In mice, liver-specific disruption of Smad4, the BMP receptors type I Alk2 or Alk3, or the ligand Bmp6 result in hepcidin deficiency and iron overload, supporting the important role of these specific BMP-SMAD pathway components, in conjunction with HJV, in hepcidin regulation in vivo (Wang et al., 2005; Andriopoulos et al., 2009; Meynard et al., 2009; Steinbicker et al., 2011a). Here, HAMP is linked to Tangier disease.