Thrombopoietin.

Abstract

Thrombopoietin (TPO) was first described as an activity in thrombocytopenic serum that could stimulate platelet production upon transfer into other animals. The molecular cloning of TPO has allowed a detailed characterisation of its precise biological activities, both in vitro and in vivo. TPO binds its specific receptor, the c-Mpl protein, which is expressed on the surface of target cells, and induces receptor dimerization and activation of intracellular signalling pathways including the Janus kinase (JAK)-signal transducers and activators of transcription (STAT) and Ras cascades. TPO is a lineage-dominant cytokine, stimulating megakaryocyte production and maturation in vitro and inducing t..