FIGURE 5. GABPα is insufficient to rescue Il7r transcription in Sfpi1−/− fetal liver hematopoietic progenitors.
A, overview of retroviral vectors. Shown in schematic form are MIGR1 (first panel), MIG-PU.1 (second panel), MIG-EBF (third panel), MIG-GABPα (fourth panel), and MIY-GABPβ1 retroviral vectors (fifth panel). B, GABPα and GABPβ1 protein expression. Western blot analysis was used to demonstrate GABPα expression from retroviral packaging cells transiently transfected with the MIGR1 or MIG-GABPα retroviral plasmids, using an anti-FLAG antibody (top panel), or from MIY-GABPβ1 retroviral plasmids, using an anti-GABPβ1 antibody (bottom panel). C, flow cytometric analysis of Sfpi1−/− fetal liver progenitor cells infected with retroviral vectors. After 24 h of culture, Sfpi1−/− fetal liver progenitor cells infected with MIG-GABPα, MIY-GABPβ1, or both MIG-GABPα and MIY-GABPβ1 were analyzed for GFP fluorescence (x axis) and YFP fluorescence (y axis). The percent cells in each quadrant are shown in the upper right corner of each panel. D, PU.1 and EBF, but not GABP rescues IL-7-dependent proliferation of Sfpi1−/− progenitors. Sfpi1−/− progenitors were infected with MIGR1, MIG-PU.1, MIG-EBF, MIG-GABPα, MIY-GABPβ1, or both GABPα and GABPβ1 retroviruses and cultured on S17 stromal cells with IL-7 for 9 days. Proliferation was evaluated by cell counting. A summary of the results obtained from three independent experiments is shown. ko, knockout.