Conditional reporter gene activation with the R26t1Δ effector mouse reveals no background activity and varies in peripheral tissues of adult mice. (A) Whole-body bioluminescence images of compound R26t1Δ/TgPtet-Wnt1-IRES-luciferase mice showing activation of luciferase after DOX exposure (right mouse, +DOX). No luciferase signal was detected in genetically identical littermates not exposed to DOX (left mouse, -DOX). The scale shown measured photon counts translated into pseudo-colours; red indicating high and blue low luciferase activity. For luciferase gene activation animals were treated for three days with 3 mg DOX/ml in the drinking water. (B) X-Gal staining of representative cryostat sections from different organs of induced double transgenic R26t1Δ/TgPtetbi-GFP/lacZ mice. To conditionally activate transgene expression, compound animals were exposed to 3 mg DOX/ml drinking water for two weeks. The indicated organs were dissected and analysed by X-Gal staining. Skin (Sk), tongue (To), colon (Co), small intestine (SI), heart (He), pancreas (Pa), bladder (Bl), lung (Lu), kidney (Ki), testis (Te), liver (Li), stomach (St). The scale bar represents 200 μm.