Biology subjects

Moulay, G.

Publications and source records attributed to Moulay, G..

4 recordsLinked to original sources

bioRxiv2024

Alternative splicing of SORBS1 affects neuromuscular junction formation and stability in myotonic dystrophy type 1

Myotonic dystrophy type 1 (DM1) is a multisystemic neuromuscular disease characterized by a CTG repeat expansion in the 3" untranslated region of the gene coding for the dystrophia myotonica protein kinase (DMPK). Presence of expanded CTG repeats in DMPK-mRNAs leads to the sequestration of RNA binding factors such as the Muscleblind like (MBNL) proteins resulting in widespread splicing defects contributing to progressive muscle weakness and myotonia. Here, we show that abnormal splicing of SORBS1 exon 25 found in skeletal muscle of myotonic dystrophy type 1 patients is a critical contributor to neuromuscular junction (NMJ) formation and maintenance. Forced exclusion of SORBS1 exon 25 in mice results in NMJ degeneration with marked denervation and postsynaptic destabilization. In zebrafish, misregulation of sorbs1 exon 25 results in reduced motor function and abnormal AChR cluster morphology. Finally, we observed that forcing SORBS1 exon 25 exclusion in hiPSC-derived skeletal muscle cells reduces the formation of large AChR clusters upon agrin stimulation. Thus, our study identifies MBNL regulated SORBS1 alternative splicing during skeletal muscle development as a critical event for NMJ formation and maintenance. The aberrant splicing of SORBS1 exon 25 in DM1 expands our understanding of how splicing dysregulation compromises neuromuscular system communication, shedding light on the broader impact of mRNA splicing regulation on NMJ integrity.

molecular biology↗

bioRxiv2023

The actin-spectrin submembrane scaffold restricts endocytosis along proximal axons

Neuronal clathrin-mediated endocytosis has unique features in compartments such as dendrites and presynaptic boutons, but how membrane and extracellular components are internalized along the axon shaft remains poorly known. Here we focused on clathrin-coated structures and endocytosis along the axon initial segment (AIS), and their relationship to the periodic actin-spectrin scaffold that lines the axonal plasma membrane. Super-resolution optical microscopy, platinum replica electron microscopy, and their correlative combination on cultured hippocampal neurons reveal that in the AIS, clathrin-coated pits form on bare membrane patches, [~]300 nm circular areas devoid of spectrin mesh and lined by actin filaments we termed "clearings". In fibroblasts and the proximal axon of neurons, spectrin depletion and drug-induced scaffold disorganization increase clathrin-coated pit formation. However, the presence of clathrin-coated pits at the AIS is not directly linked to actual endocytosis: using cargo uptake and live-cell imaging experiments, we find that most AIS clathrin-coated pits are long-lived and immobile within the spectrin mesh clearings. Direct perturbation of the spectrin scaffold as well as elevated neuronal activity could induce endocytosis downstream of clathrin pit formation, showing that spectrin clearings are structures responsible for regulated endocytosis at the AIS.

cell biology↗

bioRxiv2022

Caveolae and Bin1 form ring-shaped platforms for T-tubule initiation

Excitation-contraction coupling requires a highly specialized membrane structure, the triad, composed of a plasma membrane invagination, the T-tubule, surrounded by two sarcoplasmic reticulum terminal cisternae. Although the precise mechanisms governing T-tubule biogenesis and triad formation remain largely unknown, studies have shown that caveolae participate in T-tubule formation and mutations of several of their constituents induce muscle weakness and myopathies. Here, we demonstrate that, at the plasma membrane, caveolae composed of caveolin-3 and Bin1 assemble into ring-like structures from which emerge tubes enriched in the dihydropyridine receptor. Overexpression of Bin1 lead to the formation of both rings and tubes and we show that Bin1 forms scaffolds on which caveolae accumulate to form the initial T-tubule. Cav3 deficiency caused by either gene silencing or pathogenic mutations cause defective ring formation and perturbed Bin1-mediated tubulation that may explain defective T-tubule organization in mature muscles. Our results uncover new pathophysiological mechanisms that may prove relevant to myopathies caused by Cav3 or Bin1.

cell biology↗

bioRxiv2018

Clathrin plaques form mechanotransducing platforms

Large flat clathrin plaques are stable features of the plasma membrane associated with sites of strong adhesion suggesting that they could also play a role in force transduction. Here, we analyzed how clathrin plaques interact with the cytoskeleton and how they respond to mechanical cues in skeletal muscle myotubes. We show that branched actin networks surrounding clathrin plaques are directly regulated by dynamin 2, anchor intermediate filaments and sequester YAP at the plasma membrane. Dynamin 2, clathrin and desmin intermediate filaments are all required for basal YAP nucleocytoplasmic distribution and efficient nuclear translocation in response to mechanical stimuli. Dynamin 2 mutations that are responsible for centronuclear myopathy in humans disorganize the desmin network and deregulate YAP signaling both in vitro and in vivo. Thus, clathrin plaques and associated dynamin 2 are defined here as a new sensor conveying mechanical cues and integrate cell signaling with cytoskeletal regulation.

cell biology↗