Epigenetics Explained

Epigenetics is an emerging field of science that, eventually, could have massive implications on how we address our health and that of future generations. The world literally means “on top of the genes,” and that sums up the epigenome’s role in the body.

All of us have DNA which, unless you have an identical twin, is completely unique. Almost every cell in our body contains all of our DNA and all of the genes that make us who we are; this is known as the genome. But obviously we are not all made up of just one type of cell. Our brain cells do different things from those in our heart, for instance, who behave differently than our skin cells. If all of our cells have the same information, how is it that they do different things?

This is where epigenetics comes in. It’s basically a layer of instruction on top of our DNA that tells it what to switch on, how to perform and so forth. You can think of it like an orchestra: our DNA is the music, and the epigenome is the conductor, telling the cells what to do and when. Everyone’s personal orchestra is a little bit different. So while the epigenome doesn’t change our DNA, it’s responsible for deciding what genes will be expressed in your body’s cells.

Here’s how it works: each cell with all of your DNA waits for outside instruction to give it instructions. This comes in the form of a methyl group, a compound made from carbon and hydrogen. These methyl groups bind to the genes, letting them know when to express themselves and when to stay dormant, and they bind differently depending on where in the body the DNA is.

Histones also play a role in epigenetics and how genes express themselves. Histones are the protein molecules that DNA wind itself around. How tightly wound the DNA is around the histone plays a role in how strongly a gene expresses itself. So the methyl groups tell the cell what it is (“you’re a skin cell, and here’s what you do”), and histones decide how much the cell is going to crank up the volume, so to speak. Every cell in your body has this methyl and histone combination, instructing it what to do and how much to do. Without the epigenome giving instructions to your cells, the genome, our bodies wouldn’t know what to do.

What makes this interesting is that while our genome is the same from the time we are born to when we die, our epigenome changes throughout our lifetime, deciding what genes need to be turned on or off (expressed or not expressed). Sometimes these changes happen during major physical changes to our body, like when we hit puberty or when women are pregnant. But, as science is beginning to discover, external factors to our environment can prompt epigenetic changes as well.

Things like how much physical activity we engage in, what and how much we eat, our stress levels, whether we smoke or drink heavily and more can all make changes to our epigenome by affecting how methyl groups attach to the cells. In turn, changing the way methyl bonds to the cells can cause “mistakes,” which can lead to disease and other disorders.

It seems like because the epigenome is constantly changing, that each new human would start with a clean, fresh epigenome slate — that is, that parents wouldn’t pass their epigenomes on to their offspring. And while that’s what should happen, sometimes these epigenetic changes get “stuck” on the genes and are passed down to future generations.

One example of this is the Dutch Hunger Winter Syndrome. Babies who were exposed to famine prenatally during World War II in the Netherlands had an increased risk of metabolic disease later in life and had different DNA methylation of a particular gene when compared to their same-sex siblings who were not exposed to famine. These changes persisted six decades later. (1)

Another study found that while identical twins are largely epigenetically indistinguishable from each other when they’re first born, as they aged, there were vast differences in their methyl groups and histones, affecting how their genes express themselves, and accounting for differences in their health. (2)


3 Potential Benefits of Epigenetics 

So far, it sounds like epigenetics is just kind of scary — the worst of our habits or life situations being passed down not only to our children, but perhaps even our grandchildren. While epigenetics is still very much in its infancy, there is a lot to be excited about.

1. It could change the way we treat disease. Because the epigenome controls how genes behave, an erroneous epigenome can behave like a genetic mutation. This can lead to an increased risk for diseases like cancer or autoimmune disorders, even if the genes below the epigenome are perfectly normal. As we learn more about what causes those epigenetic errors, scientists can develop drugs that would manipulate the methyl groups or histones that are causing the epigenomic errors, potentially finding a cure for the subset of diseases caused by epigenetics.

2. It could change the way we treat addiction. We already know that some people are more vulnerable to addiction than others. But there is no one “addiction gene,” as it’s a combination of inherited and environmental factors that lead to addiction. Researchers have now found that epigenetic mechanisms play a role in the brain when it comes to addiction, influencing how the genes express themselves to develop addiction and also how the predisposition to addiction is passed along to future generations. (3) (4)

A better understanding of how the epigenome affects addiction could mean changing the way addiction is treated in order to prevent a person’s offspring from an increased risk of addiction.

3. It could change the way we address trauma. One of the earlier theories around epigenetics is how traumatic events like surviving the Holocaust might change a person epigenome, along with that of their offspring. One small study suggests that the children of Holocaust survivors inherited a specific response to stress. (5)

Another found that children of women pregnant during the September 11 attacks had lower levels of cortisol, which could leave them more vulnerable to post-traumatic stress disorder. (6) These were both small studies and have their detractors, but while these studies might not be conclusive, it’s not a stretch to think that major traumatic events could find a way of altering someone’s epigenome enough to pass down to offspring.


Precautions

Epigenetics is still extremely young, and many of the studies around the topic are quite small, so it’s hard to say anything is conclusive. Additionally, sometimes epigenetics seems like just one more thing that women who might potentially one become pregnant must worry about (though investigators believe that fathers could pass down epigenetic information at the time of conception, not enough research in humans has been done yet). This could get morally murky in terms of how we dictate what women can and cannot do because they might someday bear children.

No one is sure just how much what we do influences the epigenome, either. While doing all of the usual things like sticking to a healthy diet, exercising regularly, limiting alcohol will all positively affect your health, can they reverse previous damage to the epigenome? It’s still unclear in humans. Most of the work done on epigenetics thus far has been on animals, and how much this translates to people remains to be seen.

There is one glimmer of hope in the animal world, though. A study done on rats found that the babies of mothers who were attentive were happier than those with inattentive mothers. There was a difference in the methylation levels between the happy and less happy baby rats, which affected how the gene that controlled their stress response was expressed. But when the less happy babies were adopted by the more attentive rat mothers, they actually grew up to be happier — that is, the methyl differences weren’t permanent and were able to be changed. (7)

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