S12.18 A genetic system to study mitochondrial DNA mutations and their propagation in mice

Abstract

The number of mutations in mitochondrial DNA (mtDNA) thought to causemetabolic disorders in patients is growing. At present, we lack the technology to introduce these mutations into the mtDNA of model organisms for detailed study. In this study, random mtDNA mutations were generated using the transgenic mtDNA mutator mouse, which expresses an engineered mitochondrial polymerase defective in its proofreading function. Female lines were then established to transmit and segregate the resulting mutations. We observed the selective loss of nonsense mutations in the protein coding genes, consistent with strong purifying selection by the female germline. The selection was evident two generations after the founder mtDNA mutator mouse, eliminating these nonsense mutations before they were detectable by Sanger sequencing methods. Curiously, the tRNA and rRNA genes do not show the same rapid selection against mutations despite strong evolutionary sequence conservation. Despite this purifying selection, putative deleterious mutations were identified and propagated in the mouse lines. Also, mutations analogous to human pathogenic mtDNA mutations were identified. These results will aid in the generation of more accurate models of inheritance of disease-causing mtDNA mutations and allow for the generation of laboratory mouse models of mtDNA mutations known in human disease.