Global Stat5a/b−/− and hematopoietic-specific Stat5a/b−/− mice have a severe microcytic hypochromic anemia that is proposed to be related to the lack of Stat5 binding to the promoter of Irp2 and Tfr1, leading to the inhibition of iron uptake in erythroid cells [21]. The gene discussed is STAT5B; the disease is anemia (phenotype).