C9ORF72 hexanucleotide repeat expansion: From ALS and FTD to a broader pathogenic role?

The major gene underlying monogenic forms of amyotrophic lateral sclerosis (ALS) and fronto-temporal dementia (FTD) is C9ORF72. The causative mutation in C9ORF72 is an abnormal hexanucleotide (G4C2) repeat expansion (HRE) located in the first intron of the gene. The aim of this review is to propose a comprehensive update on recent developments on clinical, biological and therapeutics aspects related to C9ORF72 in order to highlight the current understanding of genotype-phenotype correlations, and also on biological machinery leading to neuronal death. We will particularly focus on the broad phenotypic presentation of C9ORF72-related diseases, that goes well beyond the classical phenotypes observed in ALS and FTD patients. Last, we will comment the possible therapeutical hopes for patients carrying a C9ORF72 HRE.

Treatment of hereditary amyotrophic lateral sclerosis.

Currently, only four molecules can be prescribed for amyotrophic lateral sclerosis (ALS), of which only one is approved worldwide for this indication, riluzole. Although progress in the therapeutic field remains unsatisfactory, we have to notice that genetics have undergone impressive improvements over the last three decades and, by extension, our knowledge of ALS cases linked to a pathogenic mutation that accounts for 10% of all cases (either sporadic or familiar) and is currently called hereditary ALS (hALS). In many neurological diseases treatment targeting pathogenic genes have significatively improved the natural profile of the disease: this is perfectly illustrated for familial amyloid neuropathy and spinal muscular atrophy. Because of these findings and the urgent need to find a cure for ALS, many trials have focused on familial ALS targeting the four most important genes linked to the disease: C9orf72, SOD1, TARDBP and FUS. We propose in this review an update on the perspectives of treatment that may be available in mid-term in hALS and will discuss in the last part the potential consequences for asymptomatic relatives of patients with a hALS and for ALS patients.

French National Protocol for genetic of amyotrophic lateral sclerosis.

Relationships between genes and amyotrophic lateral sclerosis (ALS) have been widely accepted since the first studies highlighting pathogenic mutations in the SOD1 gene 30years ago. Over the last three decades, scientific literature has clearly highlighted the central role played by genetic factors in the disease, in both clinics and pathophysiology, as well as in therapeutics. This implies that health professionals who care for patients with ALS are increasingly faced with patients and relatives eager to have answers to questions related to the role of genetic factors in the occurrence of the disease and the risk for their relatives to develop ALS. In order to address these public health issues, the French ALS network FILSLAN proposed to the Haute Autorité de santé (HAS) the drafting of a French National Protocol (PNDS) on ALS genetics. This PNDS was developed according to the "method for developing a national diagnosis and care protocol for rare diseases" published by the HAS in 2012 (methodological guide for PNDS available on the HAS website: http://www.has-sante.fr/). This document aims to provide the most recent data on the role of genes in ALS and to detail the implications for diagnosis and care.

Primary Lateral Sclerosis: Clinical, radiological and molecular features.

Primary Lateral Sclerosis (PLS) is an uncommon motor neuron disorder. Despite the well-recognisable constellation of clinical manifestations, the initial diagnosis can be challenging and therapeutic options are currently limited. There have been no recent clinical trials of disease-modifying therapies dedicated to this patient cohort and awareness of recent research developments is limited. The recent consensus diagnostic criteria introduced the category 'probable' PLS which is likely to curtail the diagnostic journey of patients. Extra-motor clinical manifestations are increasingly recognised, challenging the view of PLS as a 'pure' upper motor neuron condition. The post mortem literature of PLS has been expanded by seminal TDP-43 reports and recent PLS studies increasingly avail of meticulous genetic profiling. Research in PLS has gained unprecedented momentum in recent years generating novel academic insights, which may have important clinical ramifications.

Pre-symptomatic diagnosis in ALS.

Pathophysiology of amyotrophic lateral sclerosis (ALS) remains partially understood even though it is accepted worldwide that motor neuron death results from a pluri-factorial process with a variable role of genetic factors. Although not distinguishable from a clinical point of view, familial forms of ALS (fALS, 10% of cases) and sporadic forms (sALS, 90% of cases) can be described. Since the identification of superoxide dismutase 1 gene (SOD1) mutations, more than 30 genes have been linked to fALS. Among these genes, five (C9ORF72, SOD1, TARDBP, FUS, TBK1) seem predominant with mutation frequencies of 40%, 20%, 5%, <5%, <5% in fALS and 6%, 3%, and <1% for the last three in sALS, respectively. The situation that classically leads to request genetic screening is the presence of a familial history of motor neuron disorders (MND) or fronto-temporal lobar dementia (FTLD). However, this dichotomy between fALS and sALS based on familial history can lead to mistakes since illegitimacy, ignorance of MND, FTD or psychiatric disorders within the family due to a familial censorship or lack of familial relationship, or a recessive autosomal inheritance could wrongly lead to failing to recognize a familial form. The significant development of genetic research and easier access to genetic tests in fALS increase the number of situations for which gene mutations are identified. The consequence is an increase in genetic requests from relatives of ALS patients who are eager to know their own genetic status and their own individual risk to develop ALS. Pre-symptomatic testing is thus becoming a daily issue in ALS Centers. This led us to propose a framework for such pre-symptomatic genetic testing for people at risk for developing ALS.

Multiple capillary malformations of progressive onset: Capillary malformation-arteriovenous malformation syndrome (CM-AVM).

BACKGROUND: Capillary malformation-arteriovenous malformation syndrome (CM-AVM) is an autosomal dominant disorder first described in 2003. PATIENTS AND METHODS: An 8-year-old girl was referred for the progressive appearance of multiple capillary malformations in childhood, evocative of CM-AVM syndrome. Molecular analysis of the RASA1 gene revealed a mutation but further examinations did not show arteriovenous malformation. DISCUSSION: CM-AVM syndrome is an autosomal dominant disease caused by RASA1 gene mutations. More than 100 mutations have been identified to date. The EPHB4 gene may also be involved. Capillary malformations with particular characteristics are described. High-flow vascular malformations are associated in 18.5% of cases, with 7.1% being intracerebral. CONCLUSION: CM-AVM syndrome is a recent diagnostic entity. Diagnosis should be considered in the presence of multifocal capillary malformations. This diagnosis may lead to the detection of high-flow arteriovenous malformation and raises the question of specific management for these patients.

Genetics of amyotrophic lateral sclerosis.

Amyotrophic lateral sclerosis (ALS) is a fatal motor neuron disease characterized by upper and lower motor neuron damage in the bulbar and spinal territories. Although the pathophysiology of ALS is still unknown, the involvement of genetic factors is no longer a subject of debate. Familial ALS (fALS) accounts for 10-20% of cases. Since the identification of the SOD1 gene, more than 20 genes have been described, of which four can explain >50% of familial cases. This review is an update focused on major aspects of the field of ALS genetics concerning both causative and susceptibility factors.

Metabolomics in amyotrophic lateral sclerosis: how far can it take us?

Amyotrophic lateral sclerosis (ALS) is the most common adult-onset motor neuron disease. Alongside identification of aetiologies, development of biomarkers is a foremost research priority. Metabolomics is one promising approach that is being utilized in the search for diagnosis and prognosis markers. Our aim is to provide an overview of the principal research in metabolomics applied to ALS. References were identified using PubMed with the terms 'metabolomics' or 'metabolomic' and 'ALS' or 'amyotrophic lateral sclerosis' or 'MND' or 'motor neuron disorders'. To date, nine articles have reported metabolomics research in patients and a few additional studies examined disease physiology and drug effects in patients or models. Metabolomics contribute to a better understanding of ALS pathophysiology but, to date, no biomarker has been validated for diagnosis, principally due to the heterogeneity of the disease and the absence of applied standardized methodology for biomarker discovery. A consensus on best metabolomics methodology as well as systematic independent validation will be an important accomplishment on the path to identifying the long-awaited biomarkers for ALS and to improve clinical trial designs.

Biological follow-up in amyotrophic lateral sclerosis: decrease in creatinine levels and increase in ferritin levels predict poor prognosis.

BACKGROUND AND PURPOSE: Amyotrophic lateral sclerosis (ALS) is a fatal disorder of the motor neuron system, with a median survival of 2 to 4 years and a wide variety of prognosis. Thus, there is a critical need for diagnosis and prognosis biomarkers to improve the care of patients in routine practice. In this study, we aimed to determine prognostic value of routine biochemical markers in sporadic ALS (SALS). METHODS: We retrospectively collected clinical and biological data obtained during the systematic routine monitoring of 216 sporadic ALS patients. The main outcomes were disease duration and annual decline of Revised ALS Functional Rating Scale (ALSFRS-R). Changes to these biological variables over time were assessed, in link with disease progression. RESULTS: We found that concentrations of creatinine (P=0.0166) and ferritin (P=0.0306) changed significantly during the progression of ALS. A reduction of creatinine levels and an increase of ferritin levels were associated with disease progression. Multivariate analysis showed that early variation of ferritin was an independent predictive factor of patient survival (P=0.0048). CONCLUSION: Changes to ferritin and creatinine levels with time are associated with ALS progression. This is the first study describing the changes to these biological variables during ALS progression.

Xq27 FRAXA locus is a strong candidate for dyslexia: evidence from a genome-wide scan in French families.

Dyslexia is a frequent neurodevelopmental learning disorder. To date, nine susceptibility loci have been identified, one of them being DYX9, located in Xq27. We performed the first French SNP linkage study followed by candidate gene investigation in dyslexia by studying 12 multiplex families (58 subjects) with at least two children affected, according to categorical restrictive criteria for phenotype definition. Significant results emerged on Xq27.3 within DYX9. The maximum multipoint LOD score reached 3,884 between rs12558359 and rs454992. Within this region, seven candidate genes were investigated for mutations in exonic sequences (CXORF1, CXORF51, SLITRK2, FMR1, FMR2, ASFMR1, FMR1NB), all having a role during brain development. We further looked for 5'UTR trinucleotide repeats in FMR1 and FMR2 genes. No mutation or polymorphism co-segregating with dyslexia was found. This finding in French families with Dyslexia showed significant linkage on Xq27.3 enclosing FRAXA, and consequently confirmed the DYX9 region as a robust susceptibility locus. We reduced the previously described interval from 6.8 (DXS1227-DXS8091) to 4 Mb also disclosing a higher LOD score.

Respiratory onset in an ALS family with L144F SOD1 mutation.

Familial amyotrophic lateral sclerosis (FALS) cases linked to SOD1 mutations may sometimes present with unusual clinical features such as pure lower motor neuron involvement or sensory signs. The authors describe a FALS pedigree with the L144F SOD1 mutation in which all cases had respiratory involvement as a first symptom. Although atypical clinical features are not rare in ALS families, this is the first pedigree with respiratory-onset in three affected members. This unusual presentation led to delayed diagnosis in the proband and highlights the fact that respiratory-onset can occur in familial ALS cases carrying SOD1 mutation.

APOE ε4 allele is associated with an increased risk of bulbar-onset amyotrophic lateral sclerosis in men.

OBJECTIVE: Several association studies have identified possible susceptibility factors for sporadic amyotrophic lateral sclerosis (SALS). Studies on the APOE gene provided conflicting results, especially about the effect on bulbar onset. We assessed the possible role of APOE gene in a large cohort of patients with ALS and matched controls. METHODS: The APOE alleles were determined in 1482 patients with SALS and 955 controls and analysed by univariate and multivariate statistics, taking into account gender, site-of-onset and age-at-onset. RESULTS: Patients with bulbar onset were more likely to be women [odds ratio (OR)=2.17; 95% CI: 1.74-2.72] and to be older (OR=3.47; 95% CI: 2.58-4.67). The ε4-carriers were more frequent in the bulbar-onset group than in the limb-onset group (OR=1.39 bulbar onset versus limb onset; 95% CI: 1.08-1.80) but this association was observed amongst men (OR=1.78; 95% CI: 1.25-2.53) and not women (OR=1.09; 95% CI: 0.75-1.59). CONCLUSION: Our study provides evidence for a contribution of the ε4 allele in the occurrence of bulbar-onset ALS amongst men. We propose that men are normally protected by androgens against bulbar onset and that the ε4 allele inhibits this protection, perhaps by interfering with the androgen pathway.

Behavioral, Hormonal, Inflammatory, and Metabolic Effects Associated with FGF21-Pathway Activation in an ALS Mouse Model.

In amyotrophic lateral sclerosis (ALS), motor neuron degeneration occurs simultaneously with systemic metabolic dysfunction and neuro-inflammation. The fibroblast growth factor 21 (FGF21) plays an important role in the regulation of both phenomena and is a major hormone of energetic homeostasis. In this study, we aimed to determine the relevance of FGF21 pathway stimulation in a male mouse model of ALS (mutated SOD1-G93A mice) by using a pharmacological agonist of FGF21, R1Mab1. Mice (SOD1-WT and mutant SOD1-G93A) were treated with R1Mab1 or vehicle. Longitudinal data about clinical status (motor function, body weight) and biological parameters (including hormonal, immunological, and metabolomics profiles) were collected from the first symptoms to euthanasia at week 20. Multivariate models were performed to identify the main parameters associated with R1Mab1 treatment and to link them with clinical status, and metabolic pathways involving the discriminant metabolites were also determined. A beneficial clinical effect of R1Mab1 was revealed on slow rotarod (p = 0.032), despite a significant decrease in body weight of ALS mice (p < 0.001). We observed a decrease in serum TNF-α, MCP-1, and insulin levels (p = 0.0059, p = 0.003, and p = 0.01, respectively). At 16 weeks, metabolomics analyses revealed a clear discrimination (CV-ANOVA = 0.0086) according to the treatment and the most discriminant pathways, including sphingolipid metabolism, butanoate metabolism, pantothenate and CoA biosynthesis, and the metabolism of amino acids like tyrosine, arginine, proline, glycine, serine, alanine, aspartate, and glutamate. Mice treated with R1Mab1 had mildly higher performance on slow rotarod despite a decrease on body weight and could be linked with the anti-inflammatory effect of R1Mab1. These results indicate that FGF21 pathway is an interesting target in ALS, with a slight improvement in motor function combined with metabolic and anti-inflammatory effects.

Advances in disease-modifying pharmacotherapies for the treatment of amyotrophic lateral sclerosis.

INTRODUCTION: To date, riluzole and edaravone are the only two drugs that have successfully passed clinical trials for the treatment of Amyotrophic Lateral Sclerosis (ALS). Unfortunately, both drugs exhibit very modest effects. Most other drugs have failed at phase III to show significant effects in phase III when tested in larger cohorts. This pattern necessitates improvements in the approach to ALS pharmacotherapy. AREAS COVERED: The authors discuss the two approved drugs, as well as several examples of drug candidates whose clinical trials did not demonstrate efficacy in phase III. Post-hoc analyses reveal that future clinical trials should include disease-staging procedures, longer-term trials to correctly assess survival, genetic studies of participants to aid in stratification, and more similarity between the protocols on preclinical models and clinical trials. Finally, they discuss the trials in process that demonstrate some of these suggestions and improvements. EXPERT OPINION: The approval of riluzole and edaravone was essentially a desperate attempt to provide urgent pharmacotherapy to the ALS community. To evolve toward more efficient therapies, we must conduct clinical trials with optimal stratification based on rapid/slow progressors and cognitive decline. Pharmaco-metabolomics should allow for the identification of biomarkers that are adapted for a given drug.