1. Departments of Genetics and Development and
2. Neurology, Columbia University, New York, New York 10032;
3. Universitäts-Kinderklinik, Abteilung Pädiatrie/Neuropädiatrie, D-37075 Göttingen, Germany;
4. Unidad de Investigación Médica en Genética Humana, Hospital de Pediatria, Centro Médico Nacional, Mexico City, Mexico D.F. 03020; and
5. Department of Biochemistry and Molecular Pharmacology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107