Project description:Physiology is regulated by interconnected cell and tissue circadian clocks. Disruption of the rhythms generated by this interconnectedness is associated with metabolic disease. Here we tested the interactions between clocks in two critical components of organismal metabolism – liver and skeletal muscle – by rescuing clock function either in each organ separately, or in both organs simultaneously, in otherwise clock-less mice. Experiments revealed that individual clocks are partially sufficient for tissue glucose metabolism, yet the connections between both tissue clocks coupled with daily feeding rhythms maximizes systemic glucose tolerance. This synergy relies in part on local transcriptional control of the glucose machinery, feeding-responsive signals such as insulin, and metabolic cycles that connect the muscle and liver. We posit that spatiotemporal mechanisms of muscle and liver play an essential role in the maintenance of systemic glucose homeostasis, and that disrupting this diurnal coordination can contribute to the metabolic disease.
Project description:Cell-autonomous circadian oscillations strongly influence tissue physiology and pathophysiology of peripheral organs. Recent in vivo findings in the heart demonstrate that the circadian clock controls oscillatory gene expression programs in the adult myocardium. However, whether in vitro human embryonic stem (ES) cell-derived cardiomyocytes can establish circadian rhythmicity is unknown. Here we report that while undifferentiated human ES cells do not possess a functional clock, oscillatory expression of known core clock genes emerges during directed cardiac differentiation, with robust rhythms in day 30 cardiomyocytes. Our data reveal a stress related oscillatory network of genes that underlies a time-dependent response to doxorubicin, a frequently used anti-cancer drug with cardiotoxic side effects. These results provide a set of oscillatory genes that is relevant to functional cardiac studies and that can be deployed to uncover the potential contribution of the clock to other processes such as cardiac regeneration.
Project description:Circadian clocks drive ~24 hr rhythms in tissue physiology. They rely on transcriptional/translational feedback loops driven by interacting networks of clock complexes.To gain insights into the role of the mammary clock, circadian time-series microarrays were performed to identify rhythmic genes in vivo. Breast tissues were isolated at 4 hr intervals for two circadian (24 hourly) cycles, from mice kept under constant darkness to avoid any light- or dark-driven genes.
Project description:Though it is well established that immunological functions of CD4+ T cells are time of day-dependent, the underlying molecular mechanisms remain largely obscure. To address the question whether T cells themselves harbor a functional clock driving circadian rhythms of immune function, we analyzed clock gene expression and immune responses of CD4+ T cells purified from blood of healthy subjects at different time points throughout the day. Circadian clock function as well as immune function was further analyzed in cultivated T cells and circadian clock reporter systems. We found robust rhythms of clock gene expression as well as, after stimulation, of IFN-g production and CD40L expression in both freshly isolated and in cultured CD4+ T cells. Moreover, circadian luciferase reporter activities in CD4+ T cells and in thymic sections from PER2::LUCIFERASE reporter mice suggest that endogenous T cell clock rhythms are self-sustained under constant culture conditions. Microarray analysis of stimulated CD4+ T cell cultures revealed a rhythmic regulation of the NF-kB pathway as a candidate mechanism regulating circadian immune responses. Collectively, these data demonstrate for the first time that CD4+ T cell responses are regulated by an intrinsic cellular circadian oscillator capable of driving rhythmic adaptive immune responses in vitro and in vivo. The study is designed with 3 biological replicates from three different time points.
Project description:In mammals, temporally coordinated daily rhythms of behaviour and physiology are generated by a multi-oscillatory circadian system, entrained through cyclic environmental cues (e.g. light). Presence of niche-dependent physiological time cues have been proposed to allow local tissues flexibility of adopting a different phase relationship if circumstances require. Up till now, such tissue-unique stimuli have remained elusive. Here we show that cycles of mechanical loading and osmotic stimuli within physiological range drive rhythmic expression of clock genes and reset clock phase and amplitude in cartilage and intervertebral disc tissues.
Project description:Evolutionary conserved biological rhythms play a fundamental role in the physiology and behavior of all light-sensitive organisms. Generation of rhythmic expression of clock-controlled genes is orchestrated by a molecular circadian clock constitutes by interconnected negative feedback loops of transcription factors. In this study, we want to characterize gene which also present a rhythmic translation through the characterization of genes with a rhythmic polysomal/total RNA ratio.
Project description:Circadian rhythms are a series of endogenous autonomous 24-hour oscillations generated by the circadian clock. At the molecular level, the circadian clock is generated by a transcription-translation feedback loop, where BMAL1 and CLOCK transcription factors of the positive arm activate the expression of CRYPTOCHROME and PERIOD (PER) genes of the negative arm as well as the circadian clock-regulated genes. In this project, we aimed at finding the interactome of PER2 protein in human U2OS osteosarcoma cell line using proximity-dependent biotin identification (BioID) technique. U2OS clones overexpressing PER2-BioID2 or BioID2 were treated with dexamethasone in order to reset the circadian rhythm, and cells were then incubated in biotin-containing media for 12 hours to label the proteins in close proximity of PER2-BioID2. Samples were collected after 36 and 48 hours of the resetting to identify the labeled proteins by mass spectrometry. In addition to known interactors such as CRY1 and CRY2, many novel interactors were identified. In summary, we obtained a network of PER2 interactome and confirmed some of the novel interactions using classical the co-immunoprecipitation method.
Project description:We report the emergence of an endogenous circadian clock in mouse fetal kidney that regulates organogenesis. We detect circadian rhythms both in vivo with transcriptional profiling and ex vivo by bioluminescence. High-resolution structural analysis of embryonic explants reveals that global or local clock disruption results in defects that resemble human congenital abnormalities of the kidney. The onset of fetal rhythms strongly correlates with the timing of a distinct transition in branching and growth rates during a gestational window of high fetal growth demands. Defects in clock mutants typically have been attributed to accelerated aging, however, our study establishes a role for the fetal circadian clock as a developmental timer that regulates the pathways that control organogenesis, branching rate and nephron number, and thus plays a fundamental role in kidney development.
Project description:Evolutionary conserved biological rhythms play a fundamental role in the physiology and behavior of all light-sensitive organisms. Generation of rhythmic expression of clock-controlled genes is orchestrated by a molecular circadian clock constitutes by interconnected negative feedback loops of transcription factors. In this study, we want to characterize gene which also present a rhythmic translation through the characterization of genes with a rhythmic polysomal/total RNA ratio. Analyze of gene expression in liver total RNA and polysomal RNA harvested every 2 hrs during 2 series of 48 hrs, 2 mice per samples