miR-1-2 gets to the heart of the matter.

ABSTRACT

Although many microRNAs (miRNAs) and their targets have been identified, the importance of miRNAs in vivo is still unclear. In this issue, Zhao et al. (2007) generate mice deficient in a cardiac-specific miRNA, miR-1-2, and reveal that this microRNA plays a crucial role in heart development and physiology.