CATSPER1 Gene and Male Infertility (image) University of Iowa Caption Mouse studies have shown that the CATSPER1 gene is present in sperm and is essential for normal sperm motion during fertilization. The left side of the diagram illustrates normal sperm fertilizing an egg. The right side of the diagram illustrates that sperm lacking the CatSper1 protein are not able to penetrate an outer layer of the egg, known as the zona pellucida, preventing normal fertilization. Credit University of Iowa. Image adapted from Avenarius et al 2009 AJHG in press. Usage Restrictions Image may only be used with appropriate caption or credit. 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.