In vitro signaling through F36V-Mpl induces cell division and generation of immunophenotypic and functionally primitive progenitors. (A) CD34⁺ cells transduced with F36V-MPL-GFP, labeled with PKH26, and analyzed by FACS after 7 days of culture with or without CID. Bar graph shows percentage of GFP⁺ cells gated from each generation with or without CID at day 7 of culture. (B) FACS analysis of cells cultured with or without CID, after gating on generation 4 (ie, after 3 divisions). (C) Bone marrow engraftment (6 weeks after transplantation) of human cells isolated from generation 4 and transplanted into β₂-microglobulin NOD/SCID⁻/⁻ mice (40 000 cells per mouse) Control indicates mice that did not undergo transplantation. (D) Human-specific Alu PCR of CFU-Cs generated from bone marrow of mice that received transplants of human cells: lanes 1 and 2 show CFUs generated from BM of 2 mice that received transplants of generation 4 of CID-cultured cells; lanes 3 and 4 show duplicate samples of whole bone marrow from mice that received transplants of generation 4 of non-CID–cultured cells; lanes 5 and 6 show duplicate samples of whole bone marrow from control mice that did not undergo transplantation; lane 7 shows +Control (human cord blood); and lane 8 shows −Control (murine cell line).