Mitochondrial curation for the next generation

The mitochondrial genome (mtDNA) can accumulate deleterious mutations that lead to disease. Animals have evolved strategies to eliminate mtDNA mutations in the maternal germ line, increasing the likelihood that their progeny inherit healthy mitochondria. Here, we provide an overview of mitochondrial quality control in the germ line, focusing on recent findings in mammals, Drosophila, and C. elegans. We discuss three strategies for quality control: elimination of sperm mtDNA, which prevents transmission of paternal mtDNA to progeny; the genetic bottleneck, which reduces the effective number of mtDNAs in germ cells, potentially exposing mutations to selection; and purifying selection, which selects for healthier mtDNAs. Finally, we discuss outstanding questions in the field and technical advances needed to address them.