PIT1 deletion results to RBC defects in adult mice. (A) Turnover analysis of RBCs in adult mice constitutively underexpressing PIT1 (PIT1^neo/neo). Erythrocytes were biotinylated by tail vein injection and blood was drawn weekly. RBCs of PIT1^+/+ (black diamonds) and PIT1^neo/neo (white squares) mice were labeled with PE-conjugated streptavidin and analyzed by flow cytometry. Erythrocyte survival was determined by the assessment of the number of biotinylated erythrocytes relative to the starting level (100% biotinylated). (B) Six-week-old PIT1^+/+ mice spleen (left) and PIT1^neo/neo mice spleen (right). (C) Spleen section stained with H&E at 2.5 and 40× magnification. (D) In vitro differentiation of adult hematopoietic spleen cells. The number of CFU-GM and CFU-E per 10⁵ nucleated spleen cells are indicated. (E) Representative flow cytometric analysis of PIT1^+/+ and PIT1^neo/neo adult spleen. Percentages of labeled cells were calculated by taking into account the background labeling (baseline defined by omitting Ab). (G) Measurement of 2,3-DPG content of RBCs. Data indicated means ± SEM of at least 3 animals per condition. Significant differences from PIT1^+/+ mice (black bar) are indicated. *P < .05; ***P < .001).