Mutation analysis of the Cx26, Cx30, and Cx31 genes in autosomal recessive nonsyndromic hearing impairment

CONCLUSION: Biallelic Cx26 mutations are the most common cause of autosomal recessive nonsyndromic hearing impairment (ARNHI) in Switzerland. Mutations in Cx30 and 31, digenic mutations as well as large deletions/duplications, are unlikely to be a major cause of hearing loss in Swiss patients with ARNHI. Multiplex ligation-dependent probe amplification (MLPA) is a highly accurate screening method for detection of c.del(GJB6-D13S1830). OBJECTIVES: The intent of this study was to investigate the prevalence of the point and digenic mutations including large deletions and duplications in the Cx26, 30, and 31 genes in a Swiss patient cohort with ARNHI and cochlear implant. PATIENTS AND METHODS: The coding regions of Cx26, 30, and 31 were sequenced in 32 patients. Large deletions/duplications were assessed by MLPA. RESULTS: In one patient digenic heterozygous mutations involving Cx26 (c.35delG) and Cx30 (c.del(GJB6-D13S1830)) were identified. Biallelic Cx26 mutations were detected in 31%. One putative mutation (c.94C<T) was found in Cx31. MLPA analysis did not reveal any additional deletion or duplication in all three Cx genes, except for the heterozygous c.del(GJB6-D13S1830) deletion.