ChrimsonR (Red-shifted channelrhodopsin) (ChrimsonR)

ChrimsonR is a red-shifted channelrhodopsin, a light-gated ion channel originally derived from the algae Chlamydomonas noctigama (Klapoetke et al., 2014). In the context of optogenetic gene therapy, such as the GS030 program, ChrimsonR is expressed in retinal ganglion cells (RGCs) to restore vision in patients with advanced retinal degenerative diseases like retinitis pigmentosa (Sahel et al., 2021). By delivering the ChrimsonR gene via an adeno-associated virus (AAV) vector, RGCs—which are normally not photosensitive—are converted into surrogate photoreceptors that can bypass lost or damaged rods and cones. The protein is frequently fused with tdTomato, a red fluorescent reporter protein, to allow for the visualization and monitoring of transgene expression within the retina. When activated by specific wavelengths of amber light (approximately 590 nm), ChrimsonR facilitates the influx of cations, triggering action potentials that transmit visual information to the brain. This approach is particularly valuable for treating late-stage blindness where the outer retinal layers have completely degenerated, but the inner retinal architecture remains intact (GenSight Biologics, 2023).

Other names

ChrimsonR-tdTomatoRed-shifted channelrhodopsinChR-tdTomatoGS030 target

ChrimsonR acts as a light-gated cation channel that depolarizes retinal ganglion cells upon exposure to 590 nm light, bypassing degenerate photoreceptors to restore visual signaling to the brain.