Experimental design and evidence for Smad7 expression in transduced BM cells. (A) MSCV control (MIG) and Smad7 retroviral constructs. The Flag-tagged Smad7 cDNA was subcloned into the control vector backbone upstream of IRES and GFP sequences. LTR indicates long terminal repeat. (B) Experimental outline. (C) Transduction efficiencies of BM cells were determined 3 days after transduction and shown to be between 60% and 80% for MIG and 50% and 80% for Smad7. Mock indicates untransduced cultured cells. The figure shows a representative experiment. (D) Western blot analysis showing Smad7 protein expression in BM cells using an anti-Flag antibody. Actin was used as loading control.