Project description:The neuromuscular junction (NMJ) is a specialized tripartite synapse composed of the motor axon terminal, covered by perisynaptic Schwann cells (PSCs), and the muscle fibre, separated by a basal lamina. It is exposed to different kind of injures such as mechanical traumas, pathogens including neurotoxins, and neuromuscular diseases such as amyotrophic lateral sclerosis and immune-mediated disorders, and has retained throughout vertebrate evolution an intrinsic ability for repair and regeneration, at variance from central synapses1. Following peripheral nerve injury, an intense but poorly defined crosstalk takes place at the NMJ among its components, functional to nerve terminal regeneration. To identify crucial factors released by PSCs and the muscle to induce nerve regrowth, we performed a transcriptome analysis of the NMJ at different time points after injection of -latrotoxin, a presynaptic neurotoxin isolated from the venom of the black widow spider. This toxin is a simple and controlled method to induce an acute, localized and reversible nerve terminal degeneration not blurred by inflammation, and can help to identify molecules involved in the intra- and inter-cellular signalling governing NMJ regeneration.
Project description:Purpose: To investigate whether our signatures of mTORC1-driven sarcopenia originate from cells residing at the neuromuscular junction (NMJ), we followed laser-capture microdissection with RNA-seq from adult and sarcopenic tibialis anterior (TA) muscles. Methods: TA muscles were incubated in solution containing fluorescently-labeled bungarotoxin, which binds to post-synaptic AChRs and thereby marks NMJ regions. Approximately 300 synaptic regions (NMJ) and a comparable number of extra-synaptic (xNMJ) regions were collected from 30µM thick sections using laser-capture microdissection (LCM) and processed for RNA-seq. Results: As compared to xNMJ regions, NMJ regions were highly enriched for genes known to be specifically expressed at the NMJ. The analysis demonstrated that genes associated with sarcopenia are significantly enriched at the NMJ in young (10 months) and old (30 months) mice. Furthermore, the age-related reduction in expression of genes associated with extracellular matrix (ECM) remodelling was particularly prominent in NMJ regions but not in xNMJ regions. Conclusions: Diminished expression of ECM genes at the NMJ may impact the stability of the NMJ and its ability to remodel following common age-related remodelling events such as muscle fiber degeneration/regeneration and motor unit loss.
Project description:Understanding neuromuscular junction (NMJ) repair mechanisms is essential for addressing degenerative neuromuscular conditions. Here, we focus on the role of muscle-resident Schwann cells in NMJ reinnervation. Using an accepted model of progressive NMJ degeneration, Sod1-/- mice, we identified a clear NMJ ‘regenerative window’ that allowed us to define cellular and molecular regulators of synapse remodeling and muscle fiber reinnervation. High-resolution imaging and single-cell RNA sequencing provide a detailed analysis of Schwann cell number, morphology, and transcriptome revealing multiple subtypes, including a previously unrecognized terminal Schwann cell (tSC) population expressing a synapse promoting signature. We also discovered a novel SPP1-driven cellular interaction between myelin Schwann cells and tSCs and show that it promotes tSC proliferation and reinnervation following nerve injury in wild type mice. Our findings offer important insights into molecular regulators critical in NMJ reinnervation that are mediated through tSCs to maintain NMJ function.
Project description:Spinal muscular atrophy (SMA) is a neuromuscular disorder caused by mutations of the survival of motor neuron 1 (SMN1) gene. In the pathogenesis of SMA, pathological changes of the neuromuscular junction (NMJ) precede the motor neuronal loss. Therefore, it is critical to evaluate the NMJ formed by SMA patientsM-bM-^@M-^Y motor neurons (MNs), and to identify drugs that can restore the normal condition. We generated NMJ-like structures using motor neurons (MNs) derived from SMA patient-specific induced pluripotent stem cells (iPSCs), and found that the clustering of the acetylcholine receptor (AChR) is significantly impaired. Valproic acid and antisense oligonucleotide treatment ameliorated the AChR clustering defects, leading to an increase in the level of full-length SMN transcripts. Thus, the current in vitro model of AChR clustering using SMA patient-derived iPSCs is useful to dissect the pathophysiological mechanisms underlying the development of SMA, and to evaluate the efficacy of new therapeutic approaches.M-bM-^@M-^C To compare the gene expression pattern between control and patient derived iPSCs
Project description:Muscle fibroadipogenic progenitor (FAP) cells, which are muscular mesenchymal cells that originate from lateral plate mesoderm have been proposed to act as a critical regulator for adult muscle homeostasis1–7, including the maturation and proper functioning of the neuromuscular junction (NMJ)3, Prx-Bap1 paper. However, the mechanism and intercellular crosstalk by which FAPs regulate the stability and functionality of neuromuscular system remains unknown. Here we show that FAPs not only locally but also systemically regulate the neuromuscular system through the secretion of a serine-type endopeptidase Granzyme E which may imply the previously unidentified endocrine function of FAPs. Local transplantation of wild-type FAPs into the neuromuscular disease model (Prrx1Cre;Bap1f/f, hereafter, cKO) can readily prevent neuromuscular defects, including degeneration of the neuromuscular junction and loss of motor neurons. These effects are found not only in transplanted hindlimb muscles but also in the contralateral hindlimb and even forelimb muscles. Notably, subcutaneous administration of microparticles encapsulating FAP-conditioned media into cKO mice was sufficient to restore normal neuromuscular functions. By analyzing the transcriptomic and secretomic profiles of FAPs, we identified a novel protein, Granzyme E, which is specifically expressed in and secreted by FAPs, and which indispensably regulates the structure and function of NMJ and motor neuron survival. Our study has defined a unique mechanism of Granzyme E-dependent, systemic control of the neuromuscular system by FAPs, which would provide a comprehensive understanding on the neuromuscular systems and their crosstalk with non-neuronal cells. These findings may provide a therapeutic benefit to treat NMJ-related diseases.
Project description:Spinal muscular atrophy (SMA) is a neuromuscular disorder caused by mutations of the survival of motor neuron 1 (SMN1) gene. In the pathogenesis of SMA, pathological changes of the neuromuscular junction (NMJ) precede the motor neuronal loss. Therefore, it is critical to evaluate the NMJ formed by SMA patientsM-bM-^@M-^Y motor neurons (MNs), and to identify drugs that can restore the normal condition. We generated NMJ-like structures using motor neurons (MNs) derived from SMA patient-specific induced pluripotent stem cells (iPSCs), and found that the clustering of the acetylcholine receptor (AChR) is significantly impaired. Valproic acid and antisense oligonucleotide treatment ameliorated the AChR clustering defects, leading to an increase in the level of full-length SMN transcripts. Thus, the current in vitro model of AChR clustering using SMA patient-derived iPSCs is useful to dissect the pathophysiological mechanisms underlying the development of SMA, and to evaluate the efficacy of new therapeutic approaches.M-bM-^@M-^C to evaluate the effects of VPA on the expression profiles of the MNs
Project description:Spinal muscular atrophy (SMA) is a neuromuscular disorder caused by mutations of the survival of motor neuron 1 (SMN1) gene. In the pathogenesis of SMA, pathological changes of the neuromuscular junction (NMJ) precede the motor neuronal loss. Therefore, it is critical to evaluate the NMJ formed by SMA patients’ motor neurons (MNs), and to identify drugs that can restore the normal condition. We generated NMJ-like structures using motor neurons (MNs) derived from SMA patient-specific induced pluripotent stem cells (iPSCs), and found that the clustering of the acetylcholine receptor (AChR) is significantly impaired. Valproic acid and antisense oligonucleotide treatment ameliorated the AChR clustering defects, leading to an increase in the level of full-length SMN transcripts. Thus, the current in vitro model of AChR clustering using SMA patient-derived iPSCs is useful to dissect the pathophysiological mechanisms underlying the development of SMA, and to evaluate the efficacy of new therapeutic approaches.
Project description:Spinal muscular atrophy (SMA) is a neuromuscular disorder caused by mutations of the survival of motor neuron 1 (SMN1) gene. In the pathogenesis of SMA, pathological changes of the neuromuscular junction (NMJ) precede the motor neuronal loss. Therefore, it is critical to evaluate the NMJ formed by SMA patients’ motor neurons (MNs), and to identify drugs that can restore the normal condition. We generated NMJ-like structures using motor neurons (MNs) derived from SMA patient-specific induced pluripotent stem cells (iPSCs), and found that the clustering of the acetylcholine receptor (AChR) is significantly impaired. Valproic acid and antisense oligonucleotide treatment ameliorated the AChR clustering defects, leading to an increase in the level of full-length SMN transcripts. Thus, the current in vitro model of AChR clustering using SMA patient-derived iPSCs is useful to dissect the pathophysiological mechanisms underlying the development of SMA, and to evaluate the efficacy of new therapeutic approaches.
Project description:During aging and neuromuscular diseases, there is a progressive loss of skeletal muscle volume and function, which is often associated with denervation and a loss of muscle stem cells (MuSCs). A relationship between MuSCs and innervation has not been established however. Herein, we administered neuromuscular trauma to a MuSC lineage tracing model and observed a subset of MuSCs specifically engraft in a position proximal to the neuromuscular junction (NMJ). In aging and in a model of neuromuscular degeneration (Sod1-/-), this localized engraftment behavior was reduced. Genetic rescue of motor neurons in Sod1-/- mice reestablished integrity of the NMJ and partially restored MuSC ability to engraft into NMJ proximal positions. Using single cell RNA-sequencing of MuSCs, we demonstrate that a subset of MuSCs are molecularly distinguishable from MuSCs responding to myofiber injury. These data reveal unique features of MuSCs that respond to synaptic perturbations caused by aging and other stressors.