Biologists have analyzed genomic changes in cells that are active during the formation of memories in the brain of mice. It turned out that when mice gain new experience, the three-dimensional organization of their cells' DNA changes and genes become more readable, but this does not enhance their work.. Only with the reactivation of neurons (remembering information) does the work of genes increase due to the formation of new interactions with regulatory sequences. Research published in the journal Nature Neuroscience.
When a new experience is gained, neural circuits appear in the brain - engrams, which include engram neurons in the hippocampus and other brain structures.. It is engrams that are responsible for the formation of memories: in the process of memory transition from episodic to long-term, the connections of neurons in the engram become stronger. It is believed that this is due to a change in the work of genes in the cells of engrams, however, the processes underlying the strengthening of connections have still been poorly understood..
The work of genes and the number of readings depend on the three-dimensional organization of DNA molecules in the nucleus.. This is due to small DNA sequences - enhancers, the interaction with which helps enzymes sit on the desired gene and activate its work. Therefore, physical distance to enhancers plays a key role in gene function.
Biologists at the Massachusetts Institute of Technology led by Asaf Marco decided to investigate the changes in the three-dimensional organization of the genome during the formation and consolidation of memories.. To do this, the researchers created transgenic mice, whose neurons, when activated, synthesized a yellow fluorescent protein.
A classic experiment on the formation of responses to a frightening stimulus was carried out on animals: mice were placed in cages, on the floor of which current discharges were applied that hit the paws of mice. At the same time, scientists sounded a beep. After that, brain tissue samples were collected from some mice and luminous (that is, cells active in the formation of an engram) cells were determined.. Five days later, the mice were reminded of the stimulation, including the same sound signal: they were afraid of another blow and froze.. Fading indicates re-activation of the engram, which was formed after an electric shock.
After that, the researchers collected about 10 thousand cells from mice to analyze the three-dimensional organization of their genome and the work of genes.. To do this, they created a map of genomic contacts, on which they noted which DNA regions are in contact with each other more often.. The researchers also checked how accessible DNA is for enzymes based on data on the proteins on which it is " It turned out that genes within populations of cells at all stages of memory formation were in contact with enhancers more often (p Key words:.