Histocompatibility antigens in amyotrophic lateral sclerosis and parkinsonism-dementia on Guam

HLA and amyotrophic lateral sclerosis: a systematic review and meta-analysis

Background: Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease associated with loss of upper and lower motor neurones. It leads to death by respiratory failure and has a typical prognosis of 2-3 years. The immune system has been shown to play a role in the pathophysiology of ALS. Some of the most important immune genes are within the human leukocyte antigen (HLA) region, and a recent genome-wide association study (GWAS) has identified a risk allele for ALS within the HLA region. Older studies have also suggested an HLA association with ALS, with certain HLA alleles showing differing expression between patients and controls. This systematic review and meta-analysis examines the previous studies performed in this field.Methods: We used established publication search engines. Findings were excluded if they did not meet the selection criteria. We then undertook statistical meta-analysis on the eligible papers, using a fixed effects model.Results: There were eight eligible papers. There were three statistically significant meta-analysis findings, although these would not be significant after correction for multiple comparisons. The frequencies of HLA-A9 and HLA-DR4 genotypes were lower in ALS subjects than controls, and HLA-B35 was higher in ALS subjects.Discussion: This systematic review and meta-analysis do not confirm all the previously reported associations of HLA with ALS, but shows three alleles of interest. However, there are limitations to the studies, which include the use of older serotyping methodology and the small numbers of subjects. Given the recent GWAS association with HLA, further modern HLA studies are warranted.

The immunogenetics of neurological disease

Genes encoding antigen-presenting molecules within the human major histocompatibility complex (MHC) account for the highest component of genetic risk for many neurological diseases, such as multiple sclerosis, neuromyelitis optica, Parkinson's disease, Alzheimer's disease, schizophrenia, myasthenia gravis and amyotrophic lateral sclerosis. Myriad genetic, immunological and environmental factors may contribute to an individual's susceptibility to neurological disease. Here, we review and discuss the decades long research on the influence of genetic variation at the MHC locus and the role of immunogenetic killer cell immunoglobulin-like receptor (KIR) loci in neurological diseases, including multiple sclerosis, neuromyelitis optica, Parkinson's disease, Alzheimer's disease, schizophrenia, myasthenia gravis and amyotrophic lateral sclerosis. The findings of immunogenetic association studies are consistent with a polygenic model of inheritance in the heterogeneous and multifactorial nature of complex traits in various neurological diseases. Future investigation is highly recommended to evaluate both coding and non-coding variation in immunogenetic loci using high-throughput high-resolution next-generation sequencing technologies in diverse ethnic groups to fully appreciate their role in neurological diseases.

TDP-43/FUS in motor neuron disease: Complexity and challenges

Amyotrophic lateral sclerosis (ALS), a common motor neuron disease affecting two per 100,000 people worldwide, encompasses at least five distinct pathological subtypes, including, ALS-SOD1, ALS-C9orf72, ALS-TDP-43, ALS-FUS and Guam-ALS. The etiology of a major subset of ALS involves toxicity of the TAR DNA-binding protein-43 (TDP-43). A second RNA/DNA binding protein, fused in sarcoma/translocated in liposarcoma (FUS/TLS) has been subsequently associated with about 1% of ALS patients. While mutations in TDP-43 and FUS have been linked to ALS, the key contributing molecular mechanism(s) leading to cell death are still unclear. One unique feature of TDP-43 and FUS pathogenesis in ALS is their nuclear clearance and simultaneous cytoplasmic aggregation in affected motor neurons. Since the discoveries in the last decade implicating TDP-43 and FUS toxicity in ALS, a majority of studies have focused on their cytoplasmic aggregation and disruption of their RNA-binding functions. However, TDP-43 and FUS also bind to DNA, although the significance of their DNA binding in disease-affected neurons has been less investigated. A recent observation of accumulated genomic damage in TDP-43 and FUS-linked ALS and association of FUS with neuronal DNA damage repair pathways indicate a possible role of deregulated DNA binding function of TDP-43 and FUS in ALS. In this review, we discuss the different ALS disease subtypes, crosstalk of etiopathologies in disease progression, available animal models and their limitations, and recent advances in understanding the specific involvement of RNA/DNA binding proteins, TDP-43 and FUS, in motor neuron diseases.

Adult onset motor neuron disease: worldwide mortality, incidence and distribution since 1950

This review examines the commonly held premise that, apart from the Western Pacific forms, motor neuron disease (MND), has a uniform worldwide distribution in space and time; the methodological problems in studies of MND incidence; and directions for future epidemiological research. MND is more common in men at all ages. Age-specific incidence rises steeply into the seventh decade but the incidence in the very elderly is uncertain. A rise in mortality from MND over recent decades has been demonstrated wherever this has been examined and may be real rather than due to improved case ascertainment. Comparison of incidence studies in different places is complicated by non-standardised methods of case ascertainment and diagnosis but there appear to be differences between well studied populations. In developed countries in the northern hemisphere there is a weak positive correlation between standardised, age-specific incidence and distance from the equator. There is now strong evidence for an environmental factor as the cause of the Western Pacific forms of MND. A number of clusters of sporadic MND have been reported from developed countries, but no single agent identified as responsible.

Models of environmentally induced neurological disease: epidemiology and etiology of amyotrophic lateral sclerosis and parkinsonism-dementia in the Western Pacific

Amyotrophic lateral sclerosis (ALS) on Guam previously attained incidence rates 50 to 100 times that of the continental United States and Europe and accounted for one in five deaths among Chamorros over age 25. A second neurological disorder in high incidence, parkinsonism-dementia (PD), and the early appearance in those populations of neurofibrillary tangles such as are seen in Alzheimer's disease and normal ageing have also been noted. Incidence and mortality rates of both diseases have declined dramatically during the past 30 years, and today, the risk of developing either disease among Guamanian Chamorros is only several times higher than in non-Guamanian populations. The decline is most likely a consequence of increased acculturation over the past three decades, with a concomitant decrease in isolation, changes in dietary habits and local water supplies, and much less dependence on locally grown foodstuffs. Similar declines are evident in the remaining two Pacific foci of high- incidence ALS, namely the Kii Peninsula focus in Japan and southern West New Guinea where western contact and introduction of new foodstuffs have occurred.The accumulating epidemiological, genetic and environmental evidence, as well as the development of new and promising experimental animal models, support the hypothesis that a basic metabolic defect, provoked by chronic nutritional deficiencies of calcium, lead to increased intestinal absorption of toxic metals and the co-deposition of calcium, aluminium and silicon in neurons of patients with ALS and PD. This elemental deposition is thought to result in aberrant microtubule assembly and/or abnormal post-translational modification of the amyloid precursor protein leading to widespread formation of neurofibrillary tangles, the hallmark pathological features in these disorders. The naturalistic paradigms of these foci in the Western Pacific have provided insights to understanding not only ALS and PD but other neurological disorders, such as classical ALS, Parkinson's disease, Alzheimer's disease and early neuronal ageing.

Haptoglobin groups in motor neuron disease

Haptoglobin (Hp) groups were investigated in 81 patients with motor neuron disease. A significant excess of heterozygotes was observed, accentuated among males and in the progressive spinal muscular atrophy subgroup. The results are discussed in terms of a possible influence of Hp in the immunological response.

Amyotrophic lateral sclerosis: Part 2. Etiopathogenesis

The pathogenesis of the motor neuronal degeneration in amyotrophic lateral sclerosis (ALS) is unclear, though several possible etiological factors are currently being investigated. A unifying hypothesis will have to explain the diverse geographical occurrence, clinical features, and selective vulnerability and relative resistance of different neuronal populations in the disease. It is possible that different biochemical defects underlie this diversity, or alternatively that the many factors incriminated in the etiology may act upon an underlying genetic-biochemical abnormality to trigger premature neuronal death. Viruses, metals, endogenous toxins, immune dysfunction, endocrine abnormalities, impaired DNA repair, altered axonal transport, and trauma have all been etiologically linked with ALS, but convincing research evidence of a causative role for any of these factors is yet to be demonstrated.

Imaging of calcium and aluminum in neurofibrillary tangle-bearing neurons in parkinsonism-dementia of Guam

We report the distribution and imaging of calcium and aluminum in neurofibrillary tangle (NFT)-bearing neurons within Sommer's sector of the hippocampus in Guamanian patients with parkinsonism-dementia, using a method of computer-controlled electron beam x-ray micro-analysis and wavelength dispersive spectrometry. Calcium and aluminum were distributed in cell bodies and axonal processes of NFT-bearing neurons. The elemental images show that both calcium and aluminum deposits occur within the same NFT-bearing hippocampal neuron in this dementing disease, suggesting that these elements are involved in NFT formation. No prominent concentrations of calcium and aluminum were imaged in non-NFT-containing regions within the pyramidal cell layer of the parkinsonism-dementia cases or in the control cases. These findings support the hypothesis that secondary hyperparathyroidism resulting from low environmental calcium and magnesium in the high-incidence focus of amyotrophic lateral sclerosis and parkinsonism-dementia on Guam had led to abnormal deposition of calcium and aluminum in the central nervous system.

Blood groups, immunoglobulin allotypes and dermatoglyphic features of patients with amyotrophic lateral sclerosis and parkinsonism-dementia of Guam

Blood group frequencies, immunoglobulin allotypes, and dermatoglyphic patterns were determined on patients with amyotrophic lateral sclerosis (ALS) and parkinsonism-dementia (PD), two chronic, degenerative, neurologic disorders of unknown cause found commonly among the Chamorros of the Mariana Islands, in an attempt to identify a specific genetic or phenetic marker associated with either disorder. With the exception of the Kidd system, no significant differences were found in blood group frequencies nor in immunoglobulin allotypes between ALS patients, PD patients, and unaffected controls. The dermatoglyphic analysis demonstrated that ALS patients had higher frequencies of palmar patterns and accessory triradii in the IV interdigital area, and PD patients had significantly higher frequencies of complete simian creases and of palmar patterns in the thenar/I interdigital area than unaffected controls. The frequencies of the remaining dermatoglyphic traits showed no significant differences. We conclude that none of the marker systems tested show a particular pattern of association in patients and controls or a genetic predisposition to either disorder, and that early identification of at-risk individuals remains elusive.

Amyotrophic lateral sclerosis among Chamorro migrants from Guam

Amyotrophic lateral sclerosis (ALS), which occurs in unusually high incidence among the Chamorro people on the island of Guam, has developed in 28 Chamorro migrants--24 of whom had onset in the United States, Japan, Germany, or Korea--after periods of absence from Guam of 1 to 34 years. Thus, the latency period for the disease, if caused by environmental factors on Guam, may be over three decades. Four further patients developed ALS within 1 to 14 years of their return to Guam after long-term residence in the continental United States. The minimum exposure time to environmental variables on Guam, based on age at migration, was 18 years, and all patients had spent their childhood and adolescence on Guam. Estimates of crude mortality rates for ALS from these data are considerably higher than for the United States population, and lower than the ALS mortality rates for nonmigrant Chamorros on Guam.

Neuromuscular junction macromolecules in the pathogenesis of amyotrophic leteral sclerosis

An hypothesis regarding the pathogenesis of amyotrophic lateral sclerosis is presented, which places emphasis on extraneural cells. Classical experimental denervation is compared and contrasted with motor neuron disease, both from information in the literature as well as concepts deriving from the hypothesis. Background information regarding neuromuscular junction-specific (16S) acetylcholinesterase and a basal lamina-enriched surface glycoprotein (fibronectin) are presented, which suggest not only their mutual interaction, but likely parallel regulation on muscle cell surfaces by the motor nerve. Since 16S acetylcholinesterase likely contains basal lamina-type collagen and fibronectin specifically associates with collagen, a model relating activation of latent collagenase enzyme in amyotrophic lateral sclerosis is described. It is suggested that continued degeneration, including transneuronal effects, of the motor system ensues from random, continuous loss of nerve-muscle adherence resulting from collagen resorption at the neuromuscular junction.

Cellular immunity in Guamanians with amyotrophic lateral sclerosis and Parkinsonism-dementia

To test the hypothesis that host resistance factors may be abnormal in Guamanians in whom amyotrophic lateral sclerosis and Parkinsonism-dementia develop, cellular immunity was evaluated in both diseases and compared to that of Guamanians with other nervous-system diseases, normal adult Guamanians and non-Guamanians with amyotrophic lateral sclerosis and Parkinsonism. Diminished responses to skin-test antigens, lymphopenia, diminished per cent and total T cells and, less frequently, decreased mitogen responses were seen in Guamanian patients with amytorophic lateral sclerosis and Parkinsonism-dementia but not in the other patient or normal groups. Guamanian patients with amyotrophic lateral sclerosis and diminished cellular immunity had an increased frequency of HLA-Bw35 (P less than 0.005) and shorter mean duration of disease (P less than 0.05) than those with normal cellular immunity. In Parkinsonism dementia diminished cellular immunity was less strongly associated with HLA-BW35 (P less than 0.05) and was not associated with differences in duration of disease. Normal Guamanians and those with other nervous-system diseases showed no association of diminished cellular immunity with HLA-Bw35. The association appeared disease-related, with onset concomitant with the neurologic expression of Guamanian amyotrophic lateral sclerosis and Parkinsonism-dementia.