Novel TARDBP Sequence Variant and C9ORF72 Repeat Expansion in a Family With Frontotemporal Dementia.
ABSTRACT Frontotemporal lobar degeneration (FTLD) is a genetically heterogenous syndrome and has been associated most recently with a hexanucleotide repeat expansion within the C9ORF72 gene. Pathogenic TDP-43 gene (TARDBP) mutations have been identified in amyotrophic lateral sclerosis, but the role of TARDBP mutations in FTLD is more contradictory. To investigate the role of TARDBP mutations in a clinical series of Finnish FTLD patients, we sequenced TARDBP exons 1 to 6 in 77 FTLD patients. No evident pathogenic mutations were found. We identified a novel heterozygous c.876_878delCAG sequence variant in 2 related patients with behavioral variant frontotemporal dementia without amyotrophic lateral sclerosis. The variant is predicted to cause an amino acid deletion of serine at position 292 (p.Ser292del). However, p.Ser292del was also found in 1 healthy middle-aged control. Interestingly, both patients carried the C9ORF72 expansion. Therefore, the TARDBP variant p.Ser292del might be considered a rare polymorphism and the C9ORF72 repeat expansion the actual disease-causing mutation in the family. Our results suggest that TARDBP mutations are a rare cause of FTLD. However, the interaction of several genetic factors needs to be taken into account when investigating neurodegenerative diseases.
SourceAvailable from: Jennifer S Yokoyama[Show abstract] [Hide abstract]
ABSTRACT: Hexanucleotide repeat expansion in C9ORF72 is the most common genetic cause of frontotemporal dementia (FTD), a predominantly behavioral disease, and amyotrophic lateral sclerosis (ALS), a disease of motor neurons. The primary objectives of this review are to highlight the clinical heterogeneity associated with C9ORF72 pathogenic expansion and identify potential molecular mechanisms underlying selective vulnerability of distinct neural populations. The proposed mechanisms by which C9ORF72 expansion causes behavioral and motor neuron disease highlight the emerging role of impaired RNA and protein homeostasis in a spectrum of neurodegeneration and strengthen the biological connection between FTD and ALS.01/2014; 3(1):1-18.
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ABSTRACT: The C9ORF72 repeat expansion is the major cause of frontotemporal lobar degeneration (FTLD), amyotrophic lateral sclerosis (ALS), and FTLD-ALS. In the reported pedigree, the 47-year old proband, presenting a four-year history of frontotemporal dementia, carried the C9ORF72 expansion plus a novel GRN p.Cys246X mutation. The father and a paternal uncle, harboring the C9ORF72 expansion only, had died by pure ALS with onset at 63 and 76 years, respectively. The case report and a review of the literature emphasize that phenotypical variations of the FTLD-ALS spectrum could be due to digenic inheritance.Journal of Alzheimer's disease: JAD 09/2014; 44(1). DOI:10.3233/JAD-141794 · 3.61 Impact Factor
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ABSTRACT: Increasing evidence has shown that morphological and functional neuroimaging may help to understand the pathophysiological mechanisms leading to behavioral disturbances in patients with genetic or sporadic frontotemporal dementia (FTD). The C9orf72 expansion was found in association with the N267S TARDBP mutation in two siblings with behavioral-variant FTD (bvFTD). In one of them with very mild dementia, MRI showed symmetric atrophy of temporal, inferolateral and orbital frontal cortex, while [18F]FDG-PET disclosed more extended hypometabolism in dorsolateral and inferolateral frontal cortex, anterior cingulate, and caudate nucleus. Hypometabolism in right lateral and orbital frontal cortex was confirmed also in comparison with a group of sporadic bvFTD patients. These findings appear as the neuroimaging hallmark of double C9orf72 and TARDBP gene mutation with a bvFTD phenotype.Neurocase 08/2014; DOI:10.1080/13554794.2014.951057 · 1.38 Impact Factor