TARDBP mutations in amyotrophic lateral sclerosis with TDP-43 neuropathology: a genetic and histopathological analysis.
ABSTRACT TDP-43 is a major component of the ubiquitinated inclusions that characterise amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD) with ubiquitin inclusions (FTLD-U). TDP-43 is an RNA-binding and DNA-binding protein that has many functions and is encoded by the TAR DNA-binding protein gene (TARDBP) on chromosome 1. Our aim was to investigate whether TARDBP is a candidate disease gene for familial ALS that is not associated with mutations in superoxide dismutase 1 (SOD1).
TARDBP was sequenced in 259 patients with ALS, FTLD, or both. We used TaqMan-based SNP genotyping to screen for the identified variants in control groups matched to two kindreds of patients for age and ethnic origin. Additional clinical, genetic, and pathological assessments were made in these two families.
We identified two variants in TARDBP, which would encode Gly290Ala and Gly298Ser forms of TDP-43, in two kindreds with familial ALS. The variants seem to be pathogenic because they co-segregated with disease in both families, were absent in controls, and were associated with TDP-43 neuropathology in both members of one of these families for whom CNS tissue was available.
The Gly290Ala and Gly298Ser mutations are located in the glycine-rich domain of TDP-43, which regulates gene expression and mediates protein-protein interactions such as those with heterogeneous ribonucleoproteins. Owing to the varied and important cellular functions of TDP-43, these mutations might cause neurodegeneration through both gains and losses of function. The finding of pathogenic mutations in TARDBP implicates TDP-43 as an active mediator of neurodegeneration in TDP-43 proteinopathies, a class of disorder that includes ALS and FTLD-U.
National Institutes of Health (AG10124, AG17586, AG005136-22, PO1 AG14382), Department of Veterans Affairs, Friedrich-Baur Stiftung (0017/2007), US Public Health Service, ALS Association, and Fundació 'la Caixa'.
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ABSTRACT: Pathological aggregates of phosphorylated TDP-43 characterize amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD-TDP), two devastating groups of neurodegenerative disease. Kinase hyperactivity may be a consistent feature of ALS and FTLD-TDP, as phosphorylated TDP-43 is not observed in the absence of neurodegeneration. By examining changes in TDP-43 phosphorylation state, we have identified kinases controlling TDP-43 phosphorylation in a C. elegans model of ALS. In this kinome-wide survey, we identified homologs of the tau tubulin kinases 1 and 2 (TTBK1 and TTBK2), which were also identified in a prior screen for kinase modifiers of TDP-43 behavioral phenotypes. Using refined methodology, we demonstrate TTBK1 and TTBK2 directly phosphorylate TDP-43 in vitro and promote TDP-43 phosphorylation in mammalian cultured cells. TTBK1/2 overexpression drives phosphorylation and relocalization of TDP-43 from the nucleus to cytoplasmic inclusions reminiscent of neuropathologic changes in disease states. Furthermore, protein levels of TTBK1 and TTBK2 are increased in frontal cortex of FTLD-TDP patients, and TTBK1 and TTBK2 co-localize with TDP-43 inclusions in ALS spinal cord. These kinases may represent attractive targets for therapeutic intervention for TDP-43 proteinopathies such as ALS and FTLD-TDP.PLoS Genetics 12/2014; 10(12):e1004803. · 8.17 Impact Factor
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ABSTRACT: Neurodegenerative diseases share common features, including catastrophic neuronal loss that leads to cognitive or motor dysfunction. Neuronal injury occurs in an inflammatory milieu that is populated by resident and sometimes, infiltrating, immune cells-all of which participate in a complex interplay between secreted inflammatory modulators and activated immune cell surface receptors. The importance of these immunomodulators is highlighted by the number of immune factors that have been associated with increased risk of neurodegeneration in recent genome-wide association studies. One of the more difficult tasks for designing therapeutic strategies for immune modulation against neurodegenerative diseases is teasing apart beneficial from harmful signals. In this regard, learning more about the immune components of these diseases has yielded common themes. These unifying concepts should eventually enable immune-based therapeutics for treatment of Alzheimer's and Parkinson's diseases and amyotrophic lateral sclerosis. Targeted immune modulation should be possible to temper maladaptive factors, enabling beneficial immune responses in the context of neurodegenerative diseases.Brain Research 09/2014; · 2.83 Impact Factor
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ABSTRACT: Advances in research and technology has increased our quality of life, allowed us to combat diseases, and achieve increased longevity. Unfortunately, increased longevity is accompanied by a rise in the incidences of age-related diseases such as Alzheimer's disease (AD). AD is the sixth leading cause of death, and one of the leading causes of dementia amongst the aged population in the USA. It is a progressive neurodegenerative disorder, characterized by the prevalence of extracellular Aβ plaques and intracellular neurofibrillary tangles, derived from the proteolysis of the amyloid precursor protein (APP) and the hyperphosphorylation of microtubule-associated protein tau, respectively. Despite years of extensive research, the molecular mechanisms that underlie the pathology of AD remain unclear. Model organisms, such as the nematode, Caenorhabditis elegans, present a complementary approach to addressing these questions. C. elegans has many advantages as a model system to study AD and other neurodegenerative diseases. Like their mammalian counterparts, they have complex biochemical pathways, most of which are conserved. Genes in which mutations are correlated with AD have counterparts in C. elegans, including an APP-related gene, apl-1, a tau homolog, ptl-1, and presenilin homologs, such as sel-12 and hop-1. Since the neuronal connectivity in C. elegans has already been established, C. elegans is also advantageous in modeling learning and memory impairments seen during AD. This article addresses the insights C. elegans provide in studying AD and other neurodegenerative diseases. Additionally, we explore the advantages and drawbacks associated with using this model.Frontiers in Genetics 09/2014; 5:279.