Men’s and Women’s Brains Differ at the Cell Level — More Than Anyone Realised
Male and female brains look largely the same. But at the level of individual cell types, a new study finds striking differences in which genes are switched on — with direct implications…
Published in Science, the study mapped gene expression — which genes are active, and how much — across the human cerebral cortex, broken down by cell type and by sex. The cerebral cortex is the outer layer of the brain responsible for memory, language, and decision-making. Crucially, the researchers found that sex effects on gene expression vary strongly by cell type: patterns seen in neurons don’t necessarily apply to astrocytes, microglia, or oligodendrocytes — the other major cell populations in the brain.
The practical stakes are substantial. Alzheimer’s disease, Parkinson’s, depression, and schizophrenia all show sex differences in prevalence, disease trajectory, or treatment response. Those differences have typically been attributed to hormones or behaviour. This study suggests part of the explanation is more fundamental — embedded in the baseline gene activity of specific brain cell types themselves.
Microglia: the immune cells of the brain
Microglia are the brain’s resident immune cells: they clear debris, respond to damage, and help prune neuronal connections during development and throughout life. They’ve attracted intense interest from Alzheimer’s researchers, partly because many of the disease’s known genetic risk factors are most active in microglia. The new study identifies microglia as one of the cell types showing the strongest sex effects on gene expression. That finding may help explain why women face a higher lifetime risk of Alzheimer’s and why the disease often progresses differently in women than in men.
For longevity science, the findings point in two directions. First, they provide a biological basis for developing sex-specific treatments for brain diseases that are intimately tied to aging. Second, they highlight the long-standing problem of sex imbalance in neuroscience research: much of what we think we know about the human brain was derived from male animal models or male-skewed study populations.
What the study can’t yet answer
The analysis relied on post-mortem brain tissue — a snapshot rather than a dynamic picture. How these sex differences in gene expression develop over a lifetime, and whether they shift around menopause or with other hormonal changes, remains unknown. That’s a critical gap, given that women’s Alzheimer’s risk rises sharply after menopause. The map has been drawn; the timeline still needs to be filled in.