bims-axbals 2025-05-11 papers

bims-axbals

Biomed News

on Axonal biology and ALS

Issue of 2025–05–11
thirty-one papers selected by
TJ Krzystek

PI3P: Rising to the (DPR) challenge in C9-ALS/FTD.
Synaptic defects in adult drosophila motor neurons in a model of amyotrophic lateral sclerosis.
Therapeutic targeting of autosomal Parkinson's disease by modulation of Leucine-Rich Repeat Kinase 2 (LRRK2) protein.
Short-chain polyphosphates induce tau fibrillation and neurotoxicity in human iPSC-derived retinal neurons.
Molecular mechanisms and consequences of TDP-43 phosphorylation in neurodegeneration.
Huntingtin inclusion bodies have distinct immunophenotypes and ubiquitination profiles in the Huntington's disease human cerebral cortex.
Kinome screening identifies integrated stress response kinase EIF2AK1/HRI as a negative regulator of PINK1 mitophagy signaling.
Current Development of iPSC-Based Modeling in Neurodegenerative Diseases.
Neuroimmune signaling mediates astrocytic nucleocytoplasmic disruptions and stress granule formation associated with TDP-43 pathology.
Expression of a protein disulfide isomerase A3 variant associated with amyotrophic lateral sclerosis triggers disease features in mice.
Mitochondria and Endoplasmic Reticulum Contact Site as a Regulator of Proteostatic Stress Responses in Neurodegenerative Diseases.
Endosomal protein DENND10 promotes developmental competence of neurite extension.
Emergent glutamate & dopamine dysfunction in VPS35(D620N) knock-in mice and rapid reversal by LRRK2 inhibition.
Tracing mitochondrial marks of neuronal aging in iPSCs-derived neurons and directly converted neurons.
ER-to-lysosome-associated degradation.
RNA splicing modulator for Huntington's disease treatment induces peripheral neuropathy.
A Comparative Study of a Potent CNS-Permeable RARβ-Modulator, Ellorarxine, in Neurons, Glia and Microglia Cells In Vitro.
ZNRF1-dependent regulation of AKT activity modulates Nav subcellular localization and AIS position in neurons to regulate fear-related behavior.
Reduced Palmitoylation of SQSTM1/p62 in Huntington Disease Is Associated With Impaired Autophagy.
srp54 promotes motor neuron development and is required for motility in zebrafish.
In vitro models of microglia: a comparative study.
Nanoscale domains govern local diffusion and aging within FUS condensates.
Autophagy-independent role of ATG9A vesicles as carriers for galectin-9 secretion.
Mitochondrial fatty acid oxidation dysfunction impairs autophagic flux through ATP deficiency-caused lysosomal pH abnormity.
Agent-based modeling of neuronal mitochondrial dynamics using intrinsic variables of individual mitochondria.
A red-emitting, microenvironment-insensitive fluorophore for lysosome-specific imaging in live cells.
Parkin mediates the mitochondrial dysfunction through mRpL18.
Electrophysiological characterisation of intranigral-grafted hiPSC-derived dopaminergic neurons in a mouse model of Parkinson's disease.
Key Mechanisms in Lysosome Stability, Degradation and Repair.
Cerebrospinal fluid proteome profiling across the Alzheimer's disease continuum: a step towards solving the equation for 'X'.
Engineering Assembloids to Mimic Graft-Host Skeletal Muscle Interaction.

Neuron. 2025 May 07. pii: S0896-6273(25)00286-7. [Epub ahead of print]113(9): 1301-1303

PI3P: Rising to the (DPR) challenge in C9-ALS/FTD.

Janani Parameswaran, Zachary T McEachin.

A hexanucleotide G4C2 repeat expansion in C9orf72 causes accumulation of dipeptide repeat (DPR) proteins and is the leading genetic cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). In a recent issue of Neuron, Zhang et al.1 report that elevating PI3P levels mitigates endolysosomal deficits and DPR-associated neurotoxicity.

DOI: https://doi.org/10.1016/j.neuron.2025.04.007
Hum Mol Genet. 2025 May 06. pii: ddaf068. [Epub ahead of print]

Synaptic defects in adult drosophila motor neurons in a model of amyotrophic lateral sclerosis.

Tulika Malik, Jessica M Sidisky, Sam Jones, Alexander Winters, Brandon Hocking, Jocelyn Rotay, Ellen N Huhulea, Sara Moran, Bali Connors, Daniel T Babcock.

  Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease that primarily affects motor neurons in the brain and spinal cord. Like other neurodegenerative diseases, defects in synaptic integrity are among the earliest hallmarks of ALS. However, the specific impairments to synaptic integrity remain unclear. To better understand synaptic defects in ALS, we expressed either wild-type or mutant Fused in Sarcoma (FUS), an RNA binding protein that is often mis-localized in ALS, in adult motor neurons. Using optogenetic stimulation of the motor neurons innervating the Ventral Abdominal Muscles (VAMs), we found that expression of mutant FUS disrupted the functional integrity of these synapses. This functional deficit was followed by disruption of synaptic gross morphology, localization of pre- and post-synaptic proteins, and cytoskeleton integrity. We found similar synaptic defects using the motor neurons innervating the Dorsal Longitudinal Muscles (DLMs), where expression of mutant FUS resulted in a progressive loss of flight ability along with disruption of active zone distribution. Our findings uncover defects in synaptic function that precede changes in synaptic structure, suggesting that synaptic function is more sensitive to this ALS model. Highlighting the earliest synaptic defects in this disease model should help to identify strategies for preventing later stages of disease progression.

Keywords:  Drosophila; Neurodegeneration; Neuromuscular Junction; Synapse

DOI:  https://doi.org/10.1093/hmg/ddaf068
Brain Res. 2025 May 07. pii: S0006-8993(25)00233-1. [Epub ahead of print] 149674

Therapeutic targeting of autosomal Parkinson's disease by modulation of Leucine-Rich Repeat Kinase 2 (LRRK2) protein.

Zeeshan Hyderi, M Shirin Farhana, Tej Pal Singh, Arumugam Veera Ravi.

  Leucine-Rich Repeat Kinase 2 (LRRK2) is gaining attention as a key therapeutic target for autosomal dominant Parkinson's disease (PD). The primary genetic aetiology of familial PD, accounting for around 5-6 % of familial cases and 2 % of sporadic cases, is mutations in the LRRK2 gene. The most prevalent mutation, G2019S, increases kinase activity, which phosphorylates important serine residues that control LRRK2 function, such as Ser910 and Ser935, leading to the development of PD. The development of LRRK2 inhibitors has emerged as a key area of study for PD therapy. In preclinical research, these inhibitors have demonstrated promise in reducing PD-related damage by altering the cellular localisation of LRRK2 and reduced phosphorylation. In addition to kinase action, LRRK2 is involved in autophagy and mitochondrial function. This participation implies that PD markers including mitochondrial dysfunction and defective autophagy may be addressed by LRRK2-targeted treatments. Moreover, selective LRRK2 inhibitors show promise in the treatment of PD, and more research into the molecular role of LRRK2 in PD is essential to developing efficient therapies that will improve patient outcomes and reduce the course of the illness. This review discusses the role of LRRK2 in pathogenesis of PD and current treatment approaches, particularly LRRK2 kinase inhibitors, and their potential to slow disease progression, along with recent advancements in clinical trials and future outlooks for improving outcomes in PD.

Keywords:  Cellular localisation; LRRK2 inhibitors; Leucine-Rich Repeat Kinase 2 (LRRK2); Mutation; Parkinson’s Disease; Phosphorylation

DOI:  https://doi.org/10.1016/j.brainres.2025.149674
Cell Death Dis. 2025 May 09. 16(1): 369

Short-chain polyphosphates induce tau fibrillation and neurotoxicity in human iPSC-derived retinal neurons.

Lorenzo Barolo, Lorenza Mautone, Ylenia Gigante, Silvia Ghirga, Francesco Mura, Maria Vittoria Farina, Stefano Tacconi, Luciana Dini, Giancarlo Ruocco, Alberto Boffi, Edoardo Milanetti, Silvia Di Angelantonio, Paola Baiocco.

The onset of Alzheimer's Disease and Frontotemporal Dementia is closely associated with the aggregation of tau, a multifunctional protein essential for neuronal stability and function. Given the role of tau aggregation in neurodegeneration, understanding the mechanisms behind its fibril formation is crucial for developing therapeutic interventions to halt or reverse disease progression. However, the structural complexity and diverse aggregation pathways of tau present significant challenges, requiring comprehensive experimental studies. In this research, we demonstrate that short-chain polyphosphates, specifically sodium tripolyphosphate (NaTPP), effectively induce tau fibril formation in vitro using the microtubule-binding domain fragment (K18). NaTPP-induced fibrils display unique structural characteristics and aggregation kinetics compared to those induced by heparin, indicating distinct pathogenic pathways. Through molecular dynamics simulations, we show that NaTPP promotes aggregation by exposing key residues necessary for fibril formation, which remain concealed under non-aggregating conditions. This interaction drives tau into an aggregation-prone state, revealing a novel mechanism. Furthermore, our study indicates that human pluripotent stem cell-derived retinal neurons internalize NaTPP-induced fibrils within 24 h, pointing to a potential pathway for tau spread in neurodegeneration. To explore the translational implications of NaTPP-induced fibrils, we assessed their long-term effects on cellular viability, tubulin integrity, and stress responses in retinal neuron cultures. Compared to heparin, NaTPP promoted fewer but longer fibrils with initially low cytotoxicity but induced a stress response marked by increased endogenous tau and p62/SQSTM1 expression. Prolonged exposure to NaTPP-induced oligomers significantly increased cytotoxicity, leading to tubulin fragmentation, altered caspase activity, and elevated levels of phosphorylated pathological tau. These findings align with a neurodegenerative phenotype, highlighting the relevance of polyphosphates in tau pathology. Overall, this research enhances our understanding of the role of polyphosphate in tau aggregation, linking it to key cellular pathways in neurodegeneration.

DOI: https://doi.org/10.1038/s41419-025-07662-5
Mol Neurodegener. 2025 May 08. 20(1): 53

Molecular mechanisms and consequences of TDP-43 phosphorylation in neurodegeneration.

Elise A Kellett, Adekunle T Bademosi, Adam K Walker.

  Increased phosphorylation of TDP-43 is a pathological hallmark of several neurodegenerative disorders, including amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). However, the regulation and roles of TDP-43 phosphorylation remain incompletely understood. A variety of techniques have been utilized to understand TDP-43 phosphorylation, including kinase/phosphatase manipulation, phosphomimic variants, and genetic, physical, or chemical inducement in a variety of cell cultures and animal models, and via analyses of post-mortem human tissues. These studies have produced conflicting results: suggesting incongruously that TDP-43 phosphorylation may either drive disease progression or serve a neuroprotective role. In this review, we explore the roles of regulators of TDP-43 phosphorylation including the putative TDP-43 kinases c-Abl, CDC7, CK1, CK2, IKKβ, p38α/MAPK14, MEK1, TTBK1, and TTBK2, and TDP-43 phosphatases PP1, PP2A, and PP2B, in disease. Building on recent studies, we also examine the consequences of TDP-43 phosphorylation on TDP-43 pathology, especially related to TDP-43 mislocalisation, liquid-liquid phase separation, aggregation, and neurotoxicity. By comparing conflicting findings from various techniques and models, this review highlights both the discrepancies and unresolved aspects in the understanding of TDP-43 phosphorylation. We propose that the role of TDP-43 phosphorylation is site and context dependent, and includes regulation of liquid-liquid phase separation, subcellular mislocalisation, and degradation. We further suggest that greater consideration of the normal functions of the regulators of TDP-43 phosphorylation that may be perturbed in disease is warranted. This synthesis aims to build towards a comprehensive understanding of the complex role of TDP-43 phosphorylation in the pathogenesis of neurodegeneration.

Keywords:  Amyotrophic lateral sclerosis; Frontotemporal dementia; Kinase; Neurodegeneration; Phosphatase; Phosphorylation; Post-translational modifications; TDP-43

DOI:  https://doi.org/10.1186/s13024-025-00839-8
Sci Rep. 2025 May 03. 15(1): 15546

Huntingtin inclusion bodies have distinct immunophenotypes and ubiquitination profiles in the Huntington's disease human cerebral cortex.

Molly E V Swanson, Adelie Y S Tan, Lynette J Tippett, Clinton P Turner, Maurice A Curtis, Emma L Scotter, Hilal A Lashuel, Mike Dragunow, Richard L M Faull, Helen C Murray, Malvindar K Singh-Bains.

Huntington's disease (HD) is a hereditary neurodegenerative condition caused by a CAG repeat expansion mutation in the gene encoding the huntingtin (HTT) protein. The accumulation of HTT inclusion bodies is a pathological hallmark of HD and a common target for therapeutic strategies. However, the limited efficacy of treatments targeting the HTT protein highlights the need for a better understanding of the role of HTT inclusion bodies in HD pathogenesis. This study examined the heterogeneity of HTT inclusion body composition by co-labelling with three HTT epitope-specific antibodies to characterize HTT inclusion body 'immunophenotype'. We then characterized the size and sub-cellular location of HTT inclusions with distinct immunophenotypes. Using multiplex immunohistochemistry, we also examined the ubiquitination profile of each immunophenotype. Our findings demonstrate that HTT inclusions have a range of immunophenotypes, with some labelled by only one of the three antibodies and others exhibiting co-labelling by several antibodies, thus demonstrating the heterogeneity in inclusion composition and structure. We outline evidence that inclusion bodies exclusively labelled with the EM48 antibody are small, non-nuclear, and more abundant in HD cases with increased CAG repeat length, higher Vonsattel grade, and earlier age of onset. We also find that HTT inclusion bodies labelled by multiple antibodies are more likely to be ubiquitinated, predominantly by K63- rather than K48-linked ubiquitin, suggesting preferential degradation by autophagy. Lastly, we show that ubiquitinated HTT inclusion bodies are more highly immunoreactive for ubiquilin 2 than p62. Our findings highlight the need for multiple antibodies to capture the full spectrum of HTT pathology in HD and imply that future studies should consider the diversity of inclusion body composition and structure when correlating pathology formation to neurodegeneration, clinical symptoms, or disease severity.

DOI: https://doi.org/10.1038/s41598-025-00465-w
Sci Adv. 2025 May 09. 11(19): eadn2528

Kinome screening identifies integrated stress response kinase EIF2AK1/HRI as a negative regulator of PINK1 mitophagy signaling.

Pawan K Singh, Shalini Agarwal, Ilaria Volpi, Léa P Wilhelm, Giada Becchi, Andrew Keenlyside, Thomas Macartney, Rachel Toth, Adrien Rousseau, Glenn R Masson, Ian G Ganley, Miratul M K Muqit.

Loss-of-function mutations in the PINK1 kinase lead to early-onset Parkinson's disease (PD). PINK1 is activated by mitochondrial damage to phosphorylate ubiquitin and Parkin, triggering mitophagy. PINK1 also indirectly phosphorylates Rab GTPases, such as Rab8A. Using an siRNA library targeting human Ser/Thr kinases in HeLa cells, we identified EIF2AK1 [heme-regulated inhibitor (HRI) kinase], a branch of the integrated stress response (ISR), as a negative regulator of PINK1. EIF2AK1 knockdown enhances mitochondrial depolarization-induced PINK1 stabilization and phosphorylation of ubiquitin and Rab8A. These results were confirmed in SK-OV-3, U2OS, and ARPE-19 cells. Knockdown of DELE1, an activator of EIF2AK1, produced similar effects. Notably, the ISR inhibitor ISRIB also enhanced PINK1 activation. In human cells with mito-QC mitophagy reporters, EIF2AK1 knockdown or ISRIB treatment increased PINK1-dependent mitophagy without affecting deferiprone-induced mitophagy. These findings suggest that the DELE1-EIF2AK1 ISR pathway is a negative regulator of PINK1-dependent mitophagy. Further evaluation in PD-relevant models is needed to assess the therapeutic potential of targeting this pathway.

DOI: https://doi.org/10.1126/sciadv.adn2528
Int J Mol Sci. 2025 Apr 16. pii: 3774. [Epub ahead of print]26(8):

Current Development of iPSC-Based Modeling in Neurodegenerative Diseases.

Xiangge Guo, Xumeng Wang, Jiaxuan Wang, Min Ma, Qian Ren.

  Over the past two decades, significant advancements have been made in the induced pluripotent stem cell (iPSC) technology. These developments have enabled the broader application of iPSCs in neuroscience, improved our understanding of disease pathogenesis, and advanced the investigation of therapeutic targets and methods. Specifically, optimizations in reprogramming protocols, coupled with improved neuronal differentiation and maturation techniques, have greatly facilitated the generation of iPSC-derived neural cells. The integration of the cerebral organoid technology and CRISPR/Cas9 genome editing has further propelled the application of iPSCs in neurodegenerative diseases to a new stage. Patient-derived or CRISPR-edited cerebral neurons and organoids now serve as ideal disease models, contributing to our understanding of disease pathophysiology and identifying novel therapeutic targets and candidates. In this review, we examine the development of iPSC-based models in neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease, and Huntington's disease.

Keywords:  astrocyte; brain organoid; iPS cell; microglia; neural stem cell; neurodegenerative disease; neuron; oligodendrocyte; reprogramming factor

DOI:  https://doi.org/10.3390/ijms26083774
Neurobiol Dis. 2025 May 06. pii: S0969-9961(25)00155-X. [Epub ahead of print] 106939

Neuroimmune signaling mediates astrocytic nucleocytoplasmic disruptions and stress granule formation associated with TDP-43 pathology.

Constance Zhou, Evelyn J Hardin, Till S Zimmer, Stephanie Jackvony, Daniel Barnett, Noopur Khobrekar, Elisa Giacomelli, Lorenz Studer, Adam L Orr, Anna G Orr.

  Alterations in transactivating response region DNA-binding protein 43 (TDP-43) are prevalent in amyotrophic lateral sclerosis (ALS), frontotemporal dementia (FTD), and other neurological disorders. TDP-43 influences neuronal functions and might also affect glial cells. However, specific intracellular effects of TDP-43 alterations on glial cells and underlying mechanisms are not clear. We report that TDP-43 dysregulation in mouse and human cortical astrocytes causes nucleoporin mislocalization, nuclear envelope remodeling, and changes in nucleocytoplasmic protein transport. These effects are dependent on interleukin-1 (IL-1) receptor activity and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) signaling and are associated with the formation of cytoplasmic stress granules. Stimulation of IL-1 receptors and NF-κB signaling are necessary and sufficient to induce astrocytic stress granules and rapid nucleocytoplasmic changes, which are broadly alleviated by inhibition of the integrated stress response. These findings establish that TDP-43 alterations and neuroimmune factors can induce nucleocytoplasmic changes through NF-κB signaling, revealing mechanistic convergence of proteinopathy and neuroimmune pathways onto glial nucleocytoplasmic disruptions that may occur in diverse neurological conditions.

Keywords:  Astrocytes; Integrated stress response; Neurodegeneration; Neuroimmune signaling; Nuclear pore; Stress granules; TDP-43

DOI:  https://doi.org/10.1016/j.nbd.2025.106939
Neurobiol Dis. 2025 May 07. pii: S0969-9961(25)00163-9. [Epub ahead of print] 106947

Expression of a protein disulfide isomerase A3 variant associated with amyotrophic lateral sclerosis triggers disease features in mice.

Martin Sepulveda, Francisca Martinez-Traub, Patricia Ojeda, Viviana Perez, Jorge Ojeda, Jessica Mella, Rodrigo Diaz, Pablo Rozas, Matías Mansilla-Jaramillo, Amparo Zuleta, Guillermo Diaz, Bredford Kerr, Ute Woehlbier, Juan Pablo Henríquez, Danilo B Medinas, Claudio Hetz.

  Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by loss of motoneurons and compromised proteostasis. Dysfunction of the endoplasmic reticulum (ER) has been identified as a transversal pathogenic mechanism associated with motoneurons vulnerability in ALS. Protein disulfide isomerases (PDIs) are key enzymes catalyzing protein folding at the ER that are altered in the disease, involving biochemical and genetic perturbations. In ALS cases, we previously identified variants in the gene encoding PDIA3 (also known as Grp58 or ERp57), which were associated with altered neurite outgrowth in cell culture and abnormal motoneuron connectivity in zebrafish. Here, we report the generation of transgenic mice expressing the ALS-associated PDIA3Q481K variant. Moderate PDIA3Q481K overexpression resulted in altered motor capacity accompanied by decreased motoneuron number. The adverse effects of PDIA3Q481K were associated with induction of ER stress in the spinal cord and subtle morphological changes in neuromuscular junctions. Our results suggest that the PDIA3Q481K variant is likely pathogenic and its overexpression in mice recapitulate some ALS features, further supporting the concept that altered proteostasis due to PDI dysfunction may predispose an individual to develop the disease.

Keywords:  Amyotrophic lateral sclerosis; Endoplasmic reticulum; Protein disulfide isomerase; Transgenic line

DOI:  https://doi.org/10.1016/j.nbd.2025.106947
Bioessays. 2025 May 04. e70016

Mitochondria and Endoplasmic Reticulum Contact Site as a Regulator of Proteostatic Stress Responses in Neurodegenerative Diseases.

Seiji Watanabe, Koji Yamanaka.

  Recent evidence indicates that the mitochondria-endoplasmic reticulum (ER) contact site is a novel microdomain essential for cellular homeostasis. Various proteins are accumulated at the mitochondria-associated membrane (MAM), an ER subcomponent closely associated with the mitochondria, contributing to Ca2+ transfer to the mitochondria, lipid synthesis, mitochondrial fission/fusion, and autophagy. These functions are disrupted in the diseases, particularly in neurodegenerative diseases such as amyotrophic lateral sclerosis (ALS) and Alzheimer's disease. In this review, we summarize the disruption of protein homeostasis in various neurodegenerative diseases, present recent works on the mechanisms of MAM aberration, including ours mainly focused on ALS, and then discuss challenges and prospects for future MAM-targeted therapies in neurodegenerative diseases.

Keywords:  mitochondria‐associated membranes; neurodegenerative diseases; protein homeostasis

DOI:  https://doi.org/10.1002/bies.70016
iScience. 2025 May 16. 28(5): 112385

Endosomal protein DENND10 promotes developmental competence of neurite extension.

Aiqing Li, Jie Zhang, Chao Ma, Lijuan Qi, Qiuming Hu, Qian Li, Yufei Fang, Jianrui Song, Yaobo Liu, Yanling Zhang.

  A distinguishing feature of neurons is the presence of long neurites that enable far-reaching communication. Establishing this complex morphology requires precise regulation of intracellular transport and signaling. Our study identifies DENND10, an ancient endosomal protein, as a crucial factor in shaping neuron morphology. DENND10 is a potential regulator of Rab GTPase signaling and interacts with the CCC/Retriever endosomal complex. Loss of DENND10 in a neuronal cell culture model resulted in shortened neurites. Quantitative proteomics revealed two distinct processes of neurite outgrowth: differentiation-induced biochemical changes and a pre-existing vesicular transport system modulated by DENND10. Mechanistically, both Rab27 and CCC complex subunit CCDC22 act downstream of DENND10 to support neurite extension. In primary cortical neurons, loss of DENND10 or CCDC22 led to shortened dendrites and impaired axon development. These findings provide a conceptual framework for neuronal morphogenesis during differentiation and highlight the critical role of DENND10/CCC in neurite extension.

Keywords:  Biological sciences; Cellular neuroscience; Molecular neuroscience; Natural sciences; Neuroscience

DOI:  https://doi.org/10.1016/j.isci.2025.112385
NPJ Parkinsons Dis. 2025 May 03. 11(1): 106

Emergent glutamate & dopamine dysfunction in VPS35(D620N) knock-in mice and rapid reversal by LRRK2 inhibition.

A Kamesh, C A Kadgien, N Kuhlmann, S Coady, A Pietrantonio, Y Cousineau, A Khayachi, A Jurado Santos, E P Hurley, J C Barron, M P Parsons, A J Milnerwood.

The D620N variant in Vacuolar Protein Sorting 35 (VPS35) causes autosomal-dominant, late-onset Parkinson's disease. VPS35 is a core subunit of the retromer complex that canonically recycles transmembrane cargo from sorting endosomes. Although retromer cargoes include many synaptic proteins, VPS35's neuronal functions are poorly understood. To investigate the consequences of the Parkinson's mutation, striatal neurotransmission was assessed in 1- to 6-month-old VPS35 D620N knock-in (VKI) mice. Spontaneous and optogenetically-evoked corticostriatal glutamate transmission was increased in VKI spiny projection neurons by 6 months and was unaffected by acute leucine-rich repeat kinase 2 (LRRK2) inhibition. Total striatal glutamate release by iGluSnFR imaging was similar to wild-type. dLight imaging revealed robust increases in VKI striatal dopamine release by 6 months, which were reversed with acute LRRK2 kinase inhibition. We conclude that increased striatal neurotransmission in VKI mice progressively emerges in young-adulthood, and that dopamine dysfunction is likely the result of sustained, rapidly-reversible, LRRK2 hyperactivity.

DOI: https://doi.org/10.1038/s41531-025-00948-7
Commun Biol. 2025 May 10. 8(1): 723

Tracing mitochondrial marks of neuronal aging in iPSCs-derived neurons and directly converted neurons.

Nimmy Varghese, Leonora Szabo, M Zameel Cader, Imane Lejri, Amandine Grimm, Anne Eckert.

This study aims to determine if neurons derived from induced pluripotent stem cells (iPSCsNs) and directly converted neurons (iNs) from the same source cells exhibit changes in mitochondrial properties related to aging. This research addresses the uncertainty around whether aged iPSCsNs retain aging-associated mitochondrial impairments upon transitioning through pluripotency while direct conversion maintains these impairments. We observe that both aged models exhibit characteristics of aging, such as decreased ATP, mitochondrial membrane potential, respiration, NAD+/NADH ratio, and increased radicals and mitochondrial mass. In addition, both neuronal models show a fragmented mitochondrial network. However, aged iPSCsNs do not exhibit a metabolic shift towards glycolysis, unlike aged iNs. Furthermore, mRNA expression differed significantly between aged iPSCsNs and aged iNs. The study concludes that aged iPSCsNs may differ in transcriptomics and the aging-associated glycolytic shift but can be a valuable tool for studying specific feature of mitochondrial neuronal aging in vitro alongside aged iNs.

DOI: https://doi.org/10.1038/s42003-025-08152-2
Curr Biol. 2025 May 05. pii: S0960-9822(25)00384-7. [Epub ahead of print]35(9): R320-R322

ER-to-lysosome-associated degradation.

Maurizio Molinari.

Maurizio Molinari introduces ER-to-lysosome-associated degradation - the autophagic and non-autophagic pathways that deliver ERAD-resistant misfolded proteins to the lysosome for degradation to maintain cellular proteostasis.

DOI: https://doi.org/10.1016/j.cub.2025.03.068
iScience. 2025 May 16. 28(5): 112380

RNA splicing modulator for Huntington's disease treatment induces peripheral neuropathy.

Florian Krach, Tom Boerstler, Stephanie Neubert, Laura Krumm, Martin Regensburger, Jürgen Winkler, Beate Winner.

  RNA splicing modulators, a new class of small molecules with the potential to modify the protein expression levels, have quickly been translated into clinical trials. These compounds hold promise for treating neurodegenerative disorders, including branaplam for lowering huntingtin levels in Huntington's disease. However, the VIBRANT-HD trial was terminated due to the emergence of peripheral neuropathy. Here, we describe the complex mechanism whereby branaplam activates p53, induces nucleolar stress in human induced pluripotent stem cell (iPSC)-derived motor neurons (iPSC-MN), and thereby enhanced expression of the neurotoxic p53-target gene BBC3. On the cellular level, branaplam disrupts neurite integrity, reflected by elevated neurofilament light chain levels. These findings illustrate the complex pharmacology of RNA splicing modulators with a small therapeutic window between lowering huntingtin levels and the clinically relevant off-target effect of neuropathy. Comprehensive toxicological screening in human stem cell models can complement pre-clinical testing before advancing RNA-targeting drugs to clinical trials.

Keywords:  Biological sciences; Cell biology; Cellular neuroscience; Natural sciences; Neuroscience; Pharmacology

DOI:  https://doi.org/10.1016/j.isci.2025.112380
Int J Mol Sci. 2025 Apr 10. pii: 3551. [Epub ahead of print]26(8):

A Comparative Study of a Potent CNS-Permeable RARβ-Modulator, Ellorarxine, in Neurons, Glia and Microglia Cells In Vitro.

Yunxi Zhang, Lilie Gailloud, Alexander Shin, Jessica Fewkes, Rosella Pinckney, Andrew Whiting, Paul Chazot.

  Vitamin A (retinol) and its derivatives (retinoids) assume critical roles in neural development, cellular differentiation, axon elongation, programmed cell apoptosis and various fundamental cellular processes. Retinoids function by binding to specific nuclear receptors, such as retinoic acid receptors (RARs) and retinoid X receptors (RXRs), activating specific signalling pathways in the cells. The disruption of the retinoic acid signalling pathway can result in neuroinflammation, oxidative and ER stress and mitochondrial dysfunction and has been implicated in a wide range of neurodegenerative diseases. The present study explored the potential therapeutic application of our innovative CNS-permeable synthetic retinoid, Ellorarxine, for the treatment of neurodegenerative disorders in vitro. An MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) tetrazolium assay, lactate dehydrogenase (LDH) assay, enzyme-linked immunosorbent assay (ELISA), immunocytochemistry and immunofluorescence staining were performed. Ellorarxine increased Cyp26 and, selectively, RARβ protein expression in neurons, glia and microglia. Ellorarxine significantly reduced cell death (neurons, glia), increased mitochondrial viability (neurons), modulated cytokine release (microglia), and positively regulated cellular autophagy (neurons, glia, microglia). These results suggest that Ellorarxine is a promising drug candidate that should be further investigated in the treatment of neurodegenerative diseases.

Keywords:  DC645; NVG0645; RARs; autophagy; ellorarxine; mitochondrial dysfunction; neurodegeneration; neuroinflammation; neuroprotective effects; retinoid

DOI:  https://doi.org/10.3390/ijms26083551
J Biochem. 2025 May 07. pii: mvaf024. [Epub ahead of print]

ZNRF1-dependent regulation of AKT activity modulates Nav subcellular localization and AIS position in neurons to regulate fear-related behavior.

Moeka Ohno, Shuji Wakatsuki, Hiroshi Kuniishi, Masayuki Sekiguchi, Eri Takeuchi, Keizo Takao, Megumi Watase, Takaya Abe, Toshiyuki Araki.

  The axon initial segment (AIS) is a specialized compartment at the proximal axon, characterized by condensed localization of specific cytoskeletal proteins, including Ankyrin G (AnkG) and βIV-spectrin which organize voltage-gated ion channels (VGICs). The location and morphology of the AIS can change in response to neuronal activity; however, the precise mechanisms for the AIS plasticity remain unclear. Previously, we demonstrated that ubiquitin E3 ligase ZNRF1 is localized to presynaptic terminals in cultured hippocampal neurons and may play a role in Ca2+-dependent exocytosis. Here, we show that using ZNRF1 knockout (ZNRF1 KO) mice, ZNRF1-dependent AKT degradation induces AIS shift and increased cell surface localization of voltage-gated sodium channel Nav1.2. We also found that ZNRF1 KO mice exhibit enhanced short-term fear memory and increased contextual fear memory. These findings suggest that ZNRF1 may serve as a novel regulator of AIS localization.

Keywords:  axon initial segment; fear memory; ubiquitin ligase; voltage-gated ion channel

DOI:  https://doi.org/10.1093/jb/mvaf024
FASEB J. 2025 May 15. 39(9): e70549

Reduced Palmitoylation of SQSTM1/p62 in Huntington Disease Is Associated With Impaired Autophagy.

F Abrar, M C Davies, Y Alshehabi, A Kumar, A Dang, Y T N Nguyen, J Collins, N S Caron, J S Choudhary, S S Sanders, M O Collins, M R Hayden, D D O Martin.

Disruption of autophagy has emerged as a common feature in many neurodegenerative diseases. Autophagy is a membrane-dependent pathway that requires many key regulators to quickly localize on and off membranes during induction, promoting membrane fusion. Previously, our bioinformatic approaches have shown that autophagy and Huntington disease (HD) are enriched in palmitoylated proteins. Palmitoylation involves the reversible addition of long-chain fatty acids to promote membrane binding. Herein, we show that inhibition of palmitoylation regulates the abundance of several key regulators of autophagy and leads to a partial block of autophagic flux. We confirm that the autophagy receptor SQSTM1/p62 (sequestosome 1) is palmitoylated and directed to the lysosome. Importantly, we report that SQSTM1 palmitoylation is significantly reduced in HD patient and mouse model brains. This finding reveals a novel mechanism contributing to the generation of empty autophagosomes previously seen in HD models and patient-derived cells.

DOI: https://doi.org/10.1096/fj.202401781R
Neuroscience. 2025 May 04. pii: S0306-4522(25)00360-4. [Epub ahead of print]

srp54 promotes motor neuron development and is required for motility in zebrafish.

Nikaela Losievski, Pooja Kamath, Ashley Fox, Natalie M Aloi, Megan C Baird, Amy Everest, Thomas L Gallagher, Sharon L Amacher, Stephen J Kolb.

  The signal recognition particle (SRP) is a highly conserved ribonucleoprotein (RNP) that translocates a subset of secreted and integral membrane proteins to the endoplasmic reticulum for proper localization. The most conserved SRP protein component, SRP54, has been implicated in the molecular etiology of spinal muscular atrophy (SMA). A key feature of SMA is the selective loss of motor neurons; however, the mechanism underlying this selectivity is unknown. SMA arises from deficient levels of the ubiquitously expressed Survival of Motor Neuron (SMN) protein. SMN is proposed to assemble the SRP, and SMN deficiency in SMA may attenuate SRP function and contribute to motor neuron death in patients. Using zebrafish embryos homozygous for a srp54 nonsense mutation (srp54-/-), we investigated the requirement of Srp54 protein in motor axon development. The first grossly distinguishable phenotype observed in srp54-/- embryos was reduced motility at 30 h postfertilization (hpf). Additionally, we detected reduced length and branching of caudal primary motor axons in srp54-/- embryos compared to srp54+/+ and srp54+/- siblings at 30 hpf, suggesting that defective motor neurons may contribute to the observed immotility. We also examined additional neural, secretory, and migratory cell types at 30 hpf to assess whether motor neurons are especially vulnerable to Srp54 deficiency. Of the cell types evaluated, only the hatching gland had distinct expression pattern alterations in srp54-/- embryos at this developmental stage. Our findings suggest that Srp54 deficiency results in motor neuron developmental defects and support the hypothesis that SRP54 may influence motor neuron selectivity in SMA.

Keywords:  Central nervous system; Hatching gland; Neurodevelopment; Signal recognition particle; Spinal muscular atrophy

DOI:  https://doi.org/10.1016/j.neuroscience.2025.05.008
Sci Rep. 2025 May 05. 15(1): 15621

In vitro models of microglia: a comparative study.

Zoe Woolf, Taylor J Stevenson, Kevin Lee, Blake Highet, Jena Macapagal Foliaki, Ramona Ratiu, Justin Rustenhoven, Jason Correia, Patrick Schweder, Peter Heppner, Maria Weinert, Natacha Coppieters, Thomas Park, Johanna Montgomery, Amy M Smith, Michael Dragunow.

  Microglia perform key homeostatic functions to protect the central nervous system (CNS). However, in many brain disorders their protective functions are abrogated, contributing to disease progression. Therefore, studies of microglial function are critical to developing treatments for brain disorders. Different in vitro microglia models have been established, including primary human and rodent cells, induced pluripotent stem cell (iPSC)-derived models, and immortalised cell lines. However, a direct comparative analysis of the phenotypic and functional characteristics of these models has not been undertaken. Accurate modelling of human microglia in vitro is critical for ensuring the translatability of results from the bench to the brain. Therefore, our study aimed to characterise and compare commonly utilised in vitro microglia models. We assessed four established microglia models: primary human microglia, human iPSC-derived microglia, the human microglial clone 3 (HMC3) cell line, and primary mouse microglia, with primary human brain pericytes acting as a negative control. Primary human microglia, iPSC-derived microglia, and mouse microglia stained positive for myeloid-cell markers (Iba1, CD45 and PU.1), while HMC3 cells only stained positive for mural-cell markers (PDGFRβ and NG2). Distinct secretomes were observed in all cell models in response to inflammatory treatment, with iPSC-derived microglia showing the most significant inflammatory secretions. Notably, nitric oxide was only secreted by mouse microglia. Although all cell types exhibited phagocytic capacity, primary human microglia and iPSC-derived microglia displayed significantly higher levels of phagocytosis. Overall, comparative analysis revealed notable differences between human microglia, iPSC-derived microglia, HMC3 cells and mouse microglia. Such differences should be considered when using these models to study human brain diseases. Experimental findings obtained from mouse models or cell lines should ultimately be cross validated to ensure the translatability of results to the human condition.

Keywords:   In vitro models; Comparative analysis; Human microglial clone 3 (HMC3); Microglia; iPSC-derived microglia

DOI:  https://doi.org/10.1038/s41598-025-99867-z
Res Sq. 2025 Apr 14. pii: rs.3.rs-6406576. [Epub ahead of print]

Nanoscale domains govern local diffusion and aging within FUS condensates.

Guoming Gao, Emily R Sumrall, Nils G Walter.

Biomolecular condensates regulate cellular physiology by sequestering and processing RNAs and proteins, yet how these processes are locally tuned within condensates remains unclear. Moreover, in neurodegenerative diseases such as amyotrophic lateral sclerosis (ALS), condensates undergo liquid-to-solid phase transitions, but capturing early intermediates in this process has been challenging. Here, we present a surface multi-tethering approach to achieve intra-condensate single-molecule tracking of fluorescently labeled RNA and protein molecules within liquid-like condensates. Using RNA-binding protein Fused in Sarcoma (FUS) as a model for condensates implicated in ALS, we discover that RNA and protein diffusion is confined within distinct nanometer-scale domains, or nanodomains, which exhibit unique connectivity and chemical environments. During condensate aging, these nanodomains reposition, facilitating FUS fibrilization at the condensate surface, a transition enhanced by FDA-approved ALS drugs. Our findings demonstrate that nanodomain formation governs condensate function by modulating biomolecule sequestration and percolation, offering insights into condensate aging and disease-related transitions.

DOI: https://doi.org/10.21203/rs.3.rs-6406576/v1
Nat Commun. 2025 May 07. 16(1): 4259

Autophagy-independent role of ATG9A vesicles as carriers for galectin-9 secretion.

Wenting Zhang, Cuicui Ji, Xianghua Li, Tianlong He, Wei Jiang, Yukun Liu, Meiling Wu, Yunpeng Zhao, Xuechai Chen, Xiaoli Wang, Jian Li, Haolin Zhang, Juan Wang.

Galectins play vital roles in cellular processes such as adhesion, communication, and survival, yet the mechanisms underlying their unconventional secretion remain poorly understood. This study identifies ATG9A, a core autophagy protein, as a key regulator of galectin-9 secretion via a mechanism independent of classical autophagy, secretory autophagy, or the LC3-dependent extracellular vesicle loading and secretion pathway. ATG9A vesicles function as specialized carriers, with the N-terminus of ATG9A and both carbohydrate recognition domains of galectin-9 being critical for the process. TMED10 mediates the incorporation of galectin-9 into ATG9A vesicles, which then fuse with the plasma membrane via the STX13-SNAP23-VAMP3 SNARE complex. Furthermore, ATG9A regulates the secretion of other proteins, including galectin-4, galectin-8, and annexin A6, but not IL-1β, galectin-3, or FGF2. This mechanism is potentially conserved across other cell types, including monocytic cells, which underscores its broader significance in unconventional protein secretion.

DOI: https://doi.org/10.1038/s41467-025-59605-5
J Nutr Biochem. 2025 May 02. pii: S0955-2863(25)00106-8. [Epub ahead of print] 109943

Mitochondrial fatty acid oxidation dysfunction impairs autophagic flux through ATP deficiency-caused lysosomal pH abnormity.

Yan-Yu Zhang, Ze-Dong Lv, Mai Wang, Jun-Xian Wang, Samwel Mchele Limbu, Fang Qiao, Li-Qiao Chen, Mei-Ling Zhang, Yuan Luo, Zhen-Yu Du.

  Autophagy, a pivotal lysosomal degradation process, plays crucial roles in cellular homeostasis and energy metabolism. Mitochondrial fatty acid oxidation (FAO), a key mitochondrial function, is crucial for energy production. Generally, mitochondrial dysfunction exerts negative effects on autophagy, but the regulatory role of mitochondrial FAO dysfunction on the autophagic process remains unclear. The present study aimed to elucidate the role and mechanism of mitochondrial FAO in regulating autophagy process. We used Nile tilapia (Oreochromis niloticus) as a model and inhibited mitochondrial FAO by dietary mildronate feeding or knocking down carnitine palmitoyltransferase 1a. We found that mitochondrial FAO inhibition enhanced autophagy initiation and lysosomal proliferation accompanied by decreased autophagy degradation activity due to lysosomal acidification abnormity. Moreover, mitochondrial FAO inhibition decreased adenosine triphosphate (ATP) production and elevated adenosine monophosphate (AMP)/ATP promoted autophagy initiation via the AMP-activated protein kinase-serine/threonine kinase 1 pathway. Furthermore, mitochondrial FAO inhibition upregulated peroxisome proliferator-activated receptor alpha and retinoid X receptor alpha protein expression, which promoted transcription factor EB mRNA and its protein expression. Meanwhile, mitochondrial FAO inhibition led to lysosomal alkalinization, which is due to a pH increase caused by v-ATPase V1/V0 imbalance and ATP deficiency from mitochondrial dysfunction. Collectively, our results highlight the role of mitochondrial FAO in maintaining lysosomal homeostasis and autophagic flux through stabilizing lysosomal acidification.

Keywords:  autophagy; fatty acid oxidation inhibition; lysosome; mitochondrial dysfunction; vacuolar ATPase

DOI:  https://doi.org/10.1016/j.jnutbio.2025.109943
iScience. 2025 May 16. 28(5): 112390

Agent-based modeling of neuronal mitochondrial dynamics using intrinsic variables of individual mitochondria.

Garrett M Fogo, Francisco J Torres Torres, Reagan L Speas, Anthony R Anzell, Thomas H Sanderson.

  Mitochondrial networks undergo remodeling to regulate form and function. The dynamic nature of mitochondria is maintained by the dueling processes of mitochondrial fission and fusion. Dysfunctional mitochondrial dynamics have been linked to debilitating diseases and injuries, suggesting mitochondrial dynamics as a promising therapeutic target. Increasing our understanding of the factors influencing mitochondrial dynamics will help inform therapeutic development. Utilizing live imaging of primary neurons, we analyzed how intrinsic properties of individual mitochondria influence their behavior. We found that size, shape, mitochondrial membrane potential, and protein oxidation predict mitochondrial fission and fusion. We constructed an agent-based model of mitochondrial dynamics, the mitochondrial dynamics simulation (MiDyS). In silico experiments of neuronal ischemia/reperfusion injury and antioxidant treatment illustrate the utility of MiDyS for testing hypothesized mechanisms of injury progression and evaluating therapeutic strategies. We present MiDyS as a framework for leveraging in silico experimentation to inform and improve the design of therapeutic trials.

Keywords:  Cell biology; Molecular biology; Neuroscience

DOI:  https://doi.org/10.1016/j.isci.2025.112390
J Mater Chem B. 2025 May 08.

A red-emitting, microenvironment-insensitive fluorophore for lysosome-specific imaging in live cells.

Shabnam Mansuri, Subhadra Ojha, Sriram Kanvah.

Lysosomes and the endoplasmic reticulum (ER) are vital for cellular homeostasis, degradation, and signaling, making them key imaging targets. However, existing fluorescent probes suffer from limitations such as pH sensitivity, poor photostability, and cytotoxicity. To overcome these challenges, we developed two red-emitting fluorophores, DM and MM, based on a rigid DCM scaffold with morpholine linkers. DM rapidly localizes to lysosomes within 10 minutes, exhibiting exceptional photostability, pH insensitivity, and resilience in live and fixed cells. MM initially targets the ER before redistributing to lysosomes, enabling studies of inter-organelle dynamics and lysosomal maturation. Both probes, excitable at 561 nm, emit in the red spectral region, reducing autofluorescence and phototoxicity while allowing deep tissue imaging. DM efficiently tracks lysosomal dynamics under normal and stressed conditions, including mitophagy and lysosome-mitochondria interactions. MM's dual-targeting behavior provides insights into ER-lysosome crosstalk, crucial for cellular signaling. Both dyes exhibit negligible cytotoxicity (up to 100 μM), ensuring prolonged imaging without disrupting the cellular function. Their rigid scaffold imparts high stability, making them versatile tools for studying lysosomal and ER-associated processes. DM and MM set a new standard for dynamic organelle imaging, advancing biomedical research on lysosomal biology and disease mechanisms.

DOI: https://doi.org/10.1039/d5tb00296f
J Biol Chem. 2025 May 07. pii: S0021-9258(25)02057-5. [Epub ahead of print] 110208

Parkin mediates the mitochondrial dysfunction through mRpL18.

Xiuxiu Ti, Hui Zuo, Guochun Zhao, Yuwei Li, Minghui Du, Liwen Xu, Shengnan Li, Zhaoliang Shan, Yuxue Gao, Guangming Gan, Yan Wang, Qing Zhang.

  Loss of function of parkin leads to the mitochondrial dysfunction, which is closely related to Parkinson's disease. However, the in vivo mechanism is far from clear. One of the dogmas is that impaired Parkin causes dysfunction of mitophagy mediated by Pink1-Parkin axis. The other is that impaired Parkin causes Mfn accumulation which leads to mitochondrial dysfunction. Surprisingly, in Drosophila muscles, as reported, the first dogma is not applicable; for the second dogma, our study suggests that Parkin mediates the mitochondrial dysfunction through modulating mitochondrial morphology, which is determined by synergy of both Marf and mitochondrial protein mRpL18 got from our genome-wide screen, whose RNAi rescues parkin RNAi phenotype. Mechanistically, we found that impaired Parkin upregulated both the transcription and protein levels of mRpL18 dependent on its E3 ligase activity, causing the mRpL18 accumulation outside mitochondria. Consequently, cytosolic accumulated mRpL18 competitively bound Drp1, leading to the reduction of the binding of Drp1 to its receptor Fis1, which finally inhibited the mitochondrial fission and tipped the balance to mitochondrial hyperfusion, thereby affected the mitochondrial function. Taken together, our study suggests that impaired Parkin causes mitochondrial hyperfusion due to two reasons: (1) Parkin defect impairs Pink1-Parkin axis-mediated Marf degradation, which promotes mitochondrial fusion; (2) Parkin defect causes mRpL18 accumulation, which inhibits Drp1/Fis1-mediated mitochondrial fission. These two ways function together to drive Parkin-mediated mitochondrial hyperfusion. Therefore, knockdown of either marf or mRpL18 can prevent mitochondrial hyperfusion, leading to the rescue of Parkin defect-triggered fly wing phenotypes. Overall, our study unveils a new facet of how Parkin regulates mitochondrial morphology to affect mitochondrial function, which provides new insights for the understanding and treatment of Parkinson's disease.

Keywords:  Drp1; Parkin; Parkinson's disease; mRpL18

DOI:  https://doi.org/10.1016/j.jbc.2025.110208
Stem Cell Res Ther. 2025 May 09. 16(1): 232

Electrophysiological characterisation of intranigral-grafted hiPSC-derived dopaminergic neurons in a mouse model of Parkinson's disease.

Bérengère Ballion, Marie-Laure Bonnet, Sébastien Brot, Afsaneh Gaillard.

   BACKGROUND: Parkinson's disease (PD) is a complex neurological disorder characterized by the progressive degeneration of midbrain dopaminergic (mDA) neurons in the substantia nigra (SN). This degeneration disrupts the basal ganglia loops, leading to both motor and non-motor dysfunctions. Cell therapy for PD aims to replace lost mDA neurons to restore the DA neurotransmission in the denervated forebrain targets. In clinical trials for PD, mDA neurons are implanted into the target area, the striatum, and not in the SN where they are normally located. This ectopic localisation of cells may affect the functionality of transplanted neurons due to the absence of appropriate host afferent regulation. We recently demonstrated that human induced pluripotent stem cells (hiPSCs) derived mDA progenitors grafted into the substantia nigra pars compacta (SNpc) in a mouse model of PD, differentiated into mature mDA neurons, restored the degenerated nigrostriatal pathway, and induced motor recovery. The objective of the present study was to evaluate the long-term functionality of these intranigral-grafted mDA neurons by assessing their electrophysiological properties.
METHODS: We performed intranigral transplantation of hiPSC-derived mDA progenitors in a 6-hydroxydopamine RAG2-KO mouse model of PD. We recorded in vivo unit extracellular activity of grafted mDA neurons in anesthetised mice from 9 to 12 months post-transplantation. Their electrophysiological properties, including firing rates, patterns and spike characteristics, were analysed and compared with those of native nigral dopaminergic neurons from control mice.
RESULTS: We demonstrated that these grafted mDA neurons exhibited functional characteristics similar to those of native nigral dopaminergic neurons, such as large bi- or triphasic spike waveforms, low firing rates, pacemaker-like properties, and two single-spike firing patterns. Although grafted mDA neurons also displayed low discharge frequencies below 10 Hz, their mean frequency was significantly lower than that of nigral mDA neurons, with a differential pattern distribution.
CONCLUSIONS: Our findings indicate that grafted mDA neurons exhibit dopaminergic-like functional properties, including intrinsic membrane potential oscillations leading to regular firing patterns. Additionally, they demonstrated irregular and burst firing patterns, suggesting they receive modulatory inputs. However, grafted mDA neurons displayed distinct properties, potentially related to their human origin or the incomplete maturation one year after transplantation.

Keywords:  Cell therapy; Electrophysiology; HiPSC; In vivo; Intranigral transplantation; Mouse; Parkinson’s disease

DOI:  https://doi.org/10.1186/s13287-025-04344-z
Mol Cell Biol. 2025 May 09. 1-13

Key Mechanisms in Lysosome Stability, Degradation and Repair.

Rui Zhang, Marc A Vooijs, Tom Gh Keulers.

  Lysosomes are organelles that play pivotal roles in macromolecule digestion, signal transduction, autophagy, and cellular homeostasis. Lysosome instability, including the inhibition of lysosomal intracellular activity and the leakage of their contents, is associated with various pathologies, including cancer, neurodegenerative diseases, inflammatory diseases and infections. These lysosomal-related pathologies highlight the significance of factors contributing to lysosomal dysfunction. The vulnerability of the lysosomal membrane and its components to internal and external stimuli make lysosomes particularly susceptible to damage. Cells are equipped with mechanisms to repair or degrade damaged lysosomes to prevent cell death. Understanding the factors influencing lysosome stabilization and damage repair is essential for developing effective therapeutic interventions for diseases. This review explores the factors affecting lysosome acidification, membrane integrity, and functional homeostasis and examines the underlying mechanisms of lysosomal damage repair. In addition, we summarize how various risk factors impact lysosomal activity and cell fate.

Keywords:  ESCRT; Lysosome stabilization; ROS; lipid peroxidation; lysophagy; lysosomal membrane permeabilization

DOI:  https://doi.org/10.1080/10985549.2025.2494762
Mol Neurodegener. 2025 May 06. 20(1): 52

Cerebrospinal fluid proteome profiling across the Alzheimer's disease continuum: a step towards solving the equation for 'X'.

Sophia Weiner, Mathias Sauer, Laia Montoliu-Gaya, Andrea L Benedet, Nicholas J Ashton, Fernando Gonzalez-Ortiz, Joel Simrén, Nesrine Rahmouni, Cecile Tissot, Joseph Therriault, Stijn Servaes, Jenna Stevenson, Ville Leinonen, Tuomas Rauramaa, Mikko Hiltunen, Pedro Rosa-Neto, Kaj Blennow, Henrik Zetterberg, Johan Gobom.

   BACKGROUND: While the temporal profile of amyloid (Aβ) and tau cerebrospinal fluid (CSF) biomarkers along the Alzheimer's disease (AD) continuum is well-studied, chronological changes of CSF proteins reflecting other disease-relevant processes, denoted 'X' in the ATX(N) framework, remain poorly understood.
METHODS: Using an untargeted mass spectrometric approach termed tandem mass tag (TMT), we quantified over 1500 CSF proteins across the AD continuum in three independent cohorts, finely staged by Aβ/tau positron emission tomography (PET), fluid biomarkers, or brain biopsy. Weighted protein co-expression network analysis identified clusters of proteins robustly correlating in all three cohorts which sequentially changed with AD progression. Obtained protein clusters were correlated with fluid biomarker measurements (phosphorylated tau (p-tau) species including p-tau181, p-tau217, and p-tau205, as well as Aβ), Aβ/tau PET imaging, and clinical parameters to discern disease-relevant clusters which were modelled across the AD continuum.
RESULTS: Neurodegeneration-related proteins (e.g., 14-3-3 proteins, PPIA), derived from different brain cell types, strongly correlated with fluid as well as imaging biomarkers and increased early in the AD continuum. Among them, the proteins SMOC1 and CNN3 were highly associated with Aβ pathology, while the 14-3-3 proteins YWHAZ and YWHAE as well as PPIA demonstrated a strong association with both Aβ and tau pathology as indexed by PET. Endo-lysosomal proteins (e.g., HEXB, TPP1, SIAE) increased early in abundance alongside neurodegeneration-related proteins, and were followed by increases in metabolic proteins such as ALDOA, MDH1, and GOT1 at the mild cognitive impairment (MCI) stage. Finally, later AD stages were characterized by decreases in synaptic/membrane proteins (e.g., NPTX2).
CONCLUSIONS: Our study identified proxies of Aβ and tau pathology, indexed by PET, (SMOC1, YWHAE, CNN3) and highlighted the dynamic fluctuations of the CSF proteome over the disease course, identifying candidate biomarkers for disease staging beyond Aβ and tau.

Keywords:  Alzheimer’s disease; Biomarkers; Cerebrospinal fluid; Mass spectrometry; Tandem mass tag

DOI:  https://doi.org/10.1186/s13024-025-00841-0
Adv Healthc Mater. 2025 May 05. e2404111

Engineering Assembloids to Mimic Graft-Host Skeletal Muscle Interaction.

Lucia Rossi, Beatrice Auletta, Luigi Sartore, Marco La Placa, Giada Cecconi, Pietro Chiolerio, Edoardo Maghin, Silvia Angiolillo, Eugenia Carraro, Onelia Gagliano, Cecilia Laterza, Nicola Elvassore, Martina Piccoli, Anna Urciuolo.

  Skeletal muscle (SkM) tissue engineering aims to generate in vitro 3D products that can be implanted in patients to replace or repair damaged muscles. Having a humanized in vitro model able to mimic the interaction between the innervated recipient and the engineered SkMs at a functional level would greatly help in the evaluation of the graft potential. Here, a 3D in vitro model is developed that allows to investigation of the function, stability, and adaptability of the human neuromuscular (NM) system in response to an engineered SkM construct. To achieve this, decellularized SkMs (dSkM)-based constructs are used as engineered SkM and human neuromuscular organoids (NMOs) as the recipient-like NM system to create graft-host SkM assembloids. We observed the migration of myogenic cells and invasion of neural axons from the NMO to the engineered SkM construct in the assembloids, with the generation of functional neuromuscular junctions (NMJs). Finally, assembloids are able to regenerate following acute damage, with SkM regeneration and functional recovery. Despite being limited by the absence of immunocompetent cells and vasculature, the data showed that the assembloid represents a useful tool to evaluate in vitro the response of the human innervated SkM to a potential tissue-engineered SkM graft.

Keywords:  assembloids; muscle regeneration; muscle stem cell; neuromuscular organoids; organoids; skeletal muscle; tissue engineering

DOI:  https://doi.org/10.1002/adhm.202404111