Authors' contributions
Dr. Cai contributed significantly in validating antibodies in human ES cells and human EBs. Ms. Olson performed initial screening of antibodies in various cell lines. Dr. Rao initiated the project, supervised Dr. Cai, and participated in all discussions for this report. Ms. Stanley and Ms. Taylor performed Western blot analysis. Dr. Ni coordinated collaborative work between two labs, monitored the generation of the antibodies, and directed the project at R&D Systems.