Models of morphogenesis: the mechanisms and mechanics of cell rearrangement.

The directional rearrangement of cells is a key mechanism for reshaping embryos. Despite substantial recent progress in understanding the basic signal transduction pathways that allow cells to orient themselves in space, the extrinsic cues that activate these pathways are just beginning to be understood. Even less-well understood are the physical mechanisms cells use to change position, especially when those cells are epithelial, and how mechanical forces within the embryo affect those movements. Recent studies are providing clues regarding how this fundamental process occurs with such remarkable reliability. Copyright 2004 Elsevier Ltd.