Conditional deletion of FIP200 by Tie2-Cre causes severe anemia in developing embryos. (A) Lysates were prepared from E14.5 liver of control or CKO mice and analyzed by Western blotting using anti-FIP200 (top) or anti-vinculin (bottom) antibodies. (B) H&E staining of E14.5, E16.5, E18.5 fetal livers from control and CKO mice. Arrows indicate the enucleated RBCs. Scale bars, 200 μm. (C-G) RBC parameters of peripheral blood from E18.5 control and CKO mice: RBC numbers (C), hemoglobin (D), hematocrit (E), RBC distribution width (F), and mean corpuscular volume (G). n = 7-17, ^#P < .01, *P < .05. Data are mean ± SE. (H) Representative fluorescence-activated cell sorting (FACS) profile of erythroid maturation in E14.5 fetal liver of control and CKO embryos. The cells were double-labeled with anti-CD71 and anti-TER119 antibodies. Regions R4 to R8 are defined by characteristic staining pattern of cells, including CD71^medTER119⁻, CD71^highTER119⁻, CD71^highTER119⁺, CD71^medTER119⁺, and CD71^lowTER119⁺, respectively. (I-J) The cell frequency (I) and number (J) of R4-R8 population. Note that there were increased immature population (R4 and R5) and decreased R6 in CKO. n = 5-8, *P < .05, ^#P < .01. Data are mean ± SE. (K) Wright-Giemsa staining of the blood smears from E18.5 control and CKO embryos. The arrowheads indicate the erythroblasts. (L) Benzidine staining of the blood smears as in panel K. Arrowheads indicate the positively stained erythroblasts. Scale bars, 100 μm.