mtDNA sequence, phylogeny and evolution of laboratory mice.

Laboratory mice are important tools for biomedical research. Aiming to investigate the phylogeny and evolution of laboratory mice, we investigated the mtDNA sequences of classic inbred strains, classic outbred stocks and wild-derived inbred strains. Our results showed that the most classic outbred stocks and classic inbred strains are descended from a single mtDNA ancestor. The phylogenic analysis supports the topology of M. m. castaneus/M. m. domesticus as sister subspecies, and the divergence time between the two sister subspecies and M. m. musculus was 493,000 (435,000-557,000) years ago. Furthermore, the mtDNA polymorphisms accumulated in the last 100years in the laboratory mice are under a relaxed purifying selection.