Deletion of gmfA induces keratocyte-like migration in Dictyostelium

Glia maturation factor (GMF) has been established as an inactivating factor of the actin-related protein 2/3 (Arp2/3) complex, which regulates actin assembly. Regulation of actin assembly and reorganization is crucial for various cellular events, such as cell migration, cell division, and development. Here, to examine the roles of ADF-H domain-containing protein (also known as glia maturation factor; GmfA), the product of a single GMF homologous gene in Dictyostelium, gmfA-null cells were generated. They had moderate defects in cell growth and cytokinesis. Interestingly, they showed a keratocyte-like fan shape with a broader pseudopod, where Arp3 accumulated at higher levels than in wild-type cells. They migrated with higher persistence, but their velocities were comparable to those of wild-type cells. The polar pseudopods during cell division were also broader than those in wild-type cells. However, GmfA did not localize at the pseudopods in migrating cells or the polar pseudopods in dividing cells. Adhesions of mutant cells to the substratum were much stronger than that of wild-type cells. Although the mutant cells showed chemotaxis comparable to that of wild-type cells, they formed disconnected streams during the aggregation stage; however, they finally formed normal fruiting bodies. These results suggest that GmfA plays a crucial role in cell migration.