Ocular extracellular matrices in development.

The extracellular matrix is known to play important roles in regulating tissue development and cell differentiation. At a basic level the matrix is the substratum to which cells adhere and over which they migrate during morphogenesis. The recognition and adhesion of cells to matrices, especially to specialized matrices such as basal laminae, in developing tissues plays an important role in their decision to adhere or move on, to continue mitosis, to differentiate or to undergo apoptosis. The matrix is also the milieu from which growth factors and morphogens interact with the cell. Recent work demonstrates that matrix molecules are often active participants in these signaling processes, regulating the cellular response. Our understanding of the complexity of different ocular matrices continues to grow with the characterization of new proteins that modify collagen fibrils or serve as ligands for cell surface adhesion receptors. This review looks at those aspects of development in major tissues of the vertebrate eye where the extracellular matrix is known to participate, or is likely to do so based on similar roles in the development of the embryonic forebrain or other tissues. It concludes by highlighting some of the major developmental questions about the roles of the matrix in development in several ocular tissues.