February 20, 2003
BIRMINGHAM, AL — New findings suggest that extreme environmental stress can produce changes in how the body translates its genetic information into individual character traits. Details of the study by researchers at the University of Alabama at Birmingham (UAB) were published recently in Nature Genetics. “Findings indicate that environmental stress may play a significant role in evolution,” said Douglas Ruden, Ph.D., associate professor of environmental health sciences in the School of Public Health at UAB.
Under conditions of environmental stress, such as extreme temperatures, contaminated water or poor air quality, organisms produce a protein called Hsp90 that helps stabilize cell development. “In fruit flies, we found that when the activity of this protein was reduced, the flies grew hair-like bristles on the surface of their eyes, despite no change in their DNA, or underlying genetic structure,” said Ruden. “Furthermore, their eyes remained abnormal even after Hsp90 activity was restored, and they passed along the trait to their offspring.”
The phenomenon, researchers say, resulted from changes in the cell’s chromatin — the packaging that surrounds the cell’s genetic material. “Chromatin is described as either ‘open’ or ‘closed,’” Ruden said. “When open, the genetic material inside is active; when closed, it is inactive. Under environmental stress and in the absence of Hsp90, the chromatin is weakened, allowing inactive genes to become active.”
Aside from its relevance to evolutionary theory, the finding provides a better understanding of chromatin and its role in genetic expression, which is of particular interest to geneticists and those in favor of human cloning. “While scientists may be able to replicate an organism’s DNA, they can’t yet control for how chromatin is affected,” Ruden said. “It is, I imagine, why a human has not already been cloned. Until scientists are able to maintain the structural integrity of chromatin, there is great potential for severe genetic defects.”
Findings also have important implications for other fields of science, including the study and treatment of human diseases. “Many human diseases are not the result of a genetic mutation but rather a change in how the genes are expressed,” said Ruden. “Most human cancers, for instance, are caused by changes within the cell that affect its chromatin. It’s important that we continue to study and to learn why and how these changes occur and their affect on chromatin.”