Night/Day Changes in Pineal Expression of >600 Genes

Abstract

The pineal gland plays an essential role in vertebrate chronobiology by converting time into a hormonal signal, melatonin, which is always elevated at night. Here we have analyzed the rodent pineal transcriptome using Affymetrix GeneChip technology to obtain a more complete description of pineal cell biology. The effort revealed that 604 genes (1,268 probe sets) with Entrez Gene identifiers are differentially expressed greater than 2-fold between midnight and mid-day (false discovery rate <0.20). Expression is greater at night in ϳ70%. These findings were supported by the results of radiochemical in situ hybridization histology and quantitative real time-PCR studies. We also found that the regulatory mechanism controlling the night/ day changes in the expression of most genes involves norepinephrine-cyclic AMP signaling. Comparison of the pineal gene expression profile with that in other tissues identified 334 genes (496 probe sets) that are expressed greater than 8-fold higher in the pineal gland relative to other tissues. Of these genes, 17% are expressed at similar levels in the retina, consistent with a common evolutionary origin of these tissues. Functional categorization of the highly expressed and/or night/day differentially expressed genes identified clusters that are markers of specialized functions, including the immune/inflammation response, melatonin synthesis, photodetection, thyroid hormone signaling, and diverse aspects of cellular signaling and cell biology. These studies produce a paradigm shift in our understanding of the 24-h dynamics of the pineal gland from one focused on melatonin synthesis to one including many cellular processes.A defining feature of the pineal gland is a 24-h rhythm in melatonin synthesis. Melatonin provides vertebrates with a circulating signal of time and is essential for optimal integration of physiological functions with environmental lighting on a daily and seasonal basis (1-4).The melatonin rhythm in mammals is driven by a circadian clock located in the suprachiasmatic nucleus (SCN), 13 which is hard-wired to the pineal gland by a polysynaptic pathway that courses through central and peripheral neuronal structures. The pineal gland is innervated by projections from the superior cervical ganglia (SCG) in the form of a dense network of catecholamine-containing sympathetic fibers. Activation of the SCN 3 pineal pathway occurs at night and results in the release

Circadian changes in long noncoding RNAs in the pineal gland

“…NE acts through an adrenergic receptor/cAMP mechanism to broadly control gene expression. These changes seem to establish optimal conditions for the precise daily rhythm in melatonin production (25). Results presented here provide an indication that lncRNAs play a role in the vertebrate circadian system.…”

“…This evidence and the evidence that induction occurs without protein synthesis (SI Appendix, Fig. S3) provide reason to suspect that cAMP acts to induce expression of these lncRNAs through a posttranslational mechanism [e.g., phosphorylation of cAMP response element binding proteins (Crebs)], which is the case for protein-coding transcripts (25).…”

“…FPKM values and nominal length are based on the addresses given here without regard to potential exon/intron structure. The night/day (N/D) expression ratios and rEx values were calculated as described (25). The daytime levels and N/D expression ratios of selected genes in this experiment (SI Appendix, Table S1 evolutionary conservation was not evident, except lncSN016.…”

“…The transsynaptic mechanism controlling expression of the selected lncSNs was studied using in vivo and in vitro experimental designs focused on NE (25,29,(33)(34)(35)(36). Injection of the β-adrenergic agonist isoproterenol during the day elevated lncSN001 and lncSN016 transcripts (Fig.…”

“…The pineal gland is responsible for the daily rhythm in circulating melatonin, the hormone of the night. In this tissue, daily changes in the abundance of protein-coding transcripts (25) are controlled by a neural pathway linking the master mammalian circadian oscillator, the suprachiasmatic nucleus (SCN), to the pineal gland; SCN stimulation of this pathway causes release of norepinephrine (NE) from sympathetic nerve processes. NE acts through an adrenergic receptor/cAMP mechanism to broadly control gene expression.…”