Ptpn11 deletion leads to decreased quiescence and increased cell death. (A-B) Cell cycle analysis of Ptpn11^Δ/Δ HSCs and progenitors. LK (A) and LSKCD150⁺ (B) cells were subjected to 2-parameter analysis of DNA content (Hoechst 33342 [H]) vs RNA content (Pyronin [PY]). The mean percentages (± SEM) of cells in G₀ (H⁻PY⁻), G₁(H⁻PY⁺), and S/G₂M (H⁺PY⁺) are indicated. *P < .05, Student t test. (C) Lin-c-kit⁺Sca1⁻ and (D) LSKCD150⁺ cells harvested from control (n = 3) and Ptpn11^Δ/Δ (n = 3) mice were stained with annexin V to assess cell death at the indicated times after pIpC induction. The average percentage (± SEM) of annexin V⁺ cells is shown. *P < .05, Student t test. (E-F) Single SLAM-HSCs were sorted into 60-well plates (1 cell/well) and cultured in media containing SCF, TPO, Flt3L, and interleukin-11. Proliferation of each clone was evaluated microscopically over 4 days. Representative data from one of 4 experiments with similar results are shown. The average percentages (± SEM) of surviving clones from the 4 experiments are shown at the top of each panel. *P < .05, Student t test.