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Background: The 5q-associated spinal muscular atrophy (SMA) affects ~ 80–120 newborns annually. The disease is characterized by progressive paresis involving the bulbar and respiratory musculatures. The phenotypes are very heterogeneous ranging from severe courses with early death in the first years of life to loss of gait in older age. Objective: There are now an increasing number of causally targeted therapies available that can either directly interfere with the transcription of the gene causing the disease or replace the homozygous loss of the SMN1 gene. This work aims to elucidate the current state of therapy in different groups of patients with SMA. Material and methods: Presentation of clinical trials and basic studies with a focus on patients with disease onset in adulthood. Results: The clinical studies all show improvement or stabilization of motor function; however, in individual cases, the burden of the therapy for severely immobilized patients must be considered in addition to the efficacy in the treatment decision. Even if the drugs show a good safety profile, observations on the long-term efficacy and safety of the new substance classes are still lacking. Conclusion: The study landscape shows a good efficacy of the currently approved therapies across all degrees of severity and age groups. Due to the lack of comparative studies, the decision on the appropriate therapy should therefore be made according to an individual risk-benefit assessment. [ABSTRACT FROM AUTHOR]

The mode of inheritance of X-linked myotubular myopathy (XL-MTM) is still considered recessive, although female carriers are frequently symptomatic. We aimed to characterize the phenotypic spectrum and burden of disease in a carrier cohort. We performed a cross-sectional study among XL-MTM carriers in Germany, recruiting predominantly through a patient association. We used a custom-made questionnaire on medical and family history, the Checklist Individual Strength (CIS20-R), Short Form 12 (SF-12) health survey, Pain Detect, Short-Form McGill Pain Questionnaire (SF-MPQ-D), Graded Chronic Pain Scale (GCPS), and Depression Anxiety Stress Scale (DASS21). All participants received a neurologic examination including manual muscle testing (MMT), a 6-minute walking test (6MWT), and timed up-and-go (TUG) test. Where possible, we performed ultrasound of the abdomen and vastus lateralis muscles, echocardiography, pulmonary function testing, blood count, and further laboratory testing. Carriers were classified as manifesting based on the degree of muscular weakness and ambulatory status. In our study population (n=14), most carriers were classified as manifesting with a mild (n=8; independent ambulation, with limb or axial weakness) or minimal phenotype (n=3; only facial muscle weakness). We consider only the minority non-manifesting (n=3). Frequent features include a high-arched palate, fatigue, muscle pain and stiffness, and pulmonary problems. Many carriers are caregivers of boys with XL-MTM (n=11). Families are burdened with stillbirth and death in early childhood (n=8). The majority of female carriers of XL-MTM show neuromuscular and additional symptoms. This should be considered in diagnostics, clinical care, and future clinical trials. Supporting grant DFG FU 356/12-2 [ABSTRACT FROM AUTHOR]

Pathogenic variants in CHRNE encoding the epsilon subunit of acetyl choline receptor (AChR) result in impaired neuromuscular transmission and congenital myasthenic syndromes (CMS). Clinical manifestations include facial, ocular and limb fatigability and weakness, whereby severity of symptoms may vary in patients harboring the same pathogenic variant. Although the underlying pathophysiology is well-known, blood biomarkers enabling a patient-stratification are lacking. Previous studies revealed CHRNE protein in white blood cells (WBC) rendering these cells suitable for the study of cellular and minimal-invasive marker proteins. This retrospective two center-study includes 19 patients carrying biallelic pathogenic variants in CHRNE identified by molecular genetic testing. The patients were clinically characterized according to clinical severity (grade 1-4). Biomarker discovery was carried out on blood samples: proteomic profiling was performed on WBC (n =12) and on extracellular vesicles (EVs) purified from serum samples (n =7) in addition to amino acid profiling (n = 9) and miRNA screening (n = 18) on sera. In 19 patients (mean age 14.8 years) from 13 families seven known pathogenic variants in CHRNE were identified in addition to one variant previously not reported (c.1032+2_1032+3delTAinsGT). Whereas 15 patients were classified as mildly affected (group A: grade 1 and 2), 4 patients were classified as moderate or severely affected (group B: grade 3 and 4). Proteomics unveiled a significant increase of 7 and a decrease of 36 proteins in WBC in comparison to normal, age matched controls. GO-term based in silico studies of these dysregulated proteins indicated affection of secretory granules and the extracellular space. When comparing proteomic signatures of CHRNE-patients with a mild (A) versus moderate to severe phenotypes (B), 2 proteins (SCAMP2 and SNX2) were significantly increased in second group (B). These two proteins are involved in vesical transport. Prompted by this finding, proteomic profiling of EVs was initiated revealing a significant dysregulation of 20 proteins (7 are increased and 13 decreased). Three of these proteins (TARSH, ATRN & PLEC) are known to be important for synaptogenesis and synaptic function. Metabolic profiling of sera showed a decrease of 7 amino acids/ amino acid metabolites (aspartic and glutamic acids, phosphoserine, amino adipate, citrulline, ornithine & 1-methyhistidine) in terms of a metabolic fingerprint in CHRNE-related CMS patients. Moreover, miRNA screening unveiled increase of miR−365b−3p and miR−483−3p and decrease of miR-4433b-3p when comparing sera of CHRNE patients versus healthy controls. Moreover, a comparison of CHRNE patients versus other CMS-subtypes showed increase of miR−205−5p, miR−10b−5p, and miR−483−5 and decrease of miR−1290. Our combined data introduce a panel of minimal-invasive biomarkers on protein, metabolic and miRNA level with some of those play different roles along the neuromuscular axis. In the latter regard, impaired EV homeostasis impacting on synaptic function seems to be a molecular disease driver and two proteins in WBC correlate with disease severity. Our miRNA profiles introduce four miRNAs which may open new avenues in CMS patient stratification. [ABSTRACT FROM AUTHOR]

Congenital myasthenic syndromes (CMS) are inherited disorders of defective neuromuscular transmission. The clinical phenotype and treatment response vary between the over 30 genetic subtypes. Currently, there is limited published large cohort data in this population. A multicentre international study was undertaken to identify the genetic spectrum, clinical data, treatments, and standardised outcome measures in genetically confirmed CMS patients. Cross sectional data was collected at the time of routine clinic appointment within the last 12-months. Clinical, genetic information and three outcome measures (Myasthenia Gravis Quantitative Score - QMG, Myasthenia Gravis Activities of Daily Living - MG-ADL and Sit to stand in 1 minute - STS1M) were collected. Cohort data analysis was performed on complete data sets, with sub analysis of common subtypes. 187 patients were included, with AChR deficiency 29%, DOK7 20%, RAPSN 17%, COLQ 7%, and Slow Channel 6%. Median age at clinic was 25 years (range 1-83 years). Mean age at symptom onset (n=172) was 2.8 years. Median age at genetic diagnosis (n=174) was 8.4 years. Median age at treatment initiation (n=169) was 5 years. Total QMG score (n=132) was median 12/39 (range 0-34), in AChR deficiency-13 (range 3-34), DOK7-10 (range 0-29), RAPSN-8 (range 2-17). MG-ADL score (n=174), median 5/24 (range 0-20), in AChR deficiency-5 (range 0-18), DOK7-7 (range 0-14), RAPSN-3.5 (range 0-10) and STS1M (n=146), median-22 (range 0-50), AChR deficiency-21.5(range 0-38), DOK7-17.5 (range 4-45) and RAPSN-25 (range 9-50). This is the largest reported CMS cohort including genetics, clinical data, and standardised outcome measures. Significant variability in the outcome measures was noted within individual CMS subtypes. This highlights the wide spectrum but also provides pivotal information for clinical trial designs. STS1M was identified as a robust easy deliverable outcome measure of fatigable weakness across all ages. [ABSTRACT FROM AUTHOR]

Spinal muscular atrophy (SMA) ranks as the second most prevalent neurodegenerative condition in childhood, characterized by a deficiency in the survival of motor neuron (SMN) protein. This deficiency primarily results in the degeneration of alpha motor neurons, leading to progressive muscle weakness and atrophy. However, motor neuron loss in SMA may not solely result from SMN deficiency. Retrograde signals from skeletal muscles and neuromuscular junctions likely play a significant role in motor neuron vulnerability, influencing the overall clinical presentation. Despite some biomarkers, such as SMN2 copy number, being associated with disease severity, there is a notable absence of therapeutic biomarkers directly linked to neuromuscular transmission, which could indicate the impact of appropriate functioning neuromuscular junctions in SMA. In light of this, we explored the potential of Thrombospondin-4 (TSP4) as a cerebrospinal fluid (CSF) biomarker, with potential implications for indicating treatment response. We used untargeted proteomic analyses to determine clinical-relevant biomarkers in CSF samples derived from symptomatic (n=4) versus non-symptomatic (n=6) (identified via newborn screening) pediatric SMA patients. The identified biomarker candidate, TSP4, was next quantified in CSF samples derived from further pediatric and adult SMA patients (n=32), as well as non-disease (n=18) and disease controls (n=20) by enzyme-linked immunosorbent assay (ELISA). Our proteomic findings unveiled dysregulation of TSP4 in CSF derived from pediatric SMA patients, indicating a distinction between pre-symptomatic and symptomatic patients. Further analysis by ELISA demonstrated a TSP4-decrease in pediatric SMA patients, but no alteration in adult SMA patients or pediatric patients with other neurological disorders (serving as disease controls). Of note, TSP4 levels in CSF increased following the administration of Nusinersen in pediatric SMA patients. TSP4, as a neuromuscular junction resident protein, holds the potential to serve as a CSF biomarker in pediatric (but not adult) SMA patients and hereby not only indicates clinical manifestation but may even serve as a therapy marker under administration of Nusinersen. Further studies are needed to investigate the exact role of the protein in the etiology of SMA. [ABSTRACT FROM AUTHOR]

Spinal muscular atrophy (SMA) is a progressive, recessive neuromuscular disease characterized by significant reduction of SMN protein. This causes degeneration of lower motor neurons in the spinal cord and brainstem leading to weakness and muscle atrophy. Clinical severity is categorized in different subtypes (type 0-3), which is in turn influenced by residual SMN level. While the genetic basis of SMA is well described, the tissue-specific molecular pathways underlying SMA are still not fully understood and identification of marker proteins in human vulnerable tissue such as skeletal muscle is still lacking. To elucidate molecular markers in SMA-diseased muscle, we performed unbiased proteomics and transcriptomics on muscle biopsies derived from 3 SMA type 3 (walker) patients in addition to immunofluorescence including 5 additional cases and SMA myoblasts. Combined proteomic and transcriptomic studies unraveled FUS (a DNA/RNA-binding protein and aggregation marker) as a potential molecular marker increased in SMA muscle and SMA myoblasts. Results of our immunofluorescence studies showed increased FUS protein abundance in both accompanied by perimyonuclear disposition of the protein in a proportion of myofibres compared to the immunoreactivity obtained in control samples. To identify proteins that were associated with FUS we performed an interactome analysis, the results are pending. Our data classified FUS as a protein involved in SMA-based myopathology and support the concept of skeletal muscle as a primary tissue target of SMA. Further studies are crucial to define the role of mis-localized FUS in SMA muscle. [ABSTRACT FROM AUTHOR]

Spinal muscular atrophy (SMA) is a neuromuscular disorder caused by recessive pathogenic variants affecting the survival of motor neuron (SMN1) gene (localized on 5q). In consequence, cells lack expression of the corresponding protein. This pathophysiological condition is clinically associated with motor neuron (MN) degeneration leading to severe muscular atrophy. Additionally, vulnerability of other cellular populations and tissues including skeletal muscle has been demonstrated. Although the therapeutic options for SMA have considerably changed, treatment responses may differ thus underlining the persistent need for validated biomarkers. To address this need and to identify novel marker proteins for SMA, we performed unbiased proteomic profiling on cerebrospinal fluid derived (CSF) from genetically proven SMA type 1-3 cases and afterwards performed ELISA studies on CSF and serum samples to validate the potential of a novel biomarker candidates in both body fluids. To further decipher the pathophysiological impact of this biomarker, immunofluorescence studies were carried out on spinal cord and skeletal muscle derived from a 5q-SMA mouse model. Proteomics revealed an increase of LARGE1 in CSF derived from adult patients showing a clinical response upon treatment with nusinersen. Moreover, LARGE1 levels were validated in CSF samples of further SMA patients (type 1-3) by ELISA. These studies also unveiled a distinguishment between groups in improvement of motor skills: adult patients do present with lowered level per se at baseline visit while no elevation upon treatment in the pediatric cohort can be observed. ELISA-based studies of serum samples showed no changes in the pediatric cohort but unraveled elevated level in adult patients responding to future intervention with nusinersen, while non-responders did not show a significant increase. Additional immunofluorescence studies of LARGE1 in MN and skeletal muscle of a SMA type 3 mouse model revealed an increase of LARGE1 during disease progression. Our combined data unraveled LARGE1 as a protein dysregulated in serum and CSF of SMA-patients (and in MN and skeletal muscle of SMA mice) holding the potential to serve as a disease marker for SMA and enabling to differentiate between patients responding and non-responding to therapy with nusinersen. [ABSTRACT FROM AUTHOR]

GNE myopathy (GNEM) is a rare autosomal recessive distal myopathy characterized by early adult-onset, slow to moderately progressive distal muscle weakness that preferentially affects the tibialis anterior muscle and that usually spares the quadriceps femoris. Muscle biopsy reveals presence of rimmed vacuoles (inclusion body myopathy 2) and fibrosis seen in scattered areas. The disease is caused by bi-allelic variants in the GNE gene encoding the bifunctional enzyme UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase. The pathophysiology of GNE myopathy presumably involves aberrant protein sialylation. Thus far, the proteomic signature of GNE-mutant muscle has not been studied to determine a biochemical fingerprint serving as pathogenicity markers. Moreover, except myostatin, easy-accessible minimal-invasive biomarkers are still lacking for GNE myopathy. Exome sequencing was applied to identify the genetic cause of a myopathy present in three adolescents (all developed symptoms at approximately 15 years of age) of a consanguineous family from Afghanistan. In silico tools were applied to evaluate the pathogenicity of a candidate variant. Moreover, untargeted proteomics was performed to determine the proteinogenic signature of muscle biopsies derived from three additional unrelated GNEM patients with different grades of myopathology and immunostaining was completed to validate the findings and to define marker proteins of pathophysiological relevance. Additionally, proteomic profiling and ELISA were performed on serum derived from 24 GNE patients to identify novel minimal-invasive biomarkers. Genetic testing unveiled the novel homozygous p.(Val569Leu) missense variant in the 3 siblings. In silico studies confirmed a pathogenic effect of this amino acid substitution. Histological studies showed pathology including presence of vacuoles in quadriceps muscle derived from one of the patients carrying this variant. Muscle proteomics on three biopsies with other different GNEM genotypes unraveled 176 proteins (161 increased and 15 decreased) commonly affected in GNE patient-derived muscle. This defined catalogue of dysregulated proteins served to confirm the pathogenicity of the novel missense variant – in comparison to further missense variants with well-known pathogenicity – by immunostaining of paradigmatic proteins serving as tissue disease markers. Serum profiling enabled the definition of two proteins (serglycin and periostin) significantly decreased in patients. Pathophysiological relevance of altered periostin was confirmed by immunostaining on muscle biopsies showing increase in fibrotic scars. Our combined clinical, genetic and histology data extend the current genetic landscape of GNE myopathy by introducing a variant of early-onset and proximal muscle vulnerability. Muscle proteomics enabled a defined catalogue of tissue markers holding the potential to evaluate the pathogenicity of novel variants as exemplified on p.(Val569Leu) mutant muscle. Studies on serum derived from GNEM patients led to the identification of two novel blood biomarkers, serglycin and periostin, whereby an impact of periostin in fibrotic remodeling of muscle was demonstrated thus underlying the pathophysiological relevance. [ABSTRACT FROM AUTHOR]

Delandistrogene moxeparvovec, an rAAVrh74-based gene transfer therapy designed to address absent functional dystrophin by delivering a transgene encoding engineered micro-dystrophin, is approved (US, UAE, Qatar, Kuwait, Bahrain, Oman; Mar 2024) for ambulatory pediatric patients (pts) aged 4 through 5 years with Duchenne muscular dystrophy (DMD) with a confirmed DMD mutation. We report Part 1 (Week [Wk] 52) results of the two-part EMBARK trial (NCT05096221). Key inclusion criteria: Ambulatory males aged ≥4 <8 years with a confirmed DMD mutation within exons 18–79 (inclusive); screening North Star Ambulatory Assessment (NSAA) score >16 <29; rAAVrh74 antibody titers <1:400; stable daily oral corticosteroid dose (≥12 wks pre-screening). Pts received single-dose delandistrogene moxeparvovec (1.33×10¹⁴ vg/kg, intravenous) or placebo. Primary endpoint: change from baseline to Wk 52 in NSAA total score. At Wk 52 (N=125), the primary endpoint was not statistically significant—least-squares mean between-group difference for delandistrogene moxeparvovec (n=63) vs placebo (n=61) was 0.65 points (P=0.2441). Time to rise, 10-meter walk/run, stride velocity 95th centile and time to ascend 4 steps favored the treatment group (P<0.05, nominal). A prespecified global statistical test on a composite of functional endpoints supported treatment benefit (P=0.0044). Micro-dystrophin was expressed in the treatment group at Wk 12 (western blot). Mean creatine kinase levels decreased from baseline with delandistrogene moxeparvovec vs placebo (P=0.0002, nominal). Treatment-related treatment-emergent adverse events (AEs) included vomiting (54.0%), nausea (31.7%) and decreased appetite (27.0%), with no study discontinuations, deaths or complement-mediated AEs. Based on the totality of functional assessments including timed function tests, treatment with delandistrogene moxeparvovec indicates beneficial modification of disease trajectory. Safety was manageable and consistent with prior experience. [ABSTRACT FROM AUTHOR]

X-linked myotubular myopathy (XLMTM) is a rare neuromuscular disorder caused by mutations in the myotubularin (MTM1) gene, affecting 1:50000 male births. The clinical severity varies, however the need for ventilatory support is often inevitable. At present, no approved therapies are available for XLMTM. Patient management is mainly supportive. A first MTM1 gene replacement therapy tested in a clinical trial showed notable improvements on ventilator dependence and motor function but raised serious safety concerns. Forty patients have been enrolled in our European prospective natural history study of patients with XL-MTM designed to characterize the disease course by using standardized evaluations adjusted for age, ambulatory and respiratory status. At 3-year follow-up, data were available for 26 patients (65%) with a mean age of 14.3 (min 3.4, max 53.8) years. Drop-outs were due to loss to follow-up (n=1), death (n=1) and early withdrawal from the study (n=3). Nineteen percent (5/26) of patients were under the age of 6 years old. Among non-ambulant patients at baseline (n=19), only 1 acquired the ability to walk during the study. Respiratory function, strength and motor function did not statistically change. Muscle strength measured by MyoPinch and MyoGrip showed a mean decline of -1,04 kg (n=20) and -0.33kg (n=20) respectively. MFM D1 showed the most important decline of -2.98% at 36 months. Nine patients presented with a mean increase of grip strength of 1.5kg (SD 4.18) (n=13). Ten patients showed a mean increase of the pinch strength of 0.16kg (SD 0.71) (n=14). Correlation data will be presented. This first multicentric longitudinal natural history in all types of patients with XL-MTM demonstrates clearly that patients experience a decline over years that can be reliably measured. We have identified several strength-, functional and respiratory outcomes that can be used to build robust clinical trials in this population. [ABSTRACT FROM AUTHOR]

Pathogenic variants in the DNM2 gene can cause an autosomal dominant form of centronuclear myopathy (AD-CNM). The phenotypical spectrum is highly variable in severity and time of onset ranging from childhood to adulthood. Currently there are no approved treatments and patients mainly rely on supportive therapies. We set up an international, prospective natural history study in order to characterize the disease course in this patient cohort and to identify prognostic variables of the disease. At predefined intervals over 36 months, assessments of respiratory and motor function, as well as activity and muscle strength, were carried out using standardized measures. Medical files were assessed for cardiac function. Hepatic function was evaluated using ultrasound and blood analysis. We administered measures for quality of life and patient reported outcomes. 15 patients with AD-CNM caused by variants in the DNM2 gene were included for participation (female n=9 vs. male n=6; ambulant n=10 vs. non-ambulant n=5; mean age 41,5 years ±23,3 SD). 9 patients were available for assessment after 36 months (dropout n=6). Grip and pinch strength showed an age-related trajectory with peaks at 50 years of age, while the total strength assessed by the MFM32 reached its maximum just below 40 years, although with higher variability. Overall, patients remained largely stable for muscle strength and function, as well as pulmonary function over 36 months. No patient's ambulatory status changed over the 36 months period. Conclusive longitudinal data will be presented. This multicentric natural history study describes the disease trajectory of a cohort of patients with AD-CNM over 36 months. We identified outcomes and measures that can be used to assess several bodily functions relevant to both patients and investigators, as needed for the solid design of clinical trials [ABSTRACT FROM AUTHOR]

Filamin-A-interacting protein 1 (FILIP1) is a structural protein that is involved in neuronal and muscle function and integrity and interacts with FLNa and FLNc. Pathogenic variants in filamin-encoding genes have been linked to neurological disorders (FLNA) and muscle diseases characterized by myofibrillar perturbations (FLNC), but human diseases associated with FILIP1 variants have not yet been described. Here, we report on five patients from four unrelated consanguineous families with homozygous FILIP1 variants (two nonsense and two missense). Functional studies indicated altered stability of the FILIP1 protein carrying the p.[Pro1133Leu] variant. Patients exhibit a broad spectrum of neurological symptoms including brain malformations, neurodevelopmental delay, muscle weakness and pathology, and dysmorphic features. Electron and immunofluorescence microscopy on the muscle biopsy derived from the patient harbouring the homozygous p.[Pro1133Leu] missense variant revealed core-like zones of myofibrillar disintegration, autophagic vacuoles and accumulation of FLNc. Proteomic studies on the fibroblasts derived from the same patient showed dysregulation of a variety of proteins including FLNc and alpha-B-crystallin, a finding (confirmed by immunofluorescence) which is in line with the manifestation of symptoms associated with the syndromic phenotype of FILIP1opathy. The combined findings of this study show that the loss of functional FILIP1 leads to a recessive disorder characterized by neurological and muscular manifestations as well as dysmorphic features accompanied by perturbed proteostasis and myopathology. [ABSTRACT FROM AUTHOR]

Inflammatory, de- and regenerative features in sarcoglycanopathies (LGMD R3-6), one of the most prevailing types of LGMDs worldwide, are characteristic morphological hallmarks of the disease. Inflammatory processes and their complex interplay with vascular, skeletal muscle and mesenchymal cells may have a major impact on disease development and the specific immune-morphological features. We have analyzed skeletal muscle biopsies of 28 patients genetically confirmed as having LGMDR3 (9), LGMDR4 (3), LGMD5 (15) and LGMDR6 (1) by histopathological, molecular and proteomic analyses. Semiquantitative evaluation of inflammation, fibrosis and regeneration showed moderate numbers of inflammation and small foci of regenerating muscle fibres based on myosin heavy chain neonatal and developmental-positivity. Inflammation was mild in 16/28 (57%), while fibrosis was moderate or severe in 17/28 (59%), but the most prominent feature. No complement deposition on any of the sarcolemmal structures and none on capillaries was seen. Of note, in 25% of biopsies eosinophils were found. Further analysis including proteomic data are pending. Understanding disease-specific immune phenomena potentially inform about possibilities for antifibrotic and antiinflammatory therapeutic strategies, which may provide an additional approach to the direct gene correction attempts, which may be available in the future. These phenomena may also be of relevance for understanding potential therapy-related immune-mediated unwanted side effects. [ABSTRACT FROM AUTHOR]

Biochemical, histological, and ultra-structural studies are standard procedures in the diagnostic work-up of muscle and nerve biopsies derived from neuromuscular patients and moreover represent important biomedical research approaches toward a better understanding of the etiology of neuromuscular diseases (NMDs). In the era of next-generation-sequencing approaches, evaluation of the pathogenicity of genetic variants on muscle and nerve biopsies is often crucial. However, the investigation of tissue biopsies also harbours significant limitations: sampling is invasive, amount of tissue is often limited, and biopsies can only provide a snapshot of the disease at a given timepoint. Repeated biopsy sampling is not an option to monitor disease progression on a cellular level. Previous studies on certain diseases have already occasionally emphasized the potential of white blood cells (WBC) in the diagnostics and research of NMDs. This prompted us to initiate LiBi-NMD, a project systematically addressing the value of WBC in terms of liquid biopsies to study the etiology of neuromuscular diseases on a cellular level but in a minimal-invasive manner. By using mass spectrometry, we catalogued 211 out of 379 proteins (55.7%) linked to the manifestation of a NMD (covering peripheral nervous system diseases, myasthenic syndromes and myopathies) in WBC and provide information regarding their dynamics during aging. By electron microscopy, proteomics, high-dimensional cytometry and immunoblotting, we demonstrated their potential to (i) recapitulate ultra-structural perturbations usually detected in muscle biopsies, (ii) evaluate the pathogenicity of ambiguous variants, (iii) identify disease-relevant pathophysiological processes (paradigmatically shown for GAN- and SH3TC2-related neuropathies & ANO5- and CAPN3-related myopathies), and to (iv) monitor the biochemical fingerprint of disease progression (paradigmatically shown for myasthenic syndromes). Additionally, we highlight their potential to (v) monitor the success of intervention concepts in terms of the definition of cellular but minimally-invasive therapy markers. [ABSTRACT FROM AUTHOR]

Numerous studies have consistently found no serious adverse effects of reduced SMN protein expression on the development of cognitive function in SMA patients. However, the average intelligence quotient in SMA patients has been described as higher than average. The cognitive development of SMA patients identified by newborn screening remains largely unknown. A total of 47 SMA patients from 46 families identified through newborn screening between January 2018 and December 2020 were eligible for developmental testing using Bayley III (BSID) starting from the age of 12 months. A total of 40 patients, mean age 29.25 months (23 - 42 months; 23 female/17 male), 17 patients with 2 SMN2 copies, 11 patients with 3 SMN2 copies, and 12 patients with ≥ 4 SMN2 copies could be included. Cognitive scale: total: mean 94.55 (SD24.01), with 2 SMN2: 82.94 (SD25.19); 3 SMN2: 95.91 (SD19.60); 4 SMN2: 105.70 (SD16.41); Language scale: mean 86.09 (SD 26.41); Motor scale: 81.28 (SD 28.07). The post-hoc pairwise comparisons (BSID main scale type and the copy number as independent variables) showed that the cognition main scale scored significantly higher than the motor main scale (MΔ = 10.27, p = 0.014). There is no statistical effect of the SMN2 copy number on the score of the language main scale. The impaired cognitive development of SMA children with 2 SMN2 copies, despite early initiation of therapy, and in most cases near-normal motor development underlines the critical role of the SMN protein in the early stages of brain development. [ABSTRACT FROM AUTHOR]

Three different drugs have been approved by EMA and FDA for the treatment of patients with spinal muscular atrophy (SMA) in the past few years. In contrast to clinical trial data with restricted patient populations and short observation periods, SMArtCARE collects longitudinal real-world data on a broad spectrum of SMA patients as a disease-specific registry. For this data analysis, all patients under treatment with nusinersen were identified within the SMArtCARE registry. Inclusion criterion for the data analysis was that patients never had the ability to sit independently before start of treatment. Changes in motor function were evaluated with the CHOP INTEND score and motor milestones considering WHO criteria. Further, data on the need for ventilator support, tube feeding, and mortality were analyzed. In total, 143 children with SMA type 1 were included in the data analysis with a follow-up period of up to 38 months. Major improvements were observed in motor function, especially in children younger than two years of age at start of treatment. 24.5% of children gained the ability to sit independently. The need for non-invasive ventilator support and tube feeding increased despite treatment with nusinersen. Our findings confirm the increasing real-world evidence that treatment with nusinersen has a dramatic influence on disease progression in patients with SMA type 1 - especially regarding motor function and survival. Bulbar and respiratory function needs to be closely monitored, as these functions do not improve equivalent to motor function. [ABSTRACT FROM AUTHOR]

The therapeutic landscape of spinal muscular atrophy (SMA) has changed dramatically during the last 4 years but treatment responses differ remarkably among individuals and therapeutic decision-making remains challenging - underlining the persistent need for validated biomarkers. We applied untargeted proteomic analyses to determine biomarkers in cerebrospinal fluid (CSF) samples of SMA patients under treatment with nusinersen. Identified candidate proteins were validated in CSF samples of SMA patients by Western blot and ELISA. Further, levels of peripheral neurofilament H and L were determined. Untargeted proteomic analysis of CSF samples of 3 SMA type 1 patients revealed the lysosomal protease Cathepsin D as a candidate biomarker. Subsequent validation analysis in a larger cohort of 31 pediatric SMA patients (type 1=12, type 2=9, type 3=6, presymptomatically treated=4; age 0-16 years) revealed a significant decline of Cathepsin D levels in SMA patients ≥2 months at the start of treatment. While evident in all older age categories, this decline was only significant in the group of patients that showed a positive motor-response. Moreover, downregulation of Cathepsin D was evident in muscle biopsies of SMA patients. We identified a decline of Cathepsin D levels in CSF samples of SMA patients under nusinersen treatment that was more pronounced in the group of 'treatment responders' than in 'non-responders'. We believe that our results indicate a suitability of Cathepsin D levels as possible biomarker in SMA also in older patients – in combination with analysis of pNF-L in adolescents or alone in adult patients. [ABSTRACT FROM AUTHOR]

Duchenne muscular dystrophy (DMD) affects one in 3,500-5,600 of male newborns, making it the most common inherited muscular dystrophy. Becker muscular dystrophy (BMD), its milder form, is much rarer, affecting only one in about 18,000 male newborns. Both are caused by different types of mutations in the DMD gene. The encoded protein dystrophin stabilises the plasma membrane of the muscle cell as part of the dystrophin-glycoprotein-complex. Current research into DMD and BMD can explain about 92% of the phenotypes based on their genotypes through the frame-shift hypothesis. However, the remaining 8% are not adequately explained by this hypothesis, so that there is a need for further research to explain - not only - intermediate courses. We screened the cohort of DMD and BMD patients treated at the department of pediatric neurology of the University Hospital Essen for novel pathogenic DMD variants and corresponding phenotypes. We analysed the protein signatures (including post-translational modifications), measured dystrophin levels and studied the interactions of dystrophin and MAST1 in different biomaterials. Here, we report on 12 novel pathogenic variants, which have not yet been described in literature and link though to several several atypical phenotypes. Clinical findings were correlated with abundances of dystrophin and MAST1 toward an attempt of patient stratification. Knowing about novel genotypes and its corresponding (evolving) phenotype is very important in terms of counselling of affected families. Analysing the protein signatures and dystrophin levels as well as interaction partners is crucial to better understand the pathophysiology of dystrophin expression, especially in view of the development of new therapeutic approaches. [ABSTRACT FROM AUTHOR]

The centronuclear myopathies are congenital neuromuscular conditions characterised by the central location of the nucleus in muscle cells and a highly variable clinical picture. The presumably most common form is the ultra-rare X-linked myotubular myopathy (XLMTM) with an estimated incidence of 1 in 50,000-100,000 male births and a usually severe phenotype. The myotubular and centronuclear myopathy patient registry has been collecting demographic, genetic and longitudinal clinical data on affected individuals (living and deceased) and female carriers of XLMTM from all over the world, since 2013. It facilitates translational research by providing data to answer research questions or inform clinical trial feasibility studies, supporting recruitment into clinical trials and other research studies, and offering an important communication and engagement tool for this patient population. Patients and caregivers provide longitudinal data via recurring online questionnaires available in multiple languages. New developments for 2022 include the addition of 2 new languages, increased frequency of data collection, and a feature allowing participants to nominate their doctor to verify their diagnosis and contribute clinical data to their record. This poster will present the impact of the new developments and highlight the latest registry data. On 28-03-2022 the registry contained 404 participants (258 male and 146 female), of which 42 were reported as deceased (39 male and 3 female) and 362 living (219 male and 143 female). Of the 143 living females, 74 were registered as female carriers of XLMTM and 69 as patients. 52 countries are represented, with the largest cohorts being UK & Ireland (105), United States (101), and Germany (34). Causative genes reported include MTM1, DNM2, BIN1, RYR1, TTN , and SPEG. The myotubular and centronuclear myopathy patient registry contains important data on a diverse and growing international cohort of individuals affected by this group of rare and ultra-rare conditions. It aims to support all areas of translational research including epidemiology, clinical trial planning and recruitment, outcome measure development, standards of care, and real-world data for regulatory decision-making. [ABSTRACT FROM AUTHOR]