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Concerns about ethics, errors (accidental or intentional) and possible fraud have dogged the stem-cell researcher Woo Suk Hwang, from Seoul National University in South Korea, since his landmark 2004 Science paper on stem cells from a cloned human embryo. Here news@nature.com describes how events have unfolded from that initial paper - with the most recent events presented first (you may want to read from the bottom-up the first time you read this). Keep checking back for updates over the coming weeks.

Science announces that Hwang and Schatten have written to request a retraction of their 2005 paper. Science editor Donald Kennedy says the journal received the letter hours before Hwang's press conference in South Korea (see entry below). Kennedy quoted from the letter during a press conference with reporters: "After analyzing the data, our team concludes the results...could not be trusted... Therefore we are requesting to withdraw the paper." Science says it must wait for the entire research team to consent to the retraction - a process that Kennedy says should take "days or weeks - not months."

Apology and defense

Hwang tells a press briefing that he and his team did create stem cells matched to individual patients, but that there were "mistakes made, human errors, in taking photographs and in the preservation of the stem cells'. Hwang says he will seek agreement from his co-authors to retract the Science paper, and will investigate how the mistakes were made. He adds that his team is thawing some frozen stem-cell lines from the study to authenticate them.

Stem-cell pioneer accused of faking data - UPDATE

Scientific American removes Hwang from his position as a Research Leader of 2005.

Accusation of fake data

News stations across Korea report allegations from one of Hwang's collaborators that the work from May 2005 was based on fabricated data. Roh tells the MBC and two other television stations that Hwang had told him "there are no cloned embryonic stem cells".

Stem-cell pioneer accused of faking data

Schatten asks Hwang to retract their May 2005 Science paper. Schatten claims he has news of allegations from someone involved with the experiment that make him want his name removed from the paper. According to a release from the University of Pittsburgh, Schatten writes to Science and his co-authors: "My careful re-evaluations of published figures and tables, along with new problematic information, now casts substantial doubts about the paper's accuracy."

Stem-cell scientist asks for retraction

A letter from eight scientists, including Ian Wilmut, the cloner of Dolly the sheep, is published in Science calling for validation of Hwang's results: "We encourage Hwang's laboratory to cooperate with us to perform an independent test of his cell lines."

Stem-cell scientist asks for retraction

Investigation opened

Seoul National University announces an investigation of Hwang's research, as requested by Hwang himself. The university hospital treats Hwang for stress and exhaustion

TV tests call into question cloner's stem-cell success - UPDATE

Investigation opened

University of Pittsburgh officials say they have opened a preliminary inquiry into the 2005 paper.

Media outlets report that the MBC has apologized for the reporting tactics used in their 22 November programme on Hwang.

Mistake in the 2005 paper

According to Science editors, Hwang contacts them to alert them to erroneous duplications in some images published as part of the Supporting Online Material for the 2005 paper. "We made some unintentional error by using about 4 pictures redundantly," he says. Science determines that the redundant images did not appear in the PDF version of the accepted paper, but were inserted later, and says the mistake does not affect the paper's scientific conclusions.

Accusation of mis-matched DNA

The MBC challenges the credibility of Hwang's data. Pursuing a tip-off, MBC gets five samples of patient-specific cell lines from Hwang and sends them, together with corresponding tissue samples, to an independent lab for DNA analysis. The programme reports that the DNA in one cell line does not match the tissue sample as it should. There are many possible explanations for MBC's findings, such as contamination. But the mismatch also raises the possibility that the embryonic stem-cell lines were not cloned from the stated patients. Hwang stands by his science.

TV tests call into question cloner's stem-cell success

According to Science, Moon Il Park, Director and Chair of the Institutional Review Board (IRB) on Human Subjects Research and Ethics Committees at Hanyang University Hospital, reveals to them the results of an investigation by the hospital IRB and Seoul National University IRB. It finds that: "1) two researchers under Dr. Woo Suk Hwang's supervision donated oocytes voluntarily without any coercion and 2) approximately US$1,445 was paid for direct expenses." This was not illegal or in violation of the Helsinki Guidelines of 1964, which prohibit coercion of research subjects. Park also told Science: "We strongly believe that the identified concerns have no impact on the validity of the scientific conclusions."

Admission of payments for eggs

Hwang admits that his stem-cell research used eggs from paid donors and junior members of his team. He resigns from his official positions, saying he will continue his research.

Clone star admits lies over eggs

Stem-cell pioneer resigns

Seoul-based Munhwa Broadcasting Corporation (MBC) aired an investigative news programme showing further evidence that Hwang used eggs from junior members of his lab - the PD Diary program was called "The Myth of Hwang Woo-suk and Suspicions over Eggs."

Sun Il Roh, a fertility expert at MizMedi Hospital in Seoul and a co-author of the landmark paper, admits that 20 eggs he procured and gave to Hwang for his 2004 study were paid for. Roh, a co-author on the 2005 paper, insists that Hwang did not know this.

Korean stem-cell crisis deepens

Schatten publicly cuts all ties to Hwang and his team at Seoul National University.

Stem-cell brothers divide

Mistake in the 2005 paper

The 2005 paper's authors provide Science with corrections to data in the paper's table 2, which are not thought to significantly alter the work's conclusions. The corrected table is published.

According to Science, Schatten tells them he has stopped working with Hwang, because he believes Hwang misrepresented facts about consent issues related to the 2004 paper. Science asks Hwang to inform them of any concerns regarding his research. Hwang says he is looking into the matter.

According to Science, Gerald Schatten, a biologist at the University of Pittsburgh and co-author of the May 2005 Science paper, alerts them to Korean press reports alleging that researcher Sun Il Roh has illegally traded ova. Schatten reassures Science that "none of the oocytes used in Professor Hwang's '04 or '05 Science papers were obtained from reimbursed women donors."

Hwang resumes research, ending his voluntary suspension of activities.

South Korea's government launches the World Stem Cell Hub, an international network for exchanging embryonic stem-cell lines and cloning technology. Hwang is to be its head.

Korea launches network to share cloning information

Cloned dog

Hwang and colleagues announce the first cloned dog - Snuppy, an Afghan hound (Lee B. C. et al. Nature 436, 641; 2005). Some scientists hail his birth as a feat of ingenuity and perseverance, others question its value.

Snuppy rewards dogged approach

Landmark paper

Hwang's team at the Seoul National University in South Korea reports it has established 11 embryonic stem-cell lines derived from the skin cells of individual patients (W. S. Hwang et al. Science 308, 1777-1783; 2005). The experiment is hailed as a huge step towards the medical use of person-specific cell lines. It also backs up the embryo-cloning claims in the team's February 2004 paper.

Korean team lauded for stem-cell advance

The South Korean government approves Hwang's embryonic stem cell research. It is the first approval issued under the nation's new bioethics law.

South Korean bioethics law comes into effect.

The annual meeting of the Korean Bioethics Association calls on Hwang and a review board to answer questions about funding sources and the recruitment of egg donors. The association wants the National Human Rights Commission, an independent investigative body funded by the government, to pursue the case. But the commission's bioethics task force was not intended to investigate specific research projects.

Korean bioethicists call for inquiry into stem-cell work

Ethical questions

Questions are raised about ethical practices in Hwang's work after investigations by Nature. It appears that some of the eggs may have come from junior members of the research team. This is potentially problematic because obtaining human eggs is painful and risky. Hwang denies any wrongdoing, but says that he will suspend his research until a new national bioethics law comes into effect in the new year.

Korea's stem-cell stars dogged by suspicion of ethical breach

Stem-cell research: Crunch time for Korea's cloners

Biologists say that the South Korean breakthrough has alerted Western researchers to the pace of scientific and technological progress in East Asia. Hwang and colleagues attribute their success to a supportive cultural environment, well-funded laboratories, and legislation permitting human embryos to be cloned for research. Also critical to the researchers' success was their collection of 242 human eggs from 16 female volunteers.

Cloning success marks Asian nations as scientific tigers

Landmark paper

Woo Suk Hwang from Seoul National University in South Korea and colleagues announced that they have cloned 30 human embryos and harvested stem cells from one of them (W. S. Hwang et al. Science 303, 1669-1674; 2004). The work makes headlines worldwide, as a step towards stem-cell therapies for diseases such as Parkinson's. Other groups have claimed to clone human embryos, but the supporting evidence has been sketchy. This success will also need further supporting evidence.

Cloned human embryos yield stem cells