bims-axbals Biomed News
on Axonal biology and ALS
Issue of 2025–10–12
eleven papers selected by
TJ Krzystek



  1. Mol Biol Cell. 2025 Oct 08. mbcE24120539
      The neurodegenerative disorder Frontotemporal Dementia (FTD) can be caused by a repeat expansion (GGGGCC; G4C2) in C9orf72. The function of wild-type C9orf72 and the mechanism by which the C9orf72-G4C2 expansion causes FTD, however, remain unresolved. Diverse disease models, including human brain samples and differentiated neurons from patient-derived induced pluripotent stem cells (iPSCs), identified some hallmarks associated with FTD, but these models have limitations, including biopsies capturing only a static snapshot of dynamic processes and differentiated neurons being labor-intensive, costly, and post-mitotic. We find that patient-derived iPSCs, without being differentiated into neurons, exhibit established FTD hallmarks, including increased lysosome pH, decreased lysosomal cathepsin activity, cytosolic TDP-43 proteinopathy, and increased nuclear TFEB. Moreover, lowering lysosome pH in FTD iPSCs mitigates TDP-43 proteinopathy, suggesting a key role for lysosome dysfunction. RNA-seq reveals dysregulated transcripts in FTD iPSCs affecting calcium signaling, cell death, synaptic function, and neuronal development. We confirm differences in protein expression for some dysregulated genes not previously linked to FTD, including CNTFR (neuronal survival), Annexin A2 (anti-apoptotic), NANOG (neuronal development), and Moesin (cytoskeletal dynamics). Our findings underscore the potential of FTD iPSCs as a model for studying FTD cellular pathology and for drug screening to identify therapeutics.
    DOI:  https://doi.org/10.1091/mbc.E24-12-0539
  2. Brain. 2025 Oct 08. pii: awaf380. [Epub ahead of print]
      Dysregulated proteostasis and intracellular transport contribute to neurodegeneration. HDAC6, a therapeutic target of interest for neurodegenerative diseases, acts at a nexus modulating both proteostasis and intracellular transport. Inhibition of HDAC6 deacetylase activity promotes autophagic clearance of protein aggregates and increases ⍺-tubulin acetylation, thereby enhancing microtubule resiliency and motor protein-microtubule binding, which facilitates intracellular transport and, subsequently, proteostasis. Despite these benefits, advancement of HDAC6 inhibitor therapeutics for neurodegenerative disease has been hindered by inadequate selectivity and CNS-penetrance of first-generation compounds. Here we characterize a next-generation small molecule HDAC6 inhibitor, EKZ-438, in preclinical models of amyotrophic lateral sclerosis and frontotemporal dementia. We present the pharmacological properties of EKZ-438, which demonstrate high selectivity for HDAC6 (>8,500-fold selectivity for HDAC6 versus all other HDAC6 paralogs), low nanomolar potency (12 nM) for HDAC6, and, importantly, CNS-penetrance (Kp,uu,brain) ≥ 0.55 and high oral bioavailability (F% = 70). In complementary preclinical in vitro and in vivo immunolabeling and live imaging studies we tested the hypothesis that selective inhibition of HDAC6 deacetylase activity is sufficient to improve pathophysiological proteostasis and intracellular transport deficits in animal models of familial and sporadic amyotrophic lateral sclerosis and frontotemporal dementia. Notably, we extended these findings to human induced pluripotent stem cell-derived neuronal cellular models, supporting the relevance of our findings to human disease. EKZ-438 treatment fully rescued SOD1 (q < 0.0001) and TDP-43 (q < 0.001) proteostasis defects following an excitotoxic glutamate challenge, and increased survival of SOD1G93A and wildtype motor neurons by 59% (q < 0.0001) and 37% (q < 0.01), respectively, demonstrating in vitro neuroprotection. In SOD1G93A mice, EKZ-438 improved axonal transport by 16% (q < 0.05), motor performance by ∼40% (q < 0.05), and decreased plasma neurofilament light chain levels by 35% (q < 0.05), demonstrating in vivo neuroprotection. In a TDP-43 mouse model, EKZ-438 reduced TDP-43 pathology by ∼30% (q < 0.05) and neuroinflammation by ∼26% (q < 0.05) in the brain, supporting HDAC6 inhibition for sporadic amyotrophic lateral sclerosis and frontotemporal dementia. Furthermore, EKZ-438 treatment improved intracellular transport by 39% (q < 0.001), rescued cytoplasmic TDP-43 accumulation by 87% (q < 0.0001), and restored nuclear TDP-43 splicing activity (P < 0.05) in human TARDBP neurons. These mechanistic improvements aligned with nearly complete rescue of human TARDBP and C9orf72 mutant neuron survival (P < 0.0001). We conclude that selective HDAC6 inhibition represents a promising therapeutic approach for potential disease modification in amyotrophic lateral sclerosis and frontotemporal dementia.
    Keywords:  ALS; FTD; HDAC6 inhibitor; axonal transport; proteostasis
    DOI:  https://doi.org/10.1093/brain/awaf380
  3. Cell Death Discov. 2025 Oct 07. 11(1): 446
      Spinal muscular atrophy (SMA) is a paediatric neuromuscular disease caused by alterations of the survival motor neuron (SMN) gene, which results in progressive degeneration of motor neurons (MNs). Although effective treatments for SMA patients has been recently developed, the molecular pathway involved in selective MNs degeneration has not been yet elucidated. Disruption of axonal transport is a common feature of motor neuron diseases (MNDs); specifically, mutations at the C-terminal of the kinesin KIF5A, have been linked to neurodegenerative disorders involving MNs degeneration such as amyotrophic lateral sclerosis (ALS). Therefore, the present study attempts to investigate potential alterations of the axonal transport complex that includes KIF5A in a SMA mouse model. We demonstrated that KIF5A is downregulated in the spinal cord of SMA mice both in early and late phases of the disease. A miRNA-based strategy was developed in the attempt to prevent KIF5A downregulation, thus restoring its physiological levels. Indeed, we demonstrated that miR-140-3p was up-regulated in the spinal cord of SMA mice during disease progression and was able to negatively modulate KIF5A expression. Furthermore, the intracerebroventricular injection of an antagomir molecule, able to block miR140-3p function, resulted in a reduction of SMA severity in terms of improved behavioural performance. Based on these results, we indicated KIF5A as a distinctive mechanism of MNDs progression and suggested that developing a strategy able to prevent KIF5A downregulation could be beneficial, not only in SMA but also in other neurodegenerative diseases.
    DOI:  https://doi.org/10.1038/s41420-025-02663-x
  4. J Biomed Mater Res A. 2025 Oct;113(10): e38001
      Spinal cord injury (SCI) severely compromises neural regeneration due to limited intrinsic repair capacity. Combining induced pluripotent stem cell (iPSC)-derived organoids with biomaterial scaffolds offers a promising regenerative strategy. This study investigated the therapeutic potential of human spinal cord organoids (hSCOs) encapsulated within gelatin methacryloyl (GelMA) hydrogel for SCI repair. hSCOs were generated from iPSCs via stage-specific patterning (dorsoventral inhibition followed by retinoic acid/SAG-induced motor neuron specification) and encapsulated in GelMA hydrogel. The therapeutic efficacy of hSCOs/GelMA composites was evaluated in a rat T10 contusion SCI model (n = 6/group: Sham, SCI, GelMA-only, GelMA+hSCOs). Functional recovery was assessed weekly for 4 weeks using Basso-Beattie-Bresnahan (BBB) locomotor scores and inclined plane tests. Histological (H&E, Nissl) and immunofluorescence analyses (Tuj1, GFAP, NF200, CD68) quantified tissue repair, neuronal regeneration, astrogliosis, and neuroinflammation at the lesion site. hSCOs expressed key spinal cord markers (OLIG2, NKX6.1, Tuj1, Islet1) and maintained high viability within GelMA hydrogels. Implantation of GelMA+hSCOs composites significantly enhanced functional recovery (improved BBB scores and inclination angles) and reduced lesion volume compared to both SCI and GelMA-only controls. Immunofluorescence revealed that GelMA+hSCOs treatment promoted neuronal integration (increased density of Tuj1+ neurons and NF200+ neurofilaments), attenuated astrogliosis (reduced GFAP+ scarring), and suppressed neuroinflammation (decreased CD68+ macrophages) at the injury epicenter relative to control groups. The integration of iPSC-derived hSCOs with GelMA hydrogel significantly promotes structural and functional recovery after SCI by facilitating neuronal survival and integration, mitigating glial scar formation, and modulating the inflammatory response. This combinatorial organoid-hydrogel approach demonstrates substantial translational potential for neural repair strategies.
    Keywords:  GelMA hydrogel; functional recovery; iPSC‐derived organoids; neural regeneration; spinal cord injury repair
    DOI:  https://doi.org/10.1002/jbm.a.38001
  5. Stem Cell Res Ther. 2025 Oct 07. 16(1): 542
      Astrocytes are essential for maintaining brain homeostasis, as they support neurons, regulate synaptic activity, and mediate immune responses within the central nervous system (CNS). Their role in the pathophysiology of various neurological disorders, including Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis (ALS), and multiple sclerosis, is increasingly recognized. Thus, differentiation of astrocytes from human induced pluripotent stem cells (hiPSCs) acts as an important tool for studying disease mechanisms and advancing therapeutic development strategies. However, the prolonged time of up to six months required to generate fully mature astrocytes limits their utility, with most protocols yielding only fetal-like astrocytes or relying on artificial transcription factor overexpression. To address this challenge, we developed a small-molecule-based method using PD0325901 (PD), which enables the rapid generation of mature human astrocytes from gliogenic neural stem cells (NSCs) within a short time of 2-3 weeks, without the need for genetic modification. We found that inhibition of MEK1/2 signaling in NSCs via PD resulted in decreased proliferation, upregulation of astrocytic markers, and acquisition of functionally mature astrocytes. Mechanistically, this differentiation process involved AKT1-dependent phosphorylation and activation of STAT1/3 that is the classical pathway for astrocyte differentiation, along with the nuclear loss of the astrocytic transcriptional repressor OLIG2. Overall, our findings present a novel approach for accelerating astrocyte maturation using a small molecule and reveal a key role for AKT1-STAT1/3 signaling in astrocyte development. By significantly shortening the time required to generate mature human astrocytes, this rapid astrocyte differentiation protocol enables more efficient modeling of neurodegenerative diseases and drug screening efforts.
    Keywords:  AKT1; Gliogenic progenitors; Human iPSCs; MEK inhibition; Mature human astrocytes; Neural stem cells; OLIG2; Small molecule
    DOI:  https://doi.org/10.1186/s13287-025-04580-3
  6. Stem Cell Rev Rep. 2025 Oct 11.
       BACKGROUND: Stroke is a leading global health concern, with cerebral infarction accounting for 62% of cases. Despite advances in acute-phase treatments, functional impairments such as motor deficits remain prevalent. This study investigates the potential of human induced pluripotent stem cell (iPSC)-derived cerebral cortical neurons for neural regeneration and motor function recovery in a female mouse model of ischemic stroke.
    METHODS: Cerebral infarction was induced using the Rose Bengal photothrombosis method, followed by transplantation of iPSC-derived cortical neurons into the area adjacent to the infarction. Behavioral recovery was assessed using the foot fault and cylinder tests. Histological analysis was performed to evaluate graft integration and neurite extension.
    RESULTS: Foot fault test demonstrated significant improvements in fine motor function in the transplantation group compared to the vehicle group. However, no recovery was observed in the cylinder test, which assesses gross motor function. Neurite extension from grafted cells was observed along the corticospinal tract, with axonal projections reaching the spinal cord in 68% of transplanted mice. In addition, neurite outgrowth extended to the thalamus, superior colliculus, and vestibular nucleus, suggesting integration into multiple neural circuits. Histological analysis revealed that 16.4% and 47.3% of grafted cells expressed CTIP2 and SATB2, respectively, indicating the presence of both deep- and upper-layer cortical neurons.
    CONCLUSIONS: This study demonstrates that iPSC-derived cortical neurons extend axons along the corticospinal tract and can promote fine motor recovery after stroke. However, further research is needed to validate functional connectivity and long-term safety. These findings offer a promising avenue for developing cell-based therapies for stroke patients.
    Keywords:  Cell transplantation; Cerebral organoid; IPS cell; Ischemic stroke
    DOI:  https://doi.org/10.1007/s12015-025-10981-x
  7. Mol Psychiatry. 2025 Oct 06.
      Neurodegenerative diseases share common features of protein aggregation along with other pleiotropic traits, including shifts in transcriptional patterns, neuroinflammation, disruption in synaptic signaling, mitochondrial dysfunction, oxidative stress, and impaired clearance mechanisms like autophagy. However, key regulators of these pleiotropic traits have yet to be identified. Here, we used transcriptomics, mass spectrometry, and biochemical assays to define the role of a novel lncRNA on tau pathophysiology. We discovered a long non-coding RNA (lncRNA), FAM151B-DT, that is reduced in a stem cell model of frontotemporal lobar dementia with tau inclusions (FTLD-tau) and in brains from FTLD-tau, progressive supranuclear palsy, Alzheimer's disease, and Parkinson's disease patients. We show that silencing FAM151B-DT in vitro is sufficient to enhance tau and α-synuclein aggregation. To begin to understand the mechanism by which FAM151B-DT mediates tau aggregation and contributes to several neurodegenerative diseases, we deeply characterized this novel lncRNA and found that FAM151B-DT resides in the cytoplasm where it interacts with tau, α-synuclein, HSC70, and other proteins involved in protein homeostasis. When silenced, FAM151B-DT blocks autophagy, leading to the accumulation of tau and α-synuclein. Importantly, we discovered that increasing FAM151B-DT expression is sufficient to promote autophagic clearance of phosphorylated tau and α-synuclein, and reduce tau and α-synuclein aggregation. Overall, these findings pave the way for further exploration of FAM151B-DT as a promising molecular target for several neurodegenerative diseases.
    DOI:  https://doi.org/10.1038/s41380-025-03277-6
  8. J Cell Biol. 2025 Dec 01. pii: e202407013. [Epub ahead of print]224(12):
      Protein trafficking within the endosomal system involves several distinct membrane remodeling events, including those with opposing orientations that lead to the production of intraluminal vesicles (ILVs) and recycling tubules. Components of the endosomal sorting complex required for transport (ESCRT) machinery have been implicated in both pathways, although few studies have directly examined their native dynamics in mammalian cells. Here, we demonstrate that the endogenous ESCRT-III subunit Ist1 exists in at least two different pools on endosomes. High-speed, live-cell imaging further showed that one pool of Ist1 forms transiently on endosomes, while the other is relatively stable. However, upon growth factor stimulation, the stable pool of Ist1 becomes more mobile, and the transient pool accumulates more rapidly on endosomes. Our data indicate that ESCRT-III dynamics are distinct from that of other ESCRT complexes and additionally suggest an intrinsic amount of time is required for ESCRT-mediated ILV biogenesis, irrespective of environmental conditions.
    DOI:  https://doi.org/10.1083/jcb.202407013
  9. Mol Ther Methods Clin Dev. 2025 Dec 11. 33(4): 101587
      Juvenile neuronal ceroid lipofuscinosis (JNCL) is a neurodegenerative lysosomal storage disease caused by the loss of the endolysosomal transmembrane protein, CLN3. The main protein component of lysosomal storage material in JNCL is subunit c of mitochondrial ATP synthase (SCMAS), which is normally degraded within the lysosome by tripeptidyl-peptidase 1 (TPP1) during mitophagy. Previous studies have shown that TPP1 expression is elevated in JNCL, a potential compensatory response, while reduced levels of TPP1 exacerbate disease in a JNCL mouse model. These observations suggest a role for TPP1 in JNCL pathogenesis, and it is possible that lysosomal perturbations from the loss of CLN3 in JNCL could reduce the ability of TPP1 to degrade SCMAS. To test this hypothesis, we introduced a transgene that overexpresses TPP1 in a mouse model of JNCL and find that constitutively elevated TPP1 prevents SCMAS storage. This is associated with correction or significant reduction of other phenotypes of disease including neuroinflammation, an elevated plasma biomarker of neurodegeneration, and a disease-associated loss of brain mass with aging. From a clinical perspective, these results suggest that TPP1 augmentation could be a viable therapeutic strategy for JNCL and other lysosomal diseases that accumulate SCMAS where addressing the primary defect may be difficult or impossible.
    Keywords:  inherited disease; neurodegeneration; neuronal ceroid lipofuscinosis; subunit c of mitochondrial ATP synthase; tripeptidyl-peptidase 1
    DOI:  https://doi.org/10.1016/j.omtm.2025.101587
  10. Mol Cells. 2025 Oct 03. pii: S1016-8478(25)00108-6. [Epub ahead of print] 100284
      Dual SMAD inhibition is a robust and widely adopted protocol for directing human pluripotent stem cells (hPSCs) toward neuronal lineages by blocking transforming growth factor-beta and bone morphogenetic protein pathways. Suppressing TGF-β and BMP signaling enables efficient and reproducible induction of neuroectoderm, serving as the foundation for generating diverse brain region-specific neuronal subtypes. This review outlines the mechanistic basis and major achievements of the dual SMAD inhibition strategy, including its application in two recent clinical trials for Parkinson's disease, and its role in preclinical studies targeting conditions, such as spinal cord injury, retinal degeneration, and amyotrophic lateral sclerosis. In addition to its significant contribution to the generation of transplantation-ready grafts from hPSCs, the protocol serves as a valuable platform for disease modeling across various neurological and metabolic disorders. The key strengths include high efficiency, technical simplicity that enables precise control of cell fate using small molecules, versatility in both two- and three-dimensional culture systems, and reproducibility across various hPSC lines. This review also addresses key limitations, such as restricted gliogenic capacity and limited neural progenitor cell expansion. Future research should focus on incorporating emerging technologies to advance stem cell-based applications. Overall, dual SMAD inhibition represents a powerful and versatile platform for stem cell-based neuroscience and regenerative medicine.
    Keywords:  Disease modeling; Neuronal differentiation; Regenerative Medicine; Signal pathway; Small molecules for signal pathway control; human pluripotent stem cells
    DOI:  https://doi.org/10.1016/j.mocell.2025.100284
  11. Nat Cell Biol. 2025 Oct 07.
      Organisms must constantly respond to stress to maintain homeostasis, and the successful implementation of cellular stress responses is directly linked to lifespan regulation. In this Review we examine how three age-associated stressors-loss of proteostasis, oxidative damage and dysregulated nutrient sensing-alter protein synthesis. We describe how these stressors inflict cellular damage via their effects on translation and how translational changes can serve as both sensors and responses to the stressor. Finally, we compare stress-induced translational programmes to protein synthesis alterations that occur with age and discuss whether these changes are adaptive or deleterious to longevity and healthy ageing.
    DOI:  https://doi.org/10.1038/s41556-025-01765-z