Figure 1.

Flow cytometry analysis of TF-1 transfectants expressing as-SCL or dn-SCL. (top left) Decreased SCL protein in TF-1 cells expressing as-SCL. TF-1 cells were infected with a retrovirus harboring the human SCL cDNA cloned in the antisense orientation and maintained as a polyclonal population in GM-CSF containing medium in the presence of G418 (1 mg/ml). 1 wk after infection, as-SCL transfectants were fixed and permeabilized with Triton X-100 for nuclear staining with the monoclonal anti-TAL1 at a final dilution of 1:10, followed by labeling with a goat anti–mouse antibody coupled to FITC (Sigma). Cells were washed extensively for 10 min after each labeling step and analyzed by flow cytometry. Parental TF-1 cells were stained in parallel as positive controls. Both cell types were also stained with the second antibody alone (2^nd) as negative controls. In contrast to the shift in SCL nuclear staining between as-SCL transfectants and parental TF-1 cells, those of MSCV (vector alone) transfectants and TF-1 cells were comparable (data not shown). (top right) Decreased c-Kit expression in TF-1 cells expressing as-SCL or dn-SCL. The same cells as in the top left panel were analyzed for surface labeling with a biotinylated monoclonal antibody against human c-Kit and streptavidin-coupled PE (S-PE). Cells labeled with S-PE alone serve as negative controls. (middle and bottom) Surface expression of CD45 and CD116 (GM-CSF receptor [GM-R] α chain) is unaltered in TF-1 transfectants. Cells were labeled with a mouse anti–human CD45 and anti–human CD116 (GM-R), followed by FITC-labeled goat anti–mouse IgG. Labeling with the second antibody alone (2^nd) is shown.