Epo-induced PODXL expression depends on EpoR/PY343/Stat5 signaling. (A) wt-EpoR and minimal knocked-in EpoR-HM and EpoR-H alleles are diagrammed. (B) EpoR-HM fails to support efficient Epo-induced PODXL expression; Kit⁺CD71^high erythroblasts from wild-type, EpoR-HM, and EpoR-H marrow were expanded. At day 2.5, expansion cultures were shifted to SP34-EX medium lacking SCF and containing Epo at 0.1, 0.4, and 1.6 U/mL. At day 3.5, lin⁺-depleted cultures were analyzed for PODXL expression by flow cytometry (i-ii) and confocal microscopy (iii) (Images were seen with a Leica model TCS-SP confocal microscope with a 63 ×/1.32-0.6 oil lens, Vectashield (Vector, Burlingame, CA) imaging solution, and Streptavidin, Alexafluor 647, and Hoexchst 35480 (Molecular Probes, Carlsbad, CA) stains. Images were acquired using Leica TCS-NT version 1.6 and Photoshop (Adobe) version CS2 software.). Also graphed for wt-EpoR, EpoR-HM, and EpoR-H erythroblasts is the fold-induction of PODXL due to Epo (1.6 U/mL; iv). (C) In silico analyses of predicted STAT elements and STAT/ETS modules in murine PODXL and Cis1 promoters. The occurrences of consensus elements were predicted using Genomatix ChipInspector software.