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Sample records for clock genes period

  1. Finding Clocks in Genes: A Bayesian Approach to Estimate Periodicity

    PubMed Central

    Ren, Yan; Hong, Christian I.; Lim, Sookkyung; Song, Seongho

    2016-01-01

    Identification of rhythmic gene expression from metabolic cycles to circadian rhythms is crucial for understanding the gene regulatory networks and functions of these biological processes. Recently, two algorithms, JTK_CYCLE and ARSER, have been developed to estimate periodicity of rhythmic gene expression. JTK_CYCLE performs well for long or less noisy time series, while ARSER performs well for detecting a single rhythmic category. However, observing gene expression at high temporal resolution is not always feasible, and many scientists are interested in exploring both ultradian and circadian rhythmic categories simultaneously. In this paper, a new algorithm, named autoregressive Bayesian spectral regression (ABSR), is proposed. It estimates the period of time-course experimental data and classifies gene expression profiles into multiple rhythmic categories simultaneously. Through the simulation studies, it is shown that ABSR substantially improves the accuracy of periodicity estimation and clustering of rhythmic categories as compared to JTK_CYCLE and ARSER for the data with low temporal resolution. Moreover, ABSR is insensitive to rhythmic patterns. This new scheme is applied to existing time-course mouse liver data to estimate period of rhythms and classify the genes into ultradian, circadian, and arrhythmic categories. It is observed that 49.2% of the circadian profiles detected by JTK_CYCLE with 1-hour resolution are also detected by ABSR with only 4-hour resolution. PMID:27340654

  2. The Circadian Clock Gene Period1 Connects the Molecular Clock to Neural Activity in the Suprachiasmatic Nucleus

    PubMed Central

    Block, Gene D.; Colwell, Christopher S.

    2015-01-01

    The neural activity patterns of suprachiasmatic nucleus (SCN) neurons are dynamically regulated throughout the circadian cycle with highest levels of spontaneous action potentials during the day. These rhythms in electrical activity are critical for the function of the circadian timing system and yet the mechanisms by which the molecular clockwork drives changes in the membrane are not well understood. In this study, we sought to examine how the clock gene Period1 (Per1) regulates the electrical activity in the mouse SCN by transiently and selectively decreasing levels of PER1 through use of an antisense oligodeoxynucleotide. We found that this treatment effectively reduced SCN neural activity. Direct current injection to restore the normal membrane potential partially, but not completely, returned firing rate to normal levels. The antisense treatment also reduced baseline [Ca2+]i levels as measured by Fura2 imaging technique. Whole cell patch clamp recording techniques were used to examine which specific potassium currents were altered by the treatment. These recordings revealed that the large conductance [Ca2+]i-activated potassium currents were reduced in antisense-treated neurons and that blocking this current mimicked the effects of the anti-sense on SCN firing rate. These results indicate that the circadian clock gene Per1 alters firing rate in SCN neurons and raise the possibility that the large conductance [Ca2+]i-activated channel is one of the targets. PMID:26553726

  3. Functional analysis of the circadian clock gene period by RNA interference in nymphal crickets Gryllus bimaculatus.

    PubMed

    Moriyama, Yoshiyuki; Sakamoto, Tomoaki; Akira, Matsumoto; Sumihare, Noji; Tomioka, Kenji

    2009-05-01

    The circadian clock gene period (Gryllus bimaculatus period, Gb'per) plays a core role in circadian rhythm generation in adults of the cricket Gryllus bimaculatus. We examined the role of Gb'per in nymphal crickets that show a diurnal rhythm rather than the nocturnal rhythm of the adults. As in the adult optic lobes, Gb'per mRNA levels in the head of the third instar nymphs showed daily cycling in light-dark cycles with a peak at mid night, and the rhythm persisted in constant darkness. Injection of Gb'per double-stranded RNA (dsRNA) into the abdomen of third instar nymphs knocked-down the mRNA levels to 25% of that in control animals. Most Gb'per dsRNA injected nymphs lost their circadian locomotor activity rhythm, while those injected with DsRed2 dsRNA as a negative control clearly maintained the rhythm. These results suggest that nymphs and adults share a common endogenous clock mechanism involving the clock gene Gb'per.

  4. Functional analysis of the circadian clock gene period by RNA interference in nymphal crickets Gryllus bimaculatus.

    PubMed

    Moriyama, Yoshiyuki; Sakamoto, Tomoaki; Matsumoto, Akira; Noji, Sumihare; Tomioka, Kenji

    2009-02-01

    The circadian clock gene period (Gryllus bimaculatus period, Gb'per) plays a core role in circadian rhythm generation in adults of the cricket Gryllus bimaculatus. We examined the role of Gb'per in nymphal crickets that show a diurnal rhythm rather than the nocturnal rhythm of the adults. As in the adult optic lobes, Gb'per mRNA levels in the head of the third instar nymphs showed daily cycling in light-dark cycles with a peak at mid night, and the rhythm persisted in constant darkness. Injection of Gb'per double-stranded RNA (dsRNA) into the abdomen of third instar nymphs knocked-down the mRNA levels to 25% of that in control animals. Most Gb'per dsRNA injected nymphs lost their circadian locomotor activity rhythm, while those injected with DsRed2 dsRNA as a negative control clearly maintained the rhythm. These results suggest that nymphs and adults share a common endogenous clock mechanism involving the clock gene Gb'per.

  5. Cell type-specific functions of period genes revealed by novel adipocyte and hepatocyte circadian clock models.

    PubMed

    Ramanathan, Chidambaram; Xu, Haiyan; Khan, Sanjoy K; Shen, Yang; Gitis, Paula J; Welsh, David K; Hogenesch, John B; Liu, Andrew C

    2014-04-01

    In animals, circadian rhythms in physiology and behavior result from coherent rhythmic interactions between clocks in the brain and those throughout the body. Despite the many tissue specific clocks, most understanding of the molecular core clock mechanism comes from studies of the suprachiasmatic nuclei (SCN) of the hypothalamus and a few other cell types. Here we report establishment and genetic characterization of three cell-autonomous mouse clock models: 3T3 fibroblasts, 3T3-L1 adipocytes, and MMH-D3 hepatocytes. Each model is genetically tractable and has an integrated luciferase reporter that allows for longitudinal luminescence recording of rhythmic clock gene expression using an inexpensive off-the-shelf microplate reader. To test these cellular models, we generated a library of short hairpin RNAs (shRNAs) against a panel of known clock genes and evaluated their impact on circadian rhythms. Knockdown of Bmal1, Clock, Cry1, and Cry2 each resulted in similar phenotypes in all three models, consistent with previous studies. However, we observed cell type-specific knockdown phenotypes for the Period and Rev-Erb families of clock genes. In particular, Per1 and Per2, which have strong behavioral effects in knockout mice, appear to play different roles in regulating period length and amplitude in these peripheral systems. Per3, which has relatively modest behavioral effects in knockout mice, substantially affects period length in the three cellular models and in dissociated SCN neurons. In summary, this study establishes new cell-autonomous clock models that are of particular relevance to metabolism and suitable for screening for clock modifiers, and reveals previously under-appreciated cell type-specific functions of clock genes.

  6. RNA interference of the clock gene period disrupts circadian rhythms in the cricket Gryllus bimaculatus.

    PubMed

    Moriyama, Yoshiyuki; Sakamoto, Tomoaki; Karpova, Svetlana G; Matsumoto, Akira; Noji, Sumihare; Tomioka, Kenji

    2008-08-01

    Periodic expression of so-called clock genes is an essential part of the circadian clock. In Drosophila melanogaster the cyclic expression of per and tim through an autoregulatory feedback loop is believed to play a central role in circadian rhythm generation. However, it is still elusive whether this hypothesis is applicable to other insect species. Here it is shown that per gene plays a key role in the rhythm generation in the cricket Gryllus bimaculatus. Measurement of per mRNA levels in the optic lobe revealed the rhythmic expression of per in light cycles with a peak in the late day to early night, persisting in constant darkness. A single injection of per double-stranded RNA (dsRNA) into the abdomen of the final instar nymphs effectively knocked down the mRNA levels as adult to about 50% of control animals. Most of the per dsRNA-injected crickets completely lost the circadian locomotor activity rhythm in constant darkness up to 50 days after the injection, whereas those injected with DsRed2 dsRNA as a negative control clearly maintained it. The electrical activity of optic lobe efferents also became arrhythmic in the per dsRNA-injected crickets. These results not only suggest that per plays an important role in the circadian rhythm generation also in the cricket but also show that RNA interference is a powerful tool to dissect the molecular machinery of the cricket circadian clock.

  7. Melanopsin resets circadian rhythms in cells by inducing clock gene Period1

    NASA Astrophysics Data System (ADS)

    Yamashita, Shuhei; Uehara, Tomoe; Matsuo, Minako; Kikuchi, Yo; Numano, Rika

    2014-02-01

    The biochemical, physiological and behavioral processes are under the control of internal clocks with the period of approximately 24 hr, circadian rhythms. The expression of clock gene Period1 (Per1) oscillates autonomously in cells and is induced immediately after a light pulse. Per1 is an indispensable member of the central clock system to maintain the autonomous oscillator and synchronize environmental light cycle. Per1 expression could be detected by Per1∷luc and Per1∷GFP plasmid DNA in which firefly luciferase and Green Fluorescence Protein were rhythmically expressed under the control of the mouse Per1 promoter in order to monitor mammalian circadian rhythms. Membrane protein, MELANOPSIN is activated by blue light in the morning on the retina and lead to signals transduction to induce Per1 expression and to reset the phase of circadian rhythms. In this report Per1 induction was measured by reporter signal assay in Per1∷luc and Per1∷GFP fibroblast cell at the input process of circadian rhythms. To the result all process to reset the rhythms by Melanopsin is completed in single cell like in the retina projected to the central clock in the brain. Moreover, the phase of circadian rhythm in Per1∷luc cells is synchronized by photo-activated Melanopsin, because the definite peak of luciferase activity in one dish was found one day after light illumination. That is an available means that physiological circadian rhythms could be real-time monitor as calculable reporter (bioluminescent and fluorescent) chronological signal in both single and groups of cells.

  8. Case-control study of the PERIOD3 clock gene length polymorphism and colorectal adenoma formation

    PubMed Central

    ALEXANDER, MELANNIE; BURCH, JAMES B.; STECK, SUSAN E.; CHEN, CHIN-FU; HURLEY, THOMAS G.; CAVICCHIA, PHILIP; RAY, MEREDITH; SHIVAPPA, NITIN; GUESS, JACLYN; ZHANG, HONGMEI; YOUNGSTEDT, SHAWN D.; CREEK, KIM E.; LLOYD, STEPHEN; YANG, XIAOMING; HÉBERT, JAMES R.

    2015-01-01

    Clock genes are expressed in a self-perpetuating, circadian pattern in virtually every tissue including the human gastrointestinal tract. They coordinate cellular processes critical for tumor development, including cell proliferation, DNA damage response and apoptosis. Circadian rhythm disturbances have been associated with an increased risk for colon cancer and other cancers. This mechanism has not been elucidated, yet may involve dysregulation of the ‘period’ (PER) clock genes, which have tumor suppressor properties. A variable number tandem repeat (VNTR) in the PERIOD3 (PER3) gene has been associated with sleep disorders, differences in diurnal hormone secretion, and increased premenopausal breast cancer risk. Susceptibility related to PER3 has not been examined in conjunction with adenomatous polyps. This exploratory case-control study was the first to test the hypothesis that the 5-repeat PER3 VNTR sequence is associated with increased odds of adenoma formation. Information on demographics, medical history, occupation and lifestyle was collected prior to colonoscopy. Cases (n=49) were individuals with at least one histopathologically confirmed adenoma. Controls (n=97) included patients with normal findings or hyperplastic polyps not requiring enhanced surveillance. Unconditional multiple logistic regression was used to calculate odds ratios (ORs) with 95% confidence intervals (CIs), after adjusting for potential confounding. Adenomas were detected in 34% of participants. Cases were more likely to possess the 5-repeat PER3 genotype relative to controls (4/5 OR, 2.1; 95% CI, 0.9–4.8; 5/5 OR, 5.1; 95% CI, 1.4–18.1; 4/5+5/5 OR, 2.5; 95% CI, 1.7–5.4). Examination of the Oncomine microarray database indicated lower PERIOD gene expression in adenomas relative to adjacent normal tissue. Results suggest a need for follow-up in a larger sample. PMID:25501848

  9. Clock genes and sleep.

    PubMed

    Landgraf, Dominic; Shostak, Anton; Oster, Henrik

    2012-01-01

    In most species--from cyanobacteria to humans--endogenous clocks have evolved that drive 24-h rhythms of behavior and physiology. In mammals, these circadian rhythms are regulated by a hierarchical network of cellular oscillators controlled by a set of clock genes organized in a system of interlocked transcriptional feedback loops. One of the most prominent outputs of the circadian system is the synchronization of the sleep-wake cycle with external (day-) time. Clock genes also have a strong impact on many other biological functions, such as memory formation, energy metabolism, and immunity. Remarkably, large overlaps exist between clock gene and sleep (loss) mediated effects on these processes. This review summarizes sleep clock gene interactions for these three phenomena, highlighting potential mediators linking sleep and/or clock function to physiological output in an attempt to better understand the complexity of diurnal adaptation and its consequences for health and disease.

  10. Clock Genes in Glia Cells

    PubMed Central

    Chi-Castañeda, Donají

    2016-01-01

    Circadian rhythms are periodic patterns in biological processes that allow the organisms to anticipate changes in the environment. These rhythms are driven by the suprachiasmatic nucleus (SCN), the master circadian clock in vertebrates. At a molecular level, circadian rhythms are regulated by the so-called clock genes, which oscillate in a periodic manner. The protein products of clock genes are transcription factors that control their own and other genes’ transcription, collectively known as “clock-controlled genes.” Several brain regions other than the SCN express circadian rhythms of clock genes, including the amygdala, the olfactory bulb, the retina, and the cerebellum. Glia cells in these structures are expected to participate in rhythmicity. However, only certain types of glia cells may be called “glial clocks,” since they express PER-based circadian oscillators, which depend of the SCN for their synchronization. This contribution summarizes the current information about clock genes in glia cells, their plausible role as oscillators and their medical implications. PMID:27666286

  11. RNAi of the circadian clock gene period disrupts the circadian rhythm but not the circatidal rhythm in the mangrove cricket.

    PubMed

    Takekata, Hiroki; Matsuura, Yu; Goto, Shin G; Satoh, Aya; Numata, Hideharu

    2012-08-23

    The clock mechanism for circatidal rhythm has long been controversial, and its molecular basis is completely unknown. The mangrove cricket, Apteronemobius asahinai, shows two rhythms simultaneously in its locomotor activity: a circatidal rhythm producing active and inactive phases as well as a circadian rhythm modifying the activity intensity of circatidal active phases. The role of the clock gene period (per), one of the key components of the circadian clock in insects, was investigated in the circadian and circatidal rhythms of A. asahinai using RNAi. After injection of double-stranded RNA of per, most crickets did not show the circadian modulation of activity but the circatidal rhythm persisted without a significant difference in the period from controls. Thus, per is functionally involved in the circadian rhythm but plays no role, or a less important role, in the circatidal rhythm. We conclude that the circatidal rhythm in A. asahinai is controlled by a circatidal clock whose molecular mechanism is different from that of the circadian clock.

  12. Distinct patterns of Period gene expression in the suprachiasmatic nucleus underlie circadian clock photoentrainment by advances or delays.

    PubMed

    Schwartz, William J; Tavakoli-Nezhad, Mahboubeh; Lambert, Christopher M; Weaver, David R; de la Iglesia, Horacio O

    2011-10-11

    The circadian clock in the mammalian hypothalamic suprachiasmatic nucleus (SCN) is entrained by the ambient light/dark cycle, which differentially acts to cause the clock to advance or delay. Light-induced changes in the rhythmic expression of SCN clock genes are believed to be a critical step in this process, but how the two entrainment modalities--advances vs. delays--engage the molecular clockwork remains incompletely understood. We investigated molecular substrates of photic entrainment of the clock in the SCN by stably entraining hamsters to T cycles (non-24-h light/dark cycles) consisting of a single 1-h light pulse repeated as either a short (23.33-h) or a long (24.67-h) cycle; under these conditions, the light pulse of the short cycle acts as "dawn," whereas that of the long cycle acts as "dusk." Analyses of the expression of the photoinducible and rhythmic clock genes Period 1 and 2 (Per1 and Per2) in the SCN revealed fundamental differences under these two entrainment modes. Light at dawn advanced the clock, advancing the onset of the Per1 mRNA rhythm and acutely increasing mRNA transcription, whereas light at dusk delayed the clock, delaying the offset of the Per2 mRNA rhythm and tonically increasing mRNA stability. The results suggest that the underlying molecular mechanisms of circadian entrainment differ with morning (advancing) or evening (delaying) light exposure, and such differences may reflect how entrainment takes place in nocturnal animals under natural conditions.

  13. Light modulation of human sleep depends on a polymorphism in the clock gene Period3.

    PubMed

    Chellappa, Sarah L; Viola, Antoine U; Schmidt, Christina; Bachmann, Valérie; Gabel, Virginie; Maire, Micheline; Reichert, Carolin F; Valomon, Amandine; Landolt, Hans-Peter; Cajochen, Christian

    2014-09-01

    Non-image-forming (NIF) responses to light powerfully modulate human physiology. However, it remains scarcely understood how NIF responses to light modulate human sleep and its EEG hallmarks, and if there are differences across individuals. Here we investigated NIF responses to light on sleep in individuals genotyped for the PERIOD3 (PER3) variable-number tandem-repeat (VNTR) polymorphism. Eighteen healthy young men (20-28 years; mean ± SEM: 25.9 ± 1.2) homozygous for the PER3 polymorphism were matched by age, body-mass index, and ethnicity. The study protocol comprised a balanced cross-over design during the winter, during which participants were exposed to either light of 40 lx at 6,500 K (blue-enriched) or light at 2,500 K (non-blue enriched), during 2h in the evening. Compared to light at 2,500 K, light at 6,500 K induced a significant increase in all-night NREM sleep slow-wave activity (SWA: 1.0-4.5 Hz) in the occipital cortex for PER3(5/5) individuals, but not for PER3(4/4) volunteers. Dynamics of SWA across sleep cycles revealed increased occipital NREM sleep SWA for virtually all sleep episode only for PER3(5/5) individuals. Furthermore, they experienced light at 6,500 K as significantly brighter. Intriguingly, this subjective perception of brightness significantly predicted their increased occipital SWA throughout the sleep episode. Our data indicate that humans homozygous for the PER3(5/5) allele are more sensitive to NIF light effects, as indexed by specific changes in sleep EEG activity. Ultimately, individual differences in NIF light responses on sleep may depend on a clock gene polymorphism involved in sleep-wake regulation.

  14. Expression of the circadian clock gene Period2 in the hippocampus: possible implications for synaptic plasticity and learned behaviour

    PubMed Central

    Wang, Louisa M-C; Dragich, Joanna M; Kudo, Takashi; Odom, Irene H; Welsh, David K; O'Dell, Thomas J; Colwell, Christopher S

    2009-01-01

    Genes responsible for generating circadian oscillations are expressed in a variety of brain regions not typically associated with circadian timing. The functions of this clock gene expression are largely unknown, and in the present study we sought to explore the role of the Per2 (Period 2) gene in hippocampal physiology and learned behaviour. We found that PER2 protein is highly expressed in hippocampal pyramidal cell layers and that the expression of both protein and mRNA varies with a circadian rhythm. The peaks of these rhythms occur in the late night or early morning and are almost 180° out-of-phase with the expression rhythms measured from the suprachiasmatic nucleus of the same animals. The rhythms in Per2 expression are autonomous as they are present in isolated hippocampal slices maintained in culture. Physiologically, Per2-mutant mice exhibit abnormal long-term potentiation. The underlying mechanism is suggested by the finding that levels of phosphorylated cAMP-response-element-binding protein, but not phosphorylated extracellular-signal-regulated kinase, are reduced in hippocampal tissue from mutant mice. Finally, Per2-mutant mice exhibit deficits in the recall of trace, but not cued, fear conditioning. Taken together, these results provide evidence that hippocampal cells contain an autonomous circadian clock. Furthermore, the clock gene Per2 may play a role in the regulation of long-term potentiation and in the recall of some forms of learned behaviour. PMID:19570032

  15. A period-extender gene, pex, that extends the period of the circadian clock in the cyanobacterium Synechococcus sp. strain PCC 7942.

    PubMed

    Kutsuna, S; Kondo, T; Aoki, S; Ishiura, M

    1998-04-01

    We cloned the pS1K1 plasmid in the process of apparently "complementing" a circadian clock mutant of cyanobacterium Synechococcus sp. strain PCC 7942, SP22, which has a 22-h period (T. Kondo, N. F. Tsinoremas, S. S. Golden, C. H. Johnson, S. Kutsuna, and M. Ishiura, Science 266:1233-1236, 1994). Sequence analysis revealed that SP22 did not have a mutation in the genomic DNA segment carried on pS1K1, and the sp22 mutation was later found in a recently cloned new clock gene, kaiC. Therefore, the period-extender gene pex that was carried on pS1K1 was a suppressor gene for the sp22 mutation. The pex gene encoded a protein of 148 amino acid residues. No meaningful homologs were found in DNA or protein databases including the Synechocystis genome database. The pex gene was transcribed from 129 and 164 bp upstream of the translation initiation codon as 0.6-kb transcripts. The Pex protein was detected as a fusion protein with a molecular mass of 15 kDa by the epitope tag fusion method using a c-Myc epitope tag. Disruption of the pex gene in wild-type cells shortened the period of the rhythms by 1 h, although it did not affect other properties of the rhythms, whereas its overexpression extended the period by 3 h with a concomitant reduction in the amplitude of the rhythms. In various clock mutants examined, overexpression caused arrhythmicity. Thus, Pex is likely to function as a modifier of the circadian clock in Synechococcus.

  16. The clock gene period plays an essential role in photoperiodic control of nymphal development in the cricket Modicogryllus siamensis.

    PubMed

    Sakamoto, Tomoaki; Uryu, Outa; Tomioka, Kenji

    2009-10-01

    Photoperiodic regulation of development is a common strategy for insects in the temperate zone to adapt to the seasonally changing environment. Although the circadian clock is generally thought to be involved, the underlying time measurement mechanism is still elusive. Here, we demonstrate that the circadian clock gene period (per) plays an essential role in the photoperiodic regulation of nymphal development in the cricket Modicogryllus siamensis. Nymphal development of this cricket depends on photoperiods, being accelerated by long days and slowed down by short days. We examined the role of per in the nymphal photoperiodic response as well as circadian rhythm generation using parental RNA interference (pRNAi). per mRNA levels in nymphal heads showed a rhythmic expression with the pattern dependent on photoperiods, and pRNAi significantly suppressed the per mRNA level with no significant rhythmicity in the early nymphal stage. Irrespective of photoperiods, nymphs treated with per pRNAi showed adult emergence patterns neither of intact nymphs nor of DsRed2 pRNAi nymphs kept under long days or under short days but similar to those kept under constant dark conditions. Most per pRNAi adults showed arrhythmic or aberrant circadian locomotor activity. These results suggest that the photoperiodic time measurement requires the normal circadian clock that is controlled by the per gene.

  17. Inhibition of expression of the circadian clock gene Period causes metabolic abnormalities including repression of glycometabolism in Bombyx mori cells

    PubMed Central

    Tao, Hui; Li, Xue; Qiu, Jian-Feng; Cui, Wen-Zhao; Sima, Yang-Hu; Xu, Shi-Qing

    2017-01-01

    Abnormalities in the circadian clock system are known to affect the body’s metabolic functions, though the molecular mechanisms responsible remain uncertain. In this study, we achieved continuous knockdown of B. mori Period (BmPer) gene expression in the B. mori ovary cell line (BmN), and generated a Per-KD B. mori model with developmental disorders including small individual cells and slow growth. We conducted cell metabolomics assays by gas chromatography/liquid chromatography-mass spectrometry and showed that knockdown of BmPer gene expression resulted in significant inhibition of glycometabolism. Amino acids that used glucose metabolites as a source were also down-regulated, while lipid metabolism and nucleotide metabolism were significantly up-regulated. Metabolite correlation analysis showed that pyruvate and lactate were closely related to glycometabolism, as well as to metabolites such as aspartate, alanine, and xanthine in other pathways. Further validation experiments showed that the activities of the key enzymes of glucose metabolism, hexokinase, phosphofructokinase, and citrate synthase, were significantly decreased and transcription of their encoding genes, as well as that of pyruvate kinase, were also significantly down-regulated. We concluded that inhibition of the circadian clock gene BmPer repressed glycometabolism, and may be associated with changes in cellular amino acid metabolism, and in cell growth and development. PMID:28393918

  18. Mitomycin C modulates the circadian oscillation of clock gene period 2 expression through attenuating the glucocorticoid signaling in mouse fibroblasts.

    PubMed

    Kusunose, Naoki; Matsunaga, Naoya; Kimoto, Kenichi; Akamine, Takahiro; Hamamura, Kengo; Koyanagi, Satoru; Ohdo, Shigehiro; Kubota, Toshiaki

    2015-11-06

    Clock gene regulates the circadian rhythm of various physiological functions. The expression of clock gene has been shown to be attenuated by certain drugs, resulting in a rhythm disorder. Mitomycin C (MMC) is often used in combination with ophthalmic surgery, especially in trabeculectomy, a glaucoma surgical procedure. The purpose of this study was to investigate the influence of MMC on clock gene expression in fibroblasts, the target cells of MMC. Following MMC treatment, Bmal1 mRNA levels was significantly decreased, whereas Dbp, Per1, and Rev-erbα mRNA levels were significantly increased in the mouse fibroblast cell line NIH3T3 cells. Microarray analysis was performed to explore of the gene(s) responsible for MMC-induced alteration of clock gene expression, and identified Nr3c1 gene encoding glucocorticoid receptor (GR) as a candidate. MMC suppressed the induction of Per1 mRNA by dexamethasone (DEX), ligand of GR, in NIH3T3 cells. MMC also modulated the DEX-driven circadian oscillations of Per2::Luciferase bioluminescence in mouse-derived ocular fibroblasts. Our results demonstrate a previously unknown effect of MMC in GR signaling and the circadian clock system. The present findings suggest that MMC combined with trabeculectomy could increase the risk for a local circadian rhythm-disorder at the ocular surface.

  19. Disruption of CLOCK-BMAL1 Transcriptional Activity Is Responsible for Aryl Hydrocarbon Receptor–Mediated Regulation of Period1 Gene

    PubMed Central

    Xu, Can-Xin; Krager, Stacey L.; Liao, Duan-Fang; Tischkau, Shelley A.

    2010-01-01

    The aryl hydrocarbon receptor (AhR) is a period-aryl hydrocarbon receptor nuclear transporter-simple minded domain transcription factor that shares structural similarity with circadian clock genes and readily interacts with components of the molecular clock. Activation of AhR by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) alters behavioral circadian rhythms and represses the Period1 (Per1) gene in murine hematopoietic stem and progenitor cells. Per1 expression is driven by circadian locomotor activity cycles kaput-brain muscle ARNT-like (CLOCK-BMAL1)–dependent activation of Eboxes in the Per1 promoter. We hypothesized that the effects of AhR activation on the circadian clock are mediated by disruption of CLOCK-BMAL1 function and subsequent Per1 gene suppression. Effects of AhR activation on rhythmic Per1 transcripts were examined in livers of mice after treatment with the AhR agonist, TCDD; the molecular mechanisms of Per1 repression by AhR were determined in hepatoma cells using TCDD and β-napthoflavone as AhR activators. This study reports, for the first time, that AhR activation by TCDD alters the Per1 rhythm in the mouse liver and that Per1 gene suppression depends upon the presence of AhR. Furthermore, AhR interaction with BMAL1 attenuates CLOCK-BMAL1 activity and decreases CLOCK binding at Ebox1 and Ebox3 in the Per1 promoter. Taken together, these data suggest that AhR activation represses Per1 through disrupting CLOCK-BMAL1 activity, producing dysregulation of rhythmic Per1 gene expression. These data define alteration of the Per1 rhythm as novel signaling events downstream of AhR activation. Downregulation of Per1 could contribute to metabolic disease, cancer, and other detrimental effects resulting from exposure to certain environmental pollutants. PMID:20106950

  20. The expression patterns of the clock genes period and timeless are affected by photoperiod in the Mediterranean corn stalk borer, Sesamia nonagrioides.

    PubMed

    Kontogiannatos, Dimitrios; Gkouvitsas, Theodoros; Kourti, Anna

    2017-01-01

    To obtain clues to the link between the molecular mechanism of circadian and photoperiod clocks, we cloned two circadian clock genes, period (per) and timeless (tim) from the moth Sesamia nonagrioides, which undergoes facultative diapause controlled by photoperiod. Sequence analysis revealed a high degree of conservation among the compared insects fοr both genes. We also investigated the expression patterns of per and tim in brains of larvae growing under 16L:8D (long days), constant darkness (DD) and 10L:14D (short days) conditions by qPCR assays. The results showed that mRNA accumulations encoding both genes exhibited diel oscillations under different photoperiods. The oscillation of per and tim mRNA, under short-day photoperiod differed from long-day. The difference between long-day and short-day conditions in the pattern of mRNA levels of per and tim appears to distinguish photoperiodic conditions clearly and both genes were influenced by photoperiod in different ways. We infer that not all photoperiodic clocks of insects interact with circadian clocks in the same fashion. Our results suggest that transcriptional regulations of the both clock genes act in the diapause programing in S. nonagrioides. The expression patterns of these genes are affected by photoperiod but runs with 24 h by entrainment to daily environmental cues.

  1. Clock Genes in Glia Cells: A Rhythmic History.

    PubMed

    Chi-Castañeda, Donají; Ortega, Arturo

    2016-10-01

    Circadian rhythms are periodic patterns in biological processes that allow the organisms to anticipate changes in the environment. These rhythms are driven by the suprachiasmatic nucleus (SCN), the master circadian clock in vertebrates. At a molecular level, circadian rhythms are regulated by the so-called clock genes, which oscillate in a periodic manner. The protein products of clock genes are transcription factors that control their own and other genes' transcription, collectively known as "clock-controlled genes." Several brain regions other than the SCN express circadian rhythms of clock genes, including the amygdala, the olfactory bulb, the retina, and the cerebellum. Glia cells in these structures are expected to participate in rhythmicity. However, only certain types of glia cells may be called "glial clocks," since they express PER-based circadian oscillators, which depend of the SCN for their synchronization. This contribution summarizes the current information about clock genes in glia cells, their plausible role as oscillators and their medical implications.

  2. The clock gene Period3 in the nocturnal flatfish Solea senegalensis: Molecular cloning, tissue expression and daily rhythms in central areas.

    PubMed

    Martín-Robles, Agueda J; Isorna, Esther; Whitmore, David; Muñoz-Cueto, José A; Pendón, Carlos

    2011-05-01

    Clock genes are responsible for generating and sustaining most rhythmic daily functions in vertebrates. Their expression is endogenously driven, although they are entrained by external cues such as light, temperature and nutrient availability. In the present study, a full-length coding region of Solea senegalensis clock gene Period3 (Per3) has been isolated from sole brain as a first step in understanding the molecular basis underlying circadian rhythms in this nocturnal species. The complete cDNA is 4141 base pairs (bp) in length, including an ORF of 3804bp, a 5'UTR of 247bp and a 3'UTR of 90bp. It encodes a putative PERIOD3 protein (PER3) of 1267 amino acids which shares the main functional domains conserved between transcription factors regulating the circadian clock pathway. Sole PER3 displays high identity with PER3 proteins from teleost species (61-77%) and lower identity (39-46%) with other vertebrate PER3 sequences. This gene is expressed in all examined tissues, being mRNA expression particularly evident in retina, cerebellum, diencephalon, optic tectum, liver and ovary. Per3 exhibits a significant daily oscillation in retina and optic tectum but not in diencephalon and cerebellum. Our results suggest an important role of Per3 in the circadian clockwork machinery of visually-related areas of sole.

  3. The mammalian circadian clock protein period counteracts cryptochrome in phosphorylation dynamics of circadian locomotor output cycles kaput (CLOCK).

    PubMed

    Matsumura, Ritsuko; Tsuchiya, Yoshiki; Tokuda, Isao; Matsuo, Takahiro; Sato, Miho; Node, Koichi; Nishida, Eisuke; Akashi, Makoto

    2014-11-14

    The circadian transcription factor CLOCK exhibits a circadian oscillation in its phosphorylation levels. Although it remains unclear whether this phosphorylation contributes to circadian rhythm generation, it has been suggested to be involved in transcriptional activity, intracellular localization, and degradative turnover of CLOCK. Here, we obtained direct evidence that CLOCK phosphorylation may be essential for autonomous circadian oscillation in clock gene expression. Importantly, we found that the circadian transcriptional repressors Cryptochrome (CRY) and Period (PER) showed an opposite effect on CLOCK phosphorylation; CRY impaired BMAL1-dependent CLOCK phosphorylation, whereas PER protected the phosphorylation against CRY. Interestingly, unlike PER1 and PER2, PER3 did not exert a protective action, which correlates with the phenotypic differences among mice lacking the Per genes. Further studies on the regulatory mechanism of CLOCK phosphorylation would thus lead to elucidation of the mechanism of CRY-mediated transcriptional repression and an understanding of the true role of PER in the negative feedback system.

  4. Temperature cycle amplitude alters the adult eclosion time and expression pattern of the circadian clock gene period in the onion fly.

    PubMed

    Miyazaki, Yosuke; Watari, Yasuhiko; Tanaka, Kazuhiro; Goto, Shin G

    2016-03-01

    Soil temperature cycles are considered to play an important role in the entrainment of circadian clocks of underground insects. However, because of the low conductivity of soil, temperature cycles are gradually dampened and the phase of the temperature cycle is delayed with increasing soil depth. The onion fly, Delia antiqua, pupates at various soil depths, and its eclosion is timed by a circadian clock. This fly is able to compensate for the depth-dependent phase delay of temperature change by advancing the eclosion time with decreasing amplitude of the temperature cycle. Therefore, pupae can eclose at the appropriate time irrespective of their location at any depth. However, the mechanism that regulates eclosion time in response to temperature amplitude is still unknown. To understand whether this mechanism involves the circadian clock or further downstream physiological processes, we examined the expression patterns of period (per), a circadian clock gene, of D. antiqua under temperature cycles that were square wave cycles of 12-h warm phase (W) and 12-h cool phase (C) with the temperature difference of 8 °C (WC 29:21 °C) and 1 °C (WC 25.5:24.5 °C). The phase of oscillation in per expression was found to commence 3.5h earlier under WC 25.5:24.5 °C as compared to WC 29:21 °C. This difference was in close agreement with the eclosion time difference between the two temperature cycles, suggesting that the mechanism that responds to the temperature amplitude involves the circadian clock.

  5. Silencing the circadian clock gene Clock using RNAi reveals dissociation of the circatidal clock from the circadian clock in the mangrove cricket.

    PubMed

    Takekata, Hiroki; Numata, Hideharu; Shiga, Sakiko; Goto, Shin G

    2014-09-01

    Whether a clock that generates a circatidal rhythm shares the same elements as the circadian clock is not fully understood. The mangrove cricket, Apteronemobius asahinai, shows simultaneously two endogenous rhythms in its locomotor activity; the circatidal rhythm generates active and inactive phases, and the circadian rhythm modifies activity levels by suppressing the activity during subjective day. In the present study, we silenced Clock (Clk), a master gene of the circadian clock, in A. asahinai using RNAi to investigate the link between the circatidal and circadian clocks. The abundance of Clk mRNA in the crickets injected with double-stranded RNA of Clk (dsClk) was reduced to a half of that in control crickets. dsClk injection also reduced mRNA abundance of another circadian clock gene period (per) and weakened diel oscillation in per mRNA expression. Examination of the locomotor rhythms under constant conditions revealed that the circadian modification was disrupted after silencing Clk expression, but the circatidal rhythm remained unaffected. There were no significant changes in the free-running period of the circatidal rhythm between the controls and the crickets injected with dsClk. Our results reveal that Clk is essential for the circadian clock, but is not required for the circatidal clock. From these results we propose that the circatidal rhythm of A. asahinai is driven by a clock, the molecular components of which are distinct from that of the circadian clock.

  6. Clock gene evolution and functional divergence.

    PubMed

    Tauber, Eran; Last, Kim S; Olive, Peter J W; Kyriacou, C P

    2004-10-01

    In considering the impact of the earth's changing geophysical conditions during the history of life, it is surprising to learn that the earth's rotational period may have been as short as 4 h, as recently as 1900 million years ago (or 1.9 billion years ago). The implications of such figures for the origin and evolution of clocks are considerable, and the authors speculate on how this short rotational period might have influenced the development of the "protoclock" in early microorganisms, such as the Cyanobacteria, during the geological periodsin which they arose and flourished. They then discuss the subsequent duplication of clock genes that took place around and after the Cambrian period, 543 million years ago, and its consequences. They compare the relative divergences of the canonical clock genes, which reveal the Per family to be the most rapidly evolving. In addition, the authors use a statistical test to predict which residues within the PER and CRY families may have undergone functional specialization.

  7. Clock genes, pancreatic function, and diabetes.

    PubMed

    Vieira, Elaine; Burris, Thomas P; Quesada, Ivan

    2014-12-01

    Circadian physiology is responsible for the temporal regulation of metabolism to optimize energy homeostasis throughout the day. Disturbances in the light/dark cycle, sleep/wake schedule, or feeding/activity behavior can affect the circadian function of the clocks located in the brain and peripheral tissues. These alterations have been associated with impaired glucose tolerance and type 2 diabetes. Animal models with molecular manipulation of clock genes and genetic studies in humans also support these links. It has been demonstrated that the endocrine pancreas has an intrinsic self-sustained clock, and recent studies have revealed an important role of clock genes in pancreatic β cells, glucose homeostasis, and diabetes.

  8. microRNA modulation of circadian clock period and entrainment

    PubMed Central

    Cheng, Hai-Ying M.; Papp, Joseph W.; Varlamova, Olga; Dziema, Heather; Russell, Brandon; Curfman, John P.; Nakazawa, Takanobu; Shimizu, Kimiko; Okamura, Hitoshi; Impey, Soren; Obrietan, Karl

    2007-01-01

    microRNAs (miRNAs) are a class of small, non-coding, RNAs that regulate the stability or translation of mRNA transcripts. Although recent work has implicated miRNAs in development and in disease, the expression and function of miRNAs in the adult mammalian nervous system has not been extensively characterized. Here, we examine the role of two brain-specific miRNAs, miR-219 and miR-132, in modulating the circadian clock located in the suprachiasmatic nucleus. miR-219 is a target of the CLOCK/BMAL1 complex, exhibits robust circadian rhythms of expression and the in vivo knockdown of miR-219 lengthens the circadian period. miR-132 is induced by photic entrainment cues via a MAPK/CREB-dependent mechanism, modulates clock gene expression, and attenuates the entraining effects of light. Collectively, these data reveal miRNAs as clock- and light-regulated genes and provide a mechanistic examination of their roles as effectors of pacemaker activity and entrainment. PMID:17553428

  9. Crosstalk of clock gene expression and autophagy in aging

    PubMed Central

    Kalfalah, Faiza; Janke, Linda; Schiavi, Alfonso; Tigges, Julia; Ix, Alexander; Ventura, Natascia; Boege, Fritz; Reinke, Hans

    2016-01-01

    Autophagy and the circadian clock counteract tissue degeneration and support longevity in many organisms. Accumulating evidence indicates that aging compromises both the circadian clock and autophagy but the mechanisms involved are unknown. Here we show that the expression levels of transcriptional repressor components of the circadian oscillator, most prominently the human Period homologue PER2, are strongly reduced in primary dermal fibroblasts from aged humans, while raising the expression of PER2 in the same cells partially restores diminished autophagy levels. The link between clock gene expression and autophagy is corroborated by the finding that the circadian clock drives cell-autonomous, rhythmic autophagy levels in immortalized murine fibroblasts, and that siRNA-mediated downregulation of PER2 decreases autophagy levels while leaving core clock oscillations intact. Moreover, the Period homologue lin-42 regulates autophagy and life span in the nematode Caenorhabditis elegans, suggesting an evolutionarily conserved role for Period proteins in autophagy control and aging. Taken together, this study identifies circadian clock proteins as set-point regulators of autophagy and puts forward a model, in which age-related changes of clock gene expression promote declining autophagy levels. PMID:27574892

  10. Daily oscillation and photoresponses of clock gene, Clock, and clock-associated gene, arylalkylamine N-acetyltransferase gene transcriptions in the rat pineal gland.

    PubMed

    Wang, Guo-Qing; Du, Yu-Zhen; Tong, Jian

    2007-01-01

    This study was conducted to investigate the circadian rhythms and light responses of Clock and arylalkylamine N-acetyltransferase (NAT) gene expressions in the rat pineal gland under the environmental conditions of a 12 h light (05:00-17:00 h): 12 h-dark (17:00-05:00 h) cycle (LD) and constant darkness (DD). The pineal gland of Sprague-Dawley rats housed under a LD regime (n=42) for four weeks and of a regime (n=42) for eight weeks were sampled at six different times, every 4 h (n=7 animals per time point), during a 24 h period. Total RNA was extracted from each sample, and the semiquantitative reverse transcription polymerase chain reaction (RT-PCR) was used to determine temporal changes in mRNA levels of Clock and NAT genes during different circadian or zeitgeber times. The data and parameters were analyzed by the cosine function software, Clock Lab software, and the amplitude F test was used to reveal the circadian rhythm. In the DD or LD condition, both the Clock and NAT mRNA levels in the pineal gland showed robust circadian oscillation (p<0.05) with the peak at the subjective night or at nighttime. In comparison with the DD regime, the amplitudes and mRNA levels at the peaks of Clock and NAT expressions in LD in the pineal gland were significantly reduced (p<0.05). In the DD or LD condition, the circadian expressions of NAT were similar in pattern to those of Clock in the pineal gland (p>0.05). These findings indicate that the transcriptions of Clock and NAT genes in the pineal gland not only show remarkably synchronous endogenous circadian rhythmic changes, but also respond to the ambient light signal in a reduced manner.

  11. CIRCADIAN CLOCK AND CELL CYCLE GENE EXPRESSION

    PubMed Central

    Metz, Richard P.; Qu, Xiaoyu; Laffin, Brian; Earnest, David; Porter, Weston W.

    2009-01-01

    Mouse mammary epithelial cells (HC-11) and mammary tissues were analyzed for developmental changes in circadian clock, cellular proliferation and differentiation marker genes. Expression of the clock genes, Per1 and Bmal1, were elevated in differentiated HC-11 cells whereas Per2 mRNA levels were higher in undifferentiated cells. This differentiation-dependent profile of clock gene expression was consistent with that observed in mouse mammary glands as Per1 and Bmal1 mRNA levels were elevated in late pregnant and lactating mammary tissues, while Per2 expression was higher in proliferating virgin and early pregnant glands. In both HC-11 cells and mammary glands, elevated Per2 expression was positively correlated with c-Myc and Cyclin D1 mRNA levels while Per1 and Bmal1 expression changed in conjunction with ß-casein mRNA levels. Interestingly, developmental stage had differential effects on rhythms of clock gene expression in the mammary gland. These data suggest that circadian clock genes may play a role in mouse mammary gland development and differentiation. PMID:16261617

  12. Dynamics of the slowing segmentation clock reveal alternating two-segment periodicity.

    PubMed

    Shih, Nathan P; François, Paul; Delaune, Emilie A; Amacher, Sharon L

    2015-05-15

    The formation of reiterated somites along the vertebrate body axis is controlled by the segmentation clock, a molecular oscillator expressed within presomitic mesoderm (PSM) cells. Although PSM cells oscillate autonomously, they coordinate with neighboring cells to generate a sweeping wave of cyclic gene expression through the PSM that has a periodicity equal to that of somite formation. The velocity of each wave slows as it moves anteriorly through the PSM, although the dynamics of clock slowing have not been well characterized. Here, we investigate segmentation clock dynamics in the anterior PSM in developing zebrafish embryos using an in vivo clock reporter, her1:her1-venus. The her1:her1-venus reporter has single-cell resolution, allowing us to follow segmentation clock oscillations in individual cells in real-time. By retrospectively tracking oscillations of future somite boundary cells, we find that clock reporter signal increases in anterior PSM cells and that the periodicity of reporter oscillations slows to about ∼1.5 times the periodicity in posterior PSM cells. This gradual slowing of the clock in the anterior PSM creates peaks of clock expression that are separated at a two-segment periodicity both spatially and temporally, a phenomenon we observe in single cells and in tissue-wide analyses. These results differ from previous predictions that clock oscillations stop or are stabilized in the anterior PSM. Instead, PSM cells oscillate until they incorporate into somites. Our findings suggest that the segmentation clock may signal somite formation using a phase gradient with a two-somite periodicity.

  13. Segment number and axial identity in a segmentation clock period mutant.

    PubMed

    Schröter, Christian; Oates, Andrew C

    2010-07-27

    A species-specific number of segments is a hallmark of the vertebrate body plan. The first segmental structures in the vertebrate embryo are the somites, which bud sequentially from the growing presomitic mesoderm (PSM). The Clock and Wavefront model for somitogenesis proposes that the total number of somites is determined by the period of an oscillator or clock operating in the PSM and the total duration of PSM growth. Furthermore, the number of oscillations of the segmentation clock has been suggested to regulate the regional identity of segments along the body axis. Here we test these two ideas in a zebrafish mutant in which the segmentation clock is specifically slowed. This reduces segment number as predicted, but hox gene expression and posterior anatomical markers align with lower segmental counts in mutants compared to the wild-type, arguing against an instructive role of the segmentation clock in determining axial identities. Our data therefore suggest that precise control of segmentation clock period in relation to axial growth ensures a species-specific segment number and that during evolution modulating the clock's period through genetic mutations may have been a relevant way to vary segment number independently of axial regionalization.

  14. Coexisting chaotic and periodic dynamics in clock escapements.

    PubMed

    Moon, Francis C; Stiefel, Preston D

    2006-09-15

    This paper addresses the nature of noise in machines. As a concrete example, we examine the dynamics of clock escapements from experimental, historical and analytical points of view. Experiments on two escapement mechanisms from the Reuleaux kinematic collection at Cornell University are used to illustrate chaotic-like noise in clocks. These vibrations coexist with the periodic dynamics of the balance wheel or pendulum. A mathematical model is presented that shows how self-generated chaos in clocks can break the dry friction in the gear train. This model is shown to exhibit a strange attractor in the structural vibration of the clock. The internal feedback between the oscillator and the escapement structure is similar to anti-control of chaos models.

  15. Persistence, period and precision of autonomous cellular oscillators from the zebrafish segmentation clock.

    PubMed

    Webb, Alexis B; Lengyel, Iván M; Jörg, David J; Valentin, Guillaume; Jülicher, Frank; Morelli, Luis G; Oates, Andrew C

    2016-02-13

    In vertebrate development, the sequential and rhythmic segmentation of the body axis is regulated by a "segmentation clock". This clock is comprised of a population of coordinated oscillating cells that together produce rhythmic gene expression patterns in the embryo. Whether individual cells autonomously maintain oscillations, or whether oscillations depend on signals from neighboring cells is unknown. Using a transgenic zebrafish reporter line for the cyclic transcription factor Her1, we recorded single tailbud cells in vitro. We demonstrate that individual cells can behave as autonomous cellular oscillators. We described the observed variability in cell behavior using a theory of generic oscillators with correlated noise. Single cells have longer periods and lower precision than the tissue, highlighting the role of collective processes in the segmentation clock. Our work reveals a population of cells from the zebrafish segmentation clock that behave as self-sustained, autonomous oscillators with distinctive noisy dynamics.

  16. Clock gene Per2 as a controller of liver carcinogenesis

    PubMed Central

    Mteyrek, Ali; Filipski, Elisabeth; Guettier, Catherine; Okyar, Alper; Lévi, Francis

    2016-01-01

    Environmental disruption of molecular clocks promoted liver carcinogenesis and accelerated cancer progression in rodents. We investigated the specific role of clock gene Period 2 (Per2) for liver carcinogenesis and clock-controlled cellular proliferation, genomic instability and inflammation. We assessed liver histopathology, and determined molecular and physiology circadian patterns in mice on chronic diethylnitrosamine (DEN) exposure according to constitutive Per2 mutation. First, we found that Per2m/m liver displayed profound alterations in proliferation gene expression, including c-Myc derepression, phase-advanced Wee1, and arrhythmic Ccnb1 and K-ras mRNA expressions, as well as deregulated inflammation, through arrhythmic liver IL-6 protein concentration, in the absence of any DEN exposure. These changes could then make Per2m/m mice more prone to subsequently develop liver cancers on DEN. Indeed, primary liver cancers were nearly fourfold as frequent in Per2m/m mice as compared to wild-type (WT), 4 months after DEN exposure. The liver molecular clock was severely disrupted throughout the whole carcinogenesis process, including the initiation stage, i.e. within the initial 17 days on DEN. Per2m/m further exhibited increased c-Myc and Ccnb1 mean 24h expressions, lack of P53 response, and arrhythmic ATM, Wee1 and Ccnb1 expressions. DEN-induced tumor related inflammation was further promoted through increased protein concentrations of liver IL-6 and TNF-α as compared to WT during carcinogenesis initiation. Per2 mutation severely deregulated liver gene or protein expressions related to three cancer hallmarks, including uncontrolled proliferation, genomic instability, and tumor promoting inflammation, and accelerated liver carcinogenesis several-fold. Clock gene Per2 acted here as a liver tumor suppressor from initiation to progression. PMID:27494874

  17. Clock genes and clock-controlled genes in the regulation of metabolic rhythms.

    PubMed

    Mazzoccoli, Gianluigi; Pazienza, Valerio; Vinciguerra, Manlio

    2012-04-01

    Daily rotation of the Earth on its axis and yearly revolution around the Sun impose to living organisms adaptation to nyctohemeral and seasonal periodicity. Terrestrial life forms have developed endogenous molecular circadian clocks to synchronize their behavioral, biological, and metabolic rhythms to environmental cues, with the aim to perform at their best over a 24-h span. The coordinated circadian regulation of sleep/wake, rest/activity, fasting/feeding, and catabolic/anabolic cycles is crucial for optimal health. Circadian rhythms in gene expression synchronize biochemical processes and metabolic fluxes with the external environment, allowing the organism to function effectively in response to predictable physiological challenges. In mammals, this daily timekeeping is driven by the biological clocks of the circadian timing system, composed of master molecular oscillators within the suprachiasmatic nuclei of the hypothalamus, pacing self-sustained and cell-autonomous molecular oscillators in peripheral tissues through neural and humoral signals. Nutritional status is sensed by nuclear receptors and coreceptors, transcriptional regulatory proteins, and protein kinases, which synchronize metabolic gene expression and epigenetic modification, as well as energy production and expenditure, with behavioral and light-dark alternance. Physiological rhythmicity characterizes these biological processes and body functions, and multiple rhythms coexist presenting different phases, which may determine different ways of coordination among the circadian patterns, at both the cellular and whole-body levels. A complete loss of rhythmicity or a change of phase may alter the physiological array of rhythms, with the onset of chronodisruption or internal desynchronization, leading to metabolic derangement and disease, i.e., chronopathology.

  18. Daily Rhythmicity of Clock Gene Transcripts in Atlantic Cod Fast Skeletal Muscle

    PubMed Central

    Lazado, Carlo C.; Kumaratunga, Hiruni P. S.; Nagasawa, Kazue; Babiak, Igor; Giannetto, Alessia; Fernandes, Jorge M. O.

    2014-01-01

    The classical notion of a centralized clock that governs circadian rhythmicity has been challenged with the discovery of peripheral oscillators that enable organisms to cope with daily changes in their environment. The present study aimed to identify the molecular clock components in Atlantic cod (Gadus morhua) and to investigate their daily gene expression in fast skeletal muscle. Atlantic cod clock genes were closely related to their orthologs in teleosts and tetrapods. Synteny was conserved to varying degrees in the majority of the 18 clock genes examined. In particular, aryl hydrocarbon receptor nuclear translocator-like 2 (arntl2), RAR-related orphan receptor A (rora) and timeless (tim) displayed high degrees of conservation. Expression profiling during the early ontogenesis revealed that some transcripts were maternally transferred, namely arntl2, cryptochrome 1b and 2 (cry1b and cry2), and period 2a and 2b (per2a and per2b). Most clock genes were ubiquitously expressed in various tissues, suggesting the possible existence of multiple peripheral clock systems in Atlantic cod. In particular, they were all detected in fast skeletal muscle, with the exception of neuronal PAS (Per-Arnt-Single-minded) domain-containing protein (npas1) and rora. Rhythmicity analysis revealed 8 clock genes with daily rhythmic expression, namely arntl2, circadian locomotor output cycles kaput (clock), npas2, cry2, cry3 per2a, nuclear receptor subfamily 1, group D, member 1 (nr1d1), and nr1d2a. Transcript levels of the myogenic genes myogenic factor 5 (myf5) and muscleblind-like 1 (mbnl1) strongly correlated with clock gene expression. This is the first study to unravel the molecular components of peripheral clocks in Atlantic cod. Taken together, our data suggest that the putative clock system in fast skeletal muscle of Atlantic cod has regulatory implications on muscle physiology, particularly in the expression of genes related to myogenesis. PMID:24921252

  19. Clock genes in hypertension: novel insights from rodent models.

    PubMed

    Richards, Jacob; Diaz, Alexander N; Gumz, Michelle L

    2014-10-01

    The circadian clock plays an integral role in the regulation of physiological processes, including the regulation of blood pressure. However, deregulation of the clock can lead to pathophysiological states including hypertension. Recent work has implicated the circadian clock genes in the regulation of processes in the heart, kidney, vasculature, and the metabolic organs, which are all critical in the regulation of the blood pressure. The goal of this review is to provide an introduction and general overview into the role of circadian clock genes in the regulation of blood pressure with a focus on their deregulation in the etiology of hypertension. This review will focus on the core circadian clock genes CLOCK, BMAL1, Per, and Cry.

  20. C-terminal binding protein (CtBP) activates the expression of E-box clock genes with CLOCK/CYCLE in Drosophila.

    PubMed

    Itoh, Taichi Q; Matsumoto, Akira; Tanimura, Teiichi

    2013-01-01

    In Drosophila, CLOCK/CYCLE heterodimer (CLK/CYC) is the primary activator of circadian clock genes that contain the E-box sequence in their promoter regions (hereafter referred to as "E-box clock genes"). Although extensive studies have investigated the feedback regulation of clock genes, little is known regarding other factors acting with CLK/CYC. Here we show that Drosophila C-terminal binding protein (dCtBP), a transcriptional co-factor, is involved in the regulation of the E-box clock genes. In vivo overexpression of dCtBP in clock cells lengthened or abolished circadian locomotor rhythm with up-regulation of a subset of the E-box clock genes, period (per), vrille (vri), and PAR domain protein 1ε (Pdp1ε). Co-expression of dCtBP with CLK in vitro also increased the promoter activity of per, vri, Pdp1ε and cwo depending on the amount of dCtBP expression, whereas no effect was observed without CLK. The activation of these clock genes in vitro was not observed when we used mutated dCtBP which carries amino acid substitutions in NAD+ domain. These results suggest that dCtBP generally acts as a putative co-activator of CLK/CYC through the E-box sequence.

  1. Restricted feeding phase shifts clock gene and sodium glucose cotransporter 1 (SGLT1) expression in rats.

    PubMed

    Balakrishnan, Anita; Stearns, Adam T; Ashley, Stanley W; Tavakkolizadeh, Ali; Rhoads, David B

    2010-05-01

    The intestine exhibits striking diurnal rhythmicity in glucose uptake, mediated by the sodium glucose cotransporter (SGLT1); however, regulatory pathways for these rhythms remain incompletely characterized. We hypothesized that SGLT1 rhythmicity is linked to the circadian clock. To investigate this, we examined rhythmicity of Sglt1 and individual clock genes in rats that consumed food ad libitum (AL). We further compared phase shifts of Sglt1 and clock genes in a second group of rats following restricted feeding to either the dark (DF) or light (LF) phase. Rats fed during the DF were pair-fed to rats fed during the LF. Jejunal mucosa was harvested across the diurnal period to generate expression profiles of Sglt1 and clock genes Clock, Bmal1 (brain-muscle Arnt-like 1), ReverbA/B, Per(Period) 1/2, and Cry (Cryptochrome) 1/2. All clock genes were rhythmic in AL rats (P < 0.05). Sglt1 also exhibited diurnal rhythmicity, with peak expression preceding nutrient arrival (P < 0.05). Light-restricted feeding shifted the expression rhythms of Sglt1 and most clock genes (Bmal1, ReverbA and B, Per1, Per2, and Cry1) compared with dark-restricted feeding (P < 0.05). The Sglt1 rhythm shifted in parallel with rhythms of Per1 and ReverbB. These effects of restricted feeding highlight luminal nutrients as a key Zeitgeber in the intestine, capable of simultaneously shifting the phases of transporter and clock gene expression, and suggest a role for clock genes in regulating Sglt1 and therefore glucose uptake. Understanding the regulatory cues governing rhythms in intestinal function may allow new therapeutic options for conditions of dysregulated absorption such as diabetes and obesity.

  2. Diurnal oscillations of soybean circadian clock and drought responsive genes.

    PubMed

    Marcolino-Gomes, Juliana; Rodrigues, Fabiana Aparecida; Fuganti-Pagliarini, Renata; Bendix, Claire; Nakayama, Thiago Jonas; Celaya, Brandon; Molinari, Hugo Bruno Correa; de Oliveira, Maria Cristina Neves; Harmon, Frank G; Nepomuceno, Alexandre

    2014-01-01

    Rhythms produced by the endogenous circadian clock play a critical role in allowing plants to respond and adapt to the environment. While there is a well-established regulatory link between the circadian clock and responses to abiotic stress in model plants, little is known of the circadian system in crop species like soybean. This study examines how drought impacts diurnal oscillation of both drought responsive and circadian clock genes in soybean. Drought stress induced marked changes in gene expression of several circadian clock-like components, such as LCL1-, GmELF4- and PRR-like genes, which had reduced expression in stressed plants. The same conditions produced a phase advance of expression for the GmTOC1-like, GmLUX-like and GmPRR7-like genes. Similarly, the rhythmic expression pattern of the soybean drought-responsive genes DREB-, bZIP-, GOLS-, RAB18- and Remorin-like changed significantly after plant exposure to drought. In silico analysis of promoter regions of these genes revealed the presence of cis-elements associated both with stress and circadian clock regulation. Furthermore, some soybean genes with upstream ABRE elements were responsive to abscisic acid treatment. Our results indicate that some connection between the drought response and the circadian clock may exist in soybean since (i) drought stress affects gene expression of circadian clock components and (ii) several stress responsive genes display diurnal oscillation in soybeans.

  3. The mammalian clock component PERIOD2 coordinates circadian output by interaction with nuclear receptors.

    PubMed

    Schmutz, Isabelle; Ripperger, Jürgen A; Baeriswyl-Aebischer, Stéphanie; Albrecht, Urs

    2010-02-15

    Mammalian circadian clocks provide a temporal framework to synchronize biological functions. To obtain robust rhythms with a periodicity of about a day, these clocks use molecular oscillators consisting of two interlocked feedback loops. The core loop generates rhythms by transcriptional repression via the Period (PER) and Cryptochrome (CRY) proteins, whereas the stabilizing loop establishes roughly antiphasic rhythms via nuclear receptors. Nuclear receptors also govern many pathways that affect metabolism and physiology. Here we show that the core loop component PER2 can coordinate circadian output with the circadian oscillator. PER2 interacts with nuclear receptors including PPARalpha and REV-ERBalpha and serves as a coregulator of nuclear receptor-mediated transcription. Consequently, PER2 is rhythmically bound at the promoters of nuclear receptor target genes in vivo. In this way, the circadian oscillator can modulate the expression of nuclear receptor target genes like Bmal1, Hnf1alpha, and Glucose-6-phosphatase. The concept that PER2 may propagate clock information to metabolic pathways via nuclear receptors adds an important facet to the clock-dependent regulation of biological networks.

  4. l-Ornithine affects peripheral clock gene expression in mice

    PubMed Central

    Fukuda, Takafumi; Haraguchi, Atsushi; Kuwahara, Mari; Nakamura, Kaai; Hamaguchi, Yutaro; Ikeda, Yuko; Ishida, Yuko; Wang, Guanying; Shirakawa, Chise; Tanihata, Yoko; Ohara, Kazuaki; Shibata, Shigenobu

    2016-01-01

    The peripheral circadian clock is entrained by factors in the external environment such as scheduled feeding, exercise, and mental and physical stresses. In addition, recent studies in mice demonstrated that some food components have the potential to control the peripheral circadian clock during scheduled feeding, although information about these components remains limited. l-Ornithine is a type of non-protein amino acid that is present in foods and has been reported to have various physiological functions. In human trials, for example, l-ornithine intake improved a subjective index of sleep quality. Here we demonstrate, using an in vivo monitoring system, that repeated oral administration of l-ornithine at an early inactive period in mice induced a phase advance in the rhythm of PER2 expression. By contrast, l-ornithine administration to mouse embryonic fibroblasts did not affect the expression of PER2, indicating that l-ornithine indirectly alters the phase of PER2. l-Ornithine also increased plasma levels of insulin, glucose and glucagon-like peptide-1 alongside mPer2 expression, suggesting that it exerts its effects probably via insulin secretion. Collectively, these findings demonstrate that l-ornithine affects peripheral clock gene expression and may expand the possibilities of L-ornithine as a health food. PMID:27703199

  5. l-Ornithine affects peripheral clock gene expression in mice.

    PubMed

    Fukuda, Takafumi; Haraguchi, Atsushi; Kuwahara, Mari; Nakamura, Kaai; Hamaguchi, Yutaro; Ikeda, Yuko; Ishida, Yuko; Wang, Guanying; Shirakawa, Chise; Tanihata, Yoko; Ohara, Kazuaki; Shibata, Shigenobu

    2016-10-05

    The peripheral circadian clock is entrained by factors in the external environment such as scheduled feeding, exercise, and mental and physical stresses. In addition, recent studies in mice demonstrated that some food components have the potential to control the peripheral circadian clock during scheduled feeding, although information about these components remains limited. l-Ornithine is a type of non-protein amino acid that is present in foods and has been reported to have various physiological functions. In human trials, for example, l-ornithine intake improved a subjective index of sleep quality. Here we demonstrate, using an in vivo monitoring system, that repeated oral administration of l-ornithine at an early inactive period in mice induced a phase advance in the rhythm of PER2 expression. By contrast, l-ornithine administration to mouse embryonic fibroblasts did not affect the expression of PER2, indicating that l-ornithine indirectly alters the phase of PER2. l-Ornithine also increased plasma levels of insulin, glucose and glucagon-like peptide-1 alongside mPer2 expression, suggesting that it exerts its effects probably via insulin secretion. Collectively, these findings demonstrate that l-ornithine affects peripheral clock gene expression and may expand the possibilities of L-ornithine as a health food.

  6. Cloning, tissue expression pattern and daily rhythms of Period1, Period2, and Clock transcripts in the flatfish Senegalese sole, Solea senegalensis.

    PubMed

    Martín-Robles, Águeda J; Whitmore, David; Sánchez-Vázquez, Francisco Javier; Pendón, Carlos; Muñoz-Cueto, José A

    2012-07-01

    An extensive network of endogenous oscillators governs vertebrate circadian rhythmicity. At the molecular level, they are composed of a set of clock genes that participate in transcriptional-translational feedback loops to control their own expression and that of downstream output genes. These clocks are synchronized with the environment, although entrainment by external periodic cues remains little explored in fish. In this work, partial cDNA sequences of clock genes representing both positive (Clock) and negative (Period1, Period2) elements of the molecular feedback loops were obtained from the nocturnal flatfish Senegalese sole, a relevant species for aquaculture and chronobiology. All of the above genes exhibited high identities with their respective teleost clock genes, and Per-Arnt-Sim or basic helix-loop-helix binding domains were recognized in their primary structure. They showed a widespread distribution through the animal body and some of them displayed daily mRNA rhythms in central (retina, optic tectum, diencephalon, and cerebellum) and peripheral (liver) tissues. These rhythms were most robust in retina and liver, exhibiting marked Period1 and Clock daily oscillations in transcript levels as revealed by ANOVA and cosinor analysis. Interestingly, expression profiles were inverted in retina and optic tectum compared to liver. Such differences suggest the existence of tissue-dependent zeitgebers for clock gene expression in this species (i.e., light for retina and optic tectum and feeding time for liver). This study provides novel insight into the location of the molecular clocks (central vs. peripheral) and their different phasing and synchronization pathways, which contributes to better understand the teleost circadian systems and its plasticity.

  7. The Clock gene clone and its circadian rhythms in Pelteobagrus vachelli

    NASA Astrophysics Data System (ADS)

    Qin, Chuanjie; Shao, Ting

    2015-05-01

    The Clock gene, a key molecule in circadian systems, is widely distributed in the animal kingdom. We isolated a 936-bp partial cDNA sequence of the Clock gene ( Pva-clock) from the darkbarbel catfish Pelteobagrus vachelli that exhibited high identity with Clock genes of other species of fish and animals (65%-88%). The putative domains included a basic helix-loop-helix (bHLH) domain and two period-ARNT-single-minded (PAS) domains, which were also similar to those in other species of fish and animals. Pva-Clock was primarily expressed in the brain, and was detected in all of the peripheral tissues sampled. Additionally, the pattern of Pva-Clock expression over a 24-h period exhibited a circadian rhythm in the brain, liver and intestine, with the acrophase at zeitgeber time 21:35, 23:00, and 23:23, respectively. Our results provide insight into the function of the molecular Clock of P. vachelli.

  8. Clock Gene Expression in Gravid Uterus and Extra-Embryonic Tissues During Late Gestation in the Mouse

    PubMed Central

    Ratajczak, Christine K.; Herzog, Erik D.; Muglia, Louis J.

    2013-01-01

    Evidence in humans and rodents suggests the importance of circadian rhythmicity in parturition. A molecular clock underlies the generation of circadian rhythmicity. While this molecular clock has been identified in numerous tissues, the expression and regulation of clock genes in tissues relevant to parturition is largely undefined. Here, we examine the expression and regulation of the clock genes Bmal1, Clock, Cry(Cryptochrome)1/2, and Per(Period)1/2 in the murine gravid uterus, placenta, and fetal membranes during late gestation. All clock genes examined were expressed in the tissues of interest throughout the last third of gestation. Upregulation of a subset of these clock genes was observed in each of these tissues in the final two days of gestation. Oscillating expression of mRNA for a subset of the examined clock genes was detected in the gravid uterus, placenta, and fetal membranes. Furthermore, bioluminescence recording on explants from gravid Per2::luciferase mice indicated rhythmic expression of PER2 protein in these tissues. These data demonstrate expression and rhythmicity of clock genes in tissues relevant to parturition indicating a potential contribution of peripheral molecular clocks to this process. PMID:20450826

  9. Circadian Gene Clock Regulates Psoriasis-Like Skin Inflammation in Mice.

    PubMed

    Ando, Noriko; Nakamura, Yuki; Aoki, Rui; Ishimaru, Kayoko; Ogawa, Hideoki; Okumura, Ko; Shibata, Shigenobu; Shimada, Shinji; Nakao, Atsuhito

    2015-12-01

    There are several reports suggesting that the pathophysiology of psoriasis may be associated with aberrant circadian rhythms. However, the mechanistic link between psoriasis and the circadian time-keeping system, "the circadian clock," remains unclear. This study determined whether the core circadian gene, Clock, had a regulatory role in the development of psoriasis. For this purpose, we compared the development of psoriasis-like skin inflammation induced by the Toll-like receptor 7 ligand imiquimod (IMQ) between wild-type mice and mice with a loss-of-function mutation of Clock. We also compared the development of IMQ-induced dermatitis between wild-type mice and mice with a loss-of-function mutation of Period2 (Per2), another key circadian gene that inhibits CLOCK activity. We found that Clock mutation ameliorated IMQ-induced dermatitis, whereas the Per2 mutation exaggerated IMQ-induced dermatitis, when compared with wild-type mice associated with decreased or increased IL-23 receptor (IL-23R) expression in γ/δ+ T cells, respectively. In addition, CLOCK directly bound to the promoter of IL-23R in γ/δ+ T cells, and IL-23R expression in the mouse skin was under circadian control. These findings suggest that Clock is a novel regulator of psoriasis-like skin inflammation in mice via direct modulation of IL-23R expression in γ/δ+ T cells, establishing a mechanistic link between psoriasis and the circadian clock.

  10. Altered Expression Pattern of Clock Genes in a Rat Model of Depression

    PubMed Central

    Christiansen, SL; Bouzinova, EV; Fahrenkrug, J

    2016-01-01

    Background: Abnormalities in circadian rhythms may be causal factors in development of major depressive disorder. The biology underlying a causal relationship between circadian rhythm disturbances and depression is slowly being unraveled. Although there is no direct evidence of dysregulation of clock gene expression in depressive patients, many studies have reported single-nucleotide polymorphisms in clock genes in these patients. Methods: In the present study we investigated whether a depression-like state in rats is associated with alternations of the diurnal expression of clock genes. The validated chronic mild stress (CMS) animal model of depression was used to investigate rhythmic expression of three clock genes: period genes 1 and 2 (Per1 and Per2) and Bmal1. Brain and liver tissue was collected from 96 animals after 3.5 weeks of CMS (48 control and 48 depression-like rats) at a 4h sampling interval within 24h. We quantified expression of clock genes on brain sections in the prefrontal cortex, nucleus accumbens, pineal gland, suprachiasmatic nucleus, substantia nigra, amygdala, ventral tegmental area, subfields of the hippocampus, and the lateral habenula using in situ hybridization histochemistry. Expression of clock genes in the liver was monitored by real-time quantitative polymerase chain reaction (PCR). Results: We found that the effect of CMS on clock gene expression was selective and region specific. Per1 exhibits a robust diurnal rhythm in most regions of interest, whereas Bmal1 and in particular Per2 were susceptible to CMS. Conclusion: The present results suggest that altered expression of investigated clock genes is likely associated with the induction of a depression-like state in the CMS model. PMID:27365111

  11. Association between Circadian Clock Genes and Diapause Incidence in Drosophila triauraria

    PubMed Central

    Yamada, Hirokazu; Yamamoto, Masa-Toshi

    2011-01-01

    Diapause is an adaptive response triggered by seasonal photoperiodicity to overcome unfavorable seasons. The photoperiodic clock is a system that controls seasonal physiological processes, but our knowledge about its physiological mechanisms and genetic architecture remains incomplete. The circadian clock is another system that controls daily rhythmic physiological phenomena. It has been argued that there is a connection between the two clocks. To examine the genetic connection between them, we analyzed the associations of five circadian clock genes (period, timeless, Clock, cycle and cryptochrome) with the occurrence of diapause in Drosophila triauraria, which shows a robust reproductive diapause with clear photoperiodicity. Non-diapause strains found in low latitudes were compared in genetic crosses with the diapause strain, in which the diapause trait is clearly dominant. Single nucleotide polymorphism and deletion analyses of the five circadian clock genes in backcross progeny revealed that allelic differences in timeless and cryptochrome between the strains were additively associated with the differences in the incidence of diapause. This suggests that there is a molecular link between certain circadian clock genes and the occurrence of diapause. PMID:22164210

  12. The period of the somite segmentation clock is sensitive to Notch activity

    PubMed Central

    Kim, Woong; Matsui, Takaaki; Yamao, Masataka; Ishibashi, Makoto; Tamada, Kota; Takumi, Toru; Kohno, Kenji; Oba, Shigeyuki; Ishii, Shin; Sakumura, Yuichi; Bessho, Yasumasa

    2011-01-01

    The number of vertebrae is defined strictly for a given species and depends on the number of somites, which are the earliest metameric structures that form in development. Somites are formed by sequential segmentation. The periodicity of somite segmentation is orchestrated by the synchronous oscillation of gene expression in the presomitic mesoderm (PSM), termed the “somite segmentation clock,” in which Notch signaling plays a crucial role. Here we show that the clock period is sensitive to Notch activity, which is fine-tuned by its feedback regulator, Notch-regulated ankyrin repeat protein (Nrarp), and that Nrarp is essential for forming the proper number and morphology of axial skeleton components. Null-mutant mice for Nrarp have fewer vertebrae and have defective morphologies. Notch activity is enhanced in the PSM of the Nrarp−/– embryo, where the ∼2-h segmentation period is extended by 5 min, thereby forming fewer somites and their resultant vertebrae. Reduced Notch activity partially rescues the Nrarp−/– phenotype in the number of somites, but not in morphology. Therefore we propose that the period of the somite segmentation clock is sensitive to Notch activity and that Nrarp plays essential roles in the morphology of vertebrae and ribs. PMID:21795391

  13. Clock genes × stress × reward interactions in alcohol and substance use disorders.

    PubMed

    Perreau-Lenz, Stéphanie; Spanagel, Rainer

    2015-06-01

    Adverse life events and highly stressful environments have deleterious consequences for mental health. Those environmental factors can potentiate alcohol and drug abuse in vulnerable individuals carrying specific genetic risk factors, hence producing the final risk for alcohol- and substance-use disorders development. The nature of these genes remains to be fully determined, but studies indicate their direct or indirect relation to the stress hypothalamo-pituitary-adrenal (HPA) axis and/or reward systems. Over the past decade, clock genes have been revealed to be key-players in influencing acute and chronic alcohol/drug effects. In parallel, the influence of chronic stress and stressful life events in promoting alcohol and substance use and abuse has been demonstrated. Furthermore, the reciprocal interaction of clock genes with various HPA-axis components, as well as the evidence for an implication of clock genes in stress-induced alcohol abuse, have led to the idea that clock genes, and Period genes in particular, may represent key genetic factors to consider when examining gene × environment interaction in the etiology of addiction. The aim of the present review is to summarize findings linking clock genes, stress, and alcohol and substance abuse, and to propose potential underlying neurobiological mechanisms.

  14. Clock Genes × Stress × Reward Interactions in Alcohol and Substance Use Disorders

    PubMed Central

    Perreau-Lenz, Stéphanie; Spanagel, Rainer

    2015-01-01

    Adverse life events and highly stressful environments have deleterious consequences for mental health. Those environmental factors can potentiate alcohol and drug abuse in vulnerable individuals carrying specific genetic risk factors, hence producing the final risk for alcohol- and substance-use disorders development. The nature of these genes remains to be fully determined, but studies indicate their direct or indirect relation to the stress hypothalamo-pituitary-adrenal (HPA) axis and/or reward systems. Over the past decade, clock genes have been revealed to be key-players in influencing acute and chronic alcohol/drug effects. In parallel, the influence of chronic stress and stressful life events in promoting alcohol and substance use and abuse has been demonstrated. Furthermore, the reciprocal interaction of clock genes with various HPA-axis components, as well as the evidence for an implication of clock genes in stress-induced alcohol abuse, have led to the idea that clock genes, and Period genes in particular, may represent key genetic factors to consider when examining gene × environment interaction in the etiology of addiction. The aim of the present review is to summarize findings linking clock genes, stress, and alcohol and substance abuse, and to propose potential underlying neurobiological mechanisms. PMID:25943583

  15. The clock gene cycle plays an important role in the circadian clock of the cricket Gryllus bimaculatus.

    PubMed

    Uryu, Outa; Karpova, Svetlana G; Tomioka, Kenji

    2013-07-01

    To dissect the molecular oscillatory mechanism of the circadian clock in the cricket Gryllus bimaculatus, we have cloned a cDNA of the clock gene cycle (Gb'cyc) and analyzed its structure and function. Gb'cyc contains four functional domains, i.e. bHLH, PAS-A, PAS-B and BCTR domains, and is expressed rhythmically in light dark cycles, peaking at mid night. The RNA interference (RNAi) of Clock (Gb'Clk) and period (Gb'per) reduced the Gb'cyc mRNA levels and abolished the rhythmic expression, suggesting that the rhythmic expression of Gb'cyc is regulated by a mechanism including Gb'Clk and Gb'per. These features are more similar to those of mammalian orthologue of cyc (Bmal1) than those of Drosophila cyc. A single treatment with double-stranded RNA (dsRNA) of Gb'cyc effectively knocked down the Gb'cyc mRNA level and abolished its rhythmic expression. The cyc RNAi failed to disrupt the locomotor rhythm, but lengthened its free-running period in constant darkness (DD). It is thus likely that Gb'cyc is involved in the circadian clock machinery of the cricket. The cyc RNAi crickets showed a rhythmic expression of Gb'per and timeless (Gb'tim) in the optic lobe in DD, explaining the persistence of the locomotor rhythm. Surprisingly, cyc RNAi revealed a rhythmic expression of Gb'Clk in DD which is otherwise rather constitutively expressed in the optic lobe. These facts suggest that the cricket might have a unique clock oscillatory mechanism in which both Gb'cyc and Gb'Clk are rhythmically controlled and that under abundant expression of Gb'cyc the rhythmic expression of Gb'Clk may be concealed.

  16. A circadian clock in Neurospora: how genes and proteins cooperate to produce a sustained, entrainable, and compensated biological oscillator with a period of about a day.

    PubMed

    Dunlap, J C; Loros, J J; Colot, H V; Mehra, A; Belden, W J; Shi, M; Hong, C I; Larrondo, L F; Baker, C L; Chen, C-H; Schwerdtfeger, C; Collopy, P D; Gamsby, J J; Lambreghts, R

    2007-01-01

    Neurospora has proven to be a tractable model system for understanding the molecular bases of circadian rhythms in eukaryotes. At the core of the circadian oscillatory system is a negative feedback loop in which two transcription factors, WC-1 and WC-2, act together to drive expression of the frq gene. WC-2 enters the promoter region of frq coincident with increases in frq expression and then exits when the cycle of transcription is over, whereas WC-1 can always be found there. FRQ promotes the phosphorylation of the WCs, thereby decreasing their activity, and phosphorylation of FRQ then leads to its turnover, allowing the cycle to reinitiate. By understanding the action of light and temperature on frq and FRQ expression, the molecular basis of circadian entrainment to environmental light and temperature cues can be understood, and recently a specific role for casein kinase 2 has been found in the mechanism underlying circadian temperature-compensation. These data promise molecular explanations for all of the canonical circadian properties of this model system, providing biochemical answers and regulatory logic that may be extended to more complex eukaryotes including humans.

  17. Characterisation, analysis of expression and localisation of circadian clock genes from the perspective of photoperiodism in the aphid Acyrthosiphon pisum.

    PubMed

    Barberà, Miquel; Collantes-Alegre, Jorge Mariano; Martínez-Torres, David

    2017-02-22

    Aphids are typical photoperiodic insects that switch from viviparous parthenogenetic reproduction typical of long day seasons to oviparous sexual reproduction triggered by the shortening of photoperiod in autumn yielding an overwintering egg in which an embryonic diapause takes place. While the involvement of the circadian clock genes in photoperiodism in mammals is well established, there is still some controversy on their participation in insects. The availability of the genome of the pea aphid Acyrthosiphon pisum places this species as an excellent model to investigate the involvement of the circadian system in the aphid seasonal response. In the present report, we have advanced in the characterisation of the circadian clock genes and showed that these genes display extensive alternative splicing. Moreover, the expression of circadian clock genes, analysed at different moments of the day, showed a robust cycling of central clock genes period and timeless. Furthermore, the rhythmic expression of these genes was shown to be rapidly dampened under DD (continuous darkness conditions), thus supporting the model of a seasonal response based on a heavily dampened circadian oscillator. Additionally, increased expression of some of the circadian clock genes under short-day conditions suggest their involvement in the induction of the aphid seasonal response. Finally, in situ localisation of transcripts of genes period and timeless in the aphid brain revealed the site of clock neurons for the first time in aphids. Two groups of clock cells were identified: the Dorsal Neurons (DN) and the Lateral Neurons (LN), both in the protocerebrum.

  18. Using Fractional Clock-Period Delays in Telemetry Arraying

    NASA Technical Reports Server (NTRS)

    Fort, David; Rogstad, David; Rogstad, Stephen P.

    2003-01-01

    A set of special digital all-pass finite-impulse- response (FIR) filters produces phase shifts equivalent to delays that equal fractions of the sampling or clock period of a telemetry-data-processing system. These filters have been used to enhance the arraying of telemetry signals that have been received at multiple ground stations from spacecraft (see figure). Somewhat more specifically, these filters have been used to align, in the time domain, the telemetry-data sequences received by the various antennas, in order to maximize the signal-to-noise ratio of the composite telemetric signal obtained by summing the signals received by the antennas. The term arraying in this context denotes a method of enhanced reception of telemetry signals in which several antennas are used to track a single spacecraft. Each antenna receives a signal that comprises a sum of telemetry data plus noise, and these sum data are sent to an arraying combiner for processing. Correlation is the means used to align the set of data from one antenna with that from another antenna. After the data from all the antennas have been aligned in the time domain, they are all added together, sample by sample.

  19. Circadian clock gene expression in the coral Favia fragum over diel and lunar reproductive cycles.

    PubMed

    Hoadley, Kenneth D; Szmant, Alina M; Pyott, Sonja J

    2011-05-06

    Natural light cycles synchronize behavioral and physiological cycles over varying time periods in both plants and animals. Many scleractinian corals exhibit diel cycles of polyp expansion and contraction entrained by diel sunlight patterns, and monthly cycles of spawning or planulation that correspond to lunar moonlight cycles. The molecular mechanisms for regulating such cycles are poorly understood. In this study, we identified four molecular clock genes (cry1, cry2, clock and cycle) in the scleractinian coral, Favia fragum, and investigated patterns of gene expression hypothesized to be involved in the corals' diel polyp behavior and lunar reproductive cycles. Using quantitative PCR, we measured fluctuations in expression of these clock genes over both diel and monthly spawning timeframes. Additionally, we assayed gene expression and polyp expansion-contraction behavior in experimental corals in normal light:dark (control) or constant dark treatments. Well-defined and reproducible diel patterns in cry1, cry2, and clock expression were observed in both field-collected and the experimental colonies maintained under control light:dark conditions, but no pattern was observed for cycle. Colonies in the control light:dark treatment also displayed diel rhythms of tentacle expansion and contraction. Experimental colonies in the constant dark treatment lost diel patterns in cry1, cry2, and clock expression and displayed a diminished and less synchronous pattern of tentacle expansion and contraction. We observed no pattern in cry1, cry2, clock, or cycle expression correlated with monthly spawning events suggesting these genes are not involved in the entrainment of reproductive cycles to lunar light cycles in F. fragum. Our results suggest a molecular clock mechanism, potentially similar to that in described in fruit flies, exists within F. fragum.

  20. Photoperiodic diapause under the control of circadian clock genes in an insect

    PubMed Central

    2010-01-01

    Background Most organisms have evolved a circadian clock in order to anticipate daily environmental changes and many of these organisms are also capable of sophisticated measurement of daylength (photoperiodism) that is used to regulate seasonal events such as diapause, migration and polymorphism. It has been generally accepted that the same elements are involved in both circadian (daily) and seasonal (annual) rhythms because both rely upon daily light-dark cycles. However, as reasonable as this sounds, there remains no conclusive evidence of such a molecular machinery in insects. We have approached this issue by using RNA interference (RNAi) in Riptortus pedestris. Results The cuticle deposition rhythm exhibited the major properties of circadian rhythms, indicating that the rhythm is regulated by a circadian clock. RNAi directed against the circadian clock genes of period and cycle, which are negative and positive regulators in the circadian clock, respectively, disrupted the cuticle deposition rhythm and distinct cuticle layers were produced by these RNAi. Simultaneously, period RNAi caused the insect to avert diapause under a diapause-inducing photoperiod whereas cycle RNAi induced diapause under a diapause-averting photoperiod. The expression patterns of juvenile hormone-regulated genes and the application of juvenile hormone analogue suggested that neither ovarian development itself nor a downstream cascade of juvenile hormone secretion, were disturbed by period and cycle RNAi. Conclusions This study revealed that the circadian clock genes are crucial not only for daily rhythms but also for photoperiodic diapause. RNAi directed against period and cycle had opposite effects not only in the circadian cuticle deposition rhythm but also in the photoperiodic diapause. These RNAi also had opposite effects on juvenile hormone-regulated gene expression. It is still possible that the circadian clock genes pleiotropically affect ovarian development but, based on these

  1. Clock genes associate with white matter integrity in depressed bipolar patients.

    PubMed

    Bollettini, Irene; Melloni, Elisa Maria Teresa; Aggio, Veronica; Poletti, Sara; Lorenzi, Cristina; Pirovano, Adele; Vai, Benedetta; Dallaspezia, Sara; Colombo, Cristina; Benedetti, Francesco

    2017-01-01

    Human genetic studies have implicated specific genes that constitute the molecular clock in the manifestation of bipolar disorder (BD). Among the clock genes involved in the control system of circadian rhythms, CLOCK 3111 T/C and Period3 (PER3) influence core psychopathological features of mood disorders, such as patterns of sleep, rest, and activity, diurnal preference, cognitive performances after sleep loss, age at the onset of the illness, and response to antidepressant treatment. Furthermore, several studies pointed out that bipolar symptomatology is associated with dysfunctions in white matter (WM) integrity, suggesting these structural alterations as a possible biomarker of the disorder. We hypothesise that CLOCK and PER3 polymorphisms could be potential factors affecting WM microstructure integrity in bipolar patients. The relationship between these clock genes and DTI measures of WM integrity in a sample of 140 (53 M; 87 F) patients affected by BD type I was studied. Tract-based spatial statistics analyses on DTI measures of WM integrity were performed for each clock gene polymorphism, between the genetic groups. We accounted for the effect of nuisance covariates known to influence WM microstructure: age, sex, lithium treatment, age at the onset of the illness, and the number of illness episodes. We found that compared to T homozygotes, CLOCK C carriers showed a widespread increase of the mean diffusivity in several WM tracts. Compared with PER3(5/5) homozygotes, PER3(4/4) homozygotes showed significantly increased radial diffusivity and reduced fractional anisotropy in several brain WM tracts. No significant difference was observed between heterozygotes and the other subgroups. Altogether, this pattern of results suggests WM disruption in CLOCK C carrier and in PER3(4) homozygotes. Sleep promotes myelination and oligodendrocyte precursor cell proliferation and associates with higher expression of genes coding for phospholipid synthesis and myelination in

  2. Persistence, period and precision of autonomous cellular oscillators from the zebrafish segmentation clock

    PubMed Central

    Webb, Alexis B; Lengyel, Iván M; Jörg, David J; Valentin, Guillaume; Jülicher, Frank; Morelli, Luis G; Oates, Andrew C

    2016-01-01

    In vertebrate development, the sequential and rhythmic segmentation of the body axis is regulated by a “segmentation clock”. This clock is comprised of a population of coordinated oscillating cells that together produce rhythmic gene expression patterns in the embryo. Whether individual cells autonomously maintain oscillations, or whether oscillations depend on signals from neighboring cells is unknown. Using a transgenic zebrafish reporter line for the cyclic transcription factor Her1, we recorded single tailbud cells in vitro. We demonstrate that individual cells can behave as autonomous cellular oscillators. We described the observed variability in cell behavior using a theory of generic oscillators with correlated noise. Single cells have longer periods and lower precision than the tissue, highlighting the role of collective processes in the segmentation clock. Our work reveals a population of cells from the zebrafish segmentation clock that behave as self-sustained, autonomous oscillators with distinctive noisy dynamics. DOI: http://dx.doi.org/10.7554/eLife.08438.001 PMID:26880542

  3. Circadian Clock-Regulated Expression of Phytochrome and Cryptochrome Genes in Arabidopsis1

    PubMed Central

    Tóth, Réka; Kevei, Éva; Hall, Anthony; Millar, Andrew J.; Nagy, Ferenc; Kozma-Bognár, László

    2001-01-01

    Many physiological and biochemical processes in plants exhibit endogenous rhythms with a period of about 24 h. Endogenous oscillators called circadian clocks regulate these rhythms. The circadian clocks are synchronized to the periodic environmental changes (e.g. day/night cycles) by specific stimuli; among these, the most important is the light. Photoreceptors, phytochromes, and cryptochromes are involved in setting the clock by transducing the light signal to the central oscillator. In this work, we analyzed the spatial, temporal, and long-term light-regulated expression patterns of the Arabidopsis phytochrome (PHYA to PHYE) and cryptochrome (CRY1 and CRY2) promoters fused to the luciferase (LUC+) reporter gene. The results revealed new details of the tissue-specific expression and light regulation of the PHYC and CRY1 and 2 promoters. More importantly, the data obtained demonstrate that the activities of the promoter::LUC+ constructs, with the exception of PHYC::LUC+, display circadian oscillations under constant conditions. In addition, it is shown by measuring the mRNA abundance of PHY and CRY genes under constant light conditions that the circadian control is also maintained at the level of mRNA accumulation. These observations indicate that the plant circadian clock controls the expression of these photoreceptors, revealing the formation of a new regulatory loop that could modulate gating and resetting of the circadian clock. PMID:11743105

  4. Circadian Rhythmicity of Active GSK3 Isoforms Modulates Molecular Clock Gene Rhythms in the Suprachiasmatic Nucleus

    PubMed Central

    Besing, R.C.; Paul, J.R.; Hablitz, L.M.; Rogers, C.O.; Johnson, R.L.; Young, M.E.; Gamble, K.L.

    2015-01-01

    The suprachiasmatic nucleus (SCN) drives and synchronizes daily rhythms at the cellular level via transcriptional-translational feedback loops comprised of clock genes such as Bmal1 and Period (Per). Glycogen synthase kinase 3 (GSK3), a serine/threonine kinase, phosphorylates at least five core clock proteins and shows diurnal variation in phosphorylation state (inactivation) of the GSK3β isoform. Whether phosphorylation of the other primary isoform (GSK3α) varies across the subjective day-night cycle is unknown. The purpose of this study was to determine if the endogenous rhythm of GSK3 (α and β) phosphorylation is critical for rhythmic BMAL1 expression and normal amplitude and periodicity of the molecular clock in the SCN. Significant circadian rhythmicity of phosphorylated GSK3 (α and β) was observed in the SCN from wild-type mice housed in constant darkness for two weeks. Importantly, chronic activation of both GSK3 isoforms impaired rhythmicity of the GSK3 target BMAL1. Furthermore, chronic pharmacological inhibition of GSK3 with 20 μM CHIR-99021 enhanced the amplitude and shortened the period of PER2::luciferase rhythms in organotypic SCN slice cultures. These results support the model that GSK3 activity status is regulated by the circadian clock and that GSK3 feeds back to regulate the molecular clock amplitude in the SCN. PMID:25724980

  5. Core clock, SUB1, and ABAR genes mediate flooding and drought responses via alternative splicing in soybean.

    PubMed

    Syed, Naeem H; Prince, Silvas J; Mutava, Raymond N; Patil, Gunvant; Li, Song; Chen, Wei; Babu, Valliyodan; Joshi, Trupti; Khan, Saad; Nguyen, Henry T

    2015-12-01

    Circadian clocks are a great evolutionary innovation and provide competitive advantage during the day/night cycle and under changing environmental conditions. The circadian clock mediates expression of a large proportion of genes in plants, achieving a harmonious relationship between energy metabolism, photosynthesis, and biotic and abiotic stress responses. Here it is shown that multiple paralogues of clock genes are present in soybean (Glycine max) and mediate flooding and drought responses. Differential expression of many clock and SUB1 genes was found under flooding and drought conditions. Furthermore, natural variation in the amplitude and phase shifts in PRR7 and TOC1 genes was also discovered under drought and flooding conditions, respectively. PRR3 exhibited flooding- and drought-specific splicing patterns and may work in concert with PRR7 and TOC1 to achieve energy homeostasis under flooding and drought conditions. Higher expression of TOC1 also coincides with elevated levels of abscisic acid (ABA) and variation in glucose levels in the morning and afternoon, indicating that this response to abiotic stress is mediated by ABA, endogenous sugar levels, and the circadian clock to fine-tune photosynthesis and energy utilization under stress conditions. It is proposed that the presence of multiple clock gene paralogues with variation in DNA sequence, phase, and period could be used to screen exotic germplasm to find sources for drought and flooding tolerance. Furthermore, fine tuning of multiple clock gene paralogues (via a genetic engineering approach) should also facilitate the development of flooding- and drought-tolerant soybean varieties.

  6. Circadian rhythms of clock gene expression in the cerebellum of serotonin-deficient Pet-1 knockout mice.

    PubMed

    Paulus, Erin V; Mintz, Eric M

    2016-01-01

    Serotonin plays an important role in the central regulation of circadian clock function. Serotonin levels are generally higher in the brain during periods of high activity, and these periods are in turn heavily regulated by the circadian clock located in the suprachiasmatic nucleus. However, the role of serotonin as a regulator of circadian rhythms elsewhere in the brain has not been extensively examined. In this study, we examined circadian rhythms of clock gene expression in the cerebellum in mice lacking the Pet-1 transcription factor, which results in a developed brain that is deficient in serotonin neurons. If serotonin helps to synchronize rhythms in brain regions other than the suprachiasmatic nucleus, we would expect to see differences in clock gene expression in these serotonin deficient mice. We found minor differences in the expression of Per1 and Per2 in the knockout mice as compared to wild type, but these differences were small and of questionable functional importance. We also measured the response of cerebellar clocks to injections of the serotonin agonist 8-OH-DPAT during the early part of the night. No effect on clock genes was observed, though the immediate-early gene Fos showed increased expression in wild type mice but not the knockouts. These results suggest that serotonin is not an important mediator of circadian rhythms in the cerebellum in a way that parallels its regulation of the circadian clock in the suprachiasmatic nucleus.

  7. Butyrate Infusions in the Ovine Fetus Delay the Biologic Clock for Globin Gene Switching

    NASA Astrophysics Data System (ADS)

    Perrine, Susan P.; Rudolph, Abraham; Faller, Douglas V.; Roman, Christine; Cohen, Ruth A.; Chen, Shao-Jing; Kan, Yuet Wai

    1988-11-01

    The switch from fetal to adult hemoglobin expression is regulated in many mammalian species by a developmental clock-like mechanism and determined by the gestational age of the fetus. Prolonging fetal globin gene expression is of considerable interest for therapeutic potential in diseases caused by abnormal β -globin genes. Butyric acid, which is found in increased plasma concentrations in infants of diabetic mothers who have delayed globin gene switching, was infused into catheterized fetal lambs in utero during the time of the normal globin gene switch period. The globin gene switch was significantly delayed in three of four butyrate-treated fetuses compared with controls and was entirely prevented in one fetus in whom the infusion was begun before the globin switch was under way. These data provide a model for investigating and arresting the biologic clock of hemoglobin switching.

  8. Differential expression of circadian clock genes in two strains of beetles reveals candidates related to photoperiodic induction of summer diapause.

    PubMed

    Zhu, Li; Liu, Wen; Tan, Qian-Qian; Lei, Chao-Liang; Wang, Xiao-Ping

    2017-03-01

    Diapause (also known as dormancy) is a state of arrested development induced by photoperiod or temperature that allows insects to survive adverse environmental conditions. By regulating diapause induction, the circadian clock is involved in short-day-induced winter diapause but whether this is also the case in long-day (LD)-induced summer diapause remains unknown. The cabbage beetle Colaphellus bowringi could enter summer diapause under LD conditions. However, a non-photoperiodic-diapause (NPD) strain of this species, which was developed in our laboratory by artificial selection, could not enter diapause under LD photoperiod. Therefore, we identified circadian clock genes in this species and measured differences in their expression between a high diapause (HD) strain and the NPD strain to investigate the potential relationship between circadian clock genes and summer diapause induction in C. bowringi. We successfully cloned eight circadian clock genes and obtained intact ORFs of four; cryptochrome2, double-time, shaggy and vrille. Phylogenetic trees and sequence alignment analyses indicated that these circadian clock genes were conserved across insect taxa. The quantitative real-time PCR indicated that clock, cycle, period, timeless, cryptochrome2, and vrille were differentially expressed between HD and NPD strains reared under LD photoperiod during the diapause induction phase. These findings suggest the potential relationship between circadian clock genes and LD-regulated summer diapause induction in C. bowringi.

  9. Continuous activity and no cycling of clock genes in the Antarctic midge during the polar summer.

    PubMed

    Kobelkova, Alena; Goto, Shin G; Peyton, Justin T; Ikeno, Tomoko; Lee, Richard E; Denlinger, David L

    2015-10-01

    The extreme seasonal shifts of day length in polar regions, ranging from constant light in the summer to constant darkness in the winter, pose an intriguing environment for probing activity rhythms and the functioning of circadian clocks. Here, we monitor locomotor activity during the summer on the Antarctic Peninsula and under laboratory conditions, as well as the accompanying patterns of clock gene expression in the Antarctic midge, the only insect endemic to Antarctica. Larvae and adults are most active during the warmest portion of the day, but at a constant temperature they remain continuously active regardless of the photoregime, and activity also persists in constant darkness. The canonical clock genes period, timeless, Clock, and vrille are expressed in the head but we detected no cycling of expression in either the field or under diverse photoregimes in the laboratory. The timekeeping function of the clock has possibly been lost, enabling the midge to opportunistically exploit the unpredictable availability of permissive thermal conditions for growth, development, and reproduction during the short summer in Antarctica.

  10. Variations in Phase and Amplitude of Rhythmic Clock Gene Expression across Prefrontal Cortex, Hippocampus, Amygdala, and Hypothalamic Paraventricular and Suprachiasmatic Nuclei of Male and Female Rats.

    PubMed

    Chun, Lauren E; Woodruff, Elizabeth R; Morton, Sarah; Hinds, Laura R; Spencer, Robert L

    2015-10-01

    The molecular circadian clock is a self-regulating transcription/translation cycle of positive (Bmal1, Clock/Npas2) and negative (Per1,2,3, Cry1,2) regulatory components. While the molecular clock has been well characterized in the body's master circadian pacemaker, the hypothalamic suprachiasmatic nucleus (SCN), only a few studies have examined both the positive and negative clock components in extra-SCN brain tissue. Furthermore, there has yet to be a direct comparison of male and female clock gene expression in the brain. This comparison is warranted, as there are sex differences in circadian functioning and disorders associated with disrupted clock gene expression. This study examined basal clock gene expression (Per1, Per2, Bmal1 mRNA) in the SCN, prefrontal cortex (PFC), rostral agranular insula, hypothalamic paraventricular nucleus (PVN), amygdala, and hippocampus of male and female rats at 4-h intervals throughout a 12:12 h light:dark cycle. There was a significant rhythm of Per1, Per2, and Bmal1 in the SCN, PFC, insula, PVN, subregions of the hippocampus, and amygdala with a 24-h period, suggesting the importance of an oscillating molecular clock in extra-SCN brain regions. There were 3 distinct clock gene expression profiles across the brain regions, indicative of diversity among brain clocks. Although, generally, the clock gene expression profiles were similar between male and female rats, there were some sex differences in the robustness of clock gene expression (e.g., females had fewer robust rhythms in the medial PFC, more robust rhythms in the hippocampus, and a greater mesor in the medial amygdala). Furthermore, females with a regular estrous cycle had attenuated aggregate rhythms in clock gene expression in the PFC compared with noncycling females. This suggests that gonadal hormones may modulate the expression of the molecular clock.

  11. Clock gene evolution: seasonal timing, phylogenetic signal, or functional constraint?

    PubMed

    Krabbenhoft, Trevor J; Turner, Thomas F

    2014-01-01

    Genetic determinants of seasonal reproduction are not fully understood but may be important predictors of organism responses to climate change. We used a comparative approach to study the evolution of seasonal timing within a fish community in a natural common garden setting. We tested the hypothesis that allelic length variation in the PolyQ domain of a circadian rhythm gene, Clock1a, corresponded to interspecific differences in seasonal reproductive timing across 5 native and 1 introduced cyprinid fishes (n = 425 individuals) that co-occur in the Rio Grande, NM, USA. Most common allele lengths were longer in native species that initiated reproduction earlier (Spearman's r = -0.70, P = 0.23). Clock1a allele length exhibited strong phylogenetic signal and earlier spawners were evolutionarily derived. Aside from length variation in Clock1a, all other amino acids were identical across native species, suggesting functional constraint over evolutionary time. Interestingly, the endangered Rio Grande silvery minnow (Hybognathus amarus) exhibited less allelic variation in Clock1a and observed heterozygosity was 2- to 6-fold lower than the 5 other (nonimperiled) species. Reduced genetic variation in this functionally important gene may impede this species' capacity to respond to ongoing environmental change.

  12. Circadian and ultradian rhythms of clock gene expression in the suprachiasmatic nucleus of freely moving mice

    PubMed Central

    Ono, Daisuke; Honma, Ken-ichi; Honma, Sato

    2015-01-01

    In mammals, the temporal order of physiology and behavior is primarily regulated by the circadian pacemaker located in the hypothalamic suprachiasmatic nucleus (SCN). Rhythms are generated in cells by an auto-regulatory transcription/translation feedback loop, composed of several clock genes and their protein products. Taking advantage of bioluminescence reporters, we have succeeded in continuously monitoring the expression of clock gene reporters Per1-luc, PER2::LUC and Bmal1-ELuc in the SCN of freely moving mice for up to 3 weeks in constant darkness. Bioluminescence emitted from the SCN was collected with an implanted plastic optical fiber which was connected to a cooled photomultiplier tube. We found robust circadian rhythms in the clock gene expression, the phase-relation of which were the same as those observed ex vivo. The circadian rhythms were superimposed by episodic bursts which had ultradian periods of approximately 3.0 h. Episodic bursts often accompanied activity bouts, but stoichiometric as well as temporal analyses revealed no causality between them. Clock gene expression in the SCN in vivo is regulated by the circadian pacemaker and ultradian rhythms of unknown origin. PMID:26194231

  13. Circadian and ultradian rhythms of clock gene expression in the suprachiasmatic nucleus of freely moving mice.

    PubMed

    Ono, Daisuke; Honma, Ken-ichi; Honma, Sato

    2015-07-21

    In mammals, the temporal order of physiology and behavior is primarily regulated by the circadian pacemaker located in the hypothalamic suprachiasmatic nucleus (SCN). Rhythms are generated in cells by an auto-regulatory transcription/translation feedback loop, composed of several clock genes and their protein products. Taking advantage of bioluminescence reporters, we have succeeded in continuously monitoring the expression of clock gene reporters Per1-luc, PER2::LUC and Bmal1-ELuc in the SCN of freely moving mice for up to 3 weeks in constant darkness. Bioluminescence emitted from the SCN was collected with an implanted plastic optical fiber which was connected to a cooled photomultiplier tube. We found robust circadian rhythms in the clock gene expression, the phase-relation of which were the same as those observed ex vivo. The circadian rhythms were superimposed by episodic bursts which had ultradian periods of approximately 3.0 h. Episodic bursts often accompanied activity bouts, but stoichiometric as well as temporal analyses revealed no causality between them. Clock gene expression in the SCN in vivo is regulated by the circadian pacemaker and ultradian rhythms of unknown origin.

  14. Clock-associated genes in Arabidopsis: a family affair.

    PubMed Central

    Somers, D E

    2001-01-01

    The identification of components of the plant circadian clock has been advanced recently with the success of two forward genetics approaches. The ZEITLUPE and TOC1 loci were cloned and each was found to be part of two separate, larger gene families with intriguing domain structures. The ZTL family of proteins contains a subclass of the PAS domain coupled to an F box and kelch motifs, suggesting that they play a role in a novel light-regulated ubiquitination mechanism. TOC1 shares similarity to the receiver domain of the well-known two-component phosphorelay signalling systems, combined with a strong similarity to a region of the CONSTANS transcription factor, which is involved in controlling flowering time. When added to the repertoire of previously identified clock-associated genes, it is clear that both similarities and differences with other circadian systems will emerge in the coming years. PMID:11710981

  15. Functional circadian clock genes are essential for the overwintering diapause of the Northern house mosquito, Culex pipiens

    PubMed Central

    Meuti, Megan E.; Stone, Mary; Ikeno, Tomoko; Denlinger, David L.

    2015-01-01

    The short day lengths of late summer are used to program the overwintering adult diapause (dormancy) of the Northern house mosquito, Culex pipiens. Here, we investigated the role of clock genes in initiating this diapause and asked whether the circadian cycling of clock gene expression persists during diapause. We provide evidence that the major circadian clock genes continue to cycle throughout diapause and after diapause has been terminated. RNA interference (RNAi) was used to knock down the core circadian clock genes and to then assess the impact of the various clock genes on the ability of females to enter diapause. RNAi directed against negative circadian regulators (period, timeless and cryptochrome2) caused females that were reared under diapause-inducing, short day conditions to avert diapause. In contrast, knocking down the circadian-associated gene pigment dispersing factor caused females that were reared under diapause-averting, long day conditions to enter a diapause-like state. Our results implicate the circadian clock in the initiation of diapause in C. pipiens. PMID:25653422

  16. Acute melatonin treatment alters dendritic morphology and circadian clock gene expression in the hippocampus of Siberian hamsters.

    PubMed

    Ikeno, Tomoko; Nelson, Randy J

    2015-02-01

    In the hippocampus of Siberian hamsters, dendritic length and dendritic complexity increase in the CA1 region whereas dendritic spine density decreases in the dentate gyrus region at night. However, the underlying mechanism of the diurnal rhythmicity in hippocampal neuronal remodeling is unknown. In mammals, most daily rhythms in physiology and behaviors are regulated by a network of circadian clocks. The central clock, located in the hypothalamus, controls melatonin secretion at night and melatonin modifies peripheral clocks by altering expression of circadian clock genes. In this study, we examined the effects of acute melatonin treatment on the circadian clock system as well as on morphological changes of hippocampal neurons. Male Siberian hamsters were injected with melatonin in the afternoon; 4 h later, mRNA levels of hypothalamic and hippocampal circadian clock genes and hippocampal neuron dendritic morphology were assessed. In the hypothalamus, melatonin treatment did not alter Period1 and Bmal1 expression. However, melatonin treatment increased both Period1 and Bmal1 expression in the hippocampus, suggesting that melatonin affected molecular oscillations in the hippocampus. Melatonin treatment also induced rapid remodeling of hippocampal neurons; melatonin increased apical dendritic length and dendritic complexity in the CA1 region and reduced the dendritic spine density in the dentate gyrus region. These data suggest that structural changes in hippocampal neurons are regulated by a circadian clock and that melatonin functions as a nighttime signal to coordinate the diurnal rhythm in neuronal remodeling.

  17. Codon usage affects the structure and function of the Drosophila circadian clock protein PERIOD

    PubMed Central

    Fu, Jingjing; Murphy, Katherine A.; Zhou, Mian; Li, Ying H.; Lam, Vu H.; Tabuloc, Christine A.; Chiu, Joanna C.; Liu, Yi

    2016-01-01

    Codon usage bias is a universal feature of all genomes, but its in vivo biological functions in animal systems are not clear. To investigate the in vivo role of codon usage in animals, we took advantage of the sensitivity and robustness of the Drosophila circadian system. By codon-optimizing parts of Drosophila period (dper), a core clock gene that encodes a critical component of the circadian oscillator, we showed that dper codon usage is important for circadian clock function. Codon optimization of dper resulted in conformational changes of the dPER protein, altered dPER phosphorylation profile and stability, and impaired dPER function in the circadian negative feedback loop, which manifests into changes in molecular rhythmicity and abnormal circadian behavioral output. This study provides an in vivo example that demonstrates the role of codon usage in determining protein structure and function in an animal system. These results suggest a universal mechanism in eukaryotes that uses a codon usage “code” within genetic codons to regulate cotranslational protein folding. PMID:27542830

  18. Orexin signaling regulates both the hippocampal clock and the circadian oscillation of Alzheimer’s disease-risk genes

    PubMed Central

    Ma, Zhixiong; Jiang, Weiliang; Zhang, Eric Erquan

    2016-01-01

    Alzheimer’s disease (AD) is a circadian clock-related disease. However, it is not very clear whether pre-symptomatic AD leads to circadian disruption or whether malfunction of circadian rhythms exerts influence on development of AD. Here, we report a functional clock that exists in the hippocampus. This oscillator both receives input signals and maintains the cycling of the hippocampal Per2 gene. One of the potential inputs to the oscillator is orexin signaling, which can shorten the hippocampal clock period and thereby regulate the expression of clock-controlled-genes (CCGs). A 24-h time course qPCR analysis followed by a JTK_CYCLE algorithm analysis indicated that a number of AD-risk genes are potential CCGs in the hippocampus. Specifically, we found that Bace1 and Bace2, which are related to the production of the amyloid-beta peptide, are CCGs. BACE1 is inhibited by E4BP4, a repressor of D-box genes, while BACE2 is activated by CLOCK:BMAL1. Finally, we observed alterations in the rhythmic expression patterns of Bace2 and ApoE in the hippocampus of aged APP/PS1dE9 mice. Our results therefore indicate that there is a circadian oscillator in the hippocampus whose oscillation could be regulated by orexins. Hence, orexin signaling regulates both the hippocampal clock and the circadian oscillation of AD-risk genes. PMID:27796320

  19. Orexin signaling regulates both the hippocampal clock and the circadian oscillation of Alzheimer's disease-risk genes.

    PubMed

    Ma, Zhixiong; Jiang, Weiliang; Zhang, Eric Erquan

    2016-10-31

    Alzheimer's disease (AD) is a circadian clock-related disease. However, it is not very clear whether pre-symptomatic AD leads to circadian disruption or whether malfunction of circadian rhythms exerts influence on development of AD. Here, we report a functional clock that exists in the hippocampus. This oscillator both receives input signals and maintains the cycling of the hippocampal Per2 gene. One of the potential inputs to the oscillator is orexin signaling, which can shorten the hippocampal clock period and thereby regulate the expression of clock-controlled-genes (CCGs). A 24-h time course qPCR analysis followed by a JTK_CYCLE algorithm analysis indicated that a number of AD-risk genes are potential CCGs in the hippocampus. Specifically, we found that Bace1 and Bace2, which are related to the production of the amyloid-beta peptide, are CCGs. BACE1 is inhibited by E4BP4, a repressor of D-box genes, while BACE2 is activated by CLOCK:BMAL1. Finally, we observed alterations in the rhythmic expression patterns of Bace2 and ApoE in the hippocampus of aged APP/PS1dE9 mice. Our results therefore indicate that there is a circadian oscillator in the hippocampus whose oscillation could be regulated by orexins. Hence, orexin signaling regulates both the hippocampal clock and the circadian oscillation of AD-risk genes.

  20. Deletion of Rictor in brain and fat alters peripheral clock gene expression and increases blood pressure.

    PubMed

    Drägert, Katja; Bhattacharya, Indranil; Pellegrini, Giovanni; Seebeck, Petra; Azzi, Abdelhalim; Brown, Steven A; Georgiopoulou, Stavroula; Held, Ulrike; Blyszczuk, Przemyslaw; Arras, Margarete; Humar, Rok; Hall, Michael N; Battegay, Edouard; Haas, Elvira

    2015-08-01

    The mammalian target of rapamycin complex 2 (mTORC2) contains the essential protein RICTOR and is activated by growth factors. mTORC2 in adipose tissue contributes to the regulation of glucose and lipid metabolism. In the perivascular adipose tissue, mTORC2 ensures normal vascular reactivity by controlling expression of inflammatory molecules. To assess whether RICTOR/mTORC2 contributes to blood pressure regulation, we applied a radiotelemetry approach in control and Rictor knockout (Rictor(aP2KO)) mice generated using adipocyte protein-2 gene promoter-driven CRE recombinase expression to delete Rictor. The 24-hour mean arterial pressure was increased in Rictor(aP2KO) mice, and the physiological decline in mean arterial pressure during the dark period was impaired. In parallel, heart rate and locomotor activity were elevated during the dark period with a pattern similar to blood pressure changes. This phenotype was associated with mild cardiomyocyte hypertrophy, decreased cardiac natriuretic peptides, and their receptor expression in adipocytes. Moreover, clock gene expression was reduced or phase-shifted in perivascular adipose tissue. No differences in clock gene expression were observed in the master clock suprachiasmatic nucleus, although Rictor gene expression was also lower in brain of Rictor(aP2KO) mice. Thus, this study highlights the importance of RICTOR/mTORC2 for interactions between vasculature, adipocytes, and brain to tune physiological outcomes, such as blood pressure and locomotor activity.

  1. Regulation of intestinal lipid absorption by clock genes.

    PubMed

    Hussain, M Mahmood

    2014-01-01

    Plasma levels of triacylglycerols and diacylglycerols, the lipoproteins that transport them, and proteins involved in their absorption from the intestinal lumen fluctuate in a circadian manner. These changes are likely controlled by clock genes expressed in the intestine that are probably synchronized by neuronal and humoral signals from the suprachiasmatic nuclei, which constitute a master clock entrained by light signals from the eyes and from the environment, e.g., food availability. Acute changes in circadian rhythms--e.g., due to nonsynchronous work schedules or a transcontinental flight--may trigger intestinal discomfort. Chronic disruptions in circadian control mechanisms may predispose the individual to irritable bowel syndrome, gastroesophageal reflux disease, and peptic ulcer disease. A more detailed understanding of the molecular mechanisms underlying temporal changes in intestinal activity might allow us to identify novel targets for developing therapeutic approaches to these disorders.

  2. Low Variation in the Polymorphic Clock Gene Poly-Q Region Despite Population Genetic Structure across Barn Swallow (Hirundo rustica) Populations

    PubMed Central

    Dor, Roi; Lovette, Irby J.; Safran, Rebecca J.; Billerman, Shawn M.; Huber, Gernot H.; Vortman, Yoni; Lotem, Arnon; McGowan, Andrew; Evans, Matthew R.; Cooper, Caren B.; Winkler, David W.

    2011-01-01

    Recent studies of several species have reported a latitudinal cline in the circadian clock gene, Clock, which influences rhythms in both physiology and behavior. Latitudinal variation in this gene may hence reflect local adaptation to seasonal variation. In some bird populations, there is also an among-individual association between Clock poly-Q genotype and clutch initiation date and incubation period. We examined Clock poly-Q allele variation in the Barn Swallow (Hirundo rustica), a species with a cosmopolitan geographic distribution and considerable variation in life-history traits that may be influenced by the circadian clock. We genotyped Barn Swallows from five populations (from three subspecies) and compared variation at the Clock locus to that at microsatellite loci and mitochondrial DNA (mtDNA). We found very low variation in the Clock poly-Q region, as >96% of individuals were homozygous, and the two other alleles at this locus were globally rare. Genetic differentiation based on the Clock poly-Q locus was not correlated with genetic differentiation based on either microsatellite loci or mtDNA sequences. Our results show that high diversity in Clock poly-Q is not general across avian species. The low Clock variation in the background of heterogeneity in microsatellite and mtDNA loci in Barn Swallows may be an outcome of stabilizing selection on the Clock locus. PMID:22216124

  3. period-1 encodes an ATP-dependent RNA helicase that influences nutritional compensation of the Neurospora circadian clock

    SciTech Connect

    Emerson, Jillian M.; Bartholomai, Bradley M.; Ringelberg, Carol; Baker, Scott E.; Loros, Jennifer J.; Dunlap, Jay C.

    2015-12-22

    Mutants in the period-1 (prd-1) gene, characterized by a recessive allele, display a reduced growth rate and period lengthening of the developmental cycle controlled by the circadian clock. We refined the genetic location of prd-1 and used whole genome sequencing to find the mutation defining it, confirming the identity of prd-1 by rescuing the mutant circadian phenotype via transformation. PRD-1 is an RNA helicase whose orthologs, DDX5 and DDX17 in humans and Dbp2p in yeast, are implicated in various processes including transcriptional regulation, elongation, and termination, 23 ribosome biogenesis, and RNA decay. Although prdi-1smutantssiois an ATP-dependent RNA helicase, member of a sub-family display a long period (~25 hrs) circadian developmental cycle, they interestingly display a wild type period when the core circadian oscillator is tracked using a frq-luciferase transcriptional fusion under conditions of limiting nutritional carbon; the core oscillator runs with a long period under glucose-sufficient conditions. Thus PRD-1 clearly impacts the circadian oscillator and is not only part of a metabolic oscillator ancillary to the core clock. PRD-1 is an essential protein and its expression is neither light-regulated nor clock-regulated. However, it is transiently induced by glucose; in the presence of sufficient glucose PRD-1 is in the nucleus until glucose runs out which elicits its disappearance from the nucleus. Because circadian period length is carbon concentration-dependent, prd­-1 may be formally viewed as clock mutant with defective nutritional compensation of circadian period length.

  4. Reciprocity Between Robustness of Period and Plasticity of Phase in Biological Clocks

    NASA Astrophysics Data System (ADS)

    Hatakeyama, Tetsuhiro S.; Kaneko, Kunihiko

    2015-11-01

    Circadian clocks exhibit the robustness of period and plasticity of phase against environmental changes such as temperature and nutrient conditions. Thus far, however, it is unclear how both are simultaneously achieved. By investigating distinct models of circadian clocks, we demonstrate reciprocity between robustness and plasticity: higher robustness in the period implies higher plasticity in the phase, where changes in period and in phase follow a linear relationship with a negative coefficient. The robustness of period is achieved by the adaptation on the limit cycle via a concentration change of a buffer molecule, whose temporal change leads to a phase shift following a shift of the limit-cycle orbit in phase space. Generality of reciprocity in clocks with the adaptation mechanism is confirmed with theoretical analysis of simple models, while biological significance is discussed.

  5. Reciprocity Between Robustness of Period and Plasticity of Phase in Biological Clocks.

    PubMed

    Hatakeyama, Tetsuhiro S; Kaneko, Kunihiko

    2015-11-20

    Circadian clocks exhibit the robustness of period and plasticity of phase against environmental changes such as temperature and nutrient conditions. Thus far, however, it is unclear how both are simultaneously achieved. By investigating distinct models of circadian clocks, we demonstrate reciprocity between robustness and plasticity: higher robustness in the period implies higher plasticity in the phase, where changes in period and in phase follow a linear relationship with a negative coefficient. The robustness of period is achieved by the adaptation on the limit cycle via a concentration change of a buffer molecule, whose temporal change leads to a phase shift following a shift of the limit-cycle orbit in phase space. Generality of reciprocity in clocks with the adaptation mechanism is confirmed with theoretical analysis of simple models, while biological significance is discussed.

  6. EGR1 regulates hepatic clock gene amplitude by activating Per1 transcription

    PubMed Central

    Tao, Weiwei; Wu, Jing; Zhang, Qian; Lai, Shan-Shan; Jiang, Shan; Jiang, Chen; Xu, Ying; Xue, Bin; Du, Jie; Li, Chao-Jun

    2015-01-01

    The mammalian clock system is composed of a master clock and peripheral clocks. At the molecular level, the rhythm-generating mechanism is controlled by a molecular clock composed of positive and negative feedback loops. However, the underlying mechanisms for molecular clock regulation that affect circadian clock function remain unclear. Here, we show that Egr1 (early growth response 1), an early growth response gene, is expressed in mouse liver in a circadian manner. Consistently, Egr1 is transactivated by the CLOCK/BMAL1 heterodimer through a conserved E-box response element. In hepatocytes, EGR1 regulates the transcription of several core clock genes, including Bmal1, Per1, Per2, Rev-erbα and Rev-erbβ, and the rhythm amplitude of their expression is dependent on EGR1’s transcriptional function. Further mechanistic studies indicated that EGR1 binds to the proximal region of the Per1 promoter to activate its transcription directly. When the peripheral clock is altered by light or feeding behavior transposition in Egr1-deficient mice, the expression phase of hepatic clock genes shifts normally, but the amplitude is also altered. Our data reveal a critical role for EGR1 in the regulation of hepatic clock circuitry, which may contribute to the rhythm stability of peripheral clock oscillators. PMID:26471974

  7. The circadian clock component PERIOD2: from molecular to cerebral functions.

    PubMed

    Ripperger, Jürgen A; Albrecht, Urs

    2012-01-01

    The circadian clock is based on a molecular oscillator, which simulates the external day within nearly all of a body's cells. This "internalized" day then defines activity and rest phases for the cells and the organism by generating precise rhythms in the metabolism, physiology, and behavior. In its perfect state, this timing system allows for the synchronization of an organism to its environment and this may optimize energy handling and responses to daily recurring challenges. However, nowadays, we believe that desynchronization of an organism due to its lifestyle or problems with its circadian clock not only causes discomfort but also may aggravate conditions such as depression, metabolic syndrome, addiction, or cancer. In this review, we focus on one simple cogwheel of the mammalian circadian clock, the PERIOD2 (PER2) protein. Originally identified as an integral part of the molecular mechanism that yields overt rhythms of about 24h, more recently multiple other functions have been identified. In essence, the PER proteins, in addition to their important function within the molecular oscillator, can be seen not only as integrators on the input side of the circadian clock but also as mediators of clock output. This diversity in their function is possible, because the PER proteins can interact with a multitude of other proteins transferring oscillator timing information to the latter. In this fashion, the circadian clock synchronizes many rhythmic processes.

  8. Differential maturation of rhythmic clock gene expression during early development in medaka (Oryzias latipes).

    PubMed

    Cuesta, Ines H; Lahiri, Kajori; Lopez-Olmeda, Jose Fernando; Loosli, Felix; Foulkes, Nicholas S; Vallone, Daniela

    2014-05-01

    One key challenge for the field of chronobiology is to identify how circadian clock function emerges during early embryonic development. Teleosts such as the zebrafish are ideal models for studying circadian clock ontogeny since the entire process of development occurs ex utero in an optically transparent chorion. Medaka (Oryzias latipes) represents another powerful fish model for exploring early clock function with, like the zebrafish, many tools available for detailed genetic analysis. However, to date there have been no reports documenting circadian clock gene expression during medaka development. Here we have characterized the expression of key clock genes in various developmental stages and in adult tissues of medaka. As previously reported for other fish, light dark cycles are required for the emergence of clock gene expression rhythms in this species. While rhythmic expression of per and cry genes is detected very early during development and seems to be light driven, rhythmic clock and bmal expression appears much later around hatching time. Furthermore, the maturation of clock function seems to correlate with the appearance of rhythmic expression of these positive elements of the clock feedback loop. By accelerating development through elevated temperatures or by artificially removing the chorion, we show an earlier onset of rhythmicity in clock and bmal expression. Thus, differential maturation of key elements of the medaka clock mechanism depends on the developmental stage and the presence of the chorion.

  9. Analysis of clock gene-miRNA correlation networks reveals candidate drivers in colorectal cancer

    PubMed Central

    Mazzoccoli, Gianluigi; Colangelo, Tommaso; Panza, Anna; Rubino, Rosa; Tiberio, Cristiana; Palumbo, Orazio; Carella, Massimo; Trombetta, Domenico; Gentile, Annamaria; Tavano, Francesca; Valvano, Maria Rosa; Storlazzi, Clelia Tiziana; Macchia, Gemma; De Cata, Angelo; Bisceglia, Giovanni; Capocefalo, Daniele; Colantuoni, Vittorio; Sabatino, Lina; Piepoli, Ada; Mazza, Tommaso

    2016-01-01

    Altered functioning of the biological clock is involved in cancer onset and progression. MicroRNAs (miRNAs) interact with the clock genes modulating the function of genetically encoded molecular clockworks. Collaborative interactions may take place within the coding-noncoding RNA regulatory networks. We aimed to evaluate the cross-talk among miRNAs and clock genes in colorectal cancer (CRC). We performed an integrative analysis of miRNA-miRNA and miRNA-mRNA interactions on high-throughput molecular profiling of matched human CRC tissue and non-tumor mucosa, pinpointing core clock genes and their targeting miRNAs. Data obtained in silico were validated in CRC patients and human colon cancer cell lines. In silico we found severe alterations of clock gene–related coding-noncoding RNA regulatory networks in tumor tissues, which were later corroborated by the analysis of human CRC specimens and experiments performed in vitro. In conclusion, specific miRNAs target and regulate the transcription/translation of clock genes and clock gene-related miRNA-miRNA as well as mRNA-miRNA interactions are altered in colorectal cancer. Exploration of the interplay between specific miRNAs and genes, which are critically involved in the functioning of the biological clock, provides a better understanding of the importance of the miRNA-clock genes axis and its derangement in colorectal cancer. PMID:27323779

  10. Mutation at the circadian clock gene EARLY MATURITY 8 adapts domesticated barley (Hordeum vulgare) to short growing seasons.

    PubMed

    Faure, Sebastien; Turner, Adrian S; Gruszka, Damian; Christodoulou, Vangelis; Davis, Seth J; von Korff, Maria; Laurie, David A

    2012-05-22

    The circadian clock is an autonomous oscillator that produces endogenous biological rhythms with a period of about 24 h. This clock allows organisms to coordinate their metabolism and development with predicted daily and seasonal changes of the environment. In plants, circadian rhythms contribute to both evolutionary fitness and agricultural productivity. Nevertheless, we show that commercial barley varieties bred for short growing seasons by use of early maturity 8 (eam8) mutations, also termed mat-a, are severely compromised in clock gene expression and clock outputs. We identified EAM8 as a barley ortholog of the Arabidopsis thaliana circadian clock regulator EARLY FLOWERING3 (ELF3) and demonstrate that eam8 accelerates the transition from vegetative to reproductive growth and inflorescence development. We propose that eam8 was selected as barley cultivation moved to high-latitude short-season environments in Europe because it allowed rapid flowering in genetic backgrounds that contained a previously selected late-flowering mutation of the photoperiod response gene Ppd-H1. We show that eam8 mutants have increased expression of the floral activator HvFT1, which is independent of allelic variation at Ppd-H1. The selection of independent eam8 mutations shows that this strategy facilitates short growth-season adaptation and expansion of the geographic range of barley, despite the pronounced clock defect.

  11. The circadian clock-associated gene zea mays gigantea1 affects maize developmental transitions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The circadian clock is the internal timing mechanism that allows plants to make developmental decisions in accordance with environmental conditions. The genes of the maize circadian clock are not well defined. Gigantea (gi) genes are conserved across flowering plants, including maize. In model plant...

  12. Catabolic cytokines disrupt the circadian clock and the expression of clock-controlled genes in cartilage via an NFкB-dependent pathway

    PubMed Central

    Guo, B.; Yang, N.; Borysiewicz, E.; Dudek, M.; Williams, J.L.; Li, J.; Maywood, E.S.; Adamson, A.; Hastings, M.H.; Bateman, J.F.; White, M.R.H.; Boot-Handford, R.P.; Meng, Q.J.

    2015-01-01

    Summary Objective To define how the catabolic cytokines (Interleukin 1 (IL-1) and tumor necrosis factor alpha (TNFα)) affect the circadian clock mechanism and the expression of clock-controlled catabolic genes within cartilage, and to identify the downstream pathways linking the cytokines to the molecular clock within chondrocytes. Methods Ex vivo cartilage explants were isolated from the Cry1-luc or PER2::LUC clock reporter mice. Clock gene dynamics were monitored in real-time by bioluminescence photon counting. Gene expression changes were studied by qRT-PCR. Functional luc assays were used to study the function of the core Clock/BMAL1 complex in SW-1353 cells. NFкB pathway inhibitor and fluorescence live-imaging of cartilage were performed to study the underlying mechanisms. Results Exposure to IL-1β severely disrupted circadian gene expression rhythms in cartilage. This effect was reversed by an anti-inflammatory drug dexamethasone, but not by other clock synchronizing agents. Circadian disruption mediated by IL-1β was accompanied by disregulated expression of endogenous clock genes and clock-controlled catabolic pathways. Mechanistically, NFкB signalling was involved in the effect of IL-1β on the cartilage clock in part through functional interference with the core Clock/BMAL1 complex. In contrast, TNFα had little impact on the circadian rhythm and clock gene expression in cartilage. Conclusion In our experimental system (young healthy mouse cartilage), we demonstrate that IL-1β (but not TNFα) abolishes circadian rhythms in Cry1-luc and PER2::LUC gene expression. These data implicate disruption of the chondrocyte clock as a novel aspect of the catabolic responses of cartilage to pro-inflammatory cytokines, and provide an additional mechanism for how chronic joint inflammation may contribute to osteoarthritis (OA). PMID:26521744

  13. Common features in diverse insect clocks.

    PubMed

    Numata, Hideharu; Miyazaki, Yosuke; Ikeno, Tomoko

    2015-01-01

    This review describes common features among diverse biological clocks in insects, including circadian, circatidal, circalunar/circasemilunar, and circannual clocks. These clocks control various behaviors, physiological functions, and developmental events, enabling adaptation to periodic environmental changes. Circadian clocks also function in time-compensation for celestial navigation and in the measurement of day or night length for photoperiodism. Phase response curves for such clocks reported thus far exhibit close similarities; specifically, the circannual clock in Anthrenus verbasci shows striking similarity to circadian clocks in its phase response. It is suggested that diverse biological clocks share physiological properties in their phase responses irrespective of period length. Molecular and physiological mechanisms are best understood for the optic-lobe and mid-brain circadian clocks, although there is no direct evidence that these clocks are involved in rhythmic phenomena other than circadian rhythms in daily events. Circadian clocks have also been localized in peripheral tissues, and research on their role in various rhythmic phenomena has been started. Although clock genes have been identified as controllers of circadian rhythms in daily events, some of these genes have also been shown to be involved in photoperiodism and possibly in time-compensated celestial navigation. In contrast, there is no experimental evidence indicating that any known clock gene is involved in biological clocks other than circadian clocks.

  14. Natural selection against a circadian clock gene mutation in mice

    PubMed Central

    Spoelstra, Kamiel; Wikelski, Martin; Daan, Serge; Loudon, Andrew S. I.; Hau, Michaela

    2016-01-01

    Circadian rhythms with an endogenous period close to or equal to the natural light–dark cycle are considered evolutionarily adaptive (“circadian resonance hypothesis”). Despite remarkable insight into the molecular mechanisms driving circadian cycles, this hypothesis has not been tested under natural conditions for any eukaryotic organism. We tested this hypothesis in mice bearing a short-period mutation in the enzyme casein kinase 1ε (tau mutation), which accelerates free-running circadian cycles. We compared daily activity (feeding) rhythms, survivorship, and reproduction in six replicate populations in outdoor experimental enclosures, established with wild-type, heterozygous, and homozygous mice in a Mendelian ratio. In the release cohort, survival was reduced in the homozygote mutant mice, revealing strong selection against short-period genotypes. Over the course of 14 mo, the relative frequency of the tau allele dropped from initial parity to 20%. Adult survival and recruitment of juveniles into the population contributed approximately equally to the selection for wild-type alleles. The expression of activity during daytime varied throughout the experiment and was significantly increased by the tau mutation. The strong selection against the short-period tau allele observed here contrasts with earlier studies showing absence of selection against a Period 2 (Per2) mutation, which disrupts internal clock function, but does not change period length. These findings are consistent with, and predicted by the theory that resonance of the circadian system plays an important role in individual fitness. PMID:26715747

  15. Natural selection against a circadian clock gene mutation in mice.

    PubMed

    Spoelstra, Kamiel; Wikelski, Martin; Daan, Serge; Loudon, Andrew S I; Hau, Michaela

    2016-01-19

    Circadian rhythms with an endogenous period close to or equal to the natural light-dark cycle are considered evolutionarily adaptive ("circadian resonance hypothesis"). Despite remarkable insight into the molecular mechanisms driving circadian cycles, this hypothesis has not been tested under natural conditions for any eukaryotic organism. We tested this hypothesis in mice bearing a short-period mutation in the enzyme casein kinase 1ε (tau mutation), which accelerates free-running circadian cycles. We compared daily activity (feeding) rhythms, survivorship, and reproduction in six replicate populations in outdoor experimental enclosures, established with wild-type, heterozygous, and homozygous mice in a Mendelian ratio. In the release cohort, survival was reduced in the homozygote mutant mice, revealing strong selection against short-period genotypes. Over the course of 14 mo, the relative frequency of the tau allele dropped from initial parity to 20%. Adult survival and recruitment of juveniles into the population contributed approximately equally to the selection for wild-type alleles. The expression of activity during daytime varied throughout the experiment and was significantly increased by the tau mutation. The strong selection against the short-period tau allele observed here contrasts with earlier studies showing absence of selection against a Period 2 (Per2) mutation, which disrupts internal clock function, but does not change period length. These findings are consistent with, and predicted by the theory that resonance of the circadian system plays an important role in individual fitness.

  16. Transcriptome survey of phototransduction and clock genes in marine bivalves.

    PubMed

    Sun, X J; Zhou, L Q; Tian, J T; Liu, Z H; Wu, B; Dong, Y H; Yang, A G; Ma, W M

    2016-10-24

    Marine animals exhibit a variety of biological rhythms, such as solar and lunar-related cycles; however, our current molecular understanding of biological rhythms in marine animals is quite limited. Identifying and understanding the expression patterns of clock genes from available transcriptomes will help elucidate biological rhythms in marine species. Here, we perform a comprehensive survey of phototransduction and circadian genes using the mantle transcriptome of the scallop Patinopecten yessoensis and compare the results with those from three other bivalves. The comparison reveals the presence of transcripts for most of the core members of the phototransduction and circadian networks seen in terrestrial model species in the four marine bivalves. Matches were found for all 37 queried genes, and the expressed transcripts from the deep sequencing data matched 8 key insect and mammalian circadian genes. This demonstrates the high level of conservation of the timekeeping mechanism from terrestrial species to marine bivalves. The results provide a valuable gene resource for studies of "marine rhythms" and also further our understanding of the diversification and evolution of rhythms in marine species.

  17. Effects of age on clock gene expression in the rhesus macaque pituitary gland

    PubMed Central

    Sitzmann, Brandon D.; Lemos, Dario R.; Ottinger, Mary Ann; Urbanski, Henryk F.

    2009-01-01

    Recent studies have shown that circadian clock genes are expressed in various peripheral tissues, raising the possibility that multiple clocks regulate circadian physiology. To study clock gene expression in the rhesus macaque pituitary gland we used gene microarray data and found that the pituitary glands of young and old adult males express several components of the circadian clock (Per1, Per2, Cry1, Bmal1, Clock, Rev-erbα and Csnk1ε). Semi-quantitative reverse-transcription polymerase chain reaction (sqRT-PCR) confirmed the presence of these core-clock genes and detected significant age-related differences in expression of Per2. sqRT-PCR also showed differential expression of core-clock genes at two opposing time-points over the 24 hour day, with greater expression of Per2 and Bmal1 (P<0.05) at 1300 h as compared to 0100 h. Immunohistochemistry revealed rhythmic expression of REV-ERBα in the pituitary glands of female macaques. These data provide evidence that the rhesus macaque pituitary gland expresses core-clock genes and their associated protein products in a 24-hour rhythmic pattern, and that their expression is moderately impacted by aging processes. PMID:18614257

  18. Molecular clock of HIV-1 envelope genes under early immune selection

    DOE PAGES

    Park, Sung Yong; Love, Tanzy M. T.; Perelson, Alan S.; ...

    2016-06-01

    Here, the molecular clock hypothesis that genes or proteins evolve at a constant rate is a key tool to reveal phylogenetic relationships among species. Using the molecular clock, we can trace an infection back to transmission using HIV-1 sequences from a single time point. Whether or not a strict molecular clock applies to HIV-1’s early evolution in the presence of immune selection has not yet been fully examined.

  19. Identification, Characterization, and Diel Pattern of Expression of Canonical Clock Genes in Nephrops norvegicus (Crustacea: Decapoda) Eyestalk

    PubMed Central

    Sbragaglia, Valerio; Lamanna, Francesco; M. Mat, Audrey; Rotllant, Guiomar; Joly, Silvia; Ketmaier, Valerio; de la Iglesia, Horacio O.; Aguzzi, Jacopo

    2015-01-01

    The Norway lobster, Nephrops norvegicus, is a burrowing decapod with a rhythmic burrow emergence (24 h) governed by the circadian system. It is an important resource for European fisheries and its behavior deeply affects its availability. The current knowledge of Nephrops circadian biology is phenomenological as it is currently the case for almost all crustaceans. In attempt to elucidate the putative molecular mechanisms underlying circadian gene regulation in Nephrops, we used a transcriptomics approach on cDNA extracted from the eyestalk, a structure playing a crucial role in controlling behavior of decapods. We studied 14 male lobsters under 12–12 light-darkness blue light cycle. We used the Hiseq 2000 Illumina platform to sequence two eyestalk libraries (under light and darkness conditions) obtaining about 90 millions 100-bp paired-end reads. Trinity was used for the de novo reconstruction of transcriptomes; the size at which half of all assembled bases reside in contigs (N50) was equal to 1796 (light) and 2055 (darkness). We found a list of candidate clock genes and focused our attention on canonical ones: timeless, period, clock and bmal1. The cloning of assembled fragments validated Trinity outputs. The putative Nephrops clock genes showed high levels of identity (blastx on NCBI) with known crustacean clock gene homologs such as Eurydice pulchra (period: 47%, timeless: 59%, bmal1: 79%) and Macrobrachium rosenbergii (clock: 100%). We also found a vertebrate-like cryptochrome 2. RT-qPCR showed that only timeless had a robust diel pattern of expression. Our data are in accordance with the current knowledge of the crustacean circadian clock, reinforcing the idea that the molecular clockwork of this group shows some differences with the established model in Drosophila melanogaster. PMID:26524198

  20. Accurate Clock Period Comparison for PLL Using Phase-Shift Direction Detector

    NASA Astrophysics Data System (ADS)

    Makihara, Yukinobu; Ikebe, Masayuki; Motohisa, Junichi; Sano, Eiichi

    We proposed a new architecture for a phase-locked loop (PLL) obtained by comparing clock periods. We evaluated the use of a clock-period comparator (CPC) for the digitally controlled PLL we propose, where only the frequency should be locked. However, frequency control with the CPC resulted in the phase being locked. Thus, phase-lock operation was also achieved. The theoretical analysis of the phase-lock mechanism was confirmed through system simulations. We discussed about dead-zone problem caused by a time delay of circuits. We evaluated phase-shift direction detector to solve the dead zone problem. We designed the element blocks of the new PLL using a 0.25-μm CMOS process. We confirmed phase-lock operation through SPICE simulations of the MOSFET level. Moreover, we manufactured a trial circuit for the new PLL. We also confirmed phase-lock operation in the proposed PLL through measurements.

  1. The influence of GPS user clock stability during periods of degraded satellite coverage

    NASA Astrophysics Data System (ADS)

    Bowen, A. F.; Kruh, P.

    The Navstar Global Positioning System (GPS) operational orbital configuration is a constellation of 18 satellites uniformly spaced in six orbital planes inclined at 55 deg. In addition, there are three active spares to complete the constellation. This configuration will provide continuous three-dimensional coverage except for a few regions, which will experience short periods of degraded performance each day. These regions will have almost continuous coverage. Additional data, such as altitude measurements, may be used to constrain the navigation solution during periods of degradation. However, if the user set clock is very stable, additional data may not be required. This paper discusses the performance of a user set that employs only the GPS measurements, as a function of user clock stability. The results presented are based on simulation studies, employing a generic simulation of GPS user navigation software.

  2. Palmitate Inhibits SIRT1-Dependent BMAL1/CLOCK Interaction and Disrupts Circadian Gene Oscillations in Hepatocytes

    PubMed Central

    Tong, Xin; Zhang, Deqiang; Arthurs, Blake; Li, Pei; Durudogan, Leigh; Gupta, Neil; Yin, Lei

    2015-01-01

    Elevated levels of serum saturated fatty acid palmitate have been shown to promote insulin resistance, increase cellular ROS production, and trigger cell apoptosis in hepatocytes during the development of obesity. However, it remains unclear whether palmitate directly impacts the circadian clock in hepatocytes, which coordinates nutritional inputs and hormonal signaling with downstream metabolic outputs. Here we presented evidence that the molecular clock is a novel target of palmitate in hepatocytes. Palmitate exposure at low dose inhibits the molecular clock activity and suppresses the cyclic expression of circadian targets including Dbp, Nr1d1 and Per2 in hepatocytes. Palmitate treatment does not seem to alter localization or reduce protein expression of BMAL1 and CLOCK, the two core components of the molecular clock in hepatocytes. Instead, palmitate destabilizes the protein-protein interaction between BMAL1-CLOCK in a dose and time-dependent manner. Furthermore, we showed that SIRT1 activators could reverse the inhibitory action of palmitate on BMAL1-CLOCK interaction and the clock gene expression, whereas inhibitors of NAD synthesis mimic the palmitate effects on the clock function. In summary, our findings demonstrated that palmitate inhibits the clock function by suppressing SIRT1 function in hepatocytes. PMID:26075729

  3. Modulation of metabolic and clock gene mRNA rhythms by pineal and retinal circadian oscillators

    PubMed Central

    Karaganis, Stephen P.; Bartell, Paul A.; Shende, Vikram R.; Moore, Ashli F.; Cassone, Vincent M.

    2009-01-01

    Avian circadian organization involves interactions between three neural pacemakers: the suprachiasmatic nuclei (SCN), pineal, and retina. Each of these structures is linked within a neuroendocrine loop to influence downstream processes and peripheral oscillations. However, the contribution of each structure to drive or synchronize peripheral oscillators or circadian outputs in avian species is largely unknown. To explore these interactions in the chick, we measured 2-deoxy[14C]-glucose (2DG) uptake and mRNA expression of the chick clock genes bmal1, cry1, and per3 in three brain areas and in two peripheral organs in chicks that underwent pinealectomy, enucleation, or sham surgery. We found that 2DG uptake rhythms damp under constant darkness in intact animals, while clock gene mRNA levels continue to cycle, demonstrating that metabolic rhythms are not directly driven by clock gene transcription. Moreover, 2DG rhythms are not phase-locked to rhythms of clock gene mRNA. However, pinealectomy and enucleation had similar disruptive effects on both metabolic and clock gene rhythms, suggesting that both of these oscillators act similarly to reinforce molecular and physiological rhythms in the chicken. Finally, we show that the relative phasing of at least one clock gene, cry1, varies between central and peripheral oscillators in a tissue specific manner. These data point to a complex, differential orchestration of central and peripheral oscillators in the chick, and, importantly, indicate a disconnect between canonical clock gene regulation and circadian control of metabolism. PMID:19136000

  4. Circadian Rhythm Genes CLOCK and PER3 Polymorphisms and Morning Gastric Motility in Humans

    PubMed Central

    Yamaguchi, Mitsue; Kotani, Kazuhiko; Tsuzaki, Kokoro; Takagi, Ayaka; Motokubota, Naoko; Komai, Naho; Sakane, Naoki; Moritani, Toshio; Nagai, Narumi

    2015-01-01

    Background Clock genes regulate circadian rhythm and are involved in various physiological processes, including digestion. We therefore investigated the association between the CLOCK 3111T/C single nucleotide polymorphism and the Period3 (PER3) variable-number tandem-repeat polymorphism (either 4 or 5 repeats 54 nt in length) with morning gastric motility. Methods Lifestyle questionnaires and anthropometric measurements were performed with 173 female volunteers (mean age, 19.4 years). Gastric motility, evaluated by electrogastrography (EGG), blood pressure, and heart rate levels were measured at 8:30 a.m. after an overnight fast. For gastric motility, the spectral powers (% normal power) and dominant frequency (DF, peak of the power spectrum) of the EGG were evaluated. The CLOCK and PER3 polymorphisms were determined by polymerase chain reaction (PCR) restriction fragment length polymorphism analysis. Results Subjects with the CLOCK C allele (T/C or C/C genotypes: n = 59) showed a significantly lower DF (mean, 2.56 cpm) than those with the T/T genotype (n = 114, 2.81 cpm, P < 0.05). Subjects with the longer PER3 allele (PER34/5 or PER35/5 genotypes: n = 65) also showed a significantly lower DF (2.55 cpm) than those with the shorter PER34/4 genotype (n = 108, 2.83 cpm, P < 0.05). Furthermore, subjects with both the T/C or C/C and PER34/5 or PER35/5 genotypes showed a significantly lower DF (2.43 cpm, P < 0.05) than subjects with other combinations of the alleles (T/T and PER34/4 genotype, T/C or C/C and PER34/4 genotypes, and T/T and PER34/5 or PER35/5 genotypes). Conclusions These results suggest that minor polymorphisms of the circadian rhythm genes CLOCK and PER3 may be associated with poor morning gastric motility, and may have a combinatorial effect. The present findings may offer a new viewpoint on the role of circadian rhythm genes on the peripheral circadian systems, including the time-keeping function of the gut. PMID:25775462

  5. Circadian clock genes universally control key agricultural traits

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Circadian clocks are endogenous timers that enable plants to synchronize biological processes with daily and seasonal environmental conditions in order to allocate resources during the most beneficial times of day and year. The circadian clock regulates a number of central plant activities, includin...

  6. The circadian Clock gene regulates acrosin activity of sperm through serine protease inhibitor A3K

    PubMed Central

    Cheng, Shuting; Liang, Xin; Wang, Yuhui; Jiang, Zhou; Liu, Yanyou; Hou, Wang; Li, Shiping; Zhang, Jing

    2015-01-01

    Our previous study found that CLOCK knockdown in the testes of male mice led to a reduced fertility, which might be associated with the lower acrosin activity. In this present study, we examined the differential expression in proteins of CLOCK knockdown sperm. Clock gene expression was knocked down in cells to confirm those differentially expressions and serine protease inhibitor SERPINA3K was identified as a potential target. The up-regulated SERPINA3K revealed an inverse relationship with Clock knockdown. Direct treatment of normal sperm with recombinant SERPINA3K protein inhibited the acrosin activity and reduced in vitro fertilization rate. The luciferase reporter gene assay showed that the down-regulated of Clock gene could activate the Serpina3k promoter, but this activation was not affected by the mutation of E-box core sequence. Co-IP demonstrated a natural interaction between SERPIAN3K and RORs (α and β). Taken together, these results demonstrated that SERPINA3K is involved in the Clock gene-mediated male fertility by regulating acrosin activity and provide the first evidence that SERPINA3K could be regulated by Clock gene via retinoic acid-related orphan receptor response elements. PMID:26264441

  7. Molecular analyses of circadian gene variants reveal sex-dependent links between depression and clocks

    PubMed Central

    Shi, S-q; White, M J; Borsetti, H M; Pendergast, J S; Hida, A; Ciarleglio, C M; de Verteuil, P A; Cadar, A G; Cala, C; McMahon, D G; Shelton, R C; Williams, S M; Johnson, C H

    2016-01-01

    An extensive literature links circadian irregularities and/or sleep abnormalities to mood disorders. Despite the strong genetic component underlying many mood disorders, however, previous genetic associations between circadian clock gene variants and major depressive disorder (MDD) have been weak. We applied a combined molecular/functional and genetic association approach to circadian gene polymorphisms in sex-stratified populations of control subjects and case subjects suffering from MDD. This approach identified significant sex-dependent associations of common variants of the circadian clock genes hClock, hPer3 and hNpas2 with major depression and demonstrated functional effects of these polymorphisms on the expression or activity of the hCLOCK and hPER3 proteins, respectively. In addition, hCLOCK expression is affected by glucocorticoids, consistent with the sex-dependency of the genetic associations and the modulation of glucocorticoid-mediated stress response, providing a mechanism by which the circadian clock controls outputs that may affect psychiatric disorders. We conclude that genetic polymorphisms in circadian genes (especially hClock and hPer3, where functional assays could be tested) influence risk of developing depression in a sex- and stress-dependent manner. These studies support a genetic connection between circadian disruption and mood disorders, and confirm a key connection between circadian gene variation and major depression. PMID:26926884

  8. Molecular analyses of circadian gene variants reveal sex-dependent links between depression and clocks.

    PubMed

    Shi, S-q; White, M J; Borsetti, H M; Pendergast, J S; Hida, A; Ciarleglio, C M; de Verteuil, P A; Cadar, A G; Cala, C; McMahon, D G; Shelton, R C; Williams, S M; Johnson, C H

    2016-03-01

    An extensive literature links circadian irregularities and/or sleep abnormalities to mood disorders. Despite the strong genetic component underlying many mood disorders, however, previous genetic associations between circadian clock gene variants and major depressive disorder (MDD) have been weak. We applied a combined molecular/functional and genetic association approach to circadian gene polymorphisms in sex-stratified populations of control subjects and case subjects suffering from MDD. This approach identified significant sex-dependent associations of common variants of the circadian clock genes hClock, hPer3 and hNpas2 with major depression and demonstrated functional effects of these polymorphisms on the expression or activity of the hCLOCK and hPER3 proteins, respectively. In addition, hCLOCK expression is affected by glucocorticoids, consistent with the sex-dependency of the genetic associations and the modulation of glucocorticoid-mediated stress response, providing a mechanism by which the circadian clock controls outputs that may affect psychiatric disorders. We conclude that genetic polymorphisms in circadian genes (especially hClock and hPer3, where functional assays could be tested) influence risk of developing depression in a sex- and stress-dependent manner. These studies support a genetic connection between circadian disruption and mood disorders, and confirm a key connection between circadian gene variation and major depression.

  9. Alternative Splicing of Barley Clock Genes in Response to Low Temperature

    PubMed Central

    Calixto, Cristiane P. G.; Simpson, Craig G.; Waugh, Robbie; Brown, John W. S.

    2016-01-01

    Alternative splicing (AS) is a regulated mechanism that generates multiple transcripts from individual genes. It is widespread in eukaryotic genomes and provides an effective way to control gene expression. At low temperatures, AS regulates Arabidopsis clock genes through dynamic changes in the levels of productive mRNAs. We examined AS in barley clock genes to assess whether temperature-dependent AS responses also occur in a monocotyledonous crop species. We identify changes in AS of various barley core clock genes including the barley orthologues of Arabidopsis AtLHY and AtPRR7 which showed the most pronounced AS changes in response to low temperature. The AS events modulate the levels of functional and translatable mRNAs, and potentially protein levels, upon transition to cold. There is some conservation of AS events and/or splicing behaviour of clock genes between Arabidopsis and barley. In addition, novel temperature-dependent AS of the core clock gene HvPPD-H1 (a major determinant of photoperiod response and AtPRR7 orthologue) is conserved in monocots. HvPPD-H1 showed a rapid, temperature-sensitive isoform switch which resulted in changes in abundance of AS variants encoding different protein isoforms. This novel layer of low temperature control of clock gene expression, observed in two very different species, will help our understanding of plant adaptation to different environments and ultimately offer a new range of targets for plant improvement. PMID:27959947

  10. Autocatalysis-driven clock reaction II: kinetics of the pentathionate-periodate reaction.

    PubMed

    Xu, Li; Horváth, Attila K

    2014-10-23

    The pentathionate-periodate reaction has been investigated by spectrophotometrically monitoring the total amount of iodine evolved in the presence of phosphoric acid/dihydrogen phosphate buffer at 468 nm. The majority of the main characteristics of the title system is very reminiscent of that found recently in the pentathionate-iodate reaction, a system that led us to classify generally the clock reactions. Along with the pentathionate-iodate reaction the title system is proposed to belong to the autocatalysis-driven clock reactions as well. The kinetic model of the pentathionate-iodate system published recently was implemented by the necessary reactions of periodate to compose a 24-step kinetic model in which the mechanisms of the pentathionate-iodine, pentathionate-iodate, bisulfite-periodate, bisulfite-iodate, iodide-periodate, and the well-known Dushman reactions are combined. A thorough analysis revealed that the direct pentathionate-periodate reaction plays a role only to produce iodide ion via a finite sequence of reactions, and once its concentration reaches a certain level, the reaction is almost exclusively governed by the pentathionate-iodine, the iodide-periodate, and the Dushman reactions. As expected strong catalytic effect of the buffer composition is also found that can readily be explained by its well-known catalytic influence on the Dushman reaction.

  11. Estradiol differently affects melanin synthesis of malignant and normal melanocytes: a relationship with clock and clock-controlled genes.

    PubMed

    Poletini, Maristela Oliveira; de Assis, Leonardo Vinicius Monteiro; Moraes, Maria Nathalia; Castrucci, Ana Maria de Lauro

    2016-10-01

    Melanin production within melanocytes is regulated, among others, by estradiol, whose effects on melanogenesis are still not completely elucidated. Here we show that although 10(-7) M 17β-estradiol (E2) increased tyrosinase mRNA levels in B16-F10 malignant melanocytes, there was a transient decrease and abolishment of the temporal variation of melanin content. Both parameters were much higher in the malignant than in normal Melan-a cells. Considering that silencing clock machinery in human melanocytes increases melanogenesis, we investigated clock gene expression in those cell lines. Except for Melan-a Bmal1 and B16-F10 Per2 expression of control cells, Per1, Per2, and Bmal1 expression increased independently of cell type or E2 treatment after 24 h. However, melanoma cells showed a marked increase in Per1 and Bma11 expression in response to E2 at the same time points, what may rule out E2 as a synchronizer agent since the expression of those genes were not in antiphase. Next, we investigated the expression of Xpa, a clock-controlled gene, which in Melan-a cells, peaked at 18 h, and E2 treatment shifted this peak to 24 h, whereas B16-F10 Xpa expression peaked at 24 h in both control and E2 group, and it was higher compared to Melan-a cells in both groups. Therefore, malignant and normal melanocytes display profound differences on core elements of the local clock, and how they respond to E2, what is most probably determinant of the differences seen on melanin synthesis and Tyrosinase and Xpa expression. Understanding these processes at the molecular level could bring new strategies to treat melanoma.

  12. Altered dynamics in the circadian oscillation of clock genes in dermal fibroblasts of patients suffering from idiopathic hypersomnia.

    PubMed

    Lippert, Julian; Halfter, Hartmut; Heidbreder, Anna; Röhr, Dominik; Gess, Burkhard; Boentert, Mathias; Osada, Nani; Young, Peter

    2014-01-01

    From single cell organisms to the most complex life forms, the 24-hour circadian rhythm is important for numerous aspects of physiology and behavior such as daily periodic fluctuations in body temperature and sleep-wake cycles. Influenced by environmental cues - mainly by light input -, the central pacemaker in the thalamic suprachiasmatic nuclei (SCN) controls and regulates the internal clock mechanisms which are present in peripheral tissues. In order to correlate modifications in the molecular mechanisms of circadian rhythm with the pathophysiology of idiopathic hypersomnia, this study aimed to investigate the dynamics of the expression of circadian clock genes in dermal fibroblasts of idiopathic hypersomniacs (IH) in comparison to those of healthy controls (HC). Ten clinically and polysomnographically proven IH patients were recruited from the department of sleep medicine of the University Hospital of Muenster. Clinical diagnosis was done by two consecutive polysomnographies (PSG) and Multiple Sleep Latency Test (MSLT). Fourteen clinical healthy volunteers served as control group. Dermal fibroblasts were obtained via punch biopsy and grown in cell culture. The expression of circadian clock genes was investigated by semiquantitative Reverse Transcriptase-PCR qRT-PCR analysis, confirming periodical oscillation of expression of the core circadian clock genes BMAL1, PER1/2 and CRY1/2. The amplitude of the rhythmically expressed BMAL1, PER1 and PER2 was significantly dampened in dermal fibroblasts of IH compared to HC over two circadian periods whereas the overall expression of only the key transcriptional factor BMAL1 was significantly reduced in IH. Our study suggests for the first time an aberrant dynamics in the circadian clock in IH. These findings may serve to better understand some clinical features of the pathophysiology in sleep - wake rhythms in IH.

  13. Circadian Clock genes Per2 and clock regulate steroid production, cell proliferation, and luteinizing hormone receptor transcription in ovarian granulosa cells

    SciTech Connect

    Shimizu, Takashi; Hirai, Yuko; Murayama, Chiaki; Miyamoto, Akio; Miyazaki, Hitoshi; Miyazaki, Koyomi

    2011-08-19

    Highlights: {yields} Treatment with Per2 and Clock siRNAs decreased the number of granulosa cells and LHr expression. {yields}Per2 siRNA treatment did not stimulate the production of estradiol and expression of P450arom. {yields} Clock siRNA treatment inhibited the production of estradiol and expression of P450arom mRNA. {yields}Per2 and Clock siRNA treatment increased and unchanged, respectively, progesterone production in FSH-treated granulosa cells. {yields} The expression of StAR mRNA was increased by Per2 siRNA and unchanged by Clock siRNA. -- Abstract: Circadian Clock genes are associated with the estrous cycle in female animals. Treatment with Per2 and Clock siRNAs decreased the number of granulosa cells and LHr expression in follicle-stimulating hormone FSH-treated granulosa cells. Per2 siRNA treatment did not stimulate the production of estradiol and expression of P450arom, whereas Clock siRNA treatment inhibited the production of estradiol and expression of P450arom mRNA. Per2 and Clock siRNA treatment increased and unchanged, respectively, progesterone production in FSH-treated granulosa cells. Similarly, expression of StAR mRNA was increased by Per2 siRNA and unchanged by Clock siRNA. Our data provide a new insight that Per2 and Clock have different action on ovarian granulosa cell functions.

  14. Influence of the core circadian gene "Clock" on obesity and leptin resistance in mice.

    PubMed

    Xie, Xiaoping; Yang, Shuhong; Zou, Yan; Cheng, Shuting; Wang, Yuhui; Jiang, Zhou; Xiao, Jing; Wang, Zhengrong; Liu, Yanyou

    2013-01-23

    Alterations in metabolism could be due to cell-autonomous effects associated with altered expression of Clock in central nervous system feeding centers and/or peripheral tissues involved in metabolism. Clock mutant mice are hyperphagic and obese, which indicates that Clock is related to obesity. In the present study, we used intracerebroventricular injection of recombinant adenoviral vector harboring Clock genes to explore the role of Clock on diet induced obesity and the mechanisms involved in leptin resistance and leptin signaling in mice. The results demonstrated that expression of Clock in the arcuate nucleus of diet induced obesity mice was down-regulated. The recombinant adenoviral vector harboring Clock genes could reduce obesity indexes of diet induced obesity mice including body weight, BMI and total fat mass, attenuate hyperleptinemia, increase leptin sensitivity and decrease accumulated suppressor of cytokine signaling-3 in the arcuate nucleus. These results indicate that Clock plays an important role on obesity, which may be involved in leptin resistance and regulation of suppressor of cytokine signaling-3 in arcuate nucleus.

  15. Calorie restriction regulates circadian clock gene expression through BMAL1 dependent and independent mechanisms

    PubMed Central

    Patel, Sonal A.; Velingkaar, Nikkhil; Makwana, Kuldeep; Chaudhari, Amol; Kondratov, Roman

    2016-01-01

    Feeding behavior, metabolism and circadian clocks are interlinked. Calorie restriction (CR) is a feeding paradigm known to extend longevity. We found that CR significantly affected the rhythms in the expression of circadian clock genes in mice on the mRNA and protein levels, suggesting that CR reprograms the clocks both transcriptionally and post-transcriptionally. The effect of CR on gene expression was distinct from the effects of time-restricted feeding or fasting. Furthermore, CR affected the circadian output through up- or down-regulation of the expression of several clock-controlled transcriptional factors and the longevity candidate genes. CR-dependent effects on some clock gene expression were impaired in the liver of mice deficient for BMAL1, suggesting importance of this transcriptional factor for the transcriptional reprogramming of the clock, however, BMAL1- independent mechanisms also exist. We propose that CR recruits biological clocks as a natural mechanism of metabolic optimization under conditions of limited energy resources. PMID:27170536

  16. Heme Binding to the Mammalian Circadian Clock Protein Period 2 is Non-Specific†

    PubMed Central

    Airola, Michael V.; Du, Jing; Dawson, John H.; Crane, Brian R.

    2010-01-01

    The mammalian circadian clock synchronizes physical and metabolic activity with the diurnal cycle through a transcriptional-posttranslational feedback loop. An additional feedback mechanism regulating clock timing has been proposed to involve oscillation in heme availability. Period 2 (PER2), an integral component in the negative feedback loop that establishes circadian rhythms in mammals, has been identified as a heme binding protein. However, the majority of evidence for heme binding is based upon in vitro heme binding assays. We sought to ascertain if these largely spectral assays could distinguish between specific and non-specific heme interactions. Heme binding properties by a number of other well-characterized proteins, all with no known biological role involving heme interaction, corresponded to those displayed by PER2. Site-directed mutants of putative heme-binding residues identified by MCD were unable to locate a specific heme-binding site on PER2. Protein film electrochemistry also indicates that heme binds PER2 non-specifically on the protein surface. Our results establish the inability of typical in vitro assays to easily distinguish between specific and non-specific heme binding. We conclude that heme binding to PER2 is likely to be non-specific and does not involve the hydrophobic pocket within the PER2 PAS domains that in other PAS proteins commonly recognizes cofactors. These findings also question the significance of in vivo studies that implicate heme interactions with the clock proteins PER2 and nPAS2 in biological function. PMID:20411915

  17. CKIepsilon/delta-dependent phosphorylation is a temperature-insensitive, period-determining process in the mammalian circadian clock.

    PubMed

    Isojima, Yasushi; Nakajima, Masato; Ukai, Hideki; Fujishima, Hiroshi; Yamada, Rikuhiro G; Masumoto, Koh-hei; Kiuchi, Reiko; Ishida, Mayumi; Ukai-Tadenuma, Maki; Minami, Yoichi; Kito, Ryotaku; Nakao, Kazuki; Kishimoto, Wataru; Yoo, Seung-Hee; Shimomura, Kazuhiro; Takao, Toshifumi; Takano, Atsuko; Kojima, Toshio; Nagai, Katsuya; Sakaki, Yoshiyuki; Takahashi, Joseph S; Ueda, Hiroki R

    2009-09-15

    A striking feature of the circadian clock is its flexible yet robust response to various environmental conditions. To analyze the biochemical processes underlying this flexible-yet-robust characteristic, we examined the effects of 1,260 pharmacologically active compounds in mouse and human clock cell lines. Compounds that markedly (>10 s.d.) lengthened the period in both cell lines, also lengthened it in central clock tissues and peripheral clock cells. Most compounds inhibited casein kinase Iepsilon (CKIepsilon) or CKIdelta phosphorylation of the PER2 protein. Manipulation of CKIepsilon/delta-dependent phosphorylation by these compounds lengthened the period of the mammalian clock from circadian (24 h) to circabidian (48 h), revealing its high sensitivity to chemical perturbation. The degradation rate of PER2, which is regulated by CKIepsilon/delta-dependent phosphorylation, was temperature-insensitive in living clock cells, yet sensitive to chemical perturbations. This temperature-insensitivity was preserved in the CKIepsilon/delta-dependent phosphorylation of a synthetic peptide in vitro. Thus, CKIepsilon/delta-dependent phosphorylation is likely a temperature-insensitive period-determining process in the mammalian circadian clock.

  18. The core clock gene Per1 phases molecular and electrical circadian rhythms in SCN neurons

    PubMed Central

    Jones, Jeff R.

    2016-01-01

    The brain’s biological clock, the suprachiasmatic nucleus (SCN), exhibits endogenous 24-hour rhythms in gene expression and spontaneous firing rate; however, the functional relationship between these neuronal rhythms is not fully understood. Here, we used a Per1::GFP transgenic mouse line that allows for the simultaneous quantification of molecular clock state and firing rate in SCN neurons to examine the relationship between these key components of the circadian clock. We find that there is a stable, phased relationship between E-box-driven clock gene expression and spontaneous firing rate in SCN neurons and that these relationships are independent of light input onto the system or of GABAA receptor-mediated synaptic activity. Importantly, the concordant phasing of gene and neural rhythms is disrupted in the absence of the homologous clock gene Per1, but persists in the absence of the core clock gene Per2. These results suggest that Per1 plays a unique, non-redundant role in phasing gene expression and firing rate rhythms in SCN neurons to increase the robustness of cellular timekeeping. PMID:27602274

  19. Association between genetic variants of the clock gene and obesity and sleep duration.

    PubMed

    Valladares, Macarena; Obregón, Ana María; Chaput, Jean-Philippe

    2015-12-01

    Obesity is a multifactorial disease caused by the interaction of genetic and environmental factors related to lifestyle aspects. It has been shown that reduced sleep is associated with increased body mass index (BMI). Circadian Locomotor Output Cycles Kaput (CLOCK) gene variants have also been associated with obesity. The objective of this mini-review was to discuss the available literature related to CLOCK gene variants associated with adiposity and sleep duration in humans. In total, 16 articles complied with the terms of the search that reported CLOCK variants associated with sleep duration, energy intake, and BMI. Overall, six CLOCK single nucleotide polymorphisms (SNPs) have been associated with sleep duration, and three variants have been associated with energy intake variables. Overall, the most studied area has been the association of CLOCK gene with obesity; close to eight common variants have been associated with obesity. The most studied CLOCK SNP in different populations is rs1801260, and most of these populations correspond to European populations. Collectively, identifying at risk CLOCK genotypes is a new area of research that may help identify individuals who are more susceptible to overeating and gaining weight when exposed to short sleep durations.

  20. Altered Clock and Lipid Metabolism-Related Genes in Atherosclerotic Mice Kept with Abnormal Lighting Condition

    PubMed Central

    Zhu, Zhu; Hua, Bingxuan; Shang, Zhanxian; Yuan, Gongsheng; Xu, Lirong; Li, Ermin; Li, Xiaobo; Yan, Zuoqin; Qian, Ruizhe

    2016-01-01

    Background. The risk of atherosclerosis is elevated in abnormal lipid metabolism and circadian rhythm disorder. We investigated whether abnormal lighting condition would have influenced the circadian expression of clock genes and clock-controlled lipid metabolism-related genes in ApoE-KO mice. Methods. A mouse model of atherosclerosis with circadian clock genes expression disorder was established using ApoE-KO mice (ApoE-KO LD/DL mice) by altering exposure to light. C57 BL/6J mice (C57 mice) and ApoE-KO mice (ApoE-KO mice) exposed to normal day and night and normal diet served as control mice. According to zeitgeber time samples were acquired, to test atheromatous plaque formation, serum lipids levels and rhythmicity, clock genes, and lipid metabolism-related genes along with Sirtuin 1 (Sirt1) levels and rhythmicity. Results. Atherosclerosis plaques were formed in the aortic arch of ApoE-KO LD/DL mice. The serum lipids levels and oscillations in ApoE-KO LD/DL mice were altered, along with the levels and diurnal oscillations of circadian genes, lipid metabolism-associated genes, and Sirt1 compared with the control mice. Conclusions. Abnormal exposure to light aggravated plaque formation and exacerbated disorders of serum lipids and clock genes, lipid metabolism genes and Sirt1 levels, and circadian oscillation. PMID:27631008

  1. Circadian and Circalunar Clock Interactions in a Marine Annelid

    PubMed Central

    Zantke, Juliane; Ishikawa-Fujiwara, Tomoko; Arboleda, Enrique; Lohs, Claudia; Schipany, Katharina; Hallay, Natalia; Straw, Andrew D.; Todo, Takeshi; Tessmar-Raible, Kristin

    2013-01-01

    Summary Life is controlled by multiple rhythms. Although the interaction of the daily (circadian) clock with environmental stimuli, such as light, is well documented, its relationship to endogenous clocks with other periods is little understood. We establish that the marine worm Platynereis dumerilii possesses endogenous circadian and circalunar (monthly) clocks and characterize their interactions. The RNAs of likely core circadian oscillator genes localize to a distinct nucleus of the worm’s forebrain. The worm’s forebrain also harbors a circalunar clock entrained by nocturnal light. This monthly clock regulates maturation and persists even when circadian clock oscillations are disrupted by the inhibition of casein kinase 1δ/ε. Both circadian and circalunar clocks converge on the regulation of transcript levels. Furthermore, the circalunar clock changes the period and power of circadian behavior, although the period length of the daily transcriptional oscillations remains unaltered. We conclude that a second endogenous noncircadian clock can influence circadian clock function. PMID:24075994

  2. Disrupted light-dark cycle abolishes circadian expression of peripheral clock genes without inducing behavioral arrhythmicity in mice.

    PubMed

    Oishi, Katsutaka; Higo-Yamamoto, Sayaka; Yamamoto, Saori; Yasumoto, Yuki

    2015-03-06

    The environmental light-dark (LD) cycle entrains the central circadian clock located in the suprachiasmatic nucleus (SCN) of mammals. The present study examined the effects of disrupted LD cycles on peripheral clocks in mice housed under a normal 12 h light-12 h dark cycle (LD 12:12) or an ultradian LD 3:3 cycle. Drinking behavior seemed to be free-running with a long period (26.03 h) under ultradian LD 3:3 cycles, in addition to light-induced direct suppression (masking effect). Core body temperature completely lost robust circadian rhythm and acquired a 6-h rhythm with a low amplitude under LD 3:3. Robust circadian expression of Per1, Per2, Clock and Bmal1 mRNAs was similarly flattened to intermediate levels in the liver, heart and white adipose tissue under LD 3:3. Robust circadian expression of Rev-erbα mRNA was completely damped in these tissues. Circadian expression of Dbp, a clock-controlled gene, was also disrupted in these tissues from mice housed under LD 3:3. The aberrant LD cycle seemed to induce the loss of circadian gene expression at the level of transcription, because rhythmic pre-mRNA expression of these genes was also abolished under LD 3:3. In addition to the direct effect of the aberrant LD cycle, abolished systemic time cues such as those of plasma corticosterone and body temperature might be involved in the disrupted expression of these circadian genes under LD 3:3. Our findings suggest that disrupted environmental LD cycles abolish the normal oscillation of peripheral clocks and induce internal desynchrony in mammals.

  3. Daily rhythm and regulation of clock gene expression in the rat pineal gland.

    PubMed

    Simonneaux, V; Poirel, V-J; Garidou, M-L; Nguyen, D; Diaz-Rodriguez, E; Pévet, P

    2004-01-05

    Rhythms in pineal melatonin synthesis are controlled by the biological clock located in the suprachiasmatic nuclei. The endogenous clock oscillations rely upon genetic mechanisms involving clock genes coding for transcription factors working in negative and positive feedback loops. Most of these clock genes are expressed rhythmically in other tissues. Because of the peculiar role of the pineal gland in the photoneuroendocrine axis regulating biological rhythms, we studied whether clock genes are expressed in the rat pineal gland and how their expression is regulated.Per1, Per3, Cry2 and Cry1 clock genes are expressed in the pineal gland and their transcription is increased during the night. Analysis of the regulation of these pineal clock genes indicates that they may be categorized into two groups. Expression of Per1 and Cry2 genes shows the following features: (1) the 24 h rhythm persists, although damped, in constant darkness; (2) the nocturnal increase is abolished following light exposure or injection with a beta-adrenergic antagonist; and (3) the expression during daytime is stimulated by an injection with a beta-adrenergic agonist. In contrast, Per3 and Cry1 day and night mRNA levels are not responsive to adrenergic ligands (as previously reported for Per2) and daily expression of Per3 and Cry1 appears strongly damped or abolished in constant darkness. These data show that the expression of Per1 and Cry2 in the rat pineal gland is regulated by the clock-driven changes in norepinephrine, in a similar manner to the melatonin rhythm-generating enzyme arylalkylamine N-acetyltransferase. The expression of Per3 and Cry1 displays a daily rhythm not regulated by norepinephrine, suggesting the involvement of another day/night regulated transmitter(s).

  4. Periodic transition on an axial compressor stator: Incidence and clocking effects. Part 1: Experimental data

    SciTech Connect

    Walker, G.J.; Hughes, J.D.; Solomon, W.J.

    1999-07-01

    Periodic wake-induced transition on the outlet stator of a 1.5-stage axial compressor is examined using hot-film arrays on both the suction and pressure surfaces. The time-mean surface pressure distribution is varied by changing the blade incidence, while the free-stream disturbance field is altered by clocking of the stator relative to an inlet guide vane row. Ensemble-averaged plots of turbulent intermittency and relaxation factor (extent of calmed flow following the passage of a turbulent spot) are presented. These show the strength of periodic wake-induced transition phenomena to be significantly influenced by both incidence and clocking effects. The nature and extent of transition by other modes (natural, bypass, and separated flow transition) are altered accordingly. Leading edge and midchord separation bubbles are affected in a characteristically different manner by changing free-stream periodicity. There are noticeable differences between suction and pressure surface transition behavior, particularly as regards the strength and extent of calming. In Part 2 of this paper, the transition onset observations from the compressor stator are used to evaluate the quasi-steady application of conventional transition correlations to predict unsteady transition onset on the blading of an embedded axial compressor stage.

  5. Comparative study of pineal clock gene and AANAT2 expression in relation to melatonin synthesis in Atlantic salmon (Salmo salar) and European seabass (Dicentrarchus labrax).

    PubMed

    McStay, Elsbeth; Migaud, Herve; Vera, Luisa Maria; Sánchez-Vázquez, Francisco Javier; Davie, Andrew

    2014-03-01

    The photoreceptive teleost pineal is considered to be essential to the generation, synchronisation and maintenance of biological rhythms, primarily via melatonin release. The role of internal (circadian clock) and external (light) signals controlling melatonin production in the fish pineal differs between species, yet the reasons underpinning this remain largely unknown. Whilst in salmonids, pineal melatonin is apparently regulated directly by light, in all other studied teleosts, rhythmic melatonin production persists endogenously under the regulation of clock gene expression. To better understand the role of clocks in teleost pineals, this study aimed to characterise the expression of selected clock genes in vitro under different photoperiodic conditions in comparison to in vivo in both Atlantic salmon (Salmo salar) and in European seabass (Dicentrarchus labrax) (in vitro 12L:12D), a species known to display endogenous rhythmic melatonin synthesis. Results revealed no rhythmic clock gene (Clock, Period 1 &2) expression in Atlantic salmon or European seabass (Clock and Period 1) pineal in vitro. However rhythmic expression of Cryptochrome 2 and Period 1 in the Atlantic salmon pineal was observed in vivo, which infers extra-pineal regulation of clocks in this species. No rhythmic arylalkylamine N-acetyltransferase 2 (Aanat2) expression was observed in the Atlantic salmon yet in the European seabass, circadian Aanat2 expression was observed. Subsequent in silico analysis of available Aanat2 genomic sequences reveals that Atlantic salmon Aanat2 promoter sequences do not contain similar regulatory architecture as present in European seabass, and previously described in other teleosts which alludes to a loss in functional connection in the pathway.

  6. Sleep Loss Reduces the DNA-Binding of BMAL1, CLOCK, and NPAS2 to Specific Clock Genes in the Mouse Cerebral Cortex

    PubMed Central

    Curie, Thomas; Franken, Paul

    2011-01-01

    We have previously demonstrated that clock genes contribute to the homeostatic aspect of sleep regulation. Indeed, mutations in some clock genes modify the markers of sleep homeostasis and an increase in homeostatic sleep drive alters clock gene expression in the forebrain. Here, we investigate a possible mechanism by which sleep deprivation (SD) could alter clock gene expression by quantifying DNA-binding of the core-clock transcription factors CLOCK, NPAS2, and BMAL1 to the cis-regulatory sequences of target clock genes in mice. Using chromatin immunoprecipitation (ChIP), we first showed that, as reported for the liver, DNA-binding of CLOCK and BMAL1 to target clock genes changes in function of time-of-day in the cerebral cortex. Tissue extracts were collected at ZT0 (light onset), −6, −12, and −18, and DNA enrichment of E-box or E'-box containing sequences was measured by qPCR. CLOCK and BMAL1 binding to Cry1, Dbp, Per1, and Per2 depended on time-of-day, with maximum values reached at around ZT6. We then observed that SD, performed between ZT0 and −6, significantly decreased DNA-binding of CLOCK and BMAL1 to Dbp, consistent with the observed decrease in Dbp mRNA levels after SD. The DNA-binding of NPAS2 and BMAL1 to Per2 was also decreased by SD, although SD is known to increase Per2 expression in the cortex. DNA-binding to Per1 and Cry1 was not affected by SD. Our results show that the sleep-wake history can affect the clock molecular machinery directly at the level of chromatin binding thereby altering the cortical expression of Dbp and Per2 and likely other targets. Although the precise dynamics of the relationship between DNA-binding and mRNA expression, especially for Per2, remains elusive, the results also suggest that part of the reported circadian changes in DNA-binding of core clock components in tissues peripheral to the suprachiasmatic nuclei could, in fact, be sleep-wake driven. PMID:22039518

  7. Sleep loss reduces the DNA-binding of BMAL1, CLOCK, and NPAS2 to specific clock genes in the mouse cerebral cortex.

    PubMed

    Mongrain, Valérie; La Spada, Francesco; Curie, Thomas; Franken, Paul

    2011-01-01

    We have previously demonstrated that clock genes contribute to the homeostatic aspect of sleep regulation. Indeed, mutations in some clock genes modify the markers of sleep homeostasis and an increase in homeostatic sleep drive alters clock gene expression in the forebrain. Here, we investigate a possible mechanism by which sleep deprivation (SD) could alter clock gene expression by quantifying DNA-binding of the core-clock transcription factors CLOCK, NPAS2, and BMAL1 to the cis-regulatory sequences of target clock genes in mice. Using chromatin immunoprecipitation (ChIP), we first showed that, as reported for the liver, DNA-binding of CLOCK and BMAL1 to target clock genes changes in function of time-of-day in the cerebral cortex. Tissue extracts were collected at ZT0 (light onset), -6, -12, and -18, and DNA enrichment of E-box or E'-box containing sequences was measured by qPCR. CLOCK and BMAL1 binding to Cry1, Dbp, Per1, and Per2 depended on time-of-day, with maximum values reached at around ZT6. We then observed that SD, performed between ZT0 and -6, significantly decreased DNA-binding of CLOCK and BMAL1 to Dbp, consistent with the observed decrease in Dbp mRNA levels after SD. The DNA-binding of NPAS2 and BMAL1 to Per2 was also decreased by SD, although SD is known to increase Per2 expression in the cortex. DNA-binding to Per1 and Cry1 was not affected by SD. Our results show that the sleep-wake history can affect the clock molecular machinery directly at the level of chromatin binding thereby altering the cortical expression of Dbp and Per2 and likely other targets. Although the precise dynamics of the relationship between DNA-binding and mRNA expression, especially for Per2, remains elusive, the results also suggest that part of the reported circadian changes in DNA-binding of core clock components in tissues peripheral to the suprachiasmatic nuclei could, in fact, be sleep-wake driven.

  8. Chronotype and sleep quality as a subphenotype in association studies of clock genes in mood disorders.

    PubMed

    Dmitrzak-Węglarz, Monika; Pawlak, Joanna; Wiłkość, Monika; Miechowicz, Izabela; Maciukiewicz, Małgorzata; Ciarkowska, Wanda; Zaremba, Dorota; Hauser, Joanna

    2016-01-01

    Genetic background and clinical picture of mood disorders (MD) are complex and may depend on many genes and their potential interactions as well as environmental factors. Therefore, clinical variations, or endophenotypes, were suggested for association studies. The aim of the study was to investigate association between the chronotype (CH) and quality of sleep characteristics with polymorphisms CLOCK, ARNTL, TIMELESS and PER3 genes in MD. We included a total sample of 111 inpatients and 126 healthy controls. To assess CH we applied Morningness-Eveningness Questionnaire (MEQ). Additionally, we defined the quality and patterns of sleep using The Pittsburgh Sleep Quality Index (PSQI) and Epworth Sleepiness Scale (ESS). We applied Kruskal-Wallis test to determine associations. The main positive findings refer to associations between selected polymorphisms and: 1) chronotype with the ARNTL gene (rs11824092 and rs1481892) and the CLOCK (rs1268271) 2) sleep duration with the CLOCK gene (rs3805148) and the TIM gene (rs2291739) 3) daytime dysfunction with the PER3 gene (rs228727, rs228642, rs10864315) 4) subjective sleep quality with the ARNTL gene (rs11824092, rs1982350) 5) sleep disturbances with the ARNTL gene (rs11600996) We also found the significant epistatic interactions between polymorphism of the PER3 gene (rs2640909) & the CLOCK gene (rs11932595) and following sleep quality variables: sleep duration, habitual sleep efficiency and subjective sleep quality. The present study suggests a putative role of the analyzed clock genes polymorphisms in chronotype in the control group and in sleep quality disturbances in the course of MD. The results indicate that PSQI variables can be used to refine phenotype in association studies of clock genes in MD.

  9. Extra-hypothalamic brain clocks in songbirds: Photoperiodic state dependent clock gene oscillations in night-migratory blackheaded buntings, Emberiza melanocephala.

    PubMed

    Singh, Devraj; Kumar, Vinod

    2017-04-01

    The avian circadian pacemaker system is comprised of independent clocks in the retina, pineal and hypothalamus, as shown by daily and circadian oscillations of core clock genes (Per2, Cry1, Bmal1 and Clock) in several birds including migratory blackheaded buntings (Emberiza melanocephala). This study investigated the extra-hypothalamic brain circadian clocks in blackheaded buntings, and measured Per2, Cry1, Cry2, Bmal1 and Clock mRNA expressions at 4h intervals over 24h beginning 1h after light-on in the left and right telencephalon, optic tectum and cerebellum, the brain regions involved in several physiological and cognitive functions. Because of seasonal alterations in the circadian clock dependent brain functions, we measured daily clock gene oscillations in buntings photoperiod-induced with the non-migratory state under short days (SDnM), and the pre-migratory (LDpM), migratory (LDM) and post-migratory (refractory, LDR) states under long days. Daily Per2 oscillations were not altered with changes in the photoperiodic states, except for about 2-3h phase difference in the optic tectum between the SDnM and LDpM states. However, there were about 3-5h differences in the phase and 2 to 4 fold change in the amplitude of daily Bmal1 and Cry1 mRNA oscillations between the photoperiod-induced states. Further, Cry2 and Clock genes lacked a significant oscillation, except in Cb (Cry2) and TeO and Rt (Clock) under LDR state. Overall, these results show the presence of circadian clocks in extra-hypothalamic brain regions of blackheaded buntings, and suggest tissue-dependent alterations in the waveforms of mRNA oscillations with transitions in the photoperiod-induced seasonal states in a long-day species.

  10. Exploitation of host clock gene machinery by hepatitis viruses B and C

    PubMed Central

    Vinciguerra, Manlio; Mazzoccoli, Gianluigi; Piccoli, Claudia; Tataranni, Tiziana; Andriulli, Angelo; Pazienza, Valerio

    2013-01-01

    Many aspects of cellular physiology display circadian (approximately 24-h) rhythms. Dysfunction of the circadian clock molecular circuitry is associated with human health derangements, including neurodegeneration, increased risk of cancer, cardiovascular diseases and the metabolic syndrome. Viruses triggering hepatitis depend tightly on the host cell synthesis machinery for their own replication, survival and spreading. Recent evidences support a link between the circadian clock circuitry and viruses’ biological cycle within host cells. Currently, in vitro models for chronobiological studies of cells infected with viruses need to be implemented. The establishment of such in vitro models would be helpful to better understand the link between the clock gene machinery and viral replication/viral persistence in order to develop specifically targeted therapeutic regimens. Here we review the recent literature dealing with the interplay between hepatitis B and C viruses and clock genes. PMID:24379614

  11. Exploitation of host clock gene machinery by hepatitis viruses B and C.

    PubMed

    Vinciguerra, Manlio; Mazzoccoli, Gianluigi; Piccoli, Claudia; Tataranni, Tiziana; Andriulli, Angelo; Pazienza, Valerio

    2013-12-21

    Many aspects of cellular physiology display circadian (approximately 24-h) rhythms. Dysfunction of the circadian clock molecular circuitry is associated with human health derangements, including neurodegeneration, increased risk of cancer, cardiovascular diseases and the metabolic syndrome. Viruses triggering hepatitis depend tightly on the host cell synthesis machinery for their own replication, survival and spreading. Recent evidences support a link between the circadian clock circuitry and viruses' biological cycle within host cells. Currently, in vitro models for chronobiological studies of cells infected with viruses need to be implemented. The establishment of such in vitro models would be helpful to better understand the link between the clock gene machinery and viral replication/viral persistence in order to develop specifically targeted therapeutic regimens. Here we review the recent literature dealing with the interplay between hepatitis B and C viruses and clock genes.

  12. Involvement of adenosine monophosphate-activated protein kinase in the influence of timed high-fat evening diet on the hepatic clock and lipogenic gene expression in mice.

    PubMed

    Huang, Yan; Zhu, Zengyan; Xie, Meilin; Xue, Jie

    2015-09-01

    A high-fat diet may result in changes in hepatic clock gene expression, but potential mechanisms are not yet elucidated. Adenosine monophosphate-activated protein kinase (AMPK) is a serine/threonine protein kinase that is recognized as a key regulator of energy metabolism and certain clock genes. Therefore, we hypothesized that AMPK may be involved in the alteration of hepatic clock gene expression under a high-fat environment. This study aimed to examine the effects of timed high-fat evening diet on the activity of hepatic AMPK, clock genes, and lipogenic genes. Mice with hyperlipidemic fatty livers were induced by orally administering high-fat milk via gavage every evening (19:00-20:00) for 6 weeks. Results showed that timed high-fat diet in the evening not only decreased the hepatic AMPK protein expression and activity but also disturbed its circadian rhythm. Accordingly, the hepatic clock genes, including clock, brain-muscle-Arnt-like 1, cryptochrome 2, and period 2, exhibited prominent changes in their expression rhythms and/or amplitudes. The diurnal rhythms of the messenger RNA expression of peroxisome proliferator-activated receptorα, acetyl-CoA carboxylase 1α, and carnitine palmitoyltransferase 1 were also disrupted; the amplitude of peroxisome proliferator-activated receptorγcoactivator 1α was significantly decreased at 3 time points, and fatty liver was observed. These findings demonstrate that timed high-fat diet at night can change hepatic AMPK protein levels, activity, and circadian rhythm, which may subsequently alter the circadian expression of several hepatic clock genes and finally result in the disorder of hepatic lipogenic gene expression and the formation of fatty liver.

  13. Circadian dysregulation of clock genes: clues to rapid treatments in major depressive disorder.

    PubMed

    Bunney, B G; Li, J Z; Walsh, D M; Stein, R; Vawter, M P; Cartagena, P; Barchas, J D; Schatzberg, A F; Myers, R M; Watson, S J; Akil, H; Bunney, W E

    2015-02-01

    Conventional antidepressants require 2-8 weeks for a full clinical response. In contrast, two rapidly acting antidepressant interventions, low-dose ketamine and sleep deprivation (SD) therapy, act within hours to robustly decrease depressive symptoms in a subgroup of major depressive disorder (MDD) patients. Evidence that MDD may be a circadian-related illness is based, in part, on a large set of clinical data showing that diurnal rhythmicity (sleep, temperature, mood and hormone secretion) is altered during depressive episodes. In a microarray study, we observed widespread changes in cyclic gene expression in six regions of postmortem brain tissue of depressed patients matched with controls for time-of-death (TOD). We screened 12 000 transcripts and observed that the core clock genes, essential for controlling virtually all rhythms in the body, showed robust 24-h sinusoidal expression patterns in six brain regions in control subjects. In MDD patients matched for TOD with controls, the expression patterns of the clock genes in brain were significantly dysregulated. Some of the most robust changes were seen in anterior cingulate (ACC). These findings suggest that in addition to structural abnormalities, lesion studies, and the large body of functional brain imaging studies reporting increased activation in the ACC of depressed patients who respond to a wide range of therapies, there may be a circadian dysregulation in clock gene expression in a subgroup of MDDs. Here, we review human, animal and neuronal cell culture data suggesting that both low-dose ketamine and SD can modulate circadian rhythms. We hypothesize that the rapid antidepressant actions of ketamine and SD may act, in part, to reset abnormal clock genes in MDD to restore and stabilize circadian rhythmicity. Conversely, clinical relapse may reflect a desynchronization of the clock, indicative of a reactivation of abnormal clock gene function. Future work could involve identifying specific small

  14. The REVEILLE Clock Genes Inhibit Growth of Juvenile and Adult Plants by Control of Cell Size.

    PubMed

    Gray, Jennifer A; Shalit-Kaneh, Akiva; Chu, Dalena Nhu; Hsu, Polly Yingshan; Harmer, Stacey L

    2017-04-01

    The circadian clock is a complex regulatory network that enhances plant growth and fitness in a constantly changing environment. In Arabidopsis (Arabidopsis thaliana), the clock is composed of numerous regulatory feedback loops in which REVEILLE8 (RVE8) and its homologs RVE4 and RVE6 act in a partially redundant manner to promote clock pace. Here, we report that the remaining members of the RVE8 clade, RVE3 and RVE5, play only minor roles in the regulation of clock function. However, we find that RVE8 clade proteins have unexpected functions in the modulation of light input to the clock and the control of plant growth at multiple stages of development. In seedlings, these proteins repress hypocotyl elongation in a daylength- and sucrose-dependent manner. Strikingly, adult rve4 6 8 and rve3 4 5 6 8 mutants are much larger than wild-type plants, with both increased leaf area and biomass. This size phenotype is associated with a faster growth rate and larger cell size and is not simply due to a delay in the transition to flowering. Gene expression and epistasis analysis reveal that the growth phenotypes of rve mutants are due to the misregulation of PHYTOCHROME INTERACTING FACTOR4 (PIF4) and PIF5 expression. Our results show that even small changes in PIF gene expression caused by the perturbation of clock gene function can have large effects on the growth of adult plants.

  15. Long-term effect of systemic RNA interference on circadian clock genes in hemimetabolous insects.

    PubMed

    Uryu, Outa; Kamae, Yuichi; Tomioka, Kenji; Yoshii, Taishi

    2013-04-01

    RNA interference (RNAi) strategy, which enables gene-specific knock-down of transcripts, has been spread across a wide area of insect studies for investigating gene function without regard to model and non-model insects. This technique is of particular benefit to promote molecular studies on non-model insects. However, the optimal conditions for RNAi are still not well understood because of its variable efficiency depending on the species, target genes, and experimental conditions. To apply RNAi technique to long-running experiments such as chronobiological studies, the effects of RNAi have to persist throughout the experiment. In this study, we attempted to determine the optimal concentration of double-stranded RNA (dsRNA) for systemic RNAi and its effective period in two different insect species, the cricket Gryllus bimaculatus and the firebrat Thermobia domestica. In both species, higher concentrations of dsRNA principally yielded a more efficient knock-down of mRNA levels of tested clock genes, although the effect depended on the gene and the species. Surprisingly, the effect of the RNAi reached its maximum effect 1-2 weeks and 1 month after the injection of dsRNA in the crickets and the firebrats, respectively, suggesting a slow but long-term effect of RNAi. Our study provides fundamental information for utilizing RNAi technique in any long-running experiment.

  16. Search for evidence of a clock related to the solar 154 day complex of periodicities

    NASA Technical Reports Server (NTRS)

    Sturrock, P. A.; Bai, T.

    1992-01-01

    Evidence that has recently been compiled (Bai and Sturrock 1991) indicates that the enigmatic 154-day periodicity in solar activity may be viewed as part of a complex of periodicities that are approximate multiples of 25.8 days, suggesting that the Sun contains a 'clock' with frequency in the range 440 to 463 nano Hz. The clock may comprise either an oscillator or a rotator, each of which may be either real or virtual. We have reconsidered a previous spectrum analysis of the Zurich sunspot-number sequence by Knight, Schatten, and Sturrock (1979) which revealed a sharp, persistent and significant periodicity with a period of 12.072 days, corresponding to a frequency of about 958.8 nano Hz. This periodicity may be regarded as the (second) upper sideband of the second harmonic (2nu(sub R) + 2nu(sub E)) of a fundamental frequency of 447.7 nano Hz that is clearly within the search band. In this expression, nu(sub R) is the sidereal frequency of the hypothetical rotator and nu(sub E) is the frequency (31.69 nano Hz) of the Earth in its orbital motion around the Sun. In analyzing sunspot area data derived from the Greenwich data set, and on noting that any frequency is defined only to within the Nyquist frequency, we find clear evidence not only for the upper sideband of the second harmonic, but also for the second harmonic (2nu(sub R)) and the lower sideband of the second harmonic (2nu(sub R) - 2nu(sub E)). There is no strong peak at the fundamental frequency in the Greenwich data, but there is in the Zurich sunspot data. The effect of a linear oscillator is, to the lowest order in the amplitude, the same as the combined effect of two rotators of opposite polarities. A rotator that has arbitrary orientation with respect to the ecliptic may influence the outer layers of the Sun and thereby modulate the occurrence of solar activity such as sunspots. By analyzing a simple model, we find that such a rotator would influence surface activity in such a way that the spectrum of

  17. Daily and seasonal expression of clock genes in the pituitary of the European sea bass (Dicentrarchus labrax).

    PubMed

    Herrero, María Jesús; Lepesant, Julie M J

    2014-11-01

    The expression of select clock genes (clock, bmal, per1, per2, cry1, cry2) was investigated throughout the day and across the four seasons for two consecutive years in the pituitary of adult sea bass (Dicentrarchus labrax). A rhythmic pattern of daily expression was consistently observed in summer and autumn, while arrhythmicity was observed for some clock genes during spring and winter, concomitant with low water temperatures. The expression of clock and bmal showed highest values at the end of the day and during the night, while that of per and cry was mostly antiphasic, with high values during the day. Melatonin affects clock-gene expression in the pituitary of mammals. We therefore sought to test the effect of melatonin on clock-gene expression in the pituitary of sea bass both in vivo and in vitro. Melatonin modestly affected the expression of some clock genes (in particular cry genes) when added to the fish diet or the culture medium of pituitary glands. Our data show that clock genes display rhythmic daily expression in the pituitary of adult sea bass, which are profoundly modified according to the season. We suggest that the effect of photoperiod on clock gene expression may be mediated, at least in part, by melatonin, and that temperature may have a key role adjusting seasonal variations.

  18. Diabetic retinopathy alters light-induced clock gene expression and dopamine levels in the mouse retina

    PubMed Central

    Lahouaoui, Hasna; Coutanson, Christine; Cooper, Howard M.; Bennis, Mohamed

    2016-01-01

    Purpose Diabetic retinopathy is one of the most common consequences of diabetes that affects millions of working-age adults worldwide and leads to progressive degeneration of the retina, visual loss, and blindness. Diabetes is associated with circadian disruption of the central and peripheral circadian clocks, but the mechanisms responsible for such alterations are unknown. Using a streptozotocin (STZ)-induced model of diabetes, we investigated whether diabetes alters 1) the circadian regulation of clock genes in the retina and in the central clocks, 2) the light response of clock genes in the retina, and/or 3) light-driven retinal dopamine (DA), a major output marker of the retinal clock. Methods To quantify circadian expression of clock and clock-controlled genes, retinas and suprachiasmatic nucleus (SCN) from the same animals were collected every 4 h in circadian conditions, 12 weeks post-diabetes. Induction of Per1, Per2, and c-fos mRNAs was quantified in the retina after the administration of a pulse of monochromatic light (480 nm, 1.17×1014 photons/cm2/s, 15 min) at circadian time 16. Gene expression was assessed with real-time reverse transcription PCR (RT–PCR). Pooled retinas from the control and STZ-diabetic mice were collected 2 h after light ON and light OFF (Zeitgeber time (ZT)2 and ZT14), and DA and its metabolite were analyzed with high-performance liquid chromatography (HPLC). Results We found variable effects of diabetes on the expression of clock genes in the retina and only slight differences in phase and/or amplitude in the SCN. c-fos and Per1 induction by a 480 nm light pulse was abolished in diabetic animals at 12 weeks post-induction of diabetes in comparison with the control mice, suggesting a deficit in light-induced neuronal activation of the retinal clock. Finally, we quantified a 56% reduction in the total number of tyrosine hydroxylase (TH) immunopositive cells, associated with a decrease in DA levels during the subjective day (ZT2

  19. MYC/MIZ1-dependent gene repression inversely coordinates the circadian clock with cell cycle and proliferation

    PubMed Central

    Shostak, Anton; Ruppert, Bianca; Ha, Nati; Bruns, Philipp; Toprak, Umut H.; Lawerenz, Chris; Lichter, Peter; Radlwimmer, Bernhard; Eils, Jürgen; Brors, Benedikt; Radomski, Sylwester; Scholz, Ingrid; Richter, Gesine; Siebert, Reiner; Wagner, Susanne; Haake, Andrea; Richter, Julia; Aukema, Sietse; Ammerpohl, Ole; Lopez, Christina; Nagel, Inga; Vater, Inga; Wagner, Rabea; Borst, Christoph; Haas, Siegfried; Rohde, Marius; Burkhardt, Birgit; Lisfeld, Jasmin; Claviez, Alexander; Dreyling, Martin; Eberth, Sonja; Trümper, Lorenz; Kube, Dieter; Stadler, Christina; Einsele, Hermann; Frickhofen, Norbert; Hansmann, Martin-Leo; Karsch, Dennis; Kneba, Michael; Mantovani-Löffler, Luisa; Staib, Peter; Stilgenbauer, Stephan; Ott, German; Küppers, Ralf; Weniger, Marc; Hummel, Michael; Lenze, Dido; Szczepanowski, Monika; Klapper, Wolfram; Kostezka, Ulrike; Möller, Peter; Rosenwald, Andreas; Leich, Ellen; Pischimariov, Jordan; Binder, Vera; Borkhardt, Arndt; Hezaveh, Kebria; Hoell, Jessica; Rosenstiel, Philip; Schilhabel, Markus; Schreiber, Stefan; Bernhart, Stephan H.; Doose, Gero; Hoffmann, Steve; Kretzmer, Helene; Langenberger, David; Binder, Hans; Hopp, Lydia; Kreuz, Markus; Loeffler, Markus; Rosolowski, Maciej; Korbel, Jan; Sungalee, Stefanie; Stadler, Peter F.; Zenz, Thorsten; Eils, Roland; Schlesner, Matthias; Diernfellner, Axel; Brunner, Michael

    2016-01-01

    The circadian clock and the cell cycle are major cellular systems that organize global physiology in temporal fashion. It seems conceivable that the potentially conflicting programs are coordinated. We show here that overexpression of MYC in U2OS cells attenuates the clock and conversely promotes cell proliferation while downregulation of MYC strengthens the clock and reduces proliferation. Inhibition of the circadian clock is crucially dependent on the formation of repressive complexes of MYC with MIZ1 and subsequent downregulation of the core clock genes BMAL1 (ARNTL), CLOCK and NPAS2. We show furthermore that BMAL1 expression levels correlate inversely with MYC levels in 102 human lymphomas. Our data suggest that MYC acts as a master coordinator that inversely modulates the impact of cell cycle and circadian clock on gene expression. PMID:27339797

  20. Genetic Variation in Circadian Rhythm Genes CLOCK and ARNTL as Risk Factor for Male Infertility

    PubMed Central

    Hodžić, Alenka; Ristanović, Momčilo; Zorn, Branko; Tulić, Cane; Maver, Aleš; Novaković, Ivana; Peterlin, Borut

    2013-01-01

    Background The circadian system has a major role in maintaining homeostasis and proper body functions including reproductive capacity. The aim of this study was to examine whether there is an association between genetic variability in the primary clock genes CLOCK and ARNTL and male infertility in humans. Methodology/Principal Findings We performed a case-control study, where we searched for an association between polymorphisms of CLOCK and ARNTL genes and male infertility in 961 Slovenian and Serbian Caucasian men. The study group consisted of 517 patients with idiopathic infertility and a control group of 444 fertile men. A statistically significant difference was found in genotype distribution between the two groups in the CLOCK gene: rs11932595 (p = 6·10−5, q = 4·10−4, OR equaled 1.9 with 95% CI 1.4–2.7), rs6811520 (p = 2·10−3, q = 8·10−3, OR = 1.7 with 95% CI 1.2–2.2) and rs6850524 (p = 0.01, q = 0.02, OR = 1.4 with 95% CI 1.1–1.9). Further analyses of haplotypes were consistent with genotyping results. Conclusions/Significance We provide evidence that genetic variability in the CLOCK gene might be associated with male infertility warranting further confirmation and mechanistic investigations. PMID:23527142

  1. The Zebrafish Period2 Protein Positively Regulates the Circadian Clock through Mediation of Retinoic Acid Receptor (RAR)-related Orphan Receptor α (Rorα)*

    PubMed Central

    Wang, Mingyong; Zhong, Zhaomin; Zhong, Yingbin; Zhang, Wei; Wang, Han

    2015-01-01

    We report the characterization of a null mutant for zebrafish circadian clock gene period2 (per2) generated by transcription activator-like effector nuclease and a positive role of PER2 in vertebrate circadian regulation. Locomotor experiments showed that per2 mutant zebrafish display reduced activities under light-dark and 2-h phase delay under constant darkness, and quantitative real time PCR analyses showed up-regulation of cry1aa, cry1ba, cry1bb, and aanat2 but down-regulation of per1b, per3, and bmal1b in per2 mutant zebrafish, suggesting that Per2 is essential for the zebrafish circadian clock. Luciferase reporter assays demonstrated that Per2 represses aanat2 expression through E-box and enhances bmal1b expression through the Ror/Rev-erb response element, implicating that Per2 plays dual roles in the zebrafish circadian clock. Cell transfection and co-immunoprecipitation assays revealed that Per2 enhances bmal1b expression through binding to orphan nuclear receptor Rorα. The enhancing effect of mouse PER2 on Bmal1 transcription is also mediated by RORα even though it binds to REV-ERBα. Moreover, zebrafish Per2 also appears to have tissue-specific regulatory roles in numerous peripheral organs. These findings help define the essential functions of Per2 in the zebrafish circadian clock and in particular provide strong evidence for a positive role of PER2 in the vertebrate circadian system. PMID:25544291

  2. Demographic history and adaptation account for clock gene diversity in humans

    PubMed Central

    Dall'Ara, I; Ghirotto, S; Ingusci, S; Bagarolo, G; Bertolucci, C; Barbujani, G

    2016-01-01

    Circadian clocks give rise to daily oscillations in behavior and physiological functions that often anticipate upcoming environmental changes generated by the Earth rotation. In model organisms a relationship exists between several genes affecting the circadian rhythms and latitude. We investigated the allele distributions at 116 000 single-nucleotide polymorphisms (SNPs) of 25 human clock and clock-related genes from the 1000Genomes Project, and at a reference data set of putatively neutral polymorphisms. The global genetic structure at the clock genes did not differ from that observed at the reference data set. We then tested for evidence of local adaptation searching for FST outliers under both an island and a hierarchical model, and for significant association between allele frequencies and environmental variables by a Bayesian approach. A total of 230 SNPs in 23 genes, or 84 SNPs in 19 genes, depending on the significance thresholds chosen, showed signs of local adaptation, whereas a maximum of 190 SNPs in 23 genes had significant covariance with one or more environmental variables. Only two SNPs from two genes (NPAS2 and AANAT) exhibit both elevated population differentiation and covariance with at least one environmental variable. We then checked whether the SNPs emerging from these analyses fall within a set of candidate SNPs associated with different chronotypes or sleep disorders. Correlation of five such SNPs with environmental variables supports a selective role of latitude or photoperiod, but certainly not a major one. PMID:27301334

  3. Time-related dynamics of variation in core clock gene expression levels in tissues relevant to the immune system.

    PubMed

    Mazzoccoli, G; Sothern, R B; Greco, A; Pazienza, V; Vinciguerra, M; Liu, S; Cai, Y

    2011-01-01

    Immune parameters show rhythmic changes with a 24-h periodicity driven by an internal circadian timing system that relies on clock genes (CGs). CGs form interlocked transcription-translation feedback loops to generate and maintain 24-h mRNA and protein oscillations. In this study we evaluate and compare the profiles and the dynamics of variation of CG expression in peripheral blood, and two lymphoid tissues of mice. Expression levels of seven recognized key CGs (mBmal1, mClock, mPer1, mPer2, mCry1, mCry2, and Rev-erbalpha) were evaluated by quantitative RT- PCR in spleen, thymus and peripheral blood of C57BL/6 male mice housed on a 12-h light (L)-dark (D) cycle and sacrificed every 4 h for 24 h (3-4 mice/time point). We found a statistically significant time-effect in spleen (S), thymus (T) and blood (B) for the original values of expression level of mBmal1 (S), mClock (T, B), mPer1 (S, B), mPer2 (S), mCry1 (S), mCry2 (B) and mRev-Erbalpha (S, T, B) and for the fractional variation calculated between single time-point expression value of mBmal1 (B), mPer2 (T), mCry2 (B) and mRev-Erbalpha (S). A significant 24-h rhythm was validated for five CGs in blood (mClock, mPer1, mPer2, mCry2, mRev-Erbalpha), for four CGs in the spleen (mBmal1, mPer1, mPer2, mRev-Erbalpha), and for three CGs in the thymus (mClock, mPer2, mRev-Erbalpha). The original values of acrophases for mBmal1, mClock, mPer1, mPer2, mCry1 and mCry2 were very similar for spleen and thymus and advanced by several hours for peripheral blood compared to the lymphoid tissues, whereas the phases of mRev-Erbalpha were coincident for all three tissues. In conclusion, central and peripheral lymphoid tissues in the mouse show different sequences of activation of clock gene expression compared to peripheral blood. These differences may underlie the compartmental pattern of web functioning in the immune system.

  4. Unwinding the differences of the mammalian PERIOD clock proteins from crystal structure to cellular function.

    PubMed

    Kucera, Nicole; Schmalen, Ira; Hennig, Sven; Öllinger, Rupert; Strauss, Holger M; Grudziecki, Astrid; Wieczorek, Caroline; Kramer, Achim; Wolf, Eva

    2012-02-28

    The three PERIOD homologues mPER1, mPER2, and mPER3 constitute central components of the mammalian circadian clock. They contain two PAS (PER-ARNT-SIM) domains (PAS-A and PAS-B), which mediate homo- and heterodimeric mPER-mPER interactions as well as interactions with transcription factors and kinases. Here we present crystal structures of PAS domain fragments of mPER1 and mPER3 and compare them with the previously reported mPER2 structure. The structures reveal homodimers, which are mediated by interactions of the PAS-B β-sheet surface including a highly conserved tryptophan (Trp448(mPER1), Trp419(mPER2), Trp359(mPER3)). mPER1 homodimers are additionally stabilized by interactions between the PAS-A domains and mPER3 homodimers by an N-terminal region including a predicted helix-loop-helix motive. We have verified the existence of these homodimer interfaces in solution and inside cells using analytical gel filtration and luciferase complementation assays and quantified their contributions to homodimer stability by analytical ultracentrifugation. We also show by fluorescence recovery after photobleaching analyses that destabilization of the PAS-B/tryptophan dimer interface leads to a faster mobility of mPER2 containing complexes in human U2OS cells. Our study reveals structural and quantitative differences between the homodimeric interactions of the three mouse PERIOD homologues, which are likely to contribute to their distinct clock functions.

  5. Disrupted Ultradian Activity Rhythms and Differential Expression of Several Clock Genes in Interleukin-6-Deficient Mice

    PubMed Central

    Monje, Francisco J.; Cicvaric, Ana; Acevedo Aguilar, Juan Pablo; Elbau, Immanuel; Horvath, Orsolya; Diao, Weifei; Glat, Micaela; Pollak, Daniela D.

    2017-01-01

    The characteristics of the cycles of activity and rest stand out among the most intensively investigated aspects of circadian rhythmicity in humans and experimental animals. Alterations in the circadian patterns of activity and rest are strongly linked to cognitive and emotional dysfunctions in severe mental illnesses such as Alzheimer’s disease (AD) and major depression (MDD). The proinflammatory cytokine interleukin 6 (IL-6) has been prominently associated with the pathogenesis of AD and MDD. However, the potential involvement of IL-6 in the modulation of the diurnal rhythms of activity and rest has not been investigated. Here, we set out to study the role of IL-6 in circadian rhythmicity through the characterization of patterns of behavioral locomotor activity in IL-6 knockout (IL-6 KO) mice and wild-type littermate controls. Deletion of IL-6 did not alter the length of the circadian period or the amount of locomotor activity under either light-entrained or free-running conditions. IL-6 KO mice also presented a normal phase shift in response to light exposure at night. However, the temporal architecture of the behavioral rhythmicity throughout the day, as characterized by the quantity of ultradian activity bouts, was significantly impaired under light-entrained and free-running conditions in IL-6 KO. Moreover, the assessment of clock gene expression in the hippocampus, a brain region involved in AD and depression, revealed altered levels of cry1, dec2, and rev-erb-beta in IL-6 KO mice. These data propose that IL-6 participates in the regulation of ultradian activity/rest rhythmicity and clock gene expression in the mammalian brain. Furthermore, we propose IL-6-dependent circadian misalignment as a common pathogenetic principle in some neurodegenerative and neuropsychiatric disorders. PMID:28382017

  6. A cytoplasmic clock with the same period as the division cycle in Xenopus eggs.

    PubMed Central

    Hara, K; Tydeman, P; Kirschner, M

    1980-01-01

    In most species the cell cycle is arrested in the unfertilized egg. After fertilization the cell cycle is reestablished and a rapid series of cleavages ensues. Preceding the first cleavage in Xenopus the egg undergoes a contraction of its cortex, called the "surface contraction wave," which can be visualized by time-lapse cinematography. This wave of contraction is propagated in a circular manner from the animal pole to the equator. We have found that eggs prevented from cleaving by treatment with antimitotic drugs undergo a sequence of periodic surface contraction waves timed with the cleavage cycle in untreated eggs. In addition, artificially activated eggs, which fail to cleave presumably for lack of a functioning centriole, undergo the same periodic contractions. No nuclear material is required for the periodic waves because a separated egg fragment, produced by constricting a fertilized egg, still undergoes contraction waves with the same period as the cleaving nucleated fragment. These results demonstrate that some expression of the cell cycle persists in the absence of any nuclear material or centrioles, suggesting to us that a biological clock exists in the cytoplasm or cortex of vertebrate eggs, which may be involved in timing the cell cycle. Images PMID:6928638

  7. Effects of continuous white light and 12h white-12h blue light-cycles on the expression of clock genes in diencephalon, liver, and skeletal muscle in chicks.

    PubMed

    Honda, Kazuhisa; Kondo, Makoto; Hiramoto, Daichi; Saneyasu, Takaoki; Kamisoyama, Hiroshi

    2017-02-24

    The core circadian clock mechanism relies on a feedback loop comprised of clock genes, such as the brain and muscle Arnt-like 1 (Bmal1), chriptochrome 1 (Cry1), and period 3 (Per3). Exposure to the light-dark cycle synchronizes the master circadian clock in the brain, and which then synchronizes circadian clocks in peripheral tissues. Birds have long been used as a model for the investigation of circadian rhythm in human neurobiology. In the present study, we examined the effects of continuous light and the combination of white and blue light on the expression of clock genes (Bmal1, Cry1, and Per3) in the central and peripheral tissues in chicks. Seventy two day-old male chicks were weighed, allocated to three groups and maintained under three light schedules: 12h white light-12h dark-cycles group (control); 24h white light group (WW group); 12h white light-12h blue light-cycles group (WB group). The mRNA levels of clock genes in the diencephalon were significantly different between the control and WW groups. On the other hand, the alteration in the mRNA levels of clock genes was similar between the control and WB groups. Similar phenomena were observed in the liver and skeletal muscle (biceps femoris). These results suggest that 12h white-12h blue light-cycles did not disrupt the circadian rhythm of clock gene expression in chicks.

  8. Neural clocks and Neuropeptide F/Y regulate circadian gene expression in a peripheral metabolic tissue.

    PubMed

    Erion, Renske; King, Anna N; Wu, Gang; Hogenesch, John B; Sehgal, Amita

    2016-04-14

    Metabolic homeostasis requires coordination between circadian clocks in different tissues. Also, systemic signals appear to be required for some transcriptional rhythms in the mammalian liver and the Drosophila fat body. Here we show that free-running oscillations of the fat body clock require clock function in the PDF-positive cells of the fly brain. Interestingly, rhythmic expression of the cytochrome P450 transcripts, sex-specific enzyme 1 (sxe1) and Cyp6a21, which cycle in the fat body independently of the local clock, depends upon clocks in neurons expressing neuropeptide F (NPF). NPF signaling itself is required to drive cycling of sxe1 and Cyp6a21 in the fat body, and its mammalian ortholog, Npy, functions similarly to regulate cycling of cytochrome P450 genes in the mouse liver. These data highlight the importance of neuronal clocks for peripheral rhythms, particularly in a specific detoxification pathway, and identify a novel and conserved role for NPF/Npy in circadian rhythms.

  9. The regulatory network mediated by circadian clock genes is related to heterosis in rice.

    PubMed

    Shen, Guojing; Hu, Wei; Zhang, Bo; Xing, Yongzhong

    2015-03-01

    Exploitation of heterosis in rice (Oryza sativa L.) has contributed greatly to global food security. In this study, we generated three sets of reciprocal F1 hybrids of indica and japonica subspecies to evaluate the relationship between yield heterosis and the circadian clock. There were no differences in trait performance or heterosis between the reciprocal hybrids, indicating no maternal effects on heterosis. The indica-indica and indica-japonica reciprocal F1 hybrids exhibited pronounced heterosis for chlorophyll and starch content in leaves and for grain yield/biomass. In contrast, the japonica-japonica F1 hybrids showed low heterosis. The three circadian clock genes investigated expressed in an above-high-parent pattern (AHP) at seedling stage in all the hybrids. The five genes downstream of the circadian clock, and involved in chlorophyll and starch metabolic pathways, were expressed in AHP in hybrids with strong better-parent heterosis (BPH). Similarly, three of these five genes in the japonica-japonica F1 hybrids showing low BPH were expressed in positive overdominance, but the other two genes were expressed in additive or negative overdominance. These results indicated that the expression patterns of circadian clock genes and their downstream genes are associated with heterosis, which suggests that the circadian rhythm pathway may be related to heterosis in rice.

  10. Systems Chronobiology: Global Analysis of Gene Regulation in a 24-Hour Periodic World.

    PubMed

    Mermet, Jérôme; Yeung, Jake; Naef, Felix

    2017-03-01

    Mammals have evolved an internal timing system, the circadian clock, which synchronizes physiology and behavior to the daily light and dark cycles of the Earth. The master clock, located in the suprachiasmatic nucleus (SCN) of the brain, takes fluctuating light input from the retina and synchronizes other tissues to the same internal rhythm. The molecular clocks that drive these circadian rhythms are ticking in nearly all cells in the body. Efforts in systems chronobiology are now being directed at understanding, on a comprehensive scale, how the circadian clock controls different layers of gene regulation to provide robust timing cues at the cellular and tissue level. In this review, we introduce some basic concepts underlying periodicity of gene regulation, and then highlight recent genome-wide investigations on the propagation of rhythms across multiple regulatory layers in mammals, all the way from chromatin conformation to protein accumulation.

  11. Extent of mismatch between the period of circadian clocks and light/dark cycles determines time-to-emergence in fruit flies.

    PubMed

    Yadav, Pankaj; Choudhury, Deepak; Sadanandappa, Madhumala K; Sharma, Vijay Kumar

    2015-08-01

    Circadian clocks time developmental stages of fruit flies Drosophila melanogaster, while light/dark (LD) cycles delimit emergence of adults, conceding only during the "allowed gate." Previous studies have revealed that time-to-emergence can be altered by mutations in the core clock gene period (per), or by altering the length of LD cycles. Since this evidence came from studies on genetically manipulated flies, or on flies maintained under LD cycles with limited range of periods, inferences that can be drawn are limited. Moreover, the extent of shortening or lengthening of time-to-emergence remains yet unknown. In order to pursue this further, we assayed time-to-emergence of D. melanogaster under 12 different LD cycles as well as in constant light (LL) and constant dark conditions (DD). Time-to-emergence in flies occurred earlier under LL than in LD cycles and DD. Among the LD cycles, time-to-emergence occurred earlier under T4-T8, followed by T36-T48, and then T12-T32, suggesting that egg-to-emergence duration in flies becomes shorter when the length of LD cycles deviates from 24 h, bearing a strong positive and a marginally negative correlation with day length, for values shorter and longer than 24 h, respectively. These results suggest that the extent of mismatch between the period of circadian clocks and environmental cycles determines the time-to-emergence in Drosophila.

  12. Role of monochromatic light on daily variation of clock gene expression in the pineal gland of chick.

    PubMed

    Jiang, Nan; Wang, Zixu; Cao, Jing; Dong, Yulan; Chen, Yaoxing

    2016-11-01

    The avian pineal gland is a master clock that can receive external photic cues and translate them into output rhythms. To clarify whether a shift in light wavelength can influence the circadian expression in chick pineal gland, a total of 240 Arbor Acre male broilers were exposed to white light (WL), red light (RL), green light (GL) or blue light (BL). After 2weeks light illumination, circadian expressions of seven core clock genes in pineal gland and the level of melatonin in plasma were examined. The results showed after illumination with monochromatic light, 24h profiles of all clock gene mRNAs retained circadian oscillation, except that RL tended to disrupt the rhythm of cCry2. Compared to WL, BL advanced the acrophases of the negative elements (cCry1, cCry2, cPer2 and cPer3) by 0.1-1.5h and delayed those of positive elements (cClock, cBmal1 and cBmal2) by 0.2-0.8h. And, RL advanced all clock genes except cClock and cPer2 by 0.3-2.1h, while GL delayed all clock genes by 0.5-1.5h except cBmal2. Meanwhile, GL increased the amplitude and mesor of positive and reduced both parameters of negative clock genes, but RL showed the opposite pattern. Although the acrophase of plasma melatonin was advanced by both GL and RL, the melatonin level was significantly increased in GL and decreased in RL. This tendency was consistent with the variations in the positive clock gene mRNA levels under monochromatic light and contrasted with those of negative clock genes. Therefore, we speculate that GL may enhance positive clock genes expression, leading to melatonin synthesis, whereas RL may enhance negative genes expression, suppressing melatonin synthesis.

  13. Nucleotide sequences of immunoglobulin eta genes of chimpanzee and orangutan: DNA molecular clock and hominoid evolution

    SciTech Connect

    Sakoyama, Y.; Hong, K.J.; Byun, S.M.; Hisajima, H.; Ueda, S.; Yaoita, Y.; Hayashida, H.; Miyata, T.; Honjo, T.

    1987-02-01

    To determine the phylogenetic relationships among hominoids and the dates of their divergence, the complete nucleotide sequences of the constant region of the immunoglobulin eta-chain (C/sub eta1/) genes from chimpanzee and orangutan have been determined. These sequences were compared with the human eta-chain constant-region sequence. A molecular clock (silent molecular clock), measured by the degree of sequence divergence at the synonymous (silent) positions of protein-encoding regions, was introduced for the present study. From the comparison of nucleotide sequences of ..cap alpha../sub 1/-antitrypsin and ..beta..- and delta-globulin genes between humans and Old World monkeys, the silent molecular clock was calibrated: the mean evolutionary rate of silent substitution was determined to be 1.56 x 10/sup -9/ substitutions per site per year. Using the silent molecular clock, the mean divergence dates of chimpanzee and orangutan from the human lineage were estimated as 6.4 +/- 2.6 million years and 17.3 +/- 4.5 million years, respectively. It was also shown that the evolutionary rate of primate genes is considerably slower than those of other mammalian genes.

  14. Comprehensive Mapping of Regional Expression of the Clock Protein PERIOD2 in Rat Forebrain across the 24-h Day

    PubMed Central

    Harbour, Valerie L.; Weigl, Yuval; Robinson, Barry; Amir, Shimon

    2013-01-01

    In mammals, a light-entrainable clock located in the suprachiasmatic nucleus (SCN) regulates circadian rhythms by synchronizing oscillators throughout the brain and body. Notably, the nature of the relation between the SCN clock and subordinate oscillators in the rest of the brain is not well defined. We performed a high temporal resolution analysis of the expression of the circadian clock protein PERIOD2 (PER2) in the rat forebrain to characterize the distribution, amplitude and phase of PER2 rhythms across different regions. Eighty-four LEW/Crl male rats were entrained to a 12-h: 12-h light/dark cycle, and subsequently perfused every 30 min across the 24-h day for a total of 48 time-points. PER2 expression was assessed with immunohistochemistry and analyzed using automated cell counts. We report the presence of PER2 expression in 20 forebrain areas important for a wide range of motivated and appetitive behaviors including the SCN, bed nucleus, and several regions of the amygdala, hippocampus, striatum, and cortex. Eighteen areas displayed significant PER2 rhythms, which peaked at different times of day. Our data demonstrate a previously uncharacterized regional distribution of rhythms of a clock protein expression in the brain that provides a sound basis for future studies of circadian clock function in animal models of disease. PMID:24124556

  15. Structural and functional analyses of PAS domain interactions of the clock proteins Drosophila PERIOD and mouse PERIOD2.

    PubMed

    Hennig, Sven; Strauss, Holger M; Vanselow, Katja; Yildiz, Ozkan; Schulze, Sabrina; Arens, Julia; Kramer, Achim; Wolf, Eva

    2009-04-28

    PERIOD proteins are central components of the Drosophila and mammalian circadian clocks. The crystal structure of a Drosophila PERIOD (dPER) fragment comprising two PER-ARNT-SIM (PAS) domains (PAS-A and PAS-B) and two additional C-terminal alpha-helices (alphaE and alphaF) has revealed a homodimer mediated by intermolecular interactions of PAS-A with tryptophane 482 in PAS-B and helix alphaF. Here we present the crystal structure of a monomeric PAS domain fragment of dPER lacking the alphaF helix. Moreover, we have solved the crystal structure of a PAS domain fragment of the mouse PERIOD homologue mPER2. The mPER2 structure shows a different dimer interface than dPER, which is stabilized by interactions of the PAS-B beta-sheet surface including tryptophane 419 (equivalent to Trp482dPER). We have validated and quantitatively analysed the homodimer interactions of dPER and mPER2 by site-directed mutagenesis using analytical gel filtration, analytical ultracentrifugation, and co-immunoprecipitation experiments. Furthermore we show, by yeast-two-hybrid experiments, that the PAS-B beta-sheet surface of dPER mediates interactions with TIMELESS (dTIM). Our study reveals quantitative and qualitative differences between the homodimeric PAS domain interactions of dPER and its mammalian homologue mPER2. In addition, we identify the PAS-B beta-sheet surface as a versatile interaction site mediating mPER2 homodimerization in the mammalian system and dPER-dTIM heterodimer formation in the Drosophila system.

  16. Clock gene polymorphism and scheduling of migration: a geolocator study of the barn swallow Hirundo rustica

    PubMed Central

    Bazzi, Gaia; Ambrosini, Roberto; Caprioli, Manuela; Costanzo, Alessandra; Liechti, Felix; Gatti, Emanuele; Gianfranceschi, Luca; Podofillini, Stefano; Romano, Andrea; Romano, Maria; Scandolara, Chiara; Saino, Nicola; Rubolini, Diego

    2015-01-01

    Circannual rhythms often rely on endogenous seasonal photoperiodic timers involving ‘clock’ genes, and Clock gene polymorphism has been associated to variation in phenology in some bird species. In the long-distance migratory barn swallow Hirundo rustica, individuals bearing the rare Clock allele with the largest number of C-terminal polyglutamine repeats found in this species (Q8) show a delayed reproduction and moult later. We explored the association between Clock polymorphism and migration scheduling, as gauged by light-level geolocators, in two barn swallow populations (Switzerland; Po Plain, Italy). Genetic polymorphism was low: 91% of the 64 individuals tracked year-round were Q7/Q7 homozygotes. We compared the phenology of the rare genotypes with the phenotypic distribution of Q7/Q7 homozygotes within each population. In Switzerland, compared to Q7/Q7, two Q6/Q7 males departed earlier from the wintering grounds and arrived earlier to their colony in spring, while a single Q7/Q8 female was delayed for both phenophases. On the other hand, in the Po Plain, three Q6/Q7 individuals had a similar phenology compared to Q7/Q7. The Swiss data are suggestive for a role of genetic polymorphism at a candidate phenological gene in shaping migration traits, and support the idea that Clock polymorphism underlies phenological variation in birds. PMID:26197782

  17. The orphan receptor Rev-erbα gene is a target of the circadian clock pacemaker

    PubMed Central

    Triqueneaux, Gérard; Thenot, Sandrine; Kakizawa, Tomoko; Antoch, Marina P; Safi, Rachid; Takahashi, Joseph S; Delaunay, Franck; Laudet, Vincent

    2013-01-01

    Rev-erbα is a ubiquitously expressed orphan nuclear receptor which functions as a constitutive transcriptional repressor and is expressed in vertebrates according to a robust circadian rhythm. We report here that two Rev-erbα mRNA isoforms, namely Rev-erbα1 and Rev-erbα2, are generated through alternative promoter usage and that both show a circadian expression pattern in an in vitro system using serum-shocked fibroblasts. Both promoter regions P1 (Rev-erbα1) and P2 (Rev-erbα2) contain several E-box DNA sequences, which function as response elements for the core circadian-clock components: CLOCK and BMAL1. The CLOCK–BMAL1 heterodimer stimulates the activity of both P1 and P2 promoters in transient transfection assay by 3–6-fold. This activation was inhibited by the overexpression of CRY1, a component of the negative limb of the circadian transcriptional loop. Critical E-box elements were mapped within both promoters. This regulation is conserved in vertebrates since we found that the CLOCK–BMAL1 heterodimer also regulates the zebrafish Rev-erbα gene. In line with these data Rev-erbα circadian expression was strongly impaired in the livers of Clock mutant mice and in the pineal glands of zebrafish embryos treated with Clock and Bmal1 antisense oligonucleotides. Together these data demonstrate that CLOCK is a critical regulator of Rev-erbα circadian gene expression in evolutionarily distant vertebrates and suggest a role for Rev-erbα in the circadian clock output. PMID:15591021

  18. Circadian clock signaling in Arabidopsis thaliana: from gene expression to physiology and development.

    PubMed

    Más, Paloma

    2005-01-01

    The daily rotation of the earth on its axis leads to predictable periodic fluctuations of environmental conditions. Accordingly, most organisms have evolved an internal timing mechanism, the circadian clock, which is able to recognize these 24-hour rhythmic oscillations. In plants, the temporal synchronization of physiology with the environment is essential for successful plant growth and development. The intimate connection between light signaling pathways and the circadian oscillator allows the anticipation of the environmental transitions and the measurement of day-length as an indicator of changing seasons. In recent years, significant advances have been made in the genetic and molecular dissection of the plant circadian system, mostly in Arabidopsis thaliana. The overall plant clock organization is highly complex; the system seems to include several input pathways, tightly regulated central oscillators and a myriad of outputs. The molecular cloning and characterization of a number of clock components has greatly improved our view of the plant central oscillator and additional players will most likely come into place very soon. Molecular mechanisms underlying circadian clock function are also beginning to be characterized. The emerging model relies on negative feedback loops at the core of the oscillator. Additional levels of post-transcriptional and post-translational regulation also contribute to the generation and maintenance of the rhythms. Globally, these studies have shed new light on how the clock coordinates plant physiology and development with the daily and seasonal environmental cycles.

  19. Polymorphism at the Clock gene predicts phenology of long-distance migration in birds.

    PubMed

    Saino, Nicola; Bazzi, Gaia; Gatti, Emanuele; Caprioli, Manuela; Cecere, Jacopo G; Possenti, Cristina D; Galimberti, Andrea; Orioli, Valerio; Bani, Luciano; Rubolini, Diego; Gianfranceschi, Luca; Spina, Fernando

    2015-04-01

    Dissecting phenotypic variance in life history traits into its genetic and environmental components is at the focus of evolutionary studies and of pivotal importance to identify the mechanisms and predict the consequences of human-driven environmental change. The timing of recurrent life history events (phenology) is under strong selection, but the study of the genes that control potential environmental canalization in phenological traits is at its infancy. Candidate genes for circadian behaviour entrained by photoperiod have been screened as potential controllers of phenological variation of breeding and moult in birds, with inconsistent results. Despite photoperiodic control of migration is well established, no study has reported on migration phenology in relation to polymorphism at candidate genes in birds. We analysed variation in spring migration dates within four trans-Saharan migratory species (Luscinia megarhynchos; Ficedula hypoleuca; Anthus trivialis; Saxicola rubetra) at a Mediterranean island in relation to Clock and Adcyap1 polymorphism. Individuals with larger number of glutamine residues in the poly-Q region of Clock gene migrated significantly later in one or, respectively, two species depending on sex and whether the within-individual mean length or the length of the longer Clock allele was considered. The results hinted at dominance of the longer Clock allele. No significant evidence for migration date to covary with Adcyap1 polymorphism emerged. This is the first evidence that migration phenology is associated with Clock in birds. This finding is important for evolutionary studies of migration and sheds light on the mechanisms that drive bird phenological changes and population trends in response to climate change.

  20. Weight cycling promotes fat gain and altered clock gene expression in adipose tissue in C57BL/6J mice.

    PubMed

    Dankel, S N; Degerud, E M; Borkowski, K; Fjære, E; Midtbø, L K; Haugen, C; Solsvik, M H; Lavigne, A M; Liaset, B; Sagen, J V; Kristiansen, K; Mellgren, G; Madsen, L

    2014-01-15

    Repeated attempts to lose weight by temporary dieting may result in weight cycling, eventually further gain of body fat, and possible metabolic adaptation. We tested this with a controlled experiment in C57BL/6J mice subjected to four weight cycles (WC), continuous hypercaloric feeding (HF), or low-fat feeding (LF). To search for genes involved in an adaptive mechanism to former weight cycling and avoid acute effects of the last cycle, the last hypercaloric feeding period was prolonged by an additional 2 wk before euthanization. Total energy intake was identical in WC and HF. However, compared with HF, the WC mice gained significantly more total body mass and fat mass and showed increased levels of circulating leptin and lipids in liver. Both the HF and WC groups showed increased adipocyte size and insulin resistance. Despite these effects, we also observed an interesting maintenance of circulating adiponectin and free fatty acid levels after WC, whereas changes in these parameters were observed in HF mice. Global gene expression was analyzed by microarrays. Weight-cycled mice were characterized by a downregulation of several clock genes (Dbp, Tef, Per1, Per2, Per3, and Nr1d2) in adipose tissues, which was confirmed by quantitative PCR. In 3T3-L1 cells, we found reduced expression of Dbp and Tef early in adipogenic differentiation, which was mediated via cAMP-dependent signaling. Our data suggest that clock genes in adipose tissue may play a role in metabolic adaptation to weight cycling.

  1. Stochastic Regulation of her1/7 Gene Expression Is the Source of Noise in the Zebrafish Somite Clock Counteracted by Notch Signalling

    PubMed Central

    Jenkins, Robert P.; Hanisch, Anja; Soza-Ried, Cristian; Sahai, Erik

    2015-01-01

    The somite segmentation clock is a robust oscillator used to generate regularly-sized segments during early vertebrate embryogenesis. It has been proposed that the clocks of neighbouring cells are synchronised via inter-cellular Notch signalling, in order to overcome the effects of noisy gene expression. When Notch-dependent communication between cells fails, the clocks of individual cells operate erratically and lose synchrony over a period of about 5 to 8 segmentation clock cycles (2–3 hours in the zebrafish). Here, we quantitatively investigate the effects of stochasticity on cell synchrony, using mathematical modelling, to investigate the likely source of such noise. We find that variations in the transcription, translation and degradation rate of key Notch signalling regulators do not explain the in vivo kinetics of desynchronisation. Rather, the analysis predicts that clock desynchronisation, in the absence of Notch signalling, is due to the stochastic dissociation of Her1/7 repressor proteins from the oscillating her1/7 autorepressed target genes. Using in situ hybridisation to visualise sites of active her1 transcription, we measure an average delay of approximately three minutes between the times of activation of the two her1 alleles in a cell. Our model shows that such a delay is sufficient to explain the in vivo rate of clock desynchronisation in Notch pathway mutant embryos and also that Notch-mediated synchronisation is sufficient to overcome this stochastic variation. This suggests that the stochastic nature of repressor/DNA dissociation is the major source of noise in the segmentation clock. PMID:26588097

  2. Monitoring cell-autonomous circadian clock rhythms of gene expression using luciferase bioluminescence reporters.

    PubMed

    Ramanathan, Chidambaram; Khan, Sanjoy K; Kathale, Nimish D; Xu, Haiyan; Liu, Andrew C

    2012-09-27

    In mammals, many aspects of behavior and physiology such as sleep-wake cycles and liver metabolism are regulated by endogenous circadian clocks (reviewed). The circadian time-keeping system is a hierarchical multi-oscillator network, with the central clock located in the suprachiasmatic nucleus (SCN) synchronizing and coordinating extra-SCN and peripheral clocks elsewhere. Individual cells are the functional units for generation and maintenance of circadian rhythms, and these oscillators of different tissue types in the organism share a remarkably similar biochemical negative feedback mechanism. However, due to interactions at the neuronal network level in the SCN and through rhythmic, systemic cues at the organismal level, circadian rhythms at the organismal level are not necessarily cell-autonomous. Compared to traditional studies of locomotor activity in vivo and SCN explants ex vivo, cell-based in vitro assays allow for discovery of cell-autonomous circadian defects. Strategically, cell-based models are more experimentally tractable for phenotypic characterization and rapid discovery of basic clock mechanisms. Because circadian rhythms are dynamic, longitudinal measurements with high temporal resolution are needed to assess clock function. In recent years, real-time bioluminescence recording using firefly luciferase as a reporter has become a common technique for studying circadian rhythms in mammals, as it allows for examination of the persistence and dynamics of molecular rhythms. To monitor cell-autonomous circadian rhythms of gene expression, luciferase reporters can be introduced into cells via transient transfection or stable transduction. Here we describe a stable transduction protocol using lentivirus-mediated gene delivery. The lentiviral vector system is superior to traditional methods such as transient transfection and germline transmission because of its efficiency and versatility: it permits efficient delivery and stable integration into the host

  3. Effect of sleep deprivation on rhythms of clock gene expression and melatonin in humans.

    PubMed

    Ackermann, Katrin; Plomp, Rosina; Lao, Oscar; Middleton, Benita; Revell, Victoria L; Skene, Debra J; Kayser, Manfred

    2013-08-01

    This study investigated the impact of sleep deprivation on the human circadian system. Plasma melatonin and cortisol levels and leukocyte expression levels of 12 genes were examined over 48 h (sleep vs. no-sleep nights) in 12 young males (mean±SD: 23±5 yrs). During one night of total sleep deprivation, BMAL1 expression was suppressed, the heat shock gene HSPA1B expression was induced, and the amplitude of the melatonin rhythm increased, whereas other high-amplitude clock gene rhythms (e.g., PER1-3, REV-ERBα) remained unaffected. These data suggest that the core clock mechanism in peripheral oscillators is compromised during acute sleep deprivation.

  4. The Light Wavelength Affects the Ontogeny of Clock Gene Expression and Activity Rhythms in Zebrafish Larvae.

    PubMed

    Di Rosa, Viviana; Frigato, Elena; López-Olmeda, José F; Sánchez-Vázquez, Francisco J; Bertolucci, Cristiano

    2015-01-01

    Light plays a key role in synchronizing rhythms and setting the phase of early development. However, to date, little is known about the impact of light wavelengths during the ontogeny of the molecular clock and the behavioural rhythmicity. The aim of this research was to determine the effect of light of different wavelengths (white, blue and red) on the onset of locomotor activity and clock gene (per1b, per2, clock1, bmal1 and dbp) expression rhythms. For this purpose, 4 groups of zebrafish embryo/larvae were raised from 0 to 7 days post-fertilization (dpf) under the following lighting conditions: three groups maintained under light:dark (LD) cycles with white (full visible spectrum, LDW), blue (LDB), or red light (LDR), and one group raised under constant darkness (DD). The results showed that lighting conditions influenced activity rhythms. Larvae were arrhythmic under DD, while under LD cycles they developed wavelength-dependent daily activity rhythms which appeared earlier under LDB (4 dpf) than under LDW or LDR (5 dpf). The results also revealed that development and lighting conditions influenced clock gene expression. While clock1 rhythmic expression appeared in all lighting conditions at 7 dpf, per1b, per2 and dbp showed daily variations already at 3 dpf. Curiously, bmal1 showed consistent rhythmic expression from embryonic stage (0 dpf). Summarizing, the data revealed that daily rhythms appeared earlier in the larvae reared under LDB than in those reared under LDW and LDR. These results emphasize the importance of lighting conditions and wavelengths during early development for the ontogeny of daily rhythms of gene expression and how these rhythms are reflected on the behavioural rhythmicity of zebrafish larvae.

  5. From Blue Light to Clock Genes in Zebrafish ZEM-2S Cells

    PubMed Central

    Ramos, Bruno C. R.; Moraes, Maria Nathália C. M.; Poletini, Maristela O.; Lima, Leonardo H. R. G.; Castrucci, Ana Maria L.

    2014-01-01

    Melanopsin has been implicated in the mammalian photoentrainment by blue light. This photopigment, which maximally absorbs light at wavelengths between 470 and 480 nm depending on the species, is found in the retina of all classes of vertebrates so far studied. In mammals, melanopsin activation triggers a signaling pathway which resets the circadian clock in the suprachiasmatic nucleus (SCN). Unlike mammals, Drosophila melanogaster and Danio rerio do not rely only on their eyes to perceive light, in fact their whole body may be capable of detecting light and entraining their circadian clock. Melanopsin, teleost multiple tissue (tmt) opsin and others such as neuropsin and va-opsin, are found in the peripheral tissues of Danio rerio, however, there are limited data concerning the photopigment/s or the signaling pathway/s directly involved in light detection. Here, we demonstrate that melanopsin is a strong candidate to mediate synchronization of zebrafish cells. The deduced amino acid sequence of melanopsin, although being a vertebrate opsin, is more similar to invertebrate than vertebrate photopigments, and melanopsin photostimulation triggers the phosphoinositide pathway through activation of a Gq/11-type G protein. We stimulated cultured ZEM-2S cells with blue light at wavelengths consistent with melanopsin maximal absorption, and evaluated the time course expression of per1b, cry1b, per2 and cry1a. Using quantitative PCR, we showed that blue light is capable of slightly modulating per1b and cry1b genes, and drastically increasing per2 and cry1a expression. Pharmacological assays indicated that per2 and cry1a responses to blue light are evoked through the activation of the phosphoinositide pathway, which crosstalks with nitric oxide (NO) and mitogen activated protein MAP kinase (MAPK) to activate the clock genes. Our results suggest that melanopsin may be important in mediating the photoresponse in Danio rerio ZEM-2S cells, and provide new insights about the

  6. The circadian clock-related gene pex regulates a negative cis element in the kaiA promoter region.

    PubMed

    Kutsuna, Shinsuke; Kondo, Takao; Ikegami, Haruki; Uzumaki, Tatsuya; Katayama, Mitsunori; Ishiura, Masahiro

    2007-11-01

    In the cyanobacterium Synechococcus sp. strain PCC 7942, a circadian clock-related gene, pex, was identified as the gene prolonging the period of the clock. A PadR domain, which is a newly classified transcription factor domain, and the X-ray crystal structure of the Pex protein suggest a role for Pex in transcriptional regulation in the circadian system. However, the regulatory target of the Pex protein is unknown. To determine the role of Pex, we monitored bioluminescence rhythms that reported the expression activity of the kaiA gene or the kaiBC operon in pex deficiency, pex constitutive expression, and the wild-type genotype. The expression of kaiA in the pex-deficient or constitutive expression genotype was 7 or 1/7 times that of the wild type, respectively, suggesting that kaiA is the target of negative regulation by Pex. In contrast, the expression of the kaiBC gene in the two pex-related genotypes was the same as that in the wild type, suggesting that Pex specifically regulates kaiA expression. We used primer extension analysis to map the transcription start site for the kaiA gene 66 bp upstream of the translation start codon. Mapping with deletion and base pair substitution of the kaiA upstream region revealed that a 5-bp sequence in this region was essential for the regulation of kaiA. The repression or constitutive expression of the kaiA transgene caused the prolongation or shortening of the circadian period, respectively, suggesting that the Pex protein changes the period via the negative regulation of kaiA.

  7. Dissecting Daily and Circadian Expression Rhythms of Clock-Controlled Genes in Human Blood.

    PubMed

    Lech, Karolina; Ackermann, Katrin; Revell, Victoria L; Lao, Oscar; Skene, Debra J; Kayser, Manfred

    2016-02-01

    The identification and investigation of novel clock-controlled genes (CCGs) has been conducted thus far mainly in model organisms such as nocturnal rodents, with limited information in humans. Here, we aimed to characterize daily and circadian expression rhythms of CCGs in human peripheral blood during a sleep/sleep deprivation (S/SD) study and a constant routine (CR) study. Blood expression levels of 9 candidate CCGs (SREBF1, TRIB1, USF1, THRA1, SIRT1, STAT3, CAPRIN1, MKNK2, and ROCK2), were measured across 48 h in 12 participants in the S/SD study and across 33 h in 12 participants in the CR study. Statistically significant rhythms in expression were observed for STAT3, SREBF1, TRIB1, and THRA1 in samples from both the S/SD and the CR studies, indicating that their rhythmicity is driven by the endogenous clock. The MKNK2 gene was significantly rhythmic in the S/SD but not the CR study, which implies its exogenously driven rhythmic expression. In addition, we confirmed the circadian expression of PER1, PER3, and REV-ERBα in the CR study samples, while BMAL1 and HSPA1B were not significantly rhythmic in the CR samples; all 5 genes previously showed significant expression in the S/SD study samples. Overall, our results demonstrate that rhythmic expression patterns of clock and selected clock-controlled genes in human blood cells are in part determined by exogenous factors (sleep and fasting state) and in part by the endogenous circadian timing system. Knowledge of the exogenous and endogenous regulation of gene expression rhythms is needed prior to the selection of potential candidate marker genes for future applications in medical and forensic settings.

  8. Circadian Rhythms of Fetal Liver Transcription Persist in the Absence of Canonical Circadian Clock Gene Expression Rhythms In Vivo

    PubMed Central

    Li, Chengwei; Yu, Shuang; Zhong, Xiaoling; Wu, Jianguo; Li, Xiaodong

    2012-01-01

    The cellular circadian clock and systemic cues drive rhythmicity in the transcriptome of adult peripheral tissues. However, the oscillating status of the circadian clocks in fetal tissues, and their response to maternal cues, are less clear. Most clock genes do not cycle in fetal livers from mice and rats, although tissue level rhythms rapidly emerge when fetal mouse liver explants are cultured in vitro. Thus, in the fetal mouse liver, the circadian clock does not oscillate at the cellular level (but is induced to oscillate in culture). To gain a comprehensive overview of the clock status in the fetal liver during late gestation, we performed microarray analyses on fetal liver tissues. In the fetal liver we did not observe circadian rhythms of clock gene expression or many other transcripts known to be rhythmically expressed in the adult liver. Nevertheless, JTK_CYCLE analysis identified some transcripts in the fetal liver that were rhythmically expressed, albeit at low amplitudes. Upon data filtering by coefficient of variation, the expression levels for transcripts related to pancreatic exocrine enzymes and zymogen secretion were found to undergo synchronized daily fluctuations at high amplitudes. These results suggest that maternal cues influence the fetal liver, despite the fact that we did not detect circadian rhythms of canonical clock gene expression in the fetal liver. These results raise important questions on the role of the circadian clock, or lack thereof, during ontogeny. PMID:22383974

  9. Effects of bright light exposure during daytime on peripheral clock gene expression in humans

    NASA Astrophysics Data System (ADS)

    Sato, Maki; Wakamura, Tomoko; Morita, Takeshi; Okamoto, Akihiko; Akashi, Makoto; Matsui, Takuya; Sato, Motohiko

    2016-12-01

    Light is the strongest synchronizer controlling circadian rhythms. The intensity and duration of light change throughout the year, thereby influencing body weight, food preferences, and melatonin secretion in humans and animals. Although the expression of clock genes has been examined using human samples, it currently remains unknown whether bright light during the daytime affects the expression of these genes in humans. Therefore, we herein investigated the effects of bright light exposure during the daytime on clock gene expression in the hair follicular and root cells of the human scalp. Seven healthy men (20.4 ± 2.2 years old; 172.3 ± 5.8 cm; 64.3 ± 8.5 kg; BMI 21.7 ± 3.1 kg/m2, mean ± SD) participated in this study. Subjects completed 3-day experimental sessions twice in 1 month during which they were exposed to bright and dim light conditions. The mRNA expression of Per1-3, Cry1-2, Rev-erb-α (Nr1d1), Rev-erb-β (Nr1d2), and Dec1 was analyzed using branched DNA probes. No significant changes were observed in the expression of Per1, Per2, Per3, Cry1, Cry2, Rev-erb-α (Nr1d1), or Dec1 following exposure to bright light conditions. However, the expression of Rev-erb-β (Nr1d2) tended to be stronger under bright light than dim light conditions. These results suggest that the bright light stimulus did not influence the expression of clock genes in humans. Long-lasting bright light exposure during the daytime may be required to change the expression of clock genes in humans.

  10. CLOCK gene variation is associated with incidence of type-2 diabetes and cardiovascular diseases in type-2 diabetic subjects: dietary modulation in the PREDIMED randomized trial

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Background Circadian rhythms regulate key biological processes influencing metabolic pathways. Dysregulation is associated with type 2 diabetes (T2D) and cardiovascular diseases (CVD). Circadian rhythms are generated by a transcriptional autoregulatory feedback loop involving core clock genes. CLOCK...

  11. Effects of Nocturnal Light on (Clock) Gene Expression in Peripheral Organs: A Role for the Autonomic Innervation of the Liver

    PubMed Central

    van der Vliet, Jan; van Heijningen, Caroline; van Eden, Corbert G.; Kalsbeek, Andries; Pévet, Paul; Buijs, Ruud M.

    2009-01-01

    Background The biological clock, located in the hypothalamic suprachiasmatic nucleus (SCN), controls the daily rhythms in physiology and behavior. Early studies demonstrated that light exposure not only affects the phase of the SCN but also the functional activity of peripheral organs. More recently it was shown that the same light stimulus induces immediate changes in clock gene expression in the pineal and adrenal, suggesting a role of peripheral clocks in the organ-specific output. In the present study, we further investigated the immediate effect of nocturnal light exposure on clock genes and metabolism-related genes in different organs of the rat. In addition, we investigated the role of the autonomic nervous system as a possible output pathway of the SCN to modify the activity of the liver after light exposure. Methodology and Principal Findings First, we demonstrated that light, applied at different circadian times, affects clock gene expression in a different manner, depending on the time of day and the organ. However, the changes in clock gene expression did not correlate in a consistent manner with those of the output genes (i.e., genes involved in the functional output of an organ). Then, by selectively removing the autonomic innervation to the liver, we demonstrated that light affects liver gene expression not only via the hormonal pathway but also via the autonomic input. Conclusion Nocturnal light immediately affects peripheral clock gene expression but without a clear correlation with organ-specific output genes, raising the question whether the peripheral clock plays a “decisive” role in the immediate (functional) response of an organ to nocturnal light exposure. Interestingly, the autonomic innervation of the liver is essential to transmit the light information from the SCN, indicating that the autonomic nervous system is an important gateway for the SCN to cause an immediate resetting of peripheral physiology after phase-shift inducing light

  12. Differential effects of transient constant light-dark conditions on daily rhythms of Period and Clock transcripts during Senegalese sole metamorphosis.

    PubMed

    Martín-Robles, Águeda J; Whitmore, David; Pendón, Carlos; Muñoz-Cueto, José A

    2013-06-01

    Studies on the developmental onset of the teleost circadian clock have been carried out in zebrafish and, recently, in rainbow trout and Senegalese sole, where rhythms of clock gene expression entrained by light-dark (LD) cycles have been reported from the first days post fertilization. However, investigations of molecular clock rhythms during crucial developmental phases such as metamorphosis are absent in vertebrates. In this study, we documented the daily expression profile of Per1, Per2, Per3, and Clock during Senegalese sole pre-, early-, middle-, and post-metamorphic stages under LD 14:10 cycles (LD group), as well as under transient exposure to constant light (LL-LD group) or constant dark (DD-LD group) conditions. Our results revealed that robust rhythms of clock genes were maintained along the metamorphic process, although with declining amplitudes and expression levels. All daily profiles were affected by transient constant conditions, in particular Per1, Per3, and Clock amplitudes and Per2 acrophase. Rhythm parameters were progressively restored upon reversion to LD cycles but even after 9 d under cycling conditions, a prolonged effect on clock function was observed, especially in the LL-LD group. These results reflect the differential sensitivity of clock machinery of sole to transitory light cues, being Per1 and Per3 predominantly clock regulated and supporting the role of Per2 as part of the light input pathway. Interestingly, there is no reversal in the phase of clock gene rhythms between pre- and post-metamorphic animals that would be coincident with the switch from diurnal to nocturnal locomotor activity, which occurs in this species just before the beginning of this process. Whether specialized central pacemakers dictate the phase of locomotor activity or this control is exerted outside of the core clock mechanism remains to be elucidated. Our results emphasize the importance of maintaining cycling light-dark conditions in aquaculture practices

  13. [Synchronization and genetic redundancy in circadian clocks].

    PubMed

    Dardente, Hugues

    2008-03-01

    A network of feedback loops constitutes the basis for circadian timing in mammals. Complex transcriptional, post-transcriptional and post-translational events are also involved in the ticking of circadian clocks, allowing them to run autonomously with their characteristic, near-24h period. Central to the molecular mechanism is the CLOCK/BMAL1 heterodimer of transcription factors. Recent data using Clock knock-out mice however suggest that CLOCK may not be as mandatory as initially suggested from data gathered in the Clock mutant mouse model. Indeed, it appears that the Clock homolog Npas2 is able to functionally compensate for Clock genetic ablation. Furthermore, real-time imaging techniques using different clock genes knock-out lines established on a PER2 ::Luc knock-in background now demonstrate that persistent rhythmicity in the suprachiasmatic nuclei likely arises as a consequence of combined genetic redundancy and strong intercellular coupling, the latter characteristic being likely weakened in peripheral tissues such as liver or lung. The present review aims at summarizing current knowledge of the molecular basis of circadian clocks and possible differences between central and peripheral clocks in light of recent findings in Clock knock-out mice.

  14. Association of Per1 and Npas2 with autistic disorder: support for the clock genes/social timing hypothesis.

    PubMed

    Nicholas, B; Rudrasingham, V; Nash, S; Kirov, G; Owen, M J; Wimpory, D C

    2007-06-01

    Clock gene anomalies have been suggested as causative factors in autism. We screened eleven clock/clock-related genes in a predominantly high-functioning Autism Genetic Resource Exchange sample of strictly diagnosed autistic disorder progeny and their parents (110 trios) for association of clock gene variants with autistic disorder. We found significant association (P<0.05) for two single-nucleotide polymorphisms in per1 and two in npas2. Analysis of all possible combinations of two-marker haplotypes for each gene showed that in npas2 40 out of the 136 possible two-marker combinations were significant at the P<0.05 level, with the best result between markers rs1811399 and rs2117714, P=0.001. Haplotype analysis within per1 gave a single significant result: a global P=0.027 for the markers rs2253820-rs885747. No two-marker haplotype was significant in any of the other genes, despite the large number of tests performed. Our findings support the hypothesis that these epistatic clock genes may be involved in the etiology of autistic disorder. Problems in sleep, memory and timing are all characteristics of autistic disorder and aspects of sleep, memory and timing are each clock-gene-regulated in other species. We identify how our findings may be relevant to theories of autism that focus on the amygdala, cerebellum, memory and temporal deficits. We outline possible implications of these findings for developmental models of autism involving temporal synchrony/social timing.

  15. Analysis of genetic association and epistasis interactions between circadian clock genes and symptom dimensions of bipolar affective disorder.

    PubMed

    Maciukiewicz, Malgorzata; Dmitrzak-Weglarz, Monika; Pawlak, Joanna; Leszczynska-Rodziewicz, Anna; Zaremba, Dorota; Skibinska, Maria; Hauser, Joanna

    2014-07-01

    Bipolar affective disorder (BD) is a severe psychiatric disorder characterized by periodic changes in mood from depression to mania. Disruptions of biological rhythms increase risk of mood disorders. Because clinical representation of disease is heterogeneous, homogenous sets of patients are suggested to use in the association analyses. In our study, we aimed to apply previously computed structure of bipolar disorder symptom dimension for analyses of genetic association. We based quantitative trait on: main depression, sleep disturbances, appetite disturbances, excitement and psychotic dimensions consisted of OPCRIT checklist items. We genotyped 42 polymorphisms from circadian clock genes: PER3, ARNTL, CLOCK and TIMELSSS from 511 patients BD (n = 292 women and n = 219 men). As quantitative trait we used clinical dimensions, described above. Genetic associations between alleles and quantitative trait were performed using applied regression models applied in PLINK. In addition, we used the Kruskal-Wallis test to look for associations between genotypes and quantitative trait. During second stage of our analyses, we used multidimensional scaling (multifactor dimensionality reduction) for quantitative trait to compute pairwise epistatic interactions between circadian gene variants. We found association between ARNTL variant rs11022778 main depression (p = 0.00047) and appetite disturbances (p = 0.004). In epistatic interaction analyses, we observed two locus interactions between sleep disturbances (p = 0.007; rs11824092 of ARNTL and rs11932595 of CLOCK) as well as interactions of subdimension in main depression and ARNTL variants (p = 0.0011; rs3789327, rs10766075) and appetite disturbances in depression and ARNTL polymorphism (p = 7 × 10(-4); rs11022778, rs156243).

  16. The role of clock genes and rhythmicity in the liver.

    PubMed

    Schmutz, I; Albrecht, U; Ripperger, J A

    2012-02-05

    The liver is the important organ to maintain energy homeostasis of an organism. To achieve this, many biochemical reactions run in this organ in a rhythmic fashion. An elegant way to coordinate the temporal expression of genes for metabolic enzymes relies in the link to the circadian timing system. In this fashion not only a maximum of synchronization is achieved, but also anticipation of daily recurring events is possible. Here we will focus on the input and output pathways of the hepatic circadian oscillator and discuss the recently found flexibility of its circadian transcriptional networks.

  17. Expanding the view of Clock and cycle gene evolution in Diptera.

    PubMed

    Chahad-Ehlers, S; Arthur, L P; Lima, A L A; Gesto, J S M; Torres, F R; Peixoto, A A; de Brito, R A

    2017-02-24

    We expanded the view of Clock (Clk) and cycle (cyc) gene evolution in Diptera by studying the fruit fly Anastrepha fraterculus (Afra), a Brachycera. Despite the high conservation of clock genes amongst insect groups, striking structural and functional differences of some clocks have appeared throughout evolution. Clk and cyc nucleotide sequences and corresponding proteins were characterized, along with their mRNA expression data, to provide an evolutionary overview in the two major groups of Diptera: Lower Diptera and Higher Brachycera. We found that AfraCYC lacks the BMAL (Brain and muscle ARNT-like) C-terminus region (BCTR) domain and is constitutively expressed, suggesting that AfraCLK has the main transactivation function, which is corroborated by the presence of poly-Q repeats and an oscillatory pattern. Our analysis suggests that the loss of BCTR in CYC is not exclusive of drosophilids, as it also occurs in other Acalyptratae flies such as tephritids and drosophilids, however, but it is also present in some Calyptratae, such as Muscidae, Calliphoridae and Sarcophagidae. This indicates that BCTR is missing from CYC of all higher-level Brachycera and that it was lost during the evolution of Lower Brachycera. Thus, we can infer that CLK protein may play the main role in the CLK\\CYC transcription complex in these flies, like in its Drosophila orthologues.

  18. Are clock genes involved in altered circadian rhythms during space flight?

    NASA Astrophysics Data System (ADS)

    Egli, Marcel; Betram, Richard; Cogoli-Greuter, Marianne; Vadrucci, Sonia; Henggeler, Daniele

    2005-08-01

    Hormone secretion in mammals often displays circadian rhythms. These rhythms usually relay on internal "biological clocks", which adjusts to geophysical parameters like the light/dark cycle, temperature cycle, or gravity force, all functioning as time cues. In humans, synchronized external and internal rhythms are important for good performance. This study focuses on the effect of altered gravity on the rhythmic secretory pattern of prolactin (PRL), a hormone of the hypothalamic-pituitary system. Several studies have shown that space flight disturbs PRL secretion. Further, we will investigate the response of clock gene expression in the suprachiasmatic nucleus (SCN), the central circadian pacemaker implicated in the neural network for timed PRL secretion, under various gravitational fields. The results of this study will demonstrate the vulnerability of mammalian endocrine systems to changes in gravity and may help in the design of counter actions for stabilizing circadian rhythms during long-term manned space flight.

  19. THE mPER2 CLOCK GENE MODULATES COCAINE ACTIONS IN THE MOUSE CIRCADIAN SYSTEM

    PubMed Central

    Brager, Allison J.; Stowie, Adam C.; Prosser, Rebecca A.; Glass, J. David

    2014-01-01

    Cocaine is a potent disruptor of photic and non-photic pathways for circadian entrainment of the master circadian clock of the suprachiasmatic nucleus (SCN). These actions of cocaine likely involve its modulation of molecular (clock gene) components for SCN clock timekeeping. At present, however, the physiological basis of such an interaction is unclear. To address this question, we compared photic and non-photic phase-resetting responses between wild-type (WT) and Per2 mutant mice expressing nonfunctional PER2 protein to systemic and intra-SCN cocaine administrations. In the systemic trials, cocaine was administered i.p. (20 mg/kg) either at midday or prior to a light pulse in the early night to assess its non-photic and photic behavioral phase-resetting actions, respectively. In the intra-SCN trial, cocaine was administered by reverse microdialysis at midday to determine if the SCN is a direct target for its non-photic phase-resetting action. Non-photic phase-advancing responses to i.p. cocaine at midday were significantly (~3.5-fold) greater in Per2 mutants than WTs. However, the phase-advancing action of intra-SCN cocaine perfusion at midday did not differ between genotypes. In the light pulse trial, Per2 mutants exhibited larger photic phase-delays than did WTs, and the attenuating action of cocaine on this response was proportionately larger than in WTs. These data indicate that the Per2 clock gene is a potent modulator of cocaine’s actions in the circadian system. With regard to non-photic phase-resetting, the SCN is confirmed as a direct target of cocaine action; however, Per2 modulation of this effect likely occurs outside of the SCN. PMID:23333842

  20. CLOCKWORK ORANGE Enhances PERIOD Mediated Rhythms in Transcriptional Repression by Antagonizing E-box Binding by CLOCK-CYCLE

    PubMed Central

    Yu, Wangjie; Hardin, Paul E.

    2016-01-01

    The Drosophila circadian oscillator controls daily rhythms in physiology, metabolism and behavior via transcriptional feedback loops. CLOCK-CYCLE (CLK-CYC) heterodimers initiate feedback loop function by binding E-box elements to activate per and tim transcription. PER-TIM heterodimers then accumulate, bind CLK-CYC to inhibit transcription, and are ultimately degraded to enable the next round of transcription. The timing of transcriptional events in this feedback loop coincide with, and are controlled by, rhythms in CLK-CYC binding to E-boxes. PER rhythmically binds CLK-CYC to initiate transcriptional repression, and subsequently promotes the removal of CLK-CYC from E-boxes. However, little is known about the mechanism by which CLK-CYC is removed from DNA. Previous studies demonstrated that the transcription repressor CLOCKWORK ORANGE (CWO) contributes to core feedback loop function by repressing per and tim transcription in cultured S2 cells and in flies. Here we show that CWO rhythmically binds E-boxes upstream of core clock genes in a reciprocal manner to CLK, thereby promoting PER-dependent removal of CLK-CYC from E-boxes, and maintaining repression until PER is degraded and CLK-CYC displaces CWO from E-boxes to initiate transcription. These results suggest a model in which CWO co-represses CLK-CYC transcriptional activity in conjunction with PER by competing for E-box binding once CLK-CYC-PER complexes have formed. Given that CWO orthologs DEC1 and DEC2 also target E-boxes bound by CLOCK-BMAL1, a similar mechanism may operate in the mammalian clock. PMID:27814361

  1. CLOCKWORK ORANGE Enhances PERIOD Mediated Rhythms in Transcriptional Repression by Antagonizing E-box Binding by CLOCK-CYCLE.

    PubMed

    Zhou, Jian; Yu, Wangjie; Hardin, Paul E

    2016-11-01

    The Drosophila circadian oscillator controls daily rhythms in physiology, metabolism and behavior via transcriptional feedback loops. CLOCK-CYCLE (CLK-CYC) heterodimers initiate feedback loop function by binding E-box elements to activate per and tim transcription. PER-TIM heterodimers then accumulate, bind CLK-CYC to inhibit transcription, and are ultimately degraded to enable the next round of transcription. The timing of transcriptional events in this feedback loop coincide with, and are controlled by, rhythms in CLK-CYC binding to E-boxes. PER rhythmically binds CLK-CYC to initiate transcriptional repression, and subsequently promotes the removal of CLK-CYC from E-boxes. However, little is known about the mechanism by which CLK-CYC is removed from DNA. Previous studies demonstrated that the transcription repressor CLOCKWORK ORANGE (CWO) contributes to core feedback loop function by repressing per and tim transcription in cultured S2 cells and in flies. Here we show that CWO rhythmically binds E-boxes upstream of core clock genes in a reciprocal manner to CLK, thereby promoting PER-dependent removal of CLK-CYC from E-boxes, and maintaining repression until PER is degraded and CLK-CYC displaces CWO from E-boxes to initiate transcription. These results suggest a model in which CWO co-represses CLK-CYC transcriptional activity in conjunction with PER by competing for E-box binding once CLK-CYC-PER complexes have formed. Given that CWO orthologs DEC1 and DEC2 also target E-boxes bound by CLOCK-BMAL1, a similar mechanism may operate in the mammalian clock.

  2. Peripheral circadian clocks--a conserved phenotype?

    PubMed

    Weigl, Yuval; Harbour, Valerie L; Robinson, Barry; Dufresne, Line; Amir, Shimon

    2013-05-01

    The circadian system of mammals regulates the timing of occurrence of behavioral and physiological events, thereby optimizing adaptation to their surroundings. This system is composed of a single master pacemaker located in the suprachiasmatic nucleus (SCN) and a population of peripheral clocks. The SCN integrates time information from exogenous sources and, in turn, synchronizes the downstream peripheral clocks. It is assumed that under normal conditions, the circadian phenotype of different peripheral clocks would be conserved with respect to its period and robustness. To study this idea, we measured the daily wheel-running activity (WRA; a marker of the SCN output) in 84 male inbred LEW/Crl rats housed under a 12 h:12 h light-dark cycle. In addition, we assessed the mRNA expression of two clock genes, rPer2 and rBmal1, and one clock-controlled gene, rDbp, in four tissues that have the access to time cues other than those emanating from the SCN: olfactory bulbs (OBs), liver, tail skin, and white blood cells (WBCs). In contrast with the assumption stated above, we found that circadian clocks in peripheral tissues differ in the temporal pattern of the expression of circadian clock genes, in the robustness of the rhythms, and possibly in the number of functional ~24-h-clock cells. Based on the tissue diversity in the robustness of the clock output, the hepatic clock is likely to house the highest number of functional ~24-h-clock cells, and the OBs, the fewest number. Thus, the phenotype of the circadian clock in the periphery is tissue specific and may depend not only on the SCN but also on the sensitivity of the tissue to non-SCN-derived time cues. In the OBs and liver, the circadian clock phenotypes seem to be dominantly shaped by the SCN output. However, in the tail skin and WBC, other time cues participate in the phenotype design. Finally, our study suggests that the basic phenotype of the circadian clock is constructed at the transcript level of the core clock

  3. PI3K-PTEN dysregulation leads to mTOR-driven upregulation of the core clock gene BMAL1 in normal and malignant epithelial cells.

    PubMed

    Matsumoto, Camila S; Almeida, Luciana O; Guimarães, Douglas M; Martins, Manoela D; Papagerakis, Petros; Papagerakis, Silvana; Leopoldino, Andreia M; Castilho, Rogerio M; Squarize, Cristiane H

    2016-07-05

    Dysfunctional clock signaling is observed in a variety of pathological conditions. Many members of the clock gene family are upregulated in tumor cells. Here, we explored the consequences of a commonly disrupted signaling pathway in head and neck cancer on the regulation of circadian clock genes. PTEN is a key molecular controller of the PI3K signaling, and loss of PTEN function is often observed in a variety of cancers. Our main goal was to determine whether PTEN regulates circadian clock signaling. We found that oxidation-driven loss of PTEN function resulted in the activation of mTOR signaling and activation of the core clock protein BMAL1 (also known as ARNTL). The PTEN-induced BMAL1 upregulation was further confirmed using small interference RNA targeting PTEN, and in vivo conditional depletion of PTEN from the epidermis. We observed that PTEN-driven accumulation of BMAL1 was mTOR-mediated and that administration of Rapamycin, a specific mTOR inhibitor, resulted in in vivo rescue of normal levels of BMAL1. Accumulation of BMAL1 by deletion of PER2, a Period family gene, was also rescued upon in vivo administration of mTOR inhibitor. Notably, BMAL1 regulation requires mTOR regulatory protein Raptor and Rictor. These findings indicate that mTORC1 and mTORC2 complex plays a critical role in controlling BMAL1, establishing a connection between PI3K signaling and the regulation of circadian rhythm, ultimately resulting in deregulated BMAL1 in tumor cells with disrupted PI3K signaling.

  4. Temporal transcriptomics suggest that twin-peaking genes reset the clock

    PubMed Central

    Pembroke, William G; Babbs, Arran; Davies, Kay E; Ponting, Chris P; Oliver, Peter L

    2015-01-01

    The mammalian suprachiasmatic nucleus (SCN) drives daily rhythmic behavior and physiology, yet a detailed understanding of its coordinated transcriptional programmes is lacking. To reveal the finer details of circadian variation in the mammalian SCN transcriptome we combined laser-capture microdissection (LCM) and RNA-seq over a 24 hr light / dark cycle. We show that 7-times more genes exhibited a classic sinusoidal expression signature than previously observed in the SCN. Another group of 766 genes unexpectedly peaked twice, near both the start and end of the dark phase; this twin-peaking group is significantly enriched for synaptic transmission genes that are crucial for light-induced phase shifting of the circadian clock. 341 intergenic non-coding RNAs, together with novel exons of annotated protein-coding genes, including Cry1, also show specific circadian expression variation. Overall, our data provide an important chronobiological resource (www.wgpembroke.com/shiny/SCNseq/) and allow us to propose that transcriptional timing in the SCN is gating clock resetting mechanisms. DOI: http://dx.doi.org/10.7554/eLife.10518.001 PMID:26523393

  5. The REVEILLE Clock Genes Inhibit Growth of Juvenile and Adult Plants by Control of Cell Size1[OPEN

    PubMed Central

    Gray, Jennifer A.; Chu, Dalena Nhu

    2017-01-01

    The circadian clock is a complex regulatory network that enhances plant growth and fitness in a constantly changing environment. In Arabidopsis (Arabidopsis thaliana), the clock is composed of numerous regulatory feedback loops in which REVEILLE8 (RVE8) and its homologs RVE4 and RVE6 act in a partially redundant manner to promote clock pace. Here, we report that the remaining members of the RVE8 clade, RVE3 and RVE5, play only minor roles in the regulation of clock function. However, we find that RVE8 clade proteins have unexpected functions in the modulation of light input to the clock and the control of plant growth at multiple stages of development. In seedlings, these proteins repress hypocotyl elongation in a daylength- and sucrose-dependent manner. Strikingly, adult rve4 6 8 and rve3 4 5 6 8 mutants are much larger than wild-type plants, with both increased leaf area and biomass. This size phenotype is associated with a faster growth rate and larger cell size and is not simply due to a delay in the transition to flowering. Gene expression and epistasis analysis reveal that the growth phenotypes of rve mutants are due to the misregulation of PHYTOCHROME INTERACTING FACTOR4 (PIF4) and PIF5 expression. Our results show that even small changes in PIF gene expression caused by the perturbation of clock gene function can have large effects on the growth of adult plants. PMID:28254761

  6. The in vitro maintenance of clock genes expression within the rat pineal gland under standard and norepinephrine-synchronized stimulation.

    PubMed

    Andrade-Silva, Jéssica; Cipolla-Neto, José; Peliciari-Garcia, Rodrigo A

    2014-01-01

    Although the norepinephrine (NE) synchronization protocol was proved to be an important procedure for further modulating in vitro pineal melatonin synthesis, the maintenance of clock genes under the same conditions remained to be investigated. The aim of this study was to investigate the maintenance of the clock genes expression in pineal gland cultures under standard and NE-synchronized stimulation. The glands were separated into three experimental groups: Control, Standard (acute NE-stimulation), and NE-synchronized. The expression of Bmal1, Per2, Cry2, Rev-erbα, the clock controlled gene Dbp and Arylalkylamine-N-acetyltransferase were investigated, as well as melatonin content. No oscillations were observed in the expression of the investigated genes from the control group. Under Standard NE stimulation, the clock genes did not exhibit a rhythmic pattern of expression. However, in the NE-synchronized condition, a rhythmic expression pattern was observed in all cases. An enhancement in pineal gland responsiveness to NE stimulation, reflected in an advanced synthesis of melatonin was also observed. Our results reinforce our previous hypothesis that NE synchronization of pineal gland culture mimics the natural rhythmic release of NE in the gland, increasing melatonin synthesis and keeping the pineal circadian clock synchronized, ensuring the fine adjustments that are relied in the clockwork machinery.

  7. Clock genes and their genomic distributions in three species of salmonid fishes: Associations with genes regulating sexual maturation and cell cycling

    PubMed Central

    2010-01-01

    Background Clock family genes encode transcription factors that regulate clock-controlled genes and thus regulate many physiological mechanisms/processes in a circadian fashion. Clock1 duplicates and copies of Clock3 and NPAS2-like genes were partially characterized (genomic sequencing) and mapped using family-based indels/SNPs in rainbow trout (RT)(Oncorhynchus mykiss), Arctic charr (AC)(Salvelinus alpinus), and Atlantic salmon (AS)(Salmo salar) mapping panels. Results Clock1 duplicates mapped to linkage groups RT-8/-24, AC-16/-13 and AS-2/-18. Clock3/NPAS2-like genes mapped to RT-9/-20, AC-20/-43, and AS-5. Most of these linkage group regions containing the Clock gene duplicates were derived from the most recent 4R whole genome duplication event specific to the salmonids. These linkage groups contain quantitative trait loci (QTL) for life history and growth traits (i.e., reproduction and cell cycling). Comparative synteny analyses with other model teleost species reveal a high degree of conservation for genes in these chromosomal regions suggesting that functionally related or co-regulated genes are clustered in syntenic blocks. For example, anti-müllerian hormone (amh), regulating sexual maturation, and ornithine decarboxylase antizymes (oaz1 and oaz2), regulating cell cycling, are contained within these syntenic blocks. Conclusions Synteny analyses indicate that regions homologous to major life-history QTL regions in salmonids contain many candidate genes that are likely to influence reproduction and cell cycling. The order of these genes is highly conserved across the vertebrate species examined, and as such, these genes may make up a functional cluster of genes that are likely co-regulated. CLOCK, as a transcription factor, is found within this block and therefore has the potential to cis-regulate the processes influenced by these genes. Additionally, clock-controlled genes (CCGs) are located in other life-history QTL regions within salmonids suggesting that

  8. The axon-guidance roundabout gene alters the pace of the Drosophila circadian clock.

    PubMed

    Berni, Jimena; Beckwith, Esteban J; Fernández, María Paz; Ceriani, María Fernanda

    2008-01-01

    Great efforts have been directed to the dissection of the cell-autonomous circadian oscillator in Drosophila. However, less information is available regarding how this oscillator controls rhythmic rest-activity cycles. We have identified a viable allele of roundabout, robo(hy), where the period of locomotor activity is shortened. From its role in axon-pathfinding, we anticipated developmental defects in clock-relevant structures. However, robo(hy) produced minor defects in the architecture of the circuits essential for rhythmic behaviour. ROBO's presence within the circadian circuit strengthened the possibility of a novel role for ROBO at this postdevelopmental stage. Genetic interactions between pdf (01) and robo(hy) suggest that ROBO could alter the communication within different clusters of the circadian network, thus impinging on two basic properties, periodicity and/or rhythmicity. Early translocation of PERIOD to the nucleus in robo(hy) pacemaker cells indicated that shortened activity rhythms were derived from alterations in the molecular oscillator. Herein we present a mutation affecting clock function associated with a molecule involved in circuit assembly and maintenance.

  9. Placental genetic variations in circadian clock-related genes increase the risk of placental abruption

    PubMed Central

    Qiu, Chunfang; Gelaye, Bizu; Denis, Marie; Tadesse, Mahlet G; Enquobahrie, Daniel A; Ananth, Cande V; Pacora, Percy N; Salazar, Manuel; Sanchez, Sixto E; Williams, Michelle A

    2016-01-01

    The genetic architecture of placental abruption (PA) remains poorly understood. We examined variations in SNPs of circadian clock-related genes in placenta with PA risk. We also explored placental and maternal genomic contributions to PA risk. Placental genomic DNA samples were isolated from 280 PA cases and 244 controls. Genotyping was performed using the Illumina Cardio-MetaboChip. We examined 116 SNPs in 13 genes known to moderate circadian rhythms. Logistic regression models were fit to estimate odds ratios (ORs). The combined effect of multiple SNPs on PA risk was estimated using a weighted genetic risk score. We examined independent and joint associations of wGRS derived from placental and maternal genomes with PA. Seven SNPs in five genes (ARNTL2, CRY2, DEC1, PER3 and RORA), in the placental genome, were associated with PA risk. Each copy of the minor allele (G) of a SNP in the RORA gene (rs2899663) was associated with a 30% reduced odds of PA (95% CI 0.52-0.95). The odds of PA increased with increasing placental-wGRS (Ptrend<0.001). The ORs were 1.00, 2.16, 3.24 and 4.48 across quartiles. Associations persisted after the maternal-wGRS was included in the model. There was evidence of an additive contribution of placental and maternal genetic contributions to PA risk. Participants with placental- and maternal-wGRS in the highest quartile, compared with those in the lowest quartile, had a 15.57-fold (95% CI 3.34-72.60) increased odds of PA. Placental variants in circadian clock-related genes are associated with PA risk; and the association persists after control of genetic variants in the maternal genome. PMID:27186326

  10. Photoperiodic plasticity in circadian clock neurons in insects

    PubMed Central

    Shiga, Sakiko

    2013-01-01

    Since Bünning's observation of circadian rhythms and photoperiodism in the runner bean Phaseolus multiflorus in 1936, many studies have shown that photoperiodism is based on the circadian clock system. In insects, involvement of circadian clock genes or neurons has been recently shown in the photoperiodic control of developmental arrests, diapause. Photoperiod sets peaks of period (per) or timeless (tim) mRNA abundance at lights-off in Sarcophaga crassipalpis, Chymomyza costata and Protophormia terraenovae. Abundance of per and Clock mRNA changes by photoperiod in Pyrrhocoris apterus. Subcellular Per distribution in circadian clock neurons changes with photoperiod in P. terraenovae. Although photoperiodism is not known in Leucophaea maderae, under longer day length, more stomata and longer commissural fibers of circadian clock neurons have been found. These plastic changes in the circadian clock neurons could be an important constituent for photoperiodic clock mechanisms to integrate repetitive photoperiodic information and produce different outputs based on day length. PMID:23986711

  11. Defining the robust behaviour of the plant clock gene circuit with absolute RNA timeseries and open infrastructure

    PubMed Central

    Flis, Anna; Fernández, Aurora Piñas; Zielinski, Tomasz; Mengin, Virginie; Sulpice, Ronan; Stratford, Kevin; Hume, Alastair; Pokhilko, Alexandra; Southern, Megan M.; Seaton, Daniel D.; McWatters, Harriet G.; Stitt, Mark; Halliday, Karen J.; Millar, Andrew J.

    2015-01-01

    Our understanding of the complex, transcriptional feedback loops in the circadian clock mechanism has depended upon quantitative, timeseries data from disparate sources. We measure clock gene RNA profiles in Arabidopsis thaliana seedlings, grown with or without exogenous sucrose, or in soil-grown plants and in wild-type and mutant backgrounds. The RNA profiles were strikingly robust across the experimental conditions, so current mathematical models are likely to be broadly applicable in leaf tissue. In addition to providing reference data, unexpected behaviours included co-expression of PRR9 and ELF4, and regulation of PRR5 by GI. Absolute RNA quantification revealed low levels of PRR9 transcripts (peak approx. 50 copies cell−1) compared with other clock genes, and threefold higher levels of LHY RNA (more than 1500 copies cell−1) than of its close relative CCA1. The data are disseminated from BioDare, an online repository for focused timeseries data, which is expected to benefit mechanistic modelling. One data subset successfully constrained clock gene expression in a complex model, using publicly available software on parallel computers, without expert tuning or programming. We outline the empirical and mathematical justification for data aggregation in understanding highly interconnected, dynamic networks such as the clock, and the observed design constraints on the resources required to make this approach widely accessible. PMID:26468131

  12. Defining the robust behaviour of the plant clock gene circuit with absolute RNA timeseries and open infrastructure.

    PubMed

    Flis, Anna; Fernández, Aurora Piñas; Zielinski, Tomasz; Mengin, Virginie; Sulpice, Ronan; Stratford, Kevin; Hume, Alastair; Pokhilko, Alexandra; Southern, Megan M; Seaton, Daniel D; McWatters, Harriet G; Stitt, Mark; Halliday, Karen J; Millar, Andrew J

    2015-10-01

    Our understanding of the complex, transcriptional feedback loops in the circadian clock mechanism has depended upon quantitative, timeseries data from disparate sources. We measure clock gene RNA profiles in Arabidopsis thaliana seedlings, grown with or without exogenous sucrose, or in soil-grown plants and in wild-type and mutant backgrounds. The RNA profiles were strikingly robust across the experimental conditions, so current mathematical models are likely to be broadly applicable in leaf tissue. In addition to providing reference data, unexpected behaviours included co-expression of PRR9 and ELF4, and regulation of PRR5 by GI. Absolute RNA quantification revealed low levels of PRR9 transcripts (peak approx. 50 copies cell(-1)) compared with other clock genes, and threefold higher levels of LHY RNA (more than 1500 copies cell(-1)) than of its close relative CCA1. The data are disseminated from BioDare, an online repository for focused timeseries data, which is expected to benefit mechanistic modelling. One data subset successfully constrained clock gene expression in a complex model, using publicly available software on parallel computers, without expert tuning or programming. We outline the empirical and mathematical justification for data aggregation in understanding highly interconnected, dynamic networks such as the clock, and the observed design constraints on the resources required to make this approach widely accessible.

  13. [Circadian rhythms and light responses of clock gene and arylalkylamine N-acetyltransferase gene expressions in the pineal gland of rats].

    PubMed

    Wang, Guo-Qing; Du, Yu-Zhen; Tong, Jian

    2005-02-25

    This study was to investigate the circadian rhythms and light responses of Clock gene and arylalkylamine N-acetyltransferase (NAT) gene expressions in the rat pineal gland under the 12 h-light : 12 h-dark cycle condition (LD) and constant darkness (DD). Sprague-Dawley rats housed under the light regime of LD (n=36) for 4 weeks and of DD (n=36) for 8 weeks were sampled for the pineal gland once a group (n=6) every 4 h in a circadian day. The total RNA was extracted from each sample and the semiquantitative reverse transcription polymerase chain reaction (RT-PCR) was used to determine the temporal changes in mRNA levels of Clock and NAT genes during different circadian times or zeitgeber times. The data were analysed by the cosine function software, Clock Lab software and the amplitude F test was used to reveal the circadian rhythm. The main results obtained are as follows. (1) In DD or LD condition, both of Clock and NAT genes mRNA levels in the pineal gland showed robust circadian oscillation (P< 0.05) with the peak at the subjective night or at night-time. (2) In comparison with DD regime, the amplitudes and the mRNA levels at peaks of Clock and NAT genes expressions in LD in the pineal gland were significantly reduced (P< 0.05). (3) In DD or LD condition, the circadian expressions of NAT gene were similar in pattern to those of Clock gene in the pineal gland (P> 0.05). These findings suggest that the expressions of Clock and NAT genes in the pineal gland not only show remarkably synchronous endogenous circadian rhythmic changes, but also response to the ambient light signal in a reduced manner.

  14. Barley (Hordeum vulgare) circadian clock genes can respond rapidly to temperature in an EARLY FLOWERING 3-dependent manner

    PubMed Central

    Ford, Brett; Deng, Weiwei; Clausen, Jenni; Oliver, Sandra; Boden, Scott; Hemming, Megan; Trevaskis, Ben

    2016-01-01

    An increase in global temperatures will impact future crop yields. In the cereal crops wheat and barley, high temperatures accelerate reproductive development, reducing the number of grains per plant and final grain yield. Despite this relationship between temperature and cereal yield, it is not clear what genes and molecular pathways mediate the developmental response to increased temperatures. The plant circadian clock can respond to changes in temperature and is important for photoperiod-dependent flowering, and so is a potential mechanism controlling temperature responses in cereal crops. This study examines the relationship between temperature, the circadian clock, and the expression of flowering-time genes in barley (Hordeum vulgare), a crop model for temperate cereals. Transcript levels of barley core circadian clock genes were assayed over a range of temperatures. Transcript levels of core clock genes CCA1, GI, PRR59, PRR73, PRR95, and LUX are increased at higher temperatures. CCA1 and PRR73 respond rapidly to a decrease in temperature whereas GI and PRR59 respond rapidly to an increase in temperature. The response of GI and the PRR genes to changes in temperature is lost in the elf3 mutant indicating that their response to temperature may be dependent on a functional ELF3 gene. PMID:27580625

  15. Interaction of growth hormone overexpression and nutritional status on pituitary gland clock gene expression in coho salmon, Oncorhynchus kisutch.

    PubMed

    Kim, Jin-Hyoung; White, Samantha L; Devlin, Robert H

    2015-02-01

    Clock genes are involved in generating a circadian rhythm that is integrated with the metabolic state of an organism and information from the environment. Growth hormone (GH) transgenic coho salmon, Oncorhynchus kisutch, show a large increase in growth rate, but also attenuated seasonal growth modulations, modified timing of physiological transformations (e.g. smoltification) and disruptions in pituitary gene expression compared with wild-type salmon. In several fishes, circadian rhythm gene expression has been found to oscillate in the suprachiasmatic nucleus of the hypothalamus, as well as in multiple peripheral tissues, but this control system has not been examined in the pituitary gland nor has the effect of transgenic growth modification been examined. Thus, the daily expression of 10 core clock genes has been examined in pituitary glands of GH transgenic (T) and wild-type coho salmon (NT) entrained on a regular photocycle (12L: 12D) and provided either with scheduled feeding or had food withheld for 60 h. Most clock genes in both genotypes showed oscillating patterns of mRNA levels with light and dark cycles. However, T showed different amplitudes and patterns of expression compared with wild salmon, both in fed and starved conditions. The results from this study indicate that constitutive expression of GH is associated with changes in clock gene regulation, which may play a role in the disrupted behavioural and physiological phenotypes observed in growth-modified transgenic strains.

  16. The intrinsic circadian clock within the cardiomyocyte directly regulates myocardial gene expression, metabolism, and contractile function

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Virtually every mammalian cell, including cardiomyocytes, possesses an intrinsic circadian clock. The role of this transcriptionally based molecular mechanism in cardiovascular biology remains unknown. We hypothesized that the circadian clock within the cardiomyocyte plays a role in regulating myo...

  17. The intrinsic circadian clock within the cardiomyocyte directly regulates myocardial gene expression, metabolism, and contractile function

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Virtually every mammalian cell, including cardiomyocytes, possesses an intrinsic circadian clock. The role of this transcriptionally based molecular mechanism in cardiovascular biology remains unknown. We hypothesized that circadian clock within the cardiomyocyte plays a role in regulating myocardia...

  18. Existence of a photoinducible phase for ovarian development and photoperiod-related alteration of clock gene expression in a damselfish.

    PubMed

    Takeuchi, Yuki; Hada, Noriko; Imamura, Satoshi; Hur, Sung-Pyo; Bouchekioua, Selma; Takemura, Akihiro

    2015-10-01

    The sapphire devil, Chrysiptera cyanea, is a reef-associated damselfish and their ovarian development can be induced by a long photoperiod. In this study, we demonstrated the existence of a photoinducible phase for the photoperiodic ovarian development in the sapphire devil. Induction of ovarian development under night-interruption light schedules and Nanda-Hamner cycles revealed that the photoinducible phase appeared in a circadian manner between ZT12 and ZT13. To characterize the effect of photoperiod on clock gene expression in the brain of this species, we determined the expression levels of the sdPer1, sdPer2, sdCry1, and sdCry2 clock genes under constant light and dark conditions (LL and DD) and photoperiodic (short and long photoperiods). The expression of sdPer1 exhibited clear circadian oscillation under both LL and DD conditions, while sdPer2 and sdCry1 expression levels were lower under DD than under LL conditions and sdCry2 expression was lower under LL than under DD conditions. These results suggest a key role for sdPer1 in circadian clock cycling and that sdPer2, sdCry1, and sdCry2 are light-responsive clock genes in the sapphire devil. After 1 week under a long photoperiod, we observed photoperiod-related changes in sdPer1, sdPer2, and sdCry2 expression, but not in sdCry1 expression. These results suggest that the expression patterns of some clock genes exhibit seasonal variation according to seasonal changes in day length and that such seasonal alteration of clock gene expression may contribute to seasonal recognition by the sapphire devil.

  19. Suicidal behavior in the context of disrupted rhythmicity in bipolar disorder--data from an association study of suicide attempts with clock genes.

    PubMed

    Pawlak, Joanna; Dmitrzak-Weglarz, Monika; Maciukiewicz, Malgorzata; Wilkosc, Monika; Leszczynska-Rodziewicz, Anna; Zaremba, Dorota; Kapelski, Pawel; Hauser, Joanna

    2015-04-30

    Suicidal behavior exhibits both circadian and annual rhythms. We were seeking an association between selected candidate clock genes and suicidal behavior in bipolar patients. The study included 441 bipolar patients and 422 controls and we genotyped 41 SNPs of the CLOCK, ARNTL, TIMELESS, PER3 genes. The main positive findings built up associations between selected polymorphisms and.

  20. A latitudinal cline in the Chinook salmon (Oncorhynchus tshawytscha) Clock gene: evidence for selection on PolyQ length variants

    PubMed Central

    O'Malley, Kathleen G; Banks, Michael A

    2008-01-01

    A critical seasonal event for anadromous Chinook salmon (Oncorhynchus tshawytscha) is the time at which adults migrate from the ocean to breed in freshwater. We investigated whether allelic variation at the circadian rhythm genes, OtsClock1a and OtsClock1b, underlies genetic control of migration timing among 42 populations in North America. We identified eight length variants of the functionally important polyglutamine repeat motif (PolyQ) of OtsClock1b while OtsClock1a PolyQ was highly conserved. We found evidence of a latitudinal cline in average allele length and frequency of the two most common OtsClock1b alleles. The shorter 335 bp allele increases in frequency with decreasing latitude while the longer 359 bp allele increases in frequency at higher latitudes. Comparison to 13 microsatellite loci showed that 335 and 359 bp deviate significantly from neutral expectations. Furthermore, a hierarchical gene diversity analysis based on OtsClock1b PolyQ variation revealed that run timing explains 40.9 per cent of the overall genetic variance among populations. By contrast, an analysis based on 13 microsatellite loci showed that run timing explains only 13.2 per cent of the overall genetic variance. Our findings suggest that length polymorphisms in OtsClock1b PolyQ may be maintained by selection and reflect an adaptation to ecological factors correlated with latitude, such as the seasonally changing day length. PMID:18713722

  1. Postnatal ontogeny of the circadian expression of the adrenal clock genes and corticosterone rhythm in male rats.

    PubMed

    Ruiz Roa, Silvia Liliana; Martinez, Edson Zangiacomi; Martins, Clarissa Silva; Antonini, Sonir Rauber; de Castro, Margaret; Moreira, Ayrton Custódio

    2017-01-25

    The postnatal synchronization of the circadian variation of the adrenal clock genes in mammals remains unknown. We evaluated the postnatal ontogeny of daily variation of clock genes (Clock/Bmal1/Per1/Per2/Per3/Cry1/Cry2/Rorα/Rev-Erbα) and steroidogenesis-related genes (Star and Mc2r) in rat adrenals and its relationship with the emergence of plasma corticosterone rhythm using Cosinor analysis. Plasma corticosterone circadian rhythm was detected from postnatal day (P) P1, with morning acrophase, between zeitgeber time (ZT) ZT0 and ZT2. From P14, there was a nocturnal acrophase of corticosterone at ZT20, which was associated with pups' eye opening. Since P3 there was a circadian variation of the mRNA expression of Bmal1, Per2, Per3, Cry1 genes with morning acrophase whereas Rev-Erbα had nocturnal acrophase. From P14, Bmal1, Per2, Per3, Cry1 acrophases advanced by approximately 10h, as compared to early neonatal days, becoming vespertine-nocturnal. In all postnatal ages, Per2 and Cry1 circadian profiles were synchronized in phase while Bmal1 was in antiphase with the circadian rhythm of plasma corticosterone. Adult-like Star circadian rhythm profile was observed only from P21. In conclusion, our original data demonstrated a progressive postnatal maturation of the circadian variation of the adrenal clock genes in synchrony with the development of the corticosterone circadian rhythm in rats.

  2. Circadian molecular clocks and cancer.

    PubMed

    Kelleher, Fergal C; Rao, Aparna; Maguire, Anne

    2014-01-01

    Physiological processes such as the sleep-wake cycle, metabolism and hormone secretion are controlled by a circadian rhythm adapted to 24h day-night periodicity. This circadian synchronisation is in part controlled by ambient light decreasing melatonin secretion by the pineal gland and co-ordinated by the suprachiasmatic nucleus of the hypothalamus. Peripheral cell autonomous circadian clocks controlled by the suprachiasmatic nucleus, the master regulator, exist within every cell of the body and are comprised of at least twelve genes. These include the basic helix-loop-helix/PAS domain containing transcription factors; Clock, BMal1 and Npas2 which activate transcription of the periodic genes (Per1 and Per2) and cryptochrome genes (Cry1 and Cry2). Points of coupling exist between the cellular clock and the cell cycle. Cell cycle genes which are affected by the molecular circadian clock include c-Myc, Wee1, cyclin D and p21. Therefore the rhythm of the circadian clock and cancer are interlinked. Molecular examples exist including activation of Per2 leads to c-myc overexpression and an increased tumor incidence. Mice with mutations in Cryptochrome 1 and 2 are arrhythmic (lack a circadian rhythm) and arrhythmic mice have a faster rate of growth of implanted tumors. Epidemiological finding of relevance include 'The Nurses' Health Study' where it was established that women working rotational night shifts have an increased incidence of breast cancer. Compounds that affect circadian rhythm exist with attendant future therapeutic possibilities. These include casein kinase I inhibitors and a candidate small molecule KL001 that affects the degradation of cryptochrome. Theoretically the cell cycle and malignant disease may be targeted vicariously by selective alteration of the cellular molecular clock.

  3. An important role for cholecystokinin, a CLOCK target gene, in the development and treatment of manic-like behaviors.

    PubMed

    Arey, R N; Enwright, J F; Spencer, S M; Falcon, E; Ozburn, A R; Ghose, S; Tamminga, C; McClung, C A

    2014-03-01

    Mice with a mutation in the Clock gene (ClockΔ19) have been identified as a model of mania; however, the mechanisms that underlie this phenotype, and the changes in the brain that are necessary for lithium's effectiveness on these mice remain unclear. Here, we find that cholecystokinin (Cck) is a direct transcriptional target of CLOCK and levels of Cck are reduced in the ventral tegmental area (VTA) of ClockΔ19 mice. Selective knockdown of Cck expression via RNA interference in the VTA of wild-type mice produces a manic-like phenotype. Moreover, chronic treatment with lithium restores Cck expression to near wild-type and this increase is necessary for the therapeutic actions of lithium. The decrease in Cck expression in the ClockΔ19 mice appears to be due to a lack of interaction with the histone methyltransferase, MLL1, resulting in decreased histone H3K4me3 and gene transcription, an effect reversed by lithium. Human postmortem tissue from bipolar subjects reveals a similar increase in Cck expression in the VTA with mood stabilizer treatment. These studies identify a key role for Cck in the development and treatment of mania, and describe some of the molecular mechanisms by which lithium may act as an effective antimanic agent.

  4. The Mouse Clock Mutation Behaves as an Antimorph and Maps within the W(19h) Deletion, Distal of Kit

    PubMed Central

    King, D. P.; Vitaterna, M. H.; Chang, A. M.; Dove, W. F.; Pinto, L. H.; Turek, F. W.; Takahashi, J. S.

    1997-01-01

    Clock is a semidominant mutation identified from an N-ethyl-N-nitrosourea mutagenesis screen in mice. Mice carrying the Clock mutation exhibit abnormalities of circadian behavior, including lengthening of endogenous period and loss of rhythmicity. To identify the gene affected by this mutation, we have generated a high-resolution genetic map (>1800 meioses) of the Clock locus. We report that Clock is 0.7 cM distal of Kit on mouse chromosome 5. Mapping shows that Clock lies within the W(19H) deletion. Complementation analysis of different Clock and W(19H) compound genotypes indicates that the Clock mutation behaves as an antimorph. This antimorphic behavior of Clock strongly argues that Clock defines a gene centrally involved in the mammalian circadian system. PMID:9215907

  5. Regulation of behavioral circadian rhythms and clock protein PER1 by the deubiquitinating enzyme USP2

    PubMed Central

    Yang, Yaoming; Duguay, David; Bédard, Nathalie; Rachalski, Adeline; Baquiran, Gerardo; Na, Chan Hyun; Fahrenkrug, Jan; Storch, Kai-Florian; Peng, Junmin; Wing, Simon S.; Cermakian, Nicolas

    2012-01-01

    Summary Endogenous 24-hour rhythms are generated by circadian clocks located in most tissues. The molecular clock mechanism is based on feedback loops involving clock genes and their protein products. Post-translational modifications, including ubiquitination, are important for regulating the clock feedback mechanism. Previous work has focused on the role of ubiquitin ligases in the clock mechanism. Here we show a role for the rhythmically-expressed deubiquitinating enzyme ubiquitin specific peptidase 2 (USP2) in clock function. Mice with a deletion of the Usp2 gene (Usp2 KO) display a longer free-running period of locomotor activity rhythms and altered responses of the clock to light. This was associated with altered expression of clock genes in synchronized Usp2 KO mouse embryonic fibroblasts and increased levels of clock protein PERIOD1 (PER1). USP2 can be coimmunoprecipitated with several clock proteins but directly interacts specifically with PER1 and deubiquitinates it. Interestingly, this deubiquitination does not alter PER1 stability. Taken together, our results identify USP2 as a new core component of the clock machinery and demonstrate a role for deubiquitination in the regulation of the circadian clock, both at the level of the core pacemaker and its response to external cues. PMID:23213472

  6. Consecutive bursts of Pi2-band and long-period pulsations during a northward and low-clock-angle IMF period

    NASA Astrophysics Data System (ADS)

    Cheng, C.; Russell, C. T.; Baumjohann, W.; Yumoto, K.

    2013-12-01

    On 14 August 2004, four pulsation bursts, in a period up to 200 s from the Pi2 band, consecutively occurred at the SMALL and 210 MM arrays in the post-midnight sector. Meanwhile, the Double Star TC 1 probe in the plasma sheet at ~XGSM -11.0 Re, observed quasi-periodic magnetic fluctuations at each burst onset. The Cluster 4 probe in the north lobe at ~XGSM -14.0 Re, sensed Pi2-band magnetic perturbations at the second burst onset and long-period ones for the third and fourth bursts. No bursty flow activations occurred at the onset of the first and second bursts. Earthward flow bursts first appeared at TC 1 prior to the third burst onset and ~5 min later at Cluster 4. These flows persisted through the end of the last burst and appeared to have a same periodic variation as in the magnetic field at Cluster 4. Except for the second burst, geostationary LANL 97 probe at ~XGSM -2.0 Re also detected wave-like energetic proton fluxes. The mapping of ground pulsations onset timing to the solar wind observation just in front of Earth's magnetopause shows that they appear during a northward IMF period with low clock-angle variations. Spectral analyses show two distinct spectral features in which Pi2-band bursts become two harmonic and long-period ones monochromatic. Waveform comparisons show that Pi2-band bursts can result from a combination of fast magnetospheric and plasmaspheric cavity resonances and long-period ones from a fast magnetospheric cavity resonance. Although they do not have a one-to-one relationship with earthward plasma flows, these pulsations can be fast compressional waves expectedly driven by magnetic reconnection in the distant-Earth magnetotail under northward IMF as in the two-neutral-point model. Fig. 1. (a-b) The IMF By, the IMF Bz, and the IMF clock angle at 1 AU (corresponding to ~XGSM 17 Re) from 1910 UT to 2010 UT on 14 August 2004. (c-d) Three components of the magnetic field and the ion flow velocity at Cluster 4 (~XGSM -14.0Re). (e-f) Same as

  7. Modulation of learning and memory by the targeted deletion of the circadian clock gene Bmal1 in forebrain circuits.

    PubMed

    Snider, Kaitlin H; Dziema, Heather; Aten, Sydney; Loeser, Jacob; Norona, Frances E; Hoyt, Kari; Obrietan, Karl

    2016-07-15

    A large body of literature has shown that the disruption of circadian clock timing has profound effects on mood, memory and complex thinking. Central to this time keeping process is the master circadian pacemaker located within the suprachiasmatic nucleus (SCN). Of note, within the central nervous system, clock timing is not exclusive to the SCN, but rather, ancillary oscillatory capacity has been detected in a wide range of cell types and brain regions, including forebrain circuits that underlie complex cognitive processes. These observations raise questions about the hierarchical and functional relationship between the SCN and forebrain oscillators, and, relatedly, about the underlying clock-gated synaptic circuitry that modulates cognition. Here, we utilized a clock knockout strategy in which the essential circadian timing gene Bmal1 was selectively deleted from excitatory forebrain neurons, whilst the SCN clock remained intact, to test the role of forebrain clock timing in learning, memory, anxiety, and behavioral despair. With this model system, we observed numerous effects on hippocampus-dependent measures of cognition. Mice lacking forebrain Bmal1 exhibited deficits in both acquisition and recall on the Barnes maze. Notably, loss of forebrain Bmal1 abrogated time-of-day dependent novel object location memory. However, the loss of Bmal1 did not alter performance on the elevated plus maze, open field assay, and tail suspension test, indicating that this phenotype specifically impairs cognition but not affect. Together, these data suggest that forebrain clock timing plays a critical role in shaping the efficiency of learning and memory retrieval over the circadian day.

  8. Smith-Magenis syndrome results in disruption of CLOCK gene transcription and reveals an integral role for RAI1 in the maintenance of circadian rhythmicity.

    PubMed

    Williams, Stephen R; Zies, Deborah; Mullegama, Sureni V; Grotewiel, Michael S; Elsea, Sarah H

    2012-06-08

    Haploinsufficiency of RAI1 results in Smith-Magenis syndrome (SMS), a disorder characterized by intellectual disability, multiple congenital anomalies, obesity, neurobehavioral abnormalities, and a disrupted circadian sleep-wake pattern. An inverted melatonin rhythm (i.e., melatonin peaks during the day instead of at night) and associated sleep-phase disturbances in individuals with SMS, as well as a short-period circadian rhythm in mice with a chromosomal deletion of Rai1, support SMS as a circadian-rhythm-dysfunction disorder. However, the molecular cause of the circadian defect in SMS has not been described. The circadian oscillator temporally orchestrates metabolism, physiology, and behavior largely through transcriptional modulation. Data support RAI1 as a transcriptional regulator, but the genes it might regulate are largely unknown. Investigation into the role that RAI1 plays in the regulation of gene transcription and circadian maintenance revealed that RAI1 regulates the transcription of circadian locomotor output cycles kaput (CLOCK), a key component of the mammalian circadian oscillator that transcriptionally regulates many critical circadian genes. Data further show that haploinsufficiency of RAI1 and Rai1 in SMS fibroblasts and the mouse hypothalamus, respectively, results in the transcriptional dysregulation of the circadian clock and causes altered expression and regulation of multiple circadian genes, including PER2, PER3, CRY1, BMAL1, and others. These data suggest that heterozygous mutation of RAI1 and Rai1 leads to a disrupted circadian rhythm and thus results in an abnormal sleep-wake cycle, which can contribute to an abnormal feeding pattern and dependent cognitive performance. Finally, we conclude that RAI1 is a positive transcriptional regulator of CLOCK, pinpointing a novel and important role for this gene in the circadian oscillator.

  9. Clock Genes Regulate the Circadian Expression of Piezo1, TRPV4, Connexin26, and VNUT in an Ex Vivo Mouse Bladder Mucosa

    PubMed Central

    Ihara, Tatsuya; Mitsui, Takahiko; Nakamura, Yuki; Kira, Satoru; Nakagomi, Hiroshi; Sawada, Norifumi; Hirayama, Yuri; Shibata, Keisuke; Shigetomi, Eiji; Shinozaki, Yoichi; Yoshiyama, Mitsuharu; Andersson, Karl-Erik; Nakao, Atsuhito; Takeda, Masayuki

    2017-01-01

    Objectives ClockΔ19/Δ19 mice is an experimental model mouse for nocturia (NOC). Using the bladder mucosa obtained from ClockΔ19/Δ19 mice, we investigated the gene expression rhythms of mechanosensory cation channels such as transient receptor potential cation channel subfamily V member 4 (TRPV4) and Piezo1, and main ATP release pathways including vesicular nucleotide transporter (VNUT) and Connexin26(Cx26), in addition to clock genes. Materials and methods Eight- to twelve-week-old male C57BL/6 mice (WT) and age- and sex-matched C57BL/6 ClockΔ19/Δ19 mice, which were bred under 12-h light/dark conditions for 2 weeks, were used. Gene expression rhythms and transcriptional regulation mechanisms in clock genes, mechanosensor, Cx26 and VNUT were measured in the mouse bladder mucosa, collected every 4 hours from WT and ClockΔ19/Δ19 mice using quantitative RT-PCR, a Western blot analysis, and ChIP assays. Results WT mice showed circadian rhythms in clock genes as well as mechanosensor, Cx26 and VNUT. Their expression was low during the sleep phase. The results of ChIP assays showed Clock protein binding to the promotor regions and the transcriptional regulation of mechanosensor, Cx26 and VNUT. In contrast, all of these circadian expressions were disrupted in ClockΔ19/Δ19 mice. The gene expression of mechanosensor, Cx26 and VNUT was maintained at a higher level in spite of the sleep phase. Conclusions Mechanosensor, Cx26 and VNUT expressed with circadian rhythm in the mouse bladder mucosa. The disruption of circadian rhythms in these genes, induced by the abnormalities in clock genes, may be factors contributing to NOC because of hypersensitivity to bladder wall extension. PMID:28060940

  10. Circadian molecular clock in lung pathophysiology.

    PubMed

    Sundar, Isaac K; Yao, Hongwei; Sellix, Michael T; Rahman, Irfan

    2015-11-15

    Disrupted daily or circadian rhythms of lung function and inflammatory responses are common features of chronic airway diseases. At the molecular level these circadian rhythms depend on the activity of an autoregulatory feedback loop oscillator of clock gene transcription factors, including the BMAL1:CLOCK activator complex and the repressors PERIOD and CRYPTOCHROME. The key nuclear receptors and transcription factors REV-ERBα and RORα regulate Bmal1 expression and provide stability to the oscillator. Circadian clock dysfunction is implicated in both immune and inflammatory responses to environmental, inflammatory, and infectious agents. Molecular clock function is altered by exposomes, tobacco smoke, lipopolysaccharide, hyperoxia, allergens, bleomycin, as well as bacterial and viral infections. The deacetylase Sirtuin 1 (SIRT1) regulates the timing of the clock through acetylation of BMAL1 and PER2 and controls the clock-dependent functions, which can also be affected by environmental stressors. Environmental agents and redox modulation may alter the levels of REV-ERBα and RORα in lung tissue in association with a heightened DNA damage response, cellular senescence, and inflammation. A reciprocal relationship exists between the molecular clock and immune/inflammatory responses in the lungs. Molecular clock function in lung cells may be used as a biomarker of disease severity and exacerbations or for assessing the efficacy of chronotherapy for disease management. Here, we provide a comprehensive overview of clock-controlled cellular and molecular functions in the lungs and highlight the repercussions of clock disruption on the pathophysiology of chronic airway diseases and their exacerbations. Furthermore, we highlight the potential for the molecular clock as a novel chronopharmacological target for the management of lung pathophysiology.

  11. Circadian molecular clock in lung pathophysiology

    PubMed Central

    Sundar, Isaac K.; Yao, Hongwei; Sellix, Michael T.

    2015-01-01

    Disrupted daily or circadian rhythms of lung function and inflammatory responses are common features of chronic airway diseases. At the molecular level these circadian rhythms depend on the activity of an autoregulatory feedback loop oscillator of clock gene transcription factors, including the BMAL1:CLOCK activator complex and the repressors PERIOD and CRYPTOCHROME. The key nuclear receptors and transcription factors REV-ERBα and RORα regulate Bmal1 expression and provide stability to the oscillator. Circadian clock dysfunction is implicated in both immune and inflammatory responses to environmental, inflammatory, and infectious agents. Molecular clock function is altered by exposomes, tobacco smoke, lipopolysaccharide, hyperoxia, allergens, bleomycin, as well as bacterial and viral infections. The deacetylase Sirtuin 1 (SIRT1) regulates the timing of the clock through acetylation of BMAL1 and PER2 and controls the clock-dependent functions, which can also be affected by environmental stressors. Environmental agents and redox modulation may alter the levels of REV-ERBα and RORα in lung tissue in association with a heightened DNA damage response, cellular senescence, and inflammation. A reciprocal relationship exists between the molecular clock and immune/inflammatory responses in the lungs. Molecular clock function in lung cells may be used as a biomarker of disease severity and exacerbations or for assessing the efficacy of chronotherapy for disease management. Here, we provide a comprehensive overview of clock-controlled cellular and molecular functions in the lungs and highlight the repercussions of clock disruption on the pathophysiology of chronic airway diseases and their exacerbations. Furthermore, we highlight the potential for the molecular clock as a novel chronopharmacological target for the management of lung pathophysiology. PMID:26361874

  12. Conserved and Divergent Rhythms of Crassulacean Acid Metabolism-Related and Core Clock Gene Expression in the Cactus Opuntia ficus-indica1[C][W

    PubMed Central

    Mallona, Izaskun; Egea-Cortines, Marcos; Weiss, Julia

    2011-01-01

    The cactus Opuntia ficus-indica is a constitutive Crassulacean acid metabolism (CAM) species. Current knowledge of CAM metabolism suggests that the enzyme phosphoenolpyruvate carboxylase kinase (PPCK) is circadian regulated at the transcriptional level, whereas phosphoenolpyruvate carboxylase (PEPC), malate dehydrogenase (MDH), NADP-malic enzyme (NADP-ME), and pyruvate phosphate dikinase (PPDK) are posttranslationally controlled. As little transcriptomic data are available from obligate CAM plants, we created an expressed sequence tag database derived from different organs and developmental stages. Sequences were assembled, compared with sequences in the National Center for Biotechnology Information nonredundant database for identification of putative orthologs, and mapped using Kyoto Encyclopedia of Genes and Genomes Orthology and Gene Ontology. We identified genes involved in circadian regulation and CAM metabolism for transcriptomic analysis in plants grown in long days. We identified stable reference genes for quantitative polymerase chain reaction and found that OfiSAND, like its counterpart in Arabidopsis (Arabidopsis thaliana), and OfiTUB are generally appropriate standards for use in the quantification of gene expression in O. ficus-indica. Three kinds of expression profiles were found: transcripts of OfiPPCK oscillated with a 24-h periodicity; transcripts of the light-active OfiNADP-ME and OfiPPDK genes adapted to 12-h cycles, while transcript accumulation patterns of OfiPEPC and OfiMDH were arrhythmic. Expression of the circadian clock gene OfiTOC1, similar to Arabidopsis, oscillated with a 24-h periodicity, peaking at night. Expression of OfiCCA1 and OfiPRR9, unlike in Arabidopsis, adapted best to a 12-h rhythm, suggesting that circadian clock gene interactions differ from those of Arabidopsis. Our results indicate that the evolution of CAM metabolism could be the result of modified circadian regulation at both the transcriptional and posttranscriptional

  13. Conserved and divergent rhythms of crassulacean acid metabolism-related and core clock gene expression in the cactus Opuntia ficus-indica.

    PubMed

    Mallona, Izaskun; Egea-Cortines, Marcos; Weiss, Julia

    2011-08-01

    The cactus Opuntia ficus-indica is a constitutive Crassulacean acid metabolism (CAM) species. Current knowledge of CAM metabolism suggests that the enzyme phosphoenolpyruvate carboxylase kinase (PPCK) is circadian regulated at the transcriptional level, whereas phosphoenolpyruvate carboxylase (PEPC), malate dehydrogenase (MDH), NADP-malic enzyme (NADP-ME), and pyruvate phosphate dikinase (PPDK) are posttranslationally controlled. As little transcriptomic data are available from obligate CAM plants, we created an expressed sequence tag database derived from different organs and developmental stages. Sequences were assembled, compared with sequences in the National Center for Biotechnology Information nonredundant database for identification of putative orthologs, and mapped using Kyoto Encyclopedia of Genes and Genomes Orthology and Gene Ontology. We identified genes involved in circadian regulation and CAM metabolism for transcriptomic analysis in plants grown in long days. We identified stable reference genes for quantitative polymerase chain reaction and found that OfiSAND, like its counterpart in Arabidopsis (Arabidopsis thaliana), and OfiTUB are generally appropriate standards for use in the quantification of gene expression in O. ficus-indica. Three kinds of expression profiles were found: transcripts of OfiPPCK oscillated with a 24-h periodicity; transcripts of the light-active OfiNADP-ME and OfiPPDK genes adapted to 12-h cycles, while transcript accumulation patterns of OfiPEPC and OfiMDH were arrhythmic. Expression of the circadian clock gene OfiTOC1, similar to Arabidopsis, oscillated with a 24-h periodicity, peaking at night. Expression of OfiCCA1 and OfiPRR9, unlike in Arabidopsis, adapted best to a 12-h rhythm, suggesting that circadian clock gene interactions differ from those of Arabidopsis. Our results indicate that the evolution of CAM metabolism could be the result of modified circadian regulation at both the transcriptional and posttranscriptional

  14. Timing of expression of the core clock gene Bmal1 influences its effects on aging and survival

    PubMed Central

    Yang, Guangrui; Chen, Lihong; Grant, Gregory R.; Paschos, Georgios; Song, Wen-Liang; Musiek, Erik S.; Lee, Vivian; McLoughlin, Sarah C.; Grosser, Tilo; Cotsarelis, George; FitzGerald, Garret A.

    2016-01-01

    The absence of Bmal1, a core clock gene, results in a loss of circadian rhythms, an acceleration of aging, and a shortened life span in mice. To address the importance of circadian rhythms in the aging process, we generated conditional Bmal1 knockout mice that lacked the BMAL1 protein during adult life and found that wild-type circadian variations in wheel-running activity, heart rate, and blood pressure were abolished. Ocular abnormalities and brain astrogliosis were conserved irrespective of the timing of Bmal1 deletion. However, life span, fertility, body weight, blood glucose levels, and age-dependent arthropathy - which are altered in standard Bmal1 knockout mice - remained unaltered, while atherosclerosis and hair growth improved, in the conditional adult-life Bmal1 knockout mice, despite abolition of clock function. Hepatic RNA-Seq revealed that expression of oscillatory genes was dampened in the adult-life Bmal1 knockout mice, while overall gene expression was largely unchanged. Thus, many phenotypes in conventional Bmal1 knockout mice, hitherto attributed to disruption of circadian rhythms, reflect the loss of properties of BMAL1 that are independent of its role in the clock. These findings prompt re-evaluation of the systemic consequences of disruption of the molecular clock. PMID:26843191

  15. Geography of the circadian gene clock and photoperiodic response in western North American populations of the threespine stickleback Gasterosteus aculeatus

    PubMed Central

    O’Brien, C.; Unruh, L.; Zimmerman, C.; Bradshaw, W. E.; Holzapfel, C. M.; Cresko, W. A.

    2014-01-01

    The gene clock is a core component of the daily circadian oscillator in flies and mammals. This gene gained renewed interest over a decade ago when the C-terminus of the Clock protein was found to include polyglutamine repeat domains (PolyQ). Since that time, several studies have used variation in PolyQ as a proxy for variation in circadian function. Furthermore, conjectures were made about the possible role of this variation in photoperiodic control of seasonal timing in birds and fishes, generally with questionable results. Herein, we use controlled laboratory experiments to show that Oregon and Alaskan threespine stickleback, collected from populations that differ by 18° of latitude, show no significant variation in length of the polyglutamine domain of clock, or in photoperiodic response within or between latitudes despite the fact that male and female sticklebacks are photoperiodic at both latitudes. Hence, we urge caution when interpreting variation in the PolyQ domain of the clock gene in the context of seasonal activities or in relationship to photoperiodism along geographical gradients. PMID:23464546

  16. The Arabidopsis SRR1 gene mediates phyB signaling and is required for normal circadian clock function

    PubMed Central

    Staiger, Dorothee; Allenbach, Laure; Salathia, Neeraj; Fiechter, Vincent; Davis, Seth J.; Millar, Andrew J.; Chory, Joanne; Fankhauser, Christian

    2003-01-01

    Plants possess several photoreceptors to sense the light environment. In Arabidopsis cryptochromes and phytochromes play roles in photomorphogenesis and in the light input pathways that synchronize the circadian clock with the external world. We have identified SRR1 (sensitivity to red light reduced), a gene that plays an important role in phytochrome B (phyB)-mediated light signaling. The recessive srr1 null allele and phyB mutants display a number of similar phenotypes indicating that SRR1 is required for normal phyB signaling. Genetic analysis suggests that SRR1 works both in the phyB pathway but also independently of phyB. srr1 mutants are affected in multiple outputs of the circadian clock in continuous light conditions, including leaf movement and expression of the clock components, CCA1 and TOC1. Clock-regulated gene expression is also impaired during day–night cycles and in constant darkness. The circadian phenotypes of srr1 mutants in all three conditions suggest that SRR1 activity is required for normal oscillator function. The SRR1 gene was identified and shown to code for a protein conserved in numerous eukaryotes including mammals and flies, implicating a conserved role for this protein in both the animal and plant kingdoms. PMID:12533513

  17. The hepatic circadian clock modulates xenobiotic metabolism in mice.

    PubMed

    DeBruyne, Jason P; Weaver, David R; Dallmann, Robert

    2014-08-01

    The circadian clock generates daily cycles of gene expression that regulate physiological processes. The liver plays an important role in xenobiotic metabolism and also has been shown to possess its own cell-based clock. The liver clock is synchronized by the master clock in the brain, and a portion of rhythmic gene expression can be driven by behavior of the organism as a whole even when the hepatic clock is suppressed. So far, however, there is relatively little evidence indicating whether the liver clock is functionally important in modulating xenobiotic metabolism. Thus, mice lacking circadian clock function in the whole body or specifically in liver were challenged with pentobarbital and acetaminophen, and pentobarbital sleep time (PBST) and acetaminophen toxicity, respectively, was assessed at different times of day in mutant and control mice. The results suggest that the liver clock is essential for rhythmic changes in xenobiotic detoxification. Surprisingly, it seems that the way in which the clock is disrupted determines the rate of xenobiotic metabolism in the liver. CLOCK-deficient mice are remarkably resistant to acetaminophen and exhibit a longer PBST, while PERIOD-deficient mice have a short PBST. These results indicate an essential role of the tissue-intrinsic peripheral circadian oscillator in the liver in regulating xenobiotic metabolism.

  18. A Compact Model for the Complex Plant Circadian Clock

    PubMed Central

    De Caluwé, Joëlle; Xiao, Qiying; Hermans, Christian; Verbruggen, Nathalie; Leloup, Jean-Christophe; Gonze, Didier

    2016-01-01

    The circadian clock is an endogenous timekeeper that allows organisms to anticipate and adapt to the daily variations of their environment. The plant clock is an intricate network of interlocked feedback loops, in which transcription factors regulate each other to generate oscillations with expression peaks at specific times of the day. Over the last decade, mathematical modeling approaches have been used to understand the inner workings of the clock in the model plant Arabidopsis thaliana. Those efforts have produced a number of models of ever increasing complexity. Here, we present an alternative model that combines a low number of equations and parameters, similar to the very earliest models, with the complex network structure found in more recent ones. This simple model describes the temporal evolution of the abundance of eight clock gene mRNA/protein and captures key features of the clock on a qualitative level, namely the entrained and free-running behaviors of the wild type clock, as well as the defects found in knockout mutants (such as altered free-running periods, lack of entrainment, or changes in the expression of other clock genes). Additionally, our model produces complex responses to various light cues, such as extreme photoperiods and non-24 h environmental cycles, and can describe the control of hypocotyl growth by the clock. Our model constitutes a useful tool to probe dynamical properties of the core clock as well as clock-dependent processes. PMID:26904049

  19. Circadian clock circuitry in colorectal cancer

    PubMed Central

    Mazzoccoli, Gianluigi; Vinciguerra, Manlio; Papa, Gennaro; Piepoli, Ada

    2014-01-01

    Colorectal cancer is the most prevalent among digestive system cancers. Carcinogenesis relies on disrupted control of cellular processes, such as metabolism, proliferation, DNA damage recognition and repair, and apoptosis. Cell, tissue, organ and body physiology is characterized by periodic fluctuations driven by biological clocks operating through the clock gene machinery. Dysfunction of molecular clockworks and cellular oscillators is involved in tumorigenesis, and altered expression of clock genes has been found in cancer patients. Epidemiological studies have shown that circadian disruption, that is, alteration of bodily temporal organization, is a cancer risk factor, and an increased incidence of colorectal neoplastic disease is reported in shift workers. In this review we describe the involvement of the circadian clock circuitry in colorectal carcinogenesis and the therapeutic strategies addressing temporal deregulation in colorectal cancer. PMID:24764658

  20. Circadian clock circuitry in colorectal cancer.

    PubMed

    Mazzoccoli, Gianluigi; Vinciguerra, Manlio; Papa, Gennaro; Piepoli, Ada

    2014-04-21

    Colorectal cancer is the most prevalent among digestive system cancers. Carcinogenesis relies on disrupted control of cellular processes, such as metabolism, proliferation, DNA damage recognition and repair, and apoptosis. Cell, tissue, organ and body physiology is characterized by periodic fluctuations driven by biological clocks operating through the clock gene machinery. Dysfunction of molecular clockworks and cellular oscillators is involved in tumorigenesis, and altered expression of clock genes has been found in cancer patients. Epidemiological studies have shown that circadian disruption, that is, alteration of bodily temporal organization, is a cancer risk factor, and an increased incidence of colorectal neoplastic disease is reported in shift workers. In this review we describe the involvement of the circadian clock circuitry in colorectal carcinogenesis and the therapeutic strategies addressing temporal deregulation in colorectal cancer.

  1. Pigment-dispersing factor affects nocturnal activity rhythms, photic entrainment, and the free-running period of the circadian clock in the cricket gryllus bimaculatus.

    PubMed

    Hassaneen, Ehab; El-Din Sallam, Alaa; Abo-Ghalia, Ahmad; Moriyama, Yoshiyuki; Karpova, Svetlana G; Abdelsalam, Salah; Matsushima, Ayami; Shimohigashi, Yasuyuki; Tomioka, Kenji

    2011-02-01

    Pigment-dispersing factor (PDF) is a neuropeptide widely distributed in insect brains and plays important roles in the circadian system. In this study, we used RNA interference to study the role of the pigment-dispersing factor (pdf) gene in regulating circadian locomotor rhythms in the cricket, Gryllus bimaculatus. Injections of pdf double-stranded RNA (dspdf) effectively knocked down the pdf mRNA and PDF peptide levels. The treated crickets maintained the rhythm both under light-dark cycles (LD) and constant darkness (DD). However, they showed rhythms with reduced nocturnal activity with prominent peaks at lights-on and lights-off. Entrainability of dspdf-injected crickets was higher than control crickets as they required fewer cycles to resynchronize to the LD cycles shifted by 6 h. The free-running periods of the dspdf-injected crickets were shorter than those of control crickets in DD. These results suggest that PDF is not essential for the rhythm generation but involved in control of the nocturnality, photic entrainment, and fine tuning of the free-running period of the circadian clock.

  2. Pancreatic α- and β-cellular clocks have distinct molecular properties and impact on islet hormone secretion and gene expression.

    PubMed

    Petrenko, Volodymyr; Saini, Camille; Giovannoni, Laurianne; Gobet, Cedric; Sage, Daniel; Unser, Michael; Heddad Masson, Mounia; Gu, Guoqiang; Bosco, Domenico; Gachon, Frédéric; Philippe, Jacques; Dibner, Charna

    2017-02-15

    A critical role of circadian oscillators in orchestrating insulin secretion and islet gene transcription has been demonstrated recently. However, these studies focused on whole islets and did not explore the interplay between α-cell and β-cell clocks. We performed a parallel analysis of the molecular properties of α-cell and β-cell oscillators using a mouse model expressing three reporter genes: one labeling α cells, one specific for β cells, and a third monitoring circadian gene expression. Thus, phase entrainment properties, gene expression, and functional outputs of the α-cell and β-cell clockworks could be assessed in vivo and in vitro at the population and single-cell level. These experiments showed that α-cellular and β-cellular clocks are oscillating with distinct phases in vivo and in vitro. Diurnal transcriptome analysis in separated α and β cells revealed that a high number of genes with key roles in islet physiology, including regulators of glucose sensing and hormone secretion, are differentially expressed in these cell types. Moreover, temporal insulin and glucagon secretion exhibited distinct oscillatory profiles both in vivo and in vitro. Altogether, our data indicate that differential entrainment characteristics of circadian α-cell and β-cell clocks are an important feature in the temporal coordination of endocrine function and gene expression.

  3. Clock genes explain large proportion of phenotypic variance in systolic blood pressure and this control is not modified by environmental temperature

    Technology Transfer Automated Retrieval System (TEKTRAN)

    BACKGROUND: Diurnal variation in blood pressure (BP) is regulated, in part, by an endogenous circadian clock; however, few human studies have identified associations between clock genes and BP. Accounting for environmental temperature may be necessary to correct for seasonal bias. METHODS: We examin...

  4. Photoperiodic Modulation of Circadian Clock and Reproductive Axis Gene Expression in the Pre-Pubertal European Sea Bass Brain

    PubMed Central

    Martins, Rute S. T.; Gomez, Ana; Zanuy, Silvia; Carrillo, Manuel; Canário, Adelino V. M.

    2015-01-01

    The acquisition of reproductive competence requires the activation of the brain-pituitary-gonad (BPG) axis, which in most vertebrates, including fishes, is initiated by changes in photoperiod. In the European sea bass long-term exposure to continuous light (LL) alters the rhythm of reproductive hormones, delays spermatogenesis and reduces the incidence of precocious males. In contrast, an early shift from long to short photoperiod (AP) accelerates spermatogenesis. However, how photoperiod affects key genes in the brain to trigger the onset of puberty is still largely unknown. Here, we investigated if the integration of the light stimulus by clock proteins is sufficient to activate key genes that trigger the BPG axis in the European sea bass. We found that the clock genes clock, npas2, bmal1 and the BPG genes gnrh, kiss and kissr share conserved transcription factor frameworks in their promoters, suggesting co-regulation. Other gene promoters of the BGP axis were also predicted to be co-regulated by the same frameworks. Co-regulation was confirmed through gene expression analysis of brains from males exposed to LL or AP photoperiod compared to natural conditions: LL fish had suppressed gnrh1, kiss2, galr1b and esr1, while AP fish had stimulated npas2, gnrh1, gnrh2, kiss2, kiss1rb and galr1b compared to NP. It is concluded that fish exposed to different photoperiods present significant expression differences in some clock and reproductive axis related genes well before the first detectable endocrine and morphological responses of the BPG axis. PMID:26641263

  5. The aging biological clock in Neurospora crassa

    PubMed Central

    Case, Mary E; Griffith, James; Dong, Wubei; Tigner, Ira L; Gaines, Kimberly; Jiang, James C; Jazwinski, S Michal; Arnold, Jonathan

    2014-01-01

    The biological clock affects aging through ras-1 (bd) and lag-1, and these two longevity genes together affect a clock phenotype and the clock oscillator in Neurospora crassa. Using an automated cell-counting technique for measuring conidial longevity, we show that the clock-associated genes lag-1 and ras-1 (bd) are true chronological longevity genes. For example, wild type (WT) has an estimated median life span of 24 days, while the double mutant lag-1, ras-1 (bd) has an estimated median life span of 120 days for macroconidia. We establish the biochemical function of lag-1 by complementing LAG1 and LAC1 in Saccharomyces cerevisiae with lag-1 in N. crassa. Longevity genes can affect the clock as well in that, the double mutant lag-1, ras-1 (bd) can stop the circadian rhythm in asexual reproduction (i.e., banding in race tubes) and lengthen the period of the frequency oscillator to 41 h. In contrast to the ras-1 (bd), lag-1 effects on chronological longevity, we find that this double mutant undergoes replicative senescence (i.e., the loss of replication function with time), unlike WT or the single mutants, lag-1 and ras-1 (bd). These results support the hypothesis that sphingolipid metabolism links aging and the biological clock through a common stress response PMID:25535564

  6. Physical activity and sex modulate obesity risk linked to 3111T/C gene variant of the CLOCK gene in an elderly population: the SUN Project.

    PubMed

    Galbete, Cecilia; Contreras, Rafael; Martínez, J Alfredo; Martínez-González, Miguel Ángel; Guillén-Grima, Francisco; Marti, Amelia

    2012-12-01

    Genetic factors may interact with physical activity levels to modify obesity risk. Our aim was to explore the influence of rs1801260 single-nucleotide polymorphism (SNP) (3111T/C) of CLOCK gene on obesity risk, and to examine its potential interaction with lifestyle factors in an elderly population within the SUN ("Seguimiento Universidad de Navarra") Project. Subjects (n = 903, aged 69 ± 6 yrs) were recruited from the SUN Project. DNA was obtained from saliva, whereas lifestyle and dietary data were collected by validated self-report questionnaires. Genotype was assessed by reverse transcriptase-polymerase chain reaction (RT-PCR) plus allele discrimination. A significant interaction was observed between the 3111T/C SNP of CLOCK gene and sex for overweight/obesity risk (p for sex × CLOCK interaction <.001). Our results showed that women carrying the C allele of CLOCK gene had a marginally significant lower risk of overweight/obesity compared with noncarrier-TT-subjects (odds ratio [OR]: .61, 95% confidence interval [CI]: .36-1.04; p = .069). Moreover, this association of the C allele with a decreased overweight/obesity risk might be enhanced in those women with a high physical activity level. Women practicing more than 16.8 metabolic equivalent tasks (hours per week) had a significantly lower overweight/obesity risk (OR: .36, 95% CI: .17-.79; p = .011). Furthermore, a significant interaction between the 3111T/C gene variant and physical activity (PA) for overweight/obesity risk was observed but only in women (p for PA × CLOCK interaction <.050). In conclusion, it appears that physical activity levels may act by modifying the association of the 3111T/C SNP (rs1801260) of the CLOCK gene with overweight/obesity risk in elderly women in the SUN Project.

  7. Experimental and clinical aspects of melatonin and clock genes in diabetes.

    PubMed

    Peschke, Elmar; Bähr, Ina; Mühlbauer, Eckhard

    2015-08-01

    The pineal hormone melatonin influences insulin secretion, as well as glucagon and somatostatin secretion, both in vivo and in vitro. These effects are mediated by two specific, high-affinity, seven transmembrane, pertussis toxin-sensitive, Gi-protein-coupled melatonin receptors, MT1 and MT2. Both isoforms are expressed in the β-cells, α-cells as well as δ-cells of the pancreatic islets of Langerhans and are involved in the modulation of insulin secretion, leading to inhibition of the adenylate cyclase-dependent cyclic adenosine monophosphate as well as cyclic guanosine monophosphate formation in pancreatic β-cells by inhibiting the soluble guanylate cyclase, probably via MT2 receptors. In this way, melatonin also likely inhibits insulin secretion, whereas using the inositol triphosphate pathway after previous blocking of Gi-proteins by pertussis toxin, melatonin increases insulin secretion. Desynchrony of receptor signaling may lead to the development of type 2 diabetes. This notion has recently been supported by genomewide association studies pinpointing variances of the MT2 receptor as a risk factor for this rapidly spreading metabolic disturbance. As melatonin is secreted in a clearly diurnal fashion, it is safe to assume that it also has a diurnal impact on the blood-glucose-regulating function of the islet. Observations of the circadian expression of clock genes (Clock, Bmal1, Per1,2,3, and Cry1,2) in pancreatic islets, as well as in INS1 rat insulinoma cells, may indicate that circadian rhythms are generated in the β-cells themselves. The circadian secretion of insulin from pancreatic islets is clock-driven. Disruption of circadian rhythms and clock function leads to metabolic disturbances, for example, type 2 diabetes. The study of melatonin-insulin interactions in diabetic rat models has revealed an inverse relationship between these two hormones. Both type 2 diabetic rats and patients exhibit decreased melatonin levels and slightly increased

  8. Glucose Alters Per2 Rhythmicity Independent of AMPK, Whereas AMPK Inhibitor Compound C Causes Profound Repression of Clock Genes and AgRP in mHypoE-37 Hypothalamic Neurons

    PubMed Central

    Oosterman, Johanneke E.; Belsham, Denise D.

    2016-01-01

    Specific neurons in the hypothalamus are regulated by peripheral hormones and nutrients to maintain proper metabolic control. It is unclear if nutrients can directly control clock gene expression. We have therefore utilized the immortalized, hypothalamic cell line mHypoE-37, which exhibits robust circadian rhythms of core clock genes. mHypoE-37 neurons were exposed to 0.5 or 5.5 mM glucose, comparable to physiological levels in the brain. Per2 and Bmal1 mRNAs were assessed every 3 hours over 36 hours. Incubation with 5.5 mM glucose significantly shortened the period and delayed the phase of Per2 mRNA levels, but had no effect on Bmal1. Glucose had no significant effect on phospho-GSK3β, whereas AMPK phosphorylation was altered. Thus, the AMPK inhibitor Compound C was utilized, and mRNA levels of Per2, Bmal1, Cryptochrome1 (Cry1), agouti-related peptide (AgRP), carnitine palmitoyltransferase 1C (Cpt1c), and O-linked N-acetylglucosamine transferase (Ogt) were measured. Remarkably, Compound C dramatically reduced transcript levels of Per2, Bmal1, Cry1, and AgRP, but not Cpt1c or Ogt. Because AMPK was not inhibited at the same time or concentrations as the clock genes, we suggest that the effect of Compound C on gene expression occurs through an AMPK-independent mechanism. The consequences of inhibition of the rhythmic expression of clock genes, and in turn downstream metabolic mediators, such as AgRP, could have detrimental effects on overall metabolic processes. Importantly, the effects of the most commonly used AMPK inhibitor Compound C should be interpreted with caution, considering its role in AMPK-independent repression of specific genes, and especially clock gene rhythm dysregulation. PMID:26784927

  9. Phototransduction and clock gene expression in the troglobiont beetle Ptomaphagus hirtus of Mammoth cave.

    PubMed

    Friedrich, Markus; Chen, Rui; Daines, Bryce; Bao, Riyue; Caravas, Jason; Rai, Puneet K; Zagmajster, Maja; Peck, Stewart B

    2011-11-01

    Obligatory cave species exhibit dramatic trait modifications such as eye reduction, loss of pigmentation and an increase in touch receptors. As molecular studies of cave adaptation have largely concentrated on vertebrate models, it is not yet possible to probe for genetic universalities underlying cave adaptation. We have therefore begun to study the strongly cave-adapted small carrion beetle Ptomaphagus hirtus. For over 100 years, this flightless signature inhabitant of Mammoth Cave, the world's largest known cave system, has been considered blind despite the presence of residual lens structures. By deep sequencing of the adult head transcriptome, we discovered the transcripts of all core members of the phototransduction protein machinery. Combined with the absence of transcripts of select structural photoreceptor and eye pigmentation genes, these data suggest a reduced but functional visual system in P. hirtus. This conclusion was corroborated by a negative phototactic response of P. hirtus in light/dark choice tests. We further detected the expression of the complete circadian clock gene network in P. hirtus, raising the possibility of a role of light sensation in the regulation of oscillating processes. We speculate that P. hirtus is representative of a large number of animal species with highly reduced but persisting visual capacities in the twilight zone of the subterranean realm. These can now be studied on a broad comparative scale given the efficiency of transcript discovery by next-generation sequencing.

  10. Glucocorticoids affect 24 h clock genes expression in human adipose tissue explant cultures

    Technology Transfer Automated Retrieval System (TEKTRAN)

    To examine firstly whether CLOCK exhibits a circadian expression in human visceral (V) and subcutaneous (S) adipose tissue (AT) in vitro as compared with BMAL1 and PER2, and secondly to investigate the possible effect of the glucocorticoid analogue dexamethasone (DEX) on positive and negative clock ...

  11. Rapid attenuation of circadian clock gene oscillations in the rat heart following ischemia-reperfusion

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The intracellular circadian clock consists of a series of transcriptional modulators that together allow the cell to perceive the time of day. Circadian clocks have been identified within various components of the cardiovascular system (e.g., cardiomyocytes, vascular smooth muscle cells) and possess...

  12. Functional conservation of clock-related genes in flowering plants: overexpression and RNA interference analyses of the circadian rhythm in the monocotyledon Lemna gibba.

    PubMed

    Serikawa, Masayuki; Miwa, Kumiko; Kondo, Takao; Oyama, Tokitaka

    2008-04-01

    Circadian rhythms are found in organisms from cyanobacteria to plants and animals. In flowering plants, the circadian clock is involved in the regulation of various physiological phenomena, including growth, leaf movement, stomata opening, and floral transitions. Molecular mechanisms underlying the circadian clock have been identified using Arabidopsis (Arabidopsis thaliana); the functions and genetic networks of a number of clock-related genes, including CIRCADIAN CLOCK ASSOCIATED1, LATE ELONGATED HYPOCOTYL (LHY), TIMING OF CAB EXPRESSION1, GIGANTEA (GI), and EARLY FLOWERING3 (ELF3), have been analyzed. The degree to which clock systems are conserved among flowering plants, however, is still unclear. We previously isolated homologs for Arabidopsis clock-related genes from monocotyledon Lemna plants. Here, we report the physiological roles of these Lemna gibba genes (LgLHYH1, LgLHYH2, LgGIH1, and LgELF3H1) in the circadian system. We studied the effects of overexpression and RNA interference (RNAi) of these genes on the rhythmic expression of morning- and evening-specific reporters. Overexpression of each gene disrupted the rhythmicity of either or both reporters, suggesting that these four homologs can be involved in the circadian system. RNAi of each of the genes except LgLHYH2 affected the bioluminescence rhythms of both reporters. These results indicated that these homologs are involved in the circadian system of Lemna plants and that the structure of the circadian clock is likely to be conserved between monocotyledons and dicotyledons. Interestingly, RNAi of LgGIH1 almost completely abolished the circadian rhythm; because this effect appeared to be much stronger than the phenotype observed in an Arabidopsis gi loss-of-function mutant, the precise role of each clock gene may have diverged in the clock systems of Lemna and Arabidopsis.

  13. Functional Conservation of Clock-Related Genes in Flowering Plants: Overexpression and RNA Interference Analyses of the Circadian Rhythm in the Monocotyledon Lemna gibba1[W

    PubMed Central

    Serikawa, Masayuki; Miwa, Kumiko; Kondo, Takao; Oyama, Tokitaka

    2008-01-01

    Circadian rhythms are found in organisms from cyanobacteria to plants and animals. In flowering plants, the circadian clock is involved in the regulation of various physiological phenomena, including growth, leaf movement, stomata opening, and floral transitions. Molecular mechanisms underlying the circadian clock have been identified using Arabidopsis (Arabidopsis thaliana); the functions and genetic networks of a number of clock-related genes, including CIRCADIAN CLOCK ASSOCIATED1, LATE ELONGATED HYPOCOTYL (LHY), TIMING OF CAB EXPRESSION1, GIGANTEA (GI), and EARLY FLOWERING3 (ELF3), have been analyzed. The degree to which clock systems are conserved among flowering plants, however, is still unclear. We previously isolated homologs for Arabidopsis clock-related genes from monocotyledon Lemna plants. Here, we report the physiological roles of these Lemna gibba genes (LgLHYH1, LgLHYH2, LgGIH1, and LgELF3H1) in the circadian system. We studied the effects of overexpression and RNA interference (RNAi) of these genes on the rhythmic expression of morning- and evening-specific reporters. Overexpression of each gene disrupted the rhythmicity of either or both reporters, suggesting that these four homologs can be involved in the circadian system. RNAi of each of the genes except LgLHYH2 affected the bioluminescence rhythms of both reporters. These results indicated that these homologs are involved in the circadian system of Lemna plants and that the structure of the circadian clock is likely to be conserved between monocotyledons and dicotyledons. Interestingly, RNAi of LgGIH1 almost completely abolished the circadian rhythm; because this effect appeared to be much stronger than the phenotype observed in an Arabidopsis gi loss-of-function mutant, the precise role of each clock gene may have diverged in the clock systems of Lemna and Arabidopsis. PMID:18281417

  14. RNA interference of the period gene affects the rhythm of sperm release in moths.

    PubMed

    Kotwica, Joanna; Bebas, Piotr; Gvakharia, Barbara O; Giebultowicz, Jadwiga M

    2009-02-01

    The period (per) gene is 1 of the core elements of the circadian clock mechanism in animals from insects to mammals. In clock cells of Drosophila melanogaster, per mRNA and PER protein oscillate in daily cycles. Consistent with the molecular clock model, PER moves to cell nuclei and acts as a repressor of positive clock elements. Homologs of per are known in many insects; however, specific roles of per in generating output rhythms are not known for most species. The aim of this article was to determine whether per is functionally involved in the circadian rhythm of sperm release in the moth, Spodoptera littoralis. In this species, as in other moths, rhythmic release of sperm bundles from the testis into the upper vas deferens occurs only in the evening, and this rhythm continues in the isolated reproductive system. S. littoralis was used to investigate the expression of per mRNA and protein in the 2 types of cells involved in sperm release: the cyst cells surrounding sperm bundles in the testes, and the barrier cells separating testicular follicles from the vas deferens. In cyst cells, PER showed a nuclear rhythm in light/dark (LD) cycles but was constitutively cytoplasmic in constant darkness (DD). In barrier cells, nuclear cycling of PER was observed in both LD and DD. To determine the role of PER in rhythmic sperm release in moths, testes-sperm duct complexes were treated in vitro with double-stranded fragments of per mRNA (dsRNA). This treatment significantly lowered per mRNA and protein in cyst cells and barrier cells and caused a delay of sperm release. These data demonstrate that a molecular oscillator involving the period gene plays an essential role in the regulation of rhythmic sperm release in this species.

  15. The effect of white light on normal and malignant murine melanocytes: A link between opsins, clock genes, and melanogenesis.

    PubMed

    de Assis, L V M; Moraes, M N; da Silveira Cruz-Machado, S; Castrucci, A M L

    2016-06-01

    The skin possesses a photosensitive system comprised of opsins whose function is not fully understood, and clock genes which exert an important regulatory role in skin biology. Here, we evaluated the presence of opsins in normal (Melan-a cells) and malignant (B16-F10 cells) murine melanocytes. Both cell lines express Opn2, Opn4--for the first time reported in these cell types--as well as S-opsin. OPN4 protein was found in a small area capping the cell nuclei of B16-F10 cells kept in constant dark (DD); twenty-four hours after the white light pulse (WLP), OPN4 was found in the cell membrane. Despite the fact that B16-F10 cells expressed less Opn2 and Opn4 than Melan-a cells, our data indicate that the malignant melanocytes exhibited increased photoresponsiveness. The clock gene machinery is also severely downregulated in B16-F10 cells as compared to Melan-a cells. Per1, Per2, and Bmal1 expression increased in B16-F10 cells in response to WLP. Although no response in clock gene expression to WLP was observed in Melan-a cells, gene correlational data suggest a minor effect of WLP. In contrast to opsins and clock genes, melanogenesis is significantly upregulated in malignant melanocytes in comparison to Melan-a cells. Tyrosinase expression increased after WLP only in B16-F10 cells; however no increase in melanin content after WLP was seen in either cell line. Our findings may prove useful in the treatment and the development of new pharmacological approaches of depigmentation diseases and skin cancer.

  16. Periodic transition on an axial compressor stator: Incidence and clocking effects. Part 2: Transition onset predictions

    SciTech Connect

    Solomon, W.J.; Walker, G.J.; Hughes, J.D.

    1999-07-01

    Transition onset observations from a 1.5-stage axial compressor outlet stator presented in Part 1 of this paper are compared with the predictions of conventional transition correlations applied in a quasi-steady manner. The viscous/inviscid interaction code MISES is used to predict the blade surface pressure distributions, and boundary layer development. The temporal variation in transition onset is then predicted using ensemble-averaged free-stream turbulence data from the compressor measurements. This simple procedure captures most significant features of the complex transition process on the compressor, and is clearly superior to fixed transition models based on long-term average free-stream turbulence levels. Parallel computations for both natural and bypass transition modes indicate that the natural transition mode tends to dominate on the compressor. This is at variance with turbine airfoil experience, where bypass transition is clearly more important. Comparison of prediction and experiment highlights the significance of leading edge potential flow interactions in promoting periodic wake-induced transition. Viscous/inviscid interactions in the neighborhood of transition can also have an important influence on boundary layer stability and separation phenomena.

  17. [Physiological and pathophysiological role of the circadian clock system].

    PubMed

    Halmos, Tamás; Suba, Ilona

    2012-09-02

    It has been well known for ages that in living organisms the rhythmicity of biological processes is linked to the ~ 24-hour light-dark cycle. However, the exact function of the circadian clock system has been explored only in the past decades. It came to light that the photosensitive primary "master clock" is situated in the suprachiasmatic photosensitive nuclei of the special hypothalamic region, and that it is working according to ~24-hour changes of light and darkness. The master clock sends its messages to the peripheral "slave clocks". In many organs, like pancreatic β-cells, the slave clocks have autonomic functions as well. Two essential components of the clock system are proteins encoded by the CLOCK and BMAL1 genes. CLOCK genes are in interaction with endonuclear receptors such as peroxisoma-proliferator activated receptors and Rev-erb-α, as well as with the hypothalamic-pituitary-adrenal axis, regulating the adaptation to stressors, energy supply, metabolic processes and cardiovascular system. Melatonin, the product of corpus pineale has a significant role in the functions of the clock system. The detailed discovery of the clock system has changed our previous knowledge about the development of many diseases. The most explored fields are hypertension, cardiovascular diseases, metabolic processes, mental disorders, cancers, sleep apnoe and joint disorders. CLOCK genes influence ageing as well. The recognition of the periodicity of biological processes makes the optimal dosing of certain drugs feasible. The more detailed discovery of the interaction of the clock system might further improve treatment and prevention of many disorders.

  18. Differential resetting process of circadian gene expression in rat pineal glands after the reversal of the light/dark cycle via a 24 h light or dark period transition.

    PubMed

    Wu, Tao; Dong, Yue; Yang, Zhiqiu; Kato, Hisanori; Ni, Yinhua; Fu, Zhengwei

    2009-07-01

    Although studies involving the circadian response to time-zone transitions indicate that the circadian clock usually takes much longer to phase advance than delay, the discrepancy between the circadian resetting induced by photoperiod alteration via a dark or light period transition has yet to be investigated. In mammals, the pineal gland is an important component in the photoneuroendocrine axis, regulating biological rhythms. However, few studies have systematically examined the resetting process of pineal clock-gene expression to date. We investigated the resetting processes of four clock genes (Bmal1, Cry1, Per1, Dec1) and AANAT in the rat pineal gland after the light-dark (LD) reversal via a 24 h light or dark period transition. The resynchronization of the SCN-driven gene AANAT was nearly complete in three days in both situations, displaying similar resetting rates and processes after the differential LD reversals. The resetting processes of the clock genes were characterized by gene-specific, phase-shift modes and differential phase-shift rates between the two different LD reversal modes. The resetting processes of these clock genes were noticeably lengthened after the LD reversal via the light period transition in comparison to via the dark period transition. In addition, among the four examined clock genes, Per1 adjusted most rapidly after the differential LD reversals, while the rhythmic Cry1 expression adjusted most slowly.

  19. Circadian Mechanisms of Food Anticipatory Rhythms in Rats Fed Once or Twice Daily: Clock Gene and Endocrine Correlates

    PubMed Central

    Patton, Danica F.; Katsuyama, Ângela M.; Pavlovski, Ilya; Michalik, Mateusz; Patterson, Zachary; Parfyonov, Maksim; Smit, Andrea N.; Marchant, Elliott G.; Chung, John; Abizaid, Alfonso; Storch, Kai-Florian; de la Iglesia, Horacio; Mistlberger, Ralph E.

    2014-01-01

    Circadian clocks in many brain regions and peripheral tissues are entrained by the daily rhythm of food intake. Clocks in one or more of these locations generate a daily rhythm of locomotor activity that anticipates a regular mealtime. Rats and mice can also anticipate two daily meals. Whether this involves 1 or 2 circadian clocks is unknown. To gain insight into how the circadian system adjusts to 2 daily mealtimes, male rats in a 12∶12 light-dark cycle were fed a 2 h meal either 4 h after lights-on or 4 h after lights-off, or a 1 h meal at both times. After 30 days, brain, blood, adrenal and stomach tissue were collected at 6 time points. Multiple clock genes from adrenals and stomachs were assayed by RT-PCR. Blood was assayed for corticosterone and ghrelin. Bmal1 expression was quantified in 14 brain regions by in situ hybridization. Clock gene rhythms in adrenal and stomach from day-fed rats oscillated in antiphase with the rhythms in night-fed rats, and at an intermediate phase in rats fed twice daily. Corticosterone and ghrelin in 1-meal rats peaked at or prior to the expected mealtime. In 2-meal rats, corticosterone peaked only prior the nighttime meal, while ghrelin peaked prior to the daytime meal and then remained elevated. The olfactory bulb, nucleus accumbens, dorsal striatum, cerebellum and arcuate nucleus exhibited significant daily rhythms of Bmal1 in the night-fed groups that were approximately in antiphase in the day-fed groups, and at intermediate levels (arrhythmic) in rats anticipating 2 daily meals. The dissociations between anticipatory activity and the peripheral clocks and hormones in rats anticipating 2 daily meals argue against a role for these signals in the timing of behavioral rhythms. The absence of rhythmicity at the tissue level in brain regions from rats anticipating 2 daily meals support behavioral evidence that circadian clock cells in these tissues may reorganize into two populations coupled to different meals. PMID:25502949

  20. Circadian mechanisms of food anticipatory rhythms in rats fed once or twice daily: clock gene and endocrine correlates.

    PubMed

    Patton, Danica F; Katsuyama, Angela M; Pavlovski, Ilya; Michalik, Mateusz; Patterson, Zachary; Parfyonov, Maksim; Smit, Andrea N; Marchant, Elliott G; Chung, Seung Hwan; Chung, John; Abizaid, Alfonso; Storch, Kai-Florian; de la Iglesia, Horacio; Mistlberger, Ralph E

    2014-01-01

    Circadian clocks in many brain regions and peripheral tissues are entrained by the daily rhythm of food intake. Clocks in one or more of these locations generate a daily rhythm of locomotor activity that anticipates a regular mealtime. Rats and mice can also anticipate two daily meals. Whether this involves 1 or 2 circadian clocks is unknown. To gain insight into how the circadian system adjusts to 2 daily mealtimes, male rats in a 12∶12 light-dark cycle were fed a 2 h meal either 4 h after lights-on or 4 h after lights-off, or a 1 h meal at both times. After 30 days, brain, blood, adrenal and stomach tissue were collected at 6 time points. Multiple clock genes from adrenals and stomachs were assayed by RT-PCR. Blood was assayed for corticosterone and ghrelin. Bmal1 expression was quantified in 14 brain regions by in situ hybridization. Clock gene rhythms in adrenal and stomach from day-fed rats oscillated in antiphase with the rhythms in night-fed rats, and at an intermediate phase in rats fed twice daily. Corticosterone and ghrelin in 1-meal rats peaked at or prior to the expected mealtime. In 2-meal rats, corticosterone peaked only prior the nighttime meal, while ghrelin peaked prior to the daytime meal and then remained elevated. The olfactory bulb, nucleus accumbens, dorsal striatum, cerebellum and arcuate nucleus exhibited significant daily rhythms of Bmal1 in the night-fed groups that were approximately in antiphase in the day-fed groups, and at intermediate levels (arrhythmic) in rats anticipating 2 daily meals. The dissociations between anticipatory activity and the peripheral clocks and hormones in rats anticipating 2 daily meals argue against a role for these signals in the timing of behavioral rhythms. The absence of rhythmicity at the tissue level in brain regions from rats anticipating 2 daily meals support behavioral evidence that circadian clock cells in these tissues may reorganize into two populations coupled to different meals.

  1. Restricted Feeding Schedules Modulate in a Different Manner the Expression of Clock Genes in Rat Hypothalamic Nuclei

    PubMed Central

    De Araujo, Leonardo D.; Roa, Silvia L.; Bueno, Ana C.; Coeli-Lacchini, Fernanda B.; Martins, Clarissa S.; Uchoa, Ernane T.; Antunes-Rodrigues, Jose; Elias, Lucila L.; Elias, Paula C.; Moreira, Ayrton C.; De Castro, Margaret

    2016-01-01

    Food access restriction is associated to changes in gene expression of the circadian clock system. However, there are only a few studies investigating the effects of non-photic synchronizers, such as food entrainment, on the expression of clock genes in the central oscillators. We hypothesized that different feeding restriction patterns could modulate the expression of clock genes in the suprachiasmatic nucleus (SCN) “master” clock and in extra-SCN oscillators such as the paraventricular (PVN) and arcuate (ARC) hypothalamic nuclei. Wistar rats were divided into four groups: Control group (CG; food available ad libitum), Restricted night-fed (RF-n; food access during 2 h at night), Restricted day-fed (RF-d; food access during 2 h at daytime), Day-fed (DF; food access during 12 h at daytime). After 21 days, rats were decapitated between ZT2-ZT3 (0800–0900 h); ZT11-ZT12 (1700–1800 h), or ZT17-18 (2300–2400 h). Plasma corticosterone was measured by radioimmunoassay (RIA). The expression of Clock, Bmal1, Per1, Per2, Per3, Cry1, Cry2, Rev-erbα, and Rorα were assessed in SCN, PVN, and ARC hypothalamic nuclei by RT-PCR and calculated by the 2[−DeltaDeltaCT(Cyclethreshold)](2−ΔΔCT) method. Restricted food availability during few h led to decreased body weight in RF-n and RF-d groups compared to controls and DF group. We also observed an anticipatory corticosterone peak before food availability in RF-n and RF-d groups. Furthermore, the pattern of clock gene expression in response to RF-n, RF-d, and DF schedules was affected differently in the SCN, PVN, and ARC hypothalamic nuclei. In conclusion, the master oscillator in SCN as well as the oscillator in PVN and ARC, all brain areas involved in food intake, responds in a tissue-specific manner to feeding restriction. PMID:28003802

  2. Development and morphology of the clock-gene-expressing lateral neurons of Drosophila melanogaster.

    PubMed

    Helfrich-Förster, Charlotte; Shafer, Orie T; Wülbeck, Corinna; Grieshaber, Eva; Rieger, Dirk; Taghert, Paul

    2007-01-01

    The clock-gene-expressing lateral neurons are essential for the locomotor activity rhythm of Drosophila melanogaster. Traditionally, these neurons are divided into three groups: the dorsal lateral neurons (LN(d)), the large ventral lateral neurons (l-LN(v)), and the small ventral lateral neurons (s-LN(v)), whereby the latter group consists of four neurons that express the neuropeptide pigment-dispersing factor (PDF) and a fifth PDF-negative neuron. So far, only the l-LN(v) and the PDF-positive s-LN(v) have been shown to project into the accessory medulla, a small neuropil that contains the circadian pacemaker center in several insects. We show here that the other lateral neurons also arborize in the accessory medulla, predominantly forming postsynaptic sites. Both the l-LN(v) and LN(d) are anatomically well suited to connect the accessory medullae. Whereas the l-LN(v) may receive ipsilateral photic input from the Hofbauer-Buchner eyelet, the LN(d) invade mainly the contralateral accessory medulla and thus may receive photic input from the contralateral side. Both the LN(d) and the l-LN(v) differentiate during midmetamorphosis. They do so in close proximity to one another and the fifth PDF-negative s-LN(v), suggesting that these cell groups may derive from common precursors.

  3. Transcriptome Profiling of the Lungs Reveals Molecular Clock Genes Expression Changes after Chronic Exposure to Ambient Air Particles

    PubMed Central

    Song, Pengcheng; Li, Zhigang; Li, Xiaoqian; Yang, Lixin; Zhang, Lulu; Li, Nannan; Guo, Chen; Lu, Shuyu; Wei, Yongjie

    2017-01-01

    The symptoms of asthma, breathlessness, insomnia, etc. all have relevance to pulmonary rhythmic disturbances. Epidemiology and toxicology studies have demonstrated that exposure to ambient air particles can result in pulmonary dysfunction. However, there are no data directly supporting a link between air pollution and circadian rhythm disorder. In the present study, we found that breathing highly polluted air resulted in changes of the molecular clock genes expression in lung by transcriptome profiling analyses in a rodent model. Compared to those exposed to filtered air, in both pregnant and offspring rats in the unfiltered group, key clock genes (Per1, Per2, Per3, Rev-erbα and Dbp) expression level decreased and Bmal1 expression level increased. In both rat dams and their offspring, after continuous exposure to unfiltered air, we observed significant histologic evidence for both perivascular and peribronchial inflammation, increased tissue and systemic oxidative stress in the lungs. Our results suggest that chronic exposure to particulate matter can induce alterations of clock genes expression, which could be another important pathway for explaining the feedbacks of ambient particle exposure in addition to oxidative stress and inflammation. PMID:28106813

  4. Circadian Clock Control of the Cellular Response to DNA Damage

    PubMed Central

    Sancar, Aziz; Lindsey-Boltz, Laura A.; Kang, Tae-Hong; Reardon, Joyce T.; Lee, Jin Hyup; Ozturk, Nuri

    2010-01-01

    Mammalian cells possess a cell-autonomous molecular clock which controls the timing of many biochemical reactions and hence the cellular response to environmental stimuli including genotoxic stress. The clock consists of an autoregulatory transcription-translation feedback loop made up of four genes/proteins, BMal1, Clock, Cryptochrome, and Period. The circadian clock has an intrinsic period of about 24 hours, and it dictates the rates of many biochemical reactions as a function of the time of the day. Recently, it has become apparent that the circadian clock plays an important role in determining the strengths of cellular responses to DNA damage including repair, checkpoints, and apoptosis. These new insights are expected to guide development of novel mechanism-based chemotherapeutic regimens. PMID:20227409

  5. Involvement of the clock gene Rev-erb alpha in the regulation of glucagon secretion in pancreatic alpha-cells.

    PubMed

    Vieira, Elaine; Marroquí, Laura; Figueroa, Ana Lucia C; Merino, Beatriz; Fernandez-Ruiz, Rebeca; Nadal, Angel; Burris, Thomas P; Gomis, Ramon; Quesada, Ivan

    2013-01-01

    Disruption of pancreatic clock genes impairs pancreatic beta-cell function, leading to the onset of diabetes. Despite the importance of pancreatic alpha-cells in the regulation of glucose homeostasis and in diabetes pathophysiology, nothing is known about the role of clock genes in these cells. Here, we identify the clock gene Rev-erb alpha as a new intracellular regulator of glucagon secretion. Rev-erb alpha down-regulation by siRNA (60-70% inhibition) in alphaTC1-9 cells inhibited low-glucose induced glucagon secretion (p<0.05) and led to a decrease in key genes of the exocytotic machinery. The Rev-erb alpha agonist GSK4112 increased glucagon secretion (1.6 fold) and intracellular calcium signals in alphaTC1-9 cells and mouse primary alpha-cells, whereas the Rev-erb alpha antagonist SR8278 produced the opposite effect. At 0.5 mM glucose, alphaTC1-9 cells exhibited intrinsic circadian Rev-erb alpha expression oscillations that were inhibited by 11 mM glucose. In mouse primary alpha-cells, glucose induced similar effects (p<0.001). High glucose inhibited key genes controlled by AMPK such as Nampt, Sirt1 and PGC-1 alpha in alphaTC1-9 cells (p<0.05). AMPK activation by metformin completely reversed the inhibitory effect of glucose on Nampt-Sirt1-PGC-1 alpha and Rev-erb alpha. Nampt inhibition decreased Sirt1, PGC-1 alpha and Rev-erb alpha mRNA expression (p<0.01) and glucagon release (p<0.05). These findings identify Rev-erb alpha as a new intracellular regulator of glucagon secretion via AMPK/Nampt/Sirt1 pathway.

  6. Diurnal expression of clock genes in pineal gland and brain and plasma levels of melatonin and cortisol in Atlantic salmon parr and smolts.

    PubMed

    Huang, Tien-sheng; Ruoff, Peter; Fjelldal, Per G

    2010-10-01

    In Atlantic salmon, the preadaptation to a marine life, i.e., parr-smolt transformation, and melatonin production in the pineal gland are regulated by the photoperiod. However, the clock genes have never been studied in the pineal gland of this species. The aim of the present study was to describe the diurnal expression of clock genes (Per1-like, Cry2, and Clock) in the pineal gland and brain of Atlantic salmon parr and smolts in freshwater, as well as plasma levels of melatonin and cortisol. By employing an out-of-season smolt production model, the parr-smolt transformation was induced by subjecting triplicate groups of parr to 6 wks (wks 0 to 6) under a 12 h:12 h light-dark (LD) regime followed by 6 wks (wks 6 to 12) of continuous light (LL). The measured clock genes in both pineal gland and brain and the plasma levels of melatonin and cortisol showed significant daily variations in parr under LD in wk 6, whereas these rhythms were abolished in smolts under LL in wk 12. In parr, the pineal Per1-like and Cry2 expression peaked in the dark phase, whereas the pineal Clock expression was elevated during the light phase. Although this study presents novel findings on the clock gene system in the teleost pineal gland, the role of this system in the regulation of smoltification needs to be studied in more detail.

  7. Screening of Clock Gene Polymorphisms Demonstrates Association of a PER3 Polymorphism with Morningness–Eveningness Preference and Circadian Rhythm Sleep Disorder

    PubMed Central

    Hida, Akiko; Kitamura, Shingo; Katayose, Yasuko; Kato, Mie; Ono, Hiroko; Kadotani, Hiroshi; Uchiyama, Makoto; Ebisawa, Takashi; Inoue, Yuichi; Kamei, Yuichi; Okawa, Masako; Takahashi, Kiyohisa; Mishima, Kazuo

    2014-01-01

    A system of self-sustained biological clocks controls the 24-h rhythms of behavioral and physiological processes such as the sleep–wake cycle. The circadian clock system is regulated by transcriptional and translational negative feedback loops of multiple clock genes. Polymorphisms in circadian clock genes have been associated with morningness–eveningness (diurnal) preference, familial advanced sleep phase type (ASPT), and delayed sleep phase type (DSPT). We genotyped single-nucleotide polymorphisms in circadian clock genes in 182 DSPT individuals, 67 free-running type (FRT) individuals, and 925 controls. The clock gene polymorphisms were tested for associations with diurnal preference and circadian rhythm sleep disorder (CRSD) phenotypes. The PER3 polymorphism (rs228697) was significantly associated with diurnal preference and the FRT phenotype. The minor allele of rs228697 was more prevalent in evening types than in morning types (sex-adjusted odds ratio (OR), 2.483, Bonferroni-corrected P = 0.012) and in FRT individuals compared with the controls (age- and sex-adjusted OR, 2.021, permutated P = 0.017). Our findings support the notion that PER3 polymorphisms could be a potential genetic marker for an individual's circadian and sleep phenotypes. PMID:25201053

  8. Screening of clock gene polymorphisms demonstrates association of a PER3 polymorphism with morningness-eveningness preference and circadian rhythm sleep disorder.

    PubMed

    Hida, Akiko; Kitamura, Shingo; Katayose, Yasuko; Kato, Mie; Ono, Hiroko; Kadotani, Hiroshi; Uchiyama, Makoto; Ebisawa, Takashi; Inoue, Yuichi; Kamei, Yuichi; Okawa, Masako; Takahashi, Kiyohisa; Mishima, Kazuo

    2014-09-09

    A system of self-sustained biological clocks controls the 24-h rhythms of behavioral and physiological processes such as the sleep-wake cycle. The circadian clock system is regulated by transcriptional and translational negative feedback loops of multiple clock genes. Polymorphisms in circadian clock genes have been associated with morningness-eveningness (diurnal) preference, familial advanced sleep phase type (ASPT), and delayed sleep phase type (DSPT). We genotyped single-nucleotide polymorphisms in circadian clock genes in 182 DSPT individuals, 67 free-running type (FRT) individuals, and 925 controls. The clock gene polymorphisms were tested for associations with diurnal preference and circadian rhythm sleep disorder (CRSD) phenotypes. The PER3 polymorphism (rs228697) was significantly associated with diurnal preference and the FRT phenotype. The minor allele of rs228697 was more prevalent in evening types than in morning types (sex-adjusted odds ratio (OR), 2.483, Bonferroni-corrected P = 0.012) and in FRT individuals compared with the controls (age- and sex-adjusted OR, 2.021, permutated P = 0.017). Our findings support the notion that PER3 polymorphisms could be a potential genetic marker for an individual's circadian and sleep phenotypes.

  9. Multiple circadian-regulated elements contribute to cycling period gene expression in Drosophila.

    PubMed Central

    Stanewsky, R; Jamison, C F; Plautz, J D; Kay, S A; Hall, J C

    1997-01-01

    A new regulatory element necessary for the correct temporal expression of the period (per) gene was identified by monitoring real-time per expression in living individual flies carrying two different period-luciferase transgenes. luciferase RNA driven from only the per promoter was not sufficient to replicate the normal pattern of per RNA cycling; however, a per-luc fusion RNA driven from a transgene containing additional per sequences cycled identically to endogenous per. The results indicate the existence of at least two circadian-regulated elements--one within the promoter and one within the transcribed portion of the per gene. Phase and amplitude analysis of both per-luc transgenes revealed that normal per expression requires the regulation of these elements at distinct phases and suggests a mechanism by which biological clocks sustain high-amplitude feedback oscillations. PMID:9305642

  10. Effects of Photoperiod Extension on Clock Gene and Neuropeptide RNA Expression in the SCN of the Soay Sheep

    PubMed Central

    Dardente, Hugues; Wyse, Cathy A.; Lincoln, Gerald A.; Wagner, Gabriela C.; Hazlerigg, David G.

    2016-01-01

    In mammals, changing daylength (photoperiod) is the main synchronizer of seasonal functions. The photoperiodic information is transmitted through the retino-hypothalamic tract to the suprachiasmatic nuclei (SCN), site of the master circadian clock. To investigate effects of day length change on the sheep SCN, we used in-situ hybridization to assess the daily temporal organization of expression of circadian clock genes (Per1, Per2, Bmal1 and Fbxl21) and neuropeptides (Vip, Grp and Avp) in animals acclimated to a short photoperiod (SP; 8h of light) and at 3 or 15 days following transfer to a long photoperiod (LP3, LP15, respectively; 16h of light), achieved by an acute 8-h delay of lights off. We found that waveforms of SCN gene expression conformed to those previously seen in LP acclimated animals within 3 days of transfer to LP. Mean levels of expression for Per1-2 and Fbxl21 were nearly 2-fold higher in the LP15 than in the SP group. The expression of Vip was arrhythmic and unaffected by photoperiod, while, in contrast to rodents, Grp expression was not detectable within the sheep SCN. Expression of the circadian output gene Avp cycled robustly in all photoperiod groups with no detectable change in phasing. Overall these data suggest that synchronizing effects of light on SCN circadian organisation proceed similarly in ungulates and in rodents, despite differences in neuropeptide gene expression. PMID:27458725

  11. Association between the CLOCK gene 3111 T > C polymorphism and an irregular menstrual cycle in Korean adolescents.

    PubMed

    Kim, Kye-Hyun; Kim, Yunsin; Ha, Juwon; Shin, Dong-Won; Shin, Young-Chul; Oh, Kang-Seob; Woo, Hee-Yeon; Lim, Se-Won

    2015-01-01

    The menstrual cycle is an example of a human infradian rhythm, but an altered sleep-wake cycle or a disrupted circadian rhythm can change the regularity of the menstrual cycle. In this study, we investigated whether an irregular menstrual cycle is associated with polymorphisms in the CLOCK (3111T > C) and/or PER3 (variable number tandem repeat, VNTR) genes, which are known to have an impact on the circadian rhythm. One hundred ninety-seven postmenarchal, adolescent girls from two girls' high schools in Seoul, Korea, were studied. All participants were requested to complete the Perceived Stress Scale (PSS), the State-Trait Anxiety Inventory (STAI), and the Beck Depression Inventory (BDI) to assess the emotional distress that might cause menstrual irregularity. Every participant donated a blood sample from which DNA was extracted and genotyped for the CLOCK 3111T > C and PER3 VNTR polymorphisms. A significant association was found between the CLOCK 3111T > C genotype and irregular menstrual cycles. Subjects with the 3111T > C genotype had a high risk of an irregular menstrual cycle compared with 3111T/T homozygous subjects (odds ratio [OR] = 2.88; 95% confidence interval [CI]: 1.26-6.55). When multivariate logistic regression analysis was performed to adjust for age, PSS, STAI, BDI and BMI, subjects with the 3111T > C polymorphism showed a significantly increased OR for irregular menstrual cycles (OR = 3.09; 95% CI: 1.32-7.21). There was no significant association between the PER3 VNTR polymorphism and the irregularity of the menstrual cycle (p > 0.05). The results of this study suggest that the CLOCK 3111T > C polymorphism could be an independent risk factor for irregular menstrual cycles, irrespective of psychological distress and endocrine or metabolic conditions, and could be used as a molecular marker for gynecological studies on this aspect.

  12. The association of circadian clock candidate genes to increased adiposity in the TIGER study

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Obesity is a highly prevalent disease that has become a major health crisis in the United States. A number of studies have suggested a link between the altered sleep/wake patterns associated with our "24 hour" lifestyle and obesity. We hypothesize that disruption of the circadian clock intrinsic t...

  13. A tunable artificial circadian clock in clock-defective mice

    PubMed Central

    D'Alessandro, Matthew; Beesley, Stephen; Kim, Jae Kyoung; Chen, Rongmin; Abich, Estela; Cheng, Wayne; Yi, Paul; Takahashi, Joseph S.; Lee, Choogon

    2015-01-01

    Self-sustaining oscillations are essential for diverse physiological functions such as the cell cycle, insulin secretion and circadian rhythms. Synthetic oscillators using biochemical feedback circuits have been generated in cell culture. These synthetic systems provide important insight into design principles for biological oscillators, but have limited similarity to physiological pathways. Here we report the generation of an artificial, mammalian circadian clock in vivo, capable of generating robust, tunable circadian rhythms. In mice deficient in Per1 and Per2 genes (thus lacking circadian rhythms), we artificially generate PER2 rhythms and restore circadian sleep/wake cycles with an inducible Per2 transgene. Our artificial clock is tunable as the period and phase of the rhythms can be modulated predictably. This feature, and other design principles of our work, might enhance the study and treatment of circadian dysfunction and broader aspects of physiology involving biological oscillators. PMID:26617050

  14. Identification of circadian-clock-regulated enhancers and genes of Drosophila melanogaster by transposon mobilization and luciferase reporting of cyclical gene expression.

    PubMed Central

    Stempfl, Thomas; Vogel, Marion; Szabo, Gisela; Wülbeck, Corinna; Liu, Jian; Hall, Jeffrey C; Stanewsky, Ralf

    2002-01-01

    A new way was developed to isolate rhythmically expressed genes in Drosophila by modifying the classic enhancer-trap method. We constructed a P element containing sequences that encode firefly luciferase as a reporter for oscillating gene expression in live flies. After generation of 1176 autosomal insertion lines, bioluminescence screening revealed rhythmic reporter-gene activity in 6% of these strains. Rhythmically fluctuating reporter levels were shown to be altered by clock mutations in genes that specify various circadian transcription factors or repressors. Intriguingly, rhythmic luminescence in certain lines was affected by only a subset of the pacemaker mutations. By isolating genes near 13 of the transposon insertions and determining their temporal mRNA expression pattern, we found that four of the loci adjacent to the trapped enhancers are rhythmically expressed. Therefore, this approach is suitable for identifying genetic loci regulated by the circadian clock. One transposon insert caused a mutation in the rhythmically expressed gene numb. This novel numb allele, as well as previously described ones, was shown to affect the fly's rhythm of locomotor activity. In addition to its known role in cell fate determination, this gene and the phosphotyrosine-binding protein it encodes are likely to function in the circadian system. PMID:11861563

  15. Redox rhythm reinforces the circadian clock to gate immune response.

    PubMed

    Zhou, Mian; Wang, Wei; Karapetyan, Sargis; Mwimba, Musoki; Marqués, Jorge; Buchler, Nicolas E; Dong, Xinnian

    2015-07-23

    Recent studies have shown that in addition to the transcriptional circadian clock, many organisms, including Arabidopsis, have a circadian redox rhythm driven by the organism's metabolic activities. It has been hypothesized that the redox rhythm is linked to the circadian clock, but the mechanism and the biological significance of this link have only begun to be investigated. Here we report that the master immune regulator NPR1 (non-expressor of pathogenesis-related gene 1) of Arabidopsis is a sensor of the plant's redox state and regulates transcription of core circadian clock genes even in the absence of pathogen challenge. Surprisingly, acute perturbation in the redox status triggered by the immune signal salicylic acid does not compromise the circadian clock but rather leads to its reinforcement. Mathematical modelling and subsequent experiments show that NPR1 reinforces the circadian clock without changing the period by regulating both the morning and the evening clock genes. This balanced network architecture helps plants gate their immune responses towards the morning and minimize costs on growth at night. Our study demonstrates how a sensitive redox rhythm interacts with a robust circadian clock to ensure proper responsiveness to environmental stimuli without compromising fitness of the organism.

  16. Speed control: cogs and gears that drive the circadian clock.

    PubMed

    Zheng, Xiangzhong; Sehgal, Amita

    2012-09-01

    In most organisms, an intrinsic circadian (~24-h) timekeeping system drives rhythms of physiology and behavior. Within cells that contain a circadian clock, specific transcriptional activators and repressors reciprocally regulate each other to generate a basic molecular oscillator. A mismatch of the period generated by this oscillator with the external environment creates circadian disruption, which can have adverse effects on neural function. Although several clock genes have been extensively characterized, a fundamental question remains: how do these genes work together to generate a ~24-h period? Period-altering mutations in clock genes can affect any of multiple regulated steps in the molecular oscillator. In this review, we examine the regulatory mechanisms that contribute to setting the pace of the circadian oscillator.

  17. Potent Effects of Flavonoid Nobiletin on Amplitude, Period, and Phase of the Circadian Clock Rhythm in PER2::LUCIFERASE Mouse Embryonic Fibroblasts

    PubMed Central

    Shinozaki, Ayako; Misawa, Kenichiro; Ikeda, Yuko; Haraguchi, Atsushi; Kamagata, Mayo; Tahara, Yu; Shibata, Shigenobu

    2017-01-01

    Flavonoids are natural polyphenols that are widely found in plants. The effects of flavonoids on obesity and numerous diseases such as cancer, diabetes, and Alzheimer’s have been well studied. However, little is known about the relationships between flavonoids and the circadian clock. In this study, we show that continuous or transient application of flavonoids to the culture medium of embryonic fibroblasts from PER2::LUCIFERASE (PER2::LUC) mice induced various modifications in the circadian clock amplitude, period, and phase. Transient application of some of the tested flavonoids to cultured cells induced a phase delay of the PER2::LUC rhythm at the down slope phase. In addition, continuous application of the polymethoxy flavonoids nobiletin and tangeretin increased the amplitude and lengthened the period of the PER2::LUC rhythm. The nobiletin-induced phase delay was blocked by co-treatment with U0126, an ERK inhibitor. In summary, among the tested flavonoids, polymethoxy flavones increased the amplitude, lengthened the period, and delayed the phase of the PER2::LUC circadian rhythm. Therefore, foods that contain polymethoxy flavones may have beneficial effects on circadian rhythm disorders and jet lag. PMID:28152057

  18. Machine Learning Helps Identify CHRONO as a Circadian Clock Component

    PubMed Central

    Venkataraman, Anand; Ramanathan, Chidambaram; Kavakli, Ibrahim H.; Hughes, Michael E.; Baggs, Julie E.; Growe, Jacqueline; Liu, Andrew C.; Kim, Junhyong; Hogenesch, John B.

    2014-01-01

    Over the last decades, researchers have characterized a set of “clock genes” that drive daily rhythms in physiology and behavior. This arduous work has yielded results with far-reaching consequences in metabolic, psychiatric, and neoplastic disorders. Recent attempts to expand our understanding of circadian regulation have moved beyond the mutagenesis screens that identified the first clock components, employing higher throughput genomic and proteomic techniques. In order to further accelerate clock gene discovery, we utilized a computer-assisted approach to identify and prioritize candidate clock components. We used a simple form of probabilistic machine learning to integrate biologically relevant, genome-scale data and ranked genes on their similarity to known clock components. We then used a secondary experimental screen to characterize the top candidates. We found that several physically interact with known clock components in a mammalian two-hybrid screen and modulate in vitro cellular rhythms in an immortalized mouse fibroblast line (NIH 3T3). One candidate, Gene Model 129, interacts with BMAL1 and functionally represses the key driver of molecular rhythms, the BMAL1/CLOCK transcriptional complex. Given these results, we have renamed the gene CHRONO (computationally highlighted repressor of the network oscillator). Bi-molecular fluorescence complementation and co-immunoprecipitation demonstrate that CHRONO represses by abrogating the binding of BMAL1 to its transcriptional co-activator CBP. Most importantly, CHRONO knockout mice display a prolonged free-running circadian period similar to, or more drastic than, six other clock components. We conclude that CHRONO is a functional clock component providing a new layer of control on circadian molecular dynamics. PMID:24737000

  19. Clock-controlled output gene Dbp is a regulator of Arnt/Hif-1β gene expression in pancreatic islet β-cells

    SciTech Connect

    Nakabayashi, Hiroko; Ohta, Yasuharu Yamamoto, Masayoshi; Susuki, Yosuke; Taguchi, Akihiko; Tanabe, Katsuya; Kondo, Manabu; Hatanaka, Masayuki; Nagao, Yuko; Tanizawa, Yukio

    2013-05-03

    Highlights: •Arnt mRNA expressed in a circadian manner in mouse pancreatic islets. •Expressions of Dbp and Arnt damped in the islets of a diabetic model mouse. •DBP and E4BP4 regulate Arnt promoter activity by direct binding. •Arnt may have a role in connecting circadian rhythm and metabolism. -- Abstract: Aryl hydrocarbon receptor nuclear translocator (ARNT)/hypoxia inducible factor-1β (HIF-1β) has emerged as a potential determinant of pancreatic β-cell dysfunction and type 2 diabetes in humans. An 82% reduction in Arnt expression was observed in islets from type 2 diabetic donors as compared to non-diabetic donors. However, few regulators of Arnt expression have been identified. Meanwhile, disruption of the clock components CLOCK and BMAL1 is known to result in hypoinsulinemia and diabetes, but the molecular details remain unclear. In this study, we identified a novel molecular connection between Arnt and two clock-controlled output genes, albumin D-element binding protein (Dbp) and E4 binding protein 4 (E4bp4). By conducting gene expression studies using the islets of Wfs1{sup −/−} A{sup y}/a mice that develop severe diabetes due to β-cell apoptosis, we demonstrated clock-related gene expressions to be altered in the diabetic mice. Dbp mRNA decreased by 50%, E4bp4 mRNA increased by 50%, and Arnt mRNA decreased by 30% at Zeitgever Time (ZT) 12. Mouse pancreatic islets exhibited oscillations of clock gene expressions. E4BP4, a D-box negative regulator, oscillated anti-phase to DBP, a D-box positive regulator. We also found low-amplitude circadian expression of Arnt mRNA, which peaked at ZT4. Over-expression of DBP raised both mRNA and protein levels of ARNT in HEK293 and MIN6 cell lines. Arnt promoter-driven luciferase reporter assay in MIN6 cells revealed that DBP increased Arnt promoter activity by 2.5-fold and that E4BP4 competitively inhibited its activation. In addition, on ChIP assay, DBP and E4BP4 directly bound to D-box elements within the

  20. Effects of TWIN-OF-EYELESS on Clock Gene Expression and Central-Pacemaker Neuron Development in Drosophila

    PubMed Central

    Glossop, Nicholas Robert John; Gummadova, Jennet Orazmuradovna; Ghangrekar, Indrayani; Hardin, Paul Eric; Coutts, Graham Andrew

    2014-01-01

    Circadian oscillators are autonomous molecular rhythms that reside in cells to align whole organism physiology and behaviour to the 24h day. In flies, as in mammals, the oscillator operates in cells that co-express CLOCK (CLK) and CYCLE (CYC). Recent work in Drosophila has shown that CLK is unique in its ability to generate heterologous oscillators, indicating that Clk-gene-expression defines the circadian-cell-fate. Here, using standard in vitro and in vivo techniques, we show that TWIN-OF-EYELESS (TOY; dPax6) regulates Clk-expression in small ventrolateral neurons (s-LNvs) that coordinate sleep-wake cycles. Crucially, toy binds multiple sites at the Clk locus; is expressed independent of CLK-CYC in LNvs; regulates CLK protein levels under optimal photoperiodic conditions; and, sets clock-speed during endogenous free-run. Furthermore, TOY is necessary for the onset of Clk-expression in LNvs during embryogenesis. We propose that TOY contributes to a transcription complex that functions upstream of the oscillator to promote Clk-expression in s-LNvs. PMID:24916389

  1. Peripheral Circadian Clocks Mediate Dietary Restriction-Dependent Changes in Lifespan and Fat Metabolism in Drosophila.

    PubMed

    Katewa, Subhash D; Akagi, Kazutaka; Bose, Neelanjan; Rakshit, Kuntol; Camarella, Timothy; Zheng, Xiangzhong; Hall, David; Davis, Sonnet; Nelson, Christopher S; Brem, Rachel B; Ramanathan, Arvind; Sehgal, Amita; Giebultowicz, Jadwiga M; Kapahi, Pankaj

    2016-01-12

    Endogenous circadian clocks orchestrate several metabolic and signaling pathways that are known to modulate lifespan, suggesting clocks as potential targets for manipulation of metabolism and lifespan. We report here that the core circadian clock genes, timeless (tim) and period (per), are required for the metabolic and lifespan responses to DR in Drosophila. Consistent with the involvement of a circadian mechanism, DR enhances the amplitude of cycling of most circadian clock genes, including tim, in peripheral tissues. Mass-spectrometry-based lipidomic analysis suggests a role of tim in cycling of specific medium chain triglycerides under DR. Furthermore, overexpression of tim in peripheral tissues improves its oscillatory amplitude and extends lifespan under ad libitum conditions. Importantly, effects of tim on lifespan appear to be mediated through enhanced fat turnover. These findings identify a critical role for specific clock genes in modulating the effects of nutrient manipulation on fat metabolism and aging.

  2. Mutations in the circadian gene period alter behavioral and biochemical responses to ethanol in Drosophila.

    PubMed

    Liao, Jennifer; Seggio, Joseph A; Ahmad, S Tariq

    2016-04-01

    Clock genes, such as period, which maintain an organism's circadian rhythm, can have profound effects on metabolic activity, including ethanol metabolism. In turn, ethanol exposure has been shown in Drosophila and mammals to cause disruptions of the circadian rhythm. Previous studies from our labs have shown that larval ethanol exposure disrupted the free-running period and period expression of Drosophila. In addition, a recent study has shown that arrhythmic flies show no tolerance to ethanol exposure. As such, Drosophila period mutants, which have either a shorter than wild-type free-running period (perS) or a longer one (perL), may also exhibit altered responses to ethanol due to their intrinsic circadian differences. In this study, we tested the initial sensitivity and tolerance of ethanol exposure on Canton-S, perS, and perL, and then measured their Alcohol Dehydrogenase (ADH) and body ethanol levels. We showed that perL flies had slower sedation rate, longer recovery from ethanol sedation, and generated higher tolerance for sedation upon repeated ethanol exposure compared to Canton-S wild-type flies. Furthermore, perL flies had lower ADH activity and had a slower ethanol clearance compared to wild-type flies. The findings of this study suggest that period mutations influence ethanol induced behavior and ethanol metabolism in Drosophila and that flies with longer circadian periods are more sensitive to ethanol exposure.

  3. Expression and Rhythmic Modulation of Circulating MicroRNAs Targeting the Clock Gene Bmal1 in Mice

    PubMed Central

    Shende, Vikram R.; Goldrick, Marianna M.; Ramani, Suchitra; Earnest, David J.

    2011-01-01

    MicroRNAs (miRNAs) interact with 3′ untranslated region (UTR) elements of target genes to regulate mRNA stability or translation and thus play a role in regulating many different biological processes, including circadian rhythms. However, specific miRNAs mediating the regulation of essential clock genes remain largely unknown. Because vesicles containing membrane-bound miRNAs are present in the circulatory system, we examined miRNAs predicted to target the clock gene, Bmal1, for evidence of rhythmic fluctuations in circulating levels and modulatory effects on the 3′ UTR activity of Bmal1. A number of miRNAs with Bmal1 as a predicted target were expressed in the serum of mice exposed to LD 12∶12 and of these miRNAs, miR-152 and miR-494 but not miR-142-3p were marked by diurnal oscillations with bimodal peaks in expression occurring near the middle of the day and 8 or 12 hr later during the night. Co-transfection of pre-miR over-expression constructs for miR-494 and miR-142-3p in HEK293 cells had significant effects in repressing luciferase-reported Bmal1 3′ UTR activity by as much as 60%, suggesting that these miRNAs may function as post-transcriptional modulators of Bmal1. In conjunction with previous studies implicating miRNAs as extracellular regulatory signals, our results suggest that circulating miRNAs may play a role in the regulation of the molecular clockworks in peripheral circadian oscillators. PMID:21799909

  4. Npas4 Is Activated by Melatonin, and Drives the Clock Gene Cry1 in the Ovine Pars Tuberalis

    PubMed Central

    West, A.; Dupré, S.M.; Yu, L.; Paton, I.R.; Miedzinska, K.; McNeilly, A.S.; Davis, J.R.E.

    2013-01-01

    Seasonal mammals integrate changes in the duration of nocturnal melatonin secretion to drive annual physiologic cycles. Melatonin receptors within the proximal pituitary region, the pars tuberalis (PT), are essential in regulating seasonal neuroendocrine responses. In the ovine PT, melatonin is known to influence acute changes in transcriptional dynamics coupled to the onset (dusk) and offset (dawn) of melatonin secretion, leading to a potential interval-timing mechanism capable of decoding changes in day length (photoperiod). Melatonin offset at dawn is linked to cAMP accumulation, which directly induces transcription of the clock gene Per1. The rise of melatonin at dusk induces a separate and distinct cohort, including the clock-regulated genes Cry1 and Nampt, but little is known of the up-stream mechanisms involved. Here, we used next-generation sequencing of the ovine PT transcriptome at melatonin onset and identified Npas4 as a rapidly induced basic helix-loop-helix Per-Arnt-Sim domain transcription factor. In vivo we show nuclear localization of NPAS4 protein in presumptive melatonin target cells of the PT (α-glycoprotein hormone-expressing cells), whereas in situ hybridization studies identified acute and transient expression in the PT of Npas4 in response to melatonin. In vitro, NPAS4 forms functional dimers with basic helix loop helix-PAS domain cofactors aryl hydrocarbon receptor nuclear translocator (ARNT), ARNT2, and ARNTL, transactivating both Cry1 and Nampt ovine promoter reporters. Using a combination of 5′-deletions and site-directed mutagenesis, we show NPAS4-ARNT transactivation to be codependent upon two conserved central midline elements within the Cry1 promoter. Our data thus reveal NPAS4 as a candidate immediate early-response gene in the ovine PT, driving molecular responses to melatonin. PMID:23598442

  5. Punctual Transcriptional Regulation by the Rice Circadian Clock under Fluctuating Field Conditions[OPEN

    PubMed Central

    Matsuzaki, Jun; Kawahara, Yoshihiro; Izawa, Takeshi

    2015-01-01

    Plant circadian clocks that oscillate autonomously with a roughly 24-h period are entrained by fluctuating light and temperature and globally regulate downstream genes in the field. However, it remains unknown how punctual internal time produced by the circadian clock in the field is and how it is affected by environmental fluctuations due to weather or daylength. Using hundreds of samples of field-grown rice (Oryza sativa) leaves, we developed a statistical model for the expression of circadian clock-related genes integrating diurnally entrained circadian clock with phase setting by light, both responses to light and temperature gated by the circadian clock. We show that expression of individual genes was strongly affected by temperature. However, internal time estimated from expression of multiple genes, which may reflect transcriptional regulation of downstream genes, is punctual to 22 min and not affected by weather, daylength, or plant developmental age in the field. We also revealed perturbed progression of internal time under controlled environment or in a mutant of the circadian clock gene GIGANTEA. Thus, we demonstrated that the circadian clock is a regulatory network of multiple genes that retains accurate physical time of day by integrating the perturbations on individual genes under fluctuating environments in the field. PMID:25757473

  6. Nonlinear model-based method for clustering periodically expressed genes.

    PubMed

    Tian, Li-Ping; Liu, Li-Zhi; Zhang, Qian-Wei; Wu, Fang-Xiang

    2011-01-01

    Clustering periodically expressed genes from their time-course expression data could help understand the molecular mechanism of those biological processes. In this paper, we propose a nonlinear model-based clustering method for periodically expressed gene profiles. As periodically expressed genes are associated with periodic biological processes, the proposed method naturally assumes that a periodically expressed gene dataset is generated by a number of periodical processes. Each periodical process is modelled by a linear combination of trigonometric sine and cosine functions in time plus a Gaussian noise term. A two stage method is proposed to estimate the model parameter, and a relocation-iteration algorithm is employed to assign each gene to an appropriate cluster. A bootstrapping method and an average adjusted Rand index (AARI) are employed to measure the quality of clustering. One synthetic dataset and two biological datasets were employed to evaluate the performance of the proposed method. The results show that our method allows the better quality clustering than other clustering methods (e.g., k-means) for periodically expressed gene data, and thus it is an effective cluster analysis method for periodically expressed gene data.

  7. Circadian clocks, brain function, and development.

    PubMed

    Frank, Ellen; Sidor, Michelle M; Gamble, Karen L; Cirelli, Chiara; Sharkey, Katherine M; Hoyle, Nathaniel; Tikotzky, Liat; Talbot, Lisa S; McCarthy, Michael J; Hasler, Brant P

    2013-12-01

    Circadian clocks are temporal interfaces that organize biological systems and behavior to dynamic external environments. Components of the molecular clock are expressed throughout the brain and are centrally poised to play an important role in brain function. This paper focuses on key issues concerning the relationship among circadian clocks, brain function, and development, and discusses three topic areas: (1) sleep and its relationship to the circadian system; (2) systems development and psychopathology (spanning the prenatal period through late life); and (3) circadian factors and their application to neuropsychiatric disorders. We also explore circadian genetics and psychopathology and the selective pressures on the evolution of clocks. Last, a lively debate is presented on whether circadian factors are central to mood disorders. Emerging from research on circadian rhythms is a model of the interaction among genes, sleep, and the environment that converges on the circadian clock to influence susceptibility to developing psychopathology. This model may lend insight into effective treatments for mood disorders and inform development of new interventions.

  8. Heterogeneous Expression of the Core Circadian Clock Proteins among Neuronal Cell Types in Mouse Retina

    PubMed Central

    Liu, Xiaoqin; Zhang, Zhijing; Ribelayga, Christophe P.

    2012-01-01

    Circadian rhythms in metabolism, physiology, and behavior originate from cell-autonomous circadian clocks located in many organs and structures throughout the body and that share a common molecular mechanism based on the clock genes and their protein products. In the mammalian neural retina, despite evidence supporting the presence of several circadian clocks regulating many facets of retinal physiology and function, the exact cellular location and genetic signature of the retinal clock cells remain largely unknown. Here we examined the expression of the core circadian clock proteins CLOCK, BMAL1, NPAS2, PERIOD 1(PER1), PERIOD 2 (PER2), and CRYPTOCHROME2 (CRY2) in identified neurons of the mouse retina during daily and circadian cycles. We found concurrent clock protein expression in most retinal neurons, including cone photoreceptors, dopaminergic amacrine cells, and melanopsin-expressing intrinsically photosensitive ganglion cells. Remarkably, diurnal and circadian rhythms of expression of all clock proteins were observed in the cones whereas only CRY2 expression was found to be rhythmic in the dopaminergic amacrine cells. Only a low level of expression of the clock proteins was detected in the rods at any time of the daily or circadian cycle. Our observations provide evidence that cones and not rods are cell-autonomous circadian clocks and reveal an important disparity in the expression of the core clock components among neuronal cell types. We propose that the overall temporal architecture of the mammalian retina does not result from the synchronous activity of pervasive identical clocks but rather reflects the cellular and regional heterogeneity in clock function within retinal tissue. PMID:23189207

  9. Colorectal liver metastases with a disrupted circadian rhythm phase shift the peripheral clock in liver and kidney.

    PubMed

    Huisman, Sander A; Oklejewicz, Malgorzata; Ahmadi, Ali R; Tamanini, Filippo; Ijzermans, Jan N M; van der Horst, Gijsbertus T J; de Bruin, Ron W F

    2015-03-01

    Circadian clock genes regulate 10-15% of the transcriptome, and might function as tumor suppressor genes. Relatively little is known about the circadian clock in tumors and its effect on surrounding healthy tissues. Therefore, we compared the 24-hr expression levels of key circadian clock genes in liver and kidney of healthy control mice with those of mice bearing C26 colorectal tumor metastases in the liver. Metastases were induced by injection of C26 colorectal carcinoma cells into the spleen. Subsequently, tumor, liver and kidney tissue was collected around the clock to compare circadian rhythmicity. Expression levels of five clock genes (Rev-Erbα, Per1, Per2, Bmal1 and Cry1) and three clock-controlled genes (CCGs; Dbp, p21 and Wee1) were determined by qRT-PCR. Liver and kidney tissue of healthy control mice showed normal 24-hr oscillations of all clock genes and CCGs, consistent with normal circadian rhythmicity. In colorectal liver metastases, however, 24-hr oscillations were completely absent for all clock genes and CCGs except Cry1. Liver and kidney tissue of tumor-bearing mice showed a shift in clock periodicity relative to control mice. In the liver we observed a phase advance, whereas in the kidney the phase was delayed. These data show that hepatic metastases of C26 colon carcinoma with a disrupted circadian rhythm phase shift liver and kidney tissue clocks, which strongly suggests a systemic effect on peripheral clocks. The possibility that tumors may modify peripheral clocks to escape from ordinary circadian rhythms and in this way contribute to fatigue and sleep disorders in cancer patients is discussed.

  10. Chicktacking pineal clock.

    PubMed

    Okano, Toshiyuki; Fukada, Yoshitaka

    2003-12-01

    Many tissues in non-mammalian vertebrates contain both photoreceptors and circadian clock systems. Among these photosensitive clock structures, the chick pineal gland has been characterized in detail from cellular and molecular aspects of the clock oscillation and entrainment. Analyses of the pineal photic-input pathway revealed a phase-shifting mechanism mediated by activation of G11, one of the Gq-type G-proteins. A major photoreceptive molecule, pinopsin, likely triggers this pathway by transmitting the light signal to the circadian oscillator. In the chick pineal oscillator, the transcription/translation-based autoregulatory feedback loop is composed of positive and negative elements (clock gene products) that are homologous to those identified in mammals. In the molecular cycling, a CACGTG E-box located in the promoter region of the negative element genes plays a central role in the transcriptional regulation. The phase of the molecular cycling is modulated by many regulatory components, among which E4BP4 and extracellular signal-regulated kinase (ERK) are closely associated with the photic entrainment. A light-responsive element was found in the promoter region of the Pinopsin gene, and the element included a CACGTG E-box, suggesting a novel role of the E-box as a point of convergence of light and circadian signals. These observations together point to general and unique features of the chick pineal circadian system among animal clocks.

  11. Circadian Rhythms, the Molecular Clock, and Skeletal Muscle

    PubMed Central

    Lefta, Mellani; Wolff, Gretchen; Esser, Karyn A.

    2015-01-01

    Almost all organisms ranging from single cell bacteria to humans exhibit a variety of behavioral, physiological, and biochemical rhythms. In mammals, circadian rhythms control the timing of many physiological processes over a 24-h period, including sleep-wake cycles, body temperature, feeding, and hormone production. This body of research has led to defined characteristics of circadian rhythms based on period length, phase, and amplitude. Underlying circadian behaviors is a molecular clock mechanism found in most, if not all, cell types including skeletal muscle. The mammalian molecular clock is a complex of multiple oscillating networks that are regulated through transcriptional mechanisms, timed protein turnover, and input from small molecules. At this time, very little is known about circadian aspects of skeletal muscle function/metabolism but some progress has been made on understanding the molecular clock in skeletal muscle. The goal of this chapter is to provide the basic terminology and concepts of circadian rhythms with a more detailed review of the current state of knowledge of the molecular clock, with reference to what is known in skeletal muscle. Research has demonstrated that the molecular clock is active in skeletal muscles and that the muscle-specific transcription factor, MyoD, is a direct target of the molecular clock. Skeletal muscle of clock-compromised mice, Bmal1−/− and ClockΔ19 mice, are weak and exhibit significant disruptions in expression of many genes required for adult muscle structure and metabolism. We suggest that the interaction between the molecular clock, MyoD, and metabolic factors, such as PGC-1, provide a potential system of feedback loops that may be critical for both maintenance and adaptation of skeletal muscle. PMID:21621073

  12. Laser clock

    SciTech Connect

    Facklam, R.L.

    1983-05-26

    A laser clock includes a linear laser in one embodiment of the clock and a ring laser gyro in the other embodiment. The linear laser is frequency stabilized and utilizes a single active medium in the form of a low pressure gas, such as He-Ne, with a Doppler broadened gain curve. The ring laser gyro is a four frequency laser with a Faraday rotor. Detector and electronic circuitry associated with the laser of each embodiment detects a beat frequency and convert it to a clock signal.

  13. Variation in candidate genes CLOCK and ADCYAP1 does not consistently predict differences in migratory behavior in the songbird genus Junco

    PubMed Central

    Peterson, Mark P

    2013-01-01

    Recent studies exploring the molecular genetic basis for migratory variation in animals have identified polymorphisms in two genes ( CLOCK and ADCYAP1) that are linked to circadian rhythms and correlate with migratory propensity and phenology among individuals and populations. Results from these initial studies are mixed, however, and additional data are needed to assess the generality and diversity of the molecular mechanisms that regulate the biology of migration. We sequenced CLOCK and ADCYAP1 in 15 populations across the two species of the avian genus Junco, a North American lineage in which multiple recently diverged subspecies and populations range from sedentary to long-distance migrants. We found no consistent associations between allele length and migratory status across the genus for either CLOCK or ADCYAP1. However, within two subspecies groups, populations that migrate longer distances have longer CLOCK alleles on average. Additionally, there was a positive relationship between ADCYAP1 allele length and migratory restlessness (zugunruhe) among individuals within one of two captive populations studied—a result similar to those reported previously within captive blackcaps ( Sylvia atricapilla). We conclude that, while both ADCYAP1 and CLOCK may correlate with migratory propensity within or among certain populations or species, previously identified relationships between migratory behavior and sequence variants cannot be easily generalized across taxa. PMID:24627781

  14. Variation in candidate genes CLOCK and ADCYAP1 does not consistently predict differences in migratory behavior in the songbird genus Junco.

    PubMed

    Peterson, Mark P; Abolins-Abols, Mikus; Atwell, Jonathan W; Rice, Rebecca J; Milá, Borja; Ketterson, Ellen D

    2013-01-01

    Recent studies exploring the molecular genetic basis for migratory variation in animals have identified polymorphisms in two genes ( CLOCK and ADCYAP1) that are linked to circadian rhythms and correlate with migratory propensity and phenology among individuals and populations. Results from these initial studies are mixed, however, and additional data are needed to assess the generality and diversity of the molecular mechanisms that regulate the biology of migration. We sequenced CLOCK and ADCYAP1 in 15 populations across the two species of the avian genus Junco, a North American lineage in which multiple recently diverged subspecies and populations range from sedentary to long-distance migrants. We found no consistent associations between allele length and migratory status across the genus for either CLOCK or ADCYAP1. However, within two subspecies groups, populations that migrate longer distances have longer CLOCK alleles on average. Additionally, there was a positive relationship between ADCYAP1 allele length and migratory restlessness (zugunruhe) among individuals within one of two captive populations studied-a result similar to those reported previously within captive blackcaps ( Sylvia atricapilla). We conclude that, while both ADCYAP1 and CLOCK may correlate with migratory propensity within or among certain populations or species, previously identified relationships between migratory behavior and sequence variants cannot be easily generalized across taxa.

  15. The circadian clock has transient plasticity of period and is required for timing of nocturnal processes in Arabidopsis.

    PubMed

    Dodd, Antony N; Dalchau, Neil; Gardner, Michael J; Baek, Seong-Jin; Webb, Alex A R

    2014-01-01

    A circadian rhythm matched to the phase and period of the day-night cycle has measurable benefits for land plants. We assessed the contribution of circadian period to the phasing of cellular events with the light : dark cycle. We also investigated the plasticity of circadian period within the Arabidopsis circadian oscillator. We monitored the circadian oscillator in wild-type and circadian period mutants under light : dark cycles of varying total duration. We also investigated changes in oscillator dynamics during and after the transition from light : dark cycles to free running conditions. Under light : dark cycles, dawn and dusk were anticipated differently when the circadian period was not resonant with the environmental period ('T cycle'). Entrainment to T cycles differing from the free-running period caused a short-term alteration in oscillator period. The transient plasticity of period was described by existing mathematical models of the Arabidopsis circadian network. We conclude that a circadian period resonant with the period of the environment is particularly important for anticipation of dawn and the timing of nocturnal events; and there is short-term and transient plasticity of period of the Arabidopsis circadian network.

  16. Influence of simulated microgravity on clock genes expression rhythmicity and underlying blood circulating miRNAs-mRNA co-expression regulatory mechanism in C57BL/6J mice

    NASA Astrophysics Data System (ADS)

    Lv, Ke; Qu, Lina

    were consecutively performed. Blood samples and liver tissues were collected from tail-suspended and control mice under LD 12:12h and DD conditions during the 12th, 13th and 14th testing days at 4h intervals. Melatonin and corticosterone in mice plasma at different time points were assayed. NIH-3T3 cells were plated in culture dish for 22h before the experiment. For ground-based simulation of weightlessness, the medium was exchanged with DMEM containing 50% horse serum to synchronization, after 2 h, this medium was replaced with DMEM and 10% FBS. Then, at various time point (0, 6, 12, 18, 24, 30, 36, 42, 48h), cells were cultured on the roating clinostat at 30r/min. Total RNA was extracted from liver and NIH-3T3 cells and subsequently reverse-transcribed. The SYBR green I real-time quantitative PCR system was conducted to examine the mRNA expression level of clock, bmal1, per1, per2, cry1 and cry2 in mice and NIH-3T3 cells, respectively. Paired comparisons of the circadian genes expression between period, peak values, amplitude and mesor (midline estimating statistic of rhythm) were examined for evidence of circadian variation using Chronos-Fit software in mice and Cosine analyses in NIH-3T3 cells. Statistical analysis: All numerical data were expressed as the mean ± standard deviation (SD). Statistical differences among groups were analyzed by one-way analysis of variance (ANOVA) to determine time points differences in the study parameters. Statistical differences between two groups were determined by the Student's t test. Results: (1) Circadian rhythm of clock and bmal1 mRNA expression was found in each testing day with similar peak phase in both tail suspension group and control group. Compared with control group, tail suspension group showed that the peak phase of clock gene mRNA level advanced approximately 4 hours and the amplitude of bmal1 gene mRNA level significantly reduced at ZT2 and ZT6. (2) The expression of circadian genes in NIH-3T3 cells demonstrated

  17. Circadian clock gene CRY2 degradation is involved in chemoresistance of colorectal cancer

    PubMed Central

    Fang, Lekun; Yang, Zihuan; Zhou, Junyi; Tung, Jung-Yu; Hsiao, Chwan-Deng; Wang, Lei; Deng, Yanhong; Wang, Puning; Wang, Jianping; Lee, Mong-Hong

    2015-01-01

    Biomarkers for predicting chemotherapy response are important to treatment of colorectal cancer (CRC) patients. Cryptochrome 2 (CRY2) is a circadian clock protein involved in cell cycle, but the biological consequences of this activity in cancer are poorly understood. We set up biochemical and cell biology analyses to analyze CRY2 expression and chemoresistance. Here we report that CRY2 is overexpressed in chemoresistant CRC samples, and CRY2 overexpression is correlated with poor patient survival. Knockdown CRY2 increased colorectal cancer sensitivity to oxaliplatin in colorectal cancer cell. We also identify FBXW7 as a novel E3 ubiquitin ligase for targeting CRY2 through proteasomal degradation. Mechanistic studies show that CRY2 is regulated by FBXW7, in which FBXW7 binds directly to phosphorylated Thr300 of CRY2. Furthermore, FBXW7 expression leads to degradation of CRY2 through enhancing CRY2 ubiquitination and accelerating CRY2’s turnover rate. High expressed FBXW7 downregulates CRY2 and increases colorectal cancer cells sensitivity to chemotherapy. Low FBXW7 expression is correlated with high CRY2 expression in CRC patient samples. Also, low FBXW7 expression is correlated with poor patient survival. Taken together, our findings indicate that the upregulation of CRY2 caused by downregulation of FBXW7 may be a novel prognostic biomarker and may represent a new therapeutic target in colorectal cancer. PMID:25855785

  18. Circadian Clock Gene CRY2 Degradation Is Involved in Chemoresistance of Colorectal Cancer.

    PubMed

    Fang, Lekun; Yang, Zihuan; Zhou, Junyi; Tung, Jung-Yu; Hsiao, Chwan-Deng; Wang, Lei; Deng, Yanhong; Wang, Puning; Wang, Jianping; Lee, Mong-Hong

    2015-06-01

    Biomarkers for predicting chemotherapy response are important to the treatment of colorectal cancer patients. Cryptochrome 2 (CRY2) is a circadian clock protein involved in cell cycle, but the biologic consequences of this activity in cancer are poorly understood. We set up biochemical and cell biology analyses to analyze CRY2 expression and chemoresistance. Here, we report that CRY2 is overexpressed in chemoresistant colorectal cancer samples, and CRY2 overexpression is correlated with poor patient survival. Knockdown of CRY2 increased colorectal cancer sensitivity to oxaliplatin in colorectal cancer cells. We also identify FBXW7 as a novel E3 ubiquitin ligase for targeting CRY2 through proteasomal degradation. Mechanistic studies show that CRY2 is regulated by FBXW7, in which FBXW7 binds directly to phosphorylated Thr300 of CRY2. Furthermore, FBXW7 expression leads to degradation of CRY2 through enhancing CRY2 ubiquitination and accelerating the CRY2's turnover rate. High FBXW7 expression downregulates CRY2 and increases colorectal cancer cells' sensitivity to chemotherapy. Low FBXW7 expression is correlated with high CRY2 expression in colorectal cancer patient samples. Also, low FBXW7 expression is correlated with poor patient survival. Taken together, our findings indicate that the upregulation of CRY2 caused by downregulation of FBXW7 may be a novel prognostic biomarker and may represent a new therapeutic target in colorectal cancer.

  19. Circadian influences on dopamine circuits of the brain: regulation of striatal rhythms of clock gene expression and implications for psychopathology and disease

    PubMed Central

    Verwey, Michael; Dhir, Sabine; Amir, Shimon

    2016-01-01

    Circadian clock proteins form an autoregulatory feedback loop that is central to the endogenous generation and transmission of daily rhythms in behavior and physiology. Increasingly, circadian rhythms in clock gene expression are being reported in diverse tissues and brain regions that lie outside of the suprachiasmatic nucleus (SCN), the master circadian clock in mammals. For many of these extra-SCN rhythms, however, the region-specific implications are still emerging. In order to gain important insights into the potential behavioral, physiological, and psychological relevance of these daily oscillations, researchers have begun to focus on describing the neurochemical, hormonal, metabolic, and epigenetic contributions to the regulation of these rhythms. This review will highlight important sites and sources of circadian control within dopaminergic and striatal circuitries of the brain and will discuss potential implications for psychopathology and disease . For example, rhythms in clock gene expression in the dorsal striatum are sensitive to changes in dopamine release, which has potential implications for Parkinson’s disease and drug addiction. Rhythms in the ventral striatum and limbic forebrain are sensitive to psychological and physical stressors, which may have implications for major depressive disorder. Collectively, a rich circadian tapestry has emerged that forces us to expand traditional views and to reconsider the psychopathological, behavioral, and physiological importance of these region-specific rhythms in brain areas that are not immediately linked with the regulation of circadian rhythms. PMID:27635233

  20. Circadian influences on dopamine circuits of the brain: regulation of striatal rhythms of clock gene expression and implications for psychopathology and disease.

    PubMed

    Verwey, Michael; Dhir, Sabine; Amir, Shimon

    2016-01-01

    Circadian clock proteins form an autoregulatory feedback loop that is central to the endogenous generation and transmission of daily rhythms in behavior and physiology. Increasingly, circadian rhythms in clock gene expression are being reported in diverse tissues and brain regions that lie outside of the suprachiasmatic nucleus (SCN), the master circadian clock in mammals. For many of these extra-SCN rhythms, however, the region-specific implications are still emerging. In order to gain important insights into the potential behavioral, physiological, and psychological relevance of these daily oscillations, researchers have begun to focus on describing the neurochemical, hormonal, metabolic, and epigenetic contributions to the regulation of these rhythms. This review will highlight important sites and sources of circadian control within dopaminergic and striatal circuitries of the brain and will discuss potential implications for psychopathology and disease . For example, rhythms in clock gene expression in the dorsal striatum are sensitive to changes in dopamine release, which has potential implications for Parkinson's disease and drug addiction. Rhythms in the ventral striatum and limbic forebrain are sensitive to psychological and physical stressors, which may have implications for major depressive disorder. Collectively, a rich circadian tapestry has emerged that forces us to expand traditional views and to reconsider the psychopathological, behavioral, and physiological importance of these region-specific rhythms in brain areas that are not immediately linked with the regulation of circadian rhythms.

  1. Mapping-by-Sequencing Identifies HvPHYTOCHROME C as a Candidate Gene for the early maturity 5 Locus Modulating the Circadian Clock and Photoperiodic Flowering in Barley

    PubMed Central

    Pankin, Artem; Campoli, Chiara; Dong, Xue; Kilian, Benjamin; Sharma, Rajiv; Himmelbach, Axel; Saini, Reena; Davis, Seth J; Stein, Nils; Schneeberger, Korbinian; von Korff, Maria

    2014-01-01

    Phytochromes play an important role in light signaling and photoperiodic control of flowering time in plants. Here we propose that the red/far-red light photoreceptor HvPHYTOCHROME C (HvPHYC), carrying a mutation in a conserved region of the GAF domain, is a candidate underlying the early maturity 5 locus in barley (Hordeum vulgare L.). We fine mapped the gene using a mapping-by-sequencing approach applied on the whole-exome capture data from bulked early flowering segregants derived from a backcross of the Bowman(eam5) introgression line. We demonstrate that eam5 disrupts circadian expression of clock genes. Moreover, it interacts with the major photoperiod response gene Ppd-H1 to accelerate flowering under noninductive short days. Our results suggest that HvPHYC participates in transmission of light signals to the circadian clock and thus modulates light-dependent processes such as photoperiodic regulation of flowering. PMID:24996910

  2. CLOCK gene is implicated in weight reduction in obese patients participating in a dietary programme based on the Mediterranean diet

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Introduction: The success of obesity therapy is dependent on the genetic background of the patient. Circadian Locomotor Output Cycles Kaput (CLOCK), one of the transcription factors from the positive limb of the molecular clock, is involved in metabolic alterations. Objective: To investigate whethe...

  3. Compartmentalized expression of light-induced clock genes in the suprachiasmatic nucleus of the diurnal grass rat (Arvicanthis niloticus)

    PubMed Central

    Ramanathan, Chidambaram; Campbell, Amy; Tomczak, Ashley; Nunez, Antonio A.; Smale, Laura; Yan, Lily

    2009-01-01

    Photic responses of the circadian system are mediated through light-induced clock gene expression in the suprachiasmatic nucleus (SCN). In nocturnal rodents, depending on the timing of light exposure, Per1 and Per2 gene expression shows distinct compartmentalized patterns that correspond to the behavioral responses. Whether the gene-and region-specific induction patterns are unique to nocturnal animals, or are also present in diurnal species is unknown. We explored this question by examining the light-induced Per1 and Per2 gene expression in functionally distinct SCN sub regions, using diurnal grass rats Arvicanthis niloticus. Light exposure during nighttime induced Per1 and Per2 expression in the SCN, showing unique spatiotemporal profiles depending on the phase of the light exposure. After a phase delaying light pulse (LP) in the early night, strong Per1 induction was observed in the retinorecipient core region of the SCN, while strong Per2 induction was observed throughout the entire SCN. After a phase advancing LP in the late night, Per1 was first induced in the core and then extended into the whole SCN, accompanied by a weak Per2 induction. This compartmentalized expression pattern is very similar to that observed in nocturnal rodents, suggesting that the same molecular and intercellular pathways underlying acute photic responses are present in both diurnal and nocturnal species. However, after a LP in early subjective day, which induces phase advances in diurnal grass rats, but not in nocturnal rodents, we did not observe any Per1 or Per2 induction in the SCN. This result suggests that in spite of remarkable similarities in the SCN of diurnal and nocturnal rodents, unique mechanisms are involved in mediating the phase shifts of diurnal animals during the subjective day. PMID:19393297

  4. The effect of chronic morphine or methadone exposure and withdrawal on clock gene expression in the rat suprachiasmatic nucleus and AA-NAT activity in the pineal gland.

    PubMed

    Pačesová, D; Novotný, J; Bendová, Z

    2016-07-18

    The circadian rhythms of many behavioral and physiological functions are regulated by the major circadian pacemaker in the suprachiasmatic nucleus. Long-term opiate addiction and drug withdrawal may affect circadian rhythmicity of various hormones or the sleep/activity pattern of many experimental subjects; however, limited research has been done on the long-term effects of sustained opiate administration on the intrinsic rhythmicity in the suprachiasmatic nucleus and pineal gland. Here we compared the effects of repeated daily treatment of rats with morphine or methadone and subsequent naloxone-precipitated withdrawal on the expression of the Per1, Per2, and Avp mRNAs in the suprachiasmatic nucleus and on arylalkylamine N-acetyltransferase activity in the pineal gland. We revealed that 10-day administration and withdrawal of both these drugs failed to affect clock genes and Avp expression in the SCN. Our results indicate that opioid-induced changes in behavioral and physiological rhythms originate in brain structures downstream of the suprachiasmatic nucleus regulatory output pathway. Furthermore, we observed that acute withdrawal from methadone markedly extended the period of high night AA-NAT activity in the pineal gland. This suggests that withdrawal from methadone, a widely used drug for the treatment of opioid dependence, may have stronger impact on melatonin synthesis than withdrawal from morphine.

  5. Gene expression profiling in the pituitary gland of laying period and ceased period huoyan geese.

    PubMed

    Luan, Xinhong; Cao, Zhongzan; Xu, Wen; Gao, Ming; Wang, Laiyou; Zhang, Shuwei

    2013-07-01

    Huoyan goose is a Chinese local breed famous for its higher laying performance, but the problems of variety degeneration have emerged recently, especially a decrease in the number of eggs laid. In order to better understand the molecular mechanism that underlies egg laying in Huoyan geese, gene profiles in the pituitary gland of Huoyan geese taken during the laying period and ceased period were investigated using the suppression subtractive hybridization (SSH) method. Total RNA was extracted from pituitary glands of ceased period and laying period geese. The cDNA in the pituitary glands of ceased geese was subtracted from the cDNA in the pituitary glands of laying geese (forward subtraction); the reverse subtraction was also performed. After sequencing and annotation, a total of 30 and 24 up and down-regulated genes were obtained from the forward and reverse SSH libraries, respectively. These genes mostly related to biosynthetic process, cellular nitrogen compound metabolic process, transport, cell differentiation, cellular protein modification process, signal transduction, small molecule metabolic process. Furthermore, eleven genes were selected for further analyses by quantitative real-time PCR (qRT-PCR). The qRT-PCR results for the most part were consistent with the SSH results. Among these genes, Synaptotagmin-1 (SYT1) and Stathmin-2 (STMN2) were substantially over-expressed in laying period compared to ceased period. These results could serve as an important reference for elucidating the molecular mechanism of higher laying performance in Huoyan geese.

  6. Effects of circadian clock genes and health-related behavior on metabolic syndrome in a Taiwanese population: Evidence from association and interaction analysis

    PubMed Central

    Lin, Eugene; Kuo, Po-Hsiu; Liu, Yu-Li; Yang, Albert C.; Kao, Chung-Feng; Tsai, Shih-Jen

    2017-01-01

    Increased risk of developing metabolic syndrome (MetS) has been associated with the circadian clock genes. In this study, we assessed whether 29 circadian clock-related genes (including ADCYAP1, ARNTL, ARNTL2, BHLHE40, CLOCK, CRY1, CRY2, CSNK1D, CSNK1E, GSK3B, HCRTR2, KLF10, NFIL3, NPAS2, NR1D1, NR1D2, PER1, PER2, PER3, REV1, RORA, RORB, RORC, SENP3, SERPINE1, TIMELESS, TIPIN, VIP, and VIPR2) are associated with MetS and its individual components independently and/or through complex interactions in a Taiwanese population. We also analyzed the interactions between environmental factors and these genes in influencing MetS and its individual components. A total of 3,000 Taiwanese subjects from the Taiwan Biobank were assessed in this study. Metabolic traits such as waist circumference, triglyceride, high-density lipoprotein cholesterol, systolic and diastolic blood pressure, and fasting glucose were measured. Our data showed a nominal association of MetS with several single nucleotide polymorphisms (SNPs) in five key circadian clock genes including ARNTL, GSK3B, PER3, RORA, and RORB; but none of these SNPs persisted significantly after performing Bonferroni correction. Moreover, we identified the effect of GSK3B rs2199503 on high fasting glucose (P = 0.0002). Additionally, we found interactions among the ARNTL rs10832020, GSK3B rs2199503, PER3 rs10746473, RORA rs8034880, and RORB rs972902 SNPs influenced MetS (P < 0.001 ~ P = 0.002). Finally, we investigated the influence of interactions between ARNTL rs10832020, GSK3B rs2199503, PER3 rs10746473, and RORB rs972902 with environmental factors such as alcohol consumption, smoking status, and physical activity on MetS and its individual components (P < 0.001 ~ P = 0.002). Our study indicates that circadian clock genes such as ARNTL, GSK3B, PER3, RORA, and RORB genes may contribute to the risk of MetS independently as well as through gene-gene and gene-environment interactions. PMID:28296937

  7. Identification and temporal expression of putative circadian clock transcripts in the amphipod crustacean Talitrus saltator

    PubMed Central

    O’Grady, Joseph F.; Hoelters, Laura S.; Swain, Martin T.

    2016-01-01

    Background Talitrus saltator is an amphipod crustacean that inhabits the supralittoral zone on sandy beaches in the Northeast Atlantic and Mediterranean. T. saltator exhibits endogenous locomotor activity rhythms and time-compensated sun and moon orientation, both of which necessitate at least one chronometric mechanism. Whilst their behaviour is well studied, currently there are no descriptions of the underlying molecular components of a biological clock in this animal, and very few in other crustacean species. Methods We harvested brain tissue from animals expressing robust circadian activity rhythms and used homology cloning and Illumina RNAseq approaches to sequence and identify the core circadian clock and clock-related genes in these samples. We assessed the temporal expression of these genes in time-course samples from rhythmic animals using RNAseq. Results We identified a comprehensive suite of circadian clock gene homologues in T. saltator including the ‘core’ clock genes period (Talper), cryptochrome 2 (Talcry2), timeless (Taltim), clock (Talclk), and bmal1 (Talbmal1). In addition we describe the sequence and putative structures of 23 clock-associated genes including two unusual, extended isoforms of pigment dispersing hormone (Talpdh). We examined time-course RNAseq expression data, derived from tissues harvested from behaviourally rhythmic animals, to reveal rhythmic expression of these genes with approximately circadian period in Talper and Talbmal1. Of the clock-related genes, casein kinase IIβ (TalckIIβ), ebony (Talebony), jetlag (Taljetlag), pigment dispensing hormone (Talpdh), protein phosphatase 1 (Talpp1), shaggy (Talshaggy), sirt1 (Talsirt1), sirt7 (Talsirt7) and supernumerary limbs (Talslimb) show temporal changes in expression. Discussion We report the sequences of principle genes that comprise the circadian clock of T. saltator and highlight the conserved structural and functional domains of their deduced cognate proteins. Our

  8. Global synchronization of parallel processors using clock pulse width modulation

    DOEpatents

    Chen, Dong; Ellavsky, Matthew R.; Franke, Ross L.; Gara, Alan; Gooding, Thomas M.; Haring, Rudolf A.; Jeanson, Mark J.; Kopcsay, Gerard V.; Liebsch, Thomas A.; Littrell, Daniel; Ohmacht, Martin; Reed, Don D.; Schenck, Brandon E.; Swetz, Richard A.

    2013-04-02

    A circuit generates a global clock signal with a pulse width modification to synchronize processors in a parallel computing system. The circuit may include a hardware module and a clock splitter. The hardware module may generate a clock signal and performs a pulse width modification on the clock signal. The pulse width modification changes a pulse width within a clock period in the clock signal. The clock splitter may distribute the pulse width modified clock signal to a plurality of processors in the parallel computing system.

  9. Entrainment of circadian clocks in mammals by arousal and food.

    PubMed

    Mistlberger, Ralph E; Antle, Michael C

    2011-06-30

    Circadian rhythms in mammals are regulated by a system of endogenous circadian oscillators (clock cells) in the brain and in most peripheral organs and tissues. One group of clock cells in the hypothalamic SCN (suprachiasmatic nuclei) functions as a pacemaker for co-ordinating the timing of oscillators elsewhere in the brain and body. This master clock can be reset and entrained by daily LD (light-dark) cycles and thereby also serves to interface internal with external time, ensuring an appropriate alignment of behavioural and physiological rhythms with the solar day. Two features of the mammalian circadian system provide flexibility in circadian programming to exploit temporal regularities of social stimuli or food availability. One feature is the sensitivity of the SCN pacemaker to behavioural arousal stimulated during the usual sleep period, which can reset its phase and modulate its response to LD stimuli. Neural pathways from the brainstem and thalamus mediate these effects by releasing neurochemicals that inhibit retinal inputs to the SCN clock or that alter clock-gene expression in SCN clock cells. A second feature is the sensitivity of circadian oscillators outside of the SCN to stimuli associated with food intake, which enables animals to uncouple rhythms of behaviour and physiology from LD cycles and align these with predictable daily mealtimes. The location of oscillators necessary for food-entrained behavioural rhythms is not yet certain. Persistence of these rhythms in mice with clock-gene mutations that disable the SCN pacemaker suggests diversity in the molecular basis of light- and food-entrainable clocks.

  10. Dietary oleanolic acid mediates circadian clock gene expression in liver independently of diet and animal model but requires apolipoprotein A1.

    PubMed

    Gabás-Rivera, Clara; Martínez-Beamonte, Roberto; Ríos, José L; Navarro, María A; Surra, Joaquín C; Arnal, Carmen; Rodríguez-Yoldi, María J; Osada, Jesús

    2013-12-01

    Oleanolic acid is a triterpene widely distributed throughout the plant kingdom and present in virgin olive oil at a concentration of 57 mg/kg. To test the hypotheses that its long-term administration could modify hepatic gene expression in several animal models and that this could be influenced by the presence of APOA1-containing high-density lipoproteins (HDLs), diets including 0.01% oleanolic acid were provided to Apoe- and Apoa1-deficient mice and F344 rats. Hepatic transcriptome was analyzed in Apoe-deficient mice fed long-term semipurified Western diets differing in the oleanolic acid content. Gene expression changes, confirmed by reverse transcriptase quantitative polymerase chain reaction, were sought for their implication in hepatic steatosis. To establish the effect of oleanolic acid independently of diet and animal model, male rats were fed chow diet with or without oleanolic acid, and to test the influence of HDL, Apoa1-deficient mice consuming the latter diet were used. In Apoe-deficient mice, oleanolic acid intake increased hepatic area occupied by lipid droplets with no change in oxidative stress. Bmal1 and the other core component of the circadian clock, Clock, together with Elovl3, Tubb2a and Cldn1 expressions, were significantly increased, while Amy2a5, Usp2, Per3 and Thrsp were significantly decreased in mice receiving the compound. Bmal1 and Cldn1 expressions were positively associated with lipid droplets. Increased Clock and Bmal1 expressions were also observed in rats, but not in Apoa1-deficient mice. The core liver clock components Clock-Bmal1 are a target of oleanolic acid in two animal models independently of the diets provided, and this compound requires APOA1-HDL for its hepatic action.

  11. Nocturnal behavior and rhythmic period gene expression in a lancelet, Branchiostoma lanceolatum.

    PubMed

    Schomerus, Christof; Korf, Horst-Werner; Laedtke, Elke; Moret, Frédéric; Zhang, Qian; Wicht, Helmut

    2008-04-01

    The authors here present the first anatomical, molecular biological, and ethological data on the organization of the circadian system of a lancelet, Branchiostoma lanceolatum, a close invertebrate relative of vertebrates. B. lanceolatum was found to be a nocturnal animal and, since its rhythmic activity persisted under constant darkness, it also appears to possess an endogenous, circadian oscillator. The authors cloned a homolog of the clock gene Period (Per), which plays a central (inhibitory) role in the biochemical machinery of the circadian oscillators of both vertebrates and protostomians. This gene from B. lanceolatum was designated as amphiPer. Both the sequence of its cDNA and that of the predicted protein are more similar to those of the Per paralogs of vertebrates than to those of the single protostomian Per gene. A strong expression of amphiPer was found in a small cell group in the anterior neural tube. The amphiPer mRNA levels fluctuated in a rhythmic manner, being high early in the day and low late at night. The authors' data suggest a homology of the amphiPer expessing cells to the suprachiasmatic nucleus of vertebrates.

  12. The role of sleep problems and circadian clock genes in attention-deficit hyperactivity disorder and mood disorders during childhood and adolescence: an update.

    PubMed

    Dueck, Alexander; Berger, Christoph; Wunsch, Katharina; Thome, Johannes; Cohrs, Stefan; Reis, Olaf; Haessler, Frank

    2017-02-01

    A more recent branch of research describes the importance of sleep problems in the development and treatment of mental disorders in children and adolescents, such as attention-deficit hyperactivity disorder (ADHD) and mood disorders (MD). Research about clock genes has continued since 2012 with a focus on metabolic processes within all parts of the mammalian body, but particularly within different cerebral regions. Research has focused on complex regulatory circuits involving clock genes themselves and their influence on circadian rhythms of diverse body functions. Current publications on basic research in human and animal models indicate directions for the treatment of mental disorders targeting circadian rhythms and mechanisms. The most significant lines of research are described in this paper.

  13. The circadian clock in cancer development and therapy

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Most aspects of mammalian function display circadian rhythms driven by an endogenous clock. The circadian clock is operated by genes and comprises a central clock in the brain that responds to environmental cues and controls subordinate clocks in peripheral tissues via circadian output pathways. The...

  14. TIME FOR COFFEE Encodes a Nuclear Regulator in the Arabidopsis thaliana Circadian Clock[W

    PubMed Central

    Ding, Zhaojun; Millar, Andrew J.; Davis, Amanda M.; Davis, Seth J.

    2007-01-01

    The plant circadian clock is required for daily anticipation of the diurnal environment. Mutation in Arabidopsis thaliana TIME FOR COFFEE (TIC) affects free-running circadian rhythms. To investigate how TIC functions within the circadian system, we introduced markers for the evening and morning phases of the clock into tic and measured evident rhythms. The phases of evening clock genes in tic were all advanced under light/dark cycles without major expression level defects. With regard to morning-acting genes, we unexpectedly found that TIC has a closer relationship with LATE ELONGATED HYPOCOTYL (LHY) than with CIRCADIAN CLOCK ASSOCIATED1, as tic has a specific LHY expression level defect. Epistasis analysis demonstrated that there were no clear rhythms in double mutants of tic and evening-acting clock genes, although double mutants of tic and morning-acting genes exhibited a similar free-running period as tic. We isolated TIC and found that its mRNA expression is continuously present over the diurnal cycle, and the encoded protein appears to be strictly localized to the nucleus. Neither its abundance nor its cellular distribution was found to be clock regulated. We suggest that TIC encodes a nucleus-acting clock regulator working close to the central oscillator. PMID:17496120

  15. Poor Sleep Quality Is Associated with Dawn Phenomenon and Impaired Circadian Clock Gene Expression in Subjects with Type 2 Diabetes Mellitus

    PubMed Central

    Li, Yuan; Tao, Xiaoming

    2017-01-01

    Aims. We investigated whether poor sleep quality is associated with both dawn phenomenon and impaired circadian clock gene expression in subjects with diabetes. Methods. 81 subjects with diabetes on continuous glucose monitoring were divided into two groups according to the Pittsburgh Sleep Quality Index. The magnitude of dawn phenomenon was quantified by its increment from nocturnal nadir to prebreakfast. Peripheral leucocytes were sampled from 81 subjects with diabetes and 28 normal controls at 09:00. Transcript levels of circadian clock genes (BMAL1, PER1, PER2, and PER3) were determined by real-time quantitative polymerase chain reaction. Results. The levels of HbA1c and fasting glucose and the magnitude of dawn phenomenon were significantly higher in the diabetes group with poor sleep quality than that with good sleep quality. Peripheral leucocytes from subjects with poor sleep quality expressed significantly lower transcript levels of BMAL1 and PER1 compared with those with good sleep quality. Poor sleep quality was significantly correlated with magnitude of dawn phenomenon. Multiple linear regression showed that sleep quality and PER1 were significantly independently correlated with dawn phenomenon. Conclusions. Dawn phenomenon is associated with sleep quality. Furthermore, mRNA expression of circadian clock genes is dampened in peripheral leucocytes of subjects with poor sleep quality. PMID:28352282

  16. RNA around the clock – regulation at the RNA level in biological timing

    PubMed Central

    Nolte, Christine; Staiger, Dorothee

    2015-01-01

    The circadian timing system in plants synchronizes their physiological functions with the environment. This is achieved by a global control of gene expression programs with a considerable part of the transcriptome undergoing 24-h oscillations in steady-state abundance. These circadian oscillations are driven by a set of core clock proteins that generate their own 24-h rhythm through periodic feedback on their own transcription. Additionally, post-transcriptional events are instrumental for oscillations of core clock genes and genes in clock output. Here we provide an update on molecular events at the RNA level that contribute to the 24-h rhythm of the core clock proteins and shape the circadian transcriptome. We focus on the circadian system of the model plant Arabidopsis thaliana but also discuss selected regulatory principles in other organisms. PMID:25999975

  17. Organ specificity in the plant circadian system is explained by different light inputs to the shoot and root clocks.

    PubMed

    Bordage, Simon; Sullivan, Stuart; Laird, Janet; Millar, Andrew J; Nimmo, Hugh G

    2016-10-01

    Circadian clocks allow the temporal compartmentalization of biological processes. In Arabidopsis, circadian rhythms display organ specificity but the underlying molecular causes have not been identified. We investigated the mechanisms responsible for the similarities and differences between the clocks of mature shoots and roots in constant conditions and in light : dark cycles. We developed an imaging system to monitor clock gene expression in shoots and light- or dark-grown roots, modified a recent mathematical model of the Arabidopsis clock and used this to simulate our new data. We showed that the shoot and root circadian clocks have different rhythmic properties (period and amplitude) and respond differently to light quality. The root clock was entrained by direct exposure to low-intensity light, even in antiphase to the illumination of shoots. Differences between the clocks were more pronounced in conditions where light was present than in constant darkness, and persisted in the presence of sucrose. We simulated the data successfully by modifying those parameters of a clock model that are related to light inputs. We conclude that differences and similarities between the shoot and root clocks can largely be explained by organ-specific light inputs. This provides mechanistic insight into the developing field of organ-specific clocks.

  18. Temperature compensation and temperature sensation in the circadian clock

    PubMed Central

    Kidd, Philip B.; Young, Michael W.; Siggia, Eric D.

    2015-01-01

    All known circadian clocks have an endogenous period that is remarkably insensitive to temperature, a property known as temperature compensation, while at the same time being readily entrained by a diurnal temperature oscillation. Although temperature compensation and entrainment are defining features of circadian clocks, their mechanisms remain poorly understood. Most models presume that multiple steps in the circadian cycle are temperature-dependent, thus facilitating temperature entrainment, but then insist that the effect of changes around the cycle sums to zero to enforce temperature compensation. An alternative theory proposes that the circadian oscillator evolved from an adaptive temperature sensor: a gene circuit that responds only to temperature changes. This theory implies that temperature changes should linearly rescale the amplitudes of clock component oscillations but leave phase relationships and shapes unchanged. We show using timeless luciferase reporter measurements and Western blots against TIMELESS protein that this prediction is satisfied by the Drosophila circadian clock. We also review evidence for pathways that couple temperature to the circadian clock, and show previously unidentified evidence for coupling between the Drosophila clock and the heat-shock pathway. PMID:26578788

  19. Rhythmic Oxygen Levels Reset Circadian Clocks through HIF1α.

    PubMed

    Adamovich, Yaarit; Ladeuix, Benjamin; Golik, Marina; Koeners, Maarten P; Asher, Gad

    2017-01-10

    The mammalian circadian system consists of a master clock in the brain that synchronizes subsidiary oscillators in peripheral tissues. The master clock maintains phase coherence in peripheral cells through systemic cues such as feeding-fasting and temperature cycles. Here, we examined the role of oxygen as a resetting cue for circadian clocks. We continuously measured oxygen levels in living animals and detected daily rhythms in tissue oxygenation. Oxygen cycles, within the physiological range, were sufficient to synchronize cellular clocks in a HIF1α-dependent manner. Furthermore, several clock genes responded to changes in oxygen levels through HIF1α. Finally, we found that a moderate reduction in oxygen levels for a short period accelerates the adaptation of wild-type but not of HIF1α-deficient mice to the new time in a jet lag protocol. We conclude that oxygen, via HIF1α activation, is a resetting cue for circadian clocks and propose oxygen modulation as therapy for jet lag.

  20. Tissue-Specific Changes in Molecular Clocks During the Transition from Pregnancy to Lactation in Mice1

    PubMed Central

    Casey, Theresa M.; Crodian, Jennifer; Erickson, Emily; Kuropatwinski, Karen K.; Gleiberman, Anatoli S.; Antoch, Marina P.

    2014-01-01

    ABSTRACT Circadian clocks regulate homeostasis and mediate responses to stressors. Lactation is one of the most energetically demanding periods of an adult female's life. Peripartum changes occur in almost every organ so the dam can support neonatal growth through milk production while homeostasis is maintained. How circadian clocks are involved in adaptation to lactation is currently unknown. The abundance and temporal pattern of core clock genes' expression were measured in suprachiasmatic nucleus, liver, and mammary from late pregnant and early lactation mice. Tissue-specific changes in molecular clocks occurred between physiological states. Amplitude and robustness of rhythms increased in suprachiasmatic nucleus and liver. Mammary rhythms of core molecular clock genes were suppressed. Attenuated rhythms appeared to be a physiological adaptation of mammary to lactation, because manipulation of timing of suckling resulting in significant differences in plasma prolactin and corticosterone had no effect on amplitude. Analysis of core clock proteins revealed that the stoichiometric relationship between positive (CLOCK) and negative (PER2) components remained 1:1 in liver but was increased to 4:1 in mammary during physiological transition. Induction of differentiation of mammary epithelial cell line HC11 with dexamethasone, insulin, and prolactin resulted in similar stoichiometric changes among positive and negative clock regulators, and prolactin induced phase shifts in HC11 Arntl expression rhythm. Data support that distinct mechanisms drive periparturient changes in mammary clock. Stoichiometric change in clock regulators occurs with gland differentiation. Suppression of mammary clock gene expression rhythms represents a physiological adaptation to suckling cues. Adaptations in mammary clock are likely needed in part to support suckling demands of neonates. PMID:24759789

  1. Ras-Mediated Deregulation of the Circadian Clock in Cancer

    PubMed Central

    Relógio, Angela; Thomas, Philippe; Medina-Pérez, Paula; Reischl, Silke; Bervoets, Sander; Gloc, Ewa; Riemer, Pamela; Mang-Fatehi, Shila; Maier, Bert; Schäfer, Reinhold; Leser, Ulf; Herzel, Hanspeter; Kramer, Achim; Sers, Christine

    2014-01-01

    Circadian rhythms are essential to the temporal regulation of molecular processes in living systems and as such to life itself. Deregulation of these rhythms leads to failures in biological processes and eventually to the manifestation of pathological phenotypes including cancer. To address the questions as to what are the elicitors of a disrupted clock in cancer, we applied a systems biology approach to correlate experimental, bioinformatics and modelling data from several cell line models for colorectal and skin cancer. We found strong and weak circadian oscillators within the same type of cancer and identified a set of genes, which allows the discrimination between the two oscillator-types. Among those genes are IFNGR2, PITX2, RFWD2, PPARγ, LOXL2, Rab6 and SPARC, all involved in cancer-related pathways. Using a bioinformatics approach, we extended the core-clock network and present its interconnection to the discriminative set of genes. Interestingly, such gene signatures link the clock to oncogenic pathways like the RAS/MAPK pathway. To investigate the potential impact of the RAS/MAPK pathway - a major driver of colorectal carcinogenesis - on the circadian clock, we used a computational model which predicted that perturbation of BMAL1-mediated transcription can generate the circadian phenotypes similar to those observed in metastatic cell lines. Using an inducible RAS expression system, we show that overexpression of RAS disrupts the circadian clock and leads to an increase of the circadian period while RAS inhibition causes a shortening of period length, as predicted by our mathematical simulations. Together, our data demonstrate that perturbations induced by a single oncogene are sufficient to deregulate the mammalian circadian clock. PMID:24875049

  2. The intrinsic microglial clock system regulates interleukin-6 expression.

    PubMed

    Nakazato, Ryota; Hotta, Shogo; Yamada, Daisuke; Kou, Miki; Nakamura, Saki; Takahata, Yoshifumi; Tei, Hajime; Numano, Rika; Hida, Akiko; Shimba, Shigeki; Mieda, Michihiro; Hinoi, Eiichi; Yoneda, Yukio; Takarada, Takeshi

    2017-01-01

    Similar to neurons, microglia have an intrinsic molecular clock. The master clock oscillator Bmal1 modulates interleukin-6 upregulation in microglial cells exposed to lipopolysaccharide. Bmal1 can play a role in microglial inflammatory responses. We previously demonstrated that gliotransmitter ATP induces transient expression of the clock gene Period1 via P2X7 purinergic receptors in cultured microglia. In this study, we further investigated mechanisms underlying the regulation of pro-inflammatory cytokine production by clock molecules in microglial cells. Several clock gene transcripts exhibited oscillatory diurnal rhythmicity in microglial BV-2 cells. Real-time luciferase monitoring also showed diurnal oscillatory luciferase activity in cultured microglia from Per1::Luciferase transgenic mice. Lipopolysaccharide (LPS) strongly induced the expression of pro-inflammatory cytokines in BV-2 cells, whereas an siRNA targeting Brain and muscle aryl hydrocarbon receptor nuclear translocator-like protein 1 (Bmal1), a core positive component of the microglial molecular clock, selectively inhibited LPS-induced interleukin-6 (IL-6) expression. In addition, LPS-induced IL-6 expression was attenuated in microglia from Bmal1-deficient mice. This phenotype was recapitulated by pharmacological disruption of oscillatory diurnal rhythmicity using the synthetic Rev-Erb agonist SR9011. Promoter analysis of the Il6 gene revealed that Bmal1 is required for LPS-induced IL-6 expression in microglia. Mice conditionally Bmal1 deficient in cells expressing CD11b, including microglia, exhibited less potent upregulation of Il6 expression following middle cerebral artery occlusion compared with that in control mice, with a significant attenuation of neuronal damage. These results suggest that the intrinsic microglial clock modulates the inflammatory response, including the positive regulation of IL-6 expression in a particular pathological situation in the brain, GLIA 2016. GLIA 2017;65:198-208.

  3. Diversity of Human Clock Genotypes and Consequences

    PubMed Central

    Zhang, Luoying; Ptáček, Louis J.; Fu, Ying-Hui

    2014-01-01

    The molecular clock consists of a number of genes that form transcriptional and post-transcriptional feedback loops, which function together to generate circadian oscillations that give rise to circadian rhythms of our behavioral and physiological processes. Genetic variations in these clock genes have been shown to be associated with phenotypic effects in a repertoire of biological processes, such as diurnal preference, sleep, metabolism, mood regulation, addiction, and fertility. Consistently, rodent models carrying mutations in clock genes also demonstrate similar phenotypes. Taken together, these studies suggest that human clock-gene variants contribute to the phenotypic differences observed in various behavioral and physiological processes, although to validate this requires further characterization of the molecular consequences of these polymorphisms. Investigating the diversity of human genotypes and the phenotypic effects of these genetic variations shall advance our understanding of the function of the circadian clock and how we can employ the clock to improve our overall health. PMID:23899594

  4. Bovine Circadian Locomotor Output Cycles Kaput (CLOCK) and Clusterin (CLU) mRNA Quantitation in Ejaculated Crossbred Bull Spermatozoa.

    PubMed

    Kumar, S; Deb, R; Singh, U; Ganguly, I; Mandal, D K; Tyagi, S; Kumar, M; Sengar, G; Sharma, S; Singh, R; Singh, R

    2015-06-01

    Mammalian circadian locomotor output cycles kaput (CLOCK) gene encodes a transcription factor that affects both the persistence and the period of circadian rhythms. Earlier reports suggested that CLOCK gene might be associated with male infertility in human. Present investigation, for the first time, reports that CLOCK gene expresses differentially between good and poor quality crossbred bull semen. The relative expression of CLOCK was significantly (p < 0.05) higher among good quality bull semen than motility-impaired ones. Clusterins (CLU) are series of genes associated with a variety of physiological activities including spermatogenesis, apoptosis and degenerative disease conditions. In the present context, we also investigated that the expression of CLU gene was significantly (p < 0.05) higher among motility-impaired crossbred bull semen compared to the good quality one.

  5. Gene Identification Algorithms Using Exploratory Statistical Analysis of Periodicity

    NASA Astrophysics Data System (ADS)

    Mukherjee, Shashi Bajaj; Sen, Pradip Kumar

    2010-10-01

    Studying periodic pattern is expected as a standard line of attack for recognizing DNA sequence in identification of gene and similar problems. But peculiarly very little significant work is done in this direction. This paper studies statistical properties of DNA sequences of complete genome using a new technique. A DNA sequence is converted to a numeric sequence using various types of mappings and standard Fourier technique is applied to study the periodicity. Distinct statistical behaviour of periodicity parameters is found in coding and non-coding sequences, which can be used to distinguish between these parts. Here DNA sequences of Drosophila melanogaster were analyzed with significant accuracy.

  6. Periodic, Quasi-periodic and Chaotic Dynamics in Simple Gene Elements with Time Delays

    PubMed Central

    Suzuki, Yoko; Lu, Mingyang; Ben-Jacob, Eshel; Onuchic, José N.

    2016-01-01

    Regulatory gene circuit motifs play crucial roles in performing and maintaining vital cellular functions. Frequently, theoretical studies of gene circuits focus on steady-state behaviors and do not include time delays. In this study, the inclusion of time delays is shown to entirely change the time-dependent dynamics for even the simplest possible circuits with one and two gene elements with self and cross regulations. These elements can give rise to rich behaviors including periodic, quasi-periodic, weak chaotic, strong chaotic and intermittent dynamics. We introduce a special power-spectrum-based method to characterize and discriminate these dynamical modes quantitatively. Our simulation results suggest that, while a single negative feedback loop of either one- or two-gene element can only have periodic dynamics, the elements with two positive/negative feedback loops are the minimalist elements to have chaotic dynamics. These elements typically have one negative feedback loop that generates oscillations, and another unit that allows frequent switches among multiple steady states or between oscillatory and non-oscillatory dynamics. Possible dynamical features of several simple one- and two-gene elements are presented in details. Discussion is presented for possible roles of the chaotic behavior in the robustness of cellular functions and diseases, for example, in the context of cancer. PMID:26876008

  7. Oscillating Gene Expression Determines Competence for Periodic Arabidopsis Root Branching

    PubMed Central

    Moreno-Risueno, Miguel A.; Van Norman, Jaimie M.; Moreno, Antonio; Zhang, Jingyuan; Ahnert, Sebastian E.; Benfey, Philip N.

    2010-01-01

    Plants and animals produce modular developmental units in a periodic fashion. In plants, lateral roots form as repeating units along the root primary axis; however, the developmental mechanism regulating this process is unknown. We found that cyclic expression pulses of a reporter gene mark the position of future lateral roots by establishing prebranch sites and that prebranch site production and root bending are periodic. Microarray and promoter-luciferase studies revealed two sets of genes oscillating in opposite phases at the root tip. Genetic studies show that some oscillating transcriptional regulators are required for periodicity in one or both developmental processes. This molecular mechanism has characteristics that resemble molecular clock–driven activities in animal species. PMID:20829477

  8. The chlorate-iodine clock reaction.

    PubMed

    Oliveira, André P; Faria, Roberto B

    2005-12-28

    A clock reaction produced by mixing chlorate and iodine solutions in perchloric acid media is reported. This is the first example of a clock reaction using chlorate as a reagent. Increasing chlorate and acid concentration reduces the induction period. Changing the initial iodine concentration does not affect the length of the induction period. The discovery of this clock reaction opens the possibility that a new family of oscillation reactions can be built using chlorate as reagent.

  9. Effect of Mefloquine, a Gap Junction Blocker, on Circadian Period2 Gene Oscillation in the Mouse Suprachiasmatic Nucleus Ex Vivo

    PubMed Central

    Koo, Jinmi; Choe, Han Kyoung; Kim, Hee-Dae; Chun, Sung Kook; Son, Gi Hoon

    2015-01-01

    Background In mammals, the master circadian pacemaker is localized in an area of the ventral hypothalamus known as the suprachiasmatic nucleus (SCN). Previous studies have shown that pacemaker neurons in the SCN are highly coupled to one another, and this coupling is crucial for intrinsic self-sustainability of the SCN central clock, which is distinguished from peripheral oscillators. One plausible mechanism underlying the intercellular communication may involve direct electrical connections mediated by gap junctions. Methods We examined the effect of mefloquine, a neuronal gap junction blocker, on circadian Period 2 (Per2) gene oscillation in SCN slice cultures prepared from Per2::luciferase (PER2::LUC) knock-in mice using a real-time bioluminescence measurement system. Results Administration of mefloquine causes instability in the pulse period and a slight reduction of amplitude in cyclic PER2::LUC expression. Blockade of gap junctions uncouples PER2::LUC-expressing cells, in terms of phase transition, which weakens synchrony among individual cellular rhythms. Conclusion These findings suggest that neuronal gap junctions play an important role in synchronizing the central pacemaker neurons and contribute to the distinct self-sustainability of the SCN master clock. PMID:25491783

  10. Impairment of peripheral circadian clocks precedes metabolic abnormalities in ob/ob mice.

    PubMed

    Ando, Hitoshi; Kumazaki, Masafumi; Motosugi, Yuya; Ushijima, Kentarou; Maekawa, Tomohiro; Ishikawa, Eiko; Fujimura, Akio

    2011-04-01

    Recent studies have demonstrated relationships between the dysfunction of circadian clocks and the development of metabolic abnormalities, but the chicken-and-egg question remains unresolved. To address this issue, we investigated the cause-effect relationship in obese, diabetic ob/ob mice. Compared with control C57BL/6J mice, the daily mRNA expression profiles of the clock and clock-controlled genes Clock, Bmal1, Cry1, Per1, Per2, and Dbp were substantially dampened in the liver and adipose tissue, but not the hypothalamic suprachiasmatic nucleus, of 10-wk-old ob/ob mice. Four-week feeding of a low-calorie diet and administration of leptin over a 7-d period attenuated, to a significant and comparable extent, the observed metabolic abnormalities (obesity, hyperglycemia, hyperinsulinemia, and hypercholesterolemia) in the ob/ob mice. However, only leptin treatment improved the impaired peripheral clocks. In addition, clock function, assessed by measuring levels of Per1, Per2, and Dbp mRNA at around peak times, was also reduced in the peripheral tissues of 3-wk-old ob/ob mice without any overt metabolic abnormalities. Collectively these results indicate that the impairment of peripheral clocks in ob/ob mice does not result from metabolic abnormalities but may instead be at least partially caused by leptin deficiency itself. Further studies are needed to clarify how leptin deficiency affects peripheral clocks.

  11. Highly Efficient Genome Editing via CRISPR/Cas9 to Create Clock Gene Knockout Cells.

    PubMed

    Korge, Sandra; Grudziecki, Astrid; Kramer, Achim

    2015-10-01

    Targeted genome editing using CRISPR/Cas9 is a relatively new, revolutionary technology allowing for efficient and directed alterations of the genome. It has been widely used for loss-of-function studies in animals and cell lines but has not yet been used to study circadian rhythms. Here, we describe the application of CRISPR/Cas9 genome editing for the generation of an F-box and leucine-rich repeat protein 3 (Fbxl3) knockout in a human cell line. Genomic alterations at the Fbxl3 locus occurred with very high efficiency (70%-100%) and specificity at both alleles, resulting in insertions and deletions that led to premature stop codons and hence FBXL3 knockout. Fbxl3 knockout cells displayed low amplitude and long period oscillations of Bmal1-luciferase reporter activity as well as increased CRY1 protein stability in line with previously published phenotypes for Fbxl3 knockout in mice. Thus, CRISPR/Cas9 genome editing should be highly valuable for studying circadian rhythms not only in human cells but also in classic model systems as well as nonmodel organisms.

  12. Advances in understanding the peripheral circadian clocks.

    PubMed

    Richards, Jacob; Gumz, Michelle L

    2012-09-01

    In the past decade, it has become increasingly evident that the circadian clock system plays an important role in many physiological processes. The circadian clock can be divided into 2 parts: the central clock, residing in the suprachiasmatic nucleus of the hypothalamus, which receives light cues, and the peripheral clocks that reside in various tissues throughout the body. The peripheral clocks play an integral and unique role in each of their respective tissues, driving the circadian expression of specific genes involved in a variety of physiological functions. The goal of this review is to provide an introduction to and overview of the peripheral clocks, including potential mechanisms, targets, and implications for disease states. The peripheral clocks include the cardiovascular, metabolic, endocrine, immune, and reproductive systems.

  13. Differential association of circadian genes with mood disorders: CRY1 and NPAS2 are associated with unipolar major depression and CLOCK and VIP with bipolar disorder.

    PubMed

    Soria, Virginia; Martínez-Amorós, Erika; Escaramís, Geòrgia; Valero, Joaquín; Pérez-Egea, Rosario; García, Cecilia; Gutiérrez-Zotes, Alfonso; Puigdemont, Dolors; Bayés, Mònica; Crespo, José M; Martorell, Lourdes; Vilella, Elisabet; Labad, Antonio; Vallejo, Julio; Pérez, Víctor; Menchón, José M; Estivill, Xavier; Gratacòs, Mònica; Urretavizcaya, Mikel

    2010-05-01

    Disruptions in circadian rhythms have been described in mood disorders (MD), but the involvement of genetic variation in genes pertaining to the molecular circadian machinery in the susceptibility to MD has not been conclusively determined. We examined 209 single-nucleotide polymorphisms (SNPs) covering 19 circadian genes (ADCYAP1, ARNTL, ARNTL2, BHLHB2, BHLHB3, CLOCK, CRY1, CRY2, CSNK1E, DBP, NPAS2, NR1D1, PER1, PER2, PER3, RORA, TIMELESS, VIP, and VIPR2) in a sample of 534 MD patients (335 with unipolar major mood depression (MDD) and 199 with bipolar disorder (BD)) and 440 community-based screened controls. Nominally, statistically significant associations were found in 15 circadian genes. The gene-wide test, corrected for the number of SNPs analyzed in each gene, identified significant associations in CRY1 (rs2287161), NPAS2 (rs11123857), and VIPR2 (rs885861) genes with the combined MD sample. In the MDD subsample, the same SNPs in CRY1 and NPAS2 of the combined sample remained associated, whereas in the BD subsample CLOCK (rs10462028) and VIP (rs17083008) were specifically associated. The association with an SNP located 3' near CRY1 gene in MDD remained statistically significant after permutation correction at experiment level (p=0.007). Significant additive effects were found between the SNPs that were statistically significant at the gene-wide level. We also found evidence of associations between two-marker haplotypes in CRY1 and NPAS2 genes and MD. Our data support the contribution of the circadian system to the genetic susceptibility to MD and suggest that different circadian genes may have specific effects on MD polarity.

  14. Characterization of orderly spatiotemporal patterns of clock gene activation in mammalian suprachiasmatic nucleus

    PubMed Central

    Foley, Nicholas C.; Tong, Tina Y.; Foley, Duncan; LeSauter, Joseph; Welsh, David K.

    2012-01-01

    Because we can observe oscillation within individual cells and in the tissue as a whole, the suprachiasmatic nucleus (SCN) presents a unique system in the mammalian brain for the analysis of individual cells and the networks of which they are a part. While dispersed cells of the SCN sustain circadian oscillations in isolation, they are unstable oscillators that require network interactions for robust cycling. Using cluster analysis to assess bioluminescence in acute brain slices from PERIOD2∷Luciferase (PER2∷LUC) knockin mice, and immunochemistry of SCN from animals harvested at various circadian times, we assessed the spatiotemporal activation patterns of PER2 to explore the emergence of a coherent oscillation at the tissue level. The results indicate that circadian oscillation is characterized by a stable daily cycle of PER2 expression involving orderly serial activation of specific SCN subregions, followed by a silent interval, with substantial symmetry between the left and right side of the SCN. The biological significance of the clusters identified in living slices was confirmed by co-expression of LUC and PER2 in fixed, immunochemically stained brain sections, with the spatiotemporal pattern of LUC expression resembling that revealed in the cluster analysis of bioluminescent slices. We conclude that the precise timing of PER2 expression within individual neurons is dependent on their location within the nucleus, and that small groups of neurons within the SCN give rise to distinctive and identifiable subregions. We propose that serial activation of these subregions is the basis of robustness and resilience of the daily rhythm of the SCN. PMID:21488990

  15. Cadmium-Induced Disruption in 24-h Expression of Clock and Redox Enzyme Genes in Rat Medial Basal Hypothalamus: Prevention by Melatonin

    PubMed Central

    Jiménez-Ortega, Vanesa; Cano-Barquilla, Pilar; Scacchi, Pablo A.; Cardinali, Daniel P.; Esquifino, Ana I.

    2011-01-01

    In a previous study we reported that a low daily p.o. dose of cadmium (Cd) disrupted the circadian expression of clock and redox enzyme genes in rat medial basal hypothalamus (MBH). To assess whether melatonin could counteract Cd activity, male Wistar rats (45 days of age) received CdCl2 (5 ppm) and melatonin (3 μg/mL) or vehicle (0.015% ethanol) in drinking water. Groups of animals receiving melatonin or vehicle alone were also included. After 1 month, MBH mRNA levels were measured by real-time PCR analysis at six time intervals in a 24-h cycle. In control MBH Bmal1 expression peaked at early scotophase, Per1 expression at late afternoon, and Per2 and Cry2 expression at mid-scotophase, whereas neither Clock nor Cry1 expression showed significant 24-h variations. This pattern was significantly disrupted (Clock, Bmal1) or changed in phase (Per1, Per2, Cry2) by CdCl2 while melatonin counteracted the changes brought about by Cd on Per1 expression only. In animals receiving melatonin alone the 24-h pattern of MBH Per2 and Cry2 expression was disrupted. CdCl2 disrupted the 24-h rhythmicity of Cu/Zn- and Mn-superoxide dismutase (SOD), nitric oxide synthase (NOS)-1, NOS-2, heme oxygenase (HO)-1, and HO-2 gene expression, most of the effects being counteracted by melatonin. In particular, the co-administration of melatonin and CdCl2 increased Cu/Zn-SOD gene expression and decreased that of glutathione peroxidase (GPx), glutathione reductase (GSR), and HO-2. In animals receiving melatonin alone, significant increases in mean Cu/Zn and Mn-SOD gene expression, and decreases in that of GPx, GSR, NOS-1, NOS-2, HO-1, and HO-2, were found. The results indicate that the interfering effect of melatonin on the activity of a low dose of CdCl2 on MBH clock and redox enzyme genes is mainly exerted at the level of redox enzyme gene expression. PMID:21442002

  16. Small molecule modifiers of circadian clocks.

    PubMed

    Chen, Zheng; Yoo, Seung-Hee; Takahashi, Joseph S

    2013-08-01

    Circadian clocks orchestrate 24-h oscillations of essential physiological and behavioral processes in response to daily environmental changes. These clocks are remarkably precise under constant conditions yet highly responsive to resetting signals. With the molecular composition of the core oscillator largely established, recent research has increasingly focused on clock-modifying mechanisms/molecules. In particular, small molecule modifiers, intrinsic or extrinsic, are emerging as powerful tools for understanding basic clock biology as well as developing putative therapeutic agents for clock-associated diseases. In this review, we will focus on synthetic compounds capable of modifying the period, phase, or amplitude of circadian clocks, with particular emphasis on the mammalian clock. We will discuss the potential of exploiting these small molecule modifiers in both basic and translational research.

  17. The Circadian Clock Modulates Enamel Development

    PubMed Central

    Lacruz, Rodrigo S.; Hacia, Joseph G.; Bromage, Timothy G.; Boyde, Alan; Lei, Yaping; Xu, Yucheng; Miller, Joseph D.; Paine, Michael L.; Snead, Malcolm L.

    2012-01-01

    Fully mature enamel is about 98% mineral by weight. While mineral crystals appear very early during its formative phase, the newly secreted enamel is a soft gel-like matrix containing several enamel matrix proteins of which the most abundant is amelogenin (Amelx). Histological analysis of mineralized dental enamel reveals markings called cross-striations associated with daily increments of enamel formation, as evidenced by injections of labeling dyes at known time intervals. The daily incremental growth of enamel has led to the hypothesis that the circadian clock might be involved in the regulation of enamel development. To identify daily rhythms of clock genes and Amelx, we subjected murine ameloblast cells to serum synchronization to analyze the expression of the circadian transcription factors Per2 and Bmal1 by real-time PCR. Results indicate that these key genetic regulators of the circadian clock are expressed in synchronized murine ameloblast cell cultures and that their expression profile follows a circadian pattern with acrophase and bathyphase for both gene transcripts in antiphase. Immunohistological analysis confirms the protein expression of Bmal and Cry in enamel cells. Amelx expression in 2-day postnatal mouse molars dissected every 4 hours for a duration of 48 hours oscillated with an approximately 24-hour period, with a significant approximately 2-fold decrease in expression during the dark period compared to the light period. The expression of genes involved in bicarbonate production (Car2) and transport (Slc4a4), as well as in enamel matrix endocytosis (Lamp1), was greater during the dark period, indicating that ameloblasts express these proteins when Amelx expression is at the nadir. The human and mouse Amelx genes each contain a single nonconserved E-box element within 10 kb upstream of their respective transcription start sites. We also found that within 2 kb of the transcription start site of the human NFYA gene, which encodes a positive

  18. The circadian protein period 1 contributes to blood pressure control and coordinately regulates renal sodium transport genes.

    PubMed

    Stow, Lisa R; Richards, Jacob; Cheng, Kit-Yan; Lynch, I Jeanette; Jeffers, Lauren A; Greenlee, Megan M; Cain, Brian D; Wingo, Charles S; Gumz, Michelle L

    2012-06-01

    The circadian clock protein period 1 (Per1) contributes to the regulation of expression of the α subunit of the renal epithelial sodium channel at the basal level and in response to the mineralocorticoid hormone aldosterone. The goals of the present study were to define the role of Per1 in the regulation of additional renal sodium handling genes in cortical collecting duct cells and to evaluate blood pressure (BP) in mice lacking functional Per1. To determine whether Per1 regulates additional genes important in renal sodium handling, a candidate gene approach was used. Immortalized collecting duct cells were transfected with a nontarget small interfering RNA or a Per1-specific small interfering RNA. Expression of the genes for α-epithelial sodium channel and Fxyd5, a positive regulator of Na, K-ATPase activity, decreased in response to Per1 knockdown. Conversely, mRNA expression of caveolin 1, Ube2e3, and ET-1, all negative effectors of epithelial sodium channel, was induced after Per1 knockdown. These results led us to evaluate BP in Per1 KO mice. Mice lacking Per1 exhibit significantly reduced BP and elevated renal ET-1 levels compared with wild-type animals. Given the established role of renal ET-1 in epithelial sodium channel inhibition and BP control, elevated renal ET-1 is one possible explanation for the lower BP observed in Per1 KO mice. These data support a role for the circadian clock protein Per1 in the coordinate regulation of genes involved in renal sodium reabsorption. Importantly, the lower BP observed in Per1 KO mice compared with wild-type mice suggests a role for Per1 in BP control as well.

  19. Physiological links of circadian clock and biological clock of aging.

    PubMed

    Liu, Fang; Chang, Hung-Chun

    2017-01-20

    Circadian rhythms orchestrate biochemical and physiological processes in living organisms to respond the day/night cycle. In mammals, nearly all cells hold self-sustained circadian clocks meanwhile couple the intrinsic rhythms to systemic changes in a hierarchical manner. The suprachiasmatic nucleus (SCN) of the hypothalamus functions as the master pacemaker to initiate daily synchronization according to the photoperiod, in turn determines the phase of peripheral cellular clocks through a variety of signaling relays, including endocrine rhythms and metabolic cycles. With aging, circadian desynchrony occurs at the expense of peripheral metabolic pathologies and central neurodegenerative disorders with sleep symptoms, and genetic ablation of circadian genes in model organisms resembled the aging-related features. Notably, a number of studies have linked longevity nutrient sensing pathways in modulating circadian clocks. Therapeutic strategies that bridge the nutrient sensing pathways and circadian clock might be rational designs to defy aging.

  20. Strong resetting of the mammalian clock by constant light followed by constant darkness

    PubMed Central

    Chen, Rongmin; Seo, Dong-oh; Bell, Elijah; von Gall, Charlotte; Lee, Choogon

    2008-01-01

    The mammalian molecular circadian clock in the suprachiasmatic nuclei (SCN) regulates locomotor activity rhythms as well as clocks in peripheral tissues (Reppert and Weaver, 2002; Ko and Takahashi, 2006). Constant light (LL) can induce behavioral and physiological arrhythmicity, by desynchronizing clock cells in the SCN (Ohta et al., 2005). We examined how the disordered clock cells resynchronize by probing the molecular clock and measuring behavior in mice transferred from LL to constant darkness (DD). The circadian locomotor activity rhythms disrupted in LL become robustly rhythmic again from the beginning of DD, and the starting phase of the rhythm in DD is specific, not random, suggesting that the desynchronized clock cells are quickly reset in an unconventional manner by the L:D transition. By measuring mPERIOD protein rhythms, we showed that the SCN and peripheral tissue clocks quickly become rhythmic again in phase with the behavioral rhythms. We propose that this resetting mechanism may be different from conventional phase shifting, which involves light-induction of Period genes (Albrecht et al., 1997; Shearman et al., 1997; Shigeyoshi et al., 1997). Using our functional insights, we could shift the circadian phase of locomotor activity rhythms by 12 hours using a 15-hour LL treatment: essentially producing phase reversal by a single light pulse, a feat that has not been reported previously in wild-type mice and that has potential clinical utility. PMID:19005049

  1. Role of cardiomyocyte circadian clock in myocardial metabolic adaptation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Marked circadian rhythmicities in cardiovascular physiology and pathophysiology exist. The cardiomyocyte circadian clock has recently been linked to circadian rhythms in myocardial gene expression, metabolism, and contractile function. For instance, the cardiomyocyte circadian clock is essential f...

  2. Cryptochromes Define a Novel Circadian Clock Mechanism in Monarch Butterflies That May Underlie Sun Compass Navigation

    PubMed Central

    Zhu, Haisun; Sauman, Ivo; Yuan, Quan; Casselman, Amy; Emery-Le, Myai; Emery, Patrick; Reppert, Steven M

    2008-01-01

    The circadian clock plays a vital role in monarch butterfly (Danaus plexippus) migration by providing the timing component of time-compensated sun compass orientation, a process that is important for successful navigation. We therefore evaluated the monarch clockwork by focusing on the functions of a Drosophila-like cryptochrome (cry), designated cry1, and a vertebrate-like cry, designated cry2, that are both expressed in the butterfly and by placing these genes in the context of other relevant clock genes in vivo. We found that similar temporal patterns of clock gene expression and protein levels occur in the heads, as occur in DpN1 cells, of a monarch cell line that contains a light-driven clock. CRY1 mediates TIMELESS degradation by light in DpN1 cells, and a light-induced TIMELESS decrease occurs in putative clock cells in the pars lateralis (PL) in the brain. Moreover, monarch cry1 transgenes partially rescue both biochemical and behavioral light-input defects in cryb mutant Drosophila. CRY2 is the major transcriptional repressor of CLOCK:CYCLE-mediated transcription in DpN1 cells, and endogenous CRY2 potently inhibits transcription without involvement of PERIOD. CRY2 is co-localized with clock proteins in the PL, and there it translocates to the nucleus at the appropriate time for transcriptional repression. We also discovered CRY2-positive neural projections that oscillate in the central complex. The results define a novel, CRY-centric clock mechanism in the monarch in which CRY1 likely functions as a blue-light photoreceptor for entrainment, whereas CRY2 functions within the clockwork as the transcriptional repressor of a negative transcriptional feedback loop. Our data further suggest that CRY2 may have a dual role in the monarch butterfly's brain—as a core clock element and as an output that regulates circadian activity in the central complex, the likely site of the sun compass. PMID:18184036

  3. Cryptochromes define a novel circadian clock mechanism in monarch butterflies that may underlie sun compass navigation.

    PubMed

    Zhu, Haisun; Sauman, Ivo; Yuan, Quan; Casselman, Amy; Emery-Le, Myai; Emery, Patrick; Reppert, Steven M

    2008-01-01

    The circadian clock plays a vital role in monarch butterfly (Danaus plexippus) migration by providing the timing component of time-compensated sun compass orientation, a process that is important for successful navigation. We therefore evaluated the monarch clockwork by focusing on the functions of a Drosophila-like cryptochrome (cry), designated cry1, and a vertebrate-like cry, designated cry2, that are both expressed in the butterfly and by placing these genes in the context of other relevant clock genes in vivo. We found that similar temporal patterns of clock gene expression and protein levels occur in the heads, as occur in DpN1 cells, of a monarch cell line that contains a light-driven clock. CRY1 mediates TIMELESS degradation by light in DpN1 cells, and a light-induced TIMELESS decrease occurs in putative clock cells in the pars lateralis (PL) in the brain. Moreover, monarch cry1 transgenes partially rescue both biochemical and behavioral light-input defects in cry(b) mutant Drosophila. CRY2 is the major transcriptional repressor of CLOCK:CYCLE-mediated transcription in DpN1 cells, and endogenous CRY2 potently inhibits transcription without involvement of PERIOD. CRY2 is co-localized with clock proteins in the PL, and there it translocates to the nucleus at the appropriate time for transcriptional repression. We also discovered CRY2-positive neural projections that oscillate in the central complex. The results define a novel, CRY-centric clock mechanism in the monarch in which CRY1 likely functions as a blue-light photoreceptor for entrainment, whereas CRY2 functions within the clockwork as the transcriptional repressor of a negative transcriptional feedback loop. Our data further suggest that CRY2 may have a dual role in the monarch butterfly's brain-as a core clock element and as an output that regulates circadian activity in the central complex, the likely site of the sun compass.

  4. Influence of night-shift and napping at work on urinary melatonin, 17-β-estradiol and clock gene expression in pre-menopausal nurses.

    PubMed

    Bracci, M; Copertaro, A; Manzella, N; Staffolani, S; Strafella, E; Nocchi, L; Barbaresi, M; Copertaro, B; Rapisarda, V; Valentino, M; Santarelli, L

    2013-01-01

    Night-workers experience disruption of the sleep-wake cycle and light at night which may increase breast cancer risk by suppressing the nocturnal melatonin surge, resulting in higher levels of circulating estrogens. Night-work may also deregulate peripheral clock genes which have been found to be altered in breast cancer. This study investigated urinary 6-sulfatoxymelatonin (aMT6s), serum 17-beta-estradiol levels in premenopausal shift nurses at the end of the night-shift compared to a control group of daytime nurses. Peripheral clock gene expression in lymphocytes were also investigated. All participants were sampled in the follicular phase of the menstrual cycle. The effect of nurses’ ability to take a short nap during the night-shift was also explored. The shift-work group had significantly lower aMT6s levels than daytime nurses independently of a nap. Night-shift napping significantly influences 17-beta-estradiol levels resulting in higher outcomes in nurses who do not take a nap compared to napping group and daytime workers. Peripheral clock genes expression investigated was not significantly different among the groups. Our findings suggest that shift nurses experience changes in aMT6s levels after a night-shift. Napping habits influence 17-beta-estradiol levels at the end of a night-shift. These findings might be related to the increased cancer risk reported in night-shift workers and suggest that a short nap during night-shifts may exert a positive effect.

  5. Cellular circadian clocks in mood disorders.

    PubMed

    McCarthy, Michael J; Welsh, David K

    2012-10-01

    Bipolar disorder (BD) and major depressive disorder (MDD) are heritable neuropsychiatric disorders associated with disrupted circadian rhythms. The hypothesis that circadian clock dysfunction plays a causal role in these disorders has endured for decades but has been difficult to test and remains controversial. In the meantime, the discovery of clock genes and cellular clocks has revolutionized our understanding of circadian timing. Cellular circadian clocks are located in the suprachiasmatic nucleus (SCN), the brain's primary circadian pacemaker, but also throughout the brain and peripheral tissues. In BD and MDD patients, defects have been found in SCN-dependent rhythms of body temperature and melatonin release. However, these are imperfect and indirect indicators of SCN function. Moreover, the SCN may not be particularly relevant to mood regulation, whereas the lateral habenula, ventral tegmentum, and hippocampus, which also contain cellular clocks, have established roles in this regard. Dysfunction in these non-SCN clocks could contribute directly to the pathophysiology of BD/MDD. We hypothesize that circadian clock dysfunction in non-SCN clocks is a trait marker of mood disorders, encoded by pathological genetic variants. Because network features of the SCN render it uniquely resistant to perturbation, previous studies of SCN outputs in mood disorders patients may have failed to detect genetic defects affecting non-SCN clocks, which include not only mood-regulating neurons in the brain but also peripheral cells accessible in human subjects. Therefore, reporters of rhythmic clock gene expression in cells from patients or mouse models could provide a direct assay of the molecular gears of the clock, in cellular clocks that are likely to be more representative than the SCN of mood-regulating neurons in patients. This approach, informed by the new insights and tools of modern chronobiology, will allow a more definitive test of the role of cellular circadian clocks

  6. Effects of aging and genotype on circadian rhythms, sleep, and clock gene expression in APPxPS1 knock-in mice, a model for Alzheimer's disease.

    PubMed

    Duncan, Marilyn J; Smith, J Tyler; Franklin, Kathleen M; Beckett, Tina L; Murphy, M Paul; St Clair, Daret K; Donohue, Kevin D; Striz, Martin; O'Hara, Bruce F

    2012-08-01

    Profound disruptions of circadian rhythms and sleep/wake cycles constitute a major cause of institutionalization of AD patients. This study investigated whether a rodent model of AD, APP(NLH/NLH)/PS-1(P264L/264L) (APPxPS1) mice, exhibits circadian alterations. The APPxPS1 mice were generated using CD-1/129 mice and Cre-lox knock-in technology to "humanize" the mouse amyloid (A)β sequence and create a presenilin-1 mutation identified in familial early-onset AD patients. APPxPS1 and WT mice of several ages (~4, 11, and 15 months) were monitored for circadian rhythms in wheel running, cage activity, and sleep:wake behavior. After rhythm assessment, the mice were euthanized at zeitgeber time (ZT) 2 or 10 (i.e., 2 or 10 h after lights-on) and brains were dissected. Amyloidβ levels were measured in cortical samples and brain sections of the hypothalamus and hippocampus were prepared and used for in situ hybridization of circadian or neuropeptide genes. The most significant effects of the APPxPS1 transgenes were phase delays of ~2 h in the onset of daytime wakefulness bouts (P<0.005) and peak wakefulness (P<0.02), potentially relevant to phase delays previously reported in AD patients. However, genotype did not affect the major activity peaks or phases of wheel running, wake, or general movement, which were bimodal with dominant dawn and dusk activity. Expression of Period 2 in the suprachiasmatic nucleus was affected by ZT (P<0.0001) with a marginal interaction effect of age, genotype, and ZT (P<0.08). A separate analysis of the old animals indicated a robust interaction between ZT and genotype, as well as main effects of these parameters. Aging also altered sleep (e.g., bout length and amount of daytime sleep) and the amount of wheel running and cage activity. In conclusion, the APPxPS1 knock-in mice exhibit some alterations in their sleep:wake rhythm and clock gene expression, but do not show robust, genotype-related changes in activity rhythms. The prominent daytime

  7. Reciprocal interaction of the circadian clock with the iron homeostasis network in Arabidopsis.

    PubMed

    Hong, Sunghyun; Kim, Sun A; Guerinot, Mary Lou; McClung, C Robertson

    2013-02-01

    In plants, iron (Fe) uptake and homeostasis are critical for survival, and these processes are tightly regulated at the transcriptional and posttranscriptional levels. Circadian clocks are endogenous oscillating mechanisms that allow an organism to anticipate environmental changes to coordinate biological processes both with one another and with the environmental day/night cycle. The plant circadian clock controls many physiological processes through rhythmic expression of transcripts. In this study, we examined the expression of three Fe homeostasis genes (IRON REGULATED TRANSPORTER1 [IRT1], BASIC HELIX LOOP HELIX39, and FERRITIN1) in Arabidopsis (Arabidopsis thaliana) using promoter:LUCIFERASE transgenic lines. Each of these promoters showed circadian regulation of transcription. The circadian clock monitors a number of clock outputs and uses these outputs as inputs to modulate clock function. We show that this is also true for Fe status. Fe deficiency results in a lengthened circadian period. We interrogated mutants impaired in the Fe homeostasis response, including irt1-1, which lacks the major high-affinity Fe transporter, and fit-2, which lacks Fe deficiency-induced TRANSCRIPTION FACTOR1, a basic helix-loop-helix transcription factor necessary for induction of the Fe deficiency response. Both mutants exhibit symptoms of Fe deficiency, including lengthened circadian period. To determine which components are involved in this cross talk between the circadian and Fe homeostasis networks, we tested clock- or Fe homeostasis-related mutants. Mutants defective in specific clock gene components were resistant to the change in period length under different Fe conditions observed in the wild type, suggesting that these mutants are impaired in cross talk between Fe homeostasis and the circadian clock.

  8. Pacemaker-neuron–dependent disturbance of the molecular clockwork by a Drosophila CLOCK mutant homologous to the mouse Clock mutation

    PubMed Central

    Lee, Euna; Cho, Eunjoo; Kang, Doo Hyun; Jeong, Eun Hee; Chen, Zheng; Yoo, Seung-Hee; Kim, Eun Young

    2016-01-01

    Circadian clocks are composed of transcriptional/translational feedback loops (TTFLs) at the cellular level. In Drosophila TTFLs, the transcription factor dCLOCK (dCLK)/CYCLE (CYC) activates clock target gene expression, which is repressed by the physical interaction with PERIOD (PER). Here, we show that amino acids (AA) 657–707 of dCLK, a region that is homologous to the mouse Clock exon 19-encoded region, is crucial for PER binding and E-box–dependent transactivation in S2 cells. Consistently, in transgenic flies expressing dCLK with an AA657–707 deletion in the Clock (Clkout) genetic background (p{dClk-Δ};Clkout), oscillation of core clock genes’ mRNAs displayed diminished amplitude compared with control flies, and the highly abundant dCLKΔ657–707 showed significantly decreased binding to PER. Behaviorally, the p{dClk-Δ};Clkout flies exhibited arrhythmic locomotor behavior in the photic entrainment condition but showed anticipatory activities of temperature transition and improved free-running rhythms in the temperature entrainment condition. Surprisingly, p{dClk-Δ};Clkout flies showed pacemaker-neuron–dependent alterations in molecular rhythms; the abundance of dCLK target clock proteins was reduced in ventral lateral neurons (LNvs) but not in dorsal neurons (DNs) in both entrainment conditions. In p{dClk-Δ};Clkout flies, however, strong but delayed molecular oscillations in temperature cycle-sensitive pacemaker neurons, such as DN1s and DN2s, were correlated with delayed anticipatory activities of temperature transition. Taken together, our study reveals that the LNv molecular clockwork is more sensitive than the clockwork of DNs to dysregulation of dCLK by AA657–707 deletion. Therefore, we propose that the dCLK/CYC-controlled TTFL operates differently in subsets of pacemaker neurons, which may contribute to their specific functions. PMID:27489346

  9. Circadian clock regulates response to pesticides in Drosophila via conserved Pdp1 pathway.

    PubMed

    Beaver, Laura Michelle; Hooven, Louisa Ada; Butcher, Shawn Michael; Krishnan, Natraj; Sherman, Katherine Alice; Chow, Eileen Shin-Yeu; Giebultowicz, Jadwiga Maria

    2010-06-01

    Daily rhythms generated by the circadian clock regulate many life functions, including responses to xenobiotic compounds. In Drosophila melanogaster, the circadian clock consists of positive elements encoded by cycle (cyc) and Clock (Clk) and negative elements encoded by period (per) and timeless (tim) genes. The epsilon-isoform of the PAR-domain protein 1 (Pdp1epsilon) transcription factor is controlled by positive clock elements and regulates daily locomotor activity rhythms. Pdp1 target genes have not been identified, and its involvement in other clock output pathways is not known. Mammalian orthologs of Pdp1 have been implicated in the regulation of xenobiotic metabolism; therefore, we asked whether Pdp1 has a similar role in the fly. Using pesticides as model toxicants, we determined that disruption of Pdp1epsilon increased pesticide-induced mortality in flies. Flies deficient for cyc also showed increased mortality, while disruption of per and tim had no effect. Day/night and Pdp1-dependent differences in the expression of xenobiotic-metabolizing enzymes Cyp6a2, Cyp6g1, and alpha-Esterase-7 were observed and likely contribute to impaired detoxification. DHR96, a homolog of constitutive androstane receptor and pregnane X receptor, is involved in pesticide response, and DHR96 expression decreased when Pdp1 was suppressed. Taken together, our data uncover a pathway from the positive arm of the circadian clock through Pdp1 to detoxification effector genes, demonstrating a conserved role of the circadian system in modulating xenobiotic toxicity.

  10. Tissue-specific circadian clocks in plants.

    PubMed

    Endo, Motomu

    2016-02-01

    Circadian clocks affect a large proportion of differentially expressed genes in many organisms. Tissue-specific hierarchies in circadian networks in mammals have been contentiously debated, whereas little attention has been devoted to the concept in plants, owing to technical difficulties. Recently, several studies have demonstrated tissue-specific circadian clocks and their coupling in plants, suggesting that plants possess a hierarchical network of circadian clocks. The following review summarizes recent studies describing the tissue-specific functions and properties of these circadian clocks and discusses the network structure and potential messengers that might share temporal information on such a network.

  11. Independence of genetic geographical variation between photoperiodic diapause, circadian eclosion rhythm, and Thr-Gly repeat region of the period gene in Drosophila littoralis.

    PubMed

    Lankinen, P; Forsman, P

    2006-02-01

    Drosophila littoralis is a latitudinally widespread European species of the Drosophila virilis group. The species has ample genetic variation in photoperiodism (adult diapause) and circadian rhythmicity (pupal eclosion rhythm), with adaptive latitudinal clines in both of them. The possible common genetic basis between the variability of photoperiodism and circadian rhythms was studied by a long-term crossing experiment. A northern strain (65 degrees N) having long critical day length (CDL = 19.9 h) for diapause, early phase of the entrained rhythm in LD 3:21 (psi(LD3:21) = 12.3 h), and short period (tau= 18.8 h) of the free-running rhythm for the eclosion rhythm was crossed with a southern strain (42 degrees N) having short CDL (12.4 h), late eclosion phase (psi(LD3:21) = 20.2 h), and long period (tau= 22.8 h). After 54 generations, including free recombination, artificial selection, and genetic drift, a novel strain resulted, having even more "southern" diapause and more "northern" eclosion rhythm characteristics than found in any of the geographical strains. The observed complete separation of eclosion rhythm characteristics from photoperiodism is a new finding in D. littoralis; in earlier studies followed for 16 generations, the changes had been mostly parallel. Evidently, the genes controlling the variability of the eclosion rhythm and photoperiodism in D. littoralis are different but closely linked. To test for the possible gene loci underlying the observed geographical variability, the period gene was studied in 10 strains covering all the known clock variability in D. littoralis. The authors sequenced the most suspected Thr-Gly region, which is known to take part in the adaptive clock variability in Drosophila melanogaster. No coding differences were found in the strains, showing that this region is not included in the adaptive clock variability in D. littoralis.

  12. JcDof1, a Dof transcription factor gene, is associated with the light-mediated circadian clock in Jatropha curcas.

    PubMed

    Yang, Jing; Yang, Ming-Feng; Wang, Dan; Chen, Fan; Shen, Shi-Hua

    2010-07-01

    Jatropha curcas is an economically important plant in terms of its seed oil. However, the molecular mechanisms underlying this plant response to light signals are unknown. One group of DNA-binding with one finger (Dof) transcription factor genes exhibits circadian rhythms and plays a crucial role in the control of flowering time by photoperiod perception in plants. In the present study, a full-length cDNA designated JcDof1, containing a conserved Dof-DNA-binding domain, was isolated from J. curcas seedlings by yeast one hybrid library. Subcellular localization assays and yeast one hybrid systems confirmed that JcDof1 was localized to the onion epidermal cell nucleus, and exhibited DNA-binding and transcriptional activation activities in yeast. The JcDof1 expression was characterized by a circadian-clock oscillation under long day, short day and continuous light conditions, whereas in the etiolated cotyledons under continuous dark conditions, JcDof1 expression remained at relatively basal levels. Red and blue light downregulated the JcDof1 expression, but this effect was not observed under far-red light. Taken together, these results suggested that JcDof1 was a circadian clock-Dof transcription factor gene responding to light signals.

  13. A Mathematical Model of the Liver Circadian Clock Linking Feeding and Fasting Cycles to Clock Function.

    PubMed

    Woller, Aurore; Duez, Hélène; Staels, Bart; Lefranc, Marc

    2016-10-18

    To maintain energy homeostasis despite variable energy supply and consumption along the diurnal cycle, the liver relies on a circadian clock synchronized to food timing. Perturbed feeding and fasting cycles have been associated with clock disruption and metabolic diseases; however, the mechanisms are unclear. To address this question, we have constructed a mathematical model of the mammalian circadian clock, incorporating the metabolic sensors SIRT1 and AMPK. The clock response to various temporal patterns of AMPK activation was simulated numerically, mimicking the effects of a normal diet, fasting, and a high-fat diet. The model reproduces the dampened clock gene expression and NAD(+) rhythms reported for mice on a high-fat diet and predicts that this effect may be pharmacologically rescued by timed REV-ERB agonist administration. Our model thus identifies altered AMPK signaling as a mechanism leading to clock disruption and its associated metabolic effects and suggests a pharmacological approach to resetting the clock in obesity.

  14. A PTH-responsive circadian clock operates in ex vivo mouse femur fracture healing site.

    PubMed

    Kunimoto, Tatsuya; Okubo, Naoki; Minami, Yoichi; Fujiwara, Hiroyoshi; Hosokawa, Toshihiro; Asada, Maki; Oda, Ryo; Kubo, Toshikazu; Yagita, Kazuhiro

    2016-02-29

    The circadian clock contains clock genes including Bmal1 and Period2, and it maintains an interval rhythm of approximately 24 hours (the circadian rhythm) in various organs including growth plate and articular cartilage. As endochondral ossification is involved not only in growth plate but also in fracture healing, we investigated the circadian clock functions in fracture sites undergoing healing. Our fracture models using external fixation involved femurs of Period2::Luciferase knock-in mice which enables the monitoring of endogenous circadian clock state via bioluminescence. Organ culture was performed by collecting femurs, and fracture sites were observed using bioluminescence imaging systems. Clear bioluminescence rhythms of 24-hour intervals were revealed in fracture healing sites. When parathyroid hormone (PTH) was administered to fractured femurs in organ culture, peak time of Period2::Luciferase activity in fracture sites and growth plates changed, indicating that PTH-responsive circadian clock functions in the mouse femur fracture healing site. While PTH is widely used in treating osteoporosis, many studies have reported that it contributes to improvement of fracture healing. Future studies of the role of this local clock in wound healing may reveal a novel function of the circadian timing mechanism in skeletal cells.

  15. Comparative analysis of teleost fish genomes reveals preservation of different ancient clock duplicates in different fishes.

    PubMed

    Wang, Han

    2008-06-01

    Clock (Circadian locomotor output cycle kaput) was the first vertebrate circadian clock gene identified in a mouse forward genetics mutagenesis screen. It encodes a bHLH-PAS protein that is highly conserved throughout evolution. Tetrapods also have the second Clock gene, Clock2 or Npas2 (Neuronal PAS domain protein 2). Conversely, the fruit fly, an invertebrate, has only one clock gene. Interrogation of the five teleost fish genome databases revealed that the zebrafish and the Japanese pufferfish (fugu) each have three clock genes, whereas the green spotted pufferfish (tetraodon), the Japanese medaka fish and the three-spine stickleback each have two clock genes. Phylogenetic and splice site analyses indicated that zebrafish and fugu each have two clock1 genes, clock1a and clock1b and one clock2; tetraodon also have clock1a and clock1b but do not have clock2; and medaka and stickleback each have clock1b and one clock2. Genome neighborhood analysis further showed that clock1a/clock1b in zebrafish, fugu and tetraodon is an ancient duplicate. While the dN/dS ratios of these three fish clock duplicates are all <1, indicating that purifying selection has acted upon them; the Tajima relative rate test showed that all three fish clock duplicates have asymmetric evolutionary rates, implicating that one of these duplicates have been under positive selection or relaxed functional constraint. These results support the view that teleost fish clock genes were generated from an ancient genome-wide duplication, and differential gene loss after the duplication resulted in retention of different ancient duplicates in different teleost fishes, which could have contributed to the evolution of the distinct fish circadian clock mechanisms.

  16. Evolutionary links between circadian clocks and photoperiodic diapause in insects.

    PubMed

    Meuti, Megan E; Denlinger, David L

    2013-07-01

    In this article, we explore links between circadian clocks and the clock involved in photoperiodic regulation of diapause in insects. Classical resonance (Nanda-Hamner) and night interruption (Bünsow) experiments suggest a circadian basis for the diapause response in nearly all insects that have been studied. Neuroanatomical studies reveal physical connections between circadian clock cells and centers controlling the photoperiodic diapause response, and both mutations and knockdown of clock genes with RNA interference (RNAi) point to a connection between the clock genes and photoperiodic induction of diapause. We discuss the challenges of determining whether the clock, as a functioning module, or individual clock genes acting pleiotropically are responsible for the photoperiodic regulation of diapause, and how a stable, central circadian clock could be linked to plastic photoperiodic responses without compromising the clock's essential functions. Although we still lack an understanding of the exact mechanisms whereby insects measure day/night length, continued classical and neuroanatomical approaches, as well as forward and reverse genetic experiments, are highly complementary and should enable us to decipher the diverse ways in which circadian clocks have been involved in the evolution of photoperiodic induction of diapause in insects. The components of circadian clocks vary among insect species, and diapause appears to have evolved independently numerous times, thus, we anticipate that not all photoperiodic clocks of insects will interact with circadian clocks in the same fashion.

  17. Evidence for the circadian gene period as a proximate mechanism of protandry in a pollinating fig wasp.

    PubMed

    Gu, Hai-Feng; Xiao, Jin-Hua; Dunn, Derek W; Niu, Li-Ming; Wang, Bo; Jia, Ling-Yi; Huang, Da-Wei

    2014-03-01

    Protandry in insects is the tendency for adult males to emerge before females and usually results from intra-sexual selection. However, the genetic basis of this common phenomenon is poorly understood. Pollinating fig wasp (Agaonidae) larvae develop in galled flowers within the enclosed inflorescences ('figs') of fig trees. Upon emergence, males locate and mate with the still galled females. After mating, males release females from their galls to enable dispersal. Females cannot exit galls or disperse from a fig without male assistance. We sampled male and female Ceratosolen solmsi (the pollinator of Ficus hispida) every 3 h over a 24 h emergence period, and then measured the expression of five circadian genes: period (per), clock (clk), cycle (cyc), pigment-dispersing factor (pdf) and clockwork orange (cwo). We found significant male-biased sexual dimorphism in the expression of all five genes. per showed the greatest divergence between the sexes and was the only gene rhythmically expressed. Expression of per correlated closely with emergence rates at specific time intervals in both male and female wasps. We suggest that this rhythmical expression of per may be a proximate mechanism of protandry in this species.

  18. Plastic oscillators and fixed rhythms: changes in the phase of clock-gene rhythms in the PVN are not reflected in the phase of the melatonin rhythm of grass rats.

    PubMed

    Martin-Fairey, C A; Ramanathan, C; Stowie, A; Walaszczyk, E; Smale, L; Nunez, A A

    2015-03-12

    The same clock-genes, including Period (PER) 1 and 2, that show rhythmic expression in the suprachiasmatic nucleus (SCN) are also rhythmically expressed in other brain regions that serve as extra-SCN oscillators. Outside the hypothalamus, the phase of these extra-SCN oscillators appears to be reversed when diurnal and nocturnal mammals are compared. Based on mRNA data, PER1 protein is expected to peak in the late night in the paraventricular nucleus of the hypothalamus (PVN) of nocturnal laboratory rats, but comparable data are not available for a diurnal species. Here we use the diurnal grass rat (Arvicanthis niloticus) to describe rhythms of PER1 and 2 proteins in the PVN of animals that either show the species-typical day-active (DA) profile, or that adopt a night-active (NA) profile when given access to running wheels. For DA animals housed with or without wheels, significant rhythms of PER1 or PER2 protein expression featured peaks in the late morning; NA animals showed patterns similar to those expected from nocturnal laboratory rats. Since the PVN is part of the circuit that controls pineal rhythms, we also measured circulating levels of melatonin during the day and night in DA animals with and without wheels and in NA wheel runners. All three groups showed elevated levels of melatonin at night, with higher levels during both the day and night being associated with the levels of activity displayed by each group. The differential phase of rhythms in the clock-gene protein in the PVN of diurnal and nocturnal animals presents a possible mechanism for explaining species differences in the phase of autonomic rhythms controlled, in part, by the PVN. The present study suggests that the phase of the oscillator of the PVN does not determine that of the melatonin rhythm in diurnal and nocturnal species or in diurnal and nocturnal chronotypes within a species.

  19. Plastic oscillators and fixed rhythms: Changes in the phase of clock-gene rhythms in the PVN are not reflected in the phase of the melatonin rhythm of grass rats

    PubMed Central

    Martin-Fairey, Carmel A.; Ramanathan, Chidambaram; Stowie, Adam; Walaszczyk, Erin; Smale, Laura; Nunez, Antonio A.

    2015-01-01

    The same clock-genes, including Period (PER) 1 and 2, that show rhythmic expression in the suprachiasmatic nucleus (SCN) are also rhythmically expressed in other brain regions that serve as extra-SCN oscillators. Outside the hypothalamus, the phase of these extra-SCN oscillators appears to be reversed when diurnal and nocturnal mammals are compared. Based on mRNA data, PER1 protein is expected to peak in the late night in the paraventricular nucleus of the hypothalamus (PVN) of nocturnal laboratory rats, but comparable data are not available for a diurnal species. Here we use the diurnal grass rat (Arvicanthis niloticus) to describe rhythms of PER1 and 2 protein in the PVN of animals that either show the species-typical day-active profile, or that adopt a night-active profile when given access to running wheels. For day-active animals housed with or without wheels, significant rhythms of PER1 or PER2 protein expression featured peaks in the late morning; night-active animals showed patterns similar to those expected from nocturnal laboratory rats. Since the PVN is part of the circuit that controls pineal rhythms, we also measured circulating levels of melatonin during the day and night in day-active animals with and without wheels and in night-active wheel runners. All three groups showed elevated levels of melatonin at night, with higher levels during both the day and night being associated with the levels of activity displayed by each group. The differential phase of rhythms in clock-gene protein in the PVN of diurnal and nocturnal animals presents a possible mechanism for explaining species differences in the phase of autonomic rhythms controlled, in part, by the PVN. The present study suggests that the phase of the oscillator of the PVN does not determine that of the melatonin rhythm in diurnal and nocturnal species or in diurnal and nocturnal chronotypes within a species. PMID:25575946

  20. SKIP Is a Component of the Spliceosome Linking Alternative Splicing and the Circadian Clock in Arabidopsis[W

    PubMed Central

    Wang, Xiaoxue; Wu, Fangming; Xie, Qiguang; Wang, Huamei; Wang, Ying; Yue, Yanling; Gahura, Ondrej; Ma, Shuangshuang; Liu, Lei; Cao, Ying; Jiao, Yuling; Puta, Frantisek; McClung, C. Robertson; Xu, Xiaodong; Ma, Ligeng

    2012-01-01

    Circadian clocks generate endogenous rhythms in most organisms from cyanobacteria to humans and facilitate entrainment to environmental diurnal cycles, thus conferring a fitness advantage. Both transcriptional and posttranslational mechanisms are prominent in the basic network architecture of circadian systems. Posttranscriptional regulation, including mRNA processing, is emerging as a critical step for clock function. However, little is known about the molecular mechanisms linking RNA metabolism to the circadian clock network. Here, we report that a conserved SNW/Ski-interacting protein (SKIP) domain protein, SKIP, a splicing factor and component of the spliceosome, is involved in posttranscriptional regulation of circadian clock genes in Arabidopsis thaliana. Mutation in SKIP lengthens the circadian period in a temperature-sensitive manner and affects light input and the sensitivity of the clock to light resetting. SKIP physically interacts with the spliceosomal splicing factor Ser/Arg-rich protein45 and associates with the pre-mRNA of clock genes, such as PSEUDORESPONSE REGULATOR7 (PRR7) and PRR9, and is necessary for the regulation of their alternative splicing and mRNA maturation. Genome-wide investigations reveal that SKIP functions in regulating alternative splicing of many genes, presumably through modulating recognition or cleavage of 5′ and 3′ splice donor and acceptor sites. Our study addresses a fundamental question on how the mRNA splicing machinery contributes to circadian clock function at a posttranscriptional level. PMID:22942380

  1. Fast Clock Recovery for Digital Communications

    NASA Technical Reports Server (NTRS)

    Tell, R. G.

    1985-01-01

    Circuit extracts clock signal from random non-return-to-zero data stream, locking onto clock within one bit period at 1-gigabitper-second data rate. Circuit used for synchronization in opticalfiber communications. Derives speed from very short response time of gallium arsenide metal/semiconductor field-effect transistors (MESFET's).

  2. Heterologous protein-DNA interactions lead to biased allelic expression of circadian clock genes in interspecific hybrids

    PubMed Central

    Ng, Danny W-K.; Chen, Helen H. Y.; Chen, Z. Jeffrey

    2017-01-01

    Genomic interactions in allopolyploids create expression variation of homoeologous alleles through protein-protein and protein-DNA interactions. However, the molecular basis for this is largely unknown. Here we investigated the protein-protein and protein-DNA interactions among homoeologous transcription factors in the circadian-clock feedback loop, consisting of CCA1 HIKING EXPEDITION (CHE), CIRCADIAN CLOCK ASSOCIATED1 (CCA1), and TIMING OF CAB EXPRESSION1 (TOC1), plus the interaction with a chromatin factor, HISTONE DEACETYLASE1 (HD1). In the allotetraploids formed between A. thaliana (At) and Arabidopsis arenosa (Aa), AtCCA1 is expressed at lower levels than AaCCA1, which could alter clock output traits. The reduced AtCCA1 expressions in the allotetraploids are consistent with the biochemical data that AaCHE showed preferential binding to the AtCCA1 promoter, in which AaCHE interacts with a higher affinity to AtHD1 than AtCHE. AaCHE also showed a higher affinity to TOC1 than AtCHE, consistent with the effect of TOC1 on repressing CCA1. Thus, stronger AaCHE-TOC1 and AaCHE-AtHD1 interactions reduce AtCC1 allelic expression. Our current data suggest a biochemical basis for protein interactions in trans with a preference to the cis-acting elements in heterologous combinations to reduce AtCCA1 expression, while altered CCA1 expression has been shown to affect metabolic and biomass heterosis in interspecific hybrids or allotetraploids. PMID:28345627

  3. Warming Up Your Tick-Tock: Temperature-Dependent Regulation of Circadian Clocks.

    PubMed

    Ki, Yoonhee; Ri, Hwajung; Lee, Hoyeon; Yoo, Eunseok; Choe, Joonho; Lim, Chunghun

    2015-10-01

    Circadian clocks are endogenous time-keeping mechanisms to adaptively coordinate animal behaviors and physiology with daily environmental changes. So far many circadian studies in model organisms have identified evolutionarily conserved molecular frames of circadian clock genes in the context of transcription-translation feedback loops. The molecular clockwork drives cell-autonomously cycling gene expression with ~24-hour periodicity, which is fundamental to circadian rhythms. Light and temperature are two of the most potent external time cues to reset the circadian phase of the internal clocks, yet relatively little is known about temperature-relevant clock regulation. In this review, we describe recent findings on temperature-dependent clock mechanisms in homeothermic mammals as compared with poikilothermic Drosophila at molecular, neural, and organismal levels. We propose thermodynamic transitions in RNA secondary structures might have been potent substrates for the molecular evolution of temperature-relevant post-transcriptional mechanisms. Future works should thus validate the potential involvement of specific post-transcriptional steps in temperature-dependent plasticity of circadian clocks.

  4. Molecular clock is involved in predictive circadian adjustment of renal function

    PubMed Central

    Zuber, Annie Mercier; Centeno, Gabriel; Pradervand, Sylvain; Nikolaeva, Svetlana; Maquelin, Lionel; Cardinaux, Léonard; Bonny, Olivier; Firsov, Dmitri

    2009-01-01

    Renal excretion of water and major electrolytes exhibits a significant circadian rhythm. This functional periodicity is believed to result, at least in part, from circadian changes in secretion/reabsorption capacities of the distal nephron and collecting ducts. Here, we studied the molecular mechanisms underlying circadian rhythms in the distal nephron segments, i.e., distal convoluted tubule (DCT) and connecting tubule (CNT) and the cortical collecting duct (CCD). Temporal expression analysis performed on microdissected mouse DCT/CNT or CCD revealed a marked circadian rhythmicity in the expression of a large number of genes crucially involved in various homeostatic functions of the kidney. This analysis also revealed that both DCT/CNT and CCD possess an intrinsic circadian timing system characterized by robust oscillations in the expression of circadian core clock genes (clock, bma11, npas2, per, cry, nr1d1) and clock-controlled Par bZip transcriptional factors dbp, hlf, and tef. The clock knockout mice or mice devoid of dbp/hlf/tef (triple knockout) exhibit significant changes in renal expression of several key regulators of water or sodium balance (vasopressin V2 receptor, aquaporin-2, aquaporin-4, αENaC). Functionally, the loss of clock leads to a complex phenotype characterized by partial diabetes insipidus, dysregulation of sodium excretion rhythms, and a significant decrease in blood pressure. Collectively, this study uncovers a major role of molecular clock in renal function. PMID:19805330

  5. Changes in Gene Expression Patterns of Circadian-Clock, Transient Receptor Potential Vanilloid-1 and Nerve Growth Factor in Inflamed Human Esophagus

    PubMed Central

    Yang, Shu-Chuan; Chen, Chien-Lin; Yi, Chih-Hsun; Liu, Tso-Tsai; Shieh, Kun-Ruey

    2015-01-01

    Circadian rhythm is driven by the molecular circadian-clock system and regulates many physiological functions. Diurnal rhythms in the gastrointestinal tract are known to be related to feeding pattern, but whether these rhythms are also related to the gastrointestinal damage or injuries; for example, gastroesophageal reflux disease (GERD), is unclear. This study was conducted to determine whether expression of circadian-clock genes or factors involved in vagal stimulation or sensitization were altered in the esophagus of GERD patients. Diurnal patterns of PER1, PER2, BMAL1, CRY2, TRPV1, and NGF mRNA expression were found in patient controls, and these patterns were altered and significantly correlated to the GERD severity in GERD patients. Although levels of CRY1, TIM, CB1, NHE3, GDNF, and TAC1 mRNA expression did not show diurnal patterns, they were elevated and also correlated with GERD severity in GERD patients. Finally, strong correlations among PER1, TRPV1, NGF and CRY2 mRNA expression, and among PER2, TRPV1 and CRY2 expression were found. Expression levels of CRY1 mRNA highly correlated with levels of TIM, CB1, NHE3, GDNF and TAC1. This study suggests that the circadian rhythm in the esophagus may be important for the mediation of and/or the response to erosive damage in GERD patients. PMID:26337663

  6. Ultradian feeding in mice not only affects the peripheral clock in the liver, but also the master clock in the brain.

    PubMed

    Sen, Satish; Raingard, Hélène; Dumont, Stéphanie; Kalsbeek, Andries; Vuillez, Patrick; Challet, Etienne

    2017-01-01

    Restricted feeding during the resting period causes pronounced shifts in a number of peripheral clocks, but not the central clock in the suprachiasmatic nucleus (SCN). By contrast, daily caloric restriction impacts also the light-entrained SCN clock, as indicated by shifted oscillations of clock (PER1) and clock-controlled (vasopressin) proteins. To determine if these SCN changes are due to the metabolic or timing cues of the restricted feeding, mice were challenged with an ultradian 6-meals schedule (1 food access every 4 h) to abolish the daily periodicity of feeding. Mice fed with ultradian feeding that lost <10% body mass (i.e. isocaloric) displayed 1.5-h phase-advance of body temperature rhythm, but remained mostly nocturnal, together with up-regulated vasopressin and down-regulated PER1 and PER2 levels in the SCN. Hepatic expression of clock genes (Per2, Rev-erbα, and Clock) and Fgf21 was, respectively, phase-advanced and up-regulated by ultradian feeding. Mice fed with ultradian feeding that lost >10% body mass (i.e. hypocaloric) became more diurnal, hypothermic in late night, and displayed larger (3.5 h) advance of body temperature rhythm, more reduced PER1 expression in the SCN, and further modified gene expression in the liver (e.g. larger phase-advance of Per2 and up-regulated levels of Pgc-1α). While glucose rhythmicity was lost under ultradian feeding, the phase of daily rhythms in liver glycogen and plasma corticosterone (albeit increased in amplitude) remained unchanged. In conclusion, the additional impact of hypocaloric conditions on the SCN are mainly due to the metabolic and not the timing effects of restricted daytime feeding.

  7. Abnormal clock gene expression and locomotor activity rhythms in two month-old female APPSwe/PS1dE9 mice.

    PubMed

    Oyegbami, Olaide; Collins, Hilary M; Pardon, Marie C; Ebling, Fran Jp; Heery, David M; Moran, Paula M

    2017-03-17

    In addition to cognitive decline, Alzheimer's disease (AD) is also characterized by agitation and disruptions in activity and sleep. These symptoms typically occur in the evening or at night and have been referred to as 'sundowning'. These symptoms are especially difficult for carers and there are no specific drug treatments. There is increasing evidence that these symptoms reflect an underlying pathology of circadian rhythm generation and transmission. We investigated whether a transgenic mouse model relevant to AD (APPswe/PS1dE9) exhibits circadian alterations in locomotor activity and expression of clock genes involved in the regulation of the circadian cycle. Female mice at 2 months of age were investigated in their home cage. Results show that the APPswe/PS1dE9 transgene alters levels and patterns in circadian rhythm of locomotor activity. Expression of the clock genes Per1, Per2, Cry1 and Cry2 was found to increase at night compared to day in wild-type control mice in the medulla/pons. This effect was blunted for Cry1 and Cry2 gene expression in APPswe/PS1dE9. In summary, this study suggests altered circadian regulation of locomotor activity is abnormal in female APPswe/PS1dE9 mice and that this alteration has biomolecular analogies in a widely available model of AD. Furthermore, the early age at which these effects are manifest suggests that these circadian effects may precede plaque development. The APPswe/PS1dE9 mouse genetic model may have potential to serve as a tool in understanding the neuropathology of circadian abnormalities in AD and as a model system to test novel therapeutic agents for these symptoms.

  8. Period-2: a tumor suppressor gene in breast cancer

    PubMed Central

    Xiang, Shulin; Coffelt, Seth B; Mao, Lulu; Yuan, Lin; Cheng, Qi; Hill, Steven M

    2008-01-01

    Previous reports have suggested that the ablation of the Period 2 gene (Per 2) leads to enhanced development of lymphoma and leukemia in mice. Employing immunoblot analyses, we have demonstrated that PER 2 is endogenously expressed in human breast epithelial cell lines but is not expressed or is expressed at significantly reduced level in human breast cancer cell lines. Expression of PER 2 in MCF-7 breast cancer cells significantly inhibited the growth of MCF-7 human breast cancer cells, and, when PER 2 was co-expressed with the Crytochrome 2 (Cry 2) gene, an even greater growth-inhibitory effect was observed. The inhibitory effect of PER 2 on breast cancer cells was also demonstrated by its suppression of the anchorage-independent growth of MCF-7 cells as evidenced by the reduced number and size of colonies. A corresponding blockade of MCF-7 cells in the G1 phase of the cell cycle was also observed in response to the expression of PER 2 alone or in combination with CRY 2. Expression of PER 2 also induced apoptosis of MCF-7 breast cancer cells as demonstrated by an increase in PARP [poly (ADP-ribose) polymerase] cleavage. Finally, our studies demonstrate that PER 2 expression in MCF-7 breast cancer cells is associated with a significant decrease in the expression of cyclin D1 and an up-regulation of p53 levels. PMID:18334030

  9. Period-2: a tumor suppressor gene in breast cancer.

    PubMed

    Xiang, Shulin; Coffelt, Seth B; Mao, Lulu; Yuan, Lin; Cheng, Qi; Hill, Steven M

    2008-03-11

    Previous reports have suggested that the ablation of the Period 2 gene (Per 2) leads to enhanced development of lymphoma and leukemia in mice. Employing immunoblot analyses, we have demonstrated that PER 2 is endogenously expressed in human breast epithelial cell lines but is not expressed or is expressed at significantly reduced level in human breast cancer cell lines. Expression of PER 2 in MCF-7 breast cancer cells significantly inhibited the growth of MCF-7 human breast cancer cells, and, when PER 2 was co-expressed with the Crytochrome 2 (Cry 2) gene, an even greater growth-inhibitory effect was observed. The inhibitory effect of PER 2 on breast cancer cells was also demonstrated by its suppression of the anchorage-independent growth of MCF-7 cells as evidenced by the reduced number and size of colonies. A corresponding blockade of MCF-7 cells in the G1 phase of the cell cycle was also observed in response to the expression of PER 2 alone or in combination with CRY 2. Expression of PER 2 also induced apoptosis of MCF-7 breast cancer cells as demonstrated by an increase in PARP [poly (ADP-ribose) polymerase] cleavage. Finally, our studies demonstrate that PER 2 expression in MCF-7 breast cancer cells is associated with a significant decrease in the expression of cyclin D1 and an up-regulation of p53 levels.

  10. Dual attenuation of proteasomal and autophagic BMAL1 degradation in Clock Δ19/+ mice contributes to improved glucose homeostasis.

    PubMed

    Jeong, Kwon; He, Baokun; Nohara, Kazunari; Park, Noheon; Shin, Youngmin; Kim, Seonghwa; Shimomura, Kazuhiro; Koike, Nobuya; Yoo, Seung-Hee; Chen, Zheng

    2015-07-31

    Circadian clocks orchestrate essential physiology in response to various cues, yet their mechanistic and functional plasticity remains unclear. Here, we investigated Clock(Δ19/+) heterozygous (Clk/+) mice, known to display lengthened periodicity and dampened amplitude, as a model of partially perturbed clocks. Interestingly, Clk/+ mice exhibited improved glycemic control and resistance to circadian period lengthening under high-fat diet (HFD). Furthermore, BMAL1 protein levels in Clk/+ mouse liver were upregulated compared with wild-type (WT) mice under HFD. Pharmacological and molecular studies showed that BMAL1 turnover entailed proteasomal and autophagic activities, and CLOCKΔ19 attenuated both processes. Consistent with an important role of BMAL1 in glycemic control, enhanced activation of insulin signaling was observed in Clk/+ mice relative to WT in HFD. Finally, transcriptome analysis revealed reprogramming of clock-controlled metabolic genes in Clk/+ mice. Our results demonstrate a novel role of autophagy in circadian regulation and reveal an unforeseen plasticity of circadian and metabolic networks.

  11. A low maintenance Sr optical lattice clock

    NASA Astrophysics Data System (ADS)

    Hill, I. R.; Hobson, R.; Bowden, W.; Bridge, E. M.; Donnellan, S.; Curtis, E. A.; Gill, P.

    2016-06-01

    We describe the Sr optical lattice clock apparatus at NPL with particular emphasis on techniques used to increase reliability and minimise the human requirement in its operation. Central to this is a clock-referenced transfer cavity scheme for the stabilisation of cooling and trapping lasers. We highlight several measures to increase the reliability of the clock with a view towards the realisation of an optical time-scale. The clock contributed 502 hours of data over a 25 day period (84% uptime) in a recent measurement campaign with several uninterrupted periods of more than 48 hours. An instability of 2 x 10-17 was reached after 105 s of averaging in an interleaved self-comparison of the clock.

  12. The Expression of Three Opsin Genes from the Compound Eye of Helicoverpa armigera (Lepidoptera: Noctuidae) Is Regulated by a Circadian Clock, Light Conditions and Nutritional Status

    PubMed Central

    Yan, Shuo; Zhu, Jialin; Zhu, Weilong; Zhang, Xinfang; Li, Zhen; Liu, Xiaoxia; Zhang, Qingwen

    2014-01-01

    Visual genes may become inactive in species that inhabit poor light environments, and the function and regulation of opsin components in nocturnal moths are interesting topics. In this study, we cloned the ultraviolet (UV), blue (BL) and long-wavelength-sensitive (LW) opsin genes from the compound eye of the cotton bollworm and then measured their mRNA levels using quantitative real-time PCR. The mRNA levels fluctuated over a daily cycle, which might be an adaptation of a nocturnal lifestyle, and were dependent on a circadian clock. Cycling of opsin mRNA levels was disturbed by constant light or constant darkness, and the UV opsin gene was up-regulated after light exposure. Furthermore, the opsin genes tended to be down-regulated upon starvation. Thus, this study illustrates that opsin gene expression is determined by multiple endogenous and exogenous factors and is adapted to the need for nocturnal vision, suggesting that color vision may play an important role in the sensory ecology of nocturnal moths. PMID:25353953

  13. Evolutionary Links Between Circadian Clocks and Photoperiodic Diapause in Insects

    PubMed Central

    Meuti, Megan E.; Denlinger, David L.

    2013-01-01

    In this article, we explore links between circadian clocks and the clock involved in photoperiodic regulation of diapause in insects. Classical resonance (Nanda–Hamner) and night interruption (Bünsow) experiments suggest a circadian basis for the diapause response in nearly all insects that have been studied. Neuroanatomical studies reveal physical connections between circadian clock cells and centers controlling the photoperiodic diapause response, and both mutations and knockdown of clock genes with RNA interference (RNAi) point to a connection between the clock genes and photoperiodic induction of diapause. We discuss the challenges of determining whether the clock, as a functioning module, or individual clock genes acting pleiotropically are responsible for the photoperiodic regulation of diapause, and how a stable, central circadian clock could be linked to plastic photoperiodic responses without compromising the clock’s essential functions. Although we still lack an understanding of the exact mechanisms whereby insects measure day/night length, continued classical and neuroanatomical approaches, as well as forward and reverse genetic experiments, are highly complementary and should enable us to decipher the diverse ways in which circadian clocks have been involved in the evolution of photoperiodic induction of diapause in insects. The components of circadian clocks vary among insect species, and diapause appears to have evolved independently numerous times, thus, we anticipate that not all photoperiodic clocks of insects will interact with circadian clocks in the same fashion. PMID:23615363

  14. Circadian molecular clocks tick along ontogenesis.

    PubMed

    Sumová, A; Bendová, Z; Sládek, M; El-Hennamy, R; Matejů, K; Polidarová, L; Sosniyenko, S; Illnerová, H

    2008-01-01

    The circadian system controls the timing of behavioral and physiological functions in most organisms studied. The review addresses the question of when and how the molecular clockwork underlying circadian oscillations within the central circadian clock in the suprachiasmatic nuclei of the hypothalamus (SCN) and the peripheral circadian clocks develops during ontogenesis. The current model of the molecular clockwork is summarized. The central SCN clock is viewed as a complex structure composed of a web of mutually synchronized individual oscillators. The importance of development of both the intracellular molecular clockwork as well as intercellular coupling for development of the formal properties of the circadian SCN clock is also highlighted. Recently, data has accumulated to demonstrate that synchronized molecular oscillations in the central and peripheral clocks develop gradually during ontogenesis and development extends into postnatal period. Synchronized molecular oscillations develop earlier in the SCN than in the peripheral clocks. A hypothesis is suggested that the immature clocks might be first driven by external entraining cues, and therefore, serve as "slave" oscillators. During ontogenesis, the clocks may gradually develop a complete set of molecular interlocked oscillations, i.e., the molecular clockwork, and become self-sustained clocks.

  15. Conserved function of core clock proteins in the gymnosperm Norway spruce (Picea abies L. Karst).

    PubMed

    Karlgren, Anna; Gyllenstrand, Niclas; Källman, Thomas; Lagercrantz, Ulf

    2013-01-01

    From studies of the circadian clock in the plant model species Arabidopsis (Arabidopsis thaliana), a number of important properties and components have emerged. These include the genes CIRCADIAN CLOCK ASSOCIATED 1 (CCA1), GIGANTEA (GI), ZEITLUPE (ZTL) and TIMING OF CAB EXPRESSION 1 (TOC1 also known as PSEUDO-RESPONSE REGULATOR 1 (PRR1)) that via gene expression feedback loops participate in the circadian clock. Here, we present results from ectopic expression of four Norway spruce (Picea abies) putative homologs (PaCCA1, PaGI, PaZTL and PaPRR1) in Arabidopsis, their flowering time, circadian period length, red light response phenotypes and their effect on endogenous clock genes were assessed. For PaCCA1-ox and PaZTL-ox the results were consistent with Arabidopsis lines overexpressing the corresponding Arabidopsis genes. For PaGI consistent results were obtained when expressed in the gi2 mutant, while PaGI and PaPRR1 expressed in wild type did not display the expected phenotypes. These results suggest that protein function of PaCCA1, PaGI and PaZTL are at least partly conserved compared to Arabidopsis homologs, however further studies are needed to reveal the protein function of PaPRR1. Our data suggest that components of the three-loop network typical of the circadian clock in angiosperms were present before the split of gymnosperms and angiosperms.

  16. Metabolic regulation of circadian clocks.

    PubMed

    Haydon, Michael J; Hearn, Timothy J; Bell, Laura J; Hannah, Matthew A; Webb, Alex A R

    2013-05-01

    Circadian clocks are 24-h timekeeping mechanisms, which have evolved in plants, animals, fungi and bacteria to anticipate changes in light and temperature associated with the rotation of the Earth. The current paradigm to explain how biological clocks provide timing information is based on multiple interlocking transcription-translation negative feedback loops (TTFL), which drive rhythmic gene expression and circadian behaviour of growth and physiology. Metabolism is an important circadian output, which in plants includes photosynthesis, starch metabolism, nutrient assimilation and redox homeostasis. There is increasing evidence in a range of organisms that these metabolic outputs can also contribute to circadian timing and might also comprise independent circadian oscillators. In this review, we summarise the mechanisms of circadian regulation of metabolism by TTFL and consider increasing evidence that rhythmic metabolism contributes to the circadian network. We highlight how this might be relevant to plant circadian clock function.

  17. Genomic clocks and evolutionary timescales

    NASA Technical Reports Server (NTRS)

    Blair Hedges, S.; Kumar, Sudhir

    2003-01-01

    For decades, molecular clocks have helped to illuminate the evolutionary timescale of life, but now genomic data pose a challenge for time estimation methods. It is unclear how to integrate data from many genes, each potentially evolving under a different model of substitution and at a different rate. Current methods can be grouped by the way the data are handled (genes considered separately or combined into a 'supergene') and the way gene-specific rate models are applied (global versus local clock). There are advantages and disadvantages to each of these approaches, and the optimal method has not yet emerged. Fortunately, time estimates inferred using many genes or proteins have greater precision and appear to be robust to different approaches.

  18. Developmental and light-entrained expression of melatonin and its relationship to the circadian clock in the sea anemone Nematostella vectensis

    PubMed Central

    2014-01-01

    Background The primary hormone of the vertebrate pineal gland, melatonin, has been identified broadly throughout the eukaryotes. While the role for melatonin in cyclic behavior via interactions with the circadian clock has only been reported in vertebrates, comparative research has shown that the transcription-translation loops of the animal circadian clock likely date to the cnidarian-bilaterian ancestor, leaving open significant questions about the evolutionary origin of melatonin signaling in circadian behavior by interacting with the molecular clock. Results Expression of melatonin in adult anemones showed peak expression at the end of light period (zeitgeber time (ZT) = 12) when cultured under diel conditions, coinciding with expression of genes and enzyme activity for members of the melatonin synthesis pathway (tryptophan hydroxylase and hydroxyindol-O-methyltransferase), which also showed rhythmic expression. During embryogenesis and juvenile stages, melatonin showed cyclic oscillations in concentration, peaking in midday. Spatial (in situ hybridization) and quantitative (real-time PCR) transcription of clock genes during development of N. vectensis showed these ‘clock’ genes are expressed early in the development, prior to rhythmic oscillations, suggesting functions independent of a function in the circadian clock. Finally, time-course studies revealed that animals transferred from diel conditions to constant darkness lose circadian expression for most of the clock genes within 4 days, which can be reset by melatonin supplementation. Conclusions Our results support an ancient role for melatonin in the circadian behavior of animals by showing cyclic expression of this hormone under diel conditions, light-dependent oscillations in genes in the melatonin synthesis pathway, and the function of melatonin in initiating expression of circadian clock genes in the cnidarian N. vectensis. The differences in expression melatonin and the circadian clock gene

  19. Deregulation of the circadian clock constitutes a significant factor in tumorigenesis: a clockwork cancer. Part I: clocks and clocking machinery

    PubMed Central

    Uth, Kristin; Sleigh, Roger

    2014-01-01

    Many physiological processes occur in a rhythmic fashion, consistent with a 24-h cycle. The central timing of the day/night rhythm is set by a master clock, located in the suprachiasmatic nucleus (a tiny region in the hypothalamus), but peripheral clocks exist in different tissues, adjustable by cues other than light (temperature, food, hormone stimulation, etc.), functioning autonomously to the master clock. Presence of unrepaired DNA damage may adjust the circadian clock so that the phase in which checking for damage and DNA repair normally occurs is advanced or extended. The expression of many of the genes coding for proteins functioning in DNA damage-associated response pathways and DNA repair is directly or indirectly regulated by the core clock proteins. Setting up the normal rhythm of the circadian cycle also involves oscillating changes in the chromatin structure, allowing differential activation of various chromatin domains within the 24-h cycle. PMID:26019503

  20. Role of miR-142-3p in the post-transcriptional regulation of the clock gene Bmal1 in the mouse SCN.

    PubMed

    Shende, Vikram R; Neuendorff, Nichole; Earnest, David J

    2013-01-01

    MicroRNAs (miRNAs) are small non-coding RNAs that function as post-transcriptional modulators by regulating stability or translation of target mRNAs. Recent studies have implicated miRNAs in the regulation of mammalian circadian rhythms. To explore the role of miRNAs in the post-transcriptional modulation of core clock genes in the master circadian pacemaker, we examined miR-142-3p for evidence of circadian expression in the suprachiasmatic nuclei (SCN), regulation of its putative clock gene target Bmal1 via specific binding sites in the 3' UTR and overexpression-induced changes in the circadian rhythm of BMAL1 protein levels in SCN cells. In mice exposed to constant darkness (DD), miR-142-3p levels in the SCN were characterized by circadian rhythmicity with peak expression during early subjective day at CT 3. Mutagenesis studies indicate that two independent miRNA recognition elements located at nucleotides 1-7 and 335-357 contribute equally to miR-142-3p-induced repression of luciferase-reported Bmal1 3' UTR activity. Importantly, overexpression of miR-142-3p in immortalized SCN cells abolished circadian variation in endogenous BMAL1 protein levels in vitro. Collectively, our results suggest that miR-142-3p may play a role in the post-transcriptional modulation of Bmal1 and its oscillatory regulation in molecular feedback loops mediating SCN circadian function.

  1. Role of miR-142-3p in the Post-Transcriptional Regulation of the Clock Gene Bmal1 in the Mouse SCN

    PubMed Central

    Shende, Vikram R.; Neuendorff, Nichole; Earnest, David J.

    2013-01-01

    MicroRNAs (miRNAs) are small non-coding RNAs that function as post-transcriptional modulators by regulating stability or translation of target mRNAs. Recent studies have implicated miRNAs in the regulation of mammalian circadian rhythms. To explore the role of miRNAs in the post-transcriptional modulation of core clock genes in the master circadian pacemaker, we examined miR-142-3p for evidence of circadian expression in the suprachiasmatic nuclei (SCN), regulation of its putative clock gene target Bmal1 via specific binding sites in the 3′ UTR and overexpression-induced changes in the circadian rhythm of BMAL1 protein levels in SCN cells. In mice exposed to constant darkness (DD), miR-142-3p levels in the SCN were characterized by circadian rhythmicity with peak expression during early subjective day at CT 3. Mutagenesis studies indicate that two independent miRNA recognition elements located at nucleotides 1–7 and 335–357 contribute equally to miR-142-3p-induced repression of luciferase-reported Bmal1 3′ UTR activity. Importantly, overexpression of miR-142-3p in immortalized SCN cells abolished circadian variation in endogenous BMAL1 protein levels in vitro. Collectively, our results suggest that miR-142-3p may play a role in the post-transcriptional modulation of Bmal1 and its oscillatory regulation in molecular feedback loops mediating SCN circadian function. PMID:23755214

  2. VLBI clock synchronization. [for atomic clock rate

    NASA Technical Reports Server (NTRS)

    Counselman, C. C., III; Shapiro, I. I.; Rogers, A. E. E.; Hinteregger, H. F.; Knight, C. A.; Whitney, A. R.; Clark, T. A.

    1977-01-01

    The potential accuracy of VLBI (very long baseline interferometry) for clock epoch and rate comparisons was demonstrated by results from long- and short-baseline experiments. It was found that atomic clocks at widely separated sites (several thousand kilometers apart) can be synchronized to within several nanoseconds from a few minutes of VLBI observations and to within one nanosecond from several hours of observations.

  3. Altered energy intake and the amplitude of the body temperature rhythm are associated with changes in phase, but not amplitude, of clock gene expression in the rat suprachiasmatic nucleus in vivo.

    PubMed

    Goh, Grace H; Mark, Peter J; Maloney, Shane K

    2016-01-01

    Circadian rhythms in mammals are driven by a central clock in the suprachiasmatic nucleus (SCN). In vitro, temperature cycles within the physiological range can act as potent entraining cues for biological clocks. We altered the body temperature (Tc) rhythm in rats by manipulating energy intake (EI) to determine whether EI-induced changes in Tc oscillations are associated with changes in SCN clock gene rhythms in vivo. Male Wistar rats (n = 16 per diet) were maintained on either an ad libitum diet (CON), a high energy cafeteria diet (CAF), or a calorie restricted diet (CR), and Tc was recorded every 30 min for 6-7 weeks. SCN tissue was harvested from rats at zeitgeber time (ZT) 0, ZT6, ZT12, or ZT18. Expression of the clock genes Bmal1, Per2, Cry1, and Rev-erbα, the heat shock transcription factor Hsf1, and the heat shock protein Hsp90aa1, were determined using qPCR. The circadian profile of gene expression for each gene was characterized using cosinor analysis. Compared to the CON rats, the amplitude of Tc was decreased in CAF rats by 0.1 °C (p < 0.001), and increased in CR rats by 0.3 °C (p < 0.001). The amplitude of Hsp90aa1 expression was lowest in CAF rats and highest in CR rats (p = 0.045), but the amplitude of all of the clock genes and Hsf1 were unaffected by diet (p > 0.25). Compared to CON, phase advances of the Tc, Bmal1, and Per2 rhythms were observed with CR feeding (p < 0.05), but CAF feeding elicited no significant changes in phase. The present results indicate that in vivo, the SCN is largely resistant to entrainment by EI-induced changes in the Tc rhythm, although some phase entrainment may occur.

  4. Modulation of circadian clocks by nutrients and food factors.

    PubMed

    Oike, Hideaki

    2017-05-01

    Daily activity rhythms that are dominated by internal clocks are called circadian rhythms. A central clock is located in the suprachiasmatic nucleus of the hypothalamus, and peripheral clocks are located in most mammalian peripheral cells. The central clock is entrained by light/dark cycles, whereas peripheral clocks are entrained by feeding cycles. The effects of nutrients on the central and peripheral clocks have been investigated during the past decade and much interaction between them has come to light. For example, a high-fat diet prolongs the period of circadian behavior, a ketogenic diet advances the onset of locomotor activity rhythms, and a high-salt diet advances the phase of peripheral molecular clocks. Moreover, some food factors such as caffeine, nobiletin, and resveratrol, alter molecular and/or behavioral circadian rhythms. Here, we review nutrients and food factors that modulate mammalian circadian clocks from the cellular to the behavioral level.

  5. Identification of a Circadian Clock in the Inferior Colliculus and Its Dysregulation by Noise Exposure

    PubMed Central

    Park, Jung-sub; Cederroth, Christopher R.; Basinou, Vasiliki; Meltser, Inna; Lundkvist, Gabriella

    2016-01-01

    Circadian rhythms regulate bodily functions within 24 h and long-term disruptions in these rhythms can cause various diseases. Recently, the peripheral auditory organ, the cochlea, has been shown to contain a self-sustained circadian clock that regulates differential sensitivity to noise exposure throughout the day. Animals exposed to noise during the night are more vulnerable than when exposed during the day. However, whether other structures throughout the auditory pathway also possess a circadian clock remains unknown. Here, we focus on the inferior colliculus (IC), which plays an important role in noise-induced pathologies such as tinnitus, hyperacusis, and audiogenic seizures. Using PER2::LUC transgenic mice and real-time bioluminescence recordings, we revealed circadian oscillations of Period 2 protein in IC explants for up to 1 week. Clock genes (Cry1, Bmal1, Per1, Per2, Rev-erbα, and Dbp) displayed circadian molecular oscillations in the IC. Averaged expression levels of early-induced genes and clock genes during 24 h revealed differential responses to day or night noise exposure. Rev-erbα and Dbp genes were affected only by day noise exposure, whereas Per1 and Per2 were affected only by night noise exposure. However, the expression of Bdnf was affected by both day and night noise exposure, suggesting that plastic changes are unlikely to be involved in the differences in day or night noise sensitivity in the IC. These novel findings highlight the importance of circadian responses in the IC and emphasize the importance of circadian mechanisms for understanding central auditory function and disorders. SIGNIFICANCE STATEMENT Recent findings identified the presence of a circadian clock in the inner ear. Here, we present novel findings that neurons in the inferior colliculus (IC), a central auditory relay structure involved in sound processing, express a circadian clock as evidenced at both the mRNA and protein levels. Using a reporter mouse that expresses a

  6. An In Vitro ES Cell-Based Clock Recapitulation Assay Model Identifies CK2α as an Endogenous Clock Regulator

    PubMed Central

    Yoshida, Junko; Wada, Masashi; Tsuchiya, Yoshiki; Minami, Yoichi; Watanabe, Hitomi; Kondoh, Gen; Takeda, Junji; Inokawa, Hitoshi; Horie, Kyoji

    2013-01-01

    We previously reported emergence and disappearance of circadian molecular oscillations during differentiation of mouse embryonic stem (ES) cells and reprogramming of differentiated cells, respectively. Here we present a robust and stringent in vitro circadian clock formation assay that recapitulates in vivo circadian phenotypes. This assay system first confirmed that a mutant ES cell line lacking Casein Kinase I delta (CKIδ) induced ∼3 hours longer period-length of circadian rhythm than the wild type, which was compatible with recently reported results using CKIδ null mice. In addition, this assay system also revealed that a Casein Kinase 2 alpha subunit (CK2α) homozygous mutant ES cell line developed significantly longer (about 2.5 hours) periods of circadian clock oscillations after in vitro or in vivo differentiation. Moreover, revertant ES cell lines in which mutagenic vector sequences were deleted showed nearly wild type periods after differentiation, indicating that the abnormal circadian period of the mutant ES cell line originated from the mutation in the CK2α gene. Since CK2α deficient mice are embryonic lethal, this in vitro assay system represents the genetic evidence showing an essential role of CK2α in the mammalian circadian clock. This assay was successfully applied for the phenotype analysis of homozygous mutant ES cells, demonstrating that an ES cell-based in vitro assay is available for circadian genetic screening. PMID:23840637

  7. The Glyoxal Clock Reaction

    ERIC Educational Resources Information Center

    Ealy, Julie B.; Negron, Alexandra Rodriguez; Stephens, Jessica; Stauffer, Rebecca; Furrow, Stanley D.

    2007-01-01

    Research on the glyoxal clock reaction has led to adaptation of the clock reaction to a general chemistry experiment. This particular reaction is just one of many that used formaldehyde in the past. The kinetics of the glyoxal clock makes the reaction suitable as a general chemistry lab using a Calculator Based Laboratory (CBL) or a LabPro. The…

  8. Geographic Variation of Plant Circadian Clock Function in Natural and Agricultural Settings.

    PubMed

    Greenham, Kathleen; Lou, Ping; Puzey, Joshua R; Kumar, Ganesh; Arnevik, Cindy; Farid, Hany; Willis, John H; McClung, C Robertson

    2017-02-01

    The increasing demand for improved agricultural production will require more efficient breeding for traits that maintain yield under heterogeneous environments. The internal circadian oscillator is essential for perceiving and coordinating environmental cues such as day length, temperature, and abiotic stress responses within physiological processes. To investigate the contribution of the circadian clock to local adaptability, we have analyzed circadian period by leaf movement in natural populations of Mimulus guttatus and domesticated cultivars of Glycine max. We detected consistent variation in circadian period along a latitudinal gradient in annual populations of the wild plant and the selectively bred crop, and this provides novel evidence of natural and artificial selection for circadian performance. These findings provide new support that the circadian clock acts as a central regulator of plant adaptability and further highlight the potential of applying circadian clock gene variation to marker-assisted breeding programs in crops.

  9. Gigabit Ethernet Asynchronous Clock Compensation FIFO

    NASA Technical Reports Server (NTRS)

    Duhachek, Jeff

    2012-01-01

    Clock compensation for Gigabit Ethernet is necessary because the clock recovered from the 1.25 Gb/s serial data stream has the potential to be 200 ppm slower or faster than the system clock. The serial data is converted to 10-bit parallel data at a 125 MHz rate on a clock recovered from the serial data stream. This recovered data needs to be processed by a system clock that is also running at a nominal rate of 125 MHz, but not synchronous to the recovered clock. To cross clock domains, an asynchronous FIFO (first-in-first-out) is used, with the write pointer (wprt) in the recovered clock domain and the read pointer (rptr) in the system clock domain. Because the clocks are generated from separate sources, there is potential for FIFO overflow or underflow. Clock compensation in Gigabit Ethernet is possible by taking advantage of the protocol data stream features. There are two distinct data streams that occur in Gigabit Ethernet where identical data is transmitted for a period of time. The first is configuration, which happens during auto-negotiation. The second is idle, which occurs at the end of auto-negotiation and between every packet. The identical data in the FIFO can be repeated by decrementing the read pointer, thus compensating for a FIFO that is draining too fast. The identical data in the FIFO can also be skipped by incrementing the read pointer, which compensates for a FIFO draining too slowly. The unique and novel features of this FIFO are that it works in both the idle stream and the configuration streams. The increment or decrement of the read pointer is different in the idle and compensation streams to preserve disparity. Another unique feature is that the read pointer to write pointer difference range changes between compensation and idle to minimize FIFO latency during packet transmission.

  10. The Ozone-Iodine-Chlorate Clock Reaction

    PubMed Central

    Sant'Anna, Rafaela T. P.; Monteiro, Emily V.; Pereira, Juliano R. T.; Faria, Roberto B.

    2013-01-01

    This work presents a new clock reaction based on ozone, iodine, and chlorate that differs from the known chlorate-iodine clock reaction because it does not require UV light. The induction period for this new clock reaction depends inversely on the initial concentrations of ozone, chlorate, and perchloric acid but is independent of the initial iodine concentration. The proposed mechanism considers the reaction of ozone and iodide to form HOI, which is a key species for producing non-linear autocatalytic behavior. The novelty of this system lies in the presence of ozone, whose participation has never been observed in complex systems such as clock or oscillating reactions. Thus, the autocatalysis demonstrated in this new clock reaction should open the possibility for a new family of oscillating reactions. PMID:24386257

  11. The ozone-iodine-chlorate clock reaction.

    PubMed

    Sant'Anna, Rafaela T P; Monteiro, Emily V; Pereira, Juliano R T; Faria, Roberto B

    2013-01-01

    This work presents a new clock reaction based on ozone, iodine, and chlorate that differs from the known chlorate-iodine clock reaction because it does not require UV light. The induction period for this new clock reaction depends inversely on the initial concentrations of ozone, chlorate, and perchloric acid but is independent of the initial iodine concentration. The proposed mechanism considers the reaction of ozone and iodide to form HOI, which is a key species for producing non-linear autocatalytic behavior. The novelty of this system lies in the presence of ozone, whose participation has never been observed in complex systems such as clock or oscillating reactions. Thus, the autocatalysis demonstrated in this new clock reaction should open the possibility for a new family of oscillating reactions.

  12. The Arabidopsis sickle Mutant Exhibits Altered Circadian Clock Responses to Cool Temperatures and Temperature-Dependent Alternative Splicing.

    PubMed

    Marshall, Carine M; Tartaglio, Virginia; Duarte, Maritza; Harmon, Frank G

    2016-10-01

    The circadian clock allows plants to anticipate and respond to daily changes in ambient temperature. Mechanisms establishing the timing of circadian rhythms in Arabidopsis thaliana through temperature entrainment remain unclear. Also incompletely understood is the temperature compensation mechanism that maintains consistent period length within a range of ambient temperatures. A genetic screen for Arabidopsis mutants affecting temperature regulation of the PSEUDO-RESPONSE REGULATOR7 promoter yielded a novel allele of the SICKLE (SIC) gene. This mutant, sic-3, and the existing sic-1 mutant both exhibit low-amplitude or arrhythmic expression of core circadian clock genes under cool ambient temperature cycles, but not under light-dark entrainment. sic mutants also lengthen free running period in a manner consistent with impaired temperature compensation. sic mutant alleles accumulate LATE ELONGATED HYPOCOTYL (LHY) and CIRCADIAN CLOCK ASSOCIATED1 (CCA1) splice variants, among other alternatively spliced transcripts, which is exacerbated by cool temperatures. The cca1-1 lhy-20 double mutant is epistatic to sic-3, indicating the LHY and CCA1 splice variants are needed for sic-3 circadian clock phenotypes. It is not expected that SIC is directly involved in the circadian clock mechanism; instead, SIC likely contributes to pre-mRNA metabolism, and the splice variants that accumulate in sic mutants likely affect the circadian clock response to cool ambient temperature.

  13. Effects of Different PER Translational Kinetics on the Dynamics of a Core Circadian Clock Model

    PubMed Central

    Nieto, Paula S.; Revelli, Jorge A.; Garbarino-Pico, Eduardo; Condat, Carlos A.; Guido, Mario E.; Tamarit, Francisco A.

    2015-01-01

    Living beings display self-sustained daily rhythms in multiple biological processes, which persist in the absence of external cues since they are generated by endogenous circadian clocks. The period (per) gene is a central player within the core molecular mechanism for keeping circadian time in most animals. Recently, the modulation PER translation has been reported, both in mammals and flies, suggesting that translational regulation of clock components is important for the proper clock gene expression and molecular clock performance. Because translational regulation ultimately implies changes in the kinetics of translation and, therefore, in the circadian clock dynamics, we sought to study how and to what extent the molecular clock dynamics is affected by the kinetics of PER translation. With this objective, we used a minimal mathematical model of the molecular circadian clock to qualitatively characterize the dynamical changes derived from kinetically different PER translational mechanisms. We found that the emergence of self-sustained oscillations with characteristic period, amplitude, and phase lag (time delays) between per mRNA and protein expression depends on the kinetic parameters related to PER translation. Interestingly, under certain conditions, a PER translation mechanism with saturable kinetics introduces longer time delays than a mechanism ruled by a first-order kinetics. In addition, the kinetic laws of PER translation significantly changed the sensitivity of our model to parameters related to the synthesis and degradation of per mRNA and PER degradation. Lastly, we found a set of parameters, with realistic values, for which our model reproduces some experimental results reported recently for Drosophila melanogaster and we present some predictions derived from our analysis. PMID:25607544

  14. Circadian clocks and mood-related behaviors.

    PubMed

    Albrecht, Urs

    2013-01-01

    Circadian clocks are present in nearly all tissues of an organism, including the brain. The brain is not only the site of the master coordinator of circadian rhythms located in the suprachiasmatic nuclei (SCN) but also contains SCN-independent oscillators that regulate various functions such as feeding and mood-related behavior. Understanding how clocks receive and integrate environmental information and in turn control physiology under normal conditions is of importance because chronic disturbance of circadian rhythmicity can lead to serious health problems. Genetic modifications leading to disruption of normal circadian gene functions have been linked to a variety of psychiatric conditions including depression, seasonal affective disorder, eating disorders, alcohol dependence, and addiction. It appears that clock genes play an important role in limbic regions of the brain and influence the development of drug addiction. Furthermore, analyses of clock gene polymorphisms in diseases of the central nervous system (CNS) suggest a direct or indirect influence of circadian clock genes on brain function. In this chapter, I will present evidence for a circadian basis of mood disorders and then discuss the involvement of clock genes in such disorders. The relationship between metabolism and mood disorders is highlighted followed by a discussion of how mood disorders may be treated by changing the circadian cycle.

  15. CRY Drives Cyclic CK2-Mediated BMAL1 Phosphorylation to Control the Mammalian Circadian Clock

    PubMed Central

    Tamaru, Teruya; Hattori, Mitsuru; Honda, Kousuke; Nakahata, Yasukazu; Sassone-Corsi, Paolo; van der Horst, Gijsbertus T. J.; Ozawa, Takeaki; Takamatsu, Ken

    2015-01-01

    Intracellular circadian clocks, composed of clock genes that act in transcription-translation feedback loops, drive global rhythmic expression of the mammalian transcriptome and allow an organism to anticipate to the momentum of the day. Using a novel clock-perturbing peptide, we established a pivotal role for casein kinase (CK)-2-mediated circadian BMAL1-Ser90 phosphorylation (BMAL1-P) in regulating central and peripheral core clocks. Subsequent analysis of the underlying mechanism showed a novel role of CRY as a repressor for protein kinase. Co-immunoprecipitation experiments and real-time monitoring of protein–protein interactions revealed that CRY-mediated periodic binding of CK2β to BMAL1 inhibits BMAL1-Ser90 phosphorylation by CK2α. The FAD binding domain of CRY1, two C-terminal BMAL1 domains, and particularly BMAL1-Lys537 acetylation/deacetylation by CLOCK/SIRT1, were shown to be critical for CRY-mediated BMAL1–CK2β binding. Reciprocally, BMAL1-Ser90 phosphorylation is prerequisite for BMAL1-Lys537 acetylation. We propose a dual negative-feedback model in which a CRY-dependent CK2-driven posttranslational BMAL1–P-BMAL1 loop is an integral part of the core clock oscillator. PMID:26562092

  16. The ancestral circadian clock of monarch butterflies: role in time-compensated sun compass orientation.

    PubMed

    Reppert, S M

    2007-01-01

    The circadian clock has a vital role in monarch butterfly (Danaus plexippus) migration by providing the timing component of time-compensated sun compass orientation, which contributes to navigation to the overwintering grounds. The location of circadian clock cells in monarch brain has been identified in the dorsolateral protocerebrum (pars lateralis); these cells express PERIOD, TIMELESS, and a Drosophila-like cryptochrome designated CRY1. Monarch butterflies, like all other nondrosophilid insects examined so far, express a second cry gene (designated insect CRY2) that encodes a vertebrate-like CRY that is also expressed in pars lateralis. An ancestral circadian clock mechanism has been defined in monarchs, in which CRY1 functions as a blue light photoreceptor for photic entrainment, whereas CRY2 functionswithin the clockwork as themajor transcriptional repressor of an intracellular negative transcriptional feedback loop. A CRY1-staining neural pathway has been identified that may connect the circadian (navigational) clock to polarized light input important for sun compass navigation, and a CRY2-positive neural pathway has been discovered that may communicate circadian information directly from the circadian clock to the central complex, the likely site of the sun compass. The monarch butterfly may thus use the CRY proteins as components of the circadian mechanism and also as output molecules that connect the clock to various aspects of the sun compass apparatus.

  17. Modeling circadian clock-cell cycle interaction effects on cell population growth rates.

    PubMed

    El Cheikh, R; Bernard, S; El Khatib, N

    2014-12-21

    The circadian clock and the cell cycle are two tightly coupled oscillators. Recent analytical studies have shown counter-intuitive effects of circadian gating of the cell cycle on growth rates of proliferating cells which cannot be explained by a molecular model or a population model alone. In this work, we present a combined molecular-population model that studies how coupling the circadian clock to the cell cycle, through the protein WEE1, affects a proliferating cell population. We show that the cell cycle can entrain to the circadian clock with different rational period ratios and characterize multiple domains of entrainment. We show that coupling increases the growth rate for autonomous periods of the cell cycle around 24 h and above 48 h. We study the effect of mutation of circadian genes on the growth rate of cells and show that disruption of the circadian clock can lead to abnormal proliferation. Particularly, we show that Cry 1, Cry 2 mutations decrease the growth rate of cells, Per 2 mutation enhances it and Bmal 1 knockout increases it for autonomous periods of the cell cycle less than 21 h and decreases it elsewhere. Combining a molecular model to a population model offers new insight on the influence of the circadian clock on the growth of a cell population. This can help chronotherapy which takes benefits of physiological rhythms to improve anti-cancer efficacy and tolerance to drugs by administering treatments at a specific time of the day.

  18. timeless is an essential component of the circadian clock in a primitive insect, the firebrat Thermobia domestica.

    PubMed

    Kamae, Yuichi; Tomioka, Kenji

    2012-04-01

    Recent studies show that the timeless (tim) gene is not an essential component of the circadian clock in some insects. In the present study, we have investigated whether the tim gene was originally involved in the insect clock or acquired as a clock component later during the course of evolution using an apterygote insect, Thermobia domestica. A cDNA of the clock gene tim (Td'tim) was cloned, and its structural analysis showed that Td'TIM includes 4 defined functional domains, that is, 2 regions for dimerization with PERIOD (PER-1, PER-2), nuclear localization signal (NLS), and cytoplasmic localization domain (CLD), like Drosophila TIM. Td'tim exhibited rhythmic expression in its mRNA levels with a peak during late day to early night in LD, and the rhythm persisted in DD. A single injection of double-stranded RNA (dsRNA) of Td'tim (dstim) into the abdomen of adult firebrats effectively knocked down mRNA levels of Td'tim and abolished its rhythmic expression. Most dsRNA-injected firebrats lost their circadian locomotor rhythm in DD up to 30 days after injection. DsRNA of cycle (cyc) and Clock genes also abolished the rhythmic expression of Td'tim mRNA by knocking down Td'tim mRNA to its basal level of intact firebrats, suggesting that the underlying molecular clock of firebrats resembles that of Drosophila. Interestingly, however, dstim also reduced cyc mRNA to its basal level of intact animals and eliminated its rhythmic expression, suggesting the involvement of Td'tim in the regulation of cyc expression. These results suggest that tim is an essential component of the circadian clock of the primitive insect T. domestica; thus, it might have been involved in the clock machinery from a very early stage of insect evolution, but its role might be different from that in Drosophila.

  19. Differential effects of omega-3 fatty acid docosahexaenoic acid and palmitate on the circadian transcriptional profile of clock genes in immortalized hypothalamic neurons

    PubMed Central

    Greco, James A.; Oosterman, Johanneke E.

    2014-01-01

    Diets high in saturated fatty acids (SFAs) are associated with the development of circadian dysregulation, obesity, and Type 2 diabetes mellitus. Conversely, polyunsaturated fatty acids (PUFAs) have recently been identified to improve insulin sensitivity, reduce weight gain, and relieve obesity-induced inflammation. While saturated fatty acids, such as the prevalent dietary fatty acid palmitate, have been implicated in circadian disruption, there is a paucity of studies regarding the effects of PUFAs on circadian parameters. Therefore, the immortalized murine neuronal model, mHypoE-37, was utilized to examine the effects of the SFA palmitate and omega-3 PUFA docosahexaenoic acid (DHA) on circadian rhythms. The mHypoE-37 neurons express the core clock genes, Bmal1, Per2, and Rev-erbα, in a circadian manner. 25 μM of palmitate significantly increased the transcriptional expression of Bmal1, without altering the expression of inflammatory markers TLR4, IκBα, and IL-6, nor the orexigenic neuropeptide AgRP, suggesting that the observed disruption of the molecular clock is the result of a mechanism distinct from that of hypothalamic cellular inflammation. Furthermore, treatment with the PUFA DHA resulted in alterations in the circadian expression profile of Bmal1, although differentially from the effects of palmitate. In the presence of DHA, the disruptive effects of palmitate on Bmal1 were less pronounced, suggesting a protective effect of DHA. These studies are the first to identify the potential for omega-3 PUFAs to protect against palmitate-mediated dysregulation of circadian parameters and will ultimately improve the understanding of circadian control mechanisms. PMID:25144192

  20. Optimizing passive quantum clocks

    NASA Astrophysics Data System (ADS)

    Mullan, Michael; Knill, Emanuel

    2014-10-01

    We describe protocols for passive atomic clocks based on quantum interrogation of the atoms. Unlike previous techniques, our protocols are adaptive and take advantage of prior information about the clock's state. To reduce deviations from an ideal clock, each interrogation is optimized by means of a semidefinite program for atomic state preparation and measurement whose objective function depends on the prior information. Our knowledge of the clock's state is maintained according to a Bayesian model that accounts for noise and measurement results. We implement a full simulation of a running clock with power-law noise models and find significant improvements by applying our techniques.

  1. Optical clock networks

    NASA Astrophysics Data System (ADS)

    Riehle, Fritz

    2017-01-01

    Within the last decade, optical atomic clocks have surpassed the best cesium clocks, which are used to realize the unit of time and frequency, in terms of accuracy and stability by about two orders of magnitude. When remote optical atomic clocks are connected by links without degradation in the clock signals, an optical clock network is formed, with distinct advantages for the dissemination of time, geodesy, astronomy and basic and applied research. Different approaches for time and frequency transfer in the microwave and optical regime, via satellites and free-space links, optical fibre links, or transportable optical atomic clocks, can be used to form a hybrid clock network that may allow a future redefinition of the unit of time based on an optical reference transition.

  2. Entrainment in solution of an oscillating NADH oxidase activity from the bovine milk fat globule membrane with a temperature-compensated period length suggestive of an ultradian time-keeping (clock) function

    NASA Technical Reports Server (NTRS)

    Morre, D. James; Lawler, Juliana; Wang, Sui; Keenan, Thomas W.; Morre, Dorothy M.

    2002-01-01

    Entrainment in solution of an oscillating activity with a temperature compensated period of 24 min is described for a NADH oxidase (NOX) activity of the bovine milk fat globule membrane, a derivative of the mammary epithelial cell plasma membrane. The period of 24 min remained unchanged at 17 degrees C, 27 degrees C and 37 degrees C whereas the amplitude approximately doubled with each 10 degree C rise in temperature (Q(10)congruent with 2). The periodicity was observed with both intact milk fat globule membranes and with detergent-solubilized membranes, demonstrating that the oscillations did not require an association with membranes. The periodicity was not the result of instrument variation or of chemical interactions among reactants in solution. Preparations with different periodicities entrained (autosynchronized) when mixed. Upon mixing, the preparations exhibited two oscillatory patterns but eventually a single pattern representing the mean of the farthest separated maxima of the two preparations analyzed separately emerged. The cell surface NOX protein is the first reported example of an entrainable biochemical entity with a temperature-compensated periodicity potentially capable of functioning as an ultradian or circadian clock driver.

  3. Network features of the mammalian circadian clock.

    PubMed

    Baggs, Julie E; Price, Tom S; DiTacchio, Luciano; Panda, Satchidananda; Fitzgerald, Garret A; Hogenesch, John B

    2009-03-10

    The mammalian circadian clock is a cell-autonomous system that drives oscillations in behavior and physiology in anticipation of daily environmental change. To assess the robustness of a human molecular clock, we systematically depleted known clock components and observed that circadian oscillations are maintained over a wide range of disruptions. We developed a novel strategy termed Gene Dosage Network Analysis (GDNA) in which small interfering RNA (siRNA)-induced dose-dependent changes in gene expression were used to build gene association networks consistent with known biochemical constraints. The use of multiple doses powered the analysis to uncover several novel network features of the circadian clock, including proportional responses and signal propagation through interacting genetic modules. We also observed several examples where a gene is up-regulated following knockdown of its paralog, suggesting the clock network utilizes active compensatory mechanisms rather than simple redundancy to confer robustness and maintain function. We propose that these network features act in concert as a genetic buffering system to maintain clock function in the face of genetic and environmental perturbation.

  4. Noninvasive method for assessing the human circadian clock using hair follicle cells

    PubMed Central

    Akashi, Makoto; Soma, Haruhiko; Yamamoto, Takuro; Tsugitomi, Asuka; Yamashita, Shiko; Yamamoto, Takuya; Nishida, Eisuke; Yasuda, Akio; Liao, James K.; Node, Koichi

    2010-01-01

    A thorough understanding of the circadian clock requires qualitative evaluation of circadian clock gene expression. Thus far, no simple and effective method for detecting human clock gene expression has become available. This limitation has greatly hampered our understanding of human circadian rhythm. Here we report a convenient, reliable, and less invasive method for detecting human clock gene expression using biopsy samples of hair follicle cells from the head or chin. We show that the circadian phase of clock gene expression in hair follicle cells accurately reflects that of individual behavioral rhythms, demonstrating that this strategy is appropriate for evaluating the human peripheral circadian clock. Furthermore, using this method, we indicate that rotating shift workers suffer from a serious time lag between circadian gene expression rhythms and lifestyle. Qualitative evaluation of clock gene expression in hair follicle cells, therefore, may be an effective approach for studying the human circadian clock in the clinical setting. PMID:20798039

  5. Feedback Loops of the Mammalian Circadian Clock Constitute Repressilator

    PubMed Central

    Pett, J. Patrick; Korenčič, Anja; Wesener, Felix; Kramer, Achim; Herzel, Hanspeter

    2016-01-01

    Mammals evolved an endogenous timing system to coordinate their physiology and behaviour to the 24h period of the solar day. While it is well accepted that circadian rhythms are generated by intracellular transcriptional feedback loops, it is still debated which network motifs are necessary and sufficient for generating self-sustained oscillations. Here, we systematically explore a data-based circadian oscillator model with multiple negative and positive feedback loops and identify a series of three subsequent inhibitions known as “repressilator” as a core element of the mammalian circadian oscillator. The central role of the repressilator motif is consistent with time-resolved ChIP-seq experiments of circadian clock transcription factors and loss of rhythmicity in core clock gene knockouts. PMID:27942033

  6. Axial skeletal defects caused by mutation in the spondylocostal dysplasia/pudgy gene Dll3 are associated with disruption of the segmentation clock within the presomitic mesoderm.

    PubMed

    Dunwoodie, Sally L; Clements, Melanie; Sparrow, Duncan B; Sa, Xin; Conlon, Ronald A; Beddington, Rosa S P

    2002-04-01

    A loss-of-function mutation in the mouse delta-like3 (Dll3) gene has been generated following gene targeting, and results in severe axial skeletal defects. These defects, which consist of highly disorganised vertebrae and costal defects, are similar to those associated with the Dll3-dependent pudgy mutant in mouse and with spondylocostal dysplasia (MIM 277300) in humans. This study demonstrates that Dll3(neo) and Dll3(pu) are functionally equivalent alleles with respect to the skeletal dysplasia, and we suggest that the three human DLL3 mutations associated with spondylocostal dysplasia are also functionally equivalent to the Dll3(neo) null allele. Our phenotypic analysis of Dll3(neo)/Dll3(neo) mutants shows that the developmental origins of the skeletal defects lie in delayed and irregular somite formation, which results in the perturbation of anteroposterior somite polarity. As the expression of Lfng, Hes1, Hes5 and Hey1 is disrupted in the presomitic mesoderm, we suggest that the somitic aberrations are founded in the disruption of the segmentation clock that intrinsically oscillates within presomitic mesoderm.

  7. Gender disparity of hepatic lipid homoeostasis regulated by the circadian clock.

    PubMed

    Yang, Xiaoxia; Zhang, Yu-Kun Jennifer; Esterly, Noriko; Klaassen, Curtis D; Wan, Yu-Jui Yvonne

    2009-05-01

    The mammalian clock regulates major aspects of energy metabolism, including glucose and lipid homoeostasis as well as mitochondrial oxidative metabolism. This study is to identify specific patterns of circadian rhythms for lipid homoeostasis in both female and male mouse livers, and to clarify gender disparity in coupling the peripheral circadian clock to lipid metabolic outputs by nuclear receptors. To achieve this, profiling the diurnal hepatic expression of genes encoding circadian clocks, nuclear receptors and lipid metabolic enzymes was performed. Hepatic lipid levels including cholesterol, triglyceride and non-esterified fatty acids (NEFAs) were monitored over a 24-h period. The cosinor analysis revealed that several genes encoding nuclear receptors and enzymes involved in the lipid metabolic pathway were rhythmically expressed in liver in phase with the peripheral clocks, which were correlated with the diurnal changes of hepatic lipid levels. Gender disparity was observed for circadian characteristics including mesor and amplitude values, accompanied with advances in acrophases in female mouse livers. Accordingly, gender differences were also observed in diurnal lipid homoeostasis. The identification of cycling patterns for lipid metabolic pathways in both female and male mouse livers may shed light on the development of gender-based treatment for human diseases related to the coordination of the cellular clock and control of lipid homoeostasis.

  8. Fluoxetine normalizes disrupted light-induced entrainment, fragmented ultradian rhythms and altered hippocampal clock gene expression in an animal model of high trait anxiety- and depression-related behavior

    PubMed Central

    Schaufler, Jörg; Ronovsky, Marianne; Savalli, Giorgia; Cabatic, Maureen; Sartori, Simone B.; Singewald, Nicolas; Pollak, Daniela D.

    2016-01-01

    ABSTRACT Introduction Disturbances of circadian rhythms are a key symptom of mood and anxiety disorders. Selective serotonin reuptake inhibitors (SSRIs) - commonly used antidepressant drugs – also modulate aspects of circadian rhythmicity. However, their potential to restore circadian disturbances in depression remains to be investigated. Materials and methods The effects of the SSRI fluoxetine on genetically based, depression-related circadian disruptions at the behavioral and molecular level were examined using mice selectively bred for high anxiety-related and co-segregating depression-like behavior (HAB) and normal anxiety/depression behavior mice (NAB). Results The length of the circadian period was increased in fluoxetine-treated HAB as compared to NAB mice while the number of activity bouts and light-induced entrainment were comparable. No difference in hippocampal Cry2 expression, previously reported to be dysbalanced in untreated HAB mice, was observed, while Per2 and Per3 mRNA levels were higher in HAB mice under fluoxetine treatment. Discussion The present findings provide evidence that fluoxetine treatment normalizes disrupted circadian locomotor activity and clock gene expression in a genetic mouse model of high trait anxiety and depression. An interaction between the molecular mechanisms mediating the antidepressant response to fluoxetine and the endogenous regulation of circadian rhythms in genetically based mood and anxiety disorders is proposed. PMID:26679264

  9. Tutorial: Clock and Clock Systems Performance Measures

    DTIC Science & Technology

    1995-12-01

    TUTORIAL: CLOCK AND CLOCK SYSTEMS PERFORMANCE MEASURES David W. Allan Allan’s TIME Introduction This tutorial contains basic material...very important ITU Handbook being prepared at this tim; which goes much further than this tutorial has time to do. I highly recommend it as an...the world who have written the ten chapters in this handbook. The title of the Handbook is, "Selection and use of Precise Frequency and Time Systems

  10. The Neurospora circadian clock: simple or complex?

    PubMed Central

    Bell-Pedersen, D; Crosthwaite, S K; Lakin-Thomas, P L; Merrow, M; Økland, M

    2001-01-01

    The fungus Neurospora crassa is being used by a number of research groups as a model organism to investigate circadian (daily) rhythmicity. In this review we concentrate on recent work relating to the complexity of the circadian system in this organism. We discuss: the advantages of Neurospora as a model system for clock studies; the frequency (frq), white collar-1 and white collar-2 genes and their roles in rhythmicity; the phenomenon of rhythmicity in null frq mutants and its implications for clock mechanisms; the study of output pathways using clock-controlled genes; other rhythms in fungi; mathematical modelling of the Neurospora circadian system; and the application of new technologies to the study of Neurospora rhythmicity. We conclude that there may be many gene products involved in the clock mechanism, there may be multiple interacting oscillators comprising the clock mechanism, there may be feedback from output pathways onto the oscillator(s) and from the oscillator(s) onto input pathways, and there may be several independent clocks coexisting in one organism. Thus even a relatively simple lower eukaryote can be used to address questions about a complex, networked circadian system. PMID:11710976

  11. Mitigating aliasing in atomic clocks

    NASA Astrophysics Data System (ADS)

    Uys, Hermann; Akhalwaya, Ismail; Sastrawan, Jarrah; Biercuk, Michael

    2015-05-01

    Passive atomic clocks periodically calibrate a classical local oscillator against an atomic quantum reference through feedback. The periodic nature of this correction leads to undesirable aliasing noise. The Dick Effect, is a special case of aliasing noise consisting of the down-conversion of clock noise at harmonics of the correction frequency to a frequency of zero. To combat the Dick effect and aliasing noise in general, we suggest an extension to the usual feedback protocol, in which we incorporate information from multiple past measurements into the correction after the most recent measurement, approximating a crude low pass anti-aliasing filter of the noise. An analytical frequency domain analysis of the approach is presented and supported by numerical time domain simulations.

  12. Photoperiod-dependent regulation of cell growth by PpCCA1a and PpCCA1b genes encoding single-myb clock proteins in the moss Physcomitrella patens.

    PubMed

    Okada, Ryo; Satbhai, Santosh B; Aoki, Setsuyuki

    2009-10-01

    The PpCCA1a and PpCCA1b genes of the moss Physcomitrella patens are functional homologs of the Arabidopsis thaliana circadian clock genes CCA1/LHY. We made use of disruptant lines for PpCCA1a and/or PpCCA1b to elucidate the physiological significance of these genes in the growth of moss protonemal tissue under alternating day/night cycles. Protonemal cells of the double disruptant line, carrying neither of the two genes, grew faster than those of the wild-type plant (WT) in long days (LD), whereas no difference in the growth rate was detected between them in short days (SD). The double disruptant line also showed day length-dependent phenotypic changes in the PpCCA1b promoter activity: the diurnal profile of bioluminescence from the P(CCA1b)::LUC+ reporter strain was more significantly affected in LD than in SD. These observations are the first demonstration of a physiological function of the circadian clock in non-angiosperm land plants, and are consistent with recent findings that the clock controls hypocotyl elongation of A. thaliana in a photoperiod-dependent manner.

  13. Modeling Light Adaptation in Circadian Clock: Prediction of the Response That Stabilizes Entrainment

    PubMed Central

    Yoshinaga, Tetsuya; Aihara, Kazuyuki

    2011-01-01

    Periods of biological clocks are close to but often different from the rotation period of the earth. Thus, the clocks of organisms must be adjusted to synchronize with day-night cycles. The primary signal that adjusts the clocks is light. In Neurospora, light transiently up-regulates the expression of specific clock genes. This molecular response to light is called light adaptation. Does light adaptation occur in other organisms? Using published experimental data, we first estimated the time course of the up-regulation rate of gene expression by light. Intriguingly, the estimated up-regulation rate was transient during light period in mice as well as Neurospora. Next, we constructed a computational model to consider how light adaptation had an effect on the entrainment of circadian oscillation to 24-h light-dark cycles. We found that cellular oscillations are more likely to be destabilized without light adaption especially when light intensity is very high. From the present results, we predict that the instability of circadian oscillations under 24-h light-dark cycles can be experimentally observed if light adaptation is altered. We conclude that the functional consequence of light adaptation is to increase the adjustability to 24-h light-dark cycles and then adapt to fluctuating environments in nature. PMID:21698191

  14. A GPS Disciplined Rubidium Clock

    DTIC Science & Technology

    1989-11-01

    A GPS DISCIPLINED RUBIDIUM CLOCK .Wayne Dewey. Kincmctrics/TrueTime 3243 Sarita Rosa Ave. Santa Rosa, CA 95407 Abstract Sub-microsecond timing ...accuracy during periods when no satellites are visible, a highly sta1,lc local time base is required. For those cases which require Cesililll oscillat...tcrxxr stability. INTRODUCTION In recerlt years, time syr~chronization requirements between rer-note sites has becorrie rrlora clr:rriiir~tilr

  15. Cost and Precision of Brownian Clocks

    NASA Astrophysics Data System (ADS)

    Barato, Andre C.; Seifert, Udo

    2016-10-01

    Brownian clocks are biomolecular networks that can count time. A paradigmatic example are proteins that go through a cycle, thus regulating some oscillatory behavior in a living system. Typically, such a cycle requires free energy often provided by ATP hydrolysis. We investigate the relation between the precision of such a clock and its thermodynamic costs. For clocks driven by a constant thermodynamic force, a given precision requires a minimal cost that diverges as the uncertainty of the clock vanishes. In marked contrast, we show that a clock driven by a periodic variation of an external protocol can achieve arbitrary precision at arbitrarily low cost. This result constitutes a fundamental difference between processes driven by a fixed thermodynamic force and those driven periodically. As a main technical tool, we map a periodically driven system with a deterministic protocol to one subject to an external protocol that changes in stochastic time intervals, which simplifies calculations significantly. In the nonequilibrium steady state of the resulting bipartite Markov process, the uncertainty of the clock can be deduced from the calculable dispersion of a corresponding current.

  16. A putative flowering-time-related Dof transcription factor gene, JcDof3, is controlled by the circadian clock in Jatropha curcas.

    PubMed

    Yang, Jing; Yang, Ming-Feng; Zhang, Wen-Peng; Chen, Fan; Shen, Shi-Hua

    2011-12-01

    Plant-specific DNA-binding transcription factors with one finger (Dof) perform important roles in several biological processes. A yeast one-hybrid cDNA library of Jatropha curcas was used to identify Dof-type transcription factors. JcDof3, isolated from the library as a full-length cDNA, encoded a protein of 518 amino acids and contained a highly conserved Dof domain. Yeast one-hybrid systems and subcellular localization assays confirmed that JcDof3 was a typical transcription factor. In contrast to arrhythmic expression at basal level in etiolated cotyledons under continuous dark conditions, the circadian oscillations of JcDof3 transcripts were observed under long day, short day or continuous light regimes. A phylogenetic analysis showed that JcDof3 was clustered into the same clade with CYCLING DOF FACTOR (CDF), which interacts with F-box protein to regulate photoperiodic flowering. Moreover, a yeast two-hybrid assay showed that JcDof3 also interacted with F-box proteins. Our results suggest that JcDof3 is a circadian clock regulated gene, and might be involved in the flowering time regulation of J. curcas.

  17. Circadian clocks, obesity and cardiometabolic function.

    PubMed

    Scott, E M

    2015-09-01

    Life on earth is governed by the continuous 24-h cycle of light and dark. Organisms have adapted to this environment with clear diurnal rhythms in their physiology and metabolism, enabling them to anticipate predictable environmental fluctuations over the day and to optimize the timing of relevant biological processes to this cycle. These rhythms are regulated by molecular circadian clocks, and current evidence suggests that interactions between the central and peripheral molecular clocks are important in metabolic and vascular functions. Disrupting this process through mutations in the core clock genes or by interfering with the environmental zeitgebers that entrain the clock appear to modulate the function of cells and tissues, leading to an increased risk for cardiometabolic disease.

  18. Repressor Dimerization in the Zebrafish Somitogenesis Clock

    PubMed Central

    Cinquin, Olivier

    2007-01-01

    The oscillations of the somitogenesis clock are linked to the fundamental process of vertebrate embryo segmentation, yet little is known about their generation. In zebrafish, it has been proposed that Her proteins repress the transcription of their own mRNA. However, in its simplest form, this model is incompatible with the fact that morpholino knockdown of Her proteins can impair expression of their mRNA. Simple self-repression models also do not account for the spatiotemporal pattern of gene expression, with waves of gene expression shrinking as they propagate. Here we study computationally the networks generated by the wealth of dimerization possibilities amongst transcriptional repressors in the zebrafish somitogenesis clock. These networks can reproduce knockdown phenotypes, and strongly suggest the existence of a Her1–Her7 heterodimer, so far untested experimentally. The networks are the first reported to reproduce the spatiotemporal pattern of the zebrafish somitogenesis clock; they shed new light on the role of Her13.2, the only known link between the somitogenesis clock and positional information in the paraxial mesoderm. The networks can also account for perturbations of the clock by manipulation of FGF signaling. Achieving an understanding of the interplay between clock oscillations and positional information is a crucial first step in the investigation of the segmentation mechanism. PMID:17305423

  19. Clock time is absolute and universal

    NASA Astrophysics Data System (ADS)

    Shen, Xinhang

    2015-09-01

    A critical error is found in the Special Theory of Relativity (STR): mixing up the concepts of the STR abstract time of a reference frame and the displayed time of a physical clock, which leads to use the properties of the abstract time to predict time dilation on physical clocks and all other physical processes. Actually, a clock can never directly measure the abstract time, but can only record the result of a physical process during a period of the abstract time such as the number of cycles of oscillation which is the multiplication of the abstract time and the frequency of oscillation. After Lorentz Transformation, the abstract time of a reference frame expands by a factor gamma, but the frequency of a clock decreases by the same factor gamma, and the resulting multiplication i.e. the displayed time of a moving clock remains unchanged. That is, the displayed time of any physical clock is an invariant of Lorentz Transformation. The Lorentz invariance of the displayed times of clocks can further prove within the framework of STR our earth based standard physical time is absolute, universal and independent of inertial reference frames as confirmed by both the physical fact of the universal synchronization of clocks on the GPS satellites and clocks on the earth, and the theoretical existence of the absolute and universal Galilean time in STR which has proved that time dilation and space contraction are pure illusions of STR. The existence of the absolute and universal time in STR has directly denied that the reference frame dependent abstract time of STR is the physical time, and therefore, STR is wrong and all its predictions can never happen in the physical world.

  20. Mammalian retinal Müller cells have circadian clock function

    PubMed Central

    Xu, Lili; Ruan, Guoxiang; Dai, Heng; Liu, Andrew C.; Penn, John

    2016-01-01

    Purpose To test whether Müller glia of the mammalian retina have circadian rhythms. Methods We used Müller glia cultures isolated from mouse lines or from humans and bioluminescent reporters of circadian clock genes to monitor molecular circadian rhythms. The clock gene dependence of the Müller cell rhythms was tested using clock gene knockout mouse lines or with siRNA for specific clock genes. Results We demonstrated that retinal Müller glia express canonical circadian clock genes, are capable of sustained circadian oscillations in isolation from other cell types, and exhibit unique features of their molecular circadian clock compared to the retina as a whole. Mouse and human Müller cells demonstrated circadian clock function; however, they exhibited species-specific differences in the gene dependence of their clocks. Conclusions Müller cells are the first mammalian retinal cell type in which sustained circadian rhythms have been demonstrated in isolation from other retinal cells. PMID:27081298

  1. Periodization

    PubMed Central

    Lorenz, Daniel S.; Reiman, Michael P.; Walker, John C.

    2010-01-01

    Background: Clinicians are constantly faced with the challenge of designing training programs for injured and noninjured athletes that maximize healing and optimize performance. Periodization is a concept of systematic progression—that is, resistance training programs that follow predictable patterns of change in training variables. The strength training literature is abundant with studies comparing periodization schemes on uninjured, trained, and untrained athletes. The rehabilitation literature, however, is scarce with information about how to optimally design resistance training programs based on periodization principles for injured athletes. The purpose of this review is to discuss relevant training variables and methods of periodization, as well as periodization program outcomes. A secondary purpose is to provide an anecdotal framework regarding implementation of periodization principles into rehabilitation programs. Evidence Acquisition: A Medline search from 1979 to 2009 was implemented with the keywords periodization, strength training, rehabilitation, endurance, power, hypertrophy, and resistance training with the Boolean term AND in all possible combinations in the English language. Each author also undertook independent hand searching of article references used in this review. Results: Based on the studies researched, periodized strength training regimens demonstrate improved outcomes as compared to nonperiodized programs. Conclusions: Despite the evidence in the strength training literature supporting periodization programs, there is a considerable lack of data in the rehabilitation literature about program design and successful implementation of periodization into rehabilitation programs. PMID:23015982

  2. Increased Anxiety in Offspring Reared by Circadian Clock Mutant Mice

    PubMed Central

    Koizumi, Hiroko; Kurabayashi, Nobuhiro; Watanabe, Yuto; Sanada, Kamon

    2013-01-01

    The maternal care that offspring receive from their mothers early in life influences the offspring’s development of emotional behavior in adulthood. Here we found that offspring reared by circadian clock-impaired mice show elevated anxiety-related behavior. Clock mutant mice harboring a mutation in Clock, a key component of the molecular circadian clock, display altered daily patterns of nursing behavior that is fragmented during the light period, instead of long bouts of nursing behavior in wild-type mice. Adult wild-type offspring fostered by Clock mutant mice exhibit increased anxiety-related behavior. This is coupled with reduced levels of brain serotonin at postnatal day 14, whose homeostasis during the early postnatal period is critical for normal emotional behavior in adulthood. Together, disruption of the circadian clock in mothers has an adverse impact on establishing normal anxiety levels in offspring, which may increase their risk of developing anxiety disorders. PMID:23776596

  3. Egyptian "Star Clocks"

    NASA Astrophysics Data System (ADS)

    Symons, Sarah

    Diagonal, transit, and Ramesside star clocks are tables of astronomical information occasionally found in ancient Egyptian temples, tombs, and papyri. The tables represent the motions of selected stars (decans and hour stars) throughout the Egyptian civil year. Analysis of star clocks leads to greater understanding of ancient Egyptian constellations, ritual astronomical activities, observational practices, and pharaonic chronology.

  4. Biological Clocks & Circadian Rhythms

    ERIC Educational Resources Information Center

    Robertson, Laura; Jones, M. Gail

    2009-01-01

    The study of biological clocks and circadian rhythms is an excellent way to address the inquiry strand in the National Science Education Standards (NSES) (NRC 1996). Students can study these everyday phenomena by designing experiments, gathering and analyzing data, and generating new experiments. As students explore biological clocks and circadian…

  5. BUGS system clock distributor

    NASA Technical Reports Server (NTRS)

    Dietrich, Thomas M.

    1991-01-01

    A printed circuit board which will provide external clocks and precisely measure the time at which events take place was designed for the Bristol University Gas Spectrometer (BUGS). The board, which was designed to interface both mechanically and electrically to the Computer Automated Measurement and Control (CAMAC) system, has been named the BUGS system clock control. The board's design and use are described.

  6. Glucagon-like peptide-1: The missing link in the metabolic clock?

    PubMed

    Brubaker, Patricia L; Gil-Lozano, Manuel

    2016-04-01

    Circadian expression of clock genes in peripheral tissues is critical to the coordinated regulation of intestinal digestive and absorptive functions, insulin secretion, and peripheral tissue nutrient deposition during periods of nutrient ingestion, thereby preventing metabolic dysregulation. As glucagon-like peptide-1 is a key incretin hormone that regulates glucose-dependent insulin secretion, we hypothesized that this intestinal hormone is a player in the peripheral metabolic clock, linking nutrient ingestion to insulin secretion. We have now established that secretion of glucagon-like peptide-1 from the intestinal L cell shows a rhythmic pattern in rats and humans in vivo that is altered by circadian disruptors, such as constant light exposure, consumption of a Western diet and feeding at inappropriate times (i.e., during the light period in rodents). Interestingly, the alterations in the rhythm of the glucagon-like peptide-1 secretory responses were found to parallel the changes in the pattern of insulin responses in association with significant impairments in glucose tolerance. Furthermore, we have detected circadian clock gene expression, and showed circadian secretion of glucagon-like peptide-1 from both the murine and human L cell in vitro. These findings demonstrate that glucagon-like peptide-1 is a functional component of the peripheral metabolic clock, and suggest that altered release of glucagon-like peptide-1 might play a role in the metabolic perturbations that result from circadian disruption.

  7. Gravity, gauges and clocks

    NASA Astrophysics Data System (ADS)

    Teyssandier, Pierre; Tucker, Robin W.

    1996-01-01

    We discuss the definitions of standard clocks in theories of gravitation. These definitions are motivated by the invariance of actions under different gauge symmetries. We contrast the definition of a standard Weyl clock with that of a clock in general relativity and argue that the historical criticisms of theories based on non-metric compatible connections by Einstein, Pauli and others must be considered in the context of Weyl's original gauge symmetry. We argue that standard Einsteinian clocks can be defined in non-Riemannian theories of gravitation by adopting the Weyl group as a local gauge symmetry that preserves the metric and discuss the hypothesis that atomic clocks may be adopted to measure proper time in the presence of non-Riemannian gravitational fields. These ideas are illustrated in terms of a recently developed model of gravitation based on a non-Riemannian spacetime geometry.

  8. Peripheral circadian clocks are diversely affected by adrenalectomy.

    PubMed

    Soták, M; Bryndová, J; Ergang, P; Vagnerová, K; Kvapilová, P; Vodička, M; Pácha, J; Sumová, A

    2016-01-01

    Glucocorticoids are considered to synchronize the rhythmicity of clock genes in peripheral tissues; however, the role of circadian variations of endogenous glucocorticoids is not well defined. In the present study, we examined whether peripheral circadian clocks were impaired by adrenalectomy. To achieve this, we tested the circadian rhythmicity of core clock genes (Bmal1, Per1-3, Cry1, RevErbα, Rora), clock-output genes (Dbp, E4bp4) and a glucocorticoid- and clock-controlled gene (Gilz) in liver, jejunum, kidney cortex, splenocytes and visceral adipose tissue (VAT). Adrenalectomy did not affect the phase of clock gene rhythms but distinctly modulated clock gene mRNA levels, and this effect was partially tissue-dependent. Adrenalectomy had a significant inhibitory effect on the level of Per1 mRNA in VAT, liver and jejunum, but not in kidney and splenocytes. Similarly, adrenalectomy down-regulated mRNA levels of Per2 in splenocytes and VAT, Per3 in jejunum, RevErbα in VAT and Dbp in VAT, kidney and splenocytes, whereas the mRNA amounts of Per1 and Per2 in kidney and Per3 in VAT and splenocytes were up-regulated. On the other hand, adrenalectomy had minimal effects on Rora and E4bp4 mRNAs. Adrenalectomy also resulted in decreased level of Gilz mRNA but did not alter the phase of its diurnal rhythm. Collectively, these findings suggest that adrenalectomy alters the mRNA levels of core clock genes and clock-output genes in peripheral organs and may cause tissue-specific modulations of their circadian profiles, which are reflected in changes of the amplitudes but not phases. Thus, the circulating corticosteroids are necessary for maintaining the high-amplitude rhythmicity of the peripheral clocks in a tissue-specific manner.

  9. Metabolic clock generates nutrient anticipation rhythms in mTOR signaling.

    PubMed

    Khapre, Rohini V; Patel, Sonal A; Kondratova, Anna A; Chaudhary, Amol; Velingkaar, Nikkhil; Antoch, Marina P; Kondratov, Roman V

    2014-08-01

    The mTOR signaling pathway modulates metabolic processes with respect to nutrient availability and other growth-related cues. According to the existing paradigm, mTOR complex 1 (mTORC1) activityin vivo is induced by food and gradually decreases during fasting. We found that mTORC1 activity is controlled by an internal clock mechanism different from the known light-entrainable circadian clock. We observed 24-hr rhythms in phosphorylation of mTORC1 downstream targets, which were entrained by food, persisted during fasting and could be uncoupled from oscillating expression of the canonical circadian clock genes. Furthermore, these rhythms were present in tissues of mice with disrupted light-entrainable circadian clock. We propose tissue-specific rhythms in the expression of tor and its negative regulator deptor as the molecular mechanism of the mTORC1 activity oscillation. Our data demonstrate the existence of at least two independent molecular circadian clocks: one providing metabolic adaptation to periodic light/darkness and the other - to feeding.

  10. Molecular targets for small-molecule modulators of circadian clocks

    PubMed Central

    He, Baokun; Chen, Zheng

    2016-01-01

    Background Circadian clocks are endogenous timing systems that regulate various aspects of mammalian metabolism, physiology and behavior. Traditional chronotherapy refers to the administration of drugs in a defined circadian time window to achieve optimal pharmacokinetic and therapeutic efficacies. In recent years, substantial efforts have been dedicated to developing novel small-molecule modulators of circadian clocks. Methods Here, we review the recent progress in the identification of molecular targets of small-molecule clock modulators and their efficacies in clock-related disorders. Specifically, we examine the clock components and regulatory factors as possible molecular targets of small molecules, and we review several key clock-related disorders as promising venues for testing the preventive/therapeutic efficacies of these small molecules. Finally, we also discuss circadian regulation of drug metabolism. Results Small molecules can modulate the period, phase and/or amplitude of the circadian cycle. Core clock proteins, nuclear hormone receptors, and clock-related kinases and other epigenetic regulators are promising molecular targets for small molecules. Through these targets small molecules exert protective effects against clock-related disorders including the metabolic syndrome, immune disorders, sleep disorders and cancer. Small molecules can also modulate circadian drug metabolism and response to existing therapeutics. Conclusion Small-molecule clock modulators target clock components or diverse cellular pathways that functionally impinge upon the clock. Target identification of new small-molecule modulators will deepen our understanding of key regulatory nodes in the circadian network. Studies of clock modulators will facilitate their therapeutic applications, alone or in combination, for clock-related diseases. PMID:26750111

  11. NONO couples the circadian clock to the cell cycle.

    PubMed

    Kowalska, Elzbieta; Ripperger, Juergen A; Hoegger, Dominik C; Bruegger, Pascal; Buch, Thorsten; Birchler, Thomas; Mueller, Anke; Albrecht, Urs; Contaldo, Claudio; Brown, Steven A

    2013-01-29

    Mammalian circadian clocks restrict cell proliferation to defined time windows, but the mechanism and consequences of this interrelationship are not fully understood. Previously we identified the multifunctional nuclear protein NONO as a partner of circadian PERIOD (PER) proteins. Here we show that it also conveys circadian gating to the cell cycle, a connection surprisingly important for wound healing in mice. Specifically, although fibroblasts from NONO-deficient mice showed approximately normal circadian cycles, they displayed elevated cell doubling and lower cellular senescence. At a molecular level, NONO bound to the p16-Ink4A cell cycle checkpoint gene and potentiated its circadian activation in a PER protein-dependent fashion. Loss of either NONO or PER abolished this activation and circadian expression of p16-Ink4A and eliminated circadian cell cycle gating. In vivo, lack of NONO resulted in defective wound repair. Because wound healing defects were also seen in multiple circadian clock-deficient mouse lines, our results therefore suggest that coupling of the cell cycle to the circadian clock via NONO may be useful to segregate in temporal fashion cell proliferation from tissue organization.

  12. NONO couples the circadian clock to the cell cycle

    PubMed Central

    Kowalska, Elzbieta; Ripperger, Juergen A.; Hoegger, Dominik C.; Bruegger, Pascal; Buch, Thorsten; Birchler, Thomas; Mueller, Anke; Albrecht, Urs; Contaldo, Claudio; Brown, Steven A.

    2013-01-01

    Mammalian circadian clocks restrict cell proliferation to defined time windows, but the mechanism and consequences of this interrelationship are not fully understood. Previously we identified the multifunctional nuclear protein NONO as a partner of circadian PERIOD (PER) proteins. Here we show that it also conveys circadian gating to the cell cycle, a connection surprisingly important for wound healing in mice. Specifically, although fibroblasts from NONO-deficient mice showed approximately normal circadian cycles, they displayed elevated cell doubling and lower cellular senescence. At a molecular level, NONO bound to the p16-Ink4A cell cycle checkpoint gene and potentiated its circadian activation in a PER protein-dependent fashion. Loss of either NONO or PER abolished this activation and circadian expression of p16-Ink4A and eliminated circadian cell cycle gating. In vivo, lack of NONO resulted in defective wound repair. Because wound healing defects were also seen in multiple circadian clock-deficient mouse lines, our results therefore suggest that coupling of the cell cycle to the circadian clock via NONO may be useful to segregate in temporal fashion cell proliferation from tissue organization. PMID:23267082

  13. Adipose Clocks: Burning the Midnight Oil

    PubMed Central

    Henriksson, Emma; Lamia, Katja A.

    2015-01-01

    Circadian clocks optimize the timing of physiological processes in synchrony with daily recurring and therefore predictable changes in the environment. Until the late 1990s, circadian clocks were thought to exist only in the central nervous systems of animals; elegant studies in cultured fibroblasts and using genetically encoded reporters in Drosophila melanogaster and in mice showed that clocks are ubiquitous and cell autonomous. These findings inspired investigations of the advantages construed by enabling each organ to independently adjust its function to the time of day. Studies of rhythmic gene expression in several organs suggested that peripheral organ clocks might play an important role in optimizing metabolic physiology by synchronizing tissue-intrinsic metabolic processes to cycles of nutrient availability and energy requirements. The effects of clock disruption in liver, pancreas, muscle, and adipose tissues support that hypothesis. Adipose tissues coordinate energy storage and utilization and modulate behavior and the physiology of other organs by secreting hormones known as “adipokines.” Due to behavior- and environment-driven diurnal variations in supply and demand for chemical and thermal energy, adipose tissues might represent an important peripheral location for coordinating circadian energy balance (intake, storage, and utilization) over the whole organism. Given the complexity of adipose cell types and depots, the sensitivity of adipose tissue biology to age and diet composition, and the plethora of known and yet-to-be-discovered adipokines and lipokines, we have just begun to scratch the surface of understanding the role of circadian clocks in adipose tissues. PMID:25926681

  14. Adipose Clocks: Burning the Midnight Oil.

    PubMed

    Henriksson, Emma; Lamia, Katja A

    2015-10-01

    Circadian clocks optimize the timing of physiological processes in synchrony with daily recurring and therefore predictable changes in the environment. Until the late 1990s, circadian clocks were thought to exist only in the central nervous systems of animals; elegant studies in cultured fibroblasts and using genetically encoded reporters in Drosophila melanogaster and in mice showed that clocks are ubiquitous and cell autonomous. These findings inspired investigations of the advantages construed by enabling each organ to independently adjust its function to the time of day. Studies of rhythmic gene expression in several organs suggested that peripheral organ clocks might play an important role in optimizing metabolic physiology by synchronizing tissue-intrinsic metabolic processes to cycles of nutrient availability and energy requirements. The effects of clock disruption in liver, pancreas, muscle, and adipose tissues support that hypothesis. Adipose tissues coordinate energy storage and utilization and modulate behavior and the physiology of other organs by secreting hormones known as "adipokines." Due to behavior- and environment-driven diurnal variations in supply and demand for chemical and thermal energy, adipose tissues might represent an important peripheral location for coordinating circadian energy balance (intake, storage, and utilization) over the whole organism. Given the complexity of adipose cell types and depots, the sensitivity of adipose tissue biology to age and diet composition, and the plethora of known and yet-to-be-discovered adipokines and lipokines, we have just begun to scratch the surface of understanding the role of circadian clocks in adipose tissues.

  15. Dual regulation of clock gene Per2 expression in discrete brain areas by the circadian pacemaker and methamphetamine-induced oscillator in rats.

    PubMed

    Natsubori, Akiyo; Honma, Ken-ichi; Honma, Sato

    2014-01-01

    Behavioral rhythms induced by methamphetamine (MAP) treatment in rats are independent of the circadian pacemaker in the suprachiasmatic nucleus (SCN). To know the site and mechanism of an underlying oscillation (MAP-induced oscillator; MAO), extra-SCN circadian rhythms in the discrete brain areas were examined in rats with and without the SCN. To fix the phase of MAO, MAP was supplied in drinking water at a restricted time of day for 14 days (R-MAP) and subsequently given ad libitum (ad-MAP). Plain water was given to the controls at the same restricted time (R-Water). Clock gene Per2 expression was measured by a bioluminescence reporter in cultured brain tissues. In SCN-intact rats, MAO was induced by R-MAP and behavioral rhythms were phase-delayed from the restricted time under ad-MAP with relative coordination. Circadian Per2 rhythms in R-MAP rats were not affected in the SCN but were slightly phase-advanced in the olfactory bulb (OB), caudate-putamen (CPU) and substantia nigra (SN) as compared with R-Water rats. Following SCN lesion, R-MAP-induced MAO phase-shifted more slowly and did not show a sign of relative coordination. In these rats, circadian Per2 rhythms were significantly phase-shifted in the OB and SN as compared with SCN-intact rats. These findings indicate that MAO was induced by MAP given at a restricted time of day in association with phase-shifts of the extra-SCN circadian oscillators in the brain dopaminergic areas. The findings also suggest that these extra-SCN oscillators are the components of MAO and receive dual regulation by MAO and the SCN circadian pacemaker.

  16. Shifting the Circadian Rhythm of Feeding in Mice Induces Gastrointestinal, Metabolic and Immune Alterations Which Are Influenced by Ghrelin and the Core Clock Gene Bmal1

    PubMed Central

    Laermans, Jorien; Broers, Charlotte; Beckers, Kelly; Vancleef, Laurien; Steensels, Sandra; Thijs, Theo; Tack, Jan; Depoortere, Inge

    2014-01-01

    Background In our 24-hour society, an increasing number of people are required to be awake and active at night. As a result, the circadian rhythm of feeding is seriously compromised. To mimic this, we subjected mice to restricted feeding (RF), a paradigm in which food availability is limited to short and unusual times of day. RF induces a food-anticipatory increase in the levels of the hunger hormone ghrelin. We aimed to investigate whether ghrelin triggers the changes in body weight and gastric emptying that occur during RF. Moreover, the effect of genetic deletion of the core clock gene Bmal1 on these physiological adaptations was studied. Methods Wild-type, ghrelin receptor knockout and Bmal1 knockout mice were fed ad libitum or put on RF with a normal or high-fat diet (HFD). Plasma ghrelin levels were measured by radioimmunoassay. Gastric contractility was studied in vitro in muscle strips and in vivo (13C breath test). Cytokine mRNA expression was quantified and infiltration of immune cells was assessed histologically. Results The food-anticipatory increase in plasma ghrelin levels induced by RF with normal chow was abolished in HFD-fed mice. During RF, body weight restoration was facilitated by ghrelin and Bmal1. RF altered cytokine mRNA expression levels and triggered contractility changes resulting in an accelerated gastric emptying, independent from ghrelin signaling. During RF with a HFD, Bmal1 enhanced neutrophil recruitment to the stomach, increased gastric IL-1α expression and promoted gastric contractility changes. Conclusions This is the first study demonstrating that ghrelin and Bmal1 regulate the extent of body weight restoration during RF, whereas Bmal1 controls the type of inflammatory infiltrate and contractility changes in the stomach. Disrupting the circadian rhythm of feeding induces a variety of diet-dependent metabolic, immune and gastrointestinal alterations, which may explain the higher prevalence of obesity and immune

  17. Light and the circadian clock mediate time-specific changes in sensitivity to UV-B stress under light/dark cycles

    PubMed Central

    Takeuchi, Tomomi; Newton, Linsey; Burkhardt, Alyssa; Mason, Saundra; Farré, Eva M.

    2014-01-01

    In Arabidopsis, the circadian clock regulates UV-B-mediated changes in gene expression. Here it is shown that circadian clock components are able to inhibit UV-B-induced gene expression in a gene-by-gene-specific manner and act downstream of the initial UV-B sensing by COP1 (CONSTITUTIVE PHOTOMORPHOGENIC 1) and UVR8 (UV RESISTANCE LOCUS 8). For example, the UV-B induction of ELIP1 (EARLY LIGHT INDUCIBLE PROTEIN 1) and PRR9 (PSEUDO-RESPONSE REGULATOR 9) is directly regulated by LUX (LUX ARRYTHMO), ELF4 (EARLY FLOWERING 4), and ELF3. Moreover, time-dependent changes in plant sensitivity to UV-B damage were observed. Wild-type Arabidopsis plants, but not circadian clock mutants, were more sensitive to UV-B treatment during the night periods than during the light periods under diel cycles. Experiments performed under short cycles of 6h light and 6h darkness showed that the increased stress sensitivity of plants to UV-B in the dark only occurred during the subjective night and not during the subjective day in wild-type seedlings. In contrast, the stress sensitivity of Arabidopsis mutants with a compromised circadian clock was still influenced by the light condition during the subjective day. Taken together, the results show that the clock and light modulate plant sensitivity to UV-B stress at different times of the day. PMID:25147271

  18. Light and the circadian clock mediate time-specific changes in sensitivity to UV-B stress under light/dark cycles.

    PubMed

    Takeuchi, Tomomi; Newton, Linsey; Burkhardt, Alyssa; Mason, Saundra; Farré, Eva M

    2014-11-01

    In Arabidopsis, the circadian clock regulates UV-B-mediated changes in gene expression. Here it is shown that circadian clock components are able to inhibit UV-B-induced gene expression in a gene-by-gene-specific manner and act downstream of the initial UV-B sensing by COP1 (CONSTITUTIVE PHOTOMORPHOGENIC 1) and UVR8 (UV RESISTANCE LOCUS 8). For example, the UV-B induction of ELIP1 (EARLY LIGHT INDUCIBLE PROTEIN 1) and PRR9 (PSEUDO-RESPONSE REGULATOR 9) is directly regulated by LUX (LUX ARRYTHMO), ELF4 (EARLY FLOWERING 4), and ELF3. Moreover, time-dependent changes in plant sensitivity to UV-B damage were observed. Wild-type Arabidopsis plants, but not circadian clock mutants, were more sensitive to UV-B treatment during the night periods than during the light periods under diel cycles. Experiments performed under short cycles of 6h light and 6h darkness showed that the increased stress sensitivity of plants to UV-B in the dark only occurred during the subjective night and not during the subjective day in wild-type seedlings. In contrast, the stress sensitivity of Arabidopsis mutants with a compromised circadian clock was still influenced by the light condition during the subjective day. Taken together, the results show that the clock and light modulate plant sensitivity to UV-B stress at different times of the day.

  19. Plant circadian clocks increase photosynthesis, growth, survival, and competitive advantage.

    PubMed

    Dodd, Antony N; Salathia, Neeraj; Hall, Anthony; Kévei, Eva; Tóth, Réka; Nagy, Ferenc; Hibberd, Julian M; Millar, Andrew J; Webb, Alex A R

    2005-07-22

    Circadian clocks are believed to confer an advantage to plants, but the nature of that advantage has been unknown. We show that a substantial photosynthetic advantage is conferred by correct matching of the circadian clock period with that of the external light-dark cycle. In wild type and in long- and short-circadian period mutants of Arabidopsis thaliana, plants with a clock period matched to the environment contain more chlorophyll, fix more carbon, grow faster, and survive better than plants with circadian periods differing from their environment. This explains why plants gain advantage from circadian control.

  20. Algorithms to get the maximum operation frequency for skew-tolerant clocking schemes

    NASA Astrophysics Data System (ADS)

    Guerrero, D.; Bellido, M.; Juan, J.; Millan, A.; Ruiz, P.; Ostua, E.; Viejo, J.

    2005-06-01

    Nowadays it is not possible to neglect the delay of interconnection lines. The die size is rising very fast, and the delay of the interconnection lines grows quadrically with it. Also, the fact that the gate delay keeps getting smaller increases the importance of the delay of the interconnection lines. The delay of the clock lines is specially important: If the clock skew is underestimated and the clocking scheme is not properly designed, then the system may not work under any clock frequency. In this paper we evaluate the timing performance of three skew-tolerant clocking schemes. These schemes are the well known Master-Slave clocking scheme (MS) and two schemes developed by the authors: Parallel Alternating Latches Clocking Scheme (PALACS) and four-phase Parallel Alternating Latches Clocking Scheme (four-phase PALACS). To carry out these analysis, the authors introduce new algorithms to obtain the clock waveforms required by a synchronous sequential circuit. Separated algorithms were developed for every clocking scheme. The algorithms take a set of timing parameters as input and generate a chronogram of the circuit trying to minimise the clock period but ensuring the timing restrictions of the circuit are met for a given clock skew. Using these algorithms is it possible to draw a representation of the computation frequency as a function of the clock skew for every clock scheme. Once we have estimated the timing parameters and the skew, these representations can help us to choose the best clocking scheme for our design.

  1. Optical clocks and relativity.

    PubMed

    Chou, C W; Hume, D B; Rosenband, T; Wineland, D J

    2010-09-24

    Observers in relative motion or at different gravitational potentials measure disparate clock rates. These predictions of relativity have previously been observed with atomic clocks at high velocities and with large changes in elevation. We observed time dilation from relative speeds of less than 10 meters per second by comparing two optical atomic clocks connected by a 75-meter length of optical fiber. We can now also detect time dilation due to a change in height near Earth's surface of less than 1 meter. This technique may be extended to the field of geodesy, with applications in geophysics and hydrology as well as in space-based tests of fundamental physics.

  2. Optical Clocks and Relativity

    NASA Astrophysics Data System (ADS)

    Chou, C. W.; Hume, D. B.; Rosenband, T.; Wineland, D. J.

    2010-09-01

    Observers in relative motion or at different gravitational potentials measure disparate clock rates. These predictions of relativity have previously been observed with atomic clocks at high velocities and with large changes in elevation. We observed time dilation from relative speeds of less than 10 meters per second by comparing two optical atomic clocks connected by a 75-meter length of optical fiber. We can now also detect time dilation due to a change in height near Earth’s surface of less than 1 meter. This technique may be extended to the field of geodesy, with applications in geophysics and hydrology as well as in space-based tests of fundamental physics.

  3. Role of cardiotrophin-1 in the regulation of metabolic circadian rhythms and adipose core clock genes in mice and characterization of 24-h circulating CT-1 profiles in normal-weight and overweight/obese subjects.

    PubMed

    López-Yoldi, Miguel; Stanhope, Kimber L; Garaulet, Marta; Chen, X Guoxia; Marcos-Gómez, Beatriz; Carrasco-Benso, María Paz; Santa Maria, Eva M; Escoté, Xavier; Lee, Vivien; Nunez, Marinelle V; Medici, Valentina; Martínez-Ansó, Eduardo; Sáinz, Neira; Huerta, Ana E; Laiglesia, Laura M; Prieto, Jesús; Martínez, J Alfredo; Bustos, Matilde; Havel, Peter J; Moreno-Aliaga, Maria J

    2017-04-01

    Cardiotrophin (CT)-1 is a regulator of glucose and lipid homeostasis. In the present study, we analyzed whether CT-1 also acts to peripherally regulate metabolic rhythms and adipose tissue core clock genes in mice. Moreover, the circadian pattern of plasma CT-1 levels was evaluated in normal-weight and overweight subjects. The circadian rhythmicity of oxygen consumption rate (Vo2) was disrupted in aged obese CT-1-deficient (CT-1(-/-)) mice (12 mo). Although circadian rhythms of Vo2 were conserved in young lean CT-1(-/-) mice (2 mo), CT-1 deficiency caused a phase shift of the acrophase. Most of the clock genes studied (Clock, Bmal1, and Per2) displayed a circadian rhythm in adipose tissue of both wild-type (WT) and CT-1(-/-) mice. However, the pattern was altered in CT-1(-/-) mice toward a lower percentage of the rhythm or lower amplitude, especially for Bmal1 and Clock. Moreover, CT-1 mRNA levels in adipose tissue showed significant circadian fluctuations in young WT mice. In humans, CT-1 plasma profile exhibited a 24-h circadian rhythm in normal-weight but not in overweight subjects. The 24-h pattern of CT-1 was characterized by a pronounced increase during the night (from 02:00 to 08:00). These observations suggest a potential role for CT-1 in the regulation of metabolic circadian rhythms.-López-Yoldi, M., Stanhope, K. L., Garaulet, M., Chen, X. G., Marcos-Gómez, B., Carrasco-Benso, M. P., Santa Maria, E. M., Escoté, X., Lee, V., Nunez, M. V., Medici, V., Martínez-Ansó, E., Sáinz, N., Huerta, A. E., Laiglesia, L. M., Prieto, J., Martínez, J. A., Bustos, M., Havel, P. J., Moreno-Aliaga, M. J. Role of cardiotrophin-1 in the regulation of metabolic circadian rhythms and adipose core clock genes in mice and characterization of 24-h circulating CT-1 profiles in normal-weight and overweight/obese subjects.

  4. The Circadian Clock Mutation Promotes Intestinal Dysbiosis

    PubMed Central

    Voigt, Robin M.; Summa, Keith C.; Forsyth, Christopher B.; Green, Stefan J.; Engen, Phillip; Naqib, Ankur; Vitaterna, Martha H.; Turek, Fred W; Keshavarzian, Ali

    2016-01-01

    Background Circadian rhythm disruption is a prevalent feature of modern day society that is associated with an increase in pro-inflammatory diseases and there is a clear need for a better understanding of the mechanism(s) underlying this phenomenon. We have previously demonstrated that both environmental and genetic circadian rhythm disruption causes intestinal hyperpermeability and exacerbates alcohol-induced intestinal hyperpermeability and liver pathology. The intestinal microbiota can influence intestinal barrier integrity and impact immune system function; thus, in the current study, we sought to determine if genetic alteration of the core circadian clock gene, Clock, altered the intestinal microbiota community. Methods Male ClockΔ19 mutant mice (mice homozygous for a dominant-negative mutant allele) or littermate wild-type mice were fed one of three experimental diets: (1) a standard chow diet, (2) an alcohol-containing diet, or (3) an alcohol-control diet in which the alcohol calories were replaced with dextrose. Stool microbiota was assessed with 16S ribosomal RNA gene amplicon sequencing. Results The fecal microbial community of Clock mutant mice had lower taxonomic diversity, relative to wild type mice and the ClockΔ19 mutation was associated with intestinal dysbiosis when mice were fed either the alcohol-containing or the control diet. We found that alcohol consumption significantly altered the intestinal microbiota in both wild type and Clock mutant mice. Conclusion Our data support a model by which circadian rhythm disruption by the ClockΔ19 mutation perturbs normal intestinal microbial communities and this trend was exacerbated in the context of a secondary dietary intestinal stressor. PMID:26842252

  5. Biochemical basis for the biological clock

    NASA Technical Reports Server (NTRS)

    Morre, D. James; Chueh, Pin-Ju; Pletcher, Jake; Tang, Xiaoyu; Wu, Lian-Ying; Morre, Dorothy M.

    2002-01-01

    NADH oxidases at the external surface of plant and animal cells (ECTO-NOX proteins) exhibit stable and recurring patterns of oscillations with potentially clock-related, entrainable, and temperature-compensated period lengths of 24 min. To determine if ECTO-NOX proteins might represent the ultradian time keepers (pacemakers) of the biological clock, COS cells were transfected with cDNAs encoding tNOX proteins having a period length of 22 min or with C575A or C558A cysteine to alanine replacements having period lengths of 36 or 42 min. Here we demonstrate that such transfectants exhibited 22, 36, or 40 to 42 h circadian patterns in the activity of glyceraldehyde-3-phosphate dehydrogenase, a common clock-regulated protein, in addition to the endogenous 24 h circadian period length. The fact that the expression of a single oscillatory ECTO-NOX protein determines the period length of a circadian biochemical marker (60 X the ECTO-NOX period length) provides compelling evidence that ECTO-NOX proteins are the biochemical ultradian drivers of the cellular biological clock.

  6. Physical mapping of the Period gene on meiotic chromosomes of South American grasshoppers (Acridomorpha, Orthoptera).

    PubMed

    Souza, T E; Oliveira, D L; Santos, J F; Rieger, T T

    2014-12-19

    The single-copy gene Period was located in five grasshopper species belonging to the Acridomorpha group through permanent in situ hybridization (PISH). The mapping revealed one copy of this gene in the L1 chromosome pair in Ommexecha virens, Xyleus discoideus angulatus, Tropidacris collaris, Schistocerca pallens, and Stiphra robusta. A possible second copy was mapped on the L2 chromosome pair in S. robusta, which should be confirmed by further studies. Except for the latter case, the chromosomal position of the Period gene was highly conserved among the four families studied. The S. robusta karyotype also differs from the others both in chromosome number and morphology. The position conservation of the single-copy gene Period contrasts with the location diversification of multigene families in these species. The localization of single-copy genes by PISH can provide new insights about the genomic content and chromosomal evolution of grasshoppers and others insects.

  7. Atomic and gravitational clocks

    NASA Technical Reports Server (NTRS)

    Canuto, V. M.; Goldman, I.

    1982-01-01

    Atomic and gravitational clocks are governed by the laws of electrodynamics and gravity, respectively. While the strong equivalence principle (SEP) assumes that the two clocks have been synchronous at all times, recent planetary data seem to suggest a possible violation of the SEP. Past analysis of the implications of an SEP violation on different physical phenomena revealed no disagreement. However, these studies assumed that the two different clocks can be consistently constructed within the framework. The concept of scale invariance, and the physical meaning of different systems of units, are now reviewed and the construction of two clocks that do not remain synchronous - whose rates are related by a non-constant function beta sub a - is demonstrated. The cosmological character of beta sub a is also discussed.

  8. Iodine Clock Reaction.

    ERIC Educational Resources Information Center

    Mitchell, Richard S.

    1996-01-01

    Describes a combination of solutions that can be used in the study of kinetics using the iodine clock reaction. The combination slows down degradation of the prepared solutions and can be used successfully for several weeks. (JRH)

  9. Resetting Biological Clocks

    ERIC Educational Resources Information Center

    Winfree, Arthur T.

    1975-01-01

    Reports on experiments conducted on two biological clocks, in organisms in the plant and animal kingdoms, which indicate that biological oscillation can be arrested by a single stimulus of a definite strength delivered at the proper time. (GS)

  10. Real-time simulation clock

    NASA Technical Reports Server (NTRS)

    Bennington, Donald R. (Inventor); Crawford, Daniel J. (Inventor)

    1990-01-01

    The invention is a clock for synchronizing operations within a high-speed, distributed data processing network. The clock is actually a distributed system comprising a central clock and multiple site clock interface units (SCIUs) which are connected by means of a fiber optic star network and which operate under control of separate clock software. The presently preferred embodiment is a part of the flight simulation system now in current use at the NASA Langley Research Center.

  11. Postnatal ontogenesis of molecular clock in mouse striatum.

    PubMed

    Cai, Yanning; Liu, Shu; Li, Ning; Xu, Shengli; Zhang, Yanli; Chan, Piu

    2009-04-06

    Striatum is an important brain area whose function is related to motor, emotion and motivation. Interestingly, biological and physiological circadian rhythms have been found in the striatum extensively, suggesting molecular clock machinery works efficiently therein. However, the striatal expression profiles of clock genes have not been characterized systematically. In addition, little is known about when the expression rhythms start during postnatal ontogenesis. In the present study, 24 h mRNA oscillations of 6 principle clock genes (Bmal1, Clock, Npas2, Cry1, Per1 and Rev-erb alpha) were examined in mouse striatum, at early postnatal stage (postnatal day 3), pre-weaning stage (postnatal day 14) and in adult (postnatal day 60). At P3, no daily oscillation was found for all clock genes. At P14, a significant time effect was identified only for Rev-erb alpha and Npas2. At P60, the daily oscillations of these clock genes were at least borderline significant, wi