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Phenotypic and Gene Expression Features Associated with Variation in Chronic Ethanol Consumption in Heterogeneous Stock Collaborative Cross Mice

ABSTRACT: Of the more than 100 studies that have examined some aspect of the relationships between excessive ethanol consumption and the brain transcriptome, relatively few rodent studies have examined the effects of chronic consumption. The current study allowed 114 heterogeneous stock collaborative cross mice to freely consume 10% ethanol for 3 months (13 weeks), with a water choice. RNA-Seq data were then used to identify transcriptional differences within the central nucleus of the amygdala, a brain region known to impact ethanol preference. Average week 1 preference for consuming ethanol over water was modestly correlated with average preference for the final week of the study, and over the course of the 3-month trial, a sex-difference emerged. In females but not males, there was a significant escalation of preference from week 1 to week 13 and significant alignment of the transcriptome with average week 13 ethanol preference and consumption was found for female, but not male mice. The genes significantly correlated with preference were enriched in annotations associated with cilium movement, cilium organization, extracellular region and collagen-containing extracellular matrix. For the females, 376 of the total 415 genes that correlated with ethanol preference in the gene co-expression network were associated with a single network module that was enriched in genes with an astrocyte annotation. The key hub node in the module was the master regulator, orthodenticle homeobox 2 (Otx2). These data support an important role for the extracellular matrix and primary cilium in individual differences in ethanol preference and consumption in a genetically diverse population of mice.

ORGANISM(S): Mus musculus

PROVIDER: GSE151410 | GEO | 2020/05/29

REPOSITORIES: GEO

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Project description:Despite recent extensive genomic and genetic studies on behavioral responses to ethanol, relatively few new therapeutic targets for the treatment of alcohol use disorder have been validated. Here we describe a cross-species genomic approach focused on identifying gene networks associated with chronic ethanol consumption. To identify brain mechanisms underlying a chronic ethanol consumption phenotype highly relevant to human alcohol use disorder, and to elucidate potential future therapeutic targets, we conducted a genomic study in a nonhuman primate model of chronic open-access ethanol consumption. Microarray analysis of RNA expression in anterior cingulate and subgenual cortices from rhesus macaques was performed across multiple cohorts of animals. Gene networks correlating with ethanol consumption or showing enrichment for ethanol-regulated genes were identified, as were major ethanol-related hub genes within these networks. A subsequent consensus module analysis was used to co-analyze monkey data with expression data from a chronic intermittent ethanol vapor-exposure and consumption model in C57BL/6J mice. Ethanol-related gene networks conserved between primates and rodents were enriched for genes involved discrete biological functions, including; myelination, synaptic transmission, chromatin modification, Golgi apparatus function, translation, cellular respiration, and RNA processing. The myelin-related network, in particular, showed strong correlations with ethanol consumption behavior and displayed marked network reorganization between control and ethanol-drinking animals. Further bioinformatics analysis revealed that these networks also showed highly significant overlap with other ethanol-regulated gene sets. Altogether, these studies provide robust primate and rodent cross-species validation of gene networks associated with chronic ethanol consumption. Our results also suggest potential novel focal points for future therapeutic interventions in alcohol use disorder.

Project description:Purpose: Genetic factors significantly affect alcohol consumption and vulnerability to withdrawal. Some genetic models that show predisposition to severe withdrawal are also predisposed to low ethanol consumption and vice versa, even when tested independently in naïve animals. The study was undertaken to understand gene and network differences between mice selectively bred for high withdrawal/low withdrawal or low withdrawal/high consumption. Methods: Beginning with a C57BL/6J×DBA/2J F2 intercross founder population, animals were simultaneously selectively bred for both high alcohol consumption and low acute withdrawal (SOT line), or vice versa (NOT line). Using randomly chosen fourth selected generation (S4) mice (N= 18-22/sex/line), RNA-Seq was employed to assess genome-wide gene expression in the ventral striatum. The Mega-MUGA array was used to detect genome-wide genotypic differences. Differential gene expression and the weighted gene co-expression network analysis (WGCNA) were implemented. Results: The new selection of the SOT and NOT lines was similar to that reported previously (Metten et al. 2014). One thousand eight hundred and fifteen transcripts were detected as being differentially expressed between the lines. For the genes overexpressed in the SOT line there was enrichment in genes associated with cell adhesion, synapse organization and post-synaptic membrane. The genes with a cell adhesion annotation included 23 protocadherins, Mpdz & Dlg2. Genes with a postsynaptic membrane annotation included Gabrb3, Gphn, Grid1, Grin2b, Grin2c & Grm3. The genes overexpressed in the NOT line were enriched in a network module (red) with annotations associated with mitochondrial function. Several of these genes were module hub nodes and these included Nedd8, Guk1, Elof1, Ndufa8, & Atp6v1f. Conclusions: Marked effects of selection on gene expression were detected. The NOT line was characterized by the increased expression of hub nodes associated with mitochondrial function. Genes overexpressed in the SOT aligned with previous findings e.g. Colville et al. (2017) that high ethanol preference and consumption is associated with effects on cell adhesion and glutamate synaptic plasticity.

Project description:The collaborative cross (CC) founder strains include five classical inbred laboratory strains (129S1/SvlmJ, A/J, C57BL/6J (B6), NOD/ShiLtJ, and NZO/HILtJ) and three wild-derived strains (CAST/EiJ, PWK/PhJ (PWK) and WSB/EiJ) The strains encompass 89% of the genetic diversity available in Mus musculus and about 10 to 20 times more genetic diversity than found in Homo sapiens. For more than 60 years the B6 strain has been used as the model strain for high ethanol preference/high consumption. However, another one of the CC founder strains, PWK, was identified as a high ethanol preference/high consumption strain. The current study determined how the transcriptomes of the B6 and PWK strains differed from the 6 low preference CC strains across 3 nodes of the brain addiction circuit. RNA-Seq data were collected from the central nucleus of the amygdala, the nucleus accumbens core and the prelimbic cortex. Differential expression (DE) analysis was performed in each of these brain regions for all 28 possible pairwise comparisons of the CC founder strains. Unique genes for each strain were identified by selecting for genes that differed significantly (false discovery rate (FDR) < 0.05) from all other strains in the same direction. B6 was identified as the most distinct inbred laboratory strain, having the highest number of total differently expressed genes (DEGs) and DEGs with high log fold change, and unique genes compared to other CC strains. Less than 50 unique DEGs were identified in common between B6 and PWK within all three brain regions, indicating the strains potentially represent two distinct genetic signatures for risk for high ethanol-preference. 238 DEGs were found to be commonly different between B6, PWK and the average expression of the remaining CC strains within all three regions. The commonly different up-expressed genes were significantly enriched (FDR < 0.001) among genes associated with neuroimmune function. These data compliment the observation that neuroimmune signaling is key to understanding alcohol use disorder and and support use of these 8 strains and the highly heterogeneous mouse populations derived from them to identify alcohol-related brain mechanisms and treatment targets.

Project description:This study investigated changes in gene expression associated with ethanol drinking in adult male P rats under the following conditions for 8 weeks: continuous access (24 hr/day, 7 days/week), multiple scheduled access (three 1-hr sessions during the dark cycle/day, 5 days/week) and ethanol-naive (water). The objective of this study was to investigate changes in gene expression associated with ethanol drinking. Adult male alcohol-preferring (P) rats were given Ethanol in their home-cages under continuous access (CA; 24 hr/day, 7 days/week) or multiple scheduled access (MSA; three 1-hr sessions during the dark cycle/day, 5 days/week) conditions for 8 weeks. A third group was ethanol-naïve (W group). Average ethanol intakes, across the 8 weeks, for the CA and MSA groups were approximately 9.5 and 6.5 g/kg/day, respectively. Fifteen hr after the last ethanol drinking episode, rats were euthanized, the brains rapidly extracted, and the nucleus accumbens (ACB) dissected. RNA was extracted and purified for microarray analysis. The only significant differences, overall, were between the CA and W groups (p < 0.01; Storey false discovery rate = 0.15); there were 374 significant differences in unique named genes between these 2 groups. There were 20 significant Gene Ontology (GO) biological processes categories, which included ‘negative regulation of protein kinase activity’, ‘anti-apoptosis’, and ‘regulation of G-protein-coupled receptor protein signaling pathway’. Ingenuity® analysis indicated a network of transcription factors, involving oncogenes (Fos, Jun, Junb had higher expression levels in the ACB of the CA than W group), suggesting increased neuronal activity in the CA group. There were 13 genes (Hspa5, Stom, Lcn7, Tceb3, Cdc42, Rap1ga1, Ece1, Dhrs3, Plod1, Kif1b, Nmnat1, Srpr, Esam) significantly different between the CA and W groups located within both mouse and rat ethanol QTLs, suggesting that these genes may contribute to ethanol drinking behavior. In conclusion, the robust differences in gene expression found between the CA and W groups, but not observed between the MSA and W groups, may be a result of the higher daily ethanol intakes of the CA group, and/or its initial ethanol withdrawal. Keywords: comparison of gene expression profiles for treated vs. control

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Phenotypic and Gene Expression Features Associated with Variation in Chronic Ethanol Consumption in Heterogeneous Stock Collaborative Cross Mice

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