[1] UCL, UCL Inst Neurol, Sobell Dept Motor Neurosci & Movement Disorders, London WC1N 3BG, England
[2] Univ Med Ctr Hamburg Eppendorf UKE, Dept Neurol, Hamburg, Germany
[3] Univ Lubeck, Inst Neurogenet, Dept Paediat & Adult Movement Disorders & Neurops, Lubeck, Germany
[4] UCL Inst Neurol, Dept Mol Neurosci, Reta Lilla Weston Lab, London, England
[5] Univ Milan, IRCCS Ist Auxologico Italiano, Dept Neurol & Lab Neurosci, Milan, Italy
[6] Univ Milan, Dino Ferrari Ctr, Dept Pathophysiol & Transplantat, Milan, Italy
[7] UCL, MRC Ctr Neuromuscular Dis, London, England