Analysis of the biological functions of mitochondria using germline cell manipulation

摘要

Mitochondria have their own genomes, mitochondrial DNA (mtDNA), which encode 13 subunits of the respiratory chain that are essential for ATP production during oxidative phosphorylation. Mutations of mtDNA cause mitochondrial diseases that affect various tissues or organs, including the central nervous system, skeletal muscle, and the endocrine system. Furthermore, it has been proposed that mtDNA mutations are associated with cardiomyopathy, diabetes mellitus, Alzheimer's and Parkinson's disease, and aging. The generation of animal models for mitochondrial diseases has been hampered by the inability to introduce mutations into mtDNA. Recently, we found a cultured cell line with large-scale deleted mtDNA, which we used to establish a new line containing the mutant mtDNA at a high rate. The mutant mtDNA was introduced into mouse zygotes by electrofusion of cytoplasts obtained from the cultured cells. Some (31.6 percent) of the pups carried the mutant mtDNA without manifesting any phenotypes relatedto mitochondrial dysfunction. The mutant mtDNA was propagated into subsequent generations through the maternal germline, and, interestingly, the proportion of mutant mtDNA increased as the generations proceeded. Unlike the common human mitochondrial diseases, the mitochondrial dysfunction in these mice caused severe chronic renal failure, which led to the death of the mice within one year after birth. The skeletal and cardiac muscles also showed sporadic fibers negative for mitochondrial respiratory chain enzyme staining, which is characteristic of the major types of human mitochondrial disease. We expect that our mitochondrial disease mice will provide animal models that will improve our understanding of mitochondrial diseases through analyses of theirheredity, etiology, and pathophysiology, and lead to the development of new technologies for the diagnosis and treatment of these diseases.