DESYNCHRONIZATION OF CELLS ON THE DEVELOPMENTAL PATH TRIGGERS THE FORMATION OF SPIRAL WAVES OF CAMP DURING DICTYOSTELIUM AGGREGATION

Whereas it is relatively easy to account for the formation of concentr ic (target) waves of cAMP in the course of Dictyostelium discoideum ag gregation after starvation, the origin of spiral waves remains obscure , We investigate a physiologically plausible mechanism for the spontan eous formation of spiral waves of cAMP in D. discoideum, The scenario relies on the developmental path associated with the continuous change s in the activity of enzymes such as adenylate cyclase and phosphodies terase observed during the hours that follow starvation, These changes bring the cells successively from a nonexcitable state to an excitabl e state in which they relay suprathreshold cAMP pulses, and then to au tonomous oscillations of cAMP, before the system returns to an excitab le state, By analyzing a model for cAMP signaling based on receptor de sensitization, we show that the desynchronization of cells on this dev elopmental path triggers the formation of fully developed spirals of c AMP, Developmental paths that do not correspond to the sequence of dyn amic transitions no relay-relay-oscillations-relay are less able or fa il to give rise to the formation of spirals.