Connexin 26 ( GJB2 ) mutations in the Turkish population: implications for the origin and high frequency of the 35delG mutation in Caucasians

Abstract

Mutations in the Connexin 26 (GJB2/Cx26) gene are responsible for more than half of all cases of prelingual non-syndromic recessive deafness in many Caucasian populations. To determine the importance of Cx26 mutations as a cause of deafness in Turks we screened 11 families with prelingual non-syndromic deafness, seven (64%) of which were found to carry the 35delG mutation. We subsequently screened 674 Turkish subjects with no known hearing loss and found twelve 35delG heterozygotes (1.78%; 95% confidence interval: 0.9%-3%) but no examples of the 167delT mutation. To search for possible founder effects, we typed chromosomes carrying the 35delG mutation for closely linked polymorphic markers in samples from Turkey and United States and compared the allele frequencies with those of hearing subjects. The data showed a modest degree of disequilibrium in both populations. Analyses of two pedigrees from Turkey demonstrated both conserved and different haplotypes, suggesting possible founder effects and multiple origins of the 35delG mutation.

Mutations of Cx26 gene (GJB2) for prelingual deafness in Taiwan

“…The 35delG allele has been demonstrated to be the most frequently found mutation to cause non-syndromic recessive prelingual deafness in Caucasians. 9,16 Tekin et al 16 suggested that the high frequency of 35delG allele may possibly arise from a founder effect and further enhanced by assortative mating in the population. This postulation could be true, since the oriental populations, Japanese 4 and Taiwanese (this study), do not exhibit this allele and the most common mutation in both oriental populations is 235delC, indicating that different causes between the Cx26 mutations of Caucasian and those of oriental populations.…”

Autosomal recessive deafness 1A (DFNB1A) in Yakut population isolate in Eastern Siberia: extensive accumulation of the splice site mutation IVS1+1G>A in GJB2 gene as a result of founder effect

“…6 The mutation c.35delG has been found to occur with high frequency in populations of Europe, Middle East and Northern America (predominantly among Caucasians). [7][8][9][10][11][12][13][14] The mutation c.235delC has been registered mainly in East Asian populations (Japanese, Korean and Chinese); and also has been found among Thais (Southeast Asia), Mongolians (Central Asia) and Altaians (South Siberia). [15][16][17][18][19][20][21] The mutation c.167delT is specific for Ashkenazi Jews and is sporadically found in some other populations.…”

Research of genetic bases of hereditary non-syndromic hearing loss

“…Thus, a stop When considered by country, the carrier frequency of this mutation is 3.4% in Italy, 3.5% in Greece, 2.75% in France, and 2.8% in Malta and Portugal, whereas it shows a marked decrease in countries in America and Asia (16). The carrier frequency in Turkey has been reported to range between 1.17% and 1.78% in different studies (17,18). In other studies conducted in Turkey, the c.35delG mutation has been found in 5-53% of individuals with hearing impairment (7,10).…”