Retroviral constructs used for in vivo transduction. A: Map of the two RV constructs; top: encoding a truncated, dominant negative form of the alpha RA receptor (dnRARα403) along with an IRES motif and GFP in a bicistronic message; bottom: IRES-GFP alone. B: Western blot demonstrating the equivalence of GFP expression in HEK cells for the four samples illustrated in C (in order from left to right, control, dnRARα403, control + RA, dnRARα403 + RA). C: Luciferase levels for each of the four conditions indicated.