1. Department of Pediatrics, The University of Arizona, Tucson, AZ, USA
2. Department of Neurology and School of Medicine and Dentistry, University of Rochester, Rochester, NY, USA
3. The University of Iowa Wellstone Muscular Dystrophy Cooperative Research Center, Iowa City, IA, USA
4. Birth Defects Registry and Surveillance Section, New York State Department of Health, Albany, NY, USA
5. School of Medicine, University of Colorado, Denver, CO, USA
6. Department of Pediatrics, Joan and Sanford I. Weill Medical College, Cornell University, New York, NY, USA