title: Morphine epigenomically regulates behavior through alterations in histone H3 lysine 9 dimethylation in the nucleus accumbens.
abstract: Dysregulation of histone modifying enzymes has been associated with numerous psychiatric disorders. Alterations in G9a (Ehmt2), a histone methyltransferase that catalyzes the euchromatic dimethylation of histone H3 at lysine 9 (H3K9me2), has been implicated recently in mediating neural and behavioral plasticity in response to chronic cocaine administration. Here, we show that chronic morphine, like cocaine, decreases G9a expression, and global levels of H3K9me2, in mouse nucleus accumbens (NAc), a key brain reward region. In contrast, levels of other histone methyltransferases or demethylases, or of other methylated histone marks, were not affected in NAc by chronic morphine. Through viral-mediated gene transfer and conditional mutagenesis, we found that overexpression of G9a in NAc opposes morphine reward and locomotor sensitization and concomitantly promotes analgesic tolerance and naloxone-precipitated withdrawal, whereas downregulation of G9a in NAc enhances locomotor sensitization and delays the development of analgesic tolerance. We identified downstream targets of G9a by providing a comprehensive chromatin immunoprecipitation followed by massively parallel sequencing analysis of H3K9me2 distribution in NAc in the absence and presence of chronic morphine. These data provide novel insight into the epigenomic regulation of H3K9me2 by chronic morphine and suggest novel chromatin-based mechanisms through which morphine-induced addictive-like behaviors arise.
authors.affiliation: Fishberg Department of Neuroscience and Friedman Brain Institute, Mount Sinai School of Medicine, New York, New York 10029, USA.
authors.forename: Haosheng
authors.initials: H
authors.lastname: Sun
authors.forename: Ian
authors.initials: I
authors.lastname: Maze
authors.forename: David M
authors.initials: DM
authors.lastname: Dietz
authors.forename: Kimberly N
authors.initials: KN
authors.lastname: Scobie
authors.forename: Pamela J
authors.initials: PJ
authors.lastname: Kennedy
authors.forename: Diane
authors.initials: D
authors.lastname: Damez-Werno
authors.forename: Rachael L
authors.initials: RL
authors.lastname: Neve
authors.forename: Venetia
authors.initials: V
authors.lastname: Zachariou
authors.forename: Li
authors.initials: L
authors.lastname: Shen
authors.forename: Eric J
authors.initials: EJ
authors.lastname: Nestler
mesh_terms: D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects*; D019175:DNA Methylation / Q000187:drug effects; D044127:Epigenesis, Genetic / Q000187:drug effects*; D018014:Gene Transfer Techniques; D006657:Histones / Q000235:genetics* / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009020:Morphine / Q000009:adverse effects / Q000494:pharmacology*; D009043:Motor Activity / Q000187:drug effects; D009270:Naloxone / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000494:pharmacology; D009294:Narcotics / Q000009:adverse effects / Q000494:pharmacology*; D009714:Nucleus Accumbens / Q000187:drug effects* / Q000378:metabolism; D013375:Substance Withdrawal Syndrome / Q000378:metabolism
chemical_list: D006657:Histones; D009292:Narcotic Antagonists; D009294:Narcotics; D009270:Naloxone; D009020:Morphine