Neutrophils actively swell to potentiate rapid migration.

Directed extension of the plasma membrane is needed for eukaryotic cell migration. While the role of actin polymerization in generating protrusive forces is well appreciated, we have a more limited understanding of the role of transmembrane water flow in cell motility. We investigate water influx-based migration in neutrophils, which undergo directed movement to sites of injury and infection. Chemoattractant exposure increases cell volume and potentiates neutrophil migration, but the causal link between these processes is not known. By measuring single cell volumes in primary human neutrophils, we find that chemoattractant induces a biphasic volume response with spreadingmediated volume loss followed by an increase in both cell volume and migratory speed. Using a genomewide CRISPR screen, we identify the regulators of the chemoattractant-induced neutrophil swelling, including PI3K-gamma, CA2, NHE1 and AE2. Through NHE1 inhibition in primary human neutrophils, we show that cell swelling is both necessary and sufficient for rapid migration following chemoattractant stimulation. Our data demonstrate that cell swelling complements cytoskeletal inputs for chemoattractant-induced potentiation of migration.