In a new study it has been revealed that the X chromosome passed down to the child from the mother might be responsible for accelerated brain ageing, potentially increasing the risk of conditions like Alzheimer's disease.

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Females have two X chromosomes, while males have one X and one Y chromosome. The X chromosome contains substantial genetic information, and alterations to it can have significant consequences. In females, one of the two X chromosomes is randomly deactivated in each cell, which can lead to varied effects.

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X marks the brain

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Previous research has hinted that the X chromosome—of which most women have two and most men have just one—is vital to brain health.

"Given the fact that the X chromosome is enriched for brain-related genes, it became very important for us to know what roles it might be playing in brain aging," said Samira Abdulai-Saiku, a UCSF postdoctoral fellow and first author of the new work.

The experiment

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To further explore the idea, the researchers experimented with female lab mice of different ages. In some cases, the paternal X chromosomes were silenced, leaving only the mother's X active. These mice were compared with others that had a mix of maternal and paternal X's switched on.

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As per the findings, the young "Mom-X" mice were cognitively similar to young mice but the older ones showed steep cognitive decline. In the brains of these mice, the maternal X chromosome sped up biological ageing in the hippocampus - a brain area crucial for learning and memory.

"These findings raise the possibility that some women who express more of their mom's X chromosome just by pure chance may have more cognitive impairment with aging or an increased risk for diseases like Alzheimer's," said Dena Dubal, a senior author of the paper.

"Ultimately, it could also help us find constructive strategies for slowing brain aging in both sexes," she added.

Though the research was conducted on mice, the findings, if they translate to humans, could point to drivers of cognitive decline related to a particular sex and, eventually, help us find ways to prevent or treat them.

(With inputs from agencies)