A sensitive red/far-red photoswitch for controllable gene therapy in mouse models of metabolic diseases.
                            
                                red
                            
                            
                                DrBphP
                            
                                FnBphP
                            
                                PnBphP
                            
                            
                                
                                    ATDC-5
                                
                            
                                
                                    Hana3A
                                
                            
                                
                                    HEK293T
                                
                            
                                
                                    HeLa
                                
                            
                                
                                    hMSCs
                                
                            
                                
                                    mouse in vivo
                                
                            
                            
                                Transgene expression
                            
                                Endogenous gene expression
                            
                            
                            
                            
                            
                        
                        
                        
                        
                            Abstract:
                            Red light optogenetic systems are in high demand for the precise control of gene expression for gene- and cell-based therapies. Here, we report a red/far-red light-inducible photoswitch (REDLIP) system based on the chimeric photosensory protein FnBphP (Fn-REDLIP) or PnBphP (Pn-REDLIP) and their interaction partner LDB3, which enables efficient dynamic regulation of gene expression with a timescale of seconds without exogenous administration of a chromophore in mammals. We use the REDLIP system to establish the REDLIP-mediated CRISPR-dCas9 (REDLIPcas) system, enabling optogenetic activation of endogenous target genes in mammalian cells and mice. The REDLIP system is small enough to support packaging into adeno-associated viruses (AAVs), facilitating its therapeutic application. Demonstrating its capacity to treat metabolic diseases, we show that an AAV-delivered Fn-REDLIP system achieved optogenetic control of insulin expression to effectively lower blood glucose levels in type 1 diabetes model mice and control an anti-obesity therapeutic protein (thymic stromal lymphopoietin, TSLP) to reduce body weight in obesity model mice. REDLIP is a compact and sensitive optogenetic tool for reversible and non-invasive control that can facilitate basic biological and biomedical research.