Defective assembly of membrane proteins in erythroid precursors of β-thalassemic mice

Abstract

β-Thalassemic mice provide a useful model for studying the pathophysiology of human β-thalassemia in that one can perform experiments that are difficult to perform in humans. The ease of access to β-thalassemic mouse marrow provided the opportunity to explore the cause of the ineffective erythropoiesis that characterizes severe β-thalassemia in mouse and man. We hypothesized that the accumulation of excess α-globin might interfere with the normal assembly of red blood cell (RBC) membrane proteins, thus contributing to the severe intramedullary lysis. Femoral marrow was obtained from normal and β-thalassemic mice, and RBC precursors were purified (>90%) by panning and harvesting CD45 cells. The assembly of RBC membrane proteins was assessed by observing immunofluorescence patterns obtained on fixed permeabilized precursors using rabbit polyclonal antibodies directed against human spectrin, and band 4.1, and murine band 3. The distribution of the proteins was shown with a fluorescein-tagged goat antirabbit antibody. In contrast to normal mice, about 30% of intermediate and late stage erythroblasts in β-thalassemic mice appear abnormal. Neither spectrin nor band 4.1 formed crisp rim fluorescence in these erythroid precursors of thalassemic mice, whereas assembly of band 3 appeared normal. Therefore, the assembly of membrane skeletal proteins is abnormal in murine β-thalassemic erythroid precursors perhaps because of the deposition of unmatched α-globin chains. © 1994 by The American Society of Hematology.