CRB1 and retinal degeneration: In this study, we demonstrate (1) progressive retinal degeneration in Crb1 mutant rats, causing loss of visual and retinal function; (2) ultrastructural localization of CRB1 at the subapical region of MGCs, and CRB2 at the subapical region of MGCs and photoreceptors in control rats; (3) a decrease in CRB1INDEL at the subapical region of MGCs in Crb1 mutant rats; (4) tropism by subretinal and intravitreal application of AAV5, AAV9 and ShH10Y in control and Crb1 mutant rats; and (5) AAV-hCRB gene therapy at P5 for MGCs of Crb1 mutant rats does not result in a functional rescue.