101
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Bordyugov G, Westermark PO, Korenčič A, Bernard S, Herzel H. Mathematical modeling in chronobiology. Handb Exp Pharmacol 2013:335-57. [PMID: 23604486 DOI: 10.1007/978-3-642-25950-0_14] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Circadian clocks are autonomous oscillators entrained by external Zeitgebers such as light-dark and temperature cycles. On the cellular level, rhythms are generated by negative transcriptional feedback loops. In mammals, the suprachiasmatic nucleus (SCN) in the anterior part of the hypothalamus plays the role of the central circadian pacemaker. Coupling between individual neurons in the SCN leads to precise self-sustained oscillations even in the absence of external signals. These neuronal rhythms orchestrate the phasing of circadian oscillations in peripheral organs. Altogether, the mammalian circadian system can be regarded as a network of coupled oscillators. In order to understand the dynamic complexity of these rhythms, mathematical models successfully complement experimental investigations. Here we discuss basic ideas of modeling on three different levels (1) rhythm generation in single cells by delayed negative feedbacks, (2) synchronization of cells via external stimuli or cell-cell coupling, and (3) optimization of chronotherapy.
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Affiliation(s)
- G Bordyugov
- Institute for Theoretical Biology, Humboldt University, Invalidenstr. 43, 10115, Berlin, Germany.
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102
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Abstract
Rev-erbα, a component of the circadian clock, has also been known as a nuclear receptor that lacks activation function domain 2, functioning as a ligand-dependent transcriptional repressor. However, we recently reported that Rev-erbα activates connexin43 transcription by forming a complex with Sp1. Here we show that heme, a REV-ERB ligand, is dispensable for this novel mechanism and that Rev-erbβ, having homologies with Rev-erbα, does not activate connexin43, but competes with the Rev-erbα/Sp1. The A/B region of Rev-erbα, which is not conserved in Rev-erbβ, is a crucial activating domain, while the ligand binding domain, conserved in Rev-erbβ, functions as a competitor.
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103
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Korenčič A, Bordyugov G, Košir R, Rozman D, Goličnik M, Herzel H. The interplay of cis-regulatory elements rules circadian rhythms in mouse liver. PLoS One 2012; 7:e46835. [PMID: 23144788 PMCID: PMC3489864 DOI: 10.1371/journal.pone.0046835] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2012] [Accepted: 09/05/2012] [Indexed: 01/08/2023] Open
Abstract
The mammalian circadian clock is driven by cell-autonomous transcriptional feedback loops that involve E-boxes, D-boxes, and ROR-elements. In peripheral organs, circadian rhythms are additionally affected by systemic factors. We show that intrinsic combinatorial gene regulation governs the liver clock. With a temporal resolution of 2 h, we measured the expression of 21 clock genes in mouse liver under constant darkness and equinoctial light-dark cycles. Based on these data and known transcription factor binding sites, we develop a six-variable gene regulatory network. The transcriptional feedback loops are represented by equations with time-delayed variables, which substantially simplifies modelling of intermediate protein dynamics. Our model accurately reproduces measured phases, amplitudes, and waveforms of clock genes. Analysis of the network reveals properties of the clock: overcritical delays generate oscillations; synergy of inhibition and activation enhances amplitudes; and combinatorial modulation of transcription controls the phases. The agreement of measurements and simulations suggests that the intrinsic gene regulatory network primarily determines the circadian clock in liver, whereas systemic cues such as light-dark cycles serve to fine-tune the rhythms.
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Affiliation(s)
- Anja Korenčič
- Institute of Biochemistry, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia
| | - Grigory Bordyugov
- Institute for Theoretical Biology, Humboldt University, Berlin, Germany
| | - Rok Košir
- Institute of Biochemistry, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia
- Center for Functional Genomics and Bio-Chips, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia
| | - Damjana Rozman
- Institute of Biochemistry, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia
- Center for Functional Genomics and Bio-Chips, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia
| | - Marko Goličnik
- Institute of Biochemistry, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia
| | - Hanspeter Herzel
- Institute for Theoretical Biology, Humboldt University, Berlin, Germany
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104
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Molusky MM, Ma D, Buelow K, Yin L, Lin JD. Peroxisomal localization and circadian regulation of ubiquitin-specific protease 2. PLoS One 2012; 7:e47970. [PMID: 23133608 PMCID: PMC3487853 DOI: 10.1371/journal.pone.0047970] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2012] [Accepted: 09/20/2012] [Indexed: 11/18/2022] Open
Abstract
Temporal regulation of nutrient and energy metabolism is emerging as an important aspect of metabolic homeostasis. The regulatory network that integrates the timing cues and nutritional signals to drive diurnal metabolic rhythms remains poorly defined. The 45-kDa isoform of ubiquitin-specific protease 2 (USP2-45) is a deubiquitinase that regulates hepatic gluconeogenesis and glucose metabolism. In this study, we found that USP2-45 is localized to peroxisomes in hepatocytes through a canonical peroxisome-targeting motif at its C-terminus. Clustering analysis indicates that the expression of a subset of peroxisomal genes exhibits robust diurnal rhythm in the liver. Despite this, nuclear hormone receptor PPARα, a known regulator of peroxisome gene expression, does not induce USP2-45 in hepatocytes and is dispensible for its expression during starvation. In contrast, a functional liver clock is required for the proper nutritional and circadian regulation of USP2-45 expression. At the molecular level, transcriptional coactivators PGC-1α and PGC-1β and repressor E4BP4 exert opposing effects on USP2-45 promoter activity. These studies provide insights into the subcellular localization and transcriptional regulation of a clock-controlled deubiquitinase that regulates glucose metabolism.
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Affiliation(s)
- Matthew M. Molusky
- Life Sciences Institute and Department of Cell & Developmental Biology, University of Michigan Medical Center, Ann Arbor, Michigan, United States of America
| | - Di Ma
- Life Sciences Institute and Department of Cell & Developmental Biology, University of Michigan Medical Center, Ann Arbor, Michigan, United States of America
| | - Katie Buelow
- Department of Molecular & Integrative Physiology, University of Michigan Medical Center, Ann Arbor, Michigan, United States of America
| | - Lei Yin
- Department of Molecular & Integrative Physiology, University of Michigan Medical Center, Ann Arbor, Michigan, United States of America
| | - Jiandie D. Lin
- Life Sciences Institute and Department of Cell & Developmental Biology, University of Michigan Medical Center, Ann Arbor, Michigan, United States of America
- * E-mail:
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105
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Kooman JP, Usvyat L, van der Sande FM, Thijssen S, Levin N, Leunissen KM, Kotanko P. 'Time and time again': oscillatory and longitudinal time patterns in dialysis patients. Kidney Blood Press Res 2012; 35:534-48. [PMID: 22890114 DOI: 10.1159/000340022] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Oscillatory and longitudinal time patterns play a major role in human physiology. In chronic hemodialysis patients, abnormalities in both time patterns have been observed, while time patterns can also influence the response of patients to the treatment. Abnormal oscillatory patterns have been observed for ultradian rhythms (cycle time <20 h), such as an impaired heart rate variability and circadian rhythms, as reflected by reduced day-night blood pressure differences. Conversely, the circadian rhythm of body temperature may influence the hemodynamic tolerance to the dialysis treatment. With regard to infradian (cycle time >28 h) rhythms, large seasonal differences in mortality, but also in blood pressure and interdialytic weight gain, have been observed in dialysis patients. The most important longitudinal pattern is the general reduction of life span in dialysis patients. One explanation of this phenomenon relates to the concept of accelerated aging in dialysis patients, for which there are various supportive arguments. From a phenomenological point of view, this concept translates into the high prevalence of frailty, even in young dialysis patients. A multidimensional approach appears necessary to adequately address this problem. In this review, the relevance of disturbed time patterns in dialysis patients is discussed. The changes may reflect an impairment or reduction in homeostatic/homeodynamic control in dialysis patients and also may have important prognostic and therapeutic implications.
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Affiliation(s)
- Jeroen P Kooman
- University Hospital Maastricht, Maastricht, The Netherlands.
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106
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Jayanthi S, Del Vecchio D. Tuning genetic clocks employing DNA binding sites. PLoS One 2012; 7:e41019. [PMID: 22859962 PMCID: PMC3409220 DOI: 10.1371/journal.pone.0041019] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2012] [Accepted: 06/15/2012] [Indexed: 11/18/2022] Open
Abstract
Periodic oscillations play a key role in cell physiology from the cell cycle to circadian clocks. The interplay of positive and negative feedback loops among genes and proteins is ubiquitous in these networks. Often, delays in a negative feedback loop and/or degradation rates are a crucial mechanism to obtain sustained oscillations. How does nature control delays and kinetic rates in feedback networks? Known mechanisms include proper selection of the number of steps composing a feedback loop and alteration of protease activity, respectively. Here, we show that a remarkably simple means to control both delays and effective kinetic rates is the employment of DNA binding sites. We illustrate this design principle on a widely studied activator-repressor clock motif, which is ubiquitous in natural systems. By suitably employing DNA target sites for the activator and/or the repressor, one can switch the clock “on” and “off” and precisely tune its period to a desired value. Our study reveals a design principle to engineer dynamic behavior in biomolecular networks, which may be largely exploited by natural systems and employed for the rational design of synthetic circuits.
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Affiliation(s)
- Shridhar Jayanthi
- Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, Michigan, United States of America.
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107
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Goldbeter A, Gérard C, Gonze D, Leloup JC, Dupont G. Systems biology of cellular rhythms. FEBS Lett 2012; 586:2955-65. [PMID: 22841722 DOI: 10.1016/j.febslet.2012.07.041] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2012] [Revised: 07/17/2012] [Accepted: 07/17/2012] [Indexed: 12/22/2022]
Abstract
Rhythms abound in biological systems, particularly at the cellular level where they originate from the feedback loops present in regulatory networks. Cellular rhythms can be investigated both by experimental and modeling approaches, and thus represent a prototypic field of research for systems biology. They have also become a major topic in synthetic biology. We review advances in the study of cellular rhythms of biochemical rather than electrical origin by considering a variety of oscillatory processes such as Ca++ oscillations, circadian rhythms, the segmentation clock, oscillations in p53 and NF-κB, synthetic oscillators, and the oscillatory dynamics of cyclin-dependent kinases driving the cell cycle. Finally we discuss the coupling between cellular rhythms and their robustness with respect to molecular noise.
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Affiliation(s)
- A Goldbeter
- Unité de Chronobiologie théorique, Faculté des Sciences, Université Libre de Bruxelles (ULB), Campus Plaine, CP 231, B-1050 Brussels, Belgium.
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108
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Thommen Q, Pfeuty B, Corellou F, Bouget FY, Lefranc M. Robust and flexible response of theOstreococcus tauricircadian clock to light/dark cycles of varying photoperiod. FEBS J 2012; 279:3432-48. [DOI: 10.1111/j.1742-4658.2012.08666.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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109
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Ma D, Li S, Molusky MM, Lin JD. Circadian autophagy rhythm: a link between clock and metabolism? Trends Endocrinol Metab 2012; 23:319-25. [PMID: 22520961 PMCID: PMC3389582 DOI: 10.1016/j.tem.2012.03.004] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/03/2012] [Revised: 03/15/2012] [Accepted: 03/19/2012] [Indexed: 12/13/2022]
Abstract
Nutrient and energy metabolism in mammals exhibits a strong diurnal rhythm that aligns with the body clock. Circadian regulation of metabolism is mediated through reciprocal signaling between the clock and metabolic regulatory networks. Recent work has demonstrated that autophagy is rhythmically activated in a clock-dependent manner. Because autophagy is a conserved biological process that contributes to nutrient and cellular homeostasis, its cyclic induction may provide a novel link between clock and metabolism. This review discusses the mechanisms underlying circadian autophagy regulation, the role of rhythmic autophagy in nutrient and energy metabolism, and its implications in physiology and metabolic disease.
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Affiliation(s)
- Di Ma
- Life Sciences Institute, University of Michigan, 210 Washtenaw Avenue, Ann Arbor, MI 48109, USA
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110
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Zhu H, Vadigepalli R, Rafferty R, Gonye GE, Weaver DR, Schwaber JS. Integrative gene regulatory network analysis reveals light-induced regional gene expression phase shift programs in the mouse suprachiasmatic nucleus. PLoS One 2012; 7:e37833. [PMID: 22662235 PMCID: PMC3360606 DOI: 10.1371/journal.pone.0037833] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2012] [Accepted: 04/27/2012] [Indexed: 01/05/2023] Open
Abstract
We use the multigenic pattern of gene expression across suprachiasmatic nuclei (SCN) regions and time to understand the dynamics within the SCN in response to a circadian phase-resetting light pulse. Global gene expression studies of the SCN indicate that circadian functions like phase resetting are complex multigenic processes. While the molecular dynamics of phase resetting are not well understood, it is clear they involve a “functional gene expression program”, e.g., the coordinated behavior of functionally related genes in space and time. In the present study we selected a set of 89 of these functionally related genes in order to further understand this multigenic program. By use of high-throughput qPCR we studied 52 small samples taken by anatomically precise laser capture from within the core and shell SCN regions, and taken at time points with and without phase resetting light exposure. The results show striking regional differences in light response to be present in the mouse SCN. By using network-based analyses, we are able to establish a highly specific multigenic correlation between genes expressed in response to light at night and genes normally activated during the day. The light pulse triggers a complex and highly coordinated network of gene regulation. The largest differences marking neuroanatomical location are in transmitter receptors, and the largest time-dependent differences occur in clock-related genes. Nighttime phase resetting appears to recruit transcriptional regulatory processes normally active in the day. This program, or mechanism, causes the pattern of core region gene expression to transiently shift to become more like that of the shell region.
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Affiliation(s)
- Haisun Zhu
- Daniel Baugh Institute, Thomas Jefferson University, Philadelphia, Pennsylvania, United States of America
| | - Rajanikanth Vadigepalli
- Daniel Baugh Institute, Thomas Jefferson University, Philadelphia, Pennsylvania, United States of America
| | - Rachel Rafferty
- Daniel Baugh Institute, Thomas Jefferson University, Philadelphia, Pennsylvania, United States of America
| | - Gregory E. Gonye
- Daniel Baugh Institute, Thomas Jefferson University, Philadelphia, Pennsylvania, United States of America
| | - David R. Weaver
- Department of Neurobiology, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
| | - James S. Schwaber
- Daniel Baugh Institute, Thomas Jefferson University, Philadelphia, Pennsylvania, United States of America
- * E-mail:
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111
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Epigenetic Control of Circadian Clock Operation during Development. GENETICS RESEARCH INTERNATIONAL 2012; 2012:845429. [PMID: 22567402 PMCID: PMC3335631 DOI: 10.1155/2012/845429] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 08/30/2011] [Revised: 12/22/2011] [Accepted: 01/13/2012] [Indexed: 11/17/2022]
Abstract
The molecular players of circadian clock oscillation have been identified and extensively characterized. The epigenetic mechanisms behind the circadian gene expression control has also been recently studied, although there are still details to be illucidated. In this review, we briefly summarize the current understanding of the mammalian clock. We also provide evidence for the lack of circadian oscillation in particular cell types. As the circadian clock has intimate interaction with the various cellular functions in different type of cells, it must have plasticity and specicity in its operation within different epigenetic environments. The lack of circadian oscillation in certain cells provide an unique opportunity to study the required epigenetic environment in the cell that permit circadian oscillation and to idenfify key influencing factors for proper clock function. How epigenetic mechansims, including DNA methylaiton and chromatin modifications, participate in control of clock oscillation still awaits future studies at the genomic scale.
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112
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Ruts T, Matsubara S, Wiese-Klinkenberg A, Walter A. Diel patterns of leaf and root growth: endogenous rhythmicity or environmental response? JOURNAL OF EXPERIMENTAL BOTANY 2012; 63:3339-51. [PMID: 22223810 DOI: 10.1093/jxb/err334] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Plants are sessile organisms forced to adjust to their surrounding environment. In a single plant the photoautotrophic shoot is exposed to pronounced environmental variations recurring in a day-night 24 h (diel) cycle, whereas the heterotrophic root grows in a temporally less fluctuating environment. The contrasting habitats of shoots and roots are reflected in different diel growth patterns and their responsiveness to environmental stimuli. Differences between diel leaf growth patterns of mono- and dicotyledonous plants correspond to their different organization and placement of growth zones. In monocots, heterotrophic growth zones are organized linearly and protected from the environment by sheaths of older leaves. In contrast, photosynthetically active growth zones of dicot leaves are exposed directly to the environment and show characteristic, species-specific diel growth patterns. It is hypothesized that the different exposure to environmental constraints and simultaneously the sink/source status of the growing organs may have induced distinct endogenous control of diel growth patterns in roots and leaves of monocot and dicot plants. Confronted by strong temporal fluctuations in environment, the circadian clock may facilitate robust intrinsic control of leaf growth in dicot plants.
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Affiliation(s)
- Tom Ruts
- Forschungszentrum Jülich, IBG-2: Plant Sciences, Wilhelm-Johnen-Strasse, Jülich, Germany
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113
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Retinal projections and neurochemical characterization of the pregeniculate nucleus of the common marmoset (Callithrix jacchus). J Chem Neuroanat 2012; 44:34-44. [PMID: 22531294 DOI: 10.1016/j.jchemneu.2012.04.001] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2012] [Revised: 03/22/2012] [Accepted: 04/07/2012] [Indexed: 11/23/2022]
Abstract
In mammals, the suprachiasmatic nucleus (SCN) and the intergeniculate leaflet (IGL) are the main components of the circadian timing system. The SCN is the site of the endogenous biological clock that generates rhythms and synchronizes them to environmental cues. The IGL is a key structure that modulates SCN activity and is responsible for the transmission of non-photic information to the SCN, thus participating in the integration between photic and non-photic stimuli. Both the SCN and IGL receive projections of retinal ganglion cells and the IGL is connected to the SCN through the geniculohypothalamic tract. Little is known about these structures in the primate brain and the pregeniculate nucleus (PGN) has been suggested to be the primate equivalent of the rodent IGL. The aim of this study was to characterize the PGN of a primate, the common marmoset (Callithrix jacchus), and to analyze its retinal afferents. Here, the marmoset PGN was found to be organized into three subsectors based on neuronal size, pattern of retinal projections, and the distribution of neuropeptide Y-, GAD-, serotonin-, enkephalin- and substance P-labeled terminals. This pattern indicates that the marmoset PGN is equivalent to the IGL. This detailed description contributes to the understanding of the circadian timing system in this primate species considering the importance of the IGL within the context of circadian regulation.
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114
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Circadian rhythms of fetal liver transcription persist in the absence of canonical circadian clock gene expression rhythms in vivo. PLoS One 2012; 7:e30781. [PMID: 22383974 PMCID: PMC3285613 DOI: 10.1371/journal.pone.0030781] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2011] [Accepted: 12/21/2011] [Indexed: 11/30/2022] Open
Abstract
The cellular circadian clock and systemic cues drive rhythmicity in the transcriptome of adult peripheral tissues. However, the oscillating status of the circadian clocks in fetal tissues, and their response to maternal cues, are less clear. Most clock genes do not cycle in fetal livers from mice and rats, although tissue level rhythms rapidly emerge when fetal mouse liver explants are cultured in vitro. Thus, in the fetal mouse liver, the circadian clock does not oscillate at the cellular level (but is induced to oscillate in culture). To gain a comprehensive overview of the clock status in the fetal liver during late gestation, we performed microarray analyses on fetal liver tissues. In the fetal liver we did not observe circadian rhythms of clock gene expression or many other transcripts known to be rhythmically expressed in the adult liver. Nevertheless, JTK_CYCLE analysis identified some transcripts in the fetal liver that were rhythmically expressed, albeit at low amplitudes. Upon data filtering by coefficient of variation, the expression levels for transcripts related to pancreatic exocrine enzymes and zymogen secretion were found to undergo synchronized daily fluctuations at high amplitudes. These results suggest that maternal cues influence the fetal liver, despite the fact that we did not detect circadian rhythms of canonical clock gene expression in the fetal liver. These results raise important questions on the role of the circadian clock, or lack thereof, during ontogeny.
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115
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Li C, Yu S, Zhong X, Wu J, Li X. Transcriptome comparison between fetal and adult mouse livers: implications for circadian clock mechanisms. PLoS One 2012; 7:e31292. [PMID: 22363607 PMCID: PMC3283632 DOI: 10.1371/journal.pone.0031292] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2012] [Accepted: 01/05/2012] [Indexed: 11/18/2022] Open
Abstract
Microarray transcriptome analyses of fetal mouse liver did not detect circadian expression rhythms of clock genes or clock-controlled genes, although some rhythmic transcripts that were likely not driven by endogenous cellular clocks were identified. This finding reveals a key distinction between the circadian oscillators in fetal and adult mouse livers. Thus, in this study, the transcriptomes of fetal and adult livers were systematically compared to identify differences in the gene expression profiles between these two developmental stages. Approximately 1000 transcripts were differentially enriched between the fetal and adult livers. These transcripts represent genes with cellular functions characteristic of distinct developmental stages. Clock genes were also differentially expressed between the fetal and adult livers. Developmental differences in liver gene expression might have contributed to the differences in oscillation status and functional states of the cellular circadian clock between fetal and adult livers.
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Affiliation(s)
| | | | | | | | - Xiaodong Li
- National Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan, Hubei Province, People's Republic of China
- * E-mail:
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116
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Dijk DJ, Duffy JF, Silva EJ, Shanahan TL, Boivin DB, Czeisler CA. Amplitude reduction and phase shifts of melatonin, cortisol and other circadian rhythms after a gradual advance of sleep and light exposure in humans. PLoS One 2012; 7:e30037. [PMID: 22363414 PMCID: PMC3281823 DOI: 10.1371/journal.pone.0030037] [Citation(s) in RCA: 93] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2011] [Accepted: 12/08/2011] [Indexed: 11/22/2022] Open
Abstract
BACKGROUND The phase and amplitude of rhythms in physiology and behavior are generated by circadian oscillators and entrained to the 24-h day by exposure to the light-dark cycle and feedback from the sleep-wake cycle. The extent to which the phase and amplitude of multiple rhythms are similarly affected during altered timing of light exposure and the sleep-wake cycle has not been fully characterized. METHODOLOGY/PRINCIPAL FINDINGS We assessed the phase and amplitude of the rhythms of melatonin, core body temperature, cortisol, alertness, performance and sleep after a perturbation of entrainment by a gradual advance of the sleep-wake schedule (10 h in 5 days) and associated light-dark cycle in 14 healthy men. The light-dark cycle consisted either of moderate intensity 'room' light (∼90-150 lux) or moderate light supplemented with bright light (∼10,000 lux) for 5 to 8 hours following sleep. After the advance of the sleep-wake schedule in moderate light, no significant advance of the melatonin rhythm was observed whereas, after bright light supplementation the phase advance was 8.1 h (SEM 0.7 h). Individual differences in phase shifts correlated across variables. The amplitude of the melatonin rhythm assessed under constant conditions was reduced after moderate light by 54% (17-94%) and after bright light by 52% (range 12-84%), as compared to the amplitude at baseline in the presence of a sleep-wake cycle. Individual differences in amplitude reduction of the melatonin rhythm correlated with the amplitude of body temperature, cortisol and alertness. CONCLUSIONS/SIGNIFICANCE Alterations in the timing of the sleep-wake cycle and associated bright or moderate light exposure can lead to changes in phase and reduction of circadian amplitude which are consistent across multiple variables but differ between individuals. These data have implications for our understanding of circadian organization and the negative health outcomes associated with shift-work, jet-lag and exposure to artificial light.
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Affiliation(s)
- Derk-Jan Dijk
- Division of Sleep Medicine, Harvard Medical School, Boston, Massachusetts, United States of America.
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117
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Johnston JD. Adipose circadian rhythms: translating cellular and animal studies to human physiology. Mol Cell Endocrinol 2012; 349:45-50. [PMID: 21664232 DOI: 10.1016/j.mce.2011.05.008] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/07/2011] [Revised: 04/29/2011] [Accepted: 05/13/2011] [Indexed: 11/23/2022]
Abstract
Emerging links between circadian rhythms and metabolism promise much for the understanding of metabolic physiology and pathophysiology, in which white adipose tissue (WAT) plays a prominent role. Many WAT endocrine molecules, termed adipokines, display rhythmic plasma concentration. Moreover, similar to most other tissues, WAT exhibits widespread 24-h variation in gene expression, with approximately 20% of the murine adipose transcriptome estimated to undergo daily variation. A major limitation to human chronobiology research is the availability of physiologically defined peripheral tissues. To date most analyses of in vivo human peripheral clocks has been limited to blood leucocytes. However, subcutaneous adipose tissue represents a novel opportunity to study peripheral molecular rhythms that are of clearly defined metabolic relevance. This review summarises basic concepts of circadian and metabolic physiology before then comparing alternative protocols used to analyse the rhythmic properties of human adipose tissue.
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118
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O'Neill JS, Reddy AB. The essential role of cAMP/Ca2+ signalling in mammalian circadian timekeeping. Biochem Soc Trans 2012; 40:44-50. [PMID: 22260664 PMCID: PMC3399769 DOI: 10.1042/bst20110691] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Approximately daily, or circadian, rhythms are ubiquitous across eukaryotes. They are manifest in the temporal co-ordination of metabolism, physiology and behaviour, thereby allowing organisms to anticipate and synchronize with daily environmental cycles. Although cellular rhythms are self-sustained and cell-intrinsic, in mammals, the master regulator of timekeeping is localized within the hypothalamic SCN (suprachiasmatic nucleus). Molecular models for mammalian circadian rhythms have focused largely on transcriptional-translational feedback loops, but recent data have revealed essential contributions by intracellular signalling mechanisms. cAMP and Ca2+ signalling are not only regulated by the cellular clock, but also contribute directly to the timekeeping mechanism, in that appropriate manipulations determine the canonical pacemaker properties of amplitude, phase and period. It is proposed that daily auto-amplification of second messenger activity, through paracrine neuropeptidergic coupling, is necessary and sufficient to account for the increased amplitude, accuracy and robustness of SCN timekeeping.
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Affiliation(s)
- John S O'Neill
- Department of Clinical Neurosciences, University of Cambridge Metabolic Research Laboratories, Institute of Metabolic Science, University of Cambridge, Addenbrooke's Hospital, Cambridge CB2 0QQ, UK.
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Maudsley S, Chadwick W. Progressive and unconventional pharmacotherapeutic approaches to Alzheimer's disease therapy. Curr Alzheimer Res 2012; 9:1-4. [PMID: 22329648 PMCID: PMC5915359 DOI: 10.2174/156720512799015082] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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Lunghi L, Frigato E, Ferretti ME, Biondi C, Bertolucci C. Circadian variation of cell proliferation in HTR-8/SVneo cell line. Hum Cell 2011; 24:161-4. [DOI: 10.1007/s13577-011-0032-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2011] [Accepted: 08/03/2011] [Indexed: 01/08/2023]
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Son GH, Chung S, Kim K. The adrenal peripheral clock: glucocorticoid and the circadian timing system. Front Neuroendocrinol 2011; 32:451-65. [PMID: 21802440 DOI: 10.1016/j.yfrne.2011.07.003] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/01/2010] [Revised: 04/25/2011] [Accepted: 07/06/2011] [Indexed: 12/27/2022]
Abstract
The mammalian circadian timing system is organized in a hierarchy, with the master clock residing in the suprachiasmatic nucleus (SCN) of the hypothalamus and subsidiary peripheral clocks in other brain regions as well as peripheral tissues. Since the local oscillators in most cells contain a similar molecular makeup to that in the central pacemaker, determining the role of the peripheral clocks in the regulation of rhythmic physiology and behavior is an important issue. Glucocorticoids (GCs) are a class of multi-functional adrenal steroid hormones, which exhibit a robust circadian rhythm, with a peak linked with the onset of the daily activity phase. It has long been believed that the production and secretion of GC is primarily governed through the hypothalamus-pituitary-adrenal (HPA) neuroendocrine axis in mammals. Growing evidence, however, strongly supports the notion that the periodicity of GC involves the integrated activity of multiple regulatory mechanisms related to circadian timing system along with the classical HPA neuroendocrine regulation. The adrenal-intrinsic oscillator as well as the central pacemaker plays a pivotal role in its rhythmicity. GC influences numerous biological processes, such as metabolic, cardiovascular, immune and even higher brain functions, and also acts as a resetting signal for the ubiquitous peripheral clocks, suggesting its importance in harmonizing circadian physiology and behavior. In this review, we will therefore focus on the recent advances in our understanding of the circadian regulation of adrenal GC and its functional relevance.
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Affiliation(s)
- Gi Hoon Son
- Department of Biological Sciences, Seoul National University, Brain Research Center for the 21st Century Frontier Program in Neuroscience, Seoul 151-742, Republic of Korea
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Barclay J, Husse J, Oster H. Adrenal glucocorticoids as a target for jet lag therapies. Expert Rev Endocrinol Metab 2011; 6:673-679. [PMID: 30780875 DOI: 10.1586/eem.11.56] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
When traveling across time zones, our physiological functions lose synchrony relative to the external day. The endogenous circadian clocks that usually prepare our body for times of eating, sleeping and other rhythmic behavioral and physiological processes become temporally disrupted. Owing to the fact that these clocks cannot immediately realign, we experience jet lag, which is characterized by multiple physiological and psychological symptoms. Despite recent advances in understanding circadian clock function and the mechanisms of jet lag, limited therapy is available at present for the treatment of disorders associated with long-distance travel. Recent studies demonstrate that adrenal glucocorticoids are central mediators of circadian clock re-entrainment and are themselves under circadian regulation. It is therefore attractive to consider glucocorticoid signaling as a promising target for therapeutic intervention in the treatment of jet lag.
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Affiliation(s)
- Johanna Barclay
- a Circadian Rhythms Group, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany
| | - Jana Husse
- b Genes & Behavior Department, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany
| | - Henrik Oster
- a Circadian Rhythms Group, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany
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Shimizu T, Hirai Y, Murayama C, Miyamoto A, Miyazaki H, Miyazaki K. Circadian Clock genes Per2 and clock regulate steroid production, cell proliferation, and luteinizing hormone receptor transcription in ovarian granulosa cells. Biochem Biophys Res Commun 2011; 412:132-5. [PMID: 21819971 DOI: 10.1016/j.bbrc.2011.07.058] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2011] [Accepted: 07/13/2011] [Indexed: 10/17/2022]
Abstract
Circadian Clock genes are associated with the estrous cycle in female animals. Treatment with Per2 and Clock siRNAs decreased the number of granulosa cells and LHr expression in follicle-stimulating hormone FSH-treated granulosa cells. Per2 siRNA treatment did not stimulate the production of estradiol and expression of P450arom, whereas Clock siRNA treatment inhibited the production of estradiol and expression of P450arom mRNA. Per2 and Clock siRNA treatment increased and unchanged, respectively, progesterone production in FSH-treated granulosa cells. Similarly, expression of StAR mRNA was increased by Per2 siRNA and unchanged by Clock siRNA. Our data provide a new insight that Per2 and Clock have different action on ovarian granulosa cell functions.
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Affiliation(s)
- Takashi Shimizu
- Graduate School of Animal and Food Hygiene, Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Hokkaido 080-8555, Japan.
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Abstract
Many neurochemical systems interact to generate wakefulness and sleep. Wakefulness is promoted by neurons in the pons, midbrain, and posterior hypothalamus that produce acetylcholine, norepinephrine, dopamine, serotonin, histamine, and orexin/hypocretin. Most of these ascending arousal systems diffusely activate the cortex and other forebrain targets. NREM sleep is mainly driven by neurons in the preoptic area that inhibit the ascending arousal systems, while REM sleep is regulated primarily by neurons in the pons, with additional influence arising in the hypothalamus. Mutual inhibition between these wake- and sleep-regulating regions likely helps generate full wakefulness and sleep with rapid transitions between states. This up-to-date review of these systems should allow clinicians and researchers to better understand the effects of drugs, lesions, and neurologic disease on sleep and wakefulness.
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Affiliation(s)
- Rodrigo A España
- Department of Physiology and Pharmacology, Wake Forest University Health Sciences, Winston Salem, NC, USA
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Okyar A, Piccolo E, Ahowesso C, Filipski E, Hossard V, Guettier C, La Sorda R, Tinari N, Iacobelli S, Lévi F. Strain- and sex-dependent circadian changes in abcc2 transporter expression: implications for irinotecan chronotolerance in mouse ileum. PLoS One 2011; 6:e20393. [PMID: 21674030 PMCID: PMC3108586 DOI: 10.1371/journal.pone.0020393] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2011] [Accepted: 04/27/2011] [Indexed: 11/19/2022] Open
Abstract
Background ATP-binding cassette transporter abcc2 is involved in the cellular efflux of irinotecan. The drug is toxic for mouse ileum, where abcc2 is highly expressed. Here, we investigate whether circadian changes in local abcc2 expression participate in the circadian rhythm of irinotecan toxicity for ileum mucosa, and further assess whether genetic background or sex modify this relation. Methodology/Principal Findings Ileum mucosa was obtained every 3–4 h for 24 h in male and female B6D2F1 and B6CBAF1 mice synchronized with light from Zeitgeber Time (ZT)0 to ZT12 alternating with 12 h of darkness. Irinotecan (50 mg/kg i.v. daily for 4 days) was administered at the sex- and strain-specific times corresponding to least (ZT11-15) or largest drug-induced body weight loss (ZT23-03-07). Abcc2 expression was determined with qRT-PCR for mRNA and with immunohistochemistry and confocal microscopy for protein. Histopathologic lesions were graded in ileum tissues obtained 2, 4 or 6 days after treatment. Two- to six-fold circadian changes were demonstrated for mRNA and protein mean expressions of abcc2 in mouse ileum (p<0.05). ZT12 corresponded to high mRNA and protein expressions, with circadian waveforms differing according to genetic background and sex. The proportion of mice spared from ileum lesions varied three-fold according to irinotecan timing, with best tolerability at ZT11-15 (p = 0.00003). Irinotecan was also best tolerated in males (p = 0.05) and in B6CBAF1 (p = 0.0006). Conclusions/Significance Strain- and sex-dependent circadian patterns in abcc2 expressions displayed robust relations with the chronotolerance of ileum mucosa for irinotecan. This finding has strong potential implications for improving the intestinal tolerability of anticancer drugs through circadian delivery.
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Affiliation(s)
- Alper Okyar
- INSERM, U776 Rythmes Biologiques et Cancers, Hôpital Paul Brousse, Villejuif, France
- Université Paris-Sud, UMR-S0776, Orsay, France
- Department of Pharmacology, Istanbul University Faculty of Pharmacy, Beyazit, Istanbul, Turkey
| | - Enza Piccolo
- Consorzio Interuniversitario Nazionale per la Bioncologia (CINBO) CE.S.I. - Università “G. d'Annunzio”, Chieti, Italy
| | - Constance Ahowesso
- INSERM, U776 Rythmes Biologiques et Cancers, Hôpital Paul Brousse, Villejuif, France
- Université Paris-Sud, UMR-S0776, Orsay, France
| | - Elisabeth Filipski
- INSERM, U776 Rythmes Biologiques et Cancers, Hôpital Paul Brousse, Villejuif, France
- Université Paris-Sud, UMR-S0776, Orsay, France
| | - Virginie Hossard
- INSERM, U776 Rythmes Biologiques et Cancers, Hôpital Paul Brousse, Villejuif, France
- Université Paris-Sud, UMR-S0776, Orsay, France
| | - Catherine Guettier
- Assistance Publique-Hôpitaux de Paris, Laboratoire d'Anatomie et Cytologie Pathologiques, Hôpital Paul Brousse, Villejuif, France
| | - Rosanna La Sorda
- Consorzio Interuniversitario Nazionale per la Bioncologia (CINBO) CE.S.I. - Università “G. d'Annunzio”, Chieti, Italy
| | - Nicola Tinari
- Consorzio Interuniversitario Nazionale per la Bioncologia (CINBO) CE.S.I. - Università “G. d'Annunzio”, Chieti, Italy
| | - Stefano Iacobelli
- Consorzio Interuniversitario Nazionale per la Bioncologia (CINBO) CE.S.I. - Università “G. d'Annunzio”, Chieti, Italy
| | - Francis Lévi
- INSERM, U776 Rythmes Biologiques et Cancers, Hôpital Paul Brousse, Villejuif, France
- Université Paris-Sud, UMR-S0776, Orsay, France
- Assistance Publique-Hôpitaux de Paris, Unité de Chronothérapie, Département de Cancérologie, Hôpital Paul Brousse, Villejuif, France
- * E-mail:
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Del Principe D, Avigliano L, Savini I, Catani MV. Trans-plasma membrane electron transport in mammals: functional significance in health and disease. Antioxid Redox Signal 2011; 14:2289-318. [PMID: 20812784 DOI: 10.1089/ars.2010.3247] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Trans-plasma membrane electron transport (t-PMET) has been established since the 1960s, but it has only been subject to more intensive research in the last decade. The discovery and characterization at the molecular level of its novel components has increased our understanding of how t-PMET regulates distinct cellular functions. This review will give an update on t-PMET, with particular emphasis on how its malfunction relates to some diseases, such as cancer, abnormal cell death, cardiovascular diseases, aging, obesity, neurodegenerative diseases, pulmonary fibrosis, asthma, and genetically linked pathologies. Understanding these relationships may provide novel therapeutic approaches for pathologies associated with unbalanced redox state.
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Affiliation(s)
- Domenico Del Principe
- Department of Experimental Medicine and Biochemical Sciences, University of Rome Tor Vergata, Rome, Italy.
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128
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Kommedal S, Bódis G, Matkovits A, Csernus V, Nagy AD. Expression pattern of clock under acute phase-delay of the light/dark cycle in the chicken pineal model. Gen Comp Endocrinol 2011; 172:170-2. [PMID: 21291888 DOI: 10.1016/j.ygcen.2011.01.012] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/05/2010] [Revised: 01/13/2011] [Accepted: 01/19/2011] [Indexed: 11/24/2022]
Abstract
Shift workers have a higher risk of metabolic syndrome, a condition that also develops in mice carrying mutation in their circadian clock gene clock. To collect more data on the transcriptional changes of clock under phase-shifted light/dark LD conditions, we examined the 24h patterns of clock mRNA expression in vivo and in vitro in chickens exposed acutely to a reversed LD (DL) cycle. Under controlled LD conditions (lights on at 6:00, lights off at 20:00), clock mRNA expression peaked in vivo at 2:00 (Zeitgeber Time 20, ZT20) and in vitro at 22:00 (ZT16). Even higher mRNA contents were measured in the first cycle of in vivo DL conditions between 22:00 and 6:00 (lights at night), but in the second cycle by 2:00, lower mRNA contents were detected than the control peak values seen at this time point. Furthermore, no alterations were found in vitro in clock mRNA content during the first 12h of DL conditions (lights at night). The differences seen between the first and the second DL cycles in vivo and between the in vivo and in vitro data for the first DL cycle support the idea that neurohumoral signals perturbed by a phase-delayed light-dark cycle may also play a role in the in vivo rapid transcriptional resetting of the circadian clock in the chicken pineal model.
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Affiliation(s)
- Siri Kommedal
- Department of Anatomy, Medical School, University of Pécs, Hungary
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129
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Foley NC, Tong TY, Foley D, LeSauter J, Welsh DK, Silver R. Characterization of orderly spatiotemporal patterns of clock gene activation in mammalian suprachiasmatic nucleus. Eur J Neurosci 2011; 33:1851-65. [PMID: 21488990 PMCID: PMC3423955 DOI: 10.1111/j.1460-9568.2011.07682.x] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Because we can observe oscillation within individual cells and in the tissue as a whole, the suprachiasmatic nucleus (SCN) presents a unique system in the mammalian brain for the analysis of individual cells and the networks of which they are a part. While dispersed cells of the SCN sustain circadian oscillations in isolation, they are unstable oscillators that require network interactions for robust cycling. Using cluster analysis to assess bioluminescence in acute brain slices from PERIOD2::Luciferase (PER2::LUC) knockin mice, and immunochemistry of SCN from animals harvested at various circadian times, we assessed the spatiotemporal activation patterns of PER2 to explore the emergence of a coherent oscillation at the tissue level. The results indicate that circadian oscillation is characterized by a stable daily cycle of PER2 expression involving orderly serial activation of specific SCN subregions, followed by a silent interval, with substantial symmetry between the left and right side of the SCN. The biological significance of the clusters identified in living slices was confirmed by co-expression of LUC and PER2 in fixed, immunochemically stained brain sections, with the spatiotemporal pattern of LUC expression resembling that revealed in the cluster analysis of bioluminescent slices. We conclude that the precise timing of PER2 expression within individual neurons is dependent on their location within the nucleus, and that small groups of neurons within the SCN give rise to distinctive and identifiable subregions. We propose that serial activation of these subregions is the basis of robustness and resilience of the daily rhythm of the SCN.
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Affiliation(s)
- Nicholas C. Foley
- Department of Cognitive and Neural Systems, Boston University, Boston, MA, USA
| | - Tina Y. Tong
- Department of Psychology, Barnard College of Columbia University, New York, NY, USA
| | - Duncan Foley
- Department of Economics, New School for Social Research, New York, NY, USA
| | - Joseph LeSauter
- Department of Psychology, Barnard College of Columbia University, New York, NY, USA
| | - David K. Welsh
- Department of Psychiatry and Center for Chronobiology, University of California, San Diego, La Jolla, CA, USA
- Veterans Affairs San Diego Healthcare System, San Diego, CA, USA
| | - Rae Silver
- Department of Psychology, Barnard College of Columbia University, New York, NY, USA
- Department of Psychology, Columbia University, New York, NY, USA
- Department of Pathology and Cell Biology, Columbia University Health Sciences, New York, NY, USA
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Hughes ATL, Guilding C, Piggins HD. Neuropeptide signaling differentially affects phase maintenance and rhythm generation in SCN and extra-SCN circadian oscillators. PLoS One 2011; 6:e18926. [PMID: 21559484 PMCID: PMC3084722 DOI: 10.1371/journal.pone.0018926] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2011] [Accepted: 03/11/2011] [Indexed: 02/02/2023] Open
Abstract
Circadian rhythms in physiology and behavior are coordinated by the brain's dominant circadian pacemaker located in the suprachiasmatic nuclei (SCN) of the hypothalamus. Vasoactive intestinal polypeptide (VIP) and its receptor, VPAC(2), play important roles in the functioning of the SCN pacemaker. Mice lacking VPAC(2) receptors (Vipr2(-/-)) express disrupted behavioral and metabolic rhythms and show altered SCN neuronal activity and clock gene expression. Within the brain, the SCN is not the only site containing endogenous circadian oscillators, nor is it the only site of VPAC(2) receptor expression; both VPAC(2) receptors and rhythmic clock gene/protein expression have been noted in the arcuate (Arc) and dorsomedial (DMH) nuclei of the mediobasal hypothalamus, and in the pituitary gland. The functional role of VPAC(2) receptors in rhythm generation and maintenance in these tissues is, however, unknown. We used wild type (WT) and Vipr2(-/-) mice expressing a luciferase reporter (PER2::LUC) to investigate whether circadian rhythms in the clock gene protein PER2 in these extra-SCN tissues were compromised by the absence of the VPAC(2) receptor. Vipr2(-/-) SCN cultures expressed significantly lower amplitude PER2::LUC oscillations than WT SCN. Surprisingly, in Vipr2(-/-) Arc/ME/PT complex (Arc, median eminence and pars tuberalis), DMH and pituitary, the period, amplitude and rate of damping of rhythms were not significantly different to WT. Intriguingly, while we found WT SCN and Arc/ME/PT tissues to maintain a consistent circadian phase when cultured, the phase of corresponding Vipr2(-/-) cultures was reset by cull/culture procedure. These data demonstrate that while the main rhythm parameters of extra-SCN circadian oscillations are maintained in Vipr2(-/-) mice, the ability of these oscillators to resist phase shifts is compromised. These deficiencies may contribute towards the aberrant behavior and metabolism associated with Vipr2(-/-) animals. Further, our data indicate a link between circadian rhythm strength and the ability of tissues to resist circadian phase resetting.
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Affiliation(s)
- Alun T L Hughes
- Faculty of Life Sciences, University of Manchester, Manchester, United Kingdom.
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Swanson G, Forsyth CB, Tang Y, Shaikh M, Zhang L, Turek FW, Keshavarzian A. Role of intestinal circadian genes in alcohol-induced gut leakiness. Alcohol Clin Exp Res 2011; 35:1305-14. [PMID: 21463335 DOI: 10.1111/j.1530-0277.2011.01466.x] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
BACKGROUND Several studies have indicated that endotoxemia is the required co-factor for alcoholic steatohepatitis (ASH) that is seen in only about 30% of alcoholics. Recent studies have shown that gut leakiness that occurs in a subset of alcoholics is the primary cause of endotoxemia in ASH. The reasons for this differential susceptibility are not known. Since disruption of circadian rhythms occurs in some alcoholics and circadian genes control the expression of several genes that are involved in regulation of intestinal permeability, we hypothesized that alcohol induces intestinal hyperpermeability by stimulating expression of circadian clock gene proteins in the intestinal epithelial cells. METHODS We used Caco-2 monolayers grown on culture inserts as an in vitro model of intestinal permeability and performed Western blotting, permeability, and siRNA inhibition studies to examine the role of Clock and Per2 circadian genes in alcohol-induced hyperpermeability. We also measured PER2 protein levels in intestinal mucosa of alcohol-fed rats with intestinal hyperpermeability. RESULTS Alcohol, as low as 0.2%, induced time dependent increases in both Caco-2 cell monolayer permeability and in CLOCK and PER2 proteins. SiRNA specific inhibition of either Clock or Per2 significantly inhibited alcohol-induced monolayer hyperpermeability. Alcohol-fed rats with increased total gut permeability, assessed by urinary sucralose, also had significantly higher levels of PER2 protein in their duodenum and proximal colon than control rats. CONCLUSIONS Our studies: (i) demonstrate a novel mechanism for alcohol-induced intestinal hyperpermeability through stimulation of intestinal circadian clock gene expression, and (ii) provide direct evidence for a central role of circadian genes in regulation of intestinal permeability.
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Affiliation(s)
- Garth Swanson
- Department of Medicine, Division of Digestive Diseases and Nutrition, Rush University Medical Center, 1725 W. Harrison, Chicago, IL 60612, USA
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Cao R, Anderson FE, Jung YJ, Dziema H, Obrietan K. Circadian regulation of mammalian target of rapamycin signaling in the mouse suprachiasmatic nucleus. Neuroscience 2011; 181:79-88. [PMID: 21382453 DOI: 10.1016/j.neuroscience.2011.03.005] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2010] [Revised: 02/27/2011] [Accepted: 03/01/2011] [Indexed: 12/19/2022]
Abstract
Circadian (24-h) rhythms influence virtually every aspect of mammalian physiology. The main rhythm generation center is located in the suprachiasmatic nucleus (SCN) of the hypothalamus, and work over the past several years has revealed that rhythmic gene transcription and post-translational processes are central to clock timing. In addition, rhythmic translation control has also been implicated in clock timing; however the precise cell signaling pathways that drive this process are not well known. Here we report that a key translation activation cascade, the mammalian target of rapamycin (mTOR) pathway, is under control of the circadian clock in the SCN. Using phosphorylated S6 ribosomal protein (pS6) as a marker of mTOR activity, we show that the mTOR cascade exhibits maximal activity during the subjective day, and minimal activity during the late subjective night. Importantly, expression of S6 was not altered as a function of circadian time. Rhythmic S6 phosphorylation was detected throughout the dorsoventral axis of the SCN, thus suggesting that rhythmic mTOR activity was not restricted to a subset of SCN neurons. Rather, rhythmic pS6 expression appeared to parallel the expression pattern of the clock gene period1 (per1). Using a transgenic per1 reporter gene mouse strain, we found a statistically significant cellular level correlation between pS6 and per1 gene expression over the circadian cycle. Further, photic stimulation triggered a coordinate upregulation of per1 and mTOR activation in a subset of SCN cells. Interestingly, this cellular level correlation between mTOR activity and per1 expression appears to be specific, since a similar expression profile for pS6 and per2 or c-FOS was not detected. Finally, we show that mTOR activity is downstream of the ERK/MAPK signal transduction pathway. Together these data reveal that mTOR pathway activity is under the control of the SCN clock, and suggests that mTOR signaling may contribute to distinct aspects of the molecular clock timing process.
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Affiliation(s)
- R Cao
- Department of Neuroscience, Ohio State University, Columbus, OH 43210, USA
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Delvecchio C, Tiefenbach J, Krause HM. The zebrafish: a powerful platform for in vivo, HTS drug discovery. Assay Drug Dev Technol 2011; 9:354-61. [PMID: 21309713 DOI: 10.1089/adt.2010.0346] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The zebrafish (Danio rerio) is an emerging vertebrate model for drug discovery that permits whole animal drug screens with excellent throughput, combined with ease of use and low cost. This review will begin with a discussion on the background, suitability, and advantages of this vertebrate model system and then, citing specific examples, will describe the utility of zebrafish at specific stages in the drug development pipeline. We will end with a synopsis of recent drug screens based on morphological disruptions, genetic disease models, fluorescent markers, behavioral changes, and specific targets. The numerous advantages of this whole animal approach provide new promise for the discovery of safe, specific, and powerful new drugs.
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Affiliation(s)
- Chris Delvecchio
- Banting and Best Department of Medical Research, Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, Canada
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Abstract
In mammals, most metabolic processes are influenced by biological clocks and feeding rhythms. The mechanisms that couple metabolism to circadian oscillators are just emerging. NAD-dependent enzymes (e.g., Sirtuins and poly[ADP-ribose] polymerases), redox- and/or temperature-dependent transcription factors (e.g., CLOCK, NPAS2, and HSF1), nutrient-sensing transcriptional regulatory proteins (e.g., CREB-CBP-CRCT2, FOXO-p300, nuclear receptors, PGC-1, and SP1 family members) and protein kinases (e.g., AMPK), are plausible candidates for conveying a cell's metabolic state to the core clock circuitry. The intertwining between these acute regulators and circadian clock components is so tight that the discrimination between metabolic and circadian oscillations may be somewhat arbitrary.
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135
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Staiger D, Köster T. Spotlight on post-transcriptional control in the circadian system. Cell Mol Life Sci 2011; 68:71-83. [PMID: 20803230 PMCID: PMC11114774 DOI: 10.1007/s00018-010-0513-5] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2010] [Revised: 08/16/2010] [Accepted: 08/16/2010] [Indexed: 10/19/2022]
Abstract
An endogenous timing mechanism, the circadian clock, causes rhythmic expression of a considerable fraction of the genome of most organisms to optimally align physiology and behavior with their environment. Circadian clocks are self-sustained oscillators primarily based on transcriptional feedback loops and post-translational modification of clock proteins. It is increasingly becoming clear that regulation at the RNA level strongly impacts the cellular circadian transcriptome and proteome as well as the oscillator mechanism itself. This review focuses on posttranscriptional events, discussing RNA-binding proteins that, by influencing the timing of pre-mRNA splicing, polyadenylation and RNA decay, shape rhythmic expression profiles. Furthermore, recent findings on the contribution of microRNAs to orchestrating circadian rhythms are summarized.
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Affiliation(s)
- Dorothee Staiger
- Molecular Cell Physiology, Bielefeld University, 33501, Bielefeld, Germany.
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136
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5-HT1B receptor in the suprachiasmatic nucleus of the common marmoset (Callithrix jacchus). Neurosci Lett 2011; 488:6-10. [DOI: 10.1016/j.neulet.2010.10.070] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2010] [Revised: 10/02/2010] [Accepted: 10/28/2010] [Indexed: 11/18/2022]
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137
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Reppert SM, Gegear RJ, Merlin C. Navigational mechanisms of migrating monarch butterflies. Trends Neurosci 2010; 33:399-406. [PMID: 20627420 PMCID: PMC2929297 DOI: 10.1016/j.tins.2010.04.004] [Citation(s) in RCA: 112] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2010] [Revised: 04/20/2010] [Accepted: 04/26/2010] [Indexed: 12/12/2022]
Abstract
Recent studies of the iconic fall migration of monarch butterflies have illuminated the mechanisms behind their southward navigation while using a time-compensated sun compass. Skylight cues, such as the sun itself and polarized light, are processed through both eyes and are probably integrated in the brain's central complex, the presumed site of the sun compass. Time compensation is provided by circadian clocks that have a distinctive molecular mechanism and that reside in the antennae. Monarchs might also use a magnetic compass because they possess two cryptochromes that have the molecular capability for light-dependent magnetoreception. Multiple genomic approaches are now being used with the aim of identifying navigation genes. Monarch butterflies are thus emerging as an excellent model organism in which to study the molecular and neural basis of long-distance migration.
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Affiliation(s)
- Steven M Reppert
- Department of Neurobiology, University of Massachusetts Medical School, Worcester, MA 01605, USA.
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138
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Challenges in synthetically designing mammalian circadian clocks. Curr Opin Biotechnol 2010; 21:556-65. [DOI: 10.1016/j.copbio.2010.07.011] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2010] [Revised: 07/21/2010] [Accepted: 07/21/2010] [Indexed: 01/21/2023]
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139
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Harrington M. Location, location, location: important for jet-lagged circadian loops. J Clin Invest 2010; 120:2265-7. [PMID: 20577055 DOI: 10.1172/jci43632] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
It is now believed that frequent jet lag or shifts of daily rhythms caused by rotating shift work can lead to deleterious health outcomes. Indeed, many serious health problems, including breast cancer, stroke, and cardiovascular disease, have been linked to an occupational history of shift work. This has heightened interest in better understanding the biological responses to jet lag and shift work, with the hope that this will pave the way to developing compounds that can help people avoid their negative health consequences. In this context, a report in this issue of the JCI takes us to a new level of understanding of the molecular control of the resetting of the multitude of internal biological clocks disrupted in a mouse model of jet lag.
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Affiliation(s)
- Mary Harrington
- Department of Psychology, Smith College, Northampton, Massachusetts 01063, USA.
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