bims-axbals 2024-09-29 papers

bims-axbals

Biomed News

on Axonal biology and ALS

Issue of 2024–09–29
thirty-six papers selected by
TJ Krzystek, ALS Therapy Development Institute

Poly-GP accumulation due to C9orf72 loss of function induces motor neuron apoptosis through autophagy and mitophagy defects.
TDP-43 nuclear condensation and neurodegenerative proteinopathies.
A guide to selecting high-performing antibodies for Secreted frizzled-related protein 1 (sFRP-1) for use in Western Blot and immunoprecipitation.
The spinal muscular atrophy gene product regulates actin dynamics.
Expanded ATXN1 alters transcription and calcium signaling in SCA1 human motor neurons differentiated from induced pluripotent stem cells.
Morphological multiparameter filtration and persistent homology in mitochondrial image analysis.
Structural and Functional Characterization of the Most Frequent Pathogenic PRKN Substitution p.R275W.
Blood diagnostic and prognostic biomarkers in amyotrophic lateral sclerosis.
KIF5A regulates axonal repair and time-dependent axonal transport of SFPQ granules and mitochondria in human motor neurons.
Mitochondrial protein heterogeneity stems from the stochastic nature of co-translational protein targeting in cell senescence.
Multiple lines of evidence for disruption of nuclear lamina and nucleoporins in FUS amyotrophic lateral sclerosis.
TDP-43 regulates LC3ylation in neural tissue through ATG4B cryptic splicing inhibition.
The Effect of Dipeptide Repeat Proteins on FUS/TDP43-RNA Condensation in C9orf72 ALS/FTD.
Deciphering the Pathophysiological Mechanisms Underpinning Myoclonus Dystonia Using Pluripotent Stem Cell-Derived Cellular Models.
Extracellular vesicle-mediated trafficking of molecular cues during human brain development.
Altered molecular and cellular mechanisms in KIF5A-associated neurodegenerative or neurodevelopmental disorders.
Poly ADP-ribose signaling is dysregulated in Huntington disease.
14-3-3 phosphorylation inhibits 14-3-3θ's ability to regulate LRRK2 kinase activity and toxicity.
Incorporation of decellularized-ECM in graphene-based scaffolds enhances axonal outgrowth and branching in neuro-muscular co-cultures.
Tofersen for SOD1 ALS.
Small Molecular Approaches for Cellular Reprogramming and Tissue Engineering: Functions as Mediators of the Cell Signaling Pathway.
Autism and Intellectual Disability-Associated MYT1L Mutation Alters Human Cortical Interneuron Differentiation, Maturation, and Physiology.
Quality control of mitochondria involves lysosomes in multiple definitive ways.
Decreased SREBP2 of the striatal cell relates to disrupted protein degradation in Huntington's disease.
The Neuroanatomy of Induced Pluripotent Stem Cells: In Vitro Models of Subcortical Nuclei in Neurodegenerative Disorders.
The microtubule regulator EFA-6 forms cortical foci dependent on its intrinsically disordered region and interactions with tubulins.
Unlocking Hope: Therapeutic Advances and Approaches in Modulating the Wnt Pathway for Neurodegenerative Diseases.
Functional Neural Networks in Human Brain Organoids.
Autophagy receptor-inspired chimeras: a novel approach to facilitate the removal of protein aggregates and organelle by autophagy degradation.
A Human Touch: Hominid-Specific LRRC37B Regulates Axon Initial Segment Excitability.
Abnormal synaptic architecture in iPSC-derived neurons from a multi-generational family with genetic Creutzfeldt-Jakob disease.
Extracellular vesicles and their therapeutic applications: a review article (part 2).
"Mitotic" kinesin-5 is a dynamic brake for axonal growth.
Investigating the prevalence of MFN2 mutations in amyotrophic lateral sclerosis: insights from an Italian cohort.
Tracking neurons across days with high-density probes.
LM11a-31 Inhibits p75 Neurotrophin Receptor (p75 NTR ) Cleavage and is Neuroprotective in a Cell Culture Model of Parkinson's Disease.

Autophagy. 2024 Oct;20(10): 2164-2185

Poly-GP accumulation due to C9orf72 loss of function induces motor neuron apoptosis through autophagy and mitophagy defects.

Hortense de Calbiac, Solène Renault, Grégoire Haouy, Vincent Jung, Kevin Roger, Qihui Zhou, Maria-Letizia Campanari, Loïc Chentout, Doris Lou Demy, Anca Marian, Nicolas Goudin, Dieter Edbauer, Chiara Guerrera, Sorana Ciura, Edor Kabashi.

  The GGGGCC hexanucleotide repeat expansion (HRE) of the C9orf72 gene is the most frequent cause of amyotrophic lateral sclerosis (ALS), a devastative neurodegenerative disease characterized by motor neuron degeneration. C9orf72 HRE is associated with lowered levels of C9orf72 expression and its translation results in the production of dipeptide-repeats (DPRs). To recapitulate C9orf72-related ALS disease in vivo, we developed a zebrafish model where we expressed glycine-proline (GP) DPR in a c9orf72 knockdown context. We report that C9orf72 gain- and loss-of-function properties act synergistically to induce motor neuron degeneration and paralysis with poly(GP) accumulating preferentially within motor neurons along with Sqstm1/p62 aggregation indicating macroautophagy/autophagy deficits. Poly(GP) levels were shown to accumulate upon c9orf72 downregulation and were comparable to levels assessed in autopsy samples of patients carrying C9orf72 HRE. Chemical boosting of autophagy using rapamycin or apilimod, is able to rescue motor deficits. Proteomics analysis of zebrafish-purified motor neurons unravels mitochondria dysfunction confirmed through a comparative analysis of previously published C9orf72 iPSC-derived motor neurons. Consistently, 3D-reconstructions of motor neuron demonstrate that poly(GP) aggregates colocalize to mitochondria, thus inducing their elongation and swelling and the failure of their processing by mitophagy, with mitophagy activation through urolithin A preventing locomotor deficits. Finally, we report apoptotic-related increased amounts of cleaved Casp3 (caspase 3, apoptosis-related cysteine peptidase) and rescue of motor neuron degeneration by constitutive inhibition of Casp9 or treatment with decylubiquinone. Here we provide evidence of key pathogenic steps in C9ALS-FTD that can be targeted through pharmacological avenues, thus raising new therapeutic perspectives for ALS patients.

Keywords:  Amyotrophic lateral sclerosis; apoptosis; mitochondria; motor neuron; neurodegeneration; poly-GP

DOI:  https://doi.org/10.1080/15548627.2024.2358736
Trends Neurosci. 2024 Sep 25. pii: S0166-2236(24)00175-9. [Epub ahead of print]

TDP-43 nuclear condensation and neurodegenerative proteinopathies.

Florencia Vassallu, Lionel M Igaz.

  RNA-binding proteins (RBPs) can undergo phase separation and form condensates, processes that, in turn, can be critical for their functionality. In a recent study, Huang, Ellis, and colleagues show that cellular stress can trigger transient alterations in nuclear TAR DNA-binding protein 43 (TDP-43), leading to changes crucial for proper neuronal function. These findings have implications for understanding neurological TDP-43 proteinopathies.

Keywords:  RNA-binding protein; amyotrophic lateral sclerosis; frontotemporal dementia; membraneless organelles; neurodegenerative disease; phase condensation

DOI:  https://doi.org/10.1016/j.tins.2024.09.003
F1000Res. 2023 ;12 291

A guide to selecting high-performing antibodies for Secreted frizzled-related protein 1 (sFRP-1) for use in Western Blot and immunoprecipitation.

NeuroSGC/YCharOS collaborative group

  Secreted frizzled-related protein 1 (sFRP-1) is a secreted protein, belonging to the secreted glycoprotein SFRP family. As a modulator of the Wnt/β-catenin signalling pathway, sFRP-1 has implications in human cancers and neurological diseases. If the community had access to well-characterized anti-sFRP-1 antibodies, the reproducibility of sFRP-1 research would be enhanced. In this study, we characterized 11 sFRP-1 commercial antibodies for Western Blot and immunoprecipitation, using a standardized experimental protocol based on comparing read-outs in knockout cell lines and isogenic parental controls. These studies are part of a larger, collaborative initiative seeking to address the antibody reproducibility issue by characterizing commercially available antibodies for human proteins and publishing the results openly as a resource for the scientific community. While use of antibodies and protocols vary between laboratories, we encourage readers to use this report as a guide to select the most appropriate antibodies for their specific needs.

Keywords:  SFRP1; Secreted frizzled-related protein 1; Uniprot ID Q8N474; Western Blot; antibody characterization; antibody validation; immunoprecipitation

DOI:  https://doi.org/10.12688/f1000research.130991.2
FASEB J. 2024 Sep 30. 38(18): e70055

The spinal muscular atrophy gene product regulates actin dynamics.

Tobias Schüning, Andre Zeug, Katharina Strienke, Peter Franz, Georgios Tsiavaliaris, Niko Hensel, Gabriella Viero, Evgeni Ponimaskin, Peter Claus.

  Spinal Muscular Atrophy (SMA) is a neuromuscular disease caused by low levels of the Survival of Motoneuron (SMN) protein. SMN interacts with and regulates the actin-binding protein profilin2a, thereby influencing actin dynamics. Dysfunctional actin dynamics caused by SMN loss disrupts neurite outgrowth, axonal pathfinding, and formation of functional synapses in neurons. Whether the SMN protein directly interacts with and regulates filamentous (F-) and monomeric globular (G-) actin is still elusive. In a quantitative single cell approach, we show that SMN loss leads to dysregulated F-/G-actin fractions. Furthermore, quantitative assessment of cell morphology suggests an F-actin organizational defect. Interestingly, this is mediated by an interaction of SMN with G- and F-actin. In co-immunoprecipitation, in-vitro pulldown and co-localization assays, we elucidated that this interaction is independent of the SMN-profilin2a interaction. Therefore, we suggest two populations being relevant for functional actin dynamics in healthy neurons: SMN-profilin2a-actin and SMN-actin. Additionally, those two populations may influence each other and therefore regulate binding of SMN to actin. In SMA, we showed a dysregulated co-localization pattern of SMN-actin which could only partially rescued by SMN restoration. However, dysregulation of F-/G-actin fractions was reduced by SMN restoration. Taken together, our results suggest a novel molecular function of SMN in binding to actin independent from SMN-profilin2a interaction.

Keywords:  Survival of Motoneuron (SMN) protein; actin; actin dynamics; profilin2a; spinal muscular atrophy (SMA)

DOI:  https://doi.org/10.1096/fj.202300183R
Neurobiol Dis. 2024 Sep 20. pii: S0969-9961(24)00273-0. [Epub ahead of print] 106673

Expanded ATXN1 alters transcription and calcium signaling in SCA1 human motor neurons differentiated from induced pluripotent stem cells.

Carrie Sheeler, Emmanuel Labrada, Lisa Duvick, Leslie M Thompson, Ying Zhang, Harry T Orr, Marija Cvetanovic.

  Spinocerebellar ataxia type 1 (SCA1) is a dominantly inherited and lethal neurodegenerative disease caused by the abnormal expansion of CAG repeats in the ATAXIN-1 (ATXN1) gene. Pathological studies identified dysfunction and loss of motor neurons (MNs) in the brain stem and spinal cord, which are thought to contribute to premature lethality by affecting the swallowing and breathing of SCA1 patients. However, the molecular and cellular mechanisms of MN pathogenesis remain unknown. To study SCA1 pathogenesis in human MNs, we differentiated induced pluripotent stem cells (iPSCs) derived from SCA1 patients and their unaffected siblings into MNs. We examined proliferation of progenitor cells, neurite outgrowth, spontaneous and glutamate-induced calcium activity of SCA1 MNs to investigate cellular mechanisms of pathogenesis. RNA sequencing was then used to identify transcriptional alterations in iPSC-derived MN progenitors (pMNs) and MNs which could underlie functional changes in SCA1 MNs. We found significantly decreased spontaneous and evoked calcium activity and identified dysregulation of genes regulating calcium signaling in SCA1 MNs. These results indicate that expanded ATXN1 causes dysfunctional calcium signaling in human MNs.

Keywords:  Calcium signaling; Motor neurons; SCA1; Transcription; iPSCs

DOI:  https://doi.org/10.1016/j.nbd.2024.106673
PLoS One. 2024 ;19(9): e0310157

Morphological multiparameter filtration and persistent homology in mitochondrial image analysis.

Yu-Min Chung, Chuan-Shen Hu, Emily Sun, Henry C Tseng.

The complexity of branching and curvilinear morphology of a complete mitochondrial network within each cell is challenging to analyze and quantify. To address this challenge, we developed an image analysis technique using persistent homology with a multiparameter filtration framework, combining image processing techniques in mathematical morphology. We show that such filtrations contain both topological and geometric information about complex cellular organelle structures, which allows a software program to extract meaningful features. Using this information, we also develop a connectivity index that describes the morphology of the branching patterns. As proof of concept, we utilize this approach to study how mitochondrial networks are altered by genetic changes in the Optineurin gene. Mutations in the autophagy gene Optineurin (OPTN) are associated with primary open-angle glaucoma (POAG), amyotrophic lateral sclerosis (ALS), and Paget's disease of the bone, but the pathophysiological mechanism is unclear. We utilized the proposed mathematical morphology-based multiparameter filtration and persistent homology approach to analyze and quantitatively compare how changes in the OPTN gene alter mitochondrial structures from their normal interconnected, tubular morphology into scattered, fragmented pieces.

DOI: https://doi.org/10.1371/journal.pone.0310157
Cells. 2024 Sep 13. pii: 1540. [Epub ahead of print]13(18):

Structural and Functional Characterization of the Most Frequent Pathogenic PRKN Substitution p.R275W.

Bernardo A Bustillos, Liam T Cocker, Mathew A Coban, Caleb A Weber, Jenny M Bredenberg, Paige K Boneski, Joanna Siuda, Jaroslaw Slawek, Andreas Puschmann, Derek P Narendra, Neill R Graff-Radford, Zbigniew K Wszolek, Dennis W Dickson, Owen A Ross, Thomas R Caulfield, Wolfdieter Springer, Fabienne C Fiesel.

  Mutations in the PINK1 and PRKN genes are the most frequent genetic cause of early-onset Parkinson disease. The pathogenic p.R275W substitution in PRKN is the most frequent substitution observed in patients, and thus far has been characterized mostly through overexpression models that suggest a possible gain of toxic misfunction. However, its effects under endogenous conditions are largely unknown. We used patient fibroblasts, isogenic neurons, and post-mortem human brain samples from carriers with and without PRKN p.R275W to assess functional impact. Immunoblot analysis and immunofluorescence were used to study mitophagy activation, and mitophagy execution was analyzed by flow cytometry of the reporter mitoKeima. The functional analysis was accompanied by structural investigation of PRKN p.R275W. We observed lower PRKN protein in fibroblasts with compound heterozygous p.R275W mutations. Isogenic neurons showed an allele-dose dependent decrease in PRKN protein. Lower PRKN protein levels were accompanied by diminished phosphorylated ubiquitin and decreased MFN2 modification. Mitochondrial degradation was also allele-dose dependently impaired. Consistently, PRKN protein levels were drastically reduced in human brain samples from p.R275W carriers. Finally, structural simulations showed significant changes in the closed form of PRKN p.R275W. Our data suggest that under endogenous conditions the p.R275W mutation results in a loss-of-function by destabilizing PRKN.

Keywords:  PINK1; PRKN; Parkinson disease; mitophagy; parkin; ubiquitin

DOI:  https://doi.org/10.3390/cells13181540
Neural Regen Res. 2024 Sep 24.

Blood diagnostic and prognostic biomarkers in amyotrophic lateral sclerosis.

Yongting Lv, Hongfu Li.

Amyotrophic lateral sclerosis is a devastating neurodegenerative disease for which the current treatment approaches remain severely limited. The principal pathological alterations of the disease include the selective degeneration of motor neurons in the brain, brainstem, and spinal cord, as well as abnormal protein deposition in the cytoplasm of neurons and glial cells. The biological markers under extensive scrutiny are predominantly located in the cerebrospinal fluid, blood, and even urine. Among these biomarkers, neurofilament proteins and glial fibrillary acidic protein most accurately reflect the pathologic changes in the central nervous system, while creatinine and creatine kinase mainly indicate pathological alterations in the peripheral nerves and muscles. Neurofilament light chain levels serve as an indicator of neuronal axonal injury that remain stable throughout disease progression and are a promising diagnostic and prognostic biomarker with high specificity and sensitivity. However, there are challenges in using neurofilament light chain to differentiate amyotrophic lateral sclerosis from other central nervous system diseases with axonal injury. Glial fibrillary acidic protein predominantly reflects the degree of neuronal demyelination and is linked to non-motor symptoms of amyotrophic lateral sclerosis such as cognitive impairment, oxygen saturation, and the glomerular filtration rate. TAR DNA-binding protein 43, a pathological protein associated with amyotrophic lateral sclerosis, is emerging as a promising biomarker, particularly with advancements in exosome-related research. Evidence is currently lacking for the value of creatinine and creatine kinase as diagnostic markers; however, they show potential in predicting disease prognosis. Despite the vigorous progress made in the identification of amyotrophic lateral sclerosis biomarkers in recent years, the quest for definitive diagnostic and prognostic biomarkers remains a formidable challenge. This review summarizes the latest research achievements concerning blood biomarkers in amyotrophic lateral sclerosis that can provide a more direct basis for the differential diagnosis and prognostic assessment of the disease beyond a reliance on clinical manifestations and electromyography findings.

DOI: https://doi.org/10.4103/NRR.NRR-D-24-00286
bioRxiv. 2024 Sep 11. pii: 2024.09.06.611684. [Epub ahead of print]

KIF5A regulates axonal repair and time-dependent axonal transport of SFPQ granules and mitochondria in human motor neurons.

Irune Guerra San Juan, Jessie Brunner, Kevin Eggan, Ruud F Toonen, Matthijs Verhage.

Mutations in the microtubule binding motor protein, kinesin family member 5A (KIF5A), cause the fatal motor neuron disease, Amyotrophic Lateral Sclerosis. While KIF5 family members transport a variety of cargos along axons, it is still unclear which cargos are affected by KIF5A mutations. We generated KIF5A null mutant human motor neurons to investigate the impact of KIF5A loss on the transport of various cargoes and its effect on motor neuron function at two different timepoints in vitro. The absence of KIF5A resulted in reduced neurite complexity in young motor neurons (DIV14) and significant defects in axonal regeneration capacity at all developmental stages. KIF5A loss did not affect neurofilament transport but resulted in decreased mitochondria motility and anterograde speed at DIV42. More prominently, KIF5A depletion strongly reduced anterograde transport of SFPQ-associated RNA granules in DIV42 motor neuron axons. We conclude that KIF5A most prominently functions in human motor neurons to promote axonal regrowth after injury as well as to anterogradely transport mitochondria and, to a larger extent, SFPQ-associated RNA granules in a time-dependent manner.

DOI: https://doi.org/10.1101/2024.09.06.611684
Nat Commun. 2024 Sep 27. 15(1): 8274

Mitochondrial protein heterogeneity stems from the stochastic nature of co-translational protein targeting in cell senescence.

Abdul Haseeb Khan, Xuefang Gu, Rutvik J Patel, Prabha Chuphal, Matheus P Viana, Aidan I Brown, Brian M Zid, Tatsuhisa Tsuboi.

A decline in mitochondrial function is a hallmark of aging and neurodegenerative diseases. It has been proposed that changes in mitochondrial morphology, including fragmentation of the tubular mitochondrial network, can lead to mitochondrial dysfunction, yet the mechanism of this loss of function is unclear. Most proteins contained within mitochondria are nuclear-encoded and must be properly targeted to the mitochondria. Here, we report that sustained mRNA localization and co-translational protein delivery leads to a heterogeneous protein distribution across fragmented mitochondria. We find that age-induced mitochondrial fragmentation drives a substantial increase in protein expression noise across fragments. Using a translational kinetic and molecular diffusion model, we find that protein expression noise is explained by the nature of stochastic compartmentalization and that co-translational protein delivery is the main contributor to increased heterogeneity. We observed that cells primarily reduce the variability in protein distribution by utilizing mitochondrial fission-fusion processes rather than relying on the mitophagy pathway. Furthermore, we are able to reduce the heterogeneity of the protein distribution by inhibiting co-translational protein targeting. This research lays the framework for a better understanding of the detrimental impact of mitochondrial fragmentation on the physiology of cells in aging and disease.

DOI: https://doi.org/10.1038/s41467-024-52183-y
Brain. 2024 Sep 23. pii: awae224. [Epub ahead of print]

Multiple lines of evidence for disruption of nuclear lamina and nucleoporins in FUS amyotrophic lateral sclerosis.

Kensuke Okada, Daisuke Ito, Satoru Morimoto, Chris Kato, Yuki Oguma, Hitoshi Warita, Naoki Suzuki, Masashi Aoki, Junko Kuramoto, Reona Kobayashi, Munehisa Shinozaki, Masahito Ikawa, Jin Nakahara, Shinichi Takahashi, Yoshinori Nishimoto, Shinsuke Shibata, Hideyuki Okano.

  Advanced pathological and genetic approaches have revealed that mutations in fused in sarcoma/translated in liposarcoma (FUS/TLS), which is pivotal for DNA repair, alternative splicing, translation and RNA transport, cause familial amyotrophic lateral sclerosis (ALS). The generation of suitable animal models for ALS is essential for understanding its pathogenesis and developing therapies. Therefore, we used CRISPR-Cas9 to generate FUS-ALS mutation in the non-classical nuclear localization signal (NLS), H517D (mouse position: H509D) and genome-edited mice. Fus WT/H509D mice showed progressive motor impairment (accelerating rotarod and DigiGait system) with age, which was associated with the loss of motor neurons and disruption of the nuclear lamina and nucleoporins and DNA damage in spinal cord motor neurons. We confirmed the validity of our model by showing that nuclear lamina and nucleoporin disruption were observed in lower motor neurons differentiated from patient-derived human induced pluripotent stem cells (hiPSC-LMNs) with FUS-H517D and in the post-mortem spinal cord of patients with ALS. RNA sequence analysis revealed that most nuclear lamina and nucleoporin-linking genes were significantly decreased in FUS-H517D hiPSC-LMNs. This evidence suggests that disruption of the nuclear lamina and nucleoporins is crucial for ALS pathomechanisms. Combined with patient-derived hiPSC-LMNs and autopsy samples, this mouse model might provide a more reliable understanding of ALS pathogenesis and might aid in the development of therapeutic strategies.

Keywords:  FUS; amyotrophic lateral sclerosis; nuclear lamina; nuclear pore complex

DOI:  https://doi.org/10.1093/brain/awae224
Acta Neuropathol. 2024 Sep 21. 148(1): 45

TDP-43 regulates LC3ylation in neural tissue through ATG4B cryptic splicing inhibition.

Pascual Torres, Santiago Rico-Rios, Miriam Ceron-Codorniu, Marta Santacreu-Vilaseca, David Seoane-Miraz, Yahya Jad, Victòria Ayala, Guillermo Mariño, Maria Beltran, Maria P Miralles, Pol Andrés-Benito, Joaquin Fernandez-Irigoyen, Enrique Santamaria, Carlos López-Otín, Rosa M Soler, Monica Povedano, Isidro Ferrer, Reinald Pamplona, Matthew J A Wood, Miguel A Varela, Manuel Portero-Otin.

  Amyotrophic lateral sclerosis (ALS) is an adult-onset motor neuron disease with a mean survival time of three years. The 97% of the cases have TDP-43 nuclear depletion and cytoplasmic aggregation in motor neurons. TDP-43 prevents non-conserved cryptic exon splicing in certain genes, maintaining transcript stability, including ATG4B, which is crucial for autophagosome maturation and Microtubule-associated proteins 1A/1B light chain 3B (LC3B) homeostasis. In ALS mice (G93A), Atg4b depletion worsens survival rates and autophagy function. For the first time, we observed an elevation of LC3ylation in the CNS of both ALS patients and atg4b-/- mouse spinal cords. Furthermore, LC3ylation modulates the distribution of ATG3 across membrane compartments. Antisense oligonucleotides (ASOs) targeting cryptic exon restore ATG4B mRNA in TARDBP knockdown cells. We further developed multi-target ASOs targeting TDP-43 binding sequences for a broader effect. Importantly, our ASO based in peptide-PMO conjugates show brain distribution post-IV administration, offering a non-invasive ASO-based treatment avenue for neurodegenerative diseases.

Keywords:  ALS; Antisense oligonucleotides; Autophagy; Digital PCR; Post-translational modification

DOI:  https://doi.org/10.1007/s00401-024-02780-4
J Phys Chem B. 2024 Sep 23.

The Effect of Dipeptide Repeat Proteins on FUS/TDP43-RNA Condensation in C9orf72 ALS/FTD.

Mark D Driver, Jasper Postema, Patrick R Onck.

Condensation of RNA binding proteins (RBPs) with RNA is essential for cellular function. The most common familial cause of the diseases ALS and FTD is C9orf72 repeat expansion disorders that produce dipeptide repeat proteins (DPRs). We explore the hypothesis that DPRs disrupt the native condensation behavior of RBPs and RNA through molecular interactions resulting in toxicity. FUS and TDP43 are two RBPs known to be affected in ALS/FTD. We use our previously developed 1-bead-per-amino acid and a newly developed 3-bead-per-nucleotide molecular dynamics model to explore ternary phase diagrams of FUS/TDP43-RNA-DPR systems. We show that the most toxic arginine containing DPRs (R-DPRs) can disrupt the RBP condensates through cation-π interactions and can strongly sequester RNA through electrostatic interactions. The native droplet morphologies are already modified at small additions of R-DPRs leading to non-native FUS/TDP43-encapsulated condensates with a marbled RNA/DPR core.

DOI: https://doi.org/10.1021/acs.jpcb.4c04663
Cells. 2024 Sep 10. pii: 1520. [Epub ahead of print]13(18):

Deciphering the Pathophysiological Mechanisms Underpinning Myoclonus Dystonia Using Pluripotent Stem Cell-Derived Cellular Models.

Zongze Li, Laura Abram, Kathryn J Peall.

  Dystonia is a movement disorder with an estimated prevalence of 1.2% and is characterised by involuntary muscle contractions leading to abnormal postures and pain. Only symptomatic treatments are available with no disease-modifying or curative therapy, in large part due to the limited understanding of the underlying pathophysiology. However, the inherited monogenic forms of dystonia provide an opportunity for the development of disease models to examine these mechanisms. Myoclonus Dystonia, caused by SGCE mutations encoding the ε-sarcoglycan protein, represents one of now >50 monogenic forms. Previous research has implicated the involvement of the basal ganglia-cerebello-thalamo-cortical circuit in dystonia pathogenesis, but further work is needed to understand the specific molecular and cellular mechanisms. Pluripotent stem cell technology enables a patient-derived disease modelling platform harbouring disease-causing mutations. In this review, we discuss the current understanding of the aetiology of Myoclonus Dystonia, recent advances in producing distinct neuronal types from pluripotent stem cells, and their application in modelling Myoclonus Dystonia in vitro. Future research employing pluripotent stem cell-derived cellular models is crucial to elucidate how distinct neuronal types may contribute to dystonia and how disruption to neuronal function can give rise to dystonic disorders.

Keywords:  Myoclonus Dystonia; SGCE; disease modelling; dystonia; epsilon-sarcoglycan; pathogenesis; pluripotent stem cell

DOI:  https://doi.org/10.3390/cells13181520
Cell Rep. 2024 Sep 18. pii: S2211-1247(24)01106-9. [Epub ahead of print]43(10): 114755

Extracellular vesicle-mediated trafficking of molecular cues during human brain development.

Andrea Forero, Fabrizia Pipicelli, Sylvain Moser, Natalia Baumann, Christian Grätz, Mariano Gonzalez Pisfil, Michael W Pfaffl, Benno Pütz, Pavel Kielkowski, Filippo M Cernilogar, Giuseppina Maccarrone, Rossella Di Giaimo, Silvia Cappello.

  Cellular crosstalk is an essential process influenced by numerous factors, including secreted vesicles that transfer nucleic acids, lipids, and proteins between cells. Extracellular vesicles (EVs) have been the center of many studies focusing on neurodegenerative disorders, but whether EVs display cell-type-specific features for cellular crosstalk during neurodevelopment is unknown. Here, using human-induced pluripotent stem cell-derived cerebral organoids, neural progenitors, neurons, and astrocytes, we identify heterogeneity in EV protein content and dynamics in a cell-type-specific and time-dependent manner. Our results support the trafficking of key molecules via EVs in neurodevelopment, such as the transcription factor YAP1, and their localization to differing cell compartments depending on the EV recipient cell type. This study sheds new light on the biology of EVs during human brain development.

Keywords:  CP: Developmental biology; CP: Neuroscience; cerebral organoids; extracellular vesicle; neurodevelopment

DOI:  https://doi.org/10.1016/j.celrep.2024.114755
Cell Death Dis. 2024 Sep 27. 15(9): 692

Altered molecular and cellular mechanisms in KIF5A-associated neurodegenerative or neurodevelopmental disorders.

Marta Cozzi, Stefania Magri, Barbara Tedesco, Guglielmo Patelli, Veronica Ferrari, Elena Casarotto, Marta Chierichetti, Paola Pramaggiore, Laura Cornaggia, Margherita Piccolella, Mariarita Galbiati, Paola Rusmini, Valeria Crippa, Jessica Mandrioli, Davide Pareyson, Chiara Pisciotta, Stefano D'Arrigo, Antonia Ratti, Lorenzo Nanetti, Caterina Mariotti, Elisa Sarto, Viviana Pensato, Cinzia Gellera, Daniela Di Bella, Riccardo M Cristofani, Franco Taroni, Angelo Poletti.

Mutations targeting distinct domains of the neuron-specific kinesin KIF5A associate with different neurodegenerative/neurodevelopmental disorders, but the molecular bases of this clinical heterogeneity are unknown. We characterised five key mutants covering the whole spectrum of KIF5A-related phenotypes: spastic paraplegia (SPG, R17Q and R280C), Charcot-Marie-Tooth disease (CMT, R864*), amyotrophic lateral sclerosis (ALS, N999Vfs*40), and neonatal intractable myoclonus (NEIMY, C975Vfs*73) KIF5A mutants. CMT-R864*-KIF5A and ALS-N999Vfs*40-KIF5A showed impaired autoinhibition and peripheral localisation accompanied by altered mitochondrial distribution, suggesting transport competence disruption. ALS-N999Vfs*40-KIF5A formed SQSTM1/p62-positive inclusions sequestering WT-KIF5A, indicating a gain of toxic function. SPG-R17Q-KIF5A and ALS-N999Vfs*40-KIF5A evidenced a shorter half-life compared to WT-KIF5A, and proteasomal blockage determined their accumulation into detergent-insoluble inclusions. Interestingly, SPG-R280C-KIF5A and ALS-N999Vfs*40-KIF5A both competed for degradation with proteasomal substrates. Finally, NEIMY-C975Vfs*73-KIF5A displayed a similar, but more severe aberrant behaviour compared to ALS-N999Vfs*40-KIF5A; these two mutants share an abnormal tail but cause disorders on the opposite end of KIF5A-linked phenotypic spectrum. Thus, our observations support the pathogenicity of novel KIF5A mutants, highlight abnormalities of recurrent variants, and demonstrate that both unique and shared mechanisms underpin KIF5A-related diseases.

DOI: https://doi.org/10.1038/s41419-024-07096-5
Proc Natl Acad Sci U S A. 2024 Oct;121(40): e2318098121

Poly ADP-ribose signaling is dysregulated in Huntington disease.

Tamara Maiuri, Carlos Barba Bazan, Rachel J Harding, Nola Begeja, Tae-In Kam, Lauren M Byrne, Filipe B Rodrigues, Monica M Warner, Kaitlyn Neuman, Muqtasid Mansoor, Mohsen Badiee, Morgan Dasovich, Keona Wang, Leslie M Thompson, Anthony K L Leung, Sara N Andres, Edward J Wild, Ted M Dawson, Valina L Dawson, Cheryl H Arrowsmith, Ray Truant.

  Huntington disease (HD) is a genetic neurodegenerative disease caused by cytosine, adenine, guanine (CAG) expansion in the Huntingtin (HTT) gene, translating to an expanded polyglutamine tract in the HTT protein. Age at disease onset correlates to CAG repeat length but varies by decades between individuals with identical repeat lengths. Genome-wide association studies link HD modification to DNA repair and mitochondrial health pathways. Clinical studies show elevated DNA damage in HD, even at the premanifest stage. A major DNA repair node influencing neurodegenerative disease is the PARP pathway. Accumulation of poly adenosine diphosphate (ADP)-ribose (PAR) has been implicated in Alzheimer and Parkinson diseases, as well as cerebellar ataxia. We report that HD mutation carriers have lower cerebrospinal fluid PAR levels than healthy controls, starting at the premanifest stage. Human HD induced pluripotent stem cell-derived neurons and patient-derived fibroblasts have diminished PAR response in the context of elevated DNA damage. We have defined a PAR-binding motif in HTT, detected HTT complexed with PARylated proteins in human cells during stress, and localized HTT to mitotic chromosomes upon inhibition of PAR degradation. Direct HTT PAR binding was measured by fluorescence polarization and visualized by atomic force microscopy at the single molecule level. While wild-type and mutant HTT did not differ in their PAR binding ability, purified wild-type HTT protein increased in vitro PARP1 activity while mutant HTT did not. These results provide insight into an early molecular mechanism of HD, suggesting possible targets for the design of early preventive therapies.

Keywords:  Huntington’s disease; PARP1; PARylation; huntingtin; poly ADP-ribose

DOI:  https://doi.org/10.1073/pnas.2318098121
Hum Mol Genet. 2024 Sep 26. pii: ddae142. [Epub ahead of print]

14-3-3 phosphorylation inhibits 14-3-3θ's ability to regulate LRRK2 kinase activity and toxicity.

Rudradip Pattanayak, Roschongporn Ekkatine, Chad M Petit, Talene A Yacoubian.

  LRRK2 mutations are among the most common genetic causes for Parkinson's disease (PD), and toxicity is associated with increased kinase activity. 14-3-3 proteins are key interactors that regulate LRRK2 kinase activity. Phosphorylation of the 14-3-3θ isoform at S232 is dramatically increased in human PD brains. Here we investigate the impact of 14-3-3θ phosphorylation on its ability to regulate LRRK2 kinase activity. Both wildtype and the non-phosphorylatable S232A 14-3-3θ mutant reduced the kinase activity of wildtype and G2019S LRRK2, whereas the phosphomimetic S232D 14-3-3θ mutant had minimal effects on LRRK2 kinase activity, as determined by measuring autophosphorylation at S1292 and T1503 and Rab10 phosphorylation. However, wildtype and both 14-3-3θ mutants similarly reduced the kinase activity of the R1441G LRRK2 mutant. 14-3-3θ phosphorylation did not promote global dissociation with LRRK2, as determined by co-immunoprecipitation and proximal ligation assays. 14-3-3s interact with LRRK2 at several phosphorylated serine/threonine sites, including T2524 in the C-terminal helix, which can fold back to regulate the kinase domain. Interaction between 14-3-3θ and phosphorylated T2524 LRRK2 was important for 14-3-3θ's ability to regulate kinase activity, as wildtype and S232A 14-3-3θ failed to reduce the kinase activity of G2019S/T2524A LRRK2. Finally, we found that the S232D mutation failed to protect against G2019S LRRK2-induced neurite shortening in primary cultures, while the S232A mutation was protective. We conclude that 14-3-3θ phosphorylation destabilizes the interaction of 14-3-3θ with LRRK2 at T2524, which consequently promotes LRRK2 kinase activity and toxicity.

Keywords:  14-3-3θ; G2019S LRRK2; Parkinson’s disease; kinase activity; neurite length

DOI:  https://doi.org/10.1093/hmg/ddae142
Sci Prog. 2024 Jul-Sep;107(3):107(3): 368504241281469

Incorporation of decellularized-ECM in graphene-based scaffolds enhances axonal outgrowth and branching in neuro-muscular co-cultures.

Carlos Serna, Kirtana Sandepudi, Rebecca L Keate, Sophia L Zhang, Kristen Y Cotton, Alberto De La Isla, Matias Murillo, Yasmine Bouricha, Andrea A Domenighetti, Colin K Franz, Sumanas W Jordan.

  Peripheral nerve and large-scale muscle injuries result in significant disability, necessitating the development of biomaterials that can restore functional deficits by promoting tissue regrowth in an electroactive environment. Among these materials, graphene is favored for its high conductivity, but its low bioactivity requires enhancement through biomimetic components. In this study, we extrusion printed graphene-poly(lactide-co-glycolide) (graphene) lattice scaffolds, aiming to increase bioactivity by incorporating decellularized extracellular matrix (dECM) derived from mouse pup skeletal muscle. We first evaluated these scaffolds using human-induced pluripotent stem cell (hiPSC)-derived motor neurons co-cultured with supportive glia, observing significant improvements in axon outgrowth. Next, we tested the scaffolds with C2C12 mouse and human primary myoblasts, finding no significant differences in myotube formation between dECM-graphene and graphene scaffolds. Finally, using a more complex hiPSC-derived 3D motor neuron spheroid model co-cultured with human myoblasts, we demonstrated that dECM-graphene scaffolds significantly improved axonal expansion towards peripheral myoblasts and increased axonal network density compared to graphene-only scaffolds. Features of early neuromuscular junction formation were identified near neuromuscular interfaces in both scaffold types. These findings suggest that dECM-graphene scaffolds are promising candidates for enhancing neuromuscular regeneration, offering robust support for the growth and development of diverse neuromuscular tissues.

Keywords:  Graphene; co-culture; extracellular matrix; neuromuscular regeneration

DOI:  https://doi.org/10.1177/00368504241281469
Neurodegener Dis Manag. 2024 Sep 27. 1-12

Tofersen for SOD1 ALS.

William H Everett, Robert C Bucelli.

  Amyotrophic lateral sclerosis (ALS) is a neurodegenerative condition affecting the motor system. The heterogenous nature of ALS complicates trial design. Genetic forms of ALS present an opportunity to intervene in a less heterogeneous population. ALS associated with gain of function mutations in SOD1 make 'knock-down' strategies an attractive therapeutic approach. Tofersen, an antisense oligonucleotide that reduces expression of SOD1 via RNAase mediated degradation of SOD1 mRNA, has shown robust effects on ALS biomarkers. While a Phase III trial of tofersen failed to meet its primary end point, open label extension data suggests that tofersen slows progression of SOD1 ALS.

Keywords:  MRNA degradation; SOD1; amyotrophic lateral sclerosis; antisense oligonucleotide; edaravone; riluzole; sodium phenylbutyrate-taurursodiol; tofersen

DOI:  https://doi.org/10.1080/17582024.2024.2402216
Biochemistry. 2024 Sep 23.

Small Molecular Approaches for Cellular Reprogramming and Tissue Engineering: Functions as Mediators of the Cell Signaling Pathway.

Bhagyesh Parmar, Dhiraj Bhatia.

  Utilizing induced pluripotent stem cells (iPSCs) in drug screening and cell replacement therapy has emerged as a method with revolutionary applications. With the advent of patient-specific iPSCs and the subsequent development of cells that exhibit disease phenotypes, the focus of medication research will now shift toward the pathology of human diseases. Regular iPSCs can also be utilized to generate cells that assess the negative impacts of medications. These cells provide a much more precise and cost-efficient approach compared to many animal models. In this review, we explore the utilization of small-molecule drugs to enhance the growth of iPSCs and gain insights into the process of reprogramming. We mainly focus on the functions of small molecules in modulating different signaling pathways, thereby modulating cell fate. Understanding the way small molecule drugs interact with iPSC technology has the potential to significantly enhance the understanding of physiological pathways in stem cells and practical applications of iPSC-based therapy and screening systems, revolutionizing the treatment of diseases.

Keywords:  iPSC-based therapy; phenotypes; small-molecule drugs; stem cells

DOI:  https://doi.org/10.1021/acs.biochem.4c00427
bioRxiv. 2024 Sep 12. pii: 2024.09.11.612541. [Epub ahead of print]

Autism and Intellectual Disability-Associated MYT1L Mutation Alters Human Cortical Interneuron Differentiation, Maturation, and Physiology.

Ramachandran Prakasam, Julianna Determan, Mishka Narasimhan, Renata Shen, Maamoon Saleh, Gareth Chapman, Komal Kaushik, Paul Gontarz, Kesavan Meganathan, Bilal Hakim, Bo Zhang, James E Huettner, Kristen L Kroll.

MYT1L is a neuronal transcription factor highly expressed in the developing and adult brain. While pathogenic MYT1L mutation causes neurodevelopmental disorders, these have not been characterized in human models of neurodevelopment. Here, we defined the consequences of pathogenic MYT1L mutation in human pluripotent stem cell-derived cortical interneurons. During differentiation, mutation reduced MYT1L expression and increased progenitor cell cycle exit and neuronal differentiation and synapse-related gene expression, morphological complexity, and synaptic puncta formation. Conversely, interneuron maturation was compromised, while variant neurons exhibited altered sodium and potassium channel activity and reduced function in electrophysiological analyses. CRISPRi-based knockdown similarly impaired interneuron differentiation and maturation, supporting loss of function-based effects. We further defined MYT1L genome-wide occupancy in interneurons and related this to the transcriptomic dysregulation resulting from MYT1L mutation, to identify direct targets that could mediate these phenotypic consequences. Together, this work delineates contributors to the etiology of neurodevelopmental disorders resulting from MYT1L mutation.

DOI: https://doi.org/10.1101/2024.09.11.612541
Autophagy. 2024 Sep 26.

Quality control of mitochondria involves lysosomes in multiple definitive ways.

Xiaowen Ma, Wen-Xing Ding.

  Mitochondria are crucial organelles in maintaining cellular homeostasis. They are involved in processes such as energy production, metabolism of lipids and glucose, and cell death regulation. Mitochondrial dysfunction can lead to various health issues such as aging, cancer, neurodegenerative diseases, and chronic liver diseases. While mitophagy is the main process for getting rid of excess or damaged mitochondria, there are additional mechanisms for preserving mitochondrial quality. One such alternative mechanism we have discovered is a hybrid organelle called mitochondrial-lysosome-related-organelle (MLRO), which functions independently of the typical autophagy process. More recently, another type of vesicle called vesicle derived from the inner mitochondrial membrane (VDIM) has been identified to break down the inner mitochondrial membrane without involving the standard autophagy pathway. In this article, we will delve into the similarities and differences between MLRO and VDIM, including their structure, regulation, and relevance to human diseases.

Keywords:  Autophagy; DNM1L/DRP1; MLRO; VDIM; mitophagy

DOI:  https://doi.org/10.1080/15548627.2024.2408712
Brain Res. 2024 Sep 21. pii: S0006-8993(24)00504-3. [Epub ahead of print]1846 149250

Decreased SREBP2 of the striatal cell relates to disrupted protein degradation in Huntington's disease.

Kyoungjoo Cho, Gyung Whan Kim.

  This study delineated the intricate relation between cholesterol metabolism, protein degradation mechanisms, and the pathogenesis of Huntington's disease (HD). Through investigations using both animal models and cellular systems, we have observed significant alterations in cholesterol levels, particularly in the striatum, which is the primary lesion site in HD. Our findings indicate the dysregulation of cholesterol metabolism-related factors, such as LDLR and SREBP2, in HD, which may contribute to disease progression. Additionally, we uncovered disruptions in protein degradation pathways, including decreased neddylated proteins and dysregulated autophagy, which further exacerbated HD pathology. Moreover, our study highlighted the potential therapeutic implications of targeting these pathways. By restoring cholesterol levels and modulating protein degradation mechanisms, particularly through interventions, such as MLN4924, we observed potential improvements in cellular function, as indicated by the increased BDNF levels. These insights underscore the importance of simultaneously addressing cholesterol metabolism and protein degradation to alleviate HD pathology. Collectively, this study provides a basic understanding of the interplay between the decrease of SREBP2 and the dysfunctional protein degradation system derived from disrupted cholesterol metabolism in HD and HD cells.

Keywords:  Cholesterol; Huntington’s disease; Neddylation; Protein degradation; SREBP2

DOI:  https://doi.org/10.1016/j.brainres.2024.149250
Curr Issues Mol Biol. 2024 Sep 14. 46(9): 10180-10199

The Neuroanatomy of Induced Pluripotent Stem Cells: In Vitro Models of Subcortical Nuclei in Neurodegenerative Disorders.

Alessandro Galgani, Marco Scotto, Filippo S Giorgi.

  Neuromodulatory subcortical systems (NSSs) are monoaminergic and cholinergic neuronal groups that are markedly and precociously involved in the pathogenesis of many neurodegenerative disorders (NDDs), including Parkinson's and Alzheimer's diseases. In humans, although many tools have been developed to infer information on these nuclei, encompassing neuroimaging and neurophysiological methods, a detailed and specific direct evaluation of their cellular features in vivo has been difficult to obtain until recent years. The development of induced pluripotent stem cell (iPSC) models has allowed research to deeply delve into the cellular and molecular biology of NSS neurons. In fact, iPSCs can be produced easily and non-invasively from patients' fibroblasts or circulating blood monocytes, by de-differentiating those cells using specific protocols, and then be re-differentiated towards neural phenotypes, which may reproduce the specific features of the correspondent brain neurons (including NSS ones) from the same patient. In this review, we summarized findings obtained in the field of NDDs using iPSCs, with the aim to understand how reliably these might represent in vitro models of NSS. We found that most of the current literature in the field of iPSCs and NSSs in NDDs has focused on midbrain dopaminergic neurons in Parkinson's disease, providing interesting results on cellular pathophysiology and even leading to the first human autologous transplantation. Differentiation protocols for noradrenergic, cholinergic, and serotoninergic neurons have also been recently defined and published. Thus, it might be expected that in the near future, this approach could extend to other NSSs and other NDDs.

Keywords:  Alzheimer’s disease; Parkinson’s disease; acetylcholine; dopamine; induced pluripotent stem cells; neurodegeneration; noradrenaline; serotonin

DOI:  https://doi.org/10.3390/cimb46090607
Cell Rep. 2024 Sep 20. pii: S2211-1247(24)01127-6. [Epub ahead of print]43(10): 114776

The microtubule regulator EFA-6 forms cortical foci dependent on its intrinsically disordered region and interactions with tubulins.

Anjali Sandhu, Xiaohui Lyu, Xinghaoyun Wan, Xuefeng Meng, Ngang Heok Tang, Gilberto Gonzalez, Ishana N Syed, Lizhen Chen, Yishi Jin, Andrew D Chisholm.

  The EFA6 protein family, originally identified as Sec7 guanine nucleotide exchange factors, has also been found to regulate cortical microtubule (MT) dynamics. Here, we find that in the mature C. elegans epidermal epithelium, EFA-6 forms punctate foci in specific regions of the apical cortex, dependent on its intrinsically disordered region (IDR). The EFA-6 IDR can form biomolecular condensates in vitro. In genetic screens for mutants with altered GFP::EFA-6 localization, we identified a gain-of-function (gf) mutation in α-tubulin tba-1 that induces ectopic EFA-6 foci in multiple cell types. Lethality of tba-1(gf) is partially suppressed by loss of function in efa-6. The ability of TBA-1(gf) to trigger ectopic EFA-6 foci requires β-tubulin TBB-2 and the chaperon EVL-20/Arl2. tba-1(gf)-induced EFA-6 foci display slower turnover, contain the MT-associated protein TAC-1/TACC, and require the EFA-6 MT elimination domain (MTED). Our results reveal functionally important crosstalk between cellular tubulins and cortical MT regulators in vivo.

Keywords:  CP: Cell biology; TACC; biomolecular condensates; cortical cytoskeleton; epidermis; microtubule; tubulin heterodimer

DOI:  https://doi.org/10.1016/j.celrep.2024.114776
Mol Neurobiol. 2024 Sep 23.

Unlocking Hope: Therapeutic Advances and Approaches in Modulating the Wnt Pathway for Neurodegenerative Diseases.

Navid Faraji, Negar Ebadpour, Mohammad Abavisani, Ali Gorji.

  Neurodegenerative diseases (NDs) are conditions characterized by sensory, motor, and cognitive impairments due to alterations in the structure and function of neurons in the central nervous system (CNS). Despite their widespread occurrence, the exact causes of NDs remain largely elusive, and existing treatments fall short in efficacy. The Wnt signaling pathway is an emerging molecular pathway that has been linked to the development and progression of various NDs. Wnt signaling governs numerous cellular processes, such as survival, polarity, proliferation, differentiation, migration, and fate specification, via a complex network of proteins. In the adult CNS, Wnt signaling regulates synaptic transmission, plasticity, memory formation, neurogenesis, neuroprotection, and neuroinflammation, all essential for maintaining neuronal function and integrity. Dysregulation of both canonical and non-canonical Wnt signaling pathways contributes to neurodegeneration through various mechanisms, such as amyloid-β accumulation, tau protein hyperphosphorylation, dopaminergic neuron degeneration, and synaptic dysfunction, prompting investigations into Wnt modulation as a therapeutic target to restore neuronal function and prevent or delay neurodegenerative processes. Modulating Wnt signaling has the potential to restore neuronal function and impede or postpone neurodegenerative processes, offering a therapeutic approach for targeting NDs. In this article, the current knowledge about how Wnt signaling works in Alzheimer's disease and Parkinson's disease is discussed. Our study aims to explore the molecular mechanisms, recent discoveries, and challenges involved in developing Wnt-based therapies.

Keywords:  Alzheimer’s disease; Molecular targeted therapy; Neurodegeneration; Parkinson’s disease; Wnt signaling pathway

DOI:  https://doi.org/10.1007/s12035-024-04462-4
BME Front. 2024 ;5 0065

Functional Neural Networks in Human Brain Organoids.

Longjun Gu, Hongwei Cai, Lei Chen, Mingxia Gu, Jason Tchieu, Feng Guo.

Human brain organoids are 3-dimensional brain-like tissues derived from human pluripotent stem cells and hold promising potential for modeling neurological, psychiatric, and developmental disorders. While the molecular and cellular aspects of human brain organoids have been intensively studied, their functional properties such as organoid neural networks (ONNs) are largely understudied. Here, we summarize recent research advances in understanding, characterization, and application of functional ONNs in human brain organoids. We first discuss the formation of ONNs and follow up with characterization strategies including microelectrode array (MEA) technology and calcium imaging. Moreover, we highlight recent studies utilizing ONNs to investigate neurological diseases such as Rett syndrome and Alzheimer's disease. Finally, we provide our perspectives on the future challenges and opportunities for using ONNs in basic research and translational applications.

DOI: https://doi.org/10.34133/bmef.0065
J Zhejiang Univ Sci B. 2024 Sep 26. 1-5

Autophagy receptor-inspired chimeras: a novel approach to facilitate the removal of protein aggregates and organelle by autophagy degradation.

Liwen Wang, Huimei Liu, Lanfang Li.

Neurodegenerative diseases (NDDs), mainly including Huntington's disease (HD), amyotrophic lateral sclerosis (ALS), and Alzheimer's disease (AD), are sporadic and rare genetic disorders of the central nervous system. A key feature of these conditions is the slow accumulation of misfolded protein deposits in brain neurons, the excessive aggregation of which leads to neurotoxicity and further disorders of the nervous system.

DOI: https://doi.org/10.1631/jzus.B2300853
Epilepsy Curr. 2024 Jul-Aug;24(4):24(4): 286-288

A Human Touch: Hominid-Specific LRRC37B Regulates Axon Initial Segment Excitability.

Ania K Dabrowski, Ethan M Goldberg.

DOI: https://doi.org/10.1177/15357597241253683
Stem Cell Reports. 2024 Sep 12. pii: S2213-6711(24)00249-2. [Epub ahead of print]

Abnormal synaptic architecture in iPSC-derived neurons from a multi-generational family with genetic Creutzfeldt-Jakob disease.

Aldana D Gojanovich, Nhat T T Le, Robert C C Mercer, Seonmi Park, Bei Wu, Alice Anane, Janelle S Vultaggio, Gustavo Mostoslavsky, David A Harris.

  Genetic prion diseases are caused by mutations in PRNP, which encodes the prion protein (PrPC). Why these mutations are pathogenic, and how they alter the properties of PrPC are poorly understood. We have consented and accessed 22 individuals of a multi-generational Israeli family harboring the highly penetrant E200K PRNP mutation and generated a library of induced pluripotent stem cells (iPSCs) representing nine carriers and four non-carriers. iPSC-derived neurons from E200K carriers display abnormal synaptic architecture characterized by misalignment of postsynaptic NMDA receptors with the cytoplasmic scaffolding protein PSD95. Differentiated neurons from mutation carriers do not produce PrPSc, the aggregated and infectious conformer of PrP, suggesting that loss of a physiological function of PrPC may contribute to the disease phenotype. Our study shows that iPSC-derived neurons can provide important mechanistic insights into the pathogenesis of genetic prion diseases and can offer a powerful platform for testing candidate therapeutics.

Keywords:  E200K; PrP; PrPSc; genetic prion disease; iPSC; neurodegeneration; prion; prion disease; synapse

DOI:  https://doi.org/10.1016/j.stemcr.2024.08.010
Int J Physiol Pathophysiol Pharmacol. 2024 ;16(4): 81-88

Extracellular vesicles and their therapeutic applications: a review article (part 2).

Diana Rafieezadeh.

  Extracellular vesicles (EVs) have emerged as a fascinating area of research in molecular biology, with diverse therapeutic applications. These small membrane-bound structures, released by cells into the extracellular space, play a crucial role in intercellular communication and hold great potential for advancing medical treatments. The aim of this study is to have a narrative review on the use and therapeutic applications of EVs. Their unique characteristics, including stability, biocompatibility, and the ability to traverse biological barriers, make them promising tools for targeted drug delivery. By engineering EVs to encapsulate specific cargo molecules, such as therapeutic proteins, small interfering RNA (siRNA), or anti-cancer drugs, researchers can enhance drug stability and improve targeted delivery to desired cells or tissues. This approach can minimize off-target effects and improve therapeutic efficacy. Based on our literature search, we found that EVs can be used as biomarkers to predict diseases. Although much progress has been made in understanding the biology and function of exosomes, there are still unanswered questions that require further research. This includes identifying appropriate and safe techniques for producing exosomes in large quantities, determining which types of cells are suitable for exosome donor cells for therapeutic purposes, and investigating the safety of exosomes in human studies. Overall, the use of exosomes in clinical therapeutic applications requires a strong understanding of molecular signaling cascades and exosome profiles, as well as the specificity and sensitivity of biomarker and drug delivery methods.

Keywords:  Extracellular vesicles (EVs); exosomes; intercellular communication; regenerative medicine; targeted drug delivery; therapeutic applications

DOI:  https://doi.org/10.62347/AUPQ6330
bioRxiv. 2024 Sep 15. pii: 2024.09.12.612721. [Epub ahead of print]

"Mitotic" kinesin-5 is a dynamic brake for axonal growth.

Wen Lu, Brad S Lee, Helen Xue Ying Deng, Margot Lakonishok, Enrique Martin-Blanco, Vladimir I Gelfand.

During neuronal development, neurons undergo significant microtubule reorganization to shape axons and dendrites, establishing the framework for efficient wiring of the nervous system. Previous studies from our laboratory demonstrated the key role of kinesin-1 in driving microtubule-microtubule sliding, which provides the mechanical forces necessary for early axon outgrowth and regeneration in Drosophila melanogaster . In this study, we reveal the critical role of kinesin-5, a mitotic motor, in modulating the development of postmitotic neurons. Kinesin-5, a conserved homotetrameric motor, typically functions in mitosis by sliding antiparallel microtubules apart in the spindle. Here, we demonstrate that the Drosophila kinesin-5 homolog, Klp61F, is expressed in larval brain neurons, with high levels in ventral nerve cord (VNC) neurons. Knockdown of Klp61F using a pan-neuronal driver leads to severe locomotion defects and complete lethality in adult flies, mainly due to the absence of kinesin-5 in VNC motor neurons during early larval development. Klp61F depletion results in significant axon growth defects, both in cultured and in vivo neurons. By imaging individual microtubules, we observe a significant increase in microtubule motility, and excessive penetration of microtubules into the axon growth cone in Klp61F -depleted neurons. Adult lethality and axon growth defects are fully rescued by a chimeric human- Drosophila kinesin-5 motor, which accumulates at the axon tips, suggesting a conserved role of kinesin-5 in neuronal development. Altogether, our findings show that at the growth cone, kinesin-5 acts as a brake on kinesin-1-driven microtubule sliding, preventing premature microtubule entry into the growth cone. This regulatory role of kinesin-5 is essential for precise axon pathfinding during nervous system development.

DOI: https://doi.org/10.1101/2024.09.12.612721
Brain Commun. 2024 ;6(5): fcae312

Investigating the prevalence of MFN2 mutations in amyotrophic lateral sclerosis: insights from an Italian cohort.

Elena Abati, Delia Gagliardi, Arianna Manini, Roberto Del Bo, Dario Ronchi, Megi Meneri, Francesca Beretta, Annalisa Sarno, Federica Rizzo, Edoardo Monfrini, Alessio Di Fonzo, Maria Teresa Pellecchia, Alberto Brusati, Vincenzo Silani, Giacomo Pietro Comi, Antonia Ratti, Federico Verde, Nicola Ticozzi, Stefania Corti.

  The MFN2 gene encodes mitofusin 2, a key protein for mitochondrial fusion, transport, maintenance and cell communication. MFN2 mutations are primarily linked to Charcot-Marie-Tooth disease type 2A. However, a few cases of amyotrophic lateral sclerosis and amyotrophic lateral sclerosis/frontotemporal dementia phenotypes with concomitant MFN2 mutations have been previously reported. This study examines the clinical and genetic characteristics of an Italian cohort of amyotrophic lateral sclerosis patients with rare, non-synonymous MFN2 mutations. A group of patients (n = 385) diagnosed with amyotrophic lateral sclerosis at our Neurology Units between 2008 and 2023 underwent comprehensive molecular testing, including MFN2. After excluding pathogenic mutations in the main amyotrophic lateral sclerosis-related genes (i.e. C9orf72, SOD1, FUS and TARDBP), MFN2 variants were classified based on the American College of Medical Genetics and Genomics guidelines, and demographic and clinical data of MFN2-mutated patients were retrieved. We identified 12 rare, heterozygous, non-synonymous MFN2 variants in 19 individuals (4.9%). Eight of these variants, carried by nine patients (2.3%), were either pathogenic, likely pathogenic or variants of unknown significance according to the American College of Medical Genetics and Genomics guidelines. Among these patients, four exhibited a familial pattern of inheritance. The observed phenotypes included classic and bulbar amyotrophic lateral sclerosis, amyotrophic lateral sclerosis/frontotemporal dementia, flail arm, flail leg and progressive muscular atrophy. Median survival after disease onset was extremely variable, ranging from less than 1 to 13 years. This study investigates the prevalence of rare, non-synonymous MFN2 variants within an Italian cohort of amyotrophic lateral sclerosis patients, who have been extensively investigated, enhancing our knowledge of the underlying phenotypic spectrum. Further research is needed to understand whether MFN2 mutations contribute to motor neuron disease and to what extent. Improving our knowledge regarding the genetic basis of amyotrophic lateral sclerosis is crucial both in a diagnostic and therapeutic perspective.

Keywords:  amyotrophic lateral sclerosis; genetics; mitochondria; mitofusin 2

DOI:  https://doi.org/10.1093/braincomms/fcae312
Nat Methods. 2024 Sep 27.

Tracking neurons across days with high-density probes.

Enny H van Beest, Célian Bimbard, Julie M J Fabre, Sam W Dodgson, Flóra Takács, Philip Coen, Anna Lebedeva, Kenneth D Harris, Matteo Carandini.

Neural activity spans multiple time scales, from milliseconds to months. Its evolution can be recorded with chronic high-density arrays such as Neuropixels probes, which can measure each spike at tens of sites and record hundreds of neurons. These probes produce vast amounts of data that require different approaches for tracking neurons across recordings. Here, to meet this need, we developed UnitMatch, a pipeline that operates after spike sorting, based only on each unit's average spike waveform. We tested UnitMatch in Neuropixels recordings from the mouse brain, where it tracked neurons across weeks. Across the brain, neurons had distinctive inter-spike interval distributions. Their correlations with other neurons remained stable over weeks. In the visual cortex, the neurons' selectivity for visual stimuli remained similarly stable. In the striatum, however, neuronal responses changed across days during learning of a task. UnitMatch is thus a promising tool to reveal both invariance and plasticity in neural activity across days.

DOI: https://doi.org/10.1038/s41592-024-02440-1
bioRxiv. 2024 Sep 13. pii: 2024.09.10.612299. [Epub ahead of print]

LM11a-31 Inhibits p75 Neurotrophin Receptor (p75 NTR ) Cleavage and is Neuroprotective in a Cell Culture Model of Parkinson's Disease.

Poshan V Pokharel, Aaron M Newchurch, Sunny C Overby, Cassidy A Spease, Lorelei G Darzi, Bradley R Kraemer.

The p75 Neurotrophin Receptor (p75 NTR ) is a multifunctional transmembrane protein that mediates neuronal responses to pathological conditions in specific regions of the nervous system. In many biological contexts, p75 NTR signaling is initiated through sequential cleavage of the receptor by α- and γ-secretases, which releases receptor fragments for downstream signaling. Our previous work demonstrated that proteolytic processing of p75 NTR in this manner is stimulated by oxidative stress in Lund Human Mesencephalic (LUHMES) cells, a dopaminergic neuronal cell line derived from human mesencephalic tissue. Considering the vulnerability of dopaminergic neurons in the ventral mesencephalon to oxidative stress and neurodegeneration associated with Parkinson's disease (PD), we investigated the role of this signaling cascade in neurodegeneration and explored cellular processes that govern oxidative stress-induced p75 NTR signaling. In the present study, we provide evidence that oxidative stress induces cleavage of p75 NTR by promoting c-Jun N-terminal Kinase (JNK)-dependent internalization of p75 NTR from the cell surface. This activation of p75 NTR signaling is counteracted by tropomyosin-related kinase (Trk) receptor signaling; however, oxidative stress leads to Trk receptor downregulation, thereby enhancing p75 NTR processing. Importantly, we demonstrate that this pathway can be inhibited by LM11a-31, a small molecule modulator of p75 NTR , thereby conferring protection against neurodegeneration. Treatment with LM11a-31 significantly reduced p75 NTR cleavage and neuronal death associated with oxidative stress. These findings reveal novel mechanisms underlying activation of p75 NTR in response to oxidative stress, underscore a key role for p75 NTR in dopaminergic neurodegeneration, and highlight p75 NTR as a potential therapeutic target for reducing neurodegeneration in PD.

DOI: https://doi.org/10.1101/2024.09.10.612299