1. Department of Genetics, Stanford University, Stanford, CA 94305, USA.
2. Department of Bioengineering, Schools of Engineering and Medicine, Stanford University, Stanford, CA 94305, USA.
3. Department of Bioengineering and Therapeutic Sciences, Schools of Pharmacy and Medicine, University of California San Francisco, San Francisco, CA 94143-2911, USA.
4. Material Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA.
5. Institute for Human Genetics, University of California San Francisco, San Francisco, CA 94143, USA.