Expression profiling by array Non-coding RNA profiling by array
Summary
Action of alcohol on synaptic mRNA in the amygdala of mice Chronic alcohol consumption induces changes in gene expression, causing persistent long-term neuro-adaptations and the remodeling of synaptic structures. These alcohol-induced synaptic changes may rely specifically on the local translation of mRNAs in the synaptic compartments of the cell. We profiled the transcriptome from synaptoneurosomes (SN) and paired total homogenates (TH) of amygdala to analyze the synaptic adaptations induced by chronic voluntary alcohol consumption in mice. In the SN both the number of alcohol-responsive mRNAs and the magnitude of fold-change were greater than in the TH. Accordingly, the SN detected many genes with coordinated patterns of expression producing a highly connected mRNA network in gene co-expression analysis. The greater sensitivity of the SN preparation allowed for improved cell-type specificity analysis, revealing an up-regulation of alcohol-responsive astrocytic and microglial modules that correlated with alcohol consumption. Alcohol was found to induce changes in the SN functionally important biological pathways, including long-term potentiation, long-term potentiation depression, glutamate pathway, neuro-immune, RNA-processing and translational machineries and provided overlap with changes seen in human alcoholic brain. Transposable elements were responsive to alcohol and found in the down-regulated neuronal mRNA module, which may underlie some of the coordinated gene expression changes associated with alcohol. We provide evidence that enrichment of synaptic components reveals a more intricate network of coordinated gene expression. Increased resolution captures the molecular effects of synaptic manipulations and provides an improved technique for identifying therapeutic targets for alcohol abuse.
Local translation of mRNAs in the synapse plays a major role in synaptic structure and function. Chronic alcohol use causes persistent changes in synaptic mRNA expression, possibly mediated by microRNAs localized in the synapse. We profiled the transcriptome of synaptoneurosomes (SN) from the amygdala of mice chronically consuming 20% ethanol in a continuous two-bottle choice test to identify the microRNAs that target alcohol-induced mRNAs. SN are membrane vesicles containing pre- and post-synaptic compartments of neurons and astroglia and are a unique model for studying the synaptic transcriptome. We previously showed that chronic alcohol regulates mRNA expression in a coordinated manner. Here, we examine microRNAs and mRNAs from the same samples to define alcohol-responsive synaptic microRNAs and their predicted interactions with targeted mRNAs. We used a combination of unbiased bioinformatic methods (differential expression, correlation, co-expression, microRNA-mRNA target prediction, co-targeting and cell type specific analyses) to identify key alcohol-sensitive microRNAs. Bidirectional mRNA-microRNA prediction analysis showed that a subset of alcohol-responsive microRNAs were predicted to target many alcohol-responsive mRNAs. We found microRNAs-mRNAs with overlapping patterns of expression that correlated with the amount of alcohol consumed. Cell-type specific analysis revealed a significant number of the alcohol-responsive mRNAs and microRNAs that were unique to glutamate neurons and were highly predicted to target each other. Chronic alcohol appears to perturb the coordinated microRNA regulation of mRNAs in SN, a mechanism that may explain the aberrations in synaptic plasticity affecting the alcoholic brain.
Overall design
Synaptoneurosomes (SN) and Paired total homogenates (TH) were prepared from the same homogenate. 42 microarrays were used in total for the alcohol-control mRNA analysis (8 alcohol treated mice and 13 controls), 21 SN and 21 paired TH. 2 TH (control) samples were found outliers and were removed from the analysis. For the SN vs. TH analysis, the 2 TH samples found outliers were removed with the 2 paired SN samples. 40 microarrays were used in total for the alcohol-control miRNA analysis (8 alcohol treated mice and 12 controls), 20 SN and 20 paired TH.
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