Spatiotemporal sequence of mesoderm and endoderm lineage segregation during mouse gastrulation

ABSTRACT Anterior mesoderm (AM) and definitive endoderm (DE) progenitors represent the earliest embryonic cell types that are specified during germ layer formation at primitive streak (PS) of mouse embryo. Genetic experiments indicate both lineages segregate from Eomes-expressing in response to different Nodal signaling levels. However, precise spatiotemporal pattern emergence these molecular details lineage segregation remain unexplored. We combined genetic fate labeling imaging approaches with single-cell RNA sequencing (scRNA-seq) follow transcriptional identities define trajectories Eomes-dependent types. Accordingly, all cells moving through PS first day gastrulation express Eomes. AM DE specification occurs before leave Eomes-positive a distinct pattern. ScRNA-seq analysis further suggested immediate complete separation as last common bipotential progenitor.