TY - JOUR T1 - Spatiotemporal sequence of mesoderm and endoderm lineage segregation during mouse gastrulation JF - bioRxiv DO - 10.1101/2020.06.09.142265 SP - 2020.06.09.142265 AU - Simone Probst AU - Sagar AU - Jelena Tosic AU - Carsten Schwan AU - Dominic Grün AU - Sebastian J. Arnold Y1 - 2020/01/01 UR - http://biorxiv.org/content/early/2020/06/15/2020.06.09.142265.abstract N2 - Anterior mesoderm (AM) and definitive endoderm (DE) progenitors represent the earliest embryonic cell types that are specified during germ layer formation at the primitive streak (PS) of the mouse embryo. Genetic experiments indicate that both lineages segregate from Eomes expressing progenitors in response to different NODAL signaling levels. However, the precise spatiotemporal pattern of the emergence of these cell types and molecular details of lineage segregation remain unexplored. We combined genetic fate labeling and imaging approaches with scRNA-seq to follow the transcriptional identities and define lineage trajectories of Eomes dependent cell types. All cells moving through the PS during the first day of gastrulation express Eomes. AM and DE specification occurs before cells leave the PS from discrete progenitor populations that are generated in distinct spatiotemporal patterns. Importantly, we don’t find evidence for the existence of progenitors that co-express markers of both cell lineages suggesting an immediate and complete separation of AM and DE lineages.Summary statement Cells lineages are specified in the mouse embryo already within the primitive streak where Mesp1+ mesoderm and Foxa2+ endoderm are generated in a spatial and temporal sequence from unbiased progenitors.Competing Interest StatementThe authors have declared no competing interest. ER -