The major histocompatibility complex (MHC) is a complex of genes located close together on a single chromosome. The MHC, or a complex much like it, is found in probably all vertebrates. An extraordinary feature of the MHC in humans and mice and possibly many other species is that it is by far the most variable part of the entire genome. This extreme genetic diversity among individuals reflects the role of the MHC in controlling the immune system. Research by Yamazaki and his colleagues shows that the MHC may function in behavior in ways that strongly affect the frequency of various MHC genes in populations. Male mice of certain inbred strains tend to avoid mating with other mice carrying the same MHC genes as their own, a phenomenon known as disassortative mating. Because close relatives tend to carry the same genes, disassortative mating would tend to favor unrelated individuals as mates. These MHC preferences of males are learned and can be reversed by rearing pups with an appropriate foster mother. Dr. Brown's research is concerned with understanding how the MHC affects behavior and populations at a behavioral level. Preliminary work in his laboratory using other strains of mice confirms disassortative mating based on MHC genes, but with female choice and not male choice of mates. In this project, he will determine if wild mice can employ MHC-coded odors in choosing a mate, and if these mice learn their preferences for MHC types from their rearing associates, primarily the nursing mother. Other work suggests that wild mice are more choosy in mating that the inbred mice used by Yamazaki and by Brown; Brown will measure the difference in choosiness between wild and inbred strains. This research project will help to estimate how strong a role is played by the MHC in avoiding inbreeding in wild mice. In general, the project will help to explain both genetic and environmental determinants of mating preference in mammals.
