I was reading a paper by Tang & Othmer about oscillations and waves in Dictyostelium discoideum. Under certain condition like starvation period in the life cycle of a Dictyostelium discoideum community, they evolve itself into a multicellular organism in a process of cellular aggregation. I have read about Pacemaker cells among these individuals which transmits periodic cAMP and attracts other cells towards them.
So I was wondering: When and How do these Pacemaker cells develop from a "normal" cell into a pacemaker cell excreting cAMP?
References, links or answers would be very helpful for me.