NFATc2 Is a Necessary Mediator of Calcineurin-dependent Cardiac Hypertrophy and Heart Failure

One major intracellular signaling pathway involved in heart failure employs the phosphatase calcineurin and its downstream transcriptional effector nuclear factor of activated T-cells (NFAT). In vivo evidence for the involvement of NFAT factors in heart failure development is still ill defined. Here we reveal that nfatc2 transcripts outnumber those from other nfat genes in the unstimulated heart by severalfold. Transgenic mice with activated calcineurin in the postnatal myocardium crossbred with nfatc2-null mice revealed a significant abrogation of calcineurin-provoked cardiac growth, indicating that NFATc2 plays an important role downstream of calcineurin and validates the original hypothesis that calcineurin mediates myocyte hypertrophy through activation of NFAT transcription factors. In the absence of NFATc2, a clear protection against the geometrical, functional, and molecular deterioration of the myocardium following biomechanical stress was also evident. In contrast, physiological cardiac enlargement in response to voluntary exercise training was not affected in nfatc2-null mice. Combined, these results reveal a major role for the NFATc2 transcription factor in pathological cardiac remodeling and heart failure.