Fibrinogen gamma-chain splice variant gamma' alters fibrin formation and structure

Blood. 2003 Jul 15;102(2):535-40. doi: 10.1182/blood-2002-10-3150. Epub 2003 Mar 27.

Abstract

Fibrinogen gammaA/gamma' results from alternative splicing of mRNA. This variant, which constitutes approximately 8% to 15% of plasma fibrinogen, contains FXIII and thrombin binding sites. Our objective was to investigate whether gammaA/gamma' differs in fibrin formation and structure from the more common variant gammaA/gammaA. Both variants were separated and purified by anion-exchange chromatography. Fibrin formation and clot structure of the variants and unfractionated fibrinogen were investigated by turbidity and scanning electron microscopy (SEM). Thrombin cleavage of fibrinopeptides was analyzed by high-performance liquid chromatography (HPLC). Turbidity analysis showed significantly altered polymerization rates and overall fiber thickness in gammaA/gamma' clots compared with gammaA/gammaA and unfractionated fibrinogen. This finding was consistent with a range of thrombin concentrations. HPLC demonstrated reduced rates of fibrinopeptide B (FpB) release from gammaA/gamma' fibrinogen compared with gammaA/gammaA. Delayed FpB release was associated with delayed lateral aggregation of protofibrils and significant differences were found on SEM, with gammaA/gamma' clots consisting of smaller diameter fibers and increased numbers of branch points compared with both gammaA/gammaA and unfractionated fibrinogen. These results demonstrate that the gammaA/gamma' splice variant of fibrinogen directly alters fibrin formation and structure, which may help to explain the increased thrombotic risk associated with this variant.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alternative Splicing*
  • Blood Coagulation
  • Chromatography, High Pressure Liquid
  • Fibrin / chemistry*
  • Fibrinogen / chemistry*
  • Fibrinogen / genetics
  • Fibrinogen / ultrastructure
  • Fibrinopeptide B / metabolism
  • Humans
  • Microscopy, Electron, Scanning
  • Nephelometry and Turbidimetry
  • Protein Isoforms / chemistry
  • Protein Isoforms / genetics
  • Structure-Activity Relationship

Substances

  • Protein Isoforms
  • Fibrinopeptide B
  • Fibrin
  • Fibrinogen