Similar phenotypes and alopecia indicating low iron levels in the body are reported in mouse models with a global Tmprss6 knockout (Tmprss6−/−), a truncated Tmprss6 that lacks the coding sequence for the catalytic domain (mask), or an Ile286Phe substitution in the CUB domain (Fig. 1A) (10, 11, 12, 13, 14). The gene discussed is TMPRSS6; the disease is alopecia.