STAP cells claimed by Obokata were likely embryonic stem cells

An investigative panel under the government-backed Riken research institute announced Friday that the so-called STAP stem cells described in the research papers lead-authored by Haruko Obokata were created from embryonic stem (ES) cells.

It also said it discovered two more cases of research misconduct by the embattled scientist.

The panel concluded STAP stem cells . . . were derived from ES cells, based on examinations of the remaining samples, Isao Katsura, director general of the National Institute of Genetics and head of the seven-member panel, told reporters Friday in Tokyo.

Katsura also noted that the chimera mice and teratomas claimed to be developed from STAP cells were highly likely to be generated from ES cells.

However, the panel was unable to reach a conclusion on who introduced the embryonic stem cells, or whether they were introduced deliberately or by accident, citing insufficient evidence.

Moreover, the panel, which had been investigating the two papers on stimulus-triggered acquisition of pluripotency published in the British journal Nature, found two fresh instances of research misconduct by Obokata, in connection with data in one of the papers.

We concluded Obokata fabricated data for two charts on growth curves of (STAP stem) cells and DNA methylation, Katsura said.

The findings add to two counts of research misconduct found to have been committed by the 31-year-old biologist by another Riken panel earlier this year. This, along with other allegations of misconduct, prompted Riken to set up the panel headed by Katsura in September. Obokata resigned from the institute Sunday.

Meanwhile, Katsura said that Teruhiko Wakayama and Hitoshi Niwa, two of the co-authors of the STAP papers subject to the panels review, were not involved in any misconduct. He added that Yoshiki Sasai, another co-author who oversaw Obokatas writing, was not investigated because he committed suicide in August.

The Nature papers published in January claimed that the team of scientists led by Obokata found a groundbreaking method of stem cell generation, but they were retracted in July.

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STAP cells claimed by Obokata were likely embryonic stem cells