title: Neuromyotonia in mice with hereditary myelinopathies.
abstract: The purpose of this study was to further characterize neuromyotonia in mice with deletions and point mutations of myelin protein genes. Clinical observation showed irregular stretching of the hindlimbs, tremor and generalized myokymia in mice with targeted deletions of the genes encoding myelin protein zero (P0-/-) or peripheral myelin protein 22 (Pmp22-/-), and Trembler mice, which carry a point mutation of Pmp22. By electromyography (EMG), we found irregular high-frequency bursts of spontaneous motor unit activity and rhythmic doublet or multiplet discharges of motor units in these mouse models of human hereditary neuropathies. The EMG signs are typical for neuromyotonia and myokymia, respectively. The activity persisted after a proximal nerve section in many cases, localizing the generator to the peripheral nerve or the muscle. We now show that blocking neuromuscular transmission with suxamethonium abolished the spontaneous activity, ruling out a muscle origin. Phenytoin ameliorated the motor behavior. Taken together, our study shows that neuromyotonia develops in different mouse models of hereditary myelinopathies. This indicates that spontaneous motor unit activity may underlie neuromyotonia, which is occasionally observed in Charcot-Marie-Tooth disease. These animal models will be useful to study the pathogenesis of neuromyotonia.
authors.affiliation: Department of Neurology, Julius-Maximilians-University, Josef-Schneider-Str. 11, D-97080 Würzburg, Germany. NEUK152@mail.uni-wuerzburg.de
authors.forename: J
authors.initials: J
authors.lastname: Zielasek
authors.forename: R
authors.initials: R
authors.lastname: Martini
authors.forename: U
authors.initials: U
authors.lastname: Suter
authors.forename: K V
authors.initials: KV
authors.lastname: Toyka
mesh_terms: D000818:Animals; D017353:Gene Deletion; D015417:Hereditary Sensory and Motor Neuropathy / Q000188:drug therapy / Q000235:genetics* / Q000503:physiopathology; D006801:Humans; D020386:Isaacs Syndrome / Q000188:drug therapy / Q000235:genetics* / Q000503:physiopathology; D051379:Mice; D018345:Mice, Knockout; D008818:Mice, Neurologic Mutants; D009043:Motor Activity / Q000187:drug effects; D018993:Myelin P0 Protein / Q000172:deficiency / Q000235:genetics* / Q000502:physiology; D009185:Myelin Proteins / Q000172:deficiency / Q000235:genetics* / Q000502:physiology; D010672:Phenytoin / Q000627:therapeutic use; D017354:Point Mutation; D012584:Sciatic Nerve / Q000503:physiopathology
chemical_list: D018993:Myelin P0 Protein; D009185:Myelin Proteins; C073687:PMP22 protein, human; C489545:Pmp22 protein, mouse; D010672:Phenytoin