Erasure In Dictyostelium - Dedifferentiation Involving The Programmed Loss Of Chemotactic Functions

When developing cultures of the cellular slime mold Dictyostelium discoideum are disaggregated and the amebae redispersed on a fresh substratum, they will rapidly reaggregate in approximately1/10th the original time. If developing cultures are disaggregated and the amebae suspended in fresh growth medium, they will simultaneously and completely lose this capacity for rapid reaggregation in a discrete step which has been referred to as “erasure.” In this report, we tested whether all developmentally acquired characteristics are lost simultaneously at the time of erasure or whether different characteristics are lost at different times during a program of dedifferentiation. Evidence is presented that the latter case is true. The capacity to release a chemoattractant is lost at the approximate time of the erasure event and the capacity to respond to a chemoattractant in a directed fashion is lost at the approximate time of erasure stabilization, the end point of a short period immediately following the erasure event during which erasure can be reversed by the inhibition of protein synthesis. In contrast, the developmentally acquired characteristics of cAMP-stimulated, nondirected motility and EDTA-resistant cell adhesion are not lost at erasure or erasure stabilization, but are retained for at least several subsequent hours. Possible mechanisms and evolutionary reasons for the selective loss of chemotactic functions at erasure are discussed.