Affiliation: | (1) Department of Genetics, Washington University School of Medicine, 63110-1095 St. Louis, MO, USA;(2) Department of Genetics, Harvard Medical School, 02115 Boston, MA, USA;(3) Department of Biology, Washington University, 63130 St. Louis, MC, USA;(4) Present address: London School of Hygiene and Tropical Medicine, London, UK;(5) Present address: Department of Development Biology, Stanford University, Stanford, CA, USA |