Nat Neurosci: Study reveals mechanisms of memory formation.

Oct 7, 2020 //--- When the brain forms a new experience of memory, neurons called engram cells encode the details of the memory and reactivate it each time we recall it later.
a new study from the Massachusetts Institute of Technology, the process is controlled by large-scale remodeling of cell chromatin.
this remodeling, which occurs in multiple stages over several days, makes specific genes involved in memory more active.
changes in the density and arrangement of chromosomes (a highly compressed structure consisting of DNA and proteins called histones) can control the activity of a particular gene within a given cell.
Asaf Marco, a postdoctoral student at the Massachusetts Institute of Technology (photo source: www.pixabay.com), is the lead author of the paper, published today in the journal Nature Neuroscience.
the sea mass and other parts of the brain have engram cells.
recent studies have shown that these cell formations are associated with specific memories, and that these networks are activated when that part of the memory is called.
, the molecular mechanisms for coding and retrieving these memories are not yet understood.
in the early stages of memory formation, genes called "instant early genes" are activated in engram cells, but these genes soon return to normal levels of activity.
team at the Massachusetts Institute of Technology hopes to explore what happens later in the process to coordinate the storage of long-term memories.
Marco said: "Memory formation and preservation is a very delicate and coordinated event that lasts for hours or even days, and may even last for months, and we are not sure.
process, there are waves of gene expression and protein synthesis that make the connections between neurons stronger and stronger.
the authors hypothesically assume that these waves can be controlled by an ornamental genome modification, a chemical change in chromatin that controls the accessability of a particular gene.
previous studies by Cai's lab have shown that when enzymes that make chromatin incontigable are too active, they interfere with their ability to form new memories.
To study the oscic genomic changes that occur over time in a single imprint cell, the researchers used genetically engineered mice, which, after they formed a memory, permanently labeled the imprint cells in the hema with fluorescent proteins.
mice were subjected to minor foot electric shocks, and they learned to be associated with cages that were subjected to electric shocks.
when this memory is formed, the haima cells that encode the memory begin to produce yellow fluorescent protein markers.
"Then we can track these neurons forever, we can classify them and ask what happens after an hour of foot vibration, what happens five days later, and what happens when these neurons are reactivated in memory memories," Marco said.
the first stage of memory formation, the researchers found chromosome modification in many areas of DNA.
these areas, chromosomes become looser, making DNA more accessible.
the researchers, almost all of these areas are located in non-coding DNA regions and contain non-coding sequences called enhancers.
researchers also found that at this early stage, chromosomal modification had no effect on gene expression.
then analyzed the cell again five days after the memory was formed.
they found that as memory was consolidated or strengthened over the next five days, the 3-D structure around the chromatin of the enhancer changed, bringing the enhancer closer to its target gene.
still doesn't turn on the expression of those genes.
, the researchers put some of the mice back in the room where they received an electric shock from their feet, reactivated the memory of fear.
the mice's inherited cells, the researchers found that the enhancers often interacted with their target genes, leading to a surge in their expression.
genes developed in this process are involved in promoting the synthesis of proteins in synapses, helping neurons strengthen their connections with other neurons.
researchers also found that the dedes of neurons - branches extended by input from other neurons - developed more echithysts, further evidence that their connections were further strengthened.
Marco said the study was the first to show that memory formation is driven by the initiaters of the exogenomic genome, which stimulates gene expression when memory is called again.
(bioon.com) Source: Neuroscientists discover a molecular mechanism that allows to back to form Original source: Mapping the epigenomic and transcriptomic interplay when memory formation and recall in the hippocampal engram mble, Nature Neuroscience (2020). DOI: 10.1038/s41593-020-00717-0 ,