Abstract
Mutations in mitochondrial DNA are associated potentially with nonsyndromic and aminoglycoside-induced hearing loss. Several nucleotide changes associated with hearing impairment were described; however, a variable frequency of deafness-associated mutations in different populations has been observed. The aim of the present study was to determine the frequency of pathological mutations in mitochondrial 12S rRNA and tRNASer(UCN) genes in a group of 500 individuals representative of the general population of Poland. Mutational screening of 12S rRNA revealed the presence of three deafness-associated mutations, A827G, T961C, and A1555G, and one potentially pathogenic substitution, T669C. The carrier frequency of pathological mutations was estimated to be 1.2% (6/500) in the general Polish population. A deafness-associated G7444A mutation in the precursor of tRNASer(UCN) gene was identified in 8/500 (1.6%) unrelated blood donors. Seven nucleotide changes identified in 12S rRNA (G709A, G750A, G930A, T1243C, T1420C, and G1438A) and tRNASer(UCN) (C7476T), based on a frequency exceeding 1.0%, were considered as polymorphisms of 12S rRNA and tRNASer(UCN) in the studied population. Mitochondrial 12S rRNA gene seems to be the hot spot for deafness-associated mutations in the Polish population. The relatively high carrier frequency of tRNASer(UCN) G7444A (1/62) suggests that this substitution might be a nonpathogenic polymorphism in the Polish population.