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.

The role of the epigenome in age-related neurodegenerative disorders remains understudied. Here, we analyzed circulating cell-free DNA (cfDNA) from blood to detect methylation changes as a liquid biopsy for Amyotrophic Lateral Sclerosis (ALS). Our study included 20 patients with sporadic ALS, 10 patients with C9orf72-associated ALS, 10 asymptomatic carriers of the C9orf72 repeat expansion mutation, and 21 nondisease control individuals. Following targeted enzymatic methyl-sequencing (EM-seq) of approximately 4 million CpG sites, we detected numerous differentially methylated genes, including several implicated in ALS disease risk and pathogenesis. By integrating multiple epigenetic features, we delineated a distinct epigenetic signature, which achieved an average area under the curve (AUC) of 0.91 ± 0.10 upon receiver operator characteristic (ROC) analysis, which enabled detection of approximately 70% of patients with ALS with close to 100% specificity. Furthermore, we also identified a set of genes whose methylation status significantly correlated with clinical disease progression and cerebrospinal fluid (CSF) neurofilament levels. Our results reveal the potential of cfDNA-based biomarkers to accurately diagnose ALS and potentially predict disease progression.

Parkinson's disease (PD) is commonly associated with dysfunctional mitochondrial homeostasis. PINK1, a S/T kinase mutated in early-onset PD, generates phosphoserine 65 ubiquitin (pS65Ub) on damaged mitochondria facilitating their removal. Here, we show that pS65Ub translocates into the nucleus after generation at damaged mitochondria and is directly attached to substrates by resident E3 ligases. Histone H2A is a major substrate and is modified at lysine 119 (H2AK119) by the polycomb silencer, E3 ligase RING1B. At nucleosomes, pS65Ub simultaneously suppresses RING1B and potentiates H2A deubiquitinases USP16 and USP21. Epigenetic profiling and RNA sequencing reveal that pS65Ub is enriched at the promoters of poorly expressed yet dynamically regulated genes and is associated with H2AK119ub depletion. Functionally, we show that pS65Ub enrichment drives polycomb target gene expression, which accelerates the maturation of dopaminergic neurons. Importantly, post-mortem PD brains exhibit elevated nuclear pS65Ub, potentially linking nuclear pS65Ub accumulation with disease pathogenesis. Together, these data indicate that pS65Ub generated at damaged mitochondria regulates fundamental cellular processes at distant sites.

TATA-box binding protein-associated factor 15 (TAF15) is an RNA-binding protein and the primary fibrillar constituent in a subset of frontotemporal lobar degeneration (FTLD) cases. However, the molecular determinants underlying TAF15 aggregation remain unclear. Here, we show that TAF15 forms amyloid fibrils under physiological conditions and develop a cellular biosensor to monitor its propagation. Both recombinant TAF15 fibrils and pathological aggregates extracted from FTLD patient brains selectively seed TAF15 biosensor cells, demonstrating prion-like properties. The closely related protein FUS does not seed TAF15 aggregation, revealing a cross-seeding barrier, but partially incorporates into inclusions during TAF15-induced seeding, potentially explaining their pathological overlap in FTLD. Computational and peptide-based mapping identifies aggregation-prone motifs within the low-complexity domain that stabilize ex vivo fibril cores and drive TAF15 propagation. These findings establish TAF15 as an amyloid-forming, prion-like protein and define sequence determinants underlying its self-assembly, providing a mechanistic framework for FTLD-TAF15 and potential therapeutic targets.

TAR DNA-binding protein 43 (TDP-43) dysfunction is a hallmark of several neurodegenerative diseases, including frontotemporal dementia, amyotrophic lateral sclerosis, and Alzheimer's disease. Although cryptic exon inclusion is a well-characterized consequence of TDP-43 loss of function, emerging evidence reveals broader roles in RNA metabolism, notably in the regulation of alternative polyadenylation (APA) of disease-relevant transcripts. In the present study, we examined 3' untranslated region lengthening events in the brains of individuals with frontotemporal lobar degeneration with TDP-43 pathology (FTLD-TDP), focusing on the functional impact of APA dysregulation. To investigate whether TDP-43-mediated APA events occur in the postmortem brain, we measured the 3' untranslated region length of the retromer component vacuolar protein sorting 35 (VPS35) and the ETS transcription factor (ELK1) in the frontal cortex of a large cohort of FTLD-TDP patients and of healthy controls, and evaluated if these APA events are associated with FTLD-TDP clinical characteristic, markers of TDP-43 pathology [e.g., hyperphosphorylated TDP-43 and cryptic stathmin-2 RNA], or the expression of VPS35 and VPS29 proteins, the latter being essential to the retromer complex. We identified robust 3' untranslated region lengthening of VPS35 and ELK1 in FTLD-TDP, which strongly associated with markers of TDP-43 pathology, and ELK1 APA also associated with an earlier age of disease onset. Functionally, VPS35 APA was associated with reduced VPS35 and VPS29 protein expression, and lower VPS35 levels were associated with increased hyperphosphorylated TDP-43 and cryptic stathmin-2 RNA. Together, these data implicate APA dysregulation as a critical downstream consequence of TDP-43 dysfunction and suggest that TDP-43 loss may contribute to retromer impairment through APA-mediated repression of retromer subunits.

BACKGROUND:The purpose of this study was to clarify the usefulness of the 'hot cross bun' sign (HCBS) as a diagnostic imaging marker in a large cohort of patients with multiple system atrophy (MSA) and spinocerebellar ataxia (SCA). METHODS:This multicentre study included 97 patients with neuropathologically confirmed MSA, and 105 patients with genetically confirmed SCA. Neuroimaging features, including HCBS and middle cerebellar peduncle (MCP) hyperintensities, were assessed. HCBS was graded from 0 to 2: 0, none; 1, only a vertical hyperintense line; and 2, a cruciform hyperintense line. The neuropathological correlates of HCBS were evaluated in 15 patients with MSA with ≤3 months between MRI and autopsy. RESULTS:In patients with a disease duration <3 years, grade 1 or 2 HCBS was detected in 100% patients with MSA with predominant cerebellar ataxia (MSA-C) and 39.0% with SCA; whereas grade 2 HCBS was observed in 50% with MSA-C and 2.4% with SCA. Moreover, the coexistence of grade 2 HCBS and MCP hyperintensities exhibited a specificity of 100%. A neuropathological assessment revealed myelin loss, alpha-synuclein aggregates and astrocytic reaction in the MCP, transverse fibres, central zone between longitudinal fasciculi and raphe nucleus, with relative preservation in the longitudinal fasciculi and medial lemniscus in patients with MSA and grade 2 HCBS. CONCLUSIONS:Grade 1 or 2 HCBS is a highly sensitive finding in patients with MSA-C, and the observation of grade 2 HCBS within 3 years of motor symptom onset has excellent specificity for discriminating MSA-C from SCA, especially when accompanied by MCP hyperintensities.

Hypertrophic olivary degeneration (HOD) is a rare neurological condition due to hypertrophy of the inferior olivary nucleus (ION), usually due to the disruption of the Guillain-Mollaret triangle (GMT). Here, we studied a patient with primary progressive apraxia of speech (PPAOS), a neurodegenerative disease condition of impaired motor speech production, who developed HOD and Parkinsonian features later in her disease course. We examined the patient’s disease course and evaluated various clinical, pathological, and neuroimaging variables. The patient developed motor speech problems at the onset and was diagnosed with PPAOS on her first visit. Over time, she developed features of an atypical Parkinsonian disorder, but she never developed palatal or dentatorubral tremors or ocular myoclonus. MRI scans were performed yearly at each visit according to the research protocol. During her sixth visit, changes in the left ION were first observed as hyperintensity on the T2-weighted MRI consistent with HOD. Using advanced neuroimaging techniques, we identified decreased fractional anisotropy (FA) and increased mean diffusivity (MD) in white matter tracts to and from the ION, supporting the diagnosis of HOD. A pathological diagnosis of progressive supranuclear palsy was rendered at autopsy. The findings from this case study demonstrate that ION degeneration and HOD can be a late feature of PPAOS, even in the absence of associated clinical signs and symptoms.

Genetic studies have significantly advanced our understanding of tauopathies, yet the genetic aetiology of Pick's disease, a rare 3-Repeat tauopathy, remains unclear. The MAPT p.A152T variant has been identified as a risk factor for Alzheimer's disease and progressive supranuclear palsy, but its role in Pick's disease is unknown. In this study, we examined the prevalence of MAPT p.A152T in the largest series of neuropathologically confirmed Pick's disease cases to date (n = 401). Through genotyping, we identified a single mutation carrier in the Pick's disease cohort (minor allele frequency = 0.12%). We previously reported MAPT p.A152T at a 0.20% frequency in healthy controls (n = 2456), suggesting that it does not associate with 3-Repeat tauopathy risk. To further investigate the effect of the variant on MAPT transcript expression, we used bulk RNA sequencing in Alzheimer's disease and progressive supranuclear palsy A152T mutation carriers. We did not detect significant differences in 4-Repeat tau levels, though preliminary trends may indicate more nuanced effects that need to be examined with long-read sequencing in a larger series. Overall, our study suggests that MAPT p.A152T does not increase Pick's disease risk and may instead be linked to 4-Repeat or mixed tau pathologies, warranting further functional investigation.

BACKGROUND:Colony stimulating factor 1 receptor-related disorder (CSF1R-RD) is a rare, rapidly progressive neurodegenerative disease with significant clinical heterogeneity. Apolipoprotein E (ApoE) polymorphism, known to modulate microglial function and influence neurodegeneration, may act as a genetic modifier in CSF1R-RD. OBJECTIVES:The objectives were to evaluate the distribution of ApoE alleles in CSF1R-RD and assess their association with clinical and neuropathological features. METHODS:ApoE genotyping was performed in 55 individuals with CSF1R-RD. Clinical data from 25 deceased patients were analyzed based on ApoE genotype. Neuropathological evaluation was conducted on brain tissue from 14 patients, with semiquantitative scoring of white matter pathology and microglial burden. Statistical comparisons were made between carriers and noncarriers of the ApoE4 allele. RESULTS:ApoE allele frequencies in CSF1R-RD mirrored those of the general population (ε2: 7.3%, ε3: 79.1%, ε4: 13.6%). However, ApoE4 carriers exhibited significantly earlier symptom onset (median: 37.9 vs. 50.3 years, p = 0.0123) and death (median: 41.1 vs. 55.2 years, p = 0.0072). Neuropathological analysis revealed more severe white matter involvement and reduced microglial preservation in ApoE4 carriers (p = 0.034). CONCLUSIONS:Although ApoE allele distribution does not differ from the general population, the presence of the ApoE4 allele may influence the clinical trajectory and white matter pathology in CSF1R-RD. These findings suggest that ApoE polymorphism is a potential modifier of disease course and should be considered in therapeutic planning and future research. © 2026 International Parkinson and Movement Disorder Society.

AIM OF THE STUDY:This study aims to define the clinical and neuropathological features associated with the CSF1R c.2381T > C, p.Ile794Thr variant. CLINICAL RATIONALE FOR THE STUDY:Colony-stimulating factor 1 receptor (CSF1R)-related disorder (CSF1R-RD) is a rare, fatal, autosomal dominant leukoencephalopathy caused by mutations in the CSF1R gene, primarily affecting microglial function. The CSF1R c.2381T > C, p.Ile794Thr variant in exon 18 is the most frequently reported pathogenic mutation worldwide. The clinical presentation of carriers of different CSF1R mutations may vary. MATERIAL AND METHODS:We analyzed medical records and neuropathology of seven patients from four families evaluated at Mayo Clinic Florida (MCF). We compared them with 74 previously reported p.Ile794Thr cases identified through a systematic literature search (PubMed, Embase, Web of Science, and Google Scholar) up to January 2026. Data on age of onset, clinical symptoms, survival, and imaging findings were analyzed. Haplotype analysis was performed to investigate potential founder effects. RESULTS:Parkinsonism occurred significantly more frequently in the MCF cohort than in the p.Ile794Thr cases reported in the literature (85.7% vs. 40.0%; p = 0.04). Haplotype analysis indicated that the mutation likely arose independently in different lineages rather than from a common ancestor, including a confirmed de novo case. Neuropathological evaluation confirmed classic hallmarks of CSF1R-RD: white matter degeneration, axonal spheroids, and pigmented glia. CONCLUSIONS AND CLINICAL IMPLICATIONS:CSF1R-RD associated with the p.Ile794Thr variant presents a consistent clinical phenotype across cases reported globally, though the prevalence of parkinsonian features may vary by population. The high frequency of this variant across diverse haplotypes suggests a mutational hotspot in exon 18.

Identifying plasma-based biomarkers that can accurately differentiate Lewy body disease (LBD) from Alzheimer's disease (AD) remains a major challenge. Extracellular vesicles (EVs), which carry molecular cargo from their parent cells and can cross the blood-brain barrier, offer a new path forward. We developed the multiplexed Track-Etch magnetic NanoPOre (mTENPO) platform, a highly parallelized microfluidic technology for cell-specific EV isolation, and demonstrated independent enrichment of GluR2+ (neuron-derived) and GLAST+ (astrocyte-derived) EVs from the antemortem plasma of 137 autopsy-confirmed LBD, AD, mixed pathology, and control subjects. By integrating miRNA sequencing of GluR2+ and GLAST + EV cargo with plasma measurements of Aβ40, Aβ42, tau, p-Tau181, and p-Tau231, we identified a multimodal 15-feature panel that more comprehensively reflects brain pathology than conventional biomarkers. Using tenfold cross-validation to mitigate overfitting, the panel achieved an accuracy of 0.95 and an area under the curve of 0.96 for distinguishing LBD versus AD.

INTRODUCTION:Globular glial tauopathy (GGT) is a rare type of frontotemporal lobar degeneration (FTLD) characterized by deposition of 4-repeat tau. Detecting GGT with tau positron emission tomography (tau-PET) is challenging. We aim to determine the associations between tau-PET, autoradiography, and neuropathology methods in GGT. METHODS:We identified three patients with GGT who had completed antemortem tau-PET. Healthy control and two patients with Alzheimer's disease (AD) were also included for comparison. We analyzed gray matter (GM) and white matter (WM) from the superior/middle frontal gyrus (S/M-FG) and the superior/middle temporal gyrus (S/M-TG). Immunohistochemical staining was performed with antibodies against phospho-tau (AT8, PHF-1, RD4), glial fibrillary acidic protein (GFAP), and resting microglia (ionized calcium-binding adaptor molecule 1; Iba1). Immunofluorescence with a fluorescent tau-PET analog (T726) was performed. Regional tau-PET standardized uptake value ratios (SUVRs) were calculated for comparative GM and WM regions. Autoradiographic studies with 18F-AV1451 were also conducted. RESULTS:Tau-PET showed increased uptake in the WM regions of the S/M-FG and S/M-TG in GGT, and the GM regions in AD. Co-localization was observed between T726 and PHF-1, RD4, and GFAP in the WM in the patients with GGT, whereas co-localization was observed with PHF-1 predominantly in the GM in AD. Little co-localization was observed with Iba1. In vitro 18F-AV1451 autoradiography studies demonstrated minimal binding in GGT. Tau-PET differentiated underlying GGT from AD based on the relative involvement of the WM and GM. CONCLUSION:Histopathologic findings suggest that some flortaucipir uptake in GGT may represent underlying 4R tau, whereas autoradiographic analysis suggests that uptake is likely due to off-target binding. Further studies with larger cohorts are needed to determine the pathological basis of flortaucipir uptake in GGT.

TAR DNA-binding protein 43 (TDP-43) pathology frequently co-occurs with Tau neurofibrillary tangles (NFTs) and amyloid β plaques in Alzheimer's disease (AD), driving significant clinical heterogeneity. Whether TDP-43 engages autonomous molecular programs or instead amplifies Tau-driven neurodegeneration remains difficult to resolve, largely because these pathologies often co-occur. To separate these overlapping signatures, we generated regionally resolved transcriptomic profiles from cognitively normal controls (Controls), neuropathologically defined cohorts of AD, AD with limbic-predominant age-related TDP-43 encephalopathy (AD/LATE), and frontotemporal lobar degeneration (FTLD-TDP), categorizing them by their distinct TDP-43 subtypes (types α and β for AD/LATE; types A and B for FTLD-TDP). By integrating transcriptomic profiles with quantitative measures of phosphorylated TDP-43 (pTDP-43) and Tau (pTau), we separated pathology-associated signals within mixed disease contexts. We found that TDP-43 is linked to distinct transcriptomic programs in AD/LATE that are largely uncoupled from Tau burden and diverge from those observed in FTLD-TDP. These signatures showed regional specificity, with transcriptomic remodeling occurring in the amygdala across both diseases, whereas frontal cortex alterations were largely restricted to FTLD-TDP. Furthermore, by stratifying cases by TDP-43 morphological subtype, we unmasked specific biological trajectories, from immune activation to unique cellular vulnerabilities, that are not apparent in unstratified cohorts. Together, our findings provide a framework for decoupling mixed proteinopathies and demonstrate that TDP-43 shapes autonomous, subtype-dependent transcriptional landscapes in AD.

Colony stimulating factor-1 receptor-related disorder (CSF1R-RD) is a rare, autosomal dominant neurodegenerative disease caused by loss-of-function variants in the CSF1R gene, leading to microglial dysfunction and progressive white matter degeneration. Therapeutic strategies targeting microglial pathways, including activation of triggering receptor expressed on myeloid cells 2 (TREM2), have been proposed to compensate for impaired CSF1R signaling. Iluzanebart (VGL101), a monoclonal antibody TREM2 agonist, has shown promise in preclinical models. We report a longitudinal clinical course, neuroimaging findings, genetic analysis, and postmortem neuropathological examination of a 52-year-old patient with genetically confirmed CSF1R-RD (c.2507G>A, p.Ser836Asn). The patient received iluzanebart as part of a Phase 2 clinical trial. Clinical progression, MRI changes, and histopathological features at autopsy were systematically analyzed. Despite treatment, the patient experienced progressive cognitive decline, neuropsychiatric symptoms, motor impairment, and seizures, culminating in death. Serial neuroimaging demonstrated worsening white matter degeneration and brain atrophy without evidence of therapeutic response. Neuropathological examination revealed characteristic features of CSF1R-RD, including severe myelin loss, axonal spheroids, infiltration of Iba1-positive cells with macrophage-like morphology, and cortical neuronal abnormalities. There was no histological evidence of treatment-related benefit or harm. This case represents the first clinicopathological assessment of iluzanebart in CSF1R-RD and demonstrates no observable clinical, radiological, or neuropathological improvement. These findings highlight the challenges of targeting microglial dysfunction in advanced disease and suggest that TREM2 activation alone may be insufficient to alter disease progression.

Alzheimer's disease (AD) brains have variable neuropathologic and biochemical changes. Capturing epigenetic factors associated with this variability can reveal novel biological insights into AD pathophysiology. Here, we conduct an epigenome-wide association study of DNA methylation in 472 AD brains with neuropathologic and biochemical brain protein levels core to AD pathogenesis. Using a novel regional methylation (rCpGm) approach, we identify 5478 significant associations, 99.7% of which associate with tau biochemical measures, and 93 concordant associations in external datasets. Transcriptome-methylome integration reveals enrichment in oligodendrocyte genes, including known AD risk gene BIN1, myelination genes MYRF, MBP and MAG previously implicated in AD, and novel genes like LDB3. Further characterization of these perturbations in independent AD and primary tauopathy datasets highlights consistent tau-related associations. In summary, we uncover the integrative epigenomic landscape of AD, demonstrate tau-related oligodendrocyte gene perturbations as a common potential pathomechanism across tauopathies and share findings via our Multiomic Atlas.

OBJECTIVE:Pre-mortem diagnosis of parkinsonism is often challenging due to atypical presentations, overlapping syndromes, and co-pathologies. This study aimed to develop a machine learning-based algorithm predicting neuropathology in parkinsonism using chronological clinical presentations, which has previously been underexplored. METHODS:Clinical information was automatically abstracted from medical records of the Mayo Clinic Brain Bank using fine-tuned Generative Pre-trained Transformer 4 models. Patients who developed parkinsonism within 3 years of disease onset were included. Six machine learning models were trained with age, sex, family history, and 197 clinical presentations paired with onset information to predict neuropathologic diagnoses, including co-pathologies. RESULTS:Among 7,825 donors, 949 met inclusion criteria, representing 9 neuropathologic categories: Lewy body disease (LBD; n = 128), LBD with Alzheimer's disease (AD; n = 136), progressive supranuclear palsy (PSP; n = 303), PSP with AD (n = 56), PSP with LBD (n = 27), multiple system atrophy (MSA; n = 120), corticobasal degeneration (CBD; n = 99), AD (n = 43), and frontotemporal lobar degeneration (FTLD; n = 37). The CatBoost algorithm achieved an area under the receiver operating characteristic curve of 0.83 across the 9 diagnostic categories at 3 years after onset. Important predictors included age at onset, restricted eye movement, and tremor. The model remained robust to incomplete data, requiring only 23 of 200 parameters for reliable predictions with an area under the curve of 0.80. The algorithm was implemented into a user-friendly program providing diagnostic probabilities with visualizations of parameter contributions. INTERPRETATION:This neuropathology-confirmed diagnostic algorithm provides a cost-effective and interpretable screening tool for parkinsonism, bridging biomarker testing and molecular-targeted therapies. ANN NEUROL 2026;99:1405-1414.

Transactive response DNA-binding protein of 43 kDa (TDP-43) type-A is associated with frontotemporal lobar degeneration (FTLD). In primary age-related tauopathy (PART), TDP-type-α displays similar features to FTLD-TDP type-A. We compared antemortem MRI volumes of amygdala nuclei and hippocampal subfields between 16 PART-TDP-α and 12 FTLD-TDP-A autopsy-confirmed cases. Hippocampal tail and CA1 body volumes were smaller in PART-TDP-α group, which also had smaller lateral and central amygdala nuclei compared to FTLD-TDP-A group, but differences were non-significant after FDR correction. There is no evidence suggesting that TDP-43 type-A in FTLD affects hippocampal and amygdala volume loss differently than TDP-43 type-α in PART.

INTRODUCTION:Anti-amyloid beta (Aβ) monoclonal antibodies are effective at lowering amyloid in Alzheimer's disease (AD). However, whether Fc-mediated effector function is absolutely required for efficacy is not completely understood. This is important for optimizing therapeutic efficacy and mitigating side effects such as amyloid-related imaging abnormalities (ARIA). Antibodies lacking Fc effector function, like single-domain antibodies (nanobodies), offer a unique tool to dissect these mechanisms, as their small size facilitates blood-brain barrier (BBB) penetration and allows Fc-mediated functions to be studied independently. METHODS:We immunized a llama with Aβ aggregates and constructed a phage display library to screen for aggregate-specific nanobodies. Lead candidates were characterized by epitope mapping and binding affinity to amyloid plaques in both murine and human AD brain tissues. We further assessed their BBB permeability and evaluated their efficacy in clearing pre-existing plaques in amyloid precursor protein (APP)/presenilin 1 (PS1) mice. RESULTS:We identified two lead nanobodies, 3A11 and 2D10, that bind distinct epitopes and specifically bind Aβ plaques in murine and human AD brain tissues. Following systemic administration, the monovalent, unmodified (Fc-less) 2D10 nanobody, but not 3A11, successfully crossed the BBB and engaged amyloid plaques in APP/PS1 mice. However, despite robust target engagement, the Fc-less 2D10 failed to recruit microglia or reduce plaque burden. In contrast, an engineered 2D10-Fc fusion antibody potently cleared amyloid plaques, achieving a reduction in pathology comparable to aducanumab treatment. This efficacy was directly correlated with Fc-mediated microglial recruitment and activation, demonstrating that the Fc domain is essential for phagocytic plaque removal. DISCUSSION:Our findings demonstrate that Fc effector function is indispensable for microglial-mediated amyloid clearance in vivo. By clarifying this fundamental mechanism, this study provides a framework for the rational design of next-generation immunotherapies. Furthermore, 2D10-Fc represents a promising therapeutic candidate, combining the high-affinity targeting of nanobodies with the effector power necessary for robust plaque clearance.

Aggregation of the microtubule-binding protein tau is the histopathological hallmark of Alzheimer's disease (AD) and other neurodegenerative diseases, which are collectively known as tauopathies. Tau aggregation in AD patients is correlated with neuron loss, brain atrophy, and cognitive decline, and pro-aggregation tau mutations are sufficient to cause neurodegeneration and dementia in humans and tauopathy model mice. Thus, reversing tau aggregation is a potential therapeutic avenue for AD. In a previous study, we discovered CNS-11, a small molecule that disaggregates AD patient brain-extracted tau fibrils in vitro. In this study, we identify two chemical analogs of CNS-11, named CNS-11D and CNS-11G, that disaggregate AD patient brain-extracted tau fibrils and prevent seeding in a tau aggregation cell culture model. We also demonstrate that 8 weeks of treatment with either CNS-11D or CNS-11G reduces levels of insoluble tau in a mouse model of tauopathy. Our work defines the properties of two small molecules that diminish aggregation of tau in vivo and provides further support for structure-based methods to target tau for treatment of AD.