Description:
BETA-THALASSEMIA
HEMOGLOBIN--BETA LOCUS; HBB
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Repository
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NIGMS Human Genetic Cell Repository
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| Subcollection |
Heritable Diseases |
| Class |
Mutations of the Hemoglobin Loci |
| Quantity |
25 µg |
| Quantitation Method |
Please see our FAQ |
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Biopsy Source
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Peripheral vein
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Cell Type
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B-Lymphocyte
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Tissue Type
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Blood
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Transformant
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Epstein-Barr Virus
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Sample Source
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DNA from LCL
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Race
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White
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Ethnicity
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ITALIAN/IRISH
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Relation to Proband
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proband
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Confirmation
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Clinical summary/Case history
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Species
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Homo sapiens
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Common Name
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Human
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Remarks
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| IDENTIFICATION OF SPECIES OF ORIGIN |
Species of Origin Confirmed by Nucleoside Phosphorylase, Glucose-6-Phosphate Dehydrogenase, and Lactate Dehydrogenase Isoenzyme Electrophoresis |
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| Gene |
HBB |
| Chromosomal Location |
11p15.5 |
| Allelic Variant 1 |
141900.0348; BETA-ZERO-THALASSEMIA |
| Identified Mutation |
IVS2, G>A, +1; A splice junction mutant, G to A, at position 1 of IVS-2 was found in a Mediterranean by Treisman et al. (1982), in a Tunisian by Chibani et al. (1988), and in an American black by Thein et al. (1988). The same mutation was found by Hattori et al. (1992), who referred to the mutation as IVS-II-1 (G-A).
This is one of the earliest mutations at a 5-prime splice site to be described. In an analysis of 101 different examples of point mutations that lie in the vicinity of mRNA splice junctions and that have been held to be responsible for human genetic disease by altering the accuracy or efficiency of mRNA splicing, Krawczak et al. (1992) found that 62 were located at 5-prime splice sites, 26 at 3-prime splice sites, and 13 resulted in the creation of novel splice sites. They estimated that up to 15% of all point mutations causing human genetic disease result in an mRNA splicing defect. Of the 5-prime splice site mutations, 60% involve the invariant GT dinucleotides.
Sierakowska et al. (1996) found that treatment of mammalian cells stably expressing the IVS2-654 beta HBB gene with antisense oligonucleotides targeted at the aberrant splice sites restored correct splicing in a dose-dependent fashion, generating correct human beta-globin mRNA and polypeptide. Both products persisted for up to 72 hours after treatment. The oligonucleotides modified splicing by a true antisense mechanism without overt unspecific effects on cell growth and splicing of other pre-mRNAs. Sierakowska et al. (1996) stated that this novel approach in which antisense oligonucleotides are used to restore rather than to downregulate the activity of the target gene is applicable to other splicing mutants and is of potential clinical interest.
This mutation is frequent among patients in southern China and Thailand, accounting for 20% of beta-thalassemia in some regions. It causes aberrant RNA splicing. Lewis et al. (1998) modeled this mutation in mice, replacing the 2 (cis) murine adult beta-globin genes with a single copy of the human mutant HBB gene. No homozygous mice survived postnatally. Heterozygous mice carrying this mutant gene produced reduced amounts of mouse beta-globin chains and no human beta globin, and had a moderately severe form of beta-thalassemia. Heterozygotes showed the same aberrant splicing as their human counterparts and provided an animal model for testing therapies that correct splicing defects at either the RNA or DNA level.
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| Gene |
HBB |
| Chromosomal Location |
11p15.5 |
| Allelic Variant 2 |
141900.0312; BETA-ZERO-THALASSEMIA |
| Identified Mutation |
GLN39TER; Chehab et al. (1986) found evidence for new mutation in the codon at beta-39 from CAG (glutamine) to the stop codon TAG. The beta-39 nonsense mutation is the second most common beta-thalassemia lesion in Italy, accounting for a third of cases, and the most common in Sardinia, accounting for 90% of cases there. In Sardinia, the beta-39 mutation has been identified with 9 different haplotypes. All this suggested to Chehab et al. (1986) that beta-39 is a mutational hotspot. Trecartin et al. (1981) found that the form of beta-zero-thalassemia that is predominant in Sardinia is caused by a single nucleotide mutation at the position corresponding to amino acid number 39 and converting a glutamine codon (CAG) to an amber termination codon (UAG). (Epstein et al. (1963) described 'amber' mutants of phage T4 in a frequently cited paper in a Cold Spring Harbor Symposium on Quantitative Biology. The origin of the unusual name 'amber' is, as Witkowski (1990) called it, 'an interesting footnote in the history of molecular biology.' Edgar (1966) recounted that R. H. Epstein and C. M. Steinberg, then at the California Institute of Technology, had promised Harris Bernstein, then at Yale University, that the mutants, if any were found, would be named after his mother. They were found and were named 'amber,' the English equivalent of 'Bernstein.' The other 2 'stop' codons, UGA and UAA, are sometimes referred to as 'opal' and 'ochre,' respectively.) Rosatelli et al. (1992) used denaturing gradient gel electrophoresis (DGGE) followed by direct sequence analysis of amplified DNA to study 3,000 beta-thalassemia chromosomes in the Sardinian population. They confirmed that the predominant mutation, present in 95.7% of beta-thalassemia chromosomes, was gln39-to-ter.
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| Remarks |
Italian-Irish; B-zero-thalassemia; donor subject is a compound heterozygote: one allele has a splice junction mutation, a G>A change at position 1 in intron 2 of the HBB gene which is detectable with endonuclease Hph I (IVS2,G>A,+1); the second allele has a nonsense mutation, changing the beta-39 codon from glutamine to a stop codon [Gln39Ter (Q39X)] |
| Luberto C, Yoo DS, Suidan HS, Bartoli GM, Hannun YA, Chen J, Iannone MA, Li MS, Taylor JD, Rivers P, Nelsen AJ, Slentz-Kesler KA, Roses A, Weiner MP, A microsphere-based assay for multiplexed single nucleotide polymorphism analysis using single base chain extension. Genome Res10:549-57 2000 |
| PubMed ID: 10779497 |
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