How Blood Flow Dictates Gene Expression (IMAGE) University of Pennsylvania School of Medicine Caption Ultrasound of normal 12-day-old mouse embryos (wild-type) versus endothelial Klf2 knockout embryos reveals pericardial edema, a sign of heart failure (arrowhead). Credit John Lee, MD, PhD & Mark Kahn, MD of Penn; Qing Yu, PhD & Cecilia Lo, PhD, National Institutes of Health, Developmental Cell 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.