Restoring vision with light-sensitive protein
A loss of photoreceptor cells caused by retinal degenerative diseases often results
in complete blindness. Zhuo-Hua Pan of Wayne State University School of Medicine
in Detroit and colleagues explored the possibility of converting nonphotosensitive
(or inner) retinal neurons into photosensitive cells in mice to see if they could
restore retinas that lack rods and cones by making them sensitive to light.
Photoreceptor cells in the retina convert light
signals to electrical signals that are relayed through other retinal neurons
to the brain. As reported in the April 6 issue of Neuron, the researchers
injected a harmless virus that contained channelrhodopsin-2, which is a light-sensitive
protein found in green algae, into the eyes of mice. They wanted to see if the protein
would make the retinal neurons sensitive to light.
To directly observe the expression
of the light-sensitive proteins, the researchers tagged them with GFP. Three to
four weeks after the injection, bright fluorescence was seen in retinal neurons
under either a Zeiss fluorescence microscope equipped with exciter, dichroic and
emission filters and with a CCD camera or a Leica confocal microscope. The fluorescence
was still detected even 12 months after injection, with no major changes in the
The researchers believe that their results indicate that the microbial-type channel proteins may provide a potential strategy for restoring the vision in patients suffering from photoreceptor degeneration.
They hope that further studies will evaluate which types of retinal diseases may
benefit from this potential treatment strategy.
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