1. Blau Laboratory, Stanford School of Medicine, Stanford, CA 94305, USA.
2. Baxter Laboratory for Stem Cell Biology, Department of Microbiology and Immunology, Institute for Stem Cell Biology and Regenerative Medicine, Stanford School of Medicine, Stanford, CA 94305, USA.
3. Vincent Coates Foundation Mass Spectrometry Laboratory, Stanford University, Stanford, CA, USA.
4. Nolan Laboratory, Stanford School of Medicine, Stanford, CA 94305, USA.