Longitudinal Muscle Fibers (IMAGE) University of California - San Diego Caption Green muscle fibers with RCas9 (the therapeutic candidate for myotonic dystrophy) have eliminated their toxic RNA (red), whereas fibers lacking RCas9 (dark) have persisting toxic RNA (red). Credit UC San Diego Health Sciences Usage Restrictions Use photo credit 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.