Physical Limits of Cell Migration

Chemotaxis, the motion of cells directed by chemical signals, is a multi-step process in eukaryotes: molecules of the chemoattractant activate the receptors on the cell surface, which triggers a cascade of reactions that ultimately results in the motion of the cell through membrane deformation. The ultimate speed of cell migration is determined by the rate limiting step of the process. Few studies have probed the limits of chemotaxis considered as a whole, though the limits of some individual processes are known. We measured the speeds of Dictyostelium cells in response to chemoattractant waves of controlled size and speed generated using microfluidic devices. We find that cells are able to consistently follow the wave for more than hundred times their size, and for about an hour, and that their speeds are significantly higher than the observed values in static gradients. We present a model describing the relationship between the cell speed and the wave speed and discuss its implications.