Abnormal P-selectin localization during megakaryocyte development determines thrombosis in the gata1low model of myelofibrosis. (November 2014)

• Record Type: Journal Article
• Authors: Zetterberg, Eva; Verrucci, Maria; Martelli, Fabrizio; Zingariello, Maria; Sancillo, Laura; D'Amore, Emanuela; Rana, Rosa Alba; Migliaccio, Anna Rita
• Is Part Of: Platelets. Volume 25:Number 7(2014:Nov.)
• Page Start: 539
• Page End: 547
• Publication Date: 2014-11
• Subjects: Blood platelets -- Periodicals; Blood Platelets -- Periodicals; 615.39
• DOI: 10.3109/09537104.2013.840720
• Languages: English
• ISSNs: 0953-7104

Abstract

<abstract> <title>Abstract</title> <p>Patients with primary myelofibrosis have increased risk for bleeding and thrombosis. It is debated whether propensity to thrombosis is due to increased numbers of platelet microparticles and/or to pathological platelet-neutrophil interactions. Platelet neutrophil interactions are mediated by P-selectin and even though the megakaryocytes of myelofibrosis patients express normal levels of P-selectin, it remains abnormally localized to the demarcation membrane system rather than being assembled into the α-granules in platelets. Mice carrying the hypomorphic Gata1<sup>low</sup> mutation express the same megakaryocyte abnormalities presented by primary myelofibrosis patients, including abnormal P-selectin localization to the DMS and develop with age myelofibrosis, a disease that closely resembles human primary myelofibrosis. Whether these mice would also develop thrombosis has not been investigated as yet. The aim of this study was to determine whether Gata1<sup>low</sup> mice would develop thrombosis with age and, in this case, the role played by P-selectin in the development of the trait. To this aim, Gata1<sup>low</sup> mice were crossed with P-sel<sup>null</sup> mice according to standard genetic protocols and Gata1<sup>low</sup>P-sel<sup>wt</sup>, Gata1<sup>low</sup>P-sel<sup>null</sup> and Gata1<sup>WT</sup>P-sel<sup>null</sup> or Gata1<sup>wt</sup>P-sel<sup>wt</sup> (as controls) littermates obtained. It was shown that platelet counts, but not hematocrit, are reduced in Gata1<sup>low</sup> mice. Moreover, platelet microparticles are reduced in Gata1<sup>low</sup> mice and P-selectin positive platelet microparticles were not found. To determine the phenotypic implications of the different mutations, bleeding time was estimated by a tail cut procedure. Mutant mice were sacrificed and presence of thrombosis was determined by immunohistological staining of organs. Gata1<sup>low</sup> mice with or without the P-selectin null trait had a prolonged bleeding time compared to wild type mice. However, in Gata1<sup>low</sup> mice significantly higher frequency of thrombotic events was seen in adult and old Gata1<sup>low</sup> mice compared to Gata1<sup>low</sup>P-sel<sup>null</sup> mice. Thus, presence of the P-selectin null trait rescued Gata1<sup>low</sup> mice from the thrombotic phenotype, but did not change the level of platelet microparticles. Taken together these data indicate that abnormal localization of P-selectin, induced by the Gata1<sup>low</sup> mutation, and thus, increased pathological interactions with leucocytes, is responsible for the increased presence of thrombosis seen in these mice.</p> </abstract>