Role of ABCC4 in erythroid cell. (A) cGMP levels in RBCs from control (n = 7) and PEL-negative (n = 7) individuals. Data are mean ± standard error of the mean. (B) ABCC4 expression during terminal erythroid differentiation. Erythropoiesis was monitored via CD49d and band3 levels of GPA^pos cells and May-Grunwald Giemsa-staining. The ABCC4 expression was determined on the GPA^pos cells, using the anti-PEL eluate. (C) P/C ratios for ABC transporter expression in RBC membranes from 3 PEL-negative ABCC4 _null individuals (P) and 3 control individuals (C). The P/C ratio was determined after normalization of the LFQ intensity of ABC transporter proteins by the LFQ intensity of actin. (D) The GMFI of ABCG2 expression in ABCC4_null (n = 7) and control (n = 8) RBCs was analyzed by flow cytometry, using an anti-ABCG2 antibody. ***P = .0002, using the Mann-Whitney test. (E) The GMFI of ABCC4 expression in ABCG2_null (n = 11) and control (n = 11) RBCs was analyzed by flow cytometry, using an anti-PEL. ***P=.0007, using the Mann-Whitney test.