Clinical and functional characterization of p.Lys322stop variant in the SERPINC1 gene causing severe thrombophilia.

BACKGROUND

Identification of mutations in the SERPINC1 has illuminated the intricate pathways underlying antithrombin (AT) deficiency. Our group identified a variation in the SERPINC1 gene (c.964 A > T, p.Lys322stop) and further investigated the mechanism of this variant causing AT deficiency.

METHODS

Multiple in silico tools were utilized to predict the conservation of mutations and their impact on the AT structure. The coagulation state was evaluated using the thrombin generation assay. Recombinant AT was overexpressed in HEK293T cells. Intracellular kinetics and extracellular secretion of recombinant AT-K322* were scrutinized by RT-qPCR, Western blotting, ELISA, and immunocytofluorescence.

RESULTS

Analysis of conservation in silico indicated 43 out of the 143 amino acids deleted byAT-K322* in AT were highly conserved across homologous species. In vitro expression experiments showed that there was no significant difference in mRNA levels between the mutant (AT-K322*) and wild-type (AT-WT) forms of the protein. The truncated AT-K322* protein was clearly detected in cell lysates, but not in the culture medium.

CONCLUSION

AT-K322* resulted in the generation of a truncated protein, which in turn affected the secretion of AT, ultimately leading to AT deficiency.