MUNICH — The field of epigenetics is being lauded for its discoveries, which some describe as revolutionary. There's talk of a wide range of scientific textbooks being rewritten. But are the findings really that groundbreaking?
First, what is epigenetics? It is any additional information that gets tacked on top of the genome. Epigenetics refer to changes in genetic activity that don't change the DNA itself. Among the field's potential wide-ranging effects are the ways that experience of an animal or human affects its offspring, even if those experiences took place before the offspring's conception.
One study found that the grandchildren of women who had been pregnant during the Dutch famine of 1944 were, on average, fatter than their peers. The experience of the grandmothers had apparently had an impact on two generations after them.
Last year, scientists from Mount Sinai Hospital in New York reported that the children of Holocaust survivors were more likely than others to suffer from problems like post-traumatic stress. In other words, trauma could be passed from one generation to the next.
What's really spectacular about these results is that they question the basic principles of Charles Darwin's theory of evolution, which says, in a nutshell: Organisms develop certain characteristics based on their genes. Mutation allows the offspring to develop modified or new characteristics, which are then passed on to the next generation. If such a modification proves to be useful, these genes would become more widespread in a given population.
But with the recent findings, an idea that has been around for a long time but was considered outdated has now resurfaced, that is, Lamarckism from the 19th century. A classic example of giraffes illustrates the idea: The long necks of the animals apparently developed by stretching towards leaves on high trees. Their slightly stretched neck then had been passed on to their children, whose necks then stretched further, and so on.
These findings redefine parental responsibility. Now we have to ask ourselves how much our children really have to suffer from our behavior, whether it's an unhealthy diet or a lack of physical activity.
But along with enthusiasm about these findings, there's also criticism about the interpretation of these scientific studies. It has been clear for a long time that in specialized body cells specific genes can be activated, and this process can, in theory, be "passed on" to the cells of female offspring. The impact of a person's diet and other environmental factors on genes has long been evident.
What's new and actually exciting is the observation that epigenetics affects the genetic material in egg cells and sperm, which can then be passed on to offspring. Epigenetically active molecules are being removed from the DNA in these cells so that all different kinds of specialized cells can be redesigned in the embryo.
Scientists have known for a while that that's exactly what happens with some species of plants and animals through environmental factors. "It's wrong to assume that during the development, the whole genome is being cleaned," says Isabelle Mansuy, professor for neuro-epigenetics in Zurich. "Some genes' epigenetic profile will be erased, others will not." The concept of reprogramming has wrongly been generalized.
Scientists don't expect any significant medical findings from the epigenetic research so far. According to the American geneticist, John Greally, most studies that are looking for causes of illness in the epigenome "are suffering from significant problems when it comes to their design as well as conduct, which is strongly affecting their interpretability." Moreover, molecular biologist Steven Henikoff from Seattle can't imagine "a way to define at all what is really nature, and what's environmentally determined, without experiments on humans, which are, per se, forbidden."
Mansuy, on the other hand, stresses the importance of epigenetics when it comes to understanding and treating diseases. "The epigenetic inheritance is an extremely important phenomenon." According to her, it's also vital for evolution because it allows for quick adaptation to environment. In the long run, modifications of the genome might even be necessary.
"But even a few epigenetic adjustments can be stable and permanent. And there's a theory that says that epigenetic alterations can also lead to genetic alterations and can thereby contribute to classic evolution," she says.