Polymorphisms in the endothelial protein C receptor gene and thrombophilia

Thrombotic risk determined by protein C receptor (PROCR) variants among middle-aged and older adults: a population-based cohort study

BACKGROUND

The protein C (PC) anticoagulant system has a key role in maintaining hemostatic balance. One missense (Ser219Gly) variant in the protein C receptor (PROCR) was associated with venous thromboembolism (VTE) in genome-wide association studies.

OBJECTIVES

This study aimed to determine the thrombotic risk of rare and common PROCR variants in a large population-based cohort of middle-aged and older adults.

PATIENTS/METHODS

The exonic sequence of PROCR was analyzed for the Ser219Gly variant and other qualifying variants in 28,794 subjects (born 1923-1950, 60% women) without previous VTE, who participated in the Malmö Diet and Cancer study (1991-1996). Incidence of VTE was followed up until 2018. Qualifying variants were defined as loss-of-function or non-benign (PolyPhen-2) missense variants with minor allele frequencies (MAF) < 0.1%.

RESULTS

Resequencing identified 36 PROCR variants in the study population (26,210 non-VTE exomes and 2584 VTE exomes), 11 synonymous, 22 missense and three loss-of-function variants. Kaplan-Meier analysis of the known Ser219Gly variant (rs867186) showed that homozygosity for this variant increased the risk of disease whereas heterozygosity showed no effect. Cox multivariate regression analysis revealed an adjusted hazard ratio of 1.5 (95%CI 1.1-2.0). Fifteen rare variants were classified as qualifying and were included in collapsing analysis (burden test and SKAT-O). They did not contribute to risk. However, a Arg113Cys missense variant (rs146420040; MAF=0.004) showed an increased VTE risk (HR=1.3; 95%CI 1.0-1.9).

CONCLUSIONS

Homozygosity for the Ser219Gly variant and a previously identified functional PROCR variant (Arg113Cys) was associated with VTE. Other variants did not contribute to VTE.

Increased Activated Protein C Response Rates Reduce the Thrombotic Risk of Factor V Leiden Carriers But Not of Prothrombin 20210G>A Carriers

RATIONALE

Carriers of the most common prothrombotic mutations FVL (factor V Leiden) and FII (prothrombin) 20210G>A show a highly variable clinical phenotype. Using standardized in vivo coagulation activation followed by activity pattern analysis we have recently shown, that the FVL mutation accelerates thrombin and APC (activated protein C) formation in carriers without a history of venous thromboembolism (VTE).

OBJECTIVE

The aim of this prospective cohort study was to investigate, if the FII 20210G>A mutation induces a similar reaction pattern, and if the response rates differ in FVL and FII 20210G>A mutation carriers with prior VTE (VTE+).

METHODS AND RESULTS

We comparatively analyzed 30 FVL carriers, 28 FII 20210G>A carriers (thereof 13 VTE+ each) and 15 healthy controls. Changes in plasma levels of thrombin, prothrombin activation fragment 1+2 (F1+2), TAT (thrombin-antithrombin complex), APC, and D-dimer were monitored over 8 hours after infusion of recombinant factor VIIa (15 µg/kg). An increase of F1+2 and TAT levels was observed, that did neither differ between FVL and FII 20210G>A carriers nor between asymptomatic and VTE+ carriers of these mutations. Median plasma levels of APC increased more (P=0.008) in FVL carriers (from 1.39 to 7.79 pmol/L) than in FII 20210G>A carriers (from 1.03 to 5.79 pmol/L), and more in FII 20210G>A carriers (P=2×10^-4) than in healthy controls (from 0.86 to 3.00 pmol/L). Most importantly, however, the APC response was greater (P=0.015) in asymptomatic (n=13) than in VTE+ (n=12) heterozygous FVL carriers, with an increase of APC levels from 1.44 to 8.11 pmol/L versus 1.27 to 5.62 pmol/L.

CONCLUSIONS

These in vivo data demonstrate that the FII 20210G>A and FVL mutations share an intermediate phenotype that is characterized by increased thrombin formation after coagulation activation. Furthermore, our data support the conclusion that the APC activating capacity of FVL carriers modifies the thrombotic risk of this common prothrombotic mutation.

The H3 Haplotype of the EPCR Gene Determines High sEPCR Levels in Critically Ill Septic Patients

Introduction

A soluble (s) form of the endothelial protein C receptor (EPCR) circulates in plasma and inhibits activated protein C (APC) activities. The clinical impact of sEPCR and its involvement in the septic process is under investigation. This study determined the frequencies of EPCR haplotypes H1 and H3 to investigate possible associations with plasma admission levels of sEPCR in an intensive care unit (ICU) cohort of septic patients.

Methods

Three polymorphisms in the EPCR gene were genotyped in 239 Caucasian critically ill patients, and their plasma sEPCR levels were also measured at the time of admission to the ICU. Multivariate logistic regression analysis controlling for sepsis severity, age, acute physiology and chronic health evaluation (APACHE II) and sequential organ failure assessment (SOFA) scores, lactate level, sex, diagnostic category, length of ICU stay and hospital mortality was performed to determine the effect of EPCR haplotypes H1 and H3 on the levels of sEPCR.

Results

Individuals carrying at least one H3 allele had significantly higher levels of sEPCR than individuals with no H3 alleles (p < 0.001). No differences were found in the distribution of the H3 allele in the patient groups categorized using the pre-existing and current sepsis-3 definitions.

Conclusion

Using the preceding and current sepsis definitions, sEPCR levels and the H3 haplotype were not associated with sepsis severity and the risk of poor outcomes in septic patients; however, the EPCR H3 allele contributed to higher levels of sEPCR.

Uncertain thrombophilia markers

The development of venous thromboembolism (VTE), which includes deep-vein thrombosis and pulmonary embolism, may be associated with inherited or acquired risk factors that can be measured in plasma or DNA testing. The main inherited thrombophilias include the plasma deficiencies of the natural anticoagulants antithrombin, protein C and S; the gain-of-function mutations factor V Leiden and prothrombin G20210A; some dysfibrinogenaemias and high plasma levels of coagulation factor VIII. Besides these established biomarkers, which usually represent the first-level laboratory tests for thrombophilia screening, a number of additional abnormalities have been less consistently associated with an increased VTE risk. These uncertain causes of thrombophilias will be discussed in this narrative review, focusing on their clinical impact and the underlying pathogenetic mechanisms. Currently, there is insufficient ground to recommend their inclusion within the framework of conventional thrombophilia testing.

Effects of oral anticoagulant therapy and haplotype 1 of the endothelial protein C receptor gene on activated protein C levels

Oral anticoagulants (OACs) reduce activated protein C (APC) plasma levels less than those of protein C (PC) in lupus erythematosus and cardiac patients. Carriers of the H1 haplotype of the endothelial PC receptor gene (PROCR) have higher APC levels than non-carriers. We aimed to confirm these results in a large group of patients treated with OACs because of venous thromboembolism (VTE) and to assess whether the effect is influenced by the PROCR H1 haplotype. We evaluated APC, PC, and factor (F)II levels in 502 VTE patients (158 with and 344 without OACs) and in 322 healthy individuals. Mean APC, PC and FII levels were significantly lower in OAC patients than in patients not taking OACs. During anticoagulant therapy, the FII/PC ratios were independent of the PC values, whereas APC/FII and APC/PC ratios significantly increased when FII and PC levels decreased. Of the 22 OAC patients carrying the H1H1genotype, 11 (50%) showed APC/PCag ≥2.0 and 10 (45%) APC/ FIIag ratios ≥2.0, whereas for the 49 OAC patients non-carrying the H1 haplotype these figures were 6 (12%) and 4 (8%), respectively (p<0.001). Barium citrate adsorption of plasma from OAC patients showed that most of the circulating free and complexed APC, but only part of PCag, is fully carboxylated. In conclusion, during anticoagulant therapy VT patients have APC levels disproportionately higher than the corresponding PC levels, mainly due to the presence of the PROCR H1 haplotype. Furthermore, a sufficiently carboxylated PC Gla-domain seems to be essential for PC activation in vivo.

Association of common genetic variation in the protein C pathway genes with clinical outcomes in acute respiratory distress syndrome

Background

Altered plasma levels of protein C, thrombomodulin, and the endothelial protein C receptor are associated with poor clinical outcomes in patients with acute respiratory distress syndrome (ARDS). We hypothesized that common variants in these genes would be associated with mortality as well as ventilator-free and organ failure-free days in patients with ARDS.

Methods

We genotyped linkage disequilibrium-based tag single-nucleotide polymorphisms in the ProteinC, Thrombomodulin and Endothelial Protein C Reptor Genes among 320 self-identified white patients of European ancestry from the ARDS Network Fluid and Catheter Treatment Trial. We then tested their association with mortality as well as ventilator-free and organ-failure free days.

Results

The GG genotype of rs1042580 (p = 0.02) and CC genotype of rs3716123 (p = 0.002), both in the thrombomodulin gene, and GC/CC genotypes of rs9574 (p = 0.04) in the endothelial protein C receptor gene were independently associated with increased mortality. An additive effect on mortality (p < 0.001), ventilator-free days (p = 0.01), and organ failure-free days was observed with combinations of these high-risk genotypes. This association was independent of age, severity of illness, presence or absence of sepsis, and treatment allocation.

Conclusions

Genetic variants in thrombomodulin and endothelial protein C receptor genes are additively associated with mortality in ARDS. These findings suggest that genetic differences may be at least partially responsible for the observed associations between dysregulated coagulation and poor outcomes in ARDS.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-016-1330-5) contains supplementary material, which is available to authorized users.

Familial thrombotic risk based on the genetic background of Protein C Deficiency in a Portuguese Study

INTRODUCTION

Inherited protein C (PC) deficiency is a well-known risk factor for venous thrombosis (VT). Plasma PC levels are reliable in moderate to severe deficiencies; however, in mildly deficient individuals, the levels may overlap with those considered normal. Genetic studies of PROC, which encodes PC, could help identify carriers; genome-wide association studies (GWAS) have shown that approximately 50% of phenotypic variation in PC deficiency is caused by the cumulative effects of mutations in several other loci, namely in the PROCR.

PATIENTS AND METHODS

With the main objective of determining the genotype/phenotype correlation in 59 Portuguese individuals from 26 unrelated families with history of thrombosis and repeatedly low/borderline PC plasma levels, we conducted a molecular study by direct sequencing of PROC; PROC promoter haplotypes and PROCR c.4600A>G polymorphism (rs867186), which are known to influence plasma PC concentrations, were also screened.

RESULTS

Twelve different PROC mutations were identified, one of them not previously reported, p.Cys105Arg. The mutation types and locations as well as haplotype combinations correlated with the phenotypic severity. The most frequent mutation, p.Arg199X, correlated with the CGTC haplotype and was identified in nine families containing patients with higher numbers of VT episodes. This mutation in homozygous individuals for the CGTC haplotype is a significant risk factor for VT in Portuguese.

CONCLUSION

These genetic family studies allowed the identification of the unknown carriers and individuals at a higher thrombotic risk within each family, thus permitting the evaluation of the need for prophylactic measures, particularly in at-risk situations.

Functional Analysis of Two Haplotypes of the Human Endothelial Protein C Receptor Gene

Objective—

To confirm the effect of the endothelial protein receptor gene ( PROCR ) haplotypes H1 and H3 on venous thromboembolism (VTE), to study their effect on endothelial protein C receptor (EPCR) expression in human umbilical vein endothelial cells, and to investigate the functionality of H1 tagging single-nucleotide polymorphisms in an in vitro model.

Approach and Results—

Protein C (PC), activated PC, and soluble EPCR (sEPCR) levels were measured in 702 patients with VTE and 518 healthy individuals. All subjects were genotyped for PROCR H1 and H3. Human umbilical vein endothelial cells isolated from 111 umbilical cords were used to study the relation between PROCR haplotypes, PROCR mRNA, cellular distribution of EPCR, and rate of PC activation. Finally, the functionality of the intragenic PROCR H1 single-nucleotide polymorphisms was analyzed using a luciferase-based method. We confirmed that individuals carrying H1 have reduced VTE risk, increased plasma activated PC levels, and reduced plasma sEPCR levels and that individuals with the H3H3 genotype have an increased VTE risk and increased plasma sEPCR levels. In cultured human umbilical vein endothelial cells, H1 is associated with increased membrane-bound EPCR, increased rate of PC activation, and reduced sEPCR in conditioned medium, but does not significantly influence PROCR mRNA levels. In contrast, H3 is associated with reduced membrane-bound EPCR and increased sEPCR in human umbilical vein endothelial cell–conditioned medium, higher levels of a truncated mRNA isoform, and a lower rate of PC activation. Finally, we identified the g.2132T>C single-nucleotide polymorphism in intron 1 as an intragenic H1-specific functional single-nucleotide polymorphism.

Conclusions—

These results support a protective role of PROCR H1 against VTE and an increased risk of VTE associated with the H3 haplotype.

Rosmarinic acid down-regulates endothelial protein C receptor shedding in vitro and in vivo

The endothelial protein C receptor (EPCR) plays pivotal roles in coagulation and inflammation, however, its activity is markedly changed by ectodomain cleavage and release as the soluble protein (sEPCR). According to previous studies, there are approximately 100ng/ml sEPCR in human plasma and the levels increase in inflammatory diseases. EPCR can be shed from the cell surface, and this is mediated by tumor necrosis factor-α converting enzyme (TACE). We recently reported on the anti-inflammatory and barrier protective activities of rosmarinic acid (RA), an important component of the leaves of Perilla frutescens. However, little is known about the effects of RA on EPCR shedding. Here, we investigated this issue by monitoring the effects of RA on phorbol-12-myristate 13-acetate (PMA), tumor necrosis factor (TNF)-α, and interleukin (IL)-1β, and on cecal ligation and puncture (CLP)-mediated EPCR shedding and underlying mechanisms. Data showed that treatment with RA resulted in potent inhibition of PMA, TNF-α, IL-induced EPCR shedding by suppression of TACE expression. In addition, RA reduced PMA-stimulated phosphorylation of p38, extracellular regulated kinases (ERK) 1/2, and c-Jun N-terminal kinase (JNK). These results suggest the potential for use of RA as an anti-sEPCR shedding reagent against PMA, TNF-α, IL-1β and CLP-mediated EPCR shedding.

Endothelial protein C receptor polymorphisms and risk of severe sepsis in critically ill patients

Purpose

Endothelial protein C receptor (EPCR) is expressed mainly in endothelial cells and is involved in regulation of the cytoprotective and anticoagulant pathways of protein C. We assessed whether haplotypes in the EPCR gene modify the risk of severe sepsis and/or septic shock (SS/SS) development in critically ill patients.

Methods

Three polymorphisms in the EPCR gene were genotyped in 389 Caucasian critically ill patients, hospitalized in the intensive care units of two major hospitals in Athens, Greece. Multivariate logistic regression analysis controlling for age, acute physiology and chronic health evaluation (APACHE) II and sequential organ failure assessment (SOFA) scores, sex, and diagnosis was performed to determine the effect of haplotypes H1 and H3 in the EPCR gene on the development of SS/SS.

Results

H2 carriers versus all other genotypes combined had a nonsignificant excess of SS/SS (p = 0.087). SS/SS occurred in 38.8 % of critically ill patients carrying minor alleles belonging to both H1 and H3 haplotypes, in 58.0 % of H1 carriers, 64.3 % of H3 carriers, and 65.2 % of patients carrying all common alleles (H2). Compared with H2 carriers, the odds ratios (OR) for developing SS/SS were 0.34 [95 % confidence interval (CI) 0.16–0.76, p = 0.008] for simultaneous H1 and H3 carriers, 0.65 (95 % CI 0.37–1.13, p = 0.123) for H1 carriers, and 0.82 (95 % CI 0.39–1.70, p = 0.590) for H3 carriers.

Conclusions

Our results indicate that simultaneous carriers of minor alleles belonging to both the H1 and H3 haplotypes may be at reduced risk of developing SS/SS in this cohort of critically ill patients.

Thrombomodulin as a regulator of the anticoagulant pathway: implication in the development of thrombosis

Thrombomodulin is a cell surface-expressed glycoprotein that serves as a cofactor for thrombin-mediated activation of protein C (PC), an event further amplified by the endothelial cell PC receptor. The PC pathway is a major anticoagulant mechanism that downregulates thrombin formation and hedges thrombus formation. The objectives of this review were to review recent findings regarding thrombomodulin structure, its involvement in the regulation of hemostasis and further discuss the implication, if any, of the genetic polymorphisms in the thrombomodulin gene in the risk of development of thrombosis. We performed a literature search by using electronic bibliographic databases. Although the direct evaluation of risk situations associated with thrombomodulin mutations/polymorphisms could be of clinical significance, it appears that mutations that affect the function of thrombomodulin are rarely associated with venous thromboembolism. However, several polymorphisms are reported to be associated with increased risk for arterial thrombosis. Additionally studies on knock out mice as well studies on humans bearing rare mutations suggest that thrombomodulin dysfunction may be implicated in the pathogenesis of myocardial infraction.

Protein C anticoagulant and cytoprotective pathways

Plasma protein C is a serine protease zymogen that is transformed into the active, trypsin-like protease, activated protein C (APC), which can exert multiple activities. For its anticoagulant action, APC causes inactivation of the procoagulant cofactors, factors Va and VIIIa, by limited proteolysis, and APC's anticoagulant activity is promoted by protein S, various lipids, high-density lipoprotein, and factor V. Hereditary heterozygous deficiency of protein C or protein S is linked to moderately increased risk for venous thrombosis, while a severe or total deficiency of either protein is linked to neonatal purpura fulminans. In recent years, the beneficial direct effects of APC on cells which are mediated by several specific receptors have become the focus of much attention. APC-induced signaling can promote multiple cytoprotective actions which can minimize injuries in various preclinical animal injury models. Remarkably, pharmacologic therapy using APC demonstrates substantial neuroprotective effects in various murine injury models, including ischemic stroke. This review summarizes the molecules that are central to the protein C pathways, the relationship of pathway deficiencies to venous thrombosis risk, and mechanisms for the beneficial effects of APC.

Is EPCR a multi-ligand receptor? Pros and cons

In the last decade, the endothelial cell protein C/activated protein C receptor (EPCR) has received considerable attention. The role initially attributed to EPCR, i.e. the enhancement of protein C (PC) activation by the thrombin-thrombomodulin complex on the surface of the large vessels, although important, did not go beyond the haemostasis scenario. However, the discovery of the cytoprotective, anti-inflammatory and anti-apoptotic features of the activated PC (APC) and the required involvement of EPCR for APC to exert such actions did place the receptor in a privileged position in the crosstalk between coagulation and inflammation. The last five years have shown that PC/APC are not the only molecules able to interact with EPCR. Factor VII/VIIa (FVII/VIIa) and factor Xa (FXa), two other serine proteases that play a central role in haemostasis and are also involved in signalling processes influencing wound healing, tissue remodelling, inflammation or metastasis, have been reported to bind to EPCR. These observations have paved the way for an exploration of unsuspected new roles for the receptor. This review aims to offer a new image of EPCR in the light of its extended panel of ligands. A brief update of what is known about the APC-evoked EPCR-dependent cell signalling mechanisms is provided, but special care has been taken to assemble all the information available about the interaction of EPCR with FVII/VIIa and FXa.

The endothelial protein C receptor (PROCR) Ser219Gly variant and risk of common thrombotic disorders: a HuGE review and meta-analysis of evidence from observational studies

The endothelial protein C receptor (EPCR) limits thrombus formation by enhancing activation of the protein C anticoagulant pathway, and therefore may play a role in the etiology of thrombotic disorders. The rs867186 single-nucleotide polymorphism in the PROCR gene (g.6936A > G, c.4600A > G), resulting in a serine-to-glycine substitution at codon 219, has been associated with reduced activation of the protein C pathway, although its association with thrombosis risk remains unclear. The present study is a highly comprehensive systematic review and meta-analysis, including unpublished genome-wide association study results, conducted to evaluate the evidence for an association between rs867186 and 2 common thrombotic outcomes, venous thromboembolism (VTE) and myocardial infarction (MI), which are hypothesized to share some etiologic pathways. MEDLINE, EMBASE, and HuGE Navigator were searched through July 2011 to identify relevant epidemiologic studies, and data were summarized using random-effects meta-analysis. Twelve candidate genes and 13 genome-wide association studies were analyzed (11 VTE and 14 MI, including 37,415 cases and 84,406 noncases). Under the additive genetic model, the odds of VTE increased by a factor of 1.22 (95% confidence interval, 1.11-1.33, P < .001) for every additional copy of the G allele. No evidence for association with MI was observed.

Identification of novel therapeutic targets in microdissected clear cell ovarian cancers

Clear cell ovarian cancer is an epithelial ovarian cancer histotype that is less responsive to chemotherapy and carries poorer prognosis than serous and endometrioid histotypes. Despite this, patients with these tumors are treated in a similar fashion as all other ovarian cancers. Previous genomic analysis has suggested that clear cell cancers represent a unique tumor subtype. Here we generated the first whole genomic expression profiling using epithelial component of clear cell ovarian cancers and normal ovarian surface specimens isolated by laser capture microdissection. All the arrays were analyzed using BRB ArrayTools and PathwayStudio software to identify the signaling pathways. Identified pathways validated using serous, clear cell cancer cell lines and RNAi technology. In vivo validations carried out using an orthotopic mouse model and liposomal encapsulated siRNA. Patient-derived clear cell and serous ovarian tumors were grafted under the renal capsule of NOD-SCID mice to evaluate the therapeutic potential of the identified pathway. We identified major activated pathways in clear cells involving in hypoxic cell growth, angiogenesis, and glucose metabolism not seen in other histotypes. Knockdown of key genes in these pathways sensitized clear cell ovarian cancer cell lines to hypoxia/glucose deprivation. In vivo experiments using patient derived tumors demonstrate that clear cell tumors are exquisitely sensitive to antiangiogenesis therapy (i.e. sunitinib) compared with serous tumors. We generated a histotype specific, gene signature associated with clear cell ovarian cancer which identifies important activated pathways critical for their clinicopathologic characteristics. These results provide a rational basis for a radically different treatment for ovarian clear cell patients.

Heritability of plasma concentrations of activated protein C in a Spanish population

The protein C anticoagulant pathway plays a crucial role in the regulation of fibrin formation. Protein C is activated on the surface of endothelial cells by the thrombin-thrombomodulin complex with the stimulation of the endothelial protein C receptor. The levels of circulating activated protein C reflect in-vivo protein C activation, and a low level of activated protein C is a risk factor for venous thromboembolism. The objective of the study was to assess the relative contributions of genetic and environmental factors to the variation in the levels of activated protein C and protein C. Blood samples were collected from 126 individuals belonging to 19 Spanish families, and heritability and common household effect were estimated for protein C, activated protein C and its complexes with protein C and alpha1-antitrypsin. In addition, we calculated the genetic correlation between protein C and activated protein C phenotypes. Although all phenotypes showed significant heritability, activated protein C phenotype resulted in a very high heritability of 83%, which clearly shows that this phenotype is strongly influenced by the action of gene(s). Furthermore, the bivariant analyses of protein C and activated protein C phenotypes indicate that there is a high genetic correlation between them (0.74). Nevertheless, this correlation is counteracted by a negative environmental correlation (-0.54) resulting in a phenotypic correlation of 0.35. The presence of such strong genetic effects suggests that it will be possible to localize the loci that influence this phenotype and determine the contribution to the risk of thrombosis.

Association of Apo(a)isoform size with dyslipoproteinemia in male venous thrombosis patients

BACKGROUND

Lp(a) is a proatherogenic lipoprotein that may also be prothrombotic. Apo(a) size isoforms have differential effects on fibrinolysis. Whereas Lp(a) concentrations have been linked to venous thromboembolic disease (VTE) risk, apo(a) polymorphisms in VTE have not been studied.

METHODS

We used a standardized high resolution agarose gel electrophoresis technique to determine apo(a) isoform size, and a Lp(a) immunoassay insensitive to apo(a) size to measure Lp(a) concentration in 46 men with VTE and 46 age-matched healthy controls.

RESULTS

Apo(a) isoform distribution in VTE cases and controls was bimodal and VTE patients tended to have more medium-sized isoforms K(4)-(19-27) (54.3% vs. 34.8%, p=0.06). Cases and controls had the same median predominant apo(a) size isoform (23.5 K(4) repeats) and comparable Lp(a) concentrations. However, subgroup analysis based on apo(a) isoform size (K(4)< or =23 or K(4)> or =24) revealed that cases in the K(4)> or =24 subgroup had higher Lp(a) concentrations than the controls in this isofrom subgroup (14.5 mmol vs. 6.6 mmol, p=0.029). Also, dyslipoproteinemia (smaller LDL and HDL particles, higher LDL and lower HDL parameters) was strongly associated with VTE only in this larger apo(a) isoform group.

CONCLUSIONS

These observations provide the first evidence that determination of apo(a) isoforms may provide useful novel insights into VTE risk.

Paternal endothelial protein C receptor 219Gly variant as a mild and limited risk factor for deep vein thrombosis during pregnancy

BACKGROUND

Half of all venous thromboembolism (VTE) cases during pregnancy are associated with a maternal thrombophilia. The influence of paternal genotype on the placenta and in the genesis of VTE has not been described.

OBJECTIVES

To determine if the maternal and paternal Ser219Gly dimorphism of the endothelial protein C receptor (EPCR), evaluated through detection of the PROCR 6936G allele, is a risk factor for VTE during pregnancy.

METHODS

Using a case-control study nested in the NOHA first cohort of primigravidae, 66 patient couples with a first episode of gestational VTE and randomly selected non-thrombotic control couples were investigated. For each couple, factor V gene (F5) G1691A, factor II gene (F2) G20210A, factor XII gene (F12) C46T and PROCR A6936G polymorphisms were determined.

RESULTS

Only maternal F5 1691A, F2 20210A and F12 46T alleles were independently associated with iliac and infra-iliac deep vein thromboses (DVT). The maternal PROCR 6936G allele was a mild risk factor for iliac DVT (OR = 5.5 [2.3-13.0]). The paternal PROCR 6936G allele was also a mild independent risk factor for iliac DVT (OR = 2.6 [1.1-6.2]) and only during pregnancy (rather than postpartum) among maternal carriers of the F5 1691A allele (OR = 77.6 [4.2 to > 999.9]).

CONCLUSIONS

The paternal PROCR 6936G allele could be a risk factor for maternal iliac DVT. Its impact was milder than the F5 1691A and F2 20210A polymorphisms in mothers. We hypothesize that the prothrombotic effect of the paternal PROCR 6936G allele is localized. Therefore, DVT during pregnancy may be influenced by trophoblastic cell-surface proteins inherited from both maternal and paternal alleles.

Genetic variations and their influence on risk and treatment of venous thrombosis

Venous thrombosis (VT) is a highly prevalent disease. Risk factors can be genetic or acquired. The well-established genetic polymorphisms predisposing to thrombophilic disorders can be divided into rare 'loss-of-function mutations' in anticoagulant proteins and common 'gain-of-function mutations' in procoagulant proteins, which are weaker risk factors. In addition to functional polymorphisms, defects in common pathways affecting biosynthesis or clearance of plasma coagulation factors and their relations to VT risk have been detected. Recently, investigations regarding genetic variations and response to drug treatment, relevant for the pathogenesis as well as therapy of venous thromboembolism have been performed. The methodical advances in genetic research have led to the identification of a number of new variants with still unclear association to VT. This review aims to discuss the established genetic risk factors as well as some candidate predictors of VT. Further, the recent developments in pharmacogenomics are reviewed.