Gastrulation in zebrafish -- all just about adhesion?

During vertebrate gastrulation, the evolutionarily conserved morphogenetic movements of epiboly, internalization, convergence and extension cooperate to generate germ layers and to sculpt the body plan. In zebrafish, these movements are driven by a variety of cell behaviors, including slow and fast directed migration, radial and mediolateral intercalation, and cell shape changes. Whereas some signaling pathways are required for a subset of these behaviors, other molecules, such as E-cadherin or Galpha12 and Galpha13 proteins, appear to have a widespread role in different gastrulation cell behaviors.