1. University of California at Los Angeles School of Medicine, Los Angeles, California, USA
2. National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, USA
3. Klinikum der Universität München, Munich, Germany
4. Hospital for Sick Children, Toronto, Ontario, Canada
5. Ann and Robert H. Lurie Children's Hospital of Chicago, Chicago, Illinois, USA
6. Institute of Myology, Pitié-Salpêtrière Hospital, Paris, France.