Identification and analysis of the regulation of a prestalk cell-surface antigen of Dictyostelium discoideum.
The properties of two differentiation antigens, rsa 4.2 and rsa 3.1, were examined. Both appear on the cell surface early in differentiation, but they differ with respect to their cell-type specificity. rsa 4.2 appears 1-2 h after differentiation has begun and is present on all cells during all stages of differentiation. In contrast, rsa 3.1 appears after 1-2 h on all aggregating amebae and later becomes restricted to prestalk cells. The pattern of regulation of rsa 3.1 indicates that this prestalk antigen appears on all cells early in differentiation but disappears in cells that differentiate along the prespore pathway. As a result, only cells in the anterior of migrating slugs carry this antigen. Predictions of two competing models of Dictyostelium pattern formation, i.e., position-dependent differentiation and random, position-independent differentiation, were tested by flow cytometry and immunochemical staining of sections of cells at the mound and mound-with-tip stages. Our results do not rule out either model, although they are incompatible with the simplest interpretation of the model for position-independent differentiation. The results clearly indicate that cells that ultimately differentiate along the spore pathway pass through an earlier cell state that includes the presence of a prestalk cell-surface antigen identified as rsa 3.1.
D000911:Antibodies, Monoclonal; D000954:Antigens, Surface / Q000032:analysis*; D002462:Cell Membrane / Q000032:analysis; D004023:Dictyostelium / Q000166:cytology / Q000254:growth & development*; D005434:Flow Cytometry / Q000379:methods; D005455:Fluorescent Antibody Technique
D000911:Antibodies, Monoclonal; D000954:Antigens, Surface