Mouse complete embryoid development within a yolk sac recapitulates gastrulation, neurulation and early organogenesis

Embryo-like structures generated from stem cells can achieve varying developmental milestones, but none have been shown to progress through gastrulation, neurulation, and organogenesis. Here, we show that "ETiX" mouse embryoids, assembled from embryonic stem cells, trophoblast stem cells and inducible extraembryonic endoderm stem cells, can develop into gastrulating embryoids, and beyond to generate neurulating embryoids, which generate the progenitors needed to create the entire organism. The head-folds of ETiX neurulating embryoids show anterior expression of Otx2, defining forebrain and midbrain regions that resemble those of the natural mouse embryo. Neurulating embryoids also develop beating heart-like structures, trunks comprising a neural tube and somites, tail buds containing neuromesodermal progenitors and primordial germ cells, and gut tubes derived from definitive endoderm. Notably, neurulating embryoids also develop a yolk sac with blood islands. Overall, ETiX neurulating embryoid formation strongly resembles natural embryogenesis, advancing embryo-like development further than any other stem-cell derived model and within extra-embryonic membranes. Overall design: We applied tiny sci-RNA-seq3 to profile 285,640 single cell transcriptomes from multiple individual ETiX mouse embryoids (day6 and day8) and natural mouse embryos (E7.5, E8, E8.5, E8.75. and E9), in one experiment.