Microphthalmia, Isolated, With Coloboma 7

A number sign (#) is used with this entry because of evidence that isolated colobomatous microphthalmia-7 (MCOPCB7) is caused by heterozygous mutation in the ABCB6 gene (605452) on chromosome 2q35.

For a discussion of genetic heterogeneity of isolated colobomatous microphthalmia, see MCOPCB1 (300345).

Mapping

In members of a 3-generation Chinese family with autosomal dominant iris and chorioretinal coloboma who were negative for mutation in known coloboma-associated genes, Wang et al. (2012) performed genomewide linkage analysis and found linkage to chromosome 2q35. This family was originally reported by Dong et al. (2009).

Molecular Genetics

In a 3-generation Chinese family with autosomal dominant iris and chorioretinal coloboma mapping to chromosome 2q35 and known to be negative for mutation in known coloboma-associated genes, Wang et al. (2012) sequenced the exons of 76 candidate genes and identified a heterozygous missense mutation in the ABCB6 gene (L811V; 605452.0006) that segregated with disease in the family and was not found in DNA samples from 600 ethnically matched controls. Subsequent analysis of ABCB6 in 116 sporadic Indian coloboma patients, 63 of whom had microphthalmia and coloboma, 21 isolated coloboma, and 32 aniridia, who were all negative for mutation in 9 known coloboma genes, revealed heterozygosity for a different missense mutation (A57T; 605452.0007) in 3 unrelated patients with microphthalmia and coloboma; the mutation was not found in DNA samples from 200 ethnically matched controls.