bims-axbals 2025-09-28 papers

bims-axbals

Biomed News

on Axonal biology and ALS

Issue of 2025–09–28
24 papers selected by
TJ Krzystek

Dysregulation of SELENOI Is Associated with TDP-43 Neuropathology in Amyotrophic Lateral Sclerosis.
IRE1/Xbp1 promotes the clearance of poly(GR) dipeptide repeats in Amyotrophic Lateral Sclerosis.
The potential role of misfolded wild-type SOD1 protein in sporadic amyotrophic lateral sclerosis (ALS): a review of the evidence.
Frontotemporal dementia patient-derived iPSC neurons show cell pathological hallmarks and evidence for synaptic dysfunction and DNA damage.
LRRK2-Mediated Neuroinflammation-Induced Neuronal Dysfunctions in a Parkinson's and Alzheimer's Disease Cellular Model.
JIP4 and RILPL1 utilize opposing motor force to dynamically regulate lysosomal tubulation.
Exploring bioactive phytochemicals as ULK1 activators for enhancing cytoprotective autophagy in amyotrophic lateral sclerosis.
Trisomy 21 Disrupts Thyroid Hormones Signaling During Human iPSC-Derived Neural Differentiation In Vitro.
Loss of Nuclear TDP-43 Impairs Lipid Metabolism in Microglia-Like Cells.
Quantitative Profiling of Nanoscopic Protein Aggregates Reveals Specific Fingerprint of TDP-43-Positive Assemblies in Motor Neuron Disease.
In silico reconstructions underpin aberrant trafficking dynamics in deficient axons of Dst knockout and Dst/Nefl double-knockout mice.
Tau Axonal Sorting and Interaction With Synaptic Plasticity Modulators Is Domain- and Isoform-Dependent in Human iPSC-Derived Neurons.
Isolation of functional lysosomes from skeletal muscle.
Localization of mitochondria along axons and at synapses in C. elegans touch receptor neurons is necessary for touch habituation.
Functional Recovery by Transplantation of Human iPSC-Derived A2B5 Positive Neural Progenitor Cell After Spinal Cord Injury in Mice.
Segment-specific axon guidance by Wnt/Fz signaling diversifies motor commands in Drosophila larvae.
Mitochondrial Aging in the CNS: Unravelling Implications for Neurological Health and Disease.
A De Novo DNM1L Mutation in Twins with Variable Symptoms, Including Paraparesis and Optic Neuropathy.
Circulating Serum Cell-Free Mitochondrial DNA in Amyotrophic Lateral Sclerosis.
Roles of molecular motors in insulin-secreting beta cells.
Three-dimensional midbrain organoids: a next-generation tool for Parkinson's disease modelling and drug discovery.
Seed Amplification Assays as Powerful Tools for Detecting Peripheral Biomarkers in Prion-Like Diseases.
Generating a Cell Model to Study ER Stress in iPSC-Derived Medium Spiny Neurons from a Patient with Huntington's Disease.
A Simple Three-Dimensional Compartmentalized Co-Culture Model for Basal Forebrain and Hippocampal Neurons.

Cells. 2025 Sep 17. pii: 1457. [Epub ahead of print]14(18):

Dysregulation of SELENOI Is Associated with TDP-43 Neuropathology in Amyotrophic Lateral Sclerosis.

Finula I Isik, Jasmin Galper, Russell Pickford, Nicolas Dzamko, YuHong Fu, Woojin Scott Kim.

  Amyotrophic lateral sclerosis (ALS), also known as motor neuron disease, is characterized by progressive degeneration of motor neurons and accumulation of TAR DNA-binding protein 43 (TDP-43) in the brain. Increasing evidence indicates that aberration in lipid synthesis or regulation underlies neuronal dysfunction and degeneration. Phosphatidylethanolmine (PE) is an abundant phospholipid in the brain and is synthesized by the SELENOI gene. SELENOI is important in motor neuron development and function, as demonstrated in hereditary spastic paraplegia, a neurological disorder in which SELENOI is mutated. Despite this, virtually nothing was known about SELENOI in the context of ALS neuropathology. We therefore undertook a comprehensive assessment of PE in ALS brain tissues, using sophisticated liquid chromatography-mass spectrometry, and investigated how SELENOI regulates TDP-43 expression. PE levels were significantly decreased in the disease-affected motor cortex of ALS compared to controls and were inversely associated with disease duration. In contrast, PE levels were unaltered in the disease-unaffected cerebellum. Consistent with this, SELENOI expression was dysregulated only in the motor cortex of ALS. The correlation between SELENOI and TDP-43 was also lost in the motor cortex of ALS. A knockdown of SELENOI expression in neuronal cells caused an upregulation of TDP-43 expression. When put together, these results suggest that SELENOI dysregulation may contribute to TDP-43 pathology in ALS brain. Our study has provided new insights into an unrecognized pathway in ALS brain and revealed new targets for controlling TDP-43 pathology in ALS brain.

Keywords:  SELENOI; TDP-43; amyotrophic lateral sclerosis; motor cortex; motor neuron disease; phosphatidylethanolmine

DOI:  https://doi.org/10.3390/cells14181457
J Biol Chem. 2025 Sep 24. pii: S0021-9258(25)02616-X. [Epub ahead of print] 110764

IRE1/Xbp1 promotes the clearance of poly(GR) dipeptide repeats in Amyotrophic Lateral Sclerosis.

Yu Li, Dongyue Liu, Shuangxi Li.

  Amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) are neurodegenerative disorders characterized by the expansion of GGGGCC (G4C2) repeats in the C9orf72 gene and progressive motor neuron degeneration. A key pathological hallmark of these diseases is the accumulation and cytoplasmic mislocalization of dipeptide repeat (DPR) proteins, particularly poly(GR), which are neurotoxic. Enhancing the clearance of poly(GR) represents a promising therapeutic strategy; however, the molecular mechanisms regulating poly(GR) turnover are not fully understood. Our previous work demonstrated that translationally stalled poly(GR) is targeted by the ribosome-associated quality control (RQC) pathway. In the present study, we identify the IRE1/Xbp1s signaling axis as an essential regulator of poly(GR) degradation. Ectopic expression of IRE1 or its downstream effector Xbp1s, as well as pharmacological activation of IRE1 using IXA4, significantly reduces poly(GR) protein levels in a Drosophila disease model, mammalian cell lines, fibroblasts derived from C9orf72-ALS patients, and a C9orf72 transgenic mouse model. Mechanistically, RNA-sequencing analysis reveals that IRE1/Xbp1s signaling upregulates heat shock protein Hsp70Ba, which plays a critical role in maintaining poly(GR) proteostasis. Additionally, we show that the Rictor/AKT/VCP pathway contributes to the translational regulation and turnover of poly(GR). Importantly, activation of IRE1, either through ectopic expression or IXA4 treatment, mitigates motor neuron loss in the C9orf72 mouse model. Collectively, our findings highlight the IRE1/Xbp1s axis as a key modulator of poly(GR) clearance and suggest its therapeutic potential in ALS/FTD.

Keywords:  Drosophila melanogaster; IRE1; Xbp1; poly(GR)

DOI:  https://doi.org/10.1016/j.jbc.2025.110764
Neurobiol Dis. 2025 Sep 24. pii: S0969-9961(25)00341-9. [Epub ahead of print] 107124

The potential role of misfolded wild-type SOD1 protein in sporadic amyotrophic lateral sclerosis (ALS): a review of the evidence.

Thomas R Marlow, Katie M Bowden, Mark O Collins, Pamela J Shaw.

  Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disorder characterised by the selective loss of motor neurons in the motor cortex, brainstem and spinal cord. In 1993, the first ALS-linked gene mutations were identified in the Cu,Zn superoxide dismutase (SOD1) gene, which account for approximately 20 % of familial ALS cases. The mechanism of toxicity in this subset of patients is thought to arise from a gain-of-toxic function from the protein's propensity to misfold and aggregate into cytoplasmic inclusions. Immunohistochemical studies have shown that misfolded wildtype SOD1 (wtSOD1) is also detected in the motor neurons and glial cells of ALS patients without SOD1 mutations. It is proposed that disrupted, or aberrant, posttranslational modifications cause wtSOD1 to adopt a toxic conformation similar to that of the mutant protein. Subsequent mechanistic studies have shown that this misfolded wtSOD1 can disrupt cellular function and lead to motor neuron death through pathways similar to those observed in mutant SOD1-ALS. Given the limited neuroprotective treatments currently available that can effectively slow or reverse disease progression, targeting a pathogenic mechanism that features in both familial and sporadic ALS cases represents a promising therapeutic approach for a broader patient population. This review examines the growing body of evidence that supports or challenges the role of misfolded wtSOD1 in the pathophysiology of sporadic ALS and explores the potential implications of this mechanism in disease progression. Understanding how misfolded wtSOD1 contributes to disease pathogenesis provides new opportunities for developing more widely available treatments for this devastating disease.

Keywords:  ALS; Misfolded SOD1; Protein aggregation; Sporadic ALS

DOI:  https://doi.org/10.1016/j.nbd.2025.107124
Mol Psychiatry. 2025 Sep 26.

Frontotemporal dementia patient-derived iPSC neurons show cell pathological hallmarks and evidence for synaptic dysfunction and DNA damage.

Nadine Huber, Tomi Hietanen, Sami Heikkinen, Anastasia Shakirzyanova, Dorit Hoffmann, Hannah Rostalski, Ashutosh Dhingra, Salvador Rodriguez-Nieto, Sari Kärkkäinen, Marja Koskuvi, Eila Korhonen, Päivi Hartikainen, Katri Pylkäs, Johanna Krüger, Tarja Malm, Mari Takalo, Mikko Hiltunen, Jari Koistinaho, Anne M Portaankorva, Eino Solje, Annakaisa Haapasalo.

Frontotemporal dementia (FTD) is the second most common cause of dementia in patients under 65 years, characterized by diverse clinical symptoms, neuropathologies, and genetic background. Synaptic dysfunction is suggested to play a major role in FTD pathogenesis. Disturbances in the synaptic function can also be associated with the C9orf72 repeat expansion (C9-HRE), the most common genetic mutation causing FTD. C9-HRE leads to distinct pathological hallmarks, such as C9orf72 haploinsufficiency and development of toxic RNA foci and dipeptide repeat proteins (DPRs). FTD patient brains, including those carrying the C9-HRE, are also characterized by neuropathologies involving accumulation of TDP-43 and p62/SQSTM1 proteins. This study utilized induced pluripotent stem cell (iPSC)-derived cortical neurons from C9-HRE-carrying or sporadic FTD patients and healthy control individuals. We report that the iPSC neurons derived from C9-HRE carriers developed typical C9-HRE-associated hallmarks, including RNA foci and DPR accumulation. All FTD neurons demonstrated increased cytosolic accumulation of TDP-43 and p62/SQSTM1 and changes in nuclear size and morphology. In addition, the FTD neurons displayed reduced number and altered morphologies of dendritic spines and significantly altered synaptic function indicated by a decreased response to stimulation with GABA. These structural and functional synaptic disturbances were accompanied by upregulated gene expression in the FTD neurons related to synaptic function, including synaptic signaling, glutamatergic transmission, and pre- and postsynaptic membrane, as compared to control neurons. Pathways involved in DNA repair were significantly downregulated in FTD neurons. Only one gene, NUPR2, potentially involved in DNA damage response, was differentially expressed between the sporadic and C9-HRE-carrying FTD neurons. Our results show that the iPSC neurons from FTD patients recapitulate pathological changes of the FTD brain and strongly support the hypothesis of synaptic dysfunction as a crucial contributor to disease pathogenesis in FTD.

DOI: https://doi.org/10.1038/s41380-025-03272-x
Biomolecules. 2025 Sep 16. pii: 1322. [Epub ahead of print]15(9):

LRRK2-Mediated Neuroinflammation-Induced Neuronal Dysfunctions in a Parkinson's and Alzheimer's Disease Cellular Model.

Veronica Mutti, Giulia Carini, Moira Marizzoni, Alice Filippini, Federica Bono, Chiara Fiorentini, Samantha Saleri, Floriana De Cillis, Annamaria Cattaneo, Massimo Gennarelli, Paolo Martini, Isabella Russo.

  Chronic neuroinflammation plays a crucial role in the progression of neurodegenerative diseases (NDs), including Parkinson's disease (PD) and Alzheimer's disease (AD). Leucine-Rich Repeat Kinase 2 (LRRK2), a gene linked to familial and sporadic PD, has been positively associated with neuroinflammation in both in vitro and in vivo systems. These observations suggest that LRRK2 might actively contribute to neuronal damage and degeneration in NDs. Based on these premises, we explored the impact of LRRK2-mediated neuroinflammation on neurons in a PD- and AD-related context. We set up a cellular model composed of human induced pluripotent stem cell (hiPSC)-derived neurons (dopaminergic for PD and cholinergic for AD) exposed to inflamed glial medium [α-synuclein pre-formed fibrils (α-syn pffs) for PD and amyloid-β (Aβ)1-42 fibrils for AD] for several days. To dissect the effect of neuroinflammation, and specifically, the role of LRRK2, on neuronal functions, we first performed transcriptome analysis, and then, we validated the results at functional levels. Interestingly, we found that LRRK2-dependent neuroinflammation contributes to neuronal dysfunctions and death in both ND contexts and that LRRK2 kinase inhibition prevents these detrimental effects. Overall, our results suggest that lowering neuroinflammation through LRRK2 pharmacological inhibition might limit the progression of NDs and thus be neuroprotective.

Keywords:  Alzheimer’s disease; LRRK2; Parkinson’s disease; hiPSC; neurodegenerative diseases; neuroinflammation

DOI:  https://doi.org/10.3390/biom15091322
J Cell Biol. 2025 Nov 03. pii: e202404018. [Epub ahead of print]224(11):

JIP4 and RILPL1 utilize opposing motor force to dynamically regulate lysosomal tubulation.

Luis Bonet-Ponce, Tsion Tegicho, Nuria Fernandez-Martinez, Irene A Rozenberg, Mia Ashriem, Alexandra Beilina, Jillian H Kluss, Yan Li, Mark R Cookson.

Lysosomes are dynamic organelles that remodel their membrane in response to stimuli. We previously uncovered a process we term LYsosomal Tubulation/sorting driven by LRRK2 (LYTL), wherein damaged lysosomes generate tubules sorted into vesicles. LYTL is orchestrated by the Parkinson's disease kinase LRRK2 that recruits the motor adaptor protein and RHD family member JIP4 to lysosomes. JIP4 enhances LYTL tubule extension toward the plus-end of microtubules. To identify new players involved in LYTL, we mapped the lysosomal proteome after LRRK2 kinase inhibition. We found that RILPL1 is recruited to dysfunctional lysosomes in an LRRK2 kinase activity-dependent manner, facilitated by pRAB proteins. Unlike JIP4, RILPL1 induces retraction of LYTL tubules by binding to p150Glued, thereby moving lysosomal tubules toward the minus-end of microtubules. Our findings emphasize the dynamic regulation of LYTL tubules by two distinct RHD proteins and pRAB effectors, acting as opposing motor adaptor proteins. These opposing forces create a metastable lysosomal membrane deformation, enabling dynamic tubulation events.

DOI: https://doi.org/10.1083/jcb.202404018
Front Pharmacol. 2025 ;16 1661744

Exploring bioactive phytochemicals as ULK1 activators for enhancing cytoprotective autophagy in amyotrophic lateral sclerosis.

Farah Anjum, Nahed Hawsawi, Abdulraheem Ali Almalki, Anas Shamsi, Maram Jameel Hulbah, Maha Bakhuraysah, Abdulaziz Alsharif, Taj Mohammad.

   Background: Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder that results in the degeneration of motor neurons and is typically linked to toxic aggregates of mutant superoxide dismutase 1 (SOD1) protein. As autophagy is critical for the removal of these toxic protein aggregates, stimulating autophagy has emerged as a promising therapeutic approach for ALS. Unc-51-like kinase 1 (ULK1) is a key regulator of autophagy and has been shown to have the potential to prevent ALS pathology when activated. However, synthetic ULK1 activators are frequently limited by toxicity and suboptimal pharmacokinetic profiles. This study aimed to identify natural ULK1 activators using a systematic virtual screening approach for potential ALS therapy.
Materials and Methods: This study employed a comprehensive virtual screening approach to identify phytochemicals capable of activating ULK1. Natural compounds from the IMPPAT database were screened using molecular docking, followed by pan-assay interference compounds (PAINS) filtering, pharmacokinetic profiling, and density functional theory (DFT) analysis. Further, biological activity was predicted using the PASS tool, and candidate molecules were subjected to molecular dynamics (MD) simulations, essential dynamics, and binding free energy calculations via MM-PBSA.
Results: The systematic screening in this study identified Candidine and Delavinone as high-affinity binders with reference to BL-918, proposing them as potential activators of ULK1. Both compounds demonstrated favorable drug-likeness, stable interactions with ULK1 in MD simulations, and promising ALS-relevant activity profiles. Essential dynamics and MM-PBSA further supported the binding stability and energetic favorability of these interactions.
Conclusion: Candidine and Delavinone emerge as promising phytochemical activators of ULK1 with potential therapeutic relevance for ALS. These findings warrant further experimental validation and preclinical studies to explore their efficacy in autophagy modulation and neuroprotection.

Keywords:  UNC-51-like kinase 1; amyotrophic lateral sclerosis; autophagy; candidine; delavinone; small molecule activators; virtual screening

DOI:  https://doi.org/10.3389/fphar.2025.1661744
Cells. 2025 Sep 09. pii: 1407. [Epub ahead of print]14(18):

Trisomy 21 Disrupts Thyroid Hormones Signaling During Human iPSC-Derived Neural Differentiation In Vitro.

Janaina Sena de Souza, Sandra Sanchez-Sanchez, Nicolas Amelinez-Robles, B S Guerra, Gisele Giannocco, Alysson R Muotri.

  Thyroid hormones (THs) are essential for brain development, and their dysregulation is associated with cognitive deficits and neurodevelopmental disorders. Down syndrome (DS), caused by trisomy 21, is frequently associated with thyroid dysfunction and impaired neurogenesis. Here, we investigated THs signaling dynamics during neural differentiation using human induced pluripotent stem cells (hiPSCs) derived from individuals with DS and controls. We analyzed the gene expression of key THs regulators-deiodinases, transporters, and receptors-and downstream target genes in hiPSCs, hiPSC-derived neural progenitor cells (NPCs), hiPSC-derived astrocytes, and hiPSC-derived neurons. DS-derived hiPSCs, hiPSC-derived NPCs, and hiPSC-derived neurons exhibited 2- to 7-fold increases in the gene expression of DIO2 and 3- to 8-fold reductions in DIO3, alongside 1- to 3-fold downregulation of THRA and THRB isoforms. hiPSC-derived astrocytes showed a 4-fold decrease in the gene expression of DIO2, a 4-fold increase in DIO3, upregulation of SLC16A10 (2-fold), and downregulation of SLC7A5 (0.5-fold) and THs receptors (0.5- to 12-fold). hiPSC-derived neurons exhibited marked downregulation of the gene expression of HOMER1 (0.5-fold), GRIN3A (14-fold), and GRIN3B (4-fold), accompanied by impaired spontaneous activity in multi-electrode array recordings. These findings reveal a robust, cell-type-specific imbalance between THs availability and signaling competence in DS hiPSC-derived neural cells, providing mechanistic insight into THs-related contributions to the function of DS hiPSC-derived neural cells and identifying potential therapeutic targets.

Keywords:  astrocytes; deiodinase; down syndrome; gene expression; iPSC; neurons; receptors; thyroid hormones; transporters

DOI:  https://doi.org/10.3390/cells14181407
bioRxiv. 2025 Sep 17. pii: 2025.09.17.676815. [Epub ahead of print]

Loss of Nuclear TDP-43 Impairs Lipid Metabolism in Microglia-Like Cells.

Khushbu Kabra, Dallin Dressman, Ryan Talcoff, Maedot Yidenk, Olivia M Rifai, Benjamin N Hoover, Neil A Shneider, Wassim Elyaman, Estela Area-Gomez, Elizabeth M Bradshaw.

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease marked by progressive motor neuron loss, with TDP-43 pathology present in over 90% of cases. While neuroinflammation is a recognized hallmark, the role of microglia in ALS pathogenesis remains incompletely understood. Here, we demonstrate that TDP-43 regulates microglial function via triglyceride metabolism. Using shRNA-mediated TARDBP knockdown in human monocyte-derived microglia-like cells (MDMi), we observed suppressed cholesterol biosynthesis, upregulation of fatty acid metabolism genes, lipid droplet accumulation, enhanced phagocytic activity, and increased IL-1β production. Inhibiting diacylglycerol acyltransferase (DGAT) enzymes reduced lipid droplet formation, phagocytosis, and IL-1β, directly linking the triglyceride pathway to microglial activation. Patient-derived MDMi from both sporadic and TARDBP -mutant ALS cases showed overlapping as well as distinct alterations, some of which were reversed by DGAT inhibition. Our findings identify dysregulated triglyceride metabolism as a novel pathway through which TDP-43 mediates microglial dysfunction, highlighting a potential therapeutic target for ALS.
Highlights: TDP-43 nuclear depletion causes increased LD, driven by triglyceride accumulation.TDP-43 nuclear depletion causes increased phagocytosis and pro-inflammatory cytokine expression.Inhibiting triglyceride synthesis using DGAT inhibitors rescues LD and pro-inflammatory phenotype in TDP-43 depleted MDMi ALS patient-derived MDMi display increased LD and IL1B expression, rescued by DGAT inhibitors.

DOI: https://doi.org/10.1101/2025.09.17.676815
Adv Sci (Weinh). 2025 Sep 23. e05484

Quantitative Profiling of Nanoscopic Protein Aggregates Reveals Specific Fingerprint of TDP-43-Positive Assemblies in Motor Neuron Disease.

Dezerae Cox, Melanie Burke, Sara Milani, Matthew A White, Fergal M Waldron, Dorothea Böken, Evgeniia Lobanova, Jemeen Sreedharan, Jenna M Gregory, David Klenerman.

  Abnormal aggregation of TAR DNA-binding protein 43 (TDP-43) is a pathological hallmark of motor neuron disease (MND), yet current methods for quantifying these aggregates in biological samples remain limited in sensitivity and resolution. Here, single-molecule fluorescence microscopy is applied to post-mortem brain extracts to quantitatively characterize aggregates containing TDP-43 at the individual particle level. The resulting aggregate fingerprints, consisting of morphological and compositional profiles, are sufficient to distinguish MND donors from neurologically normal controls and further discriminate between clinically distinct MND subgroups. Comparative proteomic analysis confirms and extends these findings, revealing convergent and complementary molecular signatures. These results demonstrate, for the first time, that single-molecule aggregate profiling can stratify MND cases using patient-derived tissues, paving the way for the development of sensitive minimally invasive diagnostics and mechanistically informed disease monitoring tools.

Keywords:  motor neuron disease; protein aggregates; proteomics; single‐molecule microscopy

DOI:  https://doi.org/10.1002/advs.202505484
Commun Biol. 2025 Sep 24. 8(1): 1358

In silico reconstructions underpin aberrant trafficking dynamics in deficient axons of Dst knockout and Dst/Nefl double-knockout mice.

Zongmin Liu, Wei Wang, Elena Zhang, Emanuel Manzo-Casio, Audrey Liu, Annabelle Yao, Jianqing Ding, Yanmin Yang.

Aberrant neuronal trafficking is a significant hallmark of neurodegenerative pathology. Its real-time evolution remains elusive and poorly defined due to the lack of a predictive spatiotemporal framework. Building upon a general neurocytoskeletal-PDEs (iGCPs) model, we propose the concept of Virtual Cellular Dynamics for quantitative spatiotemporal simulations of mitochondrial dynamics within axons. The model integrates interactions of key cytoskeletal components such as dystonin, microtubule, neurofilament, and actin filament, providing a comprehensive framework for neuron-specific virtual cell modeling, enabling quantitative insight into axonal dysfunction and structural degradation across neurodegenerative disease. Not only does our model recapitulate the significant structural deformations and mitochondrial transport disruptions observed in Dst-deficient mice, but it further predicts that the ablation of Nefl alleviates severe neurodegenerative progression-a finding substantiated by multi-modal imaging and Dst/Nefl double-knockout murine models, which reveal phenotypic rescue and validate the potential of NF-L-targeted therapeutic strategies. Altogether, our work paves the way for next-generation virtual cell models tailored to neuron-specific disease states.

DOI: https://doi.org/10.1038/s42003-025-08728-y
Aging Cell. 2025 Sep 24. e70215

Tau Axonal Sorting and Interaction With Synaptic Plasticity Modulators Is Domain- and Isoform-Dependent in Human iPSC-Derived Neurons.

Michael Bell-Simons, Helen Breuer, Laura Wunderlich, Hanin Chmes, Daniel Adam, Jennifer Klimek, Sarah Buchholz, Hans Zempel.

  Somatodendritic missorting of the axonal microtubule-associated protein Tau is an early hallmark of Alzheimer's disease (AD) and other tauopathies. Tau missorting causes synaptic loss and neuronal dysfunction, but the mechanisms underlying both normal axonal sorting and pathological missorting remain unclear. The six human brain Tau isoforms show different axodendritic distribution, but the Tau domains governing intracellular sorting and essential interactors are unknown. Here, we aimed to identify domains or motifs of human Tau and cellular binding partners required for efficient axonal Tau sorting and to unravel isoform-specific Tau interactors. Using human MAPT-KO induced pluripotent stem cell (iPSC)-derived glutamatergic neurons, we analyzed the sorting behavior of more than 20 truncation- or phosphorylation-mutant Tau constructs and used TurboID-based proximity labeling and proteomics to identify sorting- and isoform-specific Tau interactors. We found that efficient axonal Tau sorting was independent of the N-terminal tail, the C-terminal repeat domains, AD-associated phosphorylation, and the general microtubule affinity of Tau, but it requires the presence of the proline-rich region 2 (PRR2). Our interactome data revealed peroxisomal accumulation of the Tau N-terminal half, while axonal Tau interacted with the PP2A activator HSP110. Further, we found 0N4R-specific interactions of Tau with regulators of presynaptic exocytosis and postsynaptic plasticity, which are partially associated with AD pathogenesis, including members of the CDC42 pathway and the RAB11 proteins, while 0N3R-Tau bound to various cytoskeletal elements. In sum, our study i) postulates that axonal Tau sorting relies on the PRR2 domain but not on microtubule affinity and ii) unravels a potential isoform-specific role in synaptic function and AD-related dysfunction.

Keywords:  Alzheimer's disease; human MAPT knockout; proline‐rich region 2; synaptic tau; tau isoforms; tau sorting

DOI:  https://doi.org/10.1111/acel.70215
Am J Physiol Cell Physiol. 2025 Sep 22.

Isolation of functional lysosomes from skeletal muscle.

Thulasi Mahendran, Anastasiya Kuznyetsova, Neushaw Moradi, David A Hood.

  Lysosomes are membrane-bound organelles responsible for the degradation of damaged or dysfunctional cellular components, including mitochondria. Their acidic internal environment and the presence of an array of hydrolytic enzymes facilitate the efficient breakdown of macromolecules such as proteins, lipids, and nucleic acids. Mitochondria play a critical role in maintaining skeletal muscle homeostasis to meet the energy demands under physiological and pathological conditions. Mitochondrial quality control within skeletal muscle during processes such as exercise, disuse, and injury is regulated by mitophagy, where dysfunctional mitochondria are targeted for lysosomal degradation. The limited understanding of quality control mechanisms in skeletal muscle necessitates the need for isolating intact lysosomes to assess organelle integrity and the degradative functions of hydrolytic enzymes. Although several methods exist for lysosome isolation, the complex structure of skeletal muscle makes it challenging to obtain relatively pure and functional lysosomes due to the high abundance of contractile proteins. Here we describe a method to isolate functional lysosomes from small amounts of mouse skeletal muscle tissue, preserving membrane integrity. We also describe functional assays that allow direct evaluation of lysosomal enzymatic activity and we provide data indicating reduced lysosomal degradative activity in lysosomes from aging muscle. We hope that this protocol provides a valuable tool to advance our understanding of lysosomal biology in skeletal muscle, supporting investigations into lysosome-related dysfunction in aging, disease, and exercise adaptations.

Keywords:  differential centrifugation; lysosomal enzymes; mitochondria; mitophagy; proteolysis

DOI:  https://doi.org/10.1152/ajpcell.00471.2025
J Biosci. 2025 ;pii: 72. [Epub ahead of print]50

Localization of mitochondria along axons and at synapses in C. elegans touch receptor neurons is necessary for touch habituation.

Sneha Hegde, Nayantara Varma, Parul Sood, Sandhya P Koushika.

Neuronal mitochondria are important for neuronal survival and function. Mitochondria buffer calcium, produce ATP, and contribute to reactive oxygen species (ROS) homeostasis, processes that help in neuronal outgrowth and synaptic transmission. Caenorhabditis elegans touch receptor neurons (TRNs) are essential for gentletouch perception and are also used as a model to study axon regeneration. We set up a localized touch habituation assay and investigated the role of the localization of mitochondria along axons and at synapses in the touch circuit for touch habituation behaviour. Mitochondrial transport mutant ric-7 and the metaxin-2;miro- 1 double mutant, which lack mitochondria in axons and at synapses, habituate faster to gentle touch compared with wild-type animals. The faster habituation phenotype is reversed upon restoration of mitochondria along axons and at synapses of only TRNs. Since mitochondria are shown to control actin dynamics, we asked two questions: (i) Can actin dynamics bypass the requirement of axonal mitochondria for touch habituation, and (ii) can upregulation of actin dynamics in injured axons occur independent of axonal mitochondria? Restoring axonal actin dynamics in the absence of axonal mitochondria did not restore defects in gentle-touch habituation of ric-7 animals. Axotomized TRNs in ric-7 animals show upregulation of axonal actin dynamics but do not show filopodial protrusions at the growth cone. Our study suggests that axonal mitochondria play key roles in habituation and axon regeneration independent of dynamic axonal actin.
Int J Mol Sci. 2025 Sep 13. pii: 8940. [Epub ahead of print]26(18):

Functional Recovery by Transplantation of Human iPSC-Derived A2B5 Positive Neural Progenitor Cell After Spinal Cord Injury in Mice.

Yiyan Zheng, Xiaohui Chen, Ping Bu, Haipeng Xue, Dong H Kim, Hongxia Zhou, Xugang Xia, Ying Liu, Qilin Cao.

  Human induced pluripotent stem cells (hiPSCs) hold great potential for patient-specific therapies. Transplantation of hiPSC-derived neural progenitor cells (NPCs) is a promising reparative strategy for spinal cord injury (SCI), but clinical translation requires efficient differentiation into desired neural lineages and purification before transplantation. Here, differentiated hiPSCs-reprogrammed from human skin fibroblasts using Sendai virus-mediated expression of OCT4, SOX2, KLF4, and C-MYC-into neural rosettes expressing SOX1 and PAX6, followed by neuronal precursors (β-tubulin III+/NESTIN+) and glial precursors (GFAP+/NESTIN+). Both neuronal and glial precursors expressed the A2B5 surface antigen. A2B5+ NPCs, purified by fluorescence-activated cell sorting (FACS), proliferated in vitro with mitogens, and differentiated into mature neurons and astrocytes under lineage-specific conditions. Then, NOD-SCID mice received a T9 contusion injury followed by transplantation of A2B5+ NPCs, human fibroblasts, or control medium at 8 days post-injury. At two months, grafted NPCs showed robust survival, progressive neuronal maturation (β-tubulin III+→doublecortin+→NeuN+), and astrocytic differentiation (GFAP+), particularly in spared white matter. Transplantation significantly increased spared white matter volume and improved hindlimb locomotor recovery, with no teratoma formation observed. These results demonstrate that hiPSC-derived, FACS-purified A2B5+ NPCs can survive, differentiate into neurons and astrocytes, and enhance functional recovery after SCI. This approach offers a safe and effective candidate cell source for treating SCI and potentially other neurological disorders.

Keywords:  hiPSC; neural repair; neural stem cells; spinal cord injury; transplantation

DOI:  https://doi.org/10.3390/ijms26188940
Elife. 2025 Sep 25. pii: RP98624. [Epub ahead of print]13

Segment-specific axon guidance by Wnt/Fz signaling diversifies motor commands in Drosophila larvae.

Suguru Takagi, Shiina Takano, Tomohiro Kubo, Yusaku Hashimoto, Shu Morise, Xiangsunze Zeng, Akinao Nose.

  Functional diversification of homologous neuronal microcircuits is a widespread feature observed across brain regions, as well as across species, while its molecular and developmental mechanisms remain largely unknown. We address this question in Drosophila larvae by focusing on segmentally homologous Wave command-like neurons, which diversify their wiring and function in a segment-specific manner. Anterior Wave (a-Wave) neurons extend axons anteriorly and connect to circuits inducing backward locomotion, whereas posterior Wave (p-Wave) neurons extend axons posteriorly and trigger forward locomotion. Here, we show that Frizzled receptors DFz2 and DFz4, together with the DWnt4 ligand, regulate the segment-specific Wave axon projection. DFz2 knockdown (KD) not only reroutes Wave axons to posterior neuromeres but also biases its motor command to induce forward instead of backward locomotion as tactile response. Thus, segment-specific axon guidance diversifies the function of homologous command neurons in behavioral regulation. Since control of anterior-posterior (A-P) axon guidance by Wnt/Fz signaling is evolutionarily conserved, our results reveal a potentially universal molecular principle for formation and diversification of the command system in the nerve cord. Furthermore, this work indicates that sensorimotor transduction can be rerouted by manipulating a single gene in a single class of neurons, potentially facilitating the evolutionary flexibility in action selection.

Keywords:  D. melanogaster; Wnt/Frizzled; action selection; axon guidance; developmental biology; neuroscience; segment specificity; sensory-motor transformation; tactile circuit

DOI:  https://doi.org/10.7554/eLife.98624
Biomolecules. 2025 Aug 29. pii: 1252. [Epub ahead of print]15(9):

Mitochondrial Aging in the CNS: Unravelling Implications for Neurological Health and Disease.

Davide Steffan, Camilla Pezzini, Martina Esposito, Anais Franco-Romero.

  Mitochondrial aging plays a central role in the functional decline of the central nervous system (CNS), with profound consequences for neurological health. As the brain is one of the most energy-demanding organs, neurons are particularly susceptible to mitochondrial dysfunction that arises with aging. Key features of mitochondrial aging include impaired mitochondrial dynamics, reduced mitophagy, increased production of reactive oxygen species (ROS), and accumulation of mitochondrial DNA (mtDNA) mutations. These alterations dramatically compromise neuronal bioenergetics, disrupt synaptic integrity, and promote oxidative stress and neuroinflammation, paving the path for the development of neurodegenerative diseases. This review also examines the complex mechanisms driving mitochondrial aging in the central nervous system (CNS), including the disruption of mitochondrial-organelle communication, and explores how mitochondrial dysfunction contributes to neurodegenerative diseases, such as Alzheimer's, Parkinson's, Huntington's, and amyotrophic lateral sclerosis. By synthesizing current evidence and identifying key knowledge gaps, we emphasize the urgent need for targeted strategies to restore mitochondrial function, maintain cognitive health, and delay or prevent age-related neurodegeneration.

Keywords:  CNS; aging; mitophagy; neurodegenerative diseases

DOI:  https://doi.org/10.3390/biom15091252
Biomolecules. 2025 Aug 26. pii: 1230. [Epub ahead of print]15(9):

A De Novo DNM1L Mutation in Twins with Variable Symptoms, Including Paraparesis and Optic Neuropathy.

Alessia Nasca, Alessia Catania, Andrea Legati, Rossella Izzo, Carola D'onofrio, Teresa Ciavattini, Eleonora Lamantea, Costanza Lamperti, Daniele Ghezzi.

  Mitochondrial network dynamics, encompassing processes like fission, fusion, and mitophagy, are crucial for mitochondrial function and overall cellular health. Dysregulation of these processes has been linked to various human diseases. Particularly, pathogenic variants in the gene DNM1L can lead to a broad range of clinical phenotypes, ranging from isolated optic atrophy to severe neurological conditions. DNM1L encodes DRP1 (dynamin-1-like protein), which is a key player in mitochondrial and peroxisomal fission. This study describes two twin sisters with a de novo heterozygous variant in DNM1L, due to possible paternal germline mosaicism identified through clinical exome sequencing. The two twins showed a variable clinical presentation, including paraparesis and optic neuropathy. Functional studies of patient-derived fibroblasts revealed altered mitochondrial and peroxisomal morphology, along with dysregulated DNM1L transcript levels, indicating the deleterious effect of the variant. These findings allowed us to reclassify the identified variant from a variant of uncertain significance to a likely pathogenic variant. Our report provides insight into the phenotypic spectrum of DNM1L-related disorders and highlights the need to combine genetic and functional analyses to accurately diagnose rare mitochondrial diseases.

Keywords:  DNM1L; mitochondrial and peroxisomes fission; mitochondrial disorders; mitochondrial dynamics; variant reclassification

DOI:  https://doi.org/10.3390/biom15091230
Cells. 2025 Sep 12. pii: 1433. [Epub ahead of print]14(18):

Circulating Serum Cell-Free Mitochondrial DNA in Amyotrophic Lateral Sclerosis.

Giada Zanini, Ilaria Martinelli, Giorgia Sinigaglia, Elisabetta Zucchi, Federico Banchelli, Cecilia Simonini, Giulia Gianferrari, Andrea Ghezzi, Jessica Mandrioli, Marcello Pinti.

  Mitochondrial dysfunction is a key pathological hallmark in amyotrophic lateral sclerosis (ALS), yet the role of circulating cell-free mitochondrial DNA (Cf-mtDNA) as a biomarker remains unclear. This study aimed to investigate serum Cf-mtDNA levels in ALS patients compared to healthy controls and explore its associations with disease biomarkers, clinical progression, and survival. We conducted a case-control study measuring Cf-mtDNA levels in serum samples from 54 ALS patients and 36 age- and sex-matched healthy controls using quantitative droplet digital PCR. Correlations between Cf-mtDNA levels and clinical features, neurofilament concentrations, inflammatory indices, and survival were assessed. The average Cf-mtDNA level in ALS patients was 2,426,315 copies/mL of serum (IQR: 865000-2475000), compared to 1,885,667 copies/mL of serum (IQR: 394250-2492500) in controls (p = 0.308). ROC analysis yielded an AUC of 0.595 (95% CI: 0.468-0.721), indicating very limited discriminant ability. Cf-mtDNA levels were inversely correlated with serum creatinine concentrations (r = -0.335, p = 0.018), but showed no significant associations with ALS phenotype, disease staging, neurofilaments, inflammatory indices, or survival. These findings suggest that, in a predominantly sporadic ALS cohort, serum Cf-mtDNA may not serve as a standalone diagnostic or prognostic biomarker, in contrast to previous reports. Methodological differences, cohort composition, and genetic heterogeneity may account for these discrepancies. Our results underscore the importance of further large-scale, longitudinal studies incorporating genetic stratification and multi-biomarker approaches to better elucidate the role of Cf-mtDNA in ALS pathophysiology.

Keywords:  amyotrophic lateral sclerosis; biomarker; circulating cell-free mitochondrial DNA; mitochondria; neuroinflammation; oxidative stress

DOI:  https://doi.org/10.3390/cells14181433
Curr Opin Cell Biol. 2025 Sep 22. pii: S0955-0674(25)00120-6. [Epub ahead of print]97 102582

Roles of molecular motors in insulin-secreting beta cells.

Syed N Barmaver, Guoqiang Gu, Irina Kaverina.

Pancreatic β cells are essential for glucose homeostasis through the regulated secretion of insulin in response to rising glucose levels. A critical component of this process is the precise and timely positioning of insulin secretory granules (ISGs) at the secretion sites on the plasma membrane. This positioning is mediated by molecular motors that transport ISGs along cytoskeletal tracks, including microtubules (MTs) and actin filaments. Despite their importance, the roles of molecular motors in insulin-secreting β cells remain incompletely understood. In this review, we summarize current findings on the involvement of molecular motors both in ISG transport, directly regulating granule availability for secretion, and in the organization of other subcellular structures, thereby indirectly influencing secretion. These indirect roles include kinesin-1-mediated microtubule sliding that configures the β cell-specific MT network, the spatial organization of calcium channels, and mitochondrial positioning, among others. We also draw parallels between β cells and neurons, proposing that insights from neuronal motor protein studies can guide future research directions in β cell biology.

DOI: https://doi.org/10.1016/j.ceb.2025.102582
Stem Cell Res Ther. 2025 Sep 25. 16(1): 502

Three-dimensional midbrain organoids: a next-generation tool for Parkinson's disease modelling and drug discovery.

Rosalie Elvira, Eng King Tan, Zhi Dong Zhou.

  Parkinson's disease (PD), a progressive neurodegenerative disorder marked by dopaminergic (DA) neuron loss and Lewy body formation, lacks therapies to halt neurodegeneration. Current models, including 2D cultures and animal studies, fail to fully recapitulate human midbrain complexity, underscoring the need for advanced human-relevant disease modelling systems. Midbrain organoids (MOs), three-dimensional (3D) stem cell-derived neuronal structures mimicking midbrain architecture, have emerged as transformative tools for modelling PD. These organoids replicate key pathological hallmarks and enable disease mechanistic studies and drug screening for PD. Recent advances of research in MOs include genetic modelling of PD-linked mutations (e.g., LRRK2, GBA1, DNAJC6), optogenetics-assisted α-synuclein (α-syn) protein aggregation systems, and high-throughput drug testing platforms. MOs also show promise for cell replacement therapy, with successful integration and functional recovery in animal PD models. However, challenges such as batch variability, limited vascularization, incomplete neuronal maturation, and high costs hinder reproducibility and scalability. Future directions focus on integrating vascular networks, microglia co-cultures, automated workflows, and assembloid technologies to enhance pathophysiological relevance and translational potential in PD. By addressing these limitations, research in MOs could revolutionize PD research, offering critical insights into disease mechanisms and accelerating therapeutic discovery for PD patients.

Keywords:  Disease modelling; Midbrain organoids; Neurodegeneration; Parkinson’s disease; Pathogenesis; Therapy

DOI:  https://doi.org/10.1186/s13287-025-04660-4
Subcell Biochem. 2025 ;112 293-320

Seed Amplification Assays as Powerful Tools for Detecting Peripheral Biomarkers in Prion-Like Diseases.

Ilaria Linda Dellarole, Annalisa Lombardo, Arianna Ciullini, Federico Angelo Cazzaniga, Rachele Domina, Merve Begüm Bacınoğlu, Fabio Moda.

  Seed amplification assays (SAAs) are highly sensitive and advanced techniques originally developed for the study and diagnosis of prion diseases. Thanks to their remarkably high sensitivity and specificity, SAAs are now widely employed in both research and clinical settings for prion detection, especially in peripheral tissues of patients with prion disorders. Many neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease, dementia with Lewy bodies, frontotemporal dementia, and amyotrophic lateral sclerosis, show prion-like mechanisms involving the misfolding and self-propagation of pathological proteins. As a result, SAAs are being adapted and refined for clinical use to improve the diagnosis of these conditions. This includes detecting traces of pathological proteins in cerebrospinal fluid as well as in minimally or noninvasively collected samples, such as blood, urine, skin, and olfactory mucosa. This chapter offers an overview of the role of SAAs in the clinical diagnosis of neurodegenerative diseases.

Keywords:  Neurodegenerative diseases; Peripheral biomarkers; Prion; Seed amplification assay; TDP-43; Tau; α-synuclein; β-amyloid

DOI:  https://doi.org/10.1007/978-3-031-97055-9_13
Int J Mol Sci. 2025 Sep 13. pii: 8930. [Epub ahead of print]26(18):

Generating a Cell Model to Study ER Stress in iPSC-Derived Medium Spiny Neurons from a Patient with Huntington's Disease.

Vladlena S Makeeva, Anton Yu Sivkov, Suren M Zakian, Anastasia A Malakhova.

  iPSCs and their derivatives are used to investigate the molecular genetic mechanisms of human diseases, to identify therapeutic targets, and to screen for small molecules. Combining technologies for generating patient-specific iPSC lines and genome editing allows us to create cell models with unique characteristics. We obtained and characterized three iPSC lines by reprogramming peripheral blood mononuclear cells of a patient with Huntington's disease (HD) using episomal vectors encoding Yamanaka factors. iPSC lines expressed pluripotency marker genes, had normal karyotypes and were capable of differentiating into all three germ layers. The obtained iPSC lines are useful for modeling disease progression in vitro and studying pathological mechanisms of HD, such as ER stress. A transgene of genetically encoded biosensor XBP1-TagRFP was introduced into the iPSCs to visualize ER stress state of cells. The study demonstrated that iPSC-derived medium spiny neurons develop ER stress, though the IRE1-mediated pathway does not seem to be involved in the process.

Keywords:  ER stress; Huntington’s disease; XBP1-TagRFP biosensor; iPSC-based cell model; iPSC-derived medium spiny neurons

DOI:  https://doi.org/10.3390/ijms26188930
Biology (Basel). 2025 Sep 10. pii: 1238. [Epub ahead of print]14(9):

A Simple Three-Dimensional Compartmentalized Co-Culture Model for Basal Forebrain and Hippocampal Neurons.

Xiaoman Luo, Jing Li, Zhiyu Deng, Yali Xu, Xixi Li, Miao Ren, Xiangning Li.

  The basal forebrain (BF)-hippocampus (HPC) circuit is indispensable for learning and memory, and in vitro models are essential for dissecting its age-related decline. Nonetheless, current culture methods endure brief survival or confine cells to two dimensions, leaving the circuit's progressive degeneration refractory to long-term investigation. Here, we developed a simple, three-dimensional (3D) compartmentalized co-culture model that mimics the anatomical organization of BF and HPC neurons. Results demonstrate that basal forebrain cholinergic neurons (BFCNs) co-cultured with primary HPC neurons remain viable for more than two months without exogenous growth factors, significantly promoting BFCNs growth, polarity development, and functional maturation. In this system, BFCNs somata were confined within the hydrogel, whereas cholinergic axons extended toward adjacent hippocampal area, reaching 1681.9 ± 351.8 μm by week 5-significantly longer than in BFCNs monocultures. This model can successfully recapitulate age-dependent progressive neuronal degeneration during long-term culture, validating this long-term co-culture as a platform for studying circuit aging and degeneration. Therefore, this low-cost and highly physiological platform provides a new avenue for in-depth investigations into the mechanisms of neurodegenerative diseases.

Keywords:  basal forebrain; hippocampus; primary culture; three-dimensional co-culture

DOI:  https://doi.org/10.3390/biology14091238