Identifying a novel biological mechanism for alcohol addiction associated with circRNA networks acting as potential miRNA sponges.
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ABSTRACT: Our lab and others have shown that chronic alcohol use leads to gene and miRNA expression changes across the mesocorticolimbic (MCL) system. Circular-RNA (circRNA) are noncoding RNA that form closed-looped structures and are reported to alter gene expression through miRNA sequestration, thus providing a potentially novel neurobiological mechanism for the development of alcohol dependence (AD). Genome-wide expression of circRNA was assessed in nucleus accumbens (NAc) from 32 AD matched cases/controls. Significant circRNA (unadj. p≤0.05) were identified via regression and clustered in circRNA networks via WGCNA. CircRNA interactions with previously generated mRNA and miRNA were detected via correlation and bioinformatic analyses. MatrixeQTL was used to identify eQTLs affecting circRNA expression. Genomic enrichment was used to detect overlap between eQTLs and recent GWAS of substance abuse. Significant circRNAs (N=542) clustered in 9 significant AD modules (FWER p≤0.05), within which we identified 137 circRNA hubs. We detected 23 significant circRNA:miRNA:mRNA interactions (FDR≤0.10). Among these, circRNA-406742 and miR-1200 significantly interact with the highest number of mRNA, including genes associated with neuronal functioning and alcohol addiction (HRAS, PRKCB, HOMER1, and PCLO). Finally, we identified 96 significant circRNA eQTLs (unadj. p≤0.002), showing significant enrichment within recent alcohol use disorder (AUD) and smoking GWAS. To our knowledge, this is the first study to examine the role of circRNA in the neuropathology of AD. We show that circRNA impact mRNA expression by interacting with miRNA in the NAc of AD subjects. We further identify genetic variants affecting circRNA expression impacting potential miRNA and mRNA interactions. More importantly, we provide indirect evidence for the clinical importance of circRNA in the development of AUD by detecting a significant enrichment of our circRNA eQTLs among GWAS of substance abuse.
Project description:Chronic alcohol abuse has been linked to the disruption of executive function and allostatic conditioning of reward response dysregulation in the mesocorticolimbic pathway (MCL). Here, we analyzed genome-wide mRNA and miRNA expression from matched cases with alcohol dependence (AD) and controls (n=35) via gene network analysis to identify unique and shared biological processes dysregulated in the prefrontal cortex (PFC) and nucleus accumbens (NAc). We further investigated potential mRNA/miRNA interactions at the network and individual gene expression levels to identify the neurobiological mechanisms underlying AD in the brain. By using genotyped and imputed SNP data, we identified expression quantitative trait loci (eQTL) uncovering potential genetic regulatory elements for gene networks associated with AD. At a Bonferroni corrected p≤0.05, we identified significant mRNA (NAc=6; PFC=3) and miRNA (NAc=3; PFC=2) AD modules. The gene-set enrichment analyses revealed modules preserved between PFC and NAc to be enriched for immune response processes, whereas genes involved in cellular morphogenesis/localization and cilia-based cell projection were enriched in NAc modules only. At a Bonferroni corrected p≤0.05, we identified significant mRNA/miRNA network module correlations (NAc=6; PFC=4), which at an individual transcript level implicated miR-449a/b as potential regulators for cellular morphogenesis/localization in NAc. Finally, we identified eQTLs (NAc: mRNA=37, miRNA=9; PFC: mRNA=17, miRNA=16) which potentially mediate alcohol’s effect in a brain region-specific manner. Our study highlights the neurotoxic effects of chronic alcohol abuse as well as brain region specific molecular changes that may impact the development of alcohol addiction.
Project description:Chronic alcohol abuse has been linked to the disruption of executive function and allostatic conditioning of reward response dysregulation in the mesocorticolimbic pathway (MCL). Here, we analyzed genome-wide mRNA and miRNA expression from matched cases with alcohol dependence (AD) and controls (n=35) via gene network analysis to identify unique and shared biological processes dysregulated in the prefrontal cortex (PFC) and nucleus accumbens (NAc). We further investigated potential mRNA/miRNA interactions at the network and individual gene expression levels to identify the neurobiological mechanisms underlying AD in the brain. By using genotyped and imputed SNP data, we identified expression quantitative trait loci (eQTL) uncovering potential genetic regulatory elements for gene networks associated with AD. At a Bonferroni corrected p≤0.05, we identified significant mRNA (NAc=6; PFC=3) and miRNA (NAc=3; PFC=2) AD modules. The gene-set enrichment analyses revealed modules preserved between PFC and NAc to be enriched for immune response processes, whereas genes involved in cellular morphogenesis/localization and cilia-based cell projection were enriched in NAc modules only. At a Bonferroni corrected p≤0.05, we identified significant mRNA/miRNA network module correlations (NAc=6; PFC=4), which at an individual transcript level implicated miR-449a/b as potential regulators for cellular morphogenesis/localization in NAc. Finally, we identified eQTLs (NAc: mRNA=37, miRNA=9; PFC: mRNA=17, miRNA=16) which potentially mediate alcohol’s effect in a brain region-specific manner. Our study highlights the neurotoxic effects of chronic alcohol abuse as well as brain region specific molecular changes that may impact the development of alcohol addiction.
Project description:Alcohol consumption is known to lead to gene expression changes in the brain. After performing gene co-expression network analysis (WGCNA) of genome-wide mRNA and microRNA expressions in the Nucleus Accumbens (NAc) from subjects with alcohol dependence (AD) and matched controls six mRNA and three miRNA modules significantly correlated with AD after Bonferroni correction (adj. p? 0.05) were identified. Cell-type-specific transcriptome analysis revealed two of the mRNA modules to be enriched for neuronal specific marker genes and downregulated in AD, whereas the remaining four were enriched for astrocyte and microglial specific marker genes and were upregulated in AD. Using gene set enrichment analysis, the neuronal specific modules were enriched for genes involved in oxidative phosphorylation, mitochondrial dysfunction and MAPK signaling, while the glial-specific modules were enriched mostly for genes involved in processes related to immune functions, i.e. reactome cytokine signaling in immune system (all adj. p? 0.05). In the mRNA and miRNA modules, 461 and 25 candidate hub genes were identified, respectively. In contrast to the expected miRNAs’ biological functions, the correlation analyses between mRNA and miRNA hub genes revealed a significantly higher number of positive than negative correlations (chi-square p? 0.0001). At FDR? 0.1, integration of the mRNA and miRNA hubs genes expression with genome-wide genotypic data identified 591 cis-eQTLs and 62 cis-eQTLs for the mRNA and miRNA hubs, respectively. Adjusting for the number of tests, the mRNA cis-eQTLs were significantly enriched for AD GWAS signals in the Collaborative Study on Genetics of Alcohol (COGA) sample (adj. p=0.024), providing a novel biological role for these association signals. In conclusion, our study identified coordinated mRNA and miRNA co-expression changes in the NAc of AD subjects, and our genetic (cis-eQTL) analysis provides novel insights into the etiological mechanisms of AD. Tissue samples were received from the Australian Brain Donor Programs New South Wales Tissue Resource Centre, which is supported by The University of Sydney, National Health and Medical Research Council of Australia, Schizophrenia Research Institute, National Institute of Alcohol Abuse and Alcoholism, and the New South Wales Department of Health. Cases were excluded if they had an infectious disease (i.e. HIV/AIDS, hepatitis B or C, or Creutzfeldt-Jakob disease), an unsatisfactory agonal status determined from the circumstances surrounding the death, post-mortem delays >48 hours, or significant head injury. In addition to case status, age, sex, ethnicity, brain weight, brain pH, post-mortem interval (PMI), tissue hemisphere, clinical cause of death, blood toxicology at time of death, smoking status, neuropathology and liver pathology were also provided for each subject. MiRNA and mRNA expression in 18 matched case-control pairs (N=36) with sample RINs ?6 were assessed on the Affymetrix GeneChip® Human Genome U133A 2.0 (HG-U133A 2.0) and Affymetrix GeneChip miRNA 3.0 microarray.
Project description:Alcohol consumption is known to lead to gene expression changes in the brain. After performing gene co-expression network analysis (WGCNA) of genome-wide mRNA and microRNA expressions in the Nucleus Accumbens (NAc) from subjects with alcohol dependence (AD) and matched controls six mRNA and three miRNA modules significantly correlated with AD after Bonferroni correction (adj. p≤ 0.05) were identified. Cell-type-specific transcriptome analysis revealed two of the mRNA modules to be enriched for neuronal specific marker genes and downregulated in AD, whereas the remaining four were enriched for astrocyte and microglial specific marker genes and were upregulated in AD. Using gene set enrichment analysis, the neuronal specific modules were enriched for genes involved in oxidative phosphorylation, mitochondrial dysfunction and MAPK signaling, while the glial-specific modules were enriched mostly for genes involved in processes related to immune functions, i.e. reactome cytokine signaling in immune system (all adj. p≤ 0.05). In the mRNA and miRNA modules, 461 and 25 candidate hub genes were identified, respectively. In contrast to the expected miRNAs’ biological functions, the correlation analyses between mRNA and miRNA hub genes revealed a significantly higher number of positive than negative correlations (chi-square p≤ 0.0001). At FDR≤ 0.1, integration of the mRNA and miRNA hubs genes expression with genome-wide genotypic data identified 591 cis-eQTLs and 62 cis-eQTLs for the mRNA and miRNA hubs, respectively. Adjusting for the number of tests, the mRNA cis-eQTLs were significantly enriched for AD GWAS signals in the Collaborative Study on Genetics of Alcohol (COGA) sample (adj. p=0.024), providing a novel biological role for these association signals. In conclusion, our study identified coordinated mRNA and miRNA co-expression changes in the NAc of AD subjects, and our genetic (cis-eQTL) analysis provides novel insights into the etiological mechanisms of AD.
Project description:The impact of alcohol abuse on AD is poorly understood. Here we show that the onset of neurocognitive impairment in a mouse model of AD is hastened by repeated alcohol intoxication through exposure to alcohol vapor and we provide a comprehensive gene expression dataset of the prefrontal cortex by single nucleus RNA sequencing of 113,242 cells. Several genes previously associated with AD in humans by GWAS were differentially regulated in specific neuronal populations. Gene expression patterns of AD mice with a history of alcohol intoxication were more similar to the gene expression signatures of older AD mice with more advanced disease and cognitive impairment than to those of younger AD mice with prodromic disease, suggesting that alcohol promotes transcriptional changes consistent with AD progression. Our gene expression dataset at the single cell level provides a unique resource for investigations of the molecular bases of the detrimental role of excessive alcohol intake in AD.
Project description:Chronic alcohol consumption may alter miRNA transcriptome profiles in reward-related brain regions. Given that miRNAs can regulate the expression of their target coding genes (or mRNAs) at the post-transcriptional level, alcohol-induced miRNA expression change may influence the expression of their targets mRNAs that are involved in alcohol use disorder (AUD)-related pathways, leading to increased risk of AUD. We used the Affymetrix GeneChip™ miRNA 4.0 Array to map miRNA transcriptome profiles in six reward-related regions of postmortem brains of AUD and control subjects and identified differentially expressed miRNAs.
Project description:Environmental factors, including substance abuse and stress, cause long-lasting changes in the regulation of gene expression in the brain via epigenetic mechanisms, such as DNA methylation. We examined genome-wide DNA methylation patterns in the prefrontal cortex (PFC, BA10) of 25 pairs of control and individuals with AUD, using the Infinium® MethylationEPICBeadChip. We identified 5,254 differentially methylated CpGs (pnominal<0.005). Bioinformatic analyses highlighted biological processes containing genes related to stress adaptation, including the glucocorticoid receptor (encoded by NR3C1). Considering that alcohol is a stressor, we focused our attention on differentially methylated regions of the NR3C1 gene and validated the differential methylation of several genes in the NR3C1 network. We observed that chronic alcohol drinking results in a significant increased methylation of the NR3C1 exon variant 1H, with a particular increase in the levels of 5-hydroxymethylcytosine over 5-methylcytosine. These changes in DNA methylation were associated with reduced NR3C1 mRNA and protein levels in PFC as well as other cortico-limbic regions of AUD subjects when compared to controls. Furthermore, we show that the expression of several stress-responsive genes (e.g., CRF, POMC, FKBP5) is altered in the PFC of AUD subjects. These stress-response genes were also changed in the hippocampus, a region that is highly susceptible to stress. These data suggest that alcohol-dependent aberrant DNA methylation of NR3C1 and consequent changes in other stress-related genes might be fundamental in the pathophysiology of AUD and lay the groundwork for treatments targeting the epigenetic mechanisms regulating NR3C1 in AUD.
Project description:Purpose: The goal of this study to examine mRNA transcriptomic changes in reward-related brain regions of subjects with alcohol use disorder. Methods: Total RNAs were extracted from postmortem caudate nucleus of 12 AUD and 12 control subjects. rRNA depletion RNA sequencing was performed and the sequence reads were processed using the bulk RNA-seq processing pipeline Pipeliner workflow (Federico et al. Front Genet 2019; 10, 614). AUD-associated mRNA transcriptomic changes were analyzed by the Limma-Voom method. Results: Differentially expressed mRNAs (absolute FC>2.0 & P<0.05) were identified in postmortem caudate nucleus of subjects with alcohol use disorder (AUD). Chronic alcohol consumption may alter mRNA transcriptome profiles in reward-related brain regions, resulting in alcohol-induced neuroadaptations.
Project description:Purpose: The goal of this study to examine mRNA transcriptomic changes in reward-related brain regions of subjects with alcohol use disorder. Methods: Total RNAs were extracted from postmortem amygdala of 12 AUD and 12 control subjects. rRNA depletion RNA sequencing was performed and the sequence reads were processed using the bulk RNA-seq processing pipeline Pipeliner workflow (Federico et al. Front Genet 2019; 10, 614). AUD-associated mRNA transcriptomic changes were analyzed by the Limma-Voom method. Results: Differentially expressed mRNAs (absolute FC>2.0 & P<0.05) were identified in postmortem amygdala of subjects with alcohol use disorder (AUD). Chronic alcohol consumption may alter mRNA transcriptome profiles in reward-related brain regions, resulting in alcohol-induced neuroadaptations.
Project description:Purpose: The goal of this study to examine mRNA transcriptomic changes in reward-related brain regions of subjects with alcohol use disorder. Methods: Total RNAs were extracted from postmortem cerebellum of 12 AUD and 12 control subjects. rRNA depletion RNA sequencing was performed and the sequence reads were processed using the bulk RNA-seq processing pipeline Pipeliner workflow (Federico et al. Front Genet 2019; 10, 614). AUD-associated mRNA transcriptomic changes were analyzed by the Limma-Voom method. Results: Differentially expressed mRNAs (absolute FC>2.0 & P<0.05) were identified in postmortem cerebellum of subjects with alcohol use disorder (AUD). Chronic alcohol consumption may alter mRNA transcriptome profiles in reward-related brain regions, resulting in alcohol-induced neuroadaptations.