Exon 4 was modified to contain a 2 base pair deletion in the transactivation domain (E168d2) linked to early onset severe autosomal dominant forms of cone-rod dystrophy (adCoRD) and Leber Congenital Amaurosis (adLCA). This mutation results in a frameshift and premature truncation of the expected product. Cre-mediated recombination removed the floxed neomycin resistance cassette inserted upstream of exon 4. (J:211011)