Dataset Information

Mutations to the ALS/FTD gene CCNF reveals elevated Lys48-linked ubiquitination by the SCF(cyclin F) complex

ABSTRACT: Approximately 10% of Amyotrophic lateral sclerosis (ALS) cases have a positive family history (familial ALS) and appear clinically indistinguishable from sporadic cases. ALS and frontotemporal dementia (FTD) are fatal neurodegenerative disorders that have common molecular and pathogenic characteristics; however, their biological mechanisms remain poorly understood. We have previously identified CCNF missense mutations in cohorts of familial and sporadic ALS and FTD cases [ref]. CCNF encodes cyclin F, a component of an E3 ubiquitin-protein ligase (SCFCyclin F) complex that is responsible for ubiquitinating proteins for degradation by the Ubiquitin-Proteasome System (UPS). The SCFCyclin F complex is essential for maintaining cellular homeostasis in cells; but mutations appear to lead to aberrant motor neuron development and neuron degeneration. We revealed elevated Lys48-specific ubiquitination of proteins in neuronal cells expressing mutant CCNFS621G compared to the CCNFWT control, which is consistent with increased Lys48-specific E3 ligase activity of cyclin FS621G (>1.3-fold). Different subsets of immunoprecipitated Lys48-ubiquitinated proteins were identified between CCNFWT and CCNFS621G cells indicating that transfected cyclin F contribute to the protein ubiquitination profile. These findings provide mechanistic insights into the effects of CCNF gene mutations on the function of the SCFcyclin F complex on neuronal proteostasis.

INSTRUMENT(S):

ORGANISM(S): Mus Musculus (mouse)

TISSUE(S): Neuroblast

DISEASE(S): Amyotrophic Lateral Sclerosis

SUBMITTER: Albert Lee

LAB HEAD: Albert Lee

PROVIDER: PXD002011 | Pride | 2017-12-01

REPOSITORIES: Pride

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Pathogenic mutation in the ALS/FTD gene, CCNF, causes elevated Lys48-linked ubiquitylation and defective autophagy.

Lee Albert A Rayner Stephanie L SL Gwee Serene S L SSL De Luca Alana A Shahheydari Hamideh H Sundaramoorthy Vinod V Ragagnin Audrey A Morsch Marco M Radford Rowan R Galper Jasmin J Freckleton Sarah S Shi Bingyang B Walker Adam K AK Don Emily K EK Cole Nicholas J NJ Yang Shu S Williams Kelly L KL Yerbury Justin J JJ Blair Ian P IP Atkin Julie D JD Molloy Mark P MP Chung Roger S RS

Cellular and molecular life sciences : CMLS 20170829 2

Amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) are fatal neurodegenerative disorders that have common molecular and pathogenic characteristics, such as aberrant accumulation and ubiquitylation of TDP-43; however, the mechanisms that drive this process remain poorly understood. We have recently identified CCNF mutations in familial and sporadic ALS and FTD patients. CCNF encodes cyclin F, a component of an E3 ubiquitin-protein ligase (SCF<sup>cyclin F</sup>) complex that is ...[more]

PMID: 28852778

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Project description:Importance: An intronic hexanucleotide repeat expansion (HRE) in C9orf72 is the commonest monogenic cause of the neurodegenerative diseases amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Predicting those who will develop neurodegeneration and its timing will be essential to initiating and assessing preventative therapy. This requires consideration of both compensatory, protective mechanisms and pathogenic events prior to overt neurodegeneration. Objective: To identify biochemical changes in individuals at higher risk of developing ALS or FTD via C9orf72 HRE heterozygosity. Design: Cross sectional observational study. Setting: Tertiary ALS or dementia referral centre. Participants: People with established ALS or FTD, either due to C9orf72 HRE or apparently sporadic cases; asymptomatic first-degree relatives of those with a known C9orf72 HRE; asymptomatic non-carrier controls. Exposure: C9orf72 HRE. Main outcomes: Relative abundance of 30 predefined cerebrospinal fluid biomarkers of ALS and FTD comparing asymptomatic C9orf72 HRE carriers and age-matched non-carriers. Differential abundance of proteins quantified using data independent acquisition mass spectrometry and neurofilament light chain measured by electrochemiluminescent assay. Results: Data for 19 people with sporadic ALS, 10 people with C9orf72 ALS, 14 people with sporadic FTD, 10 people with C9orf72 FTD, 48 asymptomatic C9orf72 HRE carriers and 39 non-carrier controls were analysed. Ubiquitin carboxyl-hydrolase isozyme L1 levels were higher in asymptomatic C9orf72 HRE carriers compared with age-matched non-carriers (log2fold change 0.20, FDR-adjusted p-value = 0.034). Neurofilament light chain levels did not differ significantly between groups. Ubiquitin carboxyl-hydrolase isozyme L1 levels remained elevated after exclusion of those with high neurofilament light chain levels, after adjusting for NFL level and after adjusting for age. Conclusions and relevance: Elevated cerebrospinal fluid ubiquitin carboxyl-hydrolase isozyme L1 levels in C9orf72 hexanucleotide repeat expansion carriers occurs in the absence of elevation in neurofilament light chain, potentially reflecting mechanisms that precede the phase of neurodegeneration characterised by rapid neuronal loss. Such mechanisms may have either compensatory or pathogenic roles. Ubiquitin carboxyl-terminal hydrolase isozyme L1 elevation brings forward the window on the changes associated with the C9orf72 HRE carrier state, with the potential to inform understanding penetrance and approaches to prevention.

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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