Smc3 haploinsufficiency increases stem cell self-renewal. (A) Mx1-cre–mediated deletion of Smc3 confirmed by Western blot of BM. (B) qRT-PCR showing relative expression level of Smc3 in BM and persistence of the decreased expression in the cells that replate in methylcellulose. (C) Serial plating and colony counts in methylcellulose for Smc3^fl/+ or Smc3^Δ/+ BM. Whole BM was plated in triplicate at 20K cells/well. (D–F) Flow cytometric enumeration of BM c-Kit⁺, LSK (Lin⁻ Sca1⁺ Kit⁺), and MP (Lin⁻ Sca1⁻ Kit⁺) cells (D), LT-HSCs (LSK CD150⁺ CD48⁻), ST-HSCs (LSK, Cd150⁺, Cd48⁺), and MPP cells (LSK CD150⁻ CD48⁺; E), and percentage of common myeloid progenitors (CMPs; lineage⁻, c-Kit⁺, Sca-1⁻, FcγR⁻, CD34⁺), GMPs (lineage⁻ c-Kit⁺ Sca-1⁻, FcγR⁺ CD34⁺), and MEPs (lineage⁻ c-Kit⁺ Sca-1⁻ FcγR⁻ CD34⁻; F) in Smc3^fl/+ and Smc3^Δ/+ mice (n = 4–6 mice per genotype). Mice were taken down at 4 wk after PIpC injection. Excision was confirmed at takedown. Data are expressed as frequency of live cells per femur. (G) Representative FACS analysis of BM stem cell populations of Smc3^fl/+ and Smc3^Δ/+ mice. (H) Nucleolar staining of Smc3^fl/+ and Smc3^Δ/+ BM reveals occasional cells with supernumerary nucleoli in Smc3^Δ/+ cells. (I and J) Competitive transplantation of 500K donor-derived Cd45.1 whole BM was injected by tail vein after lethal irradiation with either 500K Cd45.2 whole BM from Smc3^fl/+ or 500K Smc3^Δ/+. Chimerism was measure by percentage of Cd45.2 in the peripheral blood every 4 wk. Mice were sacrificed at 20 wk. (K–N) Flow cytometric chimerism of unsorted peripheral blood, Mac1⁺Gr1⁺ myeloid cells, B220⁺ B cells, and Cd3⁺ T cells (K), BM c-Kit⁺, LSK (Lin⁻ Sca1⁺ Kit⁺), and MP (Lin⁻ Sca1⁻ Kit⁺) cells (L), LT-HSCs (LSK CD150⁺ CD48⁻), ST-HSCs (LSK, Cd150⁺, Cd48⁺), and MPP cells (LSK CD150⁻ CD48⁺; M), and percentage of CMPs (lineage⁻, c-Kit⁺, Sca-1⁻, FcγR⁻, CD34⁺), GMPs (lineage⁻ c-Kit⁺ Sca-1⁻, FcγR⁺ CD34⁺), and MEPs (lineage⁻ c-Kit⁺ Sca-1⁻ FcγR⁻ CD34⁻; N) in Smc3^fl/+ and Smc3^Δ/+ mice (n = 5 mice per genotype). Error bars represent ± SD (B–F and I–N); *, P < 0.05; **, P < 0.01; ***, P < 0.001 (Mann–Whitney U test).