Looking within for vision

Channelrhodopsin-2 (ChR2), a directly light-gated cation channel from the green alga Chlamydomonas reinhardtii has been shown to be a directly light-switched cation-selective ion channel, which employs 11-cis retinal as its chromophore. This is the same chromophore as the mammalian photoreceptor's visual pigment-rhodopsin. Previously, investigators demonstrated that ChR2 can be used to optically control neuronal firing by depolarizing the cell. In this issue of Neuron, Bi et al. apply viral-mediated gene transfer to deliver ChR2 to retinal ganglion cells (RGC) in a rodent model of inherited blindness. In this way, the authors have genetically engineered surviving retinal neurons to take on the lost photoreceptive function. The conversion of light-insensitive retinal interneurons into photosensitive cells introduces an entirely new direction for treatments of blinding retinal degeneration.