Regulation of Cell-type-specific Gene Expression in Dictyostelium

We are interested in the problems of how gene expression is regulated uring development and how an initially homogeneous population of cells is parti-tioned into two distinct cell types. To approach these questions, we are studying a simple eukaryote, Dic-tyostelium discoideum. Approximately 10 hours after exhaustion of a food source, Dictyostelium amebae form a multicellular aggregate. Decisions are made at this time (or earlier according to some models [MacWilliams and Bonner 1979; Tasaka and Takeuchi 1981, McDonald and Durston 1984]) as to whether in-dividual cells will differentiate into prespore or pre-stalk cells, the precursors to the terminally differen-tiated spore and stalk cells. As development proceeds, these cell types become located in distinct regions of