title: Abnormal megakaryocyte development and platelet function in Nbeal2(-/-) mice.
abstract: Gray platelet syndrome (GPS) is an inherited bleeding disorder associated with macrothrombocytopenia and α-granule-deficient platelets. GPS has been linked to loss of function mutations in NEABL2 (neurobeachin-like 2), and we describe here a murine GPS model, the Nbeal2(-/-) mouse. As in GPS, Nbeal2(-/-) mice exhibit splenomegaly, macrothrombocytopenia, and a deficiency of platelet α-granules and their cargo, including von Willebrand factor (VWF), thrombospondin-1, and platelet factor 4. The platelet α-granule membrane protein P-selectin is expressed at 48% of wild-type levels and externalized upon platelet activation. The presence of P-selectin and normal levels of VPS33B and VPS16B in Nbeal2(-/-) platelets suggests that NBEAL2 acts independently of VPS33B/VPS16B at a later stage of α-granule biogenesis. Impaired Nbeal2(-/-) platelet function was shown by flow cytometry, platelet aggregometry, bleeding assays, and intravital imaging of laser-induced arterial thrombus formation. Microscopic analysis detected marked abnormalities in Nbeal2(-/-) bone marrow megakaryocytes, which when cultured showed delayed maturation, decreased survival, decreased ploidy, and developmental abnormalities, including abnormal extracellular distribution of VWF. Our results confirm that α-granule secretion plays a significant role in platelet function, and they also indicate that abnormal α-granule formation in Nbeal2(-/-) mice has deleterious effects on megakaryocyte survival, development, and platelet production.
authors.affiliation: Department of Paediatrics, University of Toronto, Division of Haematology/Oncology, and.
authors.forename: Walter H A
authors.initials: WH
authors.lastname: Kahr
authors.forename: Richard W
authors.initials: RW
authors.lastname: Lo
authors.forename: Ling
authors.initials: L
authors.lastname: Li
authors.forename: Fred G
authors.initials: FG
authors.lastname: Pluthero
authors.forename: Hilary
authors.initials: H
authors.lastname: Christensen
authors.forename: Ran
authors.initials: R
authors.lastname: Ni
authors.forename: Nima
authors.initials: N
authors.lastname: Vaezzadeh
authors.forename: Cynthia E
authors.initials: CE
authors.lastname: Hawkins
authors.forename: Andrew S
authors.initials: AS
authors.lastname: Weyrich
authors.forename: Jorge
authors.initials: J
authors.lastname: Di Paola
authors.forename: Carolina
authors.initials: C
authors.lastname: Landolt-Marticorena
authors.forename: Peter L
authors.initials: PL
authors.lastname: Gross
mesh_terms: D000818:Animals; D001792:Blood Platelets / Q000378:metabolism / Q000473:pathology*; D001798:Blood Proteins / Q000172:deficiency / Q000235:genetics*; D001853:Bone Marrow / Q000378:metabolism / Q000473:pathology*; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D002454:Cell Differentiation; D003594:Cytoplasmic Granules / Q000378:metabolism / Q000473:pathology*; D004195:Disease Models, Animal; D005260:Female; D015870:Gene Expression; D055652:Gray Platelet Syndrome / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D008297:Male; D008533:Megakaryocytes / Q000378:metabolism / Q000473:pathology*; D051379:Mice; D018345:Mice, Knockout; D019007:P-Selectin / Q000235:genetics / Q000378:metabolism; D010974:Platelet Aggregation; D010978:Platelet Factor 4 / Q000235:genetics / Q000378:metabolism; D020033:Protein Isoforms / Q000172:deficiency / Q000235:genetics; D019700:Thrombospondin 1 / Q000235:genetics / Q000378:metabolism; D014841:von Willebrand Factor / Q000235:genetics / Q000378:metabolism
chemical_list: D001798:Blood Proteins; D002352:Carrier Proteins; C561485:NBEAL2 protein, human; C585423:Nbeal2 protein, mouse; D019007:P-Selectin; D020033:Protein Isoforms; D019700:Thrombospondin 1; D014841:von Willebrand Factor; D010978:Platelet Factor 4