Date of Award

Spring 5-10-2019

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Doctor of Philosophy (PhD)

Department

Biomedical Sciences

Advisor

Alan M. Rosenwasser

Second Committee Member

Vivek Kumar

Third Committee Member

Marie J. Hayes

Additional Committee Members

Thane E. Fremouw

Kristy L. Townsend

Abstract

The C57BL/6 (B6) mouse is the most commonly used inbred strain in biomedical research, and has served as the basis for various large-scale genetic and genomic projects. Although the parental substrain, C57BL/6J (B6J), originated at The Jackson Laboratory, isolated breeding colonies are now maintained at numerous sites. This separation has resulted in genetic drift that has led to the emergence of phenotypic differences among these colonies. For instance, B6J mice display higher levels of voluntary ethanol consumption and increased locomotor responses to psychostimulants, relative to C57BL/6N mice (B6N). Initial progress has been made in elucidating the genetic bases of these phenotypic differences, as Kumar et al. (2013) identified a single nucleotide polymorphism (SNP) in the Cytoplasmic FMR1-interacting protein 2 (Cyfip2) gene that underlies the differential locomotor response to cocaine exhibited by B6J and B6N mice. The present study compared voluntary ethanol consumption, binge-like drinking, and affective behavior during forced abstinence in B6J and C57BL/6NJ (B6NJ) substrains, and when substrain differences were seen, in CRISPR-Cas9 engineered lines in which the previously identified substrain-specific Cyfip2 SNP was exchanged within the same genetic backgrounds. Results showed that B6J consumed significantly greater quantities of ethanol than B6NJ mice and allelic variation in Cyfip2 greatly contributed to observed substrain differences in two-bottle free-choice ethanol drinking; however, since these differences were completely reversed in males, but not females, it’s likely that sex-specific contributions from other polymorphisms play a role in moderating these effects. Interestingly, there were no significant substrain differences in binge-like drinking or depressive- or anxiety-like behaviors during abstinence. Overall, while B6J and B6NJ mice displayed dramatic differences in voluntary ethanol consumption, which were dependent in part on an identified cocaine-relevant SNP in Cyfip2, no substrain differences were seen in binge- like drinking or affective behavior during abstinence. These results imply that primarily non-overlapping gene sets underlie these specific ethanol-related phenotypes.

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