Identification of a large deletion and three novel mutations in exon 13 of the factor V gene in a Spanish family with normal factor V coagulant and anticoagulant properties

Abstract

As part of the GAIT (genetic analysis of idiopathic thrombophilia) project, we analyzed polymorphisms in the factor V (FV) gene to assess their role as genetic determinants of normal phenotypic variation of hemostasis-related traits in a Spanish population. During the analysis of exon 13 polymorphisms, we detected an abnormal PCR-amplified fragment in some members of the GAIT19 family. Direct sequence analysis revealed a deletion of 108 bp in eight out of 20 individuals in this family. This deletion removes exactly 36 amino acids from the B domain of FV; thus it does not alter the reading frame of the sequence. Among the deleted amino acids there is the 4070A>G polymorphism (H1299R), which could affect the level or function of FV. In addition, in the same family we identified three novel DNA variants (L1257I, Q1317Q and T1327T) in exon 13 of the F5 gene. Despite these variants, we did not detect any differences either in the coagulant or anticoagulant traits, or in the plasma protein levels involved in the blood coagulation cascade, between the carriers compared with their non-carrier relatives. From these results, we can conclude that the mutant allele is expressed and the resultant protein is functional. Moreover, it is unlikely that the 4070A>G polymorphism, within the deletion, and the novel DNA variants alter the functional properties of the mature FV protein. Further analyses of this naturally occurring mutation and the novel DNA variants should yield useful information for the understanding of the function of the B domain of FV.

A new locus on chromosome 18 that influences normal variation in activated protein C resistance phenotype and factor VIII activity and its relation to thrombosis susceptibility

“…43 Our results are consistant with a naturally occurring mutation that also provided evidence for a nonfunctional role of the His1299Arg polymorphism in the phenotypic variability of APCR values. 44 In summary, these results represent the first direct evidence that APCR and FVIII levels, which are major risk factors underlying liability to thrombosis, are jointly influenced by a QTL on chromosome 18. Our results also support the conclusion that this QTL is an important modulator of an individual's susceptibility to thrombosis.…”

Advances in understanding the bleeding diathesis in factor V deficiency

“…This is due to the fact that amino acid changes in the B domain are unlikely to cause FV deficiency, because the B domain is subject to looser structural constraints than the A and C domains. In fact, even a naturally occurring 108‐bp deletion causing the in‐frame deletion of 36 amino acids within the B domain did not affect FV expression or activity (Soria et al , 2002).…”

Novel family-based approaches to genetic risk in thrombosis

“…Other linkage studies restricted to candidate gene regions include those on a large Vermont pedigree [48,49] and an early linkage study of quantitative variation in histidine‐rich glycoprotein on a large Dutch kindred [50]. Family‐based association inferences related to thrombosis have been performed in nuclear families [35,37] and extended pedigrees [42–44,51–53].…”