Bone resorption in vitro of normal, WASp-null osteoclasts, and WASp-null osteoclasts transduced with eGFP or eGFP-WASp. Bone resorption of normal (SV129), WASp-null (WASp-/-) cells, WASp-null cells expressing eGFP (WASp-/-eGFP), or WASp-null cells expressing eGFP-WASp (WASp-/-eGFP WASp) was assessed at day 10 after plating osteoclast precursors on bone slices. Bone slices were removed from wells, immersed in 10% NaOCl for 10 minutes to remove cells, washed in distilled water, dried, and sputter-coated with gold. The extent of bone resorption was quantified according to the following parameters: percent of bone surface resorbed (A) and depth and volume of the excavated regions (D and E, respectively). Both normal (C) and WASp-null osteoclasts (B) formed complex pits consisting of multiple component excavations, however, the number of individual components in complex pits was greater in WASp-null cultures. Expression of eGFP-WASp in WASp-/- cells (G) but not expression of eGFP alone (F) reconstituted the normal morphology of the pits. The graphs illustrate the mean percentage of osteoclasts ± SD from 3 experiments. ^*P < .05 (Student t test). Bar, 50 μm.