Implication of Globin Gene Expression, Hemoglobin F and Hemoglobin E Levels on β-Thalassemia/Hb E Disease Severity.
One of the factors affecting the degree of severity in β-thalassemia disease is the presence of unmatched α-hemoglobin chains. Thus, the expression levels of globin genes in reticulocytes of β-thalassemia subjects were measured using quantitative RT-PCR, demonstrating that α/β globin mRNA ratio, as well as levels of γ-globin mRNA and Hb F, increased with progressing degree of β globin synthesis defect. The levels of γ-globin mRNA and Hb F could not be directly correlated with severity of β-thalassemia/Hb E disease due to a low statistical power of this analysis. Higher levels of Hb E were present, however, in clinically mild patients, as compared to moderately severe β-thalassemia/Hb E subjects. This suggests that in β-thalassemia/Hb E disease, elevation of Hb E level through enhancing correctly spliced β(E)-globin mRNA offers another approach in ameliorating disease severity. In addition, co-inheritance of α-thalassemia 2 trait in β-thalassemia/Hb E subjects was associated with milder outcome compared with those with the same β-thalassemia genotypes, confirming the notion of the beneficial effect of a more balanced α:β-globin chain ratio.