Homozygosity of the T allele of the 46 C->T polymorphism in the F12 gene is a risk factor for ischemic stroke in the Spanish population

Proteomics-Based Approach to Identify Novel Blood Biomarker Candidates for Differentiating Intracerebral Hemorrhage From Ischemic Stroke-A Pilot Study

Background: A reliable distinction between ischemic stroke (IS) and intracerebral hemorrhage (ICH) is required for diagnosis-specific treatment and effective secondary prevention in patients with stroke. However, in resource-limited settings brain imaging, which is the current diagnostic gold standard for this purpose, is not always available in time. Hence, an easily accessible and broadly applicable blood biomarker-based diagnostic test differing stroke subtypes would be desirable. Using an explorative proteomics approach, this pilot study aimed to identify novel blood biomarker candidates for distinguishing IS from ICH.

Material and Methods: Plasma samples from patients with IS and ICH were drawn during hospitalization and were analyzed by using liquid chromatography/mass spectrometry. Proteins were identified using the human reference proteome database UniProtKB, and label-free quantification (LFQ) data were further analyzed using bioinformatic tools.

Results: Plasma specimens of three patients with IS and four patients with ICH with a median National Institute of Health Stroke Scale (NIHSS) of 12 [interquartile range (IQR) 10.5–18.5] as well as serum samples from two healthy volunteers were analyzed. Among 495 identified protein groups, a total of 368 protein groups exhibited enough data points to be entered into quantitative analysis. Of the remaining 22 top-listed proteins, a significant difference between IS and ICH was found for Carboxypeptidase N subunit 2 (CPN2), Coagulation factor XII (FXII), Plasminogen, Mannan-binding lectin serine protease 1, Serum amyloid P-component, Paraoxonase 1, Carbonic anhydrase 1, Fibulin-1, and Granulins.

Discussion: In this exploratory proteomics-based pilot study, nine candidate biomarkers for differentiation of IS and ICH were identified. The proteins belong to the immune system, the coagulation cascade, and the apoptosis system, respectively. Further investigations in larger cohorts of patients with stroke using additional biochemical analysis methods, such as ELISA or Western Blotting are now necessary to validate these markers, and to characterize diagnostic accuracy with regard to the development of a point-of-care-system for use in resource-limited areas.

Cryptogenic Stroke in the Young: Role of Candidate Gene Polymorphisms in Indian Patients with Ischemic Etiology

CONTEXT

Strokes that remain without a definite cause even after an extensive workup, termed cryptogenic strokes, constitute up to 30-40% of ischemic strokes (ISs) in the young. Some of them can have a genetic basis. However, the well-established genetic causes account for only a small percentage of these cases.

AIM

To evaluate the association of cryptogenic young IS with 16 candidate gene polymorphisms.

SETTINGS AND DESIGN

A case-control study with cryptogenic young IS patients (South and North Indians; n = 105) and age, sex, and ethnicity-matched controls (n = 215).

SUBJECTS AND METHODS

Genotyping was carried out by PCR-RFLP method using DNA extracted from the blood.

STATISTICAL ANALYSIS USED

Association of the genotypes with the disease was studied using Chi-square test.

RESULTS

MTHFR rs1801133 and KNG1 rs710446 showed significant statistical association with cryptogenic young IS (P = 0.0261 and 0.0157, respectively) in the Indian population. Significant association of KNG1 rs710446 (P 0.0036) and FXII rs1801020 (P 0.0376) with cryptogenic young stroke in South Indian males, SERPINC1 rs2227589 in South Indian female patients (P = 0.0374), and CYP4V2 rs13146272 in North Indian males (P = 0.0293) was observed.

CONCLUSIONS

Our study indicates that in the Indian population MTHFR rs1801133, KNG rs710446, FXII rs1801020, SERPINC1 rs2227589, CYP4V2 rs13146272, and FXIII V34L may be significant risk factors for cryptogenic IS in the young. In addition, ethnicity and gender play a significant role. Further studies with larger sample size are required to completely establish these polymorphisms as risk factors for cryptogenic IS in young Indians.

Meta-Analysis of Factor V, Factor VII, Factor XII, and Factor XIII-A Gene Polymorphisms and Ischemic Stroke

Numerous studies examined the association between factors FV, FVII, FXII, and FXIII-A gene polymorphisms and ischemic stroke, but conclusive evidence is yet to be obtained. Thus, this meta-analysis aimed to investigate the novel association of FV rs1800595, FVII rs5742910, FXII rs1801020, and FXIII-A rs5982 and rs3024477 polymorphisms with ischemic stroke risk. A systematic review was performed on articles retrieved before June 2018. Relevant data were extracted from eligible studies and meta-analyzed using RevMan version 5.3. The strength of association between studied polymorphisms and ischemic stroke risk was calculated as odds ratios and 95% confidence intervals, by applying both fixed- and random-effect models. A total of 25 studies involving 6100 ischemic stroke patients and 9249 healthy controls were incorporated in the final meta-analysis model. Specifically, rs1800595, rs5742910, rs1801020, rs5982, and rs3024477 consisted of 673, 3668, 922, 433, and 404 cases, as well as 995, 4331, 1285, 1321, and 1317 controls, respectively. The pooled analysis indicated that there was no significant association of FV rs1800595, FVII rs5742910, FXII rs1801020, FXIII-A rs5982, and FXIII-A rs3024477 polymorphisms with ischemic stroke risk, under any genetic models (dominant, recessive, over-dominant, and allelic). The present meta-analysis concluded that FV rs1800595, FVII rs5742910, FXII rs1801020, and FXIII-A rs5982 and rs3024477 polymorphisms are not associated with ischemic stroke risk.

The relevance of coagulation in cardiovascular disease: what do the biomarkers tell us?

Several haemostatic factors have been associated with incident arterial cardiovascular disease in prospective studies and meta-analyses. Plasma fibrinogen shows a strong and consistent association with risk; however, this may reflect its inflammatory marker status, and causality remains to be proven. The common haemostatic gene polymorphisms for factor II, factor V and the von Willebrand factor: Factor VIII (non-O blood group) show significant associations with coronary heart disease (CHD) risk, consistent with potential causality. Increased D-dimer and t-PA antigen levels are associated with CHD risk, suggesting roles for coagulation activation and endothelial disturbance. There is little evidence for associations with CVD with other haemostatic factors.

Whole exome sequence-based association analyses of plasma amyloid-β in African and European Americans; the Atherosclerosis Risk in Communities-Neurocognitive Study

Objective

We performed single-variant and gene-based association analyses of plasma amyloid-β (aβ) concentrations using whole exome sequence from 1,414 African and European Americans. Our goal was to identify genes that influence plasma aβ₄₂ concentrations and aβ₄₂:aβ₄₀ ratios in late middle age (mean = 59 years), old age (mean = 77 years), or change over time (mean = 18 years).

Methods

Plasma aβ measures were linearly regressed onto age, gender, APOE ε4 carrier status, and time elapsed between visits (fold-changes only) separately by race. Following inverse normal transformation of the residuals, seqMeta was used to conduct race-specific single-variant and gene-based association tests while adjusting for population structure. Linear regression models were fit on autosomal variants with minor allele frequencies (MAF)≥1%. T5 burden and Sequence Kernel Association (SKAT) gene-based tests assessed functional variants with MAF≤5%. Cross-race fixed effects meta-analyses were Bonferroni-corrected for the number of variants or genes tested.

Results

Seven genes were associated with aβ in late middle age or change over time; no associations were identified in old age. Single variants in KLKB1 (rs3733402; p = 4.33x10^-10) and F12 (rs1801020; p = 3.89x10^-8) were significantly associated with midlife aβ₄₂ levels through cross-race meta-analysis; the KLKB1 variant replicated internally using 1,014 additional participants with exome chip. ITPRIP, PLIN2, and TSPAN18 were associated with the midlife aβ₄₂:aβ₄₀ ratio via the T5 test; TSPAN18 was significant via the cross-race meta-analysis, whereas ITPRIP and PLIN2 were European American-specific. NCOA1 and NT5C3B were associated with the midlife aβ₄₂:aβ₄₀ ratio and the fold-change in aβ₄₂, respectively, via SKAT in African Americans. No associations replicated externally (N = 725).

Conclusion

We discovered age-dependent genetic effects, established associations between vascular-related genes (KLKB1, F12, PLIN2) and midlife plasma aβ levels, and identified a plausible Alzheimer’s Disease candidate gene (ITPRIP) influencing cell death. Plasma aβ concentrations may have dynamic biological determinants across the lifespan; plasma aβ study designs or analyses must consider age.

Factor XII as a Risk Marker for Hemorrhagic Stroke: A Prospective Cohort Study

Background

Coagulation factor XII (FXII) is involved in pathological thrombus formation and is a suggested target of anticoagulants. It is unclear whether FXII levels are correlated with cardiovascular risk factors and whether they are associated with myocardial infarction or ischemic or hemorrhagic stroke. The aim of this study was to investigate the correlation between FXII and cardiovascular risk factors in the general population. We also aimed to study the associations between FXII levels and future myocardial infarction and ischemic and hemorrhagic stroke.

Methods

This prospective cohort study measured FXII levels in 1,852 randomly selected participants in a health survey performed in northern Sweden in 1994. Participants were followed until myocardial infarction, stroke, death, or until December 31, 2011.

Results

During the median follow-up of 17.9 years, 165 individuals were diagnosed with myocardial infarction, 108 with ischemic stroke, and 30 with hemorrhagic stroke. There were weak correlations between FXII and body mass index, cholesterol, and hypertension. There was no association between FXII and myocardial infarction or ischemic stroke, neither in univariable Cox regression analysis nor after adjustment for age, sex, smoking, body mass index, cholesterol, hypertension, and diabetes. In univariable Cox regression analysis, the hazard ratio for the association between FXII levels and hemorrhagic stroke was 1.42 per SD (95% confidence interval: 0.99–2.05). In the multivariable model, higher levels of FXII were associated with increased risk of hemorrhagic stroke (hazard ratio 1.51 per SD; 95% confidence interval: 1.03–2.21).

Conclusion

We found an independent association between FXII levels and the risk of hemorrhagic stroke, but not between FXII levels and ischemic stroke or myocardial infarction.

Quantitative variability of 342 plasma proteins in a human twin population

The degree and the origins of quantitative variability of most human plasma proteins are largely unknown. Because the twin study design provides a natural opportunity to estimate the relative contribution of heritability and environment to different traits in human population, we applied here the highly accurate and reproducible SWATH mass spectrometry technique to quantify 1,904 peptides defining 342 unique plasma proteins in 232 plasma samples collected longitudinally from pairs of monozygotic and dizygotic twins at intervals of 2–7 years, and proportioned the observed total quantitative variability to its root causes, genes, and environmental and longitudinal factors. The data indicate that different proteins show vastly different patterns of abundance variability among humans and that genetic control and longitudinal variation affect protein levels and biological processes to different degrees. The data further strongly suggest that the plasma concentrations of clinical biomarkers need to be calibrated against genetic and temporal factors. Moreover, we identified 13 cis-SNPs significantly influencing the level of specific plasma proteins. These results therefore have immediate implications for the effective design of blood-based biomarker studies.

A genetic association study of activated partial thromboplastin time in European Americans and African Americans: the ARIC Study

Reduced activated partial thromboplastin time (aPTT) is a risk marker for incident and recurrent venous thromboembolism (VTE). Genetic factors influencing aPTT are not well understood, especially in populations of non-European ancestry. The present study aimed to identify aPTT-related gene variants in both European Americans (EAs) and African Americans (AAs). We conducted a genetic association study for aPTT in 9719 EAs and 2799 AAs from the Atherosclerosis Risk in Communities (ARIC) study. Using the Candidate Gene Association Resource (CARe) consortium candidate gene array, the analyses were based on ∼50 000 SNPs in ∼2000 candidate genes. In EAs, the analyses identified a new independent association for aPTT in F5 (rs2239852, P-value = 1.9 × 10(-8)), which clusters with a coding variant rs6030 (P-value = 7.8 × 10(-7)). The remaining significant signals were located on F5, HRG, KNG1, F11, F12 and ABO and have been previously reported in EA populations. In AAs, significant signals were identified in KNG1, HRG, F12, ABO and VWF, with the leading variants in KNG1, HRG and F12 being the same as in the EAs; the significant variant in VWF (rs2229446, P-value = 1.2 × 10(-6)) was specific to the AA sample (minor allele frequency = 19% in AAs and 0.2% in EAs) and has not been previously reported. This is the first study to report aPTT-related genetic variants in AAs. Our findings in AAs demonstrate transferability of previously reported associations with KNG1, HRG and F12 in EAs. We also identified new associations at F5 in EAs and VWF in AAs that have not been previously reported for aPTT.

The factor XII -4C>T variant and risk of common thrombotic disorders: A HuGE review and meta-analysis of evidence from observational studies

Coagulation factor XII is involved in thrombus formation and therefore may play a role in the etiology of thrombotic disorders. A common variant in the factor XII (F12) gene (-4C>T, rs1801020) results in decreased plasma levels of this coagulation factor. The existence of associations between low factor XII levels or F12 variants and thrombotic outcomes has been debated for more than a decade. The authors conducted a review and meta-analysis to evaluate the evidence for an association between F12 -4C>T and 2 common thrombotic outcomes: venous thromboembolism and myocardial infarction, which are hypothesized to share some etiologic pathways. MEDLINE, EMBASE, and HuGE Navigator were searched through July 2009 to identify relevant epidemiologic studies, and data were summarized using random-effects meta-analysis. Sixteen candidate gene studies (4,386 cases, 40,089 controls) were analyzed. None of the investigated contrasts reached statistical significance at P < 0.05, apart from a very weak association with myocardial infarction for the TT + CT versus CC contrast (odds ratio = 1.13, 95% confidence interval: 1.00, 1.27). Overall, based on the synthesis of observational studies, the evidence for an association between F12 -4C>T and venous thromboembolism and myocardial infarction is weak.

Factor XII: what does it contribute to our understanding of the physiology and pathophysiology of hemostasis & thrombosis

Factor XII (FXII) is a coagulation protein that is essential for surface-activated blood coagulation tests but whose deficiency is not associated with bleeding. For over forty years, investigators in hemostasis have not considered FXII important because its deficiency is not associated with bleeding. It is because there is a dichotomy between abnormal laboratory assay findings due to FXII deficiency and clinical hemostasis that investigators sought explanations for physiologic hemostasis independent of FXII. FXII is a multidomain protein that contains two fibronectin binding consensual sequences, two epidermal growth factor regions, a kringle region, a proline-rich domain, and a catalytic domain that when proteolyzed turns into a plasma serine protease. Recent investigations with FXII deleted mice that are protected from thrombosis indicate that it contributes to the extent of developing thrombus in the intravascular compartment. These findings suggest that it has a role in thrombus formation without influencing hemostasis. Last, FXII has been newly appreciated to be a growth factor that may influence tissue injury repair and angiogenesis. These combined studies suggest that FXII may become a pharmacologic target to reduce arterial thrombosis risk and promote cell repair after injury, without influencing hemostasis.

Common variants of large effect in F12, KNG1, and HRG are associated with activated partial thromboplastin time

Activated partial thromboplastin time (aPTT) is associated with risk of thrombosis and coagulation disorders. We conducted a genome-wide association study for aPTT and identified significant associations with SNPs in three coagulation cascade genes, F12 (rs2731672, combined p = 2.16 x 10(-30)), KNG1 (rs710446, combined p = 9.52 x 10(-22)), and HRG (rs9898, combined p = 1.34 x 10(-11)). These three SNPs explain approximately 18% of phenotypic variance in aPTT in the Lothian Birth Cohorts.

Accumulation of gene polymorphisms related to plaque disruption and thrombosis is associated with cerebral infarction in subjects with type 2 diabetes

OBJECTIVE

It is believed that disruption of vulnerable atherosclerotic plaque and subsequent thrombus formation play critical roles in the pathogenesis of cerebral infarction. We simultaneously determined four relatively common genetic variants related to plaque rupture or subsequent local thrombus formation and evaluated the combined effect on cerebral infarction.

RESEARCH DESIGN AND METHODS

We enrolled 3,094 Japanese type 2 diabetic subjects (62.7% male; aged 61.5 +/- 8.4 years) and determined their genotypes regarding matrix metalloproteinase 9 C-1562T, coagulation factor XII (F12) C46T, von Willebrand factor (VWF) G-1051A, and plasminogen activator inhibitor (PAI-1) 675 4G/5G polymorphisms. The diagnosis of cerebral infarction was performed based on history, physical examination, and neuroimaging.

RESULTS

The single association analysis revealed that there were no statistically significant associations between each polymorphism and the prevalence of cerebral infarction. Interestingly, the prevalence of cerebral infarction was higher with the increase of the total number of four concomitant unfavorable proatherothrombotic alleles in each subject (P value for linear trend = 0.004). Furthermore, a multiple logistic regression analysis showed that the number of proatherothrombotic alleles was a risk factor for cerebral infarction independently of conventional risk factors (odds ratio for one-point increase in the number of proatherothrombotic allele 1.15 [95% CI 1.05-1.26], P = 0.004).

CONCLUSIONS

Accumulation of gene polymorphisms related to plaque rupture and thrombus formation is likely associated with the prevalence of cerebral infarction in type 2 diabetic patients, suggesting that the combined information about these variants is useful to assess the risk of cerebral infarction.

Sequence variation and genetic evolution at the human F12 locus: mapping quantitative trait nucleotides that influence FXII plasma levels

The level of Factor XII (FXII) is an important phenotype that exhibits a high genetic component and is associated with thrombotic disease. In a genome-wide linkage scan, we demonstrated that the F12 gene represents a quantitative trait locus (QTL) that influences FXII levels. The current study investigated the genetic architecture of the F12 gene to locate polymorphism(s) responsible for the variation of FXII levels. Re-sequencing of the F12 gene in 40 unrelated individuals (selected from the tails of normal distribution of FXII levels) identified 26 polymorphisms which were genotyped in 398 individuals belonging to 21 families from the GAIT Project. By a measured genotype association analysis, eight of 26 SNPs showed significant P-values less than 10(-5) (after multiple test correction) with FXII levels. In addition, the Bayesian Quantitative Trait Nucleotide method, which infers those polymorphisms most likely to have a direct influence on the trait under study, provided evidence that only rs1801020 variation accounted for the variance attributed to this QTL. Moreover, we have analyzed the evolutionary processes that produced the variation in F12 gene and concluded that is evolutionarily neutral and that the T allele of the rs1801020 appeared approximately 100 000 years ago and spread to most human populations rising to high frequencies by genetic drift. Our study provides a template for future genetic studies of human quantitative traits, as we move beyond QTL localization to the polymorphisms responsible for the variation of important biomedical phenotypes.

Deciphering the molecular basis of venous thromboembolism: where are we and where should we go?

Venous thromboembolism (VTE) is a frequent disease that has a major genetic component of risk. However, known identified genetic risk factors account for <30% of idiopathic (without any environmental origin) VTE cases. This article aims to review the lessons learnt during recent decades in the field of the genetics of VTE, describe the present state-of-art methods and discuss promising themes for finding new susceptibility loci.

Combined cis-regulator elements as important mechanism affecting FXII plasma levels

INTRODUCTION

Factor XII (FXII) deficiency is a recessive Mendelian trait due to mutations in the F12 gene. There is no bleeding associated with FXII deficiency, but FXII deficiency has been reported to be associated with risk of thrombosis in some studies.

MATERIAL AND METHODS

We examined the functional effect of two naturally-occurring mutations in two Spanish FXII deficient families: a C/G substitution at position -8, and a C/T substitution at position -13. Both mutations were located on a putative HNF4 binding site of F12 gene promoter. We also analyzed the F12 C46T polymorphism (rs1801020), associated with a decrease in the FXII levels, which also segregated in both families. A fragment containing each one of both -8 and -13 mutations, was cloned 5' of a reporter gene. We compared the in vitro expression of these constructs to the wild type expression.

RESULTS

Our analyses confirm that the -8C/G and the -13C/T mutations decreased expression levels, demonstrating that both mutations are involved in the observed FXII deficiency. In addition, electrophoretic shift analyses suggest that they alter the union of nuclear proteins to the promoter. Coinheritance of these mutations with the C46T polymorphism, result in a significant genotype-phenotype correlation.

CONCLUSIONS

We have identified two naturally-occurring mutations in the F12 promoter that drastically reduce FXII levels. Knowing rare genetic alterations in the F12 gene, together with the C46T common variant, may yield further understanding about the genetic architecture of FXII levels, which may have a role in the risk of thrombosis.

Polymorphism FXII 46C>T and cardiovascular risk: additional data from Spanish and Tunisian patients

BACKGROUND

Previous studies showed an association between Coagulation Factor XII 46C>T polymorphism and variation in FXII plasma levels, as 46C>T seems to affect the translation efficiency. Case-control studies in Spanish samples indicated that genotype T/T is an independent risk factor for venous thrombosis, ischemic stroke and acute coronary artery disease. In this study, we tried to reaffirm the importance of 46C>T in two samples from Spain and Tunisia.

FINDINGS

A Transmission Disequilibrium Test (TDT) based on 101 family trios from Barcelona with one offspring affected by ischemic heart disease and a classical case-control study based on 76 patients with IHD and 118 healthy individuals from North and Centre-South Tunisia were conducted. Subjects were genotyped for 46C>T and data were analyzed accordingly, revealing no association in any of the two samples (TDT: P = 0.16, relative risk 1.17; case-control study: P = 0.59, odds ratio 1.36).

CONCLUSION

The results suggest that 46C>T is not a risk factor for ischemic heart disease in any of the two analyzed samples and therefore the polymorphism seems not to be a universal risk factor for cardiovascular diseases.

The Functional Promoter Polymorphism of the Coagulation Factor XII Gene is not Associated With Peripheral Arterial Disease

Coagulation factor XII (FXII) plays a key role in both coagulation and fibrinolysis and has been associated with cardiovascular disease in some studies. Plasma FXIIa levels are strongly determined by a common functional polymorphism in the promoter of the FXII gene (F12-4C>T). To investigate the potential association of this polymorphism with peripheral arterial disease (PAD), we performed a case-control study including 668 patients with PAD and 762 controls participants without cardiovascular disease. F12 genotype frequencies were not significantly different between patients with PAD and control participants. After adjustment for classical risk factors, the odds ratio of carriers of a F12 -4T allele for PAD was 1.06 (95% confidence interval 0.86—1.32). F12 genotypes were associated with a modest increase of the mean-activated partial thromboplastin time but not with PAD stage or severity. We conclude that the functional F124C>T polymorphism is not associated with PAD.

Genetic polymorphisms for the study of multifactorial stroke

Single-gene disorders explain only a minority of stroke cases. Stroke represents a complex trait, which is usually assumed to be polygenic. On this topic, the role of a wide number of candidate genes has been investigated in stroke through association studies, with controversial results. Therefore, it is difficult for the clinician to establish the validity and the level of clinical applicability of the previously reported associations between genetic factors and stroke. This review is an update and an extensive analysis of the more recent association studies conducted in stroke. We evaluated a number of studies on several candidate genes (including F5, F2, FGA/FGB/FGG, F7, F13A1, vWF, F12, SERPINE1, ITGB3/PLA1/PLA2/ITGA2B, ITGA2, GP1BA, ACE, AGT, NOS3, APOE, LPL, PON1, PDE4D, ALOX5AP, MTHFR, MTR, and CBS), providing a final panel of genes and molecular variants. We categorized this panel in relation to the degree of association with stroke, supported by the results of meta-analyses and case-control studies. Our findings could represent a useful tool to address further molecular investigations and to realize more detailed meta-analyses.

Multiplex assay for genetic testing of thrombophilia: a method for routine clinical care

There is an increasing demand for genetic testing of patients with hypercoagulability. We have developed a multiplex-polymerase chain reaction (PCR) technique that incorporates the state-of-the art of genetic testing for thrombosis mutations (Factor V Leiden [FVL] and G20210A F2 and C46T F12). The sequences are detected by enzyme-linked immunosorbent assay (ELISA)-resolved colorimeter after hybridization with an amplification product labeled with digoxygenin. To evaluate the reliability of this method, we analyzed 122 deoxyribonucleic acid (DNA) samples of known genotypes for these three mutations. Six subjects initially assigned as heterozygous for FVL and two subjects assigned as normal for the G20210A F2 mutation showed discrepancies between the current techniques and our newly-developed ELISA-based technique. When these samples were sequenced the concordance using our method was 100%. Thus, initially they were assigned incorrectly based on the available methodologies. It is noteworthy that our method is adaptable to an Automated ELISA Analyzer that allows for routine processing of both small and large numbers of DNA samples. We present a robust, rapid, reproducible, cost-effective, and simple multiplex PCR ELISA method to simultaneously detect carriers of thrombotic genetic risk factors. Testing for thrombophilia should contribute to better diagnosis, prevention, and treatment strategies, providing valuable information to assess the risk of recurrence in the proband, and in family members who are asymptomatic.

Pharmacological regulation of factor XII activation may be a new target to control pathological coagulation

FXII was identified 50 years ago as a coagulation protein in the intrinsic pathway of blood coagulation as FXII deficient patients had marked prolongation of the in vitro surface-activated coagulation time. However, series of investigations have convincingly shown that FXII has no role in normal hemostasis. Recently, experimentally induced thrombosis in factor XII-knockout mice has provided evidence that factor XII (FXII) deficient mice are protected against ischemic brain injury after obstructive clot formation. Based on these experiments it has, therefore, been suggested, that blocking of FXII could be a unique target to prevent obstructive clot formation in arterial thrombosis without side effect of increased bleeding. FXII deficiency has, however, not convincingly been shown to protect against arterial thrombosis in humans. The target mentioned above may either be an inhibition of FXII activation or an inhibition of its proteolytic activity. FXII is a zymogen of the proteolytic enzyme, FXIIa, the substrates of which are factor XI and prekallikrein. Thus, FXIIa is not only involved in the activation of the coagulation system, but is also associated with the kallikrein/kinin system. The activation of the latter is deeply involved in inflammation and pain sensation. Furthermore, FXIIa binds to endothelial cells and to the extracellular matrix, indicating a role in vascular repair. Therefore, a complete evaluation of all these properties of FXII and FXIIa has to be considered when formulating a strategy for blocking FXII activation.

Intrinsic pathway of coagulation and arterial thrombosis

Formation of a fibrin clot is mediated by a group of tightly regulated plasma proteases and cofactors. While this system is essential for minimizing blood loss from an injured blood vessel (hemostasis), it also contributes to pathologic fibrin formation and platelet activation that may occlude vessels (thrombosis). Many antithrombotic drugs target key elements of the plasma coagulation mechanism such as thrombin and factor Xa, based on the premise that plasma elements contributing to thrombosis are primarily those involved in hemostasis. Recent studies with genetically altered mice raise questions about this paradigm. Deficiencies of the intrinsic pathway proteases factor XII and factor XI are not associated with abnormal hemostasis in mice, but impair formation of occlusive thrombi in arterial injury models, indicating that pathways not essential for hemostasis participate in arterial thrombosis. If factor XII or factor XI make similar contributions to thrombosis in humans, these proteases could be ideal targets for drugs to treat or prevent thromboembolic disease with minimal risk of therapy-associated bleeding.

Patent foramen ovale and prothrombotic markers in young stroke patients

Patent foramen ovale (PFO) is more frequent in cryptogenic stroke patients than in the general population. The aim of this study was to determine prothrombotic markers regarding PFO in young cryptogenic stroke patients. We prospectively included consecutive cryptogenic stroke patients younger than 55 years. PFO was diagnosed with simultaneous transcranial Doppler and transesophageal echocardiography. We analyzed the following prothrombotic markers: antiphospholipid antibodies (APS), protein C and protein S deficiencies, factor V Leiden FVG1691A, prothrombin gene mutation PTG20210A and coagulation factor XII mutation FXIIC46T. From June 2005 to July 2006 we studied 39 patients, mean age 44.7 +/- 8.6 years, 48.7% men. PFO was detected in 17 patients (43.6%). We found no differences between PFO and non-PFO patients regarding prothrombotic markers: APS (P = 0.851), protein S deficiency (P = 0.851), protein C deficiency (P = 0.249), FVG1691A (P = 0.202), PTG20210A (P = 0.401) or FXIIC46T (P = 0.966). Female gender was the only variable related to prothrombotic markers, independent of PFO (P = 0.001). The only prothrombotic marker related to PFO size (large PFO) was APS (P = 0.043). Large PFO were also related to deep venous thrombosis (P = 0.040) and atrial septal aneurysm (P = 0.010). PFO patients do not present more prothrombotic markers than non-PFO patients, but APS are more frequent in large PFO.

Evidence of a U-shaped association between factor XII activity and overall survival

INTRODUCTION

The clinical relevance of decreased coagulation factor XII (FXII) plasma activity as a risk factor for both venous and arterial thrombosis is still discussed controversially. The current study evaluated the predictive value of FXII levels for all-cause mortality in a large Viennese patient cohort.

PATIENTS AND METHODS

Individuals, whose FXII activity levels were determined for suspected coagulation disorders or thrombophilia screening between 1991-2003 were included in this study (n = 8936, 51% male, 49% female, median age 43 years). Death/survival was determined by record linkage with the Austrian Death Registry. The median observation period was 5 years covering a total of 46 400 person years; the death rate was 17.1%. For Cox regression analysis, FXII plasma activity was divided into 11 categories of 10% steps with the category of > 100% FXII serving as a reference category.

RESULTS

With decreasing FXII plasma activity, hazard ratios for all-cause mortality gradually increased linearly from 1.0 in the > 100% category to 1.5 (95% CI: 1.2-1.9) in the 80-90% category to 4.7 (95% CI: 3.4-6.5) in the 10-20% category. Similar results were obtained, when only vascular mortality or death as a result of ischemic heart disease was considered. No significant increase in all-cause mortality (HR: 1.4, 95%CI 0.7-2.8) was observed in the small group of FXII-deficient subjects [0-10% category (n = 58)].

CONCLUSIONS

This study first demonstrates a strong and almost linear association of FXII plasma activity between 90% and 10% with all-cause mortality in a large Viennese patient cohort. Interestingly, mortality rates are not increased when FXII activity is below 10%, resulting in a U-shaped survival curve.

Diagnostic yield of prothrombotic state studies in cryptogenic stroke

OBJECTIVES

Around 30% of ischemic strokes are considered cryptogenic. We analyzed the diagnostic yield of prothrombotic state (PS) studies in patients with an initial cryptogenic stroke (CS).

MATERIAL AND METHODS

We prospectively included consecutive CS patients according to the TOAST criteria. PS included plasmatic determinations of antiphospholipid (APL) antibodies and lupus anticoagulant (LA), S (SPd) and C (CPd) protein deficiencies, and genetic analysis of the prothrombin gene mutation (PT G20210A) and the factor V Leiden mutation (FV G1691A). We recorded age, sex and vascular risk factors.

RESULTS

From a total of 89 patients (mean age 56.9 +/- 14.3 years, 53% men), we identified 16 PS in 15 patients (16.85%): APL-6, LA-2, SPd-2, CPd-1, PT G20210A -3 and FV G1691A -2. One patient presented an association (APL and PT G20210A).

CONCLUSIONS

One of every six patients with initial CS present a PS. Age or sex and conventional cardiovascular risk factors were not related to PS study findings, supporting the relevance of such studies in all patients with an initial CS.

Stroke and pulmonary thromboembolism after a long flight

In the economy class syndrome (ECS) the patient presents a deep venous thrombosis (DVT) with or without pulmonary thromboembolism (PTE) during or after a long trip as a result of prolonged immobilization. Economy class stroke syndrome is an infrequent ECS variant in which ischemic stroke is associated with a patent foramen ovale (PFO). Few cases have been published in the literature to date. We present a patient who suffered a PTE and an ischemic stroke immediately after a transoceanic flight. A 36-year-old woman with no significant medical or familial history flew economy class from Lima, Peru, to Madrid, Spain. On disembarkation she presented sudden dyspnea and a depressed level of consciousness, global aphasia, and right hemiparesis. A pulmonary scintigraphy showed a PTE and a cranial MRI revealed an ischemic infarct in the left middle cerebral artery territory. We simultaneously performed a transesophageal echocardiography and a transcranial Doppler and observed a massive right-to-left shunt through a PFO. The patient was a heterozygous carrier of the C46T mutation of coagulation factor XII. The appearance of a stroke following a long trip is suggestive of paradoxical embolism through a PFO, mainly if it is associated with a DVT and/or a PTE. The cause of the initial event, the DVT, could be a prothrombotic state.

Defective thrombus formation in mice lacking coagulation factor XII

Blood coagulation is thought to be initiated by plasma protease factor VIIa in complex with the membrane protein tissue factor. In contrast, coagulation factor XII (FXII)–mediated fibrin formation is not believed to play an important role for coagulation in vivo. We used FXII-deficient mice to study the contributions of FXII to thrombus formation in vivo. Intravital fluorescence microscopy and blood flow measurements in three distinct arterial beds revealed a severe defect in the formation and stabilization of platelet-rich occlusive thrombi. Although FXII-deficient mice do not experience spontaneous or excessive injury-related bleeding, they are protected against collagen- and epinephrine-induced thromboembolism. Infusion of human FXII into FXII-null mice restored injury-induced thrombus formation. These unexpected findings change the long-standing concept that the FXII-induced intrinsic coagulation pathway is not important for clotting in vivo. The results establish FXII as essential for thrombus formation, and identify FXII as a novel target for antithrombotic therapy.

The 825C/T polymorphism of G-protein beta3 subunit gene and risk of ischaemic stroke

In this study, we investigated the association of G protein beta3 subunit gene (GNB 3) C825T polymorphism with ischaemic stroke and its subtypes in the Chinese Han population in a large case-control study. A total of 990 ischemic stroke patients and 1124 controls were recruited from six medical centres in China. Genotype was determined by polymerase chain reaction and restriction fragment length polymorphism (RFLP) assay. Logistic regression analysis was performed to identify the independent risk factors for stroke. The frequency of 825T carriers is significantly higher in cerebral thrombosis in male subjects (OR=1.35, 95% CI, 1.01-1.82, P=0.046). After further adjustment with traditional risk factors to stroke, the association is not significant. In conclusion, the GNB3 825T allele is not an independent risk factor to ischaemic stroke in the Chinese population.