Cell movement begins with lamellipodia. A thin sheet of actin filaments (light purple) that stretches out to the cell’s periphery, lamellipodia generate pushing forces that drive the cell forward. Microtubules (cyan) can barely penetrate this actin network, but they direct cell motility in other ways, such as controlling cell adhesion and acting as the cell’s internal compass.
Image: A human HaCat keratinocyte responds to epidermal growth factor by rapidly forming a lamellipod around most of its perimeter. The cell was fixed and processed within minutes after EGF addition. F-actin is stained with fluorescently labeled phalloidin (light purple), and microtubules are labeled with an antibody (cyan). DNA dye stains the nucleus dark purple.