Fig. 1. Time lapse series of lamellipodia crossing the holes of a perforated film. (A) GFP-actin-transfected B16F1 melanoma cell; the holes in the lamellipodium region in this sequence are 1-2 µm in diameter. (B,C) GFP-VASP-expressing B16 cells. The central 2 µm (B) and 4 µm (C) holes are indicated by arrowheads; the 4 µm hole causes a temporary delay in local protrusion. Each sequence covers approximately 10 minutes. Bar, 10 µm.