Membrane-targeted Rac1 suppresses the chemotaxis defect of PIPKI-α knockdown cells. Chemotaxis in response to a stable gradient of 10 µg/ml PDGF quiescent control or PIPKI-α–depleted HT1080 cells transfected with empty vector or vectors containing the indicated cDNAs. Chemotaxis was measured using µ-slide chemotaxis chambers. Results are shown as the percentage of migrated cells relative to control cells. Error bars indicate means ± SD (n = 3). Transfection efficiency was ∼85% based on GFP fluorescence.