RXRα is required for R1A-RARα–mediated bone marrow cell transformation. (A) The bar chart represents the relative numbers of third-round colonies of primary hematopoietic cells cotransduced with R1A-RARα, R1A-RARα(ΔRIIa), or MLL-GAS7 plus empty vector, sh563, or sh131, respectively. Data are mean ± SD of 3 independent experiments. (B) Typical colony pictures of progenitor/stem cells cotransduced with retrovirus carrying the indicated leukemia fusion gene and empty vector, sh563, or sh131 after third-round plating in methylcellulose. Scale bars represent 1 mm. (C) The bar chart represents the relative numbers of third-round colonies of primary bone marrow cells transduced with the indicated constructs in the absent or presence of indicated drugs for 7 days. Data are mean ± SD of 3 independent experiments. (D) Typical third-round colony morphology in the absence or presence of the indicated drugs generated from transduced primary hematopoietic cells. Scale bars represent 1 mm. (E) Typical morphology of methylcellulose colonies generated from bone marrow cells transduced with retroviruses expressing R1A-RARα (top panel), R1A-RARα(ΔRIIa) (middle panel), or MLL-ENL (bottom panel), in the absence or presence of the indicated drugs. Scale bars represent 100 μm. (F) Flow cytograms are shown of Mac-1– and Gr-1–stained cells transduced by R1A-RARα (top panel) or R1A-RARα(ΔRIIa) (bottom panel) in the absence or presence of indicated drugs after third-round plating.