[Congenital FⅦ Deficiency Associated with a Novel Mutation in F7 Gene].

Abstract

Objective: To identify the genetic mutation of coagulation factor Ⅶ ( F7) gene in a pedigree with coagulation factor Ⅶ (FⅦ) deficiency and explore the molecular pathogenesis.

Methods: The prothrombin time (PT), activated partial thromboplastin time (APTT), thrombin time (TT), D-dimer (DD), fibrin degradation products (FDP) and coagulation factor Ⅶ activity (FⅦ:C) of the proband and her family members were detected by Sysmex-CS5100 analyzer. All exons and exon-intron boundaries of the F7 gene were amplified by PCR followed by direct sequencing. The detected mutation was confirmed by reverse sequencing. The ClustalW software was used to analyze the conservatism of the mutant site. Pathogenicity of the mutation was assessed with Mutation Taster and PolyPhen-2 online bioinformatics software. Structure of the mutant protein was analyzed using Swiss-PdbViewer software.

Results: The results of routine coagulation tests showed that PT of the proband was markedly extended to 42.5 s, and her FⅦ:C significantly reduced to 2%. The FⅦ:C of her grandmother, mother and sister had slightly reduced to 49%, 51%, and 42%, respectively. These coagulant parameters of her father were within the normal range. Genetic analysis reveled a heterozygous G>A change at cDNA 646 in exon 6 of F7 gene in the proband, resulting in a replacement of glycine at 156 of FⅦ catalytic region with serine (p.Gly156Ser). The sequencing results of other exons and exon-intron boundaries of her F7 gene were normal. The proband's grandmother, mother and sister were all the carriers of this missense mutation except her father. Bioinformatics analysis showed that the p.Gly156Ser mutation caused polarity change of the amino acid at this site and formation of side chains, leading to increase of protein instability, which may affect catalytic activity of structural domain. Meanwhile, both Mutation Taster and PolyPhen-2 online bioinformatics software also predicted the pathogenicity of this missense mutation with high scores.

Conclusion: The heterozygous p.Gly156Ser mutation is the direct cause of the reduced FⅦ in this proband.