Effects of BM-specific Rps6 hemizygosity on selected hematopoietic lineage subpopulations. (A) Number of HSC and MPP cells from Rps6 mutant and nonmutant BM. (B) Flow cytometric profiles of the erythroid lineage from Tg.MxCre/+ and Rps6^lox/+;Tg.MxCre/+ animals. Immature erythroid precursors (Pre CFU-E) express greater levels of CD150 than mature erythroid precursors (CFU-E/ProEry); mutant animals exhibit a specific block in this step of erythroid maturation. (C) Number of megakaryocytic (MkP) and erythroid (PreMegE, Pre CFU-E, CFU-E/ProEry) cells from Rps6 mutant and nonmutant BM. (D) Number of mature erythroid cells based on expression of Ter119 and CD71 from Tg.MxCre/+, Rps6^lox/+;Tg.MxCre/+, and Rps6^lox/+;Tg.MxCre/+;Trp53^ko/ko animals. Ter119⁺CD71⁺ cells are the sum of the Ter119+CD71^high and Ter119+CD71^int populations (supplemental Figure 4). For panels A, C, and D, open bars represent mean number observed per 1 million BM cells analyzed from nonmutant animals (± SEM, n = 3), black bars represent the corresponding numbers from Rps6^lox/+;Tg.MxCre/+ animals (± SEM, n = 3) after dividing by a factor of 2.13 to account for the reduced number of total BM cells in mutant animals, and gray bars (D) represent the mean number of cells from Rps6^lox/+;Tg.MxCre/+;Trp53^ko/ko animals (± SEM, n = 2) after dividing by 1.18 (Table 2). (E-G) shRNA constructs targeting RPS6 (KD1, KD2, and KD3) or RPS14 decrease the ratio of mature erythroid (GPA⁺) to myeloid (CD11b⁺) cells (E) and also decrease the ratio of mature erythroid to immature erythroid (CD71⁺GPA⁻) cells (F-G). Each bar in panels E and G represents mean ± SEM, n = 3. P values are based on a 2-tailed t test, *P < .05, **P < .01, ***P < .001, §P = 0.07, and §§P = 0.08.