Spectrum and frequency of GJB2 (Cx26) gene mutations in patients with hearing impairments in the Republic of Buryatia

In the diagnosis of hereditary non-syndromic hearing loss (HL), the methods of molecular genetic analysis of the GJB2 (Cx26) gene mutations provide high valuable information. For the first time, in the Republic of Buryatia (Eastern Siberia), the spectrum and frequency of GJB2 gene mutations were determined in a sample of 165 individuals with HL using sequencing of significant regions of the GJB2 gene. A total of 13 known allelic variants were found (c.-254C>T, c.-49G>A, c.-23+1G>A, c.35delG, c.79G>A, c.101T>C, c.109G>A, c.235delC, c.299_300delAT, c.327_328delinsA, c.341A>G, c.457G>A u c.516G>C). In the sample of Buryat patients, the mutation spectrum was represented by five GJB2 variants: c.-23+1G>A (4.1%), c.109G>A (0.6%), c.235delC (1.4%), c.327_328delGGinsA (0.6%), c.516G>C (0.6%). Five mutations were found among Russian patients: c.35delG (25.7%), c.-23+1G>A (3.3%), c.109G>A (1.9%), c.101T>C (0.6%), c.299_300delAT (0.6%). In general, the contribution of biallelic mutations of the GJB2 gene to the etiology of HL in the total sample of patients in Buryatia was 15.8% (26/165). When the total sample of patients was divided by ethnicity the contribution of biallelic mutations of the GJB2 gene to the etiology of HL in Buryat patients was 5.1% (4/79), and in Russian patients - 28.9% (22/76). Thus, the results of our study indicate that the mutations in the GJB2 gene are not the main cause of HL in Buryats. Probably, in some GJB2-negative patients (84.2% in our study), HL may be due to the mutations in other genes responsible for the development of hereditary hearing impairments.