Emergence of Large-Scale Cell Morphology and Movement from Local Actin Filament Growth Dynamics
Outlines of migrating keratocytes overexpressing EGFP-VASP were generated from each frame of time-lapse image sequences separated by 10 s to examine the shape of cells as they migrate. Outlines are colored from blue to red to represent time (0–240 s), superimposed, and plotted on the same scale for visual comparison. Speed can be estimated from the distances traveled by each keratocyte because outlines correspond to the same total time. Fluorescent images correspond to the first (A) and fifth (B) frames of each time-lapse sequence and are scaled to match to the outlines. (A) The leading edge and overall shape of a smooth, coherent keratocyte does not vary extensively as the cell migrates. (B) In the case of a rough and rounder keratocyte, outlines show that the leading edge changes shape rapidly and widely. This keratocyte is unable to maintain persistent coordinated protrusion of its lamellipodium. Specific segments of the leading edge extend forward while adjacent regions lag behind (notice blue and orange outlines). This keratocyte migrates at approximately half the speed of the coherent keratocyte in (A).