Retraction to: Nature Published online 16 March 2006

The authors wish to retract this article. Concerns have been raised regarding figures in this article, including Fig. 2c and Supplementary Fig. 4, which show signs of excessive manipulation, including splicing, duplication and the use of an eraser tool. The data cannot be verified from the records. We consider that the appropriate course of action is to retract the article.

Ming Teng Koh, Linda Kotilinek, Rakez Kayed, Charles G. Glabe, Michela Gallagher and Karen H. Ashe agree with the retraction. Sylvain Lesné disagrees with the retraction. Austin Yang has not responded to correspondence from the Editors about this retraction.