1. Division of Genetics and Mental Retardation Center, The Children's Hospital, Department of Pediatrics, and Program in Neuroscience, Harvard Medical School, Boston, MA 02115.
2. Department of Neuropathology, Harvard Medical School, Boston, MA 02115, and Mailman Research Center, McLean Hospital, Belmont, MA 02178.
3. Division of Genetics and Mental Retardation Center, The Children's Hospital, Department of Pediatrics, and Howard Hughes Medical Institute, Harvard Medical School, Boston, MA 02115.