Mechanisms underlying platelet function defect in a pedigree with FPD/AML: potential role for candidate RUNX1-targets

GLEMBOTSKY ANA C; BLUTEAU D; ESPASANDIN YESICA R; GOETTE NORA P; MARTA ROSANA F; MARIN OYARZUN C; KORIN LAURA; LEV PAOLA R; LAGUENS RUBÉN; MOLINAS FELISA C; RASLOVA H; HELLER PAULA G

JOURNAL OF THROMBOSIS AND HAEMOSTASIS

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2014 vol. 12 p. 761 - 772

1538-7933

Background FPD/AML is an inherited platelet disorder caused by germline RUNX1 mutation and characterized by thrombocytopenia, 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 Lumi-aggregometry, alpha- and dense- granule content and release, platelet ultrastructure and alphaIIbbeta3 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 assay and chromatin immunoprecipitation were performed to study NF-E2 regulation by RUNX1. Results Severe decrease in platelet aggregation, together with defective alphaIIbbeta3 integrin activation and combined alpha-delta storage pool deficiency was found. However, while dense granules were markedly reduced, alpha-granule content was heterogeneous. A trend towards decreased platelet spreading was found, while beta3 integrin phosphorylation was impaired, reflecting altered outside-in signaling. A decrease in 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 NF-E2 promoter in primary megakaryocytes and wild-type RUNX1, but not FPD/AML mutants, was able to activate NF-E2 expression. Conclusions FPD/AML platelet function defect represents a complex trait and RUNX1 orchestrates platelet function by regulating diverse aspects of this process. This study highlights RUNX-1-target NF-E2 as part of the molecular network by which RUNX1 regulates platelet biogenesis and function.