%0 Journal Article %A Javier Frias-Aldeguer %A Maarten Kip %A Judith Vivié %A Linfeng Li %A Anna Alemany %A Jeroen Korving %A Frank Darmis %A Clemens A. Van Blitterswijk %A Alexander van Oudenaarden %A Niels Geijsen %A Nicolas C. Rivron %T Polar-like trophoblast stem cells form an embryonic-abembryonic axis in blastoids %D 2019 %R 10.1101/510362 %J bioRxiv %P 510362 %X Early mammalian embryos form a blastocyst, a structure comprising embryonic cells surrounded by a trophoblast cyst able to implant into the mother’s uterus. Following subtle symmetry-breaking events (Zhang and Hiiragi, 2018), an axis forms in the blastocyst when the embryonic cells cluster on one inner side of the trophoblast globe and induce the directional proliferation and differentiation of trophoblasts (Gardner, 2000). Trophoblast stem cells (TSCs) are in vitro analogs of early trophoblasts (Tanaka et al., 1998). Here, we show that TSCs contain a range of plastic subpopulations reflecting aspects of trophoblasts states ranging from the blastocyst trophoblasts juxtaposing the embryo (polar trophoblasts) to post-implantation trophoblasts. However, when exposed to a specific combination of embryonic inductive signals, TSCs acquire properties of polar trophoblasts (gene expression, self-renewal) and a more homogeneous, epithelial phenotype. These lines of polar-like TSCs more efficiently form blastoids, which respond to the inner embryonic cells by spontaneously generating an embryonic-abembryonic axis. Altogether, the delineation of requirements and properties of the polar cells of the trophectoderm provides the ground to better recapitulate and dissect embryonic development in vitro. %U https://www.biorxiv.org/content/biorxiv/early/2019/01/03/510362.full.pdf