Turning sticks into cones preserves vision
In experiments on a mouse model of retinal pigment degeneration – a disease that gradually leads to complete blindness – researchers at the University of Washington, working under the direction of Dr. Joseph Corbo, reprogrammed rods – light-sensitive eye cells that provide night vision. This manipulation made the cells more like cones – light–sensitive cells that provide daytime vision - and prevented retinal degeneration. Currently, scientists are conducting additional experiments, the purpose of which is to confirm the safety of animal vision.
Mutations of more than 200 genes are associated with various forms of blindness. Currently, specialists are working on methods of gene therapy for a number of similar diseases. However, Corbeau and his colleagues decided to move away from the search for treatment methods that correct the manifestations of individual mutations and direct their efforts to the development of universal therapeutic approaches that would facilitate the manifestations of many forms of visual impairment. To implement this idea, they study genetic factors that allow cells of the developing eye to acquire specialized characteristics necessary for vision.
The retina contains two types of photoreceptor cells: rods and cones, which provide night and day vision, respectively. With retinal pigment degeneration, the rods die first, which deprives the patient of the ability to see in the dark. Daytime vision is often completely preserved for a certain time, however, it also fades over time as a result of the death of cones.
The authors identified several genes whose activity is characteristic exclusively for rods or cones, but not for two types of photoreceptors at the same time. One of these genes is the Nrl gene, the protein product of which determines the differentiation of cells of the developing eye into rods. Blocking the activity of this gene in the cells of the mouse embryo leads to the appearance of animals whose retina contains only cones.
Scientists decided to check whether such a metamorphosis is possible in adulthood. To do this, they created a mouse model of retinal pigment degeneration with regulated activity of the Nrl gene. It turned out that blocking the activity of Nrl in the adult body leads to the partial transformation of rods into cones. A few months after this procedure, when the control group mice had almost completely lost their sight, the retina of the experimental group animals showed higher levels of electrical activity, which indicated that vision was preserved.
The light-sensitive cells of the eye form the upper purple and pink layers in these images. On the left are the cells whose reprogramming increased their resistance to retinal pigment degeneration, which ensured the preservation of more cells than in the right image.
Currently, researchers are searching for other critical developmental factors that will ensure a more complete transformation of rods into cones.
They hope that this manipulation will help alleviate the manifestations of other diseases in which the sticks die first, such as macular degeneration.
Article by C. L. Montana et al. Reprogramming of adult rod photoreceptors prevents retinal degeneration is published in the journal Proceedings of the National Academy of Sciences.
Evgeniya Ryabtseva
Portal "Eternal youth" http://vechnayamolodost.ru based on the materials of Washington University School of Medicine: Altering eye cells may one day restore vision.
29.01.2013