Zfp521 mediates BMP2-induced osteogenesis. (A) Confirmation of Zfp521 knockdown by qRT-PCR. (B and C) W20 cells expressing Zfp521 (shZfp521) or scrambled (shScr) shRNA were cultured with or without 100 ng/ml BMP2 for 48 h, after which alkaline-phosphatase activity was visualized by staining (B) or quantified enzymatically (C). (D) qRT-PCR of osteogenesis-related BMP target gene expression in W20 cells cultured with or without 100 ng/ml BMP2 for 24 h. (E and F) W20 cells were cotransfected with a BMP-responsive luciferase reporter together with vectors expressing shZfp521, shScr, Zfp521 cDNA (pZfp521), or empty-vector control (pCMV6) and then treated with 100 ng/ml BMP2 for 16 h. (G) shZfp521 or shScr stable W20 cells were treated with 100 ng/ml BMP2 for 1 h, after which phosphorylation of Smad1/5 was analyzed by Western blotting. The data are presented as means ± SD; n ≥ 3. *, P < 0.05; **, P < 0.01; ***, P < 0.001 relative to shScr or pCMV6 cells within the same vehicle or BMP2 treatment group; Student's t test.