Genome Engineering

The house mouse (Mus musculus domesticus) is a major pest in the house and for stored food and crops, and has developed resistance to rodent poison. Researchers have discovered that one of the ways that the house mouse can do this by hybridisation with another species.

House mice can develop resistance to anticoagulant rodenticides such as warfarin through polymorphisms in the enzyme vitamin K 2,3-epoxide reductase subcomponent 1 (VKORC1). Researchers have isolated ten or more alleles of the vkorc1 gene, found on chromosome 7, that give house mice resistance to warfarin. Six are mutations of the house mouse genome, but four have come from mating with the Algerian mouse, also known as the western Mediterranean mouse (Mus spretus), a species that diverged from M musculus around 1 million years ago.

Researchers, from Rice University, analysed the genome of warfarin-resistant mice from a German bakery. These looked like house mice but carried the resistance sequence from the Algerian mouse, perhaps from interbreeding in overlapping territories in Spain and North Africa. Generally inter-species mating doesn’t create viable offspring, but occasionally it does, and the researchers have described this as ‘catching evolution in the act’. The paper is published in Current Biology.

The original point mutation may have given the Algerian mice an ability to survive on a diet is naturally deficient in vitamin K. However, the transfer of the mutation to the hybrid mice will give them a new advantage by making them resistant to the commonly-used warfarin-based rodenticides. The cross appears to have happened relatively recently – how long will it take to spread across Europe?

The mouse genome was first sequenced in 2002, and the J Craig Venter Institute created a synthetic mouse genome in 2010.

Song Y, Endepols S, Klemann N, Richter D, Matuschka FR, Shih CH, Nachman MW, & Kohn MH (2011). Adaptive Introgression of Anticoagulant Rodent Poison Resistance by Hybridization between Old World Mice. Current biology : CB, 21 (15), 1296-301 PMID: 21782438