Myocardin-related transcription factor-A induces cardiomyocyte hypertrophy.

Myocardin is a remarkably potent transcriptional coactivator expressed specifically in cardiac muscle lineages and smooth muscle cells during postnatal development. Myocardin shares homology with myocardin-related transcription factor-A (MRTF-A), which are expressed in a broad range of embryonic and adult tissues. Our previous results show that myocardin induces cardiac hypertrophy. However, the effects of MRTF-A in cardiac hypertrophy remain poorly understood. Our present work further demonstrates that myocardin plays an important role in inducing hypertrophy. At the same time, we find that overexpression of MRTF-A in neonatal rat cardiomyocytes might induce cardiomyocyte hypertrophy. Furthermore, MRTF-A expression is induced in phenylephrine, angiotensin-II, and transforming growth factor-β-stimulated cardiac hypertrophy, whereas a dominant-negative form of MRTF-A or MRTF-A siRNA strongly inhibited upregulation of hypertrophy genes in response to hypertrophic agonists in neonatal rat cardiomyocytes. Our studies indicate that besides myocardin, MRTF-A might play an important role in cardiac hypertrophy. Our findings provide novel evidence for the future studies to explore the roles of MRTFs in cardiac hypertrophy.