Frontiers in Cellular Neuroscience

Cholinergic input origins and current response properties in rat interstitial nucleus of Cajal neurons

2026-10-23 · Original Research

Taketoshi Sugimura, Yasuhiko Saito

The interstitial nucleus of Cajal (INC) and the prepositus hypoglossi nucleus (PHN) function as the neural integrators for vertical and horizontal gaze holding, respectively. Previous studies have suggested that cholinergic inputs from the mesopontine tegmentum modulate the function of the horizontal integrator; however, the modulation properties and origins of cholinergic inputs in the vertical integrator remain unclear. In this study, we investigated the cholinergic responses of INC neurons and the anatomical origin of the cholinergic inputs in rats. Whole-cell recordings in brainstem slices revealed that local application of acetylcholine (ACh) induced inward currents in INC neurons mediated by both nicotinic and muscarinic ACh receptors (nAChRs and mAChRs). Although current responses were predominantly mediated by nAChRs in PHN neurons, the participation of nAChRs and mAChRs differed depending on the INC neuron type. Retrograde tracing using an adeno-associated virus (AAV) in choline acetyltransferase (ChAT)-tdTomato transgenic rats demonstrated that the primary origin of cholinergic inputs to the INC was the caudal magnocellular region of the medial vestibular nucleus (MVeMC). Furthermore, the primary cholinergic inputs to the PHN originated from both the caudal MVeMC and the caudal PHN itself. These results indicate that the vertical neural integrator shares a common cholinergic source in the caudal MVN with the horizontal integrator, although the relative contributions of nAChRs and mAChRs are not necessarily shared between INC and PHN neurons. These findings suggest a potential role for cholinergic modulation in both vertical and horizontal gaze holding.

Adeno-associated virus gene delivery targeting corneal-projecting trigeminal ganglion neurons

2026-10-22 · Original Research

Samuel S. Reynolds, Md Zeeshan Rasheed, Ken Niyonkuru, Sachin Parikh, Kyle Whyland, Brooklynn M. Merrill, William Perez, Sreya Mitra, Tomasz Zal, Hongmin Yun, Brian Davis, Anthony J. St. Leger, Anna Matynia, Ian D. Meng

Corneal innervation is essential for ocular surface homeostasis and protection, yet methods for selectively labeling and manipulating cornea-projecting neurons remain limited. Conventional retrograde tracers can identify cornea-projecting cell bodies in the trigeminal ganglion (TG), but they do not enable the expression of genetically encoded effector proteins, sensors, or recombinases. We describe and validate intrastromal adeno-associated virus (AAV) delivery as an approach for labeling cornea-projecting TG neurons in mice. A 1–2-μL viral injection was delivered into the corneal stroma and labeling was assessed 2–12 weeks later in cleared whole TG, TG sections, corneal whole mounts, and thick brainstem sections. Multiple AAV vectors, including tdTomato-, eGFP-, or mCherry-expressing vectors and Cre-expressing vectors in Ai14 tdTomato reporter mice, produced consistent neuronal labeling concentrated in the dorsomedial ophthalmic division of the TG. Native tdTomato fluorescence was readily detected, and eGFP labeling could be enhanced using immunolabeling with fluorophore-enhancing antibodies, increasing detection of labeled somata and axonal fibers. AAV-mediated labeling in the TG substantially overlapped with WGA and Fast Blue tracing from the cornea, although AAV labeled fewer neurons overall. Cre-expressing AAV vectors activated reporter expression in Ai14 mice, demonstrating compatibility with transgenic reporter strategies. Labeled axons were visualized at both peripheral and central projection sites. At the ocular surface, reporter expression was correlated to the extent of neuronal transduction. Central projections were observed in subnucleus principalis, the interpolaris/caudalis transition zone, and caudal subnucleus caudalis extending into upper cervical spinal cord. AAV transduction resulted in no gross immune activation. These findings indicate that intrastromal AAV delivery provides a versatile approach for anatomical tracing and genetic access to cornea-projecting neurons, enabling expression of genetically encoded tools for optogenetic and chemogenetic control, activity monitoring, and targeted genetic manipulation.

Impaired Kv4.2-DPP6 complex dynamics in a mouse model of Angelman syndrome

2026-10-21 · Original Research

Jia-Hua Hu, Ying Liu, Cole Malloy, Dax A. Hoffman

IntroductionAngelman syndrome (AS) is a neurodevelopmental disorder caused by loss of neuronal expression of the E3 ubiquitin ligase UBE3A and is associated with altered neuronal excitability. We previously identified the dendritic A-type K+ channel subunit Kv4.2 as an activity-dependent substrate of UBE3A. However, where UBE3A interacts with Kv4.2 during activity-dependent trafficking and how this pathway regulates Kv4.2 channel complexes and dendritic distribution remain unclear..MethodsWe combined live-cell bungarotoxin labeling and biochemical surface-labeling approaches to examine UBE3A association with surface-derived Kv4.2. Co-immunoprecipitation and immunoblotting were used to assess Kv4.2 association with the auxiliary subunit DPP6 and activity-dependent Kv4.2 phosphorylation in wild-type (WT), UBE3A-deficient (AS), and DPP6 knockout (KO) mice. Kv4.2 immunostaining and quantitative line-scan analysis were used to examine its proximal-to-distal distribution in hippocampal CA1 dendrites.ResultsUBE3A preferentially associated with internalized rather than surface-resident Kv4.2, supporting a post-endocytic site of UBE3A action. In AS mice, Kv4.2–DPP6 association was reduced and failed to undergo further activity-dependent remodeling following pentylenetetrazole (PTZ)-induced seizures, despite unchanged DPP6 expression and preserved basal Kv4.2 phosphorylation. In contrast, DPP6 deficiency increased basal Kv4.2 phosphorylation at T602 and T607 and disrupted its activity-dependent phosphorylation dynamics, indicating reciprocal regulation between Kv4.2 phosphorylation and DPP6 association. DPP6KO mice exhibited impaired Kv4.2 gradients along both apical and basal CA1 dendrites. Similarly, AS mice showed impaired dendritic Kv4.2 gradients and reduced activity-dependent redistribution following kainic acid-induced seizures.ConclusionThese findings support a model in which neuronal activity promotes remodeling and internalization of Kv4.2-containing channel complexes, followed by UBE3A-dependent processing of the post-endocytic Kv4.2 pool. Loss of UBE3A disrupts Kv4.2–DPP6 complex dynamics and dendritic Kv4.2 organization, thereby reducing the capacity for activity-dependent channel redistribution. These results identify UBE3A as an important regulator of Kv4.2 homeostasis and provide a mechanistic link between UBE3A deficiency, altered dendritic ion-channel organization, and neuronal dysfunction in Angelman syndrome.

An age-related decline in human fluid intelligence corresponds with immature astroglia prevalence

2026-10-20 · Brief Research Report

Aswathy Ammothumkandy, Luis Corona, Nadia A. Atai, Aidin Abedi, Nora Jimenez, Michelle Armacost, Lina M. D’Orazio, Virginia Zuverza-Chavarria, Alisha Cayce, Mohammad Shariq, Ryan McGinn, Darrin Lee, Brian Lee, Christianne Heck, Jonathan J. Russin, Charles Y. Liu, Jason A. D. Smith, Michael A. Bonaguidi

Age-related cognitive decline remains a daunting health challenge, and targeting neuronal cells alone has been insufficient to halt its progression. Astroglia are emerging as key players in cognitive function and dysfunction, yet their relevance to age-associated cognitive decline in humans remains unclear. Epilepsy patients undergo age-amplified progressive cognitive decline. Our prior research in Mesial Temporal Lobe Epilepsy (MTLE) patients identified pathological stellar Dcx + immature astroglia in epileptic, but not healthy hippocampus. In this study, we combined histology data with pre-surgical neuropsychology tests to assess (1) age-associated cognitive decline in MTLE patients (N = 40), (2) age-related changes in Dcx + immature astroglia (N = 29), and (3) the association between Dcx + immature astroglia and cognitive decline (N = 19). We observed a strong decline in fluid intelligence, visuospatial reconstruction, and memory with age. An increase in Dcx + immature astroglia positively correlated with age, whereas negatively associated with nonverbal abstract reasoning and fluid intelligence as measured by the Raven’s Progressive Matrices test. These findings reveal an interplay among aging, fluid intelligence decline, and immature astroglia prevalence in epilepsy patients. Our study suggests immature astroglia represent a new cellular target to consider for altering age-associated cognitive decline.

Case Report: Sporadic Creutzfeldt–Jakob disease initially misdiagnosed as ischemic stroke: a diagnostic challenge and biomarker-based clarification

2026-10-16 · Case Report

Wenjie Hao, Xuan Zhou, Meixia Wang, Wenming Yang, Ting Cheng

BackgroundSporadic Creutzfeldt–Jakob disease (sCJD) is a rare and uniformly fatal prion disorder characterized by rapidly progressive dementia and heterogeneous neurological manifestations. Early sCJD may be misinterpreted as cerebrovascular disease, particularly when focal neurological deficits, unilateral diffusion abnormalities, and vascular risk factors coexist.Case presentationWe report a 76-year-old man with a history of hypertension who initially presented with dizziness and gait instability, followed by progressive right-sided weakness, and was initially diagnosed with ischemic stroke in the setting of intracranial arterial stenosis. Despite antiplatelet and vascular management, the patient experienced rapid cognitive decline, psychiatric disturbances, aphasia, and progressive hemiparesis. Follow-up MRI demonstrated progressive, non-territorial cortical ribbon-like diffusion restriction predominantly involving the left insular, parietal, frontal, and temporal cortices. CSF analysis revealed markedly elevated total tau (4553.50 pg/mL; laboratory-reported cutoff: < 399 pg/mL), phosphorylated tau (66.93 pg/mL; laboratory-reported cutoff: < 50 pg/mL), and 14-3-3γ protein (50515 AU/mL; laboratory-reported cutoff: < 20,000 AU/mL). Autoimmune encephalitis antibodies and metagenomic next-generation sequencing were negative. PRNP genetic testing detected no pathogenic variant in the patient and his son. EEG showed diffuse slowing without periodic sharp wave complexes. According to the 2017 International CJD Surveillance Network criteria, the diagnosis was classified as probable sCJD on the basis of rapidly progressive cognitive impairment, two clinical features (documented cerebellar ataxia and pyramidal signs), characteristic MRI abnormalities, and positive CSF 14-3-3; the typical EEG criterion was absent and RT-QuIC was not performed.ConclusionThis case highlights the diagnostic challenge of early sCJD initially misdiagnosed as ischemic stroke in the presence of coexisting vascular pathology. Recognition of non-vascular diffusion patterns, careful reassessment of atypical clinical progression, and adjunctive CSF biomarker assessment may facilitate timely diagnostic reconsideration and help avoid unnecessary interventions.

Tissue-resident and recruited mononuclear phagocyte organization in the cochlea under homeostasis and implant-induced inflammation

2026-10-16 · Original Research

Shakila Mahmuda Fatima, Muhammad Taifur Rahman, Brian J. Mostaert, Ibrahim Razu, Bryce Hunger, Shanta Afrin, Sharar Naiarin Haque, Nashwaan Ali Khan, Zhenshen Zhang, Alexander D. Claussen, Marlan R. Hansen

BackgroundThe cochlea contains a diverse population of immune cells that contribute to tissue homeostasis and to responses to injury. Among these, mononuclear phagocytes including tissue-resident macrophages, dendritic cells, and microglia-like cells play central roles in immune surveillance and inflammation. Cochlear implantation induces a robust foreign body response, and here we sought to map the spatial distribution of mononuclear phagocytes across distinct cochlear compartments in healthy cochleae and following implantation.Materials and methodsWe used two reporter mice in this study: C57BL/6-Tmem119em2Gfng/J (TMEM119+/GFP as reporter for microglia), B6. FVB-1700016L21RikTg (Itgax-DTR/EGFP)57Lan/J (CD11c+/GFP as reporter for dendritic cells). To define the spatial organization of different types of mononuclear phagocytes in normal cochleae and after implantation, 30-μm mid-modiolar cochlear sections from these reporter mice were imaged using a confocal microscope. Immunolabeling with cell-specific and activation markers was used to further characterize the cellular distributions and responses.ResultsWe identify heterogeneous distribution of mononuclear phagocytes throughout the cochlea. CD11c-positive dendritic cells display a more restricted baseline distribution, residing primarily in Rosenthal’s canal and the spiral ligament; they selectively accumulate at the implant–tissue interface in the scala tympani after implantation and upregulate major histocompatibility complex class II expression, consistent with antigen-presenting phenotypes. In addition, expression of microglia-associated markers, including TMEM119 and P2Y12, identifies a microglia-like population within specific cochlear sub-regions that persists following implantation.ConclusionTogether, these findings reveal an immune landscape in the cochlea under both healthy and implant-associated inflammatory conditions. CD11c-positive dendritic cells appear to play a central role in the inflammatory response to cochlear implants, becoming activated and localizing to the interface with the biomaterial surface.

Neuron myelination is accelerated by Bruton’s tyrosine kinase inhibition via microglial extracellular vesicles

2026-10-14 · Original Research

Matteo Tartaglia, Arianna Ioni, Mariassunta De Luca, Laura Vilardo, Igea D’Agnano, Antonella Conte, Cristina Limatola, Myriam Catalano

IntroductionThe altered myelin repair observed in demyelinating diseases such as multiple sclerosis (MS) potentially exposes axons to various stressors, with consequent neurodegeneration. Preclinical evidence has demonstrated that Bruton’s tyrosine kinase inhibitors (BTKi), such as ibrutinib, delay MS progression by acting on myeloid cells.MethodsWe investigated the effects of ibrutinib on remyelination using a novel in vitro model of spinal cord neurons derived from postnatal mice.ResultsWe demonstrated that (1) spinal cord neuron cells represent a suitable model for investigating myelination following L‑α‑lysophosphatidylcholine (LPC) treatment; (2) ibrutinib induces remyelination and reduces stathmin‑1 expression in spinal cord cultures; and (3) ibrutinib reduces the inflammatory phenotype of microglia‑like BV2 cells, thereby modulating the expression of miR‑223 in extracellular vesicles (EVs).DiscussionAltogether, these data pave the way for a better understanding of the mechanisms underlying remyelination following ibrutinib treatment and support the hypothesis that EV‑derived microglial cells play a key role.

Editorial: The role of cellular subtypes in striatal activity

2026-10-14 · Editorial

Elodie Fino, Maxime Assous, Marc Vincent Fuccillo

Serotonergic regulation of neuronal excitability and glutamatergic synaptic transmission in rat claustrum

2026-10-13 · Original Research

Renee Rouleau, Saida Oubraim, Lizemarie Cirone, Roh-Yu Shen, Samir Haj-Dahmane

The claustrum (CLA) receives dense serotonergic innervation from dorsal raphe nucleus (DRN) serotonin (5-HT) neurons, which are implicated in regulating sleep and stress homeostasis. However, the mechanisms by which 5-HT regulates the excitability of CLA neurons remain poorly defined. In the present study, we combined whole-cell patch-clamp recordings, 5-HT uncaging, and receptor pharmacology to examine the effects of 5-HT on the excitability of CLA neurons and their glutamatergic synapses. We found that 5-HT consistently induced membrane hyperpolarization or depolarization in regular-spiking type I and type II neurons, whereas it predominantly induced hyperpolarization in strongly adapting CLA neurons. The 5-HT-induced membrane hyperpolarization and depolarization were mediated by 5-HT1A receptors (5-HT1ARs) and 5-HT2A receptors (5-HT2ARs), respectively. Furthermore, we showed that activation of presynaptic 5-HT2ARs inhibits glutamatergic synaptic transmission in the CLA by reducing glutamate release. This effect was not mediated by the canonical phospholipase C (PLC) signaling cascade. Collectively, these findings reveal cell type-specific and multifaceted serotonergic modulation of the intrinsic excitability and synaptic transmission in the claustrum.

Glucocorticoid dynamics predict susceptibility and resilience to traumatic stress in male and female rats

2026-10-09 · Original Research

Emily A. Devine, James B. Chambers, Taylorae Dunn, Ava Musarra, Sophie Porter, Christine E. Moore, Marissa Smail, Nawshaba Nawreen, Ben A. Packard, James P. Herman

IntroductionThe mammalian stress response relies on tightly regulated HPA axis signaling, and disruptions in glucocorticoid feedback are implicated in stress-related disorders such as PTSD. Although many individuals experience trauma, only some develop pathology, suggesting that individual differences in glucocorticoid responsivity may help predict susceptibility or resilience. Here, we examined whether corticosterone (CORT) responses to a mild stressor predict behavioral outcomes following single-prolonged stress (SPS) in male and female rats.MethodsMild stress reactivity was quantified using area-under-the-curve (AUC) CORT responses to light-dark box exposure, after which animals underwent SPS, behavioral assays, and post-reinstatement cFos immunohistochemical analysis.ResultsFemales exhibited SPS-induced reductions in basal AM CORT and displayed a robust traumatic stress-related phenotype in which high CORT responders displayed increased anxiety-like behavior, impaired fear extinction, and enhanced reinstatement. Correlational and permutation analyses revealed a consistent pattern in SPS-exposed females in which lower pre-stress basal AM CORT and higher mild stress-induced CORT (AUC) predicted increased fear expression, indicating a dissociation between resting and stress-evoked glucocorticoid signals. In males, mild stress reactivity did not predict SPS-related outcomes; however, reduced pre-stress basal AM CORT in control males predicted increased fear expression, suggesting sex-specific differences in the potential predictive value of CORT dynamics. SPS and CORT responder status also differentially modulated cFos expression across stress-related brain regions, including the PVN, infralimbic cortex, and amygdala in both males and females.ConclusionThese findings demonstrate that mild stress reactivity and basal glucocorticoid dynamics can predict trauma-related phenotypes in a sex-specific manner, identifying them as a potential biomarker of PTSD susceptibility in females.

Immunometabolic synaptopathy: linking metabolic syndrome to epileptogenesis through trained immunity and parvalbumin interneuron vulnerability

2026-10-09 · Hypothesis and Theory

Baihui Zhang, Wenjin Wang, Tao Li, Hua Huang

BackgroundMetabolic syndrome (MetS) and epilepsy are clinically associated, but how chronic peripheral metabolic stress might influence seizure susceptibility remains unclear. The potential links among CNS-interface dysfunction, glial responses, and inhibitory-circuit vulnerability require further clarification.Proposed frameworkWe propose immunometabolic synaptopathy as a hypothesis-driven framework linking chronic metabolic dysfunction to impaired inhibitory-circuit resilience. MetS-associated metabolic and inflammatory signals may alter blood–brain barrier function, CNS-border immune signaling, and glial homeostasis. Evidence from peripheral myeloid training and CNS immune-memory models supports the plausibility of trained-immunity-like microglial priming, but its occurrence and persistence in MetS-associated epileptogenesis remain unestablished.Circuit-level convergenceWe identify the parvalbumin-positive interneuron–perineuronal net (PV-PNN) unit as a candidate convergence point because of its energetic demands and dependence on ionic and extracellular-matrix homeostasis. Altered metabolic and trophic support, oxidative stress, impaired K+ and glutamate handling, and PNN remodeling may jointly compromise PV-mediated inhibition. Whether these processes preferentially affect PV-PNN units or precede spontaneous seizures requires direct testing.Therapeutic implicationsFive candidate nodes—NLRP3, mTOR, HIF-1α, MMP-9, and Kir4.1—provide opportunities for mechanistic testing. Their therapeutic relevance to MetS-associated epilepsy remains uncertain, and available compounds differ in selectivity, CNS exposure, and safety. The framework motivates experimental evaluation of intervention timing and target dependence rather than specific clinical treatment recommendations.ConclusionImmunometabolic synaptopathy integrates cross-context evidence into a testable hypothesis of metabolically associated seizure susceptibility. The complete pathway to spontaneous epilepsy has not been demonstrated end-to-end and requires longitudinal, cell- and pathway-specific validation.

Correction: Cerebrospinal fluid lipid profiles as exploratory biomarkers for pediatric meningitis: a proof-of-concept case series

2026-10-09 · Correction

Feng Tang, Changzhen Li, Ye Zeng, Wanjun Luo, Lei Xi, Xiaomei Wang

Cortical circuits linking peripheral inflammation to affective states

2026-10-08 · Mini Review

Dahae J. Jun, Shi Tang, Emilia Favuzzi

Affective disorders, such as anxiety and depression, are more prevalent in individuals with inflammatory diseases than in the general population. This comorbidity suggests biological links between immune activation and affective dysregulation. Indeed, there is extensive literature on the impact of inflammation on brain function. Peripheral immune challenges activate subcortical and brainstem regions that regulate emotions and physiological homeostasis. However, cortical regions are also engaged during peripheral inflammation, and cortical dysfunction is a central feature of affective pathology. Drawing primarily on mechanistic work in rodents, we review how peripheral inflammation reaches the cortical circuits that govern emotion and how it is translated into affective changes. This communication begins with two complementary routes by which immune signals reach the brain: neural and humoral pathways. In the neural pathway, cytokine-selective vagal afferents preserve the anatomical origin of inflammation and relay it to the brainstem and downstream regions. In the humoral pathway, circulating mediators act on circumventricular organs and across the blood-brain barrier. Cortical regions, such as the prefrontal cortex, insular cortex, and primary somatosensory cortex, transform these signals into altered behavior. This occurs through shifts in excitatory/inhibitory balance, top-down control of the amygdala, and interoceptive predictions of bodily state. We integrate these studies into a circuit-level model in which inflammation biases cortical processing toward threat, driving the transition from adaptive responses to maladaptive affective dysregulation. Defining which immune signals engage which circuits, and with what specificity, remains a central open question and a promising route toward targeting the affective consequences of inflammatory disease.

Assessment of the transcriptional and cellular effects of CRISPRa targeting Dopa decarboxylase and GTP cyclohydrolase 1 in HEK293 and SH-SY5Y cellular models of Parkinsonian neurotoxicity

2026-10-08 · Original Research

Siyethaba Zinhle Bhengu, Ravesh Singh, Veron Ramsuran, Zama Ndlondlo Princess Msibi

Parkinson's disease (PD) is the second most common neurodegenerative disorder and is characterized by the progressive loss of dopaminergic neurons in the substantia nigra pars compacta (SNc), leading to dopamine deficiency and motor dysfunction. Clustered regularly interspaced palindromic repeats (CRISPR)-based technologies provide a potential approach for targeted gene modulation, although their effectiveness and safety in cellular models of PD remain to be established. This study investigated the feasibility and transcriptional effects of CRISPR activation (CRISPRa) targeting Dopa decarboxylase (DDC) and GTP cyclohydrolase 1 (GCH1) in human embryonic kidney (HEK293) cells and a 6-hydroxydopamine (6-OHDA)-induced neurotoxicity model using human neuroblastoma (SH-SY5Y) cells. Parkinsonian-like toxicity was induced in SH-SY5Y cells with 6-OHDA prior to CRISPRa transfection. A vector-free CRISPRa system was used to target DDC and GCH1, with single-guide RNAs (sgRNAs) assembled with dCas9-VP64 and MS2-p65-HSF1 (MPH) to form ribonucleoprotein (RNP) complexes and delivered using Lipofectamine 3000. CRISPRa targeting of DDC was associated with increased DDC expression in SH-SY5Y cells relative to untreated controls at 24 h (p = 0.0496) and 48 h (p = 0.0064). However, expression levels did not differ significantly from those observed in the 6-OHDA-treated PD control group. In contrast, GCH1 expression was not significantly altered following CRISPRa. CRISPRa also had no significant effect on cell viability in HEK293 cells. In SH-SY5Y cells, 6-OHDA significantly reduced cell viability compared with untreated controls (p = 0.0129). Similar reductions were observed in DDC-targeted cells at 24 h (p = 0.0026) and 48 h (p = 0.0017), and in GCH1-targeted cells at 24 h (p = 0.0017) and 48 h (p = 0.0008); however, none of the CRISPRa-treated groups differed significantly from the 6-OHDA-treated PD control. These findings indicate that CRISPRa elicited a modest transcriptional response, characterized by upregulation of DDC without detectable modulation of GCH1, and did not exacerbate 6-OHDA-induced cytotoxicity. Further optimisation, together with protein-level, enzymatic activity, and dopamine measurements, is required to determine whether these transcriptional changes translate into functional effects on dopamine biosynthesis.

Caveolin-1 defines astrocyte mechanobiology in the glial lamina of the optic nerve head

2026-10-07 · Original Research

Anja K. Hoffmann, Anna Dlugosch, Michelle C. Geigenfeind, Amelie Seemann, Michael H. Elliott, Rudolf Fuchshofer, Andrea E. Dillinger

The optic nerve head is the principal site of retinal ganglion cell axonal injury in primary open angle glaucoma, where astrocyte mechanobiology and extracellular matrix remodeling are thought to play critical roles in disease progression. Caveolae, which are mechanosensitive plasma membrane invaginations formed by Caveolin and Cavin proteins, are key regulators of cellular responses to mechanical stress, yet their involvement in optic nerve head pathophysiology has not been defined. Here, we characterize the presence, regulation, and mechanobiological relevance of Caveolin and Cavin proteins in murine optic nerve astrocytes in vitro and in vivo. Primary optic nerve astrocytes exhibited classical caveolar structures and expressed Caveolin-1, Caveolin-2 and multiple Cavins. In vivo, Caveolin-1 is highly enriched in astrocytes of the glial lamina. Glaucoma-associated factors CCN2/CTGF and TGF-β2 significantly increased Caveolin-1 and Cavin-1 expression in optic nerve astrocytes, while CCN2/CTGF knockdown reduced Caveolin-1 expression. Increasing substratum stiffness enhanced Caveolin-1 expression and altered the subcellular localization of Caveolin-1. Furthermore, Caveolin-1 mRNA expression was increased in the optic nerve head of a glaucoma mouse model, while its protein levels were elevated in the entire optic nerve of the transgenic mice. Together, these findings identify caveolae and Caveolin-1 as mechanosensitive components of optic nerve astrocytes and suggest their involvement in biomechanical and molecular alterations of the glaucomatous optic nerve head. This work provides the first evidence linking astrocyte mechanobiology in the glial lamina to Caveolin-1, highlighting a potential novel contributor to glaucoma pathogenesis.

Microglia and immune signaling as architects of the brain

2026-10-07 · Review

Anna Kim, Cynthia M. Solek, Edward S. Ruthazer

The focus of studies on immune signaling in the CNS is often placed on the effects of inflammation and overactive immune mechanisms in the context of neurodevelopmental and neurodegenerative pathology. However, many immune regulatory pathways are also essential for healthy neuronal development and proper circuit refinement. Appropriate levels of cytokines and chemokines along with many other immune signaling and phagocytic pathways are required for normal neurodevelopment. The complement pathway and other “eat me” signals often studied in the context of inflammation and neurodevelopmental disorders, likewise play a crucial role in this process. Immune receptors and membrane-associated molecules regulate growth, differentiation and the refinement process to help establish a functional network. This review will focus on the roles that immune signaling mechanisms play in neurodevelopment of healthy animals.

Astrocyte maturation creates a stage-specific niche that instructs hippocampal neurogenesis

2026-10-07 · Original Research

Evangelia Masouti, Lucía Casares-Crespo, Andreas Sagner, Arne Gessner, Martin F. Fromm, Helena Mira, Ruth Beckervordersandforth

Astrocytes are a major part of the hippocampal stem cell niche and have been shown to control several steps of neurogenesis, from neural stem and precursor cell (NSPC) proliferation to the differentiation and maturation of newborn neurons. With the aim to identify new factors by which astrocytes promote neurogenesis, we isolated hippocampal astrocytes across key postnatal stages (p3, p10, and p14) and collected astrocyte conditioned medium (ACM) while keeping them for 1 week in culture. Depending on the developmental stage of the astrocytes, we uncovered a shift in the astrocyte secretome. Specifically, ACM from p3 progenitor-like astrocytes promoted a gliogenic program when applied to adult hippocampal NSPCs, while ACM derived from p10 and p14 astrocytes exhibited potent neurogenic properties. To define the molecular basis underlying the acquisition of these neurogenic properties, we performed transcriptomic profiling of astrocytes directly isolated at p3, p10 and p14 as well as astrocytes isolated at these stages that were kept in culture for 7 days. These data sets were integrated with metabolomic analysis of astrocyte-conditioned media from p3 and p14 astrocytes revealing distinct stage-specific programs enriched for secretory and metabolic pathways. Notably, we identified a combination of metabolites that accumulates as astrocytes mature and act as potent drivers of neuronal differentiation. Our findings demonstrate that astrocyte maturation establishes a metabolically and transcriptionally defined, stage-specific niche that instructs NSPC fate and drives neurogenesis.

The role of vascular pathology in SMA: implications for pathogenesis and treatment

2026-10-06 · Review

Simon H. Parson, Hazel Allardyce

Spinal muscular atrophy (SMA) has become a paradigm for precision medicine following the development of transformative therapies targeting the disease-causing deficiency of survival motor neuron (SMN) protein. As more than 98% of SMA cases arise from mutations in the SMN1 gene, restoration of SMN expression through nusinersen (Spinraza; Biogen, Cambridge, MA), risdiplam (Evrysdi; Roche, Basel, Switzerland) and onasemnogene abeparvovec (Zolgensma and Itvisma; AveXis, Novartis, Chicago, IL) has produced unprecedented clinical benefits and established SMA as the first treatable motor neuron disease. To date, therapeutic success has focused on rescuing motor neurons, the principal site of clinical pathology. However, growing evidence indicates that SMA is a multisystem disorder in which pathological changes extend beyond the motor unit. In particular, vascular pathology has emerged as a recurring feature across numerous affected tissues. Vascular abnormalities have been identified throughout the neuromuscular system, including the spinal cord and skeletal muscle, as well as in systemic organs such as the heart, kidney, gastrointestinal tract and spleen. Experimental studies suggest that endothelial dysfunction is a direct consequence of SMN deficiency, impairing angiogenesis, vascular maturation and vessel stability, while patient-derived biomarkers, including retinal vascular imaging and elevated circulating endothelial cells (CEC), provide evidence of ongoing endothelial dysfunction in patients. These vascular abnormalities have the potential to compromise tissue perfusion, promote local hypoxia, disrupt barrier integrity and enhance inflammatory signaling, thereby exacerbating disease progression. Collectively, the evidence suggests that SMN-dependent vascular pathology may represent an under-recognized feature of SMA pathogenesis and a potential therapeutic target. Here, we review the current evidence for vascular pathology in SMA, discuss its implications for disease progression, long-term patient outcomes and therapeutic response, and consider whether vascular abnormalities are adequately addressed by existing SMN-restorative therapies.

Daily regulation of glucocerebrosidase activity and impact of fixed-time rotarod training in a mouse model of Gba1-associated Parkinson's disease

2026-10-06 · Original Research

Chiara Bertasini, Shima Tavakolian Haghighi, Maria Giusy Bruno, Fabio Paio, Carlo Alberto Artusi, Matteo Brunelli, Federico Schena, Massimo Venturelli, Ugo Moretti, Maria Grazia Romanelli, Giovanna Paolone

IntroductionMutations in the glucocerebrosidase (GBA1) gene are a major genetic risk factor for Parkinson's disease (PD) and result in dysfunctional glucocerebrosidase (GCase), the lysosomal enzyme responsible for cleaving glucosylceramide into glucose and ceramide. The pathogenic L444P variant disrupts the enzyme structure and activity, leading to lysosomal accumulation of glucosylceramide and ultimately impairing the clearance of monomeric α-synuclein (α-syn). Given the functional crosstalk among lysosomal homeostasis, the molecular circadian clock, and physical activity, we investigated whether GCase activity exhibits daily rhythmicity, and can be modulated by daily, fixed-time rotarod activity in healthy and Gba1-mutant mice.MethodsC57BL/6J healthy controls and Gba1-mutant PD model mice were housed under a 12 h light/dark cycle, and blood samples were collected at four Zeitgeber times (ZT2, ZT8, ZT14, and ZT20), with and without daily, fixed-time rotarod training. A fluorometric assay was performed on plasma samples to investigate the daily pattern of GCase activity.ResultsOur results showed that rotarod performance was influenced by genotype-dependent vulnerabilities and by daily, fixed-time physical activity, with overall better performance during the dark-phase training. The fluorometric assay revealed that GCase activity shows a ZT-dependent daily pattern in healthy mice, whereas this pattern was disrupted in Gba1-mutant PD models and partially rescued by timed physical activity.DiscussionOverall, both the time of day and daily fixed-time physical activity influenced GCase regulation. Our findings reveal a functional interplay between daily biological timing and lysosomal enzyme regulation, suggesting that optimizing drug dosing and timing of administration may improve the efficacy of GCase-targeted treatments.

Maladaptive sensory coding in the enteric nervous system playing a role in gastrointestinal disorders

2026-10-05 · Mini Review

Linda Chia-Hui Yu, Ching-Ying Huang, Chia-Ying Lin, Yi-Syuan Tsai, Ying-Chieh Chang, Ching-Wen Huang, Zih-Ling Chao, Wei-Ting Kuo

Maladaptive sensory coding within the enteric nervous system (ENS) is increasingly implicated in gastrointestinal dysmotility, abnormal secretion, neuroimmune dysfunction, and visceral hypersensitivity. Intrinsic primary afferent neurons (IPANs), classically corresponding to Dogiel type II/AH neurons, constitute a major sensory arm of intrinsic enteric reflex circuits. They detect mechanical, chemical, epithelial, microbial, and immune-derived signals and relay this information to interneurons, motor neurons, and secretomotor pathways, thereby coordinating gastrointestinal function independently of central input. Experimental studies demonstrate that IPAN excitability is highly plastic: inflammation, serotonergic signaling, cytokines, neurotrophins, microbial products, and other mediators can alter firing thresholds, slow afterhyperpolarization (sAHP), and synaptic transmission. Molecularly defined IPAN populations are sufficient to initiate specific motor programs, microbial colonization is required for normal AH-neuron excitability, and cytokine-responsive subsets participate directly in neuroimmune circuits. These findings support a model in which persistent increases or decreases in sensory gain may distort enteric reflex output and contribute to disorders such as irritable bowel syndrome (IBS), inflammatory bowel disease (IBD), chronic constipation, diarrhea, and visceral pain. However, evidence linking IPAN dysfunction directly to disease remains limited. Few studies have selectively manipulated IPANs in disease models, and definitive demonstrations of IPAN-specific dysfunction causing a gastrointestinal phenotype and its reversal by targeted rescue are lacking, particularly in humans. Major unresolved questions include whether maladaptive IPAN coding is a primary driver, amplifier, or consequence of disease; how intrinsic and extrinsic afferent pathways interact; and how microbial and immune signals reshape IPAN identity over time. Resolving these issues will be essential for establishing maladaptive enteric sensory coding as a therapeutic target.

From mice to clinical relevance: humanizing neuroscience with human-based model systems

2026-04-02

Aniella Vanessa Bak, Karen M. J. van Loo, Deborah Kronenberg-Versteeg, Henner Koch

Preclinical research in neuroscience has traditionally relied on animal models to investigate disease mechanisms and develop new therapeutic strategies. While these models are valuable to gain mechanistic insights, their translational power remains limited due to interspecific differences and, hence, frequent failures in clinical translation. The uniqueness of the human brain calls for alternative approaches in neuroscientific research that more faithfully capture human physiology and pathology. In recent years, a variety of human-based model systems have emerged, ranging from dissociated neuronal cultures and stem cell-derived platforms, including organoids, to micro-engineered devices and human brain slice approaches. Each model offers distinct advantages and limitations in recapitulating neural circuits, disease mechanisms, and therapeutic responses. In this review, we critically discuss the merits and drawbacks of animal models, outline the historic development and current applications of human-based systems, and highlight their potential to complement or replace animal-based models. We further explore current challenges in human brain research, including human variability, technical challenges, as well as ethical considerations and regulatory hurdles. Together, these advances represent a shift toward more predictive, human, and ethically responsible neuroscientific research that could aid in decreasing the translational gap.

“Mind the Gap”—enlarged perivascular spaces as a potential magnetic resonance imaging biomarker of impaired glymphatic clearance in brain disorders

2026-04-01

Claudia F. Kirsch, Mackenzie Herb, Guarav Verma, Priti Balchandani

The abundant capillary network penetrating the brain parenchyma is surrounded by potential tubular, fluid-filled regions referred to as perivascular spaces (PVSs). PVSs have a unique and complex history and are believed to act as a pathway for the drainage of waste products from brain interstitial and cerebrospinal fluid (CSF) as part of the glymphatic clearance system. The unique perivascular “gap” spaces are eponymously linked to Virchow and Robin, who argued vigorously in the 1800s over PVSs’ exact location and physiology. Currently, debates are ongoing regarding whether PVSs are predominantly periarteriolar, perivenular, or both and how they aid in clearing fluids from the brain parenchyma. In neurodevelopmental, neuropsychiatric, and neuropathological conditions, PVS can enlarge, a phenomenon referred to as enlarged perivascular spaces (ePVSs), which are identifiable on magnetic resonance imaging (MRI), with improved detection and resolution at higher magnetic field strengths. Quantification of ePVS enlargement on MRI using artificial intelligence (AI) imaging algorithms may serve as a potential non-invasive imaging biomarker for impaired glymphatic clearance and brain disorders. This mini-review presents the historical background and pathophysiology of PVSs and ePVSs, current debates regarding their exact location, their potential as neuroimaging biomarkers, and how AI may aid in ePVS quantification.

Recreating the human brain: Are assembloids merely descriptive models?

2026-03-27

Yara Izhiman, Charitha Anamala, Eric A. Nauman, Volha Liaudanskaya

Assembloids, engineered fusions of region-specific brain 3D constructs, have emerged as powerful platforms to study neurodevelopment and neurological diseases. Unlike first-generation organoids, assembloids enable direct modeling of interregional communication, allowing investigation of higher-order brain functions that depend on circuit-level interactions. Over the past 5 years, rapid advances in human-derived assembloid systems have demonstrated their ability to recapitulate key features of human brain organization, including long-range projection formation, region-specific signaling, neurovascular coupling, and progressive network dysfunction. The primary application of assembloid modeling remains the study of neurodevelopment, specifically focusing on mapping biological mechanisms driving the human brain development. Another major application of assembloids is the study and modeling of neurological diseases. Recent studies have integrated multiple neural regions, alongside vascular and glial components, and disease-relevant genetic backgrounds to recreate circuit-level interactions underlying pathology. These approaches have further highlighted the importance of neuroglial interactions in shaping development, connectivity, and disease progression in the human brain. Across models and disease contexts, a consistent theme has emerged: pathological phenotypes arise primarily from disrupted intercellular communication rather than isolated cellular and more purely neuronal, defects. Despite these strengths, current assembloid platforms remain limited by incomplete maturation, variability in reproducibility, and challenges in modeling long-term disease trajectories. Together, existing evidence positions assembloids as a promising next-generation platform for studying human brain development and neurodegeneration, while highlighting the need for continued refinement to improve physiological relevance as model complexity increases.

Neuropeptide and cytokines expression in long COVID-19 related neuropsychological sequelae: insights into NK1R-mediated neuroinflammation and in silico therapeutic targeting

2026-03-26

Muhammad Abdullah, Anam Naz, Leah R. Reznikov, Javed Anver Qureshi, Ammarah Hasnain, Ayesha Obaid, Amjed Ali

BackgroundLong COVID-19 causes neurophysiological, cardiopulmonary, and musculoskeletal issues. Increased neuropeptides and cytokines lead to neuroinflammation, resulting in neurocognitive impairments, fatigue, depression, anxiety, and severe cognitive deficits. The Neurokinin 1 receptor (NK1R) is a cellular receptor for the neuropeptide Substance P, and its dysregulation links to neuropsychological issues despite antipsychotic use.ObjectivesIn the present study, neuropsychological sequelae related to long COVID-19 were screened and the expression of related neuropeptides and cytokines was evaluated. Additionally, potential drugs have been evaluated computationally to reduce neuroinflammation in long COVID-19.MethodsAfter informed consent, subjects were screened by a medical physician for long COVID-19 in an outdoor patient clinic. Various biological scales were used to assess and categorize the severity of neuropsychological symptoms related to long COVID-19. After that, peripheral blood samples were collected from subjects using ELISA and RT-qPCR. Nine drugs were selected and subjected to virtual screening to identify potential drug antagonists for NK1R. The key drug-like properties, safety profile, pharmacokinetic analysis, and biological activity of the identified hits were assessed.ResultsIn this study the mean age of 90 patients (60% males and 40% females), was 33 ± 5 years in the symptomatic group and 31 ± 6 years in the asymptomatic long COVID-19 group for 40 years age-group was 58 ± 10 years in the symptomatic group and 54 ± 11 years in the asymptomatic long COVID-19 group. The minimum persistence of duration of long COVID-19 related symptoms in the 30 weeks group of symptomatic long COVID-19. A total of 48% patients had fatigue, 47% complained about headache, 28% had anxiety, 25% faced depression, 20% had psychosocial distress, 20% felt discomfort, and 13% had cognitive impairment. A total of 10% had reported dizziness sequelae among long COVID-19 survivors. Experimental data showed upregulation of IL-6, IL-10, and SP in both symptomatic and asymptomatic individuals compared with controls (p < 0.001). Drug screening analyses revealed aprepitant (−9.3 kcal/mol) and N- acetyl- L- tryptophan (−8.7 kcal/mol) stable interactions with NK1R and maintaining molecular dynamics stability (RMSD: 1.5–2.2 Å; RMSF 0.8–1.4 Å; Rg approximately 21.6 Å). These compounds also demonstrated favorable blood-brain barrier permeability and pharmacokinetic profiles, suggesting their potential as therapeutic antagonists for treating prolonged COVID-related neuroinflammation.ConclusionIL-6, IL-10, and SP are found to be deregulated in long COVID-19 leading to neurophysiological sequelae. To overcome neuropsychological sequelae, binding of SP to NK1R can be hindered using aprepitant and N-Acetyl-L tryptophan which has been evaluated computationally and may require further in vivo and in vitro studies for validation.

Etifoxine drives macrophage M2 polarization via Schwann cell-derived progesterone activation of PPARγ to accelerate peripheral nerve repair

2026-03-23

Chao Guo, Song Liu

BackgroundPeripheral nerve injury (PNI) presents a significant clinical challenge due to limited endogenous regenerative capacity. The translocator protein (TSPO) ligand etifoxine (ETX) has shown promise in promoting nerve repair, but the underlying cellular and molecular mechanisms remain incompletely understood.MethodsUtilizing in vitro co-culture systems with human Schwann cells (HSCs) and THP-1-derived macrophages, TSPO-knockdown HSCs, conditioned medium experiments, and an in vivo rat sciatic nerve crush injury model, we investigated the effects of ETX on cellular crosstalk and macrophage polarization. Molecular analyses included RNA sequencing, western blotting, fatty acid oxidation (FAO) assays, and a Mito-QC reporter system to assess mitophagy. Functional recovery was evaluated through behavioral tests (hindlimb grip strength, mechanical pain threshold), immunofluorescence, and retrograde tracing.ResultsETX specifically activated TSPO on Schwann cells, stimulating progesterone synthesis and secretion. This Schwann cell-derived progesterone acted as a paracrine signal on macrophages, activating the PPARγ–PGC1α axis. This activation triggered dual reprogramming in macrophages: a metabolic shift toward FAO and induction of BNIP3L-mediated mitophagy, both essential for sustaining a pro-regenerative M2 phenotype. These effects were significantly attenuated by the progesterone receptor antagonist RU486 or the PPARγ antagonist GW9662. In vivo, ETX treatment accelerated functional recovery, enhanced axonal regeneration, and increased infiltration of M2 macrophages at the injury site, effects that were partially reversed by RU486 or GW9662 co-administration.ConclusionETX facilitates peripheral nerve repair by promoting Schwann cell-derived progesterone, which drives macrophage PPARγ pathway activation, orchestrating metabolic-autophagic reprogramming necessary for sustained M2 polarization. These findings identify a novel Schwann cell–macrophage metabolic crosstalk mechanism and support the therapeutic potential of targeting this axis in PNI.

Stochasticity in action potential backpropagation: consequences for neuronal computation

2026-03-23

Srdjan D. Antic, Katarina D. Milicevic, William W. Lytton

In cortical and hippocampal pyramidal neurons, backpropagating action potentials (bAPs) play a central role in dendritic signaling, synaptic integration, and spike-timing-dependent plasticity (STDP). In most experimental and theoretical frameworks, bAPs are implicitly treated as reliable signals that faithfully inform dendritic synapses of somatic spiking. Here, we review experimental evidence demonstrating that this assumption is often violated. In large portions of the pyramidal neuron dendritic tree, particularly in distal apical branches and apical tuft dendrites, bAP amplitude exhibits pronounced spatial and temporal variability, including: (i) activity-dependent attenuation, (ii) frequency-dependent amplification, (iii) branch-specific propagation failures, and (iv) trial-to-trial stochastic AP flickering. We summarize five experimentally documented forms of bAP variability and discuss how stochastic backpropagation may shape synaptic plasticity in computational neuroscience, especially STDP, by introducing probabilistic gates that limit the coincidence of: (i) dendritic depolarization (bAP) and (ii) synaptic input (EPSP). Finally, we consider broader implications of the AP flickering in dendrites for cortical information processing, including redundancy, averaging, evidence accumulation, and error-correcting strategies in cortical circuits.

Blood–spinal cord barrier disruption after spinal cord injury: a time-dependent mechanistic review

2026-03-19

Zhirui Jiang, Ce Zhang, Zejing Zhao, Bin Ning

The blood–spinal cord barrier (BSCB) is a specialized vascular interface that preserves spinal cord homeostasis by regulating molecular and cellular trafficking between blood and neural tissue. Disruption of BSCB integrity is a critical pathological event follow-ing spinal cord injury (SCI), leading to increased permeability, inflammatory cell infil-tration, and secondary neurodegeneration. Increasing evidence indicates that BSCB breakdown is not a single event but a dynamic, time-dependent process. In this review, we summarize the molecular and cellular mechanisms responsible for BSCB disruption after SCI in a chronological manner. Key pathological events occurring during the acute, subacute, and chronic phases are discussed, including pathological hemody-namic changes, endothelial stress responses, epigenetic regulation, inflammatory me-diators, immune cell–endothelial interactions, and extracellular matrix remodeling. We further highlight endogenous protective and reparative mechanisms that emerge at later stages. A comprehensive understanding of the temporal characteristics of BSCB disruption may facilitate the development of phase-specific therapeutic strate-gies aimed at preserving barrier integrity, limiting secondary injury, and improving neurological recovery after SCI. This temporal perspective underscores the need for stage-specific interventions to preserve BSCB integrity and improve outcomes after SCI.