Genes playing essential roles in iron homeostasis have yet to be identified. We report the discovery of a strong candidate gene affecting iron homeostasis in two allelic anemia mouse mutants: hea (hereditary erythroblastic anemia) and fsn (flaky skin). To clone this novel gene positionally, we established a large backcross, which generated a critical region of seven genes from which only one gene exhibited a mutation in hea mice. This was a deletion in Ttc7 (tetratricopeptide repeat domain 7) extending from exon 1 to exon 14. Correspondingly, the allelic variant fsn mice showed a mutation of an ETn retrotransposon integration into intron 14 of the Ttc7 gene, which results in an abnormal Ttc7 RNA transcript. TTC7 is a member of the TPR repeat protein family known to interact with other proteins, to facilitate transport, and to act as chaperone or scaffolding proteins. We speculate that TTC7 plays an important role in iron transport.