Association of BCL11A genetic variant (rs11886868) with severity in ß-thalassaemia major & sickle cell anaemia.

BACKGROUND & OBJECTIVES: The amount of foetal haemoglobin that persists in adulthood affects the clinical severity of haemoglobinopathies including ß-thalassaemia major and sickle cell anaemia (SCA). The present study was undertaken to analyse ß-thalassaemia as well as SCA patients for the single nucleotide polymorphism (SNP), rs11886868 (T/C) in BCL11A gene and to evaluate the association between this polymorphism and severity of ß-thalassaemia major and SCA. METHODS: a total of 620 samples (420 ß-thalassaemia major and 200 SCA cases) were analysed before blood transfusion using basic screening tests like complete blood analysis and osmotic fragility and further confirmed by high performance liquid chromatography (HPLC), amplification refractory mutation system-polymerase chain reaction (ARMS-PCR) and reverse dot blot techniques. All patients were transfusion dependent. Patients with ß-thalassaemia and SCA were classified into mild, moderate, severe according to the severity score based on Hb levels, age of onset, age at which patients received their first blood transfusion, the degree of growth retardation and splenectomy. ß-thalassaemia as well as SCA patients were analysed for the SNP, rs11886868 (T/C) in BCL11A gene and association between this polymorphism and severity of ß-thalassaemia major as well as SCA was evaluated. RESULTS: There was a significant difference in genotypic and allelic frequencies of BCL11A gene polymorphism between mild and moderate and mild and severe cases in both the groups. A significant (P<0.001) difference was observed in the mean HbF levels between the three genotypes in different severity groups. HbF levels were found to be high in CC genotype bearing individuals followed by TC and TT in ß-thalassaemia major as well as SCA. INTERPRETATION & CONCLUSIONS: This study confirms that the T/C variant (rs11886868) of the BCL11A gene causing downregulation of BCL11A gene expression in adult erythroid precursors results in the induction of HbF and ameliorates the severity of ß-thalassaemia as well as SCA.

Association of Xmn1 -158 γG variant with severity and HbF levels in ß-thalassemia major and sickle cell anaemia.

Haemoglobinopathies including ß-thalassemia and sickle cell anaemia (SCA) are considered to be classical monogenic diseases. There is considerable clinical variability between patients inheriting identical ß-globin mutations. The reasons for this variability are not well understood. Previous studies have suggested that a variety of genetic determents influence different clinical phenotypes. The genetic variants that modulate HbF levels have a very strong impact on ameliorating the clinical phenotype. In the present study 6,500 blood samples from suspected cases were analysed using HPLC, ARMS-PCR, RDB techniques. Patients with ß-thalassemia and SCA were classified into mild, moderate, severe according to the severity score based on Hb levels, age of onset, age at which patients received their first blood transfusion, the degree of growth retardation and splenectomy. Patients with ß-thalassemia and SCA were analysed for Xmn1 polymorphism and association between this polymorphism and severity of ß-thalassemia and SCA was evaluated. We found a significant difference in genotypic and allelic frequencies of Xmn1 polymorphism between mild and moderate and mild and severe cases. There was a significant difference in high and low percentage of HbF in CC, CT and TT bearing individuals. The TT bearing individuals were found to have a high percentage of HbF in ß-thalassemia as well as SCA. This study confirms that increased γG-globin expression associated with Xmn1 polymorphism ameliorates the clinical severity in ß-thalassemia as well as SCA in the study population.