Proc. Natl Acad. Sci. USA doi:10.1073/pnas.0806114105 (2008)

Expressing a light-sensitive protein in cells that normally mediate between the retina and the brain restores a degree of vision in blind mice.

Retinal ganglion cells transmit signals that they receive from rod and cone cells to several regions of the brain. Rods and cones are the eye's main photoreceptors, and loss of these cells — a result of a number of human diseases — causes blindness.

Ordinarily, only a small subset of retinal ganglion cells contains the photosensitive pigment melanopsin. Richard Masland of Massachusetts General Hospital in Boston and his colleagues used a virus to induce widespread melanopsin expression within these cells in mice with degenerated photoreceptors. The treatment allowed the animals to respond to light and dark.

The finding adds to previous research that manipulated another type of 'middleman' retinal cell into expressing a light-sensitive bacterial protein, channelrhodopsin-2.