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: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.

Dataset Information

Network preservation reveals shared and unique biological processes associated with chronic alcohol abuse in the NAc and PFC [mRNA]

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