Unknown,Transcriptomics,Genomics,Proteomics

Dataset Information

Transcription profiling of mouse liver cells with a conditionally active liver clock to descriminate between rhythmic gene expression driven by cyclic systemic cues and local oscillators

ABSTRACT: The mammalian circadian timing system consists of a master pacemaker in the suprachiasmatic nucleus (SCN) that synchronizes self-sustained oscillators in most peripheral cells. Rhythmic gene expression in peripheral tissues can be driven by cyclic systemic cues emanating from the SCN or by local oscillators. To discriminate between these two mechanisms, we engineered a mouse strain with a conditionally active liver clock. Transcriptome profiling revealed that the circadian transcription of most genes depends on functional hepatocyte clocks. However, the expression of 31 genes, including mPer2, oscillates robustly in clock-arrested hepatocytes. Such genes may be implicated in the synchronization of liver oscillators

ORGANISM(S): Mus musculus

SUBMITTER: Benoît Kornmann

PROVIDER: E-MEXP-842 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Publications

Evidence for an overlapping role of CLOCK and NPAS2 transcription factors in liver circadian oscillators.

Bertolucci Cristiano C Cavallari Nicola N Colognesi Ilaria I Aguzzi Jacopo J Chen Zheng Z Caruso Pierpaolo P Foá Augusto A Tosini Gianluca G Bernardi Francesco F Pinotti Mirko M

Molecular and cellular biology 20080303 9

The mechanisms underlying the circadian control of gene expression in peripheral tissues and influencing many biological pathways are poorly defined. Factor VII (FVII), the protease triggering blood coagulation, represents a valuable model to address this issue in liver since its plasma levels oscillate in a circadian manner and its promoter contains E-boxes, which are putative DNA-binding sites for CLOCK-BMAL1 and NPAS2-BMAL1 heterodimers and hallmarks of circadian regulation. The peaks of FVII ...[more]

PMID: 18316400

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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:Recent evidence suggest that the circadian timing system plays an important role in the control of renal function and maintaining blood pressure. Here, we analyzed circadian rhythms of urinary excretion of sodium and potassium in wild-type mice and mice lacking circadian transcriptional activator clock. Analysis of urines collected at hourly intervals over a 24-hour period revealed dramatic changes in rhythms of sodium and potassium excretion in clock(-/-) mice. In parallel, significant differences in circadian pattern of plasma aldosterone levels, but not in the 24-hour mean aldosterone levels, were observed. Microarray-based profiling of renal transcriptomes demonstrated that clock(-/-) mice exhibit dysregulation in multiple mechanisms involved in maintaining sodium and potassium balance by the kidney. The most significant changes were detected in the expression levels of several key enzymes (Cyp4a14, Cyp4a12a and Cyp4a12b) required for the conversion of arachidonic acid to 20-hydroxyeicosatetraenoic acid (20-HETE), a powerful regulator of renal sodium and potassium excretion, renal vascular tone and blood pressure. The 20-HETE levels measured in kidney microsomes of wild-type mice followed a circadian-like temporal pattern. In clock(-/-) mice, the acrophase of this rhythm was shifted by 8 hours and the 24-hour mean levels of 20-HETE were significantly decreased. These results demonstrate that circadian rhythms of urine electrolyte excretion are largely dependent on the circadian clock activity and indicate that circadian oscillations in renal 20-HETE content could be an important mechanism of blood pressure regulation. We examined the temporal profiles of gene expression in mouse whole kidney. Animals were sacrificed for microdissection every 4 hours, i.e. at ZT0, ZT4, ZT8, ZT12, ZT16 and ZT20 (ZT M-bM-^@M-^S Zeitgeber (circadian) time, indicates time of light-on as ZT0 and time of light-off as ZT12). The microarray hybridization was performed in duplicates on pools of RNA composed of equivalent amounts of RNA prepared from teo or three animals at each ZT time-point.

Dataset Information

Transcription profiling of mouse liver cells with a conditionally active liver clock to descriminate between rhythmic gene expression driven by cyclic systemic cues and local oscillators

Publications

Evidence for an overlapping role of CLOCK and NPAS2 transcription factors in liver circadian oscillators.

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