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

This article reviews the molecular bases of alpha- and beta-thalassemias in Sardinia. In addition, it describes the characteristics and the effects of a genetic program designed to prevent homozygous beta-thalassemia. In the large majority of the cases (95.7%), beta-thalassemia is caused by the nonsense mutation at codon 39, followed by frameshifts at codon 6 (2.1%). Homozygous beta-thalassemia most commonly results in thalassemia major, but in a small proportion this genotype produces milder forms referred to as thalassemia intermedia. The reasons for the attenuated forms were determined only in a small proportion of the cases. The reduced clinical severity was due to either of two factors: (a) There could be the presence of cytosine-thymidine (C----T) substitution of position - 158 G gamma, which is able to increase the G gamma chain output (as in homozygotes for frameshift at codon 6 or compound heterozygote for frameshift at codon 6 and codon 39 nonsense mutation). (b) Reduced clinical severity could be the result of co-inheritance of alpha-thalassemia in the form of two alpha-globin gene deletions of functional loss of the alpha 2-globin gene (homozygote for codon 39 nonsense mutation). The most prominent clinical form of alpha-thalassemia is hemoglobin H disease, which may result from the compound heterozygous state for deletion alpha 0- and alpha(+)-thalassemia (in 83.1% of cases) or deletion and nondeletion alpha-thalassemia (in 16.9%). Deletion Hb disease shows a milder clinical picture as compared to the nondeletion form. The most common nondeletion alpha-thalassemia is the ATG----ACG substitution at the initiation codon of the alpha 2 gene. Double heterozygotes of alpha (-alpha/-alpha) and beta-thalassemia or delta- and beta-thalassemia are relatively common and may cause confusion in carrier identification. The preventive program aimed to control beta-thalassemia is based on voluntary carrier screening., counselling, and prenatal diagnosis. Prenatal diagnosis is carried out by dot blot analysis with allelic specific oligonucleotides on amplified trophoblast DNA. This procedure gave very reliable results; in fact, no misdiagnosis has occurred so far. The preventive program was highly effective, resulting in a decline of the incidence of thalassemia major from 1:250 to 1:1,000 live births.
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PMID:Thalassemias in Sardinia: molecular pathology, phenotype-genotype correlation, and prevention. 206 29

During the course of a screening program for beta-thalassemia mutations among beta-thalassemia heterozygotes in Yugoslavia we observed a mutation (ATG----ACG) in the initiation codon of the beta-globin gene which has not been described before. The abnormality was initially detected through mapping of the beta-globin gene by Southern blot analysis using the restriction enzyme Nco I. The loss of the Nco I site resulted in the presence of an 8.3 kb band in addition to the normal 5.2 kb band. The mutation was identified by sequence analysis of amplified DNA and by dot-blot analysis of this DNA with a 32P-labeled oligonucleotide probe. An additional polymorphism (CAC----CAT) was present at codon 2 on the same chromosome; this mutation was detected by Orkin et al in 1982 (1). Hematological and in vitro chain synthesis data suggest that the beta-thalassemia is of the beta zero type.
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PMID:An initiation codon mutation as a cause of a beta-thalassemia. 227 40

A total of 72 chromosomes from 36 Indonesian patients, 23 with beta-thalassemia major and 13 with Hb E-beta-thalassemia, were analyzed by specific oligonucleotide hybridization after DNA amplification. Thirteen had the beta E mutation (codon 26 GAG----AAG). Of the 59-beta-thalassemic chromosomes, 32 were of the variant IVS-1 nt5 (G----C). Seven had the mutation IVS-2 nt654 (C----T), one had the mutation codon 41/42 (deletion CTTT), and one had the mutation codon 17 (AAG----TAG). Another six with the mutation IVS-1 nt1 (G----T), one with the mutation IVS-1 nt1 (G----A), four with the mutation codon 15 (TGG----TAG), one with a mutation codon 30 (AGG----ACG), and one with a mutation codon 35 (deletion C) were first identified by direct sequencing of a patient's genomic DNA followed by further hybridizing other patients' DNA with the appropriate oligonucleotide probes. Five did not carry the common mutations previously described in Asian populations. The four most prevalent mutations encountered made up 83% of the total number of beta-thalassemic chromosomes studied. The most common mutation, IVS-1 nt5 (G----C), was mostly associated with two different haplotypes.
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PMID:Beta-thalassemia mutations in Indonesia and their linkage to beta haplotypes. 258 24

alpha-globin is encoded by two adjacent genes, alpha 1 and alpha 2. Recent evidence suggests that these genes are not equally expressed and that the alpha 2-globin gene encodes the majority of alpha-globin. This finding would predict that a thalassemic mutation of the alpha 2-globin gene would result in a more severe loss of alpha-chain synthesis than a similar mutation in the alpha 1-globin gene. In a previous study we described a nondeletion alpha-thalassemia defect in the alpha 2-globin gene resulting from an AUG----ACG initiation codon mutation. In the present study we describe a different initiation codon mutation, AUG----GUG, present in the alpha 1-globin gene. The alpha 1- and alpha 2-globin gene initiation codon mutations result in similarly lowered levels of encoded mRNA. Despite the similarity of these two mutations, the alpha 2 mutant results in a more severe loss of alpha-globin synthesis and a more severe clinical alpha-thalassemia phenotype than the corresponding alpha 1-globin gene mutation. This difference reflects the dominant role of alpha 2-globin gene in overall alpha-globin synthesis.
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PMID:An initiation codon mutation (AUG----GUG) of the human alpha 1-globin gene. Structural characterization and evidence for a mild thalassemic phenotype. 368 May 4

Cloning and sequence analysis of the alpha-globin genes from a Sardinian patient with the nondeletion type of hemoglobin-H disease revealed a new type of thalassemia lesion. A mutation in the alpha 2-globin gene changes the initiation codon ATG to ACG and abolishes the function of this gene. Globin mRNA output from the affected alpha 2 locus is decreased relative to the alpha 1 locus. The mutation is detectable in genomic DNA by restriction analysis with the enzyme NcoI. Of the seven Sardinian patients with nondeletion alpha thalassemia screened with this enzyme, six had the initiation codon lesion.
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PMID:Initiation codon mutation as a cause of alpha thalassemia. 649 Jun 12

Investigation of microcytic anemia with normal ferrous status in two members (father and daughter) of a Swiss family originating from Bern revealed high levels of HbA2 (4%, 7.3%) and HbF (3.2%, 3.1%). Direct sequence analysis of asymmetrically amplified DNA showed the ATG-->ACG mutation in the intiation codon of the beta-globin gene. Heterozygous beta-thalassemia was not found in either of the propositus's parents or in any of his brothers and sisters. Extended restriction fragment length polymorphism haplotyping of the beta chromosomes led us to the conclusion of a recent spontaneous mutation in the paternal germ cell. The results of routine HLA and blood group testing supported the stated paternity. We also found that the intragenic sequence polymorphisms (frameworks) are not always in linkage disequilibrium with the Bam HI polymorphism downstream from the beta-globin gene as previously observed. This is the second family found to carry this initiation codon mutation in the beta-globin gene. Unlike the first reported family, of Yugoslavian origin, our patients have high HbF levels and this in the absence of a C-->T substitution at -158 site 5' to G gamma.
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PMID:De novo initiation codon mutation (ATG-->ACG) of the beta-globin gene causing beta-thalassemia in a Swiss family. 809 43

We have systematically analyzed beta-thalassemia genes using polymerase chain reaction-related techniques, dot-blot hybridization with oligonucleotide probes, allele specific-polymerase chain reaction, and sequencing of amplified DNA fragments from 41 unrelated patients, including 37 beta-thalassemia homozygotes, three with beta-thalassemia/Hb E, and one with beta-thalassemia/Hb S. Four different beta-thalassemia mutations were detected in 78 alleles. These are the IVS-I-5 (G-->C), codon 30 (AGG-->ACG) [also indicated as IVS-I (-1)], IVS-I-1 (G-->A), and codons 41/42 (-TTCT) mutations. The distribution of the beta-thalassemia mutations in the Maldives is 58 alleles (74.3%) with the IVS-I-5 (G-->C) mutation, 12 (15.4%) with the codon 30 (AGG-->ACG) mutation, seven (9%) with the IVS-I-1 (G-->A) mutation, and one with the codons 41/42 (-TTCT) mutation. The first three mutations account for 98.7% of the total number of beta-thalassemia chromosomes studied. These mutations are clustered in the region spanning 6 bp around the junction of exon 1 and the first intervening sequence of the beta-globin gene. These observations have significant implications for setting up a thalassemia prevention and control program in the Maldives. Analysis of haplotypes and frameworks of chromosomes bearing each beta-thalassemia mutation suggested that the origin and spread of these mutations were reflected by the historical record.
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PMID:Molecular basis of beta-thalassemia in the Maldives. 957 31

The beta thalassemia alleles in 53 thalassemic Indo-Mauritian patients and their families consisting of 23 homozygous beta-thalassemia, 9 HbE/beta-thalassemia, 18 HbS/beta-thalassemia, 1 HbD/beta-thalassemia, 1 deltabeta/beta-thalassemia and 1 HbH/beta-thalassemia from the island of Mauritius were studied. Characterization by polymerase chain reaction-based reverse dot blot hybridization technique revealed that the IVS1-5 (G-->C) mutation accounted for 74% of the beta thalassemic alleles, while six other mutations occurred at much lower frequencies: HbE codon 26 (G-->A); 10.4%, codon 8/9 (+G); 3.5%, codon 30 (AGG-->ACG) also called IVSI (-1).G-->C; 3.5%, codon 15 (G-->A); 3.5%, codon 41/42 (-CTTT); 2.4% and -28 (A-->G); 2.4%. Association of these mutations to specific beta globin gene sequence framework and haplotype allowed to trace their ancestral link. These data are useful in future molecular screening of the population in view of implementing a thalassemia prevention and control program in Mauritius.
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PMID:Spectrum of beta thalassemia mutations and their linkage to beta-globin gene haplotypes in the Indo-Mauritians. 1107 47

Three rare beta-thalassemia mutations, not reported previously in Asian Indians or the Pakistani population, were identified by single strand conformation polymorphism analysis followed by direct sequencing. Two mutations, IVS-II-848 (C-->A) and initiation codon (ATG-->ACG), were found in the homozygous condition in patients belonging to Balochi and Sindhi ethnic groups of Pakistan, together with heterozygous and homozygous alpha(-3.7) deletions, respectively. A frameshift mutation at codon 44 (-C) was identified in a patient belonging to the Gujrati ethnic group together with IVS-I-1 (G-->T) and a normal complement of four a-globin genes. Haplotype analysis was performed to identify the chromosomal background associated with these mutations, and for tracing the origin and spread of these mutations.
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PMID:Identification of three rare beta-thalassemia mutations in the Pakistani population. 1072 11

The beta-thalassemias are a heterogeneous group of hereditary anemias. A multitude of mutations have been reported, resulting in varied phenotypes. In each ethnic group there is always a subset of common, less common, and rare mutations, which makes population screening, prenatal diagnosis, and genetic counseling easier. In this paper we report a rare beta-thalassemia mutation found in an Indian subject by SSCP and sequencing analysis. The mutation, initiation ATG --> ACG, was found in heterozygous condition in a patient belonging to Brahmin family of Uttar Pradesh origin. Haplotype analysis was performed to identify the chromosomal background associated with the mutation and to tracing the origin and spread of the mutation. This study, as previous studies, suggests that rare beta-thalassemia mutations, such as the initiation codon mutations, have no set geographical distribution and are relatively recent.
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PMID:Initiation codon mutation in an Asian Indian family. 1235 16


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