Determination of the frequency of connexin26 mutations in inherited sensorineural deafness and carrier rates in the Tunisian population using DGGE

Editor—Congenital deafness occurs in approximately 1 in 1000 live births and at least 50% of these cases are hereditary.1 Among the prelingual genetic forms of deafness, the autosomal recessive forms ( DFNB ) are frequent (80% of the cases) and in most cases are sensorineural and severe.1 Twenty eight loci that cause autosomal recessive non-syndromic hearing loss (ARNSHL) have been identified (http://dnalab-www.uia.ac.be./dnalab/hhh/index.html). The first locus defined for recessive deafness ( DFNB1 ) is linked to chromosome 13q12-13 and was identified by homozygosity mapping in two large consanguineous families from Tunisia.2 This initial report was followed by the identification of other consanguineous families of different ethnic origins which were linked to the DFNB1 locus and of several non-consanguineous white families in which the ARNSHL phenotype cosegregated with markers from chromosome 13q12-13.3-6Mutations in connexin26 ( Cx26 ), a gene that encodes gap junction protein beta-2 (GJB-2), have been shown to result in autosomal recessive ( DFNB1 ) and dominant ( DFNA3 ) non-syndromic sensorineural deafness.7 Mutations in the Cx26 gene have been found to be the most common cause of autosomal recessive deafness and the most frequently observed mutation is 35delG.8-12 The high prevalence of Cx26 mutations and their importance as a cause of ARNSHL have prompted the development of several different mutation detection assays to screen the single Cx26 coding exon.13-16 A rapid method to detect mutations in the GJB2 …