Detection of prions in matching post-mortem skin and cerebrospinal fluid samples using second-generation real-time quaking-induced conversion assay.

Real-time quaking-induced conversion assay (RT-QuIC) exploits templating activity of pathogenic prion protein for ultrasensitive detection of prions. We have utilized second generation RT-QuIC assay to analyze matching post-mortem cerebrospinal fluid and skin samples of 38 prion disease patients and of 30 deceased neurological controls. The analysis of cerebrospinal fluid samples led to 100% sensitivity and 100% specificity, but some samples had to be diluted before the analysis to alleviate the effect of present RT-QuIC inhibitors. The analysis of the corresponding skin samples provided 89.5% sensitivity and 100% specificity. The median seeding dose present in the skin was one order of magnitude higher than in the cerebrospinal fluid, despite the overall fluorescent signal of the skin samples was comparatively lower. Our data support the use of post-mortem cerebrospinal fluid for confirmation of prion disease diagnosis and encourage further studies of the potential of skin biopsy samples for intra-vitam prion diseases´ diagnostics.

Genome-wide association studies identify novel loci in rapidly progressive Alzheimer's disease.

INTRODUCTION: Recent data suggest that distinct prion-like amyloid beta and tau strains are associated with rapidly progressive Alzheimer's disease (rpAD). The role of genetic factors in rpAD is largely unknown. METHODS: Previously known AD risk loci were examined in rpAD cases. Genome-wide association studies (GWAS) were performed to identify variants that influence rpAD. RESULTS: We identified 115 pathology-confirmed rpAD cases and 193 clinical rpAD cases, 80% and 69% were of non-Hispanic European ancestry. Compared to the clinical cohort, pathology-confirmed rpAD had higher frequencies of apolipoprotein E (APOE) ε4 and rare missense variants in AD risk genes. A novel genome-wide significant locus (P < 5×10-8 ) was observed for clinical rpAD on chromosome 21 (rs2832546); 102 loci showed suggestive associations with pathology-confirmed rpAD (P < 1×10-5 ). DISCUSSION rpAD constitutes an extreme subtype of AD with distinct features. GWAS found previously known and novel loci associated with rpAD. Highlights Rapidly progressive Alzheimer's disease (rpAD) was defined with different criteria. Whole genome sequencing identified rare missense variants in rpAD. Novel variants were identified for clinical rpAD on chromosome 21.

Large-scale validation of skin prion seeding activity as a biomarker for diagnosis of prion diseases.

Definitive diagnosis of sporadic Creutzfeldt-Jakob disease (sCJD) relies on the examination of brain tissues for the pathological prion protein (PrPSc). Our previous study revealed that PrPSc-seeding activity (PrPSc-SA) is detectable in skin of sCJD patients by an ultrasensitive PrPSc seed amplification assay (PrPSc-SAA) known as real-time quaking-induced conversion (RT-QuIC). A total of 875 skin samples were collected from 2 cohorts (1 and 2) at autopsy from 2-3 body areas of 339 cases with neuropathologically confirmed prion diseases and non-sCJD controls. The skin samples were analyzed for PrPSc-SA by RT-QuIC assay. The results were compared with demographic information, clinical manifestations, cerebrospinal fluid (CSF) PrPSc-SA, other laboratory tests, subtypes of prion diseases defined by the methionine (M) or valine (V) polymorphism at residue 129 of PrP, PrPSc types (#1 or #2), and gene mutations in deceased patients. RT-QuIC assays of the cohort #1 by two independent laboratories gave 87.3% or 91.3% sensitivity and 94.7% or 100% specificity, respectively. The cohort #2 showed sensitivity of 89.4% and specificity of 95.5%. RT-QuIC of CSF available from 212 cases gave 89.7% sensitivity and 94.1% specificity. The sensitivity of skin RT-QuIC was subtype dependent, being highest in sCJDVV1-2 subtype, followed by VV2, MV1-2, MV1, MV2, MM1, MM1-2, MM2, and VV1. The skin area next to the ear gave highest sensitivity, followed by lower back and apex of the head. Although no difference in brain PrPSc-SA was detected between the cases with false negative and true positive skin RT-QuIC results, the disease duration was significantly longer with the false negatives [12.0 ± 13.3 (months, SD) vs. 6.5 ± 6.4, p < 0.001]. Our study validates skin PrPSc-SA as a biomarker for the detection of prion diseases, which is influenced by the PrPSc types, PRNP 129 polymorphisms, dermatome sampled, and disease duration.

Evolving prion-like tau conformers differentially alter postsynaptic proteins in neurons inoculated with distinct isolates of Alzheimer's disease tau.

OBJECTIVES: Although accumulation of misfolded tau species has been shown to predict cognitive decline in patients with Alzheimer's disease (AD) and other tauopathies but with the remarkable diversity of clinical manifestations, neuropathology profiles, and time courses of disease progression remaining unexplained by current genetic data. We considered the diversity of misfolded tau conformers present in individual AD cases as an underlying driver of the phenotypic variations of AD and progressive loss of synapses. METHODS: To model the mechanism of tau propagation and synaptic toxicity of distinct tau conformers, we inoculated wild-type primary mouse neurons with structurally characterized Sarkosyl-insoluble tau isolates from the frontal cortex of six AD cases and monitored the impact for fourteen days. We analyzed the accumulation rate, tau isoform ratio, and conformational characteristics of de novo-induced tau aggregates with conformationally sensitive immunoassays, and the dynamics of synapse formation, maintenance, and their loss using a panel of pre-and post-synaptic markers. RESULTS: At the same concentrations of tau, the different AD tau isolates induced accumulation of misfolded predominantly 4-repeat tau aggregates at different rates in mature neurons, and demonstrated distinct conformational characteristics corresponding to the original AD brain tau. The time-course of the formation of misfolded tau aggregates and colocalization correlated with significant loss of synapses in tau-inoculated cell cultures and the reduction of synaptic connections implicated the disruption of postsynaptic compartment as an early event. CONCLUSIONS: The data obtained with mature neurons expressing physiological levels and adult isoforms of tau protein demonstrate markedly different time courses of endogenous tau misfolding and differential patterns of post-synaptic alterations. These and previous biophysical data argue for an ensemble of various misfolded tau aggregates in individual AD brains and template propagation of their homologous conformations in neurons with different rates and primarily postsynaptic interactors. Modeling tau aggregation in mature differentiated neurons provides a platform for investigating divergent molecular mechanisms of tau strain propagation and for identifying common structural features of misfolded tau and critical interactors for new therapeutic targets and approaches in AD.

Populations of Tau Conformers Drive Prion-like Strain Effects in Alzheimer's Disease and Related Dementias.

Recent findings of diverse populations of prion-like conformers of misfolded tau protein expand the prion concept to Alzheimer's disease (AD) and monogenic frontotemporal lobar degeneration (FTLD)-MAPT P301L, and suggest that distinct strains of misfolded proteins drive the phenotypes and progression rates in many neurodegenerative diseases. Notable progress in the previous decades has generated many lines of proof arguing that yeast, fungal, and mammalian prions determine heritable as well as infectious traits. The extraordinary phenotypic diversity of human prion diseases arises from structurally distinct prion strains that target, at different progression speeds, variable brain structures and cells. Although human prion research presents beneficial lessons and methods to study the mechanism of strain diversity of protein-only pathogens, the fundamental molecular mechanism by which tau conformers are formed and replicate in diverse tauopathies is still poorly understood. In this review, we summarize up to date advances in identification of diverse tau conformers through biophysical and cellular experimental paradigms, and the impact of heterogeneity of pathological tau strains on personalized structure- and strain-specific therapeutic approaches in major tauopathies.

Distinct populations of highly potent TAU seed conformers in rapidly progressing Alzheimer's disease.

Although genetic factors play a main role in determining the risk of developing Alzheimer's disease (AD), they do not explain extensive spectrum of clinicopathological phenotypes. Deposits of aggregated TAU proteins are one of the main predictors of cognitive decline in AD. We investigated the hypothesis that variabilities in AD progression could be due to diverse structural assemblies (strains) of TAU protein. Using sensitive biophysical methods in 40 patients with AD and markedly different disease durations, we identified populations of distinct TAU particles that differed in size, structural organization, and replication rate in vitro and in cell assay. The rapidly replicating, distinctly misfolded TAU conformers found in rapidly progressive AD were composed of ~80% misfolded four-repeat (4R) TAU and ~20% of misfolded 3R TAU isoform with the same conformational signatures. These biophysical observations suggest that distinctly misfolded population of 4R TAU conformers drive the rapid decline in AD and imply that effective therapeutic strategies might need to consider not a singular species but a cloud of differently misfolded TAU conformers.

Distinct conformers of amyloid beta accumulate in the neocortex of patients with rapidly progressive Alzheimer's disease.

Amyloid beta (Aß) deposition in the neocortex is a major hallmark of Alzheimer's disease (AD), but the extent of deposition does not readily explain phenotypic diversity and rate of disease progression. The prion strain-like model of disease heterogeneity suggests the existence of different conformers of Aß. We explored this paradigm using conformation-dependent immunoassay (CDI) for Aß and conformation-sensitive luminescent conjugated oligothiophenes (LCOs) in AD cases with variable progression rates. Mapping the Aß conformations in the frontal, occipital, and temporal regions in 20 AD patients with CDI revealed extensive interindividual and anatomical diversity in the structural organization of Aß with the most significant differences in the temporal cortex of rapidly progressive AD. The fluorescence emission spectra collected in situ from Aß plaques in the same regions demonstrated considerable diversity of spectral characteristics of two LCOs-quatroformylthiophene acetic acid and heptaformylthiophene acetic acid. Heptaformylthiophene acetic acid detected a wider range of Aß deposits, and both LCOs revealed distinct spectral attributes of diffuse and cored plaques in the temporal cortex of rapidly and slowly progressive AD and less frequent and discernible differences in the frontal and occipital cortex. These and CDI findings indicate a major conformational diversity of Aß accumulating in the neocortex, with the most notable differences in temporal cortex of cases with shorter disease duration, and implicate distinct Aß conformers (strains) in the rapid progression of AD.

Variably Protease-sensitive Prionopathy in a Middle-aged Man With Rapidly Progressive Dementia.

Variably protease-sensitive prionopathy (VPSPr) is a recently described sporadic prion disease with distinctive clinical and histopathological features. We report the clinical, imaging, and neuropathological features of VPSPr in a 46-year-old right-handed man who presented with progressive cognitive decline, behavior disturbances, and a 50-pound weight loss over 6 months. The initial evaluation revealed severe cognitive impairment with no focal neurologic deficits. His cognitive, psychiatric, and behavior symptoms progressed rapidly, and he died 12 months after the initial visit. Throughout his disease course, workup for rapid progressive dementia was unremarkable except that brain MRI diffusion-weighted imaging showed persistent diffuse cortical and thalamic signal abnormalities. Sporadic Creutzfeldt-Jakob disease was highly suspected; however, two EEGs (8 months apart) demonstrated only nonspecific cerebral dysfunction. The patient's CSF 14-3-3 protein was negative at the initial visit and again 8 months later. His CSF real-time quaking-induced conversion and total tau level were normal. An autopsy of his brain was performed, and the neuropathological findings confirmed VPSPr. Our case underlines the importance of considering VPSPr in the spectrum of prion disease phenotypes when evaluating individuals with rapidly progressive dementia.

Pathologic tau conformer ensembles induce dynamic, liquid-liquid phase separation events at the nuclear envelope.

BACKGROUND: The microtubule-associated protein tau forms aggregates in different neurodegenerative diseases called tauopathies. Prior work has shown that a single P301L mutation in tau gene, MAPT, can promote alternative tau folding pathways that correlate with divergent clinical diagnoses. Using progressive chemical denaturation, some tau preparations from the brain featured complex transitions starting at low concentrations of guanidine hydrochloride (GdnHCl) denaturant, indicating an ensemble of differently folded tau species called conformers. On the other hand, brain samples with abundant, tangle-like pathology had simple GdnHCl unfolding profile resembling the profile of fibrillized recombinant tau and suggesting a unitary conformer composition. In studies here we sought to understand tau conformer progression and potential relationships with condensed liquid states, as well as associated perturbations in cell biological processes. RESULTS: As starting material, we used brain samples from P301L transgenic mice containing tau conformer ensembles that unfolded at low GdnHCl concentrations and with signatures resembling brain material from P301L subjects presenting with language or memory problems. We seeded reporter cells expressing a soluble form of 4 microtubule-binding repeat tau fused to GFP or YFP reporter moieties, resulting in redistribution of dispersed fluorescence signals into focal assemblies that could fuse together and move within processes between adjacent cells. Nuclear envelope fluorescent tau signals and small fluorescent inclusions behaved as a demixed liquid phase, indicative of liquid-liquid phase separation (LLPS); these droplets exhibited spherical morphology, fusion events and could recover from photobleaching. Moreover, juxtanuclear tau assemblies were associated with disrupted nuclear transport and reduced cell viability in a stable cell line. Staining for thioflavin S (ThS) became more prevalent as tau-derived inclusions attained cross-sectional area greater than 3 µm2, indicating (i) a bipartite composition, (ii) in vivo progression of tau conformers, and (iii) that a mass threshold applying to demixed condensates may drive liquid-solid transitions. CONCLUSIONS: Tau conformer ensembles characterized by denaturation at low GdnHCl concentration templated the production of condensed droplets in living cells. These species exhibit dynamic changes and develop in vivo, and the larger ThS-positive assemblies may represent a waystation to arrive at intracellular fibrillar tau inclusions seen in end-stage genetic tauopathies.

Structurally distinct external solvent-exposed domains drive replication of major human prions.

There is a limited understanding of structural attributes that encode the iatrogenic transmissibility and various phenotypes of prions causing the most common human prion disease, sporadic Creutzfeldt-Jakob disease (sCJD). Here we report the detailed structural differences between major sCJD MM1, MM2, and VV2 prions determined with two complementary synchrotron hydroxyl radical footprinting techniques-mass spectrometry (MS) and conformation dependent immunoassay (CDI) with a panel of Europium-labeled antibodies. Both approaches clearly demonstrate that the phenotypically distant prions differ in a major way with regard to their structural organization, and synchrotron-generated hydroxyl radicals progressively inhibit their seeding potency in a strain and structure-specific manner. Moreover, the seeding rate of sCJD prions is primarily determined by strain-specific structural organization of solvent-exposed external domains of human prion particles that control the seeding activity. Structural characteristics of human prion strains suggest that subtle changes in the organization of surface domains play a critical role as a determinant of human prion infectivity, propagation rate, and targeting of specific brain structures.

Cellular Biology of Tau Diversity and Pathogenic Conformers.

Tau accumulation is a prominent feature in a variety of neurodegenerative disorders and remarkable effort has been expended working out the biochemistry and cell biology of this cytoplasmic protein. Tau's wayward properties may derive from germline mutations in the case of frontotemporal lobar degeneration (FTLD-MAPT) but may also be prompted by less understood cues-perhaps environmental or from molecular damage as a consequence of chronological aging-in the case of idiopathic tauopathies. Tau properties are undoubtedly affected by its covalent structure and in this respect tau protein is not only subject to changes in length produced by alternative splicing and endoproteolysis, but different types of posttranslational modifications that affect different amino acid residues. Another layer of complexity concerns alternate conformations-"conformers"-of the same covalent structures; in vivo conformers can encompass soluble oligomeric species, ramified fibrillar structures evident by light and electron microscopy and other forms of the protein that have undergone liquid-liquid phase separation to make demixed liquid droplets. Biological concepts based upon conformers have been charted previously for templated replication mechanisms for prion proteins built of the PrP polypeptide; these are now providing useful explanations to feature tau pathobiology, including how this protein accumulates within cells and how it can exhibit predictable patterns of spread across different neuroanatomical regions of an affected brain. In sum, the documented, intrinsic heterogeneity of tau forms and conformers now begins to speak to a fundamental basis for diversity in clinical presentation of tauopathy sub-types. In terms of interventions, emphasis upon subclinical events may be worthwhile, noting that irrevocable cell loss and ramified protein assemblies feature at end-stage tauopathy, whereas earlier events may offer better opportunities for diverting pathogenic processes. Nonetheless, the complexity of tau sub-types, which may be present even within intermediate disease stages, likely mitigates against one-size-fits-all therapeutic strategies and may require a suite of interventions. We consider the extent to which animal models of tauopathy can be reasonably enrolled in the campaign to produce such interventions and to slow the otherwise inexorable march of disease progression.

Correction to: Rapid and ultra-sensitive quantitation of disease-associated α-synuclein seeds in brain and cerebrospinal fluid by αSyn RT-QuIC.

An amendment to this paper has been published and can be accessed via the original article.

Ring trial of 2nd generation RT-QuIC diagnostic tests for sporadic CJD.

OBJECTIVE: Real-time quaking-induced conversion (RT-QuIC) assays detect prion-seeding activity in a variety of human biospecimens, including cerebrospinal fluid and olfactory mucosa swabs. The assay has shown high diagnostic accuracy in patients with prion disorders. Recently, advances in these tests have led to markedly improved diagnostic sensitivity and reduced assay times. Accordingly, an algorithm has been proposed that entails the use of RT-QuIC analysis of both sample types to diagnose sporadic Creutzfeldt-Jakob disease with nearly 100% accuracy. Here we present a multi-center evaluation (ring trial) of the reproducibility of these improved "second generation" RT-QuIC assays as applied to these diagnostic specimens. METHODS: Cerebrospinal fluid samples were analyzed from subjects with sporadic Creutzfeldt-Jakob (n = 55) or other neurological diseases (n = 45) at multiple clinical centers. Olfactory mucosa brushings collected by multiple otolaryngologists were obtained from nine sporadic Creutzfeldt-Jakob disease cases and 19 controls. These sample sets were initially tested blindly by RT-QuIC by a coordinating laboratory, recoded, and then sent to five additional testing laboratories for blinded ring trial testing. RESULTS: Unblinding of the results by a third party indicated 98-100% concordance between the results obtained by the testing of these cerebrospinal fluid and nasal brushings at the six laboratories. INTERPRETATION: This second-generation RT-QuIC assay is highly transferrable, reproducible, and therefore robust for the diagnosis of sporadic Creutzfeldt-Jakob disease in clinical practice.

Risk of Transmissibility From Neurodegenerative Disease-Associated Proteins: Experimental Knowns and Unknowns.

Recent studies in animal models demonstrate that certain misfolded proteins associated with neurodegenerative diseases can support templated misfolding of cognate native proteins, to propagate across neural systems, and to therefore have some of the properties of classical prion diseases like Creutzfeldt-Jakob disease. The National Institute of Aging convened a meeting to discuss the implications of these observations for research priorities. A summary of the discussion is presented here, with a focus on limitations of current knowledge, highlighting areas that appear to require further investigation in order to guide scientific practice while minimizing potential exposure or risk in the laboratory setting. The committee concluded that, based on all currently available data, although neurodegenerative disease-associated aggregates of several different non-prion proteins can be propagated from humans to experimental animals, there is currently insufficient evidence to suggest more than a negligible risk, if any, of a direct infectious etiology for the human neurodegenerative disorders defined in part by these proteins. Given the importance of this question, the potential for noninvasive human transmission of proteopathic disorders is deserving of further investigation.

Phosphorylated tau interactome in the human Alzheimer's disease brain.

Accumulation of phosphorylated tau is a key pathological feature of Alzheimer's disease. Phosphorylated tau accumulation causes synaptic impairment, neuronal dysfunction and formation of neurofibrillary tangles. The pathological actions of phosphorylated tau are mediated by surrounding neuronal proteins; however, a comprehensive understanding of the proteins that phosphorylated tau interacts with in Alzheimer's disease is surprisingly limited. Therefore, the aim of this study was to determine the phosphorylated tau interactome. To this end, we used two complementary proteomics approaches: (i) quantitative proteomics was performed on neurofibrillary tangles microdissected from patients with advanced Alzheimer's disease; and (ii) affinity purification-mass spectrometry was used to identify which of these proteins specifically bound to phosphorylated tau. We identified 542 proteins in neurofibrillary tangles. This included the abundant detection of many proteins known to be present in neurofibrillary tangles such as tau, ubiquitin, neurofilament proteins and apolipoprotein E. Affinity purification-mass spectrometry confirmed that 75 proteins present in neurofibrillary tangles interacted with PHF1-immunoreactive phosphorylated tau. Twenty-nine of these proteins have been previously associated with phosphorylated tau, therefore validating our proteomic approach. More importantly, 34 proteins had previously been associated with total tau, but not yet linked directly to phosphorylated tau (e.g. synaptic protein VAMP2, vacuolar-ATPase subunit ATP6V0D1); therefore, we provide new evidence that they directly interact with phosphorylated tau in Alzheimer's disease. In addition, we also identified 12 novel proteins, not previously known to be physiologically or pathologically associated with tau (e.g. RNA binding protein HNRNPA1). Network analysis showed that the phosphorylated tau interactome was enriched in proteins involved in the protein ubiquitination pathway and phagosome maturation. Importantly, we were able to pinpoint specific proteins that phosphorylated tau interacts with in these pathways for the first time, therefore providing novel potential pathogenic mechanisms that can be explored in future studies. Combined, our results reveal new potential drug targets for the treatment of tauopathies and provide insight into how phosphorylated tau mediates its toxicity in Alzheimer's disease.

Evaluation of a New Criterion for Detecting Prion Disease With Diffusion Magnetic Resonance Imaging.

Importance: Early diagnosis is a requirement for future treatment of prion diseases. Magnetic resonance imaging (MRI) with diffusion-weighted images and improved real-time quaking-induced conversion (RT-QuIC) in cerebrospinal fluid (CSF) have emerged as reliable tests. Objectives: To assess the sensitivity and specificity of diffusion MRI for the diagnosis of sporadic Creutzfeldt-Jakob disease (sCJD) with a new criterion (index test) of at least 1 positive brain region among the cortex of the frontal, parietal, temporal, and occipital lobes; the caudate; the putamen; and the thalamus. Design, Setting, and Participants: This diagnostic study with a prospective and a retrospective arm was performed from January 1, 2003, to October 31, 2018. MRIs were collected from 1387 patients with suspected sCJD consecutively referred to the National Prion Disease Pathology Surveillance Center as part of a consultation service. Intervention: Magnetic resonance imaging. Four neuroradiologists blinded to the diagnosis scored the MRIs of 200 randomly selected patients. One neuroradiologist scored the MRIs of all patients. Main Outcomes and Measures: Sensitivity and specificity of the index test compared with currently used criteria and CSF diagnostic (improved RT-QuIC, 14-3-3, and tau CSF tests). Results: A total of 872 patients matched the inclusion criteria (diffusion MRI and autopsy-confirmed diagnosis), with 619 having sCJD, 102 having other prion diseases, and 151 having nonprion disease. The primary analysis included 200 patients (mean [SD] age, 63.6 [12.9] years; 100 [50.0%] male). Sensitivity of the index test of 4 neuroradiologists was 90% to 95% and superior to sensitivity of current MRI criteria (69%-76%), whereas specificity was 90% to 100% and unchanged. Interrater reliability of the 4 neuroradiologists was high (κ = 0.81), and individual intrarater reliability was excellent (κ ≥0.87). The sensitivity of the index test of 1 neuroradiologist for 770 patients was 92.1% (95% CI, 89.7%-94.1%) and the specificity was 97.4% (95% CI, 93.4%-99.3%) compared with a sensitivity of 69.8% (95% CI, 66.0%-73.4%; P < .001) and a specificity of 98.0% (95% CI, 94.3%-99.6%; P > .99) according to the current criteria. For 88 patients, index test sensitivity (94.9%; 95% CI, 87.5%-98.6%) and specificity (100%; 95% CI, 66.4%-100%) were similar to those of improved RT-QuIC (86.1% [95% CI, 76.5%-92.8%] and 100% [95% CI, 66.4%-100%], respectively). Lower specificities were found for 14-3-3 and tau CSF tests in 452 patients. Conclusions and Relevance: In this study, the diagnostic performance of diffusion MRI with the new criterion was superior to that of current standard criteria and similar to that of improved RT-QuIC. These results may have important clinical implications because MRI is noninvasive and typically prescribed at disease presentation.

A Role of Low-Density Lipoprotein Receptor-Related Protein 4 (LRP4) in Astrocytic Aß Clearance.

Amyloid-ß (Aß) deposition occurs years before cognitive symptoms appear and is considered a cause of Alzheimer's disease (AD). The imbalance of Aß production and clearance leads to Aß accumulation and Aß deposition. Increasing evidence indicates an important role of astrocytes, the most abundant cell type among glial cells in the brain, in Aß clearance. We explored the role of low-density lipoprotein receptor-related protein 4 (LRP4), a member of the LDLR family, in AD pathology. We show that Lrp4 is specifically expressed in astrocytes and its levels in astrocytes were higher than those of Ldlr and Lrp1, both of which have been implicated in Aß uptake. LRP4 was reduced in postmortem brain tissues of AD patients. Genetic deletion of the Lrp4 gene augmented Aß plaques in 5xFAD male mice, an AD mouse model, and exacerbated the deficits in neurotransmission, synchrony between the hippocampus and PFC, and cognition. Mechanistically, LRP4 promotes Aß uptake by astrocytes likely by interacting with ApoE. Together, our study demonstrates that astrocytic LRP4 plays an important role in Aß pathology and cognitive function.SIGNIFICANCE STATEMENT This study investigates how astrocytes, a type of non-nerve cells in the brain, may contribute to Alzheimer's disease (AD) development. We demonstrate that the low-density lipoprotein receptor-related protein 4 (LRP4) is reduced in the brain of AD patients. Mimicking the reduced levels in an AD mouse model exacerbates cognitive impairment and increases amyloid aggregates that are known to damage the brain. We show that LRP4 could promote the clearance of amyloid protein by astrocytes. Our results reveal a previously unappreciated role of LRP4 in AD development.

Diverse, evolving conformer populations drive distinct phenotypes in frontotemporal lobar degeneration caused by the same MAPT-P301L mutation.

Tau protein accumulation is a common denominator of major dementias, but this process is inhomogeneous, even when triggered by the same germline mutation. We considered stochastic misfolding of human tau conformers followed by templated conversion of native monomers as an underlying mechanism and derived sensitive conformational assays to test this concept. Assessments of brains from aged TgTauP301L transgenic mice revealed a prodromal state and three distinct signatures for misfolded tau. Frontotemporal lobar degeneration (FTLD)-MAPT-P301L patients with different clinical phenotypes also displayed three signatures, two resembling those found in TgTauP301L mice. As physicochemical and cell bioassays confirmed diverse tau strains in the mouse and human brain series, we conclude that evolution of diverse tau conformers is intrinsic to the pathogenesis of this uni-allelic form of tauopathy. In turn, effective therapeutic interventions in FTLD will need to address evolving repertoires of misfolded tau species rather than singular, static molecular targets.

Chronic wasting disease (CWD) prion strains evolve via adaptive diversification of conformers in hosts expressing prion protein polymorphisms.

Chronic wasting disease (CWD) is caused by an unknown spectrum of prions and has become enzootic in populations of cervid species that express cellular prion protein (PrPC) molecules varying in amino acid composition. These PrPC polymorphisms can affect prion transmission, disease progression, neuropathology, and emergence of new prion strains, but the mechanistic steps in prion evolution are not understood. Here, using conformation-dependent immunoassay, conformation stability assay, and protein-misfolding cyclic amplification, we monitored the conformational and phenotypic characteristics of CWD prions passaged through deer and transgenic mice expressing different cervid PrPC polymorphisms. We observed that transmission through hosts with distinct PrPC sequences diversifies the PrPCWD conformations and causes a shift toward oligomers with defined structural organization, replication rate, and host range. When passaged in host environments that restrict prion replication, distinct co-existing PrPCWD conformers underwent competitive selection, stabilizing a new prion strain. Nonadaptive conformers exhibited unstable replication and accumulated only to low levels. These results suggest a continuously evolving diversity of CWD conformers and imply a critical interplay between CWD prion plasticity and PrPC polymorphisms during prion strain evolution.