Identifying multi-omic signatures of opioid use and relapse

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Project Summary Opioid use disorder is a life-long burden for many individuals, imposing high personal, financial, and health costs. Even after prolonged abstinence, many individuals in recovery will go on to relapse, including those that received medication-assisted treatments. Repeated opioid exposure usurps normal reward circuit function by producing long-lasting molecular changes that alter physiology and support continued drug use. These cellular adaptations have been implicated in sustained relapse vulnerability, but we lack a clear understanding of what drives their persistence. There is a further lack of information on the precise molecular adaptations underlying altered circuit function, and in which specific circuits they act to promote relapse. Understanding this “who, what, when, and where,” will be key to identifying new therapeutic targets. Here, we will answer these questions using a multi- level approach that allows us to sequence, manipulate, and record from neurons in specific circuits in the context of opioid self-administration and relapse. Our preliminary data show that both genetically-distinct and genetically-identical neuron subtypes in the ventral tegmental area (VTA) undergo differential molecular adaptations after fentanyl self-administration, which we hypothesize arises from activity-dependent transcriptional changes in specific circuits. We further hypothesize the transcriptional changes are sustained by methylation and demethylation at the gene promoters. We will first record calcium activity in VTA neurons that project to either the nucleus accumbens (NAc) or amygdala (AMY)— projections known to be important for drug intake and relapse, respectively. Then, in the same neurons from the same animals, we will identify which gene networks are transcriptionally changed after self-administration and persist until relapse testing. Next, we will identify the DNA methylation marks driving sustained differential expression, with an emphasis on genes important for synaptic plasticity. Next, we will use CRISPR/dCas9 fusion constructs to manipulate methylation states at our identified loci in specific circuits. This proposal will allow us to define the specific VTA circuits that support opioid intake and relapse, which gene networks support activity of these circuits, and how DNA methylation cements the transcriptional landscape to alter behavior. This award will allow research into neural mechanisms of opioid use disorder with unprecedented resolution, and has the potential to transform how we approach studying the genetics of substance use disorders. Together, this critical information will help inform new treatment strategies to prevent relapse.