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

The organization of alpha globin genes in normal human DNA was examined by restriction endonuclease mapping, alpha globin-specific fragments in endonuclease digests of total cell DNA were identified after electrophoresis by hybridization with [32P]cDNA following the blotting procedure of Southern [(1975) J. Mol. Biol. 98, 503--517]. The data provide direct evidence for the duplication of alpha genes and further indicate that these loci are closely linked within a single restriction fragment. The HindIII sites (codons 90/91) of these duplicated genes lie approximately 3.7 kilobases apart in the physical map proposed for this region. This organization of alpha genes can be altered in DNA of individuals with alpha-thalassemia.
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PMID:The duplicated human alpha globin genes lie close together in cellular DNA. 28 16

Five cases of HbH disease were discovered in a large family of American Blacks. Anaemia was mild with PCV ranging from 0.275 to 0.405. The amount of HbH was 2--6%. Studies of haemoglobin synthesis in peripheral blood reticulocytes demonstrated marked deficits in alpha globin production with an average alpha/beta ratio of 0.31 (range 0.22--0.36). Eighteen additional family members had evidence of thalassaemia trait and were provisionally classified as either alpha-thal-1 (average MCV 65.2 fl; range 59--70) or alpha-thal-2 (average MCV 79.6 fl; range 74--88). A subject with altha-thal-1 trait had an alpha/beta ratio of 0.56; the average for five cases of alpha-thal-2 was 0.73. One other family member was thought to be homozygous for alpha-thal-2 trait and exhibited an MCV of 65 fl with an alpha/beta ratio of 0.5. These data reconfirm that in Blacks with alpha thalassaemia the proportion of HbH is lower and the severity of anaemia is less than in certain other racial groups, e.g. Southeast Asians. However, the degree of hypochromia and microcytosis and the imbalance in alpha and beta globin synthesis appear to be similar in Blacks and other races. These results suggest that the milder clinical course of HbH disease in Blacks is not a result of greater alpha globin production in that population of thalassaemics.
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PMID:Alpha thalassaemia in American blacks: a study of a family with five cases of haemoglobin H disease. 42 29

The rarity of hemoglobin (Hb) H disease in combination with sickle trait may be due in part to the absence of actual Hb H in individuals who, nonetheless, have inherited the deletion of three alpha-globin genes. We describe here a boy with persistent microcytic, hypochromic anemia despite adequate iron stores, who exhibited splenomegaly with a normal reticulocyte count and only rare inclusions in circulating erythrocytes. Starch gel electrophoresis and isoelectric focusing at age 5 yr showed 21% Hb S, persistent Hb Bart's, but no Hb H. Recticulocyte alpha/non-alpha globin chain synthesis ratio was 0.58 at age 5. The mother (Asian) had laboratory evidence of alpha-thalassemia trait and the father (Black) had sickle trait. The nature of alpha-thalassemia in this patient was investigated both by liquid hybridization and by the Southern method of gene mapping, in which DNA is digested with restriction endonucleases and the DNA fragments that contained the alpha-globin structural gene identified by hybridization with complementary DNA. The patient had only one alpha-globin structural gene, located in a DNA fragment shorter than that found in normal or alpha-thalassemia trait individuals, but similar to that present in other patients with Hb H disease. Morphologic studies of bone marrow by light and electron microscopy revealed erythroid hyperplasia with inclusions in polychromatic and orthochromatic erythroblasts, suggesting early precipitation of an unstable hemoglobin. The lack of demonstrable Hb H may be the result of both diminished amounts of beta(A) available for Hb H formation (since one beta-globin gene is beta(S)) and the greater affinity of alpha-chains for beta(A) than beta(S)-globin chains leading to the formation of relatively more Hb A than Hb S. The presence of a beta(S) gene may thus modify the usual clinical expression of Hb H disease.
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PMID:Modification of hemoglobin H disease by sickle trait. 47 66

Molecular hybridization with synthetic radioactive DNA (cDNA) complementry to alpha globin mRNA sequences shows that, as in most other Southeast Asian populations, the alpha globin structural genes are deleted in Filipinos affected by the alpha-thalassemia syndromes. Thus, all 4 alpha-globin structural genes are deleted in homozygous alpha-thalassemia with hydrops fetalis, 3 and 2 structural genes are deleted in hemoglobin H disease and alpha-thalassemia-1 respectively.
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PMID:The molecular defects of alpha-thalassemia in the Filipino. 91 35

Three new families providing information on the linkage relationships between the delta and beta hemoglobin loci are reported. One of the families contains the first reported individuals having Hb S and Hb B2 in coupling. Analysis of the information found in the literture is compatible with a recombination frequency of 3 percent between beta thalassemia and the delta structural locus. This highly improbable frequency might be explained by either diagnostic errors or paternity problems in the pedigrees containing recombinants or by the conceivable possibility that certain thalassemia genes increase the probability for recombination in the chromosomal region containing the non alpha globin genes.
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PMID:The linkage relationships of the beta and delta hemoglobin genes. 91 37

Globin mRNAs were isolated from circulating reticulocytes both from rats carrying a homozygous, recessive mutation causing a severe thalassemia-like syndrome and from normal rats. After first identifying the rat globin chains as alpha or beta chains, the translational products primed by both polysomal and nonpolysomal mRNAs in wheat germ 30000 x g supernatant were analyzed: the ratio of alpha to beta globin mRNAs found in polysomes isolated from mutant rats is identical to the ratio of their products synthesized in vivo while the ratio of these mRNAs is quite different in the nonpolysomal fraction, the latter being enriched in alpha globin mRNA. No difference is found in the ratio of alpha and beta globin mRNAs in the polysomal and nonpolysomal RNA isolated from normal rats, both being identical to the ratio of their products synthesized in vivo. One third of the total amount of mRNA found in mutant cells is not in polysomes as compared to only 6 percent for the mRNA from normal lysates. These results suggest that a translational control mechanism is involved although the decreased globin synthesis in b/b anemia can not be fully accounted for by its operation.
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PMID:Rat b/b anemia: translation of normal and anemic globin mRNA in wheat-germ cell-free system. 100 56

Purified alpha and beta globin complementary DNAs (cDNAs) have been separated from total radioactively labeled human globin cDNA using mRNA purified from liver of a hydrops fetalis (alpha thalassemia). The beta cDNA hybridizes to the hydrops fetalis mRNA while the alpha cDNA remains single-stranded. the purified alpha and beta cDNAs were assayed for their purity by their hybridization to mRNA prepared from reticulocytes of nonthalassemia, alpha thalassemia, and beta thalassemia subjects. The results indicate that the separated cDNAs are selective in hybridization to alpha or beta globin mRNAs, respectively. The previously reported deficiency of globin mRNA in thalassemia cells has been confirmed with these purified cDNAs. The purified alpha and beta cDNAs were hybridized to cellular DNA to non-thalassemia, beta+ thalassemia, and hydrops fetalis (alpha thalassemia) DNA. The alpha cDNA hybridized to hydrops fetalis liver DNA to a much lower extent that beta cDNA, confirming the previously reported deletion of alpha globin genes in hydrops fetalis. By contrast, both the alpha and beta DNA probes hybridized to the same extent to spleen DNA from non-thalassemia and from beta+ thalassemia patients. Between two and five globin genes in non-thalassemia and beta+ thalassemia DNA hybridize to beta cDNA and one to five to alpha cDNA. These studies indicate that in beta+ thalassemia, there is no detectable deletion in beta globin genes. The genetic defect in beta+ thalassemia appears to be due to either repression of transcription of beta globin genes or abnormal processing of beta globin mRNA.
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PMID:Relative numbers of human globin genes assayed with purified alpha and beta complementary human DNA. 105 26

We describe a novel alpha-thalassaemia-1 deletion that removes the entire zeta-alpha globin gene cluster. A Chinese couple were referred for counselling after two consecutive pregnancies ended with fetal hydrops. Gene mapping was used to demonstrate that the mother is heterozygous for the South-east Asia alpha-thalassaemia-1 deletion (zeta zeta zeta alpha alpha/zeta zeta--SEA), while the father carries an alpha-thalassaemia-1 deletion of more than 100 kilobases (zeta zeta alpha alpha/----). This newly discovered deletion extends for unknown distances 3' and 5' of the zeta-alpha globin gene cluster and has been designated (--HW).
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PMID:Identification of an extensive zeta-alpha globin gene deletion in a Chinese individual. 158 Dec 18

We report a Swiss-Spanish family three members of which have the clinical picture of thalassemia intermedia. Restriction endonuclease mapping of the alpha-globin cluster and digestion with Mae I of the in vitro amplified 5' segment of the beta-globin gene shows a combination of triplicated alpha globin locus, anti-3.7 kb type, with heterozygous codon 39 C----T beta (0) thalassemic mutation. These, as well as 16 similar cases reported in the literature, permit the following conclusion: a single extra alpha-globin gene gives rise to a clinically significant degree of dyserythropoietic anemia only when it interacts with a severe beta(+) or beta(0) thalassemic mutation.
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PMID:Interaction of heterozygous beta (0)-thalassemia and triplicated alpha globin loci in a Swiss-Spanish family. 179 94

The instability of chromosomes with breaks induced by X-irradiation led to the proposal that the natural ends of chromosomes are capped by a specialized structure, the telomere. Telomeres prevent end-to-end fusions and exonucleolytic degradation, enable the end of the linear DNA molecule to replicate, and function in cell division. Human telomeric DNA comprises approximately 2-20 kilobases (kb) of the tandemly repeated sequence (TTAGGG)n oriented 5'----3' in towards the end of the chromosome, interspersed with variant repeats in the proximal region. Immediately subtelomeric lie families of unrelated repeat motifs (telomere-associated sequences) whose function, if any, is unknown. In lower eukaryotes the formation and maintenance of telomeres may be mediated enzymatically (by telomerase) or by recombination; in man the mechanisms are poorly understood, although telomerase has been identified in HeLa cells. Here we describe an alpha thalassaemia mutation associated with terminal truncation of the short arm of chromosome 16 (within band 16p13-3) to a site 50 kb distal to the alpha globin genes, and show that (TTAGGG)n has been added directly to the site of the break. The mutation is stably inherited, proving that telomeric DNA alone is sufficient to stabilize the broken chromosome end. This mechanism may occur in any genetic disease associated with chromosome truncation.
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PMID:A truncated human chromosome 16 associated with alpha thalassaemia is stabilized by addition of telomeric repeat (TTAGGG)n. 197 28


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