Reconstitution of podosomes in WASp-/- osteoclasts plated on bone slices by expression of eGFP WASp. WASp-null cells were transduced with eGFP (A-F) or eGFP-WASp (G-L). Actin organization was detected by immunostaining with Alexa 568-conjugated phalloidin (B, E, H, K). Similarly to nontransduced WASp-null cells, cells transduced with eGFP were devoid of podosomes (A-C) or assembled actin-rich plaques (D-F). eGFP did not colocalize specifically with any cytoskeletal structure (C, F). Expression of eGFP WASp resulted in the formation of actin-based structures similar to wild-type normal cells with podosomes in migratory cells (G-I) and actin rings (J-L). eGFP-WASp colocalized with podosomes (G-I) and actin rings (J-L). The micrographs are representative of the cytoskeletal organization of osteoclasts detected in 3 independent experiments. Bar, 20 μm.