Physical mapping of the globin gene deletion in (δβ)° - thalassaemia

Abstract

We have constructed a physical map of restriction endonuclease cleavage sites in the (δ+β)-globin gene region in the DNA of patients with (δβ)°-thalassaemia. This map shows that a 10 kb deletion has occurred in (δβ)°-thalassaemia to remove the entire β-globin gene and the 3′ portion of the δ-globin gene. The 5′ terminus of the deletion is in the large intron of the δ-globin gene and the 3′ terminus 1.8 kb to the 3′-side of the β-globin gene.

A similar deletion of about 7 kb has been described previously in the DNA of patients with Hb Lepore; the 5′ terminus of the deletion is also in the δ-globin gene but the 3′ terminus is in the β-globin gene. Comparison of the foetal (γ) globin gene expression in adults with (δβ)°-thalassaemia and Hb Lepore suggests that the 3′ extragenic regions of the β-globin gene contain DNA sequences involved in the regulation of γ-globin gene expression.