Neuroscience
Abstract
Epilepsy affects approximately 50 million people worldwide, yet more than half of individuals with a presumed genetic cause still lack a molecular diagnosis despite the identification of over 1,000 monogenic epilepsy genes. This diagnostic gap is unlikely to be resolved by improved variant detection alone, suggesting that variants affecting the same biological pathway may combine to cause disease. By studying epilepsy-associated actin regulatory genes, we identified a conserved “actin-mitochondria-glutamate (AMG) pathway”. We demonstrate that reduced actin polymerization promotes DRP1-mediated mitochondrial fission, increases reactive oxygen species (ROS) levels, and enhances glutamatergic transmission, leading to seizures. The glial innate immune pathway, a recently recognized contributor to epilepsy, is activated when the AMG pathway is affected. Reducing mitochondrial fission with the DRP1 inhibitor Mdivi-1, or suppressing ROS with N-acetyl-L-cysteine amide (NACA), significantly alleviates seizures. Importantly, digenic heterozygous loss‑of‑function variants in AMG‑pathway genes combine to cause seizures, and individuals with epilepsy of unknown etiology show an increased burden of such variants when compared to the controls. Modeling patient‑specific digenic combinations in Drosophila confirms that many combinations promote seizure susceptibility. Together, these findings establish the AMG pathway as a mechanistic framework for identifying digenic etiologies in epilepsy and highlight potential therapeutic targets.
Authors
Shenzhao Lu, Mengqi Ma, Shabab B. Hannan, Mingxi Deng, Hu Chen, Zhijian Yu, Lindsey D. Goodman, Haein Kim, Yun Zhao, Sandeep Kumar Dubey, Wen-Wen Lin, Xueyang Pan, Debdeep Dutta, Vishnu Anand Cuddapah, Jill A. Rosenfeld, Xi Luo, Zhandong Liu, Joshua M. Shulman, Hugo J. Bellen
Abstract
Opioids are essential analgesics for managing severe pain but can paradoxically increase pain sensitivity (hyperalgesia) and diminish analgesic efficacy (tolerance). Hyperactivity of NMDA-type glutamate receptors (NMDARs) at primary afferent terminals in the spinal cord contributes to both phenomena; however, the underlying signaling mechanisms remain unclear. Here, we report that morphine administration in rats promoted the translocation of monomeric BRAF, an oncogenic kinase, from the dorsal root ganglion (DRG) to spinal cord synaptosomes, leading to increased MEK-ERK phosphorylation at nociceptor central terminals. BRAF physically interacted with NMDARs in both rat and human spinal cords. Inhibition of BRAF activity with vemurafenib reversed morphine-induced NMDAR phosphorylation and synaptic localization of α2δ-1–bound NMDARs. Vemurafenib also abolished morphine-induced presynaptic NMDAR hyperactivity in spinal dorsal horn neurons. Correspondingly, conditional Braf knockout in DRG neurons normalized morphine-enhanced NMDAR phosphorylation, synaptic trafficking of α2δ-1–bound NMDARs, and NMDAR hyperactivity in the spinal cord. Furthermore, pharmacological inhibition of BRAF or MEK, or Braf deletion in DRG neurons, enhanced morphine analgesia while mitigated morphine-induced hyperalgesia and tolerance. These findings identify BRAF overactivity at nociceptor central terminals as a key mediator of opioid-induced NMDAR hyperactivity. Clinically approved BRAF inhibitors could be repurposed to enhance opioid analgesia while minimizing adverse effects.
Authors
Daozhong Jin, Hong Chen, Yuying Huang, Shao-Rui Chen, Hui-Lin Pan
Abstract
Trigeminal neuralgia (TN) is a severe orofacial pain disorder accompanied by anxiety, yet its central mechanisms remain elusive. Analysis of human fMRI data identified the parafascicular nucleus (PF) as a candidate region. Using a TN mouse model, we uncovered two spatially and functionally distinct PF neuronal ensembles that separately encoded sensory and affective dimensions of pain. One population received inhibitory input from GABAergic neurons in the oral spinal trigeminal nucleus (Sp5O) and mediated nociception. The second population, driven by a glutamatergic Sp5O-lateral parabrachial nucleus (lPBN)-PF pathway, encoded pain-related anxiety. The engagement of the anxiety-encoding ensemble lagged behind that of the pain-encoding ensemble, with a shorter delay in females. Single-nucleus RNA sequencing identified Col25a1 and Syn2 as markers of the anxiety-encoding ensemble. Notably, this population, localized in the medial PF, formed a reciprocal lPBN-mPF-lPBN excitatory-feedback loop that sustained affective pain. These findings positioned PF as a key node linking pain and emotion in TN.
Authors
Yitian Lu, Yangyang Yi, Jiao Liu, Hao Zhi, Qing Chang, Zihao Huang, Yumeng Chen, Han L. Tan, Yiheng Tu, Yun Wang, Cheng Cen
Abstract
Sarcopenia is the age-related loss of muscle strength and size that leads to mobility limitations and loss of independence in older adults. The underlying cellular mechanisms remain unclear, and treatments are limited. As the critical interface between the nervous system and muscle, the neuromuscular junction (NMJ) is essential for muscle activation and force production. Here, we demonstrate that weak older individuals exhibit NMJ transmission failure that correlates with muscle weakness severity. Preclinical experiments showed similar NMJ transmission failure in aged rodents that was associated with localized loss of muscle fiber excitability at the NMJ. This excitability defect, distinct from potential synaptic cholinergic transmission abnormalities, represents a novel disease mechanism of sarcopenia. Across species, immunohistochemistry identified a localized reduction in the voltage-gated sodium channel specific for skeletal muscle (NaV1.4) at the post-synaptic NMJ membrane. Acute NaV1.4 inhibition with μ-conotoxin GIIIB in adult rats reproduced findings of NMJ transmission failure observed in aged rodents and humans. Finally, ClC-1 chloride ion channel inhibition enhanced muscle excitability and improved NMJ transmission and muscle function in old rodents. Together, these findings demonstrate that NMJ transmission deficits are a key, reversible driver of sarcopenia and reveal a novel therapeutic target for addressing muscle weakness in aging.
Authors
W. David Arnold, Jeanette Jeppesen Morgen, Pernille Bogetofte Thomasen, Martin Broch-Lips, Leatha A. Clark, Thomas Groennebaek, Martin Skov, Jeppe Blichfeldt Winther, Abdullah F. Ramadan, Philippa A. Rust, Jessica H. Myers, Fereshteh B. Darvishi, Anna R. Dashtmian, Lauren A. Fish, Deepti Chugh, Jane Bold, Jorge A. Quiroz, John Hutchison, Hiroshi Nishimune, Ross A. Jones, Xueyong Wang, Justin R. Fallon, Thomas H. Gillingwater, Mark M. Rich, Thomas Holm Pedersen, Brian C. Clark
Abstract
Kleefstra syndrome (KLEFS1) results from EHMT1 haploinsufficiency and is characterized by variable neurodevelopmental delays and psychopathology. Developmental regression, marked by the sudden loss of previously acquired daily life skills during late puberty or early adulthood, has emerged as a severe complication in individuals with KLEFS1. To investigate the clinical and molecular mechanisms underlying developmental regression and assess the therapeutic potential of olanzapine, we conducted a sequential study in an international cohort of fifty-four individuals with KLEFS1. Among sixteen individuals treated with olanzapine, ten exhibited a beneficial response based upon improvement of their adaptive functioning, and four showed temporary improvement. These clinical findings informed preclinical studies using human induced pluripotent stem cell-derived and ex-vivo cortical slices from a mouse model of KLEFS1. We identified hyperactivity in EHMT1+/– neuronal networks co-cultured with EHMT1+/– astrocytes, a dysfunction reversible by olanzapine. Mechanistically, EHMT1+/– astrocytes displayed elevated levels of S100B, a neuroinflammatory marker contributing to neuronal network hyperactivity. Notably, olanzapine treatment reduced S100B levels, and pharmacological inhibition or genetic knockdown of S100B in EHMT1+/– astrocytes was sufficient to rescue the neuronal hyperactivity phenotype. These findings underscore a critical role for astrocytes in KLEFS1 pathophysiology and identify a potential cellular target for olanzapine in mitigating developmental regression.
Authors
Karlijn Vermeulen-Kalk, Shan Wang, Joost Kummeling, Britt Mossink, Kim N. Wijnant, Carlos O. González Jiménez, Zoe J. Frazier, Brian J. Rozumny, Anne O'Donnell-Luria, Ellen Hanson, Monica Frega, Katrin Linda, Moritz Negwer, Bas Lendemeijer, Astrid Oudakker, Monica Pop-Purceleanu, Joost G.E. Janzing, Linde van Dongen, Femke M.S. de Vrij, Steven A. Kushner, Ilse van der Werf, Chantal Schoenmaker, Wouter Oomens, Siddharth Srivastava, Jos I.M. Egger, Hans van Bokhoven, Dirk Schubert, Nael Nadif Kasri, Tjitske Kleefstra
Abstract
Dominant mutations in Progranulin (GRN) gene cause frontotemporal lobar degeneration (FTLD-GRN), whereas homozygous GRN mutations lead to neuronal ceroid lipofuscinosis, a childhood neurodegenerative disorder. While recent transcriptomic studies reveal profound glial and neuronal pathology in FTLD-GRN at the disease end stage, the mechanism that disrupts glia-neuron homeostasis remains unclear. Using induced pluripotent stem cell (iPSC)-derived cortical organoids, we showed that GRN-/- and GRNR493X mutations lead to precocious astrogliosis that promotes neuronal stress and synaptic loss. Single-cell transcriptomics and histopathology analyses revealed a robust activation in TGFb signaling pathway in GRN-/- and GRNR493X/R493X astrocytes, which was accompanied by features of immune activation, loss of synaptic support, and abundant pTDP-43+ fibrils in astroglial cytoplasm, a feature characteristic of FTLD-GRN. Intriguingly, blocking TGFb signaling mitigated astroglial activation and pTDP-43 proteinopathy in GRN-/- organoids. Together, these results provide new insights into the cell-autonomous role of astroglial activation in neurodegeneration caused by Progranulin deficiency.
Authors
Arren C. Ramsey, Xiao-Yan Tang, Magdalena J. Macias, Patricia R. Nano, Rufei Lu, Brian Benito, Cameron M. Lau, Jisu Park, Jiasheng Zhang, Wandy Beatty, Tanzila Mukhtar, Arnold R. Kriegstein, Aparna Bhaduri, Elise Marsan, Eric J. Huang
Abstract
BACKGROUND Liquid biopsy has emerged as a minimally invasive method for tumor diagnosis, monitoring, and therapeutic guidance. For CNS tumors, cerebrospinal fluid (CSF) provides a reliable and accessible source of tumor-derived cell-free DNA (ctDNA).METHODS This study evaluates the clinical utility of CSF liquid biopsy in a real-world prospective setting. A total of 148 CSF samples from 120 patients underwent molecular analysis using droplet digital PCR (ddPCR) and/or next-generation sequencing to detect mutations, fusions, copy number alterations, and mismatch-repair deficient signatures (MMRDness). Samples were collected via lumbar puncture (n = 82; 45% ctDNA positive) or from ventricle sources at the time of surgery or through shunts (n = 66; 65% ct DNA positive).RESULTS Overall, ctDNA was detected in 54% of samples with higher detection in high-grade gliomas at diagnosis (100%, 1 sample equivocal) compared with low-grade gliomas (50%). Among low-grade gliomas, ctDNA detection was higher in disseminated cases (80% versus 43%) and from ventricular versus lumbar samples (56% versus 38%).CONCLUSION Liquid biopsy distinguished relapse from second malignancy and serial sampling demonstrated the potential for ctDNA levels to track treatment response and disease progression. In patients with MMRD tumors, high MMRDness score from ctDNA supported active disease. These findings demonstrate that combined liquid biopsy assays facilitate diagnosis, monitoring, and personalized treatment decisions, offering a viable alternative to invasive surgical biopsies in pediatric CNS tumors.TRIAL REGISTRATION None.FUNDING Proof of Principle Grant from The Hospital for Sick Children; The Canadian Institutes of Health Research; The Canadian Cancer Society; The We Love You Connie Foundation; Garron Family Cancer Center at SickKids; SickKids Clinician Training Program; Ben Stelter Foundation through the Women and Children’s Health Research Institute; Jeffrey Brock Cancer Genetics Research Fellowship; Garron Family Cancer Center Research Fellowship/Scotiabank Clinician Scientist Fellowship; Atrium/CMCC and Hold’em for Life Oncology Fellowship; Tokyo Children’s Cancer Study Group Scholarship of the Gold Ribbons Network.
Authors
Liana Nobre, Yoshiko Nakano, Ian Burns, Robert Siddaway, Michal Zápotocky, Monique Johnson, Mansuba Rana, Cyril Li, Rodney K. Lyn, Richard Yuditskiy, Michelle Ku, Javal Sheth, Adrian B. Levine, Cody L. Nesvick, Anirban Das, Chantel Cacciotti, Shayna Zelcer, Seth A. Climans, Maria MacDonald, Logine Negm, Jiil Chung, Julie Bennett, Andrew Bondoc, Jim Loukides, Lucie Stengs, Melissa Edwards, Eric Bouffet, Vijay Ramaswamy, Anthony P.Y. Liu, Annie Huang, Ute Bartels, Peter B. Dirks, Uri Tabori, Cynthia Hawkins
Abstract
Stroke remains a leading cause of morbidity and mortality worldwide, with few effective interventions to promote recovery. Targeting circadian timing and glymphatic function may represent viable therapeutic strategies. Here, we show that the small-molecule clock modulator, KL001; high-dose melatonin; acute light pulses; and active-phase time-restricted feeding were each sufficient to enhance glymphatic function in mice. Moreover, initiating treatment with either KL001 or active-phase time-restricted feeding 3 days after preclinical models of stroke improved motor outcomes, reduced lesion volume, increased glymphatic flow, and lowered poststroke brain cytokine burden. These findings suggest that reinforcing normal daily rhythmicity after stroke can markedly enhance neurological recovery, even when interventions are initiated several days after stroke onset.
Authors
Emma Waight, Yuxi Zhu, Ashley Caudell, Velia S. Vizcarra, Evan Newbold, Michael J. Giannetto, Evalien Duyvestyn, Estephanie Balbuena, Wei Song, Tanzil M. Arefin, Yuki Mori, Maiken Nedergaard, Lauren M. Hablitz
Abstract
Chromatin remodeling is a dynamic epigenetic process that alters chromatin structure to gauge gene accessibility, enabling precise spatiotemporal gene expression, with disruptions often underlying neurodevelopmental disorders (NDDs), although the mechanistic underpinning remains incompletely understood. Despite essential roles in chromatin remodeling processes such as DNA methylation, and histone acetylation and deposition, DMAP1 has not been implicated in human disease. We identified 20 individuals from 16 families with a syndromic NDD carrying homozygous or compound heterozygous variants in DMAP1. Neural-specific knockdown of its Drosophila ortholog, dDMAP1, caused pupal lethality, structural defects in the mushroom body (MB), decreased dendrite length, abnormal social behavior and mechanical-induced seizures. Human reference DMAP1 could largely compensate for the loss of dDMAP1 in knockdown flies, whereas patient variants failed to restore or differentially rescued the phenotypes, confirming their pathogenicity with differing severity. Transcriptome profiling of dDMAP1 knockdown fly brains nominated Cbl and SF1 as downstream targets. Their overexpression rescued the aforementioned lethality and MB defects. Finally, a DNA methylation episignature was identified, leading to the molecular diagnosis of an additional patient. Our findings demonstrate that biallelic inactivating variants in DMAP1 cause a syndromic NDD, expanding the short list of recessive disease-causing genes within the epigenetic machinery.
Authors
Qin Wang, Andrew K. Sobering, Christian Tirrito, Sadegheh Haghshenas, Tina Duelund Hjortshøj, Konrad Platzer, Silke Redler, Michael E. March, Leticia S. Matsuoka, Hang Xi, Josiah Zoodsma, Yuanhua Chen, Mari Mori, Marco L. Leung, Nathalie Couque, Alain Verloes, Antoine Pouzet, Noor A.A. Giesbertz, Marleen E.H. Simon, Ashley K. Yearwood, Dominique L. Assing, Tzung-Chien Hsieh, Jing-Mei Li, Michael A. Levy, Jennifer Kerkhof, Haley McConkey, Jessica Rzasa, Carolyn Lauzon-Young, Raashda A. Sulaiman, Firdous Abdulwahab, Hanan E. Shamseldin, Naif A.M. Almontashiri, Manal Afqi, Vettaikorumakankav Vedanarayanan, Maria J. Guillen Sacoto, Ingrid M. Wentzensen, Nadirah S. Damseh, Rivka Birnbaum, Babeth van Ommeren, Saskia M.J. Hopman, Maha S. Zaki, Gehad Elmakkawy, Erum Afzal, JiHye Kim, Stephanie Efthymiou, Henry Houlden, Ambreen Nusrat, Mathias Toft, Uzma Abdullah, Zafar Iqbal, Shannon Terek, Fowzan S. Alkuraya, Elizabeth J. Bhoj, Reza Maroofian, Bekim Sadikovic, Hakon Hakonarson, Yuanquan Song, Dong Li
Abstract
Glioblastoma, IDH-wildtype (GBM, WHO grade 4) is the most common malignant glioma in adults and is characterized by a hypoxic and immunosuppressive tumor microenvironment (TME). Bone marrow-derived tumor-associated macrophages (TAMs) dominate the immune landscape in GBM and are recruited to the peri-necrotic niche following the onset of necrosis. CLEC5A has the strongest association with poor clinical outcome among immune-related genes in GBM, and is preferentially expressed in hypoxic, peri-necrotic TAMs. CLEC5A overexpression promotes TAM polarization toward an immunosuppressive phenotype, and secretion of immunoregulatory cytokines. Using an RCAS/tv-a GBM model with bone marrow transplantation from Clec5a-/- donor mice, we demonstrated that CLEC5A loss prolongs survival, delays tumor progression, and attenuates TME immunosuppression. Mechanistically, podoplanin (PDPN) expressed on glioma cells directly engages CLEC5A and triggers downstream Syk-JAK-STAT3 signaling in TAMs. Pharmacologic Syk inhibition suppresses glioma growth, diminishes TAM infiltration and polarization, reverses the immunosuppressive TME, and prolongs survival in vivo. Collectively, our findings indicate that the PDPN-CLEC5A-Syk-STAT3 axis orchestrates TAM polarization and TME immunosuppression in the peri-necrotic niche of GBM, highlighting CLEC5A/Syk as a promising therapeutic target for reversing the immunosuppressive TME and improving outcomes.
Authors
Jiabo Li, Xuya Wang, Luqing Tong, Bo Feng, Ling-kai Shih, Steven M. Markwell, Hannah Nuszen, Tomasz Gruchala, Nicholas G. Lam, Petros Basakis, Erika Ruiz-Yamamoto, Deyu Fang, Roger Stupp, Xuejun Yang, Daniel J. Brat
Copyright © 2026 American Society for Clinical Investigation
ISSN: 0021-9738 (print), 1558-8238 (online)