UNIFORM TISSUE DISTRIBUTION OF TRANSFER RNA(LYS) MUTATION IN MITOCHONDRIAL-DNA IN MERRF PATIENTS

We documented the presence of a point mutation in the tRNA(Lys) gene o f mitochondrial DNA (mtDNA) in various postmortem tissues from two pat ients with myoclonus epilepsy associated with ragged-red fibers (MERRF ). The percentages of the mutant mtDNA were similar (93 to 99%) in bot h clinically affected and unaffected tissues, suggesting that preferen tial clinical involvement of certain tissues in MERRF is based not onl y on the variation of distribution of the mutant mtDNA, but also on ot her factors such as differences in the threshold in various CNS region s and organs.