TY - JOUR

T1 - Characterization of two new dominant ClC-1 channel mutations associated with myotonia.

AU - Grunnet, Morten

AU - Jespersen, Thomas

AU - Colding-Jørgensen, Eskild

AU - Schwartz, Marianne

AU - Klaerke, Dan A

AU - Vissing, John

AU - Olesen, Søren-Peter

AU - Dunø, Morten

N1 - Keywords: Adult; Amino Acid Sequence; Animals; Child; Chloride Channels; Electrophysiology; Female; Genes, Dominant; Genetic Vectors; Humans; Ion Channel Gating; Male; Molecular Sequence Data; Mutation; Myotonia; Oocytes; Patch-Clamp Techniques; Pedigree; Transcription, Genetic; Xenopus laevis

PY - 2003

Y1 - 2003

N2 - Voltage-gated ClC-1 chloride channels encoded by the CLCN1 gene have a major role in setting the membrane potential in skeletal muscle. More than 60 CLCN1 mutations have been associated with myotonia congenita. These mutations are traditionally classified as recessive (Becker's disease) or dominant (Thomsen's disease). In this study, we have electrophysiologically characterized two new dominant ClC-1 mutations, thereby elucidating the observed phenotype in patients. The two ClC-1 mutants M128V and E193K were identified, and the DNA was isolated from patients and subsequently expressed in Xenopus laevis oocytes for electrophysiological characterization. Both ClC-1 mutants, M128V and E193K, showed a large rightward shift in the current-voltage relationship. In addition, the activation kinetics were slowed in the ClC-1 M128V mutant, as compared to the wild-type ClC-1. Interestingly, ClC-1 E193K revealed a change in reversal potential compared to wild-type channels. This finding supports the notion that the E193 amino acid is an important determinant in the selectivity filter of the human ClC-1 channel. The electrophysiological behavior of both mutants demonstrates a severe reduction in ClC-1 channel conductance under physiologically relevant membrane potentials. These studies thereby explain the molecular background for the observed myotonia in patients.

AB - Voltage-gated ClC-1 chloride channels encoded by the CLCN1 gene have a major role in setting the membrane potential in skeletal muscle. More than 60 CLCN1 mutations have been associated with myotonia congenita. These mutations are traditionally classified as recessive (Becker's disease) or dominant (Thomsen's disease). In this study, we have electrophysiologically characterized two new dominant ClC-1 mutations, thereby elucidating the observed phenotype in patients. The two ClC-1 mutants M128V and E193K were identified, and the DNA was isolated from patients and subsequently expressed in Xenopus laevis oocytes for electrophysiological characterization. Both ClC-1 mutants, M128V and E193K, showed a large rightward shift in the current-voltage relationship. In addition, the activation kinetics were slowed in the ClC-1 M128V mutant, as compared to the wild-type ClC-1. Interestingly, ClC-1 E193K revealed a change in reversal potential compared to wild-type channels. This finding supports the notion that the E193 amino acid is an important determinant in the selectivity filter of the human ClC-1 channel. The electrophysiological behavior of both mutants demonstrates a severe reduction in ClC-1 channel conductance under physiologically relevant membrane potentials. These studies thereby explain the molecular background for the observed myotonia in patients.

U2 - 10.1002/mus.10501

DO - 10.1002/mus.10501

M3 - Journal article

C2 - 14639587

VL - 28

SP - 722

EP - 732

JO - Muscle & Nerve

JF - Muscle & Nerve

SN - 0148-639X

IS - 6

ER -