Molecular bases of spinal muscular atrophy: the survival motor neuron gene

L'atròfia muscular espinal (AME) és una malaltia neuromuscular autosòmica recessiva caracteritzada per Ia degeneració i Ia pèrdua de Ies motoneurones de Ia banya anterior de Ia medul·la espinal. Les manifestacions clíniques més característiques són una debilitat proximal simètrica i una atròfia muscular progressiva. La identificació del gen SMN1 com a gen determinant de I'AME obre noves alternatives per a I'estudi de Ia malaltia. En Ia majoria dels pacients es detecta I'absència del gen SMN1 (ja sigui per deleció o per conversió), però també se n'han identificat mutacions puntuals en un petit percentatge. L'absència del gen SMN1 s'associa a un ampli espectre de manifestacions clíniques, que van des de formes congènites de Ia malaltia fins a casos asimptomàtics. Diferents factors modificadors, com el nombre de còpies del gen SMN2 – el gen homòleg present tant en controls com en malalts – poden modificar el fenotip i a Ia vegada ser útils per investigar un tractament eficaç. Tot i que el gen SMN s'expressa en diferents poblacions neuronals, només Ies motoneurones són Ies responsables de Ies manifestacions de Ia malaltia. La proteïna SMN forma part d'un complex amb altres proteïnes que participen en Ia reacció d'empalmament i aquesta funció, essencial per a totes Ies cèl·lules, sembla ser crítica per a Ies neurones motores. Cal aprofundir en I'estudi dels mecanismes que condueixen a I'atròfia muscular espinal.Spinal muscular atrophy (SMA) is an autosomal recessive neuromuscular disease characterized by degeneration and loss of motor neurons of the anterior horn of the spinal cord. The clinical manifestations include proximal symmetric weakness and progressive muscle atrophy. The identification of the SMN1 gene as determinant of SMA has opened alternative ways of studying the disease. Absence of SMN1 (either by deletion or conversion) was detected in the majority of patients and subtle mutations were described in a minority. SMN1 absence was associated with a wide spectrum of manifestations, from congenital disease to asymptomatic cases. Modifier factors, such as the number of copies of SMN2, its homologous copy present in all patients, could influence the phenotype and help to find a treatment for the disease. The SMN gene is expressed in various neuronal populations, although only motor neurons are responsible for the manifestations of the disease. The SMN protein is part of a complex with various proteins involved in the splicing reaction. This apparently essential function of all cells is critical for motor neurons, and warrants further research to elucidate the mechanisms of disease

Atrofia muscular espinal: Contribuciones para el conocimiento, prevención y tratamiento de la enfermedad y para la organización de familias

Este resumen refiere el trabajo realizado durante casi dos décadas dedicadas a la atención, investigación y experiencia en la atrofia muscular espinal (AME), una enfermedad de las neuronas motoras de la médula espinal. Casi todo el mundo conoce la poliomielitis, producida por el ataque de un virus a las neuronas motoras de la médula espinal. Los avances científicos han erradicado prácticamente la poliomielitis en nuestros niños y hoy en día constituye una enfermedad del pasado gracias a la vacunación. Si tuviéramos que describir la AME en pocas palabras la definiríamos como una poliomielitis mucho más agresiva que afecta a todo el cuerpo (a diferencia de la polio que era localizada) y a causa de un gen que está ausente o no funciona como corresponde.A diferencia de la polio, esta enfermedad genética está lejos de ser erradicada. Con una incidencia aproximada de 1/6000 a 1/10000 nacimientos, y una frecuencia de portadores de 1/40-1/60, la AME es considerada una de las principales causas hereditarias de mortalidad infantil. La AME presenta un patrón de herencia autosómico recesivo, es decir se necesitan dos copias del gen alterado para que se manifieste. Ese gen es el Survival Motor Neuron 1 (SMN1) localizado en el brazo largo del cromosoma 5 (5q13). La AME es siempre grave e invalidante y se clasifica en tres grupos (tipo I o aguda, tipo II o intermedio y tipo III crónica) de acuerdo con las manifestaciones clínicas, la edad de aparición de las mismas y su evolución

RegistrAME: the Spanish self-reported patient registry of spinal muscular atrophy

Patient registry; Self-reported registry; Spinal muscular atrophyRegistre de pacients; Registre autoinformat; Atròfia muscular espinalRegistro de pacientes; Registro autoinformado; Atrofia muscular espinalBackground Spinal Muscular Atrophy (SMA) is a rare neuromuscular disorder characterized by progressive degeneration of motor neurons and muscle weakness resulting in premature death or severe motor disability. Over the last decade, SMA has dramatically changed thanks to new advances in care and the emergence of disease-specific treatments. RegistrAME is a self-reported specific disease registry with an accurate curation system. It has collected data on SMA patients in Spain since 2015, gathering demographic, clinical, and patient-reported outcome data, all of which are patient-relevant. RegistrAME is part of the TREAT NMD network. This study aims to describe the advantages and disadvantages of a self–reported SMA registry, as well as the different variables of interest in the health status of RegistrAME patients. Results In total, 295 living patients with a confirmed diagnosis of SMA-5q were included (aged 1 to 77 years; mean 20.28). Half of the patients (50.2%) were ≥ 16 years old; 22.03% were type 1, 48.47% were type 2, 28.82% were type 3, and 0.7% were type 4. All functional statuses (non-sitter, sitter, and walkers) could be observed in each SMA type. Adult patients harbored the least aggressive SMA types, however, they presented the greatest level of disability. Patients with SMA type 1 had scoliosis surgery about five years earlier than patients with SMA type 2. None of the type 1 patients who achieved ambulation were wheelchair-free outdoors. This was also evident in 62.5% of type 2 walker patients and 44% of type 3 walker patients. Of the SMA type 1 patients, 40% had a gastrostomy (of which 84% had two SMN2 copies). One in five children with SMA type 1 (one to seven years of age) were ventilation-free. Conclusions The information provided by RegistrAME in a “real-world” setting allows better management of family expectations, an adequate approach to the disease and patients’ needs, as well as a better understanding of the impact of the disease. It also helps monitor the evolution of care, which will result in the need for updated guidelines.Funding for this project was provided by FundAME

Validation of nasospheroids to assay CFTR functionality and modulator responses in cystic fibrosis

Fibrosi quística; Marcadors predictius; Models d'aparell respiratoriFibrosis quística; Marcadores predictivos; Modelos del sistema respiratorioCystic fibrosis; Predictive markers; Respiratory system modelsThe availability of a simple, robust and non-invasive in vitro airway model would be useful to study the functionality of the cystic fibrosis transmembrane regulator (CFTR) protein and to personalize modulator therapy for cystic fibrosis (CF) patients. Our aim was to validate a CFTR functional study using nasospheroids, a patient-derived nasal cell 3D-culture. We performed live-cell experiments in nasospheroids obtained from wild-type individuals and CF patients with different genotypes and phenotypes. We extended the existing method and expanded the analysis to upgrade measurements of CFTR activity using forskolin-induced shrinking. We also tested modulator drugs in CF samples. Immobilizing suspended-nasospheroids provided a high number of samples for live-cell imaging. The diversity observed in basal sizes of nasospheroids did not affect the functional analysis of CFTR. Statistical analysis with our method was simple, making this protocol easy to reproduce. Moreover, we implemented the measurement of inner fluid reservoir areas to further differentiate CFTR functionality. In summary, this rapid methodology is helpful to analyse response to modulators in CF samples to allow individualized treatment for CF patients.This work was supported by a grant from Fundación Mutua Madrileña (Rare disorders, MM/XIV/RECERCA/2017/TIZZANO) to E.F.T. and Fundació Arcadi to S.G. and supporting M.C. and P.B.; M.C. was partially supported by Fundació Daniel Bravo Andreu

The Importance of Digging into the Genetics of SMN Genes in the Therapeutic Scenario of Spinal Muscular Atrophy

Estructura híbrida; Atrofia muscular espinal; Neurona motora de supervivencia 1Hybrid structure; Spinal muscular atrophy; Survival motor neuron 1Estructura híbrida; Atròfia muscular espinal; Neurona motora de supervivència 1After 26 years of discovery of the determinant survival motor neuron 1 and the modifier survival motor neuron 2 genes (SMN1 and SMN2, respectively), three SMN-dependent specific therapies are already approved by FDA and EMA and, as a consequence, worldwide SMA patients are currently under clinical investigation and treatment. Bi-allelic pathogenic variants (mostly deletions) in SMN1 should be detected in SMA patients to confirm the disease. Determination of SMN2 copy number has been historically employed to correlate with the phenotype, predict disease evolution, stratify patients for clinical trials and to define those eligible for treatment. In view that discordant genotype-phenotype correlations are present in SMA, besides technical issues with detection of SMN2 copy number, we have hypothesized that copy number determination is only the tip of the iceberg and that more deepen studies of variants, sequencing and structures of the SMN2 genes are necessary for a better understanding of the disease as well as to investigate possible influences in treatment responses. Here, we highlight the importance of a comprehensive approach of SMN1 and SMN2 genetics with the perspective to apply for better prediction of SMA in positive neonatal screening cases and early diagnosis to start treatments.This work was partially supported by Grants from Biogen and Roche (to E.F.T. supporting M.C.-R. and L.B.-P.), and from Spanish Instituto de Salud Carlos III, Fondo de Investigaciones Sanitarias and cofunded with ERDF funds (Grant No. FIS PI18/000687) (to E.F.T.)

Clinical Phenotype of Pediatric and Adult Patients With Spinal Muscular Atrophy With Four SMN2 Copies: Are They Really All Stable?

Clinical phenotype; Pediatric patients; Spinal muscular atrophyFenotipo clínico; Pacientes pediátricos; Atrofia muscular espinalFenotip clínic; Pacients pediàtrics; Atròfia muscular espinalObjective The aim of this study was to provide an overview of the clinical phenotypes associated with 4 SMN2 copies. Methods Clinical phenotypes were analyzed in all the patients with 4 SMN2 copies as part of a nationwide effort including all the Italian pediatric and adult reference centers for spinal muscular atrophy (SMA). Results The cohort includes 169 patients (102 men and 67 women) with confirmed 4 SMN2 copies (mean age at last follow-up = 36.9 ± 19 years). Six of the 169 patients were presymptomatic, 8 were classified as type II, 145 as type III (38 type IIIA and 107 type IIIB), and 8 as type IV. The remaining 2 patients were asymptomatic adults identified because of a familial case. The cross-sectional functional data showed a reduction of scores with increasing age. Over 35% of the type III and 25% of the type IV lost ambulation (mean age = 26.8 years ± 16.3 SD). The risk of loss of ambulation was significantly associated with SMA type (p < 0.0001), with patients with IIIB and IV less likely to lose ambulation compared to type IIIA. There was an overall gender effect with a smaller number of women and a lower risk for women to lose ambulation. This was significant in the adult (p = 0.009) but not in the pediatric cohort (p = 0.43). Interpretation Our results expand the existing literature on natural history of 4 SMN2 copies confirming the variability of phenotypes in untreated patients, ranging from type II to type IV and an overall reduction of functional scores with increasing age.S.C.P., G.P.C., and E.M. are members of the European Reference Network for Rare Neuromuscular Diseases (ERN EURO-NMD). G.Coratti is funded by grant from the Italian Ministry of Health (GR-2021-12374579). E.M. is funded by grant from the Italian Ministry of Health (RF-2019-12370334). M.C.P. is funded by grant from the Italian Ministry of Health (GR-2018-12365706). E.P. is funded by grant from the Italian Telethon (GUP21008). The ITASMAC registry is partly funded by Biogen and Roche

Recommendations for Interpreting and Reporting Silent Carrier and Disease-Modifying Variants in SMA Testing Workflows

Carrier screening; Diagnosis; Spinal muscular atrophyCribado de portadores; Diagnóstico; Atrofia muscular espinalCribratge de portadors; Diagnòstic; Atròfia muscular espinalGenetic testing for SMA diagnosis, newborn screening, and carrier screening has become a significant public health interest worldwide, driven largely by the development of novel and effective molecular therapies for the treatment of spinal muscular atrophy (SMA) and the corresponding updates to testing guidelines. Concurrently, understanding of the underlying genetics of SMA and their correlation with a broad range of phenotypes and risk factors has also advanced, particularly with respect to variants that modulate disease severity or impact residual carrier risks. While testing guidelines are beginning to emphasize the importance of these variants, there are no clear guidelines on how to utilize them in a real-world setting. Given the need for clarity in practice, this review summarizes several clinically relevant variants in the SMN1 and SMN2 genes, including how they inform outcomes for spinal muscular atrophy carrier risk and disease prognosis.This work was partially supported by Grants from Biogen ESP-SMG-17-11256 (to E.F.T. supporting L.B.-P.), Roche and Spanish Instituto de Salud Carlos III, Fondo de Investigaciones Sanitarias and co-funded with ERDF funds (Grant No. FIS PI18/000687) (to E.F.T.)

Real-World Outcomes in Patients with Spinal Muscular Atrophy Treated with Onasemnogene Abeparvovec Monotherapy: Findings from the RESTORE Registry

Motor neuron disease; Newborn screening; Spinal muscular atrophyEnfermedad de la neurona motora; Cribado neonatal; Atrofia muscular espinalMalaltia de la neurona motora; Cribratge neonatal; Atròfia muscular espinalBackground: Long-term, real-world effectiveness and safety data of disease-modifying treatments for spinal muscular atrophy (SMA) are important for assessing outcomes and providing information for a larger number and broader range of SMA patients than included in clinical trials. Objective: We sought to describe patients with SMA treated with onasemnogene abeparvovec monotherapy in the real-world setting. Methods: RESTORE is a prospective, multicenter, multinational, observational registry that captures data from a variety of sources. Results: Recruitment started in September 2018. As of May 23, 2022, data were available for 168 patients treated with onasemnogene abeparvovec monotherapy. Median (IQR) age at initial SMA diagnosis was 1 (0–6) month and at onasemnogene abeparvovec infusion was 3 (1–10) months. Eighty patients (47.6%) had two and 70 (41.7%) had three copies of SMN2, and 98 (58.3%) were identified by newborn screening. Infants identified by newborn screening had a lower age at final assessment (mean age 11.5 months) and greater mean final (SD) CHOP INTEND score (57.0 [10.0] points) compared with clinically diagnosed patients (23.1 months; 52.1 [8.0] points). All patients maintained/achieved motor milestones. 48.5% (n = 81/167) experienced at least one treatment-emergent adverse event (AE), and 31/167 patients (18.6%) experienced at least one serious AE, of which 8/31 were considered treatment-related. Conclusion: These real-world outcomes support findings from the interventional trial program and demonstrate effectiveness of onasemnogene abeparvovec over a large patient population, which was consistent with initial clinical data and published 5-year follow-up data. Observed AEs were consistent with the established safety profile of onasemnogene abeparvovec.All financial and material support for this research was provided by Novartis Gene Therapies, Inc

Combination disease-modifying treatment in spinal muscular atrophy: A proposed classification

Spinal muscular atrophyAtròfia muscular espinalAtrofia muscular espinalWe sought to devise a rational, systematic approach for defining/grouping survival motor neuron-targeted disease-modifying treatment (DMT) scenarios. The proposed classification is primarily based on a two-part differentiation: initial DMT, and persistence/discontinuation of subsequent DMT(s). Treatment categories were identified: monotherapy add-on, transient add-on, combination with onasemnogene abeparvovec, bridging to onasemnogene abeparvovec, and switching to onasemnogene abeparvovec. We validated this approach by applying the classification to the 443 patients currently in the RESTORE registry and explored the demographics of these different groups of patients. This work forms the basis to explore the safety and efficacy profile of the different combinations of DMT in SMA