Severe congenital myasthenic syndromes caused by agrin mutations affecting secretion by motoneurons

Brucella suis S2 strain inhibits IRE1/caspase-12/caspase-3 pathway-mediated apoptosis of microglia HMC3 by affecting the ubiquitination of CALR

Neurobrucellosis represents a severe complication of brucellosis, posing a considerable risk to human health and quality of life. This condition arises from an increased susceptibility to chronic Brucella infection, a significant clinical challenge. One key factor contributing to chronic neurobrucellosis is the regulation of microglial apoptosis by Brucella; however, the exact molecular mechanisms remain largely unresolved. In this study, human microglial clone 3 (HMC3) cells were infected with Brucella suis vaccine strain S2 (B. suis S2) at varying multiplicity of infection (MOI) and durations to assess its effects on the IRE1/caspase-12/caspase-3 signaling pathway. Following the suppression of this pathway by B. suis S2, calreticulin (CALR) was identified through ubiquitin-modified proteomics (data accessible via ProteomeXchange, identifier PXD056006). To further investigate, CALR-overexpression and knockdown HMC3 cell lines were infected with B. suis S2 to elucidate the mechanism by which B. suis S2 inhibits apoptosis in HMC3 cells. In conclusion, our findings demonstrate that B. suis S2 suppresses HMC3 cell apoptosis via the IRE1/caspase-12/caspase-3 pathway by modulating CALR ubiquitination. This study provides a theoretical basis for exploring the mechanisms of neurobrucellosis and offers insights into its clinical treatment.IMPORTANCENeurobrucellosis is a severe complication impacting the central nervous system (CNS) due to neurological deficits caused by Brucella, with primary clinical features including meningitis, encephalitis, brain abscesses, and demyelinating lesions. These nonspecific symptoms often lead to misdiagnosis or delayed diagnosis, increasing the risk of recurrent or chronic neurobrucellosis infections. Consequently, persistent infection and relapse are critical challenges in the clinical management of neurobrucellosis, which are closely linked to Brucella's survival and replication within microglia. Interestingly, Brucella may inhibit microglia apoptosis by mitigating endoplasmic reticulum (ER) stress, though the precise molecular mechanisms remain largely unexplored. Thus, this study will elucidate the specific mechanisms by which Brucella suppresses microglial apoptosis and provide deeper insights into the molecular pathogenesis and clinical treatment of neurobrucellosis.

Delivery of Prime editing in human stem cells using pseudoviral NanoScribes particles

Prime Editing can rewrite genes in living cells by allowing point mutations, deletions, or insertion of small DNA sequences with high precision. However, its safe and efficient delivery into human stem cells remains a technical challenge. In this report, we engineer Nanoscribes, virus-like particles that encapsidate ribonucleoprotein complexes of the Prime Editing system and allow their delivery into recipient cells. We identify key features that unlock the potential of Nanoscribes, including the use of multiple fusogens, the improvement of pegRNAs structures, their encoding by a Pol II system and the optimization of Prime-Editors. Nanoscribes edit HEK293T with an efficiency of 68% at the HEK3 locus with increased fidelity over DNA-transfection and support pegRNA-multiplexing. Importantly, Nanoscribes permit editing of myoblasts, hiPSCs and hiPSCs-derived hematopoietic stem cells with an editing efficiency up to 25%. Nanoscribes is an asset for development of next generation genome editing approaches using VLPs.

Congenital myasthenic syndromes in adults: clinical features, diagnosis and long-term prognosis

Congenital myasthenic syndromes (CMS) are clinically and genetically heterogeneous diseases caused by mutations affecting neuromuscular transmission. Even if the first symptoms mainly occur during childhood, adult neurologists must confront this challenging diagnosis and manage these patients throughout their adulthood. However, long-term follow-up data from large cohorts of CMS patients are lacking, and the long-term prognosis of these patients is largely unknown. We report the clinical features, diagnostic difficulties, and long-term prognosis of a French nationwide cohort of 235 adult patients with genetically confirmed CMS followed in 23 specialized neuromuscular centres. Data were retrospectively analysed. Of the 235 patients, 123 were female (52.3%). The diagnosis was made in adulthood in 139 patients, 110 of whom presented their first symptoms before the age of 18. Mean follow-up time between first symptoms and last visit was 34 years [standard deviation (SD) = 15.1]. Pathogenic variants were found in 19 disease-related genes. CHRNE-low expressor variants were the most common (23.8%), followed by variants in DOK7 (18.7%) and RAPSN (14%). Genotypes were clustered into four groups according to the initial presentation: ocular group (CHRNE-LE, CHRND, FCCMS), distal group (SCCMS), limb-girdle group (RAPSN, COLQ, DOK7, GMPPB, GFPT1), and a variable-phenotype group (MUSK, AGRN). The phenotypical features of CMS did not change throughout life. Only four genotypes had a proportion of patients requiring intensive care unit admission that exceeded 20%: RAPSN (54.8%), MUSK (50%), DOK7 (38.6%) and AGRN (25.0%). In RAPSN and MUSK patients most ICU admissions occurred before age 18 years and in DOK7 and AGRN patients at or after 18 years of age. Different patterns of disease course (stability, improvement and progressive worsening) may succeed one another in the same patient throughout life, particularly in AGRN, DOK7 and COLQ. At the last visit, 55% of SCCMS and 36.3% of DOK7 patients required ventilation; 36.3% of DOK7 patients, 25% of GMPPB patients and 20% of GFPT1 patients were wheelchair-bound; most of the patients who were both wheelchair-bound and ventilated were DOK7 patients. Six patients died in this cohort. The positive impact of therapy was striking, even in severely affected patients. In conclusion, even if motor and/or respiratory deterioration could occur in patients with initially moderate disease, particularly in DOK7, SCCMS and GFPT1 patients, the long-term prognosis for most CMS patients was favourable, with neither ventilation nor wheelchair needed at last visit. CHRNE-LE patients did not worsen during adulthood and RAPSN patients, often severely affected in early childhood, subsequently improved.

Rare disease research workflow using multilayer networks elucidates the molecular determinants of severity in Congenital Myasthenic Syndromes

Exploring the molecular basis of disease severity in rare disease scenarios is a challenging task provided the limitations on data availability. Causative genes have been described for Congenital Myasthenic Syndromes (CMS), a group of diverse minority neuromuscular junction (NMJ) disorders; yet a molecular explanation for the phenotypic severity differences remains unclear. Here, we present a workflow to explore the functional relationships between CMS causal genes and altered genes from each patient, based on multilayer network community detection analysis of complementary biomedical information provided by relevant data sources, namely protein-protein interactions, pathways and metabolomics. Our results show that CMS severity can be ascribed to the personalized impairment of extracellular matrix components and postsynaptic modulators of acetylcholine receptor (AChR) clustering. This work showcases how coupling multilayer network analysis with personalized -omics information provides molecular explanations to the varying severity of rare diseases; paving the way for sorting out similar cases in other rare diseases.

Nucleolar reorganization after cellular stress is orchestrated by SMN shuttling between nuclear compartments

Spinal muscular atrophy is an autosomal recessive neuromuscular disease caused by mutations in the multifunctional protein Survival of Motor Neuron, or SMN. Within the nucleus, SMN localizes to Cajal bodies, which are associated with nucleoli, nuclear organelles dedicated to the first steps of ribosome biogenesis. The highly organized structure of the nucleolus can be dynamically altered by genotoxic agents. RNAP1, Fibrillarin, and nucleolar DNA are exported to the periphery of the nucleolus after genotoxic stress and, once DNA repair is fully completed, the organization of the nucleolus is restored. We find that SMN is required for the restoration of the nucleolar structure after genotoxic stress. During DNA repair, SMN shuttles from the Cajal bodies to the nucleolus. This shuttling is important for nucleolar homeostasis and relies on the presence of Coilin and the activity of PRMT1.

Unlocking the Complexity of Neuromuscular Diseases: Insights from Human Pluripotent Stem Cell-Derived Neuromuscular Junctions

Over the past 20 years, the use of pluripotent stem cells to mimic the complexities of the human neuromuscular junction has received much attention. Deciphering the key mechanisms underlying the establishment and maturation of this complex synapse has been driven by the dual goals of addressing developmental questions and gaining insight into neuromuscular disorders. This review aims to summarise the evolution and sophistication of in vitro neuromuscular junction models developed from the first differentiation of human embryonic stem cells into motor neurons to recent neuromuscular organoids. We also discuss the potential offered by these models to decipher different neuromuscular diseases characterised by defects in the presynaptic compartment, the neuromuscular junction, and the postsynaptic compartment. Finally, we discuss the emerging field that considers the use of these techniques in drug screening assay and the challenges they will face in the future.