Phenotypes of crosses between Tmprss6 knockout mouse and other models of iron disorders.Tmprss6^−/− mice with an iron-deficient phenotype (left) have been crossed with different models of iron overload (middle). The phenotype of the double knockout mice is shown. Double Tmprss6-Bmp6 and Tmprss6-Hjv knockout (top) develop iron overload. Crossing Tmprss6^−/− with both Hfe^−/− and TFr2^−/− (middle) leads to iron-deficient double knockout mice. Loss of Tmprss6 activity in beta-thalassemia mice (bottom) reduces iron overload and improves anemia (see “Lessons from animal models of TMPRSS6 inactivation” for details).