INTRODUCTION:Tauopathies are a heterogeneous group of neurodegenerative disorders defined by abnormal aggregation of tau protein. Although cryogenic electron microscopy (cryo-EM) has uncovered disease-specific tau structures, translating these insights into diagnostic tools remains difficult. METHODS:We developed a heparin-free, salt-modulated real-time quaking-induced conversion (RT-QuIC) assay using K12 and K11 tau substrates, targeting aggregation-prone regions. This current method improves on previous methodology by minimising the number of required substrates by modulating reaction salt content in order to differentiate yet-undistinguished tauopathy strains. Thioflavin T fluorescence kinetics and attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) spectroscopy were used to classify tau aggregates from human brain homogenates. RESULTS:This method differentiated eight tauopathies, including Alzheimer's disease, Pick disease, progressive supranuclear palsy (PSP), corticobasal degeneration (CBD), argyrophilic grain disease (AGD), frontotemporal dementia with parkinsonism associated with chromosome 17 with N279K mutation (FTDP-17 N279K), and globular glial tauopathies types II and III. Subclassification of 4R tauopathies was achieved by modulating salt conditions and analyzing aggregation profiles. FTIR confirmed preservation of conformational differences. DISCUSSION:This salt-modulated, heparin-free RT-QuIC platform enables sensitive tauopathy classification based on strain-specific kinetics and structure. It offers a practical tool for diagnostic development, mechanistic studies, and therapeutic screening.

Alzheimer's disease (AD) presents with substantial clinical and anatomical heterogeneity, including both typical amnestic and atypical variants such as posterior cortical atrophy and logopenic primary progressive aphasia. Although neurofibrillary tangle (NFT) burden is a defining pathological feature of AD, its regional distribution varies across clinical phenotypes, suggesting that selective neuronal vulnerability may shape disease presentation. However, the cellular and molecular determinants underlying this vulnerability remain incompletely understood. Here, we profiled single-nucleus transcriptomes across multiple brain regions, including hippocampal (CA1) and neocortical (superior temporal gyrus and occipital cortex) regions, from individuals with typical and atypical AD and healthy controls. Integrative analysis identified major cell classes and resolved diverse excitatory and inhibitory neuronal subpopulations that were reproducibly observed across regions and individuals. Using quasi-binomial regression models to assess compositional changes, we quantified subtype-specific vulnerability associated with AD pathology. We identified a distinct excitatory neuronal subpopulation characterized by NRGN and BEX1 expression, which showed reproducible depletion across multiple regions, with the strongest evidence in amnestic AD and in neocortical regions in lvPPA. This vulnerable population showed concordance with previously reported AD-associated excitatory neuron signatures, supporting a conserved transcriptional program of susceptibility. Genes enriched in this population were associated with chemical synaptic transmission and regulation of synaptic plasticity and formed interconnected networks in protein-protein interaction analyses. These findings suggest that intrinsic properties related to synaptic function may predispose specific neuronal populations to degeneration in AD. Together, our results define a conserved, transcriptionally distinct excitatory neuron subpopulation that is selectively vulnerable across AD phenotypes and brain regions. This work provides a framework for linking regional pathology to cell-type-specific susceptibility and highlights synaptic regulatory pathways as potential contributors to neuronal degeneration in Alzheimer's disease.

Prion protein (PrP) deposits in the form of diffuse and cored plaques occur in most gray matter areas of the brain of individuals affected by Gerstmann–Sträussler–Scheinker disease (GSS) associated with the F198S mutation in PRNP; however, the PrP deposits in the retina have not been characterized. Furthermore, a comparative analysis of PrP deposits occurring in the brain and in the retina in GSS has not been carried out. We hypothesize that the PrP aggregation and seeding properties in the brain and retina differ. The aim of this study was to analyze PrP from brains and retinas of individuals affected by GSS, all carriers of the PRNP F198S mutation from the same pedigree. Postmortem tissues from these patients were analyzed using neuropathologic and biochemical methods including Real-Time Quaking Induced Conversion assay. PrP deposits in the retina were found only in the outer plexiform layer, did not have tinctorial property of amyloid and were immunopositive using nine antibodies recognizing epitopes throughout the PrP sequence. Biochemical analysis showed that PrP_F198S in the retina is partially detergent-insoluble, is assembled in large-size aggregates, and has seeding property. In addition, the glycosylation of full-length PrP in the retina was more complex than that of control PrP. Furthermore, the homogenates of retina did not contain the 8 kDa PrP internal fragments (PrPIF) as brain homogenates do; however, a PrPIF was experimentally generated using proteinase K. In conclusion, we report for the first time the neuropathologic and biochemical properties of PrP in the retina of individuals carrying PRNP F198S and compare them with those in the brain of the same individuals. The fact that in GSS F198S, PrPIF is constitutive only in the brain points to the need of identifying whether there is a difference in proteolytic mechanisms between retina and brain.

Neurodegenerative diseases are characterised by the assembly of a limited number of disease-specific proteins into amyloid filaments, which form intracellular inclusions or extracellular deposits in the central nervous system (CNS)1,2. We previously found that amyloid filaments of TATA-binding protein-associated factor 15 (TAF15) characterise a subtype of frontotemporal lobar degeneration with FET protein-immunoreactive inclusions (FTLD-FET)3, termed atypical FTLD with ubiquitin-positive inclusions (aFTLD-U)4, which causes early-onset, rapidly progressive behavioural variant frontotemporal dementia (FTD). However, it was not clear if TAF15 proteinopathy was more widespread in neurodegenerative diseases. Two additional FTLD-FET subtypes have been proposed, neuronal intermediate filament inclusion body disease (NIFID) and basophilic inclusion body disease (BIBD)5,6, which have more heterogenous clinical presentations including FTD, motor neuron diseases (MND) and movement disorders. Here, we used electron cryo-microscopy (cryo-EM) to determine a total of 32 amyloid filament structures from the brains of 17 individuals encompassing all three proposed subtypes of FTLD-FET and their diverse clinical presentations. All cases were characterised by TAF15 filaments, in the absence of filaments of the other FET proteins, fused in sarcoma (FUS) and Ewing's sarcoma (EWS). All three aFTLD-U cases had the previously-reported TAF15 fold3. Unexpectedly, we found four distinct TAF15 folds among 11 NIFID cases. Eight of these cases shared a common fold, while the remaining three were each distinct. Furthermore, we found distinct TAF15 folds for each of the three BIBD cases. Neuropathological reassessment of the neocortical TAF15 inclusion pathology of these cases distinguished the NIFID cases with the common fold from the others. Thus, TAF15 filament structures form the basis of a new, expanded classification of FTLD-FET subtypes. Moreover, we discovered a TAF15 Y38C variant in the filament fold of one of the individuals with BIBD. The structure is unable to incorporate wild-type TAF15, despite the individual being heterozygous, suggesting that this variant drives TAF15 filament assembly. This study provides structural and genetic evidence that TAF15 amyloid filaments underlie the diverse group of neurodegenerative diseases currently termed FTLD-FET, which we therefore rename FTLD-TAF15.

The assembly of TAR DNA-binding protein 43 (TDP-43) into amyloid filaments within neurons is a hallmark of multiple neurodegenerative diseases, including motor neuron diseases (MND), frontotemporal dementias (FTD) and limbic-predominant age-related TDP-43 encephalopathy (LATE). These diseases result from the deterioration and loss of neurons, with synaptic dysfunction and neuronal hyperexcitability being prominent early events. Pathogenic mutations in the TDP-43 gene, TARDBP, that promote filament formation have established a causal role for TDP-43 assembly in neurodegenerative diseases. However, the molecular mechanisms underlying filament accumulation and their contribution to neurodegeneration are poorly understood. TDP-43 filaments can propagate between neurons in a prion-like manner, which may underlie the progressive spread and accumulation of TDP-43 pathology in disease. Here, we studied early stages of TDP-43 filament accumulation following internalisation of patient-derived TDP-43 filaments by mouse and human cortical neurons. Using proximity labelling, we identified molecular environments and putative interactions of TDP-43 filaments. We found that TDP-43 filaments accumulated at synapses, particularly in proximity to the presynaptic active zone, which we confirmed in FTD patient brain sections. Electron cryo-tomography (cryo-ET) directly visualised abundant TDP-43 filaments spanning the presynaptic cytoplasm in situ, which contacted synaptic vesicles and the plasma membrane. Functional measurements revealed that the accumulation of TDP-43 filaments led to presynaptic dysfunction and subsequent neuronal hyperexcitability. These findings suggest that synapses are a major early site of TDP-43 filament accumulation, relevant to their propagation, and directly link TDP-43 filament gain of function to synaptic dysfunction.

Dominantly inherited missense and gene dosage mutations in SNCA , the α-synuclein gene, cause familial forms of Parkinson’s disease and dementia. Here we report the structures of α-synuclein filaments from the brains of such individuals. Pathogenic mutations A53T and G51D in SNCA give rise to singlets and doublets of the Lewy fold with a left-handed helical twist in the absence of a peptide-like density for island A. By contrast, filaments from the non-pathogenic variant H50Q consist of singlets of the right-handed Lewy fold with a density for island A, like filaments of wild-type α-synuclein. The structures of filaments from homozygous mice transgenic for human mutant A53T α-synuclein (line M83) are unlike those from human brains. They are more similar to the multiple system atrophy folds than to the Lewy fold of Parkinson’s disease, Parkinson’s disease dementia and dementia with Lewy bodies

Atypical frontotemporal lobar degeneration with ubiquitin-positive inclusions (aFTLD-U) is neuropathologically characterized by aggregation of the FET family of proteins and clinically manifests as sporadic young-onset frontotemporal dementia. Here we describe a major risk locus on chr15q14 identified through a genome-wide association study in 59 pathologically confirmed aFTLD-U cases and 3,153 controls (lead single nucleotide polymorphism rs549846383, P = 5.85 × 10-21, odds ratio 26.7). When combined with data from 28 additional aFTLD-U cases, 3,712 controls and 3,215 individuals with other neurodegenerative diseases and by leveraging in-house and public long-read genome sequencing data from 1,715 individuals, we identified a tandem repeat expansion on the associated haplotypes in an intron of GOLGA8A. We found variation in repeat length, motif length, and motif sequence, with long CT-dimer expansions strongly associated with aFTLD-U. Although the functional consequence of this repeat remains unknown, its presence in nearly 60% of aFTLD-U cases points to a fundamental role in disease pathogenesis.

INTRODUCTION:The genetic basis of sporadic early-onset Alzheimer's disease (EOAD) remains largely unknown, prompting evaluation of late-onset Alzheimer's disease (LOAD) polygenic risk in EOAD. METHODS:A LOAD polygenic score (PGS) was calculated in the Longitudinal Early-onset Alzheimer's Disease Study (LEADS) and Alzheimer's Disease Neuroimaging Initiative (ADNI) study and tested for associations with AD risk, cognitive performance, and imaging and fluid biomarkers. RESULTS:Though PGS was elevated in LOAD and EOAD, it was not a significant predictor of EOAD adjusting for APOE ε4 carrier status and was not associated with age of EOAD onset (p = 0.106) or with cognitive performance (p = 0.417). In LEADS, greater LOAD PGS was associated with differences in neuroimaging and fluid biomarkers, including elevated synaptosomal-associated protein 25 (SNAP-25) (p = 2.3 × 10-5). DISCUSSION:While LOAD polygenic risk contributed minimally to EOAD onset and cognitive dysfunction, PGS association with fluid biomarkers in LEADS suggests a role for LOAD polygenic risk in EOAD pathophysiology. HIGHLIGHTS:LOAD PGSs were elevated in both LOAD and EOAD compared to controls; however, LOAD PGS did not significantly predict EOAD risk, age at onset, or cognitive performance independent of APOE ε4 in the LEADS. Higher LOAD PGS was associated with lower amyloid PET Centiloids (less brain amyloid deposition) as well as lower CSF biomarker Aβ42 in LEADS (proxy marker suggesting higher brain amyloid deposition) in LEADS; these contradictory findings support the need for larger studies to further investigate whether LOAD PGS is associated with increased amyloid deposition in EOAD. Higher LOAD PGS was also associated with higher levels of CSF synaptosomal-associated protein 25 (SNAP-25), a key component of the SNARE complex, suggesting that LOAD genetic factors may contribute to dysregulation of synaptic transmission and/or pathological protein aggregation in EOAD.

Protein deposits are common hallmarks of several neurodegenerative diseases, including Alzheimer’s disease (AD), and ligands that selectively detect specific protein aggregates are crucial. Herein, we investigated the molecular requirements of a thiophene-based ligand, denoted HS-276, for selective detection of Aβ deposits in human brain tissue sections with AD pathology. The staining of Aβ deposits was altered when replacing the terminal thiophene moiety with other heterocyclic moieties. In addition, when changing the central thiophene moiety of the ligand to a phenylene, a quinoxaline, or a benzothiadiazole moiety, the staining of Aβ aggregates was completely abolished, verifying that specific molecular interactions between these ligands and the aggregates were required. The experimental observations were also verified by theoretical calculations of the ligands’ binding mode towards Aβ filaments. Our findings provide chemical insights for developing ligands that selectively target Aβ deposits and highlight the importance of certain chemical requirements for achieving a selective ligand, such as HS-276, for detecting Aβ deposits in sporadic AD. We foresee that these findings might aid in creating novel agents for clinical imaging of Aβ aggregates in AD.

Non-coding RNA species, such as microRNA (miRNA), regulate multiple biological and pathological processes by binding to target mRNAs and facilitating alteration of translation levels via complexes such as RNA-induced silencing complex (RISC). Disrupting this process could contribute to AD pathogenesis by fostering aggregation of hyperphosphorylated microtubule-associated protein tau and amyloid-β (Aβ) peptides, and neuroinflammation. Understanding how these pathological changes are regulated remains our research focus. We report that miR298 plays a vital role in maintaining APP and tau homeostasis and that miR298 imbalances may impact AD progression. Levels of miR298 from non-cognitively impaired (NCI) and AD subject brain tissue samples from different recognized sources were measured by qRT-PCR and assessed for associations with AD risk and potential covariates such as age and APOE genotype. Other biomarkers were assessed in cortical samples from the same subjects, as we previously described. Further, APP, tau, and cytokines were profiled in miR298 mimic- or its antagomiR-expressing human neuronal and astrocyte cultures. Levels of miR298 varied in postmortem temporal lobe between AD patients and age-matched NCI controls. Higher brain miR298 levels were associated with a reduced risk of AD. Subject age and APOE genotype altered this association; specifically, greater age and dose of the APOEε4 allele were associated with an increased risk of AD. However, APOEε4 dose-associated risk reduced as age increased. We identified putative binding sites for miR298 on APP, BACE1, MAPT, IL1α, and IL6 mRNAs to form RISC. We showed that treatment by miR298 reduced tau, APP, and BACE1 proteins and mRNA levels in cell cultures. These studies suggest that miR298 regulates a coordinated network of AD-related proteins APP, BACE1, and tau. Hence, such network regulation may represent a rational therapeutic target for reducing AD risk and disease modification. In addition to late-onset cases, we will profile miR298 in brain tissue samples from early-onset AD cases. Future work involves testing miR298 in AD animal models, such as in human tau-overexpressing transgenic mice. We sincerely thank grant support from NIA/NIH.

One of the neuropathologic phenotypes of Alzheimer disease (AD), associated with missense and deletion mutations in PSEN1, is the presence of cotton wool plaques (CWPs). CWPs are round amyloid β (Aβ) immunopositive structures, lacking an amyloid core; they are well recognizable in hematoxilin -eosin stained preparations and are not fluorescent using Thioflavin S (ThS), thus being morphologically different from Aβ cored plaques and Aβ diffuse deposits. Amino-terminally truncated and post-translationally modified Aβ peptide species are the main component of CWPs. Tau immunopositive neurites may be seen in CWPs and neurofibrillary tangles may be numerous amidst CWPs We used cryo-electron microscopy to study the structure of Aβ filaments extracted from the brains of two individuals affected by dominantly inherited AD caused by the PSEN1 V261I and A431E mutations, respectively. CWPs consist predominantly of two novel arrangements of type I Aβ filaments, and we have designated them as type Ic and type Id Aβ filaments. The latter filaments exhibit unique protofilament packing arrangements. While the type Ic Aβ filaments share a largely similar S-shaped monomeric configuration with type I Aβ filaments, type Id Aβ filaments display an antiparallel and asymmetric packing, in contrast to the twofold parallel arrangement characteristic of type Ib and Ic Aβ filaments. The formation of type Ic and type Id Aβ filaments in CWPs may be linked to a distinct array of Aβ peptide species present in CWPs, differing from those found in core plaques in sporadic AD. This work provides novel insights into the role that different types of Aβ filaments may play in the composition of plaque morphology. Aggregation of Aβ as type Ic and type Id Aβ filaments may be the basis for the phenotype of CWPs. The characterization of Aβ filaments from CWPs, is important for the understanding of the role that the structure and assembly of amyloid peptides may play in the morphological diversity of Aβdeposits as well as for developing new diagnostic and therapeutic strategies for AD. (Supported by NIH P30-AG010133, RF1-NS110437and RF1-AG071177)

The most common neurodegenerative disorders include Alzheimer's disease (AD), Lewy body and related dementias (ADRDs). Triggers of pathobiochemical changes in ADRDs remains unknown and appear numerous. Short non-coding RNAs, microRNA (miRNA), play a vital role in regulating biological and pathological processes leading to neurodegenerative diseases. Amyloid plaques, major hallmarks of AD, comprise abnormal aggregation of extracellular amyloid-β peptides (Aβ) derived from Aβ precursor protein (APP). Neurofibrillary tangles consist of filamentous hyper-phosphorylated tau proteins. Alpha-synuclein (SNCA) plays a critical role in the pathogenesis of Parkinson's and other synucleinopathies. Repressor Element 1-Silencing Transcription (REST) factor is altered in ADRDs. We studied the role of miR-153-3p in AD risk and in regulating levels of critical proteins. miR-153-3p reduced APP, SNCA and We measured miR153 levels in non-cognitively impaired (NCI) and AD subject brain tissue samples from different recognized sources by qRT-PCR as described (Wang et al). We utilized autopsy brain tissues and ADNI participants' genotyping and performed association studies of miR-153-3p and its single nucleotide polymorphisms (SNPs) with AD risk, and nine endophenotypes. We used iPSC-derived neuronal cells, human cell lines and miRNA transfections to study the mechanism of miR-153-3p Elevation of miR-153-3p is associated with a reduced probability of AD, while elevated REST associated with a greater likelihood of AD. MiR-153 gene SNPs are associated with nine AD-related endophenotypes. MiR-153-3p reduced REST, APP and SNCA 3’-UTR activities and respective protein levels. MiR-153-3p treatment altered REST and neuronal differentiation in iPSC-derived neuronal stem cells. RNA sequencing proteomics and interactome analysis revealed the role of miR-153-3p in axonal guidance. With the increased emphasis on comorbidities of AD and other neurodegenerative diseases, we identified that miR-153-3p, as a master regulator, reduced a key group of neurodegeneration-related proteins. MiR-153-3p reduces APP, SNCA and REST expression, all pointing towards a therapeutic and biomarker potential in ADRDs. In addition to late-onset cases, we will profile miR153 in brain tissue samples from early-onset AD cases.

Frontotemporal dementia (FTD) and Alzheimer's disease (AD) are the most common forms of early-onset dementia. Unlike AD, FTD begins with behavioral changes before the development of cognitive impairment. Dominantly inherited mutations in MAPT, the microtubule-associated protein tau gene, give rise to cases of FTD and parkinsonism linked to chromosome 17. These individuals develop abundant filamentous tau inclusions in brain cells in the absence of β-amyloid deposits. Here, we used cryo-electron microscopy to determine the structures of tau filaments from the brains of human MAPT mutants V337M and R406W. Both amino acid substitutions gave rise to tau filaments with the Alzheimer fold, which consisted of paired helical filaments in all V337M and R406W cases and of straight filaments in two V337M cases. We also identified another assembly of the Alzheimer fold into triple tau filaments in a V337M case. Filaments assembled from recombinant tau (297-391) with substitution V337M had the Alzheimer fold and showed an increased rate of assembly.

VY-TAU01 is a recombinant humanized IgG4 monoclonal antibody (mAb) directed against pathological tau for the treatment of patients with mild dementia or mild cognitive impairment due to Alzheimer’s disease (AD). Both VY-TAU01 and its parental mouse IgG1 mAb Ab-01 target an epitope in the C-terminus of tau, bind pathological tau with high affinity and selectivity over wild-type tau, block paired helical filament seed-induced tau aggregates in vitro, and selectively stain tau tangles in AD and P301S mouse (C57/B6J-Tg[Thy1-MAPT*P301S]2541Godt) brain. Ab-01 robustly inhibits seeding and propagation of pathological tau in a P301S mouse seeding model. To support toxicology studies and the initiation of the first-in-human study, nonclinical studies have been conducted to characterize the pharmacokinetics (PK) and pharmacodynamics (PD) of Ab-01 in P301S mice and the PK of VY-TAU01 in cynomolgus macaques. The PK of Ab-01 in the P301S mouse after 5 weekly intravenous or intraperitoneal doses at 10 to 120 mg/kg and VY-TAU01 in cynomolgus macaques after a single intravenous high or mid dose was evaluated with validated ELISAs using their target epitope peptide. The PD of Ab-01 in the P301S mouse was also evaluated using an ELISA to quantify unbound p-tau levels. Ab-01 and VY-TAU01 PK profiles in serum and cerebrospinal fluid (CSF) were characterized by a distribution phase followed by a typical elimination phase without evidence of substantial target-mediated disposition in the respective compartments. Serum and CSF concentrations increased with increasing dose levels in an approximately dose proportional manner, and their half-lives were approximately 9 to 13 days. CSF concentrations were 0.1 - 0.2% of serum concentrations. PD effects of Ab-01 in the P301S mouse were robust, with up to ∼90% lowering of unbound p-tau. Additional PD as well as PK/PD modeling results will also be presented. The PK of Ab-01 in the P301S mouse and VY-TAU01 in the cynomolgus macaque, and CSF to serum ratios were typical of murine IgG1 and human IgG4 administered to these respective species. The PD of Ab-01 in the P301S mouse demonstrated robust lowering of unbound p-tau. These results support VY-TAU01’s continued development and advancement into the clinic.

Down syndrome (DS) is the most common and best-known chromosomal disorder in humans and the most frequent cause of intellectual disability of genetic origin, affecting about 6 million people worldwide. Individuals with DS may develop Alzheimer disease (AD) by age 55-60 years, and sometimes as young as 40 years due to the triplication of the amyloid β precursor protein (AβPP) gene, which is located on chromosome 21. The AD neuropathological phenotype in DS includes amyloid-β (Aβ) deposition (parenchymal and vascular) and neurofibrillary tangles comprised of tau protein. Aβ peptide species ending at 42 (Aβ 42 ) are the main component of senile plaques and diffuse deposits in AD and AD in DS, while Aβ peptides ending at position 40 (Aβ 40 ) are the predominant Aβ peptides found in both leptomeningeal and cortical vessels. Whether there is a difference in the structures of Aβ and tau filaments between AD and AD in DS, is unknown. We used cryo-electron microscopy (cryo-EM) to study the structure of Aβ and tau filaments extracted from the brains of two individuals with DS. Both individuals had been clinically diagnosed with AD, which was neuropathologically confirmed. We found two types of Aβ 42 filaments (I and II) identical to those found in sporadic and familiar AD and two novel Aβ 40 filaments (type IIIa and IIIb) that differ from those previously reported in AD. Tau filaments (paired helical filaments, PHFs, and straight filaments, SFs), were identical to those from AD and related diseases. This cryo-EM study emphasizes the similarities and differences between amyloid filaments in AD and AD in DS. The relevance of the structural differences between Aβ 40 filaments in cerebral amyloid angiopathy in AD and DS is unknown. Further research is needed to determine whether type IIIa and IIIb Aβ 40 filaments are unique to DS. Tau filaments (PHFs and SFs) were identical to those in AD, supporting the notion of a common mechanism through which amyloids trigger aggregation of tau. This knowledge is crucial for understanding AD in individuals with DS and assessing whether adults with DS could be included in AD clinical trials.

Mutations in MAPT, the tau gene, give rise to frontotemporal dementia and parkinsonism linked to chromosome 17 (FTDP-17), with abundant filamentous tau inclusions in brain cells. Mutations that encode missense variants of residue P301 are the most common and result in the formation of filamentous inclusions made of mutant four-repeat tau. Here we report the cryo-electron microscopy structures of tau filaments from five individuals belonging to three different families with mutation P301L and from one individual from a family with mutation P301T. A distinct three-lobed tau fold resembling the two-layered fold of Pick's disease was present in the individuals with P301L tau. Two different tau folds were found in the individual with mutation P301T, the less abundant of which was a variant of the three-lobed fold. The major P301T tau fold was V-shaped, with partial similarity to the four-layered tau folds of corticobasal degeneration and argyrophilic grain disease.

BACKGROUND:Amyloid-β peptide (Aβ) species of 42 or 43 amino acids in length (Aβ42/43) trigger Alzheimer´s disease (AD) and are produced in abnormal amounts by mutants of the γ-secretase subunit presenilin-1 (PS1), which represent the primary cause of familial AD (FAD). Lowering these peptides by γ-secretase modulators (GSMs) is increasingly considered a safe strategy to treat AD since these compounds do not affect the overall cleavage of γ-secretase substrates. GSMs were shown to modulate not only wild-type (WT) γ-secretase but also FAD mutants, expanding their potential use also to the familial form of the disease. Unlike most other FAD mutants, the very aggressive PS1 L166P mutant is largely resistant to GSMs. However, these data were mostly obtained from overexpression models, which mimic more the less relevant homozygous state rather than the heterozygous patient situation. METHODS:Mouse embryonic fibroblast and induced pluripotent stem cell-derived neuronal PS1 L166P knock-in (KI) cell models were treated with various GSMs and Aβ responses were assessed by immunoassays and/or gel-based analysis. RESULTS:We identified GSMs that lower Aβ42 and/or Aβ43 when PS1 L166P is heterozygous, as it is the case in affected patients, and could reduce the amount of pathogenic Aβ species towards WT levels. RO7019009 was the most potent of these compounds, reducing both pathogenic species and concomitantly increasing the short Aβ37 and Aβ38, of which the latter has been associated with delayed AD progression. Another effective compound, the structurally novel indole-type GSM RO5254601 specifically acts on the Aβ42 product line leading to a selective increase of the beneficial Aβ38. Interestingly, we further found that this class of GSMs can bind not only one, but both presenilin fragments suggesting that it targets γ-secretase at an unusual binding site. CONCLUSION:Our data show that even highly refractory presenilin FAD mutants are in principle tractable with GSMs extending the possibilities for potential clinical studies in FAD with suitable GSM molecules.

Tauopathies are a class of neurodegenerative disorders that feature tau protein aggregates in the brain. Misfolded tau has the capacity to seed the fibrillization of soluble tau, leading to the prion-like spread of aggregates. Within these filaments, tau protomers always exhibit a cross-β amyloid structure. However, distinct cross-β amyloid folds correlate with specific diseases. An understanding of how these conformations impact seeding activity remains elusive. Identifying the minimal epitopes required for transcellular propagation of tau aggregates represents a key step towards more relevant models of disease progression. Here we implement a diversity-oriented peptide macrocyclization approach towards miniature tau, or 'mini-tau', proteomimetics that can seed the aggregation of tau in engineered cells and primary neurons. Structural elucidation of one such seed-competent macrocycle reveals remarkable conformational congruence with core folds from patient-derived extracts of tau. The ability to impart β-arch form and function through peptide stapling has broad-ranging implications for the minimization and mimicry of pathological tau and other amyloid proteins that drive neurodegeneration.

Our understanding of Alzheimer's disease (AD) and related dementias (ADRD) has grown exponentially, thanks to significant investments by the National Institute on Aging (NIA). This article celebrates the 40th anniversary of the NIA's Alzheimer's Disease Research Centers, highlighting the pivotal role of neuropathology as the bedrock for neurodegeneration research. Neuropathology has championed the key principles of proteinopathy, selective vulnerability, and stereotypic spread. Furthermore, neuropathologic studies advanced our understanding of ADRD prevalence, heterogeneity, clinical-pathological correlations, and genetic underpinnings, spurring biomarker development for target engagement and disease monitoring. Disease-modifying therapies for AD were inspired and informed by neuropathology. The neuropathology community is poised to refine diagnostics, leveraging digital pathology and integrating genetics and pathomics to enhance subtyping for novel precision medicine approaches. Despite some common misconceptions and logistical challenges, neuropathology continues to be a critical component of the ADRD research infrastructure, serving as a key bridge between allied basic and clinical sciences. HIGHLIGHTS: We celebrate 40 years of NIA-funded ADRCs and their contributions through neuropathology studies that have significantly advanced our understanding and treatment of ADRD. Neuropathology uncovers principles of neurodegenerative disease: proteinopathy, selective vulnerability, and stereotypic spread, informing diagnostics and therapies. Development of AD biomarkers with reference to neuropathology enhances accuracy in diagnosis and monitoring, paving the way for targeted disease-modifying therapies. Integration of digital pathology, genetics, and novel tools in neurodegeneration research promises advanced precision medicine approaches and refined diagnostics. Misconceptions and logistical challenges to neuropathological research are addressed to improve understanding and collaboration.

Limited ancestral diversity has impaired our ability to detect risk variants more prevalent in ancestry groups of predominantly non-European ancestral background in genome-wide association studies (GWAS). We construct and analyze a multi-ancestry GWAS dataset in the Alzheimer’s Disease Genetics Consortium (ADGC) to test for novel shared and population-specific late-onset Alzheimer’s disease (LOAD) susceptibility loci and evaluate underlying genetic architecture in 37,382 non-Hispanic White (NHW), 6728 African American, 8899 Hispanic (HIS), and 3232 East Asian individuals, performing within ancestry fixed-effects meta-analysis followed by a cross-ancestry random-effects meta-analysis. We identify 13 loci with cross-population associations including known loci at/near CR1, BIN1, TREM2, CD2AP, PTK2B, CLU, SHARPIN, MS4A6A, PICALM, ABCA7, APOE, and two novel loci not previously reported at 11p12 (LRRC4C) and 12q24.13 (LHX5-AS1). We additionally identify three population-specific loci with genome-wide significance at/near PTPRK and GRB14 in HIS and KIAA0825 in NHW. Pathway analysis implicates multiple amyloid regulation pathways and the classical complement pathway. Genes at/near our novel loci have known roles in neuronal development (LRRC4C, LHX5-AS1, and PTPRK) and insulin receptor activity regulation (GRB14). Using cross-population GWAS meta-analyses, we identify novel LOAD susceptibility loci in/near LRRC4C and LHX5-AS1, both with known roles in neuronal development, as well as several novel population-unique loci. Reflecting the power of diverse ancestry in GWAS, we detect the SHARPIN locus with only 13.7