Characterization of two novel Alu element-mediated α-globin gene cluster deletions causing α 0-thalassemia by targeted next-generation sequencing

Mol Genet Genomics. 2020 Mar;295(2):505-514. doi: 10.1007/s00438-019-01637-w. Epub 2020 Jan 2.

Abstract

α-thalassemia is an inherited blood disorder commonly caused by deletions or point mutations involving one or both α-globin genes. Recent studies shed new light on the critical role of upstream enhancers multi-species conserved sequences (MCSs) in the ordered regulation of α-globin gene expression. Herein, we reported two unrelated probands with deletions in α-globin genes and MCSs, respectively. The proband from Family A is a compound heterozygote carrying a known α+ mutation (-α3.7) and a novel 60.2 kb deletion causing the absence of both α-globin genes. The proband from Family B, on the other hand, is a compound heterozygote with a known α0 mutation (--SEA) and a novel deletion involving only upstream regulatory elements MCS-R1, R2 and R3, while the α-globin genes remain intact. Notably, both these two patients suffered varied extent of anemia, indicating that the loss of enhancer elements could equally lead to reduced synthesis of α-globin. Upon these observations, we then confirmed the exact breakpoints of these two novel deletions using a targeted next-generation sequencing (NGS) previously established by our group, which may enable further elucidation of the rearrangement mechanisms on these deletions and functional dissection of MCSs. Taken together, our study reports a reliable NGS-based molecular screening approach for accurate identification of copy number variations (CNVs) in the α-globin cluster and the genetic diagnosis of these two probands may help to extend the spectrum of α-thalassemia mutations in Chinese population.

Keywords: Breakpoints; Copy number variations; Multi-species conserved sequence; Rearrangement mechanisms; Targeted next-generation sequencing; α-thalassemia.

MeSH terms

  • Adult
  • Alu Elements / genetics*
  • Anemia / blood
  • Anemia / genetics*
  • Anemia / pathology
  • DNA Copy Number Variations / genetics
  • Female
  • High-Throughput Nucleotide Sequencing
  • Humans
  • Male
  • Middle Aged
  • Multigene Family / genetics
  • Pedigree
  • Point Mutation / genetics
  • Sequence Deletion / genetics
  • alpha-Globins / genetics*
  • alpha-Thalassemia / blood
  • alpha-Thalassemia / genetics*
  • alpha-Thalassemia / pathology

Substances

  • alpha-Globins