From pluripotency to differentiation: laying foundations for the body pattern in the mouse embryo

A central question in contemporary stem and developmental biology and modern medicine is how developmental potential becomes progressively restricted as development proceeds. How totipotency—namely the ability to give rise to both embryonic and extraembryonic tissues and, in an ideal situation to the entire organism—is lost. How do cells choose between alternative fates, and how do they stereotypically organize themselves into developing tissues? Today, one can strip differentiated cells of their identity by inducing pluripotency, but it is still largely unknown how pluripotency emerges in its native context within the early embryo. Indeed, the only true pluripotent cell population—the epiblast—exists in vivo within the early mammalian embryo.