Design and Mathematical Analysis of Activating Amplifiers that Enable Modular Temporal Control in Synthetic Circuits

ABSTRACT The ability to control mammalian cells such that they self-organize or enact therapeutic effects as desired has incredible implications. Not only would it further our understanding of native processes such as development and the immune response, but it would also have powerful applications in medical fields such as regenerative medicine and immunotherapy. This control is typically obtained by synthetic circuits that use synthetic receptors, but control remains incomplete. For example, the synthetic juxtacrine receptors (SJRs) are widely used as they are fully modular and enable spatial control, but they have limited gene expression amplification and temporal control. I therefore designed transcription factor based amplifiers that amplify gene expression and enable unidirectional temporal control by prolonging duration of target gene expression. Using an in silico framework for SJR signaling, I combined these amplifiers with SJRs and show that these SJR amplifier circuits can improve the quality of self-organization and direct different spatiotemporal patterning. I then show that these circuits can improve chimeric antigen receptor (CAR) T cell tumor killing against heterogenous and homogenous antigen expression tumors. These amplifiers are flexible tools that improve control over SJR based circuits and have both basic and therapeutic applications. Graphical Abstract