Clinical and genetic features of families with frontotemporal dementia and parkinsonism linked to chromosome 17 with a P301S tau mutation

An emerging role for the gut microbiome in tauopathy

Tauopathies constitute a group of neurodegenerative diseases characterized by abnormal aggregation of the protein tau, progressive neuronal and synaptic loss, and eventual cognitive and motor impairment. In this review, we will highlight the latest efforts investigating the intricate interplay between the gut microbiome and tauopathies. We discuss the physiological interactions between the microbiome and the brain as well as clinical and experimental evidence that suggests that the presence of tauopathy alters the composition of gut microbiota. We explore both animal and human studies that define causative relationships between the gut microbiome and tauopathy by directly manipulating or transferring gut microbiota. This review highlights future directions into identifying and mechanistically elucidating microbial species causally linked to tauopathies, with an ultimate goal of devising therapeutic targets towards the gut microbiome to treat tauopathies.

Behavioral and Neuropathological Phenotyping of the Tau58/2 and Tau58/4 Transgenic Mouse Models for FTDP-17

BACKGROUND

The Tau58/2 and Tau58/4 mouse lines expressing 0N4R tau with a P301S mutation mimic aspects of frontotemporal dementia and parkinsonism linked to chromosome 17 (FTDP-17). In a side-by-side comparison, we report the age-dependent development of cognitive, motor, and behavioral deficits in comparison with the spatial-temporal evolution of cellular tau pathology in both models.

METHODS

We applied the SHIRPA primary screen and specific neuromotor, behavioral, and cognitive paradigms. The spatiotemporal development of tau pathology was investigated immunohistochemically. Levels of sarkosyl-insoluble paired helical filaments were determined via a MesoScale Discovery biomarker assay.

RESULTS

Neuromotor impairments developed from age 3 months in both models. On electron microscopy, spinal cord neurofibrillary pathology was visible in mice aged 3 months; however, AT8 immunoreactivity was not yet observed in Tau58/4 mice. Behavioral abnormalities and memory deficits occurred at a later stage (>9 months) when tau pathology was fully disseminated throughout the brain. Spatiotemporally, tau pathology spread from the spinal cord via the midbrain to the frontal cortex, while the hippocampus was relatively spared, thus explaining the late onset of cognitive deficits.

CONCLUSIONS

Our findings indicate the face and construct validity of both Tau58 models, which may provide new, valuable insights into the pathologic effects of tau species in vivo and may consequently facilitate the development of new therapeutic targets to delay or halt neurodegenerative processes occurring in tauopathies.

Genotype-phenotype correlation in the spectrum of frontotemporal dementia-parkinsonian syndromes and advanced diagnostic approaches

The term frontotemporal dementia (FTD) refers to a group of progressive neurodegenerative disorders characterized mainly by atrophy of the frontal and anterior temporal lobes. Based on clinical presentation, three main clinical syndromes have traditionally been described: behavioral variant frontotemporal dementia (bvFTD), non-fluent/agrammatic primary progressive aphasia (nfPPA), and semantic variant PPA (svPPA). However, over the last 20 years, it has been recognized that cognitive phenotypes often overlap with motor phenotypes, either motor neuron diseases or parkinsonian signs and/or syndromes like progressive supranuclear palsy (PSP) and cortico-basal syndrome (CBS). Furthermore, FTD-related genes are characterized by genetic pleiotropy and can cause, even in the same family, pure motor phenotypes, findings that underlie the clinical continuum of the spectrum, which has pure cognitive and pure motor phenotypes as the extremes. The genotype-phenotype correlation of the spectrum, FTD-motor neuron disease, has been well defined and extensively investigated, while the continuum, FTD-parkinsonism, lacks a comprehensive review. In this narrative review, we describe the current knowledge about the genotype-phenotype correlation of the spectrum, FTD-parkinsonism, focusing on the phenotypes that are less frequent than bvFTD, namely nfPPA, svPPA, PSP, CBS, and cognitive-motor overlapping phenotypes (i.e. PPA + PSP). From a pathological point of view, they are characterized mainly by the presence of phosphorylated-tau inclusions, either 4 R or 3 R. The genetic correlate of the spectrum can be heterogeneous, although some variants seem to lead preferentially to specific clinical syndromes. Furthermore, we critically review the contribution of genome-wide association studies (GWAS) and next-generation sequencing (NGS) in disentangling the complex heritability of the FTD-parkinsonism spectrum and in defining the genotype-phenotype correlation of the entire clinical scenario, owing to the ability of these techniques to test multiple genes, and so to allow detailed investigations of the overlapping phenotypes. Finally, we conclude with the importance of a detailed genetic characterization and we offer to patients and families the chance to be included in future randomized clinical trials focused on autosomal dominant forms of FTLD.

Extremely Early-Onset Frontotemporal Dementia: A Case Report and Literature Review

BACKGROUND

In most cases, the onset of frontotemporal dementia (FTD) occurs between the ages of 45 and 65 years. However, some patients experience an extremely early disease onset.

OBJECTIVE

To investigate the clinical, genetic, and pathological features of extremely early-onset FTD.

METHODS

We conducted a comprehensive clinical, genetic, and neuropathological analysis of a 25-year-old patient experiencing the onset of behavioral variant frontotemporal dementia (bvFTD). In addition, we conducted a literature review and summarized the clinical, genetic, and pathological features of patients with FTD with onset age≤25 years.

RESULTS

The patient was diagnosed with bvFTD; however, there was no family history of FTD, no positive genetic test results and no deposition of TDP43, tau, ubiquitin, and synuclein in the brain. Literature screening identified 18 patients with onset age ≤25 years with FTD. The youngest patient was 14 years of age. Most patients (8/14) had a positive family history. The most common clinical phenotype was the behavioral variant (12/14). Genetic results were reported for 11 patients; the most common pathogenic gene was MAPT (10/12), with four cases of G389 R, two cases of P301 S, one case of G335 S, one case of G335A, one case of G335 V, and one case of L315 R. Pathological results were reported for 13 patients; the most common pathological subtype was tau (8/13).

CONCLUSION

FTD can start at an extremely early age. The most common phenotype of extremely early onset FTD was the behavioral variant, the most common pathogenic gene was MAPT, and the most common neuropathological type was tau.

Pathogenic tau recruits wild-type tau into brain inclusions and induces gut degeneration in transgenic SPAM mice

Pathological tau inclusions are neuropathologic hallmarks of many neurodegenerative diseases. We generated and characterized a transgenic mouse model expressing pathogenic human tau with S320F and P301S aggregating mutations (SPAM) at transgene levels below endogenous mouse tau protein levels. This mouse model develops a predictable temporal progression of tau pathology in the brain with biochemical and ultrastructural properties akin to authentic tau inclusions. Surprisingly, pathogenic human tau extensively recruited endogenous mouse tau into insoluble aggregates. Despite the early onset and rapid progressive nature of tau pathology, major neuroinflammatory and transcriptional changes were only detectable at later time points. Moreover, tau SPAM mice are the first model to develop loss of enteric neurons due to tau accumulation resulting in a lethal phenotype. With moderate transgene expression, rapidly progressing tau pathology, and a highly predictable lethal phenotype, the tau SPAM model reveals new associations of tau neurotoxicity in the brain and intestinal tract.

Tau and MAPT genetics in tauopathies and synucleinopathies

MAPT encodes the microtubule-associated protein tau, which is the main component of neurofibrillary tangles (NFTs) and found in other protein aggregates. These aggregates are among the pathological hallmarks of primary tauopathies such as frontotemporal dementia (FTD). Abnormal tau can also be observed in secondary tauopathies such as Alzheimer's disease (AD) and synucleinopathies such as Parkinson's disease (PD). On top of pathological findings, genetic data also links MAPT to these disorders. MAPT variations are a cause or risk factors for many tauopathies and synucleinopathies and are associated with certain clinical and pathological features in affected individuals. In addition to clinical, pathological, and genetic overlap, evidence also suggests that tau and alpha-synuclein may interact on the molecular level, and thus might collaborate in the neurodegenerative process. Understanding the role of MAPT variations in tauopathies and synucleinopathies is therefore essential to elucidate the role of tau in the pathogenesis and phenotype of those disorders, and ultimately to develop targeted therapies. In this review, we describe the role of MAPT genetic variations in tauopathies and synucleinopathies, several genotype-phenotype and pathological features, and discuss their implications for the classification and treatment of those disorders.

Tauopathy and Movement Disorders-Unveiling the Chameleons and Mimics

The spectrum of tauopathy encompasses heterogenous group of neurodegenerative disorders characterized by neural or glial deposition of pathological protein tau. Clinically they can present as cognitive syndromes, movement disorders, motor neuron disease, or mixed. The heterogeneity in clinical presentation, genetic background, and underlying pathology make it difficult to classify and clinically approach tauopathy. In the literature, tauopathies are thus mostly highlighted from pathological perspective. From clinical standpoint, cognitive syndromes are often been focussed while reviewing tauopathies. However, the spectrum of tauopathy has also evolved significantly in the domain of movement disorders and has transgressed beyond the domain of primary tauopathies. Secondary tauopathies from neuroinflammation or autoimmune insults and some other "novel" tauopathies are increasingly being reported in the current literature, while some of them are geographically isolated. Because of the overlapping clinical phenotypes, it often becomes difficult for the clinician to diagnose them clinically and have to wait for the pathological confirmation by autopsy. However, each of these tauopathies has some clinical and radiological signatures those can help in clinical diagnosis and targeted genetic testing. In this review, we have exposed the heterogeneity of tauopathy from a movement disorder perspective and have provided a clinical approach to diagnose them ante mortem before confirmatory autopsy. Additionally, phenotypic variability of these disorders (chameleons) and the look-alikes (mimics) have been discussed with potential clinical pointers for each of them. The review provides a framework within which new and as yet undiscovered entities can be classified in the future.

A MultiTEP platform-based epitope vaccine targeting the phosphatase activating domain (PAD) of tau: therapeutic efficacy in PS19 mice

Pathological tau correlates well with cognitive impairments in Alzheimer’s disease (AD) patients and therefore represents a promising target for immunotherapy. Targeting an appropriate B cell epitope in pathological tau could in theory produce an effective reduction of pathology without disrupting the function of normal native tau. Recent data demonstrate that the N-terminal region of tau (aa 2-18), termed the “phosphatase activation domain (PAD)”, is hidden within native Tau in a ‘paperclip’-like conformation. Conversely, PAD is exposed in pathological tau and plays an essential role in the inhibition of fast axonal transport and tau polymerization. Thus, we hypothesized that anti-tau2-18 antibodies may safely and specifically reduce pathological tau and prevent further aggregation, which in turn would neutralize tau toxicity. Therefore, we evaluated the immunogenicity and therapeutic efficacy of our MultiTEP platform-based vaccine targeting tau2-18 formulated with Advax^CpG adjuvant (AV-1980R/A) in PS19 tau transgenic mice. The AV-1980R/A induced extremely high antibody responses and the resulting sera recognized neurofibrillary tangles and plaque-associated dystrophic neurites in AD brain sections. In addition, under non-denaturing conditions AV-1980R/A sera preferentially recognized AD-associated tau. Importantly, vaccination also prevented age-related motor and cognitive deficits in PS19 mice and significantly reduced insoluble total and phosphorylated tau species. Taken together, these findings suggest that predominantly targeting misfolded tau with AV-1980R/A could represent an effective strategy for AD immunotherapy.

In vivo Bioluminescence Imaging Used to Monitor Disease Activity and Therapeutic Response in a Mouse Model of Tauopathy

Many studies of tauopathy use transgenic mice that overexpress the P301S mutant form of tau. Neuronal damage in these mice is associated with astrogliosis and induction of glial fibrillary acidic protein (GFAP) expression. GFAP-luc transgenic mice express firefly luciferase under the GFAP promoter, allowing bioluminescence to be measured non-invasively as a surrogate biomarker for astrogliosis. We bred double transgenic mice possessing both P301S and GFAP-luc cassettes and compared them to control mice bearing only the GFAP-luc transgene. We used serial bioluminescent images to define the onset and the time course of astrogliosis in these mice and this was correlated with the development of clinical deficit. Mice containing both GFAP-luc and P301S transgenes showed increased luminescence indicative of astroglial activation in the brain and spinal cord. Starting at 5 months old, the onset of clinical deterioration in these mice corresponded closely to the initial rise in the luminescent signal. Post mortem analysis showed the elevated luminescence was correlated with hyperphosphorylated tau deposition in the hippocampus of double transgenic mice. We used this method to determine the therapeutic effect of JM4 peptide [a small peptide immunomodulatory agent derived from human erythropoietin (EPO)] on double transgenic mice. JM4 treatment significantly decreased the intensity of luminescence, neurological deficit and hyperphosphorylated tau in mice with both the P301S and GFAP-luc transgenes. These findings indicate that bioluminescence imaging (BLI) is a powerful tool for quantifying GFAP expression in living P301S mice and can be used as a noninvasive biomarker of tau-induced neurodegeneration in preclinical therapeutic trials.

Genetically Engineered iPSC-Derived FTDP-17 MAPT Neurons Display Mutation-Specific Neurodegenerative and Neurodevelopmental Phenotypes

Tauopathies such as frontotemporal dementia (FTD) remain incurable to date, partially due to the lack of translational in vitro disease models. The MAPT gene, encoding the microtubule-associated protein tau, has been shown to play an important role in FTD pathogenesis. Therefore, we used zinc finger nucleases to introduce two MAPT mutations into healthy donor induced pluripotent stem cells (iPSCs). The IVS10+16 mutation increases the expression of 4R tau, while the P301S mutation is pro-aggregant. Whole-transcriptome analysis of MAPT IVS10+16 neurons reveals neuronal subtype differences, reduced neural progenitor proliferation potential, and aberrant WNT/SHH signaling. Notably, these neurodevelopmental phenotypes could be recapitulated in neurons from patients carrying the MAPT IVS10+16 mutation. Moreover, the additional pro-aggregant P301S mutation revealed additional phenotypes, such as an increased calcium burst frequency, reduced lysosomal acidity, tau oligomerization, and neurodegeneration. This series of iPSCs could serve as a platform to unravel a potential link between pathogenic 4R tau and FTD.

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Analysis of ZFN-engineered MAPT IVS10+16 with or without additional P301S mutation

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Neurodevelopmental phenotypes in ZFN and patient-derived MAPT IVS10+16 neurons

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Neurodegenerative phenotypes in MAPT IVS10+16/P301S double-mutant neurons

Frontotemporal dementia

Frontotemporal dementia (FTD) is a neurodegenerative disorder characterized by progressive changes in behavior, personality, and language with involvement of the frontal and temporal regions of the brain. About 40% of FTD cases have a positive family history, and about 10% of these cases are inherited in an autosomal-dominant pattern. These gene defects present with distinct clinical phenotypes. As the diagnosis of FTD becomes more recognizable, it will become increasingly important to keep these gene mutations in mind. In this chapter, we review the genes with known associations to FTD. We discuss protein functions, mutation frequencies, clinical phenotypes, imaging characteristics, and pathology associated with these genes.

Parkinsonism, movement disorders and genetics in frontotemporal dementia

Frontotemporal dementia (FTD) refers to a group of clinically and genetically heterogeneous neurodegenerative disorders that are a common cause of adult-onset behavioural and cognitive impairment. FTD often presents in combination with various hyperkinetic or hypokinetic movement disorders, and evidence suggests that various genetic mutations underlie these different presentations. Here, we review the known syndromatic-genetic correlations in FTD. Although no direct genotype-phenotype correlations have been identified, mutations in multiple genes have been associated with various presentations. Mutations in the genes that encode microtubule-associated protein tau (MAPT) and progranulin (PGRN) can manifest as symmetrical parkinsonism, including the phenotypes of Richardson syndrome and corticobasal syndrome (CBS). Expansions in the C9orf72 gene are most frequently associated with familial FTD, typically combined with motor neuron disease, but other manifestations, such as symmetrical parkinsonism, CBS and multiple system atrophy-like presentations, have been described in patients with these mutations. Less common gene mutations, such as those in TARDBP, CHMP2B, VCP, FUS and TREM2, can also present as atypical parkinsonism. The most common hyperkinetic movement disorders in FTD are motor and vocal stereotypies, which have been observed in up to 78% of patients with autopsy-proven FTD. Other hyperkinetic movements, such as chorea, orofacial dyskinesias, myoclonus and dystonia, are also observed in some patients with FTD.

Piericidin A aggravates Tau pathology in P301S transgenic mice

Objective

The P301S mutation in exon 10 of the tau gene causes a hereditary tauopathy. While mitochondrial complex I inhibition has been linked to sporadic tauopathies. Piericidin A is a prototypical member of the group of the piericidins, a class of biologically active natural complex I inhibitors, isolated from streptomyces spp. with global distribution in marine and agricultural habitats. The aim of this study was to determine whether there is a pathogenic interaction of the environmental toxin piericidin A and the P301S mutation.

Methods

Transgenic mice expressing human tau with the P301S-mutation (P301S^+/+) and wild-type mice at 12 weeks of age were treated subcutaneously with vehicle (N = 10 P301S^+/+, N = 7 wild-type) or piericidin A (N = 9 P301S^+/+, N = 9 wild-type mice) at a dose of 0.5 mg/kg/d for a period of 28 days via osmotic minipumps. Tau pathology was measured by stereological counts of cells immunoreative with antibodies against phosphorylated tau (AD2, AT8, AT180, and AT100) and corresponding Western blot analysis.

Results

Piericidin A significantly increased the number of phospho-tau immunoreactive cells in the cerebral cortex in P301S^+/+ mice, but only to a variable and mild extent in wild-type mice. Furthermore, piericidin A led to increased levels of pathologically phosphorylated tau only in P301S^+/+ mice. While we observed no apparent cell loss in the frontal cortex, the synaptic density was reduced by piericidin A treatment in P301S^+/+ mice.

Discussion

This study shows that exposure to piericidin A aggravates the course of genetically determined tau pathology, providing experimental support for the concept of gene-environment interaction in the etiology of tauopathies.

The role of the innate immune system in Alzheimer's disease and frontotemporal lobar degeneration: an eye on microglia

In the last few years, genetic and biomolecular mechanisms at the basis of Alzheimer's disease (AD) and frontotemporal lobar degeneration (FTLD) have been unraveled. A key role is played by microglia, which represent the immune effector cells in the central nervous system (CNS). They are extremely sensitive to the environmental changes in the brain and are activated in response to several pathologic events within the CNS, including altered neuronal function, infection, injury, and inflammation. While short-term microglial activity has generally a neuroprotective role, chronic activation has been implicated in the pathogenesis of neurodegenerative disorders, including AD and FTLD. In this framework, the purpose of this review is to give an overview of clinical features, genetics, and novel discoveries on biomolecular pathogenic mechanisms at the basis of these two neurodegenerative diseases and to outline current evidence regarding the role played by activated microglia in their pathogenesis.

New perspective on parkinsonism in frontotemporal lobar degeneration

Frontotemporal dementia (FTD) is the second most common type of presenile dementia. Three clinical prototypes have been defined; behavioral variant FTD, semantic dementia, and progressive nonfluent aphasia. Progressive supranuclear palsy, corticobasal degeneration, and motor neuron disease may possess clinical and pathological characteristics that overlap with FTD, and it is possible that they may all belong to the same clinicopathological spectrum. Frontotemporal lobar degeneration (FTLD) is a clinicopathological syndrome that encompasses a heterogenous group of neurodegenerative disorders. Owing to the advancement in the field of molecular genetics, diagnostic imaging, and pathology, FTLD has been the focus of great interest. Nevertheless, parkinsonism in FTLD has received relatively less attention. Parkinsonism is found in approximately 20–30% of patients in FTLD. Furthermore, parkinsonism can be seen in all FTLD subtypes, and some patients with familial and sporadic FTLD can present with prominent parkinsonism. Therefore, there is a need to understand parkinsonism in FTLD in order to obtain a better understanding of the disease. With regard to the clinical characteristics, the akinetic rigid type of parkinsonism has predominantly been described. Parkinsonism is frequently observed in familial FTD, more specifically, in FTD with parkinsonism linked to chromosome 17q (FTDP-17). The genes associated with parkinsonism are microtubule associated protein tau (MAPT), progranulin (GRN or PGRN), and chromosome 9 open reading frame 72 (C9ORF72) repeat expansion. The neural substrate of parkinsonism remains to be unveiled. Dopamine transporter (DAT) imaging revealed decreased uptake of DAT, and imaging findings indicated atrophic changes of the basal ganglia. Parkinsonism can be an important feature in FTLD and, therefore, increased attention is needed on the subject.

Bezafibrate administration improves behavioral deficits and tau pathology in P301S mice

Peroxisome proliferator-activated receptors (PPARs) are ligand-mediated transcription factors, which control both lipid and energy metabolism and inflammation pathways. PPARγ agonists are effective in the treatment of metabolic diseases and, more recently, neurodegenerative diseases, in which they show promising neuroprotective effects. We studied the effects of the pan-PPAR agonist bezafibrate on tau pathology, inflammation, lipid metabolism and behavior in transgenic mice with the P301S human tau mutation, which causes familial frontotemporal lobar degeneration. Bezafibrate treatment significantly decreased tau hyperphosphorylation using AT8 staining and the number of MC1-positive neurons. Bezafibrate treatment also diminished microglial activation and expression of both inducible nitric oxide synthase and cyclooxygenase 2. Additionally, the drug differentially affected the brain and brown fat lipidome of control and P301S mice, preventing lipid vacuoles in brown fat. These effects were associated with behavioral improvement, as evidenced by reduced hyperactivity and disinhibition in the P301S mice. Bezafibrate therefore exerts neuroprotective effects in a mouse model of tauopathy, as shown by decreased tau pathology and behavioral improvement. Since bezafibrate was given to the mice before tau pathology had developed, our data suggest that bezafibrate exerts a preventive effect on both tau pathology and its behavioral consequences. Bezafibrate is therefore a promising agent for the treatment of neurodegenerative diseases associated with tau pathology.

Synaptic changes in frontotemporal lobar degeneration: correlation with MAPT haplotype and APOE genotype

AIMS

This immunohistochemical study quantified synaptic changes (synaptophysin and SNAP-25) in the frontal lobe of subjects with frontotemporal lobar degeneration (FTLD) and Alzheimer's disease (AD), and related these to APOE genotype and MAPT haplotype.

METHODS

Frontal neocortex (BA9) of post mortem brains from subjects with FTLD (n = 20), AD (n = 10) and age-matched controls (n = 9) were studied immunohistochemically for synaptophysin and SNAP-25.

RESULTS

We report that patients with FTLD have a significant increase in synaptophysin and depletion in SNAP-25 proteins compared to both control subjects and individuals with AD (P < 0.001). The FTLD up-regulation of synaptophysin is disease specific (P < 0.0001), and is not influenced by age (P = 0.787) or cortical atrophy (P = 0.248). The SNAP-25 depletion is influenced by a number of factors, including family history and histological characteristics of FTLD, APOE genotype, MAPT haplotype and gender. Thus, more profound loss of SNAP-25 occurred in tau-negative FTLD, and was associated with female gender and lack of family history of FTLD. Presence of APOEε4 allele and MAPT H2 haplotype in FTLD had a significant influence on the expression of synaptic proteins, specifically invoking a decrease in SNAP-25.

CONCLUSIONS

Our results suggest that synaptic expression in FTLD is influenced by a number of genetic factors which need to be taken into account in future neuropathological and biochemical studies dealing with altered neuronal mechanisms of the disease. The selective loss of SNAP-25 in FTLD may be closely related to the core clinical non-cognitive features of the disease.

Parkinsonism and frontotemporal dementia: the clinical overlap

Frontotemporal dementia is commonly associated with parkinsonism in several sporadic (i.e., progressive supranuclear palsy, corticobasal degeneration) and familial neurodegenerative disorders (i.e., frontotemporal dementia associated with parkinsonism and MAPT or progranulin mutations in chromosome 17). The clinical diagnosis of these disorders may be challenging in view of overlapping clinical features, particularly in speech, language, and behavior. The motor and cognitive phenotypes can be viewed within a spectrum of clinical, pathologic, and genetic disorders with no discrete clinicopathologic correlations but rather lying within a dementia-parkinsonism continuum. Neuroimaging and cerebrospinal fluid analysis can be helpful, but the poor specificity of clinical and imaging features has enormously challenged the development of biological markers that could differentiate these disorders premortem. This gap is critical to bridge in order to allow testing of novel biological therapies that may slow the progression of these proteinopathies.

Astrocytic neuroprotection through induction of cytoprotective molecules; a proteomic analysis of mutant P301S tau-transgenic mouse

Hyperphosphorylated tau protein constitutes a significant portion of intracellular inclusions in some neurodegenerative diseases. In addition, mutations in tau protein cause familial forms of frontotemporal dementia (FTD), indicating that dysfunction of tau protein is responsible for neurodegeneration and dementia. P301S tau-transgenic (Tg) mouse expressing human mutant tau in neurons exhibits similar features of human tauopathies including neuronal degeneration and filament accumulation consisted of hyperphosphorylated tau protein. In the present study, we attempted to characterize protein expression profiles in P301S tau-Tg mouse by using two-dimensional differential in-gel electrophoresis (2D-DIGE) coupled by peptide mass fingerprinting (PMF). As a result, we identified four upregulated proteins; heat shock protein 27 (Hsp27), peroxiredoxin 6 (Prdx6), apolipoprotein E (ApoE), and latexin (LTXN), all of which may function as a neuroprotective mechanism against tau toxicity. In immunohistochemistry, these four proteins were increased invariably in astrocytes, and these astrocytes infiltrated the area in which there are numerous accumulations of hyperphosphorylated tau and neuronal loss. Therefore, these results may indicate that astrocytes provide a neuroprotective mechanism against tau toxicity.

Presence of reactive microglia and neuroinflammatory mediators in a case of frontotemporal dementia with P301S mutation

BACKGROUND

Recent findings, showing the presence of an inflammatory process in the brain of transgenic mice expressing P301S mutated human tau protein, indicate that neuroinflammation may contribute to tau-related degeneration in frontotemporal dementia and parkinsonism linked to chromosome 17 with tau mutations (FTDP-17T).

OBJECTIVE

To investigate the occurrence of neuroinflammatory changes in the brain of a patient affected by FTDP-17T associated with the P301S mutation and showing a frontotemporal dementia phenotype as well as in the brain of a patient affected by another FTDP-17T phenotype: multiple system tauopathy with presenile dementia.

METHODS

We used immunohistochemical methods to visualize activated microglia, interleukin-1b (IL-1b)-, cyclooxygenase-2 (COX-2)-expressing cells.

RESULTS

In the brain of the patient with the P301S mutation, a strong neuroinflammatory reaction was present. Activated microglia/infiltrating macrophages expressing the cluster of differentiation 68 and major histocampatibility complex class II cell surface receptors, encoded by the human leukocyte antigen DP-DQ-DR, were detected in the cortex and hippocampus. IL-1b and COX-2 expression were induced in neuronal and glial cells. These neuroinflammatory changes were different from those observed in the brain of the patient bearing the +3 mutation, where macrophage infiltration was absent, microglial cells displayed an earlier stage of activation and COX-2 was not detected.

CONCLUSIONS

Our findings suggest that microglial activation and the production of proinflammatory mediators by phospho-tau-positive neurons and glial cells may differentially contribute to neuronal death and disease progression in neurodegenerative tauopathies.

Tau and neurodegenerative disorders

The mechanisms that render tau a toxic agent are still unclear, although increasing evidence supports the assertion that alterations of tau can directly cause neuronal degeneration. In addition, it is unclear whether neurodegeneration in various tauopathies occurs via a common mechanism or that specific differences exist. The aim of this review is to provide an overview of tauopathies from bench to bedside. The review begins with clinicopathological findings of familial and sporadic tauopathies. It includes a discussion of the similarities and differences between these two conditions. The second part concentrates on biochemical alterations of tau such as phosphorylation, truncation and acetylation. Although pathological phosphorylation of tau has been studied for many years, recently researchers have focused on the physiological role of tau during development. Finally, the review contains a summary of the significance of tauopathy model mice for research on neurofibrillary tangles, axonopathies, and synaptic alteration.

New genes, new dilemmas: FTLD genetics and its implications for families

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.

Prominent phenotypic variability associated with mutations in Progranulin

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.