Retraction to: Nature online 25 June 2014

Upon re-examination of the bone histomorphometry data in Extended Data Figs. 1i, 2d, 3h, 4h, 5n, 6e, 9g and 10f of this Letter, anomalies were found that call into question the integrity of these data. These concerns undermine the confidence in the study and the authors thus wish to retract the Letter in its entirety. The authors regret this situation and apologize to the scientific community. All authors agree with the Retraction, but author Xunde Wang did not respond.