Although the study was underpowered for the reported associations to reach formal threshold of genome-wide significance under the assumption of independent multiple testing, the consistency of association between the 2 variants and a set of anthropometric traits makes CRIM1 and ITGA1 highly interesting for further replication and functional follow-up. Increased linkage disequilibrium between the used markers in an isolated population makes the formal significance threshold overly stringent, and changed allele frequencies in isolate population may contribute to identifying variants that would not be easily identified in large outbred populations.
This study concerned the evaluation of beta-thalassemia alleles in nearly 50 patients with beta-thalassemia major and in 130 -thalassemia heterozygotes using gene amplification and dot-blot hybridization with synthetic probes. Fourteen different mutations were observed; of these, three (IVS-I-110; IVS-I-6; IVS-I-1) account for some 75% of all beta-thalassemia alleles. Newly discovered variants, i.e. T----C in the initiation codon and AATAAA----AATGAA in the poly A site were observed in a few patients. The poly A mutation with classical beta-thalassemia alleles result in thalassemia intermedia. Hb Lepore is a rather common abnormality and combinations of this variant with beta-thalassemia often result in severe disease; a search for beta-thalassemia mutations among patients affected with this disease should include an analysis to detect this hemoglobin abnormality.
Among several hundred apparently healthy Yugoslavian adults with slightly elevated levels of fetal haemoglobin, we have identified two distinct abnormalities. (a) A G gamma A gamma(delta beta)0-thalassaemia heterozygosity with an approximately 15 kb deletion which involves part of the delta globin gene and the beta globin gene. This deletion is probably the same as that seen among Italians (Ottolenghi et al, 1982; Carè et al, 1984). (b) A nondeletion form of hereditary persistence of Hb F which is caused by a gamma globin gene triplication of the (+)G gamma.(+)G gamma.A gamma type. It is characterized by the presence of some 5% Hb F in the heterozygote containing nearly 100% G gamma chains. The C----T mutation at position--158 5' to the G gamma chain [(+)G gamma], identified through analyses of Xmn I digests, was present at both G gamma globin genes. This mutation is known to be associated with increased G gamma chain production (Gilman & Huisman, 1985), and thus is responsible for the increased G gamma chain production in these heterozygotes. The condition is different from the (+)G gamma.(+)G gamma nondeletion type of HPFH which has been observed in heterozygotes of two Black families, and is associated with the presence of 3-4% Hb F (with mainly G gamma chains) in heterozygotes.
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.
We studied a heterozygous beta zero-thalassaemia patient from Croatia with an unusually high Hb A2 level of 7.6% and an elevated Hb F level of 5.8%. The same condition was found in his father (Hb A2 8.2%; Hb F 8.5%). Gene mapping and direct sequencing analyses revealed a new deletion of 1605 bp in the 5' beta-globin gene region between positions -984/5 and +620/1. This deletion has not been observed among more than 500 beta-thalassaemia chromosomes from the Balkan countries studied in our laboratory.
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