Dissecting the shared genetic mechanisms driving fentanyl addiction, cocaine addiction, and incentive sensitization using the Collaborative Cross mouse panel - PROJECT ABSTRACT Fentanyl addiction is a highly heritable disease and a critical public health crisis. In 2022, fentanyl overdose was the leading cause of death for US adults aged 18 - 45. This striking statistic underscores the urgent need to discover and characterize the genetic drivers of fentanyl addiction. In this regard, drug-induced incentive sensitization in brain reward systems is a fundamental addiction vector. This hypothesis (the incentive sensitization theory of addiction) posits that, over time, brain reward systems become hypersensitized to the environmental stimuli that accompany drug use. The consequence is pathological incentive motivation (i.e., “wanting”) for the drug upon exposure to the drug-paired stimuli. Although fentanyl addiction and incentive sensitization are highly heritable in humans and mice, the genetic role of incentive sensitization in fentanyl addiction is unknown. The overarching goal of this project is to identify the genetic mechanisms through which incentive sensitization drives addiction-like fentanyl taking and seeking. This goal will be accomplished through the integration of advanced mouse resources, gold standard behavior and neurophysiology assays, and cutting-edge transcriptomics. The Collaborative Cross (CC) recombinant inbred mouse panel, which contains 90% of mouse alleles, will be used to maximize genetic and phenotypic diversity. In Aim 1, we will use intravenous fentanyl self-administration to identify genetic mechanisms underlying classical pharmacological phenotypes and addiction-like behaviors in male and female mice from 40 CC strains. In Aim 2, we will use Pavlovian conditioned approach and RNA-seq to identify genetic and nucleus accumbens transcriptomic mechanisms underlying incentive sensitization in male and female mice from 40 CC strains. In Aim 3, we will use snRNA-seq, Iso-seq, electrophysiology, and voltammetry to identify cell-type and isoform specific addiction mechanisms in two CC strains exhibiting extreme nucleus accumbens-driven vulnerability and resistance, respectively, to both IV fentanyl and IV cocaine self-administration. Using data from these three aims, a comprehensive systems genetics analysis including QTL mapping, eQTL mapping, genetic correlation, and differential expression will be performed to identify cell-type specific and isoform specific transcriptomic signatures in nucleus accumbens that predict both pathological incentive motivation and addiction-like fentanyl self-administration. Successful completion of these aims will provide a foundation for future deep characterization of identified mechanisms and a lasting community resource enabling genetic correlational analysis among the CC panel across phenotypes, experiments, and laboratories. Ultimately, this work will contribute to the development of novel, more effective addiction treatments.
