Congenital (hypo-)dysfibrinogenemia and bleeding: A systematic literature review.

Ranging from bleeding to thrombosis, the clinical features of congenital fibrinogen qualitative disorders, including dysfibrinogenemia and hypodysfibrinogenemia, are highly heterogeneous. Although the associations between some specific fibrinogen mutations and the thrombotic phenotypes have been well elucidated, the underlying mechanism between fibrinogen variants and bleeding events remains underestimated. After systematically reviewing the literature of (hypo-)dysfibrinogenemia patients with bleeding phenotypes, we identified several well-characterized bleeding-related fibrinogen variants in those patients. Several possible pathomechanisms are proposed to explain the genotype-phenotype associations: 1, mutations in the NH2-terminal portion of the Aα chain hamper fibrinogen fitting into the active site cleft of thrombin and drastically slow the conversion of fibrinogen into monomeric fibrin; 2, mutations adding new N-linked glycosylation sites introduce bulky and negatively charged carbohydrate side chains and undermine the alignment of fibrin monomers during polymerization; 3, mutations generating unpaired cysteine form extra disulfide bonds between the abnormal fibrinogen chains and produce highly branched and fragile fibrin networks; 4, truncation mutations in the fibrinogen αC regions impair the lateral fibril aggregation, as well as factor XIII crosslinking, endothelial cell and platelet binding. These established relationships between specific variants and the bleeding tendency will help manage (hypo-)dysfibrinogenemia patients to avoid adverse bleeding outcomes.

Thrombosis-associated hypofibrinogenemia: novel abnormal fibrinogen variant FGG c.8G>A with oxidative posttranslational modifications.

Here, we present the first case of fibrinogen variant FGG c.8G>A. We investigated the behaviour of this mutated fibrinogen in blood coagulation using fibrin polymerization, fibrinolysis, fibrinopeptides release measurement, mass spectrometry (MS), and scanning electron microscopy (SEM). The case was identified by routine coagulation testing of a 34-year-old man diagnosed with thrombosis. Initial genetic analysis revealed a heterozygous mutation in exon 1 of the FGG gene encoding gamma chain signal peptide. Fibrin polymerization by thrombin and reptilase showed the normal formation of the fibrin clot. However, maximal absorbance within polymerization was lower and fibrinolysis had a longer degradation phase than healthy control. SEM revealed a significant difference in clot structure of the patient, and interestingly, MS detected several posttranslational oxidations of fibrinogen. The data suggest that the mutation FGG c.8G>A with the combination of the effect of posttranslational modifications causes a novel case of hypofibrinogenemia associated with thrombosis.

Congenital dysfibrinogenemia in major surgery: A description of four cases and review of the literature.

BACKGROUND: Congenital dysfibrinogenemia is characterized by qualitatively abnormal fibrinogens with resultant blood coagulation dysfunction. The clinical manifestations are high heterogeneity. Treatment for dysfibrinogenemia should be personalized. Here, we reported four congenital dysfibrinogenemia patients with the major surgery, in order to discuss the treatment and diagnosis of congenital dysfibrinogenemia. METHODS: We reported four asymptomatic congenital dysfibrinogenemia patients with the major surgery (valve replacement, brain surgery, tumorectomy, hysterectomy) in our study. Routine coagulation tests, hepatorenal function and gene analysis, thrombelastogram were performed. RESULTS: Four congenital dysfibrinogenemia patients all showed prolonged TT, low level of activity fibrinogen and normal fibrinogen antigen. Case1 showed a heterozygous mutation in exon 2 of the FGA, c.1223G > C, which turns the codon for residue Aα Gly13 into Arg (p. Gly13Arg). DNA sequencing of case2 showed that a heterozygous mutation in exon 8 of the FGG (c.5877G > A) with being responsible for the Arg â†’ His substitution at position 301 of the γ chain (p. Arg301His). Case3 and case 4 failed to do genetic testing for other reason. Four congenital dysfibrinogenemia patients were asymptomatic in the daily life. Personal and family history revealed no abnormal bleeding or thrombotic events. These four patients did not receive special treatment and management before surgery. They all had a smooth operation. CONCLUSIONS: Misdiagnosis and unnecessary infusion bring huge health risks to patients. Correct diagnosis of congenital dysfibrinogenemia is the key to avoid misdiagnosis or unnecessary infusion. Asymptomatic patients with congenital dysfibrinogenemia do not need cryoprecipitate or fibrinogen input before major surgery.

Recombinant γY278H Fibrinogen Showed Normal Secretion from CHO Cells, but a Corresponding Heterozygous Patient Showed Hypofibrinogenemia.

We identified a novel heterozygous hypofibrinogenemia, γY278H (Hiroshima). To demonstrate the cause of reduced plasma fibrinogen levels (functional level: 1.12 g/L and antigenic level: 1.16 g/L), we established γY278H fibrinogen-producing Chinese hamster ovary (CHO) cells. An enzyme-linked immunosorbent assay demonstrated that synthesis of γY278H fibrinogen inside CHO cells and secretion into the culture media were not reduced. Then, we established an additional five variant fibrinogen-producing CHO cell lines (γL276P, γT277P, γT277R, γA279D, and γY280C) and conducted further investigations. We have already established 33 γ-module variant fibrinogen-producing CHO cell lines, including 6 cell lines in this study, but only the γY278H and γT277R cell lines showed disagreement, namely, recombinant fibrinogen production was not reduced but the patients' plasma fibrinogen level was reduced. Finally, we performed fibrinogen degradation assays and demonstrated that the γY278H and γT277R fibrinogens were easily cleaved by plasmin whereas their polymerization in the presence of Ca2+ and "D:D" interaction was normal. In conclusion, our investigation suggested that patient γY278H showed hypofibrinogenemia because γY278H fibrinogen was secreted normally from the patient's hepatocytes but then underwent accelerated degradation by plasmin in the circulation.

The ß-chain mutation p.Trp433Stop impairs fibrinogen secretion: A novel nonsense mutation associated with hypofibrinogenemia.

BACKGROUND: Congenital hypofibrinogenemia is characterized by proportional decreases in fibrinogen activity and immunoreactive fibrinogen levels. Here, we describe a new case with the bleeding risk identified in our hospital. METHODS: The proband was cut and bled for 3 h. Coagulation testing, gene analysis, thrombelastogram, sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), in vitro plasmid construction, and functional analyses were performed to explore the pathogenic mechanism. RESULTS: Coagulation testing of the male proband revealed low levels of fibrinogen detected by two methods (the Clauss method and the PT-derived method); his two sons had normal coagulation results. DNA sequencing of the proband revealed a heterozygous point mutation in exon 8 of the FGB gene causing Trp→Stop substitution and a polymorphic site (p.Leu92Phe). Human Trp433 was found to be highly conserved. SDS-PAGE showed that the fibrinogen level of the proband was markedly lower than that of healthy controls. Using high-performance liquid chromatography-mass spectrometry, a mutated Bß chain was not detected in circulation. In vitro expression analyses indicated that the mutation affected the secretion of fibrinogen. The TEG results indicated that the proband had a prolonged K time, a lower CI value, and a lower angle value. CONCLUSION: We report a new case with a novel nonsense mutation that resulted in hypofibrinogenemia. The results indicate that the nonsense mutation may cause misfolding of the D domain, which then affects the secretion of fibrinogen.

Congenital dysfibrinogenemia caused by γAla327Val mutation: structural abnormality of D region.

BACKGROUND: : Congenital dysfibrinogenemia (CD) is a coagulation disorder caused by mutations in the fibrinogen genes, which result in abnormal fibrinogen function. However, the precise pathogenesis underlying it remains unclear. METHODS: : In this study, we identified a novel heterozygous mutation in an asymptomatic patient with CD caused by γ Ala327Val mutation. Aimed to investigate the pathogenesis, functional studies of fibrinogen isolated from the proband and her family members were performed, such as coagulation function, fibrinogen aggregation test, and fibrin clot lysis test. Coagulation was monitored using a thromboelastometer, and the fibrin clot network structure was observed by scanning electron microscopy. The effect of the mutation on fibrinogen structure and function was predicted by molecular modeling. RESULTS: : The fibrinogen activity concentration in patients with CD was significantly lower than that in healthy individuals, indicating that fibrinogen activity was low. Proband's fibrinogen activity concentration was 0.75 g/L(Clauss method) and antigen concentration (immune turbidimetry method) was 1.59 g/L(normal reference range for both parameters: 2.0-4.0 g/L). Thromboelastography showed that the K value of patients with CD was higher than that of healthy individuals and Angle values were decreased, indicating that mutation impaired fibrinogen function. Compared to fibrinogen from healthy individuals, fiber network structure of the proband was loose, pore size was increased, and fiber branch nodes were increased. CONCLUSIONS: : Ala327Val heterozygous missense mutation leads to changes in the structure of fibrinogen D region and impairs the aggregation function of fibrinogen. This mutation is reported here for the first time.

Mutations Causing Mild or No Structural Damage in Interfaces of Multimerization of the Fibrinogen γ-Module More Likely Confer Negative Dominant Behaviors.

Different pathogenic variants in the same protein or even within the same domain of a protein may differ in their patterns of disease inheritance, with some of the variants behaving as negative dominant and others as autosomal recessive mutations. Here is presented a structural analysis and comparison of the molecular characteristics of the sites in fibrinogen γ-module, a fibrinogen component critical in multimerization processes, targeted by pathogenic variants (HGMD database) and by variants found in the healthy population (gnomAD database). The main result of this study is the identification of the molecular pathogenic mechanisms defining which pattern of disease inheritance is selected by mutations at the crossroad of autosomal recessive and negative dominant modalities. The observations in this analysis also warn about the possibility that several variants reported in the non-pathogenic gnomAD database might indeed be a hidden source of diseases with autosomal recessive inheritance or requiring a combination with other disease-causing mutations. Disease presentation might remain mostly unrevealed simply because the very low variant frequency rarely results in biallelic pathogenic mutations or the coupling with mutations in other genes contributing to the same disease. The results here presented provide hints for a deeper search of pathogenic mechanisms and modalities of disease inheritance for protein mutants participating in multimerization phenomena.

Heterozygous variant fibrinogen γA289V (Kanazawa III) was confirmed as hypodysfibrinogenemia by plasma and recombinant fibrinogens.

INTRODUCTION: Congenital fibrinogen disorders are classified as afibrinogenemia, hypofibrinogenemia, dysfibrinogenemia, and hypodysfibrinogenemia. However, difficulties are associated with discriminating between dysfibrinogenemia, hypofibrinogenemia, and hypodysfibrinogenemia using routine analyses. We previously reported a heterozygous variant fibrinogen (γA289V; Kanazawa III) as hypodysfibrinogenemia; however, the same variant had previously been described as hypofibrinogenemia. To clarify the production of γA289V fibrinogen, we expressed recombinant γA289V (r-γA289V) fibrinogen and compared it with wild-type (WT) and adjacent recombinant variant fibrinogens. METHODS: Target mutations were introduced into a fibrinogen γ-chain expression vector by site-directed mutagenesis, and the vector was then transfected into Chinese hamster ovary cells to produce recombinant fibrinogen. Fibrinogen was purified from the plasma of the proposita, and culture media and fibrinogen functions were analyzed using fibrin polymerization, plasmin protection, and FXIIIa-catalyzed fibrinogen cross-linking. RESULTS: The fibrinogen concentration ratio of the culture media to cell lysates was markedly lower for r-γA289V fibrinogen than for WT. Because the secretion of recombinant γF290L (r-γF290L) fibrinogen was similar to WT, we compared r-γF290L fibrinogen functions with WT. The fibrin polymerization of Kanazawa III plasma (K-III) fibrinogen was significantly weaker than normal plasma fibrinogen. Moreover, K-III fibrinogen showed a markedly reduced "D:D" interaction. However, all functions of r-γF290L fibrinogen were similar to WT. An in silico analysis confirmed the above results. CONCLUSION: The present results demonstrated that γA289 is crucial for the γ-module structure, and the γA289V substitution markedly reduced fibrinogen secretion. Moreover, K-III fibrinogen showed markedly reduced fibrin polymerization and "D:D" interactions. γA289V fibrinogen was confirmed as hypodysfibrinogenemia.

Congenital fibrinogen disorders with repeated thrombosis.

Congenital dysfibrinogenemia is characterized with undetectable or low fibrinogen level by Clauss assay complicated by bleeding and/or thrombosis. These may lead to a diagnostic problem to some clinicians unfamiliar with this disease. We reported a case of congenital dysfibrinogenemia manifested as hemorrhage, repeated thrombosis, low fibrinogen levels through Clauss assay and but normal levels of fibrinogen through PT-derived tests. In conclusion, to patients with thrombosis complicated by decreased fibrinogen level, clinicians and laboratory physicians should be alert to the possibility of congenital dysfibrinogenemia.

Fibrinogen Columbus II: A novel c.1075G>T mutation in the FGG gene causing hypodysfibrinogenemia and thrombosis in an adolescent male.

Hypodysfibrinogenemia, the least frequently reported congenital fibrinogen disorder is characterized by low circulating levels of a dysfunctional protein, and is associated with phenotypic features of both hypo- and dysfibrinogenemia. Herein, we report an adolescent male with unprovoked venous thromboembolism and hypodysfibrinogenemia. Patient had recurrent, progressive thrombosis despite therapeutic anticoagulation with both low molecular weight heparin and warfarin. He had clinical and radiological improvement after transition to a direct thrombin inhibitor. Sequencing of the FGG gene identified a novel heterozygous mutation, c.1075G>T. Structural visualization of the identified variant was pursued and suggested that the mutation likely destabilizes the Ca2+ -binding site of fibrinogen resulting in pathogenicity.

Inherited thrombophilia and pregnancy loss. Study of an Argentinian cohort. / Trombofilia hereditaria y pérdidas de embarazo. Estudio de una cohorte de Argentina.

BACKGROUND AND OBJECTIVES: Thrombophilia might increase the risk of suffering from obstetric complications by adversely affecting the normal placental vascular function. Our aim was to study the distributions of five thrombosis-associated genetic variants: factor V Leiden, prothrombin G20210A, -675 4G/5G PAI-1, 10034C/T gamma fibrinogen and 7872C/T factor XI and the frequencies of the deficiencies of protein C, S and antithrombin in Argentinian patients with recurrent pregnancy loss (RPL) and, therefore, to analyse their association with the risk and timing of RPL and the risk of suffering other vascular obstetric pathologies. PATIENTS AND METHODS: We performed a case-control study that included 247 patients with idiopathic RPL (cases), 107 fertile controls and 224 subjects from general population (reference group). Cases were stratified according to the gestational time of the losses (early RPL, n = 89; late losses, n = 158; foetal losses, n = 107) and according to the type of vascular obstetric pathologies. RESULTS: No differences were found in the distribution of the genetic variants among RPL group vs. control/reference group (p >.05). Similarly, no differences were observed in their distributions when analysing RPL patients stratified according to gestational times or vascular obstetric pathologies (p >.05), except for the factor V Leiden carriage in patients with foetal growth retardation vs. controls (11.8%, 4/34 vs. 1.9%, 2/107; p = .04) (OR = 7.11 [1.24-40.93], p = .03). CONCLUSIONS: Factor V Leiden might have a significant impact on certain obstetric pathologies such as foetal growth retardation. The genetic variants, 10034C/T gamma fibrinogen and 7872C/T factor XI, associated with thromboembolic disease, would not have an impact on PRE.

[Mutation analysis of a FGG gene causing hereditary abnormal fibrinogen].

OBJECTIVE: To study the clinical phenotype and gene mutation analysis of a hereditary abnormal fibrinogenemia family and explore its molecular pathogenesis. METHODS: The STA-R automatic hemagglutination analyzer to detect the proband and its family members (3 generations of 5 people) of prothrombin time(PT), activated partial thromboplastin time (APTT), thrombin time (TT), fibrinogen activity (Fg: C), D-dimer (D-D), fibrinogen and fibrin degradation products (FDPs), plasminogen activity (PLG: A); The plasma levels of Fg: C and fibrinogen (Fg: Ag) were measured by Clauss method and immunoturbidimetry respectively. All exons and flanking sequences of FGA, FGB and FGG genes of fibrinogen were amplified by PCR, and the PCR products were purified and sequenced for gene analysis. The model was analyzed by Swiss software. RESULTS: The PT and APTT of the proband, her mother and sister were slightly prolonged, TT was significantly extend, Fg: C decreased significantly, Fg: Ag, PLG: A, D-D and FDPs are within the normal range; Her brother and daughter of the results are normal. Genetic analysis showed that g.7476 G>A heterozygous missense mutation in exon 8 of FGG gene resulted in mutations in arginine at position 275 of fibrinogen gamma D domain to histidine (Arg275His). Her mother and sister have the same Arg275His heterozygous mutation, brother and daughter for the normal wild type. CONCLUSION: The heterozygous missense mutation of FGG gene Arg275His in patients with hereditary dysfibrinogenemia is associated with a decrease in plasma fibrinogen activity.

Impact of γ'γ' fibrinogen interaction with red blood cells on fibrin clots.

AIM: γ' fibrinogen has been associated with thrombosis. Here the interactions between γ'γ' or γAγA fibrinogen and red blood cells (RBCs), and their role on fibrin clot properties were studied. MATERIALS & METHODS: Atomic Force microscopy (AFM)-based force spectroscopy, rheological, electron and confocal microscopy, and computational approaches were conducted for both fibrinogen variants. RESULTS & CONCLUSION: AFM shows that the recombinant human (rh)γ'γ' fibrinogen increases the binding force and the frequency of the binding to RBCs compared with rhγAγA, promoting cell aggregation. Structural changes in rhγ'γ' fibrin clots, displaying a nonuniform fibrin network were shown by microscopy approaches. The presence of RBCs decreases the fibrinolysis rate and increases viscosity of rhγ'γ' fibrin clots. The full length of the γ' chain structure, revealed by computational analysis, occupies a much wider surface and is more flexible, allowing an increase of the binding between γ' fibers, and eventually with RBCs.

Identification of Two Novel Fibrinogen Bß Chain Mutations in Two Slovak Families with Quantitative Fibrinogen Disorders.

Congenital fibrinogen disorders are caused by mutations in one of the three fibrinogen genes that affect the synthesis, assembly, intracellular processing, stability or secretion of fibrinogen. Functional studies of mutant Bß-chains revealed the importance of individual residues as well as three-dimensional structures for fibrinogen assembly and secretion. This study describes two novel homozygous fibrinogen Bß chain mutations in two Slovak families with afibrinogenemia and hypofibrinogenemia. Peripheral blood samples were collected from all subjects with the aim of identifying the causative mutation. Coagulation-related tests and rotational thromboelastometry were performed. All exons and exon-intron boundaries of the fibrinogen genes (FGA, FGB and FGG) were amplified by PCR followed by direct sequencing. Sequence analysis of the three fibrinogen genes allowed us to identify two novel homozygous mutations in the FGB gene. A novel Bß chain truncation (BßGln180Stop) was detected in a 28-year-old afibrinogenemic man with bleeding episodes including repeated haemorrhaging into muscles, joints, and soft tissues, and mucocutaneous bleeding and a novel Bß missense mutation (BßTyr368His) was found in a 62-year-old hypofibrinogenemic man with recurrent deep and superficial venous thromboses of the lower extremities. The novel missense mutation was confirmed by molecular modelling. Both studying the molecular anomalies and the modelling of fibrinogenic mutants help us to understand the extremely complex machinery of fibrinogen biosynthesis and finally better assess its correlation with the patient's clinical course.

Fibrinogen Mahdia: A congenitally abnormal fibrinogen characterized by defective fibrin polymerization.

INTRODUCTION: Congenital dysfibrinogenemia is a rare qualitative fibrinogen deficiency. Molecular defects that result in dysfibrinogenemia are usually caused by mutations which affect fibrinopeptide release, fibrin polymerization, fibrin cross-linking or fibrinolysis. AIM: Here, we investigated the genetic basis of hypodysfibrinogenemia in two Tunisian siblings with major bleeding. METHODS: Coagulation-related tests were performed on the patients and their family members. Functional analysis was performed in plasma fibrinogen to characterize fibrin polymerization. The sequences of fibrinogen genes were amplified and analysed by sequencing. RESULTS: Coagulation studies revealed a reduced functional and a borderline low antigenic fibrinogen plasma levels with prolonged thrombin and activated partial thromboplastin times. The fibrinogen is also characterized by a markedly impaired polymerization and could incorporate into fibrin fibres to a smaller extent (22%). Mutational screening disclosed a heterozygous single nucleotide deletion (G) at c.1025, resulting in a frameshift mutation (AαGly323GlufsX79) that is predicted to delete a part of the αC-domain containing some of the FXIII cross-linking sites. Both the normal and the aberrant Aα-chain (approximately 43 kDa) were detected by electrophoretic analysis in the patients. CONCLUSION: The new dysfunctional fibrinogen, Mahdia variant, describes its impact on fibrin assembly after the loss of the αC domains which are involved in the lateral aggregation of protofibrils. The study confirms that the truncated Aα-chain could be incorporated into mature fibrinogen molecules.