Cell cycle status of CD34⁺Flt3^high versus CD34⁺Flt3^low cells. (A) Based on 7-AAD labeling, a gate was set to exclude dead cells (R1). (B) Next, a “blast gate” was set (R2). (C) With both R1 and R2 activated, gates were drawn to discriminate Flt3^low (R3) from Flt3^high (R4) cells. Histograms of Flt3 receptor (bold line) and IgG isotype control (dashed line) staining are shown. The plots in the lower panels show the Ki67 versus 7-AAD staining profiles for (D) total CD34⁺ cells, (E) CD34⁺Flt3^low, and (F) CD34⁺Flt3^high subpopulations. Cells in the lower left quadrant of each plot are defined as being in G₀, cells in the upper left quadrant as G₁, and cells in the upper right quadrant as G₂, S, or M phases of the cell cycle. For the three surface marker–defined subpopulations, the percentage of cells in each phase of the cell cycle is provided in the table. The numbers in parentheses represent the percentages of cells with the given immunophenotype and cell cycle stage within the total CD34⁺ cell population. This experiment was performed three times with CD34⁺ cells and twice with CD34⁺lin⁻ cells. Staining profiles were similar each time.