Beta globin gene cluster haplotypes of the beta thalassemia mutations observed in Denizli province of Turkey.

Objective: Our aim is to identify the beta globin gene cluster haplotypes for the beta thalassemia mutations in Turkey at regional basis. Beta thalassemia mutations included in this study were IVS-I-110 (G>A), FSC 8/9 (+G), IVS-II-1 (G>A), IVS-I-5 (G>C), IVS-I-1 (G>A), IVS-I-6 (T>C) and FSC 8 (-AA).

Methods: We studied 22 unrelated patients with β-thalassemia major and 72 unrelated healthy subjects from our Department's DNA bank. Haplotype analysis was done by polymerase chain reaction (PCR)-based restriction enzyme digestion for the beta globin gene cluster of the following polymorphic restriction sites: Hinc II 5' to ε, Hind III 5' to Gγ, Hind III in the IVS-II 5' to Aγ, Hinc II in pseudo β, Hinc II 3' to pseudo β, Ava II in β, Hinf I 3' to β. Associated haplotypes for the normal control samples (72 individuals, 144 chromosomes) were determined by Arlequin 3.1 software with unknown gametic phase.

Results: According to the results obtained, the most frequent beta globin gene cluster haplotypes in the normal population are (+----++), (+----+-), (-+-++++), (+-----+) with the frequencies of 28.6 %, 17.2 %, 9.8 % and 8.3 % respectively. IVS-I-110 mutation is linked with the haplotypes (+----++) and (+-----+). Observed haplotypes are (+----++) for FSC 8/9 (+G), (-+-+++-) for IVS-II-1 (G>A), (-+-++-+ and -+-++++) for IVS-I-5 (G>C), (+----+- and +------) for IVS-I-1 (G>A), (-++---+) for IVS-I-6 (T>C) and (+-----+) for FSC 8 (-AA).

Conclusions: In conclusion, our region shows the Mediterranean character for the beta thalassemia mutations. According to the obtained results, IVS-I-110 (G>A) mutation linked with haplotype VII (+-----+), IVS-I-5 (G>C) mutation with haplotype IV (-+-++-+), codon 8/9 (+G) linked with haplotype I (+----++) were shown for the first time in Turkish population. The linkage of haplotype (+------) with the IVS-I-1 (G>A) mutation is reported for the first time in the published literature. In Denizli province of Turkey, beta globin gene cluster haplotypes of the normal population are strongly associated with the haplotypes of I (+----++), V (+----+-) and IX (-+-++++) respectively.