[The Effect of p.Thr241Asn and p.Cys389Gly Mutations on Coagulation Factor VII Structure and Function]

To identify F7 gene mutations in one pedigree with congenital coagulation factor VII (FVII) deficiency and explore the effect of F7 gene mutations on the structure and function of FVII.

Prothrombin time (PT) and activated partial thromboplastin time (APTT) were measured based on the one-stage assay, and PT-based one stage assay was used to detect the activity of FII, V, VII and X. Genomic DNA was extracted from the peripheral blood of family members. The sequences of all the exons and exon-intron boundaries of F7 were amplified by polymerase chain reaction (PCR) using specific primers followed by Sanger sequencing. PolyPhen-2, PROVEAN and Swiss-Pdb Viewer software were used to analyze the effect of mutations on the structure and function of FVII.

The proband had a prolonged PT (33.8 s) due to low FVII activity (6.6%) and normal APTT, and had a history of epistaxis. The proband's mother and father displayed a slightly prolonged PT (13.2 and 13.9 s, respectively), and their FVII activity was 40.3% and 38.3%, respectively. The compound heterozygous c.722C>A (p.Thr241Asn) in exon 7 and c.1165T>G (p.Cys389Gly) in exon 8 of F7 gene were identified in the proband, and inherited from his father and mother, respectively. The p.Thr241Asn and p.Cys389Gly missense change were likely to have a damaging effect predicted by polyphen-2 and PROVEAN software. In silico modeling analysis showed that there was one hydrogen bond formed between wild-type Thr241 and Val249, two hydrogen bonds formed between mutant Asn241 and Val249 and between mutant Asn241 and Leu242, as well as one hydrogen bond and one disulfide bond formed between wild-type Cys389 and Leu370 and between wild-type Cys389 and Cys375, respectively. The hydrogen bond formed between mutant Gly389 and Leu370 and disulfide bond formed between mutant Gly389 and Cys375 both broke.

FVII deficiency in this family is caused by p.Thr241Asn and p.Cys389Gly mutation. In silico modeling may be a valuable tool for understanding amino acid residues from variants leading to congenital FVII deficiency.