Description: ABSTRACT Hereditary hemochromatosis, which is characterized by inappropriately low levels of hepcidin, increased dietary iron uptake, and systemic iron accumulation, has been associated to mutations in the HFE, TfR2, or HJV genes. However, it is still not clear whether these molecules intersect in vivo with BMP6/SMAD signaling, the main pathway upregulating hepcidin expression in response to elevated hepatic iron. To answer this question, we produced mice double knockout for Bmp6 and β2-microglobulin (a surrogate for the loss of Hfe) and for Bmp6 and Tfr2, and we compared their phenotype (hepcidin expression, Bmp/Smad signaling, hepatic and extrahepatic tissue iron accumulation) with that of single Bmp6 -deficient mice and that of mice deficient for Hjv, alone or in combination with Hfe or Tfr2. Whereas the phenotype of Hjv -deficient females was not affected by loss of Hfe or Tfr2, that of Bmp6 -deficient females was considerably worsened, with decreased Smad5 phosphorylation, compared with single Bmp6 -deficient mice, further repression of hepcidin gene expression, undetectable serum hepcidin, and massive iron accumulation not only in the liver but also in the pancreas, the heart and the kidneys. Conclusion : These results show that (i) BMP6 does not require HJV to transduce signal to hepcidin in response to intracellular iron, even if the loss of HJV partly reduces this signal, (ii) another BMP ligand can replace BMP6 and significantly induce hepcidin expression in response to extracellular iron, and (iii) BMP6 alone is as efficient to induce hepcidin as the other BMP in association with the HJV/HFE/TfR2 complex. They provide an explanation for the compensatory effect of BMP6 treatment on the molecular defect underlying Hfe-hemochromatosis in mice. This article is protected by copyright. All rights reserved.