplegic migraine. PMID:28123025

Intrinsic membrane hyperexcitability of amyotrophic lateral sclerosis patient-derived motor neurons.

PubMed

Wainger, Brian J; Kiskinis, Evangelos; Mellin, Cassidy; Wiskow, Ole; Han, Steve S W; Sandoe, Jackson; Perez, Numa P; Williams, Luis A; Lee, Seungkyu; Boulting, Gabriella; Berry, James D; Brown, Robert H; Cudkowicz, Merit E; Bean, Bruce P; Eggan, Kevin; Woolf, Clifford J

2014-04-10

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease of the motor nervous system. We show using multielectrode array and patch-clamp recordings that hyperexcitability detected by clinical neurophysiological studies of ALS patients is recapitulated in induced pluripotent stem cell-derived motor neurons from ALS patients harboring superoxide dismutase 1 (SOD1), C9orf72, and fused-in-sarcoma mutations. Motor neurons produced from a genetically corrected but otherwise isogenic SOD1(+/+) stem cell line do not display the hyperexcitability phenotype. SOD1(A4V/+) ALS patient-derived motor neurons have reduced delayed-rectifier potassium current amplitudes relative to control-derived motor neurons, a deficit that may underlie their hyperexcitability. The Kv7 channel activator retigabine both blocks the hyperexcitability and improves motor neuron survival in vitro when tested in SOD1 mutant ALS cases. Therefore, electrophysiological characterization of human stem cell-derived neurons can reveal disease-related mechanisms and identify therapeutic candidates. Copyright © 2014 The Authors. Published by Elsevier Inc. All rights reserved.

Patterns of Weakness, Classification of Motor Neuron Disease & Clinical Diagnosis of Sporadic ALS

PubMed Central

Statland, Jeffrey M.; Barohn, Richard J.; McVey, April L.; Katz, Jonathan; Dimachkie, Mazen M.

2015-01-01

Synopsis When approaching the patient with suspected motor neuron disease (MND) the pattern of weakness on exam helps distinguish MND from other diseases of peripheral nerves, the neuromuscular junction, or muscle. MND is a clinical diagnosis supported by findings on electrodiagnostic testing, in the absence of other abnormalities on neuroimaging or serological testing. MNDs exist on a spectrum: from a pure lower motor neuron; to mixed upper and lower motor neuron; to a pure upper motor neuron variant in addition to regional variants restricted to the arms, legs or bulbar region. Amyotrophic lateral sclerosis (ALS) is a progressive mixed upper and lower motor neuron disorder, most commonly sporadic (~85%), which is invariably fatal. The only FDA approved treatments for ALS are riluzole, which prolongs life by about 3 months, and dextromethorphan/quinidine which provides symptomatic relief for pseudobulbar affect (inappropriate bouts of laughter or crying). Here we describe a pattern approach to identifying motor neuron disease, and clinical features of sporadic ALS. PMID:26515618

Is Spinal Muscular Atrophy a disease of the motor neurons only: pathogenesis and therapeutic implications?

PubMed Central

Simone, Chiara; Ramirez, Agnese; Bucchia, Monica; Rinchetti, Paola; Rideout, Hardy; Papadimitriou, Dimitra; Re, Diane B.; Corti, Stefania

2016-01-01

Spinal Muscular Atrophy (SMA) is a genetic neurological disease that causes infant mortality; no effective therapies are currently available. SMA is due to homozygous mutations and/or deletions in the Survival Motor Neuron 1 (SMN1) gene and subsequent reduction of the SMN protein, leading to the death of motor neurons. However, there is increasing evidence that in addition to motor neurons, other cell types are contributing to SMA pathology. In this review, we will discuss the involvement of non-motor neuronal cells, located both inside and outside the central nervous system, in disease onset and progression. These contribution of non-motor neuronal cells to disease pathogenesis has important therapeutic implications: in fact, even if SMN restoration in motor neurons is needed, it has been shown that optimal phenotypic amelioration in animal models of SMA requires a more widespread SMN correction. It will be crucial to take this evidence into account before clinical translation of the novel therapeutic approaches that are currently under development. PMID:26681261

Divergent Hox Coding and Evasion of Retinoid Signaling Specifies Motor Neurons Innervating Digit Muscles

PubMed Central

Mendelsohn, Alana I.; Dasen, Jeremy S.; Jessell, Thomas M.

2017-01-01

Summary The establishment of spinal motor neuron subclass diversity is achieved through developmental programs that are aligned with the organization of muscle targets in the limb. The evolutionary emergence of digits represents a specialized adaptation of limb morphology, yet it remains unclear how the specification of digit-innervating motor neuron subtypes parallels the elaboration of digits. We show that digit-innervating motor neurons can be defined by selective gene markers and distinguished from other LMC neurons by the expression of a variant Hox gene repertoire and by the failure to express a key enzyme involved in retinoic acid synthesis. This divergent developmental program is sufficient to induce the specification of digit-innervating motor neurons, emphasizing the specialized status of digit control in the evolution of skilled motor behaviors. Our findings suggest that the emergence of digits in the limb is matched by distinct mechanisms for specifying motor neurons that innervate digit muscles. PMID:28190640

Reduced synaptic density and deficient locomotor response in neuronal activity-regulated pentraxin 2a mutant zebrafish.

PubMed

Elbaz, Idan; Lerer-Goldshtein, Tali; Okamoto, Hitoshi; Appelbaum, Lior

2015-04-01

Neuronal-activity-regulated pentraxin (NARP/NPTX2/NP2) is a secreted synaptic protein that regulates the trafficking of glutamate receptors and mediates learning, memory, and drug addiction. The role of NPTX2 in regulating structural synaptic plasticity and behavior in a developing vertebrate is indefinite. We characterized the expression of nptx2a in larvae and adult zebrafish and established a transcription activator-like effector nuclease (TALEN)-mediated nptx2a mutant (nptx2a(-/-)) to study the role of Nptx2a in regulating structural synaptic plasticity and behavior. Similar to mammals, the zebrafish nptx2a was expressed in excitatory neurons in the brain and spinal cord. Its expression was induced in response to a mechanosensory stimulus but did not change during day and night. Behavioral assays showed that loss of Nptx2a results in reduced locomotor response to light-to-dark transition states and to a sound stimulus. Live imaging of synapses using the transgenic nptx2a:GAL4VP16 zebrafish and a fluorescent presynaptic synaptophysin (SYP) marker revealed reduced synaptic density in the axons of the spinal motor neurons and the anterodorsal lateral-line ganglion (gAD), which regulate locomotor activity and locomotor response to mechanosensory stimuli, respectively. These results suggest that Nptx2a affects locomotor response to external stimuli by mediating structural synaptic plasticity in excitatory neuronal circuits. © FASEB.

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

DOP-2 D2-Like Receptor Regulates UNC-7 Innexins to Attenuate Recurrent Sensory Motor Neurons during C. elegans Copulation

PubMed Central

Correa, Paola A.; Gruninger, Todd

2015-01-01

Neuromodulation of self-amplifying circuits directs context-dependent behavioral executions. Although recurrent networks are found throughout the Caenorhabditis elegans connectome, few reports describe the mechanisms that regulate reciprocal neural activity during complex behavior. We used C. elegans male copulation to dissect how a goal-oriented motor behavior is regulated by recurrently wired sensory-motor neurons. As the male tail presses against the hermaphrodite's vulva, cholinergic and glutamatergic reciprocal innervations of post cloaca sensilla (PCS) neurons (PCA, PCB, and PCC), hook neurons (HOA, HOB), and their postsynaptic sex muscles execute rhythmic copulatory spicule thrusts. These repetitive spicule movements continue until the male shifts off the vulva or genital penetration is accomplished. However, the signaling mechanism that temporally and spatially restricts repetitive intromission attempts to vulva cues was unclear. Here, we report that confinement of spicule insertion attempts to the vulva is facilitated by D2-like receptor modulation of gap-junctions between PCB and the hook sensillum. We isolated a missense mutation in the UNC-7(L) gap-junction isoform, which perturbs DOP-2 signaling in the PCB neuron and its electrical partner, HOA. The glutamate-gated chloride channel AVR-14 is expressed in HOA. Our analysis of the unc-7 mutant allele indicates that when DOP-2 promotes UNC-7 electrical communication, AVR-14-mediated inhibitory signals pass from HOA to PCB. As a consequence, PCB is less receptive to be stimulated by its recurrent synaptic partner, PCA. Behavioral observations suggest that dopamine neuromodulation of UNC-7 ensures attenuation of recursive intromission attempts when the male disengages or is dislodged from the hermaphrodite genitalia. SIGNIFICANCE STATEMENT Using C. elegans male copulation as a model, we found that the neurotransmitter dopamine stimulates D2-like receptors in two sensory circuits to terminate futile behavioral loops. The D2-like receptors promote inhibitory electrical junction activity between a chemosensory and a mechanosensory circuit. Therefore, both systems are attenuated and the animal ceases the recursive behavior. PMID:26156999

Motor Neuron Diseases

MedlinePlus

... length SMN protein, which is critical for the maintenance of motor neurons. Physical and speech therapy, occupational ... length SMN protein, which is critical for the maintenance of motor neurons. Physical and speech therapy, occupational ...

The Crossroads of Synaptic Growth Signaling, Membrane Traffic and Neurological Disease: Insights from Drosophila.

PubMed

Deshpande, Mugdha; Rodal, Avital A

2016-02-01

Neurons require target-derived autocrine and paracrine growth factors to maintain proper identity, innervation, homeostasis and survival. Neuronal growth factor signaling is highly dependent on membrane traffic, both for the packaging and release of the growth factors themselves, and for regulation of intracellular signaling by their transmembrane receptors. Here, we review recent findings from the Drosophila larval neuromuscular junction (NMJ) that illustrate how specific steps of intracellular traffic and inter-organelle interactions impinge on signaling, particularly in the bone morphogenic protein, Wingless and c-Jun-activated kinase pathways, regulating elaboration and stability of NMJ arbors, construction of synapses and synaptic transmission and homeostasis. These membrane trafficking and signaling pathways have been implicated in human motor neuron diseases including amyotrophic lateral sclerosis and hereditary spastic paraplegia, highlighting their importance for neuronal health and survival. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

SAM68 is a physiological regulator of SMN2 splicing in spinal muscular atrophy

PubMed Central

Pagliarini, Vittoria; Pelosi, Laura; Bustamante, Maria Blaire; Nobili, Annalisa; Berardinelli, Maria Grazia; D’Amelio, Marcello; Musarò, Antonio

2015-01-01

Spinal muscular atrophy (SMA) is a neurodegenerative disease caused by loss of motor neurons in patients with null mutations in the SMN1 gene. The almost identical SMN2 gene is unable to compensate for this deficiency because of the skipping of exon 7 during pre–messenger RNA (mRNA) processing. Although several splicing factors can modulate SMN2 splicing in vitro, the physiological regulators of this disease-causing event are unknown. We found that knockout of the splicing factor SAM68 partially rescued body weight and viability of SMAΔ7 mice. Ablation of SAM68 function promoted SMN2 splicing and expression in SMAΔ7 mice, correlating with amelioration of SMA-related defects in motor neurons and skeletal muscles. Mechanistically, SAM68 binds to SMN2 pre-mRNA, favoring recruitment of the splicing repressor hnRNP A1 and interfering with that of U2AF65 at the 3′ splice site of exon 7. These findings identify SAM68 as the first physiological regulator of SMN2 splicing in an SMA mouse model. PMID:26438828

[Effects of transections and electrical coagulations in the medulla oblongata upon the activities in the respiratory muscles of the crucian carp (author's transl)].

PubMed

Fukuda, H

1975-06-01

The following conclusions may be drawn from the results in this work. The respiratory cycles are formed by the neuronal machinery in the reticular formation under the posterior part of the vagal motor nucleus. The motor neurones or the neuronal networks composing the motor nucleus of the respiratory muscles tonically discharge the action potentials, when the neurones or the networks are released from the inhibitory influences of the interneurones connecting the neuronal machinery to the motor neurones. Furthermore, the interneurones probably generate the tonic discharges after removing the inhibitory influences of the other interneurones or the neuronal machinery on them. A reflex mouth closing is elicited by a mechanical stimulus applying on the upper lip. The motor neurones of the m. adductor mandibulae are activated via only one synapse in the reflex. The reflex action potentials recorded from the motor nerve reduce in amplitude at the resting phase of the nerve in the respiratory cycles. These results suggest that the respiratory motor neurones are by nature spontaneous generators of the tonic action potentials and, in the time of the normal breathing, the tonic activity is interrupted by an inhibitory influence of the neuronal machinery generating the respiratory cycles.

Efficient differentiation of mouse embryonic stem cells into motor neurons.

PubMed

Wu, Chia-Yen; Whye, Dosh; Mason, Robert W; Wang, Wenlan

2012-06-09

Direct differentiation of embryonic stem (ES) cells into functional motor neurons represents a promising resource to study disease mechanisms, to screen new drug compounds, and to develop new therapies for motor neuron diseases such as spinal muscular atrophy (SMA) and amyotrophic lateral sclerosis (ALS). Many current protocols use a combination of retinoic acid (RA) and sonic hedgehog (Shh) to differentiate mouse embryonic stem (mES) cells into motor neurons. However, the differentiation efficiency of mES cells into motor neurons has only met with moderate success. We have developed a two-step differentiation protocol that significantly improves the differentiation efficiency compared with currently established protocols. The first step is to enhance the neuralization process by adding Noggin and fibroblast growth factors (FGFs). Noggin is a bone morphogenetic protein (BMP) antagonist and is implicated in neural induction according to the default model of neurogenesis and results in the formation of anterior neural patterning. FGF signaling acts synergistically with Noggin in inducing neural tissue formation by promoting a posterior neural identity. In this step, mES cells were primed with Noggin, bFGF, and FGF-8 for two days to promote differentiation towards neural lineages. The second step is to induce motor neuron specification. Noggin/FGFs exposed mES cells were incubated with RA and a Shh agonist, Smoothened agonist (SAG), for another 5 days to facilitate motor neuron generation. To monitor the differentiation of mESs into motor neurons, we used an ES cell line derived from a transgenic mouse expressing eGFP under the control of the motor neuron specific promoter Hb9. Using this robust protocol, we achieved 51 ± 0.8% of differentiation efficiency (n = 3; p < 0.01, Student's t-test). Results from immunofluorescent staining showed that GFP+ cells express the motor neuron specific markers, Islet-1 and choline acetyltransferase (ChAT). Our two-step differentiation protocol provides an efficient way to differentiate mES cells into spinal motor neurons.

Regulation of cerebral cortex development by Rho GTPases: insights from in vivo studies

PubMed Central

Azzarelli, Roberta; Kerloch, Thomas; Pacary, Emilie

2015-01-01

The cerebral cortex is the site of higher human cognitive and motor functions. Histologically, it is organized into six horizontal layers, each containing unique populations of molecularly and functionally distinct excitatory projection neurons and inhibitory interneurons. The stereotyped cellular distribution of cortical neurons is crucial for the formation of functional neural circuits and it is predominantly established during embryonic development. Cortical neuron development is a multiphasic process characterized by sequential steps of neural progenitor proliferation, cell cycle exit, neuroblast migration and neuronal differentiation. This series of events requires an extensive and dynamic remodeling of the cell cytoskeleton at each step of the process. As major regulators of the cytoskeleton, the family of small Rho GTPases has been shown to play essential functions in cerebral cortex development. Here we review in vivo findings that support the contribution of Rho GTPases to cortical projection neuron development and we address their involvement in the etiology of cerebral cortex malformations. PMID:25610373

An opioid-like system regulating feeding behavior in C. elegans

PubMed Central

Cheong, Mi Cheong; Artyukhin, Alexander B; You, Young-Jai; Avery, Leon

2015-01-01

Neuropeptides are essential for the regulation of appetite. Here we show that neuropeptides could regulate feeding in mutants that lack neurotransmission from the motor neurons that stimulate feeding muscles. We identified nlp-24 by an RNAi screen of 115 neuropeptide genes, testing whether they affected growth. NLP-24 peptides have a conserved YGGXX sequence, similar to mammalian opioid neuropeptides. In addition, morphine and naloxone respectively stimulated and inhibited feeding in starved worms, but not in worms lacking NPR-17, which encodes a protein with sequence similarity to opioid receptors. Opioid agonists activated heterologously expressed NPR-17, as did at least one NLP-24 peptide. Worms lacking the ASI neurons, which express npr-17, did not response to naloxone. Thus, we suggest that Caenorhabditis elegans has an endogenous opioid system that acts through NPR-17, and that opioids regulate feeding via ASI neurons. Together, these results suggest C. elegans may be the first genetically tractable invertebrate opioid model. DOI: http://dx.doi.org/10.7554/eLife.06683.001 PMID:25898004

Imaging Flow Cytometry Analysis to Identify Differences of Survival Motor Neuron Protein Expression in Patients With Spinal Muscular Atrophy.

PubMed

Arakawa, Reiko; Arakawa, Masayuki; Kaneko, Kaori; Otsuki, Noriko; Aoki, Ryoko; Saito, Kayoko

2016-08-01

Spinal muscular atrophy is a neurodegenerative disorder caused by the deficient expression of survival motor neuron protein in motor neurons. A major goal of disease-modifying therapy is to increase survival motor neuron expression. Changes in survival motor neuron protein expression can be monitored via peripheral blood cells in patients; therefore we tested the sensitivity and utility of imaging flow cytometry for this purpose. After the immortalization of peripheral blood lymphocytes from a human healthy control subject and two patients with spinal muscular atrophy type 1 with two and three copies of SMN2 gene, respectively, we used imaging flow cytometry analysis to identify significant differences in survival motor neuron expression. A bright detail intensity analysis was used to investigate differences in the cellular localization of survival motor neuron protein. Survival motor neuron expression was significantly decreased in cells derived from patients with spinal muscular atrophy relative to those derived from a healthy control subject. Moreover, survival motor neuron expression correlated with the clinical severity of spinal muscular atrophy according to SMN2 copy number. The cellular accumulation of survival motor neuron protein was also significantly decreased in cells derived from patients with spinal muscular atrophy relative to those derived from a healthy control subject. The benefits of imaging flow cytometry for peripheral blood analysis include its capacities for analyzing heterogeneous cell populations; visualizing cell morphology; and evaluating the accumulation, localization, and expression of a target protein. Imaging flow cytometry analysis should be implemented in future studies to optimize its application as a tool for spinal muscular atrophy clinical trials. Copyright © 2016 Elsevier Inc. All rights reserved.

Overexpression of human mutated G93A SOD1 changes dynamics of the ER mitochondria calcium cycle specifically in mouse embryonic motor neurons.

PubMed

Lautenschläger, Janin; Prell, Tino; Ruhmer, Julia; Weidemann, Lisa; Witte, Otto W; Grosskreutz, Julian

2013-09-01

Motor neurons vulnerable to the rapidly progressive deadly neurodegenerative disease amyotrophic lateral sclerosis (ALS) inherently express low amounts of calcium binding proteins (CaBP), likely to allow physiological motor neuron firing frequency modulation. At the same time motor neurons are susceptible to AMPA receptor mediated excitotoxicity and internal calcium deregulation which is not fully understood. We analysed ER mitochondria calcium cycle (ERMCC) dynamics with subsecond resolution in G93A hSOD1 overexpressing motor neurons as a model of ALS using fluorescent calcium imaging. When comparing vulnerable motor neurons and non-motor neurons from G93A hSOD1 mice and their non-transgenic littermates, we found a decelerated cytosolic calcium clearance in the presence of G93A hSOD1. While both non-transgenic as well as G93A hSOD1 motor neurons displayed large mitochondrial calcium uptake by the mitochondrial uniporter (mUP), the mitochondrial calcium extrusion system was altered in the presence of G93A hSOD1. In addition, ER calcium uptake by the sarco-/endoplasmic reticulum ATPase (SERCA) was increased in G93A hSOD1 motor neurons. In survival assays, blocking the mitochondrial sodium calcium exchanger (mNCE) by CGP37157 as well as inhibiting SERCA by cyclopiazonic acid showed protective effects against kainate induced excitotoxicity. Thus, our study shows for the first time that the functional consequence of G93A hSOD1 overexpression in intact motor neurons is indeed a disturbance of the ER mitochondria calcium cycle, and identified two promising targets for therapeutic intervention in the pathology of ALS. Copyright © 2013 Elsevier Inc. All rights reserved.

Non-Aggregating Tau Phosphorylation by Cyclin-Dependent Kinase 5 Contributes to Motor Neuron Degeneration in Spinal Muscular Atrophy

PubMed Central

Miller, Nimrod; Feng, Zhihua; Edens, Brittany M.; Yang, Ben; Shi, Han; Sze, Christie C.; Hong, Benjamin Taige; Su, Susan C.; Cantu, Jorge A.; Topczewski, Jacek; Crawford, Thomas O.; Ko, Chien-Ping; Sumner, Charlotte J.; Ma, Long

2015-01-01

Mechanisms underlying motor neuron degeneration in spinal muscular atrophy (SMA), the leading inherited cause of infant mortality, remain largely unknown. Many studies have established the importance of hyperphosphorylation of the microtubule-associated protein tau in various neurodegenerative disorders, including Alzheimer's and Parkinson's diseases. However, tau phosphorylation in SMA pathogenesis has yet to be investigated. Here we show that tau phosphorylation on serine 202 (S202) and threonine 205 (T205) is increased significantly in SMA motor neurons using two SMA mouse models and human SMA patient spinal cord samples. Interestingly, phosphorylated tau does not form aggregates in motor neurons or neuromuscular junctions (NMJs), even at late stages of SMA disease, distinguishing it from other tauopathies. Hyperphosphorylation of tau on S202 and T205 is mediated by cyclin-dependent kinase 5 (Cdk5) in SMA disease condition, because tau phosphorylation at these sites is significantly reduced in Cdk5 knock-out mice; genetic knock-out of Cdk5 activating subunit p35 in an SMA mouse model also leads to reduced tau phosphorylation on S202 and T205 in the SMA;p35−/− compound mutant mice. In addition, expression of the phosphorylation-deficient tauS202A,T205A mutant alleviates motor neuron defects in a zebrafish SMA model in vivo and mouse motor neuron degeneration in culture, whereas expression of phosphorylation-mimetic tauS202E,T205E promotes motor neuron defects. More importantly, genetic knock-out of tau in SMA mice rescues synapse stripping on motor neurons, NMJ denervation, and motor neuron degeneration in vivo. Altogether, our findings suggest a novel mechanism for SMA pathogenesis in which hyperphosphorylation of non-aggregating tau by Cdk5 contributes to motor neuron degeneration. PMID:25878277

Tissue-specific models of spinal muscular atrophy confirm a critical role of SMN in motor neurons from embryonic to adult stages.

PubMed

Laird, Angela S; Mackovski, Nikolce; Rinkwitz, Silke; Becker, Thomas S; Giacomotto, Jean

2016-05-01

Spinal muscular atrophy (SMA) is an autosomal recessive disease linked to survival motor neuron (SMN) protein deficiency. While SMN protein is expressed ubiquitously, its deficiency triggers tissue-specific hallmarks, including motor neuron death and muscle atrophy, leading to impaired motor functions and premature death. Here, using stable miR-mediated knockdown technology in zebrafish, we developed the first vertebrate system allowing transgenic spatio-temporal control of the smn1 gene. Using this new model it is now possible to investigate normal and pathogenic SMN function(s) in specific cell types, independently or in synergy with other cell populations. We took advantage of this new system to first test the effect of motor neuron or muscle-specific smn1 silencing. Anti-smn1 miRNA expression in motor neurons, but not in muscles, reproduced SMA hallmarks, including abnormal motor neuron development, poor motor function and premature death. Interestingly, smn1 knockdown in motor neurons also induced severe late-onset phenotypes including scoliosis-like body deformities, weight loss, muscle atrophy and, seen for the first time in zebrafish, reduction in the number of motor neurons, indicating motor neuron degeneration. Taken together, we have developed a new transgenic system allowing spatio-temporal control of smn1 expression in zebrafish, and using this model, we have demonstrated that smn1 silencing in motor neurons alone is sufficient to reproduce SMA hallmarks in zebrafish. It is noteworthy that this research is going beyond SMA as this versatile gene-silencing transgenic system can be used to knockdown any genes of interest, filling the gap in the zebrafish genetic toolbox and opening new avenues to study gene functions in this organism. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

The Isolation of Pure Populations of Neurons by Laser Capture Microdissection: Methods and Application in Neuroscience.

PubMed

Morris, Renée; Mehta, Prachi

2018-01-01

In mammals, the central nervous system (CNS) is constituted of various cellular elements, posing a challenge to isolating specific cell types to investigate their expression profile. As a result, tissue homogenization is not amenable to analyses of motor neurons profiling as these represent less than 10% of the total spinal cord cell population. One way to tackle the problem of tissue heterogeneity and obtain meaningful genomic, proteomic, and transcriptomic profiling is to use laser capture microdissection technology (LCM). In this chapter, we describe protocols for the capture of isolated populations of motor neurons from spinal cord tissue sections and for downstream transcriptomic analysis of motor neurons with RT-PCR. We have also included a protocol for the immunological confirmation that the captured neurons are indeed motor neurons. Although focused on spinal cord motor neurons, these protocols can be easily optimized for the isolation of any CNS neurons.

Astrocytes expressing ALS‐linked mutant FUS induce motor neuron death through release of tumor necrosis factor‐alpha

PubMed Central

Kia, Azadeh; McAvoy, Kevin; Krishnamurthy, Karthik; Trotti, Davide

2018-01-01

Mutations in fused in sarcoma (FUS) are linked to amyotrophic lateral sclerosis (ALS), a fatal neurodegenerative disease affecting both upper and lower motor neurons. While it is established that astrocytes contribute to the death of motor neurons in ALS, the specific contribution of mutant FUS (mutFUS) through astrocytes has not yet been studied. Here, we used primary astrocytes expressing a N‐terminally GFP tagged R521G mutant or wild‐type FUS (WTFUS) and show that mutFUS‐expressing astrocytes undergo astrogliosis, damage co‐cultured motor neurons via activation of an inflammatory response and produce conditioned medium (ACM) that is toxic to motor neurons in isolation. Time lapse imaging shows that motor neuron cultures exposed to mutFUS ACM, but not WTFUS ACM, undergo significant cell loss, which is preceded by progressive degeneration of neurites. We found that Tumor Necrosis Factor‐Alpha (TNFα) is secreted into ACM of mutFUS‐expressing astrocytes. Accordingly, mutFUS astrocyte‐mediated motor neuron toxicity is blocked by targeting soluble TNFα with neutralizing antibodies. We also found that mutant astrocytes trigger changes to motor neuron AMPA receptors (AMPAR) that render them susceptible to excitotoxicity and AMPAR‐mediated cell death. Our data provide the first evidence of astrocytic involvement in FUS‐ALS, identify TNFα as a mediator of this toxicity, and provide several potential therapeutic targets to protect motor neurons in FUS‐linked ALS. PMID:29380416

HSPB1 mutations causing hereditary neuropathy in humans disrupt non-cell autonomous protection of motor neurons.

PubMed

Heilman, Patrick L; Song, SungWon; Miranda, Carlos J; Meyer, Kathrin; Srivastava, Amit K; Knapp, Amy; Wier, Christopher G; Kaspar, Brian K; Kolb, Stephen J

2017-11-01

Heat shock protein beta-1 (HSPB1), is a ubiquitously expressed, multifunctional protein chaperone. Mutations in HSPB1 result in the development of a late-onset, distal hereditary motor neuropathy type II (dHMN) and axonal Charcot-Marie Tooth disease with sensory involvement (CMT2F). The functional consequences of HSPB1 mutations associated with hereditary neuropathy are unknown. HSPB1 also displays neuroprotective properties in many neuronal disease models, including the motor neuron disease amyotrophic lateral sclerosis (ALS). HSPB1 is upregulated in SOD1-ALS animal models during disease progression, predominately in glial cells. Glial cells are known to contribute to motor neuron loss in ALS through a non-cell autonomous mechanism. In this study, we examined the non-cell autonomous role of wild type and mutant HSPB1 in an astrocyte-motor neuron co-culture model system of ALS. Astrocyte-specific overexpression of wild type HSPB1 was sufficient to attenuate SOD1(G93A) astrocyte-mediated toxicity in motor neurons, whereas, overexpression of mutHSPB1 failed to ameliorate motor neuron toxicity. Expression of a phosphomimetic HSPB1 mutant in SOD1(G93A) astrocytes also reduced toxicity to motor neurons, suggesting that phosphorylation may contribute to HSPB1 mediated-neuroprotection. These data provide evidence that astrocytic HSPB1 expression may play a central role in motor neuron health and maintenance. Copyright © 2017 Elsevier Inc. All rights reserved.

Control of arousal by the orexin neurons.

PubMed

Alexandre, Chloe; Andermann, Mark L; Scammell, Thomas E

2013-10-01

The orexin-producing neurons in the lateral hypothalamus play an essential role in promoting arousal and maintaining wakefulness. These neurons receive a broad variety of signals related to environmental, physiological and emotional stimuli; they project to almost every brain region involved in the regulation of wakefulness; and they fire most strongly during active wakefulness, high motor activation, and sustained attention. This review focuses on the specific neuronal pathways through which the orexin neurons promote wakefulness and maintain high level of arousal, and how recent studies using optogenetic and pharmacogenetic methods have demonstrated that the locus coeruleus, the tuberomammillary nucleus, and the basal forebrain are some of the key sites mediating the arousing actions of orexins. Copyright © 2013 Elsevier Ltd. All rights reserved.

Rapid transient isoform-specific neuregulin1 transcription in motor neurons is regulated by neurotrophic factors and axon-target interactions.

PubMed

Wang, Jiajing; Hmadcha, Abdelkrim; Zakarian, Vaagn; Song, Fei; Loeb, Jeffrey A

2015-09-01

The neuregulins (NRGs) are a family of alternatively spliced factors that play important roles in nervous system development and disease. In motor neurons, NRG1 expression is regulated by activity and neurotrophic factors, however, little is known about what controls isoform-specific transcription. Here we show that NRG1 expression in the chick embryo increases in motor neurons that have extended their axons and that limb bud ablation before motor axon outgrowth prevents this induction, suggesting a trophic role from the developing limb. Consistently, NRG1 induction after limb bud ablation can be rescued by adding back the neurotrophic factors BDNF and GDNF. Mechanistically, BDNF induces a rapid and transient increase in type I and type III NRG1 mRNAs that peak at 4h in rat embryonic ventral spinal cord cultures. Blocking MAPK or PI3K signaling or blocking transcription with Actinomycin D blocks BDNF induced NRG1 gene induction. BDNF had no effect on mRNA degradation, suggesting that transcriptional activation rather than message stability is important. Furthermore, BDNF activates a reporter construct that includes 700bp upstream of the type I NRG1 start site. Protein synthesis is also required for type I NRG1 mRNA transcription as cycloheximide produced a super-induction of type I, but not type III NRG1 mRNA, possibly through a mechanism involving sustained activation of MAPK and PI3K. These results reveal the existence of highly responsive, transient transcriptional regulatory mechanisms that differentially modulate NRG1 isoform expression as a function of extracellular and intracellular signaling cascades and mediated by neurotrophic factors and axon-target interactions. Copyright © 2015 Elsevier Inc. All rights reserved.

The central nucleus of the amygdala modulates gut-related neurons in the dorsal vagal complex in rats

PubMed Central

Zhang, Xueguo; Cui, Jinjuan; Tan, Zhenjun; Jiang, Chunhui; Fogel, Ronald

2003-01-01

Using retrograde tract-tracing and electrophysiological methods, we characterized the anatomical and functional relationship between the central nucleus of the amygdala and the dorsal vagal complex. Retrograde tract-tracing techniques revealed that the central nucleus of the amygdala projects to the dorsal vagal complex with a topographic distribution. Following injection of retrograde tracer into the vagal complex, retrogradely labelled neurons in the central nucleus of the amygdala were clustered in the central portion at the rostral level and in the medial part at the middle level of the nucleus. Few labelled neurons were seen at the caudal level. Electrical stimulation of the central nucleus of the amygdala altered the basal firing rates of 65 % of gut-related neurons in the nucleus of the solitary tract and in the dorsal motor nucleus of the vagus. Eighty-one percent of the neurons in the nucleus of the solitary tract and 47 % of the neurons in the dorsal motor nucleus were inhibited. Electrical stimulation of the central nucleus of the amygdala also modulated the response of neurons in the dorsal vagal complex to gastrointestinal stimuli. The predominant effect on the neurons of the nucleus of the solitary tract was inhibition. These results suggest that the central nucleus of the amygdala influences gut-related neurons in the dorsal vagal complex and provides a neuronal circuitry that explains the regulation of gastrointestinal activity by the amygdala. PMID:14555729

Converging Mechanisms of p53 Activation Drive Motor Neuron Degeneration in Spinal Muscular Atrophy.

PubMed

Simon, Christian M; Dai, Ya; Van Alstyne, Meaghan; Koutsioumpa, Charalampia; Pagiazitis, John G; Chalif, Joshua I; Wang, Xiaojian; Rabinowitz, Joseph E; Henderson, Christopher E; Pellizzoni, Livio; Mentis, George Z

2017-12-26

The hallmark of spinal muscular atrophy (SMA), an inherited disease caused by ubiquitous deficiency in the SMN protein, is the selective degeneration of subsets of spinal motor neurons. Here, we show that cell-autonomous activation of p53 occurs in vulnerable but not resistant motor neurons of SMA mice at pre-symptomatic stages. Moreover, pharmacological or genetic inhibition of p53 prevents motor neuron death, demonstrating that induction of p53 signaling drives neurodegeneration. At late disease stages, however, nuclear accumulation of p53 extends to resistant motor neurons and spinal interneurons but is not associated with cell death. Importantly, we identify phosphorylation of serine 18 as a specific post-translational modification of p53 that exclusively marks vulnerable SMA motor neurons and provide evidence that amino-terminal phosphorylation of p53 is required for the neurodegenerative process. Our findings indicate that distinct events induced by SMN deficiency converge on p53 to trigger selective death of vulnerable SMA motor neurons. Copyright © 2017 The Author(s). Published by Elsevier Inc. All rights reserved.

Nuclear Organization in the Spinal Cord Depends on Motor Neuron Lamination Orchestrated by Catenin and Afadin Function.

PubMed

Dewitz, Carola; Pimpinella, Sofia; Hackel, Patrick; Akalin, Altuna; Jessell, Thomas M; Zampieri, Niccolò

2018-02-13

Motor neurons in the spinal cord are found grouped in nuclear structures termed pools, whose position is precisely orchestrated during development. Despite the emerging role of pool organization in the assembly of spinal circuits, little is known about the morphogenetic programs underlying the patterning of motor neuron subtypes. We applied three-dimensional analysis of motor neuron position to reveal the roles and contributions of cell adhesive function by inactivating N-cadherin, catenin, and afadin signaling. Our findings reveal that nuclear organization of motor neurons is dependent on inside-out positioning, orchestrated by N-cadherin, catenin, and afadin activities, controlling cell body layering on the medio-lateral axis. In addition to this lamination-like program, motor neurons undergo a secondary, independent phase of organization. This process results in segregation of motor neurons along the dorso-ventral axis of the spinal cord, does not require N-cadherin or afadin activity, and can proceed even when medio-lateral positioning is perturbed. Copyright © 2018 The Author(s). Published by Elsevier Inc. All rights reserved.

Attenuated response to methamphetamine sensitization and deficits in motor learning and memory after selective deletion of β-catenin in dopamine neurons.

PubMed

Diaz-Ruiz, Oscar; Zhang, Yajun; Shan, Lufei; Malik, Nasir; Hoffman, Alexander F; Ladenheim, Bruce; Cadet, Jean Lud; Lupica, Carl R; Tagliaferro, Adriana; Brusco, Alicia; Bäckman, Cristina M

2012-07-20

In the present study, we analyzed mice with a targeted deletion of β-catenin in DA neurons (DA-βcat KO mice) to address the functional significance of this molecule in the shaping of synaptic responses associated with motor learning and following exposure to drugs of abuse. Relative to controls, DA-βcat KO mice showed significant deficits in their ability to form long-term memories and displayed reduced expression of methamphetamine-induced behavioral sensitization after subsequent challenge doses with this drug, suggesting that motor learning and drug-induced learning plasticity are altered in these mice. Morphological analyses showed no changes in the number or distribution of tyrosine hydroxylase-labeled neurons in the ventral midbrain. While electrochemical measurements in the striatum determined no changes in acute DA release and uptake, a small but significant decrease in DA release was detected in mutant animals after prolonged repetitive stimulation, suggesting a possible deficit in the DA neurotransmitter vesicle reserve pool. However, electron microscopy analyses did not reveal significant differences in the content of synaptic vesicles per terminal, and striatal DA levels were unchanged in DA-βcat KO animals. In contrast, striatal mRNA levels for several markers known to regulate synaptic plasticity and DA neurotransmission were altered in DA-βcat KO mice. This study demonstrates that ablation of β-catenin in DA neurons leads to alterations of motor and reward-associated memories and to adaptations of the DA neurotransmitter system and suggests that β-catenin signaling in DA neurons is required to facilitate the synaptic remodeling underlying the consolidation of long-term memories.

Ablation of the Ferroptosis Inhibitor Glutathione Peroxidase 4 in Neurons Results in Rapid Motor Neuron Degeneration and Paralysis.

PubMed

Chen, Liuji; Hambright, William Sealy; Na, Ren; Ran, Qitao

2015-11-20

Glutathione peroxidase 4 (GPX4), an antioxidant defense enzyme active in repairing oxidative damage to lipids, is a key inhibitor of ferroptosis, a non-apoptotic form of cell death involving lipid reactive oxygen species. Here we show that GPX4 is essential for motor neuron health and survival in vivo. Conditional ablation of Gpx4 in neurons of adult mice resulted in rapid onset and progression of paralysis and death. Pathological inspection revealed that the paralyzed mice had a dramatic degeneration of motor neurons in the spinal cord but had no overt neuron degeneration in the cerebral cortex. Consistent with the role of GPX4 as a ferroptosis inhibitor, spinal motor neuron degeneration induced by Gpx4 ablation exhibited features of ferroptosis, including no caspase-3 activation, no TUNEL staining, activation of ERKs, and elevated spinal inflammation. Supplementation with vitamin E, another inhibitor of ferroptosis, delayed the onset of paralysis and death induced by Gpx4 ablation. Also, lipid peroxidation and mitochondrial dysfunction appeared to be involved in ferroptosis of motor neurons induced by Gpx4 ablation. Taken together, the dramatic motor neuron degeneration and paralysis induced by Gpx4 ablation suggest that ferroptosis inhibition by GPX4 is essential for motor neuron health and survival in vivo. © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.

Amyotrophic lateral sclerosis-related VAPB P56S mutation differentially affects the function and survival of corticospinal and spinal motor neurons

PubMed Central

Aliaga, Leonardo; Lai, Chen; Yu, Jia; Chub, Nikolai; Shim, Hoon; Sun, Lixin; Xie, Chengsong; Yang, Wan-Jou; Lin, Xian; O'Donovan, Michael J.; Cai, Huaibin

2013-01-01

The substitution of Proline with Serine at residue 56 (P56S) of vesicle-associated membrane protein-associated protein B (VAPB) has been linked to an atypical autosomal dominant form of familial amyotrophic lateral sclerosis 8 (ALS8). To investigate the pathogenic mechanism of P56S VAPB in ALS, we generated transgenic (Tg) mice that heterologously express human wild-type (WT) and P56S VAPB under the control of a pan-neuronal promoter Thy1.2. While WT VAPB Tg mice did not exhibit any overt motor behavioral phenotypes, P56S VAPB Tg mice developed progressive hyperactivities and other motor abnormalities. VAPB protein was accumulated as large punctate in the soma and proximal dendrites of both corticospinal motor neurons (CSMNs) and spinal motor neurons (SMNs) in P56S VAPB Tg mice. Concomitantly, a significant increase of endoplasmic reticulum stress and unfolded protein response and the resulting up-regulation of pro-apoptotic factor CCAAT/enhancer-binding protein homologous protein expression were observed in the CSMNs and SMNs of P56S VAPB Tg mice. However, only a progressive loss of CSMNs but not SMNs was found in P56S VAPB Tg mice. In SMNs, P56S VAPB promoted a rather selective translocation of VAPB protein onto the postsynaptic site of C-boutons that altered the morphology of C-boutons and impaired the spontaneous rhythmic discharges of SMNs. Therefore, these findings provide new pathophysiological mechanisms of P56S VAPB that differentially affect the function and survival of CSMNs and SMNs in ALS8. PMID:23771029

Architecture of Vagal Motor Units Controlling Striated Muscle of Esophagus: Peripheral Elements Patterning Peristalsis?

PubMed Central

Powley, Terry L.; Mittal, Ravinder K.; Baronowsky, Elizabeth A.; Hudson, Cherie N.; Martin, Felecia N.; McAdams, Jennifer L.; Mason, Jacqueline K.; Phillips, Robert J.

2013-01-01

Little is known about the architecture of the vagal motor units that control esophageal striated muscle, in spite of the fact that these units are necessary, and responsible, for peristalsis. The present experiment was designed to characterize the motor neuron projection fields and terminal arbors forming esophageal motor units. Nucleus ambiguus compact formation neurons of the rat were labeled by bilateral intracranial injections of the anterograde tracer dextran biotin. After tracer transport, thoracic and abdominal esophagi were removed and prepared as whole mounts of muscle wall without mucosa or submucosa. Labeled terminal arbors of individual vagal motor neurons (n = 78) in the esophageal wall were inventoried, digitized and analyzed morphometrically. The size of individual vagal motor units innervating striated muscle, throughout thoracic and abdominal esophagus, averaged 52 endplates per motor neuron, a value indicative of fine motor control. A majority (77%) of the motor terminal arbors also issued one or more collateral branches that contacted neurons, including nitric oxide synthase-positive neurons, of local myenteric ganglia. Individual motor neuron terminal arbors co-innervated, or supplied endplates in tandem to, both longitudinal and circular muscle fibers in roughly similar proportions (i.e., two endplates to longitudinal for every three endplates to circular fibers). Both the observation that vagal motor unit collaterals project to myenteric ganglia and the fact that individual motor units co-innervate longitudinal and circular muscle layers are consistent with the hypothesis that elements contributing to peristaltic programming inhere, or are “hardwired,” in the peripheral architecture of esophageal motor units. PMID:24044976

Architecture of vagal motor units controlling striated muscle of esophagus: peripheral elements patterning peristalsis?

PubMed

Powley, Terry L; Mittal, Ravinder K; Baronowsky, Elizabeth A; Hudson, Cherie N; Martin, Felecia N; McAdams, Jennifer L; Mason, Jacqueline K; Phillips, Robert J

2013-12-01

Little is known about the architecture of the vagal motor units that control esophageal striated muscle, in spite of the fact that these units are necessary, and responsible, for peristalsis. The present experiment was designed to characterize the motor neuron projection fields and terminal arbors forming esophageal motor units. Nucleus ambiguus compact formation neurons of the rat were labeled by bilateral intracranial injections of the anterograde tracer dextran biotin. After tracer transport, thoracic and abdominal esophagi were removed and prepared as whole mounts of muscle wall without mucosa or submucosa. Labeled terminal arbors of individual vagal motor neurons (n=78) in the esophageal wall were inventoried, digitized and analyzed morphometrically. The size of individual vagal motor units innervating striated muscle, throughout thoracic and abdominal esophagus, averaged 52 endplates per motor neuron, a value indicative of fine motor control. A majority (77%) of the motor terminal arbors also issued one or more collateral branches that contacted neurons, including nitric oxide synthase-positive neurons, of local myenteric ganglia. Individual motor neuron terminal arbors co-innervated, or supplied endplates in tandem to, both longitudinal and circular muscle fibers in roughly similar proportions (i.e., two endplates to longitudinal for every three endplates to circular fibers). Both the observation that vagal motor unit collaterals project to myenteric ganglia and the fact that individual motor units co-innervate longitudinal and circular muscle layers are consistent with the hypothesis that elements contributing to peristaltic programming inhere, or are "hardwired," in the peripheral architecture of esophageal motor units. © 2013.

Lack of TNF-alpha receptor type 2 protects motor neurons in a cellular model of amyotrophic lateral sclerosis and in mutant SOD1 mice but does not affect disease progression.

PubMed

Tortarolo, Massimo; Vallarola, Antonio; Lidonnici, Dario; Battaglia, Elisa; Gensano, Francesco; Spaltro, Gabriella; Fiordaliso, Fabio; Corbelli, Alessandro; Garetto, Stefano; Martini, Elisa; Pasetto, Laura; Kallikourdis, Marinos; Bonetto, Valentina; Bendotti, Caterina

2015-10-01

Changes in the homeostasis of tumor necrosis factor α (TNFα) have been demonstrated in patients and experimental models of amyotrophic lateral sclerosis (ALS). However, the contribution of TNFα to the development of ALS is still debated. TNFα is expressed by glia and neurons and acts through the membrane receptors TNFR1 and TNFR2, which may have opposite effects in neurodegeneration. We investigated the role of TNFα and its receptors in the selective motor neuron death in ALS in vitro and in vivo. TNFR2 expressed by astrocytes and neurons, but not TNFR1, was implicated in motor neuron loss in primary SOD1-G93A co-cultures. Deleting TNFR2 from SOD1-G93A mice, there was partial but significant protection of spinal motor neurons, sciatic nerves, and tibialis muscles. However, no improvement of motor impairment or survival was observed. Since the sciatic nerves of SOD1-G93A/TNFR2-/- mice showed high phospho-TAR DNA-binding protein 43 (TDP-43) accumulation and low levels of acetyl-tubulin, two indices of axonal dysfunction, the lack of symptom improvement in these mice might be due to impaired function of rescued motor neurons. These results indicate the interaction between TNFR2 and membrane-bound TNFα as an innovative pathway involved in motor neuron death. Nevertheless, its inhibition is not sufficient to stop disease progression in ALS mice, underlining the complexity of this pathology. We show evidence of the involvement of neuronal and astroglial TNFR2 in the motor neuron degeneration in ALS. Both concur to cause motor neuron death in primary astrocyte/spinal neuron co-cultures. TNFR2 deletion partially protects motor neurons and sciatic nerves in SOD1-G93A mice but does not improve their symptoms and survival. However, TNFR2 could be a new target for multi-intervention therapies. © 2015 International Society for Neurochemistry.

Calpain-2 contributes to neuropathic pain following motor nerve injury via up-regulating interleukin-6 in DRG neurons.

PubMed

Zang, Ying; Chen, Shao-Xia; Liao, Guang-Jie; Zhu, He-Quan; Wei, Xu-Hong; Cui, Yu; Na, Xiao-Dong; Pang, Rui-Ping; Xin, Wen-Jun; Zhou, Li-Jun; Liu, Xian-Guo

2015-02-01

Motor nerve injury by L5 ventral root transection (L5-VRT) initiates interleukin-6 (IL-6) up-regulation in primary afferent system contributing to neuropathic pain. However, the early upstream regulatory mechanisms of IL-6 after L5-VRT are still unknown. Here, we monitored both the activity of calpain, a calcium-dependent protease suggested as one of the earliest mediators for cytokine regulation, and the expression of IL-6 in bilateral L4-L6 dorsal root ganglias (DRGs) soon after L5-VRT. We found that the protein level of calpain-2 in DRGs, but not calpain-1 was increased transiently in the first 10 min(-1)h ipsilaterally and 20 min(-1)h contralaterally after L5-VRT, long before mechanical allodynia was initiated (5-15 h ipsilaterally and 15 h(-1)d contralaterally). The early activation of calpain evaluated by the generation of spectrin breakdown products (SBDP) correlated well with IL-6 up-regulation in bilateral DRGs. Double immunofluorescence staining revealed that almost all the calpain-2 positive neurons expressed IL-6, indicating an association between calpain-2 and IL-6. Inhibition of calpain by pre-treatment with MDL28170 (25mg/kg, i.p.) attenuated the rat mechanical allodynia and prevented the early up-regulation of IL-6 following L5-VRT. Addition of exogenous calpain-2 onto the surface of left L5 DRG triggered a temporal allodynia and increased IL-6 in bilateral DRGs simultaneously. Taken together, the early increase of calpain-2 in L5-VRT rats might be responsible for the induction of allodynia via up-regulating IL-6 in DRG neurons. Copyright © 2014 Elsevier Inc. All rights reserved.

Gene transfer of constitutively active protein kinase C into striatal neurons accelerates onset of levodopa-induced motor response alterations in parkinsonian rats

PubMed Central

Oh, Justin D.; Geller, Alfred I.; Zhang, Guo-rong; Chase, Thomas N.

2006-01-01

Alterations in motor response that complicate levodopa treatment of Parkinson’s disease appear to involve sensitization of striatal ionotropic glutamate receptors. Since protein kinase C (PKC)-mediated phosphorylation regulates glutamatergic receptors of the α-amino-3-hydroxyl-5-methyl-4-isoxazole propionic acid (AMPA) subtype and has been linked to several forms of behavioral plasticity, activation of PKC signaling in striatal spiny neurons may also contribute to the motor plasticity changes associated with chronic levodopa therapy. To evaluate this possibility, we sought to augment PKC signaling by using Herpes Simplex Virus type 1 vectors (pHSVpkcΔ) to directly transfer the catalytic domain of the PKCβII gene into striatal neurons of parkinsonian rats. Microinjection of pHSVpkcΔ vectors lead to the persistent expression of PkcΔ (35% loss over 21 days) in medium spiny neurons together with an increase in serine 831 phosphorylation on AMPA receptor GluR1 subunits and hastened the appearance of the shortened response duration produced by chronic levodopa treatment (P<0.05). In pHSVpkcΔ-infected animals, intrastriatal injection of the PKC inhibitor NPC-15437 (1.0 μg) attenuated both the increased GluR1 phosphorylation (P<0.01) and the accelerated onset of the levodopa-induced response modifications (P<0.01). However, in rats that received levodopa treatment for 21 days without the gene transfer, intrastriatal NPC-15437 had no effect on the response shortening or on GluR1 S831 phosphorylation. The results suggest that an increase in PKC-mediated signaling, including, in part, phosphorylation of AMPA receptors, on striatal spiny neurons may be sufficient to promote the initial appearance, but not necessary the ultimate expression, of the levodopa-induced motor response changes occurring in a rodent model of the human motor complication syndrome. PMID:12691833

Neuronal Atrophy Early in Degenerative Ataxia Is a Compensatory Mechanism to Regulate Membrane Excitability

PubMed Central

Dell'Orco, James M.; Wasserman, Aaron H.; Chopra, Ravi; Ingram, Melissa A. C.; Hu, Yuan-Shih; Singh, Vikrant; Wulff, Heike; Opal, Puneet; Orr, Harry T.

2015-01-01

Neuronal atrophy in neurodegenerative diseases is commonly viewed as an early event in a continuum that ultimately results in neuronal loss. In a mouse model of the polyglutamine disorder spinocerebellar ataxia type 1 (SCA1), we tested the hypothesis that cerebellar Purkinje neuron atrophy serves an adaptive role rather than being simply a nonspecific response to injury. In acute cerebellar slices from SCA1 mice, we find that Purkinje neuron pacemaker firing is initially normal but, with the onset of motor dysfunction, becomes disrupted, accompanied by abnormal depolarization. Remarkably, subsequent Purkinje cell atrophy is associated with a restoration of pacemaker firing. The early inability of Purkinje neurons to support repetitive spiking is due to unopposed calcium currents resulting from a reduction in large-conductance calcium-activated potassium (BK) and subthreshold-activated potassium channels. The subsequent restoration of SCA1 Purkinje neuron firing correlates with the recovery of the density of these potassium channels that accompanies cell atrophy. Supporting a critical role for BK channels, viral-mediated increases in BK channel expression in SCA1 Purkinje neurons improves motor dysfunction and partially restores Purkinje neuron morphology. Cerebellar perfusion of flufenamic acid, an agent that restores the depolarized membrane potential of SCA1 Purkinje neurons by activating potassium channels, prevents Purkinje neuron dendritic atrophy. These results suggest that Purkinje neuron dendritic remodeling in ataxia is an adaptive response to increases in intrinsic membrane excitability. Similar adaptive remodeling could apply to other vulnerable neuronal populations in neurodegenerative disease. SIGNIFICANCE STATEMENT In neurodegenerative disease, neuronal atrophy has long been assumed to be an early nonspecific event preceding neuronal loss. However, in a mouse model of spinocerebellar ataxia type 1 (SCA1), we identify a previously unappreciated compensatory role for neuronal shrinkage. Purkinje neuron firing in these mice is initially normal, but is followed by abnormal membrane depolarization resulting from a reduction in potassium channels. Subsequently, these electrophysiological effects are counteracted by cell atrophy, which by restoring normal potassium channel membrane density, re-establishes pacemaker firing. Reversing the initial membrane depolarization improved motor function and Purkinje neuron morphology in the SCA1 mice. These results suggest that Purkinje neuron remodeling in ataxia is an active compensatory response that serves to normalize intrinsic membrane excitability. PMID:26269637

dHb9 expressing larval motor neurons persist through metamorphosis to innervate adult-specific muscle targets and function in Drosophila eclosion.

PubMed

Banerjee, Soumya; Toral, Marcus; Siefert, Matthew; Conway, David; Dorr, Meredith; Fernandes, Joyce

2016-12-01

The Drosophila larval nervous system is radically restructured during metamorphosis to produce adult specific neural circuits and behaviors. Genesis of new neurons, death of larval neurons and remodeling of those neurons that persistent collectively act to shape the adult nervous system. Here, we examine the fate of a subset of larval motor neurons during this restructuring process. We used a dHb9 reporter, in combination with the FLP/FRT system to individually identify abdominal motor neurons in the larval to adult transition using a combination of relative cell body location, axonal position, and muscle targets. We found that segment specific cell death of some dHb9 expressing motor neurons occurs throughout the metamorphosis period and continues into the post-eclosion period. Many dHb9 > GFP expressing neurons however persist in the two anterior hemisegments, A1 and A2, which have segment specific muscles required for eclosion while a smaller proportion also persist in A2-A5. Consistent with a functional requirement for these neurons, ablating them during the pupal period produces defects in adult eclosion. In adults, subsequent to the execution of eclosion behaviors, the NMJs of some of these neurons were found to be dismantled and their muscle targets degenerate. Our studies demonstrate a critical continuity of some larval motor neurons into adults and reveal that multiple aspects of motor neuron remodeling and plasticity that are essential for adult motor behaviors. © 2016 Wiley Periodicals, Inc. Develop Neurobiol 76: 1387-1416, 2016. © 2016 Wiley Periodicals, Inc.

Human neural progenitors differentiate into astrocytes and protect motor neurons in aging rats.

PubMed

Das, Melanie M; Avalos, Pablo; Suezaki, Patrick; Godoy, Marlesa; Garcia, Leslie; Chang, Christine D; Vit, Jean-Philippe; Shelley, Brandon; Gowing, Genevieve; Svendsen, Clive N

2016-06-01

Age-associated health decline presents a significant challenge to healthcare, although there are few animal models that can be used to test potential treatments. Here, we show that there is a significant reduction in both spinal cord motor neurons and motor function over time in the aging rat. One explanation for this motor neuron loss could be reduced support from surrounding aging astrocytes. Indeed, we have previously shown using in vitro models that aging rat astrocytes are less supportive to rat motor neuron function and survival over time. Here, we test whether rejuvenating the astrocyte niche can improve the survival of motor neurons in an aging spinal cord. We transplanted fetal-derived human neural progenitor cells (hNPCs) into the aging rat spinal cord and found that the cells survive and differentiate into astrocytes with a much higher efficiency than when transplanted into younger animals, suggesting that the aging environment stimulates astrocyte maturation. Importantly, the engrafted astrocytes were able to protect against motor neuron loss associated with aging, although this did not result in an increase in motor function based on behavioral assays. We also transplanted hNPCs genetically modified to secrete glial cell line-derived neurotrophic factor (GDNF) into the aging rat spinal cord, as this combination of cell and protein delivery can protect motor neurons in animal models of ALS. During aging, GDNF-expressing hNPCs protected motor neurons, though to the same extent as hNPCs alone, and again had no effect on motor function. We conclude that hNPCs can survive well in the aging spinal cord, protect motor neurons and mature faster into astrocytes when compared to transplantation into the young spinal cord. While there was no functional improvement, there were no functional deficits either, further supporting a good safety profile of hNPC transplantation even into the older patient population. Copyright © 2016 Elsevier Inc. All rights reserved.

Amyotrophic lateral sclerosis (ALS)

MedlinePlus

Lou Gehrig disease; ALS; Upper and lower motor neuron disease; Motor neuron disease ... One out of 10 cases of ALS is due to a genetic defect. The cause is unknown in most other cases. In ALS, motor nerve cells (neurons) waste away ...

[The mirror neuron system in motor and sensory rehabilitation].

PubMed

Oouchida, Yutaka; Izumi, Shinichi

2014-06-01

The discovery of the mirror neuron system has dramatically changed the study of motor control in neuroscience. The mirror neuron system provides a conceptual framework covering the aspects of motor as well as sensory functions in motor control. Previous studies of motor control can be classified as studies of motor or sensory functions, and these two classes of studies appear to have advanced independently. In rehabilitation requiring motor learning, such as relearning movement after limb paresis, however, sensory information of feedback for motor output as well as motor command are essential. During rehabilitation from chronic pain, motor exercise is one of the most effective treatments for pain caused by dysfunction in the sensory system. In rehabilitation where total intervention unifying the motor and sensory aspects of motor control is important, learning through imitation, which is associated with the mirror neuron system can be effective and suitable. In this paper, we introduce the clinical applications of imitated movement in rehabilitation from motor impairment after brain damage and phantom limb pain after limb amputation.

Selective disruption of acetylcholine synthesis in subsets of motor neurons: a new model of late-onset motor neuron disease.

PubMed

Lecomte, Marie-José; Bertolus, Chloé; Santamaria, Julie; Bauchet, Anne-Laure; Herbin, Marc; Saurini, Françoise; Misawa, Hidemi; Maisonobe, Thierry; Pradat, Pierre-François; Nosten-Bertrand, Marika; Mallet, Jacques; Berrard, Sylvie

2014-05-01

Motor neuron diseases are characterized by the selective chronic dysfunction of a subset of motor neurons and the subsequent impairment of neuromuscular function. To reproduce in the mouse these hallmarks of diseases affecting motor neurons, we generated a mouse line in which ~40% of motor neurons in the spinal cord and the brainstem become unable to sustain neuromuscular transmission. These mice were obtained by conditional knockout of the gene encoding choline acetyltransferase (ChAT), the biosynthetic enzyme for acetylcholine. The mutant mice are viable and spontaneously display abnormal phenotypes that worsen with age including hunched back, reduced lifespan, weight loss, as well as striking deficits in muscle strength and motor function. This slowly progressive neuromuscular dysfunction is accompanied by muscle fiber histopathological features characteristic of neurogenic diseases. Unexpectedly, most changes appeared with a 6-month delay relative to the onset of reduction in ChAT levels, suggesting that compensatory mechanisms preserve muscular function for several months and then are overwhelmed. Deterioration of mouse phenotype after ChAT gene disruption is a specific aging process reminiscent of human pathological situations, particularly among survivors of paralytic poliomyelitis. These mutant mice may represent an invaluable tool to determine the sequence of events that follow the loss of function of a motor neuron subset as the disease progresses, and to evaluate therapeutic strategies. They also offer the opportunity to explore fundamental issues of motor neuron biology. Copyright © 2014 Elsevier Inc. All rights reserved.

More than a bystander: the contributions of intrinsic skeletal muscle defects in motor neuron diseases

PubMed Central

Boyer, Justin G.; Ferrier, Andrew; Kothary, Rashmi

2013-01-01

Spinal muscular atrophy (SMA), amyotrophic lateral sclerosis (ALS), and spinal-bulbar muscular atrophy (SBMA) are devastating diseases characterized by the degeneration of motor neurons. Although the molecular causes underlying these diseases differ, recent findings have highlighted the contribution of intrinsic skeletal muscle defects in motor neuron diseases. The use of cell culture and animal models has led to the important finding that muscle defects occur prior to and independently of motor neuron degeneration in motor neuron diseases. In SMA for instance, the muscle specific requirements of the SMA disease-causing gene have been demonstrated by a series of genetic rescue experiments in SMA models. Conditional ALS mouse models expressing a muscle specific mutant SOD1 gene develop atrophy and muscle degeneration in the absence of motor neuron pathology. Treating SBMA mice by over-expressing IGF-1 in a skeletal muscle-specific manner attenuates disease severity and improves motor neuron pathology. In the present review, we provide an in depth description of muscle intrinsic defects, and discuss how they impact muscle function in these diseases. Furthermore, we discuss muscle-specific therapeutic strategies used to treat animal models of SMA, ALS, and SBMA. The study of intrinsic skeletal muscle defects is crucial for the understanding of the pathophysiology of these diseases and will open new therapeutic options for the treatment of motor neuron diseases. PMID:24391590

Neuron-Type-Specific Utility in a Brain-Machine Interface: a Pilot Study.

PubMed

Garcia-Garcia, Martha G; Bergquist, Austin J; Vargas-Perez, Hector; Nagai, Mary K; Zariffa, Jose; Marquez-Chin, Cesar; Popovic, Milos R

2017-11-01

Firing rates of single cortical neurons can be volitionally modulated through biofeedback (i.e. operant conditioning), and this information can be transformed to control external devices (i.e. brain-machine interfaces; BMIs). However, not all neurons respond to operant conditioning in BMI implementation. Establishing criteria that predict neuron utility will assist translation of BMI research to clinical applications. Single cortical neurons (n=7) were recorded extracellularly from primary motor cortex of a Long-Evans rat. Recordings were incorporated into a BMI involving up-regulation of firing rate to control the brightness of a light-emitting-diode and subsequent reward. Neurons were classified as 'fast-spiking', 'bursting' or 'regular-spiking' according to waveform-width and intrinsic firing patterns. Fast-spiking and bursting neurons were found to up-regulate firing rate by a factor of 2.43±1.16, demonstrating high utility, while regular-spiking neurons decreased firing rates on average by a factor of 0.73±0.23, demonstrating low utility. The ability to select neurons with high utility will be important to minimize training times and maximize information yield in future clinical BMI applications. The highly contrasting utility observed between fast-spiking and bursting neurons versus regular-spiking neurons allows for the hypothesis to be advanced that intrinsic electrophysiological properties may be useful criteria that predict neuron utility in BMI implementation.

Loss-of-function mutations in the SIGMAR1 gene cause distal hereditary motor neuropathy by impairing ER-mitochondria tethering and Ca2+ signalling.

PubMed

Gregianin, Elisa; Pallafacchina, Giorgia; Zanin, Sofia; Crippa, Valeria; Rusmini, Paola; Poletti, Angelo; Fang, Mingyan; Li, Zhouxuan; Diano, Laura; Petrucci, Antonio; Lispi, Ludovico; Cavallaro, Tiziana; Fabrizi, Gian M; Muglia, Maria; Boaretto, Francesca; Vettori, Andrea; Rizzuto, Rosario; Mostacciuolo, Maria L; Vazza, Giovanni

2016-09-01

Distal hereditary motor neuropathies (dHMNs) are clinically and genetically heterogeneous neurological conditions characterized by degeneration of the lower motor neurons. So far, 18 dHMN genes have been identified, however, about 80% of dHMN cases remain without a molecular diagnosis. By a combination of autozygosity mapping, identity-by-descent segment detection and whole-exome sequencing approaches, we identified two novel homozygous mutations in the SIGMAR1 gene (p.E138Q and p.E150K) in two distinct Italian families affected by an autosomal recessive form of HMN. Functional analyses in several neuronal cell lines strongly support the pathogenicity of the mutations and provide insights into the underlying pathomechanisms involving the regulation of ER-mitochondria tethering, Ca 2+  homeostasis and autophagy. Indeed, in vitro, both mutations reduce cell viability, the formation of abnormal protein aggregates preventing the correct targeting of sigma-1R protein to the mitochondria-associated ER membrane (MAM) and thus impinging on the global Ca 2+  signalling. Our data definitively demonstrate the involvement of SIGMAR1 in motor neuron maintenance and survival by correlating, for the first time in the Caucasian population, mutations in this gene to distal motor dysfunction and highlight the chaperone activity of sigma-1R at the MAM as a critical aspect in dHMN pathology. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

A Cholinergic-Regulated Circuit Coordinates the Maintenance and Bi-Stable States of a Sensory-Motor Behavior during Caenorhabditis elegans Male Copulation

PubMed Central

Liu, Yishi; LeBeouf, Brigitte; Guo, Xiaoyan; Correa, Paola A.; Gualberto, Daisy G.; Lints, Robyn; Garcia, L. Rene

2011-01-01

Penetration of a male copulatory organ into a suitable mate is a conserved and necessary behavioral step for most terrestrial matings; however, the detailed molecular and cellular mechanisms for this distinct social interaction have not been elucidated in any animal. During mating, the Caenorhabditis elegans male cloaca is maintained over the hermaphrodite's vulva as he attempts to insert his copulatory spicules. Rhythmic spicule thrusts cease when insertion is sensed. Circuit components consisting of sensory/motor neurons and sex muscles for these steps have been previously identified, but it was unclear how their outputs are integrated to generate a coordinated behavior pattern. Here, we show that cholinergic signaling between the cloacal sensory/motor neurons and the posterior sex muscles sustains genital contact between the sexes. Simultaneously, via gap junctions, signaling from these muscles is transmitted to the spicule muscles, thus coupling repeated spicule thrusts with vulval contact. To transit from rhythmic to sustained muscle contraction during penetration, the SPC sensory-motor neurons integrate the signal of spicule's position in the vulva with inputs from the hook and cloacal sensilla. The UNC-103 K+ channel maintains a high excitability threshold in the circuit, so that sustained spicule muscle contraction is not stimulated by fewer inputs. We demonstrate that coordination of sensory inputs and motor outputs used to initiate, maintain, self-monitor, and complete an innate behavior is accomplished via the coupling of a few circuit components. PMID:21423722

Dynein-Dependent Transport of nanos RNA in Drosophila Sensory Neurons Requires Rumpelstiltskin and the Germ Plasm Organizer Oskar

PubMed Central

Xu, Xin; Brechbiel, Jillian L.

2013-01-01

Intracellular mRNA localization is a conserved mechanism for spatially regulating protein production in polarized cells, such as neurons. The mRNA encoding the translational repressor Nanos (Nos) forms ribonucleoprotein (RNP) particles that are dendritically localized in Drosophila larval class IV dendritic arborization (da) neurons. In nos mutants, class IV da neurons exhibit reduced dendritic branching complexity, which is rescued by transgenic expression of wild-type nos mRNA but not by a localization-compromised nos derivative. While localization is essential for nos function in dendrite morphogenesis, the mechanism underlying the transport of nos RNP particles was unknown. We investigated the mechanism of dendritic nos mRNA localization by analyzing requirements for nos RNP particle motility in class IV da neuron dendrites through live imaging of fluorescently labeled nos mRNA. We show that dynein motor machinery components mediate transport of nos mRNA in proximal dendrites. Two factors, the RNA-binding protein Rumpelstiltskin and the germ plasm protein Oskar, which are required for diffusion/entrapment-mediated localization of nos during oogenesis, also function in da neurons for formation and transport of nos RNP particles. Additionally, we show that nos regulates neuronal function, most likely independent of its dendritic localization and function in morphogenesis. Our results reveal adaptability of localization factors for regulation of a target transcript in different cellular contexts. PMID:24027279

Dynein-dependent transport of nanos RNA in Drosophila sensory neurons requires Rumpelstiltskin and the germ plasm organizer Oskar.

PubMed

Xu, Xin; Brechbiel, Jillian L; Gavis, Elizabeth R

2013-09-11

Intracellular mRNA localization is a conserved mechanism for spatially regulating protein production in polarized cells, such as neurons. The mRNA encoding the translational repressor Nanos (Nos) forms ribonucleoprotein (RNP) particles that are dendritically localized in Drosophila larval class IV dendritic arborization (da) neurons. In nos mutants, class IV da neurons exhibit reduced dendritic branching complexity, which is rescued by transgenic expression of wild-type nos mRNA but not by a localization-compromised nos derivative. While localization is essential for nos function in dendrite morphogenesis, the mechanism underlying the transport of nos RNP particles was unknown. We investigated the mechanism of dendritic nos mRNA localization by analyzing requirements for nos RNP particle motility in class IV da neuron dendrites through live imaging of fluorescently labeled nos mRNA. We show that dynein motor machinery components mediate transport of nos mRNA in proximal dendrites. Two factors, the RNA-binding protein Rumpelstiltskin and the germ plasm protein Oskar, which are required for diffusion/entrapment-mediated localization of nos during oogenesis, also function in da neurons for formation and transport of nos RNP particles. Additionally, we show that nos regulates neuronal function, most likely independent of its dendritic localization and function in morphogenesis. Our results reveal adaptability of localization factors for regulation of a target transcript in different cellular contexts.

Specific induction of PAG608 in cranial and spinal motor neurons of L-DOPA-treated parkinsonian rats.

PubMed

Shimizu, Masako; Miyazaki, Ikuko; Higashi, Youichirou; Eslava-Alva, Maria J; Diaz-Corrales, Francisco J; Asanuma, Masato; Ogawa, Norio

2008-04-01

We identified p53-activated gene 608 (PAG608) as a specifically induced gene in striatal tissue of L-DOPA (100mg/kg)-injected hemi-parkinsonian rats using differential display assay. In the present study, we further examined morphological distribution of PAG608 in the central nervous system of L-DOPA-treated hemi-parkinsonian rats. PAG608 expression was markedly induced in fibers and neuronal cells of the lateral globus pallidus and reticular thalamic nucleus adjacent to internal capsule, specifically in the parkinsonian side of L-DOPA-treated models. The protein was also constitutively expressed in motor neurons specifically in either side of the pontine nucleus and motor nuclei of trigeminal and facial nerves. Furthermore, L-DOPA-induced PAG608 expression on motor neurons in the contralateral side of the ventral horn of the spinal cord and the lateral corticospinal tract without cell loss. The specific induction of PAG608 6-48h after L-DOPA injection in the extrapyramidal tracts, pyramidal tracts and corresponding lower motor neurons of the spinal cords suggests its involvement in molecular events in stimulated motor neurons. Taken together with the constitutive expression of PAG608 in the motor nuclei of cranial nerves, PAG608 may be a useful marker of stressed or activated lower motor neurons.

Growth of primary motor neurons on horizontally aligned carbon nanotube thin films and striped patterns

NASA Astrophysics Data System (ADS)

Roberts, Megan J.; Leach, Michelle K.; Bedewy, Mostafa; Meshot, Eric R.; Copic, Davor; Corey, Joseph M.; Hart, A. John

2014-06-01

Objective. Carbon nanotubes (CNTs) are attractive for use in peripheral nerve interfaces because of their unique combination of strength, flexibility, electrical conductivity and nanoscale surface texture. Here we investigated the growth of motor neurons on thin films of horizontally aligned CNTs (HACNTs). Approach. We cultured primary embryonic rat motor neurons on HACNTs and performed statistical analysis of the length and orientation of neurites. We next presented motor neurons with substrates of alternating stripes of HACNTs and SiO2. Main results. The neurons survived on HACNT substrates for up to eight days, which was the full duration of our experiments. Statistical analysis of the length and orientation of neurites indicated that the longest neurites on HACNTs tended to align with the CNT direction, although the average neurite length was similar between HACNTs and glass control substrates. We observed that when motor neurons were presented with alternating stripes of HACNTs and SiO2, the proportion of neurons on HACNTs increases over time, suggesting that neurons selectively migrate toward and adhere to the HACNT surface. Significance. The behavior of motor neurons on CNTs has not been previously investigated, and we show that aligned CNTs could provide a viable interface material to motor neurons. Combined with emerging techniques to build complex hierarchical structures of CNTs, our results suggest that organised CNTs could be incorporated into nerve grafts that use physical and electrical cues to guide regenerating axons.

BDNF heightens the sensitivity of motor neurons to excitotoxic insults through activation of TrkB

NASA Technical Reports Server (NTRS)

Hu, Peter; Kalb, Robert G.; Walton, K. D. (Principal Investigator)

2003-01-01

The survival promoting and neuroprotective actions of brain-derived neurotrophic factor (BDNF) are well known but under certain circumstances this growth factor can also exacerbate excitotoxic insults to neurons. Prior exploration of the receptor through which BDNF exerts this action on motor neurons deflects attention away from p75. Here we investigated the possibility that BDNF acts through the receptor tyrosine kinase, TrkB, to confer on motor neurons sensitivity to excitotoxic challenge. We blocked BDNF activation of TrkB using a dominant negative TrkB mutant or a TrkB function blocking antibody, and found that this protected motor neurons against excitotoxic insult in cultures of mixed spinal cord neurons. Addition of a function blocking antibody to BDNF to mixed spinal cord neuron cultures is also neuroprotective indicating that endogenously produced BDNF participates in vulnerability to excitotoxicity. We next examined the intracellular signaling cascades that are engaged upon TrkB activation. Previously we found that inhibition of the phosphatidylinositide-3'-kinase (PI3'K) pathway blocks BDNF-induced excitotoxic sensitivity. Here we show that expression of a constitutively active catalytic subunit of PI3'K, p110, confers excitotoxic sensitivity (ES) upon motor neurons not incubated with BDNF. Parallel studies with purified motor neurons confirm that these events are likely to be occuring specifically within motor neurons. The abrogation of BDNF's capacity to accentuate excitotoxic insults may make it a more attractive neuroprotective agent.

Genetic Correction of Human Induced Pluripotent Stem Cells from Patients with Spinal Muscular Atrophy

PubMed Central

Corti, Stefania; Nizzardo, Monica; Simone, Chiara; Falcone, Marianna; Nardini, Martina; Ronchi, Dario; Donadoni, Chiara; Salani, Sabrina; Riboldi, Giulietta; Magri, Francesca; Menozzi, Giorgia; Bonaglia, Clara; Rizzo, Federica; Bresolin, Nereo; Comi, Giacomo P.

2016-01-01

Spinal muscular atrophy (SMA) is among the most common genetic neurological diseases that cause infant mortality. Induced pluripotent stem cells (iPSCs) generated from skin fibroblasts from SMA patients and genetically corrected have been proposed to be useful for autologous cell therapy. We generated iPSCs from SMA patients (SMA-iPSCs) using nonviral, nonintegrating episomal vectors and used a targeted gene correction approach based on single-stranded oligonucleotides to convert the survival motor neuron 2 (SMN2) gene into an SMN1-like gene. Corrected iPSC lines contained no exogenous sequences. Motor neurons formed by differentiation of uncorrected SMA-iPSCs reproduced disease-specific features. These features were ameliorated in motor neurons derived from genetically corrected SMA-iPSCs. The different gene splicing profile in SMA-iPSC motor neurons was rescued after genetic correction. The transplantation of corrected motor neurons derived from SMA-iPSCs into an SMA mouse model extended the life span of the animals and improved the disease phenotype. These results suggest that generating genetically corrected SMA-iPSCs and differentiating them into motor neurons may provide a source of motor neurons for therapeutic transplantation for SMA. PMID:23253609

A Drosophila Model for Amyotrophic Lateral Sclerosis Reveals Motor Neuron Damage by Human SOD1*♦

PubMed Central

Watson, Melanie R.; Lagow, Robert D.; Xu, Kexiang; Zhang, Bing; Bonini, Nancy M.

2008-01-01

Amyotrophic lateral sclerosis (ALS) is a motor neuron disease that leads to loss of motor function and early death. About 5% of cases are inherited, with the majority of identified linkages in the gene encoding copper, zinc-superoxide dismutase (SOD1). Strong evidence indicates that the SOD1 mutations confer dominant toxicity on the protein. To provide new insight into mechanisms of ALS, we have generated and characterized a model for familial ALS in Drosophila with transgenic expression of human SOD1. Expression of wild type or disease-linked (A4V, G85R) mutants of human SOD1 selectively in motor neurons induced progressive climbing deficits. These effects were accompanied by defective neural circuit electrophysiology, focal accumulation of human SOD1 protein in motor neurons, and a stress response in surrounding glia. However, toxicity was not associated with oligomerization of SOD1 and did not lead to neuronal loss. These studies uncover cell-autonomous injury by SOD1 to motor neurons in vivo, as well as non-autonomous effects on glia, and provide the foundation for new insight into injury and protection of motor neurons in ALS. PMID:18596033

N-Acetylcysteine Prevents Retrograde Motor Neuron Death after Neonatal Peripheral Nerve Injury.

PubMed

Catapano, Joseph; Zhang, Jennifer; Scholl, David; Chiang, Cameron; Gordon, Tessa; Borschel, Gregory H

2017-05-01

Neuronal death may be an overlooked and unaddressed component of disability following neonatal nerve injuries, such as obstetric brachial plexus injury. N-acetylcysteine and acetyl-L-carnitine improve survival of neurons after adult nerve injury, but it is unknown whether they improve survival after neonatal injury, when neurons are most susceptible to retrograde neuronal death. The authors' objective was to examine whether N-acetylcysteine or acetyl-L-carnitine treatment improves survival of neonatal motor or sensory neurons in a rat model of neonatal nerve injury. Rat pups received either a sciatic nerve crush or transection injury at postnatal day 3 and were then randomized to receive either intraperitoneal vehicle (5% dextrose), N-acetylcysteine (750 mg/kg), or acetyl-L-carnitine (300 mg/kg) once or twice daily. Four weeks after injury, surviving neurons were retrograde-labeled with 4% Fluoro-Gold. The lumbar spinal cord and L4/L5 dorsal root ganglia were then harvested and sectioned to count surviving motor and sensory neurons. Transection and crush injuries resulted in significant motor and sensory neuron loss, with transection injury resulting in significantly less neuron survival. High-dose N-acetylcysteine (750 mg/kg twice daily) significantly increased motor neuron survival after neonatal sciatic nerve crush and transection injury. Neither N-acetylcysteine nor acetyl-L-carnitine treatment improved sensory neuron survival. Proximal neonatal nerve injuries, such as obstetric brachial plexus injury, produce significant retrograde neuronal death after injury. High-dose N-acetylcysteine significantly increases motor neuron survival, which may improve functional outcomes after obstetrical brachial plexus injury.

Metabolic Changes Following Perinatal Asphyxia: Role of Astrocytes and Their Interaction with Neurons.

PubMed

Logica, Tamara; Riviere, Stephanie; Holubiec, Mariana I; Castilla, Rocío; Barreto, George E; Capani, Francisco

2016-01-01

Perinatal Asphyxia (PA) represents an important cause of severe neurological deficits including delayed mental and motor development, epilepsy, major cognitive deficits and blindness. The interaction between neurons, astrocytes and endothelial cells plays a central role coupling energy supply with changes in neuronal activity. Traditionally, experimental research focused on neurons, whereas astrocytes have been more related to the damage mechanisms of PA. Astrocytes carry out a number of functions that are critical to normal nervous system function, including uptake of neurotransmitters, regulation of pH and ion concentrations, and metabolic support for neurons. In this work, we aim to review metabolic neuron-astrocyte interactions with the purpose of encourage further research in this area in the context of PA, which is highly complex and its mechanisms and pathways have not been fully elucidated to this day.

Metabolic Changes Following Perinatal Asphyxia: Role of Astrocytes and Their Interaction with Neurons

PubMed Central

Logica, Tamara; Riviere, Stephanie; Holubiec, Mariana I.; Castilla, Rocío; Barreto, George E.; Capani, Francisco

2016-01-01

Perinatal Asphyxia (PA) represents an important cause of severe neurological deficits including delayed mental and motor development, epilepsy, major cognitive deficits and blindness. The interaction between neurons, astrocytes and endothelial cells plays a central role coupling energy supply with changes in neuronal activity. Traditionally, experimental research focused on neurons, whereas astrocytes have been more related to the damage mechanisms of PA. Astrocytes carry out a number of functions that are critical to normal nervous system function, including uptake of neurotransmitters, regulation of pH and ion concentrations, and metabolic support for neurons. In this work, we aim to review metabolic neuron-astrocyte interactions with the purpose of encourage further research in this area in the context of PA, which is highly complex and its mechanisms and pathways have not been fully elucidated to this day. PMID:27445788

Kinesin-5, a mitotic microtubule-associated motor protein, modulates neuronal migration

PubMed Central

Falnikar, Aditi; Tole, Shubha; Baas, Peter W.

2011-01-01

Kinesin-5 (also called Eg5 or kif11) is a homotetrameric motor protein that functions by modulating microtubule (MT)–MT interactions. In the case of mitosis, kinesin-5 slows the rate of separation of the half-spindles. In the case of the axon, kinesin-5 limits the frequency of transport of short MTs, and also limits the rate of axonal growth. Here we show that experimental inhibition of kinesin-5 in cultured migratory neurons results in a faster but more randomly moving neuron with a shorter leading process. As is the case with axons of stationary neurons, short MT transport frequency is notably enhanced in the leading process of the migratory neuron when kinesin-5 is inhibited. Conversely, overexpression of kinesin-5, both in culture and in developing cerebral cortex, causes migration to slow and even cease. Regions of anti-parallel MT organization behind the centrosome were shown to be especially rich in kinesin-5, implicating these regions as potential sites where kinesin-5 forces may be especially relevant. We posit that kinesin-5 acts as a “brake” on MT–MT interactions that modulates the advance of the entire MT apparatus. In so doing, kinesin-5 regulates the rate and directionality of neuronal migration and possibly the cessation of migration when the neuron reaches its destination. PMID:21411631

Dissecting the role of Engrailed in adult dopaminergic neurons--Insights into Parkinson disease pathogenesis.

PubMed

Rekaik, Hocine; Blaudin de Thé, François-Xavier; Prochiantz, Alain; Fuchs, Julia; Joshi, Rajiv L

2015-12-21

The homeoprotein Engrailed (Engrailed-1/Engrailed-2, collectively En1/2) is not only a survival factor for mesencephalic dopaminergic (mDA) neurons during development, but continues to exert neuroprotective and physiological functions in adult mDA neurons. Loss of one En1 allele in the mouse leads to progressive demise of mDA neurons in the ventral midbrain starting from 6 weeks of age. These mice also develop Parkinson disease-like motor and non-motor symptoms. The characterization of En1 heterozygous mice have revealed striking parallels to central mechanisms of Parkinson disease pathogenesis, mainly related to mitochondrial dysfunction and retrograde degeneration. Thanks to the ability of homeoproteins to transduce cells, En1/2 proteins have also been used to protect mDA neurons in various experimental models of Parkinson disease. This neuroprotection is partly linked to the ability of En1/2 to regulate the translation of certain nuclear-encoded mitochondrial mRNAs for complex I subunits. Other transcription factors that govern mDA neuron development (e.g. Foxa1/2, Lmx1a/b, Nurr1, Otx2, Pitx3) also continue to function for the survival and maintenance of mDA neurons in the adult and act through partially overlapping but also diverse mechanisms. Copyright © 2015 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.

Dopamine-Dependent Compensation Maintains Motor Behavior in Mice with Developmental Ablation of Dopaminergic Neurons

PubMed Central

DeMaro, Joseph A.; Knoten, Amanda; Hoshi, Masato; Pehek, Elizabeth; Johnson, Eugene M.; Gereau, Robert W.

2013-01-01

The loss of dopaminergic neurons in the substantia nigra pars compacta (SNc) and consequent depletion of striatal dopamine are known to underlie the motor deficits observed in Parkinson's disease (PD). Adaptive changes in dopaminergic terminals and in postsynaptic striatal neurons can compensate for significant losses of striatal dopamine, resulting in preservation of motor behavior. In addition, compensatory changes independent of striatal dopamine have been proposed based on PD therapies that modulate nondopaminergic circuits within the basal ganglia. We used a genetic strategy to selectively destroy dopaminergic neurons in mice during development to determine the necessity of these neurons for the maintenance of normal motor behavior in adult and aged mice. We find that loss of 90% of SNc dopaminergic neurons and consequent depletion of >95% of striatal dopamine does not result in changes in motor behavior in young-adult or aged mice as evaluated by an extensive array of motor behavior tests. Treatment of aged mutant mice with the dopamine receptor antagonist haloperidol precipitated motor behavior deficits in aged mutant mice, indicating that <5% of striatal dopamine is sufficient to maintain motor function in these mice. We also found that mutant mice exhibit an exaggerated response to l-DOPA compared with control mice, suggesting that preservation of motor function involves sensitization of striatal dopamine receptors. Our results indicate that congenital loss of dopaminergic neurons induces remarkable adaptions in the nigrostriatal system where limited amounts of dopamine in the dorsal striatum can maintain normal motor function. PMID:24155314

Expression of Terminal Effector Genes in Mammalian Neurons Is Maintained by a Dynamic Relay of Transient Enhancers.

PubMed

Rhee, Ho Sung; Closser, Michael; Guo, Yuchun; Bashkirova, Elizaveta V; Tan, G Christopher; Gifford, David K; Wichterle, Hynek

2016-12-21

Generic spinal motor neuron identity is established by cooperative binding of programming transcription factors (TFs), Isl1 and Lhx3, to motor-neuron-specific enhancers. How expression of effector genes is maintained following downregulation of programming TFs in maturing neurons remains unknown. High-resolution exonuclease (ChIP-exo) mapping revealed that the majority of enhancers established by programming TFs are rapidly deactivated following Lhx3 downregulation in stem-cell-derived hypaxial motor neurons. Isl1 is released from nascent motor neuron enhancers and recruited to new enhancers bound by clusters of Onecut1 in maturing neurons. Synthetic enhancer reporter assays revealed that Isl1 operates as an integrator factor, translating the density of Lhx3 or Onecut1 binding sites into transient enhancer activity. Importantly, independent Isl1/Lhx3- and Isl1/Onecut1-bound enhancers contribute to sustained expression of motor neuron effector genes, demonstrating that outwardly stable expression of terminal effector genes in postmitotic neurons is controlled by a dynamic relay of stage-specific enhancers. Copyright © 2016 Elsevier Inc. All rights reserved.

CXCR4 receptors in the dorsal medulla: implications for autonomic dysfunction

PubMed Central

Hermann, Gerlinda E.; Van Meter, Montina J.; Rogers, Richard C.

2014-01-01

The chemokine receptor, CXCR4, plays an essential role in guiding neural development of the CNS. Its natural agonist, CXCL12 [or stromal cell-derived factor-1 (SDF-1)], normally is derived from stromal cells, but is also produced by damaged and virus-infected neurons and glia. Pathologically, this receptor is critical to the proliferation of the HIV virus and initiation of metastatic cell growth in the brain. Anorexia, nausea and failed autonomic regulation of gastrointestinal (GI) function cause morbidity and contribute to the mortality associated with these disease states. Our previous work on the peripheral cytokine, tumor necrosis factor-alpha, demonstrated that similar morbidity factors involving GI dysfunction are attributable to agonist action on neural circuit elements of the dorsal vagal complex (DVC) of the hindbrain. The DVC includes vagal afferent terminations in the solitary nucleus, neurons in the solitary nucleus (NST) and area postrema, and visceral efferent motor neurons in the dorsal motor nucleus (DMN) that are responsible for the neural regulation of digestive functions from the oral cavity to the transverse colon. Immunohistochemical techniques demonstrate a dense concentration of CXCR4 receptors on neurons throughout the DVC and the hypoglossal nucleus. CXCR4-immunoreactivity is also intense on microglia within the DVC, though not on the astrocytes. Physiological studies show that nanoinjection of SDF-1 into the DVC produces a significant reduction in gastric motility in parallel with an elevation in the numbers of cFOS-activated neurons in the NST and DMN. These results suggest that this chemokine receptor may contribute to autonomically mediated pathophysiological events associated with CNS metastasis and infection. PMID:18333961

Phrenic long-term facilitation following intrapleural CTB-SAP-induced respiratory motor neuron death.

PubMed

Nichols, Nicole L; Craig, Taylor A; Tanner, Miles A

2017-08-16

Amyotrophic lateral sclerosis (ALS) is a devastating disease leading to progressive motor neuron degeneration and death by ventilatory failure. In a rat model of ALS (SOD1 G93A ), phrenic long-term facilitation (pLTF) following acute intermittent hypoxia (AIH) is enhanced greater than expected at disease end-stage but the mechanism is unknown. We suggest that one trigger for this enhancement is motor neuron death itself. Intrapleural injections of cholera toxin B fragment conjugated to saporin (CTB-SAP) selectively kill respiratory motor neurons and mimic motor neuron death observed in SOD1 G93A rats. This CTB-SAP model allows us to study the impact of respiratory motor neuron death on breathing without many complications attendant to ALS. Here, we tested the hypothesis that phrenic motor neuron death is sufficient to enhance pLTF. pLTF was assessed in anesthetized, paralyzed and ventilated Sprague Dawley rats 7 and 28days following bilateral intrapleural injections of: 1) CTB-SAP (25μg), or 2) un-conjugated CTB and SAP (control). CTB-SAP enhanced pLTF at 7 (CTB-SAP: 162±18%, n=8 vs. 63±3%; n=8; p<0.05), but not 28days post-injection (CTB-SAP: 64±10%, n=10 vs. 60±13; n=8; p>0.05). Thus, pLTF at 7 (not 28) days post-CTB-SAP closely resembles pLTF in end-stage ALS rats, suggesting that processes unique to the early period of motor neuron death enhance pLTF. This project increases our understanding of respiratory plasticity and its implications for breathing in motor neuron disease. Copyright © 2017 Elsevier B.V. All rights reserved.

[Schizophrenia and cortical GABA neurotransmission].

PubMed

Hashimoto, Takanori; Matsubara, Takuro; Lewis, David A

2010-01-01

Individuals with schizophrenia show disturbances in a number of brain functions that regulate cognitive, affective, motor, and sensory processing. The cognitive deficits associated with dysfunction of the dorsolateral prefrontal cortex result, at least in part, from abnormalities in GABA neurotransmission, as reflected in a specific pattern of altered expression of GABA-related molecules. First, mRNA levels for the 67-kilodalton isoform of glutamic acid decarboxylase (GAD67), an enzyme principally responsible for GABA synthesis, and the GABA membrane transporter GAT1, which regulates the reuptake of synaptically released GABA, are decreased in a subset of GABA neurons. Second, affected GABA neurons include those that express the calcium-binding protein parvalbumin (PV), because PV mRNA levels are decreased in the prefrontal cortex of subjects with schizophrenia and GAD67 mRNA is undetectable in almost half of PV-containing neurons. These changes are accompanied by decreased GAT1 expression in the presynaptic terminals of PV-containing neurons and by increased postsynaptic GABA-A receptor alpha2 subunit expression at the axon initial segments of pyramidal neurons. These findings indicate decreased GABA synthesis/release by PV-containing GABA neurons and compensatory changes at synapses formed by these neurons. Third, another subset of GABA neurons that express the neuropeptide somatostatin (SST) also appear to be affected because their specific markers, SST and neuropeptide Y mRNAs, are decreased in a manner highly correlated with the decreases in GAD67 mRNA. Finally, mRNA levels for GABA-A receptor subunits for synaptic (alpha1 and gamma2) and extra-synaptic (delta) receptors are decreased, indicating alterations in both synaptic and extra-synaptic GABA neurotransmission. Together, this pattern of changes indicates that the altered GABA neurotransmission is specific to PV-containing and SST-containing GABA neuron subsets and involves both synaptic and extra-synaptic GABA-A receptors. Our recent analyses demonstrated that this pattern exists across diverse cortical areas including the prefrontal, anterior cingulate, primary motor, and primary visual cortices. GABA neurotransmission by PV-containing and SST-containing neurons is important for the generation of cortical oscillatory activities in the gamma (30-100 Hz) and theta (4-7 Hz) bands, respectively. These oscillatory activities have been proposed to play critical roles in regulating the efficiency of information transfer between neurons and neuronal networks in the cortex. Altered cortical GABA neurotransmission appears to contribute to disturbances in diverse functions through affecting the generation of cortical oscillations in schizophrenia.

Preconditioning crush increases the survival rate of motor neurons after spinal root avulsion

PubMed Central

Li, Lin; Zuo, Yizhi; He, Jianwen

2014-01-01

In a previous study, heat shock protein 27 was persistently upregulated in ventral motor neurons following nerve root avulsion or crush. Here, we examined whether the upregulation of heat shock protein 27 would increase the survival rate of motor neurons. Rats were divided into two groups: an avulsion-only group (avulsion of the L4 lumbar nerve root only) and a crush-avulsion group (the L4 lumbar nerve root was crushed 1 week prior to the avulsion). Immunofluorescent staining revealed that the survival rate of motor neurons was significantly greater in the crush-avulsion group than in the avulsion-only group, and this difference remained for at least 5 weeks after avulsion. The higher neuronal survival rate may be explained by the upregulation of heat shock protein 27 expression in motor neurons in the crush-avulsion group. Furthermore, preconditioning crush greatly attenuated the expression of nitric oxide synthase in the motor neurons. Our findings indicate that the neuroprotective action of preconditioning crush is mediated through the upregulation of heat shock protein 27 expression and the attenuation of neuronal nitric oxide synthase upregulation following avulsion. PMID:25206852

Inherited Paediatric Motor Neuron Disorders: Beyond Spinal Muscular Atrophy

PubMed Central

Sampaio, Hugo; Mowat, David; Roscioli, Tony

2017-01-01

Paediatric motor neuron diseases encompass a group of neurodegenerative diseases characterised by the onset of muscle weakness and atrophy before the age of 18 years, attributable to motor neuron loss across various neuronal networks in the brain and spinal cord. While the genetic underpinnings are diverse, advances in next generation sequencing have transformed diagnostic paradigms. This has reinforced the clinical phenotyping and molecular genetic expertise required to navigate the complexities of such diagnoses. In turn, improved genetic technology and subsequent gene identification have enabled further insights into the mechanisms of motor neuron degeneration and how these diseases form part of a neurodegenerative disorder spectrum. Common pathophysiologies include abnormalities in axonal architecture and function, RNA processing, and protein quality control. This review incorporates an overview of the clinical manifestations, genetics, and pathophysiology of inherited paediatric motor neuron disorders beyond classic SMN1-related spinal muscular atrophy and describes recent advances in next generation sequencing and its clinical application. Specific disease-modifying treatment is becoming a clinical reality in some disorders of the motor neuron highlighting the importance of a timely and specific diagnosis. PMID:28634552

Correlation between discharge timings of pairs of motor units reveals the presence but not the proportion of common synaptic input to motor neurons

PubMed Central

Negro, Francesco; Farina, Dario

2017-01-01

We investigated whether correlation measures derived from pairs of motor unit (MU) spike trains are reliable indicators of the degree of common synaptic input to motor neurons. Several 50-s isometric contractions of the biceps brachii muscle were performed at different target forces ranging from 10 to 30% of the maximal voluntary contraction relying on force feedback. Forty-eight pairs of MUs were examined at various force levels. Motor unit synchrony was assessed by cross-correlation analysis using three indexes: the output correlation as the peak of the cross-histogram (ρ) and the number of synchronous spikes per second (CIS) and per trigger (E). Individual analysis of MU pairs revealed that ρ, CIS, and E were most often positively associated with discharge rate (87, 85, and 76% of the MU pairs, respectively) and negatively with interspike interval variability (69, 65, and 62% of the MU pairs, respectively). Moreover, the behavior of synchronization indexes with discharge rate (and interspike interval variability) varied greatly among the MU pairs. These results were consistent with theoretical predictions, which showed that the output correlation between pairs of spike trains depends on the statistics of the input current and motor neuron intrinsic properties that differ for different motor neuron pairs. In conclusion, the synchronization between MU firing trains is necessarily caused by the (functional) common input to motor neurons, but it is not possible to infer the degree of shared common input to a pair of motor neurons on the basis of correlation measures of their output spike trains. NEW & NOTEWORTHY The strength of correlation between output spike trains is only poorly associated with the degree of common input to the population of motor neurons. The synchronization between motor unit firing trains is necessarily caused by the (functional) common input to motor neurons, but it is not possible to infer the degree of shared common input to a pair of motor neurons on the basis of correlation measures of their output spike trains. PMID:28100652

Induction of motor neuron differentiation by transduction of Olig2 protein.

PubMed

Mie, Masayasu; Kaneko, Mami; Henmi, Fumiaki; Kobatake, Eiry

2012-10-26

Olig2 protein, a member of the basic helix-loop-helix transcription factor family, was introduced into the mouse embryonic carcinoma cell line P19 for induction of motor neuron differentiation. We show that Olig2 protein has the ability to permeate the cell membrane without the addition of a protein transduction domain (PTD), similar to other basic helix-loop-helix transcription factors such as MyoD and NeuroD2. Motor neuron differentiation was evaluated for the elongation of neurites and the expression of choline acetyltransferase (ChAT) mRNA, a differentiation marker of motor neurons. By addition of Olig2 protein, motor neuron differentiation was induced in P19 cells. Copyright © 2012 Elsevier Inc. All rights reserved.

Delayed Disease Onset and Extended Survival in the SOD1G93A Rat Model of Amyotrophic Lateral Sclerosis after Suppression of Mutant SOD1 in the Motor Cortex

PubMed Central

Thomsen, Gretchen M.; Gowing, Genevieve; Latter, Jessica; Chen, Maximus; Vit, Jean-Philippe; Staggenborg, Kevin; Avalos, Pablo; Alkaslasi, Mor; Ferraiuolo, Laura; Likhite, Shibi; Kaspar, Brian K.

2014-01-01

Sporadic amyotrophic lateral sclerosis (ALS) is a fatal disease with unknown etiology, characterized by a progressive loss of motor neurons leading to paralysis and death typically within 3–5 years of onset. Recently, there has been remarkable progress in understanding inherited forms of ALS in which well defined mutations are known to cause the disease. Rodent models in which the superoxide dismutase-1 (SOD1) mutation is overexpressed recapitulate hallmark signs of ALS in patients. Early anatomical changes in mouse models of fALS are seen in the neuromuscular junctions (NMJs) and lower motor neurons, and selective reduction of toxic mutant SOD1 in the spinal cord and muscle of these models has beneficial effects. Therefore, much of ALS research has focused on spinal motor neuron and NMJ aspects of the disease. Here we show that, in the SOD1G93A rat model of ALS, spinal motor neuron loss occurs presymptomatically and before degeneration of ventral root axons and denervation of NMJs. Although overt cell death of corticospinal motor neurons does not occur until disease endpoint, we wanted to establish whether the upper motor neuron might still play a critical role in disease progression. Surprisingly, the knockdown of mutant SOD1 in only the motor cortex of presymptomatic SOD1G93A rats through targeted delivery of AAV9–SOD1–shRNA resulted in a significant delay of disease onset, expansion of lifespan, enhanced survival of spinal motor neurons, and maintenance of NMJs. This datum suggests an early dysfunction and thus an important role of the upper motor neuron in this animal model of ALS and perhaps patients with the disease. PMID:25411487

Subcortical neuronal ensembles: an analysis of motor task association, tremor, oscillations, and synchrony in human patients.

PubMed

Hanson, Timothy L; Fuller, Andrew M; Lebedev, Mikhail A; Turner, Dennis A; Nicolelis, Miguel A L

2012-06-20

Deep brain stimulation (DBS) has expanded as an effective treatment for motor disorders, providing a valuable opportunity for intraoperative recording of the spiking activity of subcortical neurons. The properties of these neurons and their potential utility in neuroprosthetic applications are not completely understood. During DBS surgeries in 25 human patients with either essential tremor or Parkinson's disease, we acutely recorded the single-unit activity of 274 ventral intermediate/ventral oralis posterior motor thalamus (Vim/Vop) neurons and 123 subthalamic nucleus (STN) neurons. These subcortical neuronal ensembles (up to 23 neurons sampled simultaneously) were recorded while the patients performed a target-tracking motor task using a cursor controlled by a haptic glove. We observed that modulations in firing rate of a substantial number of neurons in both Vim/Vop and STN represented target onset, movement onset/direction, and hand tremor. Neurons in both areas exhibited rhythmic oscillations and pairwise synchrony. Notably, all tremor-associated neurons exhibited synchrony within the ensemble. The data further indicate that oscillatory (likely pathological) neurons and behaviorally tuned neurons are not distinct but rather form overlapping sets. Whereas previous studies have reported a linear relationship between power spectra of neuronal oscillations and hand tremor, we report a nonlinear relationship suggestive of complex encoding schemes. Even in the presence of this pathological activity, linear models were able to extract motor parameters from ensemble discharges. Based on these findings, we propose that chronic multielectrode recordings from Vim/Vop and STN could prove useful for further studying, monitoring, and even treating motor disorders.

Spinal Locomotor Circuits Develop Using Hierarchical Rules Based on Motorneuron Position and Identity.

PubMed

Hinckley, Christopher A; Alaynick, William A; Gallarda, Benjamin W; Hayashi, Marito; Hilde, Kathryn L; Driscoll, Shawn P; Dekker, Joseph D; Tucker, Haley O; Sharpee, Tatyana O; Pfaff, Samuel L

2015-09-02

The coordination of multi-muscle movements originates in the circuitry that regulates the firing patterns of spinal motorneurons. Sensory neurons rely on the musculotopic organization of motorneurons to establish orderly connections, prompting us to examine whether the intraspinal circuitry that coordinates motor activity likewise uses cell position as an internal wiring reference. We generated a motorneuron-specific GCaMP6f mouse line and employed two-photon imaging to monitor the activity of lumbar motorneurons. We show that the central pattern generator neural network coordinately drives rhythmic columnar-specific motorneuron bursts at distinct phases of the locomotor cycle. Using multiple genetic strategies to perturb the subtype identity and orderly position of motorneurons, we found that neurons retained their rhythmic activity-but cell position was decoupled from the normal phasing pattern underlying flexion and extension. These findings suggest a hierarchical basis of motor circuit formation that relies on increasingly stringent matching of neuronal identity and position. Copyright © 2015 Elsevier Inc. All rights reserved.

Diversification of C. elegans Motor Neuron Identity via Selective Effector Gene Repression.

PubMed

Kerk, Sze Yen; Kratsios, Paschalis; Hart, Michael; Mourao, Romulo; Hobert, Oliver

2017-01-04

A common organizational feature of nervous systems is the existence of groups of neurons that share common traits but can be divided into individual subtypes based on anatomical or molecular features. We elucidate the mechanistic basis of neuronal diversification processes in the context of C.elegans ventral cord motor neurons that share common traits that are directly activated by the terminal selector UNC-3. Diversification of motor neurons into different classes, each characterized by unique patterns of effector gene expression, is controlled by distinct combinations of phylogenetically conserved, class-specific transcriptional repressors. These repressors are continuously required in postmitotic neurons to prevent UNC-3, which is active in all neuron classes, from activating class-specific effector genes in specific motor neuron subsets via discrete cis-regulatory elements. The strategy of antagonizing the activity of broadly acting terminal selectors of neuron identity in a subtype-specific fashion may constitute a general principle of neuron subtype diversification. Copyright © 2017 Elsevier Inc. All rights reserved.

Carbachol excites sublaterodorsal nucleus neurons projecting to the spinal cord

PubMed Central

Weng, F J; Williams, R H; Hawryluk, J M; Lu, J; Scammell, T E; Saper, C B; Arrigoni, E

2014-01-01

Considerable electrophysiological and pharmacological evidence has long suggested an important role for acetylcholine in the regulation of rapid-eye-movement (REM) sleep. For example, injection of the cholinergic agonist carbachol into the dorsomedial pons produces an REM sleep-like state with muscle atonia and cortical activation, both of which are cardinal features of REM sleep. Located within this region of the pons is the sublaterodorsal nucleus (SLD), a structure thought to be both necessary and sufficient for generating REM sleep muscle atonia. Subsets of glutamatergic SLD neurons potently contribute to motor inhibition during REM sleep through descending projections to motor-related glycinergic/GABAergic neurons in the spinal cord and ventromedial medulla. Prior electrophysiological and pharmacological studies examining the effects of acetylcholine on SLD neurons have, however, produced conflicting results. In the present study, we sought to clarify how acetylcholine influences the activity of spinally projecting SLD (SLDsp) neurons. We used retrograde tracing in combination with patch-clamp recordings and recorded pre-and postsynaptic effects of carbachol on SLDsp neurons. Carbachol acted presynaptically by increasing the frequency of glutamatergic miniature excitatory postsynaptic currents. We also found that carbachol directly excited SLDsp neurons by activating an Na+–Ca2+ exchanger. Both pre-and postsynaptic effects were mediated by co-activation of M1 and M3 muscarinic receptors. These observations suggest that acetylcholine produces synergistic, excitatory pre-and postsynaptic responses on SLDsp neurons that, in turn, probably serve to promote muscle atonia during REM sleep. PMID:24344163

Carbachol excites sublaterodorsal nucleus neurons projecting to the spinal cord.

PubMed

Weng, F J; Williams, R H; Hawryluk, J M; Lu, J; Scammell, T E; Saper, C B; Arrigoni, E

2014-04-01

Considerable electrophysiological and pharmacological evidence has long suggested an important role for acetylcholine in the regulation of rapid-eye-movement (REM) sleep. For example, injection of the cholinergic agonist carbachol into the dorsomedial pons produces an REM sleep-like state with muscle atonia and cortical activation, both of which are cardinal features of REM sleep. Located within this region of the pons is the sublaterodorsal nucleus (SLD), a structure thought to be both necessary and sufficient for generating REM sleep muscle atonia. Subsets of glutamatergic SLD neurons potently contribute to motor inhibition during REM sleep through descending projections to motor-related glycinergic/GABAergic neurons in the spinal cord and ventromedial medulla. Prior electrophysiological and pharmacological studies examining the effects of acetylcholine on SLD neurons have, however, produced conflicting results. In the present study, we sought to clarify how acetylcholine influences the activity of spinally projecting SLD (SLDsp) neurons. We used retrograde tracing in combination with patch-clamp recordings and recorded pre- and postsynaptic effects of carbachol on SLDsp neurons. Carbachol acted presynaptically by increasing the frequency of glutamatergic miniature excitatory postsynaptic currents. We also found that carbachol directly excited SLDsp neurons by activating an Na(+)-Ca(2+) exchanger. Both pre- and postsynaptic effects were mediated by co-activation of M1 and M3 muscarinic receptors. These observations suggest that acetylcholine produces synergistic, excitatory pre- and postsynaptic responses on SLDsp neurons that, in turn, probably serve to promote muscle atonia during REM sleep.

Increased Levels of Rictor Prevent Mutant Huntingtin-Induced Neuronal Degeneration.

PubMed

Creus-Muncunill, Jordi; Rué, Laura; Alcalá-Vida, Rafael; Badillos-Rodríguez, Raquel; Romaní-Aumedes, Joan; Marco, Sonia; Alberch, Jordi; Perez-Otaño, Isabel; Malagelada, Cristina; Pérez-Navarro, Esther

2018-02-19

Rictor associates with mTOR to form the mTORC2 complex, which activity regulates neuronal function and survival. Neurodegenerative diseases are characterized by the presence of neuronal dysfunction and cell death in specific brain regions such as for example Huntington's disease (HD), which is characterized by the loss of striatal projection neurons leading to motor dysfunction. Although HD is caused by the expression of mutant huntingtin, cell death occurs gradually suggesting that neurons have the capability to activate compensatory mechanisms to deal with neuronal dysfunction and later cell death. Here, we analyzed whether mTORC2 activity could be altered by the presence of mutant huntingtin. We observed that Rictor levels are specifically increased in the striatum of HD mouse models and in the putamen of HD patients. Rictor-mTOR interaction and the phosphorylation levels of Akt, one of the targets of the mTORC2 complex, were increased in the striatum of the R6/1 mouse model of HD suggesting increased mTORC2 signaling. Interestingly, acute downregulation of Rictor in striatal cells in vitro reduced mTORC2 activity, as shown by reduced levels of phospho-Akt, and increased mutant huntingtin-induced cell death. Accordingly, overexpression of Rictor increased mTORC2 activity counteracting cell death. Furthermore, normalization of endogenous Rictor levels in the striatum of R6/1 mouse worsened motor symptoms suggesting an induction of neuronal dysfunction. In conclusion, our results suggest that increased Rictor striatal levels could counteract neuronal dysfunction induced by mutant huntingtin.

[CHANGES IN THE NUMBER OF NEURONS IN THE MOTOR CORTEX OF RATS AND THEIR LOCOMOTOR ACTIVITY IN THE AGE ASPECT].

PubMed

Piavchenko, G A; Shmarkova, L I; Nozdrin, V I

2015-01-01

Using Laboras hardware-software complex, which is a system of automatic registration of behavioral reactions, the locomotor activity 1-, 8- and 16-month-old male rats (12 animals in each group) was recorded followed by counting the number of neuron cell bodies of in the layer V of the motor cortex in Nissl stained slides. It was found that the number of neurons in the motor cortex varied in different age groups. Maximal number of neurons was observed in 8-month-old animals. Motor activity was found to correlate with the number of neurons.

Convergent Differential Regulation of Parvalbumin in the Brains of Vocal Learners

PubMed Central

Hara, Erina; Rivas, Miriam V.; Ward, James M.; Okanoya, Kazuo; Jarvis, Erich D.

2012-01-01

Spoken language and learned song are complex communication behaviors found in only a few species, including humans and three groups of distantly related birds – songbirds, parrots, and hummingbirds. Despite their large phylogenetic distances, these vocal learners show convergent behaviors and associated brain pathways for vocal communication. However, it is not clear whether this behavioral and anatomical convergence is associated with molecular convergence. Here we used oligo microarrays to screen for genes differentially regulated in brain nuclei necessary for producing learned vocalizations relative to adjacent brain areas that control other behaviors in avian vocal learners versus vocal non-learners. A top candidate gene in our screen was a calcium-binding protein, parvalbumin (PV). In situ hybridization verification revealed that PV was expressed significantly higher throughout the song motor pathway, including brainstem vocal motor neurons relative to the surrounding brain regions of all distantly related avian vocal learners. This differential expression was specific to PV and vocal learners, as it was not found in avian vocal non-learners nor for control genes in learners and non-learners. Similar to the vocal learning birds, higher PV up-regulation was found in the brainstem tongue motor neurons used for speech production in humans relative to a non-human primate, macaques. These results suggest repeated convergent evolution of differential PV up-regulation in the brains of vocal learners separated by more than 65–300 million years from a common ancestor and that the specialized behaviors of learned song and speech may require extra calcium buffering and signaling. PMID:22238614

A θ-γ oscillation code for neuronal coordination during motor behavior.

PubMed

Igarashi, Jun; Isomura, Yoshikazu; Arai, Kensuke; Harukuni, Rie; Fukai, Tomoki

2013-11-20

Sequential motor behavior requires a progression of discrete preparation and execution states. However, the organization of state-dependent activity in neuronal ensembles of motor cortex is poorly understood. Here, we recorded neuronal spiking and local field potential activity from rat motor cortex during reward-motivated movement and observed robust behavioral state-dependent coordination between neuronal spiking, γ oscillations, and θ oscillations. Slow and fast γ oscillations appeared during distinct movement states and entrained neuronal firing. γ oscillations, in turn, were coupled to θ oscillations, and neurons encoding different behavioral states fired at distinct phases of θ in a highly layer-dependent manner. These findings indicate that θ and nested dual band γ oscillations serve as the temporal structure for the selection of a conserved set of functional channels in motor cortical layer activity during animal movement. Furthermore, these results also suggest that cross-frequency couplings between oscillatory neuronal ensemble activities are part of the general coding mechanism in cortex.

Overexpression of survival motor neuron improves neuromuscular function and motor neuron survival in mutant SOD1 mice.

PubMed

Turner, Bradley J; Alfazema, Neza; Sheean, Rebecca K; Sleigh, James N; Davies, Kay E; Horne, Malcolm K; Talbot, Kevin

2014-04-01

Spinal muscular atrophy results from diminished levels of survival motor neuron (SMN) protein in spinal motor neurons. Low levels of SMN also occur in models of amyotrophic lateral sclerosis (ALS) caused by mutant superoxide dismutase 1 (SOD1) and genetic reduction of SMN levels exacerbates the phenotype of transgenic SOD1(G93A) mice. Here, we demonstrate that SMN protein is significantly reduced in the spinal cords of patients with sporadic ALS. To test the potential of SMN as a modifier of ALS, we overexpressed SMN in 2 different strains of SOD1(G93A) mice. Neuronal overexpression of SMN significantly preserved locomotor function, rescued motor neurons, and attenuated astrogliosis in spinal cords of SOD1(G93A) mice. Despite this, survival was not prolonged, most likely resulting from SMN mislocalization and depletion of gems in motor neurons of symptomatic mice. Our results reveal that SMN upregulation slows locomotor deficit onset and motor neuron loss in this mouse model of ALS. However, disruption of SMN nuclear complexes by high levels of mutant SOD1, even in the presence of SMN overexpression, might limit its survival promoting effects in this specific mouse model. Studies in emerging mouse models of ALS are therefore warranted to further explore the potential of SMN as a modifier of ALS. Copyright © 2014 Elsevier Inc. All rights reserved.

The laminar organization of the Drosophila ellipsoid body is semaphorin-dependent and prevents the formation of ectopic synaptic connections

PubMed Central

Xie, Xiaojun; Tabuchi, Masashi; Brown, Matthew P; Mitchell, Sarah P; Wu, Mark N; Kolodkin, Alex L

2017-01-01

The ellipsoid body (EB) in the Drosophila brain is a central complex (CX) substructure that harbors circumferentially laminated ring (R) neuron axons and mediates multifaceted sensory integration and motor coordination functions. However, what regulates R axon lamination and how lamination affects R neuron function remain unknown. We show here that the EB is sequentially innervated by small-field and large-field neurons and that early developing EB neurons play an important regulatory role in EB laminae formation. The transmembrane proteins semaphorin-1a (Sema-1a) and plexin A function together to regulate R axon lamination. R neurons recruit both GABA and GABA-A receptors to their axon terminals in the EB, and optogenetic stimulation coupled with electrophysiological recordings show that Sema-1a-dependent R axon lamination is required for preventing the spread of synaptic inhibition between adjacent EB lamina. These results provide direct evidence that EB lamination is critical for local pre-synaptic inhibitory circuit organization. DOI: http://dx.doi.org/10.7554/eLife.25328.001 PMID:28632130

A latent low-dimensional common input drives a pool of motor neurons: a probabilistic latent state-space model.

PubMed

Feeney, Daniel F; Meyer, François G; Noone, Nicholas; Enoka, Roger M

2017-10-01

Motor neurons appear to be activated with a common input signal that modulates the discharge activity of all neurons in the motor nucleus. It has proven difficult for neurophysiologists to quantify the variability in a common input signal, but characterization of such a signal may improve our understanding of how the activation signal varies across motor tasks. Contemporary methods of quantifying the common input to motor neurons rely on compiling discrete action potentials into continuous time series, assuming the motor pool acts as a linear filter, and requiring signals to be of sufficient duration for frequency analysis. We introduce a space-state model in which the discharge activity of motor neurons is modeled as inhomogeneous Poisson processes and propose a method to quantify an abstract latent trajectory that represents the common input received by motor neurons. The approach also approximates the variation in synaptic noise in the common input signal. The model is validated with four data sets: a simulation of 120 motor units, a pair of integrate-and-fire neurons with a Renshaw cell providing inhibitory feedback, the discharge activity of 10 integrate-and-fire neurons, and the discharge times of concurrently active motor units during an isometric voluntary contraction. The simulations revealed that a latent state-space model is able to quantify the trajectory and variability of the common input signal across all four conditions. When compared with the cumulative spike train method of characterizing common input, the state-space approach was more sensitive to the details of the common input current and was less influenced by the duration of the signal. The state-space approach appears to be capable of detecting rather modest changes in common input signals across conditions. NEW & NOTEWORTHY We propose a state-space model that explicitly delineates a common input signal sent to motor neurons and the physiological noise inherent in synaptic signal transmission. This is the first application of a deterministic state-space model to represent the discharge characteristics of motor units during voluntary contractions. Copyright © 2017 the American Physiological Society.

Genetic identification of a hindbrain nucleus essential for innate vocalization.

PubMed

Hernandez-Miranda, Luis Rodrigo; Ruffault, Pierre-Louis; Bouvier, Julien C; Murray, Andrew J; Morin-Surun, Marie-Pierre; Zampieri, Niccolò; Cholewa-Waclaw, Justyna B; Ey, Elodie; Brunet, Jean-Francois; Champagnat, Jean; Fortin, Gilles; Birchmeier, Carmen

2017-07-25

Vocalization in young mice is an innate response to isolation or mechanical stimulation. Neuronal circuits that control vocalization and breathing overlap and rely on motor neurons that innervate laryngeal and expiratory muscles, but the brain center that coordinates these motor neurons has not been identified. Here, we show that the hindbrain nucleus tractus solitarius (NTS) is essential for vocalization in mice. By generating genetically modified newborn mice that specifically lack excitatory NTS neurons, we show that they are both mute and unable to produce the expiratory drive required for vocalization. Furthermore, the muteness of these newborns results in maternal neglect. We also show that neurons of the NTS directly connect to and entrain the activity of spinal (L1) and nucleus ambiguus motor pools located at positions where expiratory and laryngeal motor neurons reside. These motor neurons control expiratory pressure and laryngeal tension, respectively, thereby establishing the essential biomechanical parameters used for vocalization. In summary, our work demonstrates that the NTS is an obligatory component of the neuronal circuitry that transforms breaths into calls.

Joining forces: Motor control meets mirror neurons. Comment on "Grasping synergies: A motor-control approach to the mirror neuron mechanism" by D'Ausilio, Bartoli, and Maffongelli

NASA Astrophysics Data System (ADS)

Casile, Antonino

2015-03-01

Several consistent and compelling experimental findings suggest that in primates the observation of actions or movements activates the observer's motor cortex (for a recent and very thorough review see [1]). One important piece of evidence was the discovery of mirror neurons, that are neurons in the macaque ventral pre-motor (area F5), motor and parietal cortices (area PFG) that respond both when the monkey executes a goal-directed motor act (e.g. breaking a peanut) or when it sees a similar action executed by others [2-5]. A similar system has been later reported also in humans ([6-8] but see also [9,10] for negative results).

Targeted Inactivation of a Developmentally Regulated Neural Plectin Isoform (Plectin 1c) in Mice Leads to Reduced Motor Nerve Conduction Velocity*

PubMed Central

Fuchs, Peter; Zörer, Michael; Reipert, Siegfried; Rezniczek, Günther A.; Propst, Friedrich; Walko, Gernot; Fischer, Irmgard; Bauer, Jan; Leschnik, Michael W.; Lüscher, Bernhard; Thalhammer, Johann G.; Lassmann, Hans; Wiche, Gerhard

2009-01-01

Cytolinker proteins stabilize cells mechanically, regulate cytoskeleton dynamics, and provide scaffolds for signaling molecules. For plectin, the prototype of these proteins, an unusual diversity of isoforms has been reported, which show distinct expression patterns, subcellular localizations, and functions. Plectin has been shown to have important functions in skin and muscle, but little is known about its role in neural cells. To address this issue, we generated two knock-out mouse lines, one which was selectively lacking plectin 1c (P1c), the major isoform expressed in neural cells, and another in which plectin was conditionally deleted in neuronal precursor cells. Using isoform-specific antibodies, we found P1c to be expressed late in development and to associate with postsynaptic dendrites of central nervous system neurons, motorneurons of spinal cord, sciatic nerve axons, and Schwann cells. Motor nerve conduction velocity was found significantly reduced in sciatic nerve from P1c-deficient as well as from conditional knock-out mice. This defect was traceable to an increased number of motor nerve fibers with small cross-sectional areas; the thicknesses of axons and of myelin sheaths were unaffected. This is the first report demonstrating an important role of plectin in a major nerve function. PMID:19625254

Cannabinoid-1 (CB1) receptors regulate colonic propulsion by acting at motor neurons within the ascending motor pathways in mouse colon.

PubMed

Sibaev, Andrei; Yüce, Birol; Kemmer, Markus; Van Nassauw, Luc; Broedl, Ulli; Allescher, Hans D; Göke, Burkhard; Timmermans, Jean-Pierre; Storr, Martin

2009-01-01

Cannabinoid-1 (CB(1)) receptors on myenteric neurons are involved in the regulation of intestinal motility. Our aim was to investigate CB(1) receptor involvement in ascending neurotransmission in mouse colon and to characterize the involved structures by functional and morphological means. Presence of the CB(1) receptor was investigated by RT-PCR, and immunohistochemistry was used for colabeling studies. Myenteric reflex responses were initiated by electrical stimulation (ES) at different distances, and junction potentials (JP) were recorded from circular smooth muscle cells by intracellular recording in an unpartitioned and a partitioned recording chamber. In vivo colonic propulsion was tested in wild-type and CB(1)(-/-) mice. Immunostaining with the cytoskeletal marker peripherin showed CB(1) immunoreactivity both on Dogiel type I and type II neurons. Further neurochemical characterization revealed CB(1) on choline acetyltransferase-, calretinin-, and 5-HT-immunopositive myenteric neurons, but nitrergic neurons appeared immunonegative for CB(1) immunostaining. Solitary spindle-shaped CB(1)-immunoreactive cells in between smooth muscle cells lacked specific markers for interstitial cells of Cajal or glial cells. ES elicited neuronally mediated excitatory JP (EJP) and inhibitory JP. Gradual increases in distance resulted in a wave-like EJP with EJP amplitudes being maximal at the location of stimulating electrode 6 and a maximal EJP projection distance of approximately 18 mm. The CB(1) receptor agonist WIN 55,212-2 reduced the amplitude of EJP and was responsible for shortening the oral spreading of the excitatory impulse. In a partitioned chamber, WIN 55,212-2 reduced EJP at the separated oral sites, proving that CB(1) activation inhibits interneuron-mediated neurotransmission. These effects were absent in the presence of the CB(1) antagonist SR141716A, which, when given alone, had no effect. WIN 55,212-2 inhibited colonic propulsion in wild-type mice but not in SR141716A-pretreated wild-type or CB(1)(-/-) mice. Activation of the CB(1) receptor modulates excitatory cholinergic neurotransmission in mouse colon by reducing amplitude and spatial spreading of the ascending electrophysiological impulses. This effect on electrophysiological spreading involves CB(1)-mediated effects on motor neurons and ascending interneurons and is likely to underlie the here reported in vivo reduction in colonic propulsion.

Edaravone is a candidate agent for spinal muscular atrophy: In vitro analysis using a human induced pluripotent stem cells-derived disease model.

PubMed

Ando, Shiori; Funato, Michinori; Ohuchi, Kazuki; Kameyama, Tsubasa; Inagaki, Satoshi; Seki, Junko; Kawase, Chizuru; Tsuruma, Kazuhiro; Shimazawa, Masamitsu; Kaneko, Hideo; Hara, Hideaki

2017-11-05

Spinal muscular atrophy (SMA) is an intractable disease characterized by a progressive loss of spinal motor neurons, which leads to skeletal muscle weakness and atrophy. Currently, there are no curative agents for SMA, although it is understood to be caused by reduced levels of survival motor neuron (SMN) protein. Additionally, why reduced SMN protein level results in selective apoptosis in spinal motor neurons is still not understood. Our purpose in this study was to evaluate the therapeutic potential of edaravone, a free radical scavenger, by using induced pluripotent stem cells from an SMA patient (SMA-iPSCs) and to address oxidative stress-induced apoptosis in spinal motor neurons. We first found that edaravone could improve impaired neural development of SMA-iPSCs-derived spinal motor neurons with limited effect on nuclear SMN protein expression. Furthermore, edaravone inhibited the generation of reactive oxygen species and mitochondrial reactive oxygen species upregulated in SMA-iPSCs-derived spinal motor neurons, and reversed oxidative-stress induced apoptosis. In this study, we suggest that oxidative stress might be partly the reason for selective apoptosis in spinal motor neurons in SMA pathology, and that oxidative stress-induced apoptosis might be the therapeutic target of SMA. Copyright © 2017 Elsevier B.V. All rights reserved.

Angiogenesis within the developing mouse neural tube is dependent on sonic hedgehog signaling: possible roles of motor neurons.

PubMed

Nagase, Takashi; Nagase, Miki; Yoshimura, Kotaro; Fujita, Toshiro; Koshima, Isao

2005-06-01

Embryonic morphogenesis of vascular and nervous systems is tightly coordinated, and recent studies revealed that some neurogenetic factors such as Sonic hedgehog (Shh) also exhibit angiogenetic potential. Vascularization within the developing mouse neural tube depends on vessel sprouting from the surrounding vascular plexus. Previous studies implicated possible roles of VEGF/Flk-1 and Angiopoietin-1(Ang-1)/Tie-2 signaling as candidate molecules functioning in this process. Examining gene expressions of these factors at embryonic day (E) 9.5 and 10.5, we unexpectedly found that both VEGF and Ang-1 were expressed in the motor neurons in the ventral neural tube. The motor neurons were indeed located in the close vicinity of the infiltrating vessels, suggesting involvement of motor neurons in the sprouting. To substantiate this possibility, we inhibited induction of the motor neurons in the cultured mouse embryos by cyclopamine, a Shh signaling blocker. The vessel sprouting was dramatically impaired by inhibition of Shh signaling, together with nearly complete loss of the motor neurons. Expression of Ang-1, but not VEGF, within the neural tube was remarkably reduced in the cyclopamine treated embryos. These results suggest that the neural tube angiogenesis is dependent on Shh signaling, and mediated, at least in part, by the Ang-1 positive motor neurons.

The mirror mechanism: recent findings and perspectives

PubMed Central

Rizzolatti, Giacomo; Fogassi, Leonardo

2014-01-01

Mirror neurons are a specific type of visuomotor neuron that discharge both when a monkey executes a motor act and when it observes a similar motor act performed by another individual. In this article, we review first the basic properties of these neurons. We then describe visual features recently investigated which indicate that, besides encoding the goal of motor acts, mirror neurons are modulated by location in space of the observed motor acts, by the perspective from which the others’ motor acts are seen, and by the value associated with the object on which others’ motor acts are performed. In the last part of this article, we discuss the role of the mirror mechanism in planning actions and in understanding the intention underlying the others’ motor acts. We also review some human studies suggesting that motor intention in humans may rely, as in the monkey, on the mirror mechanism. PMID:24778385

T-type calcium channels cause bursts of spikes in motor but not sensory thalamic neurons during mimicry of natural patterns of synaptic input.

PubMed

Kim, Haram R; Hong, Su Z; Fiorillo, Christopher D

2015-01-01

Although neurons within intact nervous systems can be classified as 'sensory' or 'motor,' it is not known whether there is any general distinction between sensory and motor neurons at the cellular or molecular levels. Here, we extend and test a theory according to which activation of certain subtypes of voltage-gated ion channel (VGC) generate patterns of spikes in neurons of motor systems, whereas VGC are proposed to counteract patterns in sensory neurons. We previously reported experimental evidence for the theory from visual thalamus, where we found that T-type calcium channels (TtCCs) did not cause bursts of spikes but instead served the function of 'predictive homeostasis' to maximize the causal and informational link between retinogeniculate excitation and spike output. Here, we have recorded neurons in brain slices from eight sensory and motor regions of rat thalamus while mimicking key features of natural excitatory and inhibitory post-synaptic potentials. As predicted by theory, TtCC did cause bursts of spikes in motor thalamus. TtCC-mediated responses in motor thalamus were activated at more hyperpolarized potentials and caused larger depolarizations with more spikes than in visual and auditory thalamus. Somatosensory thalamus is known to be more closely connected to motor regions relative to auditory and visual thalamus, and likewise the strength of its TtCC responses was intermediate between these regions and motor thalamus. We also observed lower input resistance, as well as limited evidence of stronger hyperpolarization-induced ('H-type') depolarization, in nuclei closer to motor output. These findings support our theory of a specific difference between sensory and motor neurons at the cellular level.

Implications of Circadian Rhythm in Dopamine and Mood Regulation.

PubMed

Kim, Jeongah; Jang, Sangwon; Choe, Han Kyoung; Chung, Sooyoung; Son, Gi Hoon; Kim, Kyungjin

2017-07-31

Mammalian physiology and behavior are regulated by an internal time-keeping system, referred to as circadian rhythm. The circadian timing system has a hierarchical organization composed of the master clock in the suprachiasmatic nucleus (SCN) and local clocks in extra-SCN brain regions and peripheral organs. The circadian clock molecular mechanism involves a network of transcription-translation feedback loops. In addition to the clinical association between circadian rhythm disruption and mood disorders, recent studies have suggested a molecular link between mood regulation and circadian rhythm. Specifically, genetic deletion of the circadian nuclear receptor Rev-erbα induces mania-like behavior caused by increased midbrain dopaminergic (DAergic) tone at dusk. The association between circadian rhythm and emotion-related behaviors can be applied to pathological conditions, including neurodegenerative diseases. In Parkinson's disease (PD), DAergic neurons in the substantia nigra pars compacta progressively degenerate leading to motor dysfunction. Patients with PD also exhibit non-motor symptoms, including sleep disorder and neuropsychiatric disorders. Thus, it is important to understand the mechanisms that link the molecular circadian clock and brain machinery in the regulation of emotional behaviors and related midbrain DAergic neuronal circuits in healthy and pathological states. This review summarizes the current literature regarding the association between circadian rhythm and mood regulation from a chronobiological perspective, and may provide insight into therapeutic approaches to target psychiatric symptoms in neurodegenerative diseases involving circadian rhythm dysfunction.

The human motor neuron pools receive a dominant slow‐varying common synaptic input

PubMed Central

Negro, Francesco; Yavuz, Utku Şükrü

2016-01-01

Key points Motor neurons in a pool receive both common and independent synaptic inputs, although the proportion and role of their common synaptic input is debated.Classic correlation techniques between motor unit spike trains do not measure the absolute proportion of common input and have limitations as a result of the non‐linearity of motor neurons.We propose a method that for the first time allows an accurate quantification of the absolute proportion of low frequency common synaptic input (<5 Hz) to motor neurons in humans.We applied the proposed method to three human muscles and determined experimentally that they receive a similar large amount (>60%) of common input, irrespective of their different functional and control properties.These results increase our knowledge about the role of common and independent input to motor neurons in force control. Abstract Motor neurons receive both common and independent synaptic inputs. This observation is classically based on the presence of a significant correlation between pairs of motor unit spike trains. The functional significance of different relative proportions of common input across muscles, individuals and conditions is still debated. One of the limitations in our understanding of correlated input to motor neurons is that it has not been possible so far to quantify the absolute proportion of common input with respect to the total synaptic input received by the motor neurons. Indeed, correlation measures of pairs of output spike trains only allow for relative comparisons. In the present study, we report for the first time an approach for measuring the proportion of common input in the low frequency bandwidth (<5 Hz) to a motor neuron pool in humans. This estimate is based on a phenomenological model and the theoretical fitting of the experimental values of coherence between the permutations of groups of motor unit spike trains. We demonstrate the validity of this theoretical estimate with several simulations. Moreover, we applied this method to three human muscles: the abductor digiti minimi, tibialis anterior and vastus medialis. Despite these muscles having different functional roles and control properties, as confirmed by the results of the present study, we estimate that their motor pools receive a similar and large (>60%) proportion of common low frequency oscillations with respect to their total synaptic input. These results suggest that the central nervous system provides a large amount of common input to motor neuron pools, in a similar way to that for muscles with different functional and control properties. PMID:27151459

Paradigms for pharmacological characterization of C. elegans synaptic transmission mutants.

PubMed

Locke, Cody; Berry, Kalen; Kautu, Bwarenaba; Lee, Kyle; Caldwell, Kim; Caldwell, Guy

2008-08-18

The nematode, Caenorhabditis elegans, has become an expedient model for studying neurotransmission. C. elegans is unique among animal models, as the anatomy and connectivity of its nervous system has been determined from electron micrographs and refined by pharmacological assays. In this video, we describe how two complementary neural stimulants, an acetylcholinesterase inhibitor, called aldicarb, and a gamma-aminobutyric acid (GABA) receptor antagonist, called pentylenetetrazole (PTZ), may be employed to specifically characterize signaling at C. elegans neuromuscular junctions (NMJs) and facilitate our understanding of antagonistic neural circuits. Of 302 C. elegans neurons, nineteen GABAergic D-type motor neurons innervate body wall muscles (BWMs), while four GABAergic neurons, called RMEs, innervate head muscles. Conversely, thirty-nine motor neurons express the excitatory neurotransmitter, acetylcholine (ACh), and antagonize GABA transmission at BWMs to coordinate locomotion. The antagonistic nature of GABAergic and cholinergic motor neurons at body wall NMJs was initially determined by laser ablation and later buttressed by aldicarb exposure. Acute aldicarb exposure results in a time-course or dose-responsive paralysis in wild-type worms. Yet, loss of excitatory ACh transmission confers resistance to aldicarb, as less ACh accumulates at worm NMJs, leading to less stimulation of BWMs. Resistance to aldicarb may be observed with ACh-specific or general synaptic function mutants. Consistent with antagonistic GABA and ACh transmission, loss of GABA transmission, or a failure to negatively regulate ACh release, confers hypersensitivity to aldicarb. Although aldicarb exposure has led to the isolation of numerous worm homologs of neurotransmission genes, aldicarb exposure alone cannot efficiently determine prevailing roles for genes and pathways in specific C. elegans motor neurons. For this purpose, we have introduced a complementary experimental approach, which uses PTZ. Neurotransmission mutants display clear phenotypes, distinct from aldicarb-induced paralysis, in response to PTZ. Wild-type worms, as well as mutants with specific inabilities to release or receive ACh, do not show apparent sensitivity to PTZ. However, GABA mutants, as well as general synaptic function mutants, display anterior convulsions in a time-course or dose-responsive manner. Mutants that cannot negatively regulate general neurotransmitter release and, thus, secrete excessive amounts of ACh onto BWMs, become paralyzed on PTZ. The PTZ-induced phenotypes of discrete mutant classes indicate that a complementary approach with aldicarb and PTZ exposure paradigms in C. elegans may accelerate our understanding of neurotransmission. Moreover, videos demonstrating how we perform pharmacological assays should establish consistent methods for C. elegans research.

Induction of human umbilical Wharton's jelly-derived mesenchymal stem cells toward motor neuron-like cells.

PubMed

Bagher, Zohreh; Ebrahimi-Barough, Somayeh; Azami, Mahmoud; Mirzadeh, Hamid; Soleimani, Mansooreh; Ai, Jafar; Nourani, Mohammad Reza; Joghataei, Mohammad Taghi

2015-10-01

The most important property of stem cells from different sources is the capacity to differentiate into various cells and tissue types. However, problems including contamination, normal karyotype, and ethical issues cause many limitations in obtaining and using these cells from different sources. The cells in Wharton's jelly region of umbilical cord represent a pool source of primitive cells with properties of mesenchymal stem cells (MSCs). The aim of this study was to determine the potential of human Wharton's jelly-derived mesenchymal stem cells (WJMSCs) for differentiation to motor neuron cells. WJMSCs were induced to differentiate into motor neuron-like cells by using different signaling molecules and neurotrophic factors in vitro. Differentiated neurons were then characterized for expression of motor neuron markers including nestin, PAX6, NF-H, Islet 1, HB9, and choline acetyl transferase (ChAT) by quantitative reverse transcription PCR and immunocytochemistry. Our results showed that differentiated WJMSCs could significantly express motor neuron biomarkers in RNA and protein levels 15 d post induction. These results suggested that WJMSCs can differentiate to motor neuron-like cells and might provide a potential source in cell therapy for neurodegenerative disease.

Specific Retrograde Transduction of Spinal Motor Neurons Using Lentiviral Vectors Targeted to Presynaptic NMJ Receptors

PubMed Central

Eleftheriadou, I; Trabalza, A; Ellison, SM; Gharun, K; Mazarakis, ND

2014-01-01

To understand how receptors are involved in neuronal trafficking and to be able to utilize them for specific targeting via the peripheral route would be of great benefit. Here, we describe the generation of novel lentiviral vectors with tropism to motor neurons that were made by coexpressing onto the lentiviral surface a fusogenic glycoprotein (mutated sindbis G) and an antibody against a cell-surface receptor (Thy1.1, p75NTR, or coxsackievirus and adenovirus receptor) on the presynaptic terminal of the neuromuscular junction. These vectors exhibit binding specificity and efficient transduction of receptor positive cell lines and primary motor neurons in vitro. Targeting of each of these receptors conferred to these vectors the capability of being transported retrogradely from the axonal tip, leading to transduction of motor neurons in vitro in compartmented microfluidic cultures. In vivo delivery of coxsackievirus and adenovirus receptor-targeted vectors in leg muscles of mice resulted in predicted patterns of motor neuron labeling in lumbar spinal cord. This opens up the clinical potential of these vectors for minimally invasive administration of central nervous system-targeted therapeutics in motor neuron diseases. PMID:24670531

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.

In Vivo Neuromechanics: Decoding Causal Motor Neuron Behavior with Resulting Musculoskeletal Function.

PubMed

Sartori, Massimo; Yavuz, Utku Ş; Farina, Dario

2017-10-18

Human motor function emerges from the interaction between the neuromuscular and the musculoskeletal systems. Despite the knowledge of the mechanisms underlying neural and mechanical functions, there is no relevant understanding of the neuro-mechanical interplay in the neuro-musculo-skeletal system. This currently represents the major challenge to the understanding of human movement. We address this challenge by proposing a paradigm for investigating spinal motor neuron contribution to skeletal joint mechanical function in the intact human in vivo. We employ multi-muscle spatial sampling and deconvolution of high-density fiber electrical activity to decode accurate α-motor neuron discharges across five lumbosacral segments in the human spinal cord. We use complete α-motor neuron discharge series to drive forward subject-specific models of the musculoskeletal system in open-loop with no corrective feedback. We perform validation tests where mechanical moments are estimated with no knowledge of reference data over unseen conditions. This enables accurate blinded estimation of ankle function purely from motor neuron information. Remarkably, this enables observing causal associations between spinal motor neuron activity and joint moment control. We provide a new class of neural data-driven musculoskeletal modeling formulations for bridging between movement neural and mechanical levels in vivo with implications for understanding motor physiology, pathology, and recovery.

The DcpS inhibitor RG3039 improves motor function in SMA mice

PubMed Central

Van Meerbeke, James P.; Gibbs, Rebecca M.; Plasterer, Heather L.; Miao, Wenyan; Feng, Zhihua; Lin, Ming-Yi; Rucki, Agnieszka A.; Wee, Claribel D.; Xia, Bing; Sharma, Shefali; Jacques, Vincent; Li, Darrick K.; Pellizzoni, Livio; Rusche, James R.; Ko, Chien-Ping; Sumner, Charlotte J.

2013-01-01

Spinal muscular atrophy (SMA) is caused by mutations of the survival motor neuron 1 (SMN1) gene, retention of the survival motor neuron 2 (SMN2) gene and insufficient expression of full-length survival motor neuron (SMN) protein. Quinazolines increase SMN2 promoter activity and inhibit the ribonucleic acid scavenger enzyme DcpS. The quinazoline derivative RG3039 has advanced to early phase clinical trials. In preparation for efficacy studies in SMA patients, we investigated the effects of RG3039 in severe SMA mice. Here, we show that RG3039 distributed to central nervous system tissues where it robustly inhibited DcpS enzyme activity, but minimally activated SMN expression or the assembly of small nuclear ribonucleoproteins. Nonetheless, treated SMA mice showed a dose-dependent increase in survival, weight and motor function. This was associated with improved motor neuron somal and neuromuscular junction synaptic innervation and function and increased muscle size. RG3039 also enhanced survival of conditional SMA mice in which SMN had been genetically restored to motor neurons. As this systemically delivered drug may have therapeutic benefits that extend beyond motor neurons, it could act additively with SMN-restoring therapies delivered directly to the central nervous system such as antisense oligonucleotides or gene therapy. PMID:23727836

Expression analysis of the N-Myc downstream-regulated gene 1 indicates that myelinating Schwann cells are the primary disease target in hereditary motor and sensory neuropathy-Lom.

PubMed

Berger, Philipp; Sirkowski, Erich E; Scherer, Steven S; Suter, Ueli

2004-11-01

Mutations in the gene encoding N-myc downstream-regulated gene-1 (NDRG1) lead to truncations of the encoded protein and are associated with an autosomal recessive demyelinating neuropathy--hereditary motor and sensory neuropathy-Lom. NDRG1 protein is highly expressed in peripheral nerve and is localized in the cytoplasm of myelinating Schwann cells, including the paranodes and Schmidt-Lanterman incisures. In contrast, sensory and motor neurons as well as their axons lack NDRG1. NDRG1 mRNA levels in developing and injured adult sciatic nerves parallel those of myelin-related genes, indicating that the expression of NDRG1 in myelinating Schwann cells is regulated by axonal interactions. Oligodendrocytes also express NDRG1, and the subtle CNS deficits of affected patients may result from a lack of NDRG1 in these cells. Our data predict that the loss of NDRG1 leads to a Schwann cell autonomous phenotype resulting in demyelination, with secondary axonal loss.

IGF-1 delivery to CNS attenuates motor neuron cell death but does not improve motor function in type III SMA mice.

PubMed

Tsai, Li-Kai; Chen, Yi-Chun; Cheng, Wei-Cheng; Ting, Chen-Hung; Dodge, James C; Hwu, Wuh-Liang; Cheng, Seng H; Passini, Marco A

2012-01-01

The efficacy of administering a recombinant adeno-associated virus (AAV) vector encoding human IGF-1 (AAV2/1-hIGF-1) into the deep cerebellar nucleus (DCN) of a type III SMA mouse model was evaluated. High levels of IGF-1 transcripts and protein were detected in the spinal cord at 2 months post-injection demonstrating that axonal connections between the cerebellum and spinal cord were able to act as conduits for the viral vector and protein to the spinal cord. Mice treated with AAV2/1-hIGF-1 and analyzed 8 months later showed changes in endogenous Bax and Bcl-xl levels in spinal cord motor neurons that were consistent with IGF-1-mediated anti-apoptotic effects on motor neurons. However, although AAV2/1-hIGF-1 treatment reduced the extent of motor neuron cell death, the majority of rescued motor neurons were non-functional, as they lacked axons that innervated the muscles. Furthermore, treated SMA mice exhibited abnormal muscle fibers, aberrant neuromuscular junction structure, and impaired performance on motor function tests. These data indicate that although CNS-directed expression of IGF-1 could reduce motor neuron cell death, this did not translate to improvements in motor function in an adult mouse model of type III SMA. Copyright © 2011 Elsevier Inc. All rights reserved.

Distinct alterations in motor & reward seeking behavior are dependent on the gestational age of exposure to LPS-induced maternal immune activation.

PubMed

Straley, Megan E; Van Oeffelen, Wesley; Theze, Sarah; Sullivan, Aideen M; O'Mahony, Siobhain M; Cryan, John F; O'Keeffe, Gerard W

2017-07-01

The dopaminergic system is involved in motivation, reward and the associated motor activities. Mesodiencephalic dopaminergic neurons in the ventral tegmental area (VTA) regulate motivation and reward, whereas those in the substantia nigra (SN) are essential for motor control. Defective VTA dopaminergic transmission has been implicated in schizophrenia, drug addiction and depression whereas dopaminergic neurons in the SN are lost in Parkinson's disease. Maternal immune activation (MIA) leading to in utero inflammation has been proposed to be a risk factor for these disorders, yet it is unclear how this stimulus can lead to the diverse disturbances in dopaminergic-driven behaviors that emerge at different stages of life in affected offspring. Here we report that gestational age is a critical determinant of the subsequent alterations in dopaminergic-driven behavior in rat offspring exposed to lipopolysaccharide (LPS)-induced MIA. Behavioral analysis revealed that MIA on gestational day 16 but not gestational day 12 resulted in biphasic impairments in motor behavior. Specifically, motor impairments were evident in early life, which were resolved by adolescence, but subsequently re-emerged in adulthood. In contrast, reward seeking behaviors were altered in offspring exposed MIA on gestational day 12. These changes were not due to a loss of dopaminergic neurons per se in the postnatal period, suggesting that they reflect functional changes in dopaminergic systems. This highlights that gestational age may be a key determinant of how MIA leads to distinct alterations in dopaminergic-driven behavior across the lifespan of affected offspring. Copyright © 2016 Elsevier Inc. All rights reserved.

Motor Neuron Rescue in Spinal Muscular Atrophy Mice Demonstrates That Sensory-Motor Defects Are a Consequence, Not a Cause, of Motor Neuron Dysfunction

PubMed Central

Gogliotti, Rocky G.; Quinlan, Katharina A.; Barlow, Courtenay B.; Heier, Christopher R.; Heckman, C. J.

2012-01-01

The loss of motor neurons (MNs) is a hallmark of the neuromuscular disease spinal muscular atrophy (SMA); however, it is unclear whether this phenotype autonomously originates within the MN. To address this question, we developed an inducible mouse model of severe SMA that has perinatal lethality, decreased motor function, motor unit pathology, and hyperexcitable MNs. Using an Hb9-Cre allele, we increased Smn levels autonomously within MNs and demonstrate that MN rescue significantly improves all phenotypes and pathologies commonly described in SMA mice. MN rescue also corrects hyperexcitability in SMA motor neurons and prevents sensory-motor synaptic stripping. Survival in MN-rescued SMA mice is extended by only 5 d, due in part to failed autonomic innervation of the heart. Collectively, this work demonstrates that the SMA phenotype autonomously originates in MNs and that sensory-motor synapse loss is a consequence, not a cause, of MN dysfunction. PMID:22423102

Proneurotrophin-3 promotes cell cycle withdrawal of developing cerebellar granule cell progenitors via the p75 neurotrophin receptor.

PubMed

Zanin, Juan Pablo; Abercrombie, Elizabeth; Friedman, Wilma J

2016-07-19

Cerebellar granule cell progenitors (GCP) proliferate extensively in the external granule layer (EGL) of the developing cerebellum prior to differentiating and migrating. Mechanisms that regulate the appropriate timing of cell cycle withdrawal of these neuronal progenitors during brain development are not well defined. The p75 neurotrophin receptor (p75(NTR)) is highly expressed in the proliferating GCPs, but is downregulated once the cells leave the cell cycle. This receptor has primarily been characterized as a death receptor for its ability to induce neuronal apoptosis following injury. Here we demonstrate a novel function for p75(NTR) in regulating proper cell cycle exit of neuronal progenitors in the developing rat and mouse EGL, which is stimulated by proNT3. In the absence of p75(NTR), GCPs continue to proliferate beyond their normal period, resulting in a larger cerebellum that persists into adulthood, with consequent motor deficits.

Muscle Mitochondrial Uncoupling Dismantles Neuromuscular Junction and Triggers Distal Degeneration of Motor Neurons

PubMed Central

Dupuis, Luc; Gonzalez de Aguilar, Jose-Luis; Echaniz-Laguna, Andoni; Eschbach, Judith; Rene, Frédérique; Oudart, Hugues; Halter, Benoit; Huze, Caroline; Schaeffer, Laurent; Bouillaud, Frédéric; Loeffler, Jean-Philippe

2009-01-01

Background Amyotrophic lateral sclerosis (ALS), the most frequent adult onset motor neuron disease, is associated with hypermetabolism linked to defects in muscle mitochondrial energy metabolism such as ATP depletion and increased oxygen consumption. It remains unknown whether muscle abnormalities in energy metabolism are causally involved in the destruction of neuromuscular junction (NMJ) and subsequent motor neuron degeneration during ALS. Methodology/Principal Findings We studied transgenic mice with muscular overexpression of uncoupling protein 1 (UCP1), a potent mitochondrial uncoupler, as a model of muscle restricted hypermetabolism. These animals displayed age-dependent deterioration of the NMJ that correlated with progressive signs of denervation and a mild late-onset motor neuron pathology. NMJ regeneration and functional recovery were profoundly delayed following injury of the sciatic nerve and muscle mitochondrial uncoupling exacerbated the pathology of an ALS animal model. Conclusions/Significance These findings provide the proof of principle that a muscle restricted mitochondrial defect is sufficient to generate motor neuron degeneration and suggest that therapeutic strategies targeted at muscle metabolism might prove useful for motor neuron diseases. PMID:19404401

Motor control in a Drosophila taste circuit

PubMed Central

Gordon, Michael D.; Scott, Kristin

2009-01-01

Tastes elicit innate behaviors critical for directing animals to ingest nutritious substances and reject toxic compounds, but the neural basis of these behaviors is not understood. Here, we use a neural silencing screen to identify neurons required for a simple Drosophila taste behavior, and characterize a neural population that controls a specific subprogram of this behavior. By silencing and activating subsets of the defined cell population, we identify the neurons involved in the taste behavior as a pair of motor neurons located in the subesophageal ganglion (SOG). The motor neurons are activated by sugar stimulation of gustatory neurons and inhibited by bitter compounds; however, experiments utilizing split-GFP detect no direct connections between the motor neurons and primary sensory neurons, indicating that further study will be necessary to elucidate the circuitry bridging these populations. Combined, these results provide a general strategy and a valuable starting point for future taste circuit analysis. PMID:19217375

Signal, noise, and variation in neural and sensory-motor latency

PubMed Central

Lee, Joonyeol; Joshua, Mati; Medina, Javier F.; Lisberger, Stephen G.

2016-01-01

Analysis of the neural code for sensory-motor latency in smooth pursuit eye movements reveals general principles of neural variation and the specific origin of motor latency. The trial-by-trial variation in neural latency in MT comprises: a shared component expressed as neuron-neuron latency correlations; and an independent component that is local to each neuron. The independent component arises heavily from fluctuations in the underlying probability of spiking with an unexpectedly small contribution from the stochastic nature of spiking itself. The shared component causes the latency of single neuron responses in MT to be weakly predictive of the behavioral latency of pursuit. Neural latency deeper in the motor system is more strongly predictive of behavioral latency. A model reproduces both the variance of behavioral latency and the neuron-behavior latency correlations in MT if it includes realistic neural latency variation, neuron-neuron latency correlations in MT, and noisy gain control downstream from MT. PMID:26971946

Neuronal matrix metalloproteinase-9 is a determinant of selective neurodegeneration

PubMed Central

Kaplan, Artem; Spiller, Krista J.; Towne, Christopher; Kanning, Kevin C.; Choe, Ginn T.; Geber, Adam; Akay, Turgay; Aebischer, Patrick; Henderson, Christopher E.

2018-01-01

SUMMARY Selective neuronal loss is the hallmark of neurodegenerative diseases. In patients with amyotrophic lateral sclerosis (ALS), most motor neurons die but those innervating extraocular, pelvic sphincter and slow limb muscles exhibit selective resistance. We identified 18 genes that show >10-fold differential expression between resistant and vulnerable motor neurons. One of these, matrix metalloproteinase-9 (MMP-9), is expressed only by fast motor neurons, which are selectively vulnerable. In ALS model mice expressing mutant SOD1, reduction of MMP-9 function using gene ablation, viral gene therapy or pharmacological inhibition significantly delayed muscle denervation. In the presence of mutant SOD1, MMP-9 expressed by fast motor neurons themselves enhances activation of ER stress and is sufficient to trigger axonal die-back. These findings define MMP-9 as a candidate therapeutic target for ALS. The molecular basis of neuronal diversity thus provides novel insights into mechanisms of selective vulnerability to neurodegeneration. PMID:24462097

Omega-3 Hastens and Omega-6 Delays the Progression of Neuropathology in a Murine Model of Familial ALS.

PubMed

Boumil, Edward F; Vohnoutka, Rishel Brenna; Liu, Yuguan; Lee, Sangmook; Shea, Thomas B

2017-01-01

Amyotrophic lateral sclerosis (ALS) is a progressive disease of motor neurons that has no cure or effective treatment. Any approach that could sustain minor motor function during terminal stages would improve quality of life. We examined the impact of omega-3 (Ω-3) and Ω-6, on motor neuron function in mice expressing mutant human superoxide dismutase-1 (SOD-1), which dominantly confers familial ALS and induces a similar sequence of motor neuron decline and eventual death when expressed in mice. Mice received standard diets supplemented with equivalent amounts of Ω-3 and Ω-6 or a 10x increase in Ω-6 with no change in Ω-3 commencing at 4 weeks of age. Motor function and biochemical/histological parameters were assayed by standard methodologies. Supplementation with equivalent Ω-3 and Ω-6 hastened motor neuron pathology and death, while 10x Ω-6 with no change in Ω-3 significantly delayed motor neuron pathology, including preservation of minor motor neuron function during the terminal stage. In the absence of a cure or treatment, affected individuals may resort to popular nutritional supplements such as Ω-3 as a form of "self-medication". However, our findings and those of other laboratories indicate that such an approach could be harmful. Our findings suggest that a critical balance of Ω-6 and Ω-3 may temporarily preserve motor neuron function during the terminal stages of ALS, which could provide a substantial improvement in quality of life for affected individuals and their caregivers.

Modeling Protein Aggregation and the Heat Shock Response in ALS iPSC-Derived Motor Neurons.

PubMed

Seminary, Emily R; Sison, Samantha L; Ebert, Allison D

2018-01-01

Amyotrophic lateral sclerosis (ALS) is a devastating neurodegenerative disorder caused by the selective loss of the upper and lower motor neurons. Only 10% of all cases are caused by a mutation in one of the two dozen different identified genes, while the remaining 90% are likely caused by a combination of as yet unidentified genetic and environmental factors. Mutations in C9orf72, SOD1 , or TDP-43 are the most common causes of familial ALS, together responsible for at least 60% of these cases. Remarkably, despite the large degree of heterogeneity, all cases of ALS have protein aggregates in the brain and spinal cord that are immunopositive for SOD1, TDP-43, OPTN, and/or p62. These inclusions are normally prevented and cleared by heat shock proteins (Hsps), suggesting that ALS motor neurons have an impaired ability to induce the heat shock response (HSR). Accordingly, there is evidence of decreased induction of Hsps in ALS mouse models and in human post-mortem samples compared to unaffected controls. However, the role of Hsps in protein accumulation in human motor neurons has not been fully elucidated. Here, we generated motor neuron cultures from human induced pluripotent stem cell (iPSC) lines carrying mutations in SOD1, TDP-43 , or C9orf72 . In this study, we provide evidence that despite a lack of overt motor neuron loss, there is an accumulation of insoluble, aggregation-prone proteins in iPSC-derived motor neuron cultures but that content and levels vary with genetic background. Additionally, although iPSC-derived motor neurons are generally capable of inducing the HSR when exposed to a heat stress, protein aggregation itself is not sufficient to induce the HSR or stress granule formation. We therefore conclude that ALS iPSC-derived motor neurons recapitulate key early pathological features of the disease and fail to endogenously upregulate the HSR in response to increased protein burden.

Modeling Protein Aggregation and the Heat Shock Response in ALS iPSC-Derived Motor Neurons

PubMed Central

Seminary, Emily R.; Sison, Samantha L.; Ebert, Allison D.

2018-01-01

Amyotrophic lateral sclerosis (ALS) is a devastating neurodegenerative disorder caused by the selective loss of the upper and lower motor neurons. Only 10% of all cases are caused by a mutation in one of the two dozen different identified genes, while the remaining 90% are likely caused by a combination of as yet unidentified genetic and environmental factors. Mutations in C9orf72, SOD1, or TDP-43 are the most common causes of familial ALS, together responsible for at least 60% of these cases. Remarkably, despite the large degree of heterogeneity, all cases of ALS have protein aggregates in the brain and spinal cord that are immunopositive for SOD1, TDP-43, OPTN, and/or p62. These inclusions are normally prevented and cleared by heat shock proteins (Hsps), suggesting that ALS motor neurons have an impaired ability to induce the heat shock response (HSR). Accordingly, there is evidence of decreased induction of Hsps in ALS mouse models and in human post-mortem samples compared to unaffected controls. However, the role of Hsps in protein accumulation in human motor neurons has not been fully elucidated. Here, we generated motor neuron cultures from human induced pluripotent stem cell (iPSC) lines carrying mutations in SOD1, TDP-43, or C9orf72. In this study, we provide evidence that despite a lack of overt motor neuron loss, there is an accumulation of insoluble, aggregation-prone proteins in iPSC-derived motor neuron cultures but that content and levels vary with genetic background. Additionally, although iPSC-derived motor neurons are generally capable of inducing the HSR when exposed to a heat stress, protein aggregation itself is not sufficient to induce the HSR or stress granule formation. We therefore conclude that ALS iPSC-derived motor neurons recapitulate key early pathological features of the disease and fail to endogenously upregulate the HSR in response to increased protein burden. PMID:29515358

Distribution and ultrastructure of dopaminergic neurons in the dorsal motor nucleus of the vagus projecting to the stomach of the rat.

PubMed

Hayakawa, Tetsu; Takanaga, Akinori; Tanaka, Koichi; Maeda, Seishi; Seki, Makoto

2004-04-23

Almost all parasympathetic preganglionic motor neurons contain acetylcholine, whereas quite a few motor neurons in the dorsal motor nucleus of the vagus (DMV) contain dopamine. We determined the distribution and ultrastructure of these dopaminergic neurons with double-labeling immunohistochemistry for tyrosine hydroxylase (TH) and the retrograde tracer cholera toxin subunit b (CTb) following its injection into the stomach. A few TH-immunoreactive (TH-ir) neurons were found in the rostral half of the DMV, while a moderate number of these neurons were found in the caudal half. Most of the TH-ir neurons (78.4%) were double-labeled for CTb in the half of the DMV caudal to the area postrema, but only a few TH-ir neurons (5.5%) were double-labeled in the rostral half. About 20% of gastric motor neurons showed TH-immunoreactivity in the caudal half of the DMV, but only 0.3% were TH-ir in the rostral half. In all gastric motor neurons, 8.1% were double-labeled for TH. The ultrastructure of the TH-ir neurons in the caudal DMV was determined with immuno-gold-silver labeling. The TH-ir neurons were small (20.4 x 12.4 microm), round or oval, and contained numerous mitochondria, many free ribosomes, several Golgi apparatuses, a round nucleus and a few Nissl bodies. The average number of axosomatic terminals per section was 4.0. More than half of them contained round synaptic vesicles and made asymmetric synaptic contacts (Gray's type I). Most of the axodendritic terminals contacting TH-ir dendrites were Gray's type I (90%), but a few contained pleomorphic vesicles and made symmetric synaptic contacts (Gray's type II).

Transcriptomics of aged Drosophila motor neurons reveals a matrix metalloproteinase that impairs motor function.

PubMed

Azpurua, Jorge; Mahoney, Rebekah E; Eaton, Benjamin A

2018-04-01

The neuromuscular junction (NMJ) is responsible for transforming nervous system signals into motor behavior and locomotion. In the fruit fly Drosophila melanogaster, an age-dependent decline in motor function occurs, analogous to the decline experienced in mice, humans, and other mammals. The molecular and cellular underpinnings of this decline are still poorly understood. By specifically profiling the transcriptome of Drosophila motor neurons across age using custom microarrays, we found that the expression of the matrix metalloproteinase 1 (dMMP1) gene reproducibly increased in motor neurons in an age-dependent manner. Modulation of physiological aging also altered the rate of dMMP1 expression, validating dMMP1 expression as a bona fide aging biomarker for motor neurons. Temporally controlled overexpression of dMMP1 specifically in motor neurons was sufficient to induce deficits in climbing behavior and cause a decrease in neurotransmitter release at neuromuscular synapses. These deficits were reversible if the dMMP1 expression was shut off again immediately after the onset of motor dysfunction. Additionally, repression of dMMP1 enzymatic activity via overexpression of a tissue inhibitor of metalloproteinases delayed the onset of age-dependent motor dysfunction. MMPs are required for proper tissue architecture during development. Our results support the idea that matrix metalloproteinase 1 is acting as a downstream effector of antagonistic pleiotropy in motor neurons and is necessary for proper development, but deleterious when reactivated at an advanced age. © 2018 The Authors. Aging Cell published by the Anatomical Society and John Wiley & Sons Ltd.

Riluzole increases the rate of glucose transport in L6 myotubes and NSC-34 motor neuron-like cells via AMPK pathway activation.

PubMed

Daniel, Bareket; Green, Omer; Viskind, Olga; Gruzman, Arie

2013-09-01

Riluzole is the only approved ALS drug. Riluzole influences several cellular pathways, but its exact mechanism of action remains unclear. Our goal was to study the drug's influence on the glucose transport rate in two ALS relevant cell types, neurons and myotubes. Stably transfected wild-type or mutant G93A human SOD1 NSC-34 motor neuron-like cells and rat L6 myotubes were exposed to riluzole. The rate of glucose uptake, translocation of glucose transporters to the cell's plasma membrane and the main glucose transport regulatory proteins' phosphorylation levels were measured. We found that riluzole increases the glucose transport rate and up-regulates the translocation of glucose transporters to plasma membrane in both types of cells. Riluzole leads to AMPK phosphorylation and to the phosphorylation of its downstream target, AS-160. In conclusion, increasing the glucose transport rate in ALS affected cells might be one of the mechanisms of riluzole's therapeutic effect. These findings can be used to rationally design and synthesize novel anti-ALS drugs that modulate glucose transport in neurons and skeletal muscles.

Decreased microRNA levels lead to deleterious increases in neuronal M2 muscarinic receptors in Spinal Muscular Atrophy models

PubMed Central

O'Hern, Patrick J; do Carmo G. Gonçalves, Inês; Brecht, Johanna; López Soto, Eduardo Javier; Simon, Jonah; Chapkis, Natalie; Lipscombe, Diane; Kye, Min Jeong; Hart, Anne C

2017-01-01

Spinal Muscular Atrophy (SMA) is caused by diminished Survival of Motor Neuron (SMN) protein, leading to neuromuscular junction (NMJ) dysfunction and spinal motor neuron (MN) loss. Here, we report that reduced SMN function impacts the action of a pertinent microRNA and its mRNA target in MNs. Loss of the C. elegans SMN ortholog, SMN-1, causes NMJ defects. We found that increased levels of the C. elegans Gemin3 ortholog, MEL-46, ameliorates these defects. Increased MEL-46 levels also restored perturbed microRNA (miR-2) function in smn-1(lf) animals. We determined that miR-2 regulates expression of the C. elegans M2 muscarinic receptor (m2R) ortholog, GAR-2. GAR-2 loss ameliorated smn-1(lf) and mel-46(lf) synaptic defects. In an SMA mouse model, m2R levels were increased and pharmacological inhibition of m2R rescued MN process defects. Collectively, these results suggest decreased SMN leads to defective microRNA function via MEL-46 misregulation, followed by increased m2R expression, and neuronal dysfunction in SMA. DOI: http://dx.doi.org/10.7554/eLife.20752.001 PMID:28463115

Motor unit recruitment by size does not provide functional advantages for motor performance

PubMed Central

Dideriksen, Jakob L; Farina, Dario

2013-01-01

It is commonly assumed that the orderly recruitment of motor units by size provides a functional advantage for the performance of movements compared with a random recruitment order. On the other hand, the excitability of a motor neuron depends on its size and this is intrinsically linked to its innervation number. A range of innervation numbers among motor neurons corresponds to a range of sizes and thus to a range of excitabilities ordered by size. Therefore, if the excitation drive is similar among motor neurons, the recruitment by size is inevitably due to the intrinsic properties of motor neurons and may not have arisen to meet functional demands. In this view, we tested the assumption that orderly recruitment is necessarily beneficial by determining if this type of recruitment produces optimal motor output. Using evolutionary algorithms and without any a priori assumptions, the parameters of neuromuscular models were optimized with respect to several criteria for motor performance. Interestingly, the optimized model parameters matched well known neuromuscular properties, but none of the optimization criteria determined a consistent recruitment order by size unless this was imposed by an association between motor neuron size and excitability. Further, when the association between size and excitability was imposed, the resultant model of recruitment did not improve the motor performance with respect to the absence of orderly recruitment. A consistent observation was that optimal solutions for a variety of criteria of motor performance always required a broad range of innervation numbers in the population of motor neurons, skewed towards the small values. These results indicate that orderly recruitment of motor units in itself does not provide substantial functional advantages for motor control. Rather, the reason for its near-universal presence in human movements is that motor functions are optimized by a broad range of innervation numbers. PMID:24144879

Motor unit recruitment by size does not provide functional advantages for motor performance.

PubMed

Dideriksen, Jakob L; Farina, Dario

2013-12-15

It is commonly assumed that the orderly recruitment of motor units by size provides a functional advantage for the performance of movements compared with a random recruitment order. On the other hand, the excitability of a motor neuron depends on its size and this is intrinsically linked to its innervation number. A range of innervation numbers among motor neurons corresponds to a range of sizes and thus to a range of excitabilities ordered by size. Therefore, if the excitation drive is similar among motor neurons, the recruitment by size is inevitably due to the intrinsic properties of motor neurons and may not have arisen to meet functional demands. In this view, we tested the assumption that orderly recruitment is necessarily beneficial by determining if this type of recruitment produces optimal motor output. Using evolutionary algorithms and without any a priori assumptions, the parameters of neuromuscular models were optimized with respect to several criteria for motor performance. Interestingly, the optimized model parameters matched well known neuromuscular properties, but none of the optimization criteria determined a consistent recruitment order by size unless this was imposed by an association between motor neuron size and excitability. Further, when the association between size and excitability was imposed, the resultant model of recruitment did not improve the motor performance with respect to the absence of orderly recruitment. A consistent observation was that optimal solutions for a variety of criteria of motor performance always required a broad range of innervation numbers in the population of motor neurons, skewed towards the small values. These results indicate that orderly recruitment of motor units in itself does not provide substantial functional advantages for motor control. Rather, the reason for its near-universal presence in human movements is that motor functions are optimized by a broad range of innervation numbers.

Abnormal Chloride Homeostasis in the Substancia Nigra Pars Reticulata Contributes to Locomotor Deficiency in a Model of Acute Liver Injury

PubMed Central

Wei, Yan-Yan; Chen, Jing; Dou, Ke-Feng; Wang, Ya-Yun

2013-01-01

Background Altered chloride homeostasis has been thought to be a risk factor for several brain disorders, while less attention has been paid to its role in liver disease. We aimed to analyze the involvement and possible mechanisms of altered chloride homeostasis of GABAergic neurons within the substantia nigra pars reticulata (SNr) in the motor deficit observed in a model of encephalopathy caused by acute liver failure, by using glutamic acid decarboxylase 67 - green fluorescent protein knock-in transgenic mice. Methods Alterations in intracellular chloride concentration in GABAergic neurons within the SNr and changes in the expression of two dominant chloride homeostasis-regulating genes, KCC2 and NKCC1, were evaluated in mice with hypolocomotion due to hepatic encephalopathy (HE). The effects of pharmacological blockade and/or activation of KCC2 and NKCC1 functions with their specific inhibitors and/or activators on the motor activity were assessed. Results In our mouse model of acute liver injury, chloride imaging indicated an increase in local intracellular chloride concentration in SNr GABAergic neurons. In addition, the mRNA and protein levels of KCC2 were reduced, particularly on neuronal cell membranes; in contrast, NKCC1 expression remained unaffected. Furthermore, blockage of KCC2 reduced motor activity in the normal mice and led to a further deteriorated hypolocomotion in HE mice. Blockade of NKCC1 was not able to normalize motor activity in mice with liver failure. Conclusion Our data suggest that altered chloride homeostasis is likely involved in the pathophysiology of hypolocomotion following HE. Drugs aimed at restoring normal chloride homeostasis would be a potential treatment for hepatic failure. PMID:23741482

The up-regulation of IL-6 in DRG and spinal dorsal horn contributes to neuropathic pain following L5 ventral root transection.

PubMed

Wei, Xu-Hong; Na, Xiao-Dong; Liao, Guang-Jie; Chen, Qiu-Ying; Cui, Yu; Chen, Feng-Ying; Li, Yong-Yong; Zang, Ying; Liu, Xian-Guo

2013-03-01

Our previous works have shown that pro-inflammatory cytokine tumor necrosis factor-alpha (TNF-α) plays an important role in neuropathic pain produced by lumber 5 ventral root transection (L5-VRT). In the present work we evaluate the role of interleukin-6 (IL-6), another key inflammatory cytokine, in the L5-VRT model. We found that IL-6 was up-regulated in the ipsilateral L4 and L5 dorsal root ganglian (DRG) neurons and in bilateral lumbar spinal cord following L5-VRT. Double immunofluorescence stainings revealed that in DRGs the increased immunoreactivity (IR) of IL-6 was almost restricted in neuronal cells, while in the spinal dorsal horn IL-6-IR up-regulated in both glial cells (astrocyte and microglia) and neurons. Intrathecal administration of IL-6 neutralizing antibody significantly delayed the induction of mechanical allodynia in bilateral hindpaws after L5-VRT. Furthermore, inhibition of TNF-α synthesis by intraperitoneal thalidomide prevented both mechanical allodynia and the up-regulation of IL-6 in DRGs following L5-VRT. These data suggested that the increased IL-6 in afferent neurons and spinal cord contribute to the development of neuropathic pain following motor fiber injury, and that TNF-α is responsible for the up-regulation of IL-6. Copyright © 2012 Elsevier Inc. All rights reserved.

A Hebbian learning rule gives rise to mirror neurons and links them to control theoretic inverse models.

PubMed

Hanuschkin, A; Ganguli, S; Hahnloser, R H R

2013-01-01

Mirror neurons are neurons whose responses to the observation of a motor act resemble responses measured during production of that act. Computationally, mirror neurons have been viewed as evidence for the existence of internal inverse models. Such models, rooted within control theory, map-desired sensory targets onto the motor commands required to generate those targets. To jointly explore both the formation of mirrored responses and their functional contribution to inverse models, we develop a correlation-based theory of interactions between a sensory and a motor area. We show that a simple eligibility-weighted Hebbian learning rule, operating within a sensorimotor loop during motor explorations and stabilized by heterosynaptic competition, naturally gives rise to mirror neurons as well as control theoretic inverse models encoded in the synaptic weights from sensory to motor neurons. Crucially, we find that the correlational structure or stereotypy of the neural code underlying motor explorations determines the nature of the learned inverse model: random motor codes lead to causal inverses that map sensory activity patterns to their motor causes; such inverses are maximally useful, by allowing the imitation of arbitrary sensory target sequences. By contrast, stereotyped motor codes lead to less useful predictive inverses that map sensory activity to future motor actions. Our theory generalizes previous work on inverse models by showing that such models can be learned in a simple Hebbian framework without the need for error signals or backpropagation, and it makes new conceptual connections between the causal nature of inverse models, the statistical structure of motor variability, and the time-lag between sensory and motor responses of mirror neurons. Applied to bird song learning, our theory can account for puzzling aspects of the song system, including necessity of sensorimotor gating and selectivity of auditory responses to bird's own song (BOS) stimuli.

A Hebbian learning rule gives rise to mirror neurons and links them to control theoretic inverse models

PubMed Central

Hanuschkin, A.; Ganguli, S.; Hahnloser, R. H. R.

2013-01-01

Mirror neurons are neurons whose responses to the observation of a motor act resemble responses measured during production of that act. Computationally, mirror neurons have been viewed as evidence for the existence of internal inverse models. Such models, rooted within control theory, map-desired sensory targets onto the motor commands required to generate those targets. To jointly explore both the formation of mirrored responses and their functional contribution to inverse models, we develop a correlation-based theory of interactions between a sensory and a motor area. We show that a simple eligibility-weighted Hebbian learning rule, operating within a sensorimotor loop during motor explorations and stabilized by heterosynaptic competition, naturally gives rise to mirror neurons as well as control theoretic inverse models encoded in the synaptic weights from sensory to motor neurons. Crucially, we find that the correlational structure or stereotypy of the neural code underlying motor explorations determines the nature of the learned inverse model: random motor codes lead to causal inverses that map sensory activity patterns to their motor causes; such inverses are maximally useful, by allowing the imitation of arbitrary sensory target sequences. By contrast, stereotyped motor codes lead to less useful predictive inverses that map sensory activity to future motor actions. Our theory generalizes previous work on inverse models by showing that such models can be learned in a simple Hebbian framework without the need for error signals or backpropagation, and it makes new conceptual connections between the causal nature of inverse models, the statistical structure of motor variability, and the time-lag between sensory and motor responses of mirror neurons. Applied to bird song learning, our theory can account for puzzling aspects of the song system, including necessity of sensorimotor gating and selectivity of auditory responses to bird's own song (BOS) stimuli. PMID:23801941

Molybdenum deprivation, purine ingestion and an astrocyte-associated motor neurone syndrome in sheep: assumed clinical effects of inosine.

PubMed

Bourke, Ca

2015-03-01

An astrocyte-associated motor neurone syndrome was produced in molybdenum-deprived sheep fed xanthosine. Mo-deprived sheep fed inosine, adenosine or guanosine would be also expected to develop astrocyte-associated motor neurone syndromes, because all these purine nucleosides can act as neuromodulators and all depend on the Mo-associated enzyme xanthine oxidase-dehydrogenase for their catabolism. To investigate the relationship between inosine ingestion and low Mo concentration, eight sheep were fed lucerne chaff with a Mo value <0.10 ppm and the Mo antagonist, sodium tungstate, for 21 weeks, with inosine (35 mg/kg/day) fed for the last 18 of these weeks. This clinical study was uncontrolled. An astrocyte-associated motor neurone syndrome was produced in three sheep 18-27 months later. It was characterised by diaphragmatic, laryngeal, lingual and pharyngeal muscle weakness. The diaphragmatic muscle weakness was the most severe and potentially lethal. These findings suggest that purinergic neuromodulation of respiration, vocalisation and swallowing is different to that of limb movement. The syndrome produced, and assumed to be caused by the treatment given, has not been reported in livestock. A similar syndrome is seen in human motor neurone disease, but not in equine motor neurone disease, and this is consistent with it being an upper, not a lower, motor neurone effect. © 2015 Australian Veterinary Association.

Neurokinin-1 receptor blocker CP-99 994 improved emesis induced by cisplatin via regulating the activity of gastric distention responsive neurons in the dorsal motor nucleus of vagus and enhancing gastric motility in rats.

PubMed

Sun, X; Xu, L; Guo, F; Luo, W; Gao, S; Luan, X

2017-10-01

Nowadays, chemotherapy induced nausea and vomiting (CINV) is still common in patients with cancer. It was reported that substance P mediated CINV via neurokinin-1 (NK 1 ) receptor and antagonists of NK 1 receptor has been proved useful for treating CINV but the mechanism are not fully understood. This study aimed to examine the role of NK 1 receptor blocker, CP-99 994, when administrated into dorsal motor nucleus of vagus (DMNV), on the cisplatin-induced emesis in rats and the possible mechanism. Rats' kaolin intake, food intake, and bodyweight were recorded every day; gastric contraction activity was recorded in conscious rats through a force transducer implanted into the stomach; gastric emptying was monitored using the phenol red method; single unit extracellular firing in the DMNV were recorded. DMNV microinjection of CP-99 994 reduced the changes of increased kaolin consumption and suppressed food intake in cisplatin-treated rats; enhanced the gastric contraction activity dose-dependently in control and cisplatin-treated rats but enhanced gastric emptying only in cisplatin-treated rats; reduced the firing rate of gastric distention inhibited (GD-I) neurons but increased the firing rate of GD excited (GD-E) neurons in the DMNV. The effects of CP-99 994 on gastric motility and neuronal activity were stronger in cisplatin-treated rats than those of control rats. Our results suggested that CP-99 994 could improve emesis induced by cisplatin by regulating gastric motility and gastric related neuronal activity in the DMNV. © 2017 John Wiley & Sons Ltd.

Delayed disease onset and extended survival in the SOD1G93A rat model of amyotrophic lateral sclerosis after suppression of mutant SOD1 in the motor cortex.

PubMed

Thomsen, Gretchen M; Gowing, Genevieve; Latter, Jessica; Chen, Maximus; Vit, Jean-Philippe; Staggenborg, Kevin; Avalos, Pablo; Alkaslasi, Mor; Ferraiuolo, Laura; Likhite, Shibi; Kaspar, Brian K; Svendsen, Clive N

2014-11-19

Sporadic amyotrophic lateral sclerosis (ALS) is a fatal disease with unknown etiology, characterized by a progressive loss of motor neurons leading to paralysis and death typically within 3-5 years of onset. Recently, there has been remarkable progress in understanding inherited forms of ALS in which well defined mutations are known to cause the disease. Rodent models in which the superoxide dismutase-1 (SOD1) mutation is overexpressed recapitulate hallmark signs of ALS in patients. Early anatomical changes in mouse models of fALS are seen in the neuromuscular junctions (NMJs) and lower motor neurons, and selective reduction of toxic mutant SOD1 in the spinal cord and muscle of these models has beneficial effects. Therefore, much of ALS research has focused on spinal motor neuron and NMJ aspects of the disease. Here we show that, in the SOD1(G93A) rat model of ALS, spinal motor neuron loss occurs presymptomatically and before degeneration of ventral root axons and denervation of NMJs. Although overt cell death of corticospinal motor neurons does not occur until disease endpoint, we wanted to establish whether the upper motor neuron might still play a critical role in disease progression. Surprisingly, the knockdown of mutant SOD1 in only the motor cortex of presymptomatic SOD1(G93A) rats through targeted delivery of AAV9-SOD1-shRNA resulted in a significant delay of disease onset, expansion of lifespan, enhanced survival of spinal motor neurons, and maintenance of NMJs. This datum suggests an early dysfunction and thus an important role of the upper motor neuron in this animal model of ALS and perhaps patients with the disease. Copyright © 2014 the authors 0270-6474/14/3415587-14$15.00/0.

Spinal muscular atrophy: Selective motor neuron loss and global defect in the assembly of ribonucleoproteins.

PubMed

Beattie, Christine E; Kolb, Stephen J

2018-08-15

Spinal muscular atrophy is caused by deletions or mutations in the SMN1 gene that result in reduced expression of the SMN protein. The SMN protein is an essential molecular chaperone that is required for the biogenesis of multiple ribonucleoprotein (RNP) complexes including spliceosomal small nuclear RNPs (snRNPs). Reductions in SMN expression result in a reduced abundance of snRNPs and to downstream RNA splicing alterations. SMN is also present in axons and dendrites and appears to have important roles in the formation of neuronal mRNA-protein complexes during development or neuronal repair. Thus, SMA is an exemplar, selective motor neuron disorder that is caused by defects in fundamental RNA processing events. A detailed molecular understanding of how motor neurons fail, and why other neurons do not, in SMA will yield important principals about motor neuron maintenance and neuronal specificity in neurodegenerative diseases. Copyright © 2018 Elsevier B.V. All rights reserved.

Cerebellar defects in a mouse model of juvenile neuronal ceroid lipofuscinosis.

PubMed

Weimer, Jill M; Benedict, Jared W; Getty, Amanda L; Pontikis, Charlie C; Lim, Ming J; Cooper, Jonathan D; Pearce, David A

2009-04-17

Juvenile neuronal ceroid lipofuscinosis (JNCL), or Batten disease, is a neurodegenerative disease resulting from a mutation in CLN3, which presents clinically with visual deterioration, seizures, motor impairments, cognitive decline, hallucinations, loss of circadian rhythm, and premature death in the late-twenties to early-thirties. Using a Cln3 null (Cln3(-/-)) mouse, we report here several deficits in the cerebellum in the absence of Cln3, including cell loss and early onset motor deficits. Surprisingly, early onset glial activation and selective neuronal loss within the mature fastigial pathway of the deep cerebellar nuclei (DCN), a region critical for balance and coordination, are seen in many regions of the Cln3(-/-) cerebellum. Additionally, there is a loss of Purkinje cells (PC) in regions of robust Bergmann glia activation in Cln3(-/-) mice and human JNCL post-mortem cerebellum. Moreover, the Cln3(-/-) cerebellum had a mis-regulation in granule cell proliferation and maintenance of PC dendritic arborization and spine density. Overall, this study defines a novel multi-faceted, early-onset cerebellar disruption in the Cln3 null brain, including glial activation, cell loss, and aberrant cell proliferation and differentiation. These early alterations in the maturation of the cerebellum could underlie some of the motor deficits and pathological changes seen in JNCL patients.

Major Histocompatibility Complex I Expression by Motor Neurons and Its Implication in Amyotrophic Lateral Sclerosis

PubMed Central

Nardo, Giovanni; Trolese, Maria Chiara; Bendotti, Caterina

2016-01-01

Neuronal expression of major histocompatibility complex I (MHCI)-related molecules in adults and during CNS diseases is involved in the synaptic plasticity and axonal regeneration with mechanisms either dependent or independent of their immune functions. Motor neurons are highly responsive in triggering the expression of MHCI molecules during normal aging or following insults and diseases, and this has implications in the synaptic controls, axonal regeneration, and neuromuscular junction stability of these neurons. We recently reported that MHCI and immunoproteasome are strongly activated in spinal motor neurons and their peripheral motor axon in a mouse model of familial amyotrophic lateral sclerosis (ALS) during the course of the disease. This response was prominent in ALS mice with slower disease progression in which the axonal structure and function was better preserved than in fast-progressing mice. This review summarizes and discusses our observations in the light of knowledge about the possible role of MHCI in motor neurons providing additional insight into the pathophysiology of ALS. PMID:27379008

Motor neuron cell-nonautonomous rescue of spinal muscular atrophy phenotypes in mild and severe transgenic mouse models

PubMed Central

Liu, Ying Hsiu; Sahashi, Kentaro; Rigo, Frank; Bennett, C. Frank

2015-01-01

Survival of motor neuron (SMN) deficiency causes spinal muscular atrophy (SMA), but the pathogenesis mechanisms remain elusive. Restoring SMN in motor neurons only partially rescues SMA in mouse models, although it is thought to be therapeutically essential. Here, we address the relative importance of SMN restoration in the central nervous system (CNS) versus peripheral tissues in mouse models using a therapeutic splice-switching antisense oligonucleotide to restore SMN and a complementary decoy oligonucleotide to neutralize its effects in the CNS. Increasing SMN exclusively in peripheral tissues completely rescued necrosis in mild SMA mice and robustly extended survival in severe SMA mice, with significant improvements in vulnerable tissues and motor function. Our data demonstrate a critical role of peripheral pathology in the mortality of SMA mice and indicate that peripheral SMN restoration compensates for its deficiency in the CNS and preserves motor neurons. Thus, SMA is not a cell-autonomous defect of motor neurons in SMA mice. PMID:25583329

Motor-circuit communication matrix from spinal cord to brainstem neurons revealed by developmental origin.

PubMed

Pivetta, Chiara; Esposito, Maria Soledad; Sigrist, Markus; Arber, Silvia

2014-01-30

Accurate motor-task execution relies on continuous comparison of planned and performed actions. Motor-output pathways establish internal circuit collaterals for this purpose. Here we focus on motor collateral organization between spinal cord and upstream neurons in the brainstem. We used a newly developed mouse genetic tool intersectionally with viruses to uncover the connectivity rules of these ascending pathways by capturing the transient expression of neuronal subpopulation determinants. We reveal a widespread and diverse network of spinal dual-axon neurons, with coincident input to forelimb motor neurons and the lateral reticular nucleus (LRN) in the brainstem. Spinal information to the LRN is not segregated by motor pool or neurotransmitter identity. Instead, it is organized according to the developmental domain origin of the progenitor cells. Thus, excerpts of most spinal information destined for action are relayed to supraspinal centers through exquisitely organized ascending connectivity modules, enabling precise communication between command and execution centers of movement. Copyright © 2014 Elsevier Inc. All rights reserved.

Distinct Laterality in Forelimb-Movement Representations of Rat Primary and Secondary Motor Cortical Neurons with Intratelencephalic and Pyramidal Tract Projections.

PubMed

Soma, Shogo; Saiki, Akiko; Yoshida, Junichi; Ríos, Alain; Kawabata, Masanori; Sakai, Yutaka; Isomura, Yoshikazu

2017-11-08

Two distinct motor areas, the primary and secondary motor cortices (M1 and M2), play crucial roles in voluntary movement in rodents. The aim of this study was to characterize the laterality in motor cortical representations of right and left forelimb movements. To achieve this goal, we developed a novel behavioral task, the Right-Left Pedal task, in which a head-restrained male rat manipulates a right or left pedal with the corresponding forelimb. This task enabled us to monitor independent movements of both forelimbs with high spatiotemporal resolution. We observed phasic movement-related neuronal activity (Go-type) and tonic hold-related activity (Hold-type) in isolated unilateral movements. In both M1 and M2, Go-type neurons exhibited bias toward contralateral preference, whereas Hold-type neurons exhibited no bias. The contralateral bias was weaker in M2 than M1. Moreover, we differentiated between intratelencephalic (IT) and pyramidal tract (PT) neurons using optogenetically evoked spike collision in rats expressing channelrhodopsin-2. Even in identified PT and IT neurons, Hold-type neurons exhibited no lateral bias. Go-type PT neurons exhibited bias toward contralateral preference, whereas IT neurons exhibited no bias. Our findings suggest a different laterality of movement representations of M1 and M2, in each of which IT neurons are involved in cooperation of bilateral movements, whereas PT neurons control contralateral movements. SIGNIFICANCE STATEMENT In rodents, the primary and secondary motor cortices (M1 and M2) are involved in voluntary movements via distinct projection neurons: intratelencephalic (IT) neurons and pyramidal tract (PT) neurons. However, it remains unclear whether the two motor cortices (M1 vs M2) and the two classes of projection neurons (IT vs PT) have different laterality of movement representations. We optogenetically identified these neurons and analyzed their functional activity using a novel behavioral task to monitor movements of the right and left forelimbs separately. We found that contralateral bias was reduced in M2 relative to M1, and in IT relative to PT neurons. Our findings suggest that the motor information processing that controls forelimb movement is coordinated by a distinct cell population. Copyright © 2017 the authors 0270-6474/17/3710904-13$15.00/0.

Predominance of Movement Speed Over Direction in Neuronal Population Signals of Motor Cortex: Intracranial EEG Data and A Simple Explanatory Model

PubMed Central

Hammer, Jiří; Pistohl, Tobias; Fischer, Jörg; Kršek, Pavel; Tomášek, Martin; Marusič, Petr; Schulze-Bonhage, Andreas; Aertsen, Ad; Ball, Tonio

2016-01-01

How neuronal activity of motor cortex is related to movement is a central topic in motor neuroscience. Motor-cortical single neurons are more closely related to hand movement velocity than speed, that is, the magnitude of the (directional) velocity vector. Recently, there is also increasing interest in the representation of movement parameters in neuronal population activity, such as reflected in the intracranial EEG (iEEG). We show that in iEEG, contrasting to what has been previously found on the single neuron level, speed predominates over velocity. The predominant speed representation was present in nearly all iEEG signal features, up to the 600–1000 Hz range. Using a model of motor-cortical signals arising from neuronal populations with realistic single neuron tuning properties, we show how this reversal can be understood as a consequence of increasing population size. Our findings demonstrate that the information profile in large population signals may systematically differ from the single neuron level, a principle that may be helpful in the interpretation of neuronal population signals in general, including, for example, EEG and functional magnetic resonance imaging. Taking advantage of the robust speed population signal may help in developing brain–machine interfaces exploiting population signals. PMID:26984895

Regulation Of Hypothalamic Signaling By Tuberoinfundibular Peptide Of 39 Residues Is Critical For The Response To Cold: A Novel Peptidergic Mechanism Of Thermoregulation

PubMed Central

Dimitrov, Eugene L.; Kim, Yoon Yi; Usdin, Ted B.

2012-01-01

Euthermia is critical for mammalian homeostasis. Circuits within the preoptic hypothalamus regulate temperature, with fine control exerted via descending GABAergic inhibition of presympathetic motor neurons that control brown adipose tissue (BAT) thermogenesis and cutaneous vascular tone. The thermoregulatory role of hypothalamic excitatory neurons is less clear. Here we report peptidergic regulation of preoptic glutamatergic neurons that contributes to temperature regulation. Tuberoinfundibular peptide of 39 residues (TIP39) is a ligand for the parathyroid hormone 2 receptor (PTH2R). Both peptide and receptor are abundant in the preoptic hypothalamus. Based on PTH2R and vesicular glutamate transporter 2 (VGlut2) immunolabeling in animals with retrograde tracer injection, PTH2R containing glutamatergic fibers are presynaptic to neurons projecting from the median preoptic nucleus (MnPO) to the dorsomedial hypothalamus. Transneuronal retrograde pathway tracing with pseudorabies virus revealed connectivity between MnPO VGlut2 and PTH2R neurons and BAT. MnPO injection of TIP39 increased body temperature by 2° C for several hours. Mice lacking TIP39 signaling, either because of PTH2R null mutation or brain delivery of a PTH2R antagonist had impaired heat production upon cold exposure, but no change in basal temperature and no impairment in response to a hot environment. Thus, TIP39 appears to act on PTH2Rs present on MnPO glutamatergic terminals to regulate their activation of projection neurons and subsequent sympathetic BAT activation. This excitatory mechanism of heat production appears to be activated on demand, during cold exposure, and parallels the tonic inhibitory GABAergic control of body temperature. PMID:22159128

Diversity of layer 5 projection neurons in the mouse motor cortex

PubMed Central

Oswald, Manfred J.; Tantirigama, Malinda L. S.; Sonntag, Ivo; Hughes, Stephanie M.; Empson, Ruth M.

2013-01-01

In the primary motor cortex (M1), layer 5 projection neurons signal directly to distant motor structures to drive movement. Despite their pivotal position and acknowledged diversity these neurons are traditionally separated into broad commissural and corticofugal types, and until now no attempt has been made at resolving the basis for their diversity. We therefore probed the electrophysiological and morphological properties of retrogradely labeled M1 corticospinal (CSp), corticothalamic (CTh), and commissural projecting corticostriatal (CStr) and corticocortical (CC) neurons. An unsupervised cluster analysis established at least four phenotypes with additional differences between lumbar and cervical projecting CSp neurons. Distinguishing parameters included the action potential (AP) waveform, firing behavior, the hyperpolarisation-activated sag potential, sublayer position, and soma and dendrite size. CTh neurons differed from CSp neurons in showing spike frequency acceleration and a greater sag potential. CStr neurons had the lowest AP amplitude and maximum rise rate of all neurons. Temperature influenced spike train behavior in corticofugal neurons. At 26°C CTh neurons fired bursts of APs more often than CSp neurons, but at 36°C both groups fired regular APs. Our findings provide reliable phenotypic fingerprints to identify distinct M1 projection neuron classes as a tool to understand their unique contributions to motor function. PMID:24137110

Generation of Spinal Motor Neurons from Human Pluripotent Stem Cells.

PubMed

Santos, David P; Kiskinis, Evangelos

2017-01-01

Human embryonic stem cells (ESCs) are characterized by their unique ability to self-renew indefinitely, as well as to differentiate into any cell type of the human body. Induced pluripotent stem cells (iPSCs) share these salient characteristics with ESCs and can easily be generated from any given individual by reprogramming somatic cell types such as fibroblasts or blood cells. The spinal motor neuron (MN) is a specialized neuronal subtype that synapses with muscle to control movement. Here, we present a method to generate functional, postmitotic, spinal motor neurons through the directed differentiation of ESCs and iPSCs by the use of small molecules. These cells can be utilized to study the development and function of human motor neurons in healthy and disease states.

State-changes in the swimmeret system: a neural circuit that drives locomotion

PubMed Central

Tschuluun, N.; Hall, W. M.; Mulloney, B.

2009-01-01

Summary The crayfish swimmeret system undergoes transitions between a silent state and an active state. In the silent state, no patterned firing occurs in swimmeret motor neurons. In the active state, bursts of spikes in power stroke motor neurons alternate periodically with bursts of spikes in return stroke motor neurons. In preparations of the isolated crayfish central nervous system (CNS), the temporal structures of motor patterns expressed in the active state are similar to those expressed by the intact animal. These transitions can occur spontaneously, in response to stimulation of command neurons, or in response to application of neuromodulators and transmitter analogues. We used single-electrode voltage clamp of power-stroke exciter and return-stroke exciter motor neurons to study changes in membrane currents during spontaneous transitions and during transitions caused by bath-application of carbachol or octopamine (OA). Spontaneous transitions from silence to activity were marked by the appearance of a standing inward current and periodic outward currents in both types of motor neurons. Bath-application of carbachol also led to the development of these currents and activation of the system. Using low Ca2+–high Mg2+ saline to block synaptic transmission, we found that the carbachol-induced inward current included a direct response by the motor neuron and an indirect component. Spontaneous transitions from activity to silence were marked by disappearance of the standing inward current and the periodic outward currents. Bath-application of OA led promptly to the disappearance of both currents, and silenced the system. OA also acted directly on both types of motor neurons to cause a hyperpolarizing outward current that would contribute to silencing the system. PMID:19880720

State-changes in the swimmeret system: a neural circuit that drives locomotion.

PubMed

Tschuluun, N; Hall, W M; Mulloney, B

2009-11-01

The crayfish swimmeret system undergoes transitions between a silent state and an active state. In the silent state, no patterned firing occurs in swimmeret motor neurons. In the active state, bursts of spikes in power stroke motor neurons alternate periodically with bursts of spikes in return stroke motor neurons. In preparations of the isolated crayfish central nervous system (CNS), the temporal structures of motor patterns expressed in the active state are similar to those expressed by the intact animal. These transitions can occur spontaneously, in response to stimulation of command neurons, or in response to application of neuromodulators and transmitter analogues. We used single-electrode voltage clamp of power-stroke exciter and return-stroke exciter motor neurons to study changes in membrane currents during spontaneous transitions and during transitions caused by bath-application of carbachol or octopamine (OA). Spontaneous transitions from silence to activity were marked by the appearance of a standing inward current and periodic outward currents in both types of motor neurons. Bath-application of carbachol also led to the development of these currents and activation of the system. Using low Ca(2+)-high Mg(2+) saline to block synaptic transmission, we found that the carbachol-induced inward current included a direct response by the motor neuron and an indirect component. Spontaneous transitions from activity to silence were marked by disappearance of the standing inward current and the periodic outward currents. Bath-application of OA led promptly to the disappearance of both currents, and silenced the system. OA also acted directly on both types of motor neurons to cause a hyperpolarizing outward current that would contribute to silencing the system.

Loss of MeCP2 in Parvalbumin-and Somatostatin-Expressing Neurons in Mice Leads to Distinct Rett Syndrome-like Phenotypes.

PubMed

Ito-Ishida, Aya; Ure, Kerstin; Chen, Hongmei; Swann, John W; Zoghbi, Huda Y

2015-11-18

Inhibitory neurons are critical for proper brain function, and their dysfunction is implicated in several disorders, including autism, schizophrenia, and Rett syndrome. These neurons are heterogeneous, and it is unclear which subtypes contribute to specific neurological phenotypes. We deleted Mecp2, the mouse homolog of the gene that causes Rett syndrome, from the two most populous subtypes, parvalbumin-positive (PV+) and somatostatin-positive (SOM+) neurons. Loss of MeCP2 partially impairs the affected neuron, allowing us to assess the function of each subtype without profound disruption of neuronal circuitry. We found that mice lacking MeCP2 in either PV+ or SOM+ neurons have distinct, non-overlapping neurological features: mice lacking MeCP2 in PV+ neurons developed motor, sensory, memory, and social deficits, whereas those lacking MeCP2 in SOM+ neurons exhibited seizures and stereotypies. Our findings indicate that PV+ and SOM+ neurons contribute complementary aspects of the Rett phenotype and may have modular roles in regulating specific behaviors. Copyright © 2015 Elsevier Inc. All rights reserved.

Disease Mechanisms and Therapeutic Approaches in Spinal Muscular Atrophy

PubMed Central

Tisdale, Sarah

2015-01-01

Motor neuron diseases are neurological disorders characterized primarily by the degeneration of spinal motor neurons, skeletal muscle atrophy, and debilitating and often fatal motor dysfunction. Spinal muscular atrophy (SMA) is an autosomal-recessive motor neuron disease of high incidence and severity and the most common genetic cause of infant mortality. SMA is caused by homozygous mutations in the survival motor neuron 1 (SMN1) gene and retention of at least one copy of the hypomorphic gene paralog SMN2. Early studies established a loss-of-function disease mechanism involving ubiquitous SMN deficiency and suggested SMN upregulation as a possible therapeutic approach. In recent years, greater knowledge of the central role of SMN in RNA processing combined with deep characterization of animal models of SMA has significantly advanced our understanding of the cellular and molecular basis of the disease. SMA is emerging as an RNA disease not limited to motor neurons, but one that involves dysfunction of motor circuits that comprise multiple neuronal subpopulations and possibly other cell types. Advances in SMA research have also led to the development of several potential therapeutics shown to be effective in animal models of SMA that are now in clinical trials. These agents offer unprecedented promise for the treatment of this still incurable neurodegenerative disease. PMID:26063904

Brains are not just neurons. Comment on “Toward a computational framework for cognitive biology: Unifying approaches from cognitive neuroscience and comparative cognition” by Fitch

NASA Astrophysics Data System (ADS)

Huber, Ludwig

2014-09-01

This comment addresses the first component of Fitch's framework: the computational power of single neurons [3]. Although I agree that traditional models of neural computation have vastly underestimated the computational power of single neurons, I am hesitant to follow him completely. The exclusive focus on neurons is likely to underestimate the importance of other cells in the brain. In the last years, two such cell types have received appropriate attention by neuroscientists: interneurons and glia. Interneurons are small, tightly packed cells involved in the control of information processing in learning and memory. Rather than transmitting externally (like motor or sensory neurons), these neurons process information within internal circuits of the brain (therefore also called 'relay neurons'). Some specialized interneuron subtypes temporally regulate the flow of information in a given cortical circuit during relevant behavioral events [4]. In the human brain approx. 100 billion interneurons control information processing and are implicated in disorders such as epilepsy and Parkinson's.

Toxic gain of function from mutant FUS protein is crucial to trigger cell autonomous motor neuron loss.

PubMed

Scekic-Zahirovic, Jelena; Sendscheid, Oliver; El Oussini, Hajer; Jambeau, Mélanie; Sun, Ying; Mersmann, Sina; Wagner, Marina; Dieterlé, Stéphane; Sinniger, Jérome; Dirrig-Grosch, Sylvie; Drenner, Kevin; Birling, Marie-Christine; Qiu, Jinsong; Zhou, Yu; Li, Hairi; Fu, Xiang-Dong; Rouaux, Caroline; Shelkovnikova, Tatyana; Witting, Anke; Ludolph, Albert C; Kiefer, Friedemann; Storkebaum, Erik; Lagier-Tourenne, Clotilde; Dupuis, Luc

2016-05-17

FUS is an RNA-binding protein involved in amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Cytoplasmic FUS-containing aggregates are often associated with concomitant loss of nuclear FUS Whether loss of nuclear FUS function, gain of a cytoplasmic function, or a combination of both lead to neurodegeneration remains elusive. To address this question, we generated knockin mice expressing mislocalized cytoplasmic FUS and complete FUS knockout mice. Both mouse models display similar perinatal lethality with respiratory insufficiency, reduced body weight and length, and largely similar alterations in gene expression and mRNA splicing patterns, indicating that mislocalized FUS results in loss of its normal function. However, FUS knockin mice, but not FUS knockout mice, display reduced motor neuron numbers at birth, associated with enhanced motor neuron apoptosis, which can be rescued by cell-specific CRE-mediated expression of wild-type FUS within motor neurons. Together, our findings indicate that cytoplasmic FUS mislocalization not only leads to nuclear loss of function, but also triggers motor neuron death through a toxic gain of function within motor neurons. © 2016 The Authors. Published under the terms of the CC BY NC ND 4.0 license.

A Subset of Autism-Associated Genes Regulate the Structural Stability of Neurons

PubMed Central

Lin, Yu-Chih; Frei, Jeannine A.; Kilander, Michaela B. C.; Shen, Wenjuan; Blatt, Gene J.

2016-01-01

Autism spectrum disorder (ASD) comprises a range of neurological conditions that affect individuals’ ability to communicate and interact with others. People with ASD often exhibit marked qualitative difficulties in social interaction, communication, and behavior. Alterations in neurite arborization and dendritic spine morphology, including size, shape, and number, are hallmarks of almost all neurological conditions, including ASD. As experimental evidence emerges in recent years, it becomes clear that although there is broad heterogeneity of identified autism risk genes, many of them converge into similar cellular pathways, including those regulating neurite outgrowth, synapse formation and spine stability, and synaptic plasticity. These mechanisms together regulate the structural stability of neurons and are vulnerable targets in ASD. In this review, we discuss the current understanding of those autism risk genes that affect the structural connectivity of neurons. We sub-categorize them into (1) cytoskeletal regulators, e.g., motors and small RhoGTPase regulators; (2) adhesion molecules, e.g., cadherins, NCAM, and neurexin superfamily; (3) cell surface receptors, e.g., glutamatergic receptors and receptor tyrosine kinases; (4) signaling molecules, e.g., protein kinases and phosphatases; and (5) synaptic proteins, e.g., vesicle and scaffolding proteins. Although the roles of some of these genes in maintaining neuronal structural stability are well studied, how mutations contribute to the autism phenotype is still largely unknown. Investigating whether and how the neuronal structure and function are affected when these genes are mutated will provide insights toward developing effective interventions aimed at improving the lives of people with autism and their families. PMID:27909399

Altered neuronal activities in the motor cortex with impaired motor performance in adult rats observed after infusion of cerebrospinal fluid from amyotrophic lateral sclerosis patients.

PubMed

Sankaranarayani, R; Nalini, A; Rao Laxmi, T; Raju, T R

2010-01-05

Although definite evidences are available to state that, neuronal activity is a prime determinant of animal behavior, the specific relationship between local field potentials of the motor cortex after intervention with CSF from human patients and animal behavior have remained opaque. The present study has investigated whether cerebrospinal fluid from sporadic amyotrophic lateral sclerosis (sALS) patients could disrupt neuronal activity of the motor cortex, which could be associated with disturbances in the motor performance of adult rats. CSF from ALS patients (ALS-CSF) was infused into the lateral ventricle of Wistar rats. After 24h, the impact of ALS-CSF on the local field potentials (LFPs) of the motor cortex and on the motor behavior of animals were examined. The results indicate that ALS-CSF produced a bivariate distribution on the relative power values of the LFPs of the motor cortex 24h following infusion. However, the behavioral results did not show bimodality, instead showed consistent decrease in motor performance: on rotarod and grip strength meter. The neuronal activity of the motor cortex negatively correlated with the duration of ALS symptoms at the time of lumbar puncture. Although the effect of ALS-CSF was more pronounced at 24h following infusion, the changes observed in LFPs and motor performance appeared to revert to baseline values at later time points of testing. In the current study, we have shown that, ALS-CSF has the potential to perturb neuronal activity of the rat motor cortex which was associated with poor performance on motor function tests.

Role of primary afferents in the developmental regulation of motor axon synapse numbers on Renshaw cells

PubMed Central

Siembab, Valerie C.; Gomez-Perez, Laura; Rotterman, Travis M.; Shneider, Neil A.; Alvarez, Francisco J.

2015-01-01

Motor function in mammalian species depends on the maturation of spinal circuits formed by a large variety of interneurons that regulate motoneuron firing and motor output. Interneuron activity is in turn modulated by the organization of their synaptic inputs, but the principles governing the development of specific synaptic architectures unique to each premotor interneuron are unknown. For example, Renshaw cells receive, at least in the neonate, convergent inputs from sensory afferents (likely Ia) and motor axons raising the question of whether they interact during Renshaw cell development. In other well-studied neurons, like Purkinje cells, heterosynaptic competition between inputs from different sources shapes synaptic organization. To examine the possibility that sensory afferents modulate synaptic maturation on developing Renshaw cells, we used three animal models in which afferent inputs in the ventral horn are dramatically reduced (Er81(−/−) knockout), weakened (Egr3(−/−) knockout) or strengthened (mlcNT3(+/−) transgenic). We demonstrate that increasing the strength of sensory inputs on Renshaw cells prevents their de-selection and reduces motor axon synaptic density and, in contrast, absent or diminished sensory afferent inputs correlate with increased densities of motor axons synapses. No effects were observed on other glutamatergic inputs. We conclude that the early strength of Ia synapses influences their maintenance or weakening during later development and that heterosynaptic influences from sensory synapses during early development regulates the density and organization of motor inputs on mature Renshaw cells. PMID:26660356

Convergence of inhibitory neural inputs regulate motor activity in the murine and monkey stomach

PubMed Central

Shaylor, Lara A.; Hwang, Sung Jin; Sanders, Kenton M.

2016-01-01

Inhibitory motor neurons regulate several gastric motility patterns including receptive relaxation, gastric peristaltic motor patterns, and pyloric sphincter opening. Nitric oxide (NO) and purines have been identified as likely candidates that mediate inhibitory neural responses. However, the contribution from each neurotransmitter has received little attention in the distal stomach. The aims of this study were to identify the roles played by NO and purines in inhibitory motor responses in the antrums of mice and monkeys. By using wild-type mice and mutants with genetically deleted neural nitric oxide synthase (Nos1−/−) and P2Y1 receptors (P2ry1−/−) we examined the roles of NO and purines in postjunctional inhibitory responses in the distal stomach and compared these responses to those in primate stomach. Activation of inhibitory motor nerves using electrical field stimulation (EFS) produced frequency-dependent inhibitory junction potentials (IJPs) that produced muscle relaxations in both species. Stimulation of inhibitory nerves during slow waves terminated pacemaker events and associated contractions. In Nos1−/− mice IJPs and relaxations persisted whereas in P2ry1−/− mice IJPs were absent but relaxations persisted. In the gastric antrum of the non-human primate model Macaca fascicularis, similar NO and purine neural components contributed to inhibition of gastric motor activity. These data support a role of convergent inhibitory neural responses in the regulation of gastric motor activity across diverse species. PMID:27634009

Convergence of inhibitory neural inputs regulate motor activity in the murine and monkey stomach.

PubMed

Shaylor, Lara A; Hwang, Sung Jin; Sanders, Kenton M; Ward, Sean M

2016-11-01

Inhibitory motor neurons regulate several gastric motility patterns including receptive relaxation, gastric peristaltic motor patterns, and pyloric sphincter opening. Nitric oxide (NO) and purines have been identified as likely candidates that mediate inhibitory neural responses. However, the contribution from each neurotransmitter has received little attention in the distal stomach. The aims of this study were to identify the roles played by NO and purines in inhibitory motor responses in the antrums of mice and monkeys. By using wild-type mice and mutants with genetically deleted neural nitric oxide synthase (Nos1 -/- ) and P2Y1 receptors (P2ry1 -/- ) we examined the roles of NO and purines in postjunctional inhibitory responses in the distal stomach and compared these responses to those in primate stomach. Activation of inhibitory motor nerves using electrical field stimulation (EFS) produced frequency-dependent inhibitory junction potentials (IJPs) that produced muscle relaxations in both species. Stimulation of inhibitory nerves during slow waves terminated pacemaker events and associated contractions. In Nos1 -/- mice IJPs and relaxations persisted whereas in P2ry1 -/- mice IJPs were absent but relaxations persisted. In the gastric antrum of the non-human primate model Macaca fascicularis, similar NO and purine neural components contributed to inhibition of gastric motor activity. These data support a role of convergent inhibitory neural responses in the regulation of gastric motor activity across diverse species. Copyright © 2016 the American Physiological Society.

A COMPUTATIONAL MODEL OF MOTOR NEURON DEGENERATION

PubMed Central

Le Masson, Gwendal; Przedborski, Serge; Abbott, L.F.

2014-01-01

SUMMARY To explore the link between bioenergetics and motor neuron degeneration, we used a computational model in which detailed morphology and ion conductance are paired with intracellular ATP production and consumption. We found that reduced ATP availability increases the metabolic cost of a single action potential and disrupts K+/Na+ homeostasis, resulting in a chronic depolarization. The magnitude of the ATP shortage at which this ionic instability occurs depends on the morphology and intrinsic conductance characteristic of the neuron. If ATP shortage is confined to the distal part of the axon, the ensuing local ionic instability eventually spreads to the whole neuron and involves fasciculation-like spiking events. A shortage of ATP also causes a rise in intracellular calcium. Our modeling work supports the notion that mitochondrial dysfunction can account for salient features of the paralytic disorder amyotrophic lateral sclerosis, including motor neuron hyperexcitability, fasciculation, and differential vulnerability of motor neuron subpopulations. PMID:25088365

A computational model of motor neuron degeneration.

PubMed

Le Masson, Gwendal; Przedborski, Serge; Abbott, L F

2014-08-20

To explore the link between bioenergetics and motor neuron degeneration, we used a computational model in which detailed morphology and ion conductance are paired with intracellular ATP production and consumption. We found that reduced ATP availability increases the metabolic cost of a single action potential and disrupts K+/Na+ homeostasis, resulting in a chronic depolarization. The magnitude of the ATP shortage at which this ionic instability occurs depends on the morphology and intrinsic conductance characteristic of the neuron. If ATP shortage is confined to the distal part of the axon, the ensuing local ionic instability eventually spreads to the whole neuron and involves fasciculation-like spiking events. A shortage of ATP also causes a rise in intracellular calcium. Our modeling work supports the notion that mitochondrial dysfunction can account for salient features of the paralytic disorder amyotrophic lateral sclerosis, including motor neuron hyperexcitability, fasciculation, and differential vulnerability of motor neuron subpopulations. Copyright © 2014 Elsevier Inc. All rights reserved.

Multimodal Encoding of Goal-Directed Actions in Monkey Ventral Premotor Grasping Neurons.

PubMed

Bruni, Stefania; Giorgetti, Valentina; Fogassi, Leonardo; Bonini, Luca

2017-01-01

Visuo-motor neurons of the ventral premotor area F5 encode "pragmatic" representations of object in terms of the potential motor acts (e.g., precision grip) afforded by it. Likewise, objects with identical pragmatic features (e.g., small spheres) but different behavioral value (e.g., edible or inedible) convey different "semantic" information and thus afford different goal-directed behaviors (e.g., grasp-to-eat or grasp-to-place). However, whether F5 neurons can extract distinct behavioral affordances from objects with similar pragmatic features is unknown. We recorded 134 F5 visuo-motor neurons in 2 macaques during a contextually cued go/no-go task in which the monkey grasped, or refrained from grasping, a previously presented edible or inedible target to eat it or placing it, respectively. Sixty-nine visuo-motor neurons showed motor selectivity for the target (35 food and 34 object), and about half of them (N = 35) exhibited congruent visual preference. Interestingly, when the monkey grasped in complete darkness and could identify the target only based on haptic feedback, visuo-motor neurons lost their precontact selectivity, but most of them (80%) showed it again 60 ms after hand-target contact. These findings suggest that F5 neurons possess a multimodal access to semantic information on objects, which are transformed into motor representations of the potential goal-directed actions afforded by them. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

Motor neuron mitochondrial dysfunction in spinal muscular atrophy

PubMed Central

Miller, Nimrod; Shi, Han; Zelikovich, Aaron S.; Ma, Yong-Chao

2016-01-01

Spinal muscular atrophy (SMA), the leading genetic cause of infant mortality, predominantly affects high metabolic tissues including motor neurons, skeletal muscles and the heart. Although the genetic cause of SMA has been identified, mechanisms underlying tissue-specific vulnerability are not well understood. To study these mechanisms, we carried out a deep sequencing analysis of the transcriptome of spinal motor neurons in an SMA mouse model, in which we unexpectedly found changes in many genes associated with mitochondrial bioenergetics. Importantly, functional measurement of mitochondrial activities showed decreased basal and maximal mitochondrial respiration in motor neurons from SMA mice. Using a reduction-oxidation sensitive GFP and fluorescence sensors specifically targeted to mitochondria, we found increased oxidative stress level and impaired mitochondrial membrane potential in motor neurons affected by SMA. In addition, mitochondrial mobility was impaired in SMA disease conditions, with decreased retrograde transport but no effect on anterograde transport. We also found significantly increased fragmentation of the mitochondrial network in primary motor neurons from SMA mice, with no change in mitochondria density. Electron microscopy study of SMA mouse spinal cord revealed mitochondria fragmentation, edema and concentric lamellar inclusions in motor neurons affected by the disease. Intriguingly, these functional and structural deficiencies in the SMA mouse model occur during the presymptomatic stage of disease, suggesting a role in initiating SMA. Altogether, our findings reveal a critical role for mitochondrial defects in SMA pathogenesis and suggest a novel target for improving tissue health in the disease. PMID:27488123

Rapid acquisition of novel interface control by small ensembles of arbitrarily selected primary motor cortex neurons

PubMed Central

Law, Andrew J.; Rivlis, Gil

2014-01-01

Pioneering studies demonstrated that novel degrees of freedom could be controlled individually by directly encoding the firing rate of single motor cortex neurons, without regard to each neuron's role in controlling movement of the native limb. In contrast, recent brain-computer interface work has emphasized decoding outputs from large ensembles that include substantially more neurons than the number of degrees of freedom being controlled. To bridge the gap between direct encoding by single neurons and decoding output from large ensembles, we studied monkeys controlling one degree of freedom by comodulating up to four arbitrarily selected motor cortex neurons. Performance typically exceeded random quite early in single sessions and then continued to improve to different degrees in different sessions. We therefore examined factors that might affect performance. Performance improved with larger ensembles. In contrast, other factors that might have reflected preexisting synaptic architecture—such as the similarity of preferred directions—had little if any effect on performance. Patterns of comodulation among ensemble neurons became more consistent across trials as performance improved over single sessions. Compared with the ensemble neurons, other simultaneously recorded neurons showed less modulation. Patterns of voluntarily comodulated firing among small numbers of arbitrarily selected primary motor cortex (M1) neurons thus can be found and improved rapidly, with little constraint based on the normal relationships of the individual neurons to native limb movement. This rapid flexibility in relationships among M1 neurons may in part underlie our ability to learn new movements and improve motor skill. PMID:24920030

An intersectional gene regulatory strategy defines subclass diversity of C. elegans motor neurons.

PubMed

Kratsios, Paschalis; Kerk, Sze Yen; Catela, Catarina; Liang, Joseph; Vidal, Berta; Bayer, Emily A; Feng, Weidong; De La Cruz, Estanisla Daniel; Croci, Laura; Consalez, G Giacomo; Mizumoto, Kota; Hobert, Oliver

2017-07-05

A core principle of nervous system organization is the diversification of neuron classes into subclasses that share large sets of features but differ in select traits. We describe here a molecular mechanism necessary for motor neurons to acquire subclass-specific traits in the nematode Caenorhabditis elegans . Cholinergic motor neuron classes of the ventral nerve cord can be subdivided into subclasses along the anterior-posterior (A-P) axis based on synaptic connectivity patterns and molecular features. The conserved COE-type terminal selector UNC-3 not only controls the expression of traits shared by all members of a neuron class, but is also required for subclass-specific traits expressed along the A-P axis. UNC-3, which is not regionally restricted, requires region-specific cofactors in the form of Hox proteins to co-activate subclass-specific effector genes in post-mitotic motor neurons. This intersectional gene regulatory principle for neuronal subclass diversification may be conserved from nematodes to mice.

Loss of Miro1-directed mitochondrial movement results in a novel murine model for neuron disease

PubMed Central

Nguyen, Tammy T.; Oh, Sang S.; Weaver, David; Lewandowska, Agnieszka; Maxfield, Dane; Schuler, Max-Hinderk; Smith, Nathan K.; Macfarlane, Jane; Saunders, Gerald; Palmer, Cheryl A.; Debattisti, Valentina; Koshiba, Takumi; Pulst, Stefan; Feldman, Eva L.; Hajnóczky, György; Shaw, Janet M.

2014-01-01

Defective mitochondrial distribution in neurons is proposed to cause ATP depletion and calcium-buffering deficiencies that compromise cell function. However, it is unclear whether aberrant mitochondrial motility and distribution alone are sufficient to cause neurological disease. Calcium-binding mitochondrial Rho (Miro) GTPases attach mitochondria to motor proteins for anterograde and retrograde transport in neurons. Using two new KO mouse models, we demonstrate that Miro1 is essential for development of cranial motor nuclei required for respiratory control and maintenance of upper motor neurons required for ambulation. Neuron-specific loss of Miro1 causes depletion of mitochondria from corticospinal tract axons and progressive neurological deficits mirroring human upper motor neuron disease. Although Miro1-deficient neurons exhibit defects in retrograde axonal mitochondrial transport, mitochondrial respiratory function continues. Moreover, Miro1 is not essential for calcium-mediated inhibition of mitochondrial movement or mitochondrial calcium buffering. Our findings indicate that defects in mitochondrial motility and distribution are sufficient to cause neurological disease. PMID:25136135

Neuronal matrix metalloproteinase-9 is a determinant of selective neurodegeneration.

PubMed

Kaplan, Artem; Spiller, Krista J; Towne, Christopher; Kanning, Kevin C; Choe, Ginn T; Geber, Adam; Akay, Turgay; Aebischer, Patrick; Henderson, Christopher E

2014-01-22

Selective neuronal loss is the hallmark of neurodegenerative diseases. In patients with amyotrophic lateral sclerosis (ALS), most motor neurons die but those innervating extraocular, pelvic sphincter, and slow limb muscles exhibit selective resistance. We identified 18 genes that show >10-fold differential expression between resistant and vulnerable motor neurons. One of these, matrix metalloproteinase-9 (MMP-9), is expressed only by fast motor neurons, which are selectively vulnerable. In ALS model mice expressing mutant superoxide dismutase (SOD1), reduction of MMP-9 function using gene ablation, viral gene therapy, or pharmacological inhibition significantly delayed muscle denervation. In the presence of mutant SOD1, MMP-9 expressed by fast motor neurons themselves enhances activation of ER stress and is sufficient to trigger axonal die-back. These findings define MMP-9 as a candidate therapeutic target for ALS. The molecular basis of neuronal diversity thus provides significant insights into mechanisms of selective vulnerability to neurodegeneration. Copyright © 2014 Elsevier Inc. All rights reserved.

Role of motoneuron-derived neurotrophin 3 in survival and axonal projection of sensory neurons during neural circuit formation.

PubMed

Usui, Noriyoshi; Watanabe, Keisuke; Ono, Katsuhiko; Tomita, Koichi; Tamamaki, Nobuaki; Ikenaka, Kazuhiro; Takebayashi, Hirohide

2012-03-01

Sensory neurons possess the central and peripheral branches and they form unique spinal neural circuits with motoneurons during development. Peripheral branches of sensory axons fasciculate with the motor axons that extend toward the peripheral muscles from the central nervous system (CNS), whereas the central branches of proprioceptive sensory neurons directly innervate motoneurons. Although anatomically well documented, the molecular mechanism underlying sensory-motor interaction during neural circuit formation is not fully understood. To investigate the role of motoneuron on sensory neuron development, we analyzed sensory neuron phenotypes in the dorsal root ganglia (DRG) of Olig2 knockout (KO) mouse embryos, which lack motoneurons. We found an increased number of apoptotic cells in the DRG of Olig2 KO embryos at embryonic day (E) 10.5. Furthermore, abnormal axonal projections of sensory neurons were observed in both the peripheral branches at E10.5 and central branches at E15.5. To understand the motoneuron-derived factor that regulates sensory neuron development, we focused on neurotrophin 3 (Ntf3; NT-3), because Ntf3 and its receptors (Trk) are strongly expressed in motoneurons and sensory neurons, respectively. The significance of motoneuron-derived Ntf3 was analyzed using Ntf3 conditional knockout (cKO) embryos, in which we observed increased apoptosis and abnormal projection of the central branch innervating motoneuron, the phenotypes being apparently comparable with that of Olig2 KO embryos. Taken together, we show that the motoneuron is a functional source of Ntf3 and motoneuron-derived Ntf3 is an essential pre-target neurotrophin for survival and axonal projection of sensory neurons.

Coding rate and duration of vocalizations of the frog, Xenopus laevis.

PubMed

Zornik, Erik; Yamaguchi, Ayako

2012-08-29

Vocalizations involve complex rhythmic motor patterns, but the underlying temporal coding mechanisms in the nervous system are poorly understood. Using a recently developed whole-brain preparation from which "fictive" vocalizations are readily elicited in vitro, we investigated the cellular basis of temporal complexity of African clawed frogs (Xenopus laevis). Male advertisement calls contain two alternating components--fast trills (∼300 ms) and slow trills (∼700 ms) that contain clicks repeated at ∼60 and ∼30 Hz, respectively. We found that males can alter the duration of fast trills without changing click rates. This finding led us to hypothesize that call rate and duration are regulated by independent mechanisms. We tested this by obtaining whole-cell patch-clamp recordings in the "fictively" calling isolated brain. We discovered a single type of premotor neuron with activity patterns correlated with both the rate and duration of fast trills. These "fast-trill neurons" (FTNs) exhibited long-lasting depolarizations (LLDs) correlated with each fast trill and action potentials that were phase-locked with motor output-neural correlates of call duration and rate, respectively. When depolarized without central pattern generator activation, FTNs produced subthreshold oscillations and action potentials at fast-trill rates, indicating FTN resonance properties are tuned to, and may dictate, the fast-trill rhythm. NMDA receptor (NMDAR) blockade eliminated LLDs in FTNs, and NMDAR activation in synaptically isolated FTNs induced repetitive LLDs. These results suggest FTNs contain an NMDAR-dependent mechanism that may regulate fast-trill duration. We conclude that a single premotor neuron population employs distinct mechanisms to regulate call rate and duration.

Pur-alpha regulates cytoplasmic stress granule dynamics and ameliorates FUS toxicity

PubMed Central

Daigle, J Gavin; Krishnamurthy, Karthik; Ramesh, Nandini; Casci, Ian; Monaghan, John; McAvoy, Kevin; Godfrey, Earl W; Daniel, Dianne C.; Johnson, Edward M.; Monahan, Zach; Shewmaker, Frank; Pasinelli, Piera; Pandey, Udai Bhan

2016-01-01

Amyotrophic lateral Sclerosis is characterized by progressive loss of motor neurons in the brain and spinal cord. Mutations in several genes, including FUS, TDP43, Matrin 3, hnRNPA2 and other RNA binding proteins, have been linked to ALS pathology. Recently, Pur-alpha a DNA/RNA binding protein was found to bind to C9orf72 repeat expansions and could possibly play a role in the pathogenesis of ALS. When overexpressed, Pur-alpha mitigates toxicities associated with Fragile X tumor ataxia syndrome (FXTAS) and C9orf72 repeat expansion diseases in Drosophila and mammalian cell culture models. However, the function of Pur-alpha in regulating ALS pathogenesis has not been fully understood. We identified Pur-alpha as a novel component of cytoplasmic stress granules (SGs) in ALS patient cells carrying disease-causing mutations in FUS. When cells were challenged with stress, we observed that Pur-alpha co-localized with mutant FUS in ALS patient cells and became trapped in constitutive SGs. We also found that FUS physically interacted with Pur-alpha in mammalian neuronal cells. Interestingly, shRNA mediated knock down of endogenous Pur-alpha significantly reduced formation of cytoplasmic stress granules in mammalian cells suggesting that Pur-alpha is essential for the formation of SGs. Furthermore, ectopic expression of Pur-alpha blocked cytoplasmic mislocalization of mutant FUS and strongly suppressed toxicity associated with mutant FUS expression in primary motor neurons. Our data emphasizes the importance of stress granules in ALS pathogenesis and identifies Pur-alpha as a novel regulator of SG dynamics. PMID:26728149

Trafficking regulates the subcellular distribution of voltage-gated sodium channels in primary sensory neurons.

PubMed

Bao, Lan

2015-09-30

Voltage-gated sodium channels (Navs) comprise at least nine pore-forming α subunits. Of these, Nav1.6, Nav1.7, Nav1.8 and Nav1.9 are the most frequently studied in primary sensory neurons located in the dorsal root ganglion and are mainly localized to the cytoplasm. A large pool of intracellular Navs raises the possibility that changes in Nav trafficking could alter channel function. The molecular mediators of Nav trafficking mainly consist of signals within the Navs themselves, interacting proteins and extracellular factors. The surface expression of Navs is achieved by escape from the endoplasmic reticulum and proteasome degradation, forward trafficking and plasma membrane anchoring, and it is also regulated by channel phosphorylation and ubiquitination in primary sensory neurons. Axonal transport and localization of Navs in afferent fibers involves the motor protein KIF5B and scaffold proteins, including contactin and PDZ domain containing 2. Localization of Nav1.6 to the nodes of Ranvier in myelinated fibers of primary sensory neurons requires node formation and the submembrane cytoskeletal protein complex. These findings inform our understanding of the molecular and cellular mechanisms underlying Nav trafficking in primary sensory neurons.

Specific induction of Akt3 in spinal cord motor neurons is neuroprotective in a mouse model of familial amyotrophic lateral sclerosis.

PubMed

Peviani, Marco; Tortarolo, Massimo; Battaglia, Elisa; Piva, Roberto; Bendotti, Caterina

2014-02-01

Evidence is accumulating that an imbalance between pathways for degeneration or survival in motor neurons may play a central role in mechanisms that lead to neurodegeneration in amyotrophic lateral sclerosis (ALS). We and other groups have observed that downregulation, or lack of induction, of the PI3K/Akt prosurvival pathway may be responsible for defective response of motor neurons to injury and their consequent cellular demise. Some of the neuroprotective effects mediated by growth factors may involve activation of Akt, but a proof of concept of Akt as a target for therapy is lacking. We demonstrate that specific expression of constitutively activated Akt3 in motor neurons through the use of the promoter of homeobox gene Hb9 prevents neuronal loss induced by SOD1.G93A both in vitro (in mixed neuron/astrocyte cocultures) and in vivo (in a mouse model of ALS). Inhibition of ASK1 and GSK3beta was involved in the neuroprotective effects of activated Akt3, further supporting the hypothesis that induction of Akt3 may be a key step in activation of pathways for survival in the attempt to counteract motor neuronal degeneration in ALS.

Neuronal modelling of baroreflex response to orthostatic stress

NASA Astrophysics Data System (ADS)

Samin, Azfar

The accelerations experienced in aerial combat can cause pilot loss of consciousness (GLOC) due to a critical reduction in cerebral blood circulation. The development of smart protective equipment requires understanding of how the brain processes blood pressure (BP) information in response to acceleration. We present a biologically plausible model of the Baroreflex to investigate the neural correlates of short-term BP control under acceleration or orthostatic stress. The neuronal network model, which employs an integrate-and-fire representation of a biological neuron, comprises the sensory, motor, and the central neural processing areas that form the Baroreflex. Our modelling strategy is to test hypotheses relating to the encoding mechanisms of multiple sensory inputs to the nucleus tractus solitarius (NTS), the site of central neural processing. The goal is to run simulations and reproduce model responses that are consistent with the variety of available experimental data. Model construction and connectivity are inspired by the available anatomical and neurophysiological evidence that points to a barotopic organization in the NTS, and the presence of frequency-dependent synaptic depression, which provides a mechanism for generating non-linear local responses in NTS neurons that result in quantifiable dynamic global baroreflex responses. The entire physiological range of BP and rate of change of BP variables is encoded in a palisade of NTS neurons in that the spike responses approximate Gaussian 'tuning' curves. An adapting weighted-average decoding scheme computes the motor responses and a compensatory signal regulates the heart rate (HR). Model simulations suggest that: (1) the NTS neurons can encode the hydrostatic pressure difference between two vertically separated sensory receptor regions at +Gz, and use changes in that difference for the regulation of HR; (2) even though NTS neurons do not fire with a cardiac rhythm seen in the afferents, pulse-rhythmic activity is regained downstream provided the input phase information in preserved centrally; (3) frequency-dependent synaptic depression, which causes temporal variations in synaptic strength due to changes in input frequency, is a possible mechanism of non-linear dynamic baroreflex gain control. Synaptic depression enables the NTS neuron to encode dBP/dt but to lose information about the steady state firing of the afferents.

Effect of light on the activity of motor cortex neurons during locomotion

PubMed Central

Armer, Madison C.; Nilaweera, Wijitha U.; Rivers, Trevor J.; Dasgupta, Namrata M.; Beloozerova, Irina N.

2013-01-01

The motor cortex plays a critical role in accurate visually guided movements such as reaching and target stepping. However, the manner in which vision influences the movement-related activity of neurons in the motor cortex is not well understood. In this study we have investigated how the locomotion-related activity of neurons in the motor cortex is modified when subjects switch between walking in the darkness and in light. Three adult cats were trained to walk through corridors of an experimental chamber for a food reward. On randomly selected trials, lights were extinguished for approximately four seconds when the cat was in a straight portion of the chamber's corridor. Discharges of 146 neurons from layer V of the motor cortex, including 51 pyramidal tract cells (PTNs), were recorded and compared between light and dark conditions. It was found that while cats’ movements during locomotion in light and darkness were similar (as judged from the analysis of three-dimensional limb kinematics and the activity of limb muscles), the firing behavior of 49% (71/146) of neurons was different between the two walking conditions. This included differences in the mean discharge rate (19%, 28/146 of neurons), depth of stride-related frequency modulation (24%, 32/131), duration of the period of elevated firing ([PEF], 19%, 25/131), and number of PEFs among stride-related neurons (26%, 34/131). 20% of responding neurons exhibited more than one type of change. We conclude that visual input plays a very significant role in determining neuronal activity in the motor cortex during locomotion by altering one, or occasionally multiple, parameters of locomotion-related discharges of its neurons. PMID:23680161

Effect of light on the activity of motor cortex neurons during locomotion.

PubMed

Armer, Madison C; Nilaweera, Wijitha U; Rivers, Trevor J; Dasgupta, Namrata M; Beloozerova, Irina N

2013-08-01

The motor cortex plays a critical role in accurate visually guided movements such as reaching and target stepping. However, the manner in which vision influences the movement-related activity of neurons in the motor cortex is not well understood. In this study we have investigated how the locomotion-related activity of neurons in the motor cortex is modified when subjects switch between walking in the darkness and in light. Three adult cats were trained to walk through corridors of an experimental chamber for a food reward. On randomly selected trials, lights were extinguished for approximately 4s when the cat was in a straight portion of the chamber's corridor. Discharges of 146 neurons from layer V of the motor cortex, including 51 pyramidal tract cells (PTNs), were recorded and compared between light and dark conditions. It was found that while cats' movements during locomotion in light and darkness were similar (as judged from the analysis of three-dimensional limb kinematics and the activity of limb muscles), the firing behavior of 49% (71/146) of neurons was different between the two walking conditions. This included differences in the mean discharge rate (19%, 28/146 of neurons), depth of stride-related frequency modulation (24%, 32/131), duration of the period of elevated firing ([PEF], 19%, 25/131), and number of PEFs among stride-related neurons (26%, 34/131). 20% of responding neurons exhibited more than one type of change. We conclude that visual input plays a very significant role in determining neuronal activity in the motor cortex during locomotion by altering one, or occasionally multiple, parameters of locomotion-related discharges of its neurons. Copyright © 2013 The Authors. Published by Elsevier B.V. All rights reserved.

Responses of mirror neurons in area F5 to hand and tool grasping observation

PubMed Central

Rochat, Magali J.; Caruana, Fausto; Jezzini, Ahmad; Escola, Ludovic; Intskirveli, Irakli; Grammont, Franck; Gallese, Vittorio; Rizzolatti, Giacomo

2010-01-01

Mirror neurons are a distinct class of neurons that discharge both during the execution of a motor act and during observation of the same or similar motor act performed by another individual. However, the extent to which mirror neurons coding a motor act with a specific goal (e.g., grasping) might also respond to the observation of a motor act having the same goal, but achieved with artificial effectors, is not yet established. In the present study, we addressed this issue by recording mirror neurons from the ventral premotor cortex (area F5) of two monkeys trained to grasp objects with pliers. Neuron activity was recorded during the observation and execution of grasping performed with the hand, with pliers and during observation of an experimenter spearing food with a stick. The results showed that virtually all neurons responding to the observation of hand grasping also responded to the observation of grasping with pliers and, many of them to the observation of spearing with a stick. However, the intensity and pattern of the response differed among conditions. Hand grasping observation determined the earliest and the strongest discharge, while pliers grasping and spearing observation triggered weaker responses at longer latencies. We conclude that F5 grasping mirror neurons respond to the observation of a family of stimuli leading to the same goal. However, the response pattern depends upon the similarity between the observed motor act and the one executed by the hand, the natural motor template. PMID:20577726

A Network of HSPG Core Proteins and HS Modifying Enzymes Regulates Netrin-Dependent Guidance of D-Type Motor Neurons in Caenorhabditis elegans

PubMed Central

Gysi, Stephan; Rhiner, Christa; Flibotte, Stephane; Moerman, Donald G.; Hengartner, Michael O.

2013-01-01

Heparan sulfate proteoglycans (HSPGs) are proteins with long covalently attached sugar side chains of the heparan sulfate (HS) type. Depending on the cellular context HS chains carry multiple structural modifications such as sulfate residues or epimerized sugars allowing them to bind to a wide range of molecules. HSPGs have been found to play extremely diverse roles in animal development and were shown to interact with certain axon guidance molecules. In this study we describe the role of the Caenorhabditis elegans HSPG core proteins Syndecan (SDN-1) and Glypican (LON-2) and the HS modifying enzymes in the dorsal guidance of D-type motor axons, a process controlled mainly by the conserved axon guidance molecule UNC-6/Netrin. Our genetic analysis established the specific HS code relevant for this axon guidance event. Using two sensitized genetic backgrounds, we isolated novel components influencing D-type motor axon guidance with a link to HSPGs, as well as new alleles of several previously characterized axon guidance genes. Interestingly, the dorsal axon guidance defects induced by mutations in zfp-1 or lin-35 depended on the transgene oxIs12 used to visualize the D-type motor neurons. oxIs12 is a large multi-copy transgene that enlarges the X chromosome by approximately 20%. In a search for genes with a comparable phenotype we found that a mutation in the known dosage compensation gene dpy-21 showed similar axon guidance defects as zfp-1 or lin-35 mutants. Thus, derepression of genes on X, where many genes relevant for HS dependent axon guidance are located, might also influence axon guidance of D-type motor neurons. PMID:24066155

Melanocortin-4-receptors Expressed by Cholinergic Neurons Regulate Energy Balance and Glucose Homeostasis

PubMed Central

Rossi, Jari; Balthasar, Nina; Olson, David; Scott, Michael; Berglund, Eric; Lee, Charlotte E.; Choi, Michelle J.; Lauzon, Danielle; Lowell, Bradford B.; Elmquist, Joel K.

2011-01-01

Summary Melanocortin-4-receptor (MC4R) mutations cause dysregulation of energy balance and hyperinsulinemia. We have used mouse models to study the physiological roles of extrahypothalamic MC4Rs. Re-expression of MC4Rs in cholinergic neurons (ChAT-Cre, loxTB MC4R mice) modestly reduced body weight gain without altering food intake and was sufficient to normalize energy expenditure and attenuate hyperglycemia and hyperinsulinemia. In contrast, restoration of MC4R expression in brainstem neurons including those in the dorsal motor nucleus of the vagus (Phox2b-Cre, loxTB MC4R mice) was sufficient to attenuate hyperinsulinemia, while the hyperglycemia and energy balance were not normalized. Additionally, hepatic insulin action and insulin mediated-suppression of hepatic glucose production were improved in ChAT-Cre, loxTB MC4R mice. These findings suggest that MC4Rs expressed by cholinergic neurons regulate energy expenditure and hepatic glucose production. Our results also provide further evidence of the dissociation in pathways mediating the effects of melanocortins on energy balance and glucose homeostasis. PMID:21284986

The alluring but misleading analogy between mirror neurons and the motor theory of speech.

PubMed

Holt, Lori L; Lotto, Andrew J

2014-04-01

Speech is commonly claimed to relate to mirror neurons because of the alluring surface analogy of mirror neurons to the Motor Theory of speech perception, which posits that perception and production draw upon common motor-articulatory representations. We argue that the analogy fails and highlight examples of systems-level developmental approaches that have been more fruitful in revealing perception-production associations.

Neurogenic differentiation of dental pulp stem cells to neuron-like cells in dopaminergic and motor neuronal inductive media.

PubMed

Chang, Chia-Chieh; Chang, Kai-Chun; Tsai, Shang-Jye; Chang, Hao-Hueng; Lin, Chun-Pin

2014-12-01

Dental pulp stem cells (DPSCs) have been proposed as a promising source of stem cells in nerve regeneration due to their close embryonic origin and ease of harvest. The aim of this study was to evaluate the efficacy of dopaminergic and motor neuronal inductive media on transdifferentiation of human DPSCs (hDPSCs) into neuron-like cells. Isolation, cultivation, and identification of hDPSCs were performed with morphological analyses and flow cytometry. The proliferation potential of DPSCs was evaluated with an XTT [(2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide)] assay. Media for the induction of dopaminergic and spinal motor neuronal differentiation were prepared. The efficacy of neural induction was evaluated by detecting the expression of neuron cell-specific cell markers in DPSCs by immunocytochemistry and quantitative real-time reverse transcription polymerase chain reaction (RT-PCR). In the XTT assay, there was a 2.6- or 2-fold decrease in DPSCs cultured in dopaminergic or motor neuronal inductive media, respectively. The proportions of βIII-tubulin (βIII-tub), glial fibrillary acidic protein (GFAP), and oligodendrocyte (O1)-positive cells were significantly higher in DPSCs cultured in both neuronal inductive media compared with those cultured in control media. Furthermore, hDPSC-derived dopaminergic and spinal motor neuron cells after induction expressed a higher density of neuron cell markers than those before induction. These findings suggest that in response to the neuronal inductive stimuli, a greater proportion of DPSCs stop proliferation and acquire a phenotype resembling mature neurons. Such neural crest-derived adult DPSCs may provide an alternative stem cell source for therapy-based treatments of neuronal disorders and injury. Copyright © 2014. Published by Elsevier B.V.

Als2 mRNA splicing variants detected in KO mice rescue severe motor dysfunction phenotype in Als2 knock-down zebrafish.

PubMed

Gros-Louis, Francois; Kriz, Jasna; Kabashi, Edor; McDearmid, Jonathan; Millecamps, Stéphanie; Urushitani, Makoto; Lin, Li; Dion, Patrick; Zhu, Qinzhang; Drapeau, Pierre; Julien, Jean-Pierre; Rouleau, Guy A

2008-09-01

Recessive ALS2 mutations are linked to three related but slightly different neurodegenerative disorders: amyotrophic lateral sclerosis, hereditary spastic paraplegia and primary lateral sclerosis. To investigate the function of the ALS2 encoded protein, we generated Als2 knock-out (KO) mice and zAls2 knock-down zebrafish. The Als2(-/-) mice lacking exon 2 and part of exon 3 developed mild signs of neurodegeneration compatible with axonal transport deficiency. In contrast, zAls2 knock-down zebrafish had severe developmental abnormalities, swimming deficits and motor neuron perturbation. We identified, by RT-PCR, northern and western blotting novel Als2 transcripts in mouse central nervous system. These Als2 transcripts were present in Als2 null mice as well as in wild-type littermates and some rescued the zebrafish phenotype. Thus, we speculate that the newly identified Als2 mRNA species prevent the Als2 KO mice from developing severe neurodegenerative disease and might also regulate the severity of the motor neurons phenotype observed in ALS2 patients.

Coordinated temporal and spatial control of motor neuron and serotonergic neuron generation from a common pool of CNS progenitors.

PubMed

Pattyn, Alexandre; Vallstedt, Anna; Dias, José M; Samad, Omar Abdel; Krumlauf, Robb; Rijli, Filippo M; Brunet, Jean-Francois; Ericson, Johan

2003-03-15

Neural progenitor cells often produce distinct types of neurons in a specific order, but the determinants that control the sequential generation of distinct neuronal subclasses in the vertebrate CNS remain poorly defined. We examined the sequential generation of visceral motor neurons and serotonergic neurons from a common pool of neural progenitors located in the ventral hindbrain. We found that the temporal specification of these neurons varies along the anterior-posterior axis of the hindbrain, and that the timing of their generation critically depends on the integrated activities of Nkx- and Hox-class homeodomain proteins. A primary function of these proteins is to coordinate the spatial and temporal activation of the homeodomain protein Phox2b, which in turn acts as a binary switch in the selection of motor neuron or serotonergic neuronal fate. These findings assign new roles for Nkx, Hox, and Phox2 proteins in the control of temporal neuronal fate determination, and link spatial and temporal patterning of CNS neuronal fates.

Src Family Kinase Inhibitors Antagonize the Toxicity of Multiple Serotypes of Botulinum Neurotoxin in Human Embryonic Stem Cell-Derived Motor Neurons

PubMed Central

Burnett, James C.; Nuss, Jonathan E.; Wanner, Laura M.; Peyser, Brian D.; Du, Hao T.; Gomba, Glenn Y.; Kota, Krishna P.; Panchal, Rekha G.; Gussio, Rick; Kane, Christopher D.; Tessarollo, Lino

2015-01-01

Botulinum neurotoxins (BoNTs), the causative agents of botulism, are potent inhibitors of neurotransmitter release from motor neurons. There are currently no drugs to treat BoNT intoxication after the onset of the disease symptoms. In this study, we explored how modulation of key host pathways affects the process of BoNT intoxication in human motor neurons, focusing on Src family kinase (SFK) signaling. Motor neurons derived from human embryonic stem (hES) cells were treated with a panel of SFK inhibitors and intoxicated with BoNT serotypes A, B, or E (which are responsible for >95 % of human botulism cases). Subsequently, it was found that bosutinib, dasatinib, KX2-391, PP1, PP2, Src inhibitor-1, and SU6656 significantly antagonized all three of the serotypes. Furthermore, the data indicated that the treatment of hES-derived motor neurons with multiple SFK inhibitors increased the antagonistic effect synergistically. Mechanistically, the small molecules appear to inhibit BoNTs by targeting host pathways necessary for intoxication and not by directly inhibiting the toxins’ proteolytic activity. Importantly, the identified inhibitors are all well-studied with some in clinical trials while others are FDA-approved drugs. Overall, this study emphasizes the importance of targeting host neuronal pathways, rather than the toxin’s enzymatic components, to antagonize multiple BoNT serotypes in motor neurons. PMID:25782580

Tissue-specific activities of the Fat1 cadherin cooperate to control neuromuscular morphogenesis

PubMed Central

2018-01-01

Muscle morphogenesis is tightly coupled with that of motor neurons (MNs). Both MNs and muscle progenitors simultaneously explore the surrounding tissues while exchanging reciprocal signals to tune their behaviors. We previously identified the Fat1 cadherin as a regulator of muscle morphogenesis and showed that it is required in the myogenic lineage to control the polarity of progenitor migration. To expand our knowledge on how Fat1 exerts its tissue-morphogenesis regulator activity, we dissected its functions by tissue-specific genetic ablation. An emblematic example of muscle under such morphogenetic control is the cutaneous maximus (CM) muscle, a flat subcutaneous muscle in which progenitor migration is physically separated from the process of myogenic differentiation but tightly associated with elongating axons of its partner MNs. Here, we show that constitutive Fat1 disruption interferes with expansion and differentiation of the CM muscle, with its motor innervation and with specification of its associated MN pool. Fat1 is expressed in muscle progenitors, in associated mesenchymal cells, and in MN subsets, including the CM-innervating pool. We identify mesenchyme-derived connective tissue (CT) as a cell type in which Fat1 activity is required for the non–cell-autonomous control of CM muscle progenitor spreading, myogenic differentiation, motor innervation, and for motor pool specification. In parallel, Fat1 is required in MNs to promote their axonal growth and specification, indirectly influencing muscle progenitor progression. These results illustrate how Fat1 coordinates the coupling of muscular and neuronal morphogenesis by playing distinct but complementary actions in several cell types. PMID:29768404

Not GABA but glycine mediates segmental, propriospinal, and bulbospinal postsynaptic inhibition in adult mouse spinal forelimb motor neurons.

PubMed

Jiang, Juan; Alstermark, Bror

2015-02-04

The general view is that both glycine (Eccles, 1964) and GABA (Curtis and Felix, 1971) evoke postsynaptic inhibition in spinal motor neurons. In newborn or juvenile animals, there are conflicting results showing postsynaptic inhibition in motor neurons by corelease of GABA and glycine (Jonas et al., 1998) or by glycine alone (Bhumbra et al., 2012). To resolve the relative contributions of GABA and glycine to postsynaptic inhibition, we performed in vivo intracellular recordings from forelimb motor neurons in adult mice. Postsynaptic potentials evoked from segmental, propriospinal, and bulbospinal systems in motor neurons were compared across four different conditions: control, after gabazine, gabazine followed by strychnine, and strychnine alone. No significant differences were observed in the proportion of IPSPs and EPSPs between control and gabazine conditions. In contrast, EPSPs but not IPSPs were recorded after adding strychnine with gabazine or administering strychnine alone, suggesting an exclusive role for glycine in postsynaptic inhibition. To test whether the injected (intraperitoneal) dose of gabazine blocked GABAergic inhibitory transmission, we evoked GABAA receptor-mediated monosynaptic IPSPs in deep cerebellar nuclei neurons by stimulation of Purkinje cell fibers. No monosynaptic IPSPs could be recorded in the presence of gabazine, showing the efficacy of gabazine treatment. Our results demonstrate that, in the intact adult mouse, the postsynaptic inhibitory effects in spinal motor neurons exerted by three different systems, intrasegmental and intersegmental as well as supraspinal, are exclusively glycinergic. These findings emphasize the importance of glycinergic postsynaptic inhibition in motor neurons and challenge the view that GABA also contributes. Copyright © 2015 the authors 0270-6474/15/351991-08$15.00/0.

Evaluation of Motor Neuron-Like Cell Differentiation of hEnSCs on Biodegradable PLGA Nanofiber Scaffolds.

PubMed

Ebrahimi-Barough, Somayeh; Norouzi Javidan, Abbas; Saberi, Hoshangh; Joghataei, Mohammad Tghi; Rahbarghazi, Reza; Mirzaei, Esmaeil; Faghihi, Faezeh; Shirian, Sadegh; Ai, Armin; Ai, Jafar

2015-12-01

Human endometrium is a high-dynamic tissue that contains human endometrial stem cells (hEnSCs) which can be differentiated into a number of cell lineages. The differentiation of hEnSCs into many cell lineages such as osteoblast, adipocyte, and neural cells has been investigated previously. However, the differentiation of these stem cells into motor neuron-like cells has not been investigated yet. Different biochemical and topographical cues can affect the differentiation of stem cells into a specific cell. The aim of this study was to investigate the capability of hEnSCs to be differentiated into motor neuron-like cells under biochemical and topographical cues. The biocompatible and biodegradable poly(lactic-co-glycolic acid) (PLGA) electrospun nanofibrous scaffold was used as a topographical cue. Human EnSCs were cultured on the PLGA scaffold and tissue culture polystyrene (TCP), then differentiation of hEnSCs into motor neuron-like cells under induction media including retinoic acid (RA) and sonic hedgehog (Shh) were evaluated for 15 days. The proliferation rate of cells was assayed by using MTT assay. The morphology of cells was studied by scanning electron microscopy imaging, and the expression of motor neuron-specific markers by real-time PCR and immunocytochemistry. Results showed that survival and differentiation of hEnSCs into motor neuron-like cells on the PLGA scaffold were better than those on the TCP group. Taken together, the results suggest that differentiated hEnSCs on PLGA can provide a suitable, three-dimensional situation for neuronal survival and outgrowth for regeneration of the central nervous system, and these cells may be a potential candidate in cellular therapy for motor neuron diseases.

The mirror neuron system: a neural substrate for methods in stroke rehabilitation.

PubMed

Garrison, Kathleen A; Winstein, Carolee J; Aziz-Zadeh, Lisa

2010-06-01

Mirror neurons found in the premotor and parietal cortex respond not only during action execution, but also during observation of actions being performed by others. Thus, the motor system may be activated without overt movement. Rehabilitation of motor function after stroke is often challenging due to severity of impairment and poor to absent voluntary movement ability. Methods in stroke rehabilitation based on the mirror neuron system--action observation, motor imagery, and imitation--take advantage of this opportunity to rebuild motor function despite impairments, as an alternative or complement to physical therapy. Here the authors review research into each condition of practice, and discuss the relevance of the mirror neuron system to stroke recovery.

Somato-Motor Haptic Processing in Posterior Inner Perisylvian Region (SII/pIC) of the Macaque Monkey

PubMed Central

Ishida, Hiroaki; Fornia, Luca; Grandi, Laura Clara; Umiltà, Maria Alessandra; Gallese, Vittorio

2013-01-01

The posterior inner perisylvian region including the secondary somatosensory cortex (area SII) and the adjacent region of posterior insular cortex (pIC) has been implicated in haptic processing by integrating somato-motor information during hand-manipulation, both in humans and in non-human primates. However, motor-related properties during hand-manipulation are still largely unknown. To investigate a motor-related activity in the hand region of SII/pIC, two macaque monkeys were trained to perform a hand-manipulation task, requiring 3 different grip types (precision grip, finger exploration, side grip) both in light and in dark conditions. Our results showed that 70% (n = 33/48) of task related neurons within SII/pIC were only activated during monkeys’ active hand-manipulation. Of those 33 neurons, 15 (45%) began to discharge before hand-target contact, while the remaining neurons were tonically active after contact. Thirty-percent (n = 15/48) of studied neurons responded to both passive somatosensory stimulation and to the motor task. A consistent percentage of task-related neurons in SII/pIC was selectively activated during finger exploration (FE) and precision grasping (PG) execution, suggesting they play a pivotal role in control skilled finger movements. Furthermore, hand-manipulation-related neurons also responded when visual feedback was absent in the dark. Altogether, our results suggest that somato-motor neurons in SII/pIC likely contribute to haptic processing from the initial to the final phase of grasping and object manipulation. Such motor-related activity could also provide the somato-motor binding principle enabling the translation of diachronic somatosensory inputs into a coherent image of the explored object. PMID:23936121

Rank-order-selective neurons form a temporal basis set for the generation of motor sequences.

PubMed

Salinas, Emilio

2009-04-08

Many behaviors are composed of a series of elementary motor actions that must occur in a specific order, but the neuronal mechanisms by which such motor sequences are generated are poorly understood. In particular, if a sequence consists of a few motor actions, a primate can learn to replicate it from memory after practicing it for just a few trials. How do the motor and premotor areas of the brain assemble motor sequences so fast? The network model presented here reveals part of the solution to this problem. The model is based on experiments showing that, during the performance of motor sequences, some cortical neurons are always activated at specific times, regardless of which motor action is being executed. In the model, a population of such rank-order-selective (ROS) cells drives a layer of downstream motor neurons so that these generate specific movements at different times in different sequences. A key ingredient of the model is that the amplitude of the ROS responses must be modulated by sequence identity. Because of this modulation, which is consistent with experimental reports, the network is able not only to produce multiple sequences accurately but also to learn a new sequence with minimal changes in connectivity. The ROS neurons modulated by sequence identity thus serve as a basis set for constructing arbitrary sequences of motor responses downstream. The underlying mechanism is analogous to the mechanism described in parietal areas for generating coordinate transformations in the spatial domain.

RANK-ORDER-SELECTIVE NEURONS FORM A TEMPORAL BASIS SET FOR THE GENERATION OF MOTOR SEQUENCES

PubMed Central

Salinas, Emilio

2009-01-01

Many behaviors are composed of a series of elementary motor actions that must occur in a specific order, but the neuronal mechanisms by which such motor sequences are generated are poorly understood. In particular, if a sequence consists of a few motor actions, a primate can learn to replicate it from memory after practicing it for just a few trials. How do the motor and premotor areas of the brain assemble motor sequences so fast? The network model presented here reveals part of the solution to this problem. The model is based on experiments showing that, during the performance of motor sequences, some cortical neurons are always activated at specific times, regardless of which motor action is being executed. In the model, a population of such rank-order-selective (ROS) cells drives a layer of downstream motor neurons so that these generate specific movements at different times in different sequences. A key ingredient of the model is that the amplitude of the ROS responses must be modulated by sequence identity. Because of this modulation, which is consistent with experimental reports, the network is able not only to produce multiple sequences accurately but also to learn a new sequence with minimal changes in connectivity. The ROS neurons modulated by sequence identity thus serve as a basis set for constructing arbitrary sequences of motor responses downstream. The underlying mechanism is analogous to the mechanism described in parietal areas for generating coordinate transformations in the spatial domain. PMID:19357265

Variation in motor output and motor performance in a centrally generated motor pattern

PubMed Central

Norris, Brian J.; Doloc-Mihu, Anca; Calabrese, Ronald L.

2014-01-01

Central pattern generators (CPGs) produce motor patterns that ultimately drive motor outputs. We studied how functional motor performance is achieved, specifically, whether the variation seen in motor patterns is reflected in motor performance and whether fictive motor patterns differ from those in vivo. We used the leech heartbeat system in which a bilaterally symmetrical CPG coordinates segmental heart motor neurons and two segmented heart tubes into two mutually exclusive coordination modes: rear-to-front peristaltic on one side and nearly synchronous on the other, with regular side-to-side switches. We assessed individual variability of the motor pattern and the beat pattern in vivo. To quantify the beat pattern we imaged intact adults. To quantify the phase relations between motor neurons and heart constrictions we recorded extracellularly from two heart motor neurons and movement from the corresponding heart segments in minimally dissected leeches. Variation in the motor pattern was reflected in motor performance only in the peristaltic mode, where larger intersegmental phase differences in the motor neurons resulted in larger phase differences between heart constrictions. Fictive motor patterns differed from those in vivo only in the synchronous mode, where intersegmental phase differences in vivo had a larger front-to-rear bias and were more constrained. Additionally, load-influenced constriction timing might explain the amplification of the phase differences between heart segments in the peristaltic mode and the higher variability in motor output due to body shape assumed in this soft-bodied animal. The motor pattern determines the beat pattern, peristaltic or synchronous, but heart mechanics influence the phase relations achieved. PMID:24717348

Intricate interplay between astrocytes and motor neurons in ALS

PubMed Central

Phatnani, Hemali P.; Guarnieri, Paolo; Friedman, Brad A.; Carrasco, Monica A.; Muratet, Michael; O’Keeffe, Sean; Nwakeze, Chiamaka; Pauli-Behn, Florencia; Newberry, Kimberly M.; Meadows, Sarah K.; Tapia, Juan Carlos; Myers, Richard M.; Maniatis, Tom

2013-01-01

ALS results from the selective and progressive degeneration of motor neurons. Although the underlying disease mechanisms remain unknown, glial cells have been implicated in ALS disease progression. Here, we examine the effects of glial cell/motor neuron interactions on gene expression using the hSOD1G93A (the G93A allele of the human superoxide dismutase gene) mouse model of ALS. We detect striking cell autonomous and nonautonomous changes in gene expression in cocultured motor neurons and glia, revealing that the two cell types profoundly affect each other. In addition, we found a remarkable concordance between the cell culture data and expression profiles of whole spinal cords and acutely isolated spinal cord cells during disease progression in the G93A mouse model, providing validation of the cell culture approach. Bioinformatics analyses identified changes in the expression of specific genes and signaling pathways that may contribute to motor neuron degeneration in ALS, among which are TGF-β signaling pathways. PMID:23388633

Inhibition of Apoptosis Blocks Human Motor Neuron Cell Death in a Stem Cell Model of Spinal Muscular Atrophy

PubMed Central

Heins, Brittany M.; McGivern, Jered V.; Ornelas, Loren; Svendsen, Clive N.

2012-01-01

Spinal muscular atrophy (SMA) is a genetic disorder caused by a deletion of the survival motor neuron 1 gene leading to motor neuron loss, muscle atrophy, paralysis, and death. We show here that induced pluripotent stem cell (iPSC) lines generated from two Type I SMA subjects–one produced with lentiviral constructs and the second using a virus-free plasmid–based approach–recapitulate the disease phenotype and generate significantly fewer motor neurons at later developmental time periods in culture compared to two separate control subject iPSC lines. During motor neuron development, both SMA lines showed an increase in Fas ligand-mediated apoptosis and increased caspase-8 and-3 activation. Importantly, this could be mitigated by addition of either a Fas blocking antibody or a caspase-3 inhibitor. Together, these data further validate this human stem cell model of SMA, suggesting that specific inhibitors of apoptotic pathways may be beneficial for patients. PMID:22723941

Assessment of the upper motor neuron in amyotrophic lateral sclerosis.

PubMed

Huynh, William; Simon, Neil G; Grosskreutz, Julian; Turner, Martin R; Vucic, Steve; Kiernan, Matthew C

2016-07-01

Clinical signs of upper motor neuron (UMN) involvement are an important component in supporting the diagnosis of amyotrophic lateral sclerosis (ALS), but are often not easily appreciated in a limb that is concurrently affected by muscle wasting and lower motor neuron degeneration, particularly in the early symptomatic stages of ALS. Whilst recent criteria have been proposed to facilitate improved detection of lower motor neuron impairment through electrophysiological features that have improved diagnostic sensitivity, assessment of upper motor neuron involvement remains essentially clinical. As a result, there is often a significant diagnostic delay that in turn may impact institution of disease-modifying therapy and access to other optimal patient management. Biomarkers of pathological UMN involvement are also required to ensure patients with suspected ALS have timely access to appropriate therapeutic trials. The present review provides an analysis of current and recently developed assessment techniques, including novel imaging and electrophysiological approaches used to study corticomotoneuronal pathology in ALS. Copyright © 2016 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

Neuron activity in rat hippocampus and motor cortex during discrimination reversal.

PubMed

Disterhoft, J F; Segal, M

1978-01-01

Chronic unit activity and gross movement were recorded from rats during two discrimination reversals in a classical appetitive conditioning situation. The anticipatory movement decreased in response to the former CS+ tone and increased to the previous CS- tone after each reversal. Hippocampus and motor cortex were differently related to these two kinds of behavioral change. Response rates of hippocampal neurons were more closely related to the increased movement response to the former CS- which now signaled food. Motor cortex neuron responses were more closely correlated with the decrease in movement responses to the former CS+ which became neutral after the reversal. It appeared that hippocampal neurons could have been involved in one cognitive aspect of the situation, motor cortex neurons in another. The data were related to current functional concepts of these brain regions.

Differentiation of neural crest stem cells from nasal mucosa into motor neuron-like cells.

PubMed

Bagher, Zohreh; Kamrava, Seyed Kamran; Alizadeh, Rafieh; Farhadi, Mohammad; Absalan, Moloud; Falah, Masoumeh; Faghihi, Faezeh; Zare-Sadeghi, Arash; Komeili, Ali

2018-05-25

Cell transplantation is a potential therapeutic approach for repairing neuropathological and neurodegenerative disorders of central nervous system by replacing the degenerated cells with new ones. Among a variety of stem cell candidates to provide these new cells, olfactory ectomesenchymal stem cells (OE-MSCs) have attracted a great attention due to their neural crest origin, easy harvest, high proliferation, and autologous transplantation. Since there is no report on differentiation potential of these cells into motor neuron-like cells, we evaluated this potential using Real-time PCR, flowcytometry and immunocytochemistry after the treatment with differentiation cocktail containing retinoic acid and Sonic Hedgehog. Immunocytochemistry staining of the isolated OE-MSCs demonstrated their capability to express nestin and vimentin, as the two markers of primitive neuroectoderm. The motor neuron differentiation of OE-MSCs resulted in changing their morphology into bipolar cells with high expression of motor neuron markers of ChAT, Hb-9 and Islet-1 at the level of mRNA and protein. Consequently, we believe that the OE-MSCs have great potential to differentiate into motor neuron-like cells and can be an ideal stem cell source for the treatment of motor neuron-related disorders of central nervous system. Copyright © 2018 Elsevier B.V. All rights reserved.

V3 spinal neurons establish a robust and balanced locomotor rhythm during walking.

PubMed

Zhang, Ying; Narayan, Sujatha; Geiman, Eric; Lanuza, Guillermo M; Velasquez, Tomoko; Shanks, Bayle; Akay, Turgay; Dyck, Jason; Pearson, Keir; Gosgnach, Simon; Fan, Chen-Ming; Goulding, Martyn

2008-10-09

A robust and well-organized rhythm is a key feature of many neuronal networks, including those that regulate essential behaviors such as circadian rhythmogenesis, breathing, and locomotion. Here we show that excitatory V3-derived neurons are necessary for a robust and organized locomotor rhythm during walking. When V3-mediated neurotransmission is selectively blocked by the expression of the tetanus toxin light chain subunit (TeNT), the regularity and robustness of the locomotor rhythm is severely perturbed. A similar degeneration in the locomotor rhythm occurs when the excitability of V3-derived neurons is reduced acutely by ligand-induced activation of the allatostatin receptor. The V3-derived neurons additionally function to balance the locomotor output between both halves of the spinal cord, thereby ensuring a symmetrical pattern of locomotor activity during walking. We propose that the V3 neurons establish a regular and balanced motor rhythm by distributing excitatory drive between both halves of the spinal cord.

Ephrin-B3 is the midline barrier that prevents corticospinal tract axons from recrossing, allowing for unilateral motor control.

PubMed

Kullander, K; Croll, S D; Zimmer, M; Pan, L; McClain, J; Hughes, V; Zabski, S; DeChiara, T M; Klein, R; Yancopoulos, G D; Gale, N W

2001-04-01

Growing axons follow highly stereotypical pathways, guided by a variety of attractive and repulsive cues, before establishing specific connections with distant targets. A particularly well-known example that illustrates the complexity of axonal migration pathways involves the axonal projections of motor neurons located in the motor cortex. These projections take a complex route during which they first cross the midline, then form the corticospinal tract, and ultimately connect with motor neurons in the contralateral side of the spinal cord. These obligatory contralateral connections account for why one side of the brain controls movement on the opposing side of the body. The netrins and slits provide well-known midline signals that regulate axonal crossings at the midline. Herein we report that a member of the ephrin family, ephrin-B3, also plays a key role at the midline to regulate axonal crossing. In particular, we show that ephrin-B3 acts as the midline barrier that prevents corticospinal tract projections from recrossing when they enter the spinal gray matter. We report that in ephrin-B3(-/-) mice, corticospinal tract projections freely recross in the spinal gray matter, such that the motor cortex on one side of the brain now provides bilateral input to the spinal cord. This neuroanatomical abnormality in ephrin-B3(-/-) mice correlates with loss of unilateral motor control, yielding mice that simultaneously move their right and left limbs and thus have a peculiar hopping gait quite unlike the alternate step gait displayed by normal mice. The corticospinal and walking defects in ephrin-B3(-/-) mice resemble those recently reported for mice lacking the EphA4 receptor, which binds ephrin-B3 as well as other ephrins, suggesting that the binding of EphA4-bearing axonal processes to ephrin-B3 at the midline provides the repulsive signal that prevents corticospinal tract projections from recrossing the midline in the developing spinal cord.

Calcium Influx and Release Cooperatively Regulate AChR Patterning and Motor Axon Outgrowth during Neuromuscular Junction Formation.

PubMed

Kaplan, Mehmet Mahsum; Sultana, Nasreen; Benedetti, Ariane; Obermair, Gerald J; Linde, Nina F; Papadopoulos, Symeon; Dayal, Anamika; Grabner, Manfred; Flucher, Bernhard E

2018-06-26

Formation of synapses between motor neurons and muscles is initiated by clustering of acetylcholine receptors (AChRs) in the center of muscle fibers prior to nerve arrival. This AChR patterning is considered to be critically dependent on calcium influx through L-type channels (Ca V 1.1). Using a genetic approach in mice, we demonstrate here that either the L-type calcium currents (LTCCs) or sarcoplasmic reticulum (SR) calcium release is necessary and sufficient to regulate AChR clustering at the onset of neuromuscular junction (NMJ) development. The combined lack of both calcium signals results in loss of AChR patterning and excessive nerve branching. In the absence of SR calcium release, the severity of synapse formation defects inversely correlates with the magnitude of LTCCs. These findings highlight the importance of activity-dependent calcium signaling in early neuromuscular junction formation and indicate that both LTCC and SR calcium release individually support proper innervation of muscle by regulating AChR patterning and motor axon outgrowth. Copyright © 2018 The Authors. Published by Elsevier Inc. All rights reserved.

Genetic visualization with an improved GCaMP calcium indicator reveals spatiotemporal activation of the spinal motor neurons in zebrafish

PubMed Central

Muto, Akira; Ohkura, Masamichi; Kotani, Tomoya; Higashijima, Shin-ichi; Nakai, Junichi; Kawakami, Koichi

2011-01-01

Animal behaviors are generated by well-coordinated activation of neural circuits. In zebrafish, embryos start to show spontaneous muscle contractions at 17 to 19 h postfertilization. To visualize how motor circuits in the spinal cord are activated during this behavior, we developed GCaMP-HS (GCaMP-hyper sensitive), an improved version of the genetically encoded calcium indicator GCaMP, and created transgenic zebrafish carrying the GCaMP-HS gene downstream of the Gal4-recognition sequence, UAS (upstream activation sequence). Then we performed a gene-trap screen and identified the SAIGFF213A transgenic fish that expressed Gal4FF, a modified version of Gal4, in a subset of spinal neurons including the caudal primary (CaP) motor neurons. We conducted calcium imaging using the SAIGFF213A; UAS:GCaMP-HS double transgenic embryos during the spontaneous contractions. We demonstrated periodic and synchronized activation of a set of ipsilateral motor neurons located on the right and left trunk in accordance with actual muscle movements. The synchronized activation of contralateral motor neurons occurred alternately with a regular interval. Furthermore, a detailed analysis revealed rostral-to-caudal propagation of activation of the ipsilateral motor neuron, which is similar to but much slower than the rostrocaudal delay observed during swimming in later stages. Our study thus demonstrated coordinated activities of the motor neurons during the first behavior in a vertebrate. We propose the GCaMP technology combined with the Gal4FF-UAS system is a powerful tool to study functional neural circuits in zebrafish. PMID:21383146

Supportive care needs of patients with amyotrophic lateral sclerosis/motor neuron disease and their caregivers: A scoping review.

PubMed

Oh, Juyeon; Kim, Jung A

2017-12-01

To identify the supportive care needs of amyotrophic lateral sclerosis/motor neuron disease patients and their caregivers, categorise and summarise them into a Supportive Care Needs Framework and identify gaps in literature. Little is known about the supportive care needs of amyotrophic lateral sclerosis/motor neuron disease patients and their caregivers, and this subject has not previously been systemically reviewed. Scoping review. We conducted a scoping review from the MEDLINE, EMBASE, CINAHL and Cochrane databases for the period January 2000-July 2016, using the following inclusion criteria: (i) written in English only, (ii) published in peer-reviewed journals, (iii) at least part of the research considered the supportive care needs perspective of amyotrophic lateral sclerosis/motor neuron disease patients or their caregivers and (iv) the population sample included patients of amyotrophic lateral sclerosis/motor neuron disease or their caregivers. Thirty-seven articles were included. Our review shows that amyotrophic lateral sclerosis/motor neuron disease patients and their caregivers' supportive care needs were mentioned across all seven domains of the Supportive Care Needs Framework. Most common were practical needs (n = 24), followed by Informational needs (n = 19), Social needs (n = 18), Psychological needs (n = 16), Physical needs (n = 15), Emotional needs (n = 13) and Spiritual needs (n = 8). From the perspectives of amyotrophic lateral sclerosis/motor neuron disease patients and their caregivers, there is a significant need for more practical, social, informational, psychological, physical, emotional and spiritual support. The Supportive Care Needs Framework has potential utility in the development of patient-centred support services or healthcare policies and serves as an important base for further studies; especially, specific examples of each supportive care needs domain can guide in clinical settings when healthcare professionals provide multidisciplinary care to amyotrophic lateral sclerosis/motor neuron disease patients and individualised care. © 2017 John Wiley & Sons Ltd.

Raphé neurons stimulate respiratory circuit activity by multiple mechanisms via endogenously released serotonin and substance P

PubMed Central

Ptak, Krzysztof; Yamanishi, Tadashi; Aungst, Jason; Milescu, Lorin S.; Zhang, Ruli; Richerson, George B.; Smith, Jeffrey C.

2010-01-01

Brainstem serotonin (5-HT) neurons modulate activity of many neural circuits in the mammalian brain, but in many cases endogenous mechanisms have not been resolved. Here, we analyzed actions of raphé 5-HT neurons on respiratory network activity including at the level of the pre–Bötzinger complex (pre-BötC) in neonatal rat medullary slices in vitro, and in the more intact nervous system of juvenile rats in arterially perfused brainstem-spinal cord preparations in situ. At basal levels of activity, excitation of the respiratory network via simultaneous release of 5-HT and substance P (SP), acting at 5-HT2A/2C, 5-HT4 and/or neurokinin-1 receptors, was required to maintain inspiratory motor output in both the neonatal and juvenile systems. The midline raphé obscurus contained spontaneously active 5-HT neurons, some of which projected to the pre-BötC and hypoglossal motoneurons, co-localized 5-HT and SP, and received reciprocal excitatory connections from the pre-BötC. Experimentally augmenting raphé obscurus activity increased motor output by simultaneously exciting pre-BötC and motor neurons. Biophysical analyses in vitro demonstrated that 5-HT and SP modulated background cation conductances in pre-BötC and motor neurons, including a non–selective cation leak current that contributed to the resting potential, which explains the neuronal depolarization that augmented motor output. Furthermore, we found that 5-HT, but not SP, can transform the electrophysiological phenotype of some pre-BötC neurons to intrinsic bursters, providing 5-HT with an additional role in promoting rhythm generation. We conclude that raphé 5-HT neurons excite key circuit components required for generation of respiratory motor output. PMID:19321769

Visuomotor signals for reaching movements in the rostro-dorsal sector of the monkey thalamic reticular nucleus.

PubMed

Saga, Yosuke; Nakayama, Yoshihisa; Inoue, Ken-Ichi; Yamagata, Tomoko; Hashimoto, Masashi; Tremblay, Léon; Takada, Masahiko; Hoshi, Eiji

2017-05-01

The thalamic reticular nucleus (TRN) collects inputs from the cerebral cortex and thalamus and, in turn, sends inhibitory outputs to the thalamic relay nuclei. This unique connectivity suggests that the TRN plays a pivotal role in regulating information flow through the thalamus. Here, we analyzed the roles of TRN neurons in visually guided reaching movements. We first used retrograde transneuronal labeling with rabies virus, and showed that the rostro-dorsal sector of the TRN (TRNrd) projected disynaptically to the ventral premotor cortex (PMv). In other experiments, we recorded neurons from the TRNrd or PMv while monkeys performed a visuomotor task. We found that neurons in the TRNrd and PMv showed visual-, set-, and movement-related activity modulation. These results indicate that the TRNrd, as well as the PMv, is involved in the reception of visual signals and in the preparation and execution of reaching movements. The fraction of neurons that were non-selective for the location of visual signals or the direction of reaching movements was greater in the TRNrd than in the PMv. Furthermore, the fraction of neurons whose activity increased from the baseline was greater in the TRNrd than in the PMv. The timing of activity modulation of visual-related and movement-related neurons was similar in TRNrd and PMv neurons. Overall, our data suggest that TRNrd neurons provide motor thalamic nuclei with inhibitory inputs that are predominantly devoid of spatial selectivity, and that these signals modulate how these nuclei engage in both sensory processing and motor output during visually guided reaching behavior. © 2016 Federation of European Neuroscience Societies and John Wiley & Sons Ltd.

Motoneuron firing in amyotrophic lateral sclerosis (ALS)

PubMed Central

de Carvalho, Mamede; Eisen, Andrew; Krieger, Charles; Swash, Michael

2014-01-01

Amyotrophic lateral sclerosis is an inexorably progressive neurodegenerative disorder involving the classical motor system and the frontal effector brain, causing muscular weakness and atrophy, with variable upper motor neuron signs and often an associated fronto-temporal dementia. The physiological disturbance consequent on the motor system degeneration is beginning to be well understood. In this review we describe aspects of the motor cortical, neuronal, and lower motor neuron dysfunction. We show how studies of the changes in the pattern of motor unit firing help delineate the underlying pathophysiological disturbance as the disease progresses. Such studies are beginning to illuminate the underlying disordered pathophysiological processes in the disease, and are important in designing new approaches to therapy and especially for clinical trials. PMID:25294995

Cerebellar defects in a mouse model of juvenile neuronal ceroid lipofuscinosis

PubMed Central

Weimer, Jill M.; Benedict, Jared W.; Getty, Amanda L.; Pontikis, Charlie C.; Lim, Ming J.; Cooper, Jonathan D.; Pearce, David A.

2013-01-01

Juvenile neuronal ceroid lipofuscinosis (JNCL), or Batten disease, is a neurodegenerative disease resulting from a mutation in CLN3, which presents clinically with visual deterioration, seizures, motor impairments, cognitive decline, hallucinations, loss of circadian rhythm, and premature death in the late-twenties to early-thirties. Using a Cln3 null (Cln3−/−) mouse, we report here several deficits in the cerebellum in the absence of Cln3, including cell loss and early onset motor deficits. Surprisingly, early onset glial activation and selective neuronal loss within the mature fastigial pathway of the deep cerebellar nuclei (DCN), a region critical for balance and coordination, are seen in many regions of the Cln3−/− cerebellum. Additionally, there is a loss of Purkinje cells (PC) in regions of robust Bergmann glia activation in Cln3−/− mice and human JNCL post-mortem cerebellum. Moreover, the Cln3−/− cerebellum had a mis-regulation in granule cell proliferation and maintenance of PC dendritic arborization and spine density. Overall, this study defines a novel multi-faceted, early-onset cerebellar disruption in the Cln3 null brain, including glial activation, cell loss, and aberrant cell proliferation and differentiation. These early alterations in the maturation of the cerebellum could underlie some of the motor deficits and pathological changes seen in JNCL patients. PMID:19230832

Redundant information encoding in primary motor cortex during natural and prosthetic motor control.

PubMed

So, Kelvin; Ganguly, Karunesh; Jimenez, Jessica; Gastpar, Michael C; Carmena, Jose M

2012-06-01

Redundant encoding of information facilitates reliable distributed information processing. To explore this hypothesis in the motor system, we applied concepts from information theory to quantify the redundancy of movement-related information encoded in the macaque primary motor cortex (M1) during natural and neuroprosthetic control. Two macaque monkeys were trained to perform a delay center-out reaching task controlling a computer cursor under natural arm movement (manual control, 'MC'), and using a brain-machine interface (BMI) via volitional control of neural ensemble activity (brain control, 'BC'). During MC, we found neurons in contralateral M1 to contain higher and more redundant information about target direction than ipsilateral M1 neurons, consistent with the laterality of movement control. During BC, we found that the M1 neurons directly incorporated into the BMI ('direct' neurons) contained the highest and most redundant target information compared to neurons that were not incorporated into the BMI ('indirect' neurons). This effect was even more significant when comparing to M1 neurons of the opposite hemisphere. Interestingly, when we retrained the BMI to use ipsilateral M1 activity, we found that these neurons were more redundant and contained higher information than contralateral M1 neurons, even though ensembles from this hemisphere were previously less redundant during natural arm movement. These results indicate that ensembles most associated to movement contain highest redundancy and information encoding, which suggests a role for redundancy in proficient natural and prosthetic motor control.

Neuroprotective role of chrysin in attenuating loss of dopaminergic neurons and improving motor, learning and memory functions in rats.

PubMed

Ahmed, Muhammad Rashid; Shaikh, Masood Ahmed; Ul Haq, Syed Hafiz Imran; Nazir, Shakila

2018-01-01

Selective degeneration of dopaminergic neurons is the pathological hallmark of Parkinson disease (PD). Enhanced oxidative stress, lipid peroxidation and susceptibility of dopaminergic neurons to apoptotic cellular death are the leading pathogenetic mechanisms. Chrysin is an active flavonoid. Its neuroprotective effects have been reported. This study examined the neuroprotective effects of chrysin in ameliorating the dopaminergic neuronal degeneration and motor behavioral changes in rotenone model of PD. Thirty Sprague-Dawley rats were assigned into three groups: Control, rotenone-treated, and rotenone+chrysin treated groups. Rotenone was given at a dose of 3 mg/kg daily intraperitoneally, and chrysin was given at a dose of 50 mg/kg daily intraperitoneally for 4 weeks. Using five neurobehavioral assessment tests, evaluation was done weekly to record the motor behavioral changes. After 4 weeks, animals were sacrificed, brains were removed, and section from striatum and substantia nigra were stained using hematoxylin and eosin and cresyl violet stains. Immunohistochemical sections were also prepared using anti-tyrosine hydroxylase (TH) antibody. Rotenone-induced Parkinson like changes were evident from deteriorating motor behavior. These animals showed extensive loss of dopaminergic neurons, decreased immunoreactivity against anti-TH antibodies and number of TH positive dopaminergic neurons in the nigrostriatal region. Chrysin treated animals showed a significant reduction in motor behavioral changes, degeneration and loss of nigrostriatal dopaminergic neurons and increased immunoreactivity to anti-TH antibody. This study concludes that chrysin confers neuroprotection in rat model of PD. It attenuates the degeneration of the nigrostriatal dopaminergic neurons and motor behavioral abnormalities.

TACE (ADAM17) inhibits Schwann cell myelination

PubMed Central

Marca, Rosa La; Cerri, Federica; Horiuchi, Keisuke; Bachi, Angela; Feltri, M Laura; Wrabetz, Lawrence; Blobel, Carl P; Quattrini, Angelo; Salzer, James L; Taveggia, Carla

2012-01-01

Tumor necrosis factor-α–converting enzyme (TACE; also known as ADAM17) is a proteolytic sheddase that is responsible for the cleavage of several membrane-bound molecules. We report that TACE cleaves neuregulin-1 (NRG1) type III in the epidermal growth factor domain, probably inactivating it (as assessed by deficient activation of the phosphatidylinositol-3-OH kinase pathway), and thereby negatively regulating peripheral nervous system (PNS) myelination. Lentivirus-mediated knockdown of TACE in vitro in dorsal root ganglia neurons accelerates the onset of myelination and results in hypermyelination. In agreement, motor neurons of conditional knockout mice lacking TACE specifically in these cells are significantly hypermyelinated, and small-caliber fibers are aberrantly myelinated. Further, reduced TACE activity rescues hypomyelination in NRG1 type III haploinsufficient mice in vivo. We also show that the inhibitory effect of TACE is neuron-autonomous, as Schwann cells lacking TACE elaborate myelin of normal thickness. Thus, TACE is a modulator of NRG1 type III activity and is a negative regulator of myelination in the PNS. PMID:21666671

PAK4 kinase is essential for embryonic viability and for proper neuronal development.

PubMed

Qu, Jian; Li, Xiaofan; Novitch, Bennet G; Zheng, Ye; Kohn, Matthew; Xie, Jian-Ming; Kozinn, Spencer; Bronson, Roderick; Beg, Amer A; Minden, Audrey

2003-10-01

The serine/threonine kinase PAK4 is a target for the Rho GTPase Cdc42 and has been shown to regulate cell morphology and cytoskeletal organization in mammalian cells. To examine the physiological and developmental functions of PAK4, we have disrupted the PAK4 gene in mice. The absence of PAK4 led to lethality by embryonic day 11.5, a result most likely due to a defect in the fetal heart. Striking abnormalities were also evident in the nervous systems of PAK4-deficient embryos. These embryos had dramatic defects in neuronal development and axonal outgrowth. In particular, spinal cord motor neurons and interneurons failed to differentiate and migrate to their proper positions. This is probably related to the role for PAK4 in the regulation of cytoskeletal organization and cell and/or extracellular matrix adhesion. PAK4-null embryos also had defects in proper folding of the caudal portion of the neural tube, suggesting an important role for PAK4 in neural tube development.

Motor neuron-like NSC-34 cells as a new model for the study of vitamin D metabolism in the brain.

PubMed

Almokhtar, Mokhtar; Wikvall, Kjell; Ubhayasekera, S J Kumari A; Bergquist, Jonas; Norlin, Maria

2016-04-01

Vitamin D3 is a pro-hormone, which is sequentially activated by 25- and 1α-hydroxylation to form 25-hydroxyvitamin D3 [25(OH)D3] and 1α,25-dihydroxyvitamin D3 [1α,25(OH)2D3], respectively. Subsequent inactivation is performed by 24-hydroxylation. These reactions are carried out by a series of CYP450 enzymes. The 25-hydroxylation involves mainly CYP2R1 and CYP27A1, whereas 1α-hydroxylation and 24-hydroxylation are catalyzed by CYP27B1 and CYP24A1, respectively, and are tightly regulated to maintain adequate levels of the active vitamin D hormone, 1α,25(OH)2D3. Altered circulating vitamin D levels, in particular 25(OH)D3, have been linked to several disorders of the nervous system, e.g., schizophrenia and Parkinson disease. However, little is known about the mechanisms of vitamin D actions in the neurons. In this study, we examined vitamin D metabolism and its regulation in a murine motor neuron-like hybrid cell line, NSC-34. We found that these cells express mRNAs for the four major CYP450 enzymes involved in vitamin D activation and inactivation, and vitamin D receptor (VDR) that mediates vitamin D actions. We also found high levels of CYP24A1-dependent 24,25-dihydroxyvitamin D3 [24,25(OH)2D3] production, that was inhibited by the well-known CYP enzyme inhibitor ketoconazole and by several inhibitors that are more specific for CYP24A1. Furthermore, CYP24A1 mRNA levels in NSC-34 cells were up-regulated by 1α,25(OH)2D3 and its synthetic analogs, EB1089 and tacalcitol. Our results suggest that NSC-34 cells could be a novel model for the studies of neuronal vitamin D metabolism and its mechanism of actions. Copyright © 2015 Elsevier Ltd. All rights reserved.

Recycling of Kinesin-1 Motors by Diffusion after Transport

PubMed Central

Blasius, T. Lynne; Reed, Nathan; Slepchenko, Boris M.; Verhey, Kristen J.

2013-01-01

Kinesin motors drive the long-distance anterograde transport of cellular components along microtubule tracks. Kinesin-dependent transport plays a critical role in neurogenesis and neuronal function due to the large distance separating the soma and nerve terminal. The fate of kinesin motors after delivery of their cargoes is unknown but has been postulated to involve degradation at the nerve terminal, recycling via retrograde motors, and/or recycling via diffusion. We set out to test these models concerning the fate of kinesin-1 motors after completion of transport in neuronal cells. We find that kinesin-1 motors are neither degraded nor returned by retrograde motors. By combining mathematical modeling and experimental analysis, we propose a model in which the distribution and recycling of kinesin-1 motors fits a “loose bucket brigade” where individual motors alter between periods of active transport and free diffusion within neuronal processes. These results suggest that individual kinesin-1 motors are utilized for multiple rounds of transport. PMID:24098765

Signals from the ventrolateral thalamus to the motor cortex during locomotion

PubMed Central

Marlinski, Vladimir; Nilaweera, Wijitha U.; Zelenin, Pavel V.; Sirota, Mikhail G.

2012-01-01

The activity of the motor cortex during locomotion is profoundly modulated in the rhythm of strides. The source of modulation is not known. In this study we examined the activity of one of the major sources of afferent input to the motor cortex, the ventrolateral thalamus (VL). Experiments were conducted in chronically implanted cats with an extracellular single-neuron recording technique. VL neurons projecting to the motor cortex were identified by antidromic responses. During locomotion, the activity of 92% of neurons was modulated in the rhythm of strides; 67% of cells discharged one activity burst per stride, a pattern typical for the motor cortex. The characteristics of these discharges in most VL neurons appeared to be well suited to contribute to the locomotion-related activity of the motor cortex. In addition to simple locomotion, we examined VL activity during walking on a horizontal ladder, a task that requires vision for correct foot placement. Upon transition from simple to ladder locomotion, the activity of most VL neurons exhibited the same changes that have been reported for the motor cortex, i.e., an increase in the strength of stride-related modulation and shortening of the discharge duration. Five modes of integration of simple and ladder locomotion-related information were recognized in the VL. We suggest that, in addition to contributing to the locomotion-related activity in the motor cortex during simple locomotion, the VL integrates and transmits signals needed for correct foot placement on a complex terrain to the motor cortex. PMID:21994259

Low signal intensity in motor cortex on susceptibility-weighted MR imaging is correlated with clinical signs of amyotrophic lateral sclerosis: a pilot study.

PubMed

Endo, Hironobu; Sekiguchi, Kenji; Shimada, Hitoshi; Ueda, Takehiro; Kowa, Hisatomo; Kanda, Fumio; Toda, Tatsushi

2018-03-01

There is no reliable objective indicator for upper motor neuron dysfunction in amyotrophic lateral sclerosis (ALS). To determine the clinical significance and potential utility of magnetic resonance (MR) signals, we investigated the relationship between clinical symptoms and susceptibility changes in the motor cortex measured using susceptibility-weighted MR imaging taken by readily available 3-T MRI in clinical practice. Twenty-four ALS patients and 14 control subjects underwent 3-T MR T1-weighted imaging and susceptibility-weighted MR imaging with the principles of echo-shifting with a train of observations (PRESTO) sequence. We analysed relationships between relative susceptibility changes in the motor cortex assessed using voxel-based analysis (VBA) and clinical scores, including upper motor neuron score, ALS functional rating scale revised score, and Medical Research Council sum score on physical examination. Patients with ALS exhibited significantly lower signal intensity in the precentral gyrus on susceptibility-weighted MR imaging compared with controls. Clinical scores were significantly correlated with susceptibility changes. Importantly, the extent of the susceptibility changes in the bilateral precentral gyri was significantly correlated with upper motor neuron scores. The results of our pilot study using VBA indicated that low signal intensity in motor cortex on susceptibility-weighted MR imaging may correspond to clinical symptoms, particularly upper motor neuron dysfunction. Susceptibility-weighted MR imaging may be a useful diagnostic tool as an objective indicator of upper motor neuron dysfunction.

Spasmodic Dysphonia: a Laryngeal Control Disorder Specific to Speech

PubMed Central

Ludlow, Christy L.

2016-01-01

Spasmodic dysphonia (SD) is a rare neurological disorder that emerges in middle age, is usually sporadic, and affects intrinsic laryngeal muscle control only during speech. Spasmodic bursts in particular laryngeal muscles disrupt voluntary control during vowel sounds in adductor SD and interfere with voice onset after voiceless consonants in abductor SD. Little is known about its origins; it is classified as a focal dystonia secondary to an unknown neurobiological mechanism that produces a chronic abnormality of laryngeal motor neuron regulation during speech. It develops primarily in females and does not interfere with breathing, crying, laughter, and shouting. Recent postmortem studies have implicated the accumulation of clusters in the parenchyma and perivascular regions with inflammatory changes in the brainstem in one to two cases. A few cases with single mutations in THAP1, a gene involved in transcription regulation, suggest that a weak genetic predisposition may contribute to mechanisms causing a nonprogressive abnormality in laryngeal motor neuron control for speech but not for vocal emotional expression. Research is needed to address the basic cellular and proteomic mechanisms that produce this disorder to provide intervention that could target the pathogenesis of the disorder rather than only providing temporary symptom relief. PMID:21248101

Spasmodic dysphonia: a laryngeal control disorder specific to speech.

PubMed

Ludlow, Christy L

2011-01-19

Spasmodic dysphonia (SD) is a rare neurological disorder that emerges in middle age, is usually sporadic, and affects intrinsic laryngeal muscle control only during speech. Spasmodic bursts in particular laryngeal muscles disrupt voluntary control during vowel sounds in adductor SD and interfere with voice onset after voiceless consonants in abductor SD. Little is known about its origins; it is classified as a focal dystonia secondary to an unknown neurobiological mechanism that produces a chronic abnormality of laryngeal motor neuron regulation during speech. It develops primarily in females and does not interfere with breathing, crying, laughter, and shouting. Recent postmortem studies have implicated the accumulation of clusters in the parenchyma and perivascular regions with inflammatory changes in the brainstem in one to two cases. A few cases with single mutations in THAP1, a gene involved in transcription regulation, suggest that a weak genetic predisposition may contribute to mechanisms causing a nonprogressive abnormality in laryngeal motor neuron control for speech but not for vocal emotional expression. Research is needed to address the basic cellular and proteomic mechanisms that produce this disorder to provide intervention that could target the pathogenesis of the disorder rather than only providing temporary symptom relief.

eGFP expression under the Uchl1 promoter labels corticospinal motor neurons and a subpopulation of degeneration resistant spinal motor neurons in ALS mouse models

NASA Astrophysics Data System (ADS)

Yasvoina, Marina V.

Current understanding of basic cellular and molecular mechanisms for motor neuron vulnerability during motor neuron disease initiation and progression is incomplete. The complex cytoarchitecture and cellular heterogeneity of the cortex and spinal cord greatly impedes our ability to visualize, isolate, and study specific neuron populations in both healthy and diseased states. We generated a novel reporter line, the Uchl1-eGFP mouse, in which cortical and spinal components of motor neuron circuitry are genetically labeled with eGFP under the Uchl1 promoter. A series of cellular and anatomical analyses combined with retrograde labeling, molecular marker expression, and electrophysiology were employed to determine identity of eGFP expressing cells in the motor cortex and the spinal cord of novel Uchl1-eGFP reporter mice. We conclude that eGFP is expressed in corticospinal motor neurons (CSMN) in the motor cortex and a subset of S-type alpha and gamma spinal motor neurons (SMN) in the spinal cord. hSOD1G93A and Alsin-/- mice, mouse models for amyotrophic lateral sclerosis (ALS), were bred to Uchl1-eGFP reporter mouse line to investigate the pathophysiology and underlying mechanisms of CSMN degeneration in vivo. Evidence suggests early and progressive degeneration of CSMN and SMN in the hSOD1G93A transgenic mice. We show an early increase of autophagosome formation in the apical dendrites of vulnerable CSMN in hSOD1G93A-UeGFP mice, which is localized to the apical dendrites. In addition, labeling S-type alpha and gamma SMN in the hSOD1G93A-UeGFP mice provide a unique opportunity to study basis of their resistance to degeneration. Mice lacking alsin show moderate clinical phenotype and mild CSMN axon degeneration in the spinal cord, which suggests vulnerability of CSMN. Therefore, we investigated the CSMN cellular and axon defects in aged Alsin-/- mice bred to Uchl1-eGFP reporter mouse line. We show that while CSMN are preserved and lack signs of degeneration, CSMN axons are vulnerable and show significant loss.

The multi-dimensional roles of astrocytes in ALS.

PubMed

Yamanaka, Koji; Komine, Okiru

2018-01-01

Despite significant progress in understanding the molecular and genetic aspects of amyotrophic lateral sclerosis (ALS), a fatal neurodegenerative disease characterized by the progressive loss of motor neurons, the precise and comprehensive pathomechanisms remain largely unknown. In addition to motor neuron involvement, recent studies using cellular and animal models of ALS indicate that there is a complex interplay between motor neurons and neighboring non-neuronal cells, such as astrocytes, in non-cell autonomous neurodegeneration. Astrocytes are key homeostatic cells that play numerous supportive roles in maintaining the brain environment. In neurodegenerative diseases such as ALS, astrocytes change their shape and molecular expression patterns and are referred to as reactive or activated astrocytes. Reactive astrocytes in ALS lose their beneficial functions and gain detrimental roles. In addition, interactions between motor neurons and astrocytes are impaired in ALS. In this review, we summarize growing evidence that astrocytes are critically involved in the survival and demise of motor neurons through several key molecules and cascades in astrocytes in both sporadic and inherited ALS. These observations strongly suggest that astrocytes have multi-dimensional roles in disease and are a viable therapeutic target for ALS. Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.

Mutant Copper-Zinc Superoxide Dismutase (SOD1) Induces Protein Secretion Pathway Alterations and Exosome Release in Astrocytes

PubMed Central

Basso, Manuela; Pozzi, Silvia; Tortarolo, Massimo; Fiordaliso, Fabio; Bisighini, Cinzia; Pasetto, Laura; Spaltro, Gabriella; Lidonnici, Dario; Gensano, Francesco; Battaglia, Elisa; Bendotti, Caterina; Bonetto, Valentina

2013-01-01

Amyotrophic lateral sclerosis is the most common motor neuron disease and is still incurable. The mechanisms leading to the selective motor neuron vulnerability are still not known. The interplay between motor neurons and astrocytes is crucial in the outcome of the disease. We show that mutant copper-zinc superoxide dismutase (SOD1) overexpression in primary astrocyte cultures is associated with decreased levels of proteins involved in secretory pathways. This is linked to a general reduction of total secreted proteins, except for specific enrichment in a number of proteins in the media, such as mutant SOD1 and valosin-containing protein (VCP)/p97. Because there was also an increase in exosome release, we can deduce that astrocytes expressing mutant SOD1 activate unconventional secretory pathways, possibly as a protective mechanism. This may help limit the formation of intracellular aggregates and overcome mutant SOD1 toxicity. We also found that astrocyte-derived exosomes efficiently transfer mutant SOD1 to spinal neurons and induce selective motor neuron death. We conclude that the expression of mutant SOD1 has a substantial impact on astrocyte protein secretion pathways, contributing to motor neuron pathology and disease spread. PMID:23592792

Prolyl hydroxylase regulates axonal rewiring and motor recovery after traumatic brain injury

PubMed Central

Miyake, S; Muramatsu, R; Hamaguchi, M; Yamashita, T

2015-01-01

Prolyl 4-hydroxylases (PHDs; PHD1, PHD2, and PHD3) are a component of cellular oxygen sensors that regulate the adaptive response depending on the oxygen concentration stabilized by hypoxia/stress-regulated genes transcription. In normoxic condition, PHD2 is required to stabilize hypoxia inducible factors. Silencing of PHD2 leads to the activation of intracellular signaling including RhoA and Rho-associated protein kinase (ROCK), which are key regulators of neurite growth. In this study, we determined that genetic or pharmacological inhibition of PHD2 in cultured cortical neurons prevents neurite elongation through a ROCK-dependent mechanism. We then explored the role of PHDs in axonal reorganization following a traumatic brain injury in adult mice. Unilateral destruction of motor cortex resulted in behavioral deficits due to disruption of the corticospinal tract (CST), a part of the descending motor pathway. In the spinal cord, sprouting of fibers from the intact side of the CST into the denervated side is thought to contribute to the recovery process following an injury. Intracortical infusion of PHD inhibitors into the intact side of the motor cortex abrogated spontaneous formation of CST collaterals and functional recovery after damage to the sensorimotor cortex. These findings suggest PHDs have an important role in the formation of compensatory axonal networks following an injury and may represent a new molecular target for the central nervous system disorders. PMID:25675298

FMRFamide produces biphasic modulation of the LFS motor neurons in the neural circuit of the siphon withdrawal reflex of Aplysia by activating Na+ and K+ currents.

PubMed

Belkin, K J; Abrams, T W

1993-12-01

The molluscan neuropeptide FMRFamide has an inhibitory effect on transmitter release from the presynaptic sensory neurons in the neural circuit for the siphon withdrawal reflex. We have explored whether FMRFamide also acts postsynaptically in motor neurons in this circuit, focusing on the LFS motor neurons. FMRFamide typically produces a biphasic response in LFS neurons: a fast excitatory response followed by a prolonged inhibitory response. We have analyzed these postsynaptic actions and compared them with the mechanism of FMRFamide's inhibition of the presynaptic sensory neurons. The transient excitatory effect of FMRFamide, which desensitizes rapidly, is due to activation of a TTX-insensitive, Na(+)-dependent inward current. The late hyperpolarizing phase of the FMRFamide response results from activation of at least two K+ currents. One component of the hyperpolarizing response is active at rest and at more hyperpolarized membrane potentials, and is blocked by 5 mM 4-aminopyridine, suggesting that it differs from the previously described FMRFamide-modulated K+ currents in the presynaptic sensory neurons. In addition, FMRFamide increases a 4-aminopyridine-insensitive K+ current. Presynaptically, FMRFamide increases K+ conductance, acting via release of arachidonic acid. In the LFS motor neurons, application of arachidonic acid mimicked the prolonged, hyperpolarizing phase of the FMRFamide response; 4-bromophenacyl bromide, an inhibitor of phospholipase A2, selectively blocked this component of the FMRFamide response. Thus, FMRFamide may act in parallel pre- and post-synaptically to inhibit the output of the siphon withdrawal reflex circuit, producing this inhibitory effect via the same second messenger in the sensory neurons and motor neurons, though a number of the K+ currents modulated in these two types of neurons are different.

Identification of a motor to auditory pathway important for vocal learning

PubMed Central

Roberts, Todd F.; Hisey, Erin; Tanaka, Masashi; Kearney, Matthew; Chattree, Gaurav; Yang, Cindy F.; Shah, Nirao M.; Mooney, Richard

2017-01-01

Summary Learning to vocalize depends on the ability to adaptively modify the temporal and spectral features of vocal elements. Neurons that convey motor-related signals to the auditory system are theorized to facilitate vocal learning, but the identity and function of such neurons remain unknown. Here we identify a previously unknown neuron type in the songbird brain that transmits vocal motor signals to the auditory cortex. Genetically ablating these neurons in juveniles disrupted their ability to imitate features of an adult tutor’s song. Ablating these neurons in adults had little effect on previously learned songs, but interfered with their ability to adaptively modify the duration of vocal elements and largely prevented the degradation of song’s temporal features normally caused by deafening. These findings identify a motor to auditory circuit essential to vocal imitation and to the adaptive modification of vocal timing. PMID:28504672

Delayed post-treatment with bone marrow-derived mesenchymal stem cells is neurorestorative of striatal medium-spiny projection neurons and improves motor function after neonatal rat hypoxia-ischemia.

PubMed

Cameron, Stella H; Alwakeel, Amr J; Goddard, Liping; Hobbs, Catherine E; Gowing, Emma K; Barnett, Elizabeth R; Kohe, Sarah E; Sizemore, Rachel J; Oorschot, Dorothy E

2015-09-01

Perinatal hypoxia-ischemia is a major cause of striatal injury and may lead to cerebral palsy. This study investigated whether delayed administration of bone marrow-derived mesenchymal stem cells (MSCs), at one week after neonatal rat hypoxia-ischemia, was neurorestorative of striatal medium-spiny projection neurons and improved motor function. The effect of a subcutaneous injection of a high-dose, or a low-dose, of MSCs was investigated in stereological studies. Postnatal day (PN) 7 pups were subjected to hypoxia-ischemia. At PN14, pups received treatment with either MSCs or diluent. A subset of high-dose pups, and their diluent control pups, were also injected intraperitoneally with bromodeoxyuridine (BrdU), every 24h, on PN15, PN16 and PN17. This permitted tracking of the migration and survival of neuroblasts originating from the subventricular zone into the adjacent injured striatum. Pups were euthanized on PN21 and the absolute number of striatal medium-spiny projection neurons was measured after immunostaining for DARPP-32 (dopamine- and cAMP-regulated phosphoprotein-32), double immunostaining for BrdU and DARPP-32, and after cresyl violet staining alone. The absolute number of striatal immunostained calretinin interneurons was also measured. There was a statistically significant increase in the absolute number of DARPP-32-positive, BrdU/DARPP-32-positive, and cresyl violet-stained striatal medium-spiny projection neurons, and fewer striatal calretinin interneurons, in the high-dose mesenchymal stem cell (MSC) group compared to their diluent counterparts. A high-dose of MSCs restored the absolute number of these neurons to normal uninjured levels, when compared with previous stereological data on the absolute number of cresyl violet-stained striatal medium-spiny projection neurons in the normal uninjured brain. For the low-dose experiment, in which cresyl violet-stained striatal medium-spiny neurons alone were measured, there was a lower statistically significant increase in their absolute number in the MSC group compared to their diluent controls. Investigation of behavior in another cohort of animals showed that delayed administration of a high-dose of bone marrow-derived MSCs, at one week after neonatal rat hypoxia-ischemia, improved motor function on the cylinder test. Thus, delayed therapy with a high- or low-dose of adult MSCs, at one week after injury, is effective in restoring the loss of striatal medium-spiny projection neurons after neonatal rat hypoxia-ischemia and a high-dose of MSCs improved motor function. Copyright © 2015 Elsevier Inc. All rights reserved.

Coordinated temporal and spatial control of motor neuron and serotonergic neuron generation from a common pool of CNS progenitors

PubMed Central

Pattyn, Alexandre; Vallstedt, Anna; Dias, José M.; Samad, Omar Abdel; Krumlauf, Robb; Rijli, Filippo M.; Brunet, Jean-Francois; Ericson, Johan

2003-01-01

Neural progenitor cells often produce distinct types of neurons in a specific order, but the determinants that control the sequential generation of distinct neuronal subclasses in the vertebrate CNS remain poorly defined. We examined the sequential generation of visceral motor neurons and serotonergic neurons from a common pool of neural progenitors located in the ventral hindbrain. We found that the temporal specification of these neurons varies along the anterior-posterior axis of the hindbrain, and that the timing of their generation critically depends on the integrated activities of Nkx- and Hox-class homeodomain proteins. A primary function of these proteins is to coordinate the spatial and temporal activation of the homeodomain protein Phox2b, which in turn acts as a binary switch in the selection of motor neuron or serotonergic neuronal fate. These findings assign new roles for Nkx, Hox, and Phox2 proteins in the control of temporal neuronal fate determination, and link spatial and temporal patterning of CNS neuronal fates. PMID:12651891

ALS-associated mutant FUS induces selective motor neuron degeneration through toxic gain of function

PubMed Central

Sharma, Aarti; Lyashchenko, Alexander K.; Lu, Lei; Nasrabady, Sara Ebrahimi; Elmaleh, Margot; Mendelsohn, Monica; Nemes, Adriana; Tapia, Juan Carlos; Mentis, George Z.; Shneider, Neil A.

2016-01-01

Mutations in FUS cause amyotrophic lateral sclerosis (ALS), including some of the most aggressive, juvenile-onset forms of the disease. FUS loss-of-function and toxic gain-of-function mechanisms have been proposed to explain how mutant FUS leads to motor neuron degeneration, but neither has been firmly established in the pathogenesis of ALS. Here we characterize a series of transgenic FUS mouse lines that manifest progressive, mutant-dependent motor neuron degeneration preceded by early, structural and functional abnormalities at the neuromuscular junction. A novel, conditional FUS knockout mutant reveals that postnatal elimination of FUS has no effect on motor neuron survival or function. Moreover, endogenous FUS does not contribute to the onset of the ALS phenotype induced by mutant FUS. These findings demonstrate that FUS-dependent motor degeneration is not due to loss of FUS function, but to the gain of toxic properties conferred by ALS mutations. PMID:26842965

ALS-associated mutant FUS induces selective motor neuron degeneration through toxic gain of function.

PubMed

Sharma, Aarti; Lyashchenko, Alexander K; Lu, Lei; Nasrabady, Sara Ebrahimi; Elmaleh, Margot; Mendelsohn, Monica; Nemes, Adriana; Tapia, Juan Carlos; Mentis, George Z; Shneider, Neil A

2016-02-04

Mutations in FUS cause amyotrophic lateral sclerosis (ALS), including some of the most aggressive, juvenile-onset forms of the disease. FUS loss-of-function and toxic gain-of-function mechanisms have been proposed to explain how mutant FUS leads to motor neuron degeneration, but neither has been firmly established in the pathogenesis of ALS. Here we characterize a series of transgenic FUS mouse lines that manifest progressive, mutant-dependent motor neuron degeneration preceded by early, structural and functional abnormalities at the neuromuscular junction. A novel, conditional FUS knockout mutant reveals that postnatal elimination of FUS has no effect on motor neuron survival or function. Moreover, endogenous FUS does not contribute to the onset of the ALS phenotype induced by mutant FUS. These findings demonstrate that FUS-dependent motor degeneration is not due to loss of FUS function, but to the gain of toxic properties conferred by ALS mutations.

Loss of MeCP2 From Forebrain Excitatory Neurons Leads to Cortical Hyperexcitation and Seizures

PubMed Central

Zhang, Wen; Peterson, Matthew; Beyer, Barbara; Frankel, Wayne N.

2014-01-01

Mutations of MECP2 cause Rett syndrome (RTT), a neurodevelopmental disorder leading to loss of motor and cognitive functions, impaired social interactions, and seizure at young ages. Defects of neuronal circuit development and function are thought to be responsible for the symptoms of RTT. The majority of RTT patients show recurrent seizures, indicating that neuronal hyperexcitation is a common feature of RTT. However, mechanisms underlying hyperexcitation in RTT are poorly understood. Here we show that deletion of Mecp2 from cortical excitatory neurons but not forebrain inhibitory neurons in the mouse leads to spontaneous seizures. Selective deletion of Mecp2 from excitatory but not inhibitory neurons in the forebrain reduces GABAergic transmission in layer 5 pyramidal neurons in the prefrontal and somatosensory cortices. Loss of MeCP2 from cortical excitatory neurons reduces the number of GABAergic synapses in the cortex, and enhances the excitability of layer 5 pyramidal neurons. Using single-cell deletion of Mecp2 in layer 2/3 pyramidal neurons, we show that GABAergic transmission is reduced in neurons without MeCP2, but is normal in neighboring neurons with MeCP2. Together, these results suggest that MeCP2 in cortical excitatory neurons plays a critical role in the regulation of GABAergic transmission and cortical excitability. PMID:24523563

RIC-3 phosphorylation enables dual regulation of excitation and inhibition of Caenorhabditis elegans muscle

PubMed Central

Safdie, Gracia; Liewald, Jana F.; Kagan, Sarah; Battat, Emil; Gottschalk, Alexander; Treinin, Millet

2016-01-01

Brain function depends on a delicate balance between excitation and inhibition. Similarly, Caenorhabditis elegans motor system function depends on a precise balance between excitation and inhibition, as C. elegans muscles receive both inhibitory, GABAergic and excitatory, cholinergic inputs from motor neurons. Here we show that phosphorylation of the ER-resident chaperone of nicotinic acetylcholine receptors, RIC-3, leads to increased muscle excitability. RIC-3 phosphorylation at Ser-164 depends on opposing functions of the phosphatase calcineurin (TAX-6), and of the casein kinase II homologue KIN-10. Effects of calcineurin down-regulation and of phosphorylated RIC-3 on muscle excitability are mediated by GABAA receptor inhibition. Thus RIC-3 phosphorylation enables effects of this chaperone on GABAA receptors in addition to nAChRs. This dual effect provides coordinated regulation of excitation and inhibition and enables fine-tuning of the excitation–inhibition balance. Moreover, regulation of inhibitory GABAA signaling by calcineurin, a calcium- and calmodulin-dependent phosphatase, enables homeostatic balancing of excitation and inhibition. PMID:27489343

The inferior parietal lobule: where action becomes perception.

PubMed

Rizzolatti, Giacomo; Ferrari, Pier Francesco; Rozzi, Stefano; Fogassi, Leonardo

2006-01-01

The view defended in this article is that action and perception share the same neural substrate. To substantiate this view, the anatomical and functional organization of the inferior parietal lobule (IPL) is reviewed. In particular, it will be shown that many IPL neurons discharge selectively when the monkey executes a given motor act (e.g. grasping). Most interestingly, most of them fire only if the coded motor act is followed by a subsequent specific motor act (e.g. placing). Some of these action-constrained motor neurons have mirror properties and selectively discharge during the observation of motor acts when these are embedded in a given action (e.g. grasping for eating, but not grasping for placing). Thus, the activation of these IPL neurons allows the observer not only to recognize the observed motor act, but also to predict what will be the next motor act of the action, that is to understand the intentions of the action's agent. The finding that the same neurons that are active during the execution of specific motor acts also mediate the understanding of the 'what' and the 'why' of others' actions provides strong evidence for a common neural substrate for action and perception.

Actin and microtubule-based cytoskeletal cues direct polarized targeting of proteins in neurons

PubMed Central

Arnold, Don B.

2010-01-01

Neuronal proteins are transported to either the axon or dendrites through the action of kinesin motors; however understanding of how cytoskeletal elements steer these cargo-motor complexes to one compartment or the other has remained elusive. Three recent developments, the discovery of an actin-based filter within the axon initial segment, the identification of the pivotal role played by myosin motors in dendritic targeting, and the determination of the properties of a kinesin motor that cause it to prefer axonal to dendritic microtubules, have now provided a structural framework for understanding polarized targeting in neurons. PMID:19671926

Chronic Exposure to Dietary Sterol Glucosides is Neurotoxic to Motor Neurons and Induces an ALS-PDC Phenotype

PubMed Central

Tabata, R. C.; Wilson, J. M. B.; Ly, P.; Zwiegers, P.; Kwok, D.; Van Kampen, J. M.; Cashman, N.; Shaw, C. A.

2008-01-01

Epidemiological studies of the Guamanian variants of amyotrophic lateral sclerosis (ALS) and parkinsonism, amyotrophic lateral sclerosis-parkinsonism dementia complex (ALS-PDC), have shown a positive correlation between consumption of washed cycad seed flour and disease occurrence. Previous in vivo studies by our group have shown that the same seed flour induces ALS and PDC phenotypes in out bred adult male mice. In vitro studies using isolated cycad compounds have also demonstrated that several of these are neurotoxic, specifically, a number of water insoluble phytosterol glucosides of which β-sitosterol β-d-glucoside (BSSG) forms the largest fraction. BSSG is neurotoxic to motor neurons and other neuronal populations in culture. The present study shows that an in vitro hybrid motor neuron (NSC-34) culture treated with BSSG undergoes a dose-dependent cell loss. Surviving cells show increased expression of HSP70, decreased cytosolic heavy neurofilament expression, and have various morphological abnormalities. CD-1 mice fed mouse chow pellets containing BSSG for 15 weeks showed motor deficits and motor neuron loss in the lumbar and thoracic spinal cord, along with decreased glutamate transporter labelling, and increased glial fibrillary acid protein reactivity. Other pathological outcomes included increased caspase-3 labelling in the striatum and decreased tyrosine-hydroxylase labelling in the striatum and substantia nigra. C57BL/6 mice fed BSSG-treated pellets for 10 weeks exhibited progressive loss of motor neurons in the lumbar spinal cord that continued to worsen even after the BSSG exposure ended. These results provide further support implicating sterol glucosides as one potential causal factor in the motor neuron pathology previously associated with cycad consumption and ALS-PDC. PMID:18196479

Loss of nuclear TDP-43 in amyotrophic lateral sclerosis (ALS) causes altered expression of splicing machinery and widespread dysregulation of RNA splicing in motor neurones.

PubMed

Highley, J Robin; Kirby, Janine; Jansweijer, Joeri A; Webb, Philip S; Hewamadduma, Channa A; Heath, Paul R; Higginbottom, Adrian; Raman, Rohini; Ferraiuolo, Laura; Cooper-Knock, Johnathan; McDermott, Christopher J; Wharton, Stephen B; Shaw, Pamela J; Ince, Paul G

2014-10-01

Loss of nuclear TDP-43 characterizes sporadic and most familial forms of amyotrophic lateral sclerosis (ALS). TDP-43 (encoded by TARDBP) has multiple roles in RNA processing. We aimed to determine whether (1) RNA splicing dysregulation is present in lower motor neurones in ALS and in a motor neurone-like cell model; and (2) TARDBP mutations (mtTARDBP) are associated with aberrant RNA splicing using patient-derived fibroblasts. Affymetrix exon arrays were used to study mRNA expression and splicing in lower motor neurones obtained by laser capture microdissection of autopsy tissue from individuals with sporadic ALS and TDP-43 proteinopathy. Findings were confirmed by quantitative reverse transcription-polymerase chain reaction (qRT-PCR) and in NSC34 motor neuronal cells following shRNA-mediated TDP-43 depletion. Exon arrays and immunohistochemistry were used to study mRNA splicing and TDP-43 expression in fibroblasts from patients with mtTARDBP-associated, sporadic and mutant SOD1-associated ALS. We found altered expression of spliceosome components in motor neurones and widespread aberrations of mRNA splicing that specifically affected genes involved in ribonucleotide binding. This was confirmed in TDP-43-depleted NSC34 cells. Fibroblasts with mtTARDBP showed loss of nuclear TDP-43 protein and demonstrated similar changes in splicing and gene expression, which were not present in fibroblasts from patients with sporadic or SOD1-related ALS. Loss of nuclear TDP-43 is associated with RNA processing abnormalities in ALS motor neurones, patient-derived cells with mtTARDBP, and following artificial TDP-43 depletion, suggesting that splicing dysregulation directly contributes to disease pathogenesis. Key functional pathways affected include those central to RNA metabolism. © 2014 British Neuropathological Society.

Transcriptomic indices of fast and slow disease progression in two mouse models of amyotrophic lateral sclerosis.

PubMed

Nardo, Giovanni; Iennaco, Raffaele; Fusi, Nicolò; Heath, Paul R; Marino, Marianna; Trolese, Maria C; Ferraiuolo, Laura; Lawrence, Neil; Shaw, Pamela J; Bendotti, Caterina

2013-11-01

Amyotrophic lateral sclerosis is heterogeneous with high variability in the speed of progression even in cases with a defined genetic cause such as superoxide dismutase 1 (SOD1) mutations. We reported that SOD1(G93A) mice on distinct genetic backgrounds (C57 and 129Sv) show consistent phenotypic differences in speed of disease progression and life-span that are not explained by differences in human SOD1 transgene copy number or the burden of mutant SOD1 protein within the nervous system. We aimed to compare the gene expression profiles of motor neurons from these two SOD1(G93A) mouse strains to discover the molecular mechanisms contributing to the distinct phenotypes and to identify factors underlying fast and slow disease progression. Lumbar spinal motor neurons from the two SOD1(G93A) mouse strains were isolated by laser capture microdissection and transcriptome analysis was conducted at four stages of disease. We identified marked differences in the motor neuron transcriptome between the two mice strains at disease onset, with a dramatic reduction of gene expression in the rapidly progressive (129Sv-SOD1(G93A)) compared with the slowly progressing mutant SOD1 mice (C57-SOD1(G93A)) (1276 versus 346; Q-value ≤ 0.01). Gene ontology pathway analysis of the transcriptional profile from 129Sv-SOD1(G93A) mice showed marked downregulation of specific pathways involved in mitochondrial function, as well as predicted deficiencies in protein degradation and axonal transport mechanisms. In contrast, the transcriptional profile from C57-SOD1(G93A) mice with the more benign disease course, revealed strong gene enrichment relating to immune system processes compared with 129Sv-SOD1(G93A) mice. Motor neurons from the more benign mutant strain demonstrated striking complement activation, over-expressing genes normally involved in immune cell function. We validated through immunohistochemistry increased expression of the C3 complement subunit and major histocompatibility complex I within motor neurons. In addition, we demonstrated that motor neurons from the slowly progressing mice activate a series of genes with neuroprotective properties such as angiogenin and the nuclear factor (erythroid-derived 2)-like 2 transcriptional regulator. In contrast, the faster progressing mice show dramatically reduced expression at disease onset of cell pathways involved in neuroprotection. This study highlights a set of key gene and molecular pathway indices of fast or slow disease progression which may prove useful in identifying potential disease modifiers responsible for the heterogeneity of human amyotrophic lateral sclerosis and which may represent valid therapeutic targets for ameliorating the disease course in humans.

System xC- is a mediator of microglial function and its deletion slows symptoms in amyotrophic lateral sclerosis mice.

PubMed

Mesci, Pinar; Zaïdi, Sakina; Lobsiger, Christian S; Millecamps, Stéphanie; Escartin, Carole; Seilhean, Danielle; Sato, Hideyo; Mallat, Michel; Boillée, Séverine

2015-01-01

Amyotrophic lateral sclerosis is the most common adult-onset motor neuron disease and evidence from mice expressing amyotrophic lateral sclerosis-causing SOD1 mutations suggest that neurodegeneration is a non-cell autonomous process where microglial cells influence disease progression. However, microglial-derived neurotoxic factors still remain largely unidentified in amyotrophic lateral sclerosis. With excitotoxicity being a major mechanism proposed to cause motor neuron death in amyotrophic lateral sclerosis, our hypothesis was that excessive glutamate release by activated microglia through their system [Formula: see text] (a cystine/glutamate antiporter with the specific subunit xCT/Slc7a11) could contribute to neurodegeneration. Here we show that xCT expression is enriched in microglia compared to total mouse spinal cord and absent from motor neurons. Activated microglia induced xCT expression and during disease, xCT levels were increased in both spinal cord and isolated microglia from mutant SOD1 amyotrophic lateral sclerosis mice. Expression of xCT was also detectable in spinal cord post-mortem tissues of patients with amyotrophic lateral sclerosis and correlated with increased inflammation. Genetic deletion of xCT in mice demonstrated that activated microglia released glutamate mainly through system [Formula: see text]. Interestingly, xCT deletion also led to decreased production of specific microglial pro-inflammatory/neurotoxic factors including nitric oxide, TNFa and IL6, whereas expression of anti-inflammatory/neuroprotective markers such as Ym1/Chil3 were increased, indicating that xCT regulates microglial functions. In amyotrophic lateral sclerosis mice, xCT deletion surprisingly led to earlier symptom onset but, importantly, this was followed by a significantly slowed progressive disease phase, which resulted in more surviving motor neurons. These results are consistent with a deleterious contribution of microglial-derived glutamate during symptomatic disease. Therefore, we show that system [Formula: see text] participates in microglial reactivity and modulates amyotrophic lateral sclerosis motor neuron degeneration, revealing system [Formula: see text] inactivation, as a potential approach to slow amyotrophic lateral sclerosis disease progression after onset of clinical symptoms. © The Author (2014). Published by Oxford University Press on behalf of the Guarantors of Brain. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Autophagy-mediated stress response in motor neurons after hypothermic spinal cord ischemia in rabbits.

PubMed

Fujita, Satoshi; Sakurai, Masahiro; Baba, Hironori; Abe, Koji; Tominaga, Ryuji

2015-11-01

The development of spinal cord injury is believed to be related to the vulnerability of spinal motor neurons to ischemia. However, the mechanisms underlying this vulnerability have not been fully investigated. Previously, we reported that spinal motor neurons are lost likely due to autophagy and that local hypothermia prevents such spinal motor neuron death. Therefore, we investigated the role of autophagy in normothermic and hypothermic spinal cord ischemia using an immunohistochemical analysis of Beclin 1 (BCLN1; B-cell leukemia 2 protein [Bcl-2] interacting protein), Bcl-2, and γ-aminobutyric acid type-A receptor-associated protein (GABARAP), which are considered autophagy-related proteins. We used rabbit normothermic and hypothermic transient spinal cord ischemia models using a balloon catheter. Neurologic function was assessed according to the Johnson score, and the spinal cord was removed at 8 hours and 1, 2, and 7 days after reperfusion, and morphologic changes were examined using hematoxylin and eosin staining. A Western blot analysis and histochemical study of BCLN1, Bcl-2, and GABARAP, and double-labeled fluorescent immunocytochemical studies were performed. There were significant differences in the physiologic function between the normothermic model and hypothermic model after the procedure (P < .05). In the normothermic model, most of the motor neurons were selectively lost at 7 days of reperfusion (P < .001 compared with the sham group), and they were preserved in the hypothermic model (P = .574 compared with the sham group). The Western blot analysis revealed that the sustained expression of the autophagy markers, BCLN1 and GABARAP, was observed (P < .001 compared with the sham group) and was associated with neuronal cell death in normothermic ischemic conditions. In hypothermic ischemic conditions, the autophagy inhibitory protein Bcl-2 was powerfully induced (P < .001 compared with the sham group) and was associated with blunted expression of BCLN1 and GABARAP and neuronal cell survival. The double-label fluorescent immunocytochemical study revealed that immunoreactivitiy for BCLN1, Bcl-2, and GABARAP was induced in the same motor neurons. These data suggest that the prolonged induction of autophagy might be a potential factor responsible for delayed motor neuron death, and the induction of the autophagy inhibitory protein Bcl-2 using hypothermia might limit autophagy and protect against delayed motor neuron death. Copyright © 2015 Society for Vascular Surgery. Published by Elsevier Inc. All rights reserved.

High-Resolution 7T MR Imaging of the Motor Cortex in Amyotrophic Lateral Sclerosis.

PubMed

Cosottini, M; Donatelli, G; Costagli, M; Caldarazzo Ienco, E; Frosini, D; Pesaresi, I; Biagi, L; Siciliano, G; Tosetti, M

2016-03-01

Amyotrophic lateral sclerosis is a progressive motor neuron disorder that involves degeneration of both upper and lower motor neurons. In patients with amyotrophic lateral sclerosis, pathologic studies and ex vivo high-resolution MR imaging at ultra-high field strength revealed the co-localization of iron and activated microglia distributed in the deep layers of the primary motor cortex. The aims of the study were to measure the cortical thickness and evaluate the distribution of iron-related signal changes in the primary motor cortex of patients with amyotrophic lateral sclerosis as possible in vivo biomarkers of upper motor neuron impairment. Twenty-two patients with definite amyotrophic lateral sclerosis and 14 healthy subjects underwent a high-resolution 2D multiecho gradient-recalled sequence targeted on the primary motor cortex by using a 7T scanner. Image analysis consisted of the visual evaluation and quantitative measurement of signal intensity and cortical thickness of the primary motor cortex in patients and controls. Qualitative and quantitative MR imaging parameters were correlated with electrophysiologic and laboratory data and with clinical scores. Ultra-high field MR imaging revealed atrophy and signal hypointensity in the deep layers of the primary motor cortex of patients with amyotrophic lateral sclerosis with a diagnostic accuracy of 71%. Signal hypointensity of the deep layers of the primary motor cortex correlated with upper motor neuron impairment (r = -0.47; P < .001) and with disease progression rate (r = -0.60; P = .009). The combined high spatial resolution and sensitivity to paramagnetic substances of 7T MR imaging demonstrate in vivo signal changes of the cerebral motor cortex that resemble the distribution of activated microglia within the cortex of patients with amyotrophic lateral sclerosis. Cortical thinning and signal hypointensity of the deep layers of the primary motor cortex could constitute a marker of upper motor neuron impairment in patients with amyotrophic lateral sclerosis. © 2016 by American Journal of Neuroradiology.

Parallel pathways from motor and somatosensory cortex for controlling whisker movements in mice

PubMed Central

Sreenivasan, Varun; Karmakar, Kajari; Rijli, Filippo M; Petersen, Carl C H

2015-01-01

Mice can gather tactile sensory information by actively moving their whiskers to palpate objects in their immediate surroundings. Whisker sensory perception therefore requires integration of sensory and motor information, which occurs prominently in the neocortex. The signalling pathways from the neocortex for controlling whisker movements are currently poorly understood in mice. Here, we delineate two pathways, one originating from primary whisker somatosensory cortex (wS1) and the other from whisker motor cortex (wM1), that control qualitatively distinct movements of contralateral whiskers. Optogenetic stimulation of wS1 drove retraction of contralateral whiskers while stimulation of wM1 drove rhythmic whisker protraction. To map brainstem pathways connecting these cortical areas to whisker motor neurons, we used a combination of anterograde tracing using adenoassociated virus injected into neocortex and retrograde tracing using monosynaptic rabies virus injected into whisker muscles. Our data are consistent with wS1 driving whisker retraction by exciting glutamatergic premotor neurons in the rostral spinal trigeminal interpolaris nucleus, which in turn activate the motor neurons innervating the extrinsic retractor muscle nasolabialis. The rhythmic whisker protraction evoked by wM1 stimulation might be driven by excitation of excitatory and inhibitory premotor neurons in the brainstem reticular formation innervating both intrinsic and extrinsic muscles. Our data therefore begin to unravel the neuronal circuits linking the neocortex to whisker motor neurons. PMID:25476605

The Src/c-Abl pathway is a potential therapeutic target in amyotrophic lateral sclerosis.

PubMed

Imamura, Keiko; Izumi, Yuishin; Watanabe, Akira; Tsukita, Kayoko; Woltjen, Knut; Yamamoto, Takuya; Hotta, Akitsu; Kondo, Takayuki; Kitaoka, Shiho; Ohta, Akira; Tanaka, Akito; Watanabe, Dai; Morita, Mitsuya; Takuma, Hiroshi; Tamaoka, Akira; Kunath, Tilo; Wray, Selina; Furuya, Hirokazu; Era, Takumi; Makioka, Kouki; Okamoto, Koichi; Fujisawa, Takao; Nishitoh, Hideki; Homma, Kengo; Ichijo, Hidenori; Julien, Jean-Pierre; Obata, Nanako; Hosokawa, Masato; Akiyama, Haruhiko; Kaneko, Satoshi; Ayaki, Takashi; Ito, Hidefumi; Kaji, Ryuji; Takahashi, Ryosuke; Yamanaka, Shinya; Inoue, Haruhisa

2017-05-24

Amyotrophic lateral sclerosis (ALS), a fatal disease causing progressive loss of motor neurons, still has no effective treatment. We developed a phenotypic screen to repurpose existing drugs using ALS motor neuron survival as readout. Motor neurons were generated from induced pluripotent stem cells (iPSCs) derived from an ALS patient with a mutation in superoxide dismutase 1 ( SOD1 ). Results of the screen showed that more than half of the hits targeted the Src/c-Abl signaling pathway. Src/c-Abl inhibitors increased survival of ALS iPSC-derived motor neurons in vitro. Knockdown of Src or c-Abl with small interfering RNAs (siRNAs) also rescued ALS motor neuron degeneration. One of the hits, bosutinib, boosted autophagy, reduced the amount of misfolded mutant SOD1 protein, and attenuated altered expression of mitochondrial genes. Bosutinib also increased survival in vitro of ALS iPSC-derived motor neurons from patients with sporadic ALS or other forms of familial ALS caused by mutations in TAR DNA binding protein ( TDP-43 ) or repeat expansions in C9orf72 Furthermore, bosutinib treatment modestly extended survival of a mouse model of ALS with an SOD1 mutation, suggesting that Src/c-Abl may be a potentially useful target for developing new drugs to treat ALS. Copyright © 2017, American Association for the Advancement of Science.

Single photon emission computed tomography in motor neuron disease with dementia.

PubMed

Sawada, H; Udaka, F; Kishi, Y; Seriu, N; Mezaki, T; Kameyama, M; Honda, M; Tomonobu, M

1988-01-01

Single photon emission computed tomography with [123 I] isopropylamphetamine was carried out on a patient with motor neuron disease with dementia. [123 I] uptake was decreased in the frontal lobes. This would reflect the histopathological findings such as neuronal loss and gliosis in the frontal lobes.

IGF-1: elixir for motor neuron diseases.

PubMed

Papanikolaou, Theodora; Ellerby, Lisa M

2009-08-13

Modulation of testosterone levels is a therapeutic approach for spinal and bulbar muscular atrophy (SBMA), a polyglutamine disorder that affects the motor neurons. The article by Palazzolo et al. in this issue of Neuron provides compelling evidence that the expression of insulin growth hormone is a potential therapeutic for SBMA.

Metabolic Reprogramming in Amyotrophic Lateral Sclerosis.

PubMed

Szelechowski, M; Amoedo, N; Obre, E; Léger, C; Allard, L; Bonneu, M; Claverol, S; Lacombe, D; Oliet, S; Chevallier, S; Le Masson, G; Rossignol, R

2018-03-02

Mitochondrial dysfunction in the spinal cord is a hallmark of amyotrophic lateral sclerosis (ALS), but the neurometabolic alterations during early stages of the disease remain unknown. Here, we investigated the bioenergetic and proteomic changes in ALS mouse motor neurons and patients' skin fibroblasts. We first observed that SODG93A mice presymptomatic motor neurons display alterations in the coupling efficiency of oxidative phosphorylation, along with fragmentation of the mitochondrial network. The proteome of presymptomatic ALS mice motor neurons also revealed a peculiar metabolic signature with upregulation of most energy-transducing enzymes, including the fatty acid oxidation (FAO) and the ketogenic components HADHA and ACAT2, respectively. Accordingly, FAO inhibition altered cell viability specifically in ALS mice motor neurons, while uncoupling protein 2 (UCP2) inhibition recovered cellular ATP levels and mitochondrial network morphology. These findings suggest a novel hypothesis of ALS bioenergetics linking FAO and UCP2. Lastly, we provide a unique set of data comparing the molecular alterations found in human ALS patients' skin fibroblasts and SODG93A mouse motor neurons, revealing conserved changes in protein translation, folding and assembly, tRNA aminoacylation and cell adhesion processes.

Decreased function of survival motor neuron protein impairs endocytic pathways.

PubMed

Dimitriadi, Maria; Derdowski, Aaron; Kalloo, Geetika; Maginnis, Melissa S; O'Hern, Patrick; Bliska, Bryn; Sorkaç, Altar; Nguyen, Ken C Q; Cook, Steven J; Poulogiannis, George; Atwood, Walter J; Hall, David H; Hart, Anne C

2016-07-26

Spinal muscular atrophy (SMA) is caused by depletion of the ubiquitously expressed survival motor neuron (SMN) protein, with 1 in 40 Caucasians being heterozygous for a disease allele. SMN is critical for the assembly of numerous ribonucleoprotein complexes, yet it is still unclear how reduced SMN levels affect motor neuron function. Here, we examined the impact of SMN depletion in Caenorhabditis elegans and found that decreased function of the SMN ortholog SMN-1 perturbed endocytic pathways at motor neuron synapses and in other tissues. Diminished SMN-1 levels caused defects in C. elegans neuromuscular function, and smn-1 genetic interactions were consistent with an endocytic defect. Changes were observed in synaptic endocytic proteins when SMN-1 levels decreased. At the ultrastructural level, defects were observed in endosomal compartments, including significantly fewer docked synaptic vesicles. Finally, endocytosis-dependent infection by JC polyomavirus (JCPyV) was reduced in human cells with decreased SMN levels. Collectively, these results demonstrate for the first time, to our knowledge, that SMN depletion causes defects in endosomal trafficking that impair synaptic function, even in the absence of motor neuron cell death.

Decreased function of survival motor neuron protein impairs endocytic pathways

PubMed Central

Dimitriadi, Maria; Derdowski, Aaron; Kalloo, Geetika; Maginnis, Melissa S.; O’Hern, Patrick; Bliska, Bryn; Sorkaç, Altar; Nguyen, Ken C. Q.; Cook, Steven J.; Poulogiannis, George; Atwood, Walter J.; Hall, David H.; Hart, Anne C.

2016-01-01

Spinal muscular atrophy (SMA) is caused by depletion of the ubiquitously expressed survival motor neuron (SMN) protein, with 1 in 40 Caucasians being heterozygous for a disease allele. SMN is critical for the assembly of numerous ribonucleoprotein complexes, yet it is still unclear how reduced SMN levels affect motor neuron function. Here, we examined the impact of SMN depletion in Caenorhabditis elegans and found that decreased function of the SMN ortholog SMN-1 perturbed endocytic pathways at motor neuron synapses and in other tissues. Diminished SMN-1 levels caused defects in C. elegans neuromuscular function, and smn-1 genetic interactions were consistent with an endocytic defect. Changes were observed in synaptic endocytic proteins when SMN-1 levels decreased. At the ultrastructural level, defects were observed in endosomal compartments, including significantly fewer docked synaptic vesicles. Finally, endocytosis-dependent infection by JC polyomavirus (JCPyV) was reduced in human cells with decreased SMN levels. Collectively, these results demonstrate for the first time, to our knowledge, that SMN depletion causes defects in endosomal trafficking that impair synaptic function, even in the absence of motor neuron cell death. PMID:27402754

Robust presynaptic serotonin 5-HT1B receptor inhibition of the striatonigral output and its sensitization by chronic fluoxetine treatment

PubMed Central

Ding, Shengyuan; Li, Li

2015-01-01

The striatonigral projection is a striatal output pathway critical to motor control, cognition, and emotion regulation. Its axon terminals in the substantia nigra pars reticulata (SNr) express a high level of serotonin (5-HT) type 1B receptors (5-HT1BRs), whereas the SNr also receives an intense 5-HT innervation that expresses 5-HT transporters, providing an anatomic substrate for 5-HT and selective 5-HT reuptake inhibitor (SSRI)-based antidepressant treatment to regulate the striatonigral output. In this article we show that 5-HT, by activating presynaptic 5-HT1BRs on the striatonigral axon terminals, potently inhibited the striatonigral GABA output, as reflected in the reduction of the striatonigral inhibitory postsynaptic currents in SNr GABA neurons. Functionally, 5-HT1BR agonism reduced the striatonigral GABA output-induced pause of the spontaneous high-frequency firing in SNr GABA neurons. Equally important, chronic SSRI treatment with fluoxetine enhanced this presynaptic 5-HT1BR-mediated pause reduction in SNr GABA neurons. Taken together, these results indicate that activation of the 5-HT1BRs on the striatonigral axon terminals can limit the motor-promoting GABA output. Furthermore, in contrast to the desensitization of 5-HT1 autoreceptors, chronic SSRI-based antidepressant treatment sensitizes this presynaptic 5-HT1BR-mediated effect in the SNr, a novel cellular mechanism that alters the striatonigral information transfer, potentially contributing to the behavioral effects of chronic SSRI treatment. PMID:25787955

Direct projections from hypothalamic orexin neurons to brainstem cardiac vagal neurons.

PubMed

Dergacheva, Olga; Yamanaka, Akihiro; Schwartz, Alan R; Polotsky, Vsevolod Y; Mendelowitz, David

2016-12-17

Orexin neurons are known to augment the sympathetic control of cardiovascular function, however the role of orexin neurons in parasympathetic cardiac regulation remains unclear. To test the hypothesis that orexin neurons contribute to parasympathetic control we selectively expressed channelrhodopsin-2 (ChR2) in orexin neurons in orexin-Cre transgenic rats and examined postsynaptic currents in cardiac vagal neurons (CVNs) in the dorsal motor nucleus of the vagus (DMV). Simultaneous photostimulation and recording in ChR2-expressing orexin neurons in the lateral hypothalamus resulted in reliable action potential firing as well as large whole-cell currents suggesting a strong expression of ChR2 and reliable optogenetic excitation. Photostimulation of ChR2-expressing fibers in the DMV elicited short-latency (ranging from 3.2ms to 8.5ms) postsynaptic currents in 16 out of 44 CVNs tested. These responses were heterogeneous and included excitatory glutamatergic (63%) and inhibitory GABAergic (37%) postsynaptic currents. The results from this study suggest different sub-population of orexin neurons may exert diverse influences on brainstem CVNs and therefore may play distinct functional roles in parasympathetic control of the heart. Copyright © 2016 IBRO. Published by Elsevier Ltd. All rights reserved.

Motor neurons and glia exhibit specific individualized responses to TDP-43 expression in a Drosophila model of amyotrophic lateral sclerosis.

PubMed

Estes, Patricia S; Daniel, Scott G; McCallum, Abigail P; Boehringer, Ashley V; Sukhina, Alona S; Zwick, Rebecca A; Zarnescu, Daniela C

2013-05-01

Amyotrophic lateral sclerosis (ALS) is a fatal disease characterized by complex neuronal and glial phenotypes. Recently, RNA-based mechanisms have been linked to ALS via RNA-binding proteins such as TDP-43, which has been studied in vivo using models ranging from yeast to rodents. We have developed a Drosophila model of ALS based on TDP-43 that recapitulates several aspects of pathology, including motor neuron loss, locomotor dysfunction and reduced survival. Here we report the phenotypic consequences of expressing wild-type and four different ALS-linked TDP-43 mutations in neurons and glia. We show that TDP-43-driven neurodegeneration phenotypes are dose- and age-dependent. In motor neurons, TDP-43 appears restricted to nuclei, which are significantly misshapen due to mutant but not wild-type protein expression. In glia and in the developing neuroepithelium, TDP-43 associates with cytoplasmic puncta. TDP-43-containing RNA granules are motile in cultured motor neurons, although wild-type and mutant variants exhibit different kinetic properties. At the neuromuscular junction, the expression of TDP-43 in motor neurons versus glia leads to seemingly opposite synaptic phenotypes that, surprisingly, translate into comparable locomotor defects. Finally, we explore sleep as a behavioral readout of TDP-43 expression and find evidence of sleep fragmentation consistent with hyperexcitability, a suggested mechanism in ALS. These findings support the notion that although motor neurons and glia are both involved in ALS pathology, at the cellular level they can exhibit different responses to TDP-43. In addition, our data suggest that individual TDP-43 alleles utilize distinct molecular mechanisms, which will be important for developing therapeutic strategies.

ALS-related misfolded protein management in motor neurons and muscle cells.

PubMed

Galbiati, Mariarita; Crippa, Valeria; Rusmini, Paola; Cristofani, Riccardo; Cicardi, Maria Elena; Giorgetti, Elisa; Onesto, Elisa; Messi, Elio; Poletti, Angelo

2014-12-01

Amyotrophic Lateral Sclerosis (ALS) is the most common form of adult-onset motor neuron disease. It is now considered a multi-factorial and multi-systemic disorder in which alterations of the crosstalk between neuronal and non-neuronal cell types might influence the course of the disease. In this review, we will provide evidence that dysfunctions of affected muscle cells are not only a marginal consequence of denervation associated to motor neurons loss, but a direct consequence of cell muscle toxicity of mutant SOD1. In muscle, the misfolded state of mutant SOD1 protein, unlike in motor neurons, does not appear to have direct effects on protein aggregation and mitochondrial functionality. Muscle cells are, in fact, more capable than motor neurons to handle misfolded proteins, suggesting that mutant SOD1 toxicity in muscle is not mediated by classical mechanisms of intracellular misfolded proteins accumulation. Several recent works indicate that a higher activation of molecular chaperones and degradative systems is present in muscle cells, which for this reason are possibly able to better manage misfolded mutant SOD1. However, several alterations in gene expression and regenerative potential of skeletal muscles have also been reported as a consequence of the expression of mutant SOD1 in muscle. Whether these changes in muscle cells are causative of ALS or a consequence of motor neuron alterations is not yet clear, but their elucidation is very important, since the understanding of the mechanisms involved in mutant SOD1 toxicity in muscle may facilitate the design of treatments directed toward this specific tissue to treat ALS or at least to delay disease progression. Copyright © 2014 Elsevier Ltd. All rights reserved.

Refinement of learned skilled movement representation in motor cortex deep output layer

PubMed Central

Li, Qian; Ko, Ho; Qian, Zhong-Ming; Yan, Leo Y. C.; Chan, Danny C. W.; Arbuthnott, Gordon; Ke, Ya; Yung, Wing-Ho

2017-01-01

The mechanisms underlying the emergence of learned motor skill representation in primary motor cortex (M1) are not well understood. Specifically, how motor representation in the deep output layer 5b (L5b) is shaped by motor learning remains virtually unknown. In rats undergoing motor skill training, we detect a subpopulation of task-recruited L5b neurons that not only become more movement-encoding, but their activities are also more structured and temporally aligned to motor execution with a timescale of refinement in tens-of-milliseconds. Field potentials evoked at L5b in vivo exhibit persistent long-term potentiation (LTP) that parallels motor performance. Intracortical dopamine denervation impairs motor learning, and disrupts the LTP profile as well as the emergent neurodynamical properties of task-recruited L5b neurons. Thus, dopamine-dependent recruitment of L5b neuronal ensembles via synaptic reorganization may allow the motor cortex to generate more temporally structured, movement-encoding output signal from M1 to downstream circuitry that drives increased uniformity and precision of movement during motor learning. PMID:28598433

A glial cell line-derived neurotrophic factor (GDNF):tetanus toxin fragment C protein conjugate improves delivery of GDNF to spinal cord motor neurons in mice.

PubMed

Larsen, Kristin E; Benn, Susanna C; Ay, Ilknur; Chian, Ru-Ju; Celia, Samuel A; Remington, Mary P; Bejarano, Michelle; Liu, Meiqin; Ross, Joshua; Carmillo, Paul; Sah, Dinah; Phillips, Kester A; Sulzer, David; Pepinsky, R Blake; Fishman, Paul S; Brown, Robert H; Francis, Jonathan W

2006-11-20

Glial cell line-derived neurotrophic factor (GDNF) has shown robust neuroprotective and neuroreparative activities in various animal models of Parkinson's Disease or amyotrophic lateral sclerosis (ALS). The successful use of GDNF as a therapeutic in humans, however, appears to have been hindered by its poor bioavailability to target neurons in the central nervous system (CNS). To improve delivery of exogenous GDNF protein to CNS motor neurons, we employed chemical conjugation techniques to link recombinant human GDNF to the neuronal binding fragment of tetanus toxin (tetanus toxin fragment C, or TTC). The predominant species present in the purified conjugate sample, GDNF:TTC, had a molecular weight of approximately 80 kDa as determined by non-reducing SDS-PAGE. Like GDNF, addition of GDNF:TTC to culture media of neuroblastoma cells expressing GFRalpha-1/c-RET produced a dose-dependent increase in cellular phospho-c-RET levels. Treatment of cultured midbrain dopaminergic neurons with either GDNF or the conjugate similarly promoted both DA neuron survival and neurite outgrowth. However, in contrast to mice treated with GDNF by intramuscular injection, mice receiving GDNF:TTC revealed intense GDNF immunostaining associated with spinal cord motor neurons in fixed tissue sections. That GDNF:TTC provided neuroprotection of axotomized motor neurons in neonatal rats further revealed that the conjugate retained its GDNF activity in vivo. These results indicate that TTC can serve as a non-viral vehicle to substantially improve the delivery of functionally active growth factors to motor neurons in the mammalian CNS.

Prolactin-releasing peptide affects gastric motor function in rat by modulating synaptic transmission in the dorsal vagal complex.

PubMed

Grabauskas, Gintautas; Zhou, Shi-Yi; Das, Sudipto; Lu, Yuanxu; Owyang, Chung; Moises, Hylan C

2004-12-15

Prolactin-releasing peptide (PrRP) is a recently discovered neuropeptide implicated in the central control of feeding behaviour and autonomic homeostasis. PrRP-containing neurones and PrRP receptor mRNA are found in abundance in the caudal portion of the nucleus tractus solitarius (NTS), an area which together with the dorsal motor nucleus of the vagus (DMV) comprises an integrated structure, the dorsal vagal complex (DVC) that processes visceral afferent signals from and provides parasympathetic motor innervation to the gastrointestinal tract. In this study, microinjection experiments were conducted in vivo in combination with whole-cell recording from neurones in rat medullary slices to test the hypothesis that PrRP plays a role in the central control of gastric motor function, acting within the DVC to modulate the activity of preganglionic vagal motor neurones that supply the stomach. Microinjection of PrRP (0.2 pmol (20 nl)(-1)) into the DMV at the level of the area postrema (+0.2 to +0.6 mm from the calamus scriptorius, CS) markedly stimulated gastric contractions and increased intragastric pressure (IGP). Conversely, administration of peptide into the DMV at sites caudal to the obex (0.0 to -0.3 mm from the CS) decreased IGP and reduced phasic contractions. These effects occurred without change in mean arterial pressure and were abolished by ipsilateral vagotomy, indicating mediation via a vagal-dependent mechanism(s). The pattern of gastric motor responses evoked by PrRP mimicked that produced by administration of L-glutamate at the same sites, and both the effects of L-glutamate and PrRP were abolished following local administration of NMDA and non-NMDA-type glutamate receptor antagonists. On the other hand, microinjection of PrRP into the medial or comissural nucleus of the solitary tract (mNTS and comNTS, respectively) resulted in less robust changes in IGP in a smaller percentage of animals, accompanied by marked alterations in arterial pressure. Superfusion of brain slices with PrRP (100-300 nm) produced a small depolarization and increased spontaneous firing in 10 of 30 retrogradely labelled gastric-projecting DMV neurones. The excitatory effects were blocked by administration of TTX (2 mum) or specific glutamate receptor antagonists, indicating that they resulted from interactions of PrRP at a presynaptic site. Congruent with this, PrRP increased the amplitude of excitatory postsynaptic currents (EPSCs, 154 +/- 33%, 12 of 25 neurones) evoked by electrical stimulation in mNTS or comNTS. In addition, administration of PrRP decreased the paired-pulse ratio of EPSCs evoked by two identical stimuli delivered 100 ms apart (from 0.95 +/- 0.08 to 0.71 +/- 0.11, P < 0.05), whereas it did not affect the amplitude of inward currents evoked by exogenous application of L-glutamate to the slice. The frequency, but not amplitude of spontaneous EPSCs and action potential-independent miniature EPSCs was also increased by administration of PrRP, suggesting that the peptide was acting at least in part at receptors on presynaptic nerve terminals to enhance glutamatergic transmission. In recordings obtained from a separate group of slices, we did not observe any direct effects of PrRP on spontaneous discharge or postsynaptic excitability in either mNTS or comNTS neurones (n = 31). These data indicate that PrRP may act within the DVC to regulate gastric motor function by modulating the efficacy of conventional excitatory synaptic inputs from the NTS onto gastric-projecting vagal motor neurones.

Prolactin-releasing peptide affects gastric motor function in rat by modulating synaptic transmission in the dorsal vagal complex

PubMed Central

Grabauskas, Gintautas; Zhou, Shi-Yi; Das, Sudipto; Lu, Yuanxu; Owyang, Chung; Moises, Hylan C

2004-01-01

Prolactin-releasing peptide (PrRP) is a recently discovered neuropeptide implicated in the central control of feeding behaviour and autonomic homeostasis. PrRP-containing neurones and PrRP receptor mRNA are found in abundance in the caudal portion of the nucleus tractus solitarius (NTS), an area which together with the dorsal motor nucleus of the vagus (DMV) comprises an integrated structure, the dorsal vagal complex (DVC) that processes visceral afferent signals from and provides parasympathetic motor innervation to the gastrointestinal tract. In this study, microinjection experiments were conducted in vivo in combination with whole-cell recording from neurones in rat medullary slices to test the hypothesis that PrRP plays a role in the central control of gastric motor function, acting within the DVC to modulate the activity of preganglionic vagal motor neurones that supply the stomach. Microinjection of PrRP (0.2 pmol (20 nl)−1) into the DMV at the level of the area postrema (+0.2 to +0.6 mm from the calamus scriptorius, CS) markedly stimulated gastric contractions and increased intragastric pressure (IGP). Conversely, administration of peptide into the DMV at sites caudal to the obex (0.0 to −0.3 mm from the CS) decreased IGP and reduced phasic contractions. These effects occurred without change in mean arterial pressure and were abolished by ipsilateral vagotomy, indicating mediation via a vagal-dependent mechanism(s). The pattern of gastric motor responses evoked by PrRP mimicked that produced by administration of l-glutamate at the same sites, and both the effects of l-glutamate and PrRP were abolished following local administration of NMDA and non-NMDA-type glutamate receptor antagonists. On the other hand, microinjection of PrRP into the medial or comissural nucleus of the solitary tract (mNTS and comNTS, respectively) resulted in less robust changes in IGP in a smaller percentage of animals, accompanied by marked alterations in arterial pressure. Superfusion of brain slices with PrRP (100–300 nm) produced a small depolarization and increased spontaneous firing in 10 of 30 retrogradely labelled gastric-projecting DMV neurones. The excitatory effects were blocked by administration of TTX (2 μm) or specific glutamate receptor antagonists, indicating that they resulted from interactions of PrRP at a presynaptic site. Congruent with this, PrRP increased the amplitude of excitatory postsynaptic currents (EPSCs, 154 ± 33%, 12 of 25 neurones) evoked by electrical stimulation in mNTS or comNTS. In addition, administration of PrRP decreased the paired-pulse ratio of EPSCs evoked by two identical stimuli delivered 100 ms apart (from 0.95 ± 0.08 to 0.71 ± 0.11, P < 0.05), whereas it did not affect the amplitude of inward currents evoked by exogenous application of l-glutamate to the slice. The frequency, but not amplitude of spontaneous EPSCs and action potential-independent miniature EPSCs was also increased by administration of PrRP, suggesting that the peptide was acting at least in part at receptors on presynaptic nerve terminals to enhance glutamatergic transmission. In recordings obtained from a separate group of slices, we did not observe any direct effects of PrRP on spontaneous discharge or postsynaptic excitability in either mNTS or comNTS neurones (n = 31). These data indicate that PrRP may act within the DVC to regulate gastric motor function by modulating the efficacy of conventional excitatory synaptic inputs from the NTS onto gastric-projecting vagal motor neurones. PMID:15486017

Targeting Neurotrophins to Specific Populations of Neurons: NGF, BDNF, and NT-3 and Their Relevance for Treatment of Spinal Cord Injury

PubMed Central

Keefe, Kathleen M.; Sheikh, Imran S.; Smith, George M.

2017-01-01

Neurotrophins are a family of proteins that regulate neuronal survival, synaptic function, and neurotransmitter release, and elicit the plasticity and growth of axons within the adult central and peripheral nervous system. Since the 1950s, these factors have been extensively studied in traumatic injury models. Here we review several members of the classical family of neurotrophins, the receptors they bind to, and their contribution to axonal regeneration and sprouting of sensory and motor pathways after spinal cord injury (SCI). We focus on nerve growth factor (NGF), brain derived neurotrophic factor (BDNF), and neurotrophin-3 (NT-3), and their effects on populations of neurons within diverse spinal tracts. Understanding the cellular targets of neurotrophins and the responsiveness of specific neuronal populations will allow for the most efficient treatment strategies in the injured spinal cord. PMID:28273811

Targeting Neurotrophins to Specific Populations of Neurons: NGF, BDNF, and NT-3 and Their Relevance for Treatment of Spinal Cord Injury.

PubMed

Keefe, Kathleen M; Sheikh, Imran S; Smith, George M

2017-03-03

Neurotrophins are a family of proteins that regulate neuronal survival, synaptic function, and neurotransmitter release, and elicit the plasticity and growth of axons within the adult central and peripheral nervous system. Since the 1950s, these factors have been extensively studied in traumatic injury models. Here we review several members of the classical family of neurotrophins, the receptors they bind to, and their contribution to axonal regeneration and sprouting of sensory and motor pathways after spinal cord injury (SCI). We focus on nerve growth factor (NGF), brain derived neurotrophic factor (BDNF), and neurotrophin-3 (NT-3), and their effects on populations of neurons within diverse spinal tracts. Understanding the cellular targets of neurotrophins and the responsiveness of specific neuronal populations will allow for the most efficient treatment strategies in the injured spinal cord.

Gene expression profiling for human iPS-derived motor neurons from sporadic ALS patients reveals a strong association between mitochondrial functions and neurodegeneration

PubMed Central

Alves, Chrystian J.; Dariolli, Rafael; Jorge, Frederico M.; Monteiro, Matheus R.; Maximino, Jessica R.; Martins, Roberto S.; Strauss, Bryan E.; Krieger, José E.; Callegaro, Dagoberto; Chadi, Gerson

2015-01-01

Amyotrophic Lateral Sclerosis (ALS) is a fatal neurodegenerative disease that leads to widespread motor neuron death, general palsy and respiratory failure. The most prevalent sporadic ALS form is not genetically inherited. Attempts to translate therapeutic strategies have failed because the described mechanisms of disease are based on animal models carrying specific gene mutations and thus do not address sporadic ALS. In order to achieve a better approach to study the human disease, human induced pluripotent stem cell (hiPSC)-differentiated motor neurons were obtained from motor nerve fibroblasts of sporadic ALS and non-ALS subjects using the STEMCCA Cre-Excisable Constitutive Polycistronic Lentivirus system and submitted to microarray analyses using a whole human genome platform. DAVID analyses of differentially expressed genes identified molecular function and biological process-related genes through Gene Ontology. REVIGO highlighted the related functions mRNA and DNA binding, GTP binding, transcription (co)-repressor activity, lipoprotein receptor binding, synapse organization, intracellular transport, mitotic cell cycle and cell death. KEGG showed pathways associated with Parkinson's disease and oxidative phosphorylation, highlighting iron homeostasis, neurotrophic functions, endosomal trafficking and ERK signaling. The analysis of most dysregulated genes and those representative of the majority of categorized genes indicates a strong association between mitochondrial function and cellular processes possibly related to motor neuron degeneration. In conclusion, iPSC-derived motor neurons from motor nerve fibroblasts of sporadic ALS patients may recapitulate key mechanisms of neurodegeneration and may offer an opportunity for translational investigation of sporadic ALS. Large gene profiling of differentiated motor neurons from sporadic ALS patients highlights mitochondrial participation in the establishment of autonomous mechanisms associated with sporadic ALS. PMID:26300727

Distribution and cellular localization of imidazoleacetic acid-ribotide, an endogenous ligand at imidazol(in)e and adrenergic receptors, in rat brain

PubMed Central

Friedrich, Victor L.; Martinelli, Giorgio P.; Prell, George D.; Holstein, Gay R.

2007-01-01

Imidazoleacetic acid-ribotide (IAA-RP) is a putative neurotransmitter/modulator recently discovered in mammalian brain. The present study examines the distribution of IAA-RP in the rat CNS using a highly specific antiserum raised in rabbit against IAA-RP with immunostaining of aldehyde-fixed rat CNS. IAA-RP-immunoreactive neurons were present throughout the neuraxis; neuroglia were not labeled. In each region, only a subset of the neuronal pool was immunostained. In the forebrain, ribotide-immunolabeled neurons were common in neocortex, in hippocampal formation, and in subcortical structures including basal ganglia, thalamus and hypothalamus. Labeling was prominent limbic areas including olfactory bulb, basal forebrain, pyriform cortex and amygdala. In the mid- and hindbrain, immunolabled neurons were concentrated in specific nuclei and, in some areas, in specific subregions of those nuclei. Structures of the motor system, including cranial nerve motor nuclei, precerebellar nuclei, the substantia nigra, and the red nucleus were clearly labeled. Staining was intense in cells and/or puncta in the rostral and caudal ventrolateral medullary reticular formation, nucleus tractus solitarius and the caudal vestibular nuclear complex. Within neurons, the ribotide was found predominantly in somata and dendrites; some myelinated axons and occasional synaptic terminals were also immunostained. These data indicate that IAA-RP contributes to the neurochemical phenotype of many neuronal populations further support our suggestion that, in autonomic structures, the IAA-RP may serve as a chemical mediator in complex circuits involved in blood pressure regulation and, more generally, sympathetic drive. PMID:17210242

Local domains of motor cortical activity revealed by fiber-optic calcium recordings in behaving nonhuman primates.

PubMed

Adelsberger, Helmuth; Zainos, Antonio; Alvarez, Manuel; Romo, Ranulfo; Konnerth, Arthur

2014-01-07

Brain mapping experiments involving electrical microstimulation indicate that the primary motor cortex (M1) directly regulates muscle contraction and thereby controls specific movements. Possibly, M1 contains a small circuit "map" of the body that is formed by discrete local networks that code for specific movements. Alternatively, movements may be controlled by distributed, larger-scale overlapping circuits. Because of technical limitations, it remained unclear how movement-determining circuits are organized in M1. Here we introduce a method that allows the functional mapping of small local neuronal circuits in awake behaving nonhuman primates. For this purpose, we combined optic-fiber-based calcium recordings of neuronal activity and cortical microstimulation. The method requires targeted bulk loading of synthetic calcium indicators (e.g., OGB-1 AM) for the staining of neuronal microdomains. The tip of a thin (200 µm) optical fiber can detect the coherent activity of a small cluster of neurons, but is insensitive to the asynchronous activity of individual cells. By combining such optical recordings with microstimulation at two well-separated sites of M1, we demonstrate that local cortical activity was tightly associated with distinct and stereotypical simple movements. Increasing stimulation intensity increased both the amplitude of the movements and the level of neuronal activity. Importantly, the activity remained local, without invading the recording domain of the second optical fiber. Furthermore, there was clear response specificity at the two recording sites in a trained behavioral task. Thus, the results provide support for movement control in M1 by local neuronal clusters that are organized in discrete cortical domains.

Differentiation of Wharton's Jelly-Derived Mesenchymal Stem Cells into Motor Neuron-Like Cells on Three-Dimensional Collagen-Grafted Nanofibers.

PubMed

Bagher, Zohreh; Azami, Mahmoud; Ebrahimi-Barough, Somayeh; Mirzadeh, Hamid; Solouk, Atefeh; Soleimani, Mansooreh; Ai, Jafar; Nourani, Mohammad Reza; Joghataei, Mohammad Taghi

2016-05-01

Cell transplantation strategies have provided potential therapeutic approaches for treatment of neurodegenerative diseases. Mesenchymal stem cells from Wharton's jelly (WJMSCs) are abundant and available adult stem cells with low immunological incompatibility, which could be considered for cell replacement therapy in the future. However, MSC transplantation without any induction or support material causes poor control of cell viability and differentiation. In this study, we investigated the effect of the nanoscaffolds on WJMSCs differentiation into motor neuronal lineages in the presence of retinoic acid (RA) and sonic hedgehog (Shh). Surface properties of scaffolds have been shown to significantly influence cell behaviors such as adhesion, proliferation, and differentiation. Therefore, polycaprolactone (PCL) nanofibers were constructed via electrospinning, surface modified by plasma treatment, and grafted by collagen. Characterization of the scaffolds by means of ATR-FTIR, contact angel, and Bradford proved grafting of the collagen on the surface of the scaffolds. WJMSCs were seeded on nanofibrous and tissue culture plate (TCP) and viability of WJMSCs were measured by MTT assay and then induced to differentiate into motor neuron-like cells for 15 days. Differentiated cells were evaluated morphologically, and real-time PCR and immunocytochemistry methods were done to evaluate expression of motor neuron-like cell markers in mRNA and protein levels. Our results showed that obtained cells could express motor neuron biomarkers at both RNA and protein levels, but the survival and differentiation of WJMSCs into motor neuron-like cells on the PCL/collagen scaffold were higher than cultured cells in the TCP and PCL groups. Taken together, WJMSCs are an attractive stem cell source for inducing into motor neurons in vitro especially when grown on nanostructural scaffolds and PCL/collagen scaffolds can provide a suitable, three-dimensional situation for neuronal survival and differentiation that suggest their potential application towards nerve regeneration.

Dysregulation of chromatin remodelling complexes in amyotrophic lateral sclerosis.

PubMed

Tibshirani, Michael; Zhao, Beibei; Gentil, Benoit J; Minotti, Sandra; Marques, Christine; Keith, Julia; Rogaeva, Ekaterina; Zinman, Lorne; Rouaux, Caroline; Robertson, Janice; Durham, Heather D

2017-11-01

Amyotrophic lateral sclerosis is a fatal neurodegenerative disease with paralysis resulting from dysfunction and loss of motor neurons. A common neuropathological finding is attrition of motor neuron dendrites, which make central connections vital to motor control. The chromatin remodelling complex, neuronal Brahma-related gene 1 (Brg1)-associated factor complex (nBAF), is critical for neuronal differentiation, dendritic extension and synaptic function. We have identified loss of the crucial nBAF subunits Brg1, Brg1-associated factor 53b and calcium responsive transactivator in cultured motor neurons expressing FUS or TAR-DNA Binding Protein 43 (TDP-43) mutants linked to familial ALS. When plasmids encoding wild-type or mutant human FUS or TDP-43 were expressed in motor neurons of dissociated spinal cord cultures prepared from E13 mice, mutant proteins in particular accumulated in the cytoplasm. Immunolabelling of nBAF subunits was reduced in proportion to loss of nuclear FUS or TDP-43 and depletion of Brg1 was associated with nuclear retention of Brg1 mRNA. Dendritic attrition (loss of intermediate and terminal dendritic branches) occurred in motor neurons expressing mutant, but not wild-type, FUS or TDP-43. This attrition was delayed by ectopic over-expression of Brg1 and was reproduced by inhibiting Brg1 activity either through genetic manipulation or treatment with the chemical inhibitor, (E)-1-(2-Hydroxyphenyl)-3-((1R, 4R)-5-(pyridin-2-yl)-2, 5-diazabicyclo[2.2.1]heptan-2-yl)prop-2-en-1-one, demonstrating the importance of Brg1 to maintenance of dendritic architecture. Loss of nBAF subunits was also documented in spinal motor neurons in autopsy tissue from familial amyotrophic sclerosis (chromosome 9 open reading frame 72 with G4C2 nucleotide expansion) and from sporadic cases with no identified mutation, pointing to dysfunction of nBAF chromatin remodelling in multiple forms of ALS. © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

The CB2 cannabinoid agonist AM-1241 prolongs survival in a transgenic mouse model of amyotrophic lateral sclerosis when initiated at symptom onset

PubMed Central

Shoemaker, Jennifer L.; Seely, Kathryn A.; Reed, Ronald L.; Crow, John P.; Prather, Paul L.

2010-01-01

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease characterized by progressive motor neuron loss, paralysis and death within 2–5 years of diagnosis. Currently, no effective pharmacological agents exist for the treatment of this devastating disease. Neuroinflammation may accelerate the progression of ALS. Cannabinoids produce anti-inflammatory actions via cannabinoid receptor 1 (CB1) and cannabinoid receptor 2 (CB2), and delay the progression of neuroinflammatory diseases. Additionally, CB2 receptors, which normally exist primarily in the periphery, are dramatically up-regulated in inflamed neural tissues associated with CNS disorders. In G93A-SOD1 mutant mice, the most well-characterized animal model of ALS, endogenous cannabinoids are elevated in spinal cords of symptomatic mice. Furthermore, treatment with non-selective cannabinoid partial agonists prior to, or upon, symptom appearance minimally delays disease onset and prolongs survival through undefined mechanisms. We demonstrate that mRNA, receptor binding and function of CB2, but not CB1, receptors are dramatically and selectively up-regulated in spinal cords of G93A-SOD1 mice in a temporal pattern paralleling disease progression. More importantly, daily injections of the selective CB2 agonist AM-1241, initiated at symptom onset, increase the survival interval after disease onset by 56%. Therefore, CB2 agonists may slow motor neuron degeneration and preserve motor function, and represent a novel therapeutic modality for treatment of ALS. PMID:17241118

Zhenbao pill protects against acute spinal cord injury via miR-146a-5p regulating the expression of GPR17

PubMed Central

Lv, Bokang; Huan, Yanqiang; Liu, Bin; Li, Yutang; Jia, Lizhou; Qu, Chenhui; Wang, Dongsheng; Yu, Hai

2018-01-01

The aim of the present study was to observe the effect of zhenbao pill on the motor function of acute spinal cord injury (ASCI) rats and the molecular mechanisms involving miR-146a-5p and G-protein-coupled receptor 17 (GPR17). ASCI rat model was established by modified Allen method, and then the rats were divided into three groups. SH-SY5Y cells were cultured overnight in hypoxia condition and transfected with miR-146a-5p mimic or miR-146a-5p inhibitor. The hind limb motor function of the rats was evaluated by Basso, Beattie, Bresnahan (BBB) scoring system. Quantitative real-time PCR (qRT-PCR) and Western blot were used to detect the expression of miR-146a-5p, GPR17, inducible nitric oxide synthase (iNOS), interleukin 1β (IL-1β), and tumor necrosis factor α (TNF-α). Neuronal apoptosis was measured using flow cytometry assay. Luciferase reporter assay was performed to determine the regulation of miR-146a-5p on GPR17. Zhenbao pill could enhance hind limb motor function and attenuate the inflammatory response caused by ASCI. Moreover, zhenbao pill increased the level of miR-146a-5p and decreased GPR17 expression in vivo and in vitro. Bioinformatics software predicted that GPR17 3′-UTR had a binding site with miR-146a-5p. Luciferase reporter assay showed that miR-146a-5p had a negative regulatory effect on GPR17 expression. Knockdown of miR-146a-5p could reverse the effect of zhenbao pill on the up-regulation of GPR17 induced by hypoxia, reversed the inhibitory effect of zhenbao pill on the cell apoptosis induced by hypoxia and the recovery of zhenbao pill on hind limb motor function in ASCI rats. Zhenbao pill could inhibit neuronal apoptosis by regulating miR-146a-5p/GPR17 expression, and then promoting the recovery of spinal cord function. PMID:29187582

Dorsal motor nucleus of the vagus neurons: a multivariate taxonomy.

PubMed

Jarvinen, M K; Powley, T L

1999-01-18

The dorsal motor nucleus of the vagus (DMNX) contains neurons with different projections and discrete functions, but little success has been achieved in distinguishing the cells cytoarchitectonically. The present experiment employed multivariate analytical techniques to evaluate DMNX neuronal morphology. Male Sprague-Dawley rats (n = 77) were perfused, and the brainstems were stained en bloc with a Golgi-Cox protocol. DMNX neurons in each of three planes (coronal, sagittal, and horizontal; total sample = 607) were digitized. Three-dimensional features quantified included dendritic length, number of segments, spine density, number of primary dendrites, dendritic orientation, and soma form factor. Cluster analyses of six independent samples of 100+ neurons and of three composite replicate pools of 200+ neurons consistently identified similar sets of four distinct neuronal profiles. One profile (spinous, limited dendrites, small somata) appears to correspond to the interneuron population of the DMNX. In contrast, the other three distinctive profiles (e.g., one is multipolar, with large dendritic fields and large somata) are different types of preganglionic neurons. Each of the four types of neurons is found throughout the DMNX, suggesting that the individual columnar subnuclei and other postulated vagal motorneuron pools are composed of all types of neurons. Within individual motor pools, ensembles of the different neuronal types must cooperatively organize different functions and project to different effectors within a target organ. By extension, specializations of the preganglionic motor pools are more likely to result from their afferent inputs, peripheral target tissues, neurochemistry, or physiological features rather than from any unique morphological profiles.

Spinal Muscular Atrophy

MedlinePlus

... length SMN protein, which is critical for the maintenance of motor neurons. Muscle relaxants such as baclofen, ... length SMN protein, which is critical for the maintenance of motor neurons. Muscle relaxants such as baclofen, ...

The role of connexin-36 gap junctions in alcohol intoxication and consumption.

PubMed

Steffensen, Scott C; Bradley, Katie D; Hansen, David M; Wilcox, Jeffrey D; Wilcox, Rebecca S; Allison, David W; Merrill, Collin B; Edwards, Jeffrey G

2011-08-01

Ventral tegmental area (VTA) GABA neurons appear to be critical substrates underlying the acute and chronic effects of ethanol on dopamine (DA) neurotransmission in the mesocorticolimbic system implicated in alcohol reward. The aim of this study was to examine the role of midbrain connexin-36 (Cx36) gap junctions (GJs) in ethanol intoxication and consumption. Using behavioral, molecular, and electrophysiological methods, we compared the effects of ethanol in mature Cx36 knockout (KO) mice and age-matched wild-type (WT) controls. Compared to WT mice, Cx36 KO mice exhibited significantly more ethanol-induced motor impairment in the open field test, but less disruption in motor coordination in the rotarod paradigm. Cx36 KO mice, and WT mice treated with the Cx36 antagonist mefloquine (MFQ), consumed significantly less ethanol than their WT controls in the drink-in-the-dark procedure. The firing rate of VTA GABA neurons in WT mice was inhibited by ethanol with an IC₅₀ of 0.25 g/kg, while VTA GABA neurons in KO mice were significantly less sensitive to ethanol. Dopamine neuron GABA-mediated sIPSC frequency was reduced by ethanol (30 mM) in WT mice, but not affected in KO mice. Cx36 KO mice evinced a significant up-regulation in DAT and D2 receptors in the VTA, as assessed by quantitative RT-PCR. These findings demonstrate the behavioral relevance of Cx36 GJ-mediated electrical coupling between GABA neurons in mature animals, and suggest that loss of coupling between VTA GABA neurons results in disinhibition of DA neurons, a hyper-DAergic state and lowered hedonic valence for ethanol consumption. Copyright © 2010 Wiley-Liss, Inc.

View-Invariant Visuomotor Processing in Computational Mirror Neuron System for Humanoid

PubMed Central

Dawood, Farhan; Loo, Chu Kiong

2016-01-01

Mirror neurons are visuo-motor neurons found in primates and thought to be significant for imitation learning. The proposition that mirror neurons result from associative learning while the neonate observes his own actions has received noteworthy empirical support. Self-exploration is regarded as a procedure by which infants become perceptually observant to their own body and engage in a perceptual communication with themselves. We assume that crude sense of self is the prerequisite for social interaction. However, the contribution of mirror neurons in encoding the perspective from which the motor acts of others are seen have not been addressed in relation to humanoid robots. In this paper we present a computational model for development of mirror neuron system for humanoid based on the hypothesis that infants acquire MNS by sensorimotor associative learning through self-exploration capable of sustaining early imitation skills. The purpose of our proposed model is to take into account the view-dependency of neurons as a probable outcome of the associative connectivity between motor and visual information. In our experiment, a humanoid robot stands in front of a mirror (represented through self-image using camera) in order to obtain the associative relationship between his own motor generated actions and his own visual body-image. In the learning process the network first forms mapping from each motor representation onto visual representation from the self-exploratory perspective. Afterwards, the representation of the motor commands is learned to be associated with all possible visual perspectives. The complete architecture was evaluated by simulation experiments performed on DARwIn-OP humanoid robot. PMID:26998923

View-Invariant Visuomotor Processing in Computational Mirror Neuron System for Humanoid.

PubMed

Dawood, Farhan; Loo, Chu Kiong

2016-01-01

Mirror neurons are visuo-motor neurons found in primates and thought to be significant for imitation learning. The proposition that mirror neurons result from associative learning while the neonate observes his own actions has received noteworthy empirical support. Self-exploration is regarded as a procedure by which infants become perceptually observant to their own body and engage in a perceptual communication with themselves. We assume that crude sense of self is the prerequisite for social interaction. However, the contribution of mirror neurons in encoding the perspective from which the motor acts of others are seen have not been addressed in relation to humanoid robots. In this paper we present a computational model for development of mirror neuron system for humanoid based on the hypothesis that infants acquire MNS by sensorimotor associative learning through self-exploration capable of sustaining early imitation skills. The purpose of our proposed model is to take into account the view-dependency of neurons as a probable outcome of the associative connectivity between motor and visual information. In our experiment, a humanoid robot stands in front of a mirror (represented through self-image using camera) in order to obtain the associative relationship between his own motor generated actions and his own visual body-image. In the learning process the network first forms mapping from each motor representation onto visual representation from the self-exploratory perspective. Afterwards, the representation of the motor commands is learned to be associated with all possible visual perspectives. The complete architecture was evaluated by simulation experiments performed on DARwIn-OP humanoid robot.

Loss of C9ORF72 impairs autophagy and synergizes with polyQ Ataxin-2 to induce motor neuron dysfunction and cell death.

PubMed

Sellier, Chantal; Campanari, Maria-Letizia; Julie Corbier, Camille; Gaucherot, Angeline; Kolb-Cheynel, Isabelle; Oulad-Abdelghani, Mustapha; Ruffenach, Frank; Page, Adeline; Ciura, Sorana; Kabashi, Edor; Charlet-Berguerand, Nicolas

2016-06-15

An intronic expansion of GGGGCC repeats within the C9ORF72 gene is the most common genetic cause of amyotrophic lateral sclerosis and frontotemporal dementia (ALS-FTD). Ataxin-2 with intermediate length of polyglutamine expansions (Ataxin-2 Q30x) is a genetic modifier of the disease. Here, we found that C9ORF72 forms a complex with the WDR41 and SMCR8 proteins to act as a GDP/GTP exchange factor for RAB8a and RAB39b and to thereby control autophagic flux. Depletion of C9orf72 in neurons partly impairs autophagy and leads to accumulation of aggregates of TDP-43 and P62 proteins, which are histopathological hallmarks of ALS-FTD SMCR8 is phosphorylated by TBK1 and depletion of TBK1 can be rescued by phosphomimetic mutants of SMCR8 or by constitutively active RAB39b, suggesting that TBK1, SMCR8, C9ORF72, and RAB39b belong to a common pathway regulating autophagy. While depletion of C9ORF72 only has a partial deleterious effect on neuron survival, it synergizes with Ataxin-2 Q30x toxicity to induce motor neuron dysfunction and neuronal cell death. These results indicate that partial loss of function of C9ORF72 is not deleterious by itself but synergizes with Ataxin-2 toxicity, suggesting a double-hit pathological mechanism in ALS-FTD. © 2016 The Authors.

The Two-Level Theory of verb meaning: An approach to integrating the semantics of action with the mirror neuron system.

PubMed

Kemmerer, David; Gonzalez-Castillo, Javier

2010-01-01

Verbs have two separate levels of meaning. One level reflects the uniqueness of every verb and is called the "root". The other level consists of a more austere representation that is shared by all the verbs in a given class and is called the "event structure template". We explore the following hypotheses about how, with specific reference to the motor features of action verbs, these two distinct levels of semantic representation might correspond to two distinct levels of the mirror neuron system. Hypothesis 1: Root-level motor features of verb meaning are partially subserved by somatotopically mapped mirror neurons in the left primary motor and/or premotor cortices. Hypothesis 2: Template-level motor features of verb meaning are partially subserved by representationally more schematic mirror neurons in Brodmann area 44 of the left inferior frontal gyrus. Evidence has been accumulating in support of the general neuroanatomical claims made by these two hypotheses-namely, that each level of verb meaning is associated with the designated cortical areas. However, as yet no studies have satisfied all the criteria necessary to support the more specific neurobiological claims made by the two hypotheses-namely, that each level of verb meaning is associated with mirror neurons in the pertinent brain regions. This would require demonstrating that within those regions the same neuronal populations are engaged during (a) the linguistic processing of particular motor features of verb meaning, (b) the execution of actions with the corresponding motor features, and (c) the observation of actions with the corresponding motor features. 2008 Elsevier Inc. All rights reserved.

THE TWO-LEVEL THEORY OF VERB MEANING: AN APPROACH TO INTEGRATING THE SEMANTICS OF ACTION WITH THE MIRROR NEURON SYSTEM

PubMed Central

Kemmerer, David; Castillo, Javier Gonzalez

2010-01-01

Verbs have two separate levels of meaning. One level reflects the uniqueness of every verb and is called the “root.” The other level consists of a more austere representation that is shared by all the verbs in a given class and is called the “event structure template.” We explore the following hypotheses about how, with specific reference to the motor features of action verbs, these two distinct levels of semantic representation might correspond to two distinct levels of the mirror neuron system. Hypothesis 1: Root-level motor features of verb meaning are partially subserved by somatotopically mapped mirror neurons in the left primary motor and/or premotor cortices. Hypothesis 2: Template-level motor features of verb meaning are partially subserved by representationally more schematic mirror neurons in Brodmann area 44 of the left inferior frontal gyrus. Evidence has been accumulating in support of the general neuroanatomical claims made by these two hypotheses—namely, that each level of verb meaning is associated with the designated cortical areas. However, as yet no studies have satisfied all the criteria necessary to support the more specific neurobiological claims made by the two hypotheses—namely, that each level of verb meaning is associated with mirror neurons in the pertinent brain regions. This would require demonstrating that within those regions the same neuronal populations are engaged during (a) the linguistic processing of particular motor features of verb meaning, (b) the execution of actions with the corresponding motor features, and (c) the observation of actions with the corresponding motor features. PMID:18996582

Cellular Links between Neuronal Activity and Energy Homeostasis.

PubMed

Shetty, Pavan K; Galeffi, Francesca; Turner, Dennis A

2012-01-01

Neuronal activity, astrocytic responses to this activity, and energy homeostasis are linked together during baseline, conscious conditions, and short-term rapid activation (as occurs with sensory or motor function). Nervous system energy homeostasis also varies during long-term physiological conditions (i.e., development and aging) and with adaptation to pathological conditions, such as ischemia or low glucose. Neuronal activation requires increased metabolism (i.e., ATP generation) which leads initially to substrate depletion, induction of a variety of signals for enhanced astrocytic function, and increased local blood flow and substrate delivery. Energy generation (particularly in mitochondria) and use during ATP hydrolysis also lead to considerable heat generation. The local increases in blood flow noted following neuronal activation can both enhance local substrate delivery but also provides a heat sink to help cool the brain and removal of waste by-products. In this review we highlight the interactions between short-term neuronal activity and energy metabolism with an emphasis on signals and factors regulating astrocyte function and substrate supply.

A neuroprotective agent that inactivates prodegenerative TrkA and preserves mitochondria

PubMed Central

Feinberg, Konstantin; Kolaj, Adelaida; Wu, Chen; Grinshtein, Natalie; Krieger, Jonathan R.; Moran, Michael F.; Rubin, Lee L.

2017-01-01

Axon degeneration is an early event and pathological in neurodegenerative conditions and nerve injuries. To discover agents that suppress neuronal death and axonal degeneration, we performed drug screens on primary rodent neurons and identified the pan-kinase inhibitor foretinib, which potently rescued sympathetic, sensory, and motor wt and SOD1 mutant neurons from trophic factor withdrawal-induced degeneration. By using primary sympathetic neurons grown in mass cultures and Campenot chambers, we show that foretinib protected neurons by suppressing both known degenerative pathways and a new pathway involving unliganded TrkA and transcriptional regulation of the proapoptotic BH3 family members BimEL, Harakiri,and Puma, culminating in preservation of mitochondria in the degenerative setting. Foretinib delayed chemotherapy-induced and Wallerian axonal degeneration in culture by preventing axotomy-induced local energy deficit and preserving mitochondria, and peripheral Wallerian degeneration in vivo. These findings identify a new axon degeneration pathway and a potentially clinically useful therapeutic drug. PMID:28877995

Foot Drop

MedlinePlus

... muscular problems, such as multiple sclerosis, stroke, and cerebral palsy; motor neuron disorders such as polio, some forms ... muscular problems, such as multiple sclerosis, stroke, and cerebral palsy; motor neuron disorders such as polio, some forms ...

Cellular mechanisms underlying behavioral state-dependent bidirectional modulation of motor cortex output.

PubMed

Schiemann, Julia; Puggioni, Paolo; Dacre, Joshua; Pelko, Miha; Domanski, Aleksander; van Rossum, Mark C W; Duguid, Ian

2015-05-26

Neuronal activity in primary motor cortex (M1) correlates with behavioral state, but the cellular mechanisms underpinning behavioral state-dependent modulation of M1 output remain largely unresolved. Here, we performed in vivo patch-clamp recordings from layer 5B (L5B) pyramidal neurons in awake mice during quiet wakefulness and self-paced, voluntary movement. We show that L5B output neurons display bidirectional (i.e., enhanced or suppressed) firing rate changes during movement, mediated via two opposing subthreshold mechanisms: (1) a global decrease in membrane potential variability that reduced L5B firing rates (L5Bsuppressed neurons), and (2) a coincident noradrenaline-mediated increase in excitatory drive to a subpopulation of L5B neurons (L5Benhanced neurons) that elevated firing rates. Blocking noradrenergic receptors in forelimb M1 abolished the bidirectional modulation of M1 output during movement and selectively impaired contralateral forelimb motor coordination. Together, our results provide a mechanism for how noradrenergic neuromodulation and network-driven input changes bidirectionally modulate M1 output during motor behavior. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.

Why do motor neurons degenerate? Actualization in the pathogenesis of amyotrophic lateral sclerosis.

PubMed

Riancho, J; Gonzalo, I; Ruiz-Soto, M; Berciano, J

2016-02-04

Amyotrophic lateral sclerosis (ALS) is the most common neurodegenerative disease affecting motor neurons. Although a small proportion of ALS cases are familial in origin and linked to mutations in specific genes, most cases are sporadic and have a multifactorial aetiology. Some recent studies have increased our knowledge of ALS pathogenesis and raised the question of whether this disorder is a proteinopathy, a ribonucleopathy, an axonopathy, or a disease related to the neuronal microenvironment. This article presents a review of ALS pathogenesis. To this end, we have reviewed published articles describing either ALS patients or ALS animal models and we discuss how the main cellular pathways (gene processing, protein metabolism, oxidative stress, axonal transport, relationship with neuronal microenvironment) may be involved in motor neurons degeneration. ALS pathogenesis has not been fully elucidated. Recent studies suggest that although initial triggers may differ among patients, the final motor neurons degeneration mechanisms are similar in most patients once the disease is fully established. Copyright © 2016 Sociedad Española de Neurología. Published by Elsevier España, S.L.U. All rights reserved.

Two-photon imaging of neuronal activity in motor cortex of marmosets during upper-limb movement tasks.

PubMed

Ebina, Teppei; Masamizu, Yoshito; Tanaka, Yasuhiro R; Watakabe, Akiya; Hirakawa, Reiko; Hirayama, Yuka; Hira, Riichiro; Terada, Shin-Ichiro; Koketsu, Daisuke; Hikosaka, Kazuo; Mizukami, Hiroaki; Nambu, Atsushi; Sasaki, Erika; Yamamori, Tetsuo; Matsuzaki, Masanori

2018-05-14

Two-photon imaging in behaving animals has revealed neuronal activities related to behavioral and cognitive function at single-cell resolution. However, marmosets have posed a challenge due to limited success in training on motor tasks. Here we report the development of protocols to train head-fixed common marmosets to perform upper-limb movement tasks and simultaneously perform two-photon imaging. After 2-5 months of training sessions, head-fixed marmosets can control a manipulandum to move a cursor to a target on a screen. We conduct two-photon calcium imaging of layer 2/3 neurons in the motor cortex during this motor task performance, and detect task-relevant activity from multiple neurons at cellular and subcellular resolutions. In a two-target reaching task, some neurons show direction-selective activity over the training days. In a short-term force-field adaptation task, some neurons change their activity when the force field is on. Two-photon calcium imaging in behaving marmosets may become a fundamental technique for determining the spatial organization of the cortical dynamics underlying action and cognition.

Can the 'neuron theory' be complemented by a universal mechanism for generic neuronal differentiation.

PubMed

Ernsberger, Uwe

2015-01-01

With the establishment of the 'neuron theory' at the turn of the twentieth century, this remarkably powerful term was introduced to name a breathtaking diversity of cells unified by a characteristic structural compartmentalization and unique information processing and propagating features. At the beginning of the twenty-first century, developmental, stem cell and reprogramming studies converged to suggest a common mechanism involved in the generation of possibly all vertebrate, and at least a significant number of invertebrate, neurons. Sox and, in particular, SoxB and SoxC proteins as well as basic helix-loop-helix proteins play major roles, even though their precise contributions to progenitor programming, proliferation and differentiation are not fully resolved. In addition to neuronal development, these transcription factors also regulate sensory receptor and endocrine cell development, thus specifying a range of cells with regulatory and communicative functions. To what extent microRNAs contribute to the diversification of these cell types is an upcoming question. Understanding the transcriptional and post-transcriptional regulation of genes coding for cell type-specific cytoskeletal and motor proteins as well as synaptic and ion channel proteins, which mark differences but also similarities between the three communicator cell types, will provide a key to the comprehension of their diversification and the signature of 'generic neuronal' differentiation. Apart from the general scientific significance of a putative universal core instruction for neuronal development, the impact of this line of research for cell replacement therapy and brain tumor treatment will be of considerable interest.

Proprioceptive coupling within motor neurons drives C. elegans forward locomotion

PubMed Central

Wen, Quan; Po, Michelle; Hulme, Elizabeth; Chen, Sway; Liu, Xinyu; Kwok, Sen Wai; Gershow, Marc; Leifer, Andrew M; Butler, Victoria; Fang-Yen, Christopher; Kawano, Taizo; Schafer, William R; Whitesides, George

2012-01-01

Summary Locomotion requires coordinated motor activity throughout an animal’s body. In both vertebrates and invertebrates, chains of coupled Central Pattern Generators (CPGs) are commonly evoked to explain local rhythmic behaviors. In C. elegans, we report that proprioception within the motor circuit is responsible for propagating and coordinating rhythmic undulatory waves from head to tail during forward movement. Proprioceptive coupling between adjacent body regions transduces rhythmic movement initiated near the head into bending waves driven along the body by a chain of reflexes. Using optogenetics and calcium imaging to manipulate and monitor motor circuit activity of moving C. elegans held in microfluidic devices, we found that the B-type cholinergic motor neurons transduce the proprioceptive signal. In C. elegans, a sensorimotor feedback loop operating within a specific type of motor neuron both drives and organizes body movement. PMID:23177960

Respiratory chain deficiency in aged spinal motor neurons☆

PubMed Central

Rygiel, Karolina A.; Grady, John P.; Turnbull, Doug M.

2014-01-01

Sarcopenia, muscle wasting, and strength decline with age, is an important cause of loss of mobility in the elderly individuals. The underlying mechanisms are uncertain but likely to involve defects of motor nerve, neuromuscular junction, and muscle. Loss of motor neurons with age and subsequent denervation of skeletal muscle has been recognized as one of the contributing factors. This study investigated aspects of mitochondrial biology in spinal motor neurons from elderly subjects. We found that protein components of complex I of mitochondrial respiratory chain were reduced or absent in a proportion of aged motor neurons–a phenomenon not observed in fetal tissue. Further investigation showed that complex I-deficient cells had reduced mitochondrial DNA content and smaller soma size. We propose that mitochondrial dysfunction in these motor neurons could lead to the cell loss and ultimately denervation of muscle fibers. PMID:24684792

Experience-dependent development of spinal motor neurons

NASA Technical Reports Server (NTRS)

Inglis, F. M.; Zuckerman, K. E.; Kalb, R. G.; Walton, K. D. (Principal Investigator)

2000-01-01

Locomotor activity in many species undergoes pronounced alterations in early postnatal life, and environmental cues may be responsible for modifying this process. To determine how these events are reflected in the nervous system, we studied rats reared under two different conditions-the presence or absence of gravity-in which the performance of motor operations differed. We found a significant effect of rearing environment on the size and complexity of dendritic architecture of spinal motor neurons, particularly those that are likely to participate in postural control. These results provide evidence that neurons subserving motor function undergo activity-dependent maturation in early postnatal life in a manner analogous to sensory systems.

Rehabilitation in practice: management of lower motor neuron weakness.

PubMed

Ramdharry, Gita M

2010-05-01

This series of articles for rehabilitation in practice aims to cover a knowledge element of the rehabilitation medicine curriculum. Nevertheless they are intended to be of interest to a multidisciplinary audience. The competency addressed in this article is 'The trainee consistently demonstrates a knowledge of the pathophysiology of various specific impairments including lower motor neuron weakness' and 'management approaches for specific impairments including lower motor neuron weakness'.This article explores weakness as a lower motor symptom. Weakness as a primary impairment of neuromuscular diseases is addressed, with recognition of the phenomenon of disuse atrophy, and how weakness impacts on the functional abilities of people with myopathy and neuropathy. Interventions to reduce weakness or address the functional consequences of weakness are evaluated with consideration of safety and clinical application. This paper will allow readers to: (1) appraise the contribution of research in rehabilitation of lower motor neuron weakness to clinical decision making and (2) engage with the issues that arise when researching rehabilitation interventions for lower motor neuron weakness. Impairments associated with neuromuscular conditions can lead to significant functional difficulties that can impact on a person's daily participation. This article focuses on the primary impairment of weakness and explores the research evidence for rehabilitation interventions that directly influence weakness or address the impact of weakness on function.

Distribution of muscle fibre conduction velocity for representative samples of motor units in the full recruitment range of the tibialis anterior muscle.

PubMed

Del Vecchio, A; Negro, F; Felici, F; Farina, D

2018-02-01

Motor units are recruited in an orderly manner according to the size of motor neurones. Moreover, because larger motor neurones innervate fibres with larger diameters than smaller motor neurones, motor units should be recruited orderly according to their conduction velocity (MUCV). Because of technical limitations, these relations have been previously tested either indirectly or in small motor unit samples that revealed weak associations between motor unit recruitment threshold (RT) and MUCV. Here, we analyse the relation between MUCV and RT for large samples of motor units. Ten healthy volunteers completed a series of isometric ankle dorsiflexions at forces up to 70% of the maximum. Multi-channel surface electromyographic signals recorded from the tibialis anterior muscle were decomposed into single motor unit action potentials, from which the corresponding motor unit RT, MUCV and action potential amplitude were estimated. Established relations between muscle fibre diameter and CV were used to estimate the fibre size. Within individual subjects, the distributions of MUCV and fibre diameters were unimodal and did not show distinct populations. MUCV was strongly correlated with RT (mean (SD) R 2  = 0.7 (0.09), P < 0.001; 406 motor units), which supported the hypothesis that fibre diameter is associated with RT. The results provide further evidence for the relations between motor neurone and muscle fibre properties for large samples of motor units. The proposed methodology for motor unit analysis has also the potential to open new perspectives in the study of chronic and acute neuromuscular adaptations to ageing, training and pathology. © 2017 Scandinavian Physiological Society. Published by John Wiley & Sons Ltd.

Neuronal Determinants of Motor Disability in MS

DTIC Science & Technology

2015-10-01

well as in partial development of fiber tracking techniques for segmentation of motor pathways in the brain, brainstem , and spinal cord. We have...of  motor  neurons  at  the  cortex   and  axons  traversing  the  brain,   brainstem  and  spinal  cord   4 - 6 Dr

Genetics of Pediatric-Onset Motor Neuron and Neuromuscular Diseases

ClinicalTrials.gov

2015-08-24

Spinal Muscular Atrophy; Charcot-Marie-Tooth Disease; Muscular Dystrophy; Spinal Muscular Atrophy With Respiratory Distress 1; Amyotrophic Lateral Sclerosis; Motor Neuron Disease; Neuromuscular Disease; Peroneal Muscular Atrophy; Fragile X Syndrome

Pathways and genes differentially expressed in the motor cortex of patients with sporadic amyotrophic lateral sclerosis.

PubMed

Lederer, Carsten W; Torrisi, Antonietta; Pantelidou, Maria; Santama, Niovi; Cavallaro, Sebastiano

2007-01-23

Amyotrophic lateral sclerosis (ALS) is a fatal disorder caused by the progressive degeneration of motoneurons in brain and spinal cord. Despite identification of disease-linked mutations, the diversity of processes involved and the ambiguity of their relative importance in ALS pathogenesis still represent a major impediment to disease models as a basis for effective therapies. Moreover, the human motor cortex, although critical to ALS pathology and physiologically altered in most forms of the disease, has not been screened systematically for therapeutic targets. By whole-genome expression profiling and stringent significance tests we identify genes and gene groups de-regulated in the motor cortex of patients with sporadic ALS, and interpret the role of individual candidate genes in a framework of differentially expressed pathways. Our findings emphasize the importance of defense responses and cytoskeletal, mitochondrial and proteasomal dysfunction, reflect reduced neuronal maintenance and vesicle trafficking, and implicate impaired ion homeostasis and glycolysis in ALS pathogenesis. Additionally, we compared our dataset with publicly available data for the SALS spinal cord, and show a high correlation of changes linked to the diseased state in the SALS motor cortex. In an analogous comparison with data for the Alzheimer's disease hippocampus we demonstrate a low correlation of global changes and a moderate correlation for changes specifically linked to the SALS diseased state. Gene and sample numbers investigated allow pathway- and gene-based analyses by established error-correction methods, drawing a molecular portrait of the ALS motor cortex that faithfully represents many known disease features and uncovers several novel aspects of ALS pathology. Contrary to expectations for a tissue under oxidative stress, nuclear-encoded mitochondrial genes are uniformly down-regulated. Moreover, the down-regulation of mitochondrial and glycolytic genes implies a combined reduction of mitochondrial and cytoplasmic energy supply, with a possible role in the death of ALS motoneurons. Identifying candidate genes exclusively expressed in non-neuronal cells, we also highlight the importance of these cells in disease development in the motor cortex. Notably, some pathways and candidate genes identified by this study are direct or indirect targets of medication already applied to unrelated illnesses and point the way towards the rapid development of effective symptomatic ALS therapies.

Visualization of Sensory Neurons and Their Projections in an Upper Motor Neuron Reporter Line.

PubMed

Genç, Barış; Lagrimas, Amiko Krisa Bunag; Kuru, Pınar; Hess, Robert; Tu, Michael William; Menichella, Daniela Maria; Miller, Richard J; Paller, Amy S; Özdinler, P Hande

2015-01-01

Visualization of peripheral nervous system axons and cell bodies is important to understand their development, target recognition, and integration into complex circuitries. Numerous studies have used protein gene product (PGP) 9.5 [a.k.a. ubiquitin carboxy-terminal hydrolase L1 (UCHL1)] expression as a marker to label sensory neurons and their axons. Enhanced green fluorescent protein (eGFP) expression, under the control of UCHL1 promoter, is stable and long lasting in the UCHL1-eGFP reporter line. In addition to the genetic labeling of corticospinal motor neurons in the motor cortex and degeneration-resistant spinal motor neurons in the spinal cord, here we report that neurons of the peripheral nervous system are also fluorescently labeled in the UCHL1-eGFP reporter line. eGFP expression is turned on at embryonic ages and lasts through adulthood, allowing detailed studies of cell bodies, axons and target innervation patterns of all sensory neurons in vivo. In addition, visualization of both the sensory and the motor neurons in the same animal offers many advantages. In this report, we used UCHL1-eGFP reporter line in two different disease paradigms: diabetes and motor neuron disease. eGFP expression in sensory axons helped determine changes in epidermal nerve fiber density in a high-fat diet induced diabetes model. Our findings corroborate previous studies, and suggest that more than five months is required for significant skin denervation. Crossing UCHL1-eGFP with hSOD1G93A mice generated hSOD1G93A-UeGFP reporter line of amyotrophic lateral sclerosis, and revealed sensory nervous system defects, especially towards disease end-stage. Our studies not only emphasize the complexity of the disease in ALS, but also reveal that UCHL1-eGFP reporter line would be a valuable tool to visualize and study various aspects of sensory nervous system development and degeneration in the context of numerous diseases.

Gene expression profiling of two distinct neuronal populations in the rodent spinal cord.

PubMed

Ryge, Jesper; Westerdahl, Ann-Charlotte; Alstrøm, Preben; Kiehn, Ole

2008-01-01

In the field of neuroscience microarray gene expression profiles on anatomically defined brain structures are being used increasingly to study both normal brain functions as well as pathological states. Fluorescent tracing techniques in brain tissue that identifies distinct neuronal populations can in combination with global gene expression profiling potentially increase the resolution and specificity of such studies to shed new light on neuronal functions at the cellular level. We examine the microarray gene expression profiles of two distinct neuronal populations in the spinal cord of the neonatal rat, the principal motor neurons and specific interneurons involved in motor control. The gene expression profiles of the respective cell populations were obtained from amplified mRNA originating from 50-250 fluorescently identified and laser microdissected cells. In the data analysis we combine a new microarray normalization procedure with a conglomerate measure of significant differential gene expression. Using our methodology we find 32 genes to be more expressed in the interneurons compared to the motor neurons that all except one have not previously been associated with this neuronal population. As a validation of our method we find 17 genes to be more expressed in the motor neurons than in the interneurons and of these only one had not previously been described in this population. We provide an optimized experimental protocol that allows isolation of gene transcripts from fluorescent retrogradely labeled cell populations in fresh tissue, which can be used to generate amplified aRNA for microarray hybridization from as few as 50 laser microdissected cells. Using this optimized experimental protocol in combination with our microarray analysis methodology we find 49 differentially expressed genes between the motor neurons and the interneurons that reflect the functional differences between these two cell populations in generating and transmitting the motor output in the rodent spinal cord.

Gene Expression Profiling of Two Distinct Neuronal Populations in the Rodent Spinal Cord

PubMed Central

Alstrøm, Preben; Kiehn, Ole

2008-01-01

Background In the field of neuroscience microarray gene expression profiles on anatomically defined brain structures are being used increasingly to study both normal brain functions as well as pathological states. Fluorescent tracing techniques in brain tissue that identifies distinct neuronal populations can in combination with global gene expression profiling potentially increase the resolution and specificity of such studies to shed new light on neuronal functions at the cellular level. Methodology/Principal Findings We examine the microarray gene expression profiles of two distinct neuronal populations in the spinal cord of the neonatal rat, the principal motor neurons and specific interneurons involved in motor control. The gene expression profiles of the respective cell populations were obtained from amplified mRNA originating from 50–250 fluorescently identified and laser microdissected cells. In the data analysis we combine a new microarray normalization procedure with a conglomerate measure of significant differential gene expression. Using our methodology we find 32 genes to be more expressed in the interneurons compared to the motor neurons that all except one have not previously been associated with this neuronal population. As a validation of our method we find 17 genes to be more expressed in the motor neurons than in the interneurons and of these only one had not previously been described in this population. Conclusions/Significance We provide an optimized experimental protocol that allows isolation of gene transcripts from fluorescent retrogradely labeled cell populations in fresh tissue, which can be used to generate amplified aRNA for microarray hybridization from as few as 50 laser microdissected cells. Using this optimized experimental protocol in combination with our microarray analysis methodology we find 49 differentially expressed genes between the motor neurons and the interneurons that reflect the functional differences between these two cell populations in generating and transmitting the motor output in the rodent spinal cord. PMID:18923679

Axon-Sorting Multifunctional Nerve Guides: Accelerating Restoration of Nerve Function

DTIC Science & Technology

2014-10-01

factor (singly & in selected combinations) in the organotypic model system for preferential sensory or motor axon extension. Use confocal microscopy to...track axon extension of labeled sensory or motor neurons from spinal cord slices (motor) or dorsal root ganglia ( DRG ) (sensory). 20 Thy1-YFP mice...RESEARCH ACCOMPLISHMENTS: • Established a system of color-coded mixed nerve tracking using GFP and RFP expressing motor and sensory neurons (Figure 1

cAMP-dependent insulin modulation of synaptic inhibition in neurons of the dorsal motor nucleus of the vagus is altered in diabetic mice

PubMed Central

Blake, Camille B.

2014-01-01

Pathologies in which insulin is dysregulated, including diabetes, can disrupt central vagal circuitry, leading to gastrointestinal and other autonomic dysfunction. Insulin affects whole body metabolism through central mechanisms and is transported into the brain stem dorsal motor nucleus of the vagus (DMV) and nucleus tractus solitarius (NTS), which mediate parasympathetic visceral regulation. The NTS receives viscerosensory vagal input and projects heavily to the DMV, which supplies parasympathetic vagal motor output. Normally, insulin inhibits synaptic excitation of DMV neurons, with no effect on synaptic inhibition. Modulation of synaptic inhibition in DMV, however, is often sensitive to cAMP-dependent mechanisms. We hypothesized that an effect of insulin on GABAergic synaptic transmission may be uncovered by elevating resting cAMP levels in GABAergic terminals. We used whole cell patch-clamp recordings in brain stem slices from control and diabetic mice to identify insulin effects on inhibitory neurotransmission in the DMV in the presence of forskolin to elevate cAMP levels. In the presence of forskolin, insulin decreased the frequency of inhibitory postsynaptic currents (IPSCs) and the paired-pulse ratio of evoked IPSCs in DMV neurons from control mice. This effect was blocked by brefeldin-A, a Golgi-disrupting agent, or indinavir, a GLUT4 blocker, indicating that protein trafficking and glucose transport were involved. In streptozotocin-treated, diabetic mice, insulin did not affect IPSCs in DMV neurons in the presence of forskolin. Results suggest an impairment of cAMP-induced insulin effects on GABA release in the DMV, which likely involves disrupted protein trafficking in diabetic mice. These findings provide insight into mechanisms underlying vagal dysregulation associated with diabetes. PMID:24990858

Extending the Cortical Grasping Network: Pre-supplementary Motor Neuron Activity During Vision and Grasping of Objects

PubMed Central

Lanzilotto, Marco; Livi, Alessandro; Maranesi, Monica; Gerbella, Marzio; Barz, Falk; Ruther, Patrick; Fogassi, Leonardo; Rizzolatti, Giacomo; Bonini, Luca

2016-01-01

Grasping relies on a network of parieto-frontal areas lying on the dorsolateral and dorsomedial parts of the hemispheres. However, the initiation and sequencing of voluntary actions also requires the contribution of mesial premotor regions, particularly the pre-supplementary motor area F6. We recorded 233 F6 neurons from 2 monkeys with chronic linear multishank neural probes during reaching–grasping visuomotor tasks. We showed that F6 neurons play a role in the control of forelimb movements and some of them (26%) exhibit visual and/or motor specificity for the target object. Interestingly, area F6 neurons form 2 functionally distinct populations, showing either visually-triggered or movement-related bursts of activity, in contrast to the sustained visual-to-motor activity displayed by ventral premotor area F5 neurons recorded in the same animals and with the same task during previous studies. These findings suggest that F6 plays a role in object grasping and extend existing models of the cortical grasping network. PMID:27733538

Inactivation of the survival motor neuron gene, a candidate gene for human spinal muscular atrophy, leads to massive cell death in early mouse embryos

PubMed Central

Schrank, Bertold; Götz, Rudolf; Gunnersen, Jennifer M.; Ure, Janice M.; Toyka, Klaus V.; Smith, Austin G.; Sendtner, Michael

1997-01-01

Proximal spinal muscular atrophy is an autosomal recessive human disease of spinal motor neurons leading to muscular weakness with onset predominantly in infancy and childhood. With an estimated heterozygote frequency of 1/40 it is the most common monogenic disorder lethal to infants; milder forms represent the second most common pediatric neuromuscular disorder. Two candidate genes—survival motor neuron (SMN) and neuronal apoptosis inhibitory protein have been identified on chromosome 5q13 by positional cloning. However, the functional impact of these genes and the mechanism leading to a degeneration of motor neurons remain to be defined. To analyze the role of the SMN gene product in vivo we generated SMN-deficient mice. In contrast to the human genome, which contains two copies, the mouse genome contains only one SMN gene. Mice with homozygous SMN disruption display massive cell death during early embryonic development, indicating that the SMN gene product is necessary for cellular survival and function. PMID:9275227

Localisation of the high-affinity choline transporter-1 in the rat skeletal motor unit.

PubMed

Lips, Katrin S; Pfeil, Uwe; Haberberger, Rainer V; Kummer, Wolfgang

2002-03-01

The rate-limiting step in neuronal acetylcholine (ACh) synthesis is the uptake of choline via a high-affinity transporter. We have generated antisera against the recently identified transporter CHT1 to investigate its distribution in rat motor neurons and skeletal muscle and have used these antisera in combination with (1) antisera against the vesicular acetylcholine transporter (VAChT) to identify cholinergic synapses and (2) Alexa-488-labelled alpha-bungarotoxin to identify motor endplates. In the motor unit, immunohistochemistry and RT-PCR have demonstrated that CHT1 is restricted to motoneurons and absent from the non-neuronal ACh-synthesizing elements, e.g. skeletal muscle fibres. In addition, CHT1 is also present in parasympathetic neurons of the tongue, as evidenced by immunohistochemistry and RT-PCR. CHT1 immunoreativity is principally found at all segments (perikaryon, dendrites, axon) of the motoneuron but is enriched at neuro-neuronal and neuro-muscular synapses. This preferential localisation matches well with its anticipated pivotal role in synaptic transmitter recycling and synthesis.

Rhythmic Oscillations of Visual Contrast Sensitivity Synchronized with Action

PubMed Central

Tomassini, Alice; Spinelli, Donatella; Jacono, Marco; Sandini, Giulio; Morrone, Maria Concetta

2016-01-01

It is well known that the motor and the sensory systems structure sensory data collection and cooperate to achieve an efficient integration and exchange of information. Increasing evidence suggests that both motor and sensory functions are regulated by rhythmic processes reflecting alternating states of neuronal excitability, and these may be involved in mediating sensory-motor interactions. Here we show an oscillatory fluctuation in early visual processing time locked with the execution of voluntary action, and, crucially, even for visual stimuli irrelevant to the motor task. Human participants were asked to perform a reaching movement toward a display and judge the orientation of a Gabor patch, near contrast threshold, briefly presented at random times before and during the reaching movement. When the data are temporally aligned to the onset of movement, visual contrast sensitivity oscillates with periodicity within the theta band. Importantly, the oscillations emerge during the motor planning stage, ~500 ms before movement onset. We suggest that brain oscillatory dynamics may mediate an automatic coupling between early motor planning and early visual processing, possibly instrumental in linking and closing up the visual-motor control loop. PMID:25948254

Silencing neuronal mutant androgen receptor in a mouse model of spinal and bulbar muscular atrophy.

PubMed

Sahashi, Kentaro; Katsuno, Masahisa; Hung, Gene; Adachi, Hiroaki; Kondo, Naohide; Nakatsuji, Hideaki; Tohnai, Genki; Iida, Madoka; Bennett, C Frank; Sobue, Gen

2015-11-01

Spinal and bulbar muscular atrophy (SBMA), an adult-onset neurodegenerative disease that affects males, results from a CAG triplet repeat/polyglutamine expansions in the androgen receptor (AR) gene. Patients develop progressive muscular weakness and atrophy, and no effective therapy is currently available. The tissue-specific pathogenesis, especially relative pathological contributions between degenerative motor neurons and muscles, remains inconclusive. Though peripheral pathology in skeletal muscle caused by toxic AR protein has been recently reported to play a pivotal role in the pathogenesis of SBMA using mouse models, the role of motor neuron degeneration in SBMA has not been rigorously investigated. Here, we exploited synthetic antisense oligonucleotides to inhibit the RNA levels of mutant AR in the central nervous system (CNS) and explore its therapeutic effects in our SBMA mouse model that harbors a mutant AR gene with 97 CAG expansions and characteristic SBMA-like neurogenic phenotypes. A single intracerebroventricular administration of the antisense oligonucleotides in the presymptomatic phase efficiently suppressed the mutant gene expression in the CNS, and delayed the onset and progression of motor dysfunction, improved body weight gain and survival with the amelioration of neuronal histopathology in motor units such as spinal motor neurons, neuromuscular junctions and skeletal muscle. These findings highlight the importance of the neurotoxicity of mutant AR protein in motor neurons as a therapeutic target. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Evaluation of motor neuron differentiation potential of human umbilical cord blood- derived mesenchymal stem cells, in vitro.

PubMed

Yousefi, Behnam; Sanooghi, Davood; Faghihi, Faezeh; Joghataei, Mohammad Taghi; Latifi, Nourahmad

2017-04-01

Many people suffer from spinal cord injuries annually. These deficits usually threaten the quality of life of patients. As a postpartum medically waste product, human Umbilical Cord Blood (UCB) is a rich source of stem cells with self- renewal properties and neural differentiation capacity which made it useful in regenerative medicine. Since there is no report on potential of human umbilical cord blood-derived mesenchymal stem cells into motor neurons, we set out to evaluate the differentiation properties of these cells into motor neuron-like cells through administration of Retinoic Acid(RA), Sonic Hedgehog(Shh) and BDNF using a three- step in vitro procedure. The results were evaluated using Real-time PCR, Flowcytometry and Immunocytochemistry for two weeks. Our data showed that the cells changed into bipolar morphology and could express markers related to motor neuron; including Hb-9, Pax-6, Islet-1, NF-H, ChAT at the level of mRNA and protein. We could also quantitatively evaluate the expression of Islet-1, ChAT and NF-H at 7 and 14days post- induction using flowcytometry. It is concluded that human UCB-MSCs is potent to express motor neuron- related markers in the presence of RA, Shh and BDNF through a three- step protocol; thus it could be a suitable cell candidate for regeneration of motor neurons in spinal cord injuries. Copyright © 2017. Published by Elsevier B.V.

Area-specific temporal control of corticospinal motor neuron differentiation by COUP-TFI

PubMed Central

Tomassy, Giulio Srubek; De Leonibus, Elvira; Jabaudon, Denis; Lodato, Simona; Alfano, Christian; Mele, Andrea; Macklis, Jeffrey D.; Studer, Michèle

2010-01-01

Transcription factors with gradients of expression in neocortical progenitors give rise to distinct motor and sensory cortical areas by controlling the area-specific differentiation of distinct neuronal subtypes. However, the molecular mechanisms underlying this area-restricted control are still unclear. Here, we show that COUP-TFI controls the timing of birth and specification of corticospinal motor neurons (CSMN) in somatosensory cortex via repression of a CSMN differentiation program. Loss of COUP-TFI function causes an area-specific premature generation of neurons with cardinal features of CSMN, which project to subcerebral structures, including the spinal cord. Concurrently, genuine CSMN differentiate imprecisely and do not project beyond the pons, together resulting in impaired skilled motor function in adult mice with cortical COUP-TFI loss-of-function. Our findings indicate that COUP-TFI exerts critical areal and temporal control over the precise differentiation of CSMN during corticogenesis, thereby enabling the area-specific functional features of motor and sensory areas to arise. PMID:20133588

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

In vivo control mechanisms of motor-cargo movement on microtubules

NASA Astrophysics Data System (ADS)

Gunawardena, Shermali

2014-03-01

Within axons, molecular motors transport essential components required for neuronal growth and viability. Although many levels of regulation must exist for proper anterograde and retrograde transport of vital proteins, little is known about these mechanisms. Previous work suggested that the amyloid precursor protein (APP) functions as a kinesin-1 receptor during transport. However, how APP vesicle motility is regulated is unclear. Using genetics and in vivo imaging in Drosophila we showed that reduction of presenilin (PS) substantially increased anterograde and retrograde APP vesicle velocities. Strikingly, PS deficiency had no effect on an unrelated cargo vesicle containing synaptotagmin, which is powered by a different kinesin motor. Increased PS-mediated velocities required functional kinesin-1 and dynein motors. We also found that these PS-mediated effects on motor protein function were mediated via a pathway that involves glycogen synthase kinase-3 β (GSK-3 β) . PS genetically interacted with GSK-3 β in an activity dependent manner. Excess of active GSK-3 β perturbed transport by causing axonal blockages, which were enhanced by reduction of kinesin-1 or dynein, while excess of non-functional GSK-3 β had no effect. Strikingly, GSK-3 β-activity dependent transport defects were enhanced by reduction of PS. Collectively, our findings suggest that PS and GSK-3 β are required for normal motor protein function, and we propose a model in which PS likely regulates GSK-3 β activity during transport. These findings have important implications for our understanding of the complex regulatory machinery that must exist in vivo and how this system is coordinated during vesicle motility on microtubules.

DREAM-Dependent Activation of Astrocytes in Amyotrophic Lateral Sclerosis.

PubMed

Larrodé, Pilar; Calvo, Ana Cristina; Moreno-Martínez, Laura; de la Torre, Miriam; Moreno-García, Leticia; Molina, Nora; Castiella, Tomás; Iñiguez, Cristina; Pascual, Luis Fernando; Mena, Francisco Javier Miana; Zaragoza, Pilar; Y Cajal, Santiago Ramón; Osta, Rosario

2018-01-01

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease of unknown origin and characterized by a relentless loss of motor neurons that causes a progressive muscle weakness until death. Among the several pathogenic mechanisms that have been related to ALS, a dysregulation of calcium-buffering proteins in motor neurons of the brain and spinal cord can make these neurons more vulnerable to disease progression. Downstream regulatory element antagonist modulator (DREAM) is a neuronal calcium-binding protein that plays multiple roles in the nucleus and cytosol. The main aim of this study was focused on the characterization of DREAM and glial fibrillary acid protein (GFAP) in the brain and spinal cord tissues from transgenic SOD1 G93A mice and ALS patients to unravel its potential role under neurodegenerative conditions. The DREAM and GFAP levels in the spinal cord and different brain areas from transgenic SOD1 G93A mice and ALS patients were analyzed by Western blot and immunohistochemistry. Our findings suggest that the calcium-dependent excitotoxicity progressively enhanced in the CNS in ALS could modulate the multifunctional nature of DREAM, strengthening its apoptotic way of action in both motor neurons and astrocytes, which could act as an additional factor to increase neuronal damage. The direct crosstalk between astrocytes and motor neurons can become vulnerable under neurodegenerative conditions, and DREAM could act as an additional switch to enhance motor neuron loss. Together, these findings could pave the way to further study the molecular targets of DREAM to find novel therapeutic strategies to fight ALS.

Parkin-Dependent Degradation of the F-Box Protein Fbw7β Promotes Neuronal Survival in Response to Oxidative Stress by Stabilizing Mcl-1

PubMed Central

Ekholm-Reed, Susanna; Goldberg, Matthew S.; Schlossmacher, Michael G.

2013-01-01

Parkinson's disease (PD) is characterized by progressive loss of midbrain dopaminergic neurons resulting in motor dysfunction. While most PD is sporadic in nature, a significant subset can be linked to either dominant or recessive germ line mutations. PARK2, encoding the ubiquitin ligase parkin, is the most frequently mutated gene in hereditary Parkinson's disease. Here, we present evidence for a neuronal ubiquitin ligase cascade involving parkin and the multisubunit ubiquitin ligase SCFFbw7β. Specifically, parkin targets the SCF substrate adapter Fbw7β for proteasomal degradation. Furthermore, we show that the physiological role of parkin-mediated regulation of Fbw7β levels is the stabilization of the mitochondrial prosurvival factor Mcl-1, an SCFFbw7β target in neurons. We show that neurons depleted of parkin become acutely sensitive to oxidative stress due to an inability to maintain adequate levels of Mcl-1. Therefore, loss of parkin function through biallelic mutation of PARK2 may lead to death of dopaminergic neurons through unregulated SCFFbw7β-mediated ubiquitylation-dependent proteolysis of Mcl-1. PMID:23858059

Motor learning induces plastic changes in Purkinje cell dendritic spines in the rat cerebellum.

PubMed

González-Tapia, D; González-Ramírez, M M; Vázquez-Hernández, N; González-Burgos, I

2017-12-14

The paramedian lobule of the cerebellum is involved in learning to correctly perform motor skills through practice. Dendritic spines are dynamic structures that regulate excitatory synaptic stimulation. We studied plastic changes occurring in the dendritic spines of Purkinje cells from the paramedian lobule of rats during motor learning. Adult male rats were trained over a 6-day period using an acrobatic motor learning paradigm; the density and type of dendritic spines were determined every day during the study period using a modified version of the Golgi method. The learning curve reflected a considerable decrease in the number of errors made by rats as the training period progressed. We observed more dendritic spines on days 2 and 6, particularly more thin spines on days 1, 3, and 6, fewer mushroom spines on day 3, fewer stubby spines on day 1, and more thick spines on days 4 and 6. The initial stage of motor learning may be associated with fast processing of the underlying synaptic information combined with an apparent "silencing" of memory consolidation processes, based on the regulation of the neuronal excitability. Copyright © 2017 Sociedad Española de Neurología. Publicado por Elsevier España, S.L.U. All rights reserved.

Role of proopiomelanocortin neuron Stat3 in regulating arterial pressure and mediating the chronic effects of leptin.

PubMed

Dubinion, John H; do Carmo, Jussara M; Adi, Ahmad; Hamza, Shereen; da Silva, Alexandre A; Hall, John E

2013-05-01

Although signal transducer and activator of transcription 3 (Stat3) is a key second messenger by which leptin regulates appetite and body weight, its role in specific neuronal populations in metabolic regulation and in mediating the chronic effects of leptin on blood pressure is unknown. The current study tested the hypothesis that Stat3 signaling in proopiomelanocortin (POMC) neurons mediates the chronic effects of leptin on mean arterial pressure (MAP), as well as on glucose regulation, energy expenditure, and food intake. Stat3(flox/flox) mice were crossed with POMC-Cre mice to generate mice with Stat3 deletion specifically in POMC neurons (Stat3(flox/flox)/POMC-Cre). Oxygen consumption (Vo2), carbon dioxide respiration (Vco2), motor activity, heat production, food intake, and MAP were measured 24 hours/d. After baseline measurements, leptin was infused (4 μg/kg per min, IP) for 7 days. Stat3(flox/flox)/POMC-Cre mice were hyperphagic, heavier, and had increased respiratory quotients compared with control Stat3(flox/flox) mice. Baseline MAP was not different between the groups, and chronic leptin infusion reduced food intake similarly in both groups (27 versus 29%). Vo2, Vco2, and heat production responses to leptin were not significantly different in control and Stat3(flox/flox)/POMC-Cre mice. However, leptin-mediated increases in MAP were completely abolished, and blood pressure responses to acute air-jet stress were attenuated in male Stat3(flox/flox)/POMC-Cre mice. These results indicate that Stat3 signaling in POMC neurons is essential for leptin-mediated increases in MAP, but not for anorexic or thermogenic effects of leptin.

Induction of Neuron-Specific Degradation of Coenzyme A Models Pantothenate Kinase-Associated Neurodegeneration by Reducing Motor Coordination in Mice.

PubMed

Shumar, Stephanie A; Fagone, Paolo; Alfonso-Pecchio, Adolfo; Gray, John T; Rehg, Jerold E; Jackowski, Suzanne; Leonardi, Roberta

2015-01-01

Pantothenate kinase-associated neurodegeneration, PKAN, is an inherited disorder characterized by progressive impairment in motor coordination and caused by mutations in PANK2, a human gene that encodes one of four pantothenate kinase (PanK) isoforms. PanK initiates the synthesis of coenzyme A (CoA), an essential cofactor that plays a key role in energy metabolism and lipid synthesis. Most of the mutations in PANK2 reduce or abolish the activity of the enzyme. This evidence has led to the hypothesis that lower CoA might be the underlying cause of the neurodegeneration in PKAN patients; however, no mouse model of the disease is currently available to investigate the connection between neuronal CoA levels and neurodegeneration. Indeed, genetic and/or dietary manipulations aimed at reducing whole-body CoA synthesis have not produced a desirable PKAN model, and this has greatly hindered the discovery of a treatment for the disease. Cellular CoA levels are tightly regulated by a balance between synthesis and degradation. CoA degradation is catalyzed by two peroxisomal nudix hydrolases, Nudt7 and Nudt19. In this study we sought to reduce neuronal CoA in mice through the alternative approach of increasing Nudt7-mediated CoA degradation. This was achieved by combining the use of an adeno-associated virus-based expression system with the synapsin (Syn) promoter. We show that mice with neuronal overexpression of a cytosolic version of Nudt7 (scAAV9-Syn-Nudt7cyt) exhibit a significant decrease in brain CoA levels in conjunction with a reduction in motor coordination. These results strongly support the existence of a link between CoA levels and neuronal function and show that scAAV9-Syn-Nudt7cyt mice can be used to model PKAN.

The neocortex of cetartiodactyls. II. Neuronal morphology of the visual and motor cortices in the giraffe (Giraffa camelopardalis).

PubMed

Jacobs, Bob; Harland, Tessa; Kennedy, Deborah; Schall, Matthew; Wicinski, Bridget; Butti, Camilla; Hof, Patrick R; Sherwood, Chet C; Manger, Paul R

2015-09-01

The present quantitative study extends our investigation of cetartiodactyls by exploring the neuronal morphology in the giraffe (Giraffa camelopardalis) neocortex. Here, we investigate giraffe primary visual and motor cortices from perfusion-fixed brains of three subadults stained with a modified rapid Golgi technique. Neurons (n = 244) were quantified on a computer-assisted microscopy system. Qualitatively, the giraffe neocortex contained an array of complex spiny neurons that included both "typical" pyramidal neuron morphology and "atypical" spiny neurons in terms of morphology and/or orientation. In general, the neocortex exhibited a vertical columnar organization of apical dendrites. Although there was no significant quantitative difference in dendritic complexity for pyramidal neurons between primary visual (n = 78) and motor cortices (n = 65), there was a significant difference in dendritic spine density (motor cortex > visual cortex). The morphology of aspiny neurons in giraffes appeared to be similar to that of other eutherian mammals. For cross-species comparison of neuron morphology, giraffe pyramidal neurons were compared to those quantified with the same methodology in African elephants and some cetaceans (e.g., bottlenose dolphin, minke whale, humpback whale). Across species, the giraffe (and cetaceans) exhibited less widely bifurcating apical dendrites compared to elephants. Quantitative dendritic measures revealed that the elephant and humpback whale had more extensive dendrites than giraffes, whereas the minke whale and bottlenose dolphin had less extensive dendritic arbors. Spine measures were highest in the giraffe, perhaps due to the high quality, perfusion fixation. The neuronal morphology in giraffe neocortex is thus generally consistent with what is known about other cetartiodactyls.

Generation and expansion of highly pure motor neuron progenitors from human pluripotent stem cells.

PubMed

Du, Zhong-Wei; Chen, Hong; Liu, Huisheng; Lu, Jianfeng; Qian, Kun; Huang, CindyTzu-Ling; Zhong, Xiaofen; Fan, Frank; Zhang, Su-Chun

2015-03-25

Human pluripotent stem cells (hPSCs) have opened new opportunities for understanding human development, modelling disease processes and developing new therapeutics. However, these applications are hindered by the low efficiency and heterogeneity of cell types, such as motorneurons (MNs), differentiated from hPSCs as well as our inability to maintain the potency of lineage-committed progenitors. Here by using a combination of small molecules that regulate multiple signalling pathways, we develop a method to guide human embryonic stem cells to a near-pure population (>95%) of motor neuron progenitors (MNPs) in 12 days, and an enriched population (>90%) of functionally mature MNs in an additional 16 days. More importantly, the MNPs can be expanded for at least five passages so that a single MNP can be amplified to 1 × 10(4). This method is reproducible in human-induced pluripotent stem cells and is applied to model MN-degenerative diseases and in proof-of-principle drug-screening assays.

Hippo/YAP-mediated rigidity-dependent motor neuron differentiation of human pluripotent stem cells

NASA Astrophysics Data System (ADS)

Sun, Yubing; Yong, Koh Meng Aw; Villa-Diaz, Luis G.; Zhang, Xiaoli; Chen, Weiqiang; Philson, Renee; Weng, Shinuo; Xu, Haoxing; Krebsbach, Paul H.; Fu, Jianping

2014-06-01

Our understanding of the intrinsic mechanosensitive properties of human pluripotent stem cells (hPSCs), in particular the effects that the physical microenvironment has on their differentiation, remains elusive. Here, we show that neural induction and caudalization of hPSCs can be accelerated by using a synthetic microengineered substrate system consisting of poly(dimethylsiloxane) micropost arrays (PMAs) with tunable mechanical rigidities. The purity and yield of functional motor neurons derived from hPSCs within 23 days of culture using soft PMAs were improved more than fourfold and tenfold, respectively, compared with coverslips or rigid PMAs. Mechanistic studies revealed a multi-targeted mechanotransductive process involving Smad phosphorylation and nucleocytoplasmic shuttling, regulated by rigidity-dependent Hippo/YAP activities and actomyosin cytoskeleton integrity and contractility. Our findings suggest that substrate rigidity is an important biophysical cue influencing neural induction and subtype specification, and that microengineered substrates can thus serve as a promising platform for large-scale culture of hPSCs.

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

Genetically identified spinal interneurons integrating tactile afferents for motor control

PubMed Central

Panek, Izabela; Farah, Carl

2015-01-01

Our movements are shaped by our perception of the world as communicated by our senses. Perception of sensory information has been largely attributed to cortical activity. However, a prior level of sensory processing occurs in the spinal cord. Indeed, sensory inputs directly project to many spinal circuits, some of which communicate with motor circuits within the spinal cord. Therefore, the processing of sensory information for the purpose of ensuring proper movements is distributed between spinal and supraspinal circuits. The mechanisms underlying the integration of sensory information for motor control at the level of the spinal cord have yet to be fully described. Recent research has led to the characterization of spinal neuron populations that share common molecular identities. Identification of molecular markers that define specific populations of spinal neurons is a prerequisite to the application of genetic techniques devised to both delineate the function of these spinal neurons and their connectivity. This strategy has been used in the study of spinal neurons that receive tactile inputs from sensory neurons innervating the skin. As a result, the circuits that include these spinal neurons have been revealed to play important roles in specific aspects of motor function. We describe these genetically identified spinal neurons that integrate tactile information and the contribution of these studies to our understanding of how tactile information shapes motor output. Furthermore, we describe future opportunities that these circuits present for shedding light on the neural mechanisms of tactile processing. PMID:26445867

Neuronal mechanisms of motor learning and motor memory consolidation in healthy old adults.

PubMed

Berghuis, K M M; Veldman, M P; Solnik, S; Koch, G; Zijdewind, I; Hortobágyi, T

2015-06-01

It is controversial whether or not old adults are capable of learning new motor skills and consolidate the performance gains into motor memory in the offline period. The underlying neuronal mechanisms are equally unclear. We determined the magnitude of motor learning and motor memory consolidation in healthy old adults and examined if specific metrics of neuronal excitability measured by magnetic brain stimulation mediate the practice and retention effects. Eleven healthy old adults practiced a wrist extension-flexion visuomotor skill for 20 min (MP, 71.3 years), while a second group only watched the templates without movements (attentional control, AC, n = 11, 70.5 years). There was 40 % motor learning in MP but none in AC (interaction, p < 0.001) with the skill retained 24 h later in MP and a 16 % improvement in AC. Corticospinal excitability at rest and during task did not change, but when measured during contraction at 20 % of maximal force, it strongly increased in MP and decreased in AC (interaction, p = 0.002). Intracortical inhibition at rest and during the task decreased and facilitation at rest increased in MP, but these metrics changed in the opposite direction in AC. These neuronal changes were especially profound at retention. Healthy old adults can learn a new motor skill and consolidate the learned skill into motor memory, processes that are most likely mediated by disinhibitory mechanisms. These results are relevant for the increasing number of old adults who need to learn and relearn movements during motor rehabilitation.

High-Frequency Stimulation of the Subthalamic Nucleus Activates Motor Cortex Pyramidal Tract Neurons by a Process Involving Local Glutamate, GABA and Dopamine Receptors in Hemi-Parkinsonian Rats.

PubMed

Chuang, Chi-Fen; Wu, Chen-Wei; Weng, Ying; Hu, Pei-San; Yeh, Shin-Rung; Chang, Yen-Chung

2018-04-30

Deep brain stimulation (DBS) is widely used to treat advanced Parkinson’s disease (PD). Here, we investigated how DBS applied on the subthalamic nucleus (STN) influenced the neural activity in the motor cortex. Rats, which had the midbrain dopaminergic neurons partially depleted unilaterally, called the hemi-Parkinsonian rats, were used as a study model. c-Fos expression in the neurons was used as an indicator of neural activity. Application of high-frequency stimulation (HFS) upon the STN was used to mimic the DBS treatment. The motor cortices in the two hemispheres of hemi-Parkinsonian rats were found to contain unequal densities of c-Fos-positive (Fos+) cells, and STN-HFS rectified this bilateral imbalance. In addition, STN-HFS led to the intense c-Fos expression in a group of motor cortical neurons which exhibited biochemical and anatomical characteristics resembling those of the pyramidal tract (PT) neurons sending efferent projections to the STN. The number of PT neurons expressing high levels of c-Fos was significantly reduced by local application of the antagonists of non-N-methyl-D-aspartate (non-NMDA) glutamate receptors, gammaaminobutyric acid A (GABAA) receptors and dopamine receptors in the upper layers of the motor cortex. The results indicate that the coincident activations of synapses and dopamine receptors in the motor cortex during STN-HFS trigger the intense expression of c-Fos of the PT neurons. The implications of the results on the cellular mechanism underlying the therapeutic effects of STN-DBS on the movement disorders of PD are also discussed.

Expression of Kv3.1b potassium channel is widespread in macaque motor cortex pyramidal cells: A histological comparison between rat and macaque

PubMed Central

Soares, David; Goldrick, Isabelle; Lemon, Roger N.; Kraskov, Alexander; Greensmith, Linda

2017-01-01

Abstract There are substantial differences across species in the organization and function of the motor pathways. These differences extend to basic electrophysiological properties. Thus, in rat motor cortex, pyramidal cells have long duration action potentials, while in the macaque, some pyramidal neurons exhibit short duration “thin” spikes. These differences may be related to the expression of the fast potassium channel Kv3.1b, which in rat interneurons is associated with generation of thin spikes. Rat pyramidal cells typically lack these channels, while there are reports that they are present in macaque pyramids. Here we made a systematic, quantitative comparison of the Kv3.1b expression in sections from macaque and rat motor cortex, using two different antibodies (NeuroMab, Millipore). As our standard reference, we examined, in the same sections, Kv3.1b staining in parvalbumin‐positive interneurons, which show strong Kv3.1b immunoreactivity. In macaque motor cortex, a large sample of pyramidal neurons were nearly all found to express Kv3.1b in their soma membranes. These labeled neurons were identified as pyramidal based either by expression of SMI32 (a pyramidal marker), or by their shape and size, and lack of expression of parvalbumin (a marker for some classes of interneuron). Large (Betz cells), medium, and small pyramidal neurons all expressed Kv3.1b. In rat motor cortex, SMI32‐postive pyramidal neurons expressing Kv3.1b were very rare and weakly stained. Thus, there is a marked species difference in the immunoreactivity of Kv3.1b in pyramidal neurons, and this may be one of the factors explaining the pronounced electrophysiological differences between rat and macaque pyramidal neurons. PMID:28213922

Neural dynamics and information representation in microcircuits of motor cortex.

PubMed

Tsubo, Yasuhiro; Isomura, Yoshikazu; Fukai, Tomoki

2013-01-01

The brain has to analyze and respond to external events that can change rapidly from time to time, suggesting that information processing by the brain may be essentially dynamic rather than static. The dynamical features of neural computation are of significant importance in motor cortex that governs the process of movement generation and learning. In this paper, we discuss these features based primarily on our recent findings on neural dynamics and information coding in the microcircuit of rat motor cortex. In fact, cortical neurons show a variety of dynamical behavior from rhythmic activity in various frequency bands to highly irregular spike firing. Of particular interest are the similarity and dissimilarity of the neuronal response properties in different layers of motor cortex. By conducting electrophysiological recordings in slice preparation, we report the phase response curves (PRCs) of neurons in different cortical layers to demonstrate their layer-dependent synchronization properties. We then study how motor cortex recruits task-related neurons in different layers for voluntary arm movements by simultaneous juxtacellular and multiunit recordings from behaving rats. The results suggest an interesting difference in the spectrum of functional activity between the superficial and deep layers. Furthermore, the task-related activities recorded from various layers exhibited power law distributions of inter-spike intervals (ISIs), in contrast to a general belief that ISIs obey Poisson or Gamma distributions in cortical neurons. We present a theoretical argument that this power law of in vivo neurons may represent the maximization of the entropy of firing rate with limited energy consumption of spike generation. Though further studies are required to fully clarify the functional implications of this coding principle, it may shed new light on information representations by neurons and circuits in motor cortex.

Implications of white matter damage in amyotrophic lateral sclerosis

PubMed Central

Zhou, Ting; Ahmad, Tina Khorshid; Gozda, Kiana; Truong, Jessica; Kong, Jiming; Namaka, Michael

2017-01-01

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease, which involves the progressive degeneration of motor neurons. ALS has long been considered a disease of the grey matter; however, pathological alterations of the white matter (WM), including axonal loss, axonal demyelination and oligodendrocyte death, have been reported in patients with ALS. The present review examined motor neuron death as the primary cause of ALS and evaluated the associated WM damage that is guided by neuronal-glial interactions. Previous studies have suggested that WM damage may occur prior to the death of motor neurons, and thus may be considered an early indicator for the diagnosis and prognosis of ALS. However, the exact molecular mechanisms underlying early-onset WM damage in ALS have yet to be elucidated. The present review explored the detailed anatomy of WM and identified several pathological mechanisms that may be implicated in WM damage in ALS. In addition, it associated the pathophysiological alterations of WM, which may contribute to motor neuron death in ALS, with similar mechanisms of WM damage that are involved in multiple sclerosis (MS). Furthermore, the early detection of WM damage in ALS, using neuroimaging techniques, may lead to earlier therapeutic intervention, using immunomodulatory treatment strategies similar to those used in relapsing-remitting MS, aimed at delaying WM damage in ALS. Early therapeutic approaches may have the potential to delay motor neuron damage and thus prolong the survival of patients with ALS. The therapeutic interventions that are currently available for ALS are only marginally effective. However, early intervention with immunomodulatory drugs may slow the progression of WM damage in the early stages of ALS, thus delaying motor neuron death and increasing the life expectancy of patients with ALS. PMID:28791401

The Effects of Motor Neurone Disease on Language: Further Evidence

ERIC Educational Resources Information Center

Bak, Thomas H.; Hodges, John R.

2004-01-01

It might sound surprising that Motor Neurone Disease (MND), regarded still by many as the very example of a neurodegenerative disease affecting selectively the motor system and sparing the sensory functions as well as cognition, can have a significant influence on language. In this article we hope to demonstrate that language dysfunction is not…

Somatosensory responses in a human motor cortex

PubMed Central

Donoghue, John P.; Hochberg, Leigh R.

2013-01-01

Somatic sensory signals provide a major source of feedback to motor cortex. Changes in somatosensory systems after stroke or injury could profoundly influence brain computer interfaces (BCI) being developed to create new output signals from motor cortex activity patterns. We had the unique opportunity to study the responses of hand/arm area neurons in primary motor cortex to passive joint manipulation in a person with a long-standing brain stem stroke but intact sensory pathways. Neurons responded to passive manipulation of the contralateral shoulder, elbow, or wrist as predicted from prior studies of intact primates. Thus fundamental properties and organization were preserved despite arm/hand paralysis and damage to cortical outputs. The same neurons were engaged by attempted arm actions. These results indicate that intact sensory pathways retain the potential to influence primary motor cortex firing rates years after cortical outputs are interrupted and may contribute to online decoding of motor intentions for BCI applications. PMID:23343902

The axonal transport of mitochondria

PubMed Central

Saxton, William M.; Hollenbeck, Peter J.

2012-01-01

Vigorous transport of cytoplasmic components along axons over substantial distances is crucial for the maintenance of neuron structure and function. The transport of mitochondria, which serves to distribute mitochondrial functions in a dynamic and non-uniform fashion, has attracted special interest in recent years following the discovery of functional connections among microtubules, motor proteins and mitochondria, and their influences on neurodegenerative diseases. Although the motor proteins that drive mitochondrial movement are now well characterized, the mechanisms by which anterograde and retrograde movement are coordinated with one another and with stationary axonal mitochondria are not yet understood. In this Commentary, we review why mitochondria move and how they move, focusing particularly on recent studies of transport regulation, which implicate control of motor activity by specific cell-signaling pathways, regulation of motor access to transport tracks and static microtubule–mitochondrion linkers. A detailed mechanism for modulating anterograde mitochondrial transport has been identified that involves Miro, a mitochondrial Ca2+-binding GTPase, which with associated proteins, can bind and control kinesin-1. Elements of the Miro complex also have important roles in mitochondrial fission–fusion dynamics, highlighting questions about the interdependence of biogenesis, transport, dynamics, maintenance and degradation. PMID:22619228

Motor neuron disease and optic neuropathy after acute exposure to a methanol-containing solvent mixture.

PubMed

Chiò, Adriano; Herrero Hernandez, Elena; Mora, Gabriele; Valentini, Consuelo; Discalzi, Gianluigi; Pira, Enrico

2004-09-01

A 34-years-old floor-layer developed optic neuropathy and motor neuron disease after being accidentally exposed to a solvent mixture containing methanol and other substances. Optic neuropathy is a complication of methanol poisoning, but the onset of a motor neuron disorder resembling amyotrophic lateral sclerosis after the exposure to these substances has not been previously described. The temporal onset of the clinical symptoms, biological plausibility, young age of the patient and absence of neurological disorders in the family history raises suspicion of a possible causative relationship.

Perturbations of Respiratory Rhythm and Pattern by Disrupting Synaptic Inhibition within Pre-Bötzinger and Bötzinger Complexes123

PubMed Central

Koizumi, Hidehiko; Mosher, Bryan; Tariq, Mohammad F.; Zhang, Ruli; Molkov, Yaroslav I.

2016-01-01

The pre-Bötzinger (pre-BötC) and Bötzinger (BötC) complexes are the brainstem compartments containing interneurons considered to be critically involved in generating respiratory rhythm and motor pattern in mammals. Current models postulate that both generation of the rhythm and coordination of the inspiratory-expiratory pattern involve inhibitory synaptic interactions within and between these regions. Both regions contain glycinergic and GABAergic neurons, and rhythmically active neurons in these regions receive appropriately coordinated phasic inhibition necessary for generation of the normal three-phase respiratory pattern. However, recent experiments attempting to disrupt glycinergic and GABAergic postsynaptic inhibition in the pre-BötC and BötC in adult rats in vivo have questioned the critical role of synaptic inhibition in these regions, as well as the importance of the BötC, which contradicts previous physiological and pharmacological studies. To further evaluate the roles of synaptic inhibition and the BötC, we bilaterally microinjected the GABAA receptor antagonist gabazine and glycinergic receptor antagonist strychnine into the pre-BötC or BötC in anesthetized adult rats in vivo and in perfused in situ brainstem–spinal cord preparations from juvenile rats. Muscimol was microinjected to suppress neuronal activity in the pre-BötC or BötC. In both preparations, disrupting inhibition within pre-BötC or BötC caused major site-specific perturbations of the rhythm and disrupted the three-phase motor pattern, in some experiments terminating rhythmic motor output. Suppressing BötC activity also potently disturbed the rhythm and motor pattern. We conclude that inhibitory circuit interactions within and between the pre-BötC and BötC critically regulate rhythmogenesis and are required for normal respiratory motor pattern generation. PMID:27200412

The mammalian neocortex new pyramidal neuron: a new conception.

PubMed

Marín-Padilla, Miguel

2014-01-06

The new cerebral cortex (neocortex) and the new type of pyramidal neuron are mammalian innovations that have evolved for operating their increasing motor capabilities while essentially using analogous anatomical and neural makeups. The human neocortex starts to develop in 6-week-old embryos with the establishment of a primordial cortical organization, which resembles the primitive cortices of amphibian and reptiles. From the 8th to the 15th week of age, new pyramidal neurons, of ependymal origin, are progressively incorporated within this primordial cortex forming a cellular plate that divides its components into those above it (neocortex first layer) and those below it (neocortex subplate zone). From the 16th week of age to birth and postnatally, the new pyramidal neurons continue to elongate functionally their apical dendrite by adding synaptic membrane to incorporate the needed sensory information for operating its developing motor activities. The new pyramidal neuron' distinguishing feature is the capacity of elongating anatomically and functionally its apical dendrite (its main receptive surface) without losing its original attachment to first layer or the location of its soma and, hence, retaining its essential nature. The number of pyramidal cell functional strata established in the motor cortex increases and reflects each mammalian species motor capabilities: the hedgehog needs two pyramidal cell functional strata to carry out all its motor activities, the mouse 3, cat 4, primates 5 and humans 6. The presence of six pyramidal cell functional strata distinguish the human motor cortex from that of others primates. Homo sapiens represent a new evolutionary stage that have transformed his primate brain for operating his unique motor capabilities, such as speaking, writing, painting, sculpturing and thinking as a premotor activity. Words used in language are the motor expression of thoughts and represent sounds produced by maneuvering the column of expiratory air by coordinated motor quivering as it passes through the larynx, pharynx, mouth, tongue, and lips. Homo sapiens cerebrum has developed new motor centers to communicate mental thoughts (and/or intention) through motor actions.

Tissue Plasminogen Activator Induction in Purkinje Neurons After Cerebellar Motor Learning

NASA Astrophysics Data System (ADS)

Seeds, Nicholas W.; Williams, Brian L.; Bickford, Paula C.

1995-12-01

The cerebellar cortex is implicated in the learning of complex motor skills. This learning may require synaptic remodeling of Purkinje cell inputs. An extracellular serine protease, tissue plasminogen activator (tPA), is involved in remodeling various nonneural tissues and is associated with developing and regenerating neurons. In situ hybridization showed that expression of tPA messenger RNA was increased in the Purkinje neurons of rats within an hour of their being trained for a complex motor task. Antibody to tPA also showed the induction of tPA protein associated with cerebellar Purkinje cells. Thus, the induction of tPA during motor learning may play a role in activity-dependent synaptic plasticity.

Methyl Vitamin B12 but not methylfolate rescues a motor neuron-like cell line from homocysteine-mediated cell death

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

Hemendinger, Richelle A., E-mail: richelle.hemendinger@carolinashealthcare.org; Armstrong, Edward J.; Brooks, Benjamin Rix

Homocysteine is an excitatory amino acid implicated in multiple diseases including amyotrophic lateral sclerosis (ALS). Information on the toxicity of homocysteine in motor neurons is limited and few studies have examined how this toxicity can be modulated. In NSC-34D cells (a hybrid cell line derived from motor neuron-neuroblastoma), homocysteine induces apoptotic cell death in the millimolar range with a TC{sub 50} (toxic concentration at which 50% of maximal cell death is achieved) of 2.2 mM, confirmed by activation of caspase 3/7. Induction of apoptosis was independent of short-term reactive oxygen species (ROS) generation. Methyl Vitamin B12 (MeCbl) and methyl tetrahydrofolatemore » (MTHF), used clinically to treat elevated homocysteine levels, were tested for their ability to reverse homocysteine-mediated motor neuron cell death. MeCbl in the micromolar range was able to provide neuroprotection (2 h pretreatment prior to homocysteine) and neurorescue (simultaneous exposure with homocysteine) against millimolar homocysteine with an IC{sub 50} (concentration at which 50% of maximal cell death is inhibited) of 0.6 {mu}M and 0.4 {mu}M, respectively. In contrast, MTHF (up to 10 {mu}M) had no effect on homocysteine-mediated cell death. MeCbl inhibited caspase 3/7 activation by homocysteine in a time- and dose-dependent manner, whereas MTHF had no effect. We conclude that MeCbl is effective against homocysteine-induced cell death in motor neurons in a ROS-independent manner, via a reduction in caspase activation and apoptosis. MeCbl decreases Hcy induced motor neuron death in vitro in a hybrid cell line derived from motor neuron-neuroblastoma and may play a role in the treatment of late stage ALS where HCy levels are increased in animal models of ALS.« less

Three-dimensional analysis of somatic mitochondrial dynamics in fission-deficient injured motor neurons using FIB/SEM.

PubMed

Tamada, Hiromi; Kiryu-Seo, Sumiko; Hosokawa, Hiroki; Ohta, Keisuke; Ishihara, Naotada; Nomura, Masatoshi; Mihara, Katsuyoshi; Nakamura, Kei-Ichiro; Kiyama, Hiroshi

2017-08-01

Mitochondria undergo morphological changes through fusion and fission for their quality control, which are vital for neuronal function. In this study, we examined three-dimensional morphologies of mitochondria in motor neurons under normal, nerve injured, and nerve injured plus fission-impaired conditions using the focused ion beam/scanning electron microscopy (FIB/SEM), because the FIB/SEM technology is a powerful tool to demonstrate both 3D images of whole organelle and the intra-organellar structure simultaneously. Crossing of dynamin-related protein 1 (Drp1) gene-floxed mice with neuronal injury-specific Cre driver mice, Atf3:BAC Tg mice, allowed for Drp1 ablation specifically in injured neurons. FIB/SEM analysis demonstrated that somatic mitochondrial morphologies in motor neurons were not altered before or after nerve injury. However, the fission impairment resulted in prominent somatic mitochondrial enlargement, which initially induced complex morphologies with round regions and long tubular processes, subsequently causing a decrease in the number of processes and further enlargement of the round regions, which eventually resulted in big spheroidal mitochondria without processes. The abnormal mitochondria exhibited several degradative morphologies: local or total cristae collapse, vacuolization, and mitophagy. These suggest that mitochondrial fission is crucial for maintaining mitochondrial integrity in injured motor neurons, and multiple forms of mitochondria degradation may accelerate neuronal degradation. © 2017 Wiley Periodicals, Inc.

Temporal Coupling with Cortex Distinguishes Spontaneous Neuronal Activities in Identified Basal Ganglia-Recipient and Cerebellar-Recipient Zones of the Motor Thalamus

PubMed Central

Nakamura, Kouichi C.; Sharott, Andrew; Magill, Peter J.

2014-01-01

Neurons of the motor thalamus mediate basal ganglia and cerebellar influences on cortical activity. To elucidate the net result of γ-aminobutyric acid-releasing or glutamatergic bombardment of the motor thalamus by basal ganglia or cerebellar afferents, respectively, we recorded the spontaneous activities of thalamocortical neurons in distinct identified “input zones” in anesthetized rats during defined cortical activity states. Unexpectedly, the mean rates and brain state dependencies of the firing of neurons in basal ganglia-recipient zone (BZ) and cerebellar-recipient zone (CZ) were matched during slow-wave activity (SWA) and cortical activation. However, neurons were distinguished during SWA by their firing regularities, low-threshold spike bursts and, more strikingly, by the temporal coupling of their activities to ongoing cortical oscillations. The firing of neurons across the BZ was stronger and more precisely phase-locked to cortical slow (∼1 Hz) oscillations, although both neuron groups preferentially fired at the same phase. In contrast, neurons in BZ and CZ fired at different phases of cortical spindles (7–12 Hz), but with similar strengths of coupled firing. Thus, firing rates do not reflect the predicted inhibitory–excitatory imbalance across the motor thalamus, and input zone-specific temporal coding through oscillatory synchronization with the cortex could partly mediate the different roles of basal ganglia and cerebellum in behavior. PMID:23042738

An ultra-sparse code underliesthe generation of neural sequences in a songbird

NASA Astrophysics Data System (ADS)

Hahnloser, Richard H. R.; Kozhevnikov, Alexay A.; Fee, Michale S.

2002-09-01

Sequences of motor activity are encoded in many vertebrate brains by complex spatio-temporal patterns of neural activity; however, the neural circuit mechanisms underlying the generation of these pre-motor patterns are poorly understood. In songbirds, one prominent site of pre-motor activity is the forebrain robust nucleus of the archistriatum (RA), which generates stereotyped sequences of spike bursts during song and recapitulates these sequences during sleep. We show that the stereotyped sequences in RA are driven from nucleus HVC (high vocal centre), the principal pre-motor input to RA. Recordings of identified HVC neurons in sleeping and singing birds show that individual HVC neurons projecting onto RA neurons produce bursts sparsely, at a single, precise time during the RA sequence. These HVC neurons burst sequentially with respect to one another. We suggest that at each time in the RA sequence, the ensemble of active RA neurons is driven by a subpopulation of RA-projecting HVC neurons that is active only at that time. As a population, these HVC neurons may form an explicit representation of time in the sequence. Such a sparse representation, a temporal analogue of the `grandmother cell' concept for object recognition, eliminates the problem of temporal interference during sequence generation and learning attributed to more distributed representations.

Layer 5 Pyramidal Neurons' Dendritic Remodeling and Increased Microglial Density in Primary Motor Cortex in a Murine Model of Facial Paralysis

PubMed Central

Urrego, Diana; Troncoso, Julieta; Múnera, Alejandro

2015-01-01

This work was aimed at characterizing structural changes in primary motor cortex layer 5 pyramidal neurons and their relationship with microglial density induced by facial nerve lesion using a murine facial paralysis model. Adult transgenic mice, expressing green fluorescent protein in microglia and yellow fluorescent protein in projecting neurons, were submitted to either unilateral section of the facial nerve or sham surgery. Injured animals were sacrificed either 1 or 3weeks after surgery. Two-photon excitation microscopy was then used for evaluating both layer 5 pyramidal neurons and microglia in vibrissal primary motor cortex (vM1). It was found that facial nerve lesion induced long-lasting changes in the dendritic morphology of vM1 layer 5 pyramidal neurons and in their surrounding microglia. Dendritic arborization of the pyramidal cells underwent overall shrinkage. Apical dendrites suffered transient shortening while basal dendrites displayed sustained shortening. Moreover, dendrites suffered transient spine pruning. Significantly higher microglial cell density was found surrounding vM1 layer 5 pyramidal neurons after facial nerve lesion with morphological bias towards the activated phenotype. These results suggest that facial nerve lesions elicit active dendrite remodeling due to pyramidal neuron and microglia interaction, which could be the pathophysiological underpinning of some neuropathic motor sequelae in humans. PMID:26064916

Ablation of ferroptosis regulator glutathione peroxidase 4 in forebrain neurons promotes cognitive impairment and neurodegeneration.

PubMed

Hambright, William Sealy; Fonseca, Rene Solano; Chen, Liuji; Na, Ren; Ran, Qitao

2017-08-01

Synaptic loss and neuron death are the underlying cause of neurodegenerative diseases such as Alzheimer's disease (AD); however, the modalities of cell death in those diseases remain unclear. Ferroptosis, a newly identified oxidative cell death mechanism triggered by massive lipid peroxidation, is implicated in the degeneration of neurons populations such as spinal motor neurons and midbrain neurons. Here, we investigated whether neurons in forebrain regions (cerebral cortex and hippocampus) that are severely afflicted in AD patients might be vulnerable to ferroptosis. To this end, we generated Gpx4BIKO mouse, a mouse model with conditional deletion in forebrain neurons of glutathione peroxidase 4 (Gpx4), a key regulator of ferroptosis, and showed that treatment with tamoxifen led to deletion of Gpx4 primarily in forebrain neurons of adult Gpx4BIKO mice. Starting at 12 weeks after tamoxifen treatment, Gpx4BIKO mice exhibited significant deficits in spatial learning and memory function versus Control mice as determined by the Morris water maze task. Further examinations revealed that the cognitively impaired Gpx4BIKO mice exhibited hippocampal neurodegeneration. Notably, markers associated with ferroptosis, such as elevated lipid peroxidation, ERK activation and augmented neuroinflammation, were observed in Gpx4BIKO mice. We also showed that Gpx4BIKO mice fed a diet deficient in vitamin E, a lipid soluble antioxidant with anti-ferroptosis activity, had an expedited rate of hippocampal neurodegeneration and behavior dysfunction, and that treatment with a small-molecule ferroptosis inhibitor ameliorated neurodegeneration in those mice. Taken together, our results indicate that forebrain neurons are susceptible to ferroptosis, suggesting that ferroptosis may be an important neurodegenerative mechanism in diseases such as AD. Copyright © 2017. Published by Elsevier B.V.

Treadmill exercise alleviates nigrostriatal dopaminergic loss of neurons and fibers in rotenone-induced Parkinson rats.

PubMed

Shin, Mal-Soon; Kim, Tae-Woon; Lee, Jae-Min; Ji, Eun-Sang; Lim, Baek-Vin

2017-02-01

Parkinson disease is one of the common brain diseases caused by dopaminergic neuronal loss in the substantia nigra and dopaminergic fiber loss in the striatum. In the present study, the effects of treadmill exercise on motor performance, dopaminergic loss of neurons and fibers, and α-synuclein expression in the nigrostriatum were evaluated using rotenone-induced Parkinson rats. For the induction of Parkinson rats, 3-mg/kg rotenone was injected, once a day for 14 consecutive days. Treadmill running was conducted for 30 min once a day during 14 consecutive days. Rota-rod test for motor balance and coordination and immunohistochemistry for tyrosine hydroxylase and α-synuclein in the nigrostriatum were performed. In the present study, motor balance and coordination was disturbed by induction of rotenone-induced Parkinson disease, in contrast, treadmill exercise alleviated motor dysfunction in the rotenone-induced Parkinson rats. Nigrostriatal dopaminergic loss of neurons and fibers was occurred by induction of rotenone-induced Parkinson disease, in contrast, treadmill exercise alleviated nigrostriatal dopaminergic loss of neurons and fibers in the rotenone-induced Parkinson rats. α-Synuclein expression in the nigrostriatum was enhanced by induction of rotenone-induced Parkinson disease, in contrast, treadmill exercise suppressed α-synuclein expression in the rotenone-induced Parkinson rats. Treadmill exercise improved motor function through preservation of nigrostriatal dopaminergic neurons and fibers and suppression of nigrostriatal formation of Lewy bodies in rotenone-induced Parkinson rats.

Deletion of the Kv2.1 delayed rectifier potassium channel leads to neuronal and behavioral hyperexcitability

PubMed Central

Speca, David J.; Ogata, Genki; Mandikian, Danielle; Bishop, Hannah I.; Wiler, Steve W.; Eum, Kenneth; Wenzel, H. Jürgen; Doisy, Emily T.; Matt, Lucas; Campi, Katharine L.; Golub, Mari S.; Nerbonne, Jeanne M.; Hell, Johannes W.; Trainor, Brian C.; Sack, Jon T.; Schwartzkroin, Philip A.; Trimmer, James S.

2014-01-01

The Kv2.1 delayed rectifier potassium channel exhibits high-level expression in both principal and inhibitory neurons throughout the central nervous system, including prominent expression in hippocampal neurons. Studies of in vitro preparations suggest that Kv2.1 is a key yet conditional regulator of intrinsic neuronal excitability, mediated by changes in Kv2.1 expression, localization and function via activity-dependent regulation of Kv2.1 phosphorylation. Here we identify neurological and behavioral deficits in mutant (Kv2.1−/−) mice lacking this channel. Kv2.1−/− mice have grossly normal characteristics. No impairment in vision or motor coordination was apparent, although Kv2.1−/− mice exhibit reduced body weight. The anatomic structure and expression of related Kv channels in the brains of Kv2.1−/− mice appears unchanged. Delayed rectifier potassium current is diminished in hippocampal neurons cultured from Kv2.1−/− animals. Field recordings from hippocampal slices of Kv2.1−/− mice reveal hyperexcitability in response to the convulsant bicuculline, and epileptiform activity in response to stimulation. In Kv2.1−/− mice, long-term potentiation at the Schaffer collateral – CA1 synapse is decreased. Kv2.1−/− mice are strikingly hyperactive, and exhibit defects in spatial learning, failing to improve performance in a Morris Water Maze task. Kv2.1−/− mice are hypersensitive to the effects of the convulsants flurothyl and pilocarpine, consistent with a role for Kv2.1 as a conditional suppressor of neuronal activity. Although not prone to spontaneous seizures, Kv2.1−/− mice exhibit accelerated seizure progression. Together, these findings suggest homeostatic suppression of elevated neuronal activity by Kv2.1 plays a central role in regulating neuronal network function. PMID:24494598

Tissue inhibitor of metalloproteinase-2(TIMP-2)-deficient mice display motor deficits.

PubMed

Jaworski, Diane M; Soloway, Paul; Caterina, John; Falls, William A

2006-01-01

The degradation of the extracellular matrix is regulated by matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs). Matrix components of the basement membrane play critical roles in the development and maintenance of the neuromuscular junction (NMJ), yet almost nothing is known about the regulation of MMP and TIMP expression in either the pre- or postsynaptic compartments. Here, we demonstrate that TIMP-2 is expressed by both spinal motor neurons and skeletal muscle. To determine whether motor function is altered in the absence of TIMP-2, motor behavior was assessed using a battery of tests (e.g., RotaRod, balance beam, hindlimb extension, grip strength, loaded grid, and gait analysis). TIMP-2(-/-) mice fall off the RotaRod significantly faster than wild-type littermates. In addition, hindlimb extension is reduced and gait is both splayed and lengthened in TIMP-2(-/-) mice. Motor dysfunction is more pronounced during early postnatal development. A preliminary analysis revealed NMJ alterations in TIMP-2(-/-) mice. Juvenile TIMP-2(-/-) mice have increased nerve branching and acetylcholine receptor expression. Adult TIMP-2(-/-) endplates are enlarged and more complex. This suggests a role for TIMP-2 in NMJ sculpting during development. In contrast to the increased NMJ nerve branching, cerebellar Purkinje cells have decreased neurite outgrowth. Thus, the TIMP-2(-/-) motor phenotype is likely due to both peripheral and central defects. The tissue specificity of the nerve branching phenotype suggests the involvement of different MMPs and/or extracellular matrix molecules underlying the TIMP-2(-/-) motor phenotype.

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.

Restoration of Motor Defects Caused by Loss of Drosophila TDP-43 by Expression of the Voltage-Gated Calcium Channel, Cacophony, in Central Neurons.

PubMed

Lembke, Kayly M; Scudder, Charles; Morton, David B

2017-09-27

Defects in the RNA-binding protein, TDP-43, are known to cause a variety of neurodegenerative diseases, including amyotrophic lateral sclerosis and frontotemporal lobar dementia. A variety of experimental systems have shown that neurons are sensitive to TDP-43 expression levels, yet the specific functional defects resulting from TDP-43 dysregulation have not been well described. Using the Drosophila TDP-43 ortholog TBPH, we previously showed that TBPH-null animals display locomotion defects as third instar larvae. Furthermore, loss of TBPH caused a reduction in cacophony , a Type II voltage-gated calcium channel, expression and that genetically restoring cacophony in motor neurons in TBPH mutant animals was sufficient to rescue the locomotion defects. In the present study, we examined the relative contributions of neuromuscular junction physiology and the motor program to the locomotion defects and identified subsets of neurons that require cacophony expression to rescue the defects. At the neuromuscular junction, we showed mEPP amplitudes and frequency require TBPH. Cacophony expression in motor neurons rescued mEPP frequency but not mEPP amplitude. We also showed that TBPH mutants displayed reduced motor neuron bursting and coordination during crawling and restoring cacophony selectively in two pairs of cells located in the brain, the AVM001b/2b neurons, also rescued the locomotion and motor defects, but not the defects in neuromuscular junction physiology. These results suggest that the behavioral defects associated with loss of TBPH throughout the nervous system can be associated with defects in a small number of genes in a limited number of central neurons, rather than peripheral defects. SIGNIFICANCE STATEMENT TDP-43 dysfunction is a common feature in neurodegenerative diseases, including amyotrophic lateral sclerosis, frontotemporal lobar dementia, and Alzheimer's disease. Loss- and gain-of-function models have shown that neurons are sensitive to TDP-43 expression levels, but the specific defects caused by TDP-43 loss of function have not been described in detail. A Drosophila loss-of-function model displays pronounced locomotion defects that can be reversed by restoring the expression levels of a voltage-gated calcium channel, cacophony. We show these defects can be rescued by expression of cacophony in motor neurons and by expression in two pairs of neurons in the brain. These data suggest that loss of TDP-43 can disrupt the central circuitry of the CNS, opening up identification of alternative therapeutic targets for TDP-43 proteinopathies. Copyright © 2017 the authors 0270-6474/17/379486-12$15.00/0.

Neurochemical, morphologic, and laminar characterization of cortical projection neurons in the cingulate motor areas of the macaque monkey

NASA Technical Reports Server (NTRS)

Nimchinsky, E. A.; Hof, P. R.; Young, W. G.; Morrison, J. H.; Bloom, F. E. (Principal Investigator)

1996-01-01

The primate cingulate gyrus contains multiple cortical areas that can be distinguished by several neurochemical features, including the distribution of neurofilament protein-enriched pyramidal neurons. In addition, connectivity and functional properties indicate that there are multiple motor areas in the cortex lining the cingulate sulcus. These motor areas were targeted for analysis of potential interactions among regional specialization, connectivity, and cellular characteristics such as neurochemical profile and morphology. Specifically, intracortical injections of retrogradely transported dyes and intracellular injection were combined with immunocytochemistry to investigate neurons projecting from the cingulate motor areas to the putative forelimb region of the primary motor cortex, area M1. Two separate groups of neurons projecting to area M1 emanated from the cingulate sulcus, one anterior and one posterior, both of which furnished commissural and ipsilateral connections with area M1. The primary difference between the two populations was laminar origin, with the anterior projection originating largely in deep layers, and the posterior projection taking origin equally in superficial and deep layers. With regard to cellular morphology, the anterior projection exhibited more morphologic diversity than the posterior projection. Commissural projections from both anterior and posterior fields originated largely in layer VI. Neurofilament protein distribution was a reliable tool for localizing the two projections and for discriminating between them. Comparable proportions of the two sets of projection neurons contained neurofilament protein, although the density and distribution of the total population of neurofilament protein-enriched neurons was very different in the two subareas of origin. Within a projection, the participating neurons exhibited a high degree of morphologic heterogeneity, and no correlation was observed between somatodendritic morphology and neurofilament protein content. Thus, although the neurons that provide the anterior and posterior cingulate motor projections to area M1 differ morphologically and in laminar origin, their neurochemical profiles are similar with respect to neurofilament protein. This suggests that neurochemical phenotype may be a more important unifying feature for corticocortical projections than morphology.

WNT-C59, a Small-Molecule WNT Inhibitor, Efficiently Induces Anterior Cortex That Includes Cortical Motor Neurons From Human Pluripotent Stem Cells.

PubMed

Motono, Makoto; Ioroi, Yoshihiko; Ogura, Takenori; Takahashi, Jun

2016-04-01

The recapitulation of human neural development in a controlled, defined manner from pluripotent stem cells (PSCs) has considerable potential for studies of human neural development, circuit formation and function, and the construction of in vitro models of neurological diseases. The inhibition of Wnt signaling, often by the recombinant protein DKK1, is important for the induction of cortical neurons. Here, we report a novel differentiation method using a small-molecule WNT inhibitor, WNT-C59 (C59), to efficiently induce human anterior cortex. We compared two types of small molecules, C59 and XAV939 (XAV), as substitutes for DKK1 to induce cortical neurons from PSCs in serum-free embryoid body-like aggregate culture. DKK1 and XAV inhibited only the canonical pathway of Wnt signaling, whereas C59 inhibited both the canonical and noncanonical pathways. C59 efficiently induced CTIP2+/COUP-TF1- cells, which are characteristic of the cells found in the anterior cortex. In addition, when grafted into the cortex of adult mice, the C59-induced cells showed abundant axonal fiber extension toward the spinal cord. These results raise the possibility of C59 contributing to cell replacement therapy for motor neuron diseases or insults. For a cell therapy against damaged corticospinal tract caused by neurodegenerative diseases or insults, cortical motor neurons are needed. Currently, their induction from pluripotent stem cells is considered very promising; however, an efficient protocol to induce motor neurons is not available. For efficient induction of anterior cortex, where motor neurons are located, various WNT inhibitors were investigated. It was found that one of them could induce anterior cortical cells efficiently. In addition, when grafted into the cortex of adult mice, the induced cells showed more abundant axonal fiber extension toward spinal cord. These results raise the possibility that this inhibitor contributes to a cell-replacement therapy for motor neuron diseases or insults. ©AlphaMed Press.

The mirror neuron analogy: Implications for rehabilitation neuroscience. Comment on "Grasping synergies: A motor-control approach to the mirror neuron mechanism" by A. D'Ausilio et al.

NASA Astrophysics Data System (ADS)

Frey, Scott H.; Chen, Pin-Wei

2015-03-01

The discovery of individual neurons that respond selectively to both the perception and execution of actions in macaques has had a profound impact on cognitive neuroscience [1]. By demonstrating a neurophysiological mechanism linking perception and motor performance, these mirror neurons have inspired a broad range of research in humans using non-invasive neuroimaging [2,3], and transcranial magnetic stimulation (TMS) [4]. In the present review, D'Ausilio and colleagues point out inconsistencies among TMS evidence concerning whether the so-called mirror neuron system (MNS) represents actions as low-level kinematic features, or more abstract goals [5]. They propose instead that actions are represented in the MNS as a modest number of motor synergies, a position arrived at through following propositional reasoning:

Neuron-Glia Crosstalk and Neuropathic Pain: Involvement in the Modulation of Motor Activity in the Orofacial Region.

PubMed

Hossain, Mohammad Zakir; Unno, Shumpei; Ando, Hiroshi; Masuda, Yuji; Kitagawa, Junichi

2017-09-26

Neuropathic orofacial pain (NOP) is a debilitating condition. Although the pathophysiology remains unclear, accumulating evidence suggests the involvement of multiple mechanisms in the development of neuropathic pain. Recently, glial cells have been shown to play a key pathogenetic role. Nerve injury leads to an immune response near the site of injury. Satellite glial cells are activated in the peripheral ganglia. Various neural and immune mediators, released at the central terminals of primary afferents, lead to the sensitization of postsynaptic neurons and the activation of glia. The activated glia, in turn, release pro-inflammatory factors, further sensitizing the neurons, and resulting in central sensitization. Recently, we observed the involvement of glia in the alteration of orofacial motor activity in NOP. Microglia and astroglia were activated in the trigeminal sensory and motor nuclei, in parallel with altered motor functions and a decreased pain threshold. A microglial blocker attenuated the reduction in pain threshold, reduced the number of activated microglia, and restored motor activity. We also found an involvement of the astroglial glutamate-glutamine shuttle in the trigeminal motor nucleus in the alteration of the jaw reflex. Neuron-glia crosstalk thus plays an important role in the development of pain and altered motor activity in NOP.