QUANTITATIVE-DETERMINATION OF HETEROPLASMY IN LEBERS HEREDITARY OPTICNEUROPATHY BY SINGLE-STRAND CONFORMATION POLYMORPHISM

Purpose. The maternal inheritance of Leber's hereditary optic neuropat hy (LHON) is caused by defects in the genes of mitochondrial DNA. (mtD NA). The most prevalent mtDNA mutation, present in 40% to 90% of famil ies with this disease, is a G to A substitution at nucleotide position 11778. The rapid and accurate quantification of heteroplasmy of this mutation will help determine the relative risk for disease expression. Methods. The authors conducted screening tests for heteroplasmy in 44 visually affected patients with the 11778 mutation and 34 unaffected members of 36 Japanese families with LHON using the single-strand conf ormation polymorphism analysis. This method can detect even a single b ase difference between the sequences of wild type and mutant DNA stran ds. The percentage of mutant mtDNA was calculated using an image analy zer. Results. Single-strand conformation polymorphism analysis allowed the detection of heteroplasmy ranging from 5% to 95%. Five (14%) of t he 36 families showed heteroplasmy, and 14 (18%) of the 78 persons tes ted had heteroplasmy ranging from 10% to 94%. Seven patients with hete roplasmy with visual loss had mutant mtDNA ranging from 62% to 94%. Co nclusions. Single-strand conformation polymorphism analysis is rapid, efficient, and accurate for detecting point mutations and quantifying heteroplasmy in mtDNA. Individuals with heteroplasmy with less than 60 % of mutant mtDNA. in circulating leukocytes are probably at lesser ri sk for developing optic atrophy.