Clinical Heterogeneity, Tissue Distribution, and Intergenerational Segregation of mtDNA Mutation A3243G.

Tissue distribution and segregation and the functional consequences of heteroplasmic mitochondrial DNA mutation A3243G were studied in 30 carriers. The mutation load in hair follicles was higher in 20 patients with a broad spectrum of clinical symptoms than in 10 nonaffected carriers. The onset of the disease negatively correlated with the mutation load in blood and muscle. The activities of respiratory chain complexes in isolated muscle mitochondria did not decrease in all patients and were normal in isolated platelets. Changes in the heteroplasmy level between pairs of mothers and offspring suggest that random genetic drift is the mechanism associated with the intergenerational transmission of the A3243G mutation. In conclusion, detailed clinical investigations and mitochondrial DNA analyses in several tissues are of the highest diagnostic value for the prognosis of the disease in carriers of the A3243G mutation.