Have you ever wondered why do animals sleep? Also, why do humans "waste" a third time of their lives in sleeping? Throughout evolution, sleep has remained universal and important to all organisms with a nervous system, including invertebrates like flies, worms, and even jellyfish. But the reason why animals sleep still remains a mystery and is considered among the biggest unanswered questions in life sciences.
Journal Natural Communications has published a new study. Researchers of Bar-Ilan University in Israel reveal a novel and unexpected function of sleep which they believe could explain how sleep and sleep disturbances affect the performance of the brain, aging, and various brain disorders.
With the help of 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 need sleep in order to perform nuclear maintenance.
The damage to DNA can be caused by many processes including oxidative stress, radiation, and even neuronal activity. The repair systems of DNA within each cell correct this damage. The current work reflects that during wakefulness, when chromosome dynamics are low, DNA damage consistently accumulates and can reach unsafe levels.
The role of sleep is to raise chromosome dynamics and normalize the DNA levels damage in every single neuron. Apparently, this DNA maintenance process is not efficient enough during the online wakefulness period and needs an offline sleep period with reduced input to the brain in order to occur. Prof. Lior Appelbaum said that it's like potholes in the road. 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 said that roads accumulate wear and tear, especially during daytime rush hours. it is most convenient and efficient to fix them at night when there is light traffic.
the accumulation of DNA damage is called the price of wakefulness by Appelbaum. 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 synchronizes and consolidates nuclear maintenance within individual neurons, and set out to confirm this theory.
With their accurate transparency, and a brain very similar to humans, zebrafish are a perfect organism for studying single cell within a live animal under physiological conditions. By taking help of a high-resolution microscope, the movement of DNA and nuclear proteins within the cell inside the fish can be observed while the fish are awake and asleep.
By: Preeti Narula