It's not always okay to remember every little detail of a past memory, as some might just bring up all the unwanted scenes back in your mind. Now, we are one step closer to understanding how engram cells work in a molecular mechanism to form memories.
Engram cells are on duty to encode the details of a specific memory and later reactivate them once you want to remember it again. A new study by MIT shows that the encoding process is operated by remodeling of the chromatin within engram cells — a highly compressed structure consisting of DNA and histones protein.
The study has been published in the journal Nature Neuroscience.
“This paper is the first to really reveal this very mysterious process of how different waves of genes become activated, and what is the epigenetic mechanism underlying these different waves of gene expression,” says Li-Huei Tsai, the director of MIT’s Picower Institute for Learning and Memory and the senior author of the study.
Engram cells can be found in different parts of the brain and they form networks containing particular memories.
What intrigued scientists was to know what would happen to those genes in engram cells after the recalling process is over and the genes are turned off.
Not a quick process
The remodeling allows specific genes taking on memory storage to become more active. However, it is not a short process. It takes gradual steps for a few days. Chromatins' density changes can actually control the genes' state of activity in a cell, the study revealed.
“The formation and preservation of memory is a very delicate and coordinated event that spreads over hours and days, and might be even months — we don’t know for sure," the lead author of the study Asaf Marco explains. “During this process, there are a few waves of gene expression and protein synthesis that make the connections between the neurons stronger and faster.”
The researchers didn't figure out how long the duration of epigenomic modifications was, though. However, the lead author of the study supports the idea that they may remain for weeks or perhaps months. Now, he plans to draw upon the current study to find out about the chromatins' role in Alzheimer's disease.