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SDS22 forms an inactive complex with nascent protein phosphatase PP1 and Inhibitor-3. SDS22:PP1:Inhibitor-3 is a substrate for the ATPase p97/VCP, which liberates PP1 for binding to canonical regulatory subunits. The exact role of SDS22 in PP1-holoenzyme assembly remains elusive. Here, we show that SDS22 stabilizes nascent PP1. In the absence of SDS22, PP1 is gradually lost, resulting in substrate hyperphosphorylation and a proliferation arrest. Similarly, we identify a female individual with a severe neurodevelopmental disorder bearing an unstable SDS22 mutant, associated with decreased PP1 levels. We furthermore find that SDS22 directly binds to Inhibitor-3 and that this is essential for the stable assembly of SDS22:PP1: Inhibitor-3, the recruitment of p97/VCP, and the extraction of SDS22 during holoenzyme assembly. SDS22 with a disabled Inhibitor-3 binding site co-transfers with PP1 to canonical regulatory subunits, thereby forming non-functional holoenzymes. Our data show that SDS22, through simultaneous interaction with PP1 and Inhibitor-3, integrates the major steps of PP1 holoenzyme assembly.
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Proteína Fosfatasa 1 , Femenino , Humanos , Células HEK293 , Holoenzimas/metabolismo , Fosforilación , Unión Proteica , Proteína Fosfatasa 1/metabolismo , Proteína Fosfatasa 1/genética , Proteína que Contiene Valosina/metabolismo , Proteína que Contiene Valosina/genéticaRESUMEN
BACKGROUND: Congenital myasthenic syndromes (CMS) are a group of inherited neuromuscular junction (NMJ) disorders arising from gene variants encoding diverse NMJ proteins. Recently, the VAMP1 gene, responsible for encoding the vesicle-associated membrane protein 1 (VAMP1), has been associated with CMS. METHODS: This study presents a characterization of five new individuals with VAMP1-related CMS, providing insights into the phenotype. RESULTS: The individuals with VAMP1-related CMS exhibited early disease onset, presenting symptoms prenatally or during the neonatal period, alongside severe respiratory involvement and feeding difficulties. Generalized weakness at birth was a common feature, and none of the individuals achieved independent walking ability. Notably, all cases exhibited scoliosis. The clinical course remained stable, without typical exacerbations seen in other CMS types. The response to anticholinesterase inhibitors and salbutamol was only partial, but the addition of 3,4-diaminopyridine (3,4-DAP) led to significant and substantial improvements, suggesting therapeutic benefits of 3,4-DAP for managing VAMP1-related CMS symptoms. Noteworthy is the identification of the VAMP1 (NM_014231.5): c.340delA; p.Ile114SerfsTer72 as a founder variant in the Iberian Peninsula and Latin America. CONCLUSIONS: This study contributes valuable insights into VAMP1-related CMS, emphasizing their early onset, arthrogryposis, facial and generalized weakness, respiratory involvement, and feeding difficulties. Furthermore, the potential efficacy of 3,4-DAP as a useful therapeutic option warrants further exploration. The findings have implications for clinical management and genetic counseling in affected individuals. Additional research is necessary to elucidate the long-term outcomes of VAMP1-related CMS.
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Amifampridina , Síndromes Miasténicos Congénitos , Fenotipo , Proteína 1 de Membrana Asociada a Vesículas , Humanos , Síndromes Miasténicos Congénitos/tratamiento farmacológico , Síndromes Miasténicos Congénitos/genética , Síndromes Miasténicos Congénitos/fisiopatología , Femenino , Masculino , Amifampridina/farmacología , Proteína 1 de Membrana Asociada a Vesículas/genética , Niño , Adolescente , 4-Aminopiridina/análogos & derivados , 4-Aminopiridina/farmacología , 4-Aminopiridina/uso terapéutico , Preescolar , Bloqueadores de los Canales de Potasio/farmacología , Bloqueadores de los Canales de Potasio/uso terapéutico , LactanteRESUMEN
OBJECTIVE: Duchenne and Becker muscular dystrophies (DMD and BMD) are dystrophinopathies caused by variants in DMD gene, resulting in reduced or absent dystrophin. These conditions, characterized by muscle weakness, also manifest central nervous system (CNS) comorbidities due to dystrophin expression in the CNS. Prior studies have indicated a higher prevalence of epilepsy in individuals with dystrophinopathy compared to the general population. Our research aimed to investigate epilepsy prevalence in dystrophinopathies and characterize associated electroencephalograms (EEGs) and seizures. METHODS: We reviewed 416 individuals with dystrophinopathy, followed up at three centers between 2010 and 2023, to investigate the lifetime epilepsy prevalence and characterize EEGs and seizures in those individuals diagnosed with epilepsy. Associations between epilepsy and type of dystrophinopathy, genotype, and cognitive involvement were studied. RESULTS: Our study revealed a higher epilepsy prevalence than the general population (1.4%; 95% confidence interval: 0.7-3.2%), but notably lower than previously reported in smaller dystrophinopathy cohorts. No significant differences were found in epilepsy prevalence between DMD and BMD or based on underlying genotypes. Cognitive impairment was not found to be linked to higher epilepsy rates. The most prevalent epilepsy types in dystrophinopathies resembled those observed in the broader pediatric population, with most individuals effectively controlled through monotherapy. INTERPRETATION: The actual epilepsy prevalence in dystrophinopathies may be markedly lower than previously estimated, possibly half or even less. Our study provides valuable insights into the epilepsy landscape in individuals with dystrophinopathy, impacting medical care, especially for those with concurrent epilepsy.
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Epilepsia , Distrofia Muscular de Duchenne , Humanos , Distrofia Muscular de Duchenne/epidemiología , Distrofia Muscular de Duchenne/complicaciones , Distrofia Muscular de Duchenne/genética , Masculino , Epilepsia/epidemiología , Epilepsia/etiología , Adolescente , Femenino , Adulto , Adulto Joven , Niño , Prevalencia , Persona de Mediana Edad , Preescolar , Electroencefalografía , Comorbilidad , Distrofina/genéticaRESUMEN
Congenital myopathies (CMs) are rare genetic disorders for which the diagnostic yield does not typically exceed 60% . We performed deep phenotyping, histopathological studies, clinical exome and trio genome sequencing and a phenotype-driven analysis of the genomic data, that led to the molecular diagnosis in a child with CM. We identified a heterozygous variant in RYR1 in the affected child, inherited from her asymptomatic mother. Given the alignment of the clinical and histopathological phenotype with RYR1-CM, we considered the potential existence of a missing second variant in trans in the proband, but also hypothesized that the variant might be mosaic in the mother, as subsequently demonstrated. Our study is an example of how heterozygous variants inherited from asymptomatic parents are frequently dismissed. When the genotype-phenotype correlation is strong, it is recommended to consider a parental mosaicism.
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Mosaicismo , Fenotipo , Canal Liberador de Calcio Receptor de Rianodina , Humanos , Estudios de Asociación Genética , Miotonía Congénita/genética , Miotonía Congénita/diagnóstico , Canal Liberador de Calcio Receptor de Rianodina/genética , Masculino , PreescolarRESUMEN
GEMIN5 exerts key biological functions regulating pre-mRNAs intron removal to generate mature mRNAs. A series of patients were reported harboring mutations in GEMIN5. No treatments are currently available for this disease. We treated two of these patients with oral Coenzyme Q10 (CoQ10), which resulted in neurological improvements, although MRI abnormalities remained. Whole Exome Sequencing demonstrated compound heterozygosity at the GEMIN5 gene in both cases: Case one: p.Lys742* and p.Arg1016Cys; Case two: p.Arg1016Cys and p.Ser411Hisfs*6. Functional studies in fibroblasts revealed a decrease in CoQ10 biosynthesis compared to controls. Supplementation with exogenous CoQ10 restored it to control intracellular CoQ10 levels. Mitochondrial function was compromised, as indicated by the decrease in oxygen consumption, restored by CoQ10 supplementation. Transcriptomic analysis of GEMIN5 patients compared with controls showed general repression of genes involved in CoQ10 biosynthesis. In the rigor mortis defective flies, CoQ10 levels were decreased, and CoQ10 supplementation led to an improvement in the adult climbing assay performance, a reduction in the number of motionless flies, and partial restoration of survival. Overall, we report the association between GEMIN5 dysfunction and CoQ10 deficiency for the first time. This association opens the possibility of oral CoQ10 therapy, which is safe and has no observed side effects after long-term therapy.
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Ataxia , Enfermedades Mitocondriales , Debilidad Muscular , Ubiquinona , Ubiquinona/deficiencia , Adulto , Humanos , Ubiquinona/genética , Ubiquinona/uso terapéutico , Ubiquinona/metabolismo , Estudios de Seguimiento , Enfermedades Mitocondriales/tratamiento farmacológico , Enfermedades Mitocondriales/genética , Mutación , Proteínas del Complejo SMN/genéticaRESUMEN
Resumen La terapia génica ha logrado avances significativos en el tratamiento de enfermedades genéticas, especial mente en enfermedades raras y monogénicas. Se han desarrollado y aprobado terapias génicas para tratar en fermedades como la atrofia muscular espinal, brindando esperanza a los pacientes y demostrando la eficacia de esta terapia. Actualmente, se están realizando numerosos ensayos clínicos para evaluar la seguridad y eficacia de la terapia génica en diversas enfermedades, particularmente en el campo de la neurología pediátrica. Estos estudios están generando datos alentadores y contribuyen al conoci miento sobre cómo mejorar las técnicas de terapia génica. A pesar de los avances, la terapia génica enfrenta desafíos importantes. Es una terapia costosa y téc nicamente compleja, lo que limita su accesibilidad. Además, aspectos como la entrega eficiente de genes, la respuesta inmunológica a los vectores y la duración de la respuesta terapéutica requieren mejoras. se está investigando activamente. En cuanto al futuro de la terapia génica, se espera que los avances en tecnología de edición génica, como CRISPR-Cas9, permitan una mayor precisión y eficiencia en la modificación de genes. Se espera que la investigación en vectores de terapia génica mejore la capacidad de entrega y la seguridad de los tratamientos. Se están desarrollando nuevas ge neraciones de vectores virales y no virales que podrían superar las limitaciones actuales y permitir una admi nistración más eficiente y precisa de genes terapéuticos.
Abstract Gene therapy has achieved significant advancements in the treatment of genetic diseases, especially in rare and monogenic diseases. Gene therapies have been de veloped and approved to treat diseases such as spinal muscular atrophy, offering hope to patients and dem onstrating the effectiveness of this therapy. Currently, numerous clinical trials are being conduct ed to evaluate the safety and efficacy of gene therapy in various diseases, particularly in the field of pediatric neurology. These studies are generating encouraging data and contributing to the knowledge on how to im prove gene therapy techniques. Despite the advancements, gene therapy faces significant challenges. It is a costly and technically complex therapy, limiting its accessibility. Addition ally, aspects such as efficient gene delivery, immune response to vectors, and duration of therapeutic re sponse require improvements and are actively being investigated. Regarding the future of gene therapy, advances in gene editing technology, such as CRISPR-Cas9, are ex pected to allow for greater precision and efficiency in gene modification. Research on gene therapy vectors is expected to en hance the delivery capacity and safety of treatments. New generations of viral and non-viral vectors are be ing developed that could overcome current limitations and enable more efficient and precise administration of therapeutic genes.
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Duchenne muscular dystrophy is a genetic disease produced by mutations in the dystrophin gene characterized by early onset muscle weakness leading to severe and irreversible disability. The cellular and molecular consequences of the lack of dystrophin in humans are only partially known, which is crucial for the development of new therapies aiming to slow or stop the progression of the disease. Here we have analyzed quadriceps muscle biopsies of seven DMD patients aged 2 to 4 years old and five age and gender matched controls using single nuclei RNA sequencing (snRNAseq) and correlated the results obtained with clinical data. SnRNAseq identified significant differences in the proportion of cell population present in the muscle samples, including an increase in the number of regenerative fibers, satellite cells, and fibro-adipogenic progenitor cells (FAPs) and a decrease in the number of slow fibers and smooth muscle cells. Muscle samples from the younger patients with stable mild weakness were characterized by an increase in regenerative fibers, while older patients with moderate and progressive weakness were characterized by loss of muscle fibers and an increase in FAPs. An analysis of the gene expression profile in muscle fibers identified a strong regenerative signature in DMD samples characterized by the upregulation of genes involved in myogenesis and muscle hypertrophy. In the case of FAPs, we observed upregulation of genes involved in the extracellular matrix regeneration but also several signaling pathways. Indeed, further analysis of the potential intercellular communication profile showed a dysregulation of the communication profile in DMD samples identifying FAPs as a key regulator of cell signaling in DMD muscle samples. In conclusion, our study has identified significant differences at the cellular and molecular levels in the different cell populations present in skeletal muscle samples of patients with DMD compared to controls.
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Distrofia Muscular de Duchenne , Humanos , Preescolar , Distrofia Muscular de Duchenne/genética , Distrofina/genética , Transcriptoma/genética , Fibras Musculares Esqueléticas , Transducción de SeñalRESUMEN
Gene therapy has achieved significant advancements in the treatment of genetic diseases, especially in rare and monogenic diseases. Gene therapies have been developed and approved to treat diseases such as spinal muscular atrophy, offering hope to patients and demonstrating the effectiveness of this therapy. Currently, numerous clinical trials are being conducted to evaluate the safety and efficacy of gene therapy in various diseases, particularly in the field of pediatric neurology. These studies are generating encouraging data and contributing to the knowledge on how to improve gene therapy techniques. Despite the advancements, gene therapy faces significant challenges. It is a costly and technically complex therapy, limiting its accessibility. Additionally, aspects such as efficient gene delivery, immune response to vectors, and duration of therapeutic response require improvements and are actively being investigated. Regarding the future of gene therapy, advances in gene editing technology, such as CRISPR-Cas9, are expected to allow for greater precision and efficiency in gene modification. Research on gene therapy vectors is expected to enhance the delivery capacity and safety of treatments. New generations of viral and non-viral vectors are being developed that could overcome current limitations and enable more efficient and precise administration of therapeutic genes.
La terapia génica ha logrado avances significativos en el tratamiento de enfermedades genéticas, especialmente en enfermedades raras y monogénicas. Se han desarrollado y aprobado terapias génicas para tratar enfermedades como la atrofia muscular espinal, brindando esperanza a los pacientes y demostrando la eficacia de esta terapia. Actualmente, se están realizando numerosos ensayos clínicos para evaluar la seguridad y eficacia de la terapia génica en diversas enfermedades, particularmente en el campo de la neurología pediátrica. Estos estudios están generando datos alentadores y contribuyen al conocimiento sobre cómo mejorar las técnicas de terapia génica. A pesar de los avances, la terapia génica enfrenta desafíos importantes. Es una terapia costosa y técnicamente compleja, lo que limita su accesibilidad. Además, aspectos como la entrega eficiente de genes, la respuesta inmunológica a los vectores y la duración de la respuesta terapéutica requieren mejoras. se está investigando activamente. En cuanto al futuro de la terapia génica, se espera que los avances en tecnología de edición génica, como CRISPR-Cas9, permitan una mayor precisión y eficiencia en la modificación de genes. Se espera que la investigación en vectores de terapia génica mejore la capacidad de entrega y la seguridad de los tratamientos. Se están desarrollando nuevas generaciones de vectores virales y no virales que podrían superar las limitaciones actuales y permitir una administración más eficiente y precisa de genes terapéuticos.
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Atrofia Muscular Espinal , Neurología , Niño , Humanos , Terapia Genética , Edición Génica , Atrofia Muscular Espinal/genética , Atrofia Muscular Espinal/terapia , TecnologíaRESUMEN
OBJECTIVE: FHL1-related reducing body myopathy is an ultra-rare, X-linked dominant myopathy. In this cross-sectional study, we characterize skeletal muscle ultrasound, muscle MRI, and cardiac MRI findings in FHL1-related reducing body myopathy patients. METHODS: Seventeen patients (11 male, mean age 35.4, range 12-76 years) from nine independent families with FHL1-related reducing body myopathy underwent clinical evaluation, muscle ultrasound (n = 11/17), and lower extremity muscle MRI (n = 14/17), including Dixon MRI (n = 6/17). Muscle ultrasound echogenicity was graded using a modified Heckmatt scale. T1 and STIR axial images of the lower extremity muscles were evaluated for pattern and distribution of abnormalities. Quantitative analysis of intramuscular fat fraction was performed using the Dixon MRI images. Cardiac studies included electrocardiogram (n = 15/17), echocardiogram (n = 17/17), and cardiac MRI (n = 6/17). Cardiac muscle function, T1 maps, T2-weighted black blood images, and late gadolinium enhancement patterns were analyzed. RESULTS: Muscle ultrasound showed a distinct pattern of increased echointensity in skeletal muscles with a nonuniform, multifocal, and "geographical" distribution, selectively involving the deeper fascicles of muscles such as biceps and tibialis anterior. Lower extremity muscle MRI showed relative sparing of gluteus maximus, rectus femoris, gracilis, and lateral gastrocnemius muscles and an asymmetric and multifocal, "geographical" pattern of T1 hyperintensity within affected muscles. Cardiac studies revealed mild and nonspecific abnormalities on electrocardiogram and echocardiogram with unremarkable cardiac MRI studies. INTERPRETATION: Skeletal muscle ultrasound and muscle MRI reflect the multifocal aggregate formation in muscle in FHL1-related reducing body myopathy and are practical and informative tools that can aid in diagnosis and monitoring of disease progression.
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Medios de Contraste , Enfermedades Musculares , Humanos , Masculino , Niño , Adolescente , Adulto Joven , Adulto , Persona de Mediana Edad , Anciano , Estudios Transversales , Proteínas Musculares , Gadolinio , Músculo Esquelético/diagnóstico por imagen , Enfermedades Musculares/diagnóstico por imagen , Enfermedades Musculares/genética , Péptidos y Proteínas de Señalización Intracelular , Proteínas con Dominio LIM/genéticaRESUMEN
BACKGROUND: Limb-girdle muscular dystrophies (LGMD) are a heterogeneous group of genetically determined muscle disorders. TRAPPC11-related LGMD is an autosomal-recessive condition characterised by muscle weakness and intellectual disability. METHODS: A clinical and histopathological characterisation of 25 Roma individuals with LGMD R18 caused by the homozygous TRAPPC11 c.1287+5G>A variant is reported. Functional effects of the variant on mitochondrial function were investigated. RESULTS: The c.1287+5G>A variant leads to a phenotype characterised by early onset muscle weakness, movement disorder, intellectual disability and elevated serum creatine kinase, which is similar to other series. As novel clinical findings, we found that microcephaly is almost universal and that infections in the first years of life seem to act as triggers for a psychomotor regression and onset of seizures in several individuals with TRAPPC11 variants, who showed pseudometabolic crises triggered by infections. Our functional studies expanded the role of TRAPPC11 deficiency in mitochondrial function, as a decreased mitochondrial ATP production capacity and alterations in the mitochondrial network architecture were detected. CONCLUSION: We provide a comprehensive phenotypic characterisation of the pathogenic variant TRAPPC11 c.1287+5G>A, which is founder in the Roma population. Our observations indicate that some typical features of golgipathies, such as microcephaly and clinical decompensation associated with infections, are prevalent in individuals with LGMD R18.
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Discapacidad Intelectual , Microcefalia , Distrofia Muscular de Cinturas , Distrofias Musculares , Romaní , Humanos , Romaní/genética , Fenotipo , Distrofia Muscular de Cinturas/genética , Debilidad Muscular , Proteínas de Transporte VesicularRESUMEN
Background: Laminopathies are caused by rare alterations in LMNA, leading to a wide clinical spectrum. Though muscular dystrophy begins at early ages, disease progression is different in each patient. We investigated variability in laminopathy phenotypes by performing a targeted genetic analysis of patients diagnosed with LMNA-related muscular dystrophy to identify rare variants in alternative genes, thereby explaining phenotypic differences. Methods: We analyzed 105 genes associated with muscular diseases by targeted sequencing in 26 pediatric patients of different countries, diagnosed with any LMNA-related muscular dystrophy. Family members were also clinically assessed and genetically analyzed. Results: All patients carried a pathogenic rare variant in LMNA. Clinical diagnoses included Emery-Dreifuss muscular dystrophy (EDMD, 13 patients), LMNA-related congenital muscular dystrophy (L-CMD, 11 patients), and limb-girdle muscular dystrophy 1B (LGMD1B, 2 patients). In 9 patients, 10 additional rare genetic variants were identified in 8 genes other than LMNA. Genotype-phenotype correlation showed additional deleterious rare variants in five of the nine patients (3 L-CMD and 2 EDMD) with severe phenotypes. Conclusion: Analysis f known genes related to muscular diseases in close correlation with personalized clinical assessments may help identify additional rare variants of LMNA potentially associated with early onset or most severe disease progression.
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Several clinical trials are working on drug development for Duchenne and Becker muscular dystrophy (DMD and BMD) treatment, and, since the expected increase in dystrophin is relatively subtle, high-sensitivity quantification methods are necessary. There is also a need to quantify dystrophin to reach a definitive diagnosis in individuals with mild BMD, and in female carriers. We developed a method for the quantification of dystrophin in DMD and BMD patients using spectral confocal microscopy. It offers the possibility to capture the whole emission spectrum for any antibody, ensuring the selection of the emission peak and allowing the detection of fluorescent emissions of very low intensities. Fluorescence was evaluated first on manually selected regions of interest (ROIs), proving the usefulness of the methodology. Later, ROI selection was automated to make it operator-independent. The proposed methodology correctly classified patients according to their diagnosis, detected even minimal traces of dystrophin, and the results obtained automatically were statistically comparable to the manual ones. Thus, spectral imaging could be implemented to measure dystrophin expression and it could pave the way for detailed analysis of how its expression relates to the clinical course. Studies could be further expanded to better understand the expression of dystrophin-associated protein complexes (DAPCs).
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Distrofina , Distrofia Muscular de Duchenne , Humanos , Femenino , Distrofina/genética , Distrofina/metabolismo , Distrofia Muscular de Duchenne/diagnóstico por imagen , Distrofia Muscular de Duchenne/metabolismoRESUMEN
BACKGROUND: Three therapeutic strategies have radically changed the therapeutic scenario for spinal muscular atrophy (SMA). However, therapeutic response differs between individuals. There is a need to identify biomarkers to further assess therapeutic response and to better understand which variables determine the extent of response. METHODS: We conducted a study using an optimized digital droplet PCR-based method for the ultra-sensitive detection of SMN transcript in serum EVs from SMA 2 individuals treated with nusinersen over 14 months. In parallel, we investigated levels of serum and CSF neurofilament heavy chain (pNF-H) in the same cohort. RESULTS: Expression of flSMN transcript in EVs of SMA 2 individuals prior to nusinersen was lower than in controls (0.40 vs 2.79 copies/ul; pâ<â0.05) and increased after 14 months of nusinersen (0.40 vs 1.11 copies/ul; pâ<â0.05). The increase in flSMN with nusinersen was significantly higher in younger individuals (pâ<â0.05). Serum pNF-h was higher in non-treated individuals with SMA 2 than in controls (230.72 vs 22.88 pg/ml; pâ<â0.05) and decreased with nusinersen (45.72 pg/ml at 6 months, 39.02 pg/ml at 14 months). CSF pNF-h in SMA 2 individuals also decreased with nusinersen (248.04 pg/ml prior to treatment, 197.10 pg/dl at 2 months, 104.43 pg/dl at 6 months, 131.03 pg/dl at 14 months). CONCLUSIONS: We identified an increase of flSMN transcript in serum EVs of SMA 2 individuals treated with nusinersen that was more pronounced in the younger individuals. Our results indicate that flSMN transcript expression in serum EVs is a possible biomarker in SMA to predict or monitor the response to treatment.
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Vesículas Extracelulares , Atrofia Muscular Espinal , Atrofias Musculares Espinales de la Infancia , Humanos , Biomarcadores , Atrofia Muscular Espinal/tratamiento farmacológico , Atrofia Muscular Espinal/genética , Atrofias Musculares Espinales de la Infancia/tratamiento farmacológicoRESUMEN
Introduction: LMNA-related muscular dystrophy is a rare entity that produce "laminopathies" such as Emery-Dreifuss muscular dystrophy (EDMD), limb-girdle muscular dystrophy type 1B (LGMD1B), and LMNA-related congenital muscular dystrophy (L-CMD). Heart failure, malignant arrhythmias, and sudden death may occur. No consensus exists on cardiovascular management in pediatric laminopathies. The aim was to perform an exhaustive cardiologic follow-up in pediatric patients diagnosed with LMNA-related muscular dystrophy. Methods: Baseline cardiac work-up consisted of clinical assessment, transthoracic Doppler echocardiography, 12-lead electrocardiogram, electrophysiological study, and implantation of a long-term implantable cardiac loop recorder (ILR). Results: We enrolled twenty-eight pediatric patients diagnosed with EDMD (13 patients), L-CMD (11 patients), LGMD1B (2 patients), and LMNA-related mild weakness (2 patients). Follow-up showed dilated cardiomyopathy (DCM) in six patients and malignant arrhythmias in five (four concomitant with DCM) detected by the ILR that required implantable cardioverter defibrillator (ICD) implantation. Malignant arrhythmias were detected in 20% of our cohort and early-onset EDMD showed worse cardiac prognosis. Discussion: Patients diagnosed with early-onset EDMD are at higher risk of DCM, while potentially life-threatening arrhythmias without DCM appear earlier in L-CMD patients. Early onset neurologic symptoms could be related with worse cardiac prognosis. Specific clinical guidelines for children are needed to prevent sudden death.
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DTNA encodes α-dystrobrevin, a component of the macromolecular dystrophin-glycoprotein complex (DGC) that binds to dystrophin/utrophin and α-syntrophin. Mice lacking α-dystrobrevin have a muscular dystrophy phenotype, but variants in DTNA have not previously been associated with human skeletal muscle disease. We present 12 individuals from four unrelated families with two different monoallelic DTNA variants affecting the coiled-coil domain of α-dystrobrevin. The five affected individuals from family A harbor a c.1585G > A; p.Glu529Lys variant, while the recurrent c.1567_1587del; p.Gln523_Glu529del DTNA variant was identified in the other three families (family B: four affected individuals, family C: one affected individual, and family D: two affected individuals). Myalgia and exercise intolerance, with variable ages of onset, were reported in 10 of 12 affected individuals. Proximal lower limb weakness with onset in the first decade of life was noted in three individuals. Persistent elevations of serum creatine kinase (CK) levels were detected in 11 of 12 affected individuals, 1 of whom had an episode of rhabdomyolysis at 20 years of age. Autism spectrum disorder or learning disabilities were reported in four individuals with the c.1567_1587 deletion. Muscle biopsies in eight affected individuals showed mixed myopathic and dystrophic findings, characterized by fiber size variability, internalized nuclei, and slightly increased extracellular connective tissue and inflammation. Immunofluorescence analysis of biopsies from five affected individuals showed reduced α-dystrobrevin immunoreactivity and variably reduced immunoreactivity of other DGC proteins: dystrophin, α, ß, δ and γ-sarcoglycans, and α and ß-dystroglycans. The DTNA deletion disrupted an interaction between α-dystrobrevin and syntrophin. Specific variants in the coiled-coil domain of DTNA cause skeletal muscle disease with variable penetrance. Affected individuals show a spectrum of clinical manifestations, with severity ranging from hyperCKemia, myalgias, and exercise intolerance to childhood-onset proximal muscle weakness. Our findings expand the molecular etiologies of both muscular dystrophy and paucisymptomatic hyperCKemia, to now include monoallelic DTNA variants as a novel cause of skeletal muscle disease in humans.
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Trastorno del Espectro Autista , Distrofias Musculares , Neuropéptidos , Ratones , Humanos , Animales , Niño , Distrofina/genética , Distrofina/metabolismo , Trastorno del Espectro Autista/metabolismo , Distrofias Musculares/metabolismo , Distroglicanos/metabolismo , Empalme Alternativo , Músculo Esquelético/patología , Neuropéptidos/genética , Neuropéptidos/metabolismo , Proteínas Asociadas a la Distrofina/genética , Proteínas Asociadas a la Distrofina/metabolismoRESUMEN
OBJECTIVE: Mutations in ANXA11 cause amyotrophic lateral sclerosis (ALS) and have recently been identified as a cause of multisystem proteinopathy and adult-onset muscular dystrophy. These conditions are adult-onset diseases and result from the substitution of Aspartate 40 (Asp40) for an apolar residue in the intrinsically disordered domain (IDD) of ANXA11. Some ALS-related variants are known to affect ANXA11 IDD; however, the mechanism by which the myopathy occurs is unknown. METHODS: Genetic analysis was performed using WES-trio. For the study of variant pathogenicity, we used recombinant proteins, muscle biopsy, and fibroblasts. RESULTS: Here we describe an individual with severe and rapidly progressive childhood-onset oculopharyngeal muscular dystrophy who carries a new ANXA11 variant at position Asp40 (p.Asp40Ile; c.118_119delGAinsAT). p.Asp40Ile is predicted to enhance the aggregation propensity of ANXA11 to a greater extent than other changes affecting this residue. In vitro studies using recombinant ANXA11p.Asp40Ile showed abnormal phase separation and confirmed this variant is more aggregation-prone than the ALS-associated variant ANXA11p.Asp40Gly . The study of the patient's fibroblasts revealed defects in stress granules dynamics and clearance, and muscle histopathology showed a myopathic pattern with ANXA11 protein aggregates. Super-resolution imaging showed aggregates expressed as pearl strips or large complex structures in the sarcoplasm, and as layered subsarcolemmal chains probably reflecting ANXA11 multifunctionality. INTERPRETATION: We demonstrate common pathophysiology for disorders associated with ANXA11 Asp40 allelic variants. Clinical phenotypes may result from different deleterious impacts of variants upon ANXA11 stability against aggregation, and differential muscle or motor neuron dysfunction expressed as a temporal and tissue-specific continuum.
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Esclerosis Amiotrófica Lateral , Enfermedades Musculares , Humanos , Esclerosis Amiotrófica Lateral/genética , Ácido Aspártico/genética , Neuronas Motoras/metabolismo , Enfermedades Musculares/patología , MutaciónRESUMEN
BACKGROUND: Up to 7% of patients with Duchenne muscular dystrophy (DMD) or Becker muscular dystrophy (BMD) remain genetically undiagnosed after routine genetic testing. These patients are thought to carry deep intronic variants, structural variants or splicing alterations not detected through multiplex ligation-dependent probe amplification or exome sequencing. METHODS: RNA was extracted from seven muscle biopsy samples of patients with genetically undiagnosed DMD/BMD after routine genetic diagnosis. RT-PCR of the DMD gene was performed to detect the presence of alternative transcripts. Droplet digital PCR and whole-genome sequencing were also performed in some patients. RESULTS: We identified an alteration in the mRNA level in all the patients. We detected three pseudoexons in DMD caused by deep intronic variants, two of them not previously reported. We also identified a chromosomal rearrangement between Xp21.2 and 8p22. Furthermore, we detected three exon skipping events with unclear pathogenicity. CONCLUSION: These findings indicate that mRNA analysis of the DMD gene is a valuable tool to reach a precise genetic diagnosis in patients with a clinical and anatomopathological suspicion of dystrophinopathy that remain genetically undiagnosed after routine genetic testing.
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Distrofia Muscular de Duchenne , Humanos , Distrofia Muscular de Duchenne/diagnóstico , Distrofia Muscular de Duchenne/genética , Distrofina/genética , ARN Mensajero/genética , Mutación , Reacción en Cadena de la Polimerasa MultiplexRESUMEN
Thymidine kinase (TK2) deficiency causes mitochondrial DNA depletion syndrome. We aimed to report the clinical, biochemical, genetic, histopathological, and ultrastructural features of a cohort of paediatric patients with TK2 deficiency. Mitochondrial DNA was isolated from muscle biopsies to assess depletions and deletions. The TK2 genes were sequenced using Sanger sequencing from genomic DNA. All muscle biopsies presented ragged red fibres (RRFs), and the prevalence was greater in younger ages, along with an increase in succinate dehydrogenase (SDH) activity and cytochrome c oxidase (COX)-negative fibres. An endomysial inflammatory infiltrate was observed in younger patients and was accompanied by an overexpression of major histocompatibility complex type I (MHC I). The immunofluorescence study for complex I and IV showed a greater number of fibres than those that were visualized by COX staining. In the ultrastructural analysis, we found three major types of mitochondrial alterations, consisting of concentrically arranged lamellar cristae, electrodense granules, and intramitochondrial vacuoles. The pathological features in the muscle showed substantial differences in the youngest patients when compared with those that had a later onset of the disease. Additional ultrastructural features are described in the muscle biopsy, such as sarcomeric de-structuration in the youngest patients with a more severe phenotype.
Asunto(s)
Miopatías Mitocondriales , Timidina Quinasa/metabolismo , ADN Mitocondrial/análisis , ADN Mitocondrial/genética , Complejo IV de Transporte de Electrones/genética , Complejo IV de Transporte de Electrones/metabolismo , Humanos , Miopatías Mitocondriales/genética , Miopatías Mitocondriales/patología , Músculo Esquelético/metabolismo , Miocardio/metabolismo , Succinato Deshidrogenasa , Timidina Quinasa/genéticaRESUMEN
Guillain-Barré syndrome (GBS) is characterized by rapidly progressive and generally ascending symmetrical muscle weakness, accompanied by decreased or absent osteotendinous reflexes. The inflammatory process may affect the myelin or the axon. There are 4 clinical forms of GBS: 1) acute inflammatory demyelinating polyradiculoneuropathy, 2) acute motor axonal neuropathy, 3) acute sensory and motor axonal neuropathy, and 4) the Miller-Fisher variant, which is characterized by ophthalmoplegia, ataxia and areflexia, with little muscle weakness. Diagnosis is based on the albumin-cytological dissociation observed at the end of the first week after the onset of symptoms and may persist until the third week, as well as on the specific neurophysiological alterations of each clinical form. The treatment of GBS will depend on the degree of severity, if the patient presents grade IV or less according to the Paradiso scale, it will be treated with Ig IV, if it presents grade V, the use of plasmapheresis and/or immunoadbosorption is recommended. In severe axonal cases, the use of corticosteroid bolus is recommended in initial stages. There is a clinical picture that overlaps GBS and chronic demyelinating polyneuropathy related to antibodies against neurophysin and contactin, in this case the appropriate therapy is rituximab.
El síndrome de Guillain-Barré (SGB) se caracteriza por debilidad muscular simétrica rápidamente progresiva y generalmente ascendente, acompañada de disminución o ausencia de reflejos osteotendinosos. El proceso inflamatorio puede afectar a la mielina o al axón. Existen 4 formas clínicas de SGB: 1) polirradiculoneuropatía desmielinizante inflamatoria aguda, 2) neuropatía axonal motora aguda, 3) neuropatía axonal sensitiva y motora aguda, y 4) la variante Miller-Fisher, que se caracteriza por oftalmoplejía, ataxia y arreflexia, con escasa debilidad muscular. El diagnóstico se basa en la disociación albúmino-citológica que se observa a final de la primera semana del inicio de los síntomas y puede persistir hasta la tercera semana, así como en las alteraciones neurofisiológicas específicas de cada forma clínica. El tratamiento el SGB, dependerá de la gravedad, si el paciente presenta grado IV o menor según la escala de Paradiso, se tratará con Ig IV, si presenta grado V, se recomienda el uso de plasmaféresis y/o inmunoadbosorción. En los casos axonales graves se recomienda el uso de bolus de corticoides en etapas iniciales. Existe un cuadro clínico que solapa SGB y polineuropatía desmielinizante crónica relacionado con anticuerpos contra neurofisina y contactina, en este caso la terapia adecuada es rituximab.
Asunto(s)
Síndrome de Guillain-Barré , Debilidad Muscular , Síndrome de Guillain-Barré/diagnóstico , Síndrome de Guillain-Barré/tratamiento farmacológico , Humanos , Debilidad Muscular/terapia , PlasmaféresisRESUMEN
Myotonic dystrophy type 1 (DM1) is a progressive, non-treatable, multi-systemic disorder. To investigate the contribution of epigenetics to the complexity of DM1, we compared DNA methylation profiles of four annotated CpG islands (CpGis) in the DMPK locus and neighbouring genes, in distinct DM1 tissues and derived cells, representing six DM1 subtypes, by bisulphite sequencing. In blood, we found no differences in CpGi 74, 43 and 36 in DNA methylation profile. In contrast, a CTCF1 DNA methylation gradient was found with 100% methylation in congenital cases, 50% in childhood cases and 13% in juvenile cases. CTCF1 methylation correlated to disease severity and CTG expansion size. Notably, 50% of CTCF1 methylated cases showed methylation in the CTCF2 regions. Additionally, methylation was associated with maternal transmission. Interestingly, the evaluation of seven families showed that unmethylated mothers passed on an expansion of the CTG repeat, whereas the methylated mothers transmitted a contraction. The analysis of patient-derived cells showed that DNA methylation profiles were highly preserved, validating their use as faithful DM1 cellular models. Importantly, the comparison of DNA methylation levels of distinct DM1 tissues revealed a novel muscle-specific epigenetic signature with methylation of the CTCF1 region accompanied by demethylation of CpGi 43, a region containing an alternative DMPK promoter, which may decrease the canonical promoter activity. Altogether, our results showed a distinct DNA methylation profile across DM1 tissues and uncovered a novel and dual epigenetic signature in DM1 muscle samples, providing novel insights into the epigenetic changes associated with DM1.