[1] United Med & Dent Sch Guys & St Thomas Hosp, Guys Hosp, Div Med & Mol Genet, London SE1 9RT, England
[2] Johns Hopkins Univ, Sch Med, Dept Psychiat, Baltimore, MD 21205 USA
[3] Johns Hopkins Univ, Sch Med, Dept Neurosci, Baltimore, MD 21205 USA
[4] Max Planck Inst Mol Genet, D-14195 Berlin, Germany