[1] Univ Calif Berkeley, Howard Hughes Med Inst, Dept Mol & Cell Biol, Berkeley, CA 94720 USA
[2] Johns Hopkins Univ, Sch Med, Dept Neurosci, Baltimore, MD 21205 USA
[3] Exelixis Pharmaceut Inc, S San Francisco, CA 94080 USA
[4] Max Planck Inst Hirnforsch, Neurochem Abt, D-60528 Frankfurt, Germany
[5] Univ Penn, Sch Med, Dept Neurosci, Philadelphia, PA 19104 USA