title: Fibrinogen gamma-chain splice variant gamma' alters fibrin formation and structure.
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.
authors.affiliation: Academic Unit of Molecular Vascular Medicine, University of Leeds, Leeds General Infirmary, United Kingdom.
authors.forename: Amy V
authors.initials: AV
authors.lastname: Cooper
authors.forename: Kristina F
authors.initials: KF
authors.lastname: Standeven
authors.forename: Robert A S
authors.initials: RA
authors.lastname: Ariëns
mesh_terms: D017398:Alternative Splicing; D001777:Blood Coagulation; D002851:Chromatography, High Pressure Liquid; D005337:Fibrin / Q000737:chemistry*; D005340:Fibrinogen / Q000737:chemistry* / Q000235:genetics / Q000648:ultrastructure; D005345:Fibrinopeptide B / Q000378:metabolism; D006801:Humans; D008855:Microscopy, Electron, Scanning; D009391:Nephelometry and Turbidimetry; D020033:Protein Isoforms / Q000737:chemistry / Q000235:genetics; D013329:Structure-Activity Relationship
chemical_list: D020033:Protein Isoforms; D005345:Fibrinopeptide B; D005337:Fibrin; D005340:Fibrinogen