[Thrombopoietic growth factor--thrombopoietin. Molecular and biological properties].

Thrombopoietin (TPO) is a newly identified hematopoietic growth factor, that stimulates both megakaryopoiesis and thrombopoiesis through its interaction with a specific cell surface receptor (c-Mpl), a member of hematopoietic receptor superfamily, encoded by the c-mpl proto-oncogene. Recently the Janus kinases and STAT proteins have emerged as important elements in signaling via this family of receptors. The complete gene for human thrombopoietin has been cloned and mapped. TPO is believed to be the major physiological regulator of circulating platelet levels and it is hoped that this hormone will be valuable in stimulating megakaryocyte and platelet recovery in patients with thrombocytopenia, just as erythropoietin and GM-CSF or G-CSF have been valuable in stimulating the production of red and white cells.