Project description:Circadian rhythms are responsive to a variety of external cues, light and metabolism being the most important. In mammals, the light signal is sensed by the retina and transmitted to the SCN master clock, where it is translated into the molecular oscillator via regulation of clock gene transcription. The signalling pathways governing the molecular translation from metabolic signals to circadian output in peripheral oscillators, in contrast, are less understood. FOXO transcription factors are known to translate external metabolic cues to internal transcriptional programs. In the past couple of years it has become evident that both FOXO transcription factors and the circadian clock are of key importance in the underlying mechanisms of ageing and the regulation of metabolism. We now show FOXO3 to be a crucial modulator of circadian rhythmicity via direct transcriptional regulation of Clock, a core component of the molecular oscillator, and identify FOXO3 as a novel link in the circadian feedback loop, which is required for circadian rhythms in liver. We propose that FOXO3 directly feeds back into the circadian oscillator in response to metabolic cues. We performed a microarray study on synchronized NIH 3T3 cells upon transient overexpression of FoxO6 (oeO6). Cells were harvested for RNA isolation 24h (time1), 30h(time2), 36h(time3) and 42h(time4) after synchronization. Experimental samples were hybridized against a reference pool of cRNA, which was derived from unsynchronized NIH 3T3 cells. Experiments were performed 4 times, of each sample group two samples were labeled with cy5 and co-hybridized with reference RNA labeled with cy3, and two samples were labeled and hybridized in the opposite way. Microarrays used were Mouse Whole Genome Gene Expression Microarrays V1 (Agilent Technologies, Belgium)
Project description:Circadian rhythms are responsive to a variety of external cues, light and metabolism being the most important. In mammals, the light signal is sensed by the retina and transmitted to the SCN master clock, where it is translated into the molecular oscillator via regulation of clock gene transcription. The signalling pathways governing the molecular translation from metabolic signals to circadian output in peripheral oscillators, in contrast, are less understood. FOXO transcription factors are known to translate external metabolic cues to internal transcriptional programs. In the past couple of years it has become evident that both FOXO transcription factors and the circadian clock are of key importance in the underlying mechanisms of ageing and the regulation of metabolism. We now show FOXO3 to be a crucial modulator of circadian rhythmicity via direct transcriptional regulation of Clock, a core component of the molecular oscillator, and identify FOXO3 as a novel link in the circadian feedback loop, which is required for circadian rhythms in liver. We propose that FOXO3 directly feeds back into the circadian oscillator in response to metabolic cues.
Project description:Circadian rhythms are responsive to a variety of external cues, light and metabolism being the most important. In mammals, the light signal is sensed by the retina and transmitted to the SCN master clock, where it is translated into the molecular oscillator via regulation of clock gene transcription. The signalling pathways governing the molecular translation from metabolic signals to circadian output in peripheral oscillators, in contrast, are less understood. FOXO transcription factors are known to translate external metabolic cues to internal transcriptional programs. In the past couple of years it has become evident that both FOXO transcription factors and the circadian clock are of key importance in the underlying mechanisms of ageing and the regulation of metabolism. We now show FOXO3 to be a crucial modulator of circadian rhythmicity via direct transcriptional regulation of Clock, a core component of the molecular oscillator, and identify FOXO3 as a novel link in the circadian feedback loop, which is required for circadian rhythms in liver. We propose that FOXO3 directly feeds back into the circadian oscillator in response to metabolic cues.
2014-06-03 | GSE41554 | GEO
Project description:FOXO3 in control of circadian rhythms via direct regulation of Clock
Project description:Circadian rhythms are responsive to a variety of external cues, light and metabolism being the most important. In mammals, the light signal is sensed by the retina and transmitted to the SCN master clock, where it is translated into the molecular oscillator via regulation of clock gene transcription. The signalling pathways governing the molecular translation from metabolic signals to circadian output in peripheral oscillators, in contrast, are less understood. FOXO transcription factors are known to translate external metabolic cues to internal transcriptional programs. In the past couple of years it has become evident that both FOXO transcription factors and the circadian clock are of key importance in the underlying mechanisms of ageing and the regulation of metabolism. We now show FOXO3 to be a crucial modulator of circadian rhythmicity via direct transcriptional regulation of Clock, a core component of the molecular oscillator, and identify FOXO3 as a novel link in the circadian feedback loop, which is required for circadian rhythms in liver. We propose that FOXO3 directly feeds back into the circadian oscillator in response to metabolic cues. We performed a microarray study on synchronized NIH 3T3 cells upon transient knock-down of FoxO3 (siO3). Cells were harvested for RNA isolation 24h (time1), 30h(time2), 36h(time3) and 42h(time4) after synchronization. Experimental samples were hybridized against a reference pool of cRNA, which was derived from unsynchronized NIH 3T3 cells. AS controlgroup a scrambled siRNA was transfected. Experiments were performed 4 times, of each sample group two samples were labeled with cy5 and co-hybridized with reference RNA labeled with cy3, and two samples were labeled and hybridized in the opposite way. Microarrays used were Mouse Whole Genome Gene Expression Microarrays V1 (Agilent Technologies, Belgium)
Project description:Study on differential gene expression and splicing between wildtype and clock mutants. This study is part of a comparative analysis of the role of Protein Methyltransferase 5 in the regulation of transcriptional and post-transcriptional processes simultaneously in Arabidopsis and Drosophila. Circadian rhythms allow organisms to time biological processes to the most appropriate phases of the day/night cycle1. Post-transcriptional regulation is emerging as an important component of circadian networks2-6, but the molecular mechanisms linking the circadian clock to the control of RNA processing are largely unknown. Here we show that Protein Arginine Methyl Transferase 5 (PRMT5), which transfers methyl groups to arginine residues present in histones7 and Sm spliceosomal proteins8,9, links the circadian clock to the control of alternative splicing in plants. Mutations in prmt5impair multiple circadian rhythms in Arabidopsis thaliana and this phenotype is caused, at least in part, by a strong alteration in alternative splicing of the core-clock gene PSEUDO RESPONSE REGULATOR 9 (PRR9). Furthermore, genome wide studies show that PRMT5 contributes to regulate many pre-mRNA splicing events most likely modulating 5´splice site (5´ss) recognition. PRMT5 expression shows daily and circadian oscillations, and this contributes to mediate the circadian regulation of expression and alternative splicing of a subset of genes. Circadian rhythms in locomotor activity are also disrupted in dart5, a mutant affected in the Drosophila melanogaster PRMT5 homolog, and this is associated with alterations in splicing of the core-clock gene period (per) and several clock associated genes. Our results reveal a key role for PRMT5 in the regulation of alternative splicing and indicate that the interplay between the circadian clock and the regulation of alternative splicing by PRMT5 constitutes a common mechanism that helps organisms to synchronize physiological processes with daily changes in environmental conditions.
Project description:Casein Kinase 2 (CK2) is an evolutionarily conserved kinase protein that phosphorylates a plethora of cellular target protein involved in processes including DNA repair, cell cycle control, and circadian rhythms. CK2 is functionally conserved across all eukaryotes, although the substrate proteins identified in targeted experiments on a diverse range of complex tissues are often different. A growing interest exists to identify conserved, core signalling principles essential to eukaryotic life. To efficiently study generic roles of CK2 in the cellular circadian clock, we used a minimal eukaryotic model organism (Ostreococcus tauri). Overexpression of CK2 leads to a slow circadian rhythm, verifying functional conservation of CK2 in cellular timekeeping. CK2 activity contributes more strongly to the clock around dusk than around dawn, and analysis of the phospho-proteome at this time revealed a strong overrepresentation of potential CK2 sites. Large changes to the phospho-proteome are reported here upon overexpression of CK2, identifying a set of CK2-responsive phospho-sites. To identify more CK2-specific phosphorylation events, the phospho-proteome of cells treated with CK2 inhibitor were analysed and compared to the overexpression lines. We thus report a full inventory of the CK2-responsive phospho-proteome to inform studies into CK2 activity in the circadian clock of more complex tissues, as science moves to understand and modulate cellular circadian rhythms to help us negate the negative effects of shiftwork or cross-continental travel.
Project description:Over the past decade, genome-wide assays have underscored the broad sweep of circadian gene expression. A substantial fraction of the transcriptome undergoes oscillations in many organisms and tissues, which governs the many biochemical, physiological and behavioral functions under circadian control. Based predominantly on the transcription feedback loops important for core circadian timekeeping, it is commonly assumed that this widespread mRNA cycling reflects circadian transcriptional cycling. To address this issue, we directly measured dynamic changes in mouse liver transcription using Nascent-Seq. Many genes are rhythmically transcribed over the 24h day, which include precursors of several non-coding RNAs as well as the expected set of core clock genes. Surprisingly however, nascent RNA rhythms overlap poorly with mRNA abundance rhythms assayed by RNA-seq. This is because most mouse liver genes with rhythmic mRNA expression manifest poor transcriptional rhythms, indicating a prominent role of post-transcriptional regulation in setting mRNA cycling amplitude. To gain further insight into circadian transcriptional regulation, we also characterized the rhythmic transcription of liver genes targeted by the transcription factors CLOCK and BMAL1; they directly target other core clock genes and sit at the top of the molecular circadian clock hierarchy in mammals. CLK:BMAL1 rhythmically bind at the same discrete phase of the circadian cycle to all target genes, which not surprisingly have a much higher percentage of rhythmic transcription than the genome as a whole. However, there is a surprisingly heterogeneous set of cycling transcription phases of direct target genes, which even include core clock genes. This indicates a disconnect between rhythmic DNA binding and the peak of transcription, which is likely due to other transcription factors that collaborate with CLK:BMAL1. In summary, the application of Nascent-Seq to a mammalian tissue provides surprising insights into the rhythmic control of gene expression and should have broad applications beyond the analysis of circadian rhythms. CLK and BMAL1 DNA binding profile in the mouse liver at ZT8, sequenced along an Input sample using GAII (ChIP-Seq) Supplementary file ChIPSeq_Mouse_Liver_Processed_data_Table1.txt represents annotated CLK and BMAL1 peaks.
Project description:The circadian clock is intricately connected with metabolism, however the precise details of these connections are incomplete. Here we used high temporal resolution metabolite profiling to determine circadian regulation of mouse liver and cell autonomous metabolism. In mouse liver, we found ~50% of metabolites were circadian, with strong enrichment of the nucleotide, amino acid, and methylation pathways. In U2OS cells, 27% of metabolites were circadian, including amino acids and NAD biosynthesis, also clock controlled in liver. To assess whether cell autonomous metabolite rhythms were clock-dependent, we used RNAi to perturb Bmal1, Cry1, and Cry2. Bmal1 knockdown eliminated most metabolite rhythms, while Cry1 generally shortened and Cry2 lengthened rhythms. Surprisingly, we found Cry1 knockdown induced 8 hr rhythms in amino acid, methylation, and vitamin metabolites, decoupling metabolite and transcriptional rhythms. These results provide the first comprehensive views of circadian liver and cell autonomous metabolism.