<i>egr3</i> is a mechanosensitive transcription factor gene required for cardiac valve morphogenesis.

Abstract

Biomechanical forces, and their molecular transducers, including key mechanosensitive transcription factor genes, such as <i>KLF2</i>, are required for cardiac valve morphogenesis. However, <i>klf2</i> mutants fail to completely recapitulate the valveless phenotype observed under no-flow conditions. Here, we identify the transcription factor EGR3 as a conserved biomechanical force transducer critical for cardiac valve formation. We first show that <i>egr3</i> null zebrafish display a complete and highly penetrant loss of valve leaflets, leading to severe blood regurgitation. Using tissue-specific loss- and gain-of-function tools, we find that during cardiac valve formation, Egr3 functions cell-autonomously in endothelial cells, and identify one of its effectors, the nuclear receptor Nr4a2b. We further find that mechanical forces up-regulate <i>egr3</i>/<i>EGR3</i> expression in the developing zebrafish heart and in porcine valvular endothelial cells, as well as during human aortic valve remodeling. Altogether, these findings reveal that EGR3 is necessary to transduce the biomechanical cues required for zebrafish cardiac valve morphogenesis, and potentially for pathological aortic valve remodeling in humans.