At the end of a long tiring day, or even a not so tiring one, we all retire for the day in the same way that has been known to mankind (and animals too!) – sleeping. Sleeping lets our systems rest, or so they say. Not only humans but all livings things with a nervous system retire for the day in the same way, by sleeping. But why is sleep so essential? That remains one of the biggest unanswered questions in life science.
A recent study by the researchers at Bar-Ilan University in Israel that’s published in the Nature Communications journal says finds out 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.
The researchers used 3D time-lapse imaging techniques in live zebrafish 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.
DNA damage can be caused by many processes including radiation, oxidative stress, and even neuronal activity. DNA repair systems within each cell correct this damage. The current work shows that during wakefulness, when chromosome dynamics are low, DNA damage consistently accumulates and can reach unsafe levels.
By allowing our bodies to sleep increases chromosome dynamics, and normalize the levels of DNA damage in every single neuron. Since, this DNA maintenance process isn’t as efficient during the wakefulness period, the need for a sleep period with reduced input to the brain increases.
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, 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.
"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," concludes Prof. Appelbaum.
