Stem cell-derived mouse embryos develop within an extra-embryonic yolk sac to form anterior brain regions and a beating heart-like structure.

Abstract Mouse embryos are an invaluable tool to study mammalian development but establishment of novel transgenic mouse lines is a costly and time-consuming endeavour. Stem cell models, on the other hand, lend themselves to quick genetic manipulation and are easily scalable, yet they do not successfully capture morphogenesis.Here, we report stem cell-based structures called ETiX-embryoids that can recapitulate mouse post-implantation morphogenesis. ETiX-embryoids form by aggregating embryonic and trophoblast stem cells to embryonic stem cells transiently expressing Gata4. Over the course of 4 days, these structures develop like mouse post-implantation egg cylinders; they then undertake and complete gastrulation on day 5 and 6, respectively. On day 7, ETiX-embryoids undergo neural induction and form the mouse anterior-posterior axis from neural folds to tail bud by movements of convergent extension. On day 8 they form a brain, establish a beating heart-like structure and a gut tube, as they develop inside extraembryonic membranes equivalent to amnion and yolk sac. We detail here the experimental set up and procedure required to generate ETiX-embryoids, and anticipate that they will establish themselves as a novel, powerful tool to study mammalian development without generating a novel mouse lines.