Figure 1: Generating induced hematopoietic progenitors from wild-type MEFs.

(a) Schema of experimental design. MEFs (P0) were purified by sorting out any contaminating hematopoietic cells and passaged to P2-3 before experiments. iHP cells induced from MEFs by reprogramming factors were used for further characterization and evaluation; negative control cultures were transduced with empty vector (EV) only. (b) Representative ‘cobblestone’ colonies at 24 dpi induced by lentiviral FuW-TetO vectors carrying 7F. Representative of three independent experiments. Scale bar: 100 μm. (c) CFU colonies derived from 27 dpi FuW-TetO-7F-induced iHP cells, representative of three independent experiments. Scale bar: 100 μm for GM, 50 μm for GEMM and E colonies. (d) Frequency of different type of CFU colonies derived from 27 dpi FuW-TetO-7F-induced iHP cells, with dox added (or withheld) at the beginning of CFC assays as indicated. Data are shown as mean±s.d. of four biological replicates from two independent experiments. (e) Representative ‘cobblestone’ colonies (27 dpi) induced by different combinations of factors: SL, SLB, SLHR or SLBR (with factors singly delivered in individual pMX vectors), representative of three independent experiments. Scale bar: 100 μm. (f) Different types of representative CFU colonies derived from 27 dpi SLHR-iHP in CFC assays (factors were singly delivered in individual FuW-TetO vectors), representative of two independent experiments. Scale bar: 100 μm for GM/G colonies; 50 μm for GEMM/E/M/Mk colonies. (g) Frequencies of different types of colonies derived from FACS-sorted Kit⁺CD41⁻, Kit⁺CD41⁺, Kit⁻CD41⁺ and Kit⁻CD41⁻ subsets of SLHR-iHP cells in CFC assays. Factors were singly delivered in individual FuW-TetO vectors. Data shown are mean±s.d. of biological triplicates. (h) Benzidine positive cells in a GEMM colony and adult (β-major) globin expression in CFU-E colonies as shown in f, representative of two independent experiments. BM: bone marrow cells. FL: E12.5 foetal liver cells. Data shown are mean±s.d. of technical triplicates. Scale bar, 100 μm. (i) Images of AchE⁺ megakaryocyte-containing colonies (CFU-mix and CFU-Mk) and phagocytic CD45⁺ cells, representative of three independent experiments. 27 dpi SLHR-iHPs (induced using pMX vectors) were used for CFU-MK assay. Scale bar, 200 μm for CFU-mix/Mk colonies; 100 μm for phagocytosis picture.