Signaling pathways regulating cell fate allocation in the early mouse embryo

Shortly after implantation mouse embryo comprises of three distinct epithelial layers. The founder tissue of the embryo proper, the epiblast, forms a radially symmetrical cup of cells that grows in close apposition to the extra-embryonic ectoderm and visceral endoderm to form a simple cylindrical structure. Reciprocal inductive interactions between these tissues, mediated by the activity of the TGFb growth factor Nodal expressed in the epiblast, are responsible for establishing initial axis polarity of the embryo. Some hours later, during gastrulation, dose-dependent Nodal activities regulate the process of cell fate allocation to generate the early body plan.

We have identified the T-box transcription factor Eomesodermin (Eomes) as a key Nodal target gene that plays multiple roles in the early embryo in specification of discrete cellular sub-sets and progenitor populations. I will focus on our current understanding as to how dynamic Eomes expression executes cell type specific roles, with a particular focus on our recent findings for Eomes requirements for the first waves of embryonic blood formation.