1. Dubowitz Neuromuscular Centre, Institute of Child Health, University College London, London, England
2. Don Carlo Gnocchi Onlus Foundation, Milan, Italy
3. Institute of Genetic Medicine, Newcastle University, Newcastle, England
4. Section of Medical Genetics, Department of Experimental and Diagnostic Medicine, University of Ferrara, Ferrara, Italy
5. Institute of Neurology, Catholic University, Rome, Italy