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Nathaniel York, Allison Lutz, De-Ann M Pillers, Bikash R Pattnaik; Oxytocin Receptor Ontogeny in the Mouse RPE. Invest. Ophthalmol. Vis. Sci. 2017;58(8):103. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
We have previously localized oxytocin receptor (OXTR) to the retinal pigment epithelium and oxytocin (OXT) to the cone photoreceptors, and have shown that RPE cells exposed to oxytocin activate OXTR signaling that may modulate the function of the RPE Kir7.1 channel. To further elucidate the role of OXTR signaling in the retina, and whether it is key during eye development or at maturity, we sought to determine the ontogeny of OXTR expression in the postnatal mouse RPE.
We considered the mouse eye at birth equivalent to 25 weeks of human gestation and each day thereafter to represent a week of gestation based on published vascular development studies. C57BL6/J mice were used, with eyes obtained from newborn (p0), p5, p10 p15, p20 and adult mice (7 weeks). We adopted the simultaneous RPE isolation and RNA stabilization method previously described by Wang et al. to isolate mRNA from RPE cells. Superscript III first scribe transcription kit (Thermo-Fisher) was used to synthesize cDNA and PCR was performed using MyTaq Red Mix (Bioline) with primers designed for mouse OXTR and RPE-65 (control to verify RPE cell lineage). Following agarose gel electrophoresis relative expression in RPE was determined by comparing OXTR band intensity with RPE65 (I-OXTR/I-RPE65) using Image Studio Lite (Li-Cor Bioscience).
mRNA we isolated from RPE cells showed OXTR expression in only 1 animal at p10 (n=4, 25%), 3 animals at p15 (n=5, 60%) and all animals by p20 (n=5, 100%). No animal showed OXTR expression prior to p10. The average expression level was 0.06 at p10, 0.23 ± 0.04 for p15, 0.48 ± 0.22 for p20 and 0.36 ± 0.18 for the adult mice (average ± SEM). Despite a trend towards higher expression the difference was not significant, likely as a result of the large variation in the expression levels within each time point. We investigated whether gender was predictive of expression level in adult mice but found no correlation as both genders demonstrated variable expression.
OXTR expression appears at a developmental stage in some mice that is comparable to late gestation in the human fetus, with all mice expressing OXTR when the eye reaches developmental maturity. Combined with our previous observation of oxytocinergic inhibition of the RPE Kir7.1 channel and localization of OXT in the cone photoreceptors, we suggest that retinal OXT-OXTR signaling plays a role in communication between photoreceptors and RPE starting as early as p10 in mice.
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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