Photo-inducible Cell Ablation and Fluorescent Chemosensors for Chemical Biology

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We are interested in developing chemical tools to probe biological complexity in vivo. Specifically, we are proposing two areas of research:1) Photo-induced Cell Ablation. Deciphering the role of entire cells during biological events has been a difficult challenge since cells function in complex networks. A powerful approach to probing their complexity is to turn “off” cells then monitor developmental/behavioral changes in the organism. To achieve this effectively, a promising strategy is to use small molecule photosensitizers that can produce reactive oxygen species in the presence of light, which will kill or turn “off” cells. However, once administered, photosensitizers accumulate in all tissues making it difficult to probe cellular function at a specific location. To address this issue, we are proposing to develop a series of photosensitizers that will require not only light but also an enzyme for its activation. With this chemical genetic approach, cells can be destroyed efficiently (low light dosage) at a specific site with minimal non-specific cell destruction of the surrounding region. Overall this strategy will enable us to accurately assign functions to cells and tissues.2) Fluorescent Chemosensors. Monitoring enzymes in their native cellular environments would be a powerful approach to truly understand their function. Tools that are capable of directly reporting on their behavior could provide an accurate map of activity in both normal and diseased states. To this regard, we are proposing to construct a series of fluorescent chemosensors for the enzyme class, methyltransferases. Our sensors will be general and selective to permit real-time sensing of all methyltransferase activity in live cells, and will be used to answer specific questions regarding their native roles that would otherwise be difficult to obtain by conventional biochemical methods. In turn, these novel tools will permit a better understanding of the network of methyltransferases in epigenetic pathways.