The SCN4A gene belongs to a family of genes that provide instructions for making sodium channels. These channels, which transport positively charged sodium atoms (sodium ions) into cells, play a key role in a cell's ability to generate and transmit electrical signals.~The SCN4A gene provides instructions for making a critical part (the alpha subunit) of sodium channels that are abundant in muscles used for movement (skeletal muscles). For the body to move, these muscles must tense (contract) and relax in a coordinated way. Muscle contractions are triggered by the flow of ions, including sodium, into skeletal muscle cells. Channels made with the SCN4A protein control the flow of sodium ions into these cells.