Molecular Neurodegeneration

BackgroundNeuromelanin (NM) is a pigment that progressively accumulates with age in catecholaminergic neurons, particularly in the substantia nigra, ventral tegmental area, and locus coeruleus. These neuronal populations are especially vulnerable to degeneration in Parkinsons disease (PD). Elevated intracellular NM levels have been linked to neurodegeneration and PD-like phenotypes in experimental models. However, the molecular mechanisms underlying NM-induced pathology remain poorly understood, as human studies cannot disentangle the specific effects of NM accumulation from those of normal aging. MethodsWe performed transcriptomic microarray analysis on laser-captured catecholaminergic neurons and regions (substantia nigra, ventral tegmental area, locus coeruleus) from NM-producing transgenic mice (tgNM) and NM-free wild-type controls across different ages, and compared them to data from postmortem human brain tissue. One of the molecular targets identified, GPNMB, was validated in mouse and human tissue, and functionally tested in vivo. ResultsWe identified region- and age-dependent transcriptional changes associated with progressive NM accumulation. NM consistently upregulated neuroinflammatory pathways with enrichment of disease-associated microglial genes, while downregulating transcription, translation, and mitochondrial functions. Locus coeruleus exhibited the earliest and strongest transcriptional alterations, whereas substantia nigra and ventral tegmental area showed a later-onset, age-progressive transcriptional dysfunction. Neuron-specific analyses revealed that many changes originated within NM-containing neurons rather than being solely glial-driven. NM-driven transcriptional profiles in mice strongly correlated with postmortem data from PD patients, underscoring their translational relevance. Among molecular targets, the glycoprotein GPNMB was consistently upregulated in NM-containing neurons and validated at RNA and protein levels in both NM-producing transgenic mice and human PD brains. Functional experiments demonstrated that GPNMB overexpression attenuated NM-linked dopaminergic neurodegeneration and improved motor performance in mice. ConclusionThis study provides a comprehensive in vivo characterization of NM-specific transcriptomic changes in catecholaminergic neurons, showing that NM accumulation drives neuroinflammatory and neurodegenerative programs. Our results support that the neuroinflammatory changes observed in tgNM mice and in human PD represent early pathological events that precede overt neurodegeneration. The disease-associated gene GPNMB emerged as a conserved NM-induced factor with protective properties, highlighting its potential as a therapeutic target in PD and aging-related neurodegeneration.

Lysosomes make key contributions to the maintenance of cellular proteostasis, and their functional compromise has been linked to aging and neurodegenerative disease. A defining characteristic of lysosomes is their relative acidity compared to other subcellular compartments, a quality that enables the efficient breakdown of macromolecules. Evidence suggests that neuronal lysosomal pH becomes dysregulated with aging and neurodegenerative disease, yet the mechanisms by which lysosomal pH is maintained remain incompletely understood. To better understand neuronal lysosomal pH regulation, we conducted a genome-wide CRISPRi-based screen in iPSC-derived iNeurons for modifiers of lysosomal pH. We validated several previously known regulators of lysosomal pH and identified novel pathways capable of modifying lysosomal pH, including protein UFMylation and mitochondrial homeostasis. We demonstrate that loss of the lysosomal cationic amino acid exporter, PQLC2, prevents lysosomal acidification in a manner independent of amino acid transport. A novel, tauopathy-associated mutation in PQLC2 impairs lysosomal acidification and drives tau accumulation. Together, this study reveals novel genes that modify lysosomal pH and highlights potential new targets for ameliorating age-related lysosome dysfunction.

Tauopathies are characterized by the accumulation and spread of pathogenic tau aggregates throughout the brain, a process that is increasingly recognized to involve not only neurons but also microglia. However, whether pathogenic MAPT directly alters microglial degradative capacity remains poorly understood. Here, using isogenic human induced pluripotent stem cell-derived microglia carrying the pathogenic MAPT IVS10+16 mutation, we identify tau as a regulator of microglial lysosomal function. MAPT IVS10+16 microglia exhibited coordinated suppression of lysosomal and autophagic pathways, reduced lysosomal protease abundance and activity, and impaired autophagosome-lysosome fusion. Mutant microglia also showed reduced uptake of extracellular tau aggregates, reduced tau accumulation in acidic compartments, and a blunted lysosomal response to proteopathic stress. Conversely, genetic loss of MAPT increased lysosomal degradative capacity and accumulation of extracellular tau aggregates within acidic compartments, supporting a cell-intrinsic role for endogenous tau in regulating microglial degradative function. Pharmacologic enhancement of the autophagy lysosome pathway in MAPT IVS10+16 microglia increased proteolytic activity and improved tau handling. Together, these findings reveal a reciprocal relationship between tau and microglial lysosome function and identify degradative capacity as a modifiable component of the microglial response to tau pathology.

BackgroundParkinsons disease (PD) is driven by -synuclein (-syn) aggregation and affects vulnerable dopaminergic and GABAergic neurons, and its incidence rises dramatically with age. In our -syn mouse model, motor impairment required both syn oligomers and the aging milieu, and pharmacological inhibition of the age hyperactivated Rho GTPase CDC42 with CASIN fully restored motor function, yet the underlying transcriptional pathways mediating this rescue remain to be elucidated. MethodsWe used an inducible -syn oligomer PD mouse model across three age groups (6, 16, and 24 months) with four conditions per group: -syn non-induced (OFF), induced (ON), and each with CASIN treatment (OFF-CASIN, ON-CASIN). Brain tissue from one hemisphere (0 to -5 mm Bregma) was sequenced using 10x Genomics 3 Chromium, with 3-4 mice per condition of both male and female mice. ResultssnRNA-seq demonstrated that CASIN robustly reverted PD-related transcriptional alterations at 24 months whereas aging-related changes were strongest at 16 months. Network and pathway analyses identified CASINs mode of action on two major downstream signaling cascades--MAPK and PI3K/AKT-- in the context of aging and MAPK signaling in PD. ConclusionConvergent gene-, transcription factor-, pathway-, and network-level evidence points to EGFR-PI3K-MAPK signaling as the axis through which CASIN may restore mitochondrial and synaptic function in PD and aging

A central challenge in post-GWAS biology is determining how inherited variation within disease-associated loci shapes molecular mechanisms and clinical phenotypes. Here, we examined four previously identified TMEM106B haplotypes (T1-T4), defined by distinct combinations of coding, structural and regulatory variants. We integrated transcriptomic, proteomic, and neuropathological data from 1,209 individuals across two independent complementary ageing cohorts. Although T2 and T3 both carry the p.Ser185 coding variant, they showed opposing associations with tau pathology, indicating that the surrounding haplotypic background modifies disease susceptibility. T3, which is enriched in cognitively healthy centenarians, was associated with lower tau pathology, lower C-terminal TMEM106B abundance, and reduced detection of an inflammatory microglial state, differing from the association pattern observed for T2. By contrast, T1 was associated with more extensive TDP-43 pathology, neuronal endolysosomal dysregulation, and increased C-terminal TMEM106B abundance. These findings identify haplotype-specific associations with differential proteinopathy burden, illustrating how haplotype-resolved analyses can connect GWAS signals to candidate molecular pathways.

Service members with traumatic brain injury are at approximately two- to four-fold higher risk of Alzheimer's disease or related dementias than those without such an injury, with risk increasing with injury severity. The amyloid/tau/neurodegeneration biomarker framework treats amyloid, tau, and neurodegeneration as independent axes but omits astroglial injury, despite evidence that reactive astrogliosis (indexed by glial fibrillary acidic protein, GFAP) must be elevated for cognitive decline to occur in amyloid-positive individuals. Total GFAP immunoassays aggregate intact protein with multiple calpain- and caspase-cleaved proteoforms, blurring the biological signal. We compared a calpain-cleaved GFAP neoepitope, the glial fibrillary acidic protein neoepitope (neoGFAP), against total GFAP across the full traumatic brain injury--mild cognitive impairment--Alzheimer's disease continuum in Veterans using a two-stage plasma-to-cerebrospinal-fluid biomarker approach. A plasma triage gate combining phosphorylated tau 217 and amyloid beta 42 was applied to 367 unique subjects; a cerebrospinal-fluid benchmarking cohort of 57 subjects (controls, chronic blast traumatic brain injury, mild cognitive impairment, and Alzheimer's disease) received head-to-head neoGFAP and total GFAP measurement. In the whole benchmarking cohort, neoGFAP discriminated mild cognitive impairment plus Alzheimer's disease from non-Alzheimer subjects with an area under the receiver-operating-characteristic curve of 0.81 versus 0.73 for total GFAP, a trend-level advantage that did not reach nominal significance. Within the gate-positive, amyloid-committed subset of 23 subjects, neoGFAP dominance became significant by McNemar's exact test (six discordant subjects favored neoGFAP, none the reverse). Across diagnostic contrasts, neoGFAP outperformed total GFAP for Alzheimer's disease versus control and, importantly for Veterans, for mild cognitive impairment versus chronic blast-exposed Veterans without cognitive impairment. In chronic blast injury, neoGFAP was paradoxically depleted relative to controls, consistent with tissue sequestration of aggregated proteoform fragments. Unbiased proteomic profiling confirmed coordinated elevation across astrocytic, neuronal, mitochondrial, and microglial compartments. An exploratory subject-level reclassification improved accuracy from 71.1 percent using plasma alone to 79.5 percent with added cerebrospinal-fluid markers and age. In a same-cohort ProQuantum replication (n=57), CSF neoGFAP preserved its discrimination advantage over total GFAP for MCI+AD versus non-AD (AUROC 0.76 vs 0.72; cross-platform Spearman {rho}=0.84), while plasma neoGFAP achieved AUROC 0.90, comparable to pTau217 (0.92) and exceeding A{beta}42/40 (0.84). In this small sample, neoGFAP is a superior proteoform-resolved diagnostic and prognostic biomarker across the continuum and supports adding an astroglial-proteoform axis to amyloid/tau/neurodegeneration biomarker frameworks in high-risk populations.

Frontotemporal lobar degeneration (FTLD) is a common cause of early-onset dementias marked by progressive declines in behavior, cognition, and/or movement. FTLD neuropathologies, including TDP-43 proteinopathies and primary tauopathies, do not have reliable fluid biomarkers for in-vivo diagnosis nor biomarkers that directly correspond to FTLD clinical features. Fluid biomarkers that forecast and track FTLD clinical progression, irrespective of pathology or clinical syndrome, are urgently needed to improve clinical trial designs. We previously identified the ratio between two cerebrospinal fluid (CSF) synaptic proteins, YWHAG and NPTX2, as a prognostic biomarker of cognitive decline in Alzheimers disease (AD), independent of core AD pathologies, amyloid and tau. Here, we evaluate its utility in sporadic and familial FTLD compared to other neurodegenerative diseases. Using CSF assays from four independent cohorts (UCSF-MAC, ALLFTD, GENFI, PDBP), we find CSF YWHAG:NPTX2 is substantially elevated across all sporadic and familial FTLD syndromes, AD, and dementia with Lewy bodies. CSF YWHAG:NPTX2 robustly correlates with clinical severity across sporadic and familial FTLD (C9orf72, GRN, or MAPT mutations), independent of current gold-standard neurodegeneration biomarker neurofilament light (NfL). In presymptomatic familial FTLD, CSF YWHAG:NPTX2 is estimated to rise roughly a decade before symptom onset and improves prediction of imminent symptomatic conversion by 1.7-fold compared to plasma NfL alone, more than halving the estimated sample size required for an FTLD prevention clinical trial. These findings underscore CSF YWHAG:NPTX2 as a cross-dementia synaptic biomarker of cognitive decline and a promising biomarker for disease staging and prognosis across the clinico-pathological continuum of FTLD.

Autophagy dysfunction and neuroinflammation are central to Alzheimer's disease (AD), yet how extracellular amyloid-{beta} (A{beta}) couples to impaired autophagic flux and heightened neuroinflammation remains unknown. Here, we identify the TAM receptor AXL as a molecular transducer that couples A{beta} sensing to the regulation of autophagy and neuroinflammation in astrocytes. A{beta} induces {gamma}-secretase-dependent cleavage of AXL, generating a nuclear intracellular domain (AXL-ICD) that forms phase-separated condensates and activates autophagy gene transcription through SIRT2-mediated recruitment of the RUVBL1/2-INO80 chromatin-remodeling complex. This axis is activated in astrocytes of postmortem AD brains. Concurrently, AXL-ICD binds to the SIRT2 catalytic domain and suppresses its deacetylase activity, increasing -tubulin acetylation and altering microtubule dynamics. While moderate AXL-ICD levels promote autophagic flux, excessive elevation paradoxically triggers microtubule hyperstabilization, thereby impairing autophagosome-lysosome fusion and causing pathological accumulation of autophagosomes and H2O2. The inhibitory peptide AxSBiP disrupts the AXL-ICD/SIRT2 interaction, restores autophagic flux, reduces plaque burden, and normalizes A{beta}-induced H2O2 production and astrogliosis in APP/PS1 mice. We propose the AXL-ICD/SIRT2 axis as an effective therapeutic target to reduce A{beta} burden and neuroinflammation in AD

BackgroundProgressive supranuclear palsy (PSP) is a primary tauopathy defined by the accumulation of 4R tau isoforms in neurons, oligodendrocytes and astrocytes. Despite evidence of genetic susceptibility operating through glial cell types, it remains poorly understood how cell type-specific epigenetic-transcriptional programs evolve with progression of tau pathology. MethodsWe conducted single-nucleus chromatin accessibility (snATACseq) and RNA sequencing (snRNAseq) on postmortem frontal cortex samples from PSP patients (n = 8) and matched controls (n = 8), yielding over 144,000 nuclei passing quality control. Tau pathology burden, including neurofibrillary tangles, coiled bodies, and tufted astrocytes, was quantified on AT8-immunostained sections from the same individuals. We integrated differential gene expression analysis, transcription factor motif enrichment, weighted gene co-expression network analysis, and pseudotime modeling anchored to cell type-specific tau pathology burden to delineate molecular pseudo-progression trajectories. ResultsIn eight cell types, 20 subclasses, and 70 subclusters, PSP brains displayed a selective depletion of certain excitatory deep-layer neurons and oligodendrocyte subclusters, with relative preservation of inhibitory neurons and vascular cells. Genetic risk enrichment was localized to astrocytes and oligodendrocytes, whereas excitatory neurons exhibited the greatest transcriptional dysregulation. Oligodendrocyte pseudo-progression indicated a transition from homeostatic myelination programs (MBP, MOBP) through glucocorticoid-responsive stress (FKBP5, ZBTB16), to compensatory myelination (PLP1, CNP) and proteostasis stress (UCHL1, CYRAB, CLU). Neuronal pseudo- progression revealed early dysregulation of synaptic (RORB2, NRG3, NPTX1), microtubule dynamics (KIF2C, RAB27B, TUBA/B), and survival (MEG3, FTX) pathways, alongside a transient increase in neuron-glia interactions (GRIP, CNTNAP4, ERBB4), converging late on ribosomal translation and vesicular trafficking modules across all neuronal subtypes. Cross-modal integration with independent cerebrospinal fluid proteomics identified a concordant subset of glial reactivity, axonal injury, and synaptic markers jointly dysregulated in inhibitory neurons, oligodendrocytes, and excitatory deep-layer neurons. ConclusionPSP pathogenesis reflects a combination of glial genetic susceptibility and staged, cell type-specific transcriptional dysfunction. Oligodendrocytes transition from myelination-competent states to FKBP5-mediated stress states, while neurons show variably timed loss of synaptic excitability and survival programs, preceded by neuron-glia interactions and followed by convergent ribosomal-proteostatic failure. These cytopathology-anchored trajectories outline a potential pathophysiological sequence and may inform candidate selection for stage-specific therapeutic interventions in PSP.

BackgroundThe African green monkey (AGM) is increasingly used as a model for early-stage Alzheimers disease (AD), with cerebrospinal fluid (CSF) targeted for biomarker discovery and longitudinal disease monitoring of shifts in the central nervous system. MicroRNAs (miRNAs) are particularly informative indicators of early neuropathological change. Despite the complementary value of an early-stage disease model and a molecular marker capable of capturing early change, the miRNA composition (miRNome) of AGM remains undefined. We established the AGM CSF miRNome from antemortem samples using miRNA sequencing and a qRT-PCR-based array. We also developed a hierarchical annotation pipeline to classify miRNAs as either family-conserved or unclassified and to assess sequence alignment across humans and other species. ResultsWe used untargeted miRNA sequencing to characterize the AGM CSF miRNome and identified 205 miRNAs that could be classified into three family-conserved categories: canonical, noncanonical, and 3'-terminal variants. Of these, 150 were also detected using a human-targeted qRT-PCR array, providing independent support for the sequence-derived miRNome. Sequencing abundance and qRT-PCR array Ct values showed significant cross-platform concordance overall, although concordance was lower for 3'-terminal isomiRs than for canonical miRNAs. Comparison with human GTEx tissue-expression data indicated that several human homologs of AGM CSF miRNAs exhibited brain-preferential expression. Notably, predicted targets of many of these miRNAs were enriched for pathways implicated in neurodegenerative disease. Finally, we identified 20 unclassified candidates that could not be assigned to established miRNA families, two of which we propose as putatively novel miRNAs. ConclusionThe AGM CSF miRNome is substantially conserved with the human miRNome but also contains 3'-terminal isomiRs and unclassified miRNA candidates. AGM CSF contains miRNAs homologous to human miRNAs associated with AD and other neuropathologies, highlighting the translational potential of this model. However, our study also reveals challenges related to species-specific sequence variation and reduced cross-platform concordance for isomiRs. Thus, comparative studies will be needed to validate the functional and biomarker relevance of these miRNAs across species. More generally, this initial miRNome provides a reference resource for future studies of miRNAs in AGM across disease-related, physiological, experimental, and evolutionary contexts.

Parkinson's disease (PD) is characterized by progressive DAergic neurodegeneration and the accumulation of aggregated -Synuclein (Syn), which drives chronic neuroinflammation through sustained activation of innate and adaptive immune responses. Regulatory T cells (Tregs) exert potent immunosuppressive functions and have shown neuroprotective effects in preclinical PD models; however, clinical translation of polyclonal Treg therapies has been limited by poor tissue specificity and insufficient therapeutic efficacy. To overcome these limitations, we engineered induced human Tregs (iTregs) expressing chimeric antigen receptors (CARs) directed against pathological Syn aggregates. Among the CAR designs tested, only a nanobody-based construct incorporating NbSyn87 displayed selective antigen-dependent activation in response to Syn preformed fibrils (PFFs). Intriguingly, despite the ability of the parental NbSyn87 nanobody to bind both monomeric and aggregated Syn, incorporation into the CAR architecture conferred functional selectivity for aggregated conformers. This feature enabled discrimination between pathological extracellular aggregates and physiological monomeric Syn, providing an important safety advantage. To evaluate therapeutic activity in vivo, we established an immunodeficient mouse model of synucleinopathy permissive to human cell engraftment. iTregs preferentially accumulated within Syn-rich brain regions and, in the presence of astrocyte-derived human IL-2 with antigen-independent mechanism. Conversely, only CAR iTregs directed against Syn significantly reduced microglial and astrocytic activation, decreased pro-inflammatory cytokine expression, and attenuated Syn pathology. Collectively, these findings demonstrate that Syn-specific CAR iTregs can selectively exert potent local immunomodulatory effects, establishing a promising antigen-specific cellular immunotherapy platform for PD and other synucleinopathies.

Dopaminergic neurons in the substantia nigra pars compacta are key targets of -synuclein pathology and neurodegeneration in Parkinson's disease (PD). It is thought that pathological accumulation of -synuclein significantly contributes to nigral neuronal dysfunction and ensuing neuronal demise. In this study, we further assessed this possibility and interrogated the role of -synuclein burden in compromising neuronal function and altering physiological neuronal pathways. In particular, we focused on nigral mitochondrial impairment and disruption of circadian regulatory pathways triggered by sustained -synuclein expression. Using an in vivo AAV-mediated model, we show that -synuclein accumulation over a period of 12 weeks is associated with mitochondrial complex I and IV deficits and leads to dopaminergic cell loss. Proximity ligation assays revealed association of both total and phosphorylated -synuclein with mitochondrial proteins at a time (between 4 and 12 weeks) that paralleled the development of mitochondrial dysfunction. Spatial transcriptomic analysis of the substantia nigra identified coordinated alterations in genes involved in mitochondrial, metabolic, and circadian pathways, including increased expression of circadian-associated genes such as Nr1d1, Nr1d2, Cry2, Arntl2, and Csnk1e. At the protein level, -synuclein overexpression was associated with a differential shift in cryptochrome protein expression, characterized by reduced CRY1 and increased CRY2. Data provide evidence of a specific window of time during which sustained -synuclein burden results in direct -synuclein-mitochondria interactions and nigral mitochondrial damage. During the same time period, a specific remodeling of molecular clock components occurs, providing a potential new mechanism contributing to metabolic and mitochondrial dysregulations and, ultimately, neuronal injury and degeneration.

Substantia nigra pars compacta dopamine neuron loss and Lewy pathology, aggregates of -synuclein, characterize Parkinsons disease and Dementia with Lewy Bodies. Lewy pathology localizes to cortical neurons, and is found as Lewy neurites in the striatum, but its effects on excitatory synaptic function are just beginning to be understood. Corticostriatal projections regulate motor and cognitive behaviors impaired in these disorders. Here, -synuclein aggregation was induced in mouse M2 cortex, a vulnerable region in human disease. Early after initiation, aggregates localized to corticostriatal vesicular glutamate transporter 1 (vGLUT1)-positive terminals, with sparing of spiny projection neuron (SPN) soma, and dopamine terminals and neurons. Corticostriatal presynaptic aggregates significantly impaired glutamatergic transmission, without overt cortical neuron loss, and were associated with decreased synaptic density and volume. Thus, formation of presynaptic -synuclein aggregates impairs corticostriatal function without degeneration of cortical neurons or striatal dopamine terminals, suggesting pathologic -synuclein is sufficient for synaptic loss. Our findings also point to early synaptic dysfunction as a therapeutic target in Lewy body diseases.

Polygenic and proteomic risk scores are both proposed for pre-symptomatic stratification, yet the extent to which they provide overlapping or complementary information has not been measured across neurodegenerative disease. To quantify this overlap, we define absorption as the fraction of a polygenic score's predictive contribution accounted for by an out-of-fold proteomic score and estimate it among 9,434 to 9,820 UK Biobank participants. Absorption did not track h2, as Alzheimer's with APOE, Alzheimer's without APOE and Parkinson's carried matched SNP h2 of 0.068, 0.061 and 0.069 yet absorbed 0.73, 0.39 and 0.19, with amyotrophic lateral sclerosis at 0.22. Residual genetic signal remained in all four, indicating that proteomic risk scores did not fully capture the predictive information contained in polygenic risk scores. The proteins associated with a polygenic score and the proteins a proteomic score selects overlap no more often than chance, converging only where APOE dominates. Across 33 plasma co-expression modules built in 41,358 disease-free participants, germline signal concentrates in modules rather than spreading, with the summary component of seven modules associated with the score for Alzheimer's with APOE and none for Parkinson's, even though Parkinson's carries the lysosomal genetic architecture that the lysosomal module M32 encodes. This module has 89% of its members associated with AD germline risk yet none was used by the proteomic score. Rebuilding the co-expression modules in All of Us gave an adjusted Rand index of 0.582 against the 0.686 attainable within that cohort, and 29 of 33 modules stayed together above a permutation null. Cross-cohort transferability was predictable from module coherence in the discovery cohort, supporting the reuse of this module partition as a fixed reference dictionary.

Background Heparan sulfate (HS) and heparan sulfate proteoglycans (HSPGs) are components of the amyloid deposits in Alzheimers disease (AD) and other amyloidoses. HS and HSPGs are canonically thought to facilitate amyloid deposition by accelerating the aggregation of amyloidogenic proteins and impairing their clearance in a HS-dependent manner. Methods Leveraging insights from large-scale proteomic data, we focused on Syndecan-4 (Sdc4), the most increased transmembrane HSPG in the AD brain and in the brain of A{beta} amyloid depositing mice. We used proximity ligation assays (PLA) to evaluate the association of Sdc4 with A{beta} in situ and assessed the impacts of the Sdc4 ectodomain on A{beta} aggregation in vitro. Overexpression studies in cells, hiPSC-derived neurons, and mouse organotypic brain slice cultures (OBSCs) coupled with structure-function studies were used to investigate impacts on A{beta} production and APP processing. Finally, effects of overexpression of Sdc4 in vivo in the CRND8 amyloid deposition model were evaluated. Results Consistent with canonical roles, PLA demonstrated a spatial association of Sdc4 with amyloid deposits, and in vitro, the Sdc4 ectodomain accelerated A{beta} fibril formation in a HS-dependent manner. Unexpectedly, Sdc4 overexpression reduced A{beta} production in CHO cells, hiPSC-derived neurons, and OBSCs. These effects were accompanied by dramatic decreases in the levels of sAPP and C83 and increased immature APP in the cell. Sdc4 promoted altered APP localization into detergent resistant membrane domains and increased APP association with ATG5+/LC3+/Cathepsin D+ vesicles. Structure-function studies revealed that the transmembrane region mediates these effects in a glycosaminoglycan-independent manner. Sdc4 overexpression in the brain of APP mice significantly reduced amyloid deposition at an early age. Conclusions Sdc4 exerts paradoxical and mechanistically distinct effects that could impact AD pathogenesis differentially, potentially promoting A{beta} fibrillization extracellularly while suppressing APP processing and A{beta} production. Such data challenge the prevailing view that increased levels of HSPGs in AD are always pro-amyloidogenic and identify Sdc4 as a previously unrecognized regulator of amyloid homeostasis in AD.

Amyotrophic lateral sclerosis (ALS) is a motor neuron disease, leading to progressive muscle weakness and motor impairment. Growing evidence indicates that cerebellar Purkinje cells, which play a central role in motor coordination, are also affected in ALS. However, it is unclear whether the molecular events that initiate neurodegeneration in these ALS-relevant motor-controlling neurons are shared or distinct. Here, we used a MATR3 S85C knock-in (KI) mouse model of early-stage ALS with stage-specific motor phenotypes and selective vulnerability of motor neurons and Purkinje cells to decipher the molecular events underlying neurodegeneration in these two neuronal populations. We found that a profound reduction in detectable MATR3 S85C immunoreactivity (hereafter referred to as MATR3 loss) in both motor neurons and Purkinje cells precedes the onset of motor dysfunction and neuropathology, implicating MATR3 loss as the earliest detectable molecular event. Our bulk cerebellar RNA profiling and motor neuron-specific RNA profiling data at the onset of MATR3 loss revealed distinct molecular signatures. In the cerebellum, Ngfr expression emerged in Purkinje cells before the onset of neuronal loss and remained elevated throughout the disease course. This increase was accompanied by activation of the JNK-mediated cell death pathway. In the motor neurons, elevated Fgf21 and integrated stress response (ISR) gene expression were the first to be observed and persisted throughout disease progression, consistent with previous findings in SOD1 mouse models. Our findings provide mechanistic insights into the initiation of neurodegeneration in ALS-relevant motor-controlling neurons and implicate potential neuron type-specific targets for future therapeutics.

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by progressive dysfunction and loss of upper and lower motor neurons. Although motor neuron degeneration ultimately drives paralysis, neuronal dysfunction may precede cell death by a prolonged interval, suggesting that vulnerable neurons engage stress-adaptive programs that permit survival despite impaired function. Cellular senescence represents one such persistent stress response and has increasingly been implicated in neurodegenerative disease, including disorders associated with TDP-43 pathology. Here, we investigated whether senescence-associated molecular states are present in vulnerable motor neurons in ALS and whether they differ according to anatomical region and phosphorylated TDP-43 (pTDP-43) pathology. Postmortem primary motor cortex, cervical spinal cord, and lumbar spinal cord were obtained from the Department of Veterans Affairs Biorepository Brain Bank from individuals with ALS classified as pTDP-43-positive or pTDP-43-negative, together with non-ALS controls. Targeted bulk transcriptomic profiling was combined with GeoMx Digital Spatial Profiling of individual motor neurons to characterize disease-, region-, and pathology-associated molecular phenotypes while preserving anatomical context. Across ALS cases, we identified alterations in pathways related to cell-cycle regulation, RNA processing, mitochondrial function, proteostasis, inflammation, and synaptic signaling. These signatures varied by anatomical region and pTDP-43 status, indicating substantial heterogeneity in the molecular response to ALS pathology. Despite these differences, both ALS groups exhibited convergent proteomic and transcriptomic features associated with cellular senescence. These findings identify senescence-associated molecular states within vulnerable neuronal populations in ALS and support a model in which persistent stress adaptation may permit neuronal survival while contributing to progressive cellular dysfunction. This spatially resolved analysis links neuronal phenotype to anatomical and pathological context and supports further evaluation of senescence-associated pathways as therapeutic vulnerabilities in ALS.

Sex is a major determinant of Alzheimers disease risk and progression, yet the molecular mechanisms underlying this dimorphism remain poorly defined, limiting the development of sex-informed therapeutics. {beta}-Arrestin2 is a pervasive, multifunctional regulator common to a host of G protein-coupled receptors (GPCRs) in the brain, but whether it has a sex-dependent role in Alzheimers disease is unknown. Here, we demonstrate that {beta}-arrestin2 deficiency produces sexually dimorphic effects on A{beta} pathology, neuroinflammation, cognition and autophagic flux in APPswe/PS1{Delta}E9 (APP/PS1) mice. In males, Arrb2 deletion reduced A{beta} oligomer burden, enhanced autophagy, suppressed astrocytic and microglial reactivity, and broadly rescued cognition encompassing spatial working memory, spatial learning, cognitive flexibility, and recognition memory. In females, A{beta} pathology and astrogliosis was unchanged and microgliosis was enhanced, with cognitive improvement limited to recognition memory. The male-specific reduction in pathology was accompanied by decreased S473-Akt and S9-GSK3{beta} phosphorylation and enhanced GSK3{beta}/ZBTB16-mediated autophagy, identifying {beta}-arrestin2 as a molecular switch driving sex-restricted A{beta} pathology, glial activation, and cognitive decline in male APP/PS1 mice. These findings identify {beta}- arrestin2 as a sex-dependent node linking A{beta} pathology to cognitive outcomes in males but not females, underscoring the necessity of sex-stratified consideration in the design of GPCR-targeted Alzheimers disease therapeutics.

Background. The VPS35 p.D620N variant causes autosomal dominant Parkinson's disease (PD) and has been shown to activate the LRRK2 kinase pathway, resulting in increased Rab substrate phosphorylation in peripheral immune cells and elevated urinary bis(monoacylglycero)phosphate (BMP) levels. Recently, a VPS35 variant of unknown significance (c.959C>T; p.A320V) was described in two late-onset sporadic PD patients. Methods. We ascertained a family from the Canary Islands in which six siblings were chronically exposed to high doses of pesticides. Three siblings developed levodopa-responsive, akinetic-rigid PD, while the other three remained unaffected. Whole-exome sequencing was performed in the three affected siblings. The frequency of the resulting candidate variant was assessed in 23,327 PD patients and 9,235 controls from four independent cohorts. Members of this pedigree and unrelated controls were assessed for LRRK2 kinase activity in monocytes and neutrophils and BMP levels in urine. Results. The three affected siblings were all heterozygous for p.A320V, whereas the three unaffected siblings did not carry the variant. In the combined PD case-control cohort, p.A320V was identified in six patients and one control. However, unlike p.D620N, heterozygous carrier status for p.A320V was not associated with increased LRRK2 kinase activity or elevated urine BMP levels. Conclusions. While VPS35 p.A320V co-segregated with PD in this family, it did not exhibit the characteristic LRRK2-associated biomarker signature observed in VPS35 p.D620N carriers. It is possible that p.A320V exerts a subtle effect on VPS35 function that was not captured by the assays performed and that chronic pesticide exposure contributed to disease penetrance in this pedigree.

Parkinson disease (PD) affects more than 1.1 million individuals in the United States and around 12 million worldwide. Although Genome Wide Association Studies (GWAS) have substantially advanced our understanding of PD genetic architecture, the regulatory mechanisms linking PD risk loci to disease-relevant gene expression remain incompletely characterized, limiting our ability to infer disease mechanisms from genetic associations. Here, we integrated disease-state parietal cortex transcriptomics with the International Parkinsons Disease Genomics Consortium (iPDGC) locus prioritization to refine PD gene nomination and identify biologically plausible candidates missed by GWAS-only approaches. Using bulk RNA-seq from 99 neuropathologically confirmed PD cases and 30 neuropathologically confirmed controls, we prioritized candidate genes across 78 loci and classified them according to concordance between genetic evidence and differential expression in diseased cortices. This integrative approach recovered candidate genes not captured by external GWAS-based prioritization methods and highlighted synaptic, lysosomal, and proteostasis pathways as major components of PD risk biology. Network and transcription factor analyses further suggested coordinated regulation of these genes, with STAT3 emerging as a putative upstream glial regulator. Together, these findings suggest that integrating disease-state transcriptomics with genetic prioritization can refine PD risk-gene nomination and uncover regulatory programs that may be missed by GWAS alone.