Project description:RNA editing is essential for the formation of functional properties of ionotropic glutamate channels. Previously, we demonstrated the regulation of RNA editing upon manipulation with neural activity in vitro. The hypothalamic suprachiasmatic nuclei (SCN), which serve as a master circadian pacemaker depends on glutamatergic neurotransmission, in particular for signal transmission from the retina, and they exhibit spontaneous 24h rhythmical neural activity. We observed changes in the extent of ionotropic glutamate receptor RNA editing in the SCN during the 24h cycle. Therefore, we aimed to understand the overall role of RNA editing for the mechanism of SCN function and to evaluate the impact of RNA under editing on gene expression.
Project description:The suprachiasmatic nucleus (SCN) acts as the central clock to coordinate circadian oscillations in mammalian behavior, physiology and gene expression. Despite our knowledge of the circadian transcriptome of the SCN, how it impacts genome-wide protein expression is not well understood. Here, we interrogated the murine SCN proteome across the circadian cycle using SILAC-based quantitative mass spectrometry.
Project description:Circadian rhythm governs a variety of biological processes in essentially all living organisms and microRNAs have been found to play important roles in the post-transcriptional regulation of circadian clocks. However, the microRNA expression profile in mouse central circadian clock – suprachiasmatic nucleus (SCN) is lacking. In this study, we systematically profiled microRNAs in mouse SCN and SCN subtype neurons by high sensitive small RNA sequencing and examined their potential circadian functions. We found that a large fraction of known microRNAs are SCN-specific and 20 of them are also oscillated significantly. Predicted targets of these 20 microRNAs were enriched in circadian rhythm pathway as well. Integrated analysis of microRNA and mRNA revealed 3 clock-related functional modules, demonstrating the regulation roles of miR-24, miR-30, miR-7a, miR-7b, miR125a and miR125b in SCN. Furthermore, we observed distinct microRNA profiles in SCN subtype neurons with divergent regulatory functions, which correlated with their differential spatial distribution. In addition, we also identified a proportion of light-response microRNAs in SCN, one of which was miR-7a. Further experiments showed that miR-7a directly target fos and regulated its translation in SCN. All these observations indicate important circadian regulation roles of microRNA in central circadian clock.
2021-08-18 | GSE133051 | GEO
Project description:Circadian regulation of gene expression in the SCN
Project description:Background: Identifying the gene regulatory networks governing physiological signal integration remains an important challenge in circadian biology. Epidermal growth factor receptor (EGFR) has been implicated in circadian function and EGFR is expressed in the suprachiasmatic nucleus (SCN), the core circadian pacemaker. The transcription networks downstream of EGFR in the SCN are unknown, but by analogy to other SCN inputs we expect the response to EGFR activation to depend on circadian timing and thus be “circadian context–dependent”. Results: We have undertaken a systems level analysis of EGFR circadian context–dependent signaling in the SCN. We collected gene expression profiles to study how the SCN response to EGFR activation depends on circadian timing. Mixed–model analysis of variance (ANOVA) was employed to identify genes with circadian context–dependent EGFR regulation. The expression data was integrated with transcription factor (TF) binding predictions through gene group enrichment analyses to generate robust hypotheses about TFs responsible for the circadian phase–dependent EGFR responses. Conclusions: The analysis results suggest that the transcriptional response to EGFR signaling in the SCN may be partly mediated by established EGFR signaling regulated TFs (AP1, Ets1), TFs involved in circadian clock entrainment (CREB), and by core clock TFs (Rorα). qRT-PCR measurements of several TF expression levels support a model in which circadian context-dependent EGFR responses are partly achieved by circadian regulation of upstream signaling components. Our study suggests an important role for EGFR signaling in SCN function and provides an example for gaining physiological insights through systems-level analysis. Keywords: dose response; repeat sample
Project description:To screen for specific circadian outputs that may distinguish the pacemaker in the mammalian suprachiasmatic nucleus (SCN) from peripheral-type oscillators in which the canonical clockworks are similarly regulated in a circadian manner, the rhythmic behavior of the transcriptome in forskolin-stimulated NIH/3T3 fibroblasts was analyzed and compared to that found in the rat SCN in vivo and SCN2.2 cells in vitro. Similar to the scope of circadian gene expression in SCN2.2 cells and the rat SCN, NIH/3T3 fibroblasts exhibited circadian fluctuations in the expression of the core clock genes, Per2, Bmal1 (Mop3), and Cry1 and 323 functionally diverse transcripts (2.6%), many of which were involved in cell communication. Overlap in rhythmically-expressed transcripts among NIH/3T3 fibroblasts, SCN2.2 cells and the rat SCN was limited to these clock genes and four other genes that mediate fatty acid and lipid metabolism or function as nuclear factors. Compared to NIH/3T3 cells, circadian gene expression in SCN oscillators was more prevalent among cellular pathways mediating glucose metabolism and neurotransmission. Coupled with evidence for the rhythmic regulation of the inducible isoform of nitric oxide synthase, the enzyme responsible for the production of nitric oxide, in SCN2.2 cells and the rat SCN but not in fibroblasts, studies examining the effects of a NOS inhibitor on metabolic rhythms in co-cultures containing SCN2.2 cells and untreated NIH/3T3 cells suggest that this gaseous neurotransmitter may play a key role in SCN pacemaker function. Thus, this comparative analysis of circadian gene expression in SCN and non-SCN cells may have important implications in the selective identification of circadian signals involved in the coupling of SCN oscillators and the regulation of rhythmicity in downstream cells or tissues. Keywords: Circadian time course
Project description:Mammalian circadian behaviors are orchestrated by suprachiasmatic nucleus (SCN) in the hypothalamus. Yet basic SCN cell types and their roles in circadian pacemaking are still unclear. In this study, we comprehensively characterized the basic cell types of SCN and their circadian and light-induced gene expression. In SCN, we identified seven major cell types among which neurons, astrocytes, ependymocytes and endothelial cells display cell-type specific circadian gene expression. We found that five SCN neuron subtypes, Avp+/Nms+, Vip+/Nms+, Vip+/Grp+, Cck+/C1ql3+ and Cck+/Bdnf+, differ in their spatial distribution, circadian rhythmicity and light responsiveness. Among the rhythmic neuron subtypes, we observed a wave of circadian gene expression propagating from the subtypes in posterior SCN to the subtypes in anterior SCN. Such wave can be explained by the neuropeptide-receptor signaling network in which Avp+/Nms+ subtype is the leader of circadian oscillations. Our study provides insights into the basic neural mechanism of circadian pacemaking in mammals.
Project description:Mammalian circadian behaviors are orchestrated by suprachiasmatic nucleus (SCN) in the hypothalamus. Yet basic SCN cell types and their roles in circadian pacemaking are still unclear. In this study, we comprehensively characterized the basic cell types of SCN and their circadian and light-induced gene expression. In SCN, we identified seven major cell types among which neurons, astrocytes, ependymocytes and endothelial cells display cell-type specific circadian gene expression. We found that five SCN neuron subtypes, Avp+/Nms+, Vip+/Nms+, Vip+/Grp+, Cck+/C1ql3+ and Cck+/Bdnf+, differ in their spatial distribution, circadian rhythmicity and light responsiveness. Among the rhythmic neuron subtypes, we observed a wave of circadian gene expression propagating from the subtypes in posterior SCN to the subtypes in anterior SCN. Such wave can be explained by the neuropeptide-receptor signaling network in which Avp+/Nms+ subtype is the leader of circadian oscillations. Our study provides insights into the basic neural mechanism of circadian pacemaking in mammals.
Project description:To screen for specific circadian outputs that may distinguish the pacemaker in the mammalian suprachiasmatic nucleus (SCN) from peripheral-type oscillators in which the canonical clockworks are similarly regulated in a circadian manner, the rhythmic behavior of the transcriptome in forskolin-stimulated NIH/3T3 fibroblasts was analyzed and compared to that found in the rat SCN in vivo and SCN2.2 cells in vitro. Similar to the scope of circadian gene expression in SCN2.2 cells and the rat SCN, NIH/3T3 fibroblasts exhibited circadian fluctuations in the expression of the core clock genes, Per2, Bmal1 (Mop3), and Cry1 and 323 functionally diverse transcripts (2.6%), many of which were involved in cell communication. Overlap in rhythmically-expressed transcripts among NIH/3T3 fibroblasts, SCN2.2 cells and the rat SCN was limited to these clock genes and four other genes that mediate fatty acid and lipid metabolism or function as nuclear factors. Compared to NIH/3T3 cells, circadian gene expression in SCN oscillators was more prevalent among cellular pathways mediating glucose metabolism and neurotransmission. Coupled with evidence for the rhythmic regulation of the inducible isoform of nitric oxide synthase, the enzyme responsible for the production of nitric oxide, in SCN2.2 cells and the rat SCN but not in fibroblasts, studies examining the effects of a NOS inhibitor on metabolic rhythms in co-cultures containing SCN2.2 cells and untreated NIH/3T3 cells suggest that this gaseous neurotransmitter may play a key role in SCN pacemaker function. Thus, this comparative analysis of circadian gene expression in SCN and non-SCN cells may have important implications in the selective identification of circadian signals involved in the coupling of SCN oscillators and the regulation of rhythmicity in downstream cells or tissues. Experiment Overall Design: Circadian profiling of the NIH/3T3 fibroblast transcriptome entailed the treatment of NIH/3T3 cells with a 15uM forskolin pulse, subsequent washout of the drug, and collection of total RNA immediately after washout and every 6 hours across two circadian cycles for each of three experiments. Timepoint values reflect the average of three samples from these biological replicates.