Formation of blastoids from mouse embryonic and trophoblast stem cells

Abstract

The blastocyst is the mammalian pre-implantation embryo. It consists of an outer epithelial layer of trophoblast cells surrounding a uid-lled cavity sheltering the embryonic and primitive endoderm cells. From the mouse blastocyst, trophoblast and embryonic stem cells lines can be derived, which have the capacity to indenitely self-renew in vitro while maintaining the ability to differentiate into all placental and embryonic lineages, respectively. Here, I describe how to form blastoids \(synthetic blastocysts) formed from trophoblast and embryonic stem cells. Blastoids morphologically and transcriptionally resemble E3.5 blastocysts, and can implant in utero. Although not recapitulating the full complexity of the embryo, blastoids are simplied models allowing new approaches in embryology. Contrary to blastocysts, blastoids can be generated in large numbers, which allows to harvest material for in-depth assays \(e.g. genomics, biochemistry), run high-throughput screens, and to rapidly perform compartment-specic genetic modications. As such, blastoids are powerful tools to study the principles of stem cell self-organization and embryonic development. _Note:_ Minor errors in this protocol were corrected on the 18th of May 2018. The previous version of the protocol can be found here; "Version 1":https://www.nature.com/protocolexchange/system/uploads/6695/original/Version_1_-_Formation_of_blastoids_from_mouse_embryonic_and_trophoblast_stem_cells.pdf?1526897870