Dicer1-dependent generation of miRNAs modulate mRNA expression and functions of platelets. MicroRNA precursors (pre-miRNA) in the megakaryocyte nucleus are processed by Drosha and are then exported in the cytoplasm, where they undergo further trimming by Dicer1. Upon recognition of their mRNA targets, functional miRNAs trigger mRNA degradation or translational repression. Dicer1-dependent miRNAs modulate mRNA profiles in platelets, such as the mRNAs coding for Itgb3 (β₃) and Itgb2 (α_IIb). The ablation of Dicer1 in platelets leads to overexpression of α_IIbβ₃ protein at the platelet surface and heightened platelet reactivity. The modulation of the platelet mRNA repertoire by microRNAs can occur in the megakaryocyte and might potentially also take place in platelets once in the blood circulation or during their storage. pri-miRNA, primary miRNA.