Flow studies on human GPVI-deficient blood under coagulating and noncoagulating conditions

Magdolna Nagy, Gina Perrella, Amanda Dalby, M. Francisca Becerra, Lourdes Garcia Quintanilla, Jeremy A. Pike, Neil Morgan, Elizabeth E. Gardiner, Johan W. M. Heemskerk, Lorena Azocar, Juan Francisco Miquel, Diego Mezzano, Steve P. Watson*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

17 Citations (Web of Science)

Abstract

The role of glycoprotein VI (GPVI) in platelets was investigated in 3 families bearing an insertion within the GP6 gene that introduces a premature stop codon prior to the transmembrane domain, leading to expression of a truncated protein in the cytoplasm devoid of the transmembrane region. Western blotting and flow cytometry of GP6(hom) (homozygous) platelets confirmed loss of the full protein. The level of the Fc receptor -gamma-chain, which associates with GPVI in the membrane, was partially reduced, but expression of other receptors and signaling proteins was not altered. Spreading of platelets on collagen and von Willebrand factor (which supports partial spreading) was abolished in GP6(hom) platelets, and spreading on uncoated glass was reduced. Anticoagulated whole blood flowed over immobilized collagen or a mixture of von Willebrand factor, laminin, and rhodocytin (noncollagen surface) generated stable platelet aggregates that express phosphatidylserine (PS). Both responses were blocked on the 2 surfaces in GP6(hom) individuals, but adhesion was not altered. Thrombin generation was partially reduced in GP6(hom) blood. The frequency of the GP6(het) (heterozygous) variant in a representative sample of the Chilean population (1212 donors) is 2.9%, indicating that there are similar to 4000 GP6(hom) individuals in Chile. These results demonstrate that GPVI supports aggregation and PS exposure under flow on collagen and noncollagen surfaces, but not adhesion. The retention of adhesion may contribute to the mild bleeding diathesis of GP6(hom) patients and account for why so few of the estimated 4000 GP6(hom) individuals in Chile have been identified.

Original languageEnglish
Pages (from-to)2953-2961
Number of pages9
JournalBlood advances
Volume4
Issue number13
DOIs
Publication statusPublished - 14 Jul 2020

Keywords

  • VON-WILLEBRAND-FACTOR
  • RECEPTOR GAMMA-CHAIN
  • GLYCOPROTEIN-VI
  • THROMBUS FORMATION
  • ALPHA-2-BETA-1 INTEGRIN
  • PLATELET-ADHESION
  • COLLAGEN
  • FIBRIN
  • ALPHA(2)BETA(1)
  • INVOLVEMENT

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