Pak2 deficiency increases megakaryocyte precursors and hematopoietic stem cells. (A) Percentage of bone marrow from wild-type or Pak2^−/− mice that are PreMegE identified by CD150⁺ and CD105⁻ after gating for Lin⁻C-kit⁺Sca1⁻ (*P < .05). (B) Percentage of bone marrow from wild-type or Pak2^−/− mice that are committed MkPs, defined by CD41⁺ and CD150⁺, after gating for Lin⁻C-kit⁺Sca1⁻ (*P < .0001). (C) MegaCult-C colony-formation assays (CFU-Mk) of 10⁵ unsorted bone marrow cells from wild-type and Pak2^−/− mice 14 DPI. Number of megakaryocyte colony-forming units (CFU-Mk) were counted after staining with acetylcholinesterase (*P < .0002). (D) Hematopoietic stem cells in bone marrow of wild-type and Pak2^−/− mice. LSK, Lin⁻/C-kit⁺/Sca1⁺; LK, Lin⁻/C-kit⁺/Sca1⁻ (*P < .05). All bone marrow measured at 14 DPI. Experiments included n > 5 mice/genotype, mean ± SEM.