Epithelial cell plasticity drives endoderm formation during gastrulation

We performed 3 single-cell RNAseq experiments to identify the mechanisms of definitive endoderm formation during gastrulation. To enrich for the rare endoderm and endoderm progenitor populations we used the FVF reporter mouse line. 103 homozygous FVF embryos were isloated at two consecutive days: 40 early to mid streak stage embryos at day 1, 39 early to mid streak embryos at day 2 , 24 mid streak to late streak embryos at day 2 . Embryonic compartments from each sample were FACS sorted according to Foxa2-Venus fluorescence intensity into FVF negative, FVF low and FVF high cell populations. Using the FVF-sorted cell populations we could identify FVF low endoderm progenitors and their continous transition into FVF high anterior defintive endoderm. 3 single-cell RNA-seq experiments were performed using 10X Genomics technology to generate single cell transcriptomic profiles of gastrulating mouse embryos. Homozygous FVF embryos were sorted to enrich for FVF low and high cell populations.