A cassette was inserted into the locus consisting of the CAG promoter, intron, floxed stop sequence, mouse Foxn1 cDNA fused to an ERT2 element, an IRES, and a GFP sequence. Cre mediated recombination is needed to induce protein expression. Protein activity in the presence of tamoxifen is similar to the endogenous protein. (J:208852)