Discovery of a new role for the p53 family in the onset of mesendodermal differentiation of embryonic stem cells

Embryonic stem cells (ESCs) are derived from and closely related to the pluripotent cells of the early mammalian embryo. ESCs are able to re-enter embryonic development to populate the entire embryonic body once introduced into the blastocyst. Furthermore, such capacity of ESCs for unrestricted differentiation is possible both in vivo and in vitro, providing an excellent platform for studying early mammalian embryogenesis (1). Moreover, because of these remarkable properties, ESCs and induced pluripotent stem cells, which bear essentially the same biological properties as ESCs (2), are regarded with great promise for use in regenerative medicine as sources of numerous transplantation-competent cell types (3). However, the directed differentiation required to generate any specific cell type from these cells is much more difficult relative to inducing the full repertoire of differentiated cells; therefore, understanding the molecular basis of each specific differentiation pathway is crucial for efficient generation of a desired differentiated cell type.