Analysis of Rare Thalassemia Genetic Variants Based on Third Generation Sequencing

Thalassemia is a group of common hereditary anemia that cause significant morbidity and mortality around the world, yet precisely diagnosing of thalassemia especially for rare thalassemia variants are still challenging. Long range PCR and long-molecule sequencing on the PacBio Sequel II platform utilized in this study could cover the entire HBA1 , HBA2 and HBB gene which enable to diagnose most of common and rare types of thalassemia variants. In this study, 100 cases of suspected thalassemia were conducted traditional thalassemia testing and third generation sequencing for thalassemia genetic diagnosing. Compared with traditional diagnostic methods, here additional 10 cases of rare clinically significant variants, including 3 cases of structure variants (SVs) and 7 cases of single nucleotide variations (SNVs) were identified, of which a case with -α 3.7 subtype III (-α 3.7III ) was first identified and validated in Chinese population. Other rare variants of 11.1 kb deletions (--11.1/αα), triplicate α-globin genes (aaa 3.7 /αα) and rare SNVs have also been thoroughly detected. The results showed that rare thalassemia variants are not rare but just been miss-diagnosed by conventional methods. The results further validated third generation sequencing as a promising method for rare thalassemia genetic testing.