Mechanisms underlying platelet function defect in a pedigree with familial platelet disorder with a predisposition to acute myelogenous leukemia: potential role for candidate RUNX1 targets

Abstract

To cite this article: Glembotsky AC, Bluteau D, Espasandin YR, Goette NP, Marta RF, Marin Oyarzun CP, Korin L, Lev PR, Laguens RP, Molinas FC, Raslova H, Heller PG. Mechanisms underlying platelet function defect in a pedigree with familial platelet disorder with a predisposition to acute myelogenous leukemia: potential role for candidate RUNX1 targets. J Thromb Haemost 2014; 12: 761-72 Summary. Background: Familial platelet disorder with a predisposition to acute myelogenous leukemia (FPD/ AML) is an inherited platelet disorder caused by a germline RUNX1 mutation and characterized by thrombocytopenia, a platelet function defect, and leukemia predisposition. The mechanisms underlying FPD/AML platelet dysfunction remain incompletely clarified. We aimed to determine the contribution of platelet structural abnormalities and defective activation pathways to the platelet phenotype. In addition, by using a candidate gene approach, we sought to identify potential RUNX1-regulated genes involved in these defects. Methods: Lumiaggregometry, a-granule and dense granule content and release, platelet ultrastructure, a IIb b 3 integrin activation and outside-in signaling were assessed in members of one FPD/AML pedigree. Expression levels of candidate genes were measured and luciferase reporter assays and chromatin immunoprecipitation were performed to study NF-E2 regulation by RUNX1. Results: A severe decrease in platelet aggregation, defective a IIb b 3 integrin activation and combined ad storage pool deficiency were found.However, whereas the number of dense granules was markedly reduced, a-granule content was heterogeneous. A trend towards decreased platelet spreading was found, and b 3 integrin phosphorylation was impaired, reflecting altered outside-in signaling. A decrease in the level of transcription factor p45 NF-E2 was shown in platelet RNA and lysates, and other deregulated genes included RAB27B and MYL9. RUNX1 was shown to bind to the NF-E2 promoter in primary megakaryocytes, and wild-type RUNX1, but not FPD/AML mutants, was able to activate NF-E2 expression. Conclusions: The FPD/AML platelet function defect represents a complex trait, and RUNX1 orchestrates platelet function by regulating diverse aspects of this process. This study highlights the RUNX1 target NF-E2 as part of the molecular network by which RUNX1 regulates platelet biogenesis and function.

RUNX1 deficiency (familial platelet disorder with predisposition to myeloid leukemia, FPDMM)

“…Dense-granule storage pool deficiency represents the most frequent abnormality [8], although other defects, such as partial alpha-granule deficiency, impaired activation of the fibrinogen receptor, GPIIbIIIa, and defective platelet spreading have also been described in some patients [23][24][25]. The bleeding diathesis is variable within and among families.…”

“…RUNX1 acts at different stages of megakaryocyte development by regulating the expression of several molecules relevant to platelet production and function. Reduced expression of RUNX1 target genes, including MPL proto-oncogene, thrombopoietin receptor (MPL), non-muscle myosin IIA/myosin heavy chain 9 (MYH9) and its regulatory chain MLC2, arachidonate 12-lipoxygenase (ALOX12) and NFE2, have been shown to underlie the defect in platelet number and function in FPDMM, which involves multiple pathways [22,24,26,27]. In addition, increased levels of non-muscle myosin IIB (MYH10), which is physiologically repressed by RUNX1 during normal megakaryocyte development, contributes to thrombocytopenia by blocking megakaryocyte polyploidization.…”

Induced Pluripotent Stem Cell–Derived Megakaryocytes and Platelets for Disease Modeling and Future Clinical Applications

“…65,66 As the name suggests, these patients present with thrombocytopenia and a greater than 40% chance of developing hematologic malignancies by age 35. 65,66 Murine models have been used to study this disease but fail to display low platelet counts unless both alleles of Runx1 are mutated.…”

“…65,66 As the name suggests, these patients present with thrombocytopenia and a greater than 40% chance of developing hematologic malignancies by age 35. 65,66 Murine models have been used to study this disease but fail to display low platelet counts unless both alleles of Runx1 are mutated. 67 With that, several laboratories have generated iPSCs from familial platelet disorder patients harboring RUNX1 mutations to further understand the mechanism of disease.…”

Myeloid Neoplasms with Germline Predisposition

“…Patients typically present with mild-tomoderate thrombocytopenia. Platelet morphology is normal, but with an associated severe decrease in platelet aggregation [16]. Distinct families have varying risks of pro-DOI: 10.1159/000490311 gression to myeloid neoplasms (range 11-100%; median 40% of family members).…”