ChReef: a newly engineered channelrhodopsin for sustained optogenetic control

Over the past decade, optogenetics has emerged as a major driver of progress in the life sciences. This technique, which involves controlling cellular behavior using a combination of genetic engineering and light, has opened new horizons in both research and therapeutic applications. Multiple clinical trials using optogenetic approaches to treat various diseases are currently in progress, and recently, the first successful clinical application of optogenetics for vision restoration was reported.

Despite its success, optogenetics faces certain limitations, primarily in terms of efficiency and precision of control. Channelrhodopsins (ChRs), which are light-activated cation channels from algae and a widely adopted optogenetic tool, are naturally low-conductance channels requiring high-intensity light for activation. Therefore, there is a significant need for engineering new ChRs to overcome limitations in conductance and light sensitivity and extend the reach of optogenetic applications.

In a recent preprint, scientists from the University Medical Center Göttingen reported on ChReef, an improved variant of the channelrhodopsin ChRmine, enabling efficient and sustained optogenetic stimulation of excitable cells. The problem with ChRmine is that it exhibits strong light-dependent inactivation, limiting its use in applications that require sustained or high-rate optogenetic stimulation. Using site-directed mutagenesis, as well as manual and automated patch clamp approaches (SyncroPatch 384 + optogenetic stimulation tool), the authors generated and characterized different ChRmine mutants. They identified the ChRmine T218L/S220A mutant (nicknamed ChReef, for “ChR that excites efficiently”) with high unitary conductance and minimal photocurrent desensitization.

ChReef has shown remarkable results in various applications. In cardiomyocyte clusters, ChReef significantly outperformed ChRmine in facilitating efficient red-light optical pacing and depolarization block, demonstrating its potential in cardiac research and possibly future therapeutic interventions. ChReef-expression in the optic nerve restored visual function in blind mice with light sources as weak as an iPad screen. ChReef also reduced the energy threshold for optogenetic activation of the auditory pathway by an order of magnitude.

In conclusion, the development of ChReef represents a significant milestone in optogenetics. Its superior performance over ChRmine, especially in terms of sustained stimulation capabilities, opens up new possibilities in both life sciences research and clinical applications.

Find the original preprint here: https://www.biorxiv.org/content/10.1101/2023.11.17.567544v1.full

Learn more about the SyncroPatch 384, a revolutionary automated patch clamp system combining high quality electrophysiological data acquisition and analysis with state-of-the-art liquid handling: https://www.nanion.de/products/syncropatch-384/