Not gonna say it;-)
Male DNA has for the first time been found inside the female brain, according to new research led by a Canadian scientist.
No, the finding doesn't explain why women sometimes know what their husbands are thinking.
But it could lead to refining what "the self," biologically speaking at least, really means.
Plus, in an unexpected finding, the researchers found that women with Alzheimer's disease had less male DNA in their brains -- and in lower concentrations in the brain region's most affected by the memory-robbing disease -- than women without Alzheimer's.
Observers said the finding also raises the hypothesis that, if male DNA can infiltrate a woman's brain, it might have some "masculinizing" affect on the female brain.
And, if that's so, "what consequences does this have on how the brain functions -- in other words, thinking and behaviour?" said neuroscientist Dr. Sandra Witelson, a professor in the department of psychiatry and behavioral neurosciences at the Michael G. DeGroote School of Medicine at McMaster University in Hamilton.
Appearing in the latest edition of the journal, PLOS ONE, the study is the first to describe the presence of male "microchimerism" in women's brains.
Microchimerism is the "intermingling" of small numbers of cells or portions of DNA in a person or animal from a genetically different inpidual.
In this case, the male DNA found in women's brains most likely came from cells from a pregnancy with a baby boy.
But women can acquire male DNA without ever having a son. In women without boys, male DNA can come from sharing her mother's womb with a male twin, from a non-irradiated blood transfusion and possibly even from an older sibling.
During pregnancy, cells are exchanged in both directions, from mother to fetus, and fetus to mother. After birth, women retain a small number of fetal cells. Although it hasn't yet been reported, the cells from an earlier pregnancy might be passed along with the maternal cells that reach a fetus in a later pregnancy.
Other scientists had already found evidence of male microchimerism in the blood, bone marrow, liver and other tissues of women from fetal cells exchanged between mother and baby via the placenta.
But until now, no one had ever looked at whether the cells could cross the blood-brain barrier, and live in the human brain, potentially for decades.
According to the researchers, "male microchimerism is frequent and widely distributed in the human female brain."
Whether this is a good thing or bad isn't yet clear. "Currently, the biological significance of harbouring male DNA and male cells in the human brain requires further investigation," lead author Dr. William Chan, of the department of biochemistry at the University of Alberta, said in a statement.
Nevertheless, "this is the first evidence that microchimerism can cross the blood-brain barrier to establish male fetal cells in the human female brain," he said.
For their study, the scientists examined brain autopsy specimens from 59 women who had died when they were between the ages of 32 and 101. Thirty-three women had Alzheimer's disease; 26 were free of Alzheimer's.
They searched the brain samples for the presence of a particular region of the Y-chromosome. The researchers looked for male DNA, because it's harder to distinguish a daughter's DNA from the mother's cells, Nelson said.
In all, 63 per cent of the women tested -- 37 of 59 -- harboured male DNA in multiple brain regions, and the cells appear to persist "across the human lifespan," according to the researchers. The oldest woman in whom male DNA was detected in the brain was 94.
Although they're relatively small in number, the biological effects of these "immigrant" cells could be significant, said senior author Dr. J. Lee Nelson, of the Fred Hutchinson Cancer Research Centre. Chan, of the University of Alberta, conducted the research while working in Nelson's lab.
The researchers found that women with Alzheimer's disease had less male DNA than women without the disease.
Alzheimer's is more prevalent in women than in men.
It doesn't prove cause-and-effect, the researchers stressed, given the small number of women and the fact that their pregnancy histories were unknown for all but a few of them. "But there's a big horizon to be explored," Nelson said.
Some studies suggest fetal cells can protect women against breast cancer. Others have proposed that the cells might help regenerate damaged or inflamed tissue, Nelson said.
Perhaps more exciting, she said, is that "it really points to the need for a new paradigm of what the self is, biologically.
"I think we're better off thinking of it as an ecosystem, rather than as a singular genetic template, with more genetic and cellular persity than we previously thought."
Male DNA found for first time in female brains
Male DNA has for the first time been found inside the female brain, according to new research led by a Canadian scientist.
No, the finding doesn't explain why women sometimes know what their husbands are thinking.
But it could lead to refining what "the self," biologically speaking at least, really means.
Plus, in an unexpected finding, the researchers found that women with Alzheimer's disease had less male DNA in their brains -- and in lower concentrations in the brain region's most affected by the memory-robbing disease -- than women without Alzheimer's.
Observers said the finding also raises the hypothesis that, if male DNA can infiltrate a woman's brain, it might have some "masculinizing" affect on the female brain.
And, if that's so, "what consequences does this have on how the brain functions -- in other words, thinking and behaviour?" said neuroscientist Dr. Sandra Witelson, a professor in the department of psychiatry and behavioral neurosciences at the Michael G. DeGroote School of Medicine at McMaster University in Hamilton.
Appearing in the latest edition of the journal, PLOS ONE, the study is the first to describe the presence of male "microchimerism" in women's brains.
Microchimerism is the "intermingling" of small numbers of cells or portions of DNA in a person or animal from a genetically different inpidual.
In this case, the male DNA found in women's brains most likely came from cells from a pregnancy with a baby boy.
But women can acquire male DNA without ever having a son. In women without boys, male DNA can come from sharing her mother's womb with a male twin, from a non-irradiated blood transfusion and possibly even from an older sibling.
During pregnancy, cells are exchanged in both directions, from mother to fetus, and fetus to mother. After birth, women retain a small number of fetal cells. Although it hasn't yet been reported, the cells from an earlier pregnancy might be passed along with the maternal cells that reach a fetus in a later pregnancy.
Other scientists had already found evidence of male microchimerism in the blood, bone marrow, liver and other tissues of women from fetal cells exchanged between mother and baby via the placenta.
But until now, no one had ever looked at whether the cells could cross the blood-brain barrier, and live in the human brain, potentially for decades.
According to the researchers, "male microchimerism is frequent and widely distributed in the human female brain."
Whether this is a good thing or bad isn't yet clear. "Currently, the biological significance of harbouring male DNA and male cells in the human brain requires further investigation," lead author Dr. William Chan, of the department of biochemistry at the University of Alberta, said in a statement.
Nevertheless, "this is the first evidence that microchimerism can cross the blood-brain barrier to establish male fetal cells in the human female brain," he said.
For their study, the scientists examined brain autopsy specimens from 59 women who had died when they were between the ages of 32 and 101. Thirty-three women had Alzheimer's disease; 26 were free of Alzheimer's.
They searched the brain samples for the presence of a particular region of the Y-chromosome. The researchers looked for male DNA, because it's harder to distinguish a daughter's DNA from the mother's cells, Nelson said.
In all, 63 per cent of the women tested -- 37 of 59 -- harboured male DNA in multiple brain regions, and the cells appear to persist "across the human lifespan," according to the researchers. The oldest woman in whom male DNA was detected in the brain was 94.
Although they're relatively small in number, the biological effects of these "immigrant" cells could be significant, said senior author Dr. J. Lee Nelson, of the Fred Hutchinson Cancer Research Centre. Chan, of the University of Alberta, conducted the research while working in Nelson's lab.
The researchers found that women with Alzheimer's disease had less male DNA than women without the disease.
Alzheimer's is more prevalent in women than in men.
It doesn't prove cause-and-effect, the researchers stressed, given the small number of women and the fact that their pregnancy histories were unknown for all but a few of them. "But there's a big horizon to be explored," Nelson said.
Some studies suggest fetal cells can protect women against breast cancer. Others have proposed that the cells might help regenerate damaged or inflamed tissue, Nelson said.
Perhaps more exciting, she said, is that "it really points to the need for a new paradigm of what the self is, biologically.
"I think we're better off thinking of it as an ecosystem, rather than as a singular genetic template, with more genetic and cellular persity than we previously thought."
Male DNA found for first time in female brains
