RUNX1c isoform accelerates and enhances hematopoietic commitment of hESC. (A) Quantitative reverse-transcriptase polymerase chain reaction analysis of the 3 main RUNX1 isoforms in the H9 hESC cell line shows that RUNX1c is the isoform almost exclusively expressed in CD31+CD45– hemato-endothelial progenitors, and is expressed at higher levels in CD45+ hematopoietic cells. Relative expression is shown normalized to undifferentiated hESCs. (B) Kinetics of hematopoietic specification from H9 hESCs transduced with the empty vector (EV) or RUNX1c-expressing vector (RUNX1c). RUNX1c accelerates and enhances hematopoietic development of hESCs. (C) Between 1 × 105 and 2.5 × 105 hESC-derived EV or RUNX1c hematopoietic derivatives were transplanted intrahepatically into newborn immunodeficient SCID–IL2Rgamma(null) mice.14 RUNX1c-hESC hematopoietic derivatives fail to engraft in vivo. FACS analysis was performed 7 to 8 weeks after transplantation (n = 12). Cord blood–CD34+ cells were transplanted as a positive control. APC, allophycocyanin; CFU, colony-forming units; FITC, fluorescein isothiocyanate; PE, Phycoerythrin.
