Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0039730 (thalassemia)
 10,305 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Delta-thalassemia is a complex group of inherited disorders of globin genes characterized by impaired synthesis of the delta-globin chain. The T-C substitution was detected at position -77 of the delta-globin gene isolated from three independent Japanese individuals who were homozygotes for delta-thalassemia. To elucidate the significance of the mutation in delta-globin gene expression, we investigated the genotype of three delta-thalassemia homozygotes and 58 normal individuals using dot blot hybridization of the polymerase chain reaction (PCR)-amplified DNA. The mutation was observed in six alleles of three homozygotes, while no mutation was detected in 116 alleles of normal individuals, thereby indicating the close association of this mutation with the thalassemia phenotype. Since the mutation (TTATCT-TCATCT) is located within the inverted binding motif of GATA-1 (T or A-G-A-T-A-G or A), an erythroid cell-specific transcription factor, we did gel retardation assays using nuclear extracts from the erythroid cells. We found that GATA-1 binds the oligonucleotide spanning positions -61 to -90, but does not bind to the oligonucleotide with the mutation at position -77. Competition gel retardation assays showed that GATA-1 binding can be competed out by the fragment with the GATA-1 motif, but not with the mutant oligonucleotide. Analysis of the transient expression of the CAT gene linked to the delta-globin gene promoter region demonstrated that the construct with the mutant promoter region was expressed about 20-fold less compared with the normal one. Thus, the mutation at position -77 impairs delta-globin gene expression by abolishing GATA-1 binding to the AGATAA sequence of the promoter region of the delta-globin gene. This provides a good example of involvement of tissue-specific transacting factors in the molecular pathogenesis of hereditary diseases.
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PMID:Delta-thalassemia caused by disruption of the site for an erythroid-specific transcription factor, GATA-1, in the delta-globin gene promoter. 151 47

The molecular basis of most beta-thalassemia syndromes has been defined, while the spectrum of mutations causing delta-thalassemia is not well characterized. In an attempt to identify such mutations, the region encompassing the delta-globin gene from three Greek Cypriot families suspected of having delta-thalassemia was amplified by polymerase chain reaction (PCR), and DNA sequence determined using an automated fluorescence-based sequencer. Four novel mutations were identified: a G----T change at codon 27 that results in an alanine to serine change; a C----T change at codon 116 converting arginine to cysteine; a T----C change at codon 141 converting leucine to proline; and an AG----GG change at the consensus 3'-acceptor site in IVS-2. While the latter is clearly a thalassemic mutation, the low hemoglobin A2 in the first three may be due to either decreased production or instability of the altered delta-globin chain. All four mutations may be detected by PCR amplification of genomic DNA followed by restriction enzyme digestion. Two mutations abolish restriction sites while two create new cleavage sites. Screening for molecular defects that cause delta-thalassemia or unstable delta-globin by PCR amplification and restriction enzyme digestion will lead to correct diagnosis of beta/delta-thalassemia compound heterozygotes and improved genetic counseling.
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PMID:Identification of four novel delta-globin gene mutations in Greek Cypriots using polymerase chain reaction and automated fluorescence-based DNA sequence analysis. 174 90

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

We have defined a new type of delta-thalassemia in which beta-globin chain synthesis is incompletely suppressed. Homozygotes have unusually low HbA2 levels, and double heterozygosity for this delta-thalassemia gene and beta-thalassemia normalizes the HbA2 level. The delta-thalassemia occurs on a chromosome that is identifiable using polymorphic restriction endonuclease sites. We call this condition delta +-thalassemia, to distinguish it from the previously described delta 0-thalassemia syndromes in which no delta-globin chain synthesis occurs.
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PMID:Delta +-thalassemia in Sardinia. 630 32

Hemoglobin (Hb) A2 (alpha2delta2) is a minor hemoglobin in human red blood cells. An abnormal increase in the level of HbA2 is the most significant parameter in the diagnosis of beta-thalassemia carriers. In this study, we produced two monoclonal antibodies (mAbs) that specifically react to the delta-globin chain of HbA2. A sandwich type ELISA was developed employing the produced anti-HbA2 mAbs. HbA2 levels quantified by the developed sandwich ELISA were highly correlated with those obtained from the standard HPLC method (r = 0.934, p < 0.001). HbA2 levels determined by the ELISA were 4.4 +/- 1.9% in beta-thalassemia heterozygotes compared to 1.4 +/- 0.8, 1.9 +/- 0.8, 1.5 +/- 0.8 and 1.5 +/- 0.6% in normal subjects, HbE heterozygotes, suspected alpha-thalassemia heterozygotes and HbE homozygotes, respectively. Using a cut-off value of 2.5%, beta-thalassemia heterozygotes could be separated from non-beta-thalassemia heterozygotes with the same accuracy as obtained using the standard HPLC method. More importantly, the developed ELISA was able to determine HbA2 levels in HbE-bearing individuals which could not be done by the HPLC method. Our results suggest that this sandwich ELISA can be applied for mass screening for beta-thalassemia heterozygotes, especially in resource-limited countries, where beta-thalassemia is highly prevalent.
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PMID:Sandwich ELISA for hemoglobin A2 quantification and identification of beta-thalassemia carriers. 2006 73