Hum Mol Genet 17:27 (2008)
Andy Peng Xiang1, Frank Fuxiang Mao2, Wei-Qiang Li1, Donghyun Park2, Bao-Feng Ma1, Tao Wang1, Tammy W. Vallender2, Eric J. Vallender2, Li Zhang2, Jaehyun Lee2, John A. Waters3, Xiu-Ming Zhang1, Xin-Bing Yu1, Shu-Nong Li1 and Bruce T. Lahn2
The full potential of embryonic stem (ES) cells to generate precise cell lineages and complex tissues can be best realized when they are differentiated in vivo—i.e. in developing blastocysts. Owing to various practical and ethical constraints, however, it is impossible to introduce ES cells of certain species into blastocysts of the same species. One solution is to introduce ES cells into blastocysts of a different species. However, it is not known whether ES cells can contribute extensively to chimerism when placed into blastocysts of a distantly related species. Here, we address this question using two divergent species, Apodemus sylvaticus and Mus musculus, whose genome sequence differs by 18% from each other. Despite this considerable evolutionary distance, injection of Apodemus ES cells into Mus blastocysts led to viable chimeras bearing extensive Apodemus contributions to all major organs, including the germline, with Apodemus contribution reaching 40% in some tissues. Immunostaining showed that Apodemus ES cells have differentiated into a wide range of cell types in the chimeras. Our esults thus provide a proof of principle for the feasibility of differentiating ES cells into a wide range of cell types and perhaps even complex tissues by allowing them to develop in vivo in an evolutionarily divergent host—a strategy that may have important plications in research and therapy. Furthermore, our study demonstrates that mammalian evolution can proceed at two starkly contrasting levels: significant divergence in genome and proteome sequence, yet striking conservation in developmental programs.