16 April 2012
ByAppeared in BioNews 652
BBC News Health, Wednesday 14 March 2012
Presented by Professor Tim Spector
Epigenetics is a complex subject, so explaining it in just two minutes is a big ask. But that's what the short film clip, 'Health Explained: Epigenetics', on the BBC website attempts to do. Aimed at a general audience, the film succeeds in giving us a very basic introduction, but doesn't manage to capture what is new and exciting about this field of research.
Professor Tim Spector, from the Department of Twin Research and Genetic Epidemiology at King's College London, uses twin research to illustrate the concept of epigenetics. He describes how identical twins, despite sharing an identical set of genes, can nonetheless have different characteristics. We are introduced to Lynn and her twin Debbie. Despite having identical genomes, Debbie has become overweight in later life while Lynn has not.
Similarly, twins Sheila and Dorothy have had remarkably different health outcomes over the course of their lives. Dorothy has experienced perfect health, while Sheila has had three strokes.
If, genetically speaking, all things are equal, why does one twin gain excess weight, or have a stroke, and the other does not?
Professor Spector says that despite the success of sequencing the human genome, our genes can only explain part of our susceptibility to diseases. Environmental factors - such as diet, stress, infection and exposure to chemicals - have a role to play too.
Most of us are familiar with this 'nature versus nurture' debate. What the film doesn't quite succeed in communicating is the idea of nature and nurture together; through epigenetics, the environment can modify gene activity and so influence disease susceptibility.
The example of the twins is intended to help explain this: Debbie and Sheila may have experienced different environmental exposures to their twin sisters, which could have led to epigenetic alterations to their genome that, in turn, could predispose them to weight gain or stroke.
The film ends with a rather unintelligible diagram depicting a red dot attaching itself to a double helix. This is meant to demonstrate that molecules from the environment can instruct our genes to be turned on or off, but it does so with little success.
What is missing from the film is a discussion of the persistence of epigenetic alterations. Exposure to environmental factors before birth or during childhood (such as malnutrition or tobacco smoke), not only has immediate consequences, but can have latent effects appearing well into adulthood. These epigenetic modifications may even persist through generations.
It was never made clear that it is not only our lifestyle now but the lifestyles we had in our youth, and even those of our parents, that influence our susceptibility to disease.
Although 'Health Explained: Epigenetics' is a short introduction aimed at a general audience, the description is, unfortunately, too basic, and so ignores some of the more interesting and novel aspects of epigenetics.