NORMAL DELTA-GLOBIN GENE-SEQUENCES IN SARDINIAN NONDELETIONAL DELTA-BETA-THALASSEMIA

In order to clarify the reasons for the reduced Hb A2 levels in Sardinian deltabeta-thalassemia, we characterized, both by cloning and sequence analysis and by direct sequencing of amplified DNA, the delta-globin gene from an individual of Sardinian descent who is a compound heterozygote for the beta-degrees-thalassemia codon 39 (C-->T) nonsense mutation and the Sardinian deltabeta-thalassemia [codon 39(C-->T)/-196(C-->T)Agamma]. The analysis of the delta-globin gene from the deltabeta-thalassemia chromosome revealed an entirely normal sequence. The defective function of the delta-globin gene in this determinant is thus likely related to a suppressive effect of the in cis nondeletional high persistence of fetal hemoglobin mutation of the A(gamma) gene, probably resulting from an increased capability of the relative promoter to interact with the locus control region