Directional sensing in PTEN^−/− neutrophils. Chemotaxis in response to a point source of chemoattractant. Neutrophils from WT or PTEN^−/− mice were plated on coverslips and exposed to a micropipette filled with 10 μM fMLP. Trajectories of migrating cells were tracked from frames taken every 20 seconds. Two videos of the experiment described in this figure are included (Movies S4 and S5). (A) Cell tracks are plotted in reference to each cell's starting point and aligned with respect to the direction of the pipette tip (black arrow, positive x-axis). (B) Average cell speed is calculated from the trajectories of migrating cells. *P < .05 versus wild-type neutrophils. (C) Average cell speed in the direction of the pipette tip (± μm/minutes). (D) Average directionality toward pipette tip (−1 to 1). *P < .05 versus PTEN^−/− neutrophils. (E) Chemotactic error, calculated as the average angle the cell deviates from the direction of the micropipette tip (degrees). *P < .05 versus wild-type neutrophils. A detailed explanation of all these parameters can be found in Figure S4. Results are mean ± SD of 10 to 13 cells from 3 different movie sequences.