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The brain liquidates billions of mutant neurons around the time we’re born
Heidi Ledford reports for Nature from Seattle, Washington.
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By the time a baby is born, its brain has lost large numbers of neurons with genetic abnormalities.Credit: Getty
Around the time of birth, the developing human brain mysteriously tidies up by purging itself of a vast number of mutation-riddled neurons, according to a painstaking analysis of more than 2,300 nerve cells.
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The analysis, published in Nature1 on 28 October, found that more than one-quarter of the sampled neurons from the brains of human fetuses had either gained or lost several segments of their chromosomes. By contrast, only about 6% of neurons from the brains of babies after birth had such abnormalities. “It suggests that the neurons that survive may be the ones that have kept the most intact genomes during development,” says Christos Proukakis, a neurologist at University College London, who was not involved in the study.
The findings reveal a new mechanism for regulating how many neurons a person has and for deciding which fetal neurons are allowed to persist in the brain, says Diane Shao, a paediatric neurogeneticist at Boston Children’s Hospital in Massachusetts and first author on the paper.
Learning more about this process could be key to understanding neurological conditions that often appear in childhood, such as autism spectrum disorder (ASD) and epilepsy.
Studies in mice2 have suggested that, during early development, mammals eliminate many brain cells by activating a molecular programme that leads to the cells’ deaths. Shao and her colleagues analysed human brain development by studying the brains of deceased individuals ranging from fetuses at 14 weeks of gestation to nonagenarians. The team focused on neurons in the cerebral cortex, a region of the brain responsible for memory, learning and consciousness, among other functions.
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