bims-axbals 2026-06-21 papers

bims-axbals

Biomed News

on Axonal biology and ALS

Issue of 2026–06–21
ten papers selected by
TJ Krzystek

Intrathecal (G4C2)149 delivery in C9orf72-deficient mice yields mild motor dysfunction and ALS/FTD pathological hallmarks.
Restoring the interplay between the endoplasmic reticulum and mitochondria by gene therapy improves Charcot-Marie-Tooth type 2A disease.
Engineering functional ventral midbrain dopaminergic neurons in human organoids through WNT modulation and bioreactor culture.
Cofilin 1-138 Promotes Mitochondrial Dysfunction and Synaptic Degeneration in Parkinson's Disease.
Miro1 mutations disrupt cellular calcium homeostasis via dysregulation of mitochondria-ER-contact-sites, rendering iPSC-derived neurons more susceptible to lipid peroxidation.
Targeting lysosomal pH restores mitochondrial quality control in GBA1-mutant Parkinson's disease.
DKK1 Targeting in Corneal Schwann Cells Rescues Axonal Regeneration and Mechanosensory Function After Corneal Injury.
Optical voltage imaging: ready to spark systems neuroscience.
Structural basis for LMBD1-dependent trafficking and cobalamin export of ABCD4.
A single-vesicle fluorescence microscopy platform to quantify phospholipid scrambling.

Acta Neuropathol Commun. 2026 Jun 18.

Intrathecal (G4C2)149 delivery in C9orf72-deficient mice yields mild motor dysfunction and ALS/FTD pathological hallmarks.

Katelyn A Russell, Amelia A Shahrabi, Suleyman C Akerman, Matthew D Byrne, Jeffrey D Rothstein, Davide Trotti, Brigid K Jensen, Aaron R Haeusler.

  A repeat expansion in C9ORF72 is the most common genetic cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD), yet existing mouse models incompletely engage spinal regions implicated in disease. Here, an adeno-associated virus encoding (G4C2)149 repeats was delivered via neonatal intrathecal injection, achieving widespread CNS expression with robust spinal cord targeting. This approach was applied to mice with graded loss of endogenous C9orf72 to interrogate both gain- and loss-of-function mechanisms. Longitudinal motor, behavioral, and pathological analyses revealed that repeat expression primarily drives mild, progressive muscle weakness, whereas coordination deficits were largely genotype dependent. Subtle gait abnormalities and hyperactivity were also observed. Within spinal motor regions, repeat-expressing mice exhibited dipeptide repeat protein accumulation, reduced NeuN-positive area, fewer motor neurons, glial activation, sparse phosphorylated TDP-43 pathology, and increased cryptic TDP-43 splicing. Cross-domain correlations further linked repeat expression, spinal pathology, and motor dysfunction. Collectively, these findings establish that CNS-wide repeat expression combined with reduced C9orf72 produces a coherent, mild ALS/FTD model.

Keywords:  ALS; ALS/FTD; C9orf72; C9orf72 repeat expansions; FTD; Motor neuron disease; Mouse models; Neurodegenerative disease

DOI:  https://doi.org/10.1186/s40478-026-02341-8
Proc Natl Acad Sci U S A. 2026 Jun 23. 123(25): e2530774123

Restoring the interplay between the endoplasmic reticulum and mitochondria by gene therapy improves Charcot-Marie-Tooth type 2A disease.

Marine Tessier, Zeinab Hamze, Nathalie Bonello-Palot, Nathalie Roeckel-Trévisiol, Nathalie Da Silva, Ilian Verlet, Natacha Broucqsault, Karine Bertaux, Emilien Delmont, Shahram Attarian, Marc Bartoli, Valérie Delague, Bernard L Schneider, Nathalie Bernard-Marissal.

  Charcot-Marie-Tooth disease type 2A (CMT2A) is the most common axonal CMT and is associated with an early onset and severe motor neuropathy. CMT2A is mainly caused by dominant mutations in the MFN2 gene, encoding mitofusin-2, a GTPase located in the outer membrane of the mitochondria and endoplasmic reticulum (ER). Mutations in MFN2 affect mitochondrial dynamics. We previously demonstrated that mutated MFN2 further disrupts contacts between the ER and the mitochondria, leading to axonal degeneration. There are no treatments for CMT2A, and those currently under development primarily focus on restoring mitochondrial function. Here, we provide proof of concept that neuronal overexpression of wild-type MFN2 (MFN2WT) provides therapeutic benefit in transgenic CMT2A mice as well as in CMT2A-motor neurons derived from induced pluripotent stem cells. Intrathecal delivery of an AAV9 vector expressing MFN2WT effectively targets motor and sensory neurons, restoring ER-mitochondria contacts and mitochondrial morphology, thereby preserving both neuromuscular junction integrity and motor function. Strikingly, therapeutic efficacy is also achieved by administering the vector after the onset of symptoms. Importantly, AAV administration was well tolerated, with no evidence of hepatotoxicity or dorsal root ganglion inflammation. We further show that CMT2A pathology can be corrected in vitro and in vivo using an ER-targeting MFN1 isoform that selectively enhances ER-mitochondria contacts. These results establish that restoring contacts between the ER and mitochondria using gene therapy is a promising therapeutic avenue for CMT2A.

Keywords:  Charcot–Marie–Tooth disease; MFN2; endoplasmic reticulum; gene therapy; mitochondria

DOI:  https://doi.org/10.1073/pnas.2530774123
Mol Psychiatry. 2026 Jun 17.

Engineering functional ventral midbrain dopaminergic neurons in human organoids through WNT modulation and bioreactor culture.

Hariam Raji, Federico Bertoli, Maria Jose Perez, Alicia Lam, Laura Volpicelli-Daley, Michela Deleidi.

Human midbrain organoids (hMOs) derived from induced pluripotent stem cells provide a powerful system to model disorders involving dopamine (DA) dysfunction, including Parkinson's disease (PD) and neuropsychiatric conditions. However, current differentiation protocols still fall short in recapitulating early specification, substantia nigra pars compacta (SNpc)-like identity, and the functional maturation of vulnerable DA neurons. Here, we established a differentiation strategy that combines tri-phasic WNT modulation with dynamic bioreactor culture to generate hMOs enriched in SNpc-like DA neurons. This approach significantly increases the yield of TH⁺/GIRK2⁺ and TH⁺/ALDH1A1⁺ DA neurons and promotes enhanced synaptic maturation, robust electrophysiological activity, and elevated DA release. Single-cell transcriptomics revealed that this strategy drives the emergence of SOX6+/GIRK2+ SNpc-like neurons, accompanied by upregulation of synaptic, metabolic, and maturation programs, alongside reduced cell stress and apoptotic signaling. Importantly, hMOs demonstrated vulnerability upon exposure to α-synuclein preformed fibrils, resulting in aggregate formation and DA neuron degeneration, supporting their use as a human model of PD-relevant pathology. Overall, this system provides a scalable and physiologically relevant approach to investigate molecular mechanisms underlying neurodegeneration and DA-related disorders.

DOI: https://doi.org/10.1038/s41380-026-03667-4
Mol Neurobiol. 2026 Jun 16. pii: 696. [Epub ahead of print]63(1):

Cofilin 1-138 Promotes Mitochondrial Dysfunction and Synaptic Degeneration in Parkinson's Disease.

Di Zhang, Yidan Chen, Haibo Zhang, Hongyang Liu, Dan Wang, Qin Li, Hualan Qin, Yue Wan, Mingmin Yan.

  Parkinson's disease (PD) is marked by α-synuclein aggregation, mitochondrial dysfunction, and synaptic degeneration, yet the molecular mediators linking these pathological events remain poorly defined. Full-length cofilin (cofilin FL), an actin-binding protein, can be cleaved by asparagine endopeptidase (AEP) to generate the truncated fragment cofilin 1-138, which is known to exert enhanced neurotoxicity in neurodegenerative disorders. However, its role in PD pathogenesis has not been established. In this study, we demonstrate that cofilin 1-138 is elevated in the striatum of PD patients and α-synuclein A53T mice, where it colocalizes with pathological p-S129 α-synuclein. In vitro, cofilin 1-138 exhibited lower phosphorylation levels than full-length cofilin (cofilin FL), suggesting that its activity may be increased. Functionally, cofilin 1-138 promoted neuronal apoptosis, as evidenced by increased Bax and cleaved-caspase-3 expression, enhanced TUNEL positivity, and reduced cell viability. In primary neurons, cofilin 1-138 exacerbated synaptic damage, including reduced synaptic protein expression and neurite degeneration. Moreover, cofilin 1-138 induced mitochondrial dysfunction, characterized by mitochondrial fragmentation, impaired fusion, decreased membrane potential, and reduced ATP production. Collectively, this study demonstrates that cofilin 1-138 is an important pathogenic factor in Parkinson's disease that promotes mitochondrial dysfunction and synaptic degeneration, providing new insights into the molecular mechanisms of PD and potential therapeutic targets.

Keywords:  Cofilin 1-138; Cofilin FL; Mitochondrial dysfunction; Parkinson’s disease; Synaptic degeneration

DOI:  https://doi.org/10.1007/s12035-026-05995-6
Neurobiol Dis. 2026 Jun 18. pii: S0969-9961(26)00237-8. [Epub ahead of print] 107492

Miro1 mutations disrupt cellular calcium homeostasis via dysregulation of mitochondria-ER-contact-sites, rendering iPSC-derived neurons more susceptible to lipid peroxidation.

Anna E Bartalis, Jack Genschmar, Julia C Fitzgerald, Andreas Hermann, Dajana Grossmann.

  The pathogenesis of Parkinson's disease is multifactorial, but disruption of calcium and iron is a common feature. The mitochondrial Rho GTPase Miro1 is a component of the mitochondrial-endoplasmic reticulum contact sites and a key regulator of calcium homeostasis. Heterozygous variants in the Miro1-encoding gene RHOT1 were identified in Parkinson's disease patients. Neurons harboring Parkinson's disease-associated variants show defects in mitochondrial calcium regulation and mitochondria-ER contact sites organization which we hypothesize to contribute to neuronal vulnerability. However, the exact mechanism is not fully understood. We systematically assessed the role of Miro1 and its different domains by using a set of isogenic lines with gene edited mutations S156A and K572R in PINK1/Parkin regulatory elements and the Parkinson's disease-associated mutation R272Q. This showed us a general role of Miro1 in the regulation of cellular calcium homeostasis and the regulation of mitochondrial-ER contact sites, but more importantly, a domain-specific involvement of local calcium distribution, impaired store operated calcium entry and vulnerability to ferroptosis. These findings indicate that Miro1-mutant specific impairments in cellular calcium handling contributes to neuronal vulnerability via mitochondria-ER contact sites and provides further insights in the mechanism how impaired regulation of Miro1 impacts neurons in the context of Parkinson's disease.

Keywords:  Calcium; Ferroptosis; Lipid peroxidation; MERCS; Miro1; Parkinson's disease

DOI:  https://doi.org/10.1016/j.nbd.2026.107492
Transl Neurodegener. 2026 Jun 17. pii: 27. [Epub ahead of print]15(1):

Targeting lysosomal pH restores mitochondrial quality control in GBA1-mutant Parkinson's disease.

Preethi Sheshadri, Maria Alicia Costa-Besada, Alessia Fisher, Szilvia Kiraly, Kritarth Singh, Ioanna Kourouzidou, Thomas S Blacker, Jialiu Zeng, Orian S Shirihai, Mark W Grinstaff, Michael R Duchen.

   BACKGROUND: Heterozygous mutations in the glucocerebrosidase gene (GBA1), which encodes the lysosomal enzyme β-glucocerebrosidase (GCase), are a genetic risk factor for Parkinson's disease (PD). The pathophysiological consequences of GBA1 mutations on dopaminergic neuronal function, especially their impact on lysosomal function, mitophagy, and mitochondrial bioenergetics, remain unclear.
METHODS: Fibroblasts and dopaminergic neurons generated from induced pluripotent stem cells (iPSCs) derived from patients with GBA1-PD were used in the study. Live-cell imaging was performed to measure lysosomal acidification, protease activity, mitochondrial membrane potential, and mitophagy. Mitochondrial morphology and autophagic vesicles were examined using transmission electron microscopy. Oxygen consumption rate was measured by Seahorse assay. V-ATPase assembly was quantified using fluorescence lifetime imaging with Förster resonance energy transfer (FLIM-FRET), and pharmacological interventions included rapamycin and acidic nanoparticles.
RESULTS: GCase activity, lysosomal acidification, protease activity, mitophagy and mitochondrial bioenergetic function were all impaired in GBA1 mutant dopaminergic neurons. Mitochondria were fragmented, with reduced membrane potential and oxygen consumption. Mechanistic target of rapamycin complex 1 (MTORC1) was constitutively phosphorylated and FLIM-FRET measurements confirmed impairment of lysosomal V-ATPase assembly, which was reversed by rapamycin treatment. Rapamycin and lysosome-targeting acidic nanoparticles rescued lysosomal pH and restored mitophagy, mitochondrial membrane potential and mitochondrial oxidative phosphorylation complex level in the GBA1 mutant dopaminergic neurons.
CONCLUSIONS: We revealed a novel mechanistic link between GBA1 mutations and mitochondrial dysfunction, as the disruption of V-ATPase assembly driven by MTORC1 activation impairs lysosomal acidification. This causes impairment of mitophagy, leading to mitochondrial dysfunction, undermining dopaminergic cell function and fate. Pharmacological intervention with rapamycin or acidic nanoparticles restores lysosomal pH and rescue mitochondrial function, representing a novel therapeutic approach for GBA1-PD .

Keywords:  Acidic nanoparticles; GBA1; Lysosomal pH; Lysosomes; MTORC1; Mitochondria; Parkinson’s disease

DOI:  https://doi.org/10.1186/s40035-026-00559-z
J Neurosci Res. 2026 Jun;104(6): e70142

DKK1 Targeting in Corneal Schwann Cells Rescues Axonal Regeneration and Mechanosensory Function After Corneal Injury.

Michael Li, Christian A Tallo, Mary Katherine Eddy, Aarush Kolli, Ricky Paramo, Paola Bargagna-Mohan, Royce Mohan.

  Stromal nerves regulate the sensory functions of the cornea, which can be disrupted by surgical, traumatic, or chemical injuries. Corneal Schwann cells (cSCs) ensheath axons to provide trophic support, but their role in axonal regeneration is still unexplored. We utilized the proteolipid protein 1-enhanced green fluorescent protein (Plp1-eGFP) reporter mice to investigate cSCs in two models of corneal nerve injury: the corneal micropocket injury (CMI) model, which causes focal stromal axonal severance, and acute exposure to nitrogen mustard (NM), which results in blunt damage across the entire cornea and limbal tissue. After CMI, the cSC network declined rapidly over 7 days post-injury (dpi) but recovered to levels of uninjured controls by 14 dpi with sprouting at both the injury and collateral areas. Axons remained significantly lower than cSCs, compromising mechanosensory functions. The NM injury led to a sustained cSC and axonal deficit with persistent mechanosensory loss through 14 dpi. Previously, we identified Dickkopf-related protein 1 (DKK1) as a novel candidate gene expressed in cSCs. In this study, we developed a micellar formulation RM4404 incorporating a small-molecule DKK1 inhibitor for topical application and tested the therapeutic potential of this drug in both injury models. Application of RM4404 during the cSC regenerative phase (7-14 dpi) enhanced cSC repair and significantly improved axonal regeneration with restoration of mechanosensory function in both injury paradigms. These findings identify a promising DKK1-targeted therapy that promotes cSC repair, enhances corneal nerve regeneration, and restores sensory function in models of corneal injury.

Keywords:  Dickkopf‐related protein 1; axons; corneal Schwann cells; corneal micropocket injury; mechanosensitivity; nitrogen mustard; proteolipid protein 1‐enhanced green fluorescent protein

DOI:  https://doi.org/10.1002/jnr.70142
Curr Opin Neurobiol. 2026 Jun 18. pii: S0959-4388(26)00074-7. [Epub ahead of print]99 103238

Optical voltage imaging: ready to spark systems neuroscience.

Laura Camila Gomez, Lucia Rodriguez, Pierre-Marie Garderes, Daniel E Feldman.

Many open questions about neural circuit and systems function could be answered if spikes and synaptic potentials could be accurately measured from many neurons simultaneously in a given network with cell-type specificity, cellular resolution, and at the millisecond time scale. Voltage imaging with genetically encoded voltage indicators (GEVIs) has advanced to the point that this is now possible for small networks or sparsely labeled neurons, and emerging optical methods promise to soon enable imaging from larger, dense cell populations. This review describes recent discoveries made using GEVIs to understand local and propagating cortical activity, network oscillations, and cortical and hippocampal microcircuit dynamics, and outlines several promising future applications in systems neuroscience.

DOI: https://doi.org/10.1016/j.conb.2026.103238
Nat Commun. 2026 Jun 16.

Structural basis for LMBD1-dependent trafficking and cobalamin export of ABCD4.

Qiwei Liu, Xingfan Li, Yingjie Wu, Kai Zheng, Mi Zhou, Tao Long.

Correct trafficking of lysosomal transporters is essential for intracellular homeostasis. While most lysosomal membrane proteins are directed to the lysosome via sorting motifs, the cobalamin exporter ABCD4 is distinct, instead relying on LMBD1 as a dedicated chaperone for its trafficking. Dysfunction of either protein causes inherited cobalamin metabolism disorders. Despite its physiological significance, the molecular mechanism underlying this chaperone-dependent trafficking remains unclear. Here, we report the cryo-EM structures of ABCD4 complex with LMBD1 in the lumen-open, substrate-bound and cytosol-open states. LMBD1 contains nine transmembrane-helices (TMs) and a cytosolic domain, both of which engage ABCD4. Cell imaging shows that disruption of these interactions impairs the trafficking of ABCD4 to lysosomes. Structural and biochemical analyses provide insights into cobalamin recognition and reveal conformational states associated with the proposed cobalamin transport cycle. These findings provide molecular insights into cobalamin metabolism and illustrate a chaperone-assisted mechanism that supports proper trafficking of a lysosomal transporter.

DOI: https://doi.org/10.1038/s41467-026-74552-5
Nat Struct Mol Biol. 2026 Jun;33(6): 1011-1019

A single-vesicle fluorescence microscopy platform to quantify phospholipid scrambling.

Sarina Veit, Grace I Dearden, Kartikeya M Menon, Faria Noor, Indu Menon, Takefumi Morizumi, Oliver P Ernst, Anant K Menon, Thomas Günther Pomorski.

Scramblases are physiologically important proteins that translocate phospholipids bidirectionally across cell membranes. For example, scrambling facilitated by dimers of the voltage-dependent anion channel 1 (VDAC1) enables endoplasmic reticulum-derived phospholipids to cross the outer membrane to enter mitochondria. Here we describe a protocol to obtain lipid translocation rates at a single-protein level, allowing for mechanistic understanding of scramblases. We reconstituted vesicles with fluorescent phospholipids and VDAC1 dimers and use high-throughput imaging to quantify their size and dimer content. We measure scrambling in each vesicle using a new assay and find that individual human VDAC1 dimers scramble lipids at rates ranging from under 100 to over 10,000 per second. This kinetic heterogeneity, masked in ensemble measurements, revealed that rapid scrambling is facilitated by specific VDAC1 dimers. Extending our analyses to bovine opsin, a monomeric G-protein-coupled receptor scramblase, we demonstrate the versatility of our platform for quantifying lipid scrambling and exploring its regulation.

DOI: https://doi.org/10.1038/s41594-026-01821-8