ASN Neuro

BackgroundMultiple sclerosis (MS) is a demyelinating disease of the central nervous system (CNS) that affects both the brain and spinal cord, although the brain has historically received greater attention. In the inducible, oligodendrocyte-specific knockout model of Myrf, which results in white matter damage to both the brain and spinal cord, our laboratory previously demonstrated that the brain undergoes partial remyelination following white matter damage, whereas the spinal cord fails to do so. We also observed that brain microglia display a much stronger activation than spinal cord microglia in this model. Microglia regulate remyelination by clearing myelin debris, processing resulting lipids, and modulating an inflammation response. ResultsHere, to test our hypothesis, we characterized microglial phenotypes during demyelination in both tissues. The brain exhibited greater early microglial recruitment and higher baseline expression of activation and phagocytic markers, suggesting a primed state for responding to damage. In contrast, spinal cord microglia showed delayed phagocytic marker expression, sustained inflammation, and a predominately amoeboid morphology during demyelination. ConclusionsTogether, these findings indicate that brain microglia mount a timely and coordinated response to demyelination that supports remyelination, whereas spinal cord microglia adopt a dysfunctional phenotype that may contribute to impaired myelin repair.

Multiple sclerosis (MS) is an autoimmune and neurological disorder characterized by myelin disruption and neuronal degeneration. Currently approved therapies focus on symptom relief but do not promote central nervous system (CNS) repair. In contrast, astrocytes proliferate and repopulate MS-related lesions. Moreover, in active lesions, they hinder regenerative processes such as neural progenitor migration. Here, we propose astrocytes as a potential target for myelin repair in the human diseased brain. To achieve this aim, we investigated whether glial fibrillary acidic protein (GFAP)+ astrocytes can be transdifferentiated into oligodendrocyte lineage cells through forced overexpression of transcription factors both in vitro and ex vivo organotypic cultures of human adult cortex. Our results show that overexpression of OLIG2 and SOX10 in human induced pluripotent stem cell-derived astrocytes gives rise to oligodendrocyte progenitor cells 12 days post-induction, as shown by morphological changes and O4 marker expression. Importantly, transdifferentiation of GFAP-expressing endogenous astrocytes in human adult cortical tissue give rise to mature oligodendrocytes, as shown by expression of CC1, after only 12 days of overexpression of OLIG2 and SOX10. To our knowledge, this is the first study to assess direct astrocyte-to-oligodendrocyte reprogramming in a human platform preserving the native three-dimensional architecture of the brain. Further work will be required to determine whether the reprogrammed cells can myelinate axons and to evaluate the potential of this approach for structural and functional repair in the demyelinated human CNS.

Quantitative assessment of optic nerve health requires metrics beyond axon counts alone. Axon density and glial coverage fraction correlate with clinical measures of visual function, yet no existing automated tool extracts optic nerve cross-sectional boundaries to enable their calculation. We developed MONICA (Morphometrics from Optic Nerve Imaging Contour Analysis), a web application that integrates AxonDeepSeg deep learning segmentation with a novel morphology-based contour extraction algorithm to automatically derive whole nerve boundaries alongside axon and myelin masks. The contour extraction algorithm was validated against manual ground truth annotations using 15 optic nerve cross-sections spanning two taxonomic orders (mouse, rabbit), two mouse strains (BXD29, BXD51), and varying preparation quality levels (modern and archival samples). Automated contour extraction demonstrated excellent agreement with manual annotations, achieving an overall Dice similarity coefficient (a measure of segmentation overlap) of 0.987 {+/-} 0.009. Balanced precision (0.985) and recall (0.989) values indicated that the algorithm neither systematically over-segments nor under-segments nerve boundaries. MONICA requires no local software installation and runs entirely in-browser, providing batch processing for high-throughput phenotyping alongside a full suite of per-axon morphometrics. MONICA provides researchers with an accessible tool for complete nerve cross-section morphometry.

BackgroundPeri-synaptic astrocyte processes (PAPs) play a fundamental role in synapse formation and function. Central afferent synapse loss and astrocyte dysfunction greatly impede sensory-motor circuitry in spinal muscular atrophy (SMA) disease progression, however mechanisms underpinning tripartite synapse dysfunction remains to be fully elucidated. The aims of this study were to further define PAP and motor neuron synaptic defects in human SMA disease pathology and implement a therapeutic intervention strategy to improve motor neuron function. MethodsWe derived astrocyte monocultures and motor neuron astrocyte co-cultures from healthy and SMA patient induced pluripotent stem cell (iPSC) lines to assess intrinsic astrocyte filopodia defects and phenotypes occurring at the synapse-PAP interface, respectively, using cell surface capture mass spectrometry proteomics, confocal and super resolution microscopy, synaptogliosome isolation, and electrophysiology. ResultsSMA astrocytes demonstrated intrinsic filopodia actin defects featuring low abundance of actin-associated cell surface N-glycoproteins, and decreased filopodia density and CDC42-GTP levels after actin remodeling stimulation. This phenotype is likely driven by the significant reduction of CD44 and phosphorylated ezrin, radixin and moesin ERM proteins (pERM) within SMA astrocyte filopodia. The dual combination of SMN1 gene therapy and forskolin treatment, an adenylyl cyclase activator leading to increased cyclic adenosine monophosphate (cAMP) levels and actin signaling pathway stimulation, led to extensive branching and increased filopodia density of SMA astrocytes during actin remodeling. SMA patient-derived motor neuron and astrocyte co-cultures, particularly samples derived from male patient iPSC lines, demonstrated a significant decrease in synapse number, actin-associated pre-synaptic neurotransmitter release protein, synapsin I (SYN1), and PAP-associated expression of pERM and glutamate transporter, EAAT1. Our astrocyte-targeted SMN1 augmentation and forskolin treatment paradigm restored SYN1 protein levels within the SMA synaptogliosome, resulting in significant increases in motor neuron synapse formation and function, but did not fully restore PAP-associated proteins levels at the synapse. ConclusionsSMA astrocytes demonstrate intrinsic actin-associated defects within filopodia, which correlates with decreased pERM levels at tripartite motor neuron synapses. We also define a SMN- and cAMP-targeted treatment paradigm that significantly increases pre-synaptic neurotransmitter release protein levels to improved SMA motor neuron synapse formation and function. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=117 SRC="FIGDIR/small/714618v1_ufig1.gif" ALT="Figure 1"> View larger version (44K): org.highwire.dtl.DTLVardef@1257ab8org.highwire.dtl.DTLVardef@19c0010org.highwire.dtl.DTLVardef@c84552org.highwire.dtl.DTLVardef@3f1e62_HPS_FORMAT_FIGEXP M_FIG C_FIG

Mutations in human LIS1 cause lissencephaly, a severe developmental brain malformation. Although most stud-ies focus on development, LIS1 is also expressed in adult mouse tissues. We previously induced LIS1 knockout (iKO) in adult mice using a Cre-Lox approach with an actin promoter driving CreERT2 expression. This proved to be rapidly lethal, with evidence pointing toward nervous system dysfunction. CreERT2 activity was observed in astrocytes, brainstem and spinal motor neurons, and axons and Schwann cells in the sciatic and phrenic nerves, suggesting dysfunctional cardiorespiratory and motor circuits. However, it is unclear how LIS1 knockout in these different cell types contributes to the lethal phenotype. We now report that LIS1 depletion from astro-cytes is not lethal to mice (male or female), although glial fibrillary protein (GFAP) expression is increased in all LIS1-depleted astrocytes. In contrast, LIS1 depletion from projection neurons causes motor deficits and rapid lethality in both males and females. This is accompanied by progressive, widespread axonal degeneration along the entire length of both motor and sensory axons. Interestingly, sensory neurons harvested from iKO mice ini-tially extend axons in culture but soon develop axonal swellings and fragmentation, indicating axonal degenera-tion. LIS1 is a prominent regulator of cytoplasmic dynein 1 (dynein, hereafter), a microtubule motor whose dis-ruption can cause both cortical malformations and later-onset neurodegenerative diseases, such as Charcot-Marie-Tooth disease. Our results raise the possibility that LIS1 depletion, through disruption of dynein function in mature axons, may lead to Wallerian-like axon degeneration without traumatic nerve injury.

Highly aggressively proliferating immortalized (HAPI) cells were initially described as a spontaneously immortalized rat cell line isolated from a mixed neonatal rat glial population. It was demonstrated that HAPI cells are phagocytic, stain for macrophage-/microglia-specific markers like CD11b and GLUT5, and exhibit lipopolysaccharide (LPS)-induced nitric oxide (NO) and tumor necrosis factor-alpha (TNF-) release. These characteristics led to their widespread use as a rat microglial cell line. Here, we report that HAPI cells are mouse cells, not rat cells, but further establish that they have a microglia-like identity and properties useful for in vitro modeling. Cell line authentication by short tandem repeat (STR) profiling, a method that detects identifying DNA signatures, indicates that HAPI cells are a 100% match for SIM-A9 cells, a mouse microglial cell line reported to be spontaneously immortalized from primary cell culture. We find that both HAPI cells and SIM-A9 cells express the microglia-selective gene Tmem119, as well as the microglia-/macrophage-selective marker Cx3cr1, supporting a microglial origin. Like primary rodent microglia or macrophages, HAPI cells respond to combined stimulation with LPS and the Type II interferon, interferon-gamma (IFN-{gamma}), with a pro-inflammatory morphology, NO production, NO-dependent suppression of mitochondrial oxygen consumption, and increased extracellular acidification (an indicator of glycolysis). The Type I interferon, interferon-alpha (IFN-), also reduces mitochondrial oxygen consumption when administered alone or in combination with LPS. Overall, results indicate that HAPI cells are SIM-A9-related mouse cells of microglial origin and support their continued use to study microglial behavior in vitro, including immunometabolism.

Traumatic spinal cord injuries (SCIs) often result in permanent disabilities in humans. One major reason for the lack of recovery is the inability of adult mammalian descending neurons to regenerate their axons after injury. In contrast, several fish species, such as the sea lamprey, exhibit spontaneous axon regeneration and successful functional recovery following a complete SCI. Recent studies have shown that a SCI in rodents and humans induces gut microbiome dysbiosis, which can impair recovery. Therefore, our goal was to examine how the microbiome changes after SCI in a regenerating animal model (the larval sea lamprey) and whether these changes influence the spontaneous regeneration of descending neuropeptidergic (cholecystokinergic) axons. Our data show that a complete SCI triggers an initial shift (5 weeks post-injury) in gut microbial communities in larval lampreys, characterized by an expansion of Legionellaceae family members. However, a treatment with broad-spectrum antibiotic gentamicin during the first 5 weeks post-injury, which completely disrupted the gut microbiome (eliminating Legionellaceae and promoting Bradyrhizobiaceae expansion), did not affect the spontaneous regeneration of descending cholecystokinergic axons at 10 weeks post-injury. This finding indicates that changes in the intestinal microbial communities following a complete SCI probably do not influence the spontaneous regeneration of descending axons in lampreys.

K+ channels are important for controlling membrane potential and regulating functional properties of microglia. Whereas the inward-rectifying K+ (Kir) channel 2.1 modulates proliferation, voltage-gated K+ channels (Kv) are linked to inflammatory response in mouse microglia (mMG). These channels serve as possible drug targets but little is known regarding their activity in human microglia. We used patch-clamp recording to study membrane currents of primary human microglia (hMG) and human induced pluripotent stem cell-derived microglia-like cells (hiPSC-MGL) and compared them with mMG. Unlike mMG, hMG and hiPSC-MGL exhibited Kir2.1 currents only after LPS+IFN-{gamma} stimulation. Interestingly, Kv currents were not observed in hMG or hiPSC-MGL under any condition. While mMG had a progressively ameboid morphology after stimulation, hMG showed few morphological changes and hiPSC-MGL increased ramification. Overall, the activity of Kir2.1 and Kv channels in hMG and hiPSC-MGL differs fundamentally from mMG. Our findings highlight differences between species and underscore the need for translational approaches.

Oligodendrocyte progenitor cells (OPCs) have the capacity to self-renew, differentiate, and remyelinate the CNS. Aging is associated with a reduction in the functional capacity of OPCs even in the absence of an autoimmune insult. To determine how aging affects the response of oligodendroglia to a strong inflammatory insult comparable to an immune-mediated demyelinating event in multiple sclerosis (MS), we performed adoptive transfer of young myelin-reactive Th17 T cells into young and aged OPC lineage tracing mice. After adoptive transfer, OPCs were enriched within spinal cord lesions of both young and aged mice. However differentiated oligodendrocytes (OLs) were significantly reduced after adoptive transfer. Both young and aged OPCs differentiated into mature OLs during adoptive transfer. Transmission electron microscopy revealed thinly myelinated axons without degenerative features that likely represent remyelinated axons in lesions of both age groups. Young and aged OPCs rise to the challenge after a strong auto-immune attack, suggesting that compensatory strategies permit both young and aged oligodendroglia to survive despite an inflammatory environment. Identifying pathways that promote resilience of oligodendroglia in the face of an inflammatory challenge will facilitate the development of remyelinating therapies for people with MS.

Acute spinal cord injury triggers a complex secondary injury cascade characterized by lesion expansion, neuroinflammation, glial reactivity, and oligodendrocyte degeneration, which together limit endogenous repair. Identifying neuroprotective interventions capable of targeting distinct components of this cascade remains a major challenge. In this study, we compared the neuroprotective profiles of minocycline, a tetracycline derivative with anti-inflammatory and antioxidant properties, and bone marrow mononuclear cells (BMMCs), which exert paracrine immunomodulatory and trophic effects, using a model of complete thoracic spinal cord transection in adult rats. Animals received either BMMCs (5 x 106 cells, intravenously, 24 h post-injury) or minocycline (50 mg/kg twice daily for 48 h, followed by 25 mg/kg for five days). Histological and immunohistochemical analyses revealed that both treatments attenuated secondary damage, reducing lesion area, microglial/macrophage activation (ED1+ cells), and oligodendrocyte pathology (Tau-1+ cells). However, the magnitude and pattern of protection differed between interventions: minocycline produced a stronger reduction in lesion area, whereas BMMCs exerted greater suppression of microglial/macrophage activation and superior preservation of oligodendrocytes. Astrocyte counts (GFAP+ cells) did not differ quantitatively among groups, despite qualitative differences in astrocytic morphology. Integrated effect size analysis further highlighted these complementary neuroprotective profiles across outcomes. Collectively, these findings indicate that minocycline and BMMCs target distinct components of secondary injury after severe spinal cord injury, providing a mechanistic rationale for future studies exploring multi-targeted or combinatorial therapeutic strategies.

Tau protein, the primary component in neurofibrillary tangles characteristic of Alzheimers Disease and related dementia disorders, normally regulates microtubule growth and stability. While tau dysfunction contributes to the progression of tauopathies, the role of microtubules in disease has remained unclear. Through forward genetic screening in Caenorhabditis elegans tauopathy models, we found multiple tubulin gene mutations that rescue tau-mediated neurodegeneration. Whole animal behavioral and in vitro biochemical assays were employed to characterize mutation-driven effects on neuron function, neurodegeneration, and effects on tubulin and tau proteins as well as microtubule function. Mutant tubulin genes were found to confer different levels of suppression correlating with the level of mutant gene expression. Mutant tubulins did not drastically alter total tau protein levels, tau phosphorylation or aggregation, however tau-induced neurodegeneration was rescued. The suppression of tau toxicity by tubulin gene mutations cannot be explained by changes in tau or tubulin expression, tau phosphorylation, or tau aggregation state. Rather the tubulin mutations appear to act by influencing global microtubule properties. In vitro experiments using C. elegans tubulin in semi-isolated and isolated contexts have indicated changes to microtubule properties without observable changes to tau-tubulin affinity. This work suggests that manipulation of microtubules can rescue tauopathy even when pathological tau species persist, supporting the importance of understanding microtubule contributions to disease progression and investigation into microtubule targeted gene therapy or small molecule approaches for tauopathy intervention.

Parkinsons Disease (PD) is the second most common neurodegenerative disease, with many cases being attributed to environmental contaminant exposures. Paraquat (PQ), is a pesticide and environmental neurotoxicant that has been strongly associated with increased risk of PD. PQ is known to be a weak inhibitor of complex I of the electron transport chain, and while its acute toxicity is well understood, the underlying mechanism by which PQ exposure contributes to PD pathophysiology remains unclear. Additionally, the mechanism of PQ neurotoxicity has yet to be effectively compared and related to genetic forms of PD. Given that PD is a heterogeneous disease with both genetic and environmental determinants, we sought to systematically compare the proteomic changes that occur in different genetic and environmental models of PD. In this study, we leveraged untargeted omics approaches to differentiate between systemic, peripheral, and CNS-specific changes in the proteome. We did this by performing a comparative proteomic analysis on the heads and bodies of Drosophila models of PQ ingestion and neuronal -synuclein expression in males. Additionally, we validated the findings with metabolomic analysis of male and female brain stems from a murine PQ inhalation model using C57BL/6J mice. Our findings indicate shared dysregulated pathways across all models, highlighting similar mechanisms of action. Specifically, we identified a glia-specific role in purine nucleotide metabolism upstream of inosine catabolism, which may protect against PQ neurotoxicity. This work identifies potential early points for biomarker detection and potential targets for drug intervention. Significance StatementNeurodegenerative diseases such as Parkinsons disease (PD) pose a growing public health burden, yet disease-modifying therapies remain limited due to lack of mechanistic understanding and disease heterogeneity. Both genetic and environmental factors contribute to PD, complicating the identification of shared therapeutic targets. Here, we identify a convergent pathway common to genetic and environmental models of Parkinsonism that not only affects the brain but also systemically. Using integrated metabolomics, proteomics, and genome-scale metabolic modeling, we demonstrate that purine metabolism is dysregulated across models. Reverse genetic screening of key enzymes in this pathway mitigates locomotor deficits induced by neurotoxic pesticide exposure in Drosophila. These findings reveal a shared metabolic vulnerability in PD and highlight purine metabolism as a potential therapeutic target.

Excitatory glutamatergic synapses in the brain are remarkably plastic. Two forms of plasticity have received the most attention: long-term potentiation (LTP) and synaptic homeostasis. While LTP requires the activation of NMDA receptors, synaptic homeostasis does not. However, both phenomena are mediated by the recruitment of postsynaptic AMPA receptors to the synapses. Recently a new form of plasticity has been described referred to as presynaptic homeostatic plasticity (PHP) (Chipman et al., 2022; Chipman et al., 2025). Pharmacological inhibition of AMPA synaptic responses in CA1 hippocampal pyramidal cells initiates a rapid homeostatic response that results in the recovery of the AMPA responses to normal values in the continued presence of the inhibitor. Accompanying this recovery is a doubling of the NMDA response which is interpreted as an increase in the release of glutamate. This is provocative since it is the first report claiming that a reduction in AMPA responses triggers an enhancement in NMDA responses. Using three different protocols to monitor synaptic responses we fail to observe any recovery of synaptic responses in the presence of an AMPA inhibitor. Furthermore, there was no enhancement in NMDA responses. Thus, we find no evidence for the presence of PHP at CA1 hippocampal synapses.

IntroductionThe exploration of alternative strategies for neural tissue regeneration and repair is giving rise to a novel paradigm in neurosurgery: fusogenic therapy. This approach promises rapid restoration of peripheral nerve and spinal cord function by circumventing Wallerian degeneration and eliminating the delay associated with axonal regrowth. Its potential stems from the capacity of fusogens to induce axonal fusion and achieve immediate membrane sealing, complemented by their pronounced neuroprotective properties. However, experimental data on fusogens and their effects are inconsistent, often contentious, and derived using heterogeneous methodologies. MethodsWe present the first comprehensive systematic review covering nearly four decades of research on fusogens for axonal membrane repair and 26 years of their experimental and clinical application in mammalian and human models for peripheral and central nervous system restoration. The review includes a meta-analysis of fusogen efficacy following traumatic spinal cord and peripheral nerve injuries. ResultsConducted in accordance with the PRISMA 2020 flow protocol and PICO criteria, our analysis incorporates 86 sources, 20 of which were included in the meta-analysis. DiscussionIn summary, we have systematized the prevailing approaches and methods for fusogen application, delineated key contentious issues, and identified promising directions for the development of axonal fusion technology.

ObjectiveTo determine whether non-axon optic nerve morphometric features correlate with clinical visual function as strongly as the traditional axon count gold standard. DesignCross-sectional histological analysis with longitudinal clinical correlation. SubjectsEighteen mice from three strains: C57BL/6J (n=6), BXD51 (n=6), and DBA/2J (n=6). MethodsLeft eye (OS) optic nerves from mice euthanized at 12 months of age were resin-embedded and stained with p-phenylenediamine. Bright-field cross-sectional images were segmented using an AxonDeepSeg-based workflow to generate axon, myelin, whole nerve, and glial coverage masks for morphometric quantification. Seven morphometrics were extracted: axon count (nAx), axon density (AxDen), glial coverage area ratio (GliaR), mean solidity (Sol), mean axon diameter (AxDiam), mean myelin area (MyArea), and mean axon-myelin area (AxMyArea). Morphometrics were correlated with longitudinal clinical data collected at 1, 3, 6, 9, and 12 months, including visual acuity (VA), contrast threshold, intraocular pressure (IOP), and pattern electroretinography P50 and N95 amplitudes (PERG P50 and N95). Main Outcome MeasuresPearson correlation coefficients were used to assess associations between morphometric features and clinical measures, and Fisher z-transformed meta-analytic correlations were used to aggregate these associations across ages. ResultsVA and contrast threshold demonstrated strong correlations with GliaR that matched or exceeded nAx. Meta-analysis across ages revealed GliaR correlated with VA (r = -0.84, p = 4.49 x 10-21) and contrast threshold (r = 0.86, p=7.55 x 10-23), comparable to nAx correlations with VA (r = 0.80, p=8.13x10-17) and contrast threshold (r = -0.80, p= 1.74x10-16). Structure-function relationships shifted with age: at 6 months, GliaR had the strongest correlation with contrast threshold (r = 0.96), while at 12 months, AxDiam became the dominant correlate of both VA (r = 0.77) and contrast threshhold (r = -0.74). IOP, PERG P50, and PERG N95 exhibited weak correlations with all morphometrics (|r| < 0.27). ConclusionsNon-axon morphometrics, particularly glial coverage area ratio, correlate with visual function as strongly as traditional axon count. Automated optic nerve assessment should incorporate glial and other non-axon features. Further, stage-aware biomarker selection may better capture structure-function relationships in glaucoma.

In mammals, a dysregulated immune response is detrimental to spinal cord repair. In zebrafish, which are capable of spinal cord regeneration, the immune response promotes regeneration. Neutrophils are the first immune cells to arrive at a spinal cord injury site, but their role in successful regeneration is not fully understood. Here we show that ablating neutrophils, including a subpopulation that expresses the cytokine il4, increases expression of il1b (coding for Il-1{beta}) in macrophages/microglia and impairs anatomical and functional recovery after a spinal cord injury in larval zebrafish. Regeneration is fully rescued by over-expression of il4 alone or experimentally reducing Il-1{beta} levels. Disruption of il4 mimics the detrimental effect of neutrophil ablation for axonal regeneration and is also rescued by reducing Il-1{beta} levels. Hence, after spinal cord injury, a pro-regenerative neutrophil subpopulation promotes spinal cord regeneration in larval zebrafish by controlling expression of il1b in macrophages/microglia. For this neutrophil action, il4 expression is necessary and sufficient. HIGHLIGHTS- Neutrophil ablation impairs spinal cord repair in zebrafish - The neutrophil response can be replaced by reducing Il-1{beta} levels - A pro-regenerative subpopulation of neutrophils expresses il4 - il4 overexpression fully rescues effects of neutrophil ablation

Voltage-gated CaV2.2 channels are essential for neurotransmitter release throughout the nervous system including areas related to learning and memory like the hippocampus. Previous results have shown that CaV2.2 channels are involved in cognitive processes. However, a link between alternative splicing of the Cacna1b (gene that encodes for CaV2.2) pre-mRNA and cognitive processes has not been described. The Cacna1b pre-mRNA undergoes extensive cell-specific alternative splicing. In this body of work, we focus on the cassette exon 18a. Alternative splicing of exon 18a generates two splice variants, +18a-Cacna1b and {Delta}18a-Cacna1b. Exon 18a encodes a 21-amino acid sequence within the SYNaptic PRotein INTeraction (synprint) site. Splice variants containing exon 18a (+18a-CaV2.2) show reduced cumulative inactivation and increased Ca{superscript 2} current density compared to splice variants lacking exon 18a ({Delta}18a-CaV2.2), suggesting functional specialization. We previously showed that +18a-Cacna1b splice variants are enriched in cholecystokinin-expressing interneurons (CCK+INs). This neuronal type is strongly implicated in associative learning. Therefore, we tested whether alternative splicing of exon 18a contributes to associative learning. To test this hypothesis, we used genetically engineered mice that constitutively express either +18a-Cacna1b (+18a) or {Delta}18a-Cacna1b ({Delta}18a). We first validated that restricted splicing of exon 18a did not alter downstream alternative or constitutive spliced exons in the Cacna1b pre-mRNA, nor total CaV2.2 protein levels. We then performed a comprehensive behavioral analysis that included assessment of associate learning. We found that in the trace fear conditioning task, +18a mice exhibited less freezing during the trace interval in both the acquisition and memory phases compared to WT mice. Whereas {Delta}18a mice showed enhanced freezing during the same intervals relative to WT mice. These bidirectional phenotypes reveal that exon 18a shapes aversive associative learning. Furthermore, exon 18a splicing did not influence spatial working memory, spatial navigation under stress, nociceptive responses in basal and inflammatory conditions, overall locomotion or exploratory behavior. These results suggest that the behavioral impact of exon 18a splicing is highly selective. Together, our findings identify alternative splicing of exon 18a as a molecular contributor to associative learning.

Glia are irreplaceable components for the nervous system development and function. However, the cellular mechanisms each glial layer utilizes to communicate with each other and the extracellular environment is not well characterized. Here, we investigated the role of a heparan-sulfate proteoglycan, Syndecan (Sdc), in regulating glial cell function and development in the Drosophila nervous system. Sdc is expressed throughout multiple glial layers and loss of Sdc in all glia resulted in disruption of both central and peripheral glia. Within the CNS loss of Sdc in all glia lead to reduced brain lobes and disruption of neuroblast proliferation. In the PNS, loss of Sdc in different glial layers resulted in impaired ensheathment in wrapping glia and abnormal septate junction morphology in subperineurial glia. We focused on the outer layer of perineurial glia and found ensheathment defects and a reduction in glial numbers with Sdc loss. These phenotypes mirror those previously observed with the loss of integrins and a mutation in the integrin {beta}-subunit enhanced the phenotypes observed with loss of Sdc within the perineurial. Thus, our results indicate Sdc has multiple roles in Drosophila nervous system development including as an integral component in regulating glial cell morphology, maintaining neuroblast populations within the optic lobe and in mediating glial-ECM interactions.

Temozolomide (TMZ) resistance remains a major obstacle in glioblastoma (GBM) therapy, yet the metabolic adaptations underlying this phenotype are incompletely understood. Here, we performed integrative lipidomic, ultrastructural, and pathway analyses to define lipid metabolic reprogramming associated with TMZ resistance and failure of statin-mediated sensitization. Targeted LC-MS lipidomics quantified 322 lipid species across 25 lipid classes in TMZ-sensitive and TMZ-resistant U251 cells under basal conditions and following TMZ, simvastatin, or combination treatment. Multivariate analyses (PCA, PLS-DA, and volcano plots) revealed a robust and treatment-resilient lipidomic signature in resistant cells characterized by enrichment of lysophospholipids, sphingolipids, and cholesteryl esters, alongside depletion of glycerolipid and phospholipid pools. Complementary univariate analysis confirmed these changes at the species level, demonstrating consistent elevation of lysophosphatidylcholine/ethanolamine, glycosphingolipid subclasses, and cholesteryl esters, together with reductions in phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol, and diacylglycerol intermediates across multiple treatment conditions. In contrast, sensitive cells displayed dynamic lipid remodeling, including phosphatidylinositol and phosphatidylethanolamine enrichment associated with autophagic membrane expansion. KEGG pathway analysis linked the resistant phenotype to Rap1, PI3K-Akt, and phospholipase D signaling networks regulating vesicle trafficking and membrane homeostasis. Transmission electron microscopy confirmed a vesicle-rich intracellular architecture consistent with persistent autophagy flux blockade in resistant cells. Collectively, these findings define a stable lipid metabolic program characterized by lysophospholipid expansion and cholesteryl ester accumulation that supports membrane integrity and therapeutic resistance. Targeting lipid buffering and cholesterol storage pathways may represent a promising strategy to overcome chemoresistance in glioblastoma. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=134 HEIGHT=200 SRC="FIGDIR/small/712341v1_ufig1.gif" ALT="Figure 1"> View larger version (78K): org.highwire.dtl.DTLVardef@178acd7org.highwire.dtl.DTLVardef@19b6a79org.highwire.dtl.DTLVardef@6b3904org.highwire.dtl.DTLVardef@16c3d01_HPS_FORMAT_FIGEXP M_FIG C_FIG Lipidomic and autophagy differences between non-resistant (NR) and temozolomide-resistant (R) glioblastoma cells. NR cells show dynamic lipid remodeling and treatment-dependent autophagy responses, whereas R cells maintain blocked autophagy flux and persistent enrichment of LPC, SM, and cholesteryl esters across treatments.

Riluzole is the most commonly prescribed among the limited approved therapies for amyotrophic lateral sclerosis (ALS), a neurodegenerative disorder characterized by progressive motoneuron loss and paralysis. It is thought to act by suppressing motoneuron excitability and glutamate release, but its clinical benefits are modest and often diminish over time. We previously showed that homeostatic mechanisms in the SOD1G93A (mSOD1) mouse model of ALS are hyperactive and prone to overcompensation. Here, we tested whether such dysregulated homeostasis antagonizes the effects of riluzole. Wild-type (WT) and presymptomatic mSOD1 mice received therapeutic doses of riluzole in drinking water for 10 days, with untreated littermates of both genotypes serving as controls. Motoneuron excitability and synaptic inputs were then examined using intracellular recordings from the isolated sacral spinal cord. The data showed that chronic riluzole treatment increased motoneuron excitability and polysynaptic inputs in mSOD1 mice but produced no detectable changes in WT motoneurons. These results suggest that hyperactive homeostatic mechanisms in ALS counteract the suppressive effects of riluzole. Notably, mSOD1 motoneurons exhibited larger membrane capacitance than WT, consistent with their increased cell size at this disease stage. Riluzole treatment reduced motoneuron membrane capacitance in mSOD1 mice to the range observed in WT animals, indicating normalization of cell size and potentially reduction in metabolic demand. Together, these findings help explain the limited clinical efficacy of riluzole while revealing a previously unrecognized neuroprotective mechanism of the drug in ALS.