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Stephan C F Neuhauss, Jennifer Keim, Jingjing Zang; Regulation of Cone Visual Transduction Shut-Off by the Circadian Clock . Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):993.
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© ARVO (1962-2015); The Authors (2016-present)
Visual behaviors are subject to regulation by the circadian clock. Here we investigate the molecular mechanisms underlying the circadian influence on the cone photoresponse shutoff kinetics in zebrafish.<br />
We use electroretinography (ERG) for functional analysis and qRT-PCR, in situ hybridization, and western blotting to assess time of day dependent fluctuations of
Key regulatory genes of the cone visual transduction cascade (recoverin, grk, arrestins, rgs) show time of day dependent fluctuations in expression levels in both in situ and qRT-PCR experiments.<br /> Changes in mRNA expression levels throughout the day are maintained when larvae were kept in continuous darkness, suggesting that this oscillation is endogenous and circadian rhythm dependent. Western blot results show that protein levels also change in a 24-hour cycle with a delay between the protein and mRNA peak.<br /> Functional ERG recordings from 5dpf larvae demonstrate that the photoresponse recovery is delayed in the evening as compared to the subjective morning. This phenomenon is maintained in darkness.<br /> Constant exposure to light for 5 days disturbs the normal oscillation of these genes in larvae and also largely reduces the difference in photoresponse kinetics. Reversing the light cycle reverses the expression level of these genes and the response recovery kinetics.<br />
The expression levels of several important regulators for cone photoresponse recovery show robust circadian rhythms, which may be correlated with the observed photoresponse kinetic change throughout the day.<br />
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