[show abstract][hide abstract] ABSTRACT: Transactivation response DNA-binding protein 43 (TDP-43) is a principal component of ubiquitinated inclusions in frontotemporal lobar degeneration with ubiquitin-positive inclusions and in amyotrophic lateral sclerosis (ALS). Mutations in TARDBP, the gene encoding TDP-43, are associated with sporadic and familial ALS, yet multiple neurodegenerative diseases exhibit TDP-43 pathology without known TARDBP mutations. While TDP-43 has been ascribed a number of roles in normal biology, including mRNA splicing and transcription regulation, elucidating disease mechanisms associated with this protein is hindered by the lack of models to dissect such functions. We have generated transgenic (TDP-43PrP) mice expressing full-length human TDP-43 (hTDP-43) driven by the mouse prion promoter to provide a tool to analyze the role of wild-type hTDP-43 in the brain and spinal cord. Expression of hTDP-43 caused a dose-dependent downregulation of mouse TDP-43 RNA and protein. Moderate overexpression of hTDP-43 resulted in TDP-43 truncation, increased cytoplasmic and nuclear ubiquitin levels, and intranuclear and cytoplasmic aggregates that were immunopositive for phosphorylated TDP-43. Of note, abnormal juxtanuclear aggregates of mitochondria were observed, accompanied by enhanced levels of Fis1 and phosphorylated DLP1, key components of the mitochondrial fission machinery. Conversely, a marked reduction in mitofusin 1 expression, which plays an essential role in mitochondrial fusion, was observed in TDP-43PrP mice. Finally, TDP-43PrP mice showed reactive gliosis, axonal and myelin degeneration, gait abnormalities, and early lethality. This TDP-43 transgenic line provides a valuable tool for identifying potential roles of wild-type TDP-43 within the CNS and for studying TDP-43-associated neurotoxicity.
Journal of Neuroscience 08/2010; 30(32):10851-9. · 6.91 Impact Factor
[show abstract][hide abstract] ABSTRACT: To characterize a kindred with a familial neurodegenerative disorder associated with a mutation in progranulin (PGRN), with emphasis on the unique clinical features in this kindred.
Antemortem and postmortem characterization of a kindred with a familial neurodegenerative disorder.
Multispecialty group academic medical center.
Affected members of a kindred with dementia with or without parkinsonism associated with a unique mutation in PGRN.
Of 10 affected individuals identified, 6 presented with early amnestic symptoms which resulted in initial diagnoses of Alzheimer disease or amnestic mild cognitive impairment. Some individuals presented with features characteristic of frontotemporal dementia. Mean age at onset was substantially younger in generation III (75.8 years; range, 69-80 years) than in generation II (60.7 years; range, 55-66 years). The pattern of cerebral atrophy varied widely in the affected individuals. Neuropathologic features in 6 individuals included frontotemporal lobar degeneration with ubiquitin-positive neuronal cytoplasmic and intranuclear inclusions (FTLD-U with NII). PGRN analysis revealed a single base pair deletion in exon 2 (c.154delA), which caused a frameshift (p.Thr52HisfsX2) and, therefore, creation of a premature termination codon and a likely null allele.
In this large kindred, most affected individuals had clinical presentations that resembled Alzheimer disease or amnestic mild cognitive impairment associated with a mutation in PGRN and underlying FTLD-U with NII neuropathologic abnormalities. This finding is in distinct contrast to previously reported kindreds, in which clinical presentations have typically been within the spectrum of FTLD. The basis for the large difference in age at onset between generations requires further study.
Archives of neurology 02/2010; 67(2):171-7. · 6.31 Impact Factor
[show abstract][hide abstract] ABSTRACT: Here, we describe the generation and characterization of a novel tau transgenic mouse model (mTau) that overexpresses wild-type murine tau protein by twofold compared with endogenous levels. Transgenic tau expression was driven by a BAC transgene containing the entire wild-type mouse tau locus, including the endogenous promoter and the regulatory elements associated with the tau gene. The mTau model therefore differs from other tau models in that regulation of the genomic mouse transgene mimics that of the endogenous gene, including normal exon splicing regulation. Biochemical data from the mTau mice demonstrated that modest elevation of mouse tau leads to tau hyperphosphorylation at multiple pathologically relevant epitopes and accumulation of sarkosyl-insoluble tau. The mTau mice show a progressive increase in hyperphosphorylated tau pathology with age up to 15 to 18 months, which is accompanied by gliosis and vacuolization. In contrast, older mice show a decrease in tau pathology levels, which may represent hippocampal neuronal loss occurring in this wild-type model. Collectively, these results describe a novel model of tauopathy that develops pathological changes reminiscent of early stage Alzheimer's disease and other related neurodegenerative diseases, achieved without overexpression of a mutant human tau transgene. This model will provide an important tool for understanding the early events leading to the development of tau pathology and a model for analysis of potential therapeutic targets for sporadic tauopathies.
American Journal Of Pathology 09/2009; 175(4):1598-609. · 4.52 Impact Factor
[show abstract][hide abstract] ABSTRACT: The TAR DNA-binding protein 43 (TDP-43) has been identified as the major disease protein in amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration with ubiquitin inclusions (FTLD-U), defining a novel class of neurodegenerative conditions: the TDP-43 proteinopathies. The first pathogenic mutations in the gene encoding TDP-43 (TARDBP) were recently reported in familial and sporadic ALS patients, supporting a direct role for TDP-43 in neurodegeneration. In this study, we report the identification and functional analyses of two novel and one known mutation in TARDBP that we identified as a result of extensive mutation analyses in a cohort of 296 patients with variable neurodegenerative diseases associated with TDP-43 histopathology. Three different heterozygous missense mutations in exon 6 of TARDBP (p.M337V, p.N345K, and p.I383V) were identified in the analysis of 92 familial ALS patients (3.3%), while no mutations were detected in 24 patients with sporadic ALS or 180 patients with other TDP-43-positive neurodegenerative diseases. The presence of p.M337V, p.N345K, and p.I383V was excluded in 825 controls and 652 additional sporadic ALS patients. All three mutations affect highly conserved amino acid residues in the C-terminal part of TDP-43 known to be involved in protein-protein interactions. Biochemical analysis of TDP-43 in ALS patient cell lines revealed a substantial increase in caspase cleaved fragments, including the approximately 25 kDa fragment, compared to control cell lines. Our findings support TARDBP mutations as a cause of ALS. Based on the specific C-terminal location of the mutations and the accumulation of a smaller C-terminal fragment, we speculate that TARDBP mutations may cause a toxic gain of function through novel protein interactions or intracellular accumulation of TDP-43 fragments leading to apoptosis.
[show abstract][hide abstract] ABSTRACT: Peripheral blood is a readily available tissue source allowing relatively noninvasive screening for a host of medical conditions. We screened total-blood progranulin (PGRN) levels in 107 patients with neurodegenerative dementias and related conditions, and 36 control subjects, and report the following findings: (1) confirmation of high progranulin expression levels in peripheral blood; (2) two subjects with reduced progranulin levels and mutations in the PGRN gene confirmed by direct sequencing; and (3) greater PGRN messenger RNA levels in patients with clinical diagnosis of Alzheimer's disease. This proof-of-principle report supports the use of gene quantification as diagnostic screen for PGRN mutations and suggests a potential role for progranulin in Alzheimer's disease.
Annals of Neurology 07/2008; 64(1):92-6. · 11.19 Impact Factor
[show abstract][hide abstract] ABSTRACT: Frontotemporal dementia with parkinsonism (FTDP) is a major neurodegenerative syndrome, particularly for those with symptoms beginning before age 65 years. A spectrum of degenerative disorders can present as sporadic or familial FTDP. Mutations in the gene encoding the microtubule-associated protein tau (MAPT; OMIM +157140) on chromosome 17 have been found in many kindreds with familial FTDP. Several other kindreds with FTDP had been linked to chromosome 17, but they had ubiquitin-positive inclusions rather than tauopathy pathology and no mutations in MAPT. This conundrum was solved in 2006 with the identification of mutations in the gene encoding progranulin (PGRN; OMIM *138945), which is only 1.7 Mb centromeric to MAPT on chromosome 17. In this review, we compare and contrast the demographic, clinical, radiologic, neuropathologic, genetic, and pathophysiologic features in patients with FTDP linked to mutations in MAPT and PGRN, highlighting the many similarities but also a few important differences. Our findings describe an intriguing oddity of nature in which 2 genes can cause a similar phenotype through apparently different mechanisms yet reside so near to each other on the same chromosome.
Archives of neurology 05/2008; 65(4):460-4. · 6.31 Impact Factor
[show abstract][hide abstract] ABSTRACT: Alzheimer's disease presents morphologically with senile plaques, primarily made of extracellular amyloid-beta (A beta) deposits, and neurofibrillary lesions, which consist of intracellular aggregates of hyperphosphorylated tau protein. To study the in vivo induction of tau pathology, dilute brain extracts from aged A beta-depositing APP23 transgenic mice were intracerebrally infused in young B6/P301L tau transgenic mice. Six months after the infusion, tau pathology was induced in the injected hippocampus but also in brain regions well beyond the injection sites such as the entorhinal cortex and amygdala, areas with neuronal projection to the injection site. No or only modest tau induction was observed when brain extracts from aged nontransgenic control mice and aged tau-depositing B6/P301L transgenic mice were infused. To further study A beta-induced tau lesions B6/P301L tau transgenic mice were crossed with APP23 mice. Although A beta deposition in double-transgenic mice did not differ from single APP23 transgenic mice, double-transgenic mice revealed increased tau pathology compared to single B6/P301L tau transgenic mice predominately in areas with high A beta plaque load. The present results suggest that both extract-derived A beta species and deposited fibrillary A beta can induce the formation of tau neurofibrillary pathology. The observation that infused A beta can trigger the tau pathology in the absence of A beta deposits provides an explanation for the discrepancy between the neuroanatomical location of A beta deposits and the development and spreading of tau lesions in Alzheimer's disease brain.
American Journal Of Pathology 01/2008; 171(6):2012-20. · 4.52 Impact Factor
[show abstract][hide abstract] ABSTRACT: After Alzheimer's disease, frontotemporal lobar degeneration (FTLD) is the second leading cause of dementia in persons less than 65 years of age. Up to 40% of FTLD cases have a positive family history. Research on these families has led to the discovery of four disease-causing genes: microtubule-associated protein tau (MAPT), progranulin (PGRN), valosin-containing protein (VCP), and charged multivesicular body protein 2B (CHMP2B). MAPT and PGRN are responsible for the largest number of familial cases. Each of these genes differs by disease mechanism. Moreover mutations in both genes are associated with significant interfamilial and intrafamilial phenotypic variation. Genetic counseling needs to address the differences between the PGRN and MAPT mutations as well as the variation in clinical symptoms. The aims of this article are to describe the genetics of the FTLD spectrum and aid in the genetic counseling of individuals who may carry genetic mutations.
American Journal of Alzheimer s Disease and Other Dementias 01/2008; 22(6):507-15. · 1.52 Impact Factor
[show abstract][hide abstract] ABSTRACT: Mutations in progranulin (PGRN) are associated with frontotemporal dementia with or without parkinsonism. We describe the prominent phenotypic variability within and among eight kindreds evaluated at Mayo Clinic Rochester and/or Mayo Clinic Jacksonville in whom mutations in PGRN were found. All available clinical, genetic, neuroimaging and neuropathologic data was reviewed. Age of onset ranged from 49 to 88 years and disease duration ranged from 1 to 14 years. Clinical diagnoses included frontotemporal dementia (FTD), primary progressive aphasia, FTD with parkinsonism, parkinsonism, corticobasal syndrome, Alzheimer's disease, amnestic mild cognitive impairment, and others. One kindred exhibited maximal right cerebral hemispheric atrophy in all four affected individuals, while another had maximal left hemisphere involvement in all three of the affected. Neuropathologic examination of 13 subjects revealed frontotemporal lobar degeneration with ubiquitin-positive inclusions plus neuronal intranuclear inclusions in all cases. Age of onset, clinical phenotypes and MRI findings associated with most PGRN mutations varied significantly both within and among kindreds. Some kindreds with PGRN mutations exhibited lateralized topography of degeneration across all affected individuals.
Neurobiology of aging 11/2007; 30(5):739-51. · 5.94 Impact Factor
[show abstract][hide abstract] ABSTRACT: The progranulin gene (GRN) is mutated in 5-10% of patients with frontotemporal lobar degeneration (FTLD) and in about 20% of patients with familial FTLD. The most common mutation in GRN is Arg493X. We aimed to establish the contribution of this mutation to FTLD and related disorders.
We measured the frequency of Arg493X in 3405 unrelated patients with various neurodegenerative diseases using Taqman single-nucleotide polymorphism (SNP) genotyping. Clinicopathological characterisation and shared haplotype analysis were done for 30 families with FTLD who carry Arg493X. To investigate the effect of potential modifying loci, we did linear regression analyses with onset age as the covariate for GRN variants, for genotypes of the apolipoprotein E gene (APOE), and for haplotypes of the microtubule-associated protein tau gene (MAPT).
Of 731 patients with FTLD, 16 (2%) carried Arg493X. This mutation was not detected in 2674 patients who did not have FTLD. In 37 patients with Arg493X from 30 families with FTLD, clinical diagnoses included frontotemporal dementia, primary progressive aphasia, corticobasal syndrome, and Alzheimer's disease. Range of onset age was 44-69 years. In all patients who came to autopsy (n=13), the pathological diagnosis was FTLD with neuronal inclusions that contained TAR DNA-binding protein or ubiquitin, but not tau. Neurofibrillary tangle pathology in the form of Braak staging correlated with overall neuropathology in the Arg493X carriers. Haplotype analyses suggested that Arg493X arose twice, with a single founder for 27 families. Linear regression analyses suggested that patients with SNP rs9897528 on their wild-type GRN allele have delayed symptom onset. Onset ages were not associated with the MAPT H1 or H2 haplotypes or APOE genotypes, but early memory deficits were associated with the presence of an APOE epsilon4 allele.
Clinical heterogeneity is associated with GRN haploinsufficiency, and genetic variability on the wild-type GRN allele might have a role in the age-related disease penetrance of GRN mutations.
The Lancet Neurology 11/2007; 6(10):857-68. · 23.92 Impact Factor
[show abstract][hide abstract] ABSTRACT: The clinical disorders associated with frontotemporal lobar degeneration (FTLD) are increasingly recognized as an important cause of early-onset dementia. Patients usually present with progressive changes in personality, behavior, or language, progressing to general cognitive impairment and ultimately death. In the past decade, improved clinical and histopathologic characterization uncovered extensive heterogeneity, and multiple clinical and pathologic FTLD subtypes were defined. Simultaneously, the discovery of four causal FTLD genes emphasized the genetic complexity associated with FTLD. More recently, the field of FTLD has gained increased attention as a result of two major findings. First, mutations in the progranulin gene (PGRN) were recognized as a major cause of FTLD with ubiquitin-positive and tau-negative inclusions (FTLD-U), and subsequently the TAR DNA-binding protein-43 (TDP-43) was identified as a key protein within the ubiquitinated inclusions in FTLD-U and amyotrophic lateral sclerosis (ALS). In this report, we outline the progress made in the study of the genetic etiologies and neuropathologic substrates in FTLD.
Current Neurology and Neuroscience Reports 10/2007; 7(5):434-42. · 3.78 Impact Factor
[show abstract][hide abstract] ABSTRACT: Leucine-rich repeat kinase 2 (LRRK2) mutation carriers can develop clinical symptoms other than typical parkinsonism such as dementia, amyotrophy or dystonia. To determine if LRRK2 mutations might be involved in frontotemporal dementia (FTD), 5 individuals with multiplex familial FTD kindreds and 41 pathologically confirmed cases of FTD, including 23 with a family history of dementia, were screened for genetic variations in the LRRK2 gene. We identified a LRRK2 mutation leading to the G2019S amino acid substitution in a 79-year-old woman with frontotemporal lobar degeneration with ubiquitinated neuronal intranuclear inclusions (FTLD-U/NII) and a possible family history of tremor. These findings may be coincidental; however, there is a small nucleus of LRRK2-positive patients displaying atypical features suggesting a role for this protein in other neurodegenerative disorders.
[show abstract][hide abstract] ABSTRACT: Neurofibrillary tangles (NFTs) are a pathological hallmark of Alzheimer's disease and other tauopathies, but recent studies in a conditional mouse model of tauopathy (rTg4510) have suggested that NFT formation can be dissociated from memory loss and neurodegeneration. This suggests that NFTs are not the major neurotoxic tau species, at least during the early stages of pathogenesis. To identify other neurotoxic tau protein species, we performed biochemical analyses on brain tissues from the rTg4510 mouse model and then correlated the levels of these tau proteins with memory loss. We describe the identification and characterization of two forms of tau multimers (140 and 170 kDa), whose molecular weight suggests an oligomeric aggregate, that accumulate early in the pathogenic cascade in this mouse model. Similar tau multimers were detected in a second mouse model of tauopathy (JNPL3) and in tissue from patients with Alzheimer's disease and FTDP-17 (frontotemporal dementia and parkinsonism linked to chromosome 17). Moreover, levels of the tau multimers correlated consistently with memory loss at various ages in the rTg4510 mouse model. Our findings suggest that accumulation of early-stage aggregated tau species, before the formation of NFT, is associated with the development of functional deficits during the pathogenic progression of tauopathy.
Journal of Neuroscience 05/2007; 27(14):3650-62. · 6.91 Impact Factor
[show abstract][hide abstract] ABSTRACT: To date, only the H1 MAPT haplotype has been consistently associated with risk of developing the neurodegenerative disease progressive supranuclear palsy (PSP). We hypothesized that additional genetic loci may be involved in conferring risk of PSP that could be identified through a pooling-based genomewide association study of >500,000 SNPs. Candidate SNPs with large differences in allelic frequency were identified by ranking all SNPs by their probe-intensity difference between cohorts. The MAPT H1 haplotype was strongly detected by this methodology, as was a second major locus on chromosome 11p12-p11 that showed evidence of association at allelic (P<.001), genotypic (P<.001), and haplotypic (P<.001) levels and was narrowed to a single haplotype block containing the DNA damage-binding protein 2 (DDB2) and lysosomal acid phosphatase 2 (ACP2) genes. Since DNA damage and lysosomal dysfunction have been implicated in aging and neurodegenerative processes, both genes are viable candidates for conferring risk of disease.
The American Journal of Human Genetics 04/2007; 80(4):769-78. · 11.20 Impact Factor
[show abstract][hide abstract] ABSTRACT: Inclusion-body myopathy, Paget's disease of bone and frontotemporal dementia is an adult-onset autosomal dominant illness (IBMPFD) caused by mutations in the valosin-containing protein (VCP) on chromosome 9p21.1-p12. The penetrance of the gene is 82% for myopathy, 49% for Paget's disease, but may be as low as 30% for frontotemporal dementia. Modifier genes could account for decreased frontotemporal dementia penetrance. In this study apolipoprotein-E (APOE) was evaluated for this role in IBMPFD families based on its known modifier effect in Alzheimer's disease.
From a database of 231 members of 15 families, 174 had APOE genotype available for analysis. Logistic regressions on APOE genotype and frontotemporal dementia were performed, using appropriate covariates.
FTD was associated with APOE 4 genotype (P=0.0002), myopathy (P=0.0006), and age (P=0.01), but not microtubule associated protein tau (MAPT) H2 haplotype (P=0.5) or gender (0.09) after adjustment for membership in pedigrees with at least one APOE 4 genotype. These data suggest a potential link between APOE 4 genotype and the specific form of frontotemporal dementia found in IBMPFD. The molecular basis of this link bears further investigation. We did not observe an association of frontotemporal dementia and H2 MAPT haplotype.
Genetics in Medicine 02/2007; 9(1):9-13. · 5.56 Impact Factor
[show abstract][hide abstract] ABSTRACT: A segregating splice site mutation in the CHMP2B gene has been shown in the single Danish family which has been reported to show linkage between dementia and chromosome 3 markers. Despite extensive analysis, no other segregating mutations have been found in other kindreds, although some point variants have been found both in sporadic cases and in controls. We recently found a premature stop codon in a person without dementia and this led us to investigate whether the splice site mutation in the Danish kindred did not explain the disease, but rather was hitchhiking on the segregating disease haplotype. We determined to test this possibility by sequencing every other gene on the haplotype in a case from the kindred. We did not find any other unique variants. The implications of these findings for the likely mode of pathogenesis of frontal temporal dementia are discussed.
[show abstract][hide abstract] ABSTRACT: Mutations in presenilin-1 (PSEN1) cause autosomal dominant Alzheimer's disease and mutations in MAPT cause the familial tauopathy Frontotemporal dementia linked to chromosome 17 (FTDP-17). However, there have been reports of mutations in PSEN1 and MAPT associated with cases of FTD with ubiquitin-positive tau-negative inclusion pathology. Here, we demonstrate that the MAPT variants are almost certainly rare benign polymorphisms as all of these cases harbour mutations in Progranulin (PGRN). Mutations in PGRN were recently shown to cause ubiquitin-positive FTDP-17.