Researchers have discovered that babies may have cells in their brains containing their mother’s DNA, and these cells may persist for decades.
The findings, which were posted on a preprint database biorxiv June 10, but not yet peer-reviewed, it is part of a growing body of work that shows that a mother and a fetus exchange cells during pregnancy — a phenomenon known as “microchimerism.” Previously, scientists had found that a mother’s brain contained cells containing her children’s DNA.
He said these findings are important for several reasons amy bodyco-director of the Microchimerism, Human Health and Evolution Project at the University of California, Santa Barbara, who was not involved in the study. Previous work has found evidence of maternal microchimerism mostly in infancy and in blood samples, he told Live Science in an email. “The exciting thing here is that it’s tissue, not blood; it’s real human data, not an animal model; and the methods are state-of-the-art.”
More broadly, the work reinforces the idea that microchimerism “is a general process of mammalian biology,” Boddy said.
hunting mother cells in the brain
Before this study, there was sparse evidence As for maternal microchimeric cells in the brain, mostly because it is difficult for researchers to obtain human brain tissue and DNA samples from both parents and their children.
A team was led to overcome this challenge Sami KananA staff scientist at the Fred Hutchinson Cancer Center in Seattle analyzed brain tissue that was surgically removed from dozens of children with severe epilepsy as part of their treatment. The patients ranged in age from 28 days to 19 years at the time of surgery, and their mothers provided DNA samples via cheek swabs.
Kanan’s team used a tool called quantitative PCR to identify and count maternal cells hidden among the millions of cells in babies’ brains.
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Of the 37 mother-child pairs, 26 children – 70% – had their mother’s cells in their brains. These mother cells were distributed in several areas of the brain, including the frontal, temporal, and parietal lobes, which are located on the outer surface of the brain, and the hippocampus, which is hidden deep inside. There was an average of 2.2 maternal cells per 100,000 in each sample, although one sample of the hippocampus had 459 maternal cells per 100,000 and 11 children had no evidence of maternal DNA in their brains.
“Due to the limitations of detecting rare cells at low frequency with this method, that prevalence is likely underestimated,” Body said.
Being the first child appears to increase the chances of having maternal cells in the brain. Of the children who had their mother’s cells, 14 were first-born and 12 were born later. In contrast, of the children who did not have these cells, only one was a firstborn and 10 were born later.
Using a technique called single nuclease RNA sequencing, which maps what a cell is doing by showing which genes are turned on within cells, the researchers found that the mother cells had turned into multiple types of brain cells. Presumably, these cells were originally Leukocytes and stem cells and was transferred to the fetus through the placenta or during pregnancy or breastfeeding.
The transformed cells included neurons; oligodendrocytes, which form protective coverings around neurons; astrocytes, which support many brain functions and help fuel neurons; Microglia, immune cells of the brain; and endothelial cells, which line blood vessels.
“It is amazing to be able to use single-nuclease RNA sequencing to identify what type of cells the maternal microchimeric cells actually are,” Body said. “We are very limited in understanding the function of these cells, and papers like this, in these ways, are getting us closer.”
During pregnancy, the mother and fetus exchange cells – a phenomenon called “microchimerism.”
(Image credit: Renizzara S via Getty Images)
examining a healthy brain
To see whether these findings also applied to people without epilepsy, researchers examined brain autopsy data from 29 individuals with no known neurodevelopmental conditions, ranging in age from 22 weeks after conception to 40 years. They also analyzed brain tissue from three men in their late 80s and early 90s with no known brain conditions, originally collected as part of an Alzheimer’s disease study.
Overall, the researchers found foreign cells in 25 of the 32 people – about 78% – including the brain of a man over the age of 90.
Researchers suspected that these foreign cells were maternal cells, but they could not confirm this because they did not contain the mother’s DNA. It is possible that the foreign cells may have come from the twin; an older sibling; previous pregnancy, miscarriage or abortion (in women); Or, more rarely, from nannies, the team wrote in their paper.
Like those in epilepsy patients, these cells matured into multiple types of functioning brain cells. In young brains, they often become a specific type of neuron, a layer 2/3 neuron, while in older brains, the mother cells are more likely to be microglia.
Given that these microchimeric cells play very different roles, it would be interesting to know whether this diversity reflects their origin – for example, whether they came from a single mother, an older biological sibling, or a maternal grandmother, as stated Dr. Sing Sing Waya microchimerism researcher at Cincinnati Children’s Hospital Medical Center who was not involved in the study.
The number of maternal cells declined with age, but they never completely disappeared.
Boddy said the findings raise mostly new questions. “Do we perhaps need microchimeric cells to ‘help’ us?”. he asked. “Is the diversity of cells in the brain important, or is it just a byproduct of being a placental mammal?”
Because microchimeric cells appear to be normal, Boddy suspects that they “serve an important function in the brain, so understanding their function may be very important to understanding healthy brain development.”
By using new analytical tools to pinpoint microchimeric cells, the study “pushes the boundaries” of previous research, Way said, but future studies would benefit from larger and more uniform datasets. This would mean obtaining more brain biopsies, analyzing more cells from each sample, collecting samples at different ages, and sampling the same brain regions across individuals to better compare results.
This article is for informational purposes only and is not intended to provide medical advice.
Canaan, S.B., McDonough, A., Gentile, C., Ozeman, J., Haynes, H., Behboudi, R., Eisenberg, D.T.A., Furlan, S.N.D., Rutledge, J., Urselli, F., Weinstein, J.R., and Nelson, J.L. (2026). Microchimerism, quantitative assessment and single nucleus profiling establish cell types and diversity in the human brain.. bioRxiv. https://doi.org/10.64898/2026.06.05.730225