While scientists have previously been able to generate stem cells from mice via parthenogenesis, the new study provides a way to select cells that are a perfect tissue match to the donor. "It's the first time parthenote-derived cells have been successfully transplanted and tolerated in mice," says Kent Vrana, a molecular biologist at Penn State University. "This work is important because it shows you can select parthenotes for [tissue] compatibility."

Daley cautions that many tests still need to be done before such therapies can be developed for patients. For example, since parthenote cells carry two sets of maternal genes, they may have abnormal gene expression. "We will try to determine if cells made from parthenotes will function normally," says Daley.

Daley's primary interest is in developing better therapies for blood diseases, such as leukemia. While bone-marrow transplants present an effective treatment for leukemia, many people can't find donors whose bone marrow is a close enough match to be suitable for transplant. The team is now testing bone-marrow transplants from parthenote-derived stem cells in mice and is trying to create parthenote-derived stem cells from human eggs.

It's not clear if the results will easily translate to humans, says Robert Lanza, vice president of scientific research at Advanced Cell Technologies, an Alameda, California-based company developing stem-cell therapies. While scientists have previously been able to generate stem cells from a primate parthenote, the process has proved elusive in human cells. For the most part, human parthenotes do not survive long enough for scientists to harvest the cells from which stem cells are derived. In July, a group of Italian scientists announced at a meeting that they had derived a line of stem-cell-like cells from a human parthenote, but the work has not yet been published in a scientific journal.