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.
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:To determine whether immortalized cells derived from the rat SCN (SCN2.2) retain intrinsic rhythm-generating properties characteristic of the SCN, oscillatory properties of the SCN2.2 transcriptome were analyzed and compared to those found in the rat SCN in vivo using rat U34A Affymetrix GeneChips. This SuperSeries is composed of the following subset Series:; GSE1654: Circadian Profiling of the Transcriptome in Immortalized Rat SCN Cells (3 biological replicates); GSE1673: Circadian Profiling of the Transcriptome in Immortalized Rat SCN Cells: Comparison to Long-Evans Rat SCN Experiment Overall Design: Refer to individual Series
Project description:In mammalian tissues circadian gene expression can be driven by local oscillators or systemic signals controlled by the master pacemaker in the suprachiasmatic nucleus. Here we show that simulated body temperature cycles, but not peripheral oscillators, can control the rhythmic expression of Cold-Inducible RNA binding Protein (CIRP) in cultured fibroblasts. In turn, loss-of-function experiments indicate that CIRP is required for high amplitude circadian gene expression. The transcriptome-wide identification of CIRP-bound RNAs by a biotin-streptavidin based CLIP-seq procedure revealed several CIRP-bound transcripts encoding circadian oscillator proteins. One of these, CLOCK, accumulated to particularly low levels in CIRP-depleted fibroblasts. Since ectopic expression of CLOCK improved circadian gene expression in these cells, we surmise that CIRP confers robustness to circadian oscillators via the regulation of CLOCK expression. Identification of CIRP-interacting RNA molecules in NIH3T3 cells and RNA expression in NIH3T3 cells treated with Control or CIRP siRNA after incubation of the cells at 33M-BM-0C for 8 hours
Project description:High-temporal resolution profiling was performed on NIH3T3 fibroblasts to detect rhythmic transcripts Experiment Overall Design: Samples were collected every hour for 48 hours from forskolin-synchronized NIH3T3 cells. Samples were analyzed using Affymetrix arrays.
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:The brain’s suprachiasmatic nucleus (SCN) is the master clock driving circadian rhythms in mammals. Vasoactive intestinal polypeptide (VIP) and its cognate receptor, VPAC2, are expressed in SCN neurons and mice with genetically targeted deletion of VPAC2 (Vipr2 -/-animals) show aberrant resetting to light, abnormal behavioral rhythms, and diminished SCN clock gene expression. Timed daily access to a running-wheel (scheduled voluntary exercise; SVE) promotes Vipr2 -/- SCN clock cell synchrony and 24h behavioral rhythms. We hypothesized that timed exercise alters the SCN transcriptome. Here, in control (Vipr2+/+) and Vipr2-/- mice under freely exercising and SVE conditions, RNAseq and qRT-PCR were used to measured gene expression of laser-dissected SCN. Compared to Vipr2+/+ mice, hundreds of genes were differentially expressed in the SCN from Vipr2-/- mice rhythmic in the freely exercising condition. Unexpectedly, SVE did not promote a Vipr2+/+-like SCN transcriptome in Vipr2-/- mice and many transcripts involved in SCN function including Avp, C1ql3, Gpr176, Prok2, Sst, Per2, and Nr1d1 remained dysregulated in the SVE condition. By contrast, circadian oscillators in the liver and lung were mostly intact in Vipr2-/- mice. This study indicates that marked molecular deficits in the SCN are sustained in behaviorally rhythmic Vipr2-/- mice, raising the possibility that a minimal functional SCN circadian clock can underpin whole animal rhythms.