Biology subjects

Saito, T.

Publications and source records attributed to Saito, T..

At least 19 recordsLinked to original sources

bioRxiv2026

A bivalent Lassa virus mRNA vaccine protects guinea pigs from lethal infection with Lassa virus

Lassa virus (LASV), the causative agent of the life-threatening febrile disease, Lassa fever, remains a major public health concern in West Africa, where hundreds of thousands of infections occur annually. However, no licensed vaccine is currently available, highlighting the urgent need for effective preventive measures. We previously demonstrated that an mRNA-lipid nanoparticle (LNP) vaccine expressing LASV glycoprotein precursor (GPC; LASgpc-mRNA-LNP) conferred protection against lethal infection with a recombinant lymphocytic choriomeningitis virus expressing LASV GPC in mice. In this study, we extended our previous work with the aim of evaluating the efficacy of an mRNA-LNP vaccine expressing LASV nucleoprotein (NP; LASnp-mRNA-LNP) and a bivalent vaccine combining LASgpc-mRNA-LNP and LASnp-mRNA-LNP. Using a lethal CBA/N mouse model of infection with ML29, an LASV live-attenuated vaccine candidate encoding LASV GPC and NP, we found that LASgpc-mRNA-LNP and LASnp-mRNA-LNP each conferred protection in the absence of detectable neutralizing antibody responses. We identified LASV GPC- and NP-derived CD4 and CD8 T-cell epitope peptides in CBA/N mice and demonstrated that vaccination induced robust antigen-specific T-cell responses. Importantly, the bivalent vaccine provided complete protection against lethal challenge with doses at which monovalent vaccines failed to protect all mice, suggesting a potential dose-sparing benefit of the bivalent formulation. Furthermore, the bivalent vaccine fully protected guinea pigs against lethal challenge with authentic LASV. Together, these findings establish LASV NP, in addition to GPC, as a protective antigen in the mRNA vaccine platform and provide a rationale for developing bivalent mRNA-LNP vaccines to improve protection against Lassa fever.

microbiology↗

bioRxiv2026

Real-time near-infrared imaging distinguishes nasopharyngeal colonization from aspiration of Streptococcus pneumoniae and identifies aspiration as a trigger of severe disease

Streptococcus pneumoniae asymptomatically colonizes the nasopharynx but can invade the lower respiratory tract to cause life-threatening disease, particularly in older adults. However, whether the initial site of bacterial deposition following intranasal inoculation determines disease progression has not been directly examined. Here, we developed a near-infrared (NIR) fluorescence imaging approach using indocyanine green (ICG)-labeled S. pneumoniae TIGR4 to visualize early bacterial distribution in real time. ICG labeling by simple mixing, without genetic or chemical modification, neither impaired bacterial growth at 33 or 37{degrees}C, nor altered acid tolerance. Continuous video imaging during the first 10 min of infection resolved two distinct patterns: bacteria confined to the nasopharynx (colonization) and those aspirated into the lower respiratory tract (aspiration). Kaplan-Meier analysis revealed markedly higher mortality in the aspiration group in both young (hazard ratio = 7.9) and aged (hazard ratio = 8.4) mice, despite a 10-fold lower inoculum used for aged animals, with deaths beginning on day 3. Systemic profiling of blood at 24 h by RNA sequencing and plasma proteomics revealed that early aspiration in aged mice was associated with the activation of inflammatory and hematopoietic programs, enrichment of complement and coagulation cascades, and phagocytic pathways. Together, these findings establish aspiration into the lower respiratory tract as a trigger of severe pneumococcal disease and introduce real-time NIR imaging as a technique for linking early infection dynamics to systemic host responses.

microbiology↗

bioRxiv2026

Recurring daytime and nighttime modes of VOC emissions in a cool-temperate oak forest

Plants emit substantial amounts of biogenic volatile organic compounds (VOCs) that link plant physiological activity to ecological interactions and atmospheric chemistry. However, the processes regulating VOC emissions within the forest air and at the interface directly above the canopy remain poorly characterized. In this study, we investigated forest-scale VOC dynamics in a cool-temperate deciduous forest dominated by Quercus crispula using high-time- and high-mass-resolution proton-transfer-reaction time-of-flight mass spectrometry (PTR-ToF-MS) integrated with positive matrix factorization (PMF). This non-targeted, process-oriented framework was applied to forest-interior and canopy-top atmospheres during rain-free summer days in 2024 and 2025 to extract dominant modes of VOC emissions. The PMF consistently resolved two recurring modes characterized by the daytime and nighttime enhancement patterns. The daytime mode was dominated by isoprene and its oxidation products and demonstrated strong light- and temperature-dependence, whereas the nighttime mode was enriched in mono- and sesquiterpenes. The daytime contribution exhibited a pronounced morning-afternoon asymmetry, indicating non-linear physiological and canopy-scale controls. These patterns were reproducible across the years. This study demonstrates that combining PTR-ToF-MS with PMF enables robust, top-down identification of recurring modes of forest VOC variability within and above forest canopies, linking leaf-level physiology and ecosystem-scale atmospheric exchange. HighlightForest-scale VOC emissions were resolved into recurring daytime and nighttime modes using a non-targeted PTR-ToF-MS and PMF framework.

physiology↗

bioRxiv2026

Tau Isoform Expression Drives Disease Outcomes Following a Single Closed Head Injury

Tau protein has been implicated as an important mediator of traumatic brain injury (TBI). Adult human brain expresses 6 tau isoforms expressing 3 (3R) or 4 (4R) microtubule binding sites; adult mouse brain expresses only 4R tau. A role for tau isoform expression on TBI disease course is tested using wild-type C57/BL6 mice (WT) and C57/BL6 with a knocked-in human tau coding region (MAPTKI). Uninjured WT and MAPTKI mice have similar brain histology and behavior as they age. At subacute times (14 days post-injury (DPI)), injured MAPTKI mice have less white matter damage with similar neuronal loss as WT. At chronic times (90DPI), MAPTKI mice demyelinate while WT mice remyelinate. At 14DPI, tau phosphorylation differs between WT and MAPTKI mice. At 90DPI, thioflavin-S+ protein aggregates in MAPTKI corpus callosum are higher than WT. At 14 or 90DPI, WT and MAPTKI mice acquire Barnes maze, WT retention is impaired at 14DPI and MAPTKI retention impaired at 90DPI. At 14DPI, only MAPTKI mice acquire and retain active place avoidance; at 90DPI, only WT mice acquire active place avoidance. At 14DPI, only injured MAPTKI mice acquire alternating T-maze. These data suggest that WT and MAPTKI differ in both subacute and chronic disease course. At 14DPI, WT mice have greater white matter damage and behavioral impairments than MAPTKI mice. At 90DPI, impairments in WT mice partially recover, yet worsen in MAPTKI mice. This data suggests that 3R tau isoform expression alters the disease course of head injury. HighlightsPost-injury disease course of MAPTKI mice expressing 3R and 4R tau differs from wild-type mice expressing only 4R tau. At subacute times post-injury, MAPTKI mice have less white matter, yet similar gray matter, injury than wild-type mice. At chronic times post-injury, white matter damage in MAPTKI worsens. At subacute times post-injury, MAPTKI mice have fewer behavioral deficits than wild type mice. At chronic times post-injury, MAPTKI mice develop behavioral deficits not present at subacute times.

neuroscience↗

bioRxiv2026

SERPINE1-AP2A1 interplay links substrate stiffness to fibroblast senescence

Cellular senescence is characterized by stable cell-cycle arrest, cytoskeletal remodeling, and altered secretion of senescence-associated secretory phenotype (SASP) factors, including SERPINE1/plasminogen activator inhibitor-1 (PAI-1). Although extracellular matrix (ECM) stiffening has been linked to fibroblast mechanotransduction and SERPINE1-associated remodeling, the molecular pathway connecting substrate stiffness to SERPINE1 regulation in senescent fibroblasts remains incompletely understood. Here, we investigated how defined substrate stiffness affects fibroblast morphology, mechanical phenotype, and SERPINE1 expression, and examined whether the clathrin adaptor AP2A1 participates in this response in replicative senescent human fibroblasts. Using tunable polyacrylamide hydrogels, we found that increasing substrate stiffness enhanced fibroblast spreading, stress fiber thickening, focal adhesion maturation, cellular stiffness, and senescence-associated marker expression. Stiff substrates also increased SERPINE1 expression and its colocalization with actin fibers, with stronger responses observed in senescent than in young fibroblasts. Functional perturbation experiments further suggested that SERPINE1 contributes to stress fiber organization in senescent cells. In addition, AP2A1 colocalized with SERPINE1, and modulation of AP2A1 under knockdown and overexpression conditions altered SERPINE1 signal intensity. Conversely, perturbation of SERPINE1 also affected AP2A1, supporting a potential bidirectional relationship between these two components. Together, these findings identify SERPINE1 as a stiffness-responsive factor associated with senescence-linked cytoskeletal remodeling and support a functional relationship between AP2A1 and SERPINE1 in senescent fibroblasts. These results suggest that the AP2A1-SERPINE1 axis may contribute to the link between extracellular mechanical cues and senescence-associated fibroblast remodeling.

cell biology↗

bioRxiv2026

Mechanical contributions of the Myp2 tail revealed by coiled-coil force sensors

Cytokinesis is driven by the constriction of an actomyosin contractile ring, yet how forces generated by individual myosin molecules are transmitted within the ring remains poorly understood. In fission yeast Schizosaccharomyces pombe, the type II myosin Myp2 plays a key role in ring constriction and stability, particularly under stress conditions. Unlike typical type-II myosins, Myp2s tail contains two coiled coils. Although numerous studies have revealed the structure and molecular function of Myp2, the mechanical contribution of its unique tail region has remained unclear. Here, we directly measured forces acting on Myp2 in living cells using genetically encoded coiled-coil force sensors. Insertion of force sensors into the neck region revealed that Myp2 experiences forces of approximately 6.6 pN within the contractile ring. To dissect the contribution of the tail region, we systematically analyzed tail-deletion mutants. Deletion of the proximal tail had little effect on force levels, whereas deletion of the distal C-terminal tail significantly reduced the forces experienced by Myp2. Quantitative analysis of force distributions further showed that truncation of the C-terminal tail reduces the characteristic force by approximately half, demonstrating a major mechanical contribution of the distal tail to the forces experienced by Myp2 at the molecular scale. Deletion of the C-terminal tail slowed the growth rate, consistent with previous macroscopic observations that this region is required for robust ring constriction under stress conditions. We further found that the C-terminal tail forms clusters, which require full-length Myp2 for proper localization to the ring. These findings, together with molecular force measurements and quantitative analysis, demonstrate that the Myp2 tail is not merely a structural or regulatory domain but functions as a load-bearing component in vivo, with its C-terminal region playing a central role in force transmission across scales.

Cell Biology↗

bioRxiv2026

Computationally hybridized pathogenic mammarenavirus receptor binding domains reveal cryptic variants that elicit cross-neutralizing immune responses

The pathogenic mammarenaviruses, Machupo (MACV) and Junin (JUNV), are under evolutionary pressure to leverage human transferrin receptor 1 (hTfR1) for cellular entry while evading host immune responses during zoonosis. We now structurally and functionally investigate cryptic, computationally hybridized JUNV-MACV GP1 sequence variants. We then evaluate the ability of those variants to facilitate internalization of pseudotyped virus-like particles (PVs) into human cells and their recognition by neutralizing antibodies, including plasma from JUNV convalescent patients. We further compare the cryoEM structures of hTfR1-bound MACV GP1 to those of two functional hTfR1-bound MACV-JUNV hybrid GP1 variants that enable robust PV internalization and are also recognized by cross-neutralizing antibodies. Immunization with these variants demonstrates they and other hybrid GP1 sequences can elicit cross-reactive, neutralizing antibodies, supporting a model in which sequence adaptation within GP1 balances receptor recognition with immune evasion. This may inform the rational design of broadly neutralizing GP1-targeted antiviral therapies.

biophysics↗

bioRxiv2026

Alzheimer disease beta-amyloid pathology accelerates age-related hearing loss: evidence from AppNL-F 'knock-in' mice

Age-related hearing loss (ARHL) is a main acquired risk factor for dementia, including Alzheimer disease (AD), but links are unknown. We are using a mouse model with traits of both aging pathologies to test mechanistic interactions. The "knock-in" AppNL-F mouse reproduces {beta}-amyloid pathology in brain regions homologous to those involved in human AD. Because it was generated from the C57BL/6J mouse, it expresses early signs of ARHL, previously reported in this inbred strain. We found evidence that the early-onset ARHL of the C57BL/6J mouse is accelerated in the AppNL-F mouse. In adult C57BL/6J mice around seven-month-old, there were significant increases in auditory thresholds. In adult age-matched AppNL-F mice, auditory thresholds were significantly more elevated, suggesting acceleration of ARHL. In old mice, past thirteen months of age, hearing thresholds were equally elevated in both strains. Outer hair cell loss was significantly increased in adult AppNL-F relative to age-matched C57BL/6J mice, progressing from basal to apical cochlear turns. Spiral ganglion neuron loss also was larger. In adult AppNL-F mice there was more atrophy and enlarged capillary lumen size in the stria vascularis (SV), supporting accelerated ARHL. These findings suggest that central {beta}-amyloid pathology worsens age-related damage to the auditory receptor, thus accelerating ARHL. Damage to the SV and its capillaries in AppNL-F mice point to exacerbation of strial and vascular pathology in the aging cochlea by central {beta}-amyloid pathology. ARHL acceleration by central {beta}-amyloid pathology may contribute to a vicious circle with implications for prevention and therapies. HighlightsO_LIAge-related hearing loss worsens in a mouse model of Alzheimer {beta}-amyloid pathology. C_LIO_LIHearing thresholds further increase relative to naturally occurring hearing loss. C_LIO_LILoss of outer hair cells and spiral ganglion neurons is larger. C_LIO_LIThe stria vascularis and its microcirculation are more atrophic and damaged. C_LIO_LIAlzheimer disease may potentiate peripheral presbycusis. C_LI

neuroscience↗

bioRxiv2026

Trem2 R47H mutation shows mild, but functionally divergent alterations in microglial phenotypes compared to Trem2 deficiency in aged AppNL-F knock-in mice

The TREM2 R47H variant increases the risk of Alzheimers disease (AD), yet its functional impact in aged mouse models remains incompletely understood. We generated a humanized Trem2 R47H knock-in (KI) line on the AppNL-F background and compared it with a Trem2 knockout (KO) line to assess the degree of TREM2 functional impairment. Accumulation of amyloid {beta} 42 and formation of dystrophic neurites were increased in Trem2 KO mice but not in Trem2 R47H KI mice at 18 or 24 months. qPCR and transcriptomic analyses revealed Trem2 KO mice showed deficits in upregulation of microglial genes while Trem2 R47H KI mice showed a response similar to control mice. Differential gene expression analysis identified altered expressions of genes responsible for ER stress/unfolded protein response and intracellular signalling in Trem2 R47H KI mice. Among the differentially expressed genes, Pmel and Gpnmb were or tended to be downregulated in Trem2 R47H KI as well as in Trem2 KO mice indicating their involvement in AD pathogenesis. These results clearly indicate that the TREM2 R47H variant confers a mild, rather than null, effect on microglial alterations during AD development and that Trem2 R47H KI mice should be used to understand pathological mechanism elicited by TREM2. Further identification and characterization of genes differentially expressed in Trem2 R47H KI mice will provide important insights into how the TREM2 risk variant modulates Alzheimers disease-related pathology. HighlightsO_LIExon2-humanized Trem2 R47H knock-in mice are established, which will serve as a platform to study the role of TREM2 in Alzheimers disease development. C_LIO_LITrem2 knockout mice exhibit deficits in clearance of highly aggregated A{beta}42, suppression of dystrophic neurites and regulation of microglial genes in AppNL-F mice, whereas Trem2 R47H knock-in mice do not. C_LIO_LIRNA-seq reveals transcriptional profiles of Trem2 R47H knock-in mice C_LIO_LIqPCR confirms that Gpnmb and Pmel are or tended to be downregulated in Trem2 R47H knock-in mice. C_LIO_LIFindings demonstrate that TREM2 R47H is hypomorphic rather than loss of function. C_LI

neuroscience↗

bioRxiv2026

Deep learning cell type classification using nuclear DNA patterns

Multicellular organisms comprise various types of cells, which are characterized by gene expression through interactions between chromosomal DNA and nuclear proteins. Many cutting-edge methods have been developed to reveal the three-dimensional organization of chromosomes. The detailed analyses of whole chromosomes have begun to uncover structural features specific to several cell types. Here, we show that cell types are instantly and highly accurately classified using conventional DNA staining and a convolutional neural network (CNN). A high-resolution single slice image of the nucleus is sufficient for the accurate classification of both live and fixed cells, including neurons and non-neural cells. These findings suggest that there may be cell-type-specific features decipherable by deep learning in a thin two-dimensional slice of the nucleus.

cell biology↗

bioRxiv2026

CXCL10 drives female-specific tau pathology progression and defines sex-dependent vulnerability in tauopathy model mice

Neuroinflammation is a central driver of tauopathy, yet the precise chemokines that orchestrate the inflammatory microenvironment remain elusive. Here, we report C-X-C motif chemokine ligand 10 (CXCL10) is markedly upregulated in the brains of tauopathy model mice, where it co-localizes with prominent tau pathology. Notably, genetic ablation of Cxcl10 in these mice significantly attenuates tau burden and extends the survival period, specifically in a female-dependent manner. Mechanistically, although Cxcl10 deficiency reduces the number of brain T cells in both sexes, this reduction does not correlate with the female-specific rescue of the phenotype. Furthermore, Cxcl10 deficiency did not alter glial cell activation or motor function, suggesting a sex-specific mechanism. We show CXCL10 is primarily produced by pathological glia, fostering a localized inflammatory microenvironment. Our findings identify CXCL10 as a key mediator of tau pathology and reveal a sex-dimorphic regulatory axis that operates independently of T cell and glial activation paradigms.

neuroscience↗

bioRxiv2026

A novel subset of hepatocytes is simultaneously gluconeogenic and de novo lipogenic in the fed state and is naturally insulin resistant

It is generally accepted that hepatic gluconeogenesis, the synthesis of glucose from non-carbohydrate substrates is active in the fasted state and inactive in the fed state. In contrast, de novo lipogenesis is active in the fed state and is inactive in the fasted state. Here, we used targeted single cell RNA-seq, HCR RNA-FISH, and PrimeFlow in normal physiological mouse liver, and identified a subpopulation of periportal hepatocytes that simultaneously co-express both gluconeogenic and lipogenic genes in the fed state. Euglycemic-hyperinsulinemic clamps further demonstrated that this novel hepatocyte subpopulation is naturally insulin resistant. Spatial metabolic imaging coupled with stable isotope tracing analyses revealed individual hepatocytes that simultaneously undergo both gluconeogenesis and de novo lipogenesis. These dual-positive hepatocytes were also present in human hepatocytes from humanized mouse livers. Moreover, the number of dual-positive hepatocytes increased in high-fat diet-fed mice, suggesting a paradigm shift in our understanding of how the liver becomes insulin resistant.

molecular biology↗

bioRxiv2026

Comprehensive genomic identification and multi-tissue transcriptomic profiling of vitamin D3-related genes in Atlantic salmon (Salmo salar)

The metabolic pathway of vitamin D3 is highly conserved across vertebrates, yet its specific organization in teleost fish remains poorly defined. This study characterizes the genomic repertoire and tissue-specific expression of 16 vitamin D3-related genes in Atlantic salmon (Salmo salar). By overcoming the limitations of automated annotation tools through manual curation and phylogenetic validation, we resolved multiple paralogs arising from the salmonid whole-genome duplication. Tissue profiling revealed unexpected regulatory strategies distinct from the mammalian paradigm. Notably, the skin lacked expression of the biosynthetic enzyme dhcr7, and the head kidney showed negligible expression of the activating enzyme cyp27b1 and the catabolic enzyme cyp24a1. These findings imply that vitamin D3 synthesis and activation in Atlantic salmon may occur in alternative tissue layers or rely on extra-renal mechanisms. Furthermore, the absence of a distinct GC ortholog points to serum albumin (alb2) as the functional transport protein. We also highlight the variability of common housekeeping genes across tissues, underscoring the need for rigorous reference gene validation in salmon transcriptomics. These results redefine our understanding of vitamin D3 metabolism in teleosts and provide a corrected genetic framework for improving dietary protocols in aquaculture.

genetics↗

bioRxiv2026

Humanized tau and amyloid-β deposition accelerate tau propagation, neuronal cell loss and neurophysiological dysfunction in novel mouse models of primary age-related tauopathy and Alzheimer's disease

In Alzheimers disease (AD), tau pathology arises in entorhinal cortex layer II (ECII) and advances through defined hippocampal circuits to CA1 and connected neocortical regions, yet the determinants of this hierarchical spread remain unclear. We previously established a circuit-defined propagation model by expressing Cre-inducible human P301L 2N4R tau selectively in Wolframin-1 (Wfs1)+ ECII neurons using AAV-FLEX-TauP301L in Wfs1-Cre mice. Here, to test how amyloid-{beta} (A{beta}) and human tau background shape propagation, we generated human MAPT knock-in Wfs1 mice and APPNL-G-F/MAPT double knock-in Wfs1 mice (T-Wfs1 and AT-Wfs1) and induced ECII-restricted TauP301L expression. Three months after injection, phosphorylated or misfolded tau-positive neurons were enriched in proximal CA1 in Wfs1 and T-Wfs1 mice, resembling primary age-related tauopathy, whereas AT-Wfs1 mice showed preferential accumulation near the CA1/subiculum (Sub) boundary, consistent with an AD-like pattern. In T-Wfs1 and AT-Wfs1 mice, tau spread extended through Sub to neocortical regions, and phosphorylated tau accumulated predominantly in excitatory rather than inhibitory neurons. Electrophysiological analyses revealed increased spontaneous neuronal firing and impaired GABAergic transmission in the CA1/Sub boundary and neocortical areas in T-Wfs1 and AT-Wfs1 mice, indicative of impaired GABAergic input and enhanced neuronal excitability in these regions. Together, these data indicate that human MAPT and A{beta} pathology shift the circuit topography of tau propagation and are associated with early network dysfunction, supporting a synergistic interaction that promotes AD-like spread and synaptic imbalance.

neuroscience↗

bioRxiv2026

APPNL-F knock-in Alzheimer's Disease model mice reveal etiological convergence of aging and amyloidosis

Alzheimers disease (AD) is the leading cause of dementia worldwide, with a steadily increasing prevalence. Despite the advent of some plaque-degrading therapies, early intervention strategies are still suboptimal, largely due to an incomplete understanding of how early pathological events of amyloid-{beta} (A{beta}) plaque deposition entail or accompany the neuroinflammatory processes that ensue. The APPNL-F mouse line is a second-generation endogenous-promoter knock-in AD model that represents a valuable tool to dissect disease mechanisms and evaluate therapeutic strategies. However, the early prodromal stage remains poorly characterized. Here we performed in-depth analyses in both homozygous (APPNL-F/NL-F) and heterozygous (APPNL-F/WT) mice at 3, 6, 9 and 12 months of age. Among a battery of behavioural tests, the first phenotype was observed at 9 months with defects in spatial memory. Using hypersensitive MSD-ELISA technology assays we quantified distinct A{beta} species and found that A{beta}42 oligomers, protofibrils, and fibrillar aggregates were detectable as early as 6 months of age in homozygous APPNL-F/NL-F mice. By 9 months, their A{beta}42 levels increased markedly and overt A{beta} plaques were detected, histologically associated with recruited glial cells. Targeted RT-qPCR analysis of neuroinflammation-related genes in the cortex also identified 9 months as a molecular tipping point in these middle aged APPNL-F mice. To characterize the etiological signal transduction at the cellular level, we isolated microglia, the brain resident immune cells, whose contribution to AD pathogenesis is now well established. Sequencing around 5,000 individual cells from both 12-month-old APPNL-F/NL-F and APPWT/WT CD11b+ myeloid cells revealed that the buildup of amyloidosis was associated with an accelerated shift of microglia from a homeostatic toward a senescent-like state. Together, these findings highlight the 6-12 month period of the APPNL-F/NL-F model as a powerful system to study the interdependence between microglial senescence and amyloidosis in driving AD progression.

neuroscience↗

bioRxiv2026

Cryo-EM structure of pro-aggregant P301L/S320F double-mutant tau filaments formed in mouse brains following peripheral AAV delivery

Tauopathies are characterized by the accumulation of abnormally phosphorylated tau filaments, with disease-specific folds revealed by cryo-electron microscopy (cryo-EM). Here, we delivered a recombinant human tau carrying the P301L/S320F double mutation into AppNL-G-F/MAPT double knock-in mice using a blood-brain-barrier-permeable AAV (AAV-PHP.eB), enabling rapid induction of tau aggregation in vivo. The mutant tau was systemically administered via retro-orbital injection, providing a minimally invasive approach for widespread neuronal transduction. Phosphorylated tau aggregation, as well as seeding activity, were observed without the need for exogenous seeds. Our cryo-EM analysis resolved a novel filament fold incorporating residues 279-329, in which the P301L and S320F mutations introduced stabilizing interactions that reinforced filament assembly. This conformation was distinct from previously reported folds, including Alzheimer and Pick tau filaments. Moreover, the filaments adopted a more compact architecture than those observed in patient-derived samples or other model mice. This finding demonstrates that P301L/S320F double-mutant tau adopts a structurally unique, highly aggregation-prone fold, and that this system provides a rapid platform for modeling tau filament formation.

neuroscience↗

bioRxiv2025

Fus depleted oligodendrocytes reduce neuronal damage and attenuate AD progression in the AppNL-G-F mouse

AbstractOligodendrocytes (OL) and myelin abnormalities have emerged as important contributors to the pathogenesis of Alzheimers Disease (AD). OL maintain neuronal health through myelin axon interactions and by supplying neurotrophic and metabolic support. To gain insight on how OL and myelin may improve neuronal deficits associated with AD, we have generated a novel mouse model (AD/cKO) by crossing the AppNL-G-F mouse which carries three human AD mutations in the mouse App gene with the FusOLcKO, which has thicker myelin associated with greater cholesterol biosynthesis. The spatial working memory deficits manifested by the aged AD mouse were fully rescued by the FusOLcKO. This outcome was associated with reduced neuronal oxidative damage, preserved presynaptic structures at the plaque niches and a shift in microglia state at the niches in both hippocampus and cortex. In contrast, plaque burden and microglia density were decreased in the hippocampus but not in cortex, uncoupling the neuronal and microglia effects from the amyloid burden. Single cell transcriptomics of AD/cKO hippocampal OL revealed upregulation of energy metabolism and antioxidant genes, suggesting a role of OL enhanced energy metabolism in protecting neurons and affecting microglia state in AD pathology.

neuroscience↗

bioRxiv2025

MARK2 in glial cells suppresses inflammatory responses and mitigates tau toxicity

Neuroinflammation is a pathological hallmark of Alzheimers disease and related neurodegenerative diseases. However, signaling molecules that regulate glial activation status are not fully understood. Microtubule affinity-regulating kinase 2 (MARK2) has been implicated in both immune responses and AD pathology. Here, we report that MARK2 negatively regulates glial immune responses, which protects against neurodegeneration. We found that MARK2 knockdown in the BV2 murine microglial cell line enhanced IL-6 expression in response to LPS. MARK2 knockdown enhanced IL-6 expression induced by TLR7 agonist but not stimulation of RLR pathways and cGAS-STING. In the brains of PS19 tauopathy mice, MARK2 was elevated in homeostatic microglia but reduced in activated microglia. In Drosophila expressing human tau in the retina, expression of AMP downstream of the Toll pathway in the pigment glia enhances degeneration of photoreceptor neurons. Glial knockdown of Par-1, the Drosophila ortholog of MARK2, enhanced Toll-mediated AMP expression and neurodegeneration, whereas overexpression of Par-1 in the pigment glia suppressed them. These results suggest that MARK2/Par-1 in glia negatively regulates Toll pathway-driven inflammation and protects against tau-induced neurodegeneration. These findings provide insight into the molecular underpinnings of glial inflammation in neurodegenerative conditions and highlight MARK2 as a potential therapeutic target for modulating neuroinflammatory responses.

neuroscience↗