Microchimerism — Male DNA Found in Women’s Brains

Microchimerism — Male DNA Found in Women’s Brains


According to a study by Canadian scientists, microchimerism, male DNA from the Y-chromosome, has been found in women’s brains. The study is still new and the number of women tested was small, so scientists are not ready to say whether this is a good thing or not. Since the brain autopsy can only be performed on women who have died, it may be difficult to get enough women for extensive studies.

The scientists studied the brain autopsy specimens from 59 women. The women died when they were between the ages of 32 and 101. Of the 59 women, 26 did not have Alzheimer’s disease. The scientists were looking for part of the Y-chromosome because it is harder to differentiate a daughter’s DNA from the mother than it is to differentiate a son’s DNA.

Thirty-seven of the women tested, or 63 percent, had the male DNA in more than one brain region. The age of the woman did not matter — the oldest woman with male DNA was 94 years old when she died.

One of the things the scientists found was that the women who did not have Alzheimer’s disease had more male DNA than the women with Alzheimer’s disease. Those women with Alzheimer’s disease and who had the male DNA had lower concentrations of it in the areas of the brain that are affected by Alzheimer’s disease. Furthermore, women are more apt to develop Alzheimer’s disease than men.

The study, which appears in PLOS ONE, is the first one to discuss microchimerism in women’s brains. Microchimerism means that cells from the DNA of a person [or animal] that are genetically different mingle with the subject’s DNA.

How Do Women Get Male DNA? As far as scientists can tell, a woman can acquire male DNA in several ways: A pregnancy with a baby boy, sharing her mother’s womb with a male twin, from an older sibling or from a non-irradiated blood transfusion.

While a mother is carrying, the body exchanges cells from the mother to the fetus and from the fetus to the mother. Once the mother gives birth, she retains some of the fetal cells. Furthermore, if a woman had a son, then became pregnant with a daughter, the “left over” cells from the son may be exchanged with the new female fetus.

Why is This So New? Actually, the transference of male DNA is nothing new. Scientists have previously found male DNA in a mother’s bone marrow, blood, liver and other tissues. This is the first time any scientists checked to see if the blood cells would or could cross the blood-brain barrier, then live in the brain for years.

The lead author of the study, Dr. William Chan, said that he doesn’t know if a female brain with male DNA is a good thing or bad thing and that it needs more research. Senior author, Dr. J. Lee Nelson of the Fred Hutchinson Cancer Research Centre said that because of the small number of women studied, it “does not prove cause-and-effect,” but said that “there’s a big horizon to be explored.”

Studies have also suggested that fetal cells might be able to protect women against breast cancer and could help to repair inflamed or otherwise damaged tissue.