Recurrent de novo SPTLC2 variant causes childhood-onset amyotrophic lateral sclerosis (ALS) by excess sphingolipid synthesis.

BACKGROUND: Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease of the upper and lower motor neurons with varying ages of onset, progression and pathomechanisms. Monogenic childhood-onset ALS, although rare, forms an important subgroup of ALS. We recently reported specific SPTLC1 variants resulting in sphingolipid overproduction as a cause for juvenile ALS. Here, we report six patients from six independent families with a recurrent, de novo, heterozygous variant in SPTLC2 c.778G>A [p.Glu260Lys] manifesting with juvenile ALS. METHODS: Clinical examination of the patients along with ancillary and genetic testing, followed by biochemical investigation of patients' blood and fibroblasts, was performed. RESULTS: All patients presented with early-childhood-onset progressive weakness, with signs and symptoms of upper and lower motor neuron degeneration in multiple myotomes, without sensory neuropathy. These findings were supported on ancillary testing including nerve conduction studies and electromyography, muscle biopsies and muscle ultrasound studies. Biochemical investigations in plasma and fibroblasts showed elevated levels of ceramides and unrestrained de novo sphingolipid synthesis. Our studies indicate that SPTLC2 variant [c.778G>A, p.Glu260Lys] acts distinctly from hereditary sensory and autonomic neuropathy (HSAN)-causing SPTLC2 variants by causing excess canonical sphingolipid biosynthesis, similar to the recently reported SPTLC1 ALS associated pathogenic variants. Our studies also indicate that serine supplementation, which is a therapeutic in SPTLC1 and SPTCL2-associated HSAN, is expected to exacerbate the excess sphingolipid synthesis in serine palmitoyltransferase (SPT)-associated ALS. CONCLUSIONS: SPTLC2 is the second SPT-associated gene that underlies monogenic, juvenile ALS and further establishes alterations of sphingolipid metabolism in motor neuron disease pathogenesis. Our findings also have important therapeutic implications: serine supplementation must be avoided in SPT-associated ALS, as it is expected to drive pathogenesis further.

Effect of nusinersen on motor, respiratory and bulbar function in early-onset spinal muscular atrophy.

5q-associated spinal muscular atrophy is a rare neuromuscular disorder with the leading symptom of a proximal muscle weakness. Three different drugs have been approved by the European Medicines Agency and Food and Drug Administration for the treatment of spinal muscular atrophy patients, however, long-term experience is still scarce. In contrast to clinical trial data with restricted patient populations and short observation periods, we report here real-world evidence on a broad spectrum of patients with early-onset spinal muscular atrophy treated with nusinersen focusing on effects regarding motor milestones, and respiratory and bulbar insufficiency during the first years of treatment. Within the SMArtCARE registry, all patients under treatment with nusinersen who never had the ability to sit independently before the start of treatment were identified for data analysis. The primary outcome of this analysis was the change in motor function evaluated with the Children's Hospital of Philadelphia Infant Test of Neuromuscular Disorders and motor milestones considering World Health Organization criteria. Further, we evaluated data on the need for ventilator support and tube feeding, and mortality. In total, 143 patients with early-onset spinal muscular atrophy were included in the data analysis with a follow-up period of up to 38 months. We observed major improvements in motor function evaluated with the Children's Hospital of Philadelphia Infant Test of Neuromuscular Disorders. Improvements were greater in children >2 years of age at start of treatment than in older children. 24.5% of children gained the ability to sit independently. Major improvements were observed during the first 14 months of treatment. The need for intermittent 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 and survival in patients with early-onset spinal muscular atrophy. Major improvements in motor function are seen in children younger than 2 years at the start of treatment. Bulbar and respiratory function needs to be closely monitored, as these functions do not improve equivalent to motor function.

Continued benefit of nusinersen initiated in the presymptomatic stage of spinal muscular atrophy: 5-year update of the NURTURE study.

INTRODUCTION/AIMS: NURTURE (NCT02386553) is an open-label study of nusinersen in children (two SMN2 copies, n = 15; three SMN2 copies, n = 10) who initiated treatment in the presymptomatic stage of spinal muscular atrophy (SMA). A prior analysis after ~3 y showed benefits on survival, respiratory outcomes, motor milestone achievement, and a favorable safety profile. An additional 2 y of follow-up (data cut: February 15, 2021) are reported. METHODS: The primary endpoint is time to death or respiratory intervention (≥6 h/day continuously for ≥7 days or tracheostomy). Secondary outcomes include overall survival, motor function, and safety. RESULTS: Median age of children was 4.9 (3.8-5.5) y at last visit. No children have discontinued the study or treatment. All were alive. No additional children utilized respiratory intervention (defined per primary endpoint) since the prior data cut. Children with three SMN2 copies achieved all World Health Organization (WHO) motor milestones, with all but one milestone in one child within normal developmental timeframes. All 15 children with two SMN2 copies achieved sitting without support, 14/15 walking with assistance, and 13/15 walking alone. Mean Hammersmith Functional Motor Scale Expanded total scores showed continued improvement. Subgroups with two SMN2 copies, minimum baseline compound muscle action potential amplitude ≥2 mV, and no baseline areflexia had better motor and nonmotor outcomes versus all children with two SMN2 copies. DISCUSSION: These results demonstrate the value of early treatment, durability of treatment effect, and favorable safety profile after ~5 y of nusinersen treatment. Inclusion/exclusion criteria and baseline characteristics should be considered when interpreting presymptomatic SMA trial data.

Risdiplam in types 2 and 3 spinal muscular atrophy: A randomised, placebo-controlled, dose-finding trial followed by 24 months of treatment.

BACKGROUND AND PURPOSE: Spinal muscular atrophy (SMA) is caused by reduced levels of survival of motor neuron (SMN) protein due to deletions and/or mutations in the SMN1 gene. Risdiplam is an orally administered molecule that modifies SMN2 pre-mRNA splicing to increase functional SMN protein. METHODS: SUNFISH Part 1 was a dose-finding study conducted in 51 individuals with types 2 and 3 SMA aged 2-25 years. A dose-escalation method was used to identify the appropriate dose for the subsequent pivotal Part 2. Individuals were randomized (2:1) to risdiplam or placebo at escalating dose levels for a minimum 12-week, double-blind, placebo-controlled period, followed by treatment for 24 months. The dose selection for Part 2 was based on safety, tolerability, pharmacokinetic, and pharmacodynamic data. Exploratory efficacy was also measured. RESULTS: There was no difference in safety findings for all assessed dose levels. A dose-dependent increase in blood SMN protein was observed; a median twofold increase was obtained within 4 weeks of treatment initiation at the highest dose level. The increase in SMN protein was sustained over 24 months of treatment. Exploratory efficacy showed improvement or stabilization in motor function. The pivotal dose selected for Part 2 was 5 mg for patients with a body weight ≥20 kg or 0.25 mg/kg for patients with a body weight <20 kg. CONCLUSIONS: SUNFISH Part 1 demonstrated a twofold increase in SMN protein after treatment with risdiplam. The observed safety profile supported the initiation of the pivotal Part 2 study. The long-term efficacy and safety of risdiplam are being assessed with ongoing treatment.

CAPRIN1P512L causes aberrant protein aggregation and associates with early-onset ataxia.

CAPRIN1 is a ubiquitously expressed protein, abundant in the brain, where it regulates the transport and translation of mRNAs of genes involved in synaptic plasticity. Here we describe two unrelated children, who developed early-onset ataxia, dysarthria, cognitive decline and muscle weakness. Trio exome sequencing unraveled the identical de novo c.1535C > T (p.Pro512Leu) missense variant in CAPRIN1, affecting a highly conserved residue. In silico analyses predict an increased aggregation propensity of the mutated protein. Indeed, overexpressed CAPRIN1P512L forms insoluble ubiquitinated aggregates, sequestrating proteins associated with neurodegenerative disorders (ATXN2, GEMIN5, SNRNP200 and SNCA). Moreover, the CAPRIN1P512L mutation in isogenic iPSC-derived cortical neurons causes reduced neuronal activity and altered stress granule dynamics. Furthermore, nano-differential scanning fluorimetry reveals that CAPRIN1P512L aggregation is strongly enhanced by RNA in vitro. These findings associate the gain-of-function Pro512Leu mutation to early-onset ataxia and neurodegeneration, unveiling a critical residue of CAPRIN1 and a key role of RNA-protein interactions.

Mechanographic analysis of the timed 4 stair climb test - methodology and reference data of healthy children and adolescents.

OBJECTIVES: The timed 4 stair climb test (4SC) is an accepted and widely used tool to assess motor function of patients with neuromuscular diseases. We aimed to establish reference data for the 4SC, and for mechanographic analysis of ascent (4SC-Up) and descent (4SC-Dn) in healthy children and adolescents. METHODS: We used a custom-made staircase measuring device to assess force, power and velocity during the ascent of 4 stairs in healthy subjects. Secondary outcome measures included mechanographic analyses such as the Chair-Rising-test and the myometric Grip Force-test. RESULTS: Data of 288 participants aged 4 to 16 years (144 males, 144 females) were analyzed. A simple algorithm integrating the minimal applied force was used to compensate for different movement strategies. Percentiles for average power, force and horizontal velocity were calculated. While results of the 4SC-Up test showed no age or gender dependency, we found 4SC-Dn results to be age dependent. Mean device measured times were significantly shorter than manually measured times (mean difference -0.19 s; p<0.001). CONCLUSIONS: Mechanographic analysis of the 4SC appears to be a promising tool for evaluation of muscle strength and function of the lower extremities as it enables physically exact measurements of a highly relevant activity of daily living.

Cathepsin D as biomarker in cerebrospinal fluid of nusinersen-treated patients with spinal muscular atrophy.

BACKGROUND AND PURPOSE: The therapeutic landscape of spinal muscular atrophy (SMA) has changed dramatically during the past 4 years, but treatment responses differ remarkably between individuals, and therapeutic decision-making remains challenging, underlining the persistent need for validated biomarkers. METHODS: 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 enzyme-linked immunosorbent assay. Furthermore, levels of peripheral neurofilament heavy and light chain were determined. RESULTS: Untargeted proteomic analysis of CSF samples of three 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, n = 12; type 2, n = 9; type 3, n = 6; presymptomatically treated, n = 4; age = 0-16 years) revealed a significant decline of cathepsin D levels in SMA patients aged ≥2 months at the start of treatment. Although evident in all older age categories, this decline was only significant in the group of patients who showed a positive motor response. Moreover, downregulation of cathepsin D was evident in muscle biopsies of SMA patients. CONCLUSIONS: 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 "nonresponders." We believe that our results indicate a suitability of cathepsin D levels as a possible biomarker in SMA also in older patients, in combination with analysis of peripheral neurofilament light chain in adolescents or alone in adult patients.

Development and Pilot Test of the Registry Evaluation and Quality Standards Tool: An Information Technology-Based Tool to Support and Review Registries.

OBJECTIVES: Health technology assessment (HTA) bodies are increasingly making use of real-world evidence and data. High-quality registries could be an asset for this; nevertheless, there is a lack of specified standards to assess the quality of data in the registry, or the registry itself. The European Network for Health Technology Assessment Joint Action 3 led the work to develop a tool for the evaluation of clinical registries: the "Registry Evaluation and Quality Standards Tool" (REQueST). METHODS: REQueST was developed in 4 steps: (1) A partnership between HTA bodies across Europe drafted the assessment criteria. (2) Multiple rounds of consultation across HTA bodies and the public domain developed an Excel version of REQueST. (3) This version was transformed into a web-based application. (4) An external pilot tested this REQueST tool with SMArtCARE and NeuroTransData registries. RESULTS: Haute Autorité de Santé, the National Institute for Health and Care Excellence, and the Croatian Institute of Public Health led the development of REQueST. Another 4 HTA bodies contributed regularly to development meetings, and all European Network for Health Technology Assessment partners were invited to contribute. Eight methodological, 12 essential, and 3 supplementary criteria were identified. Both pilot registries scored well, fulfilling the requirements for >70% of criteria, with none failed. Feedback by registry holders led to streamlining of the process and clarification of the criteria. CONCLUSIONS: The REQueST tool uses an iterative and collaborative methodology with registry holders. It has the potential to maximize the utility of registry data for decision making by regulatory and HTA bodies and provides a foundation for future research.

MLIP causes recessive myopathy with rhabdomyolysis, myalgia and baseline elevated serum creatine kinase.

Striated muscle needs to maintain cellular homeostasis in adaptation to increases in physiological and metabolic demands. Failure to do so can result in rhabdomyolysis. The identification of novel genetic conditions associated with rhabdomyolysis helps to shed light on hitherto unrecognized homeostatic mechanisms. Here we report seven individuals in six families from different ethnic backgrounds with biallelic variants in MLIP, which encodes the muscular lamin A/C-interacting protein, MLIP. Patients presented with a consistent phenotype characterized by mild muscle weakness, exercise-induced muscle pain, variable susceptibility to episodes of rhabdomyolysis, and persistent basal elevated serum creatine kinase levels. The biallelic truncating variants were predicted to result in disruption of the nuclear localizing signal of MLIP. Additionally, reduced overall RNA expression levels of the predominant MLIP isoform were observed in patients' skeletal muscle. Collectively, our data increase the understanding of the genetic landscape of rhabdomyolysis to now include MLIP as a novel disease gene in humans and solidifies MLIP's role in normal and diseased skeletal muscle homeostasis.

Parents' Perspectives on Diagnosis and Decision-Making regarding Ventilator Support in Children with SMA Type 1.

Spinal muscular atrophy (SMA) is a rare neuromuscular disorder with a broad clinical spectrum. The most severe phenotype-SMA type 1-is characterized by marked muscle weakness also affecting bulbar and respiratory function. Life expectancy of children with SMA type 1 is expected to be less than 2 years without ventilator support or disease-specific drug treatment. The aim of this study was to evaluate parents' perspectives on the process of decision-making regarding ventilator support in children with SMA type 1. Fourteen semi-structured interviews were performed with parents of children with SMA type 1 that decided either for or against ventilator support for their child. All children were diagnosed prior to the approval of SMA-specific drug treatment. Interviews were recorded and transcribed verbatim. Data analysis was performed using a qualitative content analysis approach according to Mayring. Parents experienced that they were not adequately informed about the disease and treatment options in first informed consent discussions. Especially regarding ventilator support, parents perceived that they were not offered ventilator support as an actual option for treatment. Regarding the decision of whether or not to offer ventilator support, parents reported that their attitude toward ventilator support and contact with other affected families or patient advocacy groups were more likely to influence the decision than the content of informed consent discussions with physicians. Our results underline the importance of an interdisciplinary team not only to provide parents with relevant information but also to consider the criteria of a patient-centered medicine.

Clinical and Genetic Aspects of Juvenile Onset Pompe Disease.

Little is known about clinical symptomatology and genetics of juvenile onset Pompe disease (JOPD). The aims of this study were to analyze how these children are diagnosed, what clinical problems they have, and how phenotype is related to genotype. To accomplish this, we analyzed retrospectively data of 34 patients diagnosed after their first and before completion of their 18th birthday. Median age at diagnosis was 3.9 (range 1.1-17) years. Eight patients (23.5%) developed initial symptoms in the first year, 12 (35%) between 1 and 7 years, and 6 (18%) thereafter. Eight (23.5%) had no clinical symptoms at the time of diagnosis. Indications for diagnostics were a positive family history in three (9%), hyperCKemia in eight (23.5%), motor developmental delay in three (9%), and muscle weakness and/or pain in 17 (50%). Rare clinical signs were failure to thrive, recurrent diarrhea, and suspected hepatopathy with glycogen storage. Thirty-two different mutations were identified. Twenty-seven patients (79.5%) carried the milder c.32-13T > G mutation, known to be associated with a broad range of phenotypes. Three out of eight patients manifesting within the first year of life showed generalized muscle weakness, hypertrophic cardiomyopathy, and had to be ventilated during the course of disease, thereby demonstrating clinical overlap with infantile onset Pompe disease.These findings demonstrate that the phenotype of JOPD is broad and that the differential is not only restricted to neuromuscular disorders. Genotypic analysis was useful to delineate subjects with early onset JOPD from those with IOPD, but overall genotype-phenotype correlation was poor.

Effect of Different Corticosteroid Dosing Regimens on Clinical Outcomes in Boys With Duchenne Muscular Dystrophy: A Randomized Clinical Trial.

Importance: Corticosteroids improve strength and function in boys with Duchenne muscular dystrophy. However, there is uncertainty regarding the optimum regimen and dosage. Objective: To compare efficacy and adverse effects of the 3 most frequently prescribed corticosteroid regimens in boys with Duchenne muscular dystrophy. Design, Setting, and Participants: Double-blind, parallel-group randomized clinical trial including 196 boys aged 4 to 7 years with Duchenne muscular dystrophy who had not previously been treated with corticosteroids; enrollment occurred between January 30, 2013, and September 17, 2016, at 32 clinic sites in 5 countries. The boys were assessed for 3 years (last participant visit on October 16, 2019). Interventions: Participants were randomized to daily prednisone (0.75 mg/kg) (n = 65), daily deflazacort (0.90 mg/kg) (n = 65), or intermittent prednisone (0.75 mg/kg for 10 days on and then 10 days off) (n = 66). Main Outcomes and Measures: The global primary outcome comprised 3 end points: rise from the floor velocity (in rise/seconds), forced vital capacity (in liters), and participant or parent global satisfaction with treatment measured by the Treatment Satisfaction Questionnaire for Medication (TSQM; score range, 0 to 100), each averaged across all study visits after baseline. Pairwise group comparisons used a Bonferroni-adjusted significance level of .017. Results: Among the 196 boys randomized (mean age, 5.8 years [SD, 1.0 years]), 164 (84%) completed the trial. Both daily prednisone and daily deflazacort were more effective than intermittent prednisone for the primary outcome (P < .001 for daily prednisone vs intermittent prednisone using a global test; P = .017 for daily deflazacort vs intermittent prednisone using a global test) and the daily regimens did not differ significantly (P = .38 for daily prednisone vs daily deflazacort using a global test). The between-group differences were principally attributable to rise from the floor velocity (0.06 rise/s [98.3% CI, 0.03 to 0.08 rise/s] for daily prednisone vs intermittent prednisone [P = .003]; 0.06 rise/s [98.3% CI, 0.03 to 0.09 rise/s] for daily deflazacort vs intermittent prednisone [P = .017]; and -0.004 rise/s [98.3% CI, -0.03 to 0.02 rise/s] for daily prednisone vs daily deflazacort [P = .75]). The pairwise comparisons for forced vital capacity and TSQM global satisfaction subscale score were not statistically significant. The most common adverse events were abnormal behavior (22 [34%] in the daily prednisone group, 25 [38%] in the daily deflazacort group, and 24 [36%] in the intermittent prednisone group), upper respiratory tract infection (24 [37%], 19 [29%], and 24 [36%], respectively), and vomiting (19 [29%], 17 [26%], and 15 [23%]). Conclusions and Relevance: Among patients with Duchenne muscular dystrophy, treatment with daily prednisone or daily deflazacort, compared with intermittent prednisone alternating 10 days on and 10 days off, resulted in significant improvement over 3 years in a composite outcome comprising measures of motor function, pulmonary function, and satisfaction with treatment; there was no significant difference between the 2 daily corticosteroid regimens. The findings support the use of a daily corticosteroid regimen over the intermittent prednisone regimen tested in this study as initial treatment for boys with Duchenne muscular dystrophy. Trial Registration: ClinicalTrials.gov Identifier: NCT01603407.

Deep dynamic modeling with just two time points: Can we still allow for individual trajectories?

Longitudinal biomedical data are often characterized by a sparse time grid and individual-specific development patterns. Specifically, in epidemiological cohort studies and clinical registries we are facing the question of what can be learned from the data in an early phase of the study, when only a baseline characterization and one follow-up measurement are available. Inspired by recent advances that allow to combine deep learning with dynamic modeling, we investigate whether such approaches can be useful for uncovering complex structure, in particular for an extreme small data setting with only two observations time points for each individual. Irregular spacing in time could then be used to gain more information on individual dynamics by leveraging similarity of individuals. We provide a brief overview of how variational autoencoders (VAEs), as a deep learning approach, can be linked to ordinary differential equations (ODEs) for dynamic modeling, and then specifically investigate the feasibility of such an approach that infers individual-specific latent trajectories by including regularity assumptions and individuals' similarity. We also provide a description of this deep learning approach as a filtering task to give a statistical perspective. Using simulated data, we show to what extent the approach can recover individual trajectories from ODE systems with two and four unknown parameters and infer groups of individuals with similar trajectories, and where it breaks down. The results show that such dynamic deep learning approaches can be useful even in extreme small data settings, but need to be carefully adapted.

Nusinersen versus Sham Control in Later-Onset Spinal Muscular Atrophy.

BACKGROUND: Nusinersen is an antisense oligonucleotide drug that modulates pre-messenger RNA splicing of the survival motor neuron 2 ( SMN2) gene. It has been developed for the treatment of spinal muscular atrophy (SMA). METHODS: We conducted a multicenter, double-blind, sham-controlled, phase 3 trial of nusinersen in 126 children with SMA who had symptom onset after 6 months of age. The children were randomly assigned, in a 2:1 ratio, to undergo intrathecal administration of nusinersen at a dose of 12 mg (nusinersen group) or a sham procedure (control group) on days 1, 29, 85, and 274. The primary end point was the least-squares mean change from baseline in the Hammersmith Functional Motor Scale-Expanded (HFMSE) score at 15 months of treatment; HFMSE scores range from 0 to 66, with higher scores indicating better motor function. Secondary end points included the percentage of children with a clinically meaningful increase from baseline in the HFMSE score (≥3 points), an outcome that indicates improvement in at least two motor skills. RESULTS: In the prespecified interim analysis, there was a least-squares mean increase from baseline to month 15 in the HFMSE score in the nusinersen group (by 4.0 points) and a least-squares mean decrease in the control group (by -1.9 points), with a significant between-group difference favoring nusinersen (least-squares mean difference in change, 5.9 points; 95% confidence interval, 3.7 to 8.1; P<0.001). This result prompted early termination of the trial. Results of the final analysis were consistent with results of the interim analysis. In the final analysis, 57% of the children in the nusinersen group as compared with 26% in the control group had an increase from baseline to month 15 in the HFMSE score of at least 3 points (P<0.001), and the overall incidence of adverse events was similar in the nusinersen group and the control group (93% and 100%, respectively). CONCLUSIONS: Among children with later-onset SMA, those who received nusinersen had significant and clinically meaningful improvement in motor function as compared with those in the control group. (Funded by Biogen and Ionis Pharmaceuticals; CHERISH ClinicalTrials.gov number, NCT02292537 .).

Post-dural puncture headache-a single-centre analysis in paediatric patients with and without SMA.

AIM: To gather epidemiologic data on post-dural puncture headache (PDPH) after diagnostic or therapeutic lumbar puncture (LP) in children and adolescents with SMA as well as in a cohort of paediatric patients without SMA. METHODS: We performed a retrospective, single-centre analysis via chart review and questionnaire. Patients were identified using the German procedure classification. Respective charts and SMArtCARE documentation forms (SMA patients) were reviewed concerning documentation of headaches fulfilling criteria of the IHS-classification for PDPH of 2004. Non-SMA patients received additional questionnaires. RESULTS: We identified a total of 218 LPs in 95 patients. Of those 141 were performed in 22 patients with known SMA (mean age SMA patients 9.2 years; non-SMA patients 11.4 years). Following chart review, IHS criteria for PDPH were fulfilled in 6.9% of all procedures (3.5% in SMA patients; 13.0% in non-SMA patients; p = 0.008). Data from questionnaires of non-SMA patients confirmed this result (position dependent headache within 72 h after intervention in 13.0% of procedures). CONCLUSION: The prevalence of PDPH after therapeutic LPs in our cohort of SMA patients was significantly lower than after LPs in the general paediatric cohort. Data of this retrospective analysis show a similar overall prevalence of PDPH in paediatric patients as reported in bigger adult cohorts.

Postnatal gene therapy for neuromuscular diseases - opportunities and limitations.

During the last decade a number of innovative treatments including gene therapies have been approved for the treatment of monogenic inherited diseases. For some neuromuscular diseases these approaches have dramatically changed the course of the disease. For others relevant challenges still remain and require disease specific approaches to overcome difficulties related to the immune response and the efficient transduction of target cells. This review provides an overview of the current development status of mutation specific treatments for neuromuscular diseases and concludes with on outlook on future developments and perspectives.

A novel mechanism causing imbalance of mitochondrial fusion and fission in human myopathies.

Mitochondrial dynamics play an important role in cellular homeostasis and a variety of human diseases are linked to its dysregulated function. Here, we describe a 15-year-old boy with a novel disease caused by altered mitochondrial dynamics. The patient was the second child of consanguineous Jewish parents. He developed progressive muscle weakness and exercise intolerance at 6 years of age. His muscle biopsy revealed mitochondrial myopathy with numerous ragged red and cytochrome c oxidase (COX) negative fibers and combined respiratory chain complex I and IV deficiency. MtDNA copy number was elevated and no deletions of the mtDNA were detected in muscle DNA. Whole exome sequencing identified a homozygous nonsense mutation (p.Q92*) in the MIEF2 gene encoding the mitochondrial dynamics protein of 49 kDa (MID49). Immunoblotting revealed increased levels of proteins promoting mitochondrial fusion (MFN2, OPA1) and decreased levels of the fission protein DRP1. Fibroblasts of the patient showed elongated mitochondria, and significantly higher frequency of fusion events, mtDNA abundance and aberrant mitochondrial cristae ultrastructure, compared with controls. Thus, our data suggest that mutations in MIEF2 result in imbalanced mitochondrial dynamics and a combined respiratory chain enzyme defect in skeletal muscle, leading to mitochondrial myopathy.

Nusinersen versus Sham Control in Infantile-Onset Spinal Muscular Atrophy.

BACKGROUND: Spinal muscular atrophy is an autosomal recessive neuromuscular disorder that is caused by an insufficient level of survival motor neuron (SMN) protein. Nusinersen is an antisense oligonucleotide drug that modifies pre-messenger RNA splicing of the SMN2 gene and thus promotes increased production of full-length SMN protein. METHODS: We conducted a randomized, double-blind, sham-controlled, phase 3 efficacy and safety trial of nusinersen in infants with spinal muscular atrophy. The primary end points were a motor-milestone response (defined according to results on the Hammersmith Infant Neurological Examination) and event-free survival (time to death or the use of permanent assisted ventilation). Secondary end points included overall survival and subgroup analyses of event-free survival according to disease duration at screening. Only the first primary end point was tested in a prespecified interim analysis. To control the overall type I error rate at 0.05, a hierarchical testing strategy was used for the second primary end point and the secondary end points in the final analysis. RESULTS: In the interim analysis, a significantly higher percentage of infants in the nusinersen group than in the control group had a motor-milestone response (21 of 51 infants [41%] vs. 0 of 27 [0%], P<0.001), and this result prompted early termination of the trial. In the final analysis, a significantly higher percentage of infants in the nusinersen group than in the control group had a motor-milestone response (37 of 73 infants [51%] vs. 0 of 37 [0%]), and the likelihood of event-free survival was higher in the nusinersen group than in the control group (hazard ratio for death or the use of permanent assisted ventilation, 0.53; P=0.005). The likelihood of overall survival was higher in the nusinersen group than in the control group (hazard ratio for death, 0.37; P=0.004), and infants with a shorter disease duration at screening were more likely than those with a longer disease duration to benefit from nusinersen. The incidence and severity of adverse events were similar in the two groups. CONCLUSIONS: Among infants with spinal muscular atrophy, those who received nusinersen were more likely to be alive and have improvements in motor function than those in the control group. Early treatment may be necessary to maximize the benefit of the drug. (Funded by Biogen and Ionis Pharmaceuticals; ENDEAR ClinicalTrials.gov number, NCT02193074 .).

Clinical presentation and proteomic signature of patients with TANGO2 mutations.

Transport And Golgi Organization protein 2 (TANGO2) deficiency has recently been identified as a rare metabolic disorder with a distinct clinical and biochemical phenotype of recurrent metabolic crises, hypoglycemia, lactic acidosis, rhabdomyolysis, arrhythmias, and encephalopathy with cognitive decline. We report nine subjects from seven independent families, and we studied muscle histology, respiratory chain enzyme activities in skeletal muscle and proteomic signature of fibroblasts. All nine subjects carried autosomal recessive TANGO2 mutations. Two carried the reported deletion of exons 3 to 9, one homozygous, one heterozygous with a 22q11.21 microdeletion inherited in trans. The other subjects carried three novel homozygous (c.262C>T/p.Arg88*; c.220A>C/p.Thr74Pro; c.380+1G>A), and two further novel heterozygous (c.6_9del/p.Phe6del); c.11-13delTCT/p.Phe5del mutations. Immunoblot analysis detected a significant decrease of TANGO2 protein. Muscle histology showed mild variation of fiber diameter, no ragged-red/cytochrome c oxidase-negative fibers and a defect of multiple respiratory chain enzymes and coenzyme Q10 (CoQ10 ) in two cases, suggesting a possible secondary defect of oxidative phosphorylation. Proteomic analysis in fibroblasts revealed significant changes in components of the mitochondrial fatty acid oxidation, plasma membrane, endoplasmic reticulum-Golgi network and secretory pathways. Clinical presentation of TANGO2 mutations is homogeneous and clinically recognizable. The hemizygous mutations in two patients suggest that some mutations leading to allele loss are difficult to detect. A combined defect of the respiratory chain enzymes and CoQ10 with altered levels of several membrane proteins provides molecular insights into the underlying pathophysiology and may guide rational new therapeutic interventions.

Life expectancy at birth in Duchenne muscular dystrophy: a systematic review and meta-analysis.

Several studies indicate that prognosis for survival in Duchenne muscular dystrophy (DMD) has improved in recent decades. However, published evidence is inconclusive and some estimates may be obsolete due to improvements in standards of care, in particular the routine use of mechanical ventilatory support in advanced stages of the disease. In this systematic review and meta-analysis (PROSPERO identifier: CRD42019121800), we searched MEDLINE (through PubMed), CINAHL, Embase, PsycINFO, and Web of Science for studies published from inception up until December 31, 2018, reporting results of life expectancy in DMD. We pooled median survival estimates from individual studies using the median of medians, and weighted median of medians, methods. Risk of bias was established with the Newcastle-Ottawa Scale. Results were stratified by ventilatory support and risk of bias. We identified 15 publications involving 2662 patients from 12 countries from all inhabited continents except Africa. Median life expectancy without ventilatory support ranged between 14.4 and 27.0 years (pooled median: 19.0 years, 95% CI 18.0-20.9; weighted pooled median: 19.4 years, 18.2-20.1). Median life expectancy with ventilatory support, introduced in most settings in the 1990s, ranged between 21.0 and 39.6 years (pooled median: 29.9 years, 26.5-30.8; weighted pooled median: 31.8 years, 29.3-36.2). Risk of bias had little impact on pooled results. In conclusion, median life expectancy at birth in DMD seems to have improved considerably during the last decades. With current standards of care, many patients with DMD can now expect to live into their fourth decade of life.