Cytokinesis, the process by which a cell constricts at the equator to ultimately divide into two daughter cells remains poorly understood. My primary interest has been to identify the proteins/genes involved in both the mechanics and the regulation of this process. To achieve this goal my lab uses the cellular slime mold Dictyostelium discoideum. Using Dictyostelium a molecular genetic screen was developed to identify the genes required for cytokinesis. Several genes were subsequently identified and we are in the process of describing how these genes participate in the regulation of cytokinesis. One of these genes codes for a novel small GTP-binding protein of the ras superfamily. Initial characterization of mutant cell lines containing disruptions in this gene, named racE, has revealed racE to be essential solely for cytokinesis, and all other aspects of Dictyostelium biology2 appear to be normal in these cells. A second gene has recently been identified which also functions in cytokinesis. We are still in the process of characterizing this gene but limited sequence analysis reveals strong homology to the mouse beige gene and the human gene responsible for the Chediak-Higashi syndrome. We are now in the process of trying to understand the cell biology and biochemistry of how these genes function in cytokinesis. Future work will include further characterization of these genes, as well as continuation of the screen to identify additional genes involved in cytokinesis.