Life Lessons from the Rats

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Professor Sarah Bacon Looks at the Beginning of Life
What can rats tell us about human pregnancy?

Ask biologist Sarah Bacon.

She's studying human fertility and miscarriage—30 to 80 percent of human pregnancies are lost, often even before women are aware they're pregnant—by studying reproduction in rats.

Pregnancy in rats is an excellent model for studying pregnancy in humans, Bacon notes, because, just like in humans, rat embryonic development is influenced by the mother's response to her environment: to stress, nutrition, disease, and the demands of her other offspring.

The timing of rat and human pregnancy is in near lockstep in the first weeks after conception. And, major events in rat pregnancy--like the invasion of the uterus by the embryo and the knitting together of maternal and embryonic tissues to make a placenta–are more easily studied in rats than humans.

"Pregnancy necessitates intimate contact and exchange between tissues (maternal and embryonic) that are genetically a mismatch–the baby, after all, carries paternal genes which the mother's immune system would identify as foreign," Bacon observes. "The baby is festooned with foreign (paternal) proteins, yet the mother's immune system does not reject it. Pregnancy, and in particular the placenta, have begun to teach us about ways in which the immune system can be taught to tolerate foreign tissue."

A 1987 graduate of Mount Holyoke, Bacon went on to earn a Ph.D. in organismal biology at the University of Chicago; after a one-year postdoctoral research fellowship at Cornell's College of Veterinary Medicine, she returned to Mount Holyoke as an assistant professor of biological sciences in 1998.

Bacon credits her undergraduate education with having a positive impact on her career. "There is an important way in which being here shaped how I went about my research," she says. "I consciously sought out female mentors, and it worked out very well for me." She chose a female adviser at the University of Chicago, who "modeled family life in combination with professional life in a way I did not see men doing," Bacon remembers. "I learned a huge amount from her." Bacon says the caring attention she was given by her professors at MHC also made a difference. "It can make you realize you have potentials that maybe you didn't suspect," she says. "There are people in this department who did that for me, and now I get to teach with them."