Low prevalence of GJB2 mutations in non-syndromic hearing loss in Western India

To identify the prevalence of GJB2 (Cx 26)and GJB6 (Cx 30) mutations in hearing impaired individuals from Western and South India.

Cross-sectional study.

Families with hearing impaired individuals (prelingual, non-syndromic, sensori-neural hearing loss) were enrolled and genomic DNA was extracted. Primers were designed for amplifying the coding and non-coding exons including flanking splice sites of the Cx 26 gene. Probands heterozygous or negative for Cx 26 mutations were further analyzed for the 342Kb deletion encompassing D13S1830 microsatellite marker on Cx 30.

Two hundred and eighty-eight patients were enrolled in the study and 116 (40.3%) were diagnosed to have mutations in the coding exon 2 of Cx 26 gene. Fifty-four (18.8%) probands were found to have mutations in both the alleles while the remaining 62 (21.5%) were heterozygous for Cx 26 mutations. W24X, and W77X were the common mutations identified. The prevalence of familial deafness was similar in both consanguineous and non-consanguineous families (33% and 34.9% respectively). Mutations in the non-coding exon 1 and intron 1 as well as the 342 kb deletion involving D13S1830 marker on Cx 30 were ruled out in two hundred and thirty-four deaf individuals carrying none or only one mutation in the exon 2 of Cx 26 gene.

Cx30 mutations do not contribute to the autosomal recessive non-syndromic hearing loss (NSHL) in the Indian population. Homozygous Cx26 mutations account only for about 1/5th (18.8%) of autosomal recessive non-syndromic hearing implying the need to explore other contributory loci.