Transcriptomic changes upon the formation of a functional "on demand" degradation network in microglia I
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ABSTRACT:
ORGANISM(S): Mus musculus
PROVIDER: GSE152100 | GEO | 2021/09/28
REPOSITORIES: GEO
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Project description:We report the exchange of alpha-synuclein aggregates from one cell to another and examined transcriptomic changes following protein exchange. Differential expression (DE) analysis comparing alpha-synuclein-treated with untreated microglia identified alpha-synuclein induceable genes which were linked to inflammation, apoptosis, ER stress and intracellular protein targeting, while downregulated genes included categories related to mitosis, cytoskeleton and vesicle mediated transport. Co-culturing alpha-synuclein treated with untreated microglia largely suppressed the inflammatory and apoptotic phenotype of microglia thereby rescuing cells from cell death. Most importantly, these transprictomic changes were prevented by co-culturing the cells without direct cell-cell contact (transwell).
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2019-09-30 | GSE128120 | GEO
Project description:Parkinson’s disease (PD) is characterized by the aggregation of α-synuclein into Lewy bodies and Lewy neurites in the brain. Microglia-driven neuroinflammation may contribute to neuronal death in PD, however the exact role of microglia remains unclear and has been understudied. The A53T mutation in the gene coding for α-synuclein has been linked to early-onset PD, and exposure to A53T-mutant human α-synuclein increases the potential for inflammation of murine microglia. To date, its effect has not been studied in human microglia. We aimed to study the impact of the A53T mutation on human microglia developed in a physiologically relevant context Here, we used 2-dimensional cultures of human iPSC-derived microglia and transplantation of these cells into the mouse brain to assess the effects of the A53T mutation on human microglia. We found that A53T-mutant human microglia had an intrinsically increased propensity towards pro-inflammatory activation upon inflammatory stimulus. Additionally, A53T mutant microglia showed increased oxidative stress, with a strong decrease in catalase expression in non-inflammatory conditions. Together, these results indicate that A53T mutant human microglia display cell-autonomous phenotypes that may worsen neuronal damage in early-onset PD.
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Project description:The synaptic protein α-synuclein is linked through genetics and neuropathology to the pathogenesis of Parkinson’s disease and related disorders. However, the mechanisms by which α-synuclein influences disease onset and progression are incompletely understood. To identify novel pathways and potential therapeutic targets we performed proteomic analysis in a highly penetrant new Drosophila model of α-synucleinopathy. We identified 476 significantly upregulated and 563 significantly downregulated proteins in heads from α-synucleinopathy model flies compared to controls. We then used multiple complementary analyses to identify and prioritize genes and pathways within the large set of differentially expressed proteins for functional studies. We performed Gene Ontology enrichment analysis, integrated our proteomic changes with human Parkinson’s disease genetic studies, and compared the α-synucleinopathy proteome with that of tauopathy model flies, which are relevant to Alzheimer’s disease and related disorders. These approaches identified GTP cyclohydrolase (GCH1) and folate metabolism as candidate mediators of α-synuclein neurotoxicity. In functional validation studies we found that knockdown of Drosophila Gch1 enhanced locomotor deficits in α-synuclein transgenic flies, while folate supplementation protected from α-synuclein toxicity. Our integrative analysis suggested that mitochondrial dysfunction was a common downstream mediator of neurodegeneration. Accordingly, Gch1 knockdown enhanced metabolic dysfunction in α-synuclein transgenic fly brains while folate supplementation partially normalized whole brain bioenergetics. Here we outline and implement an integrative approach to identify and validate potential therapeutic pathways using comparative proteomics and genetics and capitalizing on the facile genetic and pharmacological tools available in Drosophila.
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Project description:Abnormal accumulation of aggregated proteins and sustained microglial activation are important contributors of neurodegenerative process in neurological diseases. Recent studies have shown that aggregation-prone proteins, such as a-synuclein, the protein implicated in Parkinson’s disease (PD), are released from neuronal cells and thus present in the extracellular fluid, pointing to the possible paracrine effects of these proteins on microglial immune responses. However, the mechanism underlying the disease-associated microglial activation and the role of neuronal proteins in this process remain unknown. Here, we show that extracellular a-synuclein released from neuronal cells is an endogenous ligand of toll-like receptor 2 (TLR2) and activates microglia, which in turn induces neurodegeneration. Interaction between neuron-released a-synuclein and TLR2 and subsequent activation of the TLR2 signaling were demonstrated comprehensively by using computational modeling of signaling network and by the experimental validation in TLR2-deficient microglia both in vitro and in vivo. In contrast to the neuron-released a-synuclein, recombinant a-synuclein proteins, including monomer, oligomer, fibril, or nitrated forms, were not able to interact or activate TLR2, suggesting that neuronal cells have a mechanism of enriching specific forms of a-synuclein capable of activating TLR2 during the process of releasing this protein. Taken together, the results suggest that both neuron-released extracellular a-synuclein and TLR2 might be novel therapeutic targets for modifying neuroinflammation in PD and related neurodegenerative diseases. We collected culture media from differentiated SH-SY5Y cells overexpressing either human a-synuclein (alpha-SCM) or beta-galactosidase (LZCM) and treat these media to primary rat microglia at the concentration of a-synuclein of 1.1M. Transcriptome analyses with microglial cells treated with either aSCM or LZCM at two different time points, 6 h and 24 h.
2013-02-28 | E-GEOD-26532 | biostudies-arrayexpress
Project description:Alpha-synuclein aggregates (αSynAgg) are pathological hallmarks of Parkinson’s disease (PD) that induce microglial activation and immune-mediated neurotoxicity, although the molecular mechanisms of αSynAgg-induced immune activation are poorly defined. We used mass spectrometry to define proteomic changes induced by αSynAgg using in-vitro mouse microglia and an in-vivo fly (Drosophila melanogaster) model with neuron-specific αSyn overexpression. In mouse microglia, αSynAgg induced robust pro-inflammatory activation (increased expression of 864 genes including Irg1, Ifit1 and Pyhin) and increased nuclear proteins involved in RNA synthesis, splicing and anti-viral defense mechanisms. Conversely, αSynAgg decreased expression of 530 proteins (including Cdc123, Sod1 and Grn), which were predominantly cytosolic and involved in antigen presentation as well as metabolic, proteosomal and lysosomal mechanisms. Pathway analyses and confirmatory in -vitro studies suggested that αSynAgg partly mediates its effects via Stat3 activation. 26 proteins differentially-expressed by αSynAgg were also identified as PD risk genes in genome-wide association studies (upregulated: Brd2, Clk1, Siglec1; down-regulated: Memo1, Arhgap18, Fyn and PGgrn/Grn). We then validated progranulin (PGrn/Grn) as a lysosomal PD-associated protein that is decreased in striatal and nigral microglia in post-mortem PD brain compared to non-disease controls, congruent with our in -vitro findings.
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Project description:Protein kinase CK2 alpha prime (CK2a') is preferentially upregulated in the striatum of patients with HD and in different cellular and mouse models of HD. CK2a' happloinsufficiency in the zQ175 HD mouse model restored several HD-like phenotypes. We hypothesized that CK2a' neuronal up-regulation is linked to key transcriptional alterations in the zQ175 mouse model. We found that CK2a' haploinsufficiency rescued the expression of genes associated with synaptogenesis and glutamatergic signaling whose upstream regulator seems to be alpha-synuclein. These transcriptomic studies revealed a conection between CK2a', alpha-synuclein dysfunction and transcriptional changes in key signaling pathways.
2022-06-23 | GSE160586 | GEO
Project description:Multiple system atrophy (MSA) is a rare, neurodegenerative disorder with rapid motor and non-motor symptom progression. MSA is characterized by protein aggregations of α-synuclein found in the cytoplasm of oligodendrocytes. Despite this pathological hallmark, there is still little known about the cause of this disease, resulting in poor treatment options and quality of life post-diagnosis. In this study, we investigated differentially expressed genes via RNA-sequencing of brain samples from a validated PLP-α-synuclein transgenic mouse model, identifying a total of 40 DEGs in the MSA group compared to control, with top detected genes being Gm15446, Mcm6, Aldh7a1 and Gm3435. We observed a significant enrichment of immune pathways and endothelial cell genes among the upregulated genes, whereas downregulated genes were significantly enriched for oligodendrocyte and neuronal genes. We then calculated possible overlap of these DEGs with previously profiled human MSA RNA, resulting in the identification of significant downregulation of the Tsr2 gene. Identifying key gene expression profiles specific to MSA patients is crucial to further understanding the cause, and possible prevention, of this rapidly progressive neurodegenerative disorder.
2024-11-07 | GSE247259 | GEO
Project description:Background: Cell-to-cell propagation of α-synuclein (α-syn) aggregates is thought to contribute to the pathogenesis of Parkinson’s disease (PD) and underlie the spread of α-syn neuropathology. Increased pro-inflammatory cytokine levels and activated microglia are present in PD and activated microglia can promote α-syn aggregation. However, it is unclear how microglia influence α-syn cell-to-cell transfer. Methods: We developed a clinically relevant mouse model to monitor α-syn prion-like propagation between cells; we transplanted wild-type mouse embryonic midbrain neurons into a mouse striatum overexpressing human α-syn (huα-syn) following adeno-associated viral injection into the substantia nigra. In this system, we depleted or activated microglial cells and determined the effects on the transfer of huα-syn from host nigrostriatal neurons into the implanted dopaminergic neurons, using the presence of huα-syn within the grafted cells as a readout. Results: First, we compared α-syn cell-to-cell transfer between host mice with a normal number of microglia to mice in which we had pharmacologically ablated 80% of the microglia from the grafted striatum. With fewer host microglia, we observed increased accumulation of huα-syn in grafted dopaminergic neurons. Second, we assessed the transfer of α-syn into grafted neurons in the context of microglia activated by one of two stimuli, lipopolysaccharide (LPS) or interleukin-4 (IL-4). LPS exposure led to a strong activation of microglial cells (as determined by microglia morphology and cytokine production) and significantly higher amounts of huα-syn in grafted neurons. In contrast, injection of IL-4 did not change the proportion of grafted dopamine neurons that contained huα-syn relative to controls. RNA sequencing analysis revealed differential gene expression between LPS and IL-4 injected mice; many genes were upregulated in LPS including those involved with the inflammatory response. Conclusions: The absence or the hyperstimulation of microglia affected α-syn transfer in the brain. Our results suggest that under resting, non-inflammatory conditions, microglia modulate the transfer of α-syn. Pharmacological regulation of neuroinflammation could represent a future avenue for limiting the spread of PD neuropathology.
2019-08-12 | GSE130683 | GEO