Novel mutations in TARDBP (TDP-43) in patients with familial amyotrophic lateral sclerosis

Department of Neuroscience, Mayo Clinic, Jacksonville, Florida, United States of America.
PLoS Genetics (Impact Factor: 8.17). 10/2008; 4(9):e1000193. DOI: 10.1371/journal.pgen.1000193
Source: PubMed

ABSTRACT The TAR DNA-binding protein 43 (TDP-43) has been identified as the major disease protein in amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration with ubiquitin inclusions (FTLD-U), defining a novel class of neurodegenerative conditions: the TDP-43 proteinopathies. The first pathogenic mutations in the gene encoding TDP-43 (TARDBP) were recently reported in familial and sporadic ALS patients, supporting a direct role for TDP-43 in neurodegeneration. In this study, we report the identification and functional analyses of two novel and one known mutation in TARDBP that we identified as a result of extensive mutation analyses in a cohort of 296 patients with variable neurodegenerative diseases associated with TDP-43 histopathology. Three different heterozygous missense mutations in exon 6 of TARDBP (p.M337V, p.N345K, and p.I383V) were identified in the analysis of 92 familial ALS patients (3.3%), while no mutations were detected in 24 patients with sporadic ALS or 180 patients with other TDP-43-positive neurodegenerative diseases. The presence of p.M337V, p.N345K, and p.I383V was excluded in 825 controls and 652 additional sporadic ALS patients. All three mutations affect highly conserved amino acid residues in the C-terminal part of TDP-43 known to be involved in protein-protein interactions. Biochemical analysis of TDP-43 in ALS patient cell lines revealed a substantial increase in caspase cleaved fragments, including the approximately 25 kDa fragment, compared to control cell lines. Our findings support TARDBP mutations as a cause of ALS. Based on the specific C-terminal location of the mutations and the accumulation of a smaller C-terminal fragment, we speculate that TARDBP mutations may cause a toxic gain of function through novel protein interactions or intracellular accumulation of TDP-43 fragments leading to apoptosis.

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Available from: Caroline Vance, Aug 24, 2015
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    • "09 ; Wang et al . , 2010 ) . In addition , either UPS inhibition or overexpression of the truncated TDP - 43 fragments could result in increased level of active caspase 3 ( Suzuki et al . , 2011 ; Zhang et al . , 2009 ) , thus leading to increased proteolytic cleavage of the full - length TDP - 43 to generate more TDP - 35 and TDP - 25 fragments ( Rutherford et al . , 2008 ) . In order to exclude the above mentioned side - effects due to overexpression of the truncated TDP - 25 fragment or MG132 induction , we have carried out cyclohexamide - chase experiments and found that degradation of the endogenous full - length TDP - 43 becomes slower in the presence of the caspase 3 inhibitor Z - VAD ( Fig . 3A ) "
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    ABSTRACT: TDP-43 is a pathological signature protein of neurodegenerative diseases with TDP-43 proteinopathies including FTLD-TDP and ALS-TDP. These TDP-43 proteinopathies are characterized with cytoplasmic insoluble TDP-43(+) aggregates in the diseased cells, the formation of which requires the seeding of TDP-25 fragment generated by caspase cleavage of TDP-43. We have investigated the metabolism and mis-metabolism of TDP-43 in cultured cells and found that the endogenous and exogenously over-expressed TDP-43 are degraded not only by ubiquitin proteasome system (UPS) and macroautophagy (MA), but also by the chaperone-mediated autophagy (CMA) mediated through interaction between Hsc70 and ubiquitinated TDP-43. Furthermore, proteolytic cleavage of TDP-43 by caspase(s) is a necessary intermediate step for degradation of a majority of the TDP-43 protein, with the TDP-25/TDP-35 fragments being the main substrates. Finally, we have determined the threshold level of the TDP-25 fragment that is necessary for formation of the cytosolic TDP-43(+) aggregates in cells containing the full-length TDP-43 at an elevated level close to that found in patients with TDP-43 proteinopathies. A comprehensive model of the metabolism and mis-metabolism of TDP-43 in relation to these findings is presented.
    Journal of Cell Science 05/2014; 127(14). DOI:10.1242/jcs.136150 · 5.33 Impact Factor
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    • "For example, the 43-kDa transactive response- DNA-binding protein is the major pathologic hallmark linking ALS and FTD (Neumann et al., 2006). Mutations in the gene encoding 43-kDa transactive response-DNA-binding protein (TARDBP; MIM# 605078), however, have been largely observed only in patients with ALS (with [Benajiba et al., 2009] or without [Kabashi et al., 2008; Rutherford et al., 2008; Sreedharan et al., 2008; Van Deerlin et al., 2008] additional dementing illness), whereas several screenings in patients with FTD without motor neuron disease remained negative (Gijselinck et al., 2009; Rutherford et al., 2008; Van Deerlin et al., 2008). Thus, the genetic link is not yet well substantiated that TARDBP is indeed able to cause the full spectrum of the ALS-FTD continuum, including in particular pure FTD. "
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    ABSTRACT: Targeted high-throughput sequencing of many amyotrophic lateral sclerosis (ALS) and fronto-temporal dementia (FTD) genes in parallel has the potential to reveal novel ALS- and/or FTD-phenotypes and to provide missing links on the ALS-FTD continuum. For example, although the 43-kDa transactive response DNA binding protein is the major pathologic hallmark linking ALS and FTD, mutations in the gene encoding 43-kDa transactive response DNA binding protein (TARDBP) have been appreciated only as a cause of ALS-phenotypes, but not yet of pure FTD. Thus, the genetic link is not yet well substantiated that TARDBP mutations can cause the full spectrum of the ALS-FTD continuum. High-throughput sequencing of 18 ALS and FTD genes in an index patient presenting with early-onset pure (behavioral) FTD and a positive family history for ALS revealed an established TARDBP mutation, A382T. This finding demonstrates that a TARDPB mutation can cause early-onset pure FTD without evidence for ALS even in advanced FTD disease stages. Moreover, it indicates that TARDPB screening might be considered even in young patients with "pure" neuropsychiatric disturbances and without evidence of neurodegenerative disease in the parental generation.
    Neurobiology of aging 10/2013; 35(5). DOI:10.1016/j.neurobiolaging.2013.10.092 · 4.85 Impact Factor
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    • "Although TDP-43 positive inclusions have been described in neurons of patients affected with AD, PD and other neurodegenerative diseases, TARDBP mutations have been observed only in ALS with or without associated FTLD. Three previous reports could not find mutations in 46 AD (Rutherford, et al., 2008), 125 PD (Kabashi, et al., 2009), and 41 patients with neurodegenerative diseases other than ALS or FTLD-U (Van Deerlin, et al., 2008). Given the low mutational frequency of TARDBP in sporadic cases, we attempted to validate these results in two larger AD and PD cohorts. "
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    ABSTRACT: Neurodegenerative diseases are often characterized by the presence of aggregates of misfolded proteins. TDP-43 is a major component of these aggregates in amyotrophic lateral sclerosis (ALS), but has also been observed in Alzheimer's (AD) and Parkinson's Diseases (PD). In addition, mutations in the TARDBP gene, encoding TDP-43, have been found to be a significant cause of familial ALS (FALS). All mutations, except for one, have been found in exon 6. To confirm this observation in ALS and to investigate whether TARDBP may play a role in the pathogenesis of AD and PD, we screened for mutations in exon 6 of the TARDBP gene in three cohorts composed of 376 AD, 463 PD (18% familial PD) and 376 ALS patients (50% FALS). We found mutations in ∼ 7% of FALS and ∼0.5% of sporadic ALS (SALS) patients, including two novel mutations, p.N352T and p.G384R. In contrast, we did not find TARDBP mutations in our cohort of AD and PD patients. These results suggest that mutations in TARDBP are not a significant cause of AD and PD.
    Neurobiology of aging 11/2011; 32(11):2096-9. DOI:10.1016/j.neurobiolaging.2009.11.018 · 4.85 Impact Factor
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