mA-mRNA methylation regulates cardiac gene expression and cellular growth.

Conceptually similar to modifications of DNA, mRNAs undergo chemical modifications, which can affect their activity, localization, and stability. The most prevalent internal modification in mRNA is the methylation of adenosine at the N-position (mA). This returns mRNA to a role as a central hub of information within the cell, serving as an information carrier, modifier, and attenuator for many biological processes. Still, the precise role of internal mRNA modifications such as mA in human and murine-dilated cardiac tissue remains unknown. Transcriptome-wide mapping of mA in mRNA allowed us to catalog mA targets in human and murine hearts. Increased mA methylation was found in human cardiomyopathy. Knockdown and overexpression of the mA writer enzyme Mettl3 affected cell size and cellular remodeling both in vitro and in vivo. Our data suggest that mRNA methylation is highly dynamic in cardiomyocytes undergoing stress and that changes in the mRNA methylome regulate translational efficiency by affecting transcript stability. Once elucidated, manipulations of methylation of specific mA sites could be a powerful approach to prevent worsening of cardiac function.