The culprit of the BASS has been found
Scientists have revealed the secret of the disease that killed Stephen Hawking
An international group of researchers has discovered a gene whose excessive activity leads to the development of a disease from which the famous British astrophysicist Stephen Hawking suffered and died. His description and possible treatment options for this neurodegenerative disease were presented in the journal Nature Neuroscience (Yamada et al., RPS25 is required for efficient RAN translation of C9orf72 and other neurodegenerative disease-associated nucleotide repeats).
Amyotrophic lateral sclerosis (ALS) is a severe incurable disease of the central nervous system that leads to limb paralysis and muscle atrophy. Treatment can only slow down the development of the disease.
As a rule, patients die of lung failure after a few years. There are only two known cases of almost complete cessation of the disease – British astrophysicist Stephen Hawking and British guitarist Jason Becker. The scientist resisted it for more than 50 years, slowly losing all remaining mobility, until he died in March last year due to respiratory arrest.
A group of molecular biologists and geneticists led by Aaron Gitler revealed the secret of the development of this disease by studying how the work of genes in the nerve cells of healthy people and ALS carriers differs.
Many victims of this disease, as scientists say, have one common mutation in DNA – an excessive number of repeats in the C9orf72 gene. This section of DNA is responsible for the assembly of certain proteins involved in the transmission of signals between nerve cells, and the appearance of these repeats somehow contributes to the development of two diseases at once - ALS and one of the forms of senile dementia.
How exactly this gene was associated with the development of amyotrophic lateral sclerosis, scientists did not know, nor did they understand what role it plays in the brain. Hitler, Yamada and their colleagues tried to get an answer to this question by studying the assembly process of protein molecules associated with C9orf72.
"The problem is that these proteins, in principle, should not be produced. These repeats are located in the "junk" part of the gene and they, in theory, do not encode amino acid chains. Nevertheless, cells for some reason read and copy these repeats," explains Shizuka Yamada, a colleague of Hitler at the university (in a press release Quest for molecular cause of ALS points fingers at protein transport, say Stanford researchers - VM).
Scientists found the reason for this in a completely unexpected place – in yeast cells. It turned out that the DNA of these unicellular fungi also contains similar repeats, which are read and processed by the RPS25 gene.
This section of DNA is responsible for the assembly and operation of the protein of the same name, which is part of the so–called ribosomes - the main "protein factories" of the cell that read RNA and assemble amino acid chains.
In the past, RPS25 did not attract much attention from scientists, since this part of the ribosomes did not participate in the assembly of "normal" protein molecules and was mainly associated with various viral infections. As shown by experiments on yeast, the removal or blocking of this part of the ribosomes dramatically suppressed the reading of repeats and the production of associated proteins, reducing their concentration by 50 percent.
Having obtained a similar result, the scientists tested what would happen if the same operation was performed in the cells of people suffering from Stephen Hawking's disease. To do this, scientists created a special retrovirus that removed RPS25 and inserted a short section of DNA into the cell, similar to a key fragment of the C9orf72 gene.
"We were delighted when we saw that blocking RPS25 in human cells dramatically reduced the rate of accumulation of protein debris in cells. The structure of other DNA sites associated with toxic proteins has not changed, but disabling this part of the genome dramatically reduced their activity," the geneticist continues.
At the same time, interestingly, scientists have not recorded any other visible changes in the assembly of normal proteins and the general vital activity of both yeast and human cells. For this reason, it is still difficult to say what the removal of all copies of RPS25 will lead to.
Nevertheless, experiments on fruit flies suffering from the ALS analogue showed that a simple decrease in the activity of RPS25 significantly prolonged their life. This suggests the possibility of using a similar approach to save the lives of carriers of Stephen Hawking's disease, the scientists conclude.
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