Nat. Cell Biol. 9, 1273–1285 (2007); published online 21 October 2007; retracted online 31 October 2014

Although we believe that the key finding and conclusions are still valid, recently detected image manipulation in the published figures undermines our full confidence in the integrity of the study. We are unable to prove the authenticity of the presented results, as the original data files had been misplaced. We therefore wish to retract this Letter in compliance with the guidelines of the Japanese Ministry of Education, Culture, Sports, Science and Technology. We wish to acknowledge that the co-authors from collaborating groups (G.Y., S.T., Y.M., H.S. and K.M.) were not involved in the figure preparation.

We deeply regret any adverse consequence this retraction may cause.