Study of six mutations in the gjb2 gene in Cuban patients with nonsyndromic sensorineural deafness

Deafness is a partial or total hearing loss that can appear at any ages and with different degrees of severity. About 50% of hearing disorders have a genetic origin, and among them, the nonsyndromic sensorineural deafness represents 70% of the cases. Out of these, the 80% correspond to autosomal recessive inheritance deafness. Autosomal recessive deafness has not been characterized enough at molecular level in Cuba. The purpose of this work was to determine the frequency of six gjb2 mutations in the nonsyndromic sensorineural deafness. In order to detect W24X, M34T, E47X, V95M, W77R, and 35delG mutations in the gjb2 gene, we employed the PCR-RFLP and the heteroduplex techniques. Four out of the six tested mutations were detected only by using the PCR-RFLP technique, being the most frequent mutations 35delG (70%) and M34T (20%). The other two mutations detected employing this technique (W77R and E47X) represented 5% each one. The heteroduplex analysis was very informative because we detected the formation of seven heteroduplexes in the analyzed fragments, corresponding to six different patients. The formation of heteroduplexes was obtained in two amplified fragments corresponding to one of these patients. In two of these patients, the heteroduplex complemented one mutation previously detected by the PCR-RFLP technique. This work allowed us to identify five families in which the carrier diagnosis of the autosomal recessive inheritance deafness led to the definition of the genotype responsible for the illness.