title: LIM kinase/cofilin dysregulation promotes macrothrombocytopenia in severe von Willebrand disease-type 2B.
abstract: von Willebrand disease type 2B (VWD-type 2B) is characterized by gain-of-function mutations of von Willebrand factor (vWF) that enhance its binding to platelet glycoprotein Ibα and alter the protein's multimeric structure. Patients with VWD-type 2B display variable extents of bleeding associated with macrothrombocytopenia and sometimes with thrombopathy. Here, we addressed the molecular mechanism underlying the severe macrothrombocytopenia both in a knockin murine model for VWD-type 2B by introducing the p.V1316M mutation in the murineVwfgene and in a patient bearing this mutation. We provide evidence of a profound defect in megakaryocyte (MK) function since: (a) the extent of proplatelet formation was drastically decreased in 2B MKs, with thick proplatelet extensions and large swellings; and (b) 2B MKs presented actin disorganization that was controlled by upregulation of the RhoA/LIM kinase (LIMK)/cofilin pathway. In vitro and in vivo inhibition of the LIMK/cofilin signaling pathway rescued actin turnover and restored normal proplatelet formation, platelet count, and platelet size. These data indicate, to our knowledge for the first time, that the severe macrothrombocytopenia in VWD-type 2B p.V1316M is due to an MK dysfunction that originates from a constitutive activation of the RhoA/LIMK/cofilin pathway and actin disorganization. This suggests a potentially new function of vWF during platelet formation that involves regulation of actin dynamics.
authors.affiliation: INSERM UMR-S 1176, Univ Paris-Sud, Université Paris-Saclay, 94276 Le Kremlin-Bicêtre, France.|INSERM UMR-S 1140, Univ Paris Descartes, Sorbonne Paris Cité, Paris, France.
authors.forename: Alexandre
authors.initials: A
authors.lastname: Kauskot
authors.affiliation: INSERM UMR-S 1140, Univ Paris Descartes, Sorbonne Paris Cité, Paris, France.
authors.forename: Sonia
authors.initials: S
authors.lastname: Poirault-Chassac
authors.affiliation: INSERM UMR-S 1176, Univ Paris-Sud, Université Paris-Saclay, 94276 Le Kremlin-Bicêtre, France.
authors.forename: Frédéric
authors.initials: F
authors.lastname: Adam
authors.affiliation: INSERM UMR-S 1176, Univ Paris-Sud, Université Paris-Saclay, 94276 Le Kremlin-Bicêtre, France.
authors.forename: Vincent
authors.initials: V
authors.lastname: Muczynski
authors.affiliation: INSERM UMR-S 1176, Univ Paris-Sud, Université Paris-Saclay, 94276 Le Kremlin-Bicêtre, France.
authors.forename: Gabriel
authors.initials: G
authors.lastname: Aymé
authors.affiliation: INSERM UMR-S 1176, Univ Paris-Sud, Université Paris-Saclay, 94276 Le Kremlin-Bicêtre, France.
authors.forename: Caterina
authors.initials: C
authors.lastname: Casari
authors.affiliation: Laboratoire d'Hémostase, Hôpital Edouard Herriot, Lyon, France.|Laboratoire de Recherche sur l'Hémophilie, UCBL1, Faculté de Médecine Lyon-Est, Lyon, France.
authors.forename: Jean-Claude
authors.initials: JC
authors.lastname: Bordet
authors.affiliation: INSERM UMR-S 1176, Univ Paris-Sud, Université Paris-Saclay, 94276 Le Kremlin-Bicêtre, France.
authors.forename: Christelle
authors.initials: C
authors.lastname: Soukaseum
authors.affiliation: Centre Hémophilie, Hôpital Necker, Paris, France.
authors.forename: Chantal
authors.initials: C
authors.lastname: Rothschild
authors.affiliation: INSERM UMR-S 1176, Univ Paris-Sud, Université Paris-Saclay, 94276 Le Kremlin-Bicêtre, France.|Department of Biological Hematology, CHU Bicêtre, Hôpitaux Universitaires Paris Sud, AP-HP, Paris, France.
authors.forename: Valérie
authors.initials: V
authors.lastname: Proulle
authors.affiliation: INSERM UMR-S 1140, Univ Paris Descartes, Sorbonne Paris Cité, Paris, France.
authors.forename: Audrey
authors.initials: A
authors.lastname: Pietrzyk-Nivau
authors.affiliation: INSERM UMR-S 1176, Univ Paris-Sud, Université Paris-Saclay, 94276 Le Kremlin-Bicêtre, France.
authors.forename: Eliane
authors.initials: E
authors.lastname: Berrou
authors.affiliation: INSERM UMR-S 1176, Univ Paris-Sud, Université Paris-Saclay, 94276 Le Kremlin-Bicêtre, France.
authors.forename: Olivier D
authors.initials: OD
authors.lastname: Christophe
authors.affiliation: INSERM UMR-S 1176, Univ Paris-Sud, Université Paris-Saclay, 94276 Le Kremlin-Bicêtre, France.
authors.forename: Jean-Philippe
authors.initials: JP
authors.lastname: Rosa
authors.affiliation: INSERM UMR-S 1176, Univ Paris-Sud, Université Paris-Saclay, 94276 Le Kremlin-Bicêtre, France.
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Lenting
authors.affiliation: INSERM UMR-S 1176, Univ Paris-Sud, Université Paris-Saclay, 94276 Le Kremlin-Bicêtre, France.
authors.forename: Marijke
authors.initials: M
authors.lastname: Bryckaert
authors.affiliation: INSERM UMR-S 1176, Univ Paris-Sud, Université Paris-Saclay, 94276 Le Kremlin-Bicêtre, France.
authors.forename: Cécile V
authors.initials: CV
authors.lastname: Denis
authors.affiliation: INSERM UMR-S 1140, Univ Paris Descartes, Sorbonne Paris Cité, Paris, France.
authors.forename: Dominique
authors.initials: D
authors.lastname: Baruch
mesh_terms: D051339:Actin Depolymerizing Factors / Q000235:genetics*; D000818:Animals; D055879:Gene Knock-In Techniques; D006801:Humans; D054461:Lim Kinases / Q000235:genetics*; D008297:Male; D051379:Mice; D009154:Mutation; D015398:Signal Transduction; D013921:Thrombocytopenia / Q000503:physiopathology*; D020741:rho GTP-Binding Proteins; D020742:rhoA GTP-Binding Protein; D056728:von Willebrand Disease, Type 2 / Q000201:enzymology / Q000503:physiopathology*; D014841:von Willebrand Factor / Q000235:genetics*
chemical_list: D051339:Actin Depolymerizing Factors; D014841:von Willebrand Factor; D054461:Lim Kinases; C526380:RhoA protein, mouse; D020741:rho GTP-Binding Proteins; D020742:rhoA GTP-Binding Protein