Fig. 6.

Global depolymerization of actin in a myosin II-null cell. Numbers are seconds before and after the addition of 5 μM latrunculin A. Before addition of the drug, the cell shows typical actin network organization and a protrusion at its right side (–13-sec frame). The network is fragmented within the first 17 sec. Later on, rosette-like assemblies predominate (35 sec) before structures become diffuse (see Movie 7). Intensely labeled areas consist of dense actin clusters associated with the Arp2/3 complex (7). Notably, in the myosin II-null cells, filopods attached to the substrate are not retracted when they are depleted of their actin content. Exposure time = 100 msec. (Scale bar: 5 μm.)