Mild spherocytic hereditary elliptocytosis and altered levels of α- and γ-adducins in β-adducin-deficient mice

Abstract

The membrane skeleton, a dynamic network of proteins associated with the plasma membrane, determines the shape and mechanical properties of erythrocytes. Deficiencies or defects in membrane skeletal proteins are associated with inherited disorders of erythrocyte morphology and function. Adducin is one of the proteins localized at the spectrin-actin junction of the membrane skeleton. In this work we show that deficiency of β-adducin produces an 80% decrease of -adducin and a fourfold up-regulation of γ-adducin in erythrocytes. β-Adducin or any other isoform generated by translation of abnormally spliced messenger RNAs could not be detected by our antibodies either in ghosts or in cytoplasm of −/− erythrocytes. Actin levels were diminished in mutant mice, suggesting alterations in the actin-spectrin junctional complexes due to the absence of adducin. Elliptocytes, ovalocytes, and occasionally spherocytes were found in the blood film of −/− mice. Hematological values showed an increase in reticulocyte counts and mean corpuscular hemoglobin concentration, decreased mean corpuscular volume and hematocrit, and normal erythrocyte counts that, associated to splenomegaly, indicate that the mice suffer from mild anemia with compensated hemolysis. These modifications are due to a loss of membrane surface and dehydration that result in an increase in the osmotic fragility of red blood cells. The marked alteration in osmotic fragility together with the predominant presence of elliptocytes is reminiscent of the human disorder called spherocytic hereditary elliptocytosis. Our results suggest that the amount of adducin remaining in the mutant animals (presumably γ adducin) could be functional and might account for the mild phenotype.

β‐adducin (Add2) KO mice show synaptic plasticity, motor coordination and behavioral deficits accompanied by changes in the expression and phosphorylation levels of the α‐ and γ‐adducin subunits

“…Our data suggest that these defects are the direct consequence of β-adducin absence and might be connected to the observed reduction of α-adducin and P-adducin levels. The brain partially compensates the lack of the β-subunit by upregulating γ-adducin, as previously observed in erythrocytes (Gilligan et al 1999;Muro et al 2000).…”

The Fluid Membrane determines Mechanics of Red Blood Cell Extracellular Vesicles and is Softened in Hereditary Spherocytosis

“…RBC proteins have been studied extensively, which makes protein identification possible without immune staining. 44 From electrophoresis we see that hemoglobin and band 3 are present in the EVs, as well as small amounts of protein 4.1 and 4.2 (Fig. 3E).…”

Blood Collection from Mice and Hematological Analyses on Mouse Blood

“…Genetic alterations might directly affect proliferation and/or differentiation of hematological stem cells, e.g., due to altered responsiveness to or signaling of growth factors (Divoky et al, 2001;Ruan et al, 2005) or impaired cell division (Devlin et al, 2010). Hematological changes can also occur due to altered morphology, life-span, and/or function of blood cells (Muro et al, 2000;Shet et al, 2008), impaired hemoglobin synthesis (Bishop et al, 2011) secondary to changes in regulatory pathways (Haase, 2006) or iron metabolism (Mok et al, 2006;Vujić Spasić et al, 2007), primary diseases of other organs (Fernandez-Banares et al, 2009;Gonzalez-Casas et al, 2009), or infections (Rivera and Ganz, 2009). Therefore, additional investigations, like clinical chemistry analyses and/or microscopic evaluation of blood cells (blood smears or cytospin preparations), and/or studies of cellular properties in culture, are usually necessary to elucidate the cause of changes detected in the peripheral blood cell count.…”