Main molecular mechanisms affected in malignant megakaryopoiesis and platelet function defects. Schematic representation of (A) TPO/MPL signaling pathway together with (B) the most relevant transcriptional regulators of megakaryocyte commitment, differentiation, and maturation. GP2B (CD41) is a component of the GPIIb-IIIa glycoprotein complex. GP9 (CD42a), GP1BA (CD42b), and GP1BB (CD42c) are components of the GPIb-IX-V glycoprotein complex. HSC, hematopoietic stem cell; MEP, megakaryocyte-erythroid progenitor; MK, megakaryocyte.