A Novel 165 Kb Duplication Involving the α-Globin Gene Cluster Is Identified by Low-Pass Whole Genome Sequencing in a Chinese Thalassemia Intermedia Patient.

Abstract

Copy number variations (CNVs) involving the α-globin gene cluster can lead to an imbalance in the proportion of α- and β-globin chains and consequently cause clinical symptoms of β-thalassemia. In our case, a 6-year-old boy, clinically diagnosed with β thalassemia intermedia, was admitted for further genetic diagnosis with his family. Targeted sequencing and third generation sequencing (TGS) were used to detect the possible variants of the thalassemia genes. Low-pass whole genome sequencing (lpWGS) was conducted to specify the exact location of relevant CNVs across the genome, which was then validated by multiplex ligation-dependent probe amplification.The results revealed that the patient had a heterozygous β⁰ mutation of Codon17 (A > T) and a full duplication of the α-globin gene cluster, inherited from his mother and father, respectively. Besides, a novel point mutation within the 5' untranslated region of β-Globin (HBB: c. -175 (G > A) was only detected in the patient. This study suggests that lpWGS seems a powerful alternative to detect large CNVs related to thalassemia with second intention for more information of the breakpoints and a simultaneous genome-scale detection of other pathogenic CNVs.