MuSK cysteine-rich domain antibodies are pathogenic in a mouse model of autoimmune myasthenia gravis
Marius Halliez, Steve Cottin, Axel You, Céline Buon, Antony Grondin, Léa S. Lippens, Mégane Lemaitre, Jérome Ezan, Charlotte Isch, Yann Rufin, Mireille Montcouquiol, Nathalie Sans, Bertrand Fontaine, Julien Messéant, Rozen Le Panse, Laure Strochlic
Marius Halliez, Steve Cottin, Axel You, Céline Buon, Antony Grondin, Léa S. Lippens, Mégane Lemaitre, Jérome Ezan, Charlotte Isch, Yann Rufin, Mireille Montcouquiol, Nathalie Sans, Bertrand Fontaine, Julien Messéant, Rozen Le Panse, Laure Strochlic
View: Text | PDF
Research Article Immunology Muscle biology Neuroscience

MuSK cysteine-rich domain antibodies are pathogenic in a mouse model of autoimmune myasthenia gravis

Abstract

The neuromuscular junction (NMJ), a synapse between the motor neuron terminal and a skeletal muscle fiber, is crucial throughout life in maintaining the reliable neurotransmission required for functional motricity. Disruption of this system leads to neuromuscular disorders, such as autoimmune myasthenia gravis (MG), the most common form of NMJ disease. MG is caused by autoantibodies directed mostly against the acetylcholine receptor (AChR) or the muscle-specific kinase MuSK. Several studies report immunoreactivity to the Frizzled-like cysteine-rich Wnt-binding domain of MuSK (CRD) in patients, although the pathogenicity of the antibodies involved remains unknown. We showed here that the immunoreactivity to MuSK CRD induced by the passive transfer of anti-MuSKCRD antibodies in mice led to typical MG symptoms, characterized by a loss of body weight and a locomotor deficit. The functional and morphological integrity of the NMJ was compromised with a progressive decay of neurotransmission and disruption of the structure of presynaptic and postsynaptic compartments. We found that anti-MuSKCRD antibodies completely abolished Agrin-mediated AChR clustering by decreasing the Lrp4-MuSK interaction. These results demonstrate the role of the MuSK CRD in MG pathogenesis and improve our understanding of the underlying pathophysiological mechanisms.

Authors

Marius Halliez, Steve Cottin, Axel You, Céline Buon, Antony Grondin, Léa S. Lippens, Mégane Lemaitre, Jérome Ezan, Charlotte Isch, Yann Rufin, Mireille Montcouquiol, Nathalie Sans, Bertrand Fontaine, Julien Messéant, Rozen Le Panse, Laure Strochlic

×

Figure 4

Anti-MuSKCRD antibodies specifically inhibit Agrin-induced AChR clustering in vitro.

Options: View larger image (or click on image) Download as PowerPoint
Anti-MuSKCRD antibodies specifically inhibit Agrin-induced AChR clusteri...
(A and D) WT primary myotubes were treated with Agrin (Ag) together with increasing concentrations of MuSKCRD-immunized rabbit serum (CRD, %) or were left untreated (UT) for 16 hours (A). MuSKΔCRD primary myotubes were subjected to similar treatment with the optimal immunized rabbit serum concentration (1%, D). Cells were stained with α-bungarotoxin to label AChR clusters. Scale bar: 10 μm. (B and E) Quantitative analysis of the number of AChR clusters per mm² of myotube for A and D. (C) Lysates from WT and MuSKΔCRD primary skeletal muscle cultures were subjected to IP with control IgG or anti-MuSKCRD antibodies. Whole-lysate Western blots (Input) were performed to demonstrate the presence of the proteins of interest. The specific MuSKΔCRD (85 kDa) band overlaps with a nonspecific signal observed in all lanes. IB, immunoblot; GAPDH, loading control. The data are shown as mean ± SEM. n = 3 independent experiments; at least 50 myotubes were analyzed for each treatment in each experiment. White-filled large symbols represent the mean of all the myotubes analyzed for each biological replicate; ns, not significant; *P < 0.05; **P < 0.01; ***P < 0.001; 1-way ANOVA with Tukey’s post hoc test (B), 2-way ANOVA with Tukey’s post hoc test (E).