Direction-dependent contraction forces on cell boundaries induce collective migration of epithelial cells within their sheet.

During early embryonic development, epithelial cells form a monolayer sheet and migrate in a definite direction. This phenomenon, called epithelial cell migration, is an important topic in developmental biology. A characteristic feature of this process is attachment to adjacent cells during migration, which is necessary for maintaining the integrity of the sheet. However, it is unclear how these cohesive cells migrate without breaking their attachments. A mechanism for this phenomenon was recently proposed, in which direction-dependent contraction forces acting on cell boundaries induce unidirectional epithelial migration. In this review, we examine this proposed mechanism from various aspects and provide theoretical background for the collective migration of epithelial cells. This information may be helpful for investigators to realize the basic principles underlying collective epithelial migration and devise new mechanisms for it.