Fig. 2 Organization of actin filaments in keratocyte lamellipodia. Electron microscopy of detergent-extracted cells. (a), overview of a locomoting cell; (b), actin network in lamellipodia from the leading edge (top) to the transitional zone (bottom); (c), brush-like zone at the leading edge with numerous filament ends; (d), smooth actin filament network in the middle part of lamellipodia; (e h), T-junctions (arrowheads) between filaments at the extreme leading edge (e), within brush-like zone (f), in the central lamellipodia (g), and close to the lateral edge of the lamellipodia (h). The cell's leading edge is oriented upward in all panels. Boxed region in (a) is enlarged in (b); upper and lower boxed regions in (b) are enlarged in (c) and (d) respectively. Bars: (b), 1 µm; (e-h), 50 nm.