Sleep offers the brain a chance to repair damaged DNA that collects within neurons during the day, according to a new study, detailed in a report from The Scientist.

Despite the fact that sleep is common among all animals, with well documented benefits, its evolutionary purpose is still not well understood, in spite of a large body of research.

Lior Applebaum, of Israel’s Bar-Ilan University, theorized that the benefits of sleep could be operating on the level of individual neurons, since all organisms with a nervous system rely on sleep.

“I propose that, when we are very tired, neurons accumulate so much damage that they signal the whole brain that we have to go to sleep to fix the damage and avoid going into an unsafe zone,” said Applebaum.

To test their hypothesis, the team genetically engineered transparent zebrafish so that chromosomes within their neurons were colored, fluorescent, and visible. Using a powerful microscope, they tracked the chromosomes, both while the fish were awake and asleep.

During waking hours, the chromosomes moved very little, and broken strands gradually accumulated within the neurons­­­ as a result of normal activity. When facing sleep deprivation, the broken strands continued to build up until the neuron was at risk of dying.

During sleep, however, chromosomes changed shape more often, and the damage was repaired.

“It’s surprising, because the brain goes into a rest state, but the chromosomes move about twice as much during sleep,” Appelbaum told The Guardian. “There is repair going on in the day, but sleep allows you to catch up.”

He said the dynamic shape changing allows DNA to be repaired in various locations of the chromosomes. Since damage accumulates much slower during sleep, these repair mechanisms are able to catch up.

Applebaum said in a press release:

“It’s like potholes in the road. Roads accumulate wear and tear, especially during daytime rush hours, and it is most convenient and efficient to fix them at night, when there is light traffic.”

Next, the researchers hope to study the sleep state of mice, to see if the same principles apply to DNA repair in mammals.

The study follows research published in January, showing that sleep deprivation can cause DNA damage.

The latest research was published in the journal Nature Communications.


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