The Effect of Sleep on DNA Repair

Why do animals sleep? Why do people “waste” a third of their lives by sleeping?

Throughout evolution, sleep remained a universal and essential thing for all nervous system organisms. This includes flies, worms and even jellyfish. However, despite the constant predatory threat, the reason for sleeping animals remains a mystery.

According to a new study published in the journal Nature Communications, researchers from Bar-Ilan University in Israel discovered a brand new and unexpected function of sleep. They think that this function can explain how sleep and sleep disorders affect brain performance, aging, and various brain diseases. Using 3D time-lapse imaging techniques in living zebrafish, researchers managed to describe sleep at a single chromosome resolution and show that neurons need sleep to protect their nuclei. DNA damage can be caused by many processes, including radiation, oxidative stress, and even neuronal activity. DNA repair systems inside the cells remove this damage. Current studies show that during wake-up time, where chromosome dynamics are low, DNA damage is constantly accumulating and can even climb to unsafe levels.

The role of sleep is to increase chromosome dynamics and normalize the level of DNA damage in each neuron. It seems that this DNA maintenance process is awake and does not take place efficiently during our time and requires an offline sleep period in which the brain’s input is reduced. Professor Lior Appelbaum, who works at BarIlan University’s Mina and Everard Goodman Faculty of Life Sciences and the Gonda (Golschmied) Multidisciplinary Brain Research Center, manages this research and says, “It looks just like the rubble on asphalt.” “On the roads, especially during the day, during peak hours, wear occurs and at night it is the easiest and most efficient to repair during low traffic hours.

Appelbaum says “the price of being alert” to the accumulation of DNA damage. He and co-author Dr. Tali Lerer-Goldshtein, Dr. Irina Bronshtein and Professor Yuval Garini proposed the hypothesis that sleep reinforces and coordinates nuclear care in neurons, and they attempt to prove this theory.

This discovery was made thanks to the characteristics of the zebrafish model. Thanks to their physical transparency and human-like brains, zebra fish are well suited to examine cells under physiological conditions in a live animal. Using a high-resolution microscope, it is possible to observe the movement of DNA and core proteins in the cell while the fish is asleep and awake. Researchers were surprised to learn that the chromosomes were more mobile at night, especially when the body was asleep. This increased efficiency also increases the ability to repair DNA damage. The results show that chromosome dynamics are a potential way to find out if cells are asleep.It also suggests that the repair effect of sleep is to provide core care. “We found a causal link between sleep, chromosome dynamics, neuronal activity, DNA damage, and repair, and we have direct evidence that this applies to the whole organism,” says Professor Appelbaum. “Sleep provides an opportunity to reduce DNA damage that accumulates in the brain while awake.”

In concluding the research, “In response to the risk of environmental awareness reduction, animals have to sleep in order for their neurons to perform efficient DNA maintenance, which may be the reason for sleep to evolve and be so protected in the animal kingdom,” says Professor Applebaum.