What is epigenetics?

In the quest to learn more about ourselves on a genetic level, we must understand that genetics only helps to add more pieces to the puzzle, but still cannot answer everything. For this reason, epigenetics has become just as important as genetics when understanding ourselves.

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Everything about who we are is a result of a complex interplay or how we’re made, and what we do.

Our genes are the fundamental component that determines “how we’re made”. They can be thought of as a set of chemical instructions for how to make you, you. Despite carrying this treasure trove of information, genes have often been described as chemically ‘boring’, taking part in very little activity besides being an information store.

However, in recent decades it has become clear that this could not be further from the truth, and we now know that genes can dynamically change their activity in response to the environment we find ourselves in.

Just how does this happen? That’s where epigenetics comes in.

Genes alone cannot do much, they require other components in the cell to carry out their function. If genes are a carefully stored set of instructions, epigenetic markers are like gatekeeping librarians -  they determine which genes are read, and when.

Epigenetic modifications sit ‘above’ the genes and influence the degree to which other factors in the cell can access the genes, read the instructions and carry out a particular function.

Just as the entire collection of your genes is known as the genome, the collection of epigenetic modifications you carry is known as the epigenome. Epigenetic changes are common and occur perpetually throughout your body to regulate cellular activity. The influence of their effect ranges from relatively minor, such as increasing the production of a particular protein to help your muscles recover after training, to major effects like cell differentiation – epigenetics is the reason your skin cells are skin cells and not liver cells, for example.

The DNA genome is fixed for life, but the epigenome reacts to various factors that we encounter in our lifestyles including diet, exercise and stress. This is why epigenetics is understood as the science of change, and can even have biological ramifications that span generations. Epigenetic change is a regular occurrence but can also be influenced by several factors including age, the environment, and disease state

There are three widely accepted mechanisms that epigenetic change can take place – DNA methylation, histone (the proteins that DNA is wrapped around inside cells) modification, and RNA silencing. Of these, methylation is by far the most well understood.

One of the most well-known examples of epigenetic changes spanning generations is the Dutch hunger winter. During a period of intense famine from 1944-1945, pregnant women had to carry babies under conditions of severe calorie restriction. These extreme conditions triggered epigenetic changes not only in the mother but also in the children they carried, who grew up to be far more susceptible to obesity, diabetes and cardiovascular disease.

Research into the long-term impact of these epigenetic changes by Heijmans et al found that even 6 decades later, children of the Dutch hunger winter had less DNA methylation of the IGF2 gene (a key growth regulator) compared to their unexposed siblings. This association was very specific, it only occurred in children who were exposed prenatally, which reinforces that early development is a crucial period for establishing and maintaining epigenetic marks. This clearly illustrates how environmental conditions can affect genetic activity and lead to changes that are passed on through generations.

DNA methylation is the process of adding a methyl group to a DNA strand, which turns the gene off, while removing a methyl tag turns genes on. Abnormal methylation can be linked to diseases such as cancer, that have varying degrees of higher and lower methylation and dysregulated gene expression compared to normal cells.

Epigenetics is not only about diseases though, but can be associated with answering questions regarding skin pigmentation response to sunlight exposure, and may even contribute to left and right handedness. It is a burgeoning field and as it continues to grow, so too will our knowledge of how our genes express themselves has ongoing influence over the course of our lives.

One way that we discover more about ourselves is through studies of identical twins. Identical twins share a genetic make-up, but then what explains some identical twins being completely different as people? From this we can ascertain that differing life experiences and exposure to different lifestyles and environments has a large role to play. Two identical twins separated at a young age and living in a geographically different place will be different people, and perhaps their genes will be expressing themselves differently as well because of the external factors.

In the quest to learn more about ourselves on every level, we must understand that genetics is only one piece of the puzzle, and has a complex interplay with our environments. The good news is that we have control over many of the environmental factors that influence our epigenetic markers, and can optimise our genetic expression by exercising, eating a healthy diet, getting plenty of sleep and managing stress.

For this reason, epigenetics will become just as important as genetics for gaining a deeper understanding of ourselves. We live in an exciting time as it becomes clear that our genes are not our destiny, and that the power to reach our goals is very much in our own hands.

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