Impaired Terminal Erythroid Maturation in β0-Thalassemia/HbE Patients with Different Clinical Severity

Anemia in β-thalassemia is associated with ineffective erythropoiesis and a shortened lifespan of erythroid cells. The limited differentiation of β-thalassemic erythroblasts has been documented, but the characteristic feature of terminal erythroid maturation and its physiological relevance are not clearly described in β-thalassemias. Here, the red blood cell and reticulocyte cellular characteristics were determined in patients with β0-thalassemia/HbE in comparison to patients with iron deficiency anemia and healthy normal subjects. Severely affected β0-thalassemia/HbE patients showed the highest increase in immature reticulocytes, but the number of total erythrocytes was the lowest. Despite similar ranges of hemoglobin levels, β0-thalassemia/HbE patients had a higher number of reticulocytes and a greater proportion of immature fraction than patients with iron deficiency anemia did. In vitro CD34+ hematopoietic progenitor cells’ culture and flow cytometry analysis were conducted to investigate the erythroid maturation and mitochondrial clearance in β0-thalassemia/HbE erythroid cells as compared to normal cells. The delayed erythroid maturation and evidence of impaired mitochondria clearance were observed in β0-thalassemia/HbE cells at the terminal stage of differentiation. Additionally, increased transcript levels of genes related to erythroid mitophagy, BNIP3L and PINK1, were revealed in β0-thalassemia/HbE erythroblasts. The findings indicate that the erythroid maturation is physiologically relevant, and that the restoration of terminal maturation represents a potential therapeutic target for β-thalassemias

Impaired Terminal Erythroid Maturation in β⁰-Thalassemia/HbE Patients with Different Clinical Severity

Anemia in β-thalassemia is associated with ineffective erythropoiesis and a shortened lifespan of erythroid cells. The limited differentiation of β-thalassemic erythroblasts has been documented, but the characteristic feature of terminal erythroid maturation and its physiological relevance are not clearly described in β-thalassemias. Here, the red blood cell and reticulocyte cellular characteristics were determined in patients with β0-thalassemia/HbE in comparison to patients with iron deficiency anemia and healthy normal subjects. Severely affected β0-thalassemia/HbE patients showed the highest increase in immature reticulocytes, but the number of total erythrocytes was the lowest. Despite similar ranges of hemoglobin levels, β0-thalassemia/HbE patients had a higher number of reticulocytes and a greater proportion of immature fraction than patients with iron deficiency anemia did. In vitro CD34+ hematopoietic progenitor cells’ culture and flow cytometry analysis were conducted to investigate the erythroid maturation and mitochondrial clearance in β0-thalassemia/HbE erythroid cells as compared to normal cells. The delayed erythroid maturation and evidence of impaired mitochondria clearance were observed in β0-thalassemia/HbE cells at the terminal stage of differentiation. Additionally, increased transcript levels of genes related to erythroid mitophagy, BNIP3L and PINK1, were revealed in β0-thalassemia/HbE erythroblasts. The findings indicate that the erythroid maturation is physiologically relevant, and that the restoration of terminal maturation represents a potential therapeutic target for β-thalassemias

Genetic modifiers of Hb E/β⁰thalassemia identified by a two-stage genome-wide association study

<p>Abstract</p> <p>Background</p> <p>Patients with Hb E/β⁰thalassemia display remarkable variability in disease severity. To identify genetic modifiers influencing disease severity, we conducted a two-stage genome scan in groups of 207 mild and 305 severe unrelated patients from Thailand with Hb E/β⁰thalassemia and normal α-globin genes.</p> <p>Methods</p> <p>First, we estimated and compared the allele frequencies of approximately 110,000 gene-based single nucleotide polymorphisms (SNPs) in pooled DNAs from different severity groups. The 756 SNPs that showed reproducible allelic differences at <it>P </it>< 0.02 by pooling were selected for individual genotyping.</p> <p>Results</p> <p>After adjustment for age, gender and geographic region, logistic regression models showed 50 SNPs significantly associated with disease severity (<it>P </it>< 0.05) after Bonferroni adjustment for multiple testing. Forty-one SNPs in a large LD block within the β-globin gene cluster had major alleles associated with severe disease. The most significant was bthal_bg200 (odds ratio (OR) = 5.56, <it>P </it>= 2.6 × 10^-13). Seven SNPs in two distinct LD blocks within a region centromeric to the β-globin gene cluster that contains many olfactory receptor genes were also associated with disease severity; rs3886223 had the strongest association (OR = 3.03, <it>P </it>= 3.7 × 10^-11). Several previously unreported SNPs were also significantly associated with disease severity.</p> <p>Conclusions</p> <p>These results suggest that there may be an additional regulatory region centromeric to the β-globin gene cluster that affects disease severity by modulating fetal hemoglobin expression.</p