Kdm2b/Jhdm1b is required for Hoxa9-Meis1-induced leukemic transformation in vitro. (A) Flow chart of experimental procedure. To examine the role of Kdm2b/Jhdm1b in Hoxa9-Meis1-induced leukemic transformation in vitro, c-kit⁺ hematopoietic progenitors were isolated from E14.5 fetal liver (FL) and transduced with lentiviral (LV) vectors expressing various combinations of proteins and shRNAs. Transduced cells were then plated on methylcellulose to evaluate the effect of Kdm2b/Jhdm1b KD on colony formation and replating capacity. (B) KD of Kdm2b/Jhdm1b in Hoxa9-Meis1-induced leukemic cells impairs their methylcellulose colony replating capacity. Colony numbers for each round of replating are shown. (C) Growth curves indicate KD of Jhdm1b in Hoxa9/Meis1/GFP (J1bKD-HMG)–transformed leukemic cells impairs cell proliferation compared with Hoxa9/MeisI/GFP-transformed cells with control KD (CKD-HMG). Transformed cell colonies were picked after the third round of methylcellulose replating and cultured in liquid medium. (D) KD of Kdm2b/Jhdm1b results in a block at G₁-to-S phase transition. Flow cytometric analysis of cell cycle status shows that Kdm2b/Jhdm1b KD (J1bKD-HMG) results in a higher percentage of cells in the G₁ phase than that of control KD (CKD-HMG).