The molecular characterization of Beta globin gene in thalassemia patients reveals rare and a novel mutations in Pakistani population.

Introduction: A multicentre study (including four cities in Pakistan) aimed to investigate the frequency and spectrum of alpha and beta thalassemia genetic mutations and XmnI polymorphism of the Gamma Globin gene.

Methods: One hundred and sixty one beta thalassemia patients, identified on the ground of haematological parameters, were screened for mutations of the Alpha (HBA2 and HBA1) and Beta (HBB) Globin genes as well as Gamma (HBG2) Globin gene, -158 Gγ XmnI polymorphism, using a combination of multiplex GAP polymerase chain reaction (PCR), Sanger sequencing and restriction fragment length polymerase (RFLP) based PCR.

Results: Mutations of at least one HBB gene was identified in 157 of 161 patients screened.

Two novel mutations (HBG1: c.-250C > T and HBG2: c.-250C > T) associated with hereditary persistence of fetal hemoglobin.

Mutations within the promoters of either of the γ-globin genes [(G)γ (HBG1) and (A)γ (HBG2)] lead to variably increased levels of fetal hemoglobin (Hb) (Hb F, α2γ2) in the syndrome of hereditary persistence of fetal Hb (HPFH). Carriers of such mutations are clinically asymptomatic and the mutations are usually detected as part of routine screening or family studies. We describe two new nondeletional HPFH mutations, both C > T substitutions at position c.