Respected Japanese scientist Yoshiki Sasai, deputy director of the Riken Center for Developmental Biology, committed suicide by hanging himself after nearly seven months of criticism over a research paper that was published in Nature in January and ultimately retracted last month, reports Alexander Martin for The Wall Street Journal. He was found by a security guard earlier this morning and Fox News reports that he left behind five suicide notes addressed to different people including two senior Riken officials.

Yoshiki Sasai

Sasai failed to spot falsified data

Sasai was an expert on stem cells who built his reputation using them to grow more complex anatomical structures, but last January he co-authored a paper claiming to have found a way to do the reverse: start with spleen cells and then turn them into stem cells by subjecting them to various stresses like acid or physical pressure. Aside from shedding more light on the transition between stem cells and other types of tissue, this research would have given scientists a simple way to generate stem cells, which is normally expensive and work intensive, for their own projects.

But scientists who tried to create their own inexpensive stem cells weren’t able to replicate the results and an investigation eventually found that lead author Haruko Obokata had falsified data to prove her results and that the co-authors, including Sasai were responsible for not verifying the data themselves. None of the other researchers were found to have falsified data.

Sasai said he was ‘overwhelmed with shame’

While no one doubts Sasai’s past work, and a number of leading Japanese researchers have said that this is a major loss to the scientific community, Sasai’s career suffered a serious setback following the ordeal. He had been considered to be a candidate to eventually lead the Riken Center, but failing to properly supervise Obokata’s research (even though he was apparently brought in at the end of the project) made that unlikely.

Sasai told the Wall Street Journal that he was “overwhelmed with shame” back in April, and colleagues had described him as being physically and mentally exhausted in recent days.