Study of mitochondrial DNA A1555G and C1494T mutations in a large cohort of women individuals.

Mammalian mitochondrial A1555G and C1494T mutations are the most common causes of aminoglycoside-induced and non-syndromic hearing loss. However, these two mutations always are studied in the subject of pedigrees analysis. In the present study, we aimed to investigate the genetic characteristic of the A1555G and C1494T mutations on the population-level sampling, and to study the A1555G pattern of maternal transmission in three heteroplasmic families. Four thousand two hundred and ten unrelated women with normal hearing were enrolled as subjects. We used a mutation detection kit to screen the prevalence of these two mutations and used denaturing high performance liquid chromatography (DHPLC) and DNA sequencing to detect three A1555G heteroplasmic pedigrees. The carrier rate of A1555G was 0.33%, and the carrier rate of C1494T was 0.02% in our cohort, but the rate of heteroplasmy in A1555G mutant carriers reached 21.4%. Mitochondrial A1555G mutation rate was significantly decreased during maternal transmission of the mutant. Strong purifying selection may determine the fate of mtDNA A1555G in the transmission of human population.