Characterizing New Genes Regulating Cell-Substrate Adhesion to Discover Novel Regulatory Mechanisms of Cell Motility

Abstract

The model organism Dictyostelium has greatly facilitated our understanding of the signal transduction and cytoskeletal pathways that govern cell motility. Cell-substrate adhesion is a target of many chemotaxis signaling events and it can be used to screen for cells that have defects in cell migration. In fact, cells lacking PTEN, a negative regulator of cellular extensions, is flatter and adheres strongly to the surface. This leads to reasoning that other regulators of migration would also effect adhesion, a screening method was devised and isolated overly adherent mutants from a pool of mutagenized cells. Restriction enzyme mediated insertion (REMI) mutagenized cells, comprising more than 50000 insertions, yielded about 100 mutated cell lines with the desired phenotypes. The mutation sites in 20 of the strains have been mapped and many of the phenotypes are similar to those of PTEN knockout cells. The extent of increased adhesion, cell motility, directed migration, cell shape, and new filamentous actin at the periphery are all parameters that have been examined in these new overly adhesive cell lines. The degree in which these parameters have been effected and the correlations between these changes is providing novel insights into the networks controlling cell motility. Many of these genes have human homologs with unknown functions. Therefore, the future study of this new group of regulators of adhesion and motility genes in Dictyostelium will not only advance the knowledge of cell migration in amoeboid cells but elucidate the functions of novel human genes with potential disease relevance.