Optical control of mammalian endogenous transcription and epigenetic states

Abstract

Here the customizable TALE DNA-binding domain was integrated with the light-sensitive cryptochrome 2 protein and its interacting partner (CIB1) from Arabidopsis thaliana, thereby creating an optogenetic two-hybrid system called light-inducible transcriptional effectors (LITEs); the LITE system establishes a novel mode of optogenetic control of endogenous transcription and epigenetic states. Feng Zhang and colleagues integrated the customizable TALE DNA-binding domain with the light-sensitive cryptochrome 2 protein and its interacting partner CIB1 from Arabidopsis thaliana, which they call LITEs (light-inducible transcriptional effectors), thereby creating an optogenetic two-hybrid system. LITEs do not require additional cofactors, are readily customized to target many loci and can be quickly and reversibly activated. They can also be packaged into viral vectors and targeted to specific cell populations. The authors applied this system in primary mouse neurons and in the brains of awake mice to modulate endogenous gene expression and to target epigenetic chromatin modifications. The LITE system establishes a novel mode of optogenetic control of endogenous cellular processes. The dynamic nature of gene expression enables cellular programming, homeostasis and environmental adaptation in living systems. Dissection of causal gene functions in cellular and organismal processes therefore necessitates approaches that enable spatially and temporally precise modulation of gene expression. Recently, a variety of microbial and plant-derived light-sensitive proteins have been engineered as optogenetic actuators, enabling high-precision spatiotemporal control of many cellular functions1,2,3,4,5,6,7,8,9,10,11. However, versatile and robust technologies that enable optical modulation of transcription in the mammalian endogenous genome remain elusive. Here we describe the development of light-inducible transcriptional effectors (LITEs), an optogenetic two-hybrid system integrating the customizable TALE DNA-binding domain12,13,14 with the light-sensitive cryptochrome 2 protein and its interacting partner CIB1 from Arabidopsis thaliana. LITEs do not require additional exogenous chemical cofactors, are easily customized to target many endogenous genomic loci, and can be activated within minutes with reversibility6,15. LITEs can be packaged into viral vectors and genetically targeted to probe specific cell populations. We have applied this system in primary mouse neurons, as well as in the brain of freely behaving mice in vivo to mediate reversible modulation of mammalian endogenous gene expression as well as targeted epigenetic chromatin modifications. The LITE system establishes a novel mode of optogenetic control of endogenous cellular processes and enables direct testing of the causal roles of genetic and epigenetic regulation in normal biological processes and disease states.