Genes from mouse strains that were different from the ones embattled scientist Haruko Obokata said she was using were found in pluripotent STAP cells that featured in her groundbreaking research, the Riken Center for Developmental Biology disclosed March 25.
The finding has raised new questions about the data describing experiments that addressed a new mechanism called "stimulus-triggered acquisition of pluripotency."
The discovery alone, however, does not immediately disprove the presence of the STAP cells, partly because the mouse genes in question were found in cells used in experiments that were not described in a pair of articles that Obokata and her colleagues published in the prestigious Nature magazine in January.
Obokata, who is attached to the Riken national research institute, was the lead author of a work that created a huge buzz in the scientific community around the world.
According to the Riken CDB, Teruhiko Wakayama, a professor of developmental engineering with the University of Yamanashi, and his co-workers presented the results of their gene analysis to several researchers at the Riken CDB. As a co-author of the articles that were published in Nature, Wakayama received what Obokata said were STAP cells and demonstrated their pluripotency by growing them into special mice.
The latest analysis by Wakayama and his colleagues covered two strains of cells that he received from Obokata and has since preserved. Those cells were used in experiments that were not described in the Nature reports.
Obokata described both cell strains as derived from a mouse strain called 129 when she presented the cells to Wakayama. But gene analysis showed that one of the cell strains was derived from a mouse strain called B6, whereas the other was derived from a cross between the B6 and 129 mouse strains, the Riken CDB said.
"We are still on the stage of preliminary analysis, and we hope to cooperate with Wakayama to carry out detailed checks in the days to come," Riken CDB Director Masatoshi Takeichi said in a statement March 25.
Obokata, 30, who leads a research unit at the Riken CDB in Kobe, made a name for herself when she and her colleagues said in the Nature papers that strong external stresses, such as a weak acid bath, could reprogram lymphocyte cells from young mice into pluripotent cells, which can develop into different body organs and tissue.
Her finding promised fresh advances in the field of regenerative medicine.
But she has come under fire following revelations of suspected irregularities in her Nature reports and her Ph.D. thesis, including the use of duplicated images in different contexts and the use of text taken from other publications.
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