The Factor VII mutation F7 c.760T>C (FVII_p.Cys254Arg) is causative for Factor VII deficiency by impairing secretion

Hereditary Factor VII (FVII) deficiency is a bleeding disorder caused by mutations in the F7 gene, a diagnosis that is complicated by a weak genotype-phenotype correlation. However, accurate pathogenicity assessment of FVII variants is essential for effective clinical management.

Here, we report about the FVII_p.Cys254Arg variant, caused by the F7 c.760T>C mutation. This mutation was found in two patients, father and son, both presenting with FVII deficiency. We aimed to identify the molecular mechanism responsible for the underlying pathogenicity.

Characterization of the FVII_p.Cys254Arg variant was performed using in silico analysis as well as an in vitro expression system. Subcellular localization and secretion of recombinant FVII protein were investigated using Western blotting, a bioluminescent protein quantification assay and confocal laser scanning microscopy.

The FVII_p.Cys254Arg variant results in the loss of a disulfide bond in the protease domain near the catalytic triad, which potentially destabilizes the tertiary protein structure. This leads to impaired secretion, as demonstrated in HEK293T cells and further supported by the FVII deficiency in the patients co-segregating with the mutation.

The molecular analysis confirms the in silico prediction of the FVII_p.Cys254Arg variant as highly pathogenic and establishes this mutation as causative for hereditary FVII deficiency.