A loxP site; encephalomyocarditis virus IRES; diptheria toxin receptor (DTR) enhanced green fluorescent protein (eGFP) fusion protein; a triple SV40 polyA (STOP); a second loxP site; encephalomyocarditis virus IRES; Thy1.1; followed by a frt site-flanked PGK-Neomycin resistance gene (NEO)-BGHpA cassette (loxP-IRES-DTReGFP-STOP-loxP-IRES-Thy1.1-frt-NEO-BGHpA-frt) was inserted into the Foxp3 3' UTR via homologous recombination in ES cells. The mice were bred to FLPeR mice to excise the NEO cassette. (J:248943)