Hematopoietic potential of CD34⁺ cell–derived iPS cells after directed differentiation. Human iPS cells derived from normal control (NC, A) adult CD34⁺ cells or the PV CD34⁺ cells (D) were plated in microtiter wells and aggregated for EB formation and directed hematopoietic differentiation. After 10 to 14 days, substantial numbers of small round cells resembling immature hematopoietic cells surrounding EBs were found and increased in the next several days (A,D). Total cells were subsequently harvested and assayed for the presence of hematopoietic markers (supplemental Figure 4) and of hematopoietic colony-forming units (CFUs) formed in semisolid methylcellulose media (B-C: normal control iPS; E-F: PV-iPS). CFU-granulocyte/monocyte (B,E) and CFU-erythroid (C,F) colonies were observed after additional 10 to 14 days in culture. A similar CFU assay using purified CD34⁺CD45⁺ cells from an NC and PV sample is shown in supplemental Figure 5. (G) Wright-Giemsa staining after cytospin of individually picked myeloid and erythoid colonies generated from iPS cells derived from normal CD34⁺ cells. Cells resembling erythroblasts and multiple lineages of myeloid cells were observed. Scale bar represents 100 μm.