Analysis of cell cycling of BM progenitor cells transplanted into nonconditioned immune-compromised BALB/c Rag2^−/− γc^−/− recipients. (A) Schematic drawing of the experimental setup (3 independent experiments, total n = 10 per group). At 8 wk, 7 mice per group were sacrificed and analyzed in detail (C–G), whereas the remaining 3 mice per group were kept for long-term analysis of blood counts, chimerism, and spleen size (B and H). (B) Time course of blood counts and chimerism in granulocytes for primary recipients. (C) Representative scattergrams showing gating strategy for chimerism and CFSE dilution analyses. (D) Quantification of chimerism, with the averages of 7 WT mice and 7 V617F mice in selected BM populations. (E) Numbers of donor-derived LSKs (n = 7 per group). (F) The percentages of LSKs with >5 cell divisions or 0–2 divisions. (G) Spleen weight at terminal workup 8 wk after transplantation (n = 7 per group). (H) Spleens at 40 wk after transplantation. (I) Schematic drawing of the experimental setup for secondary transplantations. (J) Blood counts and chimerism of secondary recipients receiving 15 slow-dividing (0–2 divisions) V617F LSKs per recipient competing with 2 × 10⁵ WT BM rescue cells. Results of 3 independent experiments, total n = 6. (K) Same as in J, but with 15 slow-dividing WT cells. Total n = 4. (L) Blood counts and chimerism of secondary recipients receiving 150, 1,500, or 15,000 rapidly dividing V617F LSKs (>5 divisions) competing with 2 × 10⁵ WT BM cells. Results of 3 independent experiments, total n = 28 and total n = 6 (M) for recipients of WT cells. Statistical analysis was conducted using either Student’s t test, or one-way ANOVA with Bonferroni’s post-hoc multiple comparison test. *, P < 0.05; **, P < 0.01; ***, P < 0.001.