Frequency of the recessive 30delG mutation in the GJB2 gene in Northeast-Hungarian individuals and patients with hearing impairment.

Mutations in the GJB2 gene, which encodes a gap junction protein (connexin 26) account for up to 50% of cases of congenital autosomal recessive non-syndromic hearing impairment. A single mutation, 30delG, is responsible for 70% of this autosomal recessive hearing loss in Europe. This study describes the 30delG mutation analysis of 23 Hungarian families (64 individuals) with at least two subjects with congenital non-syndromic hearing defect and of 52 unrelated individuals from the Northeastern population of Hungary. In all patients, non-progressive hearing impairment varied from moderate to profound involving all frequencies. DNA was tested by PCR based restriction enzyme assay (BSiYI). Sixty-four percent of the patients displayed this one base deletion in GJB2. Out of these, 65.9% were homozygous for this mutation and 34.1% were heterozygotes. The latter showed compound heterozygosity since in these 14 patients, eight previously reported different nucleotide changes were observed on the second allele. The carrier frequency of the 30delG mutation among control group was one in 10.4 (9.6%). This high frequency of 30delG corresponds more to frequencies reported in Southern than in North Europeans.