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Mammalian circadian

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https://www.readbyqxmd.com/read/28217893/geniculohypothalamic-gabaergic-projections-gate-suprachiasmatic-nucleus-responses-to-retinal-input
#1
Lydia Hanna, Lauren Walmsley, Abigail Pienaar, Michael Howarth, Timothy M Brown
Sensory input to the master mammalian circadian clock, the suprachiasmatic nucleus (SCN), is vital in allowing animals to optimise physiology and behaviour alongside daily changes in the environment. Retinal inputs encoding changes in external illumination provide the principle source of such information. The SCN also receives input from other retinorecipient brain regions, primarily via the geniculohypothalamic tract (GHT), but the contribution of these indirect projections to circadian photoreception are currently poorly understood...
February 20, 2017: Journal of Physiology
https://www.readbyqxmd.com/read/28196880/agrp-to-kiss1-neuron-signaling-links-nutritional-state-and-fertility
#2
Stephanie L Padilla, Jian Qiu, Casey C Nestor, Chunguang Zhang, Arik W Smith, Benjamin B Whiddon, Oline K Rønnekleiv, Martin J Kelly, Richard D Palmiter
Mammalian reproductive function depends upon a neuroendocrine circuit that evokes the pulsatile release of gonadotropin hormones (luteinizing hormone and follicle-stimulating hormone) from the pituitary. This reproductive circuit is sensitive to metabolic perturbations. When challenged with starvation, insufficient energy reserves attenuate gonadotropin release, leading to infertility. The reproductive neuroendocrine circuit is well established, composed of two populations of kisspeptin-expressing neurons (located in the anteroventral periventricular hypothalamus, Kiss1(AVPV), and arcuate hypothalamus, Kiss1(ARH)), which drive the pulsatile activity of gonadotropin-releasing hormone (GnRH) neurons...
February 14, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/28174256/a-time-for-myc-metabolism-and-therapy
#3
Chi V Dang
The MYC oncogene is frequently deregulated in human cancers, whereas the proto-oncogene is exquisitely, tightly regulated in normal cells. Deregulated MYC drives transcriptional imbalance, thereby altering metabolism and disrupting the circadian Bmal1-Clock E-box-dependent transcriptional circuitry. Sustained oncogenic MYC expression drives a constitutive growth program with mammalian target of rapamycin (mTOR) activation that renders cells dependent on nutrients, such that glucose or glutamine deprivation could trigger cell death and key enzymes such as lactate dehydrogenase A (LDHA) and glutaminase (GLS) amenable for targeting in cancers...
February 7, 2017: Cold Spring Harbor Symposia on Quantitative Biology
https://www.readbyqxmd.com/read/28143926/formation-of-a-repressive-complex-in-the-mammalian-circadian-clock-is-mediated-by-the-secondary-pocket-of-cry1
#4
Alicia K Michael, Jennifer L Fribourgh, Yogarany Chelliah, Colby R Sandate, Greg L Hura, Dina Schneidman-Duhovny, Sarvind M Tripathi, Joseph S Takahashi, Carrie L Partch
The basic helix-loop-helix PAS domain (bHLH-PAS) transcription factor CLOCK:BMAL1 (brain and muscle Arnt-like protein 1) sits at the core of the mammalian circadian transcription/translation feedback loop. Precise control of CLOCK:BMAL1 activity by coactivators and repressors establishes the ∼24-h periodicity of gene expression. Formation of a repressive complex, defined by the core clock proteins cryptochrome 1 (CRY1):CLOCK:BMAL1, plays an important role controlling the switch from repression to activation each day...
January 31, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/28123577/per2-participates-in-akt-mediated-drug-resistance-in-a549-ddp-lung-adenocarcinoma-cells
#5
Bo Chen, Yaoxi Tan, Yan Liang, Yan Li, Lei Chen, Shuangshuang Wu, Wei Xu, Yan Wang, Weihong Zhao, Jianqing Wu
Period2 (Per2) is a key mammalian circadian clock protein, and additionally has a tumor suppressive function. The present study aimed to investigate its role in drug resistance in A549/cisplatin (DDP) lung adenocarcinoma cells. Per2 knockdown and overexpression in A549/DDP cells were used to compare cell proliferation (by MTT assay), apoptosis (active-caspase 3 western blot) and clone forming assay. The activation of AKT/mechanistic target of rapamycin (mTOR) was investigated by a western blot assay. The Per2 expression level was decreased in A549/DDP cells compared with A549 cells...
January 2017: Oncology Letters
https://www.readbyqxmd.com/read/28114877/modulation-of-circadian-clocks-by-nutrients-and-food-factors
#6
Hideaki Oike
Daily activity rhythms that are dominated by internal clocks are called circadian rhythms. A central clock is located in the suprachiasmatic nucleus of the hypothalamus, and peripheral clocks are located in most mammalian peripheral cells. The central clock is entrained by light/dark cycles, whereas peripheral clocks are entrained by feeding cycles. The effects of nutrients on the central and peripheral clocks have been investigated during the past decade and much interaction between them has come to light...
January 24, 2017: Bioscience, Biotechnology, and Biochemistry
https://www.readbyqxmd.com/read/28112045/in-depth-characterization-of-firefly-luciferase-as-a-reporter-of-circadian-gene-expression-in-mammalian-cells
#7
Kevin A Feeney, Marrit Putker, Marco Brancaccio, John S O'Neill
Firefly luciferase (Fluc) is frequently used to report circadian gene expression rhythms in mammalian cells and tissues. During longitudinal assays it is generally assumed that enzymatic substrates are in saturating excess, such that total bioluminescence is directly proportional to Fluc protein level. To test this assumption, we compared the enzyme kinetics of purified luciferase with its activity in mammalian cells. We found that Fluc activity in solution has a lower Michaelis constant (Km) for luciferin, lower temperature dependence, and lower catalytic half-life than Fluc in cells...
December 2016: Journal of Biological Rhythms
https://www.readbyqxmd.com/read/28065650/network-dynamics-mediate-circadian-clock-plasticity
#8
Abdelhalim Azzi, Jennifer A Evans, Tanya Leise, Jihwan Myung, Toru Takumi, Alec J Davidson, Steven A Brown
A circadian clock governs most aspects of mammalian behavior. Although its properties are in part genetically determined, altered light-dark environment can change circadian period length through a mechanism requiring de novo DNA methylation. We show here that this mechanism is mediated not via cell-autonomous clock properties, but rather through altered networking within the suprachiasmatic nuclei (SCN), the circadian "master clock," which is DNA methylated in region-specific manner. DNA methylation is necessary to temporally reorganize circadian phasing among SCN neurons, which in turn changes the period length of the network as a whole...
January 18, 2017: Neuron
https://www.readbyqxmd.com/read/28057520/molecular-basis-for-the-regulation-of-the-circadian-clock-kinases-ck1%C3%AE-and-ck1%C3%AE%C2%B5
#9
REVIEW
Yu Yang, Tingting Xu, Yunfei Zhang, Ximing Qin
CK1δ and CK1ε are unique in the casein kinase 1 family and play critical roles in a number of physiological intracellular pathways. In particular, these kinases are involved in composing the mammalian circadian clock by phosphorylating core clock proteins. Considering that CK1δ/ε phosphorylate other key biological molecules, such as β-catenin and p53, understanding how the kinase activity is regulated would be greatly significant, since they are potential targets to develop pharmacological agents against cancer, pain, and circadian disorders...
February 2017: Cellular Signalling
https://www.readbyqxmd.com/read/28051908/antimicrobial-capacity-of-the-freshwater-planarians-against-s-aureus-is-under-the-control-of-timeless
#10
Landry Laure Tsoumtsa, Cedric Torre, Virginie Trouplin, Benjamin Coiffard, Gregory Gimenez, Jean-Louis Mege, Eric Ghigo
Planarians, which are non-parasitic flatworms, are highly resistant to bacterial infections. To better understand the mechanisms underlying this resistance, we investigated the role of the circadian machinery in the anti-bacterial response of the freshwater planarian Schmidtea mediterranea. We identified Smed-Tim from S. mediterranea as a homolog of the mammalian clock gene Tim. We showed via RNA interference that Smed-Tim is required for the anti-microbial activities of Schmidtea mediterranea against Staphylococcus aureus infection during the light/dark cycle...
January 4, 2017: Virulence
https://www.readbyqxmd.com/read/28025148/circadian-clock-and-steroidogenic-related-gene-expression-profiles-in-mouse-leydig-cells-following-dexamethasone-stimulation
#11
Huatao Chen, Lei Gao, Yongjie Xiong, Dan Yang, Cuimei Li, Aihua Wang, Yaping Jin
Previous studies have shown that circadian clock genes are expressed in mammalian testes; however, it remains unclear if the expression patterns of these genes are cyclic. Furthermore, it is unknown whether Leydig cells, the primary androgen secreting cells in the testis, play a role in the rhythmicity of circadian clock and steroidogenic-related gene transcription. Here, we examine the circadian clock of mouse Leydig cells, and the link to steroidogenic-related gene transcription. We confirm, via sampling over a full circadian time (CT) period, a lack of circadian rhythmicity in mouse testes in comparison with the robust gene expression cycling of circadian clock genes in mouse livers...
January 29, 2017: Biochemical and Biophysical Research Communications
https://www.readbyqxmd.com/read/28017587/knockout-rescue-embryonic-stem-cell-derived-mouse-reveals-circadian-period-control-by-quality-and-quantity-of-cry1
#12
Koji L Ode, Hideki Ukai, Etsuo A Susaki, Ryohei Narumi, Katsuhiko Matsumoto, Junko Hara, Naoshi Koide, Takaya Abe, Masato T Kanemaki, Hiroshi Kiyonari, Hiroki R Ueda
To conduct comprehensive characterization of molecular properties in organisms, we established an efficient method to produce knockout (KO)-rescue mice within a single generation. We applied this method to produce 20 strains of almost completely embryonic stem cell (ESC)-derived mice ("ES mice") rescued with wild-type and mutant Cry1 gene under a Cry1(-/-):Cry2(-/-) background. A series of both phosphorylation-mimetic and non-phosphorylation-mimetic CRY1 mutants revealed that multisite phosphorylation of CRY1 can serve as a cumulative timer in the mammalian circadian clock...
January 5, 2017: Molecular Cell
https://www.readbyqxmd.com/read/28006027/evidence-for-weakened-intercellular-coupling-in-the-mammalian-circadian-clock-under-long-photoperiod
#13
M Renate Buijink, Assaf Almog, Charlotte B Wit, Ori Roethler, Anneke H O Olde Engberink, Johanna H Meijer, Diego Garlaschelli, Jos H T Rohling, Stephan Michel
For animals living in temperate latitudes, seasonal changes in day length are an important cue for adaptations of their physiology and behavior to the altered environmental conditions. The suprachiasmatic nucleus (SCN) is known as the central circadian clock in mammals, but may also play an important role in adaptations to different photoperiods. The SCN receives direct light input from the retina and is able to encode day-length by approximating the waveform of the electrical activity rhythm to the duration of daylight...
2016: PloS One
https://www.readbyqxmd.com/read/27992087/urokinase-type-plasminogen-activator-modulates-mammalian-circadian-clock-phase-regulation-in-tissue-type-plasminogen-activator-knockout-mice
#14
Joanna M Cooper, Ashutosh Rastogi, Jessica A Krizo, Eric M Mintz, Rebecca A Prosser
Glutamate phase shifts the circadian clock in the mammalian suprachiasmatic nucleus (SCN) by activating NMDA receptors. Tissue-type plasminogen activator (tPA) gates phase shifts by activating plasmin to generate m(ature)BDNF, which binds TrkB receptors allowing clock phase shifts. Here we investigate phase shifting in tPA knockout (tPA(-/-) ; B6.129S2-Plat(tm1Mlg) /J) mice, and identify urokinase-type plasminogen activator (uPA) as an additional circadian clock regulator. Behavioral activity rhythms in tPA(-/-) mice entrain to a light-dark (LD) cycle and phase shift in response to nocturnal light pulses with no apparent loss in sensitivity...
December 19, 2016: European Journal of Neuroscience
https://www.readbyqxmd.com/read/27990019/transcriptional-architecture-of-the-mammalian-circadian-clock
#15
REVIEW
Joseph S Takahashi
Circadian clocks are endogenous oscillators that control 24-hour physiological and behavioural processes in organisms. These cell-autonomous clocks are composed of a transcription-translation-based autoregulatory feedback loop. With the development of next-generation sequencing approaches, biochemical and genomic insights into circadian function have recently come into focus. Genome-wide analyses of the clock transcriptional feedback loop have revealed a global circadian regulation of processes such as transcription factor occupancy, RNA polymerase II recruitment and initiation, nascent transcription, and chromatin remodelling...
December 19, 2016: Nature Reviews. Genetics
https://www.readbyqxmd.com/read/27942033/feedback-loops-of-the-mammalian-circadian-clock-constitute-repressilator
#16
J Patrick Pett, Anja Korenčič, Felix Wesener, Achim Kramer, Hanspeter Herzel
Mammals evolved an endogenous timing system to coordinate their physiology and behaviour to the 24h period of the solar day. While it is well accepted that circadian rhythms are generated by intracellular transcriptional feedback loops, it is still debated which network motifs are necessary and sufficient for generating self-sustained oscillations. Here, we systematically explore a data-based circadian oscillator model with multiple negative and positive feedback loops and identify a series of three subsequent inhibitions known as "repressilator" as a core element of the mammalian circadian oscillator...
December 2016: PLoS Computational Biology
https://www.readbyqxmd.com/read/27936378/genome-wide-identification-of-neuronal-activity-regulated-genes-in-drosophila
#17
Xiao Chen, Reazur Rahman, Fang Guo, Michael Rosbash
Activity-regulated genes (ARGs) are important for neuronal functions like long-term memory and are well-characterized in mammals but poorly studied in other model organisms like Drosophila. Here we stimulated fly neurons with different paradigms and identified ARGs using high-throughput sequencing from brains as well as from sorted neurons: they included a narrow set of circadian neurons as well as dopaminergic neurons. Surprisingly, many ARGs are specific to the stimulation paradigm and very specific to neuron type...
December 9, 2016: ELife
https://www.readbyqxmd.com/read/27929128/extraordinary-behavioral-entrainment-following-circadian-rhythm-bifurcation-in-mice
#18
Elizabeth M Harrison, Thijs J Walbeek, Jonathan Sun, Jeremy Johnson, Qays Poonawala, Michael R Gorman
The mammalian circadian timing system uses light to synchronize endogenously generated rhythms with the environmental day. Entrainment to schedules that deviate significantly from 24 h (T24) has been viewed as unlikely because the circadian pacemaker appears capable only of small, incremental responses to brief light exposures. Challenging this view, we demonstrate that simple manipulations of light alone induce extreme plasticity in the circadian system of mice. Firstly, exposure to dim nocturnal illumination (<0...
December 8, 2016: Scientific Reports
https://www.readbyqxmd.com/read/27926536/a-minimal-titration-model-of-the-mammalian-dynamical-heat-shock-response
#19
Aude Sivéry, Emmanuel Courtade, Quentin Thommen
Environmental stress, such as oxidative or heat stress, induces the activation of the heat shock response (HSR) and leads to an increase in the heat shock proteins (HSPs) level. These HSPs act as molecular chaperones to maintain cellular proteostasis. Controlled by highly intricate regulatory mechanisms, having stress-induced activation and feedback regulations with multiple partners, the HSR is still incompletely understood. In this context, we propose a minimal molecular model for the gene regulatory network of the HSR that reproduces quantitatively different heat shock experiments both on heat shock factor 1 (HSF1) and HSPs activities...
December 7, 2016: Physical Biology
https://www.readbyqxmd.com/read/27922612/the-intricate-dance-of-post-translational-modifications-in-the-rhythm-of-life
#20
REVIEW
Arisa Hirano, Ying-Hui Fu, Louis J Ptáček
Endogenous biological rhythms with approximately 24-h periodicity are generated by the circadian clock, in which clock genes coordinate with one another and form a transcriptional-translational negative feedback loop. The precision of the circadian clock is further regulated by multiple post-translational modifications (PTMs), including phosphorylation, ubiquitination, acetylation and SUMOylation. Here, we review current understanding of the regulatory mechanisms of the core clock proteins by PTMs in the mammalian circadian clock...
December 6, 2016: Nature Structural & Molecular Biology
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