First Time Evidence: Leftover Male Fetal DNA Found In Female Brains

Lawrence LeBlond for – Your Universe Online

A small amount of male DNA can be found in the brains of women, something researchers at Fred Hutchinson Cancer Research Center (FHCRC) believe may be the result of leftover DNA in the mother´s body by a male fetus, which occurs relatively frequently.

In a first-of-its-kind study, William Chan, PhD, Department of Biochemistry at University of Alberta, and J. Lee Nelson, senior author at FHCRC, looked at microchimerism–the harboring of genetic material and cells that were exchanged between fetus and mother during pregnancy–and the link it has on autoimmune diseases and cancer. The research is published in the latest issue of PLoS ONE.

Fetal microchimerism (Mc) is common in other tissues in the female body, but this was the first time researchers found evidence of male Mc in the human female brain. Microchimerism can be beneficial to maternal health, but can be just as dangerous.

Findings of this new study support the likelihood that fetal cells frequently cross the blood-brain barrier, indicating that microchimerism in the female brain is fairly common. Until this study, it was not known whether such cells could cross that barrier in humans.

To study this, the researchers examined brain autopsy specimens from 59 women who had died between the ages of 32 and 101. They detected Mc in 63 percent of the subjects studied, found it was distributed in multiple regions of the brain, and found it potentially persisted throughout the lifespan of each individual; the oldest female with detectable Mc DNA in the brain was 94 years old.

The team further found that 26 of the females had no neurological diseases and 33 had Alzheimer´s disease. Surprisingly, the women with Alzheimer´s had a relatively lower percentage of fetal Mc, and particularly lower levels in regions of the brain most affected by the disease.

Despite the significance of the findings, the authors noted that the small number of subjects and largely unknown pregnancy history of the women means a link between Alzheimer´s and the level of male fetal cells cannot be established. The study also did not provide a link between male Mc in the female brain and relative health vs. disease.

“Currently, the biological significance of harboring male DNA and male cells in the human brain requires further investigation,” Chan said.

Previous studies of male Mc in women have found that it impacts a woman´s risk of developing some types of cancer and autoimmune disease. In some conditions (e.g. breast cancer), cells of fetal origin play a protective role; in others (e.g. colon cancer), they have increased risk of disease.

This study was funded by grants from the National Institutes of Health and the Canadian Institutes of Health Research. The study also included researchers from the University of Washington School of Medicine.

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