Most cases of developing dementia may not be associated with hereditary factors and with the advent of new “point” mutations in a small set of genes in individual cells of the brain. Write about genetics in a paper published in the journal Nature Communications.
“The population is aging rapidly, and today more and more people suffering from senile dementia. We still do not understand where are those problems and why some of us become victims and others do not. Dementia has a genetic background, but somehow this does not affect the inheritance,” says Patrick Chinnery (Patrick Chinnery) from the University of Cambridge (UK).
Extinguished the lights of reason
And Alzeihmer disease, and Parkinson’s disease are caused by the accumulation in nerve cells of various protein “garbage”, which gradually kill neurons in different parts of the brain. Their death leads to memory loss and dementia in the first and second case, and a loss of control over limbs with the development of Parkinson’s disease.
The reasons for the development of these diseases and other forms of dementia remain a mystery to scientists. The search for their roots is complicated by the fact that only 5% of cases of dementia biologists and doctors find clear hints that the patients had inherited the problem from their parents. This prevents the disclosure of the mechanisms of development of these diseases and identify risk factors.
Chinnery and his colleagues found a possible explanation for all these oddities, analyzing how small mutations distributed in different regions of the brain in about five dozens of elderly people, some of whom were suffering from the “classic” dementia and Alzheimer’s disease.
Selecting about two hundred samples of fabrics and 600 thousand cells, the researchers extracted DNA samples and read each of them five thousand times, eliminating the possibility of accidental error in compiling a list of “typos” in the genome of neurons. After that they have identified one hundred genes associated with the development of diseases of the brain, and compared their structure in each sample of brain.
The genetic kaleidoscope
As the researchers note, they were interested in two things – is the structure of these genes in cells of the same brain, and how often are such “anomalies”. Their presence, in turn, suggests that these mutations are not inherited from the parents, and appeared after fertilization of the ovum.
“These mutations occur in the DNA during cell division, which may explain why many people become victims of Alzheimer’s and Parkinson’s, not having relatives with these ailments. They are formed during brain development of the fetus, and “sitting in ambush”, waiting for when their owner is age,” explains Chinnery.
As it turned out, such “typos”, so-called somatic mutations that existed in the brain cells about half of the elderly people studied by the authors. However, they were present in the nervous tissue of healthy participants of the experiment and in the neurons of the media, dementia and Alzheimer’s disease.
Later, scientists found that these mutations were found in the brain of patients and healthy elderly people is far from random. For example, senile dementia has been associated with damage to the DNMT3A and TET2 genes that control the growth of blood vessels of the brain and the work of the barrier between the circulatory system and tissues.
A further search of similar somatic mutations in the brains of patients with dementia, as scientists hope, will help to assess how much these new “typos” in the DNA influence its development. This, according to Chinnery, it is critical to understand whether to help the medicines that are being developed for the treatment of Alzheimer’s disease, the masses of people.