title: Circadian and light-driven regulation of rod dark adaptation.
abstract: Continuous visual perception and the dark adaptation of vertebrate photoreceptors after bright light exposure require recycling of their visual chromophore through a series of reactions in the retinal pigmented epithelium (RPE visual cycle). Light-driven chromophore consumption by photoreceptors is greater in daytime vs. nighttime, suggesting that correspondingly higher activity of the visual cycle may be required. However, as rod photoreceptors are saturated in bright light, the continuous turnover of their chromophore by the visual cycle throughout the day would not contribute to vision. Whether the recycling of chromophore that drives rod dark adaptation is regulated by the circadian clock and light exposure is unknown. Here, we demonstrate that mouse rod dark adaptation is slower during the day or after light pre-exposure. This surprising daytime suppression of the RPE visual cycle was accompanied by light-driven reduction in expression of Rpe65, a key enzyme of the RPE visual cycle. Notably, only rods in melatonin-proficient mice were affected by this daily visual cycle modulation. Our results demonstrate that the circadian clock and light exposure regulate the recycling of chromophore in the RPE visual cycle. This daily melatonin-driven modulation of rod dark adaptation could potentially protect the retina from light-induced damage during the day.
authors.affiliation: Washington University School of Medicine, St. Louis, Missouri 63110, USA.|Department of Ophthalmology &Visual Sciences, Washington University School of Medicine, St. Louis, Missouri 63110, USA.|Graduate Program in Division of Biological &Biomedical Sciences, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
authors.forename: Yunlu
authors.initials: Y
authors.lastname: Xue
authors.affiliation: Washington University School of Medicine, St. Louis, Missouri 63110, USA.|Department of Pathology &Immunology, Washington University School of Medicine, St. Louis, Missouri 63110, USA.|Graduate Program in Division of Biological &Biomedical Sciences, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
authors.forename: Susan Q
authors.initials: SQ
authors.lastname: Shen
authors.affiliation: Washington University School of Medicine, St. Louis, Missouri 63110, USA.|Department of Pathology &Immunology, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
authors.forename: Joseph C
authors.initials: JC
authors.lastname: Corbo
authors.affiliation: Washington University School of Medicine, St. Louis, Missouri 63110, USA.|Department of Ophthalmology &Visual Sciences, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
authors.forename: Vladimir J
authors.initials: VJ
authors.lastname: Kefalov
mesh_terms: D000818:Animals; D057906:Circadian Clocks / Q000502:physiology*; D003623:Dark Adaptation / Q000502:physiology*; D008027:Light; D051379:Mice; D008817:Mice, Mutant Strains; D017948:Retinal Rod Photoreceptor Cells / Q000166:cytology / Q000378:metabolism*; D014785:Vision, Ocular / Q000502:physiology*