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CLEC 2 contributes to hemostasis independently of classical hemITAM signaling in mice

Elizabeth J. Haining, Deya Cherpokova, Karen Wolf, Isabelle C. Becker, Sarah Beck, Johannes A. Eble, David Stegner, Steve P. Watson and Bernhard Nieswandt

Key points

  • An inactivating point mutation in the hemITAM motif of murine CLEC 2 reproduces the lymphatic defects seen in CLEC 2-deficient mice.

  • CLEC 2 contributes to thrombus stability in vivo independently of hemITAM signaling.

Abstract

C-type lectin-like receptor 2 (CLEC 2) is a platelet receptor that is critical during development in blood-lymph separation and implicated in thrombus stability in thrombosis and hemostasis. It is the only known platelet activatory receptor that participates in both these aspects of platelet function and is the only one to signal through a hemi-immunoreceptor tyrosine-based activation motif (hemITAM). Current investigations into the function of CLEC 2 in vivo have focused on knock-out studies in which both the receptor and its signaling are deleted, making it impossible to explore the possible signaling independent functions of the receptor which are indicated by its only known physiological ligand, podoplanin, being an integral membrane protein. Here we present a novel knock-in mouse model that maintains the expression of a CLEC 2 receptor that cannot signal through its hemITAM (Y7A KI). Remarkably, this mouse phenocopies the blood-lymphatic mixing and lethality of CLEC 2 knock-out models but not their hemostatic/thrombotic defect. However, treatment of Y7A KI mice with Fab' fragments of the function blocking anti-CLEC 2 antibody, INU1, resulted in a thrombus formation defect in vivo and ex vivo, revealing a hemITAM signaling-independent role for CLEC 2 in hemostasis and thrombosis.

  • Submitted March 6, 2017.
  • Accepted August 15, 2017.