CLCN1 and Thomsen and Becker disease: Voltage-gated chloride channels are one of the main classes ofbiological chloride transporting proteins. For example, CLC-1 is the main chloride channel in skeletal muscleand is a voltage-gated channel that is deactivated at negative voltage.This is particularly interesting because in skeletal muscle the restingconductance is dominated by Cl– and not K+ like other tissues, and mutations in CLC-1 are the cause of myotonia congenita.