1. Baxter Laboratory in Stem Cell Biology, Department of Microbiology and Immunology, Stanford University, Stanford, CA 94305, USA.
2. Department of Radiology, Stanford University, Stanford, CA 94305, USA.
3. Department of Biological Sciences, Columbia University, New York, NY 10027, USA.
4. Biomedical Informatics Program, Stanford University, Stanford, CA 94305, USA.
5. University of Toronto, Toronto, ON M5S 3H6, Canada.
6. DVS Sciences, Markham, ON L3R 6E7, Canada.
7. BD Biosciences, San Diego, CA 95131, USA.