Organization of actin filaments in normal and WASp-/- osteoclasts at adhesion points on the substratum. Confocal fluorescent and IRM images were taken to detect vinculin (A, D, G, J) and F-actin distribution (B, E, H, K), showing that the adhesion points of the cells with the substratum detected by IRM (C, F, I, L) corresponded to the actin structures we detected by immunofluorescence. Adhesion points in normal osteoclasts were mediated by podosomes in noncircular clusters (A-C) or inserted in actin rings (D-F). In WASp-null osteoclasts, attachment of cells to the substratum was mediated by actin patches (G-I) or dysmorphic actin rings (J-L). Bar, 20 μm.