On the molecular interactions between alpha-thalassaemia and sickle cell gene

Using the restriction endonucleases, Bam HI, Bgl II, Hind III and EcoRI, the alpha-gene arrangements were investigated in heterozygotes and homozygotes for the sickle cell haemoglobin (Hb S). In the heterozygotes (Hb AS) group the Hb S level showed a trimodal distribution due to presence of the normal alpha-globin genes (alpha alpha/alpha alpha) or of one (-alpha/alpha alpha) or two (-alpha/-alpha) alpha-genes deletions. The haematological analytes inversely correlated with the associated alpha-thalassaemia (alpha-thal.) genes. In the Hb S homozygotes (Hb SS), associated alpha-thalassaemia was found to ameliorate the clinical manifestations and improved the haematological values. Co-existing triple alpha-gene arrangement, alpha alpha alpha anti 3.7/, with Hb AS did not influence the haematological analytes. In Hb SS, presence of alpha alpha alpha anti 3.7/ resulted in a severe sickle cell anaemia (SCA) with a high severity index (> 11) and with frequent crises, transfusion requirements and hospitalizations. It is suggested that reduced level of alpha-chain ameliorates SCA while excess of alpha-globin chain production gives rise to a severe form of SCA.