What if environmental factors and life events like stressful experiences could not only influence your genes but also those of your offspring? And what if the ageing process is better understood at the molecular level, so we can find ways to slow it down to live healthier for longer? All of this is linked to epigenetics. But what is epigenetics and why should we be interested in it?
DNA is your unique blueprint – inherited from both your parents. It’s present in every single cell and holds all the instructions your body needs to function and build itself. But what scientists now know is that there’s another layer which controls how our cell proteins use that DNA. Meet epigenetics!
Epigenetics literary means “on top of genetics”, which can be explained as additional information layered on top of your DNA. It’s the study of the way DNA interacts with the number of small molecules found within cells, which can activate or deactivate genes. Epigenetics is the set of processes which influence which genes are switched on (and therefore expressed) or switched off, without changing the DNA sequence (the order of the bases in a length of DNA).
In short, epigenetics doesn’t change your DNA, but it decides whether some genes are expressed or not.
What are epigenetic changes?
All our cells have the same DNA, so how does a skin cell know to function as a skin cell and how does a liver cell become a liver cell? You might have guessed! It’s to do with epigenetics. Specific parts of the gene in specific cells are turned on or off through epigenetic changes.
Let’s go into a little more detail. There are different types of epigenetic marks. Each one of these instructs the proteins in the cell to process that part of the DNA in a certain way.
This involves labelling the DNA with small chemical tags called methyl groups and these stick to some of the C (cytosine) letters in the DNA sequence. This in turn affects how that part of the DNA is read. In effect, DNA methylation prevents gene expression, so the gene is still there but it’s silent or inactivated.
The second type of epigenetic mark is called histone modification. But let’s first explain what histones are. Histones are proteins found inside our cells and are involved in packaging our DNA into units called nucleosomes. Our DNA molecules wrap around histones in our cells to form spool-like shapes. This allows our very long DNA molecules -each cell’s DNA stretches over 2 metres long -to be packed neatly into chromosomes, so they fit inside our cells.
Histone modification affects DNA indirectly. Methyl groups and other tags can attach to different locations on histones. Different tags have different effects on the DNA wrapped around histones. Some tags in some locations make the DNA loosen up around the histones, making the DNA more accessible to the proteins which can switch on the genes in that area. Other tags have the opposite effect, causing DNA to coil tightly around histones, making it inaccessible to be read and used – the gene is still there but it’s silent.
Epigenetic changes can also happen through RNA, which affect gene expression through several mechanisms which are rather complex and probably better left off for another article!
What controls epigenetic changes?
What’s interesting about epigenetic marks is that, unlike DNA which is fixed, these can change throughout your life. We now know that lifestyle choices and environmental factors, like exercise, diet, smoking and drinking can lead to changes in epigenetic marks. And so do diseases like cancer and certain medicines. But what we also know is that these changes can be reversible.
Epigenetic changes can be either positive or negative depending on whether they are turning on or off good or bad genes. Take the example of exercise. It’s good for you right? What about over exercising. With the emergence of epigenetic measurements, it may be possible in the very near future to have more personalised recommendations on what type of exercise, how intense it should be and how much of it is good for you. This would be specific to you and will depend on your fitness level and whether you’re healthy or have certain medical conditions. But more research is needed to find specific epigenetic biomarkers which can give an indication on how your body is responding to exercise, and as a result what you need to do to optimise your fitness.
Ageing and epigenetics
Ageing is one of the most important risk factors for developing age-related diseases like diabetes and cardiovascular disease. One of the hallmarks of ageing is epigenetic changes. What’s most exciting is that we can measure our true age – also known as biological age – using those epigenetic marks.
Your biological age considers how well your body is working given calendar age. Think of it as a reflection of your true state of health! Biological age can be assessed by measuring epigenetic changes like DNA methylation. Unlike your calendar age, your biological age can be reversible. So, measuring your biological age means knowing how quickly you’re ageing, and this means you can do something about it! Having a biological age that is lower than your calendar age can give you reassurance that you’re doing the right things and that you’re following a healthy lifestyle – you may even choose to optimise your lifestyle even further. But if your true age is higher than your calendar age, it’s time to act! As this is associated with developing a number of age-related diseases and a higher risk of dying. You can read more about biological age in my previous post here.
Can epigenetics be passed on?
Can what happen to you, how you behave, and your lifestyle choices have a biological impact on your children or even your grandchildren? This is a topic which has been long debated and which has attracted lots of attention. Most epigenetic marks are deleted when sperm meets egg, but researchers think that some of these imprints survive, passing those genetic traits on to the next generation. Your mother or your father’s experiences as a child or their choices as adults could actually shape your own epigenome. Recent research -mainly in rodents – has focused on studying the inheritance of epigenetic marks. We know for example that when mother rats didn’t care enough for their pups, these were fearful and more stressed, when compared to the offspring of more attentive mother rats. Even the DNA methylation pattern was different between two groups of pups. And these epigenetic changes might not stop with that generation.
This is an evolving area of research and there’s a lot we still don’t understand. But epigenetics could in the future give you the tools to identify the effects of lifestyle choices and the risk of developing certain diseases – and what to avoid them.
Epigenetics tests can already offer a measure of metabolic state and biological age, allowing people to measure their interventions at molecular level and make adjustments. Epigenetics science is leading to a more personalised approach to health. Although not yet mainstream, it could soon give doctors the most accurate read of your health and enable them to tailor interventions and treatments to your response. How awesome would that be?!