Beads on the run: beads as alternative tools for chemotaxis assays.

Cell migration is required for a wide variety of processes from bacteria seeking for food to correct patterning of neuronal networks. The ability to sense external cues is critical for cells to get directions and reach their goals. So far, studies on chemotaxis have mainly focused their attention on individual cells and therefore available tools are designed to monitor cell behavior at the single cell level. However, as collective cell migration is now widely accepted as a main mode of cell migration from development to cancer, the question of how chemotaxis is achieved has also to be asked on a bigger scale. Here, we present two chemotaxis assays suitable for single cells, cell sheets, and cell explants. Using a simple combination of heparin-coated beads and high vacuum silicone grease, these techniques can be adapted to a wide variety of culture conditions. They allow time-lapse study, high-resolution microscopy, and can be set up at no extra cost.