Fibrinogen Gene Research Articles

Correlation between levels of fibrinogen, beta455 g/A fibrinogen gene polymorphism and chronic periodontitis

To investigate the relationship between plasma levels of fibrinogen, the-beta455 G/A fibrinogen gene polymorphism and the severity of periodontal inflammation and to explore the possible role of fibrinogen in the association of periodontitis with coronary heart disease (CHD). A total of 121 patients with moderate to severe periodontitis and periodontally healthy and gingivitis controls were enrolled in the study. Peripheral blood samples were collected and the plasma fibrinogen levels were determined by the clotting method of Clauss. Polymerase chain reaction and restriction fragment length polymorphism analysis with Hae III were used to examine the -beta455 G/A fibrinogen gene polymorphism. Fibrinogen levels were significantly higher in moderately or severely chronic periodontitis patients [(3.45 +/- 0.68) g/L] than periodontally healthy and gingivitis controls [(2.47 +/- 0.42) g/L, P < 0.001]. The carrier status of the A allele at position -455 in the beta fibrinogen gene was associated with elevated fibrinogen levels and the frequency of the-A455 allele in the beta fibrinogen gene in the patient group was significantly higher than in the control group (P = 0.032). Carriers of the -A455 allele were about 3-fold more likely to have moderate or severe periodontitis as compare to individuals without the -A455 allele( OR = 3. =135, P= 0.008). Fg-beta455 G/A polymorphism may contribute to the elevated plasma fibrinogen levels and put individuals at higher risk of having severe periodontitis. As the independent risk factor of CHD, fibrinogen levels and Fg-beta455 G/A polymorphism may play a role in the pathogenesis of periodontitis.

Fibrinogen Genes and Myocardial Infarction

Fibrinogen has a role in inflammatory processes and participates in atherosclerotic plaque formation. Despite intensive investigation, there is no clear evidence for a role of variations in the genes coding for the fibrinogen-alpha, fibrinogen-beta, and fibrinogen-gamma polypeptide chains in myocardial infarction. We examined the association of haplotypes in the 50-kb fibrinogen gene region with myocardial infarction in 2 large case-control samples. Study sample 1 consisted of 3657 patients with myocardial infarction and 1211 control individuals and sample 2 comprised 1392 patients and 1392 controls. Haplotypes were inferred from genotype analyses of tagging single nucleotide polymorphisms dispersed among the fibrinogen genes. The frequencies of these haplotypes were not significantly different between the case and control groups in either sample (P > or = 0.07). In addition, haplotypes specific for individual fibrinogen genes were analyzed. No substantial differences in the frequencies of these haplotypes were observed between the groups (P > or = 0.13). Finally, haplotypes composed of SNPs that exhibited relatively low pairwise allelic associations among each other were examined. The proportions of the haplotypes were not significantly different between cases and controls (P > or = 0.12). A haplotype analysis did not reveal a link between genetic variations in the fibrinogen gene region and myocardial infarction.

Associations between common fibrinogen gene polymorphisms and cardiovascular disease in older adults

Elevated plasma fibrinogen is a risk factor for cardiovascular disease (CVD), but associations between fibrinogen single nucleotide polymorphisms (SNPs) and disease risk are inconsistent. We investigated whether common (> or = 5% minor allele frequency) variation in the fibrinogen genes (FGA, FGB, FGG) is associated with fibrinogen concentration, carotid artery intima-medial thickness (IMT) and risk of incident myocardial infarction (MI), ischemic stroke and CVD mortality in European- (EA) and African-descent (AA) adults (> or = 65 years) from the Cardiovascular Health Study. TagSNPs were genotyped in 3,969 EA and 719 AA free of MI or stroke at baseline. Race-specific models included multiple testing correction and adjustment for sex, age and site. Among EA, minor alleles of FGA3807, FGB1437 and FGG902 were associated with higher fibrinogen levels; whereas FGA251, FGA2224, FGA6534 and FGG10034 were associated with lower levels, p<0.004 for each. Strongest associations were seen for FGB1437; each additional copy of the minor allele was associated with 13 mg/dl (95%CI: 9-16) higher fibrinogen level. Similar trends in AA were not significant. Fibrinogen haplotypes were not significantly associated with internal or common carotid IMT. No associations with MI or CVD mortality were seen in EA, though FGB1038 and FGG902 were significantly associated with increased and decreased risk of stroke in men, respectively, as were related haplotypes. FGB1038 was also associated with CVD mortality in AA, HR = 1.9 (95%CI: 1.3-2.7). In conclusion, while fibrinogen genetic variation was strongly associated with fibrinogen levels, there was less evidence of association with the more complex outcomes of IMT and CVD events.

An Extension of the Regression of Offspring on Mid‐Parent to Test for Association and Estimate Locus‐Specific Heritability: The Revised ROMP Method

The Regression of Offspring on Mid-Parent (ROMP) method is a test of association between a quantitative trait and a candidate locus. ROMP estimates the trait heritability and the heritability attributable to a locus and requires genotyping the offspring only. In this study, the theory underlying ROMP was revised (ROMP(rev)) and extended. Computer simulations were used to determine the type I error and power of the test of association, and the accuracy of the locus-specific heritability estimate. The ROMP(rev) test had good power at the 5% significance level with properly controlled type I error. Locus-specific heritability estimates were, on average, close to simulated values. For non-zero locus-specific heritability, the proposed standard error was downwardly biased, yielding reduced coverage of 95% confidence intervals. A bootstrap approach with proper coverage is suggested as a second step for loci of interest. ROMP(rev) was applied to a study of cardiovascular-related traits to illustrate its use. An association between polymorphisms within the fibrinogen gene cluster and plasma fibrinogen was detected (p < 0.005) that accounted for 29% of the estimated fibrinogen heritability. The ROMP(rev) method provides a computationally fast and simple way of testing for association and obtaining accurate estimates of locus-specific heritability while minimizing the genotyping required.

Connection between genetically determined blood coagulation factors and haemorheology

The phenotype caracteristic of blood clotting factors are well known, however few data has been documented about effects on haemorheology. The connection among genetic polymorphisms, haemorheological factors and vascular mortality is also studied poorly. Our aim was: to study six genetic polymorphisms of blood clotting factors, which presents the role of platelet-plasmaprotein-endothel system in thrombotic course in controls and ischaemic stroke cohort. Second, to study the connection of genotypes and haemorheologic factors and both with five years vascular mortality in patients. It was studied the genetic polymorhisms of GP IIb/IIIa Leu33Pro, prothrombin gene G20210A, ACE I/D, fibrinogen gene-455 G/A, Leiden mutation and MTHFR C677T alleles or genotypes in blood samples of 433 ischaemic stroke patients and 173 controls by PCR. Haematocrit values, plasma fibrinogen (FIB) concentration, whole blood viscosity (WBV) at 90 s(-1) and also the plasma viscosity (PV) were measured. Vascular mortality of patients were followed during five years and studied by curves Kaplan-Meier. A higher plasma FIB concentration in non smoker patients, carrying A alleles of FIB gene could be observed as compared to wild types (p<0.05). Also a moderate WBV increasing in smoker patients with A alleles was found against wild types (p=0.11), at the same time we observed a significant WBV increasing in non smoker patients (p<0.05). The highest quartile of PV showed a connection with Leiden mutation in whole group of patients (p=0.01), in subgroup of young patients (<50 years) (p=0.03) and also in non smoker groups (p<0.05) as compared to patients having wild types. No association could be detected between different genetic polymorphisms and vascular mortality, however it was observed significant mortality increasing in patients having PV above 1.51 mPa s (p=0.03). Certain genetic polymorphisms of coagulation system could result unfavorable haemorheological changes, however non of them increases the mortality. The connection between higher mortality and PV focuses the attention for the necessity of PV measuring and correction in stroke patients.

Changes in gene expression and integrin-mediated structural changes are associated with long-term plasticity of a spinal cord locomotor network

Substance P evokes a long-term increase in the frequency of the lamprey locomotor network output. Although previous physiological experiments using protein synthesis inhibitors suggested separate transcription-independent and -dependent phases in the long-term network modulation, this conclusion was weakened by the non-specific effects associated with these inhibitors. We thus sought further evidence for substance P effects on gene expression here using differential display polymerase chain reaction. We found evidence for changes in gene expression in the potential transcription-independent and dependent phases. We sequenced the mRNAs that we detected, and found that one of the mRNAs shared homology with a portion of the lamprey fibrinogen alpha-2 chain. As fibrinogen is a component of the extracellular matrix, the change in fibrinogen gene expression suggested the potential involvement of structural changes in the effects of substance P. We have previously shown that the network effects of substance P are associated with a reduction of the synaptic gap at glutamatergic synapses. To determine if this ultrastructural change was related to potential fibrinogen-dependent effects we examined the effects of arginine–glycine–aspartate (RGD) peptides, which block integrin binding to fibrinogen. Electron microscope analyses showed that RGD peptides blocked the substance P–mediated reduction in the synaptic gap. In addition, physiological experiments suggested that RGD peptides blocked the maintenance of the long-term increase in the network burst frequency. These results thus support the involvement of changes in gene expression in the long-term network effects of substance P, and suggest the involvement of integrin-mediated changes in synaptic ultrastructure.

Haemostatic genetic variants, ABO blood group and bleeding risk during oral anticoagulant treatment after cerebral ischaemia of arterial origin

Oral anticoagulant treatment for secondary prevention after cerebral ischaemia of presumed arterial origin is associated with a higher bleeding rate than cardioembolic stroke. This discrepancy is only partly explained by known bleeding risk factors. Haemostatic genetic variants and AB0 blood group may be involved. We performed a nested casecontrol study in patients with cerebral ischaemia of presumed arterial origin on anticoagulant treatment (International Normalized Ratio between 3.0-4.5). All 34 cases with non-fatal haemorrhage (10 intracranial and 24 extracranial) and 68 control patients on anticoagulant treatment without such a bleeding were selected from the SPIRIT study. AB0 blood group and 11 haemostatic genetic variants were investigated. The Thr312Ala variant of the alpha fibrinogen gene was associated with a decreased bleeding risk (odds ratio (OR) 0.3 for Ala/Ala and Thr/Ala versus Thr/Thr genotype; 95% CI 0.1-0.8). Factor V Leiden was associated with an increased bleeding risk (OR 11.6; 95% CI 1.3-103). The APOE2 allele (OR 0.5; 95% CI 0.2-1.7) and the Tyr204Phe variant in the factor XIII subunit A (OR 2.1; 0.9-5) had nonsignificant relationships with bleeding risk. AB0 blood group and 7 other genetic variants in coagulation factors II and XIII, vitamin K epoxide reductase complex, beta fibrinogen and apolipoprotein E were not related with the risk of haemorrhage. The Ala312Thr variant in the alpha fibrinogen gene is associated with a decreased and factor V Leiden with an increased bleeding risk in patients on anticoagulant treatment after cerebral ischaemia of presumed arterial origin.

Haplotypes of the fibrinogen gene and cerebral small vessel disease: the Rotterdam scan study

Objective:Fibrinogen levels and fibrinogen clot structure have been implicated in the pathogenesis of vascular disease. We examined fibrinogen levels and variation in fibrinogen genes (fibrinogen γ (FGG), α (FGA) and...

Dysfibrinogen Kagoshima with the amino acid substitution γThr-314 to Ile: Analyses of molecular abnormalities and thrombophilic nature of this abnormal molecule

Introduction Emerging lines of evidence have suggested that certain dysfibrinogens present a significant risk of thrombosis. Patient/methods The thrombophilic nature of a new-type of dysfibrinogen Kagoshima identified in a 36-year-old female with deep vein thrombosis during the postpartum period was studied. Results/discussion Based on the analyses of the patient fibrinogen and the fibrinogen genes, fibrinogen Kagoshima was shown to have the amino acid substitution of γThr-314 to Ile that resulted in impaired function and hypofibrinogenemia. Polymerization of fibrin monomers derived from patient fibrinogen was severely impaired with a partial correction in the presence of calcium ions, causing very low clottability and delayed cross-linking of patient fibrin catalyzed by activated factor XIII. Because of the low clottability, a large amount of soluble fibrin was formed upon thrombin treatment, resulting in an increase of thrombin in the soluble fraction. Additionally, tPA-mediated plasmin generation on fibrin was impaired and calcium-ion-dependent integrity of the γ-chain D domain of Kagoshima fibrinogen was perturbed. The presence of many tapered-fiber ends inside the tangled fibrin networks, observed by scanning electron microscopy, suggested early termination of fibrin polymerization and the structural alteration. Conclusion These data suggest that fibrinogen Kagoshima is dysfunctional, giving rise to formation of fibrinolysis-resistant soluble fibrin polymers and entrance of soluble fibrin associating with thrombin to the circulation, partly accounting for the thrombophilic nature of the affected fibrinogen and fibrin molecules.

Fibrin deposition accelerates neurovascular damage and neuroinflammation in mouse models of Alzheimer's disease

Cerebrovascular dysfunction contributes to the pathology and progression of Alzheimer's disease (AD), but the mechanisms are not completely understood. Using transgenic mouse models of AD (TgCRND8, PDAPP, and Tg2576), we evaluated blood–brain barrier damage and the role of fibrin and fibrinolysis in the progression of amyloid-β pathology. These mouse models showed age-dependent fibrin deposition coincident with areas of blood–brain barrier permeability as demonstrated by Evans blue extravasation. Three lines of evidence suggest that fibrin contributes to the pathology. First, AD mice with only one functional plasminogen gene, and therefore with reduced fibrinolysis, have increased neurovascular damage relative to AD mice. Conversely, AD mice with only one functional fibrinogen gene have decreased blood–brain barrier damage. Second, treatment of AD mice with the plasmin inhibitor tranexamic acid aggravated pathology, whereas removal of fibrinogen from the circulation of AD mice with ancrod treatment attenuated measures of neuroinflammation and vascular pathology. Third, pretreatment with ancrod reduced the increased pathology from plasmin inhibition. These results suggest that fibrin is a mediator of inflammation and may impede the reparative process for neurovascular damage in AD. Fibrin and the mechanisms involved in its accumulation and clearance may present novel therapeutic targets in slowing the progression of AD.

Deep venous thrombosis in the antenatal period in a large cohort of pregnancies from western India.

BackgroundDeep venous thrombosis (DVT) is an important complication in the peripartal and postpartal period.MethodsWe followed up prospectively the prevalence of DVT in 34720 prenatal mothers between June 2002 and July 2006 attending the antenatal clinics of two major hospitals in Mumbai, India. Thirty two women (0.1%) presented for the first time with symptomatic DVT i.e. 17 in the first trimester, 6 in the second and 9 in the third trimester of pregnancy. Nine had history of fetal loss while in the remaining twenty three there was no history of fetal loss.ResultsThe evaluation of both acquired and heritable thrombophilia showed a conglomeration of thrombophilia in this group when compared to 100 normal pregnant women who have given birth to at least one healthy baby with no history of fetal death, DVT or other obstetrical complications. The relative risks for all the antiphospholipid antibodies (APA) studied i.e lupus anticoagulant (LA), IgG/IgM antibodies for cardiolipin (ACA), β2 glycoprotein 1 (β2 GP 1) and annexin V were significantly higher in women with pregnancy associated DVT (RR 7.4 95% CI 4.3–11.3 P < 0.05). Among the genetic thrombophilia markers studied, Protein S (PS) deficiency was the strongest risk factor (RR 5.00 95% CI 3.02–5.00 P < 0.05) followed by factor V Leiden (FVL) mutation (RR 4.57 95% CI 2.23–4.57 P < 0.05) and PAI 4G/4G homozygosity (RR 3.24 95% CI 1.85–5.12 P < 0.05). Protein C (PC) and endothelial protein C receptor (EPCR) 23 bp insertion polymorphism was also increased in the patient group as compared to controls but the difference was not statistically significant. The MTHFR C677T, fibrinogen gene β448 Arg/Lys polymorphisms were not significantly different from the normal controls, while antithrombin III (AT III) deficiency and PT G20210A polymorphism were absent in both controls and patients. Two or more risk factors were present in 22 out of 32 cases (68.75%).ConclusionWe conclude that the prevalence of DVT in India is more or less similar to other reports published and both acquired and heritable thrombophilia show strong association with DVT associated with pregnancy.

Molecular mechanisms accounting for fibrinogen deficiency: from large deletions to intracellular retention of misfolded proteins.

Fibrinogen, the soluble precursor of fibrin, which is the main protein constituent of the blood clot, is synthesized in hepatocytes in the form of a hexamer composed of two sets of three polypeptides (Aalpha, Bbeta, and gamma). Each polypeptide is encoded by a distinct gene, FGA, FGB and FGG, all three clustered in a region of 50 kb on 4q32. Congenital afibrinogenemia is characterized by the complete absence of fibrinogen. The first causative mutation for this disease was identified in Geneva in a non-consanguineous Swiss family in 1999: the four patients were homozygous for a large deletion in the fibrinogen cluster, which eliminated almost the entire FGA genomic sequence. Mutations in the fibrinogen genes may lead to deficiency of fibrinogen by several mechanisms: acting at the DNA level, at the RNA level by affecting mRNA splicing or stability, or at the protein level by affecting protein synthesis, assembly or secretion. Recent reviews have provided helpful updates for the rapidly growing number of causative mutations identified in patients with fibrinogen deficiencies, either afibrinogenemia or hypofibrinogenemia. The aim of this review is to highlight specifically the subset of mutations that allow fibrinogen chain synthesis and hexamer assembly but impair secretion. Indeed, functional studies of these mutations have shed light on the specific sequences and structures in the fibrinogen molecule involved in the quality control of fibrinogen secretion.

Previous fetal loss significantly increases the risk of pre‐partal deep‐vein thrombosis

We read with interest the report by De Stefano et al (2006) regarding the risk of recurrent venous thromboembolism in pregnancy and puerperium. This comprehensive study showed that prevalence of thrombophilia did not differ significantly in the cohort of pregnant women with or without deep-vein thrombosis (DVT) and the presence of a provoking factor for previous DVT did not increase the risk for DVT in subsequent pregnancies. Between 2002 and 2006, we studied all the pregnancy-related DVT cases that presented at two of the busiest hospitals in Mumbai. Out of 25 132 multigravida women examined, 32 had DVT during their current pregnancy, based on the clinical features that were confirmed by Doppler studies. Clinically inapparent cases (absence of oedema, redness, pain and calf tenderness) were not investigated for subclinical DVT. Nine out of 462 women with previous history of fetal loss had DVT whereas 23 out of 24 670 with no history of previous fetal loss and no other precipitating risk factor, such as toxaemia, dehydration or smoking, had a pregnancy-related DVT in the current pregnancy. Hence, the risk of clinically apparent DVT during pregnancy was 22-fold higher if there was a previous history of one or more pregnancy loss (chi-squared test P < 0·001). Laboratory investigations for thrombophilia, i.e. lupus antibodies, IgG/IgM antibodies for anticardiolipin antibodies, β2glycoprotein, annexin V, protein C, protein S, antithrombin III, factor V Leiden, F2 (PT gene), MTHFR C677T, FBG (fibrinogen gene Arg/Lys), PROCR (also known as EPCR) 23 bp insertion and SERPINE1 (also known as PAI) 4G/5G polymorphisms, did not show any significant difference in their prevalence in these two groups P > 0·05), as was reported by De Stefano et al (2006). In conclusion, we believe that previous pregnancy loss should be considered as a significant risk factor for DVT in subsequent pregnancies. The risk might have been significantly underestimated in our study as we only identified clinically significant DVT and did not investigate the prevalence of DVT in the puerperium period, which is reported to be several times higher than that of the antenatal period (Andersen et al, 1998; Simpson et al, 2001).

Molecular characterization of the first missense mutation in the fibrinogen Aalpha-chain gene identified in a compound heterozygous afibrinogenemic patient

Congenital afibrinogenemia is a rare coagulopathy characterized by extremely low levels of functional and immunoreactive fibrinogen in plasma, associated with a hemorrhagic phenotype of variable severity. It is transmitted as an autosomal recessive trait and is invariantly associated with mutations affecting 1 of the 3 fibrinogen genes ( FGA, FGB, and FGG, coding for Aα, Bβ, and γ chain, respectively). Most genetic defects causing afibrinogenemia are truncating mutations, whereas only few missense mutations (6) have been identified so far, all located in FGB. In this study, the mutational screening of an afibrinogenemic Italian male identified the first missense mutation (Met51Arg) in FGA leading to afibrinogenemia. The patient was a compound heterozygote for a previously described frameshift mutation (1215delT) in the same gene. Met51Arg involves a residue located at the very beginning of the coiled-coil domain, in a region demonstrated to play a pivotal role in hexamer formation. In-vitro expression experiments showed that Met51Arg strongly reduces secretion of hexameric fibrinogen, whereas traces of not completely assembled trimeric intermediate were found in conditioned media. Western blot analysis on the proband's plasma confirmed the presence in vivo of the trimeric fibrinogen, supporting the hypothesis that Met51Arg prevents the final step of fibrinogen assembly.

Association of Genetic Variations With Nonfatal Venous Thrombosis in Postmenopausal Women

Although the roles of clotting proteins and enzymes that activate or inhibit fibrin production and lysis are well characterized, the underlying contribution of genetic variation in these constituents to risk of venous thrombosis (VT) has not been fully investigated. To describe the association of common genetic variation in 24 coagulation, anticoagulation, fibrinolysis, and antifibrinolysis candidate genes with risk of incident nonfatal VT in postmenopausal women. Population-based case-control study conducted in a large integrated health care system in Washington State. Participants were perimenopausal and postmenopausal women aged 30 to 89 years who sustained a first VT event between January 1995 and December 2002 (n = 349) and 1680 controls matched on age, hypertension status, and calendar year (n = 1680). Risk of venous thrombosis associated with global variation within a gene as measured by common haplotypes and with individual haplotypes and single nucleotide polymorphisms (SNPs). Significance of the associations was assessed by a .20 threshold of the false-discovery rate q value, which accounts for multiple testing. Only the tissue factor pathway inhibitor gene demonstrated global association with risk (q = .13). Five significant SNP associations were identified across 3 of the candidate genes (factors V, XI, and protein C) in SNP analyses. Two associations have been previously reported. Another 22 variants across 15 genes had P values less than .05 but q values between .20 and .35. Five of these confirm previously reported associations (fibrinogen genes and protein C), 2 were inconsistent with earlier reports (thrombomodulin and plasminogen activator inhibitor 1), and 15 were new discoveries. After accounting for multiple testing, 5 SNPs associated with VT risk were identified, 3 of which have not been previously reported. Replication of these novel associations in other populations is necessary to corroborate these findings and identify which genetic factors may influence VT risk in postmenopausal women.

Elevated plasma fibrinogen gamma' concentration is associated with myocardial infarction: effects of variation in fibrinogen genes and environmental factors.

Fibrinogen gamma', a fibrinogen gamma-chain variant generated via alternative mRNA processing, has been associated with susceptibility to thrombotic disease. The present case-control study searched for potential determinants of the plasma fibrinogen gamma' concentration and examined the relationship between this variant and risk of myocardial infarction (MI). The Stockholm Coronary Artery Risk Factor study, comprising 387 postinfarction patients and 387 healthy individuals, was employed. The fibrinogen gamma (FGG) 9340T > C [rs1049636], fibrinogen alpha (FGA) 2224G > A [rs2070011] and fibrinogen beta (FGB) 1038G > A [rs1800791] polymorphisms were determined. The plasma fibrinogen gamma' concentration was measured by enzyme-linked immunosorbent assay. The multifactor dimensionality reduction method was used for interaction analyses on risk of MI. The FGG 9340T > C and FGA 2224G > A polymorphisms, total plasma concentrations of fibrinogen, insulin and high-density lipoprotein, and gender appeared to be independent determinants of plasma fibrinogen gamma' concentration in patients, and the corresponding determinants in controls included FGG 9340T > C and FGA 2224G > A polymorphisms and plasma fibrinogen concentration. An elevated plasma fibrinogen gamma' concentration proved to be an independent predictor of MI [adjusted odds ratio (OR) (95% CI): 1.24 (1.01, 1.52)]. The plasma fibrinogen gamma' concentration was involved in a high-order interaction with total plasma fibrinogen and the FGG 9340T > C and FGA 2224G > A polymorphisms, associated with a further increased risk of MI [OR (95% CI): 3.22 (2.35, 4.39)]. Plasma fibrinogen gamma' concentration influences the risk of MI, and this relationship seems to be strengthened by the presence of an elevated total plasma fibrinogen concentration and the FGG 9340T and FGA 2224G alleles.

Mutational screening of six afibrinogenemic patients: Identification and characterization of four novel molecular defects

Congenital afibrinogenemia (CAF) is a rare coagulation disorder characterized by very low or unmeasurable levels of functional and immunoreactive fibrinogen in plasma, associated with a hemorrhagic phenotype of variable severity. It is transmitted as an autosomal recessive trait (prevalence 1:1,000,000) and is invariantly associated with mutations affecting one of the three fibrinogen genes (FGA, FGB, and FGG, coding for Aalpha, Bbeta, and gamma chain, respectively). Fibrinogen is secreted by hepatocytes as a hexamer composed of two copies of each chain; the lack of one chain has been demonstrated to prevent its secretion. Most genetic defects causing afibrinogenemia are point mutations, whereas only three large deletions have been identified so far, all affecting the FGA gene. We here report the molecular characterization of six unrelated afibrinogenemic patients leading to the identification of eight different mutations, four hitherto unknown: a 4.1-Kb large deletion involving exon 1 of FGA (AC107385:g. 65682_69828del), two nonsense mutations (p.Trp229X in FGA and p.Trp266X in FGB), and an ins-del mutation (g.1787_1789del3ins12) in FGA. The molecular characterization of CAF-causing genetic defects increases our understanding on the genetic basis of this disease and might be helpful for prenatal screening purposes, as also demonstrated during this study.

Mutations in the fibrinogen gene cluster accounting for congenital afibrinogenemia: an update and report of 10 novel mutations

Fibrinogen is synthesized in hepatocytes in the form of a hexamer composed of two sets of three polypeptides (Aalpha, Bbeta, and gamma). Each polypeptide is encoded by a distinct gene, FGA, FGB, and FGG, all three clustered in a region of 50 kb on 4q31. Congenital afibrinogenemia is characterized by the complete absence of fibrinogen, the precursor of the major protein constituent of the blood clot, fibrin. Although the disease was first described in 1920, the genetic defect responsible for this disorder long remained unknown. We identified the gene and the first causative mutations for this disease in a nonconsanguineous Swiss family in 1999. Since this first report, 61 additional mutations, the majority in FGA, have been identified in patients with afibrinogenemia (in homozygosity or in compound heterozygosity) or in heterozygosity in hypofibrinogenemia, since many of these patients are in fact asymptomatic carriers of afibrinogenemia mutations. Mutations in the fibrinogen genes may lead to deficiency of fibrinogen by several mechanisms: these can act at the DNA level, at the RNA level by affecting mRNA splicing or stability, or at the protein level by affecting protein synthesis, assembly, or secretion. The expression of selected mutations has shown that mechanisms acting at all three levels play a role in the molecular basis of this disease. We report here the identification of 10 novel mutations, of which eight are localized in FGA, thus increasing the total number of causative mutations identified to 72 and confirming the relative importance of FGA in the molecular basis of fibrinogen deficiency.

The fibrinogen − 148 C/T polymorphism influences inflammatory response in experimental endotoxemia in vivo

Introduction The acute phase reactant fibrinogen plays a critical role in the coagulation system and inflammation. Recently several polymorphisms have been described regulating basal and peak fibrinogen expression. We evaluated the role of a frequent promoter polymorphism in the beta chain of the fibrinogen gene (− 148 C/T) in a human in vivo model of experimental endotoxemia. Material and methods Healthy volunteers received 2 ng/kg endotoxin (LPS, n = 73) as a bolus infusion over 2 min. Blood samples were collected by venipunctures into EDTA anticoagulated vacutainer tubes before LPS infusion. For determination of the fibrinogen promoter polymorphism, we developed a new mutagenic separated polymerase chain reaction assay. Results Carriers of the − 148 T allele had significantly lower TNFα expression throughout the whole time course of LPS stimulation and Interleukin-6 levels were trendwise lower, however only basal levels reached statistical significance. No effects were observed on markers of coagulation activation (D-Dimer, Prothrombin F 1 + 2 ). Conclusion Our findings indicate, that the common − 148 C/T polymorphism is associated with differences in the TNFα release in response to systemic LPS infusion in humans, and add to current evidence that gene-sequence changes in beta-fibrinogen locus can alter the ability of the host to respond to endotoxin.

Fibrinogen gene haplotypes in relation to risk of coronary events and coronary and extracoronary atherosclerosis: The Rotterdam Study

Fibrin network structure has been correlated with coronary disease. Fibrinogen gamma and alpha (FGG and FGA) gene haplotypes (chromosome 4q28) may be associated with fibrin network structure, and thereby with rigidity of the fibrin clot and sensitivity of the fibrin clot to the fibrinolytic system. Through these mechanisms they may influence risk of cardiovascular disease. We set out to investigate the relation between combined fibrinogen FGG and FGA gene haplotypes, representing the common variation of the fibrinogen FGG and FGA genes, coronary events and measures of coronary and extracoronary atherosclerosis. The study was embedded in the Rotterdam Study, a prospective population-based study among men and women aged >or=55 years. Common haplotypes were studied using seven tagging SNPs across a 30-kb region with the FGG and FGA genes. Incident coronary events were registered, and carotid intima-media thickness, carotid plaques, ankle-arm index, aortic calcification and coronary calcification were assessed. Seven haplotypes with frequencies >1% covered 97.5% of the genetic variation. In 5,667 participants without history of coronary heart disease (CHD), 733 CHD cases occurred during a median follow-up time of 11.9 years. Fibrinogen gene haplotypes were not associated with coronary events. Fibrinogen gene haplotypes did not show a consistent association with measures of coronary and extracoronary atherosclerosis. In conclusion, fibrinogen FGG and FGA gene haplotypes are not associated with coronary events, coronary atherosclerosis or extracoronary atherosclerosis. Confirmation of these findings by future population-based studies is warranted.