1. Department of Anatomy and Cellular Biology, Harvard Medical School, Boston, MA 02115.
2. Department of Biochemistry and Molecular Biology, Harvard University, Cambridge, MA 02138.
3. Biogen Research Corp., Cambridge, MA 02142.
4. Department of Genetics and Development and the Center for Neurobiology and Behavior, College of Physicians and Surgeons, Columbia University, New York, NY 10032.