Studies of platelet fibrinogen from a subject with a congenital plasma fibrinogen abnormality (fibrinogen Paris I).
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Human fibrinogen contains four asparagine-linked sugar chains in one molecule. All B beta and gamma subunits obtained from both normal fibrinogen and abnormal fibrinogen Nagoya contain 1 mol each of an asparagine-linked sugar chain. The sugar chains were quantitatively liberated as radioactive oligosaccharides from the polypeptide portion by hydrazinolysis followed by N-acetylation and NaB3H4 reduction. By the combination of sequential exoglycosidase digestion and methylation analysis, the structures of the sugar chains of human fibrinogen were elucidated to be NeuAc alpha 2 leads to 6Gal beta 1 leads to 4GlcNAc beta 1 leads to 2Man alpha 1 leads to 6(NeuAc alpha 2 leads to 6Gal beta 1 leads to 4GlcNac beta 1 leads to 2Man alpha 1 leads to 3)Man beta 1 leads to 4GlcNAc beta 1 leads to 4GlcNAc and Gal beta 1 leads to 4GlcNAc beta 1 leads to 2Man alpha 1 leads to 6(NeuAc alpha 2 leads to 6Gal beta 1 leads to 4GlcNAc beta 1 leads to 2Man alpha 1 leads to 3)Man beta 1 leads to 4GlcNAc beta 1 leads to 4GlcNAc. Neither quantitative nor qualitative differences were found between the sugar chain moieties of normal fibrinogen and fibrinogen Nagoya, indicating that the molecular basis of the abnormality in the latter may reside in its polypeptide moieties.
A qualitatively abnormal fibrinogen was detected in the plasma of a 53 year old woman with severe arterial thrombotic disease. The concentrations of plasma fibrinogen and serum fibrinogen related material were normal. The abnormal fibrinogen was electrophoretically normal. The defects detected were an abnormality of polymerization of fibrin monomers and a decreased rate of release of fibrinopeptide A. The absorption of radiolabelled partially degraded plasminogen on to fibrin prepared from purified fibrinogen Copenhagen was normal.
A 54-yr-old woman presented with a 23-yr history of repeated life-threatening thromboembolism. The presence of a qualitatively abnormal fibrinogen was suggested by the demonstration of delayed and incomplete coagulation of plasma or partially purified fibrinogen by thrombin or Reptilase. Two brothers showed a similar in vitro defect but were clinically not affected. The plasma fibrinogen concentration was 0.50-1.64 mg/ml when estimated by heat turbidity, clottability, or immunologic techniques. The serum contained 80-820 mug/ml of unclottable fibrinogen-related materials even after 24 hr exposure to thrombin. The fibrinogen-related material in the serum showed faster anodal mobility an immunoelectrophoresis than that of normal plasma. Immunodiffusion studies with rabbit antihuman fibrinogen antiserum showed lines of identity between control plasma and the patient's plasma and serum. Studies of the kinetics of thrombin action on fibrinogen demonstrated impaired release of fibrinopeptide A and B and defective polymerization of preformed fibrin monomers. The maximum amount of fibrinopeptide A released by exhaustive treatment with thrombin was similar (per milligram protein) for both the patient's and control fibrinogen. This abnormal fibrinogen varient is tentatively designated fibrinogen "New York"; its possible identity with one of the previously described abnormal fibrinogens has not been excluded.
A congenital dysfibrinogenemia was found in a 32-year-old asymptomatic female and her immediate family. The propositus, apparently a heterozygote for the abnormality, characteristically showed defective release of fibrinopeptide A from half of her fibrinogen molecules. No fibrinopeptide A was cleaved off from the isolated abnormal molecule by thrombin or snake venoms (Reptilase and Ancrod) as evidenced by radioimmunoassay, high performance liquid chromatography and determination of the NH2-terminal amino acids. The abnormal fibrinogen formed a solid gel solely by the release of fibrinopeptide B upon incubation with thrombin. We provisionally designate this abnormal fibrinogen as "Fibrinogen Kawaguchi", although possible identity with other abnormal fibrinogens is not excluded.
Another abnormal fibrinogen--"fibrinogen Hannover"--is reported. As known from most dysfibrinogenemias the clottability is poor, while immunologic test, heat precipitating test and the staphylococcal clumping test give normal fibrinogen concentrations. The clotting time when using thrombin or thrombin like enzymes is prolonged, it can be corrected with high thrombin concentration or thrombin combined with calcium inons, but not with thrombin like enzymes combined with calcium ions. The mild bleeding diathesis was first noted when the patient underwent an operation.
An abnormal fibrinogen (fibrinogen Cleveland II) was detected in the plasma of a 23-yr-old white man with a mild bleeding diathesis. The one-stage prothrombin time, thrombin time, and Reptilase time were all prolonged. 16 of 24 tested relatives had the defect, which appeared to be transmitted as an autosomal dominant characteristic. The thrombin time of normal plasma was slightly inhibited by the proband's plasma. The abnormally long thrombin time of fibrinogen Cleveland II was partially corrected by addition of calcium ions. Fibrinogen Cleveland II was indistinguishable from normal fibrinogen by immunoelectrophoresis, DEAE-cellulose column chromatography, or polyacrylamide gel electrophoresis of reduced fibrinogen in sodium dodecyl sulfate. The major defect detected appeared to be impaired release of fibrinopeptide A when fibrinogen Cleveland II was incubated with thrombin. This defect was localized to the NH(2)-terminal disulfide knot portion of the molecule. An abnormality of polymerization of fibrin monomers was also present, but the abnormal fibrin demonstrated relatively normal crosslinking. Despite these defects, fibrinogen Cleveland II achieved a degree of coagulability similar to normal fibrinogen and appeared to incorporate some molecules of fibrin with intact fibrinopeptide A into the clot. The fibrin clot that was formed appeared to be abnormal by electron microscopy. These functional defects and other descriptive characteristics appear to distinguish fibrinogen Cleveland II from other inherited abnormal fibrinogens.
A hereditary dysfibrinogenemia associated with defective aggregation of fibrin monomers was found in a 39-yr-old female and in the members of her immediate family, who had all been asymptomatic. The abnormality was probably due to an impaired polymerization site exposed in the DD domain of two adjacent fibrin molecules, because plasmic fragment DD derived from the propositus' cross-linked fibrin bound far less tightly to insolubilized normal fragment E than that from the normal one. Its complementary polymerization site in the E domain of fibrin, which was exposed by thrombin cleavage, and the polymerization site in the D domain of fibrinogen, which was available without activation by thrombin, were both found to be normal. More anodal migration of the abnormal fragment DD than the normal one, as shown by immunoelectrophoresis, seemed to support our concept that the mutation most likely resides in the D domain of the abnormal fibrinogen molecule at or near a region closely related to the polymerization site that is exposed when two fibrin molecules are linearly aligned. The work of others on the polymerization of normal fibrin with different techniques yielded results consistent with our conclusions. We tentatively designate this type of abnormal fibrinogen "fibrinogen Tokyo II," but its possible identity with other abnormalities of fibrinogen reported heretofore is not excluded.
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Congenital abnormalities of fibrinogen are rare disorders and all the cases reported in the literature indicate that the incidence of afibrinogenaemia is much higher than hypofibrinogenaemia. Of the total of 20 cases reported from other parts of India only one was congenital hypofibrinogenaemia. In contrast, the present study showed eight patients with congenital hypofibrinogenaemia among a total of nine unrelated North Indian patients with a fibrinogen abnormality. This disproportionately high incidence of hypofibrinogenaemia suggests the existence of a distinct genetic defect in the North Indian population.
For the first time, a correlation between a specific fibrinogen abnormality and the clinical symptoms of thrombosis has been found in unrelated families. These abnormal fibrinogens have been designated Dusart and Chapel Hill III. The abnormal fibrinogen Chapel Hill III was identified previously in a patient with thrombotic disease. We purified fibrinogen from small aliquots of patient and normal plasmas by a simple, rapid procedure. Coomassie stained sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis demonstrated that fibrinogen Chapel Hill III contained several high molecular weight forms in addition to the two forms seen with normal fibrinogen. Immunoblot analysis of Chapel Hill III fibrinogen demonstrated that essentially all the high molecular weight forms react with antiserum to albumin. Immunoblot analysis of plasmin digests of Chapel Hill III fibrinogen demonstrated that albumin is linked to the C-terminus of the A alpha chain. Using DNA analysis, we found that the patient is heterozygous for a single base change, resulting in the substitution A alpha Arg 554-->Cys. This is the same change identified in fibrinogen Dusart. The Dusart family members who are heterozygous for this substitution also suffer from recurrent thrombotic disorders.
Congenital and hereditary abnormal fibrinogen is the most common of the inherited disorders of fibrinogen. There is no uniform clinical pattern which characterizes the disease and the diagnosis is evoked on the results of laboratory tests which show an abnormal conversion of fibrinogen to fibrin. This abnormality should be confirmed on the purified defective fibrinogen. Characterization of the abnormality includes physical, immunological, functional and structural analyses. Studies related to fibrinogen behavior upon plasmin digestion and those related to polymerization also provide useful information. Recognition of the specific nature of the molecular defect is dependent on molecular analysis. A single distinctive amino acid substitution is currently recognized for Fibrinogen Detroit, Lille and München.
A slow clotting dysfibrinogen with delayed anodal immunoelectrophoretic mobility and impaired fibrinopeptide A release has been identified in a patient with recurrent portal vein and deep venous thrombosis. Affected family members tested in the initial screening were asymptomatic. The proband's father died of pulmonary embolism at age 44 years and had mesenteric thrombosis at necropsy. The association of a plasma protein abnormality with visceral thrombosis is unusual and has never been observed previously with a dysfibrinogen. The qualitative abnormality is transmitted as an autosomal codominant and is tentatively designated, fibrinogen Irvine.
A dysfibrinogen was detected in the plasma of a 14-year-old asymptomatic Caucasian boy who had tetralogy of Fallot. The mutant molecular species could be traced through four generations in an autosomal dominant type of inheritance pattern. Nine of 14 family members were found to have the coagulopathy. Following laboratory and clinical evaluation, the proband underwent radical repair of the cardiac defect without incident. This variant is tentatively designated fibrinogen Seattle pending further characterization.
In a 81 year old health woman, gross abnormalities of fibrin formation led to the discovery of an abnormal fibrinogen named fibrinogen Bondy. Clottability of purified fibrinogen Bondy was only 53% compared to 95-98% for normal fibrinogen. Functional studies revealed (i) delayed coagulation by thrombin and batroxobin (Reptilase), (ii) incomplete release of fibrino-peptides A and B, (iii) poor fibrin monomer aggregation, (iv) delayed fibrin proteolysis by plasmin. Electrophoretic mobility of fibrinogen Bondy, its three chains and the products of fibrin cross-linking, was normal. Fibrinogen NH2-terminal residues of fibrinogen Bondy were found to be normal. The presence of Ala, in addition to Gly and Tyr in the fibrin clot and its supernatant, showed that a part of fibrinogen molecules was not clotted, i.e. either copolymerised with fibrin or remaining in solutions. Gel filtration of the supernatant allowed the separation of both soluble complexes and fibrinogen. This fibrinogen population was shown to be unclottable by thrombin and to inhibit clotting of normal fibrinogen.
An abnormal fibrinogen was found in a patient associated with disabling recurrent phlebitis and pulmonary emboli, pseudotumor cerebri, gout and endometriosis. The fibrinogen is characterized by (1) abnormal side-to-side and end-to-end polymerization, (2) abnormal fibrinopeptide release, (3) a delayed gamma-gamma dimerization of the non cross-linked fibrin, (4) a pH optimum of 7--7.8, and (5) a deviation from normal amino acid composition with regard to lysine, aspartic acid, glutamic acid and serine. Since no defect has been found in any of her three children, and since the prothromin and partial thromboplastin times vary from time to time, it is assumed that the defect is acquired. Liver disease, usually associated with acquired abnormal fibrinogen, has been excluded as an etiological cause since liver function tests and biopsy are completely normal.
The molecular defects in two congenital abnormal fibrinogens, IJmuiden and Nijmegen, were determined by sequence analysis of genomic DNA amplified by the polymerase chain reaction. Both fibrinogens were heterozygous, IJmuiden having a B beta Arg14----Cys substitution and Nijmegen having a B beta Arg44----Cys substitution. Clotting induced by thrombin or Reptilase was impaired in both fibrinogens, indicating defective fibrin polymerization. Immunoblot analysis of both purified fibrinogens demonstrated that some of the abnormal molecules were linked by disulfide bonds to albumin. In addition, abnormal high molecular weight fibrinogen complexes with Mrs between 600,000 and 700,000 were present. Fibrinogen-albumin and high molecular weight complexes were also detected in the patients' plasmas. Quantitative analysis demonstrated that of the total plasma fibrinogen in the IJmuiden patient, 20% was linked to albumin and 10% was present as high molecular weight complexes. In plasma Nijmegen, 13% was linked to albumin and 15% was present as high molecular weight complexes. These results demonstrate that the additional abnormal cysteine in fibrinogens IJmuiden and Nijmegen resulted in the formation of disulfide-linked complexes with other proteins, predominantly albumin. We also found that a significant fraction of the abnormal fibrinogen molecules contained free sulfhydryl groups. These findings complicate interpretation of functional studies of these altered fibrinogens.
A gamma-chain variant with a lower molecular weight than the normal gamma chain was detected in a new congenital abnormal fibrinogen with impaired polymerization of the fibrin monomer and with normal release of fibrinopeptides A and B in a 45-year-old male. Purified fibrinogen analyzed on SDS-polyacrylamide gel electrophoresis under the reduced condition contained an abnormal protein band with an apparent molecular weight of 48,000 compared with the gamma chain with a molecular weight of 50,000. This abnormal protein band was found to be a gamma-chain variant from the molar ratio of A alpha chain:B beta chain:gamma chain:abnormal protein (about 2:2:1:1), with positive staining for carbohydrate and crosslinking ability. Crosslinked fibrin contained three types of gamma-gamma dimers with apparent molecular weights of 94,000 (the same as normal major gamma-gamma dimer), 92,000 and 90,000, and the plasmic digests of crosslinked fibrin in the presence of calcium retained three types of gamma-gamma dimer remnants. This suggests that the abnormal gamma-chain variant has a shorter polypeptide chain not in the NH2-terminal but in the COOH-terminal portion, probably at or near the polymerization site. This patient's two daughters had the same abnormal fibrinogen. This unique inherited abnormal fibrinogen was designated as fibrinogen Kyoto, and the gamma-chain variant as gamma Kyoto.