Scientists Cure Colour Blindness In Monkeys

[Papi]

http://www.theglobeandmail.com/life/health/scientists-cure-colour-blindness-in-monkeys/article1290015/

Dakhshana Bascaramurty

Globe and Mail update Last updated on Wednesday, Sep. 16, 2009 04:03PM EDT

Strawberries coloured crimson, grapes tinted deep purple and limes shaded green. For some of the estimated 422,000 Canadians who suffer from colour blindness – the most common genetic disorder – the true colour of those fruits is often replaced by dull shades of grey.

But new research published in the most recent issue of the journal Nature suggests there may be a way to correct vision disorders such as colour blindness, which were long thought to be incurable in adults.

A team of scientists from the University of Washington and the University of Florida have brought full-colour vision to two adult squirrel monkeys that suffered from red-green colour blindness using gene therapy. Because monkeys and humans have very similar retinas, the researchers believe the techniques they used could improve the vision of humans, too.

The monkeys were trained to do the Cambridge Colour Test, the standard test used to detect colour blindness in humans. They were presented with three panels on a monitor – two were blank and one had a pattern of coloured dots on it – and had to touch their noses to the panel with the pattern. If they were correct, they were rewarded with a sip of grape juice, but if they were wrong, the researchers played a buzzing sound.

Because the monkeys were colour blind, they continually guessed and had a success rate of about 33 per cent, said William Hauswirth, one of the study's authors and a professor of ophthalmology and molecular genetics at the University of Florida.

Then, scientists injected each monkey's retina with a human virus that contained the gene that allows the eye to detect red. They also injected a piece of DNA to regulate how the gene is made into protein. They anticipated the monkeys would open their eyes to a new world after the treatment.

At first, there was no change in the vision test results.

“We started losing hope,” Dr. Hauswirth said.

But after 15 weeks, he and his research partners noticed something dramatic: the monkeys' success rate jumped to 95 per cent – they could see red.

“We demonstrated that we can add a new colour response to a primate. If we can do it in a monkey, we can almost certainly do it in a human,” Dr. Hauswirth said.

This research could prove useful for those diagnosed with achromatopsia, what Dr. Hauswirth describes as a “very debilitating” form of coloured blindness. Sufferers are very sensitive to light and often have to wear red contact lenses and sunglasses when they are indoors.

This process could also benefit people suffering from a range of vision disorders that stem from a problem with the cones in their eyes, which sense light and are key to colour vision.

“This is the first demonstration that you can treat cones with the gene they're missing,” Dr. Hauswirth said.

Alex Goulet-Hanssens, a 23-year-old master's student at McGill University in Montreal, has long eschewed the label “colour blind.”

Though there have been signs of the disorder since he was in Grade 9, when he mistakenly bought a pair of baby blue cargo pants thinking they were grey, it was only a few months ago that he was formally diagnosed with the disorder.

While Mr. Goulet-Hanssens said his colour blindness doesn't bother him enough to seek treatment just yet, a cure for it would certainly help him in the laboratory.

As student of chemistry, he sometimes struggles to detect whether a compound is an acid or a base when he uses phenolphthalein, an indicator that stays colourless in acidic solutions but turns pink in basic ones. His teaching assistant usually comes to his aid to tell him if it's pink or not.

He said it may also be nice to pick out clothes that don't clash on his own.

“I learned very early on that I needed female friends with me to come shopping,” he said with a laugh. “Even if I thought something was in the ballpark, I would be wrong."