The Molecular Spectrum of Βeta Thalassemia Mutations in Southeastern, Turkey

Abstract

Objective: Beta-thalassemia (β-thalassemia), which is very common in southern Turkey, is an autosomal recessive genetic disease caused by more than 400 mutations in the Beta-globin (HBB) gene. We aimed to investigate the beta thalassemia mutation profile in this region and contribute to treatment strategies with the study we conducted from patients who applied to our Genetic Diagnosis Center from Gaziantep and its surrounding southeast Anatolian provinces.

Method: In the study, HBB gene mutations were investigated by DNA sequence analysis in 313 unrelated patients who applied to our center. 41% of the patients included in the study were from Syrian migrant families.

Results: A total of 32 different beta globin mutations were detected. The most common mutations are: IVS-I-110 G>A (HBB: c.93-21G>A) 20.65%, Codon 39 C>T (HBB: c.118C>T) 8.63%, IVS I-6 T>C (HBB: c.92+6T>C) 7.10%, IVS I-1 G>A (HBB: c.92+1G>A), 6.88%,  IVS II-1 G>A (HBB: c.315+1G>A) 6.24%, Codon 6 (GAG>GTG) (HbS) (HBB: c.20A>T) 4.52%, CAP +20 C>T (HBB: c.-31C>T) 4.52%, Codon 8 (-AA) (HBB: c.25_26del) 4.30%, -30 (T>A) (HBB: c.-80T>A) 4.09%, IVS II-745 C>G (HBB: c.316-106C>G) 3.87%. We also detected a new variation (HBB: c.92+56G>A) that was not reported before, and six different beta globin gene mutations (HBB: c.90C>T, HBB: c.47G>A, HBB: c. 93- 22_95del, HBB:c.30dup, HBB: c.180G>A , HBB: c.316-30A>C) not previously reported in Turkey. Four of these mutations were detected in Syrian patients (c.90C>T, c.47G>A, c.93-22_95del, c.30dup).

Conclusion: Our study reveals that the mutations that cause beta thalassemia and hemoglobinopathies in the Southeast Anatolia region, which includes Gaziantep and its surrounding provinces, are quite diverse and show some differences compared to other regions.