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.