Combined GM and lymphoid transcriptional priming in LSKFlt3hiMpl− BM cells. (A) Coexpression patterns of transcriptional lineage programs in single cells from BM LSK subpopulations. Cells were scored as expressing GM and/or lymphoid (Ly) programs based on the expression of one or more lineage-associated genes: GM: Csf3r and Mpo; lymphoid: Rag1, sterile IgH transcript, and Il7r. Mean plus or minus SEM values from 2 experiments with 88 cells investigated in each experiment. (B) Coexpression pattern of Mpl and Flt3 on Kit-enriched, lineage-negative (Lin−), Sca-1+ and Kit+ (LSK) fetal liver (day E14.5-E15.5) cells. Gates denote the sorting strategies used to purify LSKFlt3hiMpl− (Flt3hiMpl−), LSKFlt3hiMplhi (Flt3hiMplhi), and LSKFlt3− cells. Percentages indicate mean quadrant frequencies within LSK cells from 4 experiments. Panels below show typical purity analysis for LSKFlt3hiMpl− and LSKFlt3hiMplhi cells. (C) In vitro Mk potential of fetal liver LSKFlt3−, LSKFlt3hiMplhi, and LSKFlt3hiMpl− cells, investigated as described in “Methods” after 8 days of culture. Mean plus or minus SEM values from 4 experiments. (D) Coexpression patterns of lineage programs in single cells from fetal liver LSK subpopulations. Cells were scored as expressing MkE, GM, and/or lymphoid (Ly) programs based on the expression of one or more lineage associated genes: MkE: Gata1, VWF, and Epor; GM: Csf3r and Mpo; lymphoid: Rag1, sterile IgH transcript, and Il7r. Mean plus or minus SEM values from 2 experiments, with 88 single cells of each cell population investigated in each experiment, except for LSKFlt3− cells in which 88 cells were evaluated in total.