There is a shared hallmark of defective differentiation across genetic myopathies, a process that has been extensively described in Duchenne muscular dystrophy and also observed in Emery-Dreifuss muscular dystrophy. In this article, we broaden the discussion on myopathies associated with differentiation defects, examining their implications in less characterized muscle conditions that can have onset in adulthood, including facioscapulohumeral muscular dystrophy (FSHD), oculopharyngeal muscular dystrophy (OPMD), and myotonic dystrophies (DM), as well as myopathies caused by genetic variants in FHL1, GNE, DES, CAPN3, and members of the HNRNP family. Muscle damage can result from injury, exercise, or disease, necessitating a highly coordinated repair process to restore normal strength and function. Resident satellite cells are activated, differentiate, and fuse with the damaged tissue to facilitate this repair. This overview emphasizes the importance of muscle differentiation in the pathogenesis of myopathies with diverse etiologies and a broad range of underlying molecular mechanisms. These insights highlight differentiation as a potential convergent therapeutic target.

BACKGROUND AND PURPOSE:Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease of upper and lower motor neurons leading to progressive disability and death. Approximately 10% of cases are caused by single-gene disorders with the remaining 90% of cases presumed to be caused by a combination of environmental and genetic factors. The microbiome (the ensemble of microorganisms that colonize body surfaces and organs) was recently identified for its importance in the pathogenesis of ALS. METHODS:In this study, we recruited 100 participants from two ethnically and geographically distinct sites (71 from Calgary, Canada, and 29 from Seoul, Republic of Korea) which included 59 ALS participants and 41 controls. All participants provided saliva samples for oral microbial analysis using 16S rRNA sequencing. Basic demographic information was collected from all participants, and ALS participants provided additional clinical information including site of disease onset, disease duration, and ALS Functional Rating Scale - Revised score. RESULTS:Significant differences in beta diversity of the oral microbiomes were seen between limb- and bulbar-onset ALS participants. Two bacterial genera were differentially abundant between these groups, Bifidobacteriaceae Bifidobacterium was enriched in bulbar-onset cases, while Pasteurellaceae Haemophilus was enriched in limb-onset cases. No significant differences were found between ALS participants and controls, but there were significant differences when comparing participants from different sites of recruitment. Amongst household pairs (n=35 pairs), ALS participants differed from control participants at the Seoul site. CONCLUSIONS:Despite the cohort and household effects, our study identified differentially abundant organisms that may be important to the phenotypic variability of ALS and should be considered for future study. Our study provides novel insights into design for future multi-site microbiome research in ALS.

Contexte: Bien que rare dans la population g & eacute;n & eacute;rale, l'amyotrophie bulbospinale li & eacute;e & agrave; l'X est une affection neuromusculaire r & eacute;cessive li & eacute;e & agrave; l'X dont la pr & eacute;valence est & eacute;lev & eacute;e chez les personnes qui s'identifient comme membres des Premi & egrave;res Nations ou de la Nation m & eacute;tisse dans l'Ouest canadien. Le pr & eacute;sent guide de pratique clinique vise & agrave; am & eacute;liorer et & agrave; standardiser la prise en charge de l'amyotrophie bulbospinale li & eacute;e & agrave; l'X, ainsi qu'& agrave; accro & icirc;tre la sensibilisation & agrave; cette maladie.M & eacute;thodes: Notre groupe de travail interdisciplinaire a men & eacute; un sondage sur les besoins afin d'orienter le choix des th & egrave;mes du pr & eacute;sent guide de pratique clinique, puis une recherche documentaire, une analyse des donn & eacute;es probantes et un examen externe r & eacute;alis & eacute; par des professionnels et professionnelles de la sant & eacute; ainsi que par des personnes ayant une exp & eacute;rience v & eacute;cue de la maladie. Nous avons eu recours au processus ADAPTE pour & eacute;valuer le seul guide de pratique clinique pr & eacute;existant sur l'amyotrophie bulbospinale li & eacute;e & agrave; l'X (le protocole national de 2020), mais aussi le guide de pratique clinique canadien de 2020 sur la scl & eacute;rose lat & eacute;rale amyotrophique (SLA), l'objectif & eacute;tant d'en d & eacute;terminer la pertinence & agrave; des fins d'adaptation. Notre d & eacute;marche a respect & eacute; les principes de l'outil AGREE II (Appraisal of Guidelines for Research and Evaluation), a eu recours & agrave; la m & eacute;thode GRADE (Grading of Recommendations, Assessment, Development, and Evaluation) et a suivi les directives du GIN (Guidelines International Network)-McMaster Guideline Development Checklist. La participation des collectivit & eacute;s autochtones s'est faite sous la direction du groupe de recherche sur le bien-& ecirc;tre des Autochtones Pewaseskwan, qui a travaill & eacute; & agrave; l'& eacute;laboration du pr & eacute;sent guide de pratique clinique.Recommandations: Nous avons formul & eacute; 41 recommandations couvrant l'ensemble du continuum de soins de l'amyotrophie bulbospinale li & eacute;e & agrave; l'X : diagnostic, & eacute;quipe multidisciplinaire, prise en charge des sympt & ocirc;mes touchant les membres et des sympt & ocirc;mes bulbaires, complications respiratoires et cardiaques, manifestations polysyst & eacute;miques, femmes porteuses, soutien & eacute;motionnel et consid & eacute;rations relatives aux peuples autochtones. L'amyotrophie bulbospinale li & eacute;e & agrave; l'X doit & ecirc;tre prise en charge par une & eacute;quipe multidisciplinaire capable de s'occuper de ses manifestations tant motrices que non motrices, notamment l'atteinte cardiaque, les sympt & ocirc;mes sensitifs et le dysfonctionnement m & eacute;tabolique. Pour ce qui est des femmes porteuses, on doit se pr & eacute;occuper de la prise en charge de leurs sympt & ocirc;mes et du counseling g & eacute;n & eacute;tique. Les prestataires de soins doivent veiller & agrave; offrir aux Autochtones des soins adapt & eacute;s & agrave; leur r & eacute;alit & eacute; culturelle. Interpr & eacute;tation: Le pr & eacute;sent guide de pratique clinique sur l'amyotrophie bulbospinale li & eacute;e & agrave; l'X propose aux professionnels et professionnelles de la sant & eacute; une norme de soins adapt & eacute;e & agrave; la r & eacute;alit & eacute; culturelle des personnes touch & eacute;es par cette maladie, dans l'espoir que ce travail se traduise concr & egrave;tement par une am & eacute;lioration de la qualit & eacute; de vie de celles-ci.

Offering genetic testing is increasingly recommended for all individuals with amyotrophic lateral sclerosis (ALS), particularly following the development of gene-targeted therapies, such as tofersen for SOD1-ALS. Historically, testing was routinely offered to those with familial ALS (fALS), but inconsistently to those with sporadic ALS (sALS). We evaluated changes in genetic testing and counseling practices among Canadian ALS physicians over a five-year period spanning pivotal clinical trial results and regulatory approval of tofersen. Members of the Canadian ALS Research Network were surveyed in 2020, 2022, and 2025 about genetic testing practices for symptomatic and asymptomatic individuals, gene panel composition, access to genetic counseling, and perceived drivers of change. Clinics offering genetic testing for sALS increased from 33% of clinics in 2020 and 57% in 2022 to 100% of respondents in 2025. Genetic testing for patients with a family history (fALS) was near-universal across all timepoints. Broader use of multi-gene panel testing increased over time, coinciding with sponsored testing availability. 61% of respondents reported that Health Canada approval of tofersen directly influenced their practice. Predictive testing offerings increased from 37% in 2020 to 61% in 2025. Genetic testing practices in Canada shifted substantially during late-stage clinical development and following regulatory approval of a gene-targeted therapy (tofersen). Proactive planning during the clinical trial phase facilitated rapid, nationwide adoption. This study captures a key turning point in ALS care, illustrating how therapeutic breakthroughs can redefine national clinical standards.

Pathogenic variants in the mitochondrial protein MFN2 are typically associated with a peripheral neuropathy phenotype, but can also cause a variety of additional pathologies including myopathy. Here, we identified an uncharacterized MFN2 variant, Q367H, in a patient diagnosed with late-onset distal myopathy, but without peripheral neuropathy. Supporting the hypothesis that this variant contributes to the patient's pathology, patient fibroblasts and transdifferentiated myoblasts showed changes consistent with impairment of several MFN2 functions. We also observed mtDNA outside of the mitochondrial network that colocalized with early endosomes, and measured activation of both TLR9 and cGAS-STING inflammation pathways that sense mtDNA. Re-expressing the Q367H variant in MFN2 KO cells also induced mtDNA release, demonstrating this phenotype is a direct result of the variant. As elevated inflammation can cause myopathy, our findings linking the Q367H MFN2 variant with elevated TLR9 and cGAS-STING signalling can explain the patient's myopathy. Thus, we characterize a novel MFN2 variant in a patient with an atypical presentation that separates peripheral neuropathy and myopathy phenotypes, and establish a potential pathomechanism connecting MFN2 dysfunction to mtDNA-mediated inflammation.

INTRODUCTION:Neuromuscular diseases (NMDs) impose multifaceted challenges on individuals and their families, often resulting in significant medical and non-medical expenses. While cost-of-illness (COI) studies provide valuable quantitative data, few explore the lived experience of financial strain. This study aims to identify the complex, often hidden, financial impacts experienced by individuals with NMDs and their families. METHODS:We conducted a qualitative study involving four virtual semi-structured focus groups, with 58 participants (76% patients and 24% caregivers). Participants were recruited from Muscular Dystrophy Canada's database and had previously completed the national BIND COI survey. Participants shared firsthand accounts of direct non-medical costs, psychosocial burdens and opportunity costs, highlighting hidden expenses, substantial out-of-pocket costs, and the broader financial and emotional toll on families. Thematic analysis of the transcripts of the discussions was performed using an inductive approach, guided by a rare-disease-specific socio-economic burden framework. RESULTS:Four key themes emerged: informational costs (lack of awareness/support for navigating financial resources), time-related costs (time spent advocating for supports), opportunity costs (loss of income or career advancement), and costs to independence (emotional toll and out-of-pocket costs for assistive devices and home modifications). CONCLUSION:This study identified four interconnected categories of hidden costs for people with NMDs and their families: informational burdens, administrative and advocacy demands, employment-related opportunity costs, and reduced independence tied to out-of-pocket spending on equipment and home modifications. These findings reveal how financial and emotional pressures accumulate beyond what traditional COI estimates capture. Greater attention to these costs is critical for fostering equitable and sustainable healthcare systems. PATIENT OR PUBLIC CONTRIBUTION:This study was designed and conducted in partnership with individuals living with NMDs and caregivers. Three trained patient and family research partners contributed to the development of the focus group guide and interpretation of results. All participants contributed their lived experiences to inform and validate key findings. Their input was central to the design, analysis and preparation of this manuscript, ensuring alignment with community priorities.

Germline variants in DEPDC5 are a cause of familial focal epilepsy with variable foci. Affected individuals may have focal cortical dysplasia if a second brain somatic variant occurs. As access to brain tissue is limited, the second somatic hit in the brain is usually presumed if a clear pathogenic germline variant is present. Here, we present a patient with structural focal epilepsy due to focal cortical dysplasia. He underwent epilepsy surgery at age 2 months. Clinical genetic testing revealed a germline variant of uncertain significance (VUS) DEPDC5 c.920T>G, p. (Leu307Arg). We hypothesized that if the proband's germline DEPDC5 variant was disease-causal, a second somatic variant may be identifiable in affected cortical tissue. DNA was extracted from archived brain formalin-fixed paraffin-embedded tissue and subjected to deep gene panel analysis. This revealed an additional somatic pathogenic variant in DEPDC5, which was confirmed using droplet digital PCR. Identification of the second somatic hit in brain tissue (DEPDC5 c.982C>T, p.(Arg328*)) confirmed the two-hit situation in this patient and supported disease causality of the germline variant. In conclusion, testing tissue for somatic variants may be clinically relevant at a patient-specific level if a germline VUS affects a gene where a two-hit mechanism is known.

BACKGROUND AND OBJECTIVES:Individuals living with neuromuscular disease (NMD) often face substantial financial strain due to the chronic and progressive nature of these conditions. Despite growing awareness, the extent and determinants of financial toxicity (FT) in this population remain poorly understood. We assessed FT among individuals with NMD or their caregivers in Canada using a validated patient-reported outcome measure. METHODS:We conducted a national, cross-sectional survey of individuals with NMD or their caregivers registered with Muscular Dystrophy Canada (MDC). The survey, available in English and French, was completed online or by telephone with assistance from MDC personnel. FT was measured using the validated Comprehensive Score for Financial Toxicity (COST)-Functional Assessment of Chronic Illness Therapy questionnaire. Multivariable generalized linear models were used to identify factors associated with FT. RESULTS:A total of 1,426 participants (mean [SD] age, 52.0 [19.5] years; 52% female) completed the survey. Seventy-five percent reported household incomes below the national median, primarily because of reduced employment. The average COST score was 17.2 [10.4], significantly lower than scores reported in other chronic conditions, including cancer. Moreover, 70% of respondents had COST scores below 26, indicating moderate or severe FT. After adjusting for other factors, COST scores were significantly worse among caregivers than in adults with NMDs. Lower scores were also observed among individuals identified as racialized minority (rate ratio [RR] 0.74; 95% CI 0.64-0.87); those with lower household income (RR 0.59; 95% CI 0.51-0.69), those with lower education (RR 0.91; 95% CI 0.82-1.00), and those unable to work (RR 0.74; 95% CI 0.64-0.86); students (RR 0.54; 95% CI 0.34-0.86); or early retirees (RR 0.86, 95% CI 0.74-0.99). FT was also greater among those diagnosed with autoimmune myopathies (RR 0.82; 95% CI 0.73-0.92), spinal muscular atrophy (RR 0.79; 95% CI 0.66-0.96), and limb-girdle muscular dystrophy (RR 0.87; 95% CI 0.77-0.99). DISCUSSION:FT is highly prevalent among people living with NMDs, particularly caregivers and those with socioeconomic and clinical vulnerabilities. Policies to improve financial support and health care coverage for NMD-related needs could help alleviate this burden. Further research is required to understand the mechanisms contributing to FT within NMD subgroups.

INTRODUCTION:Neuromuscular diseases (NMDs) are rare multisystem, genetic or acquired disorders causing weakness and/or sensory loss. It is essential for governments, insurance providers, and broader society to have a better understanding of the burden of illness of NMDs. Our goal is to assess the social and economic burden of Canadians living with NMDs, encompassing schooling and education achievement, health-related quality-of-life, and labour force participation and productivity. METHODS AND ANALYSIS:We will conduct a national, cross-sectional survey of individuals living with a NMD and their caregivers who are members of Muscular Dystrophy Canada and/or are patients within our national network of neuromuscular clinics. Surveys can be completed online or via telephone. The specific sub-sections of the questionnaire will differ based on respondent's profile, whether they are 1) a minor living with a NMD, 2) an adult living with a NMD, 3) an adult who is a caregiver for someone living with a NMD, or 4) an adult who both lives with a NMD and is a caregiver for someone with a NMD. We will use descriptive statistics to describe distributions and ranges of the social and economic measures. Pearson correlations for continuous data and Spearman rho for rank data will be used to detect the strength of association of socio-demographic factors, disease characteristics, and social and economic impacts of NMDs. ETHICS AND DISSEMINATION:The study protocol has been approved by the Ottawa Health Science Network Research Ethics Board (Protocol ID # 20210601-01H). This study will provide the overall impact of NMD on costs and health-related quality of life, disseminated via a series of manuscripts which will include both between- and within-NMD/NMD subtype comparisons. The data obtained will guide governmental policy development and inform patient organisation programs to deliver more effective supports to individuals and families affected by NMDs.

BACKGROUND:Although rare in the general population, spinal bulbar muscular atrophy (SBMA) is an X-linked recessive neuromuscular condition that is highly prevalent in people identifying as First Nations and Métis in western Canada. The aim of this guideline is to improve and standardize care of SBMA, and to increase awareness of the condition. METHODS:Our interdisciplinary working group conducted a needs assessment survey to aid in the development of guideline topic questions, followed by a literature search, evidence review, and external review by health practitioners and people with lived experience. We followed the ADAPTE framework to evaluate the only pre-existing SBMA guideline (2020 French national protocol) and the 2020 Canadian amyotrophic lateral sclerosis guideline for appropriateness of adaptation. Our process adhered to the Appraisal of Guidelines for Research and Evaluation (AGREE II) tool; used the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) approach; and followed the Guidelines International Network-McMaster Guideline Development Checklist. Indigenous community engagement was led by the Pewaseskwan Indigenous Research Group, who participated in the development of the guideline. RECOMMENDATIONS:We developed 41 recommendations to address the continuum of care in SBMA, including diagnosis; multidisciplinary teams; management of limb and bulbar symptoms, respiratory and cardiac complications, and multisystem symptoms; female carriers; emotional supports; and considerations for Indigenous people. Spinal bulbar muscular atrophy is best managed by multidisciplinary teams that can address both its motor and nonmotor manifestations, including cardiac involvement, sensory symptoms, and metabolic dysfunction. Concerns for female carriers may include symptom management and genetic counselling. Providers should ensure culturally appropriate care for Indigenous people. INTERPRETATION:In this guideline, we provide health care professionals with a culturally responsive standard of care for SBMA, and hope this will translate into improved quality of life for people affected by SBMA.

Excessive mitochondrial fragmentation is associated with the pathologic mitochondrial dysfunction implicated in the pathogenesis of etiologically diverse diseases, including many neurodegenerative disorders. The integrated stress response (ISR) – comprising the four eIF2α kinases PERK, GCN2, PKR, and HRI – is a prominent stress-responsive signaling pathway that regulates mitochondrial morphology and function in response to diverse types of pathologic insult. This suggests that pharmacologic activation of the ISR represents a potential strategy to mitigate pathologic mitochondrial fragmentation associated with human disease. Here, we show that pharmacologic activation of the ISR kinases HRI or GCN2 promotes adaptive mitochondrial elongation and prevents mitochondrial fragmentation induced by the calcium ionophore ionomycin. Further, we show that pharmacologic activation of the ISR reduces mitochondrial fragmentation and restores basal mitochondrial morphology in patient fibroblasts expressing the pathogenic D414V variant of the pro-fusion mitochondrial GTPase MFN2 associated with neurological dysfunctions, including ataxia, optic atrophy, and sensorineural hearing loss. These results identify pharmacologic activation of ISR kinases as a potential strategy to prevent pathologic mitochondrial fragmentation induced by disease-relevant chemical and genetic insults, further motivating the pursuit of highly selective ISR kinase-activating compounds as a therapeutic strategy to mitigate mitochondrial dysfunction implicated in diverse human diseases.

BACKGROUND:The marked heterogeneity of Amyotrophic Lateral Sclerosis (ALS) combined with a lack of biomarkers are key contributing factors to the lack of disease-modifying treatments. The Comprehensive Analysis Platform to Understand Remedy and Eliminate ALS (CAPTURE ALS) is a Canadian platform designed to create the most comprehensive picture of people living with ALS with the objective of facilitating ALS research initiatives worldwide. OBJECTIVES:The main aims of CAPTURE ALS include: (1) to characterize ALS and healthy controls with biosamples and data in order to provide the most comprehensive picture of individuals living with ALS to date; (2) to create a de-identified database and biosample repository linked to detailed clinical information; and (3) to develop and implement an inclusive and transparent participant engagement strategy to be active throughout all stages of CAPTURE ALS. METHODS/RESULTS:CAPTURE ALS is a prospective, multicenter, observational, longitudinal study. People living with ALS, or a related disease and healthy controls undergo a harmonized protocol including the collection of detailed clinical information, neurological and cognitive examination, speech recording, advanced magnetic resonance imaging, and biosampling. Data and samples are stored in a biobank operating under an open science governance framework. An inclusive and transparent participant engagement strategy was designed and implemented throughout all stages of CAPTURE ALS. Four sites are operating in the consortium with a fifth being onboarded. The target enrollment is 120 affected participants and 50 controls, with the first participant visit having occurred in March 2022. Recruitment is ongoing. DISCUSSION:CAPTURE ALS is a scalable clinical research platform that connects scientists and patients to facilitate efficient translational research. The unique and deeply phenotyped data and biosamples are a global resource towards the development of biomarkers and understanding ALS biology. This study is registered at clinicaltrials.gov (NCT: NCT05204017).

ABSTRACT Background and Objectives Spinocerebellar ataxias (SCA) represent a clinically and genetically heterogeneous group of progressive neurodegenerative diseases with prominent cerebellar atrophy. Recently, a novel pathogenic repeat expansion in intron 1 of FGF14 was identified, causing adult‐onset SCA (SCA27B). We aimed to determine the proportion of our unsolved adult‐onset ataxia cohort harboring this expansion using several technologies, and to characterize the phenotypic presentation within our population. Methods Individuals presenting with adult‐onset ataxia (> 30 years old) and negative previous genetic testing were selected from the Care4Rare patient repository. Affected individuals were from all ethnicities, and 90% had a family history suggestive of dominant ataxia, representing 19 of the 23 families included. We used multiple tools (PCR, long‐read genome sequencing and optical genome mapping (OGM)) to identify the pathogenic GAA repeat in FGF14. Results Of the 23 families included in this study, 65.2% harbored a pathogenic GAA expansion in FGF14. Individuals of French‐Canadian descent (FC) represented most of our cohort and had a 64.7% diagnostic yield. Affected individuals presented with gaze‐evoked nystagmus, gait ataxia, cerebellar dysarthria, and early episodic features. The GAA expansion in FGF14 was visible by OGM in all individuals tested. Interpretation Our diagnostic yield demonstrates this expansion may be the most common cause of adult‐onset SCA in dominant families of FC ancestry. Our FC participants have a phenotype distinct from previously published FC patients, with gaze‐evoked nystagmus being the most common eye anomaly. From a diagnostic standpoint, the pathogenic GAA repeat can be identified by OGM, but additional tests are required to complement the interpretation.

Polymorphisms in the gene encoding CD2-associated protein (CD2AP) are associated with an increased risk for developing Alzheimer’s disease (AD). Intriguingly, variants in the gene also cause a pattern of kidney injury termed focal segmental glomerulosclerosis. Recent studies have investigated the cell types and mechanisms by which CD2AP gene dosage contributes to the key pathological features of AD. This review summarizes the fundamental roles of CD2AP in mammalian cells and systems, discusses the novel pathogenic mechanisms focused on CD2AP in AD and highlights the necessity of incorporating biological sex in CD2AP research. Finally, the article draws important parallels between kidney and brain physiology based on vascular and molecular organization, links kidney disease to AD, and suggests the existence of a kidney-brain axis in AD centered on CD2AP.

OBJECTIVE:Somatic variants causing epilepsy are challenging to detect, as they are only present in a subset of brain cells (e.g., mosaic), resulting in low variant allele frequencies. Traditional methods relying on surgically resected brain tissue are limited to patients undergoing brain surgery. We developed an improved protocol to detect somatic variants using DNA from stereoelectroencephalographic (SEEG) depth electrodes, enabling access to a larger patient cohort and diverse brain regions. This protocol mitigates issues of contamination and low yields by purifying neuronal nuclei using fluorescence-activated nuclei sorting (FANS). METHODS:SEEG depth electrodes were collected upon extraction from 41 brain regions across 17 patients undergoing SEEG. Nuclei were isolated separately from depth electrodes in the affected brain regions (seizure onset zone) and the unaffected brain regions. Neuronal nuclei were isolated using FANS, and DNA was amplified using primary template amplification. Short tandem repeat (STR) analysis and postsequencing allelic imbalance assessment were used to evaluate sample integrity. High-quality amplified DNA samples from affected brain regions, patient-matched unaffected brain regions, and genomic DNA were subjected to whole exome sequencing (WES). A bioinformatic workflow was developed to reduce false positives and to accurately detect somatic variants in the affected brain region. RESULTS:Based on DNA yield and STR analysis, 14 SEEG-derived neuronal DNA samples (seven affected and seven unaffected) across seven patients underwent WES. From the variants prioritized using our bioinformatic workflow, we chose four candidate variants in MTOR, CSDE1, KLLN, and NLE1 across four patients based on pathogenicity scores and association with phenotype. All four variants were validated using digital droplet polymerase chain reaction. SIGNIFICANCE:Our approach enhances the reliability and applicability of SEEG-derived DNA for epilepsy, offering insights into its molecular basis, facilitating epileptogenic zone identification, and advancing precision medicine.