mPHOSPHO1 is essential for stress erythropoiesis. (A) Measurements of complete blood counts from mice at indicated ages are plotted (n = 4 per group, mean + SEM). (B) Fewer Ter119⁺, CD71⁺ cells in the bone marrow of 7-week-old KO mice relative to WT mice (n = 3 per group, mean + SEM). Bone marrow cells were isolated and mature red cells were lysed before nucleated cells were stained with CD71 and Ter119 antibodies. (C) Elevated ratio of spleen to body weight of 5-week-old KO mice (n = 4 per group, mean + SEM). (D) Complete blood count measurements of 7-week-old WT and KO mice were performed during phenylhydrazine-induced anemia. Lower hematocrit of KO mice shows slower recovery of RBCs (n = 5 per group, mean ± SEM; analysis of variance [ANOVA] used for statistics). (E) Higher ratio of spleen to body weight of 7-week-old KO mice following 4 days of phenylhydrazine-induced stress erythropoiesis (n = 5 per group, mean + SEM, 2-way ANOVA were used to calculate the statistic significance). (F) Higher numbers of c-Kit⁺CD71⁺ cells in the spleens of KO mice at days 3 and 13 post-phenylhydrazine injection (n = 3 per group, mean + SEM). (G) Higher numbers of CD71⁺, Ter119⁺ cells in the spleens of KO mice at days 3 and 13 post-phenylhydrazine injection (n = 3 per group, mean + SEM). NS, not significant.