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Genome-wide identification and analysis of circular RNAs in the pineal in rats between day and night

ABSTRACT: Circular RNAs (circRNAs) are a new class of RNAs with covalently closed circular structures that are involved in many biological processes. However, information about circRNAs in the pineal gland is limited, especially in rats. In this study, 331 circRNAs were identified by the Illumina platform as being expressed in the pineal glands of rats during the night and day. Forty circRNAs with differential expression were found. A total of 737 GO terms were significantly enriched, and 121 KEGG pathways were found to contain differentially expressed genes. We predicted 6837 interactions between 65 cicRNAs and 549 miRNAs by using miRanda. We also found that high expression of miR-328a-3p in the daytime inhibits AANAT translation through targeting of the AANAT 3’UTR region. CircRNA-WNK2, which is highly expressed in the rat pineal gland during the night and functions as a miRNA sponge, removes this inhibitory effect and promotes the AANAT expression and melatonin secretion. The circadian expression profile of circRNAs in the rat pineal gland may provide more information on the roles of circRNAs in the regulation of melatonin circadian rhythm changes.

ORGANISM(S): Rattus norvegicus

PROVIDER: GSE146193 | GEO | 2020/03/03

REPOSITORIES: GEO

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Project description:The vertebrate pineal gland is dedicated to the production of the hormone melatonin, which increases at night to influence circadian and seasonal rhythms. This increase is associated with dramatic changes in the pineal transcriptome. Here, single-cell analysis of the rat pineal transcriptome was approached by sequencing mRNA from ~17,000 individual pineal cells, with the goals of profiling the cells that comprise the pineal gland and examining the proposal that there are two distinct populations of pinealocytes differentiated by the expression of Asmt, which encodes the enzyme that converts N-acetylserotonin to melatonin. In addition, this analysis provides evidence of cell-specific time-of-day dependent changes in gene expression. Nine transcriptomically distinct cell types were identified: ~90% were classified as melatonin-producing α- and β-pinealocytes (1:19 ratio). Non-pinealocytes included three astrocyte subtypes, two microglia subtypes, vascular and leptomeningeal cells, and endothelial cells. α-Pinealocytes were distinguished from β-pinealocytes by ~3-fold higher levels of Asmt transcripts. In addition, α-pinealocytes have transcriptomic differences that likely enhance melatonin formation by increasing the availability of the Asmt cofactor S-adenosylmethionine, resulting from increased production of a precursor of S-adenosylmethionine, ATP. These transcriptomic differences include ~2-fold higher levels of the ATP-generating oxidative phosphorylation transcriptome and ~8-fold lower levels of the ribosome transcriptome, which is expected to reduce the consumption of ATP by protein synthesis. These findings suggest that α-pinealocytes have a specialized role in the pineal gland: efficiently O-methylating the N-acetylserotonin produced and released by β-pinealocytes, thereby improving the overall efficiency of melatonin synthesis. We have also identified transcriptomic changes that occur between night and day in seven cell types, the majority of which occur in β-pinealocytes and to a lesser degree in α-pinealocytes; many of these changes were mimicked by adrenergic stimulation with isoproterenol. The cellular heterogeneity of the pineal gland as revealed by this study provides a new framework for understanding pineal cell biology at single-cell resolution.

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Genome-wide identification and analysis of circular RNAs in the pineal in rats between day and night

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