Regulation of dopamine-dependent transcription and cocaine action by Gadd45b

Abstract

Exposure to drugs of abuse produces robust transcriptional and epigenetic reorganization within brain reward circuits that outlives the direct effects of the drug and may contribute to addiction. DNA methylation is a covalent epigenetic modification that is altered following stimulant exposure and is critical for behavioral and physiological adaptations to drugs of abuse. Although activity-related loss of DNA methylation requires the Gadd45 (Growth arrest and DNA-damage-inducible) gene family, very little is known about how this family regulates activity within the nucleus accumbens or behavioral responses to drugs of abuse. Here, we combined genome-wide transcriptional profiling, pharmacological manipulations, electrophysiological measurements, and CRISPR tools with traditional knockout and behavioral approaches in rodent model systems to dissect the role of Gadd45b in dopamine-dependent epigenetic regulation and cocaine reward. We show that acute cocaine administration induces rapid upregulation of Gadd45b mRNA in the rat nucleus accumbens, and that knockout or site-specific CRISPR/Cas9 gene knockdown of Gadd45b blocks cocaine conditioned place preference. In vitro, dopamine treatment in primary striatal neurons increases Gadd45b mRNA expression through a dopamine receptor type 1 (DRD1)-dependent mechanism. Moreover, shRNA-induced Gadd45b knockdown decreases expression of genes involved in psychostimulant addiction, blocks induction of immediate early genes by DRD1 stimulation, and prevents DRD1-mediated changes in DNA methylation. Finally, we demonstrate that Gadd45b knockdown decreases striatal neuron action potential burst duration in vitro, without altering other electrophysiological characteristics. These results suggest that striatal Gadd45b functions as a dopamine-induced gene that is necessary for cocaine reward memory and DRD1-mediated transcriptional activity.

Exploring the Stress Impact in the Paternal Germ Cells Epigenome: Can Catecholamines Induce Epigenetic Reprogramming?

“…In line with this, we found that cocaine treatment altered Dnmt3a/b and Tet1, and increased 5-meC levels in mouse germ cells (65). Also, recent studies have shown that both DA via DRD1 and NE via b−ADRs induce alterations in DNA methylation patterns in the CNS (33,80). Moreover, we have recently reported a U-shaped DRD1-dependent key testicular mechanism mediating cocaine-triggered increase in silent chromatin mark H3K27me3, decrease in active promoter mark H3K4me3, and increase in H4K16ac mark involved in histone to protamine replacement (66).…”

The Signaling and Pharmacology of the Dopamine D1 Receptor

“…DNA methylation levels are known to be altered both in response to drugs of abuse (Massart et al, 2015 ), and in LID (Figge et al, 2016 ). D1R stimulation has specifically been shown to rapidly upregulate expression of the DNA demethylase Gadd45b both in primary cultures and in vivo (Savell et al, 2020 ; Zipperly et al, 2021 ). Knockdown of Gadd45b impairs D1R-dependent changes in DNA methylation, which appear to be required for receptor-driven transcriptional activation, as well as cocaine reward (Zipperly et al, 2021 ).…”

“…D1R stimulation has specifically been shown to rapidly upregulate expression of the DNA demethylase Gadd45b both in primary cultures and in vivo (Savell et al, 2020 ; Zipperly et al, 2021 ). Knockdown of Gadd45b impairs D1R-dependent changes in DNA methylation, which appear to be required for receptor-driven transcriptional activation, as well as cocaine reward (Zipperly et al, 2021 ). Gadd45b is similarly upregulated in LID, but interestingly, knockout of Gadd45b worsens the development of dyskinesia and increases the expression of other D1R-regulated genes such as Fos and Fosb (Park et al, 2016 ), suggesting that the demethylase may play distinct roles in different striatal subregions, or depending on specific disease context.…”

The Mechanisms and Boundary Conditions of Drug Memory Reconsolidation

“…DNA methylation in the VTA has been shown to play a role in associative memory combining environmental cues with drug reward (Day et al, 2013). Although DNA methylation was initially perceived as a stable process that cannot be rapidly modulated, subsequent studies have demonstrated that this is not the case (Miller et al, 2010;Zipperly et al, 2021). In the brain, DNA undergoes rapid methylation and demethylation, which is necessary for memory formation and synaptic plasticity (Feng et al, 2010;Miller et al, 2010;Day et al, 2013).…”