This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of Drs Hidalgo, Carrasco and Poulsen. This follows an investigation by the Danish Committee on Scientific Dishonesty (DCSD) into scientific misconduct by Dr Milena Penkowa. This statement (http://www.fi.dk/raad-og-udvalg/udvalgene-vedroerende-videnskabelig-uredelighed/afgoerelser/Afgoerelse%20af%20sag%20om%20mus.%2029.%20august%202012.pdf – in Danish only) from the DCSD is final. Although we as co-investigators were not contacted officially during the investigation, nor in the hearing process, we find it plausible that misleading or incorrect information and data regarding the mice were used in the article, and as such that there is sufficient doubt as to the veracity of the data to warrant this paper's retraction.