Larger Mouse (IMAGE) Proceedings of the National Academy of Sciences Caption The smaller mouse is wild type; the larger mouse has been genetically modified to lack myostatin and, as a result, has larger muscles. Credit Image credit: Se-Jin Lee. 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.