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Transcriptomic characterization of in vitro human iPSC-derived motor neuron systems for the exploration of cell autonomous mechanisms and modifiers of TDP-43 perturbation associated neurotoxicity

ABSTRACT: Transactive Response DNA-binding protein 43 (TDP-43) is a multifunctional nuclear protein ubiquitously expressed in all tissues. Although it is primarily nuclear, Amyotrophic Lateral Sclerosis (ALS) patients frequently present with cytoplasmic aggregates of TDP-43 in motor neurons on post-mortem examination. Although only about 5% of all ALS patients have a TARDBP mutation (Ghasemi and Brown 2018; Ingre et al. 2015), which is known to cause these insoluble cytoplasmic aggregates, 97% of ALS patients will develop cytoplasmic, insoluble TDP-43 aggregates regardless of whether they have a mutation in TARDBP or not (Ling et al. 2013). Overexpression of wild-type TDP-43 has previously been shown to be a valid model of inducing neurotoxicity as well as a limited amount of cytoplasmic re-localization and aggregation characteristic of ALS (Elden et al. 2010; Wils et al. 2010). In the search for modifiers of toxicity as conferred by TDP-43 overexpression in these models, knockout of Ataxin-2 (ATXN2) was proposed as a protective intervention in the context of TDP-43 perturbation in non-human model systems (Elden et al. 2010, Becker et al. 2017). This promising finding had not previously been validated in a human motor neuron system, nor had a thorough investigation been conducted to determine the mechanism of neuroprotection that ATXN2 knockout employs to drive the therapeutic effect. This sequencing study examines both ATXN2 intact and ATXN2 knockout motor neurons in the context of TDP-43 perturbation to explore global transcriptomic changes that arise from these changes in cellular state that are associated with progression of ALS (ATXN2 intact) and what pathways could be implicated in protection from ALS-associated neurodegeneration (ATXN2 Knockout).

ORGANISM(S): Homo sapiens

PROVIDER: GSE261875 | GEO | 2024/03/23

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 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.

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).

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Transcriptomic characterization of in vitro human iPSC-derived motor neuron systems for the exploration of cell autonomous mechanisms and modifiers of TDP-43 perturbation associated neurotoxicity

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