Exon 17 was replaced with one in which a nucleotide susbtitution resulted in an amino acid substitution of alanine for leucine at position 622 (L622A). A floxed neo cassette was also inserted downstream of exon 17 but was subsequently removed by germ-line, cre-mediated recombination. This mutation prevents binding to Hfe but does not interfer with binding to Tf.