Cell-autonomous differentiation of human primed embryonic stem cells into trophoblastic syncytia through the nascent amnion-like cell state

Human primed embryonic stem cells (pESCs) are known to be converted to cells with several trophoblast properties, but it has remained controversial whether this phenomenon represents the inherent differentiation competence of human pESCs to trophoblast lineages. In this study, we report that chemical blockage of ACTIVIN/NODAL and FGF signals is sufficient to steer human pESCs into GATA3-expressing cells that give rise to hormone-producing syncytia analogous to syncytiotrophoblasts of the post-implantation stage of the human embryo. Taking advantage of this system, we identified two distinct modes of cell-autonomous genetic programs and their coordinated actions to initiate the differentiation. We also found a transient population reminiscent of nascent amnion and then a spontaneous branch of differentiation trajectory leading to syncytiotrophoblast-like syncytial cells. These results provide insights into the possible extraembryonic differentiation pathway that is unique in primate embryogenesis and is relevant to the trophoblast competence of human primed pluripotent stem cells. ### Competing Interest Statement The authors have declared no competing interest.