7. PROJECT 3. REWIRING THERAPEUTIC CELLS: USER-CONTROLLED T CELLS & STEM CELLS SUMMARY Ultimately, a deeper understanding of the design principles of cellular regulatory networks should transform our ability to interface with and treat disease. In particular, our understanding of cellular control systems should allow us to engineer or modulate cellular networks so that they can be reprogrammed to carry out new or modified therapeutic functions. Thus for our third and most forward-looking project we have challenged ourselves to learn how to rewire and reprogram two particular types of medically relevant cell ? T lymphocytes (T cells) and Embryonic Stem Cells (ESCs). T cells have recently emerged as an exciting new platform for cell based therapy ? when engineered to express synthetic chimeric antigen receptors (CARs) that recognize tumor antigens, adoptively transferred T cells are able to recognize and eliminate B cell cancers. Yet, these engineered T cells are so powerful that they have significant on- and off-target toxicities. Thus, the goal of engineering user-controlled circuits in therapeutic T cells presents a real-world challenge for our ability to understand and manipulate cellular control networks. We aim to build circuits that allow systematic control over the gating and dynamics of therapeutic T cell activation. Stem cells hold similar promise as a platform for regeneration and repair, but in order for this promise to be realized, it is critical that we gain better control over when and where differentiation occurs and what cell fates are generated. Thus we aim to apply the approaches of synthetic biology to engineer user control over the dynamics and fate outcomes of stem cell differentiation. LEAD Investigator: LIM Co-Investigators: LIM, THOMSON, KROGAN