CD33 mRNA Has Elevated Expression Levels in the Leukocytes of Peripheral Blood in Patients with Late-Onset Alzheimer’s Disease

Gerontology ◽  
2021 ◽  
pp. 1-10
Author(s):  
Fatemeh Heidari ◽  
George Ansstas ◽  
Farzam Ajamian

<b><i>Background/Aims:</i></b> In despite of conflicting results among different ethnic groups, the rs3865444 of CD33 gene has previously been identified as a risk factor for late-onset Alzheimer’s disease (LOAD).This study was aimed to evaluate the association between rs3865444 SNP with LOAD occurrence, and to investigate whether CD33 mRNA expression will change in the leukocytes of peripheral blood in LOAD patients. <b><i>Methods:</i></b> The rs3865444 polymorphism was genotyped in 233 LOAD and 238 control subjects using the Tetra-ARMS-PCR method. CD33 mRNAs expression in leukocytes were assessed and analyzed using the real-time qPCR method. We used in silico approach to analyze potential effects imparted by rs3865444 polymorphism in LOAD pathogenesis. <b><i>Results:</i></b> Our results show a significant increase in CD33 mRNA expression levels in white blood cells of LOAD patients, however, the association between CD33 rs3865444 polymorphism and LOAD was found to be not significant. We also noticed that LOAD patients with the C/A genotype had higher CD33 mRNA levels in their peripheral blood than those of the control group. <b><i>Conclusions:</i></b> rs3865444, located upstream of the 5′CD33 coding region, might positively influence CD33 mRNAs expression in leukocytes of LOAD versus healthy people. This is likely to happen through interfering rs3865444 (C) with the functional activity of several other transcription factors given that rs3865444 is in linkage disequilibrium with other functional polymorphisms in this coding region according to an in silico study. We propose that CD33 mRNAs elevation in peripheral immune cells – as a potential biomarker in LOAD – is related to peripheral immune system impairment.

2020 ◽  
Vol 17 (7) ◽  
pp. 616-625
Author(s):  
Nattaporn Pakpian ◽  
Kamonrat Phopin ◽  
Kuntida Kitidee ◽  
Piyarat Govitrapong ◽  
Prapimpun Wongchitrat

Background: Mitochondrial dysfunction is a pathological feature that manifests early in the brains of patients with Alzheimer’s Disease (AD). The disruption of mitochondrial dynamics contributes to mitochondrial morphological and functional impairments. Our previous study demonstrated that the expression of genes involved in amyloid beta generation was altered in the peripheral blood of AD patients. Objective: The aim of this study was to further investigate the relative levels of mitochondrial genes involved in mitochondrial dynamics, including mitochondrial fission and fusion, and mitophagy in peripheral blood samples from patients with AD compared to healthy controls. Methods: The mRNA levels were analyzed by real-time polymerase chain reaction. Gene expression profiles were assessed in relation to cognitive performance. Results: Significant changes were observed in the mRNA expression levels of fission-related genes; Fission1 (FIS1) levels in AD subjects were significantly higher than those in healthy controls, whereas Dynamin- related protein 1 (DRP1) expression was significantly lower in AD subjects. The levels of the mitophagy-related genes, PTEN-induced kinase 1 (PINK1) and microtubule-associated protein 1 light chain 3 (LC3), were significantly increased in AD subjects and elderly controls compared to healthy young controls. The mRNA levels of Parkin (PARK2) were significantly decreased in AD. Correlations were found between the expression levels of FIS1, DRP1 and PARK2 and cognitive performance scores. Conclusion: Alterations in mitochondrial dynamics in the blood may reflect impairments in mitochondrial functions in the central and peripheral tissues of AD patients. Mitochondrial fission, together with mitophagy gene profiles, might be potential considerations for the future development of blood-based biomarkers for AD.


2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Hao Hu ◽  
Lan Tan ◽  
Yan-Lin Bi ◽  
Wei Xu ◽  
Lin Tan ◽  
...  

AbstractThe bridging integrator 1 (BIN1) gene is the second most important susceptibility gene for late-onset Alzheimer’s disease (LOAD) after apolipoprotein E (APOE) gene. To explore whether the BIN1 methylation in peripheral blood changed in the early stage of LOAD, we included 814 participants (484 cognitively normal participants [CN] and 330 participants with subjective cognitive decline [SCD]) from the Chinese Alzheimer’s Biomarker and LifestylE (CABLE) database. Then we tested associations of methylation of BIN1 promoter in peripheral blood with the susceptibility for preclinical AD or early changes of cerebrospinal fluid (CSF) AD-related biomarkers. Results showed that SCD participants with significant AD biological characteristics had lower methylation levels of BIN1 promoter, even after correcting for covariates. Hypomethylation of BIN1 promoter were associated with decreased CSF Aβ42 (p = 0.0008), as well as increased p-tau/Aβ42 (p = 0.0001) and t-tau/Aβ42 (p < 0.0001) in total participants. Subgroup analysis showed that the above associations only remained in the SCD subgroup. In addition, hypomethylation of BIN1 promoter was also accompanied by increased CSF p-tau (p = 0.0028) and t-tau (p = 0.0130) in the SCD subgroup, which was independent of CSF Aβ42. Finally, above associations were still significant after correcting single nucleotide polymorphic sites (SNPs) and interaction of APOE ɛ4 status. Our study is the first to find a robust association between hypomethylation of BIN1 promoter in peripheral blood and preclinical AD. This provides new evidence for the involvement of BIN1 in AD, and may contribute to the discovery of new therapeutic targets for AD.


2021 ◽  
pp. 1-21
Author(s):  
Masoud Neshan ◽  
Seyed Kazem Malakouti ◽  
Leila Kamalzadeh ◽  
Mina Makvand ◽  
Arezoo Campbell ◽  
...  

Background: Late-onset Alzheimer’s disease (LOAD) is associated with many environmental and genetic factors. The effect of systemic inflammation on the pathogenesis of neurodegenerative diseases such as AD has been strongly suggested. T helper cells (Th) are one of the important components of the immune system and can easily infiltrate the brain in pathological conditions. The development of each Th-subset depends on the production of unique cytokines and their main regulator. Objective: This study aimed to compare the mRNA levels of Th-related genes derived from peripheral blood mononuclear cells of LOAD patients with control. Also, the identification of the most important Th1/Th2 genes and downstream pathways that may be involved in the pathogenesis of AD was followed by computational approaches. Methods: This study invloved 30 patients with LOAD and 30 non-demented controls. The relative expression of T-cell cytokines (IFN-γ, TNF-α, IL-4, and IL-5) and transcription factors (T-bet and GATA-3) were assessed using real-time PCR. Additionally, protein-protein interaction (PPI) was investigated by gene network construction. Results: A significant decrease at T-bet, IFN-γ, TNF-α, and GATA-3 mRNA levels was detected in the LOAD group, compared to the controls. However, there was no significant difference in IL-4 or IL-5 mRNA levels. Network analysis revealed a list of the highly connected protein (hubs) related to mitogen-activated protein kinase (MAPK) signaling and Th17 cell differentiation pathways. Conclusion: The findings point to a molecular dysregulation in Th-related genes, which can promising in the early diagnosis or targeted interventions of AD. Furthermore, the PPI analysis showed that upstream off-target stimulation may involve MAPK cascade activation and Th17 axis induction.


2008 ◽  
Vol 4 ◽  
pp. T145-T145
Author(s):  
John S.K. Kauwe ◽  
Carlos Cruchaga ◽  
Kevin Mayo ◽  
Chiara Fenoglio ◽  
Sarah Bertelsen ◽  
...  

2020 ◽  
Vol 2020 ◽  
pp. 1-10 ◽  
Author(s):  
Xin-Yi Lu ◽  
Shun Huang ◽  
Qu-Bo Chen ◽  
Dapeng Zhang ◽  
Wanyan Li ◽  
...  

Alzheimer’s disease (AD) is the most common neurodegenerative disease. The accumulation of amyloid beta (Aβ) is the main pathology of AD. Metformin, a well-known antidiabetic drug, has been reported to have AD-protective effect. However, the mechanism is still unclear. In this study, we tried to figure out whether metformin could activate insulin-degrading enzyme (IDE) to ameliorate Aβ-induced pathology. Morris water maze and Y-maze results indicated that metformin could improve the learning and memory ability in APPswe/PS1dE9 (APP/PS1) transgenic mice. 18F-FDG PET-CT result showed that metformin could ameliorate the neural dysfunction in APP/PS1 transgenic mice. PCR analysis showed that metformin could effectively improve the mRNA expression level of nerve and synapse-related genes (Syp, Ngf, and Bdnf) in the brain. Metformin decreased oxidative stress (malondialdehyde and superoxide dismutase) and neuroinflammation (IL-1β and IL-6) in APP/PS1 mice. In addition, metformin obviously reduced the Aβ level in the brain of APP/PS1 mice. Metformin did not affect the enzyme activities and mRNA expression levels of Aβ-related secretases (ADAM10, BACE1, and PS1). Meanwhile, metformin also did not affect the mRNA expression levels of Aβ-related transporters (LRP1 and RAGE). Metformin increased the protein levels of p-AMPK and IDE in the brain of APP/PS1 mice, which might be the key mechanism of metformin on AD. In conclusion, the well-known antidiabetic drug, metformin, could be a promising drug for AD treatment.


2019 ◽  
Author(s):  
Wei Liu ◽  
Mo Li ◽  
Wenfeng Zhang ◽  
Geyu Zhou ◽  
Xing Wu ◽  
...  

AbstractTo increase statistical power to identify genes associated with complex traits, a number of transcriptome-wide association study (TWAS) methods have been proposed using gene expression as a mediating trait linking genetic variations and diseases. These methods first predict expression levels based on inferred expression quantitative trait loci (eQTLs) and then identify expression-mediated genetic effects on diseases by associating phenotypes with predicted expression levels. The success of these methods critically depends on the identification of eQTLs, which may not be functional in the corresponding tissue, due to linkage disequilibrium (LD) and the correlation of gene expression between tissues. Here, we introduce a new method called T-GEN (Transcriptome-mediated identification of disease-associatedGens withEpigenetic aNnotation) to identify disease-associated genes leveraging epigenetic information. Through prioritizing SNPs with tissue-specific epigenetic annotation, T-GEN can better identify SNPs that are both statistically predictive and biologically functional. We found that a significantly higher percentage (an increase of 18.7% to 47.2%) of eQTLs identified by T-GEN are inferred to be functional by ChromHMM and more are deleterious based on their Combined Annotation Dependent Depletion (CADD) scores. Applying T-GEN to 207 complex traits, we were able to identify more trait-associated genes (ranging from 7.7 % to 102%) than those from existing methods. Among the identified genes associated with these traits, T-GEN can better identify genes with high (>0.99) pLI scores compared to other methods. When T-GEN was applied to late-onset Alzheimer’s disease, we identified 96 genes located at 15 loci, including two novel loci not implicated in previous GWAS. We further replicated 50 genes in an independent GWAS, including one of the two novel loci.Author summaryTWAS-like methods have been widely applied to understand disease etiology using eQTL data and GWAS results. However, it is still challenging to discriminate the true disease-associated genes from those in strong LD with true genes, which is largely due to the misidentification of eQTLs. Here we introduce a novel statistical method named T-GEN to identify disease-associated genes considering epigenetic information. Compared to current TWAS methods, T-GEN can not only identify eQTLs with higher CADD scores and function potentials in gene-expression imputation models, but also identify more disease-associated genes across 207 traits and more genes with high (>0.99) pLI scores. Applying T-GEN in late-onset Alzheimer’s disease identified 96 genes at 15 loci with two novel loci. Among 96 identified genes, 50 genes were further replicated in an independent GWAS.


2020 ◽  
Author(s):  
Andy Po-Yi Tsai ◽  
Chuanpeng Dong ◽  
Christoph Preuss ◽  
Miguel Moutinho ◽  
Peter Bor-Chian Lin ◽  
...  

Abstract Background Alzheimer's disease (AD) is characterized by robust microgliosis and phenotypic changes that accompany disease pathogenesis. Indeed, genetic variants in microglial genes are linked to risk for late-onset AD (LOAD). Phospholipase C 𝛾 2 (PLCG2) participates in the transduction of signals emanating from immune cell-surface receptors that regulate the inflammatory response and is selectively expressed by microglia in the brain. A rare variant in PLCG2 (P522R) was previously found to be protective against LOAD. Here, we performed association analysis to identify a new genetic variation in PLCG2 that is associated with elevated risk for LOAD.Methods Using whole genome sequencing (N=1,894) and RNA-Seq (N=1,077) data from the AMP-AD cohort, we investigated whether a missense variant in PLCG2 (M28L) was associated with risk for LOAD. We have examined the homology model and space-filling model of PLCG2 generated with PyMOL to investigate the protein structure of PLCG2 with substitutions of LOAD risk and protective variants in PLCG2 . Gene expression analysis and expression quantitative trait loci (eQTL) of PLCG2 were conducted. We also evaluated the relationship between PLCG2 expression levels and amyloid plaque density and expression levels of microglia specific markers ( AIF1 and TMEM119 ). Age, sex, and APOE ε4 carrier status were used as covariates. Finally, we investigated the longitudinal changes PLCG2 expression in the 5XFAD mouse model of AD and it relationship to amyloid pathology progression.Results A rare missense variant in PLCG2 (M28L) confers increased AD risk ( p =0.047; OR=1.164 [95% CI=1.002-1.351]). PLCG2 is highly expressed in the brain and was significantly up-regulated in the parahippocampal gyrus, superior temporal gyrus, and inferior temporal gyrus in LOAD. Higher PLCG2 expression levels were associated with increased brain amyloid deposition. The findings were validated in 5xFAD mice, showing a disease progression-dependent increase in Plcg2 expression with amyloid pathology. Furthermore, eQTL analysis identified several variants as associated with increased PLCG2 expression levels in the brain and other organs.Conclusions Our results provide further evidence that PLCG2 and the M28L variant confers increase risk for LOAD and may play an important role in AD pathophysiology.


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