Research advances in amyotrophic lateral sclerosis, 2009 to 2010

Current therapy in amyotrophic lateral sclerosis (ALS): A review on past and future therapeutic strategies

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease that affects the first and second motoneurons (MNs), associated with muscle weakness, paralysis and finally death. The exact etiology of the disease still remains unclear. Currently, efforts to develop novel ALS treatments which target specific pathomechanisms are being studied. The mechanisms of ALS pathogenesis involve multiple factors, such as protein aggregation, glutamate excitotoxicity, oxidative stress, mitochondrial dysfunction, apoptosis, inflammation etc. Unfortunately, to date, there are only two FDA-approved drugs for ALS, riluzole and edavarone, without curative treatment for ALS. Herein, we give an overview of the many pathways and review the recent discovery and preclinical characterization of neuroprotective compounds. Meanwhile, drug combination and other therapeutic approaches are also reviewed. In the last part, we analyze the reasons of clinical failure and propose perspective on the treatment of ALS in the future.

Advances in Stem Cell Research- A Ray of Hope in Better Diagnosis and Prognosis in Neurodegenerative Diseases

Neurodegeneration and neurodegenerative disorders have been a global health issue affecting the aging population worldwide. Recent advances in stem cell biology have changed the current face of neurodegenerative disease modeling, diagnosis, and transplantation therapeutics. Stem cells also serve the purpose of a simple in-vitro tool for screening therapeutic drugs and chemicals. We present the application of stem cells and induced pluripotent stem cells (iPSCs) in the field of neurodegeneration and address the issues of diagnosis, modeling, and therapeutic transplantation strategies for the most prevalent neurodegenerative disorders. We have discussed the progress made in the last decade and have largely focused on the various applications of stem cells in the neurodegenerative research arena.

Distributed Features of Vimentin-Containing Neural Precursor Cells in Olfactory Bulb of SOD1G93A Transgenic Mice: a Study about Resource of Endogenous Neural Stem Cells

No any effective treatments can prevent from the motor neuron degeneration in amyotrophic lateral sclerosis (ALS) at present. In order to modulating the endogenous neural precursor cells (NPCs) to repairing the degenerative motor neurons in ALS, we studied the alteration of endogenous vimentin-containing NPCs in olfactory bulb (OB) at the different stages of SOD1 wlid-type and G93A transgenic mice. The results showed that the vimentin-containing cells (VCCs) were mainly distributed in the glomerular layer (Gl), the accessory OB (AOB), the OB core, the granular cell layer (GRO) and the mitral cell layer (MI)+the internal plexiform layer (IPL) of the OB of adult mice. Almost all VCCs in Gl, OB core and GRO were the GFAP positive cells. Almost all VCCs in AOB were the Oligo-2 positive cells. Fewer VCCs in MI+IPL were the NeuN positive cells. VCCs significantly increased in the OB core and Gl of adult OB at the pre-onset, onset and progression stages of ALS-like G93A transgenic disease, particularly in OB core. All increased VCCs were the GFAP positive cells. Our data suggested that there extensively existed the endogenous vimentin-containing NPCs in the OB of adult mice, which was a potential resource of neural stem cells, they could differentiate into astrocyte, oligodendrocyte and neuron cells, were a potential astrocyte neuroregenerative response in adult OB in the ALS-like disease, were a potential pathway to repair the degenerated motor neurons.

Changes in the Expression of FUS/TLS in Spinal Cords of SOD1 G93A Transgenic Mice and Correlation with Motor-Neuron Degeneration

In order to searching the possible pathogenesis of amyotrophic lateral sclerosis (ALS), we examined the expression and distribution of FUS/TLS protein in the different anatomic regions, segments and neural cells of adult spinal cord at the different stages of the SOD1 wild-type and G93A transgenic mice using the fluorescent immunohistochemistry. Result revealed that, in the SOD1 wild-type mice, the FUS/TLS expression almost wasn't detected. However, in the SOD1 G93A mice, the FUS/TLS expression in the white matter was significantly more than that in the gray matter. In the white matter, the FUS/TLS expression in the anterior funiculus was more than that in the lateral funiculus more than that in the posterior funiculus. In the gray matter, the FUS/TLS expression in the ventral horn was more than that surrounding the central canal more than that in the dorsal horn. The FUS/TLS expression in the thoracic segment was more than that in the cervical segment more than that in the lumbar segment. Almost all FUS/TLS expressed in the nuclear of the GFAP positive cell at the onset stage, but it expressed in both the nuclear and the cytoplasm of the GFAP positive cell at the progression stage, almost didn't detected FUS/TLS expression in the NeuN and Oligo positive cells. The FUS/TLS expression was positively correlated with the neuron death. Our data suggested that the expressive increase and mislocalization of FUS/TLS in the astrocyte cell might cause the motor neuron degenerative death in the SOD1 G93A transgenic mice.

Recent progress towards an effective treatment of amyotrophic lateral sclerosis using the SOD1 mouse model in a preclinical setting

Amyotrophic lateral sclerosis (ALS) is a progressive, fatal and incurable neurodegenerative disorder. Motor neurone degeneration can be caused by genetic mutation but the exact etiology of the disease, particularly for sporadic illness, still remains unclear. Therapeutics which target known pathogenic mechanisms involved in ALS, such as protein aggregation, oxidative stress, apoptosis, inflammation, endoplasmic reticulum stress and mitochondria dysfunction, are currently being pursued in order to provide neuroprotection which may be able to slow down, or perhaps even halt, disease progression. This present review focuses on the compounds which have been recently evaluated using the SOD1 mouse model, the most widely used preclinical model for ALS research.

Stem cell therapy for amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder characterized by the loss of motor neurons. Currently, no effective therapy is available to treat ALS, except for Riluzole, which has only limited clinical benefits. Stem-cell-based therapy has been intensively and extensively studied as a potential novel treatment strategy for ALS and has been shown to be effective, at least to some extent. In this article, we will review the current state of research on the use of stem cell therapy in the treatment of ALS and discuss the most promising stem cells for the treatment of ALS.

Potential therapeutic drugs and methods for the treatment of amyotrophic lateral sclerosis

Amyotrophic Lateral Sclerosis (ALS) is a neurodegenerative disorder caused by damage of motoneurons leading to paralysis state and long term disability. Riluzole is currently the only FDA-approved drug for the treatment of ALS. The proposed mechanisms of ALS include glutamate excitotoxicity, oxidative stress, mitochondrial dysfunction, protein aggregation, SOD1 accumulations, and neuronal death. In this review, we discuss potential biomarkers for the identification of patients with ALS. We further emphasize potential therapy involving the uses of neurotrophic factors such as IGFI, GDNF, VEGF, ADNF-9, colivelin and angiogenin in the treatment of ALS. Moreover, we described several existing drugs such as talampanel, ceftriaxone, pramipexole, dexpramipexole and arimoclomol potential compounds for the treatment of ALS. Interestingly, the uses of stem cell therapy and immunotherapy are promising for the treatment of ALS.

Role of mitochondria in mutant SOD1 linked amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease with an adult onset characterized by loss of both upper and lower motor neurons. In ~10% of cases, patients developed ALS with an apparent genetic linkage (familial ALS or fALS). Approximately 20% of fALS displays mutations in the SOD1 gene encoding superoxide dismutase 1. There are many proposed cellular and molecular mechanisms among which, mitochondrial dysfunctions occur early, prior to symptoms occurrence. In this review, we modeled the effect of mutant SOD1 protein via the formation of a toxic complex with Bcl2 on mitochondrial bioenergetics. Furthermore, we discuss that the shutdown of ATP permeation through mitochondrial outer membrane could lead to both respiration inhibition and temporary mitochondrial hyperpolarization. Moreover, we reviewed mitochondrial calcium signaling, oxidative stress, fission and fusion, autophagy and apoptosis in mutant SOD1-linked ALS. Functional defects in mitochondria appear early before symptoms are manifested in ALS. Therefore, mitochondrial dysfunction is a promising therapeutic target in ALS.

Proteomic analysis reveals differentially regulated protein acetylation in human amyotrophic lateral sclerosis spinal cord

Amyotrophic lateral sclerosis (ALS) is a progressive fatal neurodegenerative disease that primarily affects motor neurons in the brain and spinal cord. Histone deacetylase (HDAC) inhibitors have neuroprotective effects potentially useful for the treatment of neurodegenerative diseases including ALS; however, the molecular mechanisms underlying their potential efficacy is not well understood. Here we report that protein acetylation in urea-soluble proteins is differently regulated in post-mortem ALS spinal cord. Two-dimensional electrophoresis (2-DE) analysis reveals several protein clusters with similar molecular weight but different charge status. Liquid chromatography and tandem mass spectrometry (LC-MS/MS) identifies glial fibrillary acidic protein (GFAP) as the dominant component in the protein clusters. Further analysis indicates six heavily acetylated lysine residues at positions 89, 153, 189, 218, 259 and 331 of GFAP. Immunoprecipitation followed by Western blotting confirms that the larger form of GFAP fragments are acetylated and upregulated in ALS spinal cord. Further studies demonstrate that acetylation of the proteins additional to GFAP is differently regulated, suggesting that acetylation and/or deacetylation play an important role in pathogenesis of ALS.

Stem cell therapy in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder of upper and lower motor neurons, characterized by progressive muscular atrophy and weakness which culminates in death within 2-5 years. Despite various hypotheses about the responsible mechanisms, the etiology of ALS remains incompletely understood. However, it has been recently postulated that stem cell therapy could potentially target several mechanisms responsible for the etiology of ALS and other nervous system disorders, and could be regarded as one of the most promising therapeutic strategies for ALS treatment. We present a brief review of different methods of stem cell therapy in ALS patients and discuss the results with different cell types and routes of administration.

Amyotrophic Lateral Sclerosis: An update for 2013 Clinical Features, Pathophysiology, Management and Therapeutic Trials

Amyotrophic lateral sclerosis (ALS), first described by Jean-Martin Charcot in the 1870s, is an age-related disorder that leads to degeneration of motor neurons. The disease begins focally in the central nervous system and then spreads relentlessly. The clinical diagnosis, defined by progressive signs and symptoms of upper and lower motor neuron dysfunction, is confirmed by electromyography. Additional testing excludes other conditions. The disease is heterogeneous, but most patients die of respiratory muscle weakness less than 3 years from symptom-onset. Like other age-related neurodegenerative diseases, ALS has genetic and environmental triggers. Of the five to 10% of cases that are inherited, mutations have been discovered for a high proportion. In addition to genetic factors, age, tobacco use, and athleticism may contribute to sporadic ALS, but important etiologies are unidentified for most patients. Complex pathophysiological processes, including mitochondrial dysfunction, aggregation of misfolded protein, oxidative stress, excitotoxicity, inflammation and apoptosis, involve both motor neurons and surrounding glial cells. There is clinical and pathological overlap with other neurodegenerative diseases, particularly frontotemporal dementia. The mechanisms leading to disease propagation in the brain are a current focus of research. To date, one medication, riluzole, licensed in 1996, has been proved to prolong survival in ALS. Numerous clinical trials have so far been unable to identify another neuroprotective agent. Researchers now aim to slow disease progression by targeting known pathophysiological pathways or genetic defects. Current approaches are directed at muscle proteins such as Nogo, energetic balance, cell replacement, and abnormal gene products resulting from mutations. Until better understanding of the causes and mechanisms underlying progression lead to more robust neuroprotective agents, symptomatic therapies can extend life and improve quality of life. Palliative care programs such as hospice give emotional and physical support to patients and families throughout much of the disease course.

Neural progenitors derived from human induced pluripotent stem cells survive and differentiate upon transplantation into a rat model of amyotrophic lateral sclerosis

Human induced pluripotent stem cells (iPSCs) offer hope for personalized regenerative cell therapy in amyotrophic lateral sclerosis (ALS). We analyzed the fate of human iPSC-derived neural progenitors transplanted into the spinal cord of wild-type and transgenic rats carrying a human mutated SOD1(G93A) gene. The aim was to follow survival and differentiation of human neural progenitors until day 60 post-transplantation in two different in vivo environments, one being ALS-like. iPSC-derived neural progenitors efficiently engrafted in the adult spinal cord and survived at high numbers. Different neural progenitor, astroglial, and neuronal markers indicated that, over time, the transplanted nestin-positive cells differentiated into cells displaying a neuronal phenotype in both wild-type and transgenic SOD1 rats. Although a transient microglial phenotype was detected at day 15, astroglial staining was negative in engrafted cells from day 1 to day 60. At day 30, differentiation toward a neuronal phenotype was identified, which was further established at day 60 by the expression of the neuronal marker MAP2. A specification process into motoneuron-like structures was evidenced in the ventral horns in both wild-type and SOD1 rats. Our results demonstrate proof-of-principle of survival and differentiation of human iPSC-derived neural progenitors in in vivo ALS environment, offering perspectives for the use of iPSC-based therapy in ALS.

Clinical experience with stem cells and other cell therapies in neurological diseases

To overcome the limited capacity of the CNS for regeneration, the theoretical alternative would be to use stem cells for more effective management of chronic degenerative and inflammatory neurological conditions, and also of acute neuronal damage from injuries or cerebrovascular diseases. Although the adult brain contains small numbers of stem cells in restricted areas, this intrinsic stem cell repertoire is small and does not measurably contribute to functional recovery. Embryonic cells carrying pluripotent and self-renewal properties represent the stem cell prototype, but there are additional somatic stem cells that may be harvested and expanded from various tissues during adult life. Stem cell transplantation is based on the assumption that such cells may have the potential to regenerate or support the survival of the existing, partially damaged cells. This review summarizes the state-of-the-art and the clinical worldwide experience with the use of various types of stem cells in neurological diseases.

Technology-aided programs for assisting communication and leisure engagement of persons with amyotrophic lateral sclerosis: two single-case studies

Technology-aided programs for assisting communication and leisure engagement were assessed in single-case studies involving two men with amyotrophic lateral sclerosis (ALS). Study I involved a 51-year-old man with a virtually total loss of his motor repertoire and assessed a technology-aided program aimed at enabling him to (a) write and send out text messages and have incoming messages read to him and (b) establish videophone connections with his children (i.e., establish video contact and communicate with them). Study II involved a 66-year-old man with virtually no motor behavior and apparent depression and assessed a technology-aided program aimed at enabling him to (a) engage in leisure activities and make requests for basic needs and (b) use a low-demand messaging system. The results of both studies were highly encouraging. The participant of Study I could use the technology-aided program for effective communication and social interaction with multiple partners as well as for family interaction. The participant of Study II could use the technology-aided program for leisure engagement, requests, and basic family contacts/communication. The implications of technology for helping persons with severe ALS levels maintain an active and constructive role are discussed.

A technology-aided program to support leisure engagement and communication by a man with amyotrophic lateral sclerosis

OBJECTIVE

To assess a technology-aided programme for promoting leisure engagement and communication in a man with amyotrophic lateral sclerosis (ALS).

METHOD

The programme involved a laptop computer equipped with a Clicker 5 software package, an optic microswitch and an interface device. The participant could choose between two leisure options (i.e. songs and videos), could write requests and general messages through a virtual keyboard and a microswitch and could have the written text read out to caregivers and staff.

RESULTS

The use of the programme increased the mean frequency of words written to about 15 per 20-minute session during the second intervention phase. Those words were used by the participant for formulating a mean of over two requests/messages per session. The participant also listened to songs and watched videos.

CONCLUSION

A simple technology-aided programme may allow ALS patients to manage leisure engagement and communication.

The protective and therapeutic function of small heat shock proteins in neurological diseases

Historically, small heat shock proteins (sHSPs) have been extensively studied in the context of being intracellular molecular chaperones. However, recent studies looking at the role of sHSPs in neurological diseases have demonstrated a near universal upregulation of certain sHSPs in damaged and diseased brains. Initially, it was thought that sHSPs are pathological in these disease states because they are found in the areas of damage. However, transgenic overexpression and exogenous administration of sHSPs in various experimental disease paradigms have shown just the contrary – that sHSPs are protective, not pathological. This review examines sHSPs in neurological diseases and highlights the potential for using these neuroprotective sHSPs as novel therapeutics. It first addresses the endogenous expression of sHSPs in a variety of neurological disorders. Although many studies have examined the expression of sHSPs in neurological diseases, there are no review articles summarizing these data. Furthermore, it focuses on recent studies that have investigated the therapeutic potential of sHSPs for neurological diseases. Finally, it will explain what we think is the function of endogenous sHSPs in neurological diseases.

Research advances in gene therapy approaches for the treatment of amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a devastating neurodegenerative disease of motor neurons that causes progressive muscle weakness, paralysis, and premature death. No effective therapy is available. Research in the motor neuron field continues to grow, and recent breakthroughs have demonstrated the possibility of completely achieving rescue in animal models of spinal muscular atrophy, a genetic motor neuron disease. With adeno-associated virus (AAV) vectors, gene transfer can be achieved with systemic non-invasive injection and minimal toxicity. In the context of this success, we review gene therapy approaches for ALS, considering what has been done and the possible future directions for effective application of the latest generation of vectors for clinical translation. We focus on recent developments in the areas of RNA/antisense-mediated silencing of specific ALS causative genes like superoxide dismutase-1 and other molecular pathogenetic targets, as well as the administration of neuroprotective factors with viral vectors. We argue that gene therapy offers new opportunities to open the path for clinical progress in treating ALS.

CT fluoroscopy-guided percutaneous gastrostomy with loop gastropexy and peel-away sheath trocar technique in 31 amyotrophic lateral sclerosis patients

BACKGROUND

In amyotrophic lateral sclerosis (ALS) patients with respiratory impairment and/or advanced disease, performing even mild sedation - as is usually necessary for percutaneous endoscopic gastrostomy (PEG) placements - is fraught with risk. These patients are often referred to Interventional Radiology for alternative percutaneous gastrostomy tube placement options.

PURPOSE

To report our experience with CT fluoroscopy-guided percutaneous gastrostomy with a novel loop gastropexy and peel-away sheath trocar technique in ALS patients as an alternative to endoscopic techniques.

MATERIAL AND METHODS

A consecutive series of 31 amyotrophic lateral sclerosis patients in whom endoscopic gastrostomy was considered too dangerous or impossible to perform underwent CT-guided percutaneous gastropexy and gastrostomy and prospective follow-up. All procedures were performed with a 15 FR Freka® Pexact gastrostomy kit, a 16-row CT scanner (Aquilion 16) and single shot CT fluoroscopy mode.

RESULTS

The procedure was performed successfully in 30 of 31 patients (20 men, 11 women; median age 60 years, range 38-80 years). In the remaining case the stomach was punctured under CT fluoroscopy and CO2 insufflation was initiated thereafter, leading to successful gastrostomy without prior gastropexy and without further adverse events during follow-up. Two patients reported unproblematic exchange of a balloon tube due to skin irritations with no further adverse events. One patient reported accidental displacement of an exchanged new balloon tube in domestic environment due to balloon leakage: A new balloon tube was easily re-inserted in a hospital the same day. No serious adverse events such as peritonitis, persistent local bleeding, systemic blood loss, or any local infection requiring surgical intervention were observed. Until August 11, 2011 follow-up resulted in 7473 cumulative gastrostomy-days from the date of first placement.

CONCLUSION

Initial results suggest that the described technique under CT guidance is feasible and safe and may especially be advantageous in cases where endoscopic gastrostomy and sedation are contraindicated.

Protein misdirection inside and outside motor neurons in Amyotrophic Lateral Sclerosis (ALS): a possible clue for therapeutic strategies

Amyotrophic lateral sclerosis (ALS) is a devastating neurodegenerative disease characterized by progressive muscle wasting and weakness with no effective cure. Emerging evidence supports the notion that the abnormal conformations of ALS-linked proteins play a central role in triggering the motor neuron degeneration. In particular, mutant types of superoxide dismutase 1 (SOD1) and TAR DNA binding protein 43kDa (TDP-43) are key molecules involved in the pathogenesis of familial and sporadic ALS, respectively. The commonalities of the two proteins include a propensity to aggregate and acquire detrimental conformations through oligomerization, fragmentation, or post-translational modification that may drive abnormal subcellular localizations. Although SOD1 is a major cytosolic protein, mutated SOD1 has been localized to mitochondria, endoplasmic reticulum, and even the extracellular space. The nuclear exclusion of TDP-43 is a pathological hallmark for ALS, although the pathogenic priority remains elusive. Nevertheless, these abnormal behaviors based on the protein misfolding are believed to induce diverse intracellular and extracellular events that may be tightly linked to non-cell-autonomous motor neuron death. The generation of mutant- or misfolded protein-specific antibodies would help to uncover the distribution and propagation of the ALS-linked proteins, and to design a therapeutic strategy to clear such species. Herein we review the literature regarding the mislocalization of ALS-linked proteins, especially mutant SOD1 and TDP-43 species, and discuss the rationale of molecular targeting strategies including immunotherapy.

An overview of DNA repair in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS), also known as motor neuron disease (MND), is an adult onset neurodegenerative disorder characterised by the degeneration of cortical and spinal cord motor neurons, resulting in progressive muscular weakness and death. Increasing evidence supports mitochondrial dysfunction and oxidative DNA damage in ALS motor neurons. Several DNA repair enzymes are activated following DNA damage to restore genome integrity, and impairments in DNA repair capabilities could contribute to motor neuron degeneration. After a brief description of the evidence of DNA damage in ALS, this paper focuses on the available data on DNA repair activity in ALS neuronal tissue and disease animal models. Moreover, biochemical and genetic data on DNA repair in ALS are discussed in light of similar findings in other neurodegenerative diseases.

Alteration of protein folding and degradation in motor neuron diseases: Implications and protective functions of small heat shock proteins

Motor neuron diseases (MNDs) are neurodegenerative disorders that specifically affect the survival and function of upper and/or lower motor neurons. Since motor neurons are responsible for the control of voluntary muscular movement, MNDs are characterized by muscle spasticity, weakness and atrophy. Different susceptibility genes associated with an increased risk to develop MNDs have been reported and several mutated genes have been linked to hereditary forms of MNDs. However, most cases of MNDs occur in sporadic forms and very little is known on their causes. Interestingly, several molecular mechanisms seem to participate in the progression of both the inherited and sporadic forms of MNDs. These include cytoskeleton organization, mitochondrial functions, DNA repair and RNA synthesis/processing, vesicle trafficking, endolysosomal trafficking and fusion, as well as protein folding and protein degradation. In particular, accumulation of aggregate-prone proteins is a hallmark of MNDs, suggesting that the protein quality control system (molecular chaperones and the degradative systems: ubiquitin-proteasome-system and autophagy) are saturated or not sufficient to allow the clearance of these altered proteins. In this review we mainly focus on the MNDs associated with disturbances in protein folding and protein degradation and on the potential implication of a specific class of molecular chaperones, the small heat shock proteins (sHSPs/HSPBs), in motor neuron function and survival. How boosting of specific HSPBs may be a potential useful therapeutic approach in MNDs and how mutations in specific HSPBs can directly cause motor neuron degeneration is discussed.

P525L FUS mutation is consistently associated with a severe form of juvenile amyotrophic lateral sclerosis

Some FUS mutations have been observed in patients with the juvenile form of Amyotrophic Lateral Sclerosis starting before 25 years. We report an 11-year-old girl affected by sporadic juvenile ALS with a rapid course resulting in tracheostomy after 14 months from the onset. Sequencing FUS gene revealed a de novo P525L mutation. Our findings, together with literature data, indicate that this mutation is consistently associated with a specific phenotype characterized by juvenile onset, severe course and high proportion of de novo mutations in sporadic cases.

TDP-43 autoregulation: implications for disease

TDP-43 is a nuclear protein that has been shown to play a central role in RNA metabolism. In recent years, this protein has become very important in the study of neurodegenerative diseases such as amyotrophic lateral sclerosis and frontotemporal lobar degeneration (FTLD). These diseases share, as common feature, the presence of abnormally aggregated, posttranslationally modified, and mislocalized TDP-43 in the cell cytoplasm of both neurons and glial cells. A major question in TDP-43 research is represented by the investigation of the mechanism(s) that trigger this process and its potential consequences. Regarding the first issue, it is likely that relative protein expression levels might play an important role as has been demonstrated for many protein aggregation processes. In fact, the eventual misregulation of TDP-43 expression leading to enhanced protein production might well correlate with enhanced aggregation, and thus results in increasingly harmful gain- or loss-of-function effects on cellular metabolism. For this reason, it is important to determine the mechanisms that act to regulate TDP-43 levels within the cell. In normal conditions, it is now clear that TDP-43 can modulate its own protein levels through a negative feedback loop triggered by binding to its own RNA in the 3'UTR region leading to mRNA degradation. This work discusses how an eventual disruption of this mechanism might affect TDP-43 pathology, focusing in particular on its association with stress granules and intrinsic aggregation properties.

Senataxin mutations and amyotrophic lateral sclerosis

We studied three patients with mutations in the senataxin gene (SETX). One had juvenile onset of ALS. The second case resembled hereditary motor neuropathy. The third patient had an overlap syndrome of ataxia-tremor and motor neuron disease, phenotypes previously associated with SETX mutations. Our patients were all apparently sporadic, with no other affected relative. Two relatives of patient no. 2 carried the SETX c.4660T > G transversion but did not manifest motor neuron disease, abnormal eye movements, ataxia, or tremor suggesting that genetic or environmental modifiers may influence expression of this SETX polymorphism. Relatives of patients 1 and 3 were not available for examination or SETX mutation screening. Mutations causing ALS4 may be more frequent and heterogeneous than expected. Screening for SETX mutations should be considered in patients with apparently sporadic juvenile-onset ALS, hereditary motor neuropathy, and overlap syndromes with ataxia and motor neuron disease.