ScienceNot yet confirmed elsewhere1 publisher2 min readPublished
Maternal cells show up in the brain tissue of 26 of 37 children, sequencing finds
Sami Kanaan's team at the Fred Hutchinson Cancer Center detected maternal cells in 26 of 37 children's brain samples, averaging 2.2 per 100,000 cells. A mosaic brain is a fair inference, but whether the cells affect function or disease is a separate question.
The Scientist · Science desk
What happened
- The team used single-nucleus RNA sequencing to find genetic arrangements belonging only to the child or only to the mother, then ran its earlier tool, Cellector, to look for patterns in the data.
- The maternal cells were identified in many cell types, including neurons, microglia, astrocytes, oligodendrocytes and endothelial cells.
- The team also ran Cellector on three previously published RNA datasets, covering individuals from a 22-week-old fetus to people in their 80s.
- That reanalysis showed microchimeric cells in the brains of people of all ages.
Why it matters
- capability The maternal reference was a mouth swab [c2], so a child's brain tissue can be screened without a matching maternal brain, the pairing that had made these cells hard to study.
- constraint All 37 samples came from epilepsy surgery, so the counts cannot say whether brains without that condition carry the same number of maternal cells.
- constraint The autoimmune and tissue-repair links come from microchimeric cells in the body generally, so for the brain they remain hypotheses.
Twenty-six of 37 children is about 70% [20]. Eleven showed no maternal cells [21]. Kanaan said more of the children probably had them, but the method would have missed any pair in which mother and child have identical genetic variants [6]. So 70% is a minimum for this sample, and the 11 are not confirmed empty.
Detection is statistical. Kanaan described Cellector this way: "It models data, and it says 'that cell does not fit in that model, so it's probably a foreign cell'" [19]. The word is "probably". Each call is a model's judgement about one cell.
Hina Chaudhry of the Icahn School of Medicine at Mount Sinai, who was not involved in the research [18], said "every human brain is likely a genetic mosaic of more than one person" [12]. We think the data support "common", and they support saying the cells are present from early in life. "Every" is an extrapolation from 37 children, and the cells are sparse: on average about 0.0022% of the cells in a sample were maternal [22]. Kanaan said of such cells, "They are usually 1 in 100,000" [13].
The phrase "persist into old age" needs a qualifier. The reanalysis covered donors up to their 80s [8], but the number of cells declined with age [10]. New Scientist reports the decline may reflect apoptosis, the programmed cell death that removes damaged and old cells [11]. The data compare people of different ages, so in our view they cannot show cells dying off inside any one brain.
The thing this doesn't tell you is whether a maternal neuron or microglial cell behaves any differently from its neighbours. Kanaan said: "It is crazy that we found them in gestational samples" [16].
What to watch
- A functional experiment showing whether maternal neurons or microglia behave differently from the child's own cells.
- Counts from brains of children without epilepsy, to see whether 2.2 per 100,000 holds outside surgical patients.
- Age-spanning data that follow enough donors to test whether the decline is cell death, as the apoptosis suggestion implies.
Clarity's read
What the record supports and how the coverage leans. The claims behind it follow.
Reality
- Evidence58
- Adoption
- Insufficient
- Hype gap+15
- Incentives
- Insufficient
- Confidence50
Claim ledger
Ranked by verification strength, evidence, and original report placement.
- [1]
Kanaan and colleagues analysed genetic sequences in samples removed from the brains of 37 children, from newborns to 14-year-olds, as part of surgery to treat epilepsy.
- [2]
The children's brain sequences were compared against genetic sequences in mouth swabs taken from their mothers.
- [3]
The researchers used single-nucleus RNA sequencing to identify genetic arrangements in the samples that were from just the child or their mother, then ran a tool they had previously developed, Cellector, to computationally look for patterns in the sequence data.
- [6]
Kanaan said more of the children probably had maternal cells, but the method would have missed instances in which the mother and child had identical genetic variants.
- [7]
Kanaan and colleagues identified microchimeric cells in many cell types, including neurons, microglia, astrocytes, oligodendrocytes and endothelial cells.
- [8]
The team used Cellector to analyse RNA sequence data from three previously published studies, with individuals ranging in age from a 22-week-old fetus to people in their 80s.
- [9]
The reanalysis showed that people of all ages can have microchimeric cells in their brains.
- [11]
The decline may be the result of apoptosis, programmed cell death that removes damaged and old cells.
- [12]
every human brain is likely a genetic mosaic of more than one person
ReportedSupportedSource: Hina Chaudhry, Icahn School of Medicine at Mount Sinai, not involved in the researchView cited source - [13]
They are usually 1 in 100,000.
- [14]
Detecting such cells has required brain samples from both a mother and their child for comparison.
- [15]
Cells from mothers and other family members inside us are thought to come from a small proportion of cells crossing the placenta in utero, could influence the risk of autoimmune conditions, and may play a role in tissue repair.
- [16]
It is crazy that we found them in gestational samples
- [17]
Sami Kanaan works at the Fred Hutchinson Cancer Center in Seattle.
- [18]
Hina Chaudhry, at the Icahn School of Medicine at Mount Sinai in New York, was not involved in the research.
- [19]
It models data, and it says 'that cell does not fit in that model, so it's probably a foreign cell'
- [21]
11 of the 37 children showed no detected maternal cells.
- [22]
On average about 0.0022% of cells in a sample were maternal.
Sources
1 independent publisher whose own reporting we read for this story.
- newscientist.comCells from your mother could stay in your brain your whole life
1 article · October 13, 2026
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Topics
- MicrochimerismFollow
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- Single-Cell SequencingFollow
Entities
- Sami KanaanFollow
- Hina ChaudhryFollow
- Fred Hutchinson Cancer CenterFollow
- CellectorFollow
- Icahn School of Medicine at Mount SinaiFollow