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Modulation of miR-181 influences dopaminergic neuronal degeneration in a mouse model of Parkinson’s disease

ABSTRACT: Parkinson’s disease (PD) is caused by loss of dopaminergic (DA) neurons in the substantia nigra (SN). Although PD pathogenesis is not fully understood, studies implicate perturbations in gene regulation, mitochondrial function, and neuronal activity. MicroRNAs (miRs) are small gene regulatory RNAs that inhibit diverse subsets of target mRNAs, and several studies have noted miR expression alterations in PD brains. For example, miR-181a is abundant in brain and is increased in PD patient brain samples; however, the disease relevance of this remains unclear. Herein, we show that miR-181 target mRNAs are broadly down-regulated in aging and PD brains. To address if the miR‑181 family plays a role in PD pathogenesis, we generated adeno-associated viruses (AAV) to overexpress and inhibit miR-181 isoforms. After co-injection with AAV overexpressing alpha-synuclein (aSyn) into mouse SN (PD model), we found that moderate miR-181a/b overexpression exacerbated aSyn-induced DA neuronal loss, whereas miR‑181 inhibition was neuroprotective, relative to controls (GFP-alone and/or scrambled RNA). Also, prolonged miR-181 overexpression in SN alone elicited measurable neurotoxicity coincident with an increased immune response. RNA-seq analyses revealed that miR-181a/b inhibits genes involved in synaptic transmission, neurite outgrowth, and mitochondrial respiration, along with several genes having known protective roles and genetic links in PD.

ORGANISM(S): Mus musculus

PROVIDER: GSE196441 | GEO | 2022/03/23

REPOSITORIES: GEO

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Project description:Parkinsonâs disease (PD) and Dementia with Lewy bodies (DLB) are the two most common examples of synucleinopathies, i.e. human disorders that display intracellular deposition of the Alpha-synuclein (aSYN) protein. The two forms of aSYN deposits, intracellular Lewy bodies and Lewy neurites, are in the PD brain primarily found in the substantia nigra whereas in DLB brains they are diffusely spread in cortical and limbic areas. We are currently analyzing the protective effects on aSYN pathology by the molecular chaperone hsp70 in mice overexpressing wildtype human aSYN. Moreover, transgenic mice overexpressing hsp70 have been cross-bred with the aSYN mouse line. Intriguingly, the aSYN / hsp70 double transgenics display a pronounced reduction in biochemically assessed aSYN aggregation. Gene expression of these mice will not only provide insight into the disease mechanisms of aSYN pathology but its prevention by the overexpression of hsp70, leading to new potential avenues of treatment. Project 1: To investigate and compare alterations in gene expression profiles of brains from wild-type mice and mice overexpressing wildtype human aSYN, human hsp70 and aSYN / hsp70, respectively. The comparison of the expression profiles of the groups of mice: aSYN, Hsp70, aSYN/ Hsp70 and non-transgenic littermates will help to identify the genes that are involved in the mediation of aggregation toxicity of aSYN expression as well as the genes that may mediate an attenuation of aSYN pathology in hsp70-coexpressors. Project 1: Selection of animals Mice of 4 month old (n=6) of age of each background (aSYN, Hsp70, aSYN/ Hsp70 and non-transgenic littermates) will be used for RNA-extraction for a total of 24 mice. Preparation of samples For the proposed experiments, we will use the recommended procedures, as outlined by the consortium, for extracting and purifying RNA from whole brain homogenate. Briefly, RNA will be extracted by the trizol method and purified by using the RNeasy MinElute Cleanup (QIAGEN Inc., USA). RNA labeling and hybridization procedures will be carried out by the microarray consortium. SPECIAL NOTE: The samples will be sent upon availability. Gene Expression Microarray Analysis Six mice will be included in each group per timepoint to generate statistically testable data and limit the possible confound of individual mouse gene expression variations. The genome expression will be evaluated through the use of the GeneChipÂ® Mouse Genome 430 2.0 Array (Affymetrix) for each individual mouse constituting a total of 24 arrays for the proposed study. Gene expression data interpretation will be assisted by the Microarray Consortium Center bioinformatics core.

Project description:Purpose: miR-181 is upregulated in human liver cancer. The cancer genome atlas (TCGA) liver cancer data show that the iCluster1 subclass of hepatocellular carcinoma (HCC) has a higher expression of miR-181 than either the iCluster2 or iCluster3 subclass, suggesting it may be a driver of oncogenesis. However, the miR-181 family has also been reported to inhibit tumour progression. Thus, we aim to examine the function of miR-181 and its vital mediators in hepatocarcinogenesis. Methods: Primary liver tumours were induced with diethylnitrosamine (DEN) in global (miR-181ab1GKO), liver-specific (miR-181ab1LKO) and hematopoietic & endothelial lineage-specific (miR-181ab1vavKO) miR-181ab1 deletion mice. The molecular and cellular characterization was carried out using immunohistochemistry and whole-genome transcriptome analysis. Liver-specific miR-181a and CBX7 double knockout mice were used to investigate the role of CBX7 in mediating miR-181 effects on liver tumour progression. An AAV/Transposase Hybrid-Vector System used in this study gave a reliable long-term expression of CBX7 in vivo. Relevant gene expression profiles and patient outcomes were downloaded from TCGA database, and their correlations were analysed. The mRNA profiles of miR-181ab1 wild-type (WT) and knockout (KO) mice were generated by deep sequencing, in triplicate, using Illumina HiSeq. After quality control procedures, short reads were mapped to mouse genome assembly (mm10) by STAR version 2.7.3a. Mapped reads were quantified by featureCounts version 2.0.0 from Subread package. Ward’s hierarchical clustering method was applied to group the samples based on the gene expression matrix. Differential gene expression analysis was then conducted using R package Limma. Gene set enrichment analysis was subsequently performed with R package clusterProfiler. Overlaps between differential expressed gene sets and gene sets in MSigDB were computed with Gene Set Enrichment Analysis (GSEA). Results: The number and size of liver tumours in 181ab1GKO mice were significantly reduced by 50% and 90%, respectively, compared to WT mice at 34-week post-DEN injection. The number of tumours in 181ab1LKO mice was no different from that of control mice, but the size of liver tumours was significantly reduced by 90%. The number and size of tumours were similar in miR-181ab1vavKO and WT mice. Consistent with the roles of miR-181 in the promotion of epithelial to mesenchymal transition (EMT), the TGF-beta signalling pathway was inhibited in 181ab1GKO tumours compared with WT tumours, and expression of E-Cadherin, an EMT marker, was significantly increased in miR-181ab1 KO tumours compared to WT tumours. CBX7 was reduced in WT liver tumours compared to non-tumours, and restored CBX7 expression inhibited the progression of liver tumours in WT mice. At the same time, CBX7 was upregulated in miR-181ab1 KO tumours compared to WT tumours, and CBX7 deletion turned the reduced progression of miR-181ab1 KO liver tumours back to WT liver tumours. MiR-181a expression was the lowest and CBX7 expression the highest in iCluster 2 & 3 subclasses of human HCC compared to iCluster 1. Gene expression profiles were significantly overlapped between human low proliferative periportal-type HCCs and miR-181ab1 KO tumours. Conclusions: Primary liver tumour progression is inhibited by loss of miR-181ab1 via up-regulation of CBX7 expression at the level of the liver cancer cells themselves, but tumour induction requires both hepatic and non-hepatic expression. Tumours in miR-181ab1 KO mice resemble low-proliferative periportal-type human HCC and could represent a new model to study therapies for such difficult-to-treat tumours.

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Modulation of miR-181 influences dopaminergic neuronal degeneration in a mouse model of Parkinson’s disease

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