How amoeboid cells can modify their environment and can coordinate their motion

Collective cell migration plays an important role in many biological processes such as development, wound healing and cancer metastasis. In this talk, we will focus on the collective migration of Dictyostelium discoideum cells, a social amoeba. Upon starvation, and as part of a survival mechanism, these cells aggregate into large clusters, requiring robust coordination of signaling and motion. We will present two examples how experiments and modeling can shed light on this coordination. First, we will show that small aggregates of Dictyostelium can show dispersal behavior during which cells are moving away from, instead of towards, the aggregate. Using a combination of experiments and modeling, we show that this dispersal can arise due to a competition between the diffusible chemoattractant and the enzyme that degrades it. The latter modifies the environment such that the chemoattractant gradient near the aggregate can change sign. Second, we present results on vertically constrained aggregates in which cells rotate in a collective manner. We quantify the forces exerted on the substrate by the cells using traction force microscopy and visualize the chemoattractant signaling using fluorescent microscopy. Using modeling, we show that the interaction between signaling and motion can explain the observed traction force patterns.