Why Methylation May Be Key to Memory Formation
Methylation, the donation of methyl (CH3) molecules, is a primary mechanism by which genes in a cell’s DNA are turned off. Lack of methyl groups or removal of methyl groups (demethylation) causes genes to remain or become activated.
In a process called epigenetics, cells also use methylation to specialize later in development without relying upon the instructions contained in the cell’s DNA. This type of specialization is especially vulnerable to environmental factors, such as nutritional deficiencies and exposure to toxins.
In a recent study published in the journal Neuron, researchers suggest that this type of epigenetic methylation may be key in forming memories.
In their experiments, the researchers conditioned fearful memories in rats by giving the animals mild shocks when they were in a specific training chamber. The researchers could then test whether the rats remembered the conditioning by observing whether they froze when placed in the chamber.
Using drugs that inhibit methylation, the researchers showed that methylation was necessary for rats to form such memories. Particularly importantly, the researchers found that the level of methylation directly controlled the activity of genes known to either suppress or promote memory formation. The memory suppressor gene they studied is called protein phosphatase 1, and the memory-promoting gene is called reelin.
“To our knowledge, this study is the first to present evidence that DNA methylation, once thought to be a static process after cellular differentiation, is not only dynamically regulated in the adult nervous system but also plays an integral role in memory formation,” concluded Miller and Sweatt. They wrote that their findings indicate that DNA methylation has been co-opted by the central nervous system as a “crucial step” in regulating gene activity involved in memory formation.
This finding is big news. Twenty years ago, many people thought that since nerve cells were no longer replicating after birth, that there would be no need for methylation/demethylation to turn genes off/on. Now, though, research increasingly suggests that that isn’t the case.
Methylation disregulation is observed in many conditions, including cognitive decline, autism, schizophrenia, and cancer. For example, in autism, environmental toxins such as mercury and ethanol can directly interfere with the function of an enzyme in a critical vitamin B12-dependent methylation pathway. In schizophrenia, methylation is faulty and leads to insufficient release of reelin, the memory-promoting gene. In cancer, tumor-suppresor genes are turned off via methylation, resulting in uncontrolled cell division.
This recent research highlighting an important link between methylation and memory reinforces the importance of:
- Ensuring an adequate supply of methylation-related nutrients (e.g., folic acid, vitamin B12).
- Avoiding environmental contaminants that may interfere with proper methylation function (e.g., heavy metals).
For more on the role of nutrition and environmental factors in maintaining cognitive function, see here.
Related articles:
Key Nutrients in Helping to Prevent Cognitive Decline
More Evidence of the Importance of B12 in Preventing Dementia
March 21st, 2007 at 9:13 am
[…] Today, I would like to draw your attention to a recent post on Marc Joseph’s Nutrition Blog where he’s featuring a hot topic article (published in Neuron) on how epigenetics might drive information storage in the brain. […]