1. Department of Neurology, University of California, Los Angeles, Los Angeles, CA 90095, USA.
2. Department of Neurology, University of Utah, Salt Lake City, UT 84108, USA.
3. Department of Neurology, University of California, San Francisco, San Francisco, CA 94158, USA.
4. Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT 84602, USA.
5. Department of Neurological Sciences, University of Vermont, Burlington, VT 05401, USA.
6. Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, CA 94158, USA.