Genetic testing in motor neurone disease

Clinical trajectories of genetic variants in ALS: a European observational study within PRECISION-ALS

OBJECTIVE

To investigate the association between C9orf72, SOD1, FUS and TARDBP variants on the clinical trajectory of ALS patients in Europe.

METHODS

Nine ALS centers with population-based registries provided data on demographic and disease characteristics - at diagnosis and longitudinally - as part of PRECISION ALS. These data were harmonized and collated for analysis.

RESULTS

21,820 ALS patients were identified, 9,887 underwent genetic testing for at least one of the 4 genes of interest. 9.8% of patients carried a hexanucleotide expansion in C9orf72; 2.9% carried a pathogenic variant in SOD1; 1.4% carried a pathogenic variant in TARDBP; and 0.8% carried a pathogenic variant in FUS. Only one p.A5V variant was identified in this dataset. The most frequently identified SOD1 variant was p.D91A, with evidence of other variant clusters in Belgium, Italy and the United Kingdom. TARDBP variants were clustered in the Netherlands and Italy. Earlier ages of onset were demonstrated compared to wild-type populations; C9orf72 59.58 (IQR 62.5, p < 2.2e-16), SOD1 54.19 (IQR 19.4, p = 6.304e-14), TARDBP 58.30 (IQR 16.23, p = 0.00024) and FUS 51.16 (IQR 25.08, p = 1.58e-06). C9orf72 was more bulbar (p < 0.0001) in onset and SOD1 more spinal (p < 0.0001). Those carrying variants spent distinctly different periods in each of the King's stages.

CONCLUSIONS

Genetic forms of ALS have an earlier age of onset, have distinct patterns in their sites of disease onset, and progress differently as compared to populations without such major-effect genes. There is also evidence of disease clusters across Europe suggestive of founder effects.

Neurologists' understanding of reproductive medicine options for genetic forms of motor neuron disease

OBJECTIVES

To examine the knowledge, confidence and practice of motor neuron disease (MND) clinicians toward discussing reproductive options with people who carry a causal variant in an MND gene (both clinically affected and asymptomatic).

METHODS

An online cross-sectional survey was distributed nationwide to UK MND clinicians and clinical geneticists and genetic counselors. The survey assessed respondents' understanding on reproductive medicine techniques; their confidence in discussing reproductive medicine options and their access to information resources.

RESULTS

Seventy six clinicians responded to the online survey (45 neurology clinicians and 31 clinical geneticists). MND clinicians had limited knowledge and low confidence in discussing reproductive medicine options. Geneticists were more likely to carry out reproductive genetic counseling with very few MND clinicians reporting undertaking these discussions. Further, 57% of the 45 MND clinicians surveyed reported to have never made a referral for reproductive genetic counseling. Multiple barriers to offering reproductive counseling or referral were identified including a lack of knowledge, lack of awareness of the different options, lack of clinic time and uncertainty around issues such as funding for PGT and whose responsibility it comes under.

CONCLUSIONS

There is a need for training and education on reproductive options and referral for these options needs to be integrated within the health system. Developing more resources for both clinicians and patients is required as MND clinicians reported a lack of resources.

Elevated Cerebrospinal Fluid Ubiquitin Carboxyl-Terminal Hydrolase Isozyme L1 in Asymptomatic C9orf72 Hexanucleotide Repeat Expansion Carriers

OBJECTIVE

To identify biochemical changes in individuals at higher risk of developing amyotrophic lateral sclerosis (ALS) or frontotemporal dementia (FTD) via C9orf72 hexanucleotide repeat expansion (HRE) heterozygosity.

METHODS

Cross-sectional observational study of 48 asymptomatic C9orf72 HRE carriers, 39 asymptomatic non-carrier controls, 19 people with sporadic ALS, 10 with C9orf72 ALS, 14 with sporadic FTD, and 10 with C9orf72 FTD. Relative abundance of 30 pre-defined cerebrospinal fluid biomarkers of ALS and FTD were compared in asymptomatic C9orf72 HRE carriers and age-matched non-carrier controls. Differential abundance of these proteins was quantified using data independent acquisition mass spectrometry or electro chemiluminescent assay for neurofilament light chain. Unbiased analysis of the entire cerebrospinal fluid proteome was then carried out.

RESULTS

Ubiquitin carboxyl-hydrolase isozyme L1 levels were higher in asymptomatic C9orf72 HRE carriers compared with age-matched non-carriers (log2fold change 0.20, FDR-adjusted p-value = 0.034), whereas neurofilament light chain levels did not significantly differ. Ubiquitin carboxyl-hydrolase isozyme L1 levels remained elevated after matching of groups by neurofilament levels (p = 0.011), and after adjusting for age, sex, and neurofilament levels. A significant difference was also observed when restricting analysis to younger participants (<37) matched by neurofilament level (p = 0.007).

INTERPRETATION

Elevated cerebrospinal fluid ubiquitin carboxyl-hydrolase isozyme L1 levels in C9orf72 HRE carriers can occur in the absence of increased neurofilament levels, potentially reflecting either compensatory or pathogenic mechanisms preceding rapid neuronal loss. This brings forward the window on changes associated with the C9orf72 HRE carrier state, with potential to inform understanding of penetrance and approaches to prevention. ANN NEUROL 2025;97:449-459.

Experiences of predictive genetic testing in inherited motor neuron disease: Findings from a qualitative interview study

Predictive genetic testing is increasingly available for individuals with a heightened risk of motor neuron disease (MND). However, little is known about how they decide whether or not to get tested, and how they experience this process. This paper reports findings from a constructivist grounded theory-informed interview study with 24 family members of people with identified or suspected inherited MND (iMND). Fourteen did not know their genetic status, and nine had decided to have predictive testing, of whom six tested positive for the pathogenic gene variant identified in their family and three tested negative. One additional person was identified as negative through a parent's negative result. This paper explores the diverse ways people approached testing, and the many factors and motivations involved, based on personal attitudes and goals, experiences of living with genetic risk, and wider family considerations and circumstances. Results were met with a range of emotions; whatever the outcome, the news disrupted each person's view of the future, and they adapted in their own way and time. Support after results was variable and a perceived lack of support impacted coping and the ability to move forwards. This paper situates findings against literature on other genetic conditions, highlighting experiences as grounded in the unique characteristics of iMND. Thus, it emphasizes the need for disease-specific guidelines and support structures around predictive genetic testing in this context. Understanding people's experiences and responding to these needs is particularly timely given the uptake of testing amongst this group is anticipated to rise with increasing access to genetic testing for people with MND, and gene-specific clinical trials.

Longitudinal Magnetic Resonance Imaging in Asymptomatic C9orf72 Mutation Carriers Distinguishes Phenoconverters to Amyotrophic Lateral Sclerosis or Amyotrophic Lateral Sclerosis With Frontotemporal Dementia

OBJECTIVE

We prospectively studied asymptomatic C9orf72 mutation carriers, identifying those developing amyotrophic lateral sclerosis (ALS) or frontotemporal dementia (FTD).

METHODS

We enrolled 56 asymptomatic family members (AFM) with a C9orf72 mutation (AFM C9+), 132 non-carriers (AFM C9-), and 359 population-based controls. Using 3 T magnetic resonance imaging, we measured cortical thickness, gyrification, and subcortical volumes longitudinally. Linear mixed-effects models on non-converting AFM C9+ scans (n = 107) created a reference for these measurements, establishing individual atrophy patterns. Atrophy patterns from presymptomatic phenoconverters (n = 10 scans) served as a template for group comparisons and similarity assessments. Similarity with phenoconverters was quantified using Dice similarity coefficient (DSC) for cortical and Kullback-Leibler similarity (KLS) for subcortical measures. Using longitudinal similarity assessments, we predicted when participants would reach the average similarity level of phenoconverters at their first post-onset scan.

RESULTS

Five AFM C9+ converted to ALS or ALS-FTD. Up to 6 years before symptoms, these phenoconverters exhibited significant atrophy in frontal, temporal, parietal, and cingulate cortex, along with smaller thalamus, hippocampus, and amygdala compared to other AFM C9+. Some non-converted AFM C9+ had high DSC and KLS, approaching values of phenoconverters, whereas others, along with AFM C9- and controls, had lower values. At age 80, we predicted 27.9% (95% confidence interval, 13.2-40.1%) of AFM C9+ and no AFM C9- would reach the same DSC as phenoconverters.

INTERPRETATION

Distinctive atrophy patterns are visible years before symptom onset on presymptomatic scans of phenoconverters. Combining baseline and follow-up similarity measures may serve as a promising imaging biomarker for identifying those at risk of ALS or ALS-FTD. ANN NEUROL 2025;97:281-295.

Clinical characterization and founder effect analysis in Chinese amyotrophic lateral sclerosis patients with SOD1 common variants

OBJECTIVE

In the Asian population, SOD1 variants are the most common cause of amyotrophic lateral sclerosis (ALS). To date, more than 200 variants have been reported in SOD1. This study aimed to summarize the genotype-phenotype correlation and determine whether the patients carrying common variants derive from a common ancestor.

METHODS

A total of 103 sporadic ALS (SALS) and 11 familial ALS (FALS) probands were included and variants were screened by whole exome sequencing. Functional analyses were performed on fibroblasts derived from patients with SOD1 p.V48A and control. Haplotype analysis was performed in the probands with p.H47R or p.V48A and their familial members.

RESULTS

A total of 25 SOD1 variants were identified in 44 probands, in which p.H47R, p.V48A and p.C112Y variants were the most common variants. 94.3% and 60% of patients with p.H47R or p.V48A had lower limb onset with predominant lower motor neurons (LMNs) involvement. Patients with p.H47R had a slow progression and prolonged survival time, while patients with p.V48A exhibited a duration of 2-5 years. Patients with p.C112Y variant showed remarkable phenotypic variation in age at onset and disease course. SOD1V48A fibroblasts showed mutant SOD1 aggregate formation, enhanced intracellular reactive oxygen species level, and decreased mitochondrial membrane potential compared to the control fibroblast. Haplotype analysis showed that seven families had two different haplotypes. p.H47R and p.V48A variants did not originate from a common founder.

CONCLUSIONS

Our study expanded the understanding of the genotype-phenotype correlation of ALS with SOD1 variants and revealed that the common p.H47R or p.V48A variant did not have a founder effect.

'Outcomes of genetic testing in the London MND Center: the importance of achieving timely results and correlations to family history'

Background: Despite recognition of the importance of genetic factors in the pathogenesis of MND and the increasing availability of genetic testing, testing practice remains highly variable. With the arrival of gene-targeted therapies there is a growing need to promptly identify actionable genetic results and patient death before receipt of results raises ethical dilemmas and limits access to novel therapies. Objective: To identify pathogenic mutations within a London tertiary MND center and their correlation with family history. To record waiting times for genetic results and deaths prior to receipt of results. Methods: In this series of 100 cases, genetic testing was offered to all patients with an MND diagnosis from the tertiary clinic. Data on demographics, disease progression and a detailed family history were taken. Time to receipt of genetic results and patient deaths prior to this were recorded.  Results: Of the 97 patients who accepted testing a genetic cause was identified in 10%, including seven C9orf72 and two positive SOD1 cases. Only three patients with positive genetic findings had a family history of MND, although alternative neurological diagnoses and symptoms in the family were frequently reported. 14% of patients who underwent testing were deceased by the time results were received, including one actionable SOD1 case.  Conclusions: Genetic testing should be made available to all patients who receive an MND diagnosis as family history alone is inadequate to identify potential familial cases. Time to receipt of results remains a significant issue due to the limited life expectancy following diagnosis.

The various forms of hereditary motor neuron disorders and their historical descriptions

Motor neuron disorders comprise a clinically and pathologically heterogeneous group of neurologic diseases characterized by progressive degeneration of motor neurons (including both sporadic and hereditary diseases), affecting the upper motor neurons, lower motor neurons, or both. Hereditary motor neuron disorders themselves represent a vast and heterogeneous group, with numerous clinical and genetic overlaps that can be a source of error. This narrative review aims at providing an overview of the main types of inherited motor neuron disorders by recounting the stages in their historical descriptions. For practical purposes, this review of the literature sets out their various clinical characteristics and updates the list of all the genes involved in the various forms of inherited motor neuron disorders, including spinal muscular atrophy, familial amyotrophic lateral sclerosis, hereditary spastic paraplegia, distal hereditary motor neuropathies/neuronopathies, Kennedy's disease, riboflavin transporter deficiencies, VCPopathy and the neurogenic scapuloperoneal syndrome.

Fluctuating salience in those living with genetic risk of motor neuron disease: A qualitative interview study

BACKGROUND

Motor neuron disease (MND) (also known as amyotrophic lateral sclerosis) is a life-limiting neurodegenerative condition. In up to 20% of people with MND, a pathogenic variant associated with autosomal dominant inheritance can be identified. Children of people carrying a pathogenic variant have a 50% chance of inheriting this and a higher, although harder to predict, chance of developing the disease compared to the general adult population. This paper explores the experience of living with the genetic risk of MND.

METHODS

We undertook a UK-based interview study with 35 individuals, including: 7 people living with genetically-mediated forms of MND; 24 asymptomatic relatives, the majority of whom had an increased risk of developing the disease; and 4 unrelated partners.

RESULTS

We explore how individuals make sense of genetic risk, unpacking the interplay between genetic knowledge, personal perception, experiences of the disease in the family, age and life stage and the implications that living with risk has for different aspects of their lives. We balance an emphasis on the emotional and psychological impact described by participants, with a recognition that the salience of risk fluctuates over time. Furthermore, we highlight the diverse strategies and approaches people employ to live well in the face of uncertainty and the complex ways they engage with the possibility of developing symptoms in the future. Finally, we outline the need for open-ended, tailored support and information provision.

CONCLUSIONS

Drawing on wider literature on genetic risk, we foreground how knowledge of MND risk can disrupt individuals' taken-for-granted assumptions on life and perceptions of the future, but also its contextuality, whereby its relevance becomes more prominent at critical junctures. This research has been used in the development of a public-facing resource on the healthtalk.org website.

PATIENT OR PUBLIC CONTRIBUTION

People with experience of living with genetic risk were involved throughout the design and conduct of the study and advised on aspects including the topic guide, sampling and recruitment and the developing analysis. Two patient and public involvement contributors joined a formal advisory panel.

Variation in Resting Metabolic Rate Affects Identification of Metabolic Change in Geographically Distinct Cohorts of Patients With ALS

BACKGROUND AND OBJECTIVES

Altered metabolism is observed in amyotrophic lateral sclerosis (ALS). However, without a standardized methodology to define metabolic changes, our understanding of factors contributing to and the clinical significance of altered metabolism in ALS is limited.

METHODS

We aimed to determine how geographic variation in metabolic rates influences estimates and accuracy of predicted resting energy expenditure (REE) in patients with ALS and controls, while validating the effectiveness of cohort-specific approaches in predicting altered metabolic rate in ALS. Participants from 3 geographically distinct sites across Australia, China, and the Netherlands underwent REE assessments, and we considered 22 unique equations for estimating REE. Analyses evaluated equation performance and the influence of demographics on metabolic status. Comparisons were made using standardized and local reference values to identify metabolic alterations.

RESULTS

606 participants were included from Australia (patients with ALS: 140, controls: 154), the Netherlands (patients with ALS: 79, controls: 37) and China (patients with ALS: 67, controls: 129). Measured REE was variable across geographic cohorts, with fat-free mass contributing to this variation across all patients (p = 0.002 to p < 0.001). Of the 22 predication equations assessed, the Sabounchi Structure 4 (S4) equation performed relatively well across all control cohorts. Use of prediction thresholds generated using data from Australian controls generally increased the prevalence of hypermetabolism in Chinese (55%, [43%-67%]) and Dutch (44%, [33%-55%]) cases when compared with Australian cases (30%, [22%-38%]). Adjustment of prediction thresholds to consider geographically distinct characteristics from matched control cohorts resulted in a decrease in the proportion of hypermetabolic cases in Chinese and Dutch cohorts (25%-31% vs 55% and 20%-34% vs 43%-44%, respectively), and increased prevalence of hypometabolism in Dutch cases with ALS (1% to 8%-10%).

DISCUSSION

The identification of hypermetabolism in ALS is influenced by the formulae and demographic-specific prediction thresholds used for defining alterations in metabolic rate. A consensus approach is needed for identification of metabolic changes in ALS and will facilitate improved understanding of the cause and clinical significance of this in ALS.

Mitochondrial Inherited Disorders and their Correlation with Neurodegenerative Diseases

Mitochondria are essential organelles for the survival of a cell because they produce energy. The cells that need more mitochondria are neurons because they perform a variety of tasks that are necessary to support brain homeostasis. The build-up of abnormal proteins in neurons, as well as their interactions with mitochondrial proteins, or MAM proteins, cause serious health issues. As a result, mitochondrial functions, such as mitophagy, are impaired, resulting in the disorders described in this review. They are also due to mtDNA mutations, which alter the heritability of diseases. The topic of disease prevention, as well as the diagnosis, requires further explanation and exploration. Finally, there are treatments that are quite promising, but more detailed research is needed.

Sensory neuropathy in amyotrophic lateral sclerosis: a systematic review

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by the degeneration of both upper and lower motoneurons, leading to motor and non-motor symptoms. Recent evidence suggests that ALS is indeed a multisystem disorder, associated with cognitive impairment, dysautonomia, pain and fatigue, excess of secretions, and sensory symptoms. To evaluate whether sensory neuropathy could broaden its spectrum, we systematically reviewed its presence and characteristics in ALS, extracting data on epidemiological, clinical, neurophysiological, neuropathological, and genetic features. Sensory neuropathy can be found in up to 20% of ALS patients, affecting both large and small fibers, although there is a great heterogeneity related to different techniques used for its detection (electromyography vs skin biopsy vs nerve biopsy). Moreover, the association between CIDP-like neuropathy and ALS needs to be better explored, although it could be interpreted as part of the neuroinflammatory process in the latter disease. Sensory neuropathy in ALS may be associated with a spinal onset and might be more frequent in SOD1 patients. Moreover, it seems mutually exclusive with cognitive impairment. No associations with sex and other genetic mutation were observed. All these data in the literature reveal the importance of actively looking for sensory neuropathy in ALS patients, and suggest including sensory neuropathy among ALS non-motor features, as it may explain sensory symptoms frequently reported throughout the course of the disease. Its early identification could help avoid diagnostic delays and improve patients' treatment and quality of life.

Evaluating the Utility of REVEL and CADD for Interpreting Variants in Amyotrophic Lateral Sclerosis Genes

Amyotrophic lateral sclerosis (ALS) is a debilitating neurodegenerative disease affecting approximately two per 100,000 individuals globally. While there are many benefits to offering early genetic testing to people with ALS, this has also led to an increase in the yield of novel variants of uncertain significance in ALS-associated genes. Computational (in silico) predictors, including REVEL and CADD, are widely employed to provide supporting evidence of pathogenicity for variants in conjunction with clinical, molecular, and other genetic evidence. However, in silico predictors are developed to be broadly applied across the human genome; thus, their ability to evaluate the consequences of variation in ALS-associated genes remains unclear. To resolve this ambiguity, we surveyed 20 definitive and moderate ClinGen-defined ALS-associated genes from two large, open-access ALS sequencing datasets (total people with ALS = 8,230; controls = 9,671) to investigate REVEL and CADD's ability to predict which variants are most likely to be disease-causing in ALS. While our results indicate a predetermined pathogenicity threshold for REVEL that could be of clinical value for classifying variants in ALS-associated genes, an accurate threshold was not evident for CADD, and both in silico predictors were of limited value for resolving which variants of uncertain significance (VUS) may be likely pathogenic in ALS. Our findings allow us to provide important recommendations for the use of REVEL and CADD scores for variants and indicate that both tools should be used with caution when attempting to evaluate the pathogenicity of VUSs in ALS genetic testing.

Characterizing proteomic and transcriptomic features of missense variants in amyotrophic lateral sclerosis genes

Within recent years, there has been a growing number of genes associated with amyotrophic lateral sclerosis (ALS), resulting in an increasing number of novel variants, particularly missense variants, many of which are of unknown clinical significance. Here, we leverage the sequencing efforts of the ALS Knowledge Portal (3864 individuals with ALS and 7839 controls) and Project MinE ALS Sequencing Consortium (4366 individuals with ALS and 1832 controls) to perform proteomic and transcriptomic characterization of missense variants in 24 ALS-associated genes. The two sequencing datasets were interrogated for missense variants in the 24 genes, and variants were annotated with gnomAD minor allele frequencies, ClinVar pathogenicity classifications, protein sequence features including Uniprot functional site annotations, and PhosphoSitePlus post-translational modification site annotations, structural features from AlphaFold predicted monomeric 3D structures, and transcriptomic expression levels from Genotype-Tissue Expression. We then applied missense variant enrichment and gene-burden testing following binning of variation based on the selected proteomic and transcriptomic features to identify those most relevant to pathogenicity in ALS-associated genes. Using predicted human protein structures from AlphaFold, we determined that missense variants carried by individuals with ALS were significantly enriched in β-sheets and α-helices, as well as in core, buried or moderately buried regions. At the same time, we identified that hydrophobic amino acid residues, compositionally biased protein regions and regions of interest are predominantly enriched in missense variants carried by individuals with ALS. Assessment of expression level based on transcriptomics also revealed enrichment of variants of high and medium expression across all tissues and within the brain. We further explored enriched features of interest using burden analyses and identified individual genes were indeed driving certain enrichment signals. A case study is presented for SOD1 to demonstrate proof-of-concept of how enriched features may aid in defining variant pathogenicity. Our results present proteomic and transcriptomic features that are important indicators of missense variant pathogenicity in ALS and are distinct from features associated with neurodevelopmental disorders.

Evidence-based consensus guidelines for ALS genetic testing and counseling

OBJECTIVE

Advances in amyotrophic lateral sclerosis (ALS) gene discovery, ongoing gene therapy trials, and patient demand have driven increased use of ALS genetic testing. Despite this progress, the offer of genetic testing to persons with ALS is not yet "standard of care." Our primary goal is to develop clinical ALS genetic counseling and testing guidelines to improve and standardize genetic counseling and testing practice among neurologists, genetic counselors or any provider caring for persons with ALS.

METHODS

Core clinical questions were identified and a rapid review performed according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA-P) 2015 method. Guideline recommendations were drafted and the strength of evidence for each recommendation was assessed by combining two systems: the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) System and the Evaluation of Genomic Applications in Practice and Prevention (EGAPP). A modified Delphi approach was used to reach consensus among a group of content experts for each guideline statement.

RESULTS

A total of 35 guideline statements were developed. In summary, all persons with ALS should be offered single-step genetic testing, consisting of a C9orf72 assay, along with sequencing of SOD1, FUS, and TARDBP, at a minimum. The key education and genetic risk assessments that should be provided before and after testing are delineated. Specific guidance regarding testing methods and reporting for C9orf72 and other genes is provided for commercial laboratories.

INTERPRETATION

These evidence-based, consensus guidelines will support all stakeholders in the ALS community in navigating benefits and challenges of genetic testing.

A survey of current practice in genetic testing in amyotrophic lateral sclerosis in the UK and Republic of Ireland: implications for future planning

Objective: To determine the current practice in genetic testing for patients with apparently sporadic motor neurone disease/amyotrophic lateral sclerosis (MND/ALS) and asymptomatic at-risk relatives of familial MND/ALS patients seen in specialized care centers in the UK. Methods: An online survey with 10 questions distributed to specialist healthcare professionals with a role in requesting genetic testing working at MND/ALS care centers. Results: Considerable variation in practice was found. Almost 30% of respondents reported some discomfort in discussing genetic testing with MND/ALS patients and a majority (77%) did not think that all patients with apparently sporadic disease should be routinely offered genetic testing at present. Particular concerns were identified in relation to testing asymptomatic at-risk individuals and the majority view was that clinical genetics services should have a role in supporting genetic testing in MND/ALS, especially in asymptomatic individuals at-risk of carrying pathogenic variants. Conclusions: Variation in practice in genetic testing among MND/ALS clinics may be driven by differences in experience and perceived competence, compounded by the increasing complexity of the genetic underpinnings of MND/ALS. Clear and accessible guidelines for referral pathways between MND/ALS clinics and clinical genetics may be the best way to standardize and improve current practice, ensuring that patients and relatives receive optimal and geographically equitable support.

Clinical testing panels for ALS: global distribution, consistency, and challenges

Objective: In 2021, the Clinical Genome Resource (ClinGen) amyotrophic lateral sclerosis (ALS) spectrum disorders Gene Curation Expert Panel (GCEP) was established to evaluate the strength of evidence for genes previously reported to be associated with ALS. Through this endeavor, we will provide standardized guidance to laboratories on which genes should be included in clinical genetic testing panels for ALS. In this manuscript, we aimed to assess the heterogeneity in the current global landscape of clinical genetic testing for ALS. Methods: We reviewed the National Institutes of Health (NIH) Genetic Testing Registry (GTR) and members of the ALS GCEP to source frequently used testing panels and compare the genes included on the tests. Results: 14 clinical panels specific to ALS from 14 laboratories covered 4 to 54 genes. All panels report on ANG, SOD1, TARDBP, and VAPB; 50% included or offered the option of including C9orf72 hexanucleotide repeat expansion (HRE) analysis. Of the 91 genes included in at least one of the panels, 40 (44.0%) were included on only a single panel. We could not find a direct link to ALS in the literature for 14 (15.4%) included genes. Conclusions: The variability across the surveyed clinical genetic panels is concerning due to the possibility of reduced diagnostic yields in clinical practice and risk of a missed diagnoses for patients. Our results highlight the necessity for consensus regarding the appropriateness of gene inclusions in clinical genetic ALS tests to improve its application for patients living with ALS and their families.

Advantages of routine next-generation sequencing over standard genetic testing in the amyotrophic lateral sclerosis clinic

BACKGROUND

Next-generation sequencing has enhanced our understanding of amyotrophic lateral sclerosis (ALS) and its genetic epidemiology. Outside the research setting, testing is often restricted to those who report a family history. The aim of this study was to explore the added benefit of offering routine genetic testing to all patients in a regional ALS centre.

METHODS

C9ORF72 expansion testing and exome sequencing was offered to consecutive patients (150 with ALS and 12 with primary lateral sclerosis [PLS]) attending the Oxford Motor Neuron Disease Clinic within a defined time period.

RESULTS

A total of 17 (11.3%) highly penetrant pathogenic variants in C9ORF72, SOD1, TARDBP, FUS and TBK1 were detected, of which 10 were also found through standard clinical genetic testing pathways. The systematic approach resulted in five additional diagnoses of a C9ORF72 expansion (number needed to test [NNT] = 28), and two further missense variants in TARDBP and SOD1 (NNT = 69). Additionally, 3 patients were found to carry pathogenic risk variants in NEK1, and 13 patients harboured common missense variants in CFAP410 and KIF5A, also associated with an increased risk of ALS. We report two novel non-coding loss-of-function splice variants in TBK1 and OPTN. No relevant variants were found in the PLS patients. Patients were offered double-blinded participation, but >80% requested disclosure of the results.

CONCLUSIONS

This study provides evidence that expanding genetic testing to all patients with a clinical diagnosis of ALS enhances the potential for recruitment to clinical trials, but will have direct resource implications for genetic counselling.

Insight into Elderly ALS Patients in the Emilia Romagna Region: Epidemiological and Clinical Features of Late-Onset ALS in a Prospective, Population-Based Study

Few studies have focused on elderly (>80 years) amyotrophic lateral sclerosis (ALS) patients, who represent a fragile subgroup generally not included in clinical trials and often neglected because they are more difficult to diagnose and manage. We analyzed the clinical and genetic features of very late-onset ALS patients through a prospective, population-based study in the Emilia Romagna Region of Italy. From 2009 to 2019, 222 (13.76%) out of 1613 patients in incident cases were over 80 years old at diagnosis, with a female predominance (F:M = 1.18). Elderly ALS patients represented 12.02% of patients before 2015 and 15.91% from 2015 onwards (p = 0.024). This group presented with bulbar onset in 38.29% of cases and had worse clinical conditions at diagnosis compared to younger patients, with a lower average BMI (23.12 vs. 24.57 Kg/m2), a higher progression rate (1.43 vs. 0.95 points/month), and a shorter length of survival (a median of 20.77 vs. 36 months). For this subgroup, genetic analyses have seldom been carried out (25% vs. 39.11%) and are generally negative. Finally, elderly patients underwent less frequent nutritional- and respiratory-supporting procedures, and multidisciplinary teams were less involved at follow-up, except for specialist palliative care. The genotypic and phenotypic features of elderly ALS patients could help identify the different environmental and genetic risk factors that determine the age at which disease onset occurs. Since multidisciplinary management can improve a patient's prognosis, it should be more extensively applied to this fragile group of patients.

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.

Using gene panels in the diagnosis of neuromuscular disorders: A mini-review

The diagnosis of inherited neuromuscular disorders is challenging due to their genetic and phenotypic variability. Traditionally, neurophysiology and histopathology were primarily used in the initial diagnostic approach to these conditions. Sanger sequencing for molecular diagnosis was less frequently utilized as its application was a time-consuming and cost-intensive process. The advent and accessibility of next-generation sequencing (NGS) has revolutionized the evaluation process of genetically heterogenous neuromuscular disorders. Current NGS diagnostic testing approaches include gene panels, whole exome sequencing (WES), and whole genome sequencing (WGS). Gene panels are often the most widely used, being more accessible due to availability and affordability. In this mini-review, we describe the benefits and risks of clinical genetic testing. We also discuss the utility, benefits, challenges, and limitations of using gene panels in the evaluation of neuromuscular disorders.

The Role of Small Heat Shock Proteins in Protein Misfolding Associated Motoneuron Diseases

Motoneuron diseases (MNDs) are neurodegenerative conditions associated with death of upper and/or lower motoneurons (MNs). Proteostasis alteration is a pathogenic mechanism involved in many MNDs and is due to the excessive presence of misfolded and aggregated proteins. Protein misfolding may be the product of gene mutations, or due to defects in the translation process, or to stress agents; all these conditions may alter the native conformation of proteins making them prone to aggregate. Alternatively, mutations in members of the protein quality control (PQC) system may determine a loss of function of the proteostasis network. This causes an impairment in the capability to handle and remove aberrant or damaged proteins. The PQC system consists of the degradative pathways, which are the autophagy and the proteasome, and a network of chaperones and co-chaperones. Among these components, Heat Shock Protein 70 represents the main factor in substrate triage to folding, refolding, or degradation, and it is assisted in this task by a subclass of the chaperone network, the small heat shock protein (sHSPs/HSPBs) family. HSPBs take part in proteostasis by bridging misfolded and aggregated proteins to the HSP70 machinery and to the degradative pathways, facilitating refolding or clearance of the potentially toxic proteins. Because of its activity against proteostasis alteration, the chaperone system plays a relevant role in the protection against proteotoxicity in MNDs. Here, we discuss the role of HSPBs in MNDs and which HSPBs may represent a valid target for therapeutic purposes.