The glucocorticoid receptor is required for stress erythropoiesis

The glucocorticoid receptor (GR) coordinates a multitude of physiological r esponses in vivo. In vitro, glucocorticoids are required for sustained prol iferation of erythroid progenitors (ebls). Here, we analyze the impact of t he GR on erythropoiesis in vive, using GR-deficient mice or mice expressing a GR defective for transactivation. In vitro, sustained proliferation of p rimary ebls requires an intact GR. In vive, the GR is required for rapid ex pansion of ebls under stress situations like erythrolysis or hypoxia. A par ticular, GR-sensitive progenitor could be identified as being responsible f or the stress response. Thus, GR-mediated regulation of ebl proliferation i s essential for stress erythropoiesis in vivo.