How Changes in Grandma’s Genes Can Impact Your Baby
Exposures to certain pollutants in the environment can damage our cells and the DNA inside them. We know this. It’s what causes cancer and many other disorders. But a new science called epigenetics says there may be another way environmental contaminants are affecting us; some toxins may alter not our DNA itself but the molecules responsible for telling its specific genes when to perform their functions. These changes to what’s basically our genes’ control system essentially rewires our cells to perform differently than nature intended. And—get this—once this rewiring occurs, it may get passed on to our children and their children.
This means the effects of a toxic exposure in one generation could be experienced by subsequent generations, too, even if the original toxin was nowhere to be found.
It’s heady stuff. So we asked Dr. Richard Denison, Senior Scientist for the Environmental Defense Fund, an epigenetics expert, to help explain.
Let’s start at the beginning: What is epigenetics?
The genes that make up our chromosomes provide the blueprint for our development. But equally important is how and when those genes are turned on and off. Think of it like a computer. The hardware is akin to genetics. But without software, the computer is useless. Epigenetics is the software; it provides the detailed instructions that program our genes to turn on or off at exactly the right time.
Each cell in your body has the same DNA. Yet as you developed from that single fertilized egg to billions of cells, those cells turned into more than 200 radically different types of cells with very distinct functions – bone cells, brain cells, blood cells, etc. Epigenetics seeks to understand how this all happens.
How do exposures to toxins affect this process? Environmental factors can lead to changes in the epigenetic marks in our DNA. That means they can perturb normal gene expression in ways that can affect our health. While such changes can occur at any time, early development is a critical window of vulnerability because all of our bodies’ systems—neurological, immune, reproductive, and so on—are just being formed, all through that precise programming of our genes. Agents in our environment can disrupt normal development by interfering with that programming.
Growing scientific evidence indicates that this perturbation of normal epigenetic marking explains how an exposure early in life can lead to a disease that develops years after the initial exposure. For example, certain chemicals act as “obesogens,” increasing the likelihood of an individual to become obese and suffer from diseases such as diabetes.
Can you give an example?
An example is tributyltin, a common agent in paints. Exposure of a fetus during pregnancy can reprogram stem cells to preferentially differentiate into fat cells at the expense of bone cells through epigenetic changes.
Recent studies suggest that epigenetic changes may be transgenerational, providing a certain disorders can be passed down to future generations. Again, tributyltin is an example: a recent study found that exposure of pregnant female mice to the chemical induced a type of liver disease not only in the immediate offspring, but for two more generations. Other recent studies, all in mice, also show multi-generational transfer of effects induced by diet, chemical exposures, even stress, all apparently through epigenetic changes.
Is there anything we can do to reverse or prevent these changes?
‘Epigenetic therapy” is an active area of research, and drugs are in development that aim to “reset” epigenetic changes. But such therapies may never have broad applicability.
Prevention is challenging. A myriad of environmental factors and agents—only a few of which have been identified—likely act through epigenetic mechanisms, and those factors and agents likely interact with each other. Individuals can only do so much to identify and avoid such exposures.
What is most needed is the enhancement of policies and practices in both the public and private sectors to identify agents in our environment that have the potential to harm our health—whether they act through epigenetic or other mechanisms—and to reduce exposures to them.