scholarly journals Whole exome sequencing of ENU-induced thrombosis modifier mutations in the mouse

2017 ◽  
Author(s):  
Kärt Tomberg ◽  
Randal J. Westrick ◽  
Emilee N. Kotnik ◽  
David R Siemieniak ◽  
Guojing Zhu ◽  
...  
Keyword(s):  
Risk Factor ◽  
Venous Thrombosis ◽  
Genetic Risk ◽  
Blood Clotting ◽  
Tissue Factor Pathway Inhibitor ◽  
Factor V Leiden ◽  
Factor V ◽  
Loss Of Function ◽  
Whole Exome ◽  
Tissue Factor Pathway

AbstractAlthough the Factor V Leiden (FVL) gene variant is the most prevalent genetic risk factor for venous thrombosis, only 10% of FVL carriers will experience such an event in their lifetime. To identify potential FVL modifier genes contributing to this incomplete penetrance, we took advantage of a perinatal synthetic lethal thrombosis phenotype in mice homozygous for FVL (F5L/L) and haploinsufficient for tissue factor pathway inhibitor (Tfpi+/-) to perform a sensitized dominant ENU mutagenesis screen. Linkage analysis conducted in the 3 largest pedigrees generated from the survivingF5L/LTfpi+/-mice (‘rescues’) using ENU-induced coding variants as genetic markers was unsuccessful in identifying major suppressor loci. Whole exome sequencing was applied to DNA from 107 rescue mice to identify candidate genes enriched for ENU mutations. A total of 3,481 potentially deleterious candidate ENU variants were identified in 2,984 genes. After correcting for gene size and multiple testing,Arl6ip5was identified as the most enriched gene, though not reaching genome-wide significance. Evaluation of CRISPR/Cas9 induced loss of function in the top 6 genes failed to demonstrate a clear rescue phenotype. However, a maternally inherited (not ENU-induced)de novomutation (Plcb4R335Q) exhibited significant co-segregation with the rescue phenotype (p=0.003) in the corresponding pedigree. Thrombosis suppression by heterozygousPlcb4loss of function was confirmed through analysis of an independent, CRISPR/Cas9-inducedPlcb4mutation (p=0.01).Author summaryAbnormal blood clotting in veins (venous thrombosis) or arteries (arterial thrombosis) are major health problems, with venous thrombosis affecting approximately 1 in every thousand individuals annually in the United States. Susceptibility to venous thrombosis is governed by both genes and environment, with approximately 60% of the risk attributed to genetic influences. Though several genetic risk factors are known, >50% of genetic risk remains unexplained. Approximately 5% of people carry the most common known risk factor, Factor V Leiden. However, only 10% of these individuals will develop a blood clot in their lifetime. Mice carrying two copies of the Factor V Leiden mutation together with a mutation in a second gene called tissue factor pathway inhibitor develop fatal thrombosis shortly after birth. To identify genes that prevent this fatal thrombosis, we studied a large panel of mice carrying inactivating gene changes randomly distributed throughout the genome. We identified several genes as potential candidates to alter blood clotting balance in mice and humans with predisposition to thrombosis, and confirmed this protective function for DNA changes in one of these genes (Plcb4).

scholarly journals Sensitized mutagenesis screen in Factor V Leiden mice identifies thrombosis suppressor loci

2017 ◽  
Vol 114 (36) ◽  
pp. 9659-9664 ◽  
Author(s):  
Randal J. Westrick ◽  
Kärt Tomberg ◽  
Amy E. Siebert ◽  
Guojing Zhu ◽  
Mary E. Winn ◽  
...  
Keyword(s):  
Tissue Factor ◽  
Genetic Risk ◽  
Tissue Factor Pathway Inhibitor ◽  
Factor V Leiden ◽  
Factor V ◽  
Factor Gene ◽  
Mutagenesis Screen ◽  
Function Mechanism ◽  
Whole Exome ◽  
Tissue Factor Pathway

Factor V Leiden (F5L) is a common genetic risk factor for venous thromboembolism in humans. We conducted a sensitized N-ethyl-N-nitrosourea (ENU) mutagenesis screen for dominant thrombosuppressor genes based on perinatal lethal thrombosis in mice homozygous for F5L (F5L/L) and haploinsufficient for tissue factor pathway inhibitor (Tfpi+/−). F8 deficiency enhanced the survival of F5L/LTfpi+/− mice, demonstrating that F5L/LTfpi+/− lethality is genetically suppressible. ENU-mutagenized F5L/L males and F5L/+Tfpi+/− females were crossed to generate 6,729 progeny, with 98 F5L/LTfpi+/− offspring surviving until weaning. Sixteen lines, referred to as “modifier of Factor 5 Leiden (MF5L1–16),” exhibited transmission of a putative thrombosuppressor to subsequent generations. Linkage analysis in MF5L6 identified a chromosome 3 locus containing the tissue factor gene (F3). Although no ENU-induced F3 mutation was identified, haploinsufficiency for F3 (F3+/−) suppressed F5L/LTfpi+/− lethality. Whole-exome sequencing in MF5L12 identified an Actr2 gene point mutation (p.R258G) as the sole candidate. Inheritance of this variant is associated with suppression of F5L/LTfpi+/− lethality (P = 1.7 × 10−6), suggesting that Actr2p.R258G is thrombosuppressive. CRISPR/Cas9 experiments to generate an independent Actr2 knockin/knockout demonstrated that Actr2 haploinsufficiency is lethal, supporting a hypomorphic or gain-of-function mechanism of action for Actr2p.R258G. Our findings identify F8 and the Tfpi/F3 axis as key regulators in determining thrombosis balance in the setting of F5L and also suggest a role for Actr2 in this process.

Factor XIIIV34L is not an additional genetic risk factor for venous thrombosis in Factor V Leiden carriers

Blood ◽  
2001 ◽  
Vol 97 (6) ◽  
pp. 1894-1896 ◽  
Author(s):  
Pierre E. Morange ◽  
Mireille Henry ◽  
Dominique Brunet ◽  
Marie-Françoise Aillaud ◽  
Irène Juhan-Vague
Keyword(s):  
Risk Factor ◽  
Venous Thrombosis ◽  
Genetic Risk ◽  
Factor V Leiden ◽  
Genetic Risk Factor ◽  
Factor V

Factor V Leiden (Arg506Gln), a Confounding Genetic Risk Factor but not Mandatory for the Occurrence of Venous Thromboembolism in Homozygotes and Obligate Heterozygotes for Cystathionine β-synthase Deficiency

1999 ◽  
Vol 81 (04) ◽  
pp. 502-505 ◽  
Author(s):  
S. Yap ◽  
K. A. O’Donnell ◽  
C. O’Neill ◽  
P. D. Mayne ◽  
P. Thornton ◽  
...  
Keyword(s):  
Risk Factor ◽  
Venous Thrombosis ◽  
Genetic Risk ◽  
Activated Protein C ◽  
Factor V Leiden ◽  
Allelic Frequency ◽  
Genetic Risk Factor ◽  
Factor V ◽  
Contributing Factors ◽  
Thrombotic Risk

SummaryThrombosis is the major cause of morbidity and mortality in individuals with untreated classical homocystinuria (HCU) due to cystathionine β-synthase deficiency and characterised by severe hyperhomocysteinaemia. In addition, mild and moderate hyperhomocysteinaemia and Factor V Leiden (FVL; Arg506Gln) have recently been identified as thrombotic risk factors. FVL, which renders resistance to activated Protein C, is the most common inherited genetic risk factor for thrombosis with a high allelic frequency amongst Caucasians. As thrombophilia is a multigenic disorder, 26 individuals with HCU (median age 17.6 years, range 3.5-32.8 years) and 36 obligate heterozygotes (median age 51.5 years, range 34-74 years) were screened for FVL. All the HCU individuals received treatment, except one, within 6 weeks of birth for those who were diagnosed at birth through the national newborn screening programme (n = 20) and at the time of diagnosis for those late detected (n = 5, mean age of starting treatment 4.9 years, range 1.4-11 years). All had been free from venous thrombosis, except one HCU individual and one HCU obligate heterozygote. Neither of the two individuals with venous thrombosis carried FVL. Two independent individuals with HCU (male 14.8 years; female 18.2 years) were heterozygous for FVL (allelic frequency 3.8%) and three independent HCU obligate heterozygotes (males 40 and 45.8 years; female 45.6 years) were also heterozygous for FVL (allelic frequency 4.16%). The findings in this small group suggest that FVL is not a mandatory but a significant confounding risk factor for the occurrence of thrombosis in HCU individuals and additional contributing factors may be required for thrombosis to occur in HCU obligate heterozygotes with FVL heterozygosity. Our data also suggest that treatment of HCU not only reduces the thrombotic risk in patients with isolated HCU but also in those with the additional FVL heterozygosity.

Combined Factor V Leiden (R506Q) and prothrombin G20210A genotyping in young patients presenting with deep venous thrombosis

2006 ◽  
Vol 21 (1) ◽  
pp. 24-27 ◽  
Author(s):  
A Mansilha ◽  
F Araújo ◽  
M Severo ◽  
S M Sampaio ◽  
T Toledo ◽  
...  
Keyword(s):  
Risk Factor ◽  
Young People ◽  
Venous Thrombosis ◽  
Deep Venous Thrombosis ◽  
Young Patients ◽  
Factor V Leiden ◽  
First Episode ◽  
Control Group ◽  
Factor V ◽  
Factor V Leiden Mutation

Objective: To evaluate the association between the Factor V Leiden (FV R506Q) and prothrombin gene (FII G20210A) mutations and deep venous thrombosis (DVT) in young people. Methods: Blood samples were drawn from 199 subjects: 100 healthy controls and 99 unselected patients, with an objectively documented first episode of DVT under 40 years old. DNA analysis was performed using the polymerase chain reaction. Results: The mean age in the patient cohort was 27 years (range 16–40) and 68 (68.7%) were women. Patient prevalences were 20.6% and 10.1% for FV R506Q and FII G20210A, respectively. In the control group, carrier frequencies were 2% and 5%, respectively. We found an increased overall relative risk of DVT with statistical significance for FV R506Q carriers (OR: 12.8; 95% CI: 2.9–56.7; P < 0.001), but not for FII G20210A mutation (OR: 2.1; 95% CI: 0.7–6.5; P = 0.19). Conclusions: Our results suggest a possible increase in DVT risk for the young G20210A allele carriers, which can be more expressed in the presence of a circumstantial risk factor. There is extremely strong evidence that the Factor V Leiden mutation is an important risk factor in the development of a first episode of DVT in young people.

Abstract 43: Prothrombinase Assembled with Factor V Leiden is Resistant to Inhibition by Tissue Factor Pathway Inhibitor α Lowering the Procoagulant Threshold for Initiation of Coagulation

2016 ◽  
Vol 36 (suppl_1) ◽  
Author(s):  
Jeremy P Wood ◽  
Lisa M Baumann Kreuziger ◽  
Susan A Maroney ◽  
Rodney M Camire ◽  
Alan E Mast
Keyword(s):  
Tissue Factor ◽  
Thrombin Generation ◽  
Tissue Factor Pathway Inhibitor ◽  
Platelet Rich Plasma ◽  
Anticoagulant Activity ◽  
Factor V Leiden ◽  
Factor Xa ◽  
Factor V ◽  
Activation Threshold ◽  
Tissue Factor Pathway

Factor V (FV) assembles with factor Xa (FXa) into prothrombinase, the enzymatic complex that converts prothrombin to thrombin. Tissue factor pathway inhibitor α (TFPIα) inhibits prothrombinase by high affinity interactions with FXa-activated FV and the FXa active site, thereby blocking the initiation of coagulation. FV Leiden (FVL) is strongly linked to venous thrombosis through its resistance to degradation by activated protein C (aPC), which enhances the propagation of coagulation. FVL combined with a 50% reduction in TFPI causes severe thrombosis and perinatal lethality in mice, suggesting that FVL also promotes the initiation of coagulation. To examine this possibility, thrombin generation assays initiated with limiting FXa were performed with control or FVL plasma and platelet-rich plasma (PRP). The activation threshold for thrombin generation was 10 to 20 pM FXa in 10 control plasmas, but was 5 pM in 4 of 10 homozygous FVL plasmas. FVL PRP had a similar decrease in the activation threshold. The differences in activation threshold were totally normalized by an anti-TFPI antibody, while exogenous TFPIα and a FV-binding peptide that mimics TFPIα had reduced anticoagulant activity in FVL plasma, revealing that the procoagulant effects of FVL in these assays rely on TFPIα. Next, FVL plasmas were studied in fibrin clot formation assays, as they are sensitive to small amounts of thrombin. In reactions activated with 0.5 pM FXa, 1 of 8 control plasmas, compared to 7 of 8 homozygous FVL plasmas, clotted within 60 minutes, with differences again normalized by the anti-TFPI antibody. In prothrombinase activity assays using purified proteins, TFPIα was a 1.7-fold weaker inhibitor of prothrombinase assembled with FVL compared to FV. Thus, in addition to its aPC-mediated effect on the propagation of coagulation, FVL is resistant to TFPIα inhibition, exerting a procoagulant effect on coagulation initiation. This is evident in responses to small stimuli, where TFPIα blocks clotting in plasmas with FV but not FVL. The TFPIα-mediated modulation of the procoagulant threshold may explain the severe perinatal thrombosis in FVL mice with decreased TFPI and be clinically relevant in the clotting associated with oral contraceptives, which cause acquired TFPI deficiency.

Gene-Gene and Gene-Environment Interactions Determine Risk of Thrombosis in Families With Inherited Antithrombin Deficiency

Blood ◽  
1999 ◽  
Vol 94 (8) ◽  
pp. 2590-2594 ◽  
Author(s):  
H.H. van Boven ◽  
J.P. Vandenbroucke ◽  
E. Briët ◽  
F.R. Rosendaal
Keyword(s):  
Risk Factors ◽  
Risk Factor ◽  
Venous Thromboembolism ◽  
Genetic Risk ◽  
Factor V Leiden ◽  
Genetic Defects ◽  
Factor V ◽  
Antithrombin Deficiency ◽  
Gene Environment ◽  
Genetic And Environmental Factors

To analyze inherited antithrombin deficiency as a risk factor for venous thromboembolism in various conditions with regard to the presence or absence of additional genetic or acquired risk factors, we compared 48 antithrombin-deficient individuals with 44 nondeficient individuals of 14 selected families with inherited antithrombin deficiency. The incidence of venous thromboembolism for antithrombin deficient individuals was 20 times higher than among nondeficient individuals (1.1% v 0.05% per year). At the age of 50 years, greater than 50% of antithrombin-deficient individuals had experienced thrombosis compared with 5% of nondeficient individuals. Additional genetic risk factors, Factor V Leiden and PT20210A, were found in more than half of these selected families. The effect of exposure to 2 genetic defects was a 5-fold increased incidence (4.6% per year; 95% confidence interval [CI], 1.9% to 11.1%). Acquired risk factors were often present, determining the onset of thrombosis. The incidence among those with exposure to antithrombin deficiency and an acquired risk factor was increased 20-fold (20.3% per year; 95% CI, 12.0% to 34.3%). In conclusion, in these thrombophilia families, the genetic and environmental factors interact to bring about venous thrombosis. Inherited antithrombin deficiency proves to be a prominent risk factor for venous thromboembolism. The increased risks among those with exposure to acquired risk factors should be considered and adequate prophylactic anticoagulant therapy in high-risk situations seems indicated in selected families with inherited antithrombin deficiency.

Resistance to activated protein C is a risk factor for pregnancy-related venous thrombosis in the absence of the F5 rs6025 (factor V Leiden) polymorphism

2011 ◽  
Vol 154 (2) ◽  
pp. 241-247 ◽  
Author(s):  
Astrid Bergrem ◽  
Anders Erik Astrup Dahm ◽  
Anne Flem Jacobsen ◽  
Marie-Christine Mowinckel ◽  
Leiv Sandvik ◽  
...  
Keyword(s):  
Risk Factor ◽  
Venous Thrombosis ◽  
Protein C ◽  
Activated Protein C ◽  
Factor V Leiden ◽  
Factor V

scholarly journals Fibrinogen γ′ increases the sensitivity to activated protein C in normal and factor V Leiden plasma

Blood ◽  
2014 ◽  
Vol 124 (9) ◽  
pp. 1531-1538 ◽  
Author(s):  
Farida Omarova ◽  
Shirley Uitte de Willige ◽  
Paolo Simioni ◽  
Robert A. S. Ariëns ◽  
Rogier M. Bertina ◽  
...  
Keyword(s):  
Risk Factor ◽  
Venous Thrombosis ◽  
Protein C ◽  
Activated Protein C ◽  
Factor V Leiden ◽  
Factor V ◽  
Common Risk Factor ◽  
Apc Resistance ◽  
Key Points

Key Points Fibrinogen, and particularly fibrinogen γ′, counteracts plasma APC resistance, the most common risk factor for venous thrombosis. The C-terminal peptide of the fibrinogen γ′ chain inhibits protein C activation, but still improves the response of plasma to APC.

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