Neurofilament inclusion body disease: a new proteinopathy?

Diffuse argyrophilic grain disease with TDP-43 proteinopathy and neuronal intermediate filament inclusion disease: FTLD with mixed tau, TDP-43 and FUS pathologies

Frontotemporal lobar degeneration (FTLD) is a group of disorders characterized by degeneration of the frontal and temporal lobes, leading to progressive decline in language, behavior, and motor function. FTLD can be further subdivided into three main subtypes, FTLD-tau, FTLD-TDP and FTLD-FUS based which of the three major proteins - tau, TDP-43 or FUS - forms pathological inclusions in neurons and glia. In this report, we describe an 87-year-old woman with a 7-year history of cognitive decline, hand tremor and gait problems, who was thought to have Alzheimer's disease. At autopsy, histopathological analysis revealed severe neuronal loss, gliosis and spongiosis in the medial temporal lobe, orbitofrontal cortex, cingulate gyrus, amygdala, basal forebrain, nucleus accumbens, caudate nucleus and anteromedial thalamus. Tau immunohistochemistry showed numerous argyrophilic grains, pretangles, thorn-shaped astrocytes, and ballooned neurons in the amygdala, hippocampus, parahippocampal gyrus, anteromedial thalamus, insular cortex, superior temporal gyrus and cingulate gyrus, consistent with diffuse argyrophilic grain disease (AGD). TDP-43 pathology in the form of small, dense, rounded neuronal cytoplasmic inclusion with few short dystrophic neurites was observed in the limbic regions, superior temporal gyrus, striatum and midbrain. No neuronal intranuclear inclusion was observed. Additionally, FUS-positive inclusions were observed in the dentate gyrus. Compact, eosinophilic intranuclear inclusions, so-called "cherry spots," that were visible on histologic stains were immunopositive for α-internexin. Taken together, the patient had a mixed neurodegenerative disease with features of diffuse AGD, TDP-43 proteinopathy and neuronal intermediate filament inclusion disease. She met criteria for three subtypes of FTLD: FTLD-tau, FTLD-TDP and FTLD-FUS. Her amnestic symptoms that were suggestive of Alzheimer's type dementia are best explained by diffuse AGD and medial temporal TDP-43 proteinopathy, and her motor symptoms were likely explained by neuronal loss and gliosis due to tau pathology in the substantia nigra. This case underscores the importance of considering multiple proteinopathies in the diagnosis of neurodegenerative diseases.

Neuropathology and emerging biomarkers in corticobasal syndrome

Corticobasal syndrome (CBS) is a clinical syndrome characterised by progressive asymmetric limb rigidity and apraxia with dystonia, myoclonus, cortical sensory loss and alien limb phenomenon. Corticobasal degeneration (CBD) is one of the most common underlying pathologies of CBS, but other disorders, such as progressive supranuclear palsy (PSP), Alzheimer's disease (AD) and frontotemporal lobar degeneration with TDP-43 inclusions, are also associated with this syndrome.In this review, we describe common and rare neuropathological findings in CBS, including tauopathies, synucleinopathies, TDP-43 proteinopathies, fused in sarcoma proteinopathy, prion disease (Creutzfeldt-Jakob disease) and cerebrovascular disease, based on a narrative review of the literature and clinicopathological studies from two brain banks. Genetic mutations associated with CBS, including GRN and MAPT, are also reviewed. Clinicopathological studies on neurodegenerative disorders associated with CBS have shown that regardless of the underlying pathology, frontoparietal, as well as motor and premotor pathology is associated with CBS. Clinical features that can predict the underlying pathology of CBS remain unclear. Using AD-related biomarkers (ie, amyloid and tau positron emission tomography (PET) and fluid biomarkers), CBS caused by AD often can be differentiated from other causes of CBS. Tau PET may help distinguish AD from other tauopathies and non-tauopathies, but it remains challenging to differentiate non-AD tauopathies, especially PSP and CBD. Although the current clinical diagnostic criteria for CBS have suboptimal sensitivity and specificity, emerging biomarkers hold promise for future improvements in the diagnosis of underlying pathology in patients with CBS.

An autopsy case report of neuronal intermediate filament inclusion disease presenting with predominantly upper motor neuron features

We describe an autopsy case of neuronal intermediate filament inclusion disease (NIFID), a subtype of frontotemporal lobar degeneration (FTLD) with the appearance of fused-in-sarcoma (FUS) inclusions (FTLD-FUS). A 57-year-old man developed dysarthria and dysphagia. One year and five months later, he was admitted to a hospital, and pseudobulbar palsy and right upper motor neuron signs were observed on examination. Needle electromyography revealed no active or chronic denervation. His neurological symptoms gradually deteriorated, and behavioral alterations occurred. He died of hemoperitoneum secondary to rupture of a ureteric tumor. The total duration of the disease was six years and 10 months. Neuropathologically, the frontal cortex, including the motor cortex, and the pyramidal tract were severely affected, whereas the lower motor neurons in the spinal cord and brainstem were mildly damaged. The striatum and substantia nigra were also severely damaged. Hyaline conglomerate inclusions, neuronal cytoplasmic inclusions with a distinct eosinophilic core (so-called cherry spot), Pick body-like inclusions, and eosinophilic round inclusions were observed in the remaining neurons. Immunohistochemical examination revealed that these inclusions were immunoreactive for FUS. HC inclusions were also immunoreactive for α-internexin and phosphorylated neurofilament protein. FUS-immunoreactive NCIs were abundant in the basal ganglia but not in the hippocampus, in contrast to previously reported NIFID cases. Furthermore, Bunina bodies identified by immunohistochemistry for cystatin C were also observed in the lower motor neurons. Bunina bodies may be present in NIFID. This case confirms the pathological heterogeneity of NIFID and supports the notion of the difference between amyotrophic lateral sclerosis and NIFID.

Clinical Phenotypes in Corticobasal Syndrome with or without Amyloidosis Biomarkers

Corticobasal syndrome (CBS) is a neuropathologically heterogeneous entity. The use of cerebrospinal fluid and amyloid biomarkers enables detection of underlying Alzheimer's disease (AD) pathology. We thus compared clinical, eye movement, and 18FDG-PET imaging characteristics in CBS in two groups of patients divided according to their amyloid biomarkers profile. Fourteen patients presenting with CBS and amyloidosis (CBS-A+) were compared with 16 CBS patients without amyloidosis (CBS-A-). The two groups showed similar motor abnormalities (parkinsonism, dystonia) and global cognitive functions. Unlike CBS-A+ patients who displayed more posterior cortical abnormalities, CBS-A- patients demonstrated more anterior cortical and brain stem dysfunctions on the basis of neuropsychological testing, study of saccade velocities and brain hypometabolism areas on 18FDG-PET. Interestingly, Dopamine Transporter SPECT imaging showed similar levels of dopaminergic degeneration in both groups. These findings confirm common and distinct brain abnormalities between the different neurodegenerative diseases that result in CBS. We demonstrate the importance of a multidisciplinary approach to improve diagnosis in vivo in particular on oculomotor examination.

Neuronal intermediate filament inclusion disease may be incorrectly classified as a subtype of FTLD-FUS

Background

The majority of cases of frontotemporal lobar degeneration (FTLD) are characterized by focal cortical atrophy with an underlying tau or TDP-43 proteinopathy. A subset of FTLD cases, however, lack tau and TDP-43 immuno-reactivity, but have neuronal inclusions positive for ubiquitin, referred to as atypical FTLD (aFTLD-U). Studies have demonstrated that ubiquitin-positive inclusions in aFTLD-U are immuno-reactive for fused in sarcoma (FUS). As such, the current nosology for this entity is FTLD-FUS, which is thought to include not only aFTLD-U, but also neuronal intermediate filament inclusion disease (NIFID) and basophilic inclusion body disease.

Objective

To compare pathological features of cases of aFTLD-U and NIFID.

Methods

We reviewed the neuropathology of 15 patients (10 males and 5 females; average age at death 54 years (range 41-69 years)) with an antemortem clinical diagnosis of a frontotemporal dementia and pathological diagnosis of aFTLD-U (n=8) or NIFID (n=7). Sections were processed for immunohistochemistry and immunoelectron microscopy with FUS, TDP-43, and α-internexin (αINX) antibodies.

Results

Eight cases had pathologic features consistent with FTLD-FUS, with severe striatal atrophy (7/8 cases), as well as FUS-positive neuronal cytoplasmic and vermiform intranuclear inclusions, but no αINX immuno-reactivity. Five cases had features consistent with NIFID, with neuronal inclusions positive for both FUS and αINX. Striatal atrophy was present in only 2 of the NIFID cases. Two cases had αINX-positive neuronal inclusions consistent with NIFID, but both lacked striatal atrophy and FUS immunoreactivity. Surprisingly, one of these two NIFID cases had lesions immunoreactive for TDP-43.

Discussion

While FUS pathology remains a prominent feature of aFTLD-U, there is pathologic heterogeneity, including rare cases of NIFID with TDP-43- rather than FUS-positive inclusions.

FTD spectrum: Neuroimaging across the FTD spectrum

Frontotemporal dementia is a complex and heterogeneous neurodegenerative disease that encompasses many clinical syndromes, pathological diseases, and genetic mutations. Neuroimaging has played a critical role in our understanding of the underlying pathophysiology of frontotemporal dementia and provided biomarkers to aid diagnosis. Early studies defined patterns of neurodegeneration and hypometabolism associated with the clinical, pathological and genetic aspects of frontotemporal dementia, with more recent studies highlighting how the breakdown of structural and functional brain networks define frontotemporal dementia. Molecular positron emission tomography ligands allowing the in vivo imaging of tau proteins have also provided important insights, although more work is needed to understand the biology of the currently available ligands.

Prion-like transmission of α-synuclein pathology in the context of an NFL null background

Neurofilaments are a major component of the axonal cytoskeleton in neurons and have been implicated in a number of neurodegenerative diseases due to their presence within characteristic pathological inclusions. Their contributions to these diseases are not yet fully understood, but previous studies investigated the effects of ablating the obligate subunit of neurofilaments, low molecular mass neurofilament subunit (NFL), on disease phenotypes in transgenic mouse models of Alzheimer's disease and tauopathy. Here, we tested the effects of ablating NFL in α-synuclein M83 transgenic mice expressing the human pathogenic A53T mutation, by breeding them onto an NFL null background. The induction and spread of α-synuclein inclusion pathology was triggered by the injection of preformed α-synuclein fibrils into the gastrocnemius muscle or hippocampus in M83 versus M83/NFL null mice. We observed no difference in the post-injection time to motor-impairment and paralysis endpoint or amount and distribution of α-synuclein inclusion pathology in the muscle injected M83 and M83/NFL null mice. Hippocampal injected M83/NFL null mice displayed subtle region-specific differences in the amount of α-synuclein inclusions however, pathology was observed in the same regions as the M83 mice. Overall, we observed only minor differences in the induction and transmission of α-synuclein pathology in these induced models of synucleinopathy in the presence or absence of NFL. This suggests that NFL and neurofilaments do not play a major role in influencing the induction and transmission of α-synuclein aggregation.

Diagnostic and Prognostic Biomarkers in Amyotrophic Lateral Sclerosis: Neurofilament Light Chain Levels in Definite Subtypes of Disease

Importance

A clearer definition of the role of neurofilament light chain (NFL) as a biomarker in amyotrophic lateral sclerosis (ALS) is needed.

Objectives

To assess the ability of NFL to serve as a diagnostic biomarker in ALS and the prognostic value of cerebrospinal fluid NFL in patients with ALS.

Design, Setting, and Participants

In this single-center, retrospective, longitudinal study, disease progression was assessed by the ALS Functional Rating Score-Revised and the ALS Milano-Torino Staging system at baseline and 6, 12, 24, and 36 months. Cerebrospinal fluid samples were obtained from 176 patients admitted to the Department of Neurosciences of the University of Padua, Padova, Italy, from January 1, 2010, through February 29, 2016. Patients with ALS underwent ambulatory follow-up at the same department.

Main Outcomes and Measures

Levels of NFL.

Results

The study included 94 patients with ALS (64 men [36.4%] and 30 women [17.0%]; median age, 62.5 years), 20 patients with frontotemporal dementia (FTD) (8 men [4.5%] and 12 women [6.8%]; median age, 65 years), 18 patients with motor neuropathies (14 men [8.0%] and 4 women [2.3%]; median age, 63 years), and 44 controls (24 men [13.6%] and 20 women [11.4%]; median age, 54 years). Log-transformed NFL (log[NFL]) concentrations were higher in the ALS and FTD groups compared with the motor neuropathies and control groups (hazard ratio [HR], 2.45; 95% CI, 1.66-3.61; P < .001). Patients with typical ALS (HR, 1.0 [reference]), progressive bulbar palsy (HR, 1.48; 95% CI, 0.58-3.75; P = .41), and upper motor neuron dominant ALS (HR, 0.12; 95% CI, 0.02-0.61; P = .01) had higher levels of NFL than did those with flail arm or leg syndrome (HR, 0.28; 95% CI, 0.08-0.10; P = .049) and progressive muscular atrophy (HR, 0.17; 95% CI, 0.22-1.36; P = .10). There was an inverse correlation between log[NFL] concentration and overall survival (HR, 2.45; 95% CI, 1.66-3.61; P < .001). There was no evidence of different log[NFL] concentrations and survival in genetic ALS.

Conclusions and Relevance

This study confirms the role of NFL as a biomarker in ALS. Elevation in NFL levels in patients with upper motor neuron involvement and FTD might reflect the corticospinal tract degeneration. Low NFL levels in patients with lower motor neuron signs might be a prognostic indicator of milder phenotypes of disease.

Frontotemporal lobar degeneration: Pathogenesis, pathology and pathways to phenotype

Frontotemporal Lobar Degeneration (FTLD) is a clinically, pathologically and genetically heterogeneous group of disorders that affect principally the frontal and temporal lobes of the brain. There are three major associated clinical syndromes, behavioral variant frontotemporal dementia (bvFTD), semantic dementia (SD) and progressive non-fluent aphasia (PNFA); three principal histologies, involving tau, TDP-43 and FUS proteins; and mutations in three major genes, MAPT, GRN and C9orf72, along with several other less common gene mutations. All three clinical syndromes can exist separately or in combination with Amyotrophic Lateral Sclerosis (ALS). SD is exclusively a TDP-43 proteinopathy, and PNFA may be so, with both showing tight clinical, histological and genetic inter-relationships. bvFTD is more of a challenge with overlapping histological and genetic features, involvement of any of the three aggregating proteins, and changes in any of the three major genes. However, when ALS is present, all cases show a clear histological phenotype with TDP-43 aggregated proteins, and familial forms are associated with expansions in C9orf72. TDP-43 and FUS are nuclear carrier proteins involved in the regulation of RNA metabolism, whereas tau protein - the product of MAPT - is responsible for the assembly/disassembly of microtubules, which are vital for intracellular transport. Mutations in TDP-43 and FUS genes are linked to clinical ALS rather than FTLD (with or without ALS), suggesting that clinical ALS may be a disorder of RNA metabolism. Conversely, the protein products of GRN and C9orf72, along with those of the other minor genes, appear to form part of the cellular protein degradation machinery. It is possible therefore that FTLD is a reflection of dysfunction within lysosomal/proteasomal systems resulting in failure to remove potentially neurotoxic (TDP-43 and tau) aggregates, which ultimately overwhelm capacity to function. Spread of aggregates along distinct pathways may account for the different clinical phenotypes, and patterns of progression of disease.

Specialized roles of neurofilament proteins in synapses: Relevance to neuropsychiatric disorders

Neurofilaments are uniquely complex among classes of intermediate filaments in being composed of four subunits (NFL, NFM, NFH and alpha-internexin in the CNS) that differ in structure, regulation, and function. Although neurofilaments have been traditionally viewed as axonal structural components, recent evidence has revealed that distinctive assemblies of neurofilament subunits are integral components of synapses, especially at postsynaptic sites. Within the synaptic compartment, the individual subunits differentially modulate neurotransmission and behavior through interactions with specific neurotransmitter receptors. These newly uncovered functions suggest that alterations of neurofilament proteins not only underlie axonopathy in various neurological disorders but also may play vital roles in cognition and neuropsychiatric diseases. Here, we review evidence that synaptic neurofilament proteins are a sizable population in the CNS and we advance the concept that changes in the levels or post-translational modification of individual NF subunits contribute to synaptic and behavioral dysfunction in certain neuropsychiatric conditions.

Novel antibodies to phosphorylated α-synuclein serine 129 and NFL serine 473 demonstrate the close molecular homology of these epitopes

Pathological inclusions containing aggregated, highly phosphorylated (at serine129) α-synuclein (αS pSer129) are characteristic of a group of neurodegenerative diseases termed synucleinopathies. Antibodies to the pSer129 epitope can be highly sensitive in detecting αS inclusions in human tissue and experimental models of synucleinopathies. However, the generation of extensively specific pSer129 antibodies has been problematic, in some cases leading to the misinterpretation of αS inclusion pathology. One common issue is cross-reactivity to the low molecular mass neurofilament subunit (NFL) phosphorylated at Ser473. Here, we generated a series of monoclonal antibodies to the pSer129 αS and pSer473 NFL epitopes. We determined the relative abilities of the known αS kinases, polo-like kinases (PLK) 1, 2 and 3 and casein kinase (CK) II in phosphorylating NFL and αS, while using this information to characterize the specificity of the new antibodies. NFL can be phosphorylated by PLK1, 2 and 3 at Ser473; however CKII shows the highest phosphorylation efficiency and specificity for this site. Conversely, PLK3 is the most efficient kinase at phosphorylating αS at Ser129, but there is overlay in the ability of these kinases to phosphorylate both epitopes. Antibody 4F8, generated to the pSer473 NFL epitope, was relatively specific for phosphorylated NFL, however it could uniquely cross-react with pSer129 αS when highly phosphorylated, further showing the structural similarity between these phospho-epitopes. All of the new pSer129 antibodies detected pathological αS inclusions in human brains and mouse and cultured cell experimental models of induced synucleinopathies. Several of these pSer129 αS antibodies reacted with the pSer473 NFL epitope, but 2 clones (LS3-2C2 and LS4-2G12) did not. However, LS3-2C2 demonstrated cross-reactivity with other proteins. Our findings further demonstrate the difficulties in generating specific pSer129 αS antibodies, but highlights that the use of multiple antibodies, such as those generated here, can provide a sensitive and accurate assessment of αS pathology.

α-Internexin and Peripherin: Expression, Assembly, Functions, and Roles in Disease

α-Internexin and peripherin are neuronal-specific intermediate filament (IF) proteins. α-Internexin is a type IV IF protein like the neurofilament triplet proteins (NFTPs, which include neurofilament light chain, neurofilament medium chain, and neurofilament high chain) that are generally considered to be the primary components of the neuronal IFs. However, α-internexin is often expressed together with the NFTPs and has been proposed as the fourth subunit of the neurofilaments in the central nervous system. α-Internexin is also expressed earlier in the development than the NFTPs and is a maker for neuronal IF inclusion disease. α-Internexin can self-polymerize in vitro and in transfected cells and it is present in the absence of the NFTP in development and in granule cells in the cerebellum. In contrast, peripherin is a type III IF protein. Like α-internexin, peripherin is specific to the nervous system, but it is expressed predominantly in the peripheral nervous system (PNS). Peripherin can also self-assemble both in vitro and in transfected cells. It is as abundant as the NFTPs in the sciatic nerve and can be considered a fourth subunit of the neurofilaments in the PNS. Peripherin has multiple isoforms that arise from intron retention, cryptic intron receptor site or alternative translation initiation. The functional significance of these isoforms is not clear. Peripherin is a major component found in inclusions of patients with amyotrophic lateral sclerosis (ALS) and peripherin expression is upregulated in ALS patients.

Atypical parkinsonism: diagnosis and treatment

Atypical parkinsonism comprises typically progressive supranuclear palsy, corticobasal degeneration, and mutilple system atrophy, which are distinct pathologic entities; despite ongoing research, their cause and pathophysiology are still unknown, and there are no biomarkers or effective treatments available. The expanding phenotypic spectrum of these disorders as well as the expanding pathologic spectrum of their classic phenotypes makes the early differential diagnosis challenging for the clinician. Here, clinical features and investigations that may help to diagnose these conditions and the existing limited treatment options are discussed.

A truncating SOD1 mutation, p.Gly141X, is associated with clinical and pathologic heterogeneity, including frontotemporal lobar degeneration

Amyotrophic lateral sclerosis (ALS) is a degenerative disorder affecting upper and lower motor neurons, but it is increasingly recognized to affect other systems, with cognitive impairment resembling frontotemporal dementia (FTD) in some patients. We report clinical and pathologic findings of a family with ALS due to a truncating mutation, p.Gly141X, in copper/zinc superoxide dismutase (SOD1). The proband presented clinically with FTD and later showed progressive motor neuron disease, while all other family members had early-onset and rapidly progressive ALS without significant cognitive deficits. Pathologic examination of both the proband and her daughter revealed degeneration of corticospinal tracts and motor neurons in brain and spinal cord compatible with ALS. On the other hand, the proband also had neocortical and limbic system degeneration with pleomorphic neuronal cytoplasmic inclusions. Extramotor pathology in her daughter was relatively restricted to the hypothalamus and extrapyramidal system, but not the neocortex. The inclusions in the proband and her daughter were immunoreactive for SOD1, but negative for TAR DNA-binding protein of 43 kDa (TDP-43). In the proband, a number of the neocortical inclusions were immunopositive for α-internexin, initially suggesting a diagnosis of atypical FTLD, but there was no evidence of fused in sarcoma (FUS) immunoreactivity, which is often detected in atypical FTLD. Analogous to atypical FTLD, neuronal inclusions had variable co-localization of SOD1 and α-internexin. The current classification of FTLD is based on the major constituent protein: FTLD-tau, FTLD-TDP-43, and FTLD-FUS. The proband in this family indicates that SOD1, while rare, can also be the substrate of FTLD, in addition to the more common presentation of ALS. The explanation for clinical and pathologic heterogeneity of SOD1 mutations, including the p.Gly141X mutation, remains unresolved.

Corticobasal syndrome: Five new things

Corticobasal syndrome (CBS) is characterized by asymmetric involuntary movements including rigidity, tremor, dystonia, and myoclonus, and often associated with apraxia, cortical sensory deficits, and alien limb phenomena. Additionally, there are various nonmotor (cognitive and language) deficits. CBS is associated with several distinct histopathologies, including corticobasal degeneration, other forms of tau-related frontotemporal lobar degeneration such as progressive supranuclear palsy, and Alzheimer disease. Accurate antemortem diagnosis of underlying pathology in CBS is challenging, though certain clinical and imaging findings may be helpful. Five recent advances in the understanding of CBS are reviewed, including clinical and pathologic features, imaging and CSF biomarkers, the role of specific genes, and the concept of a spectrum of tauopathies.

Optic nerve crush induces spatial and temporal gene expression patterns in retina and optic nerve of BALB/cJ mice

Background

Central nervous system (CNS) trauma and neurodegenerative disorders trigger a cascade of cellular and molecular events resulting in neuronal apoptosis and regenerative failure. The pathogenic mechanisms and gene expression changes associated with these detrimental events can be effectively studied using a rodent optic nerve crush (ONC) model. The purpose of this study was to use a mouse ONC model to: (a) evaluate changes in retina and optic nerve (ON) gene expression, (b) identify neurodegenerative pathogenic pathways and (c) discover potential new therapeutic targets.

Results

Only 54% of total neurons survived in the ganglion cell layer (GCL) 28 days post crush. Using Bayesian Estimation of Temporal Regulation (BETR) gene expression analysis, we identified significantly altered expression of 1,723 and 2,110 genes in the retina and ON, respectively. Meta-analysis of altered gene expression (≥1.5, ≤-1.5, p < 0.05) using Partek and DAVID demonstrated 28 up and 20 down-regulated retinal gene clusters and 57 up and 41 down-regulated optic nerve clusters. Regulated gene clusters included regenerative change, synaptic plasticity, axonogenesis, neuron projection, and neuron differentiation. Expression of selected genes (Vsnl1, Syt1, Synpr and Nrn1) from retinal and ON neuronal clusters were quantitatively and qualitatively examined for their relation to axonal neurodegeneration by immunohistochemistry and qRT-PCR.

Conclusion

A number of detrimental gene expression changes occur that contribute to trauma-induced neurodegeneration after injury to ON axons. Nrn1 (synaptic plasticity gene), Synpr and Syt1 (synaptic vesicle fusion genes), and Vsnl1 (neuron differentiation associated gene) were a few of the potentially unique genes identified that were down-regulated spatially and temporally in our rodent ONC model. Bioinformatic meta-analysis identified significant tissue-specific and time-dependent gene clusters associated with regenerative changes, synaptic plasticity, axonogenesis, neuron projection, and neuron differentiation. These ONC induced neuronal loss and regenerative failure associated clusters can be extrapolated to changes occurring in other forms of CNS trauma or in clinical neurodegenerative pathological settings. In conclusion, this study identified potential therapeutic targets to address two key mechanisms of CNS trauma and neurodegeneration: neuronal loss and regenerative failure.

PRKAR1B mutation associated with a new neurodegenerative disorder with unique pathology

Pathological accumulation of intermediate filaments can be observed in neurodegenerative disorders, such as Alzheimer's disease, frontotemporal dementia and Parkinson's disease, and is also characteristic of neuronal intermediate filament inclusion disease. Intermediate filaments type IV include three neurofilament proteins (light, medium and heavy molecular weight neurofilament subunits) and α-internexin. The phosphorylation of intermediate filament proteins contributes to axonal growth, and is regulated by protein kinase A. Here we describe a family with a novel late-onset neurodegenerative disorder presenting with dementia and/or parkinsonism in 12 affected individuals. The disorder is characterized by a unique neuropathological phenotype displaying abundant neuronal inclusions by haematoxylin and eosin staining throughout the brain with immunoreactivity for intermediate filaments. Combining linkage analysis, exome sequencing and proteomics analysis, we identified a heterozygous c.149T>G (p.Leu50Arg) missense mutation in the gene encoding the protein kinase A type I-beta regulatory subunit (PRKAR1B). The pathogenicity of the mutation is supported by segregation in the family, absence in variant databases, and the specific accumulation of PRKAR1B in the inclusions in our cases associated with a specific biochemical pattern of PRKAR1B. Screening of PRKAR1B in 138 patients with Parkinson's disease and 56 patients with frontotemporal dementia did not identify additional novel pathogenic mutations. Our findings link a pathogenic PRKAR1B mutation to a novel hereditary neurodegenerative disorder and suggest an altered protein kinase A function through a reduced binding of the regulatory subunit to the A-kinase anchoring protein and the catalytic subunit of protein kinase A, which might result in subcellular dislocalization of the catalytic subunit and hyperphosphorylation of intermediate filaments.

Basophilic inclusions and neuronal intermediate filament inclusions in amyotrophic lateral sclerosis and frontotemporal lobar degeneration

Basophilic inclusions (BIs) and neuronal intermediate filament inclusions (NIFIs) are key structures of basophilic inclusion body disease and neuronal intermediate filament inclusion disease (NIFID), respectively. BIs are sharply-defined, oval or crescent neuronal intracytoplasmic inclusions that appear pale blue-gray in color with HE staining and purple in color with Nissl but are stained poorly with silver impregnation techniques. Immunohistochemically BIs are negative for tau, trans-activation response DNA 43 (TDP-43), α-synuclein, neurofilament (NF) and α-internexin, positive for p62, and variably ubiquitinated. Noticeably, BIs are consistently fused in sarcoma (FUS) positive. NIFIs are by definition immuno-positive for class IV IFs including three NF triplet subunit proteins and α-internexin but negative for tau, TDP-43, and α-synuclein. In NIFID cases several types of inclusions have been identified. Among them, hyaline conglomerate-like inclusions are the only type that meets the above immunohistochemical features of NIFIs. This type of inclusion appears upon HE staining as multilobulated, faintly eosinophilic or pale amphophilic spherical masses with a glassy appearance. These hyaline conglomerates appear strongly argyrophilic, and robustly and consistently immuno-positive for IFs. In contrast, this type of inclusion shows no or only occasional dot-like FUS immunoreactivity. Therefore, BIs and NIFIs are distinct from each other in terms of morphological, tinctorial and immunohistochemical features. However, basophilic inclusion body disease (BIBD) and NIFID are difficult to differentiate clinically. Moreover, Pick body-like inclusions, the predominant type of inclusions seen in NIFID, are considerably similar to the BIs of BIBD in that this type of inclusion is basophilic, poorly argyrophilic, negative for IFs and intensely immuno-positive for FUS. As BIBD and NIFID share FUS accumulation as the most prominent molecular pathology, whether these two diseases are discrete entities or represent a pathological continuum remains a question to be answered.

EFNS-ENS Guidelines on the diagnosis and management of disorders associated with dementia

BACKGROUND AND OBJECTIVES

The last version of the EFNS dementia guidelines is from 2007. In 2010, the revised guidelines for Alzheimer's disease (AD) were published. The current guidelines involve the revision of the dementia syndromes outside of AD, notably vascular cognitive impairment, frontotemporal lobar degeneration, dementia with Lewy bodies, corticobasal syndrome, progressive supranuclear palsy, Parkinson's disease dementia, Huntington's disease, prion diseases, normal-pressure hydrocephalus, limbic encephalitis and other toxic and metabolic disorders. The aim is to present a peer-reviewed evidence-based statement for the guidance of practice for clinical neurologists, geriatricians, psychiatrists and other specialist physicians responsible for the care of patients with dementing disorders. It represents a statement of minimum desirable standards for practice guidance.

METHODS

The task force working group reviewed evidence from original research articles, meta-analyses and systematic reviews, published by June 2011. The evidence was classified (I, II, III, IV) and consensus recommendations graded (A, B, or C) according to the EFNS guidance. Where there was a lack of evidence, but clear consensus, good practice points were provided.

RESULTS AND CONCLUSIONS

New recommendations and good practice points are made for clinical diagnosis, blood tests, neuropsychology, neuroimaging, electroencephalography, cerebrospinal fluid (CSF) analysis, genetic testing, disclosure of diagnosis, treatment of behavioural and psychological symptoms in dementia, legal issues, counselling and support for caregivers. All recommendations were revised as compared with the previous EFNS guidelines. The specialist neurologist together with primary care physicians play an important role in the assessment, interpretation and treatment of symptoms, disability and needs of dementia patients.

Progress in frontotemporal dementia research

Frontotemporal dementia (FTD) is the second most common type of presenile dementia and is the most common form of dementia with the onset before 60 years of age. Its typical symptoms include behavioral disorders, affective symptoms, and language disorders. The FTD is a genetically and pathologically heterogeneous degenerative disorder. Animal models have provided more insights into the pathogenic mechanisms. There are currently no medications that are specifically approved for the treatment of FTD by the Food and Drug Administration. In this article, we review the recent advances in the molecular pathogenesis, pathology, animal models, and therapy for FTD. Better understanding of the pathogenesis and the use of animal models will help develop novel therapeutic strategies and provide new targets for FTD treatment.

Corticospinal tract degeneration associated with TDP-43 type C pathology and semantic dementia

Four subtypes of frontotemporal lobar degeneration with TDP-43 immunoreactive inclusions have been described (types A-D). Of these four subtypes, motor neuron disease is more commonly associated with type B pathology, but has also been reported with type A pathology. We have noted, however, the unusual occurrence of cases of type C pathology having corticospinal tract degeneration. We aimed to assess the severity of corticospinal tract degeneration in a large cohort of cases with type C (n = 31). Pathological analysis included semi-quantitation of myelin loss of fibres of the corticospinal tract and associated macrophage burden, as well as axonal loss, at the level of the medullary pyramids. We also assessed for motor cortex degeneration and fibre loss of the medial lemniscus/olivocerebellar tract. All cases were subdivided into three groups based on the degree of corticospinal tract degeneration: (i) no corticospinal tract degeneration; (ii) equivocal corticospinal tract degeneration; and (iii) moderate to very severe corticospinal tract degeneration. Clinical, genetic, pathological and imaging comparisons were performed across groups. Eight cases had no corticospinal tract degeneration, and 14 cases had equivocal to mild corticospinal tract degeneration. Nine cases, however, had moderate to very severe corticospinal tract degeneration with myelin and axonal loss. In these nine cases, there was degeneration of the motor cortex without lower motor neuron degeneration or involvement of other brainstem tracts. These cases most commonly presented as semantic dementia, and they had longer disease duration (mean: 15.3 years) compared with the other two groups (10.8 and 9.9 years; P = 0.03). After adjusting for disease duration, severity of corticospinal tract degeneration remained significantly different across groups. Only one case, without corticospinal tract degeneration, was found to have a hexanucleotide repeat expansion in the C9ORF72 gene. All three groups were associated with anterior temporal lobe atrophy on MRI; however, the cases with moderate to severe corticospinal tract degeneration showed right-sided temporal lobe asymmetry and greater involvement of the right temporal lobe and superior motor cortices than the other groups. In contrast, the cases with no or equivocal corticospinal tract degeneration were more likely to show left-sided temporal lobe asymmetry. For comparison, the corticospinal tract was assessed in 86 type A and B cases, and only two cases showed evidence of corticospinal tract degeneration without lower motor neuron degeneration. These findings confirm that there exists a unique association between frontotemporal lobar degeneration with type C pathology and corticospinal tract degeneration, with this entity showing a predilection to involve the right temporal lobe.

Neuroimaging in dementia

As treatment of neurodegenerative disease moves toward therapies aimed at specific molecular abnormalities, the importance of early and accurate diagnosis will increase, as will the need for sensitive measures for tracking disease progression. Brain imaging, using MRI and PET scanning, offers a variety of highly reliable techniques that examine the structure, chemical content, metabolic state, and functional capacity of the brain. For all the major neurodegenerative disorders, relatively specific findings can be identified with some or all of these techniques. New approaches for imaging specific molecular pathology likely will revolutionize brain imaging and be combined with established imaging approaches to obtain a complete molecular, structural, and metabolic characterization, which could be used to improve diagnosis, and to stage each patient and follow disease progression and response to treatment.

The corticobasal syndrome-Alzheimer's disease conundrum

Corticobasal syndrome (CBS), once thought to be pathognomonic for corticobasal degeneration pathology, is increasingly reported with various underlying pathologies. Alzheimer's disease is one such pathology, also once believed to be unique for its clinical syndrome of dementia of the Alzheimer's type. CBS is believed to result from topography of asymmetric parietofrontal cortical lesion involvement, rather than lesion subtype. However, this topographical pattern is strikingly different to that typically associated with AD for unclear reasons. This article will focus on CBS with underlying AD pathology (CBS-AD), and will review associated clinical, imaging and demographic factors. Predicting AD pathology is of marked interest as disease-modifying therapies loom on the horizon, with biomarkers and imaging research underway. By reviewing the literature for CBS-AD case reports and series and contrasting them with CBS with underlying corticobasal degeneration pathology cases, the article aims to examine factors that may predict AD pathology. How AD pathology may produce this clinical phenotype, rather than the prototype dementia of the Alzheimer's type, will also be reviewed.

Neuroimaging in frontotemporal lobar degeneration--predicting molecular pathology

Frontotemporal lobar degeneration (FTLD) encompasses a group of diseases characterized by neuronal loss and gliosis of the frontal and temporal lobes. Almost all cases of FTLD can be classified into three categories on the basis of deposition of one of three abnormal proteins: the microtubule-associated protein tau, TAR DNA-binding protein 43, or fused in sarcoma. The specific diagnoses within each of these three categories are further differentiated by the distribution and morphological appearance of the protein-containing inclusions. Future treatments are likely to target these abnormal proteins; the clinical challenge, therefore, is to be able to predict molecular pathology during life. Clinical diagnosis alone has had variable success in helping to predict pathology, and is particularly poor in the diagnosis of behavioral variant frontotemporal dementia, which can be associated with all three abnormal proteins. Consequently, other biomarkers of disease are needed. This Review highlights how patterns of atrophy assessed on MRI demonstrate neuroanatomical signatures of the individual FTLD pathologies, independent of clinical phenotype. The roles of these patterns of atrophy as biomarkers of disease, and their potential to help predict pathology during life in patients with FTLD, are also discussed.

Staging neurodegenerative disorders: structural, regional, biomarker, and functional progressions

The notion of staging in the neurodegenerative disorders is modulated by the constant and progressive loss of several aspects of brain structural integrity, circuitry, and neuronal processes. These destructive processes eventually remove individuals' abilities to perform at sufficient and necessary functional capacity at several levels of disease severity. The classification of (a) patients on the basis of diagnosis, risk prognosis, and intervention outcome, forms the basis of clinical staging, and (b) laboratory animals on the basis of animal model of brain disorder, extent of insult, and dysfunctional expression, provides the components for the clinical staging and preclinical staging, respectively, expressing associated epidemiological, biological, and genetic characteristics. The major focus of clinical staging in the present account stems from the fundamental notions of Braak staging as they describe the course and eventual prognosis for Alzheimer's disease, Lewy Body dementia, and Parkinson's disease. Mild cognitive impairment, which expresses the decline in episodic and semantic memory performance below the age-adjusted normal range without marked loss of global cognition or activities of daily living, and the applications of longitudinal magnetic resonance imaging, major instruments for the monitoring of either disease progression in dementia, present important challenges for staging concepts. Although Braak notions present the essential basis for further developments, current staging conceptualizations seem inadequate to comply with the massive influx of information dealing with neurodegenerative processes in brain, advanced both under clinical realities, and discoveries in the laboratory setting. The contributions of various biomarkers of disease progression, e.g., amyloid precursor protein, and neurotransmitter system imbalances, e.g., dopamine receptor supersensitivity and interactive propensities, await their incorporation into the existing staging models thereby underlining the ongoing, dynamic feature of the staging of brain disorders.

Transportin1: a marker of FTLD-FUS

The term frontotemporal lobar degeneration (FTLD) describes a group of disorders that are subdivided by the presence of one of a number of pathological proteins identified in the inclusion bodies observed post-mortem. The FUS variant is defined by the presence of the fused in sarcoma protein (FUS) in the pathological inclusions. However, similar to other FTLDs, the disease pathogenesis of FTLD-FUS remains largely poorly understood. Here we present data that the protein transportin1 (TRN1) is abundant in the FUS-positive inclusions. TRN1, the protein product of the TNP01 gene, is responsible for shuttling proteins containing an M9 nuclear localisation signal between the nuclear and cytoplasmic compartments. RNA interacting proteins, including FUS, have been implicated as targets of TRN1. Using TRN1 immunohistochemistry and Western blotting in this study, we investigated 13 cases of FTLD-FUS including 6 cases with neuronal intermediate filament inclusion disease (NIFID) and 7 atypical frontotemporal lobar degeneration with ubiquitinated inclusion (aFTLD-U) cases. The data from our immunohistochemical studies show that FUS-immunoreactive inclusions are also strongly labelled with the anti-TRN1 antibody and double-label immunofluorescence studies indicate good co-localisation between the FUS and TRN1 pathologies. Our biochemical investigations demonstrate that urea-soluble TRN1 is present in aFTLD-U and NIFID, but not in normal control brains. These findings implicate abnormalities of FUS transport in the pathogenesis of FTLD-FUS.

Neuropathological background of phenotypical variability in frontotemporal dementia

Frontotemporal lobar degeneration (FTLD) is the umbrella term encompassing a heterogeneous group of pathological disorders. With recent discoveries, the FTLDs have been show to classify nicely into three main groups based on the major protein deposited in the brain: FTLD-tau, FTLD-TDP and FTLD-FUS. These pathological groups, and their specific pathologies, underlie a number of well-defined clinical syndromes, including three frontotemporal dementia (FTD) variants [behavioral variant frontotemporal dementia (bvFTD), progressive non-fluent aphasia, and semantic dementia (SD)], progressive supranuclear palsy syndrome (PSPS) and corticobasal syndrome (CBS). Understanding the neuropathological background of the phenotypic variability in FTD, PSPS and CBS requires large clinicopathological studies. We review current knowledge on the relationship between the FTLD pathologies and clinical syndromes, and pool data from a number of large clinicopathological studies that collectively provide data on 544 cases. Strong relationships were identified as follows: FTD with motor neuron disease and FTLD-TDP; SD and FTLD-TDP; PSPS and FTLD-tau; and CBS and FTLD-tau. However, the relationship between some of these clinical diagnoses and specific pathologies is not so clear cut. In addition, the clinical diagnosis of bvFTD does not have a strong relationship to any FTLD subtype or specific pathology and therefore remains a diagnostic challenge. Some evidence suggests improved clinicopathological association of bvFTD by further refining clinical characteristics. Unlike FTLD-tau and FTLD-TDP, FTLD-FUS has been less well characterized, with only 69 cases reported. However, there appears to be some associations between clinical phenotypes and FTLD-FUS pathologies. Clinical diagnosis is therefore promising in predicting molecular pathology.

Spatial patterns of FUS-immunoreactive neuronal cytoplasmic inclusions (NCI) in neuronal intermediate filament inclusion disease (NIFID)

Neuronal intermediate filament inclusion disease (NIFID), a rare form of frontotemporal lobar degeneration (FTLD), is characterized neuropathologically by focal atrophy of the frontal and temporal lobes, neuronal loss, gliosis, and neuronal cytoplasmic inclusions (NCI) containing epitopes of ubiquitin and neuronal intermediate filament (IF) proteins. Recently, the 'fused in sarcoma' (FUS) protein (encoded by the FUS gene) has been shown to be a component of the inclusions of NIFID. To further characterize FUS proteinopathy in NIFID, we studied the spatial patterns of the FUS-immunoreactive NCI in frontal and temporal cortex of 10 cases. In the cerebral cortex, sectors CA1/2 of the hippocampus, and the dentate gyrus (DG), the FUS-immunoreactive NCI were frequently clustered and the clusters were regularly distributed parallel to the tissue boundary. In a proportion of cortical gyri, cluster size of the NCI approximated to those of the columns of cells was associated with the cortico-cortical projections. There were no significant differences in the frequency of different types of spatial patterns with disease duration or disease stage. Clusters of NCI in the upper and lower cortex were significantly larger using FUS compared with phosphorylated, neurofilament heavy polypeptide (NEFH) or α-internexin (INA) immunohistochemistry (IHC). We concluded: (1) FUS-immunoreactive NCI exhibit similar spatial patterns to analogous inclusions in the tauopathies and synucleinopathies, (2) clusters of FUS-immunoreactive NCI are larger than those revealed by NEFH or ΙΝΑ, and (3) the spatial patterns of the FUS-immunoreactive NCI suggest the degeneration of the cortico-cortical projections in NIFID.

A comparative clinical, pathological, biochemical and genetic study of fused in sarcoma proteinopathies

Neuronal intermediate filament inclusion disease and atypical frontotemporal lobar degeneration are rare diseases characterized by ubiquitin-positive inclusions lacking transactive response DNA-binding protein-43 and tau. Recently, mutations in the fused in sarcoma gene have been shown to cause familial amyotrophic lateral sclerosis and fused in sarcoma-positive neuronal inclusions have subsequently been demonstrated in neuronal intermediate filament inclusion disease and atypical frontotemporal lobar degeneration with ubiquitinated inclusions. Here we provide clinical, imaging, morphological findings, as well as genetic and biochemical data in 14 fused in sarcoma proteinopathy cases. In this cohort, the age of onset was variable but included cases of young-onset disease. Patients with atypical frontotemporal lobar degeneration with ubiquitinated inclusions all presented with behavioural variant frontotemporal dementia, while the clinical presentation in neuronal intermediate filament inclusion disease was more heterogeneous, including cases with motor neuron disease and extrapyramidal syndromes. Neuroimaging revealed atrophy of the frontal and anterior temporal lobes as well as the caudate in the cases with atypical frontotemporal lobar degeneration with ubiquitinated inclusions, but was more heterogeneous in the cases with neuronal intermediate filament inclusion disease, often being normal to visual inspection early on in the disease. The distribution and severity of fused in sarcoma-positive neuronal cytoplasmic inclusions, neuronal intranuclear inclusions and neurites were recorded and fused in sarcoma was biochemically analysed in both subgroups. Fused in sarcoma-positive neuronal cytoplasmic and intranuclear inclusions were found in the hippocampal granule cell layer in variable numbers. Cortical fused in sarcoma-positive neuronal cytoplasmic inclusions were often 'Pick body-like' in neuronal intermediate filament inclusion disease, and annular and crescent-shaped inclusions were seen in both conditions. Motor neurons contained variable numbers of compact, granular or skein-like cytoplasmic inclusions in all fused in sarcoma-positive cases in which brainstem and spinal cord motor neurons were available for study (five and four cases, respectively). No fused in sarcoma mutations were found in any cases. Biochemically, two major fused in sarcoma species were found and shown to be more insoluble in the atypical frontotemporal lobar degeneration with ubiquitinated inclusions subgroup compared with neuronal intermediate filament inclusion disease. There is considerable overlap and also significant differences in fused in sarcoma-positive pathology between the two subgroups, suggesting they may represent a spectrum of the same disease. The co-existence of fused in sarcoma-positive inclusions in both motor neurons and extramotor cerebral structures is a characteristic finding in sporadic fused in sarcoma proteinopathies, indicating a multisystem disorder.

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.

Novel types of frontotemporal lobar degeneration: beyond tau and TDP-43

Most cases of frontotemporal lobar degeneration (FTLD) are characterized by the abnormal accumulation of either the microtubule-associated protein tau or the transactive response DNA-binding protein with M(r) 43 kDa, TDP-43 (FTLD-tau and FTLD-TDP, respectively). However, there remain ∼10% of cases, composed of a heterogenous collection of uncommon disorders, for which the molecular basis remains uncertain. In this review, we describe the characteristic genetic, clinical, and pathological features of the major tau/TDP-negative FTLD subtypes, with focus on recent advances in our understanding of their molecular basis. This includes the discovery that the pathological changes in atypical FTLD with ubiquitinated inclusions, neuronal intermediate filament inclusion disease, and basophilic inclusion body disease are immunoreactive for the fused in sarcoma (FUS) protein, resulting in the creation of a new molecular subgroup (FTLD-FUS), and studies clarifying the functional consequences of pathogenic CHMP2B mutations.

Imaging signatures of molecular pathology in behavioral variant frontotemporal dementia

Pathology underlying behavioral variant frontotemporal dementia (bvFTD) is heterogeneous, with the most common pathologies being Pick's disease (PiD), corticobasal degeneration (CBD), and FTLD-TDP type 1. Clinical features are unhelpful in differentiating these pathologies. We aimed to determine whether imaging atrophy patterns differ across these pathologies in bvFTD subjects. We identified 15 bvFTD subjects that had volumetric MRI during life and autopsy: five with PiD, five CBD, and five FTLD-TDP type 1. Voxel-based morphometry was used to assess atrophy patterns in each bvFTD group compared to 20 age- and gender-matched controls. All three pathological groups showed gray matter loss in frontal lobes, although specific patterns of atrophy differed across groups: PiD showed widespread loss in frontal lobes with additional involvement of anterior temporal lobes; CBD showed subtle patterns of loss involving posterior lateral and medial superior frontal lobe; and FTLD-TDP type 1 showed widespread loss in frontal, temporal, and parietal lobes. Greater parietal loss was observed in FTLD-TDP type 1 compared to both other groups, and greater anterior temporal and medial frontal loss was observed in PiD compared to CBD. Imaging patterns of atrophy in bvFTD vary according to pathological diagnosis and may therefore be helpful in predicting these pathologies in bvFTD.

A morphometric study of the spatial patterns of TDP-43 immunoreactive neuronal inclusions in frontotemporal lobar degeneration (FTLD) with progranulin (GRN) mutation

Mutations of the progranulin (GRN) gene are a major cause of familial frontotemporal lobar degeneration with transactive response (TAR) DNA-binding protein of 43 kDa (TDP-43) proteinopathy (FTLD-TDP). We studied the spatial patterns of TDP-43 immunoreactive neuronal cytoplasmic inclusions (NCI) and neuronal intranuclear inclusions (NII) in histological sections of the frontal and temporal lobe in eight cases of FTLD-TDP with GRN mutation using morphometric methods and spatial pattern analysis. In neocortical regions, the NCI were clustered and the clusters were regularly distributed parallel to the pia mater; 58% of regions analysed exhibiting this pattern. The NII were present in regularly distributed clusters in 35% of regions but also randomly distributed in many areas. In neocortical regions, the sizes of the regular clusters of NCI and NII were 400-800 μm, approximating to the size of the modular columns of the cortico-cortical projections, in 31% and 36% of regions respectively. The NCI and NII also exhibited regularly spaced clustering in sectors CA1/2 of the hippocampus and in the dentate gyrus. The clusters of NCI and NII were not spatially correlated. The data suggest degeneration of the cortico-cortical and cortico-hippocampal pathways in FTLD-TDP with GRN mutation, the NCI and NII affecting different clusters of neurons.

Distinct pathological subtypes of FTLD-FUS

Most cases of frontotemporal lobar degeneration (FTLD) are characterized by abnormal intracellular accumulation of either tau or TDP-43 protein. However, in ~10% of cases, composed of a heterogenous collection of uncommon disorders, the molecular basis remains to be uncertain. We recently discovered that the pathological changes in several tau/TDP-43-negative FTLD subtypes are immunoreactive (ir) for the fused in sarcoma (FUS) protein. In this study, we directly compared the pattern of FUS-ir pathology in cases of atypical FTLD-U (aFTLD-U, N = 10), neuronal intermediate filament inclusion disease (NIFID, N = 5) and basophilic inclusion body disease (BIBD, N = 8), to determine whether these are discrete entities or represent a pathological continuum. All cases had FUS-ir pathology in the cerebral neocortex, hippocampus and a similar wide range of subcortical regions. Although there was significant overlap, each group showed specific differences that distinguished them from the others. Cases of aFTLD-U consistently had less pathology in subcortical regions. In addition, the neuronal inclusions in aFTLD-U usually had a uniform, round shape, whereas NIFID and BIBD were characterized by a variety of inclusion morphologies. In all cases of aFTLD-U and NIFID, vermiform neuronal intranuclear inclusions (NII) were readily identified in the hippocampus and neocortex. In contrast, only two cases of BIBD had very rare NII in a single subcortical region. These findings support aFTLD-U, NIFID and BIBD as representing closely related, but distinct entities that share a common molecular pathogenesis. Although cases with overlapping pathology may exist, we recommend retaining the terms aFTLD-U, NIFID and BIBD for specific FTLD-FUS subtypes.

The spectrum and severity of FUS-immunoreactive inclusions in the frontal and temporal lobes of ten cases of neuronal intermediate filament inclusion disease

Neuronal intermediate filament inclusion disease (NIFID), a rare form of frontotemporal lobar degeneration (FTLD), is characterized neuropathologically by focal atrophy of the frontal and temporal lobes, neuronal loss, gliosis, and neuronal cytoplasmic inclusions (NCI) containing epitopes of ubiquitin and neuronal intermediate filament proteins. Recently, the 'fused in sarcoma' (FUS) protein (encoded by the FUS gene) has been shown to be a component of the inclusions of familial amyotrophic lateral sclerosis with FUS mutation, NIFID, basophilic inclusion body disease, and atypical FTLD with ubiquitin-immunoreactive inclusions (aFTLD-U). To further characterize FUS proteinopathy in NIFID, and to determine whether the pathology revealed by FUS immunohistochemistry (IHC) is more extensive than α-internexin, we have undertaken a quantitative assessment of ten clinically and neuropathologically well-characterized cases using FUS IHC. The densities of NCI were greatest in the dentate gyrus (DG) and in sectors CA1/2 of the hippocampus. Anti-FUS antibodies also labeled glial inclusions (GI), neuronal intranuclear inclusions (NII), and dystrophic neurites (DN). Vacuolation was extensive across upper and lower cortical layers. Significantly greater densities of abnormally enlarged neurons and glial cell nuclei were present in the lower compared with the upper cortical laminae. FUS IHC revealed significantly greater numbers of NCI in all brain regions especially the DG. Our data suggest: (1) significant densities of FUS-immunoreactive NCI in NIFID especially in the DG and CA1/2; (2) infrequent FUS-immunoreactive GI, NII, and DN; (3) widely distributed vacuolation across the cortex, and (4) significantly more NCI revealed by FUS than α-internexin IHC.

Neuronal degeneration in autonomic nervous system of Dystonia musculorum mice

Background

Dystonia musculorum (dt) is an autosomal recessive hereditary neuropathy with a characteristic uncoordinated movement and is caused by a defect in the bullous pemphigoid antigen 1 (BPAG1) gene. The neural isoform of BPAG1 is expressed in various neurons, including those in the central and peripheral nerve systems of mice. However, most previous studies on neuronal degeneration in BPAG1-deficient mice focused on peripheral sensory neurons and only limited investigation of the autonomic system has been conducted.

Methods

In this study, patterns of nerve innervation in cutaneous and iridial tissues were examined using general neuronal marker protein gene product 9.5 via immunohistochemistry. To perform quantitative analysis of the autonomic neuronal number, neurons within the lumbar sympathetic and parasympathetic ciliary ganglia were calculated. In addition, autonomic neurons were cultured from embryonic dt/dt mutants to elucidate degenerative patterns in vitro. Distribution patterns of neuronal intermediate filaments in cultured autonomic neurons were thoroughly studied under immunocytochemistry and conventional electron microscopy.

Results

Our immunohistochemistry results indicate that peripheral sensory nerves and autonomic innervation of sweat glands and irises dominated degeneration in dt/dt mice. Quantitative results confirmed that the number of neurons was significantly decreased in the lumbar sympathetic ganglia as well as in the parasympathetic ciliary ganglia of dt/dt mice compared with those of wild-type mice. We also observed that the neuronal intermediate filaments were aggregated abnormally in cultured autonomic neurons from dt/dt embryos.

Conclusions

These results suggest that a deficiency in the cytoskeletal linker BPAG1 is responsible for dominant sensory nerve degeneration and severe autonomic degeneration in dt/dt mice. Additionally, abnormally aggregated neuronal intermediate filaments may participate in neuronal death of cultured autonomic neurons from dt/dt mutants.

TDP-43 and FUS in amyotrophic lateral sclerosis and frontotemporal dementia

Abnormal intracellular protein aggregates comprise a key characteristic in most neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). The seminal discoveries of accumulation of TDP-43 in most cases of ALS and the most frequent form of FTD, frontotemporal lobar degeneration with ubiquitinated inclusions, followed by identification of FUS as the novel pathological protein in a small subset of patients with ALS and various FTD subtypes provide clear evidence that these disorders are related. The creation of a novel molecular classification of ALS and FTD based on the identity of the predominant protein abnormality has, therefore, been possible. The striking functional and structural similarities of TDP-43 and FUS, which are both DNA/RNA binding proteins, imply that abnormal RNA metabolism is a pivotal event, but the mechanisms leading to TDP-43 and FUS accumulation and the resulting neurodegeneration are currently unknown. Nonetheless, TDP-43 and FUS are promising candidates for the development of novel biomarker assays and targeted therapies.

Brain biopsy in dementia: clinical indications and diagnostic approach

Brain biopsy may be performed to make a definitive diagnosis in patients with rapidly progressive dementia. To assess the value of this procedure, we previously studied 90 consecutive cerebral biopsies performed in the tertiary referral centre of the National Hospital for Neurology and Neurosurgery, Queen Square between 1989 and 2003 (6 biopsies/year). Fifty-seven percent of all biopsies were diagnostic with Alzheimer's disease (18%), Creutzfeldt-Jakob disease (CJD) (12%) and inflammatory disorders (9%) being the most frequent. In the non-diagnostic group and for the series as a whole non-specific gliosis was the commonest diagnosis (37%). Treatment was altered because of information obtained from neuropathological findings in 11% of cases. To identify changes in practice that may have occurred due to recent advances in clinical assessment and improved histopathological techniques, we performed a follow-up study of 19 brain biopsies (approximately 3 cases/year) carried out for a dementing illness in the same centre between 2004 and 2009. These data suggest that brain biopsy may be less frequently used to help clinical diagnosis whilst its diagnostic yield increased from 57 to 74%. The commonest diagnosis was CJD, mostly suspected during life. Amongst the diagnoses, there were two cases of vasculitis and two cases of primary neurodegenerative dementia. These data suggest that improved clinical selection criteria supported by advances in diagnostic testing may result in brain biopsy being less frequently required, although it may still provide useful diagnostic information in difficult cases. We propose algorithms to aid the clinician in selecting appropriate patients for a biopsy and the neuropathologist in assessing a biopsy specimen.