Nurture impacts nature: Experiences leave genetic mark on brain, behavior

The studies focus on an area of research called epigenetics, in which the environment and experiences can turn genes "on" or "off," while keeping underlying DNA intact. These changes affect normal brain processes, such as development or memory, and abnormal brain processes, such as depression, drug dependence, and other psychiatric disease -- and can pass down to subsequent generations.

Today's new findings show that:

• Long-term heroin abusers show differences in small chemical modifications of their DNA and the histone proteins attached to it, compared to non-abusers. These differences could account for some of the changes in DNA/histone structures that develop during addiction, suggesting a potential biological difference driving long-term abuse versus overdose
• Male rats exposed to cocaine may pass epigenetic changes on to their male offspring, thereby altering the next generation's response to the drug. Researchers found that male offspring in particular responded much less to the drug's influence
• Drug addiction can remodel mouse DNA and chromosomal material in predictable ways, leaving "signatures," or signs of the remodeling, over time. A better understanding of these signatures could be used to diagnose drug addiction in humans

Other recent findings discussed show that:

• Researchers have identified a potentially new genetic mechanism, called piRNA, underlying long-term memory. Molecules of piRNA were previously thought to be restricted to egg and sperm cells
• Epigenetic DNA remodeling is important for forming memories. Blocking this process causes memory deficits and stunts brain cell structure, suggesting a mechanism for some types of intellectual disability

"DNA may shape who we are, but we also shape our own DNA," said press conference moderator Schahram Akbarian, of the Icahn School of Medicine at Mount Sinai, an expert in epigenetics. "These findings show how experiences like learning or drug exposure change the way genes are expressed, and could be incredibly important in developing treatments for addiction and for understanding processes like memory."