Cell sorting strategy to isolate CD34⁺cells during ex vivo G₀-G₁ progression. (A) MPB CD34⁺ cells in G₀ were isolated in a first Hst/PY sort and either directly injected into recipient animals or plated in ex vivo conditions. (B) After 36 hours, a second Hst/PY sort was used to separate cultured cells transiting to G₁ from those remaining in G₀. Both cell subsets were then assayed in NOD/SCID mice. Cell-cycle status of cells isolated in G₁(C) or G₀ (D) after culture was confirmed by restaining samples of sorted cells with 7-AAD and Ki-67. Percentages of cells detected in each quadrant are indicated.