TOKYO—Yoshiki Sasai, a noted stem cell scientist at the RIKEN Center for Developmental Biology (CDB) in Kobe, Japan, who co-authored two controversial and later retracted papers that reported a simple way of reprogramming mature cells, was confirmed dead this morning, an apparent suicide. Local media reported he was found hanging from a stairway railing in the RIKEN complex in Kobe. Sasai was rushed to a nearby hospital but efforts to revive him were unsuccessful. He reportedly left a suicide note, but it has not been made public.
Sasai, 52, was a corresponding author on one of the papers and a co-author of the other. Together, they reported the discovery of a new phenomenon the researchers called stimulus-triggered acquisition of pluripotency (STAP). The papers, whose lead author was Haruko Obokata, also of RIKEN CDB, appeared online in Nature on 29 January. After months of mounting claims of problems and a finding of research misconduct by Obokata by a RIKEN committee, Nature retracted the studies on 2 July. The retraction notices cite duplicated and mixed-up images, mislabeling, faulty descriptions, and "inexplicable discrepancies in genetic background and transgene insertion sites between the donor mice and the reported" STAP cells.
To date, no other groups have succeeded in reproducing the work. RIKEN has a team attempting to determine what went wrong and conclusively determine if the STAP phenomenon is real. A separate committee has been charged with determining disciplinary measures for Obokata and her RIKEN co-authors and supervisors, including Sasai, although decisions have been put off pending the results of the ongoing investigation.
A prolific developmental biologist, Sasai had risen to be deputy director of the center and was considered a contender to become its director. He was credited with helping recruit Obokata. Adding his name to her papers gave them credibility because of his reputation and standing in the community.
Researchers were shocked and saddened by the news. "So very very sad! My sincere sympathy to Sasai's family. Community lost a great developmental biologist!" Kenneth Lee, a stem cell researcher at the Chinese University of Hong Kong, tweeted shortly after the news broke. “This is a tragedy and thoughts go out to his family, friends, and lab members,” wrote stem cell researcher Paul Knoepfler, of the University of California, Davis, School of Medicine in Sacramento, on his blog.