If South Korean cloning hero Hwang Woo-suk falls from grace in what could turn out to be one of the biggest scientific frauds in years, he might take U.S. stem cell researcher Gerald Schatten with him.

In May, Schatten had the honor of serving as "senior author" on Hwang's groundbreaking cloning report. That has now turned into a curse for the University of Pittsburgh researcher, whose questionable involvement with Hwang is not his first brush with scientific controversy.

At the very least, Schatten faces a formal reprimand once an internal school investigation is concluded.

"I will consider what disciplinary actions are appropriate in this case pending the findings," said Dr. Arthur Levine, dean of the medical school and Schatten's boss.

Schatten, 56, and another collaborator on the cloning paper, Roh Sung-il, have accused Hwang of fabricating key evidence in a landmark scientific article this year describing how South Korean researchers used DNA from sick patients to clone 11 human embryos and extract tailor-made stem cells.

Hwang defended his research Friday, but still said he will ask the journal Science to withdraw the report due to "fatal errors and loopholes in reporting the scientific accomplishment."

Schatten has declined to comment on the growing scandal, referring numerous e-mail and telephone inquiries to the school's public relations department.

Scientists say that as "senior author" on the paper, it was his responsibility to catch the many errors Hwang has admitted.

However, Pittsburgh officials and the paper itself described Schatten's involvement in the cloning research as limited to consultation, helping the South Koreans prepare their manuscript and serving as their English-language translator.

Schatten did little, if any, actual research.

Levine said it's unclear why Schatten was given senior author status among the 24 South Korean scientists who also signed on to the paper.

"One should only be the senior author of a scientific paper when one has prepared and was responsible for all the data in that paper," Levine said. "It also implies the senior author is the chief of the lab where the experiment took place."

Many other scientists are also calling for an investigation of another high-profile paper Hwang and Schatten published this year describing the world's first cloned dog.

"Now that Hwang has withdrawn his human cloning paper, I think we need to be suspicious of his dog cloning work as well," said Dr. Robert Lanza, a rival cloning expert with biotechnology company Advanced Cell Technology Inc.

Since publication of the human cloning article in May, Schatten has served as the Western face for the South Korean cloning team vying for worldwide respect.

He squired Hwang and other Korean researchers to meetings with top U.S. and British stem cell scientists this fall, attempting to garner support for the World Stem Cell Hub — an international project Hwang had launched in October that envisioned California and British labs in addition to a facility in Korea.

Schatten gave numerous interviews to mainstream U.S. media outlets, touting Hwang's technical prowess, and served as the Koreans' representative at scientific gatherings.

In return, Schatten quickly rose along with Hwang to prominence in the cloistered cloning research field. That sudden renown came even as he foundered with his own cloning research. The National Institutes of Health awarded him a $6.4 million grant to clone monkeys, but his biggest scientific achievement came in 2003, when he reported his failure to achieve the cloning.

Scientists said Schatten was a candidate to head the United Kingdom lab in Oxford when he announced in November that he was pulling out of the project and cutting ties with Hwang, who once called Schatten "my brother."

The breakup was just the latest professional tangle for the researcher who earned his doctorate in cell biology at the University of California, Berkeley in 1975.

Ten years ago, a criminal investigation of a UC Irvine fertility clinic reached Schatten's lab at the University of Wisconsin.

The Irvine clinic was supplying Schatten with eggs that had been illegally obtained from women for research without their consent. One Irvine doctor was convicted and two others fled the country.

Schatten believed the Irvine eggs were legally and ethically obtained, said Wisconsin bioethics professor Alto Charo, who helped with the school's investigation. Charo said the Irvine doctors gave Schatten fraudulent documents asserting the eggs were collected properly.

"Jerry Schatten was absolved of any wrongdoing," Charo said.