Objectives: Imbalance in alpha/beta-globin chains is an important determinant of thalassemia disease severity. This study examined the relationship between alpha/beta-globin mRNA ratio and disease severity in various thalassemia genotypes.
Design and methods: alpha- and beta-globin mRNA contents of red blood cells of 75 alpha- and 32 beta-thalassemia subjects (5 with beta(0)-thalassemia/Hb E) and 14 normal controls were measured using multiplex quantitative real-time reverse transcription-polymerase chain reaction (qRT-PCR). The alpha/beta-globin mRNA ratio of each sample was calculated based on the 2(-DeltaDeltaC)(T) method.
Results: A decrease of alpha/beta-globin mRNA ratios in alpha-thalassemia subjects compared to normal controls correlated with the numbers of defective alpha-globin genes, whereas an increase of the ratios was observed in beta-thalassemia. Subjects with beta(0)-thalassemia/Hb E disease had the highest alpha/beta-globin mRNA ratio, followed by beta(0)-thalassemia trait and then beta(+)-thalassemia trait, which correlated with decrease in severity of anemia. Coinheritance of alpha-thalassemia in beta(0)-thalassemia/Hb E resulted in a more balanced alpha/beta-globin mRNA ratio and an amelioration of the anemia.
Conclusions: This study indicates that imbalance in globin gene expression, the major factor affecting clinical severity of thalassemia, could be demonstrated by measuring alpha/beta-globin mRNA ratio, which was conveniently and accurately determined by qRT-PCR. In alpha-thalassemia, alpha/beta-globin mRNA ratio correlated with the number of functional alpha-globin genes present, whereas in beta-thalassemia, the ratio provided a good indicator of disease severity.