In the myocardial deletion mutants, downregulated ion transport genes included Snta1 and Fxyd1. SNTA1 associates with the cardiac sodium channel SCN5A and the plasma membrane Ca2+-ATPase PMCA4B (also known as ATP2B4), and mutations in SNTA1 are associated with long QT syndrome 12 (Ueda et al., 2008). This evidence concerns the gene FXYD1 and familial long QT syndrome.