Optogenetics-Mediated Gene Therapy for Retinal Diseases.

The visual system consists of various types of neurons and a single-nucleotide mutation can sometimes lead to blindness. The phototransduction pathway in the retina starts from the first-order neurons, the photoreceptor cells, and transmits the signals to second-order neurons. Finally, the output signal from third-order neurons, the ganglion cells, is carried to the brain. The photoreceptor cells are the only neurons in the retina that can respond to a light signal; they are hyperpolarised when they receive light, and the ganglion cells carry the signals to the brain following the depolarization. Recently, various types of channelrhodopsins have been found and developed. It is expected that the gene therapies using the cation channel as well as anion channelrhodopsin genes would be effective against diseases that cause severe destruction of visual function, such as the retinitis pigmentosa and age-related macular degeneration. In this review, we mainly describe mVChR1-mediated gene therapy for retinitis pigmentosa and the future application of optogenetic genes in retinal diseases.