Prevalence and nature of connexin 26 mutations in children with non-syndromic deafness

Objective: To determine (1) the prevalence and nature of connexin 26 mutations in a cohort of Australian children with non-syndromic hearing loss, and (2) the carrier frequency of the common connexin 26 mutation (35delG) in the general population. Design: A cohort, case-finding study. Mutation analysis was performed on DNA extracted from white blood cells, buccal cells, or Guthrie blood spots. Setting: A hearing loss investigation clinic and a deafness centre in two Australian capital cities, 1 January 1998 to 31 October 2000. Participants: (1) 243 children (age range, 4 weeks to 16 years; median, 4 years), attending hearing loss clinics in Sydney and Melbourne; (2) 1000 blood samples obtained from anonymous Guthrie card blood spots collected in 1986 by the Victorian Clinical Genetics Service as part of the newborn screening program. Main outcome measures: (1) The prevalence and types of connexin 26 mutations in a cohort of children with prelingual deafness; (2) the carrier frequency of the common connexin 26 mutation, 35delG, in the general population. Results: Connexin 26 mutations were identified and characterised in 52 (21%) of the 243 children; 14 different mutations, including four previously unreported mutations (I35S, C53R, T123N and R127C), were identified. The common 35delG mutation was found in 56 of the 104 alleles (ie, 86 of the connexin 26 alleles in which a mutation was positively identified). The mutations V37I and M34T were also relatively common. The carrier frequency of connexin 26 mutations and of the common 35delG connexin 26 mutation in the Victorian population was estimated to be 1 in 54 and 1 in 100, respectively. Conclusions: Mutations in the connexin 26 gene (especially the 35delG mutation) are a common cause of prelingual hearing loss in Australia.