Mutant APP Research Articles

NCRAD Family Study and NIA‐LOAD brain tissue: A NCRAD resource

Brain tissue is an invaluable resource for researchers investigating the pathological etiology and molecular basis of Alzheimer's disease (AD), but this resource is scarce and difficult to obtain compared to other types of biospecimens. The National Centralized Repository for Alzheimer's Disease and Related Dementias (NCRAD) stores and distributes brain tissue to researchers to address this research gap.NCRAD stores fresh frozen, formalin fixed brain tissue collected from participants of the NCRAD Family Study, as well as the NIA Genetics Initiative/NIA-LOAD Family Based Study (FBS). Approved researchers can obtain tissue from NCRAD, and can also obtain access to genetic data for select subjects from the National Institute on Aging Genetics of Alzheimer's Disease Data Storage Site (NIAGADS).The NCRAD Family Study brain tissue collection includes specimens from 249 subjects from 180 families. 65% of participants were female, the average age of death was 81.4 years, with an average age of dementia onset of 70.18 years for those with reported data. 199 subjects had confirmed or probable AD. 14 subjects had known pathogenic AD mutations in PS1, APP, MAPT, or PGRN. Currently, 186 subjects have been sent for RNA-sequencing, 123 have GWAS available through NIAGADS, and 71 have sequencing available through NIAGADS. NCRAD has sent DNA from an additional 125 subjects for GWAS and 170 for whole exome sequencing, which will be made available through NIAGADS. The NIA-LOAD FBS Study includes specimens from 87 subjects from 66 families. 57% of participants were female, the average age of death was 82.9 years, with an average age of dementia onset of 73.5 years. 81 subjects had definite or probable AD. 84 subjects have GWAS data, and 66 subjects have sequencing available through NIAGADS. Subjects from both studies have autopsy data available, including Braak stage, CERAD category, and Reagan category.The brain tissue and clinical information from both these studies are valuable resources for the AD research community, particularly as they are augmented by a growing collection of genetic data. NCRAD strongly encourages researchers to leverage these valuable resources to advance the state of knowledge regarding AD research and therapeutic development.

Single nuclei RNA-sequencing of GWAS loci variant carriers elucidates cell-types and transcriptional profile alterations associated with Alzheimer disease.

AD has a substantial genetic, molecular and cellular heterogeneity associated with its etiology. We sought to investigate the glial and neuronal pathways affected by AD at a cell specific resolution. To do so, we generated single-nuclei RNA-seq (snRNA-seq) from the parietal cortex of Mendelian mutation carriers, sporadic AD and neuropath-free donors from the Knight-ADRC and Dominantly Inherited Alzheimer Network banks. We generated snRNAseq (10X chemistry v3) for 18 APP and PSEN1 mutation carriers, 36 sporadic AD and 9 controls. After data cleaning and quality control, 336,892 nuclei remained for clustering and downstream analyses (Figure 1). Our analytical approach is based on the identification of cellular states (subclusters), their characterization and identification of genes associated with AD genetic strata. We identified a myriad of transcriptional states for the most representative brain cell-types (Figure 1) with distinguishing expression profiles (mean of 600 genes overexpressed; FDR<0.05). We identified that neuronal and glial cells have specific transcriptional states enriched in nuclei from brains with APP and PSEN1 mutations. For example, an astrocyte cell state specific for these brains shows overexpression of genes identified in the Disease Associated Astrocytes (DAA) expression signature. We also noted a microglia cell state enriched for a subset of TREM2 variant carriers showing overexpression of genes related to cell migration and lamellipodium assembly. We developed a unique molecular atlas to study the pathways dysregulated in AD. Our analyses indicate that in the backdrop of neuropath free and even sporadic AD brains, ADAD samples have distinctive cell states and altered pathways in neurons and glia.

Multi-omics data integration reveals clinically meaningful molecular profiles of Alzheimer disease.

Alzheimer disease (AD) is a complex polygenic disease in which multiple molecular pathways and biological processes are affected in distinct cell-types of the brain. Increasingly, novel machine learning approaches have been applied in other areas of similarly high complexity (e.g., cancer) to integrate different modalities of "-omics" data and provide novel insights. We sought to apply high-throughput "multi-omics" and machine learning approaches to a large assembly of clinically and neuropathologically well-characterized brain samples to identify genes and biological pathways that may lead to new biomarkers and therapies for AD. We analyzed high-throughput transcriptomics, proteomics, metabolomics and lipidomics profiles of postmortem parietal cortex samples from the Knight ADRC (n=328) and the DIAN (n =21) participants including APP, PSEN1 and PSEN2 autosomal dominant AD mutation carriers (ADAD, n=28), sporadic AD (sAD, n=282), presymptomatic AD (preAD, n=14), and controls with minimal neuropathologic changes (n=25). We applied a Bayesian integrative clustering method (iClusterBayes), designed to identify disease subtypes, to cluster sAD samples on the basis of 2,676 transcripts, 1,067 proteins, 350 metabolites, and 277 lipids. Our analyses identified four different molecular signatures among sAD cases (Figure 1A). Cluster 4 was associated with higher Clinical Dementia Rating (CDR; p=2.2 x10-20) scores and shorter life span (p=5.6 x10-3, HR=1.6; Figure 1B). In particular, alpha-synuclein (SNCA) transcriptomic and proteomic levels were differentially expressed between samples in cluster 4 and others representing sAD, ADAD, preAD, and controls (Figure 1C) suggesting a unique role for SNCA in sAD cases with unfavorable outcomes. The lower levels of soluble SNCA protein in AD samples may be associated with insoluble aggregated SNCA (Lewy bodies) reported in 50-60% of sAD. By applying machine learning approaches to sAD samples with high-throughput multi-omic profiles, we identified novel molecular signatures missed by single layer analyses. These signatures are associated with clinical phenotypes and offer new insights into which molecules may wax or wane as cognition declines. The association of SNCA with poor outcomes suggests that concomitant Lewy bodies may be a negative prognostic factor in sAD. Currently, we are extending these analyses to incorporate replication cohorts and to perform downstream pathway and enrichment analyses.

Decreased expression of protein O-linked mannose β1,2-n-acetylglucosaminyltransferase 1 contributes to Alzheimer's disease-like pathologies.

Mannosylation was proven to be related to tau phosphorylation and amyloid beta regulation. The expression of POMGnT1 was measured in AD-like models [β-amyloid precursor protein (APP)/presenilin-1 (PS1) transgenic mice, an AD-like animal model; N2a cells stably transfected with Swedish mutant APP (N2a/APP), an AD-like cell model]. POMGnT1-overexpressing N2a/APP cells were created by retroviral transfection. Real time-PCR. western blot, and immunofluorescence were conducted to measure the expression of target values. The expression of POMGnT1 decreased in AD-like animal and cell models. The POMGnT1 overexpression could decrease the Aβ levels by reducing APP generation and downregulating β-and γ-secretase activities. It also increased Aβ clearance by upregulating insulin-degrading enzymes and ameliorated Tau hyperphosphorylation. POMGnT1 was involved in the pathogenic process of AD, and the decreased expression of POMGnT1 contributed to AD-like pathologies.

The influence of known pathogenic gene mutation and ApoEε4 on neuropsychological evaluation and imaging markers in preclinical stage of familial Alzheimer’s disease

AbstractBackgroundIn the preclinical stage of familial Alzheimer's disease (FAD), there have been changes in multi‐dimensional indicators, such as pathology, neuropsychology and imaging. This study explored the effects of known pathogenic gene mutation and ApoE on neuropsychology and imaging markers before the appearance of FAD symptoms.Method102 cases of asymptomatic mutation non‐carriers (26 cases of ApoEε4) and 38 cases of asymptomatic mutation carriers (17 APP, 21 PS1) in FAD families were assessed by a series of neuropsychological scales, including mini mental state scale (MMSE), auditory verbal learning test (AVLT), etc. MRI images were collected. The volume of representative brain regions was obtained, including subregions of striatum, hippocampus, rostral middle frontal gyrus (rMFG), and posterior cingulate cortex (PCC). Diffusion indices and functional connectivity (FC) of neural pathways (striatum subregions to rMFG, hippocampus to PCC) were also obtained. The neuropsychological scores and imaging indexes were compared between groups, and the imaging indexes with group differences were further correlated with neuropsychological scores.ResultCompared with asymptomatic mutation non‐carriers, APP group showed a trend increase in delayed recall score in AVLT (P = 0.08), significantly increased cued recall score, and increased radial diffusivity (RD) of bilateral caudate‐rMFG pathway (fig 1, P's &lt; 0.05). In asymptomatic mutation non‐carriers, compared with APOEε4 non‐carriers, APOEε4 carriers showed increased right hippocampal volume, decreased fractional anisotropy (FA) of bilateral hippocampus‐PCC pathway, and increased FC of left caudate‐rMFG pathway (fig 2, P's &lt; 0.05). The RD of right caudate‐rMFG pathway in PS1 group was positively correlated with MMSE total score (r = 0.749). The FC of left caudate‐rMFG pathway was negatively correlated with MMSE total score (fig 3, r = ‐ 0.623, P’s &lt; 0.05).ConclusionThere are neuropsychological and imaging changes in the early stage of FAD, which are affected by the known pathogenic gene mutation and ApoEε4. APP mutation affected memory domain in cognitive function and the structural connectivity of fronto‐striatal pathway. ApoEε4 mainly affected the structural connectivity of hippocampus‐PCC pathway. The hippocampal volume and the functional connectivity of fronto‐striatal pathway increased compensatively. The overall cognitive function is differently related to the structural and functional connectivity of fronto‐striatal pathway in APP, PS1 and ApoEε4.

Genotype-phenotype of PSEN1 p.CYS263PHE carriers in Flanders-Belgian Alzheimer's disease patients.

We identified 13 unrelated index patients carrying the presenilin 1 (PSEN1) missense mutation, p.Cys263Phe in a Flanders-Belgian cohort of Alzheimer's disease (AD) patients. Seven affected relatives in three different families also carried the PSEN1 p.Cys263Phe mutation (n=20). We aimed to delineate a clinicopathological phenotype of p.Cys263Phe carriers. We compared the p.Cys263Phe genotype-phenotype with that of AD patients carrying autosomal dominant mutations i.e. PSEN1 (n=29), PSEN2 (n=1), and APP (n=5). Reviewing of medical records of autosomal dominant mutation carriers to obtain clinical and pathological data for defining genotype-phenotype data. Mean onset age of the p.Cys263Phe carriers is 63.9±5.5 years (range 53-79), with a disease duration of 7.0±3.5 years (range 4-13). APOE genotypes have no significant effects on onset age. A positive familial history is present in 92.9% of the carriers. Segregation with disease is present in two families with autosomal dominant inheritance of AD (figure 1). In all carriers the clinical presentation is predominantly amnestic, although 35.7% (5/14) of the patients also show significant frontal symptoms. Structural neuroimaging displays diffuse (sub)cortical atrophy with evident hippocampal atrophy in 26.7% (4/15) of the carriers. In 40.0% (6/15) of the patients we observe severe signs of small vessel disease. Brain perfusion SPECT or fluorodeoxyglucose PET imaging shows bilateral temporoparietal involvement in 57.1% (4/7) of carriers. Cerebrospinal fluid AD biomarkers were analyzed in eight carriers, and all are characteristic for AD. Neuropathological examination in three carriers shows severe levels of hallmark AD lesions combined with pronounced cerebral amyloid angiopathy (CAA) and multiple intracerebral hemorrhages in one patient. Carriers of p.Cys263Phe have a later age at onset (63.9 years) compared to PSEN1 carriers (50.9 years) and other PSEN1, PSEN2 and APP mutation carriers (51.4 years) (figure 2). PSEN1 p.Cys263Phe carriers present with early-onset familial AD with autosomal dominant co-segregation. Important is that frontal symptoms are seen in 35.7% of the carrier while neuropathological examination reveals severe levels of AD neuropathology with prominent presence of CAA. The disease onset of PSEN1 p.Cys263Phe carriers is later in comparison with other autosomal dominant gene mutation carriers.

The pathogenic role of tubulin tyrosine ligase and D2 tubulin in Alzheimer's disease.

Neurons possess both stable and dynamic microtubules (MTs), and regulation of the balance between these two states is critical to avoid disease. Post-translational modifications (PTMs) of tubulin can alter MT stability. We have preliminary evidence indicating that premature MT longevity and accumulation of D2 tubulin, a tubulin PTM associated with long-lived and hyperstable MTs, play a pathogenic role in AD. D2 tubulin is derived from the cleavage of the last two residues of alpha-tubulin by the sequential actions of VASH1/2 and the CCP family of tubulin carboxypeptidases. De-tyrosinated tubulin, lacking just one terminal residue, can be returned to its original, tyrosinated state by TTL, a rate-limiting enzyme. Immunoblot analyses of TTL and D2 levels were carried out on frozen human hippocampal tissue. Western blot and microtubule dynamics experiments were performed on human cortical neurons derived from iPSC lines in which the London familial APP mutation V717I was knocked into one allele of the IMR90 control backbone using CRISPR/Cas9 technology to mimic fAD. Lentiviral infection with cDNA shRNA against TTL was used on primary rat hippocampal cultures. Spine density and morphology was quantified by DioListic labelling prior to imaging and reconstruction. We found that levels of TTL were decreased in lysates from AD brains compared to age-matched controls and that, in contrast, D2 tubulin was significantly higher in the AD brains. In the APP London cortical neurons, which accumulate amyloid beta(1-42) and hyperphosphorylated tau in an age-dependent manner, TTL levels again decreased while D2 tubulin increased. We examined whether these changes correlated with an increase in MT stability by measuring MT dynamics and found that in the APP London line, dynamic MTs demonstrated decreased catastrophe frequency and longer comet lifetimes, conditions that are compatible with MT hyperstabilization. We found that depletion of TTL expression in rat hippocampal cells promoted accumulation of D2 tubulin and caused dendritic spine loss. Together, our results indicate that loss of TTL and accompanying accumulation of D2 tubulin are hallmarks of both sporadic and familial AD and that loss of MT dynamicity is a feature of familial AD that may contribute to synapse loss and disease progression.

Osteoblastic Swedish mutant APP expedites brain deficits by inducing endoplasmic reticulum stress-driven senescence

Patients with Alzheimer’s disease (AD) often have osteoporosis or osteopenia. However, their direct link and relationship remain largely unclear. Previous studies have detected osteoporotic deficits in young adult Tg2576 and TgAPPsweOCN mice, which express APPswe (Swedish mutant) ubiquitously and selectively in osteoblast (OB)-lineage cells. This raises the question, whether osteoblastic APPswe contributes to AD development. Here, we provide evidence that TgAPPsweOCN mice also exhibit AD-relevant brain pathologies and behavior phenotypes. Some brain pathologies include age-dependent and regional-selective increases in glial activation and pro-inflammatory cytokines, which are accompanied by behavioral phenotypes such as anxiety, depression, and altered learning and memory. Further cellular studies suggest that APPswe, but not APPwt or APPlon (London mutant), in OB-lineage cells induces endoplasmic reticulum-stress driven senescence, driving systemic and cortex inflammation as well as behavioral changes in 6-month-old TgAPPsweOCN mice. These results therefore reveal an unrecognized function of osteoblastic APPswe to brain axis in AD development.

An App knock-in rat model for Alzheimer\u2019s disease exhibiting A\u03b2 and tau pathologies, neuronal death and cognitive impairments

A major obstacle in Alzheimer’s disease (AD) research is the lack of predictive and translatable animal models that reflect disease progression and drug efficacy. Transgenic mice overexpressing amyloid precursor protein (App) gene manifest non-physiological and ectopic expression of APP and its fragments in the brain, which is not observed in AD patients. The App knock-in mice circumvented some of these problems, but they do not exhibit tau pathology and neuronal death. We have generated a rat model, with three familiar App mutations and humanized Aβ sequence knocked into the rat App gene. Without altering the levels of full-length APP and other APP fragments, this model exhibits pathologies and disease progression resembling those in human patients: deposit of Aβ plaques in relevant brain regions, microglia activation and gliosis, progressive synaptic degeneration and AD-relevant cognitive deficits. Interestingly, we have observed tau pathology, neuronal apoptosis and necroptosis and brain atrophy, phenotypes rarely seen in other APP models. This App knock-in rat model may serve as a useful tool for AD research, identifying new drug targets and biomarkers, and testing therapeutics.

Unraveling the Gordian knot: genetics and the troubled road to effective therapeutics for Alzheimer's disease.

In the late 20th century, identification of the major protein components of amyloid plaques and neurofibrillary tangles provided a window into the molecular pathology of Alzheimer’s disease, ushering in an era of optimism that targeted therapeutics would soon follow. The amyloid-cascade hypothesis took hold very early, supported by discoveries that dominant mutations in APP, PSEN1, and PSEN2 cause the very rare, early-onset, familial forms of the disease. However, in the past decade, a stunning series of failed Phase-3 clinical trials, testing anti-amyloid antibodies or processing-enzyme inhibitors, prompts the question, What went wrong? The FDA’s recent controversial approval of aducanumab, despite widespread concerns about efficacy and safety, only amplifies the question. The assumption that common, late-onset Alzheimer’s is a milder form of familial disease was not adequately questioned. The differential timing of discoveries, including blood–brain–barrier-penetrant tracers for imaging of plaques and tangles, made it easy to focus on amyloid. Furthermore, the neuropathology community initially implemented Alzheimer’s diagnostic criteria based on plaques only. The discovery that MAPT mutations cause frontotemporal dementia with tauopathy made it even easier to overlook the tangles in Alzheimer’s. Many important findings were simply ignored. The accepted mouse models did not predict the human clinical trials data. Given this lack of pharmacological validity, input from geneticists in collaboration with neuroscientists is needed to establish criteria for valid models of Alzheimer’s disease. More generally, scientists using genetic model organisms as whole-animal bioassays can contribute to building the pathogenesis network map of Alzheimer’s disease.

Effects of ApoE genotype on clinical phenotypes in early-onset and late-onset Alzheimer's disease in China: Data from the PUMCH dementia cohort.

IntroductionTo investigate the heterogeneous effect of Apolipoprotein E (ApoE) genotype on clinical phenotypes in early‐onset Alzheimer's disease (EOAD) and late‐onset Alzheimer's disease (LOAD), respectively.Methods785 probable AD patients were enrolled from the dementia cohort of Peking Union Medical College Hospital (PUMCH), China. There were 386 EOAD and 399 LOAD cases. All individuals finished history inquiry, neurological examination, blood biochemical test, neuropsychological screening test, electroencephalography, brain CT/MRI, and ApoE genotyping. Some participants had neuropsychological domain assessment (n = 317), MRI morphometry (n = 130), CSF testing of Aβ42, p‐tau, t‐tau (n = 144), or DNA sequencing (n = 690). The variables were compared mainly between ɛ4 carriers and non‐carriers in EOAD and LOAD, respectively.ResultsIn LOAD, ɛ4 carriers showed female predominance; worse performance in trail making test, delayed recall of auditory verbal learning test (AVLT) and rey complex figure; smaller hippocampal, parahippocampal, and entorhinal volume, as compared to ɛ4 non‐carriers. In EOAD, ɛ4 carriers had lower scores in AVLT, episodic memory and modified Luria's tapping task; but less cortical atrophy in entorhinal, middle cingulate, inferior frontal, and parieto‐occipital regions, in comparison to ɛ4 non‐carriers. 6.2% (43/690) subjects harbored potential causative mutations in APP, PSEN1, and PSEN2. In both EOAD and LOAD, no differences were observed between ɛ4 carriers and non‐carriers in CSF levels of Aβ42, p‐tau, t‐tau, or mutation frequency.ConclusionsApoE exerts a heterogeneous effect on clinical phenotypes in EOAD and LOAD, which might be related to the different genetic and pathological basis underlying them.

Protective effects of mitophagy enhancers against amyloid beta-induced mitochondrial and synaptic toxicities in Alzheimer disease.

The purpose of our study is to determine the protective effects of mitophagy enhancers against mutant APP and amyloid beta (Aβ)-induced mitochondrial and synaptic toxicities in Alzheimer's disease (ad). Over two decades of research from our lab and others revealed that mitochondrial abnormalities are largely involved in the pathogenesis of both early-onset and late-onset ad. Emerging studies from our lab and others revealed that impaired clearance of dead or dying mitochondria is an early event in the disease process. Based on these changes, it has been proposed that mitophagy enhancers are potential therapeutic candidates to treat patients with ad. In the current study, we optimized doses of mitophagy enhancers urolithin A, actinonin, tomatidine, nicotinamide riboside in immortalized mouse primary hippocampal (HT22) neurons. We transfected HT22 cells with mutant APP cDNA and treated with mitophagy enhancers and assessed mRNA and protein levels of mitochondrial dynamics, biogenesis, mitophagy and synaptic genes, cell survival; assessed mitochondrial respiration in mAPP-HT22 cells treated and untreated with mitophagy enhancers. We also assessed mitochondrial morphology in mAPP-HT22 cells treated and untreated with mitophagy enhancers. Mutant APP-HT22 cells showed increased fission, decreased fusion, synaptic & mitophagy genes, reduced cell survival and defective mitochondrial respiration, and excessively fragmented and reduced length of mitochondria. However, these events were reversed in mitophagy-enhancers-treated mutant mAPP-HT22 cells. Cell survival was significantly increased, mRNA and protein levels of mitochondrial fusion, synaptic and mitophagy genes were increased, mitochondrial number is reduced, and mitochondrial length is increased, and mitochondrial fragmentation is reduced in mitophagy-enhancers-treated mutant APP-HT22 cells. Further, urolithin A showed strongest protective effects against mutant APP and Aβ-induced mitochondrial and synaptic toxicities in ad. Based on these findings, we cautiously propose that mitophagy enhancers are promising therapeutic drugs to treat mitophagy in patients with ad.

The Uppsala APP deletion causes early onset autosomal dominant Alzheimer's disease by altering APP processing and increasing amyloid β fibril formation.

Point mutations in the amyloid precursor protein gene (APP) cause familial Alzheimer's disease (AD) by increasing generation or altering conformation of amyloid β (Aβ). Here, we describe the Uppsala APP mutation (Δ690-695), the first reported deletion causing autosomal dominant AD. Affected individuals have an age at symptom onset in their early forties and suffer from a rapidly progressing disease course. Symptoms and biomarkers are typical of AD, with the exception of normal cerebrospinal fluid (CSF) Aβ42 and only slightly pathological amyloid-positron emission tomography signals. Mass spectrometry and Western blot analyses of patient CSF and media from experimental cell cultures indicate that the Uppsala APP mutation alters APP processing by increasing β-secretase cleavage and affecting α-secretase cleavage. Furthermore, in vitro aggregation studies and analyses of patient brain tissue samples indicate that the longer form of mutated Aβ, AβUpp1-42Δ19-24, accelerates the formation of fibrils with unique polymorphs and their deposition into amyloid plaques in the affected brain.

Hepta-Histidine Inhibits Tau Aggregation.

Tau aggregation is a central hallmark of tauopathies such as frontotemporal lobar degeneration and progressive supranuclear palsy as well as of Alzheimer's disease, and it has been a target for therapeutic development. Herein, we unexpectedly found that hepta-histidine (7H), an inhibitor of the interaction between Ku70 and Huntingtin proteins, suppresses aggregation of Tau-R3 peptides in vitro. Addition of the trans-activator of transcription (TAT) sequence (YGRKKRRQRRR) derived from the TAT protein to 7H increased its permeability into cells, and TAT-7H treatment of iPS cell-derived neurons carrying Tau or APP mutations suppressed Tau phosphorylation. These results indicate that 7H is a promising lead compound for developing anti-aggregation drugs against Tau-related neurodegenerative diseases including Alzheimer's disease (AD).

Genetic profiles of familial late-onset Alzheimer's disease in China: The Shanghai FLOAD study

Compared with early-onset familial AD (FAD), the heritability of most familial late-onset Alzheimer's disease (FLOAD) cases still remains unclear. However, there are few reported genetic profiles of FLOAD to date. In the present study, targeted sequencing of selected candidate genes was conducted for each of 90 probands with FLOAD and 101 unrelated matched normal controls among Chinese Han population. Results show a significantly lower rate of mutation in APP and PSENs, and APOE ε4 genetic risk is higher for FLOAD. Among the Chinese FLOAD population, the most frequent variant was CR1 rs116806486 [5.6%, 95% CI (1.8%, 12.5%)], followed by coding variants of TREM2 (4.4%, 95%CI (1.2%, 10.9%)) and novel mutations of ACE [3.3%, 95%CI (0.7%, 9.4%)]. Next, we found that novel pathogenic mutations in ACE including frame-shift and nonsense mutations were in association with FLOAD regardless of APOE ε4 status. Evidence from the Alzheimer's disease Neuroimaging Initiative (ADNI) database also supported this finding in different ethnicities. Results of in vitro analysis suggest that frame-shift and nonsense mutations in ACE may be involved in LOAD through decreased ACE protein levels without affecting direct processing of APP.

Tyrosine phosphatase PTP1B impairs presynaptic NMDA receptor-mediated plasticity in a mouse model of Alzheimer's disease

Mutations in the beta-amyloid protein (APP) cause familial Alzheimer's disease. In hAPP-J20 mice expressing mutant APP, pharmacological inhibition or genetic ablation of the tyrosine phosphatase PTP1B prevents CA3 hippocampus neuron loss and cognitive decline. However, how targeting PTP1B affects the cellular mechanisms underlying these cognitive deficits remains unknown. Changes in synaptic strength at the hippocampus can affect information processing for learning and memory. While prior studies have focused on post-synaptic mechanisms to account for synaptic deficits in Alzheimer's disease models, presynaptic mechanisms may also be affected. Here, using whole cell patch-clamp recording, coefficient of variation (CV) analysis suggested a profound presynaptic deficit in long-term potentiation (LTP) of CA3:CA1 synapses in hAPP-J20 mice. While the membrane-impermeable ionotropic NMDA receptor (NMDAR) blocker norketamine in the post-synaptic recording electrode had no effect on LTP, additional bath application of the ionotropic NMDAR blockers MK801 could replicate the deficit in LTP in wild type mice. In contrast to LTP, the paired-pulse ratio and short-term facilitation (STF) were aberrantly increased in hAPP-J20 mice. These synaptic deficits in hAPP-J20 mice were associated with reduced phosphorylation of NMDAR GluN2B and the synaptic vesicle recycling protein NSF (N-ethylmaleimide sensitive factor). Phosphorylation of both proteins, together with synaptic plasticity and cognitive function, were restored by PTP1B ablation or inhibition by the PTP1B-selective inhibitor Trodusquemine. Taken together, our results indicate that PTP1B impairs presynaptic NMDAR-mediated synaptic plasticity required for spatial learning in a mouse model of Alzheimer's disease. Since Trodusquemine has undergone phase 1/2 clinical trials to treat obesity, it could be repurposed to treat Alzheimer's disease.

TREM2-mediated activation of microglia breaks link between amyloid and tau

The amyloid hypothesis of Alzheimer's disease is predicated on data showing that mutations in APP (the gene that encodes for the amyloid precursor protein) and, by implication, amyloid β deposition, drive the formation of tau tangles in the brain of people with Alzheimer's disease, and also in doubly transgenic APP and MAPT mutant mice. 1 Selkoe DJ Hardy J The amyloid hypothesis of Alzheimer's disease at 25 years. EMBO Mol Med. 2016; 8: 595-608 Crossref PubMed Scopus (2466) Google Scholar , 2 Lewis J Dickson DW Lin WL et al. Enhanced neurofibrillary degeneration in transgenic mice expressing mutant tau and APP. Science. 2001; 293: 1487-1491 Crossref PubMed Scopus (1209) Google Scholar This hypothesis is usually drawn as a cell-autonomous process, with amyloid β released outside a neuron, but inducing tangle formation within the same neuron. However, this cell-autonomous view has become increasingly untenable. 3 De Strooper B Karran E The cellular phase of Alzheimer's disease. Cell. 2016; 164: 603-615 Summary Full Text Full Text PDF PubMed Scopus (719) Google Scholar

A Rare Variation in the 3' Untranslated Region of the Presenilin 2 Gene Is Linked to Alzheimer's Disease.

Rare variations in coding regions may alter the amino acid sequence and function of presenilins (PSENs), which results in the dysfunction of gamma-secretase, in turn contributing to the development of familial Alzheimer's disease (AD). However, whether rare variations in the 3' untranslated region (UTR) may change the expression level of PSEN2 leading to AD remains unclear. In a familial AD pedigree, DNA samples of the patients were screened for APP, PSEN1, and PSEN2 gene mutations using Sanger sequencing. Allele A of rs537889666, a rare variation located in the 3' UTR of PSEN2, was found in all AD patients, but not in the healthy control in the family. Cosegregation analysis (n = 5) revealed that allele A of rs537889666 may be a pathogenic rare variation. The dual-luciferase assay revealed that allele A suppressed the combination of miR-183-5p and the 3' UTR of PSEN2, which may block the miR-183-5p-mediated suppression of PSEN2 expression. Further study showed an elevated ratio of Aβ42/40 under overexpressed PSEN2 conditions. Measurements of the cerebrospinal fluid showed that PSEN2 levels were increased in both sporadic and AD in this family, suggesting that elevated PSEN2 was associated with the disease. In addition, the miR-183-5p inhibitor or mimic can increase or decrease Aβ42/40 ratios. In conclusion, the results indicate that allele A of rs537889666 upregulated PSEN2 levels, increasing the Aβ42/40 ratio and contributing to AD development.

Regulation of Aβ40 and Aβ42 by formaldehyde exposure in a three‐dimensional (3D) human neural cell culture model for Alzheimer's Disease

Alzheimer's disease (AD), a chronic neurodegenerative disorder characterized by rapidly progressive cognitive dysfunction and behavior impairment, is the most common form of dementia which accounts for 60 to 70 percent of cases. Pathologically, AD is characterized by severe atrophy and neuronal loss, extracellular neuritic plaques composed mainly of aggregated amyloid-b (Ab), and intracellular neurofibrillary tangles consisting of hyperphosphorylated tau protein. Multilevel complex interactions between genetic, epigenetic, and environmental factors contribute to the occurrence and progression of AD. Formaldehyde (FA) is the simplest saturated aldehyde which is one of the most typical environmental and occupational aldehyde pollutants. Recent studies suggested that elevation of FA in the brain, blood or urine by endogenous and/or exogenous exposure may play important roles in AD development. A three-dimensional (3D) human neural cell culture model for AD which can recapitulate key events of AD pathology including β-amyloid plaques and neurofibrillary tangles was used to investigate the effect of FA exposure in AD development and progression in human cells. Immortalized human neural progenitor cells (ReNcell VM (ReN)) were virally transfected with AD-related mutant genes including mutant APP and/or PSEN1 and enriched based on GFP and/or mCherry signals by Fluorescence-activated cell sorting (FACS). In order to mimic the restrictive environment of human brain and allow Aβ deposition and aggregation, the FACS-sorted ReN cells were differentiated into neurons and maintained in a 3D Matrigel culture system. The AD Model and primary ReN cells were treated with different concentrations of FA as well as vehicle controls for 16 weeks. Expression of Aβ40 and Aβ42 were measured in 4, 6, 12 16 weeks by ELISA and cytotoxicity was evaluated by LDH activity assay. The results revealed that FA significantly elevates expression of Aβ40 and Aβ42 in a concentration-dependent manner both in AD model and ReN cells. It indicated that FA exposure may play a critical role in AD development and progression.

Generation of a gene-corrected human isogenic iPSC line from an Alzheimer’s disease iPSC line carrying the London mutation in APP (V717I)

We report the genome-editing of an existing iPSC line carrying the London mutation in APP (V717I) into an iPSC line in which the pathogenic mutation was corrected. The resulting isogenic iPSC line maintained pluripotent stem cell morphology, a normal karyotype, expression of pluripotency markers and the ability to differentiate into the three germ-layers in vitro.