Brain (IMAGE) University of North Carolina Health Care Caption When the gene Rabep2 is deficient, the number and diameter of collateral blood vessels -- normally present during brain development -- are reduced by 50 to 60 percent, and the amount of brain tissue that dies after stroke is more than doubled. Credit Courtesy of the Faber lab, UNC School of Medicine Usage Restrictions credit properly 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.