Genetic epidemiology of amyotrophic lateral sclerosis

Energy intake and amyotrophic lateral sclerosis

Roy Walford, a physician and scientist who pioneered research on the anti-aging effects of caloric restriction and subjected himself to a low-energy diet, recently died from amyotrophic lateral sclerosis (ALS). Information from his case, epidemiological findings, and recent controlled studies in mouse models of ALS suggest that low-energy diets might render motor neurons vulnerable to degeneration, whereas high-energy diets are ameliorative. This contrasts with the effects of low-energy diets on various neuronal populations in the brain that respond adaptively, activating pathways that promote plasticity and resistance to disease. One reason that motor neurons might be selectively vulnerable to low-energy diets is that they are unable to engage neuroprotective responses to energetic stress response involving the protein chaperones, such as, heat-shock protein-70.

KNS-760704 [(6R)-4,5,6,7-tetrahydro-N6-propyl-2, 6-benzothiazole-diamine dihydrochloride monohydrate] for the treatment of amyotrophic lateral sclerosis

Developing effective treatments for chronic neurodegenerative disorders such as amyotrophic lateral sclerosis (ALS) has proven extremely difficult. ALS is universally fatal, characterized by progressive weakness due to the degeneration of upper and lower motor neurons, and leads eventually to respiratory failure which is the usual cause of death. Only a single treatment has been approved, the modestly effective nonspecific neuroprotectant Rilutek (riluzole; 2-amino-6-(trifluoromethoxy)benzothiazole). KNS-760704 [(6R)-4,5,6,7-tetrahydro-N6-propyl-2,6-benzothiazole-diamine dihydrochloride, RPPX], a synthetic amino-benzothiazole with demonstrated activity in maintaining mitochondrial function, is being developed as a treatment for ALS. It has proven to be effective in multiple in vitro and in vivo assays of neuroprotection, including the G93A-SOD1 mutant mouse model; however, its specific mechanism of action remains unknown. The potential of KNS-760604 as a treatment for ALS was first suggested by studies showing that its optical enantiomer, Mirapex[(6S)-4,5,6,7-tetrahydro-N6-propyl-2,6-benzothiazole-diamine; pramipexole dihydrochloride; PPX], a high-affinity agonist at dopamine D2, D3, and D4 receptors, exhibits important neuroprotective properties independent of its dopamine receptor agonism. In cell-based assays, both RPPX and PPX reduce the production of reactive oxygen species (ROS), attenuate the activation of apoptotic pathways, and increase cell survival in response to a variety of neurotoxins. However, PPX has limited utility as a clinical neuroprotective agent because the drug concentrations required for neuroprotection would likely produce unacceptable dopaminergic side effects. RPPX, on the other hand, while possessing the same neuroprotective potential as PPX, is a much lower-affinity dopamine receptor agonist and may therefore be more useful in the treatment of ALS. This review will examine the data supporting the hypothesis that the RPPX may have therapeutic potential for the treatment of neurodegenerative disorders including ALS. In addition, we will briefly review recent preclinical data in support of RPPX, and discuss the current status of its clinical development.

50bp deletion in the promoter for superoxide dismutase 1 (SOD1) reduces SOD1 expression in vitro and may correlate with increased age of onset of sporadic amyotrophic lateral sclerosis

The objective was to test the hypothesis that a described association between homozygosity for a 50bp deletion in the SOD1 promoter 1684bp upstream of the SOD1 ATG and an increased age of onset in SALS can be replicated in additional SALS and control sample sets from other populations. Our second objective was to examine whether this deletion attenuates expression of the SOD1 gene. Genomic DNA from more than 1200 SALS cases from Ireland, Scotland, Quebec and the USA was genotyped for the 50bp SOD1 promoter deletion. Reporter gene expression analysis, electrophoretic mobility shift assays and chromatin immunoprecipitation studies were utilized to examine the functional effects of the deletion. The genetic association for homozygosity for the promoter deletion with an increased age of symptom onset was confirmed overall in this further study (p=0.032), although it was only statistically significant in the Irish subset, and remained highly significant in the combined set of all cohorts (p=0.001). Functional studies demonstrated that this polymorphism reduces the activity of the SOD1 promoter by approximately 50%. In addition we revealed that the transcription factor SP1 binds within the 50bp deletion region in vitro and in vivo. Our findings suggest the hypothesis that this deletion reduces expression of the SOD1 gene and that levels of the SOD1 protein may modify the phenotype of SALS within selected populations.

Protein biomarkers for amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a progressive motor neuron disease with largely unknown pathogenesis that typically results in death within a few years from diagnosis. There are currently no effective therapies for ALS. Clinical diagnosis usually takes several months to complete and the long delay between symptom onset and diagnosis limits the possibilities for effective intervention and clinical trials. The establishment of protein biomarkers for ALS may aid an earlier diagnosis, facilitating the search for effective therapeutic interventions and monitoring drug efficacy during clinical trials. Biomarkers could also be used to discriminate between subtypes of ALS, to measure disease progression and to detect susceptibility for developing ALS or monitor adverse effects of drug treatment. The present review will discuss the opportunities and proteomic platforms used for biomarker discovery efforts in ALS, summarizing putative ALS protein biomarkers identified in different biofluids.

New application of intelligent agents in sporadic amyotrophic lateral sclerosis identifies unexpected specific genetic background

BACKGROUND

Few genetic factors predisposing to the sporadic form of amyotrophic lateral sclerosis (ALS) have been identified, but the pathology itself seems to be a true multifactorial disease in which complex interactions between environmental and genetic susceptibility factors take place. The purpose of this study was to approach genetic data with an innovative statistical method such as artificial neural networks to identify a possible genetic background predisposing to the disease. A DNA multiarray panel was applied to genotype more than 60 polymorphisms within 35 genes selected from pathways of lipid and homocysteine metabolism, regulation of blood pressure, coagulation, inflammation, cellular adhesion and matrix integrity, in 54 sporadic ALS patients and 208 controls. Advanced intelligent systems based on novel coupling of artificial neural networks and evolutionary algorithms have been applied. The results obtained have been compared with those derived from the use of standard neural networks and classical statistical analysis

RESULTS

Advanced intelligent systems based on novel coupling of artificial neural networks and evolutionary algorithms have been applied. The results obtained have been compared with those derived from the use of standard neural networks and classical statistical analysis. An unexpected discovery of a strong genetic background in sporadic ALS using a DNA multiarray panel and analytical processing of the data with advanced artificial neural networks was found. The predictive accuracy obtained with Linear Discriminant Analysis and Standard Artificial Neural Networks ranged from 70% to 79% (average 75.31%) and from 69.1 to 86.2% (average 76.6%) respectively. The corresponding value obtained with Advanced Intelligent Systems reached an average of 96.0% (range 94.4 to 97.6%). This latter approach allowed the identification of seven genetic variants essential to differentiate cases from controls: apolipoprotein E arg158cys; hepatic lipase -480 C/T; endothelial nitric oxide synthase 690 C/T and glu298asp; vitamin K-dependent coagulation factor seven arg353glu, glycoprotein Ia/IIa 873 G/A and E-selectin ser128arg.

CONCLUSION

This study provides an alternative and reliable method to approach complex diseases. Indeed, the application of a novel artificial intelligence-based method offers a new insight into genetic markers of sporadic ALS pointing out the existence of a strong genetic background.

Genetic susceptibility to environmental toxicants in ALS

Environmental toxicants such as heavy metals, pesticides, and chemicals appear to be risk factors for sporadic amyotrophic lateral sclerosis (SALS). An impaired ability to break down these toxicants because of differences in detoxification genes could underlie some cases of this disease. We therefore examined the frequencies of single nucleotide polymorphisms (SNPs) in 186 SALS patients and 186 controls at the allele, genotype, and haplotype levels for the metallothionein (MT) family of genes, metal transcription factor-1 (MTF-1), and glutathione synthetase (GSS). Exposure to heavy metals, solvents/chemicals, and pesticides/herbicides was assessed by questionnaire, and gene-toxicant interactions were analyzed. An intronic SNP upstream of MT-Ie differed in SALS patients and controls at the allele and genotype levels. Haplotypes covering MT-I isoforms also differed between the two groups. Alleles and genotypes of one MTF-1 SNP differed in female SALS patients. One GSS haplotype interacted with both metals and solvents/chemicals to increase the risk of the disease. Differences in genes involved in handling toxicants, and interactions between toxicants and these genes, appear to be present in some patients with SALS. This suggests that impaired detoxification mechanisms play a role in SALS.

Emerging disease-modifying therapies for the treatment of motor neuron disease/amyotropic lateral sclerosis

It has been > 130 years since the first description of the upper and lower motor neuron disease called amyotropic lateral sclerosis (ALS). Sadly, there has been little change in the long interval over which this disease is diagnosed, or in its poor prognosis. Significant gains have been made, however, in understanding its pathophysiology and in symptomatic care. Disease-causing mutations have been identified and used to create animal models. Other identified mutations may increase susceptibility and cause disease only in a particular environment and at a particular age. A number of 'downstream' molecular pathways have been implicated, including transcriptional disturbances, protein aggregation, excitotoxicity, mitochondrial dysfunction, oxidative stress, neuroinflammation, cytoskeletal and axonal transport derangements, growth factor dysregulation and apoptosis. This knowledge has led to an impressive pipeline of candidate therapies that offer hope for finally being able to alter ALS disease progression. These are described and prioritized herein, and suggestions are offered for efficiently sifting through them.

An immunological epitope selective for pathological monomer-misfolded SOD1 in ALS

Misfolding of Cu/Zn-superoxide dismutase (SOD1) is emerging as a mechanism underlying motor neuron degeneration in individuals with amyotrophic lateral sclerosis (ALS) who carry a mutant SOD1 gene (SOD1 ALS). Here we describe a structure-guided approach to developing an antibody that specifically recognizes monomer-misfolded forms of SOD1. We raised this antibody to an epitope that is normally buried in the SOD1 native homodimer interface. The SOD1 exposed dimer interface (SEDI) antibody recognizes only those SOD1 conformations in which the native dimer is disrupted or misfolded and thereby exposes the hydrophobic dimer interface. Using the SEDI antibody, we established the presence of monomer-misfolded SOD1 in three ALS mouse models, with G37R, G85R and G93A SOD1 mutations, and in a human individual with an A4V SOD1 mutation. Despite ubiquitous expression, misfolded SOD1 was found primarily within degenerating motor neurons. Misfolded SOD1 appeared before the onset of symptoms and decreased at the end stage of the disease, concomitant with motor neuron loss.

Genes and the environment in neurodegeneration

Neurodegenerative diseases are a heterogeneous group of pathologies which includes complex multifactorial diseases, monogenic disorders and disorders for which inherited, sporadic and transmissible forms are known. Factors associated with predisposition and vulnerability to neurodegenerative disorders may be described usefully within the context of gene-environment interplay. There are many identified genetic determinants for neurodegeneration, and it is possible to duplicate many elements of recognized human neurodegenerative disorders in animal models of the disease. However, there are similarly several identifiable environmental influences on outcomes of the genetic defects; and the course of a progressive neurodegenerative disorder can be greatly modified by environmental elements. In this review we highlight some of the major neurodegenerative disorders (Alzheimer's disease, Parkinson's disease, Amyotrophic lateral sclerosis, Huntington's disease, and prion diseases.) and discuss possible links of gene-environment interplay including, where implicated, mitochondrial genes.

Physiotherapeutic conduct in amyotrophic lateral sclerosis

Amyotrophic Lateral Sclerosis (ALS) is a fatal progressive neurodegenerative disease with multifactorial etiology for which, so far, there is no effective medicinal treatment. However, by means of kinesiotherapy intervention and patient guidance and care, physiotherapy can delay physical functional losses, muscle fatigue and immobility of the joint-muscle system, thereby improving the quality of life. This survey had the aim of reviewing the physiotherapeutic conduct currently used in ALS cases. Monthly monitoring is recommended, with changes in goals and conduct at each stage of the disease, activities to be pursued around the home, and emphasis on stretching, muscle strengthening, posture adequacy and respiratory kinesiotherapy.

Structure, folding, and misfolding of Cu,Zn superoxide dismutase in amyotrophic lateral sclerosis

Fourteen years after the discovery that mutations in Cu, Zn superoxide dismutase (SOD1) cause a subset of familial amyotrophic lateral sclerosis (fALS), the mechanism by which mutant SOD1 exerts toxicity remains unknown. The two principle hypotheses are (a) oxidative damage stemming from aberrant SOD1 redox chemistry, and (b) misfolding of the mutant protein. Here we review the structure and function of wild-type SOD1, as well as the changes to the structure and function in mutant SOD1. The relative merits of the two hypotheses are compared and a common unifying principle is outlined. Lastly, the potential for therapies targeting SOD1 misfolding is discussed.

Ascending neuropathology in the CNS of a mutant SOD1 mouse model of amyotrophic lateral sclerosis

Transgenic mice expressing a mutated human Cu/Zn superoxide dismutase (SOD1) gene develop a motor neuron disease similar to familial amyotrophic lateral sclerosis (FALS). While the histopathology and the inflammatory reactions in the spinal cord of these mice are well described, their spatiotemporal extension into brain areas and the relationship between degenerative and inflammatory events remain obscure. In the present study, we investigated the time course and extent of degenerative changes and inflammatory reactions in the CNS during progression of the disease in a transgenic FALS model, the SOD1-G93A mouse with histological and immunohistochemical methods. Compared to non-transgenic littermates, the SOD1-G93A transgenics developed widespread degeneration in both motor and extra-motor regions up to telencephalic regions, including the cerebral cortex but sparing distinct regions like the striatum and hippocampus. We provide evidence that these degenerative processes are accompanied by intense inflammatory reactions in the brain, which spatiotemporally correlate with degeneration and comprise besides strong astro- and microgliotic reactions also an influx of peripheral immune cells such as T-lymphocytes and dendritic cells. Both degeneration and inflammatory reactions spread caudocranially, starting at 2 months in the spinal cord and reaching the telencephalon at 5 months of age. Since the corticospinal tract lacked any signs of degeneration, we conclude that the upper and the lower motor neurons degenerate independently of each other.

VEGF at the neurovascular interface: therapeutic implications for motor neuron disease

VEGF was discovered almost 25 years ago, and its angiogenic activity has been extensively studied ever since. Accumulating evidence indicates, however, that VEGF also has direct effects on neuronal cells. VEGF exerts neuroprotective effects on various cultured neurons of the central nervous system. In vivo, VEGF controls the correct migration of facial branchiomotor neurons in the developing hindbrain and stimulates the proliferation of neural stem cells in enriched environments and after cerebral ischemia. Transgenic mice expressing reduced levels of VEGF develop late-onset motor neuron degeneration, reminiscent of amyotrophic lateral sclerosis (ALS), whereas reduced levels of VEGF have been implicated in a polyglutamine-induced model of motor neuron degeneration. Recent data further reveal that intracerebroventricular delivery of recombinant VEGF protein delays disease onset and prolongs survival of ALS rats, whereas intramuscular administration of a VEGF-expressing lentiviral vector increases the life expectancy of ALS mice by as much as 30%. Deciphering the precise role of VEGF at the neurovascular interface promises to uncover new insights into the development and pathology of the nervous system, helpful to design novel strategies to treat (motor) neurodegenerative disorders.

Mutational analysis of the Cu/Zn superoxide dismutase gene in a Catalan ALS population: should all sporadic ALS cases also be screened for SOD1?

BACKGROUND

SOD1 gene mutations are the most common identified cause of ALS, accounting for approximately 20% of familial ALS cases and around 4% of sporadic ALS cases. However, the prevalence of SOD1 varies in different ethnic groups. No previous epidemiological studies have been carried out in Catalonia.

OBJECTIVE

To determine the prevalence of SOD1 gene mutations in a Catalan ALS population, and to analyze the genotype-phenotype relationship.

MATERIALS AND METHODS

30 different FALS pedigrees and 94 sporadic ALS patients were screened for SOD1 mutations using direct sequence analysis.

RESULTS

Five of the 30 FALS pedigrees (16.6%) carried a SOD1 mutant. The mutations identified in this group were G37R, D76V, S105L, I112M and N139H. Four SOD1 mutants (4.25%) were found in the sporadic ALS group (SALS). The overall frequency (FALS plus SALS) of SOD1 mutations in our series was 6.45%. In the SALS group, D90A was identified in a patient presenting the typical Scandinavian phenotype. A 53-year-old woman with no family history of ALS carried the N139H mutation. Two unrelated sporadic ALS cases carried the A140A SOD1 mutant.

CONCLUSIONS

The prevalence of the SOD1 mutation in FALS in Catalonia is similar to levels in other Mediterranean countries, but lower than those in reports studying the Belgian, Japanese, and Scottish populations. The prevalence of the SOD1 mutation was 4.25% in patients with no family history of ALS. These results may have significant repercussions on genetic counseling, and screening for the SOD1 mutation in sporadic ALS cases must therefore be considered.

Amyotrophic lateral sclerosis: contemporary concepts in etiopathogenesis and pharmacotherapy

Among the neurodegenerative diseases associated with ageing, amyotrophic lateral sclerosis (ALS) remains the most devastating. The disease inexorably progresses, the vast majority of pharmacotherapies have failed to modify the disease course, death ensues on average within 5 years of symptom onset and increasing numbers of individuals are afflicted with the disease. However, significant advances in our understanding of the natural history of ALS and of the fundamental nature of the biological defect underlying motor neuron degeneration have been gained, providing hope for the development of novel pharmacotherapies for ALS. Among these is the recognition that ALS is a biologically heterogeneous disorder in which genetics, environment and ageing all interrelate. The observation of clinical heterogeneity, with initial clinical manifestations serving as predictors of survivorship, is of considerable importance in designing therapeutic trials. The presence of frontotemporal dysfunction in a subset of patients has led to increased interest in the relationship between ALS and the degenerative tauopathies. Ultimately, the degenerating motor neurons do not die alone. The contribution of both microglia and astrocytes to the degenerative process are increasingly recognised. Understanding how these processes interrelate has become critical to understanding the pharmacotherapy of ALS and in the design of clinical trials. This review will highlight recent epidemiological and neurochemical advances in our understanding of ALS, and place them into the context of understanding the development of novel treatment avenues for this devastating disease.

Effects of cadmium on structure and enzymatic activity of Cu,Zn-SOD and oxidative status in neural cells

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disorder disease. Ten percent of the ALS patients are congenital (familial ALS), and the other 90% are sporadic ALS (SALS). It has been shown that mutations found in the Cu,Zn-SOD cause 20% of the familial ALS due to its low enzyme activity. We hypothesized that heavy metals may interfere the structure of Cu,Zn-SOD protein to suppress its activity in some of the SALS. In this study, we expressed and characterized the recombinant human Cu,Zn-SOD under various concentrations of Cu(2+), Zn(2+), and Cd(2+). By atomic absorption spectrophotometry, we demonstrated that adding of cadmium significantly increased the content of cadmium ion, but reduced its Zn(2+) content and enzyme activity of the Cu,Zn-SOD protein. The data of circular dichroism spectra demonstrated that the secondary structure of Cu,Zn-SOD/Cd is different from Cu,Zn-SOD, but close to apo-SOD. In addition to the effect of cadmium on Cu,Zn-SOD, cadmium was also shown to induce neural cell apoptosis. To further investigate the mechanism of neural cell apoptosis induced by cadmium, we used proteomics to analyze the altered protein expressions in neural cells treated with cadmium. The altered proteins include cellular structural proteins, stress-related and chaperone proteins, proteins involved in reactive oxygen species (ROS), enzyme proteins, and proteins that mediated cell death and survival signaling. Taken together, in this paper, we demonstrate that cadmium decreases the content of Zn(2+), changes the conformation of Cu,Zn-SOD protein to decrease its enzyme activity, and causes oxidative stress-induced neural cell apoptosis.

Diagnostic investigation and multidisciplinary management in motor neuron disease

Amyotrophic lateral sclerosis (ALS) is the most common adult-onset motor neuron disease. ALS is a progressive neurodegenerative disorder, involving motor neurons in the cerebral cortex, brainstem and spinal cord, presenting with a combination of upper and lower motor neuron signs. Etiology remains undetermined, although a multifactorial origin is widely accepted including genetic factors, auto-immunity, oxidative stress, glutamate excitotoxicity and abnormal neurofilament aggregation. The absence of specific diagnostic testing, and variable clinical presentations make the diagnosis of ALS challenging, relying upon correlation of clinical, electrophysiological and neuroimaging data. The disease is relentlessly progressive, with dysarthria, dysphagia, tetraparesis, and respiratory insufficiency due to ongoing respiratory muscle paresis. There is no specific treatment for ALS. Riluzole, a glutamate antagonist, is the only FDA approved drug for ALS, but has only a modest effect on survival. The multiplicity and progressiveness of the disabilities in ALS, highlights the need for a coordinated multidisciplinary rehabilitation program managing symptoms, respiratory care, dysphagia and nutrition, dysarthria and communication, physical and occupational therapy. The main goals are to prolong independence, prevent complications and improve quality of life.

Acquired nucleic acid changes may trigger sporadic amyotrophic lateral sclerosis

This article brings together evidence to support the hypothesis that acquired nucleic acid changes are the proximate causes, "triggers," or "initiators" of sporadic amyotrophic lateral sclerosis (ALS). Clinical features that support this hypothesis include focal onset and spread, and the individualized rate of progression. Clues from the epidemiology of sporadic ALS include the increase in its incidence with age, suggesting accrual of time-dependent changes, and the emergence of smoking, a known carcinogen, as its first "more likely than not" exogenous risk factor. The identification of any exogenous risk factor suggests that a large proportion of sporadic cases have a triggering mechanism susceptible to that factor. Ingestion of the products of cycad circinalis has been hypothesized to be implicated in causing Western Pacific ALS. Cycad contains both neurotoxic factors and carcinogens. The dissimilarity of Western Pacific ALS from neurotoxic diseases suggests a greater likelihood that the effects of DNA alkylation are its proximate cause.

The genetic epidemiology of neurodegenerative disease

Gene defects play a major role in the pathogenesis of degenerative disorders of the nervous system. In fact, it has been the very knowledge gained from genetic studies that has allowed the elucidation of the molecular mechanisms underlying the etiology and pathogenesis of many neurodegenerative disorders. In this review, we discuss the current status of genetic epidemiology of the most common neurodegenerative diseases: Alzheimer disease, Parkinson disease, Lewy body dementia, frontotemporal dementia, amyotrophic lateral sclerosis, Huntington disease, and prion diseases, with a particular focus on similarities and differences among these syndromes.

The Pathobiology of Amyotrophic Lateral Sclerosis: A Proteinopathy?

Amyotrophic lateral sclerosis (ALS) is increasingly considered to be a disorder of multiple etiologies that have in common progressive degeneration of both upper and lower motor neurons, ultimately giving rise to a relentless loss of muscle function. This progressive degeneration is associated with heightened levels of oxidative injury, excitotoxicity, and mitochondrial dysfunction--all occurring concurrently. In this article, we review the evidence that suggests, in common with other age-dependent neurodegenerative disorders, that ALS can be considered a disorder of protein aggregation. Morphologically, this is evident as Bunina bodies, ubiquitin-immunoreactive fibrils or aggregates, neurofilamentous aggregates, mutant copper/zinc superoxide dismutase (SOD1) aggregates in familial ALS variants harboring mutations in SOD1, peripherin-immunoreactive aggregates within spinal motor neurons and as neuroaxonal spheroids, and in an increasingly greater population of patients with ALS with cognitive impairment, both intra- and extraneuronal tau aggregates. We review the evidence that somatotopically specific patterns of altered kinase and phosphatase activity are associated with alterations in the phosphorylation state of these proteins, altering either solubility or assembly characteristics. The role of nonneuronal cells in mediating motor neuronal injury is discussed in the context of alterations in tyrosine kinase activity and enhanced protein phosphorylation.

Amyotrophic lateral sclerosis: possible role of environmental influences

This treatise briefly discusses the genetic features of ALS and reviews environmental exposures in sporadic ALS. At least 10 genetic foci are responsible for cases of familial motor neuron disease and more are yet to be discovered. Research into sporadic ALS suggests that abundant factors apparently participate in the disease process. A singular cause and unifying disease and nerve dysfunction in polyneuropathies, a multitude of genetic, toxic, autoimmune, infectious, and systematic processes seem to be at play. The ALS syndrome likely will not be dissimilar.

Hsp27 and Hsp70 administered in combination have a potent protective effect against FALS-associated SOD1-mutant-induced cell death in mammalian neuronal cells

Amyotrophic lateral sclerosis (ALS) is an adult-onset degenerative disorder characterised by the death of motor neurons in the cortex, brainstem, and spinal cord; resulting in progressive muscle weakness, atrophy, and death from respiratory paralysis, usually within 3-5 years of symptom onset. Approximately 10% of ALS cases are familial (FALS). Mutations in superoxide dismutase-1 (SOD1) cause approximately 20% of FALS cases and there is overwhelming evidence that a toxic gain of function is the cause of the disease. We have previously shown that FALS-associated SOD1 disease mutants enhanced neuronal death in response to a wide range of stimuli tested whereas wt-SOD1 protected against all insults. We demonstrate for the first time that over-expression of either heat shock protein Hsp27 or Hsp70 has a protective effect against SOD1 disease associated mutant-induced cell death. However, over-expression of Hsp27 and Hsp70 together has a greater potent anti-apoptotic effect, than when expressed singly, against the damaging effects of mutant SOD1. Our results indicate that FALS-associated SOD1 disease mutants possess enhanced death-inducing properties and lead to increased apoptosis which can be prevented by either the use of specific caspase inhibitors or Hsp27 and/or Hsp70 over-expression. This potent protective effect of Hsp27 and Hsp70 against the FALS-associated SOD1 disease mutants may be of potential therapeutic importance.

Scale-free neurodegeneration: cellular heterogeneity and the stretched exponential kinetics of cell death

Neurodegenerative disorders are an insidious group of diseases characterized by severe physical and cognitive effects that often have devastating consequences for the lives of affected individuals and their families. One feature common to a significant proportion of these diseases is that affected neurons commit to undergoing an active form of degeneration known as programmed cell death, or apoptosis. Although intense effort over the past several years has resulted is a remarkable increase in our understanding of the molecular events involved in neurodegeneration, our knowledge regarding the cellular and tissue properties that determine the temporal patterns of neuronal attrition is limited. We recently demonstrated that neurodegenerative kinetics in various diseases fit well to exponential decay functions, and proposed a universal one-hit switch mechanism in which mutant and injured neurons exist in a viable state characterized by an increased but constant risk of initiating apoptosis (Nature, 406, p. 195). Here we show that a heavy-tailed stretched exponential function is better able to account for neurodegenerative kinetic data. Moreover, normalization of all available data according to their corresponding best-fit stretched exponential parameters suggest that the generalized model is consistent with a universal mechanism of neuronal cell death that is greatly improved over the constant risk model. In contrast to the original model in which all cells exhibit an identical risk of initiating apoptosis, the stretched exponential model is consistent with each neuron experiencing a constant risk that is different from that experienced by other cells in the degenerating population, perhaps due to spatial differences in the cellular microenvironment. Intriguingly, the predicted distribution of risk across the cell population can be fit by a power-law function, further suggesting that scale-free properties of degenerating neuronal tissues might act as potent regulators of the kinetics of cell death in neural tissue.

Spinal cord molecular profiling provides a better understanding of amyotrophic lateral sclerosis pathogenesis

Research efforts in amyotrophic lateral sclerosis (ALS) have not yet provided a comprehensive explanation of the disease pathogenesis, which is emerging as a complex interaction between multiple factors. Gene expression studies traditionally based on single mRNA specie analysis have recently progressed to allow entire transcriptional profiles of affected tissues to be obtained through array-based methods. This experimental approach has significantly improved our understanding of the molecular changes occurring in ALS, although its limitations in the detection of low-abundance transcripts in tissues with a high level of complexity are becoming increasingly recognized. In this paper, experimental findings based on an expression study in post-mortem spinal cord from sporadic ALS individuals will be discussed in light of recently published data using array analysis in an animal model of the disease. Previous expression data obtained using conventional techniques are also compared. Through the analysis of the information arising from ALS post-mortem and animal model tissues studies, we have identified a pattern of molecular events in which factors implicated in the immune response, cytoprotection and growth-differentiation are differentially regulated in a time-dependent way from early to advanced stages of disease progression.

A novel exon 5 mutation (N139H) in the SOD1 gene in a Spanish family associated with incomplete penetrance

BACKGROUND

Allelic heterogeneity and phenotype variability-especially in age at onset, penetrance and progression-are reported in ALS1 families. For this reason, SOD1 gene mutation data in ALS1 patients are currently being gathered to better understand the genotype-phenotype relationship in this disorder. Here, we report the clinical and molecular characteristics of a Spanish ALS1 family with incomplete penetrance.

PATIENTS AND METHODS

Clinical data including age at onset, initial topography, progression and survival were available in three affected members. Erythrocyte SOD1 activity was measured in four individuals. Analysis of the SOD1 gene was performed by PCR and direct sequencing.

RESULTS

A novel missense mutation in the exon 5 of the SOD1 gene, an A-to-C transversion at nucleotide position 1485 leading to N139H residue change, was identified in three family members. The phenotype was similar in all cases, with initial symptoms in the distal limb muscles and a mean survival time of around 4 years. Incomplete penetrance was observed in our family, as two obligate carriers did not develop any symptoms of amyotrophic lateral sclerosis (ALS).

CONCLUSIONS

N139H is the fifth SOD1 gene mutation reported in Spain, and the first one presenting with incomplete penetrance. Genetic counseling for at-risk relatives in these low-penetrance families could be difficult as some individuals harbouring the mutation remain asymptomatic throughout their lives. Further genetic characterisation of ALS1 families should provide information regarding the distribution of SOD1 mutants in different ethnic groups.

DNA/RNA helicase gene mutations in a form of juvenile amyotrophic lateral sclerosis (ALS4)

Juvenile amyotrophic lateral sclerosis (ALS4) is a rare autosomal dominant form of juvenile amyotrophic lateral sclerosis (ALS) characterized by distal muscle weakness and atrophy, normal sensation, and pyramidal signs. Individuals affected with ALS4 usually have an onset of symptoms at age <25 years, a slow rate of progression, and a normal life span. The ALS4 locus maps to a 1.7-Mb interval on chromosome 9q34 flanked by D9S64 and D9S1198. To identify the molecular basis of ALS4, we tested 19 genes within the ALS4 interval and detected missense mutations (T3I, L389S, and R2136H) in the Senataxin gene (SETX). The SETX gene encodes a novel 302.8-kD protein. Although its function remains unknown, SETX contains a DNA/RNA helicase domain with strong homology to human RENT1 and IGHMBP2, two genes encoding proteins known to have roles in RNA processing. These observations of ALS4 suggest that mutations in SETX may cause neuronal degeneration through dysfunction of the helicase activity or other steps in RNA processing.

VEGF: necessary to prevent motoneuron degeneration, sufficient to treat ALS?

Since Charcot recognized the devastating disorder amyotrophic lateral sclerosis (ALS) in 1874, many theories have been proposed to explain its pathogenesis, but it remains as deadly and incurable as ever. Three years ago it was reported that reduced levels of vascular endothelial growth factor (VEGF) caused ALS-like motoneuron degeneration in mice. Recent evidence indicates that insufficient VEGF is also a risk factor for ALS in humans. Although VEGF was once considered to be only a specific angiogenic factor, emerging evidence indicates that it also displays important neuroprotective activity. These insights have primed widespread interest in developing VEGF-based therapies for (moto)neuron degenerative disorders, raising new hope for the treatment of ALS and other neurodegenerative diseases.

Identification of two novel mutations in the Cu/Zn superoxide dismutase gene with familial amyotrophic lateral sclerosis: mass spectrometric and genomic analyses

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disorder affecting motor neurons. The majority of patients are sporadic cases, while 5-10% of the patients have a family history of ALS (fALS). Mutations in the gene that encodes cytoplasmic Cu/Zn superoxide dismutase (SOD1) have been identified in about 25% of fALS cases. Although the precise pathogenesis of ALS is still unknown, experimental studies including animal models suggest that fALS is caused by the toxic gain-of-function of the SOD1 mutant. We have analyzed not only SOD1 gene mutation by genomic sequencing, but also SOD1 mutant protein by liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS). We analyzed 33 fALS patients and found 10 mutations in SOD1 gene, in which two were novel: Asp101His substitution in exon 4 and Gly141Glu substitution in exon 5. Here, we present their mass spectrometric protein analyses and clinical features.

Monomeric Cu,Zn-superoxide dismutase is a common misfolding intermediate in the oxidation models of sporadic and familial amyotrophic lateral sclerosis

Proteinacious intracellular aggregates in motor neurons are a key feature of both sporadic and familial amyotrophic lateral sclerosis (ALS). These inclusion bodies are often immunoreactive for Cu,Zn-superoxide dismutase (SOD1) and are implicated in the pathology of ALS. On the basis of this and a similar clinical presentation of symptoms in the familial (fALS) and sporadic forms of ALS, we sought to investigate the possibility that there exists a common disease-related aggregation pathway for fALS-associated mutant SODs and wild type SOD1. We have previously shown that oxidation of fALS-associated mutant SODs produces aggregates that have the same morphological, structural, and tinctorial features as those found in SOD1 inclusion bodies in ALS. Here, we show that oxidative damage of wild type SOD at physiological concentrations ( approximately 40 microm) results in destabilization and aggregation in vitro. Oxidation of either mutant or wild type SOD1 causes the enzyme to dissociate to monomers prior to aggregation. Only small changes in secondary and tertiary structure are associated with monomer formation. These results indicate a common aggregation prone monomeric intermediate for wild type and fALS-associated mutant SODs and provides a link between sporadic and familial ALS.