title: Novel chloride channel mutations leading to mild myotonia among Chinese.
abstract: We describe two Chinese families with a mild form of the myotonia congenita due to novel chloride channel (ClCN1) mutations. In one case, heterozygous I553F and H555N mutations were found. The patient shared the I553F mutation with his healthy father, and his mother had a history of mild myotonia when she was younger. In another family, autosomal dominant myotonia congenita was due to a L844F change. The physiological effects of the mutations were examined by using the two-electrode voltage-clamp technique after expression of the channels in Xenopus oocytes. All mutations drastically shifted the voltage required for half-maximal activation, more under conditions mimicking the homozygous situation, than under conditions mimicking the heterozygous situation. The larger effect was seen in the compound heterozygous situation combining the I553F and the H555N mutations. Our data suggest that myotonia congenita caused by CLCN1 mutations in Chinese have similar variable features to those found in the West.
authors.affiliation: Division of Neurology, Department of Medicine, Yong Loo Lin School of Medicine, National University of Singapore, Singapore. jm.burgunder@dkf6.unibe.ch
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Burgunder
authors.forename: Shang
authors.initials: S
authors.lastname: Huifang
authors.forename: Pascal
authors.initials: P
authors.lastname: Beguin
authors.forename: Roland
authors.initials: R
authors.lastname: Baur
authors.forename: Chew Soh
authors.initials: CS
authors.lastname: Eng
authors.forename: Raymond C S
authors.initials: RC
authors.lastname: Seet
authors.forename: Erle C H
authors.initials: EC
authors.lastname: Lim
authors.forename: Benjamin K C
authors.initials: BK
authors.lastname: Ong
authors.forename: Walter
authors.initials: W
authors.lastname: Hunziker
authors.forename: Erwin
authors.initials: E
authors.lastname: Sigel
mesh_terms: D000293:Adolescent; D000818:Animals; D002681:China; D018118:Chloride Channels / Q000235:genetics* / Q000502:physiology; D018076:DNA, Complementary / Q000235:genetics; D004576:Electromyography; D004594:Electrophysiology; D015444:Exercise / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D018482:Muscle, Skeletal / Q000473:pathology / Q000503:physiopathology; D009154:Mutation / Q000235:genetics* / Q000502:physiology*; D009222:Myotonia / Q000235:genetics* / Q000473:pathology; D009460:Neurologic Examination; D009865:Oocytes / Q000378:metabolism; D010146:Pain / Q000209:etiology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014981:Xenopus
chemical_list: C086321:CLC-1 channel; D018118:Chloride Channels; D018076:DNA, Complementary