RGR and retinal degeneration: Accordingly, histological examination of retinal sections from Rgr+/+ and RgrS/S animals, at ages from 1 to 12 months, revealed normal retinal morphology and comparable thickness of all retinal layers including the outer nuclear layer (ONL), indicating the absence of any detectable retinal degeneration associated with the RGR loss (Figures 3F and 3G).