A recent breakthrough in genetic therapy is promising a viable cure to red-green colour blindness in humans; one of the most common single locus genetic disorders in society.
The dichromatic vision associated with red-green colour blindness arises from a faulty or lacking L-opsin gene which creates visual photo pigments, which are sensitive to long and middle wavelengths used to detect red and green light. The idea behind this new gene therapy is to establish this gene within the eye of a patient, initiating the production of L-opsin and in turn enabling full trichromatic, or normal, vision.
Two monkeys, colour blind from birth, at the University of Washington were able to experience ‘normal’ vision for the first time with the use of this therapy. In order to do this a harmless recombinant virus containing the human L-opsin gene was inserted into the photoreceptor layer of the retina, where red and green cones are normally found. Once in the retina it was established that the pigment production of some of the blue-yellow cones were restricted, allowing the processing of red-green light at these sites while still maintaining blue-yellow vision.
After twenty weeks of daily testing, the monkeys began to respond to visual colour tests for both green and red colours, with their results eventually matching those of a control monkey known to have trichromatic vision.
One of the most interesting and promising aspects of this new technology is the fact that the monkeys who received trichromatic vision successfully were ‘middle-aged’. At first researchers believed that due to a lack of trichromatic neural pathways which are normally established during birth and development, that the monkeys would not be able to process the input of the red green light. Much to their surprise the middle aged monkeys were able to have full colour vision implying that in regards to colour blindness there is no need for evolutionary changes, just a third set of photo pigment cones. This is especially relevant for the possible treatment of adult human’s that have suffered colour blindness since birth, with the option of having colour vision restored at almost any age.
Although experimentation on this new gene therapy is in the early stages, the astounding results are promising a more colourful future for that suffer colour blindness.
By Elizabeth McCourt, 41777882
Original article: http://www.nature.com/nature/journal/vaop/ncurrent/full/nature08401.html
