Persistent self-renewal of primary hematopoietic progenitor/stem cells by R1A-RARα. (A) Schematic diagram of R1A-RARα, PLZF-RARα, PML-RARα, and their mutant forms used in RTTA (left). The RIIa homodimerization domain of R1A and the B, C, D, E, and F domains of RARα are indicated. The bar chart (right) represents the corresponding numbers of colonies after each round of plating in methylcellulose culture medium. Data are mean ± SD of 4 independent experiments. (B) Typical third-round colony (left and middle panels) and cell morphology after May-Grunwald-Giemsa staining (right panel) of primary bone marrow cells transduced with the indicated constructs. Scale bars from left to right represent 1 mm, 100 μm, and 10 μm, respectively. (C) Flow cytogram of bone marrow cells transduced by R1A-RARα or R1A-RARα(ΔRIIa) and stained for Mac-1 or Gr-1 as indicated. The ellipse frames unstained negative control cells.