Molecular characterization of beta-thalassemiamutations in Ninawa governorate


Objectives: There are currently more than 200 known mutations affecting the beta globin gene; about 20 mutations account for 90 % of beta globin gene mutations in the world, and each ethnic population has its own unique and frequency of beta globin mutations. Prenatal diagnosis requires identification of the mutation spectrum in each population, and then it is possible to do direct identification for these mutations in the majority of the population. The aim of this study is to characterize the spectrum of beta globin gene mutations in Ninawa governorate patients with beta- thalassemia major.
Patients and methods: Twenty four thalassemic patients were included; they were transfusion dependent and they were diagnosed and registered in thalassemia center of Ninawa governorate. After DNA extraction from venous blood and PCR based DNA amplification, the allele's characterization was achieved by reverse hybridization to specific oligonucleotide probe designed to detect 22 beta-thalassemic mutations.
Results: Out of the forty eight alleles studied, 42 (87.5%) alleles were characterized, while 6 (12.5%) alleles were undetermined.
Eight alleles causing beta-thalassemia in Ninawa governorate were identified in these patients, and these alleles with their frequencies were:
IVS 1.110 (G>A)(27.08%), IVS 1.6 (T>C)(14.5%), cod 8 (-AA)(12.5%), cod 39 (C>T)(12.5%), IVS 2.1 (G>A)(12.5%), cod 44 (-C)(4.16%), IVS 1.5(GC)(2.08%) and Cod 5(-CT)(2.08%).
More than 1/3 of the families have more than one affected sibling.
Eleven (45.83%) patients had homozygous alleles, and 12 (50%) patients with compound heterozygous alleles; In 1 (4.16%) patient the genotype was unknown.
Keywords: Thalassemia, beta globin genes mutations, Ninawa, oligonucleotide, reverse hybridization.