Kinetic analysis of primitive and definitive hematopoietic colonies generated from WT (SIRT1^+/+) and knockout (KO; SIRT1^−/−) EB cells under normoxia (20% O₂) and 5%O₂. Primitive erythroid colonies generated from SIRT1^+/+ and SIRT1^−/− EB-derived cells under (A) normoxia and (B) lower (5%) O₂ tension. Definitive GEMM, multilineage progenitors of granulocytes, erythroid cells, macrophages, megakaryocytes; GM, multilineage progenitors of granulocytes and macrophages; and secondary EBs generated from SIRT1^+/+ and SIRT1^−/− EB-derived cells under normoxia condition and lower (5%) O₂ tension at day 6 (C) and day 8 (D). Data are shown as mean ± SD. N = 3; *P < .05. Relative mRNA expression of embryonic globin (E) and adult globin (F) genes from SIRT1^+/+ and SIRT1^−/− day 0, 2, 4, 6, 8, and 10 EBs by real-time RT-PCR. Error bars indicate SDs from the average of 3 independent experiments, each performed in triplicate; ***P < .001; **P < .01; *P < .05.