[A case of complex partial seizure with reversible MRI abnormalities in the elderly]

A 79-year-old woman was admitted to our hospital because of prolonged impaired consciousness and right hemiparesis. She was treated for acute cerebral infarction because her brain magnetic resonance imaging showed extensive cortical lesions similar to acute infarction in diffusion weighted image, fluid attenuated inversion recovery, and T2 weighted images. On the fifth day, she had a focal seizure on the right side. A new lesion during imaging and electroencephalogram abnormality were observed at that time. After the antiepileptic drug treatment was started, her right hemiparesis considered as ictal paresis, confusion, and the magnetic resonance imaging findings gradually improved. There was also an old, irreversible lesion in the left hippocampus, which was considered as the focus of her complex partial seizure. In the elderly, the post-ictal period of confusion, which occurs with complex partial seizure, may be prolonged. In our case, improvement of hemiparesis and confusion occurred after about 2 weeks.

Nivolumab-induced chronic inflammatory demyelinating polyradiculoneuropathy mimicking rapid-onset Guillain-Barré syndrome: a case report

Nivolumab, an anti-programmed death-1-specific monoclonal antibody, has demonstrated a durable response and effect on overall survival and has become one of the standard treatments for patients with advanced melanoma. Reported herein is a case of nivolumab-induced chronic inflammatory demyelinating polyradiculoneuropathy, in which an 85-year-old woman with stage IV melanoma developed grade 1 paresthesia 2 weeks after the initial dose of nivolumab was administered. With continued treatment, the neurological deficiency deteriorated rapidly, mimicking Guillain-Barré syndrome, causing such a dramatic decrease in her activities of daily living that she could no longer function in daily life. Thus, nivolumab treatment was discontinued. A course of intravenous immunoglobulin infusion yielded a dramatic clinical improvement; in particular, improved motor control was observed within a few days. Her initial presentation was suggestive of acute inflammatory demyelinating polyradiculoneuropathy, a subtype of Guillain-Barré syndrome; however, the good response to steroids and exacerbation 8 weeks after the onset were suggestive of chronic inflammatory demyelinating polyradiculoneuropathy induced by nivolumab. This is the first case of Guillain-Barré syndrome-like autoimmune polyradiculoneuropathy induced by programmed death-1/programmed death-ligand 1 inhibitors. Although neurological adverse events related to nivolumab are rare, they can become severe, requiring early diagnosis and intervention. Intravenous immunoglobulin may be considered as an effective initial treatment for patients who develop acute autoimmune nervous system disorders due to nivolumab.

[Dyslipidemia and Dementia]

Several lines of evidences support a possible involvement of serum cholesterol in the development of dementia/Alzheimer's disease (AD), with hypercholesterolemia as one of the risk factors that can be targeted by therapeutic interventions. It has also been suggested that statins, prescribed as lipid-lowering drugs to patients at risk for cardiovascular conditions, may be useful in both the prevention and treatment of AD. Currently, conflicting evidences from epidemiological studies indicate a controversial association between dyslipidemia and dementia/AD risk. In randomized clinical trials, virtually no beneficial effect of statin therapy has been observed. On the other hand, in vitro and in vivo animal experiments have revealed that statins suppress amyloid β protein (Aβ) generation. All these findings suggest that statins can be potentially used as preventive or therapeutic agents for AD. In addition, currently the pathophysiological process of AD is thought to begin many years before the diagnosis of AD dementia. Then, statin treatment as well as some disease-modifying therapies may be more efficacious at an early stage of AD including preclinical AD or mild cognitive impairment due to AD.

Vestibular Impairment in Frontotemporal Dementia Syndrome

Background

No studies to date have attempted to evaluate frontotemporal lobar degeneration from the perspective of the vestibular system.

Objective

The present study examined vestibular function in patients with frontotemporal dementia (FTD) clinical syndrome and evaluated whether vestibular disorders are involved in the clinical symptoms due to FTD.

Methods

Fourteen patients with FTD syndrome, as well as healthy elderly controls without dementia, were included in the present study. All subjects underwent vestibular function tests using electronystagmography, such as caloric tests and visual suppression (VS) tests, in which the induced caloric nystagmus was suppressed by visual stimuli. The association between clinical symptoms and vestibular function in the FTD syndrome group was further examined.

Results

In the FTD syndrome group, caloric nystagmus was not necessarily suppressed during VS tests. Furthermore, VS was observed to be significantly impaired in FTD syndrome patients with gait disturbance as compared to those without such disturbance.

Conclusion

The present study revealed that impairment of VS in patients with FTD results in an inability to regulate vestibular function by means of visual perception, regardless of multiple presumed neuropathological backgrounds. This could also be associated with gait disturbance in patients with FTD syndrome.

Vestibular Function Impairment in Alzheimer's Disease

BACKGROUND

Falls and fractures due to impaired balance in patients with Alzheimer's disease (AD) have an adverse effect on the clinical course of the disease.

OBJECTIVE

To evaluate balance impairment in AD from the viewpoint of vestibular functional impairment.

METHODS

The subjects were 12 patients with AD, 12 dementia-free elderly adults, and 12 younger adults. Vestibular function was assessed using a stepping test, caloric nystagmus, and a visual suppression (VS) test.

RESULTS

The stepping test was abnormal in 9 of the 12 patients in the AD group. An abnormal stepping test was not associated with self-reported dizziness or tendency to fall. Significant VS abnormalities were present in the AD group. The suppression rate of VS was lower in AD patients with either a tendency to fall or constructional apraxia than in AD patients without either. The velocity of the rapid phase of caloric nystagmus before the VS test was similar in the AD group and the elderly control group. Significant abnormalities of both caloric nystagmus and VS were not present in either the elderly or the younger control groups.

CONCLUSION

AD could involve impairments in the vestibular control of balance. The VS test is useful for assessing the tendency to fall in AD. Impairment of VS in AD might arise from cerebral vestibular cortex impairment rather than comorbid peripheral vestibular disorders.

α-Synuclein Fibrils Exhibit Gain of Toxic Function, Promoting Tau Aggregation and Inhibiting Microtubule Assembly

α-Synuclein is the major component of Lewy bodies and Lewy neurites in Parkinson disease and dementia with Lewy bodies and of glial cytoplasmic inclusions in multiple system atrophy. It has been suggested that α-synuclein fibrils or intermediate protofibrils in the process of fibril formation may have a toxic effect on neuronal cells. In this study, we investigated the ability of soluble monomeric α-synuclein to promote microtubule assembly and the effects of conformational changes of α-synuclein on Tau-promoted microtubule assembly. In marked contrast to previous findings, monomeric α-synuclein had no effect on microtubule polymerization. However, both α-synuclein fibrils and protofibrils inhibited Tau-promoted microtubule assembly. The inhibitory effect of α-synuclein fibrils was greater than that of the protofibrils. Dot blot overlay assay and spin-down techniques revealed that α-synuclein fibrils bind to Tau and inhibit microtubule assembly by depleting the Tau available for microtubule polymerization. Using various deletion mutants of α-synuclein and Tau, the acidic C-terminal region of α-synuclein and the basic central region of Tau were identified as regions involved in the binding. Furthermore, introduction of α-synuclein fibrils into cultured cells overexpressing Tau protein induced Tau aggregation. These results raise the possibility that α-synuclein fibrils interact with Tau, inhibit its function to stabilize microtubules, and also promote Tau aggregation, leading to dysfunction of neuronal cells.

Clinical, biochemical and molecular investigation of adult-onset glutaric acidemia type II: Characteristics in comparison with pediatric cases

INTRODUCTION

An increasing number of adult patients have been diagnosed with fatty acid β-oxidation disorders with the rising use of diagnostic technologies. In this study, clinical, biochemical, and molecular characteristics of 2 Japanese patients with adult-onset glutaric acidemia type II (GA2) were investigated and compared with those of pediatric cases.

METHODS

The patients were a 58-year-old male and a 31-year-old male. In both cases, episodes of myopathic symptoms, including myalgia, muscle weakness, and liver dysfunction of unknown cause, had been noted for the past several years. Muscle biopsy, urinary organic acid analysis (OA), acylcarnitine (AC) analysis in dried blood spots (DBS) and serum, immunoblotting, genetic analysis, and an in vitro probe acylcarnitine (IVP) assay were used for diagnosis and investigation.

RESULTS

In both cases, there was no obvious abnormality of AC in DBS or urinary OA, although there was a increase in medium- and long-chain ACs in serum; also, fat deposits were observed in the muscle biopsy. Immunoblotting and gene analysis revealed that both patients had GA2 due to a defect in electron transfer flavoprotein dehydrogenase (ETFDH). The IVP assay indicated no special abnormalities in either case.

CONCLUSION

Late-onset GA2 is separated into the intermediate and myopathic forms. In the myopathic form, episodic muscular symptoms or liver dysfunction are primarily exhibited after later childhood. Muscle biopsy and serum (or plasma) AC analysis allow accurate diagnosis in contrast with other biochemical tests, such as analysis of AC in DBS, urinary OA, or the IVP assay, which show fewer abnormalities in the myopathic form compared to intermediate form.

Amyloid β accumulation assessed with ¹¹C-Pittsburgh compound B PET and postmortem neuropathology

¹¹C-Pittsburgh compound B (PiB) uptake in PET images is frequently used to analyze β amyloid (Aβ) deposition in living individuals, but its correlation with histologically determined Aβ has not been examined. Six individuals with dementia underwent PiB-PET imaging, and their brains were analyzed neuropathologically (mean interval between imaging and death: 816 days; PiB positive:negative, 3:3; male:female, 3:3; mean age: 84.0 years). PiB uptake (reported as standardized uptake value ratio [SUVR]) was analyzed in 11 cortical regions and 10 subcortical grey matter areas and compared with the Aβ load (% area [the percentage of total area positive for Aβ] and number of neuritic plaques) seen with immunohistochemical staining with an anti-Aβ 11-28 antibody. Two PiB-positive subjects had abundant neuritic plaques and were diagnosed with Alzheimer’s disease (AD). SUVR and % area were strongly correlated in the cortical regions of these subjects (subject 1: r = 0.65, p = 0.03; subject 2: r = 0.80, p = 0.003). The other PiBpositive subject (subject 3) showed focal PiB uptake. In subject 3 and the 3 PiB-negative subjects (subjects 4-6), there was no correlation between regional SUVR and % area or neuritic plaques. PiB uptake was not correlated with Aβ deposition in subcortical regions. High PiB positivity in the cerebral cortex suggests the presence of substantial Aβ deposition and neuritic plaques associated with the pathologic changes of AD. Our results suggest that high cortical SUVR is a reliable marker of AD. Subcortical PiB positivity must be interpreted more carefully.

[A representative case of joint contracture as a main feature of AL amyloid deposits identified in the skeletal muscles]

A 68-year-old man, with a history of type 2 diabetes mellitus and chronic kidney impairment, had been suffering from progressive knee joint contracture and dysesthesia of the lower extremities for 4 years. When he walked, his knees remained bent owing to contracture of the knee joints. There was no evidence of muscle pseudohypertrophy, intramuscular nodules, or muscle weakness. Clinical examination revealed IgA λ M-protein, reticular high-signal intensity lesions demonstrated by magnetic resonance T2-short TI IR(STIR) imaging of the lower extremity muscles, and a mixture of neurogenic and myogenic changes demonstrated by needle electromyography. A biopsy specimen from the vastus lateralis muscle identified Aλ amyloid deposits around the vessels, establishing a diagnosis of amyloid myopathy based on systemic AL amyloidosis. This case demonstrated that joint contracture and reticular lesions shown by magnetic resonance STIR imaging of the muscles can alert the physician to consider muscle biopsy to investigate deposition of amyloid in the skeletal muscles even in the absence of muscle pseudohypertrophy or weakness, both of which are characteristic of amyloid myopathy.

Immunohistochemical characterization of CD33 expression on microglia in Nasu-Hakola disease brains

Nasu-Hakola disease (NHD) is a rare autosomal recessive disorder, characterized by formation of multifocal bone cysts and development of leukoencephalopathy, caused by genetic mutations of either DNAX-activation protein 12 (DAP12) or triggering receptor expressed on myeloid cells 2 (TREM2). Although increasing evidence suggests a defect in microglial TREM2/DAP12 function in NHD, the molecular mechanism underlying leukoencephalopathy with relevance to microglial dysfunction remains unknown. TREM2, by transmitting signals via the immunoreceptor tyrosine-based activation motif (ITAM) of DAP12, stimulates phagocytic activity of microglia, and ITAM signaling is counterbalanced by sialic acid-binding immunoglobulin (Ig)-like lectins (Siglecs)-mediated immunoreceptor tyrosine-based inhibitory motif (ITIM) signaling. To investigate a role of CD33, a member of the Siglecs family acting as a negative regulator of microglia activation, in the pathology of NHD, we studied CD33 expression patterns in five NHD brains and 11 controls by immunohistochemistry. In NHD brains, CD33 was identified exclusively on ramified and amoeboid microglia accumulated in demyelinated white matter lesions but not expressed in astrocytes, oligodendrocytes, or neurons. However, the number of CD33-immunoreactive microglia showed great variability from case to case and from lesion to lesion without significant differences between NHD and control brains. These results do not support the view that CD33-expressing microglia play a central role in the development of leukoencephalopathy in NHD brains.

Improvement of gait ability with a short-term intensive gait rehabilitation program using body weight support treadmill training in community dwelling chronic poststroke survivors

[Purpose] Most previous studies have shown that body weight support treadmill training (BWSTT) can improve gait speed poststroke patients. The purpose of this study was to evaluate effectiveness of a short-term intensive program using BWSTT among community dwelling poststroke survivors. [Subjects] Eighteen subjects participated in this study. The treatment group was composed of 10 subjects (2 women; 8 men; mean age, 59.1 ± 12.5 years; time since stroke onset, 35.3 ± 33.2 months), whereas the control group was made up of 8 subjects (3 women; 5 men; mean age, 59.8 ± 6.3 years; time since stroke onset, 39.3 ± 27.3 months). [Methods] The treatment group received BWSTT 3 times a week for 4 weeks (a total of 12 times), with each session lasting 20 minutes. The main outcome measures were maximum gait speed on a flat floor, cadence, and step length. [Results] No differences were observed in the baseline clinical data between the 2 groups. The gait speed in the treatment group was significantly improved compared with that in the control by 2-way ANOVA, while the other parameters showed no significant interaction. [Conclusion] These results suggested that short-term intensive gait rehabilitation using BWSTT was useful for improving gait ability among community dwelling poststroke subjects.

[Ten-years records of organic arsenic (diphenylarsinic acid) poisoning: epidemiology, clinical feature, metabolism, and toxicity]

We report here the symptoms of diphenylarsinic acid (DPAA) poisoning recorded over 10 years since the DPAA contamination of the potable well water was first detected in the Kamisu City, Ibaraki Prefecture, in 2003. The poisoning symptoms associated with the cerebellum and brainstem included nystagmus, tremors, myoclonus, and cerebellar ataxia as well as the symptoms associated with the temporal and occipital lobes such as memory impairment, sleep disorder, and visual disturbance. Some of the affected children exhibited mental retardation. Moreover, reduced blood flow and reduced glucose metabolism in the cerebella, brainstem, and temporal and occipital lobes persisted for several years among the DPAA-exposed persons. Based on the animal studies for DPAA intoxication, the target organs for the DPAA toxicity were determined to be the central nervous system (CNS), liver, and biliary system. In particular, DPAA tends to persist in the brain for a long time, resulting in long-term impacts on the brain. The cerebral blood flow and brain glucose metabolism, which can be measured by positron emission tomography (PET) and single photon emission computed tomography (SPECT), respectively, are useful objective clinical markers to determine the effect of DPAA on CNS. We believe that continuous monitoring of the DPAA-exposed people may promote the effect of carcinogen and accelerate brain aging.

Amyloid beta-protein and lipid rafts: focused on biogenesis and catabolism

Cerebral accumulation of amyloid β-protein (Aβ) is thought to play a key role in the molecular pathology of Alzheimer's disease (AD). Three secretases (β-, γ-, and α-secretase) are proteases that control the production of Aβ from amyloid precursor protein. Increasing evidence suggests that cholesterol-rich membrane microdomains termed 'lipid rafts' are involved in the biogenesis and accumulation of Aβ as well as Aβ-mediated neurotoxicity. γ-Secretase is enriched in lipid rafts, which are considered an important site for Aβ generation. Additionally, Aβ-degrading peptidases located in lipid rafts, such as neprilysin, appear to play a role in Aβ catabolism. This mini-review focuses on the roles of lipid rafts in the biogenesis and catabolism of Aβ, covering recent research on the relationship between lipid rafts and the three secretases or Aβ-degrading peptidases. Furthermore, the significance of lipid rafts in Aβ aggregation and neurotoxicity is briefly summarized.

LC3, an autophagosome marker, is expressed on oligodendrocytes in Nasu-Hakola disease brains

Background

Nasu-Hakola disease (NHD) is a rare autosomal recessive disorder characterized by sclerosing leukoencephalopathy and multifocal bone cysts, caused by a loss-of-function mutation of either DAP12 or TREM2. TREM2 and DAP12 constitute a receptor/adaptor signaling complex expressed exclusively on osteoclasts, dendritic cells, macrophages, and microglia. Neuropathologically, NHD exhibits profound loss of myelin and accumulation of axonal spheroids, accompanied by intense gliosis accentuated in the white matter of the frontal and temporal lobes. At present, the molecular mechanism responsible for development of leukoencephalopathy in NHD brains remains totally unknown.

Methods

By immunohistochemistry, we studied the expression of microtubule-associated protein 1 light chain 3 (LC3), an autophagosome marker, in 5 NHD and 12 control brains.

Results

In all NHD brains, Nogo-A-positive, CNPase-positive oligodendrocytes surviving in the non-demyelinated white matter intensely expressed LC3. They also expressed ubiquitin, ubiquilin-1, and histone deacetylase 6 (HDAC6) but did not express Beclin 1 or sequestosome 1 (p62). Substantial numbers of axonal spheroids were also labeled with LC3 in NHD brains. In contrast, none of oligodendrocytes expressed LC3 in control brains. Furthermore, surviving oligodendrocytes located at the demyelinated lesion edge of multiple sclerosis (MS) did not express LC3, whereas infiltrating Iba1-positive macrophages and microglia intensely expressed LC3 in MS lesions.

Conclusions

These results propose a novel hypothesis that aberrant regulation of autophagy might induce oligodendrogliopathy causative of leukoencephalopathy in NHD brains.

Glossopharyngeal nerve and vagus nerve palsies associated with influenza vaccination

We herein report the first case of glossopharyngeal nerve and vagus nerve palsies that appeared after an influenza vaccination. A 15-year-old boy developed dysphagia and dysarthria seven days after receiving an inoculation of the inactivated influenza vaccine. Massive intravenous immunoglobulin (IVIg) treatment was applied, as the patient's symptoms were considered to be immunological adverse effects of the influenza vaccine. He responded well to IVIg, and the symptoms immediately diminished. The mechanisms underlying the development of neurologic symptoms following vaccination are difficult to determine; however, providing immediate immunological treatment, such as IVIg, is effective and beneficial in countering these symptoms.

[The pathophysiology of Alzheimer's disease with special reference to "amyloid cascade hypothesis"]

The neuropathological characteristics of the Alzheimer's disease (AD) brain include senile plaques, neurofibrillary tangles and neuronal cell loss extensively recognized in brain cortices. Biochemical studies revealed that senile plaques and neuronfibrillary tangles are composed mainly of amyloid beta protein and highly phosphorylated tau protein, a microtubule-associated protein, respectively. Abeta deposition in senile plaques was previously considered to initiate the pathological cascade of Alzheimer's disease (AD), suggesting that the aggregation of Abeta in insoluble Abeta fibrils plays an important role in its neurotoxicity ('amyloid cascade hypothesis'). However, the concentrations of Abeta required for fibrillization are higher than its physiological concentrations. In addition, cognitive decline in AD patients is not correlated with the levels of senile plaque formation. Currently, AD is believed to begin with synaptic dysfunction caused by soluble Abeta oligomers, playing a more important role in the etiology of AD than insoluble Abeta ibrils ('oligomer hypothesis').

Differential diagnosis of amyotrophic lateral sclerosis from Guillain-Barré syndrome by quantitative determination of TDP-43 in cerebrospinal fluid

The aim of this study was to investigate whether an increased level of TAR DNA-binding protein 43 (TDP-43) in the cerebrospinal fluid (CSF) could be a biomarker for amyotrophic lateral sclerosis (ALS) and facilitate differential diagnosis of ALS from peripheral motor neuropathy. TDP-43 is the major constituent of neuronal and glial inclusions that neuropathologically characterize both ALS and tau-negative frontotemporal lobar degeneration. Recent discoveries of various missense mutations in the TDP-43 gene in familial ALS indicate a pivotal role of the aberrant accumulation of TDP-43 in neurodegeneration. Increased TDP-43 in the CSF could be a hallmark of ALS and other TDP-43 proteinopathy. Sandwich enzyme-linked immunosorbent assay (ELISA) was established to measure the concentration of TDP-43 in biological fluids. Culture supernatants of cells transfected with various TDP-43 constructs were used to confirm that the ELISA detected TDP-43. TDP-43 in the culture supernatant of TDP-43 transfected cells was detected by immunoprecipitation with subsequent immunoblotting and concentrations were successfully measured by sandwich ELISA. We then measured TDP-43 concentrations in the CSF of patients with ALS and Guillain-Barré syndrome (GBS). TDP-43 concentrations in CSF were significantly higher in ALS than in GBS (p = 0.016). The sensitivity of the diagnostic test was 71.4% and the specificity was 84.6%. Quantitative determination of TDP-43 concentrations in the CSF by sandwich ELISA is a potential laboratory test for differentiating ALS from peripheral motor neuropathies such as GBS.

The CHC22 clathrin-GLUT4 transport pathway contributes to skeletal muscle regeneration

Mobilization of the GLUT4 glucose transporter from intracellular storage vesicles provides a mechanism for insulin-responsive glucose import into skeletal muscle. In humans, clathrin isoform CHC22 participates in formation of the GLUT4 storage compartment in skeletal muscle and fat. CHC22 function is limited to retrograde endosomal sorting and is restricted in its tissue expression and species distribution compared to the conserved CHC17 isoform that mediates endocytosis and several other membrane traffic pathways. Previously, we noted that CHC22 was expressed at elevated levels in regenerating rat muscle. Here we investigate whether the GLUT4 pathway in which CHC22 participates could play a role in muscle regeneration in humans and we test this possibility using CHC22-transgenic mice, which do not normally express CHC22. We observed that GLUT4 expression is elevated in parallel with that of CHC22 in regenerating skeletal muscle fibers from patients with inflammatory and other myopathies. Regenerating human myofibers displayed concurrent increases in expression of VAMP2, another regulator of GLUT4 transport. Regenerating fibers from wild-type mouse skeletal muscle injected with cardiotoxin also showed increased levels of GLUT4 and VAMP2. We previously demonstrated that transgenic mice expressing CHC22 in their muscle over-sequester GLUT4 and VAMP2 and have defective GLUT4 trafficking leading to diabetic symptoms. In this study, we find that muscle regeneration rates in CHC22 mice were delayed compared to wild-type mice, and myoblasts isolated from these mice did not proliferate in response to glucose. Additionally, CHC22-expressing mouse muscle displayed a fiber type switch from oxidative to glycolytic, similar to that observed in type 2 diabetic patients. These observations implicate the pathway for GLUT4 transport in regeneration of both human and mouse skeletal muscle, and demonstrate a role for this pathway in maintenance of muscle fiber type. Extrapolating these findings, CHC22 and GLUT4 can be considered markers of muscle regeneration in humans.

A unique mouse model for investigating the properties of amyotrophic lateral sclerosis-associated protein TDP-43, by in utero electroporation

TDP-43 is a discriminative protein that is found as intracellular aggregations in the neurons of the cerebral cortex and spinal cord of patients with amyotrophic lateral sclerosis (ALS); however, the mechanisms of neuron loss and its relation to the aggregations are still unclear. In this study, we generated a useful model to produce TDP-43 aggregations in the motor cortex using in utero electroporation on mouse embryos. The plasmids used were full-length TDP-43 and C-terminal fragments of TDP-43 (wild-type or M337V mutant) tagged with GFP. For the full-length TDP-43, both wild-type and mutant, electroporated TDP-43 localized mostly in the nucleus, and though aggregations were detected in embryonic brains, they were very rarely observed at P7 and P21. In contrast, TDP-43 aggregations were generated in the brains electroporated with the C-terminal TDP-43 fragments as previously reported in in vitro experiments. TDP-43 protein was distributed diffusely-not only in the nucleus, but also in the cytoplasm-and the inclusion bodies were ubiquitinated and included phosphorylated TDP-43, which reflects the human pathology of ALS. This model using in utero electroporation of pathogenic genes into the brain of the mouse will likely become a useful model for studying ALS and also for evaluation of agents for therapeutic purpose, and may be applicable to other neurodegenerative diseases, as well.

Altered CpG methylation in sporadic Alzheimer's disease is associated with APP and MAPT dysregulation

The hallmark of Alzheimer's disease (AD) pathology is an accumulation of amyloid β (Aβ) and phosphorylated tau, which are encoded by the amyloid precursor protein (APP) and microtubule-associated protein tau (MAPT) genes, respectively. Less than 5% of all AD cases are familial in nature, i.e. caused by mutations in APP, PSEN1 or PSEN2. Almost all mutations found in them are related to an overproduction of Aβ1-42, which is prone to aggregation. While these genes are mutation free, their function, or those of related genes, could be compromised in sporadic AD as well. In this study, pyrosequencing analysis of post-mortem brains revealed aberrant CpG methylation in APP, MAPT and GSK3B genes of the AD brain. These changes were further evaluated by a newly developed in vitro-specific DNA methylation system, which in turn highlighted an enhanced expression of APP and MAPT. Cell nucleus sorting of post-mortem brains revealed that the methylation changes of APP and MAPT occurred in both neuronal and non-neuronal cells, whereas GSK3B was abnormally methylated in non-neuronal cells. Further analysis revealed an association between abnormal APP CpG methylation and apolipoprotein E ε4 allele (APOE ε4)-negative cases. The presence of a small number of highly methylated neurons among normal neurons contribute to the methylation difference in APP and MAPT CpGs, thus abnormally methylated cells could compromise the neural circuit and/or serve as 'seed cells' for abnormal protein propagation. Our results provide a link between familial AD genes and sporadic neuropathology, thus emphasizing an epigenetic pathomechanism for sporadic AD.

Reduction of β-amyloid accumulation by reticulon 3 in transgenic mice

Inhibition of the β-secretase, BACE1, which cleaves amyloid precursor protein (APP) to produce β-amyloid protein (Aβ), is thought to be a feasible therapeutic strategy for Alzheimer's disease. Reticulon (RTN) proteins such as RTN3 have been identified as membrane proteins that interact with BACE1 and inhibit its Aβ-generating activity. In this study, we investigated whether RTN3 can regulate Aβ production in vivo, using transgenic (Tg) mice expressing APP with Swedish and London mutations (APP Tg mice) and those expressing RTN3; the latter mice showed ~1.4-fold higher expression levels of RTN3 protein in the cerebral cortex than non-Tg controls. We analyzed the brains of single APP Tg and double APP/RTN3 Tg mice at the age of approximately 15 months. The levels of secreted APP-β, a direct BACE1 cleavage product of APP, in Tris-soluble fraction were considerably reduced in the hippocampus and cerebral cortex of APP/RTN3 Tg mice relative to those in APP Tg mice. Immunohistochemical analyses demonstrated that Aβ burden and plaques were significantly (by approximately 50%) decreased in both the hippocampus and cerebral cortex of double Tg mice compared to APP Tg mice. Furthermore, the levels of guanidine-soluble Aβ40 and Aβ42 in these brain regions of APP/RTN3 Tg mice were relatively lower than those in APP Tg mice. These findings indicate that even a small increase in RTN3 expression exerts suppressive effects on amyloidogenic processing of APP and Aβ accumulation through modulation of BACE1 activity in vivo, and suggest that induction of RTN3 might be an effective therapeutic strategy against Alzheimer's disease.

Downbeat nystagmus associated with damage to the medial longitudinal fasciculus of the pons: a vestibular balance control mechanism via the lower brainstem paramedian tract neurons

The paramedian tract (PMT) neurons, a group of neurons associated with eye movement that project into the cerebellar flocculus, are present in or near the medial longitudinal fasciculus (MLF) in the paramedian region of the lower brainstem. A 66-year-old man with multiple sclerosis in whom downbeat nystagmus appeared along with right MLF syndrome due to a unilateral pontomedullary lesion is described. In light of these findings, a possible schema for the vestibular balance control mechanism circuit of the PMT neurons via the flocculus is presented. Damage to the PMT neurons impaired the elective inhibitory control mechanism of the anterior semicircular canal neural pathway by the flocculus. This resulted in the appearance of anterior semicircular canal-dominant vestibular imbalance and the formation of downbeat nystagmus. From the pathogenesis of this vertical vestibular nystagmus, the action of the PMT neurons in the vestibular eye movement neuronal pathway to maintain vestibular balance was conjectured to be as follows. PMT neurons transmit vestibular information from the anterior semicircular canals to the cerebellum, forming a cerebellum/brainstem feedback loop. Vestibular information from that loop is integrated in the cerebellum, inhibiting only the anterior semicircular canal neuronal pathway via the flocculus and controlling vestibular balance.

[Fall risk and fracture. Falls and fractures in patients with neurological disorders]

Neurological disorders are frequently associated with risk factors for falls, such as gait and balance disorders, deficits of lower extremity strength, sensation and coordination, in addition to cognitive impairments. Patients with various kinds of neurological disorders, including Parkinson's disease, Parkinson's syndrome, amyotrophic lateral sclerosis, peripheral neuropathy, stroke, etc, easily suffer from falls. To prevent falls among such patients, treatments of the underlying neurological diseases and assessments risk factors for falls are most important to cope effectively with these patients. In general, maintenance of the appropriate environment, consideration of the injury prevention, rehabilitation for increasing muscular strength, etc, are useful for the prevention of falls in patients with neurological disorders.

Drug screening for ALS using patient-specific induced pluripotent stem cells

Amyotrophic lateral sclerosis (ALS) is a late-onset, fatal disorder in which the motor neurons degenerate. The discovery of new drugs for treating ALS has been hampered by a lack of access to motor neurons from ALS patients and appropriate disease models. We generate motor neurons from induced pluripotent stem cells (iPSCs) from familial ALS patients, who carry mutations in Tar DNA binding protein-43 (TDP-43). ALS patient-specific iPSC-derived motor neurons formed cytosolic aggregates similar to those seen in postmortem tissue from ALS patients and exhibited shorter neurites as seen in a zebrafish model of ALS. The ALS motor neurons were characterized by increased mutant TDP-43 protein in a detergent-insoluble form bound to a spliceosomal factor SNRPB2. Expression array analyses detected small increases in the expression of genes involved in RNA metabolism and decreases in the expression of genes encoding cytoskeletal proteins. We examined four chemical compounds and found that a histone acetyltransferase inhibitor called anacardic acid rescued the abnormal ALS motor neuron phenotype. These findings suggest that motor neurons generated from ALS patient-derived iPSCs may provide a useful tool for elucidating ALS disease pathogenesis and for screening drug candidates.

Molecular analysis and biochemical classification of TDP-43 proteinopathy

Amyotrophic lateral sclerosis and frontotemporal lobar degeneration with TAR DNA-binding protein of 43 kDa pathology are progressive neurodegenerative diseases that are characterized by intracytoplasmic aggregates of hyperphosphorylated TAR DNA-binding protein of 43 kDa. These TAR DNA-binding protein 43 proteinopathies can be classified into subtypes, which are closely correlated with clinicopathological phenotypes, although the differences in the molecular species of TAR DNA-binding protein 43 in these diseases and the biological significance thereof, remain to be clarified. Here, we have shown that although the banding patterns of abnormally phosphorylated C-terminal fragments of TAR DNA-binding protein 43 differ between the neuropathological subtypes, these are indistinguishable between multiple brain regions and spinal cord in individual patients. Immunoblot analysis of protease-resistant TAR DNA-binding protein 43 demonstrated that the fragment patterns represent different conformations of TAR DNA-binding protein 43 molecular species in the diseases. These results suggest a new clinicopathological classification of TAR DNA-binding protein 43 proteinopathies based on their molecular properties.

Neuronal β-amyloid generation is independent of lipid raft association of β-secretase BACE1: analysis with a palmitoylation-deficient mutant

β-Secretase, BACE1 is a neuron-specific membrane-associated protease that cleaves amyloid precursor protein (APP) to generate β-amyloid protein (Aβ). BACE1 is partially localized in lipid rafts. We investigated whether lipid raft localization of BACE1 affects Aβ production in neurons using a palmitoylation-deficient mutant and further analyzed the relationship between palmitoylation of BACE1 and its shedding and dimerization. We initially confirmed that BACE1 is mainly palmitoylated at four C-terminal cysteine residues in stably transfected neuroblastoma cells. We found that raft localization of mutant BACE1 lacking the palmitoylation modification was markedly reduced in comparison to wild-type BACE1 in neuroblastoma cells as well as rat primary cortical neurons expressing BACE1 via recombinant adenoviruses. In primary neurons, expression of wild-type and mutant BACE1 enhanced production of Aβ from endogenous or overexpressed APP to similar extents with the β-C-terminal fragment (β-CTF) of APP mainly distributed in nonraft fractions. Similarly, β-CTF was recovered mainly in nonraft fractions of neurons expressing Swedish mutant APP only. These results show that raft association of BACE1 does not influence β-cleavage of APP and Aβ production in neurons, and support the view that BACE1 cleaves APP mainly in nonraft domains. Thus, we propose a model of neuronal Aβ generation involving mobilization of β-CTF from nonraft to raft domains. Additionally, we obtained data indicating that palmitoylation plays a role in BACE1 shedding but not dimerization.