In atherosclerosis-prone end.SclCreERT;R26RstopYfp;ApoE−/− mice, endothelial-specific Cre expression is induced by tamoxifen administration to irrevocably activate the yellow fluorescence protein (Yfp) gene, resulting in continuous Yfp expression regardless of any change in cell phenotype26, 27. The gene discussed is APOE; the disease is atherosclerosis.