New research surfacing in PNAS details the downward spiral cocaine induces in heterochromatin in the reward center of our brains.
Over the years researchers have found that cocaine can regulate chromatin structure in the nucleus accumbens, a reward region in the brain and an area closely tied to addiction. DNA methylation machinery has also been on the receiving end of cocaine’s molecular mayhem. Most of these studies though, have focused on the more open, active chromatin regions. Far less attention has been directed to the transcriptionally silent regions of the brain. Using ChiP-Seq, a Mount Sinai Medical School research team produced high-resolution profiles of heterochromatic regions in this region in the brain and how they’re impacted by cocaine treatment.
The uber-effective, repressive mark, H3K9me3 typically dominates the silenced heterochromatic regions in the nucleus accumbens, but the team found:
- Both acute and repeated cocaine administration can significantly alter the expression of H3K9me3, increasing in some places, while decreasing it in others
- After repeated exposure, reduced H3K9me3 presence can persist well into drug abstinence, suggesting a role in the long-term effects of the drug
- The decrease in H3K9me3 boosted the expression of the typically silenced, LINE-1 like repetitive elements
The authors believe this mechanism might be behind some of the lasting effects of drug use and addiction. Check out all the details in PNAS, February 2011.