The reason why humans and other animals sleep is considered to be one of the most important unanswered questions in life sciences. A new study from Bar-Ilan University in Israel has proposed an unexpected function of sleep that may explain why deprivation has such a strong impact on cognitive performance and aging.
The research, which was focused on zebrafish, was conducted using 3D time-lapse imaging technology. For the first time, the researchers showed that individual neurons require sleep in order to perform nuclear maintenance.
DNA damage can be caused by many processes such as radiation, oxidative stress, and neuronal activity, and each cell contains repair systems that correct this damage. The current study demonstrates that DNA damage consistently accumulates and can reach unsafe levels during wakefulness, when chromosome dynamics are low.
According to the experts, the role of sleep is to increase chromosome dynamics and to return DNA to normal in each individual neuron. This suggests that a period of reduced brain input is required to repair DNA damage.
“It’s like potholes in the road,” said study lead author Professor Lior Appelbaum. “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.”
The discovery may not have been possible without the unique characteristics of zebrafish, who have absolute transparency and a brain very similar to humans. The movement of DNA and nuclear proteins within cells inside the fish can be observed using a high resolution microscope.
The researchers did not expect to find that chromosomes are more active at night when the body rests. This increased activity is what enables the body to efficiently repair DNA damage.
“We’ve found a causal link between sleep, chromosome dynamics, neuronal activity, and DNA damage and repair with direct physiological relevance to the entire organism,” said Professor Appelbaum. “Sleep gives an opportunity to reduce DNA damage accumulated in the brain during wakefulness.”’
“Despite the risk of reduced awareness to the environment, animals – ranging from jellyfish to zebrafish to humans – have to sleep to allow their neurons to perform efficient DNA maintenance, and this is possibly the reason why sleep has evolved and is so conserved in the animal kingdom.”
The study is published in the journal Nature Communications.
By Chrissy Sexton, Earth.com Staff Writer