Histone methyltransferase, Setd2, in substance use disorders

About This Grant

Substance use disorders (SUDs) are characterized by long-lasting neuroadaptations, including changes in gene expression and the epigenome. The relevance of the epigenome in SUDs has been shown using overexpression or inhibition of epigenome modifying enzymes. However, such manipulations cannot distinguish between direct and indirect action of epigenetic modifications at a target gene. To address this, we apply locus-specific epigenetic editing with CRISPR/dCas9 to establish the direct causal relevance of a specific epigenetic modification to SUDs. We and others find that the epigenetic enzyme, SET domain containing 2 (Setd2), regulates cocaine-induced mouse behavior, gene expression, and alternative splicing. Setd2 specifically writes H3K36me3, a histone modification associated with active transcription and alternative splicing, which is altered in mouse brain regions by cocaine exposure. We and others have identified a role for Setd2/H3K36me3 in alternative splicing which mirrors cocaine-induced splicing events and is associated with cocaine-related behaviors in mice. We find that overexpression of Set2 in mouse brain reward regions increases H3K36me3 and drives mouse cocaine reward behavior. Together, these data provide strong evidence for Setd2/H3K36me3 in mediating the behavioral response to cocaine in mice through epigenetic and alternative splicing events. The overall goal of this proposal is to establish that Setd2 inhibition attenuates cocaine self-administration through cell-type specific regulation of alternative splicing and gene expression. First, we will determine both sufficiency and necessity of Setd2 to drive cocaine behavior, using pathway-specific Setd2 overexpression and small-molecule Setd2 inhibition (Setd2i), respectively. We hypothesize that NAc Setd2 inhibition will reduce cocaine self-administration. Second, we will define the pathway-specific effects of Setd2 on behavior, H3K36me3 and gene expression by cell-type specific epigenomic profiling and targeted epigenetic editing. Third, we will interrogate mechanisms by which Setd2 regulates alternative splicing by identifying interacting RNA-binding proteins (RBPs). Finally, this proposal will investigate non-enzymatic roles of a histone modifying enzyme in addiction. Recent studies and our preliminary data suggest non-enzymatic function of Setd2 through protein binding domains. We will distinguish Setd2 and H3K36me3 using combinatorial Setd2 overexpression, Setd2i, and epigenetic editing.