We study how ion channels regulate the electrical excitability of cells and how defects in these channels lead to human disease. In the past three decades, mutations of ion channel genes have been found to be the primary cause for over 100 human diseases. The focus of our laboratory has been to understand the mechanistic basis for a group of inherited disorders of skeletal muscle caused by mutations of voltage-gated ion channels (Na, Ca, K, or Cl). The derangements in electrical excitability of affected muscle may cause involuntary after-contractions (myotonia) or transient episodes of severe weakness (periodic paralysis). Our lab studies the consequences of mutations identified in patients with myotonia or periodic paralysis on channel function, uses computational models of muscle excitability to explore the impact of altered channel behavior, and developed genetically-engineered mouse models to gain insights on the pathomechanisms of these disorders and to test pre-clinical strategies for therapeutics and disease modification.