基金Acknowledgements We thank the RIKEN BRC in Japan for provision of all full-length cDNA in this study. National Natural Science Foundation of China (grants numbers 30530100 and 90408010), the State Key Program of Basic Research of China (grant numbers 2007CB947600 and 2007CB108800), and Hi-Tech Research and Development Program of China (grant number 2006AA02Z313) supported this project.