First molecular screening of deafness in the Altai Republic population

BACKGROUND: We studied the molecular basis of NSHL in Republic of Altai (South Siberia, Russia). The Altaians are the indigenous Asian population of the Altai Mountain region considered as a melting-pot and a dispersion center for world-wide human expansions in the past. METHODS: A total of 76 patients of Altaian, Russian or mixed ethnicity and 130 Altaian controls were analyzed by PCR-DHPLC and sequencing in the GJB2 gene. The GJB6 deletion and the common non-syndromic deafness-causing mitochondrial mutations were also tested when appropriate. RESULTS: 8.3% of the Altaian chromosomes were carrying GJB2 mutations versus 46.9% of the Russian chromosomes. The 235delC mutation was predominant among Altaians, whereas the 35delG mutation was most prevalent among Russian patients. CONCLUSION: We found an Asian-specific GJB2 diversity among Altaians, and different GJB2 contribution for deafness in the Altaian and Russian patients. The high carrier frequency of 235delC in Altaians (4.6%) is probably defined by gene drift/founder effect in a particular group. The question whether the Altai region could be one of founder sources for the 235delC mutation widespread in Asia is open.