bims-axbals 2026-10-04 papers

bims-axbals

Biomed News

on Axonal biology and ALS

Issue of 2026–10–04
nineteen papers selected by
TJ Krzystek

LRSAM1, an E3 ubiquitin ligase, modulates TDP-43 proteostasis in amyotrophic lateral sclerosis.
A guide to selecting high-performing antibodies for Prosaposin (UniProt ID: P07602) for use in western blot and immunoprecipitation.
PPM1H loss alters intrasynaptic alpha-synuclein localization in a LRRK2-dependent manner.
Tau hyperphosphorylation impairs cooperative binding to microtubules and perturbs organelle trafficking in neurons.
Tubulin polyglutamylation modulates Golgi morphodynamics and neurite branching during neuronal morphogenesis.
KIF1A-Mediated Axonal Transport of Netrin-1 in iPSC-Derived Human Forebrain Neurons.
Neuroinflammation and Autophagy in Neurodegeneration: Cellular Mechanisms and Therapeutic Strategies.
A guide to selecting high-performing antibodies for ARID1B (UniProt ID: Q8NFD5) for use in western blot and immunoprecipitation.
Profiling of Aggregated Amyloid β42-induced Proteomic Alterations in KOLF2.1J Induced Pluripotent Stem Cell-derived Neurons.
Neuromuscular junction formation by compartmentalized culture using human iPS cell-derived motor neurons and skeletal muscle cells.
Proteostasis (in)action: the role of co-pathologies in neurodegenerative disease.
BAG3 coordinates astrocytic proteostasis of Alzheimer's disease-linked proteins via proteasome, autophagy, and retromer interactions.
Phenotyping iPSC-derived neurons from Angelman patients and partial rescue via JNK pathway inactivation.
Expression of mutant Huntingtin induces proteasomal defects, mitochondrial abnormalities, and cell death in Drosophila muscles.
Pathogenic mutations in ATAD3A cause dysregulation of RagC/D-TFEB axis and disrupt lysosomal homeostasis.
The endo-lysosomal system drives lumen formation in a human epiblast model.
The Cytoplasmic MicroRNA-Production Complex Regulates MicroRNA Sorting to Extracellular Vesicles During Synaptogenesis.
Cell Biology of Botrytis: Live-Cell Imaging Techniques and Protein Localization Protocols.
Insights into X-linked Dystonia-Parkinsonism and Spinocerebellar Ataxia type 36 Through the Lens of Amyotrophic Lateral Sclerosis/Frontotemporal Dementia.

Brain. 2026 Sep 28. pii: awag334. [Epub ahead of print]

LRSAM1, an E3 ubiquitin ligase, modulates TDP-43 proteostasis in amyotrophic lateral sclerosis.

Takayuki Shirakawa, Satsuki Mikuriya, Yuki Inoue, Kota Murasaki, Florencia Salinas, Tomo Takegawa-Araki, Makoto Tamura.

  Amyotrophic lateral sclerosis is a fatal neurodegenerative disease characterized by the cytoplasmic mislocalization, aberrant phosphorylation and pathological aggregation of TDP-43, a nuclear RNA-binding protein essential for RNA metabolism. Despite its central involvement in ALS pathogenesis, the molecular mechanisms that govern TDP-43 proteostasis remain incompletely understood. Here, we investigated the role of LRSAM1, an E3 ubiquitin ligase, in regulating TDP-43 localization and degradation. Postmortem spinal cord tissues from five patients with sporadic amyotrophic lateral sclerosis and five healthy controls were examined. Immunohistochemical analyses revealed that LRSAM1 preferentially colocalized with diffusely mislocalized cytoplasmic TDP-43 but not with dense cytoplasmic aggregates, suggesting a potential role in early-stage pathological processing. To model these effects in vitro, induced pluripotent stem cell-derived motor neurons from three patients with amyotrophic lateral sclerosis and four healthy control participants were used. Knockdown of LRSAM1 in induced pluripotent stem cell-derived motor neurons from patients with amyotrophic lateral sclerosis significantly increased cytoplasmic TDP-43 accumulation and phosphorylation, as measured by immunofluorescence imaging. Moreover, STMN2 mRNA splicing, a well-established TDP-43 functional readout, was disrupted upon LRSAM1 depletion. Conversely, overexpression of LRSAM1 ameliorated stress-induced TDP-43 mislocalization and phosphorylation in induced pluripotent stem cell-derived motor neurons from patients with amyotrophic lateral sclerosis but had minimal impact in control cells, indicating disease-specific vulnerability. Mechanistically, LRSAM1 interacted directly with the aggregation-prone C-terminal fragments of TDP-43 via the RRM2 domain of TDP-43 and promoted their proteasomal degradation. This selective interaction reduced the accumulation of toxic TDP-43 species and supported cytoplasmic proteostasis, particularly under conditions of cellular stress. In summary, our study identifies LRSAM1 as a novel modulator of cytoplasmic TDP-43 dynamics in amyotrophic lateral sclerosis. By facilitating degradation of pathogenic TDP-43 fragments, LRSAM1 preserves neuronal RNA processing and mitigates molecular hallmarks of amyotrophic lateral sclerosis. These findings enhance our understanding of post-translational control of TDP-43 and highlight LRSAM1 as a promising therapeutic target for modifying disease progression in amyotrophic lateral sclerosis.

Keywords:  RNA-binding proteins; iPSC-derived motor neurons; motor neuron disease; proteasomal degradation; proteinopathy; ubiquitination

DOI:  https://doi.org/10.1093/brain/awag334
F1000Res. 2026 ;15 1065

A guide to selecting high-performing antibodies for Prosaposin (UniProt ID: P07602) for use in western blot and immunoprecipitation.

Vera Ruíz Moleón, Sara González Bolívar Bolívar, Riham Ayoubi, Vincent Francis, Peter S McPherson, Carl Laflamme.

  Prosaposin functions as a regulator of lysosomal enzymatic activity and as a neuroprotective player when secreted. Here we have characterized nine Prosaposin commercial antibodies for western blot and immunoprecipitation using a standardized experimental protocol based on comparing read-outs in knockout cell lines and isogenic parental controls. These studies are part of a larger, collaborative initiative seeking to address antibody reproducibility issues by characterizing commercially available antibodies for human proteins and publishing the results openly as a resource for the scientific community. While the use of antibodies and protocols vary between laboratories, we encourage readers to use this report as a guide to select the most appropriate antibodies for their specific needs.

Keywords:  P07602; PSAP; Prosaposin; Sphingolipid activator protein 1 (SAP-1); antibody characterization; antibody validation; immunofluorescence; immunoprecipitation; western blot

DOI:  https://doi.org/10.12688/f1000research.177779.1
Mol Brain. 2026 Sep 29. pii: 66. [Epub ahead of print]19(1):

PPM1H loss alters intrasynaptic alpha-synuclein localization in a LRRK2-dependent manner.

Lennart Evers, Jessica M Grein, C Alexander Boecker.

  Mutations in the LRRK2 gene are a major genetic cause of Parkinson's disease (PD) and induce hyperphosphorylation of RAB GTPases through increased LRRK2 kinase activity. The phosphatase PPM1H counteracts this activity by selectively dephosphorylating LRRK2-phosphorylated RAB proteins. Here, we used primary PPM1H knockout neurons to investigate how loss of PPM1H and the resulting hyperphosphorylation of RAB proteins affect the distribution of alpha-synuclein (aSyn), a key protein in PD pathology, at presynaptic terminals. We found that PPM1H deficiency significantly increased the distance between aSyn and the presynaptic marker Bassoon, indicating displacement of aSyn away from the presynapse. Pharmacological LRRK2 kinase inhibition rescued this phenotype, restoring intrasynaptic aSyn positioning to wild-type values. These findings show that loss of PPM1H alters aSyn localization in a LRRK2 kinase activity-dependent manner, suggesting that elevated levels of LRRK2-phosphorylated RAB proteins disrupt the nanoscale organization of aSyn at the presynapse.

Keywords:  Alpha-synuclein; LRRK2; PPM1H; Presynapse; RAB GTPases; Synapse

DOI:  https://doi.org/10.1186/s13041-026-01352-9
Elife. 2026 Sep 28. pii: RP110011. [Epub ahead of print]15

Tau hyperphosphorylation impairs cooperative binding to microtubules and perturbs organelle trafficking in neurons.

Daniel Beaudet, Christopher L Berger, Adam G Hendricks.

  Tau, a neuronal microtubule-associated protein (MAP), organizes the axonal cytoskeleton, and regulates intracellular transport. Tau hyperphosphorylation is linked to neurodegeneration in tauopathies, including Alzheimer's disease. Tau binds microtubules cooperatively to form cohesive envelopes, which are thought to control access to the microtubule lattice and regulate the activity of motor proteins and other MAPs. However, how disease-related perturbations affect tau dynamics and its function as a selective barrier to intracellular transport remains unclear. Using tau phospho-variants in vitro and in live neurons, we show that tau hyperphosphorylation disrupts cooperative microtubule binding and dysregulates lysosome transport. Hyperphosphorylated tau does not form envelopes, distributes more uniformly along the axon, and dissociates faster from microtubules. Tau weakly inhibits KIF5C motility, but strongly inhibits KIF1A. Hyperphosphorylation reduces KIF5C inhibition but increases KIF1A inhibition by decreasing processivity and accelerating detachment. Consistent with these effects, hyperphosphorylated tau alters lysosome transport in neurons. While phospho-resistant tau inhibits processive lysosome motility, hyperphosphorylated tau weakens tau-mediated regulation of lysosome transport, mimicking tau knockout neurons that exhibit enhanced processivity. Altogether, these findings show that hyperphosphorylation disrupts tau envelopes and impairs lysosome trafficking, likely contributing to early defects in degradative pathways that drive neurodegeneration.

Keywords:  Alzheimer's disease; cell biology; iPSCs; in vitro reconstitution; microtubule-associated protein; neuroscience; tau

DOI:  https://doi.org/10.7554/eLife.110011
J Cell Sci. 2026 Oct 02. pii: jcs.264960. [Epub ahead of print]

Tubulin polyglutamylation modulates Golgi morphodynamics and neurite branching during neuronal morphogenesis.

Chih-Hsuan Hsu, Alexander Josiah Kinrade, Sarah Cohen.

  Neurons establish functional networks through morphological remodeling during neuronal differentiation. Microtubule polyglutamylation is a key microtubule post-translational modification that is highly enriched during this process and plays an important role in differentiation. However, how remodeling of organelle features such as morphology, distribution and interactions depends on tubulin polyglutamylation during neuronal differentiation remain unclear. Here, we employed multispectral imaging combined with quantitative 3D organelle analysis to comprehensively profile eight organelles simultaneously in human induced pluripotent stem cell-derived neurons. We discovered that depletion of tubulin polyglutamylation induces pronounced alterations in somatic Golgi morphology and associated organelle interactions. In addition, Golgi-derived compartments in proximal neurites exhibited altered morphology and dynamics, namely decreased anterograde transport together with less efficient movement. These changes were accompanied by increased neurite branching and tortuosity. Together, our findings reveal a previously unrecognized role for tubulin polyglutamylation in coordinating organelle organization with neurite architecture, providing a mechanistic link between tubulin post-translational modification, Golgi morphology, dynamics, and neuronal morphogenesis.

Keywords:  Cell biology; Golgi; INeurons; Microscopy; Microtubules; Organelles; Polyglutamylation

DOI:  https://doi.org/10.1242/jcs.264960
Cytoskeleton (Hoboken). 2026 Sep 26. e70207

KIF1A-Mediated Axonal Transport of Netrin-1 in iPSC-Derived Human Forebrain Neurons.

T Y Leung, J Sidhu, A Hsieh, Y Ma, J Liu, M A Silverman.

  Netrin-1 is a secreted laminin-like protein that functions as a guidance cue for axon pathfinding in development. Netrin-1 also modulates synapse formation in developing neurons and long-term potentiation in mature neurons. Netrin-1 is expressed in human neurons; however, its intracellular distribution and trafficking have not been assessed. Moreover, there is a genetic association in Caenorhabditis elegans between UNC-6/netrin-1 and UNC-104/KIF1A, a kinesin-3 motor protein required for axonal transport. We characterized the endogenous expression of netrin-1 via immunocytochemistry and demonstrated it is localized to both the axon and dendrites of induced pluripotent stem cell (iPSC)-derived human forebrain neurons. Next, live-cell imaging of netrin-1-mRFP revealed rapid, bidirectional axonal transport, comparable to that of other cargos undergoing microtubule-based trafficking in vertebrate neurons. To identify the netrin-1 vesicle population, co-localization analyses demonstrated that netrin-1 puncta overlap with the dense-core vesicle marker Chromogranin A. Netrin-1-mRFP and Chromogranin A-eGFP also undergo co-transport within the axon. Finally, we demonstrated a role for the kinesin-3 motor protein, KIF1A, in Netrin-1 transport by demonstrating that KIF1A-associated neurological disease (KAND) patient variants significantly reduce netrin-1 axonal transport.

Keywords:  KIF1A; axon transport; induced pluripotent stem cell derived—neurons; kinesin; live cell imaging; netrin

DOI:  https://doi.org/10.1002/cm.70207
CNS Neurol Disord Drug Targets. 2026 Sep 29.

Neuroinflammation and Autophagy in Neurodegeneration: Cellular Mechanisms and Therapeutic Strategies.

Anushka Verma, Swatantra Kumar Singh Kushwaha, Neelottama Kushwaha, Sayantan Dutta, Parul Nigam.

  Neurodegenerative diseases, including Huntington's disease, Parkinson's disease, Alzheimer's disease, and Amyotrophic Lateral Sclerosis (ALS), are characterized by progressive neuronal dysfunction and loss, often accompanied by toxic protein aggregation and chronic neuroinflammation. Increasing evidence indicates that dysregulated autophagy and persistent inflammatory responses are central drivers of disease onset and progression. Autophagy, a fundamental cellular degradation and recycling process, is essential for maintaining neuronal homeostasis by removing damaged organelles and misfolded proteins through mechanisms such as macroautophagy and mitophagy. However, key regulators of this pathway, including ULK1, Beclin-1, LC3, and p62/SQSTM1, are frequently impaired in neurodegenerative conditions, leading to the accumulation of pathogenic proteins such as tau, α-synuclein, and amyloid-β. Concurrently, aberrant activation of microglia and inflammasomes promotes the sustained release of pro-inflammatory cytokines, creating a neurotoxic environment that exacerbates neuronal injury. This review examines the molecular crosstalk between autophagy and neuroinflammation, with particular emphasis on disease-specific mechanisms, including LC3-associated endocytosis (LANDO) in Alzheimer's disease, tau-mediated pathology, and dopaminergic neurodegeneration in Parkinson's disease. Importantly, this review introduces a unifying conceptual framework in which neuroinflammation and autophagy are integrated as a dynamic, stagedependent immune-autophagy axis that governs neurodegenerative disease progression and therapeutic responsiveness. In addition, emerging multimodal therapeutic strategies targeting both autophagic flux and immune modulation are discussed, including mTOR inhibitors, mitophagy enhancers, GLP-1 receptor agonists, and nanomedicine-based delivery systems. Advances in three-dimensional organoids, induced Pluripotent Stem Cell (iPSC) models, and biomarker-driven clinical trials are further enhancing translational potential. In conclusion, understanding the interplay between autophagy and neuroinflammation provides critical insights into the pathophysiology of neurodegeneration and offers promising avenues for the development of targeted, disease-modifying therapies.

Keywords:  Neuroinflammatory; autophagy; neurodegeneration; pathology.; receptors; therapeutic strategies

DOI:  https://doi.org/10.2174/0118715273459017260922073618
F1000Res. 2026 ;15 631

A guide to selecting high-performing antibodies for ARID1B (UniProt ID: Q8NFD5) for use in western blot and immunoprecipitation.

Vera Ruíz Moleón, Sara González Bolívar, Riham Ayoubi, Vincent Francis, Peter S McPherson, Carl Laflamme.

  ARID1B encodes a core subunit of the SWI/SNF (BAF) ATP-dependent chromatin-remodeling complex and plays a critical role in transcriptional regulation, cell differentiation, and development. Here we have characterized seven ARID1B commercial antibodies for western blot and immunoprecipitation by using a standardized experimental protocol based on comparing read-outs in knockout cell lines and isogenic parental controls. These studies are part of a larger, collaborative initiative seeking to address antibody reproducibility issues by characterizing commercially available antibodies for human proteins and publishing the results openly as a resource for the scientific community. While the use of antibodies and protocols vary between laboratories, we encourage readers to use this report as a guide to select the most appropriate antibodies for their specific needs.

Keywords:  ARID1B; BAF250B antibody characterization; Q8NFD5; antibody validation; immunoprecipitation; western blot

DOI:  https://doi.org/10.12688/f1000research.179398.1
bioRxiv. 2026 Sep 25. pii: 2026.09.20.753014. [Epub ahead of print]

Profiling of Aggregated Amyloid β42-induced Proteomic Alterations in KOLF2.1J Induced Pluripotent Stem Cell-derived Neurons.

Benjamin Jin, Ziyi Li, Ying Hao, Isabelle Kowal, Jacob Epstein, Marianita Santiana, Cory Weller, Mike A Nalls, Dingying Tao, Shengyun Fang, Priyanka Narayan, Andrew B Singleton, Kendall Van Keuren-Jensen, Luigi Ferrucci, Michael E Ward, Mark R Cookson, Erika Lara, Veronica H Ryan, Yue Andy Qi.

Amyloid[beta]; (A[beta];) plaques are a hallmark of Alzheimer[prime]s disease (AD). A human cellular neuronal model that recaptures A[beta];-induced pathology is critical for advancing AD research. However, comprehensive proteomic profiling of A[beta];-induced cellular model remains elusive. In this study, we investigated the proteomic changes in induced pluripotent stem cell (iPSC)-derived neurons (iNs) exposed to synthetic A[beta]; (1-42) peptides (A[beta];42A) to improve our understanding of the cellular responses of A[beta]; aggregates and to establish a human-related platform for AD research. A[beta];42A formed extracellular aggregates around neuronal soma and neurites, impaired neurite outgrowth, and induced the expression of multiple AD-associated genes, such as APOE, BACE1, ADAM10. To define the molecular landscape of A[beta];-induced neuronal dysfunction, we performed proteomic analyses of whole-cell lysates as well as soma- and neurite-enriched fractions. Proteomic profiling revealed extensive gene alterations in pathways associated with synaptic function, neuronal maintenance, and AD pathogenesis, such as the upregulation of APOE. Importantly, the A[beta];42A-iNs system recapitulated molecular signatures observed in AD brain tissue and cerebrospinal fluid. Representative protein changes, including APOE upregulation and its colocalization with A[beta]; aggregates, were further validated in postmortem human AD brain tissue. Together, these findings manifest that the A[beta];42A-iNs system reproduces multiple cellular and molecular features of AD and exhibits strongly consensus with clinical observations. It provides a valuable platform for investigating A[beta];-driven neurodegeneration and for the discovery of therapeutic targets for AD.

DOI: https://doi.org/10.64898/2026.09.20.753014
Front Neural Circuits. 2026 ;20 1838276

Neuromuscular junction formation by compartmentalized culture using human iPS cell-derived motor neurons and skeletal muscle cells.

Masayoshi Kamon, Moe Yamashita, SokeLee Siew, Shuji Wakatsuki, Toshiyuki Araki.

  The neuromuscular junction (NMJ) is a synapse that connects the nerve terminal of a motor neuron to a skeletal muscle fiber. The mechanisms underlying NMJ formation have been elucidated primarily through studies in animal models. However, elucidation of the pathophysiological mechanisms of human neuromuscular diseases and identification of potential therapeutic agents require the establishment of a human NMJ model. In this study, we established a human NMJ model using a compartmentalized culture system with cells derived from human induced pluripotent stem (iPS) cells, which enables quantitative and reproducible assessment of NMJ formation. During extended NMJ culture, morphological changes in the NMJ were observed, along with alterations in the expression of genes related to NMJ and skeletal muscle development, suggesting progressive NMJ maturation. The functionality of the formed NMJs was also confirmed using fluorescent live-cell imaging. These findings suggest that this human NMJ culture model may be applicable for investigating the pathological mechanisms of human neuromuscular diseases and exploring therapeutic agents.

Keywords:  MyoD; culture modeling; imaging; induced pluripoten stem cell; motor neuron (MN); neuromuscular junction (NMJ); skeletal muscle cell (SMC); synaptogeneisis

DOI:  https://doi.org/10.3389/fncir.2026.1838276
Philos Trans R Soc Lond B Biol Sci. 2026 Oct 01. pii: 20250273. [Epub ahead of print]381(1960):

Proteostasis (in)action: the role of co-pathologies in neurodegenerative disease.

James F Morley.

  Clinically distinct neurodegenerative diseases, including Alzheimer's disease (AD), Parkinson's disease (PD) and amyotrophic lateral sclerosis (ALS), share in common progressive neuronal dysfunction and cell death associated with the accumulation of misfolded proteins. Central to these processes are the cellular and organismal proteostasis networks responsible for maintaining protein homeostasis through coordinated actions of molecular chaperones, the ubiquitin-proteasome system and autophagy-lysosomal pathways. As a consequence of ageing, genetic modifications and other disease-specific conditions, the proteostatic network becomes compromised, leading to the accumulation of toxic protein aggregates that disrupt neuronal function and lead to neurodegeneration. Specific misfolded proteins are associated with each neurodegenerative disease (i.e. α-synuclein in PD, amyloid-β/tau in AD and TAR DNA-binding protein 43/SOD in ALS). However, increasing evidence implicates more complex interactions of co-pathologies across these disorders, as Lewy bodies are common in AD brains and Alzheimer pathology is present in the majority of PD autopsy cases. These observations are consistent with the idea that disruption of proteostasis networks by one aggregation-prone protein could result in misfolding and aggregation of other neurodegeneration-related species. This review will examine the characteristics and consequences of co-pathologies in neurodegenerative disorders. Additionally, the review will outline emerging therapeutic strategies targeted at restoring proteostasis and mitigating the effects of co-pathological processes associated with neurodegenerative diseases. This article is part of the Theo Murphy meeting issue 'ProteostaSys: a systems view of proteostasis'.

Keywords:  co-pathology; neurodegeneration; proteostasis

DOI:  https://doi.org/10.1098/rstb.2025.0273
Proc Natl Acad Sci U S A. 2026 Oct 06. 123(40): e2528514123

BAG3 coordinates astrocytic proteostasis of Alzheimer's disease-linked proteins via proteasome, autophagy, and retromer interactions.

Zachary M Augur, Garrett M Fogo, Courtney R Benoit, Masin A Kearney, Gizem Terzioglu, Zachary R Murphy, Mason R Arbery, Natacha Comandante-Lou, Duc M Duong, Nicholas T Seyfried, Philip L De Jager, Tracy L Young-Pearse.

  Bcl-2-associated athanogene 3 (BAG3) is a mediator of chaperone-assisted selective autophagy, and in the brain, is most highly expressed in astrocytes. However, its role in astrocytes remains poorly defined. Given the genetic and pathological links of BAG3 to proteostasis and neurodegenerative diseases, we investigated how BAG3 contributes to astrocyte function and Alzheimer's disease (AD). To define its function and relevance, we used single-nucleus RNA sequencing to confirm BAG3 enrichment in astrocytes and employed CRISPR/Cas9 editing of human induced pluripotent stem cells followed by proteomic and transcriptomic profiling, which revealed that BAG3 loss caused greater disruption in astrocytes than in neurons. BAG3-deficient astrocytes displayed reduced autophagy, lysosomal abundance and activity, and proteasome function. Coimmunoprecipitation identified BAG3 known binding partners (e.g., HSPB8, proteasome regulators), as well as an interactor in the retromer complex, VPS35. BAG3 deficiency resulted in altered retromer activity as measured by amyloid precursor protein (APP) localization in endosomes. In addition to validating these binding partners, integrative -omics analyses showed that BAG3 regulates AD-relevant proteins (GFAP, BIN1), as well as HSPB8. Functionally, BAG3 knockout astrocytes exhibited impaired amyloid-β proteostasis when cocultured with APP/PSEN1 mutant neurons, directly linking BAG3 to a disease-relevant astrocyte phenotype. Finally, analysis of postmortem human brain revealed that BAG3 expression marks a stress-responsive astrocyte subtype in aged individuals. Together, these findings demonstrate that BAG3 coordinates astrocyte proteostasis through interactions with regulators of autophagy, proteasome activity, and retromer function, positioning it as a potential therapeutic target and central node of astrocytic protein quality control in neurodegeneration.

Keywords:  Alzheimer’s disease; BAG3; astrocytes; autophagy; iPSC

DOI:  https://doi.org/10.1073/pnas.2528514123
J Neurodev Disord. 2026 Aug 28. pii: 56. [Epub ahead of print]18(1):

Phenotyping iPSC-derived neurons from Angelman patients and partial rescue via JNK pathway inactivation.

Valentina Alari, Clara Cambria, Chiara De Cesari, Alessandro Vimercati, Milena Crippa, Sara Perego, Lidia Larizza, Ilaria Tonazzini, Flavia Antonucci, Silvia Russo.

   BACKGROUND: Angelman Syndrome (AS, MIM #105,830) is a rare neurodevelopmental disorder caused by imprinting defects, and it is marked by motor impairment, intellectual disability, speech limitations, and seizures. The condition arises due to the loss of function in neurons of the maternally-inherited UBE3A gene, mapping in the imprinted chromosomal region 15q11.2-q13, through a variety of genetic and epigenetic mechanisms. UBE3A encodes a ubiquitin E3 ligase, which is essential for synaptic plasticity. Most studies of AS have been performed on animal models, while induced pluripotent stem cells (IPSCs), mainly generated from patients with deletion, remain limited in number.
METHODS: Here we report on the generation and characterization of human cortical neurons derived from IPSCs obtained from children representative of the main AS genotypes: 3 with 15q11-13 deletion, 3 with UBE3A mutations, 3 with uniparental disomy, and 2 with imprinting defects.
RESULTS: During early neuronal differentiation, morphological analyses highlighted a reduced dendritic branching and an increased number of thin filopodia, while migration assays revealed reduced neurite mobility in AS human neurons with the most severe genetic defect, namely the 15q11-13 deletion. At a later differentiation time point, electrophysiological analyses revealed impaired neuronal activity in AS patient-derived neurons. To investigate pathways potentially involved in synaptic dysfunction, we examined the JNK (c-Jun N-terminal kinase) signalling pathway, which plays key roles in neuroinflammation and synaptic development. We found increased JNK activation and, importantly, treatment with a JNK-inhibitor, D-JNKI1, partially rescued the neuronal morphological defects, significantly reducing the number of immature protrusions, as well as defects in electrophysiological properties.
CONCLUSIONS: Our patient-specific models contribute elucidate how loss of UBE3A leads to aberrant neuronal maturation and function in the precocious stages of neuronal development and how treatment with D-JNKI1 may pave the way for new therapeutic possibilities.

Keywords:  E6AP; JNK inhibitor; Neurite mobility; Patch-clamp recordings; Thin spines; i-neurons

DOI:  https://doi.org/10.1186/s11689-026-09728-7
Biochem Biophys Res Commun. 2026 Sep 24. pii: S0006-291X(26)01396-3. [Epub ahead of print]838 154630

Expression of mutant Huntingtin induces proteasomal defects, mitochondrial abnormalities, and cell death in Drosophila muscles.

Athira M Sarath, Naorem Tarundas Singh, Bhavani Shankar Sahu, Mayanglambam Dhruba Singh.

  Huntington's disease is an inherited neurodegenerative disorder characterized by the progressive loss of neurons, particularly in the basal ganglia, resulting from a mutation in the Huntingtin gene. Recently, skeletal muscle defects have emerged as a contributing factor in HD pathogenesis. However, the mechanistic role of mutant HTT on muscle abnormality remains elusive. In this study, we sought to elucidate the pathogenesis of Huntington's disease in skeletal muscles using Drosophila melanogaster as a model organism. We employed two transgenic fly lines - HTT.ex1.Q120 expressing the exon 1 fragment of the human HTT gene along with 120 polyQ repeats and mRFP-HTT.588.Q138 expressing 588 amino acids at the N-terminal of the human HTT gene along with 138 polyQ repeats. We combined behavioural, molecular, and imaging techniques to study the effect of mutant HTT on skeletal muscles. When mutant HTT proteins are expressed in the indirect flight muscles, these flies exhibited severe defects, including reduced climbing and locomotor abilities and a significantly shortened lifespan. These phenotypes were associated with the formation of mHTT aggregates in the muscles. Furthermore, we found that mitochondrial integrity is compromised, as evidenced by abnormal mitochondrial morphology. Additionally, increased proteasomal dysfunction and apoptosis were observed in the muscles of flies expressing HTT.ex1.Q120 and mRFP-HTT.588.Q138. The study offers valuable insights into muscle pathogenesis in Huntington's disease and suggests that skeletal muscle may represent a major peripheral contributor to disease progression. It highlights the need for further investigation into the pathogenesis of skeletal muscle to develop HD therapeutics.

Keywords:  Dorsal longitudinal muscles; Drosophila; Huntingtin; Huntington's disease; Neurodegenerative disorder

DOI:  https://doi.org/10.1016/j.bbrc.2026.154630
bioRxiv. 2026 Sep 25. pii: 2026.09.23.753918. [Epub ahead of print]

Pathogenic mutations in ATAD3A cause dysregulation of RagC/D-TFEB axis and disrupt lysosomal homeostasis.

Mathew B McDougal, Abigail Sandoval, Mike Kinter, Antrix Jain, Sukyeong Lee, Sung Yun Jung, Wan Hee Yoon.

We previously discovered that a de novo variant p.R528W in ATAD3A , encoding a mitochondrial membrane-anchored protein, causes a human neurological syndrome. While ATAD3A mutations induce aberrant lysosomal expansion accompanied by undigested material in the lysosomes, how mutant ATAD3A disrupts lysosomal homeostasis and whether this contributes to neurodevelopmental defects remain unknown. Here we show that pathogenic ATAD3A p.R528W expression disrupts the mTORC1-TFEB axis as revealed by dysregulation of mTORC1 substrate phosphorylation, TFEB nuclear localization, and CLEAR gene activation associated with lysosomal biogenesis. ATAD3A binds to lysosome-localized Rag C/D GTPases, which constitute a platform for TFEB recruitment, with pathogenic variants increasing this association and thereby decreasing lysosomal localization of Rag GTPases. Importantly, overexpression of RagC or RagD restores TFEB phosphorylation in human cells expressing p.R528W, and RagC- D overexpression or TFEB/Mitf knockdown rescues lysosomal expansion and neurodevelopmental defects in Drosophila . These data indicate that disrupted Rag GTPase recruitment to lysosomes and subsequent aberrant TFEB/Mitf activation contribute to neurodevelopmental and lysosomal phenotypes caused by pathogenic mutations in ATAD3A . Our work reveals a novel role for the mitochondrial resident protein ATAD3A in modulating lysosomal homeostasis through regulation of the mTORC1-TFEB axis, providing a mechanistic link between impaired mitochondrial and lysosomal homeostasis in a neurodevelopmental disorder.

DOI: https://doi.org/10.64898/2026.09.23.753918
Nat Commun. 2026 Aug 27. pii: 10255. [Epub ahead of print]17(1):

The endo-lysosomal system drives lumen formation in a human epiblast model.

Anusha Rengarajan, Sicong Wang, Chien-Wei Lin, Lauren E Elberfeld, Jenna C Wettstein, Amber E Carleton, Nikola Sekulovski, Linnea E Taniguchi, Bailey E Schultz, Mara C Duncan, Kenichiro Taniguchi.

Epiblast lumen formation is a critical step that occurs during human embryo implantation. It begins with the apicosome, an apical compartment partly derived from endocytosed material. However, how the endo-lysosomal system contributes to apicosome formation and later lumen development remains unclear. Using a human pluripotent stem cell-derived model of epiblast formation, we show that apicosome formation is accompanied by transient expansion of early endosomes, late endosomes, and lysosomes, as well as the formation of hybrid compartments with features of both early and late endo-lysosomal stages. These changes depend on the RAB GTPases RAB35 and RAB7, which are required for proper apicosome formation and lumen morphology of the human epiblast model. Our findings identify RAB35- and RAB7-dependent endo-lysosomal remodeling as a key mechanism driving apical membrane morphogenesis during human epiblast development.

DOI: https://doi.org/10.1038/s41467-026-77140-9
Adv Sci (Weinh). 2026 Sep 30. e78067

The Cytoplasmic MicroRNA-Production Complex Regulates MicroRNA Sorting to Extracellular Vesicles During Synaptogenesis.

Yuzhou Zeng, Selina Luhmann, Aditi Saha, Marta Orlando, Haider Sami, Timo Glatter, Anna Antoniou.

  Extracellular vesicles (EVs) have emerged as novel players of cell communication, in part via the transfer of microRNA (miRNA) cargo to recipient cells. Although several RNA-binding proteins (RBPs) were shown to shuttle miRNAs to EVs, how they are loaded with miRNA is unknown. This study demonstrates that the core accessory protein of the cytoplasmic miRNA production machinery TRBP interacts with several EV-RBPs and differentially regulates miRNA secretion in small EVs. TRBP-regulated EV-miRNAs were highly enriched in a Syncrip-recognition sequence motif. Moreover, we show that Syncrip associates with TRBP via its C-terminal domain at the surface of the endoplasmic reticulum (ER), a nucleation site of the miRNA production machinery. The recruitment of Syncrip to ER-associated TRBP was regulated by ER-endosome membrane contact sites (MCS), whereby increased MCS formation promotes Syncrip loading to endosomes as well as Argonaute 2-positive RNA granules. Functionally, this pathway is important for the regulation of synapse formation in developing neurons, as expression of miRNA- or TRBP-binding deficient mutants of Syncrip differentially regulated synapse formation in EV-donor and recipient neurons. Overall, this work highlights an important role of TRBP as a gatekeeper for microRNA sorting, which could be crucial for the fine-tuning of neuronal circuits during postnatal development.

Keywords:  RNA granule; RNA‐binding protein; extracellular vesicle; microRNA sorting; organelle contact sites; synapse formation

DOI:  https://doi.org/10.1002/advs.78067
Methods Mol Biol. 2027 ;3076 37-43

Cell Biology of Botrytis: Live-Cell Imaging Techniques and Protein Localization Protocols.

H M Suraj, André Fleissner, Jan A L van Kan.

  Botrytis cinerea is a widely studied model organism for plant-fungal interactions. This chapter provides simple and easy protocols for live-cell imaging techniques and subcellular protein localization studies in B. cinerea in vitro. Using a simple microscopy setup, we describe methods for imaging spore germlings and hyphae and for studying protein dynamics in response to the antifungal compound α-tomatine. The protocols highlight the application of fluorescence microscopy to visualize sterol distribution and protein localization patterns, enabling deeper insights into fungal cell biology.

Keywords:   Botrytis cinerea; Live-cell imaging; Microscopy; Protein localization; Staining

DOI:  https://doi.org/10.1007/978-1-0716-5551-1_6
Mol Neurobiol. 2026 Sep 26. pii: 926. [Epub ahead of print]63(1):

Insights into X-linked Dystonia-Parkinsonism and Spinocerebellar Ataxia type 36 Through the Lens of Amyotrophic Lateral Sclerosis/Frontotemporal Dementia.

Mansee Patel, Soumalya Das, Aditi Pramod Kumari, Amit Kumar.

  The abnormal expansion of repetitive DNA sequences falls within the spectrum of neurological conditions driven by dual pathogenic pathways of RNA toxicity and protein toxicity. Within this spectrum, hexanucleotide repeat disorders (HRDs) represent a rare but important subgroup: C9orf72-amyotrophic lateral sclerosis/frontotemporal dementia (C9orf72-ALS/FTD), X-linked dystonia-parkinsonism (XDP) and spinocerebellar ataxia type 36 (SCA36), unified by the presence of expanded intronic repeats capable of forming non-canonical nucleic acid structures. Despite this shared repeat architecture, they differ in critical molecular and genetic respects: C9orf72-ALS/FTD is hallmarked by TDP-43 aggregation and prominent proteinopathy; SCA36 lacks TDP-43 pathology entirely; and XDP uniquely harbors a SINE-VNTR-Alu (SVA) retrotransposon insertion within the expanded locus and follows an X-linked recessive inheritance pattern. Among these, C9orf72-ALS/FTD is relatively well characterized, with established pathogenic mechanisms including G-quadruplex (G4) formation, dipeptide repeat (DPR) protein toxicity, RNA foci formation, and downstream cellular disruptions. The molecular mechanism underlying SCA36 and XDP remains comparatively less characterized. Given the mechanistic overlap with ALS/FTD, downstream disruptions such as RNA toxicity, mitochondrial dysfunction, impaired DNA repair and proteasomal dysfunction could similarly result from these core molecular processes. However, direct experimental evidence supporting these mechanisms in SCA36 and XDP remains limited. This review compares established, emerging and hypothetical mechanisms across HRDs to distinguish shared pathogenic pathways from disease-specific molecular features. Through horizontal comparison, this review identifies opportunities and limitations for translating ALS/FTD therapeutics to XDP and SCA36, establishing a unified analytical framework for mechanistic research and clinical intervention in rare repeat expansion disorders.

Keywords:   C9orf72-amyotrophic lateral sclerosis/frontotemporal dementia (ALS/FTD); Antisense oligonucleotides (ASOs); Clustered regularly interspaced short palindromic repeats (CRISPR); Dipeptide repeat (DPR) proteins; G-quadruplex (G4) structures; Immunotherapy; R-loop; RNA foci; Repeat-associated non-canonical (RAN) translation; SINE-VNTR-Alu (SVA) retrotransposon; Small molecules; Somatic repeat instability; Spinocerebellar ataxia type 36 (SCA36); TDP-43 proteinopathy; X-linked dystonia-parkinsonism (XDP)

DOI:  https://doi.org/10.1007/s12035-026-06209-9