Big-Hearted Fish (IMAGE) University of Pennsylvania School of Medicine Caption This is the enlarged heart of a 48-hour-post-fertilization zebrafish embryo lacking the gene for ccm2. Nuclei from endothelial cells are red and junctions in between are green. Credit Yannick Blum and Markus Affolter, University of Basel, Switzerland Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.