The importance of the AR in cardiac development and function is highlighted by the phenotype of AR knockout animals, as ARKO mice have a significant reduction in cardiac hypertrophy induced by Ang II and heart-to-body weight ratio compared with WT, events associated with lower activation of extracellular signal-regulated kinases (ERKs) 1/2 and ERK5. The gene discussed is AR; the disease is cardiac hypertrophy.