LSK cells from JAK2^V617F mice exhibit increased DNA damage, reduced cell cycling, and reduced apoptosis. (A) Intensities of γ-H2AX foci relative to DAPI obtained for BM cells (70-138 nuclei per mouse) and LSK cells (33-112 nuclei per mouse) from JAK2^V617F mice at both 6 and 26 weeks after pIpC. Histograms show significantly higher relative intensities of γ-H2AX foci in cells from JAK2^V617F mice compared with the cells from the control mice at 26 weeks, but not at 6 weeks after pIpC. (B) LSK cell-cycle analysis showing increased quiescence in JAK2^V617F 26 weeks after pIpC. LSK cells were subjected to 2-parameter analysis with DNA content versus Ki-67 expression, and the percentages of LSK cells in each of the cell-cycle phases were obtained (G₀, Ki-67^lowPI^low; G₁, Ki-67^hiPI^low; S/G₂/M, Ki-67^hiPI^hi). *P < .05. (C) Representative FACS plots and histograms showing reduced apoptosis in LSK cells from JAK2^V617F mice. Annexin V and 7AAD staining was analyzed on gated LSK cell populations from JAK2^V617F mice at both 6 and 26 weeks after pIpC. *P < .05. **P < .01. ***P < .001. NS indicates not significant.