Cell lineage, embryogenesis and mouse molecular genetics

Pluripotent stem cells are present in the murine embryo until at least the 64-cell stage (day 3.5 of development). These cells can be cultured in vitro and genetically modified to fulfill various specific requirements. After re-introduction into a host blastocyst, which then develops to maturity, they colonize all tissues, including the germ-line. Thus, it is now possible to create mice with pre-determined mutations in genes of clinical, developmental and commercial interest. (C) 1996 by Elsevier Science Inc.