A) Osteoblastic transduction was performed using the lentivirus RRL transfer vector harboring a stop codon-less human (hu) hnRNPC1 cDNA and a green fluorescent protein (GFP) cassette driven by the bone-specific mouse col1a1 2.3kB promoter. The lenti vector backbone also contains the central polypurine tract (cPPT) from the HIV-1 integrase gene to increase the copy number of lentivirus integrating into the host genome to enhance viral titer. B) FACS sorting of GFP-positive MC3T3-E1 osteoblasts transduced with the hu hnRNPC1 and empty lentivirus vectors for the isolation and generation of stable clones. C) 15 hu hnRNPC1-over expressing stable lines were created (data not shown), whereby five (clones 3', 5', 8', 10', 11') lines with variable hnRNPC1 over expression were further evaluated for 1,25(OH)2D (10 nM, 6 hrs) mediated induction of endogenous mouse (mu) Cyp24a1 mRNA.