GRM6 and retinal degeneration: In P20 and P30 RCS rats, the proportion of floating ribbons to total ribbons increased markedly as retinal degeneration progressed, while the proportion of normal synapse ribbons decreased significantly in RCS rats (Figures 3B–D), suggesting that the decrease in the number of paired CtBP2- and mGluR6-positive structures resulted from rod synapse disintegration.