[1] Univ Pavia, Monza Policlin & Pavia Mondino, Neurosci Consortium, Pavia, Italy
[2] Natl Hosp Neurol & Neurosurg, UCL Inst Neurol, MRC Ctr Neuromuscular Dis, Queen Sq, London, England
[3] UCL Inst Neurol, Dept Mol Neurosci, London, England
[4] Natl Hosp Neurol & Neurosurg, Queen Sq, London, England