Summary
A bioRxiv preprint reports maternal microchimerism in epilepsy surgery tissue and healthy-brain datasets, with cells matching several neuronal, immune and vascular identities. The reported frequency declined with age.
A bioRxiv preprint reports that cells of maternal origin occur in human brain tissue and correspond to several brain cell types. The researchers detected maternal microchimerism in most of the surgically resected epilepsy brains they examined, and also found it in healthy-brain datasets spanning gestation to old age. They report that its frequency diminished in older brains.
Microchimerism is the presence of a small number of cells that are genetically distinct from the person whose body contains them. During pregnancy, cells can pass between mother and fetus, leaving populations of cells in both individuals. The new study examines whether maternal-origin cells are present in the human brain and what cellular identities they may have.
How the researchers identified the cells
The team used two approaches. First, polymorphism-specific quantitative PCR (qPCR)—a method that detects selected genetic differences—was used on epilepsy surgery specimens. Maternal microchimerism was identified across temporal, frontal and parietal regions and the hippocampus.
For a broader view of cell identity, the researchers analysed single-nucleus RNA sequencing data. This method profiles gene activity in individual cell nuclei. They applied cellector, a genetic demultiplexing tool, to distinguish rare cells with a different genetic origin from the host. This analysis covered epilepsy specimens as well as publicly available datasets from healthy brains, with samples from gestation through old age.
The researchers report maternal-origin cells in both groups. Their gene-activity profiles matched diverse neuronal, glial, immune and vascular identities. Layer 2/3 intratelencephalic neuronal subtypes and microglia or perivascular macrophages were the most prominent profiles. The identified cells also showed varied transcriptional patterns and differences from host nuclei.
What the findings establish
The results bring together evidence of maternal microchimerism in surgically sampled brain regions and evidence that these cells can have multiple cellular identities. The age-related pattern is a decline in frequency, rather than a report that the cells disappear: the authors detected microchimerism into advanced age.
The evidence has important scope limits. The qPCR analysis used tissue removed during epilepsy surgery, while the healthy-brain analysis relied on public sequencing datasets. The preprint’s abstract describes the findings qualitatively—such as detection in a “majority” of epilepsy brains—but does not give sample counts or numerical frequencies. The work is posted on bioRxiv as a preprint and has not yet undergone peer review.
The study profiles the cells and their gene activity; the findings described here do not determine what role, if any, maternal-origin cells play in brain function or health.