By Carl Zimmer, Yahoo! News
A team of scientists announced Monday that they had partially restored the sight of a blind man by building light-catching proteins in one of his eyes. Their report, which appeared in the journal Nature Medicine, is the first published study to describe the successful use of this treatment. “Seeing for the first time that it did work — even if only in one patient and in one eye — is exciting,” said Ehud Isacoff, a neuroscientist at the University of California, Berkeley, who was not involved in the study.
The procedure is a far cry from full vision. The volunteer, a 58-year-old man who lives in France, had to wear special goggles that gave him the ghostly perception of objects in a narrow field of view. But the authors of the report say that the trial — the result of 13 years of work — is a proof of concept for more effective treatments to come.
“It’s obviously not the end of the road, but it’s a major milestone,” said José-Alain Sahel, an ophthalmologist who splits his time between the University of Pittsburgh and the Sorbonne in Paris.
Sahel and other scientists have tried for decades to find a cure for inherited forms of blindness. These genetic disorders rob the eyes of essential proteins required for vision.
When light enters the eye, it is captured by photoreceptor cells. The photoreceptors then send an electrical signal to their neighbors, called ganglion cells, which can identify important features like motion. They then send signals of their own to the optic nerve, which delivers the information to the brain.
In previous studies, researchers have been able to treat a genetic form of blindness called Leber congenital amaurosis, by fixing a faulty gene that would otherwise cause photoreceptors to gradually degenerate.
But other forms of blindness cannot be treated so simply, because their victims lose their photoreceptors completely.
“Once the cells are dead, you cannot repair the gene defect,” Sahel said.
For these diseases, Sahel and other researchers have been experimenting with a more radical kind of repair. They are using gene therapy to turn ganglion cells into new photoreceptor cells, even though they don’t normally capture light.
The scientists are taking advantage of proteins derived from algae and other microbes that can make any nerve cell sensitive to light.
In the early 2000s, neuroscientists figured out how to install some of these proteins into the brain cells of mice and other lab animals by injecting viruses carrying their genes. The viruses infected certain types of brain cells, which then used the new gene to build light-sensitive channels.
Originally, researchers developed this technique, called optogenetics, as a way to probe the workings of the brain. By inserting a tiny light into the animal’s brain, they could switch a certain type of brain cell on or off with the flick of a switch. The method has enabled them to discover the circuitry underlying many kinds of behavior.
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