Studies of in vitro differentiation with embryonic stem cells.

Embryonic stem (ES) cells were first cultured from mouse embryos little more than a decade ago, yet they are now widely used in transgenic studies which are revolutionizing mammalian genetics. Although drawing less attention, in vitro studies of mouse ES cells have also contributed widely to the understanding of mechanisms of embryonic cell differentiation and proliferation. This review focusses on the application of ES cells as in vitro models for cellular and molecular events in the early mammalian embryo. Future studies with cultured ES cells of mouse and other species should provide insights into the factors regulating the differentiation of intermediate stem cells and terminal cells for the various embryonic lineages, thus contributing profoundly to the understanding of mammalian embryogenesis as well as providing cells for therapeutic applications.