Red-Green color blindness is caused by a deficiency in opsin genes. These genes code for photoreceptor proteins positioned in the cone cells of the eye's retina. When light hits these proteins a tiny molecule buried inside the protein called retinal (aka vitamin A) changes its shape by swinging its bond angles and begins a signal transduction cascade. The signal of "red" or "green" is passed from this single "g-coupled" protein receptor along the optic nerve and eventually to the brain's visual cortex where the mind perceives the hue of that specific wavelength of light. This gene for this opsin resides on the X chromosome which means colorblindness has a higher incidence in males as females have two chances to get a good copy while men only have one.
A paper published this week in Nature describes research that essentially cured colorblindness in monkeys. This cure is miraculous because A.) it was done using gene therapy and B.) it was given to adult monkeys not monkey embryos. The researchers took a virus, inserted the corrected copy of the opsin gene into the virus' genetic material then locally injected the virus near the monkey's deficient retina where the virus proceeded to "invade" and insert the correct copy into the genomes of the retinal cells. Lo and behold, the monkeys were able to see color for the first time in their lives!
The researches say if they are able to hone the technique to where it is as safe as Lasik surgery it may one day be applied to humans. Research like this raises some questions as to enhancing our natural abilities. If we extrapolate this technique to brain proteins we need to ask some tough questions. If we knew of a gene that could make a human brain work more efficiently, thus making the individual smarter, should we allow people to have "corrected" brain genes injected? If Joe Millionaire could afford this but Joe six-pack could not should the government step in to avoid the rise of a genetic cast system paralleling the present day financial cast system? The prospect of broadly applied corrective gene therapy really is the pinnacle goal of so much bio-medical research, specifically when it comes to inborn errors of metabolism and other very clear single gene, single disease situations. But who will guide society through the slippery slope of choosing which genes are worthy of correction. Work continues on the "can we" side but I think all citizens regardless of their scientific background need to take part in the "should we" conversation. If this is not a healthy conversation I fear that very useful and beneficial gene therapy treatments will be the proverbial baby in the bathwater when the anti-GMO, anti-vaccine masses catch wind of these kind of available "treatments."
What do you think about this? Listen to the primary researcher - Jay Neitz - discuss the experiments in the following Nature podcast.
Mancuso, K., Hauswirth, W., Li, Q., Connor, T., Kuchenbecker, J., Mauck, M., Neitz, J., & Neitz, M. (2009). Gene therapy for red–green colour blindness in adult primates Nature DOI: 10.1038/nature08401