Figure 4. Implication of Rho GTPases in the cyclic resorption function of osteoclasts. Scanning electron micrographs (S4000 scanning microscope, Hitachi, sides), schemes and immunofluorescent staining of actin (blue), and vinculin (green) staining (Axioplan2/LSM 510 META confocal microscope, Zeiss, middle) showing morphologies and cytoskeleton structures of osteoclasts alternating between stationary resorption and migration phases. Polarized osteoclasts have the unique ability to resorb bone (1). Then, the sealing zone (SZ) is disassembled and osteoclasts can spread under a Rac/Rho effect (2). Rac/Cdc42/RhoE are implicated in actin reorganization (3) into another sealing zone stabilized by Rac/Rho and followed by osteoclasts polarization involving Cdc42 (4). Thereby, osteoclasts can resorb bone again and form another resorption lacuna (red arrows) (5). This cyclic process takes place until osteoclasts die of apoptosis implicating Cdc42 and Rac (6). Scale bars = 15 µm. Figure adapted from reference 47 with permission of the editor ASCB.