Ubiquitin-positive intraneuronal inclusions in the extramotor cortices of presenile dementia patients with motor neuron disease

Frontotemporal lobar degeneration with TAR DNA-binding protein 43 (TDP-43): its journey of more than 100 years

Frontotemporal lobar degeneration (FTLD) with TDP-43-immunoreactive inclusions (FTLD-TDP) is a neurodegenerative disease associated with clinical, genetic, and neuropathological heterogeneity. An association between TDP-43, FTLD and amyotrophic lateral sclerosis (ALS) was first described in 2006. However, a century before immunohistochemistry existed, atypical dementias displaying behavioral, language and/or pyramidal symptoms and showing non-specific FTLD with superficial cortical neuronal loss, gliosis and spongiosis were often confused with Alzheimer's or Pick's disease. Initially this pathology was termed dementia lacking distinctive histopathology (DLDH), but this was later renamed when ubiquitinated inclusions originally found in ALS were also discovered in (DLDH), thus warranting a recategorization as FTLD-U (ubiquitin). Finally, the ubiquitinated protein was identified as TDP-43, which aggregates in cortical, subcortical, limbic and brainstem neurons and glial cells. The topography and morphology of TDP-43 inclusions associate with specific clinical syndromes and genetic mutations which implies different pathomechanisms that are yet to be discovered; hence, the TDP-43 journey has actually just begun. In this review, we describe how FTLD-TDP was established and defined clinically and neuropathologically throughout the past century.

Neuropathology of primary lateral sclerosis

Published descriptions of the neuropathology of clinically defined primary lateral sclerosis (PLS) are reviewed in order to clarify the pathogenesis and the relationship between PLS and classical amyotrophic lateral sclerosis (ALS). Degeneration of the primary motor cortex and corticospinal tracts with preservation of lower motor neurons (LMN) has been reported in most cases. Studies that employed immunohistochemistry found ubiquitin and/or TDP-43-positive neuronal inclusions in the motor cortex and often in the extramotor neocortex. Ubiquitin/TDP-43-immunoreactive inclusions in LMN have been reported in just over half of cases; however, these have never been numerous. The finding of TDP-43 pathology in most cases indicates that PLS and ALS are closely related conditions; however, the fact that cases of PLS consistently show minimal involvement of LMN suggests that PLS represents a distinct entity, rather than an early stage of ALS.

The Clinical and Radiological Spectrum of Hippocampal Pathology in Amyotrophic Lateral Sclerosis

Hippocampal pathology in Amyotrophic Lateral Sclerosis (ALS) remains surprisingly under recognized despite compelling evidence from neuropsychology, neuroimaging and neuropathology studies. Hippocampal dysfunction contributes significantly to the clinical heterogeneity of ALS and requires structure-specific cognitive and neuroimaging tools for accurate in vivo evaluation. Recent imaging studies have generated unprecedented insights into the presymptomatic and longitudinal processes affecting this structure and have contributed to the characterisation of both focal and network-level changes. Emerging neuropsychology data suggest that memory deficits in ALS may be independent from executive dysfunction. In the era of precision medicine, where the development of individualized care strategies and patient stratification for clinical trials are key priorities, the comprehensive review of hippocampal dysfunction in ALS is particularly timely.

Exploring the genetics and non-cell autonomous mechanisms underlying ALS/FTLD

Although amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig's disease, was first described in 1874, a flurry of genetic discoveries in the last 10 years has markedly increased our understanding of this disease. These findings have not only enhanced our knowledge of mechanisms leading to ALS, but also have revealed that ALS shares many genetic causes with another neurodegenerative disease, frontotemporal lobar dementia (FTLD). In this review, we survey how recent genetic studies have bridged our mechanistic understanding of these two related diseases and how the genetics behind ALS and FTLD point to complex disorders, implicating non-neuronal cell types in disease pathophysiology. The involvement of non-neuronal cell types is consistent with a non-cell autonomous component in these diseases. This is further supported by studies that identified a critical role of immune-associated genes within ALS/FTLD and other neurodegenerative disorders. The molecular functions of these genes support an emerging concept that various non-autonomous functions are involved in neurodegeneration. Further insights into such a mechanism(s) will ultimately lead to a better understanding of potential routes of therapeutic intervention. Facts ALS and FTLD are severe neurodegenerative disorders on the same disease spectrum. Multiple cellular processes including dysregulation of RNA homeostasis, imbalance of proteostasis, contribute to ALS/FTLD pathogenesis. Aberrant function in non-neuronal cell types, including microglia, contributes to ALS/FTLD. Strong neuroimmune and neuroinflammatory components are associated with ALS/FTLD patients. Open Questions Why can patients with similar mutations have different disease manifestations, i.e., why do C9ORF72 mutations lead to motor neuron loss in some patients while others exhibit loss of neurons in the frontotemporal lobe? Do ALS causal mutations result in microglial dysfunction and contribute to ALS/FTLD pathology? How do microglia normally act to mitigate neurodegeneration in ALS/FTLD? To what extent do cellular signaling pathways mediate non-cell autonomous communications between distinct central nervous system (CNS) cell types during disease? Is it possible to therapeutically target specific cell types in the CNS?

Neuropathology of Amyotrophic Lateral Sclerosis and Its Variants

The neuropathologic molecular signature common to almost all sporadic amyotrophic lateral sclerosis (ALS) and most familial ALS is TDP-43 immunoreactive neuronal cytoplasmic inclusions. The neuropathologic and molecular neuropathologic features of ALS variants, primarily lateral sclerosis and progressive muscular atrophy, are less certain but also seem to share the primary features of ALS. Genetic causes, including mutations in SOD1, TDP-43, FUS, and C9orf72, all have distinctive molecular neuropathologic signatures. Neuropathology will continue to play an increasingly key role in solving the puzzle of ALS pathogenesis.

Heterogeneity of cerebral TDP-43 pathology in sporadic amyotrophic lateral sclerosis: Evidence for clinico-pathologic subtypes

Frontotemporal lobar degeneration (FTLD) and amyotrophic lateral sclerosis (ALS) are types of major TDP-43 (43-kDa TAR DNA-binding protein) proteinopathy. Cortical TDP-43 pathology has been analyzed in detail in cases of FTLD-TDP, but is still unclear in cases of ALS. We attempted to clarify the cortical and subcortical TDP-43 pathology in Japanese cases of sporadic ALS (n = 96) using an antibody specific to phosphorylated TDP-43 (pTDP-43). The cases were divided into two groups: those without pTDP-43-positive neuronal cytoplasmic inclusions in the hippocampal dentate granule cells (Type 1, n = 63), and those with such inclusions (Type 2, n = 33). Furthermore, the Type 2 cases were divided into two subgroups based on semi-quantitative estimation of pTDP-43-positive dystrophic neurites (DNs) in the temporal neocortex: Type 2a (accompanied by no or few DNs, n = 22) and Type 2b (accompanied by abundant DNs, n = 11). Clinico-pathologic analysis revealed that cognitive impairment was a feature in patients with Type 2a and Type 2b, but not in those with Type 1, and that importantly, Type 2b is a distinct subtype characterized by a poor prognosis despite the less severe loss of lower motor neurons, the unusual subcortical dendrospinal pTDP-43 pathology, and more prominent glial involvement in cortical pTDP-43 pathology than other two groups. Considering the patient survival time and severity of motor neuron loss in each group, transition from Type 1 to Type 2, or from Type 2a to Type 2b during the disease course appeared unlikely. Therefore, each of these three groups was regarded as an independent subtype.

Significance and limitation of the pathological classification of TDP-43 proteinopathy

Based on the cerebral tans-activation response DNA protein 43 (TDP-43) immunohistochemistry, frontotemporal lobar degeneration with TDP-43 pathology (FTLD-TDP) is classified into four subtypes: type A has numerous neuronal cytoplasmic inclusions (NCIs) and dystrophic neurites (DNs); type B has numerous NCIs with few DNs; type C is characterized by DNs which are often longer and thicker than DNs in type A, with few NCIs; and type D has numerous neuronal intranuclear inclusions and DNs with few NCIs. The relevance of this classification system is supported by clinical, biochemical and genetic correlations, although there is still significant heterogeneity, especially in cases with type A pathology. The subtypes of TDP-43 pathology should be determined in cases with other neurodegenerative disorders, including Alzheimer's disease and dementia with Lewy bodies, to evaluate the pathological significance of TDP-43 abnormality in them. The results of the biochemical analyses of the diseased brains and the cellular models suggest that different strains of TDP-43 with different conformations may determine the clinicopathological phenotypes of TDP-43 proteinopathy, like prion disease. Clarifying the mechanism of the conformational changes of TDP-43 leading to the formation of multiple abnormal strains may be important for differential diagnosis and developing disease-modifying therapy for TDP-43 proteinopathy.

Expression and cellular distribution of ubiquitin in response to injury in the developing spinal cord of Monodelphis domestica

Ubiquitin, an 8.5 kDa protein associated with the proteasome degradation pathway has been recently identified as differentially expressed in segment of cord caudal to site of injury in developing spinal cord. Here we describe ubiquitin expression and cellular distribution in spinal cord up to postnatal day P35 in control opossums (Monodelphis domestica) and in response to complete spinal transection (T10) at P7, when axonal growth through site of injury occurs, and P28 when this is no longer possible. Cords were collected 1 or 7 days after injury, with age-matched controls and segments rostral to lesion were studied. Following spinal injury ubiquitin levels (western blotting) appeared reduced compared to controls especially one day after injury at P28. In contrast, after injury mRNA expression (qRT-PCR) was slightly increased at P7 but decreased at P28. Changes in isoelectric point of separated ubiquitin indicated possible post-translational modifications. Cellular distribution demonstrated a developmental shift between earliest (P8) and latest (P35) ages examined, from a predominantly cytoplasmic immunoreactivity to a nuclear expression; staining level and shift to nuclear staining was more pronounced following injury, except 7 days after transection at P28. After injury at P7 immunostaining increased in neurons and additionally in oligodendrocytes at P28. Mass spectrometry showed two ubiquitin bands; the heavier was identified as a fusion product, likely to be an ubiquitin precursor. Apparent changes in ubiquitin expression and cellular distribution in development and response to spinal injury suggest an intricate regulatory system that modulates these responses which, when better understood, may lead to potential therapeutic targets.

[Frontotemporal lobar degeneration (FTLD) - changes of its concept and classification based on aggregated proteins]

FTLD is a purely anatomically defined concept, being unrelated to the underling cellular pathology; the sine qua non is only the presence of main lesions in the frontal and temporal lobes. FTLD, therefore, is destined to include various maladies that involve the two areas. Cases reported by Arnold Pick, "Pick's disease", are a prototype of FTLD. Because of lack of histopathological description of the brains in his reports, however, the nomenclature brought about a great confusion in its nosology; the history of establishing the concept of FTLD was that of how to seperate genuine Pick's disease. After a long chaos, the present molecular neuropathology has ultimately resolved this problem by clarifying protein constituents of neuronal and glial aggregates in FTLD. TDP-43 was first found in ALS and ALS with dementia (ALSD), and soon FUS/TLS was detected in some TDP-43-negative FTLD-U groups. At the present time, FTLD consists of three main subgroups; 1) FTLD-tau, which includes Pick disease, PSP, CBD, etc., 2) FTLD-TDP, which is subdivided into types A-D, with ALSD belonging to type B, and 3) FTLD-FUS, the members of which are aFTLD-U, NIFID, and BIBD. Further discovery of yet-undetected proteins of some FTLD-U subsets will add more subclasses.

[Frontotemporal lobar degeneration (FTLD) concept and classification update]

FTLD is a neuroanatomical disease concept defined only by the presence of degeneration of the frontal and temporal lobes regardless of the underlying histopathological features, and therefore inevitably includes heterogeneous diseases that affect those cerebral regions. The ambiguous idea of Pick disease, the prototype of FTLD, constantly caused great nosological confusion as to FTLD. Progress in molecular neuropathology aimed at clarification of the protein constituents of the inclusion bodies seen in conditions causing FTLD, however, has resolved this problem by providing FTLD with a new concise nomenclature and classification based on the inclusion body proteins. The substances in inclusions in FTLD with ubiquitin-only inclusions (FTLD-U) have been discovered one after another; TDP-43 was the first, being found in inclusions in ALS and ALS with dementia (ALSD) too, and soon FUS/TLS was identified in some TDP-43-negative FTLD-U groups. Thus, FTLD has been divided into three main subgroups; 1) FTLD-tau, which includes Pick disease, PSP, CBD, etc., 2) FTLD-TDP, which is further divided to types A-D, ALSD belonging to type B, and 3) FTLD-FUS, which includes aFTLD-U, NIFID, and BIBD. Further deciphering of yet-unidentified proteins of some FTLD-U subsets will add more subclasses.

TDP-43 proteinopathy and motor neuron disease in chronic traumatic encephalopathy

Epidemiological evidence suggests that the incidence of amyotrophic lateral sclerosis is increased in association with head injury. Repetitive head injury is also associated with the development of chronic traumatic encephalopathy (CTE), a tauopathy characterized by neurofibrillary tangles throughout the brain in the relative absence of β-amyloid deposits. We examined 12 cases of CTE and, in 10, found a widespread TAR DNA-binding protein of approximately 43kd (TDP-43) proteinopathy affecting the frontal and temporal cortices, medial temporal lobe, basal ganglia, diencephalon, and brainstem. Three athletes with CTE also developed a progressive motor neuron disease with profound weakness, atrophy, spasticity, and fasciculations several years before death. In these 3 cases, there were abundant TDP-43-positive inclusions and neurites in the spinal cord in addition to tau neurofibrillary changes, motor neuron loss, and corticospinal tract degeneration. The TDP-43 proteinopathy associated with CTE is similar to that found in frontotemporal lobar degeneration with TDP-43 inclusions, in that widespread regions of the brain are affected. Akin to frontotemporal lobar degeneration with TDP-43 inclusions, in some individuals with CTE, the TDP-43 proteinopathy extends to involve the spinal cord and is associated with motor neuron disease. This is the first pathological evidence that repetitive head trauma experienced in collision sports might be associated with the development of a motor neuron disease.

Ubiquitin-positive tau-negative intraneuronal inclusions in dementia with motor neuron disease: The 50th Anniversary of Japanese Society of Neuropathology

We first reported ubiquitin-positive tau-negative intraneuronal inclusions in the hippocampal granular cell layer and entorhinal cortices in patients with amyotrophic lateral sclerosis (ALS). We then found that those inclusions occur frequently in patients with presenile dementia and motor neuron disease. The ultrastructure of the inclusions consists mainly of granules with a few filaments. In 2006, TDP-43 was identified as a major component of the inclusions specific for frontotemporal lobar degeneration and ALS. Here, we review the current knowledge regarding ubiquitin-positive tau-negative intraneuronal inclusions.

FUS pathology in basophilic inclusion body disease

Basophilic Inclusion Body Disease (BIBD) is a tau-negative form of frontotemporal lobar degeneration (FTLD), characterized by neuronal cytoplasmic inclusions (NCI) that are visible on hematoxylin and eosin stain (HE), contain RNA, and are inconsistently ubiquitin-immunoreactive (ir). The normal nuclear expression of TDP-43 is not altered. Here we investigate whether the distribution of the structurally and functionally related protein fused in sarcoma (FUS) is altered in BIBD. Mutations in the FUS gene have recently been identified as a cause of familial amyotrophic lateral sclerosis (ALS). In addition to these familial ALS cases, FUS protein has recently been demonstrated in NCI in a subset of FTLD with ubiquitinated inclusions (atypical FTLD-U) and in neuronal intermediate filament inclusion disease (NIFID). We examined seven BIBD brains of patients with average age at onset 46 (range 29-57) and average duration of disease 8 years (range 5-12). Three cases presented with the behavioural variant of fronto-temporal dementia (FTD-bv) and one with FTD-bv combined with severe dysarthria. All four developed motor neuron disease/ALS syndrome (MND/ALS) several years later. In the other three cases, presentation was predominantly with motor symptoms, construed as MND/ALS in two, and progressive supranuclear palsy (PSP) in one. Severity of cortical degeneration varied, but all cases shared severe nigrostriatal atrophy and lower motor neuron pathology. In spared areas of cortex, FUS antibodies showed intense labelling of neuronal nuclei and weak positivity of cytoplasm, whereas, in affected areas, intense labelling of NCI was accompanied by reduction or disappearance of the normal IR pattern. The number of FUS-ir NCI was much greater than the number detected by HE or with ubiquitin or P62 immunohistochemistry. FUS-ir glial cytoplasmic inclusions (GCI) were abundant in the grey and white matter in all cases, whereas neuronal intranuclear inclusions were rare and only seen in 2/7 cases. Thus, BIBD shares with atypical FTLD-U and NIFID the presence of FUS-ir NCI and GCI, and together comprise a new biochemical category of neurodegenerative disease (FUS proteinopathies). The consistent involvement of motorneurons in BIBD indicates that the association of FTLD and MND/ALS can occur on a FUS or TDP-43 pathological substrate.

The molecular basis of frontotemporal dementia

Frontotemporal dementia (FTD) is a clinical syndrome with a heterogeneous molecular basis. Familial FTD has been linked to mutations in several genes, including those encoding the microtubule-associated protein tau (MAPT), progranulin (GRN), valosin-containing protein (VCP) and charged multivescicular body protein 2B (CHMP2B). The associated neuropathology is characterised by selective degeneration of the frontal and temporal lobes (frontotemporal lobar degeneration, FTLD), usually with the presence of abnormal intracellular protein accumulations. The current classification of FTLD neuropathology is based on the identity of the predominant protein abnormality, in the belief that this most closely reflects the underlying pathogenic process. Major subgroups include those characterised by the pathological tau, TDP-43, intermediate filaments and a group with cellular inclusions composed of an unidentified ubiquitinated protein. This review will focus on the current understanding of the molecular basis of each of the major FTLD subtypes. It is anticipated that this knowledge will provide the basis of future advances in the diagnosis and treatment of FTD.

What is 'early onset dementia'?

There are two types of dementia with early onset: (i) presenile dementias; and (ii) senile dementias with early onset. Most patients who develop dementia before 65 years of age have Alzheimer's disease (AD). The remainder are likely to have vascular dementia (VaD), frontotemporal dementia, head injury, alcohol intoxication, or metabolic disorder. Presenile dementias, caused by frontotemporal lobar degeneration, progressive supranuclear palsy, and corticobasal degeneration, usually occur in patients of presenile and are rarely seen in patients of senile age. Although the factors responsible for the accelerated onset of the illness are not fully known, genetic abnormalities appear to be important in some types of presenile dementia, such as frontotemporal dementia with parkinsonism linked to chromosome 17. Conversely, senile dementias such as sporadic AD and VaD commonly occur in patients of senile age. These disorders may also occur in patients of presenile age, although less frequently. Alzheimer's disease was originally classified as a 'presenile dementia'. Since the 1980s, 'senile dementia of Alzheimer type' (SDAT) and 'Alzheimer's disease' have been considered to belong to the same pathological entity and both are now known as 'dementia of Alzheimer's type (DAT)' or merely 'Alzheimer's disease'. Rapid progression of cognitive impairment with neuropsychological syndromes and neurological symptoms has been considered a characteristic of early onset AD. However, recently, neurological symptoms such as spastic paraparesis, seizures, and myoclonic convulsions have been reported to occur infrequently in early onset AD, although language problems and visuospatial dysfunctions are common. There are at least three dominant genes that have been identified in cases of familial Alzheimer's disease with early onset, namely the amyloid precursor gene (APP), and the genes encoding presenilin 1 (PSEN1) and presenilin 2 (PSEN2). Therefore, genetic abnormalities are important factors contributing to the earlier onset of the illness. It is also important to investigate the pathophysiological mechanism in relation to genetic abnormalities, environmental factors, physical illnesses, and metabolic disturbances to understand the processes underlying the development of dementia with early onset.

The role of transactive response DNA-binding protein-43 in amyotrophic lateral sclerosis and frontotemporal dementia

PURPOSE OF REVIEW

We examine current evidence that the transactive response DNA-binding protein (TDP-43) plays a pathogenic role in both amyotrophic lateral sclerosis and frontotemporal dementia.

RECENT FINDINGS

TDP-43 was recently identified as the major pathological protein in sporadic amyotrophic lateral sclerosis and in the most common pathological subtype of frontotemporal dementia, frontotemporal lobar degeneration with ubiquitinated inclusions. In these conditions, abnormal C-terminal fragments of TDP-43 are ubiquitinated, hyperphosphorylated and accumulate as cellular inclusions in neurons and glia. Cells with inclusions show absence of the normal nuclear TDP-43 localization. Recently, missense mutations in the gene encoding TDP-43 have been identified in patients with sporadic and familial amyotrophic lateral sclerosis.

SUMMARY

The recent discovery of pathological TDP-43 in both amyotrophic lateral sclerosis and frontotemporal lobar degeneration with ubiquitinated inclusions confirms that these are closely related conditions within a new biochemical class of neurodegenerative disease, the TDP-43 proteinopathies.

Ultrastructural localization of TDP-43 in filamentous neuronal inclusions in various neurodegenerative diseases

Using post-embedding immunogold electron microscopy, TAR DNA-binding protein of 43 kDa (TDP-43) was localized to neuronal cytoplasmic (NCI) and intranuclear (NII) inclusions, as well as unmyelinated neurites, in frontotemporal lobar degeneration with ubiquitinated inclusions (FTLD-U), amyotrophic lateral sclerosis (ALS), Alzheimer's (AD), Pick's disease (PiD) and Lewy body disease (LBD). The TDP-43 immunoreactive structures were morphologically heterogeneous. The most common was characterized by bundles of 10-20 nm diameter straight filaments with electron dense granular material within NCI, NII and neurites. This type of pathology was found in FTLD-U, ALS and some cases of AD. Less often, inclusions in neuritic processes of FTLD-U and some cases of AD contained 10-17 nm diameter straight filaments without granular material. A final type of TDP-43 immunoreactivity was labeling of filaments and granular material associated with tau filaments in neurofibrillary tangles of AD and Pick bodies of PiD or alpha-synuclein filaments in Lewy bodies of LBD. The results suggest that TDP-43 is the primary component of the granulofilamentous inclusions in FTLD-U and ALS. Similar inclusions sometimes accompany filamentous aggregates composed of other abnormal proteins in AD, PiD and LBD.

Sporadic amyotrophic lateral sclerosis: two pathological patterns shown by analysis of distribution of TDP-43-immunoreactive neuronal and glial cytoplasmic inclusions

A nuclear protein, 43-kDa TAR DNA-binding protein (TDP-43), was recently identified as a component of the ubiquitinated inclusions (UIs) in frontotemporal lobar degeneration (FTLD-U) and sporadic amyotrophic lateral sclerosis (SALS). In the present study using immunohistochemistry, we examined various regions of the nervous system in a series of 35 SALS cases using a polyclonal antibody against TDP-43. Seven of the 35 cases had disease durations of more than 10 years with artificial respiratory support (ARS; duration: 69-156 months). In all cases, TDP-43-immunoreactive (ir) neuronal and glial cytoplasmic inclusions (NCIs and GCIs) were found together in many regions, including the histologically affected lower motor neuron nuclei. Cluster analysis of the distribution pattern of TDP-43-ir NCIs for cases without ARS (n = 28) identified two types (type 1, n = 16; type 2, n = 12). Type 2 was distinguished from type 1 by the presence of TDP-43-ir NCIs in the frontotemporal cortex, hippocampal formation, neostriatum and substantia nigra, and was significantly associated with dementia. Eleven of the 28 cases showed UIs in the hippocampal dentate granule cells, all of which had type-2 distribution pattern. Cases with ARS (n = 7) were also classified into the same types (type 1, n = 5; type 2, n = 2). Cases having type-1 distribution pattern (n = 21) showed no evident neuronal loss in most of the non-motor neuron nuclei where TDP-43-ir NCIs were present, whereas cases having type-2 distribution pattern (n = 14) often showed evident neuronal loss in the frontotemporal cortices, amygdaloid nuclei and substantia nigra. These findings indicate that SALS is a multisystem degenerative disease widely affecting both neurons and glial cells with a heterogeneous pattern of TDP-43-ir NCI distribution (SALS showing type-2 distribution pattern being closely linked to FTLD-U), and that long-term survival supported by a respirator has no apparent influence on the TDP-43 neuronal distribution pattern.

Atypical frontotemporal lobar degeneration with ubiquitin-positive, TDP-43-negative neuronal inclusions

Frontotemporal lobar degeneration with ubiquitinated inclusions (FTLD-U) is the most common neuropathology associated with the clinical syndrome of frontotemporal dementia (FTD). Recently, TDP-43 was identified as the ubiquitinated pathological protein in both FTLD-U and sporadic amyotrophic lateral sclerosis. Although a number of studies have now confirmed that most sporadic and familial cases of FTLD-U are TDP-43 proteinopathies, there are exceptions. We describe six cases of early onset FTD with FTLD-U pathology that was negative for TDP-43, which we refer to as 'atypical' FTLD-U. All cases were sporadic and had very early onset FTD (mean age = 35 years), characterized by severe progressive psychobehavioural abnormalities in the absence of significant aphasia, cognitive-intellectual dysfunction or motor features. The neuropathological features were highly consistent, with small, round, neuronal cytoplasmic inclusions that were immunoreactive for ubiquitin (ub-ir), but negative for tau, alpha-synuclein, intermediate filaments and TDP-43. Cytoplasmic inclusions were most numerous in the neocortex, dentate granule cells and hippocampal pyramidal neurons. Ub-ir neuronal intra-nuclear inclusions were also present in neocortical and hippocampal neurons and had the unusual appearance of straight, curved or twisted filaments. We believe that these cases represent a new entity that is clinically and pathologically distinct from all currently recognized subtypes of FTLD. Moreover, the existence of such cases indicates that the designations of 'FTLD-U' and 'TDP-43 proteinopathy' should not be considered to be synonymous.

The neuropathology of FTD associated With ALS

There is increasing recognition of a clinical overlap between frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS). Recent advances in our understanding of the neuropathologic, biochemical, and genetic basis of these conditions provides evidence for a common underlying pathogenesis. The neuropathology in most cases of FTD with ALS is a subtype of frontotemporal lobar degeneration, characterized by neuronal inclusions that are immunoreactive for ubiquitin but not tau (frontotemporal lobar degeneration with ubiquitinated inclusions). These cases show significant pathologic overlap with clinically pure FTD and those with classic ALS. Moreover, the ubiquitinated pathologic protein in all these conditions has recently been identified as TDP-43. A number of families have been reported with autosomal dominant FTD-ALS linked to chromosome 9p and these also have TDP-43-positive frontotemporal lobar degeneration with ubiquitinated inclusions pathology. Together, these findings suggest that FTD-ALS is part of a clinicopathologic spectrum of disease, now identified as TDP-43 proteinopathies.

TDP-43-immunoreactive neuronal and glial inclusions in the neostriatum in amyotrophic lateral sclerosis with and without dementia

TDP-43 is a major component of ubiquitin-positive, tau-negative inclusions in amyotrophic lateral sclerosis (ALS), and frontotemporal lobar degeneration. We immunohistochemically examined the neostriatum from 14 cases of classic ALS (cALS), six cases of ALS with dementia (ALS-D), and 20 control subjects. TDP-43-positive, crescent or circular inclusions were found in neostriatal small neurons in 19 of 20 cases of ALS, but not in controls. Two types of inclusions were found in the large neurons: ubiquitin-positive, TDP-43-negative rod-like inclusions, and ubiquitin- and TDP-43-positive pleomorphic inclusions. The latter were specific to ALS; they were found in seven cases of cALS and in all of ALS-D. TDP-43-positive glial inclusions were also found in 12 cases of cALS and in all of ALS-D. These TDP-43-positive neuronal and glial inclusions were more numerous in ALS-D than cALS. In ALS-D, neuronal loss in the substantia nigra was found in all the cases, whereas mild gliosis without obvious neuronal loss was noted in the neostriaum in only two cases. These findings suggest that the neostriatum is also involved in the disease process of ALS with and without dementia.

A reassessment of the neuropathology of frontotemporal dementia linked to chromosome 3

A large Danish family has previously been reported in which autosomal dominant frontotemporal dementia (FTD) is genetically linked to chromosome 3 (FTD-3). A mutation was recently identified in the CHMP2B gene that is probably responsible for causing disease in this family. Because of its neuropathologic findings, FTD-3 was originally categorized as a subtype of frontotemporal lobar degeneration, termed "dementia lacking distinctive histopathology." We now report a reevaluation of the neuropathologic changes in this family. Postmortem material from 4 affected family members was available for examination. Gross examination revealed generalized cortical atrophy that was most severe in frontal and temporal cortices. Microscopy showed loss of cortical neurons, microvacuolation of layer II, mild gliosis, and demyelination of the deep white matter. Results of immunohistochemical staining for alpha-synuclein, prion protein, neurofilament, and tau protein were unremarkable. Variable numbers of small, round, ubiquitin-positive cytoplasmic inclusions were present in the dentate granule layer of the hippocampus in all 4 cases. Rare ubiquitin-positive inclusions were also found in frontal and temporal cortical neurons. These inclusions were also positive for p62 but not for TDP-43. The finding of ubiquitin- and p62-positive, TDP-43-negative cytoplasmic inclusions in the hippocampus and neocortex suggests reclassification of the neuropathology of FTD-3 as a unique subtype of frontotemporal lobar degeneration with ubiquitin-positive inclusions that are TDP-43-negative.

The molecular genetics and neuropathology of frontotemporal lobar degeneration: recent developments

The past year has seen a number of significant advances in our understanding of the neuropathological and molecular genetic basis of frontotemporal lobar degeneration (FTLD). Whereas, in the past, most attention focused on FTLD associated with tau-based pathology and microtubule associated protein tau gene (MAPT) mutations, there has recently been greater attention paid to non-tau FTLD. FTLD with tau-negative, ubiquitinated inclusions (FTLD-U) is now recognized as the most common pathology associated with clinical FTLD. Mutations in the progranulin gene (PGRN) have been identified as the cause of FTLD-U linked to chromosome 17. A rapidly growing number of PGRN mutations have been identified, and to date, all appear to cause FTLD by reducing the amount of functional PGRN protein (haploinsufficiency). The neuropathology associated with each of the known non-MAPT FTLD genes and loci (PGRN, valosin-containing protein gene, CHMP2B and 9p), has been shown to be a specific subtype of FTLD-U. The ubiquitinated pathological protein in FTLD-U has been identified as TAR deoxyribonucleic acid-binding protein with M (r) 43 kDa (TDP-43). Immunohistochemical and biochemical studies of TDP-43 have helped to clarify the relationship between different sub-types of FTLD-U and related conditions. It is anticipated that these discoveries will facilitate the development of new diagnostic tests and therapeutics.

TDP-43 immunoreactivity in hippocampal sclerosis and Alzheimer's disease

OBJECTIVE

This study aimed to determine the frequency of frontotemporal lobar degeneration with ubiquitinated inclusions (FTLD-U) in the setting of hippocampal sclerosis (HpScl) and Alzheimer's disease (AD) using immunohistochemistry for TAR DNA binding protein 43 (TDP-43), a putative marker for FTLD-U.

METHODS

Initially, 21 cases of HpScl associated with a variety of other pathological processes and 74 cases of AD were screened for FTLD-U with TDP-43 immunohistochemistry. A confirmation study was performed on 93 additional AD cases. Specificity of TDP-43 antibodies was assessed using double-immunolabeling confocal microscopy, immunoelectron microscopy, and biochemistry.

RESULTS

TDP-43 immunoreactivity was detected in 71% of HpScl and 23% of AD cases. Double immunostaining of AD cases for TDP-43 and phospho-tau showed that the TDP-43-immunoreactive inclusions were usually distinct from neurofibrillary tangles. At the ultrastructural level, TDP-43 immunoreactivity in AD was associated with granular and filamentous cytosolic material and only occasionally associated with tau filaments. Western blots of AD cases showed a band that migrated at a higher molecular weight than normal TDP-43 that was not present in AD cases without TDP-43 immunoreactivity.

INTERPRETATION

These results suggest that as many as 20% of AD cases and more than 70% of HpScl cases have pathology similar to that found in FTLD-U. Whether this represents concomitant FTLD-U or is analogous to colocalization of alpha-synuclein and tau in AD, reflecting a propensity for codeposition of abnormal protein conformers, remains to be determined.

TDP-43 in differential diagnosis of motor neuron disorders

Motor neuron disorders are clinically and pathologically heterogeneous. They can be classified into those that affect primarily upper motor neurons, lower motor neurons or both. The most common disorder to affect both upper and lower motor neurons is amyotrophic lateral sclerosis (ALS). Some forms of motor neuron disease (MND) affect primarily motor neurons in the spinal cord or brainstem, while others affect motor neurons at all levels of the neuraxis. A number of genetic loci have been identified for the various motor neuron disorders. Several of the MND genes encode for proteins important for cytoskeletal stability and axoplasmic transport. Despite these genetic advances, the relationship of the various motor neuron disorders to each other is unclear. Except for rare familial forms of ALS associated with mutations in superoxide dismutase type 1 (SOD1), which are associated with neuronal inclusions that contain SOD1, specific molecular or cellular markers that differentiate ALS from other motor neuron disorders have not been available. Recently, the TAR DNA binding protein 43 (TDP-43) has been shown to be present in neuronal inclusions in ALS, and it has been suggested that TDP-43 may be a specific marker for ALS. This pilot study aimed to determine the value of TDP-43 in the differential diagnosis of MND. Immunohistochemistry for TDP-43 was used to detect neuronal inclusions in the medulla of disorders affecting upper motor neurons, lower motor neurons or both. Medullary motor neuron pathology also was assessed in frontotemporal lobar degeneration (FTLD) that had no evidence of MND. TDP-43 immunoreactivity was detected in the hypoglossal nucleus in all cases of ALS, all cases of FTLD-MND and some of cases of primary lateral sclerosis (PLS). It was not detected in FTLD-PLS. Surprisingly, sparse TDP-43 immunoreactivity was detected in motor neurons in about 10% of FTLD that did not have clinical or pathologic features of MND. The results suggest that TDP-43 immunoreactivity is useful in differentiating FTLD-MND and ALS from other disorders associated with upper or lower motor neuron pathology. It also reveals subclinical MND in a subset of cases of FTLD without clinical or pathologic evidence of MND.

Dementia lacking distinctive histology (DLDH) revisited

Although immunohistochemistry has helped to classify the histology of frontotemporal lobar degeneration (FTLD), there have been many cases, described in the literature as showing "dementia lacking distinctive histology" (DLDH), in which this technique has failed to disclose signature pathological changes. Using an automated procedure we have repeated immunostaining for ubiquitin protein (UBQ) in 41 patients with FTLD, 25 of whom were previously considered, on the basis of UBQ immunostaining performed in Manchester, UK, to show FTLD-ubiquitin (FTLD-U) histology and 16 described as DLDH. Both the quality and amount of UBQ immunoreactive (UBQ-ir) pathology (neurites and intraneuronal cytoplasmic inclusions) was significantly increased using the newer staining method. Although the original histological diagnosis was confirmed in the 25 cases previously classified as FTLD-U, the median UBQ score for slides stained in Vancouver increased significantly compared to those stained in Manchester. More importantly, however, some degree of UBQ-ir changes was now disclosed in 13 of the 16 cases previously classified as DLDH and these were now classed as definite or probable FTLD-U. Of the remaining three DLDH cases, clinical diagnostic uncertainties could have explained the lack of specific pathology in two instances. Hence, we conclude that DLDH is a very rare disorder, and that lack of sensitivity for UBQ immunostaining is likely responsible for the failure to disclose this pathology and to provide a diagnosis of FTLD-U.

TDP-43 is a component of ubiquitin-positive tau-negative inclusions in frontotemporal lobar degeneration and amyotrophic lateral sclerosis

Ubiquitin-positive tau-negative neuronal cytoplasmic inclusions and dystrophic neurites are common pathological features in frontotemporal lobar degeneration (FTLD) with or without symptoms of motor neuron disease and in amyotrophic lateral sclerosis (ALS). Using biochemical and immunohistochemical analyses, we have identified a TAR DNA-binding protein of 43 kDa (TDP-43), a nuclear factor that functions in regulating transcription and alternative splicing, as a component of these structures in FTLD. Furthermore, skein-like inclusions, neuronal intranuclear inclusions, and glial inclusions in the spinal cord of ALS patients are also positive for TDP-43. Dephosphorylation treatment of the sarkosyl insoluble fraction has shown that abnormal phosphorylation takes place in accumulated TDP-43. The common occurrence of intracellular accumulations of TDP-43 supports the hypothesis that these disorders represent a clinicopathological entity of a single disease, and suggests that they can be newly classified as a proteinopathy of TDP-43.

Pathological heterogeneity of frontotemporal lobar degeneration with ubiquitin-positive inclusions delineated by ubiquitin immunohistochemistry and novel monoclonal antibodies

Frontotemporal lobar degeneration with ubiquitin-positive inclusions (FTLD-U) is a common neuropathological subtype of frontotemporal dementia. Although this subtype of frontotemporal dementia is defined by the presence of ubiquitin-positive but tau- and alpha-synuclein-negative inclusions, it is unclear whether all cases of FTLD-U have the same underlying pathogenesis. Examination of tissue sections from FTLD-U brains stained with anti-ubiquitin antibodies revealed heterogeneity in the morphological characteristics of pathological inclusions among subsets of cases. Three types of FTLD-U were delineated based on morphology and distribution of ubiquitin-positive inclusions. To address the hypothesis that FTLD-U is pathologically heterogeneous, novel monoclonal antibodies (mAbs) were generated by immunization of mice with high molecular mass (Mr > 250 kd) insoluble material prepared by biochemical fractionation of FTLD-U brains. Novel mAbs were identified that immunolabeled all of the ubiquitin-positive inclusions in one subset of FTLD-U cases, whereas other mAbs stained the ubiquitin-positive inclusions in a second subset of cases. These novel mAbs did not stain inclusions in other neurodegenerative disorders, including tauopathies and alpha-synucleinopathies. Therefore, ubiquitin immunohistochemistry and the immunostaining properties of the novel mAbs generated here suggest that FTLD-U is pathologically heterogeneous. Identification of the disease proteins recognized by these mAbs will further advance understanding of molecular substrates of FTLD-U neurodegenerative pathways.

Ubiquitin immunohistochemistry of frontotemporal lobar degeneration differentiates cases with and without motor neuron disease

Frontotemporal lobar degeneration (FTLD) without tau pathology is clinically and pathologically heterogeneous. The present report describes the neuropathology of 52 brains with FTLD without tau pathology compared with 10 brains of amyotrophic lateral sclerosis (ALS) without dementia using ubiquitin immunohistochemistry. The 52 cases were classified into 47 cases of FTLD with motor neuron disease (MND)-type inclusions but without MND (FTLD-MNI), three cases of FTLD with MND (FTLD-MND), and two cases of dementia lacking distinctive histopathology (DLDH) based on the features of ubiquitin-immunoreactive (ubiquitin-ir) structures in the caudate, frontotemporal cortices and dentate fascia, and presence or absence of neuronal loss in lower motor neurons. Many ubiquitin-ir neuronal inclusions and neurites in the caudate nucleus, frontotemporal cortices, and ubiquitin-ir crescent-or ring-shaped neuronal inclusions in the dentate fascia characterized FTLD-MNI. Ubiquitin-ir neuronal intranuclear inclusions (NII) were observed in 26 of 43 cases and associated with many neurites in the caudate nucleus as well as a familial history in most cases. A subset of cases had Pick-body-like inclusions in the dentate fascia and caudate nucleus with paucity of neuritic pathology and no NII; another had crescent-shaped inclusions in the dentate fascia and neuritic pathology with NII in the caudate. FTLD with MND was characterized by a few or no ubiquitin-ir inclusions in the caudate nucleus and frontotemporal cortices and ubiquitin-ir granular inclusions in the dentate fascia, as well as loss of lower motor neurons. These features were similar to ALS, but different from FTLD-MNI. The findings suggest that FTLD-MNI has a different pathogenesis from FTLD-MND and ALS.

Ubiquitin-positive inclusions and progression of pathology in frontotemporal dementia and motor neurone disease identifies a group with mainly early pathology

Frontotemporal lobar degeneration (FTLD) with tau-negative, ubiquitin-positive inclusions has been a topic of major interest in recent years, with this group now accounting for the majority of tau-negative cases of frontotemporal degeneration. The severity of neurodegeneration in FTLD is dependent on the stage of disease and is substantial even in the earliest stages. Elucidating the pathogenesis of FTLD requires evaluation of changes during the earliest possible stage of disease. However, the long survival of most frontotemporal dementia cases means that cases with early neuropathology are not frequently encountered. Cases of FTLD with the shortest survival are those with coexisting motor neurone disease (FTLD + MND), making these the ideal group for studying early FTLD pathology. It is not clear, however, what the pathological contribution of MND is in these cases. This study evaluates the pathology of 20 cases of FTLD (11 with no clinical signs of MND and nine with FTLD + MND) as well as 10 cases of MND without dementia. Our findings indicate that the deposition of ubiquitin does not play a key role in the neurodegenerative process in FTLD, and that the severity of neurodegeneration in FTLD is similar in cases with and without clinical MND.

"Forme fruste" of amyotrophic lateral sclerosis with dementia: a report of five autopsy cases without dementia and with ubiquitinated intraneuronal inclusions

We clinicopathologically investigated five autopsy cases of ALS without dementia and with ubiquitinated intraneuronal inclusions. The age at onset of symptoms ranged from 52 to 81 years and the duration of the disease was from 10 months to 3 years, 3 months. All five patients initially developed lower motor neuron signs, including bulbar signs, and upper motor neuron signs were found in the middle to late clinical stages, but dementia was not observed in all five cases. Thus, the clinical diagnoses of all five patients were ALS without dementia. Neuropathological examination of all five cases revealed not only obvious degeneration of upper motor neurons with neuronal loss of Betz cells, but also lower motor neuron involvement associated with Bunina bodies. In addition, ubiquitin-immunoreactive intraneuronal inclusions in the hippocampal dentate granular cells and degeneration of the substantia nigra were observed in all five cases. Furthermore, neuronal loss with astrocytosis in the dorsomedial portion of the anterior first temporal gyrus was observed in all three cases in which this structure was examined. Neuronal loss with astrocytosis in the subiculum was found in four cases. Neuronal loss of the parahippocampal gyrus was observed in three of the five autopsy cases, and amygdala involvement was encountered in three of four cases in which this structure was investigated. Based on these clinicopathological findings and a review of the published literature, we concluded that our five cases were ALS without dementia, but with pathological hallmarks compatible with ALS with dementia. We also concluded that there is a "forme fruste" of ALS with dementia showing no overt dementia clinically.

Histopathological changes underlying frontotemporal lobar degeneration with clinicopathological correlation

We have investigated the pathological correlates of dementia in the brains from a consecutive series of 70 patients dying with a clinical diagnosis of frontotemporal lobar degeneration (FTLD). Clinical misdiagnosis rate was low with only 3 patients (4%) failing to show pathological changes consistent with this diagnosis; 1 patient had Alzheimer's disease and 2 had cerebrovascular disease (CVD). In the remaining 67 patients, the most common underlying histological cause was ubiquitin pathology with 24 (36%) cases so affected. In these, ubiquitin-positive inclusions were present in the cerebral cortex as small, rounded or crescent-shaped structures within the cytoplasm of neurones of layer II, together with coiled or curvilinear bodies within neurites, and in the hippocampus as small, solid and more spherical-shaped inclusion bodies within the cytoplasm of dentate gyrus granule cells. In one patient, "cat's eye" or "lentiform" intranuclear ubiquitin inclusions were also present. The second most common histological type was dementia lacking distinctive histology (DLDH), in which neither tau nor ubiquitin inclusions were present, with 16 cases (24%) being affected. Pick-type histology was seen in 14 cases (21%) and tau histological changes associated with frontotemporal dementia (FTD) linked to chromosome 17 (FTDP-17) were present in 11 cases (16%). One case (1%) showed an unusual tau pathology that could not be allocated to any of the other tau groups. Only 1 case (1%) had neuronal intermediate filament inclusion dementia. No cases with ubiquitinated, valosin-containing protein-immunoreactive intranuclear inclusion bodies of the type seen in inclusion body myopathy with Paget's disease of bone and frontotemporal dementia were seen. Clinicopathological correlation showed that any of these histological subtypes can be associated with FTD. However, for FTD with motor neurone disease (FTD+MND), semantic dementia or primary progressive aphasia (PA), the histological profile was either ubiquitin type or DLDH type; Pick-type histology was seen in only 1 case of PA. None of these latter three clinical subtypes was associated with a mutation in tau gene and FTDP-17 type of tau pathology. All cases of progressive apraxia were associated with Pick-type histology. Present data therefore indicate that, although ubiquitin pathology is the most common histological form associated with FTLD, this pathology is not tightly linked with, nor is pathologically diagnostic for, any particular clinical form of the disease, including FTD+MND.

Ubiquitin Immunohistochemistry Suggests Classic Motor Neuron Disease, Motor Neuron Disease With Dementia, and Frontotemporal Dementia of the Motor Neuron Disease Type Represent a Clinicopathologic Spectrum

One of the characteristic pathologic changes in classic motor neuron disease (MND) is the presence of ubiquitin-immunoreactive (ub-ir) inclusions in the cytoplasm of lower motor neurons. In addition, cases of MND with dementia (MND-d) also have ub-ir neuronal cytoplasmic inclusions and dystrophic neurites in extramotor neocortex and hippocampus. Although this extramotor pathology is a highly sensitive marker for dementia in MND, similar changes are found in a subset of patients with frontotemporal dementia (FTD) with no motor symptoms (FTD-MND type). The purpose of this study is to more fully describe and compare the pattern of ub-ir pathology in these 3 conditions. We performed ubiquitin immunohistochemistry on postmortem tissue, representing a wide range of neuroanatomic structures, in cases of classic MND (n = 20), MND-d (n = 15), and FTD-MND type (n = 15). We found the variety of morphologies and the anatomic distribution of ub-ir pathology to be greater than previously documented. Moreover, the degree of overlap suggests that MND, MND-d, and FTD-MND type represent a spectrum of clinical disease with a common pathologic substrate. The only finding restricted to a specific subgroup of patients was the presence of ub-ir neuronal intranuclear inclusions in some cases of familial FTD.

Morphological differences of intraneuronal ubiquitin-positive inclusions in the dentate gyrus and parahippocampal gyrus of motor neuron disease with dementia

Semiquantitative morphological analysis of cerebral intraneuronal ubiquitin-positive tau-negative inclusions, a pathologic marker for motor neuron disease with dementia (MND-D), was performed in the dentate gyrus and parahippocampal gyrus of 20 clinicopathologically confirmed patients with MND-D. The forms of the inclusions were tentatively classified into three types: (i) C-type, consisting of relatively large and intensely stained crescent or circular structures; (ii) L-type, showing fine linear structures around the nuclei; and (iii) G-type, showing faintly stained granular structures. The frequencies of the C-type, L-type and G-type was 0.5-9.3%,0.2-6.5% and 0-6.6% of dentate granule cells, respectively. In contrast to the dentate gyrus, almost all inclusions showed either the C-type or L-type form in the parahippocampal gyrus. A positive correlation was noted only between incidences of C-type inclusion of the dentate gyrus and that of the parahippocampal gyrus (r = 0.69, P < 0.05). The morphological differences of the inclusions probably reflect different stages of their formation.

Ubiquitin and ubiquitin-related proteins in the brains of patients with atypical Pick's disease without Pick bodies and dementia with motor neuron disease

Nine cases of atypical Pick's disease without Pick bodies (aPiD) and seven cases of dementia with motor neuron diseases (D-MND) were compared using immunohistochemistry of ubiquitin (ub) and ub-related proteins. All cases showed rostral-dominant atrophy in the temporal and frontal lobes, although the degree of atrophy with neuronal loss was much more severe in the aPiD cases. In both aPiD and D-MND cases, ub-positive and tau-negative structures were found mainly in the hippocampal dentate gyrus and cerebral cortex. Granular cells of the dentate gyrus showed similar ub-positive intraneuronal inclusions in both cases. In the aPiD cases, most of the ub-positive cortical structures were ub-positive dendrites in layers II-IIIab and layers V-VI, although some neurons also showed diffuse ub-positive staining in the cytoplasm. In the D-MND cases, some neurons showed ub-positive inclusions in layers II-IIIab, and ub-positive dendrites were unremarkable. The number of ub-positive neurons and dendrites in relation to the degree of neuronal loss in the cerebral cortex were then evaluated. The number of ub-positive neurons in the regions showing very mild to mild neuronal loss was significantly greater in the D-MND cases than in the aPiD cases. However, in the aPiD cases, the number of ub-positive neurons was significantly greater in the regions showing moderate neuronal loss. When double-immunostained, almost all ub-positive structures were positive for ub-binding protein p62. Some ub-positive or negative neurons in the cerebral cortex were immunostained with anti-ub ligase (Parkin) and anti-ub C-terminal hydrolase (UCH-L1) antibodies. Granular cells of the dentate gyrus were weakly positive for UCH-L1. There could be some differences in the mechanism by which neurons in the cerebral cortex accumulate ub between aPiD and D-MND.

Sporadic amyotrophic lateral sclerosis of long duration mimicking spinal progressive muscular atrophy exists: Additional autopsy case with a clinical course of 19 years

This report concerns an autopsy case of sporadic amyotrophic lateral sclerosis (ALS) clinically diagnosed as having spinal progressive muscular atrophy (SPMA). The patient was a Japanese woman without hereditary burden. She developed muscle weakness in the distal part of the right upper extremity at age 52, followed by muscle weakness in the left upper extremity and lower extremities at age 54 and 64, respectively. At age 66 she could not walk, even with assistance. Fasciculation and atrophy of the tongue appeared at age 68, followed by dysphagia and dysarthria at age 70. She died of respiratory disturbance at age 71. During the clinical course, neurological examination revealed neither Babinski sign nor hyperreflexia. No respirator administration was performed throughout the clinical course. Neuropathological examination disclosed not only neuronal loss with gliosis in the hypoglossal nucleus and anterior horns of the spinal cord, but also loss of Betz cells and degeneration of the pyramidal tract. Based on these clinicopathological findings and a literature review of sporadic autopsy cases of ALS with long clinical course (10 years or more), including four cases without pyramidal signs, we believe that sporadic ALS of long clinical course mimicking SPMA exists.

Motor neuron disease group accompanied by inclusions of unidentified protein signaled by ubiquitin

Peculiar tau-negative, ubiquitin-positive inclusions appear in dementia with ALS (ALS-D), the majority of lobar atrophy (Pick's disease) without Pick body and a small portion of ALS. Another common neuropathological lesion in these diseases is the motor neuron involvement with the degenerative processes. The lower motor neuron is predominantly involved in ALS and ALS-D the upper motor neuron is predominantly involved, but in varying degrees in a considerable number of patients with lobar atrophy that lack Pick bodies. There are, however, some points that have yet to be elucidated. The boundary between these diseases is not always clear and a significant number of cases are considered to be the transitional form. Lobar atrophy without Pick body seems to be a heterogeneous disease group. The nature of ubiquitin inclusions also needs to be clarified. Nevertheless, we postulate that these diseases are grouped with the concept of motor neuron disease-inclusion dementia.

Word retrieval in amyotrophic lateral sclerosis: a functional magnetic resonance imaging study

The cognitive impairment revealed in some non- demented amyotrophic lateral sclerosis (ALS) patients is characterized by executive dysfunction with widely repeated deficits on tests of verbal (letter) fluency. However, conflicting evidence exists of an impairment on other word retrieval tasks, such as confrontation naming, which do not place heavy demands on executive processes. Previous research has demonstrated intact confrontation naming in the presence of verbal fluency deficits, although naming deficits have been described in other studies. In this investigation, functional MRI (fMRI) techniques were employed to explore whether word retrieval deficits and underlying cerebral abnormalities were specific to letter fluency, which are more likely to indicate executive dysfunction, or were also present in confrontation naming, indicating language dysfunction. Twenty-eight non-demented ALS patients were compared with 18 healthy controls. The two groups were matched for age, intelligence quotient, years of education, and anxiety and depression scores. Two compressed-sequence overt fMRI activation paradigms were employed, letter fluency and confrontation naming, which were developed for use with an older and potentially impaired population. In ALS patients relative to controls, the letter fluency fMRI task revealed significantly impaired activation in the middle and inferior frontal gyri and anterior cingulate gyrus, in addition to regions of the parietal and temporal lobes. The confrontation naming fMRI task also revealed impaired activation in less extensive prefrontal regions, including the inferior frontal gyrus and regions of the temporal, parietal and occipital lobes. These changes were present despite matched performance between patients and controls during each activation paradigm. The pattern of dysfunction corresponded to the presence of cognitive deficits on both letter fluency and confrontation naming in the ALS group. This study provides evidence of cerebral abnormalities in ALS in the network of regions involved in language and executive functions. Moreover, the findings further illustrate the heterogeneity of cognitive and cerebral change in ALS.

Amyotrophic lateral sclerosis with dementia: the clinicopathological spectrum

Amyotrophic lateral sclerosis with dementia (ALS-D) is a non-Alzheimer-type dementia characterized by both frontotemporal degeneration and motor neuron disease and marked by ubiquitin-positive, tau- and alpha-synuclein-negative intraneuronal inclusions and dystrophic neurites. New neuropathological diagnostic criteria for ALS-D are proposed on the basis of the present investigation of 28 autopsy cases. Clinical features included those of typical ALS-D, primary lateral sclerosis, atypical ALS with frontotemporal atrophy and atypical Pick's disease without Pick's bodies. Macroscopically anterior frontotemporal atrophy was observed involving or not involving the precentral gyrus. Microscopically non-specific neuronal loss and gliosis with spongiosis were seen, particularly in superficial layers II and III of the frontotemporal cortices. Diffuse fibrous gliosis was seen in the frontotemporal white matter. The substantia nigra and amygdala showed neuronal loss and gliosis. In all 28 cases, degeneration of both the lower and upper motor neuron systems, consistent with classic sporadic ALS, was present. The distribution and degree of degenerative frontotemporal lesions and motor neuron disturbance were of various patterns. Ubiquitin-positive and tau- and alpha-synuclein negative intraneuronal inclusions and dystrophic neurites in extramotor cortices were observed in all cases. Furthermore, ubiquitin-positive inclusions in lower motor neurons were found in all cases. The distribution pattern and density differed between neuronal inclusions and dystrophic neurites and correlated with clinicopathological phenotypes. Therefore, the ALS-D spectrum may be broader than that previously recognized, extending to primary lateral sclerosis, atypical ALS and to atypical Pick's disease without Pick bodies. Further investigation is needed to determine the characteristics of the ubiquitinated component in ALS-D.

Cortical selective vulnerability in motor neuron disease: a morphometric study

Neuroimaging and neuropsychological studies have revealed that the primary motor cortex (PMC) and the extramotor cortical areas are functionally abnormal in motor neuron disease (MND, amyotrophic lateral sclerosis), but the nature of the cortical lesions that underlie these changes is poorly understood. In particular, there have been few attempts to quantify neuronal loss in the PMC and in other cortical areas in MND. We used SMI-32, an antibody against an epitope on non-phosphorylated neurofilament heavy chain, to analyse the size and density of SMI-32-positive cortical pyramidal neurons in layer V of the PMC, the dorsolateral prefrontal cortex (DLPFC) and the supragenual anterior cingulate cortex (ACC) in 13 MND and eight control subjects. There was a statistically significant reduction in the density of SMI-32-immunoreactive (IR) pyramidal neurons within cortical layer V in the PMC, the DLPFC and the ACC in MND subjects compared with controls [t (19) = 2.91, P = 0.009; estimated reduction 25%; 95% CI = 8%, 40%]. In addition, we studied the density and size of interneurons immunoreactive for the calcium-binding proteins calbindin-D(28K) (CB), parvalbumin (PV) and calretinin (CR) in the same areas (PMC, DLPFC and ACC). Statistically significant differences in the densities of CB-IR neurons were observed within cortical layers V (P = 0.003) and VI (P = 0.001) in MND cases compared with controls. The densities of CR- and PV-IR neurons were not significantly different between MND and control cases, although there were trends towards reductions of CR-IR neuronal density within the same layers and of PV-IR neuronal density within cortical layer VI. Loss of pyramidal neurons and of GABAergic interneurons is more widespread than has been appreciated and is present in areas associated with neuroimaging and cognitive abnormalities in MND. These findings support the notion that MND should be considered a multisystem disorder.

Ubiquitin and ubiquitin-related proteins in neurons and dendrites of brains of atypical Pick's disease without Pick bodies

Nine cases of atypical Pick's disease without Pick bodies were investigated immunohistochemically. Ubiquitin (ub)-positive and tau-negative structures were mainly found in the cerebral cortex and hippocampal dentate gyrus. In the cerebral cortex, most of the ub-positive structures had ub-positive dendrites in the neuropil, although some also showed diffuse ub-positive staining in the neuronal cytoplasm. These ub-positive structures were distributed throughout layers II-IIIab and layers V-VI. Granular cells of the dentate gyrus had ub-positive intraneuronal inclusions. When the numbers of ub-positive neurons and dendrites were evaluated in relation to the degree of neuronal loss in the cerebral cortex, the number of ub-positive neurons was significantly lower in regions showing very mild neuronal loss and higher in regions showing moderate neuronal loss. In contrast, ub-positive dendrites were detected even in cortical regions showing very mild neuronal loss. Immunoelectron-microscopically, ub-positive structures contained ub-positive ribosome-like granular components in the neuronal cytoplasm and dendrites, which were occasionally related to the rough endoplasmic reticulum and accompanied by a few filamentous components. Almost all ub-positive structures were positive for ub-binding protein p62 in double-immunostaining method. Some ub-positive or negative neurons in the cerebral cortex were positively immunolabeled with anti-ub ligase (Parkin) and anti-ub C-terminal hydrolase antibodies, whereas dendrites were not labeled by these antibodies. From the present study, it is suggested that in the cerebral cortex, these ubiquitinated proteins may firstly accumulate in the dendrites at the onset of neuronal degeneration, then appear in the neuronal cytoplasm before finally disappearing with neuronal loss.

Pathological involvement of the motor neuron system and hippocampal formation in motor neuron disease-inclusion dementia

We report two patients with motor neuron disease-inclusion dementia, with special reference to the pathology of the motor neuron system and hippocampal formation. The ages of the patients at death were 55 and 62 years, and the disease durations were 8 and 3 years, respectively. The two patients exhibited progressive frontotemporal dementia in the absence of motor neuron signs. At autopsy, both cases exhibited frontotemporal lobar atrophy with ubiquitin-positive, and tau- and alpha-synuclein-negative neuronal inclusions. As expected from the clinical signs, in both cases, the upper and lower motor neuron systems were well preserved: no Bunina bodies or ubiquitinated inclusions were detected in the motor neurons. However, of great importance was that when visualized immunohistochemically, the Golgi apparatus and trans-Golgi network often exhibited fragmentation in the lower motor neurons (the spinal anterior horn cells). In one of the cases, a decrease in the amount of Golgi apparatus was also a frequent feature in the upper motor neurons (Betz cells in the motor cortex). Moreover, in both cases, circumscribed degeneration affecting the CA1-subiculum border zone was evident in the hippocampal formation. These findings further strengthen the idea that, pathologically, motor neuron disease-inclusion dementia is a rare phenotype of amyotrophic lateral sclerosis.

Vacuole-creating protein in neurodegenerative diseases in humans

Vacuole-creating protein (VCP) is a member of the ATPases associated with diverse cellular activities and is a putative sensor protein for degenerative proteins. Immunohistochemical examinations demonstrated that VCP was observed in ubiquitin-positive intraneuronal inclusions in motor neuron disease with dementia, ballooned neurons in Creutzfeldt-Jakob disease, dystrophic neurites of senile plaque in Alzheimer's disease, and Lewy and Marinesco bodies and Lewy neurites in Parkinson's disease, while granules of granulovacuolar degeneration and neurofibrillary tangles in Alzheimer's disease were not positively stained for VCP. These results indicate that VCP reacts with abnormal or misfolded proteins and plays a role in accelerating the process of degeneration and cell death. The elucidation of an association between VCP and these degenerative proteins will provide an important clue for understanding common mechanisms underlying neurodegenerative diseases.