Opportunities and challenges with stem cell-based embryo models

Stem cell-based embryo models open an unprecedented avenue for modeling embryogenesis, cell lineage differentiation, tissue morphogenesis, and organogenesis in mammalian development. Experimentation on these embryo models can lead to a better understanding of the mechanisms of development and offers opportunities for functional genomic studies of disease-causing mechanisms, identification of therapeutic targets, and preclinical modeling of advanced therapeutics for precision medicine. An immediate challenge is to create embryo models of high fidelity to embryogenesis and organogenesis in vivo, to ensure that the knowledge gleaned is biologically meaningful and clinically relevant. In this article, Rossant and Tam review the current progress in stem cell-based embryo models in both mouse and human. They provide a classification of such models based on the presence or absence of early extraembryonic lineages. They provide a glimpse of the future where interdisciplinary approaches will be able to program development in vitro, leading to truly synthetic embryology.