Subject(s)
Globins/genetics , Thalassemia/genetics , DNA/analysis , Female , Homozygote , Humans , Middle Aged , Mutation , Oligonucleotide ProbesABSTRACT
A new deletion of the beta-globin gene cluster has been characterized in two Italian brothers who are heterozygous carriers of a G gamma A gamma hereditary persistence of fetal hemoglobin (HPFH). Restriction endonuclease mapping and DNA sequencing of the region encompassing the breakpoint show that the deletion starts 3.2 kilobases (kb) upstream from the delta gene and ends within the enhancer region 3' to the beta-globin gene. Here the deletion removes one of the four binding sites for an erythroid specific transcriptional factor (NF-E1). The molecular comparison of the new deletion with others of similar size and location but associated with a delta beta-thalassemia phenotype suggests that the residual enhancer element, relocated near gamma genes, may increase the fetal hemoglobin (HbF) expression above the level observed in delta beta-thalassemia.
Subject(s)
Beta-Globulins/genetics , Chromosome Deletion , Enhancer Elements, Genetic , Fetal Hemoglobin/genetics , Hemoglobinopathies/genetics , Adult , Base Sequence , Beta-Globulins/physiology , Blotting, Southern , DNA/analysis , DNA/genetics , Gene Amplification/genetics , Humans , Male , Molecular Sequence Data , PhenotypeABSTRACT
Hemoglobin Lepore Boston is characterized by abnormal non-alpha-chains that are the product of a fusion delta beta gene originated from an unequal crossing over between misaligned delta and beta genes. The investigation of the restriction fragment length polymorphisms (RFLP) of the beta-globin gene cluster in 18 Italian Lepore Boston chromosomes indicates that the hybrid gene is linked to two RFLP patterns. The majority of chromosomes show a pattern which corresponds to haplotype V and a minority to haplotype I according to Orkin's classification. A single Hb Lepore Boston homozygote was homozygous for haplotype V. The two haplotypes differ only for a single site 3' to the beta cluster. Our data allow the speculation that in Italy the Lepore Boston gene might be the result of multiple recombination events.
