Actin dynamics and cell-cell adhesion in epithelia

Recent advances in the field of intercellular adhesion highlight the import ance of adherens junction association with the underlying actin cytoskeleto n. In skin epithelial cells a dynamic feature of adherens junction formatio n involves filopodia, which physically project into the membrane of adjacen t cells, catalyzing the clustering of adherens junction protein complexes a t their tips. In turn, actin polymerization is stimulated at the cytoplasmi c interface of these complexes. Although the mechanism remains unclear, the VASP/Mena family of proteins seems to be involved in organizing actin poly merization at these sites. In vivo, adherens junction formation appears to rely upon filopodia in processes where epithelial sheets must be physically moved closer to form stable intercellular connections, for example, in ven tral closure in embryonic development or wound healing in the postnatal ani mal.