Frequence and the mutation spectrum of GJB2-related hearing loss in children of Dagestan as compared with the central European part of Russia

The sequencing of the entire coding region and the donor site of the splicing of the GJB2 gene has shown that prelingual neurosensory nonsyndromic autosomal recessive deafness/poor hearing in Dagestan Republic is genetically more heterogeneous than in the central European part of Russia. Thus, the number of the revealed mutations in the GJB2 gene in Dagestan was only 28% of the total number of alleles in patients tested. The main mutations in the GJB2 gene in Dagestan were represented by three forms typical for West Asia: 35delG mutation (22% of all mutant alleles), ΔE120 mutation (22%), both in the coding region, and IVS 1+1 G>A (44%) in the donor site of splicing. In addition, a novel mutation, ΔE187, was revealed in the coding region. All mutations were found in a compound heterozygous or a heterozygous state. This result allows one to explain the deafness/poor hearing by pathogenic mutations in the GJB2 gene only in 19% of Dagestan families with neurosensory nonsyndromic autosomal recessive disorders of hearing. We suggest that the origin and maintenance of the allele diversity of inherited deafness/poor hearing in Dagestan can be explained by the national and cultural peculiarities of small populations of nations of North Caucasus.