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

Abstract

The nonconserved primitive streak In human development, a linear structure called the primitive streak appears 14 days after fertilization. This structure marks the transition of the embryo from having radial to bilateral symmetry. The primitive streak also gives anterior-posterior and dorsal-ventral spatial information to cells undergoing gastrulation and forming the various body cell types. In a Review, Sheng et al . present a phylogenetic and ontogenetic overview of the primitive streak. They discuss organismal, cellular, and molecular features of the primitive streak and how it functions in amniote gastrulation. The observation that this structure is not conserved and is not required for development in vitro has implications for embryonic stem cell–based models and considerations about human development research. —BAP