title: Mutation in blood coagulation factor V associated with resistance to activated protein C.
abstract: Activated protein C (APC) is a serine protease with potent anticoagulant properties, which is formed in blood on the endothelium from an inactive precursor. During normal haemostasis, APC limits clot formation by proteolytic inactivation of factors Va and VIIIa (ref. 2). To do this efficiently the enzyme needs a nonenzymatic cofactor, protein S (ref. 3). Recently it was found that the anticoagulant response to APC (APC resistance) was very weak in the plasma of 21% of unselected consecutive patients with thrombosis and about 50% of selected patients with a personal or family history of thrombosis; moreover, 5% of healthy individuals show APC resistance, which is associated with a sevenfold increase in the risk for deep vein thrombosis. Here we demonstrate that the phenotype of APC resistance is associated with heterozygosity or homozygosity for a single point mutation in the factor V gene (at nucleotide position 1,691, G-->A substitution) which predicts the synthesis of a factor V molecule (FV Q506, or FV Leiden) that is not properly inactivated by APC. The allelic frequency of the mutation in the Dutch population is approximately 2% and is at least tenfold higher than that of all other known genetic risk factors for thrombosis (protein C (ref. 8), protein S (ref. 9), antithrombin10 deficiency) together.
authors.affiliation: Hemostasis and Thrombosis Research Center, University Hospital, Leiden, The Netherlands.
authors.forename: R M
authors.initials: RM
authors.lastname: Bertina
authors.forename: B P
authors.initials: BP
authors.lastname: Koeleman
authors.forename: T
authors.initials: T
authors.lastname: Koster
authors.forename: F R
authors.initials: FR
authors.lastname: Rosendaal
authors.forename: R J
authors.initials: RJ
authors.lastname: Dirven
authors.forename: H
authors.initials: H
authors.lastname: de Ronde
authors.forename: P A
authors.initials: PA
authors.lastname: van der Velden
authors.forename: P H
authors.initials: PH
authors.lastname: Reitsma
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D001778:Blood Coagulation Disorders / Q000201:enzymology / Q000235:genetics; D017931:DNA Primers; D004789:Enzyme Activation; D005165:Factor V / Q000235:genetics* / Q000502:physiology; D005260:Female; D006579:Heterozygote; D006720:Homozygote; D006801:Humans; D008297:Male; D008969:Molecular Sequence Data; D010375:Pedigree; D017354:Point Mutation; D011486:Protein C / Q000378:metabolism*; D013924:Thrombophlebitis / Q000201:enzymology / Q000235:genetics*
chemical_list: D017931:DNA Primers; D011486:Protein C; D005165:Factor V