APOE3 Christchurch Heterozygosity and Autosomal Dominant Alzheimer's Disease.

BACKGROUND: Variants in APOE and PSEN1 (encoding apolipoprotein E and presenilin 1, respectively) alter the risk of Alzheimer's disease. We previously reported a delay of cognitive impairment in a person with autosomal dominant Alzheimer's disease caused by the PSEN1 E280A variant who also had two copies of the apolipoprotein E3 Christchurch variant (APOE3 Ch). Heterozygosity for the APOE3 Ch variant may influence the age at which the onset of cognitive impairment occurs. We assessed this hypothesis in a population in which the PSEN1 E280A variant is prevalent. METHODS: We analyzed data from 27 participants with one copy of the APOE3 Ch variant among 1077 carriers of the PSEN1 E280A variant in a kindred from Antioquia, Colombia, to estimate the age at the onset of cognitive impairment and dementia in this group as compared with persons without the APOE3 Ch variant. Two participants underwent brain imaging, and autopsy was performed in four participants. RESULTS: Among carriers of PSEN1 E280A who were heterozygous for the APOE3 Ch variant, the median age at the onset of cognitive impairment was 52 years (95% confidence interval [CI], 51 to 58), in contrast to a matched group of PSEN1 E280A carriers without the APOE3 Ch variant, among whom the median age at the onset was 47 years (95% CI, 47 to 49). In two participants with the APOE3 Ch and PSEN1 E280A variants who underwent brain imaging, 18F-fluorodeoxyglucose positron-emission tomographic (PET) imaging showed relatively preserved metabolic activity in areas typically involved in Alzheimer's disease. In one of these participants, who underwent 18F-flortaucipir PET imaging, tau findings were limited as compared with persons with PSEN1 E280A in whom cognitive impairment occurred at the typical age in this kindred. Four studies of autopsy material obtained from persons with the APOE3 Ch and PSEN1 E280A variants showed fewer vascular amyloid pathologic features than were seen in material obtained from persons who had the PSEN1 E280A variant but not the APOE3 Ch variant. CONCLUSIONS: Clinical data supported a delayed onset of cognitive impairment in persons who were heterozygous for the APOE3 Ch variant in a kindred with a high prevalence of autosomal dominant Alzheimer's disease. (Funded by Good Ventures and others.).

Cleavage site-directed antibodies reveal the prion protein in humans is shed by ADAM10 at Y226 and associates with misfolded protein deposits in neurodegenerative diseases.

Proteolytic cell surface release ('shedding') of the prion protein (PrP), a broadly expressed GPI-anchored glycoprotein, by the metalloprotease ADAM10 impacts on neurodegenerative and other diseases in animal and in vitro models. Recent studies employing the latter also suggest shed PrP (sPrP) to be a ligand in intercellular communication and critically involved in PrP-associated physiological tasks. Although expectedly an evolutionary conserved event, and while soluble forms of PrP are present in human tissues and body fluids, for the human body neither proteolytic PrP shedding and its cleavage site nor involvement of ADAM10 or the biological relevance of this process have been demonstrated thus far. In this study, cleavage site prediction and generation (plus detailed characterization) of sPrP-specific antibodies enabled us to identify PrP cleaved at tyrosin 226 as the physiological and apparently strictly ADAM10-dependent shed form in humans. Using cell lines, neural stem cells and brain organoids, we show that shedding of human PrP can be stimulated by PrP-binding ligands without targeting the protease, which may open novel therapeutic perspectives. Site-specific antibodies directed against human sPrP also detect the shed form in brains of cattle, sheep and deer, hence in all most relevant species naturally affected by fatal and transmissible prion diseases. In human and animal prion diseases, but also in patients with Alzheimer`s disease, sPrP relocalizes from a physiological diffuse tissue pattern to intimately associate with extracellular aggregated deposits of misfolded proteins characteristic for the respective pathological condition. Findings and research tools presented here will accelerate novel insight into the roles of PrP shedding (as a process) and sPrP (as a released factor) in neurodegeneration and beyond.

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

INTRODUCTION: 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. METHODS: 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. RESULTS: 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. DISCUSSION: 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.

APOE Christchurch-mimetic therapeutic antibody reduces APOE-mediated toxicity and tau phosphorylation.

INTRODUCTION: We discovered that the APOE3 Christchurch (APOE3Ch) variant may provide resistance to Alzheimer's disease (AD). This resistance may be due to reduced pathological interactions between ApoE3Ch and heparan sulfate proteoglycans (HSPGs). METHODS: We developed and characterized the binding, structure, and preclinical efficacy of novel antibodies targeting human ApoE-HSPG interactions. RESULTS: We found that one of these antibodies, called 7C11, preferentially bound ApoE4, a major risk factor for sporadic AD, and disrupts heparin-ApoE4 interactions. We also determined the crystal structure of a Fab fragment of 7C11 and used computer modeling to predict how it would bind to ApoE. When we tested 7C11 in mouse models, we found that it reduced recombinant ApoE-induced tau pathology in the retina of MAPT*P301S mice and curbed pTau S396 phosphorylation in brains of systemically treated APOE4 knock-in mice. Targeting ApoE-HSPG interactions using 7C11 antibody may be a promising approach to developing new therapies for AD.

Cerebral Small Vessel Disease in Sporadic and Familial Alzheimer Disease.

Alzheimer disease (AD) is the most common cause of dementia. Biological definitions of AD are limited to the cerebral burden of amyloid ß plaques, neurofibrillary pathology, and neurodegeneration. However, current evidence suggests that various features of small vessel disease (SVD) are part of and covertly modify both sporadic and familial AD. Neuroimaging studies suggest that white matter hyperintensities explained by vascular mechanisms occurs frequently in the AD spectrum. Recent advances have further emphasized that frontal periventricular and posterior white matter hyperintensities are associated with cerebral amyloid angiopathy in familial AD. Although whether SVD markers precede the classically recognized biomarkers of disease is debatable, post-mortem studies show that SVD pathology incorporating small cortical and subcortical infarcts, microinfarcts, microbleeds, perivascular spacing, and white matter attenuation is commonly found in sporadic as well as in mutation carriers with confirmed familial AD. Age-related cerebral vessel pathologies such as arteriolosclerosis and cerebral amyloid angiopathy modify progression or worsen risk by shifting the threshold for cognitive impairment and AD dementia. The incorporation of SVD as a biomarker is warranted in the biological definition of AD. Therapeutic interventions directly reducing the burden of brain amyloid ß have had no major impact on the disease or delaying cognitive deterioration, but lowering the risk of vascular disease seems the only rational approach to tackle both early- and late-onset AD dementia.

Targeting Runt-Related Transcription Factor 1 Prevents Pulmonary Fibrosis and Reduces Expression of Severe Acute Respiratory Syndrome Coronavirus 2 Host Mediators.

Pulmonary fibrosis (PF) can arise from unknown causes, as in idiopathic PF, or as a consequence of infections, including severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Current treatments for PF slow, but do not stop, disease progression. We report that treatment with a runt-related transcription factor 1 (RUNX1) inhibitor (Ro24-7429), previously found to be safe, although ineffective, as a Tat inhibitor in patients with HIV, robustly ameliorates lung fibrosis and inflammation in the bleomycin-induced PF mouse model. RUNX1 inhibition blunted fundamental mechanisms downstream pathologic mediators of fibrosis and inflammation, including transforming growth factor-ß1 and tumor necrosis factor-α, in cultured lung epithelial cells, fibroblasts, and vascular endothelial cells, indicating pleiotropic effects. RUNX1 inhibition also reduced the expression of angiotensin-converting enzyme 2 and FES Upstream Region (FURIN), host proteins critical for SARS-CoV-2 infection, in mice and in vitro. A subset of human lungs with SARS-CoV-2 infection overexpress RUNX1. These data suggest that RUNX1 inhibition via repurposing of Ro24-7429 may be beneficial for PF and to battle SARS-CoV-2, by reducing expression of viral mediators and by preventing respiratory complications.

Distinct tau neuropathology and cellular profiles of an APOE3 Christchurch homozygote protected against autosomal dominant Alzheimer's dementia.

We describe in vivo follow-up PET imaging and postmortem findings from an autosomal dominant Alzheimer's disease (ADAD) PSEN1 E280A carrier who was also homozygous for the APOE3 Christchurch (APOE3ch) variant and was protected against Alzheimer's symptoms for almost three decades beyond the expected age of onset. We identified a distinct anatomical pattern of tau pathology with atypical accumulation in vivo and unusual postmortem regional distribution characterized by sparing in the frontal cortex and severe pathology in the occipital cortex. The frontal cortex and the hippocampus, less affected than the occipital cortex by tau pathology, contained Related Orphan Receptor B (RORB) positive neurons, homeostatic astrocytes and higher APOE expression. The occipital cortex, the only cortical region showing cerebral amyloid angiopathy (CAA), exhibited a distinctive chronic inflammatory microglial profile and lower APOE expression. Thus, the Christchurch variant may impact the distribution of tau pathology, modulate age at onset, severity, progression, and clinical presentation of ADAD, suggesting possible therapeutic strategies.

A multifactorial model of pathology for age of onset heterogeneity in familial Alzheimer's disease.

Presenilin-1 (PSEN1) mutations cause familial Alzheimer's disease (FAD) characterized by early age of onset (AoO). Examination of a large kindred harboring the PSEN1-E280A mutation reveals a range of AoO spanning 30 years. The pathophysiological drivers and clinical impact of AoO variation in this population are unknown. We examined brains of 23 patients focusing on generation and deposition of beta-amyloid (Aß) and Tau pathology profile. In 14 patients distributed at the extremes of AoO, we performed whole-exome capture to identify genotype-phenotype correlations. We also studied kinome activity, proteasome activity, and protein polyubiquitination in brain tissue, associating it with Tau phosphorylation profiles. PSEN1-E280A patients showed a bimodal distribution for AoO. Besides AoO, there were no clinical differences between analyzed groups. Despite the effect of mutant PSEN1 on production of Aß, there were no relevant differences between groups in generation and deposition of Aß. However, differences were found in hyperphosphorylated Tau (pTau) pathology, where early onset patients showed severe pathology with diffuse aggregation pattern associated with increased activation of stress kinases. In contrast, late-onset patients showed lesser pTau pathology and a distinctive kinase activity. Furthermore, we identified new protective genetic variants affecting ubiquitin-proteasome function in early onset patients, resulting in higher ubiquitin-dependent degradation of differentially phosphorylated Tau. In PSEN1-E280A carriers, altered γ-secretase activity and resulting Aß accumulation are prerequisites for early AoO. However, Tau hyperphosphorylation pattern, and its degradation by the proteasome, drastically influences disease onset in individuals with otherwise similar Aß pathology, hinting toward a multifactorial model of disease for FAD. In sporadic AD (SAD), a wide range of heterogeneity, also influenced by Tau pathology, has been identified. Thus, Tau-induced heterogeneity is a common feature in both AD variants, suggesting that a multi-target therapeutic approach should be used to treat AD.

Deficits in developmental neurogenesis and dendritic spine maturation in mice lacking the serine protease inhibitor neuroserpin.

Neuroserpin is a serine protease inhibitor of the nervous system required for normal synaptic plasticity and regulating cognitive, emotional and social behavior in mice. The high expression level of neuroserpin detected at late stages of nervous system formation in most regions of the brain points to a function in neurodevelopment. In order to evaluate the contribution of neuroserpin to brain development, we investigated developmental neurogenesis and neuronal differentiation in the hippocampus of neuroserpin-deficient mice. Moreover, synaptic reorganization and composition of perineuronal net were studied during maturation and stabilization of hippocampal circuits. We showed that absence of neuroserpin results in early termination of neuronal precursor proliferation and premature neuronal differentiation in the first postnatal weeks. Additionally, at the end of the critical period neuroserpin-deficient mice had changed morphology of dendritic spines towards a more mature phenotype. This was accompanied by increased protein levels and reduced proteolytic cleavage of aggrecan, a perineuronal net core protein. These data suggest a role for neuroserpin in coordinating generation and maturation of the hippocampus, which is essential for establishment of an appropriate neuronal network.

Amyloid polymorphisms constitute distinct clouds of conformational variants in different etiological subtypes of Alzheimer's disease.

The molecular architecture of amyloids formed in vivo can be interrogated using luminescent conjugated oligothiophenes (LCOs), a unique class of amyloid dyes. When bound to amyloid, LCOs yield fluorescence emission spectra that reflect the 3D structure of the protein aggregates. Given that synthetic amyloid-ß peptide (Aß) has been shown to adopt distinct structural conformations with different biological activities, we asked whether Aß can assume structurally and functionally distinct conformations within the brain. To this end, we analyzed the LCO-stained cores of ß-amyloid plaques in postmortem tissue sections from frontal, temporal, and occipital neocortices in 40 cases of familial Alzheimer's disease (AD) or sporadic (idiopathic) AD (sAD). The spectral attributes of LCO-bound plaques varied markedly in the brain, but the mean spectral properties of the amyloid cores were generally similar in all three cortical regions of individual patients. Remarkably, the LCO amyloid spectra differed significantly among some of the familial and sAD subtypes, and between typical patients with sAD and those with posterior cortical atrophy AD. Neither the amount of Aß nor its protease resistance correlated with LCO spectral properties. LCO spectral amyloid phenotypes could be partially conveyed to Aß plaques induced by experimental transmission in a mouse model. These findings indicate that polymorphic Aß-amyloid deposits within the brain cluster as clouds of conformational variants in different AD cases. Heterogeneity in the molecular architecture of pathogenic Aß among individuals and in etiologically distinct subtypes of AD justifies further studies to assess putative links between Aß conformation and clinical phenotype.

Discriminative Accuracy of Plasma Phospho-tau217 for Alzheimer Disease vs Other Neurodegenerative Disorders.

Importance: There are limitations in current diagnostic testing approaches for Alzheimer disease (AD). Objective: To examine plasma tau phosphorylated at threonine 217 (P-tau217) as a diagnostic biomarker for AD. Design, Setting, and Participants: Three cross-sectional cohorts: an Arizona-based neuropathology cohort (cohort 1), including 34 participants with AD and 47 without AD (dates of enrollment, May 2007-January 2019); the Swedish BioFINDER-2 cohort (cohort 2), including cognitively unimpaired participants (n = 301) and clinically diagnosed patients with mild cognitive impairment (MCI) (n = 178), AD dementia (n = 121), and other neurodegenerative diseases (n = 99) (April 2017-September 2019); and a Colombian autosomal-dominant AD kindred (cohort 3), including 365 PSEN1 E280A mutation carriers and 257 mutation noncarriers (December 2013-February 2017). Exposures: Plasma P-tau217. Main Outcomes and Measures: Primary outcome was the discriminative accuracy of plasma P-tau217 for AD (clinical or neuropathological diagnosis). Secondary outcome was the association with tau pathology (determined using neuropathology or positron emission tomography [PET]). Results: Mean age was 83.5 (SD, 8.5) years in cohort 1, 69.1 (SD, 10.3) years in cohort 2, and 35.8 (SD, 10.7) years in cohort 3; 38% were women in cohort 1, 51% in cohort 2, and 57% in cohort 3. In cohort 1, antemortem plasma P-tau217 differentiated neuropathologically defined AD from non-AD (area under the curve [AUC], 0.89 [95% CI, 0.81-0.97]) with significantly higher accuracy than plasma P-tau181 and neurofilament light chain (NfL) (AUC range, 0.50-0.72; P < .05). The discriminative accuracy of plasma P-tau217 in cohort 2 for clinical AD dementia vs other neurodegenerative diseases (AUC, 0.96 [95% CI, 0.93-0.98]) was significantly higher than plasma P-tau181, plasma NfL, and MRI measures (AUC range, 0.50-0.81; P < .001) but not significantly different compared with cerebrospinal fluid (CSF) P-tau217, CSF P-tau181, and tau-PET (AUC range, 0.90-0.99; P > .15). In cohort 3, plasma P-tau217 levels were significantly greater among PSEN1 mutation carriers, compared with noncarriers, from approximately 25 years and older, which is 20 years prior to estimated onset of MCI among mutation carriers. Plasma P-tau217 levels correlated with tau tangles in participants with (Spearman ρ = 0.64; P < .001), but not without (Spearman ρ = 0.15; P = .33), ß-amyloid plaques in cohort 1. In cohort 2, plasma P-tau217 discriminated abnormal vs normal tau-PET scans (AUC, 0.93 [95% CI, 0.91-0.96]) with significantly higher accuracy than plasma P-tau181, plasma NfL, CSF P-tau181, CSF Aß42:Aß40 ratio, and MRI measures (AUC range, 0.67-0.90; P < .05), but its performance was not significantly different compared with CSF P-tau217 (AUC, 0.96; P = .22). Conclusions and Relevance: Among 1402 participants from 3 selected cohorts, plasma P-tau217 discriminated AD from other neurodegenerative diseases, with significantly higher accuracy than established plasma- and MRI-based biomarkers, and its performance was not significantly different from key CSF- or PET-based measures. Further research is needed to optimize the assay, validate the findings in unselected and diverse populations, and determine its potential role in clinical care.

Cerebrospinal Fluid Mitochondrial DNA in Rapid and Slow Progressive Forms of Alzheimer's Disease.

Alzheimer's type dementia (AD) exhibits clinical heterogeneity, as well as differences in disease progression, as a subset of patients with a clinical diagnosis of AD progresses more rapidly (rpAD) than the typical AD of slow progression (spAD). Previous findings indicate that low cerebrospinal fluid (CSF) content of cell-free mitochondrial DNA (cf-mtDNA) precedes clinical signs of AD. We have now investigated the relationship between cf-mtDNA and other biomarkers of AD to determine whether a particular biomarker profile underlies the different rates of AD progression. We measured the content of cf-mtDNA, beta-amyloid peptide 1-42 (Aß), total tau protein (t-tau) and phosphorylated tau (p-tau) in the CSF from a cohort of 95 subjects consisting of 49 controls with a neurologic disorder without dementia, 30 patients with a clinical diagnosis of spAD and 16 patients with rpAD. We found that 37% of controls met at least one AD biomarker criteria, while 53% and 44% of subjects with spAD and rpAD, respectively, did not fulfill the two core AD biomarker criteria: high t-tau and low Aß in CSF. In the whole cohort, patients with spAD, but not with rpAD, showed a statistically significant 44% decrease of cf-mtDNA in CSF compared to control. When the cohort included only subjects selected by Aß and t-tau biomarker criteria, the spAD group showed a larger decrease of cf-mtDNA (69%), whereas in the rpAD group cf-mtDNA levels remained unaltered. In the whole cohort, the CSF levels of cf-mtDNA correlated positively with Aß and negatively with p-tau. Moreover, the ratio between cf-mtDNA and p-tau increased the sensitivity and specificity of spAD diagnosis up to 93% and 94%, respectively, in the biomarker-selected cohort. These results show that the content of cf-mtDNA in CSF correlates with the earliest pathological markers of the disease, Aß and p-tau, but not with the marker of neuronal damage t-tau. Moreover, these findings confirm that low CSF content of cf-mtDNA is a biomarker for the early detection of AD and support the hypothesis that low cf-mtDNA, together with low Aß and high p-tau, constitute a distinctive CSF biomarker profile that differentiates spAD from other neurological disorders.

Distinct microglia profile in Creutzfeldt-Jakob disease and Alzheimer's disease is independent of disease kinetics.

Activated microglia represent a common pathological feature of neurodegenerative diseases. Sporadic Creutzfeldt-Jakob disease (sCJD) patients show more pronounced microglial activation than Alzheimer's disease (AD) patients. Whether these differences are due to differences in disease kinetics or represent disease-specific changes is unknown. We investigated microglial phenotypes in brains of rapidly progressive AD (rpAD) and sCJD patients matched for clinical presentation, including disease duration. We immunostained the frontal cortex, basal ganglia and cerebellum in 16 patients with rpAD and sCJD using antibodies against markers of microglia and recruited monocytes (ionized calcium-binding adaptor molecule 1, human leukocyte antigen DPQR, Cluster of Differentiation 68), an antibody unique to brain-resident microglia (transmembrane protein 119 (TMEM119)), in addition to antibodies against a marker of astrocytes (glial fibrillary acidic protein), amyloid-ß (Aß) and pathological prion protein. rpAD patients showed a distinct microglial phenotype with a high abundance of TMEM119-positive microglia in all investigated regions. Presence of Aß deposits seen in a sCJD patient with concomitant deposition of Aß led to increase of TMEM119-positive microglia. Our data suggest that in rpAD, activation of brain-resident microglia significantly contributes to microgliosis, whereas in sCJD the TMEM119 signature of resident microglial cells is barely detectable. This is irrespective of disease duration and may indicate disease-specific microglial reaction.

Epidermal growth factor receptor overexpression is common and not correlated to gene copy number in ependymoma.

PURPOSE: The aim of this study was to investigate the epidermal growth factor receptor (EGFR) status in ependymoma specimens, as there is a need for new prognostic and druggable targets in this disease. METHODS: Ependymomas (WHO grade II, n = 40; WHO grade III, n = 15) located spinal (n = 35), infratentorial (n = 14), and supratentorial (n = 6) of 53 patients with a median age of 40 (range, 2-79) years were analyzed for Ki-67, p53, and EGFR expression by immunohistochemistry using a tissue microarray and for EGFR gene copy number alterations/mutations. Results were correlated to clinical data. RESULTS: EGFR overexpression was found in 30/60% of ependymomas depending on the antibody used and was more pronounced in WHO grade III. High EGFR gene copy number gains were found in 6 (11%) ependymomas with half of them being amplifications. EGFR amplified ependymomas displayed an EGFR overexpression with both antibodies in two of three cases. A missense mutation in exon 20 of EGFR (S768I) was detected in one amplified case. CONCLUSIONS: EGFR is frequently overexpressed in ependymomas. Other mechanisms than amplification of the EGFR gene appear to contribute to EGFR overexpression in most cases. EGFR mutations may be present in a small subset of ependymomas.

Mutations modifying sporadic Alzheimer's disease age of onset.

The identification of mutations modifying the age of onset (AOO) in Alzheimer's disease (AD) is crucial for understanding the natural history of AD and, therefore, for early interventions. Patients with sporadic AD (sAD) from a genetic isolate in the extremes of the AOO distribution were whole-exome genotyped. Single- and multi-locus linear mixed-effects models were used to identify functional variants modifying AOO. A posteriori enrichment and bioinformatic analyses were applied to evaluate the non-random clustering of the associate variants to physiopathological pathways involved in AD. We identified more than 20 pathogenic, genome-wide statistically significant mutations of major modifier effect on the AOO. These variants are harbored in genes implicated in neuron apoptosis, neurogenesis, inflammatory processes linked to AD, oligodendrocyte differentiation, and memory processes. This set of new genes harboring these mutations could be of importance for prediction, follow-up and eventually as therapeutical targets of AD. © 2016 Wiley Periodicals, Inc.

High molecular mass assemblies of amyloid-ß oligomers bind prion protein in patients with Alzheimer's disease.

Alzheimer's disease is the most common form of dementia and the generation of oligomeric species of amyloid-ß is causal to the initiation and progression of it. Amyloid-ß oligomers bind to the N-terminus of plasma membrane-bound cellular prion protein (PrP(C)) initiating a series of events leading to synaptic degeneration. Composition of bound amyloid-ß oligomers, binding regions within PrP(C), binding affinities and modifiers of this interaction have been almost exclusively studied in cell culture or murine models of Alzheimer's disease and our knowledge on PrP(C)-amyloid-ß interaction in patients with Alzheimer's disease is limited regarding occurrence, binding regions in PrP(C), and size of bound amyloid-ß oligomers. Here we employed a PrP(C)-amyloid-ß binding assay and size exclusion chromatography on neuropathologically characterized Alzheimer's disease and non-demented control brains (n = 15, seven female, eight male, average age: 79.2 years for Alzheimer's disease and n = 10, three female, seven male, average age: 66.4 years for controls) to investigate amyloid-ß-PrP(C) interaction. PrP(C)-amyloid-ß binding always occurred in Alzheimer's disease brains and was never detected in non-demented controls. Neither expression level of PrP(C) nor known genetic modifiers of Alzheimer's disease, such as the PrP(C) codon 129 polymorphism, influenced this interaction. In Alzheimer's disease brains, binding of amyloid-ß to PrP(C) occurred via the PrP(C) N-terminus. For synthetic amyloid-ß42, small oligomeric species showed prominent binding to PrP(C), whereas in Alzheimer's disease brains larger protein assemblies containing amyloid-ß42 bound efficiently to PrP(C). These data confirm Alzheimer's disease specificity of binding of amyloid-ß to PrP(C) via its N-terminus in a large cohort of Alzheimer's disease/control brains. Differences in sizes of separated protein fractions between synthetic and brain-derived amyloid-ß binding to PrP(C) suggest that larger assemblies of amyloid-ß or additional non-amyloid-ß components may play a role in binding of amyloid-ß42 to PrP(C) in Alzheimer's disease.

Single-nucleus RNA sequencing demonstrates an autosomal dominant Alzheimer's disease profile and possible mechanisms of disease protection.

Highly penetrant autosomal dominant Alzheimer's disease (ADAD) comprises a distinct disease entity as compared to the far more prevalent form of AD in which common variants collectively contribute to risk. The downstream pathways that distinguish these AD forms in specific cell types have not been deeply explored. We compared single-nucleus transcriptomes among a set of 27 cases divided among PSEN1-E280A ADAD carriers, sporadic AD, and controls. Autophagy genes and chaperones clearly defined the PSEN1-E280A cases compared to sporadic AD. Spatial transcriptomics validated the activation of chaperone-mediated autophagy genes in PSEN1-E280A. The PSEN1-E280A case in which much of the brain was spared neurofibrillary pathology and harbored a homozygous APOE3-Christchurch variant revealed possible explanations for protection from AD pathology including overexpression of LRP1 in astrocytes, increased expression of FKBP1B, and decreased PSEN1 expression in neurons. The unique cellular responses in ADAD and sporadic AD require consideration when designing clinical trials.

APOE3 Christchurch modulates ß-catenin/Wnt signaling in iPS cell-derived cerebral organoids from Alzheimer's cases.

A patient with the PSEN1 E280A mutation and homozygous for APOE3 Christchurch (APOE3Ch) displayed extreme resistance to Alzheimer's disease (AD) cognitive decline and tauopathy, despite having a high amyloid burden. To further investigate the differences in biological processes attributed to APOE3Ch, we generated induced pluripotent stem (iPS) cell-derived cerebral organoids from this resistant case and a non-protected control, using CRISPR/Cas9 gene editing to modulate APOE3Ch expression. In the APOE3Ch cerebral organoids, we observed a protective pattern from early tau phosphorylation. ScRNA sequencing revealed regulation of Cadherin and Wnt signaling pathways by APOE3Ch, with immunostaining indicating elevated ß-catenin protein levels. Further in vitro reporter assays unexpectedly demonstrated that ApoE3Ch functions as a Wnt3a signaling enhancer. This work uncovered a neomorphic molecular mechanism of protection of ApoE3 Christchurch, which may serve as the foundation for the future development of protected case-inspired therapeutics targeting AD and tauopathies.

Distinct patterns of APP processing in the CNS in autosomal-dominant and sporadic Alzheimer disease.

Autosomal-dominant Alzheimer disease (ADAD) is a genetic disorder caused by mutations in Amyloid Precursor Protein (APP) or Presenilin (PSEN) genes. Studies from families with ADAD have been critical to support the amyloid cascade hypothesis of Alzheimer disease (AD), the basis for the current development of amyloid-based disease-modifying therapies in sporadic AD (SAD). However, whether the pathological changes in APP processing in the CNS in ADAD are similar to those observed in SAD remains unclear. In this study, we measured ß-site APP-cleaving enzyme (BACE) protein levels and activity, APP and APP C-terminal fragments in brain samples from subjects with ADAD carrying APP or PSEN1 mutations (n = 18), patients with SAD (n = 27) and age-matched controls (n = 22). We also measured sAPPß and BACE protein levels, as well as BACE activity, in CSF from individuals carrying PSEN1 mutations (10 mutation carriers and 7 non-carrier controls), patients with SAD (n = 32) and age-matched controls (n = 11). We found that in the brain, the pattern in ADAD was characterized by an increase in APP ß-C-terminal fragment (ß-CTF) levels despite no changes in BACE protein levels or activity. In contrast, the pattern in SAD in the brain was mainly characterized by an increase in BACE levels and activity, with less APP ß-CTF accumulation than ADAD. In the CSF, no differences were found between groups in BACE activity or expression or sAPPß levels. Taken together, these data suggest that the physiopathological events underlying the chronic Aß production/clearance imbalance in SAD and ADAD are different. These differences should be considered in the design of intervention trials in AD.