Familial frontotemporal dementia with neuronal intranuclear inclusions is not a polyglutamine expansion disease

Department of Pathology, University of British Columbia, Vancouver, BC, Canada.
BMC Neurology (Impact Factor: 2.04). 02/2006; 6(1):32. DOI: 10.1186/1471-2377-6-32
Source: PubMed


Many cases of frontotemporal dementia (FTD) are familial, often with an autosomal dominant pattern of inheritance. Some are due to a mutation in the tau- encoding gene, on chromosome 17, and show an accumulation of abnormal tau in brain tissue (FTDP-17T). Most of the remaining familial cases do not exhibit tau pathology, but display neuropathology similar to patients with dementia and motor neuron disease, characterized by the presence of ubiquitin-immunoreactive (ub-ir), dystrophic neurites and neuronal cytoplasmic inclusions in the neocortex and hippocampus (FTLD-U). Recently, we described a subset of patients with familial FTD with autopsy-proven FTLD-U pathology and with the additional finding of ub-ir neuronal intranuclear inclusions (NII). NII are a characteristic feature of several other neurodegenerative conditions for which the genetic basis is abnormal expansion of a polyglutamine-encoding trinucleotide repeat region. The genetic basis of familial FTLD-U is currently not known, however the presence of NII suggests that a subset of cases may represent a polyglutamine expansion disease.
We studied DNA and post mortem brain tissue from 5 affected members of 4 different families with NII and one affected individual with familial FTLD-U without NII. Patient DNA was screened for CAA/CAG trinucleotide expansion in a set of candidate genes identified using a genome-wide computational approach. Genes containing CAA/CAG trinucleotide repeats encoding at least five glutamines were examined (n = 63), including the nine genes currently known to be associated with human disease. CAA/CAG tract sizes were compared with published normal values (where available) and with those of healthy controls (n = 94). High-resolution agarose gel electrophoresis was used to measure allele size (number of CAA/CAG repeats). For any alleles estimated to be equal to or larger than the maximum measured in the control population, the CAA/CAG tract length was confirmed by capillary electrophoresis. In addition, immunohistochemistry using a monoclonal antibody that recognizes proteins containing expanded polyglutamines (1C2) was performed on sections of post mortem brain tissue from subjects with NII.
No significant polyglutamine-encoding repeat expansions were identified in the DNA from any of our FTLD-U patients. NII in the FTLD-U cases showed no 1C2 immunoreactivity.
We find no evidence to suggest that autosomal dominant FTLD-U with NII is a polyglutamine expansion disease.

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Available from: Scott J Neal, Oct 09, 2015
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    • "Some neurological TRDs show a preferential maternal transmission, such as fragile X syndrome, [132] Friedreich ataxia, [133] spino-cerebellar ataxia type 8 [63] and myotonic dystrophy [134]. Trinucleotide expansions may also be involved in some cases of frontotemporal dementia, although results are not conclusive [135,136]. There is currently no evidence for trinucleotide repeat expansions in AD. "
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    ABSTRACT: After advanced age, having a parent affected with Alzheimer's disease (AD) is the most significant risk factor for developing AD among cognitively normal (NL) individuals. Although rare genetic mutations have been identified among the early-onset forms of familial AD (EOFAD), the genetics of the more common forms of late-onset AD (LOAD) remain elusive. While some LOAD cases appear to be sporadic in nature, genetically mediated risk is evident from the familial aggregation of many LOAD cases. The patterns of transmission and biological mechanisms through which a family history of LOAD confers risk to the offspring are not known. Brain imaging studies using 2-[ (18) F]fluoro-2-deoxy-D-glucose positron emission tomography ((18)F-FDG PET) have shown that NL individuals with a maternal history of LOAD, but not with a paternal family history, express a phenotype characterised by a pattern of progressive reductions of brain glucose metabolism, similar to that in AD patients. As maternally inherited AD may be associated with as many as 20 per cent of the total LOAD population, understanding the causes and mechanisms of expression of this form of AD is of great relevance. This paper reviews known genetic mutations implicated in EOFAD and their effects on brain chemistry, structure and function; epidemiology and clinical research findings in LOAD, including in vivo imaging findings showing selective patterns of hypometabolism in maternally inherited AD; possible genetic mechanisms involved in maternal transmission of AD, including chromosome X mutations, mitochondrial DNA and imprinting; and genetic mechanisms involved in other neurological disorders with known or suspected maternal inheritance. The review concludes with a discussion of the potential role of brain imaging for identifying endophenotypes in NL individuals at risk for AD, and for directing investigation of potential susceptibility genes for AD.
    Human genomics 02/2010; 4(3):170-93. DOI:10.1186/1479-7364-4-3-170 · 2.15 Impact Factor
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    • "Many families in this group carry mutations in the gene encoding microtubule-associated protein tau (MAPT) and neuropathological examination reveals neuronal and glial tau-positive inclusions affected areas. Recently, it was shown that several large kindreds linked to chromosome 17 but lacking tau mutations and tau-immunoreactive inclusions represented a subtype of FTLD characterized by neuronal ubiquitin-positive, tau-negative inclusions (FTLD-U) [Mackenzie et al., 2006; Mukherjee et al., 2006; Rosso et al., 2001; Behrens et al., 2007]. Null mutations in the progranulin gene (GRN; MIM# 138945) were reported to cause disease in these families [Baker et al., 2006; Cruts et al., 2006]. "
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    ABSTRACT: Frontotemporal dementia (FTD) is a clinical term encompassing dementia characterized by the presence of two major phenotypes: 1) behavioral and personality disorder, and 2) language disorder, which includes primary progressive aphasia and semantic dementia. Recently, the gene for familial frontotemporal lobar degeneration (FTLD) with ubiquitin-positive, tau-negative inclusions (FTLD-U) linked to chromosome 17 was cloned. In the present study, 62 unrelated patients from the Washington University Alzheimer's Disease Research Center and the Midwest Consortium for FTD with clinically diagnosed FTD and/or neuropathologically characterized cases of FTLD-U with or without motor neuron disease (MND) were screened for mutations in the progranulin gene (GRN; also PGRN). We discovered two pathogenic mutations in four families: 1) a single-base substitution within the 3' splice acceptor site of intron 6/exon 7 (g.5913A>G [IVS6-2A>G]) causing skipping of exon 7 and premature termination of the coding sequence (PTC); and 2) a missense mutation in exon 1 (g.4068C>A) introducing a charged amino acid in the hydrophobic core of the signal peptide at residue 9 (p.A9D). Functional analysis in mutation carriers for the splice acceptor site mutation revealed a 50% decrease in GRN mRNA and protein levels, supporting haploinsufficiency. In contrast, there was no significant difference in the total GRN mRNA between cases and controls carrying the p.A9D mutation. Further, subcellular fractionation and confocal microscopy indicate that although the mutant protein is expressed, it is not secreted, and appears to be trapped within an intracellular compartment, possibly resulting in a functional haploinsufficiency.
    Human Mutation 04/2008; 29(4):512-21. DOI:10.1002/humu.20681 · 5.14 Impact Factor
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    ABSTRACT: INTRODUCCIÓN: La demencia frontotemporal (DFT) es una enfermedad neurodegenerativa, caracterizada por la atrofia circunscrita de los lóbulos frontales y temporales. Se acompaña de cambios en el comportamiento o alteraciones del lenguaje. Su inicio es insidioso, y su curso, progresivo. OBJETIVO: Revisar de manera general la DFT, haciendo hincapié en sus bases genéticas. MÉTODOS: Revisión de la literatura médica actual sobre el tema. RESULTADOS: Últimamente se han estudiado familias con herencia autosómica dominante de esta enfermedad, entre las cuales se han hallado diferentes genes causales. De estos los más importantes son el gen de la proteína asociada con los microtúbulos tau y el gen de la progranulina. Conclusión: Es necesario considerar un abordaje genético en el momento de enfrentarse a un paciente con DFT, para así indagar profundamente en los antecedentes familiares, con el fin de brindar una adecuada asesoría genética que permita aclarar las principales dudas de los pacientes y sus familias sobre este aspecto. [ABSTRACT] INTRODUCTION: Frontotemporal dementia (FTD) is a neurodegenerative disease characterized by the circumscribed atrophy of the frontal and temporal lobes along with progressive and insidious changes in behaviour and/or language impairment. OBJECTIVE: To review FTD, emphasizing its genetic bases. Methods: Review of the current medical literature about the subject. RESULTS: Families with a dominant autosomic inheritance pattern of this disease have been recently studied and different causal genes have been found, the most important being the microtubule associated protein tau gene and the progranulin gene, among others. CONCLUSIONS: It is important to consider a genetic approach in the assessment of a patient with FTD, investigating deeply into his family background. This way a proper genetic counseling can be performed thus solving the main doubts that the patient and relatives may have.
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