Opinion: more mouse models and more translation needed for ALS.

Amyotrophic lateral sclerosis is a complex disorder most of which is 'sporadic' of unknown origin but approximately 10% is familial, arising from single mutations in any of more than 30 genes. Thus, there are more than 30 familial ALS subtypes, with different, often unknown, molecular pathologies leading to a complex constellation of clinical phenotypes. We have mouse models for many genetic forms of the disorder, but these do not, on their own, necessarily show us the key pathological pathways at work in human patients. To date, we have no models for the 90% of ALS that is 'sporadic'. Potential therapies have been developed mainly using a limited set of mouse models, and through lack of alternatives, in the past these have been tested on patients regardless of aetiology. Cancer researchers have undertaken therapy development with similar challenges; they have responded by producing complex mouse models that have transformed understanding of pathological processes, and they have implemented patient stratification in multi-centre trials, leading to the effective translation of basic research findings to the clinic. ALS researchers have successfully adopted this combined approach, and now to increase our understanding of key disease pathologies, and our rate of progress for moving from mouse models to mechanism to ALS therapies we need more, innovative, complex mouse models to address specific questions.

Pathogenesis of amyotrophic lateral sclerosis.

INTRODUCTION: Amyotrophic lateral sclerosis (ALS) or motor neuron disease is a rapidly progressive neurodegenerative disorder. The primary involvement is of motor neurons in the brain, spinal cord and peripherally. There is secondary weakness of muscles and primary involvement of other brain regions, especially involving cognition. SOURCES OF DATA: Peer-reviewed journal articles and reviews. PubMed.gov AREAS OF AGREEMENT: The pathogenesis of ALS remains largely unknown. There are a wide range of potential mechanisms related to neurodegeneration. An increasing number of genetic factors are recognized. AREAS OF CONTROVERSY: There remains controversy, or lack of knowledge, in explaining how cellular events manifest as the complex human disease. There is controversy as to how well cellular and animal models of disease relate to the human disease. GROWING POINTS: Large-scale international collaborative genetic epidemiological studies are replacing local studies. Therapies related to pathogenesis remain elusive, with the greatest advances to date relating to provision of care (including multidisciplinary management) and supportive care (nutrition and respiratory support). AREAS TIMELY FOR DEVELOPING RESEARCH: The identification of C9orf72 hexanucleotide repeats as the most frequent genetic background to ALS, and the association with frontotemporal dementia, gives the potential of a genetic background against which to study other risk factors, triggers and pathogenic mechanisms, and to develop potential therapies.

ß-Catenin is central to DUX4-driven network rewiring in facioscapulohumeral muscular dystrophy.

Facioscapulohumeral muscular dystrophy (FSHD) is an incurable disease, characterized by skeletal muscle weakness and wasting. Genetically, FSHD is characterized by contraction or hypomethylation of repeat D4Z4 units on chromosome 4, which causes aberrant expression of the transcription factor DUX4 from the last repeat. Many genes have been implicated in FSHD pathophysiology, but an integrated molecular model is currently lacking. We developed a novel differential network methodology, Interactome Sparsification and Rewiring (InSpiRe), which detects network rewiring between phenotypes by integrating gene expression data with known protein interactions. Using InSpiRe, we performed a meta-analysis of multiple microarray datasets from FSHD muscle biopsies, then removed secondary rewiring using non-FSHD datasets, to construct a unified network of rewired interactions. Our analysis identified ß-catenin as the main coordinator of FSHD-associated protein interaction signalling, with pathways including canonical Wnt, HIF1-α and TNF-α clearly perturbed. To detect transcriptional changes directly elicited by DUX4, gene expression profiling was performed using microarrays on murine myoblasts. This revealed that DUX4 significantly modified expression of the genes in our FSHD network. Furthermore, we experimentally confirmed that Wnt/ß-catenin signalling is affected by DUX4 in murine myoblasts. Thus, we provide the first unified molecular map of FSHD signalling, capable of uncovering pathomechanisms and guiding therapeutic development.

Analysis of amyotrophic lateral sclerosis as a multistep process: a population-based modelling study.

BACKGROUND: Amyotrophic lateral sclerosis shares characteristics with some cancers, such as onset being more common in later life, progression usually being rapid, the disease affecting a particular cell type, and showing complex inheritance. We used a model originally applied to cancer epidemiology to investigate the hypothesis that amyotrophic lateral sclerosis is a multistep process. METHODS: We generated incidence data by age and sex from amyotrophic lateral sclerosis population registers in Ireland (registration dates 1995-2012), the Netherlands (2006-12), Italy (1995-2004), Scotland (1989-98), and England (2002-09), and calculated age and sex-adjusted incidences for each register. We regressed the log of age-specific incidence against the log of age with least squares regression. We did the analyses within each register, and also did a combined analysis, adjusting for register. FINDINGS: We identified 6274 cases of amyotrophic lateral sclerosis from a catchment population of about 34 million people. We noted a linear relationship between log incidence and log age in all five registers: England r(2)=0·95, Ireland r(2)=0·99, Italy r(2)=0·95, the Netherlands r(2)=0·99, and Scotland r(2)=0·97; overall r(2)=0·99. All five registers gave similar estimates of the linear slope ranging from 4·5 to 5·1, with overlapping confidence intervals. The combination of all five registers gave an overall slope of 4·8 (95% CI 4·5-5·0), with similar estimates for men (4·6, 4·3-4·9) and women (5·0, 4·5-5·5). INTERPRETATION: A linear relationship between the log incidence and log age of onset of amyotrophic lateral sclerosis is consistent with a multistage model of disease. The slope estimate suggests that amyotrophic lateral sclerosis is a six-step process. Identification of these steps could lead to preventive and therapeutic avenues. FUNDING: UK Medical Research Council; UK Economic and Social Research Council; Ireland Health Research Board; The Netherlands Organisation for Health Research and Development (ZonMw); the Ministry of Health and Ministry of Education, University, and Research in Italy; the Motor Neurone Disease Association of England, Wales, and Northern Ireland; and the European Commission (Seventh Framework Programme).

TRPA1 insensitivity of human sural nerve axons after exposure to lidocaine.

TRPA1 is an ion channel of the TRP family that is expressed in some sensory neurons. TRPA1 activity provokes sensory symptoms of peripheral neuropathy, such as pain and paraesthesia. We have used a grease gap method to record axonal membrane potential and evoked compound action potentials (ECAPs) in vitro from human sural nerves and studied the effects of mustard oil (MO), a selective activator of TRPA1. Surprisingly, we failed to demonstrate any depolarizing response to MO (50, 250 µM) in any human sural nerves. There was no effect of MO on the A wave of the ECAP, but the C wave was reduced at 250 µM. In rat saphenous nerve fibres MO (50, 250 µM) depolarized axons and reduced the C wave of the ECAP but had no effect on the A wave. By contrast, both human and rat nerves were depolarized by capsaicin (0.5 to 5 µM) or nicotine (50 to 200 µM). Capsaicin caused a profound reduction in C fibre conduction in both species but had no effect on the amplitude of the A component. Lidocaine (30 mM) depolarized rat saphenous nerves acutely, and when rat nerves were pretreated with 30 mM lidocaine to mimic the exposure of human nerves to local anaesthetic during surgery, the effects of MO were abolished whilst the effects of capsaicin were unchanged. This study demonstrates that the local anaesthetic lidocaine desensitizes TRPA1 ion channels and indicates that it may have additional mechanisms for treating neuropathic pain that endure beyond simple sodium channel blockade.

Pathogenic VCP mutations induce mitochondrial uncoupling and reduced ATP levels.

Valosin-containing protein (VCP) is a highly expressed member of the type II AAA+ ATPase family. VCP mutations are the cause of inclusion body myopathy, Paget's disease of the bone, and frontotemporal dementia (IBMPFD) and they account for 1%-2% of familial amyotrophic lateral sclerosis (ALS). Using fibroblasts from patients carrying three independent pathogenic mutations in the VCP gene, we show that VCP deficiency causes profound mitochondrial uncoupling leading to decreased mitochondrial membrane potential and increased mitochondrial oxygen consumption. This mitochondrial uncoupling results in a significant reduction of cellular ATP production. Decreased ATP levels in VCP-deficient cells lower their energy capacity, making them more vulnerable to high energy-demanding processes such as ischemia. Our findings propose a mechanism by which pathogenic VCP mutations lead to cell death.

Large C9orf72 hexanucleotide repeat expansions are seen in multiple neurodegenerative syndromes and are more frequent than expected in the UK population.

Hexanucleotide repeat expansions in C9orf72 are a major cause of frontotemporal lobar degeneration (FTLD) and amyotrophic lateral sclerosis (ALS). Understanding the disease mechanisms and a method for clinical diagnostic genotyping have been hindered because of the difficulty in estimating the expansion size. We found 96 repeat-primed PCR expansions: 85/2,974 in six neurodegenerative diseases cohorts (FTLD, ALS, Alzheimer disease, sporadic Creutzfeldt-Jakob disease, Huntington disease-like syndrome, and other nonspecific neurodegenerative disease syndromes) and 11/7,579 (0.15%) in UK 1958 birth cohort (58BC) controls. With the use of a modified Southern blot method, the estimated expansion range (smear maxima) in cases was 800-4,400. Similarly, large expansions were detected in the population controls. Differences in expansion size and morphology were detected between DNA samples from tissue and cell lines. Of those in whom repeat-primed PCR detected expansions, 68/69 were confirmed by blotting, which was specific for greater than 275 repeats. We found that morphology in the expansion smear varied among different individuals and among different brain regions in the same individual. Expansion size correlated with age at clinical onset but did not differ between diagnostic groups. Evidence of instability of repeat size in control families, as well as neighboring SNP and microsatellite analyses, support multiple expansion events on the same haplotype background. Our method of estimating the size of large expansions has potential clinical utility. C9orf72-related disease might mimic several neurodegenerative disorders and, with potentially 90,000 carriers in the United Kingdom, is more common than previously realized.

Diagnosing and managing muscular dystrophy.

Muscular dystrophy refers to a range of muscle diseases caused by defects in muscle proteins, leading to death of the muscle cells, with loss of muscle tissue, and weakness. The development of clinical symptoms is usually gradual, and the earliest features may be difficult to identify and determine. With established disease the presence of muscle weakness and wasting is clear. In children, the presentation may be delayed walking, or poor performance in sporting activity. In children and adults presenting symptoms may include: difficulty raising from a squat; difficulty raising from a chair; difficulty lifting the arms above the head; poor balance; drooping eyelids; and joint contractures. In the presence of slowly progressive muscle weakness and wasting, an elevated serum creatine kinase would be a strong pointer to a muscle disease. Retention of limb reflexes would favour a myopathy over a neuropathy. The major differential diagnosis is an inflammatory myopathy, such as polymyositis. The muscular dystrophies have a genetic basis. There may be important genetic issues to discuss with the family, including the possibility of prenatal diagnosis. In Duchenne muscular dystrophy the inheritance is X-linked, with typically only boys affected. Many limb girdle muscular dystrophies are autosomal recessive, affecting only one generation of a family and facioscapulohumeral dystrophy is autosomal dominant.

Scapular fixation in muscular dystrophy.

BACKGROUND: Winging of the scapula is caused by weakness of the thoracoscapular muscles, which allows the scapula to lift off the chest wall during shoulder movements. In facioscapulohumeral muscular dystrophy (and occasionally in other muscular dystrophies) there is selective weakness of the thoracoscapular muscles which may spare other shoulder muscles such as the deltoid muscle. This imbalance results in significant winging and loss of shoulder function. Historically, a number of different surgical and non-surgical interventions have been used to achieve scapular stability. This review examines the evidence available for the use of all scapular fixation techniques in muscular dystrophy, especially facioscapulohumeral muscular dystrophy. OBJECTIVES: To examine the evidence for the relative efficacy of scapular fixation techniques in muscular dystrophy (especially facioscapulohumeral muscular dystrophy) in improving upper limb function. SEARCH STRATEGY: We searched the Cochrane Neuromuscular Disease Group Trials Specialized Register (20 July 2009), The Cochrane Central Register of Controlled Trials (The Cochrane Library Issue 3, 2009) Medline (1966 to July 2009) and EMBASE (1980 to July 2009) for randomised trials. We also contacted authors of trials and other experts in the field. SELECTION CRITERIA: All reports of scapular fixation for muscular dystrophy, including quasi-randomised or randomised controlled trials, comparing any form of scapular fixation (surgical and non-surgical) in people (of all ages and of all severity) with scapular winging due to muscular dystrophy. Our primary outcome measure was objective improvement in shoulder abduction. Our secondary outcome measures were: patient-perceived improvement in performance of activities of daily living, cosmetic results, subjective improvement in pain and proportion of patients with significant postoperative complications. DATA COLLECTION AND ANALYSIS: We collated and summarised studies on the treatment of scapular winging in muscular dystrophy. MAIN RESULTS: No randomised trials were identified. We therefore present a review of the non-randomised literature available. AUTHORS' CONCLUSIONS: There is no evidence from randomised trials to support the suggestion from observational studies that operative interventions produce significant benefits. However, these have to be balanced against postoperative immobilisation, need for physiotherapy and potential complications. We conclude that a randomised trial would be difficult, but a register of cases and the use of a standardised assessment protocol would allow more accurate comparison of the disparate techniques.

Investigation of MGF mRNA expression in patients with amyotrophic lateral sclerosis using parallel in vivo and in vitro approaches.

In an animal model of ALS, intramuscular administration of MGF, the IGF-I Ec gene splice variant, improved muscle strength and increased both motor unit and motor neuron survival. Here we investigated whether there is a deficit in MGF production in the muscles of patients with ALS. We used complementary in vivo and in vitro techniques to study the IGF-I splice variant response of human muscle to exercise or mechanical stretch. We assessed the levels of MGF and IGF-IEa mRNA in muscle biopsy samples from healthy subjects and patients with ALS, before and after exercise. We used primary muscle cells to build three-dimensional collagen constructs and subjected them to a ramp stretch. Patients with ALS had similar baseline levels of MGF and IGF-IEa mRNA to healthy controls. No up-regulation was seen in either group within a short time of a single bout of low intensity exercise. Three-dimensional human muscle constructs also detected no response to a mechanical stretch from either control subjects or ALS. We conclude that the pathology of ALS does not include a deficit in baseline levels of MGF and IGF-IEa mRNA splice variants in muscle.

Brachial plexus hypertrophy in chronic inflammatory demyelinating polyradiculoneuropathy.

We present the clinical, imaging and neuropathological findings in three patients with predominant brachial plexus neuropathy. MR scanning was key to determining the brachial plexus involvement. Biopsy of the brachial plexus was performed in one patient. The appearances of the brachial plexus on MRI, in conjunction with the clinical presentations of these patients, suggest that they are unusual variants within the spectrum of chronic inflammatory demyelinating polyradiculoneuropathy.

AEOL-10150 (Aeolus).

AEOL-10150, a small-molecule antioxidant analogous to the catalytic site of superoxide dismutase, is under development by Aeolus (formerly Incara) as a potential subcutaneous treatment for amyotrophic lateral sclerosis (ALS), stroke, spinal cord injury, lung inflammation and mucositis. The compound is currently undergoing a phase I clinical trial for ALS. In October 2005, the company had applied for Fast Track status, and planned to submit a special protocol assessment for a pivotal phase II/III trial.

A novel RAB7 mutation associated with ulcero-mutilating neuropathy.

There are two known autosomal dominant genes for the hereditary ulcero-mutilating neuropathies: SPTLC1 (hereditary sensory neuropathy type 1) and RAB7 (Charcot-Marie-Tooth disease type 2B). We report a family with autosomal dominant ulcero-mutilating neuropathy, developing in the teens and characterized by ulcers, amputations, sensory involvement in the feet but no motor features. Sequencing the RAB7 gene showed a novel heterozygous A to C mutation, changing asparagine to threonine at codon 161. The mutation is situated adjacent to a previously identified valine to methionine mutation at codon 162, implying a hotspot for mutations in the highly conserved C terminus of RAB7.

Coexistent hereditary and inflammatory neuropathy.

Classically, the course of Charcot-Marie-Tooth (CMT) disease is gradually progressive. We describe eight atypical patients who developed acute or subacute deterioration. Seven of these had genetically proven CMT disease type 1A (CMT1A) due to chromosome 17p11.2-12 duplication, and one had X-linked disease (CMTX) due to a mutation in the GJB1 gene. In this group there was sufficient clinical, electrophysiological and neuropathological information to indicate a diagnosis of a superimposed inflammatory polyneuropathy. The age range of the patients was 18-69 years, with a mean of 39 years. A family history of a similar neuropathic condition was present in only four patients. All eight had an acute or subacute deterioration following a long asymptomatic or stable period. Seven had neuropathic pain or prominent positive sensory symptoms. Nerve biopsy demonstrated excess lymphocytic infiltration in all eight patients. Five patients were treated with steroids and/or intravenous immunoglobulin, with variable positive response; three patients received no immunomodulatory treatment. Inflammatory neuropathy has previously been recognized in patients with hereditary neuropathy, with uncharacterized genetic defects and with CMT1B. We present detailed assessments of patients with CMT1A and CMTX, including nerve biopsy, and conclude that coexistent inflammatory neuropathy is not genotype-specific in hereditary motor and sensory neuropathy. Although this was not a formal epidemiological study, estimates of the prevalence of CMT disease and chronic inflammatory demyelinating polyneuropathy indicate that the association is more frequent than would be expected by chance. This has implications for understanding the pathogenesis of inflammatory neuropathies and raises important considerations in the management of patients with hereditary neuropathies. If a patient with CMT disease experiences an acute or subacute deterioration in clinical condition, treatment of a coexistent inflammatory neuropathy with steroids or immunoglobulin should be considered.

No association with common Caucasian genotypes in exons 8, 13 and 14 of the human cytoplasmic dynein heavy chain gene (DNCHC1) and familial motor neuron disorders.

We have shown in a mouse model of motor neuron disease, the legs-at-odd-angles (Loa) mutant, and that mutations in the cytoplasmic dynein heavy chain gene (Dnchc1) cause motor neuron degeneration. Mice exhibiting the Loa phenotype suffer progressive loss of locomotor function and homozygous animals have neuronal inclusion bodies that are positive for SOD1, CDK5, neurofilament and ubiquitin proteins. As this phenotype models some aspects of human motor neuron degeneration disorders, we think there is a reasonable likelihood that dynein may be a causative gene or susceptibility factor in human motor neuron disease. Therefore we have screened exons of this gene in a set of human patients with familial forms of disparate motor neuron degeneration diseases, affecting both upper and lower motor neurons: amyotrophic lateral sclerosis (ALS), spinal muscular atrophy (SMA), and hereditary spastic paraplegia. As part of this study, we have determined that DNCHC1 is a large gene of 78 exons spanning 86 kb genomic length. We have focused on the exons known to be mutated in Loa, and in a very similar mouse mutation, cramping 1 (Cra1); both mutations result in loss of anterior horn cells. The exons studied are highly conserved in a wide range of eukaryotes. We screened our patient samples by sequencing and although we detect single nucleotide polymorphisms, our results show these occur at the same frequency in our patient group as in control samples of unaffected individuals. Therefore we do not find any association between familial motor neuron disease and the genotypes presented here in the exons screened.