1 Division of Biological Science, Graduate School of Science, Nagoya University, Furo-Cho, Chikusa-ku, Nagoya 464-8602, Japan. Electronic address: goshima@bio.nagoya-u.ac.jp.
2 PSL, UMR 3215 U934 Department of Genetics and Developmental Biology, Institut Curie, Paris, France. Electronic address: yohanns.bellaiche@curie.fr.