Molecular mechanisms and animal models of spinal muscular atrophy

AbstractSpinal muscular atrophy (SMA), the leading genetic cause of infant mortality, is characterized by the degeneration of spinal motor neurons and muscle atrophy. Although the genetic cause of SMA has been mapped to the Survival Motor Neuron1 (SMN1) gene, mechanisms underlying selective motor neuron degeneration in SMA remain largely unknown. Here we review the latest developments and our current understanding of the molecular mechanisms underlying SMA pathogenesis, focusing on the animal model systems that have been developed, as well as new diagnostic and treatment strategies that have been identified using these model systems. This article is part of a special issue entitled: Neuromuscular Diseases: Pathology and Molecular Pathogenesis

NaV channel variants in patients with painful and nonpainful peripheral neuropathy

Objective: To examine the incidence of nonsynonymous missense variants in SCN9A (NaV1.7), SCN10A (NaV1.8), and SCN11A (NaV1.9) in patients with painful and nonpainful peripheral neuropathy. Methods: Next-generation sequencing was performed on 457 patient DNA samples provided by the Peripheral Neuropathy Research Registry (PNRR). The patient diagnosis was as follows: 278 idiopathic peripheral neuropathy (67% painful and 33% nonpainful) and 179 diabetic distal polyneuropathy (77% painful and 23% nonpainful). Results: We identified 36 (SCN9A), 31 (SCN10A), and 15 (SCN11A) nonsynonymous missense variants, with 47.7% of patients carrying a low-frequency (minor allele frequency <5%) missense variant in at least 1 gene. The incidence of previously reported gain-of-function missense variants was low (≤3%), and these were detected in patients with and without pain. There were no significant differences in missense variant allele frequencies of any gene, or SCN9A haplotype frequencies, between PNRR patients with painful or nonpainful peripheral neuropathy. PNRR patient SCN9A and SCN11A missense variant allele frequencies were not significantly different from the Exome Variant Server, European American (EVS-EA) reference population. For SCN10A, there was a significant increase in the alternate allele frequency of the common variant p.V1073A and low-frequency variant pS509P in PNRR patients compared with EVS-EA and the 1000 Genomes European reference populations. Conclusions: These results suggest that identification of a genetically defined subpopulation for testing of NaV1.7 inhibitors in patients with peripheral neuropathy is unlikely and that additional factors, beyond expression of previously reported disease “mutations,” are more important for the development of painful neuropathy than previously discussed

NaV channel variants in patients with painful and nonpainful peripheral neuropathy

Objective: To examine the incidence of nonsynonymous missense variants in SCN9A (NaV1.7), SCN10A (NaV1.8), and SCN11A (NaV1.9) in patients with painful and nonpainful peripheral neuropathy. Methods: Next-generation sequencing was performed on 457 patient DNA samples provided by the Peripheral Neuropathy Research Registry (PNRR). The patient diagnosis was as follows: 278 idiopathic peripheral neuropathy (67% painful and 33% nonpainful) and 179 diabetic distal polyneuropathy (77% painful and 23% nonpainful). Results: We identified 36 (SCN9A), 31 (SCN10A), and 15 (SCN11A) nonsynonymous missense variants, with 47.7% of patients carrying a low-frequency (minor allele frequency <5%) missense variant in at least 1 gene. The incidence of previously reported gain-of-function missense variants was low (≤3%), and these were detected in patients with and without pain. There were no significant differences in missense variant allele frequencies of any gene, or SCN9A haplotype frequencies, between PNRR patients with painful or nonpainful peripheral neuropathy. PNRR patient SCN9A and SCN11A missense variant allele frequencies were not significantly different from the Exome Variant Server, European American (EVS-EA) reference population. For SCN10A, there was a significant increase in the alternate allele frequency of the common variant p.V1073A and low-frequency variant pS509P in PNRR patients compared with EVS-EA and the 1000 Genomes European reference populations. Conclusions: These results suggest that identification of a genetically defined subpopulation for testing of NaV1.7 inhibitors in patients with peripheral neuropathy is unlikely and that additional factors, beyond expression of previously reported disease “mutations,” are more important for the development of painful neuropathy than previously discussed

Quality of life outcomes in APOLLO, the phase 3 trial of the RNAi therapeutic patisiran in patients with hereditary transthyretin-mediated amyloidosis

Introduction: Hereditary transthyretin-mediated (hATTR) amyloidosis is a rare, fatal, multisystem disease leading to deteriorating quality of life (QOL). The impact of patisiran on QOL in patients with hATTR amyloidosis with polyneuropathy from the phase 3 APOLLO study (NCT01960348) is evaluated.Methods: Patients received either patisiran 0.3 mg/kg (n = 148) or placebo (n = 77) intravenously once every three weeks for 18 months. Multiple measures were used to assess varying aspects of QOL.Results: At 18 months, compared with placebo, patisiran improved Norfolk Quality of Life-Diabetic Neuropathy (Norfolk QOL-DN) score; (least squares [LS] mean difference: -21.1; p = 1.10 × 10-10; improved across all domains), EuroQoL 5-dimensions 5-levels (LS mean difference: 0.2; p = 1.4 × 10-12), EuroQoL-visual analog scale (LS mean difference: 9.5; p=.0004), Rasch-built Overall Disability Scale (LS mean difference: 9.0; p = 4.07 × 10-16) and Composite Autonomic Symptom Score-31(COMPASS-31; LS mean difference: -7.5; p=.0008). Placebo-treated patients experienced rapid QOL deterioration; treatment effects for patisiran were observed as early as 9 months. At 18 months, patisiran improved Norfolk QOL-DN total score and three individual domains as well as COMPASS-31 total scores relative to baseline. Consistent benefits were also observed in the cardiac subpopulation.Conclusion: The benefits of patisiran across all QOL measures and the rapid deterioration observed with placebo, highlight the urgency in early treatment for patients with hATTR amyloidosis with polyneuropathy.This study was funded by Alnylam Pharmaceuticalsinfo:eu-repo/semantics/publishedVersio

Long-term safety and efficacy of patisiran for hereditary transthyretin-mediated amyloidosis with polyneuropathy: 12-month results of an open-label extension study

Background Hereditary transthyretin-mediated amyloidosis is a rare, inherited, progressive disease caused by mutations in the transthyretin (TTR) gene. We assessed the safety and efficacy of long-term treatment with patisiran, an RNA interference therapeutic that inhibits TTR production, in patients with hereditary transthyretin-mediated amyloidosis with polyneuropathy

The natural history of ALS: Baseline characteristics from a multicenter clinical cohort

Amyotrophic lateral sclerosis (ALS) is a rare disease with urgent need for improved treatment. Despite the acceleration of research in recent years, there is a need to understand the full natural history of the disease. As only 40% of people living with ALS are eligible for typical clinical trials, clinical trial datasets may not generalize to the full ALS population. While biomarker and cohort studies have more generous inclusion criteria, these too may not represent the full range of phenotypes, particularly if the burden for participation is high. To permit a complete understanding of the heterogeneity of ALS, comprehensive data on the full range of people with ALS is needed. The ALS Natural History Consortium (ALS NHC) consists of nine ALS clinics and was created to build a comprehensive dataset reflective of the ALS population. At each clinic, most patients are asked to participate and about 95% do. After obtaining consent, a minimum dataset is abstracted from each participant’s electronic health record. Participant burden is therefore minimal. Data on 1925 ALS patients were submitted as of 9 December 2022. ALS NHC participants were more heterogeneous relative to anonymized clinical trial data from the Pooled Resource Open-Access ALS Clinical Trials (PRO-ACT) database. The ALS NHC includes ALS patients of older age of onset and a broader distribution of El Escorial categories, than the PRO-ACT database. ALS NHC participants had a higher diversity of diagnostic and demographic data compared to ALS clinical trial participants.Key MessagesWhat is already known on this topic: Current knowledge of the natural history of ALS derives largely from regional and national registries that have broad representation of the population of people living with ALS but do not always collect covariates and clinical outcomes. Clinical studies with rich datasets of participant characteristics and validated clinical outcomes have stricter inclusion and exclusion criteria that may not be generalizable to the full ALS population.What this study adds: To bridge this gap, we collected baseline characteristics for a sample of the population of people living with ALS seen at a consortium of ALS clinics that collect extensive, pre-specified participant-level data, including validated outcome measures.How this study might affect research, practice, or policy: A clinic-based longitudinal dataset can improve our understanding of the natural history of ALS and can be used to inform the design and analysis of clinical trials and health economics studies, to help the prediction of clinical course, to find matched controls for open label extension trials and expanded access protocols, and to document real-world evidence of the impact of novel treatments and changes in care practice. What is already known on this topic: Current knowledge of the natural history of ALS derives largely from regional and national registries that have broad representation of the population of people living with ALS but do not always collect covariates and clinical outcomes. Clinical studies with rich datasets of participant characteristics and validated clinical outcomes have stricter inclusion and exclusion criteria that may not be generalizable to the full ALS population. What this study adds: To bridge this gap, we collected baseline characteristics for a sample of the population of people living with ALS seen at a consortium of ALS clinics that collect extensive, pre-specified participant-level data, including validated outcome measures. How this study might affect research, practice, or policy: A clinic-based longitudinal dataset can improve our understanding of the natural history of ALS and can be used to inform the design and analysis of clinical trials and health economics studies, to help the prediction of clinical course, to find matched controls for open label extension trials and expanded access protocols, and to document real-world evidence of the impact of novel treatments and changes in care practice.</p