The Jak-Stat pathway in normal and perturbed hematopoiesis

The Janus kinase-signal transducer and activator of transcription (Jak-Stat ) pathway stands as a paradigm of how diverse extracellular signals can eli cit rapid changes in gene expression in specific target cells. This pathway is widely used by members of the cytokine receptor superfamily, including those for the clinically important cytokines granulocyte colony-stimulating factor (G-CSF), erythropoietin, thrombopoietin, the interferons, and numer ous interleukins, which makes it central to hematopoietic cell biology and hematologic therapy alike. Indeed, study of the Jak-Stat pathway has provid ed a wealth of information on hematopoiesis and hematopoietic disease, and conversely, studies of hematopoietic disorders have yielded new insights in to the functions of Jaks and Stats. This review aims to detail the role of the Jak-Stat pathway in the normal development and function of hematopoieti c cells and to describe how several hematopoietic disorders are caused, at least in part, by perturbations of this pathway.