[1] UCL Inst Neurol, Dept Neurodegenerat Dis, Div Neuropathol, London WC1N 3BG, England
[2] UCL Inst Child Hlth, Neural Dev Unit, London, England
[3] Great Ormond St Hosp Sick Children, Dept Histopathol, London, England
[4] UCL Inst Neurol, MRC Pr Unit, London WC1N 3BG, England
[5] Univ Calif San Francisco, Dept Neurosurg, San Francisco, CA 94143 USA
[6] Univ Calif San Francisco, Dev & Stem Cell Biol Program, San Francisco, CA 94143 USA