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Identification of Candidate Genes for Sporadic Amyotrophic Lateral Sclerosis by Array Comparative Genomic Hybridisation

ABSTRACT: Background: Amyotrophic lateral sclerosis (ALS) is a devastating disorder of the central nervous system that leads to progressive loss of upper and lower motor neurons. Most cases are sporadic and of unknown aetiology. In this study, we screened 71 patients with sporadic ALS for the presence of DNA copy number variations, in order to identify novel candidate disease genes. Methods: We have used sub-megabase resolution BAC array comparative genomic hybridisation to detect genomic imbalances in our ALS patient cohort. In order to distinguish phenotypically neutral copy number variations occurring frequently in the normal population from disease-associated aberrations, we screened our results against both the Database of Genomic Variants and a reference data set of approximately 700 normal individuals and probands with other disorders analysed in our laboratory. Aberrations with potential relevance for disease aetiology were verified by oligo array CGH. Findings: In 71 patients with sporadic ALS, we identified a total of six duplications and seven deletions that scored above our threshold. Twelve of these thirteen variations were smaller than 1Mb. Seven were observed exclusively in ALS patients and thus likely play causal roles in the disorder. Analysis of these regions highlighted, for example, the SLC1A7 (EAAT5) glutamate transporter and the kinesin family member KIF9 as good positional and functional candidate genes for ALS. Interpretation: Non-polymorphic sub-microscopic duplications and deletions observable by array CGH are frequent in patients with sporadic ALS. Analysis of such aberrations serves as an excellent starting point in deciphering the aetiology of this complex disease. Keywords: array CGH

ORGANISM(S): Homo sapiens

PROVIDER: GSE7950 | GEO | 2008/12/25

SECONDARY ACCESSION(S): PRJNA100131

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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Identification of Candidate Genes for Sporadic Amyotrophic Lateral Sclerosis by Array Comparative Genomic Hybridisation

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