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Shunsuke Tsuchiya, Ethan Buhr, Tomomi Higashide, Kazuhisa Sugiyama, Russell N Van Gelder; Mechanisms of light entrainment of the mammalian ciliary body circadian clock. Invest. Ophthalmol. Vis. Sci. 2017;58(8):4131.
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Intraocular pressure has a strong circadian rhythm, due in part to rhythmicity of ciliary body function. This rhythm is normally entrained to the 24-hour light-dark cycle. Recent work has demonstrated that some ocular tissues, including cornea and retina, are directly light entrained through a neuropsin (OPN5)-dependent mechanism. The purpose of this study was to assess whether the mammalian ciliary body uses a similar mechanism for light entrainment.
Iris-ciliary body complexes were obtained from PERIOD2::LUCIFERASE (PER2::LUC) mice and cultured to measure bioluminescence rhythmicity using a Lumicycle. Pairs of the iris-ciliary body complex were exposed to antiphasic 9:15 light-dark cycle in vitro in the presence of 9-cis-retinaldehyde. After 4 days of exposure to light/dark cycles, bioluminescence was recorded to establish circadian phase. In addition, pairs of the iris-ciliary body complex cultured with the retinas of mice without PER2::LUC (i.e. C57Bl/6J) were exposed to light/dark cycle in vitro and their bioluminescence was obtained. Opn5 expression of the iris-ciliary body was analyzed using RT-PCR.
Cultured PER2::LUC iris-ciliary body complexes showed sustained circadian rhythmicity of bioluminescence in vitro. Neither the complex nor the co-cultured complex was directly entrained by light-dark cycle in vitro. Opn5 mRNA expression could not be detected in the iris-ciliary body complex.
The iris-ciliary body complex does not express OPN5 and is not entrained by light-dark cycle in vitro. Local retinal signals do not appear sufficient for entrainment. This suggests that central circadian phase cues from the suprachiasmatic nucleus likely control circadian entrainment of the ciliary body in vivo.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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