Naïve human pluripotent stem cells respond to Wnt, Nodal and LIF signalling to produce expandable naïve extra-embryonic endoderm

After maternal predetermination gives way to zygotic regulation, a ground state is established within the mammalian embryo. This tabula rasa for embryogenesis is present only transiently in the preimplantation epiblast. Here, we consider how unrestricted cells are first generated and then prepared for lineage commitment. We propose that two phases of pluripotency can be defined: naive and primed. This distinction extends to pluripotent stem cells derived from embryos or by molecular reprogramming ex vivo.

Across the animal kingdom, gastrulation represents a key developmental event during which embryonic pluripotent cells diversify into lineage-specific precursors that will generate the adult organism. Here we report the transcriptional profiles of 116,312 single cells from mouse embryos collected at nine sequential time-points ranging from 6.5 to 8.5 days post-fertilisation. We reconstruct a molecular map of cellular differentiation from pluripotency towards all major embryonic lineages, and explore the complex events involved in the convergence of visceral and primitive streak-derived endoderm. Furthermore, we demonstrate how combining temporal and transcriptional information illuminates gene function by single-cell profiling of Tal1 −/− chimeric embryos, with our analysis revealing defects in early mesoderm diversification. Taken together, this comprehensive delineation of mammalian cell differentiation trajectories in vivo represents a baseline for understanding the effects of gene mutations during development as well as a baseline for the optimisation of in vitro differentiation protocols for regenerative medicine.

Murine embryonic stem (ES) cells are pluripotent cell lines established directly from the early embryo which can contribute differentiated progeny to all adult tissues, including the germ-cell lineage, after re-incorporation into the normal embryo. They provide both a cellular vector for the generation of transgenic animals and a useful system for the identification of polypeptide factors controlling differentiation processes in early development. In particular, medium conditioned by Buffalo rat liver cells contains a polypeptide factor, ES cell differentiation inhibitory activity (DIA), which specifically suppresses the spontaneous differentiation of ES cells in vitro, thereby permitting their growth as homogeneous stem cell populations in the absence of heterologous feeder cells. ES cell pluripotentiality, including the ability to give rise to functional gametes, is preserved after prolonged culture in Buffalo rat liver media as a source of DIA. Here, we report that purified DIA is related in structure and function to the recently identified hematopoietic regulatory factors human interleukin for DA cells and leukaemia inhibitory factor. DIA and human interleukin DA/leukaemia inhibitory factor have thus been identified as related multifunctional regulatory factors with distinct biological activities in both early embryonic and hematopoietic stem cell systems.