The control of chemotactic cell movement during Dictyostelium morphogenesis

Differential cell movement is an important mechanism in the development and morphogenesis of many organisms. In many cases there are indications that chemotaxis is a key mechanism controlling differential cell movement. This can be particularly well studied in the starvation-induced multicellular de velopment of the social amoeba Dictyostelium discoideum. Upon starvation, u p to 10(5) individual amoebae aggregate to form a fruiting bed): The cells aggregate by chemotaxis in response to propagating waves of cAMP, initiated by an aggregation centre. During their chemotactic aggregation the cells s tart to differentiate into prestalk and prespore cells, precursors to the s talk and spores that form the fruiting body. These cells enter the aggregat e in a random order but then sort out to form a simple axial pattern in the slug. Our experiments strongly suggest that the multicellular aggregates ( mounds) and slugs are also organized by propagating cAMP waves and, further more, that cell-type-specific differences in signalling and chemotaxis resu lt in cell sorting, slug formation and movement.