Imbalanced globin chain synthesis determines erythroid cell pathology in thalassemic mice

Abstract

Background β-thalassemia occurs from the imbalanced globin chain synthesis due to the absence or inadequate β-globin chain production. The excessive unbound α-globin chains precipitate in erythroid precursors and mature red blood cells leading to ineffective erythropoiesis and hemolysis. Design and MethodsIn vitro globin chain synthesis in reticulocytes from different types of thalassemic mice was performed. The effect of imbalanced globin chain synthesis was assessed from changes of red blood cell properties including increased numbers of red blood cells vesicles and apoptotic red blood cells, increased reactive oxygen species and decreased red blood cell survival. ResultsThe α/β-globin chain ratio in β -thalassemic mice, 1.26±0.03, was significantly higher than that of wild type mice, 0.96±0.05. The thalassemic mice show abnormal hematologic data and defective red blood cell properties. These values were improved significantly in doubly heterozygous thalassemic mice harboring 4 copies of human β E -globin transgene, with a more balanced globin chain synthesis, 0.92±0.05. Moreover, transgenic mice harboring 8 extra copies of the human β E -globin transgene showed inversely imbalanced α/β-globin synthesis ratio, 0.83±0.01, that resulted in a mild β-thalassemia phenotype due to the excessive β-globin chains. The degree of ineffective erythropoiesis also correlated with the degree of imbalanced globin chain synthesis. Bone marrow and splenic erythroid precursor cells of β -thalassemic mice showed increased phosphatidylserine exposure in basophilic and polychromatophilic stages, which was restored to the normal level in doubly heterozygous mice. ConclusionsImbalanced α/β-globin chain as a consequence of either reduction or enhancement of β-globin chain synthesis can cause abnormal red blood cell properties in mouse models.Key words: thalassemia, transgenic mice, ineffective erythropoiesis, globin chain synthesis. mice. Haematologica 2009;94:1211-1219. doi:10.3324/haematol.2009 This is an open-access paper. Citation: Srinoun K, Svasti S, Chumworathayee W, Vadolas J, Vattanaviboon P, Fucharoen S, and Winichagoon P. Imbalanced globin chain synthesis determines erythroid cell pathology in thalassemic Imbalanced globin chain synthesis determines erythroid cell pathology in thalassemic mice

Impaired bone formation and osteopenia in heterozygous βIVSII-654 knockin thalassemic mice

“…The genotype of each mouse was verified from the tail DNA. The heterozygous b IVSII-654 knockin mouse had a phenotype of b-thalassemia intermedia, which was consistent to the previous report (Lewis et al 1998;Srinoun et al 2009), whereas the homozygous genotype was lethal. The animals were acclimatized in the husbandry unit (polystylene shoebox cages) with room temperature of 25°C and humidity of 55% for at least 7 days under 12/12 h dark-light cycle, and were fed regular chow (containing 1.0% calcium and 0.9% phosphorus) and distilled water ad libitum.…”

α-Hemoglobin-stabilizing Protein (AHSP) Perturbs the Proximal Heme Pocket of Oxy-α-hemoglobin and Weakens the Iron-Oxygen Bond

“…Oxidative damage occurs in erythroid cells of ␤-thalassaemic mice that contain elevated levels of unpaired ␣Hb (21)(22)(23)(24). Kong et al (6) showed similar increases in reactive oxygen species in AHSP Ϫ/Ϫ mice, suggesting that AHSP has a role in limiting reactive oxygen species production during normal erythropoiesis.…”

Bone microstructural defects and osteopenia in hemizygous βIVSII-654knockin thalassemic mice: sex-dependent changes in bone density and osteoclast function

“…Tail DNA was used to verify the genotype of each mouse. The phenotype of hemizygous ␤ IVSII-654 mice was categorized as ␤-thalassemic intermedia with iron deposition in the heart and liver, and imbalanced globin synthesis with ␣-to-␤-globin ratio of 1.26 (19,24,26). The homozygous ␤ IVSII-654 genotype is lethal, and the fetus usually dies in utero.…”