As discussed above, fruiting body branching patterns reflect how and when competing pacemakers for cAMP waves appear on multicellular structures. The production of cAMP waves by D. discoideum cells consists of a positive feedback loop where extracellular cAMP acting on cAR1 stimulates further cAMP production by adenylyl cyclase A (ACA), and a negative feedback loop where cAMP inhibits ACA and stimulates its own hydrolysis. (54) (55) (56) Variation in a range of parameters, such as the relative expression levels of the component proteins, diffusion or cell movement barriers generated by structural components, and the relative motility or cohesiveness of responding cells can potentially affect the dynamics of the signalling process in a such a way as to allow competing pacemakers to arise in a variety of configurations.