Enhanced cycling and decreased apoptosis in Ptpn11^D61G/+ LSK cells. (A) BM cells freshly harvested from 5- to 7-month-old Ptpn11^D61G/+ (n = 6) and WT (n = 5) littermates were assayed by multiparameter flow cytometric analysis to determine cell-cycle status of HSC-enriched LSK cells as described in “Methods.” (B) Percentages of LSK cells in G₀, G₁, and S/G₂/M phases identified based on Pyronin Y and Hoechst staining profiles were determined. (C-D) BM cells from Ptpn11^D61G/+ and WT littermates (n = 5 per group) were analyzed by multiparameter flow cytometric analysis to determine apoptosis (annexin V positive cells) in the LSK population as described in “Apoptosis and cell-cycle analysis.”