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Proteomics analysis of prefrontal cortex from Alzheimer’s Disease patients revealed novel dysregulated proteins associated to the pathology.

ABSTRACT: Alzheimer’s disease (AD) is a neurodegenerative disease and the most common cause of dementia worldwide, but the mechanisms underlying AD are far from being elucidated. Thu, the study of proteins involved in its pathogenesis would allow getting further insights into the disease and identifying new markers for early diagnosis of AD. Our aim here is to analyze protein dysregulation in AD tissues by quantitative proteomics to identify proteins associated to the disease by 10-Plex TMT (Tandem Mass Tags)-based quantitative proteomics experiments were performed using frozen tissue samples from the left prefrontal cortex of AD patients, and healthy individuals and patients with other dementias as controls. LC-MS/MS analyses were performed using a Q Exactive mass spectrometer, and a total of 3281 proteins were identified and quantified using MaxQuant. After analysis with Perseus, 31 and 250 proteins were identified as upregulated and downregulated, respectively, at two or three Braak stages with a statistically significant ≥1.5-fold expression difference in AD patients in comparison to controls. After bioinformatics analysis, 41 dysregulated proteins were selected as more prone to be associated to AD, and 10 out of them were selected to investigate their role in the pathogenesis of AD and to verify their dysregulation in the disease by qPCR, WB, immunohistochemistry (IHC), immunofluorescence (IF), immunoprecipitation (IP) and/or ELISA, using tissue and serum samples of AD patients, patients with other dementias and healthy individuals.

INSTRUMENT(S): Q Exactive HF

ORGANISM(S): Homo Sapiens (human)

TISSUE(S): Brain

DISEASE(S): Alzheimer's Disease

SUBMITTER: Ana Montero Calle

LAB HEAD: Rodrigo Barderas

PROVIDER: PXD030751 | Pride | 2024-01-24

REPOSITORIES: pride

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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:Unravel the mechanisms underlying brain aging and Alzheimer´s disease (AD) has been difficult because of complexity of the networks that drive these aging-related changes. Analysis of the gene expression in the brain is a valuable tool to study the function of the brain under normal and pathological conditions. Gene microarray technology allows massively parallel analysis of most genes expressed in a tissue, and therefore is an important research tool that potentially can provide the investigative power needed to address the complexity of brain aging and neurodegenerative processes. One of the reasons that account for the resistance of AD pathogenesis to analysis is that clinically normal subjects may exhibit considerable AD pathology, blurring criteria for distinguishing subjects with normal aging or AD. Here, we analyzed hippocampal and cortex frontal gene expression from 32 subjects separated in individuals presenting, 1) both pathologic and clinical AD (definitive AD); 2) AD pathology and normal clinic (pathologic AD); 3) cognitive impairment, without AD pathology (others dementias); and 4) no cognitive impairment, without AD pathology (normal individuals). Our results show that based on gene expression profile these individuals we could verify similarity between the definitive AD group and the group that only had AD-type pathology (pathologic AD). Specimens of hippocampus and cortex frontal used in this study were obtained at autopsy from 32 subjects. Neuropathology, specifically NFT and NP, was assessed in accordance to the Braak staging and CERAD scores, respectively. Based on pathologic and clinic criteria, subjects were categorized into four groups: 1) nine subjects with AD neuropathologic (Braak = IV / V / VI and CERAD ≠ 0) presenting cognitive impairment (CDR ≥ 1), termed “definitive AD” (dAD); 2) five subjects with AD neuropathologic (Braak = IV / V / VI and CERAD ≠ 0) and without cognitive impairment (CDR = 0), termed “pathologic AD” (pAD); 3) nine subjects without AD neuropathologic (Braak = 0 / I / II and CERAD ≠ C) presenting cognitive impairment (CDR ≥ 1), termed “other dementias” (OD); 4) - nine subjects without AD neuropathologic (Braak = 0 / I / II and CERAD ≠ C) and without cognitive impairment (CDR = 0), termed “normal” (N). RNA isolation and Amplification. From total RNA, a two-round linear amplification procedure (T7-based protocol) was carried out for all samples and for a pool of RNAs obtained from 15 distinct human cell lines used as reference. Labeled cDNA was generated in a reverse transcriptase reaction using amplified RNA (aRNA). Equal amounts of test and reference cDNA reverse color Cy-labeled aRNA targets were competitively hybridized against the cDNA probes in a customized cDNA platform with 4,608 ORESTES representing human genes. Dye-swap was performed for each sample as control for dye bias and used as replicate.

Project description:Alzheimer's Disease (AD) is a devastating neurodegenerative disorder affecting approximately 4 million people in the U.S. alone. AD is characterized by the presence of senile plaques and neurofibrillary tangles in cortical regions of the brain. These pathological markers are thought to be responsible for the massive cortical neurodegeneration and concomitant loss of memory, reasoning, and often aberrant behaviors that are seen in patients with AD. Understanding the molecular mechanisms whereby these histopathological markers develop will greatly enhance our understanding of AD development and progression. A clearer understanding of the mechanisms underlying neurofibrillary tangle formation specifically may help to clarify the basis for dementia of AD as well as the dementias associated with other diseases that are collectively referred to as "tauopathies."; To expression profile both neurons containing neurofibrillary tangles and normal neurons from the entorhinal cortex of 10 mid-stage AD cases. The gene expression profile of neurons that contain neurofibrillary tangles will differ from the expression profile of histopathologically normal neurons from the same patient and from the same brain region. Some of these differences will be informative as to the mechanisms of tangle formation. Experiment Overall Design: First use laser capture microdissection to select 1000 neurons bearing neurofibrillary tangles and 1000 normal neurons from the layer 2 stellate island neurons of the entorhinal cortex of 10 mid-stage AD cases. Second, to isolate the RNA from these captured neurons, perform double round linear amplification and hybridize the labeled cRNA to affymetrix U133A arrays. Third, to use paired, permutational t-tests to analyze the microarray data to select tangle-specific differences in gene expression. For the purposes of submitting this proposal, a value of 1 ug of RNA was entered due to web site constraints on values placed in that field. However, all samples are from LCM captured cells and the actual RNA yield is likely closer to 100 pg.

			Action	DRS
	SEARCH_TMT_AD.zip	Other
	TMT_AD_F1.raw	Raw
	TMT_AD_F2.raw	Raw
	TMT_AD_F3.raw	Raw
	TMT_AD_F4.raw	Raw

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Proteomics analysis of prefrontal cortex from Alzheimer’s Disease patients revealed novel dysregulated proteins associated to the pathology.

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