Transition of starving Dictyostelium cells to differentiation phase at a particular position of the cell cycle

Pattern Formation in a Cell‐Cycle Dependent Manner during the Development of Dictyostelium discoideum

“…Recent studies (1,10,22,26,32,41,52,56) have provided data suggesting that Dictyosteliurn cells sort out naturally in a cell-cycle dependent manner during the establishment of the prestalk/ prespore pattern in a migrating slug.…”

“…In cultures of D. discoideurn Ax-2 cells, three main methods have been used for cell synchrony: 1) a mitosis wash-off procedure (27), 2) a stationary-phase release method in which cells in the stationary phase are released from growth inhibition by fresh medium (51,55), and 3) a temperature-shift method in which exponentially growing cells at 22.0% are shifted to a low temperature of about 11.5"C, shaken for 20.0 hr, and then re-incubated to 22.0"C (20). The wash-off procedure and the stationaryphase release method are either ineffective or result in only partial synchrony, as pointed out previously (20,22). In contrast, the temperatureshift method results in very synchronous growth of Ax-2 cells (20).…”

“…When synchronized cell populations at various phases of the cell cycle (referred to as Tt cells), obtained by shift-up from 11.5"C to 22.0°C, were harvested, washed, and allowed to develop on…”

“…Our recent analysis of the relation of the cell cycle to differentiation, using Ax-2 cells synchronized by temperature shift, demonstrated that increase in cell number and subsequent DNA synthesis occur in cells just before mitosis (referred to as T0.5 cells and T1 cells, 0.5 hr and 1 hr, respectively, after the shift-up from 11.5"C to 22.0"C) even in the absence of nutrients, but not in T3, T5, or T7 cells (22). When T1 cells were incubated for 6 hr in the absence of external nutrients, their developmental features were similar to those of T7 cells (22).…”

“…Although the reason for these conflicting findings is presently unknown, it seems likely that the methods used for cell synchronization as well as the efficiency of cell synchrony may have great influences on the sorting behavior of the cells. In this connection it is noteworthy that the stationary-phase release method for cell synchrony gives only partial synchrony, thus making it difficult to analyze the precise relationship between the cell-cycle phase and the subsequent cell sorting, as pointed out previously (22).…”