EPO and Pancytopenia: In a study by Gruber M (Gruber et al., 2007), both newborn and adult rats with EPAS1 knockout presented with anemia or severe pancytopenia with suppressed EPO production, indicating the pro-erythrocytosis effect of HIF-2α by transcriptionally regulating EPO production (Scortegagna et al., 2003; Scortegagna et al., 2005).