Written by Arda Kizilkaya
Epigenetics is the study of how environmental influences and behaviors can cause changes that can affect the way that your genes work. However, epigenetic influences do not change your DNA sequence, but it does change how your body reads a DNA sequence.
How Epigenetics Work:
Epigenetic changes affect the reading of a DNA sequence in multiple different ways such as:
DNA Methylation and Demethylation:
DNA methylation involves the covalent transfer of a methyl group to the C5 position of the cytosine ring of DNA. In plants, cytosines are methylated in both symmetrical or asymmetrical, but in mammals, DNA methylation occurs at cytosines in any context of the genome. Usually, this chemical group is added to specific places in the DNA, where it blocks the proteins that attach to DNA to “read” the gene. This group can be removed by a process called Demethylation. DNA demethylation can be passive and active. The passive process takes place when methylation is absent in newly synthesized DNA strands. While the active process occurs via direct removal of a methyl group independently of DNA replication.
Non-Coding RNA
Non-coding RNAs are a cluster of RNAs that do not encode functional proteins and were originally considered to merely regulate gene expression at the post-transcriptional level, but a wide variety of recent studies have suggested that miRNAs, piRNAs, siRNAs, and long non-coding RNAs are the most common regulatory RNAs, and there is growing evidence that regulatory non-coding RNAs play an important role in epigenetic control. Therefore, these non-coding RNAs (ncRNAs) highlight the prominent role of RNA in regulating gene expression.
When Epigenetics Was Found:
The term "epigenetics" was introduced in 1942 by embryologist Conrad Waddington, relating it to the 17th-century concept of "epigenesis", which defined it as the complex developmental processes between the genotype and phenotype. in the years that followed, these processes, in particular gene regulation, were tackled, not in the frame of epigenetics but of genetics, research labeled "epigenetics" rose strongly only in the 21st century.
How can your Epigenetics Change:
Your epigenetics change as you age, as part of normal development and aging, and in response to your behaviors and environment.
Epigenetics and Development:
Epigenetic changes begin before you are born. All of your cells have the same genes but look and act differently. As you grow and develop, epigenetics helps determine which function a cell will have, for example, whether it will become a heart cell or a skin cell.
Epigenetics and Age:
Your epigenetics change throughout your life. Your epigenetics at birth is not the same as your epigenetics during childhood and adulthood.
Epigenetics and Reversibility:
Not all epigenetic changes are permanent. Some changes can be added or removed in response to changes in behavior or environment e.g. smoking can result in epigenetic changes. The difference is bigger for heavy smokers and long-term smokers. After they quit smoking, former smokers can begin to have increased DNA methylation at this gene. After some time, they can reach levels similar to those of non-smokers. The recovery time depends on how long and how much someone smoked before quitting.
Infections:
Germs can make epigenetic changes to weaken your immune system. This helps the germ survive. For example, Mycobacterium tuberculosis causes tuberculosis. The type of infections with these germs can cause changes to histones in some of your immune cells that result in turning off the IL-12B gene. Turning off that gene weakens your immune system and improves the survival of Mycobacterium tuberculosis.
Cancer:
Certain mutations make you more susceptible to developing cancer. For example, having a mutation in the BRCA1 gene that prevents it from working properly makes you more likely to get cancer. Similar to that, increased DNA methylation that results in decreased BRCA1 gene expression raises your risk for cancer. While cancer cells have increased DNA methylation at certain genes, overall DNA methylation levels are lower in cancer cells compared with normal cells. Different types of cancer that look alike can have different DNA methylation patterns. Epigenetics can also be used to help determine which type of cancer a person has or can help to find hard-to-detect cancers earlier. Epigenetics alone can't diagnose cancer, and cancers would need to be confirmed with further screening tests.
Nutrition During Pregnancy:
A pregnant woman’s environment and behavior during pregnancy can change the baby’s epigenetics. Some of these changes can remain for decades and might make the child more open to getting certain diseases.
References:
DNA methylation: Superior or subordinate in the epigenetic hierarchy? (2022). PubMed Central (PMC). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3174260/
Non-coding RNAs as regulators in epigenetics (Review). (2022). PubMed. https://pubmed.ncbi.nlm.nih.gov/27841002/
(n.d.). ScienceDirect. https://www.sciencedirect.com/topics/biochemistry-genetics-and-molecular-biology/
What is epigenetics? The answer to the nature vs. nurture debate. (2020, October 30). Center on the Developing Child at Harvard University. https://developingchild.harvard.edu/resources/what-is-epigenetics-and-how-does-it-relate-to-child-development/
What is epigenetics? (2022, September 15). Centers for Disease Control and Prevention. https://www.cdc.gov/genomics/disease/epigenetics.htm#ref2
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