CGS-authored

THE BREAKUP of a U.S.-Korean scientific partnership on Friday may derail what supporters had hoped would become a promising source of research into cloning and human embryonic stem cells.

At the heart of the rift is an issue that researchers call a limiting factor in high-tech cloning research: the difficulty of legally and ethically obtaining large numbers of human egg cells.

Human eggs are needed for cloning research, which could lead to customized stem-cell treatments, but they are difficult and costly to obtain. And the procedure poses a small risk to women from the strong hormones used to generate eggs. "It's the pinch-point in the whole technology," says Ronald Green, an ethicist at Dartmouth College in New Hampshire.

Only weeks ago, in Seoul, South Korea, American biologist Gerald Schatten had joined Woo Suk Hwang, director of the cloning laboratory at Seoul National University, to announce an international program to share the fruits of recent Korean stem-cell exploits world-wide.

But on Friday, Dr. Schatten, a professor at the University of Pittsburgh, accused Dr. Hwang of misleading him about the source of...