Protein 4.1R–deficient mice are viable but have erythroid membrane skeleton abnormalities
Zheng-Tao Shi, … , Edward Rubin, John G. Conboy
Zheng-Tao Shi, … , Edward Rubin, John G. Conboy
Published February 1, 1999
Citation Information: J Clin Invest. 1999;103(3):331-340. https://doi.org/10.1172/JCI3858.
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Article

Protein 4.1R–deficient mice are viable but have erythroid membrane skeleton abnormalities

Abstract

A diverse family of protein 4.1R isoforms is encoded by a complex gene on human chromosome 1. Although the prototypical 80-kDa 4.1R in mature erythrocytes is a key component of the erythroid membrane skeleton that regulates erythrocyte morphology and mechanical stability, little is known about 4.1R function in nucleated cells. Using gene knockout technology, we have generated mice with complete deficiency of all 4.1R protein isoforms. These 4.1R-null mice were viable, with moderate hemolytic anemia but no gross abnormalities. Erythrocytes from these mice exhibited abnormal morphology, lowered membrane stability, and reduced expression of other skeletal proteins including spectrin and ankyrin, suggesting that loss of 4.1R compromises membrane skeleton assembly in erythroid progenitors. Platelet morphology and function were essentially normal, indicating that 4.1R deficiency may have less impact on other hematopoietic lineages. Nonerythroid 4.1R expression patterns, viewed using histochemical staining for lacZ reporter activity incorporated into the targeted gene, revealed focal expression in specific neurons in the brain and in select cells of other major organs, challenging the view that 4.1R expression is widespread among nonerythroid cells. The 4.1R knockout mice represent a valuable animal model for exploring 4.1R function in nonerythroid cells and for determining pathophysiological sequelae to 4.1R deficiency.

Authors

Zheng-Tao Shi, Veena Afzal, Barry Coller, Dipti Patel, Joel A. Chasis, Marilyn Parra, Gloria Lee, Chris Paszty, Mary Stevens, Loren Walensky, Luanne L. Peters, Narla Mohandas, Edward Rubin, John G. Conboy

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Figure 4

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Erythroid parameters. (a) Red cell morphology in blood from normal (left...
Erythroid parameters. (a) Red cell morphology in blood from normal (left) and knockout (right) mice. Normal cells at left show the typical biconcave disk morphology, while homozygous 4.1-deficient red cells at right exhibit a more heterogeneous morphology marked by the presence of numerous cell fragments. Red cells from heterozygous mice were morphologically normal. (b) Red cell indices. Cell hemoglobin content and cell hemoglobin concentration histograms of whole blood from normal (upper panels) and knockout (lower panels) mice. The dark areas of the histogram represent reticulocytes, and the gray areas represent mature red cells. Significant numbers of fragmented red cells with decreased hemoglobin content (< 10 pg) can be seen in knockout mice. Cell dehydration is also a feature of knockout mice red cells, as indicated by the shift in hemoglobin concentration from reticulocytes (black area in lower right panel) to mature red cells (gray area in lower right panel). (c). Osmotic gradient deformability profiles of red cells from normal (+/+), heterozygous (+/–), and homozygous (–/–) 4.1R-deficient mice. The maximum value of the deformability index, a direct measure of red cell surface area, is reduced in (+/–) red cells and more dramatically reduced in (–/–) red cells.