Nat. Cell Biol. 5, 224–230 (2003); published online 24 February 2003; 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 have been unable to locate the original data files and confirm the validity of published results; we therefore wish to retract this Letter. We wish to emphasize that the co-authors from collaborating groups (T.Y., T.K., Y.T., H.S., Y.G. and K.M.) were not involved in the figure preparation. Junn Yanagisawa could not be reached by the journal for comment on the retraction but he has signed a previous retraction draft.

We deeply regret any inconvenience this retraction may cause.