Actin Flows Mediate a Universal Coupling between Cell Speed and Cell Persistence

Cell movement has essential functions in development, immunity, and cancer. Various cell migration patterns have been reported, but no general rule has emerged so far. Here, we show on the basis of experimental data in vitro and in vivo that cell persistence, which quantifies the straightness of trajectories, is robustly coupled to cell migration speed. We suggest that this universal coupling constitutes a generic law of cell migration, which originates in the advection of polarity cues by an actin cytoskeleton undergoing flows at the cellular scale. Our analysis relies on a theoretical model that we validate by measuring the persistence of cells upon modulation of actin flow speeds and upon optogenetic manipulation of the binding of an actin regulator to actin filaments. Beyond the quantitative prediction of the coupling, the model yields a generic phase diagram of cellular trajectories, which recapitulates the full range of observed migration patterns. [Display omitted] •Speed and persistence of cells are exponentially correlated (the UCSP law)•Faster cells turn less: speed stabilizes cell directionality•The UCSP originates from transport of polarity factors by the retrograde actin flow•A physical model explains the UCSP and predicts a diagram of cell trajectories Despite the fact that different cell types follow distinct migration patterns, the locomotion of all cellular types follows one simple universal rule: the straightness of movement (persistence) is an exponential function of speed. This general law of cell migration is explained by a physical model based on the transport of polarity factors by the actin retrograde flows and predicts a diagram of possible cell trajectories.