Karolinska Institutet

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Epigenetics – the Link Between Genes and Environmental Factors?

A couple of weeks ago, we talked to Louise Sjöholm, Assistant Professor at Karolinska Institutet in Stockholm from the department of Clinical Neuroscience. She investigates the role of the gastrointestinal ecosystem in autoimmune diseases, and is a true expert in the field of epigenetic research. We asked her to tell us about epigenetics.

The term epigenetics, like so many other terms, was derived from a Greek word. The Greek prefix epi– implies features that are “on top of” or “in addition to”, in this case, genetics. However, to fully understand the concept of epigenetics, we need more information. For example, what is genetics? Genetics is the study of heredity in living organisms and explains why living things pass on characteristics (or traits), like height or hair color. Genetics also explains why some diseases, like multiple sclerosis (MS), breast cancer and type 1 diabetes, are passed down from parents to child. We are all born with a set of inherited genes.

Our genetic code or DNA contains a lot of information. The DNA is like an encyclopedia and the different books are our chromosomes. A mutation, a change in DNA, could be viewed as a spelling mistake. All cells have access to the complete encyclopedia, but they are only interested in a couple of pages here and there. This is where epigenetics comes in. It guides the cell and tells it where to look for relevant information: in which book, and more specifically, in which chapter and on what page. The cell is guided by so called epigenetic marks. They are like underlines, crossed out text and bookmarks, telling the cell exactly where to read. Thus, epigenetics influences all physiological processes, from when the egg is fertilized to the day we die. But what happens when things go wrong? Unfortunately, if these physiological, epigenetic, processes are disturbed it can also lead to disease.

What about the influence from environmental factors on these epigenetic marks?
Different types of food have potential to influence these epigenetic marks, or bookmarks in the encyclopedia. One of the most studied epigenetic marks is methylcytosine (a methyl group is added to the base cytosine, C). DNA methylation, the process of adding a methyl group to the DNA, is essential for normal development, and one of the nutrients needed for proper methylation is folate. High folate foods include spinach and other leafy greens. Folate can also be produced by intestinal bacteria. Other environmental factors that can influence the epigenetic process such as methylation, besides from what we eat, are long-term stress, viral infections and smoking. When these essential epigenetic processes are disturbed, we are at an increased risk of developing diseases. Also, if you in addition were born with a genetic variant predisposing you to a certain disease, epigenetics can have a negative synergistic effect.

You are born with a set of genes, but the expression of those genes is not set in stone. Epigenetics is the link between genetics and environmental factors.

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