Viable interspecies chimeras created by injection of Apodemus embryonic stem cells into Mus blastocysts.

Embryonic stem (ES) cells can differentiate into a variety of specialized cell types when introduced into early embryos (i.e., morulas or blastocysts) of the same species. A question of medical and basic biological importance is whether ES cells of one species can differentiate properly and contribute significantly to chimerism when placed within early embryos of another distantly related species. Here, we address this question using two divergent mammalian model organisms, Apodemus sylvaticus and Mus musculus, whose genomes differ by about 15%. Despite this considerable evolutionary distance, injection of Apodemus ES cells into Mus blastocysts led to viable chimeras bearing extensive Apodemus contributions in all the major organs. Immunostaining showed that Apodemus ES cells had differentiated into a wide range of cell types in the chimeras. These results support the feasibility of deriving a variety of specialized cells or perhaps even complex tissues from ES cells of one species by placing them in the blastocysts of another divergent species. Our data also highlight the remarkable evolutionary conservation of developmental signaling by revealing its compatibility between two rathe distantly related organisms. [ABSTRACT FROM AUTHOR]