1. Department of Human Genetics, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, U.S.A.
2. Departments of Neurology and Pediatrics, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, U.S.A.
3. Duchenne Muscular Dystrophy Research Center, University of California, Los Angeles, CA 90095, U.S.A.