Human connexin 30 (GJB6), a candidate gene for nonsyndromic hearing loss: Molecular cloning, tissue-specific expression, and assignment to chromosome13q12

Mutations in connexin 26 are responsible for approximately 20% of genetic h earing loss and 10% of all childhood hearing loss. However, only about 75% of the mutations predicted to be in Cx26 are actually observed. While this may be due to mutations in non coding regulatory regions, an alternative hy pothesis is that some cases may be due to mutations in another gene immedia tely adjacent to Cx26. Another gap junction gene, connexin 30 (HGMW-approve d symbol GJB6), is found to lie on the same PAC clone that hybridizes to ch romosome 13q12. Human connexin 26 and connexin 30 are expressed in the same cells of the cochlea. Cx26 and Cx30 share 77% identity in amino acid seque nce but Cx30 has an additional 37 amino acids at its C-terminus. These cons iderations led us to hypothesize that mutations in Cx30 might also be respo nsible for hearing loss. Eight-eight recessive nonsyndromic hearing loss fa milies from both American and Japanese populations were screened for mutati ons. In addition, 23 dominant hearing loss families and 6 singleton familie s presumed to be recessive were tested. No significant mutation has been fo und in the dominant or recessive families. (C) 1999 Academic Press.