During mouse development, the brain expresses high level of EPOR mid-gestation, localized using reporter gene expression, and mice that lack EPOR exhibit thinning of the neuroepithelium, reduced neural progenitor cells with increased sensitivity to hypoxia, and increased brain apoptosis prior to embryonic death due to severe anemia (Liu et al., 1997; Yu et al., 2002; Figure 2B). The gene discussed is EPOR; the disease is anemia.