cAMP receptor affinity controls wave dynamics, geometry and morphogenesis in Dictyostelium

Serpentine G-protein-coupled cAMP receptors are key components in the detec tion and relay of the extracellular cAMP waves that control chemotactic cel l movement during Dictyostelium development. During development the cells s equentially express four closely related cAMP receptors of decreasing affin ity. In this study, we investigated the effect of cAMP receptor type and af finity on the dynamics of cell-cell signalling in vivo, by measuring the dy namics of wave initiation and propagation in a variety of cAMP receptor mut ants. We found that receptor affinity controls the frequency of wave initia tion, but it does not determine wave propagation velocity, thus resulting i n dramatic changes in wave geometry. In the limiting case, the affinity of the receptor is so low that waves can still be initiated but no stable cent res form-thus, the cells cannot aggregate. In mounds, expression of low aff inity receptors results in slow concentric waves instead of the normally ob served multiarmed spiral waves. Under these conditions there is no rotation al cell movement and the hemispherical mounds cannot transform into slugs. These results highlight the importance of receptor number and affinity in t he proper control of cell-cell signalling dynamics required for the success ful completion of development.