bims-axbals 2025-08-17 papers

bims-axbals

Biomed News

on Axonal biology and ALS

Issue of 2025–08–17
23 papers selected by
TJ Krzystek

Aberrant splicing exonizes C9orf72 repeat expansion in ALS/FTD.
Mitochondrial damage triggers the concerted degradation of negative regulators of neuronal autophagy.
Deep mapping of the endomembrane system of cerebellar Purkinje neurons.
Bezafibrate treatment rescues neurodevelopmental and neurodegenerative defects in 3D cortical organoid model of MAPT frontotemporal dementia.
Retrograde axonal transport of autophagic vesicles and dynein-dynactin protein interaction are attenuated during aging in the rat optic nerve in vivo.
Biallelic variants in DNAJC7 cause familial amyotrophic lateral sclerosis with the TDP-43 pathology.
Glutamatergic synaptic resilience to overexpressed human alpha-synuclein.
Neuroaxonal Degeneration as a Converging Mechanism in Motor Neuron Diseases (MNDs): Molecular Insights into RNA Dysregulation and Emerging Therapeutic Targets.
Morphological profiling reveals neuroprotection via mitochondrial uncoupling in human dopaminergic neurons.
Identifying Therapeutic Targets for Amyotrophic Lateral Sclerosis Through Modeling of Multi-Omics Data.
Boosting Brain Clean-Up: Can Targeting UPS Genes Offer Neuroprotection?
Genotype-Phenotype Distinctions in Spastic Paraplegia 4 Reveal HDAC6 as a Therapeutic Target.
Cortical hyperexcitability drives dying forward amyotrophic lateral sclerosis symptoms and pathology in mice.
A unique subpopulation of wild-type neurons recapitulating familial Alzheimer's disease phenotypes.
Design considerations for C9orf72 disease prevention trials.
BDNF Overexpression Enhances Neuronal Activity and Axonal Growth in Human iPSC-Derived Neural Cultures.
CK1δ-Dependent SNAPIN Dysregulation Drives Lysosomal Failure in HIV-1 Vpr-Exposed Neurons: A Targetable Mechanism in HAND.
Neurodevelopmental disorder mutations in the exchange factor DENN/MADD disrupt activation of Rab GTPases.
RNA triggers chronic stress during neuronal aging.
In vivo self-assembled SOD1-siRNAs mitigate muscle atrophy and denervation in amyotrophic lateral sclerosis.
Smarter stem cells: how AI is supercharging iPSC technology.
Alpha-synuclein inclusions reduced by PIKfyve inhibition in Parkinson's disease cell models.
Plant-specific mitochondrial fission machinery connects mitochondrial dynamics and mitophagosome formation for piecemeal mitophagy.

Nat Neurosci. 2025 Aug 11.

Aberrant splicing exonizes C9orf72 repeat expansion in ALS/FTD.

Suzhou Yang, Denethi Wijegunawardana, Udit Sheth, Austin M Veire, Juliana M S Salgado, Tanina Arab, Manasi Agrawal, Jeffrey Zhou, João D Pereira, Tania F Gendron, Junjie U Guo.

A nucleotide repeat expansion (NRE) (GGGGCC)n within the first annotated intron of the C9orf72 (C9) gene is a common cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). While previous studies have shown that C9 NRE produces several toxic dipeptide repeat (DPR) proteins, the mechanism by which an intronic RNA segment can access the cytoplasmic translation machinery remains unclear. By selectively capturing and sequencing NRE-containing RNAs (NRE-capture-seq) from patient-derived fibroblasts and neurons, we found that, in contrast to previous models, C9 NRE is retained as part of an extended exon 1 due to the usage of various downstream alternative 5' splice sites. These aberrant splice isoforms accumulate in C9-ALS/FTD brains, and their production is promoted by serine/arginine-rich splicing factor 1 (SRSF1). Antisense oligonucleotides targeting either SRSF1 or the aberrant C9 splice isoforms reduced the levels of DPR. Together, our findings revealed a crucial role of aberrant splicing in the biogenesis of NRE-containing RNAs and demonstrated potential therapeutic strategies to target these pathogenic transcripts.

DOI: https://doi.org/10.1038/s41593-025-02039-5
Nat Commun. 2025 Aug 09. 16(1): 7367

Mitochondrial damage triggers the concerted degradation of negative regulators of neuronal autophagy.

Bishal Basak, Erika L F Holzbaur.

Mutations that disrupt the clearance of damaged mitochondria via mitophagy are causative for neurological disorders including Parkinson's. Here, we identify a Mitophagic Stress Response (MitoSR) activated by mitochondrial damage in neurons and operating in parallel to canonical Pink1/Parkin-dependent mitophagy. Increasing levels of mitochondrial stress trigger a graded response that induces the concerted degradation of negative regulators of autophagy including Myotubularin-related phosphatase (MTMR)5, MTMR2 and Rubicon via the ubiquitin-proteasome pathway and selective proteolysis. MTMR5/MTMR2 inhibit autophagosome biogenesis; consistent with this, mitochondrial engulfment by autophagosomes is enhanced upon MTMR2 depletion. Rubicon inhibits lysosomal function, blocking later steps of neuronal autophagy; Rubicon depletion relieves this inhibition. Targeted depletion of both MTMR2 and Rubicon is sufficient to enhance mitophagy, promoting autophagosome biogenesis and facilitating mitophagosome-lysosome fusion. Together, these findings suggest that therapeutic activation of MitoSR to induce the selective degradation of negative regulators of autophagy may enhance mitochondrial quality control in stressed neurons.

DOI: https://doi.org/10.1038/s41467-025-62379-5
bioRxiv. 2025 Jul 14. pii: 2025.07.08.663701. [Epub ahead of print]

Deep mapping of the endomembrane system of cerebellar Purkinje neurons.

Matthias G Haberl, Silvia Viana da Silva, Sebastien Phan, Eric Bushong, Thomas Deerinck, Mark H Ellisman.

Neuronal function relies on the precise spatial organization of intracellular membrane-bounded organelles involved in anabolism and Ca 2+ sequestration, such as the Golgi apparatus, mitochondria and the endoplasmic reticulum (ER), along with structures involved in catabolism, such as lysosomes. Despite their known roles in energy supply, calcium homeostasis, and proteostasis, our understanding of how the anabolism-linked organelles are structurally arranged within neurons remains incomplete. Due to the tremendous complexity in the morphologies and fine structural features and interwoven nature of these intracellular organelles, particularly the ER, our understanding of their structural organization is limited, particularly, with regard to quantitative assessments of their sites of interaction and accurate measures of their volumetric proportions inside of a single large neuron. To approach this challenge, we used serial block-face scanning electron microscopy (SBEM) to generate large-scale 3D EM volumes and electron tomography on high-pressure frozen tissue of the rodent cerebellum, including the largest cells in the vertebrate brain, the cerebellar Purkinje neuron as well as the most abundant cell type in the vertebrate brain, the much smaller cerebellar granule neuron. We reconstructed the neuronal ultrastructure of these different cell types, focusing on the ER, mitochondria and membrane contact sites, to then characterize intracellular motifs and organization principles in detail, providing a first full map to quantitatively describe a neuronal endoarchitectome . At the gross level organization, we found that the intracellular composite of organelles are cell type specific features, with specific differences between Purkinje neurons and Granule cells. At the level of fine structure, we mapped ultrastructural domains within Purkinje neurons where ER and mitochondria associate directly. In addition to cell type specific differences, we observed significant subcellular regional variation, particularly within the axon initial segment (AIS) of Purkinje neurons, where we identified ultrastructural domains with sharply contrasting distributions of ER and mitochondria. These findings suggest a finely tuned spatial organization of organelles that may underpin the distinct functional demands along the axon. We expect that our subcellular map, along with the methods developed to obtain these maps, will facilitate future studies in health, aging and disease to characterize defined features, by developing a framework for quantitative analysis of the neuronal ultrastructure.

DOI: https://doi.org/10.1101/2025.07.08.663701
Alzheimers Dement. 2025 Aug;21(8): e70419

Bezafibrate treatment rescues neurodevelopmental and neurodegenerative defects in 3D cortical organoid model of MAPT frontotemporal dementia.

Federica Cordella, Lorenza Mautone, Debora Salerno, Lucrezia Tondo, Silvia Ghirga, Chiara D'Antoni, Erika Parente, Maria Anele Romeo, Mara Cirone, Paola Bezzi, Silvia Di Angelantonio.

   INTRODUCTION: The intronic MAPT mutation IVS10+16 is linked to familial frontotemporal dementia, causing hyperphosphorylation and accumulation of tau protein, resulting in synaptic and neuronal loss and neuroinflammation in patients. This mutation disrupts MAPT gene splicing, increasing exon 10 inclusion and leading to an imbalance of 3R and 4R Tau isoforms.
METHODS: We generated patterned cortical organoids from isogenic control and mutant human induced pluripotent stem cell (iPSC) lines. Nanostring gene expression analysis, immunofluorescence, and calcium imaging recordings were used to study the impact of the MAPT IVS10+16 mutation on neuronal development and function.
RESULTS: Tau mutant cortical organoids showed altered mitochondrial function and gene expression related to neuronal development, with synaptic markers and neuronal activity reduction. Bezafibrate treatment restored mitochondrial content and rescued synaptic functionality and tau physiology.
DISCUSSION: These findings suggest that targeting mitochondrial function with bezafibrate could potentially reverse tau-induced neurodevelopmental deficits, highlighting its therapeutic potential for tauopathies like frontotemporal dementia.
HIGHLIGHTS: The IVS 10+16 MAPT mutation significantly disrupts cortical differentiation and synaptic maturation, evidenced by downregulated genes associated with synapses and neuronal development. Tau-mutant cortical organoids exhibit mitochondrial dysfunction, with fewer and smaller mitochondria alongside tau hyperphosphorylation and aggregation, which further contribute to neuronal damage and disease progression. Treatment with bezafibrate effectively normalizes mitochondrial parameters, enhances neuronal integrity and synaptic maturation, and restores network functionality, showcasing its promise as a therapeutic strategy for tauopathies. The 3D in vitro disease model used in this study proves valuable for studying tauopathies and testing new drugs, effectively mimicking key aspects of tau-related neurodegeneration.

Keywords:  calcium imaging; cortical organoids; mitochondria; neurodegeneration; neurodevelopment; synapses; tau; tauopathies; transcriptomics

DOI:  https://doi.org/10.1002/alz.70419
Neural Regen Res. 2025 Aug 13.

Retrograde axonal transport of autophagic vesicles and dynein-dynactin protein interaction are attenuated during aging in the rat optic nerve in vivo.

Xiaoyue Luo, Jiong Zhang, Johan Tolö, Sebastian Kügler, Uwe Michel, Mathias Bähr, Jan Christoph Koch.

  Aging is characterized by a decreased autophagic activity contributing to the intracellular deposition of damaged organelles and macromolecules. Autophagy is particularly challenging in neurons since autophagic vesicles are formed at the axonal tip and must be transported to the soma where final degradation occurs. Here, we examined if axonal transport of autophagic vesicles is altered during aging. We employed two-photon microscopy for in vivo imaging in the optic nerve of young and aged rats. In old animals (> 18 months old), retrograde autophagic vesicle transport was significantly reduced with regard to motility and velocity. While activation of autophagy was decreased, expression of key proteins of the autophagy-lysosomal pathway including p62 and procathepsin D and the number of autophagolysosomes was increased. Maturation of autophagic vesicles was shifted to more distal regions of the axon and axonal lysosomal clearing was impaired. In a pull-down assay, the protein binding between dynein and dynactin was decreased by half, which could explain the retrograde axonal transport effects. Taken together, retrograde axonal autophagic vesicle transport in vivo is diminished during aging accompanied by decreased autophagy activation, alterations of the lysosomal pathway, and a reduced dynein-dynactin binding.

Keywords:  aging; autophagic vesicles; autophagy; autophagy-lysosomal pathway; axonal transport; dynein; optic nerve; p150Glued; retrograde transport; two-photon microscopy

DOI:  https://doi.org/10.4103/NRR.NRR-D-24-01326
Acta Neuropathol. 2025 Aug 13. 150(1): 19

Biallelic variants in DNAJC7 cause familial amyotrophic lateral sclerosis with the TDP-43 pathology.

Toru Yamashita, Osamu Yokota, Daiki Ousaka, Hongming Sun, Takashi Haraguchi, Ricardo Satoshi Ota-Elliott, Chika Matsuoka, Tomohito Kawano, Hanae Nakashima-Yasuda, Yusuke Fukui, Yumiko Nakano, Ryuta Morihara, Masato Hasegawa, Yasuyuki Hosono, Seishi Terada, Manabu Takaki, Hiroyuki Ishiura.

  Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder characterized by the progressive degeneration of motor neurons. ALS pathology primarily involves the failure of protein quality control mechanisms, leading to the accumulation of misfolded proteins, particularly TAR DNA-binding protein 43 (TDP-43). TDP-43 aggregation is a central pathological feature of ALS. Maintaining protein homeostasis is critical and facilitated by heat shock proteins (HSPs), particularly the HSP40 family, which includes co-chaperones such as DNAJC7. Here, we report a family with three siblings affected by ALS who carry a homozygous c.518dupC frameshift variant in DNAJC7, a member of the HSP40 family. All three patients exhibited progressive muscle weakness, limb atrophy, bulbar palsy, and respiratory failure. Pathological examination revealed degeneration of both upper and lower motor neurons, with phosphorylated TDP-43-positive neuronal cytoplasmic inclusions in the frontal and temporal cortices. Immunoblot analysis were consistent with a type B pattern of phosphorylated TDP-43 in the precentral gyrus. Immunohistochemistry and RNA sequencing analyses demonstrated a substantial reduction in DNAJC7 expression at both the protein and RNA levels in affected brain regions. In a TDP-43 cell model, DNAJC7 knockdown impaired the disassembly of TDP-43 following arsenite-induced stress, whereas DNAJC7 overexpression suppressed the assembly and promoted the disassembly of arsenite-induced TDP-43 condensates. Furthermore, in a zebrafish ALS model, dnajc7 knockdown resulted in increased TDP-43 aggregation in motor neurons and reduced survival. To the best of our knowledge, this study provides the first evidence linking biallelic loss-of-function variants in DNAJC7 to familial ALS with TDP-43 pathology.

Keywords:   DNAJC7 ; Amyotrophic lateral sclerosis; Heat shock protein; Live-cell imaging; TDP-43; Zebrafish disease model

DOI:  https://doi.org/10.1007/s00401-025-02899-y
NPJ Parkinsons Dis. 2025 Aug 12. 11(1): 238

Glutamatergic synaptic resilience to overexpressed human alpha-synuclein.

Patrícia I Santos, Inés Hojas García-Plaza, Ali Shaib, Jeong Seop Rhee, Abed Alrahman Chouaib, Nils Brose, Silvio O Rizzoli, James Daniel, Tiago F Outeiro.

Alpha synuclein (aSyn) is abundant in the brain and strongly implicated in Parkinson's disease (PD), genetically and through its accumulation in neuronal pathognomonic inclusions. While mutations or increased expression of wild-type aSyn can cause familial PD, it remains unclear whether increased aSyn alone impairs presynaptic function. Here, we overexpressed human aSyn (haSyn) in rodent glutamatergic neurons and analysed presynaptic function. Expression levels mimicked SNCA gene triplications, as seen in certain familial forms of PD. In continental cultures, haSyn overexpression was not toxic nor did it alter the levels of presynaptic SNAP-25 or postsynaptic PSD-95. Analyses of autaptic neurons revealed no significant differences in evoked or spontaneous neurotransmission release, nor in synaptic plasticity. These results indicate that rodent glutamatergic neurons are resilient to aSyn overexpression. Our findings suggest neurotoxicity associated with aSyn overexpression is not universal, and that a deeper understanding of aSyn biology and pathobiology is necessary.

DOI: https://doi.org/10.1038/s41531-025-01085-x
Int J Mol Sci. 2025 Aug 07. pii: 7644. [Epub ahead of print]26(15):

Neuroaxonal Degeneration as a Converging Mechanism in Motor Neuron Diseases (MNDs): Molecular Insights into RNA Dysregulation and Emerging Therapeutic Targets.

Minoo Sharbafshaaer, Roberta Pepe, Rosaria Notariale, Fabrizio Canale, Alessandro Tessitore, Gioacchino Tedeschi, Francesca Trojsi.

  Motor Neuron Diseases (MNDs) such as Amyotrophic Lateral Sclerosis (ALS), Primary Lateral Sclerosis (PLS), Hereditary Spastic Paraplegia (HSP), Spinal Muscular Atrophy with Respiratory Distress Type 1 (SMARD1), Multisystem Proteinopathy (MSP), Spinal and Bulbar Muscular Atrophy (SBMA), and ALS associated to Frontotemporal Dementia (ALS-FTD), have traditionally been studied as distinct entities, each one with unique genetic and clinical characteristics. However, emerging research reveals that these seemingly disparate conditions converge on shared molecular mechanisms that drive progressive neuroaxonal degeneration. This narrative review addresses a critical gap in the field by synthesizing the most recent findings into a comprehensive, cross-disease mechanisms framework. By integrating insights into RNA dysregulation, protein misfolding, mitochondrial dysfunction, DNA damage, kinase signaling, axonal transport failure, and immune activation, we highlight how these converging pathways create a common pathogenic landscape across MNDs. Importantly, this perspective not only reframes MNDs as interconnected neurodegenerative models but also identifies shared therapeutic targets and emerging strategies, including antisense oligonucleotides, autophagy modulators, kinase inhibitors, and immunotherapies that transcend individual disease boundaries. The diagnostic and prognostic potential of Neurofilament Light Chain (NfL) biomarkers is also emphasized. By shifting focus from gene-specific to mechanism-based approaches, this paper offers a much-needed roadmap for advancing both research and clinical management in MNDs, paving the way for cross-disease therapeutic innovations.

Keywords:  DNA repair; RNA-binding proteins; axonal transport; kinase signaling; mitochondrial dysfunction; motor neuron diseases; neurofilament biomarkers; neuroinflammation; protein aggregation; targeted therapies

DOI:  https://doi.org/10.3390/ijms26157644
Sci Rep. 2025 Aug 12. 15(1): 29507

Morphological profiling reveals neuroprotection via mitochondrial uncoupling in human dopaminergic neurons.

Vyron Gorgogietas, Amélie Weiss, Loïc Cousin, David Hoffmann, Karen Schmitt, Arnaud Ogier, Peter A Barbuti, Bruno F R Santos, Ibrahim Boussaad, Annika Wittich, Andrea Zaliani, Ole Pless, Rejko Krüger, Peter Sommer, Johannes H Wilbertz.

Parkinson's disease (PD) involves multiple pathological processes in midbrain dopaminergic (mDA) neurons, including protein degradation defects, vesicular trafficking disruption, endolysosomal dysfunction, mitochondrial issues, and oxidative stress. Current PD models often lack complexity and focus on single phenotypes. We used patient-derived SNCA triplication (SNCA-4x) and isogenic control (SNCA-corr) mDA neurons, applying high-content imaging-based morphological profiling to identify and rescue multiple phenotypes. Screening 1,020 compounds, we identified top-scoring compounds that restored healthy profiles in SNCA-4x neurons, increasing Tyrosine hydroxylase (TH) and decreasing α-synuclein (αSyn) levels. Several hits were linked to mitochondrial biology. Tyrphostin A9, a mitochondrial uncoupler, and several of its structural analogues decreased ROS levels, normalized mitochondrial membrane potential, and increased respiration. Western blotting confirmed that Tyrphostin A9 reduces αSyn levels. Our study highlights the neuroprotective potential of mild mitochondrial uncoupling in mDA neurons.

DOI: https://doi.org/10.1038/s41598-025-14735-0
Int J Mol Sci. 2025 Jul 23. pii: 7087. [Epub ahead of print]26(15):

Identifying Therapeutic Targets for Amyotrophic Lateral Sclerosis Through Modeling of Multi-Omics Data.

François Xavier Blaudin de Thé, Cornelius J H M Klemann, Ward De Witte, Joanna Widomska, Philippe Delagrange, Clotilde Mannoury La Cour, Mélanie Fouesnard, Sahar Elouej, Keith Mayl, Nicolas Lévy, Johannes Krupp, Ross Jeggo, Philippe Moingeon, Geert Poelmans.

  Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease that primarily affects motor neurons, leading to loss of muscle control, and, ultimately, respiratory failure and death. Despite some advances in recent years, the underlying genetic and molecular mechanisms of ALS remain largely elusive. In this respect, a better understanding of these mechanisms is needed to identify new and biologically relevant therapeutic targets that could be developed into treatments that are truly disease-modifying, in that they address the underlying causes rather than the symptoms of ALS. In this study, we used two approaches to model multi-omics data in order to map and elucidate the genetic and molecular mechanisms involved in ALS, i.e., the molecular landscape building approach and the Patrimony platform. These two methods are complementary because they rely upon different omics data sets, analytic methods, and scoring systems to identify and rank therapeutic target candidates. The orthogonal combination of the two modeling approaches led to significant convergences, as well as some complementarity, both for validating existing therapeutic targets and identifying novel targets. As for validating existing targets, we found that, out of 217 different targets that have been or are being investigated for drug development, 10 have high scores in both the landscape and Patrimony models, suggesting that they are highly relevant for ALS. Moreover, through both models, we identified or corroborated novel putative drug targets for ALS. A notable example of such a target is MATR3, a protein that has strong genetic, molecular, and functional links with ALS pathology. In conclusion, by using two distinct and highly complementary disease modeling approaches, this study enhances our understanding of ALS pathogenesis and provides a framework for prioritizing new therapeutic targets. Moreover, our findings underscore the potential of leveraging multi-omics analyses to improve target discovery and accelerate the development of effective treatments for ALS, and potentially other related complex human diseases.

Keywords:  MATR3; amyotrophic lateral sclerosis (ALS); molecular landscape; multi-omics modeling; patrimony; therapeutic targets

DOI:  https://doi.org/10.3390/ijms26157087
Mol Neurobiol. 2025 Aug 16.

Boosting Brain Clean-Up: Can Targeting UPS Genes Offer Neuroprotection?

Ashi Mannan, Akhil Sharma, Thakur Gurjeet Singh.

  The ubiquitin-proteasome system (UPS) plays a critical role in protein homeostasis within eukaryotic cells. This review article examines the UPS's role in neuronal morphology and neurodegeneration through systematic analysis of current research. In neurodegenerative disorders (NDDs) such as Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), and amyotrophic lateral sclerosis (ALS), UPS dysfunction contributes significantly to pathogenesis through accumulation of ubiquitinated misfolded proteins, disruption of cellular proteostasis, impaired substrate ubiquitination, and proteasomal deterioration. The UPS maintains normal central nervous system (CNS) function by regulating protein degradation. When this system fails, cellular proteostasis becomes compromised, accelerating neurodegeneration. Recent research has identified potential interventions for UPS activation through genetic modification and synthetic compounds. This review assesses how specific UPS components could serve as pharmacological targets for treating NDDs. By modulating UPS-mediated genes and pathways, novel therapeutic strategies may emerge for conditions including AD, PD, HD), and ALS. Current evidence suggests the UPS represents a promising therapeutic target for addressing the fundamental protein homeostasis disruptions underlying these devastating neurological conditions. Targeting this system could potentially slow disease progression by restoring proper protein degradation mechanisms and preventing toxic protein accumulation characteristic of NDDs.

Keywords:  Alzheimer’s disease (AD); Amyotrophic lateral sclerosis (ALS); Huntington disease (HD); Neurodegenerative disorders (NDDs); Parkinson’s disease (PD); Ubiquitin–proteasome system (UPS)

DOI:  https://doi.org/10.1007/s12035-025-05263-z
bioRxiv. 2025 Jul 18. pii: 2025.07.15.664947. [Epub ahead of print]

Genotype-Phenotype Distinctions in Spastic Paraplegia 4 Reveal HDAC6 as a Therapeutic Target.

Neha Mohan, Skandha Ramakrishnan, Xiaohuan Sun, Ying Sun, Theresa Connors, Victor Chai, Emanuela Piermarini, Peter W Baas, James Cai, Mei Liu, Liang Qiang.

Spastic Paraplegia 4 (SPG4) is the most prevalent form of Hereditary Spastic Paraplegia (HSP), a neurodegenerative disorder characterized by progressive lower limb spasticity and debilitating gait impairment, primarily driven by axonal degeneration of corticospinal motor neurons (CSMNs). Caused by mutations in the SPAST gene encoding spastin, an AAA-ATPase involved in microtubule severing and intracellular organelle function, SPG4 accounts for 40-50% of autosomal dominant HSP cases, yet without effective treatments. Although reduced microtubule acetylation has emerged as a key pathological mechanism, whether and how distinct mutations lead to microtubule deacetylation and subsequent neurodegeneration remains unclear. To address this, we generated isogenic human induced pluripotent stem cell (hiPSC) lines with two distinct heterozygous SPAST mutations - SPAST WT/C448Y (missense) and SPAST WT/S245X (truncation). Employing an innovative differentiation protocol, we created human motor cortical organoids enriched in CSMNs, providing a robust platform to study SPG4 pathophysiology. These organoids revealed striking genotype-phenotype distinctions, with mutation-specific variations in CSMN loss, axonal degeneration and neuronal activities, mirroring clinical heterogeneity. Mechanistic studies identified aberrant activation of histone deacetylase 6 (HDAC6), a major neuronal microtubule deacetylase, as a key driver of SPG4 pathology. This dysregulation was specifically attributed to mutant M1-spastin, the longer isoform of spastin. Remarkably, pharmacological inhibition of HDAC6 with Tubastatin A restored microtubule acetylation status and mitigated axonal degeneration in both SPAST-mutant organoids, with corresponding improvements in corticospinal tract integrity and gait deficits validated in SPG4-transgenic mice. Collectively, our study establishes isogenic hiPSC-derived motor cortical organoids as a robust human model for corticospinal motor neuron degeneration and identifies HDAC6 hyperactivation as a central pathogenic mechanism and viable therapeutic target in SPG4.

DOI: https://doi.org/10.1101/2025.07.15.664947
Prog Neurobiol. 2025 Aug 08. pii: S0301-0082(25)00100-5. [Epub ahead of print]252 102809

Cortical hyperexcitability drives dying forward amyotrophic lateral sclerosis symptoms and pathology in mice.

Mouna Haidar, Aida Viden, Christin Daniel, Brittany Cuic, Taide Wang, Marius Rosier, Doris Tomas, Samuel A Mills, Alistair Govier-Cole, Elvan Djouma, Nirma D Perera, Sophia Luikinga, Valeria Rytova, Samantha K Barton, David G Gonsalvez, Lucy M Palmer, Catriona McLean, Matthew C Kiernan, Steve Vucic, Bradley J Turner.

  Degeneration of both upper motor neurons in the brain and lower motor neurons in the spinal cord defines amyotrophic lateral sclerosis (ALS), but how they are linked in ALS pathophysiology is unclear. Here, we uncover a cortical origin of neurodegeneration in ALS mediated by upper motor neuron hyperexcitability. Chronic hyperexcitability of upper motor neurons induced by excitatory chemogenetics in healthy adult mice induced progressive motor deficits, weakness and core pathological hallmarks of ALS, including upper motor neurons loss, synaptic pathology, corticospinal tract degeneration and reactive gliosis. Importantly, upper motor neuron hyperexcitability and loss were sufficient to drive degeneration of lower motor neurons and their distal axons and neuromuscular junctions, associated with astrocyte and microglial activation in spinal cord. Cortical hyperexcitability also triggered cytoplasmic TAR DNA binding protein 43 (TDP-43) aggregation in upper motor neurons and lower motor neurons, placing hyperexcitability upstream of TDP-43 proteinopathy in ALS. These findings establish a cortical origin of ALS mediated by upper motor neurons, consistent with an anterograde mechanism of neurodegeneration throughout the central and peripheral nervous systems.

Keywords:  Amyotrophic lateral sclerosis; chemogenetics; hyperexcitability; mouse models; upper motor neurons

DOI:  https://doi.org/10.1016/j.pneurobio.2025.102809
Cell Death Dis. 2025 Aug 09. 16(1): 604

A unique subpopulation of wild-type neurons recapitulating familial Alzheimer's disease phenotypes.

Midori Yokomizo, Michael Sadek, Emily Williams, Mei C Q Houser, Natalia Wieckiewicz, Sebastian Torres, Oksana Berezovska, Masato Maesako.

Mutations in the genes encoding APP, Presenilin-1 (PSEN1), and PSEN2 result in early-onset Alzheimer's disease (AD). Previous studies, using iPSC-derived neurons and/or knock-in mice, elucidated the characteristics of neurons expressing familial AD (fAD) mutations. Here, we employ biochemical and state-of-the-art fluorescence imaging assays and report the discovery of a unique subpopulation of wild-type neurons strikingly recapitulating key phenotypes previously identified in the fAD neurons, including the favored production of longer over shorter β-amyloid (Aβ) peptides, endo-lysosomal abnormalities, and increased vulnerability phenotypes in response to toxic insults. Importantly, mechanistic studies define inefficient γ-secretase and impaired endo-lysosomes as the upstream events of increased neuronal susceptibility. This discovery of the unique population of neurons with disease phenotypes would open a new avenue to develop novel therapeutics targeting neuronal vulnerability.

DOI: https://doi.org/10.1038/s41419-025-07934-0
Brain. 2025 Aug 05. pii: awaf290. [Epub ahead of print]

Design considerations for C9orf72 disease prevention trials.

Michael Benatar, Adam M Staffaroni, Joanne Wuu, Michael P McDermott, Melanie Quintana, Jean Swidler, Gail Andersen, Edward D Huey, Martin R Turner, Eric A Macklin, James D Berry, Corey T McMillan, Tania Gendron, Chiadi Onyike, Howard Rosen, Hilary W Heuer, Anne-Laure Grignon, Kuldip D Dave, Calaneet Balas, Amanda Gleixner, Andrew Satlin, Billy Dunn, Penny Dacks, Adam L Boxer.

  The idea that it might be possible to prevent some forms of amyotrophic lateral sclerosis and frontotemporal dementia has finally come of age. The hexanucleotide repeat expansion in the C9orf72 gene accounts for ∼10% of all amyotrophic lateral sclerosis and 10-15% of all frontotemporal dementia diagnoses, with the two clinical syndromes co-manifesting in a significant number of patients. As a result, clinically unaffected carriers of pathogenic C9orf72 repeat expansions are currently the largest identifiable population at significantly elevated risk for both amyotrophic lateral sclerosis and frontotemporal dementia, and in whom it might be possible to prevent the emergence of clinically manifest disease. Strategies for the design of disease prevention trials among clinically unaffected C9orf72 carriers have begun to emerge separately in the amyotrophic lateral sclerosis and frontotemporal dementia fields. However, recognition of the need to define neurodegenerative diseases based on biology underscores the need to consider all potential clinical manifestations of a C9orf72 repeat expansion together, rather than the traditional siloed approach of focusing on only amyotrophic lateral sclerosis or only frontotemporal dementia. Indeed, emerging clinical and biological markers that might be used to quantify pre-symptomatic disease progression and to predict the short-term risk of phenoconversion to clinically manifest disease are shared across the phenotypic spectrum. Given the anticipated progress in the development of therapeutic strategies to target the C9orf72 repeat expansion, and the enthusiasm for prevention trials among the unaffected C9orf72 repeat expansion carrier population, now is the time to begin work on the design of disease prevention trials. To this end, The Association for Frontotemporal Degeneration and the ALS Association supported a multi-stakeholder workshop (in Washington D.C., June 2024) to unify efforts to design a prevention trial for the population at elevated genetic risk for the phenotypic spectrum of C9orf72 disease. Here we describe recommendations emanating from this Workshop for the selection of outcome measures, delineation of eligibility criteria, optimal use of biomarkers and digital health technologies, potential analytic frameworks, and relevant regulatory considerations related to C9orf72 disease prevention trials. We also emphasize the importance of the amyotrophic lateral sclerosis and frontotemporal dementia communities working together in partnership with the C9orf72 repeat expansion carrier community, the regulatory authorities, and the broader drug development community.

Keywords:  amyotrophic lateral sclerosis (ALS); biomarker; frontotemporal dementia (FTD); phenoconversion; pre-symptomatic; regulatory considerations

DOI:  https://doi.org/10.1093/brain/awaf290
Int J Mol Sci. 2025 Jul 27. pii: 7262. [Epub ahead of print]26(15):

BDNF Overexpression Enhances Neuronal Activity and Axonal Growth in Human iPSC-Derived Neural Cultures.

Alba Ortega-Gasco, Francesca Percopo, Ares Font-Guixe, Santiago Ramos-Bartolome, Andrea Cami-Bonet, Marc Magem-Planas, Marc Fabrellas-Monsech, Emma Esquirol-Albala, Luna Goulet, Sergi Fornos-Zapater, Ainhoa Arcas-Marquez, Anna-Christina Haeb, Claudia Gomez-Bravo, Clelia Introna, Josep M Canals, Daniel Tornero.

  As the global population continues to age, the incidence of neurodegenerative diseases and neural injuries is increasing, presenting major challenges for healthcare systems. Due to the brain's limited regenerative capacity, there is an urgent need for strategies that promote neuronal repair and functional integration. Brain-derived neurotrophic factor (BDNF) is a key regulator of synaptic plasticity and neuronal development. In this study, we investigated whether constitutive BDNF expression in human induced pluripotent stem cell (iPSC)-derived neural progenitor cells (NPCs) enhances their neurogenic and integrative potential in vitro. We found that NPCs engineered to overexpress BDNF produced neuronal cultures with increased numbers of mature and spontaneously active neurons, without altering the overall structure or organization of functional networks. Furthermore, BDNF-expressing neurons exhibited significantly greater axonal outgrowth, including directed axon extension in a compartmentalized microfluidic system, suggesting a chemoattractive effect of localized BDNF secretion. These effects were comparable to those observed with the early supplementation of recombinant BDNF. Our results demonstrate that sustained BDNF expression enhances neuronal maturation and axonal projection without disrupting network integrity. These findings support the use of BDNF not only as a therapeutic agent to improve cell therapy outcomes but also as a tool to accelerate the development of functional neural networks in vitro.

Keywords:  axonal growth; brain-derived neurotrophic factor (BDNF); human iPSCs; neural progenitor cells (NPCs); neuronal activity; regenerative medicine

DOI:  https://doi.org/10.3390/ijms26157262
bioRxiv. 2025 Jul 16. pii: 2025.07.11.664248. [Epub ahead of print]

CK1δ-Dependent SNAPIN Dysregulation Drives Lysosomal Failure in HIV-1 Vpr-Exposed Neurons: A Targetable Mechanism in HAND.

Bassel E Sawaya, Maryline Santerre.

HIV-associated neurocognitive disorders (HAND) persist in nearly 40% of virally suppressed individuals despite antiretroviral therapy (ART). Lysosomal dysfunction has emerged as a key contributor to HAND pathogenesis, yet the molecular mechanisms linking chronic HIV exposure to impaired neuronal degradation remain incompletely defined. Here, we identify HIV-1 Viral Protein R (Vpr) as a driver of lysosomal acidification failure, clustering, and degradative impairment in neurons. We uncovered casein kinase 1 delta (CK1δ) as a central mediator of this dysfunction, acting via phosphorylation of the adaptor protein SNAPIN. Vpr-induced CK1δ activation leads to hyperphosphorylation of SNAPIN, disrupting lysosomal positioning and motility. These defects are rescued by selective CK1δ inhibition, which restores lysosomal acidification, positioning, and mitophagy. Our findings define a novel Vpr-CK1δ-SNAPIN axis contributing to HAND and highlight lysosomal transport as a targetable mechanism in neurodegeneration.

DOI: https://doi.org/10.1101/2025.07.11.664248
J Biol Chem. 2025 Aug 12. pii: S0021-9258(25)02439-1. [Epub ahead of print] 110588

Neurodevelopmental disorder mutations in the exchange factor DENN/MADD disrupt activation of Rab GTPases.

Maleeha Khan, Rahul Kumar, Jean-François Trempe, Vincent Francis, Emily Banks, Riham Ayoubi, Luis Aguilera Luna, Peter S McPherson.

  DENN/MADD, a differentially expressed in normal and neoplastic cells (DENN) domain-containing protein functions in membrane trafficking. DENN domain-bearing proteins have guanine nucleotide exchange factor (GEF) activity towards Rab GTPases. Here, we identify Rab GTPase substrates for DENN/MADD using a cell-based assay involving DENN-domain mediated recruitment of Rab substrates to mitochondria. We confirmed known interactions of DENN/MADD with Rab3A, Rab3B, Rab3C, Rab3D, and Rab27B, and identified four new potential substrates, Rab8B, Rab15, Rab26, and Rab37, results confirmed with biochemical experiments. Mutations in the DENN domain of DENN/MADD result in diverse pathophysiological manifestations, ranging from predominant neurological dysfunction to a multisystem disorder. Structural analysis using AlphaFold suggested that these mutations affect DENN/MADD's interaction with Rab GTPases. Introducing such mutations into DENN/MADD's DENN domain influenced the mitochondrial recruitment of Rabs. This study identifies new DENN/MADD protein interactions and cellular pathways, the disruption of which results in human disorders.

Keywords:  DENN/MADD; Rab GTPases; cell biology; genetic disease; guanine nucleotide exchange factor (GEF); imaging; membrane trafficking; neurodevelopmental disorder; protein-protein interaction

DOI:  https://doi.org/10.1016/j.jbc.2025.110588
bioRxiv. 2025 Aug 05. pii: 2025.08.04.668575. [Epub ahead of print]

RNA triggers chronic stress during neuronal aging.

Kevin Rhine, Elle Epstein, Natasha M Carlson, Xuezhen Ge, Orel Mizrahi, Anika Kamat, Anita Hermann, William R Brothers, John Ravits, Eric J Bennett, Gülçin Pekkurnaz, Gene W Yeo.

Neurodegenerative diseases are linked with dysregulation of the integrated stress response (ISR), which coordinates cellular homeostasis during and after stress events. Cellular stress can arise from several sources, but there is significant disagreement about which stress might contribute to aging and neurodegeneration. Here, we leverage directed transdifferentiation of human fibroblasts into aged neurons to determine the source of ISR activation. We demonstrate that increased accumulation of cytoplasmic double-stranded RNA (dsRNA) activates the eIF2α kinase PKR, which in turn triggers the ISR in aged neurons and leads to sequestration of dsRNA in stress granules. Aged neurons accumulate endogenous mitochondria-derived dsRNA that directly binds to PKR. This mitochondrial dsRNA leaks through damaged mitochondrial membranes and forms cytoplasmic foci in aged neurons. Finally, we demonstrate that PKR inhibition leads to the cessation of stress, resumption of cellular translation, and restoration of RNA-binding protein expression. Together, our results identify a source of RNA stress that destabilizes aged neurons and may contribute to neurodegeneration.

DOI: https://doi.org/10.1101/2025.08.04.668575
Brain. 2025 Aug 08. pii: awaf291. [Epub ahead of print]

In vivo self-assembled SOD1-siRNAs mitigate muscle atrophy and denervation in amyotrophic lateral sclerosis.

Jingwei Guo, Qian Zou, Jiawei Xu, Jieqiong Lei, Xin Yin, Botao Li, Jinyu Fu, Junjie Mi, Yanbo Wang, Huan Huang, Chen-Yu Zhang, Xi Chen.

  Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder characterized by the death of both upper and lower motor neurons. Approximately 20% of familial ALS cases are associated with mutations in the superoxide dismutase type 1 (SOD1) gene. Developing a specific strategy to characteristically silence the pathogenic SOD1 gene remains a crucial goal amidst significant challenges. In this study, we developed a synthetic biology strategy to reprogram the liver as a tissue chassis for the in vivo self-assembly of small extracellular vesicles (sEVs)-encapsulated SOD1-siRNA, aiming to target spinal neurons and silence mutant SOD1 specifically in Tg(SOD1G93A) transgenic mice. We designed a CMV promoter-directed synthetic construct to encode a SOD1-siRNA along with a neuron-targeting rabies virus glycoprotein (RVG) tagged on sEV surface. Theoretically, upon liver uptake, this construct reprograms liver cells to generate and self-assemble SOD1-siRNAs into RVG-tagged sEVs. Subsequently, the sEV-encapsulated SOD1-siRNAs are transported via the endogenous sEV circulation and guided by the RVG tag to the spinal neurons. Experimental results illustrated that intravenous administration of this synthetic construct effectively facilitated in vivo self-assembly of SOD1-siRNAs into circulating sEVs. The functional delivery of SOD1-siRNAs to the spinal cord and cerebral cortex was confirmed through in vivo tracking of sEVs and sEV-encapsulated siRNAs. Treatment of Tg(SOD1G93A) transgenic mice with this construct significantly reduced mutant SOD1 protein levels in the spinal cord and cerebral cortex. Consequently, the characteristic symptoms of ALS, including decreased body weight, shortened lifespan, compromised motor function, muscle atrophy, neuroinflammation, motor neuron loss, and neuromuscular junction degeneration, were substantially ameliorated by the synthetic construct. Furthermore, an AAV-based strategy was devised for the enduring self-assembly of sEV-encapsulated SOD1-siRNA, whereby a single injection led to substantial and sustained inhibition of mutant SOD1 and significant symptom amelioration in transgenic mice. Overall, this study established an effective and convenient therapeutic approach for mitigating muscle atrophy and denervation in animal model, presenting a promising solution for future ALS treatment.

Keywords:   in vivo self-assembly siRNA; amyotrophic lateral sclerosis; motor neuron; neuromuscular junction; synthetic biology; synthetic construct

DOI:  https://doi.org/10.1093/brain/awaf291
Cell Tissue Res. 2025 Aug 14.

Smarter stem cells: how AI is supercharging iPSC technology.

Hany E Marei.

  Integrated with artificial intelligence (AI), induced pluripotent stem cell (iPSC) technology could enhance disease modeling, cellular biology, regenerative medicine, and pharmaceutical development. AI has enhanced iPSC differentiation, cultural conditions, and speed of disease-specific model development. Furthermore, AI-based massive omics database analysis exposes hidden biological tendencies, enhancing customized treatment. Investigating new AI algorithms will enable one to solve problems, including interpretability and data quality, resulting from AI's interaction with iPSC technology. These advances fundamentally alter stem cell research and therapeutic applications, therefore facilitating the emergence of regenerative medicine and precision healthcare. AI has evolved in biomedical research into a transformational technology unique in great data analysis, predictive modeling, and automation capacity. AI integration increases the development of patient-specific cell types for disease modeling, pharmacological research, and regenerative medicine by substantially improving IPSC-based technologies. Emphasizing changes in disease models, alternative methodologies, and cellular reprogramming, this work examines current advancements in the use of AI in iPSC technology. The argument on significant obstacles and possibilities reveals how AI could alter the objectives of iPSC research and implementation.

Keywords:  AI; Cellular reprogramming; DL; Differentiation protocols; Disease modeling; Drug discovery; High-content imaging; Induced pluripotent stem cells (iPSCs); ML(ML); Multi-omics; Personalized medicine; Predictive modeling; Regenerative medicine; Reinforcement learning; Transcriptomics

DOI:  https://doi.org/10.1007/s00441-025-03999-7
Neurobiol Dis. 2025 Aug 12. pii: S0969-9961(25)00269-4. [Epub ahead of print] 107053

Alpha-synuclein inclusions reduced by PIKfyve inhibition in Parkinson's disease cell models.

Sara Lucas-Del-Pozo, Giuseppe Uras, Federico Fierli, Veronica Lentini, Sofia Koletsi, Carlos Lazaro-Hernandez, Kai-Yin Chau, Derralynn A Hughes, Anthony H V Schapira.

   OBJECTIVE: Parkinson's disease (PD) pathophysiology is associated with a progressive loss of dopaminergic neurons in the substantia nigra and accumulation of insoluble inclusions of misfolded alpha-synuclein. In this study, we used a neuroblastoma-derived cell model overexpressing a pro-aggregation form of alpha-synuclein and human-derived induced-pluripotent stem cells (iPSCs) to investigate the efficacy of PIKfyve-mediated lysosomal biogenesis to reduce alpha-synuclein inclusions.
METHODS: We used high-content imaging and enzymatic assays to follow the progression of lysosomal biogenesis, lysosomal catabolism and alpha-synuclein accumulation. The cell models used recapitulated important elements of the biochemical phenotype observed in PD dopaminergic neurons, including alpha-synuclein inclusions and impaired glucocerebrosidase.
RESULTS: PIKfyve inhibition by YM201636 resulted in a lysosomal-dependant reduction of alpha-synuclein inclusions as early as 24 h post-treatment. YM201636 induced an increase in nuclear translocation of TFEB, and an increase in lysosomal markers LAMP1 and HEXA. PIKfyve-inhibition was also tested in neuronal-differentiated neuroblastoma-derived cells and iPSCs-derived dopaminergic neurons. In these cells, YM201636 substantially reduced alpha-synuclein inclusions and increased TFEB nuclear localisation.
CONCLUSION: These findings suggest that PIKfyve signalling pathways could represent a therapeutic target to reduce alpha-synuclein in PD.

Keywords:  Alpha-synuclein; PIKfyve; Parkinson's disease; TFEB

DOI:  https://doi.org/10.1016/j.nbd.2025.107053
Proc Natl Acad Sci U S A. 2025 Aug 19. 122(33): e2504921122

Plant-specific mitochondrial fission machinery connects mitochondrial dynamics and mitophagosome formation for piecemeal mitophagy.

Juncai Ma, Chaorui Li, Kaike Ren, Kaiyan Zhang, Lanlan Feng, Kai Ching Law, Ka Kit Chung, Yizhou Bing, Caiji Gao, Byung-Ho Kang, Xiaohong Zhuang.

  As the energy center of the cell, mitochondria display enormous metabolic plasticity to meet the cellular demand for plant growth and development, which is tightly linked to their structural and dynamic plasticity. Mitochondrial number and morphology are coordinated through the actions of the mitochondrial division and fusion. Meanwhile, damaged mitochondrial contents are removed to avoid excess toxicity to the plant cells. Mitophagy, a selective degradation pathway of mitochondria through a double-membrane sac named autophagosome (also known as mitophagosome), plays a crucial role in maintaining mitochondrial homeostasis. Typically, wholesale mitophagy requires the elongation of a cup-shaped phagophore along the entire mitochondrion, which finally seals and closes as a mitophagosome. How plant mitophagosome formation and mitochondria sequestration are coordinated remains incompletely understood. In this work, we report an unappreciated role of the plant-specific mitochondrial fission regulator ELM1, together with the dynamin-related protein family DRP3 and the autophagic regulator SH3P2, to coordinate mitochondria segregation for piecemeal mitophagy under heat stress conditions. Dysfunction in mitochondrial fission activity impairs heat-induced mitophagy, leading to an accumulation of interconnected megamitochondria which are partially sequestered by the ATG8-positive phagophore. Furthermore, we show that the ELM1-mediated piecemeal mitophagy also engages the plant archetypal selective autophagic receptor NBR1. Using 3D tomography analysis, we illustrate the morphological features and spatial relationship of the megamitochondria and phagophore intermediates in connection with the mitochondrial fission sites. Collectively, our study provides an updated model of mitophagosome formation for piecemeal mitophagy mediated by the plant-unique mitochondrial fission machinery.

Keywords:  ELM1; SH3P2; mitochondrial fission; mitophagosome; mitophagy

DOI:  https://doi.org/10.1073/pnas.2504921122