Depletion of fascin-1 blocks haptotaxis but not chemotaxis. (A) TIRF montage, representative of 13 cells, showing filopodia-templated protrusion in IA32 MEFs coexpressing EGFP-fascin (inverted grayscale) and mCherry Akt-PH (pseudocolored). Bar, 10 µm. In the example shown, protrusions over filopodia coalesce to form a broad lamellipod (see also Video 10). Arrowheads mark filopodia that preceded lamellipodial protrusion. (B) Representative immunoblot showing relative fascin-1 expression levels in the nontargeting shRNA, fascin shRNA (#1), and fascin rescue IA32 cells used in directed migration experiments. (C) Chemotaxis assay results: wind-rose plots showing the distributions of overall cell migration directionality, expressed as an angle relative to an external gradient of PDGF, are shown for control (n = 74) and fascin-1 shRNA (n = 131). Mean FMI and velocity and persistence (D/T) are displayed ±95% confidence intervals. (D) Haptotaxis assay results are shown for control (n = 128), fascin-1 shRNA (n = 124), and fascin rescue (n = 57) tracks. Mean FMI and velocity and persistence (D/T) are displayed ±95% confidence intervals.