Stem cell researchers in Boston and in Stockholm confronted a bizarre and uncomfortable situation last week: accusations of scientific fraud from an anonymous e-mail address, sent not only to the researchers in question but also to other prominent stem cell biologists, several scientific journals, and reporters. In response, the journal in which one of the papers was published, Nature, has contacted some of those on the original list to make a case for the scientific veracity of the paper. In the other case, the scientists themselves have responded, and the journal, the Proceedings of the National Academy of Sciences (PNAS), has decided no further action is necessary.
For Konrad Hochedlinger of the Harvard Stem Cell Institue, it was a bad start to the week: Just after 6 a.m. last Monday, he and a bevy of others received an unsigned e-mail from a virtually untraceable address, email@example.com , pointing out what it said "appears to be duplicated images and embryos used in a Nature manuscript  published in 2009." The e-mailer went on to detail misconduct claims, asserting that in Figure 3C, Hochedlinger and his co-authors had used two pictures of the same embryo while claiming they were different.
"I was quite shocked and upset that this anonymous e-mail was sent to us and copied to half the stem cell world and the [Boston] Globe and Nature, Cell, and Science," says Hochedlinger. Uncertain how to respond, he began compiling images to demonstrate that he had photographed two different embryos, including one original photo that showed both in the same image. "We have quite clear proof that these accusations are unfounded," he says.
Nature has declined to comment on the case, but Hochedlinger says the journal subsequently e-mailed some of those copied on the e-mail with original images that Hochedlinger had supplied. Scientists told him they either ignored the e-mail or saw obvious differences in the two embryos.
On Friday 22 October, the group surfaced again, this time charging that a stem cell paper  in PNAS published in 2009 contained duplicated images, pointing to Figure 5A. Contacted by Science about the e-mail, one of the corresponding authors, Thomas Perlmann of the Karolinska Institute in Stockholm, responded that the images are from triple immunohistochemistry staining, so are indeed from the same set of cells "displayed as double staining for clarity."
Perlmann didn't stop there. In a response  sent on Sunday to those on the stemcellwatch e-mail list, he and the second corresponding author, his Karolinska colleague Johan Ericson, gave a detailed rebuttal of the charges. They also noted that a sentence indicating that the images were derived from triple immunohistochemistry was deleted from the original manuscript to save space. Perlmann says that PNAS Editor Randy Schekman decided no published clarification is necessary.
At the end of their note, Perlmann and Ericson wrote: "We regret that these serious accusations were made anonymously, as we strongly believe in the concept of an open and transparent communication about suspected errors in published data." The elusive e-mailers, who claim to be part of a group called the Stem Cell Research Watch Group, responded to an e-mail from Science saying that they are "a group of students majoring in biology and often discuss papers that are taught in class." They did not sign their names or say where they were based, and did not respond to a subsequent e-mail asking for additional information.
Contrary to what appears here, PNAS is working to publish a correction to the figure legend in question.