bims-axbals 2026-08-02 papers

bims-axbals

Biomed News

on Axonal biology and ALS

Issue of 2026–08–02
thirty-one papers selected by
TJ Krzystek

The LRRK2 G2019S variant rewires Rab GTPase phosphorylation after lysosomal damage and promotes cell death in human macrophages.
KIF1A-mediated trafficking is required for neuronal autophagy in human neurons.
Microscale dysfunction and mesoscale compensation in degenerating neuronal networks.
Scalable human neuronal models of tauopathy producing endogenous seed-competent 4R tau.
Myosin 5A mediates membrane-associated periodic skeleton reassembly during axon regeneration in response to ROCK-2 inhibition.
Altered neuronal start codon stringency favors cap-independent repeat-associated non-AUG translation.
Targeting TDP-43 in ALS: Regulatory hurdles, trial design deficiencies, and the causal evidence gap for CTx1000.
LINE-1 Retrotransposons and Amyotrophic Lateral Sclerosis.
Signatures of aging and disease in a single organelle.
A Phosphorylation-Induced Micellization Switch in the Low-Complexity Domain of TDP-43.
In-cell cryo-electron tomography reveals differential effects of type I and type II kinase inhibitors on LRRK2 filament formation and microtubule association.
Microglia extract neuronal proteolytic organelles via skoupocytosis.
Kinesin-3 and the cargo adaptor Hook1 regulate early endosome and peroxisome motility and are required for mitochondrial and endoplasmic reticulum spatial organization during polarized fungal cell growth in Podospora anserina.
ATL2 Recruits TRAK1 to Promote Mitochondrial Transport at ER-Mitochondria Contact Sites.
Context-dependent YEATS-domain inhibition enhances neuronal resilience and improves ALS phenotypes.
In vivo CRISPR base editing for treatment of Huntington's disease.
Atlas of lysosomal aging reveals a metabolite signature shared with lysosomal storage disorders.
Nanoscale biointerfaces in inter-organelle communication: membrane contact sites, organelle trafficking, and cell fate control.
Molecular Mechanisms of Neurodegenerative Diseases: Emerging Biomarkers and Therapeutic Targets.
Human-specific SRGAP2 paralogs synchronize neotenic microglial maturation and synaptic development.
Rabs in the driving seat: Coordinating vesicular traffic and membrane contact site dynamics.
A systems-level proteomic analysis identifies kinesin targets of KIFBP during neuronal development.
Impaired Motor Function in a Zebrafish Stathmin-2 Knockout Model.
Microtubule-Associated Proteins: From Dynamic Regulation of Microtubules to Cellular Architecture.
Mitophagy in neurodegeneration: crosstalk between PRKN/parkin-dependent and PRKN-independent pathways.
Single-neuron resolution mapping of dopaminergic connectivity across development, adulthood, and degeneration.
Single-cell transcriptomic atlas of frontoinsular cortex reveals molecular correlates of selective neuronal vulnerability in FTD.
Protocol for induction and quantification of injury-primed axon outgrowth in adult mouse DRG neurons.
HDDF2-A Novel Patient-Derived Fibroblast Line from Huntington's Disease with Prominent Cellular Senescence and polyQ Pathology.
Actin Quantification Using the Filamentous Actin Segmentation Tool (FAST).
Spatiotemporal control of Atg2 association with the ER during autophagosome formation.

J Cell Sci. 2026 Jul 15. pii: jcs265083. [Epub ahead of print]139(14):

The LRRK2 G2019S variant rewires Rab GTPase phosphorylation after lysosomal damage and promotes cell death in human macrophages.

Rebecca Morrison, Simeon R Mihaylov, Chak Hon Luk, Cyril Lemerle, Angela Rodgers, Natalia Athanasiadi, Huw R Morris, Enrica Pellegrino, Sila K Ultanir, Maximiliano G Gutierrez.

  Variants in leucine-rich repeat kinase 2 (LRRK2) are the most common genetic cause of Parkinson's disease, yet how these variants alter immune cell function remains unclear. Because LRRK2 is activated by lysosomal damage in macrophages, we investigated how the pathogenic G2019S variant affects macrophage responses to lysosomal damage. Here, we show that LRRK2 G2019S has an effect during lysosomal damage through kinase-dependent and kinase-independent mechanisms. Phosphoproteomic analysis revealed that lysosomal damage induces selective rewiring of LRRK2-dependent Rab GTPase phosphorylation, characterised by increased Rab12 phosphorylation and reduced Rab35 phosphorylation without global kinase hyperactivation. Strikingly, LRRK2 G2019S macrophages showed increased susceptibility to apoptosis following lysosomal damage. This increase in cell death occurred independently of the kinase activity, indicating a distinct kinase-independent role of LRRK2 in regulating cell survival. We generated isogenic induced pluripotent stem cells from patients carrying the LRRK2 G2019S variant and confirmed that LRRK2 G2019S macrophages are more susceptible to cell death in a kinase-independent manner. Together, our findings support a model in which the LRRK2 G2019S variant selectively changes the phosphorylation of Rab GTPases in macrophages and increases cell death after lysosomal damage in macrophages.

Keywords:  Apoptosis; LRRK2; Lysosomal damage; Macrophage; Parkinson's disease; Rab GTPase

DOI:  https://doi.org/10.1242/jcs.265083
bioRxiv. 2026 Jul 24. pii: 2026.07.22.740140. [Epub ahead of print]

KIF1A-mediated trafficking is required for neuronal autophagy in human neurons.

Carris Borland, Jacob Popolow, Erika L F Holzbaur.

Mutations in the molecular motor protein KIF1A result in a spectrum of neurodevelopmental and neurodegenerative disorders termed KIF1A-Associated Neurological Disorder (KAND). KIF1A mutations variably disrupt synaptic vesicle trafficking, but the effects of KIF1A mutations on other trafficking pathways remain unexplored. Autophagy is a conserved pathway required for neuronal homeostasis. We investigated the role of KIF1A in autophagy using gene-edited human IPSC-derived neurons. KIF1A loss inhibited the trafficking of ATG9, a transmembrane lipid scramblase necessary for autophagosome biogenesis. This deficit significantly reduced autophagosome biogenesis and the density of axonal autophagosomes. KIF1A loss also depleted lysosomes from the axon, inhibiting autophagosome maturation. In neurons gene-edited to heterozygously express a pathogenic variant linked to a Rett-like syndrome in KAND patients, we also noted significant deficits in autophagy and lysosomal trafficking. Together, these results suggest that KIF1A-mediated transport is critical to neuronal autophagy and that deficits in autophagy may contribute to pathogenesis in KAND.
GRAPHICAL ABSTRACT:

DOI: https://doi.org/10.64898/2026.07.22.740140
Netw Neurosci. 2026 ;10(3): 594-612

Microscale dysfunction and mesoscale compensation in degenerating neuronal networks.

Vegard Fiskum, Nicolai Winter-Hjelm, Nicholas Christiansen, Axel Sandvig, Ioanna Sandvig.

  Progressive neurodegenerative diseases involve neuronal dysfunction across cellular, circuit, and whole-brain levels. Despite differences in anatomical origins, vulnerable neuronal subtypes, and specific misfolded proteins, these diseases share key features. In presymptomatic phases, neural networks engage compensatory processes to maintain function, including increased centralization and reliance on a rich-club of hub nodes. While such mechanisms have supporting evidence in some disorders, they remain less established in amyotrophic lateral sclerosis (ALS), limiting understanding of potential shared presymptomatic responses. To address this, we investigated structural and functional properties of ALS patient-derived motor neuron networks compared with healthy controls using longitudinal multielectrode array recordings and graph theory-based analysis. We observed microscale dysfunction marked by TAR DNA-binding protein 43 proteinopathy, hyperactivity, and reduced spike amplitude. Structurally, ALS networks exhibited neurite hypertrophy, suggesting attempts to form new connections. Mesoscale analyses revealed functional reconfigurations, including increased rich-club connectivity and network assortativity, indicating compensatory centralization. Our findings provide novel evidence that ALS network features can be recapitulated in in vitro models, and that these networks progressively become more centralized to preserve computational capacity, imposing growing demands on hub nodes and predisposing them to further damage. These results support models proposing common network reconfiguration mechanisms across neurodegenerative diseases.

Keywords:  ALS; Functional connectivity; Graph theory; Hyperexcitability; Multielectrode array; Rich club

DOI:  https://doi.org/10.1162/NETN.a.552
Sci Adv. 2026 Jul 31. 12(31): eaeg1445

Scalable human neuronal models of tauopathy producing endogenous seed-competent 4R tau.

Eliona Tsefou, Sumi Bez, Timothy J Y Birkle, Martha Foiani, Naoto Watamura, Mathieu Bourdenx, Daria Gavriouchkina, Emir Turkes, Samuel Crawford, Rachel Coneys, Adrian M Isaacs, Karen E Duff.

The accumulation of pathological four-repeat (4R) tau is central to several frontotemporal dementia (FTD) subtypes, but human neuronal models amenable to high-throughput screening of 4R tau-targeting therapies remain very limited. To address this, we developed induced pluripotent stem cell (iPSC)-derived i3Neuron (i3N) lines expressing >75% 4R tau, driven by FTD splice-shifting mutations (Ser305Asn; S305N or S305N/IVS10 + 3). These neurons develop hyperphosphorylated tau and demonstrate somatodendritic mislocalization. These i3N neurons develop endogenous seed-competent tau and present pentameric formyl thiophene acetic acid-(pFTAA)-positive tau assemblies after 28 days in culture. For scalable screening, we CRISPR-engineered an HiBiT luminescence tag at the endogenous MAPT locus into the S305N/IVS10 + 3 iPSC line, enabling precise quantification of tau levels and pharmacological responses. The model responded predictably to compounds affecting tau clearance, demonstrating its suitability for drug discovery. Overall, this i3N platform recapitulates key features of 4R tauopathy and provides a robust system to identify therapeutic modulators of pathological tau.

DOI: https://doi.org/10.1126/sciadv.aeg1445
bioRxiv. 2026 Jul 13. pii: 2026.07.09.737468. [Epub ahead of print]

Myosin 5A mediates membrane-associated periodic skeleton reassembly during axon regeneration in response to ROCK-2 inhibition.

Atrayee Basu, Elisa M Howard, Tanina Arab, Nabab Khan, Jean Kanyo, TuKiet Lam, Stephen M Strittmatter.

  The membrane-associated periodic skeleton (MPS) is a submembrane lattice composed of actin rings and spectrin tetramers that repeats every 190 nm along axons and maintains mechanical stability. Loss of the MPS precedes axon fragmentation during degeneration, but during axon regrowth after injury the extent and timing of MPS reformation are not clear. We used stimulated emission depletion (STED) microscopy to track βII-spectrin periodicity in regenerating axons from mouse cortical neurons, human iPSC-derived cortical neurons, and human iPSC-derived motor neurons following mechanical axotomy. Regrowing axons initially lack periodic βII-spectrin organization, particularly near the growth cone. Over 8 to 15 days, periodicity is partially restored in intermediate axonal regions, while distal segments remain disorganized. We found that reducing Rho kinase ROCK-2 activity either pharmacologically or by CRISPRi promotes axon regrowth and accelerates MPS recovery rate five-fold, reaching near-normal levels by 3 days post-injury. To identify the key effectors, we performed co-immunoprecipitation mass spectrometry of the βII-spectrin complex under injury and ROCK-2-inhibited conditions. Myosin 5A (MYO5A) association with spectrin rose sharply upon injury and further increased when ROCK-2 was absent. Functional experiments positioned MYO5A downstream of ROCK-2. Knocking down MYO5A abolished the enhanced regrowth of ROCK-2-deficient neurons, while overexpressing MYO5A increased regrowth in wild-type neurons. Depleting MYO5A also partially disrupted βII-spectrin periodicity in healthy, uninjured axons, indicating a requirement for MYO5A in MPS maintenance under physiological conditions. STED imaging demonstrated that ROCK-2 is arranged periodically along the axon at 190 nm intervals, suggesting it regulates the local lattice. These findings define a ROCK-2/MYO5A pathway linking a targetable kinase to nanoscale cytoskeletal repair and axon regeneration.

Keywords:  Axon regeneration; MPS; MYO5A; ROCK-2; STED-imaging; βII-Spectrin

DOI:  https://doi.org/10.64898/2026.07.09.737468
bioRxiv. 2026 Jul 21. pii: 2026.07.16.739042. [Epub ahead of print]

Altered neuronal start codon stringency favors cap-independent repeat-associated non-AUG translation.

Clare M Wieland, Shannon E Wright, Sydney Willey, Ishita Purwar, Samantha J Grudzien, Amy Krans, Erinn Laimon, Melissa J Asher, Adrian Isaacs, Amanda L Garner, Peter K Todd.

Intronic GGGGCC repeat expansions in C9orf72 cause amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). This expansion supports a non-canonical form of translational initiation known as repeat-associated non-AUG (RAN) translation to produce toxic dipeptide repeat proteins that contribute to neurodegeneration. Here, we find that the efficiency of RAN translation and its dependency on the 5' 7-methylguanosine mRNA cap are variable across cell types, with both rodent neurons and human iNeurons favoring cap-independent RAN translation from two distinct repeats (CGG and GGGGCC) across multiple reading frames. Treatment with an eIF4E inhibitor that blocks global cap-dependent translation enhances RAN translation specifically in neurons. Intriguingly, cap-independent RAN translation exhibits less reliance on near-cognate codons for initiation than cap-dependent RAN translation. This finding led us to identify a surprising global increase in start codon stringency in neurons as a contributor to the relatively higher cap-independent RAN translation in this cell type. This effect correlates with a cytoplasmic redistribution of eIF1 in neurons and is reversed with neuronal overexpression of the eukaryotic initiation factor eIF5, which relaxes start codon stringency and selectively enhances cap-dependent RAN translation. Taken together, these findings reveal several neuron-specific features of translational regulation that favor cap-independent RAN translation with implications for nucleotide repeat expansion disorder pathogenesis and neuronal translational regulation.
GRAPHICAL ABSTRACT:

DOI: https://doi.org/10.64898/2026.07.16.739042
Drug Discov Today. 2026 Jul 29. pii: S1359-6446(26)00157-1. [Epub ahead of print] 104752

Targeting TDP-43 in ALS: Regulatory hurdles, trial design deficiencies, and the causal evidence gap for CTx1000.

Michael A S Guth.

  The therapeutic landscape for amyotrophic lateral sclerosis (ALS) has been characterized by decades of clinical trial failures, often attributed to biological heterogeneity, end-point insensitivity, and a profound evidence gap regarding target engagement. With TAR DNA-binding protein 43 (TDP-43) aggregation emerging as a hallmark feature in the vast majority of ALS cases, new precision-medicine modalities - most notably the proteolysis-targeting chimera (PROTAC) CTx1000 - aim to address the underlying causal pathology through selective degradation of mislocalized TDP-43. This review critically evaluates the regulatory hurdles and trial design deficiencies that have historically undermined ALS clinical development, and incorporates the dual sequestration hypothesis as a framework to interpret the convergence of TDP-43 pathology across neurodegenerative diseases. It concludes that it is imperative that the field adopts more rigorous biomarker-led methodologies, and that although target-specific degraders offer a sophisticated technological leap, their success depends on addressing fundamental knowledge gaps in target engagement, age-dependent vector tropism, and trial design architecture.

Keywords:  14-3-3 protein; AAV9 (adeno-associated virus serotype 9); TDP-43; amyotrophic lateral sclerosis (ALS); biomarker; clinical trial design; gene therapy

DOI:  https://doi.org/10.1016/j.drudis.2026.104752
Int J Mol Sci. 2026 Jul 14. pii: 6244. [Epub ahead of print]27(14):

LINE-1 Retrotransposons and Amyotrophic Lateral Sclerosis.

Tinkara Korošec, Boris Rogelj, Vera Župunski.

  Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by the progressive degeneration of upper and lower motor neurons. While monogenic causes account for a minority of cases, in most cases, ALS is sporadic and likely arises from multilayer interactions of genetic architecture, aging-associated loss of genome regulation, and inflammatory stress. Long interspersed nuclear element-1 (LINE-1) retrotransposons are endogenous mobile elements that are tightly controlled through various cellular mechanisms under normal conditions. When abnormally active, they are involved in gene inactivation, expression regulation, and genomic instability, leading to cellular processes such as innate immunity and cell death. Here, we present mechanistic links between LINE-1 and ALS. These include evidence that the burden of retrotransposition-competent LINE-1s (RC-L1s) is increased in ALS genomes, positioning RC-L1 load as a candidate contributor to missing heritability in sporadic disease. We also integrate emerging data showing that LINE-1 RNA can be intrinsically toxic independently of new insertions, as it promotes chromatin opening and transcriptional epigenetic noise, particularly when nuclear RNA surveillance pathways fail in TDP-43 pathology. Finally, we review how LINE-1-derived DNA/RNA intermediates can engage innate immune sensors, highlighting the cGAS-STING axis as a plausible route from LINE-1 de-repression to neuroinflammation. Together, these concepts support a model in which genetic RC-L1 load and age-/pathology-driven LINE-1 de-repression converge on nuclear dysfunction and inflammatory amplification, suggesting concrete molecular nodes for therapeutic intervention.

Keywords:  LINE-1; TDP-43; amyotrophic lateral sclerosis; cGAS–STING; epigenetic dysregulation; neuroinflammation; retrotransposons

DOI:  https://doi.org/10.3390/ijms27146244
Science. 2026 Jul 30. 393(6810): 461

Signatures of aging and disease in a single organelle.

Jeeyoon Na, Anne Brunet.

Changes in lysosomal metabolites are associated with both aging organs and lysosomal storage diseases.

DOI: https://doi.org/10.1126/science.aej5901
Adv Sci (Weinh). 2026 Jul 28. e76625

A Phosphorylation-Induced Micellization Switch in the Low-Complexity Domain of TDP-43.

Rodrigo F Dillenburg, Anastasia Lopatina, Hao Ruan, Tom Scheidt, Simone Mosna, Emre Pekbilir, Julia Bieber, Frank Schäfer-Depoix, Katharina Landfester, Carla Schmidt, Martin M Möckel, Svenja Morsbach, Friederike Schmid, Dorothee Dormann, Lukas Stelzl, Martin Girard, Edward A Lemke.

  Phase separation (PS) of the low-complexity domain (LCD) of TAR DNA-binding protein 43 kDa (TDP-43) is linked to pathogenic aggregates in amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD-TDP). Here, we show that extensive phosphorylation of the LCD C-terminus redirects its self-assembly. Coarse-grained Monte Carlo simulations predicted that 12 Ser phosphorylations partition the 148-residue LCD into a hydrophobic N-terminal and highly charged C-terminal block, favouring finite-sized micellization over macroscopic PS. In vitro, LCD phosphorylated by casein kinase 1 delta (CK1δ; mean of 12 phosphorylations by native mass spectrometry) and phosphomimetic 12D/12DD mutants formed spherical nanoparticles (≈ 20-50 nm) above a low-micromolar critical micelle concentration, whereas the unphosphorylated LCD underwent reversible PS that matured into fibrils. Increasing ionic strength shifted the mutants toward anisotropic morphologies (wormlike 12D micelles and rigid 12DD nanocylinders). Turbidity assays and confocal imaging directly visualized the absence of PS in the phosphorylated form. Negative-stain and cryo-electron microscopy (cryo-EM) confirmed the spherical micellar architecture for the phosphorylated LCD and 12D/12DD mimics. Our data identify phosphorylation as a molecular switch tuning macrophase separation and fibril formation of TDP-43 LCD, providing a framework for an aggregation-protective role through microphase separation into size-limited micelles. Whether these assemblies are stable or kinetically trapped on pathological timescales remains unclear.

Keywords:  TDP‐43; intrinsically disordered proteins; low‐complexity domain; micellization; micro phase separation; protein phosphorylation; wormlike micelles

DOI:  https://doi.org/10.1002/advs.76625
Elife. 2026 Jul 27. pii: RP111075. [Epub ahead of print]15

In-cell cryo-electron tomography reveals differential effects of type I and type II kinase inhibitors on LRRK2 filament formation and microtubule association.

Tamar Basiashvili, Joshua Hutchings, Siyu Chen, Eva P Karasmanis, William Alexander Flaherty, Andres E Leschziner, Elizabeth Villa.

  Mutations in leucine-rich repeat kinase 2 (LRRK2) are a leading contributor to developing familial and idiopathic Parkinson's disease (PD). Most PD-causing LRRK2 mutations increase the kinase activity, leading to increased phosphorylation of Rab GTPases, disrupting vesicular trafficking, cytoskeletal dynamics, and autophagy. Under homeostatic conditions, the bulk of WT and PD-mutant LRRK2 is found in the cellular cytosol. However, exogenously expressed LRRK2 can form microtubule-associated filaments that have been shown to affect molecular transport along microtubules in vitro. While the physiological relevance of microtubule binding has not been established yet, inhibitors being designed and tested as therapeutics have been shown to either promote or prevent filament formation of LRRK2. In this study, we examine the localization and resulting molecular organization of hyperactive LRRK2-I2020T, a common PD mutant, in HEK 293FT cells treated with type I (MLi-2) or type II (GZD-824) kinase inhibitors. Treatment with a type I kinase inhibitor results in extensive LRRK2-I2020T decoration around microtubules and microtubule bundling. Stabilization of LRRK2-I2020T filaments by type I inhibitor treatment allowed us to build a full-length closed-kinase model of LRRK2-I2020T in its cellular environment. Conversely, treatment with a type II inhibitor resulted in minimal microtubule decoration by LRRK2-I2020T compared to type I inhibitor-treated cells. This study provides a structural framework for understanding how type I and type II kinase inhibitors differentially modulate LRRK2 filament formation, demonstrating that type I inhibitor treatment promotes a distinct filament architecture, whereas such assemblies are not observed with type II inhibitors.

Keywords:  LRRK2; Parkinson's disease; cryo-ET; human; molecular biophysics; structural biology

DOI:  https://doi.org/10.7554/eLife.111075
bioRxiv. 2026 Jul 24. pii: 2026.07.22.740182. [Epub ahead of print]

Microglia extract neuronal proteolytic organelles via skoupocytosis.

Renee Pepper, Jacqueline M Griswold, Frances Middleton-Davis, Sarah Syed, Yuuta Imoto, Lani Tran, Eunbin Park, Yu Kang T Xu, Dwight Bergles, JoAnn Buchanan, Shigeki Watanabe.

Neurons face unique challenges in maintaining protein homeostasis due to their tortuous morphology and extended processes. Proteolytic organelles are typically transported retrogradely towards their soma for degradation where lysosomes are enriched, but some organelles are larger than these neuronal processes, questioning how these organelles are degraded. Here we show that microglia, the resident immune cells of the brain, extract proteolytic organelles from neurons both in vitro and in vivo . Microglia make transient contact with neuronal membranes where proteolytic organelles are stationed beneath. At these sites of interaction, microglia pinch off a small portion of the neuronal process containing the organelle, leaving the rest of the process intact. We term this process 'skoupocytosis' after the Greek word for garbage. Phosphatidylserine (PS) lipase ABHD16a accumulates near these proteolytic organelles and converts PS into lyso-PS to initiate microglial skoupocytosis. Skoupocytosis bypasses the need for retrograde organelle transport, providing homeostatic advantages for neurons that must maintain function in processes that extend extraordinarily long distances from the cell soma.

DOI: https://doi.org/10.64898/2026.07.22.740182
Biochim Biophys Acta Mol Cell Res. 2026 Jul 29. pii: S0167-4889(26)00098-4. [Epub ahead of print] 120199

Kinesin-3 and the cargo adaptor Hook1 regulate early endosome and peroxisome motility and are required for mitochondrial and endoplasmic reticulum spatial organization during polarized fungal cell growth in Podospora anserina.

Fernando Hernández-Sánchez, Yovanna A Pardo-Fermín, Sara Schroder, Fernanda Frutis-Osorio, Sylvain Brun, Leonardo Peraza-Reyes.

  Microtubule-based organelle transport is essential for organelle positioning within cells and defines the architecture and function of highly polarized cells, like animal neurons and fungal hyphae. Early endosome transport depends on kinesin-3 motors and on cytoplasmic dynein, which binds to this organelle via Hook adaptor proteins. In filamentous fungi, these proteins can propel the indirect transport of additional organelles that hitchhike on early endosomes, like peroxisomes. However, early endosomes carry different cargoes in different fungi, and the contribution of these systems to the subcellular organization of different polarized cells is unclear. Here, we analyzed the function of the kinesin-3 motor KIN2 and of the HOOK1 adaptor in the model fungus Podospora anserina. We found that hyphal growth and morphogenesis require KIN2 and HOOK1, and that early endosome, peroxisome, vacuole, endoplasmic reticulum and mitochondrial motility depends on microtubules. We show that KIN2 and HOOK1 are required for mitochondrial localization at the sites of polarized cell growth, and for the polarized arrangement of the endoplasmic reticulum and vacuoles. Both proteins are required for the bidirectional transport of early endosomes and peroxisomes, but they differently affect their distribution. We found that KIN2 associates with some peroxisomes, and observed a low frequency of peroxisome-early endosome co-transport. Finally, we show that the GTPase RAB5B is required for the distribution and motility of early endosomes but not of peroxisomes, suggesting independent transport systems for these organelles in P. anserina. Our findings reveal a major role for KIN2 and HOOK1 in organelle dynamics during polarized cell growth.

Keywords:  Motor protein; cargo adaptor; endoplasmic reticulum; endosome; kinesin; mitochondria; peroxisome; vacuole

DOI:  https://doi.org/10.1016/j.bbamcr.2026.120199
Adv Sci (Weinh). 2026 Jul 30. e76972

ATL2 Recruits TRAK1 to Promote Mitochondrial Transport at ER-Mitochondria Contact Sites.

Yiru Cheng, Peiyuan Chai, Xiayuhe Pei, Yiwen Chen, Xiaoshuai Huang, Bei Liu, Yiqian Wu, Junlin Teng, Pengli Zheng, Jianguo Chen.

  Mitochondrial transport and distribution are crucial for cellular homeostasis, yet whether and how they are regulated by endoplasmic reticulum (ER)-mitochondria contact sites remains unclear. Here, we demonstrate that the ER protein atlastin-2 (ATL2) orchestrates mitochondrial transport and distribution by promoting assembly of the transport machinery at ER-mitochondria contact sites. Mechanistically, ATL2 recruits the adaptor trafficking kinesin-binding protein 1 (TRAK1) to the ER membrane, strengthening the interaction of TRAK1 with the mitochondrial transport adaptor MIRO1 to promote anterograde mitochondrial transport. Loss of ATL2 disrupts this process, leading to perinuclear mitochondrial clustering. We further find that ATL2 stabilizes ER-mitochondria contact sites by interacting with MFN2, providing a platform for mitochondrial transport complex assembly. Moreover, in hypoxia, ATL2 is ubiquitinated at lysine 567 by the E3 ligase SYVN1, leading to its degradation and a resulting defect in mitochondrial distribution. Our findings elucidate a novel ER-mediated mechanism for mitochondrial transport.

Keywords:  ATL2; ER–mitochondria contact sites; TRAK1; hypoxia; mitochondrial transport

DOI:  https://doi.org/10.1002/advs.76972
Neurobiol Dis. 2026 Jul 27. pii: S0969-9961(26)00294-9. [Epub ahead of print]228 107549

Context-dependent YEATS-domain inhibition enhances neuronal resilience and improves ALS phenotypes.

Luca Lo Piccolo, Chansunee Panto, Ranchana Yeewa, Ruedeemars Yubolphan, Puttachat Poound, Saranyapin Potikanond, Salinee Jantrapirom.

  Neuronal loss in neurodegenerative disease is driven in part by maladaptive stress signaling and impaired adaptation to proteotoxic challenges. ENL and AF9 are YEATS-domain acyl-lysine reader proteins best characterized in leukemia, but their functions in neurons remains unclear. Here, we defined the role of the ENL/AF9 YEATS domain using complementary chemical and genetic perturbations. We applied the selective YEATS inhibitor SR-0813 in differentiated human neurons and modulated ENL/AF9 activity in Drosophila using either SR-0813 or ENL/AF9 knockdown. In flies, SR-0813 phenocopied ENL/AF9 knockdown by extending lifespan and enhancing stress tolerance. To test disease-context specificity, we performed a Drosophila genetic modifier screen across neurodegeneration models. ENL/AF9 reduction was beneficial in UBQLN2P497H and SOD1G94A but showed reduced efficacy or became detrimental in chronic aggregation or mitochondrial stress models such as (GGGGCC)49 and polyQ disease. In human neurons, SR-0813 improved survival across multiple stress conditions, with the strongest protection during endoplasmic reticulum stress. Mechanistically, ENL/AF9 YEATS inhibition dampened PERK-dependent integrated stress response signaling and reduced apoptotic commitment without broadly enhancing proteostasis capacity. Together, these findings identified ENL/AF9 as modulators of neuronal stress-response dynamics and established ENL/AF9 YEATS-domain inhibition as a context-dependent strategy to enhance neuronal resilience with relevance to ALS and related proteotoxic disorders.

Keywords:  Amyotrophic lateral sclerosis; Chemical probe; Chromatin reader; ENL/AF9; Integrated stress response

DOI:  https://doi.org/10.1016/j.nbd.2026.107549
Nat Biomed Eng. 2026 Jul 29.

In vivo CRISPR base editing for treatment of Huntington's disease.

Shraddha Shirguppe, Michael Gapinske, Devyani Swami, Kyrollos Shenouda, Angelo Miskalis, Nicholas Gosstola, Daniela Del Bosque Siller, Isabelle Guerra, Pankaj Acharya, Dana Joulani, Maddie G Szkwarek, Ananthan Nambiar, Abhishek Bhattacharjee, Anagha S Dangi, Norah Odle, Gabrielle E Nathan, Gianna Elias, Michelle Stilger, Jackson Winter, Wendy S Woods, Daphine Anand, Colin K W Lim, Sergei Maslov, Thomas Gaj, Pablo Perez-Pinera.

Huntington's disease (HD) is a fatal neurodegenerative disorder caused by an expanded CAG repeat within exon 1 of the huntingtin (HTT) gene, resulting in a mutant protein that drives neuronal dysfunction and loss. A key event in the pathogenesis of HD is proteolytic cleavage of mutant HTT, which generates aggregation-prone N-terminal fragments that contribute to toxicity. Strategies that prevent this process thus hold therapeutic potential. Here we develop CRISPR base editors that generate proteolysis-resistant HTT isoforms by disrupting the splice acceptor of HTT exon 13, an exon that encodes critical proteolytic cleavage sites implicated in N-terminal fragment production. When delivered to the striatum of an HD rodent model, these editors reduced HTT fragment formation, decreased aggregation, improved functional deficits and attenuated brain atrophy. Collectively, these results demonstrate the potential of base editing and splice-site modulation to mitigate mutant HTT toxicity in HD.

DOI: https://doi.org/10.1038/s41551-026-01747-y
Science. 2026 Jul 30. 393(6810): eady0832

Atlas of lysosomal aging reveals a metabolite signature shared with lysosomal storage disorders.

Anna M Puszynska, Thao P Nguyen, Andrew L Cangelosi, Andrea Armani, Justin M Roberts, Kristin A Singh, James C Cameron, Tenzin Tseyang, Grace Y Liu, Steven Lai, Hans-Georg Sprenger, Jason Yang, William N Colgan, Jibril F Kedir, Kathrin M Kajderowicz, Theodore K Esantsi, Yuancheng Ryan Lu, Millenia Waite, Tenzin Kunchok, Caroline A Lewis, Fabian Schulte, George W Bell, David M Sabatini, Jonathan S Weissman.

Lysosomal dysfunction is a well-recognized feature of aging. Here, we used a suite of tools for rapid lysosomal isolation to construct a multitissue atlas of the metabolite changes lysosomes undergo during aging. Aged lysosomes in brain, heart, muscle, and white adipose tissue accumulated glycerophosphodiesters and cystine, metabolites that are causally linked to juvenile lysosomal storage disorders, Batten disease, and cystinosis. Levels of these metabolites increased linearly with age, preceding organismal decline. Caloric restriction, a lifespan-extending intervention, mitigated these changes in the heart and muscle but not the brain. Our findings link lysosomal storage disorders to aging-related dysfunction and open avenues for the mechanistic investigation of how lysosomal functions deteriorate during aging and in age-associated diseases.

DOI: https://doi.org/10.1126/science.ady0832
Front Cell Dev Biol. 2026 ;14 1901757

Nanoscale biointerfaces in inter-organelle communication: membrane contact sites, organelle trafficking, and cell fate control.

Mohamed R Abdel-Hamed, Sameh Saber, Elsayed A Elmorsy, Basem H Elesawy, Maha M Amer, Abdel-Moneim Hafez Abdel-Moneim, Alaa El-Din L Firgany, Enas A Mohamed, Huda Eltayeb, Ageeb M Hassan, Mohamed El-Sayed, Ahmed Y Kira.

  Cellular and tissue organization depends on the spatial arrangement, ultrastructure, and functional coupling of organelles. This review reframes intracellular nanomaterials as nanoscale tools for interrogating and modulating membrane contact sites (MCSs), rather than simply as delivery systems. We focus on mitochondria, the endoplasmic reticulum, lysosomes, endosomes, and the nucleus because these compartments form dynamic contact networks that regulate metabolism, calcium and redox signaling, membrane trafficking, autophagy, mitophagy, chromatin organization, stress adaptation, and cell fate. Emphasis is placed on morphological and ultrastructural readouts, including mitochondrial cristae organization, fission-fusion balance, membrane-potential-dependent localization, endosomal and lysosomal trafficking, ER-mitochondria and lysosome-mitochondria communication, nuclear-pore access, chromatin organization, and inter-organelle contact-site remodeling. We discuss how particle size, surface charge, geometry, ligand presentation, and stimulus-responsive behavior influence cellular uptake, endosomal escape, organelle localization, and structural consequences within cells and tissues. A central distinction is made between intentional organelle nano-regulation, in which engineered systems are designed to engage defined subcellular mechanisms and organelle interfaces, and incidental stress responses, in which altered morphology or gene expression reflects oxidative, lysosomal, mitochondrial, inflammatory, or genotoxic injury. By organizing current evidence around MCS biology, subcellular compartmentalization, membrane trafficking, organelle dynamics, and tissue-relevant cell fate decisions, this review provides a morphology-centered framework for evaluating intracellular nanomaterials in health, disease, stem-cell biology, and regenerative bioengineering.

Keywords:  ER–mitochondria crosstalk; cell fate regulation; endolysosomal trafficking; inter-organelle communication; membrane contact sites; organelle-targeted nanomaterials

DOI:  https://doi.org/10.3389/fcell.2026.1901757
Brain Sci. 2026 Jun 27. pii: 675. [Epub ahead of print]16(7):

Molecular Mechanisms of Neurodegenerative Diseases: Emerging Biomarkers and Therapeutic Targets.

Sunanda Yogi, Amit Singh.

  Neurodegenerative diseases (NDs), such as Alzheimer's disease (AD), Parkinson's disease (PD), Amyotrophic lateral sclerosis (ALS), and Huntington's disease (HD), involve the gradual loss of structure or function of neurons in the nervous system and are an increasing threat to the aging population worldwide. Although these disorders have different clinical features which affect cognition, movement and other vital body functions, they share key underlying molecular and cellular processes. This starts with protein misfolding and aggregation, mitochondrial dysfunction, oxidative stress, dysregulated protein homeostasis, neuroinflammation, and disrupted cell death pathways. Recent findings have added disease-specific processes, like amyloid-β and tau aggregates in AD, α-synuclein aggregation and mitophagy failure in PD's, TDP-43-related impaired RNA metabolism in ALS, and mutant huntingtin causing transcription aberrations in HD. Protein interactome network analysis showed mechanistic crosstalk between pathogenic proteins of AD and PD. New evidence highlights how lysosomal dysfunction, endoplasmic reticulum stress, and microglial activation, act as a common axis in neurodegeneration. Advancements in genomics and epigenomics have found shared genetic risk loci and regulatory processes that affect how diseases develop and progress. Simultaneously, new biomarkers like circulating microRNAs, exosome-related pathological proteins, neurofilament light chain, inflammatory cytokines, and microglial activation markers are powering early diagnosis tools and disease variations. New imaging techniques also allow for the identification of protein aggregations before symptoms appear. Overall, these findings are accelerating targeted treatments and personalized medicine aimed at disease progression. This review highlights current insights into the molecular mechanisms of NDs and discusses new biomarkers and treatment targets that help future diagnostic and treatment strategies.

Keywords:  Alzheimer’s disease; Huntington disease; Parkinson disease; amyotrophic lateral sclerosis; biomarkers; molecular mechanism; neurodegenerative disease; therapeutic targets

DOI:  https://doi.org/10.3390/brainsci16070675
Neuron. 2026 Jul 22. pii: S0896-6273(26)00536-2. [Epub ahead of print]

Human-specific SRGAP2 paralogs synchronize neotenic microglial maturation and synaptic development.

Carlos Diaz-Salazar, JaeYeon Kim, Marine Krzisch, Juyoun Yoo, Patricia R Nano, Aparna Bhaduri, Rudolf Jaenisch, Mercedes Paredes, Franck Polleux.

  The human brain is distinguished by unusually prolonged developmental timing, yet the genetic mechanisms coordinating this neoteny across cell types remain incompletely understood. Here, we show that human cortical microglia undergo neotenic structural and transcriptional maturation relative to mouse microglia. We identify SRGAP2B/C, human-specific paralogs of the ancestral SRGAP2A, as the only human-specific gene duplications expressed in human microglia. Using xenotransplantation of human induced pluripotent stem cell (hiPSC)-derived microglia and mouse genetic models, we demonstrate that human-specific SRGAP2B/C, previously shown to reduce SRGAP2A protein abundance, are both necessary and sufficient to induce neotenic structural microglial maturation. Our results reveal that neotenic microglial maturation modifies the timing of synaptic development, linking microglial developmental programs to the timing of circuit formation. Together with previous evidence for neuronal SRGAP2A function, our results suggest that the human-specific SRGAP2B/C paralogs coordinated the emergence of neotenic synaptic development by acting in both neurons and microglia during human brain evolution.

Keywords:  brain; evolution; human; human-specific gene duplication; microglia; mouse; neoteny; neurons; synapses; xenotransplantation

DOI:  https://doi.org/10.1016/j.neuron.2026.07.007
Curr Opin Cell Biol. 2026 Jul 30. pii: S0955-0674(26)00065-7. [Epub ahead of print]102 102677

Rabs in the driving seat: Coordinating vesicular traffic and membrane contact site dynamics.

Yogita Phogat, Sankalita Paul, Mahak Sharma.

Rab GTPases are central regulators of intracellular membrane organization, ensuring the specificity and directionality of vesicular transport. Operating as 'molecular switches,' Rab GTPases cycle between an active GTP-bound and an inactive GDP-bound state, a process regulated by GEFs (guanine nucleotide exchange factors) and GAPs (GTPase-activating proteins). The dynamic switch-like behaviour and compartment-specific localization of Rab GTPases establish membrane identity and generate discrete membrane subdomains, providing spatiotemporal control over intracellular trafficking events. Rab GTPases also facilitate compartment maturation through coordinated Rab conversion, leading to transitions between different membrane identities. Membrane-localized Rab GTPases function as a recruitment platform for a cohort of effector proteins, which regulate the sequential steps of vesicular transport. The features discussed above also enable Rabs to participate in the formation of membrane contact sites, which facilitate direct transport of phospholipids and small molecules between compartments and regulate organelle motility and positioning. Here we review current insights into the mechanisms governing Rab GTPase regulation, including post translational modifications and interactions with effectors. We also discuss their roles in membrane domain formation, compartment maturation via Rab cascades, and non-vesicular communication pathways. These findings enhance our understanding of the multifaceted functions of Rab GTPases in compartmentalization and highlight emerging areas for future investigation.

DOI: https://doi.org/10.1016/j.ceb.2026.102677
bioRxiv. 2026 Jul 20. pii: 2026.07.17.739260. [Epub ahead of print]

A systems-level proteomic analysis identifies kinesin targets of KIFBP during neuronal development.

Sarah-Catherine Paschall, Teresa Lynne Blasius, Alex Missman, Princess Rodriguez, Michael A Cianfrocco, Kristen J Verhey, Jason Stumpff.

Kinesins are molecular motor proteins essential for organizing and remodeling the cytoskeleton during neuronal development and maintenance. One key regulator is kinesin family binding protein (KIFBP), which inhibits a subset of kinesins by blocking motor-microtubule interactions. Homozygous mutations in KIFBP cause Goldberg-Shprintzen Syndrome (GOSHS), a neurodevelopmental disorder characterized by intellectual disability, microcephaly, and axonal neuropathy. Although loss of KIFBP has been linked to reduced neurite length and microtubule disorganization, the specific kinesins underlying these phenotypes remain unclear. Here we use a CRISPR-Cas9 generated KIFBP knockout Neuro-2a cell line to demonstrate that KIFBP is required for neurite extension and use inducible GFP-KIFBP to define the KIFBP interactome during neuronal differentiation. Immunoprecipitation coupled with mass spectrometry identified both known and novel KIFBP-associated kinesins. Single molecule TIRF microscopy confirmed direct inhibition of a subset of kinesins that co-immunoprecipitated with KIFBP. Notably, we identified KIF5A and KIF18B as previously unrecognized regulatory targets with potential roles in neuronal development. Together, these findings establish Neuro-2a cells as a model for studying KIFBP function and provide new insight into the regulation of kinesin activity and cytoskeletal dynamics in neurons.

DOI: https://doi.org/10.64898/2026.07.17.739260
Dev Neurobiol. 2026 Oct;86(4): e70054

Impaired Motor Function in a Zebrafish Stathmin-2 Knockout Model.

Tyler J N Gurberg, Ziyaan A Harji, Christian J Rampal, Joséphine Sacy-Richer, Amy Wang, Esteban C Rodríguez, Gary A B Armstrong.

Stathmin-2 (STMN2) is a microtubule-associated protein that plays a role in the stability of microtubules in axons of the nervous system of animals. In this study, we generated a novel zebrafish STMN2 knockout (KO) model. STMN2 is represented by two genes in the zebrafish genome: stmn2a and stmn2b. Using the CRISPR/Cas9 mutagenic system, we selected founder fish lines harboring frameshift mutations in both genes and bred these together to generate a double stmn2a and stmn2b KO model. Using these models, we observed increased developmental lethality in our double stmn2a and stmn2b KO model and impaired motor function at embryonic stages of development. Examination of the neuromuscular junction (NMJ) revealed a slight increase in the number of orphaned NMJs in trunk musculature as well as a reduction in the amplitude of miniature endplate currents in our double stmn2a and stmn2b KO model. In a final series of experiments, we show impaired ventral root axon regrowth following transection in double stmn2a and stmn2b KO zebrafish. Our findings suggest that while not essential for motor function development, loss of stmn2a and stmn2b expression results in a minor motor phenotype and impairs the ability to regenerate motor axons following injury.

DOI: https://doi.org/10.1002/dneu.70054
Cells. 2026 Jul 18. pii: 1289. [Epub ahead of print]15(14):

Microtubule-Associated Proteins: From Dynamic Regulation of Microtubules to Cellular Architecture.

Eva Pais, Kenneth Bødtker Schou.

  Microtubule-associated proteins (MAPs) are key regulators of microtubule architecture and dynamics, orchestrating microtubule stability, post-translational modification, and spatial organization across diverse cellular contexts. Through these activities, MAPs govern essential processes including cell division, intracellular transport, signaling, and differentiation. This review synthesizes current insights into how MAPs regulate a diverse range of cellular processes, including maintenance of structural integrity, centriole assembly, cell division, the dynamic transition between centrosomal and ciliary states, and neuronal growth and connectivity. We discuss advances from structural biology, proteomics, and cell imaging that are redefining the molecular landscape of centriole and cilia regulation, and we highlight emerging themes linking MAP dysfunction to human disease, including cancer, ciliopathies, and neurodegenerative disorders. By integrating these diverse perspectives, the review outlines a unifying framework for understanding how MAPs orchestrate microtubule function and identifies key challenges and opportunities for future research.

Keywords:  axoneme; basal bodies; centrioles; centrosome; cilia; ciliogenesis; microtubule inner proteins; microtubule outer proteins; microtubule-associated proteins; mitotic spindle

DOI:  https://doi.org/10.3390/cells15141289
Autophagy. 2026 Jul 31.

Mitophagy in neurodegeneration: crosstalk between PRKN/parkin-dependent and PRKN-independent pathways.

Laura Kristine Rasmussen, Diana Gomes Moreira, Justyna Okarmus, Anne Simonsen, Morten Meyer.

  Mitochondrial quality control is essential for cellular homeostasis, particularly in neurons, where mitochondrial dysfunction is implicated in the pathogenesis of neurodegenerative diseases. Mitophagy, the selective degradation of damaged or superfluous mitochondria, plays a central role in maintaining mitochondrial integrity and metabolic balance. This review provides a comprehensive overview of the best-characterized PINK1-PRKN/parkin-dependent mitophagy pathway and the expanding repertoire of PRKN-independent mechanisms, including additional ubiquitin-dependent, receptor-mediated, and lipid-mediated pathways. We explore how these pathways intersect and compensate for one another, highlighting the complexity and adaptability of mitochondrial quality control networks. Furthermore, we discuss how dysregulated mitophagy contributes to the onset and progression of neurodegenerative diseases. By examining the interplay between mitophagy pathways and their regulation under physiological and pathological conditions, this review underscores the therapeutic potential of targeting mitophagy in neurodegeneration. Future studies should aim to decode the spatiotemporal dynamics of these pathways to uncover novel opportunities for clinical intervention.

Keywords:  Autophagy receptors; E3 ubiquitin ligases; PINK-PRKN/parkin pathway; PRKN-independent mitophagy; mitochondrial dysfunction; mitochondrial quality control; mitophagy; neurodegeneration; therapeutic targets

DOI:  https://doi.org/10.1080/15548627.2026.2711596
Neuron. 2026 Jul 31. pii: S0896-6273(26)00538-6. [Epub ahead of print]

Single-neuron resolution mapping of dopaminergic connectivity across development, adulthood, and degeneration.

Laurens M Grossouw, Nik Heijmink, Oxana Garritsen, Tess van de Mheen, Willem Naert, Roberto D'Angelo, Mateja Rybiczka-Tešulov, Youri Adolfs, Nicky C H van Kronenburg, Mark H Broekhoven, Grace P Smith, Frank J Meye, Eljo Y van Battum, R Jeroen Pasterkamp.

  Individual midbrain dopamine (mDA) neurons exhibit complex morphologies, a feature that may underlie their different functions and disease vulnerability. However, the developmental programs and wiring principles underlying this morphological complexity, particularly in terms of axonal and dendritic architecture, remain largely unknown. To address this, we developed and employed a unique intersectional genetic strategy in mice (Gucy2c-iCre:Pitx3-FlpE:Ai65D [GPA]) that enables specific sparse labeling of mDA neurons across the midbrain from early developmental stages onward. Using this approach, we generated the largest dataset to date of 3D-reconstructed mDA neurons at key developmental stages, in adulthood, and in models simulating Parkinson's disease-related degeneration. Our work identifies previously uncharacterized morphological features across anatomical and molecular mDA neuron subtypes and during axonal degeneration. Moreover, we identify organizational principles-including pre-target axon sorting and subtype-specific connectivity patterns among ventral tegmental area (VTA) neurons-that offer key entry points for understanding how mDA circuitry is established and functions.

Keywords:  Parkinson’s disease; axon; axonal arbors; dendrite; development; intersectional genetics; mDA neuron; neuron morphology; pre-target axon sorting

DOI:  https://doi.org/10.1016/j.neuron.2026.07.009
bioRxiv. 2026 Jul 14. pii: 2026.07.13.738307. [Epub ahead of print]

Single-cell transcriptomic atlas of frontoinsular cortex reveals molecular correlates of selective neuronal vulnerability in FTD.

Arnar Breevoort, Dimitar Ivanov, Liam Horan-Portelance, Alissa Nana, Sarat Vatsavayai, Àlex Tudoras Miravet, Jenelle L Wallace, Jingwen W Ding, Felipe L Pereira, Kristen Fernhoff, Maria Luisa Gorno-Tempini, Salvatore Spina, Jennifer S Yokoyama, Howard J Rosen, Lea T Grinberg, Frank M J Jacobs, Bruce L Miller, William W Seeley, Alex A Pollen.

  Frontotemporal dementia (FTD) is characterized by selective neuronal vulnerability, yet the features that predispose specific neuron types to degeneration remain unclear. We performed single-nucleus RNA sequencing of frontoinsular cortex, a region affected early in behavioral variant FTD, across individuals with C9orf72-associated and sporadic FTD-MND spectrum disease. By enriching for large projection neurons, we resolved molecular subtypes of layer 5 extratelencephalic neurons, including von Economo neurons, and identified selective depletion of specific layer 2/3 and layer 5 neuron subtypes, convergent across genotypes. Despite selective neuronal loss, disease-associated transcriptional changes were convergent across excitatory neuron populations, suggesting that they reflect upstream pathophysiology or shared responses to local neurodegeneration. By relating neighborhood-level depletion in disease to gene expression in controls, we found that baseline cellular respiration and ATP synthesis predict neuronal vulnerability in disease. These findings define molecular correlates of selective neuronal vulnerability in FTD and provide a framework linking cell type and state to neurodegeneration.

Keywords:  Single-cell; TDP-43; amyotrophic lateral sclerosis; frontoinsular cortex; frontotemporal dementia; selective vulnerability; single-nucleus; von Economo neurons

DOI:  https://doi.org/10.64898/2026.07.13.738307
STAR Protoc. 2026 Jul 30. pii: S2666-1667(26)00408-9. [Epub ahead of print]7(3): 104755

Protocol for induction and quantification of injury-primed axon outgrowth in adult mouse DRG neurons.

Eliana Seburn, Brett J Hilton.

  Adult dorsal root ganglion (DRG) neurons provide a powerful model to study axon growth. Dissociated lumbar L3-L5 DRG neurons extend axons de novo in culture, enabling the measurement of baseline outgrowth. Here, we present a protocol for inducing and quantifying injury-primed axon outgrowth in adult mouse DRG neurons. We describe steps for sciatic nerve conditioning injury, isolating and culturing injured L3-L5 DRG neurons, and quantifying axon outgrowth. This protocol is compatible with cytoskeletal imaging and molecular profiling of injury-induced changes.

Keywords:  Cell culture; Cell isolation; Neuroscience

DOI:  https://doi.org/10.1016/j.xpro.2026.104755
Biomedicines. 2026 Jun 30. pii: 1484. [Epub ahead of print]14(7):

HDDF2-A Novel Patient-Derived Fibroblast Line from Huntington's Disease with Prominent Cellular Senescence and polyQ Pathology.

Polina Parfenova, Nina Kraskovskaya, Anna Koltsova, Alla Shatrova, Natalia Yartseva, Natalia Mikhailova.

  Background/Objectives: Patient-derived cell lines retaining donor-specific age-related and genomic features are essential for modeling late-onset neurodegenerative disorders like Huntington's disease (HD). This study aims to establish and comprehensively characterize HDDF2, a novel dermal fibroblast line from an HD patient, to provide a relevant cellular model. Methods: Dermal fibroblasts were isolated and cultured from a 44-year-old male HD patient carrying 46 CAG repeats in the HTT gene. Cells were evaluated for senescence markers (p16, lamin B1, SA-β-Gal activity, proliferation rates) and polyglutamine (polyQ) aggregation. Direct reprogramming protocols were applied to convert these fibroblasts into induced neurons. Results: HDDF2 fibroblasts exhibited a pronounced senescence-associated phenotype, evidenced by increased p16 expression, reduced lamin B1 levels, elevated SA-β-Gal activity, and decreased proliferation. Notably, polyQ deposition was preferentially detected within the senescent subpopulation, displaying distinct localization patterns differentiating senescent from proliferating cells. Despite this, HDDF2 cells retained their capacity for direct reprogramming and were successfully converted into induced neurons. Conclusions: HDDF2 represents a well-characterized, patient-specific cellular model for HD. The observed co-occurrence of polyQ deposition and cellular senescence, combined with successful neuronal conversion, establishes this line as a valuable resource for investigating the relationship between cellular aging and HD pathogenesis.

Keywords:  Huntington’s disease; cell line; direct reprogramming; fibroblasts; huntingtin; polyQ

DOI:  https://doi.org/10.3390/biomedicines14071484
Bio Protoc. 2026 Jul 20. 16(14): e5765

Actin Quantification Using the Filamentous Actin Segmentation Tool (FAST).

Vineeth Aljapur, Adam Gardner, Jason Carayanniotis, Andrew R Harris.

  Studying actin-filament assembly into distinct subcellular structures can provide insights into both physiological cellular processes and the mechanisms of disease. However, there are a limited number of tools that can quantify the organization and abundance of different actin structures from confocal microscopy images of cells expressing Lifeact or fixed and stained with phalloidin. Filamentous actin segmentation tool (FAST) is a deep learning model trained with a unique approach of antibody-assisted annotation, resulting in accurate and efficient quantification of distinct classes of actin structures. Here, we detail the protocol for using antibody-assisted annotation to generate datasets that could be applied to train machine learning models. Additionally, we provide step-by-step instructions for applying FAST on phalloidin-stained or live-cell confocal imaging data using our pretrained model. FAST is open source and freely available, with user-friendly notebooks that enable quantification of different classes of actin structure, without the need for structure-specific antibodies. As such, FAST can be a practical tool for researchers investigating the role of cytoskeletal organization in a range of processes. Key features • This antibody-assisted labeling approach can be used for identifying different classes of actin structure and generating labeled datasets for training machine learning algorithms. • The trained FAST model then enables the detection of distinct classes of actin structure without the need for multiple structure-specific antibodies. • FAST generates segmentation masks that can be used to quantify the abundance and organization of detected classes. • This protocol provides a graphical user interface for fine-tuning custom phalloidin-stained images and provides instructions on using trained model on Ilastik interface.

Keywords:  Actin; Cell segmentation; Confocal microscopy; Cytoskeleton; Deep learning; Fluorescence microscopy

DOI:  https://doi.org/10.21769/BioProtoc.5765
Proc Natl Acad Sci U S A. 2026 Aug 04. 123(31): e2606606123

Spatiotemporal control of Atg2 association with the ER during autophagosome formation.

Tetsuya Kotani, Haruki Tanabe, Shinri Kitta, Momoko Higashi, Tatsuya Niwa, Tatsuya Kaminishi, Chika Kakuta, Junko Shimasaki, Hidetaka Kosako, Tamotsu Yoshimori, Akiko Kuma, Hitoshi Nakatogawa.

  Autophagy degrades various intracellular components by sequestering them within membrane vesicles called autophagosomes and delivering them to lysosomes or vacuoles. Previous studies have revealed that the conserved, bridge-like lipid transfer protein Atg2 tethers autophagosome precursors to the endoplasmic reticulum (ER) and mediates lipid supply from the ER to drive their expansion into autophagosomes. However, how Atg2 docks onto the ER has remained unclear. Here, we show in Saccharomyces cerevisiae that Atg2 interacts with the ER-resident VAP family protein Scs2. This interaction is mediated by a phospho-FFAT motif in Atg2 and the major sperm protein domain of Scs2 and enhanced by phosphorylation of the motif by the autophagy-initiating kinase Atg1, which is activated at the autophagosome formation site upon autophagy induction. This interaction cooperates with the N-terminal region of Atg2, which contains a weakly amphipathic helix, to mediate Atg2 association with the ER. Thus, the Atg2-Scs2 interaction functions as a spatiotemporal switch that controls Atg2-ER association. We also show that mammalian ATG2 interacts with the VAP-like proteins MOSPD1 and MOSPD3 to promote autophagosome formation. Collectively, this study reveals a conserved mechanism that initiates lipid transfer during autophagosome formation.

Keywords:  Atg2; VAP protein; autophagy; lipid transfer protein; phospho-FFAT motif

DOI:  https://doi.org/10.1073/pnas.2606606123