By editing the genes of certain hereditary diseases can be if not cured completely, or at least significantly weaken.


The motor neuron of the spinal cord; motor neurons die during his illness, Lou Gehrig. (Photo: Harris Lab / Georgetown University.)

The hair cells of the inner ear perceive the sound vibrations and converts them into electrical signals. Mutations in the Tmc1 gene cause the death of hair cells and, as a consequence, gradually progressive deafness. (Photo: budgyd / Flickr.com.) ”

New method for genome editing CRISPR/Cas9 continues to demonstrate its effectiveness: recently released two articles about how using CRISPR/Cas9 managed to cope with deafness and neurodegenerative Lou Gehrig’s disease (or amyotrophic lateral sclerosis) . However, it is worth to say that the experiment is so far only on mice, and neither deafness, nor from disease, Lou Gehrig animals to deliver to the end failed; however, it is important that all managed to find some remedy for genetic disorders previously considered incurable.

The feature of the method of CRISPR/Cas9 is that it allows quickly and precisely to correct a specific location in the genome. Have amyotrophic lateral sclerosis are hereditary forms associated with certain mutations among hereditary forms 20% of cases are attributed to mutations in the gene SOD1, which encodes the enzyme superoxiddismutase-1. As we know, any gene exists in our genome in at least two variants, paternal and maternal, so it would seem that if one of them is out of order, can save the situation another. However, mutations can not only disable the gene, they can do so that he will be the main and that all the work in normal protein intercept of the mutant protein.

Disease Lou Gehrig is often exactly what happens: because of the strong, or, to put it more scientifically, dominant mutations in the gene superoxide dismutase-1 cells get the wrong enzyme, and resulted in nervous tissue begin neurodegenerative processes. Motor neurons in the brain and spinal cord die, which developed paralysis and muscle atrophy, leading eventually to death. Researchers from the University of California at Berkeley “unleashed” molecular machine CRISPR/Cas9 for a mutation in the gene SOD1. Genetic editor using modified viral particles were delivered to the neurons of the spinal cord, where it would shut off the mutant gene, which is even now not interfere with its normal copy.

In an article in Science Advances says that the mice that received the genetic editor, the disease occurred later, and the survival of animals increased by 25% (if without treatment, mice with Lou Gehrig’s disease lived 4 months, with a genetic treatment for a month longer). Obviously, you can achieve greater success if the system edit will affect a greater number of diseased neurons, but in principle, as we see, against some forms of amyotrophic lateral sclerosis CRISPR/Cas9 can be used. (In fairness, it should be clarified that although, as we said, a mutation in the gene SOD1 underlie 20% of cases of the disease Lou Gehrig, in General they make up only 2% of the total number of cases.)

Another example of a successful edit is described in Nature Xue Gao (Gao Xue) and her colleagues from Harvard. They used the CRISPR/Cas9 against mutations in a gene called Tmc1, from which depends the auditory cells in the inner ear. In Tmc1 also can appear dominant mutations that “score” a healthy version of the gene, and if a person got such, he begins to lose his hearing since childhood – his auditory cells gradually die.

The researchers injected system CRISPR/Cas9 directly into the inner ear of the mice of line Beethoven who are born with a mutation in one copy of the gene Tmc1 and they become completely deaf to the eighth week of life. Editing machine was introduced to each animal only in one ear that was with what to compare. While editing for the delivery of molecules into cells used modified viruses, and lipid special wrapper – this method of delivery, according to the authors, allowed the system to work with far greater precision.

By the fourth week of life mice the ear not treated, heard sounds quieter 75-80 decibels, which can be compared with some appliances. On the contrary, the ear that has been treated with CRISPR/Cas9, deconstructing the sounds of 60 decibels and above, which corresponds to a quiet conversation. On the other hand, healthy mice begin to hear 30-40 dB, so in spite of the genetic correction, mutant ears still heard worse, and the sensitivity continued to fall.

At the same time, according to the portal The Scientist, man the difference of 10-15 dB is very noticeable, that is, even if the method will work not at full strength, he still significantly improve the hearing to the patient. And while talking about the clinical application of genetic editing is too early, perhaps already not far off those times when using CRISPR/Cas9 to treat hereditary forms of deafness, neurodegenerative disorders and other diseases.