Dataset Information

Unravelling the Complexity of the +33 C>G [HBB:c.-18C>G] Variant in Beta Thalassemia.

ABSTRACT: The +33 C>G variant [NM_000518.5(HBB):c.-18C>G] in the 5' untranslated region (UTR) of the β-globin gene is described in the literature as both mild and silent, while it causes a phenotype of thalassemia intermedia in the presence of a severe β-thalassemia allele. Despite its potential clinical significance, the determination of its pathogenicity according to established standards requires a greater number of published cases and co-segregation evidence than what is currently available. The present study provides an extensive phenotypic characterization of +33 C>G using 26 heterozygous and 11 compound heterozygous novel cases detected in Cyprus and employs computational predictors (CADD, RegulomeDB) to better understand its impact on clinical severity. Genotype identification of globin gene variants, including α- and δ-thalassemia determinants, and rs7482144 (XmnI) was carried out using Sanger sequencing, gap-PCR, and restriction enzyme digestion methods. The heterozygous state of +33 C>G had a silent phenotype without apparent microcytosis or hypochromia, while compound heterozygosity with a β+ or β0 allele had a spectrum of clinical phenotypes. Awareness of the +33 C>G is required across Mediterranean populations where β-thalassemia is frequent, particularly in Cyprus, with significant relevance in population screening and fetal diagnostic applications.

SUBMITTER: Stephanou C

PROVIDER: S-EPMC10886608 | biostudies-literature | 2024 Jan

REPOSITORIES: biostudies-literature

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Unravelling the Complexity of the +33 C>G [HBB:c.-18C>G] Variant in Beta Thalassemia.

Stephanou Coralea C Petrou Miranda M Kountouris Petros P Makariou Christiana C Christou Soteroula S Hadjigavriel Michael M Kleanthous Marina M Papasavva Thessalia T

Biomedicines 20240127 2

The +33 C>G variant [NM_000518.5(HBB):c.-18C>G] in the 5' untranslated region (UTR) of the β-globin gene is described in the literature as both mild and silent, while it causes a phenotype of thalassemia intermedia in the presence of a severe β-thalassemia allele. Despite its potential clinical significance, the determination of its pathogenicity according to established standards requires a greater number of published cases and co-segregation evidence than what is currently available. The prese ...[more]

PMID: 38397898

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Project description:BackgroundThe frequency of the beta-thalassemia (β-thalassemia) gene in Indonesia ranges from 3 to 10%. However, in the East Java province, there is still limited information on the prevalence of β-thalassemia mutations in clinically diagnosed beta-thalassemia patients of East Java. Therefore, this study aimed to characterize β-thalassemia mutations in selected patients in the East Java province of Indonesia.MethodsThis is an analytical observational study. Diagnosis of β-thalassemia was based on clinical presentation, complete blood count (CBC), and hemoglobin (Hb) electrophoresis. Blood specimens taken from each patient in three ethylenediaminetetraacetic acid (EDTA) tubes were analyzed for CBC and Hb electrophoresis and processed for DNA extraction and subsequent polymerase chain reaction (PCR). Detection of mutations in Hemoglobin Subunit Beta (HBB) gene exons 1-3 of the β-thalassemia gene as the common mutation in Indonesia was done using PCR followed by Sanger sequencing.ResultsIn total, 33 (n = 33) participants were involved in this study with ages ranging from 5 to 17 years comprising 19 women and 14 men. Their ethnic origins were Javanese (n = 30) and Chinese (n = 3). CBC results showed that mean ± standard deviation (SD) for Hb, red blood cell (RBC), mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration (MCHC), and red cell distribution width (RDW)-CV were 81.2 ± 7.0 g/L; 3.40 ± 0.39 × 109/L; 71.05 ± 5.72 fL; 24.12 ± 2.45 pg; 33.91 ± 1.47 g/dl; 24.38 ± 6.02%, respectively. Hb electrophoresis revealed that 5 out of 33 participants had beta-thalassemia and 28 out of 33 participants had hemoglobinopathy (Hb) E/beta-thalassemia. Results of Sanger sequencing showed the following genotype variations in the samples: 12 (36.4%) with β CD26 /β IVS-I-5; 6 (18.2%) with β CD26 /β CD35; 3 (9.1%) with β CD26 /β IVS-I-2; 2 (6.1%) with β CD27/28 /β CD40; 2 (6.1%) with β IVS-I-1 /β CAP+1; and β CD26 /β IVS-I-1; β IVS-I-5 /β CAP+1; β IVS-I-5 /β CD35; β CD26 /β CD37; β CD26 /β CD15; β CD26 /β CD40; and β IVS-I-5 /β CD19 in 1 (3%) sample, respectively, and 1 (3%) had no abnormality detected in sequencing even though electrophoresis showed abnormality in the migration pattern. The β CD26 /β IVS-I-5 mutation was found in samples that were noted to have Hb E/beta-thalassemia on Hb electrophoresis.ConclusionThe underlying genetic variations are heterogeneous in thalassemia patients in East Java, where 12 variants were found. The most common variant was β CD26 /β IVS-I-5, which all accounted for Hb E/beta-thalassemia on Hb electrophoresis. Furthermore, 28 out of 33 participants had hemoglobinopathy (Hb) E/beta-thalassemia.

Project description:Amyloids, large intermolecular sandwiched β-sheet structures, underlie several protein misfolding diseases but have also been shown to have functional roles and can be a basis for designing smart and responsive nanomaterials. Short segments of proteins, called aggregation-prone regions (APRs), have been identified that nucleate amyloid formation. Here we present the database of 173 APR crystal structures currently available in the PDB, and a tool, ACW, for analyzing their topologies and the 267 inter-β-sheet interfaces of zipper regions assigned in these structures. We defined a new descriptor of zipper interfaces, the surface detail index (SDi), which quantifies the intertwining between the side chains of both β-sheets of the zipper, an important factor for the molecular recognition and self-assembly of these mesostructures. This allowed a comparative analysis of the zipper interfaces and identification of 6 clusters with different intertwining, steric fit, and size characteristics using three complementary descriptors, SDi, shape complementarity, and buried surface area. 60% of the APR structures are formed by parallel β-sheets, of which 52% belong to the topological class 1. This could be explained by the better fit and a deeper entanglement of the zipper regions of the parallel structures than of the antiparallel structures, as the analysis showed that both their shape complementarity (0.79 vs 0.70) and SDi (1.53 vs 1.32) were higher. The higher abundance of certain residues (Asn and Gln in parallel and Leu and Ala in antiparallel β-sheets) can be explained by their ability to form different ladder-like secondary interaction patterns within β-sheets. Analogous to the hierarchy of protein structure, we interpreted the primary, secondary, tertiary, and quaternary structure levels of APRs revealing different characteristics of the zipper regions for both parallel and antiparallel β-sheet structures, which may provide clues to the structural conditions of amyloid core formation and the rational design of amyloid polymorphs.

Dataset Information

Unravelling the Complexity of the +33 C>G [HBB:c.-18C>G] Variant in Beta Thalassemia.

Publications

Unravelling the Complexity of the +33 C>G [HBB:c.-18C>G] Variant in Beta Thalassemia.

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