Extracellular optogenetic control in the study of epithelial collective cell signaling

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Project Summary Cell signaling in multicellular tissues is extraordinarily complex, ensuring that cells coordinate their proliferation, survival and movement for proper tissue function. One model context for multicellular signaling is the skin, an important organ that remains highly proliferative throughout the life of the animal and must balance this constant proliferation and repair with tight regulation to prevent tumorigenesis. Recent work using a live-cell Erk biosensor has revealed complex tissue-level signaling dynamics in epidermal tissues, both in cell culture and in living mammals. Taken together with previous studies showing that Erk signaling is both necessary and sufficient for wound healing and skin cell proliferation suggests that cells share crucial information through the local transmission of complex, dynamic growth factor signals. The current proposal aims to shed new light on growth factor signaling by developing optogenetic tools to activate and inhibit growth factor receptors with high precision. Current optogenetic approaches modulate signaling dynamics by altering intracellular protein activity, which requires substantial genome engineering and thus has limited use in vivo or as a therapeutic approach. In contrast, we have devised two new photosensitive tools to modulate cell signaling from the extracellular environment. We will engineer light-controllable ligands and inhibitors against receptor tyrosine kinases, to enable spatial and temporal control over the signals transmitted between cells. We will then use these tools to dissect complex Erk dynamics in primary mouse keratinocytes, a model system for the mammalian epidermis. Achieving a better understanding of the complex signals transmitted between cells will enable future studies to dissect their roles in wound healing and skin cancer. Additionally, the development of new optogenetic systems for manipulating extracellular binding events could lead to highly generalizable tools with the potential to control many other cellular processes.