The focus of the new study, conducted in the lab of Andrew Feinberg, M.D., was whether Hopkins-developed human embryonic germ cells and their more specialized "daughter" cells would have correct "imprinting," a way cells determine which of the two copies of a gene to use in making proteins. For imprinted genes, which copy is active depends only on which parent it came from.

The scientists showed that imprinting remains normal as the embryonic germ cells, a kind of pluripotent stem cell from fetal tissue, become more specialized, says Feinberg. Earlier reports by researchers studying mouse stem cells had raised concerns that those from humans might not be properly imprinted, casting some doubt on their value for cell-based therapies, he adds.

"Imprinting is normal in human embryonic germ cells," says Feinberg, King Fahd Professor of Medicine in the McKusick-Nathans Institute of Genetic Medicine at Hopkins. "Researchers still have to figure out the logistics and other critical aspects of stem cells to advance to clinical applications, but this work shows that imprinting is not going to be the issue some had anticipated."

Their report, to be published online during the week of July 8 in the Proceedings of the National Academy of Sciences, is likely to cheer researchers hoping that these cells or specialized cells obtained from them will someday be safe and useful for treating diseases.

"It's reassuring to learn that the cells we have derived from primordial germ cells are imprinted normally. This is critical information for their possible safe clinical use in the future," says stem cell pioneer and study co-author John D. Gearhart, Ph.D., the C. Michael Armstrong Professor at Johns Hopkins Medicine and professor of gynecology and obstetrics.

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Contact: Joanna Downer
jdowner1@jhmi.edu
410-614-5105
Johns Hopkins Medical Institutions
8-Jul-2002