The Epigenetics Revolution

This is one of the ways that epigenetics is described scientifically, where things which are genetically identical can actually appear quite different to one another. But there has to be a mechanism that brings out this mismatch between the genetic script and the final outcome. These epigenetic effects must be caused by some sort of physical change, some alterations in the vast array of molecules that make up the cells of every living organism. This leads us to the other way of viewing epigenetics – the molecular description. In this model, epigenetics can be defined as the set of modifications to our genetic material that change the ways genes are switched on or off, but which don’t alter the genes themselves.

Although it may seem confusing that the word ‘epigenetics’ can have two different meanings, it’s just because we are describing the same event at two different levels. It’s a bit like looking at the pictures in old newspapers with a magnifying glass, and seeing that they are made up of dots. If we didn’t have a magnifying glass we might have thought that each picture was just made in one solid piece and we’d probably never have been able to work out how so many new images could be created each day. On the other hand, if all we ever did was look through the magnifying glass, all we would see would be dots, and we’d never see the incredible image that they formed together and which we’d see if we could only step back and look at the big picture.

The revolution that has happened very recently in biology is that for the first time we are actually starting to understand how amazing epigenetic phenomena are caused. We’re no longer just seeing the large image, we can now also analyse the individual dots that created it. Crucially, this means that we are finally starting to unravel the missing link between nature and nurture; how our environment talks to us and alters us, sometimes forever.

The ‘epi’ in epigenetics is derived from Greek and means at, on, to, upon, over or beside. The DNA in our cells is not some pure, unadulterated molecule. Small chemical groups can be added at specific regions of DNA. Our DNA is also smothered in special proteins. These proteins can themselves be covered with additional small chemicals. None of these molecular amendments changes the underlying genetic code. But adding these chemical groups to the DNA, or to the associated proteins, or removing them, changes the expression of nearby genes. These changes in gene expression alter the functions of cells, and the very nature of the cells themselves. Sometimes, if these patterns of chemical modifications are put on or taken off at a critical period in development, the pattern can be set for the rest of our lives, even if we live to be over a hundred years of age.

There’s no debate that the DNA blueprint is a starting point. A very important starting point and absolutely necessary, without a doubt. But it isn’t a sufficient explanation for all the sometimes wonderful, sometimes awful, complexity of life. If the DNA sequence was all that mattered, identical twins would always be absolutely identical in every way. Babies born to malnourished mothers would gain weight as easily as other babies who had a healthier start in life. And as we shall see in Chapter 1, we would all look like big amorphous blobs, because all the cells in our bodies would be completely identical.

Huge areas of biology are influenced by epigenetic mechanisms, and the revolution in our thinking is spreading further and further into unexpected frontiers of life on our planet. Some of the other examples we’ll meet in this book include why we can’t make a baby from two sperm or two eggs, but have to have one of each. What makes cloning possible? Why is cloning so difficult? Why do some plants need a period of cold before they can flower? Since queen bees and worker bees are genetically identical, why are they completely different in form and function? Why are all tortoiseshell cats female? Why is it that humans contain trillions of cells in hundreds of complex organs, and microscopic worms contain about a thousand cells and only rudimentary organs, but we and the worm have the same number of genes?

Scientists in both the academic and commercial sectors are also waking up to the enormous impact that epigenetics has on human health. It’s implicated in diseases from schizophrenia to rheumatoid arthritis, and from cancer to chronic pain. There are already two types of drugs that successfully treat certain cancers by interfering with epigenetic processes. Pharmaceutical companies are spending hundreds of millions of dollars in a race to develop the next generation of epigenetic drugs to treat some of the most serious illnesses afflicting the industrialised world. Epigenetic therapies are the new frontiers of drug discovery.