Fending for a Braveheart.

Cell (2013) 152, 570–583 Dev Cell (2013) 24, 206–214 Recent articles by Klattenhoff et al (2013) and Grote et al (2013) identify long non-coding RNAs, or lncRNAs, important for specifying the cardiac lineage. Depletion of a lncRNA, aptly named , resulted in loss of beating cardiomyocytes during embryonic stem (ES) cell differentiation and failure to activate a key network of cardiac transcription factors. Immunoprecipitation of the protein complex associated with revealed that the lncRNA physically interacts with epigenetic machinery that regulates cardiac gene expression. Similarly, a second lncRNA, also interacts with epigenetic regulators to promote proper cardiac gene expression and function in mice. These studies highlight the importance of lncRNAs during lineage commitment and provide a new layer of regulation involved in determining cardiac cell fate.