Energy Balance Drives Diurnal and Nocturnal Brain Transcriptome Rhythms
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ABSTRACT: Plasticity in the daily timing of activity has been observed in a wide variety of species, yet the underlying mechanisms driving nocturnality and diurnality remain to be discovered. By regulating how much wheel-running activity will be rewarded with a food pellet, we can manipulate energy balance, and switch mice to be nocturnal or diurnal. Here we present the rhythmic transcriptome of 21 tissues, including 17 brain regions (hypothalamic, thalamic, cortical), sampled every 4 hours over a 24-hour period from nocturnal and diurnal male CBA/CaJ mice. Rhythmic gene expression across tissues comprised a different set of genes with minimal overlap between nocturnal and diurnal mice. We show that genes other than clock genes in the suprachiasmatic nucleus (SCN) of nocturnal and diurnal mice change, and the habenula was the most affected tissue. Our results indicate that adaptive flexibility in daily timing of behavior is supported by gene expression dynamics in many tissues and brain regions, especially in the habenula, which suggests a crucial role for the observed nocturnal-diurnal switch.
Project description:Spatio-temporal gene expression patterns underlie time-of-the day specific functional specialization of different organs. Although circadian gene expression atlases from model organisms including the nocturnal mouse are available, they are limited to a few peripheral organs. Here we report the circadian transcriptome of 64 different tissues, including 22 different brain regions, sampled every 2 h over 24 h, from the diurnal primate Papio Anubis. We found that the primate genome is vastly rhythmic with up to 67% of genes showing daily rhythms in expression. In addition to the diversity of transcripts in each tissue, the repertoire and phases of expression of cycling transcripts impart another layer of functional specialization to each tissue. Transcripts that are ubiquitously expressed and participate in essential cellular functions are more likely to exhibit rhythmic expression in a tissue-specific manner. At the whole organism level, the peak phases of rhythmic transcripts are largely clustered around dawn and dusk with a "quiescent period" during the first half of the night. Our findings also unveil a different temporal organization of central and peripheral tissues between diurnal and nocturnal animals. This study will contribute significantly to understanding circadian regulation of organs function and contribution of circadian rhythm disruption to diseases.
Project description:The cellular landscape of most eukaryotic cells changes dramatically over the course of a 24h day. Whilst the proteome responds directly to daily environmental cycles, it is also regulated by a cellular circadian clock that anticipates the differing demands of day and night. To quantify the relative contribution of diurnal versus circadian regulation, we mapped spatiotemporal proteome dynamics under 12h:12h light:dark cycles compared with constant light. Using Ostreococcus tauri, a prototypical eukaryotic cell, we achieved 85% coverage of the theoretical proteome and provided an unprecedented insight into the identity of proteins that drive and facilitate rhythmic cellular functions. Surprisingly, the overlap between diurnally- and circadian-regulated proteins was quite modest (11%). These proteins exhibited different phases of oscillation between the two conditions, consistent with an interaction between intrinsic and extrinsic regulatory factors. The relative amplitude of rhythmic protein abundance was much lower than would be expected from daily variations in transcript abundance. Transcript rhythmicity was poorly predictive of daily variation in abundance of the encoded protein. We observed coordination between the rhythmic regulation of organelle-encoded proteins with the nuclear-encoded proteins that are targeted to organelles. Rhythmic transmembrane proteins showed a remarkably different phase distribution compared with rhythmic soluble proteins, indicating the existence of a novel circadian regulatory process specific to the biogenesis and/or degradation of membrane proteins. Taken together, our observations argue that the daily spatiotemporal regulation of cellular proteome composition is not dictated solely by clock-regulated gene expression. Instead, it also involves extensive rhythmic post-transcriptional, translational, and post-translational regulation that is further modulated by environmental timing cues.
Project description:Rhythmic oscillations of physiological processes depend on integrating the circadian clock and diurnal environment. DNA methylation is epigenetically responsive to daily rhythms, as a subset of CpG dinucleotides in brain exhibit diurnal rhythmic methylation. A major genetic effect on rhythmic methylation was identified in a mouse Snord116 deletion model of the imprinted disorder Prader-Willi syndrome (PWS). > 23,000 diurnally rhythmic CpGs were identified in wild-type cortex, with nearly all lost or phase-shifted in PWS. Circadian dysregulation of a second imprinted Snord cluster at the Temple/Kagami-Ogata syndrome locus was observed at the level of methylation, transcription, and chromatin, providing mechanistic evidence of cross-talk. Genes identified by diurnal epigenetic changes in PWS mice overlapped rhythmic and PWS-specific genes in human brain and were enriched for PWS-relevant phenotypes and pathways. These results support the proposed evolutionary relationship between imprinting and sleep, and suggest possible chronotherapy in the treatment of PWS and related disorders.
Project description:Diurnal oscillations of gene expression controlled by the circadian clock underlie rhythmic physiology across most living organisms. Although such rhythms have been extensively studied at the level of transcription and mRNA accumulation, little is known about the accumulation patterns of proteins. Here, we quantified temporal profiles in the murine hepatic proteome under physiological light–dark conditions using stable isotope labeling by amino acids quantitative MS. To measure the daily accumulation of proteins, we designed an SILAC MS experiment, in which total protein extracts were harvested from C57BL/6J mice every 3 h for 2 d (eight samples per day). Relative protein abundance in each of 16 samples was quantified against a common reference sample labeled using the SILAC method. The generated mass spectra allowed the identification of a total of 5,827 distinct proteins, of which 70% yielded relative measurements in at least 8 of 16 samples. Our analysis identified over 5,000 proteins, of which several hundred showed robust diurnal oscillations with peak phases enriched in the morning and during the night and related to core hepatic physiological functions. Combined mathematical modeling of temporal protein and mRNA profiles indicated that proteins accumulate with reduced amplitudes and significant delays, consistent with protein half-life data. Moreover, a group comprising about one-half of the rhythmic proteins showed no corresponding rhythmic mRNAs, indicating significant translational or posttranslational diurnal control. Such rhythms were highly enriched in secreted proteins accumulating tightly during the night. Also, these rhythms persisted in clock-deficient animals subjected to rhythmic feeding, suggesting that food-related entrainment signals influence rhythms in circulating plasma factors
Project description:The blood brain barrier (BBB) is critical for maintaining brain homeostasis but is susceptible to inflammatory breakdown. Permeability of the BBB to polar molecules shows circadian variation due to rhythmic transporter expression, while basal permeability to polar molecules in non-rhythmic. Whether daily timing influences BBB permeability in response to inflammation is unknown. Here, we induced systemic inflammation through repeated lipopolysaccharide (LPS) injections either in the morning (ZT1) or evening (ZT13) under standard lighting conditions, then examined BBB permeability to a polar molecule. We observed clear diurnal variation in inflammatory BBB permeability, with a striking increase in BBB breakdown specifically following evening LPS injection. Evening LPS led to persisting glia activation and inflammation in the brain that was not observed in the periphery. The exaggerated evening neuroinflammation and BBB disruption were suppressed by microglial depletion, were associated with enhanced expression of the Nos2 gene, and could be prevented in vivo by treatment with an iNOS inhibitor. Our data show that diurnal rhythms in microglial inflammatory responses to LPS drive daily variability in BBB breakdown, and reveals time-of-day as a key regulator of inflammatory BBB disruption.
Project description:Nocturnal home hemodialysis (NHD) [5 – 6 times a week, 6-8 hours per session] augments uremia clearance and is associated with an increase in hemoglobin level. We have used microarray to have a global image of the changes at the gene expression. Keywords: Treatment
Project description:Altered daily patterns of hormone action are suspected to contribute to metabolic disease. It is poorly understood how the adrenal glucocorticoid hormones contribute to the coordination of daily global patterns of transcription and metabolism. Here, we examined diurnal metabolite and transcriptome patterns in a zebrafish glucocorticoid deficiency model by RNA-Seq, NMR spectroscopy and liquid chromatography-based methods. We observed dysregulation of metabolic pathways including glutaminolysis, the citrate and urea cycles and glyoxylate detoxification. Constant, non-rhythmic glucocorticoid treatment rescued many of these changes, with some notable exceptions among the amino acid related pathways. Surprisingly, the non-rhythmic glucocorticoid treatment rescued almost half of the entire dysregulated diurnal transcriptome patterns. A combination of E-box and glucocorticoid response elements is enriched in the rescued genes. This simple enhancer element combination is sufficient to drive rhythmic circadian reporter gene expression under non-rhythmic glucocorticoid exposure, revealing a permissive function for the hormones in glucocorticoid-dependent circadian transcription. Our work highlights metabolic pathways potentially contributing to morbidity in patients with glucocorticoid deficiency, even under glucocorticoid replacement therapy. Moreover, we provide mechanistic insight into the interaction between the circadian clock and glucocorticoids in the transcriptional regulation of metabolism.
Project description:Most animals restrict their activity to specific part of the day, being either diurnal, nocturnal, or crepuscular. The genetic basis underlying this diurnal preference is largely unknown. Under laboratory conditions, Drosophila melanogaster is crepuscular, showing a bi-modal activity profile. However, recent experiments in our lab indicated that high variability among individuals exist, particularly in strains that derive from different wild populations. By assembling together flies from various geographical strains, we have generated a highly diverse population whose progeny exhibited extreme diurnal preference, including diurnal and nocturnal flies. We have used this population as a starting point for an artificial selection experiment in which we selected males that show the most extreme diurnal preference and mated them to their sisters. The response to selection was strong, and already after 10 selection cycles we obtained highly diurnal (D) and nocturnal (N) strains. Another strain that was not selected and showed intermediate behaviour (crepuscular) served as a control (C). These strains provide us with a unique opportunity to understand the genetics of diurnal preference.