DNA from Male Fetus May Alter Maternal Brain

Maternal-fetal exchange of cells may result in deposition of male DNA to the mother’s brain that lasts a lifetime and has potential health effects. So say the results of a study published in PLoS One of autopsied brain tissue from women aged 32 to 101 without neurologic disease or with Alzheimer’s disease.

Of the 59 brain autopsy specimens analyzed with real-time quantitative polymerase chain reaction (PCR) by researchers from the University of Washington, Seattle, 37 (63%) harbored microchimerism (Mc)-cells from a genetically distinct organism, in this case, a male. The DNA was found in multiple brain regions and highest in the medulla but absent from the frontal lobe and putamen. Of the 9 women known to have borne at least 1 son, 5 had male DNA in at least 1 brain region, all of whom had Alzheimer’s. The cells also were found in 1 of 2 women with no history of delivering sons, who had no history of neurologic disease.

The prevalence (P=0.03) and concentration (P=0.06) of male DNA in the brains of women with Alzheimer’s were lower than in women without neurologic disease. Analysis of specimens only from the five brain regions believed to be most affected by Alzheimer’s showed that odds of having the disease were 52% lower for those with male DNA than without it, despite the fact that Alzheimer’s is more prevalent in women than in men.

The researchers believe their study is the first of male DNA in women’s brains and specific brain regions and that further investigation is needed of the health implications, particularly given the unexpected results related to Alzheimer’s. The findings, they say, show that “fetal DNA and likely cells can cross the human blood-brain barrier (BBB) and reside in the brain.” Potential sources of male DNA, they postulate, include an abortion, miscarriage, male twin, older male sibling, or a non-irradiated blood transfusion. According to the investigators, however, “the most likely source of male Mc in female brain is acquisition of fetal Mc from pregnancy with a male fetus.”

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