Dominant thalassemia-like phenotypes associated with mutations in exon 3 of the β-globin gene

H. H. Kazazian, C. E. Dowling, R. L. Hurwitz, M. Coleman, A. Stopeck, J. G. Adams

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Abstract

Mutations producing β-thalassemia reach individual gene frequencies greater than .01 in malarial-endemic regions because β-thalassemia trait individuals have increased genetic fitness over that of normal individuals. Exon 3 of the β-globin gene has been relatively spared as a site of common β-thalassemia mutations. Frameshifts caused by the loss of a single nucleotide and nonsense mutations produce β-thalassemia trait when they occur in exons 1 and 2. In contrast, they usually produce chronic hemolytic anemia when present in exon 3. Certain missense mutations in exon 3 produce unstable globins and thalassemia intermedia with hemolysis in heterozygotes. Here we report two new mutations in exon 3 of the β-globin gene. One is a single nucleotide deletion in codon 109 in a 78-year-old Lithuanian with chronic hemolytic anemia and features of thalassemia. It leads to an abnormal globin (βManhattan) that is elongated to 156 amino acids. The second is a CAG-CGG missense mutation at codon 127 that causes a Gln → Pro substitution (βHouston) and a thalassemia intermedia with hemolysis in three generations of a British-American family. Although the clinical phenotypes of these two patients differed little, differences in globin-synthetic ratios were significant, presumably reflecting differences in the ability of each abnormal β-globin to form αβ dimers. The paucity of high-frequency exon 3 mutations and their worldwide distribution is likely attributable to their phenotypic severity and loss of increased genetic fitness vis-a-vis malaria.

Original languageEnglish (US)
Pages (from-to)3014-3018
Number of pages5
JournalBlood
Volume79
Issue number11
StatePublished - Jan 1 1992

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ASJC Scopus subject areas

  • Biochemistry
  • Immunology
  • Hematology
  • Cell Biology

Cite this

Kazazian, H. H., Dowling, C. E., Hurwitz, R. L., Coleman, M., Stopeck, A., & Adams, J. G. (1992). Dominant thalassemia-like phenotypes associated with mutations in exon 3 of the β-globin gene. Blood, 79(11), 3014-3018.