A transgene-free approach to construct a mouse post-implantation embryo model that completes gastrulation

The development of synthetic embryo models using early stem cells has emerged as a powerful platform for studying mammalian development in vitro. However, the generation of high-quality post-implantation embryo models in mice has typically relied on embryonic stem cells (ESCs) engineered to transiently express master regulators of extraembryonic lineages. This strategy diverges from the natural in vivo process of extraembryonic lineage specification.

To address this limitation, researchers have developed a transgene-free method utilizing mouse extended pluripotent stem (EPS) cells to generate embryoids that recapitulate key features of post-implantation development. The approach begins with the induction of trophectoderm (TE)-like cells from EPS cells through sequential modulation of diverse signaling pathways, including WNT, TGF-β, HIPPO, FGF, BMP, and PKA. The resulting TE-like cells exhibit transcriptional profiles and in vivo developmental potential similar to pre-implantation TE.

These TE-like cells were then combined with EPS-derived epiblast/primitive endoderm bilineage structures to generate embryo-like structures termed EPS-embryoids. These embryoids successfully recapitulate critical developmental milestones of post-implantation mouse embryos, including the formation of the pro-amniotic cavity, anterior-posterior axis establishment, primitive streak formation, gastrulation, and development of complex extraembryonic tissues. Importantly, single-cell transcriptomic analysis showed that day 6 EPS-embryoids display high transcriptional similarity to natural E7.5 mouse embryos.

This work provides compelling evidence for the feasibility of constructing transgene-free embryo models that mimic post-implantation development, offering a new system to study the molecular mechanisms governing mouse gastrulation and early organogenesis. This study, titled “Trophectoderm-like cells from EPS cells enable generating EPS cell-derived post-implantation embryoids that complete gastrulation”, was published in Protein & Cell.