Self-patterning of human stem cells into post-implantation lineages.

Investigating human development is a significant scientific challenge due to the technical and ethical limitations of working with embryonic samples. In the face of these difficulties, stem cells have provided an alternative to experimentally model inaccessible stages of human development in vitro 1-13 . Here, we show that human pluripotent stem cells can be triggered to self-organise into three-dimensional structures that recapitulate some key spatiotemporal events of early human post-implantation embryonic development. Importantly, our system reproducibly captures spontaneous differentiation and co-development of embryonic epiblast and extra-embryonic hypoblast-like lineages, establishes key signalling hubs with secreted modulators, and can undergo symmetry breaking-like events. Single-cell transcriptomics confirms differentiation into diverse cell states of the peri-gastrulating human embryo 14,15 without establishing placental cell types, including signatures of post-implantation epiblast, amniotic ectoderm, primitive streak, mesoderm, early extra-embryonic endoderm, as well as initial yolk sac induction. Collectively, our system captures key features of human embryonic development spanning from Carnegie-stage 16 (CS) 4 to CS7, offering a reproducible, tractable, and scalable experimental platform to understand the basic cellular and molecular mechanisms that underlie human development, including new opportunities to dissect congenital pathologies with high throughput.