Showing papers by "Véronique Bernard published in 2009"
TL;DR: 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.
Abstract: 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 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 α-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.
154 citations
TL;DR: Surprisingly, in the striatum of the PRiMA knock-out mouse, despite a normal level of AChE mRNA, only 2–3% of wild type A cholinesterase activity is found, with the residual AchE localized in the endoplasmic reticulum, demonstrating thatPRiMA in vivo is necessary for intracellular processing of A ChE in neurons.
Abstract: Acetylcholinesterase (AChE) accumulates on axonal varicosities and is primarily found as tetramers associated with a proline-rich membrane anchor (PRiMA). PRiMA is a small transmembrane protein that efficiently transforms secreted AChE to an enzyme anchored on the outer cell surface. Surprisingly, in the striatum of the PRiMA knock-out mouse, despite a normal level of AChE mRNA, we find only 2-3% of wild type AChE activity, with the residual AChE localized in the endoplasmic reticulum, demonstrating that PRiMA in vivo is necessary for intracellular processing of AChE in neurons. Moreover, deletion of the retention signal of the AChE catalytic subunit in mice, which is the domain of interaction with PRiMA, does not restore AChE activity in the striatum, establishing that PRiMA is necessary to target and/or to stabilize nascent AChE in neurons. These unexpected findings open new avenues to modulating AChE activity and its distribution in CNS disorders.
58 citations
TL;DR: It is found that deletion of the full AChE gene is required for a pronounced alteration in respiratory phenotype, BChE is involved in respiratory muscles contraction and temperature control in del E5+6 and i1RR knockout mice, and A ChE expression requiring a gene product splice to either exons 5 and 6 or regulated by intron1 influences temperature control.
12 citations