1. Department of Stem Cell and Regenerative Biology, Department of Molecular and Cellular Biology, Harvard Stem Cell Institute, Harvard University, 16 Divinity Avenue, Cambridge, MA 02138, USA.
2. Department of Cell Biology, University of Virginia School of Medicine, Charlottesville, VA 22908, USA.
3. Institute for Molecular Bioscience, University of Queensland, St Lucia 4072, Australia.
4. Department of Physics and Biology, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA.
5. Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA.
6. Departments of Pediatrics and Neurological Surgery, Howard Hughes Medical Institute, University of California San Francisco, 35 Medical Center Way, San Francisco, CA 94143, USA.
7. Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, MA 02115, USA.