The shortest isoform of LSD1 positively regulates the self-renewal of HSCs. (A) We transduced LSK and Lin⁻/Sca-1⁻/c-Kit⁺ cells from normal mouse bone marrow with an empty plasmid (Mock) or expression vectors for LSD1 isoforms (−/−) and (+/−) for 48 hours, and cultured them in methylcellulose medium for 7 days to evaluate the clonogenic growth. Signal intensity of DsRed is shown in the left panel as a surrogate marker of LSD1 expression in starting materials. (B) Total cellular RNA was isolated from LSK cells transduced with LSD1 isoforms (−/−) or (+/−), and subjected to real-time quantitative RT-PCR for the expression of the indicated genes. Data were quantified by the 2^-∆∆Ct method using simultaneously amplified GAPDH as a reference and shown as fold increases against mock-transfected controls. (C) c-Kit–positive bone marrow mononuclear (BM) cells were transduced with an empty vector (Control), LSD1 isoform (−/−) or (+/−), and transplanted into lethally irradiated recipient mice. We isolated bone marrow mononuclear cells from recipient mice 10 months after transplantation and performed colony-replating assays in the presence of murine stem cell factor (mSCF), FLT3 ligand (FL), and murine interleukin-3 (IL-3) at 50, 50, and 10 ng/mL, respectively. (D) The means ± SD (bars) of colony numbers in each passage (i) and representative photographs of colonies (ii) are shown. *P < .01 and **P < .05 determined by a 1-way ANOVA with the Bonferroni post hoc test (n = 3).