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1.  Neuropsychiatric Disturbances in Alzheimer’s Disease: What Have We Learned from Neuropathological Studies? 
Current Alzheimer Research  2016;13(10):1145-1164.
Neuropsychiatric symptoms (NPS) are an integral part of the dementia syndrome and were therefore recently included in the core diagnostic criteria of dementia. The near universal prevalence of NPS in Alzheimer’s disease (AD), combined with their disabling effects on patients and caregivers, is contrasted by the fact that few effective and safe treatments exist, which is in part to be attributed to our incomplete understanding of the neurobiology of NPS. In this review, we describe the pathological alterations typical for AD, including spreading and evolution of burden, effect on the molecular and cellular integrity, functional consequences and atrophy of NPS-relevant brain regions and circuits in correlation with specific NPS assessments. It is thereby clearly established that NPS are fundamental expressions of the underlying neurodegenerative brain disease and not simply reflect the patients’ secondary response to their illness. Neuropathological studies, moreover, include a majority of end-stage patient samples, which may not correctly represent the pathophysiological environment responsible for particular NPS that may already be present in an early stage, or even prior to AD diagnosis. The burdensome nature and high prevalence of NPS, in combination with the absence of effective and safe pharmacotherapies, provide a strong incentive to continue neuropathological and neurochemical, as well as imaging and other relevant approaches to further improve our apprehension of the neurobiology of NPS.
PMCID: PMC5070416  PMID: 27137218
Aggression; amyloid; depression; neurofibrillary tangles; neuronal loss; psychosis; neurotransmitter
2.  Rare Variants in PLD3 Do Not Affect Risk for Early‐Onset Alzheimer Disease in a European Consortium Cohort 
Human Mutation  2015;36(12):1226-1235.
Rare variants in the phospholipase D3 gene (PLD3) were associated with increased risk for late‐onset Alzheimer disease (LOAD). We identified a missense mutation in PLD3 in whole‐genome sequence data of a patient with autopsy confirmed Alzheimer disease (AD) and onset age of 50 years. Subsequently, we sequenced PLD3 in a Belgian early‐onset Alzheimer disease (EOAD) patient (N = 261) and control (N = 319) cohort, as well as in European EOAD patients (N = 946) and control individuals (N = 1,209) ascertained in different European countries. Overall, we identified 22 rare variants with a minor allele frequency <1%, 20 missense and two splicing mutations. Burden analysis did not provide significant evidence for an enrichment of rare PLD3 variants in EOAD patients in any of the patient/control cohorts. Also, meta‐analysis of the PLD3 data, including a published dataset of a German EOAD cohort, was not significant (P = 0.43; OR = 1.53, 95% CI 0.60–3.31). Consequently, our data do not support a role for PLD3 rare variants in the genetic etiology of EOAD in European EOAD patients. Our data corroborate the negative replication data obtained in LOAD studies and therefore a genetic role of PLD3 in AD remains to be demonstrated.
PMCID: PMC5057316  PMID: 26411346
Alzheimer dementia; EOAD; PLD3; next‐generation sequencing; rare variants; meta‐analysis
3.  Alzheimer’s disease cerebrospinal fluid biomarker in cognitively normal subjects 
Brain  2015;138(9):2701-2715.
In a large multicentre study, Toledo et al. examine core Alzheimer’s disease CSF biomarkers in 1233 cognitively normal subjects aged 40–85 years. Alzheimer disease-like changes in Aβ1-42 are seen as early as middle age, while APOE genotype strongly modifies age-related effects on both Aβ1–42 and phosphorylated/total tau.
In a large multicentre study, Toledo et al. examine core Alzheimer’s disease CSF biomarkers in 1233 cognitively normal subjects aged 40–85 years. Alzheimer disease-like changes in Aβ1-42 are seen as early as middle age, while APOE genotype strongly modifies age-related effects on both Aβ1–42 and phosphorylated/total tau.
In a large multicentre sample of cognitively normal subjects, as a function of age, gender and APOE genotype, we studied the frequency of abnormal cerebrospinal fluid levels of Alzheimer’s disease biomarkers including: total tau, phosphorylated tau and amyloid-β1-42. Fifteen cohorts from 12 different centres with either enzyme-linked immunosorbent assays or Luminex® measurements were selected for this study. Each centre sent nine new cerebrospinal fluid aliquots that were used to measure total tau, phosphorylated tau and amyloid-β1-42 in the Gothenburg laboratory. Seven centres showed a high correlation with the new Gothenburg measurements; therefore, 10 cohorts from these centres are included in the analyses here (1233 healthy control subjects, 40–84 years old). Amyloid-β amyloid status (negative or positive) and neurodegeneration status (negative or positive) was established based on the pathological cerebrospinal fluid Alzheimer’s disease cut-off values for cerebrospinal fluid amyloid-β1-42 and total tau, respectively. While gender did not affect these biomarker values, APOE genotype modified the age-associated changes in cerebrospinal fluid biomarkers such that APOE ε4 carriers showed stronger age-related changes in cerebrospinal fluid phosphorylated tau, total tau and amyloid-β1-42 values and APOE ε2 carriers showed the opposite effect. At 40 years of age, 76% of the subjects were classified as amyloid negative, neurodegeneration negative and their frequency decreased to 32% at 85 years. The amyloid-positive neurodegeneration-negative group remained stable. The amyloid-negative neurodegeneration-positive group frequency increased slowly from 1% at 44 years to 16% at 85 years, but its frequency was not affected by APOE genotype. The amyloid-positive neurodegeneration-positive frequency increased from 1% at 53 years to 28% at 85 years. Abnormally low cerebrospinal fluid amyloid-β1-42 levels were already frequent in midlife and APOE genotype strongly affects the levels of cerebrospinal fluid amyloid-β1-42, phosphorylated tau and total tau across the lifespan without influencing the frequency of subjects with suspected non-amyloid pathology.
PMCID: PMC4643624  PMID: 26220940
Alzheimer’s disease; dementia; biomarkers; cognitive ageing; imaging
4.  Phenotypic characteristics of Alzheimer patients carrying an ABCA7 mutation 
Neurology  2016;86(23):2126-2133.
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.
We performed a retrospective review of available data records, medical records, results of CSF analyses and neuroimaging studies, and neuropathology data.
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.
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.
PMCID: PMC4917260  PMID: 27037232
5.  A comprehensive study of the genetic impact of rare variants in SORL1 in European early-onset Alzheimer’s disease 
Acta Neuropathologica  2016;132:213-224.
The sortilin-related receptor 1 (SORL1) gene has been associated with increased risk for Alzheimer’s disease (AD). Rare genetic variants in the SORL1 gene have also been implicated in autosomal dominant early-onset AD (EOAD). Here we report a large-scale investigation of the contribution of genetic variability in SORL1 to EOAD in a European EOAD cohort. We performed massive parallel amplicon-based re-sequencing of the full coding region of SORL1 in 1255 EOAD patients and 1938 age- and origin-matched control individuals in the context of the European Early-Onset Dementia (EOD) consortium, originating from Belgium, Spain, Portugal, Italy, Sweden, Germany, and Czech Republic. We identified six frameshift variants and two nonsense variants that were exclusively present in patients. These mutations are predicted to result in haploinsufficiency through nonsense-mediated mRNA decay, which could be confirmed experimentally for SORL1 p.Gly447Argfs*22 observed in a Belgian EOAD patient. We observed a 1.5-fold enrichment of rare non-synonymous variants in patients (carrier frequency 8.8 %; SkatOMeta p value 0.0001). Of the 84 non-synonymous rare variants detected in the full patient/control cohort, 36 were only detected in patients. Our findings underscore a role of rare SORL1 variants in EOAD, but also show a non-negligible frequency of these variants in healthy individuals, necessitating the need for pathogenicity assays. Premature stop codons due to frameshift and nonsense variants, have so far exclusively been found in patients, and their predicted mode of action corresponds with evidence from in vitro functional studies of SORL1 in AD.
Electronic supplementary material
The online version of this article (doi:10.1007/s00401-016-1566-9) contains supplementary material, which is available to authorized users.
PMCID: PMC4947104  PMID: 27026413
SORL1; Haploinsufficiency; Loss-of-function; Rare variants; Alzheimer; Early onset; Meta-analysis
6.  Clinical features of TBK1 carriers compared with C9orf72, GRN and non-mutation carriers in a Belgian cohort 
Brain  2015;139(2):452-467.
Loss-of-function mutations in TBK1 have been identified in frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS). Van Mossevelde et al. compare TBK1-mutation carriers with FTD, ALS or FTD-ALS to patients carrying GRN or C9orf72 mutations. Differences are seen in age of onset, extrapyramidal symptoms, and in memory, language and behaviour.
Loss-of-function mutations in TBK1 have been identified in frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS). Van Mossevelde et al. compare TBK1-mutation carriers with FTD, ALS or FTD-ALS to patients carrying GRN or C9orf72 mutations. Differences are seen in age of onset, extrapyramidal symptoms, and in memory, language and behaviour.
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.
PMCID: PMC4805085  PMID: 26674655
TBK1; frontotemporal lobar degeneration; amyotrophic lateral sclerosis; C9orf72; genotype–phenotype correlations
7.  Loss of TBK1 is a frequent cause of frontotemporal dementia in a Belgian cohort 
Neurology  2015;85(24):2116-2125.
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.
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.
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.
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.
PMCID: PMC4691687  PMID: 26581300
8.  Investigating the role of filamin C in Belgian patients with frontotemporal dementia linked to GRN deficiency in FTLD-TDP brains 
TAR DNA-binding protein 43 (TDP-43) inclusions are pathological hallmarks of patients with frontotemporal lobar degeneration (FTLD) and amyotrophic lateral sclerosis (ALS). Loss of TDP-43 in zebrafish engenders a severe muscle and vascular phenotype with a concomitant elevation of filamin C (FLNC) levels, an observation confirmed in the frontal cortex of FTLD-TDP patients. Here, we aimed to further assess the contribution of FLNC to frontotemporal dementia (FTD) etiology. We conducted a mutational screening of FLNC in a cohort of 529 unrelated Belgian FTD and FTD-ALS patients, and a control cohort of 920 unrelated and age-matched individuals. Additionally we performed an in-depth characterization of FLNC expression levels in FTD patients and a murine FTD model.
In total 68 missense variants were identified of which 19 (MAF < 1 %) were patient-only. Gene burden analysis demonstrated a significant association between the presence of rare variants in FLNC and disease (P = 0.0349, RR = 1.46 [95 % CI 1.03–2.07]). Furthermore, elevated FLNC expression levels, observed previously in FTLD-TDP patients, were mainly attributable to FTD patients with the progranulin (GRN) p.0(IVS1 + 5G > C) loss-of-function mutation. Increased FLNC levels were, to a lesser extent, also identified in a FLNC p.V831I variant carrier and in FTD patients with the p.R159H mutation in valosin-containing protein (VCP). The GRN-associated increase of FLNC was confirmed in the frontal cortex of aged Grn knockout mice starting at 16–18 months of age. Combined quantitative proteomic and bioinformatic analyses of the frontal cortex of FTD patients possessing elevated FLNC levels, identified multiple altered protein factors involved in accelerated aging, neurodegeneration and synaptogenesis.
Our findings further support the involvement of aberrant FLNC expression levels in FTD pathogenesis. Identification of increased FLNC levels in aged Grn mice and impaired pathways related to aging and neurodegeneration, implies a potential role for FLNC in mediating or accelerating the aging process.
Electronic supplementary material
The online version of this article (doi:10.1186/s40478-015-0246-7) contains supplementary material, which is available to authorized users.
PMCID: PMC4641381  PMID: 26555887
Filamin C; Genetics; Frontotemporal lobar degeneration; Granulin GRN; Haploinsufficiency; Proteomics
9.  Euthanasia requests, procedures and outcomes for 100 Belgian patients suffering from psychiatric disorders: a retrospective, descriptive study 
BMJ Open  2015;5(7):e007454.
To identify patterns in euthanasia requests and practices relating to psychiatric patients; to generate recommendations for future research.
Retrospective analysis of data obtained through medical file review.
Outpatient psychiatric clinical setting in the Dutch-speaking region of Belgium, between October 2007 and December 2011; follow-up at the end of December 2012.
100 consecutive psychiatric patients requesting euthanasia based on psychological suffering associated with psychiatric disorders (77 women, 23 men; mean age 47 years; age range 21–80 years).
Main outcome measures
Patient sociodemographic characteristics; diagnoses; decisions on euthanasia requests; circumstances of euthanasia procedures; patient outcomes at follow-up.
Most patients had been referred for psychiatric counselling by their physician (n=55) or by LEIF (Life End Information Forum) (n=36). 90 patients had >1 disorder; the most frequent diagnoses were depression (n=58) and personality disorder (n=50). 38 patients required further testing and/or treatment, including 13 specifically tested for autism spectrum disorder (ASD); 12 received an ASD diagnosis (all Asperger syndrome). In total, 48 of the euthanasia requests were accepted and 35 were carried out. Of the 13 remaining patients whose requests were accepted, 8 postponed or cancelled the procedure, because simply having this option gave them enough peace of mind to continue living. In December 2012, 43 patients had died, including 35 by euthanasia; others died by suicide (6), palliative sedation (1) and anorexia nervosa (1).
Depression and personality disorders are the most common diagnoses in psychiatric patients requesting euthanasia, with Asperger syndrome representing a neglected disease burden. Further research is needed, especially prospective quantitative and qualitative studies, to obtain a better understanding of patients with psychiatric disorders who request euthanasia due to unbearable psychological suffering.
PMCID: PMC4530448  PMID: 26216150
10.  Cerebrospinal Fluid P-Tau181P: Biomarker for Improved Differential Dementia Diagnosis 
The goal of this study is to investigate the value of tau phosphorylated at threonine 181 (P-tau181P) in the Alzheimer’s disease (AD) cerebrospinal fluid (CSF) biomarker panel for differential dementia diagnosis in autopsy confirmed AD and non-AD patients. The study population consisted of 140 autopsy confirmed AD and 77 autopsy confirmed non-AD dementia patients. CSF concentrations of amyloid-β peptide of 42 amino acids (Aβ1–42), total tau protein (T-tau), and P-tau181P were determined with single analyte ELISA-kits (INNOTEST®, Fujirebio, Ghent, Belgium). Diagnostic accuracy was assessed through receiver operating characteristic (ROC) curve analyses to obtain area under the curve (AUC) values and to define optimal cutoff values to discriminate AD from pooled and individual non-AD groups. ROC curve analyses were only performed on biomarkers and ratios that differed significantly between the groups. Pairwise comparison of AUC values was performed by means of DeLong tests. The Aβ1–42/P-tau181P ratio (AUC = 0.770) performed significantly better than Aβ1–42 (AUC = 0.677, P = 0.004), T-tau (AUC = 0.592, P < 0.001), and Aβ1–42/T-tau (AUC = 0.678, P = 0.001), while P-tau181P (AUC = 0.720) performed significantly better than T-tau (AUC = 0.592, P < 0.001) to discriminate between AD and the pooled non-AD group. When comparing AD and the individual non-AD diagnoses, Aβ1–42/P-tau181P (AUC = 0.894) discriminated AD from frontotemporal dementia significantly better than Aβ1–42 (AUC = 0.776, P = 0.020) and T-tau (AUC = 0.746, P = 0.004), while P-tau181P/T-tau (AUC = 0.958) significantly improved the differentiation between AD and Creutzfeldt-Jakob disease as compared to Aβ1–42 (AUC = 0.688, P = 0.004), T-tau (AUC = 0.874, P = 0.040), and Aβ1–42/P-tau181P (AUC = 0.760, P = 0.003). In conclusion, this study demonstrates P-tau181P is an essential component of the AD CSF biomarker panel, and combined assessment of Aβ1–42, T-tau, and P-tau181P renders, to present date, the highest diagnostic power to discriminate between AD and non-AD dementias.
PMCID: PMC4470274  PMID: 26136723
Alzheimer’s disease; dementia; differential diagnosis; biomarkers; cerebrospinal fluid; neuropathology; tau
11.  Signal loss due to oligomerization in ELISA analysis of amyloid-beta can be recovered by a novel sample pre-treatment method 
MethodsX  2015;2:112-123.
Graphical abstract
According to the predominant theories, soluble amyloid-beta (Aβ) aggregates are the principal neurotoxic agents in Alzheimer’s disease pathology, making them a popular target for the development of therapeutics and diagnostic markers. One of the most commonly used methods for determining the concentration of Aβ is ELISA. However, ELISA was developed for monomeric proteins and may be ill-suited for detecting aggregates. Therefore, we investigated the effect of aggregation on the ELISA measurement and developed a novel chemical pre-treatment method, designed to disaggregate Aβ peptides, to improve the ELISA measurement of the total Aβ concentration.
Synthetic Aβ40 monomers, Aβ42 oligomers and biological samples from mice and humans were subjected to a chemical pre-treatment protocol with: trifluoroacetic acid (TFA), formic acid (FA) or hexafluoroisopropanol (HFIP) prior to ELISA analysis. In our study we have shown that:
•Aβ oligomerization leads to epitope masking and steric hindrance and results in an underestimation of the total Aβ content with ELISA.•Chemically pre-treating samples to disaggregate oligomers can (partially) recover the signal loss.•This novel sample pre-treatment method could provide a more accurate ELISA measurement of the total Aβ concentration in samples with a high oligomer content.
PMCID: PMC4487349  PMID: 26150979
Sample pre-treatment for amyloid-beta ELISA analysis; Alzheimer’s disease; Amyloid-beta; ELISA; Sample pre-treatment; Oligomers; Steric hindrance; AD, Alzheimers disease; Aβ, amyloid-beta; TFA, trifluoroacetic acid; HFIP, hexafluoroisopropanol; FA, formic acid; DMSO, dimethyl sulfoxide; SDS, sodium dodecyl sulphate; WT, wild-type; PMSF, phenylmethylsulfonyl fluoride; SP, soluble proteins; PBS, phosphate-buffered saline
12.  The monoaminergic footprint of depression and psychosis in dementia with Lewy bodies compared to Alzheimer’s disease 
Depression and psychosis are two of the most severe neuropsychiatric symptoms (NPS) in dementia with Lewy bodies (DLB) and Alzheimer’s disease (AD). Both NPS have negative effects on cognitive performance and life expectancy. The current study aimed to investigate and compare monoaminergic etiologies between both neurodegenerative conditions, given the lack of an efficient pharmacological treatment until present.
Eleven behaviorally relevant brain regions of the left frozen hemisphere of 10 neuropathologically confirmed AD patients with/without depression (AD + D/-D; 5 were psychotic within AD + D), 10 confirmed DLB patients, all of whom were depressed (DLB + D; 5 psychotic patients), and, finally, 10 confirmed control subjects were regionally dissected. All patients were retrospectively assessed before death using the Behavioral Pathology in Alzheimer’s Disease Rating Scale (Behave-AD) and Cornell Scale for Depression in Dementia amongst others. The concentrations of dopamine (DA), serotonin (5-HT), (nor)adrenaline and respective metabolites, i.e. 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA), 5-hydroxy-3-indoleacetic acid (5-HIAA), and, 3-methoxy-4-hydroxyphenylglycol (MHPG), were determined using reversed-phase high-performance liquid chromatography with electrochemical detection.
DLB subjects had the overall lowest monoamine and metabolite concentrations regarding 33 out of 41 significant monoaminergic group alterations. Moreover, MHPG levels were significantly decreased in almost 8 out of 11 brain regions of DLB- compared to AD patients. We also observed the lowest 5-HT and 5-HIAA levels, and 5-HIAA/5-HT turnover ratios in DLB + D compared to AD + D subjects. Additionally, a 4- and 7-fold increase of DOPAC/DA and HVA/DA turnover ratios, and, a 10-fold decrease of thalamic DA levels in DLB + D compared to AD + D patients and control subjects was noticed. Regarding psychosis, hippocampal DA levels in the overall DLB group significantly correlated with Behave-AD AB scores. In the total AD group, DA levels and HVA/DA ratios in the amygdala significantly correlated with Behave-AD AB scores instead.
Monoaminergic neurotransmitter alterations contribute differently to the pathophysiology of depression and psychosis in DLB as opposed to AD, with a severely decreased serotonergic neurotransmission as the main monoaminergic etiology of depression in DLB. Similarly, psychosis in DLB might, in part, be etiologically explained by dopaminergic alterations in the hippocampus, whereas in AD, the amygdala might be involved.
PMCID: PMC4339739  PMID: 25717350
13.  Lethal phenotype in conditional late-onset arginase 1 deficiency in the mouse 
Molecular genetics and metabolism  2013;110(3):222-230.
Human arginase deficiency is characterized by hyperargininemia and infrequent episodes of hyperammonemia, which lead to neurological impairment with spasticity, loss of ambulation, seizures, and severe mental and growth retardation; uncommonly, patients suffer early death from this disorder. In a murine targeted knockout model, onset of the phenotypic abnormality is heralded by weight loss at around day 15, and death occurs typically by postnatal day 17 with hyperargininemia and markedly elevated ammonia. This discrepancy between the more attenuated juvenile-onset human disease and the lethal neonatal murine model has remained suboptimal for studying and developing therapy for the more common presentation of argianse deficiency. These investigations aimed to address this issue by creating an adult conditional knockout mouse to determine whether later onset of arginase deficiency also resulted in lethality. Animal survival and ammonia levels, body weight, circulating amino acids, and tissue arginase levels were examined as outcome parameters after widespread Cre-recombinase activation in a conditional knockout model of arginase 1 deficiency. One hundred percent of adult female and 70 percent of adult male mice died an average of 21.0 and 21.6 days, respectively, after the initiation of tamoxifen administration. Animals demonstrated elevated circulating ammonia and arginine at the onset of phenotypic abnormalities. In addition, brain and liver amino acids demonstrated abnormalities. These studies demonstrate that (a) the absence of arginase in adult animals results in a disease profile (leading to death) similar to that of the targeted knockout and (b) the phenotypic abnormalities seen in the juvenile-onset model are not exclusive to the age of the animal but instead to the biochemistry of the disorder. This adult model will be useful for developing gene- and cell-based therapies for this disorder that will not limited by by the small animal size of neonatal therapy and for developing a better understanding of the characteristics of hyperargininemia.
PMCID: PMC3800271  PMID: 23920045
Arginase deficiency; Hyperargininemia; Conditional knockout; Animal model
14.  Promoter DNA methylation regulates progranulin expression and is altered in FTLD 
Frontotemporal lobar degeneration (FTLD) is a heterogeneous group of neurodegenerative diseases associated with personality changes and progressive dementia. Loss-of-function mutations in the growth factor progranulin (GRN) cause autosomal dominant FTLD, but so far the pathomechanism of sporadic FTLD is unclear.
We analyzed whether DNA methylation in the GRN core promoter restricts GRN expression and, thus, might promote FTLD in the absence of GRN mutations. GRN expression in human lymphoblast cell lines is negatively correlated with methylation at several CpG units within the GRN promoter. Chronic treatment with the DNA methyltransferase inhibitor 5-aza-2′-deoxycytidine (DAC) strongly induces GRN mRNA and protein levels. In a reporter assay, CpG methylation blocks transcriptional activity of the GRN core promoter. In brains of FTLD patients several CpG units in the GRN promoter are significantly hypermethylated compared to age-matched healthy controls, Alzheimer and Parkinson patients. These CpG motifs are critical for GRN promoter activity in reporter assays. Furthermore, DNA methyltransferase 3a (DNMT3a) is upregulated in FTLD patients and overexpression of DNMT3a reduces GRN promoter activity and expression.
These data suggest that altered DNA methylation is a novel pathomechanism for FTLD that is potentially amenable to targeted pharmacotherapy.
PMCID: PMC3893557  PMID: 24252647
5-aza-2′-deoxycytidine; DNA methylation; Epigenetics; FTLD; Progranulin
15.  Genetic and Clinical Features of Progranulin-Associated Frontotemporal Lobar Degeneration 
Archives of neurology  2011;68(4):488-497.
To assess the relative frequency of unique mutations and their associated characteristics in 97 individuals with mutations in progranulin (GRN), an important cause of frontotemporal lobar degeneration (FTLD).
Participants and Design
A 46-site International Frontotemporal Lobar Degeneration Collaboration was formed to collect cases of FTLD with TAR DNA-binding protein of 43-kDa (TDP-43)–positive inclusions (FTLD-TDP). We identified 97 individuals with FTLD-TDP with pathogenic GRN mutations (GRN+ FTLD-TDP), assessed their genetic and clinical characteristics, and compared them with 453 patients with FTLD-TDP in which GRN mutations were excluded (GRN− FTLD-TDP). No patients were known to be related. Neuropathologic characteristics were confirmed as FTLD-TDP in 79 of the 97 GRN+ FTLDTDP cases and all of the GRN− FTLD-TDP cases.
Age at onset of FTLD was younger in patients with GRN+ FTLD-TDP vs GRN− FTLD-TDP (median, 58.0 vs 61.0 years; P<.001), as was age at death (median, 65.5 vs 69.0 years; P<.001). Concomitant motor neuron disease was much less common in GRN+ FTLDTDP vs GRN− FTLD-TDP (5.4% vs 26.3%; P<.001). Fifty different GRN mutations were observed, including 2 novel mutations: c.139delG (p.D47TfsX7) and c.378C>A (p.C126X). The 2 most common GRN mutations were c.1477C>T (p.R493X, found in 18 patients, representing 18.6% of GRN cases) and c.26C>A (p.A9D, found in 6 patients, representing 6.2% of cases). Patients with the c.1477C>T mutation shared a haplotype on chromosome 17; clinically, they resembled patients with other GRN mutations. Patients with the c.26C>A mutation appeared to have a younger age at onset of FTLD and at death and more parkinsonian features than those with other GRN mutations.
GRN+ FTLD-TDP differs in key features from GRN− FTLD-TDP.
PMCID: PMC3160280  PMID: 21482928
16.  Both common variations and rare non-synonymous substitutions and small insertion/deletions in CLU are associated with increased Alzheimer risk 
We have followed-up on the recent genome-wide association (GWA) of the clusterin gene (CLU) with increased risk for Alzheimer disease (AD), by performing an unbiased resequencing of all CLU coding exons and regulatory regions in an extended Flanders-Belgian cohort of Caucasian AD patients and control individuals (n = 1930). Moreover, we have replicated genetic findings by targeted resequencing in independent Caucasian cohorts of French (n = 2182) and Canadian (n = 573) origin and by performing meta-analysis combining our data with previous genetic CLU screenings.
In the Flanders-Belgian cohort, we identified significant clustering in exons 5-8 of rare genetic variations leading to non-synonymous substitutions and a 9-bp insertion/deletion affecting the CLU β-chain (p = 0.02). Replicating this observation by targeted resequencing of CLU exons 5-8 in 2 independent Caucasian cohorts of French and Canadian origin identified identical as well as novel non-synonymous substitutions and small insertion/deletions. A meta-analysis, combining the datasets of the 3 cohorts with published CLU sequencing data, confirmed that rare coding variations in the CLU β-chain were significantly enriched in AD patients (ORMH = 1.96 [95% CI = 1.18-3.25]; p = 0.009). Single nucleotide polymorphisms (SNPs) association analysis indicated the common AD risk association (GWA SNP rs11136000, p = 0.013) in the 3 combined datasets could not be explained by the presence of the rare coding variations we identified. Further, high-density SNP mapping in the CLU locus mapped the common association signal to a more 5' CLU region.
We identified a new genetic risk association of AD with rare coding CLU variations that is independent of the 5' common association signal identified in the GWA studies. At this stage the role of these coding variations and their likely effect on the β-chain domain and CLU protein functioning remains unclear and requires further studies.
PMCID: PMC3296573  PMID: 22248099
Alzheimer disease; clusterin gene (CLU); genomic resequencing; non-synonymous substitutions; insertions/deletions; β-chain domain; meta-analysis
17.  Common variants in ABCA7, MS4A6A/MS4A4E, EPHA1, CD33 and CD2AP are associated with Alzheimer’s disease 
Hollingworth, Paul | Harold, Denise | Sims, Rebecca | Gerrish, Amy | Lambert, Jean-Charles | Carrasquillo, Minerva M | Abraham, Richard | Hamshere, Marian L | Pahwa, Jaspreet Singh | Moskvina, Valentina | Dowzell, Kimberley | Jones, Nicola | Stretton, Alexandra | Thomas, Charlene | Richards, Alex | Ivanov, Dobril | Widdowson, Caroline | Chapman, Jade | Lovestone, Simon | Powell, John | Proitsi, Petroula | Lupton, Michelle K | Brayne, Carol | Rubinsztein, David C | Gill, Michael | Lawlor, Brian | Lynch, Aoibhinn | Brown, Kristelle S | Passmore, Peter A | Craig, David | McGuinness, Bernadette | Todd, Stephen | Holmes, Clive | Mann, David | Smith, A David | Beaumont, Helen | Warden, Donald | Wilcock, Gordon | Love, Seth | Kehoe, Patrick G | Hooper, Nigel M | Vardy, Emma R. L. C. | Hardy, John | Mead, Simon | Fox, Nick C | Rossor, Martin | Collinge, John | Maier, Wolfgang | Jessen, Frank | Schürmann, Britta | Rüther, Eckart | Heun, Reiner | Kölsch, Heike | van den Bussche, Hendrik | Heuser, Isabella | Kornhuber, Johannes | Wiltfang, Jens | Dichgans, Martin | Frölich, Lutz | Hampel, Harald | Hüll, Michael | Gallacher, John | Rujescu, Dan | Giegling, Ina | Goate, Alison M | Kauwe, John S K | Cruchaga, Carlos | Nowotny, Petra | Morris, John C | Mayo, Kevin | Sleegers, Kristel | Bettens, Karolien | Engelborghs, Sebastiaan | De Deyn, Peter P | Van Broeckhoven, Christine | Livingston, Gill | Bass, Nicholas J | Gurling, Hugh | McQuillin, Andrew | Gwilliam, Rhian | Deloukas, Panagiotis | Al-Chalabi, Ammar | Shaw, Christopher E | Tsolaki, Magda | Singleton, Andrew B | Guerreiro, Rita | Mühleisen, Thomas W | Nöthen, Markus M | Moebus, Susanne | Jöckel, Karl-Heinz | Klopp, Norman | Wichmann, H-Erich | Pankratz, V Shane | Sando, Sigrid B | Aasly, Jan O | Barcikowska, Maria | Wszolek, Zbigniew K | Dickson, Dennis W | Graff-Radford, Neill R | Petersen, Ronald C | van Duijn, Cornelia M | Breteler, Monique MB | Ikram, M Arfan | DeStefano, Anita L | Fitzpatrick, Annette L | Lopez, Oscar | Launer, Lenore J | Seshadri, Sudha | Berr, Claudine | Campion, Dominique | Epelbaum, Jacques | Dartigues, Jean-François | Tzourio, Christophe | Alpérovitch, Annick | Lathrop, Mark | Feulner, Thomas M | Friedrich, Patricia | Riehle, Caterina | Krawczak, Michael | Schreiber, Stefan | Mayhaus, Manuel | Nicolhaus, S | Wagenpfeil, Stefan | Steinberg, Stacy | Stefansson, Hreinn | Stefansson, Kari | Snædal, Jon | Björnsson, Sigurbjörn | Jonsson, Palmi V. | Chouraki, Vincent | Genier-Boley, Benjamin | Hiltunen, Mikko | Soininen, Hilkka | Combarros, Onofre | Zelenika, Diana | Delepine, Marc | Bullido, Maria J | Pasquier, Florence | Mateo, Ignacio | Frank-Garcia, Ana | Porcellini, Elisa | Hanon, Olivier | Coto, Eliecer | Alvarez, Victoria | Bosco, Paolo | Siciliano, Gabriele | Mancuso, Michelangelo | Panza, Francesco | Solfrizzi, Vincenzo | Nacmias, Benedetta | Sorbi, Sandro | Bossù, Paola | Piccardi, Paola | Arosio, Beatrice | Annoni, Giorgio | Seripa, Davide | Pilotto, Alberto | Scarpini, Elio | Galimberti, Daniela | Brice, Alexis | Hannequin, Didier | Licastro, Federico | Jones, Lesley | Holmans, Peter A | Jonsson, Thorlakur | Riemenschneider, Matthias | Morgan, Kevin | Younkin, Steven G | Owen, Michael J | O’Donovan, Michael | Amouyel, Philippe | Williams, Julie
Nature genetics  2011;43(5):429-435.
We sought to identify new susceptibility loci for Alzheimer’s disease (AD) through a staged association study (GERAD+) and by testing suggestive loci reported by the Alzheimer’s Disease Genetic Consortium (ADGC). First, we undertook a combined analysis of four genome-wide association datasets (Stage 1) and identified 10 novel variants with P≤1×10−5. These were tested for association in an independent sample (Stage 2). Three SNPs at two loci replicated and showed evidence for association in a further sample (Stage 3). Meta-analyses of all data provide compelling evidence that ABCA7 (meta-P 4.5×10−17; including ADGC meta-P=5.0×10−21) and the MS4A gene cluster (rs610932, meta-P=1.8×10−14; including ADGC meta-P=1.2×10−16; rs670139, meta-P=1.4×10−9; including ADGC meta-P=1.1×10−10) are novel susceptibility loci for AD. Second, we observed independent evidence for association for three suggestive loci reported by the ADGC GWAS, which when combined shows genome-wide significance: CD2AP (GERAD+ P=8.0×10−4; including ADGC meta-P=8.6×10−9), CD33 (GERAD+ P=2.2×10−4; including ADGC meta-P=1.6×10−9) and EPHA1 (GERAD+ P=3.4×10−4; including ADGC meta-P=6.0×10−10). These findings support five novel susceptibility genes for AD.
PMCID: PMC3084173  PMID: 21460840
18.  Sinus Sigmoideus Thrombosis Secondary to Graves' Disease: A Case Description 
Case Reports in Neurology  2011;3(3):203-209.
Cerebral venous thrombosis (CVT) is a distinct cerebrovascular condition that represents 0.5-1% of all strokes in the general population. Because of its procoagulant and antifibrinolytic effects [Horne et al.: J Clin Endocrinol Metab 2004;89:4469-4473], hyperthyroidism has been proposed as a predisposing factor for CVT [Saposnik et al.: Stroke 2011;42:1158-1192]. For the first time, we describe a 22-year-old right-handed woman with a sinus sigmoideus thrombosis due to Graves' disease. Although subclinical hyperthyroidism had been detected 2 years before the onset of neurological symptoms, she did not receive any medical follow-up. Early recognition, diagnosis and treatment are of crucial importance, as Graves' disease is a risk factor for CVT and stroke.
PMCID: PMC3214671  PMID: 22114580
Graves' disease; Cerebral venous thrombosis; Subclinical hyperthyroidism; Sinus sigmoideus thrombosis
19.  TMEM106B is associated with frontotemporal lobar degeneration in a clinically diagnosed patient cohort 
Brain  2011;134(3):808-815.
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.
PMCID: PMC3044834  PMID: 21354975
frontotemporal lobar degeneration; TMEM106B; genetic association; risk factor
20.  FUS pathology defines the majority of tau- and TDP-43-negative frontotemporal lobar degeneration 
Acta neuropathologica  2010;120(1):33-41.
Through an international consortium, we have collected 37 tau- and TAR DNA-binding protein 43 (TDP-43)-negative frontotemporal lobar degeneration (FTLD) cases, and present here the first comprehensive analysis of these cases in terms of neuropathology, genetics, demographics and clinical data. 92% (34/37) had fused in sarcoma (FUS) protein pathology, indicating that FTLD-FUS is an important FTLD subtype. This FTLD-FUS collection specifically focussed on aFTLD-U cases, one of three recently defined subtypes of FTLD-FUS. The aFTLD-U subtype of FTLD-FUS is characterised clinically by behavioural variant frontotemporal dementia (bvFTD) and has a particularly young age of onset with a mean of 41 years. Further, this subtype had a high prevalence of psychotic symptoms (36% of cases) and low prevalence of motor symptoms (3% of cases). We did not find FUS mutations in any aFTLD-U case. To date, the only subtype of cases reported to have ubiquitin-positive but tau-, TDP-43- and FUS-negative pathology, termed FTLD-UPS, is the result of charged multivesicular body protein 2B gene (CHMP2B) mutation. We identified three FTLD-UPS cases, which are negative for CHMP2B mutation, suggesting that the full complement of FTLD pathologies is yet to be elucidated.
PMCID: PMC2887939  PMID: 20490813
FTLD; FUS; FTLD-UPS; Frontotemporal; FTD
21.  FUS pathology defines the majority of tau- and TDP-43-negative frontotemporal lobar degeneration 
Acta Neuropathologica  2010;120(1):33-41.
Through an international consortium, we have collected 37 tau- and TAR DNA-binding protein 43 (TDP-43)-negative frontotemporal lobar degeneration (FTLD) cases, and present here the first comprehensive analysis of these cases in terms of neuropathology, genetics, demographics and clinical data. 92% (34/37) had fused in sarcoma (FUS) protein pathology, indicating that FTLD-FUS is an important FTLD subtype. This FTLD-FUS collection specifically focussed on aFTLD-U cases, one of three recently defined subtypes of FTLD-FUS. The aFTLD-U subtype of FTLD-FUS is characterised clinically by behavioural variant frontotemporal dementia (bvFTD) and has a particularly young age of onset with a mean of 41 years. Further, this subtype had a high prevalence of psychotic symptoms (36% of cases) and low prevalence of motor symptoms (3% of cases). We did not find FUS mutations in any aFTLD-U case. To date, the only subtype of cases reported to have ubiquitin-positive but tau-, TDP-43- and FUS-negative pathology, termed FTLD-UPS, is the result of charged multivesicular body protein 2B gene (CHMP2B) mutation. We identified three FTLD-UPS cases, which are negative for CHMP2B mutation, suggesting that the full complement of FTLD pathologies is yet to be elucidated.
PMCID: PMC2887939  PMID: 20490813
FTLD; FUS; FTLD-UPS; Frontotemporal; FTD
22.  Neutrophil Gelatinase-Associated Lipocalin and its Receptors in Alzheimer’s Disease (AD) Brain Regions: Differential Findings in AD with and without Depression 
Journal of Alzheimer's Disease  null;55(2):763-776.
Co-existing depression worsens Alzheimer’s disease (AD) pathology. Neutrophil gelatinase-associated lipocalin (NGAL) is a newly identified (neuro)inflammatory mediator in the pathophysiologies of both AD and depression. This study aimed to compare NGAL levels in healthy controls, AD without depression (AD–D), and AD with co-existing depression (AD+D) patients. Protein levels of NGAL and its receptors, 24p3R and megalin, were assessed in nine brain regions from healthy controls (n = 19), AD–D (n = 19), and AD+D (n = 21) patients. NGAL levels in AD–D patients were significantly increased in brain regions commonly associated with AD. In the hippocampus, NGAL levels were even further increased in AD+D subjects. Unexpectedly, NGAL levels in the prefrontal cortex of AD+D patients were comparable to those in controls. Megalin levels were increased in BA11 and amygdala of AD+D patients, while no changes in 24p3R were detected. These findings indicate significant differences in neuroimmunological regulation between AD patients with and without co-existing depression. Considering its known effects, elevated NGAL levels might actively promote neuropathological processes in AD with and without depression.
PMCID: PMC5147520  PMID: 27716662
24p3R; Alzheimer’s disease; depression; hippocampus; inflammation; lipocalin 2; megalin; NGAL

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