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Circadian regulation of retinoschisin in the chick retina.

ABSTRACT: To investigate the circadian regulation and acute illumination effects on the expression and secretion of retinoschisin from vertebrate retinas.Retinas were studied on the second day of constant darkness (DD) after several days of entrainment to 12-hour light/12-hour dark (LD) cycles in ovo or in vitro. Quantitative real-time PCR and Western immunoblotting were used to examine the mRNA and protein expressions of retinoschisin at different circadian time points. Pharmacologic treatments in whole retina and dissociated retinal cell cultures were used to investigate the cellular mechanisms underlying the circadian regulation of retinoschisin content and secretion. Different illumination conditions were given to examine changes in retinoschisin content in association with acute light/dark adaptation.The mRNA level, protein expression, and secretion of retinoschisin were under circadian control, all of which were higher at night and lower during the day. The Ras, MAP kinase Erk, CaMKII pathway served as part of the circadian output regulating the rhythmicity of retinoschisin. Blockage of L-type VGCCs dampened the retinoschisin rhythm, but inhibition of L-type VGCCs did not completely abolish the secretion of retinoschisin. The protein expression of retinoschisin also responded to acute illumination changes.The mRNA and protein expression, as well as retinoschisin secretion, are under circadian control. L-type VGCCs play a role in the circadian regulation of retinoschisin, but the molecular mechanism underlying retinoschisin secretion does not depend on L-type VGCCs. Protein expression of retinoschisin in response to acute illumination changes depends on previous light exposure experience.

SUBMITTER: Ko ML

PROVIDER: S-EPMC2367121 | biostudies-literature | 2008 Apr

REPOSITORIES: biostudies-literature

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Circadian regulation of retinoschisin in the chick retina.

Ko Michael L ML Liu Yilin Y Shi Liheng L Trump Dorothy D Ko Gladys Y-P GY

Investigative ophthalmology & visual science 20080401 4

<h4>Purpose</h4>To investigate the circadian regulation and acute illumination effects on the expression and secretion of retinoschisin from vertebrate retinas.<h4>Methods</h4>Retinas were studied on the second day of constant darkness (DD) after several days of entrainment to 12-hour light/12-hour dark (LD) cycles in ovo or in vitro. Quantitative real-time PCR and Western immunoblotting were used to examine the mRNA and protein expressions of retinoschisin at different circadian time points. Ph ...[more]

PMID: 18385082

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Project description:BackgroundChick pinealocytes exhibit all the characteristics of a complete circadian system, comprising photoreceptive inputs, molecular clockworks and an easily measured rhythmic output, melatonin biosynthesis. These properties make the in vitro pineal a particularly useful model for exploring circadian control of gene transcription in a pacemaker tissue, as well as regulation of the transcriptome by primary inputs to the clock (both photic and noradrenergic).ResultsWe used microarray analysis to investigate the expression of approximately 8000 genes within cultured pinealocytes subjected to both LD and DD. We report that a reduced subset of genes was rhythmically expressed in vitro compared to those previously published in vivo, and that gene expression rhythms were lower in amplitude, although the functional distribution of the rhythmic transcriptome was largely similar. We also investigated the effects of 6-hour pulses of light or of norepinephrine on gene expression in free-running cultures during both subjective day and night. As expected, both light and norepinephrine inhibited melatonin production; however, the two treatments differentially enhanced or suppressed specific sets of genes in a fashion that was dependent upon time of day.ConclusionOur combined approach of utilizing a temporal, photic and pharmacological microarray experiment allowed us to identify novel genes linking clock input to clock function within the pineal. We identified approximately 30 rhythmic, light-responsive, NE-insensitive genes with no previously known clock function, which may play a role in circadian regulation of the pineal. These are candidates for future functional genomics experiments to elucidate their potential role in circadian physiology. Further, we hypothesize that the pineal circadian transcriptome is reduced but functionally conserved in vitro, and supports an endogenous role for the pineal in regulating local rhythms in metabolism, immune function, and other conserved pathways.

Dataset Information

Circadian regulation of retinoschisin in the chick retina.

Publications

Circadian regulation of retinoschisin in the chick retina.

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