Sporadic Alzheimer's Disease Patients Research Articles

PS1/gamma-secretase acts as rogue chaperone of glutamate transporter EAAT2/GLT-1 in Alzheimer’s disease

The recently discovered interaction between presenilin 1 (PS1), a subunit of γ-secretase involved in amyloid-β (Aβ) peptide production, and GLT-1, the major brain glutamate transporter (EAAT2 in the human), may link two pathological aspects of Alzheimer’s disease: abnormal Aβ occurrence and neuronal network hyperactivity. In the current study, we employed a FRET-based fluorescence lifetime imaging microscopy (FLIM) to characterize the PS1/GLT-1 interaction in brain tissue from sporadic AD (sAD) patients. sAD brains showed significantly less PS1/GLT-1 interaction than those with frontotemporal lobar degeneration or non-demented controls. Familial AD (fAD) PS1 mutations, inducing a “closed” PS1 conformation similar to that in sAD brain, and gamma-secretase modulators (GSMs), inducing a “relaxed” conformation, respectively reduced and increased the interaction. Furthermore, PS1 influences GLT-1 cell surface expression and homomultimer formation, acting as a chaperone but not affecting GLT-1 stability. The diminished PS1/GLT-1 interaction suggests that these functions may not work properly in AD.

Astrocytic centrin-2 expression in entorhinal cortex correlates with Alzheimer's disease severity.

Astrogliosis is a condition shared by acute and chronic neurological diseases and includes morphological, proteomic, and functional rearrangements of astroglia. In Alzheimer's disease (AD), reactive astrocytes frame amyloid deposits and exhibit structural changes associated with the overexpression of specific proteins, mostly belonging to intermediate filaments. At a functional level, amyloid beta triggers dysfunctional calcium signaling in astrocytes, which contributes to the maintenance of chronic neuroinflammation. Therefore, the identification of intracellular players that participate in astrocyte calcium signaling can help unveil the mechanisms underlying astrocyte reactivity and loss of function in AD. We have recently identified the calcium-binding protein centrin-2 (CETN2) as a novel astrocyte marker in the human brain and, in order to determine whether astrocytic CETN2 expression and distribution could be affected by neurodegenerative conditions, we examined its pattern in control and sporadic AD patients. By immunoblot, immunohistochemistry, and targeted-mass spectrometry, we report a positive correlation between entorhinal CETN2 immunoreactivity and neurocognitive impairment, along with the abundance of amyloid depositions and neurofibrillary tangles, thus highlighting a linear relationship between CETN2 expression and AD progression. CETN2-positive astrocytes were dispersed in the entorhinal cortex with a clustered pattern and colocalized with reactive glia markers STAT3, NFATc3, and YKL-40, indicating a human-specific role in AD-induced astrogliosis. Collectively, our data provide the first evidence that CETN2 is part of the astrocytic calcium toolkit undergoing rearrangements in AD and adds CETN2 to the list of proteins that could play a role in disease evolution.

Human fibroblasts from sporadic Alzheimer's disease (AD) patients show mitochondrial alterations and lysosome dysfunction

Mitophagy is a mechanism that maintains mitochondrial integrity and homeostasis and is thought to promote longevity and reduce the risk of age-related neurodegenerative diseases, including Alzheimer's disease (AD). Here, we investigate the abundance of mitochondrial reactive oxygen species (ROS), mitochondrial function, and mitophagy in primary fibroblasts from patients with sporadic AD (sAD) and normal healthy controls. The results show increased levels of mitochondrial ROS, changes in mitochondrial morphology, altered bioenergetic properties, and defects in autophagy, mitophagy, and lysosome-mediated degradation pathways in sAD fibroblasts relative to control fibroblasts. Interestingly, lysosome abundance and the staining of lysosomal markers remained high, while the capacity of lysosome-dependent degradation was lower in sAD fibroblasts than in controls fibroblasts. Nicotinamide riboside supplementation decreased mitochondrial ROS, while capacity for lysosomal degradation remained unchanged in sAD fibroblasts relative to healthy control fibroblasts. These findings provide insight into molecular mechanisms involving the dysregulation of lysosome and autophagy/mitophagy pathways that may contribute significantly to clinical signs and pathological features of sAD.

Mitochondrial alterations in fibroblasts from sporadic Alzheimer's disease (AD) patients correlate with AD-related clinical hallmarks

Mitochondrial dysfunctions are key features of Alzheimer’s disease (AD). The occurrence of these disturbances in the peripheral cells of AD patients and their potential correlation with disease progression are underinvestigated. We studied mitochondrial structure, function and mitophagy in fibroblasts from healthy volunteers and AD patients at the prodromal (AD-MCI) or demented (AD-D) stages. We carried out correlation studies with clinical cognitive scores, namely, (i) Mini-Mental State Examination (MMSE) and (ii) Dementia Rating-Scale Sum of Boxes (CDR-SOB), and with (iii) amyloid beta (Aβ) plaque burden (PiB-PET imaging) and (iv) the accumulation of peripheral amyloid precursor protein C-terminal fragments (APP-CTFs). We revealed alterations in mitochondrial structure as well as specific mitochondrial dysfunction signatures in AD-MCI and AD-D fibroblasts and revealed that defective mitophagy and autophagy are linked to impaired lysosomal activity in AD-D fibroblasts. We reported significant correlations of a subset of these dysfunctions with cognitive decline, AD-related clinical hallmarks and peripheral APP-CTFs accumulation. This study emphasizes the potential use of peripheral cells for investigating AD pathophysiology.

Sildenafil as a Candidate Drug for Alzheimer's Disease: Real-World Patient Data Observation and Mechanistic Observations from Patient-Induced Pluripotent Stem Cell-Derived Neurons.

Alzheimer's disease (AD) is a chronic neurodegenerative disease needing effective therapeutics urgently. Sildenafil, one of the approved phosphodiesterase-5 inhibitors, has been implicated as having potential effect in AD. To investigate the potential therapeutic benefit of sildenafil on AD. We performed real-world patient data analysis using the MarketScan® Medicare Supplemental and the Clinformatics® databases. We conducted propensity score-stratified analyses after adjusting confounding factors (i.e., sex, age, race, and comorbidities). We used both familial and sporadic AD patient induced pluripotent stem cells (iPSC) derived neurons to evaluate the sildenafil's mechanism-of-action. We showed that sildenafil usage is associated with reduced likelihood of AD across four new drug compactor cohorts, including bumetanide, furosemide, spironolactone, and nifedipine. For instance, sildenafil usage is associated with a 54% reduced incidence of AD in MarketScan® (hazard ratio [HR] = 0.46, 95% CI 0.32- 0.66) and a 30% reduced prevalence of AD in Clinformatics® (HR = 0.70, 95% CI 0.49- 1.00) compared to spironolactone. We found that sildenafil treatment reduced tau hyperphosphorylation (pTau181 and pTau205) in a dose-dependent manner in both familial and sporadic AD patient iPSC-derived neurons. RNA-sequencing data analysis of sildenafil-treated AD patient iPSC-derived neurons reveals that sildenafil specifically target AD related genes and pathobiological pathways, mechanistically supporting the beneficial effect of sildenafil in AD. These real-world patient data validation and mechanistic observations from patient iPSC-derived neurons further suggested that sildenafil is a potential repurposable drug for AD. Yet, randomized clinical trials are warranted to validate the causal treatment effects of sildenafil in AD.

Genetic modifiers of cognitive decline in PSEN1 E280A Alzheimer's disease.

Rate of cognitive decline (RCD) in Alzheimer's disease (AD) determines the degree of impairment for patients and of burden for caretakers. We studied the association of RCD with genetic variants in AD. RCD was evaluated in 62 familial AD (FAD) and 53 sporadic AD (SAD) cases, and analyzed by whole-exome sequencing for association with common exonic functional variants. Findings were validated in post mortem brain tissue. One hundred seventy-two gene variants in FAD, and 227 gene variants in SAD associated with RCD. In FAD, performance decline of the immediate recall of the Rey-Osterrieth figure test associated with 122 genetic variants. Olfactory receptor OR51B6 showed the highest number of associated variants. Its expression was detected in temporal cortex neurons. Impaired olfactory function has been associated with cognitive impairment in AD. Genetic variants in these or other genes could help to identify risk of faster memory decline in FAD and SAD patients.

Uncovering elevated tau TPP motif phosphorylation in the brain of Alzheimer's disease patients.

A wide array of post-translational modifications of the tau protein occurs in Alzheimer's disease (AD) and they are critical to pathogenesis and biomarker development. Several promising tau markers, pT181, pT217, and pT231, rely on increased phosphorylation within a common molecular motif threonine-proline-proline (TPP). We validated new and existing antibodies against pT217, pT231, pT175, and pT181, then combined immunohistochemistry (IHC) and immunoassays (ELISA) to broadly examine the phosphorylation of the tau TPP motif in AD brains. The tau burden, as examined by IHC and ELISA, correlates to Braak stages across all TPP sites. Moreover, we observed regional variability across four TPP motif phosphorylation sites in multiple brains of sporadic AD patients. We conclude that there is an elevation of TPP tau phosphorylation in AD brains as disease advances. The regional variability of pTPP tau suggests that examining different phosphorylation sites is essential for a comprehensive assessment of tau pathology.

Cortical microinfarcts along the Alzheimer’s disease continuum in adults with Down syndrome ‐ an update

AbstractBackgroundCortical microinfarcts (CMI) are emerging biomarkers of vascular damage associated with cognitive decline and are frequent in sporadic AD (sAD) patients. However, no study assessed CMI in Down syndrome (DS), a genetically determined form of AD. Therefore, we aimed to assess CMI’s frequency in adults with DS, sAD, and cognitively unimpaired euploid controls and its relationship with age, sex, clinical status, and APOE ε4 carriership.MethodCross‐sectional study. We included 175 participants with 3T‐MRI: 64 with DS (39 asymptomatic [aDS], 11 prodromal AD [pDS], and 14 AD‐dementia [dDS]), 62 with sAD (41 prodromal AD, 21 AD dementia), and 49 controls. A neuroradiologist blind to participants’ data visually analyzed the 3T‐MRI images following a validated protocol to detect CMI (Figure 1). We compared CMI’s prevalence in the different clinical groups along the AD continuum in DS and sAD, in APOE ε4 carriers vs. non‐carriers, and males vs. females using Chi‐square, Mann‐Whitney, or Kruskal‐Wallis tests when appropriate.ResultCMI’s prevalence was 7.8% in DS (5.1% in aDS, 21.4% in pDS, and 0% in dDS [p = 0.085]), 17.7% in sAD (22.0% in prodromal AD and 9.5% in AD dementia [p = 0.389]), and 10.2% in controls (p = 0.207). CMI frequency increased with age in DS, sAD, and controls (Table 1). Regarding sex, CMI’s frequency was 10% in men and 5.9% in women with DS (p = 0.884), and 27.3% in men and 12.5% in women with sAD (p = 0.267). In controls, CMIs’ frequency was 10% in men and 10.3% in women (p = 1.000). Regarding APOEε4 carriership, CMI’s prevalence was 21.4% in APOEε4 carriers and 9.1% in non‐carriers in sAD (p = 0.428), 8.7% in carriers and 6.0% in non‐carriers in DS (p = 1.000), and 8.3% in carriers and 8.6% in non‐carriers controls (p = 1.000) (Table 2).ConclusionCMI’s prevalence increased with age, but was not different in DS, sporadic AD, and controls. Also, sex and APOEε4 carriership did not impact the prevalence of CMI in the three study groups.

Developing Topics.

We hypothesized that lithium inhibits critical upper stream Ca2+ dysregulation via inhibition of methyl-D-aspartate (NMDARs) and/or InsP3 (InsP3Rs) receptors and downstream mitochondria dysfunction and cell death in a cell model of sporadic Alzheimer's Disease (SAD). Induced pluripotent stem cells (iPSCs) were derived from the skin fibroblasts of a SAD patient with parental ApoE4/E4, and then gene-edited to isogenic ApoE3/E3 cells as control. Cells were cultured with mTeSR1 plus medium on Matrigel-coated plates, differentiated to NPC by Dual-SMAD inhibition. Mitochondrial function and cell viability of both ApoE4/E4 vs. ApoE3/E3 iPSCs were determined using MTT reduction assay. Cells were pretreated with lithium and then challenged with glutamate for 24 hrs. Calcium concentration in cytosol space ([Ca2+]c) was measured using jellyfish-specific photo protein aequorin-based probes or microscopy Fura-2 dye. Mitochondria oxygen consumption rate (OCR) and ATP production were measured using the Seahorse ® Mito Stress Assay. Compared to ApoE3/E3 cells, ApoE4/E4 cells have significantly decreased cell viability, which could be inhibited by lithium at clinically low concentrations. ApoE4/E4 iPSCs had significantly increased baseline levels of [Ca2+]c and a significantly higher elevation of [Ca2+]c after glutamate treatment than its isogenic ApoE3/E3 iPSCs. Lithium at a clinical concentration (1mM) significantly inhibited the pathological elevation of baseline [Ca2+]c in ApoE4/E4 iPSCs. Lithium-inhibited mitochondria proton leak as an indicator of cell damage induced by glutamate (15mM) in ApoE4/E4 iPSCs. Glutamate induced mitochondrial and cell damage dose-dependently. Lithium at a clinically low concentration (0.25mM) significantly inhibited glutamate (15mM)-induced mitochondria and cell damage in ApoE4/E4 iPSCs. Glutamate treatment for 24 hours significantly inhibited the proliferation of NPCs derived from SAD iPSCs with parental ApoE4/E4 and isogenic E3/E3. Lithium (1mM) significantly inhibited the glutamate-mediated impairment of ApoE3/E3 NPCs proliferation. Our results suggest that ApoE4 plays an important role in critical upstream Ca2+ dysregulation and downstream mitochondrial dysfunction and cell damage, particularly under the stress of glutamate excitotoxicity. Lithium at clinically low concentrations ameliorated critical Ca2+ dysregulation and AD pathologies, warranting further studies to repurpose lithium as future effective drug for AD treatment.

The Role of CSF Transthyretin in Human Alzheimer's Disease: Offense, Defense, or not so Innocent Bystander.

Transthyretin (TTR) is secreted by hepatocytes, retinal pigment epithelial cells, pancreatic α and β cells, choroid plexus epithelium, and neurons under stress. The choroid plexus product is the main transporter of the thyroid hormone thyroxine (T4) to the brain during early development. TTR is one of three relatively abundant cerebrospinal fluid (CSF) proteins (Apolipoprotein J [ApoJ] (also known as clusterin), Apolipoprotein E [ApoE], and TTR) that interact with Aβ peptides in vitro, in some instances inhibiting their aggregation and toxicity. It is now clear that clusterin functions as an extracellular, and perhaps intracellular, chaperone for many misfolded proteins and that variation in its gene (Clu) is associated with susceptibility to sporadic Alzheimer's disease (AD). The function of ApoE in AD is not yet completely understood, although the ApoE4 allele has the strongest genetic association with the development of sporadic late onset AD. Despite in vitro and in vivo evidence of the interaction between TTR and Aβ, genomewide association studies including large numbers of sporadic Alzheimer's disease patients have failed to show significant association between variation in the TTR gene and disease prevalence. Early clinical studies suggested an inverse relationship between CSF TTR levels and AD and the possibility of using the reduced CSF TTR concentration as a biomarker. Later, more extensive analyses indicated that CSF TTR concentrations may be increased in some patients with AD. While the observed changes in TTR may be pathogenetically or biologically interesting because of the inconsistency and lack of specificity, they offered no benefit diagnostically or prognostically either independently or when added to currently employed CSF biomarkers, i.e., decreased Aβ1-42 and increased Tau and phospho-Tau. While some clinical data suggest that increases in CSF TTR may occur early in the disease with a significant decrease late in the course, without additional, more granular data, CSF TTR changes are neither consistent nor specific enough to warrant their use as a specific AD biomarker.

Localized proteomic differences in the choroid plexus of Alzheimer's disease and epilepsy patients.

Alzheimer's disease (AD) and epilepsy are reciprocally related. Among sporadic AD patients, clinical seizures occur in 10-22% and subclinical epileptiform abnormalities occur in 22-54%. Cognitive deficits, especially short-term memory impairments, occur in most epilepsy patients. Common neurophysiological and molecular mechanisms occur in AD and epilepsy. The choroid plexus undergoes pathological changes in aging, AD, and epilepsy, including decreased CSF turnover, amyloid beta (Aβ), and tau accumulation due to impaired clearance and disrupted CSF amino acid homeostasis. This pathology may contribute to synaptic dysfunction in AD and epilepsy. We evaluated control (n = 8), severe AD (n = 8; A3, B3, C3 neuropathology), and epilepsy autopsy cases (n = 12) using laser capture microdissection (LCM) followed by label-free quantitative mass spectrometry on the choroid plexus adjacent to the hippocampus at the lateral geniculate nucleus level. Proteomics identified 2,459 proteins in the choroid plexus. At a 5% false discovery rate (FDR), 616 proteins were differentially expressed in AD vs. control, 1 protein in epilepsy vs. control, and 438 proteins in AD vs. epilepsy. There was more variability in the epilepsy group across syndromes. The top 20 signaling pathways associated with differentially expressed proteins in AD vs. control included cell metabolism pathways; activated fatty acid beta-oxidation (p = 2.00 x 10-7, z = 3.00), and inhibited glycolysis (p = 1.00 x 10-12, z = -3.46). For AD vs. epilepsy, the altered pathways included cell metabolism pathways, activated complement system (p = 5.62 x 10-5, z = 2.00), and pathogen-induced cytokine storm (p = 2.19 x 10-2, z = 3.61). Of the 617 altered proteins in AD and epilepsy vs. controls, 497 (81%) were positively correlated (p < 0.0001, R2 = 0.27). We found altered signaling pathways in the choroid plexus of severe AD cases and many correlated changes in the protein expression of cell metabolism pathways in AD and epilepsy cases. The shared molecular mechanisms should be investigated further to distinguish primary pathogenic changes from the secondary ones. These mechanisms could inform novel therapeutic strategies to prevent disease progression or restore normal function. A focus on dual-diagnosed AD/epilepsy cases, specific epilepsy syndromes, such as temporal lobe epilepsy, and changes across different severity levels in AD and epilepsy would add to our understanding.

Pooled analysis of frontal lobe transcriptomic data identifies key mitophagy gene changes in Alzheimer's disease brain.

The growing prevalence of Alzheimer's disease (AD) is becoming a global health challenge without effective treatments. Defective mitochondrial function and mitophagy have recently been suggested as etiological factors in AD, in association with abnormalities in components of the autophagic machinery like lysosomes and phagosomes. Several large transcriptomic studies have been performed on different brain regions from AD and healthy patients, and their data represent a vast source of important information that can be utilized to understand this condition. However, large integration analyses of these publicly available data, such as AD RNA-Seq data, are still missing. In addition, large-scale focused analysis on mitophagy, which seems to be relevant for the aetiology of the disease, has not yet been performed. In this study, publicly available raw RNA-Seq data generated from healthy control and sporadic AD post-mortem human samples of the brain frontal lobe were collected and integrated. Sex-specific differential expression analysis was performed on the combined data set after batch effect correction. From the resulting set of differentially expressed genes, candidate mitophagy-related genes were identified based on their known functional roles in mitophagy, the lysosome, or the phagosome, followed by Protein-Protein Interaction (PPI) and microRNA-mRNA network analysis. The expression changes of candidate genes were further validated in human skin fibroblast and induced pluripotent stem cells (iPSCs)-derived cortical neurons from AD patients and matching healthy controls. From a large dataset (AD: 589; control: 246) based on three different datasets (i.e., ROSMAP, MSBB, & GSE110731), we identified 299 candidate mitophagy-related differentially expressed genes (DEG) in sporadic AD patients (male: 195, female: 188). Among these, the AAA ATPase VCP, the GTPase ARF1, the autophagic vesicle forming protein GABARAPL1 and the cytoskeleton protein actin beta ACTB were selected based on network degrees and existing literature. Changes in their expression were further validated in AD-relevant human in vitro models, which confirmed their down-regulation in AD conditions. Through the joint analysis of multiple publicly available data sets, we identify four differentially expressed key mitophagy-related genes potentially relevant for the pathogenesis of sporadic AD. Changes in expression of these four genes were validated using two AD-relevant human in vitro models, primary human fibroblasts and iPSC-derived neurons. Our results provide foundation for further investigation of these genes as potential biomarkers or disease-modifying pharmacological targets.

Melatonin reduces β-amyloid accumulation and improves short-term memory in streptozotocin-induced sporadic Alzheimer's disease model.

Melatonin is a hormone secreted by the pineal gland, it can be associated with circadian rhythms, aging and neuroprotection. Melatonin levels are decreased in sporadic Alzheimer's disease (sAD) patients, which suggests a relationship between the melatonergic system and sAD. Melatonin may reduce inflammation, oxidative stress, TAU protein hyperphosphorylation, and the formation of β-amyloid (Aβ) aggregates. Therefore, the objective of this work was to investigate the impact of treatment with 10mg/kg of melatonin (i.p) in the animal model of sAD induced by the intracerebroventricular (ICV) infusion of 3mg/kg of streptozotocin (STZ). ICV-STZ causes changes in the brain of rats similar to those found in patients with sAD. These changes include; progressive memory decline, the formation of neurofibrillary tangles, senile plaques, disturbances in glucose metabolism, insulin resistance and even reactive astrogliosis characterized by the upregulation of glucose levels and glial fibrillary acidic protein (GFAP). The results show that ICV-STZ caused short-term spatial memory impairment in rats after 30 days of STZ infusion without locomotor impairment which was evaluated on day 27 post-injury. Furthermore, we observed that a prolonged 30-day treatment with melatonin can improve the cognitive impairment of animals in the Y-maze test, but not in the object location test. Finally, we demonstrated that animals receiving ICV-STZ have high levels of Aβ and GFAP in the hippocampus and that treatment with melatonin reduces Aβ levels but does not reduce GFAP levels, concluding that melatonin may be useful to control the progression of amyloid pathology in the brain.

Octapeptide repeat alteration mutations of the prion protein gene in clinically diagnosed Alzheimer's disease and frontotemporal dementia.

Studies focusing on octapeptide repeat alteration mutations in PRNP in Alzheimer's disease (AD) and frontotemporal dementia (FTD) cohorts have been rare. We aim to screen sporadic AD and FTD patients with unknown etiology for the octapeptide repeat insertions and deletions in PRNP. Two hundred and six individuals were screened for alterations to the repeat region in the PRNP gene, including 146 sporadic AD and 60 sporadic FTD patients. Our study showed a 1.5% (3/206) occurrence of the octapeptide repeat alteration mutations in PRNP in a Chinese cohort of sporadic dementia. One late-onset FTD patient and one early-onset AD patient each had a two-octapeptide repeat deletion in PRNP, while one early-onset AD patient had a five-octapeptide repeat insertion mutation. PRNP octapeptide repeat alteration mutations are present in sporadic AD and FTD patients. The genetic investigation for PRNP octapeptide repeat alteration mutations in sporadic dementia patients should be carried out in future clinical studies.

Alterations of ATG4A and LC3B in neurons derived from Alzheimer's disease patients.

We investigated the alterations in autophagy-related molecules in neurons differentiated from induced pluripotent stem cells obtained from patients with Alzheimer's disease (AD). Consistent with our previous microarray data, ATG4A protein was upregulated in the neurons derived from a familial AD patient with an APP-E693Δ mutation who showed accumulation of intracellular amyloid β peptide (Aβ). This upregulation was reversed by inhibiting Aβ production, suggesting that the intracellular Aβ may be responsible for the upregulation of ATG4A. The LC3B-II/LC3B-I ratio, an index of autophagosome formation, was lower in the neurons derived from the AD patient with APP-E693Δ as well as the neurons derived from other familial and sporadic AD patients. These findings indicate that dysregulation of autophagy-related molecules may accelerate the pathogenesis of AD.

PS1 Affects the Pathology of Alzheimer's Disease by Regulating BACE1 Distribution in the ER and BACE1 Maturation in the Golgi Apparatus.

Neuritic plaques are one of the major pathological hallmarks of Alzheimer's disease. They are formed by the aggregation of extracellular amyloid-β protein (Aβ), which is derived from the sequential cleavage of amyloid-β precursor protein (APP) by β- and γ-secretase. BACE1 is the main β-secretase in the pathogenic process of Alzheimer's disease, which is believed to be a rate-limiting step of Aβ production. Presenilin 1 (PS1) is the active center of the γ-secretase that participates in the APP hydrolysis process. Mutations in the PS1 gene (PSEN1) are the most common cause of early onset familial Alzheimer's disease (FAD). The PSEN1 mutations can alter the activity of γ-secretase on the cleavage of APP. Previous studies have shown that PSEN1 mutations increase the expression and activity of BACE1 and that BACE1 expression and activity are elevated in the brains of PSEN1 mutant knock-in mice, compared with wild-type mice, as well as in the cerebral cortex of FAD patients carrying PSEN1 mutations, compared with sporadic AD patients and controls. Here, we used a Psen1 knockout cell line and a PS1 inhibitor to show that PS1 affects the expression of BACE1 in vitro. Furthermore, we used sucrose gradient fractionation combined with western blotting to analyze the distribution of BACE1, combined with a time-lapse technique to show that PS1 upregulates the distribution and trafficking of BACE1 in the endoplasmic reticulum, Golgi, and endosomes. More importantly, we found that the PSEN1 mutant S170F increases the distribution of BACE1 in the endoplasmic reticulum and changes the ratio of mature BACE1 in the trans-Golgi network. The effect of PSEN1 mutations on BACE1 may contribute to determining the phenotype of early onset FAD.

Association of rs2072446 in the NGFR gene with the risk of Alzheimer's disease and amyloid-β deposition in the brain.

Alzheimer's disease (AD) is the most common form of dementia with a complex genetic background. The cause of sporadic AD (sAD) remains largely unknown. Increasing evidence shows that genetic variations play a crucial role in sAD. P75 neurotrophin receptor (p75NTR, encoded by NGFR) plays a critical role in the pathogenesis of AD. Yet, the relationship between NGFR gene polymorphisms and AD was less studied. This study aims to analyze the relationship of NGFR gene polymorphism with the risk of AD in the Chinese Han population and amyloid-β deposition in the ADNI cohort. This case-control association study was conducted in a Chinese Han cohort consisting of 366 sporadic AD (sAD) patients and 390 age- and sex-matched controls. Twelve tag-SNPs were selected and genotyped with a multiplex polymerase chain reaction-ligase detection reaction (PCR-LDR) method. The associations between tag-SNPs and the risk of AD were analyzed by logistic regression. Moreover, another cohort from the Alzheimer's Disease Neuroimaging Initiative (ADNI) database was included to examine the association of one tag-SNP (rs2072446) with indicators of amyloid deposition. Kaplan-Meier survival analysis and Cox proportional hazards models were used to test the predictive abilities of rs2072446 genotypes for AD progression. The mediation effects of Aβ deposition on this association were subsequently tested by mediation analyses. After multiple testing corrections, one tag-SNP, rs2072446, was associated with an increased risk of sAD (additive model, OR=1.79, Padjustment =0.0144). Analyses of the ADNI cohort showed that the minor allele (T) of rs2072446 was significantly associated with the heavier Aβ burden, which further contributed to an increased risk of AD progression in APOE ε4 non-carrier. Our study found that rs2072446 in NGFR is associated with both the risk of sAD in the Chinese Han population and the amyloid burden in the ADNI cohort, which reveals the role of p75NTR in AD from a genetic perspective.

Whole Exome Sequencing Reveals a Novel APOE Mutation in a Patient With Sporadic Early-Onset Alzheimer's Disease.

Apolipoprotein (APOE) is implicated and verified as the main risk factor for early-onset Alzheimer's disease (AD). APOE is a protein that binds to lipids and is involved in cholesterol stability. Our paper reports a case of a sporadic early-onset AD (sEOAD) patient of a 54-year-old Korean man, where a novel APOE Leu159Pro heterozygous mutation was revealed upon Whole Exome Sequence analysis. The proband's CSF showed downregulated levels of Aβ42, with unchanged Tau levels. The mutation is in the Low-Density Lipoprotein Receptor (LDLR) region of the APOE gene, which mediates the clearance of APOE lipoproteins. LDLR works as a high-affinity point for APOE. Studies suggest that APOE-LDLR interplay could have varying effects. The LDLR receptor pathway has been previously suggested as a therapeutic target to treat tauopathy. However, the APOE-LDLR interaction has also shown a significant correlation with memory retention. Leu159Pro could be an interesting mutation that could be responsible for a less damaging pattern of AD by suppressing tau-association neurodegeneration while affecting the patient's memory retention and cognitive performance.

The genetic risk effects of APOE ε4 and novel variants on Chinese familial and sporadic AD.

The genetic risk effects of apolipoprotein E (APOE) on familial Alzheimer's disease (FAD) with or without gene mutations, sporadic AD (SAD), and normal controls (NC) remain unclear in the Chinese population. Previous genome-wide association studies (GWAS) have identified dozens of susceptibility loci for sporadic Alzheimer's disease, but few of these loci have been validated in longitudinal cohorts. More than 15 thousand Chinese subjects, including FAD patients with or without pathogenic mutations (PSENs/APP), SAD patients, and normal controls (NC) were included from our large multi-center FAD and SAD cohorts. We analyzed the risk effects of APOE ε4 and performed a two-stage GWAS and built predictive models. The prevalence of the APOE ε4 genotype in FAD (unknown), FAD (PSENs/APP), SAD, and NC groups was 56.27%, 26.19%, 36.23%, and 19.54%, respectively. The APOE ε4 positive genotype had predictive power for FAD (unknown) risk (fig. 1, odds ratio: 4.51, 95% confidence interval: 3.57-5.45, P<.001). Four novel variants (rs3777215, rs6859823, rs234434, and rs2255835) as well as nine variants in the APOE region were identified with genome-wide significance. They are related to APP transport and metabolism, antioxidation, and neurogenesis. Using these variants, we built 11 predictive models that were all significant in predicting AD onset in both stages (fig. 2, peak of area under the curve reached 0.73). These models were validated using a separate longitudinal cohort, and results showed that individuals carrying risk variants included in the models had a shorter latency and higher incidence of AD. APOE ε4 positive genotype may cause familial aggregation, and the investigation of multiple interventions targeting APOE pathological function to reduce the risk for this disease warrants attention. This is the first study to validate GWAS-based predictive models for evaluating the risk of AD onset in a large Chinese population. The clinical application of these models will be beneficial for individuals harbouring these risk variants.

Correlation of R219K polymorphism of ABCA1 gene and the risk of Alzheimer's disease in the southwest of Iran

IntroductionAlzheimer's disease (AD), as a neurodegenerative disease, is the most common reason for dementia in the elderly. ATP- binding cassette transporter 1 (ABCA1) is a cell membrane transporter protein which is involved in cholesterol efflux. The aim of this study is to evaluate the correlation between polymorphisms of G/A (rs2230806) in ABCA1 gene with sporadic Alzheimer's disease in the southwest of Iran. MethodsThis case-control study was conducted in 180 subjects, including 100 sporadic AD patients and 80 healthy subjects. Genotypes of all samples were determined using the PCR–restriction fragment length polymorphism (PCR–RFLP) technique. ResultsThe analysis of the R219K Polymorphism of ABCA1 gene indicated that there was no significant distinction between AD patients and controls. In this study when groups were stratified by age and sex, results showed that in the control group with less than 75 years, the risk of developing AD was significantly lower than subjects who were older than 75 years (P = 0.019, OR = 0.46, 95% CI = 0.24–0.88). A significant difference was detected in the risk of AD between patient and control in females older than 75 years (P = 0.028). ConclusionThe results of this study confirm that aging is an important risk factor for AD. Also, it has been found that AD is more prevalent in women compared to men. However, our results do not support the hypothesis that R219K polymorphism in the rs2230806 region of the ABCA1 as a genetic risk factor for developing AD in our study population.