A genetically diverse brain
The brain can change its DNA
Alexey Timoshenko, GZT.RUBrain cells are genetically heterogeneous.
Neuroscientists and geneticists from the USA and Spain offer a unique explanation of the nature of human personality. The work of scientists radically changes many of the established ideas.
Researchers who published their article in the journal Nature have made a discovery that contradicts most textbooks of physiology and general biology. Previously, it was believed that all human cells carry the same set of genes. Today, scientists have discovered the exact opposite: the cells from which the human brain is formed undergo genetic modifications during their development and their DNA is not the same at all.
Chimeric brainScientists have known before that the human body can consist of cells with different genetic sets.
For example, in the summer of 2009, it was reported that human blood sometimes carries different DNA than that found in other tissues. The researchers also knew that a certain number of mother cells can enter the child's body: most people are also "chimeric" for this reason.
(Chimera is a mythical monster made up of different animals – a lion, a goat and a dragon. Biologists call chimeric organisms those that carry genetically heterogeneous cells.)
The group led by Fred Gage managed to discover something else. Firstly, scientists have identified genetic diversity in the brain and, secondly, have shown that the mother's cells that accidentally got into the body have nothing to do with it. Fred Gage and his colleagues have discovered a mechanism that changes the genome of future nerve cells. Judging by the results of the study, these changes play a very important role in the work of the brain.
Jumping on DNA
Figuratively speaking, the human genome can be represented in the form of several dozen books, each of which is one chromosome and each of which includes about 20 thousand chapters, genes. Each chapter describes how to synthesize a certain molecule, As a result, according to these instructions, the cells of the body collect everything necessary for life. The set of chapters (genes) is unique and, as biologists once believed, fixed once and for all immediately after fertilization of the egg. Someone receives genetic instructions for the synthesis of a large number of melanocytes in the skin (then the skin becomes dark), someone receives a set of enzymes for more efficient splitting of milk sugar (this allows milk to be absorbed), and someone will be unlucky and in one of the "chapters" a protein will be described, the presence of which will lead to increased risk of developing obesity.
These instructions remained unshakable for quite a short time. Biologists have also identified so–called retrotransposons - pieces of DNA that can move independently from place to place. In a book analogy, it would look as if a part of the text suddenly moved from the beginning of the book to the middle or even to the end, which significantly affects the overall meaning of what is happening in the book, more precisely, in life. In corn, for example, such jumps of transposons along DNA lead to a change in the color of individual grains (W.P.Armstrong 2000; photo from the website waynesword.palomar.edu ).
Not so long ago, it was believed that about 600 thousand copies of retrotransposons in the human body do not have a serious impact on such a delicate area as the work of the brain. This opinion is now recognized as erroneous.
The change will happen not in the minds, but in the genes
Experimenting with human brain cells, scientists have found out that the movements of DNA fragments, retrotransposons, occur in them as well. It was not easy to demonstrate this effect: the researchers had to place a special label in the DNA, which was activated only when copying and inserting a retrotransposon and at the same time triggered the synthesis of a fluorescent protein.
The presence of fluorescent green labels in the grown cell cultures allowed not only to confirm the hypothesis of DNA variability in the brain. Scientists have found along the way that these changes affect neurons, and not cells that play an auxiliary role and provide neurons with nutrition. In addition, it was also possible to show that the period of activity of retrotransposons lasts only a few days – this was also a discovery.
Thus, if a mechanism that ensures genetic diversity is activated in a developing organism for a very short time compared to the full term of pregnancy, then with a high probability this means that such inclusion is not accidental. Perhaps this is how human (and not only) individuality is ensured, because even twins with initially identical DNA have a brain built from genetically dissimilar cells.
It is important to note that this work was carried out on human, and not on mouse or rat cells. Obtaining human cell cultures is more difficult and is associated with a large number of ethical restrictions, but the results are much closer to people.
Portal "Eternal youth" http://vechnayamolodost.ru01.09.2009