Cell is looking into whether the authors of a widely hailed study published last week claiming to have turned human skin cells into embryonic stem cells manipulated images inappropriately, Retraction Watch has learned.
The potential image problems came to light on PubPeer, a site designed to allow for post-publication peer review. A commenter, identified as Peer1, identified “several examples of image reuse which might be of interest to PubPeer members and readers:”
– Fig. 2F is a slightly cropped version of the cell microscopy image in Fig. 6D top left.
– Fig. 6D top right, the cell microscopy image is a slightly cropped version of supplementary Fig. s5, top right. The cells in 6D are labelled as “h-ESO-NT1 Ph” yet in figure s5 they are labelled to be “hESO-7″. We understand the former to inherit caffeine-treated somatic nuclei whereas the latter are original stem cells.
Under pressure to assemble the figures for rapid publication, one can understand making a cut and paste figure assembly mistake. Nevertheless it should be noted that image cropping does take extra work.
– Figure S6 top centre and top right are the same image.
– Figure S6 middle left and lower right are reported to be biological replicates of microarray expression quantitation. In those cases however the narrow spread indicates that the data are extremely similar and are only understandable as technical replicates (where the same RNA sample is hybridised to two different arrays). It is useful to do technical replicates to control experimental reproducibility, but biological replicates are more valuable when reporting results. They are not the same thing and should not be conflated. (For the record, we did check the microarray data deposited at Gene Expression Omnibus (GSE46397)).
Cell tells us that
Our editorial team is currently assessing the allegations brought up in the PubPeer piece.
It’s not clear whether these alleged manipulations are central to the claims of the paper. We’ll keep an eye on this and update as we learn more from Cell.
Please see an update on this post, with more details from Cell.
Hat tip: Ed Yong