Compound hemizygous variants in SERPINA7 gene cause thyroxine-binding
globulin deficiency
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