Mitsunori Yamada

Expanded polyglutamine stretches interact with TAFII130, interfering with CREB-dependent transcription.

At least eight inherited neurodegenerative diseases are caused by expanded CAG repeats encoding polyglutamine (polyQ) stretches. Although cytotoxicities of expanded polyQ stretches are implicated, the molecular mechanisms of neurodegeneration remain unclear. We found that expanded polyQ stretches preferentially bind to TAFII130, a coactivator involved in cAMP-responsive element binding protein (CREB)-dependent transcriptional activation, and strongly suppress CREB-dependent transcriptional activation. The suppression of CREB-dependent transcription and the cell death induced by polyQ stretches were restored by the co-expression of TAFII130. Our results indicate that interference of transcription by the binding of TAFII130 with expanded polyQ stretches is involved in the pathogenetic mechanisms underlying neurodegeneration.

Suppression of aggregate formation and apoptosis by transglutaminase inhibitors in cells expressing truncated DRPLA protein with an expanded polyglutamine stretch

To elucidate the molecular mechanisms whereby expanded polyglutamine stretches elicit a gain of toxic function, we expressed full-length and truncated DRPLA (dentatorubral-pallidoluysian atrophy) cDNAs with or without expanded CAG repeats in COS-7 cells. We found that truncated DRPLA proteins containing an expanded polyglutamine stretch form filamentous peri- and intranuclear aggregates and undergo apoptosis. The apoptotic cell death was partially suppressed by the transglutaminase inhibitors cystamine and monodansyl cadaverine (but not putrescine), suggesting involvement of a transglutaminase reaction and providing a potential basis for the development of therapeutic measures for CAG-repeat expansion diseases.

Accumulation of α-synuclein/NACP is a cytopathological feature common to Lewy body disease and multiple system atrophy

Abstract Recently, we have shown that the precursor of the non-Aβ component of Alzheimer’s disease amyloid (NACP), also known as α-synuclein, is a major component of Lewy bodies (LBs) as well as neuronal and glial cytoplasmic inclusions in multiple system atrophy (MSA). To elucidate whether the accumulation of NACP is specific to LB disease and MSA, we further studied 83 autopsied cases with various neurological disorders, using anti-NACP antibodies. In LB disease, NACP immunoreactivity was present in all of the LBs and Lewy neurites in both the central and peripheral nervous systems, the pale bodies in the substantia nigra, and dystrophic neurites in the hippocampal CA2/3 region. Immunoelectron microscopy revealed that the reaction product was localized within filamentous structures and associated granular structures. In MSA, NACP immunoreactivity was found in the intracytoplasmic inclusions of both neuronal and oligodendroglial cells, neuronal intranuclear inclusions, and swollen neuronal processes. No NACP immunoreactivity was found in a variety of other neuronal or glial inclusions in other disorders, including Alzheimer’s disease, Pick’s disease, progressive supranuclear palsy, corticobasal degeneration, motor neuron disease and triplet-repeat diseases. These findings strongly suggest that the accumulation of NACP is a cytopathological feature common to LB disease and MSA.

Animal model of axonal Guillain‐Barré syndrome induced by sensitization with GM1 ganglioside

Some humans develop the axonal form of Guillain‐Barré syndrome after receiving bovine brain ganglioside. On sensitization with the ganglioside mixture, all of a group of rabbits injected developed high anti‐GM1 IgG antibody titers, flaccid limb weakness of acute onset, and a monophasic illness course. Pathological findings for the peripheral nerves showed predominant Wallerian‐like degeneration, with neither lymphocytic infiltration nor demyelination. IgG was deposited on the axons of the anterior roots, and GM1 was proved to be present on the axons of peripheral nerves. Sensitization with purified GM1 also induced axonal neuropathy, indicating that GM1 was the immunogen in the mixture. A model of human axonal Guillain‐Barré syndrome has been established that uses inoculation with a bovine brain ganglioside mixture or isolated GM1. This model may help to clarify the molecular pathogenesis of the syndrome and to develop new treatments for it.

Neuropathology with clinical correlations of sporadic amyotrophic lateral sclerosis: 102 autopsy cases examined between 1962 and 2000.

Sporadic amyotrophic lateral sclerosis (ALS) is a fatal neurological disorder affecting adults. We studied the neuropathology and clinical correlations in 102 autopsy cases of ALS. The age at onset of the disease was significantly higher for the bulbar‐onset form (30 cases) than for the limb‐onset form (72 cases). Dementia was confirmed in 7 cases. These 102 cases were divided into 4 pathological subgroups: typical ALS (59 cases), lower‐motor‐predominant ALS (23 cases), ALS with temporal lesions (18 cases), and ALS with pallido‐nigro‐luysian degeneration (2 cases). The age at onset was significantly higher for lower‐motor‐predominant ALS and ALS with temporal lesions than for typical ALS. In the lower motor neurons, Bunina bodies were detected in 88 cases, whereas ubiquitin‐immunoreactive skein and/or spherical inclusions were detected in all 102 cases. Of the 100 available cases, 50 and 16 also showed ubiquitin‐immunoreactive inclusions in the neostriatal and temporal small neurons, respectively. Ubiquitin‐immunoreactive dystrophic neurites were also observed in the neostriatum in 3 of the 50 cases with neostriatal inclusions, and in the temporal cortex in 4 of the 16 cases with temporal inclusions. There was a significant association between the bulbar‐onset form, temporal lesions, neostriatal inclusions and temporal inclusions, and between dementia, temporal lesions and temporal inclusions. Neostriatal and temporal dystrophic neurites were associated with dementia and bulbar‐onset form through temporal lesions and temporal inclusions. The present findings may be helpful for designing further studies on the mechanisms underlying the development of ALS.

Mutations in COQ2 in familial and sporadic multiple-system atrophy the multiple-system atrophy research collaboration

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.).

Nuclear Accumulation of Truncated Atrophin-1 Fragments in a Transgenic Mouse Model of DRPLA

Dentatorubral and pallidoluysian atrophy (DRPLA) is a member of a family of progressive neurodegenerative diseases caused by polyglutamine repeat expansion. Transgenic mice expressing full-length human atrophin-1 with 65 consecutive glutamines exhibit ataxia, tremors, abnormal movements, seizures, and premature death. These mice accumulate atrophin-1 immunoreactivity and inclusion bodies in the nuclei of multiple populations of neurons. Subcellular fractionation revealed 120 kDa nuclear fragments of mutant atrophin-1, whose abundance increased with age and phenotypic severity. Brains of DRPLA patients contained apparently identical 120 kDa nuclear fragments. By contrast, mice overexpressing atrophin-1 with 26 glutamines were phenotypically normal and did not accumulate the 120 kDa fragments. We conclude that the evolution of neuropathology in DRPLA involves proteolytic processing of mutant atrophin-1 and nuclear accumulation of truncated fragments.

Loss of poly(ADP-ribose) glycohydrolase causes progressive neurodegeneration in Drosophila melanogaster

Poly(ADP-ribosyl)ation has been suggested to be involved in regulation of DNA repair, transcription, centrosome duplication, and chromosome stability. However, the regulation of degradation of poly(ADP-ribose) and its significance are not well understood. Here we report a loss-of-function mutant Drosophila with regard to poly(ADP-ribose) glycohydrolase, a major hydrolyzing enzyme of poly(ADP-ribose). The mutant lacks the conserved catalytic domain of poly(ADP-ribose) glycohydrolase, and exhibits lethality in the larval stages at the normal development temperature of 25°C. However, one-fourth of the mutants progress to the adult stage at 29°C but showed progressive neurodegeneration with reduced locomotor activity and a short lifespan. In association with this, extensive accumulation of poly(ADP-ribose) could be detected in the central nervous system. These results suggest that poly(ADP-ribose) metabolism is required for maintenance of the normal function of neuronal cells. The phenotypes observed in the parg mutant might be useful to understand neurodegenerative conditions such as the Alzheimers and Parkinsons diseases that are caused by abnormal accumulation of substances in nervous tissue.

Histologic evidence of absorption of sequestration-type herniated disc.

Study Design The reactions to sequestrated disc fragments, which were removed surgically from 35 patients, were examined histologically. Objectives To elucidate whether or not there is histologic evidence of absorption of sequestrated discs. Summary of Background Data Spontaneous disappearance of diminution of lumbar herniated discs in the spinal canal has been recognized, and this could be a possible explanation for relief of symptoms without surgery. The mechanism of this phenomenon is unclear. Methods Sequestrated discs removed surgically from 35 patients were examined histologically. Results In 30 cases, neovascularization was observed at the periphery of the sequestrated discs. Many foamy cells (macrophages) were present in the vascularized areas. In addition, immunohistochemistry revealed that many spindle-shaped, fibroblast-like cells were positive for CD68, a marker of macrophages. No fibrous scar formation was observed in any region. Conclusion These findings suggest that organization is not a main course for this type of herniated disc and that a kind of “absorption” process occurs predominantly in the healing stage.

CAG repeat disorder models and human neuropathology: similarities and differences

CAG repeat diseases are hereditary neurodegenerative disorders caused by expansion of a polyglutamine tract in each respective disease protein. They include at least nine disorders, including Huntington’s disease (HD), dentatorubral pallidoluysian atrophy (DRPLA), spinal and bulbar muscular atrophy (SBMA), and the spinocerebellar ataxias SCA1, SCA2, SCA3 (also known as Machado-Joseph disease), SCA6, SCA7, and SCA17. It is thought that a gain of toxic function resulting from the protein mutation plays important and common roles in the pathogenesis of these diseases. Recent studies have disclosed that, in addition to the presence of clinical phenotypes and conventional neuropathology in each disease, human brains affected by CAG repeat diseases share several polyglutamine-related changes in their neuronal nuclei and cytoplasm including the formation of intranuclear inclusions. Although these novel pathologic changes also show a distribution pattern characteristic to each disease, they are generally present beyond the lesion distribution of neuronal loss, suggesting that neurons are affected much more widely than has been recognized previously. Various mouse models of CAG repeat diseases have revealed that CAG repeat lengths, which are responsible for polyglutamine diseases in humans, are not sufficient for creating the conditions characteristic of each disease in mice. Although high expression of mutant proteins in mice results in the successful generation of polyglutamine-related changes in the brain, there are still some differences from human pathology in the lesion distribution or cell types that are affected. In addition, no model has yet successfully reproduced the specific neuronal loss observed in humans. Although there are no models that fully represent the neuropathologic changes present in humans, the data obtained have provided evidence that clinical onset is not clearly associated with neuronal cell death, but depends on intranuclear accumulation of mutant proteins in neurons.