Maternal germ-line transmission of mutant mtDNAs from embryonic stem cell-derived chimeric mice

We report a method for introducing mtDNA mutations into the mouse female ge rm line by means of embryonic stem (ES) cell cybrids. Mitochondria were rec overed from the brain of a NZB mouse by fusion of synaptosomes to a mtDNA-d eficient (rho degrees) cell line. These cybrids were enucleated and the cyt oplasts were electrofused to rhodamine-6G (R-6G)-treated female ES cells. T he resulting ES cell cybrids permitted transmission of the NZB mtDNAs throu gh the mouse maternal lineage for three generations. Similarly, mtDNAs from a partially respiratory-deficient chloramphenicol-resistant (CAP(R)) cell line also were introduced into female chimeric mice and were transmitted to the progeny. CAP(R) chimeric mice developed a variety of ocular abnormalit ies, including congenital cataracts, decreased retinal function, and hamara tomas of the optic nerve. The germ-line transmission of the CAP(R) mutation resulted in animals with growth retardation, myopathy, dilated cardiomyopa thy, and perinatal or in utero lethality. Skeletal and heart muscle mitocho ndria of the CAP(R) mice were enlarged and atypical with inclusions. This m ouse ES cell-cybrid approach now provides the means to generate a wide vari ety of mouse models of mitochondrial disease.