Multicellular organisms clearly require mechanisms for intercellular communication and, perhaps even more basically, for intercellular cohesion. The most primitive sponges and coelenterates depend on cell adhesion for their organismal organization; so do insects, nematodes and vertebrates. What molecules and mechanisms are common among these different phyla and which ones differ and why?
The availability of the euchromatic genomic sequences of Drosophila melanogaster (Adams et al. 2000; Rubin et al. 2000; http://www.celera.com) and Caenorhabditis elegans (http://www.sanger.ac.uk/Projects/C_elegans/) makes it possible to address these questions with much more confidence than heretofore. We searched the Drosophila (and, to a lesser extent, the C. elegans) genomic sequences using a large number of vertebrate sequences of adhesion proteins. We also conducted searches for particular domains prevalent in adhesion proteins (Kreis and Vale 1999) and made extensive use of the...
