The primitive streak and cellular principles of building an amniote body through gastrulation

The primitive streak, a transient embryonic structure, marks bilateral symmetry in mammalian and avian embryos and helps confer anterior-posterior and dorsal-ventral spatial information to early differentiating cells during gastrulation. Its recapitulation in vitro may facilitate derivation of tissues and organs with in vivo-like complexity. Proper understanding of the primitive streak and what it entails in human development is key to achieving such research objectives. Here we provide an overview of the primitive streak and conclude that this structure is neither conserved nor necessary for gastrulation or early lineage diversification. We offer a model in which the primitive streak is viewed as part of a morphologically diverse yet molecularly conserved process of spatial coordinate acquisition. We predict that recapitulation of the primitive streak is dispensable for development in vitro.

Automated summary

The primitive streak is a transient embryonic structure that plays a crucial role in bilateral symmetry and spatial information during gastrulation. While its in vitro recapitulation can aid in deriving tissues and organs with complexity, it is not conserved or necessary for gastrulation in human development. It is viewed as part of a morphologically diverse yet molecularly conserved process of spatial coordinate acquisition, and its recapitulation is predicted to be dispensable for development in vitro.