On 1 September, Yasuo Kawasaki, a 42-year-old assistant professor at Osaka University, was found dead in his lab after ingesting poison. The investigation into the case so far has left many questions unanswered — including whether the death was connected to a recently withdrawn article on which Kawasaki was a co-author.

That paper suggested that a type of DNA helicase called MCM2p plays an important role in DNA replication (W. Nakai et al. J. Biol. Chem. 10.1074/jbc.M603586200; 2006). It was published online on 12 July. But on 2 August, the journal marked it as “withdrawn”.

Osaka University began an investigation on 9 August into whether the paper contained false data. In the midst of the inquiry, Kawasaki's body was found — police suspect that his death was a suicide, although they are still working on the case.

Many who knew Kawasaki have expressed surprise and shock at his death. “He was a talented young scientist,” says John Diffley, an expert in DNA replication at Cancer Research UK's London Research Institute, who knew him since Kawasaki was a postdoc at Cornell University in Ithaca, New York. “His career seemed to be going very well.”

Hisato Kondoh, dean of the Graduate School of Frontier Biosciences at Osaka, dismisses any suspicion that Kawasaki might have killed himself after being caught engaging in scientific misconduct. “The person who committed suicide was not involved in scientific fraud,” he says. Kondoh declined to comment further on the ongoing investigation into the paper, saying only that the results will be made public when they are complete.

But the events leading up to the withdrawal of the paper are far from clear. Nature has learned that Akio Sugino, head of Kawasaki's lab and corresponding author on the paper, had submitted it for publication without checking with all of his co-authors. According to Japanese press reports, Kawasaki subsequently found that some of his data had been changed, so he asked Sugino to withdraw the article, and informed Kondoh. The university is also investigating several other related papers from the group.

Sugino was not available for comment. Robert Simoni, deputy editor of the Journal of Biological Chemistry, also declined Nature's request for information about why the paper was withdrawn, and refused to clarify how a withdrawal differs from a retraction. But scientists in the field describe Sugino as well respected and of high integrity — “a venerable old hand at DNA replication” as Diffley puts it.

Some of the details surrounding Kawasaki's death are also mysterious. Although suicide is relatively common in Japan, the cause of death tends to be hanging or gassing. Kawasaki died from ingesting sodium azide, a white, odourless solid that causes convulsions and respiratory failure within minutes. Such a method of suicide is extremely rare in Japan, according to National Police Agency statistics.

The suicide note was also unusual — rather than being handwritten, it was printed out from a computer. And despite being addressed to his family, it was found, along with an empty container of sodium azide, in the lab where Kawasaki's body was discovered. According to the Osaka police department, the note was an explanation of Kawasaki's emotions. It did not mention the withdrawn paper or specific problems at work. It began: “Things at work have settled down. I want to resolve the problem.”

I really hope the university gets to the bottom of this. It will be a shame if it is a whitewash.

When asked about rumours that there was intense pressure on Kawasaki before his death, Kondoh said that measures had been in place to protect whistleblowers since the beginning of the incident. He added that there is no evidence of a connection between the apparent suicide and the withdrawn paper.

Japanese universities often respond slowly to suspicions of fraud, and aren't known for their transparency. Diffley says he now hopes Osaka will buck that trend. “I really hope the university gets to the bottom of what happened,” he says. “It will be a shame if it is a whitewash.” He points out that without a definitive investigation result, rumours of misconduct could blight the whole group. “The careers of many scientists will be affected.”

Kiyoshi Kurokawa, president of the Science Council of Japan, agrees. “Japanese universities and institutions may not always take the right approach to resolving problems,” he says. “But do they realize that the science community around the world is watching?”