[1] Univ Zurich, Inst Plant Biol, CH-8008 Zurich, Switzerland
[2] Univ Zurich, Zurich Basel Plant Sci Ctr, CH-8008 Zurich, Switzerland
[3] Emory Univ, Dept Biol, Atlanta, GA 30322 USA
[4] Univ Cambridge, Dept Physiol Dev & Neurosci, Cambridge CB2 3EG, England
[5] Univ Cambridge, Ctr Trophoblast Res, Cambridge CB2 3EG, England
[6] UCL, Inst Child Hlth, Clin & Mol Genet Unit, London WC1N 1EH, England
[7] Univ Bristol, Avon Longitudinal Study Parents & Children, Sch Social & Community Med, Bristol BS8 2BN, Avon, England
[8] MIT, Nine Cambridge Ctr, Whitehead Inst Biomed Res, Howard Hughes Med Inst, Cambridge, MA 02142 USA