Jeanine Koenig

Publications of Jeanine Koenig

• Identification of an Agrin Mutation that Causes Congenital Myasthenia and Affects Synapse Function.

  Authors: Caroline Huzé, Stéphanie Bauché, Pascale Richard, Frédéric Chevessier, Evelyne Goillot, Karen Gaudon, Asma Ben Ammar, Annie Chaboud, Isabelle Grosjean, Heba-Aude Lecuyer [......] Nektaria Alexandri, Thierry Kuntzer, Michel Fardeau, Emmanuel Fournier, Andrea Brancaccio, Markus A Rüegg, Jeanine Koenig, Bruno Eymard, Laurent Schaeffer, Daniel Hantaï

  American journal of human genetics. 07/2009;

  We report the case of a congenital myasthenic syndrome due to a mutation in AGRN, the gene encoding agrin, an extracellular matrix molecule released by the nerve and critical for formation of theWe report the case of a congenital myasthenic syndrome due to a mutation in AGRN, the gene encoding agrin, an extracellular matrix molecule released by the nerve and critical for formation of the neuromuscular junction. Gene analysis identified a homozygous missense mutation, c.5125G>C, leading to the p.Gly1709Arg variant. The muscle-biopsy specimen showed a major disorganization of the neuromuscular junction, including changes in the nerve-terminal cytoskeleton and fragmentation of the synaptic gutters. Experiments performed in nonmuscle cells or in cultured C2C12 myotubes and using recombinant mini-agrin for the mutated and the wild-type forms showed that the mutated form did not impair the activation of MuSK or change the total number of induced acetylcholine receptor aggregates. A solid-phase assay using the dystrophin glycoprotein complex showed that the mutation did not affect the binding of agrin to alpha-dystroglycan. Injection of wild-type or mutated agrin into rat soleus muscle induced the formation of nonsynaptic acetylcholine receptor clusters, but the mutant protein specifically destabilized the endogenous neuromuscular junctions. Importantly, the changes observed in rat muscle injected with mutant agrin recapitulated the pre- and post-synaptic modifications observed in the patient. These results indicate that the mutation does not interfere with the ability of agrin to induce postsynaptic structures but that it dramatically perturbs the maintenance of the neuromuscular junction.

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• A mouse model for congenital myasthenic syndrome due to MuSK mutations reveals defects in structure and function of neuromuscular junctions.

  Authors: Frédéric Chevessier, Emmanuelle Girard, Jordi Molgó, Bartling Sönke, Jeanine Koenig, Daniel Hantaï, Veit Witzemann

  Human molecular genetics. 09/2008;

  In the muscle-specific tyrosine kinase receptor gene MUSK a heteroallelic missense and a null mutation were identified in a patient suffering from a congenital myasthenic syndrome. We generated oneIn the muscle-specific tyrosine kinase receptor gene MUSK a heteroallelic missense and a null mutation were identified in a patient suffering from a congenital myasthenic syndrome. We generated one mouse line carrying the homozygous missense mutation V789M in musk (musk(V789M/V789M) mice) and a second hemizygous line, resembling the patient genotype, with the V789M mutation on one allele and an allele lacking the kinase domain (musk(V789M/-)mice). We report here that musk(V789M/V789M) mice present no obvious abnormal phenotype regarding weight, muscle function, and viability. In contrast, adult musk(V789M/-) mice suffer from severe muscle weakness, exhibit shrinkage of pelvic and scapular regions, and hunchback. Musk(V789M/-) diaphragm develops less force upon direct or nerve-induced stimulation. A profound tetanic fade is observed following nerve-evoked muscle contraction and fatigue resistance is severely impaired upon a train of tetanic nerve stimulations. Electrophysiological measurements indicate that fatigable muscle weakness is due to impaired neurotransmission as observed in a patient suffering from a congenital myasthenic syndrome. The diaphragm of adult musk(V789M/-) mice exhibits pronounced changes in endplate architecture, distribution and innervation pattern. Thus, the missense mutation V789M in MuSK acts as a hypomorphic mutation and leads to insufficiency in MuSK function in musk(V789M/-) mutants. These mutant mice represent valuable models for elucidating the roles of MuSK for synapse formation, maturation, and maintenance as well as for studying the pathophysiology of a congenital myasthenic syndrome due to MuSK mutations.

• A synonymous CHRNE mutation responsible for an aberrant splicing leading to congenital myasthenic syndrome.

  Authors: Pascale Richard, Karen Gaudon, Emmanuel Fournier, Christopher Jackson, Stéphanie Bauché, Hafedh Haddad, Jeanine Koenig, Bernard Echenne, Daniel Hantaï, Bruno Eymard

  Neuromuscular disorders : NMD. 06/2007; 17(5):409-14.

  Congenital myasthenic syndromes (CMSs) are rare hereditary disorders transmitted in a recessive or dominant pattern, and are caused by mutations in the genes encoding proteins of the neuromuscularCongenital myasthenic syndromes (CMSs) are rare hereditary disorders transmitted in a recessive or dominant pattern, and are caused by mutations in the genes encoding proteins of the neuromuscular junction. They are classified in three groups depending on the origin of the molecular defect. Postsynaptic defects are the most frequent and have been reported to be partly due to abnormalities of the acetylcholine receptor, and particularly to mutations in CHRNE, the gene encoding the acetylcholine receptor epsilon-subunit. In a Portuguese patient with a mild form of recessive CMS, CHRNE sequencing identified an unknown homozygous transition. This variation affects the third nucleotide of the glycine 285 condon, and leads to a synonymous variant. Analysis of transcripts demonstrated that this single change creates a new splice donor site located 4 nucleotides upstream of the normal site, leading to a deletion and generating a frameshift in exon 9 followed by a premature termination codon. This paper relates the identification of a synonymous mutation in CHRNE that creates a new splice donor site leading to an aberrant splicing of pre-mRNAs and so to their instability. This is the first synonymous mutation in CHRNE known to generate a cryptic splice site, and mRNA quantification strongly suggests that it is the disease-causing mutation.

• The origin of tubular aggregates in human myopathies.

  Authors: Frédéric Chevessier, Stéphanie Bauché-Godard, Jean-Paul Leroy, Jeanine Koenig, Marion Paturneau-Jouas, Bruno Eymard, Daniel Hantaï, Martine Verdière-Sahuqué

  The Journal of pathology. 12/2005; 207(3):313-23.

  Tubular aggregates are morphological abnormalities characterized by the accumulation of densely packed tubules in skeletal muscle fibres. To improve knowledge of tubular aggregates, the formation andTubular aggregates are morphological abnormalities characterized by the accumulation of densely packed tubules in skeletal muscle fibres. To improve knowledge of tubular aggregates, the formation and role of which are still unclear, the present study reports the electron microscopic analysis and protein characterization of tubular aggregates in six patients with 'tubular aggregate myopathy'. Three of the six patients also presented with myasthenic features. A large panel of immunochemical markers located in the sarcoplasmic reticulum, T-tubules, mitochondria, and nucleus was used. Despite differences in clinical phenotype, the composition of tubular aggregates, which contained proteins normally segregated differently along the sarcoplasmic reticulum architecture, was similar in all patients. All of these proteins, calsequestrin, RyR, triadin, SERCAs, and sarcalumenin, are involved in calcium uptake, storage, and release. The dihydropyridine receptor, DHPR, specifically located in the T-tubule, was also present in tubular aggregates in all patients. COX-2 and COX-7 mitochondrial proteins were not found in tubular aggregates, despite being observed close to them in the muscle fibre. The nuclear membrane protein emerin was found in only one case. Electron microscopy revealed vesicular budding from nuclei, and the presence of SAR-1 GTPase protein in tubular aggregates shown by immunochemistry, in all patients, suggests that tubular aggregates could arise from endoplasmic reticulum exit sites. Taken together, these results cast new light on the composition and significance of tubular aggregates.

• [Pathophysiological characterization of congenital myasthenic syndromes: the example of mutations in the MUSK gene]

  Authors: Frédéric Chevessier, Brice Faraut, Aymeric Ravel-Chapuis, Pascale Richard, Karen Gaudon, Stéphanie Bauché, Cassandra Prioleau, Ruth Herbst, Evelyne Goillot, Christine Ioos [......] Shahram Attarian, Jean-Paul Leroy, Emmanuel Fournier, Claire Legay, Laurent Schaeffer, Jeanine Koenig, Michel Fardeau, Bruno Eymard, Jean Pouget, Daniel Hantaï

  Journal de la Société de biologie. 02/2005; 199(1):61-77.

  Congenital myasthenic syndromes (CMS) are rare genetic diseases affecting the neuromuscular junction (NMJ) and are characterized by a dysfunction of the neurotransmission. They are heterogeneous atCongenital myasthenic syndromes (CMS) are rare genetic diseases affecting the neuromuscular junction (NMJ) and are characterized by a dysfunction of the neurotransmission. They are heterogeneous at their pathophysiological level and can be classified in three categories according to their presynaptic, synaptic and postsynaptic origins. We report here the first case of a human neuromuscular transmission dysfunction due to mutations in the gene encoding a postsynaptic molecule, the muscle-specific receptor tyrosine kinase (MuSK). Gene analysis identified two heteroallelic mutations, a frameshift mutation (c.220insC) and a missense mutation (V790M). The muscle biopsy showed dramatic pre- and postsynaptic structural abnormalities of the neuromuscular junction and severe decrease in acetylcholine receptor (AChR) epsilon-subunit and MuSK expression. In vitro and in vivo expression experiments were performed using mutant MuSK reproducing the human mutations. The frameshift mutation led to the absence of MuSK expression. The missense mutation did not affect MuSK catalytic kinase activity but diminished expression and stability of MuSK leading to decreased agrin-dependent AChR aggregation, a critical step in the formation of the neuromuscular junction. In electroporated mouse muscle, overexpression of the missense mutation induced, within a week, a phenotype similar to the patient muscle biopsy: a severe decrease in synaptic AChR and an aberrant axonal outgrowth. These results strongly suggest that the missense mutation, in the presence of a null mutation on the other allele, is responsible for the dramatic synaptic changes observed in the patient.

• MUSK, a new target for mutations causing congenital myasthenic syndrome.

  Authors: Frédéric Chevessier, Brice Faraut, Aymeric Ravel-Chapuis, Pascale Richard, Karen Gaudon, Stéphanie Bauché, Cassandra Prioleau, Ruth Herbst, Evelyne Goillot, Christine Ioos [......] Shahram Attarian, Jean-Paul Leroy, Emmanuel Fournier, Claire Legay, Laurent Schaeffer, Jeanine Koenig, Michel Fardeau, Bruno Eymard, Jean Pouget, Daniel Hantaï

  Human molecular genetics. 01/2005; 13(24):3229-40.

  We report the first case of a human neuromuscular transmission dysfunction due to mutations in the gene encoding the muscle-specific receptor tyrosine kinase (MuSK). Gene analysis identified twoWe report the first case of a human neuromuscular transmission dysfunction due to mutations in the gene encoding the muscle-specific receptor tyrosine kinase (MuSK). Gene analysis identified two heteroallelic mutations, a frameshift mutation (c.220insC) and a missense mutation (V790M). The muscle biopsy showed dramatic pre- and postsynaptic structural abnormalities of the neuromuscular junction and severe decrease in acetylcholine receptor (AChR) epsilon-subunit and MuSK expression. In vitro and in vivo expression experiments were performed using mutant MuSK reproducing the human mutations. The frameshift mutation led to the absence of MuSK expression. The missense mutation did not affect MuSK catalytic kinase activity but diminished expression and stability of MuSK leading to decreased agrin-dependent AChR aggregation, a critical step in the formation of the neuromuscular junction. In electroporated mouse muscle, overexpression of the missense mutation induced, within a week, a phenotype similar to the patient muscle biopsy: a severe decrease in synaptic AChR and an aberrant axonal outgrowth. These results strongly suggest that the missense mutation, in the presence of a null mutation on the other allele, is responsible for the dramatic synaptic changes observed in the patient.

• Congenital myasthenic syndromes.

  Authors: Daniel Hantaï, Pascale Richard, Jeanine Koenig, Bruno Eymard

  Current opinion in neurology. 11/2004; 17(5):539-51.

  PURPOSE OF REVIEW: Congenital myasthenic syndromes are a heterogeneous group of diseases caused by genetic defects affecting neuromuscular transmission. In this article, a strategy that leads to thePURPOSE OF REVIEW: Congenital myasthenic syndromes are a heterogeneous group of diseases caused by genetic defects affecting neuromuscular transmission. In this article, a strategy that leads to the diagnosis of congenital myasthenic syndromes is presented, and recent advances in the clinical, genetic and molecular aspects of congenital myasthenic syndrome are outlined. RECENT FINDINGS: Besides the identification of new mutations in genes already known to be implicated in congenital myasthenic syndromes (genes for the acetylcholine receptor subunits and the collagen tail of acetylcholinesterase), mutations in other genes have more recently been discovered and characterized (genes for choline acetyltransferase, rapsyn, and the muscle sodium channel SCN4A). Fluoxetine has recently been proposed as an alternative treatment for 'slow channel' congenital myasthenic syndrome. SUMMARY: The characterization of congenital myasthenic syndromes comprises two complementary steps: establishing the diagnosis and identifying the pathophysiological type of congenital myasthenic syndrome. Characterization of the type of congenital myasthenic syndrome has allowed it to be classified as caused by presynaptic, synaptic and postsynaptic defects. A clinically and muscle histopathologically oriented genetic study has identified several genes in which mutations cause the disease. Despite comprehensive characterization, the phenotypic expression of one given gene involved is variable, and the aetiology of many congenital myasthenic syndromes remains to be discovered.

• Thrombin reduces MuSK and acetylcholine receptor expression along with neuromuscular contact size in vitro.

  Authors: Brice Faraut, Aymeric Ravel-Chapuis, Sylvie Bonavaud, Martine Jandrot-Perrus, Martine Verdière-Sahuqué, Laurent Schaeffer, Jeanine Koenig, Daniel Hantaï

  The European journal of neuroscience. 05/2004; 19(8):2099-108.

  In the course of studies on thrombin and its inhibitor(s) in synaptic plasticity, we addressed the question of their roles in the formation of neuromuscular junctions (NMJ) and used a model of ratIn the course of studies on thrombin and its inhibitor(s) in synaptic plasticity, we addressed the question of their roles in the formation of neuromuscular junctions (NMJ) and used a model of rat neuron-myotube cocultures. We report that the size of acetylcholinesterase (AChE) patches used as a marker of neuromuscular contacts was decreased in the presence of either thrombin or SFLLRN, the agonist peptide of the thrombin receptor PAR-1, whereas it was increased with hirudin, a specific thrombin inhibitor. In an attempt to relate these neuromuscular contact size variations to molecular changes, we studied muscle-specific tyrosine kinase receptor (MuSK), acetylcholine receptor (AChR) and rapsyn expression in the presence of thrombin. We showed that thrombin did not change rapsyn gene and protein expression. However, the expression of MuSK and surface AChR proteins was diminished in both myotube cultures and neuron-myotube cocultures. These reductions in protein expression were associated with a decrease in MuSK and AChR alpha-subunit gene expression in myotube cultures but not in neuron-myotube cocultures. Moreover, the expression of the AChR epsilon-subunit gene, specifically enhanced by neuron-released factors, was not modified by thrombin in neuron-myotube cocultures. This suggests that thrombin did not affect the expression of synaptic AChRs enhanced by neuron-released factors but rather reduced the level of extrasynaptic AChRs. Taken together, these results indicate that thrombin in balance with its inhibitor(s) could modulate the formation of neuromuscular contacts in vitro by affecting the expression of two essential molecules in NMJ postsynaptic differentiation, MuSK and AChR.

• Electrophysiological and morphological characterization of a case of autosomal recessive congenital myasthenic syndrome with acetylcholine receptor deficiency due to a N88K rapsyn homozygous mutation.

  Authors: Eriko Yasaki, Cassandra Prioleau, Julien Barbier, Pascale Richard, Frédéric Andreux, Jean-Paul Leroy, Philippe Dartevelle, Jeanine Koenig, Jordi Molgó, Michel Fardeau, Bruno Eymard, Daniel Hantaï

  Neuromuscular disorders : NMD. 02/2004; 14(1):24-32.

  Congenital myasthenic syndromes are rare heterogeneous hereditary disorders, which lead to defective neuromuscular transmission resulting in fatigable muscle weakness. Post-synaptic congenitalCongenital myasthenic syndromes are rare heterogeneous hereditary disorders, which lead to defective neuromuscular transmission resulting in fatigable muscle weakness. Post-synaptic congenital myasthenic syndromes are caused by acetylcholine receptor kinetic abnormalities or by acetylcholine receptor deficiency. Most of the congenital myasthenic syndromes with acetylcholine receptor deficiency are due to mutations in acetylcholine receptor subunit genes. Some have recently been attributed to mutations in the rapsyn gene. Here, we report the case of a 28-year-old French congenital myasthenic syndrome patient who had mild diplopia and fatigability from the age of 5 years. His muscle biopsy revealed a marked reduction in rapsyn and acetylcholine receptor at neuromuscular junctions together with a simplification of the subneural apparatus structure. In this patient, we excluded mutations in the acetylcholine receptor subunit genes and identified the homozygous N88K rapsyn mutation, which has already been shown by cell expression to impair rapsyn and acetylcholine receptor aggregation at the neuromuscular junction. The detection of the N88K mutation at the heterozygous state in five of 300 unrelated control subjects shows that this mutation is not infrequent in the healthy population. Electrophysiological measurements on biopsied intercostal muscle from this patient showed that his rapsyn mutation-induced fatigable weakness is expressed not only in a diminution in acetylcholine receptor membrane density but also in a decline of endplate potentials evoked at low frequency.

• Thrombin downregulates muscle acetylcholine receptors via an IP3 signaling pathway by activating its G-protein-coupled protease-activated receptor-1.

  Authors: Brice Faraut, Julien Barbier, Aymeric Ravel-Chapuis, Marie-Agnès Doyennette, Martine Jandrot-Perrus, Martine Verdière-Sahuqué, Laurent Schaeffer, Jeanine Koenig, Daniel Hantaï

  Journal of cellular physiology. 08/2003; 196(1):105-12.

  Regulation of thrombin activity may be required during skeletal muscle differentiation since the thrombin tissue inhibitor protease nexin-1 appears at the myotube stage before being localized at theRegulation of thrombin activity may be required during skeletal muscle differentiation since the thrombin tissue inhibitor protease nexin-1 appears at the myotube stage before being localized at the neuromuscular synapse. Here, we have used a model of rat fetal myotube primary cultures to study the effect of thrombin on acetylcholine receptor (AChR) expression, which is enhanced at the myotube stage. Our results show that thrombin decreases both the number of surface AChRs (AChRn) and AChR alpha-subunit gene expression. Using the agonist peptide SFLLRN, we establish that the AChRn decrease is mediated by the G protein-coupled thrombin receptor "protease-activated receptor-1" (PAR-1). Moreover, the specific thrombin inhibitor hirudin increases AChRn by inhibiting the thrombin intrinsically present in the cultures. We further demonstrate that the activation of PAR-1 by thrombin induces intracellular calcium movements that are blocked by 2-APB, an inhibitor of inositol 1,4,5-triphosphate (IP3)-induced calcium release. These calcium signals are more intense in nuclei than in the cytoplasm and are consistent with the intracellular distribution of IP3 receptor that we find in the cytoplasm in a cross-striated pattern and at a high level in the nuclear envelope zone. Finally, we show that the blockade of these IP3-induced calcium signals by 2-APB prevents the AChRn decrease induced by thrombin. Our results thus demonstrate that thrombin downregulates AChR expression by activating PAR-1 and that this effect is mediated via an IP3 signaling pathway.

• Two novel mutations in the COLQ gene cause endplate acetylcholinesterase deficiency.

  Authors: Keiko Ishigaki, Delphine Nicolle, Eric Krejci, Jean-Paul Leroy, Jeanine Koenig, Michel Fardeau, Bruno Eymard, Daniel Hantaï

  Neuromuscular disorders : NMD. 04/2003; 13(3):236-44.

  Congenital myasthenic syndromes with endplate acetylcholinesterase deficiency are very rare autosomal recessive diseases, characterized by onset of the disease in childhood, general weaknessCongenital myasthenic syndromes with endplate acetylcholinesterase deficiency are very rare autosomal recessive diseases, characterized by onset of the disease in childhood, general weakness increased by exertion, ophthalmoplegia and refractoriness to anticholinesterase drugs. To date, all reported cases are due to mutations within the gene encoding ColQ, a specific collagen that anchors acetylcholinesterase in the basal lamina at the neuromuscular junction. We identified two new cases of congenital myasthenic syndromes with endplate acetylcholinesterase deficiency. The two patients showed different phenotypes. The first patient had mild symptoms in childhood, which worsened at 46 years with severe respiratory insufficiency. The second patient had severe symptoms from birth but improved during adolescence. In both cases, the absence of acetylcholinesterase was demonstrated by morphological and biochemical analyses, and heteroallelic mutations in the COLQ gene were found. Both patients presented a novel splicing mutation (IVS1-1G-->A) affecting the exon encoding the proline-rich attachment domain (PRAD), which interacts with acetylcholinesterase. This splicing mutation was associated with two different mutations, both of which cause truncation of the collagen domain (a known 788insC mutation belonging to one patient and a novel R236X to the other) and may impair its trimeric organization. The close similarity of the mutations of these two patients with different phenotypes suggests that other factors may modify the severity of this disease.

• A mouse model for congenital myasthenic syndrome due to MuSK mutations reveals defects in structure and function of neuromuscular junctions

  Authors: Frédéric Chevessier, Emmanuelle Girard, Jordi Molgó, Sönke Bartling, Jeanine Koenig, Daniel Hantaï, Veit Witzemann

  In the muscle-specific tyrosine kinase receptor gene MUSK , a heteroallelic missense and a null mutation were identified in a patient suffering from a congenital myasthenic syndrome (CMS). WeIn the muscle-specific tyrosine kinase receptor gene MUSK , a heteroallelic missense and a null mutation were identified in a patient suffering from a congenital myasthenic syndrome (CMS). We generated one mouse line carrying the homozygous missense mutation V789M in musk ( musk V789M/V789M mice) and a second hemizygous line, resembling the patient genotype, with the V789M mutation on one allele and an allele lacking the kinase domain ( musk V789M/− mice). We report here that musk V789M/V789M mice present no obvious abnormal phenotype regarding weight, muscle function and viability. In contrast, adult musk V789M/− mice suffer from severe muscle weakness, exhibit shrinkage of pelvic and scapular regions and hunchback. Musk V789M/− diaphragm develops less force upon direct or nerve-induced stimulation. A profound tetanic fade is observed following nerve-evoked muscle contraction, and fatigue resistance is severely impaired upon a train of tetanic nerve stimulations. Electrophysiological measurements indicate that fatigable muscle weakness is due to impaired neurotransmission as observed in a patient suffering from a CMS. The diaphragm of adult musk V789M/− mice exhibits pronounced changes in endplate architecture, distribution and innervation pattern. Thus, the missense mutation V789M in MuSK acts as a hypomorphic mutation and leads to insufficiency in MuSK function in musk V789M/− mutants. These mutant mice represent valuable models for elucidating the roles of MuSK for synapse formation, maturation and maintenance as well as for studying the pathophysiology of a CMS due to MuSK mutations.