Molecular pathology of haemoglobin H disease in Sardinians.
We investigated the molecular basis for haemoglobin H disease in 50 Sardinian patients by restriction endonuclease analysis. We found that the majority (78% of the cases) are due to gene deletion (- -/- alpha). Among those with a combination of deletion and nondeletion defects (- -/alpha alpha th), the most prevalent nondeletion lesion (70% of the nondeletion defects) was the initiation codon mutation of the alpha 2 gene (alpha Nco alpha), previously discovered in this population. Of the remaining patients with the (- -/alpha alpha th) genotype, two showed the IVS-1 splice junction lesion and one a mutation in the alpha 1 gene, removing the Nco I site within the 5' part of the alpha 1 gene, which may arise from a process of gene conversion from the initiation codon mutant of the alpha 2 gene. A single patient had the homozygous state for the initiation codon mutant of the alpha 2 gene. Study of genotype-phenotype correlations indicates that the (alpha Nco alpha) haplotype is associated with a more severe defect in the alpha-globin chain output than that resulting from the (-alpha) haplotype. We may conclude that restriction endonuclease analysis is a powerful method for the definition of the molecular heterogeneity of haemoglobin H disease.
D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D002872:Chromosome Deletion; D002874:Chromosome Mapping; D004262:DNA Restriction Enzymes; D005820:Genetic Testing; D005914:Globins / Q000235:genetics*; D006801:Humans; D007223:Infant; D009154:Mutation; D013789:Thalassemia / Q000097:blood / Q000235:genetics*
D005914:Globins; D004262:DNA Restriction Enzymes