1. Molecular Neurogenetics Laboratory, Massachusetts General Hospital, Charlestown, MA 02129 and Harvard Medical School, Boston, MA 02115.
2. Program in Neuroscience, Harvard Medical School, and Division of Medical Genetics, The Children's Hospital, Boston, MA 02115.
3. Department of Pediatrics and Division of Medical Genetics, The Children's Hospital, and Harvard Medical School, Boston, MA 02115.
4. Day Neuromuscular Research Laboratory, Massachusetts General Hospital, Charlestown, MA 02129 and Harvard Medical School, Boston, MA 02115.