Identification of a FUS splicing mutation in a large family with amyotrophic lateral sclerosis.

Center of Excellence in Neuromics of Université de Montréal, CHUM Research Center, Montreal, Quebec, Canada.
Journal of Human Genetics (Impact Factor: 2.37). 12/2010; 56(3):247-9. DOI: 10.1038/jhg.2010.162
Source: PubMed

ABSTRACT Amyotrophic lateral sclerosis (ALS) is a severe neurodegenerative disease characterized by the degeneration of upper and lower motor neurons. Genetic studies have led, thus far, to the identification of 12 loci and 9 genes for familial ALS (FALS). Although the distribution and impact of superoxide dismutase 1 mutations has been extensively examined for over a decade, the recently identified FALS-associated FUS gene has been less studied. Therefore, we set out to screen our collection of FALS cases for FUS mutations. All 15 exons of FUS were amplified and sequenced in 154 unrelated FALS cases and 475 ethnically matched healthy individuals. One substitution located in the acceptor splice site of intron 14 was identified in all affected members of a large family, causing the skipping of the last 13 amino acids of the protein and the translation of 7 novel amino acids, resulting from the new translation of a part of the 3' untranslated region. Our study identified a new splicing mutation in the highly conserved C-terminal of the FUS protein. Thus far most FUS mutations are missenses, and our findings, combined with those of others, confirm the importance of the C-terminal portion of the protein, adding additional support for FUS mutations having a critical role in ALS.

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    ABSTRACT: Mutations in the gene encoding Fused in Sarcoma (FUS) cause amyotrophic lateral sclerosis (ALS), a fatal neurodegenerative disorder. FUS is a predominantly nuclear DNA and RNA binding protein that is involved in RNA processing. Large FUS immuno-reactive inclusions fill the perikaryon of surviving motor neurons of ALS patients carrying mutations at post-mortem. This sequestration of FUS is predicted to disrupt RNA processing and initiate neurodegeneration. Here we demonstrate that C-terminal ALS mutations disrupt the nuclear localising signal (NLS) of FUS resulting in cytoplasmic accumulation in transfected cells and patient fibroblasts. FUS mislocalisation is rescued by the addition of the wild-type FUS NLS to mutant proteins. We also show that oxidative stress recruits mutant FUS to cytoplasmic stress granules where it is able to bind and sequester wild-type FUS. While FUS interacts with itself directly by protein-protein interaction, the recruitment of FUS to stress granules and interaction with PABP is RNA dependent. These findings support a two-hit hypothesis whereby cytoplasmic mislocalisation of FUS protein, followed by cellular stress contributes to the formation of cytoplasmic aggregates that may sequester FUS, disrupt RNA processing and initiate motor neuron degeneration.
    Human Molecular Genetics 03/2013; · 7.69 Impact Factor
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    ABSTRACT: Systematic review data demonstrate that 5% of ALS cases are familial (FALS). Causative superoxide dismutase-1 (SOD1) mutations are identified in 10-20% of FALS. Few reports of FALS epidemiology exist in Canada. We completed a retrospective review of all FALS cases within the province of Alberta between 2002 and 2011. Descriptive summaries of genotypes identified and calculation of prevalences were performed. We reviewed 946 clinic database records and 49 subjects with FALS were identified (5.2%). Clinic charts for 47/49 were available and reviewed. Causative SOD1 mutations were observed in 17/47 (36%). The SOD1 I113T mutation was identified in 11/47 unrelated patients and was associated with a less variable survival than previously reported. The period and point prevalences of FALS in Alberta are approximately 2.05 per 100,000 (95% CI 1.51-2.73) and 4.68 per 1,000,000 (95% CI 2.42-8.18), respectively. In conclusion, we report 47 cases of FALS in Alberta over the past decade. The proportion of SOD1-positive FALS cases is higher than reported elsewhere. The high proportion of I113T mutations is comparable to that previously observed in the adjacent province of British Columbia.
    Amyotrophic lateral sclerosis and frontotemporal degeneration. 05/2013; 14(4):273-277.
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    ABSTRACT: Mutations in the TAR DNA Binding Protein gene (TARDBP), encoding the protein TDP-43, were identified in amyotrophic lateral sclerosis (ALS) patients. Interestingly, TDP-43 positive inclusion bodies were first discovered in ubiquitin-positive, tau negative ALS and frontotemporal dementia (FTD) inclusion bodies, and subsequently observed in the majority of neurodegenerative disorders. To date, 47 missense and one truncating mutations have been described in a large number of familial (FALS) and sporadic (SALS) patients. Fused in Sarcoma (FUS) was found to be responsible for a previously identified ALS6 locus, being mutated in both FALS and SALS patients. TARDBP and FUS have a structural and functional similarity and most of mutations in both genes are also clustered in the C-terminus of the proteins. The molecular mechanisms through which mutant TDP-43 and FUS may cause motor neuron degeneration are not well understood. Both proteins play an important role in mRNA transport, axonal maintenance and motor neuron development. Functional characterization of these mutations in in vitro and in vivo systems is helping to better understand how motor neuron degeneration occurs. This report summarizes the biological and clinical relevance of TARDBP and FUS mutations in ALS. All the data reviewed here has been submitted to a database based on the Leiden Open (source) Variation Database(LOVD) and is accessible online at,
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