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TRAP-seq of spinal cord motor neurons from ALS diseased mice versus healthy mice

ABSTRACT: Amyotrophic lateral sclerosis (ALS) is an incurable neurological disease featuring progressive loss of motor neuron (MN) function in the brain and spinal cord. Mutations in TARDBP, encoding the RNA-binding protein TDP-43, are one cause of ALS and TDP-43 mislocalization in MNs is a key pathological feature of >95% of ALS cases. While numerous studies support altered RNA regulation by TDP-43 as a major cause of disease, specific changes within MNs that trigger disease onset remain unclear. Here, we combined Translating Ribosome Affinity Purification (TRAP) with RNA sequencing to identify molecular changes in spinal MNs of TDP-43–driven ALS at motor symptom onset. By comparing the MN translatome of hTDP-43A315T mice to littermate controls and to mice expressing wildtype hTDP-43, we identify hundreds of mRNAs that were selectively up- or downregulated in MNs. We validated effects on Tex26, Syngr4, and Plekhb1 mRNAs in an independent TRAP experiment. Moreover, by quantitative immunostaining of spinal cord MNs we found corresponding protein level changes for SYNGR4 and PLEKHB1. We also observed these changes in spinal MNs of an independent ALS mouse model caused by a different patient mutant allele of TDP-43, suggesting that they may be a general feature of TDP-43-driven ALS. Thus, we have identified two new proteins deregulated in MNs at motor symptom onset in TDP-43-driven ALS models. This spatial and temporal pattern suggests that deregulation of these proteins could be functionally important for driving the transition to the symptomatic phase of disease.

ORGANISM(S): Mus musculus

PROVIDER: GSE144640 | GEO | 2023/01/01

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).

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TRAP-seq of spinal cord motor neurons from ALS diseased mice versus healthy mice

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