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 6

Animals immunized with MuSKCRD peptide do not display myasthenia-like characteristics.

Options: View larger image (or click on image) Download as PowerPoint
Animals immunized with MuSKCRD peptide do not display myasthenia-like ch...
(A) EAMG active transfer protocol. Black arrows indicate the days on which clinical tests were performed. (B) ELISA for total anti-MuSKCRD antibody dosing in control (CFA, n = 10) and immunized (acCRD, n = 16) animal serum (1:1,000) during the protocol. (C) ELISA for anti-MuSKCRD Ig1 and Ig2b antibody dosing in mouse serum (1:500) at the end of the immunization protocol. (D) Body weight normalized to the value obtained during the preimmunization clinical tests (day –3). (E) Forelimb muscle strength in the grip test in CFA and acCRD animals on day 91. Data are normalized relative to the CFA group. (F) Global clinical score for control and immunized animals. (G) Representative traces of CMAPs from TA muscles of a CFA and an acCRD animal after a train of 10 stimulations at 10 Hz. (H) Quantitative analysis and representation of CMAPs as described in Figure 2G. (I) Representative confocal images of isolated TA muscle fibers from CFA or immunized acCRD mice. Muscles were stained as described in Figure 3A, except that an anti-synaptophysin (Syn) antibody was used to stain nerve terminals. Scale bar: 10 μm. (J–L) Quantitative analysis of the area labeled for AChR (J), the number of AChR fragments per NMJ (K), and the percentage of presynaptic and postsynaptic overlap (L). The data are shown as mean ± SEM. n = 10 CFA and n = 16 acCRD for A–H. For J–L, n = 3 for each group, with at least 20 NMJs analyzed for each muscle. White-filled large symbols represent the mean of all the NMJs for each biological replicate (J–L); ns, not significant; **P < 0.01; ***P < 0.001; ****P < 0.0001; 2-way ANOVA with Tukey’s post hoc test (B, D, F, and H), Mann-Whitney U test (C, E, K, and L), and 2-tailed Student’s t test (J).