FUS immunogold labeling TEM analysis of the neuronal cytoplasmic inclusions of neuronal intermediate filament inclusion disease: a frontotemporal lobar degeneration with FUS proteinopathy.

Fused in sarcoma (FUS)-immunoreactive neuronal and glial inclusions define a novel molecular pathology called FUS proteinopathy. FUS has been shown to be a component of inclusions of familial amyotrophic lateral sclerosis with FUS mutation and three frontotemporal lobar degeneration entities, including neuronal intermediate filament inclusion disease (NIFID). The pathogenic role of FUS is unknown. In addition to FUS, many neuronal cytoplasmic inclusions (NCI) of NIFID contain aggregates of α-internexin and neurofilament proteins. Herein, we have shown that: (1) FUS becomes relatively insoluble in NIFID and there are no apparent posttranslational modifications, (2) there are no pathogenic abnormalities in the FUS gene in NIFID, and (3) immunoelectron microscopy demonstrates the fine structural localization of FUS in NIFID which has not previously been described. FUS localized to euchromatin, and strongly with paraspeckles, in nuclei, consistent with its RNA/DNA-binding functions. NCI of varying morphologies were observed. Most frequent were the "loosely aggregated cytoplasmic inclusions," 81% of which had moderate or high levels of FUS immunoreactivity. Much rarer "compact cytoplasmic inclusions" and "tangled twine ball inclusions" were FUS-immunoreactive at their granular peripheries, or heavily FUS-positive throughout, respectively. Thus, FUS may aggregate in the cytoplasm and then admix with neuronal intermediate filament accumulations.

TARDBP 3'-UTR variant in autopsy-confirmed frontotemporal lobar degeneration with TDP-43 proteinopathy.

Pathogenic mutations in the gene encoding TDP-43, TARDBP, have been reported in familial amyotrophic lateral sclerosis (FALS) and, more recently, in families with a heterogeneous clinical phenotype including both ALS and frontotemporal lobar degeneration (FTLD). In our previous study, sequencing analyses identified one variant in the 3'-untranslated region (3'-UTR) of the TARDBP gene in two affected members of one family with bvFTD and ALS and in one unrelated clinically assessed case of FALS. Since that study, brain tissue has become available and provides autopsy confirmation of FTLD-TDP in the proband and ALS in the brother of the bvFTD-ALS family and the neuropathology of those two cases is reported here. The 3'-UTR variant was not found in 982 control subjects (1,964 alleles). To determine the functional significance of this variant, we undertook quantitative gene expression analysis. Allele-specific amplification showed a significant increase of 22% (P < 0.05) in disease-specific allele expression with a twofold increase in total TARDBP mRNA. The segregation of this variant in a family with clinical bvFTD and ALS adds to the spectrum of clinical phenotypes previously associated with TARDBP variants. In summary, TARDBP variants may result in clinically and neuropathologically heterogeneous phenotypes linked by a common molecular pathology called TDP-43 proteinopathy.

Novel presenilin 1 variant (P117A) causing Alzheimer's disease in the fourth decade of life.

Over 160 rare genetic variants in presenilin 1 (PSEN1) are known to cause Alzheimer's disease (AD). In this study we screened a family with early-onset AD for mutations in PSEN1 using direct DNA sequencing. We identified a novel PSEN1 genetic variant which results in the substitution of a Proline with an Alanine at codon 117 (P117A). The P117A variant was present in all demented individuals and fifty percent of at risk individuals. This variant occurs at a site where three other disease-causing variants have been previously observed. In vitro functional studies demonstrate that the P117A variant results in an altered Abeta42/total Abeta ratio consistent with an AD causing mutation. The P117A variant is a novel mutation in PSEN1, which causes early-onset AD in an autosomal dominant manner.

TDP-43 A315T mutation in familial motor neuron disease.

To identify novel causes of familial neurodegenerative diseases, we extended our previous studies of TAR DNA-binding protein 43 (TDP-43) proteinopathies to investigate TDP-43 as a candidate gene in familial cases of motor neuron disease. Sequencing of the TDP-43 gene led to the identification of a novel missense mutation, Ala-315-Thr, which segregates with all affected members of an autosomal dominant motor neuron disease family. The mutation was not found in 1,505 healthy control subjects. The discovery of a missense mutation in TDP-43 in a family with dominantly inherited motor neuron disease provides evidence of a direct link between altered TDP-43 function and neurodegeneration.

Molecular characterization of novel progranulin (GRN) mutations in frontotemporal dementia.

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.

Neuropathologic heterogeneity in HDDD1: a familial frontotemporal lobar degeneration with ubiquitin-positive inclusions and progranulin mutation.

Hereditary dysphasic disinhibition dementia (HDDD) describes a familial disorder characterized by personality changes, and language and memory deficits. The neuropathology includes frontotemporal lobar atrophy, neuronal loss and gliosis and, in most cases, abundant Abeta plaques and neurofibrillary tangles (NFTs). A Pick/Alzheimer's spectrum was proposed for the original family (HDDD1). Here we report the clinicopathologic case of an HDDD1 individual using modern immunohistochemical methods, contemporary neuropathologic diagnostic criteria to distinguish different frontotemporal lobar degenerations (FTLDs), and progranulin (PRGN) mutation analysis. Clinical onset was at age 62 years with personality changes and disinhibition, followed by nonfluent dysphasia, and memory loss that progressed to muteness and total dependence with death at age 84 years. There was severe generalized brain atrophy (weight=570 g). Histopathology showed superficial microvacuolation, marked neuronal loss, gliosis, and ubiquitin-positive, tau-negative cytoplasmic and intranuclear neuronal inclusions in frontal, temporal, and parietal cortices. There were also frequent neuritic plaques and NFTs in parietal and occipital cortices. The case met neuropathologic criteria for both FTLD with ubiquitin-positive, tau-negative inclusions (FTLD-U), and Alzheimer disease (Braak NFT stage V). We discovered a novel pathogenic PGRN mutation c.5913 A>G (IVS6-2 A>G) segregating with FTLD-U in this kindred. In conclusion, HDDD1 is an FTLD-U caused by a PGRN mutation and is neuropathologically heterogeneous with Alzheimer disease as a common comorbidity.

Extreme cerebrospinal fluid amyloid beta levels identify family with late-onset Alzheimer's disease presenilin 1 mutation.

OBJECTIVE: Aggregation and deposition of amyloid beta (Abeta) in the brain is thought to be central to the pathogenesis of Alzheimer's disease (AD). Recent studies suggest that cerebrospinal fluid (CSF) Abeta levels are strongly correlated with AD status and progression, and may be a meaningful endophenotype for AD. Mutations in presenilin 1 (PSEN1) are known to cause AD and change Abeta levels. In this study, we have investigated DNA sequence variation in the presenilin (PSEN1) gene using CSF Abeta levels as an endophenotype for AD. METHODS: We sequenced the exons and flanking intronic regions of PSEN1 in clinically characterized research subjects with extreme values of CSF Abeta levels. RESULTS: This novel approach led directly to the identification of a disease-causing mutation in a family with late-onset AD. INTERPRETATION: This finding suggests that CSF Abeta may be a useful endophenotype for genetic studies of AD. Our results also suggest that PSEN1 mutations can cause AD with a large range in age of onset, spanning both early- and late-onset AD.

HDDD2 is a familial frontotemporal lobar degeneration with ubiquitin-positive, tau-negative inclusions caused by a missense mutation in the signal peptide of progranulin.

OBJECTIVE: Familial autosomal dominant frontotemporal dementia with ubiquitin-positive, tau-negative inclusions in the brain linked to 17q21-22 recently has been reported to carry null mutations in the progranulin gene (PGRN). Hereditary dysphasic disinhibition dementia (HDDD) is a frontotemporal dementia with prominent changes in behavior and language deficits. A previous study found significant linkage to chromosome 17 in a HDDD family (HDDD2), but no mutation in the MAPT gene. Longitudinal follow-up has enabled us to identify new cases and to further characterize the dementia in this family. The goals of this study were to develop research criteria to classify the different clinical expressions of dementia observed in this large kindred, to identify the causal mutation in affected individuals and correlate this with phenotypic characteristics in this pedigree, and to assess the neuropathological characteristics using immunohistochemical techniques. METHODS: In this study we describe a detailed clinical, pathological and mutation analysis of the HDDD2 kindred. RESULTS: Neuropathologically, HDDD2 represents a familial frontotemporal lobar degeneration with ubiquitin-positive, tau-negative inclusions (FTLD-U). We developed research classification criteria and identified three distinct diagnostic thresholds, which helped localize the disease locus. The chromosomal region with the strongest evidence of linkage lies within the minimum critical region for FTLD-U. Sequencing of each exon of the PGRN gene led to the identification of a novel missense mutation, Ala-9 Asp, within the signal peptide. INTERPRETATION: HDDD2 is an FTLD-U caused by a missense mutation in the PGRN gene that cosegregates with the disease and with the disease haplotype in at-risk individuals. This mutation is the first reported pathogenic missense mutation in the signal peptide of the PGRN gene causing FTLD-U. In light of the previous reports of null mutations and its position in the gene, two possible pathological mechanisms are proposed: (1) the protein may accumulate within the endoplasmic reticulum due to inefficient secretion; and (2) mutant RNA may have a lower expression because of degradation via nonsense-mediated decay.

Novel presenilin 1 mutation (S170F) causing Alzheimer disease with Lewy bodies in the third decade of life.

BACKGROUND: Cases of early-onset Alzheimer disease (AD) with an autosomal dominant inheritance pattern (familial AD [FAD]) are rare but have greatly advanced our understanding of the molecular pathogenesis of AD. We describe herein a kindred with very early-onset FAD (age, <40 years) with unusual pathological features and a novel mutation in the presenilin 1 (PSEN1) gene (S170F) and review the existing literature on very early-onset FAD. OBJECTIVE: To analyze the neuropathological and genetic features of a family with onset of AD in the third decade of life. DESIGN, SETTING, AND PARTICIPANTS: The proband underwent full clinical assessment and postmortem examination at the Washington University Alzheimer's Disease Research Center, St Louis, Mo. Limited pathological samples and autopsy records of 2 affected family members were available. The proband underwent screening for mutations in genes linked with FAD. RESULTS: Dementia developed in 3 family members in this kindred at a mean age of 27 years; the proband had myoclonus, seizures, and rigidity, similar to findings in previously described kindreds with PSEN1 mutations. All 3 family members were confirmed to have AD by neuropathological examination. The proband also had widespread Lewy body pathology in the brainstem, limbic areas, and neocortex; specific staining for Lewy bodies was not performed in the other 2 family members. The proband had a single mutation (S170F) in exon 6 of the PSEN1 gene, which segregates with disease. CONCLUSIONS: A novel PSEN1 mutation causes very-early-onset FAD with associated Lewy bodies. To our knowledge, this kindred has the earliest reported onset of pathologically confirmed FAD and dementia with Lewy bodies.

Novel haplotypes in 17q21 are associated with progressive supranuclear palsy.

Progressive supranuclear palsy (PSP) and corticobasal degeneration (CBD) are sporadic neurodegenerative diseases presenting as atypical parkinsonian disorders, characterized by the presence of tau-positive neurofibrillary tangles. Recently, an extended haplotype (H1E) of 787.6 kb that comprises several genes including MAPT showed increased association with PSP. The objective of this study was to determine the size of the H1E haplotype associated with PSP and CBD in different populations and to identify specific subhaplotypes in the background of H1E haplotype. Nineteen single nucleotide polymorphisms (SNPs) in the 17q21 region were genotyped in two case-control samples. The SNPs that were associated with higher risk for the disease in the homozygous state delimit a region of more that 1 Mb. Haplotype analyses in the Spanish sample showed that the most frequent haplotype found among the patients (H1E'), which extends 1.04 Mb and contains several genes such as MAPT, CRHR1, IMP5, Saitohin, WTN3, and NSF. A specific subhaplotype (H1E'A) was present in 16% of PSP patients but was not observed in the controls. Furthermore, the H2E'A haplotype, was rarely present in the disease group suggesting that it plays a protective role. The identification of these specific subhaplotypes that modify risk for PSP/CBD supports the hypothesis that a pathogenic allele exists in a subgroup of PSP patients.

No evidence for tau duplications in frontal temporal dementia families showing genetic linkage to the tau locus in which tau mutations have not been found.

Given the remarkable similarities between the genetics of tau diseases and the genetics of alpha-synuclein diseases, and given the fact that we have recently found a triplication of the alpha-synuclein locus in a family in which we had shown linkage to the alpha-synuclein locus, we determined to test whether some of the several families with autosomal dominant frontal temporal dementia which show genetic linkage to the tau locus but in which tau mutations have not been found could be caused by similar structural mutations. We did not find any such mutations.

Apolipoprotein Eepsilon4 modifies Alzheimer's disease onset in an E280A PS1 kindred.

We previously have identified a large kindred from Colombia in which Alzheimer's disease (AD) is caused by the E280A presenilin 1 (PS1) mutation. The objective of this study was to examine whether environmental and genetic factors are responsible for variation in the phenotypic expression of the E280A PS1 mutation. We genotyped coding and promoter polymorphisms of the APOE gene in carriers of the E280A PS1 mutation. Kaplan-Meier product-limit and Cox proportional hazard models were used in the statistical analyses. DNA was available from 114 carriers of the E280A PS1 mutation, including 52 subjects with AD. APOE epsilon 4 allele carriers were more likely to develop AD at an earlier age than subjects without the epsilon 4 allele (hazard ratio, 2.07; 95% confidence interval, 1.07-3.99; p = 0.030). Subjects with low education were more likely to develop AD later than those with higher education (hazard ratio, 0.476; 95% confidence interval, 0.26-0.87). Low educational level was associated with rural residence (p < 0.001). Promoter APOE variants did not influence either the onset or the duration of the disease. This study is the first to our knowledge to demonstrate that genetic and environmental factors influence age of onset in a kindred with a familial AD mutation.