Balearic archipelago: three islands, three beta-thalassemia population patterns

A First Clinical and Molecular Study of Rare IVS-II-806 (G > C) (HBB:c.316-45G > C) Variant in the β-globin Gene: A Possibly Benign Variant

Introduction

β-thalassemia is a common genetic disease affecting a single gene, disease with a high incidence in South China. We hereby, aim to provide the clinical and hematological features of a rare β-globin gene variant in the Chinese population.

Methods

Ten subjects from three unrelated Chinese families were enrolled in this study. Hematological analysis and thalassemia gene testing were preformed to screen for common α and β-thalassemia variants. Gap-polymerase chain reaction (Gap-PCR) and DNA sequencing were utilized to examine the rare or novel thalassemia variants.

Results

Six cases were identified carrying the rare IVS-II-806 (G > C) (HBB:c.316-45G > C) variant in the β-globin gene. The proband in family 1 carry three rare β-globin gene mutations including CD39 (C > T), IVS-II-81 (C > T) and IVS-II-806 (G > C) combined with a --SEA/αα deletion, exhibiting the β-thalassemia trait. Further pedigree investigation indicated that the genotype of the proband in family 1 was --SEA/αα, βCD39 (C>T), IVS-II-81(C>T)/βIVS-II-806(G>C). Meanwhile, the twin girls in family 1 carrying the IVS-II-806 (G > C) mutation demonstrated a normal hematological phenotype. In family 2, the proband and his sister carry the IVS-II-806 (G > C) mutation, eliciting high levels of Hb A2 and slightly low levels of MCV and MCH. Moreover, the proband in family 3 carrying the same mutation exhibited a slightly low MCV level as well.

Conclusions

In this study, clinical and hematological analysis of the IVS-II-806 (G > C) mutation was first conducted within the Chinese population, with results indicating that it may be a benign variant.

Genetic variation patterns of β-thalassemia in Western Andalusia (Spain) reveal a structure of specific mutations within the Iberian Peninsula

BACKGROUND

Analyses of the genomic variation in the western Mediterranean population are being used to reveal its evolutionary history and to understand the molecular basis of particular diseases.

AIM

To observe the β-thalassemia mutational spectrum in western Andalusia, Spain, in the context of the Mediterranean. In addition, associations between disease and neutral gene variants within the β-globin gene (HBB) were also evaluated.

SUBJECTS AND METHODS

This study included 63 unrelated individuals diagnosed with β-thalassemia. In addition, 97 unrelated, healthy subjects of the same territory were also analysed as proxies of the normal genetic background. Allele associations and population genetic structure analyses were performed using different methodologies.

RESULTS

Data have revealed a rather restricted spectrum of β-thalassemia mutations in the analysed sample. Although the detected variants fit well with the Mediterranean pattern, certain singularities support a structure of some specific β-thalassemia alleles. The IVSI-1 (G > A) shows a strong regionalisation. The spatial correlogram revealed a typically narrow wave structure, presumably linked to genetic isolation and genetic drift.

CONCLUSIONS

The long history of endemic malaria in the study territory, the rather high consanguinity rates among its autochthonous population, and other demographic features have been used here to understand the western Andalusian β-thalassemia molecular portrait.

Presence of the IVS-I-6-Mutated Allele in Beta-Thalassemia Major Patients Correlates with Extramedullary Hematopoiesis Incidence

Extramedullary hematopoiesis (EMH) results from the extension of hematopoietic tissue beyond the confines of the bones. Since the initiation of regular transfusion programs from an early age for all thalassemia major (ΤΜ) patients, EMH has not been considered a clinical issue anymore. The present study aims to record the prevalence of EMH in chronically transfused ΤΜ patients followed at our institution and to investigate possible risk factors associated with its occurrence. The project was designed as a retrospective, nonexperimental, descriptive, exploratory study. In total, the study enrolled 104 patients. EMH was revealed in 15/104 (14%) patients. The presence of intravening sequence (IVS)-I-6 was significantly related with the development of EMH (p < 0.05). No other demographic or biological factor studied was found to be related with the presence of EMH. The study stresses a profound incidence of asymptomatic EMH in a solid group of well-transfused ΤΜ patients. Given the high incidence of the IVS-I-6 allele in the Mediterranean and Middle Eastern region, high-quality, prospective, multicenter studies could confirm the association of EMH occurrence with the presence of the IVS-I-6 mutation and further evaluate the exact role of this mutation in the EMH process.

Mismatch repair genes founder mutations and cancer susceptibility in Lynch syndrome

Founder mutations in specific populations are common in several Mendelian disorders. They are shared by apparently unrelated families that inherited them from a common ancestor that existed hundreds to thousands of years ago. They have been proven to impact in molecular diagnostics strategies in specific populations, where they can be assessed as the first screening step and, if positive, avoid further expensive gene scanning. In Lynch syndrome (LS), a dominantly inherited colorectal cancer disease, more than 50 founder pathogenic mutations have been described so far in the mismatch repair (MMR) genes (MLH1, MSH2, MSH6 and PMS2). We here provide a comprehensive summary of the founder mutations found in the MMR genes and an overview of their main characteristics. At a time when high-throughput strategies are being introduced in the molecular diagnostics of cancer, genetic testing for founder mutations can complement next generation sequencing (NGS) technologies to most efficiently identify MMR gene mutations in any given population. Additionally, special attention is paid to MMR founder mutations with interesting anthropological significance.

Utility and importance of accurate Hb A2 measurements for defining a strategy for β-thalassemia screening: experience in the Balearic Islands, Spain

The high heterogeneity in regional profiles of β-thalassemia (β-thal) mutations highlights the need for population-specific carrier detection strategies. Our aim was to analyze the relationship between hematological values and β(0) and β(+) mutations in 154 Balearic β-thal heterozygotes, in order to establish the most optimized mutation carrier detection strategy to be used to manage the disease in our population. The Hb A2 level was the best parameter for discriminating between both types of carriers. Taking into account the cut-off point value of 4.85% (Hb A2), obtained by a receiver-operating characteristic (ROC) curve analysis, we proposed an algorithm that would use a real-time polymerase chain reaction (RT-PCR) hybridization probe assay technique to detect one of the two most common mutations in the Balearic population, namely codon 39 (C>T) and IVS-I-110 (G>A), depending on the Hb A2 value of the patient.