Regulation of cell adhesion and migration in lens development.

Cell movements during lens development and differentiation involve dynamic regulation of cell-matrix and cell-cell adhesion. How these processes are regulated depends on the particular array of matrix components and adhesion proteins that are expressed, as well as the signaling pathways that affect them. This review examines what is known about adhesion proteins and their regulation in the lens in light of recent findings about the mechanism of cell migration. The characteristic shape and organization of the lens depends on highly regulated cell movements during development and differentiation. Epithelial cells at the equator migrate posteriorly, bringing them into contact with factors in the vitreous humor and initiating differentiation. Elongation of the differentiating fiber cells is coupled with directed migration, posteriorly along the capsule and anteriorly along the fiber cell-epithelial interface, to generate a symmetrically organized fiber cell mass with aligned suture planes. To make these movements, cells systematically create and dissolve cell-cell and cell-matrix adhesions, form connections between these adhesions and the cytoskeleton, and generate contractile force. Since errors in cell migration may lead to aberrant lens shape or misplacement of the lens sutures, precise regulation of each step is essential for the optical quality of the lens. Recent advances in cellular developmental biology have begun to shed light on the molecular mechanisms underlying cell movements and the changes in adhesion that make them possible. This review will summarize those findings and relate them to relevant studies of the lens to provide an outline of the cellular events that lead to lens morphogenesis.