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Circadian Clock

Andreas Arendt, El-Sayed Baz, Monika Stengl
The circadian pacemaker of the Madeira cockroach Rhyparobia (Leucophaea) maderae is located in the accessory medulla (AME). Ipsi- and contralateral histaminergic compound eyes are required for photic entrainment. Light pulses delayed locomotor activity rhythms during the early night and advanced during the late night. Thus, different neuronal pathways might relay either light-dependent delays or advances to the clock. Injections of neuroactive substances combined with running-wheel assays suggested that GABA, PDF, myoinhibitory peptides (MIPs), and orcokinins (ORCs) are part of both entrainment pathways, while allatotropin (AT) only delayed locomotor rhythms at the early night...
October 20, 2016: Journal of Comparative Neurology
Víctor Resco de Dios, Arthur Gessler, Juan Pedro Ferrio, Josu G Alday, Michael Bahn, Jorge Del Castillo, Sébastien Devidal, Sonia García-Muñoz, Zachary Kayler, Damien Landais, Paula Martín-Gómez, Alexandru Milcu, Clément Piel, Karin Pirhofer-Walzl, Olivier Ravel, Serajis Salekin, David T Tissue, Mark G Tjoelker, Jordi Voltas, Jacques Roy
BACKGROUND: Molecular clocks drive oscillations in leaf photosynthesis, stomatal conductance, and other cell and leaf-level processes over ~24 h under controlled laboratory conditions. The influence of such circadian regulation over whole-canopy fluxes remains uncertain; diurnal CO2 and H2O vapor flux dynamics in the field are currently interpreted as resulting almost exclusively from direct physiological responses to variations in light, temperature and other environmental factors. We tested whether circadian regulation would affect plant and canopy gas exchange at the Montpellier European Ecotron...
October 20, 2016: GigaScience
Gregory D M Potter, Debra J Skene, Josephine Arendt, Janet E Cade, Peter J Grant, Laura J Hardie
Circadian (∼ 24 hour) timing systems pervade all kingdoms of life, and temporally optimize behaviour and physiology in humans. Relatively recent changes to our environments, such as the introduction of artificial lighting, can disorganize the circadian system, from the level of the molecular clocks that regulate the timing of cellular activities to the level of synchronization between our daily cycles of behaviour and the solar day. Sleep/wake cycles are intertwined with the circadian system, and global trends indicate that these too are increasingly subject to disruption...
October 20, 2016: Endocrine Reviews
Dirk Jan Stenvers, Rick van Dorp, Ewout Foppen, Jorge Mendoza, Anne-Loes Opperhuizen, Eric Fliers, Peter H Bisschop, Johanna H Meijer, Andries Kalsbeek, Tom Deboer
Exposure to light at night (LAN) is associated with insomnia in humans. Light provides the main input to the master clock in the hypothalamic suprachiasmatic nucleus (SCN) that coordinates the sleep-wake cycle. We aimed to develop a rodent model for the effects of LAN on sleep. Therefore, we exposed male Wistar rats to either a 12 h light (150-200lux):12 h dark (LD) schedule or a 12 h light (150-200 lux):12 h dim white light (5 lux) (LDim) schedule. LDim acutely decreased the amplitude of daily rhythms of REM and NREM sleep, with a further decrease over the following days...
October 20, 2016: Scientific Reports
Joseph F O'Grady, Laura S Hoelters, Martin T Swain, David C Wilcockson
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...
2016: PeerJ
Aurore Woller, Hélène Duez, Bart Staels, Marc Lefranc
To maintain energy homeostasis despite variable energy supply and consumption along the diurnal cycle, the liver relies on a circadian clock synchronized to food timing. Perturbed feeding and fasting cycles have been associated with clock disruption and metabolic diseases; however, the mechanisms are unclear. To address this question, we have constructed a mathematical model of the mammalian circadian clock, incorporating the metabolic sensors SIRT1 and AMPK. The clock response to various temporal patterns of AMPK activation was simulated numerically, mimicking the effects of a normal diet, fasting, and a high-fat diet...
October 18, 2016: Cell Reports
Alberto Ugolini, Laura S Hoelters, Alice Ciofini, Vittorio Pasquali, David C Wilcockson
Animals that use astronomical cues to orientate must make continuous adjustment to account for temporal changes in azimuth caused by Earth's rotation. For example, the Monarch butterfly possesses a time-compensated sun compass dependent upon a circadian clock in the antennae. The amphipod Talitrus saltator possesses both a sun compass and a moon compass. We reasoned that the time-compensated compass mechanism that enables solar orientation of T. saltator is located in the antennae, as is the case for Monarch butterflies...
October 19, 2016: Scientific Reports
Jan Hansen, Silvie Timmers, Esther Moonen-Kornips, Helene Duez, Bart Staels, Matthijs K C Hesselink, Patrick Schrauwen
Cell and animal studies have demonstrated that circadian rhythm is governed by autonomous rhythmicity of clock genes. Although disturbances in circadian rhythm have been implicated in metabolic disease development, it remains unknown whether muscle circadian rhythm is altered in human models of type 2 diabetes. Here we used human primary myotubes (HPM) to investigate if rhythmicity of clock- and metabolic gene expression is altered in donors with obesity or type 2 diabetes compared to metabolically healthy donors...
October 19, 2016: Scientific Reports
Eunjoo Cho, Euna Lee, Eun Young Kim
The circadian clock system enables organisms to anticipate the rhythmic environmental changes and to manifest behavior and physiology at advantageous times of day. Transcriptional/translational feedback loop (TTFL) is the basic feature of eukaryotic circadian clock and is based on the rhythmic association of circadian transcriptional activator and repressor. In Drosophila, repression of dCLOCK/CYCLE (dCLK/CYC) mediated transcription by PERIOD (PER) is critical for inducing circadian rhythms of gene expression...
October 19, 2016: BMB Reports
Casey O Diekman, Amitabha Bose
Circadian oscillators found across a variety of species are subject to periodic external light-dark forcing. Entrainment to light-dark cycles enables the circadian system to align biological functions with appropriate times of day or night. Phase response curves (PRCs) have been used for decades to gain valuable insights into entrainment; however, PRCs may not accurately describe entrainment to photoperiods with substantial amounts of both light and dark due to their reliance on a single limit cycle attractor...
October 17, 2016: Journal of Biological Rhythms
Huan Wang, Hui Chen
OBJECTIVE: Circadian rhythm disruption is shown to be the cause of various health disorders. CLOCK and BMAL1, two core circadian transcription factors, were associated with the regulation of glucose homeostasis. This study evaluated the association between single nucleotide polymorphisms in CLOCK and BMAL1 gene and insulin resistance (IR) in hypertensive patients. DESIGN AND METHOD: We collected 334 outpatients with essential hypertension (EH), who have not taken any antihypertensive agents or stopped the medications for at least a week for this case-control study...
September 2016: Journal of Hypertension
Stefano Schiaffino, Bert Blaauw, Kenneth A Dyar
The circadian oscillations of muscle genes are controlled either directly by the intrinsic muscle clock or by extrinsic factors, such as feeding, hormonal signals, or neural influences, which are in turn regulated by the central pacemaker, the suprachiasmatic nucleus of the hypothalamus. A unique feature of circadian rhythms in skeletal muscle is motor neuron-dependent contractile activity, which can affect the oscillation of a number of muscle genes independently of the muscle clock. The role of the intrinsic muscle clock has been investigated using different Bmal1 knockout (KO) models...
2016: Skeletal Muscle
Masaaki Sugiyama, Hirokazu Yagi, Kentaro Ishii, Lionel Porcar, Anne Martel, Katsuaki Oyama, Masanori Noda, Yasuhiro Yunoki, Reiko Murakami, Rintaro Inoue, Nobuhiro Sato, Yojiro Oba, Kazuki Terauchi, Susumu Uchiyama, Koichi Kato
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...
October 18, 2016: Scientific Reports
Henrik Oster, Etienne Challet, Volker Ott, Emanuela Arvat, E Ronald de Kloet, Derk-Jan Dijk, Stafford Lightman, Alexandros Vgontzas, Eve Van Cauter
Adrenal glucocorticoids are major modulators of multiple functions, including energy metabolism, stress responses, immunity, and cognition. The endogenous secretion of glucocorticoids is normally characterized by a prominent and robust circadian (around 24 hours) oscillation, with a daily peak around the time of the habitual sleep-wake transition and minimal levels in the evening and early part of the night. It has been long recognized that this 24-h rhythm partly reflects the activity of a master circadian pacemaker located in the suprachiasmatic nucleus of the hypothalamus...
October 17, 2016: Endocrine Reviews
Naoya Matsunaga, Eriko Ikeda, Keisuke Kakimoto, Miyako Watanabe, Naoya Shindo, Akito Tsuruta, Hisako Ikeyama, Kengo Hamamura, Kazuhiro Higashi, Tomohiro Yamashita, Hideaki Kondo, Yuya Yoshida, Masaki Matsuda, Takashi Ogino, Kazutaka Tokushige, Kazufumi Itcho, Yoko Furuichi, Takaharu Nakao, Kaori Yasuda, Atsushi Doi, Toshiaki Amamoto, Hironori Aramaki, Makoto Tsuda, Kazuhide Inoue, Akio Ojida, Satoru Koyanagi, Shigehiro Ohdo
Chronic kidney disease (CKD) is a global health problem, and novel therapies to treat CKD are urgently needed. Here, we show that inhibition of G0/G1 switch 2 (G0s2) ameliorates renal inflammation in a mouse model of CKD. Renal expression of chemokine (C-C motif) ligand 2 (Ccl2) was increased in response to p65 activation in the kidneys of wild-type 5/6 nephrectomy (5/6Nx) mice. Moreover, 5/6Nx Clk/Clk mice, which carry homozygous mutations in the gene encoding circadian locomotor output cycles kaput (CLOCK), did not exhibit aggravation of apoptosis or induction of F4/80-positive cells...
October 6, 2016: EBioMedicine
Malini Riddle, Erica Mezias, Duncan Foley, Joseph LeSauter, Rae Silver
The hypothalamic suprachiasmatic nucleus (SCN), locus of the master circadian clock, bears many neuronal types. At the cellular-molecular level, the clock is comprised of feedback loops involving "clock" genes including Period1 and Period2, and their protein products, PERIOD1 and PERIOD2 (PER1/2). In the canonical model of circadian oscillation, the PER1/2 proteins oscillate together. While their rhythmic expression in the SCN as a whole has been described, the possibility of regional differences is unknown...
October 14, 2016: European Journal of Neuroscience
Susanne A Bengesser, Eva Z Reininghaus, Nina Lackner, Armin Birner, Frederike T Fellendorf, Martina Platzer, Nora Kainzbauer, Bernhard Tropper, Christa Hörmanseder, Robert Queissner, Hans-Peter Kapfhammer, Sandra J Wallner-Liebmann, Robert Fuchs, Erwin Petek, Christian Windpassinger, Mario Schnalzenberger, Bernd Reininghaus, Bernd Evert, Andreas Waha
OBJECTIVES: The clock gene ARNTL is associated with the transcription activation of monoamine oxidase A according to previous literature. Thus, we hypothesised that methylation of ARNTL may differ between bipolar disorder (BD) and controls. METHODS: The methylation status of one CpG island covering the first exon of ARNTL (PS2) and one site in the 5' region of ARNTL (cg05733463) were analysed in patients with BD (n = 151) versus controls (n = 66). Methylation analysis was performed by bisulphite-conversion of DNA from fasting blood with the EpiTect Bisulfite Kit, PCR and pyrosequencing...
October 14, 2016: World Journal of Biological Psychiatry
Amandine Chaix, Amir Zarrinpar, Satchidananda Panda
Circadian clocks are cell-autonomous timing mechanisms that organize cell functions in a 24-h periodicity. In mammals, the main circadian oscillator consists of transcription-translation feedback loops composed of transcriptional regulators, enzymes, and scaffolds that generate and sustain daily oscillations of their own transcript and protein levels. The clock components and their targets impart rhythmic functions to many gene products through transcriptional, posttranscriptional, translational, and posttranslational mechanisms...
October 10, 2016: Journal of Cell Biology
Jing-Fen Wu, Huang-Lung Tsai, Ignasius Joanito, Yi-Chen Wu, Chin-Wen Chang, Yi-Hang Li, Ying Wang, Jong Chan Hong, Jhih-Wei Chu, Chao-Ping Hsu, Shu-Hsing Wu
A double-negative feedback loop formed by the morning genes CIRCADIAN CLOCK ASSOCIATED1 (CCA1)/LATE ELONGATED HYPOCOTYL (LHY) and the evening gene TIMING OF CAB EXPRESSION1 (TOC1) contributes to regulation of the circadian clock in Arabidopsis. A 24-h circadian cycle starts with the peak expression of CCA1 at dawn. Although CCA1 is targeted by multiple transcriptional repressors, including PSEUDO-RESPONSE REGULATOR9 (PRR9), PRR7, PRR5 and CCA1 HIKING EXPEDITION (CHE), activators of CCA1 remain elusive. Here we use mathematical modelling to infer a co-activator role for LIGHT-REGULATED WD1 (LWD1) in CCA1 expression...
October 13, 2016: Nature Communications
Idan Elbaz, David Zada, Adi Tovin, Tslil Braun, Tali Lerer-Goldshtein, Gordon Wang, Philippe Mourrain, Lior Appelbaum
Sleep is tightly regulated by the circadian clock and homeostatic mechanisms. Although the sleep/wake cycle is known to be associated with structural and physiological synaptic changes that benefit the brain, the function of sleep is still debated. The hypothalamic hypocretin/orexin (Hcrt) neurons regulate various functions including feeding, reward, sleep, and wake. Continuous imaging of single neuronal circuits in live animals is vital to understanding the role of sleep in regulating synaptic dynamics, and the transparency of the zebrafish model enables time-lapse imaging of single synapses during both day and night...
October 12, 2016: Molecular Neurobiology
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