Live Imaging with Genetically Encoded Physiologic Sensors and Optogenetic Tools.

Barrier tissues such as the epidermis employ complex signal transduction systems to execute morphogenetic programs and to rapidly respond to environmental cues to promote homeostasis. Recent advances in live-imaging techniques and tools allow precise spatial and temporal monitoring and manipulation of intracellular signaling cascades. Leveraging the chemistry of naturally occurring light-sensitive proteins, genetically encoded fluorescent biosensors have emerged as robust tools for visualizing dynamic signaling events. In contrast, optogenetic protein constructs permit laser-mediated control of signal receptors and effectors within live cells, organoids, and even model organisms. In this paper, we review the basic principles underlying novel biosensors and optogenetic tools and highlight how recent studies in cutaneous biology have leveraged these imaging strategies to illuminate the spatiotemporal signals regulating epidermal development, barrier formation, and tissue homeostasis.