The Lmo3 Gene: A Regulator Of Anxiety And Behavioral Responses To Alcohol
thesisposted on 01.11.2017, 00:00 authored by Antonia Savarese
Anxiety disorders and alcohol use disorders share common neural circuitry and molecular mechanisms that may underlie a shared pathology, including alterations in CRF signaling in the extended amygdala. Because both disorders are highly heritable, finding target genes that may be implicated in alcohol-related and anxiety-like behaviors is critical toward targeting novel and effective treatments. Genes that regulate CRF signaling in the extended amygdala may be especially promising, given the alterations in this system in both anxiety and alcohol use. LMO proteins are transcriptional regulators that can also function in the cytosol to regulate protein activity levels. Recent work has implicated several LMO proteins in behaviors involved in both alcohol/substance abuse and anxiety. LMO3 is involved in central nervous system development and is highly expressed throughout the brain in adulthood, making it an excellent candidate for regulation of neural signaling and behavior. Indeed, recent work in our lab has supported a role for Lmo3 in the regulation of several alcohol-related phenotypes, including sensitivity to the sedative effects of alcohol and low-to-moderate alcohol consumption. In this dissertation, I sought to characterize the role of Lmo3 in regulation of anxiety-like behavior and high-risk binge-like alcohol consumption. Utilizing the Lmo3 null (Lmo3Z) mouse and its wild type littermates, Lmo3 was found to promote anxiety-like behavior and inhibit excessive alcohol consumption. In an effort to target a brain region in which Lmo3 could be acting to produce these behaviors, viral-mediated RNA interference was utilized to knockdown Lmo3 expression in brain regions in two areas of the amygdala and in the nucleus accumbens (NAc). Knockdown of Lmo3 in the basolateral amygdala (BLA) replicated the anxiolytic phenotype observed in Lmo3Z mice, but Lmo3 knockdown in the neighboring central nucleus of the amygdala (CeA) did not, suggesting that Lmo3 regulates anxiety-like behavior via its actions in the BLA. Targeted knockdown of Lmo3 in the BLA and the NAc did not replicate the binge drinking phenotype observed in Lmo3Z mice. The mechanism driving elevated binge drinking in these mice is yet unknown. In an effort to identify potential downstream targets of Lmo3, brain tissue from Lmo3Z and wild type mice was collected to measure differences in mRNA and protein expression of relevant genes: Crh, Crhr1, Gabra1, Gabra4, and Gabrd. Lmo3Z mice had a reduction of Crhr1 mRNA and CRF1R protein expression in the BLA. Additionally, Lmo3Z mice showed a reduction of Crhr1 mRNA in the CeA, increased Gabra4 mRNA in the BLA, and a sex-specific increase in Gabrd mRNA in the BLA of only females. No corresponding changes in protein expression were observed for these genes. In addition to basal anxiety and binge drinking, Lmo3Z mice showed sex-specific alterations in ethanol conditioned place preference (CPP, a measure of alcohol reward), cocaine CPP, and ethanol-induced anxiolysis. Female Lmo3Z mice failed to develop ethanol CPP or ethanol-induced anxiolysis, though they showed an enhanced response to the rewarding effects of cocaine. Taken together, these results suggest a novel role for Lmo3 in the regulation of both anxiety and alcohol abuse and suggest that Lmo3 may be a good candidate gene to further understand the neural mechanisms driving these pathologies.