The Nbeal2−/− mouse as a model for the gray platelet syndrome

The gray platelet syndrome (GPS) is a rare, autosomal-recessive platelet disorder characterized by thrombocytopenia, large platelets lacking α-granules, and variable bleeding. GPS has been linked to mutations in the neurobeachin-like 2 gene (NBEAL2). We have recently characterized Nbeal2-deficient mice and shown that the absence of Nbeal2 results in defective protein sorting in megakaryocytes (MKs) and impaired α-granule biogenesis, a finding also seen for human MKs. In the mice, the lack of α-granules results in impaired aggregation, defective platelet adhesion to collagen under flow and reduced pro-coagulant activity; findings that translate into defective hemostasis and thrombosis in vivo indicating that α-granule secretion is critical for platelet plug stability. Furthermore, we revealed a role of α-granule proteins in ischemic stroke and wound healing. Thus, Nbeal2-deficient mice recapitulate the hallmarks of human GPS without showing its phenotypic heterogeneity and are a promising model to investigate the (patho-)physiological relevancy of α-granules.