Project description:Recently, several studies using cultures of human embryos together with single-cell RNA-seq (scRNA-seq) analyses have revealed differences between humans and mice, necessitating the study of human embryos. Despite the importance of human embryology, ethical and legal restrictions have limited post-implantation stage studies. Thus, recent efforts have focused on developing in vitro self-organising models using human stem cells. Here, we established a genetic approach to generate authentic hypoblast cells (nHyC) - known to give rise to one of the two extraembryonic tissues essential for embryonic development - from naïve human pluripotent stem cells (hPSCs). Our nHyCs spontaneously assemble with naïve hPSCs to form a three-dimensional bilaminar structure (bilaminoids) with a pro-amniotic-like cavity. In the presence of additional naïve hPSC-derived analogues of the second extraembryonic tissue, the trophectoderm, the efficiency of bilaminoid formation increases from 20% to 40%, and the epiblast within the bilaminoids continues to grow due to IL6 secreted by the trophectoderm. Furthermore, we show that bilaminoids robustly recapitulate the patterning of the anterior-posterior axis and the formation of cells reflecting the pre-gastrula stage, whose emergence can be shaped by genetically manipulating the DKK1/OTX2 hypoblast-like domain. We therefore model and reveal mechanisms by which the two extraembryonic tissues efficiently guide the stage-specific growth and progression of the epiblast as it establishes the post-implantation landmarks of human embryogenesis.
Project description:Recently, several studies using cultures of human embryos together with single-cell RNA-seq (scRNA-seq) analyses have revealed differences between humans and mice, necessitating the study of human embryos 1-8. Despite the importance of human embryology, ethical and legal restrictions have limited post-implantation stage studies. Thus, recent efforts have focused on developing in vitro self-organising models using human stem cells 9-18. Here, we established a genetic approach to generate authentic hypoblast cells (nHyC) - known to give rise to one of the two extraembryonic tissues essential for embryonic development - from naïve human pluripotent stem cells (hPSCs). Our nHyCs spontaneously assemble with naïve hPSCs to form a three-dimensional bilaminar structure (bilaminoids) with a pro-amniotic-like cavity. In the presence of additional naïve hPSC-derived analogues of the second extraembryonic tissue, the trophectoderm, the efficiency of bilaminoid formation increases from 20% to 40%, and the epiblast within the bilaminoids continues to grow due to IL6 secreted by the trophectoderm. Furthermore, we show that bilaminoids robustly recapitulate the patterning of the anterior-posterior axis and the formation of cells reflecting the pre-gastrula stage, whose emergence can be shaped by genetically manipulating the DKK1/OTX2 hypoblast-like domain. We therefore model and reveal mechanisms by which the two extraembryonic tissues efficiently guide the stage-specific growth and progression of the epiblast as it establishes the post-implantation landmarks of human embryogenesis.
Project description:Human naïve pluripotent cells can differentiate to extraembryonic trophoblast and hypoblast cells. Here we report formation of human blastocyst models by self-organization solely of naïve pluripotent stem cells. The embryo models comprise the three founding lineages, epiblast, trophoblast and hypoblast, arranged to mimic the natural blastocyst. Single-cell RNA sequencing validated the identity of each cell type.
Project description:Transcriptional comparison of mouse embryonic stem cells, inner cell mass, epiblast and pluripotent cells derived from mouse epiblast under defined culture conditions.
Project description:The epiblast is the first cell type that forms apical-basal polarity de novo as the mouse embryo implants into the maternal uterus, while the extraembryonic neighbours of the epiblast - trophectoderm and primitive endoderm - retain their pre-established polarity beyond implantation [1]; however, it is still unclear how the epiblast establishes apical-basal polarity de novo. Here, we focused on Rap1 signaling pathway, which is activated during the transition of the epiblast from the naïve to primed state of pluripotency during implantation [2]. Through the preestablished in vitro three-dimensional culture system [3], genetic knockouts and proximity-biotinylation analyses, we found that Rap1 integrates multiple signals that contribute to de novo formation of apical-basal polarity. Importantly, formation of apical-basal polarity in the epiblast is essential for its correct patterning and proper communication with the extraembryonic lineages. Altogether, these results not only dissect molecular details of de novo apical-basal polarity formation, but also have broader implications for epithelial polarity and development.
Project description:The pluripotency of mammalian early and late epiblast could be recapitulated by naïve embryonic stem cells (ESCs) and primed epiblast stem cells (EpiSCs), respectively. However, these two states of pluripotency may not be sufficient to reflect the full complexity and developmental potency of the epiblast during mammalian early development. Here we report the establishment of self-renewing formative pluripotent stem cells (fPSCs) which manifest features of epiblast cells poised for gastrulation. fPSCs can be established from different mouse ESCs, pre-/early-gastrula epiblasts and induced PSCs. Similar to pre-/early-gastrula epiblasts, fPSCs show the transcriptomic features of formative pluripotency, which are distinct from naïve ESCs and primed EpiSCs. fPSCs show the unique epigenetic states of E6.5 epiblast, including the super-bivalency of a large set of developmental genes. Just like epiblast cells immediately before gastrulation, fPSCs can efficiently differentiate into three germ layers and primordial germ cells (PGCs) in vitro. Thus, fPSCs highlight the feasibility of using PSCs to explore the development of mammalian epiblast.
Project description:The human embryo undergoes morphogenetic transformations following implantation into the uterus and yet our knowledge of this crucial stage is limited by the inability to observe the embryo in vivo. Here, we establish a stem cell-derived human post-implantation embryo model comprised of embryonic and extraembryonic tissues. Overexpression of the transcription factors GATA6 and SOX17 or GATA3 and AP2g in hESCs allowed us to generate hypoblast-like and trophoblast-like cells, respectively. We established conditions to combine these extraembryonic-like cells with wildtype embryonic stem cells and promote their self-organization into structures that mimic aspects of the post-implantation human embryo. These aggregates contain an inner pluripotent epiblast-like domain surrounded by both hypoblast- and trophoblast-like tissues. We show that this human embryo stem cell model robustly generates several cell types, including amnion-, extraembryonic mesenchyme- and primordial germ cell-like cells. Using perturbation experiments, we demonstrated that these populations arise in response to BMP signaling. This model also allowed us to identify an inhibitory role for SOX17 in the specification of anterior hypoblast-like cells. Modulation of the subpopulations in the hypoblast-like compartment demonstrated that these extraembryonic-like cells impact epiblast-like domain differentiation, highlighting functional tissue-tissue crosstalk. In conclusion, this modular, tractable model of the human embryo that includes both embryonic- and extraembryonic-like cells has the potential to probe key questions of human post-implantation development.