1. MRC Centre for Neuromuscular Diseases, UCL Institute of Neurology and National Hospital for Neurology and Neurosurgery, Queen Square, London WC1N 3BG, UK;2. Mitochondrial Research Group, Clinical and Molecular Genetics Unit, UCL Institute of Child Health, London WC1N 1EH, UK;3. Neurogenetics Unit, National Hospital for Neurology and Neurosurgery, Queen Square, London WC1N 3BG, UK;4. Neurometabolic Unit, National Hospital for Neurology and Neurosurgery, Queen Square, London WC1N 3BG, UK;5. Dubowitz Neuromuscular Centre, UCL Institute of Child Health and Great Ormond Street Hospital for Children NHS Foundation Trust, London WC1N 1EH, UK;6. Department of Molecular Neuroscience, UCL Institute of Neurology, Queen Square, London WC1N 3BG, UK;7. The Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge CB10 1SA, UK;8. Department of Clinical Neuroscience, UCL Institute of Neurology, London NW3 2PF, UK