“…It is conceivable that cardiomyocyte dedifferentiation and proliferation contribute to heart regeneration in zebrafish 6,7 . Over the past decades, a number of signaling pathways and transcription factors have been reported to regulate myocardial proliferation and regeneration in zebrafish, including fibroblast growth factor, sonic hedgehog, retinoic acid, insulin-like growth factor, Notch, GATA4, Hand2, NF-kB, and Stat3 [8][9][10][11][12][13] . Retinaldehyde dehydrogenase 2, which produces retinoic acid, is activated in the epicardium and endocardium within hours after injury, and transgenic inhibition of retinoic acid receptors impairs myocardial proliferation 8 .…”