ENCODE: Twins and epigenetics

How can identical twins have differences between them? The answer may lie in epigentics - a new research field studying chemicals and factors that influence the switching on and off of our genes.

Traditionally, studying twins by comparing identical and non-identical pairs helped us understand this branch of science. However, twin studies can only highlight genetic factors and point scientists to general areas of interest. ENCODE, on the other hand, can be used in tandem with twin studies as a detailed map which helps scientists to pinpoint the exact genes of interest and the epigenetic factors around them.

Image courtesy of TwinsUK

Tim Spector, Professor of Epidemiology at Kings College London and Director of TwinsUK, who has studied and written about the genetics of twins, shares his thoughts on how a deeper understanding of epigentics may be harnessed to cure disease, and why the nature versus nurture argument may no longer be relevant.

You were involved in twin studies for a long time. How will information from ENCODE complement twin studies, which were the traditional epigenetic means of study?
"Traditional" in this case means only the last few years!

Twin studies will show us the rough areas of the genome that are epigenetically regulated in diseases and traits. Once you know the rough areas, ENCODE acts as a detailed map. You’ll then be able to look at that map and say "Right next to that gene, or near that gene, are areas that can affect the way DNA is switched on or off". These key areas can then be tested in animal models. Or we can get drugs to target those areas and let those genes work properly. So twin studies and ENCODE are complementary.

So one is a guide, and one is a detailed roadmap?
Yes. ENCODE is a very detailed map of just a few people. We have to combine feasible epigenetic studies in hundreds or thousands of twins, then look at the detailed map which shows, for most people, where the interesting differences between individuals are originating and what they do.

Are twin studies still valuable for insight and direction for further studies?
Yes - you can't go from ENCODE straight to some novel epigenetic finding. You need the discovery first, and then you need to find out what’s in that area - that’s what ENCODE does. It’s like an Ordnance Survey map.

Image courtesy of TwinsUK

What will a deeper understanding of epigenetics lead to in the future?
Epigenetics is key to how genes communicate with cells, how all our genes function, how our environment and choices affect our genes, and ultimately how disease mechanisms work. By understanding epigenetics, you can find new drug targets. Amazing strides are being made in discovering which genes are being switched on or off by cancer. In some cases, we can reverse the process with epigenetic drugs.

Is it more difficult now to draw a line between nature and nurture, given environmental influences?
Yes, the nature/nurture line is no longer divisible or relevant - the two are interchangeable. Epigenetics has shown that most clearly. For example, smoking can change your genes, but smoking is not just an environmental agent itself - genes also control whether you’re likely to smoke or not. It’s the same for exercise - whether you exercise or not is a heritable trait, but exercise modifies your genes, possibly over generations. There’s no environmental effect that doesn’t have a genetic basis. I don’t think it’s valid to label things nature or nurture any more. We’re all a mixture of both. The key point is that we can modify the way our genes function via our lifestyle and environment.

Find out more about the discovery on Nature.com