Unknown,Transcriptomics,Genomics,Proteomics

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MRNA microarray analysis of the substantia nigra in a mouse model of multiple system atrophy

ABSTRACT: Multiple system atrophy (MSA) is a fatal rapidly progressive Î±-synucleinopathy, characterized by prominent Î±-synuclein accumulation in oligodendrocytes. In this study we investigated mRNA expression in substantia nigra of MSA transgenic mice (Tg(Plp1-SNCA)1Haa) and wild type controls. This forms part of a larger study in which we investigated miRNA-mRNA regulatory network in substantia nagra and striatum of MSA transgenic mice in pre-motor stage of neurodegenration.

INSTRUMENT(S): fluidic station 450 and Affymetrix scanner 3000

ORGANISM(S): Mus musculus

SUBMITTER: Rimpi Khurana

PROVIDER: E-MTAB-3985 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Implications for neuroprotection in Parkinson's disease Parkinson’s disease and its characteristic symptoms are thought to arise from the progressive degeneration of specific midbrain dopamine (DA) neurons. In humans, DA neurons of the substantia nigra (SN) and their projections to the striatum show selective vulnerability, while neighboring DA neurons of the ventral tegmental area (VTA) are relatively spared from degeneration. This pattern of cell loss is mimicked in humans, primates, and certain rodents by the neurotoxin MPTP. In this study, we aimed to test the hypothesis that there are factors in the VTA that are potentially neuroprotective against MPTP and that these factors change over time. We have found a differential transcriptional response within the cells of the SN and VTA to sustained exposure to a low dose of MPTP. Specifically, the VTA has increased expression of 148 genes as an early response to MPTP and 113 genes as a late response to MPTP toxicity. This response encompasses many areas of cellular function, including protein regulation (Phf6) and ion/metal regulation (PANK2, Car4). Notably, these responses were largely absent from the cells of the SN. Our data show a clear dynamic response in maintaining the homeostasis and viability of the neurons in the VTA that is lacking in the SN after neurotoxin challenge. We used microarrays to analyze the differential response of the substantia nigra (SN) and ventral tegmental area (VTA) to a chronic low dose of the neurotoxin MPTP. Transgenic hTH-GFP mice were treated with MPTP (4mg/kg) for either 2 or 10 days. Control mice were given an equal volume of saline for 10 days. Dopamine neurons from the substantia nigra and ventral tegmental areas of control and MPTP treated animals were laser captured. The RNA was isolated and processed for microarray hybridization. Each group had three biological replicates, for a total of 18 samples. Three each in the following: Control SN, Control VTA, 2 day MPTP SN, 2 day MPTP VTA, 10 day MPTP SN, 10 day MPTP VTA. Samples were log2 transformed and RMA normalized using Agilent Genespring 10.0 GX.

Project description:Rett syndrome (RTT) is a neurodevelopmental disorder characterized by developmental regression around 6-18 months after birth, followed by a lifetime of intellectual disability, stereotyped behaviors, and motor deficits. RTT is caused by mutations in MeCP2, a methyl-CpG binding protein that was traditionally believed to repress gene expression. Gene expression studies of individual brain regions, however, have revealed that MeCP2 loss-of-function leads to the subtle activation and repression of its gene targets. However, these results may be confounded by the extensive neuronal cell heterogeneity inherent in these brain structures. To minimalize this issue of heterogeneity, we assessed whether Mecp2-null mice exhibited alterations in gene expression patterns in the striatum, a brain nucleus with relatively homogenous neuronal types and is highly relevant to the motor deficits observed in RTT. Despite the homogeneity of the tissue, the fold-change of the 127 differentially expressed genes we identified remained low with a mean change consistent with other studies. However, many of those genes differentially expressed in the striatum have not been previously identified in gene expression analyses of other brain regions. This suggests therefore that the differential expression of genes following loss of MeCP2 occurs in a tissue, or cell-type specific manner and thus MeCP2 function should be understood in a cellular context. In initiating this study, we reasoned that reducing the number of cell types in a microarray experiment may reveal transcriptional changes that are masked in a whole tissue analysis. We therefore focused on tissues more homogeneous in regards to the diversity of neuronal cell types they contain in order to discern gene expression changes in the absence of MeCP2. We chose to isolate the striatum, a tissue composed predominantly of GABAergic medium spiny neurons (MSNs). The striatum was resected from five symptomatic Mecp2-null (KO) male mice bearing the Bird allele and five wild-type (WT) littermates in a C57BL/6 background. We also isolated liver from the same individuals to serve as a non-neuronal control. RNA was isolated from these tissues, converted to cDNA, and hybridized to a single-channel Affymetrix GeneChip Mouse Exon 1.0 ST array for a total of 20 individual arrays.

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MRNA microarray analysis of the substantia nigra in a mouse model of multiple system atrophy

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