Bioluminescence analysis of Smad-dependent TGF-beta signaling in live mice.

TGF-beta signaling via the Smad2/3 pathway has key roles in development and tissue homeostasis. Perturbations of the TGF-beta signaling are involved in the pathogenesis of many human diseases, including cancer, fibrotic disorders, developmental defects, and neurodegeneration. To study the temporal and spatial patterns of Smad2/3-dependent signaling in living animals, we engineered transgenic mice with a Smad-responsive luciferase reporter (SBE-luc mice). Smad2/3-dependent signaling can be assessed non-invasively in living mice by bioluminescence imaging. To identify the cellular source of the bioluminescence signal, we generated new reporter mice expressing a trifusion protein containing luciferase, red fluorescent protein (RFP), and thymidine kinase under the control of the same SBE promoter (SBE-lucRT mice). SBE-luc and SBE-lucRT mice can be used to study temporal, tissue-specific activation of Smad2/3-dependent signaling in living mice as well as for the identification of endogenous or synthetic modulators of this pathway.