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Integrating mRNA and miRNA Co-Expression Networks with eQTLs in the Nucleus Accumbens of Human Chronic Alcoholics

ABSTRACT: 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.

ORGANISM(S): synthetic construct Homo sapiens

PROVIDER: GSE62699 | GEO | 2015/05/22

SECONDARY ACCESSION(S): PRJNA264834

REPOSITORIES: GEO

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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: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:We addressed the integrated analysis of mRNA and miRNA expression levels of Tg6799 AD model mice at 4 month and 8 months of age. Total 8 gene cluster modules for co-expression network were predicted from transcriptome data and 6 modules were show relation with AD or aging. We constructed early stage AD network using data integration between mRNA and miRNA profiles and predicted miRNAs strongly involved in module regulation. We found that ARRDC3 showed AD mutation dependent changes of expression and was related metabolic dysfunction in early stage AD. These results demonstrate that candidate genes on the simultaneous profiling of mRNA and miRNA expressions in genome wide can be used for the understanding of non-coding RNA related gene expression in early stage AD. We suggested that our results could be future candidate to be developed as early biomarkers in progressive AD pathology. This result can be used for the further application in neurodegenerative diseases. Tg6799 transgenic mice were purchased from The Jackson Laboratory (USA) and were housed under a 12h light-dark cycle with free access to food and water. Female Tg6799 mice are maintained until 4 months and 8 months of age (for littermate control: LM and mutant subjects: MT). RNA samples were isolated from hippocampus of mice using TRI-Reagent (Sigma-Aldrich, St. Louis, MO) according to the manufacturer’s instructions. Gene expression was analyzed with GeneChip® Mouse Genome 430 2.0 Arrays (Affymetrix, Santa Clara, CA), which is comprised of over 45,000 probe sets representing approximately 28,700 well-characterized mouse genes. The Ion Total RNA-Seq Kit v2 (Lifetechnologies, USA) was used for the preparation of micro RNA libraries according to the manufacturer's instructions. Total numbers of subject used are as followed: 1) LM 4 months : MT 4 months : LM 8 months : MT 8 months (2:4:2:4) for screening mRMA and miRNA, 2) LM 4 months : MT 4 months : LM 8 months : MT 8 months (4:4:4:4) for expression verification.

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Integrating mRNA and miRNA Co-Expression Networks with eQTLs in the Nucleus Accumbens of Human Chronic Alcoholics

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