Study of β-Thalassemia Mutations Using the Polymerase Chain Reaction-Amplification Refractory Mutation System and Direct DNA Sequencing Techniques in a Group of Egyptian Thalassemia Patients

Abstract

The aim of this study was the molecular characterization of β-thalassemia (thal) mutations in a group of 95 Egyptian thalassemic patients from Fayoum in Upper Egypt, Cairo, Alexandria and Tanta in Lower Egypt and the Nile Delta. To identify these anomalies, the polymerase chain reaction-amplification refractory mutation system (PCR-ARMS) technique was used, complemented by direct DNA sequencing for uncharacterized cases.

In 80 of the 95 patients, the β-thal mutation was detected by PCR-ARMS. The most common allele encountered in our study was IVS-I-6 (T→C) (36.3%); the second most common mutation was IVS-I-110 (G→A) (25.8%). In addition, we report three homozygous cases for the promoter region −87 (C→G) allele with a frequency of 3.2%. DNA sequencing of uncharacterized cases (14 cases, 15 alleles) revealed six cases (six alleles) of codon 27 (G→T), and three cases (three alleles) of the IVS-II-848 (C→A) mutation. Codon 37 (G→A) in the homozygous state was found in one patient with positive consanguinity. The frameshift codon 5 (−CT) mutation was detected in two of our uncharacterized cases. The codon 15 (TGG→TGA) mutations was detected in one patient (one allele, 0.5%). All studied cases were fully characterized by this strategy.

Screening for β-thalassemic mutations using ARMS-PCR for the seven most frequent alleles in Egypt succeeded in determining the β-globin genotype in 84.2% of our patients (91.6% of the expected alleles). To improve the efficiency of routine screening, the PCR-ARMS mutation panel should be updated to include the reported rare alleles. Direct DNA sequencing is an additional way to allow a full characterization of β-thal patients in the Egyptian population.

Keywords:

• β-Thalassemia (thal) mutations
• DNA sequencing
• β-Thalassemia in Egypt