Defective spectrin integrity and neonatal thrombosis in the first mouse model for severe hereditary elliptocytosis

Mutations affecting the conversion of spectrin dimers to tetramers result in hereditary elliptocytosis (HE), whereas a deficiency of human erythroid α- or β-spectrin results in hereditary spherocytosis (HS). All spontaneous mutant mice with cytoskeletal deficiencies of spectrin reported to date have HS. Here, the first spontaneous mouse mutant, sph^Dem/sph^Dem, with severe HE is described. The sph^Dem mutation is the insertion of an intracisternal A particle element in intron 10 of the erythroid α-spectrin gene. This causes exon skipping, the inframe deletion of 46 amino acids from repeat 5 of α-spectrin and alters spectrin dimer/tetramer stability and osmotic fragility. The disease is more severe in sph^Dem/sph^Dem neonates than in α-spectrin-deficient mice with HS. Thrombosis and infarction are not, as in the HS mice, limited to adults but occur soon after birth. Genetic background differences that exist between HE and HS mice are suspect, along with red blood cell morphology differences, as modifiers of thrombosis timing. sph^Dem/sph^Dem mice provide a unique model for analyzing spectrin dimerto-tetramer conversion and identifying factors that influence thrombosis.