In vitro signaling through F36V-Mpl expands the number of transduced CD34⁺ cells and maintains multilineage potential. (A) Lymphomyeloid (CD34⁺CD38⁻Lin⁻CD7⁻) progenitors transduced with F36V-MPL-GFP or control (F36V-GFP) vector were cultured on MS5 stroma without growth factors with or without CID. Fold increase (mean, SEM) in total number and CD34⁺GFP⁺ cells relative to cells plated on day 0 (D0) is shown (n = 5 experiments, in triplicates); P = .002 and .023, respectively, for F36V-MPL-GFP–transduced cells with or without CID. (B) Immunophenotype of transduced CD34⁺CD38⁻Lin⁻CD7⁻ cells cultured as in panel A, showing generation of CD34⁺GFP⁺ (day 25), lymphoid (day 35), and myeloerythroid (day 49) cells. (C) Total number of cells in culture (left panel), number of CD34⁺ cells in culture (middle panel), frequency of clonogenic cells (mean, SEM percentage of CFU-Cs; right panel), generated from transduced CD34⁺CD38⁻Lin⁻CD7⁻ progenitors cultured with CID or Tpo, and control nontransduced CD34⁺CD38⁻Lin⁻CD7⁻ progenitors cultured with Tpo (n = 3 independent experiments, each in triplicate).