Leftover DNA from sons may alter their mothers’ brains, study says | Health | The Seattle Times

The Fred Hutchinson Cancer Research Center study also found that women with more male DNA in their brains were less likely to have suffered from Alzheimer’s disease.

By Melissa Lee Phillips

A new study shows that male DNA — likely left over from pregnancy with a male fetus — can persist in a woman’s brain throughout her life. Although the impact of this foreign DNA is unclear, the study also found that women with more male DNA in their brains were less likely to have suffered from Alzheimer’s disease.

The Alzheimer’s trend hinted that the male DNA could help protect mothers from the disease, the researchers say.

During mammalian pregnancy, the mother and fetus exchange DNA and cells. Previous work has shown fetal cells can linger in the mother’s blood and bone for decades, a condition researchers call fetal microchimerism.

The lingering of the fetal DNA, research suggests, may be a mixed blessing: The cells may help the mother’s health by promoting tissue repair and improving the immune system, but the cells may also cause adverse effects, such as autoimmune reactions.

Researchers have shown that fetal microchimerism occurs in mouse brains, but they had not shown this in humans. So a team led by autoimmunity researcher and rheumatologist Dr. J. Lee Nelson of the Fred Hutchinson Cancer Research Center in Seattle took samples from autopsied brains of 59 women who died between the ages of 32 and 101. By testing for a gene specific to the Y chromosome, they found evidence of male DNA in the brains of 63 percent of the women. (The researchers did not have the history of the women’s pregnancies.) The male DNA was scattered across multiple brain regions, the team reported online Wednesday in PLoS ONE.

Because some studies have suggested that the risk of Alzheimer’s disease increases with an increasing number of pregnancies, the team also examined the brains for signs of the disease.

Of the 59 women, 33 had Alzheimer’s, but contrary to the team’s expectation, the women with Alzheimer’s had significantly less male DNA in their brains than did the 26 women who did not have Alzheimer’s.

Whether that correlation means that fetal male DNA helps protect women against Alzheimer’s is unclear, however. “To me, this suggests that the presence of fetal cells in the female brain prevents disease,” says cardiologist Hina Chaudhry of Mount Sinai School of Medicine in New York City.

In a study published online in Circulation Research last year, Chaudhry and colleagues found that fetal cells in mice migrated to the mother’s heart, differentiated into functioning cardiac cells, and accelerated repair to damaged heart tissue. So, Chaudhry says, a similar thing could be happening when fetal cells migrate to the brain. “I would bet these cells are getting into the maternal brain and are able to differentiate into neurons.”

Nelson said it is also difficult to reach any firm conclusions about a potential link between microchimerism and Alzheimer’s. Part of the problem is her team had little information about the pregnancy histories of the women in their study. “We have to say we really don’t know,” she says. “I hope that kind of work can be done in the future, but it’s very difficult to do with human samples.”

~ by Butch on September 29, 2012.

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