Purchase this article with an account.
Ethan D Buhr, Russell N Van Gelder; Opn5-mediated regulation of clock genes in the mouse retina. Invest. Ophthalmol. Vis. Sci. 2016;57(12):4662.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
The mammalian retina has the ability to synchronize its local circadian rhythms of gene expression to light: dark cycles independently of behavior and does not require rods, cones, or melanopsin. OPN5 is necessary for the photoentrainment of mouse retinal cells in culture. We wished to assess the role of OPN5 on retinal circadian rhythms in vivo.
Mice without OPN5 (Opn5-/-) and wild-type littermates were behaviorally entrained to light: dark cycles for at least 2 weeks. The retinas and livers were then removed at 3 hour intervals across a daily cycle. RNA transcript levels of the clock genes Per1 and Per2 were analyzed by quantitative RT-PCR. Similar cohorts of mice were exposed to 24 hours of darkness and then given 30 or 90 minutes of bright violet (417 nm) and blue (475 nm) light. Retinas were then collected and RNA transcript levels of Per1, Per2, Bmal1 and c-Fos were measured by quantitative RT-PCR.
The transcripts of Per1 and Per2 show predictable differences across the 24 hour day as has been previously reported. However, these transcripts showed variable levels from retina to retina among Opn5-/- mice. The circadian component to the expression of Per1 and Per2 transcripts was not observed in the cohort of Opn5-/- retinas. The rhythms of Per1 and Per2 were not different in the livers of wild-type and Opn5-/- mice. In addition, an induction of both Per1 and Per2 was observed in retinas of wild-type animals exposed to an acute light pulse. Neither of these genes were induced in response to light in retinas of Opn5-/- mice. However, induction of c-Fos was observed in the retinas of both cohorts of mice.
These results demonstrate that Opn5-/- is necessary for the normal circadian photoentrainment of cells in the mammalian retina in vivo. These results complement our previous findings that Opn5-/- retinas fail to photoentrain ex vivo. The current experiments used individual mice for each time point. It is possible that circadian rhythms of the Per genes are present in the individual retinas in vivo, but due to a lack of synchrony to the light: dark cycle the averaging of multiple retinas causes peak phases to be obscured. The loss of induction of Per transcripts to acute light pulses further demonstrates the role of OPN5 in circadian light responses, while the induction of c-Fos demonstrates that Opn5-/- are nevertheless still photoresponsive.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
This PDF is available to Subscribers Only