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Genetic editing to prevent the blindness

Using the method of genetic modification CRISPR managed to slow the death of photoreceptors in the retina in mice.

Method for genome editing called CRISPR (or CRISPR/Cas) in the last two years has become one of the most debated topics in science. It literally borrowed from bacteria: in his natural form, the mechanism of CRISPR/Cas is used for destruction of viral DNA in the bacterial cell.


The retina is formed by several tens of types of cells that are stacked in it in several layers, the green cellular layer – photoreceptors rods and cones. (Photo by ZEISS Microscopy / Flickr.com.)

To distinguish viral sequences from its, the bacteria are pretty clever molecular trick that molecular biologists decided to use for their own purposes. The essence of the molecular-genetic method called CRISPR that using enzymes bacterial antiviral defense, genome of different cells can be made very exact changes . As it turned out, this can be done even for a human embryo (about which all of last year in the scientific world was raging stormy ethical discussions). Ethics ethics, however, should not be discounted that from a medical point of view, CRISPR-edit looks very promising, because it can be used to correct mutated genes, thus preventing the development of dangerous diseases.

How this works can be illustrated by the example of experiments by Anand swaroop (Anand Swaroop) and his colleagues from the National eye Institute. The researchers were able to stop retinal degeneration in mice, making using CRISPR to silence one of the genes that regulate the development of photoreceptors – rods and cones. As we know, rods and cones convert light into neural impulses: cones are responsible for color vision and operate in bright light; sticks, on the contrary, help us to see when light is low, in addition, they nourish and support the cones. From mutations are more likely to suffer a stick, but because of the dying begin to die sticks and cones. As a result, developing retinitis pigmentosa – an inherited degenerative disease, ending in complete blindness.

Like the solution suggests itself: if we have a method that allows you to edit the genes, then why not fix the mutation in the sticks? So I tried to do, but even in one and the same individual deleterious mutations in the sticks are quite varied, and fix them all at once is almost impossible. But there is a workaround: in an article in Nature Communications says that bad influence of a variety of genetic defects can be overcome, if you disable the sticks only one gene Nrl. This gene encodes one of many transcription factors, the so – called proteins, which are associated with certain sequences of DNA and thus affect the activity of genes.

And cones, and sticks during development of the retina obtained from the same precursor cells, and gene Nrl depends on who will stick and who the cones. Moreover, Mature coli gene Nrl are needed in order to maintain its “Palacavicchi”. If the gene Nrl stops, the stick begins to resemble the cones – but, moreover, as mentioned above, the negative mutation in the sticks lose their force and in the end, and sticks (though similar to cones), the cones remain in place and continue to work.

The authors used a genome editing method called CRISPR in order to disable the chopsticks gene Nrl. Experimenting with mice genetically predisposed to degenerative disorders of the retina. Molecular machine system genetic editing, animals were injected with a special virus-a porter (usual in such cases, reception) – virus smuggled editing molecules directly into the cells of the retina.

Everything happened as expected: sticks with disabled Nrl become like cones, thus they ceased to feel the light, but remained alive and continued to support and nurture cones. In older mice, the effect was weaker, but anyway, all experimental animals retinal degeneration, if not stopped, at least slowed markedly. While it is unknown whether there are any negative side effects, but if you can’t find them in animal experiments, nothing puts to begin clinical trials with patients suffering from progressive blindness.

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