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Teruhiko Wakayama facing the press on 16 June.

Teruhiko Wakayama facing the press on 16 June.

D. Normile

Evidence mounts against new stem cell method

KOFU, JAPAN—A genetic analysis of what was claimed to be a new type of pluripotent stem cell has cast fresh doubts on the research. The independent analysis shows that the cells, called STAP cells, don't match the mouse strain supposedly used in the experiments—possibly indicating inadvertent or deliberate switching of cellular material.

"This doesn't definitively show that STAP cells don't exist, but there is no evidence supporting their existence," said Teruhiko Wakayama, a mouse cloning pioneer at University of Yamanashi here, at a press conference today.

The simple approach, known as stimulus-triggered acquisition of pluripotency, or STAP, was described in a pair of papers published online in Nature on 29 January by Haruko Obokata of the RIKEN Center for Developmental Biology (CDB) in Kobe and co-authors in Japan and at Brigham and Women's Hospital, a Harvard Medical School affiliate in Boston. A RIKEN investigative panel documented plagiarism, image falsification, and other problems with the papers and concluded that Obokata had committed research misconduct.

So far, no one has reported being able to replicate the reprogramming method, which involves exposing cells to various stresses. A RIKEN team is attempting to redo every step of the experiments described in the Nature papers. Wakayama, who was previously at CDB and is a co-author of both papers and a corresponding author on one, had supplied the mice for the experiments. He had a third party conduct a genetic analysis of what were supposed to be STAP cells that he’d received from Obokata. The tests showed that some of the cells were from a mouse strain that Wakayama had not provided.

At the press conference, Wakayama acknowledged sharing responsibility for the problems with the Nature papers. But he noted that Obokata has an impressive educational background, had trained at Harvard, and was known as a superior researcher. She worked in his lab briefly and had consistently presented data at weekly meetings indicating her research was going well—so Wakayama says he didn't think he needed to ask to see her notebooks or raw data. But as a co-author, he says, "I should have confirmed [research data] at least to some extent."

A RIKEN committee is now deliberating punitive measures for Obokata and others involved, including CDB officials. Wakayama says he deserves and is willing to accept some punishment. He declined to specify what he thinks that should be.