CRB2 and retinal degeneration: Although zebrafish Crb2b proteins are expressed in adult PRCs, and human CRB1 and CRB2 and Drosophila crb protect against retinal degeneration (reviewed in Pichaud, 2018; Slavotinek, 2016), we did not observe any gross defects in the structure of the retina nor in the ultrastructure of PRCs in old crb2be40 fish.