CM cell autonomously impairs erythroid lineage commitment and deregulates expression of key erythroid/Mk lineage-determining regulators. (A) Schematic of experimental design. Cbfb^+/56M/Mx1-Cre/Rosa26^mT/mG (CM) or control Mx1-Cre/Rosa26^mT/mG (Ctrl) mice (CD45.2⁺) were induced as above. Sorted CM-expressing or Ctrl GFP⁺ LSKs (500 cells) were cotransplanted with 2 × 10⁵mTmG⁺ (CD45.2⁺; dTomato⁺) supporter BM cells into lethally irradiated (11 Gy) CD45.1⁺ congenic recipients. Phenotypic HSPCs and GFP chimerism in the BM were analyzed 8 weeks after transplantation by flow cytometry. (B) Representative FACS plots of GFP⁺ and dTomato⁺ chimerism within each HSPC compartment. (C) The frequency of lineage-committed (Lin⁺) and lineage-negative (Lin⁻) cells within Ctrl (n = 7) or CM (n = 11) GFP⁺ donor-derived population. (D) The frequency of LSK or MP (left), and phenotypic composition (right) of GFP⁺/Lin⁻ cells derived from Ctrl (n = 4) or CM (n = 7) donors. Mean ± SEM is shown. (E) Relative expression levels of Spi-1, Zfpm1, Klf1, Gata1, Gata2, Gfi1b, Lmo2, Tal1, Nfe2, Runx1, Fli1, Pf4, Vwf, and Mpl mRNA in sorted Ctrl or CM Pre-Meg/Es (n = 4-6) assessed by Taqman-based qRT-PCR assays. Shown is the relative expression level (mean ± SEM) for each gene normalized to the mean expression levels in Ctrl Pre-Meg/Es (indicated by dashed line). *P < .05; **P < .01; ***P < .001.