Irene D. Bezemer

Gene variants associated with deep vein thrombosis.

CONTEXT The genetic causes of deep vein thrombosis (DVT) are not fully understood. OBJECTIVE To identify single-nucleotide polymorphisms (SNPs) associated with DVT. DESIGN, SETTING, AND PATIENTS We used 3 case-control studies of first DVT. A total of 19 682 gene-centric SNPs were genotyped in 443 cases and 453 controls from the Leiden Thrombophilia Study (LETS, 1988-1992). Twelve hundred six SNPs associated with DVT were reinvestigated in the Multiple Environmental and Genetic Assessment of Risk Factors for Venous Thrombosis study (MEGA-1, 1999-2004) in a subset of 1398 cases and 1757 controls. Nine SNPs associated with DVT in both LETS and MEGA-1 were investigated a third time in 1314 cases and 2877 controls from MEGA-2, a second subset of MEGA. Additional SNPs close to one SNP in CYP4V2 were genotyped in LETS and MEGA-1. MAIN OUTCOME MEASURE Odds ratios (ORs) for DVT were estimated by logistic regression. False discovery rates served to investigate the effect of multiple hypothesis testing. RESULTS Of 9 SNPs genotyped in MEGA-2, 3 were strongly associated with DVT (P < .05; false discovery rate < or =.10): rs13146272 in CYP4V2 (risk allele frequency, 0.64), rs2227589 in SERPINC1 (risk allele frequency, 0.10), and rs1613662 in GP6 (risk allele frequency, 0.84). The OR for DVT per risk allele was 1.24 (95% confidence interval [95%CI], 1.11-1.37) for rs13146272, 1.29 (95% CI, 1.10-1.49) for rs2227589, and 1.15 (95% CI, 1.01-1.30) for rs1613662. In the region of CYP4V2, we identified 4 additional SNPs (in CYP4V2, KLKB1, and F11) that were also associated with both DVT (highest OR per risk allele, 1.39; 95% CI, 1.11-1.74) and coagulation factor XI level (highest increase per risk allele, 8%; 95% CI, 5%-11%). CONCLUSIONS We identified SNPs in several genes that were associated with DVT. We also found SNPs in the region around the SNP in CYP4V2 (rs13146272) that were associated with both DVT and factor XI levels. These results show that common genetic variation plays an important role in determining thrombotic risk.

The Value of Family History as a Risk Indicator for Venous Thrombosis

BACKGROUND A positive family history of venous thrombosis may reflect the presence of genetic risk factors. Once a risk factor has been identified, it is not known whether family history is of additional value in predicting an individuals risk. We studied the contribution of family history to the risk of venous thrombosis in relation to known risk factors. METHODS In the Multiple Environmental and Genetic Assessment of risk factors for venous thrombosis, a population-based case-control study, we collected blood samples and information about family history and environmental triggers from 1605 patients with a first venous thrombosis and 2159 control subjects. RESULTS A total of 505 patients (31.5%) and 373 controls (17.3%) reported having 1 or more first-degree relatives with a history of venous thrombosis. A positive family history increased the risk of venous thrombosis more than 2-fold (odds ratio [95% confidence interval], 2.2 [1.9-2.6]) and up to 4-fold (3.9 [2.7-5.7]) when more than 1 relative was affected. Family history corresponded poorly with known genetic risk factors. Both in those with and without genetic or environmental risk factors, family history remained associated with venous thrombosis. The risk increased with the number of factors identified; for those with a genetic and environmental risk factor and a positive family history, the risk was about 64-fold higher than for those with no known risk factor and a negative family history. CONCLUSIONS Family history is a risk indicator for a first venous thrombosis, regardless of the other risk factors identified. In clinical practice, family history may be more useful for risk assessment than thrombophilia testing.

Multiple SNP testing improves risk prediction of first venous thrombosis

There are no risk models available yet that accurately predict a persons risk for developing venous thrombosis. Our aim was therefore to explore whether inclusion of established thrombosis-associated single nucleotide polymorphisms (SNPs) in a venous thrombosis risk model improves the risk prediction. We calculated genetic risk scores by counting risk-increasing alleles from 31 venous thrombosis-associated SNPs for subjects of a large case-control study, including 2712 patients and 4634 controls (Multiple Environmental and Genetic Assessment). Genetic risk scores based on all 31 SNPs or on the 5 most strongly associated SNPs performed similarly (areas under receiver-operating characteristic curves [AUCs] of 0.70 and 0.69, respectively). For the 5-SNP risk score, the odds ratios for venous thrombosis ranged from 0.37 (95% confidence interval [CI], 0.25-0.53) for persons with 0 risk alleles to 7.48 (95% CI, 4.49-12.46) for persons with more than or equal to 6 risk alleles. The AUC of a risk model based on known nongenetic risk factors was 0.77 (95% CI, 0.76-0.78). Combining the nongenetic and genetic risk models improved the AUC to 0.82 (95% CI, 0.81-0.83), indicating good diagnostic accuracy. To become clinically useful, subgroups of high-risk persons must be identified in whom genetic profiling will also be cost-effective.

Genetic variants associated with deep vein thrombosis: the F11 locus.

Summary.  Background : Recent studies have found associations between deep vein thrombosis (DVT) and single nucleotide polymorphisms (SNPs) in a 4q35.2 locus that contains genes encoding factor XI (F11), a cytochrome P450 family member (CYP4V2), and prekallikrein (KLKB1).

A Follow-Up Study of a Genome-wide Association Scan Identifies a Susceptibility Locus for Venous Thrombosis on Chromosome 6p24.1

To identify genetic susceptibility factors conferring increased risk of venous thrombosis (VT), we conducted a multistage study, following results of a previously published GWAS that failed to detect loci for developing VT. Using a collection of 5862 cases with VT and 7112 healthy controls, we identified the HIVEP1 locus on chromosome 6p24.1 as a susceptibility locus for VT. Indeed, the HIVEP1 rs169713C allele was associated with an increased risk for VT, with an odds ratio of 1.20 (95% confidence interval 1.13-1.27, p = 2.86 x 10(-9)). HIVEP1 codes for a protein that participates in the transcriptional regulation of inflammatory target genes by binding specific DNA sequences in their promoter and enhancer regions. The current results provide the identification of a locus involved in VT susceptibility that lies outside the traditional coagulation/fibrinolysis pathway.

New gene variants associated with venous thrombosis: a replication study in White and Black Americans

Summary.  Background: We evaluated 10 single‐nucleotide polymorphisms (SNPs) identified in three European case–control studies as risk factors for venous thrombosis. Objectives: We sought to replicate the positive findings from this report among Whites and to evaluate the association of these SNPs with venous thrombosis for the first time among Blacks. Patient/methods: These SNPs were evaluated in a case–control study of deep vein thrombosis and pulmonary embolism that included 1076 cases and 1239 controls. About 50% of subjects were African Americans. We measured plasma factor (F) XI on a subset of subjects. Results: Among Whites, positive findings for rs13146272 in the CYP4V2 gene, for rs3087505 in the KLKB1 gene and for rs3756008 and rs2036914 in the F11 gene were found. We did not find significant associations for rs2227589 in the SERPINC1 gene and for rs1613662 in the GP6 gene. Among Blacks, rs2036914 in F11 and rs670659 in RGS7 were related to venous thrombosis, but the study had limited statistical power for many SNPs. Among Blacks, plasma FXI was related to two SNPs and the OR relating to the 90th percentile of the control distribution of plasma FXI was 2.6 (95% CI, 1.4, 5.0). Conclusions: Our study supports the finding that genetic variants in the F11 gene are risk factors for venous thrombosis among both Whites and Blacks, although the findings in Blacks require confirmation. A meta‐analysis of five case–control studies indicates that rs2227589 in the SERPINC1 gene, rs13146272 in the CYP4V2 gene and rs1613662 in the GP6 gene are risk factors for venous thrombosis among Whites.

Cell adhesion molecule 1: a novel risk factor for venous thrombosis

Protein C (PC) deficiency increases the risk of venous thrombosis (VT) among members of Kindred Vermont II but fails to fully account for the inheritance pattern. A genome scan of the pedigree supported the presence of a prothrombotic gene on chromosome 11q23 (nominal P < .0001), with weaker support on chromosomes 10p12 (P < .0003) and 18p11.2-q11 (P < .0007). Resequencing of 109 genes in the linkage regions identified 5030 variants in a sample of 20 kindred members. Of 16 single nucleotide polymorphisms in 6 genes tested in the larger family set, only single nucleotide polymorphisms in cell adhesion molecule 1 (CADM1) associated with VT. Among the 8 CADM1 single nucleotide polymorphisms genotyped in the complete sample, rs6589488 was most strongly supported (P < .000007), but the association was limited to the PC-deficient subset of the sample (P < .000001). Haplotype analysis narrowed the region containing the causative variant to the coding region of the CADM1 gene. CADM1 gene expression analyzed in blood outgrowth endothelial cells cultured from family members was decreased compared with control subjects, lending phenotypic support to this conclusion. Finally, we have for the first time demonstrated CADM1 in endothelial cells, where it appears to be selectively involved in endothelial cell migration, suggesting a role in endothelial barrier repair.

Mechanisms of the Factor V Leiden Paradox

Objective—Carriers of the factor V Leiden mutation (FVL-carriers) have a substantially increased risk of deep venous thrombosis (DVT), whereas the risk of pulmonary embolism (PE) is only mildly increased compared with noncarriers. So far few studies have investigated possible mechanisms for this so-called FVL paradox. Methods and Results—Consecutive patients with a first DVT or PE were included in a large population-based case–control study (MEGA study). Patients, aged 18 to 70 years, provided a questionnaire, DNA (n=3313), or plasma (n=1474). Surgery, injury, and travel were considered thrombosis-provocative. Of 2063 patients with isolated DVT, 20% were FVL-carrier, as were 8% of the 885 patients with isolated PE. Among DVT patients, FVL-carriers had their thrombi more often proximal and a higher number of affected veins than noncarriers. No differences were observed between FVL-carriers and noncarriers in time between provocation and diagnosis, in vitro coagulation time, and thrombus density. Compared with patients with both DVT and PE, isolated DVT patients more often had thrombi located distally and had a similar number of affected veins. Compared with isolated PE patients, isolated DVT patients had a similar time between provocation and diagnosis, and similar in vitro coagulation time and thrombus density. Conclusion—Although some effects were differential for FVL-carriers and noncarriers, and some were differential for PE and DVT patients, none of the potential mechanisms offered a clear explanation.

Protein S levels and the risk of venous thrombosis: results from the MEGA case-control study

In thrombophilic families, protein S deficiency is clearly associated with venous thrombosis. We aimed to determine whether the same holds true in a population-based case-control study (n = 5317). Subjects were regarded protein S deficient when protein S levels were < 2.5th percentile of the controls. Free and total protein S deficiency was not associated with venous thrombosis: free protein S < 53 U/dL, odds ratio [OR] 0.82 (95% confidence interval [CI], 0.56-1.21) and total protein S < 68 U/dL, OR 0.90 (95% CI, 0.62-1.31). When lower cutoff values were applied, it appeared that subjects at risk of venous thrombosis could be identified at levels < 0.10th percentile of free protein S (< 33 U/dL, OR 5.4; 95% CI, 0.61-48.8). In contrast, even extremely low total protein S levels were not associated with venous thrombosis. PROS1 was sequenced in 48 subjects with free protein S level < 1st percentile (< 4 6 U/dL), and copy number variations were investigated in 2718 subjects, including all subjects with protein S (free or total) < 2.5th percentile. Mutations in PROS1 were detected in 5 patients and 5 controls reinforcing the observation that inherited protein S deficiency is rare in the general population. Protein S testing and PROS1 testing should not be considered in unselected patients with venous thrombosis.

Updated Analysis of Gene Variants Associated With Deep Vein Thrombosis

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