PHOTOISOMERASE RETINAL G PROTEIN COUPLED RECEPTOR (RGR) IS LOCALIZED IN THE GANGLION CELL LAYER OF THE CHICKEN RETINA

DÍAZ, N.M.; VALDEZ D J; VERRA D; GUIDO M

Fort Lauderdale

Encuentro; 2011 ARVO Annual Meeting; 2011

THE ASSOCIATION FOR RESEARCH IN VISION AND OPHTALMOLOGY

Purpose: In the present work we investigated the presence and expression of Retinal G protein coupled receptor (RGR) in retinal ganglion cells (RGCs) and inner retina of wild type (WT) and GUCY1* birds, an animal model of blindness lacking functional photoreceptor cells in which persist photic responses associated to non-visual functions. Absorption of a photon by visual pigments induces isomerization of 11-cis-retinaldehyde (RAL) chromophore to all-trans-RAL. Since opsins in the absence of 11-cis-RAL lose light sensitivity, sustained vision requires continuous regeneration of 11-cis-RAL via a process called visual cycle. Subpopulations of RGCs expressing the photopigment melanopsin have been shown to be intrinsically photoresponsive (ipRGCs) and responsible for the photic regulation of diverse non-visual functions. To date very little is known about how these ipRGCs do regenerate the chromophore needed for light detection. RGR has been localized to the RPE and Müller cells, and has been shown to interact with proteins involved in the “visual cycle”, and it is currently believed that RGR behaves as a cofactor in the retinoid cycle that modulates isomerohydrolase activity. Methods: Retinas from embryonic (E) day 4 to 19 or post-hatch day 10 (P10) WT chickens were used for western blotting (WB), immunohistochemistry (IHC) or RT-PCR. GUCY1* birds used were 2-3 month–old, time at which the outer retina is degenerated. Primary RGC cultures were obtained by Thy-1 antibody immunopanning at E8. RGC preparations were obtained from lyophilized retinas by the Scotch tape method. Results: We found detectable levels of RGR mRNA in the whole embryonic retina from E4 and in the primary RGC cultures at E8. After hatching, we found appreciable levels of RGR mRNA and protein in retinas of both the WT and GUCY1* chickens as well as in RGC preparations. By immunofluorescence, we observed positive staining for RGR localized in the GC layer. Conclusions: The results demonstrated that RGR is expressed at both mRNA and protein levels in the RGCs of WT and GUCY1* chickens at embryonic and postnatal ages. Observations suggest that RGR may play somehow a role in the regulation of the chromophore regeneration within the inner retina.