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Temporal transcriptomics suggest that twin-peaking genes reset the clock.

ABSTRACT: The mammalian suprachiasmatic nucleus (SCN) drives daily rhythmic behavior and physiology, yet a detailed understanding of its coordinated transcriptional programmes is lacking. To reveal the finer details of circadian variation in the mammalian SCN transcriptome we combined laser-capture microdissection (LCM) and RNA-seq over a 24 hr light / dark cycle. We show that 7-times more genes exhibited a classic sinusoidal expression signature than previously observed in the SCN. Another group of 766 genes unexpectedly peaked twice, near both the start and end of the dark phase; this twin-peaking group is significantly enriched for synaptic transmission genes that are crucial for light-induced phase shifting of the circadian clock. 341 intergenic non-coding RNAs, together with novel exons of annotated protein-coding genes, including Cry1, also show specific circadian expression variation. Overall, our data provide an important chronobiological resource (www.wgpembroke.com/shiny/SCNseq/) and allow us to propose that transcriptional timing in the SCN is gating clock resetting mechanisms.

SUBMITTER: Pembroke WG

PROVIDER: S-EPMC4718813 | biostudies-literature | 2015 Nov

REPOSITORIES: biostudies-literature

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Temporal transcriptomics suggest that twin-peaking genes reset the clock.

Pembroke William G WG Babbs Arran A Davies Kay E KE Ponting Chris P CP Oliver Peter L PL

eLife 20151102

The mammalian suprachiasmatic nucleus (SCN) drives daily rhythmic behavior and physiology, yet a detailed understanding of its coordinated transcriptional programmes is lacking. To reveal the finer details of circadian variation in the mammalian SCN transcriptome we combined laser-capture microdissection (LCM) and RNA-seq over a 24 hr light / dark cycle. We show that 7-times more genes exhibited a classic sinusoidal expression signature than previously observed in the SCN. Another group of 766 g ...[more]

PMID: 26523393

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Project description:BackgroundBased on the peak expression times during infection, early, middle, and late genes have been characterized in viruses (cyanophages) that infect the unicellular cyanobacterium Prochlorococcus. Laboratory experiments show that some cyanophages can only replicate in the light and thus exhibit diurnal infection rhythms under light-dark cycles. Field evidence also suggests synchronized infection of Prochlorococcus by cyanophages in the oceans, which should result in progressive expression of cyanophage early, middle, and late genes. However, distinct temporal expression patterns have not been observed in cyanophage field populations.ResultsIn this study, we reanalyzed a previous metatranscriptomic dataset collected in the North Pacific Subtropical Gyre. In this dataset, it was previously shown that aggregate transcripts from cyanophage scaffolds display diurnal transcriptional rhythms with transcript abundances decreasing at night. By mapping metatranscriptomic reads to individual viral genes, we identified periodically expressed genes from putative viruses infecting the cyanobacteria Prochlorococcus and Synechococcus, heterotrophic bacteria, and algae. Of the 41 cyanophage genes, 35 were from cyanomyoviruses. We grouped the periodically expressed cyanomyovirus genes into early, middle, and late genes based on the conserved temporal expression patterns of their orthologs in cyanomyovirus laboratory cultures. We found that the peak expression times of late genes in cyanophage field populations were significantly later than those of early and middle genes, which were similar to the temporal expression patterns of synchronized cyanophage laboratory cultures.ConclusionsThe significantly later peak expression times of late genes in cyanomyovirus field populations suggest that cyanophage infection of Prochlorococcus is synchronized in the North Pacific Subtropical Gyre. The night-time peak expression of late genes also suggests synchronized lysis of Prochlorococcus at night, which might result in synchronized release of dissolved organic matter to the marine food web. Video abstract.

Project description:BACKGROUND:Tardigrades are renowned for their ability to enter cryptobiosis (latent life) and endure extreme stress, including desiccation and freezing. Increased focus is on revealing molecular mechanisms underlying this tolerance. Here, we provide the first transcriptomes from the heterotardigrade Echiniscoides cf. sigismundi and the eutardigrade Richtersius cf. coronifer, and compare these with data from other tardigrades and six eukaryote models. Investigating 107 genes/gene families, our study provides a thorough analysis of tardigrade gene content with focus on stress tolerance. RESULTS:E. cf. sigismundi, a strong cryptobiont, apparently lacks expression of a number of stress related genes. Most conspicuous is the lack of transcripts from genes involved in classical Non-Homologous End Joining. Our analyses suggest that post-cryptobiotic survival in tardigrades could rely on high fidelity transcription-coupled DNA repair. Tardigrades seem to lack many peroxins, but they all have a comprehensive number of genes encoding proteins involved in antioxidant defense. The "tardigrade unique proteins" (CAHS, SAHS, MAHS, RvLEAM), seem to be missing in the heterotardigrade lineage, revealing that cryptobiosis in general cannot be attributed solely to these proteins. Our investigation further reveals a unique and highly expressed cold shock domain. We hypothesize that the cold shock protein acts as a RNA-chaperone involved in regulation of translation following freezing. CONCLUSIONS:Our results show common gene family contractions and expansions within stress related gene pathways in tardigrades, but also indicate that evolutionary lineages have a high degree of divergence. Different taxa and lineages may exhibit unique physiological adaptations towards stress conditions involving possible unknown functional homologues and/or novel physiological and biochemical mechanisms. To further substantiate the current results genome assemblies coupled with transcriptome data and experimental investigations are needed from tardigrades belonging to different evolutionary lineages.

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Temporal transcriptomics suggest that twin-peaking genes reset the clock.

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Temporal transcriptomics suggest that twin-peaking genes reset the clock.

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