title: Correction of ClC-1 splicing eliminates chloride channelopathy and myotonia in mouse models of myotonic dystrophy.
abstract: In myotonic dystrophy (dystrophia myotonica [DM]), an increase in the excitability of skeletal muscle leads to repetitive action potentials, stiffness, and delayed relaxation. This constellation of features, collectively known as myotonia, is associated with abnormal alternative splicing of the muscle-specific chloride channel (ClC-1) and reduced conductance of chloride ions in the sarcolemma. However, the mechanistic basis of the chloride channelopathy and its relationship to the development of myotonia are uncertain. Here we show that a morpholino antisense oligonucleotide (AON) targeting the 3' splice site of ClC-1 exon 7a reversed the defect of ClC-1 alternative splicing in 2 mouse models of DM. By repressing the inclusion of this exon, the AON restored the full-length reading frame in ClC-1 mRNA, upregulated the level of ClC-1 mRNA, increased the expression of ClC-1 protein in the surface membrane, normalized muscle ClC-1 current density and deactivation kinetics, and eliminated myotonic discharges. These observations indicate that the myotonia and chloride channelopathy observed in DM both result from abnormal alternative splicing of ClC-1 and that antisense-induced exon skipping offers a powerful method for correcting alternative splicing defects in DM.
authors.affiliation: Department of Neurology, University of Rochester, Rochester, New York 14618, USA.
authors.forename: Thurman M
authors.initials: TM
authors.lastname: Wheeler
authors.forename: John D
authors.initials: JD
authors.lastname: Lueck
authors.forename: Maurice S
authors.initials: MS
authors.lastname: Swanson
authors.forename: Robert T
authors.initials: RT
authors.lastname: Dirksen
authors.forename: Charles A
authors.initials: CA
authors.lastname: Thornton
mesh_terms: D000200:Action Potentials / Q000187:drug effects / Q000235:genetics; D017398:Alternative Splicing / Q000187:drug effects* / Q000235:genetics; D000818:Animals; D053447:Channelopathies / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism; D018118:Chloride Channels / Q000096:biosynthesis* / Q000235:genetics; D005091:Exons / Q000235:genetics; D051379:Mice; D009224:Myotonia Congenita / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism; D009223:Myotonic Dystrophy / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism; D020319:Oligodeoxyribonucleotides, Antisense / Q000494:pharmacology* / Q000627:therapeutic use; D022821:RNA Splice Sites / Q000235:genetics; D012508:Sarcolemma / Q000235:genetics / Q000378:metabolism
chemical_list: C086321:CLC-1 channel; D018118:Chloride Channels; D020319:Oligodeoxyribonucleotides, Antisense; D022821:RNA Splice Sites