Mutant mtDNA at 1555 A to G in 12S rRNA Gene and Hypersusceptibility of Mitochondrial Translation to Streptomycin Can Be Co-Transferred to ρ0HeLa Cells

Human skin fibroblast line 95–119, which had been isolated from the mother of a Japanese patient with aminoglycoside-induced deafness and a 1555 A to G mutation at 12S rRNA gene in mitochondrial DNA (mtDNA), was used to investigate the relationship between the 1555 mtDNA mutation and its pathogenicity. By the intercellular transfer of mtDNA with or without the 1555 mutation to mtDNA-less (ρ0) HeLa cells, we isolated cybrid clones and found that the mitochondrial translation in a cybrid clone repopulated with the homoplasmic 1555 mutation showed the highest susceptibility to streptomycin. These observations suggest that the genotype of the mutant mtDNA and the phenotype of hypersusceptibility to streptomycin observed in 95–119 fibroblasts were co-transferred simultaneously to ρ0HeLa cells, supporting the idea that the homoplasmic 1555 mtDNA mutation is involved in the pathogenesis leading to aminoglycoside-induced hearing loss.