Cell surface expression of wild-type and mutant c-mpl on UT-7. (A) Schematic representation of c-mplwt and deletion mutants. (B) UT-mplwt, UT-mpl▵7, UT-mpl▵7▵C, and UT-mpl▵8 cells express similar levels of receptor as detected by their ability to bind a TPO-Fc fusion protein (see Materials and Methods). No binding was detected on UT-7 cells infected with empty MCSV-pIRES-GFP virus (UT-GFP).