Project description:a circadian proteome atlas of eight organs, namely suprachiasmatic nucleus (SCN), hypothalamus (HPOA), liver (LIV), gall bladder (GBD), brown adipose tissue (BAT), kidney (KDN), heart (HEA) and muscle (MUS), from wild-type (WT) and Per1-/-/Per2-/- (DKO) mice housed under constant darkness and ad libitum feeding, collected every two hours for deep proteomic analysis over two days
Project description:Sirtuin 1 (SIRT1) is involved in both aging and circadian-clock regulation, yet the link between the two processes in relation to SIRT1 function is not clear. Using Sirt1-deficient mice, we found that Sirt1 and Period 2 (Per2) constitute a reciprocal negative regulation loop that plays important roles in modulating hepatic circadian rhythmicity and aging. Sirt1-deficient mice exhibited profound premature aging and enhanced acetylation of histone H4 on lysine16 (H4K16) in the promoter of Per2, the latter of which leads to its overexpression; in turn, Per2 suppresses Sirt1 transcription through binding to the Sirt1 promoter at the Clock/Bmal1 site. This negative reciprocal relationship between SIRT1 and PER2 was also observed in human hepatocytes. We further demonstrated that the absence of Sirt1 or the ectopic overexpression of Per2 in the liver resulted in a dysregulated pace of the circadian rhythm. The similar circadian rhythm was also observed in aged wild type mice. The interplay between Sirt1 and Per2 modulates aging gene expression and circadian-clock maintenance. To investigate hepatic SIRT1-dependent aging related genes, livers from wild type mice at 3 months (young), 12 months (middle age), and 19 months (old) of age, as well as Sirt1-deficient mice at 3 months of age were snap frozen and subject to RNA isolation and microarray analysis.
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.
Project description:Sirtuin 1 (SIRT1) is involved in both aging and circadian-clock regulation, yet the link between the two processes in relation to SIRT1 function is not clear. Using Sirt1-deficient mice, we found that Sirt1 and Period 2 (Per2) constitute a reciprocal negative regulation loop that plays important roles in modulating hepatic circadian rhythmicity and aging. Sirt1-deficient mice exhibited profound premature aging and enhanced acetylation of histone H4 on lysine16 (H4K16) in the promoter of Per2, the latter of which leads to its overexpression; in turn, Per2 suppresses Sirt1 transcription through binding to the Sirt1 promoter at the Clock/Bmal1 site. This negative reciprocal relationship between SIRT1 and PER2 was also observed in human hepatocytes. We further demonstrated that the absence of Sirt1 or the ectopic overexpression of Per2 in the liver resulted in a dysregulated pace of the circadian rhythm. The similar circadian rhythm was also observed in aged wild type mice. The interplay between Sirt1 and Per2 modulates aging gene expression and circadian-clock maintenance.
Project description:SIRT1 is involved in both aging and circadian clock regulation, yet the link between the two processes in relation to SIRT1 function is unclear. Analyzing SIRT1-deficient cells and mice, we demonstrated that SIRT1 and Per2 constitute a reciprocal negative regulation loop that plays important roles in modulating circadian rhythmicity, metabolism and aging. SIRT1-deficient mice exhibit profound premature aging and enhanced H4K16 acetylation in the promoter of Per2 leading to its overexpression; in turn, Per2 suppresses SIRT1 transcription through binding to SIRT1 promoter at the CLOCK/BMAL1 site. We further demonstrated that absence of SIRT1 or ectopic overexpression of Per2 in the liver resulted in an accelerated pace of circadian rhythm and dysregulated amplitude, mimicking the natural process of circadian shortening in aged mice. Thus the interplay between SIRT1 and Per2 provides a link between the life-long sequence of aging and circadian clock maintenance.
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:Fibroblasts can be reprogrammed to induced neurons (iNs) via transducion of Ascl1, Brn2, and Myt1l. To understand the roles of the circadian regulators Per1 and Per2 on the reprogramming, embryonic fibroblasts from wild type (WT), Per1-/-, and Per2-/- mice were transduced with the three genes and cells were harvested for scRNA-seq on days 4, 7, and 10 after transduction.
Project description:Fibroblasts can be reprogrammed to induced neurons (iNs) via transducion of Brn2, Ascl1, and Myt1l (BAM). To understand the roles of the circadain regulators Per1 and Per2 on the reprogramming, embryonic fibroblasts from wild type (WT), Per1-/-, and Per2-/- mice were transduced with the three genes and the cells were harvested on day 0, 2, and 4 after transduction for RNA-seq.
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