Genetic determinants of activity and antigen levels of contact system factors

Whole-Exome Sequencing in a Family with an Unexplained Tendency for Venous Thromboembolism: Multicomponent Prediction of Low-Frequency Variant Deleteriousness and of Individual Protein Interaction

Whole-exome sequencing (WES) in families with an unexplained tendency for venous thromboembolism (VTE) may favor detection of low-frequency variants in genes with known contribution to hemostasis or associated with VTE-related phenotypes. WES analysis in six family members, three of whom affected by documented VTE, filtered for MAF < 0.04 in 192 candidate genes, revealed 22 heterozygous (16 missense and six synonymous) variants in patients. Functional prediction by multi-component bioinformatics tools, implemented by a database/literature search, including ClinVar annotation and QTL analysis, prioritized 12 missense variants, three of which (CRP Leu61Pro, F2 Asn514Lys and NQO1 Arg139Trp) were present in all patients, and the frequent functional variants FGB Arg478Lys and IL1A Ala114Ser. Combinations of prioritized variants in each patient were used to infer functional protein interactions. Different interaction patterns, supported by high-quality evidence, included eight proteins intertwined in the "acute phase" (CRP, F2, SERPINA1 and IL1A) and/or in the "fibrinogen complex" (CRP, F2, PLAT, THBS1, VWF and FGB) significantly enriched terms. In a wide group of candidate genes, this approach highlighted six low-frequency variants (CRP Leu61Pro, F2 Asn514Lys, SERPINA1 Arg63Cys, THBS1 Asp901Glu, VWF Arg1399His and PLAT Arg164Trp), five of which were top ranked for predicted deleteriousness, which in different combinations may contribute to disease susceptibility in members of this family.

Venous thromboembolism-related genetic determinant F11 rs4253417 is a potential prognostic factor in ischaemic stroke

Ischaemic stroke (IS) and venous thromboembolism (VTE) are two forms of thromboembolism that, although distinct, seem to share numerous risk factors. Concerning genetic risk factors, while many VTE genetic markers have been reported, inclusively by genome-wide association studies (GWAS), the identification and validation of genetic determinants underlying IS pathogenesis have been challenging. Considering that IS and VTE shared biological pathways and aetiological factors, the severity of IS might be also influenced by VTE-related genetic variants. Thus, the present study was designed to analyse the impact of six VTE GWAS-identified genetic variants on the clinical outcome of 363 acute IS patients. Results revealed that the single-nucleotide polymorphism (SNP) F11 rs4253417 was an independent predictor of the 5-year risk of death among patients with total anterior circulation infarct (TACI). Namely, the ones carrying the SNP C allele presented a fourfold increase in the 5-year risk of death compared to TT genotype carriers (CC/CT vs. TT; adjusted HR, 4.240; 95% CI, 1.260-14.270; P = 0.020). This SNP is known to be associated with coagulation factor XI (FXI) levels, thus with implications in haemostasis and inflammation. As such, F11 rs4253417 might be a promising prognostic biomarker among TACI patients to aid in clinical decision-making. However, additional investigation is required to confirm the study's results and dissect the underlying mechanisms.

Stroke genetics informs drug discovery and risk prediction across ancestries

Previous genome-wide association studies (GWASs) of stroke - the second leading cause of death worldwide - were conducted predominantly in populations of European ancestry1,2. Here, in cross-ancestry GWAS meta-analyses of 110,182 patients who have had a stroke (five ancestries, 33% non-European) and 1,503,898 control individuals, we identify association signals for stroke and its subtypes at 89 (61 new) independent loci: 60 in primary inverse-variance-weighted analyses and 29 in secondary meta-regression and multitrait analyses. On the basis of internal cross-ancestry validation and an independent follow-up in 89,084 additional cases of stroke (30% non-European) and 1,013,843 control individuals, 87% of the primary stroke risk loci and 60% of the secondary stroke risk loci were replicated (P < 0.05). Effect sizes were highly correlated across ancestries. Cross-ancestry fine-mapping, in silico mutagenesis analysis3, and transcriptome-wide and proteome-wide association analyses revealed putative causal genes (such as SH3PXD2A and FURIN) and variants (such as at GRK5 and NOS3). Using a three-pronged approach4, we provide genetic evidence for putative drug effects, highlighting F11, KLKB1, PROC, GP1BA, LAMC2 and VCAM1 as possible targets, with drugs already under investigation for stroke for F11 and PROC. A polygenic score integrating cross-ancestry and ancestry-specific stroke GWASs with vascular-risk factor GWASs (integrative polygenic scores) strongly predicted ischaemic stroke in populations of European, East Asian and African ancestry5. Stroke genetic risk scores were predictive of ischaemic stroke independent of clinical risk factors in 52,600 clinical-trial participants with cardiometabolic disease. Our results provide insights to inform biology, reveal potential drug targets and derive genetic risk prediction tools across ancestries.

Ischemic Stroke and Sleep: The Linking Genetic Factors

This review summarizes the available data about genetic factors which can link ischemic stroke and sleep. Sleep patterns (subjective and objective measures) are characterized by heritability and comprise up to 38-46%. According to Mendelian randomization analysis, genetic liability for short sleep duration and frequent insomnia symptoms is associated with ischemic stroke (predominantly of large artery subtype). The potential genetic links include variants of circadian genes, genes encoding components of neurotransmitter systems, common cardiovascular risk factors, as well as specific genetic factors related to certain sleep disorders.

Prospective study of plasma high molecular weight kininogen and prekallikrein and incidence of coronary heart disease, ischemic stroke and heart failure

INTRODUCTION

High molecular weight kininogen (HK) and prekallikrein (PK) are proteins in the kallikrein/kinin system of the coagulation cascade. They play an important role in the contact activation system of the intrinsic coagulation pathway, renin-angiotensin activation, and inflammation. Hence these proteins have been posited to affect the occurrence of cardiovascular events and thus to be potential therapeutic targets. Previous case-control studies have provided inconsistent evidence for an association of HK and PK with cardiovascular disease.

METHODS

In the prospective population-based Atherosclerosis Risk in Communities(ARIC) Study, we used Cox proportional hazards regression models to investigate the association in 4195 middle-aged adults of plasma HK and PK concentrations in 1993-95 (linearly and in quartiles) with incident coronary heart disease, ischemic stroke, and heart failure through 2016.

RESULTS

Over a mean of 18 years follow-up, we identified incident cardiovascular events (coronary heart disease and ischemic stroke) in 618 participants and heart failure in 667. We observed no significant relation between HK or PK and cardiovascular disease or heart failure, before and after adjusting for several potential confounding variables.

CONCLUSIONS

We found no compelling evidence to support an association of plasma HK or PK concentrations with incident CHD, ischemic stroke, or heart failure.

The contact system at the crossroads of various key patho- physiological functions: Update on present understanding, laboratory exploration and future perspectives

The contact system initiates the intrinsic pathway of coagulation and is started by Factor XII activation, which then activates prekallicrein to kallicrein and Factor XI to Factor XIa and, in the presence of high molecular weight kininogen, forms a "contact phase activation loop", that amplifies Factor XII activation. FXII deficiency is not associated with bleeding tendencies, but when the blood clots, the thrombus is less dense, thus favoring antithrombotic protection. Activated Factor XII inhibition emerges as an efficient target for preventing thrombo-embolic diseases without inducing a hemorrhagic risk. Activated Factor XII exhibits other activities, in that it can activate complement and provoke inflammation, contributing to innate immunity. It also stimulates fibrinolysis through uPA activation from scu-PA. Among the other components of the contact phase, Factor XI has a more important role in coagulation pathways and can directly activate FX, FVIII and FV, in a FIX independent pathway. Its deficiency is associated with a mild bleeding diathesis ("pseudo-hemophilia" or hemophilia C), with a variable incidence among kindreds. Recently, the occurrence of thrombotic events the same day following infusion of immunoglobulin concentrates has been demonstrated to be caused by the presence of trace amounts of activated Factor XI, pointing out the key role of this factor for thrombogenicity. Prekallicrein can be activated at the endothelial surface in the presence of high molecular weight kininogen, whose cleavage generates bradykinins and contributes to vessel tonicity and inflammation. The contact phase, through its activation loop, is then an important physiological system, which can initiate and regulate various biological functions and is at the crossroads of various biological activities. Many of the body's physiological functions are intimately linked between them, making the global approach of special usefulness for understanding the interactions which can result from any abnormality of one of them. New pharmaceutical drugs targeting a defined activity need to be investigated for all the possible interferences or side effects. In this article we aim to present and summarize the present understanding of contact phase system activation and regulation, its involvement in various physiological functions, and the laboratory tools for its exploration.