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

The most common forms of hereditary persistence of fetal hemoglobin synthesis (HPFH) and delta beta zero-thalassemia result from simple deletions of the beta-globin gene cluster or from point mutations in the gamma-globin gene promoters. These naturally occurring mutants extend our understanding of globin gene regulation and hemoglobin switching. Furthermore, they provide the opportunity to test in vivo hypothetical switching models that are based on the experimental approach. We report here a family with delta beta zero-thalassemia from Turkey with a complex rearrangement of the beta-globin gene cluster that involves two deletions of 11.5 kb and 1.6 kb, and an inversion of 7.6 kb. The larger deletion removes both the delta-and the beta-globin genes with 3' flanking sequences, whereas the smaller deletion affects DNA of unknown function. The inversion contains the entire L1 repeat 3' of the beta-globin gene. There are structural motifs near the breakpoints (introduction of an "orphan" nucleotide, multiple direct and inverted repeats) suggesting a nonhomologous type of recombination event. The hematologic phenotype and the molecular structure of the rearranged beta-globin gene cluster are consistent with a competitive relationship between the fetal and the adult globin genes and/or with the translocation of enhancer sequences into the gamma-globin gene region.
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PMID:A deletion/inversion rearrangement of the beta-globin gene cluster in a Turkish family with delta beta zero-thalassemia intermedia. 157 56

Mutations producing beta-thalassemia reach individual gene frequencies greater than .01 in malarial-endemic regions because beta-thalassemia trait individuals have increased genetic fitness over that of normal individuals. Exon 3 of the beta-globin gene has been relatively spared as a site of common beta-thalassemia mutations. Frameshifts caused by the loss of a single nucleotide and nonsense mutations produce beta-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 beta-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 (beta Manhattan) that is elongated to 156 amino acids. The second is a CAG-CGG missense mutation at codon 127 that causes a Gln----Pro substitution (beta Houston) 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 beta-globin to form alpha beta 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.
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PMID:Dominant thalassemia-like phenotypes associated with mutations in exon 3 of the beta-globin gene. 158 46

A 26-year-old Chinese-Malaysian female patient with beta-thalassemia is presented. The main hematological values found in this patient were as follows: 1) normocytic hypochromic anemia (RBC 444 x 10(4)/microliters, Hb 11.8 g/dl) with marked anisopoikilocytosis, 2) erythroid hyperplasia, and 3) increased HbF (HbA 41.4%, HbA2 2.9%, HbF 48.9%). DNA obtained from peripheral leukocytes was analyzed using dot blot hybridization of the polymerase chain reaction (PCR)-amplified DNA with allele-specific oligonucleotide probes. A C----T substitution at position 654 of the second intervening sequence (IVS-2) was detected in her beta-globin clone.
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PMID:A case of beta-thalassemia with a C----T substitution at position 654 of the second intervening sequence of the beta-globin gene. 160 Feb 78

In order to delineate the spectrum and the relative abundance of beta-globin gene defects causing thalassaemia in the Portuguese population, a representative sample was analysed including 51 beta-thalassaemia carriers along with 26 patients representing different clinical phenotypes. Seven mutations were identified, four of which [codon 39 (C----T), 39%; intervening sequence (IVS) 1 nucleotide (nt) 1 (G----A), 26%; IVS 1 nt 110 (G----A), 17%; IVS 1 nt 6 (T----C), 15%] account for 97% of 93 beta-thalassaemia chromosomes. Two previously undescribed mutations, namely a C----T substitution at position--90 in the proximal CACCC box, and the deletion of nucleotides 4 and 5 (AG) in IVS2 were identified. The uncommon, though ubiquitous, G----T transversion at codon 121 was found once upon haplotype V. Direct prenatal diagnosis can be offered to 95% of couples at risk of bearing a thalassaemic child.
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PMID:Novel promoter and splice junction defects add to the genetic, clinical or geographic heterogeneity of beta-thalassaemia in the Portuguese population. 163 36

This paper describes a family of Central Italian origin in which three patients in two generations had either thalassaemia intermedia or a late presenting form of thalassaemia major. Sequence analysis of the patients' DNA revealed that only one of the beta-globin genes was affected by a beta-thalassaemia mutation (the codon 39 nonsense mutation), the other being completely normal, apart from the complex rearrangement (-T +ATA) at position -530 5' to the CAP site of the beta-globin gene, which has uncertain clinical significance. Haematologically, all these patients were characterized by unusually low HbF levels (1.8-7.3%) for a beta-thalassaemia major or intermedia phenotype. The mother of the two patients with thalassaemia intermedia was heterozygous for beta-thalassaemia (codon 39 nonsense mutation), while the father had thalassaemia-like red cell indices, an increased alpha/non alpha chain synthesis ratio, a slight increase of HbF and a low HbA2 level, but showed entirely normal beta-globin gene sequences, apart from the complex rearrangement (-T +ATA) at position -530 5' to the CAP site. One of the thalassaemia intermedia patients married a normal woman and they had a child with thalassaemia major who inherited only the codon 39 nonsense mutation but not the complex rearrangement at position -530. The clinical phenotype of thalassaemia-intermedia or major in the patients from this family may be explained by postulating the inheritance of the double heterozygous state for beta-thalassaemia and for a mutation in a gene coding for an erythroid-specific DNA binding protein which may impair the function of the normal beta-globin gene. Heterozygosity for this postulated mutation (father of the patients with thalassaemia intermedia) may result in the production of a beta-thalassaemia carrier state with normal HbA2 level.
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PMID:A beta-thalassaemia phenotype not linked to the beta-globin cluster in an Italian family. 164 26

The polymerase chain reaction and oligonucleotide probe hybridization technique were applied to the detection of two common mutations of the beta-globin gene found in Chinese, namely the 4-base pair deletion at the 41-42 codons and the C to T substitution at nucleotide 654 of IVS-2. The accuracy of the method was established using beta-thalassemia cases with known mutations or haplotypes of the restriction fragment length polymorphism (RFLP). A further 11 cases of thalassemia intermediate and thalassemia minor were then analysed with the same approach. Our results showed that 5 of the 11 cases carried the TCTT-deletion at codons 41-42. Our method is economical both in terms of materials and time needed and in an alternative to the use of the molecular RFLP approach in the prenatal diagnosis of beta-thalassemia.
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PMID:Detection of beta-globin gene mutations by polymerase chain reaction. 168 65

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.
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PMID:A new hereditary persistence of fetal hemoglobin deletion has the breakpoint within the 3' beta-globin gene enhancer. 168 88

The beta-thalassemic mouse provides a useful model for testing hypotheses about the pathophysiology in human beta-thalassemia. The clinical picture of these mice and their red blood cell deformability characteristics are quite similar to those observed in human beta-thalassemia intermedia. The creation of transgenic mice that express human beta-globin (beta s) has provided an opportunity to study the effect of increasing the non-alpha-globin chain production on the thalassemic phenotype. A small increase in beta-globin production produces transgenic mice that are healthier, have almost normal hemoglobin values, and whose red blood cell deformability is increased. We quantified and characterized the membrane skeletal-associated globin in normal, transgenic thal/sickle, and thalassemic mice and showed that only alpha-globin was associated with the membrane skeleton in the pathologic red blood cells, and that the degree of rigidity as measured in the rheoscope correlated directly and closely with the amount of membrane skeletal-associated globin in these abnormal red blood cells.
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PMID:The role of membrane skeletal-associated alpha-globin in the pathophysiology of beta-thalassemia. 169 33

Hb A2 and its variant B2 (alpha 2 delta 2(16)(A13)Gly----Arg) were quantitated in the blood of subjects with three different types of beta-thalassemia and with the delta-B2 anomaly in cis or in trans to the beta-thalassemia determinant. In one family, the delta-B2 mutation was in cis to a newly discovered codon 47 (+A) frameshift. The levels of Hbs A2 and B2 were nearly the same and approximately 70% higher than those in simple Hb B2 heterozygotes. In two additional families, the delta-B2 variant was in trans to either a deletional beta-thalassemia (1,393 bp) involving part of the beta-globin gene and part of the beta-globin gene promoter, or to the -88 C----T promoter mutation. In both instances, the Hb B2 level was increased by approximately 80%, but the Hb A2 level was increased by approximately 270% and 200%, respectively. These data indicate two mechanisms that will cause an increase in delta chain production. One is consistent with a general mechanism concerning the relative excess of alpha chains in beta chain deficiencies which will combine with delta chains to form variable levels of Hb A2 dependent on the severity of the beta chain deficiency. The second concerns the loss of beta-globin gene promoter activity, perhaps by an absence of (or decreased) binding of specific protein(s) to this segment of DNA and a concomitant increase in delta-globin gene promoter activity in cis.
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PMID:Observations on the levels of Hb A2 in patients with different beta-thalassemia mutations and a delta chain variant. 169 2

Synthesis of normal human hemoglobin A, alpha 2 beta 2, is based upon balanced expression of genes in the alpha-globin gene cluster on chromosome 16 and the beta-globin gene cluster on chromosome 11. Full levels of erythroid-specific activation of the beta-globin cluster depend on sequences located at a considerable distance 5' to the beta-globin gene, referred to as the locus-activating or dominant control region. The existence of an analogous element(s) upstream of the alpha-globin cluster has been suggested from observations on naturally occurring deletions and experimental studies. We have identified an individual with alpha-thalassemia in whom structurally normal alpha-globin genes have been inactivated in cis by a discrete de novo 35-kilobase deletion located approximately 30 kilobases 5' from the alpha-globin gene cluster. We conclude that this deletion inactivates expression of the alpha-globin genes by removing one or more of the previously identified upstream regulatory sequences that are critical to expression of the alpha-globin genes.
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PMID:Inactivation of human alpha-globin gene expression by a de novo deletion located upstream of the alpha-globin gene cluster. 170 Dec 60


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