title: Physiological regulation of early and late stages of megakaryocytopoiesis by thrombopoietin.
abstract: Thrombopoietin (TPO) has recently been cloned and shown to regulate megakaryocyte and platelet production by activating the cytokine receptor c-mpl. To determine whether TPO is the only ligand for c-mpl and the major regulator of megakaryocytopoiesis, TPO deficient mice were generated by gene targeting. TPO-/- mice have a >80% decrease in their platelets and megakaryocytes but have normal levels of all the other hematopoietic cell types. A gene dosage effect observed in heterozygous mice suggests that the TPO gene is constitutively expressed and that the circulating TPO level is directly regulated by the platelet mass. Bone marrow from TPO-/- mice have decreased numbers of megakaryocyte-committed progenitors as well as lower ploidy in the megakaryocytes that are present. These results demonstrate that TPO alone is the major physiological regulator of both proliferation and differentiation of hematopoietic progenitor cells into mature megakaryocytes but that TPO is not critical to the final step of platelet production.
authors.affiliation: Department of Molecular Biology, Genentech Inc., South San Francisco, California 94080, USA.
authors.forename: F J
authors.initials: FJ
authors.lastname: de Sauvage
authors.forename: K
authors.initials: K
authors.lastname: Carver-Moore
authors.forename: S M
authors.initials: SM
authors.lastname: Luoh
authors.forename: A
authors.initials: A
authors.lastname: Ryan
authors.forename: M
authors.initials: M
authors.lastname: Dowd
authors.forename: D L
authors.initials: DL
authors.lastname: Eaton
authors.forename: M W
authors.initials: MW
authors.lastname: Moore
mesh_terms: D000818:Animals; D001483:Base Sequence; D001772:Blood Cell Count; D001792:Blood Platelets / Q000187:drug effects / Q000502:physiology*; D015152:Blotting, Northern; D018628:Gene Dosage; D005838:Genotype; D007377:Interleukin-3 / Q000494:pharmacology; D008533:Megakaryocytes / Q000187:drug effects / Q000502:physiology*; D051379:Mice; D008969:Molecular Sequence Data; D016296:Mutagenesis; D011003:Ploidies; D016133:Polymerase Chain Reaction; D011995:Recombination, Genetic; D019089:Stem Cell Factor / Q000494:pharmacology; D013234:Stem Cells; D013926:Thrombopoietin / Q000172:deficiency* / Q000235:genetics / Q000494:pharmacology
chemical_list: D007377:Interleukin-3; D019089:Stem Cell Factor; D013926:Thrombopoietin