Environmental toxins can affect gene
expression—for better or for worse.
A study in rats suggests that exposure to environmental toxins could be contributing to an inherited vulnerability to common diseases like breast cancer and high cholesterol.
Washington State University molecular biologist Michael Skinner had previously shown that sperm abnormalities induced by vinclozolin, a toxic fungicide used on wine grapes, strawberries, and other fruits, can pass from father to son for four generations in rats. In a new study, he has found that the rats' offspring were inheriting more than just testis troubles. They also had up to 10 times higher rates of breast cancer, prostate and kidney disease, high cholesterol, and immune abnormalities.
The rats, Skinner says, aren't inheriting bad genes so much as their recent ancestors' toxin exposure. In this type of novel inheritance, called epigenetic, changes don't occur in a DNA sequence as they do in a mutation. Instead, the changes happen to certain chemical markers on the DNA that control how much any particular gene is expressed. Previous studies in lab rats have shown that this type of nongenetic inheritance can influence traits like fur color and obesity. Skinner's work shows it could also be crucial for understanding how our parents pass along vulnerability to a wide range of diseases.
The amount of vinclozolin Skinner gave the rats was much higher than a person is likely to encounter, but "just knowing this mechanism exists might change the way we do medicine," Skinner says. Epigenetic markers could be found that diagnose a disease before symptoms appear, and "we could come up with therapies that would keep it from developing," he says. "If indeed this turns out to be one of the main mechanisms for disease, we now have a whole host of diagnostic and therapeutic techniques that we didn't have before."
Get the full scoop on epigenetics in Discover's November cover story, DNA is Not Destiny