Similar topographical distribution of neurofibrillary tangles in amyotrophic lateral sclerosis and parkinsonism-dementia complex in people living in the Kii peninsula of Japan suggests a single tauopathy

Endemic parkinsonism: clusters, biology and clinical features

The term 'endemic parkinsonism' refers to diseases that manifest with a dominant parkinsonian syndrome, which can be typical or atypical, and are present only in a particular geographically defined location or population. Ten phenotypes of endemic parkinsonism are currently known: three in the Western Pacific region; two in the Asian-Oceanic region; one in the Caribbean islands of Guadeloupe and Martinique; and four in Europe. Some of these disease entities seem to be disappearing over time and therefore are probably triggered by unique environmental factors. By contrast, other types persist because they are exclusively genetically determined. Given the geographical clustering and potential overlap in biological and clinical features of these exceptionally interesting diseases, this Review provides a historical reference text and offers current perspectives on each of the 10 phenotypes of endemic parkinsonism. Knowledge obtained from the study of these disease entities supports the hypothesis that both genetic and environmental factors contribute to the development of neurodegenerative diseases, not only in endemic parkinsonism but also in general. At the same time, this understanding suggests useful directions for further research in this area.

Expression of Mutant Ubiquitin and Proteostasis Impairment in Kii Amyotrophic Lateral Sclerosis/Parkinsonism-Dementia Complex Brains

Kii amyotrophic lateral sclerosis/parkinsonism-dementia complex (ALS/PDC) is a progressive neurodegenerative disorder that is endemic to the Kii peninsula of Japan. The disorder is clinically characterized by a variable combination of parkinsonism, dementia, and motor neuron symptoms. Despite extensive investigations, the etiology and pathogenesis of ALS/PDC remain unclear. At the neuropathological level, Kii ALS/PDC is characterized by neuronal loss and tau-dominant polyproteinopathy. Here, we report the accumulation of several proteins involved in protein homeostasis pathways, that is, the ubiquitin-proteasome system and the autophagy-lysosome pathway, in postmortem brain tissue from a number of Kii ALS/PDC cases (n = 4). Of particular interest is the presence of a mutant ubiquitin protein (UBB+1), which is indicative of disrupted ubiquitin homeostasis. The findings suggest that abnormal protein aggregation is linked to impaired protein homeostasis pathways in Kii ALS/PDC.

Tau imaging detects distinctive distribution of tau pathology in ALS/PDC on the Kii Peninsula

Objective

To characterize the distribution of tau pathology in patients with amyotrophic lateral sclerosis/parkinsonism dementia complex on the Kii Peninsula (Kii ALS/PDC) by tau PET using [¹¹C]PBB3 as ligand.

Methods

This is a cross-sectional study of 5 patients with ALS/PDC and one asymptomatic participant with a dense family history of ALS/PDC from the Kii Peninsula who took part in this study. All were men, and their age was 76 ± 8 (mean ± SD) years. Thirteen healthy men (69 ± 6 years) participated as healthy controls (HCs). Dynamic PET scans were performed following injection of [¹¹C]PBB3, and parametric PET images were generated by voxel-by-voxel calculation of binding potential (BP*_ND) using a multilinear reference tissue model. [¹¹C] Pittsburgh compound B (PiB) PET, MRI, and cognitive tests were also performed.

Results

A voxel-based comparison of [¹¹C]PBB3 BP*_ND illustrated PET-detectable tau deposition in the cerebral cortex and white matter, and pontine basis including the corticospinal tract in Kii ALS/PDC patients compared with HCs (uncorrected p < 0.05). Group-wise volume of interest analysis of [¹¹C]PBB3 BP*_ND images showed increased BP*_ND in the hippocampus and in frontal and parietal white matters of Kii ALS/PDC patients relative to HCs (p < 0.05, Holm-Sidak multiple comparisons test). BP*_ND in frontal, temporal, and parietal gray matters correlated with Mini-Mental State Examination scores in Kii ALS/PDC patients (p < 0.05). All Kii ALS/PDC patients were negative for [¹¹C]PiB (β-amyloid) except one with marginal positivity.

Conclusion

[¹¹C]PBB3 PET visualized the characteristic topography of tau pathology in Kii ALS/PDC, corresponding to clinical phenotypes of this disease.

Amyotrophic lateral sclerosis and parkinsonism-dementia complex of the Hohara focus of the Kii Peninsula: A multiple proteinopathy?

The high incidence of amyotrophic lateral sclerosis (ALS) and parkinsonism-dementia complex (PDC) has been previously known in the Kii Peninsula of Japan and in Guam. Recently, the accumulation of various proteins, such as tau, trans-activation response DNA binding protein 43 kDa (TDP-43), and alpha-synuclein (αSyn), was reported in the brains of patients with ALS/PDC in Guam. To confirm whether similar findings are present in Kii ALS/PDC, we neuropathologically examined the brains and spinal cords of 18 patients with ALS/PDC (clinical diagnoses: eight ALS and 10 PDC) in Hohara Village, which is the eastern focus of Kii ALS. The average age at death was 71.6 years, and 16 patients (88.9%) had a family history of ALS/PDC. Autopsy specimens were immunohistochemically examined with antibodies against four major proteins. Neurofibrillary tangles, including ghost tangles, and tau-positive astrocytes were distributed widely in all of the brains examined, and TDP-43-positive neuronal cytoplasmic inclusions were observed mainly in the limbic system. Synuclein pathology was present in 14 patients (77.8%). These patients were classified into three pathological subtypes according to the most prominent proteinopathy: the tauopathy-dominant type, the TDP-43 proteinopathy-dominant type, and the synucleinopathy-dominant type. Five patients with severe tau deposition showed clinical features of atypical parkinsonism and dementia with or without motor neuron disease. Eight patients were predominated by phosphorylated TDP-43 inclusions and clinically showed ALS, and five patients were predominated by synuclein pathology and clinically showed signs of PDC. Based on the common characteristic tau pathology, three subtypes seemed to be pathologically continuous on a spectrum of a single disease. Thus, we conclude that ALS/PDC in the Hohara focus of the Kii Peninsula is a single disease characterized neuropathologically by a multiple proteinopathy, even though the clinical manifestations of the three subtypes differed from each other. It remains unclear whether the coexistence of the three proteinopathies was incidental or pathogenetically related.

A critical review of the postulated role of the non-essential amino acid, β-N-methylamino-L-alanine, in neurodegenerative disease in humans

The compound BMAA (β-N-methylamino-L-alanine) has been postulated to play a significant role in four serious neurological human diseases: Amyotrophic Lateral Sclerosis/Parkinsonism Dementia Complex (ALS/PDC) found on Guam, and ALS, Parkinsonism, and dementia that occur globally. ALS/PDC with symptoms of all three diseases first came to the attention of the scientific community during and after World War II. It was initially associated with cycad flour used for food because BMAA is a product of symbiotic cycad root-dwelling cyanobacteria. Human consumption of flying foxes that fed on cycad seeds was later suggested as a source of BMAA on Guam and a cause of ALS/PDC. Subsequently, the hypothesis was expanded to include a causative role for BMAA in other neurodegenerative diseases including Alzheimer's disease (AD) through exposures attributed to proximity to freshwaters and/or consumption of seafood due to its purported production by most species of cyanobacteria. The hypothesis that BMAA is the critical factor in the genesis of these neurodegenerative diseases received considerable attention in the medical, scientific, and public arenas. This review examines the history of ALS/PDC and the BMAA-human disease hypotheses; similarities and differences between ALS/PDC and the other diseases with similar symptomologies; the relationship of ALS/PDC to other similar diseases, studies of BMAA-mediated effects in lab animals, inconsistencies and data gaps in the hypothesis; and other compounds and agents that were suggested as the cause of ALS/PDC on Guam. The review concludes that the hypothesis of a causal BMAA neurodegenerative disease relationship is not supported by existing data.

Potential Environmental Factors in Amyotrophic Lateral Sclerosis

The causes of amyotrophic lateral sclerosis (ALS) are largely unknown, and may always be multiple, including environmental factors. Monogenetic determinants of ALS are involved in roughly 20% of all cases (including 10% familial cases). Less well understood multigenetic causes may contribute to another 20% to 80%. Environmental factors likely play a role in the development of ALS in susceptible individuals, but proved causation remains elusive. This article discusses the possible factors of male gender (males are selectively exposed to different influences, or genetically predisposed to be susceptible), smoking, military service, exercise, electrical exposure, heavy metals, agricultural chemicals, and geographic clusters.

Alzheimer disease and amyotrophic lateral sclerosis: an etiopathogenic connection

The etiopathogenesis of neither the sporadic form of Alzheimer disease (AD) nor of amyotrophic lateral sclerosis (ALS) is well understood. The activity of protein phosphatase-2A (PP2A), which regulates the phosphorylation of tau and neurofilaments, is negatively regulated by the myeloid leukemia-associated protein SET, also known as inhibitor-2 of PP2A, I2(PP2A). In AD brain, PP2A activity is compromised, probably because I2(PP2A) is overexpressed and is selectively cleaved at asparagine 175 into an N-terminal fragment, I2NTF, and a C-terminal fragment, I2CTF, and both fragments inhibit PP2A. Here, we analyzed the spinal cords from ALS and control cases for I2(PP2A) cleavage and PP2A activity. As observed in AD brain, we found a selective increase in the cleavage of I2(PP2A) into I2NTF and I2CTF and inhibition of the activity and not the expression of PP2A in the spinal cords of ALS cases. To test the hypothesis that both AD and ALS could be triggered by I2CTF, a cleavage product of I2(PP2A), we transduced by intracerebroventricular injections newborn rats with adeno-associated virus serotype 1 (AAV1) containing human I2CTF. AAV1-I2CTF produced reference memory impairment and tau pathology, and intraneuronal accumulation of Aβ by 5-8 months, and motor deficit and hyperphosphorylation and proliferation of neurofilaments, tau and TDP-43 pathologies, degeneration and loss of motor neurons and axons in the spinal cord by 10-14 months in rats. These findings suggest a previously undiscovered etiopathogenic relationship between sporadic forms of AD and ALS that is linked to I2(PP2A) and the potential of I2(PP2A)-based therapeutics for these diseases.

α-Synuclein pathology in the amyotrophic lateral sclerosis/parkinsonism dementia complex in the Kii Peninsula, Japan

α-Synuclein pathology was examined in the brains and spinal cords of 10 patients with amyotrophic lateral sclerosis (ALS)/parkinsonism-dementia complex (PDC) in the Kii Peninsula, Japan. Various types of phosphorylated α-synuclein-positive structures including neuronal cytoplasmic inclusions, dystrophic neurites, and glial cytoplasmic inclusions were found in all ALS/PDC cases. There were phosphorylated α-synuclein-positive neurons in 8 cases (80%), and the amygdala was most severely affected. Phosphorylated α-synuclein was distributed mainly in the limbic system and brainstem; tau pathology was more prevalent than α-synuclein pathology in most affected areas. In the substantia nigra, periaqueductal gray, locus coeruleus, raphe nuclei, dorsal nucleus of the vagus nerve, hypoglossal nucleus or ventral horn, and intermediolateral nucleus of the spinal cord, α-synuclein pathology was more predominant than tau pathology in only 1 or 2 patients. Phosphorylated α-synuclein- positive structures were not found in the molecular layer of the cerebellum. Phosphorylated α-synuclein frequently colocalized with tau in neuron cell bodies, neurites, and glia. Immunoblots of sarkosyl-insoluble fractions extracted from the brain of 1 patient showed a triplet of α-synuclein-immunoreactive bands that were ubiquitinated. These results suggest that interaction between tau and α-synuclein be involved in the pathogenesis of Kii ALS/PDC.

Is neurodegenerative disease a long-latency response to early-life genotoxin exposure?

Western Pacific amyotrophic lateral sclerosis and parkinsonism-dementia complex, a disappearing neurodegenerative disease linked to use of the neurotoxic cycad plant for food and/or medicine, is intensively studied because the neuropathology (tauopathy) is similar to that of Alzheimer's disease. Cycads contain neurotoxic and genotoxic principles, notably cycasin and methylazoxymethanol, the latter sharing chemical relations with nitrosamines, which are derived from nitrates and nitrites in preserved meats and fertilizers, and also used in the rubber and leather industries. This review includes new data that influence understanding of the neurobiological actions of cycad and related genotoxins and the putative mechanisms by which they might trigger neurodegenerative disease.

Motor neuron disease and frontotemporal dementia: One, two, or three diseases?

The relationship between motor neurone disease (MND) and frontotemporal dementia (FTD) has been a topic of scientific exploration for over hundred years. A connection between both diseases was first postulated in 1932 and has been strengthened by a steady stream of case reports since then. By the late 20th century, the link between both diseases was firmly established, with the resulting condition often referred to as MND/FTD. Several strands of evidence support the notion of an MND/FTD overlap. First, a small but well-documented group of patients present with a full-blown FTD, associated with MND. Second, subtle but characteristic changes in frontal-executive functions and social cognition have been described in non-demented MND patients, often in association with frontal atrophy/hypoactivity on neuroimaging. Third, amyotrophic features have been documented in patients primarily diagnosed with FTD. Moreover, the same genetic defect can lead to FTD and MND phenotypes in different members of the same family. However, as the current research is moving toward a more fine-grained evaluation, an increasingly complex picture begins to emerge. Some features, such as psychotic symptoms or severe language deficits (particularly in comprehension and verb processing), seem to occur more often in MND/dementia than in the classical FTD. On the basis of the review of 100 years of literature as well as 10 years of clinical experience of longitudinal follow-up of MND/dementia patients, this review argues in favor of MND/dementia (or, more precisely, MND/dementia/aphasia) as a separate clinical entity, not sufficiently explained by a combination of MND and FTD.

Identification of novel susceptibility loci for Guam neurodegenerative disease: challenges of genome scans in genetic isolates

Amyotrophic lateral sclerosis/parkinsonism-dementia complex (ALS/PDC) is a fatal neurodegenerative disease found in the Chamorro people of Guam and other Pacific Island populations. The etiology is unknown, although both genetic and environmental factors appear important. To identify loci for ALS/PDC, we conducted both genome-wide linkage and association analyses, using approximately 400 microsatellite markers, in the largest sample assembled to date, comprising a nearly complete sample of all living and previously sampled deceased cases. A single, large, complex pedigree was ascertained from a village on Guam, with smaller families and a case-control sample ascertained from the rest of Guam by population-based neurological screening and archival review. We found significant evidence for two regions with novel ALS/PDC loci on chromosome 12 and supportive evidence for the involvement of the MAPT region on chromosome 17. D12S1617 on 12p gave the strongest evidence of linkage (maximum LOD score, Z(max) = 4.03) in our initial scan, with additional support in the complete case-control sample in the form of evidence of allelic association at this marker and another nearby marker. D12S79 on 12q also provided significant evidence of linkage (Z(max) = 3.14) with support from flanking markers. Our results suggest that ALS/PDC may be influenced by as many as three loci, while illustrating challenges that are intrinsic in genetic analyses of isolated populations, as well as analytical strategies that are useful in this context. Elucidation of the genetic basis of ALS/PDC should improve our understanding of related neurodegenerative disorders including Alzheimer disease, Parkinson disease, frontotemporal dementia and ALS.

Pathological TDP-43 in parkinsonism-dementia complex and amyotrophic lateral sclerosis of Guam

Pathological TDP-43 is the major disease protein in frontotemporal lobar degeneration characterized by ubiquitin inclusions (FTLD-U) with/without motor neuron disease (MND) and in amyotrophic lateral sclerosis (ALS). As Guamanian parkinsonism-dementia complex (PDC) or Guamanian ALS (G-PDC or G-ALS) of the Chamorro population may present clinically similar to FTLD-U and ALS, TDP-43 pathology may be present in the G-PDC and G-ALS. Thus, we examined cortical or spinal cord samples from 54 Guamanian subjects for evidence of TDP-43 pathology. In addition to cortical neurofibrillary and glial tau pathology, G-PDC was associated with cortical TDP-43 positive dystrophic neurites and neuronal and glial inclusions in gray and/or white matter. Biochemical analyses showed the presence of FTLD-U-like insoluble TDP-43 in G-PDC, but not in Guam controls (G-C). Spinal cord pathology of G-PDC or G-ALS was characterized by tau positive tangles as well as TDP-43 positive inclusions in lower motor neurons and glial cells. G-C had variable tau and negligible TDP-43 pathology. These results indicate that G-PDC and G-ALS are associated with pathological TDP-43 similar to FTLD-U with/without MND as well as ALS, and that neocortical or hippocampal TDP-43 pathology distinguishes controls from disease subjects better than tau pathology. Finally, we conclude that the spectrum of TDP-43 proteinopathies should be expanded to include neurodegenerative cognitive and motor diseases, affecting the Chamorro population of Guam.