THROMBOPOIETIN, THE C-MPL LIGAND, IS A MAJOR REGULATOR OF PLATELET PRODUCTION

Hematopoiesis is regulated by a family of glycoproteins, the hematopoietic growth factors, Although the cytokines that influence the late stages of granulopoiesis (granulocyte colony-stimulating factor and granulocyte-macrophage colony-stimulating factor) or erythropoiesis (erythropoietin) have been identified, characterized, and cloned, and have been in clinical use since that late 1980's, the cytokine that stimulates thrombopoiesis had remained elusive, By using strategies based on the c-mpl receptor, several groups have recently succeeded in purifying and cloning thrombopoietin [1-6], This study outlines the cloning and biological characterization in vitro and in vivo of thrombopoietin, a major regulator of platelet production.