IL-7 signaling induces proliferation of early BCP but does not profoundly affect proliferation of pre-BII large cells. (A) Flow cytometric quantification of Ki-67 expression in individual BM BCP populations in controls vs patients, shown for 1 representative control and 1 patient. (B) Cells were assigned to the different cell cycle phases as described in "Methods.” UMAP plot of the entire combined data set of controls and patients, showing the cell cycle phase of each cell (blue: G1; green: S phase; and pink: G2/M phase). (C) Distribution of cell cycle phases per cluster shown for controls vs patients. Bars indicate percentages per cluster. (D) Dot plot showing expression of proliferation markers for individual clusters in controls vs patients. (E) GSEA analysis with the G2M hallmark gene set performed for the pro-B4/pre-BI cluster with the differentially expressed genes between patients and controls, showing enrichment of the gene set in the controls. (F) Dot plot showing expression of CCND3 in early BCP clusters in controls vs patients. (G-H) Flow cytometric quantification of Ki-67 expression in individual BCP populations in IL-7 stimulated vs unstimulated CB (G) and BM (H) cultures. The black bar denotes gate for positive cells. Bar graphs show mean with error bars representing standard error of the mean. Statistical analysis was performed with multiple unpaired t tests and corrected for multiple comparisons with the Holm-Šídák method. All replicates are shown (CB: n = 7, each with 2-5 replicates; BM: n = 3, each with 3-6 replicates). P values are denoted as follows: ∗P < .05; ∗∗∗P < .001; ∗∗∗∗P < .0001.