Oligodendroglial microtubular tangles in olivopontocerebellar atrophy

Current Landscape of Clinical Diagnosis in Multiple System Atrophy: A 15-Year Analysis From 2008 to 2022

BACKGROUND AND OBJECTIVES

Clinical diagnosis of multiple system atrophy (MSA) is challenging. In 2022, new diagnostic criteria for MSA were proposed. We hypothesized that the positive predictive value (PPV) of clinical diagnosis of MSA improved because of advanced diagnostic tools, including brain MRI. This study aimed to understand temporal changes in PPV of MSA.

METHODS

We conducted a retrospective analysis of patients clinically diagnosed with MSA whose brains were examined in the Mayo Clinic brain bank from 2008 to 2022. PPV was compared between 2 periods (2008-2017 and 2018-2022) and successively with a 4-year moving average. PPV for each clinical subtype (parkinsonism type [MSA-P] and cerebellar type [MSA-C]) was assessed.

RESULTS

This study included 321 patients (136 women, age at death 68 ± 9 years) with a clinical diagnosis of MSA. Among them, 225 were pathologically confirmed as MSA, resulting in an overall PPV of 70%. The remaining 30% had alternative pathologic diagnoses including Lewy body disease (18%), progressive supranuclear palsy (4%), cerebrovascular disease (1%), corticobasal degeneration (1%), and others (6%). PPV improved from 63% in 2008-2017 to 78% in 2018-2022 (odds ratio [OR] 2.0 [1.2-3.5], p = 0.005). Linear analysis also demonstrated increased PPV over time (r = 0.66 [0.14-0.89], p = 0.02). Brain MRI scans were more frequently performed in 2018-2022 compared with 2008-2017 (91% vs 80%; OR 2.4 [1.2-5.0], p = 0.012). PPV was higher in patients with brain MRI compared with those without (73% vs 52%; OR 2.5 [1.3-4.9], p = 0.0057). PPV for MSA-C was similar in both groups (87% in 2008-2017 and 93% in 2018-2022), while that for MSA-P improved from 59% in 2008-2017 to 72% in 2018-2022 (OR 1.8 [1.0-3.2], p = 0.04).

DISCUSSION

This study demonstrates an improvement in the PPV of MSA in recent years, potentially attributed to the increased use of brain MRI. Nevertheless, it also highlights that it remains difficult to make a correct diagnosis for some patients based on their clinical presentation. These findings provide a baseline for future clinicopathologic research on MSA.

Role of complement activation and disruption of the blood-brain barrier in the pathogenesis of multiple system atrophy

Multiple system atrophy (MSA) is a progressive and sporadic neurodegenerative disorder characterized by the histological appearance of glial cytoplasmic inclusions primarily composed of α-synuclein. Recently, complement-mediated neuroinflammation has been proposed as a key factor in the pathogenesis of numerous neurodegenerative disorders. We conducted immunohistochemical/immunofluorescent assays targeting a number of complements to explore the role of complements in MSA pathogenesis using brain samples from deceased patients and controls. Complement deposition was notably increased in the cerebral vasculature and myelin sheath in the MSA brains. Furthermore, fibrinogen leakage resulting from the disruption of the blood-brain barrier (BBB) was observed, along with the presence of C1q-positive microglia clusters surrounding the MSA brain vessels. These immunohistochemical/immunofluorescent findings suggest that complement activation and BBB disruption play critical roles in MSA progression.

Neuropathology of Multiple System Atrophy, a Glioneuronal Degenerative Disease

Multiple system atrophy (MSA) is a fatal disease characterized pathologically by the widespread occurrence of aggregated α-synuclein in the oligodendrocytes referred to as glial cytoplasmic inclusions (GCIs). α-Synuclein aggregates are also found in the oligodendroglial nuclei and neuronal cytoplasm and nuclei. It is uncertain whether the primary source of α-synuclein in GCIs is originated from neurons or oligodendrocytes. Accumulating evidence suggests that there are two degenerative processes in this disease. One possibility is that numerous GCIs are associated with the impairment of oligo-myelin-axon-neuron complex, and the other is that neuronal inclusion pathology is also a primary event from the early stage. Both oligodendrocytes and neurons may be primarily affected in MSA, and the damage of one cell type contributes to the degeneration of the other. Vesicle-mediated transport plays a key role in the nuclear translocation of α-synuclein as well as in the formation of glial and neuronal α-synuclein inclusions. Recent studies have shown that impairment of autophagy can occur along with or as a result of α-synuclein accumulation in the brain of MSA and Lewy body disease. Activated autophagy may be implicated in the therapeutic approach for α-synucleinopathies.

Validation Study of the MDS Criteria for the Diagnosis of Multiple System Atrophy in the Mayo Clinic Brain Bank

BACKGROUND AND OBJECTIVE

The second consensus criteria in 2008 have been used in diagnosing multiple system atrophy (MSA). The International Parkinson and Movement Disorder Society (MDS) proposed new diagnostic criteria for MSA in 2022. This study aimed to compare the diagnostic accuracy between these 2 criteria and validate the clinical utility of the newly proposed criteria for MSA.

METHODS

We conducted a retrospective autopsy cohort study of consecutive patients with a clinical or pathologic diagnosis of MSA from the Mayo Clinic brain bank between 1998 and 2021. We studied 352 patients (250 pathologically diagnosed MSA and 102 non-MSA); MDS criteria and the second consensus criteria were applied. The sensitivity, specificity, and area under the curve (AUC) of receiver operating characteristic curves were compared between these criteria. Comparison was conducted between clinical subtypes and among clinically challenging cases (those with different clinical diagnoses or those with suspected but undiagnosed MSA before death). We also used machine learning algorithm, eXtreme Gradient Boosting, to identify clinical features contributing diagnostic performance.

RESULTS

The sensitivity and specificity of clinically established and probable MSA by the MDS criteria were 16% and 99% and 64% and 74%, respectively. The sensitivity and specificity of probable MSA and possible MSA by the second consensus criteria were 72% and 52% and 93% and 21%, respectively. The AUC of MDS clinically probable MSA was the highest (0.69). The diagnostic performance did not differ between clinical subtypes. In clinically challenging cases, MDS clinically established MSA maintained high specificity and MDS clinically probable MSA demonstrated the highest AUC (0.62). MRI findings contributed to high specificity. In addition, combining core clinical features with 2 or more from any of the 13 supporting features and the absence of exclusion criteria also yielded high specificity. Among supporting features, rapid progression was most important for predicting MSA pathology.

DISCUSSION

The MDS criteria showed high specificity with clinically established MSA and moderate sensitivity and specificity with clinically probable MSA. The observation that high specificity could be achieved with clinical features alone suggests that MSA diagnosis with high specificity is possible even in areas where MRI is not readily available.

α-Synuclein Conformational Strains as Drivers of Phenotypic Heterogeneity in Neurodegenerative Diseases

The synucleinopathies, which include Parkinson's disease, dementia with Lewy bodies, and multiple system atrophy, are a class of human neurodegenerative disorders unified by the presence of α-synuclein aggregates in the brain. Considerable clinical and pathological heterogeneity exists within and among the individual synucleinopathies. A potential explanation for this variability is the existence of distinct conformational strains of α-synuclein aggregates that cause different disease manifestations. Like prion strains, α-synuclein strains can be delineated based on their structural architecture, with structural differences among α-synuclein aggregates leading to unique biochemical attributes and neuropathological properties in humans and animal models. Bolstered by recent high-resolution structural data from patient brain-derived material, it has now been firmly established that there are conformational differences among α-synuclein aggregates from different human synucleinopathies. Moreover, recombinant α-synuclein can be polymerized into several structurally distinct aggregates that exhibit unique pathological properties. In this review, we outline the evidence supporting the existence of α-synuclein strains and highlight how they can act as drivers of phenotypic heterogeneity in the human synucleinopathies.

Exploring the mechanism of astragalus membranaceus in the treatment of multiple system atrophy based on network pharmacology and molecular docking

Multiple system atrophy (MSA) is a fatal neurodegenerative disease, it causes functional degradation of multiple organs and systems throughout the body. Astragalus membranaceus (AM), a well-known traditional Chinese medicine, has been used to improve muscle wasting-related disorders for a long history. In this study, we used network pharmacology and molecular docking to predict the mechanism underlying AM for the treatment of MSA. We screened the active compounds of AM and its related targets, as well as the target proteins of MSA. We made a Venn diagram to obtain the intersecting targets and then constructed a protein-protein interaction network to find the core targets and build an active ingredient-target network map. After subjecting the intersecting targets to gene ontology and Kyoto encyclopedia of genes and genomes analysis, the binding ability of core compounds and core target proteins were validated by molecular docking. A total of 20 eligible compounds and 274 intersecting targets were obtained. The core components of treatment are quercetin, kaempferol, and isorhamnetin, and the core targets are TP53, RELA, and TNF. The main biological processes are related to cellular responses and regulation. Molecular functions are mainly associated with apoptosis, inflammation, and tumorigenesis. Molecular docking results show good and standard binding abilities. This study illustrates that AM treats MSA through multiple targets and pathways, and provides a reference for subsequent research.

Understanding the Role of CDH4 in Multiple System Atrophy Brain

BACKGROUND

Multiple system atrophy (MSA) is a rapidly progressive neurodegenerative disease clinically characterized by parkinsonism, cerebellar ataxia, and autonomic dysfunction. A major pathological feature of MSA is the presence of α-synuclein aggregates in oligodendrocytes, the myelinating cells of the central nervous system. A genome-wide association study revealed that the CDH4 gene is associated with MSA. However, virtually nothing is known about the role of CDH4 in the context of MSA.

OBJECTIVE

Our aim was to compare the expression of CDH4 between MSA and control brains, and to investigate its relationship with α-synuclein in oligodendrocytes.

METHODS

RNA and protein were prepared from putamen, motor cortex white matter, cerebellum, and superior occipital cortex tissues collected from MSA (N = 11) and control (N = 13) brains. The expression of CDH4 was measured at mRNA and protein levels by qPCR and western blotting. Oligodendrocyte cells were cultured on plates and transfected with CDH4 cDNA and its impact on α-synuclein was analyzed.

RESULTS

Firstly, we found that CDH4 in MSA brain was significantly elevated in the disease-affected motor cortex white matter in MSA (N = 11) compared to controls (N = 13) and unaltered in the disease-unaffected superior occipital cortex. Secondly, we determined that increases in CDH4 expression caused changes in the cellular levels of α-synuclein in oligodendrocytes.

CONCLUSIONS

When put together, these results provide evidence that support the GWAS association of CDH4 with MSA.

Phosphorylation of Tau at Threonine 231 in Patients With Multiple System Atrophy and in a Mouse Model

Multiple system atrophy (MSA) is a sporadic neurodegenerative disorder pathologically characterized by the presence of glial cytoplasmic inclusions (GCIs). Some MSA patients exhibit motor deficits with accompanying cognitive impairment. Of note, some patients suffering from MSA with longer disease duration have AT8-positive signals, which correspond to phosphorylated tau (P-tau) at 202/205 (P-tau202/205). However, P-tau sites other than the AT8 antibody epitope antibody are less well studied. Here, we focused on the effect of α-synuclein (Syn) expression on the phosphorylation of tau in MSA model mice. Among the 6 kinds of antibodies against P-tau, we confirmed that antibodies against P-tau at 231 (P-tau231) were phospho-specific and found that P-tau231 level was increased in parallel with disease progression in MSA model mice. Additional studies of human brains revealed that P-tau231 was mainly expressed in the temporal cortex in MSA brains and that its expression level was significantly higher in MSA patients than in controls. Immunohistochemical analysis showed that anti-P-tau231-, but not AT8, antibodies mainly immunolabeled hippocampal CA2/3 pyramidal neurons, and some GCIs in MSA. These data suggest that P-tau231 occurs in MSA differently from P-tau202/205.

Macroscopic diagnostic clue for parkinsonism

The neuropathological background of parkinsonism includes various neurodegenerative disorders, including Lewy body disease (LBD), multiple system atrophy (MSA), progressive supranuclear palsy (PSP), and corticobasal degeneration (CBD). The pathological diagnostic procedure begins by assessing the macroscopic findings to evaluate the degenerative lesions in brains with the naked eye. Usually, degenerative lesions show variable atrophy and brownish discoloration in accordance with disease-specific profiles. These macroscopic appearances support neuropathologists in identifying the relevant regions for microscopic examination. The neuropathological diagnosis of parkinsonism is based on regional distribution and fundamental proteinopathies in neurons and glia cells. LBD and MSA are synucleinopathies, and PSP and CBD are tauopathies. Among them, glial-predominant proteinopathy (MSA, PSP, and CBD) may play a significant role in volume reduction. Therefore, macroscopic inspection provides the appropriate direction for assessment. The disease duration, the severity of lesions, and mixed pathologies make the validation of macroscopic observations more complicated. In this review, we outline the macroscopic diagnostic clues in LBD, MSA, PSP, and CBD that could help with pathological refinement.

Clinical and pathological characteristics of later onset multiple system atrophy

BACKGROUND

In the current consensus criteria, onset after age 75 is considered as non-supporting for diagnosis of multiples system atrophy (MSA); however, some MSA patients present after age 75. Clinical and pathological characteristics of such later onset MSA (LO-MSA) compared to usual onset MSA (UO-MSA) remain poorly understood.

METHODS

The clinical cohort included patients from Kobe University Hospital and Amagasaki General Medical Center Hospital, while the autopsy cohort was from the brain bank at Mayo Clinic Florida. We identified 83 patients in the clinical cohort and 193 patients in the autopsy cohort. We divided MSA into two groups according to age at onset: UO-MSA (≤ 75) and LO-MSA (> 75). We compared clinical features and outcomes between the two groups in the clinical cohort and compared the findings to the autopsy cohort.

RESULTS

LO-MSA accounted for 8% in the clinical cohort and 5% in the autopsy cohort. The median time from onset to death or to life-saving tracheostomy was significantly shorter in LO-MSA than in UO-MSA in both cohorts (4.8 vs 7.9 years in the clinical cohort and 3.9 vs 7.5 years in the autopsy cohort; P = 0.043 and P < 0.0001, respectively). The median time from diagnosis to death was less than 3 years in LO-MSA in the clinical cohort.

CONCLUSIONS

Some MSA patients have late age of onset and short survival, limiting time for clinical decision making. MSA should be considered in the differential diagnosis of elderly patients with autonomic symptoms and extrapyramidal and/or cerebellar syndromes.

Simple and clear differentiation of spinocerebellar degenerations: Overview of macroscopic and low-power view findings

Spinocerebellar degenerations (SCDs) are a diverse group of rare and slowly progressive neurological diseases that include spinocerebellar ataxia type 1 (SCA1), SCA2, SCA3, SCA6, SCA7, dentatorubral-pallidoluysian atrophy (DRPLA) and multiple system atrophy (MSA). They are often inherited, and affect the cerebellum and related pathways. The combination of clinical findings and lesion distribution has been the gold-standard for classifying SCDs. This conventional approach has not been very successful in providing a solid framework shared among researchers because their points of views have been quite variable. After identification of genetic abnormalities, classification was overwhelmed by genotyping, replacing the conventional approach far behind. In this review, we describe a stepwise operational approach that we constructed based only on macroscopic findings without microscopy to classify SCDs into three major groups: pure cerebellar type for SCA6 and SCA31; olivopontocerebellar (OPC) type for SCA1, SCA2, SCA7 and MSA; and dentatorubral-pallidoluysian (DRPL) type for SCA1, SCA3, DRPLA and progressive supranuclear palsy (PSP). Spinocerebellar tract involvement distinguishes SCA1 and SCA3 from DRPLA. Degeneration of the internal segment of the pallidum is accentuated in SCA3 and PSP, while degeneration of the external segment is accentuated in SCA1 and DRPLA. These contrasts are helpful in subdividing OPC and DRPL types to predict their genotypes. Lesion distribution represents disease-specific selective vulnerability, which is readily differentiated macroscopically using our stepwise operational approach. Precise prediction of the major genotypes will provide a basis to understand how genetic abnormalities lead to corresponding phenotypes through disease-specific selective vulnerabilities.

Development of α-Synuclein Real-Time Quaking-Induced Conversion as a Diagnostic Method for α-Synucleinopathies

Parkinson’s disease, dementia with Lewy bodies, and multiple system atrophy are characterized by aggregation of abnormal α-synuclein (α-syn) and collectively referred to as α-synucleinopathy. Because these diseases have different prognoses and treatments, it is desirable to diagnose them early and accurately. However, it is difficult to accurately diagnose these diseases by clinical symptoms because symptoms such as muscle rigidity, postural dysreflexia, and dementia sometimes overlap among these diseases. The process of conformational conversion and aggregation of α-syn has been thought similar to that of abnormal prion proteins that cause prion diseases. In recent years, in vitro conversion methods, such as real-time quaking-induced conversion (RT-QuIC), have been developed. This method has succeeded in amplifying and detecting trace amounts of abnormal prion proteins in tissues and central spinal fluid of patients by inducing conversion of recombinant prion proteins via shaking. Additionally, it has been used for antemortem diagnosis of prion diseases. Recently, aggregated α-syn has also been amplified and detected in patients by applying this method and many clinical studies have examined diagnosis using tissues or cerebral spinal fluid from patients. In this review, we discuss the utility and problems of α-syn RT-QuIC for antemortem diagnosis of α-synucleinopathies.

Hippocampal α-synuclein pathology correlates with memory impairment in multiple system atrophy

Recent post-mortem studies reported 22-37% of patients with multiple system atrophy can develop cognitive impairment. With the aim of identifying associations between cognitive impairment including memory impairment and α-synuclein pathology, 148 consecutive patients with pathologically proven multiple system atrophy were reviewed. Among them, 118 (79.7%) were reported to have had normal cognition in life, whereas the remaining 30 (20.3%) developed cognitive impairment. Twelve of them had pure frontal-subcortical dysfunction, defined as the presence of executive dysfunction, impaired processing speed, personality change, disinhibition or stereotypy; six had pure memory impairment; and 12 had both types of impairment. Semi-quantitative analysis of neuronal cytoplasmic inclusions in the hippocampus and parahippocampus revealed a disease duration-related increase in neuronal cytoplasmic inclusions in the dentate gyrus and cornu ammonis regions 1 and 2 of patients with normal cognition. In contrast, such a correlation with disease duration was not found in patients with cognitive impairment. Compared to the patients with normal cognition, patients with memory impairment (pure memory impairment: n = 6; memory impairment + frontal-subcortical dysfunction: n = 12) had more neuronal cytoplasmic inclusions in the dentate gyrus, cornu ammonis regions 1-4 and entorhinal cortex. In the multiple system atrophy mixed pathological subgroup, which equally affects the striatonigral and olivopontocerebellar systems, patients with the same combination of memory impairment developed more neuronal inclusions in the dentate gyrus, cornu ammonis regions 1, 2 and 4, and the subiculum compared to patients with normal cognition. Using patients with normal cognition (n = 18), frontal-subcortical dysfunction (n = 12) and memory impairment + frontal-subcortical dysfunction (n = 18), we further investigated whether neuronal or glial cytoplasmic inclusions in the prefrontal, temporal and cingulate cortices or the underlying white matter might affect cognitive impairment in patients with multiple system atrophy. We also examined topographic correlates of frontal-subcortical dysfunction with other clinical symptoms. Although no differences in neuronal or glial cytoplasmic inclusions were identified between the groups in the regions examined, frontal release signs were found more commonly when patients developed frontal-subcortical dysfunction, indicating the involvement of the frontal-subcortical circuit in the pathogenesis of frontal-subcortical dysfunction. Here, investigating cognitive impairment in the largest number of pathologically proven multiple system atrophy cases described to date, we provide evidence that neuronal cytoplasmic inclusion burden in the hippocampus and parahippocampus is associated with the occurrence of memory impairment in multiple system atrophy. Further investigation is necessary to identify the underlying pathological basis of frontal-subcortical dysfunction in multiple system atrophy.

Therapeutic antisense oligonucleotides for movement disorders

Movement disorders are a group of neurological conditions characterized by abnormalities of movement and posture. They are broadly divided into akinetic and hyperkinetic syndromes. Until now, no effective symptomatic or disease-modifying therapies have been available. However, since many of these disorders are monogenic or have some well-defined genetic component, they represent strong candidates for antisense oligonucleotide (ASO) therapies. ASO therapies are based on the use of short synthetic single-stranded ASOs that bind to disease-related target RNAs via Watson-Crick base-pairing and pleiotropically modulate their function. With information arising from the RNA sequence alone, it is possible to design ASOs that not only alter the expression levels but also the splicing defects of any protein, far exceeding the intervention repertoire of traditional small molecule approaches. Following the regulatory approval of ASO therapies for spinal muscular atrophy and Duchenne muscular dystrophy in 2016, there has been tremendous momentum in testing such therapies for other neurological disorders. This review article initially focuses on the chemical modifications aimed at improving ASO effectiveness, the mechanisms by which ASOs can interfere with RNA function, delivery systems and pharmacokinetics, and the common set of toxicities associated with their application. It, then, describes the pathophysiology and the latest information on preclinical and clinical trials utilizing ASOs for the treatment of Parkinson's disease, Huntington's disease, and ataxias 1, 2, 3, and 7. It concludes with issues that require special attention to realize the full potential of ASO-based therapies.

Shared Metabolic Profile of Caffeine in Parkinsonian Disorders

Objective

The objective of this study was to determine comprehensive metabolic changes of caffeine in the serum of patients with parkinsonian disorders including Parkinson's disease (PD), progressive supranuclear palsy (PSP), and multiple system atrophy (MSA) and to compare this with healthy control serum.

Methods

Serum levels of caffeine and its 11 downstream metabolites from independent double cohorts consisting of PD (n = 111, 160), PSP (n = 30, 19), MSA (n = 23, 17), and healthy controls (n = 43, 31) were examined by liquid chromatography–mass spectrometry. The association of each metabolite with clinical parameters and medication was investigated. Mutations in caffeine‐associated genes were investigated by direct sequencing.

Results

A total of 9 metabolites detected in more than 50% of participants in both cohorts were decreased in 3 parkinsonian disorders compared with healthy controls without any significant association with age at sampling, sex, or disease severity (Hoehn and Yahr stage and Unified Parkinson's Disease Rating Scale motor section) in PD, and levodopa dose or levodopa equivalent dose in PSP and MSA. Of the 9 detected metabolites, 8 in PD, 5 in PSP, and 3 in MSA were significantly decreased in both cohorts even after normalizing to daily caffeine consumption. No significant genetic variations in CYP1A2 or CYP2E1 were detected when compared with controls.

Conclusion

Serum caffeine metabolic profiles in 3 parkinsonian diseases show a high level of overlap, indicative of a common potential mechanism such as caffeine malabsorption from the small intestine, hypermetabolism, increased clearance of caffeine, and/or reduced caffeine consumption. © 2020 The Authors. Movement Disorders published by Wiley Periodicals, Inc. on behalf of International Parkinson and Movement Disorder Society.

Cross-examining candidate genes implicated in multiple system atrophy

Multiple system atrophy (MSA) is a devastating neurodegenerative disease characterized by the clinical triad of parkinsonism, cerebellar ataxia and autonomic failure, impacting on striatonigral, olivopontocerebellar and autonomic systems. At early stage of the disease, the clinical symptoms of MSA can overlap with those of Parkinson's disease (PD). The key pathological hallmark of MSA is the presence of glial cytoplasmic inclusions (GCI) in oligodendrocytes. GCI comprise insoluble proteinaceous filaments composed chiefly of α-synuclein aggregates, and therefore MSA is regarded as an α-synucleinopathy along with PD and dementia with Lewy bodies. The etiology of MSA is unknown, and the pathogenesis of MSA is still largely speculative. Much data suggests that MSA is a sporadic disease, although some emerging evidence suggests rare genetic variants increase susceptibility. Currently, there is no general consensus on the susceptibility genes as there have been differences due to geographical distribution or ethnicity. Furthermore, many of the reported studies have been conducted on patients that were only clinically diagnosed without pathological verification. The purpose of this review is to bring together available evidence to cross-examine the susceptibility genes and genetic pathomechanisms implicated in MSA. We explore the possible involvement of the SNCA, COQ2, MAPT, GBA1, LRRK2 and C9orf72 genes in MSA pathogenesis, highlight the under-explored areas of MSA genetics, and discuss future directions of research in MSA.

Clinical and Imaging Features of Multiple System Atrophy: Challenges for an Early and Clinically Definitive Diagnosis

Multiple system atrophy (MSA) is an adult-onset, progressive neurodegenerative disorder. Patients with MSA show various phenotypes during the course of their illness, including parkinsonism, cerebellar ataxia, autonomic failure, and pyramidal signs. Patients with MSA sometimes present with isolated autonomic failure or motor symptoms/ signs. The median duration from onset to the concomitant appearance of motor and autonomic symptoms is approximately 2 years but can range up to 14 years. As the presence of both motor and autonomic symptoms is essential for the current diagnostic criteria, early diagnosis is difficult when patients present with isolated autonomic failure or motor symptoms/signs. In contrast, patients with MSA may show severe autonomic failure and die before the presentation of motor symptoms/signs, which are currently required for the diagnosis of MSA. Recent studies have also revealed that patients with MSA may show nonsupporting features of MSA such as dementia, hallucinations, and vertical gaze palsy. To establish early diagnostic criteria and clinically definitive categorization for the successful development of disease-modifying therapy or symptomatic interventions for MSA, research should focus on the isolated phase and atypical symptoms to develop specific clinical, imaging, and fluid biomarkers that satisfy the requirements for objectivity, for semi- or quantitative measurements, and for uncomplicated, worldwide availability. Several novel techniques, such as automated compartmentalization of the brain into multiple parcels for the quantification of gray and white matter volumes on an individual basis and the visualization of α-synuclein and other candidate serum and cerebrospinal fluid biomarkers, may be promising for the early and clinically definitive diagnosis of MSA.

A case of multiple system atrophy-parkinsonian type with stuttering- and palilalia-like dysfluencies and putaminal atrophy

Both developmental and acquired stuttering are related to the function of the basal ganglia-thalamocortical loop, which includes the putamen. Here, we present a case of stuttering- and palilalia-like dysfluencies that manifested as an early symptom of multiple system atrophy-parkinsonian type (MSA-P) and bilateral atrophy of the putamen. The patient was a 72-year-old man with no history of developmental stuttering who presented with a stutter for consultation with our otorhinolaryngology department. The patient was diagnosed with MSA-P based on parkinsonism, autonomic dysfunction, and bilateral putaminal atrophy revealed by T2-weighted magnetic resonance imaging. Treatment with levodopa improved both the motor functional deficits related to MSA-P and stuttering-like dysfluencies while reading; however, the palilalia-like dysfluencies were much less responsive to levodopa therapy. The patient died of aspiration pneumonia two years after his first consultation at our hospital. In conclusion, adult-onset stuttering- and palilalia-like dysfluencies warrant careful examination of the basal ganglia-thalamocortical loop, and especially the putamen, using neuroimaging techniques. Acquired stuttering may be related to deficits in dopaminergic function.

Corpus callosal involvement is correlated with cognitive impairment in multiple system atrophy

OBJECTIVE

We examined the anatomical involvement related to cognitive impairment in patients with multiple system atrophy (MSA).

METHODS

We examined 30 patients with probable MSA and 15 healthy controls. All MSA patients were assessed by the Unified MSA-Rating scale and Addenbrooke's Cognitive Examination-Revised (ACE-R). We classified 15 MSA patients with ACE-R scores > 88 as having normal cognition (MSA-NC) and 15 with scores ≤ 88 as having cognitive impairment (MSA-CI). All subjects underwent 3 T MRI scanning and were investigated using voxel-based morphometry and diffusion tensor imaging.

RESULTS

Both the MSA-NC and MSA-CI patients exhibited cerebellar but not cerebral atrophy in voxel-based morphometry compared to controls. In contrast, tract-based spatial statistics revealed widespread and significantly decreased fractional anisotropy (FA) values, as well as increased mean diffusivity, radial diffusivity, and axial diffusivity in both the cerebrum and cerebellum in MSA-CI patients compared to controls. MSA-NC patients also exhibited similar involvement of the cerebellum but less extensive involvement of the cerebrum compared with the MSA-CI patients. In particular, FA values in MSA-CI patients were significantly decreased in the anterior part of the left corpus callosum compared with those in MSA-NC patients. The mean FA values in the left anterior part of the corpus callosum were significantly correlated with total ACE-R scores and subscores (memory, fluency, and language) in MSA patients.

CONCLUSIONS

Decreased FA values in the anterior corpus callosum showed a significant correlation with cognitive impairment in MSA.

A diagnostic decision tree for adult cerebellar ataxia based on pontine magnetic resonance imaging

Cerebellar ataxias (CAs) are heterogeneous conditions often require differential diagnosis. This study aimed to establish a diagnostic decision tree for differentiating CAs based on pontine MRI findings. Two-hundred and two consecutive ataxia patients were clinically classified into 4 groups: (1) spinocerebellar ataxia (SCA) with brainstem involvement (SCA-BSI), (2) Pure cerebellar SCA, (3) cerebellar dominant multiple system atrophy (MSA-c), and (4) Other CA. Signal intensity in pons was graded into 3 types: hot cross bun sign (HCBS), pontine midline linear T2-hyperintensity (PMH), or normal. The distance ratio of pontine base to tegmentum, named "BT-ratio", was measured. The presence of HCBS indicated either MSA-c with a specificity of 97.7%, or SCA2. When PMH was observed, a BT-ratio above 3.54 strongly indicated SCA-BSI, namely Machado-Joseph disease, SCA1, or dentatorubral-pallidoluysian atrophy, whereas a BT-ratio below 3.54 indicated MSA-c or SCA2. When the signal intensity was normal, a BT-ratio above 3.52 indicated SCA-BSI, whereas a BT-ratio below 3.52 suggested Pure cerebellar SCA or Other CA with pure cerebellar type. The decision tree was confirmed useful in a different 30 CA patients. We propose that differential diagnosis of CAs can be supported by combining pontine MRI signal intensity changes and BT-ratio.

AMBRA1, a novel α-synuclein-binding protein, is implicated in the pathogenesis of multiple system atrophy

The accumulation of abnormal α-synuclein is the major histopathological feature of Lewy body disease and multiple system atrophy (MSA), which are referred to as synucleinopathies. Cytoplasmic degradation systems, such as the autophagy-lysosome and proteasome pathways, are involved in their pathogenesis. Autophagy is tightly regulated by several upstream proteins including UNC-51-like kinase 1/2, beclin1, vacuolar protein sorting-associated protein 34 and autophagy/beclin1 regulator 1 (AMBRA1). Recently, we revealed that both cortical and brainstem-type Lewy bodies were immunopositive for several upstream proteins of autophagy. Therefore, we conducted the present study to elucidate the role of upstream proteins of autophagy in the pathogenesis of MSA. Pathological and biochemical analyses using human brain samples revealed that AMBRA1 is a component of the pathological hallmarks of MSA and upstream proteins of autophagy are impaired in the MSA brain. In vitro and in vivo analyses revealed a ninefold stronger affinity of AMBRA1 with α-synuclein phosphorylated at serine 129 compared with non-phosphorylated α-synuclein. Furthermore, a weak but significant correlation between AMBRA1 overexpression and reduction of abnormal α-synuclein was observed. Silencing AMBRA1 function caused aggregates of α-synuclein in the cytoplasm of mouse primary cultured neurons, which was simulated by the treatment of Bafilomycin, an autophagy inhibitor. Our results demonstrated for the first time that AMBRA1 is a novel hub binding protein of α-synuclein and plays a central role in the pathogenesis of MSA through the degradative dynamics of α-synuclein. These results raise the possibility that molecular modulation targeting AMBRA1 can be a promising candidate for the treatment of synucleinopathies.

Activated caspase-9 immunoreactivity in glial and neuronal cytoplasmic inclusions in multiple system atrophy

The mitochondria play an important role in apoptotic cell death, and the released cytochrome c from the mitochondria promotes the formation of the apoptosome, which contains cytochrome c, Apaf-1 and caspase-9, resulting in the activation of caspase-9 and the promotion of the apoptotic cascade. To investigate the role of mitochondria-dependent apoptotic cell death in patients with multiple system atrophy (MSA), we performed immunohistochemical studies on apoptosome-related proteins in formalin-fixed, paraffin-embedded sections from 8 normal subjects and 10 patients with MSA. We then performed double-labeling immunohistochemistry for activated caspase-9 and α-synuclein in some sections from 10 patients with MSA. In the brains with MSA, glial cytoplasmic inclusions (GCIs) and neuronal cytoplasmic inclusions (NCIs) were intensely immunoreactive for cytochrome c, Apaf-1 and caspase-9. Activated caspase-9 immunoreactivities were also confirmed to be densely localized to both GCIs and NCIs using two types of anti-cleaved caspase-9 antibodies. The semiquantitative analyses using the upper pontine sections double-immunostained with cleaved caspase-9 and α-synuclein demonstrated that approximately 80% of GCIs and NCIs were immunopositive for cleaved caspase-9. Our results suggest that the formation of the apoptosome accompanied by the activation of caspase-9 may occur in brains affected by MSA, and that a mitochondria-dependent apoptotic pathway may be partially associated with the pathogenesis of MSA.

Accumulation of phosphorylated α-synuclein in subpial and periventricular astrocytes in multiple system atrophy of long duration

The histological hallmark of multiple system atrophy (MSA) is accumulation of phosphorylated α-synuclein in oligodendrocytes. However, it is uncertain whether phosphorylated α-synuclein accumulates in astrocytes of MSA patients. We immunohistochemically examined the frontal and temporal lobes, basal ganglia, cerebellum, brainstem and spinal cord of patients with MSA (n = 15) and Lewy body disease (n = 20), and also in control subjects (n = 20). Accumulation of abnormally phosphorylated and aggregated α-synuclein was found in subpial and periventricular astrocytes in six of the 15 patients with MSA (40%). The structures were confined to the subpial surface of the ventro-lateral part of the spinal cord and brainstem, as well as the subependymal region of the lateral ventricles. They were not visualized by Gallyas-Braak staining, and were immunonegative for ubiquitin and p62. Immunoelectron microscopy revealed that the phosphorylated α-synuclein-immunoreactive structures in astrocytes were non-fibrillar and associated with granular and vesicular structures. The extent of phosphorylated α-synuclein-immunoreactive astrocytes was correlated with disease duration. No such structures were found in Lewy body disease or controls. Accumulation of phosphorylated α-synuclein can occur in subpial and periventricular astrocytes in patients with MSA, especially in those with a long disease duration.

Filamentous aggregations of phosphorylated α-synuclein in Schwann cells (Schwann cell cytoplasmic inclusions) in multiple system atrophy

BACKGROUND

The histological hallmark of multiple system atrophy (MSA) is the presence of filamentous aggregations of phosphorylated α-synuclein in oligodendrocytes, referred to as glial cytoplasmic inclusions (GCIs). Although GCIs can occur widely in the central nervous system, accumulation of phosphorylated α-synuclein in Schwann cells has not been reported in MSA. We immunohistochemically examined the cranial and spinal nerves, peripheral ganglia and visceral autonomic nervous system of patients with MSA (n = 14) and control subjects (n = 20).

RESULTS

In MSA, accumulation of phosphorylated α-synuclein was found in the cytoplasm of Schwann cells. These Schwann cell cytoplasmic inclusions (SCCIs) were also immunopositive for ubiquitin and p62. SCCIs were found in 12 of 14 patients with MSA (85.7 %). They were most frequent in the anterior nerve of the sacral cord and, to a lesser extent, in the cranial nerves (oculomotor, glossopharyngeal-vagus and hypoglossal nerves), and spinal and sympathetic ganglia. SCCIs were rarely found in the visceral organs. Immunoelectron microscopy demonstrated that the SCCIs consisted of abnormal filaments, 15-20 nm in diameter. No such inclusions were found in controls.

CONCLUSION

The present findings indicate that Schwann cells are also involved in the disease process of MSA.

Variants associated with Gaucher disease in multiple system atrophy

OBJECTIVE

Glucocerebrosidase gene (GBA) variants that cause Gaucher disease are associated with Parkinson disease (PD) and dementia with Lewy bodies (DLB). To investigate the role of GBA variants in multiple system atrophy (MSA), we analyzed GBA variants in a large case-control series.

METHODS

We sequenced coding regions and flanking splice sites of GBA in 969 MSA patients (574 Japanese, 223 European, and 172 North American) and 1509 control subjects (900 Japanese, 315 European, and 294 North American). We focused solely on Gaucher-disease-causing GBA variants.

RESULTS

In the Japanese series, we found nine carriers among the MSA patients (1.65%) and eight carriers among the control subjects (0.89%). In the European series, we found three carriers among the MSA patients (1.35%) and two carriers among the control subjects (0.63%). In the North American series, we found five carriers among the MSA patients (2.91%) and one carrier among the control subjects (0.34%). Subjecting each series to a Mantel-Haenszel analysis yielded a pooled odds ratio (OR) of 2.44 (95% confidence interval [CI], 1.14-5.21) and a P-value of 0.029 without evidence of significant heterogeneity. Logistic regression analysis yielded similar results, with an adjusted OR of 2.43 (95% CI 1.15-5.37) and a P-value of 0.022. Subtype analysis showed that Gaucher-disease-causing GBA variants are significantly associated with MSA cerebellar subtype (MSA-C) patients (P = 7.3 × 10(-3)).

INTERPRETATION

The findings indicate that, as in PD and DLB, Gaucher-disease-causing GBA variants are associated with MSA.

Relocation of p25α/tubulin polymerization promoting protein from the nucleus to the perinuclear cytoplasm in the oligodendroglia of sporadic and COQ2 mutant multiple system atrophy

p25α/tubulin polymerization promoting protein (TPPP) is an oligodendroglial protein that plays crucial roles including myelination, and the stabilization of microtubules. In multiple system atrophy (MSA), TPPP is suggested to relocate from the myelin sheath to the oligodendroglial cell body, before the formation of glial cytoplasmic inclusions (GCIs), the pathologic hallmark of MSA. However, much is left unknown about the re-distribution of TPPP in MSA. We generated new antibodies against the N- and C-terminus of TPPP, and analyzed control and MSA brains, including the brain of a familial MSA patient carrying homozygous mutations in the coenzyme Q2 gene (COQ2). In control brain tissues, TPPP was localized not only in the cytoplasmic component of the oligodendroglia including perinuclear cytoplasm and peripheral processes in the white matter, but also in the nucleus of a fraction (62.4%) of oligodendroglial cells. Immunoelectron microscopic analysis showed TPPP in the nucleus and mitochondrial membrane of normal oligodendroglia, while western blot also supported its nuclear and mitochondrial existence. In MSA, the prevalence of nuclear TPPP was 48.6% in the oligodendroglia lacking GCIs, whereas it was further decreased to 19.6% in the oligodendroglia with phosphorylated α-synuclein (pα-syn)-positive GCIs, both showing a significant decrease compared to controls (62.4%). In contrast, TPPP accumulated in the perinuclear cytoplasm where mitochondrial membrane (TOM20 and cytochrome C) and fission (DRP1) proteins were often immunoreactive. We conclude that in MSA-oligodendroglia, TPPP is reduced, not only in the peripheral cytoplasm, but also in the nucleus and relocated to the perinuclear cytoplasm.

Genomic aspects of sporadic neurodegenerative diseases

Sporadic neurodegenerative diseases are complex in nature, that is, they involve multiple genetic and environmental factors that may play roles at the molecular level. In contrast to diseases with Mendelian inheritance, the genomic signatures of common sporadic forms of neurodegenerative diseases largely remain unknown. Over the past decade, genome-wide association studies employing common single-nucleotide polymorphisms have been intensively conducted, in which the theoretical framework is based on the "common disease-common variants" hypothesis. Another paradigm is a sequence-based association study under the "common disease-multiple rare variants" hypothesis. Because current next-generation sequencing technologies enable us to obtain virtually all the variants in human genome irrespective of allele frequencies, it is anticipated that sequence-based association studies will become the mainstream approach. In this review, we present brief overviews of molecular genetic approaches to elucidate the molecular bases of sporadic forms of neurodegenerative diseases, including Alzheimer disease, Parkinson disease, and multiple system atrophy as examples.

[Cellular pathology of neurodegenerative disorders]

Common cellular and molecular mechanisms including protein aggregation and inclusion body formation are involved in many neurodegenerative diseases. α-Synuclein is a major component of Lewy bodies in Parkinson's disease (PD) as well as in glial cytoplasmic inclusions in multiple system atrophy (MSA). Tau is a principal component of neurofibrillary and glial tangles in tauopathies. Recently, TDP-43 was identified as a component of ubiquitinated inclusions in amyotrophic lateral sclerosis and frontotemporal lobar degeneration. PD is traditionally considered a movement disorder with hallmark lesions in the brainstem pigmented nuclei. However, pathological changes occur in widespread regions of the central and peripheral nervous systems in this disease. Furthermore, primary glial involvement ("gliodegeneration") can be observed in PD and MSA as well as in tauopathy. The present article reviews abnormal protein accumulation and inclusion body formation inside and outside the central nervous system.

Application of diffusion tensor imaging in multiple system atrophy: the involvement of pontine transverse and longitudinal fibers

PURPOSE

Many studies have demonstrated the degeneration of pontine transverse and longitudinal tracts in multiple system atrophy (MSA). One purpose of this study was to assess whether diffusion tensor imaging (DTI) can show microstructural abnormalities in these tracts in patients with MSA cerebellar type (MSA-C). Another purpose was to determine the correlation between cross sign progress and pontine fiber degeneration in these patients.

MATERIALS AND METHODS

Thirty patients with MSA-C and 30 healthy volunteers underwent conventional magnetic resonance imaging (MRI) and DTI. Regions of interest were placed in both cerebral peduncles, the posterior limbs of the internal capsule and the pontine crossing tract of each subject. Quantitative indexes such as fractional anisotropy (FA) and mean diffusivity (MD) were compared between groups by analysis of variance. Cross sign was divided into three grades as follows: 0, no cross sign; 1, vertical line only; 2, clear cross sign. Spearman rank correlation analysis was used between FA, MD, and the cross grade in patients with MSA-C.

RESULTS

FA and MD in the MSA-C group, and each cross grade, showed statistically significant differences compared to control groups. There was a close correlation between all measures. FA decreased and MD increased, and cross grade formed gradually in the patients.

CONCLUSION

DTI can identify microstructural abnormalities in pontine transverse and longitudinal fibers even in patients without abnormalities on conventional MRI. Along with pontine transverse tract degeneration, the cross sign develops accompanied by the start of longitudinal tract degeneration, ultimately resulting in the complete formation of a cross sign.

Towards translational therapies for multiple system atrophy

Multiple system atrophy (MSA) is a fatal adult-onset neurodegenerative disorder of uncertain etiopathogenesis manifesting with autonomic failure, parkinsonism, and ataxia in any combination. The underlying neuropathology affects central autonomic, striatonigral and olivopontocerebellar pathways and it is associated with distinctive glial cytoplasmic inclusions (GCIs, Papp-Lantos bodies) that contain aggregates of α-synuclein. Current treatment options are very limited and mainly focused on symptomatic relief, whereas disease modifying options are lacking. Despite extensive testing, no neuroprotective drug treatment has been identified up to now; however, a neurorestorative approach utilizing autologous mesenchymal stem cells has shown remarkable beneficial effects in the cerebellar variant of MSA. Here, we review the progress made over the last decade in defining pathogenic targets in MSA and summarize insights gained from candidate disease-modifying interventions that have utilized a variety of well-established preclinical MSA models. We also discuss the current limitations that our field faces and suggest solutions for possible approaches in cause-directed therapies of MSA.

Neuroprotective function of 14-3-3 proteins in neurodegeneration

14-3-3 proteins are abundantly expressed adaptor proteins that interact with a vast number of binding partners to regulate their cellular localization and function. They regulate substrate function in a number of ways including protection from dephosphorylation, regulation of enzyme activity, formation of ternary complexes and sequestration. The diversity of 14-3-3 interacting partners thus enables 14-3-3 proteins to impact a wide variety of cellular and physiological processes. 14-3-3 proteins are broadly expressed in the brain, and clinical and experimental studies have implicated 14-3-3 proteins in neurodegenerative disease. A recurring theme is that 14-3-3 proteins play important roles in pathogenesis through regulating the subcellular localization of target proteins. Here, we review the evidence that 14-3-3 proteins regulate aspects of neurodegenerative disease with a focus on their protective roles against neurodegeneration.

Mutations in COQ2 in familial and sporadic multiple-system atrophy

BACKGROUND

Multiple-system atrophy is an intractable neurodegenerative disease characterized by autonomic failure in addition to various combinations of parkinsonism, cerebellar ataxia, and pyramidal dysfunction. Although multiple-system atrophy is widely considered to be a nongenetic disorder, we previously identified multiplex families with this disease, which indicates the involvement of genetic components.

METHODS

In combination with linkage analysis, we performed whole-genome sequencing of a sample obtained from a member of a multiplex family in whom multiple-system atrophy had been diagnosed on autopsy. We also performed mutational analysis of samples from members of five other multiplex families and from a Japanese series (363 patients and two sets of controls, one of 520 persons and one of 2383 persons), a European series (223 patients and 315 controls), and a North American series (172 patients and 294 controls). On the basis of these analyses, we used a yeast complementation assay and measured enzyme activity of parahydroxybenzoate-polyprenyl transferase. This enzyme is encoded by the gene COQ2 and is essential for the biosynthesis of coenzyme Q10. Levels of coenzyme Q10 in lymphoblastoid cells and brain tissue were measured on high-performance liquid chromatography.

RESULTS

We identified a homozygous mutation (M78V-V343A/M78V-V343A) and compound heterozygous mutations (R337X/V343A) in COQ2 in two multiplex families. Furthermore, we found that a common variant (V343A) and multiple rare variants in COQ2, all of which are functionally impaired, are associated with sporadic multiple-system atrophy. The V343A variant was exclusively observed in the Japanese population.

CONCLUSIONS

Functionally impaired variants of COQ2 were associated with an increased risk of multiple-system atrophy in multiplex families and patients with sporadic disease, providing evidence of a role of impaired COQ2 activities in the pathogenesis of this disease. (Funded by the Japan Society for the Promotion of Science and others.).

Loss of DARPP-32 and calbindin in multiple system atrophy

We evaluated the immunohistochemical intensities of α-synuclein, phosphorylated α-synuclein (p-syn), dopamine- and cAMP-regulated phosphoprotein of 32 kDa (DARPP-32), calbindin-D 28k, calpain-cleaved carboxy-terminal 150-kDa spectrin fragment, and tyrosine hydroxylase in multiple system atrophy (MSA). The caudate head, anterior putamen, posterior putamen, substantia nigra, pontine nucleus, and cerebellar cortex from six MSA brains, six age-matched disease control brains (amyotrophic lateral sclerosis), and five control brains were processed for immunostaining by standard methods. Immunostaining for α-synuclein, p-syn, or both was increased in all areas examined in oligodendrocytes in MSA. Immunostaining for DARPP-32 and calbindin-D 28k was most prominently decreased in the posterior putamen, where neuronal loss was most prominent. Immunostaining for DARPP-32 and calbindin-D 28k was also diminished in the anterior putamen and caudate head, where neuronal loss was less prominent or absent. Calbindin immunostaining was also decreased in the dorsal tier of the substantia nigra and cerebellar cortex. Loss of immunostaining for DARPP-32 and calbindin-D 28k compared with that of neurons indicates calcium toxicity and disturbance of the phosphorylated state of proteins as relatively early events in the pathogenesis of MSA.

The prion hypothesis in Parkinson's disease: Braak to the future

Parkinson’s disease (PD) is a progressive neurodegenerative disorder typified by the presence of intraneuronal inclusions containing aggregated alpha synuclein (αsyn). The progression of parkinsonian pathology and clinical phenotype has been broadly demonstrated to follow a specific pattern, most notably described by Braak and colleagues. In more recent times it has been hypothesized that αsyn itself may be a critical factor in mediating transmission of disease pathology from one brain area to another. Here we investigate the growing body of evidence demonstrating the ability of αsyn to spread transcellularly and induce pathological aggregation affecting neurons by permissive templating and provide a critical analysis of some irregularities in the hypothesis that the progression of PD pathology may be mediated by such a prion-like process. Finally we discuss some key questions that remain unanswered which are vital to determining the potential contribution of a prion-like process to the pathogenesis of PD.

An autopsy case of preclinical multiple system atrophy (MSA-C)

Multiple system atrophy (MSA) is divided into two clinical subtypes: MSA with predominant parkinsonian features (MSA-P) and MSA with predominant cerebellar dysfunction (MSA-C). We report a 71-year-old Japanese man without clinical signs of MSA, in whom post mortem examination revealed only slight gliosis in the pontine base and widespread occurrence of glial cytoplasmic inclusions in the central nervous system, with the greatest abundance in the pontine base and cerebellar white matter. Neuronal cytoplasmic inclusions (NCIs) and neuronal nuclear inclusions (NNIs) were almost restricted to the pontine and inferior olivary nuclei. It was noteworthy that most NCIs were located in the perinuclear area, and the majority of NNIs were observed adjacent to the inner surface of the nuclear membrane. To our knowledge, only four autopsy cases of preclinical MSA have been reported previously, in which neuronal loss was almost entirely restricted to the substantia nigra and/or putamen. Therefore, the present autopsy case of preclinical MSA-C is considered to be the first of its kind to have been reported. The histopathological features observed in preclinical MSA may represent the early pattern of MSA pathology.

Immunohistochemical localization of aggresomal proteins in glial cytoplasmic inclusions in multiple system atrophy

AIMS

Multiple system atrophy (MSA) is pathologically characterized by the formation of α-synuclein-containing glial cytoplasmic inclusions (GCIs) in oligodendrocytes. However, the mechanisms of GCI formation are not fully understood. Cellular machinery for the formation of aggresomes has been linked to the biogenesis of the Lewy body, a characteristic α-synuclein-containing inclusion of Parkinson's disease and dementia with Lewy bodies. Here, we examined whether GCIs contain the components of aggresomes by immunohistochemistry.

METHODS

Sections from five patients with MSA were stained immunohistochemically with antibodies against aggresome-related proteins and analysed in comparison with sections from five patients with no neurological disease. We evaluated the presence or absence of aggresome-related proteins in GCIs by double immunofluorescence and immunoelectron microscopy.

RESULTS

GCIs were clearly immunolabelled with antibodies against aggresome-related proteins, such as γ-tubulin, histone deacetylase 6 (HDAC6) and 20S proteasome subunits. Neuronal cytoplasmic inclusions (NCIs) were also immunopositive for these aggresome-related proteins. Double immunofluorescence staining and quantitative analysis demonstrated that the majority of GCIs contained these proteins, as well as other aggresome-related proteins, such as Hsp70, Hsp90 and 62-kDa protein/sequestosome 1 (p62/SQSTM1). Immunoelectron microscopy demonstrated immunoreactivities for γ-tubulin and HDAC6 along the fibrils comprising GCIs.

CONCLUSIONS

Our results indicate that GCIs, and probably NCIs, share at least some characteristics with aggresomes in terms of their protein components. Therefore, GCIs and NCIs may be another manifestation of aggresome-related inclusion bodies observed in neurodegenerative diseases.

Localization of CHMP2B-immunoreactivity in the brainstem of Lewy body disease

Alpha-synuclein (αS) is one of the major constituents of Lewy bodies (LBs). Several lines of evidence suggest that the autophagy-lysosome pathway (ALP) is involved in the removal of αS. We have previously reported that granulovacuolar degeneration (GVD) in neurons involved a subunit of the endosomal sorting complexes required for transport (ESCRT). In this study, we examined the association between alpha-synucleinopathy and autophagy through immunohistochemical analysis of charged multivesicular body protein 2B (CHMP2B), a component of the ESCRT-pathway. We examined the brainstems of 17 patients with Parkinson's disease (PD), incidental Lewy body disease (ILBD), multiple system atrophy (MSA), and Alzheimer's disease (AD) immunohistochemically using antibodies against phosphorylated αS (pαS), phosphorylated tau and CHMP2B. LBs and a proportion of glial cytoplasmic inclusions (GCIs) were immunopositive for pαS and CHMP2B. Neurons containing CHMP2B-immunoreactive granules were detected in PD and ILBD, but not in MSA and AD brains. CHMP2B immunoreactivity was increased in the dorsal motor nucleus of the vagus nerve (DMNX) in PD and ILBD brains, relative to that in MSA and AD. These findings indicate that the ESCRT-pathway is implicated in the formation of αS inclusions, especially in PD and ILBD.

[Multiple system atrophy - synuclein and neuronal degeneration]

Multiple system atrophy (MSA) is a sporadic neurodegenerative disorder that encompasses olivopontocerebellar atrophy (OPCA), striatonigral degeneration (SND) and Shy-Drager syndrome (SDS). The histopathological hallmarks are α-synuclein (AS) positive glial cytoplasmic inclusions (GCIs) in oligodendroglias. AS aggregation is also found in glial nuclear inclusions (GNIs), neuronal cytoplasmic inclusions (NCIs), neuronal nuclear inclusions (NNIs) and dystrophic neurties. Reviewing the pathological features of 102 MSA cases, OPCA-type was relatively more frequent and SND-type was less frequent in Japanese MSA cases, which suggested different phenotypic pattern of MSA might exist between races, compared to the relatively high frequency of SND-type in western countries. In early stage of MSA, NNIs, NCIs and diffuse homogenous stain of AS in neuronal nuclei and cytoplasm were observed in various vulnerable lesions including the pontine nuclei, putamen, substantia nigra, locus ceruleus, inferior olivary nucleus, intermediolateral column of thoracic cord, lower motor neurons and cortical pyramidal neurons, in additions to GCIs. These findings indicated that the primary nonfibrillar and fibrillar AS aggregation also occurred in neurons. Therefore both the direct involvement of neurons themselves and the oligodendroglia-myelin-axon mechanism may synergistically accelerate the degenerative process of MSA.

Alteration of autophagosomal proteins in the brain of multiple system atrophy

Autophagosomal formation is an initial step for macroautophagy. Similar to the yeast autophagy-related gene 8 (ATG8), mammalian ATG8 is responsible for autophagosomal formation, and categorized into LC3 and GABARAPs/GATE-16. Recent studies have shown that impairment of the autophagy-lysosome system is associated with formation of cytoplasmic inclusions observed in various neurodegenerative disorders including Parkinson's disease (PD) and dementia with Lewy bodies (DLB). Although abnormal α-synuclein accumulation is a cardinal neuropathological feature in PD, DLB and multiple system atrophy (MSA), it is unclear whether autophagy is altered in MSA. We here demonstrated that the level of matured GABARAPs was significantly decreased in the cerebellum of MSA relative to controls, and that the higher levels of matured and lipidated LC3 were detected in detergent-insoluble fraction of MSA. Immunohistochemical analysis showed that the vast majority of glial cytoplasmic inclusions, a hallmark of MSA, were positive for LC3, whereas they were unstained or barely stained with anti-GABARAPs or anti-GATE-16 antibodies. Our data suggest that autophagy maturation is impaired through the repressed levels of autophagosomal proteins in MSA.

Binding of neuronal α-synuclein to β-III tubulin and accumulation in a model of multiple system atrophy

Multiple system atrophy (MSA) is a neurodegenerative disease caused by α-synuclein (α-syn) accumulation in oligodendrocytes and neurons. We generated a transgenic (Tg) mouse model in which human α-syn was overexpressed in oligodendrocytes. Our previous studies have revealed that oligodendrocytic α-syn inclusions induced neuronal α-syn accumulation, thereby resulting in progressive neuronal degeneration in mice. We also demonstrated that an insoluble complex of α-syn and β-III tubulin in microtubules progressively accumulated in neurons, thereby leading to neuronal degeneration. In the present study, we demonstrated that neuronal accumulation of the insoluble complex was derived from binding of α-syn to β-III tubulin and not from α-syn self-aggregation. Thus, interaction between α-syn and β-III tubulin plays an important role in neuronal α-syn accumulation in an MSA mouse model.

Multiple system atrophy: a clinical and neuropathological perspective

Multiple system atrophy (MSA) is a neurodegenerative disease involving motor abnormalities that include akinesia, rigidity and postural instability. While improved diagnostic criteria have aided the accurate diagnosis of MSA, our understanding of the neuropathological aspects underlying MSA was bolstered by the identification of α-synuclein (α-syn) as the primary constituent of the abnormal protein aggregates observed in the brains of MSA patients. The generation of transgenic animal models of MSA coupled with an increasing understanding of the biochemical structure and function of α-syn has highlighted a number of key pathological pathways thought to underlie the neurodegeneration observed in MSA. This review summarizes key findings in the field, discusses current areas of debate, and describes current experimental approaches towards disease-modifying therapies.

Extensive distribution of glial cytoplasmic inclusions in an autopsied case of multiple system atrophy with a prolonged 18-year clinical course

We describe herein an autopsied case of multiple system atrophy (MSA) with prolonged clinical course of 18 years, and evaluate the extent of neurodegeneration and glial cytoplasmic inclusions (GCIs) in the entire brain of this rare case. A 64-year-old woman presented with typical neurological symptoms and imaging features of MSA. Thereafter, she became bedridden, and breathing was assisted through a tracheostomy for 12 years. She died at the age of 82 after 18 years from the initial symptom. Post mortem examination revealed severe neurodegeneration in the inferior olive, pontine nuclei, substantia nigra, locus ceruleus, putamen and cerebellum. Notably, phosphorylated α-synuclein (p-α-syn)-positive GCIs were found in these areas, but their number was very low. In contrast, the density of GCIs was much higher in such regions as the tectum/tegmentum of the brainstem, pyramidal tracts, neocortices and limbic system, which usually contain a small number of GCIs. Another constituent of GCIs, ubiquitin (Ub) and Ub-associated autophagy substrate p62, were also positive in some GCIs, and distribution of Ub/p62 immunoreactivity was proportionate to that of p-α-syn+ GCIs despite the very long duration of the disease. Furthermore, this case had complicated hypoxic encephalopathy, but p-α-syn+ GCIs were also found in the damaged white matter, indicating the contribution of α-syncleinopathy as well as hypoxic effect to the secondary myelin and axonal loss in the white matter. Together, this rare case suggests the contribution of the disease duration to the prevalence of GCIs, and the possible involvement of the limbic system in extensive-stage disease.

Tau-positive glial cytoplasmic granules in multiple system atrophy

Multiple system atrophy (MSA) is a sporadic neurodegenerative disease that is pathologically characterized by the filamentous aggregation of α-synuclein. We report a case of MSA showing unusual neuropathological findings and review six autopsied cases of MSA. The patient progressively developed parkinsonism and ataxia for the 9 years prior to her death at the age of 72 years. Neuropathological examinations revealed neuronal loss restricted to the olivopontocerebellar and striatonigral region, which was more severe in the putamen. Staining with anti-α-synuclein antibody demonstrated widespread occurrence of glial cytoplasmic inclusions, which mainly accumulated in oligodendroglial cells and corresponded closely to the degree of disease progression. In addition, tau-positive granules were detected within the glial cytoplasm in the neurodegenerative region, which was especially prominent in the putamen and internal capsule. Tau accumulation was also clearly recognized by staining with specific antibodies against three-repeat or four-repeat tau. The glia that demonstrated deposition of tau-positive granules were distinguished from α-synuclein-positive oligodendroglia by double immunohistochemical staining. These characteristic glial accumulations of tau were also present in all six cases of MSA. These results indicate that tau-positive granules in glia are common findings in MSA and that tau aggregation might be another pathway to neurodegeneration in MSA.

Involvement of the peripheral nervous system in synucleinopathies, tauopathies and other neurodegenerative proteinopathies of the brain

Involvement of the peripheral nervous system (PNS) is relatively common in some neurodegenerative proteinopathies of the brain and may be pathogenetically and diagnostically important. In Parkinson's disease, neuronal alpha-synuclein aggregates are distributed throughout the nervous system, including the central nervous system (CNS), sympathetic ganglia, enteric nervous system, cardiac and pelvic plexuses, submandibular gland, adrenal medulla and skin. The pathological process may target the PNS and CNS at the same time. In multiple system atrophy, numerous glial cytoplasmic inclusions composed of filamentous alpha-synuclein are widely distributed in the CNS, while alpha-synuclein accumulation is minimal in the sympathetic ganglia and is restricted to neurons. Neurofibrillary tangles can occur in the sympathetic and spinal ganglia in tauopathy, although they appear to develop independently of cerebral Alzheimer's disease pathology. In amyotrophic lateral sclerosis, neuronal loss with TDP-43-positive neuronal cytoplasmic inclusions in the spinal ganglia is more frequent than previously thought. Peripheral ganglia and visceral organs are also involved in polyglutamine diseases. Further elucidation and characterization of PNS lesions will have implications for intravital biopsy diagnosis in neurodegenerative proteinopathy, particularly in Parkinson's disease.

Genetic variants of the alpha-synuclein gene SNCA are associated with multiple system atrophy

Background

Multiple system atrophy (MSA) is a progressive neurodegenerative disorder characterized by parkinsonism, cerebellar ataxia and autonomic dysfunction. Pathogenic mechanisms remain obscure but the neuropathological hallmark is the presence of α-synuclein-immunoreactive glial cytoplasmic inclusions. Genetic variants of the α-synuclein gene, SNCA, are thus strong candidates for genetic association with MSA. One follow-up to a genome-wide association of Parkinson's disease has identified association of a SNP in SNCA with MSA.

Methodology/Findings

We evaluated 32 SNPs in the SNCA gene in a European population of 239 cases and 617 controls recruited as part of the Neuroprotection and Natural History in Parkinson Plus Syndromes (NNIPPS) study. We used 161 independently collected samples for replication. Two SNCA SNPs showed association with MSA: rs3822086 (P = 0.0044), and rs3775444 (P = 0.012), although only the first survived correction for multiple testing. In the MSA-C subgroup the association strengthened despite more than halving the number of cases: rs3822086 P = 0.0024, OR 2.153, (95% CI 1.3–3.6); rs3775444 P = 0.0017, OR 4.386 (95% CI 1.6–11.7). A 7-SNP haplotype incorporating three SNPs either side of rs3822086 strengthened the association with MSA-C further (best haplotype, P = 8.7×10⁻⁴). The association with rs3822086 was replicated in the independent samples (P = 0.035).

Conclusions/Significance

We report a genetic association between MSA and α-synuclein which has replicated in independent samples. The strongest association is with the cerebellar subtype of MSA.

Trial Registration

ClinicalTrials.gov NCT00211224. [NCT00211224]