Regaining the Rainbow: A Gene Therapy Approach to Color Blindness

Interesting article here from Scientific American on genetically engineering a cure for color blindness and the interplay between retinal photoreceptors and brain plasticity(affects 8% of men and less than 1% of woman as it as an X linked trait).
Uvealblues
(..)
Color Correction
Unlike humans, most mammals possess just two kinds of retinal cones. Thus, mice, cats and dogs see the world much the way a red-green color-blind person does, making them ideal experimental subjects. A few years ago scientists at the Johns Hopkins School of Medicine inserted the gene for the human L-type photopigment into mice. After several generations of breeding, the mice responded to the extra hue information. They had changed from dichromats to trichromats—a remarkable feat of bioengineering. The experiment also showed that mouse brains are flexible enough to receive and make use of the additional wavelength information.
An even more ambitious experiment, extending over a decade, came recently to fruition.

It was conducted by the husband-and-wife team of Jay Neitz and Maureen Neitz, both professors at the University of Washington School of Medicine, and their collaborators. The work involved squirrel monkeys, a species indigenous to Central and South America. Among these primates, most females are trichromats, but the males are dichromats, possessing only the S- and M-type photopigments. Accordingly, it is the females that lead troops of monkeys to search for ripe fruits among the foliage, a quest that requires superior color discrimination skills.


The Neitzes wondered: Could gene therapy “cure” the male monkeys’ color blindness? To find out, the biologists developed a way to incorporate the gene for the human L-type photopigment into a small virus known as adeno-associated virus. Next they injected tens of trillions of viral particles into the monkeys’ eyes. Twenty weeks later up to one third of the M-type cones in the animals’ retinas had begun to express the L-type photopigment. In other words, the monkeys now had not two but three cone types: in addition to their original S-type and M-type cones, they had new M-type cones whose sensitivity had shifted toward the long-wavelength part of the spectrum.
The million-dollar question was whether the rest of the animals’ central nervous system could reprogram itself to make use of this additional information. Using a computer-administered color test, the Neitzes demonstrated that the treated monkeys, like the mice from the earlier experiment, did indeed discriminate among colors.