[1] Univ Basel Hosp, Inst Pathol, CH-4031 Basel, Switzerland
[2] Univ Basel Hosp, Dept Neurol, CH-4031 Basel, Switzerland
[3] MRC, Mol Biol Lab, Cambridge CB2 2QH, England
[4] Univ Basel Hosp, Dept Biomed, Neuromuscular Res Ctr, CH-4031 Basel, Switzerland