FGB Gene Research Articles

The prevalent deep intronic c. 639+919 G>A GLA mutation causes pseudoexon activation and Fabry disease by abolishing the binding of hnRNPA1 and hnRNP A2/B1 to a splicing silencer.

Fabry disease is an X-linked recessive inborn disorder of the glycosphingolipid metabolism, caused by total or partial deficiency of the lysosomal α-galactosidase A enzyme due to mutations in the GLA gene. The prevalent c.639+919 G>A mutation in GLA leads to pathogenic insertion of a 57bp pseudoexon sequence from intron 4, which is responsible for the cardiac variant phenotype. In this study we investigate the splicing regulatory mechanism leading to GLA pseudoexon activation. Splicing analysis of GLA minigenes revealed that pseudoexon activation is influenced by cell-type. We demonstrate that the wild-type sequence harbors an hnRNP A1 and hnRNP A2/B1-binding exonic splicing silencer (ESS) overlapping the 5'splice site (5'ss) that prevents pseudoexon inclusion. The c.639+919 G>A mutation disrupts this ESS allowing U1 snRNP recognition of the 5'ss. We show that the wild-type GLA 5'ss motif with the ESS is also able to inhibit inclusion of an unrelated pseudoexon in the FGB gene, and that also in the FGB context inactivation of the ESS by the c.639+919 G>A mutation causes pseudoexon activation, underscoring the universal nature of the ESS. Finally, we demonstrate that splice switching oligonucleotide (SSO) mediated blocking of the pseudoexon 3'ss and 5'ss effectively restores normal GLA splicing. This indicates that SSO based splicing correction may be a therapeutic alternative in the treatment of Fabry disease.

Congenital afibrinogenemia: Identification and characterization of two novel homozygous fibrinogen Aα and Bβ chain mutations in two Tunisian families

IntroductionInherited abnormalities of fibrinogen (FG) are rare coagulation disorders divided into two types: quantitative abnormalities (afibrinogenemia and hypofibrinogenemia) or qualitative abnormalities (dysfibrinogenemia and hypo-dysfibrinogenemia) of circulating fibrinogen. In particular, congenital afibrinogenemia is inherited as an autosomal recessive mode and is usually determined by homozygous or compound heterozygous mutations affecting any of the three fibrinogen genes (FGA, FGB and FGG), resulting in the complete absence or extremely reduced amount of fibrinogen. The aim of the present study was to characterize the fibrinogen abnormalities in two Tunisian families. MethodsCoagulation studies were performed on the patients and family members. All the exons and the flanking intron regions of fibrinogen genes were screened by direct sequencing. ResultsProbands had concomitant bleeding complications with infinitely prolonged standard coagulation assays. Mutational screening of the fibrinogen gene cluster of each proband, disclosed two previously undescribed homozygous point mutations. The first mutation was a major truncation (AαArg252Stop) leads to a severe premature termination codon in the exon 5 of the FGA gene. This mutation defines in vivo the importance of the αC flexible segment in the secretion of a stable fibrinogen molecule. The second afibrinogenemic mutation (BβGly295Ala) occurs in the exon 7 of the FGB gene. This missense mutation would probably lead to significant conformational change not allowing the expression of the fibrinogen protein. ConclusionCurrent molecular characterization of these two fibrinogen abnormalities confirms the importance of the first portion of αC-region (αC-connector) as well as the Bβ globular domain in the secretion processes.

Association of rs1800790 in FGB and Endometrium in Iranian Women

Background/Objectives: Endometriosis is a disease with the growth of endometrium-like tissue in aberrant locations outside of the uterine. Variants of a number of genes have been associated to endometriosis; however, the contributions of these genetic variants in different ethnic groups are not similar. Methods/Statistical Analysis: Our study is Association of rs1800790 in FGB and endometrium in Iranian women. The case-control study included 100 affected patients and 100 controls. The genetic variants on FGB gene was genotyped using Tetra Amplification Refractory Mutation System-Polymerase Chain Reaction (Tetra-ARMS-PCR). Findings: Association of risk allele with endometriosis was examined using SPSS software. Results showed that FGB gene polymorphism genotype frequencies were compared in the patients and control. Frequency of AA, AG and GG genotypes of the gene polymorphismfibrinogen beta polypeptide chain were 28, 48 and 24% in patients respectively, and 66, 31and 3% in control group respectively. Results showed that relation between patients and control group is significant (P = 4.619e-11). Applications/Improvements: This study showed that there was meaningful relationship between FGB gene polymorphism and increased risk of endometriosis in women studied

A novel missense mutation in the FGB gene (p.Gly302Arg) leading to afibrinogenemia

The propositus was a 26-year-old Argentinian with afibrinogenemia. FGA, FGB and FGG exons and flanking regions were screened by sequencing and the mutant protein was analyzed in silico. A novel missense mutation in the FGB gene (Bbeta Gly272Arg, p.Gly302Arg) was identified. In silico analysis revealed its location in a highly conserved region, which preserves the core fold of the C-terminal beta-chain and is important for proper secretion. A substitution by a positively charged large Arg residue in this area would most likely disturb the core fold by additional interactions with adjacent residues (p.Asp291, p.Asp297, p.Asp311), or by forming of non-native interactions with other proteins, thereby hindering the action of molecular chaperones. Both alternatives would disturb the regular secretion of the beta-chain. The novel missense mutation in the FGB gene causes afibrinogenemia most probably by affecting the secretion of the fibrinogen beta-chain.

Variants of the Coagulation and Inflammation Genes Are Replicably Associated with Myocardial Infarction and Epistatically Interact in Russians

BackgroundIn spite of progress in cardiovascular genetics, data on genetic background of myocardial infarction are still limited and contradictory. This applies as well to the genes involved in inflammation and coagulation processes, which play a crucial role in the disease etiopathogenesis.Methods and ResultsIn this study we found genetic variants of TGFB1, FGB and CRP genes associated with myocardial infarction in discovery and replication groups of Russian descent from the Moscow region and the Republic of Bashkortostan (325/185 and 220/197 samples, correspondingly). We also found and replicated biallelic combinations of TGFB1 with FGB, TGFB1 with CRP and IFNG with PTGS1 genetic variants associated with myocardial infarction providing a detectable cumulative effect. We proposed an original two-component procedure for the analysis of nonlinear (epistatic) interactions between the genes in biallelic combinations and confirmed the epistasis hypothesis for the set of alleles of IFNG with PTGS. The procedure is applicable to any pair of logical variables, e.g. carriage of two sets of alleles. The composite model that included three single gene variants and the epistatic pair has AUC of 0.66 both in discovery and replication groups.ConclusionsThe genetic impact of TGFB1, FGB, CRP, IFNG, and PTGS and/or their biallelic combinations on myocardial infarction was found and replicated in Russians. Evidence of epistatic interactions between IFNG with PTGS genes was obtained both in discovery and replication groups.

Polymicrobial Oral Infection with Four Periodontal Bacteria Orchestrates a Distinct Inflammatory Response and Atherosclerosis in ApoE null Mice.

Periodontal disease (PD) develops from a synergy of complex subgingival oral microbiome, and is linked to systemic inflammatory atherosclerotic vascular disease (ASVD). To investigate how a polybacterial microbiome infection influences atherosclerotic plaque progression, we infected the oral cavity of ApoEnull mice with a polybacterial consortium of 4 well-characterized periodontal pathogens, Porphyromonas gingivalis, Treponema denticola, Tannerealla forsythia and Fusobacterium nucleatum, that have been identified in human atherosclerotic plaque by DNA screening. We assessed periodontal disease characteristics, hematogenous dissemination of bacteria, peripheral T cell response, serum inflammatory cytokines, atherosclerosis risk factors, atherosclerotic plaque development, and alteration of aortic gene expression. Polybacterial infections have established gingival colonization in ApoEnull hyperlipidemic mice and displayed invasive characteristics with hematogenous dissemination into cardiovascular tissues such as the heart and aorta. Polybacterial infection induced significantly higher levels of serum risk factors oxidized LDL (p < 0.05), nitric oxide (p < 0.01), altered lipid profiles (cholesterol, triglycerides, Chylomicrons, VLDL) (p < 0.05) as well as accelerated aortic plaque formation in ApoEnull mice (p < 0.05). Periodontal microbiome infection is associated with significant decreases in Apoa1, Apob, Birc3, Fga, FgB genes that are associated with atherosclerosis. Periodontal infection for 12 weeks had modified levels of inflammatory molecules, with decreased Fas ligand, IL-13, SDF-1 and increased chemokine RANTES. In contrast, 24 weeks of infection induced new changes in other inflammatory molecules with reduced KC, MCSF, enhancing GM-CSF, IFNγ, IL-1β, IL-13, IL-4, IL-13, lymphotactin, RANTES, and also an increase in select inflammatory molecules. This study demonstrates unique differences in the host immune response to a polybacterial periodontal infection with atherosclerotic lesion progression in a mouse model.

CLINICAL-GENETIC RISKOMETER FOR THE ISCHEMIC STROKE RISK ASSESSMENT IN ATRIAL FIBRILLATION

Aim. To assess genetic issues in the ischemic stroke development in AF and to invent an analytical programmed complex for genetic risk estimation of stroke development in a patient with AF. Material and methods. Totally 43 patients studied with AF and stroke in anamnesis, 78 — with AF and no stroke. Controls consisted of 188 persons without cardiovascular pathology. The participants underwent ECG, EchoCG, Holter ECG-monitoring, exercise test, TELAS, thyroid gland hormones analysis. For confirmation of the ischemic nature of stroke in participating probands we performed computed tomography of the brain. All participants also underwent molecular genetic testing. Results. According to the odds ratio, allele A polymorphism -455G&gt;A of gene FGB increases the risk of ischemic stroke development in atrial fibrillation 1,7 times comparing to those patients without the allele; genotypes with the rare T allele in homoand heterozygous state of polymorphism 807С&gt;Т of gene GPI? increases 2,5 times the risk of stroke in AF; presence of allele C polymorphism -5Т&gt;С of gene GPI?? increases 1,9 times the risk of stroke comparing to its absence; presence of the rare genotypes allele C in homoand heterozygous state -5Т&gt;С of gene GPI?? increases 2,3 times stroke risk; allele A of the polymorphism 10976G&gt;A gene FVII decreases the risk of stroke 2,6 times. According to the results, there was a “Clinical-genetic riskometer of the ischemic stroke in AF” developed. Using this informational-analytic complex it is possible to estimate genetic risk of the stroke. Conclusion. Therefore, the study has shown that homozygous genotype AA of the rare polymorphism 455G&gt;A gene FGB, heterozygous genotype СТ and homozygous genotype ТТ of the rare polymorphism allele 807С&gt;Т gene GPI?, heterozygous genotype TC and homozygous genotype CC by the rare allele polymorphism -5Т&gt;С gene GPI?? are defined as genetic predictors of ischemic stroke development in atrial fibrillation. Allele А of polymorphism 10976G&gt;A gene FVII is protective against ischemic stroke in patients with AF. Knowing the parameters of genetic assessment in AF, it is possible to calculate genetic risk of ischemic stroke development in AF via invented by us a “Clinical-Genetic riskometer of ischemic stroke in AF”.

GENETIC PREDICTORS FOR CARDIOEMBOLIC STROKE IN PATIENTS WITH ATRIAL FIBRILLATION

Aim. To reveal genetic predictors of the ischemic stroke in patients with AF. Material and methods. Totally 121 patient studied with AF and 155 their relatives of I-III grade of relation. First group consisted of 43 probands with AF and stroke anamesis and 54 their relatives, the second group – 78 probands with AF without stroke and 101 their relative. Control group consists of 188 subjects. The patients underwent ECG, EchoCG, Holter ECG-monitoring, VEM, TELAS, molecular-genetic investigation. Results. Genotype AA of polymorphism -455 G>A of gene FGB statistically significantly predominated in subjects with AF and stroke comparing to those with AF without stroke (20,94% vs 6,4%; p=0,036). Risk relation shows that the chance of stroke development with AA homozygous genotype at rare allele is 3,9 times higher than in its absence. Overall the genotypes CT and TT by the rare allele 807C>T gene ITGA2 statistically significantly predominated in the patients with AF and stroke comparing to controls (76,7% vs 56,9%, p=0,026). The chance of stroke development while carrying CT and TT by the rare allele is 2,5 times higher than in their absence. Genotypes TC and CC by the rare polymorphism 5 T>C gene GPIBA statistically more significantly were found in patients with AF and credibly increases the chance for stroke 2,3 times. Allele A of polymorphism 10796 G>A gene F7 statistically more significant rarer found in patients with AF and stroke comparing to controls (6,98% vs 16,22%; p=0,043). Chance of stroke in absence of allele A is 2,6 times higher, than in its presence. Conclusion. The study revealed that homozygous genotype AA by the rare polymorphism -455G>A gene FBG, heterozygous CT and homozygous TT by the rare allele 807C>T gene ITGA2, heterozygous TC anf homozygous CC by the rare – 5 T>C gene GPIAB are set as genetic predictors for ischemic stroke development in AF. Allele A of the polymorphism 10976 G>A gene F7 show protective effect in the ischemic stroke development in AF. Genetic risk estimation might improve the primary ischemic stroke prevention in AF.

13 Final stage of hemostasis and FGB gene polymorphism in patients with cystic fibrosis

Objective To estimate the final stage parameters of blood coagulation – fibrinogen and D-dimer in patients with cystic fibrosis (CF). Methods 30 CF patients were enrolled. The comparison group included 17 children with congenital malformations of lung (CML). The level of fibrinogen and D-dimer in blood as well as fibrinogen gene polymorphism were studied. Results Level of fibrinogen in CF patients was significantly higher than in CML – 3.73 g/l vs 2.8 g/l (p = 0.018). Thrombophilic polymorphism of fibrinogen genes was identified in 43.4% of CF patients and in 30% of patients with CML (p Conclusion The changes of blood coagulation can indicate about increasing of plasma thrombogenic potential with the development of thrombosis. It is advisable to add antiplatelet agents to a complex therapy in CF patients.

Molecular characterization of 7 patients affected by dys- or hypo-dysfibrinogenemia: Identification of a novel mutation in the fibrinogen Bbeta chain causing a gain of glycosylation

Fibrinogen is a hexameric glycoprotein consisting of two sets of three polypeptides (the Aα, Bβ, and γ chains, encoded by the three genes FGA, FGB, and FGG). It is involved in the final phase of the coagulation process, being the precursor of the fibrin monomers necessary for the formation of the hemostatic plug. Rare inherited fibrinogen disorders can manifest as quantitative deficiencies, qualitative defects, or both. In particular, dysfibrinogenemia and hypo-dysfibrinogenemia are characterized by reduced functional activity associated with normal or reduced antigen levels, and are usually determined by heterozygous mutations affecting any of the three fibrinogen genes.In this study, we investigated the genetic basis of dys- and hypo-dysfibrinogenemia in seven unrelated patients. Mutational screening disclosed six different variants, two of which novel (FGB-p.Asp185Asn and FGG-p.Asn230Lys). The molecular characterization of the FGG-p.Asn230Lys mutation, performed by transient expression experiments of the recombinant mutant protein, demonstrated that it induces an almost complete impairment in fibrinogen secretion, according to a molecular mechanism often associated with quantitative fibrinogen disorders. Conversely, the FGB-p.Asp185Asn variant was demonstrated to be a gain-of-glycosylation mutation leading to a hyperglycosylation of the Bβ chain, not affecting fibrinogen assembly and secretion. To our knowledge, this is the second gain-of-glycosylation mutation involving the FGB gene.

Clinical and molecular characterisation of 21 patients affected by quantitative fibrinogen deficiency.

Fibrinogen is a plasma glycoprotein mainly synthesised by hepatocytes and circulating as a 340-kDa hexamer consisting of two sets of three different polypeptide chains (Aα, Bβ, and γ, encoded by the FGA, FGB, and FGG gene, respectively). Congenital afibrinogenaemia and hypofibrinogenaemia are rare bleeding disorders characterised by abnormally low levels of functional and immunoreactive fibrinogen in plasma, associated with haemorrhagic manifestations of variable severity. While afibrinogenaemia is caused by mutations in the homozygous or compound heterozygous state in one of the three fibrinogen genes, hypofibrinogenaemia is generally due to heterozygous mutations, and is usually characterised by a milder phenotype. The mutational spectrum of these quantitative fibrinogen disorders includes large deletions, point mutations causing premature termination codons, and missense mutations often affecting fibrinogen assembly and/or secretion. Here we report the clinical and molecular characterisation of 13 unrelated afibrinogenaemic and eight hypofibrinogenaemic patients, leading to the identification of 17 different mutations (10 hitherto unknown). All the newly-identified missense and splicing mutations werein vitro expressed to verify their pathogenic role. Our data increase the number of mutations causing quantitative fibrinogen deficiencies by about 7 %. The high number of private mutations identified in the analysed probands indicates that the full mutational screening of the three fibrinogen genes is still required for molecular diagnosis.

Association between the FGB gene polymorphism and ischemic stroke: a meta-analysis.

To clarify the relationship between the β-fibrinogen (FGB) genetic polymorphism (-148C>T) and ischemic stroke, we identified studies by searching PubMed, EMBASE, and the Chinese National Knowledge Infrastructure (CKNI) databases. Data from eligible studies were extracted and subjected to meta-analysis. Publication bias was tested using a funnel plot. We identified 12 independent case-control studies containing 1536 ischemic stroke patients and 1329 control subjects. Our results showed that the -148C>T polymorphism in the FGB gene was associated with an increased risk of ischemic stroke [CC vs (TT+CT), odds ratio = 0.69, 95% confidence interval (CI) = 0.59-0.80, P < 0.0001; TT vs (CC+CT), odds ratio = 3.01, 95%CI = 1.29-7.05; P = 0.01; T vs C, odds ratio = 1.32, 95%CI = 1.15-1.52, P < 0.0001] by a meta-analysis. The results of our meta-analysis suggested that the -148C>T polymorphism in the FGB gene is a susceptibility marker of ischemic stroke.

Genetic polymorphisms influencing total and γ' fibrinogen levels and fibrin clot properties in Africans.

Inter-ethnic variation in fibrinogen levels is hypothesized to be the result of differences in genetic background. No information is available regarding the contribution of genetics to fibrinogen γ' in Africans. Only limited information is available regarding the interaction between genotypes and total and γ' fibrinogen concentration in determining fibrin clot properties. Our aim was to investigate the effect of polymorphisms in the fibrinogen and Factor XIII genes on total and γ' fibrinogen and clot properties (turbidimetry) in 2010 black Africans as well as to determine their interactions. Significant associations were observed between rs1049636 (FGG gene), with total fibrinogen levels and between rs2070011 (FGA promoter area) and fibrinogen γ' levels. Significant associations were observed between single nucleotide polymorphisms (SNPs) in the FGA (rs2070011), FGB (rs1800787) and FGG (rs1049636) genes and fibre size. Significant interactions were found between total and/or γ' fibrinogen levels and SNPs in the FGA (rs2070011), FGB (rs2227385, rs1800787, rs1800788, rs4220) and F13A1 genes (rs5985) in determining clot properties. The different SNPs influenced the relationships between total and γ' fibrinogen levels with clot properties in opposing directions. Genetic influences may be ethnic-specific and should not only focus on fibrinogen concentration, but also on functionality in determining its role in CVD.

FGBGene − 148C&gt;T Polymorphism Is Associated with Increased Risk of Ischemic Stroke in a Chinese Population: A Meta-Analysis Based on 18 Case–Control Studies

Several published articles investigated the relationship between a polymorphism -148C>T in the β-fibrinogen gene (FGB) and risk of ischemic stroke, and did not reach the same conclusion. To shed light on these inconclusive findings, we performed a meta-analysis of studies relating the FGB genetic polymorphism (-148C>T) to the risk of ischemic stroke. We identified articles by searching PubMed, EMBASE, Chinese National Knowledge Infrastructure databases (CNKI), and Wanfang database in China and by reviewing the references of retrieved articles. We included studies that reported odds ratio (OR) with 95% confidence interval (CI) for the association between the FGB -148C>T polymorphism and stroke risk. Data from eligible studies were extracted for meta-analysis. Stroke risk associated with FGB -148C>T polymorphism was estimated by pooled ORs and 95% CIs. The software Review Manager (version 5.2) was utilized for meta-analysis. Publication bias was tested by funnel plot. Eighteen independent case-control studies containing 2159 ischemic stroke patients and 3222 control subjects were included. Our results showed that -148C>T polymorphism in the FBG gene was associated with increased risk of ischemic stroke ([TT+CT] vs. CC: OR=1.40, 95% CI [1.20-1.45], p<0.0001; T vs. C: OR=1.35, 95% CI [1.18-1.56], p<0.0001, respectively] by a meta-analysis. The results of our meta-analysis suggested that the-148C>T polymorphism in the FGB gene is a susceptibility marker of ischemic stroke.

Clinical and genetic analysis of 8 Chinese pedigrees with inherited dysfibrinogenemia

To analyze clinical manifestation and genetic mutations in 8 Chinese pedigrees featuring hereditary dysfibrinogenemia. Prothrombin time(PT), activated partial thromboplastin time(APTT), thrombin time(TT), calibration of plasma protamine sulfate against TT, fibrinogen (Fg) activity, coagulation factors II, V, VII, VIII, IX, X, XI and XII of all probands and their family members were detected with an automatic blood coagulation analyzer; D-dimer(D-D) and fibrin(ogen) degradation products(FDPs) were also dtected by automatic blood coagulation analyzer, Fg antigen were detected with an immunoturbidimetry method. Exons of fibrinogen genes FGA, FGB and FGG and flanking sequences were amplified by polymerase chain reaction(PCR) and sequenced. All of the probands showed normal levels of FDPs, D-dimer(D-D) and activity of coagulation factor II,V,VII, VIII, IX,X,XI, XII. Plasma PT and APTT were normal or slightly prolonged. Prolonged TT was found in all of the probands, whilst TT was not significantly shortened by protamine sulfate. Fg antigen was within the normal range, but Fg activity was significantly decreased. The Fg antigen/activity ratio was greater than 2. One proband has carried a heterozygous variant of the FGA gene g.1233G>A(p.A α Arg35His). Four have carried a heterozygous mutation of the FGB gene g.9692A>G(p.Bβ Asn190Ser). The remaining 3 had heterozygous substitution of FGG gene g.10819G>A(p.γ Arg301His). In addition, 2 polymorphisms (p.A α Thr331Ala) and p.B β Arg478Lys) were identified in FGA and FGB genes. p.A α Arg35His, p.B β Asn190Ser and p. γ Arg301His are responsible for the inherited dysfibrinogenemia in the 8 Chinese pedigrees. p.B β Asn190Ser is firstly reported in China. p.B β Asn190Ser and p. γ Arg301His may be mutation hot spot in the Chinese population.

The clinical and genetic characteristics of long-lived people from the Moscow region

The frequencies of the LPL, CETP, APOE, F2, F5, F7, F13, FGB, ITGA2, ITGB3, PAI-1, MTHFR, MTRR, HLA-DRB1, HLA-DQA1, HLA-DQB1 gene polymorphisms associated with a predisposition to age-related pathologies were analyzed in long-lived people from the Moscow region. The long-lived people were characterized by a favorable course of cardiovascular diseases against the presence of certain genetic factors. Among the latter are the H-H- genotype of the LPL gene and the ɛ2 allele of the APOE gene from the group of genes involved in lipid exchange; the CC genotype of the MTHFR gene (677C > T) from the group of genes regulating the folate cycle; the TC genotype of the ITGB3 gene and the GA genotype of the FGB gene from the group of genes that are responsible for the coagulation system; and HLA-DRB1*11 from the group of the major histocompatibility complex genes.

Congenital afibrinogenemia caused by a novel insertion mutation in the FGB gene

To investigate the genetic defect and its mechanism in a patient with congenital afibrinogenemia. The plasma fibrinogen activity and antigen of the patient was determined using the Clauss method and immuno-nephelometric assay, respectively. Genomic DNA was isolated from peripheral blood of the proband and his related family members. All exons and exon-intron boundaries of the three fibrinogen genes (FGA, FGB, FGG) were amplified by PCR followed by direct sequencing. Thrombin fibrin aggregation curve were detected in the plasma of the patient. Wild-type and mutation type fibrinogen vectors were constructed, and then transfected into COS-7 cells. The wild-type and mutant proteins from the culture media and cell lysates were tested by Western blot and ELISA. APTT, PT, TT were significantly longer in the proband. Plasma fibrinogen activity and antigen of the patient could not be detected using the Clauss method and immuno-nephelometry, respectively. Gene analysis revealed that a novel homozygous GTTT insertion between nucleotides 2833 and 2834 in FGB exon 2 in the proband. The proband's father, mother, brother and son were heterozygous. The polymerization curves of the patient did not show a lag phase or final turbidity, compared with the normal controls. Western blot analysis showed the lack of complete half-molecules of the fibrinogen molecule and fibrinogen in patient's plasma under non-reducing conditions. It also could not detect the truncated Bβ chain under reducing conditions. Abnormal fibrinogen molecule (molecule weight>340 000) were found in transfected COS-7 cells by Western blot, which indicated that the mutation caused the abnormal intracellular fibrinogen molecule assembly. The fibrinogen band was absent in culture media transfected by the mutation. Fibrinogen levels of mutant fibrinogen were no significant different from those of wild-type fibrinogen in cell lysates by ELISA analysis [(2.47 ± 0.30) μg/ml vs (2.65±0.60) μg/ml, P=0.0889]; However, the levels of the mutant fibrinogen were statistically significant lower than those of wild type fibrinogen in culture media [(0.01 ± 0.01) μg/ml vs (3.80±0.80) μg/ml, P=0.0001]. Congenital afibrinogenemia was caused by this frameshift mutation in exon 2 of FGB. This novel mutation impaired fibrinogen assembly and secretion.

Fibrinogen

Fibrinogen (coagulation factor I) is a major player in thrombus formation; it is cleaved by thrombin to form fibrin, which is the most abundant component of a blood clot.1 Beyond the role played in the coagulation and cardiovascular diseases (CVDs), fibrinogen is a proinflammatory factor in autoimmune and inflammatory diseases (such as rheumatoid arthritis, vasculitides, inflammatory bowel disease, multiple sclerosis, chronic obstructive pulmonary diseases, kidney disorders, and posttransplantation fibrosis)2 and in several types of cancer.3 Fibrinogen has been demonstrated to interfere with the immunoinflammatory responses through binding to inflammatory cells via ligand - receptor interactions that are different from those involved in the coagulation cascade.2 Fibrinogen also stimulates angioneogenesis in vitro and in vivo4 and acts as a mitogen for fibroblasts.5 Therefore, fibrinogen is a multifaceted molecule that plays various roles in several human diseases. Article see p 1310 Family studies have demonstrated a major genetic component of the variance of fibrinogen (44%),6 and increased levels of fibrinogen have proved to be a marker of risk for CVD. Therefore, the elucidation of the genetic architecture of plasma fibrinogen levels is becoming a major undertaking in translational research and an emerging clinical need. Fibrinogen is a large, soluble plasma hexameric glycoprotein (360 kDa) composed of pairs of 3 polypeptides (Aα, Bβ, and γγ) that are encoded by the FGA (MIM+134820), FGB (MIM+134850), and FGG (MIM+134830) genes, all mapping in a cluster on chromosome 4 (4q28). The FGA , FGB , and FGG genes are expressed almost exclusively in hepatocytes; the expression is regulated by both proximal promoters and enhancers and posttranscriptionally by miRNAs and is influenced by functional regulatory variants and acute-phase stimulation.7 The highly variable range of plasma fibrinogen levels in the general population (1.5–4 g/L) is the dynamic result of genetic …

A novel mutation in the FGB: c.1105C&gt;T turns the codon for amino acid Bβ Q339 into a stop codon causing hypofibrinogenemia

Routine coagulation tests on a 14year-old male with frequent epistaxis showed a prolonged thrombin time together with diminished functional (162mg/dl) and gravimetric (122mg/dl) fibrinogen concentrations. His father showed similar aberrant results and sequencing of the three fibrinogen genes revealed a novel heterozygous nonsense mutation in the FGB gene c.1105C>T, which converts the codon for residue Bβ 339Q to stop, causing deletion of Bβ chain residues 339-461. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and RP-HPLC (reverse-phase high-pressure liquid chromatography) of purified fibrinogen showed only normal Aα, Bβ, and γ chains, indicating that molecules with the truncated 37,990Da β chain were not secreted into plasma. Functional analysis showed impaired fibrin polymerization, fibrin porosity, and elasticity compared to controls. By laser scanning confocal microscopy the patient's fibers were slightly thinner than normal. Electrospray ionization mass spectrometry (ESI MS) presented normal sialylation of the oligosaccharide chains, and liver function tests showed no evidence of liver dysfunction that might explain the functional abnormalities.

Combined congenital dysfibrinogenemia and factor VII deficiency from mutations in the FGB and F7 genes

Dysfibrinogenemia and factor VII (FVII) deficiency are rare congenital coagulopathies. In this report, the authors describe a man with both defects confirmed by molecular genetic tests. The patient was a 51-year-old man referred for prolonged prothrombin time (PT) that had been accidentally detected on preoperative screening. He had no history of bleeding tendency even on occasions of surgery. Routine coagulation studies revealed prolonged PT (1.53 INR) and thrombin time (42.2 s), and decreased fibrinogen level (57 mg/dl) and FVII activity (44%). Direct sequencing analyses were performed on FGA, FGB, and FGG genes to confirm dysfibrinogenemia and on the F7 gene to confirm FVII deficiency. As a result, the patient was shown to be heterozygous for a point mutation in exon 8 of the FGB gene (c.1475A > G, p.*492Trpext*12; Fibrinogen Magdeburg II) and for a missense mutation in exon 6 of the F7 gene (c.466G > A, p.Gly156Ser). To our knowledge, this is the first report on a case of combined dysfibrinogenemia and FVII deficiency confirmed by molecular genetic tests.