Fetal ME induction enhances postnatal myeloid priming. (A) UMAPs representing single-cell gene expression in P28 LK cells after fetal or postnatal ME induction. Controls reflect Cre^– littermates. Black lines reflect differentiation trajectories as calculated by Slingshot. (B) Cell identities by cluster based on surface marker phenotypes. (C-D) Distribution of cells within indicated clusters of P28 LK progenitors following fetal or postnatal ME induction. ∗∗∗P < .001 by Wilcoxon signed-rank test. (E) MLL::ENL transgene expression in all clusters (left panel), HSC/MPP (c19, middle panel), and pGM/GMP (c12/22, right panel) based on alignment of the human MLL::ENL transcript in n = 4 pseudoreplicates. ∗∗∗P < .001 by Wilcoxon signed-rank test. (F) Hoxa9 expression in control and ME-expressing HSCs/MPPs (cluster 19), ∗∗∗P < .001 by Wilcoxon signed-rank test. (G) Quadratic programming-derived myeloid identity scores for clusters along the HSC/MPP to GMP-neu trajectory in P28 wild-type mice. (H) Histogram showing distribution of myeloid identity score in all cells along the HSC/MPP to GMP-neu trajectory after fetal or postnatal ME induction. (I) Distribution of myeloid identity score in all cells and immature myeloid progenitors (c19 and c29) after fetal or postnatal ME induction. ∗P < .05, ∗∗∗P < .001 by Wilcoxon signed-rank test. (J) EdU incorporation for P28 LSKs and GMPs following E10.5 ME induction. ∗∗P < .01 by Student t test. (K) Expression of self-renewal genes in HSCs/MPPs after fetal or postnatal ME induction. ∗∗∗P < .001 relative to age-matched control by Wilcoxon signed-rank test. Ctl, control; N.S., not significant; UMAP, uniform manifold approximation and projection.