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Background: The protein C pathway plays an important role in the maintenance of endothelial barrier function and in the inflammatory and coagulant processes that are characteristic of patients on dialysis. We investigated whether common single nucleotide variants (SNV) in genes encoding protein C pathway components were associated with all-cause 5 years mortality risk in dialysis patients., Methods: Single nucleotides variants in the factor V gene (F5 rs6025; factor V Leiden), the thrombomodulin gene (THBD rs1042580), the protein C gene (PROC rs1799808 and 1799809) and the endothelial protein C receptor gene (PROCR rs867186, rs2069951, and rs2069952) were genotyped in 1070 dialysis patients from the NEtherlands COoperative Study on the Adequacy of Dialysis (NECOSAD) cohort) and in 1243 dialysis patients from the German 4D cohort., Results: Factor V Leiden was associated with a 1.5-fold (95% CI 1.1-1.9) increased 5-year all-cause mortality risk and carriers of the AG/GG genotypes of the PROC rs1799809 had a 1.2-fold (95% CI 1.0-1.4) increased 5-year all-cause mortality risk. The other SNVs in THBD, PROC, and PROCR were not associated with 5-years mortality., Conclusion: Our study suggests that factor V Leiden and PROC rs1799809 contributes to an increased mortality risk in dialysis patients.

The procoagulant function of activated factor V (FVa) is inhibited by activated Protein C (APC) through proteolytic cleavages at R306, R506 and R679. Recombinant FVa mutated at all three APC-cleavage sites, FVa-GQA, was still inactivated by APC through at least two cleavages in the heavy chain of FVa; relatively rapid cleavage at R(x1) close to residue 506 and slower cleavage at R(x2) nearby residue 306. We investigated the exact location of these two cleavages, by substitution of arginines by glutamine within the R(x1)-region (R501, R505 or R510) and the R(x2)-region (R313, R316, R317 or R321). Immunoblot and kinetic analyses of the inactivation of activated R(x1)-mutants by APC revealed that using mutant FVa-GQA-505Q no R(x2)-R(x1) fragment was formed and that the inactivation reaction was first order with a rate constant of 1.0 x 10(4) M(-1) s(-1), similar to the rate constant of R(x2) cleavage (k(2)=1.3 x 10(4) M(-1) s(-1)). No single arginine could be pinpointed identified as R(x2). Individual replacement of arginine by glutamine at positions 313, 316, 317 or 321 in FV-GQA-505Q did not result in the disappearance of R(x2) as judged from kinetic and immunoblot analyses. However, replacement of all four arginines by glutamine completely prevented formation of the R(x2)-R(709) fragment. We conclude that substitution of arginine 506 by glutamine as in FV-Leiden, leads to the detection of a novel cleavage site at arginine 505 (R(x1)). Substitution of arginine 306 by glycine, like in FV-Cambridge, reveals several alternative cleavage sites near arginine 306, which together constitute a secondary cleavage site., (Copyright (c) 2009 Elsevier Ltd. All rights reserved.)

Background: Selectins (E-, L- and P-selectin) and their most important counter-receptor P-selectin glycoprotein ligand (SELPLG) facilitate the interaction of platelets, leukocytes and endothelial cells at inflammatory sites. Selectin polymorphisms/haplotypes have been associated with cardiovascular disease., Objectives: We investigated the association between haplotypes (H) of these four genes and deep venous thrombosis (DVT) risk. We additionally explored the effect of linkage disequilibrium (LD) with the nearby Factor V Leiden mutation (FVL). Furthermore, interactions between SELPLG polymorphisms and selectin polymorphisms were investigated., Patients/methods: Leiden Thrombophilia Study (LETS) subjects were genotyped for 24 polymorphisms by TaqMan or PCR-RFLP, detecting all common haplotypes in four blocks. P-selectin was analyzed in two blocks, upstream (SELPup) and downstream (SELPdown) of the recombination hotspot., Results: In E- and L-selectin, none of the haplotypes was associated with DVT risk. In SELPup, H2-carriers had a 1.3-fold increased risk (95% CI, 1.0-1.7), whereas H4-carriers had a 1.4-fold decreased risk (95% CI, 0.5-1.0). In SELPdown, H2-carriers had a 1.3-fold increased risk (95% CI, 1.0-1.7). Because of LD with FVL, we subsequently excluded all FVL-carriers and all risks disappeared. Mutual adjustment within a logistic regression model resulted in disappearance of the risks for the SELP haplotypes, whereas FVL risk remained., Conclusions: After adjustment for LD with FVL, none of the selectin haplotypes was associated with DVT risk, showing that the increased risks of the selectin haplotypes were a reflection of the effect of FVL on thrombosis risk.

Background: Patients with Crohn's disease (CD) and ulcerative colitis (UC) have a three- to fourfold greater risk of venous thrombosis compared with the general population. We aimed to determine if patients with CD and UC had a greater likelihood of mutations in genes that increase clotting risk, in a population-based case-control study., Methods: Subjects were drawn from the University of Manitoba IBD Research Registry and controls were drawn from Manitoba Health's administrative database. Cases (CD, N = 327; UC, N = 165) and controls (N = 412) underwent venipuncture. DNA was purified from whole blood. Genotypes for wild-type and common mutations that have been associated with venous thrombosis for each of Factor II (prothrombin) (G20210A), Factor V (G1691A:'Leiden'), methylenetetrahydrofolate reductase (MTHFR, C677T), and Factor XIII (val34leu) were assessed., Results: A total of 1.5% and 6.1% were heterozygous for Factor II and Factor V variants, respectively, without differences among cases and controls. Only one subject was homozygous for Factor V Leiden (and none were homozygous for Factor II mutation). Although some differences were observed among cases and controls in the prevalence of MTHFR C677T (decrease in mutant allele carriership in UC) and FXIII val34leu (increase in double mutant allele carriership in CD), these did not explain an excess risk of thrombosis. Age, sex, or disease phenotypes were not associated with prothrombotic genotypes., Conclusions: While there was a slightly greater prevalence of Factor XIII mutation carriership in CD, we did not find that gene mutations for these four common factors could explain the greater risk of venous thrombosis in CD and UC.

Background: During the study of a family with hereditary factor (F)V deficiency (FV Amersfoort, 1102 A > T in exon 7) we identified an individual with 5% FV heavy chain antigen (FV(HC)) and 50% FV light chain antigen (FV(LC)). Further testing revealed that apart from the FV Amersfoort allele a second variant FV allele was segregating in this family, which encodes for a FV molecule with a reduced affinity for mAb V-23 used in the FV heavy chain ELISA (ELISA(HC))., Objective: Identification and characterization of the molecular basis responsible for the reduced affinity of the variant FV for mAb V-23., Methods: Family members of the proband were screened for mutations in the exons coding for the heavy chain of FV, after which the recombinant variant FV could be generated and characterized. Next, the cases and controls of the Leiden Thrombophilia Study (LETS) were genotyped for carriership of the variant FV., Results: In the variant FV allele a polymorphism in exon 3 (409G > C) was identified, which predicts the replacement of aspartic acid 79 by histidin (D79H). Introduction of this mutation in recombinant FV confirmed that it reduces the affinity for binding to mAb V-23. The substitution has no effect on FV(a) stability and Xa-cofactor activity. In Caucasians the frequency of the FV-79H allele is approximately 5%. Analysis of the LETS revealed that the FV-79H allele is not associated with FV levels (FV(LC)), activated protein C sensitivity (using an activated partial thromboplastin time-based test) or risk of venous thrombosis (OR 1.07, CI 95: 0.7-1.7)., Conclusion: The D79H substitution in FV should be considered as a neutral polymorphism. The monoclonal antibody V-23, which has a strongly reduced affinity for FV-79H, is not suitable for application in diagnostic tests.

A re-emerging strategy in the search for disease susceptibility genes is the evaluation of candidate genes, which are thought to play a role in disease pathogenesis. Candidate genes are screened for single nucleotide polymorphisms (SNPs) in a case-control study. The factor V Leiden (FVL) mutation (1691G --> A in the F5 gene) is an important risk factor for venous thrombosis. We asked ourselves whether the FVL mutation would have been found using the candidate gene approach in the absence of prior knowledge of the haplotype structure of the F5 gene. We typed four SNPs in the F5 gene in the Leiden Thrombophilia study, that is, promoter (99930G --> A), exon 13 (55907A --> G), exon 16 (42855A --> G), and intron 19 (37833T --> G). These SNPs were known to have different population frequencies, making their presence in distinct haplotypes likely. None of these SNPs has previously been associated with venous thrombotic risk. Subsequently we derived haplotypes. One haplotype was clearly more frequent in patients than controls (GAAT; 20 versus 9%), suggesting that a polymorphism in or near the F5 gene in this haplotype is associated with an increased thrombotic risk. If we had sequenced the F5 gene in patients homozygous for this haplotype, in order to locate the possible causal polymorphism, we would have found that 16 (76%) patients were homozygous or heterozygous for a missense mutation in exon 10 (1691G --> A), which predicts the replacement of Arg506 by Gln in one of the cleavage sites for activated protein C, a mutation that we now know as the FVL mutation.

The R2 haplotype of the FV gene spans from exon 8 through 25 and comprises several strongly linked polymorphisms in the FV gene, including some missense mutations. Carriership of the R2-FV allele has been associated with reduced plasma FV levels, increased FV1/FV2 ratios and mild APC resistance. Some studies have reported that carriership of the R2-FV allele is associated with an increased risk of venous thombosis. At this moment, the individual contribution to the R2-associated phenotypes of the different mutations linked to the R2 haplotype of FV is unclear. The main objective of our study was to obtain insight in the influence of the R2-related Asp2194Gly mutation on FV expression, FV structure and FV function using Bdomainless rFV mutants. Replacing Asp at position 2194 by Gly resulted in a more than threefold reduction of rFV expression compared to rFV wild-type. Therefore, we propose that the R2-linked Asp2194Gly mutation is an important determinant of the association of the R2-FV allele with lower FV levels. Furthermore, the light chains from Asp2194Gly containing rFV mutants showed similar molecular weights as the light chains of the non-glycosylated rFVwt or the plasma FV2 isoform, indicating that glycosylation at Asn2181 is not stimulated by the presence of a glycine in position 2194. Finally, the apparent K(d) for dissociation of the FXaVa complex (K(1/2Xa)) was not higher in rFV mutants with the Asp2194Gly mutation than for rFVwt, suggesting that also the affinity for negatively charged phospholipids is not affected by substitution of Asp into Gly at position at 2194.

Recently, new missense mutations in the activated protein C (APC) cleavage sites of human factor V (FV) distinct from the R506Q (FV Leiden) mutation have been reported. These mutations affect the APC cleavage site at arginine (Arg) 306 in the heavy chain of activated FV. Whether these mutations result in APC resistance and are associated with a risk of thrombosis is not clear. The main objective of the present study was to identify the APC-resistant phenotype of FV molecules with different mutations in APC cleavage sites. To study this, recombinant FV mutants were reconstituted in FV-deficient plasma, after which normalized APC-sensitivity ratios (n-APC-SRs) were measured in activated partial thromboplastin time-based and Russell's Viper Venom time-based APC-resistance tests. The mutations introduced in FV were R306G, R306T, R506Q, R679A and combinations of these mutations. Based on the APC-sensitivity ratios, we conclude that the naturally occurring mutations at Arg306 (i.e. FV HongKong and FV Cambridge) result in a mildly reduced sensitivity for APC (n-APC-SR, 0.74-0.87), whereas much lower values (n-APC-SR, 0.41-0.51) are obtained for the mutation at Arg506 (FV Leiden). No effect on the n-APC-SR was observed for the recombinant FV mutant containing the single Ala679 mutation. Because reduced sensitivity for APC, not due to FV Leiden, is a risk factor for venous thrombosis, these data suggest that mutations at Arg306 might be associated with a mild risk of venous thrombosis.

Context: Estrogens are known to be prothrombotic, and findings from the Heart and Estrogen/progestin Replacement Study suggest that in women with clinically recognized heart disease, hormone replacement therapy (HRT) may be associated with early harm and late benefit in terms of coronary events., Objective: To assess whether, as hypothesized, prothrombotic mutations modify the association between HRT use and incidence of first myocardial infarction (MI)., Design and Setting: Population-based, case-control study conducted in a Seattle-based health maintenance organization., Participants: Cases were 232 postmenopausal women aged 30 to 79 years who had their first nonfatal MI between 1995 and 1998. Controls were a stratified random sample of 723 postmenopausal women without MI who were frequency-matched to cases by age, calendar year, and hypertension status., Main Outcome Measure: Risk of first nonfatal MI based on current use of HRT and the presence or absence of coagulation factor V Leiden and prothrombin 20210 G-->A variants among cases and controls, stratified by hypertension., Results: One hundred eight MI cases and 387 controls had hypertension and 124 MI cases and 336 controls did not. Among hypertensive women, the prothrombin variant was a risk factor for MI (odds ratio [OR], 4.32; 95% confidence interval [CI], 1.52-12.1) and, in this stratum, there was also a significant interaction between use of HRT and presence of the prothrombin variant on risk of MI. Compared with nonusers of HRT with wild-type genotype, women who were current users and who had the prothrombin variant (n = 8) had a nearly 11-fold increase in risk of a nonfatal MI (OR, 10.9; 95% CI, 2.15-55.2). The interaction with the prothrombin variant was more pronounced in analyses assuming 100% compliance than in those assuming 80% compliance with HRT. The interaction was absent among nonhypertensive women and was less pronounced if hypertensive and nonhypertensive women were combined into 1 group. No interaction was found for factor V Leiden in either hypertensive or nonhypertensive women. Among hypertensive women, the estimates were affected only in trivial ways by adjustment, and the interaction with the prothrombin variant was specific to HRT., Conclusions: Our results suggest that among postmenopausal hypertensive women, the association between HRT use and MI risk differed between those with and without the prothrombin 20210 G-->A variant. If these findings are confirmed in other studies, screening for the prothrombin variant may permit a better assessment of the risks and benefits associated with HRT in postmenopausal women.

The HR2 haplotype of the factor V gene, which contains the histidine to arginine substitution at position 1299, has been reported to be associated with reduced factor V levels. Because high factor V levels have been found to be associated with an increased risk of myocardial infarction, we examined how the presence of the R2 allele affected the risk of myocardial infarction in the case-control "Study of Myocardial Infarctions Leiden". Among 560 men with a first myocardial infarction before the age of 70 years, 9.5% were heterozygous carriers of the R2 allele. The control group consisted of 646 men, in which 9.9% were heterozygous and 0.2% homozygous carriers of the R2 allele. The risk of myocardial infarction in the presence of the R2 allele was not increased (odds ratio, 0.9; 95% confidence interval 0.6 to 1.4). Exclusion of factor V Leiden carriers did not change this result. The risk was 4.4-fold increased for smokers who carried the R2 allele compared to non-smoking noncarriers. No synergy was found between metabolic risk factors and the presence of the R2 allele. We conclude that the risk of myocardial infarction for men in the presence of the R2 allele of the His1299Arg polymorphism is neither increased nor decreased.

We studied the HR2 haplotype of the factor V gene in a case-control study for venous thrombosis including 474 patients with a first deep-vein thrombosis and 474 age- and sex-matched healthy controls (Leiden Thrombophilia Study, LETS). We investigated both the original His1299Arg (A4070G) polymorphism and the Met385Thr (T1328C) polymorphism. This latter polymorphism, located in exon 8 (heavy chain), is always present in the HR2 haplotype, but also occurs on its own in a His1299 (wt) background. The HR2 haplotype was not associated with an increased risk of venous thrombosis (OR = 1.2, 95% confidence interval: 0.8-2.0). We did not find an association between the HR2 haplotype and a reduced sensitivity for activated protein C (APC) in non-carriers of factor V Leiden (FVL). However, in compound heterozygous FVL/HR2 carriers the sensitivity for APC was reduced. The HR2 haplotype was also associated with reduced factor V antigen levels in both patients and controls. Sequence analysis of the promoter region of factor V in HR2 homozygotes did not reveal any sequence variations that could explain the reduced FV levels. Our results show that the HR2 haplotype is not associated with an increased risk of venous thrombosis or with a reduced sensitivity for APC in non-FVL carriers. However, the HR2 haplotype is associated with a reduced sensitivity for APC in carriers of FVL and with reduced factor V antigen levels.

Background and Purpose: Factor V Leiden and a prothrombin gene variant, G20210A, are mutations associated with a thrombotic risk. The aim of our study was to assess whether these mutations increase the risk of stroke in women under 45 years of age., Methods: We conducted a case-control study in western Washington state. Case patients were women aged 18 to 44 years with a first stroke (n = 106). Control subjects were women without stroke recruited from the same region by use of random-digit telephone dialing (n = 391). All were interviewed and provided blood specimens, which were genotyped for these mutations., Results: Factor V Leiden was found in 0.9% of case patients, a single patient with a subarachnoid hemorrhage, and in 4.1% of control subjects. The odds ratio (OR) for any stroke was 0.2 (95% confidence interval [CI], 0.03 to 1.7). The prothrombin variant was found in 1.9% of case patients, 1 with a venous stroke and 1 with an ischemic stroke, and in 1.6% of control subjects. The OR for any stroke was 1.48 (95% CI, 0.14 to 9.17). ORs for stroke types were also not statistically significant., Conclusions: In this study, neither factor V Leiden nor the prothrombin variant (G20210A) was an important risk factor for stroke in young women. In this setting, screening for these mutations cannot be recommended. Unanswered by this study is whether screening would be useful in select patients, such as those with a strong family history of thrombophilia or those with venous strokes.