Researchers reveal reason for a good night's sleep

Why do animals sleep? Why do humans “waste” a third time of their lives sleeping? Throughout evolution sleep has remained universal and essential to all organisms with a nervous system, including invertebrates such as flies, worms, and even jellyfish.  But the reason why animals sleep -- despite the continuous threat of predators -- still remains a mystery, and is considered among the biggest unanswered questions in life sciences.  

In a new study, published  in the journal Nature Communications, researchers at Bar-Ilan University in Israel reveal a novel and unexpected function of sleep that they believe could explain how sleep and sleep disturbances affect brain performance, aging and various brain disorders.

Using 3D time-lapse imaging techniques in live zebrafish, the researchers were able to define sleep in a single chromosome resolution and show, for the first time, that single neurons require sleep in order to perform nuclear maintenance. 

The role of sleep is to increase chromosome dynamics, and normalize the levels of DNA damage in each single neuron.  Apparently, this DNA maintenance process is not efficient enough during the online wakefulness period and requires an offline sleep period with reduced input to the brain in order to occur. "It's like potholes in the road," says Prof. Lior Appelbaum, of Bar-Ilan University's Mina and Everard Goodman Faculty of Life Sciences and Gonda (Goldschmied) Multidisciplinary Brain Research Center, who led the study. "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."

Appelbaum calls the accumulation of DNA damage the "price of wakefulness".  He and his doctoral student David Zada, first author of the study, as well as co-authors, Dr. Tali Lerer-Goldshtein, Dr. Irina Bronshtein and Prof. Yuval Garini, hypothesized that sleep consolidates and synchronizes nuclear maintenance within individual neurons, and set out to confirm this theory.


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