Zebrafish Gastrulation.

The primordial body architecture of vertebrates is established during gastrulation, a critical period of development characterized by the emergence of the three germ layers (ectoderm, mesoderm, and endoderm) and the formation of an embryo with clearly identifiable dorso-ventral and anterior-posterior axes. In zebrafish, gastrulation involves molecular and cellular mechanisms that are broadly conserved among vertebrates, with species-specific features imposed by the deterministic role of maternally deposited determinants, the architecture of extraembryonic structures that create a dynamic and physically constrained environment, and the mesenchymal nature of early cells that underpins the migratory nature of mesendoderm internalization. Significant progress has been made in the genetic networks, signaling pathways, and cell dynamics involved, and the unique features of the zebrafish embryo are helping to elucidate the intricate coordination between gene expression, mechanical forces, self-organization, and morphogenetic movements that shape the early embryo. These advances have provided insights into the fundamental principles of vertebrate morphogenesis.