Psychostimulant abuse is a public health crisis that affects millions of individuals in the United States and
results in profound economic, social, and individual harm. However, despite rapid increases in overdose
deaths linked to stimulant drugs like cocaine, there are still no approved therapeutic options for stimulant
abuse disorders. Psychostimulant drugs act through well-defined signaling mechanisms to elevate
dopaminergic neurotransmission in the nucleus accumbens (NAc), a key reward-linked brain structure that
integrates information from diverse brain regions to directly influence motivated behavior. Further, cocaine
causes epigenetic and transcriptional reorganization in medium spiny neurons (MSNs) in the NAc, promoting
maladaptive shifts in cell signaling and synaptic function. Our preliminary data indicates that expression of
Gadd45b (Growth, arrest, and DNA-damage inducible protein 45b) mRNA is upregulated in the MSNs after
both cocaine and dopamine receptor stimulation, and that Gadd45b is required for cocaine-related memory
formation. However, although Gadd45b plays a critical role in epigenetic reprogramming and memory
formation in other brain regions, the role of Gadd45b in cocaine-related epigenetic, molecular, and behavioral
adaptations is not clear. In this proposal, we will test the overarching hypothesis that Gadd45b regulates drug-
induced behavioral plasticity by control of activity-dependent DNA demethylation in the NAc. Specific Aim 1 of
this proposal will combine bidirectional CRISPR-based manipulations and single-nucleus RNA sequencing to
determine how Gadd45b signaling impacts transcriptional responses to cocaine. Specific Aim 2 will use novel
Gadd45b tools and genome-wide DNA methylation profiling to identify the molecular interactions that regulate
Gadd45b-dependent epigenetic programming in the NAc. Finally, Specific Aim 3 will use cell-specific in vivo
Gadd45b manipulations in combination with behavioral assays of cocaine and natural reward to test the
hypothesis that Gadd45b enhances the behavioral effects of cocaine. Together, these experiments will identify
Gadd45b target genes in the NAc, dissect epigenetic mechanisms by which Gadd45b contributes to cocaine’s
epigenetic effects, and define a role for Gadd45b in cocaine-related behavioral plasticity. These studies will
reveal fundamental mechanisms by which Gadd45b contributes to psychostimulant response, and will pave the
way for future experiments to explore how drugs of abuse engage the epigenome to alter motivated behavior.