A True Cause of Nonagouti Coat Color (IMAGE) Research Organization of Information and Systems Caption Nested insertion of new type of endogeneous retrovirus β4 into the VL30 is a true cause of nonagouti coat color. Credit Tsuyushi Koide, the National Institute of Genetics (NIG) in Japan Usage Restrictions Credit required. 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.