DNA POLYMORPHISM IN THE BETA-GLOBIN GENE-CLUSTER IN SAUDI ARABS - RELATION TO SEVERITY OF SICKLE-CELL-ANEMIA

Significant DNA polymorphisms have been reported in the beta-globin gene cluster of epsilon-Ggamma-Agamma - psibeta-delta-beta-gene region, in normal (Hb AA) individuals and in patients with sickle cell anaemia (SCA). Investigations of the extent of the DNA polymorphisms in the beta(A)- and beta(S)-globin gene cluster using Hind III, Hinc II, Ava II, Xmn I, and Hpa I, revealed several associations with mild SCA. The correlation of the presence (+) or absence (-) of the restriction endonuclease site to clinical severity in patients homozygous for beta(S)-gene showed that the mild form of SCA was associated mainly (> 90%) with the Xmn I polymorphic site 5' to Ggamma, and to a lesser extent with Hinc II polymorphic site 5' to epsilon and in the psibeta-gene, with Hind III polymorphic site in Ggamma and Hpa I polymorphic site 3' to the beta-globin gene, while in the severe form of SCA these polymorphic sites were absent in most patients. The polymorphism in the beta-globin gene cluster was significantly related to the expression of the beta(S)-gene and clinical severity of SCA.