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Query: UMLS:C0039730 (thalassemia)
 10,305 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

High molecular weight DNA from a Japanese individual homozygous for delta beta-thalassemia was analyzed by the blot hybridization technique of Southern. Results indicated a large deletion of the non-alpha-globin gene cluster, starting in the vicinity of 3' to the A gamma-globin gene and extending through the 3' side of the beta-globin gene. Persistent expression of the gamma-globin gene in adult life has been supposed to be caused by loss of a region located about 3-4 kb 5' to the delta-globin gene from comparison of the extents of deletions in several different forms of delta beta-thalassemia and HPFH (hereditary persistence of fetal hemoglobin). But the novel deletion found in the present case of delta beta-thalassemia suggests that the above putative regulatory region does not have this effect on expression of the gamma-globin gene. Some explanations of expression of fetal type globin genes in this delta beta-thalassemia are discussed.
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PMID:A novel deletion in delta beta-thalassemia found in Japan. 298 69

In this study, we used cloning and sequence analysis to define the molecular defect in two delta-thalassemia genes, one associated with reduced output of delta-globin chains (delta +thal) from a Sardinian and the other with a complete suppression of delta-chain production from the affected locus (delta zerp thal) from a Southern Italian. Sequence analysis of the delta +thal gene showed a G----T substitution at the first nucleotide of codon 27 (delta +27) which produces an amino acid change (Ala----Ser) and presumably activates a cryptic splice site located at this position. Therefore, only a fraction of the transcript is processed from this site, as indicated by the clinical phenotype of delta +thal. DNA sequencing of the delta zero thal gene revealed a T----C substitution at position 1 of IVS-1, which abolishes the splicing at this site and thus leads to complete deficiency of normal mRNA explaining the clinical phenotype of delta zero thal. Oligonucleotide analysis was used to confirm the coinheritance of the delta +27 mutation in a group of Sardinians with thalassemia like phenotype and normal HbA2 level who, on the basis of genetic criteria, were supposed to be double heterozygous for delta-thalassemia and beta-thalassemia. The definition of delta-thalassemia defects in each high-risk area facilitates identification of double heterozygotes for delta- and beta-thalassemia by DNA analysis and may thus improve genetic counseling.
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PMID:Delineation of the molecular basis of delta- and normal HbA2 beta-thalassemia. 340 92

Three Japanese individuals with homozygous delta zero-thalassemia from different families were the subjects of molecular genetic analysis. They were homozygous for seven polymorphic sites in the beta-globin gene cluster. Nucleotide sequence analysis of the delta-globin gene cloned from each patient revealed a single nucleotide substitution (T-C) 77 base pairs 5' to the cap site, just upstream of the CCAAC box of the delta-globin gene. When introduced into COS cells, the gene was expressed at normal levels with proper processing of RNA. These results suggest that the complete suppression of delta-globin chain synthesis in these patients is not due to a defective promoter, a defective RNA processing or a chain terminator mutation, but rather to impaired regulation of gene expression specific to erythroid cells. The region around the CCAAC box may have a significant role in expression of the delta-globin gene in erythroid cells.
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PMID:A delta-globin gene derived from patients with homozygous delta zero-thalassemia functions normally on transient expression in heterologous cells. 347 64

The Dutch beta zero-thalassemia has relatively few clinical symptoms in the homozygote. Heterozygotes have levels of fetal hemoglobin (4-11%) comparable to delta beta-thalassemia, and much higher than in typical beta zero-thalassemia. To analyze this deletion, we have cloned the abnormal 10 kb Bgl II fragment that contains the delta-globin gene into phage lambda vector EMBL4. A Hind III-Xba I fragment that includes the endpoints of the deletion was subcloned into plasmid pUC 19 and partially sequenced by the dideoxy method. The sequence of the Dutch beta zero-thalassemia DNA is like that of normal 5' DNA to 8920 (the numbering system is from reference 2). The sequence from 8915-8920 is AAATTT, which is also the normal 3' sequence from 21537-21542. From this point on, the Dutch beta zero-thalassemia sequence is like that of the normal 3' DNA. The deletion is therefore 12.6 kilobases, rather than 10 as originally estimated. It is similar to several other beta-globin gene deletions in terminating in a region of Kpn I repeated sequences, and having several base pairs of homology between 5' and 3' sequences at the break points.
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PMID:DNA sequence analysis of the Dutch beta zero-thalassemia deletion. 359 92

In this study we have carried out haplotype analysis at the beta-globin gene cluster and defined the beta-thalassaemia mutations in a large Sardinian family, ascertained through a proband with thalassaemia major, in which several members were carriers of a beta-thalassaemia allele characterized by microcytosis, hypochromia and normal Hb A2 levels (type 2 normal Hb A2 heterozygous beta-thalassemia). The proband was a compound heterozygote for the beta zero 39 and the beta + IVS-2, nt 745 mutations and all the beta-thalassaemia heterozygotes with normal Hb A2 showed the beta + IVS-2, nt 745 mutation, always associated with haplotype VII. Because of the consistent association of a specific beta-thalassaemia mutation and normal Hb A2 levels, we postulate that this beta-thalassaemia chromosome carries a delta gene (delta-thalassaemia) which is unable to increase the delta-globin output in response to beta-thalassaemia.
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PMID:Molecular characterization of a normal Hb A2 beta-thalassaemia determinant in a Sardinian family. 367 10

In gamma-beta-thalassaemia, human gamma- and beta-globin gene expression is suppressed; this results in a severe anaemia in newborns which subsequently develops into a beta-thalassaemia syndrome in adult life. This hereditary disease is now shown to be the result of a deletion of at least 40,000 base pairs of the gammadeltabeta-globin gene locus. The gamma- and delta-globin genes are deleted in the affected chromosome but, surprisingly, the beta-globin gene is still present, together with a large segment of the DNA sequences flanking the gene on its 5'-side and the entire region on the 3'-side of the gene. Hence, a deletion of DNA far from the beta-globin gene results in the suppression of its activity.
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PMID:gamma-beta-Thalassaemia studies showing that deletion of the gamma- and delta-genes influences beta-globin gene expression in man. 615 59

By restriction endonuclease mapping, gene cloning, and DNA sequencing we have determined the region of DNA that is deleted in a family with gamma delta beta-thalassemia. The deletion removes the linked epsilon, gamma-, and delta-globin structural genes and terminates within the coding portion of the beta-globin gene. Since the extent of DNA deletion in this family differs from that reported in another family, we conclude that gamma delta beta-thalassemia is heterogeneous at the molecular level.
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PMID:Heterogeneity of DNA deletion in gamma delta beta-thalassemia. 616 60

The hematological phenotypes of several Mediterranean patients with delta beta-thalassemia and hereditary persistence of fetal hemoglobin have been characterized. Although clinical and hematological characteristics are essentially superimposable in all heterozygous delta beta-thalassemics, these patients show typical G gamma/A gamma ratios in their Hb F, ranging from approximately 0.07 in Sardinian to approximately 0.15 in Sicilian and approximately 0.35 in Spanish patients. A gamma Sardinian-(isoleucine-75 leads to threonine) is found in Spanish patients and accounts for all of the A gamma production in heterozygotes, indicating that persistent production of gamma chains occurs cis to the delta beta-thalassemia gene. The molecular heterogeneity of these conditions is demonstrated by restriction enzyme mapping of DNA; Sicilian and Calabrian patients show a deletion starting from the delta-globin intron and extending several kilobases 3' to the beta-globin gene; in Spanish patients the deletion starts approximately 2-3 kilobases 5' to the delta-globin gene and extends well beyond the beta-globin gene. Comparison of these deletions with previously described ones in Negro and in a new Southern Italian case of hereditary persistence of fetal hemoglobin suggests that the deletion of a region centered at a cluster of repetitive sequences approximately 3.5 kilobases 5' to the delta-globin gene may be critical for the persistent expression of high levels of gamma-globin in hereditary persistence of fetal hemoglobin compared to delta beta-thalassemia. The concept that the deletion or mutation of specific areas (rather than nonspecific changes brought about by large deletions in the globin cluster) is important in determining the persistent expression of gamma-globin genes is supported by the finding of a nondeletion type of delta beta-thalassemia in Sardinians.
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PMID:Molecular comparison of delta beta-thalassemia and hereditary persistence of fetal hemoglobin DNAs: evidence of a regulatory area? 617 97

In hereditary persistence of fetal haemoglobin (HPFH) and delta 0-beta 0-thalassaemia, increased levels of fetal haemoglobin (HbF) are found in adult individuals. HbF production is particularly noticeable in the former condition in which HbF levels of 20-40% are found in heterozygous patients, as opposed to 5-20% in delta 0-beta 0-thalassaemia. In a minority of these cases, no obvious abnormalities have been found in the globin gene region by DNA mapping, indicating that small deletions or perhaps even point mutations in critical DNA sequences in the globin gene cluster may be responsible for these conditions. However, most cases of HPFH and delta 0-beta 0-thalassaemia are associated with extensive deletions in the globin gene cluster. Genetic data and gene mapping investigations provided some evidence for the location of a regulatory area, whose deletion results in continuing activity of gamma-globin genes in adults, in a DNA region between the A gamma- and delta-globin genes, possibly 3-4 kilobases (kb) 5' to the delta gene. The precise nature of these sequences is of great interest, because it might help elucidate the molecular mechanisms regulating globin gene expression during development. Recently, Jagadeeswaran et al. cloned the DNA encompassing the region of a gene deletion in a type of HPFH and showed that the 5' end point of the deletion lies in the middle of an AluI repetitive DNA sequence. We have now cloned the corresponding region from the DNA of a delta 0 -beta 0-thalassaemia patient and we report here that the deletion ends in a different AluI sequence, congruent to 700 nucleotides 3' to the AluI repeat involved in the HPFH deletion, and in the opposite orientation.
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PMID:The deletion in a type of delta 0-beta 0-thalassaemia begins in an inverted AluI repeat. 618 21

A new polymorphism in the beta-globin is described, using the restriction enzyme Asu I. A radioactive probe specifically representing the large intervening sequence (IVS 2) of the beta-globin gene has been used to detect this polymorphism. Normally, a 0.8-kilobase fragment containing beta-IVS 2 is generated by Asu I; however, a 1.0-kilobase fragment is seen in association with 18% of beta A-genes, and 38% of beta-thalassemia genes in an Israeli population studied. By contrast, the Asu I polymorphism has rarely been seen in blacks examined to date. An additional Asu I change is seen the the delta-globin gene with a delta-IVS probe. The beta-Asu I polymorphism is shown to be useful in the antenatal diagnosis of beta-thalassemia.
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PMID:A new polymorphism in the human beta-globin gene useful in antenatal diagnosis. 627 Jan 95


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