Gamma delta beta-thalassemia due to a de novo mutation deleting the 5' beta-globin gene activation-region hypersensitive sites.
gamma delta beta-Thalassemia is a rare disorder of hemoglobin biosynthesis, characterized molecularly by partial or complete deletions of the beta-globin gene complex of 100 kilobases (kb) or greater. Common to all mutants described has been the deletion of the most-5' sequences of the beta-globin complex. We have used the techniques of pulsed-field gel electrophoresis and polymerase chain reaction to study a patient with a clinical gamma delta beta-thalassemia phenotype. This subject developed a de novo deletion on a maternally inherited beta-globin gene chromosome involving approximately 30 kb of sequences 5' to the epsilon gene; the deletion extends from -9.5 kb to -39 kb 5' of epsilon and includes three of the four DNase I hypersensitive sites (at -10.9 kb, -14.7 kb, and -18 kb 5' of epsilon). The remaining sequences of the beta-globin complex, including the DNase I hypersensitive sites at -6.1 kb and all structural genes in cis to the deletion are physically intact, but presumably nonfunctional, as evidenced by the presence of a beta S-globin gene that is not expressed as a sickle hemoglobin. Deletion of DNase I hypersensitive sites on a previously functional beta-globin gene complex confirms the significance of these sites in regulating globin gene expression.
Driscoll
M C
MC
Department of Medicine, Albert Einstein College of Medicine, Bronx, NY 10461.
Dobkin
C S
CS
Alter
B P
BP
D001483:Base Sequence; D002872:Chromosome Deletion; D005786:Gene Expression Regulation; D005796:Genes; D005914:Globins / Q000235:genetics*; D006239:Haplotypes; D006801:Humans; D008969:Molecular Sequence Data; D009154:Mutation; D015345:Oligonucleotide Probes; D010641:Phenotype; D016133:Polymerase Chain Reaction; D015183:Restriction Mapping; D013789:Thalassemia / Q000235:genetics*; D015533:Transcriptional Activation
D015345:Oligonucleotide Probes; D005914:Globins