TFAP2A and microphthalmia: However, injection of tfap2a morpholinostcf7l1a−/+ andtcf7l1a−/− mutants results incoloboma/anophthalmia, respectively, while injection intobmp4−/− mutants causes microphthalmia and/orcoloboma.229tcf7l1a and bmp4 variants sensitise thedeveloping eye to the effects of additional deleterious mutations, implyinghuman hypomorphic TFAP2A variants may contribute todevelopmental eye disorders when on a background with additional mutations,potentially explaining phenotypic variability.