2022 A red light–responsive photoswitch for deep tissue optogenetics

Authors:Kuwasaki, Y., Suzuki, K., Yu, G. et al.Journal:Applied Materials Today，Volume 27, June 2022, 101446; DOI.org/10.1016/j.apmt.2022.101446Institute:Graduate School of Arts and Sciences, The University of Tokyo, Tokyo, JapanAbstract:Red light penetrates deep into mammalian tissues and has low phototoxicity, but few optogenetic tools that use red light have been developed. Here we present MagRed, a red light–activatable photoswitch that consists of a red light–absorbing bacterial phytochrome incorporating a mammalian endogenous chromophore, biliverdin and a photo-state-specific binder that we developed using Affibody library selection. Red light illumination triggers the binding of the two components of MagRed and the assembly of split-proteins fused to them. Using MagRed, we developed a red light–activatable Cre recombinase, which enables light-activatable DNA recombination deep in mammalian tissues. We also created red light–inducible transcriptional regulators based on CRISPR–Cas9 that enable an up to 378-fold activation (average, 135-fold induction) of multiple endogenous target genes. MagRed will facilitate optogenetic applications deep in mammalian organisms in a variety of biological research areas.