Mechanisms of epithelial fusion and repair

One of the principal functions of any epithelium in the embryonic or adult organism is to act as a self-sealing barrier layer. From the earliest stage s of development, embryonic epithelia are required to close naturally occur ring holes and to fuse wherever two free edges are brought together, and at the simplest level that is precisely what the epidermis must do to repair itself wherever it is damaged. Parallels can be drawn between the artificia lly triggered epithelial movements of wound repair and the naturally occurr ing epithelial movements that shape the embryo during morphogenesis. Recent in vitro end in vivo wound-healing studies and analysis of paradigm morpho genetic movements in genetically tractable embryos, like those of Drosophil a and Caenorhabditis elegans, have begun to identify both the signals that initiate these movement's and the cytoskeletal machinery that drives motili ty. We are also gaining insight into the nature of the brakes and stop sign als, and the mechanisms by which the confronting epithelial sheets knit tog ether to form a seam.