Project description:Circadian clocks coordinate time-of-day specific metabolic and physiological processes to maximize performance and fitness. In addition to light, which is considered the strongest time cue to entrain animal circadian clocks, metabolic input has emerged as an important signal for clock modulation and entrainment, especially in peripheral clocks. Circadian clock proteins have been to be substrates of O-GlcNAcylation, a nutrient sensitive post-translational modification (PTM), and the interplay between clock protein O-GlcNAcylation and other PTMs, like phosphorylation, is expected to facilitate the regulation of circadian physiology by metabolic signals. Here, we used mass spectrometry proteomics to identify PTMs on PERIOD, the key biochemical timer of the Drosophila clock, over the circadian cycle.
Project description:Circadian clocks have evolved as time-measuring molecular devices to help organisms adapt their physiology to daily changes in light and temperature. Cycling transcription has been long hypothesized to account for the wealth of rhythmic protein abundance. However, cyclic degradation signals such as ubiquitylation could shape the rhythmic protein landscape as well. In order to document the circadian ubiquitylated proteome of Drosophila melanogaster, we took advantage of a new means of Ub purification based on in vivo biotinylation of AviTag-tagged ubiquitin by the BirA protein, the bioUb system. NeutrAvidin-bound fractions of head lysates were collected at four circadian times six hours apart and proteins were identified and quantified using a proteomic-based approach.
Project description:Most organisms on the earth exhibit circadian rhythms in behavior and physiology, which are driven by endogenous clocks. Phosphorylation plays a central role in timing the clock, but how this contributes to overt rhythms is unclear. Here we conducted phosphoprotemoics in conjunction with transcriptome and proteome profiling using fly heads.
Project description:Organisms have adapted to the changing environmental conditions within the 24h cycle of the day by temporally segregating tissue physiology to the optimal time of the day. On the cellular level temporal segregation of physiological processes is established by the circadian clock, a Bmal1 dependent transcriptional oscillator network. The circadian clocks within individual cells of a tissue are synchronised by environmental signals, mainly light, in order to reach temporally segregated physiology on the tissue level. However, how light mediated synchronisation of peripheral tissue clocks is achieved mechanistically and whether circadian clocks in different organs are autonomous or interact with each other to achieve rhythmicity is unknown. Here we report that light can synchronise core circadian clocks in two peripheral tissues, the epidermis and liver hepatocytes, even in the complete absence of functional clocks in any other tissue within the whole organism. On the other hand, tissue extrinsic circadian clock rhythmicity is necessary to retain rhythmicity of the epidermal clock in the absence of light, proving for the first time that the circadian clockwork acts as a memory of time for the synchronisation of peripheral clocks in the absence of external entrainment signals. Furthermore, we find that tissue intrinsic Bmal1 is an important regulator of the epidermal differentiation process whose deregulation leads to a premature aging like phenotype of the epidermis. Thus, our results establish a new model for the segregation of peripheral tissue physiology whereby the synchronisation of peripheral clocks is acquired by the interaction of a light dependent but circadian clock independent pathway with circadian clockwork dependent cues.
Project description:Organisms have adapted to the changing environmental conditions within the 24h cycle of the day by temporally segregating tissue physiology to the optimal time of the day. On the cellular level temporal segregation of physiological processes is established by the circadian clock, a Bmal1 dependent transcriptional oscillator network. The circadian clocks within individual cells of a tissue are synchronised by environmental signals, mainly light, in order to reach temporally segregated physiology on the tissue level. However, how light mediated synchronisation of peripheral tissue clocks is achieved mechanistically and whether circadian clocks in different organs are autonomous or interact with each other to achieve rhythmicity is unknown. Here we report that light can synchronise core circadian clocks in two peripheral tissues, the epidermis and liver hepatocytes, even in the complete absence of functional clocks in any other tissue within the whole organism. On the other hand, tissue extrinsic circadian clock rhythmicity is necessary to retain rhythmicity of the epidermal clock in the absence of light, proving for the first time that the circadian clockwork acts as a memory of time for the synchronisation of peripheral clocks in the absence of external entrainment signals. Furthermore, we find that tissue intrinsic Bmal1 is an important regulator of the epidermal differentiation process whose deregulation leads to a premature aging like phenotype of the epidermis. Thus, our results establish a new model for the segregation of peripheral tissue physiology whereby the synchronisation of peripheral clocks is acquired by the interaction of a light dependent but circadian clock independent pathway with circadian clockwork dependent cues.
Project description:Organisms exhibit daily oscillations in metabolite abundance. These oscillations could arise from circadian clock control of metabolic pathways in peripheral tissues, or may be secondary to rhythmic food intake, which is primarily controlled by central circadian clocks in the brain. To determine the relative contribution of central and peripheral clocks and behavioral cycles to metabolic rhythms in the fruit fly, Drosophila melanogaster, we conducted large-scale metabolite profiling with fine temporal resolution across multiple days in control flies with intact molecular clocks and in flies where CRISPR/Cas9 gene editing was used to specifically eliminate molecular circadian clock function in the fat body, a peripheral metabolic tissue, or the brain. As these latter flies lack feeding rhythms due to central circadian clock dysfunction, we also included an experimental cohort of flies which lacked central brain clocks but were subjected to time-restricted feeding (TRF) protocols to impose feeding rhythms. Single-nuclei RNA sequencing confirmed selective molecular clock elimination following fat body manipulations, which was associated with predicted alterations in clock gene expression and an attenuation of time-of-day differences in the abundance of fat body transcripts involved in key metabolic pathways. Interestingly, we identified few rhythmically expressed metabolites in flies that were allowed ad libitum food access. In contrast, flies which lacked brain clocks but were raised on TRF exhibited robust circadian abundance rhythms across a large range of metabolites. These findings suggest that metabolic rhythms in Drosophila are more strongly regulated by feeding cycles than by direct circadian clock control of metabolic pathways despite the presence of metabolic genes that exhibit local-clock dependent modulation of expression across the day.
Project description:Mammals rely on a network of circadian clocks to control daily systemic metabolism and physiology. The central pacemaker in the suprachiasmatic nucleus (SCN) is considered hierarchically dominant over peripheral clocks, whose degree of independence, or tissue-level autonomy, has never been ascertained in vivo. Using arrhythmic Bmal1-null mice, we generated animals with reconstituted circadian expression of BMAL1 exclusively in the liver (Liver-RE). High-throughput transcriptomics and metabolomics show that the liver has independent circadian functions specific for metabolic processes such as the NAD+ salvage pathway and glycogen turnover. However, although BMAL1 occupies chromatin at most genomic targets in Liver-RE mice, circadian expression is restricted to ∼10% of normally rhythmic transcripts. Finally, rhythmic clock gene expression is lost in Liver-RE mice under constant darkness. Hence, full circadian function in the liver depends on signals emanating from other clocks, and light contributes to tissue-autonomous clock function.
Project description:Polymethoxylated flavones (PMFs) are a group of natural compounds known to display a wide array of beneficial effects to promote physiological fitness. Recent studies revealed circadian clocks as an important cellular mechanism mediating the preventive efficacy of the major PMF Nobiletin against metabolic disorders. Sudachitin is a PMF enriched in Citrus sudachi, and its functions and mechanism of action are poorly understood. Using circadian reporter cells, we showed that Sudachitin modulated circadian amplitude and period of Bmal1 promoter-driven reporter rhythms, and real-time qPCR analysis showed that Sudachitin altered expression of core clock genes, notably Bmal1, at both transcript and protein levels. Mass-spec analysis revealed systemic exposure in vivo. In mice fed with high-fat diet with or without Sudachitin, we observed increased nighttime activity and daytime sleep, accompanied by significant metabolic improvements in a circadian time-dependent manner, including respiratory quotient, blood lipid and glucose profiles and liver physiology. Focusing on the liver, RNA-sequencing and metabolomic analyses revealed prevalent diurnal remodeling in both gene expression and metabolite accumulation. Taken together, our study elucidates Sudachitin as a new clock-modulating PMF with hepatic remodeling functions to improve systemic metabolic homeostasis, and highlights the circadian clock as a fundamental mechanism to safeguard physiological well-being.