The Dynamics of Morphogenesis in the Early Mouse Embryo

Over the past two decades, our understanding of mouse development from implantation to gastrulation has grown exponentially with an upsurge of genetic, molecular, cellular, and morphogenetic information. New discoveries have exalted the role of extraembryonic tissues in orchestrating embryonic patterning and axial specification. At the same time, the identification of unexpected morphogenetic processes occurring during mouse gastrulation has challenged established dogmas and brought new insights into the mechanisms driving germ layer formation. In this article, we summarize the key findings that have reinvigorated the contemporary view of early postimplantation mammalian development. Outline 1 Developmental anatomy-From blastocyst to egg cylinder 2 Heterogeneity of egg cylinder tissues 3 The anterior visceral endoderm: Movement, form, and function 4 Shifting the anteroposterior axis: Cause or consequence of gastrulation? 5 The primitive streak: A hub of morphogenetic cellular activity 6 Formation of mesoderm and definitive endoderm