Only a few years after Marisa Bartolomei ’88 earned her Ph.D. from the Johns Hopkins University School of Medicine, she left her mark on the entire field of epigenetics.

During her postdoctoral research at Princeton University, Bartolomei discovered one of the earliest examples of an imprinted gene — genes that are expressed or silenced, depending on which parent they’re inherited from. She found that the activity of a gene named H19 plays a key role in embryonic and fetal development. Her work has opened doors for many of the interventions in use today to diagnose and treat infants who have developmental diseases.

She continues her pioneering work as director of the Center for Women’s Health and Reproductive Medicine at the University of Pennsylvania’s Perelman School of Medicine, where she is the Perelman Professor of Cell and Developmental Biology.

Bartolomei’s research addresses the epigenetic mechanisms of genomic imprinting and X inactivation, as well as environmental effects on epigenetic gene regulation and how they relate to fetal development.

“We’ve been interested in this idea that very early gestational exposures [to environmental hazards] may be the most dramatic,” she said in an interview with Nature Structural & Molecular Biology. “That’s because that’s when there’s a lot of reprogramming going on. [Researchers] now have the capacity to profile what’s happening in the early embryo.”

Last year, she was the recipient of the March of Dimes Richard B. Johnston Jr., MD Prize, which honors researchers whose work has advanced scientific knowledge related to pregnancy, birth and prenatal development.

“Science is such that we can now do a lot of things that we hoped we could do 20 years ago,” says Bartolomei, who was elected as a fellow of the American Association for the Advancement of Science in 2014 and was appointed to the National Academy of Sciences in 2021.