MicroRNAs: redefining mechanisms in cardiac disease.

MicroRNAs (miRs) regulate protein expression by inhibiting translation of expressed mRNAs. Targeting by one or more miRs of multiple mRNA transcripts encoding proteins with common functions confers nodal control over cardiac development and stress response. Dynamic coregulation of miRs and their mRNA targets has complicated understanding their biology but also provides opportunities for clinical diagnostics and therapeutics. Here, the biology of miRs is reviewed as it relates to the cardiac system, recent findings are described that illuminate miR control of cardiac development and myofiber identity, and the clinical ramifications of miR expression profiling are illustrated.