Loss of SKP2 results in defective short-term engraftment in competitive repopulation assays. CRA. BM CD45.2 Lin⁻ cells purified from Skp2^+/+ (gray bars) or Skp2^−/− (black bars) mice were transplanted into lethally irradiated CD45.1 recipients together with 10⁵ competitor cells (CD45.1). Analysis of CD45.2⁺ cells in PB was performed at 4, 8, 12, 16, and 24 weeks after transplantation. (A) Transplantation was performed with 7.5 × 10⁴ donor cells. Bar graph represents average expression of CD45.2 donor cells in the PB. Each group n = 12-18 mice in 3 independent experiments. (B) Lin⁻CD45.2⁺ cells were sorted at week 12 after transplantation from primary recipients and 7.5 × 10⁴ donor cells transplanted in secondary recipients. Bar graph represents average expression of CD45.2 donor cells in the PB. n = 3 from a representative experiment. (C) Lin⁻ CD45.2⁺ cells from Skp2^−/− and Skp2^+/+ mice were sorted and transplanted in recipients at decreasing doses: 7.5 × 10⁴, 5 × 10⁴, or 2.5 × 10⁴. Bar graph represents average expression of CD45.2 donor cells in the PB. n = 4-6. #P < .05 vs 7.5 × 10⁴ cells. $P < .05 vs 5 × 10⁴ cells. (D) Analysis of the LSK (left) and ST-HSC (right) content in BM of recipients at week 12 after transplantation. n = 3 from a representative experiment. (E) Homing at 48 hours. Bar graph shows percentage of CD45.2⁺ donor cells recovered at 48 hours after transplantation of Lin⁻ cells into CD45.1 recipients; n = 4 in 2 independent experiments. Data expressed as mean ± SEM *P < .05 vs Skp2^+/+. **P < .005 vs Skp2^+/+.