CONTENT OF MUTANT MITOCHONDRIAL-DNA AND ORGAN DYSFUNCTION IN A PATIENT WITH A MELAS SUBGROUP OF MITOCHONDRIAL ENCEPHALOMYOPATHIES

A point mutation of mitochondrial tRNA(Leu(UUR)) gene is responsible f or a MELAS (mitochondrial myopathy, encephalopathy, lactic acidosis an d stroke-like episodes) subgroup of mitochondrial encephalomyopathies. In most cases, the mutant mitochondrial DNA (mtDNA) coexists with nor mal mtDNA in a heteroplasmic manner. In order to quantify the content of mutant mtDNA, we developed a quantitative method of PCR. Using this method, the distribution of the mutant mtDNA was examined in 32 diffe rent tissues among 18 autopsied organs from a patient with MELAS, who had shown hypophyseal dysfunction. The percentage of the mutant mtDNA at nucleotide number 3243 in each tissue was ranged between 22% and 95 %. The content of the mutant mtDNA was at the highest (95%) in the hyp ophysis and higher in the cerebral cortex than in the white matter. Th is study shows a possible correlation of tissue dysfunction with accum ulation of the mutant mtDNA within the brain.