title: Platelets and platelet-derived factor Va confer hemostatic competence in complete factor V deficiency.
abstract: Whole genome sequencing of an individual completely devoid of plasma- and platelet-derived factor V (FV) identified 167 variants in his F5 gene including previously identified and damaging missense mutations at rs6027 and Leu90Ser. Because the administration of fresh frozen plasma (FFP) prevents gastrointestinal bleeding in this individual, its effects on his plasma- and platelet-derived FV concentrations were assessed. The patient's plasma FV levels peaked by 2 hours following FFP administration and were undetectable 96 hours later. In contrast, increased platelet-derived FV/Va concentrations were observed within 6 hours, peaked at 24 hours, decreased slowly over 7 days, and originated from megakaryocyte endocytosis and intracellular processing of plasma FV. Ten days after transfusion, no thrombin was generated in a tissue factor-initiated whole blood clotting assay unless exogenous FV was added, consistent with the complete absence of plasma FV. In marked contrast, release of the patient's platelet-derived FV/Va (7% of normal) following platelet activation resulted in robust thrombin generation, similar to that in an individual with normal plasma- and platelet-derived FV concentrations. Thus, total FV deficiency can be corrected by plasma administration, which partially repletes and sustains the platelet cofactor pool, thereby highlighting the critical role of platelet-derived FV/Va in ensuring hemostatic competence.
authors.affiliation: Department of Biochemistry, and.
authors.forename: Beth A
authors.initials: BA
authors.lastname: Bouchard
authors.affiliation: Department of Biochemistry, and.
authors.forename: John
authors.initials: J
authors.lastname: Chapin
authors.affiliation: Department of Biochemistry, and.
authors.forename: Kathleen E
authors.initials: KE
authors.lastname: Brummel-Ziedins
authors.affiliation: Department of Pathology, University of Vermont College of Medicine, Burlington, VT; and.
authors.forename: Peter
authors.initials: P
authors.lastname: Durda
authors.affiliation: Department of Medicine, Division of Hematology/Oncology, University of North Carolina, Chapel Hill, NC.
authors.forename: Nigel S
authors.initials: NS
authors.lastname: Key
authors.affiliation: Department of Biochemistry, and.
authors.forename: Paula B
authors.initials: PB
authors.lastname: Tracy
mesh_terms: D000368:Aged; D019943:Amino Acid Substitution; D016913:Blood Component Transfusion; D001792:Blood Platelets; D005166:Factor V Deficiency / Q000097:blood* / Q000150:complications / Q000235:genetics / Q000628:therapy*; D015943:Factor Va / Q000008:administration & dosage* / Q000235:genetics / Q000378:metabolism; D006471:Gastrointestinal Hemorrhage / Q000097:blood / Q000209:etiology / Q000235:genetics / Q000628:therapy; D006801:Humans; D008297:Male; D008533:Megakaryocytes / Q000378:metabolism / Q000473:pathology; D020125:Mutation, Missense; D010949:Plasma; D013918:Thrombin Time
chemical_list: D015943:Factor Va