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From www.bloodjournal.org by guest on June 17, 2017. For personal use only. Fibrinogen Bern I: Substitution y 337 Asn + Lys Is Responsible for Defective Fibrin Monomer Polymerization By Colette Steinmann, Peter Reber, Myriam Jungo, Bernhard LBmmle, Gabriela Heinemann, Bendicht Wermuth, and Miha Furlan An inherited fibrinogen variant, fibrinogen Bern I, was isolated from plasma of an asymptomatic woman. Routine coagulation studies showed prolonged thrombin and reptilase clotting times. Fibrinogen concentration was diminished when determined by a functional assay, but was normal by the heat precipitation method. The release of fibrinopeptides A and B was not delayed. Two-dimensional gel electrophoresis of mercaptolyzedfragments D of fibrinogen, obtained by digestion with plasmin, showed an abnormal electrophoretic mobility in the y-chain remnants of fragments D, and D, from fibrinogen Bern 1, whereas conversion of D, to D, by plasmin resulted in the loss of the abnormal charge, suggesting that the structural abnormality in this variant is located in the region y 303 through 356. The molecular defect in fibrinogen Bern I was identified by sequence analysis of genomic DNA amplified by polymerase chain reaction and cloned in M13mpl9. ‘The triplet AAC coding for asparagine at position y 337 was found to be substituted by AAA coding for lysine. W e conclude that the substitution y 3 3 7 Asn -+ Lys in fibrinogen Bern I is responsible for defective polymerization of fibrin monomers and for impaired protection by calcium against plasmic degradation. 0 1993 by The American Society of Hematology. C site. Recently, the binding site for Gly-Pro-Arg was located to the y-chain residues 337 through 379 by photoaffinity labeling.’ Functionally abnormal fibrinogens with structural defects in the y-chain include variants with amino acid substitutions between positions y 275’”,” and y 375.” In the present study, we identified the defect in fibrinogen Bern I, a dysfunctional variant characterized by delayed clotting in the absence of calcium ion^.'^,'^ Residue y 337 Asn was found to be replaced by Lys, which seems to be responsible for delayed polymerization of fibrin monomers derived from this variant. ONGENITAL dysfibrinogenemia defines an inherited functional defect caused by structural alteration in the fibrinogen molecule. Most dysfibrinogenemias have thus far been detected by virtue of a prolonged thrombin clotting time and, therefore, mainly represent variants with defective fibrinogen to fibrin conversion. More than 240 abnormal fibrinogen variants have been described.’ In a large proportion of abnormal fibrinogens, the defective release of fibrinopeptides A and/or B is caused by an amino acid substitution interfering with the thrombin-induced cleavage of the peptide bonds ACI 16-17 or BP 14-15, Furthermore, in several fibrinogen variants, the functional defect is associated with an abnormal or absent amino terminal polymerization site. Polymerization of fibrin is initiated by exposure of amino terminal binding sites, Gly-Pro-Arg (a-chain) and Gly-His-Arg (P-chain) after proteolytic cleavage of fibrinopeptides A and B, re~pectively.~,~ Fibrin monomers interact with complementary carboxy terminal domains of neighboring fibrin(ogen) m01ecules.~~’The carboxy terminal region of the y-chain plays an important role in fibrin monomer polymerization. The synthetic peptide Gly-Pro-Arg-Pro, an analogue of the amino terminus of the fibrin a-chain, was found to bind to fragment D, and to inhibit polymerization of fibrin monomers.* However, peptides with the sequence Gly-Pro-Arg did not bind to the plasmin-generated fragment D, lacking the carboxy terminal 109 residues of the y-chain. Thus, the carboxy terminal third of the y-chain is supposed to bear the polymerization From the Central Hematology Laboratory and the Central Clinical Chemistry Laboratory, Inselspital, University of Bern, Switzerland. Submitted March 24, 1993; accepted May 20, 1993. Supported by Swiss National Science Foundation Grant No. 3228785.90. Address reprint requests to Miha Furlan. PhD, Central Hematology Laboratory, Inselspital, CH-3010 Bern, Switzerland. The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. section 1734 solely to indicate this fact. 0 1993 by The American Society of Hematology. 0006-4971/93/8207-0110$3.00/0 2104 MATERIALS AND METHODS Materials. Taq DNA polymerase, 123-bp ladder-size standard and JM 10 1 Escherichia coli cells for transformation were obtained from Bethesda Research Laboratories (Gaithersburg, MD). Sequenase Version 2.0 kit was from US Biochemicals (Cleveland, OH). Deoxyadenosine 5’[a35S]thiotriphosphatewas from Amersham (Amersham, UK). M 13mp19 cloning vector, Sma I restriction endonuclease, dATP, dCTP, dGTP, dTTP, proteinase K, RNase A, ethidium bromide, isopropylthio-P-D-galactoside, 5bromo-4-chloro-3-indolyl-~-D-galactoside, T4 DNA polymerase, and T4 DNA ligase were purchased from Boehringer (Mannheim, Germany). Agarose Type I1 DNA grade was from Sigma (St. Louis, MO). QIAGEN-tip 5 mini columns were from DIAGEN (Dusseldorf, Germany) and Sephadex G-25 DNA grade (NapTM25) columns from Pharmacia (Uppsala, Sweden). All other chemicals were of analytical grade. Purification ofjbrinogen. Fibrinogen was purified from normal and proposita’s plasma by affinity chromatography on fibrin monomer Sepharose CL-2B.I’ No attempt was made to separate normal and abnormal fibrinogen molecules isolated from the heterozygous carrier of defective fibrinogen. Determination of coagulation parameters in plasma. Activated partial thromboplastin time (APTT), prothrombin time (Quick), thrombin time (TT), and reptilase time (RT) were determined by conventional methods. Concentration of fibrinogen was measured by the functional assay of Clauss16 and by the heat precipitation method of Schu1z.l’ Fibrinopeptide release. High performance liquid chromatography (HPLC)analysis of fibrinopeptides was performed according to Kehl et all*with minor modifications. Fibrinogen (final concentration, 1 mg/mL) in 0.15 mol/L ammonium acetate buffer (pH 7.4), containing 0.1 mmol/L CaCl,, was incubated for various time intervals at 37°C with 0.1 NIH U/mL bovine thrombin (HoffmannL a Roche, Basel, Switzerland). The reaction was stopped by addiBlood, Vol 82, No 7 (October 1). 1993: pp 2104-2108 From www.bloodjournal.org by guest on June 17, 2017. For personal use only. ABNORMAL FIBRINOGEN VARIANT BERN I tion of concentrated formic acid (l/lO, vol/vol). Fibrin was precipitated by neutralizing the solution with 25% NH,. After centrifugation, the supernatant was lyophilized. The fibrinopeptides were dissolved in 0.025 mol/L ammonium acetate, pH 6.0, and analyzed by HPLC. Chromatographywas performed on a Beckman (Fullerton, CA) Ultrasphere-ODS RP-18/5 pm (0.46 X 25 cm) column. Buffers used were the following: solvent A, 0.025 mol/L ammonium acetate, pH 6.0; solvent B, 50% acetonitrile (Fluka, Buchs, Switzerland) in 0.05 mol/L ammonium acetate, pH 6.0; gradient, 18%to 28% B in 20 minutes at a flow rate of 1.5 mL/min. Two-dimensional gel electrophoresisof plasmin-digestedfibrinogenfragments D,,D,,and D,. Normal fibrinogen and fibrinogen Bern I were digested by plasmin (Kabi, Stockholm, Sweden) in the presence of 10 mmol/L CaCl,. The resulting fragment D, was isolated by affinity chromatography on ly~ine-agarosel~ and dialyzed against 0.05 mol/L triethanolamine, 0.1 mol/L NaCl, 10 mmol/L EGTA, pH 7.4. Fragment D, (2 mg/mL) was incubated for 3 hours at 37°C with 0.3 U/mL plasminogen (Kabi) and 6 U/mL streptokinase (Kabi). The resulting fragmentsD,, D,, and D, were reduced with 2% dithiothreitol (Fluka) and separated by isoelectric focusing and sodium dodecyl sulfate (SDS) polyacrylamidegel electrophoresis according to Reber et aLzo DNA isolation from whole blood. Twenty milliliters fresh EDTA (final concentration 4 mmol/L) blood of the proposita's mother were centrifuged for 20 minutes at 1,800g at room temperature. Plasma was aspirated to approximately 5 mm above the buffy coat and discarded. Ice-cold lysis buffet' (0.32 mol/L sucrose, 10 mmol/L Tris-HCI, 5 mmol/L MgCl,, I % Triton X-100, pH 7.5) was added to the cell pellet to a final volume of 50 mL. The suspension was mixed gently by inverting, set on ice for 15 minutes, and then centrifuged for 15 minutes at 1,800g and 4°C. The supernatant was discarded, and the pellet resuspended in fresh lysis buffer to a final volume of 50 mL. The suspension was centrifuged immediately for 10 minutes at 1,SOOg (4"C), and the resulting nuclear pellet was resuspended in 3 mL of a solution containing 10 mmol/L Tris-HCI, 1 mmol/L EDTA, 0.5% SDS, pH 8.0, 500 pg/mL proteinase K and 50 pg/mL RNase. Digestion was performed for 3 hours at 50°C. The DNA was then extracted with phenol-chloroform according to Gustafsonet aIz2and precipitated with 2 volumes of ice-cold ethanol after addition of0.2 vol of 10 mol/L ammonium acetate. High molecular weight DNA was washed twice with 70% ethanol, lyophilized, and dissolved in 1.5 mL 10 mmol/L Tris-HC1, 1 mmol/L EDTA, pH 8.0. The absorbance was measured at 260 nm, and the calculated yield of DNA was approximately 360 pg from 20 mL fresh blood. Amplification by polymerase chain reaction (PCR). A 3 12-bp fragment of the fibrinogen y-chain gene23containing the DNA sequence of exon VI11 coding for amino acids 259 through 350 was amplified with the following 22-base-long primer pair: sense primer, 5'-TCAGCATGTGATGGTTGTATTT-3'; antisense primer, 5'-CTTGGTAATAAACTCCATTGAG-3'.These oligonucleotide primers had been synthesizedby L. Edenharter (Institute of Microbiology, Bern, Switzerland) using an Applied Biosvstem 38 1A DNA synthesizer by the P-cyanoethyl phosphoramidine method. Amplification was performed in a 100 pL reeztion volume containing 1 pg genomic DNA, 4 U Taq DNA polymerase, 200 pmol/L each of d-adenosine triphosphate (dATP), d-cytidine triphosphate (dCTP), d-thymidine triphosphate (dTTP), d-guanosine triphosphate (dGTP), 0.1 pmol/L, and 0.5 pmol/L of sense and antisense primer, respectively, in 10 mmol/L Tris-HC1, at 25"C, 50 mmol/L KCI, 1.5 mmol/L MgCl,, and 0.01%(wt/vol) gelatin, pH 8.4. Sixty cycles of amplification were performed by using a DNA thermal cycler (Perkin-Elmer-Cetus, Nonvalk, CT). Incubation times for each cycle were 1 minute at 94"C, I minute at 45"C, and 2 2105 minutes at 72°C. Similar procedure was used for amplification of a 290-bp fragment of the y-chain gene, containing exon IX and coding for amino acids 35 I through 407, using the following pair of 2 I-mer primers, 5'-GCACTTCGTAATAGACAGCTC-3'and 5'CATATTCTGTTTCCGCAGGGT-3' (Microsynth, Windisch, Switzerland). Incubation times were 1 minute at 9 4 T , 1 minute at 47"C, and 2 minutes at 72°C for a total of 60 cycles. The size ofthe PCR products was examined using a 123-bpladder-size standard in a 1.4%(wt/vol) agarose gel stained with 0.66 pg/mL ethidium bromide in 0.09 mol/L Tris-borate, 2.6 mmol/L EDTA, pH 8.3. Molecular cloning and sequencing of normal and variant exon VIII offibrinogen Bern I. Amplification of double-stranded exon VI11 fragment was performed under similar conditions as described above with the following modifications: 0.42 pmol/L each of sense and antisense primer, 2 U Taq DNA polymerase, and 50 cycles. The PCR product was purified on a QIAGEN-tip 5 mini column according to manufacturer's instructions and cloned into Sma I polycloning site of M 1 3 m ~ 1 9Individual .~~ clones were sequenced using the 17-mer sequencing primer (-40) and [c~-~'S] dATP by using the Sequenase Version 2.0 kit. Dideoxynucleotide termination reaction products were run on a 8% polyacrylamide sequencing gel in a Sequi-Gen Nucleic Acid SequencingCell from Bio Rad (Richmond, CA). The gel was dried on a Slab Gel Dryer SE 1160 (Hoefer ScientificInstruments, San Francisco, CA), and autoradiography was performed using 3M Trimax medical imaging film (3M, Ferrani, Italy). RESULTS Case report. Dysfibrinogen Bern I was discovered in 1978 in a 24-year-old woman without a history of bleeding or thrombotic tendency. Upon admission to the hospital, her TT and RT were found to be prolonged (Table 1). Fibrinogen concentration determined by the functional assay was markedly decreased, whereas the heat precipitation method indicated normal fibrinogen values. Family members were studied, and their laboratory parameters were consistent with the diagnosis of hereditary dysfibrinogenemia. The proposita, her sisters, and her brother have inherited the functionally abnormal fibrinogen from their mother, whereas the father was not affected. Neither the mother nor any of her children had bleeding symptoms or thrombotic episodes. Fibrinopeptide release. The kinetics of fibrinopeptide release by thrombin from the normal and the variant fibrinogen are shown in Fig 1. The amounts of fibrinopeptides A and B cleaved from normal fibrinogen within 1 hour were taken as 100%.Our results indicate that delayed clotting of fibrinogen Bern I cannot be ascribed to an impaired fibrinopeptide cleavage by thrombin, because fibrinopeptide A cleavage from fibrinogen-Bern I appeared to proceed even faster than that from normal fibrinogen, and fibrinopeptide B release was normal. These results suggest that the structural defect is not situated in the amino terminal domain of fibrinogen near the thrombin cleavage sites. Two-dimensional gel electrophoresis offragments D,, D2, and D3. Two-dimensional gel electrophoresis of mercaptolyzed plasmic degradation products D,, D,, and D, is shown in Fig 2. An abnormal y-chain remnant, denoted as y*D2was observed in fragment D, of fibrinogen Bern I, but not in fragment D,. This difference suggests an excess positive charge in the y-chain remnant of fragment D,. Plasmin- From www.bloodjournal.org by guest on June 17, 2017. For personal use only. STEINMANN ET AL 2106 Table 1. Results of Laboratory Tests on Plasma Samples From the Proposita and the Members of Her Family R.Z. 1954 T.Z. 1960 H.-P.Z. 1956 H.F.-Z. 1952 H.Z. 1922 M.Z. 1925 Proposita Sister Brother Sister Father Mother Normal Range 85 48 23.5 22 66 54 20.3 19 85 48 23.5 23 90 53 22 26 >70 40-60 12-15 13-14 70 Quick (%) APTT (s) TT 1s) RT (s) Fibrinogen (g/L) Functional assay Heat precipitation 45 21.8 32.1 0.25 1.80 0.32 1.60 0.40 1.50 0.32 1.80 >loo 48 13.2 ND 3.80 4.00 0.25 2.10 1.50-3.00 1.50-3.00 Abbreviation: ND, not determined induced cleavage at position y 302-303 during conversion of D2 to D, apparently results in the loss of the abnormal peptide. AmplSfication and DNA sequence analysis. Two DNA fragments of 3 12- and 290-bp, comprising exons VI11 and IX and coding for amino acids 259 through 350 and 351 through 407 of the y-chain, respectively, were amplified by asymmetric PCR. The DNA sequence of the amplified exon IX was indistinguishable from the normal DNA sequence. The sequence analysis of exon VI11 showed the presence of two bands at the same migration distance with about equal radioactivity (data not shown), suggesting that the patient is heterozygous for the mutation AAC + AAA, corresponding to amino acid substitution y 337 Asn + Lys. To improve quality of the sequence analysis of exon VIII, cloning experiments were performed. Five of eighty-eight clones contained the insert. The sequence of two of them, both representing antisense strands from either normal or abnormal y-chain gene fragments, is shown in Fig 3. A guanine in the normal amplified exon VI11 was found to be substituted by thymine. Thus, the single base substitution altered the codon in the sense strand for y 337 Asn (AAC) to Lys (AAA). loo r 60 40 20 I I 0 0 10 5 15 Time (min) Fig 1. Fibrinopeptide release by thrombin from fibrinogen Bern I and from normal fibrinogen. (0)Fibrinopeptide A, normal fibrinogen; ( 0 )fibrinopeptide A, fibrinogen Bern I; (A) fibrinopeptide B. normal fibrinogen; and (A)fibrinopeptide B, fibrinogen Bern I. DISCUSSION An abnormal fibrinogen variant, denoted as fibrinogen Bern I, was detected in a clinically asymptomatic woman. Thrombin and reptilase clotting times were prolonged. Fibrinogen concentration was decreased when measured by the functional assay but was normal by the heat precipitation method (Table 1). Family study confirmed the hereditary nature of this dysfibrinogenemia. Fibrinogen Bern I was isolated from the proposita’s plasma and displayed normal fibrinopeptide A and B release (Fig 1). Fibrinopeptide A was cleaved even faster from fibrinogen Bern I than from normal fibrinogen. As shown previou~ly,’~ the rate of fibrin monomer polymerization was decreased at low concentration ofcalcium ions, but it was fully normalized only at high (5 mmol/L) calcium concentration, suggesting that calcium binding site might be functionally inadequate in fibrinogen Bern I. A complete correction of fibrin polymerization by high concentration of calcium has also been observed in fibrinogen Osaka VI2,a variant with an amino acid substitution y 375 Arg + Gly, lacking 2 of the 3 high-affinity calcium binding sites. It is obvious that the functional defect in fibrinogen Bern I cannot be explained solely by deficient calcium binding, because in the presence of EDTA, the defective clotting of fibrinogen Bern I even became more prominent. l 4 Our previous experiments showed impaired protection by calcium of the carboxy terminal portion of the y-chain of fibrinogen Bern I against proteolytic degradation by plasmin.I4 Similarly, in fibrinogen variants Haifa (y 275 Arg + His),2’Osaka V (y 375 Arg + Gly),” Kyoto I (y 308 Asn + LYS)?~ and Vlissingen (deletion y 3 19 Asn and 320 Asp),27 the carboxy terminus of the y-chain was degraded by plasmin despite the presence of Ca2+ ions. Thus, our former observations with fibrinogen Bern I hinted at a structural defect in the carboxyterminal part of the y-chain, affecting calcium binding. The carboxy terminal portion of the y-chain not only contains one high-affinity binding site for Ca2+ions, tentatively located between residues y 3 11 through 336,28but also appears to be involved in polymerization of fibrin monomers. Synthetic peptides, beginning with the amino terminal sequence (Gly-Pro-Arg) of the fibrin a-chain were shown to bind strongly to plasmin-generated fragment D,, whereas no binding occurred to fragment D,, which lacks From www.bloodjournal.org by guest on June 17, 2017. For personal use only. 2107 ABNORMAL FIBRINOGEN VARIANT BERN I 61 tu I a nl . Fig 2. Two-dimensional electrophoresis of reduced fibrinogen fragments D,, D2, and D,. The abnormal 7-chain remnant in fibrinogen Bern I is denoted with an asterisk. 1 .................... .................... 5’ 3’ To identify the structural defect in fibrinogen Bern 1. PCR was used for amplification and sequence analysis of the exons VI11 and IX coding for amino acid residues 259 through 350 and 35 1 through 407 of the y-chain,” respectively. The DNA sequence of the amplified exon IX was indistinguishable from the normal DNA sequence. Direct sequence analysis of exon VI11 showed the presence of two bands at the same migration distance, corresponding to Lys (AAC + AAA). amino acid substitution y 337 Asn The purified double-stranded PCR-derived fragment was cloned and subjected to sequence analysis. Normal and mutated alleles of fibrinogen Bern I were obtained, showing a G + T transition in the noncoding strand (Fig 3). Thus, codon AAC in the sense strand of the exon VI11 of the ychain gene was substituted by AAA, leading to a replacement of Asn by Lys at position y 337 in fibrinogen Bern I. In conclusion, PCR was used to determine the structural defect in the abnormal fibrinogen variant Bern I. A new point mutation was found in the y-chain of fibrinogen Bern I, leading to the substitution of the amino acid y 337 Asn by Lys. This mutation results in defective expression of the polymerization site and in impaired protection by calcium ions against plasmic digestion of the carboxy terminus of the y-chain. GC REFERENCES the carboxy terminal 109 residues ofthe y-chain.’ The binding site for Gly-Pro-Arg has recently been more precisely ascribed to y-chain residues 337 through 379.9 Using twodimensional electrophoresis in polyacrylamide gel of the reduced fragments D,, D,, and D, derived from fibrinogen Bern I by plasmic degradation. a y-chain remnant of fragment D, with an increased isoelectric point was noted (Fig 2 ) . whereas the abnormal charge disappeared during conversion of fragment D, to D, suggesting that the molecular defect is situhed within the amino acid sequence y 303 through 356, which corresponds to the peptide released from fragment D, by plasmin. BERN I NORMAL G A T C G A - T C ._ \A Asn A T IC G AT TA Fig 3. DNA sequence analysis of individual clones containing the amplified exon Vlll of the 7-chain gene coding for the normal and mutated alleles of fibrinogen Bem I. A cytosine was substituted by adenine, changing the triplet AAC to AAA in the coding strand. The brackets indicate the change of y 337 Asn to Lys. - I . Ebert R F Index of Variant Human Fibrinogens. Boca Raton. FL, CRC, 1991 2. Henschen A. Kehl M. Southan C Genetically abnormal fibrinogens: Strategies for structure elucidation including fibrinopeptide analysis, in Beck EA, Furlan M (eds): Variants of Human Fibrinogen. Bern, Switzerland. Hans Huber. 1984. p 273 3. Southan C: Molecular and genetic abnormalities of fibrinogen, in Francis JL (ed): Fibrinogen, Fibrin Stabilisation, and Fibrinolysis. Chichester, UK, Ellis Horwood. 1988. p 65 4. Doolittle R F Fibrinogen and fibrin. in Bloom AL, Thomas DP (eds): Haemostasis and Thrombosis (ed 2). Edinburgh. Scotland. Churchill Livingstone. 1988. p 192 5. Mosesson MW: Fibrin polymerization and its regulatory role in hemostasis. J Lab Clin Med 116% 1990 6. Blomback B. Hessel B, Hogg D. Therkildsen L A two-step From www.bloodjournal.org by guest on June 17, 2017. For personal use only. 2108 fibrinogen-fibrin transition in blood coagulation. Nature 275501, 1978 7. Olexa SA, Budzynski AZ: Evidence for four different polymerization sites involved in human fibrin formation. Proc Natl Acad Sci USA 77:1374, 1980 8. Laudano AP, Cottrell BA, Doolittle R F Synthetic peptides modeled on fibrin polymerization sites. Ann NY Acad Sci 408:3 15, 1983 9. Shimizu A, Nagel GM, Doolittle R F Photoaffinity labeling of the primary fibrin polymerization site: Isolation and characterization of a labeled cyanogen bromide fragment corresponding to ychain residues 337-379. Proc Natl Acad Sci USA 89:2888, 1992 10. Reber P, Furlan M, Henschen A, Kaudewitz H, Barbui T, Hilgard P, Nenci GG, Berrettini M, Beck EA: Three abnormal fibrinogen variants with the same amino acid substitution (y 275 Arg + His): Fibrinogens Bergamo 11, Essen, and Perugia. Thromb Haemost 56:401, 1986 I I . Yoshida N, Ota K, Moroi M, Matsuda M: An apparently higher molecular weight y-chain variant in a new congenital abnormal fibrinogen Tochigi characterized by the replacement of y arginine 275 by cysteine. Blood 7 l :480, 1988 12. Yoshida N, Hirata H, Morigami Y , Imaoka S, Matsuda M, Yamazumi K, Asakura S: Characterization ofan abnormal fibrinogen Osaka V with the replacement of y-arginine 375 by glycine: The lack of high affinity calcium binding to D-domains and the lack of protective effect of calcium on fibrinolysis. J Biol Chem 267:2753, 1992 13. Rupp C, Kuyas C, Haeberli A, Furlan M, von Fliedner V, Beck EA: Fibrinogen Bern I und Bern 11: Zwei hereditare Fibrinogenvarianten mit unterschiedlichen biochemischen Eigenschaften. Schweiz Med Wochenschr 1 1 I :1543, 1981 14. Rupp C, Kuyas C, Haberli A, Furlan M, Perret BA, Beck EA: Fibrinogen Bern I: A hereditary fibrinogen variant with defective conformational stabilization by calcium ions, in Henschen A, Graeff H, Lottspeich F (eds): Fibrinogen: Recent Biochemical and Medical Aspects. Berlin, Germany, Walter de Gruyter, 1982, p 167 15. Furlan M, Rupp C, Beck EA, Svendsen L: Effect of calcium and synthetic peptides on fibrin polymerization. Thromb Haemost 47:118, 1982 16. Clauss A: Gerinnungsphysiologische Schnellmethode zur Bestimmung des Fibrinogens. Acta Haematol 17:237, 1957 17. Schulz FH: Eine einfache Bewertungsmethode von Leber- STEINMANN ET AL parenchymschaden (volumetrische Fibrinbestimmung). Acta Hepatol 3:306, 1955 18. Kehl M, Lottspeich F, Henschen A: Analysis of human fibrinopeptides by high-performance liquid chromatography. HoppeSeyler's Z Physiol Chem 362: I66 1, 198I 19. Rupp C, Sievi R, Furlan M: Fractionation of plasmic fib ogen digest on lysine-agarose: Isolation of two fragments D, fragment E, and simultaneous removal of plasmin. Thromb Res 27: 1 17, 1982 20. Reber P, Furlan M, Rupp C, Kehl M, Henschen A, Mannucci PM, Beck EA: Characterization of fibrinogen Milano I: Amino acid exchange y 330 Asp + Val impairs fibrin polymerization. Blood67:1751, 1986 2 I . Buffone GJ, Darlington GJ: Isolation of DNA from biological specimens without extraction with phenol. Clin Chem 3 1:164, 1985 22. Gustafson S, Proper JA, Bowie EJW, Sommer SS: Parameters affecting the yield of DNA from human blood. Anal Biochem 165:294, 1987 23. Rixon MW, Chung DW, Davie EW: Nucleotide sequence of the gene for the y chain of human fibrinogen. Biochemistry 24:2077, 1985 24. Sambrock J, Fritsch EF, Maniatis T: Molecular Cloning: A Laboratory Manual, vol 1. Cold Spring Harbor, NY, Cold Spring Harbor Laboratory, 1989 25. Soria J, Soria C, Samama M, Tabori S, Kehl M, Henschen A, Nieuwenhuizen W, Rimon A, Tatarski I: Fibrinogen Haifa: Fibrinogen variant with absence of protective effect of calcium on plasmin degradation ofgamma chains. Thromb Haemost 57:3 IO, 1987 26. Yoshida N, Terukina S, Okuma M, Moroi M, Aoki N, Matsuda M: Characterization of an apparently lower molecular weight y-chain variant in fibrinogen Kyoto I: The replacement of y-asparagine 308 by lysine which causes accelerated cleavage of fragment D, by plasmin and the generation of a new plasmin cleavage site. J Biol Chem 263:13848, 1988 27. Koopman J, Haverkate F, Bnet E, Lord ST: A congenitally abnormal fibrinogen (Vlissingen) with a 6-base deletion in the ychain, causing defective calcium binding and impaired fibrin polymerization. J Biol Chem 266: 13456, 199 1 28. Dang CV, Ebert RF, Bell WR: Localization of a fibrinogen calcium binding site between y-subunit position 3 I 1 and 336 by terbium fluorescence. J Biol Chem 260:9713, 1985 From www.bloodjournal.org by guest on June 17, 2017. For personal use only. 1993 82: 2104-2108 Fibrinogen Bern I: substitution gamma 337 Asn-->Lys is responsible for defective fibrin monomer polymerization C Steinmann, P Reber, M Jungo, B Lammle, G Heinemann, B Wermuth and M Furlan Updated information and services can be found at: http://www.bloodjournal.org/content/82/7/2104.full.html Articles on similar topics can be found in the following Blood collections Information about reproducing this article in parts or in its entirety may be found online at: http://www.bloodjournal.org/site/misc/rights.xhtml#repub_requests Information about ordering reprints may be found online at: http://www.bloodjournal.org/site/misc/rights.xhtml#reprints Information about subscriptions and ASH membership may be found online at: http://www.bloodjournal.org/site/subscriptions/index.xhtml Blood (print ISSN 0006-4971, online ISSN 1528-0020), is published weekly by the American Society of Hematology, 2021 L St, NW, Suite 900, Washington DC 20036. 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