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Reduced cortico-muscular output is associated with intrinsic hypoexcitability and reduced persistent inward currents in motor cortex neurons of TDP-43Q331K ALS mice.

ABSTRACT: Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by spinal and cortical motor neuron loss and progressive neuromuscular decline. When ALS pathology involves the primary motor cortex (PMC), cortical excitability is often disrupted, yet how these alterations map onto motor deficits during symptomatic ALS remains unclear. To investigate this, we examined the neuromuscular function, cortico-muscular output, and neuronal excitability of symptomatic 4-month-old TDP-43Q331K mice. TDP-43 mice exhibited reduced neuromuscular excitability and impaired strength compared to WT mice. Cranial motor evoked potentials were significantly reduced in TDP-43 mice, indicating decreased cortical output to muscle. Compared to WT mice, whole-cell patch-clamp recordings from TDP-43 PMC layer V pyramidal neurons revealed intrinsic hypoexcitability, diminished persistent inward currents (PICs), and decreased excitatory synaptic activity. Corroborating PIC findings, immunohistochemical analysis showed reduced colocalization of the PIC-associated proteins Nav1.6 and 5-HT2C with PMC layer V neurons. Bulk RNA-seq of the cortex showed distinct transcriptional profiles in TDP-43 mice, with enrichment analysis indicating altered pathways relating to ion transport, synaptic signaling, and neuronal excitability. These results suggest that cortex-wide transcriptional changes may reflect broader and additional molecular mechanisms underlying cortical hypoexcitability in ALS. Together, our results demonstrate that symptomatic TDP-43Q331K mice exhibit a reduction in cortico-muscular output and PMC neuron excitability, accompanied by reduced PICs and PIC-associated proteins within these neurons. These findings identify cortical hypoexcitability as a defining feature of the TDP-43Q331k ALS mouse model and establish multi-level associations between cortical cellular-level dysfunction and impaired motor systems output.

ORGANISM(S): Mus musculus

PROVIDER: GSE310019 | GEO | 2025/12/27

REPOSITORIES: GEO

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Project description:Aims: Loss of nuclear TDP-43 characterises sporadic and most familial forms of amyotrophic lateral sclerosis (ALS). TDP-43 (encoded by TARDBP) has multiple roles in RNA processing. We aimed to determine whether 1) RNA splicing dysregulation is present in lower motor neurons in ALS and in a motor neuron-like cell model, and 2) TARDBP mutations (mtTARDBP) are associated with aberrant RNA splicing using patient-derived fibroblasts. Methods: Affymetrix exon arrays were used to study mRNA expression and splicing in lower motor neurons obtained by laser capture microdissection of autopsy tissue from individuals with sporadic ALS and TDP-43 proteinopathy. Findings were confirmed by qRT-PCR and in NSC34 motor neuronal cells following shRNA-mediated TDP-43 depletion. Exon arrays and immunohistochemistry were used to study mRNA splicing and TDP-43 expression in fibroblasts from patients with mtTARDBP-associated, sporadic and mutant SOD1-associated ALS. Results: We found altered expression of spliceosome components in motor neurons and widespread aberrations of mRNA splicing that specifically affected genes involved in ribonucleotide binding. This was confirmed in TDP-43 depleted NSC34 cells. Fibroblasts with mtTARDBP showed loss of nuclear TDP-43 protein and demonstrated similar changes in splicing and gene expression, that were not present in fibroblasts from patients with sporadic or SOD1-related ALS. Conclusion: Loss of nuclear TDP-43 is associated with RNA processing abnormalities in ALS motor neurons, patient-derived cells with mtTARDBP, and following artificial TDP-43 depletion, suggesting that splicing dysregulation directly contributes to disease pathogenesis. Key functional pathways affected include those central to RNA metabolism. RNA was extracted from lower motor neurons obtained by laser capture microdissection from autopsy material from neurologically healthy controls (n=6) and cases of sporadic ALS (n=3) and ALS due to C9ORF72 mutations (n=3).

Project description:Aims: Loss of nuclear TDP-43 characterises sporadic and most familial forms of amyotrophic lateral sclerosis (ALS). TDP-43 (encoded by TARDBP) has multiple roles in RNA processing. We aimed to determine whether 1) RNA splicing dysregulation is present in lower motor neurons in ALS and in a motor neuron-like cell model, and 2) TARDBP mutations (mtTARDBP) are associated with aberrant RNA splicing using patient-derived fibroblasts. Methods: Affymetrix exon arrays were used to study mRNA expression and splicing in lower motor neurons obtained by laser capture microdissection of autopsy tissue from individuals with sporadic ALS and TDP-43 proteinopathy. Findings were confirmed by qRT-PCR and in NSC34 motor neuronal cells following shRNA-mediated TDP-43 depletion. Exon arrays and immunohistochemistry were used to study mRNA splicing and TDP-43 expression in fibroblasts from patients with mtTARDBP-associated, sporadic and mutant SOD1-associated ALS. Results: We found altered expression of spliceosome components in motor neurons and widespread aberrations of mRNA splicing that specifically affected genes involved in ribonucleotide binding. This was confirmed in TDP-43 depleted NSC34 cells. Fibroblasts with mtTARDBP showed loss of nuclear TDP-43 protein and demonstrated similar changes in splicing and gene expression, that were not present in fibroblasts from patients with sporadic or SOD1-related ALS. Conclusion: Loss of nuclear TDP-43 is associated with RNA processing abnormalities in ALS motor neurons, patient-derived cells with mtTARDBP, and following artificial TDP-43 depletion, suggesting that splicing dysregulation directly contributes to disease pathogenesis. Key functional pathways affected include those central to RNA metabolism. RNA was extracted from fibroblasts grown from neurologically healthy controls (n=6) and 3 groups of patients with ALS: 1) sporadic cases (n=6); 2) cases due to mutations of SOD1 (n=4); 3) cases due to mutations of TARDBP (n=3). The three ALS groups were compared to the controls.

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Reduced cortico-muscular output is associated with intrinsic hypoexcitability and reduced persistent inward currents in motor cortex neurons of TDP-43Q331K ALS mice.

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