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2.
medRxiv ; 2024 Apr 05.
Article in English | MEDLINE | ID: mdl-38633784

ABSTRACT

Background and Objectives: TMEM106B has been proposed as a modifier of disease risk in FTLD-TDP, particularly in GRN mutation carriers. Furthermore, TMEM106B has been investigated as a disease modifier in the context of healthy aging and across multiple neurodegenerative diseases. The objective of this study is to evaluate and compare the effect of TMEM106B on gray matter volume and cognition in each of the common genetic FTD groups and in sporadic FTD patients. Methods: Participants were enrolled through the ARTFL/LEFFTDS Longitudinal Frontotemporal Lobar Degeneration (ALLFTD) study, which includes symptomatic and presymptomatic individuals with a pathogenic mutation in C9orf72, GRN, MAPT, VCP, TBK1, TARDBP, symptomatic non-mutation carriers, and non-carrier family controls. All participants were genotyped for the TMEM106B rs1990622 SNP. Cross-sectionally, linear mixed-effects models were fitted to assess an association between TMEM106B and genetic group interaction with each outcome measure (gray matter volume and UDS3-EF for cognition), adjusting for education, age, sex and CDR®+NACC-FTLD sum of boxes. Subsequently, associations between TMEM106B and each outcome measure were investigated within the genetic group. For longitudinal modeling, linear mixed-effects models with time by TMEM106B predictor interactions were fitted. Results: The minor allele of TMEM106B rs1990622, linked to a decreased risk of FTD, associated with greater gray matter volume in GRN mutation carriers under the recessive dosage model. This was most pronounced in the thalamus in the left hemisphere, with a retained association when considering presymptomatic GRN mutation carriers only. The minor allele of TMEM106B rs1990622 also associated with greater cognitive scores among all C9orf72 mutation carriers and in presymptomatic C9orf72 mutation carriers, under the recessive dosage model. Discussion: We identified associations of TMEM106B with gray matter volume and cognition in the presence of GRN and C9orf72 mutations. This further supports TMEM106B as modifier of TDP-43 pathology. The association of TMEM106B with outcomes of interest in presymptomatic GRN and C9orf72 mutation carriers could additionally reflect TMEM106B's impact on divergent pathophysiological changes before the appearance of clinical symptoms.

4.
Brain ; 146(10): 4055-4064, 2023 10 03.
Article in English | MEDLINE | ID: mdl-37100087

ABSTRACT

Transmembrane protein 106B (TMEM106B) is a tightly regulated glycoprotein predominantly localized to endosomes and lysosomes. Genetic studies have implicated TMEM106B haplotypes in the development of multiple neurodegenerative diseases with the strongest effect in frontotemporal lobar degeneration with TDP-43 pathology (FTLD-TDP), especially in progranulin (GRN) mutation carriers. Recently, cryo-electron microscopy studies showed that a C-terminal fragment (CTF) of TMEM106B (amino acid residues 120-254) forms amyloid fibrils in the brain of patients with FTLD-TDP, but also in brains with other neurodegenerative conditions and normal ageing brain. The functional implication of these fibrils and their relationship to the disease-associated TMEM106B haplotype remain unknown. We performed immunoblotting using a newly developed antibody to detect TMEM106B CTFs in the sarkosyl-insoluble fraction of post-mortem human brain tissue from patients with different proteinopathies (n = 64) as well as neuropathologically normal individuals (n = 10) and correlated the results with age and TMEM106B haplotype. We further compared the immunoblot results with immunohistochemical analyses performed in the same study population. Immunoblot analysis showed the expected ∼30 kDa band in the sarkosyl-insoluble fraction of frontal cortex tissue in at least some individuals with each of the conditions evaluated. Most patients with GRN mutations showed an intense band representing TMEM106B CTF, whereas in most neurologically normal individuals it was absent or much weaker. In the overall cohort, the presence of TMEM106B CTFs correlated strongly with both age (rs = 0.539, P < 0.001) and the presence of the TMEM106B risk haplotype (rs = 0.469, P < 0.001). Although there was a strong overall correlation between the results of immunoblot and immunohistochemistry (rs = 0.662, P < 0.001), 27 cases (37%) were found to have higher amounts of TMEM106B CTFs detected by immunohistochemistry, including most of the older individuals who were neuropathologically normal and individuals who carried two protective TMEM106B haplotypes. Our findings suggest that the formation of sarkosyl-insoluble TMEM106B CTFs is an age-related feature which is modified by TMEM106B haplotype, potentially underlying its disease-modifying effect. The discrepancies between immunoblot and immunohistochemistry in detecting TMEM106B pathology suggests the existence of multiple species of TMEM106B CTFs with possible biological relevance and disease implications.


Subject(s)
Frontotemporal Dementia , Frontotemporal Lobar Degeneration , Humans , Frontotemporal Dementia/pathology , Haplotypes , Cryoelectron Microscopy , Membrane Proteins/genetics , Membrane Proteins/metabolism , Nerve Tissue Proteins/genetics , Nerve Tissue Proteins/metabolism , Frontotemporal Lobar Degeneration/pathology , Brain/pathology
6.
Acta Neuropathol ; 145(3): 285-302, 2023 03.
Article in English | MEDLINE | ID: mdl-36527486

ABSTRACT

Several studies using cryogenic electron microscopy (cryo-EM) techniques recently reported the isolation and characterization of novel protein filaments, composed of a C-terminal fragment (CTF) of the endolysosomal transmembrane protein 106B (TMEM106B), from human post-mortem brain tissue with various neurodegenerative conditions and normal aging. Genetic variation in TMEM106B is known to influence the risk and presentation of several neurodegenerative diseases, especially frontotemporal dementia (FTD) caused by mutations in the progranulin gene (GRN). To further elucidate the significance of TMEM106B CTF, we performed immunohistochemistry with antibodies directed against epitopes within the filament-forming C-terminal region of TMEM106B. Accumulation of TMEM106B C-terminal immunoreactive (TMEM-ir) material was a common finding in all the conditions evaluated, including frontotemporal lobar degeneration with TDP-43 pathology (FTLD-TDP), Alzheimer's disease, tauopathies, synucleinopathies and neurologically normal aging. TMEM-ir material was present in a wide range of brain cell types and in a broad neuroanatomical distribution; however, there was no co-localization of TMEM-ir material with other neurodegenerative proteins in cellular inclusions. In most conditions, the presence and abundance of TMEM-ir aggregates correlated strongly with patient age and showed only a weak correlation with the TMEM106B haplotype or the primary pathological diagnosis. However, all patients with FTD caused by GRN mutations were found to have high levels of TMEM-ir material, including several who were relatively young (< 60 years). These findings suggest that the accumulation of TMEM106B CTF is a common age-related phenomenon, which may reflect lysosomal dysfunction. Although its significance in most neurodegenerative conditions remains uncertain, the consistent finding of extensive TMEM-ir material in cases of FTLD-TDP with GRN mutations further supports a pathomechanistic role of TMEM106B and lysosomal dysfunction in this specific disease population.


Subject(s)
Frontotemporal Dementia , Frontotemporal Lobar Degeneration , Neurodegenerative Diseases , Humans , Frontotemporal Dementia/genetics , Frontotemporal Dementia/pathology , Intercellular Signaling Peptides and Proteins , Neurodegenerative Diseases/genetics , Membrane Proteins/genetics , Membrane Proteins/metabolism , Nerve Tissue Proteins/genetics , Nerve Tissue Proteins/metabolism , Frontotemporal Lobar Degeneration/genetics , Aging/genetics
7.
Neurobiol Aging ; 67: 84-94, 2018 07.
Article in English | MEDLINE | ID: mdl-29653316

ABSTRACT

We previously reported a granulin (GRN) null mutation, originating from a common founder, in multiple Belgian families with frontotemporal dementia. Here, we used data of a 10-year follow-up study to describe in detail the clinical heterogeneity observed in this extended founder pedigree. We identified 85 patients and 40 unaffected mutation carriers, belonging to 29 branches of the founder pedigree. Most patients (74.4%) were diagnosed with frontotemporal dementia, while others had a clinical diagnosis of unspecified dementia, Alzheimer's dementia or Parkinson's disease. The observed clinical heterogeneity can guide clinical diagnosis, genetic testing, and counseling of mutation carriers. Onset of initial symptomatology is highly variable, ranging from age 45 to 80 years. Analysis of known modifiers, suggested effects of GRN rs5848, microtubule-associated protein tau H1/H2, and chromosome 9 open reading frame 72 G4C2 repeat length on onset age but explained only a minor fraction of the variability. Contrary, the extended GRN founder family is a valuable source for identifying other onset age modifiers based on exome or genome sequences. These modifiers might be interesting targets for developing disease-modifying therapies.


Subject(s)
Frontotemporal Dementia/genetics , Genetic Association Studies , Intercellular Signaling Peptides and Proteins/genetics , Loss of Function Mutation , Adult , Age of Onset , Aged , Aged, 80 and over , Belgium , Dimethylhydrazines , Female , Follow-Up Studies , Humans , Male , Middle Aged , Pedigree , Progranulins , Propionates
8.
Neurobiol Aging ; 66: 181.e3-181.e10, 2018 06.
Article in English | MEDLINE | ID: mdl-29555433

ABSTRACT

We investigated the genetic role of sortilin (SORT1) in frontotemporal dementia (FTD). SORT1 is the neuronal receptor for granulin, encoded by the progranulin gene (GRN), a major causal gene for inherited FTD. In Belgian cohorts of 636 FTD patients and 1066 unaffected control individuals, we identified 5 patient-only nonsynonymous rare variants in SORT1. Rare variant burden analysis showed a significant increase in rare coding variants in patients compared to control individuals (p = 0.04), particularly in the ß-propeller domain (p = 0.04), with 2 rare variants located in the predicted binding site for GRN (p = 0.001). We extended these observations by analyzing 3 independent patient/control cohorts sampled in Spain, Italy, and Portugal by partners of the European Early-Onset Dementia Consortium, together with 1155 FTD patients and 1161 control persons. An additional 7 patient-only nonsynonymous variants were observed in SORT1 in European patients. Meta-analysis of the rare nonsynonymous variants in the Belgian and European patient/control cohorts revealed a significant enrichment in FTD patients (p = 0.006), establishing SORT1 as a genetic risk factor for FTD.


Subject(s)
Adaptor Proteins, Vesicular Transport/genetics , Genetic Association Studies , Genetic Variation/genetics , Adaptor Proteins, Vesicular Transport/chemistry , Aged , Belgium , Binding Sites , Cohort Studies , Europe , Female , Humans , Intercellular Signaling Peptides and Proteins , Male , Middle Aged , Progranulins , Protein Binding , Protein Domains , Risk
9.
JAMA Neurol ; 74(4): 445-452, 2017 04 01.
Article in English | MEDLINE | ID: mdl-28192553

ABSTRACT

Importance: Patients carrying a C9orf72 repeat expansion leading to frontotemporal dementia and/or amyotrophic lateral sclerosis have highly variable ages at onset of disease, suggesting the presence of modifying factors. Objective: To provide clinical-based evidence for disease anticipation in families carrying a C9orf72 repeat expansion by analyzing age at onset, disease duration, and age at death in successive generations. Design, Setting, and Participants: This cohort study was performed from June 16, 2000, to June 1, 2016, in 36 extended Belgian families in which a C9orf72 repeat expansion was segregating. The generational effect on age at onset, disease duration, and age at death was estimated using a mixed effects Cox proportional hazards regression model, including random-effects terms for within-family correlation and kinship. Time until disease onset or last examination, time from disease onset until death or last examination, or age at death was collected for for 244 individuals (132 proven or obligate C9orf72 carriers), of whom 147 were clinically affected (89 proven or obligate C9orf72 carriers). Main Outcomes and Measures: Generational effect on age at onset, disease duration, and age at death. Results: Among the 111 individuals with age at onset available (66 men and 45 women; mean [SD] age, 57.2 [9.1] years), the mean (SD) age at onset per generation (from earliest-born to latest-born generation) was 62.5 (8.3), 57.1 (8.2), 54.6 (10.2), and 49.3 (7.5) years. Censored regression analysis on all affected and unaffected at-risk relatives confirmed a decrease in age at onset in successive generations (P < .001). No generational effect was observed for disease duration or age at death. Conclusions and Relevance: The clinical data provide supportive evidence for the occurrence of disease anticipation in families carrying a C9orf72 repeat expansion by means of a decrease in age at onset across successive generations. This finding may help clinicians decide from which age onward it may be relevant to clinically follow presymptomatic individuals who carry a C9orf72 repeat expansion.


Subject(s)
Amyotrophic Lateral Sclerosis/genetics , DNA Repeat Expansion/genetics , Frontotemporal Dementia/genetics , Pedigree , Proteins/genetics , Age of Onset , Aged , C9orf72 Protein , Cohort Studies , Female , Humans , Male , Middle Aged , Proportional Hazards Models
10.
Neurology ; 86(23): 2126-33, 2016 06 07.
Article in English | MEDLINE | ID: mdl-27037232

ABSTRACT

OBJECTIVE: To generate a clinical and pathologic phenotype of patients carrying rare loss-of-function mutations in ABCA7, identified in a Belgian Alzheimer patient cohort and in an autosomal dominant family. METHODS: We performed a retrospective review of available data records, medical records, results of CSF analyses and neuroimaging studies, and neuropathology data. RESULTS: The mean onset age of the mutation carriers (n = 22) was 73.4 ± 8.4 years with a wide age range of 36 (54-90) years, which was independent of APOE genotype and cerebrovascular disease. The mean disease duration was 5.7 ± 3.0 years (range 2-12 years). A positive family history was recorded for 10 carriers (45.5%). All patient carriers except one presented with memory complaints. The 4 autopsied brains showed typical immunohistochemical changes of late-onset Alzheimer disease. CONCLUSIONS: All patients carrying a loss-of-function mutation in ABCA7 exhibited a classical Alzheimer disease phenotype, though with a striking wide onset age range, suggesting the influence of unknown modifying factors.


Subject(s)
ATP-Binding Cassette Transporters/genetics , Alzheimer Disease/genetics , Alzheimer Disease/physiopathology , Mutation , Age of Onset , Aged , Aged, 80 and over , Alzheimer Disease/diagnostic imaging , Alzheimer Disease/pathology , Apolipoprotein E4/genetics , Biomarkers/cerebrospinal fluid , Brain/diagnostic imaging , Brain/pathology , Cerebrovascular Disorders/complications , Cerebrovascular Disorders/diagnostic imaging , Cerebrovascular Disorders/genetics , Cerebrovascular Disorders/pathology , Disease Progression , Female , Heterozygote , Humans , Male , Middle Aged , Retrospective Studies
11.
Brain ; 139(Pt 2): 452-67, 2016 Feb.
Article in English | MEDLINE | ID: mdl-26674655

ABSTRACT

We identified in a cohort of patients with frontotemporal dementia (n = 481) or amyotrophic lateral sclerosis (n = 147), 10 index patients carrying a TBK1 loss of function mutation reducing TBK1 expression by 50%. Here, we describe the clinical and pathological characteristics of the 10 index patients and six of their affected relatives carrying a TBK1 mutation. Six TBK1 carriers were diagnosed with frontotemporal dementia, seven with amyotrophic lateral sclerosis, one with both clinical phenotypes and two with dementia unspecified. The mean age at onset of all 16 TBK1 carriers was 62.1 ± 8.9 years (range 41-73) with a mean disease duration of 4.7 ± 4.5 years (range 1-13). TBK1 carriers with amyotrophic lateral sclerosis had shorter disease duration than carriers with frontotemporal dementia. Six of seven TBK1 carriers were diagnosed with the behavioural variant of frontotemporal dementia, presenting predominantly as disinhibition. Memory loss was an important associated symptom in the initial phase of the disease in all but one of the carriers with frontotemporal dementia. Three of the patients with amyotrophic lateral sclerosis exhibited pronounced upper motor neuron symptoms. Overall, neuroimaging displayed widespread atrophy, both symmetric and asymmetric. Brain perfusion single-photon emission computed tomography or fluorodeoxyglucose-positron emission tomography showed asymmetric and predominantly frontotemporal involvement. Neuropathology in two patients demonstrated TDP-43 type B pathology. Further, we compared genotype-phenotype data of TBK1 carriers with frontotemporal dementia (n = 7), with those of frontotemporal dementia patients with a C9orf72 repeat expansion (n = 65) or a GRN mutation (n = 52) and with frontotemporal dementia patients (n = 259) negative for mutations in currently known causal genes. TBK1 carriers with frontotemporal dementia had a later age at onset (63.3 years) than C9orf72 carriers (54.3 years) (P = 0.019). In clear contrast with TBK1 carriers, GRN carriers were more often diagnosed with the language variant than the behavioural variant, and presented in case of the diagnosis of behavioural variant, more often than TBK1 carriers with apathy as the predominant characteristic (P = 0.004). Also, TBK1 carriers exhibited more often extrapyramidal symptoms than C9orf72 carriers (P = 0.038). In conclusion, our study identified clinical differences between the TBK1, C9orf72 and GRN carriers, which allows us to formulate guidelines for genetic diagnosis. After a negative result for C9orf72, patients with both frontotemporal dementia and amyotrophic lateral sclerosis should be tested first for mutations in TBK1. Specifically in frontotemporal dementia patients with early memory difficulties, a relatively late age at onset or extrapyramidal symptoms, screening for TBK1 mutations should be considered.


Subject(s)
Amyotrophic Lateral Sclerosis/genetics , Frontotemporal Dementia/genetics , Heterozygote , Intercellular Signaling Peptides and Proteins/genetics , Protein Serine-Threonine Kinases/genetics , Proteins/genetics , Adult , Aged , Amyotrophic Lateral Sclerosis/diagnosis , Amyotrophic Lateral Sclerosis/epidemiology , Belgium/epidemiology , C9orf72 Protein , Cohort Studies , Female , Frontotemporal Dementia/diagnosis , Frontotemporal Dementia/epidemiology , Humans , Male , Middle Aged , Mutation/genetics , Pedigree , Progranulins
12.
Neurology ; 85(24): 2116-25, 2015 Dec 15.
Article in English | MEDLINE | ID: mdl-26581300

ABSTRACT

OBJECTIVE: To assess the genetic contribution of TBK1, a gene implicated in amyotrophic lateral sclerosis (ALS), frontotemporal dementia (FTD), and FTD-ALS, in Belgian FTD and ALS patient cohorts containing a significant part of genetically unresolved patients. METHODS: We sequenced TBK1 in a hospital-based cohort of 482 unrelated patients with FTD and FTD-ALS and 147 patients with ALS and an extended Belgian FTD-ALS family DR158. We followed up mutation carriers by segregation studies, transcript and protein expression analysis, and immunohistochemistry. RESULTS: We identified 11 patients carrying a loss-of-function (LOF) mutation resulting in an overall mutation frequency of 1.7% (11/629), 1.1% in patients with FTD (5/460), 3.4% in patients with ALS (5/147), and 4.5% in patients with FTD-ALS (1/22). We found 1 LOF mutation, p.Glu643del, in 6 unrelated patients segregating with disease in family DR158. Of 2 mutation carriers, brain and spinal cord was characterized by TDP-43-positive pathology. The LOF mutations including the p.Glu643del mutation led to loss of transcript or protein in blood and brain. CONCLUSIONS: TBK1 LOF mutations are the third most frequent cause of clinical FTD in the Belgian clinically based patient cohort, after C9orf72 and GRN, and the second most common cause of clinical ALS after C9orf72. These findings reinforce that FTD and ALS belong to the same disease continuum.


Subject(s)
Frontotemporal Dementia/diagnosis , Frontotemporal Dementia/genetics , Mutation/genetics , Protein Serine-Threonine Kinases/deficiency , Protein Serine-Threonine Kinases/genetics , Adult , Aged , Aged, 80 and over , Belgium/epidemiology , Cohort Studies , Female , Frontotemporal Dementia/epidemiology , Humans , Male , Middle Aged , Pedigree
13.
Acta Neuropathol ; 128(3): 397-410, 2014 Sep.
Article in English | MEDLINE | ID: mdl-24899140

ABSTRACT

Mutations in the gene coding for Sequestosome 1 (SQSTM1) have been genetically associated with amyotrophic lateral sclerosis (ALS) and Paget disease of bone. In the present study, we analyzed the SQSTM1 coding sequence for mutations in an extended cohort of 1,808 patients with frontotemporal lobar degeneration (FTLD), ascertained within the European Early-Onset Dementia consortium. As control dataset, we sequenced 1,625 European control individuals and analyzed whole-exome sequence data of 2,274 German individuals (total n = 3,899). Association of rare SQSTM1 mutations was calculated in a meta-analysis of 4,332 FTLD and 10,240 control alleles. We identified 25 coding variants in FTLD patients of which 10 have not been described. Fifteen mutations were absent in the control individuals (carrier frequency <0.00026) whilst the others were rare in both patients and control individuals. When pooling all variants with a minor allele frequency <0.01, an overall frequency of 3.2 % was calculated in patients. Rare variant association analysis between patients and controls showed no difference over the whole protein, but suggested that rare mutations clustering in the UBA domain of SQSTM1 may influence disease susceptibility by doubling the risk for FTLD (RR = 2.18 [95 % CI 1.24-3.85]; corrected p value = 0.042). Detailed histopathology demonstrated that mutations in SQSTM1 associate with widespread neuronal and glial phospho-TDP-43 pathology. With this study, we provide further evidence for a putative role of rare mutations in SQSTM1 in the genetic etiology of FTLD and showed that, comparable to other FTLD/ALS genes, SQSTM1 mutations are associated with TDP-43 pathology.


Subject(s)
Adaptor Proteins, Signal Transducing/genetics , Frontotemporal Lobar Degeneration/genetics , Genetic Predisposition to Disease/genetics , Polymorphism, Single Nucleotide/genetics , Adult , Aged , Aged, 80 and over , Amyotrophic Lateral Sclerosis , Animals , Cohort Studies , DNA Mutational Analysis , DNA-Binding Proteins/genetics , Europe , Female , Frontotemporal Lobar Degeneration/pathology , Humans , International Cooperation , Male , Meta-Analysis as Topic , Middle Aged , Sequestosome-1 Protein
14.
J Med Genet ; 51(6): 419-24, 2014 Jun.
Article in English | MEDLINE | ID: mdl-24706941

ABSTRACT

BACKGROUND: The GGGGCC-repeat expansion in C9orf72 is the most frequent mutation found in patients with amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Most of the studies on C9orf72 have relied on repeat-primed PCR (RP-PCR) methods for detection of the expansions. To investigate the inherent limitations of this technique, we compared methods and results of 14 laboratories. METHODS: The 14 laboratories genotyped DNA from 78 individuals (diagnosed with ALS or FTD) in a blinded fashion. Eleven laboratories used a combination of amplicon-length analysis and RP-PCR, whereas three laboratories used RP-PCR alone; Southern blotting techniques were used as a reference. RESULTS: Using PCR-based techniques, 5 of the 14 laboratories got results in full accordance with the Southern blotting results. Only 50 of the 78 DNA samples got the same genotype result in all 14 laboratories. There was a high degree of false positive and false negative results, and at least one sample could not be genotyped at all in 9 of the 14 laboratories. The mean sensitivity of a combination of amplicon-length analysis and RP-PCR was 95.0% (73.9-100%), and the mean specificity was 98.0% (87.5-100%). Overall, a sensitivity and specificity of more than 95% was observed in only seven laboratories. CONCLUSIONS: Because of the wide range seen in genotyping results, we recommend using a combination of amplicon-length analysis and RP-PCR as a minimum in a research setting. We propose that Southern blotting techniques should be the gold standard, and be made obligatory in a clinical diagnostic setting.


Subject(s)
Clinical Laboratory Services/standards , Genetic Testing/methods , Genetic Testing/standards , Proteins/genetics , Amyotrophic Lateral Sclerosis/genetics , C9orf72 Protein , Female , Frontotemporal Dementia/genetics , Humans , Male , Reproducibility of Results
15.
JAMA Neurol ; 70(3): 365-73, 2013 Mar 01.
Article in English | MEDLINE | ID: mdl-23338682

ABSTRACT

OBJECTIVE: To characterize patients with frontotemporal lobar degeneration (FTLD) with a repeat expansion mutation in the gene C9orf72, and to determine whether there are differences in the clinical presentation compared with FTLD carriers of a mutation in GRN or MAPT or with patients with FTLD without mutation. DESIGN: Patient series. SETTING: Dementia clinics in Flanders, Belgium. PATIENTS: Two hundred seventy-five genetically and phenotypically thoroughly characterized patients with FTLD. MAIN OUTCOME MEASURES: Clinical and demographic characteristics of 26 C9orf72 expansion carriers compared with patients with a GRN or MAPT mutation, as well as patients with familial and sporadic FTLD without mutation. RESULTS: C9orf72 expansion carriers developed FTLD at an early age (average, 55.3 years; range, 42-69 years), significantly earlier than in GRN mutation carriers or patients with FTLD without mutation. Mean survival (6.2 years; range, 1.5-17.0 years) was similar to other patient groups. Most developed behavioral variant frontotemporal dementia (85%), with disinhibited behavior as the prominent feature. Concomitant amyotrophic lateral sclerosis is a strong distinguishing feature for C9orf72 -associated FTLD. However, in most patients (73%), amyotrophic lateral sclerosis symptoms were absent. Compared with C9orf72 expansion carriers, nonfluent aphasia and limb apraxia were significantly more common in GRN mutation carriers. CONCLUSIONS: C9orf72 -associated FTLD most often presents with early-onset behavioral variant frontotemporal dementia with disinhibition as the prominent feature, with or without amyotrophic lateral sclerosis. Based on the observed genotype-phenotype correlations between the different FTLD syndromes and different genetic causes, we propose a decision tree to guide clinical genetic testing in patients clinically diagnosed as having FTLD.


Subject(s)
DNA Repeat Expansion/genetics , Frontotemporal Lobar Degeneration/genetics , Genetic Carrier Screening , Intercellular Signaling Peptides and Proteins/genetics , Proteins/genetics , tau Proteins/genetics , Adult , Age of Onset , Aged , Belgium/epidemiology , C9orf72 Protein , Cohort Studies , Female , Frontotemporal Lobar Degeneration/epidemiology , Humans , Male , Middle Aged , Mutation/genetics , Progranulins
16.
Neurobiol Aging ; 33(3): 629.e5-629.e18, 2012 Mar.
Article in English | MEDLINE | ID: mdl-22118943

ABSTRACT

Based on the substantial overlap in clinical and pathological characteristics of dementia with Lewy bodies (DLB) and Parkinson disease with dementia (PDD) with Alzheimer disease (AD) and Parkinson disease (PD) we hypothesized that these disorders might share underlying genetic factors. The contribution of both sequence and copy number variants (CNVs) in known AD and PD genes to the genetic etiology of DLB and PDD however is currently unclear. Therefore, we performed a gene-based mutation analysis of all major AD and PD genes in 99 DLB and 75 PDD patients, including familial and sporadic forms, from Flanders, Belgium. Also, copy number variants in APP, SNCA, and PARK2 were determined. In the AD genes we detected proven pathogenic missense mutations in PSEN1 and PSEN2, and 2 novel missense variants in PSEN2 and MAPT. In the PD genes we identified 1 SNCA duplication, the LRRK2 R1441C founder mutation and 4 novel heterozygous missense variants with unknown pathogenicity. Our results suggest a contribution of established AD and PD genes to the genetic etiology of DLB and PDD though to a limited extent. They do support the hypothesis of a genetic overlap between members of the Lewy body disease spectrum, but additional genes still have to exist.


Subject(s)
Genetic Predisposition to Disease/genetics , Lewy Body Disease/genetics , Parkinson Disease/genetics , Point Mutation/genetics , Adult , Aged , Aged, 80 and over , Amyloid beta-Protein Precursor/genetics , Case-Control Studies , Cohort Studies , DNA Copy Number Variations/genetics , Female , Genetic Predisposition to Disease/epidemiology , Humans , Lewy Body Disease/epidemiology , Lewy Body Disease/metabolism , Male , Parkinson Disease/epidemiology , Parkinson Disease/metabolism , Pedigree , Prospective Studies
17.
Neurobiol Aging ; 33(5): 1004.e17-20, 2012 May.
Article in English | MEDLINE | ID: mdl-22035589

ABSTRACT

There exists considerable clinical and pathological overlap between frontotemporal lobar degeneration (FTLD) and amyotrophic lateral sclerosis (ALS), which implies that these 2 neurodegenerative conditions share common pathogenic mechanisms. Recently, intermediate-length (27-33) polyglutamine (polyQ) expansions in ataxin-2 (ATXN2) have been associated with increased risk for ALS, while expansions of > 34 repeats are known to cause spinocerebellar ataxia type 2 (Sca-2). We identified in 72 ALS patients one patient with a 33 polyQ expansion that was absent in 810 control individuals. This allele was also found in one patient with concomitant ALS-Sca-2. In contrast, in a Flanders-Belgian series of 270 FTLD and 22 FTLD-ALS patients, we found no association with intermediate-length polyQ expansions nor did we observe patient-specific long expansions in agreement with the recent observation in a screening of a substantial sized cohort of patients with diverse neurodegenerative brain diseases. Our results provide further support to the notion that ATXN2 associated polyglutamine amplification is specific to the ALS-end of the FTLD-ALS disease spectrum.


Subject(s)
Amyotrophic Lateral Sclerosis/epidemiology , Amyotrophic Lateral Sclerosis/genetics , DNA Repeat Expansion/genetics , Frontotemporal Lobar Degeneration/epidemiology , Frontotemporal Lobar Degeneration/genetics , Nerve Tissue Proteins/genetics , Aged , Amyotrophic Lateral Sclerosis/ethnology , Ataxins , Belgium/epidemiology , Cohort Studies , Female , Frontotemporal Lobar Degeneration/ethnology , Genetic Association Studies , Humans , Male , Middle Aged
18.
Lancet Neurol ; 11(1): 54-65, 2012 Jan.
Article in English | MEDLINE | ID: mdl-22154785

ABSTRACT

BACKGROUND: Amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD) are extremes of a clinically, pathologically, and genetically overlapping disease spectrum. A locus on chromosome 9p21 has been associated with both disorders, and we aimed to identify the causal gene within this region. METHODS: We studied 305 patients with FTLD, 137 with ALS, and 23 with concomitant FTLD and ALS (FTLD-ALS) and 856 controls from Flanders (Belgium); patients were identified from a hospital-based cohort and were negative for mutations in known FTLD and ALS genes. We also examined the family of one patient with FTLD-ALS previously linked to 9p21 (family DR14). We analysed 130 kbp at 9p21 in association and segregation studies, genomic sequencing, repeat genotyping, and expression studies to identify the causal mutation. We compared genotype-phenotype correlations between mutation carriers and non-carriers. FINDINGS: In the patient-control cohort, the single-nucleotide polymorphism rs28140707 within the 130 kbp region of 9p21 was associated with disease (odds ratio [OR] 2·6, 95% CI 1·5-4·7; p=0·001). A GGGGCC repeat expansion in C9orf72 completely co-segregated with disease in family DR14. The association of rs28140707 with disease in the patient-control cohort was abolished when we excluded GGGGCC repeat expansion carriers. In patients with familial disease, six (86%) of seven with FTLD-ALS, seven (47%) of 15 with ALS, and 12 (16%) of 75 with FTLD had the repeat expansion. In patients without known familial disease, one (6%) of 16 with FTLD-ALS, six (5%) of 122 with ALS, and nine (4%) of 230 with FTLD had the repeat expansion. Mutation carriers primarily presented with classic ALS (10 of 11 individuals) or behavioural variant FTLD (14 of 15 individuals). Mean age at onset of FTLD was 55·3 years (SD 8·4) in 21 mutation carriers and 63·2 years (9·6) in 284 non-carriers (p=0·001); mean age at onset of ALS was 54·5 years (9·9) in 13 carriers and 60·4 years (11·4) in 124 non-carriers. Postmortem neuropathological analysis of the brains of three mutation carriers with FTLD showed a notably low TDP-43 load. In brain at postmortem, C9orf72 expression was reduced by nearly 50% in two carriers compared with nine controls (p=0·034). In familial patients, 14% of FTLD-ALS, 50% of ALS, and 62% of FTLD was not accounted for by known disease genes. INTERPRETATION: We identified a pathogenic GGGGCC repeat expansion in C9orf72 on chromosome 9p21, as recently also reported in two other studies. The GGGGCC repeat expansion is highly penetrant, explaining all of the contribution of chromosome 9p21 to FTLD and ALS in the Flanders-Belgian cohort. Decreased expression of C9orf72 in brain suggests haploinsufficiency as an underlying disease mechanism. Unidentified genes probably also contribute to the FTLD-ALS disease spectrum. FUNDING: Full funding sources listed at end of paper (see Acknowledgments).


Subject(s)
Amyotrophic Lateral Sclerosis/genetics , Chromosomes, Human, Pair 9 , DNA Repeat Expansion , Frontotemporal Lobar Degeneration/genetics , Promoter Regions, Genetic , Adult , Age of Onset , Aged , Cohort Studies , DNA Mutational Analysis , Female , Genetic Loci , Genotype , Humans , Male , Middle Aged , Polymorphism, Single Nucleotide
19.
Brain ; 134(Pt 3): 808-15, 2011 Mar.
Article in English | MEDLINE | ID: mdl-21354975

ABSTRACT

In a genome-wide association study of frontotemporal lobar degeneration with pathological inclusions of TAR DNA-binding protein, significant association was obtained with three single nucleotide polymorphisms at 7p21.3, in a region encompassing the gene TMEM106B. This study also suggested a potential modifying effect of TMEM106B on disease since the association was strongest in progranulin mutation carriers. Further, the risk effect seemed to correlate with increased TMEM106B expression in patients. In the present study, we sought to replicate these three findings using an independent Flanders-Belgian cohort of primarily clinically diagnosed patients with frontotemporal lobar degeneration (n = 288). We were able to confirm the association with TMEM106B with a P-value of 0.008 for rs1990622, the top marker from the genome-wide association study [odds ratio 0.75 (95% confidence interval 0.61-0.93)]. Further, high-density single nucleotide polymorphism mapping suggested that the association was solely driven by the gene TMEM106B. Homozygous carriers of the TMEM106B protective alleles had a 50% reduced risk of developing frontotemporal lobar degeneration. However, we were unable to detect a modifying effect of the TMEM106B single nucleotide polymorphisms on onset age in progranulin mutation carriers belonging to an extended, clinical and pathological well-documented founder family segregating a progranulin null mutation. Also, we could not observe significant differences in messenger RNA expression between patients and control individuals in lymphoblast cell lines and in brain frontal cortex. In conclusion, we replicated the genetic TMEM106B association in a primarily clinically diagnosed cohort of patients with frontotemporal lobar degeneration from Flanders-Belgium. Additional studies are needed to unravel the molecular role of TMEM106B in disease onset and pathogenesis.


Subject(s)
Frontotemporal Lobar Degeneration/diagnosis , Frontotemporal Lobar Degeneration/genetics , Genetic Predisposition to Disease , Membrane Proteins/genetics , Nerve Tissue Proteins/genetics , Polymorphism, Single Nucleotide/genetics , Age of Onset , Aged , Cohort Studies , Female , Frontal Lobe/pathology , Frontotemporal Lobar Degeneration/pathology , Gene Expression Regulation/physiology , Gene Frequency , Genome-Wide Association Study , Genotype , Humans , Linkage Disequilibrium , Lymphocytes/metabolism , Lymphocytes/pathology , Male , Middle Aged
20.
Stroke ; 41(5): 863-8, 2010 May.
Article in English | MEDLINE | ID: mdl-20360539

ABSTRACT

BACKGROUND AND PURPOSE: Data on the prevalence of Fabry disease in patients with central nervous system pathology are limited and controversial. In this study, we assessed the prevalence of Fabry disease in young patients presenting with cerebrovascular disease in Belgium. METHODS: In this national, prospective, multicenter study, we screened for Fabry disease in 1000 patients presenting with ischemic stroke, transient ischemic attack, or intracranial hemorrhage; unexplained white matter lesions; or vertebrobasilar dolichoectasia. In male patients, we measured alpha-galactosidase A (alpha-GAL A) activity in dried blood spots. Female patients were screened for mutations by exonic DNA sequencing of the alpha-GAL A gene. RESULTS: alpha-GAL A activity was deficient in 19 men (3.5%), although all had normal alpha-GAL A gene sequences. Enzymatic deficiency was confirmed on repeat assessment in 2 male patients (0.4%). We identified missense mutations in 8 unrelated female patients (1.8%): Asp313Tyr (n=5), Ala143Thr (n=2), and Ser126Gly (n=1). The pathogenicity of the 2 former missense mutations is controversial. Ser126Gly is a novel mutation that can be linked to late-onset Fabry disease. CONCLUSIONS: alpha-GAL A deficiency may play a role in up to 1% of young patients presenting with cerebrovascular disease. These findings suggest that atypical variants of Fabry disease with late-onset cerebrovascular disease exist, although the clinical relevance is unclear in all cases.


Subject(s)
Cerebrovascular Disorders/epidemiology , Fabry Disease/epidemiology , Adolescent , Adult , Age Factors , Belgium/epidemiology , Cerebrovascular Disorders/diagnosis , Cerebrovascular Disorders/enzymology , Cerebrovascular Disorders/genetics , Cohort Studies , Fabry Disease/diagnosis , Fabry Disease/enzymology , Fabry Disease/genetics , Female , Humans , Male , Middle Aged , Prevalence , Prospective Studies , Young Adult , alpha-Galactosidase/genetics
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