Research Frontiers: The Study of Epigenetics

Martie
Callaghan

Are your genes turned on?

When scientists began The Human Genome Project in the early 1990s, their hope was to discover and interpret the entire blueprint for life, to decode not only how the human body is put together, but also to find the genetic cause and cure for every disease. Imagine their surprise when they discovered not the anticipated 100,000 genes, but rather 20,000 genes making up the human genome-about the same as that of fish and mice, and less than many plants!

If the genes themselves do not define the complexity of the human body, then what is responsible for differences between and among the species? Scientists believe that a revolutionary discovery-epigenetics (literally, "on" genes)-will help to answer that question and many, many more about genetics, environment, and disease.

Dr. Walter Kaufmann of the Kennedy Krieger Institute describes epigenetics as one of the main mechanisms by which genes are turned on or off. "The genome is like a book," he explains. "The book can be in one of two main states: open so it can be read or closed so it cannot be read. That is the difference between a gene being expressed and not being expressed. The gene (book) itself remains unchanged."

Epigenetics may play a role in the development of diseases such as diabetes, autism and cancer. Consider the phenomenon of identical twins who are alike in every aspect of appearance, even in their physical milestones, until one of them is diagnosed with autism. Their genetic material is identical, so the difference must be environmental. Scientists believe that such factors as diet and exposure to chemicals-perhaps even methods of parenting-can turn genes on or off.

"We know environmental stimulation has an impact on brain development and brain function," says Dr. Kaufmann. "And this impact we now know is mediated, at least in part, by epigenetic mechanisms."

Research into the epigenetics of identical twins gives way to relevant hypotheses regarding the general population.

"The twin with autism does not have a mutation in the gene or the other twin would have it too," Dr. Kaufmann says. "Rather, the gene in the autistic twin is turned on and the gene in the other twin is turned off or vice versa. When we know which gene is different, we can then go to the general population and see if any children with autism have that gene with a mutation."

There was a lot of excitement in the scientific community when it was discovered in 1999 that mutations in the gene MECP2 were associated with Rett syndrome, a neurologic disorder that occurs almost exclusively in girls and is characterized by severe problems with language, learning, hand use, and other motor and neurologic functions.

"The discovery of the relationship between MECP2 and Rett syndrome was the reason I became interested in the role of epigenetic mechanisms in developmental disorders," Dr. Kaufmann says. "We became so impressed by the link between MECP2 and Rett, that we were able to see the importance of epigenetics in understanding other neurologic problems."

Further studies will focus on connections between gender, diet, and other environmental factors that can be linked to disease and life expectancy in succeeding generations.

"We know that epigenetic phenomena can be transmitted from generation to generation," says Dr. Kaufmann. "We must now identify specific diets or other lifestyle dynamics that can influence and potentially reverse these epigenetic labels that you inherited from your ancestors."

The implications and applications of epigenetics reach even farther.

"We use a lot of medications in young children and many times there is no alternative but to do that," Dr. Kaufmann says. "We may be able to think about interventions that are more environment based."