1. Institut de Myologie, Groupe Hospitalier Pitié-Salpêtrière, boulevard de l’Hôpital, 75651 Paris Cedex 13, France
2. The Dubowitz Neuromuscular Centre, Molecular Neurosciences Section, Developmental Neurosciences Programme, UCL Great Ormond Street Institute of Child Health, 30 Guilford Street, London, UK