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Sample records for circadian protein bmal1

  1. Insulin post-transcriptionally modulates Bmal1 protein to affect the hepatic circadian clock

    PubMed Central

    Dang, Fabin; Sun, Xiujie; Ma, Xiang; Wu, Rong; Zhang, Deyi; Chen, Yaqiong; Xu, Qian; Wu, Yuting; Liu, Yi

    2016-01-01

    Although food availability is a potent synchronizer of the peripheral circadian clock in mammals, the underlying mechanisms are unclear. Here, we show that hepatic Bmal1, a core transcription activator of the molecular clock, is post-transcriptionally regulated by signals from insulin, an important hormone that is temporally controlled by feeding. Insulin promotes postprandial Akt-mediated Ser42-phosphorylation of Bmal1 to induce its dissociation from DNA, interaction with 14-3-3 protein and subsequently nuclear exclusion, which results in the suppression of Bmal1 transcriptional activity. Inverted feeding cycles not only shift the phase of daily insulin oscillation, but also elevate the amplitude due to food overconsumption. This enhanced and reversed insulin signalling initiates the reset of clock gene rhythms by altering Bmal1 nuclear accumulation in mouse liver. These results reveal the molecular mechanism of insulin signalling in regulating peripheral circadian rhythms. PMID:27576939

  2. Insulin post-transcriptionally modulates Bmal1 protein to affect the hepatic circadian clock.

    PubMed

    Dang, Fabin; Sun, Xiujie; Ma, Xiang; Wu, Rong; Zhang, Deyi; Chen, Yaqiong; Xu, Qian; Wu, Yuting; Liu, Yi

    2016-01-01

    Although food availability is a potent synchronizer of the peripheral circadian clock in mammals, the underlying mechanisms are unclear. Here, we show that hepatic Bmal1, a core transcription activator of the molecular clock, is post-transcriptionally regulated by signals from insulin, an important hormone that is temporally controlled by feeding. Insulin promotes postprandial Akt-mediated Ser42-phosphorylation of Bmal1 to induce its dissociation from DNA, interaction with 14-3-3 protein and subsequently nuclear exclusion, which results in the suppression of Bmal1 transcriptional activity. Inverted feeding cycles not only shift the phase of daily insulin oscillation, but also elevate the amplitude due to food overconsumption. This enhanced and reversed insulin signalling initiates the reset of clock gene rhythms by altering Bmal1 nuclear accumulation in mouse liver. These results reveal the molecular mechanism of insulin signalling in regulating peripheral circadian rhythms. PMID:27576939

  3. A Novel Bmal1 Mutant Mouse Reveals Essential Roles of the C-Terminal Domain on Circadian Rhythms

    PubMed Central

    Cheon, Solmi; Row, Hansang; Lee, Jiyeon; Han, Dong-Hee; Cho, Sehyung; Kim, Kyungjin

    2015-01-01

    The mammalian circadian clock is an endogenous biological timer comprised of transcriptional/translational feedback loops of clock genes. Bmal1 encodes an indispensable transcription factor for the generation of circadian rhythms. Here, we report a new circadian mutant mouse from gene-trapped embryonic stem cells harboring a C-terminus truncated Bmal1 (Bmal1GTΔC) allele. The homozygous mutant (Bmal1GTΔC/GTΔC) mice immediately lost circadian behavioral rhythms under constant darkness. The heterozygous (Bmal1+/GTΔC) mice displayed a gradual loss of rhythms, in contrast to Bmal1+/- mice where rhythms were sustained. Bmal1GTΔC/GTΔC mice also showed arrhythmic mRNA and protein expression in the SCN and liver. Lack of circadian reporter oscillation was also observed in cultured fibroblast cells, indicating that the arrhythmicity of Bmal1GTΔC/GTΔC mice resulted from impaired molecular clock machinery. Expression of clock genes exhibited distinct responses to the mutant allele in Bmal1+/GTΔC and Bmal1GTΔC/GTΔC mice. Despite normal cellular localization and heterodimerization with CLOCK, overexpressed BMAL1GTΔC was unable to activate transcription of Per1 promoter and BMAL1-dependent CLOCK degradation. These results indicate that the C-terminal region of Bmal1 has pivotal roles in the regulation of circadian rhythms and the Bmal1GTΔC mice constitute a novel model system to evaluate circadian functional mechanism of BMAL1. PMID:26394143

  4. 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

  5. Antioxidant N-acetyl-L-cysteine ameliorates symptoms of premature aging associated with the deficiency of the circadian protein BMAL1

    PubMed Central

    Kondratov, Roman V.; Vykhovanets, Olena; Kondratova, Anna A.; Antoch, Marina P.

    2009-01-01

    Deficiency of the circadian clock protein BMAL1 leads to premature aging and increased levels of reactivate oxygen species in several tissues of mice. In order to investigate the role of oxidative stress in accelerated aging and development of age-related pathologies, we continuously administered the antioxidant N-acetyl-L-cysteine toBmal1-deficient mice through their entire lifespan by supplementing drinking water. We found that the life long treatment with antioxidant significantly increased average and maximal lifespan and reduced the rate of age-dependent weight loss and development of cataracts. At the same time, it had no effect on time of onset and severity of other age-related pathologies characteristic of Bmal1-/- mice, such as joint ossification, reduced hair regrowth and sarcopenia. We conclude that chronic oxidative stress affects longevity and contributes to the development of at least some age-associated pathology, although ROS-independent mechanisms may also play a role. Our bioinformatics analysis identified the presence of a conservative E box element in the promoter regions of several genes encoding major antioxidant enzymes. We speculate that BMAL1 controls antioxidant defense by regulating the expression of major antioxidant enzymes. PMID:20157581

  6. Bmal1 is an essential regulator for circadian cytosolic Ca²⁺ rhythms in suprachiasmatic nucleus neurons.

    PubMed

    Ikeda, Masayuki; Ikeda, Masaaki

    2014-09-01

    The hypothalamic suprachiasmatic nucleus (SCN) plays a pivotal role in the mammalian circadian clock system. Bmal1 is a clock gene that drives transcriptional-translational feedback loops (TTFLs) for itself and other genes, and is expressed in nearly all SCN neurons. Despite strong evidence that Bmal1-null mutant mice display arrhythmic behavior under constant darkness, the function of Bmal1 in neuronal activity is unknown. Recently, periodic changes in the levels of intracellular signaling messengers, such as cytosolic Ca(2+) and cAMP, were suggested to regulate TTFLs. However, the opposite aspect of how clock gene TTFLs regulate cytosolic signaling remains unclear. To investigate intracellular Ca(2+) dynamics under Bmal1 perturbations, we cotransfected some SCN neurons with yellow cameleon together with wild-type or dominant-negative Bmal1 using a gene-gun applied for mouse organotypic cultures. Immunofluorescence staining for a tag protein linked to BMAL1 showed nuclear expression of wild-type BMAL1 and its degradation within 1 week after transfection in SCN neurons. However, dominant-negative BMAL1 did not translocate into the nucleus and the cytosolic signals persisted beyond 1 week. Consistently, circadian Ca(2+) rhythms in SCN neurons were inhibited for longer periods by dominant-negative Bmal1 overexpression. Furthermore, SCN neurons transfected with a Bmal1 shRNA lengthened, whereas those overexpressing wild-type Bmal1 shortened, the periods of Ca(2+) rhythms, with a significant reduction in their amplitude. BMAL1 expression was intact in the majority of neighboring neurons in organotypic cultures. Therefore, we conclude that proper intrinsic Bmal1 expression, but not passive signaling via cell-to-cell interactions, is the determinant of circadian Ca(2+) rhythms in SCN neurons. PMID:25186748

  7. Investigations of the CLOCK and BMAL1 Proteins Binding to DNA: A Molecular Dynamics Simulation Study.

    PubMed

    Xue, Tuo; Song, Chunnian; Wang, Qing; Wang, Yan; Chen, Guangju

    2016-01-01

    The circadian locomotor output cycles kaput (CLOCK), and brain and muscle ARNT-like 1 (BMAL1) proteins are important transcriptional factors of the endogenous circadian clock. The CLOCK and BMAL1 proteins can regulate the transcription-translation activities of the clock-related genes through the DNA binding. The hetero-/homo-dimerization and DNA combination of the CLOCK and BMAL1 proteins play a key role in the positive and negative transcriptional feedback processes. In the present work, we constructed a series of binary and ternary models for the bHLH/bHLH-PAS domains of the CLOCK and BMAL1 proteins, and the DNA molecule, and carried out molecular dynamics simulations, free energy calculations and conformational analysis to explore the interaction properties of the CLOCK and BMAL1 proteins with DNA. The results show that the bHLH domains of CLOCK and BMAL1 can favorably form the heterodimer of the bHLH domains of CLOCK and BMAL1 and the homodimer of the bHLH domains of BMAL1. And both dimers could respectively bind to DNA at its H1-H1 interface. The DNA bindings of the H1 helices in the hetero- and homo-bHLH dimers present the rectangular and diagonal binding modes, respectively. Due to the function of the α-helical forceps in these dimers, the tight gripping of the H1 helices to the major groove of DNA would cause the decrease of interactions at the H1-H2 interfaces in the CLOCK and BMAL1 proteins. The additional PAS domains in the CLOCK and BMAL1 proteins affect insignificantly the interactions of the CLOCK and BMAL1 proteins with the DNA molecule due to the flexible and long loop linkers located at the middle of the PAS and bHLH domains. The present work theoretically explains the interaction mechanisms of the bHLH domains of the CLOCK and BMAL1 proteins with DNA.

  8. Circadian factor BMAL1 in histaminergic neurons regulates sleep architecture.

    PubMed

    Yu, Xiao; Zecharia, Anna; Zhang, Zhe; Yang, Qianzi; Yustos, Raquel; Jager, Polona; Vyssotski, Alexei L; Maywood, Elizabeth S; Chesham, Johanna E; Ma, Ying; Brickley, Stephen G; Hastings, Michael H; Franks, Nicholas P; Wisden, William

    2014-12-01

    Circadian clocks allow anticipation of daily environmental changes. The suprachiasmatic nucleus (SCN) houses the master clock, but clocks are also widely expressed elsewhere in the body. Although some peripheral clocks have established roles, it is unclear what local brain clocks do. We tested the contribution of one putative local clock in mouse histaminergic neurons in the tuberomamillary nucleus to the regulation of the sleep-wake cycle. Histaminergic neurons are silent during sleep, and start firing after wake onset; the released histamine, made by the enzyme histidine decarboxylase (HDC), enhances wakefulness. We found that hdc gene expression varies with time of day. Selectively deleting the Bmal1 (also known as Arntl or Mop3) clock gene from histaminergic cells removes this variation, producing higher HDC expression and brain histamine levels during the day. The consequences include more fragmented sleep, prolonged wake at night, shallower sleep depth (lower nonrapid eye movement [NREM] δ power), increased NREM-to-REM transitions, hindered recovery sleep after sleep deprivation, and impaired memory. Removing BMAL1 from histaminergic neurons does not, however, affect circadian rhythms. We propose that for mammals with polyphasic/nonwake consolidating sleep, the local BMAL1-dependent clock directs appropriately timed declines and increases in histamine biosynthesis to produce an appropriate balance of wake and sleep within the overall daily cycle of rest and activity specified by the SCN.

  9. Circadian factor BMAL1 in histaminergic neurons regulates sleep architecture.

    PubMed

    Yu, Xiao; Zecharia, Anna; Zhang, Zhe; Yang, Qianzi; Yustos, Raquel; Jager, Polona; Vyssotski, Alexei L; Maywood, Elizabeth S; Chesham, Johanna E; Ma, Ying; Brickley, Stephen G; Hastings, Michael H; Franks, Nicholas P; Wisden, William

    2014-12-01

    Circadian clocks allow anticipation of daily environmental changes. The suprachiasmatic nucleus (SCN) houses the master clock, but clocks are also widely expressed elsewhere in the body. Although some peripheral clocks have established roles, it is unclear what local brain clocks do. We tested the contribution of one putative local clock in mouse histaminergic neurons in the tuberomamillary nucleus to the regulation of the sleep-wake cycle. Histaminergic neurons are silent during sleep, and start firing after wake onset; the released histamine, made by the enzyme histidine decarboxylase (HDC), enhances wakefulness. We found that hdc gene expression varies with time of day. Selectively deleting the Bmal1 (also known as Arntl or Mop3) clock gene from histaminergic cells removes this variation, producing higher HDC expression and brain histamine levels during the day. The consequences include more fragmented sleep, prolonged wake at night, shallower sleep depth (lower nonrapid eye movement [NREM] δ power), increased NREM-to-REM transitions, hindered recovery sleep after sleep deprivation, and impaired memory. Removing BMAL1 from histaminergic neurons does not, however, affect circadian rhythms. We propose that for mammals with polyphasic/nonwake consolidating sleep, the local BMAL1-dependent clock directs appropriately timed declines and increases in histamine biosynthesis to produce an appropriate balance of wake and sleep within the overall daily cycle of rest and activity specified by the SCN. PMID:25454592

  10. Circadian Factor BMAL1 in Histaminergic Neurons Regulates Sleep Architecture

    PubMed Central

    Yu, Xiao; Zecharia, Anna; Zhang, Zhe; Yang, Qianzi; Yustos, Raquel; Jager, Polona; Vyssotski, Alexei L.; Maywood, Elizabeth S.; Chesham, Johanna E.; Ma, Ying; Brickley, Stephen G.; Hastings, Michael H.; Franks, Nicholas P.; Wisden, William

    2014-01-01

    Summary Circadian clocks allow anticipation of daily environmental changes [1]. The suprachiasmatic nucleus (SCN) houses the master clock, but clocks are also widely expressed elsewhere in the body [1]. Although some peripheral clocks have established roles [1], it is unclear what local brain clocks do [2, 3]. We tested the contribution of one putative local clock in mouse histaminergic neurons in the tuberomamillary nucleus to the regulation of the sleep-wake cycle. Histaminergic neurons are silent during sleep, and start firing after wake onset [4–6]; the released histamine, made by the enzyme histidine decarboxylase (HDC), enhances wakefulness [7–11]. We found that hdc gene expression varies with time of day. Selectively deleting the Bmal1 (also known as Arntl or Mop3 [12]) clock gene from histaminergic cells removes this variation, producing higher HDC expression and brain histamine levels during the day. The consequences include more fragmented sleep, prolonged wake at night, shallower sleep depth (lower nonrapid eye movement [NREM] δ power), increased NREM-to-REM transitions, hindered recovery sleep after sleep deprivation, and impaired memory. Removing BMAL1 from histaminergic neurons does not, however, affect circadian rhythms. We propose that for mammals with polyphasic/nonwake consolidating sleep, the local BMAL1-dependent clock directs appropriately timed declines and increases in histamine biosynthesis to produce an appropriate balance of wake and sleep within the overall daily cycle of rest and activity specified by the SCN. PMID:25454592

  11. Circadian clocks govern calorie restriction-mediated life span extension through BMAL1- and IGF-1-dependent mechanisms.

    PubMed

    Patel, Sonal A; Chaudhari, Amol; Gupta, Richa; Velingkaar, Nikkhil; Kondratov, Roman V

    2016-04-01

    Calorie restriction (CR) increases longevity in many species by unknown mechanisms. The circadian clock was proposed as a potential mediator of CR. Deficiency of the core component of the circadian clock-transcriptional factor BMAL1 (brain and muscle ARNT [aryl hydrocarbon receptor nuclear translocator]-like protein 1)-results in accelerated aging. Here we investigated the role of BMAL1 in mechanisms of CR. The 30% CR diet increased the life span of wild-type (WT) mice by 20% compared to mice on anad libitum(AL) diet but failed to increase life span ofBmal1(-/-)mice. BMAL1 deficiency impaired CR-mediated changes in the plasma levels of IGF-1 and insulin. We detected a statistically significantly reduction of IGF-1 in CRvs.AL by 50 to 70% in WT mice at several daily time points tested, while inBmal1(-/-)the reduction was not significant. Insulin levels in WT were reduced by 5 to 9%, whileBmal1(-/-)induced it by 10 to 35% at all time points tested. CR up-regulated the daily average expression ofBmal1(by 150%) and its downstream target genesPeriods(by 470% forPer1and by 130% forPer2). We propose that BMAL1 is an important mediator of CR, and activation of BMAL1 might link CR mechanisms with biologic clocks.-Patel, S. A., Chaudhari, A., Gupta, R., Velingkaar, N., Kondratov, R. V. Circadian clocks govern calorie restriction-mediated life span extension through BMAL1- and IGF-1-dependent mechanisms.

  12. Cryptochrome 1 regulates the circadian clock through dynamic interactions with the BMAL1 C-terminus

    PubMed Central

    Sammons, Patrick J.; Khan, Sanjoy K.; Parsley, Nicole C.; Ramanathan, Chidambaram; Lee, Hsiau-Wei; Liu, Andrew C.; Partch, Carrie L.

    2015-01-01

    The molecular circadian clock in mammals is generated from transcriptional activation by the bHLH-PAS transcription factor CLOCK–BMAL1 and subsequent repression by PERIOD and CRYPTOCHROME (CRY). The mechanism by which CRYs repress CLOCK–BMAL1 to close the negative feedback loop and generate 24-hour timing is not known. Here we show that CRY1 competes for binding with coactivators to the intrinsically unstructured C-terminal transactivation domain (TAD) of BMAL1 to establish a functional switch between activation and repression of CLOCK–BMAL1. Mutations within the TAD that alter affinities for coregulators change the balance of repression and activation to consequently change intrinsic circadian period or eliminate cycling altogether. Our results suggest that CRY1 fulfills its role as an essential circadian repressor by sequestering the TAD from coactivators and highlight regulation of the BMAL1 TAD as a critical mechanism for establishing circadian timing. PMID:25961797

  13. Investigations of the CLOCK and BMAL1 Proteins Binding to DNA: A Molecular Dynamics Simulation Study

    PubMed Central

    Xue, Tuo; Song, Chunnian; Wang, Qing; Wang, Yan; Chen, Guangju

    2016-01-01

    The circadian locomotor output cycles kaput (CLOCK), and brain and muscle ARNT-like 1 (BMAL1) proteins are important transcriptional factors of the endogenous circadian clock. The CLOCK and BMAL1 proteins can regulate the transcription-translation activities of the clock-related genes through the DNA binding. The hetero-/homo-dimerization and DNA combination of the CLOCK and BMAL1 proteins play a key role in the positive and negative transcriptional feedback processes. In the present work, we constructed a series of binary and ternary models for the bHLH/bHLH-PAS domains of the CLOCK and BMAL1 proteins, and the DNA molecule, and carried out molecular dynamics simulations, free energy calculations and conformational analysis to explore the interaction properties of the CLOCK and BMAL1 proteins with DNA. The results show that the bHLH domains of CLOCK and BMAL1 can favorably form the heterodimer of the bHLH domains of CLOCK and BMAL1 and the homodimer of the bHLH domains of BMAL1. And both dimers could respectively bind to DNA at its H1-H1 interface. The DNA bindings of the H1 helices in the hetero- and homo-bHLH dimers present the rectangular and diagonal binding modes, respectively. Due to the function of the α-helical forceps in these dimers, the tight gripping of the H1 helices to the major groove of DNA would cause the decrease of interactions at the H1-H2 interfaces in the CLOCK and BMAL1 proteins. The additional PAS domains in the CLOCK and BMAL1 proteins affect insignificantly the interactions of the CLOCK and BMAL1 proteins with the DNA molecule due to the flexible and long loop linkers located at the middle of the PAS and bHLH domains. The present work theoretically explains the interaction mechanisms of the bHLH domains of the CLOCK and BMAL1 proteins with DNA. PMID:27153104

  14. Investigations of the CLOCK and BMAL1 Proteins Binding to DNA: A Molecular Dynamics Simulation Study.

    PubMed

    Xue, Tuo; Song, Chunnian; Wang, Qing; Wang, Yan; Chen, Guangju

    2016-01-01

    The circadian locomotor output cycles kaput (CLOCK), and brain and muscle ARNT-like 1 (BMAL1) proteins are important transcriptional factors of the endogenous circadian clock. The CLOCK and BMAL1 proteins can regulate the transcription-translation activities of the clock-related genes through the DNA binding. The hetero-/homo-dimerization and DNA combination of the CLOCK and BMAL1 proteins play a key role in the positive and negative transcriptional feedback processes. In the present work, we constructed a series of binary and ternary models for the bHLH/bHLH-PAS domains of the CLOCK and BMAL1 proteins, and the DNA molecule, and carried out molecular dynamics simulations, free energy calculations and conformational analysis to explore the interaction properties of the CLOCK and BMAL1 proteins with DNA. The results show that the bHLH domains of CLOCK and BMAL1 can favorably form the heterodimer of the bHLH domains of CLOCK and BMAL1 and the homodimer of the bHLH domains of BMAL1. And both dimers could respectively bind to DNA at its H1-H1 interface. The DNA bindings of the H1 helices in the hetero- and homo-bHLH dimers present the rectangular and diagonal binding modes, respectively. Due to the function of the α-helical forceps in these dimers, the tight gripping of the H1 helices to the major groove of DNA would cause the decrease of interactions at the H1-H2 interfaces in the CLOCK and BMAL1 proteins. The additional PAS domains in the CLOCK and BMAL1 proteins affect insignificantly the interactions of the CLOCK and BMAL1 proteins with the DNA molecule due to the flexible and long loop linkers located at the middle of the PAS and bHLH domains. The present work theoretically explains the interaction mechanisms of the bHLH domains of the CLOCK and BMAL1 proteins with DNA. PMID:27153104

  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. Dynamical mechanism of Bmal 1 / Rev- erbα loop in circadian clock

    NASA Astrophysics Data System (ADS)

    Li, Ying; Liu, Zengrong

    2015-07-01

    In mammals, the circadian clock is driven by multiple integrated transcriptional feedback loops involving three kinds of central clock-controlled elements (CCEs): E-boxes, D-boxes and ROR-elements. With the aid of CCEs, the concentrations of the active proteins are approximated by the delayed concentrations of mRNAs, which simplifies the circadian system drastically. The regulatory loop composed by BMAL1 and REV-ERB- α plays important roles in circadian clock. With delay differential equations, we gave a mathematical model of this loop and investigated its dynamical mechanisms. Specially, we theoretically provided the sufficient conditions for sustained oscillation of the loop with Hopf bifurcation theory. The total of delays determines the emergence of oscillators, which explains the crucial roles of delays in circadian clock revealed by biological experiments. Numerically, we studied the amplitude and period against the variations of delays and the degradation rates. The different sensitivities of amplitude and period on these factors provide ideas to adjust the amplitude or period of circadian oscillators.

  17. Histone mono-ubiquitination by a Clock–Bmal1 complex marks Per1 and Per2 genes for circadian feedback

    PubMed Central

    Tamayo, Alfred G.; Duong, Hao A.; Robles, Maria S.; Mann, Matthias; Weitz, Charles J.

    2015-01-01

    Circadian rhythms in mammals are driven by a feedback loop in which the transcription factor Clock–Bmal1 activates expression of Per and Cry proteins, which together form a large nuclear complex (Per complex) that represses Clock–Bmal1 activity. We found that mouse Clock–Bmal1 recruits the Ddb1–Cullin-4 ubiquitin ligase to Per, Cry, and other circadian target genes. Histone 2B mono-ubiquitination at Per genes was rhythmic and depended on Bmal1, Ddb1, and Cullin-4a. Depletion of Ddb1–Cullin-4a or independent reduction of Histone 2B mono-ubiquitination caused defective circadian feedback and reduced the association of the Per complex with DNA-bound Clock–Bmal1. Clock–Bmal1 thus covalently marks Per genes for subsequent recruitment of the Per complex. Our results reveal a chromatin-mediated signal from the positive to the negative limb of the clock that provides a licensing mechanism for circadian feedback. PMID:26323038

  18. Identification of a novel circadian clock modulator controlling BMAL1 expression through a ROR/REV-ERB-response element-dependent mechanism.

    PubMed

    Lee, Jiyeon; Lee, Seungbeom; Chung, Sooyoung; Park, Noheon; Son, Gi Hoon; An, Hongchan; Jang, Jaebong; Chang, Dong-Jo; Suh, Young-Ger; Kim, Kyungjin

    2016-01-15

    Circadian rhythms, biological oscillations with a period of about 24 h, are maintained by an innate genetically determined time-keeping system called the molecular circadian clockwork. Despite the physiological and clinical importance of the circadian clock, development of small molecule modulators targeting the core clock machinery has only recently been initiated. BMAL1, a core clock gene, is controlled by a ROR/REV-ERB-response element (RORE)-dependent mechanism, which plays an important role in stabilizing the period of the molecular circadian clock. Therefore, we aimed to identify a novel small molecule modulator that regulates Bmal1 gene expression in RORE-dependency, thereby influencing the molecular feedback loop of the circadian clock. For this purpose, we carried out a cell-based screen of more than 1000 drug-like compounds, using a luciferase reporter driven by the proximal region of the mouse Bmal1 promoter. One compound, designated KK-S6, repressed the RORE-dependent transcriptional activity of the mBmal1 promoter and reduced endogenous BMAL1 protein expression. More importantly, KK-S6 significantly altered the amplitude of circadian oscillations of Bmal1 and Per2 promoter activities in a dose-dependent manner, but barely affected the period length. KK-S6 effectively decreased mRNA expression of metabolic genes acting downstream of REV-ERBα, Pai-1 and Citrate synthase, that contain RORE cis-element in their promoter. KK-S6 likely acts in a RORE-dependent manner by reinforcing the REV-ERBα activity, though not by the same mechanism as known REV-ERB agonists. In conclusion, the present study demonstrates that KK-S6 functions as a novel modulator of the amplitude of molecular circadian rhythms by influencing RORE-mediated BMAL1 expression.

  19. Smooth-muscle BMAL1 participates in blood pressure circadian rhythm regulation

    PubMed Central

    Xie, Zhongwen; Su, Wen; Liu, Shu; Zhao, Guogang; Esser, Karyn; Schroder, Elizabeth A.; Lefta, Mellani; Stauss, Harald M.; Guo, Zhenheng; Gong, Ming Cui

    2014-01-01

    As the central pacemaker, the suprachiasmatic nucleus (SCN) has long been considered the primary regulator of blood pressure circadian rhythm; however, this dogma has been challenged by the discovery that each of the clock genes present in the SCN is also expressed and functions in peripheral tissues. The involvement and contribution of these peripheral clock genes in the circadian rhythm of blood pressure remains uncertain. Here, we demonstrate that selective deletion of the circadian clock transcriptional activator aryl hydrocarbon receptor nuclear translocator–like (Bmal1) from smooth muscle, but not from cardiomyocytes, compromised blood pressure circadian rhythm and decreased blood pressure without affecting SCN-controlled locomotor activity in murine models. In mesenteric arteries, BMAL1 bound to the promoter of and activated the transcription of Rho-kinase 2 (Rock2), and Bmal1 deletion abolished the time-of-day variations in response to agonist-induced vasoconstriction, myosin phosphorylation, and ROCK2 activation. Together, these data indicate that peripheral inputs contribute to the daily control of vasoconstriction and blood pressure and suggest that clock gene expression outside of the SCN should be further evaluated to elucidate pathogenic mechanisms of diseases involving blood pressure circadian rhythm disruption. PMID:25485682

  20. Bidirectional CLOCK/BMAL1-dependent circadian gene regulation by retinoic acid in vitro

    SciTech Connect

    Shirai, Hidenori; Oishi, Katsutaka; Ishida, Norio . E-mail: n.ishida@aist.go.jp

    2006-12-15

    A central circadian clock located in the suprachiasmatic nucleus (SCN) of the mammalian hypothalamus entrains peripheral clocks through both neural and humoral factors. Although candidates for entrainment factors have been described, their details remain obscure. Here, we screened ligands for nuclear receptors that affect CLOCK/BMAL1-dependent transactivation of the mouse Period1 (mPer1) gene in NIH3T3 cells. We found that retinoic acids (RAs) significantly up-regulate mPer1 expression in an E-box-dependent manner. We also found that RAs up-regulate the expression of other E-box-dependent circadian genes such as mPer2, arginine vasopressin (mAVP), and peroxisome proliferator-activated receptor {alpha} (mPPAR{alpha}). Surprisingly, the effect of RAs on CLOCK/BMAL1 (E-box)-dependent mRNA expression was bidirectional and depended on the presence of exogenous retinoic acid receptor {alpha} (RAR{alpha}). These results suggest that RAs regulate the CLOCK/BMAL1-dependent transcription of circadian genes in a complex manner.

  1. Differential effects of light and feeding on circadian organization of peripheral clocks in a forebrain Bmal1 mutant

    PubMed Central

    Izumo, Mariko; Pejchal, Martina; Schook, Andrew C; Lange, Ryan P; Walisser, Jacqueline A; Sato, Takashi R; Wang, Xiaozhong; Bradfield, Christopher A; Takahashi, Joseph S

    2014-01-01

    In order to assess the contribution of a central clock in the hypothalamic suprachiasmatic nucleus (SCN) to circadian behavior and the organization of peripheral clocks, we generated forebrain/SCN-specific Bmal1 knockout mice by using floxed Bmal1 and pan-neuronal Cre lines. The forebrain knockout mice showed >90% deletion of BMAL1 in the SCN and exhibited an immediate and complete loss of circadian behavior in constant conditions. Circadian rhythms in peripheral tissues persisted but became desynchronized and damped in constant darkness. The loss of synchrony was rescued by light/dark cycles and partially by restricted feeding (only in the liver and kidney but not in the other tissues) in a distinct manner. These results suggest that the forebrain/SCN is essential for internal temporal order of robust circadian programs in peripheral clocks, and that individual peripheral clocks are affected differently by light and feeding in the absence of a functional oscillator in the forebrain. DOI: http://dx.doi.org/10.7554/eLife.04617.001 PMID:25525750

  2. 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. PMID:27091299

  3. 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.

  4. The circadian clock gene Bmal1 acts as a potential anti-oncogene in pancreatic cancer by activating the p53 tumor suppressor pathway.

    PubMed

    Jiang, Weiliang; Zhao, Senlin; Jiang, Xiaohua; Zhang, Erquan; Hu, Guoyong; Hu, Bin; Zheng, Ping; Xiao, Junhua; Lu, Zhanjun; Lu, Yingying; Ni, Jianbo; Chen, Congying; Wang, Xingpeng; Yang, Lijuan; Wan, Rong

    2016-02-28

    Disruption of the circadian clock has been shown to be associated with tumor development. This study aimed to investigate the role of the core circadian gene Bmal1 in pancreatic cancer (PC). We first found that the levels of Bmal1 were downregulated in PC samples and were closely correlated with the clinicopathological features of patients. To dissect the underlying mechanism, we performed a RNA-seq assay followed by systematic gene function and pathway enrichment analyses. We detected an anti-apoptotic and pro-proliferative transcriptome profile after Bmal1 knockdown in PC cells. Further in vitro and in vivo studies confirmed that Bmal1 overexpression significantly inhibited cell proliferation and invasion and induced G2/M cell cycle arrest, whereas Bmal1 knockdown promoted PC growth, as demonstrated in Bmal1-manipulated AsPC-1 and BxPC-3 cell lines. Our mechanistic studies indicated that Bmal1 could directly bind to the p53 gene promoter and thereby transcriptionally activate the downstream tumor suppressor pathway in a p53-dependent manner. In sum, our findings suggest that Bmal1 acts as an anti-oncogene in PC and represents a potential biomarker for its diagnosis.

  5. Circadian factors BMAL1 and RORα control HIF-1α transcriptional activity in nucleus pulposus cells: implications in maintenance of intervertebral disc health

    PubMed Central

    Suyama, Kaori; Silagi, Elizabeth S.; Choi, Hyowon; Sakabe, Kou; Mochida, Joji; Shapiro, Irving M.; Risbud, Makarand V.

    2016-01-01

    BMAL1 and RORα are major regulators of the circadian molecular oscillator. Since previous work in other cell types has shown cross talk between circadian rhythm genes and hypoxic signaling, we investigated the role of BMAL1 and RORα in controlling HIF-1-dependent transcriptional responses in NP cells that exist in the physiologically hypoxic intervertebral disc. HIF-1-dependent HRE reporter activity was further promoted by co-transfection with either BMAL1 or RORα. In addition, stable silencing of BMAL1 or inhibition of RORα activity resulted in decreased HRE activation. Inhibition of RORα also modulated HIF1α-TAD activity. Interestingly, immunoprecipitation studies showed no evidence of BMAL1, CLOCK or RORα binding to HIF-1α in NP cells. Noteworthy, stable silencing of BMAL1 as well as inhibition of RORα decreased expression of select HIF-1 target genes including VEGF, PFKFB3 and Eno1. To delineate if BMAL1 plays a role in maintenance of disc health, we studied the spinal phenotype of BMAL1-null mice. The lumbar discs of null mice evidenced decreased height, and several parameters associated with vertebral trabecular bone quality were also affected in nulls. In addition, null animals showed a higher ratio of cells to matrix in NP tissue and hyperplasia of the annulus fibrosus. Taken together, our results indicate that BMAL1 and RORα form a regulatory loop in the NP and control HIF-1 activity without direct interaction. Importantly, activities of these circadian rhythm molecules may play a role in the adaptation of NP cells to their unique niche. PMID:27049729

  6. Bmal1 and Beta cell clock are required for adaptation to circadian disruption, and their loss of function leads to oxidative stress-induced Beta cell failure in mice

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Circadian disruption has deleterious effects on metabolism. Global deletion of Bmal1, a core clock gene, results in Beta cell dysfunction and diabetes. However, it is unknown if this is due to loss of cell-autonomous function of Bmal1 in Beta cells. To address this, we generated mice with Beta cell ...

  7. 2,2,2-Trichloroethanol lengthens the circadian period of Bmal1-driven circadian bioluminescence rhythms in U2OS cells.

    PubMed

    Gao, Jie; Yang, Caixia; Ding, Hui; Zhang, Yanli; Xue, Jinhua; Cai, Yanning

    2015-07-01

    2,2,2-Trichloroethanol (TCOH) is responsible for the pharmacological actions of chloral hydrate (CH), and is a major metabolite of trichloroethylene. Human exposure to TCOH is known to be increasing. Recently, it was reported that TCOH causes a significant phase delay of Per2 expression in mouse liver when injected daily over the course of several days. However, it is not clear whether TCOH directly modulates the molecular clock. In the present study we used a cell-based assay system to test this possibility. We found that the daily oscillation period of Bmal1 was lengthened to 3 h following treatment with 1.5 mM TCOH, and increased to 5 h with 3 mM TCOH treatment. However, low concentrations of TCOH had no noticeable effects. The effect of TCOH on Per2 oscillation was marginal. Interestingly, serum from rats anesthetized with CH also modulated Bmal1 period, suggesting that exposure to anesthesia should be taken into consideration for circadian rhythm studies. In summary, our study reveals a direct regulation of TCOH on molecular clock. PMID:25956065

  8. Effects of BMAL1-SIRT1-positive cycle on estrogen synthesis in human ovarian granulosa cells: an implicative role of BMAL1 in PCOS.

    PubMed

    Zhang, Jiaou; Liu, Jiansheng; Zhu, Kai; Hong, Yan; Sun, Yun; Zhao, Xiaoming; Du, Yanzhi; Chen, Zi-Jiang

    2016-08-01

    Brain and muscle ARNT-like protein 1 (BMAL1) is necessary for fertility and has been found to be essential to follicle growth and steroidogenesis. Sirtuin1 (SIRT1) has been reported to interact with BMAL1 and function in a circadian manner. Evidence has shown that SIRT1 regulates aromatase expression in estrogen-producing cells. We aimed to ascertain if there is a relationship between polycystic ovary syndrome (PCOS) and BMAL1, and whether and how BMAL1 takes part in estrogen synthesis in human granulosa cells (hGCs). Twenty-four women diagnosed with PCOS and 24 healthy individuals undergoing assisted reproduction were studied. BMAL1 expression in their granulosa cells (GCs) was observed by quantitative real-time polymerase chain reaction (qRT-PCR). The level of expression in the PCOS group was lower than that of the group without PCOS (p < 0.05). We also analyzed estrogen synthesis and aromatase expression in KGN cell lines. Both were downregulated after BMAL1 and SIRT1 knock-down and, conversely, upregulated after overexpression treatments of these two genes in KGN cells. Both BMAL1 and SIRT1 had a mutually positive regulation, as did the phosphorylation of JNK. Furthermore, JNK overexpression increased estrogen synthesis activity and the expression levels of aromatase, BMAL1, and SIRT1. In KGN and hGCs, estrogen synthesis and aromatase expression were downregulated after treatment with JNK and SIRT1 inhibitors. In addition, BMAL1, SIRT1, and JNK expression levels were all downregulated. Our results demonstrate the effects of BMAL1 on estrogen synthesis in hGCs and suggest a BMAL1-SIRT1-JNK positive feedback cycle in this process, which points out an important role of BMAL1 in the development of PCOS. PMID:27117143

  9. Effects of BMAL1-SIRT1-positive cycle on estrogen synthesis in human ovarian granulosa cells: an implicative role of BMAL1 in PCOS.

    PubMed

    Zhang, Jiaou; Liu, Jiansheng; Zhu, Kai; Hong, Yan; Sun, Yun; Zhao, Xiaoming; Du, Yanzhi; Chen, Zi-Jiang

    2016-08-01

    Brain and muscle ARNT-like protein 1 (BMAL1) is necessary for fertility and has been found to be essential to follicle growth and steroidogenesis. Sirtuin1 (SIRT1) has been reported to interact with BMAL1 and function in a circadian manner. Evidence has shown that SIRT1 regulates aromatase expression in estrogen-producing cells. We aimed to ascertain if there is a relationship between polycystic ovary syndrome (PCOS) and BMAL1, and whether and how BMAL1 takes part in estrogen synthesis in human granulosa cells (hGCs). Twenty-four women diagnosed with PCOS and 24 healthy individuals undergoing assisted reproduction were studied. BMAL1 expression in their granulosa cells (GCs) was observed by quantitative real-time polymerase chain reaction (qRT-PCR). The level of expression in the PCOS group was lower than that of the group without PCOS (p < 0.05). We also analyzed estrogen synthesis and aromatase expression in KGN cell lines. Both were downregulated after BMAL1 and SIRT1 knock-down and, conversely, upregulated after overexpression treatments of these two genes in KGN cells. Both BMAL1 and SIRT1 had a mutually positive regulation, as did the phosphorylation of JNK. Furthermore, JNK overexpression increased estrogen synthesis activity and the expression levels of aromatase, BMAL1, and SIRT1. In KGN and hGCs, estrogen synthesis and aromatase expression were downregulated after treatment with JNK and SIRT1 inhibitors. In addition, BMAL1, SIRT1, and JNK expression levels were all downregulated. Our results demonstrate the effects of BMAL1 on estrogen synthesis in hGCs and suggest a BMAL1-SIRT1-JNK positive feedback cycle in this process, which points out an important role of BMAL1 in the development of PCOS.

  10. 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

  11. Generation of myometrium-specific Bmal1 knockout mice for parturition analysis.

    PubMed

    Ratajczak, Christine K; Asada, Minoru; Allen, Gregg C; McMahon, Douglas G; Muglia, Lisa M; Smith, Donté; Bhattacharyya, Sandip; Muglia, Louis J

    2012-01-01

    Human and rodent studies indicate a role for circadian rhythmicity and associated clock gene expression in supporting normal parturition. The importance of clock gene expression in tissues besides the suprachiasmatic nucleus is emerging. Here, a Bmal1 conditional knockout mouse line and a novel Cre transgenic mouse line were used to examine the role of myometrial Bmal1 in parturition. Ninety-two percent (22/24) of control females but only 64% (14/22) of females with disrupted myometrial Bmal1 completed parturition during the expected time window of 5p.m. on Day 19 through to 9a.m. on Day 19.5 of gestation. However, neither serum progesterone levels nor uterine transcript expression of the contractile-associated proteins Connexin43 and Oxytocin receptor differed between females with disrupted myometrial Bmal1 and controls during late gestation. The data indicate a role for myometrial Bmal1 in maintaining normal time of day of parturition.

  12. Quantitative Analyses of Cryptochrome-mBMAL1 Interactions

    PubMed Central

    Czarna, Anna; Breitkreuz, Helena; Mahrenholz, Carsten C.; Arens, Julia; Strauss, Holger M.; Wolf, Eva

    2011-01-01

    The mammalian cryptochromes mCRY1 and mCRY2 act as transcriptional repressors within the 24-h transcription-translational feedback loop of the circadian clock. The C-terminal tail and a preceding predicted coiled coil (CC) of the mCRYs as well as the C-terminal region of the transcription factor mBMAL1 are involved in transcriptional feedback repression. Here we show by fluorescence polarization and isothermal titration calorimetry that purified mCRY1/2CCtail proteins form stable heterodimeric complexes with two C-terminal mBMAL1 fragments. The longer mBMAL1 fragment (BMAL490) includes Lys-537, which is rhythmically acetylated by mCLOCK in vivo. mCRY1 (but not mCRY2) has a lower affinity to BMAL490 than to the shorter mBMAL1 fragment (BMAL577) and a K537Q mutant version of BMAL490. Using peptide scan analysis we identify two mBMAL1 binding epitopes within the coiled coil and tail regions of mCRY1/2 and document the importance of positively charged mCRY1 residues for mBMAL1 binding. A synthetic mCRY coiled coil peptide binds equally well to the short and to the long (wild-type and K537Q mutant) mBMAL1 fragments. In contrast, a peptide including the mCRY1 tail epitope shows a lower affinity to BMAL490 compared with BMAL577 and BMAL490(K537Q). We propose that Lys-537mBMAL1 acetylation enhances mCRY1 binding by affecting electrostatic interactions predominantly with the mCRY1 tail. Our data reveal different molecular interactions of the mCRY1/2 tails with mBMAL1, which may contribute to the non-redundant clock functions of mCRY1 and mCRY2. Moreover, our study suggests the design of peptidic inhibitors targeting the interaction of the mCRY1 tail with mBMAL1. PMID:21521686

  13. The effect of new monochromatic light regimes on egg production and expression of the circadian gene BMAL1 in pigeons1.

    PubMed

    Wang, Y; Ding, J T; Yang, H M; Cao, W; Li, Y B

    2015-05-01

    We examined the effect of monochromatic light supplementation on pigeon reproductive performance and on the expression of the brain and muscle aryl hydrocarbon receptor nuclear translocator-like (BMAL1) protein in the hypothalamic-pituitary-gonadal (HPG) axis. White King pigeons were selected randomly from 4 lofts (510 pairs/loft) with 3 subgroups/loft. The lofts were exposed to one of 4 light treatments for 3 months administered in the morning and evening as follows: blue light (480 nm), green light (540 nm), red light (660 nm), and control white light. The laying rate, fertility rate, and birth rate were recorded. After 3 months, 48 birds were selected randomly from the 4 lofts (6 females and 6 males from each loft), sacrificed, and the HPG axis was isolated. Following exposure to red light, laying rate was greater than the control group (P = 0.013), but there were no significant differences in the fertility rate (P = 0.41) or birth rate (P = 0.66). Expression of BMAL1 in the hypothalamus was unaffected by the light regime but was greater in the pituitary of females exposed to red light (P = 0.046) and in the pituitary of males exposed to the control white light (P = 0.059). The change in BMAL1 expression in the pituitary of females was negatively correlated with birth rate in monochromatic light (P = 0.021). We suggest that reproductive performance of pigeons is improved by light supplementation in the morning and evening. According to these data, 100 pigeons exposed to red light could lay 26.68 more eggs per month than the control group. Additionally, BMAL1 expression in the HPG axis of pigeons exposed to monochromatic light correlated with birth rate.

  14. PER and TIM inhibit the DNA binding activity of a Drosophila CLOCK-CYC/dBMAL1 heterodimer without disrupting formation of the heterodimer: a basis for circadian transcription.

    PubMed

    Lee, C; Bae, K; Edery, I

    1999-08-01

    The Drosophila CLOCK (dCLOCK) and CYCLE (CYC) (also referred to as dBMAL1) proteins are members of the basic helix-loop-helix PAS (PER-ARNT-SIM) superfamily of transcription factors and are required for high-level expression of the circadian clock genes period (per) and timeless (tim). Several lines of evidence indicate that PER, TIM, or a PER-TIM heterodimer somehow inhibit the transcriptional activity of a putative dCLOCK-CYC complex, generating a negative-feedback loop that is a core element of the Drosophila circadian oscillator. In this report we show that PER and/or TIM inhibits the binding of a dCLOCK-CYC heterodimer to an E-box-containing DNA fragment that is present in the 5' nontranscribed region of per and acts as a circadian enhancer element. Surprisingly, inhibition of this DNA binding activity by PER, TIM, or both is not accompanied by disruption of the association between dCLOCK and CYC. The results suggest that the interaction of PER, TIM, or both with the dCLOCK-CYC heterodimer induces a conformational change or masks protein regions in the heterodimer, leading to a reduction in DNA binding activity. Together with other findings, our results strongly suggest that daily cycles in the association of PER and TIM with the dCLOCK-CYC complex probably contribute to rhythmic expression of per and tim.

  15. Circadian clock proteins and immunity.

    PubMed

    Curtis, Anne M; Bellet, Marina M; Sassone-Corsi, Paolo; O'Neill, Luke A J

    2014-02-20

    Immune parameters change with time of day and disruption of circadian rhythms has been linked to inflammatory pathologies. A circadian-clock-controlled immune system might allow an organism to anticipate daily changes in activity and feeding and the associated risk of infection or tissue damage to the host. Responses to bacteria have been shown to vary depending on time of infection, with mice being more at risk of sepsis when challenged ahead of their activity phase. Studies highlight the extent to which the molecular clock, most notably the core clock proteins BMAL1, CLOCK, and REV-ERBα, control fundamental aspects of the immune response. Examples include the BMAL1:CLOCK heterodimer regulating toll-like receptor 9 (TLR9) expression and repressing expression of the inflammatory monocyte chemokine ligand (CCL2) as well as REV-ERBα suppressing the induction of interleukin-6. Understanding the daily rhythm of the immune system could have implications for vaccinations and how we manage infectious and inflammatory diseases.

  16. Circadian clock proteins control adaptation to novel environment and memory formation

    PubMed Central

    A.Kondratova, Anna; V.Dubrovsky, Yuliya; Antoch, Marina P.; Kondratov, Roman V.

    2010-01-01

    Deficiency of the transcription factor BMAL1, a core component of the circadian clock, results in an accelerated aging phenotype in mice. The circadian clock regulates many physiological processes and was recently implicated in control of brain-based activities, such as memory formation and the regulation of emotions. Aging is accompanied by the decline in brain physiology, particularly decline in the response and adaptation to novelty. We investigated the role of the circadian clock in exploratory behavior and habituation to novelty using the open field paradigm. We found that mice with a deficiency of the circadian transcription factor BMAL1 display hyperactivity in novel environments and impaired intra- and intersession habituation, indicative of defects in short- and long-term memory formation. In contrast, mice double-deficient for the circadian proteins CRY1 and CRY2 (repressors of the BMAL1-mediated transcription) demonstrate reduced activity and accelerated habituation when compared to wild type mice. Mice with mutation in theClock gene (encoding the BMAL1 transcription partner) show normal locomotion, but increased rearing activity and impaired intersession habituation. BMAL1 is highly expressed in the neurons of the hippocampus - a brain region associated with spatial memory formation; BMAL1 deficiency disrupts circadian oscillation in gene expression and reactive oxygen species homeostasis in the brain, which may be among the possible mechanisms involved. Thus, we suggest that the BMAL1:CLOCK activity is critical for the proper exploratory and habituation behavior, and that the circadian clock prepares organism for a new round of everyday activities through optimization of behavioral learning. PMID:20519775

  17. BMAL1-dependent regulation of the mTOR signaling pathway delays aging.

    PubMed

    Khapre, Rohini V; Kondratova, Anna A; Patel, Sonal; Dubrovsky, Yuliya; Wrobel, Michelle; Antoch, Marina P; Kondratov, Roman V

    2014-01-01

    The circadian clock, an internal time-keeping system, has been linked with control of aging, but molecular mechanisms of regulation are not known. BMAL1 is a transcriptional factor and core component of the circadian clock; BMAL1 deficiency is associated with premature aging and reduced lifespan. Here we report that activity of mammalian Target of Rapamycin Complex 1 (mTORC1) is increased upon BMAL1 deficiency both in vivo and in cell culture. Increased mTOR signaling is associated with accelerated aging; in accordance with that, treatment with the mTORC1 inhibitor rapamycin increased lifespan of Bmal1-/- mice by 50%. Our data suggest that BMAL1 is a negative regulator of mTORC1 signaling. We propose that the circadian clock controls the activity of the mTOR pathway through BMAL1-dependent mechanisms and this regulation is important for control of aging and metabolism.

  18. The Transcriptional Repressor ID2 Can Interact with the Canonical Clock Components CLOCK and BMAL1 and Mediate Inhibitory Effects on mPer1 Expression*

    PubMed Central

    Ward, Sarah M.; Fernando, Shanik J.; Hou, Tim Y.; Duffield, Giles E.

    2010-01-01

    ID2 is a rhythmically expressed HLH transcriptional repressor. Deletion of Id2 in mice results in circadian phenotypes, highlighted by disrupted locomotor activity rhythms and an enhanced photoentrainment response. ID2 can suppress the transactivation potential of the positive elements of the clock, CLOCK-BMAL1, on mPer1 and clock-controlled gene (CCG) activity. Misregulation of CCGs is observed in Id2−/− liver, and mutant mice exhibit associated alterations in lipid homeostasis. These data suggest that ID2 contributes to both input and output components of the clock and that this may be via interaction with the bHLH clock proteins CLOCK and BMAL1. The aim of the present study was to explore this potential interaction. Coimmunoprecipitation analysis revealed the capability of ID2 to complex with both CLOCK and BMAL1, and mammalian two-hybrid analysis revealed direct interactions of ID2, ID1 and ID3 with CLOCK and BMAL1. Deletion of the ID2 HLH domain rendered ID2 ineffective at inhibiting CLOCK-BMAL1 transactivation, suggesting that interaction between the proteins is via the HLH region. Immunofluorescence analysis revealed overlapping localization of ID2 with CLOCK and BMAL1 in the cytoplasm. Overexpression of CLOCK and BMAL1 in the presence of ID2 resulted in a significant reduction in their nuclear localization, revealing that ID2 can sequester CLOCK and BMAL1 to the cytoplasm. Serum stimulation of Id2−/− mouse embryonic fibroblasts resulted in an enhanced induction of mPer1 expression. These data provide the basis for a molecular mechanism through which ID2 could regulate aspects of both clock input and output through a time-of-day specific interaction with CLOCK and BMAL1. PMID:20861012

  19. Deficiency of circadian protein CLOCK reduces lifespan and increases age-related cataract development in mice.

    PubMed

    Dubrovsky, Yulia V; Samsa, William E; Kondratov, Roman V

    2010-12-01

    Circadian clock is implicated in the regulation of aging. The transcription factor CLOCK, a core component of the circadian system, operates in complex with another circadian clock protein BMAL1. Recently it was demonstrated that BMAL1 deficiency results in premature aging in mice. Here we investigate the aging of mice deficient for CLOCK protein. Deficiency of the CLOCK protein significantly affects longevity: the average lifespan of Clock-/- mice is reduced by 15% compared with wild type mice, while maximum lifespan is reduced by more than 20%. CLOCK deficiency also results in the development of two age-specific pathologies in these mice, cataracts and dermatitis, at a much higher rate than in wild type mice. In contrast to BMAL1 deficient animals, Clock-/- mice do not develop a premature aging phenotype and do not develop the multiple age-associated pathologies characteristic of BMAL1 deficiency. Thus, although CLOCK and BMAL1 form a transcriptional complex, the physiological result of their deficiency is different. Our results suggest that CLOCK plays an important role in aging, specifically; CLOCK activity is critical for the regulation of normal physiology and aging of the lens and skin.

  20. PKCγ participates in food entrainment by regulating BMAL1.

    PubMed

    Zhang, Luoying; Abraham, Diya; Lin, Shu-Ting; Oster, Henrik; Eichele, Gregor; Fu, Ying-Hui; Ptáček, Louis J

    2012-12-11

    Temporally restricted feeding (RF) can phase reset the circadian clocks in numerous tissues in mammals, contributing to altered timing of behavioral and physiological rhythms. However, little is known regarding the underlying molecular mechanism. Here we demonstrate a role for the gamma isotype of protein kinase C (PKCγ) in food-mediated entrainment of behavior and the molecular clock. We found that daytime RF reduced late-night activity in wild-type mice but not mice homozygous for a null mutation of PKCγ (PKCγ(-/-)). Molecular analysis revealed that PKCγ exhibited RF-induced changes in activation patterns in the cerebral cortex and that RF failed to substantially phase shift the oscillation of clock gene transcripts in the absence of PKCγ. PKCγ exerts effects on the clock, at least in part, by stabilizing the core clock component brain and muscle aryl hydrocarbon receptor nuclear translocator like 1 (BMAL1) and reducing its ubiquitylation in a deubiquitination-dependent manner. Taken together, these results suggest that PKCγ plays a role in food entrainment by regulating BMAL1 stability.

  1. Dual attenuation of proteasomal and autophagic BMAL1 degradation in ClockΔ19/+ mice contributes to improved glucose homeostasis

    PubMed Central

    Jeong, Kwon; He, Baokun; Nohara, Kazunari; Park, Noheon; Shin, Youngmin; Kim, Seonghwa; Shimomura, Kazuhiro; Koike, Nobuya; Yoo, Seung-Hee; Chen, Zheng

    2015-01-01

    Circadian clocks orchestrate essential physiology in response to various cues, yet their mechanistic and functional plasticity remains unclear. Here, we investigated ClockΔ19/+ 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. PMID:26228022

  2. Dynamic circadian protein-protein interaction networks predict temporal organization of cellular functions.

    PubMed

    Wallach, Thomas; Schellenberg, Katja; Maier, Bert; Kalathur, Ravi Kiran Reddy; Porras, Pablo; Wanker, Erich E; Futschik, Matthias E; Kramer, Achim

    2013-03-01

    Essentially all biological processes depend on protein-protein interactions (PPIs). Timing of such interactions is crucial for regulatory function. Although circadian (~24-hour) clocks constitute fundamental cellular timing mechanisms regulating important physiological processes, PPI dynamics on this timescale are largely unknown. Here, we identified 109 novel PPIs among circadian clock proteins via a yeast-two-hybrid approach. Among them, the interaction of protein phosphatase 1 and CLOCK/BMAL1 was found to result in BMAL1 destabilization. We constructed a dynamic circadian PPI network predicting the PPI timing using circadian expression data. Systematic circadian phenotyping (RNAi and overexpression) suggests a crucial role for components involved in dynamic interactions. Systems analysis of a global dynamic network in liver revealed that interacting proteins are expressed at similar times likely to restrict regulatory interactions to specific phases. Moreover, we predict that circadian PPIs dynamically connect many important cellular processes (signal transduction, cell cycle, etc.) contributing to temporal organization of cellular physiology in an unprecedented manner. PMID:23555304

  3. Global and hepatocyte-specific ablation of Bmal1 induces hyperlipidaemia and enhances atherosclerosis

    PubMed Central

    Pan, Xiaoyue; Bradfield, Christopher A.; Hussain, M. Mahmood

    2016-01-01

    Circadian rhythms controlled by clock genes affect plasma lipids. Here we show that global ablation of Bmal1 in Apoe−/− and Ldlr−/− mice and its liver-specific ablation in Apoe−/− (L-Bmal1−/−Apoe−/−) mice increases, whereas overexpression of BMAL1 in L-Bmal1−/−Apoe−/− and Apoe−/−mice decreases hyperlipidaemia and atherosclerosis. Bmal1 deficiency augments hepatic lipoprotein secretion and diminishes cholesterol excretion to the bile. Further, Bmal1 deficiency reduces expression of Shp and Gata4. Reductions in Shp increase Mtp expression and lipoprotein production, whereas reductions in Gata4 diminish Abcg5/Abcg8 expression and biliary cholesterol excretion. Forced SHP expression normalizes lipoprotein secretion with no effect on biliary cholesterol excretion, while forced GATA4 expression increases cholesterol excretion to the bile and reduces plasma lipids in L-Bmal1−/−Apoe−/− and Apoe−/− mice. Thus, our data indicate that Bmal1 modulates lipoprotein production and biliary cholesterol excretion by regulating the expression of Mtp and Abcg5/Abcg8 via Shp and Gata4. PMID:27721414

  4. The chondrocyte clock gene Bmal1 controls cartilage homeostasis and integrity

    PubMed Central

    Dudek, Michal; Gossan, Nicole; Yang, Nan; Im, Hee-Jeong; Ruckshanthi, Jayalath P.D.; Yoshitane, Hikari; Li, Xin; Jin, Ding; Wang, Ping; Boudiffa, Maya; Bellantuono, Ilaria; Fukada, Yoshitaka; Boot-Handford, Ray P.; Meng, Qing-Jun

    2015-01-01

    Osteoarthritis (OA) is the most prevalent and debilitating joint disease, and there are currently no effective disease-modifying treatments available. Multiple risk factors for OA, such as aging, result in progressive damage and loss of articular cartilage. Autonomous circadian clocks have been identified in mouse cartilage, and environmental disruption of circadian rhythms in mice predisposes animals to OA-like damage. However, the contribution of the cartilage clock mechanisms to the maintenance of tissue homeostasis is still unclear. Here, we have shown that expression of the core clock transcription factor BMAL1 is disrupted in human OA cartilage and in aged mouse cartilage. Furthermore, targeted Bmal1 ablation in mouse chondrocytes abolished their circadian rhythm and caused progressive degeneration of articular cartilage. We determined that BMAL1 directs the circadian expression of many genes implicated in cartilage homeostasis, including those involved in catabolic, anabolic, and apoptotic pathways. Loss of BMAL1 reduced the levels of phosphorylated SMAD2/3 (p-SMAD2/3) and NFATC2 and decreased expression of the major matrix-related genes Sox9, Acan, and Col2a1, but increased p-SMAD1/5 levels. Together, these results define a regulatory mechanism that links chondrocyte BMAL1 to the maintenance and repair of cartilage and suggest that circadian rhythm disruption is a risk factor for joint diseases such as OA. PMID:26657859

  5. Transcription factor NF-Y is a functional regulator of the transcription of core clock gene Bmal1.

    PubMed

    Xiao, Jun; Zhou, Yongchun; Lai, Hao; Lei, Shi; Chi, Lisa H; Mo, Xianwei

    2013-11-01

    The circadian clock enables organisms to adjust to daily environmental changes and synchronize multiple molecular, biochemical, physiological, and behavioral processes accordingly. In mammalian clock work, Bmal1 is the most important core clock gene, which works with another core clock gene Clock to drive the expression of other clock genes and clock-controlled genes. However, the regulation of Bmal1 has not been fully understood. This work was aimed at identifying the positive regulator(s) of Bmal1 transcription. A series of 5' deletion reporter constructs was generated, and binding site mutations of mouse Bmal1 promoter fragments were cloned into pGL3-basic and pGL3(R2.1)-basic plasmids and transfected into NIH 3T3 cells. Luciferase activity was either measured 48 h after transfection or recorded for 4 days after serum shock. DNA affinity precipitation assay was used to detect the transcription factors binding to Bmal1 promoter. Small interfering RNA against nuclear factor Y, subunit A (NF-YA) and dominant negative NF-YA were employed to study the role of NF-Y in Bmal1 transcription regulation. Deletion and mutation analyses identified two clusters of CCAAT/GC-boxes at the proximal region of Bmal1 promoter as the activating cis-elements. Bmal1 promoter activity was up-regulated by NF-Y and/or Sp1 and repressed by dominant negative NF-YA or siRNA against NF-YA. The activation of Bmal1 promoter activity by NF-Y and Sp1 was inhibited by Rev-Erbα. DNA affinity precipitation assay showed that NF-Y and Sp1 bound to the two CCAAT/GC clusters of Bmal1 promoter. These results indicate that NF-Y is a functional activator of Bmal1 transcription and it cooperates with Sp1 and Rev-Erbα to generate the daily cycle of Bmal1 expression.

  6. Local renal circadian clocks control fluid-electrolyte homeostasis and BP.

    PubMed

    Tokonami, Natsuko; Mordasini, David; Pradervand, Sylvain; Centeno, Gabriel; Jouffe, Céline; Maillard, Marc; Bonny, Olivier; Gachon, Frédéric; Gomez, R Ariel; Sequeira-Lopez, Maria Luisa S; Firsov, Dmitri

    2014-07-01

    The circadian timing system is critically involved in the maintenance of fluid and electrolyte balance and BP control. However, the role of peripheral circadian clocks in these homeostatic mechanisms remains unknown. We addressed this question in a mouse model carrying a conditional allele of the circadian clock gene Bmal1 and expressing Cre recombinase under the endogenous Renin promoter (Bmal1(lox/lox)/Ren1(d)Cre mice). Analysis of Bmal1(lox/lox)/Ren1(d)Cre mice showed that the floxed Bmal1 allele was excised in the kidney. In the kidney, BMAL1 protein expression was absent in the renin-secreting granular cells of the juxtaglomerular apparatus and the collecting duct. A partial reduction of BMAL1 expression was observed in the medullary thick ascending limb. Functional analyses showed that Bmal1(lox/lox)/Ren1(d)Cre mice exhibited multiple abnormalities, including increased urine volume, changes in the circadian rhythm of urinary sodium excretion, increased GFR, and significantly reduced plasma aldosterone levels. These changes were accompanied by a reduction in BP. These results show that local renal circadian clocks control body fluid and BP homeostasis. PMID:24652800

  7. Gene model 129 (Gm129) encodes a novel transcriptional repressor that modulates circadian gene expression.

    PubMed

    Annayev, Yunus; Adar, Sheera; Chiou, Yi-Ying; Lieb, Jason D; Sancar, Aziz; Ye, Rui

    2014-02-21

    The mammalian circadian clock is a molecular oscillator composed of a feedback loop that involves transcriptional activators CLOCK and BMAL1, and repressors Cryptochrome (CRY) and Period (PER). Here we show that a direct CLOCK·BMAL1 target gene, Gm129, is a novel regulator of the feedback loop. ChIP analysis revealed that the CLOCK·BMAL1·CRY1 complex strongly occupies the promoter region of Gm129. Both mRNA and protein levels of GM129 exhibit high amplitude circadian oscillations in mouse liver, and Gm129 gene encodes a nuclear-localized protein that directly interacts with BMAL1 and represses CLOCK·BMAL1 activity. In vitro and in vivo protein-DNA interaction results demonstrate that, like CRY1, GM129 functions as a repressor by binding to the CLOCK·BMAL1 complex on DNA. Although Gm129(-/-) or Cry1(-/-) Gm129(-/-) mice retain a robust circadian rhythm, the peaks of Nr1d1 and Dbp mRNAs in liver exhibit a significant phase delay compared with control. Our results suggest that, in addition to CRYs and PERs, the GM129 protein contributes to the transcriptional feedback loop by modulating CLOCK·BMAL1 activity as a transcriptional repressor.

  8. Premature aging of the hippocampal neurogenic niche in adult Bmal1-deficient mice.

    PubMed

    Ali, Amira A H; Schwarz-Herzke, Beryl; Stahr, Anna; Prozorovski, Timour; Aktas, Orhan; von Gall, Charlotte

    2015-06-01

    Hippocampal neurogenesis undergoes dramatic age-related changes. Mice with targeted deletion of the clock geneBmal1 (Bmal1(-/-)) show disrupted regulation of reactive oxygen species homeostasis, accelerated aging, neurodegeneration and cognitive deficits. As proliferation of neuronal progenitor/precursor cells (NPCs) is enhanced in young Bmal1(-/-) mice, we tested the hypothesis that this results in premature aging of hippocampal neurogenic niche in adult Bmal1(-/-) mice as compared to wildtype littermates. We found significantly reduced pool of hippocampal NPCs, scattered distribution, enhanced survival of NPCs and an increased differentiation of NPCs into the astroglial lineage at the expense of the neuronal lineage. Immunoreaction of the redox sensitive histone deacetylase Sirtuine 1, peroxisomal membrane protein at 70 kDa and expression of the cell cycle inhibitor p21(Waf1/CIP1) were increased in adult Bmal1(-/-) mice. In conclusion, genetic disruption of the molecular clockwork leads to accelerated age-dependent decline in adult neurogenesis presumably as a consequence of oxidative stress.

  9. The PXDLS linear motif regulates circadian rhythmicity through protein–protein interactions

    PubMed Central

    Shalev, Moran; Aviram, Rona; Adamovich, Yaarit; Kraut-Cohen, Judith; Shamia, Tal; Ben-Dor, Shifra; Golik, Marina; Asher, Gad

    2014-01-01

    The circadian core clock circuitry relies on interlocked transcription-translation feedback loops that largely count on multiple protein interactions. The molecular mechanisms implicated in the assembly of these protein complexes are relatively unknown. Our bioinformatics analysis of short linear motifs, implicated in protein interactions, reveals an enrichment of the Pro-X-Asp-Leu-Ser (PXDLS) motif within circadian transcripts. We show that the PXDLS motif can bind to BMAL1/CLOCK and disrupt circadian oscillations in a cell-autonomous manner. Remarkably, the motif is evolutionary conserved in the core clock protein REV-ERBα, and additional proteins implicated in the clock's function (NRIP1, CBP). In this conjuncture, we uncover a novel cross talk between the two principal core clock feedback loops and show that BMAL/CLOCK and REV-ERBα interact and that the PXDLS motif of REV-ERBα participates in their binding. Furthermore, we demonstrate that the PXDLS motifs of NRIP1 and CBP are involved in circadian rhythmicity. Our findings suggest that the PXDLS motif plays an important role in circadian rhythmicity through regulation of protein interactions within the clock circuitry and that short linear motifs can be employed to modulate circadian oscillations. PMID:25260595

  10. Conditional Deletion of Bmal1 in Ovarian Theca Cells Disrupts Ovulation in Female Mice.

    PubMed

    Mereness, Amanda L; Murphy, Zachary C; Forrestel, Andrew C; Butler, Susan; Ko, CheMyong; Richards, JoAnne S; Sellix, Michael T

    2016-02-01

    Rhythmic events in female reproductive physiology, including ovulation, are tightly controlled by the circadian timing system. The molecular clock, a feedback loop oscillator of clock gene transcription factors, dictates rhythms of gene expression in the hypothalamo-pituitary-ovarian axis. Circadian disruption due to environmental factors (eg, shift work) or genetic manipulation of the clock has negative impacts on fertility. Although the central pacemaker in the suprachiasmatic nucleus classically regulates the timing of ovulation, we have shown that this rhythm also depends on phasic sensitivity to LH. We hypothesized that this rhythm relies on clock function in a specific cellular compartment of the ovarian follicle. To test this hypothesis we generated mice with deletion of the Bmal1 locus in ovarian granulosa cells (GCs) (Granulosa Cell Bmal1 KO; GCKO) or theca cells (TCs) (Theca Cell Bmal1 KO; TCKO). Reproductive cycles, preovulatory LH secretion, ovarian morphology and behavior were not grossly altered in GCKO or TCKO mice. We detected phasic sensitivity to LH in wild-type littermate control (LC) and GCKO mice but not TCKO mice. This decline in sensitivity to LH is coincident with impaired fertility and altered patterns of LH receptor (Lhcgr) mRNA abundance in the ovary of TCKO mice. These data suggest that the TC is a pacemaker that contributes to the timing and amplitude of ovulation by modulating phasic sensitivity to LH. The TC clock may play a critical role in circadian disruption-mediated reproductive pathology and could be a target for chronobiotic management of infertility due to environmental circadian disruption and/or hormone-dependent reprogramming in women. PMID:26671182

  11. 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

  12. Bmal1 is required for beta cell compensatory expansion, survival and metabolic adaptation to diet-induced obesity in mice

    PubMed Central

    Rakshit, Kuntol; Hsu, Tu Wen

    2016-01-01

    Aims/hypothesis Obesity and consequent insulin resistance are known risk factors for type 2 diabetes. A compensatory increase in beta cell function and mass in response to insulin resistance permits maintenance of normal glucose homeostasis, whereas failure to do so results in beta cell failure and type 2 diabetes. Recent evidence suggests that the circadian system is essential for proper metabolic control and regulation of beta cell function. We set out to address the hypothesis that the beta cell circadian clock is essential for the appropriate functional and morphological beta cell response to insulin resistance. Methods We employed conditional deletion of the Bmal1 (also known as Arntl) gene (encoding a key circadian clock transcription factor) in beta cells using the tamoxifen-inducible CreERT recombination system. Upon adulthood, Bmal1 deletion in beta cells was achieved and mice were exposed to either chow or high fat diet (HFD). Changes in diurnal glycaemia, glucose tolerance and insulin secretion were longitudinally monitored in vivo and islet morphology and turnover assessed by immunofluorescence. Isolated islet experiments in vitro were performed to delineate changes in beta cell function and transcriptional regulation of cell proliferation. Results Adult Bmal1 deletion in beta cells resulted in failed metabolic adaptation to HFD characterised by fasting and diurnal hyperglycaemia, glucose intolerance and loss of glucose-stimulated insulin secretion. Importantly, HFD-induced beta cell expansion was absent following beta cell Bmal1 deletion indicating impaired beta cell proliferative and regenerative potential, which was confirmed by assessment of transcriptional profiles in isolated islets. Conclusion/interpretation Results of the study suggest that the beta cell circadian clock is a novel regulator of compensatory beta cell expansion and function in response to increased insulin demand associated with diet-induced obesity. PMID:26762333

  13. Lipoic acid entrains the hepatic circadian clock and lipid metabolic proteins that have been desynchronized with advanced age.

    PubMed

    Keith, Dove; Finlay, Liam; Butler, Judy; Gómez, Luis; Smith, Eric; Moreau, Régis; Hagen, Tory

    2014-07-18

    It is well established that lipid metabolism is controlled, in part, by circadian clocks. However, circadian clocks lose temporal precision with age and correlates with elevated incidence in dyslipidemia and metabolic syndrome in older adults. Because our lab has shown that lipoic acid (LA) improves lipid homeostasis in aged animals, we hypothesized that LA affects the circadian clock to achieve these results. We fed 24 month old male F344 rats a diet supplemented with 0.2% (w/w) LA for 2 weeks prior to sacrifice and quantified hepatic circadian clock protein levels and clock-controlled lipid metabolic enzymes. LA treatment caused a significant phase-shift in the expression patterns of the circadian clock proteins Period (Per) 2, Brain and Muscle Arnt-Like1 (BMAL1), and Reverse Erythroblastosis virus (Rev-erb) β without altering the amplitude of protein levels during the light phase of the day. LA also significantly altered the oscillatory patterns of clock-controlled proteins associated with lipid metabolism. The level of peroxisome proliferator-activated receptor (PPAR) α was significantly increased and acetyl-CoA carboxylase (ACC) and fatty acid synthase (FAS) were both significantly reduced, suggesting that the LA-supplemented aged animals are in a catabolic state. We conclude that LA remediates some of the dyslipidemic processes associated with advanced age, and this mechanism may be at least partially through entrainment of circadian clocks. PMID:24944020

  14. Facilitated physiological adaptation to prolonged circadian disruption through dietary supplementation with essence of chicken.

    PubMed

    Wu, Tao; Yao, Cencen; Tsang, Fai; Huang, Liangfeng; Zhang, Wanjing; Jiang, Jianguo; Mao, Youxiang; Shao, Yujian; Kong, Boda; Singh, Paramjeet; Fu, Zhengwei

    2015-01-01

    Synchrony between circadian and metabolic processes is critical to the maintenance of energy homeostasis. Studies on essence of chicken (EC), a chicken meat extract rich in proteins, amino acids and peptides, showed its effectiveness in alleviating fatigue and promoting metabolism. A recent study revealed that it facilitated the re-entrainment of clock genes (Bmal1, Cry1, Dec1, Per1 and Per2) in the pineal gland and liver in a rat model of circadian disruption. Here, we investigated the role of EC-facilitated circadian synchrony in the maintenance of the energy homeostasis using a mouse model of prolonged circadian disruption. Prolonged circadian disruption (12 weeks) resulted in hepatic maladaptation, manifested by a mild but significant (p < 0.05) hepatomegaly, accompanied by disturbed hepatic lipid metabolism and liver injury (indicated by increased circulating hepatic enzymes). Evidently, there was marked elevations of hepatic inflammatory mediators (interleukin-1beta and interleukin-6), suggesting an underlying inflammation leading to the hepatic injury and functional impairment. Importantly, the disruption paradigm caused the decoupling between key metabolic regulators (e.g. mTOR and AMPK) and hepatic clock genes (Per1, Cry1, Dec1, Bmal1). Further, we showed that the loss of circadian synchrony between the master and hepatic clock genes (Per1, Cry1, Dec1, Bmal1) could be the underlying cause of the maladaptation. When supplemented with EC, the functional impairment and inflammation were abolished. The protective effects could be linked to its effectiveness in maintaining the synchrony between the master and hepatic clocks, and the resultant improved coupling of the circadian oscillators (Per1, Cry1, Dec1, Bmal1) and metabolic regulators (mTOR, AMPK). Overall, EC supplementation promoted the physiological adaptation to the prolonged circadian disruption through facilitation of endogenous circadian synchrony and the coupling of circadian oscillators and

  15. Facilitated physiological adaptation to prolonged circadian disruption through dietary supplementation with essence of chicken.

    PubMed

    Wu, Tao; Yao, Cencen; Tsang, Fai; Huang, Liangfeng; Zhang, Wanjing; Jiang, Jianguo; Mao, Youxiang; Shao, Yujian; Kong, Boda; Singh, Paramjeet; Fu, Zhengwei

    2015-01-01

    Synchrony between circadian and metabolic processes is critical to the maintenance of energy homeostasis. Studies on essence of chicken (EC), a chicken meat extract rich in proteins, amino acids and peptides, showed its effectiveness in alleviating fatigue and promoting metabolism. A recent study revealed that it facilitated the re-entrainment of clock genes (Bmal1, Cry1, Dec1, Per1 and Per2) in the pineal gland and liver in a rat model of circadian disruption. Here, we investigated the role of EC-facilitated circadian synchrony in the maintenance of the energy homeostasis using a mouse model of prolonged circadian disruption. Prolonged circadian disruption (12 weeks) resulted in hepatic maladaptation, manifested by a mild but significant (p < 0.05) hepatomegaly, accompanied by disturbed hepatic lipid metabolism and liver injury (indicated by increased circulating hepatic enzymes). Evidently, there was marked elevations of hepatic inflammatory mediators (interleukin-1beta and interleukin-6), suggesting an underlying inflammation leading to the hepatic injury and functional impairment. Importantly, the disruption paradigm caused the decoupling between key metabolic regulators (e.g. mTOR and AMPK) and hepatic clock genes (Per1, Cry1, Dec1, Bmal1). Further, we showed that the loss of circadian synchrony between the master and hepatic clock genes (Per1, Cry1, Dec1, Bmal1) could be the underlying cause of the maladaptation. When supplemented with EC, the functional impairment and inflammation were abolished. The protective effects could be linked to its effectiveness in maintaining the synchrony between the master and hepatic clocks, and the resultant improved coupling of the circadian oscillators (Per1, Cry1, Dec1, Bmal1) and metabolic regulators (mTOR, AMPK). Overall, EC supplementation promoted the physiological adaptation to the prolonged circadian disruption through facilitation of endogenous circadian synchrony and the coupling of circadian oscillators and

  16. Circadian Regulation of Myocardial Sarcomeric Titin-cap (Tcap, Telethonin): Identification of Cardiac Clock-Controlled Genes Using Open Access Bioinformatics Data

    PubMed Central

    Podobed, Peter S.; Alibhai, Faisal J.; Chow, Chi-Wing; Martino, Tami A.

    2014-01-01

    Circadian rhythms are important for healthy cardiovascular physiology and are regulated at the molecular level by a circadian clock mechanism. We and others previously demonstrated that 9–13% of the cardiac transcriptome is rhythmic over 24 h daily cycles; the heart is genetically a different organ day versus night. However, which rhythmic mRNAs are regulated by the circadian mechanism is not known. Here, we used open access bioinformatics databases to identify 94 transcripts with expression profiles characteristic of CLOCK and BMAL1 targeted genes, using the CircaDB website and JTK_Cycle. Moreover, 22 were highly expressed in the heart as determined by the BioGPS website. Furthermore, 5 heart-enriched genes had human/mouse conserved CLOCK:BMAL1 promoter binding sites (E-boxes), as determined by UCSC table browser, circadian mammalian promoter/enhancer database PEDB, and the European Bioinformatics Institute alignment tool (EMBOSS). Lastly, we validated findings by demonstrating that Titin cap (Tcap, telethonin) was targeted by transcriptional activators CLOCK and BMAL1 by showing 1) Tcap mRNA and TCAP protein had a diurnal rhythm in murine heart; 2) cardiac Tcap mRNA was rhythmic in animals kept in constant darkness; 3) Tcap and control Per2 mRNA expression and cyclic amplitude were blunted in ClockΔ19/Δ19 hearts; 4) BMAL1 bound to the Tcap promoter by ChIP assay; 5) BMAL1 bound to Tcap promoter E-boxes by biotinylated oligonucleotide assay; and 6) CLOCK and BMAL1 induced tcap expression by luciferase reporter assay. Thus this study identifies circadian regulated genes in silico, with validation of Tcap, a critical regulator of cardiac Z-disc sarcomeric structure and function. PMID:25121604

  17. Lipoic acid entrains the hepatic circadian clock and lipid metabolic proteins that have been desynchronized with advanced age

    SciTech Connect

    Keith, Dove; Finlay, Liam; Butler, Judy; Gómez, Luis; Smith, Eric; Moreau, Régis; Hagen, Tory

    2014-07-18

    Highlights: • 24 month old rats were supplemented with 0.2% lipoic acid in the diet for 2 weeks. • Lipoic acid shifts phase of core circadian clock proteins. • Lipoic acid corrects age-induced desynchronized lipid metabolism rhythms. - Abstract: It is well established that lipid metabolism is controlled, in part, by circadian clocks. However, circadian clocks lose temporal precision with age and correlates with elevated incidence in dyslipidemia and metabolic syndrome in older adults. Because our lab has shown that lipoic acid (LA) improves lipid homeostasis in aged animals, we hypothesized that LA affects the circadian clock to achieve these results. We fed 24 month old male F344 rats a diet supplemented with 0.2% (w/w) LA for 2 weeks prior to sacrifice and quantified hepatic circadian clock protein levels and clock-controlled lipid metabolic enzymes. LA treatment caused a significant phase-shift in the expression patterns of the circadian clock proteins Period (Per) 2, Brain and Muscle Arnt-Like1 (BMAL1), and Reverse Erythroblastosis virus (Rev-erb) β without altering the amplitude of protein levels during the light phase of the day. LA also significantly altered the oscillatory patterns of clock-controlled proteins associated with lipid metabolism. The level of peroxisome proliferator-activated receptor (PPAR) α was significantly increased and acetyl-CoA carboxylase (ACC) and fatty acid synthase (FAS) were both significantly reduced, suggesting that the LA-supplemented aged animals are in a catabolic state. We conclude that LA remediates some of the dyslipidemic processes associated with advanced age, and this mechanism may be at least partially through entrainment of circadian clocks.

  18. Dietary proanthocyanidins modulate BMAL1 acetylation, Nampt expression and NAD levels in rat liver

    PubMed Central

    Ribas-Latre, Aleix; Baselga-Escudero, Laura; Casanova, Ester; Arola-Arnal, Anna; Salvadó, M-Josepa; Bladé, Cinta; Arola, Lluís

    2015-01-01

    Metabolism follows circadian rhythms, which are driven by peripheral clocks. Clock genes in the liver are entrained by daytime meals and food components. Proanthocyanidins (PAs), the most abundant flavonoids in the human diet, modulate lipid and glucose metabolism. The aim of this study was to determine whether PAs could adjust the clock system in the liver. Male Wistar rats were orally gavaged with 250 mg grape seed proanthocyanidin extract (GSPE)/kg body weight at zeitgeber time (ZT) 0 (light turned on), at ZT12 (light turned off), or before a 6 hour jet-lag and sacrificed at different times. The 24 hour rhythm of clock-core and clock-controlled gene expression indicated that nicotinamide phosphoribosyltransferase (Nampt) was the most sensitive gene to GSPE. However, Nampt was repressed or overexpressed after GSPE administration at ZT0 or ZT12, respectively. NAD levels, which are controlled by Nampt and also exhibit circadian rhythm, decreased or increased according to Nampt expression. Moreover, the ratio of acetylated Bmal1, that directly drives Nampt expression, only increased when GSPE was administered at ZT12. Therefore, GSPE modulated the clock system in the liver, suggesting that PAs can regulate lipid and glucose metabolism by adjusting the circadian rhythm in the liver. PMID:26051626

  19. Differential maturation of circadian rhythms in clock gene proteins in the suprachiasmatic nucleus and the pars tuberalis during mouse ontogeny

    PubMed Central

    Ansari, Nariman; Agathagelidis, Manuel; Lee, Choogon; Korf, Horst-Werner; von Gall, Charlotte

    2009-01-01

    Circadian rhythms of many body functions in mammals are controlled by a master pacemaker residing in the hypothalamic suprachiasmatic nucleus (SCN) that synchronises peripheral oscillators. The SCN and peripheral oscillators share several components of the molecular clockwork and comprise transcriptional activators (BMAL1 and CLOCK/NPAS2) and inhibitors (mPER1/2 and mCRY1/2). Here we compared the ontogenetic maturation of the clockwork in the SCN and pars tuberalis (PT). The PT is a peripheral oscillator that strongly depends on rhythmic melatonin signals. Immunoreactions for clock gene proteins were determined in the SCN and PT at four different timepoints during four differential stages of mouse ontogeny: foetal (embryonic day 18), newborn (2-day-old), infantile (10-day-old), and adult. In the foetal SCN levels of immunoreactions of all clock proteins were significantly lower as compared to adult levels except for BMAL1. In the newborn SCN the clock protein immunoreactions had not yet reached adult levels, but the infantile SCN showed similar levels of immunreactions as the adult. In contrast, immunoreactions for all clock gene proteins in the foetal PT were as intense as in newborn, infantile, and adult and showed the same phase. As the foetal pineal gland is not yet capable of rhythmic melatonin production, the rhythms in clock gene proteins in the foetal PT are presumably dependent on the maternal melatonin signal. Thus, our data provide the first evidence that maternal melatonin is important for establishing and maintaining circadian rhythms in a foetal peripheral oscillator. PMID:19222558

  20. Glucocorticoid-mediated Period2 induction delays the phase of circadian rhythm

    PubMed Central

    Cheon, Solmi; Park, Noheon; Cho, Sehyung; Kim, Kyungjin

    2013-01-01

    Glucocorticoid (GC) signaling synchronizes the circadian rhythm of individual peripheral cells and induces the expression of circadian genes, including Period1 (Per1) and Period2 (Per2). However, no GC response element (GRE) has been reported in the Per2 promoter region. Here we report the molecular mechanisms of Per2 induction by GC signaling and its relevance to the regulation of circadian timing. We found that GC prominently induced Per2 expression and delayed the circadian phase. The overlapping GRE and E-box (GE2) region in the proximal Per2 promoter was responsible for GC-mediated Per2 induction. The GRE in the Per2 promoter was unique in that brain and muscle ARNT-like protein-1 (BMAL1) was essential for GC-induced Per2 expression, whereas other GRE-containing promoters, such as Per1 and mouse mammary tumor virus, responded to dexamethasone in the absence of BMAL1. This specialized regulatory mechanism was mediated by BMAL1-dependent binding of the GC receptor to GRE in Per2 promoter. When Per2 induction was abrogated by the mutation of the GRE or E-box, the circadian oscillation phase failed to be delayed compared with that of the wild-type. Therefore, the current study demonstrates that the rapid Per2 induction mediated by GC is crucial for delaying the circadian rhythm. PMID:23620290

  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. SRC-2 is an essential coactivator for orchastrating metabolism and circadian rhythm

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Synchrony of the mammalian circadian clock is achieved by complex transcriptional and translational feedback loops centered on the BMAL1:CLOCK heterodimer. Modulation of circadian feedback loops is essential for maintaining rhythmicity, yet the role of transcriptional coactivators in driving BMAL1:C...

  3. Modeling the mammalian circadian clock: sensitivity analysis and multiplicity of oscillatory mechanisms.

    PubMed

    Leloup, Jean-Christophe; Goldbeter, Albert

    2004-10-21

    We extend the study of a computational model recently proposed for the mammalian circadian clock (Proc. Natl Acad. Sci. USA 100 (2003) 7051). The model, based on the intertwined positive and negative regulatory loops involving the Per, Cry, Bmal1, and Clock genes, can give rise to sustained circadian oscillations in conditions of continuous darkness. These limit cycle oscillations correspond to circadian rhythms autonomously generated by suprachiasmatic nuclei and by some peripheral tissues. By using different sets of parameter values producing circadian oscillations, we compare the effect of the various parameters and show that both the occurrence and the period of the oscillations are generally most sensitive to parameters related to synthesis or degradation of Bmal1 mRNA and BMAL1 protein. The mechanism of circadian oscillations relies on the formation of an inactive complex between PER and CRY and the activators CLOCK and BMAL1 that enhance Per and Cry expression. Bifurcation diagrams and computer simulations nevertheless indicate the possible existence of a second source of oscillatory behavior. Thus, sustained oscillations might arise from the sole negative autoregulation of Bmal1 expression. This second oscillatory mechanism may not be functional in physiological conditions, and its period need not necessarily be circadian. When incorporating the light-induced expression of the Per gene, the model accounts for entrainment of the oscillations by light-dark (LD) cycles. Long-term suppression of circadian oscillations by a single light pulse can occur in the model when a stable steady state coexists with a stable limit cycle. The phase of the oscillations upon entrainment in LD critically depends on the parameters that govern the level of CRY protein. Small changes in the parameters governing CRY levels can shift the peak in Per mRNA from the L to the D phase, or can prevent entrainment. The results are discussed in relation to physiological disorders of the

  4. c-MYC targets the central oscillator gene Per1 and is regulated by the circadian clock at the post-transcriptional level.

    PubMed

    Repouskou, Anastasia; Prombona, Anastasia

    2016-04-01

    Cell proliferation in mammals follows a circadian rhythm while disruption of clock gene expression has been linked to tumorigenesis. Expression of the c-Myc oncogene is frequently deregulated in tumors, facilitating aberrant cell proliferation. c-MYC protein levels display circadian rhythmicity, which is compatible with an in vitro repressive role of the clock-activating complex BMAL1/CLOCK on its promoter. In this report, we provide evidence for the in vivo binding of the core circadian factor BMAL1 on the human c-Myc promoter. In addition, analysis of protein synthesis and degradation rates, as well as post-translational acetylation, demonstrate that the clock tightly controls cellular MYC levels. The oncoprotein itself is a transcription factor that by responding to mitogenic signals regulates the expression of several hundred genes. c-MYC-driven transcription is generally exerted upon dimerization with MAX and binding to E-box elements, a sequence that is also recognized by the circadian heterodimer. Our reporter assays reveal that the MYC/MAX dimer cannot affect transcription of the circadian gene Per1. However, when overexpressed, c-MYC is able to repress Per1 transactivation by BMAL1/CLOCK via targeting selective E-box sequences. Importantly, upon serum stimulation, MYC was detected in BMAL1 protein complexes. Together, these data demonstrate a novel interaction between MYC and circadian transactivators resulting in reduced clock-driven transcription. Perturbation of Per1 expression by MYC constitutes a plausible alternative explanation for the deregulated expression of clock genes observed in many types of cancer.

  5. A baculovirus photolyase with DNA repair activity and circadian clock regulatory function.

    PubMed

    Biernat, Magdalena A; Eker, André P M; van Oers, Monique M; Vlak, Just M; van der Horst, Gijsbertus T J; Chaves, Inês

    2012-02-01

    Cryptochromes and photolyases belong to the same family of flavoproteins but, despite being structurally conserved, display distinct functions. Photolyases use visible light to repair ultraviolet-induced DNA damage. Cryptochromes, however, function as blue-light receptors, circadian photoreceptors, or repressors of the CLOCK/BMAL1 heterodimer, the transcription activator controlling the molecular circadian clock. Here, we present evidence that the functional divergence between cryptochromes and photolyases is not so univocal. Chrysodeixis chalcites nucleopolyhedrovirus possesses 2 photolyase-like genes: phr1 and phr2. We show that PHR1 and PHR2 are able to bind the CLOCK protein. Only for PHR2, however, the physical interaction with CLOCK represses CLOCK/BMAL1-driven transcription. This result shows that binding of photolyase per se is not sufficient to inhibit the CLOCK/BMAL1 heterodimer. PHR2, furthermore, affects the oscillation of immortalized mouse embryonic fibroblasts, suggesting that PHR2 can regulate the molecular circadian clock. These findings are relevant for further understanding the evolution of cryptochromes and photolyases as well as behavioral changes induced in insects by baculoviruses. PMID:22306969

  6. The De-Ubiquitinylating Enzyme, USP2, Is Associated with the Circadian Clockwork and Regulates Its Sensitivity to Light

    PubMed Central

    Scoma, Heather Dehlin; Humby, Monica; Yadav, Geetha; Zhang, Qingjiong; Fogerty, Joseph; Besharse, Joseph C.

    2011-01-01

    We have identified a novel component of the circadian clock that regulates its sensitivity to light at the evening light to dark transition. USP2 (Ubiquitin Specific Protease 2), which de-ubiquitinylates and stabilizes target proteins, is rhythmically expressed in multiple tissues including the SCN. We have developed a knockout model of USP2 and found that exposure to low irradiance light at ZT12 increases phase delays of USP2−/− mice compared to wildtype. We additionally show that USP2b is in a complex with several clock components and regulates the stability and turnover of BMAL1, which in turn alters the expression of several CLOCK/BMAL1 controlled genes. Rhythmic expression of USP2 in the SCN and other tissues offers a new level of control of the clock machinery through de-ubiqutinylation and suggests a role for USP2 during circadian adaptation to environmental day length changes. PMID:21966515

  7. Glucocorticoids mediate circadian timing in peripheral osteoclasts resulting in the circadian expression rhythm of osteoclast-related genes.

    PubMed

    Fujihara, Yuko; Kondo, Hisataka; Noguchi, Toshihide; Togari, Akifumi

    2014-04-01

    Circadian rhythms are prevalent in bone metabolism. However, the molecular mechanisms involved are poorly understood. Recently, we suggested that output signals from the suprachiasmatic nucleus (SCN) are transmitted from the master circadian rhythm to peripheral osteoblasts through β-adrenergic and glucocorticoid signaling. In this study, we examined how the master circadian rhythm is transmitted to peripheral osteoclasts and the role of clock gene in osteoclast. Mice were maintained under 12-hour light/dark periods and sacrificed at Zeitgeber times 0, 4, 8, 12, 16 and 20. mRNA was extracted from femur (cancellous bone) and analyzed for the expression of osteoclast-related genes and clock genes. Osteoclast-related genes such as cathepsin K (CTSK) and nuclear factor of activated T-cells, cytoplasmic 1 (NFATc1) showed circadian rhythmicity like clock genes such as period 1 (PER1), PER2 and brain and muscle Arnt-like protein 1 (BMAL1). In an in vitro study, not β-agonist but glucocorticoid treatment remarkably synchronized clock and osteoclast-related genes in cultured osteoclasts. Chromatin immunoprecipitation (ChIP) assay showed the interaction between BMAL1 proteins and promoter region of CTSK and NFATc1. To examine whether endogenous glucocorticoids influence the osteoclast circadian rhythms, mice were adrenalectomized (ADX) and maintained under 12-hour light/dark periods at least two weeks before glucocorticoid injection. A glucocorticoid injection restarted the circadian expression of CTSK and NFATc1 in ADX mice. These results suggest that glucocorticoids mediate circadian timing to peripheral osteoclasts and osteoclast clock contributes to the circadian expression of osteoclast-related genes such as CTSK and NFATc1.

  8. Circadian rhythm transcription factor CLOCK regulates the transcriptional activity of the glucocorticoid receptor by acetylating its hinge region lysine cluster: potential physiological implications

    PubMed Central

    Nader, Nancy; Chrousos, George P.; Kino, Tomoshige

    2009-01-01

    Glucocorticoids, end products of the hypothalamic-pituitary-adrenal axis, influence functions of virtually all organs and tissues through the glucocorticoid receptor (GR). Circulating levels of glucocorticoids fluctuate naturally in a circadian fashion and regulate the transcriptional activity of GR in target tissues. The basic helix-loop-helix protein CLOCK, a histone acetyltransferase (HAT), and its heterodimer partner BMAL1 are self-oscillating transcription factors that generate circadian rhythms in both the central nervous system and periphery. We found that CLOCK/BMAL1 repressed GR-induced transcriptional activity in a HAT-activity- dependent fashion. In serum-shock-synchronized cells, transactivational activity of GR, accessed by mRNA expression of an endogenous-responsive gene, fluctuated spontaneously in a circadian fashion in reverse phase with CLOCK/BMAL1 mRNA expression. CLOCK and GR interacted with each other physically, and CLOCK suppressed binding of GR to its DNA recognition sequences by acetylating multiple lysine residues located in its hinge region. These findings indicate that CLOCK/BMAL1 functions as a reverse-phase negative regulator of glucocorticoid action in target tissues, possibly by antagonizing biological actions of diurnally fluctuating circulating glucocorticoids. Further, these results suggest that a peripheral target tissue circadian rhythm indirectly influences the functions of every organ and tissue inside the body through modulation of the ubiquitous and diverse actions of glucocorticoids.—Nader, N., Chrousos, G. P., Kino, T. Circadian rhythm transcription factor CLOCK regulates the transcriptional activity of the glucocorticoid receptor by acetylating its hinge region lysine cluster: potential physiological implications. PMID:19141540

  9. 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.

  10. 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

  11. Astakine 2--the dark knight linking melatonin to circadian regulation in crustaceans.

    PubMed

    Watthanasurorot, Apiruck; Saelee, Netnapa; Phongdara, Amornrat; Roytrakul, Sittiruk; Jiravanichpaisal, Pikul; Söderhäll, Kenneth; Söderhäll, Irene

    2013-03-01

    Daily, circadian rhythms influence essentially all living organisms and affect many physiological processes from sleep and nutrition to immunity. This ability to respond to environmental daily rhythms has been conserved along evolution, and it is found among species from bacteria to mammals. The hematopoietic process of the crayfish Pacifastacus leniusculus is under circadian control and is tightly regulated by astakines, a new family of cytokines sharing a prokineticin (PROK) domain. The expression of AST1 and AST2 are light-dependent, and this suggests an evolutionarily conserved function for PROK domain proteins in mediating circadian rhythms. Vertebrate PROKs are transmitters of circadian rhythms of the suprachiasmatic nucleus (SCN) in the brain of mammals, but the mechanism by which they function is unknown. Here we demonstrate that high AST2 expression is induced by melatonin in the brain. We identify RACK1 as a binding protein of AST2 and further provide evidence that a complex between AST2 and RACK1 functions as a negative-feedback regulator of the circadian clock. By DNA mobility shift assay, we showed that the AST2-RACK1 complex will interfere with the binding between BMAL1 and CLK and inhibit the E-box binding activity of the complex BMAL1-CLK. Finally, we demonstrate by gene knockdown that AST2 is necessary for melatonin-induced inhibition of the complex formation between BMAL1 and CLK during the dark period. In summary, we provide evidence that melatonin regulates AST2 expression and thereby affects the core clock of the crustacean brain. This process may be very important in all animals that have AST2 molecules, i.e. spiders, ticks, crustaceans, scorpions, several insect groups such as Hymenoptera, Hemiptera, and Blattodea, but not Diptera and Coleoptera. Our findings further reveal an ancient evolutionary role for the prokineticin superfamily protein that links melatonin to direct regulation of the core clock gene feedback loops. PMID:23555281

  12. Circadian rhythmicity of active GSK3 isoforms modulates molecular clock gene rhythms in the suprachiasmatic nucleus.

    PubMed

    Besing, Rachel C; Paul, Jodi R; Hablitz, Lauren M; Rogers, Courtney O; Johnson, Russell L; Young, Martin E; Gamble, Karen L

    2015-04-01

    The suprachiasmatic nucleus (SCN) drives and synchronizes daily rhythms at the cellular level via transcriptional-translational feedback loops comprising clock genes such as Bmal1 and Period (Per). Glycogen synthase kinase 3 (GSK3), a serine/threonine kinase, phosphorylates at least 5 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 2 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.

  13. Harmine lengthens circadian period of the mammalian molecular clock in the suprachiasmatic nucleus.

    PubMed

    Kondoh, Daisuke; Yamamoto, Saori; Tomita, Tatsunosuke; Miyazaki, Koyomi; Itoh, Nanako; Yasumoto, Yuki; Oike, Hideaki; Doi, Ryosuke; Oishi, Katsutaka

    2014-01-01

    The circadian clock is a cell-autonomous endogenous system that generates circadian rhythms in the behavior and physiology of most organisms. We previously reported that the harmala alkaloid, harmine, lengthens the circadian period of Bmal1 transcription in NIH 3T3 fibroblasts. Clock protein dynamics were examined using real-time reporter assays of PER2::LUC to determine the effects of harmine on the central clock in the suprachiasmatic nucleus (SCN). Harmine significantly lengthened the period of PER2::LUC expression in embryonic fibroblasts, in neuronal cells differentiated from neuronal progenitor cells and in SCN slices obtained from PER2::LUC mice. Although harmine did not induce the transient mRNA expression of clock genes such as Per1, Per2 and Bmal1 in embryonic fibroblasts, it significantly extended the half-life of PER2::LUC protein in neuronal cells and SCN slices. Harmine might lengthen the circadian period of the molecular clock by increasing PER2 protein stability in the SCN.

  14. Cell autonomous regulation of herpes and influenza virus infection by the circadian clock.

    PubMed

    Edgar, Rachel S; Stangherlin, Alessandra; Nagy, Andras D; Nicoll, Michael P; Efstathiou, Stacey; O'Neill, John S; Reddy, Akhilesh B

    2016-09-01

    Viruses are intracellular pathogens that hijack host cell machinery and resources to replicate. Rather than being constant, host physiology is rhythmic, undergoing circadian (∼24 h) oscillations in many virus-relevant pathways, but whether daily rhythms impact on viral replication is unknown. We find that the time of day of host infection regulates virus progression in live mice and individual cells. Furthermore, we demonstrate that herpes and influenza A virus infections are enhanced when host circadian rhythms are abolished by disrupting the key clock gene transcription factor Bmal1. Intracellular trafficking, biosynthetic processes, protein synthesis, and chromatin assembly all contribute to circadian regulation of virus infection. Moreover, herpesviruses differentially target components of the molecular circadian clockwork. Our work demonstrates that viruses exploit the clockwork for their own gain and that the clock represents a novel target for modulating viral replication that extends beyond any single family of these ubiquitous pathogens.

  15. The Cardiomyocyte Molecular Clock Regulates the Circadian Expression of Kcnh2 and Contributes to Ventricular Repolarization

    PubMed Central

    Schroder, Elizabeth A.; Burgess, Don E.; Zhang, Xiping; Lefta, Mellani; Smith, Jennifer L.; Patwardhan, Abhijit; Bartos, Daniel C.; Elayi, Claude S.; Esser, Karyn A.; Delisle, Brian P.

    2015-01-01

    Background Sudden Cardiac Death (SCD) follows a diurnal variation. Data suggest the timing of SCD is influenced by circadian (~24 hour) changes in neurohumoral and cardiomyocyte-specific regulation of the heart’s electrical properties. Objective The basic helix-loop-helix transcription factors BMAL1 and CLOCK coordinate the circadian expression of select genes. We tested whether Bmal1 expression in cardiomyocytes contributes to K+ channel expression and diurnal changes in ventricular repolarization. Methods We utilized transgenic mice that allow for the inducible cardiomyocyte-specific deletion of Bmal1 (iCSΔBmal1−/−). We used quantitative PCR, voltage-clamping, promoter-reporter bioluminescence assays, and electrocardiographic (ECG) telemetry. Results Although several K+ channel gene transcripts were downregulated in iCSΔBmal1−/− mouse hearts, only Kcnh2 exhibited a robust circadian pattern of expression that was disrupted in iCSΔBmal1−/− hearts. Kcnh2 underlies the rapidly activating delayed-rectifier K+ current (IKr), and IKr recorded from iCSΔBmal1−/− ventricular cardiomyocytes was ~50% compared to control myocytes. Promoter-reporter assays demonstrated that the human Kcnh2 promoter is transactivated by the co-expression of BMAL1 and CLOCK. ECG analysis showed iCSΔBmal1−/− mice developed a prolongation in the heart rate corrected QT (QTc) interval during the light (resting)-phase. This was secondary to an augmented circadian rhythm in the uncorrected QT interval without a corresponding change in the RR interval. Conclusion The molecular clock in the heart regulates the circadian expression of Kcnh2, modifies K+ channel gene expression and is important for normal ventricular repolarization. Disruption of the cardiomyocyte circadian clock mechanism likely unmasks diurnal changes in ventricular repolarization that could contribute to an increased risk of cardiac arrhythmias/SCD. PMID:25701773

  16. Hypoxia disrupts the expression levels of circadian rhythm genes in hepatocellular carcinoma.

    PubMed

    Yu, Chao; Yang, Sheng-Li; Fang, Xiefan; Jiang, Jian-Xin; Sun, Cheng-Yi; Huang, Tao

    2015-05-01

    Disturbance in the expression of circadian rhythm genes is a common feature in certain types of cancer, however the mechanisms mediating this disturbance remain to be elucidated. The present study aimed to investigate the effect of hypoxia on the expression of circadian rhythm genes in liver cancer cells and to identify the mechanisms underlying this effect in hepatocellular carcinoma (HCC). The HCC cell line, PLC/PRF/5. was treated with either a vehicle control or CoCl2 at 50, 100 or 200 µΜ for 24 h. Following treatment, the protein expression levels of hypoxia‑inducible factor (HIF)‑1α and HIF‑2α were detected by western blotting and the mRNA expression levels of circadian rhythm genes, including circadian locomotor output cycles kaput (Clock), brain and muscle Arnt‑like 1 (Bmal1), period (Per)1, Per2, Per3, cryptochrome (Cry)1, Cry2 and casein kinase Iε (CKIε), were detected by reverse transcription quantitative polymerase chain reaction (RT‑qPCR). Expression plasmids containing HIF‑1α or HIF‑2α were transfected into the PLC/PRF/5 cells using liposomes and RT‑qPCR was used to determine the effects of the transfections on the expression levels of circadian rhythm genes. Following treatment with CoCl2, the protein expression levels of HIF‑1α and HIF‑2α were upregulated in a CoCl2 concentration‑dependent manner. The mRNA expression levels of Clock, Bmal1 and Cry2 were increased, and the mRNA expression levels of Per1, Per2, Per3, Cry1 and CKIε were decreased following CoCl2 treatment (P<0.05). In the PLC/PRF/5 cells transfected with the plasmid containing HIF‑1α, the mRNA expression levels of Clock, Bmal1 and Cry2 were increased, and the mRNA expression levels of Per1, Per2, Per3, Cry1 and CKIε were decreased. In the PLC/PRF/5 cells transfected with the plasmid containing HIF‑2α, the mRNA expression levels of Clock, Bmal1, Per1, Cry1, Cry2 and CKIε were upregulated, and the mRNA expression levels of Per2 and Per3 were

  17. Long-Range Chromosome Interactions Mediated by Cohesin Shape Circadian Gene Expression

    PubMed Central

    Xu, Yichi; Guo, Weimin; Li, Ping; Zhang, Yan; Zhao, Meng; Fan, Zenghua; Zhao, Zhihu; Yan, Jun

    2016-01-01

    Mammalian circadian rhythm is established by the negative feedback loops consisting of a set of clock genes, which lead to the circadian expression of thousands of downstream genes in vivo. As genome-wide transcription is organized under the high-order chromosome structure, it is largely uncharted how circadian gene expression is influenced by chromosome architecture. We focus on the function of chromatin structure proteins cohesin as well as CTCF (CCCTC-binding factor) in circadian rhythm. Using circular chromosome conformation capture sequencing, we systematically examined the interacting loci of a Bmal1-bound super-enhancer upstream of a clock gene Nr1d1 in mouse liver. These interactions are largely stable in the circadian cycle and cohesin binding sites are enriched in the interactome. Global analysis showed that cohesin-CTCF co-binding sites tend to insulate the phases of circadian oscillating genes while cohesin-non-CTCF sites are associated with high circadian rhythmicity of transcription. A model integrating the effects of cohesin and CTCF markedly improved the mechanistic understanding of circadian gene expression. Further experiments in cohesin knockout cells demonstrated that cohesin is required at least in part for driving the circadian gene expression by facilitating the enhancer-promoter looping. This study provided a novel insight into the relationship between circadian transcriptome and the high-order chromosome structure. PMID:27135601

  18. Circadian timing in central and peripheral tissues in a migratory songbird: dependence on annual life-history states.

    PubMed

    Singh, Devraj; Trivedi, Amit Kumar; Rani, Sangeeta; Panda, Satchidananda; Kumar, Vinod

    2015-10-01

    Predictable seasonal change in photoperiod triggers a sequential change in the daily activity-rest pattern, adaptive for migration in several bird species. The night-migratory black-headed bunting (Emberiza melanocephala) is day active under short photoperiods (8 h light:16 h dark, short day sensitive). Under long photoperiods (16 h light:8 h dark), the buntings are initially day active (long day premigratory) but subsequently become intensely night active (long day migratory) and after few weeks again return to a day active pattern (long day refractory). However, it is unclear how the daily expression of circadian genes changes during photoperiod-induced seasonal life-history states (LHSs). We measured period 2 (Per2), cryptochrome 1 (Cry1), brain and muscle arnt-like protein 1 (Bmal1), and circadian locomotor output cycles kaput (Clock) mRNA expressions in various neural and peripheral tissues of buntings in different LHSs and discovered differences of ∼2 to 6 h in the phase and 2- to 4-fold in amplitude of circadian oscillations of Per2, Cry1, and Bmal1 between photoperiod-induced LHSs. Phase relationship in mRNA oscillations was altered between oscillator components in the circadian pacemaker system (retina, pineal, hypothalamus) as well as in the peripheral (liver, muscle) tissues. These results show for the first time altered waveforms of clock gene expressions in all tissues in parallel with behavioral shifts and suggest the involvement of circadian system in photoperiod induction of seasonal LHSs in a migratory species.

  19. Closing the circadian loop: CLOCK-induced transcription of its own inhibitors per and tim.

    PubMed

    Darlington, T K; Wager-Smith, K; Ceriani, M F; Staknis, D; Gekakis, N; Steeves, T D; Weitz, C J; Takahashi, J S; Kay, S A

    1998-06-01

    The circadian oscillator generates a rhythmic output with a period of about 24 hours. Despite extensive studies in several model systems, the biochemical mode of action has not yet been demonstrated for any of its components. Here, the Drosophila CLOCK protein was shown to induce transcription of the circadian rhythm genes period and timeless. dCLOCK functioned as a heterodimer with a Drosophila homolog of BMAL1. These proteins acted through an E-box sequence in the period promoter. The timeless promoter contains an 18-base pair element encompassing an E-box, which was sufficient to confer dCLOCK responsiveness to a reporter gene. PERIOD and TIMELESS proteins blocked dCLOCK's ability to transactivate their promoters via the E-box. Thus, dCLOCK drives expression of period and timeless, which in turn inhibit dCLOCK's activity and close the circadian loop.

  20. When the circadian clock meets the melanin pigmentary system.

    PubMed

    Slominski, Andrzej T; Hardeland, Rüdiger; Reiter, Russel J

    2015-04-01

    Silencing of BMAL1 and PER1 stimulates melanogenic activity of follicular and epidermal melanocytes, indicating a novel role for peripheral circadian clock processes in the regulation of melanin pigmentation. Linking the expression levels of BMAL1/PER1 with changes in melanogenesis opens exciting opportunities to study the role of the local molecular clock in modulation of melanocyte functions in the hair follicle and the epidermis with attendant effects on epidermal barrier functions in general. PMID:25785947

  1. [BMAL1 gene regulates the osteogenic differentiation of bone marrow mesenchymal stem cells].

    PubMed

    Xiaoguang, Li; Xiao-long, Guo; Bin, Guo

    2016-06-01

    Periodontitis is a chronic infective disease characterized as the destruction of the supporting tissues of the teeth. Bone marrow mesenchymal stem cells, which are ideal adult stem cells for the regeneration of supporting tissues, may play important roles in restoring the structure and function of the periodontium and in promoting the treatment of periodontal disease. As a consequence, the characteristics, especially osteogenic differentiation mechanism, of these stem cells have been extensively investigated. The regulation of the physiological behavior of these stem cells is associated with BMAL1 gene. This gene is a potential treatment target for periodontal disease, although the specific mechanism remains inconclusive. This study aimed to describe the characteristics of BMAL1 gene and its ability to regulate the osteogenic differentiation of stem cells. PMID:27526460

  2. Physiological importance of a circadian clock outside the suprachiasmatic nucleus.

    PubMed

    Storch, K-F; Paz, C; Signorovitch, J; Raviola, E; Pawlyk, B; Li, T; Weitz, C J

    2007-01-01

    Circadian clocks are widely distributed in mammalian tissues, but little is known about the physiological functions of clocks outside the suprachiasmatic nucleus of the brain. The retina has an intrinsic circadian clock, but its importance for vision is unknown. Here, we show that mice lacking Bmal1, a gene required for clock function, had abnormal retinal transcriptional responses to light and defective inner retinal electrical responses to light, but normal photoreceptor responses to light and retinas that appeared structurally normal as observed by light and electron microscopy. We generated mice with a retina-specific genetic deletion of Bmal1, and they had defects of retinal visual physiology essentially identical to those of mice lacking Bmal1 in all tissues and lacked a circadian rhythm of inner retinal electrical responses to light. Our findings indicate that the intrinsic circadian clock of the retina regulates retinal visual processing in vivo.

  3. SRC-2 Is an Essential Coactivator for Orchestrating Metabolism and Circadian Rhythm

    PubMed Central

    Stashi, Erin; Lanz, Rainer B.; Mao, Jianqiang; Michailidis, George; Zhu, Bokai; Kettner, Nicole M.; Putluri, Nagireddy; Reineke, Erin L.; Reineke, Lucas C.; Dasgupta, Subhamoy; Dean, Adam; Stevenson, Connor R.; Sivasubramanian, Natarajan; Sreekumar, Arun; DeMayo, Francesco; York, Brian; Fu, Loning; O'Malley, Bert W.

    2014-01-01

    SUMMARY Synchrony of the mammalian circadian clock is achieved by complex transcriptional and translational feedback loops centered on the BMAL1: CLOCK heterodimer. Modulation of circadian feedback loops is essential for maintaining rhythmicity, yet the role of transcriptional coactivators in driving BMAL1:CLOCK transcriptional networks is largely unexplored. Here, we show diurnal hepatic steroid receptor coactivator 2 (SRC-2) recruitment to the genome that extensively overlaps with the BMAL1 cistrome during the light phase, targeting genes that enrich for circadian and metabolic processes. Notably, SRC-2 ablation impairs wheel-running behavior, alters circadian gene expression in several peripheral tissues, alters the rhythmicity of the hepatic metabolome, and deregulates the synchronization of cell-autonomous metabolites. We identify SRC-2 as a potent coregulator of BMAL1:CLOCK and find that SRC-2 targets itself with BMAL1:CLOCK in a feedforward loop. Collectively, our data suggest that SRC-2 is a transcriptional coactivator of the BMAL1:CLOCK oscillators and establish SRC-2 as a critical positive regulator of the mammalian circa-dian clock. PMID:24529706

  4. SRC-2 is an essential coactivator for orchestrating metabolism and circadian rhythm.

    PubMed

    Stashi, Erin; Lanz, Rainer B; Mao, Jianqiang; Michailidis, George; Zhu, Bokai; Kettner, Nicole M; Putluri, Nagireddy; Reineke, Erin L; Reineke, Lucas C; Dasgupta, Subhamoy; Dean, Adam; Stevenson, Connor R; Sivasubramanian, Natarajan; Sreekumar, Arun; Demayo, Francesco; York, Brian; Fu, Loning; O'Malley, Bert W

    2014-02-27

    Synchrony of the mammalian circadian clock is achieved by complex transcriptional and translational feedback loops centered on the BMAL1:CLOCK heterodimer. Modulation of circadian feedback loops is essential for maintaining rhythmicity, yet the role of transcriptional coactivators in driving BMAL1:CLOCK transcriptional networks is largely unexplored. Here, we show diurnal hepatic steroid receptor coactivator 2 (SRC-2) recruitment to the genome that extensively overlaps with the BMAL1 cistrome during the light phase, targeting genes that enrich for circadian and metabolic processes. Notably, SRC-2 ablation impairs wheel-running behavior, alters circadian gene expression in several peripheral tissues, alters the rhythmicity of the hepatic metabolome, and deregulates the synchronization of cell-autonomous metabolites. We identify SRC-2 as a potent coregulator of BMAL1:CLOCK and find that SRC-2 targets itself with BMAL1:CLOCK in a feedforward loop. Collectively, our data suggest that SRC-2 is a transcriptional coactivator of the BMAL1:CLOCK oscillators and establish SRC-2 as a critical positive regulator of the mammalian circadian clock. PMID:24529706

  5. A Role for Id2 in Regulating Photic Entrainment of the Mammalian Circadian System

    PubMed Central

    Duffield, Giles E.; Watson, Nathan P.; Mantani, Akio; Peirson, Stuart N.; Robles-Murguia, Maricela; Loros, Jennifer J.; Israel, Mark A.; Dunlap, Jay C.

    2009-01-01

    Summary Inhibitor of DNA binding genes (Id1–Id4) encode helix-loop-helix (HLH) transcriptional repressors associated with development and tumorigenesis [1, 2], but little is known concerning the function(s) of these genes in normal adult animals. Id2 was identified in DNA microarray screens for rhythmically expressed genes [3–5], and further analysis revealed a circadian pattern of expression of all four Id genes in multiple tissues including the suprachiasmatic nucleus. To explore an in vivo function, we generated and characterized deletion mutations of Id2 and of Id4. Id2−/− mice exhibit abnormally rapid entrainment and an increase in the magnitude of the phase shift of the pacemaker. A significant proportion of mice also exhibit disrupted rhythms when maintained under constant darkness. Conversely, Id4−/− mice did not exhibit a noticeable circadian phenotype. In vitro studies using an mPer1 and an AVP promoter reporter revealed the potential for ID1, ID2, and ID3 proteins to interact with the canonical basic HLH clock proteins BMAL1 and CLOCK. These data suggest that the Id genes may be important for entrainment and operation of the mammalian circadian system, potentially acting through BMAL1 and CLOCK targets. PMID:19217292

  6. The circadian molecular clock creates epidermal stem cell heterogeneity.

    PubMed

    Janich, Peggy; Pascual, Gloria; Merlos-Suárez, Anna; Batlle, Eduard; Ripperger, Jürgen; Albrecht, Urs; Cheng, Hai-Ying M; Obrietan, Karl; Di Croce, Luciano; Benitah, Salvador Aznar

    2011-11-09

    Murine epidermal stem cells undergo alternate cycles of dormancy and activation, fuelling tissue renewal. However, only a subset of stem cells becomes active during each round of morphogenesis, indicating that stem cells coexist in heterogeneous responsive states. Using a circadian-clock reporter-mouse model, here we show that the dormant hair-follicle stem cell niche contains coexisting populations of cells at opposite phases of the clock, which are differentially predisposed to respond to homeostatic cues. The core clock protein Bmal1 modulates the expression of stem cell regulatory genes in an oscillatory manner, to create populations that are either predisposed, or less prone, to activation. Disrupting this clock equilibrium, through deletion of Bmal1 (also known as Arntl) or Per1/2, resulted in a progressive accumulation or depletion of dormant stem cells, respectively. Stem cell arrhythmia also led to premature epidermal ageing, and a reduction in the development of squamous tumours. Our results indicate that the circadian clock fine-tunes the temporal behaviour of epidermal stem cells, and that its perturbation affects homeostasis and the predisposition to tumorigenesis.

  7. Circadian rhythms. A protein fold switch joins the circadian oscillator to clock output in cyanobacteria.

    PubMed

    Chang, Yong-Gang; Cohen, Susan E; Phong, Connie; Myers, William K; Kim, Yong-Ick; Tseng, Roger; Lin, Jenny; Zhang, Li; Boyd, Joseph S; Lee, Yvonne; Kang, Shannon; Lee, David; Li, Sheng; Britt, R David; Rust, Michael J; Golden, Susan S; LiWang, Andy

    2015-07-17

    Organisms are adapted to the relentless cycles of day and night, because they evolved timekeeping systems called circadian clocks, which regulate biological activities with ~24-hour rhythms. The clock of cyanobacteria is driven by a three-protein oscillator composed of KaiA, KaiB, and KaiC, which together generate a circadian rhythm of KaiC phosphorylation. We show that KaiB flips between two distinct three-dimensional folds, and its rare transition to an active state provides a time delay that is required to match the timing of the oscillator to that of Earth's rotation. Once KaiB switches folds, it binds phosphorylated KaiC and captures KaiA, which initiates a phase transition of the circadian cycle, and it regulates components of the clock-output pathway, which provides the link that joins the timekeeping and signaling functions of the oscillator.

  8. Circadian Mechanisms in Murine and Human Bone Marrow Mesenchymal Stem Cells Following Dexamethasone Exposure

    PubMed Central

    Wu, Xiying; Yu, Gang; Parks, Helen; Hebert, Teddi; Goh, Brian C.; Dietrich, Marilyn A.; Pelled, Gadi; Izadpanah, Reza; Gazit, Dan; Bunnell, Bruce A.; Gimble, Jeffrey M.

    2008-01-01

    A core group of transcriptional regulatory factors regulate circadian rhythms in mammalian cells. While the suprachiasmatic nucleus in the brain serves as the central core circadian oscillator, circadian clocks also exist within peripheral tissues and cells. A growing body of evidence has demonstrated that >20% of expressed mRNAs in bone and adipose tissues oscillate in a circadian manner. The current manuscript reports evidence of the core circadian transcriptional apparatus within primary cultures of murine and human bone marrow-derived mesenchymal stem cells (BMSCs). Exposure of confluent, quiescent BMSCs to dexamethasone synchronized the oscillating expression of the mRNAs encoding the albumin D binding protein (dbp), brain-muscle arnt-like 1 (bmal1), period 3 (per3), rev-erb α, and rev-erb β. The genes displayed a mean oscillatory period of 22.2 to 24.3 hours. The acrophase or peak expression of mRNAs encoding “positive” (bmal1) and “negative” (per3) transcriptional regulatory factors were out of phase with each other by ∼8-12 hours, consistent with in vivo observations. In vivo, glycogen synthase kinase 3β (GSK3β) mediated phosphorylation regulates the turnover of per3 and core circadian transcriptional apparatus. In vitro addition of lithium chloride, a GSK3β inhibitor, significantly shifted the acrophase of all genes by 4.2-4.7 hours oscillation in BMSCs; however, only the male murine BMSCs displayed a significant increase in the length of the period of oscillation. We conclude that human and murine BMSCs represent a valid in vitro model for the analysis of circadian mechanisms in bone metabolism and stem cell biology. PMID:18302991

  9. Relationship between circadian blood pressure variation and circadian protein excretion in CKD.

    PubMed

    Agarwal, Rajiv

    2007-09-01

    Circadian blood pressure changes are blunted in patients with chronic kidney disease (CKD). Proteinuria is the most important correlate of hypertension in CKD. However, little is known about the influence of circadian blood pressure changes and variation in protein excretion rate. Furthermore, the impact of blood pressure components, e.g., mean arterial pressure and pulse pressure, on proteinuria has not been evaluated. To analyze the relationship of circadian changes in blood pressure on urinary protein excretion patterns, glomerular filtration rate was measured with iothalamate clearance and 24-h ambulatory blood pressure with SpaceLabs 90207 monitor in 22 patients with CKD. It was found that hourly protein excretion rates were 31% higher during the night. Excretion results of sodium, potassium, chloride, urea, and creatinine were also between 30 and 40% higher at night. Systolic, mean arterial, and pulse pressures but not diastolic pressure were related to daytime protein excretion rate. At night, the relationship of systolic, diastolic, and mean arterial pressures was significantly lower and essentially flat with respect to protein excretion rate, but the relationship of pulse pressure and proteinuria was not different from that seen during the day. Circadian variation in blood pressure did not impact circadian sodium excretion rate. In conclusion, these data suggest that patients with CKD have patterns of proteinuria that share different relationships with blood pressure components depending on the awake-sleep state. Pulse pressure is related to proteinuria independent of the awake-sleep state. Reducing mean arterial pressure during the day and pulse pressure during the day or night may be effective antiproteinuric strategies. PMID:17581923

  10. Circadian rhythm of contrast sensitivity is regulated by a dopamine-neuronal PAS-domain protein 2-adenylyl cyclase 1 signaling pathway in retinal ganglion cells.

    PubMed

    Hwang, Christopher K; Chaurasia, Shyam S; Jackson, Chad R; Chan, Guy C-K; Storm, Daniel R; Iuvone, P Michael

    2013-09-18

    Spatial variation in light intensity, called spatial contrast, comprises much of the visual information perceived by mammals, and the relative ability to detect contrast is referred to as contrast sensitivity (Purves et al., 2012). Recently, retinal dopamine D4 receptors (D4Rs) have been implicated in modulating contrast sensitivity (Jackson et al., 2012); however, the cellular and molecular mechanisms have not been elucidated. Our study demonstrates a circadian rhythm of contrast sensitivity that peaks during the daytime, and that its regulation involves interactions of D4Rs, the clock gene Npas2, and the clock-controlled gene adenylyl cyclase 1 (Adcy1) in a subset of retinal ganglion cells (RGCs). Targeted disruption of the gene encoding D4Rs reduces the amplitude of the contrast sensitivity rhythm by reducing daytime sensitivity and abolishes the rhythmic expression of Npas2 and Adcy1 mRNA in the ganglion cell layer (GCL) of the retina. Npas2(-/-) and Adcy1(-/-) mice show strikingly similar reductions in the contrast sensitivity rhythm to that in mice lacking D4Rs. Moreover, Adcy1 transcript rhythms were abolished in the GCL of Npas2(-/-) mice. Luciferase reporter assays demonstrated that the Adcy1 promoter is selectively activated by neuronal PAS-domain protein 2 (NPAS2)/BMAL1. Our results indicate that the contrast sensitivity rhythm is modulated by D4Rs via a signaling pathway that involves NPAS2-mediated circadian regulation of Adcy1. Hence, we have identified a circadian clock mechanism in a subset of RGCs that modulates an important aspect of retinal physiology and visual processing.

  11. 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.

  12. Cloning of circadian rhythmic pathway genes and perturbation of oscillation patterns in endocrine disrupting chemicals (EDCs)-exposed mangrove killifish Kryptolebias marmoratus.

    PubMed

    Rhee, Jae-Sung; Kim, Bo-Mi; Lee, Bo-Young; Hwang, Un-Ki; Lee, Yong Sung; Lee, Jae-Seong

    2014-08-01

    To investigate the effect of endocrine disrupting chemicals (EDCs) on the circadian rhythm pathway, we cloned clock and circadian rhythmic pathway-associated genes (e.g. Per2, Cry1, Cry2, and BMAL1) in the self-fertilizing mangrove killifish Kryptolebias marmoratus. The promoter region of Km-clock had 1 aryl hydrocarbon receptor element (AhRE, GTGCGTGACA) and 8 estrogen receptor (ER) half-sites, indicating that the AhRE and ER half sites would likely be associated with regulation of clock protein activity during EDCs-induced cellular stress. The Km-clock protein domains (bHLH, PAS1, PAS2) were highly conserved in five additional fish species (zebrafish, Japanese medaka, Southern platyfish, Nile tilapia, and spotted green pufferfish), suggesting that the fish clock protein may play an important role in controlling endogenous circadian rhythms. The promoter regions of Km-BMAL1, -Cry1, -Cry2, and -Per2 were found to contain several xenobiotic response elements (XREs), indicating that EDCs may be able to alter the expression of these genes. To analyze the endogenous circadian rhythm in K. marmoratus, we measured expression of Km-clock and other circadian rhythmic genes (e.g. Per2, Cry1, Cry2, and BMAL1) in different tissues, and found ubiquitous expression, although there were different patterns of transcript amplification during different developmental stages. In an estrogen (E2)-exposed group, Km-clock expression was down-regulated, however, a hydroxytamoxifen (TMX, nonsteroid estrogen antagonist)-exposed group showed an upregulated pattern of Km-clock expression, suggesting that the expression of Km-clock is closely associated with exposure to EDCs. In response to the exposure of bisphenol A (BPA) and 4-tert-octyphenol (OP), Km-clock expression was down-regulated in the pituitary/brain, muscle, and skin in both gender types (hermaphrodite and secondary male). In juvenile K. marmoratus liver tissue, expression of Km-clock and other circadian rhythmic pathway

  13. Circadian Clock Genes Are Essential for Normal Adult Neurogenesis, Differentiation, and Fate Determination.

    PubMed

    Malik, Astha; Kondratov, Roman V; Jamasbi, Roudabeh J; Geusz, Michael E

    2015-01-01

    Adult neurogenesis creates new neurons and glia from stem cells in the human brain throughout life. It is best understood in the dentate gyrus (DG) of the hippocampus and the subventricular zone (SVZ). Circadian rhythms have been identified in the hippocampus, but the role of any endogenous circadian oscillator cells in hippocampal neurogenesis and their importance in learning or memory remains unclear. Any study of stem cell regulation by intrinsic circadian timing within the DG is complicated by modulation from circadian clocks elsewhere in the brain. To examine circadian oscillators in greater isolation, neurosphere cultures were prepared from the DG of two knockout mouse lines that lack a functional circadian clock and from mPer1::luc mice to identify circadian oscillations in gene expression. Circadian mPer1 gene activity rhythms were recorded in neurospheres maintained in a culture medium that induces neurogenesis but not in one that maintains the stem cell state. Although the differentiating neural stem progenitor cells of spheres were rhythmic, evidence of any mature neurons was extremely sparse. The circadian timing signal originated in undifferentiated cells within the neurosphere. This conclusion was supported by immunocytochemistry for mPER1 protein that was localized to the inner, more stem cell-like neurosphere core. To test for effects of the circadian clock on neurogenesis, media conditions were altered to induce neurospheres from BMAL1 knockout mice to differentiate. These cultures displayed unusually high differentiation into glia rather than neurons according to GFAP and NeuN expression, respectively, and very few BetaIII tubulin-positive, immature neurons were observed. The knockout neurospheres also displayed areas visibly devoid of cells and had overall higher cell death. Neurospheres from arrhythmic mice lacking two other core clock genes, Cry1 and Cry2, showed significantly reduced growth and increased astrocyte proliferation during

  14. Circadian Clock Genes Are Essential for Normal Adult Neurogenesis, Differentiation, and Fate Determination

    PubMed Central

    Kondratov, Roman V.; Jamasbi, Roudabeh J.

    2015-01-01

    Adult neurogenesis creates new neurons and glia from stem cells in the human brain throughout life. It is best understood in the dentate gyrus (DG) of the hippocampus and the subventricular zone (SVZ). Circadian rhythms have been identified in the hippocampus, but the role of any endogenous circadian oscillator cells in hippocampal neurogenesis and their importance in learning or memory remains unclear. Any study of stem cell regulation by intrinsic circadian timing within the DG is complicated by modulation from circadian clocks elsewhere in the brain. To examine circadian oscillators in greater isolation, neurosphere cultures were prepared from the DG of two knockout mouse lines that lack a functional circadian clock and from mPer1::luc mice to identify circadian oscillations in gene expression. Circadian mPer1 gene activity rhythms were recorded in neurospheres maintained in a culture medium that induces neurogenesis but not in one that maintains the stem cell state. Although the differentiating neural stem progenitor cells of spheres were rhythmic, evidence of any mature neurons was extremely sparse. The circadian timing signal originated in undifferentiated cells within the neurosphere. This conclusion was supported by immunocytochemistry for mPER1 protein that was localized to the inner, more stem cell-like neurosphere core. To test for effects of the circadian clock on neurogenesis, media conditions were altered to induce neurospheres from BMAL1 knockout mice to differentiate. These cultures displayed unusually high differentiation into glia rather than neurons according to GFAP and NeuN expression, respectively, and very few BetaIII tubulin-positive, immature neurons were observed. The knockout neurospheres also displayed areas visibly devoid of cells and had overall higher cell death. Neurospheres from arrhythmic mice lacking two other core clock genes, Cry1 and Cry2, showed significantly reduced growth and increased astrocyte proliferation during

  15. Genetic Disruption of the Core Circadian Clock Impairs Hippocampus-Dependent Memory

    ERIC Educational Resources Information Center

    Wardlaw, Sarah M.; Phan, Trongha X.; Saraf, Amit; Chen, Xuanmao; Storm, Daniel R.

    2014-01-01

    Perturbing the circadian system by electrolytically lesioning the suprachiasmatic nucleus (SCN) or varying the environmental light:dark schedule impairs memory, suggesting that memory depends on the circadian system. We used a genetic approach to evaluate the role of the molecular clock in memory. Bmal1[superscript -/-] mice, which are arrhythmic…

  16. Deregulated expression of circadian clock and clock-controlled cell cycle genes in chronic lymphocytic leukemia.

    PubMed

    Rana, Sobia; Munawar, Mustafa; Shahid, Adeela; Malik, Meera; Ullah, Hafeez; Fatima, Warda; Mohsin, Shahida; Mahmood, Saqib

    2014-01-01

    Circadian rhythms are endogenous and self-sustained oscillations of multiple biological processes with approximately 24-h rhythmicity. Circadian genes and their protein products constitute the molecular components of the circadian oscillator that form positive/negative feedback loops and generate circadian rhythms. The circadian regulation extends from core clock genes to various clock-controlled genes that include various cell cycle genes. Aberrant expression of circadian clock genes, therefore, may lead to genomic instability and accelerated cellular proliferation potentially promoting carcinogenesis. The current study encompasses the investigation of simultaneous expression of four circadian clock genes (Bmal1, Clock, Per1 and Per2) and three clock-controlled cell cycle genes (Myc, Cyclin D1 and Wee1) at mRNA level and determination of serum melatonin levels in peripheral blood samples of 37 CLL (chronic lymphocytic leukemia) patients and equal number of age- and sex-matched healthy controls in order to indicate association between deregulated circadian clock and manifestation of CLL. Results showed significantly down-regulated expression of Bmal1, Per1, Per2 and Wee1 and significantly up-regulated expression of Myc and Cyclin D1 (P < 0.0001) in CLL patients as compared to healthy controls. When expression of these genes was compared between shift-workers and non-shift-workers within the CLL group, the expression was found more aberrant in shift-workers as compared to non-shift-workers. However, this difference was found statistically significant for Myc and Cyclin D1 only (P < 0.05). Serum melatonin levels were found significantly low (P < 0.0001) in CLL subjects as compared to healthy controls whereas melatonin levels were found still lower in shift-workers as compared to non-shift-workers within CLL group (P < 0.01). Our results suggest that aberrant expression of circadian clock genes can lead to aberrant expression of their downstream targets that are

  17. A Long Noncoding RNA Perturbs the Circadian Rhythm of Hepatoma Cells to Facilitate Hepatocarcinogenesis12

    PubMed Central

    Cui, Ming; Zheng, Minying; Sun, Baodi; Wang, Yue; Ye, Lihong; Zhang, Xiaodong

    2015-01-01

    Clock circadian regulator (CLOCK)/brain and muscle arnt-like protein-1 (BMAL1) complex governs the regulation of circadian rhythm through triggering periodic alterations of gene expression. However, the underlying mechanism of circadian clock disruption in hepatocellular carcinoma (HCC) remains unclear. Here, we report that a long noncoding RNA (lncRNA), highly upregulated in liver cancer (HULC), contributes to the perturbations in circadian rhythm of hepatoma cells. Our observations showed that HULC was able to heighten the expression levels of CLOCK and its downstream circadian oscillators, such as period circadian clock 1 and cryptochrome circadian clock 1, in hepatoma cells. Strikingly, HULC altered the expression pattern and prolonged the periodic expression of CLOCK in hepatoma cells. Mechanistically, the complementary base pairing between HULC and the 5' untranslated region of CLOCK mRNA underlay the HULC-modulated expression of CLOCK, and the mutants in the complementary region failed to achieve the event. Moreover, immunohistochemistry staining and quantitative real-time polymerase chain reaction validated that the levels of CLOCK were elevated in HCC tissues, and the expression levels of HULC were positively associated with those of CLOCK in clinical HCC samples. In functional experiments, our data exhibited that CLOCK was implicated in the HULC-accelerated proliferation of hepatoma cells in vitro and in vivo. Taken together, our data show that an lncRNA, HULC, is responsible for the perturbations in circadian rhythm through upregulating circadian oscillator CLOCK in hepatoma cells, resulting in the promotion of hepatocarcinogenesis. Thus, our finding provides new insights into the mechanism by which lncRNA accelerates hepatocarcinogenesis through disturbing circadian rhythm of HCC. PMID:25622901

  18. A long noncoding RNA perturbs the circadian rhythm of hepatoma cells to facilitate hepatocarcinogenesis.

    PubMed

    Cui, Ming; Zheng, Minying; Sun, Baodi; Wang, Yue; Ye, Lihong; Zhang, Xiaodong

    2015-01-01

    Clock circadian regulator (CLOCK)/brain and muscle arnt-like protein-1 (BMAL1) complex governs the regulation of circadian rhythm through triggering periodic alterations of gene expression. However, the underlying mechanism of circadian clock disruption in hepatocellular carcinoma (HCC) remains unclear. Here, we report that a long noncoding RNA (lncRNA), highly upregulated in liver cancer (HULC), contributes to the perturbations in circadian rhythm of hepatoma cells. Our observations showed that HULC was able to heighten the expression levels of CLOCK and its downstream circadian oscillators, such as period circadian clock 1 and cryptochrome circadian clock 1, in hepatoma cells. Strikingly, HULC altered the expression pattern and prolonged the periodic expression of CLOCK in hepatoma cells. Mechanistically, the complementary base pairing between HULC and the 5' untranslated region of CLOCK mRNA underlay the HULC-modulated expression of CLOCK, and the mutants in the complementary region failed to achieve the event. Moreover, immunohistochemistry staining and quantitative real-time polymerase chain reaction validated that the levels of CLOCK were elevated in HCC tissues, and the expression levels of HULC were positively associated with those of CLOCK in clinical HCC samples. In functional experiments, our data exhibited that CLOCK was implicated in the HULC-accelerated proliferation of hepatoma cells in vitro and in vivo. Taken together, our data show that an lncRNA, HULC, is responsible for the perturbations in circadian rhythm through upregulating circadian oscillator CLOCK in hepatoma cells, resulting in the promotion of hepatocarcinogenesis. Thus, our finding provides new insights into the mechanism by which lncRNA accelerates hepatocarcinogenesis through disturbing circadian rhythm of HCC.

  19. Maternal obesity disrupts circadian rhythms of clock and metabolic genes in the offspring heart and liver.

    PubMed

    Wang, Danfeng; Chen, Siyu; Liu, Mei; Liu, Chang

    2015-06-01

    Early life nutritional adversity is tightly associated with the development of long-term metabolic disorders. Particularly, maternal obesity and high-fat diets cause high risk of obesity in the offspring. Those offspring are also prone to develop hyperinsulinemia, hepatic steatosis and cardiovascular diseases. However, the precise underlying mechanisms leading to these metabolic dysregulation in the offspring remain unclear. On the other hand, disruptions of diurnal circadian rhythms are known to impair metabolic homeostasis in various tissues including the heart and liver. Therefore, we investigated that whether maternal obesity perturbs the circadian expression rhythms of clock, metabolic and inflammatory genes in offspring heart and liver by using RT-qPCR and Western blotting analysis. Offspring from lean and obese dams were examined on postnatal day 17 and 35, when pups were nursed by their mothers or took food independently. On P17, genes examined in the heart either showed anti-phase oscillations (Cpt1b, Pparα, Per2) or had greater oscillation amplitudes (Bmal1, Tnf-α, Il-6). Such phase abnormalities of these genes were improved on P35, while defects in amplitudes still existed. In the liver of 17-day-old pups exposed to maternal obesity, the oscillation amplitudes of most rhythmic genes examined (except Bmal1) were strongly suppressed. On P35, the oscillations of circadian and inflammatory genes became more robust in the liver, while metabolic genes were still kept non-rhythmic. Maternal obesity also had a profound influence in the protein expression levels of examined genes in offspring heart and liver. Our observations indicate that the circadian clock undergoes nutritional programing, which may contribute to the alternations in energy metabolism associated with the development of metabolic disorders in early life and adulthood.

  20. Potential Conservation of Circadian Clock Proteins in the phylum Nematoda as Revealed by Bioinformatic Searches

    PubMed Central

    Romanowski, Andrés; Garavaglia, Matías Javier; Goya, María Eugenia; Ghiringhelli, Pablo Daniel; Golombek, Diego Andrés

    2014-01-01

    Although several circadian rhythms have been described in C. elegans, its molecular clock remains elusive. In this work we employed a novel bioinformatic approach, applying probabilistic methodologies, to search for circadian clock proteins of several of the best studied circadian model organisms of different taxa (Mus musculus, Drosophila melanogaster, Neurospora crassa, Arabidopsis thaliana and Synechoccocus elongatus) in the proteomes of C. elegans and other members of the phylum Nematoda. With this approach we found that the Nematoda contain proteins most related to the core and accessory proteins of the insect and mammalian clocks, which provide new insights into the nematode clock and the evolution of the circadian system. PMID:25396739

  1. Potential conservation of circadian clock proteins in the phylum Nematoda as revealed by bioinformatic searches.

    PubMed

    Romanowski, Andrés; Garavaglia, Matías Javier; Goya, María Eugenia; Ghiringhelli, Pablo Daniel; Golombek, Diego Andrés

    2014-01-01

    Although several circadian rhythms have been described in C. elegans, its molecular clock remains elusive. In this work we employed a novel bioinformatic approach, applying probabilistic methodologies, to search for circadian clock proteins of several of the best studied circadian model organisms of different taxa (Mus musculus, Drosophila melanogaster, Neurospora crassa, Arabidopsis thaliana and Synechoccocus elongatus) in the proteomes of C. elegans and other members of the phylum Nematoda. With this approach we found that the Nematoda contain proteins most related to the core and accessory proteins of the insect and mammalian clocks, which provide new insights into the nematode clock and the evolution of the circadian system.

  2. Circadian Rhythm Disruption Promotes Lung Tumorigenesis.

    PubMed

    Papagiannakopoulos, Thales; Bauer, Matthew R; Davidson, Shawn M; Heimann, Megan; Subbaraj, Lakshmipriya; Bhutkar, Arjun; Bartlebaugh, Jordan; Vander Heiden, Matthew G; Jacks, Tyler

    2016-08-01

    Circadian rhythms are 24-hr oscillations that control a variety of biological processes in living systems, including two hallmarks of cancer, cell division and metabolism. Circadian rhythm disruption by shift work is associated with greater risk for cancer development and poor prognosis, suggesting a putative tumor-suppressive role for circadian rhythm homeostasis. Using a genetically engineered mouse model of lung adenocarcinoma, we have characterized the effects of circadian rhythm disruption on lung tumorigenesis. We demonstrate that both physiologic perturbation (jet lag) and genetic mutation of the central circadian clock components decreased survival and promoted lung tumor growth and progression. The core circadian genes Per2 and Bmal1 were shown to have cell-autonomous tumor-suppressive roles in transformation and lung tumor progression. Loss of the central clock components led to increased c-Myc expression, enhanced proliferation, and metabolic dysregulation. Our findings demonstrate that both systemic and somatic disruption of circadian rhythms contribute to cancer progression.

  3. Circadian Rhythm Disruption Promotes Lung Tumorigenesis.

    PubMed

    Papagiannakopoulos, Thales; Bauer, Matthew R; Davidson, Shawn M; Heimann, Megan; Subbaraj, Lakshmipriya; Bhutkar, Arjun; Bartlebaugh, Jordan; Vander Heiden, Matthew G; Jacks, Tyler

    2016-08-01

    Circadian rhythms are 24-hr oscillations that control a variety of biological processes in living systems, including two hallmarks of cancer, cell division and metabolism. Circadian rhythm disruption by shift work is associated with greater risk for cancer development and poor prognosis, suggesting a putative tumor-suppressive role for circadian rhythm homeostasis. Using a genetically engineered mouse model of lung adenocarcinoma, we have characterized the effects of circadian rhythm disruption on lung tumorigenesis. We demonstrate that both physiologic perturbation (jet lag) and genetic mutation of the central circadian clock components decreased survival and promoted lung tumor growth and progression. The core circadian genes Per2 and Bmal1 were shown to have cell-autonomous tumor-suppressive roles in transformation and lung tumor progression. Loss of the central clock components led to increased c-Myc expression, enhanced proliferation, and metabolic dysregulation. Our findings demonstrate that both systemic and somatic disruption of circadian rhythms contribute to cancer progression. PMID:27476975

  4. Rhythmicity of the intestinal microbiota is regulated by gender and the host circadian clock

    PubMed Central

    Liang, Xue; Bushman, Frederic D.; FitzGerald, Garret A.

    2015-01-01

    In mammals, multiple physiological, metabolic, and behavioral processes are subject to circadian rhythms, adapting to changing light in the environment. Here we analyzed circadian rhythms in the fecal microbiota of mice using deep sequencing, and found that the absolute amount of fecal bacteria and the abundance of Bacteroidetes exhibited circadian rhythmicity, which was more pronounced in female mice. Disruption of the host circadian clock by deletion of Bmal1, a gene encoding a core molecular clock component, abolished rhythmicity in the fecal microbiota composition in both genders. Bmal1 deletion also induced alterations in bacterial abundances in feces, with differential effects based on sex. Thus, although host behavior, such as time of feeding, is of recognized importance, here we show that sex interacts with the host circadian clock, and they collectively shape the circadian rhythmicity and composition of the fecal microbiota in mice. PMID:26240359

  5. Microgravity influences circadian clock oscillation in human keratinocytes

    PubMed Central

    Ranieri, Danilo; Cucina, Alessandra; Bizzarri, Mariano; Alimandi, Maurizio; Torrisi, Maria Rosaria

    2015-01-01

    Microgravity and sudden changes of gravitational forces exert numerous effects on tissues, organs and apparatus. Responses to these forces variably applied to cells indicate the existence of mechanotransduction pathways able to modulate transcription. Oscillation of circadian clocks similarly influences many cellular and metabolic processes. Here we hypothesized that signals derived from changes of gravitational forces applied to epidermal cells might influence their physiology in harmony with the oscillation of the molecular clock. In this study, we describe amplified oscillations of Bmal1 circadian clock gene in human keratinocytes exposed to short simulated microgravity and to rapid variation of gravitational forces. We found that exposure to microgravity enhances the amplitude of the Bmal1 feedback loop sustained by an apparently lower variability of Rev-erbα transcription, while recovery from microgravity is characterized by increased amplitude of Bmal1 expression and elongation of the oscillatory periods of Bmal1 and Rev-erbα. These data highlight the existence of integrated signaling network connecting mechanosensitive pathways to circadian gene regulation. PMID:26448904

  6. Robust Circadian Rhythm and Parathyroid Hormone-Induced Resetting during Hypertrophic Differentiation in ATDC5 Chondroprogenitor Cells.

    PubMed

    Hosokawa, Toshihiro; Tsuchiya, Yoshiki; Okubo, Naoki; Kunimoto, Tatsuya; Minami, Yoichi; Fujiwara, Hiroyoshi; Umemura, Yasuhiro; Koike, Nobuya; Kubo, Toshikazu; Yagita, Kazuhiro

    2015-12-25

    Cartilage tissues possess intrinsic circadian oscillators, which influence chondrocyte function and chondrocyte specific gene expression. However, it is not fully understood how chondrogenesis influences the circadian clock, and vice versa. Thus, we established ATDC5 cells which were stably transfected with the Bmal1:luc reporter and revealed robust circadian rhythms in ATDC5 cells during differentiation. Moreover, the circadian clock in ATDC5 cells was strongly reset by PTH in a circadian time-dependent manner. This assay system is expected to be useful for investigating the role of the circadian clock in chondrogenic differentiation and the precise molecular mechanisms underlying PTH action on the chondrocyte circadian clock.

  7. [Molecular mechanisms of circadian clock functioning].

    PubMed

    Karbovskyĭ, L L; Minchenko, D O; Garmash, Ia A; Minchenko, O G

    2011-01-01

    Most physiological processes of all organisms are rhythmic with a period of about 24 h and are generated by an endogenous biological CLOCK present in all cells. However, there is also a central CLOCK--the primary circadian pacemaker which is localized in the suprachiasmatic nuclei of the mammalian hypothalamus. Factors of groups Period (PER1, PER2 and PER3), BMAL (BMAL1 and BMAL2), CRYptochromes (CRY1 and CRY2) as well as some other factors are the components of this circadian CLOCK system. Some of these genes contain E-box sequences and their expression is regulated by a transcription factor complex CLOCK-BMAL1. The enzymes responsible for the post-translational modification of circadian gene products are also the components of circadian CLOCK system. These enzymes define CLOCK's work and determine the duration of circadian biorhythm and functional state of the whole organism. The most important of these enzymes are casein kinase-1epsilon and -1delta. We have analysed data about the interconnection between the circadian CLOCK system, cell cycle, and cancerogenesis as well as about the sensitivity of circadian gene expression to the action of toxic agents and nanomaterials.

  8. Circadian rhythm reprogramming during lung inflammation.

    PubMed

    Haspel, Jeffrey A; Chettimada, Sukrutha; Shaik, Rahamthulla S; Chu, Jen-Hwa; Raby, Benjamin A; Cernadas, Manuela; Carey, Vincent; Process, Vanessa; Hunninghake, G Matthew; Ifedigbo, Emeka; Lederer, James A; Englert, Joshua; Pelton, Ashley; Coronata, Anna; Fredenburgh, Laura E; Choi, Augustine M K

    2014-09-11

    Circadian rhythms are known to regulate immune responses in healthy animals, but it is unclear whether they persist during acute illnesses where clock gene expression is disrupted by systemic inflammation. Here we use a genome-wide approach to investigate circadian gene and metabolite expression in the lungs of endotoxemic mice and find that novel cellular and molecular circadian rhythms are elicited in this setting. The endotoxin-specific circadian programme exhibits unique features, including a divergent group of rhythmic genes and metabolites compared with the basal state and a distinct periodicity and phase distribution. At the cellular level, endotoxin treatment also alters circadian rhythms of leukocyte counts within the lung in a bmal1-dependent manner, such that granulocytes rather than lymphocytes become the dominant oscillating cell type. Our results show that inflammation produces a complex re-organization of cellular and molecular circadian rhythms that are relevant to early events in lung injury.

  9. Mass spectrometry-based absolute quantification reveals rhythmic variation of mouse circadian clock proteins.

    PubMed

    Narumi, Ryohei; Shimizu, Yoshihiro; Ukai-Tadenuma, Maki; Ode, Koji L; Kanda, Genki N; Shinohara, Yuta; Sato, Aya; Matsumoto, Katsuhiko; Ueda, Hiroki R

    2016-06-14

    Absolute values of protein expression levels in cells are crucial information for understanding cellular biological systems. Precise quantification of proteins can be achieved by liquid chromatography (LC)-mass spectrometry (MS) analysis of enzymatic digests of proteins in the presence of isotope-labeled internal standards. Thus, development of a simple and easy way for the preparation of internal standards is advantageous for the analyses of multiple target proteins, which will allow systems-level studies. Here we describe a method, termed MS-based Quantification By isotope-labeled Cell-free products (MS-QBiC), which provides the simple and high-throughput preparation of internal standards by using a reconstituted cell-free protein synthesis system, and thereby facilitates both multiplexed and sensitive quantification of absolute amounts of target proteins. This method was applied to a systems-level dynamic analysis of mammalian circadian clock proteins, which consist of transcription factors and protein kinases that govern central and peripheral circadian clocks in mammals. Sixteen proteins from 20 selected circadian clock proteins were successfully quantified from mouse liver over a 24-h time series, and 14 proteins had circadian variations. Quantified values were applied to detect internal body time using a previously developed molecular timetable method. The analyses showed that single time-point data from wild-type mice can predict the endogenous state of the circadian clock, whereas data from clock mutant mice are not applicable because of the disappearance of circadian variation. PMID:27247408

  10. Circadian rhythm of the Leydig cells endocrine function is attenuated during aging.

    PubMed

    Baburski, Aleksandar Z; Sokanovic, Srdjan J; Bjelic, Maja M; Radovic, Sava M; Andric, Silvana A; Kostic, Tatjana S

    2016-01-01

    Although age-related hypofunction of Leydig cells is well illustrated across species, its circadian nature has not been analyzed. Here we describe changes in circadian behavior in Leydig cells isolated from adult (3-month) and aged (18- and 24-month) rats. The results showed reduced circadian pattern of testosterone secretion in both groups of aged rats despite unchanged LH circadian secretion. Although arrhythmic, the expression of Insl3, another secretory product of Leydig cells, was decreased in both groups. Intracellular cAMP and most important steroidogenic genes (Star, Cyp11a1 and Cyp17a1), together with positive steroidogenic regulator (Nur77), showed preserved circadian rhythm in aging although rhythm robustness and expression level were attenuated in both aged groups. Aging compromised cholesterol mobilization and uptake by Leydig cells: the oscillatory transcription pattern of genes encoding HDL-receptor (Scarb1), hormone sensitive lipase (Lipe, enzyme that converts cholesterol esters from lipid droplets into free cholesterol) and protein responsible for forming the cholesterol esters (Soat2) were flattened in 24-month group. The majority of examined clock genes displayed circadian behavior in expression but only a few of them (Bmal1, Per1, Per2, Per3 and Rev-Erba) were reduced in 24-month-old group. Furthermore, aging reduced oscillatory expression pattern of Sirt1 and Nampt, genes encoding key enzymes that connect cellular metabolism and circadian network. Altogether circadian amplitude of Leydig cell's endocrine function decreased during aging. The results suggest that clock genes are more resistant to aging than genes involved in steroidogenesis supporting the hypothesis about peripheral clock involvement in rhythm maintenance during aging.

  11. Circadian Clock in a Mouse Colon Tumor Regulates Intracellular Iron Levels to Promote Tumor Progression.

    PubMed

    Okazaki, Fumiyasu; Matsunaga, Naoya; Okazaki, Hiroyuki; Azuma, Hiroki; Hamamura, Kengo; Tsuruta, Akito; Tsurudome, Yuya; Ogino, Takashi; Hara, Yukinori; Suzuki, Takuya; Hyodo, Kenji; Ishihara, Hiroshi; Kikuchi, Hiroshi; To, Hideto; Aramaki, Hironori; Koyanagi, Satoru; Ohdo, Shigehiro

    2016-03-25

    Iron is an important biological catalyst and is critical for DNA synthesis during cell proliferation. Cellular iron uptake is enhanced in tumor cells to support increased DNA synthesis. Circadian variations in DNA synthesis and proliferation have been identified in tumor cells, but their relationship with intracellular iron levels is unclear. In this study, we identified a 24-h rhythm in iron regulatory protein 2 (IRP2) levels in colon-26 tumors implanted in mice. Our findings suggest that IRP2 regulates the 24-h rhythm of transferrin receptor 1 (Tfr1) mRNA expression post-transcriptionally, by binding to RNA stem-loop structures known as iron-response elements. We also found thatIrp2mRNA transcription is promoted by circadian clock genes, including brain and muscle Arnt-like 1 (BMAL1) and the circadian locomotor output cycles kaput (CLOCK) heterodimer. Moreover, growth in colon-26(Δ19) tumors expressing the clock-mutant protein (CLOCK(Δ19)) was low compared with that in wild-type colon-26 tumor. The time-dependent variation of cellular iron levels, and the proliferation rate in wild-type colon-26 tumor was decreased by CLOCK(Δ19)expression. Our findings suggest that circadian organization contributes to tumor cell proliferation by regulating iron metabolism in the tumor.

  12. Long-Lasting Effect of Perinatal Exposure to L-tryptophan on Circadian Clock of Primary Cell Lines Established from Male Offspring Born from Mothers Fed on Dietary Protein Restriction

    PubMed Central

    Nascimento, Elizabeth; Guzman-Quevedo, Omar; Delacourt, Nellie; da Silva Aragão, Raquel; Perez-Garcia, Georgina; de Souza, Sandra Lopes; Manhães-de-Castro, Raul; Bolaños-Jiménez, Francisco; Kaeffer, Bertrand

    2013-01-01

    Background & Aims Maternal undernutrition programs metabolic adaptations which are ultimately detrimental to adult. L-tryptophan supplementation was given to manipulate the long-term sequelae of early-life programming by undernutrition and explore whether cultured cells retain circadian clock dysregulation. Methods Male rat pups from mothers fed on low protein (8%, LP) or control (18%, CP) diet were given, one hour before light off, an oral bolus of L-tryptophan (125 mg/kg) between Day-12 and Day-21 of age. Body weight, food intake, blood glucose along with the capacity of colonization of primary cells from biopsies were measured during the young (45–55 days) and adult (110–130 days) phases. Circadian clock oscillations were re-induced by a serum shock over 30 hours on near-confluent cell monolayers to follow PERIOD1 and CLOCK proteins by Fluorescent Linked ImmunoSorbent Assay (FLISA) and period1 and bmal1 mRNA by RT-PCR. Cell survival in amino acid-free conditions were used to measure circadian expression of MAP-LC3B, MAP-LC3B-FP and Survivin. Results Tryptophan supplementation did not alter body weight gain nor feeding pattern. By three-way ANOVA of blood glucose, sampling time was found significant during all phases. A significant interaction between daily bolus (Tryptophan, saline) and diets (LP, CP) were found during young (p = 0.0291) and adult (p = 0.0285) phases. In adult phase, the capacity of colonization at seeding of primary cells was twice lower for LP rats. By three-way ANOVA of PERIOD1 perinuclear/nuclear immunoreactivity during young phase, we found a significant effect of diets (p = 0.049), daily bolus (p<0.0001) and synchronizer hours (p = 0.0002). All factors were significantly interacting (p = 0.0148). MAP-LC3B, MAP-LC3B-FP and Survivin were altered according to diets in young phase. Conclusions Sequelae of early-life undernutrition and the effects of L-tryptophan supplementation can be monitored non-invasively by

  13. The circadian rhythm controls telomeres and telomerase activity.

    PubMed

    Chen, Wei-Dar; Wen, Ming-Shien; Shie, Shian-Sen; Lo, Yu-Lun; Wo, Hung-Ta; Wang, Chun-Chieh; Hsieh, I-Chang; Lee, Tsong-Hai; Wang, Chao-Yung

    2014-08-29

    Circadian clocks are fundamental machinery in organisms ranging from archaea to humans. Disruption of the circadian system is associated with premature aging in mice, but the molecular basis underlying this phenomenon is still unclear. In this study, we found that telomerase activity exhibits endogenous circadian rhythmicity in humans and mice. Human and mouse TERT mRNA expression oscillates with circadian rhythms and are under the control of CLOCK-BMAL1 heterodimers. CLOCK deficiency in mice causes loss of rhythmic telomerase activities, TERT mRNA oscillation, and shortened telomere length. Physicians with regular work schedules have circadian oscillation of telomerase activity while emergency physicians working in shifts lose the circadian rhythms of telomerase activity. These findings identify the circadian rhythm as a mechanism underlying telomere and telomerase activity control that serve as interconnections between circadian systems and aging.

  14. Disruption of Sirtuin 1-Mediated Control of Circadian Molecular Clock and Inflammation in Chronic Obstructive Pulmonary Disease.

    PubMed

    Yao, Hongwei; Sundar, Isaac K; Huang, Yadi; Gerloff, Janice; Sellix, Michael T; Sime, Patricia J; Rahman, Irfan

    2015-12-01

    Chronic obstructive pulmonary disease (COPD) is the fourth most common cause of death, and it is characterized by abnormal inflammation and lung function decline. Although the circadian molecular clock regulates inflammatory responses, there is no information available regarding the impact of COPD on lung molecular clock function and its regulation by sirtuin 1 (SIRT1). We hypothesize that the molecular clock in the lungs is disrupted, leading to increased inflammatory responses in smokers and patients with COPD and its regulation by SIRT1. Lung tissues, peripheral blood mononuclear cells (PBMCs), and sputum cells were obtained from nonsmokers, smokers, and patients with COPD for measurement of core molecular clock proteins (BMAL1, CLOCK, PER1, PER2, and CRY1), clock-associated nuclear receptors (REV-ERBα, REV-ERBβ, and RORα), and SIRT1 by immunohistochemistry, immunofluorescence, and immunoblot. PBMCs were treated with the SIRT1 activator SRT1720 followed by LPS treatment, and supernatant was collected at 6-hour intervals. Levels of IL-8, IL-6, and TNF-α released from PBMCs were determined by ELISA. Expression of BMAL1, PER2, CRY1, and REV-ERBα was reduced in PBMCs, sputum cells, and lung tissues from smokers and patients with COPD when compared with nonsmokers. SRT1720 treatment attenuated LPS-mediated reduction of BMAL1 and REV-ERBα in PBMCs from nonsmokers. Additionally, LPS differentially affected the timing and amplitude of cytokine (IL-8, IL-6, and TNF-α) release from PBMCs in nonsmokers, smokers, and patients with COPD. Moreover, SRT1720 was able to inhibit LPS-induced cytokine release from cultured PBMCs. In conclusion, disruption of the molecular clock due to SIRT1 reduction contributes to abnormal inflammatory response in smokers and patients with COPD.

  15. Genetic disruption of the core circadian clock impairs hippocampus-dependent memory

    PubMed Central

    Wardlaw, Sarah M.; Phan, Trongha X.; Saraf, Amit; Chen, Xuanmao

    2014-01-01

    Perturbing the circadian system by electrolytically lesioning the suprachiasmatic nucleus (SCN) or varying the environmental light:dark schedule impairs memory, suggesting that memory depends on the circadian system. We used a genetic approach to evaluate the role of the molecular clock in memory. Bmal1−/− mice, which are arrhythmic under constant conditions, were examined for hippocampus-dependent memory, LTP at the Schaffer-collateral synapse, and signal transduction activity in the hippocampus. Bmal1−/− mice exhibit impaired contextual fear and spatial memory. Furthermore, LTP in hippocampal slices from Bmal1−/− mice is also significantly decreased relative to that from wild-type mice. Activation of Erk1,2 MAP kinase (MAPK) during training for contextual fear memory and diurnal oscillation of MAPK activity and cAMP in the hippocampus is also lost in Bmal1−/− mice, suggesting that the memory defects are due to reduction of the memory consolidation pathway in the hippocampus. We conclude that critical signaling events in the hippocampus required for memory depend on BMAL1. PMID:25034823

  16. Common Genetic Variation in Circadian Rhythm Genes and Risk of Epithelial Ovarian Cancer (EOC)

    PubMed Central

    Jim, Heather S.L.; Lin, Hui-Yi; Tyrer, Jonathan P.; Lawrenson, Kate; Dennis, Joe; Chornokur, Ganna; Chen, Zhihua; Chen, Ann Y.; Permuth-Wey, Jennifer; Aben, Katja KH.; Anton-Culver, Hoda; Antonenkova, Natalia; Bruinsma, Fiona; Bandera, Elisa V.; Bean, Yukie T.; Beckmann, Matthias W.; Bisogna, Maria; Bjorge, Line; Bogdanova, Natalia; Brinton, Louise A.; Brooks-Wilson, Angela; Bunker, Clareann H.; Butzow, Ralf; Campbell, Ian G.; Carty, Karen; Chang-Claude, Jenny; Cook, Linda S.; Cramer, Daniel W.; Cunningham, Julie M.; Cybulski, Cezary; Dansonka-Mieszkowska, Agnieszka; du Bois, Andreas; Despierre, Evelyn; Sieh, Weiva; Doherty, Jennifer A.; Dörk, Thilo; Dürst, Matthias; Easton, Douglas F.; Eccles, Diana M.; Edwards, Robert P.; Ekici, Arif B.; Fasching, Peter A.; Fridley, Brooke L.; Gao, Yu-Tang; Gentry-Maharaj, Aleksandra; Giles, Graham G.; Glasspool, Rosalind; Goodman, Marc T.; Gronwald, Jacek; Harter, Philipp; Hasmad, Hanis N.; Hein, Alexander; Heitz, Florian; Hildebrandt, Michelle A.T.; Hillemanns, Peter; Hogdall, Claus K.; Hogdall, Estrid; Hosono, Satoyo; Iversen, Edwin S.; Jakubowska, Anna; Jensen, Allan; Ji, Bu-Tian; Karlan, Beth Y.; Kellar, Melissa; Kiemeney, Lambertus A.; Krakstad, Camilla; Kjaer, Susanne K.; Kupryjanczyk, Jolanta; Vierkant, Robert A.; Lambrechts, Diether; Lambrechts, Sandrina; Le, Nhu D.; Lee, Alice W.; Lele, Shashi; Leminen, Arto; Lester, Jenny; Levine, Douglas A.; Liang, Dong; Lim, Boon Kiong; Lissowska, Jolanta; Lu, Karen; Lubinski, Jan; Lundvall, Lene; Massuger, Leon F.A.G.; Matsuo, Keitaro; McGuire, Valerie; McLaughlin, John R.; McNeish, Ian; Menon, Usha; Milne, Roger L.; Modugno, Francesmary; Thomsen, Lotte; Moysich, Kirsten B.; Ness, Roberta B.; Nevanlinna, Heli; Eilber, Ursula; Odunsi, Kunle; Olson, Sara H.; Orlow, Irene; Orsulic, Sandra; Palmieri Weber, Rachel; Paul, James; Pearce, Celeste L.; Pejovic, Tanja; Pelttari, Liisa M.; Pike, Malcolm C.; Poole, Elizabeth M.; Schernhammer, Eva; Risch, Harvey A.; Rosen, Barry; Rossing, Mary Anne; Rothstein, Joseph H.; Rudolph, Anja; Runnebaum, Ingo B.; Rzepecka, Iwona K.; Salvesen, Helga B.; Schwaab, Ira; Shu, Xiao-Ou; Shvetsov, Yurii B.; Siddiqui, Nadeem; Song, Honglin; Southey, Melissa C.; Spiewankiewicz, Beata; Sucheston-Campbell, Lara; Teo, Soo-Hwang; Terry, Kathryn L.; Thompson, Pamela J.; Tangen, Ingvild L.; Tworoger, Shelley S.; van Altena, Anne M.; Vergote, Ignace; Walsh, Christine S.; Wang-Gohrke, Shan; Wentzensen, Nicolas; Whittemore, Alice S.; Wicklund, Kristine G.; Wilkens, Lynne R.; Wu, Anna H.; Wu, Xifeng; Woo, Yin-Ling; Yang, Hannah; Zheng, Wei; Ziogas, Argyrios; Amankwah, Ernest; Berchuck, Andrew; Schildkraut, Joellen M.; Kelemen, Linda E.; Ramus, Susan J.; Monteiro, Alvaro N.A.; Goode, Ellen L.; Narod, Steven A.; Gayther, Simon A.; Pharoah, Paul D. P.; Sellers, Thomas A.; Phelan, Catherine M.

    2016-01-01

    Disruption in circadian gene expression, whether due to genetic variation or environmental factors (e.g., light at night, shiftwork), is associated with increased incidence of breast, prostate, gastrointestinal and hematologic cancers and gliomas. Circadian genes are highly expressed in the ovaries where they regulate ovulation; circadian disruption is associated with several ovarian cancer risk factors (e.g., endometriosis). However, no studies have examined variation in germline circadian genes as predictors of ovarian cancer risk and invasiveness. The goal of the current study was to examine single nucleotide polymorphisms (SNPs) in circadian genes BMAL1, CRY2, CSNK1E, NPAS2, PER3, REV1 and TIMELESS and downstream transcription factors KLF10 and SENP3 as predictors of risk of epithelial ovarian cancer (EOC) and histopathologic subtypes. The study included a test set of 3,761 EOC cases and 2,722 controls and a validation set of 44,308 samples including 18,174 (10,316 serous) cases and 26,134 controls from 43 studies participating in the Ovarian Cancer Association Consortium (OCAC). Analysis of genotype data from 36 genotyped SNPs and 4600 imputed SNPs indicated that the most significant association was rs117104877 in BMAL1 (OR = 0.79, 95% CI = 0.68–0.90, p = 5.59 × 10−4]. Functional analysis revealed a significant down regulation of BMAL1 expression following cMYC overexpression and increasing transformation in ovarian surface epithelial (OSE) cells as well as alternative splicing of BMAL1 exons in ovarian and granulosa cells. These results suggest that variation in circadian genes, and specifically BMAL1, may be associated with risk of ovarian cancer, likely through disruption of hormonal pathways. PMID:26807442

  17. Visualizing and Quantifying Intracellular Behavior and Abundance of the Core Circadian Clock Protein PERIOD2.

    PubMed

    Smyllie, Nicola J; Pilorz, Violetta; Boyd, James; Meng, Qing-Jun; Saer, Ben; Chesham, Johanna E; Maywood, Elizabeth S; Krogager, Toke P; Spiller, David G; Boot-Handford, Raymond; White, Michael R H; Hastings, Michael H; Loudon, Andrew S I

    2016-07-25

    Transcriptional-translational feedback loops (TTFLs) are a conserved molecular motif of circadian clocks. The principal clock in mammals is the suprachiasmatic nucleus (SCN) of the hypothalamus. In SCN neurons, auto-regulatory feedback on core clock genes Period (Per) and Cryptochrome (Cry) following nuclear entry of their protein products is the basis of circadian oscillation [1, 2]. In Drosophila clock neurons, the movement of dPer into the nucleus is subject to a circadian gate that generates a delay in the TTFL, and this delay is thought to be critical for oscillation [3, 4]. Analysis of the Drosophila clock has strongly influenced models of the mammalian clock, and such models typically infer complex spatiotemporal, intracellular behaviors of mammalian clock proteins. There are, however, no direct measures of the intracellular behavior of endogenous circadian proteins to support this: dynamic analyses have been limited and often have no circadian dimension [5-7]. We therefore generated a knockin mouse expressing a fluorescent fusion of native PER2 protein (PER2::VENUS) for live imaging. PER2::VENUS recapitulates the circadian functions of wild-type PER2 and, importantly, the behavior of PER2::VENUS runs counter to the Drosophila model: it does not exhibit circadian gating of nuclear entry. Using fluorescent imaging of PER2::VENUS, we acquired the first measures of mobility, molecular concentration, and localization of an endogenous circadian protein in individual mammalian cells, and we showed how the mobility and nuclear translocation of PER2 are regulated by casein kinase. These results provide new qualitative and quantitative insights into the cellular mechanism of the mammalian circadian clock. PMID:27374340

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

    PubMed

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

    2015-01-01

    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

  19. 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

  20. 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

  1. Circadian rhythms, the molecular clock, and skeletal muscle.

    PubMed

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

    2011-01-01

    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 Clock(Δ19) 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.

  2. Protein phosphatase PHLPP1 controls the light-induced resetting of the circadian clock

    PubMed Central

    Masubuchi, Satoru; Gao, Tianyan; O'Neill, Audrey; Eckel-Mahan, Kristin; Newton, Alexandra C.; Sassone-Corsi, Paolo

    2010-01-01

    The pleckstrin homology domain leucine-rich repeat protein phosphatase 1 (PHLPP1) differentially attenuates Akt, PKC, and ERK1/2 signaling, thereby controlling the duration and amplitude of responses evoked by these kinases. PHLPP1 is expressed in the mammalian central clock, the suprachiasmatic nucleus, where it oscillates in a circadian fashion. To explore the role of PHLPP1 in vivo, we have generated mice with a targeted deletion of the PHLPP1 gene. Here we show that PHLPP1-null mice, although displaying normal circadian rhythmicity, have a drastically impaired capacity to stabilize the circadian period after light-induced resetting, producing a large phase shift after light resetting. Our findings reveal that PHLPP1 exerts a previously unappreciated role in circadian control, governing the consolidation of circadian periodicity after resetting. PMID:20080691

  3. Protein phosphatase-dependent circadian regulation of intermediate-term associative memory.

    PubMed

    Michel, Maximilian; Gardner, Jacob S; Green, Charity L; Organ, Chelsea L; Lyons, Lisa C

    2013-03-01

    The endogenous circadian clock is a principal factor modulating memory across species. Determining the processes through which the circadian clock modulates memory formation is a key issue in understanding and identifying mechanisms to improve memory. We used the marine mollusk Aplysia californica to investigate circadian modulation of intermediate-term memory (ITM) and the mechanisms through which the circadian clock phase specifically suppresses memory using the operant learning paradigm, learning that food is inedible. We found that ITM, a temporally and mechanistically distinct form of memory, is rhythmically expressed under light-dark and constant conditions when induced by either massed or spaced training. Strong circadian regulation of ITM occurs with memory exhibited only by animals trained during the early subjective day; no apparent memory is expressed when training occurs during the late subjective day or night. Given the necessity of multiple persistent kinase cascades for ITM, we investigated whether protein phosphatase activity affected circadian modulation. Inhibition of protein phosphatases 1 and 2A blocked ITM when animals were trained during the early (subjective) day while resulting in phase-specific memory rescue when animals were trained late in the subjective day and early night. In contrast, inhibition of calcineurin did not block ITM when animals were trained during the early day and permitted ITM when animals were trained during the late subjective day, early evening, and throughout the night. These results demonstrate that levels of protein phosphatase activity are critical regulators of ITM and one mechanism through which the circadian clock regulates memory formation.

  4. A molecular clock regulates angiopoietin-like protein 2 expression.

    PubMed

    Kadomatsu, Tsuyoshi; Uragami, Shota; Akashi, Makoto; Tsuchiya, Yoshiki; Nakajima, Hiroo; Nakashima, Yukiko; Endo, Motoyoshi; Miyata, Keishi; Terada, Kazutoyo; Todo, Takeshi; Node, Koichi; Oike, Yuichi

    2013-01-01

    Various physiological and behavioral processes exhibit circadian rhythmicity. These rhythms are usually maintained by negative feedback loops of core clock genes, namely, CLOCK, BMAL, PER, and CRY. Recently, dysfunction in the circadian clock has been recognized as an important foundation for the pathophysiology of lifestyle-related diseases, such as obesity, cardiovascular disease, and some cancers. We have reported that angiopoietin-like protein 2 (ANGPTL2) contributes to the pathogenesis of these lifestyle-related diseases by inducing chronic inflammation. However, molecular mechanisms underlying regulation of ANGPTL2 expression are poorly understood. Here, we assess circadian rhythmicity of ANGPTL2 expression in various mouse tissues. We observed that ANGPTL2 rhythmicity was similar to that of the PER2 gene, which is regulated by the CLOCK/BMAL1 complex. Promoter activity of the human ANGPTL2 gene was significantly induced by CLOCK and BMAL1, an induction markedly attenuated by CRY co-expression. We also identified functional E-boxes in the ANGPTL2 promoter and observed occupancy of these sites by endogenous CLOCK in human osteosarcoma cells. Furthermore, Cry-deficient mice exhibited arrhythmic Angptl2 expression. Taken together, these data suggest that periodic expression of ANGPTL2 is regulated by a molecular clock.

  5. Circadian rhythms, Wnt/beta-catenin pathway and PPAR alpha/gamma profiles in diseases with primary or secondary cardiac dysfunction

    PubMed Central

    Lecarpentier, Yves; Claes, Victor; Duthoit, Guillaume; Hébert, Jean-Louis

    2014-01-01

    Circadian clock mechanisms are far-from-equilibrium dissipative structures. Peroxisome proliferator-activated receptors (PPAR alpha, beta/delta, and gamma) play a key role in metabolic regulatory processes, particularly in heart muscle. Links between circadian rhythms (CRs) and PPARs have been established. Mammalian CRs involve at least two critical transcription factors, CLOCK and BMAL1 (Gekakis et al., 1998; Hogenesch et al., 1998). PPAR gamma plays a major role in both glucose and lipid metabolisms and presents circadian properties which coordinate the interplay between metabolism and CRs. PPAR gamma is a major component of the vascular clock. Vascular PPAR gamma is a peripheral regulator of cardiovascular rhythms controlling circadian variations in blood pressure and heart rate through BMAL1. We focused our review on diseases with abnormalities of CRs and with primary or secondary cardiac dysfunction. Moreover, these diseases presented changes in the Wnt/beta-catenin pathway and PPARs, according to two opposed profiles. Profile 1 was defined as follows: inactivation of the Wnt/beta-catenin pathway with increased expression of PPAR gamma. Profile 2 was defined as follows: activation of the Wnt/beta-catenin pathway with decreased expression of PPAR gamma. A typical profile 1 disease is arrhythmogenic right ventricular cardiomyopathy, a genetic cardiac disease which presents mutations of the desmosomal proteins and is mainly characterized by fatty acid accumulation in adult cardiomyocytes mainly in the right ventricle. The link between PPAR gamma dysfunction and desmosomal genetic mutations occurs via inactivation of the Wnt/beta-catenin pathway presenting oscillatory properties. A typical profile 2 disease is type 2 diabetes, with activation of the Wnt/beta-catenin pathway and decreased expression of PPAR gamma. CRs abnormalities are present in numerous pathologies such as cardiovascular diseases, sympathetic/parasympathetic dysfunction, hypertension, diabetes

  6. Clock Genes Show Circadian Rhythms in Salivary Glands

    PubMed Central

    Zheng, L.; Seon, Y.J.; McHugh, J.; Papagerakis, S.; Papagerakis, P.

    2012-01-01

    Circadian rhythms are endogenous self-sustained oscillations with 24-hour periods that regulate diverse physiological and metabolic processes through complex gene regulation by “clock” transcription factors. The oral cavity is bathed by saliva, and its amount and content are modified within regular daily intervals. The clock mechanisms that control salivary production remain unclear. Our objective was to evaluate the expression and periodicity of clock genes in salivary glands. Real-time quantitative RT-PCR, in situ hybridization, and immunohistochemistry were performed to show circadian mRNA and protein expression and localization of key clock genes (Bmal1, Clock, Per1, and Per2), ion and aqua channel genes (Ae2a, Car2, and Aqp5), and salivary gland markers. Clock gene mRNAs and clock proteins were found differentially expressed in the serous acini and duct cells of all major salivary glands. The expression levels of clock genes and Aqp5 showed regular oscillatory patterns under both light/dark and complete-dark conditions. Bmla1 overexpression resulted in increased Aqp5 expression levels. Analysis of our data suggests that salivary glands have a peripheral clock mechanism that functions both in normal light/dark conditions and in the absence of light. This finding may increase our understanding of the control mechanisms of salivary content and flow. PMID:22699207

  7. The circadian molecular clock regulates adult hippocampal neurogenesis by controlling the timing of cell-cycle entry and exit.

    PubMed

    Bouchard-Cannon, Pascale; Mendoza-Viveros, Lucia; Yuen, Andrew; Kærn, Mads; Cheng, Hai-Ying M

    2013-11-27

    The subgranular zone (SGZ) of the adult hippocampus contains a pool of quiescent neural progenitor cells (QNPs) that are capable of entering the cell cycle and producing newborn neurons. The mechanisms that control the timing and extent of adult neurogenesis are not well understood. Here, we show that QNPs of the adult SGZ express molecular-clock components and proliferate in a rhythmic fashion. The clock proteins PERIOD2 and BMAL1 are critical for proper control of neurogenesis. The absence of PERIOD2 abolishes the gating of cell-cycle entrance of QNPs, whereas genetic ablation of bmal1 results in constitutively high levels of proliferation and delayed cell-cycle exit. We use mathematical model simulations to show that these observations may arise from clock-driven expression of a cell-cycle inhibitor that targets the cyclin D/Cdk4-6 complex. Our findings may have broad implications for the circadian clock in timing cell-cycle events of other stem cell populations throughout the body.

  8. The Pentose Phosphate Pathway Regulates the Circadian Clock.

    PubMed

    Rey, Guillaume; Valekunja, Utham K; Feeney, Kevin A; Wulund, Lisa; Milev, Nikolay B; Stangherlin, Alessandra; Ansel-Bollepalli, Laura; Velagapudi, Vidya; O'Neill, John S; Reddy, Akhilesh B

    2016-09-13

    The circadian clock is a ubiquitous timekeeping system that organizes the behavior and physiology of organisms over the day and night. Current models rely on transcriptional networks that coordinate circadian gene expression of thousands of transcripts. However, recent studies have uncovered phylogenetically conserved redox rhythms that can occur independently of transcriptional cycles. Here we identify the pentose phosphate pathway (PPP), a critical source of the redox cofactor NADPH, as an important regulator of redox and transcriptional oscillations. Our results show that genetic and pharmacological inhibition of the PPP prolongs the period of circadian rhythms in human cells, mouse tissues, and fruit flies. These metabolic manipulations also cause a remodeling of circadian gene expression programs that involves the circadian transcription factors BMAL1 and CLOCK, and the redox-sensitive transcription factor NRF2. Thus, the PPP regulates circadian rhythms via NADPH metabolism, suggesting a pivotal role for NADPH availability in circadian timekeeping.

  9. Early doors (Edo) mutant mouse reveals the importance of period 2 (PER2) PAS domain structure for circadian pacemaking

    PubMed Central

    Militi, Stefania; Maywood, Elizabeth S.; Sandate, Colby R.; Chesham, Johanna E.; Parsons, Michael J.; Vibert, Jennifer L.; Joynson, Greg M.; Partch, Carrie L.; Hastings, Michael H.; Nolan, Patrick M.

    2016-01-01

    The suprachiasmatic nucleus (SCN) defines 24 h of time via a transcriptional/posttranslational feedback loop in which transactivation of Per (period) and Cry (cryptochrome) genes by BMAL1–CLOCK complexes is suppressed by PER–CRY complexes. The molecular/structural basis of how circadian protein complexes function is poorly understood. We describe a novel N-ethyl-N-nitrosourea (ENU)-induced mutation, early doors (Edo), in the PER-ARNT-SIM (PAS) domain dimerization region of period 2 (PER2) (I324N) that accelerates the circadian clock of Per2Edo/Edo mice by 1.5 h. Structural and biophysical analyses revealed that Edo alters the packing of the highly conserved interdomain linker of the PER2 PAS core such that, although PER2Edo complexes with clock proteins, its vulnerability to degradation mediated by casein kinase 1ε (CSNK1E) is increased. The functional relevance of this mutation is revealed by the ultrashort (<19 h) but robust circadian rhythms in Per2Edo/Edo; Csnk1eTau/Tau mice and the SCN. These periods are unprecedented in mice. Thus, Per2Edo reveals a direct causal link between the molecular structure of the PER2 PAS core and the pace of SCN circadian timekeeping. PMID:26903623

  10. Oscillating perceptions: the ups and downs of the CLOCK protein in the mouse circadian system.

    PubMed

    Debruyne, Jason P

    2008-12-01

    A functional mouse CLOCK protein has long been thought to be essential for mammalian circadian clockwork function, based mainly on studies of mice bearing a dominant negative, antimorphic mutation in the Clock gene. However, new discoveries using recently developed Clock-null mutant mice have shaken up this view. In this review, I discuss how this recent work impacts and alters the previous view of the role of CLOCK in the mouse circadian clockwork.

  11. Disruption of the circadian timing systems: molecular mechanisms in mood disorders.

    PubMed

    Mendlewicz, Julien

    2009-01-01

    Depression is one of the leading causes of morbidity worldwide and represents a huge burden to society. As with many other psychiatric disorders, a genetic basis for depression has been identified. Evidence for the role of circadian genes in depression is particularly compelling. Circadian gene mutations are also associated with circadian rhythm disorders such as familial advanced sleep phase syndrome, delayed sleep phase syndrome, and non-24-hour sleep-wake syndrome. Such disorders, plus the other manifestations of a disrupted circadian system such as hormone dysregulation, are often observed among those with depression. This suggests a shared aetiology between circadian disruption and depression, although the exact mechanisms underlying the association are unclear. This paper reviews the molecular mechanisms involved in depression, with an emphasis on circadian genes. Twin studies in depression have reported probandwise concordance rates of 40% and 70% using narrow and broad diagnostic criteria, respectively, and heritability of over 85% for bipolar disorder. In association studies, increased susceptibility to depression has been noted in those with polymorphisms in the following: D-amino-acid-oxidase activator/G30 gene complex, glucocorticoid receptor gene, serotonin transporter gene, tryptophan hydroxylase 2 gene, dopamine transporter gene and G protein-coupled receptor 50 gene. Polymorphisms in these genes have also been linked to a better or worse response to antidepressant therapy, an increased likelihood of responding poorly to adversity and increased suicide ideation. Polymorphisms in the CLOCK, BMAL1, Per3 and TIMELESS genes have been associated with susceptibility to mood disorder, and single nucleotide polymorphisms and haplotypes in several circadian genes have been observed among those displaying certain circadian phenotypes, including worse mood in the evening, insomnia in mania and early, middle or late insomnia in depression. Manipulation of the

  12. Disruption of the circadian timing systems: molecular mechanisms in mood disorders.

    PubMed

    Mendlewicz, Julien

    2009-01-01

    Depression is one of the leading causes of morbidity worldwide and represents a huge burden to society. As with many other psychiatric disorders, a genetic basis for depression has been identified. Evidence for the role of circadian genes in depression is particularly compelling. Circadian gene mutations are also associated with circadian rhythm disorders such as familial advanced sleep phase syndrome, delayed sleep phase syndrome, and non-24-hour sleep-wake syndrome. Such disorders, plus the other manifestations of a disrupted circadian system such as hormone dysregulation, are often observed among those with depression. This suggests a shared aetiology between circadian disruption and depression, although the exact mechanisms underlying the association are unclear. This paper reviews the molecular mechanisms involved in depression, with an emphasis on circadian genes. Twin studies in depression have reported probandwise concordance rates of 40% and 70% using narrow and broad diagnostic criteria, respectively, and heritability of over 85% for bipolar disorder. In association studies, increased susceptibility to depression has been noted in those with polymorphisms in the following: D-amino-acid-oxidase activator/G30 gene complex, glucocorticoid receptor gene, serotonin transporter gene, tryptophan hydroxylase 2 gene, dopamine transporter gene and G protein-coupled receptor 50 gene. Polymorphisms in these genes have also been linked to a better or worse response to antidepressant therapy, an increased likelihood of responding poorly to adversity and increased suicide ideation. Polymorphisms in the CLOCK, BMAL1, Per3 and TIMELESS genes have been associated with susceptibility to mood disorder, and single nucleotide polymorphisms and haplotypes in several circadian genes have been observed among those displaying certain circadian phenotypes, including worse mood in the evening, insomnia in mania and early, middle or late insomnia in depression. Manipulation of the

  13. Circadian and feeding rhythms differentially affect rhythmic mRNA transcription and translation in mouse liver

    PubMed Central

    Atger, Florian; Gobet, Cédric; Marquis, Julien; Martin, Eva; Wang, Jingkui; Weger, Benjamin; Lefebvre, Grégory; Descombes, Patrick; Naef, Felix; Gachon, Frédéric

    2015-01-01

    Diurnal oscillations of gene expression are a hallmark of rhythmic physiology across most living organisms. Such oscillations are controlled by the interplay between the circadian clock and feeding rhythms. Although rhythmic mRNA accumulation has been extensively studied, comparatively less is known about their transcription and translation. Here, we quantified simultaneously temporal transcription, accumulation, and translation of mouse liver mRNAs under physiological light–dark conditions and ad libitum or night-restricted feeding in WT and brain and muscle Arnt-like 1 (Bmal1)-deficient animals. We found that rhythmic transcription predominantly drives rhythmic mRNA accumulation and translation for a majority of genes. Comparison of wild-type and Bmal1 KO mice shows that circadian clock and feeding rhythms have broad impact on rhythmic gene expression, Bmal1 deletion affecting surprisingly both transcriptional and posttranscriptional levels. Translation efficiency is differentially regulated during the diurnal cycle for genes with 5′-Terminal Oligo Pyrimidine tract (5′-TOP) sequences and for genes involved in mitochondrial activity, many harboring a Translation Initiator of Short 5′-UTR (TISU) motif. The increased translation efficiency of 5′-TOP and TISU genes is mainly driven by feeding rhythms but Bmal1 deletion also affects amplitude and phase of translation, including TISU genes. Together this study emphasizes the complex interconnections between circadian and feeding rhythms at several steps ultimately determining rhythmic gene expression and translation. PMID:26554015

  14. Altered Stra13 and Dec2 circadian gene expression in hypoxic cells

    SciTech Connect

    Guillaumond, Fabienne; Lacoche, Samuel; Dulong, Sandrine; Grechez-Cassiau, Aline; Filipski, Elisabeth; Li, Xiao-Mei; Levi, Francis; Berra, Edurne; Delaunay, Franck; Teboul, Michele

    2008-05-16

    The circadian system regulates rhythmically most of the mammalian physiology in synchrony with the environmental light/dark cycle. Alteration of circadian clock gene expression has been associated with tumour progression but the molecular links between the two mechanisms remain poorly defined. Here we show that Stra13 and Dec2, two circadian transcriptional regulators which play a crucial role in cell proliferation and apoptosis are overexpressed and no longer rhythmic in serum shocked fibroblasts treated with CoCl{sub 2,} a substitute of hypoxia. This effect is associated with a loss of circadian expression of the clock genes Rev-erb{alpha} and Bmal1, and the clock-controlled gene Dbp. Consistently, cotransfection assays demonstrate that STRA13 and DEC2 both antagonize CLOCK:BMAL1 dependent transactivation of the Rev-erb{alpha} and Dbp promoters. Using a transplantable osteosarcoma tumour model, we show that hypoxia is associated with altered circadian expression of Stra13, Dec2, Rev-erb{alpha}, Bmal1 and Dbp in vivo. These observations collectively support the notion that overexpression of Stra13 and Dec2 links hypoxia signalling to altered circadian clock gene expression.

  15. CUL1 regulates TOC1 protein stability in the Arabidopsis circadian clock

    PubMed Central

    Harmon, Frank; Imaizumi, Takato; Gray, William M.

    2010-01-01

    Summary The circadian clock is the endogenous timer that coordinates physiological processes with daily and seasonal environmental changes. In Arabidopsis thaliana, establishment of the circadian period relies on targeted degradation of TIMING OF CAB EXPRESSION 1 (TOC1) by the 26S proteasome. ZEITLUPE (ZTL) is the F-box protein that associates with the SCF (Skp/Cullin/F-box) E3 ubiquitin ligase that is responsible for marking TOC1 for turnover. CULLIN1 (CUL1) is a core component of SCF complexes and is involved in multiple signaling pathways. To assess the contribution of CUL1-containing SCF complexes to signaling within the plant oscillator, circadian rhythms were examined in the recessive, temperature-sensitive CUL1 allele axr6-3. The activity of CUL1 in this mutant declines progressively with increasing ambient temperature, resulting in more severe defects in CUL1-dependent activities at elevated temperature. Examination of circadian rhythms in axr6-3 revealed circadian phenotypes comparable to those observed in ztl null mutants; namely, lengthened circadian period, altered expression of core oscillator genes, and limited degradation of TOC1. In addition, treatment of seedlings with exogenous auxin did not alter TOC1 stability. These results demonstrate that CUL1 is required for TOC1 degradation and further suggest that this protein is the functional cullin for the SCFZTL complex. PMID:18433436

  16. 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

  17. Toward a detailed computational model for the mammalian circadian clock

    NASA Astrophysics Data System (ADS)

    Leloup, Jean-Christophe; Goldbeter, Albert

    2003-06-01

    We present a computational model for the mammalian circadian clock based on the intertwined positive and negative regulatory loops involving the Per, Cry, Bmal1, Clock, and Rev-Erb genes. In agreement with experimental observations, the model can give rise to sustained circadian oscillations in continuous darkness, characterized by an antiphase relationship between Per/Cry/Rev-Erb and Bmal1 mRNAs. Sustained oscillations correspond to the rhythms autonomously generated by suprachiasmatic nuclei. For other parameter values, damped oscillations can also be obtained in the model. These oscillations, which transform into sustained oscillations when coupled to a periodic signal, correspond to rhythms produced by peripheral tissues. When incorporating the light-induced expression of the Per gene, the model accounts for entrainment of the oscillations by light-dark cycles. Simulations show that the phase of the oscillations can then vary by several hours with relatively minor changes in parameter values. Such a lability of the phase could account for physiological disorders related to circadian rhythms in humans, such as advanced or delayed sleep phase syndrome, whereas the lack of entrainment by light-dark cycles can be related to the non-24h sleep-wake syndrome. The model uncovers the possible existence of multiple sources of oscillatory behavior. Thus, in conditions where the indirect negative autoregulation of Per and Cry expression is inoperative, the model indicates the possibility that sustained oscillations might still arise from the negative autoregulation of Bmal1 expression.

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

    PubMed

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

    2016-08-01

    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

  19. Small Heterodimer Partner (NR0B2) Coordinates Nutrient Signaling and the Circadian Clock in Mice.

    PubMed

    Wu, Nan; Kim, Kang Ho; Zhou, Ying; Lee, Jae Man; Kettner, Nicole M; Mamrosh, Jennifer L; Choi, Sungwoo; Fu, Loning; Moore, David D

    2016-09-01

    Circadian rhythm regulates multiple metabolic processes and in turn is readily entrained by feeding-fasting cycles. However, the molecular mechanisms by which the peripheral clock senses nutrition availability remain largely unknown. Bile acids are under circadian control and also increase postprandially, serving as regulators of the fed state in the liver. Here, we show that nuclear receptor Small Heterodimer Partner (SHP), a regulator of bile acid metabolism, impacts the endogenous peripheral clock by directly regulating Bmal1. Bmal1-dependent gene expression is altered in Shp knockout mice, and liver clock adaptation is delayed in Shp knockout mice upon restricted feeding. These results identify SHP as a potential mediator connecting nutrient signaling with the circadian clock. PMID:27427832

  20. Glial fibrillary acidic protein (GFAP) shows circadian oscillations in crayfish Procambarus clarkii putative pacemakers.

    PubMed

    Rodríguez-Muñoz, María de la Paz; Escamilla-Chimal, Elsa G

    2015-01-01

    Although several studies of glia have examined glial fibrillary acid protein (GFAP) and its relationship to the circadian rhythms of different organisms, they have not explored the daily GFAP oscillations in the putative pacemakers of the crayfish Procambarus clarkii or in other crustaceans. In this study we investigated the daily variations in GFAP concentrations in the eyestalk and brain, which are considered to be putative pacemakers in adult P. clarkii. In both structures, the glial GFAP was quantified using the indirect enzyme-linked immunosorbent assay (ELISA), and double labeling immunofluorescence was used to detect it and its co-localization with protein Period (PER), an important component of the circadian clock, in various regions of both structures. The ELISA results were analyzed using Cosinor and one-way ANOVA with Bonferroni and Scheffé's post hoc tests. The results of this analysis showed that the GFAP levels present circadian oscillations in both structures. Moreover, GFAP was localized in different structures of the eyestalk and brain; however, co-localization with PER occurred only in the lamina ganglionaris, specifically in the cartridges of the eyestalk and in some of the cluster 9 brain cells. These results suggest that as in other invertebrates and vertebrates, glial cells could be involved in the circadian system of P. clarkii; however, thus far we cannot know whether the glial cells are only effectors, participate in afferent pathways, or are part of the circadian clock.

  1. Protein sequestration versus Hill-type repression in circadian clock models.

    PubMed

    Kim, Jae Kyoung

    2016-08-01

    Circadian (∼24 h) clocks are self-sustained endogenous oscillators with which organisms keep track of daily and seasonal time. Circadian clocks frequently rely on interlocked transcriptional-translational feedback loops to generate rhythms that are robust against intrinsic and extrinsic perturbations. To investigate the dynamics and mechanisms of the intracellular feedback loops in circadian clocks, a number of mathematical models have been developed. The majority of the models use Hill functions to describe transcriptional repression in a way that is similar to the Goodwin model. Recently, a new class of models with protein sequestration-based repression has been introduced. Here, the author discusses how this new class of models differs dramatically from those based on Hill-type repression in several fundamental aspects: conditions for rhythm generation, robust network designs and the periods of coupled oscillators. Consistently, these fundamental properties of circadian clocks also differ among Neurospora, Drosophila, and mammals depending on their key transcriptional repression mechanisms (Hill-type repression or protein sequestration). Based on both theoretical and experimental studies, this review highlights the importance of careful modelling of transcriptional repression mechanisms in molecular circadian clocks. PMID:27444022

  2. Robust circadian clocks from coupled protein-modification and transcription-translation cycles.

    PubMed

    Zwicker, David; Lubensky, David K; ten Wolde, Pieter Rein

    2010-12-28

    The cyanobacterium Synechococcus elongatus uses both a protein phosphorylation cycle and a transcription-translation cycle to generate circadian rhythms that are highly robust against biochemical noise. We use stochastic simulations to analyze how these cycles interact to generate stable rhythms in growing, dividing cells. We find that a protein phosphorylation cycle by itself is robust when protein turnover is low. For high decay or dilution rates (and compensating synthesis rates), however, the phosphorylation-based oscillator loses its integrity. Circadian rhythms thus cannot be generated with a phosphorylation cycle alone when the growth rate, and consequently the rate of protein dilution, is high enough; in practice, a purely posttranslational clock ceases to function well when the cell doubling time drops below the 24-h clock period. At higher growth rates, a transcription-translation cycle becomes essential for generating robust circadian rhythms. Interestingly, although a transcription-translation cycle is necessary to sustain a phosphorylation cycle at high growth rates, a phosphorylation cycle can dramatically enhance the robustness of a transcription-translation cycle at lower protein decay or dilution rates. In fact, the full oscillator built from these two tightly intertwined cycles far outperforms not just each of its two components individually, but also a hypothetical system in which the two parts are coupled as in textbook models of coupled phase oscillators. Our analysis thus predicts that both cycles are required to generate robust circadian rhythms over the full range of growth conditions.

  3. 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.

  4. The Transcription Factor Runx2 Is under Circadian Control in the Suprachiasmatic Nucleus and Functions in the Control of Rhythmic Behavior

    PubMed Central

    Reale, Meghan E.; Webb, Ian C.; Wang, Xu; Baltazar, Ricardo M.; Coolen, Lique M.; Lehman, Michael N.

    2013-01-01

    Runx2, a member of the family of runt-related transcription factors, is rhythmically expressed in bone and may be involved in circadian rhythms in bone homeostasis and osteogenesis. Runx2 is also expressed in the brain, but its function is unknown. We tested the hypothesis that in the brain, Runx2 may interact with clock-controlled genes to regulate circadian rhythms in behavior. First, we demonstrated diurnal and circadian rhythms in the expression of Runx2 in the mouse brain. Expression of Runx2 mRNA and protein mirrored that of the core clock genes, Period1 and Period2, in the suprachiasmatic nucleus (SCN), the paraventricular nucleus and the olfactory bulb. The rhythm of Runx2 expression was eliminated in the SCN of Bmal1−/− mice. Moreover, by crossbreeding mPer2Luc mice with Runx2+/− mice and recording bioluminescence rhythms, a significant lengthening of the period of rhythms was detected in cultured SCN of Runx2−/− animals compared to either Runx2+/− or Runx2+/+ mice. Behavioral analyses of Runx2 mutant mice revealed that Runx2+/− animals displayed a significantly lengthened free-running period of running wheel activity compared to Runx2+/+ littermates. Taken together, these findings provide evidence for clock gene-mediated rhythmic expression of Runx2, and its functional role in regulating circadian period at the level of the SCN and behavior. PMID:23372705

  5. The epigenetic language of circadian clocks.

    PubMed

    Sahar, Saurabh; Sassone-Corsi, Paolo

    2013-01-01

    Epigenetic control, which includes DNA methylation and histone modifications, leads to chromatin remodeling and regulated gene expression. Remodeling of chromatin constitutes a critical interface of transducing signals, such as light or nutrient availability, and how these are interpreted by the cell to generate permissive or silenced states for transcription. CLOCK-BMAL1-mediated activation of clock-controlled genes (CCGs) is coupled to circadian changes in histone modification at their promoters. Several chromatin modifiers, such as the deacetylases SIRT1 and HDAC3 or methyltransferase MLL1, have been shown to be recruited to the promoters of the CCGs in a circadian manner. Interestingly, the central element of the core clock machinery, the transcription factor CLOCK, also possesses histone acetyltransferase activity. Rhythmic expression of the CCGs is abolished in the absence of these chromatin modifiers. Here we will discuss the evidence demonstrating that chromatin remodeling is at the crossroads of circadian rhythms and regulation of metabolism and cellular proliferation. PMID:23604474

  6. Protein kinase A and casein kinases mediate sequential phosphorylation events in the circadian negative feedback loop.

    PubMed

    Huang, Guocun; Chen, She; Li, Shaojie; Cha, Joonseok; Long, Chengzu; Li, Lily; He, Qiyang; Liu, Yi

    2007-12-15

    Regulation of circadian clock components by phosphorylation plays essential roles in clock functions and is conserved from fungi to mammals. In the Neurospora circadian negative feedback loop, FREQUENCY (FRQ) protein inhibits WHITE COLLAR (WC) complex activity by recruiting the casein kinases CKI and CKII to phosphorylate the WC proteins, resulting in the repression of frq transcription. On the other hand, CKI and CKII progressively phosphorylate FRQ to promote FRQ degradation, a process that is a major determinant of circadian period length. Here, by using whole-cell isotope labeling and quantitative mass spectrometry methods, we show that the WC-1 phosphorylation events critical for the negative feedback process occur sequentially-first by a priming kinase, then by the FRQ-recruited casein kinases. We further show that the cyclic AMP-dependent protein kinase A (PKA) is essential for clock function and inhibits WC activity by serving as a priming kinase for the casein kinases. In addition, PKA also regulates FRQ phosphorylation, but unlike CKI and CKII, PKA stabilizes FRQ, similar to the stabilization of human PERIOD2 (hPER2) due to the phosphorylation at the familial advanced sleep phase syndrome (FASPS) site. Thus, PKA is a key clock component that regulates several critical processes in the circadian negative feedback loop. PMID:18079175

  7. Circadian Clock-Specific Roles for the Light Response Protein WHITE COLLAR-2

    PubMed Central

    Collett, Michael A.; Dunlap, Jay C.; Loros, Jennifer J.

    2001-01-01

    To understand the role of white collar-2 in the Neurospora circadian clock, we examined alleles of wc-2 thought to encode partially functional proteins. We found that wc-2 allele ER24 contained a conservative mutation in the zinc finger. This mutation results in reduced levels of circadian rhythm-critical clock gene products, frq mRNA and FRQ protein, and in a lengthened period of the circadian clock. In addition, this mutation altered a second canonical property of the clock, temperature compensation: as temperature increased, period length decreased substantially. This temperature compensation defect correlated with a temperature-dependent increase in overall FRQ protein levels, with the relative increase being greater in wc-2 (ER24) than in wild type, while overall frq mRNA levels were largely unaltered by temperature. We suggest that this temperature-dependent increase in FRQ levels partially rescues the lowered levels of FRQ resulting from the wc-2 (ER24) defect, yielding a shorter period at higher temperatures. Thus, normal activity of the essential clock component WC-2, a positive regulator of frq, is critical for establishing period length and temperature compensation in this circadian system. PMID:11283242

  8. Survival of adult generated hippocampal neurons is altered in circadian arrhythmic mice.

    PubMed

    Rakai, Brooke D; Chrusch, Michael J; Spanswick, Simon C; Dyck, Richard H; Antle, Michael C

    2014-01-01

    The subgranular zone of the hippocampal formation gives rise to new neurons that populate the dentate gyrus throughout life. Cells in the hippocampus exhibit rhythmic clock gene expression and the circadian clock is known to regulate the cycle of cell division in other areas of the body. These facts suggest that the circadian clock may regulate adult neurogenesis in the hippocampus as well. In the present study, neurogenesis in the hippocampal subgranular zone was examined in arrhythmic Bmal1 knockout (-KO) mice and their rhythmic heterozygous and wildtype littermates. Proliferation and survival of newly generated subgranular zone cells were examined using bromodeoxyuridine labelling, while pyknosis (a measure of cell death) and hippocampal volume were examined in cresyl violet stained sections. There was no significant difference in cellular proliferation between any of the groups, yet survival of proliferating cells, 6 weeks after the bromodeoxyuridine injection, was significantly greater in the BMAL1-KO animals. The number of pyknotic cells was significantly decreased in Bmal1-KO animals, yet hippocampal volume remained the same across genotypes. These findings suggest that while a functional circadian clock is not necessary for normal proliferation of neuronal precursor cells, the normal pruning of newly generated neurons in the hippocampus may require a functional circadian clock. PMID:24941219

  9. 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

  10. Versatile function of the circadian protein CIPC as a regulator of Erk activation.

    PubMed

    Matsunaga, Ryota; Nishino, Tasuku; Yokoyama, Atsushi; Nakashima, Akio; Kikkawa, Ushio; Konishi, Hiroaki

    2016-01-15

    The CLOCK-interacting protein, Circadian (CIPC), has been identified as an additional negative-feedback regulator of the circadian clock. However, recent study on CIPC knockout mice has shown that CIPC is not critically required for basic circadian clock function, suggesting other unknown biological roles for CIPC. In this study, we focused on the cell cycle dependent nuclear-cytoplasmic shuttling function of CIPC and on identifying its binding proteins. Lys186 and 187 were identified as the essential amino acid residues within the nuclear localization signal (NLS) of CIPC. We identified CIPC-binding proteins such as the multifunctional enzyme CAD protein (carbamoyl-phosphate synthetase 2, aspartate transcarbamoylase, and dihydroorotase), which is a key enzyme for de novo pyrimidine synthesis. Compared to control cells, HEK293 cells overexpressing wild-type CIPC showed suppressed cell proliferation and retardation of cell cycle. We also found that PMA-induced Erk activation was inhibited with expression of wild-type CIPC. In contrast, the NLS mutant of CIPC, which reduced the ability of CIPC to translocate into the nucleus, did not exhibit these biological effects. Since CAD and Erk have significant roles in cell proliferation and cell cycle, CIPC may work as a cell cycle regulator by interacting with these binding proteins. PMID:26657846

  11. Activity and circadian rhythm influence synaptic Shank3 protein levels in mice.

    PubMed

    Sarowar, Tasnuva; Chhabra, Resham; Vilella, Antonietta; Boeckers, Tobias M; Zoli, Michele; Grabrucker, Andreas M

    2016-09-01

    Various recent studies revealed that the proteins of the Shank family act as major scaffold organizing elements in the post-synaptic density of excitatory synapses and that their expression level is able to influence synapse formation, maturation and ultimately brain plasticity. An imbalance in Shank3 protein levels has been associated with a variety of neuropsychological and neurodegenerative disorders including autism spectrum disorders and Phelan-McDermid syndrome. Given that sleep disorders and low melatonin levels are frequently observed in autism spectrum disorders, and that circadian rhythms may be able to modulate Shank3 signaling and thereby synaptic function, here, we performed in vivo studies on CBA mice using protein biochemistry to investigate the synaptic expression levels of Shank3α during the day in different brain regions. Our results show that synaptic Shank3 protein concentrations exhibit minor oscillations during the day in hippocampal and striatal brain regions that correlate with changes in serum melatonin levels. Furthermore, as circadian rhythms are tightly connected to activity levels in mice, we increased physical activity using running wheels. The expression of Shank3α increases rapidly by induced activity in thalamus and cortex, but decreases in striatum, superimposing the circadian rhythms of different brain regions. We conclude that synaptic Shank3 proteins build highly dynamic platforms that are modulated by the light:dark cycles but even more so driven by activity. Using wild-type CBA mice, we show that Shank3 is a highly dynamic and activity-regulated protein at synapses. In the hippocampus, changes in synaptic Shank3 levels are influenced by circadian rhythm/melatonin concentration, while running activity increases and decreases levels of Shank3 in the cortex and striatum respectively. PMID:27329942

  12. A Bioluminescence Resonance Energy Transfer (BRET) System: Application to Interacting Circadian Clock Proteins

    NASA Astrophysics Data System (ADS)

    Xu, Yao; Piston, David W.; Hirschie Johnson, Carl

    1999-01-01

    We describe a method for assaying protein interactions that offers some attractive advantages over previous assays. This method, called bioluminescence resonance energy transfer (BRET), uses a bioluminescent luciferase that is genetically fused to one candidate protein, and a green fluorescent protein mutant fused to another protein of interest. Interactions between the two fusion proteins can bring the luciferase and green fluorescent protein close enough for resonance energy transfer to occur, thus changing the color of the bioluminescent emission. By using proteins encoded by circadian (daily) clock genes from cyanobacteria, we use the BRET technique to demonstrate that the clock protein KaiB interacts to form homodimers. BRET should be particularly useful for testing protein interactions within native cells, especially with integral membrane proteins or proteins targeted to specific organelles.

  13. A post-transcriptional mechanism contributes to circadian cycling of a per-beta-galactosidase fusion protein.

    PubMed Central

    Zwiebel, L J; Hardin, P E; Liu, X; Hall, J C; Rosbash, M

    1991-01-01

    The period gene (per) of Drosophila melanogaster affects circadian rhythms. Circadian fluctuations in per mRNA levels are thought to contribute to circadian fluctuations in per protein levels in the heads of adult flies. To address the mechanisms underlying these oscillatory phenomena, we have analyzed RNA and protein cycling from two per-beta-galactosidase fusion genes. These studies demonstrate that 5' noncoding sequences from per are sufficient to cause the fusion mRNA levels to cycle in a wild-type (rhythmic) background. Protein cycling requires additional sequences derived from the per coding region. The data suggest that there is a per-dependent posttranscriptional mechanism that is under circadian clock control required for per protein levels to fluctuate in a rhythmic fashion. Images PMID:1902573

  14. USP7 and TDP-43: Pleiotropic Regulation of Cryptochrome Protein Stability Paces the Oscillation of the Mammalian Circadian Clock

    PubMed Central

    Yoshitane, Hikari; Oyama, Masaaki; Kozuka-Hata, Hiroko; Lanjakornsiripan, Darin; Fukada, Yoshitaka

    2016-01-01

    Mammalian Cryptochromes, CRY1 and CRY2, function as principal regulators of a transcription-translation-based negative feedback loop underlying the mammalian circadian clockwork. An F-box protein, FBXL3, promotes ubiquitination and degradation of CRYs, while FBXL21, the closest paralog of FBXL3, ubiquitinates CRYs but leads to stabilization of CRYs. Fbxl3 knockout extremely lengthened the circadian period, and deletion of Fbxl21 gene in Fbxl3-deficient mice partially rescued the period-lengthening phenotype, suggesting a key role of CRY protein stability for maintenance of the circadian periodicity. Here, we employed a proteomics strategy to explore regulators for the protein stability of CRYs. We found that ubiquitin-specific protease 7 (USP7 also known as HAUSP) associates with CRY1 and CRY2 and stabilizes CRYs through deubiquitination. Treatment with USP7-specific inhibitor or Usp7 knockdown shortened the circadian period of the cellular rhythm. We identified another CRYs-interacting protein, TAR DNA binding protein 43 (TDP-43), an RNA-binding protein. TDP-43 stabilized CRY1 and CRY2, and its knockdown also shortened the circadian period in cultured cells. The present study identified USP7 and TDP-43 as the regulators of CRY1 and CRY2, underscoring the significance of the stability control process of CRY proteins for period determination in the mammalian circadian clockwork. PMID:27123980

  15. Circadian rhythm of C-reactive protein in patients with rheumatoid arthritis.

    PubMed

    Herold, M; Günther, R

    1987-01-01

    Ten men with classic rheumatoid arthritis were studied for 23 days in Badgastein, Austria, in August, 1980. One man (patient 07) showed a marked increase of disease activity after a few days. C-reactive protein (CRP) concentrations increased from 8.7 mg/dl on day 2 to 13.0 mg/dl on day 16. CRP values expressed as percent mean of a day showed a significant circadian rhythm with the acrophase at -30 degrees. For the same patient we also found significant circadian rhythms in grip strength and pearl stringing with acrophases in the evening and a circadian rhythm in walking time with the acrophase in the early morning. Seven of the ten men in the study had elevated CRP concentrations during the 3 weeks of observation. Population-mean cosinor results of CRP, grip strength, pearl stringing, and walking time revealed acrophases similar to the single cosinor results of patient 07. Our results suggest that inflammation in rheumatoid arthritis is a circadian rhythmic process with lowest disease activity in the evening.

  16. Setting the PAS, the role of circadian PAS domain proteins during environmental adaptation in plants

    PubMed Central

    Vogt, Julia H. M.; Schippers, Jos H. M.

    2015-01-01

    The per-ARNT-sim (PAS) domain represents an ancient protein module that can be found across all kingdoms of life. The domain functions as a sensing unit for a diverse array of signals, including molecular oxygen, small metabolites, and light. In plants, several PAS domain-containing proteins form an integral part of the circadian clock and regulate responses to environmental change. Moreover, these proteins function in pathways that control development and plant stress adaptation responses. Here, we discuss the role of PAS domain-containing proteins in anticipation, and adaptation to environmental changes in plants. PMID:26217364

  17. 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. PMID:24099911

  18. ELF3 Encodes a Circadian Clock–Regulated Nuclear Protein That Functions in an Arabidopsis PHYB Signal Transduction Pathway

    PubMed Central

    Liu, Xing Liang; Covington, Michael F.; Fankhauser, Christian; Chory, Joanne; Wagner, D. Ry

    2001-01-01

    Many aspects of plant development are regulated by photoreceptor function and the circadian clock. Loss-of-function mutations in the Arabidopsis EARLY FLOWERING 3 (ELF3) and PHYTOCHROME B (PHYB) genes cause early flowering and influence the activity of circadian clock–regulated processes. We demonstrate here that the relative abundance of the ELF3 protein, which is a novel nucleus-localized protein, displays circadian regulation that follows the pattern of circadian accumulation of ELF3 transcript. Furthermore, the ELF3 protein interacts with PHYB in the yeast two-hybrid assay and in vitro. Genetic analyses show that ELF3 requires PHYB function in early morphogenesis but not for the regulation of flowering time. This suggests that ELF3 is a component of a PHYB signaling complex that controls early events in plant development but that ELF3 and PHYB control flowering via independent signal transduction pathways. PMID:11402161

  19. Protracted cocaine withdrawal produces circadian rhythmic alterations of phosphorylated GSK-3β in reward-related brain areas in rats.

    PubMed

    Wei, Yi-ming; Li, Su-xia; Shi, Hai-shui; Ding, Zeng-bo; Luo, Yi-xiao; Xue, Yan-xue; Lu, Lin; Yu, Chang-xi

    2011-03-17

    Protracted cocaine withdrawal can extend for months and contribute to cocaine seeking and relapse. However, no previous studies have reported the manifestation of protracted withdrawal from chronic cocaine in rats. Glycogen synthase kinase 3β (GSK-3β) can phosphorylate PER2, CRY2, Rev-erbα, and BMAL1 in mammals. The circadian rhythmic expression of GSK-3β in reward-related brain areas is unclear. We examined rodent behaviors and circadian disturbances of GSK-3β expression during 30 days of protracted cocaine withdrawal. The behavioral tests included open field, elevated plus maze, weight gain, and sucrose preference tests performed 3, 10, and 30 days after stopping cocaine. At these three assessment points, we collected brain samples every 4h for 24h to examine the circadian rhythmic expression of GSK-3β. Decreased locomotor activity, weight loss, decreased sucrose consumption on day 3, and increased time spent in the open arms of the elevated plus maze on day 10 after cocaine administration were found. Blunted circadian rhythms of phosphorylated GFK-3β (pGSK-3β) persisted for at least 30 days in all examined brain areas, with the exception of 10 days in the suprachiasmatic nucleus (SCN) and nucleus accumbens (NAc). The expression of pGSK-3β decreased in the SCN and increased in the NAc and ventral tegmental area persisted for at least 30 days, whereas in the prefrontal cortex decreased during withdrawal for 10 days but then reversed to abnormally high levels with protracted withdrawal. These long-lasting changes disrupted circadian rhythms and produced abnormal levels of phosphorylated GSK-3β protein in reward-related brain circuits, which may play a role in protracted cocaine withdrawal and contribute to relapse.

  20. Circadian rhythm of autophagy proteins in hippocampus is blunted by sleep fragmentation.

    PubMed

    He, Yi; Cornelissen-Guillaume, Germaine G; He, Junyun; Kastin, Abba J; Harrison, Laura M; Pan, Weihong

    2016-01-01

    Autophagy is essential for normal cellular survival and activity. Circadian rhythms of autophagy have been studied in several peripheral organs but not yet reported in the brain. Here, we measured the circadian rhythm of autophagy-related proteins in mouse hippocampus and tested the effect of sleep fragmentation (SF). Expressions of the autophagy-related proteins microtubule-associated protein 1 light chain 3 (LC3) and beclin were determined by western blotting and immunohistochemistry. Both the hippocampal LC3 signal and the ratio of its lipid-conjugated form LC3-II to its cytosolic form LC3-I showed a 24 h rhythm. The peak was seen at ZT6 (1 pm) and the nadir at ZT16 (1 am). The LC3 immunoreactivity in hippocampal CA1 pyramidal neurons also distributed differently, with more diffuse cytoplasmic appearance at ZT16. Chronic SF had a mild effect to disrupt the 24 h rhythm of LC3 and beclin expression. Interestingly, a greater effect of SF was seen after 24 h of recovery sleep when LC3-II expression was attenuated at both the peak and trough of circadian activities. Overall, the results show for the first time that the hippocampus has a distinct rhythm of autophagy that can be altered by SF.

  1. Endotoxin Disrupts Circadian Rhythms in Macrophages via Reactive Oxygen Species

    PubMed Central

    Wang, Yusi; Pati, Paramita; Xu, Yiming; Chen, Feng; Stepp, David W.; Huo, Yuqing; Rudic, R. Daniel; Fulton, David J. R.

    2016-01-01

    The circadian clock is a transcriptional network that functions to regulate the expression of genes important in the anticipation of changes in cellular and organ function. Recent studies have revealed that the recognition of pathogens and subsequent initiation of inflammatory responses are strongly regulated by a macrophage-intrinsic circadian clock. We hypothesized that the circadian pattern of gene expression might be influenced by inflammatory stimuli and that loss of circadian function in immune cells can promote pro-inflammatory behavior. To investigate circadian rhythms in inflammatory cells, peritoneal macrophages were isolated from mPer2luciferase transgenic mice and circadian oscillations were studied in response to stimuli. Using Cosinor analysis, we found that LPS significantly altered the circadian period in peritoneal macrophages from mPer2luciferase mice while qPCR data suggested that the pattern of expression of the core circadian gene (Bmal1) was disrupted. Inhibition of TLR4 offered protection from the LPS-induced impairment in rhythm, suggesting a role for toll-like receptor signaling. To explore the mechanisms involved, we inhibited LPS-stimulated NO and superoxide. Inhibition of NO synthesis with L-NAME had no effect on circadian rhythms. In contrast, inhibition of superoxide with Tempol or PEG-SOD ameliorated the LPS-induced changes in circadian periodicity. In gain of function experiments, we found that overexpression of NOX5, a source of ROS, could significantly disrupt circadian function in a circadian reporter cell line (U2OS) whereas iNOS overexpression, a source of NO, was ineffective. To assess whether alteration of circadian rhythms influences macrophage function, peritoneal macrophages were isolated from Bmal1-KO and Per-TKO mice. Compared to WT macrophages, macrophages from circadian knockout mice exhibited altered balance between NO and ROS release, increased uptake of oxLDL and increased adhesion and migration. These results

  2. Acute light exposure suppresses circadian rhythms in clock gene expression.

    PubMed

    Grone, Brian P; Chang, Doris; Bourgin, Patrice; Cao, Vinh; Fernald, Russell D; Heller, H Craig; Ruby, Norman F

    2011-02-01

    Light can induce arrhythmia in circadian systems by several weeks of constant light or by a brief light stimulus given at the transition point of the phase response curve. In the present study, a novel light treatment consisting of phase advance and phase delay photic stimuli given on 2 successive nights was used to induce circadian arrhythmia in the Siberian hamster ( Phodopus sungorus). We therefore investigated whether loss of rhythms in behavior was due to arrhythmia within the suprachiasmatic nucleus (SCN). SCN tissue samples were obtained at 6 time points across 24 h in constant darkness from entrained and arrhythmic hamsters, and per1, per2 , bmal1, and cry1 mRNA were measured by quantitative RT-PCR. The light treatment eliminated circadian expression of clock genes within the SCN, and the overall expression of these genes was reduced by 18% to 40% of entrained values. Arrhythmia in per1, per2, and bmal1 was due to reductions in the amplitudes of their oscillations. We suggest that these data are compatible with an amplitude suppression model in which light induces singularity in the molecular circadian pacemaker.

  3. Tissue-intrinsic dysfunction of circadian clock confers transplant arteriosclerosis.

    PubMed

    Cheng, Bo; Anea, Ciprian B; Yao, Lin; Chen, Feng; Patel, Vijay; Merloiu, Ana; Pati, Paramita; Caldwell, R William; Fulton, David J; Rudic, R Daniel

    2011-10-11

    The suprachiasmatic nucleus of the brain is the circadian center, relaying rhythmic environmental and behavioral information to peripheral tissues to control circadian physiology. As such, central clock dysfunction can alter systemic homeostasis to consequently impair peripheral physiology in a manner that is secondary to circadian malfunction. To determine the impact of circadian clock function in organ transplantation and dissect the influence of intrinsic tissue clocks versus extrinsic clocks, we implemented a blood vessel grafting approach to surgically assemble a chimeric mouse that was part wild-type (WT) and part circadian clock mutant. Arterial isografts from donor WT mice that had been anastamosed to common carotid arteries of recipient WT mice (WT:WT) exhibited no pathology in this syngeneic transplant strategy. Similarly, when WT grafts were anastamosed to mice with disrupted circadian clocks, the structural features of the WT grafts immersed in the milieu of circadian malfunction were normal and absent of lesions, comparable to WT:WT grafts. In contrast, aortic grafts from Bmal1 knockout (KO) or Period-2,3 double-KO mice transplanted into littermate control WT mice developed robust arteriosclerotic disease. These lesions observed in donor grafts of Bmal1-KO were associated with up-regulation in T-cell receptors, macrophages, and infiltrating cells in the vascular grafts, but were independent of hemodynamics and B and T cell-mediated immunity. These data demonstrate the significance of intrinsic tissue clocks as an autonomous influence in experimental models of arteriosclerotic disease, which may have implications with regard to the influence of circadian clock function in organ transplantation.

  4. Effect of peripheral circadian dysfunction on metabolic disease in response to a diabetogenic diet.

    PubMed

    Pijut, Sonja S; Corbett, Danielle E; Wang, Yuhuan; Li, Jianing; Charnigo, Richard J; Graf, Gregory A

    2016-06-01

    BMAL1 is a core component of the transcription/translation machinery that regulates central and peripheral circadian rhythms that coordinate behavior and metabolism, respectively. Our objective was to determine the impact of BMAL1 in adipose alone or in combination with liver on metabolic phenotypes. Control, adipose-Bmal1 knockout (ABKO), and liver- and adipose-Bmal1 knockout (LABKO) female mice were placed in TSE System metabolic chambers for metabolic phenotyping. A second cohort of male mice was fed a control or diabetogenic diet, and body weight and composition, glucose tolerance, insulin sensitivity, and serum and hepatic lipids were measured. Both female ABKO and LABKO mice exhibited increased food consumption compared with control mice. ABKO mice also exhibited increased overall activity predominantly during the light phase compared with both control and LABKO mice and were protected from increased weight gain. When the male cohort was challenged with a diabetogenic diet, LABKO mice had increased body weight due to increased fat mass compared with control and ABKO mice. However, these mice did not present further impairments in glycemic control, adipose inflammation, or liver injury. LABKO mice had increased hepatic cholesterol and elevated expression of cholesterol synthesis and uptake genes. Our data indicate that deletion of this allele in adipose or in combination with liver alters feeding behavior and locomotor activity. However, obesity is exacerbated only with the combination of liver and adipose deletion. PMID:27048996

  5. Gpr176 is a Gz-linked orphan G-protein-coupled receptor that sets the pace of circadian behaviour

    PubMed Central

    Doi, Masao; Murai, Iori; Kunisue, Sumihiro; Setsu, Genzui; Uchio, Naohiro; Tanaka, Rina; Kobayashi, Sakurako; Shimatani, Hiroyuki; Hayashi, Hida; Chao, Hsu-Wen; Nakagawa, Yuuki; Takahashi, Yukari; Hotta, Yunhong; Yasunaga, Jun-ichirou; Matsuoka, Masao; Hastings, Michael H.; Kiyonari, Hiroshi; Okamura, Hitoshi

    2016-01-01

    G-protein-coupled receptors (GPCRs) participate in a broad range of physiological functions. A priority for fundamental and clinical research, therefore, is to decipher the function of over 140 remaining orphan GPCRs. The suprachiasmatic nucleus (SCN), the brain's circadian pacemaker, governs daily rhythms in behaviour and physiology. Here we launch the SCN orphan GPCR project to (i) search for murine orphan GPCRs with enriched expression in the SCN, (ii) generate mutant animals deficient in candidate GPCRs, and (iii) analyse the impact on circadian rhythms. We thereby identify Gpr176 as an SCN-enriched orphan GPCR that sets the pace of circadian behaviour. Gpr176 is expressed in a circadian manner by SCN neurons, and molecular characterization reveals that it represses cAMP signalling in an agonist-independent manner. Gpr176 acts independently of, and in parallel to, the Vipr2 GPCR, not through the canonical Gi, but via the unique G-protein subclass Gz. PMID:26882873

  6. Central circadian control of female reproductive function.

    PubMed

    Miller, Brooke H; Takahashi, Joseph S

    2013-01-01

    Over the past two decades, it has become clear just how much of our physiology is under the control of the suprachiasmatic nucleus (SCN) and the cell-intrinsic molecular clock that ticks with a periodicity of approximately 24 h. The SCN prepares our digestive system for meals, our adrenal axis for the stress of waking up in the morning, and the genes expressed in our muscles when we prepare to exercise. Long before molecular studies of genes such as Clock, Bmal1, and the Per homologs were possible, it was obvious that female reproductive function was under strict circadian control at every level of the hypothalamic-pituitary-gonadal axis, and in the establishment and successful maintenance of pregnancy. This review highlights our current understanding of the role that the SCN plays in regulating female reproductive physiology, with a special emphasis on the advances made possible through the use of circadian mutant mice.

  7. Central Circadian Control of Female Reproductive Function

    PubMed Central

    Miller, Brooke H.; Takahashi, Joseph S.

    2014-01-01

    Over the past two decades, it has become clear just how much of our physiology is under the control of the suprachiasmatic nucleus (SCN) and the cell-intrinsic molecular clock that ticks with a periodicity of approximately 24 h. The SCN prepares our digestive system for meals, our adrenal axis for the stress of waking up in the morning, and the genes expressed in our muscles when we prepare to exercise. Long before molecular studies of genes such as Clock, Bmal1, and the Per homologs were possible, it was obvious that female reproductive function was under strict circadian control at every level of the hypothalamic-pituitary-gonadal axis, and in the establishment and successful maintenance of pregnancy. This review highlights our current understanding of the role that the SCN plays in regulating female reproductive physiology, with a special emphasis on the advances made possible through the use of circadian mutant mice. PMID:24478756

  8. Circadian Rhythms in Dinoflagellates: What Is the Purpose of Synthesis and Destruction of Proteins?

    PubMed Central

    Hastings, J. Woodland

    2013-01-01

    There is a prominent circadian rhythm of bioluminescence in many species of light-emitting dinoflagellates. In Lingulodinium polyedrum a daily synthesis and destruction of proteins is used to regulate activity. Experiments indicate that the amino acids from the degradation are conserved and incorporated into the resynthesized protein in the subsequent cycle. A different species, Pyrocystis lunula, also exhibits a rhythm of bioluminescence, but the luciferase is not destroyed and resynthesized each cycle. This paper posits that synthesis and destruction constitutes a cellular mechanism to conserve nitrogen in an environment where the resource is limiting.

  9. The calcineurin-NFAT pathway controls activity-dependent circadian gene expression in slow skeletal muscle

    PubMed Central

    Dyar, Kenneth A.; Ciciliot, Stefano; Tagliazucchi, Guidantonio Malagoli; Pallafacchina, Giorgia; Tothova, Jana; Argentini, Carla; Agatea, Lisa; Abraham, Reimar; Ahdesmäki, Miika; Forcato, Mattia; Bicciato, Silvio; Schiaffino, Stefano; Blaauw, Bert

    2015-01-01

    Objective Physical activity and circadian rhythms are well-established determinants of human health and disease, but the relationship between muscle activity and the circadian regulation of muscle genes is a relatively new area of research. It is unknown whether muscle activity and muscle clock rhythms are coupled together, nor whether activity rhythms can drive circadian gene expression in skeletal muscle. Methods We compared the circadian transcriptomes of two mouse hindlimb muscles with vastly different circadian activity patterns, the continuously active slow soleus and the sporadically active fast tibialis anterior, in the presence or absence of a functional skeletal muscle clock (skeletal muscle-specific Bmal1 KO). In addition, we compared the effect of denervation on muscle circadian gene expression. Results We found that different skeletal muscles exhibit major differences in their circadian transcriptomes, yet core clock gene oscillations were essentially identical in fast and slow muscles. Furthermore, denervation caused relatively minor changes in circadian expression of most core clock genes, yet major differences in expression level, phase and amplitude of many muscle circadian genes. Conclusions We report that activity controls the oscillation of around 15% of skeletal muscle circadian genes independently of the core muscle clock, and we have identified the Ca2+-dependent calcineurin-NFAT pathway as an important mediator of activity-dependent circadian gene expression, showing that circadian locomotor activity rhythms drive circadian rhythms of NFAT nuclear translocation and target gene expression. PMID:26629406

  10. Phosphorylation Regulating the Ratio of Intracellular CRY1 Protein Determines the Circadian Period

    PubMed Central

    Liu, Na; Zhang, Eric Erquan

    2016-01-01

    The core circadian oscillator in mammals is composed of transcription/translation feedback loop, in which cryptochrome (CRY) proteins play critical roles as repressors of their own gene expression. Although post-translational modifications, such as phosphorylation of CRY1, are crucial for circadian rhythm, little is known about how phosphorylated CRY1 contributes to the molecular clockwork. To address this, we created a series of CRY1 mutants with single amino acid substitutions at potential phosphorylation sites and performed a cell-based, phenotype-rescuing screen to identify mutants with aberrant rhythmicity in CRY-deficient cells. We report 10 mutants with an abnormal circadian period length, including long period (S280D and S588D), short period (S158D, S247D, T249D, Y266D, Y273D, and Y432D), and arrhythmicity (S71D and S404D). When expressing mutated CRY1 in HEK293 cells, we show that most of the mutants (S71D, S247D, T249D, Y266D, Y273D, and Y432D) exhibited reduction in repression activity compared with wild-type (WT) CRY1, whereas other mutants had no obvious change. Correspondingly, these mutants also showed differences in protein stability and cellular localization. We show that most of mutants are more stable than WT, except S158D, T249D, and S280D. Although the characteristics of the 10 mutants are various, they all impair the ratio balance of intracellular CRY1 protein. Thus, we conclude that the mutations caused distinct phenotypes most likely through the ratio of functional CRY1 protein in cells. PMID:27721804

  11. 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

  12. Chamber-dependent circadian expression of cardiac natriuretic peptides.

    PubMed

    Goetze, Jens Peter; Georg, Birgitte; Jørgensen, Henrik L; Fahrenkrug, Jan

    2010-02-25

    Atrial natriuretic peptide (ANP) and B-type natriuretic peptide (BNP) have important local functions within the myocardium, where they protect against accelerated fibrosis. As circadian expression of cardiac natriuretic peptides could be of importance in local cardiac protection against disease, we examined the diurnal changes of the mRNAs encoding ANP, BNP, and their common receptor NPR-A in atrial and ventricular myocardium. Forty eight mice were killed at the following ZT times: 4, 8, 12, 16, 20, and 24, where ZT designates Zeitgeber; ZT 0 corresponds to lights ON and ZT 12 corresponds to lights OFF. Eight animals (4 males and 4 females) were included at each time point. Another 48 animals were killed during the second cycle of dark/dark (designated Circadian Time or CT: CT 4, CT 8, CT 12, CT 16, CT 20, and CT 24). The cellular contents of the clock genes Per1 and Bmal1 as well as ANP, BNP, and their common receptor (NPR-A) were determined using RT-PCR. Per1 and Bmal1 mRNA contents oscillated in antiphase in both atrial and ventricular regions, where Bmal1 mRNA peaked 12h out of phase relative to Per1 mRNA. ANP and NPR-A atrial mRNA contents revealed borderline significant diurnal changes, whereas ventricular BNP mRNA contents exhibited pronounced oscillation during constant darkness with nadir at CT 12 (P<0.0001). In conclusion, we report a chamber-dependent circadian profile of cardiac BNP mRNA contents, which is not paralleled by the related ANP gene. Our findings suggest that the BNP mRNA pattern could be associated with increased cardiac susceptibility and response to disease.

  13. Machine learning helps identify CHRONO as a circadian clock component.

    PubMed

    Anafi, Ron C; Lee, Yool; Sato, Trey K; Venkataraman, Anand; Ramanathan, Chidambaram; Kavakli, Ibrahim H; Hughes, Michael E; Baggs, Julie E; Growe, Jacqueline; Liu, Andrew C; Kim, Junhyong; Hogenesch, John B

    2014-04-01

    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.

  14. Class IIa Histone Deacetylases Are Conserved Regulators of Circadian Function*

    PubMed Central

    Fogg, Paul C. M.; O'Neill, John S.; Dobrzycki, Tomasz; Calvert, Shaun; Lord, Emma C.; McIntosh, Rebecca L. L.; Elliott, Christopher J. H.; Sweeney, Sean T.; Hastings, Michael H.; Chawla, Sangeeta

    2014-01-01

    Class IIa histone deacetylases (HDACs) regulate the activity of many transcription factors to influence liver gluconeogenesis and the development of specialized cells, including muscle, neurons, and lymphocytes. Here, we describe a conserved role for class IIa HDACs in sustaining robust circadian behavioral rhythms in Drosophila and cellular rhythms in mammalian cells. In mouse fibroblasts, overexpression of HDAC5 severely disrupts transcriptional rhythms of core clock genes. HDAC5 overexpression decreases BMAL1 acetylation on Lys-537 and pharmacological inhibition of class IIa HDACs increases BMAL1 acetylation. Furthermore, we observe cyclical nucleocytoplasmic shuttling of HDAC5 in mouse fibroblasts that is characteristically circadian. Mutation of the Drosophila homolog HDAC4 impairs locomotor activity rhythms of flies and decreases period mRNA levels. RNAi-mediated knockdown of HDAC4 in Drosophila clock cells also dampens circadian function. Given that the localization of class IIa HDACs is signal-regulated and influenced by Ca2+ and cAMP signals, our findings offer a mechanism by which extracellular stimuli that generate these signals can feed into the molecular clock machinery. PMID:25271152

  15. 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

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

    PubMed

    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

    2012-08-15

    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.

  17. MicroRNA-mediated regulation in the mammalian circadian rhythm.

    PubMed

    Liu, Kaihui; Wang, Ruiqi

    2012-07-01

    Mammalian circadian rhythms have been extensively studied for many years and many computational models have been presented. Most of the circadian rhythms are based on interlocked positive and negative feedback loops involving coding regions of some 'clock' genes. Recent works have implicated that microRNAs (miRNAs) may play crucial roles in modulating the circadian clock. Here we develop a computational model involving four genes, Per, Cry, Bmal1, and Clock, and two miRNAs, miRNA-219 and miRNA-132, to show their post-transcriptional roles in the modulation of the circadian rhythm. The model is based on experimental observations, by which the miRNAs are incorporated into a classic model including only coding genes. In agreement with experimental observations, the model predicts that miRNA-mediated regulation plays critical roles in modulating the circadian clock. In addition, parameter sensitivity analysis indicates that the period of circadian rhythm with miRNA-mediated regulation is more insensitive to perturbations, showing that the miRNA-mediated regulation can enhance the robustness of the circadian rhythms. This study may help us understand the microRNA-mediated regulation in the mammalian circadian rhythm more clearly.

  18. Circadian regulation of food-anticipatory activity in molecular clock-deficient mice.

    PubMed

    Takasu, Nana N; Kurosawa, Gen; Tokuda, Isao T; Mochizuki, Atsushi; Todo, Takeshi; Nakamura, Wataru

    2012-01-01

    In the mammalian brain, the suprachiasmatic nucleus (SCN) of the anterior hypothalamus is considered to be the principal circadian pacemaker, keeping the rhythm of most physiological and behavioral processes on the basis of light/dark cycles. Because restriction of food availability to a certain time of day elicits anticipatory behavior even after ablation of the SCN, such behavior has been assumed to be under the control of another circadian oscillator. According to recent studies, however, mutant mice lacking circadian clock function exhibit normal food-anticipatory activity (FAA), a daily increase in locomotor activity preceding periodic feeding, suggesting that FAA is independent of the known circadian oscillator. To investigate the molecular basis of FAA, we examined oscillatory properties in mice lacking molecular clock components. Mice with SCN lesions or with mutant circadian periods were exposed to restricted feeding schedules at periods within and outside circadian range. Periodic feeding led to the entrainment of FAA rhythms only within a limited circadian range. Cry1(-/-) mice, which are known to be a "short-period mutant," entrained to a shorter period of feeding cycles than did Cry2(-/-) mice. This result indicated that the intrinsic periods of FAA rhythms are also affected by Cry deficiency. Bmal1(-/-) mice, deficient in another essential element of the molecular clock machinery, exhibited a pre-feeding increase of activity far from circadian range, indicating a deficit in circadian oscillation. We propose that mice possess a food-entrainable pacemaker outside the SCN in which canonical clock genes such as Cry1, Cry2 and Bmal1 play essential roles in regulating FAA in a circadian oscillatory manner.

  19. 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. PMID:24454829

  20. Effects of dietary protein alterations on circadian rhythms of gastrointestinal peptides in rats.

    PubMed

    Pasley, J N; Rayford, P L

    1990-10-01

    Altered protein diets and circadian rhythms of gastrin and cholecystokinin (CCK) were investigated in 126 male and 126 female Sprague-Dawley rats acclimated for two weeks to a 12:12 hr light-dark cycle. Rats were divided equally and fed low-protein (8%), high-protein (64%) or normal protein (27%) diets for four weeks. All animals were fasted for 24 hr prior to blood collections. Blood samples were collected at 4-hr intervals for 24 hr for determination of plasma gastrin and CCK using specific radioimmunoassays. A significant rhythm for gastrin was detected in males on normal and low-protein diets (P less than 0.03) and in females on low-protein diets (P less than .02). A significant rhythm for CCK was detected (P less than 0.05) in rats of both sexes fed normal and high-protein diets. Mean plasma levels of both peptides were lower in females than males. In a separate study, food intake and body weight were monitored in male rats receiving the three diets over 21 days. Animals on the low-protein diet exhibited reduced food intake and body weight compared to rats fed the normal or high-protein diets.

  1. Rhythmic expression of circadian clock genes in human leukocytes and beard hair follicle cells.

    PubMed

    Watanabe, Makiko; Hida, Akiko; Kitamura, Shingo; Enomoto, Minori; Ohsawa, Yosuke; Katayose, Yasuko; Nozaki, Kentaro; Moriguchi, Yoshiya; Aritake, Sayaka; Higuchi, Shigekazu; Tamura, Miyuki; Kato, Mie; Mishima, Kazuo

    2012-09-01

    Evaluating individual circadian rhythm traits is crucial for understanding the human biological clock system. The present study reports characterization of physiological and molecular parameters in 13 healthy male subjects under a constant routine condition, where interfering factors were kept to minimum. We measured hormonal secretion levels and examined temporal expression profiles of circadian clock genes in peripheral leukocytes and beard hair follicle cells. All 13 subjects had prominent daily rhythms in melatonin and cortisol secretion. Significant circadian rhythmicity was found for PER1 in 9 subjects, PER2 in 3 subjects, PER3 in all 13 subjects, and BMAL1 in 8 subjects in leukocytes. Additionally, significant circadian rhythmicity was found for PER1 in 5 of 8 subjects tested, PER2 in 2 subjects, PER3 in 6 subjects, and BMAL1 in 3 subjects in beard hair follicle cells. The phase of PER1 and PER3 rhythms in leukocytes correlated significantly with that of physiological rhythms. Our results demonstrate that leukocytes and beard hair follicle cells possess an endogenous circadian clock and suggest that PER1 and PER3 expression would be appropriate biomarkers and hair follicle cells could be a useful tissue source for the evaluation of biological clock traits in individuals. PMID:22902636

  2. Timing Matters: Circadian Rhythm in Sepsis, Obstructive Lung Disease, Obstructive Sleep Apnea, and Cancer.

    PubMed

    Truong, Kimberly K; Lam, Michael T; Grandner, Michael A; Sassoon, Catherine S; Malhotra, Atul

    2016-07-01

    Physiological and cellular functions operate in a 24-hour cyclical pattern orchestrated by an endogenous process known as the circadian rhythm. Circadian rhythms represent intrinsic oscillations of biological functions that allow for adaptation to cyclic environmental changes. Key clock genes that affect the persistence and periodicity of circadian rhythms include BMAL1/CLOCK, Period 1, Period 2, and Cryptochrome. Remarkable progress has been made in our understanding of circadian rhythms and their role in common medical conditions. A critical review of the literature supports the association between circadian misalignment and adverse health consequences in sepsis, obstructive lung disease, obstructive sleep apnea, and malignancy. Circadian misalignment plays an important role in these disease processes and can affect disease severity, treatment response, and survivorship. Normal inflammatory response to acute infections, airway resistance, upper airway collapsibility, and mitosis regulation follows a robust circadian pattern. Disruption of normal circadian rhythm at the molecular level affects severity of inflammation in sepsis, contributes to inflammatory responses in obstructive lung diseases, affects apnea length in obstructive sleep apnea, and increases risk for cancer. Chronotherapy is an underused practice of delivering therapy at optimal times to maximize efficacy and minimize toxicity. This approach has been shown to be advantageous in asthma and cancer management. In asthma, appropriate timing of medication administration improves treatment effectiveness. Properly timed chemotherapy may reduce treatment toxicities and maximize efficacy. Future research should focus on circadian rhythm disorders, role of circadian rhythm in other diseases, and modalities to restore and prevent circadian disruption.

  3. Circadian Regulation of Lipid Mobilization in White Adipose Tissues

    PubMed Central

    Shostak, Anton; Meyer-Kovac, Judit; Oster, Henrik

    2013-01-01

    In mammals, a network of circadian clocks regulates 24-h rhythms of behavior and physiology. Circadian disruption promotes obesity and the development of obesity-associated disorders, but it remains unclear to which extent peripheral tissue clocks contribute to this effect. To reveal the impact of the circadian timing system on lipid metabolism, blood and adipose tissue samples from wild-type, ClockΔ19, and Bmal1−/− circadian mutant mice were subjected to biochemical assays and gene expression profiling. We show diurnal variations in lipolysis rates and release of free fatty acids (FFAs) and glycerol into the blood correlating with rhythmic regulation of two genes encoding the lipolysis pacemaker enzymes, adipose triglyceride (TG) lipase and hormone-sensitive lipase, by self-sustained adipocyte clocks. Circadian clock mutant mice show low and nonrhythmic FFA and glycerol blood content together with decreased lipolysis rates and increased sensitivity to fasting. Instead circadian clock disruption promotes the accumulation of TGs in white adipose tissue (WAT), leading to increased adiposity and adipocyte hypertrophy. In summary, circadian modulation of lipolysis rates regulates the availability of lipid-derived energy during the day, suggesting a role for WAT clocks in the regulation of energy homeostasis. PMID:23434933

  4. 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

  5. The period of the circadian oscillator is primarily determined by the balance between casein kinase 1 and protein phosphatase 1.

    PubMed

    Lee, Hyeong-min; Chen, Rongmin; Kim, Hyukmin; Etchegaray, Jean-Pierre; Weaver, David R; Lee, Choogon

    2011-09-27

    Mounting evidence suggests that PERIOD (PER) proteins play a central role in setting the speed (period) and phase of the circadian clock. Pharmacological and genetic studies have shown that changes in PER phosphorylation kinetics are associated with changes in circadian rhythm period and phase, which can lead to sleep disorders such as Familial Advanced Sleep Phase Syndrome in humans. We and others have shown that casein kinase 1δ and ε (CK1δ/ε) are essential PER kinases, but it is clear that additional, unknown mechanisms are also crucial for regulating the kinetics of PER phosphorylation. Here we report that circadian periodicity is determined primarily through PER phosphorylation kinetics set by the balance between CK1δ/ε and protein phosphatase 1 (PP1). In CK1δ/ε-deficient cells, PER phosphorylation is severely compromised and nonrhythmic, and the PER proteins are constitutively cytoplasmic. However, when PP1 is disrupted, PER phosphorylation is dramatically accelerated; the same effect is not seen when PP2A is disrupted. Our work demonstrates that the speed and rhythmicity of PER phosphorylation are controlled by the balance between CK1δ/ε and PP1, which in turn determines the period of the circadian oscillator. Thus, our findings provide clear insights into the molecular basis of how the period and phase of our daily rhythms are determined. PMID:21930935

  6. Paraoxonase 1 (PON1) and pomegranate influence circadian gene expression and period length.

    PubMed

    Loizides-Mangold, Ursula; Koren-Gluzer, Marie; Skarupelova, Svetlana; Makhlouf, Anne-Marie; Hayek, Tony; Aviram, Michael; Dibner, Charna

    2016-01-01

    The circadian timing system regulates key aspects of mammalian physiology. Here, we analyzed the effect of the endogenous antioxidant paraoxonase 1 (PON1), a high-density lipoprotein-associated lipolactonase that hydrolyses lipid peroxides and attenuates atherogenesis, on circadian gene expression in C57BL/6J and PON1KO mice fed a normal chow diet or a high-fat diet (HFD). Expression levels of core-clock transcripts Nr1d1, Per2, Cry2 and Bmal1 were altered in skeletal muscle in PON1-deficient mice in response to HFD. These findings were supported by circadian bioluminescence reporter assessments in mouse C2C12 and human primary myotubes, synchronized in vitro, where administration of PON1 or pomegranate juice modulated circadian period length. PMID:27010443

  7. Circadian Rhythms

    MedlinePlus

    ... chronobiology. Are circadian rhythms the same thing as biological clocks? No, but they are related. Our biological clocks drive our circadian rhythms. What are biological clocks? The biological clocks that control circadian rhythms ...

  8. Structural and biochemical characterization of a cyanobacterium circadian clock-modifier protein.

    PubMed

    Arita, Kyouhei; Hashimoto, Hiroshi; Igari, Kumiko; Akaboshi, Mayuko; Kutsuna, Shinsuke; Sato, Mamoru; Shimizu, Toshiyuki

    2007-01-12

    Circadian clocks are self-sustained biochemical oscillators. The oscillator of cyanobacteria comprises the products of three kai genes (kaiA, kaiB, and kaiC). The autophosphorylation cycle of KaiC oscillates robustly in the cell with a 24-h period and is essential for the basic timing of the cyanobacterial circadian clock. Recently, period extender (pex), mutants of which show a short period phenotype, was classified as a resetting-related gene. In fact, pex mRNA and the pex protein (Pex) increase during the dark period, and a pex mutant subjected to diurnal light-dark cycles shows a 3-h advance in rhythm phase. Here, we report the x-ray crystallographic analysis and biochemical characterization of Pex from cyanobacterium Synechococcus elongatus PCC 7942. The molecule has an (alpha+beta) structure with a winged-helix motif and is indicated to function as a dimer. The subunit arrangement in the dimer is unique and has not been seen in other winged-helix proteins. Electrophoresis mobility shift assay using a 25-base pair complementary oligonucleotide incorporating the kaiA upstream sequence demonstrates that Pex has an affinity for the double-stranded DNA. Furthermore, mutation analysis shows that Pex uses the wing region to recognize the DNA. The in vivo rhythm assay of Pex shows that the constitutive expression of the pex gene harboring the mutation that fails to bind to DNA lacks the period-prolongation activity in the pex-deficient Synechococcus, suggesting that Pex is a DNA-binding transcription factor.

  9. Phosphorylation modulates rapid nucleocytoplasmic shuttling and cytoplasmic accumulation of Neurospora clock protein FRQ on a circadian time scale

    PubMed Central

    Diernfellner, Axel C.R.; Querfurth, Christina; Salazar, Carlos; Höfer, Thomas; Brunner, Michael

    2009-01-01

    The Neurospora clock protein FREQUENCY (FRQ) is an essential regulator of the circadian transcription factor WHITE COLLAR COMPLEX (WCC). In the course of a circadian period, the subcellular distribution of FRQ shifts from mainly nuclear to mainly cytosolic. This shift is crucial for coordinating the negative and positive limbs of the clock. We show that the subcellular redistribution of FRQ on a circadian time scale is governed by rapid, noncircadian cycles of nuclear import and export. The rate of nuclear import of newly synthesized FRQ is progressively reduced in a phosphorylation-dependent manner, leading to an increase in the steady-state level of cytoplasmic FRQ. The long-period frq7 mutant displays reduced kinetics of FRQ7 protein phosphorylation and a prolonged accumulation in the nucleus. We present a mathematical model that describes the cytoplasmic accumulation of wild-type and mutant FRQ on a circadian time scale on the basis of frequency-modulated rapid nucleocytoplasmic shuttling cycles. PMID:19759264

  10. Circadian variation in gastric vagal afferent mechanosensitivity.

    PubMed

    Kentish, Stephen J; Frisby, Claudine L; Kennaway, David J; Wittert, Gary A; Page, Amanda J

    2013-12-01

    Food intake is coordinated to cellular metabolism by clock gene expression with a master clock in the suprachiasmatic nucleus synchronized by light exposure. Gastric vagal afferents play a role in regulating food intake, but it is unknown whether they exhibit circadian variation in their mechanosensitivity. We aimed to determine whether gastric vagal afferents express clock genes and whether their response to mechanical stimuli oscillates throughout the light/dark cycle. Nodose ganglia were collected from 8-week-old female C57BL/6 mice every 3 h starting at lights off (1800 h) to quantify Bmal1, Per1, Per2, and Nr1d1 mRNA by qRT-PCR. Additionally in vitro single-fiber recordings of gastric vagal mechanoreceptors were taken at all time points. Per1, Per2, Bmal1, and Nr1d1 mRNA is expressed in the nodose ganglia and levels oscillated over a 24 h period. In mice fed ad libitum, gastric content was 3 times higher at 0000 h and 0300 h than 1200 h. The response of tension receptors to 3 g stretch was reduced by up to 70% at 2100 h, 0000 h, and 0300 h compared with 1200 h. Gastric mucosal receptor response to stroking with a 50 mg von Frey hair was 3 times greater at 1200 h and 1500 h than the response at 0000 h. Similar findings were obtained in mice fasted for 6 h or maintained in darkness for 3 d before study. Therefore, these changes do not result from food intake or the light/dark cycle. Thus, gastric vagal mechanoreceptors display circadian rhythm, which may act to control food intake differentially at different times of the day. PMID:24305819

  11. Expression of clock proteins in developing tooth.

    PubMed

    Zheng, Li; Papagerakis, Silvana; Schnell, Santiago D; Hoogerwerf, Willemijntje A; Papagerakis, Petros

    2011-01-01

    Morphological and functional changes during ameloblast and odontoblast differentiation suggest that enamel and dentin formation is under circadian control. Circadian rhythms are endogenous self-sustained oscillations with periods of 24h that control diverse physiological and metabolic processes. Mammalian clock genes play a key role in synchronizing circadian functions in many organs. However, close to nothing is known on clock genes expression during tooth development. In this work, we investigated the expression of four clock genes during tooth development. Our results showed that circadian clock genes Bmal1, clock, per1, and per2 mRNAs were detected in teeth by RT-PCR. Immunohistochemistry showed that clock protein expression was first detected in teeth at the bell stage (E17), being expressed in EOE and dental papilla cells. At post-natal day four (PN4), all four clock proteins continued to be expressed in teeth but with different intensities, being strongly expressed within the nucleus of ameloblasts and odontoblasts and down-regulated in dental pulp cells. Interestingly, at PN21 incisor, expression of clock proteins was down-regulated in odontoblasts of the crown-analogue side but expression was persisting in root-analogue side odontoblasts. In contrast, both crown and root odontoblasts were strongly stained for all four clock proteins in first molars at PN21. Within the periodontal ligament (PDL) space, epithelial rests of Malassez (ERM) showed the strongest expression among other PDL cells. Our data suggests that clock genes might be involved in the regulation of ameloblast and odontoblast functions, such as enamel and dentin protein secretion and matrix mineralization.

  12. Genome-Wide Analysis of SREBP1 Activity around the Clock Reveals Its Combined Dependency on Nutrient and Circadian Signals

    PubMed Central

    Naldi, Aurélien; Baruchet, Michaël; Canella, Donatella; Le Martelot, Gwendal; Guex, Nicolas; Desvergne, Béatrice; Delorenzi, Mauro; Deplancke, Bart; Desvergne, Béatrice; Guex, Nicolas; Herr, Winship; Naef, Felix; Rougemont, Jacques; Schibler, Ueli; Deplancke, Bart; Guex, Nicolas; Herr, Winship; Guex, Nicolas; Andersin, Teemu; Cousin, Pascal; Gilardi, Federica; Gos, Pascal; Martelot, Gwendal Le; Lammers, Fabienne; Canella, Donatella; Gilardi, Federica; Raghav, Sunil; Fabbretti, Roberto; Fortier, Arnaud; Long, Li; Vlegel, Volker; Xenarios, Ioannis; Migliavacca, Eugenia; Praz, Viviane; Guex, Nicolas; Naef, Felix; Rougemont, Jacques; David, Fabrice; Jarosz, Yohan; Kuznetsov, Dmitry; Liechti, Robin; Martin, Olivier; Delafontaine, Julien; Sinclair, Lucas; Cajan, Julia; Krier, Irina; Leleu, Marion; Migliavacca, Eugenia; Molina, Nacho; Naldi, Aurélien; Rey, Guillaume; Symul, Laura; Guex, Nicolas; Naef, Felix; Rougemont, Jacques; Bernasconi, David; Delorenzi, Mauro; Andersin, Teemu; Canella, Donatella; Gilardi, Federica; Martelot, Gwendal Le; Lammers, Fabienne; Baruchet, Michaël; Raghav, Sunil

    2014-01-01

    In mammals, the circadian clock allows them to anticipate and adapt physiology around the 24 hours. Conversely, metabolism and food consumption regulate the internal clock, pointing the existence of an intricate relationship between nutrient state and circadian homeostasis that is far from being understood. The Sterol Regulatory Element Binding Protein 1 (SREBP1) is a key regulator of lipid homeostasis. Hepatic SREBP1 function is influenced by the nutrient-response cycle, but also by the circadian machinery. To systematically understand how the interplay of circadian clock and nutrient-driven rhythm regulates SREBP1 activity, we evaluated the genome-wide binding of SREBP1 to its targets throughout the day in C57BL/6 mice. The recruitment of SREBP1 to the DNA showed a highly circadian behaviour, with a maximum during the fed status. However, the temporal expression of SREBP1 targets was not always synchronized with its binding pattern. In particular, different expression phases were observed for SREBP1 target genes depending on their function, suggesting the involvement of other transcription factors in their regulation. Binding sites for Hepatocyte Nuclear Factor 4 (HNF4) were specifically enriched in the close proximity of SREBP1 peaks of genes, whose expression was shifted by about 8 hours with respect to SREBP1 binding. Thus, the cross-talk between hepatic HNF4 and SREBP1 may underlie the expression timing of this subgroup of SREBP1 targets. Interestingly, the proper temporal expression profile of these genes was dramatically changed in Bmal1 −/− mice upon time-restricted feeding, for which a rhythmic, but slightly delayed, binding of SREBP1 was maintained. Collectively, our results show that besides the nutrient-driven regulation of SREBP1 nuclear translocation, a second layer of modulation of SREBP1 transcriptional activity, strongly dependent from the circadian clock, exists. This system allows us to fine tune the expression timing of SREBP1 target genes

  13. Genome-wide analysis of SREBP1 activity around the clock reveals its combined dependency on nutrient and circadian signals.

    PubMed

    Gilardi, Federica; Migliavacca, Eugenia; Naldi, Aurélien; Baruchet, Michaël; Canella, Donatella; Le Martelot, Gwendal; Guex, Nicolas; Desvergne, Béatrice

    2014-03-01

    In mammals, the circadian clock allows them to anticipate and adapt physiology around the 24 hours. Conversely, metabolism and food consumption regulate the internal clock, pointing the existence of an intricate relationship between nutrient state and circadian homeostasis that is far from being understood. The Sterol Regulatory Element Binding Protein 1 (SREBP1) is a key regulator of lipid homeostasis. Hepatic SREBP1 function is influenced by the nutrient-response cycle, but also by the circadian machinery. To systematically understand how the interplay of circadian clock and nutrient-driven rhythm regulates SREBP1 activity, we evaluated the genome-wide binding of SREBP1 to its targets throughout the day in C57BL/6 mice. The recruitment of SREBP1 to the DNA showed a highly circadian behaviour, with a maximum during the fed status. However, the temporal expression of SREBP1 targets was not always synchronized with its binding pattern. In particular, different expression phases were observed for SREBP1 target genes depending on their function, suggesting the involvement of other transcription factors in their regulation. Binding sites for Hepatocyte Nuclear Factor 4 (HNF4) were specifically enriched in the close proximity of SREBP1 peaks of genes, whose expression was shifted by about 8 hours with respect to SREBP1 binding. Thus, the cross-talk between hepatic HNF4 and SREBP1 may underlie the expression timing of this subgroup of SREBP1 targets. Interestingly, the proper temporal expression profile of these genes was dramatically changed in Bmal1-/- mice upon time-restricted feeding, for which a rhythmic, but slightly delayed, binding of SREBP1 was maintained. Collectively, our results show that besides the nutrient-driven regulation of SREBP1 nuclear translocation, a second layer of modulation of SREBP1 transcriptional activity, strongly dependent from the circadian clock, exists. This system allows us to fine tune the expression timing of SREBP1 target genes, thus

  14. 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.

  15. A dual-color luciferase assay system reveals circadian resetting of cultured fibroblasts by co-cultured adrenal glands.

    PubMed

    Noguchi, Takako; Ikeda, Masaaki; Ohmiya, Yoshihiro; Nakajima, Yoshihiro

    2012-01-01

    In mammals, circadian rhythms of various organs and tissues are synchronized by pacemaker neurons in the suprachiasmatic nucleus (SCN) of the hypothalamus. Glucocorticoids released from the adrenal glands can synchronize circadian rhythms in other tissues. Many hormones show circadian rhythms in their plasma concentrations; however, whether organs outside the SCN can serve as master synchronizers to entrain circadian rhythms in target tissues is not well understood. To further delineate the function of the adrenal glands and the interactions of circadian rhythms in putative master synchronizing organs and their target tissues, here we report a simple co-culture system using a dual-color luciferase assay to monitor circadian rhythms separately in various explanted tissues and fibroblasts. In this system, circadian rhythms of organs and target cells were simultaneously tracked by the green-emitting beetle luciferase from Pyrearinus termitilluminans (ELuc) and the red-emitting beetle luciferase from Phrixothrix hirtus (SLR), respectively. We obtained tissues from the adrenal glands, thyroid glands, and lungs of transgenic mice that expressed ELuc under control of the promoter from a canonical clock gene, mBmal1. The tissues were co-cultured with Rat-1 fibroblasts as representative target cells expressing SLR under control of the mBmal1 promoter. Amplitudes of the circadian rhythms of Rat-1 fibroblasts were potentiated when the fibroblasts were co-cultured with adrenal gland tissue, but not when co-cultured with thyroid gland or lung tissue. The phases of Rat-1 fibroblasts were reset by application of adrenal gland tissue, whereas the phases of adrenal gland tissue were not influenced by Rat-1 fibroblasts. Furthermore, the effect of the adrenal gland tissue on the fibroblasts was blocked by application of a glucocorticoid receptor (GR) antagonist. These results demonstrate that glucocorticoids are strong circadian synchronizers for fibroblasts and that this co

  16. Nocturnin in the demosponge Suberites domuncula: a potential circadian clock protein controlling glycogenin synthesis in sponges.

    PubMed

    Müller, Werner E G; Wang, Xiaohong; Grebenjuk, Vlad A; Korzhev, Michael; Wiens, Matthias; Schlossmacher, Ute; Schröder, Heinz C

    2012-12-01

    Sponges are filter feeders that consume a large amount of energy to allow a controlled filtration of water through their aquiferous canal systems. It has been shown that primmorphs, three-dimensional cell aggregates prepared from the demosponge Suberites domuncula and cultured in vitro, change their morphology depending on the light supply. Upon exposure to light, primmorphs show a faster and stronger increase in DNA, protein and glycogen content compared with primmorphs that remain in the dark. The sponge genome contains nocturnin, a light/dark-controlled clock gene, the protein of which shares a high sequence similarity with the related molecule of higher metazoans. The sponge nocturnin protein was found showing a poly(A)-specific 3'-exoribonuclease activity. In addition, the cDNA of the glycogenin gene was identified for subsequent expression studies. Antibodies against nocturnin were raised and used in parallel with the cDNA to determine the regional expression of nocturnin in intact sponge specimens; the highest expression of nocturnin was seen in the epithelial layer around the aquiferous canals. Quantitative PCR analyses revealed that primmorphs after transfer from light to dark show a 10-fold increased expression in the nocturnin gene. In contrast, the expression level of glycogenin decreases in the dark by 3-4-fold. Exposure of primmorphs to light causes a decrease in nocturnin transcripts and a concurrent increase in glycogenin transcripts. It was concluded that sponges are provided with the molecular circadian clock protein nocturnin that is highly expressed in the dark where it controls the stability of a key metabolic enzyme, glycogenin.

  17. PERIOD2 is a circadian negative regulator of PAI-1 gene expression in mice.

    PubMed

    Oishi, Katsutaka; Miyazaki, Koyomi; Uchida, Daisuke; Ohkura, Naoki; Wakabayashi, Miyuki; Doi, Ryosuke; Matsuda, Juzo; Ishida, Norio

    2009-04-01

    An increased level of obesity-induced plasma plasminogen activator inhibitor-1 (PAI-1) is considered a risk factor for cardiovascular disease. To determine whether the circadian clock component PERIOD2 (PER2) is involved in the regulation of PAI-1 gene expression, we performed transient transfection assays in vitro, and generated transgenic (Tg) mice overexpressing PER2. We then compared PAI-1 expression in Tg and wild-type (WT) mice with or without obesity induced by a high-fat/high-sucrose diet. PER2 suppressed CLOCK:BMAL1- and CLOCK:BMAL2-dependent transactivation of the PAI-1 promoter in vitro. Furthermore, nuclear translocation is dispensable for PER2 to suppress CLOCK:BMAL1-dependent transactivation of the PAI-1 promoter, because functional loss of the nuclear localization domain did not affect either the interaction with BMAL1 or the suppressive role of PER2. The diurnal expression of clock and clock-controlled genes was disrupted in a gene-specific manner, whereas that of PAI-1 mRNA was significantly damped in the hearts of PER2 Tg mice fed with a normal diet. Obesity-induced plasma PAI-1 increase was significantly suppressed in Tg mice in accordance with cardiac PAI-1 mRNA levels, whereas body weight gain and changes in metabolic parameters were identical between WT and Tg mice. Endogenous PAI-1 gene expression induced by transforming growth factor-beta1 was significantly attenuated in embryonic fibroblasts derived from Tg mice compared with those from WT mice. Our results demonstrated that PER2 represses PAI-1 gene transcription in a BMAL1/2-dependent manner. The present findings also suggest that PER2 attenuates obesity-induced hypofibrinolysis by downregulating PAI-1 expression independently of metabolic disorders.

  18. Transcriptional regulation of NHE3 and SGLT1 by the circadian clock protein Per1 in proximal tubule cells.

    PubMed

    Solocinski, Kristen; Richards, Jacob; All, Sean; Cheng, Kit-Yan; Khundmiri, Syed J; Gumz, Michelle L

    2015-12-01

    We have previously demonstrated that the circadian clock protein period (Per)1 coordinately regulates multiple genes involved in Na(+) reabsorption in renal collecting duct cells. Consistent with these results, Per1 knockout mice exhibit dramatically lower blood pressure than wild-type mice. The proximal tubule is responsible for a majority of Na(+) reabsorption. Previous work has demonstrated that expression of Na(+)/H(+) exchanger 3 (NHE3) oscillates with a circadian pattern and Na(+)-glucose cotransporter (SGLT)1 has been demonstrated to be a circadian target in the colon, but whether these target genes are regulated by Per1 has not been investigated in the kidney. The goal of the present study was to determine if Per1 regulates the expression of NHE3, SGLT1, and SGLT2 in the kidney. Pharmacological blockade of nuclear Per1 entry resulted in decreased mRNA expression of SGLT1 and NHE3 but not SGLT2 in the renal cortex of mice. Per1 small interfering RNA and pharmacological blockade of Per1 nuclear entry in human proximal tubule HK-2 cells yielded the same results. Examination of heterogeneous nuclear RNA suggested that the effects of Per1 on NHE3 and SGLT1 expression occurred at the level of transcription. Per1 and the circadian protein CLOCK were detected at promoters of NHE3 and SGLT1. Importantly, both membrane and intracellular protein levels of NHE3 and SGLT1 were decreased after blockade of nuclear Per1 entry. This effect was associated with reduced activity of Na(+)-K(+)-ATPase. These data demonstrate a role for Per1 in the transcriptional regulation of NHE3 and SGLT1 in the kidney.

  19. Inhibitory role of REV-ERBα in the expression of bone morphogenetic protein gene family in rat uterus endometrium stromal cells.

    PubMed

    Tasaki, Hirotaka; Zhao, Lijia; Isayama, Keishiro; Chen, Huatao; Yamauchi, Nobuhiko; Shigeyoshi, Yasufumi; Hashimoto, Seiichi; Hattori, Masa-aki

    2015-04-01

    Uterus circadian rhythms have been implicated in the gestation processes of mammals through entraining of the clock proteins to numerous downstream genes. Bone morphogenetic proteins (BMPs), having clock-controlled regulatory sites in their gene promoters, are expressed in the uterus during decidualization, but the regulation of the Bmp gene expression is poorly understood. The present study was designed to dissect the physiological roles of the uterus oscillators in the Bmp expression using the uterus endometrial stromal cells (UESCs) isolated from Per2-dLuc transgenic rats on day 4.5 of gestation. The in vitro decidualization of UESCs was induced by medroxyprogesterone acetate and 2-O-dibutyryl cAMP. A significant decline of Per2-dLuc bioluminescence activity was induced in decidual cells, and concomitantly, the expression of canonical clock genes was downregulated. Conversely, the expression of the core Bmp genes Bmp2, Bmp4, Bmp6, and Bmp7 was upregulated. In UESCs transfected with Bmal1-specific siRNA, in which Rev-erbα expression was downregulated, Bmp genes, such as Bmp2, Bmp4, and Bmp6 were upregulated. However, Bmp1, Bmp7, and Bmp8a were not significantly affected by Bmal1 silencing. The expression of all Bmp genes was enhanced after treatment with the REV-ERBα antagonist (SR8278), although their rhythmic profiles were differed from each other. The binding of REV-ERBα to the proximal regions of the Bmp2 and Bmp4 promoters was revealed by chromatin immunoprecipitation-PCR analysis. Collectively, these results indicate that the Bmp genes are upregulated by the attenuation of the cellular circadian clock; in particular, its core component REV-ERBα functions as a transcriptional silencer in the Bmp gene family.

  20. Light and feeding entrainment of the molecular circadian clock in a marine teleost (Sparus aurata).

    PubMed

    Vera, L M; Negrini, P; Zagatti, C; Frigato, E; Sánchez-Vázquez, F J; Bertolucci, C

    2013-06-01

    Daily light and feeding cycles act as powerful synchronizers of circadian rhythmicity. Ultimately, these external cues entrain the expression of clock genes, which generate daily rhythmic behavioral and physiological responses in vertebrates. In the present study, we investigated clock genes in a marine teleost (gilthead sea bream). Partial cDNA sequences of key elements from both positive (Bmal1, Clock) and negative (Per2, Cry1) regulatory loops were cloned before studying how feeding time affects the daily rhythms of locomotor activity and clock gene expression in the central (brain) and peripheral (liver) oscillators. To this end, all fish were kept under a light-dark (LD) cycle and were divided into three experimental groups, depending on the time of their daily meal: mid-light (ML), mid-darkness (MD), or at random (RD) times. Finally, the existence of circadian control on gene expression was investigated in the absence of external cues (DD + RD). The behavioral results showed that seabream fed at ML or RD displayed a diurnal activity pattern (>91% of activity during the day), whereas fish fed at MD were nocturnal (89% of activity during the night). Moreover, seabream subjected to regular feeding cycles (ML and MD groups) showed food-anticipatory activity (FAA). Regardless of the mealtime, the daily rhythm of clock gene expression in the brain peaked close to the light-dark transition in the case of Bmal1 and Clock, and at the beginning of the light phase in the case of Per2 and Cry1, showing the existence of phase delay between the positive and negative elements of the molecular clock. In the liver, however, the acrophases of the daily rhythms differed depending on the feeding regime: the maximum expression of Bmal1 and Clock in the ML and RD groups was in antiphase to the expression pattern observed in the fish fed at MD. Under constant conditions (DD + RD), Per2 and Cry1 showed circadian rhythmicity in the brain, whereas Bmal1, Clock, and Per2 did in

  1. The Circadian Clock Maintains Cardiac Function by Regulating Mitochondrial Metabolism in Mice

    PubMed Central

    Kohsaka, Akira; Das, Partha; Hashimoto, Izumi; Nakao, Tomomi; Deguchi, Yoko; Gouraud, Sabine S.; Waki, Hidefumi; Muragaki, Yasuteru; Maeda, Masanobu

    2014-01-01

    Cardiac function is highly dependent on oxidative energy, which is produced by mitochondrial respiration. Defects in mitochondrial function are associated with both structural and functional abnormalities in the heart. Here, we show that heart-specific ablation of the circadian clock gene Bmal1 results in cardiac mitochondrial defects that include morphological changes and functional abnormalities, such as reduced enzymatic activities within the respiratory complex. Mice without cardiac Bmal1 function show a significant decrease in the expression of genes associated with the fatty acid oxidative pathway, the tricarboxylic acid cycle, and the mitochondrial respiratory chain in the heart and develop severe progressive heart failure with age. Importantly, similar changes in gene expression related to mitochondrial oxidative metabolism are also observed in C57BL/6J mice subjected to chronic reversal of the light-dark cycle; thus, they show disrupted circadian rhythmicity. These findings indicate that the circadian clock system plays an important role in regulating mitochondrial metabolism and thereby maintains cardiac function. PMID:25389966

  2. Circadian expression of clock and putative clock-controlled genes in skeletal muscle of the zebrafish.

    PubMed

    Amaral, Ian P G; Johnston, Ian A

    2012-01-01

    To identify circadian patterns of gene expression in skeletal muscle, adult male zebrafish were acclimated for 2 wk to a 12:12-h light-dark photoperiod and then exposed to continuous darkness for 86 h with ad libitum feeding. The increase in gut food content associated with the subjective light period was much diminished by the third cycle, enabling feeding and circadian rhythms to be distinguished. Expression of zebrafish paralogs of mammalian transcriptional activators of the circadian mechanism (bmal1, clock1, and rora) followed a rhythmic pattern with a ∼24-h periodicity. Peak expression of rora paralogs occurred at the beginning of the subjective light period [Zeitgeber time (ZT)07 and ZT02 for roraa and rorab], whereas the highest expression of bmal1 and clock paralogs occurred 12 h later (ZT13-15 and ZT16 for bmal and clock paralogs). Expression of the transcriptional repressors cry1a, per1a/1b, per2, per3, nr1d2a/2b, and nr1d1 also followed a circadian pattern with peak expression at ZT0-02. Expression of the two paralogs of cry2 occurred in phase with clock1a/1b. Duplicated genes had a high correlation of expression except for paralogs of clock1, nr1d2, and per1, with cry1b showing no circadian pattern. The highest expression difference was 9.2-fold for the activator bmal1b and 51.7-fold for the repressor per1a. Out of 32 candidate clock-controlled genes, only myf6, igfbp3, igfbp5b, and hsf2 showed circadian expression patterns. Igfbp3, igfbp5b, and myf6 were expressed in phase with clock1a/1b and had an average of twofold change in expression from peak to trough, whereas hsf2 transcripts were expressed in phase with cry1a and had a 7.2-fold-change in expression. The changes in expression of clock and clock-controlled genes observed during continuous darkness were also observed at similar ZTs in fish exposed to a normal photoperiod in a separate control experiment. The role of circadian clocks in regulating muscle maintenance and growth are discussed

  3. Suprachiasmatic nucleus function and circadian entrainment are modulated by G protein-coupled inwardly rectifying (GIRK) channels

    PubMed Central

    Hablitz, L M; Molzof, H E; Paul, J R; Johnson, R L; Gamble, K L

    2014-01-01

    Abstract G protein signalling within the central circadian oscillator, the suprachiasmatic nucleus (SCN), is essential for conveying time-of-day information. We sought to determine whether G protein-coupled inwardly rectifying potassium channels (GIRKs) modulate SCN physiology and circadian behaviour. We show that GIRK current and GIRK2 protein expression are greater during the day. Pharmacological inhibition of GIRKs and genetic loss of GIRK2 depolarized the day-time resting membrane potential of SCN neurons compared to controls. Behaviourally, GIRK2 knockout (KO) mice failed to shorten free running period in response to wheel access in constant darkness and entrained more rapidly to a 6 h advance of a 12 h:12 h light–dark (LD) cycle than wild-type (WT) littermate controls. We next examined whether these effects were due to disrupted signalling of neuropeptide Y (NPY), which is known to mediate non-photic phase shifts, attenuate photic phase shifts and activate GIRKs. Indeed, GIRK2 KO SCN slices had significantly fewer silent cells in response to NPY, likely contributing to the absence of NPY-induced phase advances of PER2::LUC rhythms in organotypic SCN cultures from GIRK2 KO mice. Finally, GIRK channel activation is sufficient to cause a non-photic-like phase advance of PER2::LUC rhythms on a Per2Luc+/− background. These results suggest that rhythmic regulation of GIRK2 protein and channel function in the SCN contributes to day-time resting membrane potential, providing a mechanism for the fine tuning responses to non-photic and photic stimuli. Further investigation could provide insight into disorders with circadian disruption comorbidities such as epilepsy and addiction, in which GIRK channels have been implicated. PMID:25217379

  4. NPAS2 Compensates for Loss of CLOCK in Peripheral Circadian Oscillators

    PubMed Central

    Landgraf, Dominic; Wang, Lexie L.; Diemer, Tanja; Welsh, David K.

    2016-01-01

    Heterodimers of CLOCK and BMAL1 are the major transcriptional activators of the mammalian circadian clock. Because the paralog NPAS2 can substitute for CLOCK in the suprachiasmatic nucleus (SCN), the master circadian pacemaker, CLOCK-deficient mice maintain circadian rhythms in behavior and in tissues in vivo. However, when isolated from the SCN, CLOCK-deficient peripheral tissues are reportedly arrhythmic, suggesting a fundamental difference in circadian clock function between SCN and peripheral tissues. Surprisingly, however, using luminometry and single-cell bioluminescence imaging of PER2 expression, we now find that CLOCK-deficient dispersed SCN neurons and peripheral cells exhibit similarly stable, autonomous circadian rhythms in vitro. In CLOCK-deficient fibroblasts, knockdown of Npas2 leads to arrhythmicity, suggesting that NPAS2 can compensate for loss of CLOCK in peripheral cells as well as in SCN. Our data overturn the notion of an SCN-specific role for NPAS2 in the molecular circadian clock, and instead indicate that, at the cellular level, the core loops of SCN neuron and peripheral cell circadian clocks are fundamentally similar. PMID:26895328

  5. Human skeletal myotubes display a cell-autonomous circadian clock implicated in basal myokine secretion

    PubMed Central

    Perrin, Laurent; Loizides-Mangold, Ursula; Skarupelova, Svetlana; Pulimeno, Pamela; Chanon, Stephanie; Robert, Maud; Bouzakri, Karim; Modoux, Christine; Roux-Lombard, Pascale; Vidal, Hubert; Lefai, Etienne; Dibner, Charna

    2015-01-01

    Objective Circadian clocks are functional in all light-sensitive organisms, allowing an adaptation to the external world in anticipation of daily environmental changes. In view of the potential role of the skeletal muscle clock in the regulation of glucose metabolism, we aimed to characterize circadian rhythms in primary human skeletal myotubes and investigate their roles in myokine secretion. Methods We established a system for long-term bioluminescence recording in differentiated human myotubes, employing lentivector gene delivery of the Bmal1-luciferase and Per2-luciferase core clock reporters. Furthermore, we disrupted the circadian clock in skeletal muscle cells by transfecting siRNA targeting CLOCK. Next, we assessed the basal secretion of a large panel of myokines in a circadian manner in the presence or absence of a functional clock. Results Bioluminescence reporter assays revealed that human skeletal myotubes, synchronized in vitro, exhibit a self-sustained circadian rhythm, which was further confirmed by endogenous core clock transcript expression. Moreover, we demonstrate that the basal secretion of IL-6, IL-8 and MCP-1 by synchronized skeletal myotubes has a circadian profile. Importantly, the secretion of IL-6 and several additional myokines was strongly downregulated upon siClock-mediated clock disruption. Conclusions Our study provides for the first time evidence that primary human skeletal myotubes possess a high-amplitude cell-autonomous circadian clock, which could be attenuated. Furthermore, this oscillator plays an important role in the regulation of basal myokine secretion by skeletal myotubes. PMID:26629407

  6. Circadian Modulation of 8-Oxoguanine DNA Damage Repair

    PubMed Central

    Manzella, Nicola; Bracci, Massimo; Strafella, Elisabetta; Staffolani, Sara; Ciarapica, Veronica; Copertaro, Alfredo; Rapisarda, Venerando; Ledda, Caterina; Amati, Monica; Valentino, Matteo; Tomasetti, Marco; Stevens, Richard G.; Santarelli, Lory

    2015-01-01

    The DNA base excision repair pathway is the main system involved in the removal of oxidative damage to DNA such as 8-Oxoguanine (8-oxoG) primarily via the 8-Oxoguanine DNA glycosylase (OGG1). Our goal was to investigate whether the repair of 8-oxoG DNA damage follow a circadian rhythm. In a group of 15 healthy volunteers, we found a daily variation of Ogg1 expression and activity with higher levels in the morning compared to the evening hours. Consistent with this, we also found lower levels of 8-oxoG in morning hours compared to those in the evening hours. Lymphocytes exposed to oxidative damage to DNA at 8:00 AM display lower accumulation of 8-oxoG than lymphocytes exposed at 8:00 PM. Furthermore, altered levels of Ogg1 expression were also observed in a group of shift workers experiencing a deregulation of circadian clock genes compared to a control group. Moreover, BMAL1 knockdown fibroblasts with a deregulated molecular clock showed an abolishment of circadian variation of Ogg1 expression and an increase of OGG1 activity. Our results suggest that the circadian modulation of 8-oxoG DNA damage repair, according to a variation of Ogg1 expression, could render humans less susceptible to accumulate 8-oxoG DNA damage in the morning hours. PMID:26337123

  7. Rats with minimal hepatic encephalopathy show reduced cGMP-dependent protein kinase activity in hypothalamus correlating with circadian rhythms alterations.

    PubMed

    Felipo, Vicente; Piedrafita, Blanca; Barios, Juan A; Agustí, Ana; Ahabrach, Hanan; Romero-Vives, María; Barrio, Luis C; Rey, Beatriz; Gaztelu, Jose M; Llansola, Marta

    2015-01-01

    Patients with liver cirrhosis show disturbances in sleep and in its circadian rhythms which are an early sign of minimal hepatic encephalopathy (MHE). The mechanisms of these disturbances are poorly understood. Rats with porta-caval shunt (PCS), a model of MHE, show sleep disturbances reproducing those of cirrhotic patients. The aims of this work were to characterize the alterations in circadian rhythms in PCS rats and analyze the underlying mechanisms. To reach these aims, we analyzed in control and PCS rats: (a) daily rhythms of spontaneous and rewarding activity and of temperature, (b) timing of the onset of activity following turning-off the light, (c) synchronization to light after a phase advance and (d) the molecular mechanisms contributing to these alterations in circadian rhythms. PCS rats show altered circadian rhythms of spontaneous and rewarding activities (wheel running). PCS rats show more rest bouts during the active phase, more errors in the onset of motor activity and need less time to re-synchronize after a phase advance than control rats. Circadian rhythm of body temperature is also slightly altered in PCS rats. The internal period length (tau) of circadian rhythm of motor activity is longer in PCS rats. We analyzed some mechanisms by which hypothalamus modulate circadian rhythms. PCS rats show increased content of cGMP in hypothalamus while the activity of cGMP-dependent protein kinase was reduced by 41% compared to control rats. Altered cGMP-PKG pathway in hypothalamus would contribute to altered circadian rhythms and synchronization to light.

  8. Ras-mediated deregulation of the circadian clock in cancer.

    PubMed

    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

  9. 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

  10. The C-terminal Kinase and ERK-binding Domains of Drosophila S6KII (RSK) Are Required for Phosphorylation of the Protein and Modulation of Circadian Behavior*

    PubMed Central

    Tangredi, Michelle M.; Ng, Fanny S.; Jackson, F. Rob

    2012-01-01

    A detailed structure/function analysis of Drosophila p90 ribosomal S6 kinase (S6KII) or its mammalian homolog RSK has not been performed in the context of neuronal plasticity or behavior. We previously reported that S6KII is required for normal circadian periodicity. Here we report a site-directed mutagenesis of S6KII and analysis of mutants, in vivo, that identifies functional domains and phosphorylation sites critical for the regulation of circadian period. We demonstrate, for the first time, a role for the S6KII C-terminal kinase that is independent of its known role in activation of the N-terminal kinase. Both S6KII C-terminal kinase activity and its ERK-binding domain are required for wild-type circadian period and normal phosphorylation status of the protein. In contrast, the N-terminal kinase of S6KII is dispensable for modulation of circadian period and normal phosphorylation of the protein. We also show that particular sites of S6KII phosphorylation, Ser-515 and Thr-732, are essential for normal circadian behavior. Surprisingly, the phosphorylation of S6KII residues, in vivo, does not follow a strict sequential pattern, as implied by certain cell-based studies of mammalian RSK protein. PMID:22447936

  11. Shifting the feeding of mice to the rest phase creates metabolic alterations, which, on their own, shift the peripheral circadian clocks by 12 hours

    PubMed Central

    Mukherji, Atish; Kobiita, Ahmad; Chambon, Pierre

    2015-01-01

    The molecular mechanisms underlying the events through which alterations in diurnal activities impinge on peripheral circadian clocks (PCCs), and reciprocally how the PCCs affect metabolism, thereby generating pathologies, are still poorly understood. Here, we deciphered how switching the diurnal feeding from the active to the rest phase, i.e., restricted feeding (RF), immediately creates a hypoinsulinemia during the active phase, which initiates a metabolic reprogramming by increasing FFA and glucagon levels. In turn, peroxisome proliferator-activated receptor alpha (PPARα) activation by free fatty acid (FFA), and cAMP response element-binding protein (CREB) activation by glucagon, lead to further metabolic alterations during the circadian active phase, as well as to aberrant activation of expression of the PCC components nuclear receptor subfamily 1, group D, member 1 (Nr1d1/RevErbα), Period (Per1 and Per2). Moreover, hypoinsulinemia leads to an increase in glycogen synthase kinase 3β (GSK3β) activity that, through phosphorylation, stabilizes and increases the level of the RevErbα protein during the active phase. This increase then leads to an untimely repression of expression of the genes containing a RORE DNA binding sequence (DBS), including the Bmal1 gene, thereby initiating in RF mice a 12-h PCC shift to which the CREB-mediated activation of Per1, Per2 by glucagon modestly contributes. We also show that the reported corticosterone extraproduction during the RF active phase reflects an adrenal aberrant activation of CREB signaling, which selectively delays the activation of the PPARα–RevErbα axis in muscle and heart and accounts for the retarded shift of their PCCs. PMID:26627259

  12. Evidence for clock genes circadian rhythms in human full-term placenta.

    PubMed

    Pérez, Silvia; Murias, Lucía; Fernández-Plaza, Catalina; Díaz, Irene; González, Celestino; Otero, Jesús; Díaz, Elena

    2015-01-01

    Biological rhythms are driven by endogenous biological clocks; in mammals, the master clock is located in the suprachiasmatic nucleus (SCN) of the hypothalamus. This master pacemaker can synchronize other peripheral oscillators in several tissues such as some involved in endocrine or reproductive functions. The presence of an endogenous placental clock has received little attention. In fact, there are no studies in human full-term placentas. To test the existence of an endogenous pacemaker in this tissue we have studied the expression of circadian locomoter output cycles kaput (Clock), brain and muscle arnt-like (Bmal)1, period (Per)2, and cryptochrome (Cry)1 mRNAs at 00, 04, 08, 12, 16, and 20 hours by qPCR. The four clock genes studied are expressed in full-term human placenta. The results obtained allow us to suggest that a peripheral oscillator exists in human placenta. Data were analyzed using Fourier series where only the Clock and Bmal1 expression shows a circadian rhythm.

  13. Natural variation reveals that intracellular distribution of ELF3 protein is associated with function in the circadian clock

    PubMed Central

    Anwer, Muhammad Usman; Boikoglou, Eleni; Herrero, Eva; Hallstein, Marc; Davis, Amanda Melaragno; Velikkakam James, Geo; Nagy, Ferenc; Davis, Seth Jon

    2014-01-01

    Natural selection of variants within the Arabidopsis thaliana circadian clock can be attributed to adaptation to varying environments. To define a basis for such variation, we examined clock speed in a reporter-modified Bay-0 x Shakdara recombinant inbred line and localized heritable variation. Extensive variation led us to identify EARLY FLOWERING3 (ELF3) as a major quantitative trait locus (QTL). The causal nucleotide polymorphism caused a short-period phenotype under light and severely dampened rhythm generation in darkness, and entrainment alterations resulted. We found that ELF3-Sha protein failed to properly localize to the nucleus, and its ability to accumulate in darkness was compromised. Evidence was provided that the ELF3-Sha allele originated in Central Asia. Collectively, we showed that ELF3 protein plays a vital role in defining its light-repressor action in the circadian clock and that its functional abilities are largely dependent on its cellular localization. DOI: http://dx.doi.org/10.7554/eLife.02206.001 PMID:24867215

  14. The impact of HIF1α on the Per2 circadian rhythm in renal cancer cell lines.

    PubMed

    Okabe, Takashi; Kumagai, Megumi; Nakajima, Yoshihiro; Shirotake, Suguru; Kodaira, Kiichiro; Oyama, Masafumi; Ueno, Munehisa; Ikeda, Masaaki

    2014-01-01

    In mammals, the circadian rhythm central generator consists of interactions among clock genes, including Per1/2/3, Cry1/2, Bmal1, and Clock. Circadian rhythm disruption may lead to increased risk of cancer in humans, and deregulation of clock genes has been implicated in many types of cancers. Among these genes, Per2 is reported to have tumor suppressor properties, but little is known about the correlation between Per2 and HIF, which is the main target of renal cell carcinoma (RCC) therapy. In this study, the rhythmic expression of the Per2 gene was not detectable in renal cancer cell lines, with the exception of Caki-2 cells. In Caki-2 cells, HIF1α increased the amplitude of Per2 oscillation by directly binding to the HIF-binding site located on the Per2 promoter. These results indicate that HIF1α may enhance the amplitude of the Per2 circadian rhythm.

  15. Circadian Disruption

    PubMed Central

    Voigt, Robin M.; Forsyth, Christopher B.; Keshavarzian, Ali

    2013-01-01

    Circadian rhythms are a prominent and critical feature of cells, tissues, organs, and behavior that help an organism function most efficiently and anticipate things such as food availability. Therefore, it is not surprising that disrupted circadian rhythmicity, a prominent feature of modern-day society, promotes the development and/or progression of a wide variety of diseases, including inflammatory, metabolic, and alcohol-associated disorders. This article will discuss the influence of interplay between alcohol consumption and circadian rhythmicity and how circadian rhythm disruption affects immune function and metabolism as well as potential epigenetic mechanisms that may be contributing to this phenomenon. PMID:24313168

  16. Mitogen and stress-activated protein kinase 1 (MSK1) modulates photic entrainment of the suprachiasmatic circadian clock

    PubMed Central

    Cao, Ruifeng; Butcher, Greg Q.; Karelina, Kate; Arthur, J. Simon C.; Obrietan, Karl

    2013-01-01

    The master circadian clock in mammals, the suprachiasmatic nucleus (SCN), is under the entraining influence of the external light cycle. At a mechanistic level, intracellular signaling via the p42/44 mitogen-activated protein kinase (MAPK) pathway appears to play a central role in light-evoked clock entrainment; however, the precise downstream mechanisms by which this pathway influences clock timing are not known. Within this context, we have previously reported that light stimulates activation of the MAPK effector mitogen stress activated kinase 1 (MSK1) in the SCN. In this study we utilized MSK1-/- mice to further investigate the potential role of MSK1 in circadian clock timing and entrainment. Locomotor activity analysis revealed that MSK1 null mice entrained to a 12h light/dark cycle and exhibited circadian free-running rhythms in constant darkness. Interestingly, the free running period in MSK1 null mice was significantly longer than WT control animals, and MSK1 null mice exhibited a significantly greater variance in activity onset. Further, MSK1 null mice exhibited a significant reduction in the phase delaying response to an early night light pulse (100 lux, 15 min), and, using an 8-hr phase-advancing “jet-lag” experimental paradigm MSK1 knockout animals exhibited a significantly delayed rate of re-entrainment. At the molecular level, early night light-evoked CREB phosphorylation, histone phosphorylation and Period1 gene expression were markedly attenuated in MSK1-/- animals relative to WT mice. Together, these data provide key new insights into the molecular mechanisms by which MSK1 affects the SCN clock. PMID:23127194

  17. Structural characterization of the circadian clock protein complex composed of KaiB and KaiC by inverse contrast-matching small-angle neutron scattering

    PubMed Central

    Sugiyama, Masaaki; Yagi, Hirokazu; Ishii, Kentaro; Porcar, Lionel; Martel, Anne; Oyama, Katsuaki; Noda, Masanori; Yunoki, Yasuhiro; Murakami, Reiko; Inoue, Rintaro; Sato, Nobuhiro; Oba, Yojiro; Terauchi, Kazuki; Uchiyama, Susumu; Kato, Koichi

    2016-01-01

    The molecular machinery of the cyanobacterial circadian clock consists of three proteins: KaiA, KaiB, and KaiC. Through interactions among the three Kai proteins, the phosphorylation states of KaiC generate circadian oscillations in vitro in the presence of ATP. Here, we characterized the complex formation between KaiB and KaiC using a phospho-mimicking mutant of KaiC, which had an aspartate substitution at the Ser431 phosphorylation site and exhibited optimal binding to KaiB. Mass-spectrometric titration data showed that the proteins formed a complex exclusively in a 6:6 stoichiometry, indicating that KaiB bound to the KaiC hexamer with strong positive cooperativity. The inverse contrast-matching technique of small-angle neutron scattering enabled selective observation of KaiB in complex with the KaiC mutant with partial deuteration. It revealed a disk-shaped arrangement of the KaiB subunits on the outer surface of the KaiC C1 ring, which also serves as the interaction site for SasA, a histidine kinase that operates as a clock-output protein in the regulation of circadian transcription. These data suggest that cooperatively binding KaiB competes with SasA with respect to interaction with KaiC, thereby promoting the synergistic release of this clock-output protein from the circadian oscillator complex. PMID:27752127

  18. PPAR{alpha} is a potential therapeutic target of drugs to treat circadian rhythm sleep disorders

    SciTech Connect

    Shirai, Hidenori; Oishi, Katsutaka; Kudo, Takashi; Shibata, Shigenobu; Ishida, Norio . E-mail: n.ishida@aist.go.jp

    2007-06-08

    Recent progress at the molecular level has revealed that nuclear receptors play an important role in the generation of mammalian circadian rhythms. To examine whether peroxisome proliferator-activated receptor alpha (PPAR{alpha}) is involved in the regulation of circadian behavioral rhythms in mammals, we evaluated the locomotor activity of mice administered with the hypolipidemic PPAR{alpha} ligand, bezafibrate. Circadian locomotor activity was phase-advanced about 3 h in mice given bezafibrate under light-dark (LD) conditions. Transfer from LD to constant darkness did not change the onset of activity in these mice, suggesting that bezafibrate advanced the phase of the endogenous clock. Surprisingly, bezafibrate also advanced the phase in mice with lesions of the suprachiasmatic nucleus (SCN; the central clock in mammals). The circadian expression of clock genes such as period2, BMAL1, and Rev-erb{alpha} was also phase-advanced in various tissues (cortex, liver, and fat) without affecting the SCN. Bezafibrate also phase-advanced the activity phase that is delayed in model mice with delayed sleep phase syndrome (DSPS) due to a Clock gene mutation. Our results indicated that PPAR{alpha} is involved in circadian clock control independently of the SCN and that PPAR{alpha} could be a potent target of drugs to treat circadian rhythm sleep disorders including DSPS.

  19. A PTH-responsive circadian clock operates in ex vivo mouse femur fracture healing site

    PubMed Central

    Kunimoto, Tatsuya; Okubo, Naoki; Minami, Yoichi; Fujiwara, Hiroyoshi; Hosokawa, Toshihiro; Asada, Maki; Oda, Ryo; Kubo, Toshikazu; Yagita, Kazuhiro

    2016-01-01

    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. PMID:26926165

  20. Overexpression of circadian clock protein cryptochrome (CRY) 1 alleviates sleep deprivation-induced vascular inflammation in a mouse model.

    PubMed

    Qin, Bing; Deng, Yunlong

    2015-01-01

    Disturbance of the circadian clock by sleep deprivation has been proposed to be involved in the regulation of inflammation. However, the underlying mechanism of circadian oscillator components in regulating the pro-inflammatory process during sleep deprivation remains poorly understood. Using a sleep deprivation mouse model, we showed here that sleep deprivation increased the expression of pro-inflammatory cytokines expression and decreased the expression of cryptochrome 1 (CRY1) in vascular endothelial cells. Furthermore, the adhesion molecules including intercellular adhesion molecule-1, vascular cell adhesion molecule-1 and E-selectin were elevated in vascular endothelial cells and the monocytes binding to vascular endothelial cells were also increased by sleep deprivation. Interestingly, overexpression of CRY1 in a mouse model by adenovirus vector significantly inhibited the expression of inflammatory cytokines and adhesion molecules, and NF-κB signal pathway activation, as well as the binding of monocytes to vascular endothelial cells. Using a luciferase reporter assay, we found that CRY1 could repress the transcriptional activity of nuclear factor (NF)-κB in vitro. Subsequently, we demonstrated that overexpression of CRY1 inhibited the basal concentration of cyclic adenosine monophosphate (cAMP), leading to decreased protein kinase A activity, which resulted in decreased phosphorylation of p65. Taken together, these results suggested that the overexpression of CRY1 inhibited sleep deprivation-induced vascular inflammation that might be associated with NF-κB and cAMP/PKA pathways.

  1. Structure of the frequency-interacting RNA helicase: a protein interaction hub for the circadian clock.

    PubMed

    Conrad, Karen S; Hurley, Jennifer M; Widom, Joanne; Ringelberg, Carol S; Loros, Jennifer J; Dunlap, Jay C; Crane, Brian R

    2016-08-01

    In the Neurospora crassa circadian clock, a protein complex of frequency (FRQ), casein kinase 1a (CK1a), and the FRQ-interacting RNA Helicase (FRH) rhythmically represses gene expression by the white-collar complex (WCC). FRH crystal structures in several conformations and bound to ADP/RNA reveal differences between FRH and the yeast homolog Mtr4 that clarify the distinct role of FRH in the clock. The FRQ-interacting region at the FRH N-terminus has variable structure in the absence of FRQ A known mutation that disrupts circadian rhythms (R806H) resides in a positively charged surface of the KOW domain, far removed from the helicase core. We show that changes to other similarly located residues modulate interactions with the WCC and FRQ A V142G substitution near the N-terminus also alters FRQ and WCC binding to FRH, but produces an unusual short clock period. These data support the assertion that FRH helicase activity does not play an essential role in the clock, but rather FRH acts to mediate contacts among FRQ, CK1a and the WCC through interactions involving its N-terminus and KOW module. PMID:27340124

  2. Circadian rhythms, the molecular clock, and skeletal muscle.

    PubMed

    Harfmann, Brianna D; Schroder, Elizabeth A; Esser, Karyn A

    2015-04-01

    Circadian rhythms are the approximate 24-h biological cycles that function to prepare an organism for daily environmental changes. They are driven by the molecular clock, a transcriptional:translational feedback mechanism that in mammals involves the core clock genes Bmal1, Clock, Per1/2, and Cry1/2. The molecular clock is present in virtually all cells of an organism. The central clock in the suprachiasmatic nucleus (SCN) has been well studied, but the clocks in the peripheral tissues, such as heart and skeletal muscle, have just begun to be investigated. Skeletal muscle is one of the largest organs in the body, comprising approximately 45% of total body mass. More than 2300 genes in skeletal muscle are expressed in a circadian pattern, and these genes participate in a wide range of functions, including myogenesis, transcription, and metabolism. The circadian rhythms of skeletal muscle can be entrained both indirectly through light input to the SCN and directly through time of feeding and activity. It is critical for the skeletal muscle molecular clock not only to be entrained to the environment but also to be in synchrony with rhythms of other tissues. When circadian rhythms are disrupted, the observed effects on skeletal muscle include fiber-type shifts, altered sarcomeric structure, reduced mitochondrial respiration, and impaired muscle function. Furthermore, there are detrimental effects on metabolic health, including impaired glucose tolerance and insulin sensitivity, which skeletal muscle likely contributes to considering it is a key metabolic tissue. These data indicate a critical role for skeletal muscle circadian rhythms for both muscle and systems health. Future research is needed to determine the mechanisms of molecular clock function in skeletal muscle, identify the means by which skeletal muscle entrainment occurs, and provide a stringent comparison of circadian gene expression across the diverse tissue system of skeletal muscle. PMID:25512305

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

    PubMed Central

    Harfmann, Brianna D.; Schroder, Elizabeth A.; Esser, Karyn A.

    2015-01-01

    Circadian rhythms are the approximate 24-h biological cycles that function to prepare an organism for daily environmental changes. They are driven by the molecular clock, a transcriptional:translational feedback mechanism that in mammals involves the core clock genes Bmal1, Clock, Per1/2, and Cry1/2. The molecular clock is present in virtually all cells of an organism. The central clock in the suprachiasmatic nucleus (SCN) has been well studied, but the clocks in the peripheral tissues, such as heart and skeletal muscle, have just begun to be investigated. Skeletal muscle is one of the largest organs in the body, comprising approximately 45% of total body mass. More than 2300 genes in skeletal muscle are expressed in a circadian pattern, and these genes participate in a wide range of functions, including myogenesis, transcription, and metabolism. The circadian rhythms of skeletal muscle can be entrained both indirectly through light input to the SCN and directly through time of feeding and activity. It is critical for the skeletal muscle molecular clock not only to be entrained to the environment but also to be in synchrony with rhythms of other tissues. When circadian rhythms are disrupted, the observed effects on skeletal muscle include fiber-type shifts, altered sarcomeric structure, reduced mitochondrial respiration, and impaired muscle function. Furthermore, there are detrimental effects on metabolic health, including impaired glucose tolerance and insulin sensitivity, which skeletal muscle likely contributes to considering it is a key metabolic tissue. These data indicate a critical role for skeletal muscle circadian rhythms for both muscle and systems health. Future research is needed to determine the mechanisms of molecular clock function in skeletal muscle, identify the means by which skeletal muscle entrainment occurs, and provide a stringent comparison of circadian gene expression across the diverse tissue system of skeletal muscle. PMID:25512305

  4. Circadian rhythms, the molecular clock, and skeletal muscle.

    PubMed

    Harfmann, Brianna D; Schroder, Elizabeth A; Esser, Karyn A

    2015-04-01

    Circadian rhythms are the approximate 24-h biological cycles that function to prepare an organism for daily environmental changes. They are driven by the molecular clock, a transcriptional:translational feedback mechanism that in mammals involves the core clock genes Bmal1, Clock, Per1/2, and Cry1/2. The molecular clock is present in virtually all cells of an organism. The central clock in the suprachiasmatic nucleus (SCN) has been well studied, but the clocks in the peripheral tissues, such as heart and skeletal muscle, have just begun to be investigated. Skeletal muscle is one of the largest organs in the body, comprising approximately 45% of total body mass. More than 2300 genes in skeletal muscle are expressed in a circadian pattern, and these genes participate in a wide range of functions, including myogenesis, transcription, and metabolism. The circadian rhythms of skeletal muscle can be entrained both indirectly through light input to the SCN and directly through time of feeding and activity. It is critical for the skeletal muscle molecular clock not only to be entrained to the environment but also to be in synchrony with rhythms of other tissues. When circadian rhythms are disrupted, the observed effects on skeletal muscle include fiber-type shifts, altered sarcomeric structure, reduced mitochondrial respiration, and impaired muscle function. Furthermore, there are detrimental effects on metabolic health, including impaired glucose tolerance and insulin sensitivity, which skeletal muscle likely contributes to considering it is a key metabolic tissue. These data indicate a critical role for skeletal muscle circadian rhythms for both muscle and systems health. Future research is needed to determine the mechanisms of molecular clock function in skeletal muscle, identify the means by which skeletal muscle entrainment occurs, and provide a stringent comparison of circadian gene expression across the diverse tissue system of skeletal muscle.

  5. Circadian systems biology in Metazoa.

    PubMed

    Lin, Li-Ling; Huang, Hsuan-Cheng; Juan, Hsueh-Fen

    2015-11-01

    Systems biology, which can be defined as integrative biology, comprises multistage processes that can be used to understand components of complex biological systems of living organisms and provides hierarchical information to decoding life. Using systems biology approaches such as genomics, transcriptomics and proteomics, it is now possible to delineate more complicated interactions between circadian control systems and diseases. The circadian rhythm is a multiscale phenomenon existing within the body that influences numerous physiological activities such as changes in gene expression, protein turnover, metabolism and human behavior. In this review, we describe the relationships between the circadian control system and its related genes or proteins, and circadian rhythm disorders in systems biology studies. To maintain and modulate circadian oscillation, cells possess elaborative feedback loops composed of circadian core proteins that regulate the expression of other genes through their transcriptional activities. The disruption of these rhythms has been reported to be associated with diseases such as arrhythmia, obesity, insulin resistance, carcinogenesis and disruptions in natural oscillations in the control of cell growth. This review demonstrates that lifestyle is considered as a fundamental factor that modifies circadian rhythm, and the development of dysfunctions and diseases could be regulated by an underlying expression network with multiple circadian-associated signals.

  6. Regulation of cAMP response element binding protein (CREB) binding in the mammalian clock pacemaker by light but not a circadian clock.

    PubMed

    Kako, K; Banasik, M; Lee, K; Ishida, N

    1997-02-01

    Mammalian circadian rhythms are considered to be regulated by a clock pacemaker located in the suprachiasmatic nuclei (SCN) of the hypothalamus. The molecular mechanism of entrainment and oscillation of circadian rhythm are not well understood but photic induction of immediate-early gene (IEG) expression in the SCN is thought to play a role. Here we show that under 12 h light:12 h dark (LD) condition, the cAMP response element binding protein (CREB) binding to cAMP responsive promoter element (CRE) of NMDAR1/zeta1 promoter region in the SCN is higher during the light than the dark by electro-mobility shift assay (EMSA). When animals are placed in constant dark, CREB DNA binding activity in the SCN is low and does not vary with circadian time when compared with cortex nuclear extract as a control. Most significantly, photic induction of CREB binding activity in the SCN occurs at all circadian times tested, indicating that CREB DNA binding in the SCN is not gated by the endogenous clock. These results implicate the role of CREB in photic neuronal signaling in the SCN and suggest that CREB DNA binding activities may not be regulated by a circadian clock. PMID:9030696

  7. 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

  8. Sleep Deprivation Influences Circadian Gene Expression in the Lateral Habenula.

    PubMed

    Zhang, Beilin; Gao, Yanxia; Li, Yang; Yang, Jing; Zhao, Hua

    2016-01-01

    Sleep is governed by homeostasis and the circadian clock. Clock genes play an important role in the generation and maintenance of circadian rhythms but are also involved in regulating sleep homeostasis. The lateral habenular nucleus (LHb) has been implicated in sleep-wake regulation, since LHb gene expression demonstrates circadian oscillation characteristics. This study focuses on the participation of LHb clock genes in regulating sleep homeostasis, as the nature of their involvement is unclear. In this study, we observed changes in sleep pattern following sleep deprivation in LHb-lesioned rats using EEG recording techniques. And then the changes of clock gene expression (Per1, Per2, and Bmal1) in the LHb after 6 hours of sleep deprivation were detected by using real-time quantitative PCR (qPCR). We found that sleep deprivation increased the length of Non-Rapid Eye Movement Sleep (NREMS) and decreased wakefulness. LHb-lesioning decreased the amplitude of reduced wake time and increased NREMS following sleep deprivation in rats. qPCR results demonstrated that Per2 expression was elevated after sleep deprivation, while the other two genes were unaffected. Following sleep recovery, Per2 expression was comparable to the control group. This study provides the basis for further research on the role of LHb Per2 gene in the regulation of sleep homeostasis. PMID:27413249

  9. Sleep Deprivation Influences Circadian Gene Expression in the Lateral Habenula

    PubMed Central

    Gao, Yanxia

    2016-01-01

    Sleep is governed by homeostasis and the circadian clock. Clock genes play an important role in the generation and maintenance of circadian rhythms but are also involved in regulating sleep homeostasis. The lateral habenular nucleus (LHb) has been implicated in sleep-wake regulation, since LHb gene expression demonstrates circadian oscillation characteristics. This study focuses on the participation of LHb clock genes in regulating sleep homeostasis, as the nature of their involvement is unclear. In this study, we observed changes in sleep pattern following sleep deprivation in LHb-lesioned rats using EEG recording techniques. And then the changes of clock gene expression (Per1, Per2, and Bmal1) in the LHb after 6 hours of sleep deprivation were detected by using real-time quantitative PCR (qPCR). We found that sleep deprivation increased the length of Non-Rapid Eye Movement Sleep (NREMS) and decreased wakefulness. LHb-lesioning decreased the amplitude of reduced wake time and increased NREMS following sleep deprivation in rats. qPCR results demonstrated that Per2 expression was elevated after sleep deprivation, while the other two genes were unaffected. Following sleep recovery, Per2 expression was comparable to the control group. This study provides the basis for further research on the role of LHb Per2 gene in the regulation of sleep homeostasis. PMID:27413249

  10. Circadian rhythms and memory formation: regulation by chromatin remodeling.

    PubMed

    Sahar, Saurabh; Sassone-Corsi, Paolo

    2012-01-01

    Epigenetic changes, such as DNA methylation or histone modification, can remodel the chromatin and regulate gene expression. Remodeling of chromatin provides an efficient mechanism of transducing signals, such as light or nutrient availability, to regulate gene expression. CLOCK:BMAL1 mediated activation of clock-controlled genes (CCGs) is coupled to circadian changes in histone modification at their promoters. Several chromatin modifiers, such as the deacetylases SIRT1 and HDAC3 or methyltransferase MLL1, have been shown to be recruited to the promoters of the CCGs in a circadian manner. Interestingly, the central element of the core clock machinery, the transcription factor CLOCK, also possesses histone acetyltransferase activity. Rhythmic expression of the CCGs is abolished in the absence of these chromatin modifiers. Recent research has demonstrated that chromatin remodeling is at the cross-roads of circadian rhythms and regulation of metabolism and aging. It would be of interest to identify if similar pathways exist in the epigenetic regulation of memory formation. PMID:22470318

  11. EFFECT OF SEASONAL CHANGES ON TESTICULAR MORPHOLOGY AND THE EXPRESSION OF CIRCADIAN CLOCK GENES IN JAPANESE WOOD MICE (APODEMUS SPECIOSUS).

    PubMed

    Akiyama, M; Takino, S; Sugano, Y; Yamada, T; Nakata, A; Miura, T; Fukumoto, M; Yamashiro, H

    2015-01-01

    This study aimed to determine the seasonality of reproduction throughout the year in Japanese wood mice (Apodemus speciosus). The effect of seasonal changes on testicular morphology and the periodic expression of circadian clock genes in the hypothalamus and testes of male individuals was evaluated. We also examined the morphology of the testes and caudae epididymides of male mice. In addition, RT-PCR analysis was carried out with mRNA extracted from the hypothalamus and testes to evaluate the expression of the circadian clock genes Clock, Bmal1, Per1, and Cry1. The complete induction of testicular activity was detected from February to April and from August to October, with testes weight increasing with the completion of spermatogenesis (reproductive season). From May to early June and from November to early January, testicular weight declined, the seminiferous tubules reduced in size, spermatogenesis was arrested, and sperm were not produced (non-reproductive season). From mid- June to July and mid-January, the re-induction of testicular activity for spermatogenesis was observed in the seminiferous tubules (transitional season). Out of the four examined genes, Cry1 had the highest expression level in both the hypothalamus and testes throughout the year, followed by Bmal1, Per1, and Clock. The expression of Bmal1 was significantly lower in the hypothalamus and testes during the transitional season compared to the reproductive and non-reproductive seasons. Cry1 transcript levels were also significantly lower in the hypothalamus and testes during the transitional season compared to the reproductive season. In conclusion, the results indicating changes in testicular morphology revealed annual reproductive, non-reproductive, and transmission periods in Japanese wood mice. When an increase in testicular activity was observed indicating the onset of the reproductive season, the mean day length was approximately 11–13 h. The expression of the circadian clock genes Bmal1

  12. Feeding period restriction alters the expression of peripheral circadian rhythm genes without changing body weight in mice.

    PubMed

    Jang, Hagoon; Lee, Gung; Kong, Jinuk; Choi, Goun; Park, Yoon Jeong; Kim, Jae Bum

    2012-01-01

    Accumulating evidence suggests that the circadian clock is closely associated with metabolic regulation. However, whether an impaired circadian clock is a direct cause of metabolic dysregulation such as body weight gain is not clearly understood. In this study, we demonstrate that body weight gain in mice is not significantly changed by restricting feeding period to daytime or nighttime. The expression of peripheral circadian clock genes was altered by feeding period restriction, while the expression of light-regulated hypothalamic circadian clock genes was unaffected by either a normal chow diet (NCD) or a high-fat diet (HFD). In the liver, the expression pattern of circadian clock genes, including Bmal1, Clock, and Per2, was changed by different feeding period restrictions. Moreover, the expression of lipogenic genes, gluconeogenic genes, and fatty acid oxidation-related genes in the liver was also altered by feeding period restriction. Given that feeding period restriction does not affect body weight gain with a NCD or HFD, it is likely that the amount of food consumed might be a crucial factor in determining body weight. Collectively, these data suggest that feeding period restriction modulates the expression of peripheral circadian clock genes, which is uncoupled from light-sensitive hypothalamic circadian clock genes.

  13. Regulation of MAPK/ERK Signaling and Photic Entrainment of the Suprachiasmatic Nucleus Circadian Clock by Raf Kinase Inhibitor Protein

    PubMed Central

    Antoun, Ghadi; Cannon, Pascale Bouchard; Cheng, Hai-Ying Mary

    2013-01-01

    Activation of the MAPK/ERK signaling cascade in the suprachiasmatic nucleus (SCN) is a key event that couples light to circadian clock entrainment. However, we do not fully understand the mechanisms that shape the properties of MAPK/ERK signaling in the SCN, and how these mechanisms may influence overt circadian rhythms. Here we show that Raf kinase inhibitor protein (RKIP) controls the kinetics of light-induced MAPK/ERK activity in the SCN and photic entrainment of behavioral rhythms. Light triggers robust phosphorylation of RKIP in the murine SCN and dissociation of RKIP and c-Raf. Overexpression of a nonphosphorylatable form of RKIP in the SCN of transgenic mice blocks light-induced ERK1/2 activation in the SCN and severely dampens light-induced phase delays in behavioral rhythms. Conversely, in RKIP knock-out (RKIP−/−) mice, light-induced ERK1/2 activity in the SCN is prolonged in the early and late subjective night, resulting in augmentation of the phase-delaying and -advancing effects of light. Reentrainment to an advancing light cycle was also accelerated in RKIP−/− mice. In relation to the molecular clockwork, genetic deletion of RKIP potentiated light-evoked PER1 and PER2 protein expression in the SCN in the early night. Additionally, RKIP−/− mice displayed enhanced transcriptional activation of mPeriod1 and the immediate early gene c-Fos in the SCN in response to a phase-delaying light pulse. Collectively, our data reveal an important role of RKIP in the regulation of MAPK/ERK signaling in the SCN and photic entrainment of the SCN clock. PMID:22492043

  14. Insulin effects on glucose tolerance, hypermetabolic response, and circadian-metabolic protein expression in a rat burn and disuse model

    PubMed Central

    Pidcoke, Heather F.; Baer, Lisa A.; Wu, Xiaowu; Wolf, Steven E.; Aden, James K.

    2014-01-01

    Insulin controls hyperglycemia after severe burns, and its use opposes the hypermetabolic response. The underlying molecular mechanisms are poorly understood, and previous research in this area has been limited because of the inadequacy of animal models to mimic the physiological effects seen in humans with burns. Using a recently published rat model that combines both burn and disuse components, we compare the effects of insulin treatment vs. vehicle on glucose tolerance, hypermetabolic response, muscle loss, and circadian-metabolic protein expression after burns. Male Sprague-Dawley rats were assigned to three groups: cage controls (n = 6); vehicle-treated burn and hindlimb unloading (VBH; n = 11), and insulin-treated burn and hindlimb unloading (IBH; n = 9). With the exception of cage controls, rats underwent a 40% total body surface area burn with hindlimb unloading, then IBH rats received 12 days of subcutaneous insulin injections (5 units·kg−1·day−1), and VBH rats received an equivalent dose of vehicle. Glucose tolerance testing was performed on day 14, after which blood and tissues were collected for analysis. Body mass loss was attenuated by insulin treatment (VBH = 265 ± 17 g vs. IBH = 283 ± 14 g, P = 0.016), and glucose clearance capacity was increased. Soleus and gastrocnemius muscle loss was decreased in the IBH group. Insulin receptor substrate-1, AKT, FOXO-1, caspase-3, and PER1 phosphorylation was altered by injury and disuse, with levels restored by insulin treatment in almost all cases. Insulin treatment after burn and during disuse attenuated the hypermetabolic response, increased glucose clearance, and normalized circadian-metabolic protein expression patterns. Therapies aimed at targeting downstream effectors may provide the beneficial effects of insulin without hypoglycemic risk. PMID:24760998

  15. 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.

  16. Circadian Regulation of Macronutrient Absorption.

    PubMed

    Hussain, M Mahmood; Pan, Xiaoyue

    2015-12-01

    Various intestinal functions exhibit circadian rhythmicity. Disruptions in these rhythms as in shift workers and transcontinental travelers are associated with intestinal discomfort. Circadian rhythms are controlled at the molecular level by core clock and clock-controlled genes. These clock genes are expressed in intestinal cells, suggesting that they might participate in the circadian regulation of intestinal functions. A major function of the intestine is nutrient absorption. Here, we will review absorption of proteins, carbohydrates, and lipids and circadian regulation of various transporters involved in their absorption. A better understanding of circadian regulation of intestinal absorption might help control several metabolic disorders and attenuate intestinal discomfort associated with disruptions in sleep-wake cycles.

  17. Obesity alters the peripheral circadian clock in the aorta and microcirculation

    PubMed Central

    Nernpermpisooth, Nitirut; Qiu, Shuiqing; Mintz, James D; Suvitayavat, Wisuda; Thirawarapan, Suwan; Rudic, Daniel R.; Fulton, David J.; Stepp, David W.

    2015-01-01

    Perturbation of daily rhythm increases cardiovascular risk. The aim of this study was to determine whether obesity alters circadian gene expression and microvascular function in lean mice and obese (db/db) mice. Mice were subjected to normal light-dark cycle or constant darkness (DD) to alter circadian rhythm. Metabolic parameters and microvascular vasoreactivity were evaluated. Array studies were conducted in the AM and PM cycles to assess the rhythmicity of the entire genomics. Rhythmic expression of specific clock genes (Bmal1, Clock, Npas2, Per1, Per2, and Cry1), clock output genes (dbp), and vascular relaxation-related genes (eNOS, GTPCH1) were assessed. Obesity was associated with metabolic dysfunction and impaired endothelial dilation in the microvasculature. Circadian rhythm of gene expression was suppressed 80% in both macro- and microcirculations of obese mice. Circadian disruption with DD increased fasting serum glucose and HbA1C in obese but not lean mice. Endothelium-dependent dilation was attenuated in obese mice and in lean mice subjected to DD. Rhythmic expression of per1 and dbp was depressed in obesity. Expression of eNOS expression was suppressed and GTPCH1 lost rhythmic expression both in obesity and by constant darkness. These results suggest that obesity reduces circadian gene expression in concert with impaired endothelial function. The causal relationship remains to be determined. PMID:25660131

  18. Negative reciprocal regulation between Sirt1 and Per2 modulates the circadian clock and aging

    PubMed Central

    Wang, Rui-Hong; Zhao, Tingrui; Cui, Kairong; Hu, Gangqing; Chen, Qiang; Chen, Weiping; Wang, Xin-Wei; Soto-Gutierrez, Alejandro; Zhao, Keji; Deng, Chu-Xia

    2016-01-01

    Sirtuin 1 (SIRT1) is involved in both aging and circadian-clock regulation, yet the link between the two processes in relation to SIRT1 function is not clear. Using Sirt1-deficient mice, we found that Sirt1 and Period 2 (Per2) constitute a reciprocal negative regulation loop that plays important roles in modulating hepatic circadian rhythmicity and aging. Sirt1-deficient mice exhibited profound premature aging and enhanced acetylation of histone H4 on lysine16 (H4K16) in the promoter of Per2, the latter of which leads to its overexpression; in turn, Per2 suppresses Sirt1 transcription through binding to the Sirt1 promoter at the Clock/Bmal1 site. This negative reciprocal relationship between SIRT1 and PER2 was also observed in human hepatocytes. We further demonstrated that the absence of Sirt1 or the ectopic overexpression of Per2 in the liver resulted in a dysregulated pace of the circadian rhythm. The similar circadian rhythm was also observed in aged wild type mice. The interplay between Sirt1 and Per2 modulates aging gene expression and circadian-clock maintenance. PMID:27346580

  19. Hepatic, duodenal, and colonic circadian clocks differ in their persistence under conditions of constant light and in their entrainment by restricted feeding.

    PubMed

    Polidarová, Lenka; Sládek, Martin; Soták, Matúš; Pácha, Jiří; Sumová, Alena

    2011-04-01

    Physiological functions of the gastrointestinal tract (GIT) are temporally controlled such that they exhibit circadian rhythms. The circadian rhythms are synchronized with the environmental light-dark cycle via signaling from the central circadian clock located in the suprachiasmatic nucleus (SCN) of the hypothalamus, and by food intake. The aim of the study was to determine the extent to which disturbance in the SCN signaling via prolonged exposure to constant light affects circadian rhythms in the liver, duodenum, and colon, as well as to determine whether and to what extent food intake can restore rhythmicity in individual parts of the GIT. Adult male rats were maintained in constant light (LL) for 30 days and fed ad libitum throughout the entire interval or exposed to a restricted feeding (RF) regime for the last 14 days in LL. Locomotor and feeding behaviors were recorded throughout the experiment. On the 30th day, daily expression profiles of clock genes (Per1, Per2, Rev-erbα, and Bmal1) and of clock-controlled genes (Wee1 and Dbp) were measured by real-time reverse transcriptase-polymerase chain reaction (RT-PCR) in the duodenum, colon, and liver. By the end of the LL exposure, rats fed ad libitum had completely lost their circadian rhythms in activity and food intake. Daily expression profiles of clock genes and clock-controlled genes in the GIT were impaired to an extent depending on the tissue and gene studied, but not completely abolished. In the liver and colon, exposure to LL abolished circadian rhythms in expression of Per1, Per2, Bmal1, and Wee1, whereas it impaired, but preserved, rhythms in expression of Rev-erbα and Dbp. In the duodenum, all but Wee1 expression rhythms were preserved. Restricted feeding restored the rhythms to a degree that varied with the tissue and gene studied. Whereas in the liver and duodenum the profiles of all clock genes and clock-controlled genes became rhythmic, in the colon only Per1, Bmal1, and Rev-erbα-but not Per2

  20. On the Role of Histamine Receptors in the Regulation of Circadian Rhythms

    PubMed Central

    Rozov, Stanislav V.; Porkka-Heiskanen, Tarja; Panula, Pertti

    2015-01-01

    Several lines of evidence suggest a regulatory role of histamine in circadian rhythms, but little is known about signaling pathways that would be involved in such a putative role. The aim of this study was to examine whether histamine mediates its effects on the circadian system through Hrh1 or Hrh3 receptors. We assessed both diurnal and free-running locomotor activity rhythms of Hrh1-/- and Hrh3-/- mice. We also determined the expression of Per1, Per2 and Bmal1 genes in the suprachiasmatic nuclei, several areas of the cerebral cortex and striatum under symmetric 24 h light-dark cycle at zeitgeber times 14 and 6 by using radioactive in situ hybridization. We found no differences between Hrh1-/- and wild type mice in the length, amplitude and mesor of diurnal and free-running activity rhythms as well as in expression of Per1, Per2 and Bmal1 genes in any of the examined brain structures. The amplitude of free-running activity rhythm of the Hrh3-/- mice was significantly flattened, whereas the expression of the clock genes in Hrh3-/- mice was similar to the wild type animals in all of the assessed brain structures. Therefore, the knockout of Hrh1 receptor had no effects on the circadian rhythm of spontaneous locomotion, and a knockout of Hrh3 receptor caused a substantial reduction of free-running activity rhythm amplitude, but none of these knockout models affected the expression patterns of the core clock genes in any of the studied brain structures. PMID:26660098

  1. The Liver Clock Controls Cholesterol Homeostasis through Trib1 Protein-mediated Regulation of PCSK9/Low Density Lipoprotein Receptor (LDLR) Axis.

    PubMed

    Ma, Di; Liu, Tongyu; Chang, Lin; Rui, Crystal; Xiao, Yuanyuan; Li, Siming; Hogenesch, John B; Chen, Y Eugene; Lin, Jiandie D

    2015-12-25

    Disruption of the body clock has been recognized as a risk factor for cardiovascular disease. How the circadian pacemaker interacts with the genetic factors associated with plasma lipid traits remains poorly understood. Recent genome-wide association studies have identified an expanding list of genetic variants that influence plasma cholesterol and triglyceride levels. Here we analyzed circadian regulation of lipid-associated candidate genes in the liver and identified two distinct groups exhibiting rhythmic and non-rhythmic patterns of expression during light-dark cycles. Liver-specific inactivation of Bmal1 led to elevated plasma LDL/VLDL cholesterol levels as a consequence of the disruption of the PCSK9/LDL receptor regulatory axis. Ablation of the liver clock perturbed diurnal regulation of lipid-associated genes in the liver and markedly reduced the expression of the non-rhythmically expressed gene Trib1. Adenovirus-mediated rescue of Trib1 expression lowered plasma PCSK9 levels, increased LDL receptor protein expression, and restored plasma cholesterol homeostasis in mice lacking a functional liver clock. These results illustrate an unexpected mechanism through which the biological clock regulates cholesterol homeostasis through its regulation of non-rhythmic genes in the liver.

  2. Prediction of the protein components of a putative Calanus finmarchicus (Crustacea, Copepoda) circadian signaling system using a de novo assembled transcriptome

    PubMed Central

    Christie, Andrew E.; Fontanilla, Tiana M.; Nesbit, Katherine T.; Lenz, Petra H.

    2013-01-01

    Diel vertical migration and seasonal diapause are critical life history events for the copepod Calanus finmarchicus. While much is known about these behaviors phenomenologically, little is known about their molecular underpinnings. Recent studies in insects suggest that some circadian genes/proteins also contribute to the establishment of seasonal diapause. Thus, it is possible that in Calanus these distinct timing regimes share some genetic components. To begin to address this possibility, we used the well-established Drosophila melanogaster circadian system as a reference for mining clock transcripts from a 200,000+ sequence Calanus transcriptome; the proteins encoded by the identified transcripts were also deduced and characterized. Sequences encoding homologs of the Drosophila core clock proteins CLOCK, CYCLE, PERIOD and TIMELESS were identified, as was one encoding CRYPTOCHROME 2, a core clock protein in ancestral insect systems, but absent in Drosophila. Calanus transcripts encoding proteins known to modulate the Drosophila core clock were also identified and characterized, e.g. CLOCKWORK ORANGE, DOUBLETIME, SHAGGY and VRILLE. Alignment and structural analyses of the deduced Calanus proteins with their Drosophila counterparts revealed extensive sequence conservation, particularly in functional domains. Interestingly, reverse BLAST analyses of these sequences against all arthropod proteins typically revealed non-Drosophila isoforms to be most similar to the Calanus queries. This, in combination with the presence of both CRYPTOCHROME 1 (a clock input pathway protein) and CRYPTOCHROME 2 in Calanus, suggests that the organization of the copepod circadian system is an ancestral one, more similar to that of insects like Danaus plexippus than to that of Drosophila. PMID:23727418

  3. A blue-violet laser irradiation stimulates bone nodule formation of mesenchymal stromal cells by the control of the circadian clock protein

    NASA Astrophysics Data System (ADS)

    Kushibiki, Toshihiro; Awazu, Kunio

    2007-02-01

    Mesenchymal stromal cells (MSCs) are multipotent cells, which are present in adult bone marrow, that can replicate as undifferentiated cells and that have the potential to differentiate to lineages of mesenchymal tissues, including bone, cartilage, fat, tendon, and muscle. Their rapid and selective differentiation should provide the potential of new therapeutic approaches for the restoration of damaged or diseased tissue. However, several fundamental questions must be answered before it will be feasible to usefully predict and control MSCs responses to exogenous cytokines or genes. In particular, a better understanding of how specific factor may alter the fate of differentiation of MSCs is needed. In recent reports, circadian clock protein controls osteogenesis in vitro and in vivo. Here we show that a stimulation of a blue-violet laser irradiation regulates the differentiation of mouse MSCs to osteoblasts by change of the localization of a circadian rhythm protein, mouse Cryptochrome 1 (mCRY1). We found that a blue laser irradiation accelerated osteogenesis of MSCs. After laser irradiation, mCRY1 protein was translocated from cytoplasm to nucleus and mCRY1 mRNA level was downregulated thereafter. These results indicate that mCRY1, a blue-violet-light receptor and a master regulator of circadian rhythm, plays important roles in the regulation of the differentiation of MSCs. Since the differentiation of MSCs was easily regulated only by a laser irradiation, the potential of new therapeutic approaches for the restoration of damaged or diseased tissue is anticipated. Furthermore, our results obtained in this study may prove an excellent opportunity to gain insights into cross-talk between circadian rhythms and bone formation.

  4. Altered circadian clock gene expression in patients with schizophrenia.

    PubMed

    Johansson, Anne-Sofie; Owe-Larsson, Björn; Hetta, Jerker; Lundkvist, Gabriella B

    2016-07-01

    Impaired circadian rhythmicity has been reported in several psychiatric disorders. Schizophrenia is commonly associated with aberrant sleep-wake cycles and insomnia. It is not known if schizophrenia is associated with disturbances in molecular rhythmicity. We cultured fibroblasts from skin samples obtained from patients with chronic schizophrenia and from healthy controls, respectively, and analyzed the circadian expression during 48h of the clock genes CLOCK, BMAL1, PER1, PER2, CRY1, CRY2, REV-ERBα and DBP. In fibroblasts obtained from patients with chronic schizophrenia, we found a loss of rhythmic expression of CRY1 and PER2 compared to cells from healthy controls. We also estimated the sleep quality in these patients and found that most of them suffered from poor sleep in comparison with the healthy controls. In another patient sample, we analyzed mononuclear blood cells from patients with schizophrenia experiencing their first episode of psychosis, and found decreased expression of CLOCK, PER2 and CRY1 compared to blood cells from healthy controls. These novel findings show disturbances in the molecular clock in schizophrenia and have important implications in our understanding of the aberrant rhythms reported in this disease. PMID:27132483

  5. Light at night alters daily patterns of cortisol and clock proteins in female Siberian hamsters.

    PubMed

    Bedrosian, T A; Galan, A; Vaughn, C A; Weil, Z M; Nelson, R J

    2013-06-01

    Humans and other organisms have adapted to a 24-h solar cycle in response to life on Earth. The rotation of the planet on its axis and its revolution around the sun cause predictable daily and seasonal patterns in day length. To successfully anticipate and adapt to these patterns in the environment, a variety of biological processes oscillate with a daily rhythm of approximately 24 h in length. These rhythms arise from hierarchally-coupled cellular clocks generated by positive and negative transcription factors of core circadian clock gene expression. From these endogenous cellular clocks, overt rhythms in activity and patterns in hormone secretion and other homeostatic processes emerge. These circadian rhythms in physiology and behaviour can be organised by a variety of cues, although they are most potently entrained by light. In recent history, there has been a major change from naturally-occurring light cycles set by the sun, to artificial and sometimes erratic light cycles determined by the use of electric lighting. Virtually every individual living in an industrialised country experiences light at night (LAN) but, despite its prevalence, the biological effects of such unnatural lighting have not been fully considered. Using female Siberian hamsters (Phodopus sungorus), we investigated the effects of chronic nightly exposure to dim light on daily rhythms in locomotor activity, serum cortisol concentrations and brain expression of circadian clock proteins (i.e. PER1, PER2, BMAL1). Although locomotor activity remained entrained to the light cycle, the diurnal fluctuation of cortisol concentrations was blunted and the expression patterns of clock proteins in the suprachiasmatic nucleus and hippocampus were altered. These results demonstrate that chronic exposure to dim LAN can dramatically affect fundamental cellular function and emergent physiology.

  6. Influence of torpor on cardiac expression of genes involved in the circadian clock and protein turnover in the Siberian hamster (Phodopus sungorus).

    PubMed

    Crawford, Fiona I J; Hodgkinson, Cassandra L; Ivanova, Elena; Logunova, Larisa B; Evans, Gary J; Steinlechner, Stephan; Loudon, Andrew S I

    2007-11-14

    The Siberian hamster exhibits the key winter adaptive strategy of daily torpor, during which metabolism and heart rate are slowed for a few hours and body temperature declines by up to 20 degrees C, allowing substantial energetic savings. Previous studies of hibernators in which temperature drops by >30 degrees C for many days to weeks have revealed decreased transcription and translation during hypometabolism and identified several key physiological pathways involved. Here we used a cDNA microarray to define cardiac transcript changes over the course of a daily torpor bout and return to normothermia, and we show that, in common with hibernators, a relatively small proportion of the transcriptome (<5%) exhibited altered expression over a torpor bout. Pathways exhibiting significantly altered gene expression included transcriptional regulation, RNA stability and translational control, globin regulation, and cardiomyocyte function. Remarkably, gene representatives of the entire ubiquitylation pathway were significantly altered over the torpor bout, implying a key role for cardiac protein turnover and translation during a low-temperature torpor bout. The circadian clock maintained rhythmic transcription during torpor. Quantitative PCR profiling of heart, liver, and lung and in situ hybridization studies of clock genes in the hypothalamic circadian clock in the suprachiasmatic nucleus revealed that many circadian regulated transcripts exhibited synchronous alteration in expression during arousal. Our data highlight the potential importance of genes involved in protein turnover as part of the adaptive strategy of low-temperature torpor in a seasonal mammal.

  7. Sleep Disturbance and Altered Expression of Circadian Clock Genes in Patients With Sudden Sensorineural Hearing Loss.

    PubMed

    Yang, Chao-Hui; Hwang, Chung-Feng; Lin, Pai-Mei; Chuang, Jiin-Haur; Hsu, Cheng-Ming; Lin, Sheng-Fung; Yang, Ming-Yu

    2015-07-01

    The cause of sudden sensorineural hearing loss (SSNHL) remains unclear and therefore it is often considered as idiopathic. Sleep disturbance has been linked to SSNHL and circadian rhythm disruption, but the link between circadian rhythm disruption and SSNHL has never been investigated.In this study, we surveyed the sleep quality of 38 patients with SSNHL using a simple insomnia sleep questionnaire. The expression of circadian clock genes in peripheral blood (PB) leukocytes from 38 patients with SSNHL and 71 healthy subjects was accessed using real-time quantitative reverse transcriptase-polymerase chain reaction and validated using immunocytochemical staining.We found that 61.8% of patients with SSNHL suffered from insomnia before the insult of hearing loss. Besides, significantly decreased expression of PER1, CRY1, CRY2, CLOCK, BMAL1, and CKlε was found in PB leukocytes of patients with SSNHL when compared with healthy subjects. SSNHL patients with vertigo had significantly lower expression of CRY1 and CKlε than patients without vertigo symptoms. Our results imply the association of sleep disturbance and disrupted circadian rhythm in SSNHL.

  8. 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

  9. Bioinformatics analysis of transcriptional regulation of circadian genes in rat liver

    PubMed Central

    2014-01-01

    Background The circadian clock is a critical regulator of biological functions controlling behavioral, physiological and biochemical processes. Because the liver is the primary regulator of metabolites within the mammalian body and the disruption of circadian rhythms in liver is associated with severe illness, circadian regulators would play a strong role in maintaining liver function. However, the regulatory structure that governs circadian dynamics within the liver at a transcriptional level remains unknown. To explore this aspect, we analyzed hepatic transcriptional dynamics in Sprague-Dawley rats over a period of 24 hours to assess the genome-wide responses. Results Using an unsupervised consensus clustering method, we identified four major gene expression clusters, corresponding to central carbon and nitrogen metabolism, membrane integrity, immune function, and DNA repair, all of which have dynamics which suggest regulation in a circadian manner. With the assumption that transcription factors (TFs) that are differentially expressed and contain CLOCK:BMAL1 binding sites on their proximal promoters are likely to be clock-controlled TFs, we were able to use promoter analysis to putatively identify additional clock-controlled TFs besides PARF and RORA families. These TFs are both functionally and temporally related to the clusters they regulate. Furthermore, we also identified significant sets of clock TFs that are potentially transcriptional regulators of gene clusters. Conclusions All together, we were able to propose a regulatory structure for circadian regulation which represents alternative paths for circadian control of different functions within the liver. Our prediction has been affirmed by functional and temporal analyses which are able to extend for similar studies. PMID:24666587

  10. 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

  11. NAD+-SIRT1 control of H3K4 trimethylation through circadian deacetylation of MLL1

    PubMed Central

    Aguilar-Arnal, Lorena; Katada, Sayako; Orozco-Solis, Ricardo

    2015-01-01

    The circadian clock controls the transcription of hundred genes through specific chromatin remodeling events. The histone methyltransferase Mixed-Lineage Leukemia 1 (MLL1) coordinates recruitment of CLOCK–BMAL1 activator complexes to chromatin, an event associated to cyclic H3K4 tri-methylation at circadian promoters. Remarkably, in mouse liver circadian H3K4me3 is modulated by SIRT1, a NAD+ dependent deacetylase involved in clock control. We show that mammalian MLL1 is acetylated at two conserved residues, K1130 and K1133. Notably, MLL1 acetylation is cyclic, controlled by the clock and by SIRT1, and impacts the methyltransferase activity of MLL1. Moreover, H3K4 methylation at clock-controlled gene promoters is influenced by pharmacological or genetic inactivation of SIRT1. Finally, MLL1 acetylation and H3K4me3 levels at circadian gene promoters depend on NAD+ circadian levels. These findings reveal a previously unappreciated regulatory pathway between energy metabolism and histone methylation. PMID:25751424

  12. Metabolic and Nontranscriptional Circadian Clocks: Eukaryotes

    PubMed Central

    Reddy, Akhilesh B.; Rey, Guillaume

    2016-01-01

    Circadian clocks are cellular timekeeping mechanisms that coordinate behavior and physiology around the 24-h day in most living organisms. Misalignment of an organism’s clock with its environment is associated with long-term adverse fitness consequences, as exemplified by the link between circadian disruption and various age-related diseases in humans. Current eukaryotic models of the circadian oscillator rely on transcription/translation feedback loop mechanisms, supplemented with accessory cytosolic loops that connect them to cellular physiology. However, there is mounting evidence questioning the absolute necessity of transcription-based oscillators for circadian rhythmicity, supported by the recent discovery of oxidation-reduction cycles of peroxiredoxin proteins, which persist even in the absence of transcription. A more fundamental mechanism based on metabolic cycles could thus underlie circadian transcriptional and cytosolic rhythms, thereby promoting circadian oscillations to integral properties of cellular metabolism. PMID:24606143

  13. Aberrant Development of the Suprachiasmatic Nucleus and Circadian Rhythms in Mice Lacking the Homeodomain Protein Six6

    PubMed Central

    Clark, Daniel D.; Gorman, Michael R.; Hatori, Megumi; Meadows, Jason D.; Panda, Satchidananda; Mellon, Pamela L.

    2013-01-01

    The suprachiasmatic nucleus (SCN) of the mammalian hypothalamus is the central pacemaker for peripheral and organismal circadian rhythms. The development of this hypothalamic structure depends on genetic programs throughout embryogenesis. We have investigated the role of the homeodomain transcription factor Six6 in the development of the SCN. We first showed that Six6 mRNA has circadian regulation in the mouse SCN. We then characterized the behavioral activity patterns of Six6-null mice under various photoperiod manipulations and stained their hypothalami using SCN-specific markers. Six6-null mice display abnormal patterns of circadian behavior indicative of SCN abnormalities. The ability of light exposure to reset rhythms correlates with the presence or absence of optic nerves, but all Six6-null mice show irregular rhythms. In contrast, wild-type mice with crushed optic nerves maintain regular rhythms regardless of light exposure. Using immunohistochemistry for arginine vasopressin (AVP), vasoactive intestinal polypeptide (VIP), and β-galactosidase, we demonstrated the lack of these SCN markers in all Six6- null mice regardless of the presence of optic nerve or partial circadian rhythms. Therefore, Six6 is required for the normal development of the SCN, and the Six6-null mouse can mount independent, although irregular, circadian rhythms despite the apparent absence of a histochemically defined SCN. PMID:23382588

  14. Circadian gene expression predicts patient response to neoadjuvant chemoradiation therapy for rectal cancer.

    PubMed

    Lu, Haijie; Chu, Qiqi; Xie, Guojiang; Han, Hao; Chen, Zheng; Xu, Benhua; Yue, Zhicao

    2015-01-01

    Preoperative neoadjuvant chemoradiation therapy may be useful in patients with operable rectal cancer, but treatment responses are variable. We examined whether expression levels of circadian clock genes could be used as biomarkers to predict treatment response. We retrospectively analyzed clinical data from 250 patients with rectal cancer, treated with neoadjuvant chemoradiation therapy in a single institute between 2011 and 2013. Gene expression analysis (RT-PCR) was performed in tissue samples from 20 patients showing pathological complete regression (pCR) and 20 showing non-pCR. The genes analyzed included six core clock genes (Clock, Per1, Per2, Cry1, Cry2 and Bmal1) and three downstream target genes (Wee1, Chk2 and c-Myc). Patient responses were analyzed through contrast-enhanced pelvic MRI and endorectal ultrasound, and verified by histological assessment. pCR was defined histologically as an absence of tumor cells. Among the 250 included patients, 70.8% showed regression of tumor size, and 18% showed pCR. Clock, Cry2 and Per2 expressions were significantly higher in the pCR group than in the non-pCR group (P<0.05), whereas Per1, Cry1 and Bmal1 expressions did not differ significantly between groups. Among the downstream genes involved in cell cycle regulation, c-Myc showed significantly higher expression in the pCR group (P<0.05), whereas Wee1 and Chk2 expression did not differ significantly between groups. Circadian genes are potential biomarkers for predicting whether a patient with rectal cancer would benefit from neoadjuvant chemoradiation therapy. PMID:26617816

  15. Circadian control of oscillations in mitochondrial rate-limiting enzymes and nutrient utilization by PERIOD proteins.

    PubMed

    Neufeld-Cohen, Adi; Robles, Maria S; Aviram, Rona; Manella, Gal; Adamovich, Yaarit; Ladeuix, Benjamin; Nir, Dana; Rousso-Noori, Liat; Kuperman, Yael; Golik, Marina; Mann, Matthias; Asher, Gad

    2016-03-22

    Mitochondria are major suppliers of cellular energy through nutrients oxidation. Little is known about the mechanisms that enable mitochondria to cope with changes in nutrient supply and energy demand that naturally occur throughout the day. To address this question, we applied MS-based quantitative proteomics on isolated mitochondria from mice killed throughout the day and identified extensive oscillations in the mitochondrial proteome. Remarkably, the majority of cycling mitochondrial proteins peaked during the early light phase. We found that rate-limiting mitochondrial enzymes that process lipids and carbohydrates accumulate in a diurnal manner and are dependent on the clock proteins PER1/2. In this conjuncture, we uncovered daily oscillations in mitochondrial respiration that peak during different times of the day in response to different nutrients. Notably, the diurnal regulation of mitochondrial respiration was blunted in mice lacking PER1/2 or on a high-fat diet. We propose that PERIOD proteins optimize mitochondrial metabolism to daily changes in energy supply/demand and thereby, serve as a rheostat for mitochondrial nutrient utilization. PMID:26862173

  16. Circadian control of oscillations in mitochondrial rate-limiting enzymes and nutrient utilization by PERIOD proteins

    PubMed Central

    Neufeld-Cohen, Adi; Robles, Maria S.; Aviram, Rona; Manella, Gal; Adamovich, Yaarit; Ladeuix, Benjamin; Nir, Dana; Rousso-Noori, Liat; Kuperman, Yael; Golik, Marina; Mann, Matthias; Asher, Gad

    2016-01-01

    Mitochondria are major suppliers of cellular energy through nutrients oxidation. Little is known about the mechanisms that enable mitochondria to cope with changes in nutrient supply and energy demand that naturally occur throughout the day. To address this question, we applied MS-based quantitative proteomics on isolated mitochondria from mice killed throughout the day and identified extensive oscillations in the mitochondrial proteome. Remarkably, the majority of cycling mitochondrial proteins peaked during the early light phase. We found that rate-limiting mitochondrial enzymes that process lipids and carbohydrates accumulate in a diurnal manner and are dependent on the clock proteins PER1/2. In this conjuncture, we uncovered daily oscillations in mitochondrial respiration that peak during different times of the day in response to different nutrients. Notably, the diurnal regulation of mitochondrial respiration was blunted in mice lacking PER1/2 or on a high-fat diet. We propose that PERIOD proteins optimize mitochondrial metabolism to daily changes in energy supply/demand and thereby, serve as a rheostat for mitochondrial nutrient utilization. PMID:26862173

  17. Insulin Restores an Altered Corneal Epithelium Circadian Rhythm in Mice with Streptozotocin-induced Type 1 Diabetes.

    PubMed

    Song, Fang; Xue, Yunxia; Dong, Dong; Liu, Jun; Fu, Ting; Xiao, Chengju; Wang, Hanqing; Lin, Cuipei; Liu, Peng; Zhong, Jiajun; Yang, Yabing; Wang, Zhaorui; Pan, Hongwei; Chen, Jiansu; Li, Yangqiu; Cai, Dongqing; Li, Zhijie

    2016-01-01

    The mechanisms of corneal epithelial lesions and delayed wound repair, as well as their association with diabetes mellitus, are critical issues for clinical ophthalmologists. To test whether the diabetic condition alters the circadian rhythm in a mouse cornea and whether insulin can synchronise the corneal clock, we studied the effects of streptozotocin-induced diabetes on the mitosis of epithelial cells, the recruitment of leukocytes to the cornea, and the expression of main core clock genes (Clock, Bmal1, Per2, Cry1, and Rev-erbα) in the corneal epithelium. We also assessed the possible effect of insulin on these modifications. Diabetes downregulated Clock, Bmal1, and Per2 expression, upregulated Cry1 and Rev-erbα expression, reduced corneal epithelial mitosis, and increased leukocyte (neutrophils and γδ T-cells) recruitment to the cornea. Early treatments with insulin partially restored the altered rhythmicity in the diabetic cornea. In conclusion, insulin-dependent diabetes altered the normal rhythmicity of the cornea, and insulin administration had a beneficial effect on restoring normal rhythmicity in the diabetic cornea. PMID:27611469

  18. Insulin Restores an Altered Corneal Epithelium Circadian Rhythm in Mice with Streptozotocin-induced Type 1 Diabetes

    PubMed Central

    Song, Fang; Xue, Yunxia; Dong, Dong; Liu, Jun; Fu, Ting; Xiao, Chengju; Wang, Hanqing; Lin, Cuipei; Liu, Peng; Zhong, Jiajun; Yang, Yabing; Wang, Zhaorui; Pan, Hongwei; Chen, Jiansu; Li, Yangqiu; Cai, Dongqing; Li, Zhijie

    2016-01-01

    The mechanisms of corneal epithelial lesions and delayed wound repair, as well as their association with diabetes mellitus, are critical issues for clinical ophthalmologists. To test whether the diabetic condition alters the circadian rhythm in a mouse cornea and whether insulin can synchronise the corneal clock, we studied the effects of streptozotocin-induced diabetes on the mitosis of epithelial cells, the recruitment of leukocytes to the cornea, and the expression of main core clock genes (Clock, Bmal1, Per2, Cry1, and Rev-erbα) in the corneal epithelium. We also assessed the possible effect of insulin on these modifications. Diabetes downregulated Clock, Bmal1, and Per2 expression, upregulated Cry1 and Rev-erbα expression, reduced corneal epithelial mitosis, and increased leukocyte (neutrophils and γδ T-cells) recruitment to the cornea. Early treatments with insulin partially restored the altered rhythmicity in the diabetic cornea. In conclusion, insulin-dependent diabetes altered the normal rhythmicity of the cornea, and insulin administration had a beneficial effect on restoring normal rhythmicity in the diabetic cornea. PMID:27611469

  19. Daily restricted feeding resets the circadian clock in the suprachiasmatic nucleus of CS mice.

    PubMed

    Abe, Hiroshi; Honma, Sato; Honma, Ken-Ichi

    2007-01-01

    Circadian rhythms in clock gene expressions in the suprachiasmatic nucleus (SCN) of CS mice and C57BL/6J mice were measured under a daily restricted feeding (RF) schedule in continuous darkness (DD), and entrainment of the SCN circadian pacemaker to RF was examined. After 2-3 wk under a light-dark cycle with free access to food, animals were released into DD and fed for 3 h at a fixed time of day for 3-4 wk. Subsequently, they returned to having free access to food for 2-3 wk. In CS mice, wheel-running rhythms entrained to RF with a stable phase relationship between the activity onset and feeding time, and the rhythms started to free run from the feeding time after the termination of RF. mPer1, mPer2, and mBMAL1 mRNA rhythms in the SCN showed a fixed phase relationship with feeding time, indicating that the circadian pacemaker in the SCN entrained to RF. On the other hand, in C57BL/6J mice, wheel-running rhythms free ran under RF, and clock gene expression rhythms in the SCN showed a stable phase relation not to feeding time but to the behavioral rhythms, indicating that the circadian pacemaker in the SCN did not entrain. These results indicate that the SCN circadian pacemaker of CS mice is entrainable to RF under DD and suggest that CS mice have a circadian clock system that can be reset by a signal associated with feeding time.

  20. Circadian regulation of electrolyte absorption in the rat colon.

    PubMed

    Soták, M; Polidarová, L; Musílková, J; Hock, M; Sumová, A; Pácha, J

    2011-12-01

    The intestinal transport of nutrients exhibits distinct diurnal rhythmicity, and the enterocytes harbor a circadian clock. However, temporal regulation of the genes involved in colonic ion transport, i.e., ion transporters and channels operating in absorption and secretion, remains poorly understood. To address this issue, we assessed the 24-h profiles of expression of genes encoding the sodium pump (subunits Atp1a1 and Atp1b1), channels (α-, β-, and γ-subunits of Enac and Cftr), transporters (Dra, Ae1, Nkcc1, Kcc1, and Nhe3), and the Na(+)/H(+) exchanger (NHE) regulatory factor (Nherf1) in rat colonic mucosa. Furthermore, we investigated temporal changes in the spatial localization of the clock genes Per1, Per2, and Bmal1 and the genes encoding ion transporters and channels along the crypt axis. In rats fed ad libitum, the expression of Atp1a1, γEnac, Dra, Ae1, Nhe3, and Nherf1 showed circadian variation with maximal expression at circadian time 12, i.e., at the beginning of the subjective night. The peak γEnac expression coincided with the rise in plasma aldosterone. Restricted feeding phase advanced the expression of Dra, Ae1, Nherf, and γEnac and decreased expression of Atp1a1. The genes Atp1b1, Cftr, αEnac, βEnac, Nkcc1, and Kcc1 did not show any diurnal variations in mRNA levels. A low-salt diet upregulated the expression of βEnac and γEnac during the subjective night but did not affect expression of αEnac. Similarly, colonic electrogenic Na(+) transport was much higher during the subjective night than the subjective day. These findings indicate that the transporters and channels operating in NaCl absorption undergo diurnal regulation and suggest a role of an intestinal clock in the coordination of colonic NaCl absorption.

  1. Circadian light-input pathways in Drosophila.

    PubMed

    Yoshii, Taishi; Hermann-Luibl, Christiane; Helfrich-Förster, Charlotte

    2016-01-01

    Light is the most important environmental cue to entrain the circadian clock in most animals. In the fruit fly Drosophila melanogaster, the light entrainment mechanisms of the clock have been well-studied. The Drosophila brain contains approximately 150 neurons that rhythmically express circadian clock genes. These neurons are called "clock neurons" and control behavioral activity rhythms. Many clock neurons express the Cryptochrome (CRY) protein, which is sensitive to UV and blue light, and thus enables clock neurons deep in the brain to directly perceive light. In addition to the CRY protein, external photoreceptors in the Drosophila eyes play an important role in circadian light-input pathways. Recent studies have provided new insights into the mechanisms that integrate these light inputs into the circadian network of the brain. In this review, we will summarize the current knowledge on the light entrainment pathways in the Drosophila circadian clock. PMID:27066180

  2. Cold-Induced Cysts of the Photosynthetic Dinoflagellate Lingulodinium polyedrum Have an Arrested Circadian Bioluminescence Rhythm and Lower Levels of Protein Phosphorylation1[C][W

    PubMed Central

    Roy, Sougata; Letourneau, Louis; Morse, David

    2014-01-01

    Dinoflagellates are microscopic, eukaryotic, and primarily marine plankton. Temporary cyst formation is a well-known physiological response of dinoflagellate cells to environmental stresses. However, the molecular underpinnings of cold-induced cyst physiology have never been described. Cultures of the photosynthetic dinoflagellate Lingulodinium polyedrum readily form temporary cysts when placed at low (8°C ± 1°C) temperature and excyst to form normal motile cells following a return to normal temperature (18°C ± 1°C). The normal circadian bioluminescence rhythm and the expected changes in Luciferin Binding Protein abundance were arrested in L. polyedrum cysts. Furthermore, after excystment, the bioluminescence rhythm initiates at a time corresponding to zeitgeber 12, independent of the time when the cells encysted. Phosphoprotein staining after two-dimensional polyacrylamide gel electrophoresis, as well as column-based phosphoprotein enrichment followed by liquid chromatography tandem mass spectrometry, showed cyst proteins are hypophosphorylated when compared with those from motile cells, with the most marked decreases found for predicted Casein Kinase2 target sites. In contrast to the phosphoproteome, the cyst proteome is not markedly different from motile cells, as assessed by two-dimensional polyacrylamide gel electrophoresis. In addition to changes in the phosphoproteome, RNA sequencing revealed that cysts show a significant decrease in the levels of 132 RNAs. Of the 42 RNAs that were identified by sequence analysis, 21 correspond to plastid-encoded gene products and 11 to nuclear-encoded cell wall/plasma membrane components. Our data are consistent with a model in which the highly reduced metabolism in cysts is achieved primarily by alterations in the phosphoproteome. The stalling of the circadian rhythm suggests temporary cysts may provide an interesting model to address the circadian system of dinoflagellates. PMID:24335505

  3. Influence of photoperiodic history on clock genes and the circadian pacemaker in the rat retina.

    PubMed

    Rohleder, Nils; Langer, Christina; Maus, Christian; Spiwoks-Becker, Isabella; Emser, Angela; Engel, Lydia; Spessert, Rainer

    2006-01-01

    The influence of seasonal lighting conditions on expression of clock genes and the circadian pacemaker was investigated in the rat retina. For this purpose, the 24-h profiles of nine clock genes (bmal1, clock, per1, per2, per3, dec1, dec2, cry1 and cry 2) and the arylalkylamine N-acetyltransferase gene as an indicator of the circadian pacemaker output were compared between light-dark periods of 8 : 16 and 16 : 8 h. The photoperiod influenced the daily patterns of the amount of transcript for per1, per3, dec2 and arylalkylamine N-acetyltransferase. This indicates that photoperiodic information modulates clock gene expression in addition to the circadian pacemaker of the retina. Under constant darkness, photoperiod-dependent changes in the daily profile of the level of transcript persisted for the arylalkylamine N-acetyltransferase gene but not for any of the clock genes. Hence, quantitative expression of each clock gene is influenced by the photoperiod only under the acute light-dark cycle, whereas the pacemaker is capable of storing photoperiodic information from past cycles.

  4. Altered circadian rhythm and metabolic gene profile in rats subjected to advanced light phase shifts.

    PubMed

    Herrero, Laura; Valcarcel, Lorea; da Silva, Crhistiane Andressa; Albert, Nerea; Diez-Noguera, Antoni; Cambras, Trinitat; Serra, Dolors

    2015-01-01

    The circadian clock regulates metabolic homeostasis and its disruption predisposes to obesity and other metabolic diseases. However, the effect of phase shifts on metabolism is not completely understood. We examined whether alterations in the circadian rhythm caused by phase shifts induce metabolic changes in crucial genes that would predispose to obesity. Three-month-old rats were maintained on a standard diet under lighting conditions with chronic phase shifts consisting of advances, delays or advances plus delays. Serum leptin, insulin and glucose levels decreased only in rats subjected to advances. The expression of the clock gene Bmal 1 increased in the hypothalamus, white adipose tissue (WAT), brown adipose tissue (BAT) and liver of the advanced group compared to control rats. The advanced group showed an increase in hypothalamic AgRP and NPY mRNA, and their lipid metabolism gene profile was altered in liver, WAT and BAT. WAT showed an increase in inflammation and ER stress and brown adipocytes suffered a brown-to-white transformation and decreased UCP-1 expression. Our results indicate that chronic phase advances lead to significant changes in neuropeptides, lipid metabolism, inflammation and ER stress gene profile in metabolically relevant tissues such as the hypothalamus, liver, WAT and BAT. This highlights a link between alteration of the circadian rhythm and metabolism at the transcriptional level.

  5. Altered Circadian Rhythm and Metabolic Gene Profile in Rats Subjected to Advanced Light Phase Shifts

    PubMed Central

    Herrero, Laura; Valcarcel, Lorea; da Silva, Crhistiane Andressa; Albert, Nerea; Diez-Noguera, Antoni; Cambras, Trinitat; Serra, Dolors

    2015-01-01

    The circadian clock regulates metabolic homeostasis and its disruption predisposes to obesity and other metabolic diseases. However, the effect of phase shifts on metabolism is not completely understood. We examined whether alterations in the circadian rhythm caused by phase shifts induce metabolic changes in crucial genes that would predispose to obesity. Three-month-old rats were maintained on a standard diet under lighting conditions with chronic phase shifts consisting of advances, delays or advances plus delays. Serum leptin, insulin and glucose levels decreased only in rats subjected to advances. The expression of the clock gene Bmal 1 increased in the hypothalamus, white adipose tissue (WAT), brown adipose tissue (BAT) and liver of the advanced group compared to control rats. The advanced group showed an increase in hypothalamic AgRP and NPY mRNA, and their lipid metabolism gene profile was altered in liver, WAT and BAT. WAT showed an increase in inflammation and ER stress and brown adipocytes suffered a brown-to-white transformation and decreased UCP-1 expression. Our results indicate that chronic phase advances lead to significant changes in neuropeptides, lipid metabolism, inflammation and ER stress gene profile in metabolically relevant tissues such as the hypothalamus, liver, WAT and BAT. This highlights a link between alteration of the circadian rhythm and metabolism at the transcriptional level. PMID:25837425

  6. The suprachiasmatic nuclei are involved in determining circadian rhythms during restricted feeding.

    PubMed

    Froy, O; Chapnik, N; Miskin, R

    2008-09-01

    The circadian clock in the suprachiasmatic nuclei (SCN) responds to light and regulates peripheral circadian rhythms. Feeding regimens also reset the clock, so that time-restricted feeding (RF) dictates rhythms in peripheral tissues, whereas calorie restriction (CR) affects the SCN clock. To better understand the influence of RF vs. CR on circadian rhythms, we took advantage of the transgenic alphaMUPA mice that exhibit spontaneously reduced eating, and can serve as a model for CR under ad libitum feeding, and a model for temporal CR under RF compared with wild type (WT) mice. Our results show that RF advanced and generally increased the amplitude of clock gene expression in the liver under LD in both mouse types. However, under disruptive light conditions, RF resulted in a different clock gene phase in WT mice compared with alphaMUPA mice, suggesting a role for the reduced calories in resetting the SCN that led to the change of phase in alphaMUPA mice. Comparison of the RF regimen in the two lighting conditions in WT mice revealed that mPer1, mClock, and mBmal1 increased, whereas mPer2 decreased in amplitude under ultradian light in WT mice, suggesting a role for the SCN in determining clock gene expression in the periphery during RF. In summary, herein we reinforce a role for calorie restriction in resetting the SCN clock, and unravel a role for the SCN in determining peripheral rhythms under RF.

  7. Early Appearance of Nonvisual and Circadian Markers in the Developing Inner Retinal Cells of Chicken

    PubMed Central

    Díaz, Nicolás M.; Morera, Luis P.; Verra, Daniela M.; Contin, María A.; Guido, Mario E.

    2014-01-01

    The retina is a key component of the vertebrate circadian system; it is responsible for detecting and transmitting the environmental illumination conditions (day/night cycles) to the brain that synchronize the circadian clock located in the suprachiasmatic nucleus (SCN). For this, retinal ganglion cells (RGCs) project to the SCN and other nonvisual areas. In the chicken, intrinsically photosensitive RGCs (ipRGCs) expressing the photopigment melanopsin (Opn4) transmit photic information and regulate diverse nonvisual tasks. In nonmammalian vertebrates, two genes encode Opn4: the Xenopus (Opn4x) and the mammalian (Opn4m) orthologs. RGCs express both Opn4 genes but are not the only inner retinal cells expressing Opn4x: horizontal cells (HCs) also do so. Here, we further characterize primary cultures of both populations of inner retinal cells (RGCs and HCs) expressing Opn4x. The expression of this nonvisual photopigment, as well as that for different circadian markers such as the clock genes Bmal1, Clock, Per2, and Cry1, and the key melatonin synthesizing enzyme, arylalkylamine N-acetyltransferase (AA-NAT), appears very early in development in both cell populations. The results clearly suggest that nonvisual Opn4 photoreceptors and endogenous clocks converge all together in these inner retinal cells at early developmental stages. PMID:24977155

  8. Disruption of the circadian clock due to the Clock mutation has discrete effects on aging and carcinogenesis

    PubMed Central

    Antoch, Marina P.; Gorbacheva, Victoria Y.; Vykhovanets, Olena; Toshkov, Illia A.; Kondratov, Roman V.; Kondratova, Anna A.; Lee, Choogon; Nikitin, Alexander Yu.

    2009-01-01

    The mammalian circadian system has been implicated in the regulation of various biological processes including those involved in genotoxic stress responses and tumor suppression. Here we report that mice with the functional deficiency in circadian transcription factor CLOCK (Clock/Clock mutant mice) do not display predisposition to tumor formation both during their normal lifespan or when challenged by γ-radiation. This phenotype is consistent with high apoptotic and low proliferation rate in lymphoid tissues of Clock mutant mice and is supported by the gene expression profiling of a number of apoptosis and cell cycle-related genes, as well as by growth inhibition of cells with CLOCK downregulation. At the same time, Clock mutant mice respond to low-dose irradiation by accelerating their aging program, and develop phenotypes that are reminiscent of those in Bmal1-deficient mice. Taken together, our results demonstrate the dichotomy in biological consequences of the disruption of the circadian clock with respect to ageing and cancer. They also highlight the existence of a complex interconnection between ageing, carcinogenesis and individual components of the circadian clock machinery. PMID:18418054

  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. Circadian Clocks: Unexpected Biochemical Cogs

    PubMed Central

    Mori, Tetsuya; Mchaourab, Hassane; Johnson, Carl Hirschie

    2015-01-01

    A circadian oscillation can be reconstituted in vitro from three proteins that cycles with a period of ~24 h. Two recent studies provide surprising biochemical answers to why this remarkable oscillator has such a long time constant and how it can switch effortlessly between alternating enzymatic modes. PMID:26439342

  11. Circadian oscillations of cytosolic and chloroplastic free calcium in plants

    NASA Technical Reports Server (NTRS)

    Johnson, C. H.; Knight, M. R.; Kondo, T.; Masson, P.; Sedbrook, J.; Haley, A.; Trewavas, A.

    1995-01-01

    Tobacco and Arabidopsis plants, expressing a transgene for the calcium-sensitive luminescent protein apoaequorin, revealed circadian oscillations in free cytosolic calcium that can be phase-shifted by light-dark signals. When apoaequorin was targeted to the chloroplast, circadian chloroplast calcium rhythms were likewise observed after transfer of the seedlings to constant darkness. Circadian oscillations in free calcium concentrations can be expected to control many calcium-dependent enzymes and processes accounting for circadian outputs. Regulation of calcium flux is therefore fundamental to the organization of circadian systems.

  12. Chronic mild stress alters circadian expressions of molecular clock genes in the liver.

    PubMed

    Takahashi, Kei; Yamada, Tetsuya; Tsukita, Sohei; Kaneko, Keizo; Shirai, Yuta; Munakata, Yuichiro; Ishigaki, Yasushi; Imai, Junta; Uno, Kenji; Hasegawa, Yutaka; Sawada, Shojiro; Oka, Yoshitomo; Katagiri, Hideki

    2013-02-01

    Chronic stress is well known to affect metabolic regulation. However, molecular mechanisms interconnecting stress response systems and metabolic regulations have yet to be elucidated. Various physiological processes, including glucose/lipid metabolism, are regulated by the circadian clock, and core clock gene dysregulation reportedly leads to metabolic disorders. Glucocorticoids, acting as end-effectors of the hypothalamus-pituitary-adrenal (HPA) axis, entrain the circadian rhythms of peripheral organs, including the liver, by phase-shifting core clock gene expressions. Therefore, we examined whether chronic stress affects circadian expressions of core clock genes and metabolism-related genes in the liver using the chronic mild stress (CMS) procedure. In BALB/c mice, CMS elevated and phase-shifted serum corticosterone levels, indicating overactivation of the HPA axis. The rhythmic expressions of core clock genes, e.g., Clock, Npas2, Bmal1, Per1, and Cry1, were altered in the liver while being completely preserved in the hypothalamic suprachiasmatic nuculeus (SCN), suggesting that the SCN is not involved in alterations in hepatic core clock gene expressions. In addition, circadian patterns of glucose and lipid metabolism-related genes, e.g., peroxisome proliferator activated receptor (Ppar) α, Pparγ-1, Pparγ-coactivator-1α, and phosphoenolepyruvate carboxykinase, were also disturbed by CMS. In contrast, in C57BL/6 mice, the same CMS procedure altered neither serum corticosterone levels nor rhythmic expressions of hepatic core clock genes and metabolism-related genes. Thus, chronic stress can interfere with the circadian expressions of both core clock genes and metabolism-related genes in the liver possibly involving HPA axis overactivation. This mechanism might contribute to metabolic disorders in stressful modern societies.

  13. Circadian rhythm sleep disorders.

    PubMed

    Zhu, Lirong; Zee, Phyllis C

    2012-11-01

    There have been remarkable advances in our understanding of the molecular, cellular, and physiologic mechanisms underlying the regulation of circadian rhythms, and of the impact of circadian dysfunction on health and disease. This information has transformed our understanding of the effect of circadian rhythm sleep disorders (CRSD) on health, performance, and safety. CRSDs are caused by alterations of the central circadian timekeeping system, or a misalignment of the endogenous circadian rhythm and the external environment. This article reviews circadian biology and discusses the pathophysiology, clinical features, diagnosis, and treatment of the most commonly encountered CRSDs in clinical practice.

  14. Circadian regulation of chloroplasts.

    PubMed

    Atkins, Kelly A; Dodd, Antony N

    2014-10-01

    Circadian rhythms produce a biological measure of time that increases plant performance. The mechanisms that underlie this increase in productivity require investigation to provide information that will underpin future crop improvement. There is a growing body of evidence that a sophisticated signalling network interconnects the circadian oscillator and chloroplasts. We consider this in the context of circadian signalling to chloroplasts and the relationship between retrograde signalling and circadian regulation. We place circadian signalling to chloroplasts by sigma factors within an evolutionary context. We describe selected recent developments in the integration of light and circadian signals that control chloroplast gene expression.

  15. Circadian Rhythm Sleep Disorders

    PubMed Central

    Zhu, Lirong; Zee, Phyllis C.

    2012-01-01

    There have been remarkable advances in our understanding of the molecular, cellular and physiological mechanisms underlying the regulation of circadian rhythms, as well as the impact of circadian dysfunction on health and disease. This information has transformed our understanding of the effect of circadian rhythm sleep disorders (CRSD) on health, performance and safety. CRSDs are caused by alterations of the central circadian time-keeping system, or a misalignment of the endogenous circadian rhythm and the external environment. In this section, we provide a review of circadian biology and discuss the pathophysiology, clinical features, diagnosis, and treatment of the most commonly encountered CRSDs in clinical practice. PMID:23099133

  16. Circadian regulators of intestinal lipid absorption.

    PubMed

    Hussain, M Mahmood; Pan, Xiaoyue

    2015-04-01

    Among all the metabolites present in the plasma, lipids, mainly triacylglycerol and diacylglycerol, show extensive circadian rhythms. These lipids are transported in the plasma as part of lipoproteins. Lipoproteins are synthesized primarily in the liver and intestine and their production exhibits circadian rhythmicity. Studies have shown that various proteins involved in lipid absorption and lipoprotein biosynthesis show circadian expression. Further, intestinal epithelial cells express circadian clock genes and these genes might control circadian expression of different proteins involved in intestinal lipid absorption. Intestinal circadian clock genes are synchronized by signals emanating from the suprachiasmatic nuclei that constitute a master clock and from signals coming from other environmental factors, such as food availability. Disruptions in central clock, as happens due to disruptions in the sleep/wake cycle, affect intestinal function. Similarly, irregularities in temporal food intake affect intestinal function. These changes predispose individuals to various metabolic disorders, such as metabolic syndrome, obesity, diabetes, and atherosclerosis. Here, we summarize how circadian rhythms regulate microsomal triglyceride transfer protein, apoAIV, and nocturnin to affect diurnal regulation of lipid absorption.

  17. New models for circadian systems in microorganisms.

    PubMed

    Lakin-Thomas, Patricia L

    2006-06-01

    Microorganisms provide important model systems for studying circadian rhythms, and they are overturning established ideas about the molecular mechanisms of rhythmicity. The transcription/translation feedback model that has been accepted as the basis of circadian clock mechanisms in eukaryotes does not account for old data from the alga Acetabularia demonstrating that transcription is not required for rhythmicity. Moreover, new results showing in vitro rhythmicity of KaiC protein phosphorylation in the cyanobacterium Synechococcus, and rhythmicity in strains of the fungus Neurospora carrying clock gene null mutations, require new ways of looking at circadian systems.

  18. Circadian rhythms, alcohol and gut interactions

    PubMed Central

    Forsyth, Christopher B.; Voigt, Rbin M.; Burgess, Helen J.; Swanson, Garth R.; Keshavarzian, Ali

    2015-01-01

    The circadian clock establishes rhythms throughout the body with an approximately 24 hour period that affect expression of hundreds of genes. Epidemiological data reveal chronic circadian misalignment, common in our society, significantly increases the risk for a myriad of diseases, including cardiovascular disease, diabetes, cancer, infertility and gastrointestinal disease. Disruption of intestinal barrier function, also known as gut leakiness, is especially important in alcoholic liver disease (ALD). Several studies have shown that alcohol causes ALD in only a 20–30% subset of alcoholics. Thus, a better understanding is needed of why only a subset of alcoholics develops ALD. Compelling evidence shows that increased gut leakiness to microbial products and especially LPS play a critical role in the pathogenesis of ALD. Clock and other circadian clock genes have been shown to regulate lipid transport, motility and other gut functions. We hypothesized that one possible mechanism for alcohol-induced intestinal hyper-permeability is through disruption of central or peripheral (intestinal) circadian regulation. In support of this hypothesis, our recent data shows that disruption of circadian rhythms makes the gut more susceptible to injury. Our in vitro data show that alcohol stimulates increased Clock and Per2 circadian clock proteins and that siRNA knockdown of these proteins prevents alcohol-induced permeability. We also show that intestinal Cyp2e1-mediated oxidative stress is required for alcohol-induced upregulation of Clock and Per2 and intestinal hyperpermeability. Our mouse model of chronic alcohol feeding shows that circadian disruption through genetics (in ClockΔ19 mice) or environmental disruption by weekly 12h phase shifting results in gut leakiness alone and exacerbates alcohol-induced gut leakiness and liver pathology. Our data in human alcoholics show they exhibit abnormal melatonin profiles characteristic of circadian disruption. Taken together our

  19. Circadian rhythms, alcohol and gut interactions.

    PubMed

    Forsyth, Christopher B; Voigt, Robin M; Burgess, Helen J; Swanson, Garth R; Keshavarzian, Ali

    2015-06-01

    The circadian clock establishes rhythms throughout the body with an approximately 24 hour period that affect expression of hundreds of genes. Epidemiological data reveal chronic circadian misalignment, common in our society, significantly increases the risk for a myriad of diseases, including cardiovascular disease, diabetes, cancer, infertility and gastrointestinal disease. Disruption of intestinal barrier function, also known as gut leakiness, is especially important in alcoholic liver disease (ALD). Several studies have shown that alcohol causes ALD in only a 20-30% subset of alcoholics. Thus, a better understanding is needed of why only a subset of alcoholics develops ALD. Compelling evidence shows that increased gut leakiness to microbial products and especially LPS play a critical role in the pathogenesis of ALD. Clock and other circadian clock genes have been shown to regulate lipid transport, motility and other gut functions. We hypothesized that one possible mechanism for alcohol-induced intestinal hyperpermeability is through disruption of central or peripheral (intestinal) circadian regulation. In support of this hypothesis, our recent data shows that disruption of circadian rhythms makes the gut more susceptible to injury. Our in vitro data show that alcohol stimulates increased Clock and Per2 circadian clock proteins and that siRNA knockdown of these proteins prevents alcohol-induced permeability. We also show that intestinal Cyp2e1-mediated oxidative stress is required for alcohol-induced upregulation of Clock and Per2 and intestinal hyperpermeability. Our mouse model of chronic alcohol feeding shows that circadian disruption through genetics (in Clock(▵19) mice) or environmental disruption by weekly 12h phase shifting results in gut leakiness alone and exacerbates alcohol-induced gut leakiness and liver pathology. Our data in human alcoholics show they exhibit abnormal melatonin profiles characteristic of circadian disruption. Taken together our

  20. Circadian rhythms, alcohol and gut interactions.

    PubMed

    Forsyth, Christopher B; Voigt, Robin M; Burgess, Helen J; Swanson, Garth R; Keshavarzian, Ali

    2015-06-01

    The circadian clock establishes rhythms throughout the body with an approximately 24 hour period that affect expression of hundreds of genes. Epidemiological data reveal chronic circadian misalignment, common in our society, significantly increases the risk for a myriad of diseases, including cardiovascular disease, diabetes, cancer, infertility and gastrointestinal disease. Disruption of intestinal barrier function, also known as gut leakiness, is especially important in alcoholic liver disease (ALD). Several studies have shown that alcohol causes ALD in only a 20-30% subset of alcoholics. Thus, a better understanding is needed of why only a subset of alcoholics develops ALD. Compelling evidence shows that increased gut leakiness to microbial products and especially LPS play a critical role in the pathogenesis of ALD. Clock and other circadian clock genes have been shown to regulate lipid transport, motility and other gut functions. We hypothesized that one possible mechanism for alcohol-induced intestinal hyperpermeability is through disruption of central or peripheral (intestinal) circadian regulation. In support of this hypothesis, our recent data shows that disruption of circadian rhythms makes the gut more susceptible to injury. Our in vitro data show that alcohol stimulates increased Clock and Per2 circadian clock proteins and that siRNA knockdown of these proteins prevents alcohol-induced permeability. We also show that intestinal Cyp2e1-mediated oxidative stress is required for alcohol-induced upregulation of Clock and Per2 and intestinal hyperpermeability. Our mouse model of chronic alcohol feeding shows that circadian disruption through genetics (in Clock(▵19) mice) or environmental disruption by weekly 12h phase shifting results in gut leakiness alone and exacerbates alcohol-induced gut leakiness and liver pathology. Our data in human alcoholics show they exhibit abnormal melatonin profiles characteristic of circadian disruption. Taken together our

  1. Daily Fasting Blood Glucose Rhythm in Male Mice: A Role of the Circadian Clock in the Liver.

    PubMed

    Ando, Hitoshi; Ushijima, Kentaro; Shimba, Shigeki; Fujimura, Akio

    2016-02-01

    Fasting blood glucose (FBG) and hepatic glucose production are regulated according to a circadian rhythm. An early morning increase in FBG levels, which is pronounced among diabetic patients, is known as the dawn phenomenon. Although the intracellular circadian clock generates various molecular rhythms, whether the hepatic clock is involved in FBG rhythm remains unclear. To address this issue, we investigated the effects of phase shift and disruption of the hepatic clock on the FBG rhythm. In both C57BL/6J and diabetic ob/ob mice, FBG exhibited significant daily rhythms with a peak at the beginning of the dark phase. Light-phase restricted feeding altered the phase of FBG rhythm mildly in C57BL/6J mice and greatly in ob/ob mice, in concert with the phase shifts of mRNA expression rhythms of the clock and glucose production-related genes in the liver. Moreover, the rhythmicity of FBG and Glut2 expression was not detected in liver-specific Bmal1-deficient mice. Furthermore, treatment with octreotide suppressed the plasma growth hormone concentration but did not affect the hepatic mRNA expression of the clock genes or the rise in FBG during the latter half of the resting phase in C57BL/6J mice. These results suggest that the hepatic circadian clock plays a critical role in regulating the daily FBG rhythm, including the dawn phenomenon. PMID:26653333

  2. Daily Fasting Blood Glucose Rhythm in Male Mice: A Role of the Circadian Clock in the Liver.

    PubMed

    Ando, Hitoshi; Ushijima, Kentaro; Shimba, Shigeki; Fujimura, Akio

    2016-02-01

    Fasting blood glucose (FBG) and hepatic glucose production are regulated according to a circadian rhythm. An early morning increase in FBG levels, which is pronounced among diabetic patients, is known as the dawn phenomenon. Although the intracellular circadian clock generates various molecular rhythms, whether the hepatic clock is involved in FBG rhythm remains unclear. To address this issue, we investigated the effects of phase shift and disruption of the hepatic clock on the FBG rhythm. In both C57BL/6J and diabetic ob/ob mice, FBG exhibited significant daily rhythms with a peak at the beginning of the dark phase. Light-phase restricted feeding altered the phase of FBG rhythm mildly in C57BL/6J mice and greatly in ob/ob mice, in concert with the phase shifts of mRNA expression rhythms of the clock and glucose production-related genes in the liver. Moreover, the rhythmicity of FBG and Glut2 expression was not detected in liver-specific Bmal1-deficient mice. Furthermore, treatment with octreotide suppressed the plasma growth hormone concentration but did not affect the hepatic mRNA expression of the clock genes or the rise in FBG during the latter half of the resting phase in C57BL/6J mice. These results suggest that the hepatic circadian clock plays a critical role in regulating the daily FBG rhythm, including the dawn phenomenon.

  3. Neonatal capsaicin treatment in rats affects TRPV1-related noxious heat sensation and circadian body temperature rhythm.

    PubMed

    Jeong, Keun-Yeong; Seong, Jinsil

    2014-06-15

    The transient receptor potential vanilloid 1 (TRPV1) is a cation channel that serves as a polymodal detector of noxious stimuli such as capsaicin. Therefore, capsaicin treatment has been used to investigate the physiological function of TRPV1. Here, we report physiological changes induced by treating neonatal rats with capsaicin. Capsaicin (50mg/kg) (cap-treated) or vehicle (vehicle-treated) was systemically administered to newborn SD rat pups within 48 h after birth. TRPV1 expression, intake volume of capsaicin water, and noxious heat sensation were measured 6 weeks after capsaicin treatment. Circadian body temperature and locomotion were recorded by biotelemetry. Expression of Per1, Per2, Bmal1 and Hsf1 (clock genes) was also investigated. Neonatal capsaicin treatment not only decreased TRPV1 expression but also induced desensitization to noxious heat stimuli. Circadian body temperature of cap-treated rats increased significantly compared with that of vehicle-treated rats. Additionally, the amplitude of the circadian body temperature was reversed in cap-treated rats. Expression of the hypothalamic Hsf1 and liver Per2 clock genes followed a similar trend. Therefore, we suggest that these findings will be useful in studying various physiological mechanisms related to TRPV1.

  4. Evidences of Polymorphism Associated with Circadian System and Risk of Pathologies: A Review of the Literature.

    PubMed

    Valenzuela, F J; Vera, J; Venegas, C; Muñoz, S; Oyarce, S; Muñoz, K; Lagunas, C

    2016-01-01

    The circadian system is a supraphysiological system that modulates different biological functions such as metabolism, sleep-wake, cellular proliferation, and body temperature. Different chronodisruptors have been identified, such as shift work, feeding time, long days, and stress. The environmental changes and our modern lifestyle can alter the circadian system and increase the risk of developing pathologies such as cancer, preeclampsia, diabetes, and mood disorder. This system is organized by transcriptional/tranductional feedback loops of clock genes Clock, Bmal1, Per1-3, and Cry1-2. How molecular components of the clock are able to influence the development of diseases and their risk relation with genetic components of polymorphism of clock genes is unknown. This research describes different genetic variations in the population and how these are associated with risk of cancer, metabolic diseases such as diabetes, obesity, and dyslipidemias, and also mood disorders such as depression, bipolar disease, excessive alcohol intake, and infertility. Finally, these findings will need to be implemented and evaluated at the level of genetic interaction and how the environment factors trigger the expression of these pathologies will be examined. PMID:27313610

  5. Evidences of Polymorphism Associated with Circadian System and Risk of Pathologies: A Review of the Literature

    PubMed Central

    Valenzuela, F. J.; Vera, J.; Venegas, C.; Muñoz, S.; Oyarce, S.; Muñoz, K.; Lagunas, C.

    2016-01-01

    The circadian system is a supraphysiological system that modulates different biological functions such as metabolism, sleep-wake, cellular proliferation, and body temperature. Different chronodisruptors have been identified, such as shift work, feeding time, long days, and stress. The environmental changes and our modern lifestyle can alter the circadian system and increase the risk of developing pathologies such as cancer, preeclampsia, diabetes, and mood disorder. This system is organized by transcriptional/tranductional feedback loops of clock genes Clock, Bmal1, Per1–3, and Cry1-2. How molecular components of the clock are able to influence the development of diseases and their risk relation with genetic components of polymorphism of clock genes is unknown. This research describes different genetic variations in the population and how these are associated with risk of cancer, metabolic diseases such as diabetes, obesity, and dyslipidemias, and also mood disorders such as depression, bipolar disease, excessive alcohol intake, and infertility. Finally, these findings will need to be implemented and evaluated at the level of genetic interaction and how the environment factors trigger the expression of these pathologies will be examined. PMID:27313610

  6. 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

  7. 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

  8. 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

  9. Carcinogenic effects of circadian disruption: an epigenetic viewpoint.

    PubMed

    Salavaty, Abbas

    2015-08-08

    Circadian rhythms refer to the endogenous rhythms that are generated to synchronize physiology and behavior with 24-h environmental cues. These rhythms are regulated by both external cues and molecular clock mechanisms in almost all cells. Disruption of circadian rhythms, which is called circadian disruption, affects many biological processes within the body and results in different long-term diseases, including cancer. Circadian regulatory pathways result in rhythmic epigenetic modifications and the formation of circadian epigenomes. Aberrant epigenetic modifications, such as hypermethylation, due to circadian disruption may be involved in the transformation of normal cells into cancer cells. Several studies have indicated an epigenetic basis for the carcinogenic effects of circadian disruption. In this review, I first discuss some of the circadian genes and regulatory proteins. Then, I summarize the current evidence related to the epigenetic modifications that result in circadian disruption. In addition, I explain the carcinogenic effects of circadian disruption and highlight its potential role in different human cancers using an epigenetic viewpoint. Finally, the importance of chronotherapy in cancer treatment is highlighted.

  10. Aging and Circadian Rhythms.

    PubMed

    Duffy, Jeanne F; Zitting, Kirsi-Marja; Chinoy, Evan D

    2015-12-01

    Aging is associated with numerous changes, including changes in sleep timing, duration, and quality. The circadian timing system interacts with a sleep-wake homeostatic system to regulate human sleep, including sleep timing and structure. This article reviews key features of the human circadian timing system, age-related changes in the circadian timing system, and how those changes may contribute to the observed alterations in sleep. PMID:26568120

  11. Assignment of circadian function for the Neurospora clock gene frequency.

    PubMed

    Merrow, M; Brunner, M; Roenneberg, T

    1999-06-10

    Circadian clocks consist of three elements: entrainment pathways (inputs), the mechanism generating the rhythmicity (oscillator), and the output pathways that control the circadian rhythms. It is difficult to assign molecular clock components to any one of these elements. Experiments show that inputs can be circadianly regulated and outputs can feed back on the oscillator. Mathematical simulations indicate that under- or overexpression of a gene product can result in arrhythmicity, whether the protein is part of the oscillator or substantially part of a rhythmically expressed input pathway. To distinguish between these two possibilities, we used traditional circadian entrainment protocols on a genetic model system, Neurospora crassa.

  12. The role of circadian rhythm in breast cancer.

    PubMed

    Li, Shujing; Ao, Xiang; Wu, Huijian

    2013-08-01

    The circadian rhythm is an endogenous time keeping system shared by most organisms. The circadian clock is comprised of both peripheral oscillators in most organ tissues of the body and a central pacemaker located in the suprachiasmatic nucleus (SCN) of the central nervous system. The circadian rhythm is crucial in maintaining the normal physiology of the organism including, but not limited to, cell proliferation, cell cycle progression, and cellular metabolism; whereas disruption of the circadian rhythm is closely related to multi-tumorigenesis. In the past several years, studies from different fields have revealed that the genetic or functional disruption of the molecular circadian rhythm has been found in various cancers, such as breast, prostate, and ovarian. In this review, we will investigate and present an overview of the current research on the influence of circadian rhythm regulating proteins on breast cancer.

  13. Regulation of alternative splicing by the circadian clock and food related cues

    PubMed Central

    2012-01-01

    Background The circadian clock orchestrates daily rhythms in metabolism, physiology and behaviour that allow organisms to anticipate regular changes in their environment, increasing their adaptation. Such circadian phenotypes are underpinned by daily rhythms in gene expression. Little is known, however, about the contribution of post-transcriptional processes, particularly alternative splicing. Results Using Affymetrix mouse exon-arrays, we identified exons with circadian alternative splicing in the liver. Validated circadian exons were regulated in a tissue-dependent manner and were present in genes with circadian transcript abundance. Furthermore, an analysis of circadian mutant Vipr2-/- mice revealed the existence of distinct physiological pathways controlling circadian alternative splicing and RNA binding protein expression, with contrasting dependence on Vipr2-mediated physiological signals. This view was corroborated by the analysis of the effect of fasting on circadian alternative splicing. Feeding is an important circadian stimulus, and we found that fasting both modulates hepatic circadian alternative splicing in an exon-dependent manner and changes the temporal relationship with transcript-level expression. Conclusions The circadian clock regulates alternative splicing in a manner that is both tissue-dependent and concurrent with circadian transcript abundance. This adds a novel temporal dimension to the regulation of mammalian alternative splicing. Moreover, our results demonstrate that circadian alternative splicing is regulated by the interaction between distinct physiological cues, and illustrates the capability of single genes to integrate circadian signals at different levels of regulation. PMID:22721557

  14. Circadian Clocks and Metabolism

    PubMed Central

    Marcheva, Biliana; Ramsey, Kathryn M.; Peek, Clara B.; Affinati, Alison; Maury, Eleonore; Bass, Joseph

    2014-01-01

    Circadian clocks maintain periodicity in internal cycles of behavior, physiology, and metabolism, enabling organisms to anticipate the 24-h rotation of the Earth. In mammals, circadian integration of metabolic systems optimizes energy harvesting and utilization across the light/dark cycle. Disruption of clock genes has recently been linked to sleep disorders and to the development of cardiometabolic disease. Conversely, aberrant nutrient signaling affects circadian rhythms of behavior. This chapter reviews the emerging relationship between the molecular clock and metabolic systems and examines evidence that circadian disruption exerts deleterious consequences on human health. PMID:23604478

  15. Housing under abnormal light-dark cycles attenuates day/night expression rhythms of the clock genes Per1, Per2, and Bmal1 in the amygdala and hippocampus of mice.

    PubMed

    Moriya, Shunpei; Tahara, Yu; Sasaki, Hiroyuki; Ishigooka, Jun; Shibata, Shigenobu

    2015-10-01

    Although the results of previous studies have suggested that disruptions in circadian rhythms are involved in the pathogenesis of depression, no studies have examined the interaction of clock gene expression deficit and depression state. In this study, we examined clock gene expression levels and depressive-like behavior in mice housed under 3.5h light, 3.5h dark (T = 7) conditions to investigate the association between clock gene expression and depressive state. C57BL/6J mice were housed under a T = 24 cycle (12h light, 12h dark) or a T = 7 cycle and clock gene expression levels in the hippocampus and the amygdala were measured by real-time RT-PCR. Depressive state was evaluated by the forced swim test (FST). Although circadian rhythms of Per1 and Per2 clock gene expression in the hippocampus and amygdala were still detected under T = 7 conditions, rhythmicity and expression levels of both significantly decreased. Mice housed with a T = 7 cycle showed increased immobile time in the FST than those with a T = 24 cycle. The present results suggest that the presence of a depressive state around the early active phase of activity may be related to impairment of rhythmicity and expression levels of Per1 and Per2 genes under abnormal light-dark conditions.

  16. Synergistic interactions between the molecular and neuronal circadian networks drive robust behavioral circadian rhythms in Drosophila melanogaster.

    PubMed

    Weiss, Ron; Bartok, Osnat; Mezan, Shaul; Malka, Yuval; Kadener, Sebastian

    2014-04-01

    Most organisms use 24-hr circadian clocks to keep temporal order and anticipate daily environmental changes. In Drosophila melanogaster CLOCK (CLK) and CYCLE (CYC) initiates the circadian system by promoting rhythmic transcription of hundreds of genes. However, it is still not clear whether high amplitude transcriptional oscillations are essential for circadian timekeeping. In order to address this issue, we generated flies in which the amplitude of CLK-driven transcription can be reduced partially (approx. 60%) or strongly (90%) without affecting the average levels of CLK-target genes. The impaired transcriptional oscillations lead to low amplitude protein oscillations that were not sufficient to drive outputs of peripheral oscillators. However, circadian rhythms in locomotor activity were resistant to partial reduction in transcriptional and protein oscillations. We found that the resilience of the brain oscillator is depending on the neuronal communication among circadian neurons in the brain. Indeed, the capacity of the brain oscillator to overcome low amplitude transcriptional oscillations depends on the action of the neuropeptide PDF and on the pdf-expressing cells having equal or higher amplitude of molecular rhythms than the rest of the circadian neuronal groups in the fly brain. Therefore, our work reveals the importance of high amplitude transcriptional oscillations for cell-autonomous circadian timekeeping. Moreover, we demonstrate that the circadian neuronal network is an essential buffering system that protects against changes in circadian transcription in the brain. PMID:24698952

  17. Enhancement of NAD+-dependent SIRT1 deacetylase activity by methylselenocysteine resets the circadian clock in carcinogen-treated mammary epithelial cells

    PubMed Central

    Fang, Mingzhu; Guo, Wei-Ren; Park, Youngil; Kang, Hwan-Goo; Zarbl, Helmut

    2015-01-01

    We previously reported that dietary methylselenocysteine (MSC) inhibits N-methyl-N-nitrosourea (NMU)-induced mammary tumorigenesis by resetting circadian gene expression disrupted by the carcinogen at the early stage of tumorigenesis. To investigate the underlying mechanism, we developed a circadian reporter system comprised of human mammary epithelial cells with a luciferase reporter driven by the promoter of human PERIOD 2 (PER2), a core circadian gene. In this in vitro model, NMU disrupted cellular circadian rhythm in a pattern similar to that observed with SIRT1-specific inhibitors; in contrast, MSC restored the circadian rhythms disrupted by NMU and protected against SIRT1 inhibitors. Moreover, NMU inhibited intracellular NAD+/NADH ratio and reduced NAD+-dependent SIRT1 activity in a dose-dependent manner, while MSC restored NAD+/NADH and SIRT1 activity in the NMU-treated cells, indicating that the NAD+-SIRT1 pathway was targeted by NMU and MSC. In rat mammary tissue, a carcinogenic dose of NMU also disrupted NAD+/NADH oscillations and decreased SIRT1 activity; dietary MSC restored NAD+/NADH oscillations and increased SIRT1 activity in the mammary glands of NMU-treated rats. MSC-induced SIRT1 activity was correlated with decreased acetylation of BMAL1 and increased acetylation of histone 3 lysine 9 at the Per2 promoter E-Box in mammary tissue. Changes in SIRT1 activity were temporally correlated with loss or restoration of rhythmic Per2 mRNA expression in NMU-treated or MSC-rescued rat mammary glands, respectively. Together with our previous findings, these results suggest that enhancement of NAD+-dependent SIRT1 activity contributes to the chemopreventive efficacy of MSC by restoring epigenetic regulation of circadian gene expression at early stages of mammary tumorigenesis. PMID:26544624

  18. GABA-mediated repulsive coupling between circadian clock neurons in the SCN encodes seasonal time

    PubMed Central

    Myung, Jihwan; Hong, Sungho; DeWoskin, Daniel; De Schutter, Erik; Forger, Daniel B.; Takumi, Toru

    2015-01-01

    The mammalian suprachiasmatic nucleus (SCN) forms not only the master circadian clock but also a seasonal clock. This neural network of ∼10,000 circadian oscillators encodes season-dependent day-length changes through a largely unknown mechanism. We show that region-intrinsic changes in the SCN fine-tune the degree of network synchrony and reorganize the phase relationship among circadian oscillators to represent day length. We measure oscillations of the clock gene Bmal1, at single-cell and regional levels in cultured SCN explanted from animals raised under short or long days. Coupling estimation using the Kuramoto framework reveals that the network has couplings that can be both phase-attractive (synchronizing) and -repulsive (desynchronizing). The phase gap between the dorsal and ventral regions increases and the overall period of the SCN shortens with longer day length. We find that one of the underlying physiological mechanisms is the modulation of the intracellular chloride concentration, which can adjust the strength and polarity of the ionotropic GABAA-mediated synaptic input. We show that increasing day-length changes the pattern of chloride transporter expression, yielding more excitatory GABA synaptic input, and that blocking GABAA signaling or the chloride transporter disrupts the unique phase and period organization induced by the day length. We test the consequences of this tunable GABA coupling in the context of excitation–inhibition balance through detailed realistic modeling. These results indicate that the network encoding of seasonal time is controlled by modulation of intracellular chloride, which determines the phase relationship among and period difference between the dorsal and ventral SCN. PMID:26130804

  19. GABA-mediated repulsive coupling between circadian clock neurons in the SCN encodes seasonal time.

    PubMed

    Myung, Jihwan; Hong, Sungho; DeWoskin, Daniel; De Schutter, Erik; Forger, Daniel B; Takumi, Toru

    2015-07-21

    The mammalian suprachiasmatic nucleus (SCN) forms not only the master circadian clock but also a seasonal clock. This neural network of ∼10,000 circadian oscillators encodes season-dependent day-length changes through a largely unknown mechanism. We show that region-intrinsic changes in the SCN fine-tune the degree of network synchrony and reorganize the phase relationship among circadian oscillators to represent day length. We measure oscillations of the clock gene Bmal1, at single-cell and regional levels in cultured SCN explanted from animals raised under short or long days. Coupling estimation using the Kuramoto framework reveals that the network has couplings that can be both phase-attractive (synchronizing) and -repulsive (desynchronizing). The phase gap between the dorsal and ventral regions increases and the overall period of the SCN shortens with longer day length. We find that one of the underlying physiological mechanisms is the modulation of the intracellular chloride concentration, which can adjust the strength and polarity of the ionotropic GABAA-mediated synaptic input. We show that increasing day-length changes the pattern of chloride transporter expression, yielding more excitatory GABA synaptic input, and that blocking GABAA signaling or the chloride transporter disrupts the unique phase and period organization induced by the day length. We test the consequences of this tunable GABA coupling in the context of excitation-inhibition balance through detailed realistic modeling. These results indicate that the network encoding of seasonal time is controlled by modulation of intracellular chloride, which determines the phase relationship among and period difference between the dorsal and ventral SCN.

  20. Ketogenic diet delays the phase of circadian rhythms and does not affect AMP-activated protein kinase (AMPK) in mouse liver.

    PubMed

    Genzer, Yoni; Dadon, Maayan; Burg, Chen; Chapnik, Nava; Froy, Oren

    2015-12-01

    Ketogenic diet (KD) is used for weight loss or to treat epilepsy. KD leads to liver AMP-activated protein kinase (AMPK) activation, which would be expected to inhibit gluconeogenesis. However, KD leads to increased hepatic glucose output. As AMPK and its active phosphorylated form (pAMPK) show circadian oscillation, this discrepancy could stem from wrong-time-of-day sampling. The effect of KD was tested on mouse clock gene expression, AMPK, mTOR, SIRT1 and locomotor activity for 2 months and compared to low-fat diet (LFD). KD led to 1.5-fold increased levels of blood glucose and insulin. Brain pAMPK/AMPK ratio was 40% higher under KD, whereas that in liver was not affected. KD led to 40% and 20% down-regulation of the ratio of pP70S6K/P70S6K, the downstream target of mTOR, in the brain and liver, respectively. SIRT1 levels were 40% higher in the brain, but 40% lower in the liver of KD-fed mice. Clock genes showed delayed rhythms under KD. In the brain of KD-fed mice, amplitudes of clock genes were down-regulated, whereas 6-fold up-regulation was found in the liver. The metabolic state under KD indicates reduced satiety in the brain and reduced anabolism alongside increased gluconeogenesis in the liver.

  1. The Arabidopsis Circadian System

    PubMed Central

    McClung, C. Robertson; Salomé, Patrice A.; Michael, Todd P.

    2002-01-01

    Rhythms with periods of approximately 24 hr are widespread in nature. Those that persist in constant conditions are termed circadian rhythms and reflect the activity of an endogenous biological clock. Plants, including Arabidopsis, are richly rhythmic. Expression analysis, most recently on a genomic scale, indicates that the Arabidopsis circadian clock regulates a number of key metabolic pathways and stress responses. A number of sensitive and high-throughput assays have been developed to monitor the Arabidopsis clock. These assays have facilitated the identification of components of plant circadian systems through genetic and molecular biological studies. Although much remains to be learned, the framework of the Arabidopsis circadian system is coming into focus. Dedication This review is dedicated to the memory of DeLill Nasser, a wonderful mentor and an unwavering advocate of both Arabidopsis and circadian rhythms research. PMID:22303209

  2. Circadian rhythm sleep disorders.

    PubMed

    Kanathur, Naveen; Harrington, John; Lee-Chiong, Teofilo

    2010-06-01

    Because there is insufficient cellular energy for organisms to perform their functions at the same constant rate and at the same time, all biologic processes show rhythmicity, each with its own unique frequency, amplitude, and phase. Optimal sleep and wakefulness requires proper timing and alignment of desired sleep-wake schedules and circadian rhythm-related periods of alertness. Persistent or recurrent mismatch between endogenous circadian rhythms and the conventional sleep-wake schedules of the environmental day can give rise to several circadian rhythm sleep disorders. Evaluation of suspected circadian rhythm sleep disorders requires proper monitoring of sleep diaries, often over several days to weeks. This article discusses the disorders of the circadian sleep-wake cycle and the therapeutic measures to correct the same.

  3. Circadian Rhythm Abnormalities

    PubMed Central

    Zee, Phyllis C.; Attarian, Hrayr; Videnovic, Aleksandar

    2013-01-01

    Purpose: This article reviews the recent advances in understanding of the fundamental properties of circadian rhythms and discusses the clinical features, diagnosis, and treatment of circadian rhythm sleep disorders (CRSDs). Recent Findings: Recent evidence strongly points to the ubiquitous influence of circadian timing in nearly all physiologic functions. Thus, in addition to the prominent sleep and wake disturbances, circadian rhythm disorders are associated with cognitive impairment, mood disturbances, and increased risk of cardiometabolic disorders. The recent availability of biomarkers of circadian timing in clinical practice has improved our ability to identify and treat these CRSDs. Summary: Circadian rhythms are endogenous rhythms with a periodicity of approximately 24 hours. These rhythms are synchronized to the physical environment by social and work schedules by various photic and nonphotic stimuli. CRSDs result from a misalignment between the timing of the circadian rhythm and the external environment (eg, jet lag and shift work) or a dysfunction of the circadian clock or its afferent and efferent pathways (eg, delayed sleep-phase, advanced sleep-phase, non–24-hour, and irregular sleep-wake rhythm disorders). The most common symptoms of these disorders are difficulties with sleep onset and/or sleep maintenance and excessive sleepiness that are associated with impaired social and occupational functioning. Effective treatment for most of the CRSDs requires a multimodal approach to accelerate circadian realignment with timed exposure to light, avoidance of bright light at inappropriate times, and adherence to scheduled sleep and wake times. In addition, pharmacologic agents are recommended for some of the CRSDs. For delayed sleep-phase, non–24-hour, and shift work disorders, timed low-dose melatonin can help advance or entrain circadian rhythms; and for shift work disorder, wake-enhancing agents such as caffeine, modafinil, and armodafinil are options

  4. Protein-energy malnutrition induces an aberrant acute-phase response and modifies the circadian rhythm of core temperature.

    PubMed

    Smith, Shari E; Ramos, Rafaela Andrade; Refinetti, Roberto; Farthing, Jonathan P; Paterson, Phyllis G

    2013-08-01

    Protein-energy malnutrition (PEM), present in 12%-19% of stroke patients upon hospital admission, appears to be a detrimental comorbidity factor that impairs functional outcome, but the mechanisms are not fully elucidated. Because ischemic brain injury is highly temperature-sensitive, the objectives of this study were to investigate whether PEM causes sustained changes in temperature that are associated with an inflammatory response. Activity levels were recorded as a possible explanation for the immediate elevation in temperature upon introduction to a low protein diet. Male, Sprague-Dawley rats (7 weeks old) were fed a control diet (18% protein) or a low protein diet (PEM, 2% protein) for either 7 or 28 days. Continuous core temperature recordings from bioelectrical sensor transmitters demonstrated a rapid increase in temperature amplitude, sustained over 28 days, in response to a low protein diet. Daily mean temperature rose transiently by day 2 (p = 0.01), falling to normal by day 4 (p = 0.08), after which mean temperature continually declined as malnutrition progressed. There were no alterations in activity mean (p = 0.3) or amplitude (p = 0.2) that were associated with the early rise in mean temperature. Increased serum alpha-2-macroglobulin (p < 0.001) and decreased serum albumin (p ≤ 0.005) combined with a decrease in serum alpha-1-acid glycoprotein (p < 0.001) suggest an atypical acute-phase response. In contrast, a low protein diet had no effect on the signaling pathway of the pro-inflammatory transcription factor, NFκB, in the hippocampus. In conclusion, PEM induces an aberrant and sustained acute-phase response coupled with long-lasting effects on body temperature.

  5. A circadian rhythm in the expression of PERIOD2 protein reveals a novel SCN-controlled oscillator in the oval nucleus of the bed nucleus of the stria terminalis.

    PubMed

    Amir, Shimon; Lamont, Elaine Waddington; Robinson, Barry; Stewart, Jane

    2004-01-28

    Circadian rhythms in mammals are regulated not only globally by the master clock in the suprachiasmatic nucleus (SCN), but also locally by widely distributed populations of clock cells in the brain and periphery that control tissue-specific rhythmic outputs. Here we show that the oval nucleus of the bed nucleus of the stria terminalis (BNST-OV) exhibits a robust circadian rhythm in expression of the Period2 (PER2) clock protein. PER2 expression is rhythmic in the BNST-OV in rats housed under a light/dark cycle or in constant darkness, in blind rats, and in mice, and is in perfect synchrony with the PER2 rhythm of the SCN. Constant light or bilateral SCN lesions abolish the rhythm of PER2 in the BNST-OV. Large abrupt shifts in the light schedule transiently uncouple the BNST-OV rhythm from that of the SCN. Re-entrainment of the PER2 rhythm is faster in the SCN than in the BNST-OV, and it is faster after a delay than an advance shift. Bilateral adrenalectomy blunts the PER2 rhythm in the BNST-OV. Thus, the BNST-OV contains circadian clock cells that normally oscillate in synchrony with the SCN, but these cells appear to require both input from the SCN and circulating glucocorticoids to maintain their circadian oscillation. Taken together with what is known about the functional organization of the connections of the BNST-OV with systems of the brain involved in stress and motivational processes, these findings place BNST-OV oscillators in a position to influence specific physiological and behavioral rhythms downstream from the SCN clock. PMID:14749422

  6. Biophotonics: Circadian photonics

    NASA Astrophysics Data System (ADS)

    Rea, Mark S.

    2011-05-01

    A growing body of medical evidence suggests that disrupting the body's biological clock can have adverse effects on health. Researchers are now creating the photonic tools to monitor, predict and influence the circadian rhythm.

  7. Calcium and SOL Protease Mediate Temperature Resetting of Circadian Clocks

    PubMed Central

    Tataroglu, Ozgur; Zhao, Xiaohu; Busza, Ania; Ling, Jinli; O’Neill, John S.; Emery, Patrick

    2015-01-01

    Summary Circadian clocks integrate light and temperature input to remain synchronized with the day/night cycle. Although light input to the clock is well studied, the molecular mechanisms by which circadian clocks respond to temperature remain poorly understood. We found that temperature phase shifts Drosophila circadian clocks through degradation of the pacemaker protein TIM. This degradation is mechanistically distinct from photic CRY-dependent TIM degradation. Thermal TIM degradation is triggered by cytosolic calcium increase and CALMODULIN binding to TIM and is mediated by the atypical calpain protease SOL. This thermal input pathway and CRY-dependent light input thus converge on TIM, providing a molecular mechanism for the integration of circadian light and temperature inputs. Mammals use body temperature cycles to keep peripheral clocks synchronized with their brain pacemaker. Interestingly, downregulating the mammalian SOL homolog SOLH blocks thermal mPER2 degradation and phase shifts. Thus, we propose that circadian thermosensation in insects and mammals share common principles. PMID:26590423

  8. Circadian systems biology: When time matters

    PubMed Central

    Fuhr, Luise; Abreu, Mónica; Pett, Patrick; Relógio, Angela

    2015-01-01

    The circadian clock is a powerful endogenous timing system, which allows organisms to fine-tune their physiology and behaviour to the geophysical time. The interplay of a distinct set of core-clock genes and proteins generates oscillations in expression of output target genes which temporally regulate numerous molecular and cellular processes. The study of the circadian timing at the organismal as well as at the cellular level outlines the field of chronobiology, which has been highly interdisciplinary ever since its origins. The development of high-throughput approaches enables the study of the clock at a systems level. In addition to experimental approaches, computational clock models exist which allow the analysis of rhythmic properties of the clock network. Such mathematical models aid mechanistic understanding and can be used to predict outcomes of distinct perturbations in clock components, thereby generating new hypotheses regarding the putative function of particular clock genes. Perturbations in the circadian timing system are linked to numerous molecular dysfunctions and may result in severe pathologies including cancer. A comprehensive knowledge regarding the mechanistic of the circadian system is crucial to develop new procedures to investigate pathologies associated with a deregulated clock. In this manuscript we review the combination of experimental methodologies, bioinformatics and theoretical models that have been essential to explore this remarkable timing-system. Such an integrative and interdisciplinary approach may provide new strategies with regard to chronotherapeutic treatment and new insights concerning the restoration of the circadian timing in clock-associated diseases. PMID:26288701

  9. Circadian regulation of intestinal lipid absorption by apolipoprotein AIV involves forkhead transcription factors A2 and O1 and microsomal triglyceride transfer protein.

    PubMed

    Pan, Xiaoyue; Munshi, Mohamed Khalid; Iqbal, Jahangir; Queiroz, Joyce; Sirwi, Alaa Ahmed; Shah, Shrenik; Younus, Abdullah; Hussain, M Mahmood

    2013-07-12

    We have shown previously that Clock, microsomal triglyceride transfer protein (MTP), and nocturnin are involved in the circadian regulation of intestinal lipid absorption. Here, we clarified the role of apolipoprotein AIV (apoAIV) in the diurnal regulation of plasma lipids and intestinal lipid absorption in mice. Plasma triglyceride in apoAIV(-/-) mice showed diurnal variations similar to apoAIV(+/+) mice; however, the increases in plasma triglyceride at night were significantly lower in these mice. ApoAIV(-/-) mice absorbed fewer lipids at night and showed blunted response to daytime feeding. To explain reasons for these lower responses, we measured MTP expression; intestinal MTP was low at night, and its induction after food entrainment was less in apoAIV(-/-) mice. Conversely, apoAIV overexpression increased MTP mRNA in hepatoma cells, indicating transcriptional regulation. Mechanistic studies revealed that sequences between -204/-775 bp in the MTP promoter respond to apoAIV and that apoAIV enhances expression of FoxA2 and FoxO1 transcription factors and their binding to the identified cis elements in the MTP promoter at night. Knockdown of FoxA2 and FoxO1 abolished apoAIV-mediated MTP induction. Similarly, knockdown of apoAIV in differentiated Caco-2 cells reduced MTP, FoxA2, and FoxO1 mRNA levels, cellular MTP activity, and media apoB. Moreover, FoxA2 and FoxO1 expression showed diurnal variations, and their expression was significantly lower in apoAIV(-/-) mice. These data indicate that apoAIV modulates diurnal changes in lipid absorption by regulating forkhead transcription factors and MTP and that inhibition of apoAIV expression might reduce plasma lipids.

  10. Pathogen and Circadian Controlled 1 (PCC1) Protein Is Anchored to the Plasma Membrane and Interacts with Subunit 5 of COP9 Signalosome in Arabidopsis

    PubMed Central

    Mir, Ricardo; León, José

    2014-01-01

    The Pathogen and Circadian Controlled 1 (PCC1) gene, previously identified and further characterized as involved in defense to pathogens and stress-induced flowering, codes for an 81-amino acid protein with a cysteine-rich C-terminal domain. This domain is essential for homodimerization and anchoring to the plasma membrane. Transgenic plants with the ß-glucuronidase (GUS) reporter gene under the control of 1.1 kb promoter sequence of PCC1 gene display a dual pattern of expression. At early post-germination, PCC1 is expressed only in the root vasculature and in the stomata guard cells of cotyledons. During the transition from vegetative to reproductive development, PCC1 is strongly expressed in the vascular tissue of petioles and basal part of the leaf, and it further spreads to the whole limb in fully expanded leaves. This developmental pattern of expression together with the late flowering phenotype of long-day grown RNA interference (iPCC1) plants with reduced PCC1 expression pointed to a regulatory role of PCC1 in the photoperiod-dependent flowering pathway. iPCC1 plants are defective in light perception and signaling but are not impaired in the function of the core CO-FT module of the photoperiod-dependent pathway. The regulatory effect exerted by PCC1 on the transition to flowering as well as on other reported phenotypes might be explained by a mechanism involving the interaction with the subunit 5 of the COP9 signalosome (CSN). PMID:24475254

  11. Intact Interval Timing in Circadian CLOCK Mutants

    PubMed Central

    Cordes, Sara; Gallistel, C. R.

    2008-01-01

    While progress has been made in determining the molecular basis for the circadian clock, the mechanism by which mammalian brains time intervals measured in seconds to minutes remains a mystery. An obvious question is whether the interval timing mechanism shares molecular machinery with the circadian timing mechanism. In the current study, we trained circadian CLOCK +/− and −/− mutant male mice in a peak-interval procedure with 10 and 20-s criteria. The mutant mice were more active than their wild-type littermates, but there were no reliable deficits in the accuracy or precision of their timing as compared with wild-type littermates. This suggests that expression of the CLOCK protein is not necessary for normal interval timing. PMID:18602902

  12. Genome-wide analyses of circadian systems.

    PubMed

    Reddy, Akhilesh B

    2013-01-01

    Circadian gene expression is a pervasive feature of tissue physiology, regulating approx. 10% of transcript and protein abundance in tissues such as the liver. Technological developments have accelerated our ability to probe circadian variation of gene expression, in particular by using microarrays. Recent advances in high-throughput sequencing have similarly led to novel insights into the regulation of genes at the DNA and chromatin levels. Furthermore, tools such as RNA interference are being used to perturb gene function at a truly systems level, allowing dissection of the clockwork in increasing depth. This chapter will highlight progress in these areas, focusing on key techniques that have helped, and will continue to help, with the investigation of circadian physiology.

  13. A metabolomic study of adipose tissue in mice with a disruption of the circadian system.

    PubMed

    Castro, C; Briggs, W; Paschos, G K; FitzGerald, G A; Griffin, J L

    2015-07-01

    Adipose tissue functions in terms of energy homeostasis as a rheostat for blood triglyceride, regulating its concentration, in response to external stimuli. In addition it acts as a barometer to inform the central nervous system of energy levels which can vary dramatically between meals and according to energy demand. Here a metabolomic approach, combining both Mass Spectrometry and Nuclear Magnetic Resonance spectroscopy, was used to analyse both white and brown adipose tissue in mice with adipocyte-specific deletion of Arntl (also known as Bmal1), a gene encoding a core molecular clock component. The results are consistent with a peripheral circadian clock playing a central role in metabolic regulation of both brown and white adipose tissue in rodents and show that Arntl induced global changes in both tissues which were distinct for the two types. In particular, anterior subcutaneous white adipose tissue (ASWAT) tissue was effected by a reduction in the degree of unsaturation of fatty acids, while brown adipose tissue (BAT) changes were associated with a reduction in chain length. In addition the aqueous fraction of metabolites in BAT were profoundly affected by Arntl disruption, consistent with the dynamic role of this tissue in maintaining body temperature across the day-night cycle and an upregulation in fatty acid oxidation and citric acid cycle activity to generate heat during the day when rats are inactive (increases in 3-hydroxybutyrate and glutamate), and increased synthesis and storage of lipids during the night when rats feed more (increased concentrations of glycerol, choline and glycerophosphocholine).

  14. A metabolomic study of adipose tissue in mice with a disruption of the circadian system.

    PubMed

    Castro, C; Briggs, W; Paschos, G K; FitzGerald, G A; Griffin, J L

    2015-07-01

    Adipose tissue functions in terms of energy homeostasis as a rheostat for blood triglyceride, regulating its concentration, in response to external stimuli. In addition it acts as a barometer to inform the central nervous system of energy levels which can vary dramatically between meals and according to energy demand. Here a metabolomic approach, combining both Mass Spectrometry and Nuclear Magnetic Resonance spectroscopy, was used to analyse both white and brown adipose tissue in mice with adipocyte-specific deletion of Arntl (also known as Bmal1), a gene encoding a core molecular clock component. The results are consistent with a peripheral circadian clock playing a central role in metabolic regulation of both brown and white adipose tissue in rodents and show that Arntl induced global changes in both tissues which were distinct for the two types. In particular, anterior subcutaneous white adipose tissue (ASWAT) tissue was effected by a reduction in the degree of unsaturation of fatty acids, while brown adipose tissue (BAT) changes were associated with a reduction in chain length. In addition the aqueous fraction of metabolites in BAT were profoundly affected by Arntl disruption, consistent with the dynamic role of this tissue in maintaining body temperature across the day-night cycle and an upregulation in fatty acid oxidation and citric acid cycle activity to generate heat during the day when rats are inactive (increases in 3-hydroxybutyrate and glutamate), and increased synthesis and storage of lipids during the night when rats feed more (increased concentrations of glycerol, choline and glycerophosphocholine). PMID:25907923

  15. Circadian Gene Variants and Susceptibility to Type 2 Diabetes: A Pilot Study

    PubMed Central

    Kelly, M. Ann; Rees, Simon D.; Hydrie, M. Zafar I.; Shera, A. Samad; Bellary, Srikanth; O’Hare, J. Paul; Kumar, Sudhesh; Taheri, Shahrad; Basit, Abdul; Barnett, Anthony H.

    2012-01-01

    Background Disruption of endogenous circadian rhythms has been shown to increase the risk of developing type 2 diabetes, suggesting that circadian genes might play a role in determining disease susceptibility. We present the results of a pilot study investigating the association between type 2 diabetes and selected single nucleotide polymorphisms (SNPs) in/near nine circadian genes. The variants were chosen based on their previously reported association with prostate cancer, a disease that has been suggested to have a genetic link with type 2 diabetes through a number of shared inherited risk determinants. Methodology/Principal Findings The pilot study was performed using two genetically homogeneous Punjabi cohorts, one resident in the United Kingdom and one indigenous to Pakistan. Subjects with (N = 1732) and without (N = 1780) type 2 diabetes were genotyped for thirteen circadian variants using a competitive allele-specific polymerase chain reaction method. Associations between the SNPs and type 2 diabetes were investigated using logistic regression. The results were also combined with in silico data from other South Asian datasets (SAT2D consortium) and white European cohorts (DIAGRAM+) using meta-analysis. The rs7602358G allele near PER2 was negatively associated with type 2 diabetes in our Punjabi cohorts (combined odds ratio [OR] = 0.75 [0.66–0.86], p = 3.18×10−5), while the BMAL1 rs11022775T allele was associated with an increased risk of the disease (combined OR = 1.22 [1.07–1.39], p = 0.003). Neither of these associations was replicated in the SAT2D or DIAGRAM+ datasets, however. Meta-analysis of all the cohorts identified disease associations with two variants, rs2292912 in CRY2 and rs12315175 near CRY1, although statistical significance was nominal (combined OR = 1.05 [1.01–1.08], p = 0.008 and OR = 0.95 [0.91–0.99], p = 0.015 respectively). Conclusions/significance None of the selected circadian gene

  16. Structures of KaiC Circadian Clock Mutant Proteins: A New Phosphorylation Site at T426 and Mechanisms of Kinase, ATPase and Phosphatase

    SciTech Connect

    Pattanayek, Rekha; Mori, Tetsuya; Xu, Yao; Pattanayek, Sabuj; Johnson, Carl H.; Egli, Martin

    2010-09-02

    The circadian clock of the cyanobacterium Synechococcus elongatus can be reconstituted in vitro by three proteins, KaiA, KaiB and KaiC. Homo-hexameric KaiC displays kinase, phosphatase and ATPase activities; KaiA enhances KaiC phosphorylation and KaiB antagonizes KaiA. Phosphorylation and dephosphorylation of the two known sites in the C-terminal half of KaiC subunits, T432 and S431, follow a strict order (TS {yields} pTS {yields} pTpS {yields} TpS {yields} TS) over the daily cycle, the origin of which is not understood. To address this void and to analyze the roles of KaiC active site residues, in particular T426, we determined structures of single and double P-site mutants of S. elongatus KaiC. The conformations of the loop region harboring P-site residues T432 and S431 in the crystal structures of six KaiC mutant proteins exhibit subtle differences that result in various distances between Thr (or Ala/Asn/Glu) and Ser (or Ala/Asp) residues and the ATP {gamma}-phosphate. T432 is phosphorylated first because it lies consistently closer to P{gamma}. The structures of the S431A and T432E/S431A mutants reveal phosphorylation at T426. The environments of the latter residue in the structures and functional data for T426 mutants in vitro and in vivo imply a role in dephosphorylation. We provide evidence for a third phosphorylation site in KaiC at T426. T426 and S431 are closely spaced and a KaiC subunit cannot carry phosphates at both sites simultaneously. Fewer subunits are phosphorylated at T426 in the two KaiC mutants compared to phosphorylated T432 and/or S431 residues in the structures of wt and other mutant KaiCs, suggesting that T426 phosphorylation may be labile. The structures combined with functional data for a host of KaiC mutant proteins help rationalize why S431 trails T432 in the loss of its phosphate and shed light on the mechanisms of the KaiC kinase, ATPase and phosphatase activities.

  17. Structures of KaiC Circadian Clock Mutant Proteins: A New Phosphorylation Site at T426 and Mechanisms of Kinase, ATPase and Phosphatase

    PubMed Central

    Pattanayek, Rekha; Mori, Tetsuya; Xu, Yao; Pattanayek, Sabuj; Johnson, Carl H.; Egli, Martin

    2009-01-01

    Background The circadian clock of the cyanobacterium Synechococcus elongatus can be reconstituted in vitro by three proteins, KaiA, KaiB and KaiC. Homo-hexameric KaiC displays kinase, phosphatase and ATPase activities; KaiA enhances KaiC phosphorylation and KaiB antagonizes KaiA. Phosphorylation and dephosphorylation of the two known sites in the C-terminal half of KaiC subunits, T432 and S431, follow a strict order (TS→pTS→pTpS→TpS→TS) over the daily cycle, the origin of which is not understood. To address this void and to analyze the roles of KaiC active site residues, in particular T426, we determined structures of single and double P-site mutants of S. elongatus KaiC. Methodology and Principal Findings The conformations of the loop region harboring P-site residues T432 and S431 in the crystal structures of six KaiC mutant proteins exhibit subtle differences that result in various distances between Thr (or Ala/Asn/Glu) and Ser (or Ala/Asp) residues and the ATP γ-phosphate. T432 is phosphorylated first because it lies consistently closer to Pγ. The structures of the S431A and T432E/S431A mutants reveal phosphorylation at T426. The environments of the latter residue in the structures and functional data for T426 mutants in vitro and in vivo imply a role in dephosphorylation. Conclusions and Significance We provide evidence for a third phosphorylation site in KaiC at T426. T426 and S431 are closely spaced and a KaiC subunit cannot carry phosphates at both sites simultaneously. Fewer subunits are phosphorylated at T426 in the two KaiC mutants compared to phosphorylated T432 and/or S431 residues in the structures of wt and other mutant KaiCs, suggesting that T426 phosphorylation may be labile. The structures combined with functional data for a host of KaiC mutant proteins help rationalize why S431 trails T432 in the loss of its phosphate and shed light on the mechanisms of the KaiC kinase, ATPase and phosphatase activities. PMID:19956664

  18. Feeding and circadian clocks.

    PubMed

    Pardini, Lissia; Kaeffer, Bertrand

    2006-01-01

    The mammalian genome encodes at least a dozen of genes directly involved in the regulation of the feedback loops constituting the circadian clock. The circadian system is built up on a multitude of oscillators organized according to a hierarchical model in which neurons of the suprachiasmatic nuclei of the hypothalamus may drive the central circadian clock and all the other somatic cells may possess the molecular components allowing tissues and organs to constitute peripheral clocks. Suprachiasmatic neurons are driving the central circadian clock which is reset by lighting cues captured and integrated by the melanopsin cells of the retina and define the daily rhythms of locomotor activity and associated physiological regulatory pathways like feeding and metabolism. This central clock entrains peripheral clocks which can be synchronized by non-photic environmental cues and uncoupled from the central one depending on the nature and the strength of the circadian signal. The human circadian clock and its functioning in central or peripheral tissues are currently being explored to increase the therapeutic efficacy of timed administration of drugs or radiation, and to offer better advice on lighting and meal timing useful for frequent travelers suffering from jet lag and for night workers' comfort. However, the molecular mechanism driving and coordinating the central and peripheral clocks through a wide range of synchronizers (lighting, feeding, physical or social activities) remains a mystery.

  19. Physiology of circadian entrainment.

    PubMed

    Golombek, Diego A; Rosenstein, Ruth E

    2010-07-01

    Mammalian circadian rhythms are controlled by endogenous biological oscillators, including a master clock located in the hypothalamic suprachiasmatic nuclei (SCN). Since the period of this oscillation is of approximately 24 h, to keep synchrony with the environment, circadian rhythms need to be entrained daily by means of Zeitgeber ("time giver") signals, such as the light-dark cycle. Recent advances in the neurophysiology and molecular biology of circadian rhythmicity allow a better understanding of synchronization. In this review we cover several aspects of the mechanisms for photic entrainment of mammalian circadian rhythms, including retinal sensitivity to light by means of novel photopigments as well as circadian variations in the retina that contribute to the regulation of retinal physiology. Downstream from the retina, we examine retinohypothalamic communication through neurotransmitter (glutamate, aspartate, pituitary adenylate cyclase-activating polypeptide) interaction with SCN receptors and the resulting signal transduction pathways in suprachiasmatic neurons, as well as putative neuron-glia interactions. Finally, we describe and analyze clock gene expression and its importance in entrainment mechanisms, as well as circadian disorders or retinal diseases related to entrainment deficits, including experimental and clinical treatments. PMID:20664079

  20. The pervasiveness and plasticity of circadian oscillations: the coupled circadian-oscillators framework

    PubMed Central

    Patel, Vishal R.; Ceglia, Nicholas; Zeller, Michael; Eckel-Mahan, Kristin; Sassone-Corsi, Paolo; Baldi, Pierre

    2015-01-01

    Motivation: Circadian oscillations have been observed in animals, plants, fungi and cyanobacteria and play a fundamental role in coordinating the homeostasis and behavior of biological systems. Genetically encoded molecular clocks found in nearly every cell, based on negative transcription/translation feedback loops and involving only a dozen genes, play a central role in maintaining these oscillations. However, high-throughput gene expression experiments reveal that in a typical tissue, a much larger fraction (∼10%) of all transcripts oscillate with the day–night cycle and the oscillating species vary with tissue type suggesting that perhaps a much larger fraction of all transcripts, and perhaps also other molecular species, may bear the potential for circadian oscillations. Results: To better quantify the pervasiveness and plasticity of circadian oscillations, we conduct the first large-scale analysis aggregating the results of 18 circadian transcriptomic studies and 10 circadian metabolomic studies conducted in mice using different tissues and under different conditions. We find that over half of protein coding genes in the cell can produce transcripts that are circadian in at least one set of conditions and similarly for measured metabolites. Genetic or environmental perturbations can disrupt existing oscillations by changing their amplitudes and phases, suppressing them or giving rise to novel circadian oscillations. The oscillating species and their oscillations provide a characteristic signature of the physiological state of the corresponding cell/tissue. Molecular networks comprise many oscillator loops that have been sculpted by evolution over two trillion day–night cycles to have intrinsic circadian frequency. These oscillating loops are coupled by shared nodes in a large network of coupled circadian oscillators where the clock genes form a major hub. Cells can program and re-program their circadian repertoire through epigenetic and other mechanisms

  1. Circadian rhythms and endocrine functions in adult insects.

    PubMed

    Bloch, Guy; Hazan, Esther; Rafaeli, Ada

    2013-01-01

    Many behavioral and physiological processes in adult insects are influenced by both the endocrine and circadian systems, suggesting that these two key physiological systems interact. We reviewed the literature and found that experiments explicitly testing these interactions in adult insects have only been conducted for a few species. There is a shortage of measurements of hormone titers throughout the day under constant conditions even for the juvenile hormones (JHs) and ecdysteroids, the best studied insect hormones. Nevertheless, the available measurements of hormone titers coupled with indirect evidence for circadian modulation of hormone biosynthesis rate, and the expression of genes encoding proteins involved in hormone biosynthesis, binding or degradation are consistent with the hypothesis that the circulating levels of many insect hormones are influenced by the circadian system. Whole genome microarray studies suggest that the modulation of farnesol oxidase levels is important for the circadian regulation of JH biosynthesis in honey bees, mosquitoes, and fruit flies. Several studies have begun to address the functional significance of circadian oscillations in endocrine signaling. The best understood system is the circadian regulation of Pheromone Biosynthesis Activating Neuropeptide (PBAN) titers which is important for the temporal organization of sexual behavior in female moths. The evidence that the circadian and endocrine systems interact has important implications for studies of insect physiology and behavior. Additional studies on diverse species and physiological processes are needed for identifying basic principles underlying the interactions between the circadian and endocrine systems in insects.

  2. Intrinsic, nondeterministic circadian rhythm generation in identified mammalian neurons.

    PubMed

    Webb, Alexis B; Angelo, Nikhil; Huettner, James E; Herzog, Erik D

    2009-09-22

    Circadian rhythms are modeled as reliable and self-sustained oscillations generated by single cells. The mammalian suprachiasmatic nucleus (SCN) keeps near 24-h time in vivo and in vitro, but the identity of the individual cellular pacemakers is unknown. We tested the hypothesis that circadian cycling is intrinsic to a unique class of SCN neurons by measuring firing rate or Period2 gene expression in single neurons. We found that fully isolated SCN neurons can sustain circadian cycling for at least 1 week. Plating SCN neurons at <100 cells/mm(2) eliminated synaptic inputs and revealed circadian neurons that contained arginine vasopressin (AVP) or vasoactive intestinal polypeptide (VIP) or neither. Surprisingly, arrhythmic neurons (nearly 80% of recorded neurons) also expressed these neuropeptides. Furthermore, neurons were observed to lose or gain circadian rhythmicity in these dispersed cell cultures, both spontaneously and in response to forskolin stimulation. In SCN explants treated with tetrodotoxin to block spike-dependent signaling, neurons gained or lost circadian cycling over many days. The rate of PERIOD2 protein accumulation on the previous cycle reliably predicted the spontaneous onset of arrhythmicity. We conclude that individual SCN neurons can generate circadian oscillations; however, there is no evidence for a specialized or anatomically localized class of cell-autonomous pacemakers. Instead, these results indicate that AVP, VIP, and other SCN neurons are intrinsic but unstable circadian oscillators that rely on network interactions to stabilize their otherwise noisy cycling. PMID:19805326

  3. Circadian clocks and breast cancer.

    PubMed

    Blakeman, Victoria; Williams, Jack L; Meng, Qing-Jun; Streuli, Charles H

    2016-01-01

    Circadian clocks respond to environmental time cues to coordinate 24-hour oscillations in almost every tissue of the body. In the breast, circadian clocks regulate the rhythmic expression of numerous genes. Disrupted expression of circadian genes can alter breast biology and may promote cancer. Here we overview circadian mechanisms, and the connection between the molecular clock and breast biology. We describe how disruption of circadian genes contributes to cancer via multiple mechanisms, and link this to increased tumour risk in women who work irregular shift patterns. Understanding the influence of circadian rhythms on breast cancer could lead to more efficacious therapies, reformed public health policy and improved patient outcome. PMID:27590298

  4. Molecular Mechanisms of Circadian Regulation During Spaceflight

    NASA Technical Reports Server (NTRS)

    Zanello, Susana; Boyle, Richard

    2011-01-01

    Disruption of the regular environmental circadian cues in addition to stringent and demanding operational schedules are two main factors that undoubtedly impact sleep patterns and vigilant performance in the astronaut crews during spaceflight. Most research is focused on the behavioral aspects of the risk of circadian desynchronization, characterized by fatigue and health and performance decrement. A common countermeasure for circadian re-entrainment utilizes blue-green light to entrain the circadian clock and mitigate this risk. However, an effective countermeasure targeting the photoreceptor system requires that the basic circadian molecular machinery remains intact during spaceflight. The molecular clock consists of sets of proteins that perform different functions within the clock machinery: circadian oscillators (genes whose expression levels cycle during the day, keep the pass of cellular time and regulate downstream effector genes), the effector or output genes (those which impact the physiology of the tissue or organism), and the input genes (responsible for sensing the environmental cues that allow circadian entrainment). The main environmental cue is light. As opposed to the known photoreceptors (rods and cones), the non-visual light stimulus is received by a subset of the population of retinal ganglion cells called intrinsically photosensitive retinal ganglion cells (ipRGC) that express melanopsin (opsin 4 -Opn4-) as the photoreceptor. We hypothesize that spaceflight may affect ipRGC and melanopsin expression, which may be a contributing cause of circadian disruption during spaceflight. To answer this question, eyes from albino Balb/cJ mice aboard STS-133 were collected for histological analysis and gene expression profiling of the retina at 1 and 7 days after landing. Both vivarium and AEM (animal enclosure module) mice were used as ground controls. Opn4 expression was analyzed by real time RT/qPCR and retinal sections were stained for Opn4

  5. Circadian Rhythms and Mood Disorders: Are the Phenomena and Mechanisms Causally Related?

    PubMed Central

    Bechtel, William

    2015-01-01

    This paper reviews some of the compelling evidence of disrupted circadian rhythms in individuals with mood disorders (major depressive disorder, seasonal affective disorder, and bipolar disorder) and that treatments such as bright light, designed to alter circadian rhythms, are effective in treating these disorders. Neurotransmitters in brain regions implicated in mood regulation exhibit circadian rhythms. A mouse model originally employed to identify a circadian gene has proven a potent model for mania. While this evidence is suggestive of an etiological role for altered circadian rhythms in mood disorders, it is compatible with other explanations, including that disrupted circadian rhythms and mood disorders are effects of a common cause and that genes and proteins implicated in both simply have pleiotropic effects. In light of this, the paper advances a proposal as to what evidence would be needed to establish a direct causal link between disruption of circadian rhythms and mood disorders. PMID:26379559

  6. Crosstalk between circadian rhythmicity, mitochondrial dynamics and macrophage bactericidal activity

    PubMed Central

    Oliva-Ramírez, Jacqueline; Moreno-Altamirano, María Maximina B; Pineda-Olvera, Benjamín; Cauich-Sánchez, Patricia; Sánchez-García, F Javier

    2014-01-01

    Biological functions show rhythmic fluctuations with 24-hr periodicity regulated by circadian proteins encoded by the so-called ‘clock’ genes. The absence or deregulation of circadian proteins in mice leads to metabolic disorders and in vitro models have shown that the synthesis of pro-inflammatory cytokines by macrophages follows a circadian rhythm so showing a link between circadian rhythmicity, metabolism and immunity. Recent evidence reveals that mitochondrial shape, position and size, collectively referred to as mitochondrial dynamics, are related to both cell metabolism and immune function. However, studies addressing the simultaneous crosstalk between circadian rhythm, mitochondrial dynamics and cell immune function are scarce. Here, by using an in vitro model of synchronized murine peritoneal macrophages, we present evidence that the mitochondrial dynamics and the mitochondrial membrane potential (Δψm) follow a circadian rhythmic pattern. In addition, it is shown that the fusion of mitochondria along with high Δψm, indicative of high mitochondrial activity, precede the highest phagocytic and bactericidal activity of macrophages on Salmonella typhimurium. Taken together, our results suggest a timely coordination between circadian rhythmicity, mitochondrial dynamics, and the bactericidal capacity of macrophages. PMID:24903615

  7. Socially synchronized circadian oscillators

    PubMed Central

    Bloch, Guy; Herzog, Erik D.; Levine, Joel D.; Schwartz, William J.

    2013-01-01

    Daily rhythms of physiology and behaviour are governed by an endogenous timekeeping mechanism (a circadian ‘clock’). The alternation of environmental light and darkness synchronizes (entrains) these rhythms to the natural day–night cycle, and underlying mechanisms have been investigated using singly housed animals in the laboratory. But, most species ordinarily would not live out their lives in such seclusion; in their natural habitats, they interact with other individuals, and some live in colonies with highly developed social structures requiring temporal synchronization. Social cues may thus be critical to the adaptive function of the circadian system, but elucidating their role and the responsible mechanisms has proven elusive. Here, we highlight three model systems that are now being applied to understanding the biology of socially synchronized circadian oscillators: the fruitfly, with its powerful array of molecular genetic tools; the honeybee, with its complex natural society and clear division of labour; and, at a different level of biological organization, the rodent suprachiasmatic nucleus, site of the brain's circadian clock, with its network of mutually coupled single-cell oscillators. Analyses at the ‘group’ level of circadian organization will likely generate a more complex, but ultimately more comprehensive, view of clocks and rhythms and their contribution to fitness in nature. PMID:23825203

  8. [Circadian rhythm sleep disorder].

    PubMed

    Mishima, Kazuo

    2013-12-01

    Primary pathophysiology of circadian rhythm sleep disorders(CRSDs) is a misalignment between the endogenous circadian rhythm phase and the desired or socially required sleep-wake schedule, or dysfunction of the circadian pacemaker and its afferent/efferent pathways. CRSDs consist of delayed sleep phase type, advanced sleep phase type, free-running type, irregular sleep-wake type, shift work type and jet lag type. Chronotherapy using strong zeitgebers (time cues), such as bright light and melatonin/ melatonin type 2 receptor agonist, is effective when administered with proper timing. Bright light is the strongest entraining agent of circadian rhythms. Bright light therapy (appropriately-timed exposure to bright light) for CRSDs is an effective treatment option, and can shift the sleep-wake cycle to earlier or later times, in order to correct for misalignment between the circadian system and the desired sleep-wake schedule. Timed administration of melatonin, either alone or in combination with light therapy has also been shown to be useful in the treatment of CRSDs.

  9. Circadian Rhythms in Cyanobacteria.

    PubMed

    Cohen, Susan E; Golden, Susan S

    2015-12-01

    Life on earth is subject to daily and predictable fluctuations in light intensity, temperature, and humidity created by rotation of the earth. Circadian rhythms, generated by a circadian clock, control temporal programs of cellular physiology to facilitate adaptation to daily environmental changes. Circadian rhythms are nearly ubiquitous and are found in both prokaryotic and eukaryotic organisms. Here we introduce the molecular mechanism of the circadian clock in the model cyanobacterium Synechococcus elongatus PCC 7942. We review the current understanding of the cyanobacterial clock, emphasizing recent work that has generated a more comprehensive understanding of how the circadian oscillator becomes synchronized with the external environment and how information from the oscillator is transmitted to generate rhythms of biological activity. These results have changed how we think about the clock, shifting away from a linear model to one in which the clock is viewed as an interactive network of multifunctional components that are integrated into the context of the cell in order to pace and reset the oscillator. We conclude with a discussion of how this basic timekeeping mechanism differs in other cyanobacterial species and how information gleaned from work in cyanobacteria can be translated to understanding rhythmic phenomena in other prokaryotic systems. PMID:26335718

  10. System identification of the Arabidopsis plant circadian system

    NASA Astrophysics Data System (ADS)

    Foo, Mathias; Somers, David E.; Kim, Pan-Jun

    2015-02-01

    The circadian system generates an endogenous oscillatory rhythm that governs the daily activities of organisms in nature. It offers adaptive advantages to organisms through a coordination of their biological functions with the optimal time of day. In this paper, a model of the circadian system in the plant Arabidopsis (species thaliana) is built by using system identification techniques. Prior knowledge about the physical interactions of the genes and the proteins in the plant circadian system is incorporated in the model building exercise. The model is built by using primarily experimentally-verified direct interactions between the genes and the proteins with the available data on mRNA and protein abundances from the circadian system. Our analysis reveals a great performance of the model in predicting the dynamics of the plant circadian system through the effect of diverse internal and external perturbations (gene knockouts and day-length changes). Furthermore, we found that the circadian oscillatory rhythm is robust and does not vary much with the biochemical parameters except those of a light-sensitive protein P and a transcription factor TOC1. In other words, the circadian rhythmic profile is largely a consequence of the network's architecture rather than its particular parameters. Our work suggests that the current experimental knowledge of the gene-to-protein interactions in the plant Arabidopsis, without considering any additional hypothetical interactions, seems to suffice for system-level modeling of the circadian system of this plant and to present an exemplary platform for the control of network dynamics in complex living organisms.

  11. Orexin as an input of circadian system in goldfish: Effects on clock gene expression and locomotor activity rhythms.

    PubMed

    Nisembaum, Laura G; de Pedro, Nuria; Delgado, María J; Sánchez-Bretaño, Aída; Isorna, Esther

    2014-02-01

    Orexins are neuropeptides mainly known for regulating feeding behavior and sleep-wakefulness cycle in vertebrates. Daily variations of orexin-A expression have been reported in fish, with the highest levels preceding feeding time. However, it is unknown if such variations could be related with daily rhythms of clock genes, which form the molecular core of circadian oscillators. The aim of the present study was to identify the possible role of orexin as an input element of the goldfish circadian system. It was investigated the effects of orexin-A (10ng/gbw) intracerebroventricular injections on the expression of clock genes, NPY and ghrelin, as well as on daily locomotor activity rhythms. Goldfish held under 12L:12D photoperiod and injected at midday with orexin or saline, were sacrificed at 1 and 3h post-injection. The analysis of genes expression by qReal Time PCR showed an increment of Per genes in hypothalamus and foregut at 3h post-injection, but not in hindgut and liver. The gBmal1a expression remained unaltered in all the studied tissues. Orexin induced NPY in the hypothalamus and ghrelin in the foregut. Locomotor activity was studied in fish daily injected with orexin for several consecutive days under different experimental conditions. Orexin synchronized locomotor activity in goldfish maintained in 24L and fasting conditions. Present results support a cross-talking between orexin-A and other feeding regulators at central and peripheral level, and suggest, for the first time, a role of this peptide as an input of the circadian system in fish.

  12. Dephosphorylation of the core clock protein KaiC in the cyanobacterial KaiABC circadian oscillator proceeds via an ATP synthase mechanism.

    PubMed

    Egli, Martin; Mori, Tetsuya; Pattanayek, Rekha; Xu, Yao; Qin, Ximing; Johnson, Carl H

    2012-02-28

    The circadian clock of the cyanobacterium Synechococcus elongatus can be reconstituted in vitro from three proteins, KaiA, KaiB, and KaiC in the presence of ATP, to tick in a temperature-compensated manner. KaiC, the central cog of this oscillator, forms a homohexamer with 12 ATP molecules bound between its N- and C-terminal domains and exhibits unusual properties. Both the N-terminal (CI) and C-terminal (CII) domains harbor ATPase activity, and the subunit interfaces between CII domains are the sites of autokinase and autophosphatase activities. Hydrolysis of ATP correlates with phosphorylation at threonine and serine sites across subunits in an orchestrated manner, such that first T432 and then S431 are phosphorylated, followed by dephosphorylation of these residues in the same order. Although structural work has provided insight into the mechanisms of ATPase and kinase, the location and mechanism of the phosphatase have remained enigmatic. From the available experimental data based on a range of approaches, including KaiC crystal structures and small-angle X-ray scattering models, metal ion dependence, site-directed mutagenesis (i.e., E318, the general base), and measurements of the associated clock periods, phosphorylation patterns, and dephosphorylation courses as well as a lack of sequence motifs in KaiC that are typically associated with known phosphatases, we hypothesized that KaiCII makes use of the same active site for phosphorylation and dephosphorlyation. We observed that wild-type KaiC (wt-KaiC) exhibits an ATP synthase activity that is significantly reduced in the T432A/S431A mutant. We interpret the first observation as evidence that KaiCII is a phosphotransferase instead of a phosphatase and the second that the enzyme is capable of generating ATP, both from ADP and P(i) (in a reversal of the ATPase reaction) and from ADP and P-T432/P-S431 (dephosphorylation). This new concept regarding the mechanism of dephosphorylation is also supported by the

  13. Dephosphorylation of the Core Clock Protein KaiC in the Cyanobacterial KaiABC Circadian Oscillator Proceeds via an ATP Synthase Mechanism

    SciTech Connect

    Egli, Martin; Mori, Tetsuya; Pattanayek, Rekha; Xu, Yao; Qin, Ximing; Johnson, Carl H.

    2014-10-02

    The circadian clock of the cyanobacterium Synechococcus elongatus can be reconstituted in vitro from three proteins, KaiA, KaiB, and KaiC in the presence of ATP, to tick in a temperature-compensated manner. KaiC, the central cog of this oscillator, forms a homohexamer with 12 ATP molecules bound between its N- and C-terminal domains and exhibits unusual properties. Both the N-terminal (CI) and C-terminal (CII) domains harbor ATPase activity, and the subunit interfaces between CII domains are the sites of autokinase and autophosphatase activities. Hydrolysis of ATP correlates with phosphorylation at threonine and serine sites across subunits in an orchestrated manner, such that first T432 and then S431 are phosphorylated, followed by dephosphorylation of these residues in the same order. Although structural work has provided insight into the mechanisms of ATPase and kinase, the location and mechanism of the phosphatase have remained enigmatic. From the available experimental data based on a range of approaches, including KaiC crystal structures and small-angle X-ray scattering models, metal ion dependence, site-directed mutagenesis (i.e., E318, the general base), and measurements of the associated clock periods, phosphorylation patterns, and dephosphorylation courses as well as a lack of sequence motifs in KaiC that are typically associated with known phosphatases, we hypothesized that KaiCII makes use of the same active site for phosphorylation and dephosphorlyation. We observed that wild-type KaiC (wt-KaiC) exhibits an ATP synthase activity that is significantly reduced in the T432A/S431A mutant. We interpret the first observation as evidence that KaiCII is a phosphotransferase instead of a phosphatase and the second that the enzyme is capable of generating ATP, both from ADP and P{sub i} (in a reversal of the ATPase reaction) and from ADP and P-T432/P-S431 (dephosphorylation). This new concept regarding the mechanism of dephosphorylation is also supported by the

  14. Circadian acetylome reveals regulation of mitochondrial metabolic pathways.

    PubMed

    Masri, Selma; Patel, Vishal R; Eckel-Mahan, Kristin L; Peleg, Shahaf; Forne, Ignasi; Ladurner, Andreas G; Baldi, Pierre; Imhof, Axel; Sassone-Corsi, Paolo

    2013-02-26

    The circadian clock is constituted by a complex molecular network that integrates a number of regulatory cues needed to maintain organismal homeostasis. To this effect, posttranslational modifications of clock proteins modulate circadian rhythms and are thought to convert physiological signals into changes in protein regulatory function. To explore reversible lysine acetylation that is dependent on the clock, we have characterized the circadian acetylome in WT and Clock-deficient (Clock(-/-)) mouse liver by quantitative mass spectrometry. Our analysis revealed that a number of mitochondrial proteins involved in metabolic pathways are heavily influenced by clock-driven acetylation. Pathways such as glycolysis/gluconeogenesis, citric acid cycle, amino acid metabolism, and fatty acid metabolism were found to be highly enriched hits. The significant number of metabolic pathways whose protein acetylation profile is altered in Clock(-/-) mice prompted us to link the acetylome to the circadian metabolome previously characterized in our laboratory. Changes in enzyme acetylation over the circadian cycle and the link to metabolite levels are discussed, revealing biological implications connecting the circadian clock to cellular metabolic state.

  15. Circadian Rhythm Sleep Disorders

    PubMed Central

    Kim, Min Ju; Lee, Jung Hie; Duffy, Jeanne F.

    2014-01-01

    Objective To review circadian rhythm sleep disorders, including underlying causes, diagnostic considerations, and typical treatments. Methods Literature review and discussion of specific cases. Results Survey studies 1,2 suggest that up to 3% of the adult population suffers from a circadian rhythm sleep disorder (CRSD). However, these sleep disorders are often confused with insomnia, and an estimated 10% of adult and 16% of adolescent sleep disorders patients may have a CRSD 3-6. While some CRSD (such as jet lag) can be self-limiting, others when untreated can lead to adverse medical, psychological, and social consequences. The International Classification of Sleep Disorders classifies CRSD as dyssomnias, with six subtypes: Advanced Sleep Phase Type, Delayed Sleep Phase Type, Irregular Sleep Wake Type, Free Running Type, Jet Lag Type, and Shift Work Type. The primary clinical characteristic of all CRSD is an inability to fall asleep and wake at the desired time. It is believed that CRSD arise from a problem with the internal biological clock (circadian timing system) and/or misalignment between the circadian timing system and the external 24-hour environment. This misalignment can be the result of biological and/or behavioral factors. CRSD can be confused with other sleep or medical disorders. Conclusions Circadian rhythm sleep disorders are a distinct class of sleep disorders characterized by a mismatch between the desired timing of sleep and the ability to fall asleep and remain asleep. If untreated, CRSD can lead to insomnia and excessive daytime sleepiness, with negative medical, psychological, and social consequences. It is important for physicians to recognize potential circadian rhythm sleep disorders so that appropriate diagnosis, treatment, and referral can be made. PMID:25368503

  16. Circadian Disruption in Psychiatric Disorders.

    PubMed

    Jones, Stephanie G; Benca, Ruth M

    2015-12-01

    Evidence suggests that abnormalities in circadian rhythms might prove causally or pathophysiologically significant in psychiatric illness. The circadian regulation of hormonal and behavioral timekeeping processes is often altered in patients with major depression, bipolar disorder, and schizophrenia, and a susceptibility to rhythm instability may contribute to the functional impairment. For some patients, interventions that stabilize or resynchronize circadian rhythms prove therapeutically effective. Circadian disruption in the clinical profiles of most psychiatric illnesses and the treatment efficacy of chronobiological interventions suggest that attention to circadian phenotypes in a range of psychiatric disorders may help to uncover shared pathophysiologic mechanisms. PMID:26568124

  17. Circadian Clocks, Stress, and Immunity

    PubMed Central

    Dumbell, Rebecca; Matveeva, Olga; Oster, Henrik

    2016-01-01

    In mammals, molecular circadian clocks are present in most cells of the body, and this circadian network plays an important role in synchronizing physiological processes and behaviors to the appropriate time of day. The hypothalamic–pituitary–adrenal endocrine axis regulates the response to acute and chronic stress, acting through its final effectors – glucocorticoids – released from the adrenal cortex. Glucocorticoid secretion, characterized by its circadian rhythm, has an important role in synchronizing peripheral clocks and rhythms downstream of the master circadian pacemaker in the suprachiasmatic nucleus. Finally, glucocorticoids are powerfully anti-inflammatory, and recent work has implicated the circadian clock in various aspects and cells of the immune system, suggesting a tight interplay of stress and circadian systems in the regulation of immunity. This mini-review summarizes our current understanding of the role of the circadian clock network in both the HPA axis and the immune system, and discusses their interactions. PMID:27199894

  18. 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…

  19. Circadian rhythm in handwriting.

    PubMed

    Jasper, Isabelle; Häussler, Andreas; Marquardt, Christian; Hermsdörfer, Joachim

    2009-06-01

    The aim of the present study was to determine whether the motor process of handwriting is influenced by a circadian rhythm. Nine healthy young male subjects underwent a 40-h sleep deprivation protocol under constant routine conditions. Starting at 09:00 hours, subjects performed every 3 h two handwriting tasks of different complexity. Handwriting performance was evaluated by writing speed, writing fluency and script size. The frequency of handwriting, as a measure of movement speed, revealed a circadian rhythm, validated by harmonic regression, with a slowing at the time of the onset of melatonin secretion (22:17 hours) and a trough in the very early morning at around 03:30 hours. In the temporal variability of handwriting an effect of task complexity was suggested in the direction of circadian variations in parallel with speed only for the sentence. Despite deficits of speed and temporal variability, writing fluency did not change significantly across sessions indicating that the basic automation of handwriting was preserved at any time. On the second day, daytime levels of the kinematics of handwriting did not reflect impaired performance after sleep deprivation. Our results show for the first time a clear circadian rhythm for the production of handwriting.

  20. Circadian Mechanisms Underlying Reward-Related Neurophysiology and Synaptic Plasticity

    PubMed Central

    Parekh, Puja K.; McClung, Colleen A.

    2016-01-01

    Evidence from clinical and preclinical research provides an undeniable link between disruptions in the circadian clock and the development of psychiatric diseases, including mood and substance abuse disorders. The molecular clock, which controls daily patterns of physiological and behavioral activity in living organisms, when desynchronized, may exacerbate or precipitate symptoms of psychiatric illness. One of the outstanding questions remaining in this field is that of cause and effect in the relationship between circadian rhythm disruption and psychiatric disease. Focus has recently turned to uncovering the role of circadian proteins beyond the maintenance of homeostatic systems and outside of the suprachiasmatic nucleus (SCN), the master pacemaker region of the brain. In this regard, several groups, including our own, have sought to understand how circadian proteins regulate mechanisms of synaptic plasticity and neurotransmitter signaling in mesocorticolimbic brain regions, which are known to be critically involved in reward processing and mood. This regulation can come in the form of direct transcriptional control of genes central to mood and reward, including those associated with dopaminergic activity in the midbrain. It can also be seen at the circuit level through indirect connections of mesocorticolimbic regions with the SCN. Circadian misalignment paradigms as well as genetic models of circadian disruption have helped to elucidate some of the complex interactions between these systems and neural activity influencing behavior. In this review, we explore findings that link circadian protein function with synaptic adaptations underlying plasticity as it may contribute to the development of mood disorders and addiction. In light of recent advances in technology and sophisticated methods for molecular and circuit-level interrogation, we propose future directions aimed at teasing apart mechanisms through which the circadian system modulates mood and reward

  1. Circadian Mechanisms Underlying Reward-Related Neurophysiology and Synaptic Plasticity.

    PubMed

    Parekh, Puja K; McClung, Colleen A

    2015-01-01

    Evidence from clinical and preclinical research provides an undeniable link between disruptions in the circadian clock and the development of psychiatric diseases, including mood and substance abuse disorders. The molecular clock, which controls daily patterns of physiological and behavioral activity in living organisms, when desynchronized, may exacerbate or precipitate symptoms of psychiatric illness. One of the outstanding questions remaining in this field is that of cause and effect in the relationship between circadian rhythm disruption and psychiatric disease. Focus has recently turned to uncovering the role of circadian proteins beyond the maintenance of homeostatic systems and outside of the suprachiasmatic nucleus (SCN), the master pacemaker region of the brain. In this regard, several groups, including our own, have sought to understand how circadian proteins regulate mechanisms of synaptic plasticity and neurotransmitter signaling in mesocorticolimbic brain regions, which are known to be critically involved in reward processing and mood. This regulation can come in the form of direct transcriptional control of genes central to mood and reward, including those associated with dopaminergic activity in the midbrain. It can also be seen at the circuit level through indirect connections of mesocorticolimbic regions with the SCN. Circadian misalignment paradigms as well as genetic models of circadian disruption have helped to elucidate some of the complex interactions between these systems and neural activity influencing behavior. In this review, we explore findings that link circadian protein function with synaptic adaptations underlying plasticity as it may contribute to the development of mood disorders and addiction. In light of recent advances in technology and sophisticated methods for molecular and circuit-level interrogation, we propose future directions aimed at teasing apart mechanisms through which the circadian system modulates mood and reward

  2. Chronic exposure to low doses of pharmaceuticals disturbs the hepatic expression of circadian genes in lean and obese mice

    SciTech Connect

    Anthérieu, Sébastien; Le Guillou, Dounia; Coulouarn, Cédric; Begriche, Karima; Trak-Smayra, Viviane; Martinais, Sophie; Porceddu, Mathieu; Robin, Marie-Anne; Fromenty, Bernard

    2014-04-01

    Drinking water can be contaminated with pharmaceuticals. However, it is uncertain whether this contamination can be harmful for the liver, especially during obesity. Hence, the goal of our study was to determine whether chronic exposure to low doses of pharmaceuticals could have deleterious effects on livers of lean and obese mice. To this end, lean and ob/ob male mice were treated for 4 months with a mixture of 11 drugs provided in drinking water at concentrations ranging from 10 to 10{sup 6} ng/l. At the end of the treatment, some liver and plasma abnormalities were observed in ob/ob mice treated with the cocktail containing 10{sup 6} ng/l of each drug. For this dosage, a gene expression analysis by microarray showed altered expression of circadian genes (e.g. Bmal1, Dbp, Cry1) in lean and obese mice. RT-qPCR analyses carried out in all groups of animals confirmed that expression of 8 different circadian genes was modified in a dose-dependent manner. For some genes, a significant modification was observed for dosages as low as 10{sup 2}–10{sup 3} ng/l. Drug mixture and obesity presented an additive effect on circadian gene expression. These data were validated in an independent study performed in female mice. Thus, our study showed that chronic exposure to trace pharmaceuticals disturbed hepatic expression of circadian genes, particularly in obese mice. Because some of the 11 drugs can be found in drinking water at such concentrations (e.g. acetaminophen, carbamazepine, ibuprofen) our data could be relevant in environmental toxicology, especially for obese individuals exposed to these contaminants. - Highlights: • The contamination of drinking water with drugs may have harmful effects on health. • Some drugs can be more hepatotoxic in the context of obesity and fatty liver. • Effects of chronic exposure of trace drugs were studied in lean and obese mouse liver. Drugs and obesity present additive effects on circadian gene expression and toxicity. • Trace

  3. Circadian clocks and cell division

    PubMed Central

    2010-01-01

    Evolution has selected a system of two intertwined cell cycles: the cell division cycle (CDC) and the daily (circadian) biological clock. The circadian clock keeps track of solar time and programs biological processes to occur at environmentally appropriate times. One of these processes is the CDC, which is often gated by the circadian clock. The intermeshing of these two cell cycles is probably responsible for the observation that disruption of the circadian system enhances susceptibility to some kinds of cancer. The core mechanism underlying the circadian clockwork has been thought to be a transcription and translation feedback loop (TTFL), but recent evidence from studies with cyanobacteria, synthetic oscillators and immortalized cell lines suggests that the core circadian pacemaking mechanism that gates cell division in mammalian cells could be a post-translational oscillator (PTO). PMID:20890114

  4. Best practices for fluorescence microscopy of the cyanobacterial circadian clock

    PubMed Central

    Cohen, Susan E.; Erb, Marcella L.; Pogliano, Joe; Golden, Susan S.

    2015-01-01

    Summary This chapter deals with methods of monitoring the subcellular localization of proteins in single cells in the circadian model system Synechococcus elongatus PCC 7942. While genetic, biochemical and structural insights into the cyanobacterial circadian oscillator have flourished, difficulties in achieving informative subcellular imaging in cyanobacterial cells have delayed progress of the cell biology aspects of the clock. Here, we describe best practices for using fluorescent protein tags to monitor localization. Specifically we address how to vet fusion proteins and overcome challenges in microscopic imaging of very small autofluorescent cells. PMID:25662459

  5. CIRCADIAN REGULATION OF METABOLISM

    PubMed Central

    Bailey, Shannon M.; Udoh, Uduak S.; Young, Martin E.

    2014-01-01

    In association with sleep/wake and fasting/feeding cycles, organisms experience dramatic oscillations in energetic demands and nutrient supply. It is therefore not surprising that various metabolic parameters, ranging from the activity status of molecular energy sensors to circulating nutrient levels, oscillate in time-of-day-dependent manners. It has become increasingly clear that rhythms in metabolic processes are not simply in response to daily environmental/behavioral influences, but are driven in part by cell autonomous circadian clocks. By synchronizing the cell with its environment, clocks modulate a host of metabolic processes in a temporally appropriate manner. The purpose of this article is to review current understanding of the interplay between circadian clocks and metabolism, in addition to the pathophysiologic consequences of disruption of this molecular mechanism, in terms of cardiometabolic disease development. PMID:24928941

  6. Sleep and circadian rhythms

    NASA Technical Reports Server (NTRS)

    Monk, Timothy H.

    1991-01-01

    Three interacting processes are involved in the preservation of circadian rhythms: (1) endogenous rhythm generation mechanisms, (2) entrainment mechanisms to keep these rhythms 'on track', and (3) exogenous masking processes stemming from changes in environment and bahavior. These processes, particularly the latter two, can be dramatically affected in individuals of advanced age and in space travelers, with a consequent disruption in sleep and daytime functioning. This paper presents results of a phase-shift experiment investigating the age-related effects of the exogeneous component of circadian rhythms in various physiological and psychological functions by comparing these functions in middle aged and old subjects. Dramatic differences were found between the two age groups in measures of sleep, mood, activation, and performance efficiency.

  7. Sleep and circadian schedule disorders.

    PubMed

    Labyak, Susan

    2002-12-01

    The timing and synchronization of human circadian rhythms is important for health and well-being. Some individuals, for reasons that remain unclear, display less resilience or flexibility in their ability to synchronize to the 24-hour world and are thus diagnosed with a circadian schedule disorder. The objective of this article is to briefly introduce concepts about human circadian timing and to review what is known about chronic, long-term circadian schedule disorders such as delayed sleep phase syndrome, advanced sleep phase syndrome, irregular sleep-wake patterns, and non-24-hour sleep-wake disorder. Practical considerations for the clinician caring for these individuals are discussed. PMID:12587363

  8. Circadian Regulation of Synaptic Plasticity

    PubMed Central

    Frank, Marcos G.

    2016-01-01

    Circadian rhythms refer to oscillations in biological processes with a period of approximately 24 h. In addition to the sleep/wake cycle, there are circadian rhythms in metabolism, body temperature, hormone output, organ function and gene expression. There is also evidence of circadian rhythms in synaptic plasticity, in some cases driven by a master central clock and in other cases by peripheral clocks. In this article, I review the evidence for circadian influences on synaptic plasticity. I also discuss ways to disentangle the effects of brain state and rhythms on synaptic plasticity. PMID:27420105

  9. Circadian Regulation of Synaptic Plasticity.

    PubMed

    Frank, Marcos G

    2016-01-01

    Circadian rhythms refer to oscillations in biological processes with a period of approximately 24 h. In addition to the sleep/wake cycle, there are circadian rhythms in metabolism, body temperature, hormone output, organ function and gene expression. There is also evidence of circadian rhythms in synaptic plasticity, in some cases driven by a master central clock and in other cases by peripheral clocks. In this article, I review the evidence for circadian influences on synaptic plasticity. I also discuss ways to disentangle the effects of brain state and rhythms on synaptic plasticity. PMID:27420105

  10. Circadian Timing in the Lung; A Specific Role for Bronchiolar Epithelial Cells

    PubMed Central

    Gibbs, J. E.; Beesley, S.; Plumb, J.; Singh, D.; Farrow, S.; Ray, D. W.; Loudon, A. S. I.

    2015-01-01

    In addition to the core circadian oscillator, located within the suprachiasmatic nucleus, numerous peripheral tissues possess self-sustaining circadian timers. In vivo these are entrained and temporally synchronized by signals conveyed from the core oscillator. In the present study, we examine circadian timing in the lung, determine the cellular localization of core clock proteins in both mouse and human lung tissue, and establish the effects of glucocorticoids (widely used in the treatment of asthma) on the pulmonary clock. Using organotypic lung slices prepared from transgenic mPER2::Luc mice, luciferase levels, which report PER2 expression, were measured over a number of days. We demonstrate a robust circadian rhythm in the mouse lung that is responsive to glucocorticoids. Immunohistochemical techniques were used to localize specific expression of core clock proteins, and the glucocorticoid receptor, to the epithelial cells lining the bronchioles in both mouse and human lung. In the mouse, these were established to be Clara cells. Murine Clara cells retained circadian rhythmicity when grown as a pure population in culture. Furthermore, selective ablation of Clara cells resulted in the loss of circadian rhythm in lung slices, demonstrating the importance of this cell type in maintaining overall pulmonary circadian rhythmicity. In summary, we demonstrate that Clara cells are critical for maintaining coherent circadian oscillations in lung tissue. Their coexpression of the glucocorticoid receptor and core clock components establishes them as a likely interface between humoral suprachiasmatic nucleus output and circadian lung physiology. PMID:18787022

  11. Crystal Structure of the Redox-Active Cofactor Dibromothymoquinone Bound to Circadian Clock Protein KaiA and Structural Basis for Dibromothymoquinone's Ability to Prevent Stimulation of KaiC Phosphorylation by KaiA

    SciTech Connect

    Pattanayek, Rekha; Sidiqi, Said K.; Egli, Martin

    2013-09-19

    KaiA protein that stimulates KaiC phosphorylation in the cyanobacterial circadian clock was recently shown to be destabilized by dibromothymoquinone (DBMIB), thus revealing KaiA as a sensor of the plastoquinone (PQ) redox state and suggesting an indirect control of the clock by light through PQ redox changes. Here we show using X-ray crystallography that several DBMIBs are bound to KaiA dimer. Some binding modes are consistent with oligomerization of N-terminal KaiA pseudoreceiver domains and/or reduced interdomain flexibility. DBMIB bound to the C-terminal KaiA (C-KaiA) domain and limited stimulation of KaiC kinase activity by C-KaiA in the presence of DBMIB demonstrate that the cofactor may weakly inhibit KaiA-KaiC binding.

  12. The Catalytic and Non-catalytic Functions of the Brahma Chromatin-Remodeling Protein Collaborate to Fine-Tune Circadian Transcription in Drosophila.

    PubMed

    Kwok, Rosanna S; Li, Ying H; Lei, Anna J; Edery, Isaac; Chiu, Joanna C

    2015-07-01

    Daily rhythms in gene expression play a critical role in the progression of circadian clocks, and are under regulation by transcription factor binding, histone modifications, RNA polymerase II (RNAPII) recruitment and elongation, and post-transcriptional mechanisms. Although previous studies have shown that clock-controlled genes exhibit rhythmic chromatin modifications, less is known about the functions performed by chromatin remodelers in animal clockwork. Here we have identified the Brahma (Brm) complex as a regulator of the Drosophila clock. In Drosophila, CLOCK (CLK) is the master transcriptional activator driving cyclical gene expression by participating in an auto-inhibitory feedback loop that involves stimulating the expression of the main negative regulators, period (per) and timeless (tim). BRM functions catalytically to increase nucleosome density at the promoters of per and tim, creating an overall restrictive chromatin landscape to limit transcriptional output during the active phase of cycling gene expression. In addition, the non-catalytic function of BRM regulates the level and binding of CLK to target promoters and maintains transient RNAPII stalling at the per promoter, likely by recruiting repressive and pausing factors. By disentangling its catalytic versus non-catalytic functions at the promoters of CLK target genes, we uncovered a multi-leveled mechanism in which BRM fine-tunes circadian transcription.

  13. Circadian clock system in the pineal gland.

    PubMed

    Fukada, Yoshitaka; Okano, Toshiyuki

    2002-02-01

    The pineal gland is a neuroendocrine organ that functions as a central circadian oscillator in a variety of nonmammalian vertebrates. In many cases, the pineal gland retains photic input and endocrinal-output pathways both linked tightly to the oscillator. This contrasts well with the mammalian pineal gland equipped only with the output of melatonin production that is subject to neuronal regulation by central circadian oscillator located in the suprachiasmatic nucleus (SCN) of the hypothalamus. Molecular studies on animal clock genes were performed first in Drosophila and later developed in rodents. More recently, clock genes such as Per, Cry, Clock, and Bmal have been found in a variety of vertebrate clock structures including the avian pineal gland. The profiles of the temporal change of the clock gene expression in the avian pineal gland are more similar to those in the mammalian SCN rather than to those in the mammalian pineal gland. Avian pineal gland and mammalian SCN seem to share a fundamental molecular framework of the clock oscillator composed of a transcription/translation-based autoregulatory feedback loop. The circadian time-keeping mechanism also requires several post-translational events, such as protein translocation and degradation processes, in which protein phosphorylation plays a very important role for the stable 24-h cycling of the oscillator and/or the photic-input pathway for entrainment of the clock. PMID:11890455

  14. Circadian rhythms have broad implications for understanding brain and behavior

    PubMed Central

    Silver, Rae; Kriegsfeld, Lance J.

    2015-01-01

    Circadian rhythms are generated by an endogenously organized timing system that drives daily rhythms in behavior, physiology and metabolism. In mammals, the suprachiasmatic nucleus (SCN) of the hypothalamus is the locus of a master circadian clock. The SCN is synchronized to environmental changes in the light:dark cycle by direct, monosynaptic innervation via the retino-hypothalamic tract. In turn, the SCN coordinates the rhythmic activities of innumerable subordinate clocks in virtually all bodily tissues and organs. The core molecular clockwork is composed of a transcriptional/post-translational feedback loop in which clock genes and their protein products periodically suppress their own transcription. This primary loop connects to downstream output genes by additional, interlocked transcriptional feedback loops to create tissue-specific ‘circadian transcriptomes’. Signals from peripheral tissues inform the SCN of the internal state of the organism and the brain’s master clock is modified accordingly. A consequence of this hierarchical, multilevel feedback system is that there are ubiquitous effects of circadian timing on genetic and metabolic responses throughout the body. This overview examines landmark studies in the history of the study of circadian timing system, and highlights our current understanding of the operation of circadian clocks with a focus on topics of interest to the neuroscience community. PMID:24799154

  15. 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

  16. Mammalian circadian clock and metabolism - the epigenetic link.

    PubMed

    Bellet, Marina Maria; Sassone-Corsi, Paolo

    2010-11-15

    Circadian rhythms regulate a wide variety of physiological and metabolic processes. The clock machinery comprises complex transcriptional-translational feedback loops that, through the action of specific transcription factors, modulate the expression of as many as 10% of cellular transcripts. This marked change in gene expression necessarily implicates a global regulation of chromatin remodeling. Indeed, various descriptive studies have indicated that histone modifications occur at promoters of clock-controlled genes (CCGs) in a circadian manner. The finding that CLOCK, a transcription factor crucial for circadian function, has intrinsic histone acetyl transferase (HAT) activity has paved the way to unraveling the molecular mechanisms that govern circadian chromatin remodeling. A search for the histone deacetylase (HDAC) that counterbalances CLOCK activity revealed that SIRT1, a nicotinamide adenin dinucleotide (NAD(+))-dependent HDAC, functions in a circadian manner. Importantly, SIRT1 is a regulator of aging, inflammation and metabolism. As many transcripts that oscillate in mammalian peripheral tissues encode proteins that have central roles in metabolic processes, these findings establish a functional and molecular link between energy balance, chromatin remodeling and circadian physiology. Here we review recent studies that support the existence of this link and discuss their implications for understanding mammalian physiology and pathology. PMID:21048160

  17. Circadian genes and lithium response in bipolar disorders: associations with PPARGC1A (PGC-1α) and RORA.

    PubMed

    Geoffroy, P A; Etain, B; Lajnef, M; Zerdazi, E-H; Brichant-Petitjean, C; Heilbronner, U; Hou, L; Degenhardt, F; Rietschel, M; McMahon, F J; Schulze, T G; Jamain, S; Marie-Claire, C; Bellivier, F

    2016-09-01

    Preliminary studies suggest that lithium (Li) response might be associated with some circadian gene polymorphisms, we therefore performed a pharmacogenetic study on the core clock genes in two independent samples suffering from bipolar disorder (BD) and thoroughly characterized for their Li response. Two independent Caucasian samples (165 and 58 bipolar patients) treated with Li were selected from samples recruited in a French multicenter study and assessed for their Li response using the Alda scale. The two samples were genotyped using the Human660 (H660) and OmniExpress (OE) BeadChips and gene-based association analyses of 22 core clock genes were conducted. In the first sample (H660 chip), the RAR-related orphan receptor-a gene (RORA) and the Peroxisome Proliferator-Activated Receptor Gamma, Coactivator 1 Alpha gene (PPARGC1A or PGC-1α) were significantly associated with the Li response (empirical P-value = 0.0015 and 0.04, respectively), and remained significant only for RORA after Bonferroni correction. In the second sample (OE chip), PPARGC1A was significantly associated with the Li response (empirical P-value = 0.04), and did not remain significant after Bonferroni correction. PPARGC1A is a master regulator of mitochondrial function and a key component of the endogenous clock that stimulates the expression of Bmal1 and Rev-erb-alpha through coactivation of RORA. Although the observed associations deserve further replication and investigation, our results suggest genetic associations between Li response and these two close biological partners: PPARGC1A and RORA involved in circadian rhythms and bioenergetics processes in Li response. PMID:27324142

  18. Resveratrol restores the circadian rhythmic disorder of lipid metabolism induced by high-fat diet in mice.

    PubMed

    Sun, Linjie; Wang, Yan; Song, Yu; Cheng, Xiang-Rong; Xia, Shufang; Rahman, Md Ramim Tanver; Shi, Yonghui; Le, Guowei

    2015-02-27

    Circadian rhythmic disorders induced by high-fat diet are associated with metabolic diseases. Resveratrol could improve metabolic disorder, but few reports focused on its effects on circadian rhythm disorders in a variety of studies. The aim of the present study was to analyze the potential effects of resveratrol on high-fat diet-induced disorders about the rhythmic expression of clock genes and clock-controlled lipid metabolism. Male C57BL/6 mice were divided into three groups: a standard diet control group (CON), a high-fat diet (HFD) group and HFD supplemented with 0.1% (w/w) resveratrol (RES). The body weight, fasting blood glucose and insulin, plasma lipids and leptin, whole body metabolic status and the expression of clock genes and clock-controlled lipogenic genes were analyzed at four different time points throughout a 24-h cycle (8:00, 14:00, 20:00, 2:00). Resveratrol, being associated with rhythmic restoration of fasting blood glucose and plasma insulin, significantly decreased the body weight in HFD mice after 11 weeks of feeding, as well as ameliorated the rhythmities of plasma leptin, lipid profiles and whole body metabolic status (respiratory exchange ratio, locomotor activity, and heat production). Meanwhile, resveratrol modified the rhythmic expression of clock genes (Clock, Bmal1 and Per2) and clock-controlled lipid metabolism related genes (Sirt1, Pparα, Srebp-1c, Acc1 and Fas). The response pattern of mRNA expression for Acc1 was similar to the plasma triglyceride. All these results indicated that resveratrol reduced lipogenesis and ultimately normalized rhythmic expression of plasma lipids, possibly via its action on clock machinery.

  19. [Circadian rhythm sleep-wake disorder (circadian rhythm sleep disorder)].

    PubMed

    Tagaya, Hirokuni; Murayama, Norio; Fukase, Yuko

    2015-06-01

    The role of the circadian system is forecasting the daily and yearly change of environment. Circadian rhythm sleep-wake disorder (CRSWD) is defined as physical and social impairment caused by misalignment between circadian rhythm and desirable social schedule. CRSWDs are induced by medical or environmental factors as well as dysfunctions of circadian system. Clinicians should be aware that sleep-inducing medications, restless legs syndrome, delirium and less obedience to social schedule are frequent cause of CRSWD among elderly. Bright light therapy and orally administered small dose of melatonin or melatonin agonist at proper circadian phase are recommended treatments. Sleep-inducing medications should not be considered as CRSWD treatments, especially to elderly.

  20. GRK2: putting the brakes on the circadian clock

    PubMed Central

    Mendoza-Viveros, Lucia; Cheng, Arthur H.

    2016-01-01

    G protein-coupled receptor kinases (GRKs) are a family of serine/threonine protein kinases that terminate G protein-coupled receptor (GPCR) signaling by phosphorylating the receptor and inducing its internalization. In addition to their canonical function, some GRKs can phosphorylate non-GPCR substrates and regulate GPCR signaling in a kinase-independent manner. GPCRs are abundantly expressed in the suprachiasmatic nucleus (SCN), a structure in the mammalian brain that serves as the central circadian pacemaker. Various facets of circadian timekeeping are under the influence of GPCR signaling, and thus are potential targets for GRK regulation. Despite this, little attention has been given to the role of GRKs in circadian rhythms. In this research highlight, we discuss our latest findings on the functional involvement of GRK2 in mammalian circadian timekeeping in the SCN. Using grk2 knockout mice, we demonstrate that GRK2 is critical for maintaining proper clock speed and ensuring that the clock is appropriately synchronized to environmental light cycles. Although grk2 deficiency expectedly alters the expression of a key GPCR in the SCN, our study also reveals that GRK2 has a more direct function that touches the heart of the circadian clock. PMID:27088110

  1. Circadian Disorganization Alters Intestinal Microbiota

    PubMed Central

    Voigt, Robin M.; Forsyth, Christopher B.; Green, Stefan J.; Mutlu, Ece; Engen, Phillip; Vitaterna, Martha H.; Turek, Fred W.; Keshavarzian, Ali

    2014-01-01

    Intestinal dysbiosis and circadian rhythm disruption are associated with similar diseases including obesity, metabolic syndrome, and inflammatory bowel disease. Despite the overlap, the potential relationship between circadian disorganization and dysbiosis is unknown; thus, in the present study, a model of chronic circadian disruption was used to determine the impact on the intestinal microbiome. Male C57BL/6J mice underwent once weekly phase reversals of the light:dark cycle (i.e., circadian rhythm disrupted mice) to determine the impact of circadian rhythm disruption on the intestinal microbiome and were fed either standard chow or a high-fat, high-sugar diet to determine how diet influences circadian disruption-induced effects on the microbiome. Weekly phase reversals of the light:dark (LD) cycle did not alter the microbiome in mice fed standard chow; however, mice fed a high-fat, high-sugar diet in conjunction with phase shifts in the light:dark cycle had significantly altered microbiota. While it is yet to be established if some of the adverse effects associated with circadian disorganization in humans (e.g., shift workers, travelers moving across time zones, and in individuals with social jet lag) are mediated by dysbiosis, the current study demonstrates that circadian disorganization can impact the intestinal microbiota which may have implications for inflammatory diseases. PMID:24848969

  2. Circadian disorganization alters intestinal microbiota.

    PubMed

    Voigt, Robin M; Forsyth, Christopher B; Green, Stefan J; Mutlu, Ece; Engen, Phillip; Vitaterna, Martha H; Turek, Fred W; Keshavarzian, Ali

    2014-01-01

    Intestinal dysbiosis and circadian rhythm disruption are associated with similar diseases including obesity, metabolic syndrome, and inflammatory bowel disease. Despite the overlap, the potential relationship between circadian disorganization and dysbiosis is unknown; thus, in the present study, a model of chronic circadian disruption was used to determine the impact on the intestinal microbiome. Male C57BL/6J mice underwent once weekly phase reversals of the light:dark cycle (i.e., circadian rhythm disrupted mice) to determine the impact of circadian rhythm disruption on the intestinal microbiome and were fed either standard chow or a high-fat, high-sugar diet to determine how diet influences circadian disruption-induced effects on the microbiome. Weekly phase reversals of the light:dark (LD) cycle did not alter the microbiome in mice fed standard chow; however, mice fed a high-fat, high-sugar diet in conjunction with phase shifts in the light:dark cycle had significantly altered microbiota. While it is yet to be established if some of the adverse effects associated with circadian disorganization in humans (e.g., shift workers, travelers moving across time zones, and in individuals with social jet lag) are mediated by dysbiosis, the current study demonstrates that circadian disorganization can impact the intestinal microbiota which may have implications for inflammatory diseases. PMID:24848969

  3. Circadian gene variants in cancer

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Humans as diurnal beings are active during the day and rest at night. This daily oscillation of behavior and physiology is driven by an endogenous circadian clock not environmental cues. In modern societies, changes in lifestyle have led to a frequent disruption of the endogenous circadian homeostas...

  4. Circadian timing in cancer treatments.

    PubMed

    Lévi, Francis; Okyar, Alper; Dulong, Sandrine; Innominato, Pasquale F; Clairambault, Jean

    2010-01-01

    The circadian timing system is composed of molecular clocks, which drive 24-h changes in xenobiotic metabolism and detoxification, cell cycle events, DNA repair, apoptosis, and angiogenesis. The cellular circadian clocks are coordinated by endogenous physiological rhythms, so that they tick in synchrony in the host tissues that can be damaged by anticancer agents. As a result, circadian timing can modify 2- to 10-fold the tolerability of anticancer medications in experimental models and in cancer patients. Improved efficacy is also seen when drugs are given near their respective times of best tolerability, due to (a) inherently poor circadian entrainment of tumors and (b) persistent circadian entrainment of healthy tissues. Conversely, host clocks are disrupted whenever anticancer drugs are administered at their most toxic time. On the other hand, circadian disruption accelerates experimental and clinical cancer processes. Gender, circadian physiology, clock genes, and cell cycle critically affect outcome on cancer chronotherapeutics. Mathematical and systems biology approaches currently develop and integrate theoretical, experimental, and technological tools in order to further optimize and personalize the circadian administration of cancer treatments.

  5. Effects of light on the circadian rhythm of diabetic rats under restricted feeding.

    PubMed

    Wu, Tao; ZhuGe, Fen; Zhu, Yali; Wang, Nan; Jiang, Qianru; Fu, Haoxuan; Li, Yongjun; Fu, Zhengwei

    2014-03-01

    The aim of this study was to investigate whether the entrainment of light cue is affected or not in diabetic animals. We found that the individual light/dark (LD) reversal showed a tissue- and gene-specific effect on the circadian phases of peripheral clock genes, which was generally similar between the control and diabetic rats. In the liver and heart, the peak phases of examined clock genes (Bmal1, Rev-erbα, Per1, and Per2) were slightly shifted by 0∼4 h in the liver and heart of control and diabetic rats. However, we found that the peak phases of these clock genes were greatly shifted by 8∼12 h after the LD reversal for 7 days in the pineal gland of both control and diabetic rats. However, the activity rhythm was greatly different between two groups. After the individual LD reversal, the activity rhythm was completely shifted in the control rats but retained in the diabetic rats. These observations suggested that the behavioral rhythm of diabetic rats may be uncoupled from the master clock after the individual LD reversal. Moreover, we also found that the serum glucose levels of diabetic rats kept equally high throughout the whole day without any shift of peak phase after the individual reversal of LD cycle. While the serum glucose levels of control rats were tightly controlled during the normal and LD reversal conditions. Thus, the impaired insulin secretion induced uncontrollable serum glucose level may result in uncoupled activity rhythm in the diabetic rats after the individual LD reversal.

  6. Circadian rhythms. Atomic-scale origins of slowness in the cyanobacterial circadian clock.

    PubMed

    Abe, Jun; Hiyama, Takuya B; Mukaiyama, Atsushi; Son, Seyoung; Mori, Toshifumi; Saito, Shinji; Osako, Masato; Wolanin, Julie; Yamashita, Eiki; Kondo, Takao; Akiyama, Shuji

    2015-07-17

    Circadian clocks generate slow and ordered cellular dynamics but consist of fast-moving bio-macromolecules; consequently, the origins of the overall slowness remain unclear. We identified the adenosine triphosphate (ATP) catalytic region [adenosine triphosphatase (ATPase)] in the amino-terminal half of the clock protein KaiC as the minimal pacemaker that controls the in vivo frequency of the cyanobacterial clock. Crystal structures of the ATPase revealed that the slowness of this ATPase arises from sequestration of a lytic water molecule in an unfavorable position and coupling of ATP hydrolysis to a peptide isomerization with high activation energy. The slow ATPase is coupled with another ATPase catalyzing autodephosphorylation in the carboxyl-terminal half of KaiC, yielding the circadian response frequency of intermolecular interactions with other clock-related proteins that influences the transcription and translation cycle.

  7. Circadian rhythms. Atomic-scale origins of slowness in the cyanobacterial circadian clock.

    PubMed

    Abe, Jun; Hiyama, Takuya B; Mukaiyama, Atsushi; Son, Seyoung; Mori, Toshifumi; Saito, Shinji; Osako, Masato; Wolanin, Julie; Yamashita, Eiki; Kondo, Takao; Akiyama, Shuji

    2015-07-17

    Circadian clocks generate slow and ordered cellular dynamics but consist of fast-moving bio-macromolecules; consequently, the origins of the overall slowness remain unclear. We identified the adenosine triphosphate (ATP) catalytic region [adenosine triphosphatase (ATPase)] in the amino-terminal half of the clock protein KaiC as the minimal pacemaker that controls the in vivo frequency of the cyanobacterial clock. Crystal structures of the ATPase revealed that the slowness of this ATPase arises from sequestration of a lytic water molecule in an unfavorable position and coupling of ATP hydrolysis to a peptide isomerization with high activation energy. The slow ATPase is coupled with another ATPase catalyzing autodephosphorylation in the carboxyl-terminal half of KaiC, yielding the circadian response frequency of intermolecular interactions with other clock-related proteins that influences the transcription and translation cycle. PMID:26113637

  8. The systemic control of circadian gene expression.

    PubMed

    Gerber, A; Saini, C; Curie, T; Emmenegger, Y; Rando, G; Gosselin, P; Gotic, I; Gos, P; Franken, P; Schibler, U

    2015-09-01

    The mammalian circadian timing system consists of a central pacemaker in the brain's suprachiasmatic nucleus (SCN) and subsidiary oscillators in nearly all body cells. The SCN clock, which is adjusted to geophysical time by the photoperiod, synchronizes peripheral clocks through a wide variety of systemic cues. The latter include signals depending on feeding cycles, glucocorticoid hormones, rhythmic blood-borne signals eliciting daily changes in actin dynamics and serum response factor (SRF) activity, and sensors of body temperature rhythms, such as heat shock transcription factors and the cold-inducible RNA-binding protein CIRP. To study these systemic signalling pathways, we designed and engineered a novel, highly photosensitive apparatus, dubbed RT-Biolumicorder. This device enables us to record circadian luciferase reporter gene expression in the liver and other organs of freely moving mice over months in real time. Owing to the multitude of systemic signalling pathway involved in the phase resetting of peripheral clocks the disruption of any particular one has only minor effects on the steady state phase of circadian gene expression in organs such as the liver. Nonetheless, the implication of specific pathways in the synchronization of clock gene expression can readily be assessed by monitoring the phase-shifting kinetics using the RT-Biolumicorder.

  9. Metabolic Cycles in Yeast Share Features Conserved among Circadian Rhythms

    PubMed Central

    Causton, Helen C.; Feeney, Kevin A.; Ziegler, Christine A.; O’Neill, John S.

    2015-01-01

    Summary Cell-autonomous circadian rhythms allow organisms to temporally orchestrate their internal state to anticipate and/or resonate with the external environment [1, 2]. Although ∼24-hr periodicity is observed across aerobic eukaryotes, the central mechanism has been hard to dissect because few simple models exist, and known clock proteins are not conserved across phylogenetic kingdoms [1, 3, 4]. In contrast, contributions to circadian rhythmicity made by a handful of post-translational mechanisms, such as phosphorylation of clock proteins by casein kinase 1 (CK1) and glycogen synthase kinase 3 (GSK3), appear conserved among phyla [3, 5]. These kinases have many other essential cellular functions and are better conserved in their contribution to timekeeping than any of the clock proteins they phosphorylate [6]. Rhythmic oscillations in cellular redox state are another universal feature of circadian timekeeping, e.g., over-oxidation cycles of abundant peroxiredoxin proteins [7–9]. Here, we use comparative chronobiology to distinguish fundamental clock mechanisms from species and/or tissue-specific adaptations and thereby identify features shared between circadian rhythms in mammalian cells and non-circadian temperature-compensated respiratory oscillations in budding yeast [10]. We find that both types of oscillations are coupled with the cell division cycle, exhibit period determination by CK1 and GSK3, and have peroxiredoxin over-oxidation cycles. We also explore how peroxiredoxins contribute to YROs. Our data point to common mechanisms underlying both YROs and circadian rhythms and suggest two interpretations: either certain biochemical systems are simply permissive for cellular oscillations (with frequencies from hours to days) or this commonality arose via divergence from an ancestral cellular clock. PMID:25866393

  10. Circadian gene variants in cancer.

    PubMed

    Kettner, Nicole M; Katchy, Chinenye A; Fu, Loning

    2014-06-01

    Humans as diurnal beings are active during the day and rest at night. This daily oscillation of behavior and physiology is driven by an endogenous circadian clock not environmental cues. In modern societies, changes in lifestyle have led to a frequent disruption of the endogenous circadian homeostasis leading to increased risk of various diseases including cancer. The clock is operated by the feedback loops of circadian genes and controls daily physiology by coupling cell proliferation and metabolism, DNA damage repair, and apoptosis in peripheral tissues with physical activity, energy homeostasis, immune and neuroendocrine functions at the organismal level. Recent studies have revealed that defects in circadian genes due to targeted gene ablation in animal models or single nucleotide polymorphism, deletion, deregulation and/or epigenetic silencing in humans are closely associated with increased risk of cancer. In addition, disruption of circadian rhythm can disrupt the molecular clock in peripheral tissues in the absence of circadian gene mutations. Circadian disruption has recently been recognized as an independent cancer risk factor. Further study of the mechanism of clock-controlled tumor suppression will have a significant impact on human health by improving the efficiencies of cancer prevention and treatment. PMID:24901356

  11. Circadian gene variants in cancer

    PubMed Central

    Kettner, Nicole M.; Katchy, Chinenye A.; Fu, Loning

    2014-01-01

    Humans as diurnal beings are active during the day and rest at night. This daily oscillation of behavior and physiology is driven by an endogenous circadian clock not environmental cues. In modern societies, changes in lifestyle have led to a frequent disruption of the endogenous circadian homeostasis leading to increased risk of various diseases including cancer. The clock is operated by the feedback loops of circadian genes and controls daily physiology by coupling cell proliferation and metabolism, DNA damage repair, and apoptosis in peripheral tissues with physical activity, energy homeostasis, immune and neuroendocrine functions at the organismal level. Recent studies have revealed that defects in circadian genes due to targeted gene ablation in animal models or single nucleotide polymorphism, deletion, deregulation and/or epigenetic silencing in humans are closely associated with increased risk of cancer. In addition, disruption of circadian rhythm can disrupt the molecular clock in peripheral tissues in the absence of circadian gene mutations. Circadian disruption has recently been recognized as an independent cancer risk factor. Further study of the mechanism of clock-controlled tumor suppression will have a significant impact on human health by improving the efficiencies of cancer prevention and treatment. PMID:24901356

  12. Statistical inference of regulatory networks for circadian regulation.

    PubMed

    Aderhold, Andrej; Husmeier, Dirk; Grzegorczyk, Marco

    2014-06-01

    We assess the accuracy of various state-of-the-art statistics and machine learning methods for reconstructing gene and protein regulatory networks in the context of circadian regulation. Our study draws on the increasing availability of gene expression and protein concentration time series for key circadian clock components in Arabidopsis thaliana. In addition, gene expression and protein concentration time series are simulated from a recently published regulatory network of the circadian clock in A. thaliana, in which protein and gene interactions are described by a Markov jump process based on Michaelis-Menten kinetics. We closely follow recent experimental protocols, including the entrainment of seedlings to different light-dark cycles and the knock-out of various key regulatory genes. Our study provides relative network reconstruction accuracy scores for a critical comparative performance evaluation, and sheds light on a series of highly relevant questions: it quantifies the influence of systematically missing values related to unknown protein concentrations and mRNA transcription rates, it investigates the dependence of the performance on the network topology and the degree of recurrency, it provides deeper insight into when and why non-linear methods fail to outperform linear ones, it offers improved guidelines on parameter settings in different inference procedures, and it suggests new hypotheses about the structure of the central circadian gene regulatory network in A. thaliana. PMID:24864301

  13. Statistical inference of regulatory networks for circadian regulation.

    PubMed

    Aderhold, Andrej; Husmeier, Dirk; Grzegorczyk, Marco

    2014-06-01

    We assess the accuracy of various state-of-the-art statistics and machine learning methods for reconstructing gene and protein regulatory networks in the context of circadian regulation. Our study draws on the increasing availability of gene expression and protein concentration time series for key circadian clock components in Arabidopsis thaliana. In addition, gene expression and protein concentration time series are simulated from a recently published regulatory network of the circadian clock in A. thaliana, in which protein and gene interactions are described by a Markov jump process based on Michaelis-Menten kinetics. We closely follow recent experimental protocols, including the entrainment of seedlings to different light-dark cycles and the knock-out of various key regulatory genes. Our study provides relative network reconstruction accuracy scores for a critical comparative performance evaluation, and sheds light on a series of highly relevant questions: it quantifies the influence of systematically missing values related to unknown protein concentrations and mRNA transcription rates, it investigates the dependence of the performance on the network topology and the degree of recurrency, it provides deeper insight into when and why non-linear methods fail to outperform linear ones, it offers improved guidelines on parameter settings in different inference procedures, and it suggests new hypotheses about the structure of the central circadian gene regulatory network in A. thaliana.

  14. Nocturia: The circadian voiding disorder

    PubMed Central

    Moon, Young Tae; Kim, Kyung Do

    2016-01-01

    Nocturia is a prevalent condition of waking to void during the night. The concept of nocturia has evolved from being a symptomatic aspect of disease associated with the prostate or bladder to a form of lower urinary tract disorder. However, recent advances in circadian biology and sleep science suggest that it might be important to consider nocturia as a form of circadian dysfunction. In the current review, nocturia is reexamined with an introduction to sleep disorders and recent findings in circadian biology in an attempt to highlight the importance of rediscovering nocturia as a problem of chronobiology. PMID:27195315

  15. Nocturia: The circadian voiding disorder.

    PubMed

    Kim, Jin Wook; Moon, Young Tae; Kim, Kyung Do

    2016-05-01

    Nocturia is a prevalent condition of waking to void during the night. The concept of nocturia has evolved from being a symptomatic aspect of disease associated with the prostate or bladder to a form of lower urinary tract disorder. However, recent advances in circadian biology and sleep science suggest that it might be important to consider nocturia as a form of circadian dysfunction. In the current review, nocturia is reexamined with an introduction to sleep disorders and recent findings in circadian biology in an attempt to highlight the importance of rediscovering nocturia as a problem of chronobiology. PMID:27195315

  16. Neurobiology of Circadian Rhythm Regulation.

    PubMed

    Rosenwasser, Alan M; Turek, Fred W

    2015-12-01

    Over the past few decades, multilevel research has elucidated the basic neuroanatomy, neurochemistry, and molecular neurobiology of the master circadian pacemaker located in the hypothalamic suprachiasmatic nucleus (SCN). The circadian timing system is composed of a large number of cellular oscillators located in the SCN, in non-SCN brain structures, and throughout the body. Cellular-level oscillations are generated by a molecular feedback loop in which circadian clock genes rhythmically regulate their own transcription, as well as that of hundreds of clock-controlled genes. The maintenance of proper coordination within this network of cellular- and tissue-level clocks is essential for health and well-being. PMID:26568118

  17. Neurobiology of Circadian Rhythm Regulation.

    PubMed

    Rosenwasser, Alan M; Turek, Fred W

    2015-12-01

    Over the past few decades, multilevel research has elucidated the basic neuroanatomy, neurochemistry, and molecular neurobiology of the master circadian pacemaker located in the hypothalamic suprachiasmatic nucleus (SCN). The circadian timing system is composed of a large number of cellular oscillators located in the SCN, in non-SCN brain structures, and throughout the body. Cellular-level oscillations are generated by a molecular feedback loop in which circadian clock genes rhythmically regulate their own transcription, as well as that of hundreds of clock-controlled genes. The maintenance of proper coordination within this network of cellular- and tissue-level clocks is essential for health and well-being.

  18. Circadian misalignment increases cardiovascular disease risk factors in humans

    PubMed Central

    Morris, Christopher J.; Purvis, Taylor E.; Hu, Kun; Scheer, Frank A. J. L.

    2016-01-01

    Shift work is a risk factor for hypertension, inflammation, and cardiovascular disease. This increased risk cannot be fully explained by classic risk factors. One of the key features of shift workers is that their behavioral and environmental cycles are typically misaligned relative to their endogenous circadian system. However, there is little information on the impact of acute circadian misalignment on cardiovascular disease risk in humans. Here we show—by using two 8-d laboratory protocols—that short-term circadian misalignment (12-h inverted behavioral and environmental cycles for three days) adversely affects cardiovascular risk factors in healthy adults. Circadian misalignment increased 24-h systolic blood pressure (SBP) and diastolic blood pressure (DBP) by 3.0 mmHg and 1.5 mmHg, respectively. These results were primarily explained by an increase in blood pressure during sleep opportunities (SBP, +5.6 mmHg; DBP, +1.9 mmHg) and, to a lesser extent, by raised blood pressure during wake periods (SBP, +1.6 mmHg; DBP, +1.4 mmHg). Circadian misalignment decreased wake cardiac vagal modulation by 8–15%, as determined by heart rate variability analysis, and decreased 24-h urinary epinephrine excretion rate by 7%, without a significant effect on 24-h urinary norepinephrine excretion rate. Circadian misalignment increased 24-h serum interleukin-6, C-reactive protein, resistin, and tumor necrosis factor-α levels by 3–29%. We demonstrate that circadian misalignment per se increases blood pressure and inflammatory markers. Our findings may help explain why shift work increases hypertension, inflammation, and cardiovascular disease risk. PMID:26858430

  19. Circadian misalignment increases cardiovascular disease risk factors in humans.

    PubMed

    Morris, Christopher J; Purvis, Taylor E; Hu, Kun; Scheer, Frank A J L

    2016-03-01

    Shift work is a risk factor for hypertension, inflammation, and cardiovascular disease. This increased risk cannot be fully explained by classic risk factors. One of the key features of shift workers is that their behavioral and environmental cycles are typically misaligned relative to their endogenous circadian system. However, there is little information on the impact of acute circadian misalignment on cardiovascular disease risk in humans. Here we show-by using two 8-d laboratory protocols-that short-term circadian misalignment (12-h inverted behavioral and environmental cycles for three days) adversely affects cardiovascular risk factors in healthy adults. Circadian misalignment increased 24-h systolic blood pressure (SBP) and diastolic blood pressure (DBP) by 3.0 mmHg and 1.5 mmHg, respectively. These results were primarily explained by an increase in blood pressure during sleep opportunities (SBP, +5.6 mmHg; DBP, +1.9 mmHg) and, to a lesser extent, by raised blood pressure during wake periods (SBP, +1.6 mmHg; DBP, +1.4 mmHg). Circadian misalignment decreased wake cardiac vagal modulation by 8-15%, as determined by heart rate variability analysis, and decreased 24-h urinary epinephrine excretion rate by 7%, without a significant effect on 24-h urinary norepinephrine excretion rate. Circadian misalignment increased 24-h serum interleukin-6, C-reactive protein, resistin, and tumor necrosis factor-α levels by 3-29%. We demonstrate that circadian misalignment per se increases blood pressure and inflammatory markers. Our findings may help explain why shift work increases hypertension, inflammation, and cardiovascular disease risk.

  20. Identification of the molecular components of a Tigriopus californicus (Crustacea, Copepoda) circadian clock.

    PubMed

    Nesbit, Katherine T; Christie, Andrew E

    2014-12-01

    Copepods of the genus Tigriopus have been proposed as marine models for investigations of environmental perturbation. One rapidly increasing anthropogenic stressor for intertidal organisms is light pollution. Given the sensitivity of circadian rhythms to exogenous light, the genes/proteins of a Tigriopus circadian pacemaker represent a potential system for investigating the influences of artificial light sources on circadian behavior in an intertidal species. Here, the molecular components of a putative Tigriopus californicus circadian clock were identified using publicly accessible transcriptome data; the recently deduced circadian proteins of the copepod Calanus finmarchicus were used as a reference. Transcripts encoding homologs of all commonly recognized ancestral arthropod core clock proteins were identified (i.e. CLOCK, CRYPTOCHROME 2, CYCLE, PERIOD and TIMELESS), as were ones encoding proteins likely to modulate the core clock (i.e. CASEIN KINASE II, CLOCKWORK ORANGE, DOUBLETIME, PROTEIN PHOSPHATASE 1, PROTEIN PHOSPHATASE 2A, SHAGGY, SUPERNUMERARY LIMBS and VRILLE) or to act as inputs to it (i.e. CRYPTOCHROME 1). PAR DOMAIN PROTEIN 1 was the only circadian-associated protein not identified in Tigriopus; it appears absent in Calanus too. These data represent just the third full set of molecular components for a crustacean circadian pacemaker (Daphnia pulex and C. finmarchicus previously), and only the second obtained from transcribed sequences (C. finmarchicus previously). Given Tigriopus' proposed status as a model for investigating the influences of anthropogenic stressors in the marine environment, these data provide the first suite of gene/protein targets for understanding how light pollution may influence circadian physiology and behavior in an intertidal organism.

  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. Role of phosphorylation in the mammalian circadian clock.

    PubMed

    Vanselow, K; Kramer, A

    2007-01-01

    Circadian clocks regulate a wide variety of processes ranging from gene expression to behavior. At the molecular level, circadian rhythms are thought to be produced by a set of clock genes and proteins interconnected to form transcriptional-translational feedback loops. Rhythmic gene expression was formerly regarded as the major drive for rhythms in clock protein abundance, but recent findings underline the crucial importance of posttranslational mechanisms for both the generation and dynamics of circadian rhythms. In particular, the reversible phosphorylation of PER proteins-essential components within the negative feedback loop in Drosophila and mammals-seems to have a key role for the correct timing of nuclear repression. To understand how PER protein phosphorylation regulates the dynamics of the circadian oscillator, we have mapped endogenous phosphorylation sites in mPER2. Detailed investigation of the functional role of one particular phosphorylation site (Ser-659, which is mutated in the familial advanced sleep phase syndrome [FASPS]) led us propose a model of functionally different phosphorylation sites in PER2. This concept explains not only the FASPS phenotype, but also the effect of the tau mutation in hamster. PMID:18419274

  3. Epigenetic and Posttranslational Modifications in Light Signal Transduction and the Circadian Clock in Neurospora crassa.

    PubMed

    Proietto, Marco; Bianchi, Michele Maria; Ballario, Paola; Brenna, Andrea

    2015-01-01

    Blue light, a key abiotic signal, regulates a wide variety of physiological processes in many organisms. One of these phenomena is the circadian rhythm presents in organisms sensitive to the phase-setting effects of blue light and under control of the daily alternation of light and dark. Circadian clocks consist of autoregulatory alternating negative and positive feedback loops intimately connected with the cellular metabolism and biochemical processes. Neurospora crassa provides an excellent model for studying the molecular mechanisms involved in these phenomena. The White Collar Complex (WCC), a blue-light receptor and transcription factor of the circadian oscillator, and Frequency (FRQ), the circadian clock pacemaker, are at the core of the Neurospora circadian system. The eukaryotic circadian clock relies on transcriptional/translational feedback loops: some proteins rhythmically repress their own synthesis by inhibiting the activity of their transcriptional factors, generating self-sustained oscillations over a period of about 24 h. One of the basic mechanisms that perpetuate self-sustained oscillations is post translation modification (PTM). The acronym PTM generically indicates the addition of acetyl, methyl, sumoyl, or phosphoric groups to various types of proteins. The protein can be regulatory or enzymatic or a component of the chromatin. PTMs influence protein stability, interaction, localization, activity, and chromatin packaging. Chromatin modification and PTMs have been implicated in regulating circadian clock function in Neurospora. Research into the epigenetic control of transcription factors such as WCC has yielded new insights into the temporal modulation of light-dependent gene transcription. Here we report on epigenetic and protein PTMs in the regulation of the Neurospora crassa circadian clock. We also present a model that illustrates the molecular mechanisms at the basis of the blue light control of the circadian clock.

  4. Circadian Regulation of Cellular Physiology

    PubMed Central

    Peek, C.B; Ramsey, K.M; Levine, D.C; Marcheva, B; Perelis, M; Bass, J

    2015-01-01

    The circadian clock synchronizes behavioral and physiological processes on a daily basis in anticipation of the light–dark cycle. In mammals, molecular clocks are present in both the central pacemaker neurons and in nearly all peripheral tissues. Clock transcription factors in metabolic tissues coordinate metabolic fuel utilization and storage with alternating periods of feeding and fasting corresponding to the rest–activity cycle. In vitro and in vivo biochemical approaches have led to the discovery of mechanisms underlying the interplay between the molecular clock and the metabolic networks. For example, recent studies have demonstrated that the circadian clock controls rhythmic synthesis of the cofactor nicotinamide adenine dinucleotide (NAD+) and activity of NAD+-dependent sirtuin deacetylase enzymes to regulate mitochondrial function across the circadian cycle. In this chapter, we review current state-of-the-art methods to analyze circadian cycles in mitochondrial bioenergetics, glycolysis, and nucleotide metabolism in both cell-based and animal models. PMID:25707277

  5. Circadian regulation of cellular physiology.

    PubMed

    Peek, C B; Ramsey, K M; Levine, D C; Marcheva, B; Perelis, M; Bass, J

    2015-01-01

    The circadian clock synchronizes behavioral and physiological processes on a daily basis in anticipation of the light-dark cycle. In mammals, molecular clocks are present in both the central pacemaker neurons and in nearly all peripheral tissues. Clock transcription factors in metabolic tissues coordinate metabolic fuel utilization and storage with alternating periods of feeding and fasting corresponding to the rest-activity cycle. In vitro and in vivo biochemical approaches have led to the discovery of mechanisms underlying the interplay between the molecular clock and the metabolic networks. For example, recent studies have demonstrated that the circadian clock controls rhythmic synthesis of the cofactor nicotinamide adenine dinucleotide (NAD(+)) and activity of NAD(+)-dependent sirtuin deacetylase enzymes to regulate mitochondrial function across the circadian cycle. In this chapter, we review current state-of-the-art methods to analyze circadian cycles in mitochondrial bioenergetics, glycolysis, and nucleotide metabolism in both cell-based and animal models.

  6. Circadian Control of Global Transcription

    PubMed Central

    Li, Shujing; Zhang, Luoying

    2015-01-01

    Circadian rhythms exist in most if not all organisms on the Earth and manifest in various aspects of physiology and behavior. These rhythmic processes are believed to be driven by endogenous molecular clocks that regulate rhythmic expression of clock-controlled genes (CCGs). CCGs consist of a significant portion of the genome and are involved in diverse biological pathways. The transcription of CCGs is tuned by rhythmic actions of transcription factors and circadian alterations in chromatin. Here, we review the circadian control of CCG transcription in five model organisms that are widely used, including cyanobacterium, fungus, plant, fruit fly, and mouse. Comparing the similarity and differences in the five organisms could help us better understand the function of the circadian clock, as well as its output mechanisms adapted to meet the demands of diverse environmental conditions. PMID:26682214

  7. Analysis of the redox oscillations in the circadian clockwork

    PubMed Central

    Milev, Nikolay B.; Rey, Guillaume; Valekunja, Utham K.; Edgar, Rachel S.; O’Neill, John S.; Reddy, Akhilesh B.

    2016-01-01

    The evolution of tight coupling between the circadian system and redox homeostasis of the cell has been proposed to coincide roughly with the appearance of the first aerobic organisms, around 3 billion years ago. The rhythmic production of oxygen and its effect on core metabolism are thought to have exerted selective pressure for the temporal segregation of numerous metabolic pathways. Until recently, the only evidence for such coupling came from studies showing circadian cycles in the abundance of various redox metabolites, with many arguing that these oscillations are simply an output from the transcription/translation-feedback loop (TTFL). The recent discovery that the peroxiredoxin (PRX) proteins exhibit circadian cycles in their oxidation status, even in the absence of transcription, demonstrated the existence of autonomous oscillations in the redox status of the cell. The PRXs are a family of cellular thiol peroxidases whose abundance and high reaction rate make them the major cellular sink for cellular peroxides. Interestingly, as part of the normal catalytic cycle, PRXs become inactivated by their own substrate via over-oxidation of the catalytic residue, with the inactivated form of the enzyme displaying circadian accumulation. Here, we describe the biochemical properties of the PRX system, with particular emphasis on the features important for the experimental analysis of these enzymes. We will also present a detailed protocol for measuring PRX over-oxidation across circadian time in adherent cell cultures, red blood cells and fruit flies (Drosophila melanogaster), providing practical suggestions for ensuring consistency and reproducibility of the results. PMID:25707278

  8. Circadian Dysrhythmias, Physiological Aberrations, and the Link to Skin Cancer

    PubMed Central

    Gutierrez, Daniel; Arbesman, Joshua

    2016-01-01

    Circadian rhythms are core regulators of a variety of mammalian physiologic processes and oscillate in a 24-h pattern. Many peripheral organs possess endogenous rhythmicity that is then modulated by a master clock; the skin is one of these peripheral organs. The dysregulation of rhythms is associated with decreased ability to ameliorate cellular stressors at a local and global level, which then increases the propensity for the development of neoplastic growths. In this article, we review the implications of altered circadian rhythms on DNA repair as well as modified gene expression of core clock proteins with particular focus on skin models. These findings are then correlated with epidemiologic data regarding skin cancer to showcase the effects of circadian disruption on this phenomenon. PMID:27128901

  9. Nocturnin: A Circadian Target of Pparg- Induced Adipogenesis

    PubMed Central

    Kawai, Masanobu; Green, Carla B; Horowitz, Mark; Lecka-Czernik, Beata; Rosen, Clifford J

    2012-01-01

    Nuclear receptors (NRs) control cell fate and regulate tissue function. Some of the NRs are expressed in a circadian and tissue specific manner. Clock genes are part of the circadian network and fine tune gene expression in adipose and skeletal tissues. Pparg, a master transcription factor that determines adipogenesis exhibits a circadian expression pattern in white adipose tissue and liver. In this paper we found that message and protein for a peripheral clock gene, nocturnin, is markedly up-regulated with Pparg activation in adipocytes and bone marrow stromal cells. Nocturnin is also expressed in relatively high amounts in other tissues which may have physiologic relevance for bone, including the brain and hypothalamus. Importantly, we found polymorphic strain differences in bone marrow nocturnin expression that relate to phenotypic determinants of skeletal acquisition. Defining the function of nocturnin in peripheral tissues should provide new insights into lineage allocation and the intimate relationship between nuclear receptors and physiologic timekeeping. PMID:20392228

  10. 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.

  11. 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

  12. Phenotyping Circadian Rhythms in Mice

    PubMed Central

    Eckel-Mahan, Kristin; Sassone-Corsi, Paolo

    2015-01-01

    Circadian rhythms take place with a periodicity of twenty-four hours, temporally following the rotation of the earth around its axis. Examples of circadian rhythms are the sleep/wake cycle, feeding, and hormone secretion. Light powerfully entrains the mammalian clock and assists in keeping animals synchronized to the 24-hour cycle of the earth by activating specific neurons in the “central pacemaker” of the brain, the suprachiasmatic nucleus. Absolute periodicity of an animal can deviate slightly from 24 hours as manifest when an animal is placed into constant dark- or “free running”- conditions. Simple measurements of an organism's activity in free running conditions reveal its intrinsic circadian period. Mice are a particularly useful model for studying circadian rhythmicity due to the ease of genetic manipulation, thus identifying molecular contributors to rhythmicity. Furthermore, their small size allows for monitoring locomotion or activity in their home cage environment with relative ease. Several tasks commonly used to analyze circadian periodicity and plasticity in mice are outlined here including the process of entrainment, determination of tau (period length) in free running conditions, determination of circadian periodicity in response to light disruption (i.e. jet lag studies), and evaluation of clock plasticity in non-twenty-four hour conditions (T-cycles). Studying the properties of circadian periods such as their phase, amplitude, and length in response to photic perturbation, can be particularly useful in understanding how humans respond to jet lag, night shifts, rotating shifts, or other transient or chronic disruption of one's environmental surroundings. PMID:26331760

  13. Predicted Role of NAD Utilization in the Control of Circadian Rhythms during DNA Damage Response

    PubMed Central

    Luna, Augustin; McFadden, Geoffrey B.; Aladjem, Mirit I.; Kohn, Kurt W.

    2015-01-01

    The circadian clock is a set of regulatory steps that oscillate with a period of approximately 24 hours influencing many biological processes. These oscillations are robust to external stresses, and in the case of genotoxic stress (i.e. DNA damage), the circadian clock responds through phase shifting with primarily phase advancements. The effect of DNA damage on the circadian clock and the mechanism through which this effect operates remains to be thoroughly investigated. Here we build an in silico model to examine damage-induced circadian phase shifts by investigating a possible mechanism linking circadian rhythms to metabolism. The proposed model involves two DNA damage response proteins, SIRT1 and PARP1, that are each consumers of nicotinamide adenine dinucleotide (NAD), a metabolite involved in oxidation-reduction reactions and in ATP synthesis. This model builds on two key findings: 1) that SIRT1 (a protein deacetylase) is involved in both the positive (i.e. transcriptional activation) and negative (i.e. transcriptional repression) arms of the circadian regulation and 2) that PARP1 is a major consumer of NAD during the DNA damage response. In our simulations, we observe that increased PARP1 activity may be able to trigger SIRT1-induced circadian phase advancements by decreasing SIRT1 activity through competition for NAD supplies. We show how this competitive inhibition may operate through protein acetylation in conjunction with phosphorylation, consistent with reported observations. These findings suggest a possible mechanism through which multiple perturbations, each dominant during different points of the circadian cycle, may result in the phase advancement of the circadian clock seen during DNA damage. PMID:26020938

  14. Preferential retention of circadian clock genes during diploidization following whole genome triplication in Brassica rapa.

    PubMed

    Lou, Ping; Wu, Jian; Cheng, Feng; Cressman, Laura G; Wang, Xiaowu; McClung, C Robertson

    2012-06-01

    Much has been learned about the architecture and function of the circadian clock of Arabidopsis thaliana, a model for plant circadian rhythms. Circadian rhythms contribute to evolutionary fitness, suggesting that circadian rhythmicity may also contribute to agricultural productivity. Therefore, we extend our study of the plant circadian clock to Brassica rapa, an agricultural crop. Since its separation from Arabidopsis, B. rapa has undergone whole genome triplication and subsequent diploidization that has involved considerable gene loss. We find that circadian clock genes are preferentially retained relative to comparison groups of their neighboring genes, a set of randomly chosen genes, and a set of housekeeping genes broadly conserved in eukaryotes. The preferential retention of clock genes is consistent with the gene dosage hypothesis, which predicts preferential retention of highly networked or dose-sensitive genes. Two gene families encoding transcription factors that play important roles in the plant core oscillator--the PSEUDO-RESPONSE REGULATORS, including TIMING OF CAB EXPRESSION1, and the REVEILLE family, including CIRCADIAN CLOCK ASSOCIATED1 and LATE ELONGATED HYPOCOTYL--exhibit preferential retention consistent with the gene dosage hypothesis, but a third gene family, including ZEITLUPE, that encodes F-Box proteins that regulate posttranslational protein stability offers an exception.

  15. Nutrition and the Circadian System

    PubMed Central

    Potter, Gregory D M; Cade, Janet E; Grant, Peter J; Hardie, Laura J

    2016-01-01

    The human circadian system anticipates and adapts to daily environmental changes to optimise behaviour according to time of day and temporally partition incompatible physiological processes. At the helm of this system is a master clock in the suprachiasmatic nuclei (SCN) of the anterior hypothalamus. The SCN are primarily synchronised to the 24 hour day by the light/dark cycle; however, feeding/fasting cycles are the primary time cues for clocks in peripheral tissues. Aligning feeding/fasting cycles with clock-regulated metabolic changes optimises metabolism, and studies of other animals suggest that feeding at inappropriate times disrupts circadian system organisation and thereby contributes to adverse metabolic consequences and chronic disease development. ‘High-fat diets’ (HFDs) produce particularly deleterious effects on circadian system organisation in rodents by blunting feeding/fasting cycles. Time-of-day-restricted feeding, where food availability is restricted to a period of several hours, offsets many adverse consequences of HFDs in these animals; however, further evidence is required to assess whether the same is true in humans. Several nutritional compounds have robust effects on the circadian system. Caffeine, for example, can speed synchronisation to new time zones after jetlag. An appreciation of the circadian system has many implications for nutritional science and may ultimately help reduce the burden of chronic diseases. PMID:27221157

  16. Making circadian cancer therapy practical.

    PubMed

    Block, Keith I; Block, Penny B; Fox, Susan Reynolds; Birris, Jamie Stouffer; Feng, April Y; de la Torre, Michael; Nathan, Deva; Tothy, Peter; Maki, Amanda K; Gyllenhaal, Charlotte

    2009-12-01

    Practical circadian therapy for the cancer patient involves 3 spheres of intervention-improving lifestyle, optimizing internal biochemical milieu, and adjusting treatment times. The potential value of improving overall circadian functioning is shown in the work of Mormont et al in which pronounced rest-activity rhythms were associated with better survival in colorectal cancer patients receiving chronomodulated chemotherapy. Lifestyle interventions that may improve circadian functioning involve diet, physical activity, and mind-body therapies. A diet that is anti-inflammatory and has appropriate carbohydrate intake, as well as regular meal timing, encourages normal circadian cycles. Adequate daytime physical activity encourages restful sleep, and morning light exposure during exercise may entrain melatonin rhythms. Meditation and other mind-body therapies can reduce anxiety and depression that may disrupt sleep. Aspects of the biochemical milieu that specifically disrupt circadian functioning are inflammation and stress hormones. Inflammation and cytokine disruption can be addressed with diet, herbs, and other natural substances. Chronomodulation of chemotherapy in a US clinical setting will be discussed. A series of 12 cases will be presented of patients who experienced grade 3 to 4 toxicities with various chemotherapy regimens for colorectal cancer. When rechallenged with the same regimens administered chronotherapeutically, none of the patients experienced grade 3 to 4 toxicity. Integrating all the above treatment modalities has the potential to improve both the quality of life and disease outcomes in cancer patients.

  17. Analysis of Circadian Leaf Movements.

    PubMed

    Müller, Niels A; Jiménez-Gómez, José M

    2016-01-01

    The circadian clock is a molecular timekeeper that controls a wide variety of biological processes. In plants, clock outputs range from the molecular level, with rhythmic gene expression and metabolite content, to physiological processes such as stomatal conductance or leaf movements. Any of these outputs can be used as markers to monitor the state of the circadian clock. In the model plant Arabidopsis thaliana, much of the current knowledge about the clock has been gained from time course experiments profiling expression of endogenous genes or reporter constructs regulated by the circadian clock. Since these methods require labor-intensive sample preparation or transformation, monitoring leaf movements is an interesting alternative, especially in non-model species and for natural variation studies. Technological improvements both in digital photography and image analysis allow cheap and easy monitoring of circadian leaf movements. In this chapter we present a protocol that uses an autonomous point and shoot camera and free software to monitor circadian leaf movements in tomato. PMID:26867616

  18. Analysis of Circadian Regulation of Poly(A) Tail Length

    PubMed Central

    Kojima, Shihoko; Green, Carla B.

    2015-01-01

    The poly(A) tail is found on the 3’-end of most eukaryotic mRNAs, and its length significantly contributes to the mRNAs half-life and translational competence. Circadian regulation of poly(A) tail length is a powerful mechanism to confer rhythmicity in gene expression post-transcriptionally, and provides a means to regulate protein levels independent of rhythmic transcription in the nucleus. Therefore, analysis of circadian poly(A) tail length regulation is important for a complete understanding of rhythmic physiology, since rhythmically expressed proteins are the ultimate mediators of rhythmic function. Nevertheless, it has previously been challenging to measure changes in poly(A) tail length, especially at a global level, due to technical constraints. However, new methodology based on differential fractionation of mRNAs based on the length of their tails has recently been developed. In this chapter, we will describe these methods as used for examining the circadian regulation of poly(A) tail length and will provide detailed experimental procedures to measure poly(A) tail length both at a the single mRNA level and the global level. Although this chapter concentrates on methods we used for analyzing poly(A) tail length in the mammalian circadian system, the methods described here can be applicable to any organisms and any biological processes. PMID:25662466

  19. Circadian Clock, Cancer, and Chemotherapy

    PubMed Central

    2015-01-01

    The circadian clock is a global regulatory system that interfaces with most other regulatory systems and pathways in mammalian organisms. Investigations of the circadian clock–DNA damage response connections have revealed that nucleotide excision repair, DNA damage checkpoints, and apoptosis are appreciably influenced by the clock. Although several epidemiological studies in humans and a limited number of genetic studies in mouse model systems have indicated that clock disruption may predispose mammals to cancer, well-controlled genetic studies in mice have not supported the commonly held view that circadian clock disruption is a cancer risk factor. In fact, in the appropriate genetic background, clock disruption may instead aid in cancer regression by promoting intrinsic and extrinsic apoptosis. Finally, the clock may affect the efficacy of cancer treatment (chronochemotherapy) by modulating the pharmacokinetics and pharmacodynamics of chemotherapeutic drugs as well as the activity of the DNA repair enzymes that repair the DNA damage caused by anticancer drugs. PMID:25302769

  20. Nitrogen regulates CRY1 phosphorylation and circadian clock input pathways.

    PubMed

    Zhou, Yang-Hong; Zhang, Zhong-Wei; Zheng, Chong; Yuan, Shu; He, Yikun

    2016-09-01

    The delayed flowering phenotype caused by nitrogen (N) fertilizer application has been known for a long time, but we know little about the specific molecular mechanism for this phenomenon before. Our study indicated that low nitrogen increases the NADPH/NADP(+) and ATP/AMP ratios which affect adenosine monophosphate-activated protein kinase (AMPK) activity and phosphorylation and abundance of nuclear CRY1 protein. Then CRY1 acts in the N signal input pathway to the circadian clock. Here we further discuss: (1) the role of C/N ratio in flowering, (2) circadian oscillation of plant AMPK transcripts and proteins, (3) conservation of nutrition-mediated CRY1 phosphorylation and degradation, and (4) crosstalks between nitrogen signals and nitric oxide (NO) signals in flowering. PMID:27617369

  1. The circadian clock regulates inflammatory arthritis

    PubMed Central

    Hand, Laura E.; Hopwood, Thomas W.; Dickson, Suzanna H.; Walker, Amy L.; Loudon, Andrew S. I.; Ray, David W.; Bechtold, David A.; Gibbs, Julie E.

    2016-01-01

    There is strong diurnal variation in the symptoms and severity of chronic inflammatory diseases, such as rheumatoid arthritis. In addition, disruption of the circadian clock is an aggravating factor associated with a range of human inflammatory diseases. To investigate mechanistic links between the biological clock and pathways underlying inflammatory arthritis, mice were administered collagen (or saline as a control) to induce arthritis. The treatment provoked an inflammatory response within the limbs, which showed robust daily variation in paw swelling and inflammatory cytokine expression. Inflammatory markers were significantly repressed during the dark phase. Further work demonstrated an active molecular clock within the inflamed limbs and highlighted the resident inflammatory cells, fibroblast-like synoviocytes (FLSs), as a potential source of the rhythmic inflammatory signal. Exposure of mice to constant light disrupted the clock in peripheral tissues, causing loss of the nighttime repression of local inflammation. Finally, the results show that the core clock proteins cryptochrome (CRY) 1 and 2 repressed inflammation within the FLSs, and provide novel evidence that a CRY activator has anti-inflammatory properties in human cells. We conclude that under chronic inflammatory conditions, the clock actively represses inflammatory pathways during the dark phase. This interaction has exciting potential as a therapeutic avenue for treatment of inflammatory disease.—Hand, L. E., Hopwood, T. W., Dickson, S. H., Walker, A. L., Loudon, A. S. I., Ray, D. W., Bechtold, D. A., Gibbs, J. E. The circadian clock regulates inflammatory arthritis. PMID:27488122

  2. Circadian variation of the pancreatic islet transcriptome.

    PubMed

    Rakshit, Kuntol; Qian, Jingyi; Ernst, Jason; Matveyenko, Aleksey V

    2016-09-01

    Pancreatic islet failure is a characteristic feature of impaired glucose control in diabetes mellitus. Circadian control of islet function is essential for maintaining proper glucose homeostasis. Circadian variations in transcriptional pathways have been described in diverse cell types and shown to be critical for optimization of cellular function in vivo. In the current study, we utilized Short Time Series Expression Miner (STEM) analysis to identify diurnally expressed transcripts and biological pathways from mouse islets isolated at 4 h intervals throughout the 24 h light-dark cycle. STEM analysis identified 19 distinct chronological model profiles, and genes belonging to each profile were subsequently annotated to significantly enriched Kyoto Encyclopedia of Genes and Genomes biological pathways. Several transcriptional pathways essential for proper islet function (e.g., insulin secretion, oxidative phosphorylation), cell survival (e.g., insulin signaling, apoptosis) and cell proliferation (DNA replication, homologous recombination) demonstrated significant time-dependent variations. Notably, KEGG pathway analysis revealed "protein processing in endoplasmic reticulum - mmu04141" as one of the most enriched time-dependent pathways in islets. This study provides unique data set on time-dependent diurnal profiles of islet gene expression and biological pathways, and suggests that diurnal variation of the islet transcriptome is an important feature of islet homeostasis, which should be taken into consideration for optimal experimental design and interpretation of future islet studies. PMID:27495157

  3. Metabolism and the circadian clock converge.

    PubMed

    Eckel-Mahan, Kristin; Sassone-Corsi, Paolo

    2013-01-01

    Circadian rhythms occur in almost all species and control vital aspects of our physiology, from sleeping and waking to neurotransmitter secretion and cellular metabolism. Epidemiological studies from recent decades have supported a unique role for circadian rhythm in metabolism. As evidenced by individuals working night or rotating shifts, but also by rodent models of circadian arrhythmia, disruption of the circadian cycle is strongly associated with metabolic imbalance. Some genetically engineered mouse models of circadian rhythmicity are obese and show hallmark signs of the metabolic syndrome. Whether these phenotypes are due to the loss of distinct circadian clock genes within a specific tissue versus the disruption of rhythmic physiological activities (such as eating and sleeping) remains a cynosure within the fields of chronobiology and metabolism. Becoming more apparent is that from metabolites to transcription factors, the circadian clock interfaces with metabolism in numerous ways that are essential for maintaining metabolic homeostasis.

  4. Nutrients and Circadian Rhythms in Mammals.

    PubMed

    Wu, Tao; Yao, Cencen; Huang, Liangfeng; Mao, Youxiang; Zhang, Wanjing; Jiang, Jianguo; Fu, Zhengwei

    2015-01-01

    The circadian rhythm is generally existed in mammalian behavior and metabolic processes, which results from the self-sustained circadian clocks. The mammalian circadian clocks are composed of a master clock located in the hypothalamic suprachiasmatic nucleus (SCN), and of many peripheral clocks in tissues and extra-SCN brain regions. It is indicated that feeding could take over part of the SCN signaling, and affect internal synchrony between the master clock and the peripheral clocks. Thus, recent studies focus more on the relationship between the nutrients and circadian rhythms. Various nutrient components (glucose, amino acid, alcohol) are found to be able to directly affect the circadian rhythm of clock genes. Moreover, the feeding schedule of nutrients is as important as the nutrient components in maintaining a healthy circadian rhythm. Therefore, the circadian homeostasis needs not only balanced nutrient components but also regular timed nutrients.

  5. Thyroxine differentially modulates the peripheral clock: lessons from the human hair follicle.

    PubMed

    Hardman, Jonathan A; Haslam, Iain S; Farjo, Nilofer; Farjo, Bessam; Paus, Ralf

    2015-01-01

    The human hair follicle (HF) exhibits peripheral clock activity, with knock-down of clock genes (BMAL1 and PER1) prolonging active hair growth (anagen) and increasing pigmentation. Similarly, thyroid hormones prolong anagen and stimulate pigmentation in cultured human HFs. In addition they are recognized as key regulators of the central clock that controls circadian rhythmicity. Therefore, we asked whether thyroxine (T4) also influences peripheral clock activity in the human HF. Over 24 hours we found a significant reduction in protein levels of BMAL1 and PER1, with their transcript levels also decreasing significantly. Furthermore, while all clock genes maintained their rhythmicity in both the control and T4 treated HFs, there was a significant reduction in the amplitude of BMAL1 and PER1 in T4 (100 nM) treated HFs. Accompanying this, cell-cycle progression marker Cyclin D1 was also assessed appearing to show an induced circadian rhythmicity by T4 however, this was not significant. Contrary to short term cultures, after 6 days, transcript and/or protein levels of all core clock genes (BMAL1, PER1, clock, CRY1, CRY2) were up-regulated in T4 treated HFs. BMAL1 and PER1 mRNA was also up-regulated in the HF bulge, the location of HF epithelial stem cells. Together this provides the first direct evidence that T4 modulates the expression of the peripheral molecular clock. Thus, patients with thyroid dysfunction may also show a disordered peripheral clock, which raises the possibility that short term, pulsatile treatment with T4 might permit one to modulate circadian activity in peripheral tissues as a target to treat clock-related disease.

  6. Studying circadian rhythm and sleep using genetic screens in Drosophila.

    PubMed

    Axelrod, Sofia; Saez, Lino; Young, Michael W

    2015-01-01

    The power of Drosophila melanogaster as a model organism lies in its ability to be used for large-scale genetic screens with the capacity to uncover the genetic basis of biological processes. In particular, genetic screens for circadian behavior, which have been performed since 1971, allowed researchers to make groundbreaking discoveries on multiple levels: they discovered that there is a genetic basis for circadian behavior, they identified the so-called core clock genes that govern this process, and they started to paint a detailed picture of the molecular functions of these clock genes and their encoded proteins. Since the discovery that fruit flies sleep in 2000, researchers have successfully been using genetic screening to elucidate the many questions surrounding this basic animal behavior. In this chapter, we briefly recall the history of circadian rhythm and sleep screens and then move on to describe techniques currently employed for mutagenesis and genetic screening in the field. The emphasis lies on comparing the newer approaches of transgenic RNA interference (RNAi) to classical forms of mutagenesis, in particular in their application to circadian behavior and sleep. We discuss the different screening approaches in light of the literature and published and unpublished sleep and rhythm screens utilizing ethyl methanesulfonate mutagenesis and transgenic RNAi from our lab.

  7. Interdependence of nutrient metabolism and the circadian clock system: Importance for metabolic health

    PubMed Central

    Ribas-Latre, Aleix; Eckel-Mahan, Kristin

    2016-01-01

    Background While additional research is needed, a number of large epidemiological studies show an association between circadian disruption and metabolic disorders. Specifically, obesity, insulin resistance, cardiovascular disease, and other signs of metabolic syndrome all have been linked to circadian disruption in humans. Studies in other species support this association and generally reveal that feeding that is not in phase with the external light/dark cycle, as often occurs with night or rotating shift workers, is disadvantageous in terms of energy balance. As food is a strong driver of circadian rhythms in the periphery, understanding how nutrient metabolism drives clocks across the body is important for dissecting out why circadian misalignment may produce such metabolic effects. A number of circadian clock proteins as well as their accessory proteins (such as nuclear receptors) are highly sensitive to nutrient metabolism. Macronutrients and micronutrients can function as zeitgebers for the clock in a tissue-specific way and can thus impair synchrony between clocks across the body, or potentially restore synchrony in the case of circadian misalignment. Circadian nuclear receptors are particularly sensitive to nutrient metabolism and can alter tissue-specific rhythms in response to changes in the diet. Finally, SNPs in human clock genes appear to be correlated with diet-specific responses and along with chronotype eventually may provide valuable information from a clinical perspective on how to use diet and nutrition to treat metabolic disorders. Scope of review This article presents a background of the circadian clock components and their interrelated metabolic and transcriptional feedback loops, followed by a review of some recent studies in humans and rodents that address the effects of nutrient metabolism on the circadian clock and vice versa. We focus on studies in which results suggest that nutrients provide an opportunity to restore or, alternatively

  8. Keeping circadian time with hormones.

    PubMed

    Challet, E

    2015-09-01

    Daily variations of metabolism, physiology and behaviour are controlled by a network of coupled circadian clocks, comprising a master clock in the suprachiasmatic nuclei of the hypothalamus and a multitude of secondary clocks in the brain and peripheral organs. Light cues synchronize the master clock that conveys temporal cues to other body clocks via neuronal and hormonal signals. Feeding at unusual times can reset the phase of most peripheral clocks. While the neuroendocrine aspect of circadian regulation has been underappreciated, this review aims at showing that the role of hormonal rhythms as internal time-givers is the rule rather than the exception. Adrenal glucocorticoids, pineal melatonin and adipocyte-derived leptin participate in internal synchronization (coupling) within the multi-oscillatory network. Furthermore, pancreatic insulin is involved in food synchronization of peripheral clocks, while stomach ghrelin provides temporal signals modulating behavioural anticipation of mealtime. Circadian desynchronization induced by shift work or chronic jet lag has harmful effects on metabolic regulation, thus favouring diabetes and obesity. Circadian deregulation of hormonal rhythms may participate in internal desynchronization and associated increase in metabolic risks. Conversely, adequate timing of endocrine therapies can promote phase-adjustment of the master clock (e.g. via melatonin agonists) and peripheral clocks (e.g. via glucocorticoid agonists).

  9. Cannabinoids excite circadian clock neurons.

    PubMed

    Acuna-Goycolea, Claudio; Obrietan, Karl; van den Pol, Anthony N

    2010-07-28

    Cannabinoids, the primary active agent in drugs of abuse such as marijuana and hashish, tend to generate a distorted sense of time. Here we study the effect of cannabinoids on the brain's circadian clock, the suprachiasmatic nucleus (SCN), using patch clamp and cell-attached electrophysiological recordings, RT-PCR, immunocytochemistry, and behavioral analysis. The SCN showed strong expression of the cannabinoid receptor CB1R, as detected with RT-PCR. SCN neurons, including those using GABA as a transmitter, and axons within the SCN, expressed CB1R immunoreactivity. Behaviorally, cannabinoids did not alter the endogenous free-running circadian rhythm in the mouse brain, but did attenuate the ability of the circadian clock to entrain to light zeitgebers. In the absence of light, infusion of the CB1R antagonist AM251 caused a modest phase shift, suggesting endocannabinoid modulation of clock timing. Interestingly, cannabinoids had no effect on glutamate release from the retinohypothalamic projection, suggesting a direct action of cannabinoids on the retinohypothalamic tract was unlikely to explain the inhibition of the phase shift. Within the SCN, cannabinoids were excitatory by a mechanism based on presynaptic CB1R attenuation of axonal GABA release. These data raise the possibility that the time dissociation described by cannabinoid users may result in part from altered circadian clock function and/or entrainment to environmental time cues. PMID:20668190

  10. Circadian influences on myocardial infarction

    PubMed Central

    Virag, Jitka A. I.; Lust, Robert M.

    2014-01-01

    Components of circadian rhythm maintenance, or “clock genes,” are endogenous entrainable oscillations of about 24 h that regulate biological processes and are found in the suprachaismatic nucleus (SCN) and many peripheral tissues, including the heart. They are influenced by external cues, or Zeitgebers, such as light and heat, and can influence such diverse phenomena as cytokine expression immune cells, metabolic activity of cardiac myocytes, and vasodilator regulation by vascular endothelial cells. While it is known that the central master clock in the SCN synchronizes peripheral physiologic rhythms, the mechanisms by which the information is transmitted are complex and may include hormonal, metabolic, and neuronal inputs. Whether circadian patterns are causally related to the observed periodicity of events, or whether they are simply epi-phenomena is not well established, but a few studies suggest that the circadian effects likely are real in their impact on myocardial infarct incidence. Cycle disturbances may be harbingers of predisposition and subsequent response to acute and chronic cardiac injury, and identifying the complex interactions of circadian rhythms and myocardial infarction may provide insights into possible preventative and therapeutic strategies for susceptible populations. PMID:25400588

  11. Elucidating the Ticking of an In Vitro Circadian Clockwork

    PubMed Central

    Qin, Ximing; Egli, Martin; Mchaourab, Hassane S; Stewart, Phoebe L; Johnson, Carl Hirschie

    2007-01-01

    A biochemical oscillator can be reconstituted in vitro with three purified proteins, that displays the salient properties of circadian (daily) rhythms, including self-sustained 24-h periodicity that is temperature compensated. We analyze the biochemical basis of this oscillator by quantifying the time-dependent interactions of the three proteins (KaiA, KaiB, and KaiC) by electron microscopy and native gel electrophoresis to elucidate the timing of the formation of complexes among the Kai proteins. The data are used to derive a dynamic model for the in vitro oscillator that accurately reproduces the rhythms of KaiABC complexes and of KaiC phosphorylation, and is consistent with biophysical observations of individual Kai protein interactions. We use fluorescence resonance energy transfer (FRET) to confirm that monomer exchange among KaiC hexamers occurs. The model demonstrates that the function of this monomer exchange may be to maintain synchrony among the KaiC hexamers in the reaction, thereby sustaining a high-amplitude oscillation. Finally, we apply the first perturbation analyses of an in vitro oscillator by using temperature pulses to reset the phase of the KaiABC oscillator, thereby testing the resetting characteristics of this unique circadian oscillator. This study analyzes a circadian clockwork to an unprecedented level of molecular detail. PMID:17388688

  12. Dim light at night disrupts molecular circadian rhythms and increases body weight.

    PubMed

    Fonken, Laura K; Aubrecht, Taryn G; Meléndez-Fernández, O Hecmarie; Weil, Zachary M; Nelson, Randy J

    2013-08-01

    With the exception of high latitudes, life has evolved under bright days and dark nights. Most organisms have developed endogenously driven circadian rhythms that are synchronized to this daily light/dark cycle. In recent years, humans have shifted away from the naturally occurring solar light cycle in favor of artificial and sometimes irregular light schedules produced by electric lighting. Exposure to unnatural light cycles is increasingly associated with obesity and metabolic syndrome; however, the means by which environmental lighting alters metabolism are poorly understood. Thus, we exposed mice to dim light at night and investigated changes in the circadian system and metabolism. Here we report that exposure to ecologically relevant levels of dim (5 lux) light at night altered core circadian clock rhythms in the hypothalamus at both the gene and protein level. Circadian rhythms in clock expression persisted during light at night; however, the amplitude of Per1 and Per2 rhythms was attenuated in the hypothalamus. Circadian oscillations were also altered in peripheral tissues critical for metabolic regulation. Exposure to dimly illuminated, as compared to dark, nights decreased the rhythmic expression in all but one of the core circadian clock genes assessed in the liver. Additionally, mice exposed to dim light at night attenuated Rev-Erb expression in the liver and adipose tissue. Changes in the circadian clock were associated with temporal alterations in feeding behavior and increased weight gain. These results are significant because they provide evidence that mild changes in environmental lighting can alter circadian and metabolic function. Detailed analysis of temporal changes induced by nighttime light exposure may provide insight into the onset and progression of obesity and metabolic syndrome, as well as other disorders involving sleep and circadian rhythm disruption.

  13. Drosophila spaghetti and doubletime link the circadian clock and light to caspases, apoptosis and tauopathy.

    PubMed

    Means, John C; Venkatesan, Anandakrishnan; Gerdes, Bryan; Fan, Jin-Yuan; Bjes, Edward S; Price, Jeffrey L

    2015-05-01

    While circadian dysfunction and neurodegeneration are correlated, the mechanism for this is not understood. It is not known if age-dependent circadian dysfunction leads to neurodegeneration or vice-versa, and the proteins that mediate the effect remain unidentified. Here, we show that the knock-down of a regulator (spag) of the circadian kinase Dbt in circadian cells lowers Dbt levels abnormally, lengthens circadian rhythms and causes expression of activated initiator caspase (Dronc) in the optic lobes during the middle of the day or after light pulses at night. Likewise, reduced Dbt activity lengthens circadian period and causes expression of activated Dronc, and a loss-of-function mutation in Clk also leads to expression of activated Dronc in a light-dependent manner. Genetic epistasis experiments place Dbt downstream of Spag in the pathway, and Spag-dependent reductions of Dbt are shown to require the proteasome. Importantly, activated Dronc expression due to reduced Spag or Dbt activity occurs in cells that do not express the spag RNAi or dominant negative Dbt and requires PDF neuropeptide signaling from the same neurons that support behavioral rhythms. Furthermore, reduction of Dbt or Spag activity leads to Dronc-dependent Drosophila Tau cleavage and enhanced neurodegeneration produced by human Tau in a fly eye model for tauopathy. Aging flies with lowered Dbt or Spag function show markers of cell death as well as behavioral deficits and shortened lifespans, and even old wild type flies exhibit Dbt modification and activated caspase at particular times of day. These results suggest that Dbt suppresses expression of activated Dronc to prevent Tau cleavage, and that the circadian clock defects confer sensitivity to expression of activated Dronc in response to prolonged light. They establish a link between the circadian clock factors, light, cell death pathways and Tau toxicity, potentially via dysregulation of circadian neuronal remodeling in the optic lobes.

  14. Into the Evening: Complex Interactions in the Arabidopsis Circadian Clock.

    PubMed

    Huang, He; Nusinow, Dmitri A

    2016-10-01

    In Arabidopsis thaliana an assembly of proteins named the evening complex (EC) has been established as an essential component of the circadian clock with conserved functions in regulating plant growth and development. Recent studies identifying EC-regulated genes and EC-interacting proteins have expanded our understanding of EC function. In this review we focus on new progress uncovering how the EC contributes to the circadian network through the integration of environmental inputs and the direct regulation of key clock genes. We also summarize new findings of how the EC directly regulates clock outputs, such as photoperiodic and thermoresponsive growth, and provide new perspectives on future experiments to address unsolved questions related to the EC. PMID:27594171

  15. Therapeutics for Circadian Rhythm Sleep Disorders

    PubMed Central

    Dodson, Ehren R.; Zee, Phyllis C

    2010-01-01

    Synopsis The sleep-wake cycle is regulated by the interaction of endogenous circadian and homeostatic processes. The circadian system provides timing information for most physiological rhythms, including the sleep and wake cycle. In addition, the central circadian clock located in the suprachiasmatic nucleus of the hypothalamus has been shown to promote alertness during the day. Circadian rhythm sleep disorders arise when there is a misalignment between the timing of the endogenous circadian rhythms and the external environment or when there is dysfunction of the circadian clock or its entrainment pathways. The primary synchronizing agents of the circadian system are light and melatonin. Light is the strongest entraining agent of circadian rhythms and timed exposure to bright light is often used in the treatment of circadian rhythm sleep disorders. In addition, timed administration of melatonin, either alone or in combination with light therapy has been shown to be useful in the treatment of the following circadian rhythm sleep disorders: delayed sleep phase, advanced sleep phase, free-running, irregular sleep wake, jet lag and shift work. PMID:21243069

  16. Modelling and Analysis of the Feeding Regimen Induced Entrainment of Hepatocyte Circadian Oscillators Using Petri Nets

    PubMed Central

    Tareen, Samar Hayat Khan; Ahmad, Jamil

    2015-01-01

    Circadian rhythms are certain periodic behaviours exhibited by living organism at different levels, including cellular and system-wide scales. Recent studies have found that the circadian rhythms of several peripheral organs in mammals, such as the liver, are able to entrain their clocks to received signals independent of other system level clocks, in particular when responding to signals generated during feeding. These studies have found SIRT1, PARP1, and HSF1 proteins to be the major influencers of the core CLOCKBMAL1:PER-CRY circadian clock. These entities, along with abstracted feeding induced signals were modelled collectively in this study using Petri Nets. The properties of the model show that the circadian system itself is strongly robust, and is able to continually evolve. The modelled feeding regimens suggest that the usual 3 meals/day and 2 meals/day feeding regimens are beneficial with any more or less meals/day negatively affecting the system. PMID:25789928

  17. 'Cold cuts' added to the circadian smorgasbord of regulatory mechanisms.

    PubMed

    Green, Carla B

    2016-09-01

    In mammals, rhythms in body temperature help to entrain and synchronize circadian rhythms throughout the organism, and the cold-inducible RNA-binding protein (CIRBP) is one of the mediators of these daily temperature changes. Cirbp mRNA expression is regulated by the daily subtle rhythms in body temperature, and a new study by Gotic and colleagues (pp. 2005-2017) reveals a surprising and novel mechanism that involves temperature-dependent enhancement of splicing efficiency. PMID:27664233

  18. Genomic identification of a putative circadian system in the cladoceran crustacean Daphnia pulex

    PubMed Central

    Tilden, Andrea R.; McCoole, Matthew D.; Harmon, Sarah M.; Baer, Kevin N.; Christie, Andrew E.

    2011-01-01

    Essentially nothing is known about the molecular underpinnings of crustacean circadian clocks. The genome of Daphnia pulex, the only crustacean genome available for public use, provides a unique resource for identifying putative circadian proteins in this species. Here, the Daphnia genome was mined for putative circadian protein genes using Drosophila melanogaster queries. The sequences of core clock (e.g. CLOCK, CYCLE, PERIOD, TIMELESS and CRYPTOCHROME 2), clock input (CRYPTOCHROME 1) and clock output (PIGMENT DISPERSING HORMONE RECEPTOR) proteins were deduced. Structural analyses and alignment of the Daphnia proteins with their Drosophila counterparts revealed extensive sequence conservation, particularly in functional domains. Comparisons of the Daphnia proteins with other sequences showed that they are, in most cases, more similar to homologs from other species, including vertebrates, than they are to those of Drosophila. The presence of both CRYPTOCHROME 1 and 2 in Daphnia suggests the organization of its clock may be more similar to that of the butterfly Danaus plexippus than to that of Drosophila (which possesses CRYPTOCHROME 1 but not CRYPTOCHROME 2). These data represent the first description of a putative circadian system from any crustacean, and provide a foundation for future molecular, anatomical and physiological investigations of circadian signaling in Daphnia. PMID:21798832

  19. Dominant-Negative CK2α Induces Potent Effects on Circadian Rhythmicity

    PubMed Central

    Smith, Elaine M; Lin, Jui-Ming; Meissner, Rose-Anne; Allada, Ravi

    2008-01-01

    Circadian clocks organize the precise timing of cellular and behavioral events. In Drosophila, circadian clocks consist of negative feedback loops in which the clock component PERIOD (PER) represses its own transcription. PER phosphorylation is a critical step in timing the onset and termination of this feedback. The protein kinase CK2 has been linked to circadian timing, but the importance of this contribution is unclear; it is not certain where and when CK2 acts to regulate circadian rhythms. To determine its temporal and spatial functions, a dominant negative mutant of the catalytic alpha subunit, CK2αTik, was targeted to circadian neurons. Behaviorally, CK2αTik induces severe period lengthening (∼33 h), greater than nearly all known circadian mutant alleles, and abolishes detectable free-running behavioral rhythmicity at high levels of expression. CK2αTik, when targeted to a subset of pacemaker neurons, generates period splitting, resulting in flies exhibiting both long and near 24-h periods. These behavioral effects are evident even when CK2αTik expression is induced only during adulthood, implicating an acute role for CK2α function in circadian rhythms. CK2αTik expression results in reduced PER phosphorylation, delayed nuclear entry, and dampened cycling with elevated trough levels of PER. Heightened trough levels of per transcript accompany increased protein levels, suggesting that CK2αTik disturbs negative feedback of PER on its own transcription. Taken together, these in vivo data implicate a central role of CK2α function in timing PER negative feedback in adult circadian neurons. PMID:18208335

  20. Parathyroid hormone resets the cartilage circadian clock of the organ-cultured murine femur

    PubMed Central

    Okubo, Naoki; Fujiwara, Hiroyoshi; Minami, Yoichi; Kunimoto, Tatsuya; Hosokawa, Toshihiro; Umemura, Yasuhiro; Inokawa, Hitoshi; Asada, Maki; Oda, Ryo; Kubo, Toshikazu

    2015-01-01

    Background and purpose The circadian clock governs endogenous day-night variations. In bone, the metabolism and growth show diurnal rhythms. The circadian clock is based on a transcription-translation feedback loop composed of clock genes including Period2 (Per2), which encodes the protein period circadian protein homolog 2. Because plasma parathyroid hormone (PTH) levels show diurnal variation, we hypothesized that PTH could carry the time information to bone and cartilage. In this study, we analyzed the effect of PTH on the circadian clock of the femur. Patients and methods Per2::Luciferase (Per2::Luc) knock-in mice were used and their femurs were organ-cultured. The bioluminescence was measured using photomultiplier tube-based real-time bioluminescence monitoring equipment or real-time bioluminescence microscopic imaging devices. PTH or its vehicle was administered and the phase shifts were calculated. Immunohistochemistry was performed to detect PTH type 1 receptor (PTH1R) expression. Results Real-time bioluminescence monitoring revealed that PTH reset the circadian rhythm of the Per2::Luc activity in the femurs in an administration time-dependent and dose-dependent manner. Microscopic bioluminescence imaging revealed that Per2::Luc activity in the growth plate and the articular cartilage showed that the circadian rhythms and their phase shifts were induced by PTH. PTH1R was expressed in the growth plate cartilage. Interpretation In clinical practice, teriparatide (PTH (1-34)) treatment is widely used for osteoporosis. We found that PTH administration regulated the femoral circadian clock oscillation, particularly in the cartilage. Regulation of the local circadian clock by PTH may lead to a more effective treatment for not only osteoporosis but also endochondral ossification in bone growth and fracture repair. PMID:25765847

  1. Melanopsin--shedding light on the elusive circadian photopigment.

    PubMed

    Brown, R Lane; Robinson, Phyllis R

    2004-03-01

    Circadian photoentrainment is the process by which the brain's internal clock becomes synchronized with the daily external cycle of light and dark. In mammals, this process is mediated exclusively by a novel class of retinal ganglion cells that send axonal projections to the suprachiasmatic nuclei (SCN), the region of the brain that houses the circadian pacemaker. In contrast to their counterparts that mediate image-forming vision, SCN-projecting RGCs are intrinsically sensitive to light, independent of synaptic input from rod and cone photoreceptors. The recent discovery of these photosensitive RGCs has challenged the long-standing dogma of retinal physiology that rod and cone photoreceptors are the only retinal cells that respond directly to light and has explained the perplexing finding that mice lacking rod and cone photoreceptors can still reliably entrain their circadian rhythms to light. These SCN-projecting RGCs selectively express melanopsin, a novel opsin-like protein that has been proposed as a likely candidate for the photopigment in these cells. Research in the past three years has revealed that disruption of the melanopsin gene impairs circadian photo- entrainment, as well as other nonvisual responses to light such as the pupillary light reflex. Until recently, however, there was no direct demonstration that melanopsin formed a functional photopigment capable of catalyzing G-protein activation in a light-dependent manner. Our laboratory has recently succeeded in expressing melanopsin in a heterologous tissue culture system and reconstituting a pigment with the 11-cis-retinal chromophore. In a reconstituted biochemical system, the reconstituted melanopsin was capable of activating transducin, the G-protein of rod photoreceptors, in a light-dependent manner. The absorbance spectrum of this heterologously expressed melanopsin, however, does not match that predicted by previous behavioral and electophysiological studies. Although melanopsin is clearly the

  2. Caffeine lengthens circadian rhythms in mice.

    PubMed

    Oike, Hideaki; Kobori, Masuko; Suzuki, Takahiro; Ishida, Norio

    2011-07-01

    Although caffeine alters sleep in many animals, whether or not it affects mammalian circadian clocks remains unknown. Here, we found that incubating cultured mammalian cell lines, human osteosarcoma U2OS cells and mouse fibroblast NIH3T3 cells, with caffeine lengthened the period of circadian rhythms. Adding caffeine to ex vivo cultures also lengthened the circadian period in mouse liver explants from Per2::Luciferase reporter gene knockin mice, and caused a phase delay in brain slices containing the suprachiasmatic nucleus (SCN), where the central circadian clock in mammals is located. Furthermore, chronic caffeine consumption ad libitum for a week delayed the phase of the mouse liver clock in vivo under 12 h light-dark conditions and lengthened the period of circadian locomotor rhythms in mice under constant darkness. Our results showed that caffeine alters circadian clocks in mammalian cells in vitro and in the mouse ex vivo and in vivo. PMID:21684260

  3. Unraveling the circadian clock in Arabidopsis

    PubMed Central

    Wang, Xiaoxue; Ma, Ligeng

    2013-01-01

    The circadian clock is an endogenous timing system responsible for coordinating an organism’s biological processes with its environment. Interlocked transcriptional feedback loops constitute the fundamental architecture of the circadian clock. In Arabidopsis, three feedback loops, the core loop, morning loop and evening loop, comprise a network that is the basis of the circadian clock. The components of these three loops are regulated in distinct ways, including transcriptional, post-transcriptional and posttranslational mechanisms. The discovery of the DNA-binding and repressive activities of TOC1 has overturned our initial concept of its function in the circadian clock. The alternative splicing of circadian clock-related genes plays an essential role in normal functioning of the clock and enables organisms to sense environmental changes. In this review, we describe the regulatory mechanisms of the circadian clock that have been identified in Arabidopsis. PMID:23221775

  4. Analysis of circadian rhythms in zebrafish.

    PubMed

    Hirayama, Jun; Kaneko, Maki; Cardone, Luca; Cahill, Gregory; Sassone-Corsi, Paolo

    2005-01-01

    The zebrafish probably constitutes the best animal system to study the complexity of the circadian clock machinery and the influence that light has on it. The possibilities of producing transgenic fishes, to establish light-responsive cultured cells, and to directly explore light phototransduction on single clock cells are all remarkable features of this circadian system. This article describes some of the most useful methodologies to analyze the behavioral, cellular, and molecular aspects of the zebrafish circadian clock system. PMID:15817288

  5. [Genetic Control of Circadian Rhythms and Aging].

    PubMed

    Solovyeva, I A; Dobrovolskayaa, E V; Moskalev, A A

    2016-04-01

    The review establishes a link between a group of genes which are conserved in evolution and form a molecular oscillator responsible for generation of circadian rhythms and genetic determinants of aging including associated pathways of intracellular signaling. An analysis of mechanisms of development of age-dependent pathologies is conducted from the viewpoint of circadian genetics. Systematic data of circadian gene expression studies in animals demonstrating different rates of aging from accelerated to negligible are presented. PMID:27529973

  6. Circadian misalignment in mood disturbances.

    PubMed

    Lewy, Alfred J

    2009-12-01

    Recent refinements in methodology allow chronobiological researchers to answer the following questions: is there circadian misalignment in sleep and mood disturbances, and, if so, is it of the phase-advance or phase-delay type? Measurement of the dim light melatonin onset-to-midsleep interval, or phase-angle difference, in sleep and mood disorders should answer these questions. Although the phase-advance hypothesis of affective disorders was formulated three decades ago, recent studies suggest that many, if not all, mood disturbances have a circadian misalignment component of the phase-delay type, operationally defined as a delay in the dim light melatonin onset relative to the sleep/wake cycle. Phase-delayed disorders can be treated with bright light in the morning and/or low-dose melatonin in the afternoon/evening. Phase-advanced disorders can be treated with bright light in the evening and/or low-dose melatonin in the morning.

  7. Circadian Rhythm Control: Neurophysiological Investigations

    NASA Technical Reports Server (NTRS)

    Glotzbach, S. F.

    1985-01-01

    The suprachiasmatic nucleus (SCN) was implicated as a primary component in central nervous system mechanisms governing circadian rhythms. Disruption of the normal synchronization of temperature, activity, and other rhythms is detrimental to health. Sleep wake disorders, decreases in vigilance and performance, and certain affective disorders may result from or be exacerbated by such desynchronization. To study the basic neurophysiological mechanisms involved in entrainment of circadian systems by the environment, Parylene-coated, etched microwire electrode bundles were used to record extracellular action potentials from the small somata of the SCN and neighboring hypothalamic nuclei in unanesthetized, behaving animals. Male Wistar rats were anesthetized and chronically prepared with EEG ane EMG electrodes in addition to a moveable microdrive assembly. The majority of cells had firing rates 10 Hz and distinct populations of cells which had either the highest firing rate or lowest firing rate during sleep were seen.

  8. Circadian clocks in the ovary.

    PubMed

    Sellix, Michael T; Menaker, Michael

    2010-10-01

    Clock gene expression has been observed in tissues of the hypothalamic-pituitary-gonadal (HPG) axis. Whereas the contribution of hypothalamic oscillators to the timing of reproductive biology is well known, the role of peripheral oscillators like those in the ovary is less clear. Circadian clocks in the ovary might play a role in the timing of ovulation. Disruption of the clock in ovarian cells or desynchrony between ovarian clocks and circadian oscillators elsewhere in the body may contribute to the onset and progression of various reproductive pathologies. In this paper, we review evidence for clock function in the ovary across a number of species and offer a novel perspective into the role of this clock in normal ovarian physiology and in diseases that negatively affect fertility.

  9. Circadian clocks: lessons from fish.

    PubMed

    Idda, M Laura; Bertolucci, Cristiano; Vallone, Daniela; Gothilf, Yoav; Sánchez-Vázquez, Francisco Javier; Foulkes, Nicholas S

    2012-01-01

    Our understanding of the molecular and cellular organization of the circadian timing system in vertebrates has increased enormously over the past decade. In large part, progress has been based on genetic studies in the mouse as well as on fundamental similarities between vertebrate and Drosophila clocks. The zebrafish was initially considered as a potentially attractive genetic model for identifying vertebrate clock genes. However, instead, fish have ultimately proven to be valuable complementary models for studying various aspects of clock biology. For example, many fish can shift from diurnal to nocturnal activity implying specific flexibility in their clock function. We have learned much about the function of light input pathways, and the ontogeny and function of the pineal organ, the fish central pacemaker. Finally, blind cavefish have also provided new insight into the evolution of the circadian clock under extreme environmental conditions. PMID:22877658

  10. Circadian rhythmometry of mammalian radiosensitivity

    NASA Technical Reports Server (NTRS)

    Haus, E.; Halberg, F.; Loken, M. K.; Kim, Y. S.

    1974-01-01

    In the case of human bone marrow, the largest number of mitoses is seen in the evening in diurnally active men, mitotic activity being at a minimum in the morning. The opposite pattern is observed for nocturnal animals such as rats and mice on a regimen of light during the daytime alternating with darkness during the night hours. The entirety of these rhythms plays an important role in the organism's responses to environmental stimuli, including its resistance to potentially harmful agents. Conditions under which circadian rhythms can be observed and validated by inferential statistical means are discussed while emphasizing how artifacts of the laboratory environment can be shown to obscure circadian periodic variations in radiosensitivity.

  11. Circadian rhythm and the influence of physical activity on circulating surfactant protein D in early and long-standing rheumatoid arthritis.

    PubMed

    Christensen, A F; Hoegh, S V; Lottenburger, T; Holmskov, U; Tornoe, I; Hørslev-Petersen, K; Sørensen, G L; Junker, P

    2011-12-01

    Surfactant protein D (SP-D) belongs to the collectin family and has pro-and anti-inflammatory capacities depending on its oligomerization. Previously, circulating SP-D was shown to be decreased in early rheumatoid arthritis (RA) and negatively correlated to disease activity. This study aimed at assessing the diurnal rhythmicity and the influence of physical activity on circulating SP-D in patients with RA at different stages compared with healthy individuals. Patients with early RA (ERA) with disease duration <6 months and with long-standing RA (LRA) with disease duration 5-15 years were included in two sub-studies. Healthy individuals served as controls. Diurnal variation: blood samples were collected every 3 h from 7 a.m to 10 p.m and the following morning. Physical activity: blood sampling was done before and after standardized physical challenge. SP-D was measured by ELISA. SP-D exhibited diurnal variation in healthy controls (n = 15) and in patients with ERA (n = 9) and LRA (n = 9) with peak values at 10 a.m. and nadir in the evening (controls: P < 0.001, ERA: P = 0.004 and LRA: P = 0.009). Three hours after cessation of physical activity, SP-D decreased below pre-exercise levels in both ERA (n = 10), LRA (n = 10) and controls (n = 13) (ERA: P < 0.001, LRA: P < 0.001 and controls: P = 0.005). In patients with RA, the decline was already observed 1 h post-exercise. Circulating SP-D exhibits diurnal variation both in patients with RA at different stages and in healthy controls. SP-D in serum decreases following physical activity in health and RA disease. This study underscores the need of standardized blood sampling conditions in future studies on SP-D.

  12. Circadian rhythm dysfunction in glaucoma: A hypothesis

    PubMed Central

    Jean-Louis, Girardin; Zizi, Ferdinand; Lazzaro, Douglas R; Wolintz, Arthur H

    2008-01-01

    The absence of circadian zeitgebers in the social environment causes circadian misalignment, which is often associated with sleep disturbances. Circadian misalignment, defined as a mismatch between the sleep-wake cycle and the timing of the circadian system, can occur either because of inadequate exposure to the light-dark cycle, the most important synchronizer of the circadian system, or reduction in light transmission resulting from ophthalmic diseases (e.g., senile miosis, cataract, diabetic retinopathy, macular degeneration, retinitis pigmentosa, and glaucoma). We propose that glaucoma may be the primary ocular disease that directly compromises photic input to the circadian time-keeping system because of inherent ganglion cell death. Glaucomatous damage to the ganglion cell layer might be particularly harmful to melanopsin. According to histologic and circadian data, a subset of intrinsically photoresponsive retinal ganglion cells, expressing melanopsin and cryptochromes, entrain the endogenous circadian system via transduction of photic input to the thalamus, projecting either to the suprachiasmatic nucleus or the lateral geniculate nucleus. Glaucoma provides a unique opportunity to explore whether in fact light transmission to the circadian system is compromised as a result of ganglion cell loss. PMID:18186932

  13. Circadian Rhythm Sleep-Wake Disorders.

    PubMed

    Abbott, Sabra M; Reid, Kathryn J; Zee, Phyllis C

    2015-12-01

    The circadian system regulates the timing and expression of nearly all biological processes, most notably, the sleep-wake cycle, and disruption of this system can result in adverse effects on both physical and mental health. The circadian rhythm sleep-wake disorders (CRSWDs) consist of 5 disorders that are due primarily to pathology of the circadian clock or to a misalignment of the timing of the endogenous circadian rhythm with the environment. This article outlines the nature of these disorders, the association of many of these disorders with psychiatric illness, and available treatment options.

  14. Circadian rhythms: glucocorticoids and arthritis.

    PubMed

    Cutolo, Maurizio; Sulli, Alberto; Pizzorni, Carmen; Secchi, Maria Elena; Soldano, Stefano; Seriolo, Bruno; Straub, Rainer H; Otsa, Kati; Maestroni, Georges J

    2006-06-01

    Circadian rhythms are driven by biological clocks and are endogenous in origin. Therefore, circadian changes in the metabolism or secretion of endogenous glucocorticoids are certainly responsible in part for the time-dependent changes observed in the inflammatory response and arthritis. More recently, melatonin (MLT), another circadian hormone that is the secretory product of the pineal gland, has been found implicated in the time-dependent inflammatory reaction with effects opposite those of cortisol. Interestingly, cortisol and MLT show an opposite response to the light. The light conditions in the early morning have a strong impact on the morning cortisol peak, whereas MLT is synthesized in a strictly nocturnal pattern. Recently, a diurnal rhythmicity in healthy humans between cellular (Th1 type) or humoral (Th2 type) immune responses has been found and related to immunomodulatory actions of cortisol and MLT. The interferon (IFN)-gamma/interleukin (IL)-10 ratio peaked during the early morning and correlated negatively with plasma cortisol and positively with plasma MLT. Accordingly, the intensity of the arthritic pain varies consistently as a function of the hour of the day: pain is greater after waking up in the morning than in the afternoon or evening. The reduced cortisol and adrenal androgen secretion, observed during testing in rheumatoid arthritis (RA) patients not treated with glucocoticoids, should be clearly considered as a "relative adrenal insufficiency" in the presence of a sustained inflammatory process, and allows Th1 type cytokines to be produced in higher amounts during the late night. In conclusion, the right timing (early morning) for the glucocorticoid therapy in arthritis is fundamental and well justified by the circadian rhythms of the inflammatory mechanisms. PMID:16855156

  15. Changes in the daily rhythm of lipid metabolism in the diabetic retina.

    PubMed

    Wang, Qi; Tikhonenko, Maria; Bozack, Svetlana N; Lydic, Todd A; Yan, Lily; Panchy, Nicholas L; McSorley, Kelly M; Faber, Matthew S; Yan, Yuanqing; Boulton, Michael E; Grant, Maria B; Busik, Julia V

    2014-01-01

    Disruption of circadian regulation was recently shown to cause diabetes and metabolic disease. We have previously demonstrated that retinal lipid metabolism contributed to the development of diabetic retinopathy. The goal of this study was to determine the effect of diabetes on circadian regulation of clock genes and lipid metabolism genes in the retina and retinal endothelial cells (REC). Diabetes had a pronounced inhibitory effect on the negative clock arm with lower amplitude of the period (per) 1 in the retina; lower amplitude and a phase shift of per2 in the liver; and a loss of cryptochrome (cry) 2 rhythmic pattern in suprachiasmatic nucleus (SCN). The positive clock arm was increased by diabetes with higher amplitude of circadian locomotor output cycles kaput (CLOCK) and brain and muscle aryl-hydrocarbon receptor nuclear translocator-like 1 (bmal1) and phase shift in bmal1 rhythmic oscillations in the retina; and higher bmal1 amplitude in the SCN. Peroxisome proliferator-activated receptor (PPAR) α exhibited rhythmic oscillation in retina and liver; PPARγ had lower amplitude in diabetic liver; sterol regulatory element-binding protein (srebp) 1c had higher amplitude in the retina but lower in the liver in STZ- induced diabetic animals. Both of Elongase (Elovl) 2 and Elovl4 had a rhythmic oscillation pattern in the control retina. Diabetic retinas lost Elovl4 rhythmic oscillation and had lower amplitude of Elovl2 oscillations. In line with the in vivo data, circadian expression levels of CLOCK, bmal1 and srebp1c had higher amplitude in rat REC (rREC) isolated from diabetic rats compared with control rats, while PPARγ and Elovl2 had lower amplitude in diabetic rREC. In conclusion, diabetes causes dysregulation of circadian expression of clock genes and the genes controlling lipid metabolism in the retina with potential implications for the development of diabetic retinopathy. PMID:24736612

  16. The Cyanobacterial Circadian System: From Biophysics to Bioevolution

    PubMed Central

    Stewart, Phoebe L.; Egli, Martin

    2011-01-01

    Recent studies have unveiled the molecular machinery responsible for the biological clock in cyanobacteria and found that it exerts pervasive control over cellular processes including global gene expression. Indeed, the entire chromosome undergoes daily cycles of topology/compaction! The circadian system comprises both a posttranslational oscillator (PTO) and a transcriptional/translational feedback loop (TTFL). The PTO can be reconstituted in vitro with three purified proteins (KaiA, KaiB, and KaiC) and ATP. These are the only circadian proteins for which high-resolution structures are available. Phase in this nanoclockwork has been associated with key phosphorylations of KaiC. Structural considerations illuminate the mechanism by which the KaiABC oscillator ratchets unidirectionally. Models of the complete in vivo system have important implications for our understanding of circadian clocks in higher organisms, including mammals. The conjunction of structural, biophysical, and biochemical approaches to this system has brought our understanding of the molecular mechanisms of biological timekeeping to an unprecedented level. PMID:21332358

  17. Circadian Profiling of the Arabidopsis Proteome Using 2D-DIGE

    PubMed Central

    Choudhary, Mani K.; Nomura, Yuko; Shi, Hua; Nakagami, Hirofumi; Somers, David E.

    2016-01-01

    Clock-generated biological rhythms provide an adaptive advantage to an organism, resulting in increased fitness and survival. To better elucidate the plant response to the circadian system, we surveyed protein oscillations in Arabidopsis seedlings under constant light. Using large-scale two-dimensional difference in gel electrophoresis (2D-DIGE) the abundance of more than 1000 proteins spots was reproducibly resolved quantified and profiled across a circadian time series. A comparison between phenol-extracted samples and RuBisCO-depleted extracts identified 71 and 40 rhythmically-expressed proteins, respectively, and between 30 and 40% of these derive from non-rhythmic transcripts. These included proteins influencing transcriptional regulation, translation, metabolism, photosynthesis, protein chaperones, and stress-mediated responses. The phasing of maximum expression for the cyclic proteins was similar for both datasets, with a nearly even distribution of peak phases across the time series. STRING clustering analysis identified two interaction networks with a notable number of oscillating proteins: plastid-based and cytosolic chaperones and 10 proteins involved in photosynthesis. The oscillation of the ABA receptor, PYR1/RCAR11, with peak expression near dusk adds to a growing body of evidence that intimately ties ABA signaling to the circadian system. Taken together, this study provides new insights into the importance of post-transcriptional circadian control of plant physiology and metabolism. PMID:27462335

  18. Circadian Profiling of the Arabidopsis Proteome Using 2D-DIGE.

    PubMed

    Choudhary, Mani K; Nomura, Yuko; Shi, Hua; Nakagami, Hirofumi; Somers, David E

    2016-01-01

    Clock-generated biological rhythms provide an adaptive advantage to an organism, resulting in increased fitness and survival. To better elucidate the plant response to the circadian system, we surveyed protein oscillations in Arabidopsis seedlings under constant light. Using large-scale two-dimensional difference in gel electrophoresis (2D-DIGE) the abundance of more than 1000 proteins spots was reproducibly resolved quantified and profiled across a circadian time series. A comparison between phenol-extracted samples and RuBisCO-depleted extracts identified 71 and 40 rhythmically-expressed proteins, respectively, and between 30 and 40% of these derive from non-rhythmic transcripts. These included proteins influencing transcriptional regulation, translation, metabolism, photosynthesis, protein chaperones, and stress-mediated responses. The phasing of maximum expression for the cyclic proteins was similar for both datasets, with a nearly even distribution of peak phases across the time series. STRING clustering analysis identified two interaction networks with a notable number of oscillating proteins: plastid-based and cytosolic chaperones and 10 proteins involved in photosynthesis. The oscillation of the ABA receptor, PYR1/RCAR11, with peak expression near dusk adds to a growing body of evidence that intimately ties ABA signaling to the circadian system. Taken together, this study provides new insights into the importance of post-transcriptional circadian control of plant physiology and metabolism. PMID:27462335

  19. Circadian regulation of metabolic homeostasis: causes and consequences.

    PubMed

    McGinnis, Graham R; Young, Martin E

    2016-01-01

    Robust circadian rhythms in metabolic processes have been described in both humans and animal models, at the whole body, individual organ, and even cellular level. Classically, these time-of-day-dependent rhythms have been considered secondary to fluctuations in energy/nutrient supply/demand associated with feeding/fasting and wake/sleep cycles. Renewed interest in this field has been fueled by studies revealing that these rhythms are driven, at least in part, by intrinsic mechanisms and that disruption of metabolic synchrony invariably increases the risk of cardiometabolic disease. The objectives of this paper are to provide a comprehensive review regarding rhythms in glucose, lipid, and protein/amino acid metabolism, the relative influence of extrinsic (eg, neurohumoral factors) versus intrinsic (eg, cell autonomous circadian clocks) mediators, the physiologic roles of these rhythms in terms of daily fluctuations in nutrient availability and activity status, as well as the pathologic consequences of dyssynchrony. PMID:27313482

  20. Circadian regulation of metabolic homeostasis: causes and consequences

    PubMed Central

    McGinnis, Graham R; Young, Martin E

    2016-01-01

    Robust circadian rhythms in metabolic processes have been described in both humans and animal models, at the whole body, individual organ, and even cellular level. Classically, these time-of-day-dependent rhythms have been considered secondary to fluctuations in energy/nutrient supply/demand associated with feeding/fasting and wake/sleep cycles. Renewed interest in this field has been fueled by studies revealing that these rhythms are driven, at least in part, by intrinsic mechanisms and that disruption of metabolic synchrony invariably increases the risk of cardiometabolic disease. The objectives of this paper are to provide a comprehensive review regarding rhythms in glucose, lipid, and protein/amino acid metabolism, the relative influence of extrinsic (eg, neurohumoral factors) versus intrinsic (eg, cell autonomous circadian clocks) mediators, the physiologic roles of these rhythms in terms of daily fluctuations in nutrient availability and activity status, as well as the pathologic consequences of dyssynchrony. PMID:27313482

  1. Drosophila TRPA1 functions in temperature control of circadian rhythm in pacemaker neurons.

    PubMed

    Lee, Youngseok; Montell, Craig

    2013-04-17

    Most animals from flies to humans count on circadian clocks to synchronize their physiology and behaviors. Daily light cycles are well known environmental cues for setting circadian rhythms. Warmer and cooler temperatures that mimic day and night are also effective in entraining circadian activity in most animals. Even vertebrate organisms can be induced to show circadian responses through exposure to temperature cycles. In poikilothermic animals such as Drosophila, temperature differences of only 2-3°C are sufficient to synchronize locomotor rhythms. However, the molecular sensors that participate in temperature regulation of circadian activity in fruit flies or other animals are enigmatic. It is also unclear whether such detectors are limited to the periphery or may be in the central brain. Here, we showed that Drosophila TRPA1 (transient receptor potential cation channel A1) was necessary for normal activity patterns during temperature cycles. The trpA1 gene was expressed in a subset of pacemaker neurons in the central brain. In response to temperature entrainment, loss of trpA1 impaired activity, and altered expression of the circadian clock protein period (Per) in a subset of pacemaker neurons. These findings underscore a role for a thermoTRP in temperature regulation that extends beyond avoidance of noxious or suboptimal temperatures. PMID:23595730

  2. Drosophila TRPA1 functions in temperature control of circadian rhythm in pacemaker neurons.

    PubMed

    Lee, Youngseok; Montell, Craig

    2013-04-17

    Most animals from flies to humans count on circadian clocks to synchronize their physiology and behaviors. Daily light cycles are well known environmental cues for setting circadian rhythms. Warmer and cooler temperatures that mimic day and night are also effective in entraining circadian activity in most animals. Even vertebrate organisms can be induced to show circadian responses through exposure to temperature cycles. In poikilothermic animals such as Drosophila, temperature differences of only 2-3°C are sufficient to synchronize locomotor rhythms. However, the molecular sensors that participate in temperature regulation of circadian activity in fruit flies or other animals are enigmatic. It is also unclear whether such detectors are limited to the periphery or may be in the central brain. Here, we showed that Drosophila TRPA1 (transient receptor potential cation channel A1) was necessary for normal activity patterns during temperature cycles. The trpA1 gene was expressed in a subset of pacemaker neurons in the central brain. In response to temperature entrainment, loss of trpA1 impaired activity, and altered expression of the circadian clock protein period (Per) in a subset of pacemaker neurons. These findings underscore a role for a thermoTRP in temperature regulation that extends beyond avoidance of noxious or suboptimal temperatures.

  3. Quantifying the robustness of circadian oscillations at the single-cell level

    NASA Astrophysics Data System (ADS)

    Lambert, Guillaume; Rust, Michael

    2014-03-01

    Cyanobacteria are light-harvesting microorganisms that contribute to 30% of the photosynthetic activity on Earth and contain one of the simplest circadian systems in the animal kingdom. In Synechococcus elongatus , a species of freshwater cyanobacterium, circadian oscillations are regulated by the KaiABC system, a trio of interacting proteins that act as a biomolecular pacemaker of the circadian system. While the core oscillator precisely anticipates Earth's 24h light/dark cycle, it is unclear how much individual cells benefit from the expression and maintenance of a circadian clock. By studying the growth dynamics of individual S . elongatus cells under sudden light variations, we show that several aspects of cellular growth, such as a cell's division probability and its elongation rate, are tightly coupled to the circadian clock. We propose that the evolution and maintenance of a circadian clock increases the fitness of cells by allowing them to take advantage of cyclical light/dark environments by alternating between two phenotypes: expansionary, where cells grow and divide at a fast pace during the first part of the day, and conservative, where cells enter a more quiescent state to better prepare to the stresses associated with the night's prolonged darkness.

  4. Circadian profiles in the embryonic chick heart: L-type voltage-gated calcium channels and signaling pathways.

    PubMed

    Ko, Michael L; Shi, Liheng; Grushin, Kirill; Nigussie, Fikru; Ko, Gladys Y-P

    2010-10-01

    Circadian clocks exist in the heart tissue and modulate multiple physiological events, from cardiac metabolism to contractile function and expression of circadian oscillator and metabolic-related genes. Ample evidence has demonstrated that there are endogenous circadian oscillators in adult mammalian cardiomyocytes. However, mammalian embryos cannot be entrained independently to light-dark (LD) cycles in vivo without any maternal influence, but circadian genes are well expressed and able to oscillate in embryonic stages. The authors took advantage of using chick embryos that are independent of maternal influences to investigate whether embryonic hearts could be entrained under LD cycles in ovo. The authors found circadian regulation of L-type voltage-gated calcium channels (L-VGCCs), the ion channels responsible for the production of cardiac muscle contraction in embryonic chick hearts. The mRNA levels and protein expression of VGCCα1C and VGCCα1D are under circadian control, and the average L-VGCC current density is significantly larger when cardiomyocytes are recorded during the night than day. The phosphorylation states of several kinases involved in insulin signaling and cardiac metabolism, including extracellular signal-regulated kinase (Erk), stress-activated protein kinase (p38), protein kinase B (Akt), and glycogen synthase kinase-3β (GSK-3β), are also under circadian control. Both Erk and p38 have been implicated in regulating cardiac contractility and in the development of various pathological states, such as cardiac hypertrophy and heart failure. Even though both Erk and phosphoinositide 3-kinase (PI3K)-Akt signaling pathways participate in complex cellular processes regarding physiological or pathological states of cardiomyocytes, the circadian oscillators in the heart regulate these pathways independently, and both pathways contribute to the circadian regulation of L-VGCCs.

  5. Molecular Mechanisms of Circadian Regulation During Spaceflight

    NASA Technical Reports Server (NTRS)

    Zanello, S. B.; Boyle, R.

    2012-01-01

    The physiology of both vertebrates and invertebrates follows internal rhythms coordinated in phase with the 24-hour daily light cycle. This circadian clock is governed by a central pacemaker, the suprachiasmatic nucleus (SCN) in the brain. However, peripheral circadian clocks or oscillators have been identified in most tissues. How the central and peripheral oscillators are synchronized is still being elucidated. Light is the main environmental cue that entrains the circadian clock. Under the absence of a light stimulus, the clock continues its oscillation in a free-running condition. In general, three functional compartments of the circadian clock are defined. The vertebrate retina contains endogenous clocks that control many aspects of retinal physiology, including retinal sensitivity to light, neurohormone synthesis (melatonin and dopamine), rod disk shedding, signalling pathways and gene expression. Neurons with putative local circadian rhythm generation are found among all the major neuron populations in the mammalian retina. In the mouse, clock genes and function are more localized to the inner retinal and ganglion cell layers. The photoreceptor, however, secrete melatonin which may still serve a an important circadian signal. The reception and transmission of the non-visual photic stimulus resides in a small subpopulation (1-3%) or retinal ganglion cells (RGC) that express the pigment melanopsin (Opn4) and are called intrisically photoreceptive RGC (ipRGC). Melanopsin peak absorption is at 420 nm and all the axons of the ipRGC reach the SCN. A common countermeasure for circadian re-entrainment utilizes blue-green light to entrain the circadian clock and mitigate the risk of fatigue and health and performance decrement due to circadian rhythm disruption. However, an effective countermeasure targeting the photoreceptor system requires that the basic circadian molecular machinery remains intact during spaceflight. We hypothesize that spaceflight may affect ip

  6. Ubiquitin-specific proteases UBP12 and UBP13 act in circadian clock and photoperiodic flowering regulation in Arabidopsis.

    PubMed

    Cui, Xia; Lu, Falong; Li, Yue; Xue, Yongming; Kang, Yanyuan; Zhang, Shuaibin; Qiu, Qi; Cui, Xiekui; Zheng, Shuzhi; Liu, Bin; Xu, Xiaodong; Cao, Xiaofeng

    2013-06-01

    Protein ubiquitination is involved in most cellular processes. In Arabidopsis (Arabidopsis thaliana), ubiquitin-mediated protein degradation regulates the stability of key components of the circadian clock feedback loops and the photoperiodic flowering pathway. Here, we identified two ubiquitin-specific proteases, UBP12 and UBP13, involved in circadian clock and photoperiodic flowering regulation. Double mutants of ubp12 and ubp13 display pleiotropic phenotypes, including early flowering and short periodicity of circadian rhythms. In ubp12 ubp13 double mutants, CONSTANS (CO) transcript rises earlier than that of wild-type plants during the day, which leads to increased expression of FLOWERING LOCUS T. This, and analysis of ubp12 co mutants, indicates that UBP12 and UBP13 regulate phot