Molecular heterogeneity of beta-thalassaemia in a Spanish population from the area centre of Spain

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.

First Spanish Case Of Thalassemia Major Due to a Compound Heterozygosity for the IVS-II-848 (C→A) And Codon 39 (C→T) Mutations Of The β-Globin Gene

This report describes the first case in Spain of a severe form of beta-thalassemia (thal) due to a compound heterozygosity for the IVS-II-848 (C --> A) and the nonsense codon 39 (C --> T) mutations. Five members of a family from Cadiz (southern Spain) were studied. The proband was an 8-year-old girl diagnosed as anemic at the age of 13 months. Her father had the codon 39 (C --> T) mutation and her mother the C --> A change at nucleotide (nt) 848 of IVS-II. Haplotype analysis showed that the proband was a compound heterozygote for haplotypes I [+ --> + +] and VII [+ --> +]. This is the first description in Spain of the IVS-II-848 (C --> A) mutation. It appears, from restriction fragment length polymorphism (RFLP) analysis, that this mutation has a different origin in the various populations, where it was found. This observation shows that in this case the association of a beta(0)- and a beta(+)-thal mutation does not lead to a thalassemia intermedia but to a severe thalassemia with very low hemoglobin (Hb) levels. From a therapeutic point of view, early introduction of a transfusion regimen may improve the clinical picture of these children, allowing for better development and growth.

Hb Johnstown [beta 109 (G11) Val-->Leu]: second case described and associated for the first time with beta(0)-thalassemia in two Spanish families

Hb Johnstown, a high oxygen affinity hemoglobin, was identified in four members from two unrelated Spanish families with erythrocytosis and left-shifted hemoglobin-oxygen dissociation curve. This hemoglobin variant, electrophoretically silent, was analyzed by reverse-phase high-performance liquid chromatography, and the mutation was characterized at the DNA level by beta gene sequencing. In one of these families, two members are affected with Hb Johnstown in association with beta(0)-thalassemia. In these cases the erythrocytosis and low values for P(50) due to Hb Johnstown remain in spite of the beta-thalassemia.