Molecular Brain

Glutamatergic neuronal synapses in the mouse neocortex mature during the first two months after birth. A key event during synaptic maturation is a change in short-term synaptic plasticity (STP), i.e. a switch from strong synaptic depression to a weaker depression or even facilitation. Glutamatergic pyramidal neurons located in the cortical layers II/III, layer V, and layer VI project axons through the corpus callosum where they release glutamate along their shafts and form glutamatergic synapses with oligodendrocyte precursor cells (OPCs). Here, we used single-cell electrophysiological recordings in brain slices to investigate synaptic plasticity at neuron-OPC synapses along axonal shafts in the white matter, and applied computation approaches to pinpoint the mechanisms of this plasticity. We found that during postnatal development of mice, there is a switch from short-term synaptic depression to short-term synaptic facilitation at glutamatergic neuron-OPC synapses in the corpus callosum. Synaptic delay of phasic neuron-OPC excitatory postsynaptic current shortens, and the amount of asynchronous release at neuron-OPC synapses decrease as animals mature, indicating that glutamate release becomes more synchronized. Our computational modelling suggests that both pre- and postsynaptic changes may contribute to the functional development and changes of plasticity at neuron-OPC synapses in the white matter. Taking together, our findings indicate that synaptic release machineries located at different sites along the same axon (i.e. axonal shaft in the white matter vs synaptic boutons in the grey matter) mature in a very similar fashion, STP occurs at both synaptic sites, and STP dynamics represent an important event during brain maturation.

CommentaryElucidating how normal aging increases vulnerability to neurodegeneration remains a major gap in our understanding of disease risk and progression. The dorsal striatum serves as the primary input nucleus of the basal ganglia and is a key region implicated in multiple neurodegenerative diseases (NDDs) (1). In Colon et al. 2025 (2), we examined the impact of normal aging on neuroinflammatory signaling and perineuronal net (PNN) homeostasis within the dorsal striatum. We observed age-associated shifts in the inflammatory landscape and evidence of increased microglial activation, yet PNN homeostasis was largely preserved (2). PNNs are highly organized extracellular matrix (ECM) specializations that preferentially enwrap the soma and proximal dendrites of fast-spiking GABAergic parvalbumin (PV) interneurons, where they contribute to the regulation of synaptic plasticity and provide protection against oxidative stress (3,4). Building on these findings, we developed a working hypothesis to explain the apparent preservation of PNN homeostasis despite an aging-associated pro-inflammatory environment. The shift toward a pro-inflammatory milieu, together with increased gliosis and phagocytic activity, would be expected to impact the maintenance and integrity of perineuronal nets. The observed increase in phagocytosis-related markers may reflect microglia-directed activity as well as contributions from additional central nervous system (CNS) cell populations. Microglia are specialized embryonic-derived myeloid cells that serve as the resident immune cells of the brain and contribute to PNN homeostasis under physiological conditions (5). In Colon et al. 2025, we observed evidence of microgliosis (e.g., morphological changes, Iba1, Trem2) along with elevated expression of markers associated with phagocytosis (e.g., Cd68) and extracellular matrix-modifying proteases (e.g., Mmp9, Adam17) capable of cleaving key PNN components (2). Importantly, Cd68 expression is not exclusive to microglia and has been detected in brain infiltrating macrophages, reactive astrocytes, and neutrophils during inflammation (6-8). Thus, increased Cd68 levels may not solely reflect microglial phagocytic activation but may also reflect astrocyte reactivity and phagocytic phenotypes. Furthermore, astrocytes are the most abundant glial cell in the brain, and they play a major role in maintaining CNS homeostasis by regulating extracellular neurotransmitter concentrations, providing metabolic support, contributing to the synthesis and remodeling of PNN components, and modulating neuronal communication through their involvement in the tetrapartite synapse (9-12). Astrocytes can also phagocytosis microglial debris, myelin, and synapses (7). To better define the cellular source of phagocytic activity and its relationship to PNN remodeling in aging, we performed immunostaining for microglia (Iba1+), astrocytes (GFAP+), phagolysosomal activity (CD68+), and PNNs using Wisteria floribunda agglutinin (WFA+), enabling us to assess the spatial relationship between phagocytosis and PNN components.

BackgroundChoroid plexus (ChP) produces cerebrospinal fluid (CSF), and regulates brain development and adult subventricular zone (SVZ) neurogenesis, but its role in hippocampal subgranular zone (SGZ) neurogenesis in adulthood and early postnatal stages is not well understood. Current tools to directly manipulate neonatal ChP/CSF volume are very limited, representing an urgent need in the field. MethodsWe first discovered the specific "leaky" expression of DTR gene in the ChP of adult ROSA26-iDTR mice which can be used to specifically ablate ChP in adult brain that generated robust and long-lasting ablation of ChP and reduction of CSF volume. In this study, we the effectiveness of ROSA26-iDTR allele in ablating neonatal ChP. We also developed a novel AAV2/5-CMV-DTR vector with validated ChP tropism in both neonatal and adult mice, which induces substantial CSF loss in both neonates and adult mice. With both the ROSA26-iDTR genetic and AAV2/5-DTR viral-mediated ChP ablation in young adults and at defined postnatal ages, we quantified ventricular CSF volume by MRI and characterized postnatal neurogenesis. Doublecortin-positive (DCX+) neuroblasts, Ki67+ proliferating cells, and TUNEL+ apoptotic cells were quantified in SVZ and SGZ using confocal microscopy and machine learning-assisted cell counting. ResultsWe show that ROSA26-iDTR-mediated ChP ablation is inefficient before postnatal day 10, suggesting that this line may be of limited utility for CSF reduction in the early neonatal period before P10. P3-5 Dtx treatment of a previously used dosage of 20ng/g dosage did not lead to a reduction in CSF volume. Higher dosage of 40ng/gX3 Dtx dosage at p3-5 generated only moderate partial reduction of CSF in third ventricle and total CSF volume, with indication of toxicity associated with high Dtx dosage in general. In contrast, p10-12 injection of 20ng/gX3 Dtx led to robust CSF reduction. To target early neonatal days, AAV2/5 CMV-DTR virus shows high tropism for ChP epithelial cells and leads to near-complete ablation of CSF in neonatal brains. ChP/CSF loss in neonates or young adult mice leads to a substantial reduction of DCX+ cells at the SVZ but a moderate but significant reduction of SGZ DCX+ neuroblasts, without changes in Ki67+ or TUNEL+ cells. ConclusionsThis study reports a novel role of the ChP/CSF in maintaining the neuroblast pool in the neurogenic niches in both early postnatal and adult stages. Moreover, we expand the available tools to target the ChP and CSF production in the neonate, with potential uses in treating conditions such as neonatal hydrocephalus.

Insulin-like growth factor-1 (IGF-1) plays a critical role in neuronal signaling. Disrupted insulin/IGF-1 signaling is implicated in Alzheimers disease, among other conditions, yet its specific influence on glutamate receptor-mediated calcium responses remains unclear. We examined the impacts of IGF-1 on glutamate receptor function in primary rat neurons monitored for intraneuronal calcium following stimulation with glutamate, AMPA, or NMDA/glycine. Pharmacological blockers (CNQX for AMPA receptors, APV for NMDA receptors, and nimodipine for L-type calcium channels) were applied to define receptor-specific contributions. In hippocampal neurons, IGF-1 and insulin altered responses to glutamate in different directions, with IGF-1 tending to evoke and enhanced response. In neocortical neurons, by contrast, IGF-1 consistently reduced glutamate- and AMPA-evoked calcium peaks, suggesting an inhibitory effect on AMPA receptors. To rule out effects on voltage-gated calcium channels downstream of AMPA receptors, we tested effects of IGF-1 on depolarization with potassium chloride; calcium elevation in this case was unaffected by IGF-1. Likewise, IGF-1 did not inhibit responses to NMDA/glycine; and IGF-1 did not affect glutamate responses in the presence of CNQX, a selective AMPA receptor blocker. These findings, combined with the observation that IGF-1 effects persisted in the presence of APV (an NMDA receptor antagonist), indicate that the inhibition of glutamate responses by IGF-1 is mediated by suppression of AMPA receptor activity. IGF-1 may thus contribute to normal neurophysiology, and given the role that glutamate receptors play in excitotoxicity, IGF-1 may confer neuroprotection in the neocortex. Disruption of IGF-1 signaling, as seen in states resembling insulin resistance, may therefore worsen glutamate-driven excitotoxicity and contribute to adverse outcomes.

The muscarinic acetylcholine receptor 1 (mAChR1, M1) has been identified as a primary target for Alzheimers disease (AD) and better understanding of the receptor biology, especially in regard to biased signalling of the receptor, will allow for the development of improved drugs targeting cholinergic dysfunction in AD. The aim of this study was to determine the contribution of phosphorylation of M1 to the learning and memory (LM) effects of M1 agonism. The contribution of M1 phosphorylation dependent signalling in LM was assessed using the mAChR1 positive allosteric modulator, VU0486846, in a scopolamine (1.5 mg/kg) induced LM deficit model in mice expressing HA-tagged M1 (M1-WT), phosphorylation deficient HA-tagged M1 (M1-PD), or mice deficient in M1 (M1-KO). LM was assessed using a fear conditioning (FC) testing paradigm where context and cued memory retrieval was measured 24 hrs after training and a higher level of freezing indicated intact memory. Results demonstrated that scopolamine induced a significant LM deficit in both context and cued retrieval in M1-WT mice which was partially rescued by VU0486846 confirming a contribution of M1 signalling in LM. The scopolamine induced deficit in contextual retrieval in M1-KO mice was not rescued by VU0486846, which is an M1 selective ligand, while scopolamine did not induce a deficit in cued retrieval in M1-KO mice. In M1-PD mice, scopolamine induced a LM deficit in contextual retrieval, however this was also not rescued by VU0486846 treatment. Similarly to M1-KO animals, M1-PD mice did not display a scopolamine induced deficit in cued retrieval. When freezing responses were compared across strains, M1-PD mice displayed a deficit compared to M1-WT and M1-KO mice in contextual retrieval, while both M1-PD and M1-KO mice displayed a deficit compared to M1-WT mice in cued retrieval. These results demonstrate that although M1 agonism can restore a LM deficit in both contextual and cued testing paradigms, only the cued retrieval response is dependent on the M1. Additionally, biased Gq M1 signalling is not sufficient to restore contextual memory and requires phosphorylation of the receptor. Furthermore, biased M1 signalling results in LM deficits not seen with KO of the receptor. Overall, these results reiterate the importance of considering the bias of ligands when developing M1 agonists for dementia in the future.

An increasing number of epidemiological and experimental studies have demonstrated a bidirectional relationship between mood disorders and the circadian system, with disrupted circadian rhythms contributing to depressive states, and their restoration playing a key role in antidepressants effects. In this context, we sought to examine whether key molecular targets of antidepressants exhibit diurnal regulatory patterns. Naive adult male and female C57BL/6 mice were euthanized at 3-hour intervals beginning at Zeitgeber Time 0 (ZT0), and hippocampal (HC) and medial prefrontal cortex (mPFC) tissues were collected for RT-qPCR and western blot analyses. We observed statistically significant diurnal rhythmicity in all analyzed transcripts (cFos, Arc, Nr4a1, Dusp1, Dusp5, and Dusp6) in both HC and mPFC samples, with peak expression occurring during the dark (active) phase (ZT15-18). Phosphorylation levels of TrkBY816 (tropomyosin-related kinase) and GSK3{beta}S9 (glycogen synthase kinase 3{beta}) also showed periodic rhythmicity, peaking during the light (inactive) phase. Levels of p-ERK2T185/Y187 (extracellular-signal regulated kinase) did not display rhythmicity, but peaked during the light phase in the HC, especially in males. Collectively, these findings demonstrate that antidepressant targets are subject to diurnal regulation, highlighting the importance of integrating circadian biology and time-of-day as relevant variables in the development of translationally relevant antidepressant research. HighlightsO_LIKey molecular targets of antidepressants exhibit diurnal regulation in adult mice C_LIO_LIDiurnal patterns were conserved across targets, sexes, and brain regions (HC&PFC) C_LIO_LIcFos, Arc, Nr4a1, Dusp1,5,6 mRNAs display peak expression during the dark phase C_LIO_LITrkBY816 and GSK3{beta}S9 phosphorylation peak during the light (inactive) phase C_LIO_LIAntidepressant mechanisms may be linked with circadian and sleep-wake dynamics C_LI Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=102 SRC="FIGDIR/small/716906v1_ufig1.gif" ALT="Figure 1"> View larger version (25K): org.highwire.dtl.DTLVardef@1e65e60org.highwire.dtl.DTLVardef@13e302corg.highwire.dtl.DTLVardef@1ccc25forg.highwire.dtl.DTLVardef@1ed10d3_HPS_FORMAT_FIGEXP M_FIG C_FIG

Perceptual learning is a temporally dynamic process involving the acquisition and integration of sensory information necessary for adaptive decision making. Resolving the neural basis of perceptual learning could uncover new therapeutic targets for schizophrenia and other neurodevelopmental disorders that implicate impaired perceptual acuity. In the present study, we developed a novel touchscreen task which utilizes orientation discrimination to assess visual perceptual learning (VPL) in male and female rats. Based on previous evidence we hypothesised that VPL would depend on inhibitory neurotransmission mediated by {gamma}-amino butyric acid (GABA). Segregating subjects based on poor learning (lower tertile) and good learning (upper tertile) revealed dose-dependent improvements in VPL in poor learners following the administration of a GABA-B agonist (R-baclofen) and an 5 subunit specific GABA-A (GABRA5) positive allosteric modulator (alogabat) administered early in learning. Poor VPL performance was associated with a significant reduction in GABRA5 expression in dorsal regions of the prefrontal cortex (PFC), most notably the prelimbic cortex. Reduced GABRA5 expression in this region was co-localized to somatostatin- and parvalbumin-expressing interneurons. These findings indicate that inter-individual variation in the expression of GABRA5 in selective PFC populations of inhibitory interneurons may determine the speed and acuity of VPL. Based on these findings, interventions that restore GABRA5 signalling in the PFC may hold therapeutic relevance for neuropsychiatric disorders involving deficits in perceptual learning.

The accumulation of A{beta} plaques and hyperphosphorylation of Tau neuropathologically characterize Alzheimers disease (AD). Synaptic dysfunction and endoplasmic reticulum (ER) stress precede overt neuropathology. ER stress is characterized by the accumulation of unfolded/misfolded proteins, which leads to activation of the adaptive signaling pathway, the unfolded protein response (UPR). Chronic or unresolved ER stress, as in disease, is maladaptive and triggers the integrated stress response (ISR). We hypothesize that targeted attenuation of ISR activation would mitigate the early cognitive deficits and molecular pathology in the triple transgenic (3xTg) mouse model of AD. To test this hypothesis, we used an adeno-associated viral (AAV) vector to overexpress BiP, the key ER chaperone and UPR regulator, in the hippocampi of young 3xTg mice. BiP overexpression reduced phosphorylated PERK (pPERK), a marker of ISR activation, and increased synaptic proteins BDNF, PSD95, and choline acetyltransferase marker (ChAT). Hippocampal-dependent working memory, social memory, long-term spatial memory, and REM theta power were improved without changes in locomotion. BiP overexpression reduced neuroinflammation, as evidenced by a decrease in the astrocyte marker GFAP. Additionally, A{beta} and A{beta}42 levels were reduced in the hippocampus and cortex. Collectively, these findings indicate that modulation of ER stress via BiP overexpression ameliorates early cognitive and molecular alterations associated with AD.

Anatomically and biophysically detailed models of neurons have been widely used to study information processing in these cells. Most studies focused on understanding specific phenomena, while more general models that aim to capture various cellular processes simultaneously remain rare even though such models are required to predict neuronal behavior under more complex, natural conditions. In this study, we aimed to develop a detailed, data-driven, general-purpose biophysical model of hippocampal CA1 pyramidal neurons. We leveraged extensive morphological, biophysical and physiological data available for this cell type, and established a systematic workflow for model construction and validation that relies on our recently developed software tools. The model is based on a high-quality morphological reconstruction and includes a diverse curated set of ion channel models. After incorporating the available constraints on the distribution of ion channels, the remaining free parameters were optimized using the Neuroptimus tool to fit a variety of electrophysiological features extracted from somatic whole-cell recordings. Validation using HippoUnit confirmed the models ability to replicate key electrophysiological features, including somatic voltage responses to current input, the attenuation of synaptic potentials and backpropagating action potentials, and nonlinear synaptic integration in oblique dendrites. Our model also included active dendritic spines, modeled either explicitly or by merging their biophysical mechanisms into those of the parent dendrite. We found that many aspects of neuronal behavior were unaffected by the level of detail in modeling spines, but modeling nonlinear synaptic integration accurately required the explicit modeling of spines. Our data-driven model of CA1 pyramidal cells matching diverse experimental constraints is a general tool for the investigation of the activity and plasticity of these cells and can also be a reliable component of detailed models of the hippocampal network. Our systematic approach to building and validating general-purpose models should apply to other cell types as well. Author SummaryThe brain processes information through the activity of billions of individual neurons. To understand how these cells work, scientists build detailed computer models that reproduce their electrical behavior. These models make it possible to explore situations that are difficult or impossible to test experimentally. However, many existing neuron models were designed to explain only a few specific phenomena, which limits their usefulness in more complex settings. In this study, we developed a comprehensive computer model of a hippocampal CA1 pyramidal neuron, a cell type that plays a central role in learning and memory. We built the model using extensive experimental data and applied automated methods to ensure that it reproduces a broad range of observed neuronal behaviors. We also examined how small structures called dendritic spines--tiny protrusions where most synaptic communication occurs--affect how neurons combine incoming signals. We found that even simplified models without individual spines can capture many aspects of neuronal activity, but understanding more complex forms of signal integration requires modeling spines explicitly. Our work also supports the development of more realistic simulations of brain circuits.

Ferroptosis is a form of non-apoptotic cell death in which iron catalyzes the formation of reactive oxygen species, leading to lipid peroxidation. Experimentally, this process has recently been associated with seizures based on the increased levels of specific markers (4-hydroxynonenal and malondialdehyde) in the brain and plasma. Clinically, iron deposits have been identified in resected tissue from patients with refractory temporal lobe epilepsy. Quantitative susceptibility mapping (QSM) offers an opportunity to detect these accumulations in vivo. In this study, we investigated how pilocarpine-induced status epilepticus contributes to the generation of iron deposits in diverse cerebral regions and whether QSM can detect these deposits longitudinally. We scanned 14 animals (n=10 experimental; n=4 control) at five different time points (pre-status epilepticus induction and 1, 7, 14, 21 days post-induction) using QSM. We identified iron deposits in the caudate putamen, hippocampus, thalamus, and primary somatosensory cortex of experimental animals, which is consistent with histological findings. The initial size of the hippocampal iron deposits significantly increased over the following weeks. None of these effects was observed in the control animals. The presence of cerebral iron depositions in an animal model of pilocarpine-induced status epilepticus suggests that ferroptosis may be involved in the onset, development, and progression of spontaneous recurrent seizures. Furthermore, non-invasive, longitudinal in vivo mapping of brain iron deposits could be a potential imaging marker in neurological disorders such as epilepsy. Future experiments will be required to determine the origin of the iron and avoid its progressive accumulation. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=70 SRC="FIGDIR/small/712677v1_ufig1.gif" ALT="Figure 1"> View larger version (36K): org.highwire.dtl.DTLVardef@14abf67org.highwire.dtl.DTLVardef@5c08fborg.highwire.dtl.DTLVardef@51c40forg.highwire.dtl.DTLVardef@1eb5f9_HPS_FORMAT_FIGEXP M_FIG C_FIG

BackgroundGene expression changes in response to developmental and environmental cues rely on cis-regulatory sequence elements (cREs). BRG1/BRM-Associated Factors (BAF) chromatin remodeling complexes maintain chromatin accessibility at many cREs, enabling binding by transcription factors (TFs). However, cREs exhibit a broad range of sensitivity to loss of BAF function, and the basis of this variability remains unknown. ResultsTo identify the characteristics of BAF-dependent cREs, we mapped chromatin accessibility changes following acute pharmacologic BAF inhibition in GM12878 lymphoblastoid cells. We integrated these results with over 100 TF and histone modification ChIP-seq datasets and used machine learning to identify features that predict chromatin accessibility changes. We found that Activator Protein 1 (AP-1) factors and lymphoid lineage-defining TFs including RUNX3 and PU.1 predicted BAF-dependence. Strikingly, we found that cREs bearing the chromatin signature of "primed" enhancers - enriched for H3K4me1 but lacking H3K27ac - were significantly more sensitive to BAF inhibition than typical active enhancers. As primed enhancers are known to facilitate transcriptional responses to stimuli, we tested the requirement of BAF activity in these responses. Acute BAF inhibition was sufficient to prevent both chromatin and transcriptional responses to interferon gamma and dexamethasone. cREs which normally gained accessibility in response to stimulation failed to do so with BAF inhibition, and these cREs were linked to genes with suppressed transcriptional induction. ConclusionsCollectively, our results demonstrate a requirement for continuous BAF activity to enable stimulus response and suggest that defective signal responsiveness may be a pathogenic mechanism in disease states caused by loss-of-function mutations in BAF subunits.

Alzheimers disease (AD) is the most prevalent form of dementia, characterized by progressive memory loss, cognitive decline, and emotional dysregulation. Adult hippocampal neurogenesis (AHN) critically contributes to cognition and mood but undergoes precipitous decline during AD progression. Here, we investigated whether enhancing AHN through genetic expansion of endogenous neural stem cells (NSC) ameliorates AD-related phenotypes. Using lentiviral overexpression of the cell cycle regulators Cdk4 and CyclinD1 in the dentate gyrus of 3xTg-AD mouse, we show that enhancing AHN partially rescues hippocampal-specific cognitive functions, namely: spatial navigation and exploratory behavior. These findings show that endogenous NSC can be exploited to ameliorate hippocampal cognitive functions in AD, providing additional evidence for exploiting AHN as a promising therapeutic target for neurodegenerative disease.

The circadian clock controls a vast array of cellular and organismal functions, from the molecular scale to behavior. While each cell is regimented by a cell-autonomous clock, few studies in the brain have dissected the circuit and behavioral contributions of cell-specific clocks. Relatedly, astrocytes are now known to play key roles in regulating synaptic function, circuit activity and behavior, but whether these functions are guided by astrocyte-autonomous clocks is unknown. Here, we report that post-natal deletion of the critical circadian clock gene Bmal1 in astrocytes, which abrogates core clock function in a cell type specific manner, induced expression of genes related to extracellular matrix (ECM) production, maintenance, and remodeling. Circadian variations have been shown in a specific ECM structure, perineuronal nets (PNNs), which are implicated in synaptic function and plasticity. In astrocyte-specific Bmal1 knockouts, hippocampal PNN abundance was decreased, and the circadian rhythm of these structures was also abolished. In line with evidence implicating PNNs, and the ECM in general, in synaptic function and plasticity, we found that astrocyte-specific Bmal1 KO mice had increased synaptic strength but blunted long term potentiation (LTP), as well as impaired learning and memory performance in a novel object recognition task. Taken together, these findings suggest that the astrocyte circadian clock regulates circadian rhythms in perineuronal net abundance as well as synaptic plasticity and behavioral learning and memory.

Astrocytes are crucial mediators of diverse aspects of brain function, including energy metabolism and synapse formation and maturation. Calcium is the primary information carrier in astrocytes, reporting cellular health and activity, and can be measured using fluorescent indicators. However, this readout is not yet widely used to screen and evaluate disease models and drug candidates. Here, we adapted a simple automated calcium imaging pipeline with key output parameters that characterize changes in astrocytic calcium signaling. We compared calcium responses in mouse astrocyte monocultures and astrocyte-neuron cocultures using GFAP-driven membrane-targeted GCaMP6f, with human astrocytes differentiated from two different induced pluripotent stem-cell lines using the calcium dye Cal520-AM. Event-based analysis reported similarities and differences in mean fluorescence, amplitude, frequency, duration, and area of calcium responses. We benchmarked the pipeline using the purinergic receptor agonist ATP to increase astrocyte activity, and the ER calcium pump blocker CPA to decrease activity across all culture models. Glutamatergic and serotonergic receptor function was tested with glutamate and lysergic acid diethylamide (LSD). LSD decreased activity in mouse cocultured astrocytes, but increased activity in human astrocytes. Furthermore, the addition of human recombinant Tau oligomers, an in vitro model of Alzheimers disease pathology, decreased activity in both mouse and human astrocytes. This pipeline can be used to quickly and easily characterize effects of astrocyte-targeting compounds, effects of non-astrocyte-targeting compounds on astrocyte activity, and rescue of disease models that affect astrocyte function, in mouse and human astrocytes and astrocyte-neuron cocultures.

Wolfram syndrome is a rare autosomal recessive disorder characterized by antibody-negative early-onset diabetes mellitus, optic atrophy, sensorineural hearing loss, arginine-vasopressin deficiency, and progressive neurodegeneration of the brainstem and cerebellum. It is caused primarily by pathogenic variants in the WFS1 gene, which encodes a transmembrane endoplasmic reticulum-resident protein involved in the unfolded protein response and cellular calcium homeostasis. Although multiple rodent models of Wolfram syndrome have been developed and shown to exhibit visual defects, some studies have reported significant vision loss prior to any detectable axonal degeneration or myelin abnormalities, and the mechanisms underlying these early visual deficits remain poorly understood. Recent in vitro studies have demonstrated altered synaptic contacts and aberrant neurite morphology in WFS1-deficient cerebral organoids and human iPSC-derived neurons, respectively. These findings prompted us to investigate, for the first time in vivo, whether synaptic and dendritic abnormalities occur in the retina of Wfs1 knockout mice. Using confocal microscopy, we examined retinal and optic nerve histology in Wfs1 knockout mice at 4 and 7 months of age. Our analysis reveals progressive synaptic alterations in the inner plexiform layer, driven by early presynaptic compartment failure. These changes represent the earliest detectable phenotype associated with vision loss in this model and precede overt axonal degeneration.

Motor performance and coordination deficits are hallmarks of spinocerebellar ataxias, yet effective disease-modifying therapies remain limited. Here, we investigate the expression of the interleukin 17 receptor subunit A (IL-17RA) in cerebellum and assess the therapeutic potential of its ligand in a mouse model for Spinocerebellar Ataxia Type 2 (SCA2). We found that IL-17RA is highly enriched in cerebellar molecular layer interneurons (MLIs), which provide inhibitory input to Purkinje neurons. In-vitro electrophysiological recordings revealed that symptomatic SCA2 mice exhibited increased spontaneous inhibitory synaptic input onto Purkinje neurons, which was normalized by IL-17A application to control levels. Concomitantly, IL-17A application restored Purkinje neuron firing, a parameter characteristically reduced in SCA2 mice. Behaviorally, intranasal administration of IL-17A restored motor performance of symptomatic SCA2 mice to control levels in both rotarod and beam-crossing assays. Collectively, our results indicate that IL-17A rescues Purkinje neuron dysfunction and motor deficits in SCA2 mice, highlighting IL-17A signaling as a promising therapeutic target for spinocerebellar ataxia.

The vagus nerve conveys interoceptive information, yet how specific vagal sensory afferents regulate pain remains unclear. Here, we tested whether vagus nerve stimulation (VNS) modulates temporomandibular disorder (TMD)-related pain. In a mouse model of TMD, auricular VNS (aVNS) attenuated temporomandibular joint (TMJ) pain behaviors and suppressed sensitization of trigeminal nociceptors. We identified a subset of vagal sensory afferents with dopaminergic features that was sufficient to mediate these effects, as selective activation of these afferents recapitulated the analgesic actions of aVNS. These findings highlight an underappreciated peripheral interoceptive pathway and provide a mechanistic framework for targeted neuromodulation in chronic craniofacial pain.

Synapses are the basic unit of information transfer between neurons. Their dysfunction is a common trigger of cognitive diseases and disorders. However, high-throughput analysis methods to assess synaptic function and dysfunction are lacking. Calcium imaging in cultured neurons in the absence of Mg2+ and presence of TTX allows visualization of NMDAR-dependent spontaneous synaptic calcium transients, which report pre and postsynaptic function. Here, we introduce a high-throughput automated analysis pipeline that combines Suite2p ROI detection and Python scripts to analyze tens of thousands of synapses and quantify changes in presynaptic vesicle fusion rates (frequency), postsynaptic function (amplitude), and the number of functional synapses. We use this pipeline to test known NMDAR agonists (glycine) and antagonists (ketamine, memantine, APV), presynaptic function modulating compounds (PDBu), and encephalitis patient-derived NMDAR auto-antibodies, where our pipeline proved more sensitive in detecting dysfunction at the single-synapse level than other methods. The ability to detect, track, and quantify activity across tens of thousands of synapses and millions of synaptic calcium transients using this pipeline will aid drug discovery of compounds that protect synapse function.

Alzheimers disease (AD) is a devastating neurodegenerative disorder characterized by memory loss and a decline in cognitive function. Hallmarks of AD include an age-dependent accumulation of toxic amyloid beta (A{beta}) 42 in the brain, energy dyshomeostasis caused by mitochondrial dysfunction, and iron overload. However, the role of iron overload and mitochondrial dysfunction in AD pathology is unknown and their precise relationship with A{beta} 42 toxicity in AD pathology is unclear. C. elegans provide a powerful model system to untangle and clarify these relationships. In this study, we quantify the temperature-dependence of iron toxicity (16, 20 and 25C) in neurons and muscle of C. elegans that overexpress A{beta} 42. We found that A{beta} 42, regardless of the cell-type expression, caused accelerated paralysis compared to age-matched WT worms with the greatest degree of paralysis observed at an elevated temperature (25C). Moreover, the combination of iron toxicity and A{beta} 42 results in an enhanced paralytic phenotype at 16C. Thus, iron exposure potentiates A{beta} toxicity observed at low temperatures. Iron toxicity stimulated both maximum (State 3) and leak (State 4) respiration in WT and A{beta} 42 worms. A{beta} 42 worms also exhibited increased leak respiration at baseline that was further exacerbated by iron toxicity. Iron burden and sensitivity increased A{beta} 42 peptide toxicity. A{beta} 42 worms exhibited reduced levels of Ca, Zn, Mn, and K. Overall, our results suggest that iron potentiates A{beta} toxicity at low temperature and enhances A{beta} peptide mediated mitochondrial bioenergetic dysfunction in C. elegans. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=140 SRC="FIGDIR/small/714217v1_ufig1.gif" ALT="Figure 1"> View larger version (29K): org.highwire.dtl.DTLVardef@9eaf46org.highwire.dtl.DTLVardef@542eforg.highwire.dtl.DTLVardef@16d9678org.highwire.dtl.DTLVardef@1b1b16d_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LITemperature stress modulates the synergetic interactions of iron toxicity and A{beta} 42 pathology C_LIO_LIIron sensitivity drives increased cell-type specific A{beta} 42 pathology C_LIO_LIEnergy dyshomeostasis via impaired mitochondrial function and increased proton leak contributes to iron- and A{beta}-induced pathology C_LI

A large subset of ASD associated genes, almost 50% of the highest confidence risk genes listed on the Simons Foundation Autism Research Institute database, are epigenetic modifiers. This suggests that the organization of sensory biology and its coupling to underlying genetic control are an important element underpinning this discord. Furthermore, sensory processing changes in individuals with autism spectrum disorder (ASD) has been a growing area of study in recent years. C. elegans have robust readouts for both developmental and sensory biology allowing these signatures of ASD to be systematically modelled. 52 epigenetic modifiers (65 strains) were selected for study in C. elegans based on gene function, presence of orthologues in C. elegans and the availability of viable putative null strains. This highlighted significant changes to reproduction, gross development and sensory processing across the range of epigenetic modifiers. Each strain was filtered against selective criteria for significant sensory and developmental phenotypes allowing for selective phenotypic profiles to emerge. These were three primary groups, those with sensory perturbations but unaffected gross development (6), developmentally affected genes with intact sensory function (10) and finally genes with impaired gross development and sensory function (11). Thus, this study provides a link between sensory and developmental outcomes in ASD associated mutant strains and suggests that more regular sensory testing should be performed in human cohorts to further refine sub-categorisation of ASD cohorts.