Project description:Many different functions are regulated by circadian rhythms, including those orchestrated by discrete clock neurons within animal brains. To comprehensively characterize and assign cell identity to the 75 pairs of Drosophila circadian neurons, we optimized a single cell RNA sequencing method and assayed clock neuron gene expression at different times of day. The data identify at least 17 clock neuron categories with striking spatial regulation of gene expression. Transcription factor regulation is prominent and likely contributes to the robust circadian oscillation of many transcripts, including those that encode cell-surface proteins previously shown to be important for cell recognition and synapse formation during development. The many other clock-regulated genes also constitute an important resource for future mechanistic and functional studies between clock neurons and/or for temporal signaling to circuits elsewhere in the fly brain.
Project description:Comparison of pancreatic islet transcriptome at 4hr intervals around the clock helps to identify genes that are cycling under the control of the circadian clock. We used Agilent microarrays to analyze pancreatic islet transcriptome at different time points across the circadian cycle.
Project description:To compare circadian gene expression within highly discrete neuronal populations, we separately purified and characterized two adjacent but distinct groups of Drosophila adult circadian neurons: the 8 small and 10 large PDF (pigment-dispersing factor)-expressing ventral lateral neurons (s-LNvs and l-LNvs, respectively). The s-LNvs are the principal circadian pacemaker cells, whereas recent evidence indicates that the l-LNvs are involved in sleep and light-mediated arousal. Although half of the l-LNv-enriched mRNA population including core clock mRNAs is shared between the l-LNvs and s-LNvs, the other half is l-LNv- and s-LNv specific. The distribution of four specific mRNAs is consistent with prior characterization of the four encoded proteins and therefore indicates successful purification of the two neuronal types. Moreover, an octopamine receptor mRNA is selectively enriched in l-LNvs, and only these neurons respond to in vitro application of octopamine. Dissection and purification of l-LNvs from flies collected at different times indicate that these neurons contain cycling clock mRNAs with higher circadian amplitudes as well as at least a 10-fold higher fraction of oscillating mRNAs than all previous analyses of head RNA. Many of these cycling l-LNv mRNAs are well-expressed but do not cycle or cycle much less well elsewhere in heads. The results suggest that RNA cycling is much more prominent in circadian neurons than elsewhere in heads and may be particularly important for the functioning of these neurons. Gene expression was profiled in purified large PDF neurons across 4 time-points and small PDF neurons at two time-points under an LD cycle. Circadian neurons (PDF large and small cells), general neurons (ELAV) and per01:large PDF cells were labeled by GFP using specfic drivers. Expression of these cells types were profiled after manual cell sorting of GFP-positive cells at different time-points under a light/dark (LD) cycle. The time-points included ZT0, ZT6, ZT12, and ZT18 in the case of large PDF cells, and ZT0 and ZT12 in the case of small PDF cells, ELAV cells and per01:large PDF cells. 3 biological replicates were collected for the large PDF cells and ELAV cells at ZT0 and ZT12. 2 replicates were collected for large PDF cells at ZT6 and ZT18, small PDF cells, and per01:large PDF cells.
Project description:To compare circadian gene expression within highly discrete neuronal populations, we separately purified and characterized two adjacent but distinct groups of Drosophila adult circadian neurons: the 8 small and 10 large PDF (pigment-dispersing factor)-expressing ventral lateral neurons (s-LNvs and l-LNvs, respectively). The s-LNvs are the principal circadian pacemaker cells, whereas recent evidence indicates that the l-LNvs are involved in sleep and light-mediated arousal. Although half of the l-LNv-enriched mRNA population including core clock mRNAs is shared between the l-LNvs and s-LNvs, the other half is l-LNv- and s-LNv specific. The distribution of four specific mRNAs is consistent with prior characterization of the four encoded proteins and therefore indicates successful purification of the two neuronal types. Moreover, an octopamine receptor mRNA is selectively enriched in l-LNvs, and only these neurons respond to in vitro application of octopamine. Dissection and purification of l-LNvs from flies collected at different times indicate that these neurons contain cycling clock mRNAs with higher circadian amplitudes as well as at least a 10-fold higher fraction of oscillating mRNAs than all previous analyses of head RNA. Many of these cycling l-LNv mRNAs are well-expressed but do not cycle or cycle much less well elsewhere in heads. The results suggest that RNA cycling is much more prominent in circadian neurons than elsewhere in heads and may be particularly important for the functioning of these neurons.
Project description:Peripheral nervous system injuries lead to long-term neurological disability due to limited axonal regenerative ability. Injury-dependent and more recently injury-independent physiological mechanisms have provided important molecular insight into regenerative mechanisms. However, whether common molecular denominators underpinning both injury-dependent and independent biological processes exist remains unclear. We initially performed a comparative analysis of recently generated transcriptomic datasets associated with the regenerative ability of sciatic dorsal root ganglia (DRG). Surprisingly, circadian rhythms were identified as a the most significantly enriched biological process associated with regenerative capability. We demonstrate that DRG neurons possess an endogenous circadian clock with a 24h oscillations of circadian genes and that their regenerative ability displays a diurnal oscillation in a mouse model of sciatic nerve injury. Consistently, transcriptomic analysis of DRG neurons showed a significant time-of-day dependent enrichment for processes associated with neuronal development and axonal growth, for regeneration and circadian associated genes, including the core clock genes Bmal1 and Clock. Indeed, DRG-specific ablation of the non-redundant clock gene Bmal1showed that it is required for regenerative gene expression, neuronal intrinsic circadian axonal regeneration and target reinnervation. Lastly, Lithium, a chrono-active compound, enhanced nerve regeneration, in wildtype but not in clock genes Bmal1 and Cry1/2-deficient mice. Together, these data demonstrate that daily rhythms and the circadian clock fine-tune the regenerative response of DRG neurons, and they advocate for the use of chrono-active strategies in time-day dependent modulation of nerve repair.
Project description:The circadian clock is comprised of proteins that form negative feedback loops, which regulate the timing of global gene expression in a coordinated 24 hour cycle. As a result, the plant circadian clock is responsible for regulating numerous physiological processes central to growth and survival. To date, most plant circadian clock studies have relied on diurnal transcriptome changes to elucidate molecular connections between the circadian clock and observable phenotypes in wild-type plants. Here, we have combined high-throughput RNA-sequencing and mass spectrometry to comparatively characterize the lhycca1, prr7prr9, gi and toc1 circadian clock mutant rosette transcriptome and proteome at the end-of-day and end-of-night.
Project description:The contribution of cis-regulatory elements to Drosophila circadian gene expression is poorly understood. We generated a series of CRISPR-mediated deletions within the regulatory regions of the circadian gene timeless (tim) and characterized them through multiple high-throughput sequencing experiments. We isolated heads from wild-type and mutant flies around the clock and performed RNA-Seq on them to determine the effects of regulatory element deletions on circadian gene expression.
Project description:As a circadian organ, liver executes diverse functions in different phase of the circadian clock. This process is believed to be driven by a transcription program. Here, we present a TF DNA-binding activity centered multi-dimensional proteomics landscape, including DNA-binding activity of TFs, the phosphorylation pattern, ubiquitylation pattern, the nuclear sub-proteome, the whole proteome as well as the transcriptome, to portrait the hierarchical circadian clock network of mouse liver. The TF DNA-binding activity indicates diurnal oscillation in four major pathways, immune response, glucose metabolism, fatty acid metabolism, and the cell cycle. We also isolated the mouse liver Kupffer cells and measured their proteomes in the circadian clock to reveal cell type resolved circadian clock. These are the most comprehensive datasets for circadian clock in the mouse liver and provided the richest data resource for the understanding of mouse liver physiology around the circadian clock.
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.