Background The molecular etiology of hearing impairment in Russia has not been fully investigated. Study of GJB2, GJÂ6, GJB3, 12SrRNA, tRNA Ser(UCN) and MYO7A genes revealed that 55% of the patients with hearing loss carried GJB2 mutations in different regions of Russia. The SLC26A4 and SLC26A5 genes mutations are analyzed in this study.
Methods Two hundred and fifty unrelated deaf patients were included. The all coding exons of SLC26A4 and first ten exons of SLC26A5 genes were sequenced in all 250 patients, including 130 patients carrying bi- and mono-allelic recessive GJB2 mutations, two patients carrying a known GJB2 dominant mutation c.224G>A (p.Arg75Gln), as well as six patients with mtDNA (m.1555A>G, m.961insC(n), m.961delTinsC(n) and m.7444G>A) mutations.
Results Eight patients (3.2%, 8/250) with non-syndromic hearing loss were found carrying SLC26A4 and SLC26A5 mutation and polymorphic variants. Among them, one patient with bi-allelic SLC26A4 mutations (c.85G>C (p.Glu29Gln) and c.149T>G (p.Leu50Arg)) had EVA by CT scan. One patient with non-syndromic hearing loss was heterozygous for mutations c.919–2A>G in SLC26A4 gene. The most common SLC26A5 gene mutation, g.-53–2A>G, accounted for 0.4% (1/250) of all SLC26A4 mutant alleles. Two patients with non-syndromic hearing loss were heterozygous for polymorphic variant c.49548A>G (p.Gly740Ser) in SLC26A4, and one was heterozygous for polymorphic variant g.38190T>C in SLC26A5. The novel SLC26A4 gene mutation g.29607delA was identified in one patient with EVA.
Conclusion Our results suggest that GJB2, SLC26A4 and SLC26A5 mutations together make up a major cause of congenital hearing loss in the different populations from Russia.