1. Laboratory of Molecular Genetics and Howard Hughes Medical Institute (T.A., C.A.P., J.M.F.), Rockefeller University, New York, New York 10065
2. Department of Obstetrics and Gynecology (T.A.), New York University Medical Center, New York, New York 10016
3. Department of Pharmacology (L.Z., A.S.G., L.K.H.), University of Cambridge, Cambridge CB2 1PD, United Kingdom