PU.1 overexpression generates more osteoclasts than C/EBPα overexpression from pre-committed BMMs. A, gene expression analysis from BMMs expressing a GFP control (GFP), FLAG-C/EBPα, or FLAG-PU stimulated by M-CSF for 4 days by Western blotting. B, TRAP staining for osteoclast differentiation from BMMs expressing GFP, FLAG-C/EBPα (C/EBPα), or FLAG-PU.1(PU.1) stimulated by M-CSF plus RANKL for 4 days. Scale bars = 200 μm. C, quantifications for B are shown. D and E, quantifications of the osteoclast size for B via the number of nuclei (D) and area (E) of TRAP-positive multinucleated cells. The numbers in parentheses show concentrations in nanograms per milliliter. Error bars show averages ± S.D. *, p < 0.05; NS, not significant.