IDENTIFICATION OF INHERITANCE MODES OF MITOCHONDRIAL DISEASES BY INTRODUCTION OF PURE NUCLEI FROM MTDNA-LESS HELA-CELLS TO PATIENT-DERIVED FIBROBLASTS

A nuclear genome delivery system was developed to deduce the modes of inheritance of the clinical phenotypes observed in patients with mitoc hondrial diseases by transfer of pure nuclei from normal cells to fibr oblasts from the patients, The problem of possible contamination of th e nuclei with a small amount of mtDNA was overcome by using mtDNA-less (rho(O)) human cells as nuclear donors, In this study, intercellular transfer of pure nuclei was carried out by simple fusion of rho(O) HeL a cells with 533 fibroblasts from a patient with a fatal mitochondrial disease, which were deficient in cytochrome c oxidase and succinate d ehydrogenase activities. The results showed that the cytochrome c oxid ase and succinate dehydrogenase activities were restored by the introd uction of pure HeLa nuclei, suggesting that the observed phenotypes of mitochondrial dysfunction were not due to mtDNA mutations but to nucl ear, recessive mutations, Thus, our nuclear transfer system is effecti ve for determining whether a mitochondrial or nuclear genome of a pati ent is responsible for a disease and whether deficiency of mitochondri al enzymes, including enzymes exclusively encoded by nuclear genomes, is transmitted in a nuclear recessive or nuclear dominant way, providi ng the parents of the patients with valuable information for genetic c ounseling on the risk of mitochondrial diseases in their next babies.