Building a Brain Requires DNA Shredding

Building a brain turns out to require a step nobody put in the textbook: your neurons have to destroy their own DNA to get there.

Getting a neuron to its destination in the brain cortex is a physical gauntlet. Each newborn nerve cell must force its way through packed tissue, past neighboring cells and fibers, to reach the region where it will eventually wire into a neural circuit. The Kyoto University WPI-iCeMS team, publishing in Nature, found that navigating those corridors inflicts extensive DNA damage — including complete double-strand breaks where the helix is severed on both sides.

It had long been assumed that this journey, however arduous, leaves the neuron's genetic material fundamentally intact. Zhang et al. now challenge that assumption. The culprit is mechanical stress. Unlike the random, lethal DNA damage observed in migrating cancer cells, the breaks in neurons are primarily mediated by Topoisomerase IIβ, an enzyme that normally relieves torsional strain but becomes trapped under mechanical stress during migration; the resulting breaks are subsequently repaired via the non-homologous end joining pathway.

The damage also lands somewhere that matters. These breaks concentrate in genomically silent territory, away from actively expressed genes, leaving the neuron able to function normally. The body, it seems, thought ahead.

To find out what happens when repair fails, the team engineered mice whose new cerebellar neurons lacked Ligase 4, a key repair enzyme. Those mice developed progressive balance and coordination difficulties from early adulthood, mirroring human genomic instability syndromes.

The neurons break. The body fixes it. Most of the time, that's enough.

Read the full story at Neuroscience News, June 17, 2026

Hot Take: It turns out building a brain is less about order and more about surviving a traumatic journey.