ChrimsonR channelrhodopsin (ChrimsonR)

ChrimsonR is a red-shifted channelrhodopsin, a light-gated ion channel originally derived from the green alga Chlamydomonas noctigama (Klapoetke et al., 2014, Nature Methods). It is engineered to respond to longer wavelengths of light, specifically in the amber-to-red spectrum with a peak sensitivity around 590 nm, which is safer for the retina and offers better tissue penetration than blue-light-sensitive opsins (Sahel et al., 2021, Nature Medicine). In therapeutic applications, ChrimsonR is delivered via an adeno-associated virus (AAV) vector to retinal ganglion cells (RGCs) in patients suffering from late-stage retinitis pigmentosa (GenSight Biologics, 2023). By expressing ChrimsonR, these RGCs are converted into primary photosensors, effectively bypassing the lost or damaged photoreceptor layer (Gauvain et al., 2021, Communications Biology). When stimulated by external light-emitting goggles that project high-intensity pulses of the appropriate wavelength, the ChrimsonR channels open, causing RGC depolarization and the transmission of visual information to the brain (Sahel et al., 2021, Nature Medicine). This optogenetic strategy aims to restore functional vision in patients who have lost their natural light-sensing capabilities due to outer retinal degeneration.

Other names

Red-shifted channelrhodopsinChrimsonR opsinChrimson variantChrimsonR-tdTomato

ChrimsonR acts as a light-gated cation channel; upon illumination with amber light (~590 nm), the channel opens, allowing the influx of cations into the retinal ganglion cells, which triggers action potentials that are transmitted to the visual cortex (Sahel et al., 2021, Nature Medicine).