A floxed neo STOP cassette and an I-Scel-GR-IRES-tdTomato cassette were inserted into intron 1 via homologous recombination. The I-Scel-GR-IRES-tdTomato cassette encodes an I-Scel meganuclease-glucocorticoid receptor fusion protein that can be activated via triamcinolone acetonide. Cre mediated recombination removed the neo cassette. (J:220884)