Overexpression of Tusc2 has no effect on osteoblast differentiation and function. (A, B) Osteoblasts were transduced with pMX-IRES-EGFP (control) or Tusc2 retrovirus and cultured in an osteogenic medium (OGM) containing BMP2, ascorbic acid, and β-glycerophosphate. (A) Cells cultured for 3 days were subjected to an alkaline phosphatase (ALP) activity assay. ALP activity was measured as change in the absorbance at 405 nm. (B) Cells cultured for 9 days were fixed and stained for alizarin red (left panel), which was quantified by densitometry at 562 nm (right panel). n.s., not significant.