[1] Univ Bonn, Dept Neuropathol, D-5300 Bonn, Germany
[2] Univ Wurzburg, Dept Neurosurg, Wurzburg, Germany
[3] Univ Cologne, Dept Pediat Oncol, Cologne, Germany
[4] Univ Erlangen Nurnberg, Dept Expt Med 2, Erlangen, Germany
[5] Max Delbruck Ctr Mol Med, Berlin, Germany