1. Généthon, Centre National de la Recherche Scientifique, Unité Mixte de Recherche 8587, 91000 Evry, France.
2. Folkhälsan Institute of Genetics, Department of Medical Genetics, and Haartman Institute, University of Helsinki, FIN-00290 Helsinki, Finland.
3. Neuromuscular Research Center, Department of Neurology, Tampere University Hospital and University of Tampere, FIN-33520 Tampere, Finland.
4. Department of Neurology, Vaasa Central Hospital, FIN-65130 Vaasa, Finland.