1. Department of Genetics, Blavatnik Institute, Harvard Medical School, Harvard University , Boston , MA 02115, USA
2. Drosophila RNAi Screening Center, Harvard Medical School , 77 Avenue Louis Pasteur, Boston , MA 02115, USA
3. Department of Physiology, Development and Neuroscience, University of Cambridge , Downing Street, Cambridge CB2 3DY, UK
4. Department of Biology, Indiana University , Bloomington , IN 47405, USA
5. Howard Hughes Medical Institute , Boston , MA 02138, USA