12/15-LOX regulates proliferation and function of LT-HSC. (A) Flow cytometric analysis of phenotypic subsets demonstrated depletion of the most primitive HSC phenotype and a concomitant increase in a more mature MPP phenotype in Alox15 compared with B6 LSK (n = 5). (B-C) 12/15-LOX regulates the function of LT-HSC. Lethally irradiated congenic mice were reconstituted with 500 CD34⁻Flt3⁻LSK (B) or 500 CD150⁺CD48⁻LSK (C) from B6 or Alox15 BM mixed with 2 × 10⁵ competitor cells. (Top) Reconstitution was analyzed by flow cytometry of CD45.2⁺ of total CD45⁺ WBCs. (Bottom) Analysis at 12 weeks after BM transfer for CD45.2⁺ LSK and CD34⁻Flt3⁻LSK (B) or CD150⁺CD48⁻LSK (C) by flow cytometric analysis of n = 8 in 2 independent experiments. (D-E) Increased proliferation of Alox15 compared with B6 determined by flow cytometric analysis by incorporation of Hoechst 33342 and PyroninY into DNA and RNA, respectively, of cells in the total LSK population (D) and CD34⁻LSK–gated population (E). Shown are a representative flow cytometric analysis and a summary of 4 independent experiments; *P < .05, **P < .01. All error bars represent the average (± SEM).