Cell differentiation and pattern formation in a cell-cycle dependent manner in slime mold cells

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The sorting behaver of Dictyostelium discoideum Ax-2 cells and its relation to the cell-cycle phase at the onset of starvation were analyzed with reference to pattern formation, using beta-galactosidase as a cell maker and the temperature shift method for cell synchronization. Cells (T7) starved just before the PS-point from which cells enter the differentiation phase when starved aggregated most rapidly and possibly functioned as aggregation centers, but were eventurally sorted out to the posterior zone of migrating slugs. In contrast, T1 cells starved just after the PS-point exhibited slower aggregation compared with T7 cells. During further culture, T1 cells then sorted out to the apical tips of tipped aggregates and were located predominantly in the anterior zone of migrating slugs.The gene expressions associated with the swotchover from cell proliferation to differentiation were also analyzed using the differential plaque hybridization. As a result, Quit1 was cloned as a specifically expressed gene when cells were starved just beforethe PS-point. The coding region of Quit1 gene was identical with that of the cAMP recepter 1 gene, which is essential for development. The Quit1 mRNA was asecifically expressed just after starvation of cells around the PS-point, thus indicating the importance of the cAMP recepter 1 for cellular differentiation as well as the actual existence of the PS-point.