Tissue morphogenesis coupled with cell shape changes.

When different tissues successively emerge during development, they need to be morphologically segregated from each other. Morphological segregation of tissues is often accompanied by robust changes in cell shape, and these two events are precisely coordinated. We overview recent progress in understanding how such coordination is regulated at the cellular and molecular levels using vertebrate somitogenesis asa unique model. In the formation of the somitic gap and its concomitant cell epithelialization, Ephrin-Eph intercellular signals play a central role, with Ephrin transducing intracellular signals via suppression of Cdc42. These signals lead to the activation of integrin where the segment border of somites forms, which in turn induces the assembly of fibronectin, the final player for the coordination. Intimate coupling of tissue-shape and cell-shape changes is also relevant to tumor suppression.