David I. Ratner
Professor of Biology, Amherst College
Ph.D.: Harvard University Postdoctoral Training: Oxford University
Embryonic tissues of a multicellular eukaryote diverge through the selective expression of their common genetic constitution. The long-term goal of our research is to understand the basis of cell-specific gene expression during differentiation. Our experimental system is the cellular slime mold, Dictyostelium discoideum, in which spore and stalk cells develop from common vegetative precursors. One aspect of our research involves the analysis of the function of a developmentally regulated Dictyostelium gene, DG17. DG17 encodes a protein with homology to a small class of zinc finger proteins known as "RING fingers" and to the TRAF family of signal transduction proteins. The function of DG17 is presently unknown but may involve gene regulation. Our approach has been to create DG17 null mutants through gene targeting. We have replaced the DG17 gene of amoebae with an interrupted, inactive copy, but before a phenotype can be determined we must also inactivate a newly discovered DG17 homologue which we have now cloned. As part of these gene targeting experiments, we have investigated the mechanism of chromosomal integration of added DNA and especially the fate of the ends of targeting DNA molecules. A more open-ended search for components of the transcriptional machinery involves the use of green fluorescent protein (GFP) reporter constructs and fluorescence activated cell sorting, or FACS. We have shown that FACS can purify cells in which GFP has been activated by a Dictyostelium promoter and hope to select developmental mutants altered in signal transduction or transcriptional activation. Finally, our lab collaborates with several other groups at Amherst College in an analysis of the structure and function of mouse catalytic antibodies.