Abstract
Platelets are enriched in miRNAs and harbor Ago2 as the principal RNA silencing Argonaute. However, roles in thrombopoiesis and platelet function remain poorly understood. We generated megakaryocyte/platelet-specific Ago2-deleted (Ago2 KO) mice and assessed proteomic and functional effects. We predicted platelet hyperreactivity with Ago2 deletion due to large-scale upregulated protein expression. Platelet counts were normal. Mean volumes were increased, associated with larger, though fewer megakaryocytes. Ago2-deleted platelets from male mice showed hyperreactivity to thromboxane but not to other agonists compared to controls, whereas Ago2-deleted platelets from female mice showed normal reactivity. Ago2 KO mice displayed normal hemostasis and clot dynamics. Proteomes of Ago2-deleted and wild type platelets were mostly similar. However, Ago1 - undetectable in wild type platelets - was upregulated in Ago2-deleted platelets in both males and females, confirmed by immunoblotting. Female Ago2-deleted platelets selectively showed downregulation of a protein cohort established in breast cancer cells to be transcriptionally regulated by estrogen receptor-beta coupled to Ago2, whereas male Ago2-deleted platelets did not. Thus, Ago2 is important for platelet development and function, putatively partially rescued by upregulation of Ago1. Platelet reactivity controlled by Ago2 reflects sex-specific regulation of gene expression potentially at both transcriptional and translational levels in megakaryocytes and platelets.