DNA Epigenetics in Addiction Susceptibility.

Addiction is a chronically relapsing neuropsychiatric disease that occurs in some, but not all, individuals who use substances of abuse. Relatively little is known about the mechanisms which contribute to individual differences in susceptibility to addiction. Neural gene expression regulation underlies the pathogenesis of addiction, which is mediated by epigenetic mechanisms, such as DNA modifications. A growing body of work has demonstrated distinct DNA epigenetic signatures in brain reward regions that may be associated with addiction susceptibility. Furthermore, factors that influence addiction susceptibility are also known to have a DNA epigenetic basis. In the present review, we discuss the notion that addiction susceptibility has an underlying DNA epigenetic basis. We focus on major phenotypes of addiction susceptibility and review evidence of cell type-specific, time dependent, and sex biased effects of drug use. We highlight the role of DNA epigenetics in these diverse processes and propose its contribution to addiction susceptibility differences. Given the prevalence and lack of effective treatments for addiction, elucidating the DNA epigenetic mechanism of addiction vulnerability may represent an expeditious approach to relieving the addiction disease burden.

DNA Methyltransferase 3A Is Involved in the Sustained Effects of Chronic Stress on Synaptic Functions and Behaviors.

Emerging evidence suggests that epigenetic mechanisms regulate aberrant gene transcription in stress-associated mental disorders. However, it remains to be elucidated about the role of DNA methylation and its catalyzing enzymes, DNA methyltransferases (DNMTs), in this process. Here, we found that male rats exposed to chronic (2-week) unpredictable stress exhibited a substantial reduction of Dnmt3a after stress cessation in the prefrontal cortex (PFC), a key target region of stress. Treatment of unstressed control rats with DNMT inhibitors recapitulated the effect of chronic unpredictable stress on decreased AMPAR expression and function in PFC. In contrast, overexpression of Dnmt3a in PFC of stressed animals prevented the loss of glutamatergic responses. Moreover, the stress-induced behavioral abnormalities, including the impaired recognition memory, heightened aggression, and hyperlocomotion, were partially attenuated by Dnmt3a expression in PFC of stressed animals. Finally, we found that there were genome-wide DNA methylation changes and transcriptome alterations in PFC of stressed rats, both of which were enriched at several neural pathways, including glutamatergic synapse and microtubule-associated protein kinase signaling. These results have therefore recognized the potential role of DNA epigenetic modification in stress-induced disturbance of synaptic functions and cognitive and emotional processes.

Role of Long Noncoding RNA Gas5 in Cocaine Action.

BACKGROUND: Long noncoding RNAs (lncRNAs) are a class of transcribed RNA molecules greater than 200 nucleotides in length. Although lncRNAs do not encode proteins, they play numerous functional roles in gene expression regulation. lncRNAs are notably abundant in brain; however, their neural functions remain largely unknown. METHODS: We examined the expression of the lncRNA Gas5 in nucleus accumbens (NAc), a key brain reward region, of adult male mice after cocaine administration. We then performed viral-mediated overexpression of Gas5 in NAc neurons to determine its role in addiction-related behaviors. We also carried out RNA sequencing to investigate Gas5-mediated transcriptomic changes. RESULTS: We demonstrated that repeated short-term or long-term cocaine administration decreased expression of Gas5 in NAc. Viral-mediated overexpression of Gas5 in NAc neurons decreased cocaine-induced conditioned place preference. Likewise, Gas5 overexpression led to decreased cocaine intake, decreased motivation, and compulsive-like behavior to acquire cocaine, and it facilitated extinction of cocaine-seeking behavior. Transcriptome profiling identified numerous Gas5-mediated gene expression changes that are enriched in relevant neural function categories. Interestingly, these Gas5-regulated gene expression changes significantly overlap with chronic cocaine-induced transcriptome alterations, suggesting that Gas5 may serve as an important regulator of transcriptional responses to cocaine. CONCLUSIONS: Altogether, our study demonstrates a novel lncRNA-based molecular mechanism of cocaine action.