[The first developmental decisions--cell differentiation in preimplantation mouse embryo]

The question, how multicellular fetus emerges from a totipotent single cell, the zygote, raises ceaseless curiosity of researchers. During embryogenesis, the cells of the embryo gradually lose their full developmental potency and begin to differentiate. The initial period of embryonic development of mammals, including the mouse, is primarily devoted to cell commitment of the pluripotent lineage that will give rise to all of the tissues of the embryo proper, as well as to the formation of extraembryonic tissues essential for embryo survival within the mother's uterus. The milestone in the studies of early stages of embryogenesis was derivation and maintenance of in vitro cultured stem cells that mimic the identity and properties of the primary cell lineages. It made possible to explore the mechanisms responsible for the critical early cell fate decisions taking place in vivo within the embryo.