(A and B) Percent contributions (A) and frequencies (B) of CD150hi HSC, CD150lo HSC, and CD150neg MPP within the K+L−S+CD41−CD48− compartment in 5A3+/del mice (n = 12) and their WT littermates (n = 11) at 24–30 months of age. (C and D) Competitive transplantation of BM cells from 24- to 30-month-old WT or 5A3+/del mice. Percent donor contribution of 5A3+/del cells to K+L−S+ (KLS), K+L−S− (MP), myeloid, B cell, and T cell populations in the BM of recipient mice 4 months after primary (C) and secondary (D) competitive transplantation (n = 5 donors and 10 recipients of each genotype). Data shown are mean values ±SEM of results from two independent experiments. (E) Total numbers of BM cells from 2 femurs and 2 tibiae in 5A3+/del mice, Gata2+/− mice, compound Gata2+/−; 5A3+/del mice and WT littermates at 8–12 weeks of age. (F) Spleen weights in 5A3+/del mice, Gata2+/− mice, compound Gata2+/−; 5A3+/del mice, and WT littermates at 8–12 weeks of age. (G) Percent contributions of cells with high (CD150hi HSC), low (CD150lo HSC), and absent CD150 expression (CD150neg MPP) within the K+L−S+CD41−CD48− compartment of WT, 5A3+/del, Gata2+/−, and compound Gata2+/−; 5A3+/del mice at 8–12 weeks of age (n = 5 of each genotype). (H) BM cells from WT, 5A3+/del, Gata2+/− or compound Gata2+/−; 5A3+/del mice (n = 5 of each genotype) were each mixed at ratios of 1:1 with WT competitor cells and transplanted into two irradiated WT recipients. Percent contribution to the K+L−S+ (KLS), K+L−S− (MP), myeloid, B and T cell lineages in the BM of recipient mice 6 months after primary transplants. Data shown are mean values ±SEM from five independent experiments with significant differences designed by asterisks as follows: *p < 0.05, **p < 0.01, ***p < 0.001. The enhanced repopulating ability of compound Gata2+/−; 5A3+/del vs Gata2 singly mutant HSC achieved borderline statistical significance in three myeloid populations (KLS (p = 0.09), MP (p = 0.09), and myeloid cells (p = 0.12)).