noun, plural: thrombopoietins
Thrombopoietin is a glycoprotein hormone produced and secreted by liver (particularly, parenchymal cells and sinusoidal epithelial cells) and kidney (particularly, the cells of proximal convoluted tubule). The THPO gene codes for it. In humans, the gene is located on the long arm of chromosome 3.
Thrombopoietin stimulates megakaryopoiesis, which is the process whereby a promegakaryocyte differentiates into a mature megakaryocyte. In the megakaryopoiesis, a multipotent stem cell, called a hemocytoblast, gives rise to a common myeloid progenitor cell. The progenitor cell, in turn gives rise to colony forming unit (particularly, CFU-Me) fated to become megakaryocytes. The CFU-Me develops into megakaryoblasts, which in turn develop into promegakaryocytes. These promegakaryocytes mature into megakaryocytes. A megakaryocyte is a large cell in the bone marrow with a characteristic lobulate nucleus. The megakaryocyte is ten times the size of an erythrocyte. Its large size is due to the DNA that replicates but the cell does not undergo cytokinesis. As such, a megakaryocyte would appear to contain many nuclei but it is a single nucleus that has become large and lobulated. A demarcation membrane system forms in the cell to demarcate platelets. These will break off from the cell and move to the peripheral blood. Thrombopoietin regulates the differentiation of megakaryocytes and platelets.
Word origin: Greek thrómbo(s) ("clot") + poiēt(ḗs) ("maker")
- megakaryocyte growth and development factor