NODAL 1 (IMAGE) Rice University Caption Rice postdoctoral researcher Lizhong Liu is lead author of a study that details the mechanism by which a protein known as Lefty pumps the brakes as human embryos begin to differentiate into bones, soft tissues and organs. Credit Warmflash Lab/Rice University Usage Restrictions None License Original 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.