Date of Award

Spring 5-8-2020

Level of Access

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Biochemistry

Advisor

Elissa J. Chesler

Second Committee Member

Alan M. Rosenwasser

Third Committee Member

Greg A. Cox

Abstract

Drug addiction is a heritable disease characterized by compulsive drug use. The biological mechanisms driving addiction remain largely unknown.1 Previous studies show shared genetic mechanisms underlying addiction risk phenotypes such as anxiety, depression, and novelty/sensation seeking.2,3 Therefore, high-throughput behavioral screening of these traits in single gene knockout mice can allow for the rapid detection of addiction risk candidate genes and mechanisms. Many of these traits are represented in the Knock-Out Mouse Program (KOMP) phenotyping pipeline. Of the initial two hundred twenty-one strains screened in this program, we tested nineteen phenodeviant knock-out mouse strains with C57BL/6NJ controls (N = 951) for effects on drug consumption and preference using a two-bottle choice paradigm with either ethanol (EtOH), methamphetamine (MA), or nicotine. Initial screening confirmed that fifteen of the nineteen gene deletions significantly affected EtOH consumption or preference (EtOH-related traits), MA consumption or preference (MA-related traits), or both. Thirteen strains exhibited drug specific effects and two exhibited significantly altered patterns of consumption, preference, or both for MA and EtOH. To investigate the shared relationships underlying drug consumption and predisposing drug-naïve phenotypes, we ran a principle component analysis. This revealed a complex relationship among predisposing behaviors and their effects on drug-related phenotypes across different strains, instead of consistent predictive relationships between predisposing behaviors and drug consumption phenotypes. Using a multivariate strategy, a second screening approach was performed based on multidimensional phenodeviance across predisposing traits. In this analysis, based on four hundred two inbred strains, fifteen KOMP lines chosen based on phenodeviance, in addition to six expert nominated strains, and were assessed with controls (N=608) using both methamphetamine two- bottle choice and ethanol drinking-in-the-dark paradigms. Results from second screening revealed ten more genes affecting drug phenotypes, three of which altered both methamphetamine and ethanol related traits. This shows that using a multidimensional assessment of predisposing traits enriched our candidate genes with a higher rate of effects across multiple drugs. Collectively this project provided twenty-five new confirmed gene deletion mutants with addiction risk effects, representing multiple distinct, novel biological mechanisms of addiction.

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