Connexin 26 (GJB2) mutations in the Turkish population: implications for the origin and high frequency of the 35delG mutation in Caucasians

Mutations in the Connexin 26 (GJB2/Cx26) gene are responsible for more than half of all cases of prelingual non-syndromic recessive deafness in many C aucasian populations. To determine the importance of Cx26 mutations as a ca use of dearness in Turks we screened 11 families with prelingual non-syndro mic deafness, seven (64%) of which were found to carry the 35delG mutation. We subsequently screened 674 Turkish subjects with no known hearing loss a nd found twelve 35delG heterozygotes (1.78%; 95% confidence interval: 0.9%- 3%) but no examples of the 167delT mutation. To search for possible founder effects, we typed chromosomes carrying the 35delG mutation for closely lin ked polymorphic markers in samples from Turkey and United States and compar ed the allele frequencies with those of hearing subjects. The data showed a modest degree of disequilibrium in both populations. Analyses of two pedig rees from Turkey demonstrated both conserved and different haplotypes, sugg esting possible founder effects and multiple origins of the 35delG mutation .