Soontornpanawet C, Singha K, Srivorakun H, Tepakhan W, Fucharoen G, Fucharoen S. Molecular basis of a high Hb A
2/Hb F
β-thalassemia trait: a retrospective analysis, genotype-phenotype interaction, diagnostic implication, and identification of a novel interaction with
α-globin gene triplication.
PeerJ 2023;
11:e15308. [PMID:
37159832 PMCID:
PMC10163868 DOI:
10.7717/peerj.15308]
[Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2023] [Accepted: 04/06/2023] [Indexed: 05/11/2023] Open
Abstract
Background
β 0-thalassemia deletion removing 5´β-globin promoter usually presents phenotype with high hemoglobin (Hb) A2 and Hb F levels. We report the molecular characteristics and phenotype-genotype correlation in a large cohort of the β 0-thalassemia with 3.4 kb deletion.
Methods
A total of 148 subjects, including 127 heterozygotes, 20 Hb E-β-thalassemia patients, and a double heterozygote with α-globin gene triplication, were recruited. Hb and DNA analysis were performed to identify thalassemia mutations and four high Hb F single nucleotide polymorphisms (SNPs) including four base pair deletion (-AGCA) at A γ-globin promoter, rs5006884 on OR51B6 gene, -158 G γ-XmnI, BCL11A binding motifs (TGGTCA) between 3´A γ-globin gene and 5´δ-globin gene.
Results
It was found that heterozygous β 0-thalassemia and Hb E-β 0-thalassemia with 3.4 kb deletion had significantly higher Hb, hematocrit, mean corpuscular volume, mean corpuscular hemoglobin and Hb F values as compared with those with other mutations. Co-inheritance of heterozygous β 0-thalassemia with 3.4 kb deletion and α-thalassemia was associated with even higher MCV and MCH values. The Hb E-β 0-thalassemia patients carried a non-transfusion-dependent thalassemia phenotype with an average Hb of around 10 g/dL without blood transfusion. A hitherto undescribed double heterozygous β 0-thalassemia with 3.4 kb deletion and α-globin gene triplication presented as a plain β-thalassemia trait. Most of the subjects had wild-type sequences for the four high Hb F SNPs examined. No significant difference in Hb F was observed between those of subjects with and without these SNPs. Removal of the 5´β-globin promoter may likely be responsible for this unusual phenotype.
Conclusions
The results indicate that β 0-thalassemia with 3.4 kb deletion is a mild β-thalassemia allele. This information should be provided at genetic counseling and prenatal thalassemia diagnosis.
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