The scheme of lentivirus vector with shRNA specifically targeting Spred2, PLKO.1-shSpred2, was shown in A. 48h after transduced with 5 multiplicity of infection (MOI) PLKO.1-shSpred2 or PLKO.1-shScramble, the expression of Spred2 was detected to confirm the interference efficiency by Western-blotting (B) in human NBM CD34+ cells. Human NBM CD34+ cells were infected by PLKO.1-sh-Scramble or PLKO.1-sh-Spred2 at a MOI of 10 and cultured in GEMM medium. At day 0, 3 and 7 post-infection, the expression Spred2 was confirmed by real-time PCR (C), and the expression of CD34, CD235a and CD11b were analyzed by flow cytometer (E-F). Furthermore, the mRNA expression of CD235a (G), GATA1 (H) and PU.1 were detected by real-time RT-PCR. The expression of GATA1 expression was normalized by the expression level at day 0. And, the PU.1 expression at day 3 post-infection was normalized by the expression in PLKO.1-sh-Scramble group (I). PLKO.1-sh-Scramble or PLKO.1-sh-Spred2 transduced CD34+ cells were plated in 24-well plateand cultured in GEMM medium plus 1% methylcellulose for 14 days the presence of colonies (>40 cells) was counted and scored (D). Data are mean±s.d. of three independent experiments. *, p<0.05; **, p<0.01 vs the PLKO.1-sh-Scramble group at the same time point.