Role of extracellular matrix in regulating embryonic epithelial-mesenchymal transition

Embryogenesis and morphogenesis are characterized by complex cell rearrangements and movements which require appropriate interactions of cells with the surrounding extracellular matrix (ECM) by means of specific membrane receptors. Interest in the identifi cation and purifi cation of ECM components, as well as in conducting functional studies of them, including their ligands and other molecules involved in cell-matrix adhesion, has intensifi ed in recent years, increasing our knowledge of developmental machinery. Cellular movements play an important role during the epithelial-mesenchymal transition (EMT) events, which are key processes in normal embryogenesis as well as in pathological conditions, such as fi brotic diseases and cancer. Thus, to more fully understand mechanisms underlying the EMT process, and for better knowledge of the embryonic defects related to this process, it would be useful to study the substrates on which EMT cells move during embryo development. This review focuses on a few different embryonic systems, taking into account the cell migration that occurs during EMT and highlighting, in particular, studies describing the direct involvement of ECM molecules.