ArhGAP15-null neutrophils showed increased directional migration but decreased turning ability. (A-E) Under-agarose migration experiments. (A) Center-zeroed tracks of ArhGAP15^+/+ and ArhGAP15^−/− neutrophils migrating toward C5a (left). (B) Single-cell tracks of a typical ArhGAP15^+/+ and ArhGAP15^−/− neutrophil. (C) Measurement of chemotactic index toward C5a (Δx). (D) Center-zeroed tracks of ArhGAP15^+/+ and ArhGAP15^−/− neutrophils migrating from a primary CXCL2 gradient in the x-axis (left) toward a secondary C5a gradient in the y-axis (bottom). (E) Measurement of chemotactic index toward C5a (Δy). For each experiment, n = 4 movies/genotype. #P < .05.