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.
