Basophilic cytoplasmic inclusions in a case of sporadic juvenile amyotrophic lateral sclerosis

Deficient RNA-editing enzyme ADAR2 in an amyotrophic lateral sclerosis patient with a FUS(P525L) mutation

Mutations in the fused in sarcoma (FUS) gene can cause amyotrophic lateral sclerosis (ALS), and FUS gene mutations have been reported in sporadic ALS patients with basophilic cytoplasmic inclusions. Deficiency of adenosine deaminase acting on RNA 2 (ADAR2), an enzyme that specifically catalyzes GluA2 Q/R site-editing, has been reported in considerable proportions of spinal motor neurons of the majority of sporadic ALS patients. We describe the relationship between GluA2 Q/R site-editing efficiency and FUS-positive inclusions in a patient with FUS(P525L). A 24-year-old woman with ALS presented with basophilic cytoplasmic inclusions, significantly reduced GluA2 Q/R site-editing efficiency in the spinal motor neurons, and markedly decreased ADAR2 mRNA levels. Neuropathologic examination showed that not all spinal motor neurons expressed ADAR2 and revealed FUS-positive cytoplasmic inclusions in motor neurons irrespective of ADAR2 immunoreactivity. There were no phosphorylated transactive response (TAR) DNA-binding protein 43 kDa (TDP-43)-positive inclusions, indicating that there was no tight correlation between ADAR2 deficiency and TDP-43 deposition. ADAR2 deficiency can occur in ALS patients with a FUS(P525L) mutation and is unrelated to the presence of FUS-positive inclusions. FUS-associated ALS may share neurodegenerative characteristics with classical sporadic ALS.

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.

Topography of FUS pathology distinguishes late-onset BIBD from aFTLD-U

Background

Multiple neurodegenerative diseases are characterized by the abnormal accumulation of FUS protein including various subtypes of frontotemporal lobar degeneration with FUS inclusions (FTLD-FUS). These subtypes include atypical frontotemporal lobar degeneration with ubiquitin-positive inclusions (aFTLD-U), basophilic inclusion body disease (BIBD) and neuronal intermediate filament inclusion disease (NIFID). Despite considerable overlap, certain pathologic features including differences in inclusion morphology, the subcellular localization of inclusions, and the relative paucity of subcortical FUS pathology in aFTLD-U indicate that these three entities represent related but distinct diseases. In this study, we report the clinical and pathologic features of three cases of aFTLD-U and two cases of late-onset BIBD with an emphasis on the anatomic distribution of FUS inclusions.

Results

The aFTLD-U cases demonstrated FUS inclusions in cerebral cortex, subcortical grey matter and brainstem with a predilection for anterior forebrain and rostral brainstem. In contrast, the distribution of FUS pathology in late-onset BIBD cases demonstrated a predilection for pyramidal and extrapyramidal motor regions with relative sparing of cerebral cortex and limbic regions.

Conclusions

The topography of FUS pathology in these cases demonstrate the diversity of sporadic FUS inclusion body diseases and raises the possibility that late-onset motor neuron disease with BIBD neuropathology may exhibit unique clinical and pathologic features.

Familial ALS with FUS P525L mutation: two Japanese sisters with multiple systems involvement

We evaluated the clinicopathological features of familial amyotrophic lateral sclerosis (ALS) with the fused in sarcoma (FUS) P525L mutation. Two sisters and their mother had a similar clinical course, which was characterized by the development of limb weakness at a young age with rapid disease progression. An elder sister, patient 1, progressed into a totally locked-in state requiring mechanical ventilation and died 26 years after the onset of the disease. In contrast, the younger sister, patient 2, died in the early stages of the disease. The patients had neuropathological findings that indicated a very active degeneration of motor neurons and multiple system degeneration, which led to marked brain and spinal cord atrophy in the long term clinical outcome. The multiple system degeneration included the frontal lobe, the basal ganglia and substantia nigra, cerebellum and related area. Compared with previously reported ALS cases, the severe degeneration of the frontal lobe and the striatum were the characteristic features in the patient 1 in this case study. The degeneration spread over multiple systems might be caused not only by the appearance of the FUS immunoreactive neuronal cytoplasmic inclusions but also by the degeneration of neuronal connections from the primary motor cortex and related areas.

P525L FUS mutation is consistently associated with a severe form of juvenile amyotrophic lateral sclerosis

Some FUS mutations have been observed in patients with the juvenile form of Amyotrophic Lateral Sclerosis starting before 25 years. We report an 11-year-old girl affected by sporadic juvenile ALS with a rapid course resulting in tracheostomy after 14 months from the onset. Sequencing FUS gene revealed a de novo P525L mutation. Our findings, together with literature data, indicate that this mutation is consistently associated with a specific phenotype characterized by juvenile onset, severe course and high proportion of de novo mutations in sporadic cases.

Pathological heterogeneity in amyotrophic lateral sclerosis with FUS mutations: two distinct patterns correlating with disease severity and mutation

Mutations in the gene encoding the fused in sarcoma (FUS) protein are responsible for ~3% of familial amyotrophic lateral sclerosis (ALS) and <1% of sporadic ALS (ALS-FUS). Descriptions of the associated neuropathology are few and largely restricted to individual case reports. To better define the neuropathology associated with FUS mutations, we have undertaken a detailed comparative analysis of six cases of ALS-FUS that include sporadic and familial cases, with both juvenile and adult onset, and with four different FUS mutations. We found significant pathological heterogeneity among our cases, with two distinct patterns that correlated with the disease severity and the specific mutation. Frequent basophilic inclusions and round FUS-immunoreactive (FUS-ir) neuronal cytoplasmic inclusions (NCI) were a consistent feature of our early-onset cases, including two with the p.P525L mutation. In contrast, our late-onset cases that included two with the p.R521C mutation had tangle-like NCI and numerous FUS-ir glial cytoplasmic inclusions. Double-labeling experiments demonstrated that many of the glial inclusions were in oligodendrocytes. Comparison with the neuropathology of cases of frontotemporal lobar degeneration with FUS-ir pathology showed significant differences and suggests that FUS mutations are associated with a distinct pathobiology.

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.

Juvenile ALS with basophilic inclusions is a FUS proteinopathy with FUS mutations

BACKGROUND

Juvenile amyotrophic lateral sclerosis (ALS) with basophilic inclusions is a form of ALS characterized by protein deposits in motor neurons that are morphologically and tinctorially distinct from those of classic sporadic ALS. The nosologic position of this type of ALS in the molecular pathologic and genetic classification of ALS is unknown.

METHODS

We identified neuropathologically 4 patients with juvenile ALS with basophilic inclusions and tested the hypothesis that specific RNA binding protein pathology may define this type of ALS. Immunohistochemical findings prompted us to sequence the fused in sarcoma (FUS) gene.

RESULTS

Motor symptoms began between ages 17 and 22. Disease progression was rapid without dementia. No family history was identified. Basophilic inclusions were strongly positive for FUS protein but negative for TAR DNA binding protein 43 (TDP-43). Granular and compact FUS deposits were identified in glia and neuronal cytoplasm and nuclei. Ultrastructure of aggregates was in keeping with origin from fragmented rough endoplasmic reticulum. Sequencing of all 15 exons of the FUS gene in 3 patients revealed a novel deletion mutation (c.1554_1557delACAG) in 1 individual and the c.1574C>T (P525L) mutation in 2 others.

CONCLUSION

Juvenile ALS with basophilic inclusions is a FUS proteinopathy and should be classified as ALS-FUS. The FUS c.1574C>T (P525L) and c.1554_1557delACAG mutations are associated with this distinct phenotype. The molecular genetic relationship with frontotemporal lobar degeneration with FUS pathology remains to be clarified.

Extensive FUS-immunoreactive pathology in juvenile amyotrophic lateral sclerosis with basophilic inclusions

Juvenile amyotrophic lateral sclerosis (ALS) with basophilic inclusions is a well-recognized entity. However, the molecular underpinnings of this devastating disease are poorly understood. Here, we present genetic and neuropathological characterizations in two young women with fatal rapidly progressive ALS with basophilic inclusions. In one case, a germline mutation (P525L) was detected in the fused in sarcoma/translocated in liposarcoma (FUS/TLS) gene, whereas no mutation was identified in the other case. Postmortem examination in both cases revealed severe loss of spinal motor neurons with remaining neurons showing basophilic inclusions that contain abnormal aggregates of FUS proteins and disorganized intracellular organelles, including mitochondria and endoplasmic reticulum. In both patients, the FUS-positive inclusions were also detected in neurons in layers IV-V of cerebral cortex and several brainstem nuclei. In contrast, spinal motor neurons in patients with late-onset sporadic ALS showed no evidence of abnormal accumulation of FUS protein. These results underscore the importance of FUS mutations and pathology in rapidly progressive juvenile ALS. Furthermore, our study represents the first detailed characterizations of neuropathological findings in rapidly progressive juvenile ALS patients with a mutation in the FUS/TLS gene.

Occurrence of basophilic inclusions and FUS-immunoreactive neuronal and glial inclusions in a case of familial amyotrophic lateral sclerosis

Basophilic inclusions (BIs) are the pathological feature in a subset of frontotemporal lobar degeneration (FTLD), sporadic amyotrophic lateral sclerosis (SALS) and familial ALS (FALS) cases. Mutations in the fused in sarcoma (FUS) gene have been recently identified as the cause of FALS type 6. FUS-immunoreactive (ir) inclusions are consistently found in cases of FTLD with BIs, but the association between ALS cases with BIs and FUS accumulation is still not well understood. In this study, we immunohistochemically analyzed the autopsied case of FALS with BIs using anti-FUS antibodies. The case was a 42-year-old woman who developed proximal weakness of the bilateral upper limbs, followed by weakness of other parts including the bulbar regions, and died at age 45. Since this case is a member of a family with FALS harboring the R521C mutation of the FUS gene, she may have carried the same FUS mutation. Histopathologically, neuronal loss was evident in the motor system and other areas including the cuneate nucleus of the medulla oblongata. BIs appeared in the brain stem, cerebellum and anterior horn of the lumbar cord. FUS-ir neuronal cytoplasmic inclusions, glial cytoplasmic inclusions and dystrophic neurites were more abundantly and widely occurring than BIs, especially in the cuneate nucleus and globus pallidus. These findings support the idea that both BIs and FUS-ir structures are pathological hallmarks of a subset of ALS cases.

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.

Frontotemporal dementia and related disorders: deciphering the enigma

In the past century, particularly the last decade, there has been enormous progress in our understanding of frontotemporal dementia, a non-Alzheimer's type dementia. Large clinicopathological series have been published that have clearly demonstrated an overlap between the clinical syndromes subsumed under the term frontotemporal dementia and the progressive supranuclear palsy syndrome, corticobasal syndrome, and motor neuron disease. There have also been significant advancements in brain imaging, neuropathology, and molecular genetics that have led to different approaches to classification. Unfortunately, the field is complicated by a barrage of overlapping clinical syndromes and histopathological diagnoses that does not allow one to easily identify relations between individual clinical syndromic presentations and underlying neuropathology. This review deciphers this web of terminology and highlights consistent, and hence important, associations between individual clinical syndromes and neuropathology. These associations could ultimately allow the identification of appropriate patient phenotypes for future targeted treatments.

Basophilic inclusion body disease and neuronal intermediate filament inclusion disease: a comparative clinicopathological study

While both neuronal intermediate filament inclusion disease (NIFID) and basophilic inclusion body disease (BIBD) show frontotemporal lobar degeneration and/or motor neuron disease, it remains unclear whether, and how, these diseases differ from each other. Here, we compared the clinicopathological characteristics of four BIBD and two NIFID cases. Atypical initial symptoms included weakness, dysarthria, and memory impairment in BIBD, and dysarthria in NIFID. Dementia developed more than 1 year after the onset in some BIBD and NIFID cases. Upper and lower motor neuron signs, parkinsonism, and parietal symptoms were noted in both diseases, and involuntary movements in BIBD. Pathologically, severe caudate atrophy was consistently found in both diseases. Cerebral atrophy was distributed in the convexity of the fronto-parietal region in NIFID cases. In both BIBD and NIFID, the frontotemporal cortex including the precentral gyrus, caudate nucleus, putamen, globus pallidus, thalamus, amygdala, hippocampus including the dentate gyrus, substantia nigra, and pyramidal tract were severely affected, whereas lower motor neuron degeneration was minimal. While alpha-internexin-positive inclusions without cores were found in both NIFID cases, one NIFID case also had alpha-internexin- and neurofilament-negative, but p62-positive, cytoplasmic spherical inclusions with eosinophilic p62-negative cores. These two types of inclusions frequently coexisted in the same neuron. In three BIBD cases, inclusions were tau-, alpha-synuclein-, alpha-internexin-, and neurofilament-negative, but occasionally p62-positive. These findings suggest that: (1) the clinical features and distribution of neuronal loss are similar in BIBD and NIFID, and (2) an unknown protein besides alpha-internexin and neurofilament may play a pivotal pathogenetic role in at least some NIFID cases.

Young-onset sporadic amyotrophic lateral sclerosis: a distinct nosological entity?

There are few reports describing young-onset amyotrophic lateral sclerosis (ALS). Age at onset is a prognostic factor in ALS, and thus it is relevant to investigate the clinical features of very young ALS patients. We describe three young-onset ALS cases and review the literature. SOD1 mutations were not identified. Our cases and 24 others from the literature indicate that young-onset ALS is characterized by slowly progressive symmetrical weakness; nevertheless, progression is variable. Young-onset ALS seems to be a distinct clinical syndrome but its aetiological background is largely unknown.

Golgi apparatus of the motor neurons in patients with amyotrophic lateral sclerosis and in mice models of amyotrophic lateral sclerosis

We examined the Golgi apparatus (GA) of motor neurons of patients with ALS and in mice models of ALS by immunohistological method using antiserum against MG160 and against components of the trans-Golgi network (TGN46). The GA of half of the remaining spinal cord motor neurons of patients with sporadic ALS showed fragmentation, where the GA were dispersed or fragmented into numerous small, isolated elements. The GA of Betz cells in sporadic ALS were fragmented similar to that of anterior horn cells, and the GA of spinal cord motor neurons of those with familial ALS and of those with ALS with basophilic inclusions were fragmented or diminished. The GA in the majority of the motor neurons contained Bunina bodies, basophilic inclusions and superoxide dismutase 1 (SOD1)-positive aggregates were fragmented. The motor neurons in transgenic mice expressing G93A mutation of the SOD1 gene showed the fragmentation of the GA months before the onset of paralysis. These findings suggest that the fragmentation of GA may be related to the neuronal degeneration in patients with ALS.

Frontotemporal and motor neurone degeneration with neurofilament inclusion bodies: additional evidence for overlap between FTD and ALS

We present the case of a patient who had clinical frontal lobe dementia without apparent motor neurone disease (MND), with pathologic findings not typical of any single currently classified frontotemporal degeneration (FTD). At autopsy, the brain had frontal and temporal atrophy with neuronal loss, gliosis, and superficial spongiosis, typical of all FTDs. There were at least three different morphologic types of intracytoplasmic neuronal inclusions in a variety of brain and brainstem regions, including the hippocampal dentate gyrus and pyramidal neurones, the neocortex (in particular, the motor cortex), basal ganglia, thalamus, subthalamic nucleus, basis pontis, and inferior olivary nuclei. Inclusions had the morphologies of Pick-like bodies, pleomorphic inclusions, and hyaline conglomerate (HC)-like inclusions. None of these were positive with tau immunostains. Pick-like bodies in the dentate gyrus were labelled with ubiquitin. The pleomorphic inclusions in the neocortex and dentate gyrus and the HC-like inclusions in the motor and parietal cortex were strongly positive with immunostains for neurofilament. We discuss the differential diagnosis and compare this case with those disorders to which it is most similar. In particular, we compare the unique neurofilament-positive inclusions to the inclusions of FTD-MND, to Pick bodies, and to the basophilic and HC inclusions that are occasionally seen in amytrophic lateral sclerosis (ALS). Although FTD-MND may be found in ALS, the findings in this case may have additional implications for a link between FTD and ALS.

Human spinal motoneurons express low relative abundance of GluR2 mRNA: an implication for excitotoxicity in ALS

AMPA receptor-mediated neurotoxicity is currently the most plausible hypothesis for the etiology of amyotrophic lateral sclerosis (ALS). The mechanism initiating this type of neuronal death is believed to be exaggerated Ca2+-influx through AMPA receptors, which is critically determined by the presence or absence of the glutamate receptor subunit 2 (GluR2) in the assembly. We have provided the first quantitative measurements of the expression profile of AMPA receptor subunits mRNAs in human single neurons by means of quantitative RT-PCR with a laser microdissector. Among the AMPA subunits, GluR2 shared the vast majority throughout the neuronal subsets and tissues examined. Furthermore, both the expression level and the proportion of GluR2 mRNA in motoneurons were the lowest among all neuronal subsets examined, whereas those in motoneurons of ALS did not differ from the control group, implying that selective reduction of the GluR2 subunit cannot be a mechanism of AMPA receptor-mediated neurotoxicity in ALS. However, the low relative abundance of GluR2 might provide spinal motoneurons with conditions that are easily affected by changes of AMPA receptor properties including deficient GluR2 mRNA editing in ALS.

Pathogenesis of axonal dystrophy and demyelination in alphaA-crystallin-expressing transgenic mice

We recently described a transgenic mouse strain overexpressing hamster alphaA-crystallin, a small heat shock protein, under direction of the hamster vimentin promoter. As a result myelin was degraded and axonal dystrophy in both central nervous system (especially spinal cord) and peripheral nervous system occurred. Homozygous transgenic mice developed hind limb paralysis after 8 weeks of age and displayed progressive loss of myelin and axonal dystrophy in both the central and peripheral nervous system with ongoing age. Pathologically the phenotype resembled, to a certain extent, neuroaxonal dystrophy. The biochemical findings presented in this paper (activity of the enzymes superoxide dismutase, catalase and transglutamase, myelin protein zero expression levels and blood sugar levels) confirm this pathology and exclude other putative pathologies like Amyothrophic Lateral Sclerosis and Hereditary Motor and Sensory Neuropathy. Consequently, an excessive cytoplasmic accumulation of the transgenic protein or a disturbance of the normal metabolism are considered to cause the observed neuropathology. Therefore, extra-ocular alphaA-crystallin-expressing transgenic mice may serve as a useful animal model to study neuroaxonal dystrophy.