Genetic diversity of HindIIIG polymorphism in second intron IVSII-I Gγ gene and its association with HbF level in β-thalassemia and intermedia thalassemia in Isfahan province

Beta thalassemia is an autosomal recessive disease. The synthesis of HbF in patients with β-thalassemia seems to ameliorate the severity of symptoms.
In this study, 150 β-thalassemia major patients, 34 thalassemia intermedia patients, and 50 healthy individuals as the control were studied. HindIIIG polymorphism in IVSII-I Gγ gene was determined using RFLP-PCR method. HbF levels with electrophoresis method were taken from clinical files. Then, the linkage disequilibrium of this polymorphism with XmnI polymorphism in 5' Gγ gene was determined by D' Power Marker software.
After data analysis, an association was observed between the A allele and thalassemia intermedia. In the dominant effect of the A allele (comparison between AA vs. CC), AA genotypes associates with intermedia thalassemia (p = 0.014, OR = 9.30, CI(95%) = 1.14-75.9) but there is no association with major thalassemia (p = 0.1, OR = 1, CI(95%) = 0.41-1.19). The means of HbF levels in β-thalassemia major and thalassemia intermedia patients were 94.3 g/dl and 84.4 g/dl, respectively. High linkage disequilibrium was seen between the two polymorphisms.
It is concluded that A allele may act as a dominant allele and increase disease amelioration. It showed that A allele of HindIIIG polymorphism has a positive effect on HbF level. Furthermore, the A allele of HindIIIG polymorphism is strongly correlated with T allele of XmII polymorphism in thalassemia intermedia patients and C allele of HindIIIG polymorphism is strongly correlated with C allele of XmnI polymorphism in β-thalassemia major.