Mouse Erythropoietin (EPO) is a glycoprotein hormone belonging to the type I cytokine family that regulates erythropoiesis, the production of red blood cells. In mice (Mus musculus), erythropoietin is produced primarily by peritubular interstitial cells in the kidney, with additional production in the liver, in response to hypoxia or decreased oxygen-carrying capacity of the blood. Mouse EPO binds to the erythropoietin receptor (EPOR) expressed on erythroid progenitor cells in the bone marrow, activating intracellular signaling pathways including JAK2–STAT5, PI3K–AKT, and MAPK, which promote the survival, proliferation, and differentiation of erythroid precursor cells into mature red blood cells. In murine physiology, erythropoietin is essential for maintaining normal hematocrit and systemic oxygen delivery, and disruption of the Epo–Epor signaling pathway leads to severe anemia and embryonic lethality in knockout models. Mice are widely used as animal models for studying erythropoiesis, anemia, and kidney disease, and mouse EPO has been extensively investigated in genetic models of anemia and hypoxia, including studies of hypoxia-inducible factor (HIF) regulation of Epo expression, which have helped define the molecular mechanisms controlling oxygen sensing and red blood cell production relevant to human physiology and disease.