Phosphorylated TDP-43 Staging of Primary Age-Related Tauopathy

Primary age-related tauopathy(PART) is characterized by tau neurofibrillary tangles(NFTs) in the absence of amyloid plaque pathology. In the present study,we analyzed the distribution patterns of phosphorylated43-kDa TAR DNA-binding protein(pTDP-43) in the brains of patients with PART. Immunohistochemistry and immunofluorescence double-labeling in multiple brain regions was performed on brain tissues from PART,Alzheimer's disease(AD), and aging control cases. We examined the regional distribution patterns of pTDP-43 intraneuronal inclusions in PART with Braak NFT stages[ 0 and B IV, and a Thal phase of 0(no beta-amyloid present). We found four stages which indicated potentially sequential dissemination of pTDP-43 in PART. Stage I was characterized by the presence of pTDP-43 lesions in the amygdala, stage II by such lesions in the hippocampus,stage III by spread of pTDP-43 to the neocortex, and stage IV by pTDP-43 lesions in the putamen, pallidum, and insular cortex. In general, the distribution pattern of pTDP-43 pathology in PART cases was similar to the early TDP-43 stages reported in AD, but tended to be more restricted to the limbic system. However, there were some differences in the distribution patterns of pTDP-43 between PART and AD, especially in the dentate gyrus of the hippocampus. Positive correlations were found in PART between the Braak NFT stage and the pTDP-43 stage and density.     

Amyotrophic lateral sclerosis with TDP-43 abnormalities exhibiting globular glial tau inclusions in frontotemporal lobes and pallido-nigral system

Here we present the autopsy case of an 80-year-old woman with a 9-year history of motor neuron disease and atypical Parkinsonism. Her initial symptom was gait disturbance, and she subsequently developed limb weakness and Parkinsonism without response to levodopa. Her motor symptoms progressed to bulbar palsy, and she died of respiratory failure. Postmortem examination revealed characteristic findings of amyotrophic lateral sclerosis (ALS), including motor neuronal loss with astrogliosis, corticospinal tract degeneration, and TAR DNA-binding protein of 43 kDa abnormalities, including nuclear loss and skein-like inclusions. In contrast, severe tau pathological changes were seen in the frontotemporal lobes and pallido-nigral system. Tau pathologies affected not only neuronal components, such as neurofibrillary tangles and neuropil threads, but also glial cells (astrocytes and oligodendrocytes). Some glial tau pathologies exhibited peculiar round accumulations, reminiscent of globular glial inclusions (GGIs) in globular glial tauopathy. This unique autopsy case demonstrates that ALS with TDP-43 could be comorbid with globular glial tau inclusions and indicates that common pathological mechanisms exist among ALS and GGI formation.     

Cellular tau pathology and immunohistochemical study of tau isoforms in sporadic tauopathies

Pathological inclusions in neurons and glial cells containing fibrillary aggregates of abnormally hyperphosphorylated tau protein are characteristic features in sporadic tauopathies. In the first part of this paper we outline the morphological features of some major sporadic tauopathies. In the second part, to better define the tau isoform composition, we report on the immunohistochemistry of tau isoforms in autopsied brains, including two cases with AD, two with diffuse neurofibrillary tangles with calcification, four with Pick’s disease with Pick bodies (PiD), seven with progressive supranuclear palsy (PSP), six with corticobasal degeneration (CBD) and seven cases with argyrophilic grain disease. We used two monoclonal antibodies, RD3 and RD4, and a polyclonal antibody for exon 10 that effectively distinguish between three‐repeat (3R) tau and four‐repeat (4R) tau. Neuronal neurofibrillary tangles (NFT) in AD and diffuse neurofibrillary tangles with calcification contained both 3R‐tau and 4R‐tau. The Pick bodies were immunopositive for 3R‐tau in two cases; however, in two other cases they were mainly immunopositive for 4R‐tau. Thus, Pick bodies demonstrated heterogeneity. 3R‐tau PiD contained 3R‐tau glial inclusions, and 4R‐tau PiD contained mainly 4R‐tau glial inclusions. Glial inclusions were more abundant in 4R‐tau PiD cases. In progressive supranuclear palsy and CBD, both neuronal and glial tau accumulation forming NFT, pretangles, tuft‐shaped astrocytes, astrocytic plaques, coiled bodies and threads demonstrated 4R‐tau in the cerebral cortices, although in the basal ganglia and brainstem neuronal and glial inclusions were occasionally immunopositive for 3R‐tau in addition to 4R‐tau. Argyrophilic grains (AG) were immunopositive for 4R‐tau, although pretangles were weakly stained for 4R‐tau. Thus the immunoreactivity for 4R‐tau was different between AG and pretangles. Therefore, the isoform composition on immunohistochemical study showed heterogeneity in PiD, and was not uniform in the basal ganglia and brain stem in PSP and CBD. It is suggested that the isoform composition of sporadic tauopathies may have a spectrum in individual cases, and cellular isoform composition may differ in various brain regions.     

Hirano bodies contain tau protein

Hirano bodies are intraneuronal inclusions whose frequency increases with age and Alzheimer's disease. These paracrystalline inclusions have been shown previously using immunocytochemistry to share epitopes with actin, tropomyosin, alpha-actinin and vinculin. Hirano bodies have not previously been demonstrated to share components with neurofibrillary tangles, another intraneuronal inclusion characteristic of Alzheimer's disease. In this study, we show that Hirano bodies bind antibodies to the microtubule-associated protein tau, a component of Alzheimer neurofibrillary tangles.     

Glial fibrillary tangles in diffuse neurofibrillary tangles with calcification

In the present study the occurrence and distribution of glial fibrillary tangles (GFT) and their related structures in diffuse neurofibrillary tangles with calcification (DNTC) were investigated using Gallyas-Braak (GB) stain. Six cases neuropathologically diagnosed as DNTC were studied (two males and four females). The age at death ranged from 56 to 73 years, with an average of 63.5+/-7.5 years. GFT were classified morphologically, and their immunoreactivites for tau and ubiquitin were examined. Glial cells with GFT were identified with astrocytes and oligodendrocytes by immunostain for glial fibrillary acidic protein and transferrin, respectively. A small number of coiled bodies detected within the oligodendrocytes in the white matter of the cerebrum were positive for tau and ubiquitin. Cell clusters of thorn-shaped astrocytes were detected in the subcortical and subpial regions where gliosis occurred. Thorn-shaped astrocytes were positive for tau, but negative for ubiquitin. A small number of tuft-shaped astrocytes detected prominently in the temporal cortex and amygdala with numerous neurofibrillary tangles were positive for tau and ubiquitin. All three types of GFT were detected, especially in the temporal and limbic lobes, which were the most severely affected sites in DNTC. Moreover, various-shaped neurofibrillary tangles, aggregated rods and some argyrophilic threads were differentiated from GFT. They were positive for GB, but not detected within the glial cells.     

Argyrophilic grain disease: A late‐onset dementia with distinctive features among tauopathies

Argyrophilic grain disease (AgD) is a late‐onset dementia morphologically characterized by the presence of abundant spindle‐shaped argyrophilic grains (ArG) in neuronal processes and coiled bodies in oligodendrocytes. AgD changes consist of the microtubule‐associated protein tau in an abnormally and hyperphosphorylated state and are mainly found in limbic regions, for example, in the hippocampus, the entorhinal and transentorhinal cortices and the amygdala. AgD shows a significant correlation with advancing age, and it became apparent from recent clinicopathological studies that it might account for approximately 5% of all dementia cases. Further immunohistochemical and biochemical studies revealed that AgD is a four‐repeat (4R) tauopathy similar to PSP and corticobasal degeneration (CBD), but distinct from Alzheimer's disease (AD) and Pick's disease. Moreover, a common genetic background regarding the tau gene haplotype has been suggested for AgD, PSP and CBD. However, although there are currently only limited data available, AgD seems to be clinically distinct from PSP and CBD and shares rather features of (mild) AD or other forms of ‘limbic’ dementias, among them senile dementia with tangles and the localized form of AD.     

Accelerated extinction of conditioned taste aversion in P301L tau transgenic mice

Neurofibrillary tangles, insoluble protein deposits composed of filamentous tau aggregates, are neuropathological hallmarks of Alzheimer's disease and familial frontotemporal dementia (FTDP-17). Transgenic mice expressing the FTDP-17 mutation P301L of tau recapitulate key features of the human pathology, that is, tau proteins aggregate and neurofibrillary tangles begin to appear in the amygdala at 6 months of age. To detect early signs of tau aggregate-associated changes, we investigated behavioral alterations and cognitive deficits in such mice using an amygdala-specific test battery for anxiety-related and cognitive behavior. P301L mice had anxiety levels not different from wild-types, but their exploratory behavior was significantly increased. Acquisition of a fear response to tone and context as well as taste aversion was comparable to wild-types. However, extinction of a conditioned taste aversion was significantly accelerated. We conclude that already aggregation of tau proteins not yet accompanied by massive formation of neurofibrillary tangles causes selective behavioral deficits.     

A neuropathologic study of long-term, Economo-type postencephalitic parkinsonism with a prolonged clinical course

Abstract In this report, the neuropathologic features of five autopsied cases of postencephalitic parkinsonism of the Economo-type (PEPE) with a mean age of 66.6 years and a mean duration of the illness of 53.6 years are described. All five patients had presented with personality changes and severe parkinsonism. In addition, four patients had also had ocular symptoms. A pronounced chronic progression of the symptoms characterized all five cases. Active degenerating lesions were found in the substantia nigra (patients 3, 4 and 5) and the oculomotor nucleus (patient 5) which might explain the clinical observation of chronic active disease in these patients. We found that the intraneuronal neurofibrillary tangles (NFT) were immunoreactive to paired helical filaments (PHF), tau and ubiquitin; but ghost tangles demonstrated immunoreactivity only to glial fibrillary acid protein (GFAP). The ghost tangles consisted of dispersed bundles of abnormal tubules, and electron-dense glial filaments would surround and occasionally invade the ghost tangles. The present study suggests that NFT in PEPE are similar in their immunohistochemistry and ultrastructure to those observed in the case of Alzheimer-type dementia.     

Ultrastructural characteristics of tau filaments in tauopathies: Immuno‐electron microscopic demonstration of tau filaments in tauopathies

The microtubule‐associated protein tau aggregates into filaments in the form of neurofibrillary tangles, neuropil threads and argyrophilic grains in neurons, in the form of variable astrocytic tangles in astrocytes and in the form of coiled bodies and argyrophilic threads in oligodendrocytes. These tau filaments may be classified into two types, straight filaments or tubules with 9–18 nm diameters and “twisted ribbons” composed of two parallel aligned components. In the same disease, the fine structure of tau filaments in glial cells roughly resembles that in neurons. In sporadic tauopathies, individual tau filaments show characteristic sizes, shapes and arrangements, and therefore contribute to neuropathologic differential diagnosis. In frontotemporal dementias caused by tau gene mutations, variable filamentous profiles were observed in association with mutation sites and insoluble tau isoforms, including straight filaments or tubules, paired helical filament‐like filaments, and twisted ribbons. Pre‐embedding immunoelectron microscopic studies were carried out using anti‐3‐repeat tau and anti‐4‐repeat tau specific antibodies, RD3 and RD4. Straight tubules in neuronal and astrocytic Pick bodies were immunolabeled by the anti‐3‐repeat tau antibody. The anti‐4‐repeat tau antibody recognized abnormal tubules comprising neurofibrillary tangles, coiled bodies and argyrophilic threads in progressive supranuclear palsy (PSP) and corticobasal degeneration. In the pre‐embedding immunoelectron microscopic study using the phosphorylated tau AT8 antibody, tuft‐shaped astrocytes of PSP were found to be composed of bundles of abnormal tubules in processes and perikarya of protoplasmic astrocytes. In this study, the 3‐repeat tau or 4‐repeat tau epitope was detected in situ at the ultrastructural level in abnormal tubules in representative pathological lesions in Pick’s disease, PSP and corticobasal degeneration.     

Hypersialylation is a common feature of neurofibrillary tangles and granulovacuolar degenerations in Alzheimer's disease and tauopathy brains

Glycosylation is one of the major post‐translational modifications of proteins. The status of sialylation of the neuropathological hallmarks of various neurodegenerative disorders was investigated in this study. Here, we report the novel findings that two phosphorylated tau (p‐tau)‐containing structures associated with Alzheimer's disease (AD), that is, neurofibrillary tangles (NFTs) and granulovacuolar degenerations (GVDs), were hypersialylated. The NFTs, GVDs and dystrophic neurites of senile plaques (SPs) in AD hippocampi were clearly visualized by immunohistochemistry using an anti‐sialic acid (SA) antibody. In contrast, the amyloid core of SPs was not sialylated at all. Interestingly, other p‐tau‐containing structures, that is, globose‐type NFTs in progressive supranuclear palsy and Pick bodies and ballooned neurons in frontotemporal lobar degeneration with Pick bodies, were also hypersialylated. Unlike the p‐tau‐containing structures observed in tauopathies, the hallmarks of other neurodegenerative disorders, such as Lewy bodies in Parkinson's disease, glial cytoplasmic inclusions in multiple system atrophy, Bunina bodies, skein‐like inclusions and round inclusions in amyotrophic lateral sclerosis, intranuclear inclusions in neuronal intranuclear inclusion disease and physiological bodies or granules (lipofuscin granules, corpora amylacea and melanin granules), were not immunolabeled by the anti‐SA antibody. Because this antibody specifically identified NFTs and GVDs, immunostaining for sialylation represents a useful tool to screen these structures in a diagnostic setting. These results clearly indicate that the pathological hallmarks of various tauopathies are commonly hypersialylated, and that sialylation plays an important role in the process of p‐tau accumulation in AD and other tauopathies.     

Cognitive decline associated with pathological burden in primary age-related tauopathy

Introduction

Primary age-related tauopathy (PART) is a neuropathological diagnosis characterized by tau neurofibrillary tangles (NFTs) in the absence of amyloid plaque pathology. Although most individuals over 50 years of age have evidence of NFTs, the clinical and cognitive consequences of PART are not known.

Diffuse Lewy body disease with dementia and oculomotor dysfunction

The case is presented of an elderly patient who had dementia, axial rigidity, and bradykinesia with limitation of horizontal and vertical gaze. Pathological examination disclosed Lewy and Lewy-like bodies in the substantia nigra, locus ceruleus, and neocortex, leading to a final diagnosis of diffuse Lewy body disease. Similar inclusions were found in areas of the pons and midbrain believed to be associated with gaze control. Moderate numbers of neuritic plaques, but no neurofibrillary tangles, were present in limbic cortex and neocortex. Review of the literature has not shown previous association of diffuse Lewy body disease with both horizontal and vertical gaze anomalies.     

Increased neocortical neurofibrillary tangle density in subjects with Alzheimer disease and psychosis

BACKGROUND: Psychosis is common in patients with Alzheimer disease. While the relationship between psychosis and clinical variables has been examined frequently, few studies have examined the relationship between psychosis and the 2 major neuropathological hallmarks of Alzheimer disease: neurofibrillary tangles and senile plaques. We characterized the occurrence of psychosis in relation to dementia severity and determined if subjects with Alzheimer disease and psychosis had a greater neurofibrillary tangle or senile plaque burden than subjects with Alzheimer disease and no psychosis. METHODS: One hundred nine subjects with Alzheimer disease were followed longitudinally with semistructured assessments in order to assign a Clinical Dementia Rating and determine whether psychosis was present. After the subjects died, their brains were obtained for histological examination. Analysis of variance was used to compare the densities of neurofibrillary tangles, total senile plaques, and cored senile plaques in subjects with psychosis vs subjects without psychosis, in several neocortical regions, the hippocampus, and the entorhinal cortex. RESULTS: Psychosis occurred commonly in Alzheimer disease, affecting 63% of subjects. The frequency of psychosis increased with increasing dementia severity. More importantly, we found that subjects with psychosis had a 2.3-fold (95% confidence interval, 1.2-3.9) greater density of neocortical neurofibrillary tangles than did subjects without psychosis. The increase was independent of dementia severity. No similar relationship with psychosis was seen for total senile plaques or cored senile plaques. CONCLUSIONS: The increase in psychosis frequency that occurs with the progression of dementia severity and the independent association between psychosis and neurofibrillary tangle density suggest the possibility that some common underlying process or processes specific to Alzheimer disease may regulate both phenomena. Arch Gen Psychiatry. 2000;57:1165-1173.     

Tau and alpha-synuclein inclusions in a case of familial frontotemporal dementia and progressive aphasia

Recent studies have shown that neurofibrillary tangles are frequently accompanied by alpha-synuclein inclusions in sporadic and familial Alzheimer disease, in Down syndrome, in progressive supranuclear palsy, and Parkinsonism dementia complex of Guam. Here we report the cases of 2 brothers with familial progressive aphasia who developed features of frontotemporal dementia with predominant tau pathology but also alpha-synuclein pathology. The 2 patients' brains revealed abundant tau pathology in the hippocampus and basal ganglia, whereas tau and alpha-synuclein aggregates coexisted only in the nucleus basalis of Meynert, the only region where alpha-synuclein was present. In this brain region, abundant Lewy bodies, Lewy neurites, and tau inclusions were found; the pathology was more abundant in the older than in the younger brother. Sarkosyl-insoluble tau extracted from brains of the 2 patients showed the presence of tau filaments that contained 3 major tau bands of 60, 64, and 68 kDa on Western blot analysis. These bands contained mainly tau with 3 and 4 repeats and no amino-terminal inserts and tau with 4 repeats and one amino-terminal insert. No mutations were identified in the tau, alpha-synuclein, beta-synuclein, or parkin genes. We think that this is the first report showing a specific colocalization of neurofibrillary tangles and Lewy bodies in a family with progressive aphasia.     

Invited review: Prion‐like transmission and spreading of tau pathology

Filaments made of hyperphosphorylated tau protein are encountered in a number of neurodegenerative diseases referred to as ‘tauopathies’. In the most prevalent tauopathy, Alzheimer's disease, tau pathology progresses in a stereotypical manner with the first lesions appearing in the locus coeruleus and the entorhinal cortex from where they appear to spread to the hippocampus and neocortex. Propagation of tau pathology is also characteristic of argyrophilic grain disease, where the tau lesions appear to spread throughout distinct regions of the limbic system. These findings strongly implicate neurone‐to‐neurone propagation of tau aggregates. Isoform composition and morphology of tau filaments can differ between tauopathies suggesting the existence of conformationally diverse tau strains. Altogether, this points to prion‐like mechanisms in the pathogenesis of tauopathies.     

Hyperphosphorylated tau is a cause of neuronal dysfunction in tauopathy

Pathological studies show that neurofibrillary tangles are found in regions where neuronal death occurs. This observation raises the question: Are neurofibrillary tangles toxic or protective? Findings from various mouse models expressing human tau with the FTDP17 mutation suggest that some component involved in the formation of neurofibrillary tangles, rather than the neurofibrillary tangles themselves, might be responsible for the toxicity leading to neuronal death. Here, I review our current understanding of a toxic species of tau and the mechanism by which it contributes to neuronal dysfunction and death. Recent studies suggest that, before forming fibrils but after becoming hyperphosphorylated, tau is involved in neurodegenerative disease.     

Pathological tau tangles localize to focal cortical dysplasia in older patients

PURPOSE: Reactivation of neurodevelopmental processes may contribute to neurodegeneration. For example, the proteins cyclin dependent kinase 5 (cdk5) and glycogen synthase kinase 3 beta (GSK3beta), which are essential to normal cortical development, can hyperphosphorylate tau and might contribute to the pathogenesis of Alzheimer's disease. Focal cortical dysplasia (FCD) is an important neurodevelopmental cause of refractory human epilepsy within which dysplastic neurons exhibit increased immunoreactivity for cdk5 and GSK3beta as well as neurofilamentous accumulations. We therefore hypothesized that the developmentally abnormal cortex of FCD might be more susceptible to tau-mediated neurodegeneration than adjacent histologically normal cortex. MATERIALS AND METHODS: We examined a series of 15 cases of FCD, spanning a wide age range, for beta-amyloid, pathologically phosphorylated tau and neurofibrillary tangles using silver staining, immunohistochemistry for tau, AT8, RD3, RD4 and two-dimensional cell counting. RESULTS: Beta-amyloid plaques, aberrantly phosphorylated tau and neurofibrillary tangles are only found in older patients. The hyperphosphorylated tau tangles are confined to dysplastic neurons. Immunoreactivity for 3- and 4-repeat tau was again only detected within regions of FCD in older patients. With increasing age, the dysplastic cortex became hypocellular and a higher proportion of dysplastic neurons exhibited pathological tau phosphorylation. CONCLUSIONS: In older patients, FCD appears more susceptible to formation of pathologically phosphorylated tau neurofibrillary tangles than adjacent histologically normal cortex. Our results suggest a novel convergence of pathological neurodevelopment with pathological age-related neurodegeneration.     

Chameleons and mimics: Progressive supranuclear palsy and corticobasal degeneration

Progressive supranuclear palsy (PSP) and corticobasal degeneration (CBD) are neurodegenerative disorders that show parkinsonism as their main symptom. Both PSP and CBD are sporadic tauopathies associated with hyperphosphorylated four-repeat tau aggregation in neurons and glial cells. The characteristic pathologies of PSP are midbrain atrophy and the appearance of tufted astrocytes and globose-type neurofibrillary tangles. PSP shows severe degeneration in the globus pallidus, substantia nigra, subthalamic nucleus, and cerebellar dentate nuclei. Conversely, the characteristic pathologies of CBD are cortical atrophy and the appearance of astrocytic plaques and argyrophilic threads. CBD is associated with severe degeneration in the cerebral white matter, substantia nigra, and globus pallidus. Clinical symptoms depend on the topographical distribution and severity of degeneration rather than on the type of aggregated protein or inclusions. PSP and CBD present clinically differential diagnostic difficulties because of their overlapping pathological distributions.     

An autopsy case of dementia with motor neuron disease accompanying Alzheimer's disease lesion]

We report the case of a 60-year-old man with autopsy-proven dementia with motor neuron disease (D-MND) and Alzheimer's disease lesion. The patient presented with clumsiness of his right hand at the age of 55 years old and subsequently developed dysarthria, weakness and atrophy of his upper limbs. He was unaffectionate towards his family, repeated the same phrase, and showed severe disorientation of time and place. Neurological examination on admission showed not only diffuse lower motor neuron signs, such as weakness, atrophy, fasciculation and areflexia in both upper limbs, but also dementia (HDS-R 9/30). He died of respiratory insufficiency. Neuropathological examination showed mild atrophy of the frontal and temporal lobes and anterior spinal roots. Microscopic examination of cortical sections revealed degenerative changes with simple atrophy and gliosis, and these changes were predominant in layers 1 and 2 of the frontal and temporal cortices. Using immunohistochemical staining, ubiquitin-positive but tau-negative inclusions were frequently found in neurons of the hippocampal granular cell layers and temporal lobes. Many senile plaques and neurofibrillary tangles were present in all sections of the brain. Our final diagnosis was dementia with motor neuron disease accompanying Alzheimer's disease lesion, because of hypoperfusion in the parietal lobe as well as the frontal lobe demonstrated by SPECT, and the presence of many senile plaques and neurofibrillary tangles in the cerebral cortex. Overlapping of pathologically-proven D-MND and Alzheimer's disease lesion is extremely rare, and this case may improve our understanding of the process of neurodegeneration.