Affiliation: | From the ‡Department of Biological Sciences, Michigan Technological University, Houghton, Michigan 49931.;the §College of Life Sciences, Peking-Tsinghua Center for Life Sciences, Peking University, Beijing 100871, China, and ;the ¶Institute of Genetics and Molecular and Cellular Biology, Department of Development and Stem cells, University of Strasbourg, 67404 Illkirch, France |