Cell-cell adhesion via the ECM: integrin genetics in fly and worm

Integrins are essential for the development of the two genetically tractable invertebrate model organisms, the nematode worm Caenorhabditis elegans and the fruit fly Drosophila melanogaster. Just two integrins are present in C. elegans: one putative RGD binding integrin alpha pat-2 beta pat-3, corresponding to Drosophila alpha PS2 beta PS and vertebrate alpha 5 beta 1, alpha V beta 1 and alpha 8 beta 1, and one putative laminin binding integrin alpha rina-1 beta pat-3, corresponding to Drosophila alpha PS1 beta PS and vertebrate alpha 3 beta 1, alpha 6 beta 1 and alpha 7 beta 1. in this review, the function of this minimal set of integrins during the development of these two invertebrates is compared. Despite the differences in bodyplan and developmental strategy, integrin adhesion to the extracellular matrix is required for similar processes: the formation of the link that translates muscle contraction into movement of the exoskeleton, cell migration, and morphogenetic interactions between epithelia. Other integrin functions, such as regulation of gene expression, have not yet been experimentally demonstrated in both organisms. Additional proteins have been characterised in each organism that are essential for integrin function, including extracellular matrix ligands and intracellular interacting proteins, but so far different proteins have been found in the two organisms. This in part represents the fact that the characterisation of the full set of interacting proteins is not complete in either system. However, in other cases different proteins appear to be used for similar functions in the two animals. The continued use of genetic approaches to identify proteins required for integrin function in these two model organisms should lead to the identification of the minimal set of conserved components that form integrin adhesive structures. (C) 2000 Elsevier Science B.V./International Society of Matrix Biology. All rights reserved.