Late-onset Alzheimer's Disease Research Articles

Predictive network analysis identifies JMJD6 and other potential key drivers in Alzheimer’s disease

Despite decades of genetic studies on late-onset Alzheimer’s disease, the underlying molecular mechanisms remain unclear. To better comprehend its complex etiology, we use an integrative approach to build robust predictive (causal) network models using two large human multi-omics datasets. We delineate bulk-tissue gene expression into single cell-type gene expression and integrate clinical and pathologic traits, single nucleotide variation, and deconvoluted gene expression for the construction of cell type-specific predictive network models. Here, we focus on neuron-specific network models and prioritize 19 predicted key drivers modulating Alzheimer’s pathology, which we then validate by knockdown in human induced pluripotent stem cell-derived neurons. We find that neuronal knockdown of 10 of the 19 targets significantly modulates levels of amyloid-beta and/or phosphorylated tau peptides, most notably JMJD6. We also confirm our network structure by RNA sequencing in the neurons following knockdown of each of the 10 targets, which additionally predicts that they are upstream regulators of REST and VGF. Our work thus identifies robust neuronal key drivers of the Alzheimer’s-associated network state which may represent therapeutic targets with relevance to both amyloid and tau pathology in Alzheimer’s disease.

Why Are Perivascular Spaces Important?

Perivascular spaces (PVS) and their enlargement (EPVS) have been gaining interest as EPVS can be visualized non-invasively by magnetic resonance imaging (MRI) when viewing T-2-weighted images. EPVS are most commonly observed in the regions of the basal ganglia and the centrum semiovale; however, they have also been identified in the frontal cortex and hippocampal regions. EPVS are known to be increased in aging and hypertension, and are considered to be a biomarker of cerebral small vessel disease (SVD). Interest in EPVS has been significantly increased because these PVS are now considered to be an essential conduit necessary for the glymphatic pathway to provide the necessary efflux of metabolic waste. Metabolic waste includes misfolded proteins of amyloid beta and tau that are known to accumulate in late-onset Alzheimer's disease (LOAD) within the interstitial fluid that is delivered to the subarachnoid space and eventually the cerebral spinal fluid (CSF). The CSF acts as a sink for accumulating neurotoxicities and allows clinical screening to potentially detect if LOAD may be developing early on in its clinical progression via spinal fluid examination. EPVS are thought to occur by obstruction of the PVS that associates with excessive neuroinflammation, oxidative stress, and vascular stiffening that impairs flow due to a dampening of the arterial and arteriolar pulsatility that aids in the convective flow of the metabolic debris within the glymphatic effluxing system. Additionally, increased EPVS has also been associated with Parkinson's disease and non-age-related multiple sclerosis (MS).

Exome sequence analysis of rare frequency variants in Late-Onset Alzheimer Disease

Alzheimer disease (AD) is a leading cause of dementia in elderly patients who continue to live between 3 and 11 years of diagnosis. A steep rise in AD incidents is observed in the elderly population in East-Asian countries. The disease progresses through several changes, including memory loss, behavioural issues, and cognitive impairment. The etiology of AD is hard to determine because of its complex nature. The whole exome sequences of late-onset AD (LOAD) patients of Korean origin are investigated to identify rare genetic variants that may influence the complex disorder. Computational annotation was performed to assess the function of candidate variants in LOAD. The in silico pathogenicity prediction tools such as SIFT, Polyphen-2, Mutation Taster, CADD, LRT, PROVEAN, DANN, VEST3, fathmm-MKL, GERP + + , SiPhy, phastCons, and phyloP identified around 17 genes harbouring deleterious variants. The variants in the ALDH3A2 and RAD54B genes were pathogenic, while in 15 other genes were predicted to be variants of unknown significance. These variants can be potential risk candidates contributing to AD. In silico computational techniques such as molecular docking, molecular dynamic simulation and steered molecular dynamics were carried out to understand the structural insights of RAD54B with ATP. The simulation of mutant (T459N) RAD54B with ATP revealed reduced binding strength of ATP at its binding site. In addition, lower binding free energy was observed when compared to the wild-type RAD54B. Our study shows that the identified uncommon variants are linked to AD and could be probable predisposing genetic factors of LOAD.

Mutation analysis of the ECE1 gene in late-onset Alzheimer’s disease

We recently identified a rare coding mutation (R186C) in the ECE2 gene in a late-onset AD (LOAD) family, and demonstrated ECE2 is a risk gene for AD development. ECE1 is a homologous enzyme that shares catalytic activity with ECE2. Although ECE1 has been regarded as a potential candidate gene for AD, few studies have investigated the role of ECE1 variants in patients with AD. In this study, we aimed to investigate rare variants in ECE1 in a cohort of 610 patients with LOAD (age of onset ≥65 years). The summary data of ECE1 variants from ChinaMAP database were used as controls (n = 10,588). We found four rare variants (p.R50W, p.A166=, p.R650Q, and p.P751=) in the patients with sporadic LOAD, while we identified a large number of controls carrying rare variants in ECE1. Moreover, there was no significant association between LOAD and non-synonymous rare damaging variants at the gene level. Our results suggest rare coding variants of ECE1 might not play an important role in AD risk in the Chinese population.

Multiomics Analyses Identify Proline Endopeptidase-Like Protein As a Key Regulator of Protein Trafficking, a Pathway Underlying Alzheimer's Disease Pathogenesis.

Current treatments for Alzheimer's disease (AD) help reduce symptoms for a limited time but do not treat the underlying pathology. To identify potential therapeutic targets for AD, an integrative network analysis was previously carried out using 364 human postmortem control, mild cognitive impairment, and AD brains. This analysis identified proline endopeptidase-like protein (PREPL), an understudied protein, as a downregulated protein in late-onset AD patients. In this study we investigate the role of PREPL. Analyses of data from human postmortem samples and PREPL knockdown (KD) cells suggest that PREPL expression modulates pathways associated with protein trafficking, synaptic activities, and lipid metabolism. Furthermore, PREPL KD impairs cell proliferation and modulates the structure of vesicles, levels of neuropeptide-processing enzymes, and secretion of neuropeptides. In addition, decrease in PREPL levels leads to changes in the levels of a number of synaptic proteins as well as changes in the levels of secreted amyloid beta (Aβ) 42 peptide and Tau phosphorylation. Finally, we report that local decrease in PREPL levels in mouse hippocampus attenuates long-term potentiation, suggesting a role in synaptic plasticity. Together, our results indicate that PREPL affects neuronal function by modulating protein trafficking and synaptic function, an important mechanism of AD pathogenesis. SIGNIFICANCE STATEMENT: Integrative network analysis reveals proline endopeptidase-like protein (PREPL) to be downregulated in human sporadic late-onset Alzheimer's disease brains. Down regulation of PREPL leads to increases in amyloid beta secretion, Tau phosphorylation, and decreases in protein trafficking and long-term potentiation.

Agregación y propagación de Aβ en modelos transgénicos de la enfermedad de Alzheimer

Alzheimer´s disease (AD) is a complex neurodegenerative disorder that affects mainly the elder population. To date, modifying therapies have not proven to be successful, and therefore, a major effort is necessary to unravel the pathogenic processes underlying AD. New evidences indicate that AD and many other neurodegenerative diseases have commonly the accumulation of misfolded proteins that have the potential to act as infectious agents, and propagate through the entire brain, affecting native proteins. The amyloid peptide (Aβ), characteristic of AD, can adopt a β-sheet conformation acquiring the potential to aggregate and generate misfolded intermediates that can act as ‘’seeds’’ to propagate disease in the brain. Recent findings suggest that these seeds are structurally different depending on the patients and AD subtype, showing different propagation capacity and toxicity. In order to find out which Aβ species or isoforms are more toxic and have greater potential to aggregate, brain extracts from AD patients have been inoculated into transgenic AD mice brains. These approaches have provided much information, however, most of the models contain one or multiple dominant mutations of familial AD cases. This is of great value to mimic the familial forms of the disease, but not the late onset AD (LOAD), which constitute the majority of the cases. Therefore, new animal models are urgently necessary to circumvent these limitations and properly dissect the pathogenic mechanisms of this common form of the disease. As such, a new humanized Aβ model, called hAβ-KI, that has been generated by UCI-MODEL AD center at California, recapitulates certain features of LOAD. This might represent a useful LOAD model to understand how Aβ spreads and favors the progression of the pathology in the brain, hopefully enabling the development of effective therapeutic interventions for AD.

Epigenetic and non-epigenetic mechanisms in the accelerated cellular aging in late-onset Alzheimer’s disease

Late-onset Alzheimer’s disease (LOAD) is the most common form of Alzheimer’s disease (AD) and its risk increases exponentially with aging. The incidence of LOAD is reported to increase from 1 in every 1,000 people aged 37 to 65 in every 100 people aged 80 years and older. LOAD is extensively associated with aging and cognition decline. Several risk factors, including lifestyle choices, environmental factors, and medical ailments, affect cellular stress. The cellular stress can bring upon epigenetic alterations that affect cellular aging making the individual more susceptible to LOAD development. In due course the cellular stress resulting into epigenetic deregulation, oxidative burden, and genomic mutations leads to increased disease risk. Role of epigenetic and non-epigenetic mechanisms in accelerated cellular aging that are reported to increase the risk of LOAD development are summarized in this review. The underlying biological mechanism of cellular aging and the risk factors that could predispose cellular aging and LOAD development are also discussed in the upcoming sections.

What does heritability of Alzheimer's disease represent?

Both late-onset Alzheimer's disease (AD) and ageing have a strong genetic component. In each case, many associated variants have been discovered, but how much missing heritability remains to be discovered is debated. Variability in the estimation of SNP-based heritability could explain the differences in reported heritability. We compute heritability in five large independent cohorts (N = 7,396, 1,566, 803, 12,528 and 3,963) to determine whether a consensus for the AD heritability estimate can be reached. These cohorts vary by sample size, age of cases and controls and phenotype definition. We compute heritability a) for all SNPs, b) excluding APOE region, c) excluding both APOE and genome-wide association study hit regions, and d) SNPs overlapping a microglia gene-set. SNP-based heritability of late onset Alzheimer's disease is between 38 and 66% when age and genetic disease architecture are correctly accounted for. The heritability estimates decrease by 12% [SD = 8%] on average when the APOE region is excluded and an additional 1% [SD = 3%] when genome-wide significant regions were removed. A microglia gene-set explains 69-84% of our estimates of SNP-based heritability using only 3% of total SNPs in all cohorts. The heritability of neurodegenerative disorders cannot be represented as a single number, because it is dependent on the ages of cases and controls. Genome-wide association studies pick up a large proportion of total AD heritability when age and genetic architecture are correctly accounted for. Around 13% of SNP-based heritability can be explained by known genetic loci and the remaining heritability likely resides around microglial related genes.

Apolipoprotein E Recognizes Alzheimer's Disease Associated 3-O Sulfation of Heparan Sulfate.

Apolipoprotein E (ApoE)'s ϵ4 alle is the most important genetic risk factor for late onset Alzheimer's Disease (AD). Cell-surface heparan sulfate (HS) is a cofactor for ApoE/LRP1 interaction and the prion-like spread of tau pathology between cells. 3-O-sulfo (3-O-S) modification of HS has been linked to AD through its interaction with tau, and enhanced levels of 3-O-sulfated HS and 3-O-sulfotransferases in the AD brain. In this study, we characterized ApoE/HS interactions in wildtype ApoE3, AD-linked ApoE4, and AD-protective ApoE2 and ApoE3-Christchurch. Glycan microarray and SPR assays revealed that all ApoE isoforms recognized 3-O-S. NMR titration localized ApoE/3-O-S binding to the vicinity of the canonical HS binding motif. In cells, the knockout of HS3ST1-a major 3-O sulfotransferase-reduced cell surface binding and uptake of ApoE. 3-O-S is thus recognized by both tau and ApoE, suggesting that the interplay between 3-O-sulfated HS, tau and ApoE isoforms may modulate AD risk.

Apolipoprotein E Recognizes Alzheimer's Disease Associated 3‐O Sulfation of Heparan Sulfate

AbstractApolipoprotein E (ApoE)’s ϵ4 alle is the most important genetic risk factor for late onset Alzheimer's Disease (AD). Cell‐surface heparan sulfate (HS) is a cofactor for ApoE/LRP1 interaction and the prion‐like spread of tau pathology between cells. 3‐O‐sulfo (3‐O‐S) modification of HS has been linked to AD through its interaction with tau, and enhanced levels of 3‐O‐sulfated HS and 3‐O‐sulfotransferases in the AD brain. In this study, we characterized ApoE/HS interactions in wildtype ApoE3, AD‐linked ApoE4, and AD‐protective ApoE2 and ApoE3‐Christchurch. Glycan microarray and SPR assays revealed that all ApoE isoforms recognized 3‐O‐S. NMR titration localized ApoE/3‐O‐S binding to the vicinity of the canonical HS binding motif. In cells, the knockout of HS3ST1‐a major 3‐O sulfotransferase‐reduced cell surface binding and uptake of ApoE. 3‐O‐S is thus recognized by both tau and ApoE, suggesting that the interplay between 3‐O‐sulfated HS, tau and ApoE isoforms may modulate AD risk.

Is Alzheimer's disease a manifestation of brain quantum decoherence resulting from mitochondrial and microtubular deterioration?

The etiology of Alzheimer's dementia is, at best multifactorial. Before the emergence of cognitive impairment, symptoms such as thinning of the cortex, accumulation of β-amyloid, and decreased hippocampal volume are common. Hence, the accumulation of β-amyloid and hyperphosphorylated tau fibrillary tangles are two pathological hallmarks in Alzheimer's disease brains, but antibody therapy aimed to decrease β-amyloid has been a failure and, in most optimistic opinions, may delay somewhat disease progression. However, 31-38 % of subjects develop cerebral micro-hemorrhages in aducanumab therapy, an antibody to the amyloid beta plaque by Biogen. Genetics such as Apo E3/E3 have demonstrated defects in the blood-brain barrier in early-onset dementia. Late Onset Alzheimer’s Dementia, has implicated microbe cerebral infections and numerous genetic single nucleotide polymorphisms. However, several cellular biological signatures of Alzheimer's disease have been identified, such as synaptic dysfunction, β-amyloid plaques, hyperphosphorylated tau, cofilin-actin rods, and Hirano bodies which are related to the actin cytoskeleton. Cofilin is one of the most affluent and common actin-binding proteins and plays a role in cell motility, migration, shape, and metabolism. They also play an important role in severing actin filament, nucleating, depolymerizing, and bundling activities. This review summarizes the structure of cofilins appearing after ATP interruptions and deficits in mitochondrial and microtubules and their functional and regulating roles, focusing on the synaptic dysfunction, β-amyloid plaques, hyperphosphorylated tau, cofilin-actin rods, and Hirano bodies of Alzheimer's disease. These findings strengthen our hypothesis that Alzheimer’s dementia is characterized by “Quantum Decoherence” resulting from mitochondrial and microtubular deterioration and responding to near-infrared transcranial photobiomodulation to support mitochondrial and microtubule repair, regrowth and neuronal synaptic renormalization.

Digital Clock Drawing as an Alzheimer’s Disease Susceptibility Biomarker: Associations with Genetic Risk Score and APOE in Older Adults

BackgroundAlzheimer’s disease (AD) is the leading cause of dementia in older adults, but most people are not diagnosed until significant neuronal loss has likely occurred along with a decline in cognition. Non-invasive and cost-effective digital biomarkers for AD have the potential to improve early detection.ObjectiveWe examined the validity of DCTclock™ (a digitized clock drawing task) as an AD susceptibility biomarker.DesignWe used two primary independent variables, Apolipoprotein E (APOE) ε4 allele carrier status and polygenic risk score (PRS). We examined APOE and PRS associations with DCTclock™ composite scores as dependent measures.SettingWe used existing data from the Framingham Heart Study (FHS), a community-based study with the largest dataset of digital clock drawing data to date.ParticipantsThe sample consisted of 2,398 older adults ages 60–94 with DCTclock™ data (mean age of 72.3, 55% female and 92% White).MeasurementsPRS was calculated using 38 variants identified in a recent large genome-wide association study (GWAS) and meta-analysis of late-onset AD (LOAD).ResultsResults showed that DCTclock™ performance decreased with advancing age, lower education, and the presence of one or more copies of APOE ε4. Lower DCTclock™ Total Score as well as lower composite scores for Information Processing Speed (both command & copy conditions) and Drawing Efficiency (command condition) were significantly associated with higher PRS levels and more copies of APOE ε4. APOE and PRS associations displayed similar effect sizes in both men and women.ConclusionsOur results indicate that higher AD genetic risk is associated with poorer DCTclock™ performance in older adults without dementia. This is the first study to demonstrate significant differences in clock drawing performance on the basis of APOE status or PRS.

Diagnostic Application of Automated Brain MRI Volumetry in Comparing Alzheimer Disease, Behavioral Variant Frontotemporal Dementia and Traumatic Brain Injury (P12-6.005)

<h3>Objective:</h3> To evaluate if application of automated brain MRI volumetry can improve delineation of neurocognitive disorders. <h3>Background:</h3> Assessment of regional structural differences with brain MRI volumetric quantification can improve diagnostic separation of multiple neurodegenerative and non-neurodegenerative disorders. <h3>Design/Methods:</h3> We utilized 136 participants with traumatic brain injury (TBI; n=40), early (EOAD; n=45) and late onset Alzheimer disease (LOAD; n=31) and behavioral variant frontotemporal dementia (bvFTD; n=20). Participants had brain MRI including 3D T1 and analyzed with an FDA cleared software program, Neuroreader. At the time of analysis, Mini-Mental State Exam (MMSE) scores were available on majority of participants (n=125). One-way ANOVA compared mean age, MMSE, and brain volumes across all four groups with Bonferroni correction for multiple comparisons. Volumes were adjusted for total intracranial volume (TIV). Discriminant analysis was done with leave-one-out cross validation on measured brain volumes to determine diagnostic delineation. Automated linear regression identified predictive features. <h3>Results:</h3> LOAD was the oldest compared to other groups (p&lt;.001). There were no statistically significant differences in sex (p=.58) with 54.4% women. EOAD and LOAD had the lowest MMSE scores compared to TBI (p=.04 for EOAD and p=.01 for LOAD). Regional volume difference across groups showed lowest hippocampal volumes in LOAD (p=.005), low white matter volume in TBI (p=.007), lower parietal lobe volumes in EOAD (p&lt;.01), and lower frontal lobe volumes in bvFTD (p&lt;.001). Regional volume differences resulted in a correct classification of 89%, 79.4% after cross validation. Predictive features included caudate, amygdala, frontal, parietal, temporal lobar and total white matter volumes. <h3>Conclusions:</h3> Lower parietal lobe volumes in EOAD and hippocampal volumes in LOAD as well as frontal atrophy of bvFTD reflect known anatomical distribution of pathology in those conditions. White matter volume loss in TBI has been noted with that condition. Brain MRI volumetry may be beneficial in clinical practice. <b>Disclosure:</b> Dr. Meysami has nothing to disclose. Prof. Raji has received personal compensation in the range of $10,000-$49,999 for serving as a Consultant for Brainreader ApS. Prof. Raji has received personal compensation in the range of $10,000-$49,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Apollo Health . Prof. Raji has received personal compensation in the range of $10,000-$49,999 for serving as an Expert Witness for Neurevolution Medicine. Dr. Porter has nothing to disclose. David Merrill has nothing to disclose. Dr. Mendez has received personal compensation in the range of $500-$4,999 for serving on a Speakers Bureau for Medical Education Speakers’ Bureau. Dr. Mendez has received personal compensation in the range of $500-$4,999 for serving as an Editor, Associate Editor, or Editorial Advisory Board Member for UpToDate. The institution of Dr. Mendez has received research support from NIH. Dr. Mendez has received publishing royalties from a publication relating to health care.

Effect of APOE ɛ4 genotype on age at onset and comorbid pathologies in multiple system atrophy (P8-11.004)

<h3>Objective:</h3> To elucidate the effect of apolipoprotein (APOE) ɛ4 genotype on age at onset and comorbid pathologies in multiple system atrophy (MSA). <h3>Background:</h3> APOE ɛ4 increases risk of Alzheimer’s disease (AD) and lowers age of onset of late-onset AD. In synucleinopathy, APOE ɛ4 has been reported to correlate with the severity of Lewy body pathology in Lewy body disease and to lower the age of onset of Parkinson’s disease. The association of APOE E4 with MSA is not well understood. <h3>Design/Methods:</h3> This study included 145 pathologically confirmed MSA patients (female 43%) in the Mayo Clinic Brain Bank. We reviewed the medical records to identify the age at onset at which motor or autonomic symptoms presented. MSA patients were divided into two groups: APOE ɛ4 carriers and non-carriers. We examined comorbid pathologies, including AD pathology, Lewy-related pathology, TDP-43 proteinopathy, argyrophilic grains, cerebral amyloid angiopathy (CAA), and aging-related tau astrogliopathy (ARTAG). We defined the presence of AD pathology based on the Braak neurofibrillary tangle stage and the Thal amyloid phase if both were equal or greater than 3. We compared the frequency of each pathology between APOE ɛ4 carriers and non-carriers. <h3>Results:</h3> Among 145 MSA patients, 26% (37/145) had APOE ɛ4 (female 41%) and 74% (108/145) had non-ɛ4 (female 44%). Age at onset was significantly younger in MSA with APOE ɛ4 than non-ɛ4 (P = 0.028, 56 ± 6 vs. 60 ± 10 years old). The frequency of CAA was significantly greater in MSA with APOE ɛ4 than non-ɛ4 (P = 0.0032, 43% vs. 18%); however, there was no significant difference in the frequency of AD pathology, Lewy-related pathology, TDP-43 proteinopathy, argyrophilic grains, and ARTAG. <h3>Conclusions:</h3> Our results indicate that APOE ɛ4 is associated with CAA in MSA, as well as lower age at onset, but not AD or Lewy-related pathologies. <b>Disclosure:</b> Dr. Sekiya has nothing to disclose. Dr. Koga has nothing to disclose. Dr. Ross has nothing to disclose. Dr. Dickson has nothing to disclose.

Characterizing Early-Onset Alzheimer Disease Using Multiprobe PET/MRI: An AT(N) Framework-Based Study.

Early-onset Alzheimer disease (EOAD) is rare, highly heterogeneous, and associated with poor prognosis. This AT(N) Framework-based study aimed to compare multiprobe PET/MRI findings between EOAD and late-onset Alzheimer disease (LOAD) patients and explore potential imaging biomarkers for characterizing EOAD. Patients with AD who underwent PET/MRI in our PET center were retrospectively reviewed and grouped according to the age at disease onset: EOAD, younger than 60 years; and LOAD, 60 years or older. Clinical characteristics were recorded. All study patients had positive β-amyloid PET imaging; some patients also underwent 18 F-FDG and 18 F-florzolotau PET. Imaging of the EOAD and LOAD groups was compared using region-of-interest and voxel-based analysis. Correlation of onset age and regional SUV ratios were also evaluated. One hundred thirty-three patients were analyzed (75 EOAD and 58 LOAD patients). Sex ( P = 0.515) and education ( P = 0.412) did not significantly differ between groups. Mini-Mental State Examination score was significantly lower in the EOAD group (14.32 ± 6.74 vs 18.67 ± 7.20, P = 0.004). β-Amyloid deposition did not significantly differ between groups. Glucose metabolism in the frontal, parietal, precuneus, temporal, occipital lobe, and supramarginal and angular gyri was significantly lower in the EOAD group (n = 49) than in the LOAD group (n = 44). In voxel-based morphometry analysis, right posterior cingulate/precuneus atrophy was more obvious in the EOAD ( P < 0.001), although no voxel survived family-wise error correction. Tau deposition in the precuneus, parietal lobe, and angular, supramarginal, and right middle frontal gyri was significantly higher in the EOAD group (n = 18) than in the LOAD group (n = 13). Multiprobe PET/MRI showed that tau burden and neuronal damage are more severe in EOAD than in LOAD. Multiprobe PET/MRI may be useful to assess the pathologic characteristics of EOAD.

Association between APOE genotype and microglial cell morphology.

APOE is the largest genetic risk factor for late-onset Alzheimer disease (AD) with E4 conferring an increased risk for AD compared to E3. The ApoE protein can impact diverse pathways in the brain including neuroinflammation but the precise impact of ApoE isoforms on inflammation remains unknown. As microglia are a primary source of neuroinflammation, this study determined whether ApoE isoforms have an impact on microglial morphology and activation using immunohistochemistry and digital analyses. Analysis of ionized calcium-binding adaptor molecule 1 (Iba1) immunoreactivity indicated greater microglial activation in both the hippocampus and superior and middle temporal gyrus (SMTG) in dementia participants versus non-demented controls. Further, only an increase in activation was seen in E3-Dementia participants in the entire SMTG, whereas in the grey matter of the SMTG, only a diagnosis of dementia impacted activation. Specific microglial morphologies showed a reduction in ramified microglia in the dementia group. For rod microglia, a reduction was seen in E4-Control patients in the hippocampus whereas in the SMTG an increase was seen in E4-Dementia patients. These findings suggest an association between ApoE isoforms and microglial morphologies and highlight the importance of considering ApoE isoforms in studies of AD pathology.

A Phenome-Wide Association Study (PheWAS) of Late Onset Alzheimer Disease Genetic Risk in Children of European Ancestry at Middle Childhood: Results from the ABCD Study.

Genetic risk for Late Onset Alzheimer Disease (AD) has been associated with lower cognition and smaller hippocampal volume in healthy young adults. However, whether these and other associations are present during childhood remains unclear. Using data from 5556 genomically-confirmed European ancestry youth who completed the baseline session of the ongoing the Adolescent Brain Cognitive DevelopmentSM Study (ABCD Study®), our phenome-wide association study estimating associations between four indices of genetic risk for late-onset AD (i.e., AD polygenic risk scores (PRS), APOE rs429358 genotype, AD PRS with the APOE region removed (ADPRS-APOE), and an interaction between ADPRS-APOE and APOE genotype) and 1687 psychosocial, behavioral, and neural phenotypes revealed no significant associations after correction for multiple testing (all ps > 0.0002; all pfdr > 0.07). These data suggest that AD genetic risk may not phenotypically manifest during middle-childhood or that effects are smaller than this sample is powered to detect.

The Alzheimer's disease risk factor INPP5D restricts neuroprotective microglial responses in amyloid beta-mediated pathology.

Mutations in INPP5D, which encodes for the SH2-domain-containing inositol phosphatase SHIP-1, have recently been linked to an increased risk of developing late-onset Alzheimer's disease. While INPP5D expression is almost exclusively restricted to microglia in the brain, little is known regarding how SHIP-1 affects neurobiology or neurodegenerative disease pathogenesis. We generated and investigated 5xFAD Inpp5dfl/fl Cx3cr1Ert2Cre mice to ascertain the function of microglial SHIP-1 signaling in response to amyloid beta (Aβ)-mediated pathology. SHIP-1 deletion in microglia led to substantially enhanced recruitment of microglia to Aβ plaques, altered microglial gene expression, and marked improvements in neuronal health. Further, SHIP-1 loss enhanced microglial plaque containment and Aβ engulfment when compared to microglia from Cre-negative 5xFAD Inpp5dfl/fl littermate controls. These results define SHIP-1 as a pivotal regulator of microglial responses during Aβ-driven neurological disease and suggest that targeting SHIP-1 may offer a promising strategy to treat Alzheimer's disease. Inpp5d deficiency in microglia increases plaque-associated microglia numbers. Loss of Inpp5d induces activation and phagocytosis transcriptional pathways. Plaque encapsulation and engulfment by microglia are enhanced with Inpp5d deletion. Genetic ablation of Inpp5d protects against plaque-induced neuronal dystrophy.

Interaction between KLOTHO-VS Heterozygosity and APOE ε4 Allele Predicts Rate of Cognitive Decline in Late-Onset Alzheimer's Disease.

KLOTHO-VS heterozygosity (KL-VShet+) promotes longevity and protects against cognitive decline in aging. To determine whether KL-VShet+ mitigates Alzheimer's disease (AD) progression, we used longitudinal linear-mixed models to compare the rate of change in multiple cognitive measures in AD patients stratified by APOE ε4 carrier status. We aggregated data on 665 participants (208 KL-VShet-/ε4-, 307 KL-VShet-/ε4+, 66 KL-VShet+/ε4-, and 84 KL-VShet+/ε4+) from two prospective cohorts, the National Alzheimer's Coordinating Center and the Alzheimer's Disease Neuroimaging Initiative. All participants were initially diagnosed with mild cognitive impairment, later developed AD dementia during the study, and had at least three subsequent visits. KL-VShet+ conferred slower cognitive decline in ε4 non-carriers (+0.287 MMSE points/year, p = 0.001; -0.104 CDR-SB points/year, p = 0.026; -0.042 ADCOMS points/year, p < 0.001) but not in ε4 carriers who generally had faster rates of decline than non-carriers. Stratified analyses showed that the protective effect of KL-VShet+ was particularly prominent in male participants, those who were older than the median baseline age of 76 years, or those who had an education level of at least 16 years. For the first time, our study provides evidence that KL-VShet+ status has a protective effect on AD progression and interacts with the ε4 allele.

E674Q (Shanghai APP mutant), a novel amyloid precursor protein mutation, in familial late-onset Alzheimer's disease

Identified as the pathogenic genes of Alzheimer's disease (AD), APP, PSEN1, and PSEN2 mainly lead to early-onset AD, whose course is more aggressive, and atypical symptoms are more common than sporadic AD. Here, a novel missense mutation, APP E674Q (also named “Shanghai APP”), was detected in a Chinese index patient with typical late-onset AD (LOAD) who developed memory decline in his mid-70s. The results from neuroimaging were consistent with AD, where widespread amyloid β deposition was demonstrated in 18F-florbetapir Positron Emission Tomography (PET). APP E674Q is close to the β-secretase cleavage site and the well-studied Swedish APP mutation (KM670/671NL), which was predicted to be pathogenic in silico. Molecular dynamics simulation indicated that the E674Q mutation resulted in a rearrangement of the interaction mode between APP and BACE1 and that the E674Q mutation was more prone to cleavage by BACE1. The in vitro results suggested that the E674Q mutation was pathogenic by facilitating the BACE1-mediated processing of APP and the production of Aβ. Furthermore, we applied an adeno-associated virus (AAV)-mediated transfer of the human E674Q mutant APP gene to the hippocampi of two-month-old C57Bl/6 J mice. AAV-E674Q-injected mice exhibited impaired learning behavior and increased pathological burden in the brain, implying that the E674Q mutation had a pathogenicity that bore a comparison with the classical Swedish mutation. Collectively, we report a strong amyloidogenic effect of the E674Q substitution in AD. To our knowledge, E674Q is the only pathogenic mutation within the amyloid processing sequence causing LOAD.