Translational Neurodegeneration

Background: Alzheimer's disease (AD) is clinicopathologically heterogeneous. A proportion of patients living with AD present clinically at a younger onset of cognitive symptoms before 65 years old and/or non-amnestic clinical syndromes. Neuropathologically, corticolimbic distribution of neurofibrillary tangle pathology occurs on a continuum with some cases having greater cortical tau pathology relative to limbic regions and others with relatively restricted accumulation in limbic structures. These patterns of corticolimbic tangle distribution are associated with clinical presentation and age at onset. This study sought to examine protein expression differences across the spectrum of clinicopathologic heterogeneity using the NULISA targeted proteomics platform. Methods: A series of thirteen neuropathologically diagnosed AD cases from Mayo Clinic prospectively followed research studies were selected to reflect heterogeneity of clinical syndromes and corticolimbic distribution of tangle pathology. Frozen postmortem brain tissue samples were isolated from inferior parietal cortex and homogenized in RIPA buffer for analysis using Alamar Biosciences NULISA CNS disease 120 panel. Applying a conservative detection threshold of 75% level of detection for the novel application of NULISA in human brain, we evaluated levels of 69 of 129 protein targets across samples. We examined associations between age at onset cognitive symptoms and corticolimbic distribution of tangles (CLix) separately with individual protein targets using linear regression analysis. Results: AD cases with a younger age at onset had higher measured levels of ubiquitin, while older age was associated with higher levels of total tau, CRH, and NPTX2. Investigations of corticolimbic heterogeneity revealed AD cases with lower CLix score (i.e., cortical predominant distribution of tau) had higher measured p-tau181, p-tau231, ubiquitin, and p62. AD cases with higher CLix (i.e., relative cortical sparing) had higher levels of total tau, CRH, NPTX2, MDH1, and HBA1. Brain-derived total tau consistently showed a stronger association in both models. Conclusion: This work demonstrates the utility of postmortem proteomics for investigating biomarkers associated with AD clinicopathologic heterogeneity. We observed proteomic differences in synapse integrity, tau post-translational modification, and ubiquitination associated with age at symptomatic onset and corticolimbic distribution of tangle pathology.

Synucleinopathies are a group of neurodegenerative disorders characterized by the accumulation of aggregated -synuclein (-syn), including Parkinson's disease, Dementia with Lewy Bodies, and Multiple System Atrophy. These diseases are marked by locomotor and non-motor impairments, as well as mitochondrial dysfunction and the loss of dopaminergic (DA) neurons. We have developed several anti--syn single-domain antibodies (sdAbs) and demonstrated the diagnostic imaging potential of two of them and the acute therapeutic benefit of one in clearing -syn in a mouse model. However, whether these sdAbs can suppress -syn-mediated neuronal loss and locomotor impairment in vivo remains unclear. We evaluated the therapeutic potential of five anti--syn sdAbs to clear pathological -syn in mouse neuronal culture and then demonstrated their in vivo efficacy in a Drosophila model of synucleinopathy. The sdAbs differed in their efficacy to lower levels of phospho-serine 129 -syn, prevent loss of DA neurons, alleviate mitochondrial dysfunction, improve motor function, and prolong survival in synucleinopathy flies. The most effective sdAb, 2H1, has not been reported before. It binds strongly to the aggregation prone region of -syn and robustly improves all these disease parameters. Additionally, that sdAb is associated with -syn in the fly neurons, as shown through proximity dependent turboID biotinylation assays. The sdAb-turboID also biotinylated -syn-associated proteins involved in synapse/vesicle trafficking pathways, pinpointing the location of their intracellular interaction. Our findings provide an insight into the therapeutic mechanism of action of these sdAbs and strongly support their clinical development.

Adults with Down syndrome (DS) develop Alzheimer's disease (AD) brain pathology by age 40 due to triplication of the Amyloid Precursor Protein (APP) gene on chromosome 21. Inheritance of the apolipoprotein E-{epsilon}4 (APOE4) allele of the APOE gene on chromosome 19 remains the greatest genetic risk factor for AD in the typical population, yet its role in DS-associated AD (DS-AD) neuropathogenesis in people with DS is unclear. We generated human induced pluripotent stem cell (hiPSC)-derived neurons, astrocytes, and cerebral organoids (COs) using cells from people with DS and from euploid individuals. Aged DS COs were smaller than aged euploid COs and showed robust amyloid-{beta} neuropathology that was positively correlated with the levels of apoE expression. We then captured extracellular vesicles (EVs) from the conditioned media of COs and observed a decrease in the levels of secreted AD-related proteins, including amyloid, contained within the EVs and in the media from which the EVs were isolated. We also identified distinct neuronal and astrocytic gene expression signatures in DS COs relative to euploid COs, including a set of genes known to interact with both APOE and APP at the gene and/or protein levels. Lastly, we determined that, despite differences in the expression levels of the specific genes involved, several common pathways were upregulated in T21 hiPSC-derived neurons, astrocytes, and COs, including apoptosis, the endolysosome, and structural stabilization pathways. Taken together, our findings provide novel insights into molecular mechanisms that may contribute to DS-AD and indicate that apoE plays an important role in the disease process.

Alzheimer's disease (AD) is characterized not only by amyloid-beta; plaques, tau neurofibrillary tangles and associated neuronal loss, but also by alterations in non-neuronal cell types essential for neuronal support. Oligodendrocytes and their myelin sheaths play a central role in maintaining axonal function, yet detailed molecular profiling of myelin dynamics in the human AD brain remains limited. Although neuroimaging studies increasingly highlight myelin degeneration in white matter as an important contributor to AD pathophysiology, the status of myelin within cortical grey matter is less well understood. Here, we performed a detailed histopathological characterization of myelin integrity and oligodendrocyte dynamics in both grey and white matter of the middle temporal gyrus (MTG), making use of post-mortem tissue from AD cases (n = 15) and age-, sex-, and APOE genotype-matched controls (n = 15). Strikingly, we identified a specific vulnerability of cortical grey matter myelin in AD, whereas white matter myelin appeared relatively preserved. This selective grey matter disruption was accompanied by a seemingly insufficient oligodendrocyte regenerative response, suggesting ongoing attempts at myelin repair, yet featured by a differentiation block. Importantly, the extent of myelin damage and OPC differentiation strongly correlated with proximity to tau pathology, linking cortical demyelination to neuronal and synaptic dysfunction within vulnerable AD regions. Together, our findings reveal cortical grey matter myelin disruption as a previously underrecognized, highly localized feature of AD pathology. By highlighting the tight intertwining of oligodendrocyte and myelin dynamics with tau-associated neurodegeneration, this work positions cortical myelin pathology as a potential new mechanistic and therapeutic avenue in AD.

Tau pathology is a central hallmark of Alzheimer's disease (AD) and strongly correlates with cognitive decline, yet the development of tau-targeted therapies has been hindered by the inability of existing models to capture human-specific disease features, particularly the mature forms of AD tau pathology. Moreover, species-specific mechanisms underlying tau pathology remain poorly understood. Here, we establish a patient-derived tau-seeded human neuronal chimera model by transplanting human pluripotent stem cell (hPSC)-derived neural progenitor cells into neonatal mouse brains, followed by intracerebral injection of pathological tau seeds from postmortem AD brains. Human neurons matured in vivo and recapitulated adult human tau features, including all six isoforms with an approximately 1:1 3R:4R ratio. Upon seeding, aged human neurons without FTD mutations faithfully developed robust, mature AD tau pathology, including neurofibrillary tangles (NFTs) and neuropil threads composed of paired helical filaments (PHFs) and straight filaments (SFs) containing 3R and 4R tau, closely mirroring advanced-stage AD. This pathology accumulated and spread across anatomically connected regions, accompanied by neurodegeneration, elevated plasma pTau-217, and memory deficits. Strikingly, tau pathology was largely restricted to human neurons, revealing a pronounced human-specific vulnerability. Mechanistically, snRNA-seq showed that human neurons exhibited higher basal expression of tau-uptake genes and widespread synaptic suppression following tau exposure, whereas mouse neurons remained transcriptomically resilient. Finally, the familial AD mutation PSEN2 N141I exacerbated tau pathology and synaptic loss in human neurons. Together, this model recapitulates the molecular, structural, and functional hallmarks of mature AD tau pathology in human neurons in vivo and reveals intrinsic, species-specific vulnerability, providing a human-relevant in vivo platform for mechanistic studies and therapeutic development.

Background. L-Dopa remains the primary treatment for Parkinson's disease (PD), but chronic administration frequently leads to L-Dopa-induced dyskinesia (LID). While D1 and D2 medium spiny neuron (MSN) specific structural changes on the spine level have been observed in the striatum of PD and LID, studying microglia mediated synapse loss has not been done to date. Methods. Here we generated novel reporter mice by crossing floxed PSD95c(mCherry/eGFP) mice with D1-Cre and D2-Cre lines, producing D1-PSD95-EGFP and D2-PSD95-EGFP strains for MSN-specific synapse visualization. Using the 6-OHDA mouse model of PD and LID we assessed microglia mediated MSN subtype specific synapse loss in these mice while PLX3397 was used to investigate effects of microglia depletion and repopulation on LID development and synapse loss. Results. Both D1- and D2-MSNs exhibited significant PSD95 synapse loss in PD, with D1-MSN loss further exacerbated in LID. Microglia displayed increased phagocytic activity and accumulated PSD95 material within lysosomes, particularly in LID. PLX3397-mediated microglial depletion reduced LID severity and preserved D1-MSN synapses. A depletion and repopulation paradigm attenuated LID severity, preserved D1-MSN synapses, and reduced synaptic material within microglia. Conclusions. Microglia-mediated synapse loss in MSN subtypes contributes to PD and LID pathogenesis. Pharmacological microglial depletion and repopulation mitigate synapse loss and dyskinesia, highlighting microglial turnover as a promising therapeutic strategy for LID.

Many nonhuman primate species recapitulate the neuropathological features of sporadic Alzheimer's disease (AD) to varying degrees. As with humans, the assessment of AD-related pathology in nonhuman primates has historically relied on the use of postmortem brain tissues. In vivo alternatives, such as PET imaging tracers and fluid biomarkers, have been developed for use in humans but require further validation in nonhuman primates before replacing postmortem analyses. Here we employed the Nucleic Acid-Linked Immuno-Sandwich Assay (NULISATM) CNS Disease panel to compare age-related changes in plasma biomarkers in two nonhuman primate species (rhesus monkeys and baboons). In addition, we examined whether amyloid and tau biomarkers were associated with brain atrophy, as measured by gray matter volume. We found significant associations between age and multiple biomarkers of neurodegeneration for both species, as well as significant differences in the patterns of these associations between the two species. For the phosphorylated tau measures, though rhesus monkeys had higher values, baboons showed significant and stronger associations with age. By contrast, rhesus monkeys exhibited an earlier age-related decline in A{beta}42/A{beta}40 ratio than baboons. Finally, in both species, lower A{beta}42/A{beta}40 ratios were associated with lower gray matter volumes. This is the first systematic comparative study of age-related changes in neurodegeneration biomarkers in two closely related nonhuman primates using comparable age ranges and sample sizes, and the same multiplex assay. Future studies should examine longitudinal changes in these biomarkers as well as validate the plasma findings using cerebral spinal fluid.

The neuropathology of Parkinson's disease is characterized by -synuclein (-syn) aggregation and dopaminergic (DAergic) neurodegeneration. While neuronal loss in C. elegans -syn-induced neurodegeneration models is temporally age-dependent, prior research indicates it is uncoupled from the organismal aging process. Here we examined transgenic C. elegans expressing human A53T -syn in DAergic neurons to determine the impact of localized DA metabolism on both neurodegeneration and organismal lifespan. Increasing endogenous DA levels through overexpression of tyrosine hydroxylase (CAT-2) exacerbated A53T-induced DAergic degeneration, whereas DA depletion via{Delta} cat-2 mutation rescued neuronal survival. By mutating a DA interaction motif within -syn, neurodegeneration was rendered insensitive to DA manipulation, thus confirming a structural basis for in vivo toxicity. We identified a DA--syn interaction that acts as a common upstream bridge whereby localized stress induces physiological responses in C. elegans. Genetically, this biochemical interaction acts as a pleiotropic trigger driving two compartmentalized responses: localized DAergic neurodegeneration via oxidative stress, and organism-wide, TFEB/hlh-30-dependent proteostatic remodeling that extends lifespan. Modulating autophagy, without exacerbating DA-mediated oxidative stress, represents a promising strategy to preserve adaptive systemic remodeling while limiting targeted neuronal damage.

Background: Alzheimer's disease (AD) involves complex molecular alterations in the cerebrospinal fluid (CSF) proteome, yet the links between these protein changes and hallmark AD pathology remain incompletely defined. We investigated the relationship between the CSF proteome with CSF biomarkers of Alzheimer's disease (AD). Methods: CSF was collected in 500 individuals of non-Hispanic white, African Americans, and Caribbean Hispanic individuals. CSF biomarkers of AD were measured including P-tau181, A{beta}40, A{beta}42, total-tau, neurofilament light chain (NfL) and glial fibrillary acidic protein (GFAP). CSF was depleted of abundant proteins followed by precipitation, cysteine reduction/alkylation, and proteolytic cleavage by trypsin. Peptides were measured using a Q-Exactive HF mass spectrometer (Thermo Scientific). Association of individual and co-abundant modules of proteins were tested using elevated CSF P-tau181 and reduced A{beta}42/A{beta}40 to confirm the diagnosis of AD. We validated results in CSF from 397 participants in the Accelerated Medicine Partnership-Alzheimer's Disease cohort. Associated proteins were functionally validated in postmortem human brains and zebrafish. Results: We detected 1030 proteins, yielding an overall data completeness value of 97%. CSF levels of 75 (7.3%) proteins were significantly associated with CSF P-tau181 levels after multiple testing correction. Notably phospholipase D3 (PLD3, p=2.41E-09), apoE (p=4.25e-08) and osteopontin (OPN p=1.4E-16) were increased and autotaxin (ATX/ENPP2, p= 8.39E-09) and ceruloplasmin (CP) (p=2.72E-07) were lower among individuals with high P-tau181 levels. These proteins were also associated with CSF A{beta}42/A{beta}40 ratio and total tau levels but not with NfL. OPN was also associated with CSF levels of GFAP (p=1.32e-05). Among proteins associated with P-tau181 levels, pathways related to axon development (p=2.4E-12), axonogenesis (p=1.45E-11) and regulation of axonogenesis (p=5.1E-09) were enriched. Immunostaining on postmortem human and zebrafish brain found that ENPP2 expression, the gene encoding ATX, was significantly reduced in AD brain and in the amyloidosis model in zebrafish. Reduced ENPP2 expression was consistent with reduced lysophosphatidic acid (LPA) levels in the CSF of individuals with AD. LPA administration into zebrafish CSF reduced the pathological changes in synapses and vasculature due to A{beta}42. Conclusion: Unbiased profiling of circulating CSF proteins among individuals with antemortem diagnosis of AD, identified key proteins PLD3, apoE, OPN, ATX, and ceruloplasmin. Validation in postmortem human brains and zebrafish models support potential roles in endosomal sorting and APP processing, inflammation, angiogenesis, lipid transport, and oxidative stress.

Alzheimer's disease is clinically and biologically heterogeneous. We asked whether plasma proteomics separates patients into discrete molecular subtypes or instead reflects continuous biological variation. We studied 5,895 Global Neurodegeneration Proteomics Consortium (GNPC) participants with Alzheimer's disease or mild cognitive impairment using protein coexpression networks, clustering, and continuous molecular-axis analysis. External analyses used Stanford Alzheimer's Disease Research Center (ADRC) biomarker/imaging data and UK Biobank proteomics.Four continuous axes captured 81.5% of module-level proteomic variation. Although a two-cluster solution was reproducible, separation was weak and added little clinical information beyond the continuous axes. Stanford ADRC analyses showed selected fluid biomarker associations, but imaging and PET results did not provide consistent support. In UK Biobank, projected axes were more strongly related to APOE genotype and systemic hematologic, renal, lipid, inflammatory, and hepatic traits than to clear dementia-risk replication. Plasma proteomics did not support robust Alzheimer's disease subtypes. Continuous molecular coordinates better describe plasma proteomic heterogeneity and may guide future biological stratification.

Transcriptional dysregulation and proteostatic collapse are cardinal yet mechanistically separate features of Huntington disease (HD), and how the polyglutamine (polyQ) expansion in huntingtin (HTT) rewires its interactome to produce both remains unresolved. We integrated four published HTT affinity-proteomics datasets and contrasted wild-type and polyQexpanded HTT within one Bayesian model (BayesInteractomics). Of 4,338 proteins, 275 were condition-dependent: the expansion strips HTT of the transcription-activation machinery (Mediator, the ASCOM H3K4-methyltransferase, CREBBP, CDK9) while gaining contacts with the 26S proteasome, HSP70 chaperones and a synaptic and actin-cytoskeletal network, around an intact chaperonin-HAP40 core. This picture emerges only from integration: the datasets overlap so little that a reproducible in at least 2 studies consensus would recover approximately 21% of the high-confidence interactors. By reconciling the transcriptional and proteotoxic arms of HD within one quantitative interactome, this loss-plus-gain model recasts two historically separate disease mechanisms as complementary and nominates prioritised interfaces (HTT-Mediator/ASCOM, HTT-proteasome) for validation and therapeutic targeting.

Introduction: Progressive multiple sclerosis (MS), including primary progressive MS (PPMS) and non-active secondary progressive MS (nSPMS), remains an unmet need, as few treatments target innate immune pathways. Masitinib (AB1010) is a selective tyrosine kinase inhibitor that targets c-Kit and colony-stimulating factor 1 receptor pathways. This mechanism disrupts mast cell-microglia interactions, key innate immune effectors in progressive MS pathogenesis, reducing neuroinflammation and neuronal damage. In the phase 3 AB07002 trial, masitinib (4.5 mg/kg/d) over 96 weeks met its primary endpoint. Comparable signals in PPMS and nSPMS indicated masitinib benefited both phenotypes. Secondary analyses showed that masitinib lowered the progression to wheelchair dependence (EDSS [≥]7, 12 weeks) and reduced the 12-week confirmed EDSS progression risk by 37% versus placebo, although the results were underpowered for these endpoints. Methods: This study aimed to confirm that oral masitinib achieves central nervous system (CNS) concentrations sufficient to modulate CSF1R and wild-type c-Kit, thereby underpinning its neuroprotective potential. Male Sprague Dawley rats (n=12, ~200 g) were administered a single oral dose (30 mg/kg). Plasma and brain samples were collected at 2, 4, 8, and 24 hours post-dose (n=3 per time point). Masitinib (AB1010) and its metabolite (AB3280) were quantified in plasma and brain homogenates using LC-MS/MS. Results: Masitinib reached a brain Cmax of 223.5 ng/mL (~450 nM), exceeding IC50 values for CSF1R and wild-type c-KIT by ~5-fold and 2-fold, respectively, indicating effective CNS target engagement. The active metabolite AB3280 also achieved brain Cmax levels with full inhibitory activity. Masitinib demonstrated consistent CNS penetration supported by a proportional plasma-to-brain exposure relationship. Conclusion: The favorable CNS penetration and safety profile of masitinib, alongside its unique mast cell inhibition, position it as a compelling candidate for progressive MS treatment, either as monotherapy or in combination with other agents. This multifaceted immunomodulatory approach addresses critical unmet needs in progressive MS and supports further clinical development.

The hippocampus supports spatial memory by dynamically integrating external sensory inputs with intrinsic neural circuit dynamics during novel experience. In Alzheimers disease (AD), despite impaired hippocampal spatial remapping, spatial learning and memory abilities can remain partially preserved, a phenomenon consistent with cognitive resilience (Gomez-Isla and Frosch 2022, Jia, Xu et al. 2025). However, the hippocampal ensemble coding patterns associated with these preserved learning and memory abilities remain remains unclear. We hypothesize that intrinsic temporal structures of neuronal firing continue to facilitate the encoding of new spatial information. Using the AppNL-G-F rat model, we longitudinally tracked hippocampal CA1 activity during a familiar-novel context alternating task. We found a dissociation between impaired explicit spatial coding and preserved implicit temporal coding in the AD hippocampal network. Explicit spatial coding was impaired, as place cells showed weak discrimination between distinct contexts and failed to improve with learning. In contrast, implicit temporal coding exhibited learning-dependent refinement, with cofiring dynamic becoming increasingly context-specific across long-term experience. Further analysis suggested that the enhancement of implicit cofiring may be associated with the increased consistency of neural ensemble reactivation during sharp wave ripples in awake rest. Taken together, these findings reveal an explicit-implicit dissociation in the AD hippocampal network, suggesting that the learning-dependent refinement of implicit temporal coding may support preserved learning capacity despite impaired spatial remapping.

Canagliflozin (Cana), an SGLT2 inhibitor prescribed for type 2 diabetes, extends median lifespan by 14% in male but not female UM-HET3 mice at 180 ppm, with male-specific neuroprotective effects, despite females accumulating higher drug concentrations in blood and brain. Here, we tested whether reducing the dose to a subclinical level of 60 ppm could provide neuroprotective benefits in females by reducing drug accumulation. Starting treatment at 7 months of age, Cana at 60 ppm improved glucose tolerance in both sexes at 18 months and increased water and food intake, consistent with SGLT2 inhibition, but produced only a transient reduction in fat mass in males after one month on diet, with no sustained effect on body weight in either sex. At 60 ppm, Cana did not improve cognitive function at 18 months or reduce neuroinflammation in males, whereas females showed reduced hippocampal microgliosis and astrogliosis at 24 months. Pharmacokinetic analysis demonstrated that females accumulated 3- to 5-fold higher Cana concentrations than males across brain regions, blood, and liver. Together, these findings demonstrate that neither dose reduction nor greater drug accumulation drives neuroprotective benefit in females, indicating fundamental sex differences in the biological response to SGLT2 inhibition and suggesting that the sex-specific longevity effects of Cana are not simply a matter of dose.

Myelin, once regarded as a static insulating structure, is now recognized as a dynamic component of the nervous system, capable of remodeling in response to experience. Its breakdown is linked to cognitive decline and neurodegenerative diseases, often preceding neuronal dysfunction. While the myelin proteome has been studied, the age- and sex-related changes it undergoes remain poorly understood. In this study, we purified myelin proteins from young, middle-aged, and aged male and female mice. Using mass spectrometry-based proteomics, we identified 4,095 unique proteins in males and 3,931 in females, with roughly 30% showing significant age-related changes in both sexes. We find an age-related increase in compact myelin structural proteins, such as MBP, MOBP, and CLDN11, and a selective vulnerability in non-compact myelin cytoskeletal proteins, such as SEPTIN2, SEPTIN8, and OPALIN. Notably, disease-associated proteins previously characterized in single-cell transcriptomics appear at the protein level in aged myelin. To firmly distinguish between proteins derived from oligodendrocytes and other cell types in vivo, we labeled nascent oligodendrocyte proteins with bio-orthogonal non-canonical amino acid tagging (BONCAT). We discovered a dramatic age-related increase in lysosomal and vesicle-associated proteins, while translation and synaptic proteins decrease in myelin with age in both sexes. This dataset highlights molecular mechanisms underlying the loss of myelin integrity and function with age and provides a novel tool for studying oligodendrocyte-derived nascent proteins in vivo.

We showed before that the endogenous peptide Nociceptin blocks the premature differentiation of oligodendrocytes (OLGs), preventing untimely precocious myelination in the developing brain. Consistent with this early function, Nociceptin brain expression is developmentally regulated, sharply decreasing with the initiation and progression of myelination. However, we now found that at difference with controls and relapsing-remitting multiple sclerosis (RRMS), Nociceptin levels are highly elevated in cerebrospinal fluid from patients with the most severe progressive MS (PMS) forms. This questioned whether Nociceptin early developmental effects could be latter recapitulated, interfering with remyelination in PMS. This possibility was tested by inducing experimental autoimmune encephalomyelitis in older mice, at an age equivalent to that with increased risk of RRMS transition into PMS. Older animals develop persistently highly debilitating clinical symptoms, and display both brain and spinal cord demyelination. Importantly, these mice exhibit elevated brain Nociceptin levels, and their treatment with an antagonist of the Nociceptin receptor (NOR) elicits a regression of clinical scoring that is accompanied by higher ratios of OLGs/OLG progenitor cells, increased myelination, and reduction of reactive astrocytes. These findings suggest that Nociceptin may be a crucial player in the age-related progression of MS; interfering with OLG maturation and remyelination, and perhaps further exacerbating neurological dysfunction by targeting astrocyte populations. The upregulation of Nociceptin secretion by human astrocytes in response to proinflammatory cytokines, also points to this peptide as a mediator of microglia-astrocyte interactions supporting MS progression with aging. NOR may offer a novel pharmacological target for ameliorating the devastating effects of MS progression.

Long non-coding RNAs (lncRNAs) are increasingly recognized as regulators of cellular identity and disease associated gene expression programs, yet their role in astrocyte reactivity remains poorly understood. Here, we profiled lncRNA expression in primary mouse astrocytes exposed to inflammatory activation paradigms that model microglia driven signaling. This identified a conserved set of activation responsive lncRNAs, among which Gm16685 emerged as one of the most strongly induced candidates. Gm16685 and its human homolog MITA1 were enriched in the nucleus, and MITA1 expression was increased in selected human datasets from Alzheimer's disease, Parkinson's disease and frontotemporal dementia patients. Functional depletion of Gm16685 attenuated inflammatory gene expression and several activation associated astrocyte phenotypes, including reactive oxygen species production, glutamate handling, phagocytic activity and proliferation. Time-resolved transcriptomic analysis indicated that Gm16685 is required for the timely induction of inflammatory response genes. Mechanistically, Gm16685/MITA1 interacted with the RNA binding protein PCBP2, and Gm16685 depletion was associated with reduced PCBP2 protein abundance, altered splicing of Inhibitor of NF-{kappa}B Kinase Subunit Beta (IKK{beta}) and a shift in downstream inflammatory signaling. Together, our findings identify Gm16685/MITA1 as a conserved lncRNA regulator of astrocyte reactivity and suggest that non-coding RNA dependent control of RNA binding proteins contributes to inflammatory signaling in neurodegenerative disease relevant contexts.

Background: Norepinephrine (NE) released from locus coeruleus (LC) projections regulates astrocyte structure and function through adrenergic receptor signaling. We previously showed that increasing noradrenergic tone with the NE reuptake inhibitor desipramine increases astrocyte ramification in the molecular layer of the dentate gyrus. However, whether tonic LC-derived noradrenergic tone is required to maintain astrocyte morphological complexity in vivo, and whether {beta}-adrenergic receptor activation is the effector pathway, remained unclear. Methods: Adult male C57BL/6J mice received DSP-4 (50 mg/kg X 3 days i.p.), a selective LC neurotoxin, with or without concurrent isoproterenol that continued for 21 additional days post cessation of DSP-4 treatment (ISO; 2 mg/kg/day X 24 days), or saline (n = 4 mice per group). Animals were sacrificed 22 days after the final DSP-4 injection. Noradrenergic denervation was confirmed by dopamine {beta}-hydroxylase (DBH) immunostaining. GFAP-immunostained astrocytes in the molecular layer of the dentate gyrus were morphologically characterized using Sholl analysis. Astrocyte density was quantified by SOX9 immunostaining. Results: DSP-4 produced >83% reduction in DBH fiber coverage in the molecular layer. Sholl analysis revealed significant reductions in astrocyte branching complexity in both treatment groups, with the reductions concentrated at distances of 5-15 m from the soma. The maximum number of intersections was also significantly reduced in both groups. Unexpectedly, ISO did not rescue morphological complexity. While DSP-4 alone did not alter astrocyte density, as measured by the number of SOX9-expressing astrocytes, DSP-4+ISO increased SOX9-positive cell density, dissociating the effects of adrenergic signaling on morphology from those on cell numbers. Conclusions: LC-derived noradrenergic tone is required for the maintenance of astrocyte arbour complexity in the dentate gyrus molecular layer. {beta}-adrenergic receptor activation alone is insufficient to restore structural integrity following noradrenergic denervation, yet promotes astrocyte density independently of structural remodeling. These findings have implications for understanding how LC neurodegeneration in Alzheimer's disease and depression may compromise hippocampal astrocyte structure and function.

Single-nucleus transcriptomic atlases offer an unprecedented opportunity to connect cellular molecular states with Alzheimer's disease (AD) neuropathology, but whether these profiles encode reproducible, predictive information about pathological burden remains unclear. We present the SEA-AD DREAM Challenge, an open, international, model-to-data competition built on the Seattle Alzheimer's Disease Brain Cell Atlas to predict Alzheimer's disease neuropathological severity from single-nucleus RNA-sequencing data. Participants developed containerized models to predict categorical neuropathological staging, including overall Alzheimer's disease neuropathologic change, Braak stage, Thal phase, and CERAD score, as well as quantitative amyloid-{beta} and phospho-tau burden measured by 6E10 and AT8 immunohistochemistry. Across 17 eligible teams from 15 countries, the crowdsourcing framework enabled systematic comparison of diverse computational approaches and surfaced a broad landscape of modeling strategies and candidate predictive features. Top-performing methods achieved near-perfect prediction of categorical staging, with the best submission reaching a quadratic weighted kappa of 1.0 for the Overall AD Neuropathological Change score (ADNC), and competitive prediction of quantitative pathological burden in held-out data, with a best concordance correlation coefficient of 0.48. Post hoc perturbation analyses revealed that top categorical-stage predictions relied heavily on donor-level metadata-driven signals rather than transcriptomic features, whereas quantitative pathology prediction was more robust and supported by transcriptomic and cell-type-associated features with potential biological relevance to AD progression. The challenge also introduced the first AI Agent Track in a DREAM Challenge, providing an early benchmark for autonomous and human-guided agentic model development in single-cell neuroscience. This work demonstrates that single-nucleus transcriptomes encode substantial information about Alzheimer's disease pathology, establishes a reproducible benchmark for molecular neuropathology prediction, and highlights critical principles for designing privacy-preserving, leakage-aware community challenges using deeply phenotyped human brain data.

Charcot-Marie-Tooth disease type 2D (CMT2D) results from gain-of-function mutations in GARS1, which encodes glycyl-tRNA synthetase (GlyRS), the enzyme responsible for charging transfer RNA (tRNA) with glycine. There are several CMT2D mouse models, but Gars{Delta}ETAQ/+ is the only one that bears a patient-sourced mutation. Created using CRISPR/Cas9 to model a 12-nucleotide de novo GARS1 deletion identified in an unusually severe CMT2D patient, Gars{Delta}ETAQ/+ mice have previously been shown to display several neuromuscular phenotypes; motor axon loss, denervated neuromuscular junctions (NMJs) and reduced muscle function. Here, we extend these analyses to provide a more comprehensive understanding of both motor and sensory nerve deficits across hind- and fore-limbs. At 3 months, Gars{Delta}ETAQ/+ mice possess sex-independent alterations in the levels of neuropathy biomarkers - including decreased NfL and increased periaxin - alongside reduced muscle endurance and strength, and impairments in the sensory modalities of mechanosensation, proprioception and nociception. Underpinning these dysfunctions, we identified site-specific defects comprising altered sensory neuron populations, muscle spindle loss, reduced motor neuron size, disrupted NMJ innervation and maturation, and reduced axonal transport of signalling endosomes in vivo. Together, these experiments show that Gars{Delta}ETAQ/+ mice display robust and selective peripheral nerve pathology that manifests in a general distal-to-proximal fashion, priming this CMT2D allele for testing treatments and evaluating mechanisms underlying peripheral nerve vulnerability. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=200 SRC="FIGDIR/small/736541v1_ufig1.gif" ALT="Figure 1"> View larger version (70K): org.highwire.dtl.DTLVardef@2b25d2org.highwire.dtl.DTLVardef@c00d77org.highwire.dtl.DTLVardef@b41173org.highwire.dtl.DTLVardef@1e5cdcc_HPS_FORMAT_FIGEXP M_FIG C_FIG