Intrinsic and extrinsic factors affecting the viability of Mus caroli x M. musculus hybrid embryos

Abstract

Interspecific hybrids between M. musculus and M. caroli, a wild species of mouse, were produced by artificial insemination, although the species do not normally interbreed. However, the success rate was low, with many embryos dying at various stages of pregnancy. Hybrid embryos were retarded in comparison with either parent species from the earliest stages of development, suggesting that intrinsic problems of genomic incompatibility play a major role in poor hybrid survival. However, failure of normal embryo-uterine interactions may also be important, since M. caroli x M. caroli embryos transferred to the M. musculus uterus also failed to survive to term. It is suggested that a maternal immune response to antigens on the foreign trophoblast may be involved.