Scl gene dosage and the cell-cycle status of LT-HSCs. (A) The cell-cycle status of adult LT-HSCs was assessed within the Kit⁺Sca1⁺Lin⁻CD150⁺CD48⁻ population by Hoechst 33342 and Pyronin Y staining. Box plots represent pooled data from 6 experiments with Scl^+/+ and Scl^+/− bone marrow cells at steady state, together with the medians and extreme values of the 2 distributions, illustrating the percentages of cells in G₁ (left panel) and S-G₂M (right panel). (B) BrdU incorporation in LT-HSCs was analyzed within the Kit⁺Sca1⁺Lin⁻CD150⁺CD48⁻ population. Representative histograms are shown from Scl^+/+ and Scl^+/− bone marrows. Numbers shown are the mean ± SEM of 3 experiments. (C) The cell-cycle status of perinatal LT-HSCs (week 3) from Scl^+/+ and Scl^+/− bone marrows was assessed by flow cytometry, as in panel A. The 2 distributions do not differ significantly.