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Compound hemizygous variants in SERPINA7 gene cause thyroxine-binding globulin deficiency
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  • Yanlan Fang,
  • Hong Chen,
  • Qingqing Chen,
  • Chunlin Wang,
  • Li Liang
Yanlan Fang
Zhejiang University School of Medicine First Affiliated Hospital
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Hong Chen
Zhejiang University
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Qingqing Chen
Zhejiang University
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Chunlin Wang
Zhejiang University School of Medicine
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Li Liang
Zhejiang University School of Medicine
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Abstract

Thyroxine-binding globulin (TBG) is encoded by SERPINA7 which located on Xq22.2. SERPINA7 variants caused TBG deficiency which does not require treatment, but the decreased thyroxine may be misdiagnosed as hypothyroidism. We discovered some variants of TBG caused by alterations that differ from previously reported. In this study, we enrolled 32 subjects from 10 families and sequenced the SERPINA7 genes of TBG-deficient subjects. Then variants were analyzed to assess their effect on TBG expression and secretion. Bioinformatics database, protein structure and dynamics simulation were used to evaluate the deleterious effects. Finally, we identified 2 novel and 4 known variants, and found 26 of 30 subjects carried the p.L303F. The DynaMut predictions indicated the variants (p.E91K, p.I92T, p.R294C and p.L303F) exhibited decreased stability. Analyses revealed the p.L303F change the protein stability and flexibility, and it had an impact on the function of TBG, but when coexisted with other variants it might change the conformational structure of the protein and aggravate the damage to the protein. We speculated that the existence of a higher number of variants resulted in lower TBG secretion. Keywords: Thyroxine-binding globulin deficiency; SERPINA7 gene; compound variants; single-nucleotide variants