Functional characterization of a novel missense mutation identified in a Turkish patient affected by severe coagulation factor V deficiency.

Factor V (FV) deficiency is a rare coagulation disorder, characterized by a bleeding phenotype varying from mild to severe. To date, 115 mutations have been described along the gene encoding for FV (F5) but only few of them have been functionally characterized. Aim of this study was the identification and the molecular characterization of genetic defects underlying severe FV deficiency in a 7-month-old Turkish patient. Mutation detection was performed by sequencing the whole F5 coding region, exon-intron boundaries and about 300 bp of the promoter region. Functional analysis of the identified missense mutation was conducted by transient expression of wild-type and mutant FV recombinant molecules in COS-1 cells. Two novel mutations: a missense (Pro132Arg) and a 1-bp deletion (Ile1890TyrfsX19) were identified in the F5 gene. While the frameshift mutation is responsible for the introduction of a premature stop codon, likely triggering F5 mRNA to nonsense-mediated mRNA degradation, the demonstration of the pathogenic role of the Pro132Arg mutation required an experimental validation. Expression experiments showed that the missense mutation causes a significant reduction in FV secretion and in the specific activity of the residual secreted molecule (77% and 78% decrease, respectively). This paper reports the identification of two novel mutations responsible for FV deficiency, thus widening the mutational spectrum of the F5 gene. The Pro132Arg mutation adds to the only other two functionally characterized missense defects in the FV A1 domain.

The association of factor V Leiden with myocardial infarction is replicated in 1880 patients with premature disease.

AIMS: Gain-of-function variants of genes encoding coagulation factor V (F5 G1691A) and prothrombin (F2 G20210A) cause hypercoagulability and are established risk factors for venous thrombosis. A meta-analysis of 66,155 cases and 91,307 controls found that either polymorphism is associated with a moderately increased risk of coronary artery disease (CAD). Because genetic factors play a particularly important role when acute myocardial infarction (AMI) occurs in the young, we chose to replicate these results by investigating, in the frame of a case-control study, a large cohort of Italian patients who had AMI before the age of 45years. METHODS AND RESULTS: In 1880 patients with AMI (1680 men and 210 women) and an equal number of controls, the minor A allele of F5 G1691A (2.6% frequency in cases and 1.7% in controls) was associated with an increased risk of AMI, the association remaining significant after adjustment for traditional risk factors (OR, 1.66; 95% CI, 1.15-2.38; P=0.006). The positive association with AMI for the minor A allele of F2 G20210A (2.5% frequency in cases and 1.9% in controls) did not reach statistical significance (OR, 1.32; 95% CI, 0.96-1.80; P=0.159). CONCLUSIONS: In a large cohort of young AMI patients the gain-of-function variant F5 G1691A was associated with an increased risk of AMI. The findings on the variant F2 G20210A confirmed the previously reported results, but the association was statistically not significant. These data suggest that a number of young patients with AMI carry gene variants associated with a procoagulant phenotype.