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The expression profiling of the early stage of multiple system atrophy model mice

ABSTRACT: Global transcriptional analysis of the brain of multiple system atrophy model mice after synuclein induction by tamoxifen. Multiple system atrophy (MSA) is pathologically characterized by accumulation of phosphorylated α-synuclein in the oligodendrocytes. The pathophisiological mechinism under the early staige of disease pregression has been unknown. To clarify molecular alteration just after α-synuclein overexpression in the oligodendrocytes, we performed whole transcriptome analysis of the brain obtained from MSA model mice and control at 10 days after α-synuclein induction.

ORGANISM(S): Mus musculus

PROVIDER: GSE129531 | GEO | 2021/06/01

REPOSITORIES: GEO

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Project description:As the resident macrophages of the CNS, microglia fulfill manifold functions important for brain development and homeostasis. In the context of neurodegenerative diseases, they are crucial for de- and regenerative as well as immunological processes. The discovery of distinct activation patterns and increased phagocytosis indicated a damaging role of microglia in multiple system atrophy. This devastating, rapidly progressing atypical parkinsonian disorder is characterized by alpha-synuclein accumulation in the cytoplasm of oligodendrocytes. Alpha-synuclein aggregates have been related to myelin loss, severe neurodegeneration, and motor deficits accompanied by a region-specific myeloid immune response. Analyzing the gene expression profile of microglia in a mouse model of multiple system atrophy, MBP29-hα-syn mice, we identified a disease-assoctiated expression profile with an upregulation of the colony-stimulating factor 1 (Csf1). Thus, we hypothesized that targeting the CSF1 receptor using the small-molecule inhibitor PLX5622 reduces myeloid cells and thereby modifies the disease progression and neuropathological phenotype in this mouse model. After validation of a widespread depletion of myeloid cells after CSF1R inhibition, we consequently analyzed the survival, motor functions, neuropathological characteristics, and gene expression of affected brain regions in MBP29-hα-syn mice. Intriguingly, we identified a two-faced outcome comprising (1) an improved survival rate (24%) accompanied by delayed onset of neurological symptoms in contrast to (2) severely impaired motor functions in beam walking, pole test, and RotaRod of PLX5622-treated MBP29-hα-syn mice. Gene expression analysis revealed that PLX5622 reversed myeloid cell activation, however, predominantly reduced the expression of genes related to transsynaptic signaling and signal release. While these transcriptional changes were accompanied by a reduction of dopaminergic neurons in the substantia nigra pars compacta (19%) of PLX5622-treated MBP29-hα-syn mice, an increase of the striatal neuritic density was observed without changes in alpha-synuclein levels or myelin lipids in the forebrain. Together, our findings provide insight into the complex role of myeloid cell depletion in multiple system atrophy by demonstrating a two-faced outcome on the behavioral and neuronal phenotype of MBP29-hα-syn mice. Therefore, it is important to carefully balance the beneficial and adversive effects of CSF1R inhibition in different models of neurodegenerative disorders prior to clinical translation.

Project description:Multiple system atrophy (MSA) is a rare adult-onset neurodegenerative disease of unknown cause, with no effective therapeutic options, and no cure. Limited work to date has attempted to characterize the transcriptional changes associated with the disease, which presents as either predominating parkinsonian (MSA-P) or cerebellar (MSC-C) symptoms. We report here the results of RNA expression profiling of cerebellar white matter (CWM) tissue from two independent cohorts of MSA patients (n = 66) and healthy controls (HC; n = 66). RNA samples from bulk brain tissue and from oligodendrocytes obtained by laser capture microdissection (LCM) were sequenced. Differentially expressed genes (DEGs) were obtained and were examined before and after stratifying by MSA clinical sub-type. We detected the highest number of DEGs in the MSA-C group (n = 747) while only one gene was noted in MSA-P, highlighting the larger dysregulation of the transcriptome in the MSA-C CWM. Results from both bulk tissue and LCM analysis showed a downregulation of oligodendrocyte genes and an enrichment for myelination processes with a key role noted for the QKI gene. Additionally, we observed a significant upregulation of neuron-specific gene expression in MSA-C and enrichment for synaptic processes. A third cluster of genes was associated with the upregulation of astrocyte and endothelial genes, two cell types with a key role in inflammation processes. Finally, network analysis in MSA-C showed enrichment for β-amyloid related functional classes, including the known Alzheimer’s disease (AD) genes, APP and PSEN1. This is the largest RNA profiling study ever conducted on post-mortem brain tissue from MSA patients. We were able to define specific gene expression signatures for MSA-C highlighting the different stages of the complex neurodegenerative cascade of the disease that included alterations in several cell-specific transcriptional programs. Finally, several results suggest a common transcriptional dysregulation between MSA and AD-related genes despite the clinical and neuropathological distinctions between the two diseases.

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The expression profiling of the early stage of multiple system atrophy model mice

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