Despite its universal importance to all eukaryotes, the implications of defects in the mitochondrial genome are poorly understood. The mitochondrial genome is refractory to genetic manipulation; normal approaches to the isolation of mutations are foiled by the high copy number and random segregation of the genomes. It is not even known whether mitochondrial DNA undergoes recombination. We developed an efficient selection for heritable mitochondrial genome (mtDNA) mutations in Drosophila. We targeted a restriction enzyme to mitochondria in the germline, which compromised fertility but led to the isolation of escaper progeny carrying homoplasmic mtDNA mutations lacking the cleavage site. These mutations altered the function of encoded gene products and, despite the fact that mutations were limited to a single 6-base stretch of DNA, resulted in a wide range of phenotypes. Use of alternative restriction enzymes allowed us to target different gene products.
From the seminal paper: expression of mito-Xho1 in the eye ablates the tissue (B & C); the phenotype is rescued in a mitochondrial mutant background (D; A is wt) (see Xu, 2008
Projects in the lab have focussed on the exploitation of this genetic system to probe a number of conundrums in mitochondrial biology: mechanisms that select against unfavorable mitochondrial mutations; the uniparental inheritance of the mitochondrial genome; the tissue specificity of human syndromes that are caused by mitochondrial dysfunction.