Four novel large deletions and complex variants were identified in α-globin locus in Chinese population

Background: At present, the usual methods used to detect a-thalassemia mutations are confined to detect the common mutations, which may easy to result in misdiagnosis or missed diagnosis. Single molecule real time sequencing (SMRT) enables long-read single-molecule sequencing with high detection accuracy, and long-length DNA chain reads in high-fidelity reads mode. Methods: : Herein, we used SMRT to detect rare and complex variants in a-globin locus in four individuals whose hematological data indicated microcytic hypochromic anemia but conventional thalassemia detecting result was negative. Multiplex ligation-dependent probe amplification (MLPA) and droplet digital polymerase chain reaction (ddPCR) were used to confirm the results of SMRT. Results: : We found 4 novel large deletions ranging from 23 kb to 81 kb in a-globin locus, among which one patient also has a duplication inserted in the deletional fragment. In addition, one patient with 27.31 kb deletion on chromosome 16 (hg 38) was also detected to be abnormal hemoglobin Siriraj (Hb Siriraj). Conclusion: We first identified the four novel deletions in a-globin locus by using SMRT. Given that conventional methods may lead to misdiagnosis or missed diagnosis, SMRT served as a good method to discover rare and complex variants in thalassemia, especially in prenatal diagnosis.