Actin treadmilling in a mouse melanoma cell

The video shows a B16 melanoma cell that was transfected with actin-GFP. A scanning laser beam was used to photobleach the fluorescence of actin in the region behind the lamellipodium marked by the square. This is immediately followed by incorporation of the bleached molecules at the lamellipodium tip. Note: the changes in fluorescence observed correspond to the fluorescence from polymerised filaments; monomeric actin diffuses very rapidly and adds only a weak homogeneous background to the image.