High-Performance Chemical and Light-Inducible Recombinases in Mammalian Cells

Site-specific DNA recombinases are some of the most powerful genome engineering tools in biology. Chemical and light-inducible recombinases, in particular, enable spatiotemporal control of gene expression. However, the availability of inducible recombinases is scarce due to the challenge of engineering high performance systems with low basal activity and sufficient dynamic range. This limitation constrains the sophistication of genetic circuits and animal models that can be created. To expand the number of available inducible recombinases, here we present a library of >20 orthogonal split recombinases that can be inducibly-dimerized and activated by different small molecules, light, and temperature in mammalian cells. Furthermore, we have engineered inducible split Cre systems with better performance than existing inducible Cre systems. To demonstrate novel capability with our split recombinases, we created a tripartite inducible Flp and a 4-Input AND gate. We have performed extensive quantitative characterization of the inducible recombinases for benchmarking their performances. This library significantly expands our capacity for precise and multiplexed mammalian gene expression control.