Connexin mutations and hearing loss

Kelsell et al.1 provide convincing evidence that mutations in the gene encoding the gap-junction protein connexin 26 (Cx26) are responsible for autosomal recessive non-syndromic hearing loss at the DFNB1 locus on chromosome 13q12. They also report a small family with apparent autosomal dominant congenital hearing loss and autosomal dominant palmoplantar keratoderma (PPK) in which two siblings with profound hearing loss are heterozygous for a single base-pair substitution resulting in a methionine-to-threonine (ATG-to-ACG) change in codon 34 (M34T) of Cx26 (12). The authors conclude that the M34T change is the genetic basis of profound hearing loss in this family and suggest, on this basis, that the Cx26 gene is responsible for autosomal dominant non-syndromic hearing loss (ADNSHL) at the DFNA3 locus chromosome 13q12 (ref. 3). We have identified a family in which the M34T variant is not associated with hearing loss, suggesting that this conclusion might be premature.