Mitochondrial diseases are due to a defect of cellular energy production. They are clinically and genetically extremely heterogeneous. Our project is to compensate for the effect of mutations in nuclear genes involved in the maintenance of mitochondrial DNA, a small genome located inside the mitochondria and otherwise perfectly normal. Rather than correcting these nuclear genes, we will introduce mitochondrial DNA outside the mitochondria and thus out of the action of the mutated proteins that are in the mitochondria. This will be tested first in mouse models. This approach could make it possible to perform gene therapy against mutations of different nuclear genes.