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Comparative Transcriptomics of Choroid Plexus in Alzheimer's Disease, Huntington's Disease and Frontotemporal Dementia: Implications for CSF Homeostasis and Dynamics

ABSTRACT: Background: In aging and Alzheimer’s disease there are striking changes in CSF composition that may relate to altered choroid plexus function. Studying CP tissue gene expression at the BCSFB provides further insight into epithelial and stromal responses to aging and diseased states. Results: Highly significant differences in gene expression occurred in CP of advanced AD patients vs. normal controls. Immune-related pathways including acute phase response, cytokine/JAK/STAT signaling and cell adhesion were the most significantly enriched among the genes upregulated in AD patients, while methionine degradation, and protein translation genes were most notably downregulated. While the majority of gene expression changes in AD patients was also observed in FTD and HuD, there were significant differences among the disease groups. AD had the most unique expression findings, these genes being enriched in upregulated VEGF signaling and immune response proteins, e.g., interleukins. HuD/FTD patients uniquely displayed upregulated cadherin-mediated adhesion. Conclusions: This unique database of changes in CP tissue gene expression provides mechanistic insight into the effects of neurodegenerative diseases on CSF dynamics and hydrocephalus, particularly in regards to choroidal immune activation, metabolic homeostasis and resiliency of the CP.

ORGANISM(S): Homo sapiens

PROVIDER: GSE110226 | GEO | 2018/02/08

REPOSITORIES: GEO

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Project description:Background: Dementia is one of the most common diseases in elderly people and hundreds of thousand new cases per year of Alzheimer’s disease (AD) are estimated. While the recent decade has seen significant advances in the development of novel biomarkers to identify dementias at their early stage, a great effort has been recently made to identify biomarkers able to improve differential diagnosis. However, only few potential candidates, mainly detectable in cerebrospinal fluid (CSF), have been described so far. Methods: We searched for miRNAs regulating MAPT translation. We employed a capture technology able to find the miRNAs directly bound to the MAPT transcript in cell lines. Afterwards, we evaluated the levels of these miRNAs in plasma samples from FTD (n = 42) and AD patients (n = 33) and relative healthy controls (HCs) (n = 42) by using qRT-PCR. Results: Firstly, we found all miRNAs that interact with the MAPT transcript. Ten miRNAs have been selected to verify their effect on Tau levels increasing or reducing miRNA levels by using cell transfections with plasmids expressing the miRNAs genes or LNA antagomiRs. Following the results obtained, miR-92a-3p, miR-320a and miR-320b were selected to analyse their levels in plasma samples of patients with FTD and AD respect to HCs. The analysis showed that the miR-92a-1-3p was under-expressed in both AD and FTD compared to HCs. Moreover, miR-320a was upregulated in FTD vs. AD patients, particularly in men when we stratified by sex. Respect to HC, the only difference is showed in men with AD who have reduced levels of this miRNA. Instead, miR-320b is up-regulated in both dementias, but only patients with FTD maintain this trend in both genders. Conclusions: Our results seem to identify miR-92a-3p and miR-320a as possible good biomarkers to discriminate AD from HC, while miR-320b to discriminate FTD from HC, particularly in males. Combining three miRNAs improves the accuracy only in females, particularly for differential diagnosis (FTD vs. AD) and to distinguish FTD from HC.

Project description:Alzheimer’s disease (AD) is a major neurodegenerative disease characterized by extracellular amyloid β (Aβ) plaques and intracellular hyperphosphorylated tau (P-tau). Increasing evidence indicates that extracellular vesicles (EVs) play an important role in AD pathogenesis. We previously reported that the choroid plexus epithelial (CPE) cells, present at the interface between blood and cerebrospinal fluid (CSF), show increased secretion of EVs into the CSF in response to peripheral inflammation. Here, we studied the importance of CP-derived EVs in AD pathogenesis. We observed increased EV levels in the CSF of 7 weeks old transgenic APP/PS1 mice, correlating with higher Aβ CSF levels at this age, while levels normalized with age. To study whether the elevated Aβ CSF levels might be responsible for this increase, mice were intracerebroventricularly (icv) injected with Aβ oligomers (AβO) which revealed a significant increase in the amount of CD9 and CD81 positive EVs in the CSF. The importance of the CPE cells as EV source was shown by in vitro analysis of AβO stimulated primary CPE cells and in vivo analysis of the CP by transmission electron microscopy (TEM). Evaluation of EV marker immunostaining, both from AβO icv injected mice and APP/PS1 mice, confirmed the upregulation of EV biogenesis in the CP. Interestingly, AβO-induced, CP-derived EVs induced pro-inflammatory effects in mixed cortical cultures (MCC) whereas proteome analysis revealed the presence of complement protein C3, amongst other inflammatory proteins. Additionally, we could show for the first time that AβO induce an upregulation of C3 in CPE cells. These data highlight the CP and CP-derived, C3-containing EVs as novel players in the emerging importance of the complement pathway in the pathogenesis of AD. Strikingly, inhibition of EV production using GW4869 resulted in protection against the AβO-induced cognitive decline. In conclusion, our results show that intraventricular AβO induce both C3 activation and EV secretion by the CP and that these EVs contain pro-inflammatory molecules, including C3, which play a role in neuroinflammation and loss of cognition. This suggests that inhibition of EV production by the CP might be an interesting therapeutic approach to be explored in the prevention or treatment of AD.

Project description:Background Semantic dementia (SD) is a subtype of frontotemporal dementia (FTD) characterized by language deficits due to severe temporal lobe degeneration. The consistent neuropathological diagnosis is FTD-TDP subtype C, with characteristic round TDP-43 protein inclusions in the dentate gyrus. Despite this striking clinicopathological concordance, the pathogenic mechanisms are largely unexplained forestalling the development of targeted therapeutics. Methods We carried out laser capture microdissection of the dentate gyrus of 15 SD patients and 17 non-demented controls, and assessed relative protein abundance changes by label-free quantitative mass spectrometry. To identify SD specific proteins, we compared our results to eight other FTD and Alzheimer’s disease (AD) proteomic datasets of cortical brain tissue, parallel with functional enrichment analyses and protein-protein interactions (PPI). Results Of the total 5,354 quantified proteins, 151 showed differential abundance (FDR<1%) in SD patients. Seventy-two proteins were previously found altered with the same directional change in at least one FTD/AD proteomic study, while 79 proteins were considered as showing potentially SD specific dysregulation. Functional enrichment indicated an overrepresentation of pathways related to the immune response, metabolic processes, and cell-junction assembly. PPI analysis highlighted a cluster of interacting proteins associated with adherens junction and cadherin binding– the cadherin-catenin complex. Multiple proteins in this complex showed strong and apparent specific upregulation in SD, including β-catenin (CTNNB1), γ-catenin (JUP), and N-cadherin (CDH2). Conclusions We discovered an increase of cell adhesion proteins in SD specifically constituting the cadherin-catenin complex at the synaptic membrane, essential for synaptic signaling. Although further validation is warranted, we anticipate that these findings will help unravel the disease processes underlying SD.

Dataset Information

Comparative Transcriptomics of Choroid Plexus in Alzheimer's Disease, Huntington's Disease and Frontotemporal Dementia: Implications for CSF Homeostasis and Dynamics

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