About the Authors
Institut de Neurobiologie Alfred Fessard, CNRS UPR3294, Gif-sur-Yvette, France
Département de Biologie, Université Paris Sud, Orsay, France
The authors have declared that no competing interests exist.
The author(s) have made the following declarations about their contributions: Conceived and designed the experiments: BG AD AL FR. Performed the experiments: BG AD AL EC. Analyzed the data: BG AD AL EC FR. Wrote the paper: FR.