Hugoline G. de Haan

Genome-wide association study with additional genetic and post-transcriptional analyses reveals novel regulators of plasma factor XI levels

&NA; Coagulation factor XI (FXI) has become increasingly interesting for its role in pathogenesis of thrombosis. While elevated plasma levels of FXI have been associated with venous thromboembolism and ischemic stroke, its deficiency is associated with mild bleeding. We aimed to determine novel genetic and post‐transcriptional plasma FXI regulators. We performed a genome‐wide association study (GWAS) for plasma FXI levels, using novel data imputed to the 1000 Genomes reference panel. Individual GWAS analyses, including a total of 16,169 European individuals from the ARIC, GHS, MARTHA and PROCARDIS studies, were meta‐analysed and further replicated in 2,045 individuals from the F5L family, GAIT2 and MEGA studies. Additional association with activated partial thromboplastin time (aPTT) was tested for the top SNPs. In addition, a study on the effect of miRNA on FXI regulation was performed using in silico prediction tools and in vitro luciferase assays. Three loci showed robust, replicating association with circulating FXI levels: KNG1 (rs710446, P‐value = 2.07 × 10‐302), F11 (rs4253417, P‐value = 2.86 × 10‐193), and a novel association in GCKR (rs780094, P‐value = 3.56 ×10‐09), here for the first time implicated in FXI regulation. The two first SNPs (rs710446 and rs4253417) also associated with aPTT. Conditional and haplotype analyses demonstrated a complex association signal, with additional novel SNPs modulating plasma FXI levels in both the F11 and KNG1 loci. Finally, eight miRNAs were predicted to bind F11 mRNA. Over‐expression of either miR‐145 or miR‐181 significantly reduced the luciferase activity in cells transfected with a plasmid containing FXI‐3’UTR. These results should open the door to new therapeutic targets for thrombosis prevention.

Single Nucleotide Variant rs2232710 in the Protein Z-Dependent Protease Inhibitor (ZPI, SERPINA10) Gene Is Not Associated with Deep Vein Thrombosis.

Rare mutations in PROC, PROS1 or SERPINC1 as well as common variants in F5, F2, F11 and SERPINC1 have been identified as risk factors for deep vein thrombosis (DVT). To identify novel genetic risk factors for DVT, we have developed and applied next-generation DNA sequencing (NGS) of the coding area of hemostatic and proinflammatory genes. Using this strategy, we previously identified a single nucleotide variant (SNV) rs6050 in the FGA gene and novel, rare SNVs in the ADAMTS13 gene associated with DVT. To identify novel coding variants in the genetic predisposition to DVT, we applied NGS analysis of the coding area of 186 hemostatic and proinflammatory genes in 94 DVT cases and 98 controls and we identified 18 variants with putative role in DVT. A group of 585 Italian idiopathic DVT patients and 550 healthy controls was used to genotype all the 18 risk-associated variants identified by NGS. Replication study in the Italian population identified the rs2232710 variant in the protein Z-dependent protease inhibitor (ZPI) gene to be associated with an increased risk of DVT (OR 2.74; 95% CI 1.33–5.65; P = 0.0045; Bonferroni P = 0.081). However, the rs2232710 SNV showed no association with DVT in two Dutch replication cohorts the LETS study (454 patients and 451 controls) and the MEGA study (3799 patients and 4399 controls), indicating that the rs2232710 variant is not a risk factor for DVT.

Identification of coagulation gene 3′UTR variants that are potentially regulated by microRNAs

MicroRNAs have been recognized as critical regulators of gene expression and might affect the risk of venous thrombosis. We aimed to identify 3′ untranslated region (UTR) variants in coagulation genes that influence coagulation factor levels and venous thrombosis risk. The 3′UTR of coagulation genes were sequenced in subjects with extremely high or low plasma levels of these factors in two case‐control studies. In total, 28 variants were identified. Five single nucleotide polymorphisms (SNPs) were predominantly present in one extreme level group (F2 rs1799963, F8 rs1050705 and F11 rs4253429, rs4253430 and rs1062547). Additional to F2 rs1799963, F8 rs1050705 (in men) and F11 rs4253430 were associated with an increased risk of venous thrombosis albeit confidence intervals were wide. The three F11 SNPs were in high linkage disequilibrium with functional variants rs2289252 and rs2036914. Rs1062547 and rs4253430 were associated with a significant increase of plasma FXI activity in heterozygotes and homozygotes in wild‐type controls. In silico prediction revealed that these SNPs might disturb the binding sites of miR‐544 and miR‐513a‐3p. Only miR‐544 provoked a significant decrease of the luciferase activity that was not observed with a rs4253430 mutated vector. In conclusion, these results reinforce that microRNAs are candidates to play a role in haemostasis and complex disorders, such as thrombosis.

Genome-Wide Association Study Identifies a Novel Genetic Risk Factor for Recurrent Venous Thrombosis

Background: Genetic risk factors for a first venous thrombosis (VT) seem to have little effect on recurrence risk. Therefore, we aimed specifically to identify novel genetic determinants of recurrent VT. To date, genome-wide association studies are lacking. Methods and Results: We performed a genome-wide association scan in 1279 patients from the MEGA (Multiple Environmental and Genetic Assessment of risk factors for venous thrombosis) follow-up study; 832 patients who remained recurrence free during a median follow-up time of 6.1 years and 447 recurrent VT patients with a median time-to-recurrence of 2.6 years. We analyzed genotype probabilities of ≈8.6 million variants, imputed to the Genome of the Netherlands project reference panel, with a minor allele frequency ≥1% for an association with recurrent VT. One region exceeded genome-wide significance (P⩽5×10−8), mapping to the well-known factor V Leiden locus. Conditional association analyses on factor V Leiden did not yield any secondary association signals. We also identified 52 suggestive association signals (P<1×10−5) at 17 additional loci. None of these loci were previously implicated in VT risk. Replication analyses for 17 lead variants were performed in 350 patients with recurrent VT and 1866 patients with a single VT event from the MEGA follow-up study, THE-VTE (Thrombophilia, Hypercoagulability and Environmental Risks in Venous Thromboembolism) study, and LETS (Leiden Thrombophilia Study). We observed an association with recurrence for an intergenic variant at 18q22.1 with an odds ratio of 1.7 (95% confidence interval, 1.2–2.6) per copy of the minor allele. Conclusions: We confirmed the association of factor V Leiden and identified a novel risk locus at 18q22.1 in the first large genetic study on recurrent VT.

Next-generation sequencing and in vitro expression study of ADAMTS13 single nucleotide variants in deep vein thrombosis

Background Deep vein thrombosis (DVT) genetic predisposition is partially known. Objectives This study aimed at assessing the functional impact of nine ADAMTS13 single nucleotide variants (SNVs) previously reported to be associated as a group with DVT in a burden test and the individual association of selected variants with DVT risk in two replication studies. Methods Wild-type and mutant recombinant ADAMTS13 were transiently expressed in HEK293 cells. Antigen and activity of recombinant ADAMTS13 were measured by ELISA and FRETS-VWF73 assays, respectively. The replication studies were performed in an Italian case-control study (Milan study; 298/298 patients/controls) using a next-generation sequencing approach and in a Dutch case-control study (MEGA study; 4306/4887 patients/controls) by TaqMan assays. Results In vitro results showed reduced ADAMTS13 activity for three SNVs (p.Val154Ile [15%; 95% confidence interval [CI] 14–16], p.Asp187His [19%; 95%[CI] 17–21], p.Arg421Cys [24%; 95%[CI] 22–26]) similar to reduced plasma ADAMTS13 levels of patients carriers for these SNVs. Therefore these three SNVs were interrogated for risk association. The first replication study identified 3 heterozygous carriers (2 cases, 1 control) of p.Arg421Cys (odds ratio [OR] 2, 95%[CI] 0.18–22.25). The second replication study identified 2 heterozygous carriers (1 case, 1 control) of p.Asp187His ([OR] 1.14, 95%[CI] 0.07–18.15) and 10 heterozygous carriers (4 cases, 6 controls) of p.Arg421Cys ([OR] 0.76, 95%[CI] 0.21–2.68). Conclusions Three SNVs (p.Val154Ile, p.Asp187His and p.Arg421Cys) showed reduced ex vivo and in vitro ADAMTS13 levels. However, the low frequency of these variants makes it difficult to confirm their association with DVT.

Genetic variants in Cell Adhesion Molecule 1 (CADM1): A validation study of a novel endothelial cell venous thrombosis risk factor

INTRODUCTION In a protein C deficient family, we recently identified a candidate gene, CADM1, which interacted with protein C deficiency in increasing the risk of venous thrombosis (VT). This study aimed to determine whether CADM1 variants also interact with protein C pathway abnormalities in increasing VT risk outside this family. MATERIALS AND METHODS We genotyped over 300 CADM1 variants in the population-based MEGA case-control study. We compared VT risks between cases with low protein C activity (n=194), low protein S levels (n=23), high factor VIII activity (n=165) or factor V Leiden carriers (n=580), and all 4004 controls. Positive associations were repeated in all 3496 cases and 4004 controls. RESULTS We found 22 variants which were associated with VT in one of the protein C pathway risk groups. After mutual adjustment, six variants remained associated with VT. The strongest evidence was found for rs220842 and rs11608105. For rs220842, the odds ratio (OR) for VT was 3.2 (95% CI 1.2-9.0) for cases with high factor VIII activity compared with controls. In addition, this variant was associated with an increased risk of VT in the overall study population (OR: 1.5, 95% CI 1.0-2.2). The other variant, rs11608105, was not associated with VT in the overall study population (OR: 1.0, 95% CI 0.8-1.1), but showed a strong effect on VT risk (OR: 21, 95% CI 5.1-88) when combined with low protein C or S levels. CONCLUSIONS In a population-based association study, we confirm a role for CADM1 variants in increasing the risk of VT by interaction with protein C pathway abnormalities.

Next-generation DNA sequencing to identify novel genetic risk factors for cerebral vein thrombosis

BACKGROUND Cerebral vein thrombosis (CVT) is a rare, life-threatening disease affecting one adult per 100,000 per year. Genetic risk factors are deficiencies of the natural anticoagulant proteins antithrombin, protein C, protein S or single nucleotide polymorphisms such as factor V Leiden and prothrombin 20210A. In 20% of patients, the cause of CVT remains unknown. AIM To identify novel genetic risk factors for CVT using targeted next-generation DNA sequencing (NGS). METHODS We investigated 171 CVT patients and 298 healthy controls. Patients were selected using the following criteria: objective diagnosis of CVT, no active cancer. We performed targeted NGS analysis of the protein-coding regions of 734 candidate genes related to hemostasis and inflammation, 150 ancestry informative markers and 28 thrombosis-associated variants. RESULTS We identified 3723 common and low frequency variants with minor allele frequency (MAF) >1% in 590 genes. Single variant association testing using logistic regression analysis identified rs8176719 insertion/deletion (indel) variant in the ABO gene associated with CVT (age and sex adjusted OR 2.03; 95% CI 1.52-2.73; P = 2.07 × 10-6; Bonferroni P = 0.008). In addition, we identified 8839 rare variants (MAF ≤ 1%) in 723 genes. Gene-based association analysis of these rare variants using a burden test revealed only a tentative association of non-coding variants located in the F8 locus with CVT. CONCLUSION Targeted NGS identified a common indel variant rs8176719 in the ABO gene. Gene-based tests of association failed to reveal genomic loci with a cumulative burden of rare variants associated with CVT.

Correction to: Assessing the causal relationship between obesity and venous thromboembolism through a Mendelian Randomization study

The co-author name Immaculata DeVivo was incorrectly published. The correct name is given below: