Mother’s DNA Found in Children’s Brains for Decades

Researchers have discovered that children’s brains can contain cells with their mother’s DNA, which can persist for decades, according to a study published on bioRxiv. The findings, part of a growing body of research on microchimerism, suggest that maternal cells may integrate into the brain during pregnancy and remain there throughout life. The study, led by Sami Kanaan of the Fred Hutchinson Cancer Center in Seattle, analyzed brain tissue from 37 children with epilepsy and found that 70% had maternal cells in their brains, with some samples containing hundreds of such cells per 100,000 brain cells. Methodology and findings
The research team used quantitative PCR to detect maternal DNA in brain tissue samples from 37 children, aged 28 days to 19 years, who had undergone surgery for epilepsy. Mothers provided DNA samples via cheek swabs, allowing scientists to compare genetic material. Of the 37 cases, 26 children—70%—had maternal cells in their brains, with these cells distributed across multiple regions, including the frontal, temporal, and parietal lobes, as well as the hippocampus. The average number of maternal cells per 100,000 brain cells was 2.2, though one hippocampal sample contained 459 maternal cells. The study also examined brain tissue from 29 individuals without neurodevelopmental conditions, finding foreign cells in 25 of them—about 78%. Among these, a man in his 90s showed evidence of maternal cells, though researchers could not confirm the source due to lack of maternal DNA. The cells appeared to transform into various brain cell types, including neurons, oligodendrocytes, astrocytes, microglia, and endothelial cells, according to single-nucleus RNA sequencing. Amy Boddy, co-director of the Microchimerism, Human Health and Evolution Project at the University of California, Santa Barbara, highlighted the study’s significance. “What’s exciting here is that it’s tissue, not blood; it’s real human data, not an animal model; and the methods are cutting-edge,” she said. Past research had primarily identified maternal microchimerism in blood samples or infancy, but this study provides direct evidence of its presence in brain tissue. Implications and future research
The findings raise questions about the role of maternal cells in brain development and function. Boddy noted that microchimeric cells might perform critical tasks, though their exact function remains unclear. “Do we maybe need microchimeric cells to ‘help out’?” she asked. The study also found that firstborn children were more likely to carry maternal cells, with 14 of 26 children with maternal cells being firstborns. Dr. Sing Sing Way, a microchimerism researcher at Cincinnati Children’s Hospital Medical Center, emphasized the need to understand how these cells originate. “It would be interesting to know whether that diversity reflects their origins—such as whether they came from a mother, an older biological sibling, or a maternal grandmother,” he said. The study’s authors acknowledged limitations, including the use of preterm brain tissue from epilepsy patients and the inability to confirm maternal origin in some cases. They also noted that the prevalence of maternal cells might be underestimated due to detection method constraints. Microchimerism, the exchange of cells between mother and fetus during pregnancy, has been observed in other organs, but this study expands its known scope to the brain. While the research does not establish causation, it underscores the complexity of human biology and the potential long-term impact of prenatal cell exchange. Future studies should aim to analyze larger, more diverse datasets, including brain biopsies from individuals of varying ages and genetic backgrounds. Researchers also plan to investigate whether maternal cells contribute to neurological health or disease. Its findings add to a growing body of evidence suggesting that microchimerism is a fundamental aspect of mammalian biology, with implications for understanding human development and disease. According to the study, the presence of maternal cells in the brain does not appear to correlate with epilepsy or other neurological conditions, but further research is needed to explore potential links. The work also highlights the importance of advanced genomic techniques in uncovering previously hidden biological processes. As the field of microchimerism research advances, scientists hope to clarify the functional roles of these cells and their impact on lifelong health. For now, the study offers a new perspective on the intricate connections between mothers and their children, extending beyond genetics to the very structure of the brain.