Tuning the Response of Synthetic Mechanogenetic Gene Circuits Using Mutations in TRPV4.

Conventional gene therapy approaches for drug delivery generally rely on constitutive expression of the transgene and thus lack precise control over the timing and magnitude of delivery. Synthetic gene circuits with promoters that are responsive to user-defined stimuli can provide a molecular switch that can be utilized by cells to control drug production. Our laboratory has previously developed a mechanogenetic gene circuit that can deliver biological drugs, such as interleukin-1 receptor antagonist (IL-1Ra), on-demand through the activation of Transient receptor potential family, vanilloid 4 (TRPV4), a mechanosensory ion channel that has been shown to be activated transiently in response to physical stimuli such as physiological mechanical loading or hypo-osmotic stimuli. The goal of this study was to use mutations in TRPV4 to further tune the response of this mechanogenetic gene circuit. Human iPSC-derived chondrocytes harboring targeted gain-of-function mutations of TRPV4 were chondrogenically differentiated. Both mutants-V620I and T89I-showed greater total IL-1Ra production compared with wild type following TRPV4 agonist treatment, as well as mechanical or osmotic loading, but with altered temporal dynamics. Gene circuit output was dependent on the degree of TRPV4 activation secondary to GSK101 concentration or strain magnitude during loading. V620I constructs secreted more IL-1Ra compared with T89I across all experimental conditions, indicating that two mutations that cause similar functional changes to TRPV4 can result in distinct circuit activation profiles that differ from wild-type cells. In summary, we successfully demonstrate proof-of-concept that point mutations in TRPV4 that alter channel function can be used to tune the therapeutic output of mechanogenetic gene circuits.