Project description:The mammalian circadian clock, expressed throughout the brain and body, controls daily metabolic homeostasis. Clock function in peripheral tissues is required, but not sufficient, for this task. Due to lack of specialized animal models, it is unclear how tissue clocks interact with extrinsic signals to drive molecular oscillations. Here, we present a model in which the interaction between feeding and the liver clock can be isolated in vivo by reconstituting Bmal1 exclusively in hepatocytes (Liver-RE) in otherwise clock-less mice. We found that the cooperative action of BMAL1 and the transcription factor CEBPB regulates daily liver metabolic transcriptional programs. Functionally, the liver clock and feeding rhythm are sufficient to drive temporal glucose homeostasis. By contrast, liver rhythms tied to redox and lipid metabolism required communication with the skeletal muscle clock, demonstrating peripheral clock cross-talk. Our results highlight how the inner workings of the clock system rely on communicating signals to maintain daily metabolism.
Project description:The mammalian circadian clock, expressed throughout the brain and body, controls daily metabolic homeostasis. Clock function in peripheral tissues is required, but not sufficient, for this task. Due to lack of specialized animal models, it is unclear how tissue clocks interact with extrinsic signals to drive molecular oscillations. Here, we present a model in which the interaction between feeding and the liver clock can be isolated in vivo by reconstituting Bmal1 exclusively in hepatocytes (Liver-RE) in otherwise clock-less mice. We found that the cooperative action of BMAL1 and the transcription factor CEBPB regulates daily liver metabolic transcriptional programs. Functionally, the liver clock and feeding rhythm are sufficient to drive temporal glucose homeostasis. By contrast, liver rhythms tied to redox and lipid metabolism required communication with the skeletal muscle clock, demonstrating peripheral clock cross-talk. Our results highlight how the inner workings of the clock system rely on communicating signals to maintain daily metabolism.
Project description:Circadian profiling was performed in mouse livers from three different genotypes/treatments: Wildtype, Clock mutant, and brain-specific Clock rescue. Rescuing Clock specifically in the brain partially rescued robust circadian and harmonic rhythms.
Project description:Circadian profiling was performed in mouse livers from three different genotypes/treatments: Wildtype, Clock mutant, and brain-specific Clock rescue. Rescuing Clock specifically in the brain partially rescued robust circadian and harmonic rhythms. Samples were collected every 2 hours for 48 hours from 2-4 mice per time point; samples were pooled and analyzed using Affymetrix Mouse Exon arrays, analyzed at the gene level.
Project description:Ketone bodies, intermediates in energy metabolism and signaling, have attracted significant attention due to their role in health and disease. We performed around the clock study on ketone bodies and ketogenesis with mice on different diets. We found that caloric restriction, a dietary intervention that improves metabolism and longevity, induced high amplitude circadian rhythms in blood βOHB. The blood βOHB rhythms resulted from rhythmic ketogenesis in the liver controlled by the interaction between the circadian clock and PPAR transcriptional networks. This interaction results in transcriptional reprogramming of in beta-oxidation and ketogenesis enzymes. The reprogramming is impaired in circadian clock mutant mice. The circadian clock gated ketogenesis contributes to the diet impact on health and longevity.
Project description:Chromatin organization plays a crucial role in gene regulation by controlling the accessibility of DNA to transcription machinery. While significant progress has been made in understanding the regulatory role of clock proteins in circadian rhythms, how chromatin organization affects circadian rhythms remains poorly understood. Here, we employed ATAC-seq (Assay for Transposase-Accessible Chromatin with Sequencing) on FAC-sorted Drosophila clock neurons to assess genome-wide chromatin accessibility at dawn and dusk over the circadian cycle. We observed significant oscillations in chromatin accessibility at promoter and enhancer regions of hundreds of genes, with enhanced accessibility either at dusk or dawn, which correlated with their peak transcriptional activity. Notably, genes with enhanced accessibility at dusk were enriched with E-box motifs, while those more accessible at dawn were enriched with VRI/PDP1-box motifs, indicating that they are regulated by the core circadian feedback loops, PER/CLK and VRI/PDP1, respectively. Further, we observed a complete loss of chromatin accessibility rhythms in per01 null mutants, with chromatin consistently accessible at both dawn and dusk, underscoring the critical role of Period protein in driving chromatin compaction during the repression phase at dawn. Together, this study demonstrates the significant role of chromatin organization in circadian regulation, revealing how the interplay between clock proteins and chromatin structure orchestrates the precise timing of biological processes throughout the day. This work further implies that variations in chromatin accessibility might play a central role in the generation of diverse circadian gene expression patterns in clock neurons.
Project description:Circadian clocks drive 24-h rhythms of physiology and behavior. The circadian clock of hepatocytes has been shown to regulate glucose metabolism, and we were interested if rescuing liver clock function can reverse metabolic impairments in hyperphagic/obese Clock-D19 mutant mice. We compared transcripomte regulation in livers (at Zeitgeber time ZT10) of wild-type (C57BL/6J) and Clock-D19 mice and Clock-D19 mice with genetic rescue of liver clock function using hydrodynamic tail vein injection of a WT-CLOCK expression plasmid