CRB1 and Leber congenital amaurosis: Four mouse models show a more severe phenotype similar to LCA: (i) Crb1+/−Crb2 cKO with reduced level of CRB1 and absence of CRB2 in RPCs; (ii) Crb1Crb2 cKO with CRB1 and CRB2 ablated in RPCs; (iii) Crb1KOCrb2ΔimmPRC mice with CRB1 and CRB2 ablated in immature PRCs but remaining levels of CRB2 in MCs and RPCs; and (iv) Crb1KOCrb2ΔMG mice with CRB1 and CRB2 ablated in MCs but remaining levels of CRB2 in PRCs and RPCs.