Whole Gene Sequencing Based Screening Approach to Detect β-Thalassemia Mutations

Abstract

About 200 causative mutations are characterized in the β-globin gene. Beta thalassemia diagnosis is very complicated due to the genetic diversity of HBB gene across different geographical regions of the world. In the present study, we have analyzed 138 clinical specimens among them 66 were from 21 unrelated families (trio samples which had DNA from father, mother and chorionic villus sample/amniotic fluid sample) and 72 individual specimens using newly developed sequencing and PCR based assay. We observed 11 different HBB gene mutations in 138 samples, which were also cited by literature as the most prevalent mutations in Indian sub- continent population. The most common mutation observed in our study was HBB.C.92+5 G>C (GC+CC genotype was observed to be 44.93%). Few interesting case studies like co-inheritance of sickle cell anemia and β- thalassemia traits, compound heterozygosity of beta thalassemia major mutation in the case of twin pregnancy were also focused briefly. Commercially available molecular diagnostic kits of HBB gene can detect and identify targeted mutations but will not detect novel and non-targeted mutations of beta thalassemia in parental blood and fetal samples. Hence, a screening technique involving complete sequencing of HBB gene (β-globin gene) is required along with gap PCR approach to provide complete diagnosis of beta thalassemia disease.