1. Department of Neurological Surgery, University of California, San Francisco, San Francisco, CA 94143, USA.
2. Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell Research, University of California, San Francisco, San Francisco, CA 94143, USA.
3. Medical Scientist Training Program, University of California, San Francisco, San Francisco, CA 94143, USA.
4. Biomedical Sciences Graduate Program, University of California, San Francisco, San Francisco, CA 94143, USA.
5. Neuroscience Graduate Program, University of California, San Francisco, San Francisco, CA 94143, USA.
6. San Francisco Veterans Affairs Medical Center, San Francisco, CA 94121, USA.
7. Department of Human Anatomy, West China School of Basic Medical Sciences and Forensic Medicine, Sichuan University, Chengdu 610041, Sichuan, P.R. China.
8. Developmental and Stem Cell Biology Graduate Program, University of California, San Francisco, San Francisco, CA 94143, USA.
9. Department of Pathology, University of Michigan, Ann Arbor, MI 48109, USA.