Gordon Keller, University Health Network (IMAGE) University Health Network Caption Dr. Gordon Keller and stem cell scientists identify key regulator controlling formation of blood-forming stem cells. Credit UHN Usage Restrictions Credit UHN for photo. 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.