[1] Univ Virginia, Hlth Sci Ctr, Dept Neurosci, Charlottesville, VA 22908 USA
[2] Univ Virginia, Hlth Sci Ctr, Dept Neurosurg, Charlottesville, VA 22908 USA
[3] Univ Penn, Sch Med, Dept Neurosurg, Philadelphia, PA 19104 USA
[4] Georgetown Univ, Med Ctr, Dept Cell Biol, Washington, DC 20007 USA
[5] Salk Inst Biol Studies, Genet Lab, La Jolla, CA 92037 USA