Uni- and bidirectional forcing in <i>Dictyostelium discoideum</i> streaming

The head-to-tail collective motion of cells, called streaming, is an important method of collective migration utilized by a wide range of cells including metastatic cancer cells. Streaming has been extensively studied in the simple model organism D. discoideum in the context of collective guidance by chemical signals. Separately, our group has investigated bidirectional guidance of D. discoideum cells by nano-ridged surfaces. Here we investigate the combination of chemical and topographic guidance cues. We find that nano-ridges alter streaming of cells in a density dependent manner. To gain insights into how the streaming phenotype can be disturbed by physical cues, we supplement our experiments with coarse-grained simulations that model the cells as self-propelled disks guided by chemical signals and directional forcing.