Here, news@nature compiles a guide to the main characters in a major stem-cell scandal, at the centre of which stands South Korean scientist Woo Suk Hwang. After Hwang published work claiming his team had extracted patient-matched stem cells from cloned embryos, it was shown to be a complete fake. For all our news stories and a timeline of events see our special on Hwang.

Woo Suk Hwang

Woo Suk Hwang: from fame to infamy© Nature

Hwang grew up in a poor village in Korea (see 'Profile: Woo-Suk Hwang'). He became a veterinarian who later turned to medical science, hoping, he has told Nature, to improve the lot of his countrymen. He created the country's first cow born from in vitro fertilization in 1993, then became something of a national hero after cloning one in 1999. Hwang went on to try to clone an endangered tiger, tried his hand at pigs, and even claimed to have developed a cow resistant to mad cow disease in 2003. Critics point out that many of Hwang's early cloning achievements, including his cow, were not supported by journal publications. Then, in 2004, Science published a paper by Hwang reporting the first stem-cell line derived from a cloned human embryo, and in 2005 a paper claiming that he had created patient-specific stem cells. The work shot him to international fame, and then infamy.

Korean scientists

Netizens: scientists went online to express their doubts about the work anonymously.© Biological Research Information Center

Korea's young scientist community came alive in late 2005, albeit anonymously. Websites such as those of the Biological Research Information Center and Scieng are clearing houses for science-related news, often of the mundane variety. But in early December 2005, the 'netizens' started posting doubts about DNA fingerprints and images in Hwang's papers. In a situation where it was difficult to criticize a top scientist, especially one who had ties stretching up to the president of the country, these anonymous portals offered freedom of speech and provided vital information for investigators of the case.

Journalists

Nature 's reporter David Cyranoski wrote a story in 2004 questioning the ethics of Hwang's research.© Nature

As early as May 2004, Nature presented doubts about Hwang's research, in an article that questioned the ethical integrity of his source of eggs. The article was roundly condemned by Hwang and the South Korean press. Nature expected an official investigation, but none came. Then, in 2005, an investigative programme from the Munhwa Broadcasting Company (MBC), played a vital role exposing Hwang. PD Notebook 's previous targets included such giants as the national intelligence agency. But Hwang was the hardest fish to fry, says 36-year-old producer and reporter Hak Soo Han. PD Notebook 's programme about Hwang's egg procurement on 22 November led to a confession from Hwang two days later. Further evidence gathered by the programme concerning his scientific papers was crucial in sparking official investigations.

The egg donors

Donating eggs for stem cell research can be a painful and risky procedure.© Photodisk

Hwang told Nature he had not used eggs from paid donors or laboratory members. But it turns out that of 129 known donors (only 34 of which were noted in his papers), many were paid and at least two, Ja Min Koo and Eul Soon, were workers in his own laboratory. A investigative committee from Seoul National University reported that not only did Hwang know of one woman's donation, he accompanied her to the hospital.

Ja Min Koo is a 35-year-old mother of two who had been working as a PhD student with Hwang since the late 1990s. She had previously worked culturing egg cells from pigs, which prepared her for working on human cells for Hwang's 2004 Science paper, on which she is a co-author. She told Nature that she was a donor in spring 2004, saying she was happy to contribute to the drive for cures for spinal-cord injuries.

Eul Soon Park was a research fellow in Hwang's laboratory and co-author on Hwang's 2004 Science paper. She helped to develop the method that Hwang's lab uses to remove an intact nucleus from an egg, by squeezing it out rather than sucking it with a needle. The method was also used in monkey cloning research at Gerald Schatten's laboratory in Pittsburgh, Pennsylvania, to which Park moved in 2004. It has been questioned whether her egg donation was voluntary, or if she was pressured after hundreds of eggs were ruined in early experiments.

The whistle-blowers

In June 2005, a former member of Hwang's laboratory tipped off MBC producers to the possibility that the 2005 Science paper was a fake. Another one gave PD Notebook stem-cell line number 2, one of 11 cells supposedly tailored to a patient, and told them to test it. A third informer backed up some of MBC's information. "These informers were worried about the future of Korean science," says producer Han. Friction between members of the lab, he adds, did not seem to be an issue.

Sung Il Roh is a senior fertility expert at MizMedi Hospital. Roh secured at least 1,200 eggs for Hwang's experiments. He told Nature he comes from a long line of fertility specialists and did not need the kudos of being associated with the 2004 Science paper: he says he turned down co-authorship. He was, however, second author on the 2005 Science paper. In November, he publicly admitted that egg donors were paid, later adding a claim that Hwang knew about it. On 16 December he broke down in tears at a press conference in which he accused Hwang of fabricating data.

Sun Jong Kim is a researcher in his mid-30s, and co-author on both Science papers. He has said that he doctored photos for the papers at Hwang's behest, telling MBC that he had produced images for eleven lines from two that he was give from Hwang. Hwang later accused Kim or others of switching lines. Nature awaits the outcome of further investigation. Hwang, Roh, Kim and others remain in South Korea under a travel ban while prosecutors investigate.

Curie Ahn

A xenotransplant expert at Seoul National University, Ahn has told Nature she one day hopes to make pig organs that could solve the organ donor crisis. She was one of Hwang's most ardent supporters throughout 2004 and 2005, and became an unofficial spokeswoman when he was not in contact with the media. She later distanced herself, telling Nature that her role was limited to developing the cell lines produced by Hwang for clinical applications.

Gerald Schatten

This energetic, 56-year-old developmental biologist has long sought to unravel the secrets of cloning in primates. In 2001, he led the creation of the world's first genetically modified monkey, while at the Oregon Health and Science University in Portland. Later that year, he was recruited to lead a research institute at the University of Pittsburgh Medical School, where he still works today. His investigations into monkey cloning led him to seek advice from Hwang; their collaboration resulted in co-authorship, with others, of the 2005 Science paper. Schatten was also involved with the 2004 Science paper. The effusive Schatten often served as Hwang's ambassador in the West. Later, he publicly distanced himself from Hwang, and his comments helped to spur investigations into the research.

Ky Young Park

A former plant biologist turned consumer-advocate in areas related to genetically modified organisms, Park is co-author on the 2004 Science paper. But her professional role as a bioethicist, she has told Nature, is limited to surveying people's attitudes on cloning and other biomolecular techniques, not including issues such as egg donation. Some suspect she was added to the paper for political reasons: Park later became science and technology adviser to South Korea's president, and a great supporter of Hwang's research. On 9 January, following the release of Seoul National University's investigation, which found that the 2004 paper was a fabrication, Park announced that she would resign as adviser. The Science Minister is also being replaced following the scandal.

Investigative panel

The investigating panel reported its damning conclusions on 10 January, 2006.© David Cyranoski/Nature

Seoul National University set up a nine-member committee, led by pharmacologist Myung Hee Chung from the College of Medicine, to investigate Hwang's lab. The panel was established after problems were highlighted in December 2005; it quickly filed both preliminary and final reports. After its first discovery of fraud in Hwang's papers, Hwang and his supporters accused the committee of bias and lack of expertise. Nature has no reason to think this is the case.

Additional reporting by Erika Check