Familial Forms Of Amyotrophic Lateral Sclerosis Research Articles

Skeletal muscle-restricted expression of human SOD1 causes motor neuron degeneration in transgenic mice

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease of motor neurons (MNs) that causes skeletal muscle paralysis. Familial forms of ALS are linked to mutations in the superoxide dismutase-1 (SOD1) gene. The mechanisms of human SOD1 (hSOD1) toxicity to MNs are unknown. We hypothesized that skeletal muscle is a primary site of pathogenesis in ALS that triggers MN degeneration. We created transgenic (tg) mice expressing wild-type-, G37R- and G93A-hSOD1 gene variants only in skeletal muscle. These tg mice developed age-related neurologic and pathologic phenotypes consistent with ALS. Affected mice showed limb weakness and paresis with motor deficits. Skeletal muscles developed severe pathology involving oxidative damage, protein nitration, myofiber cell death and marked neuromuscular junction (NMJ) abnormalities. Spinal MNs developed distal axonopathy and formed ubiquitinated inclusions and degenerated through an apoptotic-like pathway involving capsase-3. Mice expressing wild-type and mutant forms of hSOD1 developed MN pathology. These results demonstrate that human SOD1 in skeletal muscle has a causal role in ALS and identify a new non-autonomous mechanism for MN degeneration explaining their selective vulnerability. The discovery of instigating molecular toxicities or disease progression determinants within skeletal muscle could be very valuable for the development of new effective therapies for the treatment and cure of ALS.

Global Analysis of TDP-43 Interacting Proteins Reveals Strong Association with RNA Splicing and Translation Machinery

TDP-43 is a highly conserved and ubiquitously expressed member of the heterogeneous nuclear ribonucleoprotein (hnRNP) family of proteins. Recently, TDP-43 was shown to be a major disease protein in the ubiquitinated inclusions characteristic of most cases of amyotrophic lateral sclerosis (ALS), tau-negative frontotemporal lobar degeneration (FTLD), and inclusion body myopathy. In these diseases, TDP-43 is redistributed from its predominantly nuclear location to ubiquitin-positive, cytoplasmic foci. The extent to which TDP-43 drives pathophysiology is unknown, but the identification of mutations in TDP-43 in familial forms of ALS and FTLD-U suggests an important role for this protein in pathogenesis. Little is known about TDP-43 function and only a few TDP-43 interacting proteins have been previously identified, which makes further insight into both the normal and pathological functions of TDP-43 difficult. Here we show, via a global proteomic approach, that TDP-43 has extensive interaction with proteins that regulate RNA metabolism. Some interactions with TDP-43 were found to be dependent on RNA-binding, whereas other interactions are RNA-independent. Disease-causing mutations in TDP-43 (A315T and M337V) do not alter its interaction profile. TDP-43 interacting proteins largely cluster into two distinct interaction networks, a nuclear/splicing cluster and a cytoplasmic/translation cluster, strongly suggesting that TDP-43 has multiple roles in RNA metabolism and functions in both the nucleus and the cytoplasm. Finally, we found numerous TDP-43 interactors that are known components of stress granules, and indeed, we find that TDP-43 is also recruited to stress granules.

Recent advances in motor neuron disease

Amyotrophic lateral sclerosis (ALS) is the most common and most aggressive form of adult onset motor neuron degeneration. Despite intensive research, riluzole remains the only drug with proven efficacy. The cause and pathogenesis of the motor neuron degeneration in ALS appears to be a complex and multifactorial process. In this study, we review recent advances in our understanding of the molecular basis of sporadic and familial forms of ALS and improvements in the treatment of ALS patients. The discovery of mutations in the DNA/RNA-binding proteins transactive response DNA-binding protein 43 (TDP-43) and fused in sarcoma in familial ALS and the cytosolic sequestration of TDP-43 occurring in sporadic ALS opens new avenues in ALS research and suggests that altered RNA processing may be involved in the disease pathogenesis. The survival of ALS patients continues to increase most likely due to noninvasive respiratory ventilation, early percutaneous endoscopic gastrostomy and multidisciplinary care in ALS clinics. Recent insights in the pathology and genetics of ALS have improved our understanding of motor neuron degeneration and will hopefully lead to novel treatment strategies in ALS. Awaiting these, the beneficial effect of multidisciplinary care of ALS patients on survival and quality of life has become clear.

Treatment for familial amyotrophic lateral sclerosis/motor neuron disease.

Amyotrophic lateral sclerosis (ALS), also known as motor neuron disease (MND), is a rare neurodegenerative disease. Approximately 5% to 7% of ALS/MND patients report a family history of a similarly affected relative. Superoxide dismutase-1 gene mutations are the cause in about 20% of familial cases. In those with non-familial (sporadic) ALS/MND the cause is unknown. Also unknown is whether patients with familial and sporadic ALS/MND respond differently to treatment. To systematically review the literature and to answer the specific question: 'Is there a difference in the response to treatment between patients with sporadic and familial forms of ALS?' In May 2006 we searched the Cochrane Neuromuscular Disease Group Trials Register, MEDLINE (January 1966 to May 2006) and EMBASE (January 1980 to May 2006) for randomized controlled trials (RCTs). Two review authors read the titles and abstracts of all articles and reviewed the full text of all possibly relevant articles. We scanned references of all included trials to identify additional relevant articles. For all trials eligible for inclusion we contacted the authors to request the necessary raw data. Studies had to meet two criteria: (a) randomized controlled study design, and (b) inclusion of patients with both familial and sporadic ALS/MND. We attempted to contact authors of all trials that met inclusion criteria. We obtained data regarding ALS/MND type (sporadic versus familial), treatment assignment (active versus placebo), survival and ALS Functional Rating Scale scores for four large RCTs that included 822 sporadic and 41 familial ALS patients. We could not obtain data from 25 potentially eligible studies (17 trial authors could not be contacted and eight were unwilling to provide data). There was no statistical evidence for a different response to treatment in patients with familial ALS/MND compared to those with sporadic ALS/MND. The pooled estimate of the hazard ratio for the interaction term (treatment x familial ALS) suggested a more beneficial response with respect to survival among patients with familial ALS/MND, but the result was not statistically significant. Estimates of the rate of decline on the ALS Functional Rating Scale also suggested a slightly better response to treatment among those with familial ALS/MND, but the result was not statistically significant. Future RCTs should document whether patients with familial ALS/MND are included and the presence or absence of a mutation in the superoxide dismutase-1 gene amongst those with familial ALS/MND.

Enrichment of C-Terminal Fragments in TAR DNA-Binding Protein-43 Cytoplasmic Inclusions in Brain but not in Spinal Cord of Frontotemporal Lobar Degeneration and Amyotrophic Lateral Sclerosis

TAR DNA-binding protein (TDP-43) has been recently described as a major pathological protein in both frontotemporal dementia with ubiquitin-positive inclusions (FTLD-U) and amyotrophic lateral sclerosis. However, little is known about the relative abundance and distribution of different pathological TDP-43 species, which include hyperphosphorylated, ubiquitinated, and N-terminally cleaved TDP-43. Here, we developed novel N-terminal (N-t) and C-terminal (C-t)-specific TDP-43 antibodies and performed biochemical and immunohistochemical studies to analyze cortical, hippocampal, and spinal cord tissue from frontotemporal dementia with ubiquitin-positive inclusions and amyotrophic lateral sclerosis cases. C-t-specific TDP-43 antibodies revealed similar abundance, morphology, and distribution of dystrophic neurites and neuronal cytoplasmic inclusions in cortex and hippocampus compared with previously described pan-TDP-43 antibodies. By contrast, N-t-specific TDP-43 antibodies only detected a small subset of these lesions. Biochemical studies confirmed the presence of C-t TDP-43 fragments but not extreme N-t fragments. Surprisingly, immunohistochemical analysis of inclusions in spinal cord motor neurons in both diseases showed that they are N-t and C-t positive. TDP-43 inclusions in Alzheimer's disease brains also were examined, and similar enrichment in C-t TDP-43 fragments was observed in cortex and hippocampus. These results show that the composition of the inclusions in brain versus spinal cord tissues differ, with an increased representation of C-t TDP-43 fragments in cortical and hippocampal regions. Therefore, regionally different pathogenic processes may underlie the development of abnormal TDP-43 proteinopathies.

Cognition and amyotrophic lateral sclerosis (ALS).

Amyotrophic lateral sclerosis (ALS) is classically described as a pure motor disease; however, there is growing evidence of a range of cognitive impairment. Cognitive abnormalities include deficiencies in frontal executive skills, varying from mild deficits to meeting criteria for diagnosis of frontotemporal dementia (FTD). Cognitive impairment occurs in sporadic and familial forms of ALS. Patients may present with cognitive deficits before, after, or at the onset of motor neuron disease. Structural and functional imaging studies have shown extramotor cortical degeneration corresponding to levels of frontal executive impairment on neuropsychologic testing. In addition, ALS and a subset of FTD patients display common pathological findings on immunohistochemistry staining. It is believed that these disorders represent a continuum between motor and nonmotor cortical degeneration. The purpose of this article is to review the literature on cognitive deficits in ALS. Identifying changes in cognition is critical for physicians and caregivers of ALS patients, as cognitive decline may interfere with patient compliance. Diagnosis and treatment of cognitive symptoms in ALS patients may improve quality of life.

Role of heat shock response and Hsp27 in mutant SOD1-dependent cell death

The fatal neurodegenerative disorder amyotrophic lateral sclerosis (ALS) is characterized by selective loss of motor neurons and mutations in the copper-zinc superoxide dismutase (SOD1) enzyme underlie one form of familial ALS. The pathogenic mechanism of these mutations is elusive but is thought to involve oxidative stress and protein aggregation. These two phenomena are known to induce heat shock proteins (Hsps) which protect stressed cells through their chaperoning and anti-apoptotic activity. In order to investigate the role of Hsp27 in mutant SOD1-dependent cell death, we used mutant and wild type SOD1 overexpressing N2a mouse neuroblastoma cells. Mutant SOD1-dependent cell death could be induced by heat shock, and by treating the cells with cyclosporine A or lactacystin. Transfection with an Hsp27 expression construct did not protect the N2a cells against mutant SOD1-dependent cell death. However, pre-conditioning N2a cells with a mild heat shock was accompanied by a significant upregulation of Hsp27 in the mutant SOD1 cells, and protected these cells against subsequent cell death induced by a more severe heat shock. Selective inhibition of the Hsp27 upregulation, through the use of Hsp27 siRNA, did not attenuate the protective effect of this treatment. These results show that activation of the heat shock response protects cells against mutant SOD1-dependent cell death, but that Hsp27 is not an essential component of the stress response leading to protection.

Benefit of tianeptine and morphine in a transgenic model of familial amyotrophic lateral sclerosis

The familial form of amyotrophic lateral sclerosis (FALS) has been linked in some cases to dominant mutations in the gene encoding the Cu/Zn superoxide dismutase (SOD1) mutation. Transgenic mice bearing the G93A SOD1 mutation develop clinical symptoms and pathological features similar to those described in the human disease and represent a good model to explore the potential benefit of therapeutic agents. Using this animal model, we tested the efficacy of morphine and tianeptine treatments, separately and in association, on both disease progression and survival. Acute injection of either of them, administered daily and before the onset of the disease, significantly prolonged the survival of the transgenic mice.

Identification of candidate genes in patients with amyotrophic lateral sclerosis by breakpoint characterisation

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder characterized by the selective loss of upper and lower motor neurons in the brain and spinal cord. Familial forms of ALS (FALS) account for 5–10% of all ALS patients and to date two disease genes, SOD1 and ALS2, have been identified.

High dose vitamin E therapy in amyotrophic lateral sclerosis as add-on therapy to riluzole: results of a placebo-controlled double-blind study

Increasing evidence has suggested that oxidative stress may be involved in the pathogenesis of amyotrophic lateral sclerosis (ALS). The antioxidant vitamin E (alpha-tocopherol) has been shown to slow down the onset and progression of the paralysis in transgenic mice expressing a mutation in the superoxide dismutase gene found in certain forms of familial ALS. The current study, a double blind, placebo-controlled, randomised, stratified, parallel-group clinical trial, was designed to determine whether vitamin E (5000 mg per day) may be efficacious in slowing down disease progression when added to riluzole. 160 patients in 6 German centres with either probable or definite ALS (according to the El Escorial Criteria) and a disease duration of less than 5 years, treated with riluzole, were included in this study and were randomly assigned to receive either alpha-tocopherol (5000 mg per day) or placebo for 18 months. The Primary outcome measure was survival, calculating time to death, tracheostomy or permanent assisted ventilation, according to the WFN-Criteria of clinical trials. Secondary outcome measures were the rate of deterioration of function assessed by the modified Norris limb and bulbar scales, manual muscle testing (BMRC), spasticity scale, ventilatory function and the Sickness Impact Profile (SIP ALS/19). Patients were assessed at entry and every 4 months thereafter during the study period until month 16 and at a final visit at month 18. Vitamin E samples were taken for compliance check and Quality Control of the trial. For Safety, a physical examination was performed at baseline and then every visit until the treatment discontinuation at month 18. Height and weight were recorded at baseline and weight alone at the follow-up visits. A neurological examination as well as vital signs (heart rate and blood pressure), an ECG and VEP's were recorded at each visit. Furthermore, spontaneously reported adverse experiences and serious adverse events were documented and standard laboratory tests including liver function tests performed. For Statistical Analysis, the population to be considered for the primary outcome measure was an "intent-to-treat" (ITT) population which included all randomised patients who had received at least one treatment dose (n = 160 patients). For the secondary outcome measures, a two way analysis of variance was performed on a patient population that included all randomised patients who had at least one assessment after inclusion. Concerning the primary endpoint, no significant difference between placebo and treatment group could be detected either with the stratified Logrank or the Wilcoxon test. The functional assessments showed a marginal trend in favour of vitamin E, without reaching significance. Neither the primary nor the secondary outcome measures could determine whether a megadose of vitamin E is efficacious in slowing disease progression in ALS as an add-on therapy to riluzol. Larger or longer studies might be needed. However, administration of this megadose does not seem to have any significant side effects in this patient population.

P38α stress-activated protein kinase phosphorylates neurofilaments and is associated with neurofilament pathology in amyotrophic lateral sclerosis

Neurofilament middle and heavy chains (NFM and NFH) are heavily phosphorylated on their carboxy-terminal side-arm domains in axons. The mechanisms that regulate this phosphorylation are complex. Here, we demonstrate that p38α, a member of the stress-activated protein kinase family, will phosphorylate NFM and NFH on their side-arm domains. Aberrant accumulations of neurofilaments containing phosphorylated NFM and NFH side-arms are a pathological feature of amyotrophic lateral sclerosis (ALS) and we also demonstrate that p38α and active forms of p38 family kinases are associated with these accumulations. This is the case for sporadic and familial forms of ALS and also in a transgenic mouse model of ALS caused by expression of mutant superoxide dismutase-1 (SOD1). Thus, p38 kinases may contribute to the aberrant phosphorylation of NFM and NFH side-arms in ALS.

Overexpression of Metallothionein Protects Cultured Motor Neurons Against Oxidative Stress, but not Mutant Cu/Zn-Superoxide Dismutase Toxicity

Mutations in Cu/Zn-superoxide dismutase 1 (SOD1) are responsible for a familial form of amyotrophic lateral sclerosis (FALS). It has been proposed that oxidative stress and abnormal metal homeostasis contribute to death of motor neurons in this disease. Also, inability of motor neurons to upregulate protective proteins under stress may contribute to their preferential vulnerability to toxicity. Metallothioneins (MT) are low molecular weight, metal-binding proteins with established antioxidant capabilities. This study investigated the ability of motor neurons to upregulate MT isoforms in response to expression of mutant SOD1 G93A or exposure to other neurotoxicants, and the ability of MT-I gene transfer to protect motor neurons from these stresses. MT isoform-I and -II were expressed constitutively in astrocytes and other non-neuronal cells of dissociated spinal cord cultures, but not in motor neurons. MT-I/II was upregulated in astrocytes, but not motor neurons, following treatment with ZnCl 2 or excitotoxic concentrations of glutamate. MT-III expression was restricted to neurons and was unaffected by treatment with ZnCl 2, paraquat, or glutamate. Overexpression of MT-I in motor neurons by gene transfer reduced the toxicity of ZnCl 2 and paraquat, but failed to protect them against glutamate or SOD1 G93A. These data are evidence against metal-catalyzed, oxidative stress being the primary mechanisms of toxicity conferred by disease-causing mutations in SOD1.

Alsin is a Rab5 and Rac1 guanine nucleotide exchange factor.

ALS2 is the gene mutated in a recessive juvenile form of amyotrophic lateral sclerosis (ALS2). ALS2 encodes a large protein termed alsin, which contains a number of predicted cell signaling and protein trafficking sequence motifs. To gain insight into the overall function of alsin and to begin to evaluate its role in motor neuron maintenance, we examined the subcellular localization of alsin and the biochemical activities associated with its individual subdomains. We found that the Vps9p domain of alsin has Rab5 guanine nucleotide exchange activity. In addition, alsin interacted specifically with and acted as a guanine nucleotide exchange factor for Rac1. Immunofluorescence and fractionation experiments in both fibroblasts and neurons revealed that alsin is a cytosolic protein, with a significant portion associated with small, punctate membrane structures. Many of these membrane structures also contained Rab5 or Rac1. Upon overexpression of full-length alsin, the overexpressed material was largely cytosolic, indicating that the association with membrane structures could be saturated. We also found that alsin was present in membrane ruffles and lamellipodia. These data suggest that alsin is involved in membrane transport events, potentially linking endocytic processes and actin cytoskeleton remodeling.

Amyotrophic lateral sclerosis: progress and prospects for treatment.

Fifteen years ago, a role for excitotoxic damage in the pathology of amyotrophic lateral sclerosis (ALS) was postulated. This stimulated the development of riluzole, the only available treatment for the disease. Since then, the identification of abnormal forms of superoxide dismutase as the genetic basis of certain familial forms of ALS has provided a huge impetus to the search for new effective treatments for this devastating disease. Transgenic mouse models have been developed expressing these aberrant mutants that develop a form of motor neurone disease the progress of which can be slowed by riluzole. Studies in these mice have provided evidence for a role for excitotoxic, apoptotic and oxidative processes in the development of pathology. The mice can be used for testing molecules targeting these processes as potential therapies, to allow the most promising to be evaluated in humans. Several such agents are currently in clinical trials. Many previous clinical trials in ALS were insufficiently powered to demonstrate any relevant effect on disease progression. This situation has been to some extent remedied in the more recent trials, which have recruited many hundreds of patients. However, with the exception of studies with riluzole, the results of these have been disappointing. In particular, a number of large trials with neurotrophic agents have revealed no evidence for efficacy. Nonetheless, the need for large multinational trials of long duration limits the number that can be carried out and makes important demands on investment. For this reason, surrogate markers that can be used for rapid screening in patients of potential treatments identified in the transgenic mice are urgently needed.

Insights into Lou Gehrig's Disease from the Structure and Instability of the A4V Mutant of Human Cu,Zn Superoxide Dismutase

Mutations in human superoxide dismutase (HSOD) have been linked to the familial form of amyotrophic lateral sclerosis (FALS). Amyotrophic lateral sclerosis (ALS or Lou Gehrig's disease) is one of the most common neurodegenerative disorders in humans. In ALS patients, selective killing of motor neurons leads to progressive paralysis and death within one to five years of onset. The most frequent FALS mutation in HSOD, Ala4→Val, is associated with the most rapid disease progression. Here we identify and characterize key differences in the stability between the A4V mutant protein and its thermostable parent (HSOD-AS), in which free cysteine residues were mutated to eliminate interferences from cysteine oxidation. Denaturation studies reveal that A4V unfolds at a guanidine–HCl concentration 1 M lower than HSOD-AS, revealing that A4V is significantly less stable than HSOD-AS. Determination and analysis of the crystallographic structures of A4V and HSOD-AS reveal structural features likely responsible for the loss of architectural stability of A4V observed in the denaturation experiments. The combined structural and biophysical results presented here argue that architectural destabilization of the HSOD protein may underlie the toxic function of the many HSOD FALS mutations.

Copper-dependent oxidative stress and neurodegeneration.

Copper is an essential trace element, but its redox reactivity leads to risks of damage to cell and tissues. These are well exemplified by several forms of neurodegenerative diseases, either arising as inherited disorders of copper metabolism, such as Menkes' and Wilson's disease, or as conformational diseases such as Alzheimer's disease and prion diseases. This review will cover some aspects of the involvement of copper-mediated oxidative stress in degenerative processes in the central nervous system, with special focus on the familial form of amyotrophic lateral sclerosis (FALS). Furthermore, a possible role of copper reactivity in inducing critical steps in the apoptotic pathways leading to neurodegeneration is envisaged.

Aggregates of mutant protein appear progressively in dendrites, in periaxonal processes of oligodendrocytes, and in neuronal and astrocytic perikarya of mice expressing the SOD1 G93A mutation of familial amyotrophic lateral sclerosis

Mice expressing the G93A and other mutations of Cu,Zn superoxide dismutase (SOD1 G93A) are valid models for the familial form of amyotrophic lateral sclerosis (FALS) with SOD1 mutations and, probably, for sporadic ALS. Adult mice become progressively paralyzed and show most of the histopathological lesions reported in sporadic ALS, i.e. neuronal loss, astrogliosis, ubiquitin and Lewy body-like inclusions, dystrophic axons and fragmentation of the Golgi apparatus (GA) of motor neurons. In transgenic mice, the mutant protein and ubiquitin aggregate within pathological 13 nm thick filaments [Stieber A, Gonatas JO, Gonatas NK. J Neurol Sci 2000;173:53–62]. This immunocytochemical and quantitative study of mice expressing SOD1 G93A establishes the chronological order and cellular localization of aggregates of SOD1 and their correlation with fragmentation of the GA. Young asymptomatic mice expressing SOD1 G93A showed aggregates of mutant SOD1 within neurites, prior to the detection of SOD1 in the perikarya of spinal cord motor neurons and astrocytes. Both dendrites and the periaxonal oligodendroglial cytoplasm, surrounding atrophic axons, contained SOD1 as revealed by immunoelectron microscopy The perikarya of a small percentage of spinal cord motor neurons contained both fragmented GA and aggregates of SOD1; however, about 50% of motor neurons with fragmented GA did not contain SOD1 in the perikaryon, suggesting that aggregates of mutant protein may not directly cause fragmentation of the GA. The mechanism of the putative toxic effect by the mutant protein remains to be clarified. The isolation and biochemical characterization of the filamentous aggregates of mutant protein and ubiquitin from spinal cords of transgenic mice expressing mutations of the SOD1 gene may offer clues on pathogenetic mechanisms.

Familial amyotrophic lateral sclerosis and Cu/Zn superoxide dismutase mutation

Amyotrophic lateral sclerosis (ALS) is a devastating neurodegenerative disorder that involves mainly the motor neuron system. Five to 10 percent of the ALS cases are familial; most others are sporadic. Several mutations in the superoxide dismutase‐1 (SOD1) gene have recently been shown to be associated with about 20% of familial ALS patients. The reduced enzyme activity of many mutant SOD1 points to the possibility that a loss‐of‐function effect of the mutant enzyme is responsible for the pathogenesis of the disease. However, this conflicts with the autosomal dominant inheritance of SOD1 mutation‐associated ALS and the normal SOD1 activity in homozygous patients in a SOD1‐linked ALS family. Current biochemical investigations have provided evidence that mutant SOD1 may catalyze the peroxynitrite‐mediated nitration of protein tyrosine residues, release copper and zinc ions, facilitate apoptosis of neurons and have enhanced peroxidase activity. Immunocytochemical studies demonstrated the presence of intense SOD1 immunoreactivity in Lewy body‐like inclusions, which are characteristic features of a certain form of familial ALS with posterior column involvement, in the lower motor neurons of patients in ALS families with different SOD1 mutations. More recently, strains of transgenic mice expressing mutant SOD1 have been established. These mice clinicopathologically develop a motor neuron disease mimicking human ALS with the exception of pronounced intraneuronal vacuolar degeneration. The overexpression of wild‐type SOD1 in mice has failed to give rise to the disease. Only one transgene for mutant SOD1 is enough to cause motor neuron degeneration and the severity of clinical course correlates with the transgene copy number. These observations in SOD1‐linked familial ALS and its transgenic mouse model suggest a novel neurotoxic function of mutant SOD1.

Molecular biology findings in amyotrophic lateral sclerosis

At presently, the etiology and pathogenesis of amyotrophic lateral sclerosis (ALS) are unknown. In recent years, the genetic background of hereditary motor neuron diseases has been partly defined. In particular, these advances represent an opportunity to improve our understanding of the pathogenesis of the familial and sporadic forms of ALS and thus provide a basis for rational therapeutic approaches. In this article, recent findings on the pathogenesis of the familial form of ALS and their implications for the sporadic form are discussed.

Inherited neurodegenerative diseases and transgenic models.

In recent years, the identification of mutations in specific genes in several inherited neurodegenerative disorders, combined with advances in the field of transgenic methods, has provided neuroscientists and neuropathologists with information and strategies to develop transgenic (Tg) models to study human diseases. These approaches have proved to be extraordinarily useful in modeling familial forms of amyotrophic lateral sclerosis (FALS) and Alzheimer's disease (FAD) and the spectrum of triplet-repeat disorders. Investigations of these models have begun to provide new insights into the roles of disease-specific mutant proteins and the pathogenic mechanisms of disease as well as opportunities to test therapeutic interventions.